Nonaqueous alkali metal power storage element and production method therefor

Abstract

A nonaqueous alkali metal power storage element (precursor) according to the present disclosure comprises a positive electrode (precursor), a negative electrode (precursor), a separator, an exterior material, and a nonaqueous electrolyte solution, wherein: the negative electrode (precursor) contains, as an active material, a material that absorbs and releases lithium ions; and the positive electrode (precursor) has a positive electrode active material layer that contains a positive electrode active material which absorbs and releases alkali metal ions. The nonaqueous alkali metal power storage element (precursor) contains an alkali metal carbonate in the positive electrode active material layer, in an arbitrary intermediate layer between the positive electrode active material layer and the separator, or in both. The nonaqueous electrolyte solution further contains a carbonate decomposition promoter. The oxidation commencement potential of the carbonate decomposition promoter is not less than 3.8 V (vsLi / Li+) and not more than 4.7 V.

Description

Nonaqueous alkali metal storage element and method for manufacturing same

[0001] The present disclosure relates to a nonaqueous alkali metal storage element such as a lithium ion secondary battery, a precursor thereof, a method for manufacturing a capacity-recovered nonaqueous alkali metal storage element, and a capacity-recoverable nonaqueous alkali metal storage element.

[0002] In recent years, from the viewpoint of preserving the global environment and effectively utilizing energy with the aim of saving resources, attention has been drawn to power smoothing systems or late-night power storage systems for wind power generation, distributed home power storage systems based on solar power generation technology, power storage systems for electric vehicles, etc. As a promising candidate for a high-energy density battery that can meet such demands, the development of non-aqueous alkali metal power storage elements, typified by lithium-ion secondary batteries (hereinafter referred to as LiBs), has been vigorously pursued.

[0003] For the non-aqueous alkali metal electricity storage elements used in these electricity storage systems, technological development is being actively pursued to achieve both high capacity density and durability.

[0004] Conventionally, in non-aqueous alkali metal storage elements, alkali metal ions corresponding to the initial irreversible capacity of the negative electrode are trapped at the solid electrolyte interface (SEI) or the like during the initial charge, resulting in a loss of capacity equivalent to the irreversible capacity in the discharge capacity of the full cell.

[0005] Pre-doping technology is a technique for improving the capacity density of non-aqueous alkali metal storage elements. By using pre-doping technology, it is possible to compensate for capacity loss equivalent to the initial irreversible capacity of the negative electrode. For example, Patent Documents 1 and 2 disclose a technique in which an alkali metal carbonate is incorporated into a positive electrode and used as a pre-doping source upon charging. However, these techniques have the following remaining problems. Specifically, charging at a high voltage is required to fully decompose the alkali metal carbonate, which increases resistance. On the other hand, charging at a low voltage does not fully decompose the alkali metal carbonate. Other issues include the effective utilization rate of the positive electrode active material, capacity density, gas volume during storage at 40°C, positive electrode active material loss, capacity retention rate after cycle testing, and micro-short circuiting.

[0006] On the other hand, in recent years, the demand for LiBs has been rapidly expanding for applications such as electric vehicles, and while there are supply risks for resources used in LiBs (e.g., cobalt), the use of lithium transition metal compounds such as lithium iron phosphate, which have low resource risks, has been expanding. Lithium transition metal compounds have a stable crystal structure and are expected to have a long life among LiB positive electrode materials, but they have poor energy density. Furthermore, lithium transition metal compounds are inexpensive, and the recycling process of decomposing used LiBs and regenerating them into materials (positive electrode materials or various elements) is complicated, making it difficult to achieve economic profitability through recycling.

[0007] Generally, LiBs lose capacity and have a shorter lifespan due to charge / discharge cycles and use in high-temperature environments. Therefore, research and development efforts to improve the durability of LiBs by improving battery materials and battery design have been actively conducted, and various technologies have been disclosed (Patent Documents 3 to 6).

[0008] Patent Literature 3 describes an LiB that contains an additive in the electrolyte or positive electrode that has an oxidation potential that exceeds the nominal voltage of the LiB and is less than the decomposition potential of the electrolyte and that can be oxidized at the positive electrode. After degradation, the LiB can recover its battery capacity by charging at a potential equal to or greater than the oxidation potential of the additive.

[0009] Patent Document 4 describes a technique for improving the durability of LiB by pre-doping the LiB with a positive electrode containing an alkali metal carbonate.

[0010] Patent Document 5 describes a technique for improving the charge / discharge cycle durability of a hybrid capacitor by incorporating activated carbon and lithium iron phosphate into the positive electrode.

[0011] Patent Document 6 describes a technology in which degraded LiB is overdischarged to reactivate inactive lithium incorporated in the negative electrode SEI (Solid Electrolyte Interphase) or the non-facing portion of the negative electrode, thereby recovering the capacity of the LiB.

[0012] In the present disclosure, the mesopore volume is calculated by the BJH method, and the micropore volume is calculated by the MP method. The BJH method is proposed in Non-Patent Document 1. The MP method refers to a method for determining the micropore volume, micropore area, and micropore distribution using the "t-plot method" (Non-Patent Document 2), and such a method is shown in Non-Patent Document 3.

[0013] International Publication No. WO 2017 / 126682 International Publication No. WO 2020 / 017515 JP 2012-174437 A International Publication No. WO 2017 / 126682 International Publication No. WO 2019 / 098197 International Publication No. WO 2022 / 196114

[0014] EP Barrett, LGJoyner, and P.Halenda, "The Determination of Pore Volume and Area Distributions in Porous Substances", J.Am.Chem.Soc., (1951), 73, pp.373-380B.C.Lippens, and JHde Boer, "Studies on pore Systems in Catalysis V. The t Method", J.Catalysis, (1965), 4, pp.319-323R.S.Mikhail, S.Brunauer, and EEBodor, "Investigations of a Complete Pore Structure Analysis", J.Colloid Interface Sci., (1968), 26, pp.45-53

[0015] The object of the invention of the first embodiment of the present disclosure is to enable decomposition of the alkali metal carbonate at a relatively low decomposition voltage when using the alkali metal carbonate as a pre-dope source for a non-aqueous alkali metal storage element, thereby increasing the volumetric efficiency of the pre-dope. Also, in one aspect of the present disclosure, the object is to improve the effective utilization rate of the positive electrode active material, the capacity density, and the capacity retention rate after a cycle test, and to suppress the resistance, the amount of gas when stored at 40°C, the loss of the positive electrode active material, and the micro-short circuit after a cycle test.

[0016] An object of the invention of the second embodiment of the present disclosure is to provide a technology that can control the decomposition of alkali metal carbonate, suppress the decomposition of alkali metal carbonate during the manufacturing and use of an energy storage element, and decompose the alkali metal carbonate in the energy storage element after deterioration through a simple electrochemical operation, thereby restoring the capacity of the energy storage element.

[0017] Examples of embodiments of the present disclosure are listed below. [1] A non-aqueous alkali metal storage element precursor having a positive electrode precursor, a negative electrode precursor, a separator, an outer casing, and a non-aqueous electrolyte solution containing alkali metal ions, wherein the negative electrode precursor contains a material that occludes and releases alkali metal ions as a negative electrode active material, the positive electrode precursor has a positive electrode active material layer containing the positive electrode active material that occludes and releases alkali metal ions, an alkali metal carbonate is contained in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or in both, the non-aqueous electrolyte solution further contains a carbonate decomposition accelerator, and the oxidation onset potential of the carbonate decomposition accelerator is 3.8 V (vs. Li / Li ＋ ) or more 4.7V (vs Li / Li ＋ [2] A non-aqueous alkali metal storage element precursor, wherein the initial charge capacity per area of ​​the positive electrode active material is A １ (Ah / cm ２ ), the theoretical capacity per area of ​​the alkali metal carbonate is B １ (Ah / cm ２ ), the initial charge capacity per area of ​​the negative electrode active material is C １ (Ah / cm ２ ) and then (A １ +0.3 x B １ ) / C １≦0.98. [3] The nonaqueous alkali metal storage element precursor according to item 1 or 2, wherein the carbonate decomposition accelerator contains at least one selected from the group consisting of methoxybenzene derivatives, phenyl-containing organic compounds, 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) derivatives, pyridine-N-oxide derivatives, and cyclohexylbenzene derivatives. [4] The nonaqueous alkali metal storage element precursor according to item 1 or 2, wherein the carbonate decomposition accelerator contains at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds. [5] The nonaqueous alkali metal storage element precursor according to item 1 or 2, wherein the carbonate decomposition accelerator contains at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds excluding biphenyl. [6] The nonaqueous alkali metal electricity storage element precursor according to item 1 or 2, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, biphenyl, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, 4-picoline-N-oxide, and 4-tert-butylpyridine-N-oxide.[7] The nonaqueous alkali metal capacitor element precursor according to item 1 or 2, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, and 4-picoline-N-oxide. [8] The irreversible capacity per area of ​​the positive electrode precursor is D. １ (mAh / cm ２ ), the irreversible capacity per area of ​​the negative electrode precursor is E １ (mAh / cm ２ ) , 1.05<E １ / D １[9] The nonaqueous alkali metal storage element precursor according to any one of items 1 to 7, wherein the positive electrode active material layer of the positive electrode precursor contains the alkali metal carbonate in an amount of 0.2 to 15 mass % based on the total mass of the positive electrode active material layer.

[10] The nonaqueous alkali metal storage element precursor according to any one of items 1 to 9, wherein the intermediate layer contains the alkali metal carbonate in an amount of 20 to 95 mass % based on the total mass of the intermediate layer.

[11] The nonaqueous alkali metal storage element precursor according to any one of items 1 to 10, wherein the nonaqueous electrolytic solution contains the carbonate decomposition accelerator in an amount of 0.0001 mol / L to 1.5 mol / L based on the total mass of the nonaqueous electrolytic solution.

[12] The nonaqueous alkali metal storage element precursor according to any one of items 1 to 11, wherein the negative electrode active material comprises at least one selected from the group consisting of an alloy-based negative electrode material that forms an alloy with the alkali metal of the alkali metal ion, and an amorphous carbon material.

[13] The nonaqueous alkali metal storage element precursor according to any one of items 1 to 12, wherein the negative electrode active material comprises an alloy-based negative electrode material that forms an alloy with the alkali metal of the alkali metal ion, and the alloy-based negative electrode material is at least one selected from the group consisting of silicon, a silicon compound, tin, a tin compound, and a composite material of any one of these with carbon or a carbonaceous material.

[14] A non-aqueous alkali metal storage element comprising a positive electrode, a negative electrode, a separator, an exterior body, and a non-aqueous electrolyte solution containing alkali metal ions, wherein the negative electrode contains a material that occludes and releases the alkali metal ions as a negative electrode active material, the positive electrode has a positive electrode active material layer containing a positive electrode active material that occludes and releases the alkali metal ions, the non-aqueous electrolyte solution further contains a carbonate decomposition accelerator, and the oxidation onset potential of the carbonate decomposition accelerator is 3.8 V (vs Li / Li ＋ ) or more 4.7V (vs Li / Li ＋) or less, and the effective utilization rate of the positive electrode active material is 85 to 99.5%.

[15] The nonaqueous alkali metal storage element according to item 14, wherein the amount of alkali metal measured by solid-state NMR is 0.06 mmol / g or less per negative electrode active material layer.

[16] The nonaqueous alkali metal storage element according to item 14 or 15, wherein the carbonate decomposition accelerator contains at least one selected from the group consisting of methoxybenzene derivatives, phenyl group-containing organic compounds, TEMPO derivatives, pyridine-N-oxide derivatives, and cyclohexylbenzene derivatives.

[17] The nonaqueous alkali metal storage element according to item 14 or 15, wherein the carbonate decomposition accelerator contains at least one selected from the group consisting of methoxybenzene derivatives and phenyl group-containing organic compounds.

[18] The nonaqueous alkali metal storage element according to item 14 or 15, wherein the carbonate decomposition accelerator contains at least one selected from the group consisting of methoxybenzene derivatives and phenyl group-containing organic compounds excluding biphenyl.

[19] The nonaqueous alkali metal storage element according to item 14 or 15, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, biphenyl, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, 4-picoline-N-oxide, and 4-tert-butylpyridine-N-oxide.

[20] The nonaqueous alkali metal storage element according to item 14 or 15, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, and 4-picoline-N-oxide.

[21] The excess capacity per area of ​​the positive electrode is F. １ (mAh / cm ２ ), the irreversible capacity per area of ​​the negative electrode is G １ (mAh / cm ２ ) and 0.01<F １ / G １<0.9.

[22] The nonaqueous alkali metal storage element according to any one of items 14 to 21, wherein the positive electrode active material layer further contains an alkali metal carbonate in an amount of 0.02 to 1.5 mass% based on the total mass of the positive electrode active material layer.

[23] The nonaqueous alkali metal storage element according to any one of items 14 to 22, further including an optional intermediate layer between the positive electrode active material layer and the separator, the intermediate layer containing an alkali metal carbonate in an amount of 0.2 to 9.5 mass% based on the total mass of the intermediate layer.

[24] The nonaqueous alkali metal storage element according to any one of items 14 to 23, wherein the carbonate decomposition accelerator is contained in the nonaqueous electrolyte solution in an amount of 0.0001 mol / L to 1.5 mol / L.

[25] The nonaqueous alkali metal storage element according to any one of items 14 to 24, wherein the negative electrode active material comprises at least one selected from the group consisting of an alloy-based negative electrode material that forms an alloy with the alkali metal of the alkali metal ions, and an amorphous carbon material.

[26] The nonaqueous alkali metal storage element according to any one of items 14 to 25, wherein the negative electrode active material comprises an alloy-based negative electrode material that forms an alloy with the alkali metal of the alkali metal ions, and the alloy-based negative electrode material is at least one selected from the group consisting of silicon, a silicon compound, tin, a tin compound, and a composite material of any one of these with carbon or a carbonaceous material.

[27] A method for producing a non-aqueous alkali metal storage element, the method comprising: applying a voltage between a positive electrode precursor and a negative electrode precursor to a non-aqueous alkali metal storage element precursor having a positive electrode precursor, a negative electrode precursor, a separator, an outer casing, and a non-aqueous electrolyte solution containing alkali metal ions, thereby doping a negative electrode active material of the negative electrode precursor with alkali metal ions; the negative electrode precursor includes a material that occludes and releases alkali metal ions as the negative electrode active material; the positive electrode precursor has a positive electrode active material layer including a positive electrode active material that occludes and releases alkali metal ions; an alkali metal carbonate is contained in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or in both; the non-aqueous electrolyte solution further includes a carbonate decomposition accelerator, and the carbonate decomposition accelerator has an oxidation onset potential of 3.8 V (vs Li / Li). ＋ ) or more 4.7V (vs Li / Li ＋

[28] The method, wherein the potential of the positive electrode precursor is 4.15 to 4.75 V (vs Li / Li ＋ Item 27, the method comprising applying a voltage between the positive electrode precursor and the negative electrode precursor so that the negative electrode active material is doped with alkali metal ions.

[29] The method of item 27, the method comprising applying a voltage of 4.1 V or more and 4.6 V or less between the positive electrode precursor and the negative electrode precursor to dope the lithium ions into the negative electrode active material.

[30] The method of item 27, the method comprising applying a voltage of 4.2 V or more and less than 4.5 V between the positive electrode precursor and the negative electrode precursor to dope the lithium ions into the negative electrode active material.

[31] The method of item 27, the method comprising applying a voltage of 3.8 V or more and 4.3 V or less between the positive electrode precursor and the negative electrode precursor to dope the sodium ions into the negative electrode active material.

[32] The method of item 27, the method comprising applying a voltage of 3.8 V or more and 4.3 V or less between the positive electrode precursor and the negative electrode precursor to dope the sodium ions into the negative electrode active material. １ (Ah / cm ２ ), the theoretical capacity per area of ​​the alkali metal carbonate is B １ (Ah / cm２ ), the initial charge capacity per area of ​​the negative electrode active material is C １ (Ah / cm ２ ) and then (A １ +0.3 x B １ ) / C １≦0.98.

[33] The method according to any one of items 27 to 32, wherein the carbonate decomposition accelerator contains at least one selected from the group consisting of methoxybenzene derivatives, phenyl-containing organic compounds, 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) derivatives, pyridine-N-oxide derivatives, and cyclohexylbenzene derivatives.

[34] The method according to any one of items 27 to 32, wherein the carbonate decomposition accelerator contains at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds.

[35] The method according to any one of items 27 to 32, wherein the carbonate decomposition accelerator contains at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds excluding biphenyl.

[36] The method according to any one of items 27 to 32, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, biphenyl, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, 4-picoline-N-oxide, and 4-tert-butylpyridine-N-oxide.

[37] The method according to any one of items 27 to 32, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, and 4-picoline-N-oxide.

[38] D is the irreversible capacity per area of ​​the positive electrode precursor. １ (Ah / cm ２ ), the irreversible capacity per area of ​​the negative electrode precursor is E １ (Ah / cm ２ ) 1.05 × D １ <E １

[39] A method for producing a capacity-restored nonaqueous alkali metal storage element, wherein the nonaqueous alkali metal storage element before capacity recovery includes a positive electrode including a positive electrode active material layer disposed on a positive electrode current collector, a negative electrode including a negative electrode active material layer disposed on a negative electrode current collector, a separator, and a nonaqueous electrolyte solution containing alkali metal ions, and the positive electrode active material layer includes a positive electrode active material that occludes and releases alkali metals, the nonaqueous alkali metal storage element before capacity recovery contains an alkali metal carbonate in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or in both, and the nonaqueous electrolyte solution further contains a carbonate decomposition accelerator, and the oxidation onset potential of the carbonate decomposition accelerator is equal to or higher than the stable operating potential of the positive electrode active material and equal to or lower than 4.7 V (vs. Li / Li+), The method includes recovering the capacity of the nonaqueous alkali metal storage element by increasing the potential of the positive electrode of the nonaqueous alkali metal storage element before the capacity recovery to a stable operating potential of the positive electrode active material or higher. １ (Ah / cm ２ ), the remaining capacity per area of ​​the negative electrode active material is J １ (Ah / cm ２ ), the total capacity per area of ​​the negative electrode active material is J ２ (Ah / cm ２ ) , 0.1≦J １ / J ２ ≦0.5, and 0.03≦0.3×B １ / J １Item 39. The method according to Item 39, wherein the relationship satisfies ≦0.98, and the method further comprises suppressing decomposition of the alkali metal carbonate in the nonaqueous alkali metal electricity storage element until the potential of the positive electrode of the nonaqueous alkali metal electricity storage element before the capacity recovery is increased to or above the stable working potential of the positive electrode active material.

[41] The method according to Item 39 or 40, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives, phenyl-containing organic compounds, TEMPO derivatives, pyridine-N-oxide derivatives, and cyclohexylbenzene derivatives.

[42] The method according to Item 39 or 40, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds.

[43] The method according to Item 39 or 40, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds excluding biphenyl.

[44] The method according to item 39 or 40, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, biphenyl, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, 4-picoline-N-oxide, and 4-tert-butylpyridine-N-oxide.

[45] The method according to item 39 or 40, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, and 4-picoline-N-oxide.

[46] The method further comprises determining an initial capacity P of the nonaqueous alkali metal electricity storage element. １ The method according to any one of items 39 to 45, comprising recovering 2% or more of the capacity of the nonaqueous alkali metal storage element before capacity recovery, the capacity of which is 95% or less based on the capacity (mAh).

[47] The method according to any one of items 39 to 46, comprising recovering the capacity of the nonaqueous alkali metal storage element by increasing the voltage of the nonaqueous alkali metal storage element to an upper limit of a stable operating voltage of the positive electrode active material or higher.

[48] The positive electrode active material layer further contains the alkali metal carbonate, and the mass ratio of the alkali metal carbonate is X based on the total mass of the positive electrode active material layer. ３ (mass%), X ３

[49] The nonaqueous alkali metal storage element before capacity recovery further comprises the intermediate layer containing the alkali metal carbonate, and the mass ratio of the alkali metal carbonate based on the total mass of the intermediate layer is X ４ (mass%), X ４

[50] The method according to any one of items 39 to 48, wherein the mass ratio of the positive electrode active material in the nonaqueous alkali metal storage element before capacity recovery is X based on the total mass of the positive electrode active material layer. ２ (mass%), X ２

[51] The method according to any one of items 39 to 49, wherein the discharge capacity of a positive electrode half cell using the positive electrode removed from the nonaqueous alkali metal storage element before capacity recovery, or using the positive electrode and the intermediate layer if an intermediate layer is present, is determined by calculating K １ (mAh / cm ２ ) and the discharge capacity of the negative electrode half-cell of the negative electrode taken out from the nonaqueous alkali metal storage element before the capacity recovery was K ３ (mAh / cm ２ ) and 0.80≦K １ / K ３

[52] The method according to any one of items 39 to 51, wherein the voltage applied to the nonaqueous alkali metal energy storage element during capacity recovery is equal to or higher than the upper limit of the stable operating voltage of the positive electrode active material and is 4.6 V or lower.

[53] The method according to any one of items 39 to 52, wherein the nonaqueous alkali metal energy storage element before capacity recovery is in the form of a battery pack formed by combining a plurality of unit cells of the nonaqueous alkali metal energy storage element before capacity recovery, and the capacity of the battery pack is restored without disassembling the battery pack into the unit cells.

[54] The method according to any one of items 39 to 53, wherein the method for restoring the capacity of the nonaqueous alkali metal energy storage element comprises restoring the capacity multiple times.

[55] The method according to any one of items 39 to 54, comprising restoring the capacities of a plurality of nonaqueous alkali metal electricity storage elements, wherein at least two of the plurality of nonaqueous alkali metal electricity storage elements have different capacities from one another, and the capacities of the plurality of nonaqueous alkali metal electricity storage elements are restored and the difference in capacity is reduced by controlling at least one selected from the group consisting of the potential, temperature, and charge current capacity of the positive electrode.

[56] The method according to any one of items 39 to 55, wherein the carbonate decomposition accelerator is contained in an electrolyte solution at 0.0001 mol / L to 1.5 mol / L.

[57] A non-aqueous alkali metal storage element comprising: a positive electrode including a positive electrode active material layer disposed on a positive electrode current collector; a negative electrode including a negative electrode active material layer disposed on a negative electrode current collector; a separator; and a non-aqueous electrolyte solution containing alkali metal ions, wherein the positive electrode active material layer comprises a positive electrode active material that absorbs and releases alkali metals; the non-aqueous alkali metal storage element contains an alkali metal carbonate in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or in both; and the non-aqueous electrolyte solution further contains a carbonate decomposition accelerator, and the oxidation onset potential of the carbonate decomposition accelerator is 4.7 V (vs. Li / Li) or higher than the stable operating potential of the positive electrode active material. ＋

[58] A non-aqueous alkali metal storage element, wherein the theoretical capacity per area of ​​the alkali metal carbonate is B １ (Ah / cm ２ ), the remaining capacity per area of ​​the negative electrode active material is J １(Ah / cm ２ ), the total capacity per area of ​​the negative electrode active material is F ２ (Ah / cm ２ ) , 0.1≦J １ / J ２ ≦0.5, and 0.03≦0.3×B １ / J １≦0.98.

[59] The nonaqueous alkali metal storage element according to item 57 or 58, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives, phenyl group-containing organic compounds, TEMPO derivatives, pyridine-N-oxide derivatives, and cyclohexylbenzene derivatives.

[60] The nonaqueous alkali metal storage element according to item 57 or 58, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives and phenyl group-containing organic compounds.

[61] The nonaqueous alkali metal storage element according to item 57 or 58, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives and phenyl group-containing organic compounds excluding biphenyl.

[62] The nonaqueous alkali metal electricity storage element according to item 57 or 58, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, biphenyl, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, 4-picoline-N-oxide, and 4-tert-butylpyridine-N-oxide.

[63] The nonaqueous alkali metal storage element according to item 57 or 58, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, and 4-picoline-N-oxide.

[64] The positive electrode active material layer further contains the alkali metal carbonate, and the mass ratio of the alkali metal carbonate is X based on the total mass of the positive electrode active material layer. ３ (mass%), X ３

[65] The nonaqueous alkali metal storage element according to any one of items 57 to 63, wherein the mass ratio of the alkali metal carbonate to the total mass of the intermediate layer is X ４ (mass%), X ４

[66] The nonaqueous alkali metal storage element according to any one of items 57 to 64, wherein the initial capacity P １ The nonaqueous alkali metal storage element according to any one of items 57 to 66, which is used to recover 2% or more of the capacity when the capacity has deteriorated to 95% or less based on the standard capacity (mAh) by increasing the potential of the positive electrode to an oxidative decomposition potential of the alkali metal carbonate or higher.

[68] The nonaqueous alkali metal storage element according to any one of items 57 to 67, which is used to recover the capacity when the capacity has deteriorated by increasing the voltage of the nonaqueous alkali metal storage element to an upper limit of a stable operating voltage of the positive electrode active material or higher.

[69] The nonaqueous alkali metal storage element according to any one of items 57 to 68, which contains the carbonate decomposition accelerator in an electrolyte solution at 0.0001 mol / L to 1.5 mol / L.

[70] A battery pack comprising a plurality of the nonaqueous alkali metal storage elements according to any one of items 57 to 69.

[0018] According to the first embodiment, in a nonaqueous alkali metal storage element precursor or a nonaqueous alkali metal storage element, alkali metal carbonate decomposition at a relatively low decomposition voltage is possible, thereby increasing the volumetric efficiency of the pre-dope. Furthermore, the effective utilization rate of the positive electrode active material, capacity density, and capacity retention rate after cycle testing are improved, and resistance, gas volume during storage at 40°C, positive electrode active material loss, and micro-short circuiting after cycle testing are suppressed. According to a second embodiment of the present disclosure, a technology is provided that can restore the capacity of the storage element by a simple electrochemical operation.

[0019] 1 is a schematic diagram of a positive electrode, a negative electrode, a separator, a lithium (Li) reference electrode, and a separator-attached Li reference electrode according to one embodiment of the present disclosure. 2 is a schematic perspective view for explaining the positional relationship between an electrode stack and a Li reference electrode according to one embodiment of the present disclosure. 3 is a graph showing the relationship between the capacity per weight of the positive electrode active material (mAh / g of positive electrode active material) and the positive electrode potential (V vs. Li / Li) in the presence of a promoter (Curve 1) and in the absence of a promoter (Curve 2). ＋ 3 (Measurement of the oxidation onset potential of the accelerator) is a graph showing the difference curve (Curve 1-2) at the same positive electrode potential and the oxidation onset potential of the accelerator, both plotted against the positive electrode potential (V vs Li / Li) in the case of the accelerator (Curve 1) and the case of the accelerator (Curve 2). ＋ ) is a graph plotting the difference curve (curve 1-2) at the same positive electrode potential and the oxidation onset potential of the accelerator in method B (measurement of the oxidation onset potential of the accelerator) in FIG. 5 . FIG. 7 is a schematic diagram of a battery pack in which four unit cells are connected in series.

[0020] Hereinafter, an embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described in detail, but the present disclosure is not limited to the present embodiment. The upper and lower limits of each numerical range in the present embodiment can be arbitrarily combined to form any numerical range.

[0021] In this embodiment, the alkali metal storage element before pre-doping described below is defined as a "nonaqueous alkali metal storage element precursor," the positive electrode before pre-doping described below is defined as a "positive electrode precursor," the negative electrode before pre-doping described below is defined as a "negative electrode precursor," the alkali metal storage element after pre-doping is defined as a "nonaqueous alkali metal storage element," the positive electrode after pre-doping is defined as a "positive electrode," and the negative electrode after pre-doping is defined as a "negative electrode."

[0022] In this embodiment, the non-aqueous alkali metal storage element precursor includes a positive electrode precursor including a positive electrode active material layer disposed on a positive electrode current collector, a negative electrode precursor including a negative electrode active material layer disposed on a negative electrode current collector, a separator, an outer casing, and a non-aqueous electrolyte solution containing alkali metal ions, wherein the positive electrode active material layer contains a positive electrode active material that occludes and releases alkali metal ions. The non-aqueous alkali metal storage element precursor includes an alkali metal carbonate in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or in both, and the non-aqueous electrolyte solution further includes a carbonate decomposition accelerator (also simply referred to as "accelerator"), and the accelerator has an oxidation onset potential of 3.8 V (vs. Li / Li ＋ ) or more 4.7V (vs Li / Li ＋ ) below.

[0023] In another embodiment, the non-aqueous alkali metal storage element includes a positive electrode including a positive electrode active material layer disposed on a positive electrode current collector, a negative electrode including a negative electrode active material layer disposed on a negative electrode current collector, a separator, an outer casing, and a non-aqueous electrolyte solution containing alkali metal ions, wherein the positive electrode active material layer contains a positive electrode active material that occludes and releases alkali metal ions. The non-aqueous alkali metal storage element includes an alkali metal carbonate in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or in both, and the non-aqueous electrolyte solution further includes a promoter, and the oxidation onset potential of the promoter is 3.8 V (vs. Li / Li ＋ ) or more 4.8V (vs Li / Li ＋ ) or less, and the effective utilization rate of the positive electrode active material is 85 to 99.5%.

[0024] In yet another embodiment, a method for producing a nonaqueous alkali metal storage element includes applying a voltage between the positive electrode precursor and the negative electrode precursor to a nonaqueous alkali metal storage element precursor having a positive electrode precursor, a negative electrode precursor, a separator, an outer casing, and a nonaqueous electrolyte solution containing alkali metal ions, thereby doping the alkali metal ions into the negative electrode active material of the negative electrode precursor. The negative electrode precursor contains a material that occludes and releases alkali metal ions as the negative electrode active material, and the positive electrode precursor has a positive electrode active material layer containing a positive electrode active material that occludes and releases alkali metal ions. The nonaqueous alkali metal storage element precursor also contains an alkali metal carbonate in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or in both, and the nonaqueous electrolyte solution further contains a promoter, and the oxidation onset potential of the promoter is 3.8 V (vs. Li / Li ＋ ) or more 4.7V (vs Li / Li ＋ ) below.

[0025] Non-aqueous alkali metal storage elements generally experience capacity degradation due to the deactivation of some alkali metal ions through repeated charge-discharge cycles, resulting in a misalignment between the positive and negative electrode utilization regions. The inventors conceived the idea of ​​pre-loading an alkali metal carbonate into a non-aqueous alkali metal storage element, and then electrochemically decomposing the alkali metal carbonate to generate alkali metal ions after capacity degradation, thereby restoring the capacity by compensating for the total amount of deactivated alkali metal ions. Furthermore, by further incorporating a specific promoter into the electrolyte, the alkali metal carbonate can be efficiently decomposed at a potential higher than the voltage range typically used for non-aqueous alkali metal storage elements, thereby replenishing alkali metal ions in the negative electrode of the storage element after degradation. Therefore, the capacity of the storage element can be restored without decomposing the storage element, simply by raising the positive electrode potential above the stable operating potential of the positive electrode active material. Furthermore, since the promoter in the electrolyte promotes the decomposition of the alkali metal carbonate, there is no need to add a catalyst to the positive electrode to promote the decomposition of the alkali metal carbonate, and a decrease in the initial capacity density of the storage element can be avoided.

[0026] Therefore, even non-aqueous lithium storage elements that use inexpensive lithium transition metal compounds such as lithium iron phosphate, which have previously been impossible to recycle from the perspective of economic viability, can now be recycled while maintaining economic viability.

[0027] A second embodiment of the present disclosure provides a nonaqueous alkali metal storage element before capacity restoration (hereinafter also referred to as a "battery before capacity restoration") suitable for the capacity restoration method of the present disclosure. In the present disclosure, the "nonaqueous alkali metal storage element before capacity restoration" encompasses everything from a nonaqueous alkali metal storage element immediately after an initial charging process to an (unused) nonaqueous alkali metal storage element that has undergone an aging process and a degassing process, as well as a nonaqueous alkali metal storage element whose capacity has deteriorated due to use. The degree of capacity deterioration is not limited, and the nonaqueous alkali metal storage element may be in any state of deterioration.

[0028] The nonaqueous alkali metal storage element of the present disclosure before capacity recovery is a nonaqueous alkali metal storage element including a positive electrode including a positive electrode active material layer disposed on a positive electrode current collector, a negative electrode including a negative electrode active material layer disposed on a negative electrode current collector, a separator, and a nonaqueous electrolyte solution containing alkali metal ions. The positive electrode active material layer includes a positive electrode active material that occludes and releases alkali metal ions. The nonaqueous alkali metal storage element before capacity recovery contains an alkali metal carbonate in the positive electrode active material layer, in an optional intermediate layer between the positive electrode active material layer and the separator, or in both. The nonaqueous electrolyte solution further contains a promoter, and the oxidation onset potential of the promoter is equal to or greater than the stable operating potential of the positive electrode active material and equal to or less than 4.7 V (vs. Li / Li+). When an alkali metal carbonate is further added to a system containing a positive electrode active material that occludes and releases alkali metals and the capacity recovery step described below is performed, the oxidative decomposition reaction of the alkali metal carbonate may not proceed sufficiently, preventing the replenishment of the alkali metal to the negative electrode and making it impossible to recover the capacity. The promoter contained in the electrolyte promotes the oxidative decomposition reaction of the alkali metal carbonate, thereby achieving a capacity recovery effect and eliminating the need to add a catalyst for decomposing the alkali metal carbonate to the positive electrode active material layer, which is preferable from the viewpoint of the initial capacity density of the energy storage element.

[0029] In another embodiment, a method for manufacturing a capacity-restored non-aqueous alkali metal storage element includes restoring the capacity of the non-aqueous alkali metal storage element by increasing the potential of the positive electrode of the non-aqueous alkali metal storage element before capacity restoration as described above to a stable operating potential of the positive electrode active material or higher.

[0030] In the first and second embodiments, the alkali metal may be at least one selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and francium. The alkali metal ion may be at least one selected from the group consisting of lithium ion, sodium ion, potassium ion, rubidium ion, cesium ion, and francium ion. Among these, lithium, sodium, and potassium are preferred, and lithium is particularly preferred, from the viewpoints of energy density, resource amount, and the like.

[0031] <Positive electrode, positive electrode precursor> The positive electrode in the first embodiment is formed by pre-doping a negative electrode precursor with alkali metal ions in a non-aqueous alkali metal energy storage element precursor containing a positive electrode precursor during the production of an energy storage element described below. The positive electrode precursor includes a positive electrode active material layer containing a positive electrode active material that occludes and releases alkali metal ions. As a pre-doping method in this embodiment, it is preferable to assemble an energy storage element precursor using a positive electrode precursor, a negative electrode precursor, a separator, and a non-aqueous electrolyte solution, and then apply a voltage between the positive electrode precursor and the negative electrode precursor.

[0032] In a first embodiment, the alkali metal carbonate is contained in the positive electrode active material layer of the positive electrode precursor, in the intermediate layer between the positive electrode active material layer and the separator of the nonaqueous alkali metal electric storage element precursor, or in both of these. The alkali metal carbonate decomposes in the nonaqueous alkali metal electric storage element precursor to release alkali metal ions, which can be reduced in the negative electrode to perform pre-doping.

[0033] When the pre-doped positive electrode active material layer contains an alkali metal carbonate, the content of the alkali metal carbonate is preferably 0.02% by mass or more and 1.5% by mass or less. If the content of the alkali metal carbonate in the pre-doped positive electrode active material layer is 0.02% by mass or more and 1.5% by mass or less, it is preferable from the viewpoint of suppressing gas swelling during high-temperature storage.

[0034] When an alkali metal carbonate is contained in the intermediate layer between the positive electrode active material layer and the separator after pre-doping, the content of the alkali metal carbonate is preferably 0.2% by mass or more and 9.5% by mass or less, and more preferably 2% by mass or more and 9.5% by mass or less. If the content of the alkali metal carbonate in the intermediate layer after pre-doping is 0.2% by mass or more and 9.5% by mass or less, it is preferable from the viewpoint of suppressing gas swelling during high-temperature storage.

[0035] A second embodiment of the present disclosure provides a positive electrode for use in a pre-capacity-restoring battery suitable for the capacity restoration method of the present disclosure. The positive electrode includes a positive electrode active material layer disposed on a positive electrode current collector, the positive electrode active material layer including a positive electrode active material that occludes and releases alkali metal ions, and an alkali metal carbonate is contained in the positive electrode active material layer, in an optional intermediate layer between the positive electrode active material layer and a separator, or in both.

[0036] As long as the pre-capacity-recovery battery obtained in the initial storage element manufacturing process exhibits the capacity recovery effect, a portion of the alkali metal compound may be oxidatively decomposed and alkali metal ions may be pre-doped into the negative electrode during the initial storage element manufacturing process.

[0037] The alkali metal carbonate may be contained in any form in the positive electrode, for example, it may be present at the interface between the positive electrode active material layer and the positive electrode current collector, or it may be present on the surface of the positive electrode active material layer. From the viewpoint of the reactivity of the alkali metal compound in the capacity recovery step, the alkali metal carbonate is preferably contained in the positive electrode active material layer in a particulate form and dispersed therein. The alkali metal carbonate may be present in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or in both.

[0038] A coating liquid used for producing a positive electrode is referred to as a "positive electrode coating liquid." The positive electrode coating liquid may be in the form of a known coating liquid, as well as a known suspension, dispersion, emulsion, composition, or mixture. The positive electrode coating liquid may also be simply referred to as a slurry, coating liquid, or the like.

[0039] The positive electrode precursor in the first embodiment has a positive electrode active material layer containing a positive electrode active material. The positive electrode precursor may include an alkali metal carbonate in the positive electrode active material layer, in an intermediate layer between the positive electrode active material layer and the separator, or in both.

[0040] The positive electrode precursor may have a positive electrode current collector and a positive electrode active material layer present on one or both sides thereof so as to constitute a positive electrode of a non-aqueous alkali metal energy storage element. The positive electrode precursor constitutes a positive electrode after assembling the energy storage element and pre-doping. As described below, in this embodiment, it is preferable to pre-dope alkali metal ions from an alkali metal carbonate into a negative electrode precursor during the manufacturing process of the energy storage element. A preferred pre-doping method is to assemble an energy storage element precursor using a positive electrode precursor, a negative electrode precursor, a separator, an outer casing, and a non-aqueous electrolyte solution, and then apply a voltage between the positive electrode precursor and the negative electrode precursor and charge the precursor to a voltage at which an oxidation reaction of the alkali metal carbonate occurs.

[0041] (Positive Electrode Active Material Layer) The positive electrode active material layer of the first embodiment or the second embodiment contains a positive electrode active material described later, and may further contain optional components such as a conductive filler, a binder, a dispersion stabilizer, a dispersant, and a pH adjuster, as necessary.

[0042] The positive electrode active material layer may contain an alkali metal carbonate, which will be described later. The positive electrode active material layer of the second embodiment can obtain a capacity recovery effect by performing an electrochemical operation for capacity recovery after the capacity has deteriorated.

[0043] (Positive electrode active material) The positive electrode active material in the first or second embodiment absorbs and releases alkali metal ions. Known materials used in known non-aqueous alkali metal storage elements can be used as the positive electrode active material that absorbs and releases alkali metal ions. For example, a material containing an alkali metal and at least one transition metal is preferred. Examples of such compounds include alkali metal-containing transition metal oxides and alkali metal-containing transition metal phosphate compounds. Two types of active materials may also be used in combination.

[0044] The positive electrode active material is not particularly limited. Positive electrode active materials used in known alkali metal storage elements can be used. Examples of positive electrode active materials containing an alkali metal and at least one transition metal include oxides containing at least one element selected from the group consisting of cobalt, nickel, manganese, iron, vanadium, and chromium.

[0045] Specifically, when the alkali metal is lithium, for example, Li ｘ CoO ２ , Li ｘ NiO ２ , Li ｘ Ni ｙ M （１－ｙ） O ２ (wherein M is at least one element selected from the group consisting of Co, Mn, Al, Fe, Mg, and Ti, and y satisfies 0.2<y<0.97), Li ｘ Ni １／３ Co １／３ Mn １／３ O ２ , Li ｘ MnO ２ , α-Li ｘ FeO ２ , Li ｘ VO ２ , Li ｘ CrO ２ , Li ｘ FePO ４ , LiMn ｘ Fe １－ｘ P.O. ４ , Li ｘ Mn ２ O ４ , Li ｘ Mｙ Mn （２－ｙ） O ４ (wherein M is at least one element selected from the group consisting of Co, Mn, Al, Fe, Mg, and Ti, and y satisfies 0.2<y<0.97), Li ｘ Ni ａ Co ｂ Al （１－ａ－ｂ） O ２ (wherein a and b satisfy 0.2<a<0.97 and 0.2<b<0.97), Li ｘ Ni ｃ Co ｄ Mn （１－ｃ－ｄ） O ２ (wherein c and d satisfy 0.2<c<0.97 and 0.2<d<0.97, respectively) (wherein in all formulas, x satisfies 0≦x≦1), etc. can be mentioned.

[0046] Specific representative examples include LiCoO ２ (LCO), LiFePO ４ (LFP), LiMn ０．６ Fe ０．４ P.O. ４ (LMFP), LiNi １／３ Co １／３ Mn １／３ O ２ (NCM111), LiNi ０．８ Co ０．１５ Al ０．０５ O ２ (NCA), LiMn ２ O ４ (LMO), etc. can be suitably used.

[0047] Specifically, when the alkali metal is sodium, other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may be used. These materials may include sodium transition metal oxides, polyanion compounds, and Prussian blue compounds. In the sodium transition metal oxides, the transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The sodium transition metal oxide may be, for example, Na ｘ MO ２where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0<x≦1. The polyanionic compound contains sodium ions, transition metal ions, and tetrahedral (YO ４ ) ｎ－ The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y may be at least one of P, S, and Si, and n may be any of (YO ４ ) ｎ－ The polyanionic compound also contains sodium ions, transition metal ions, tetrahedral ions (YO ４ ) ｎ－ The anionic unit may be a compound such as a halogen anion. The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y may be at least one of P, S, and Si, and n may be (YO ４ ) ｎ－ The halogen may be at least one of F, Cl, and Br. The polyanionic compound also contains sodium ions, tetrahedral (YO ４ ) ｎ－ Anionic unit, polyhedral unit (ZO ｙ ) ｍ＋ and a compound having a selectable halogen anion. Y may be at least one of P, S, and Si, and n may be (YO ４ ) ｎ－ Z represents a transition metal and may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m represents a valence of (ZO ｙ ) ｍ＋ The halogen may be at least one of F, Cl, and Br. The polyanion compound is, for example, NaFePO ４ , Na ３ V ２ (P.O. ４ ) ３ , NaM'PO ４F (wherein M' is one or more of V, Fe, Mn, and Ni) and Na ３ (VO ｙ ) ２ (P.O. ４ ) ２ F ３－２ｙ (wherein 0≦y≦1). The Prussian blue compound is at least one of sodium ions, transition metal ions, and cyanide ions (CN － The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue compound may be, for example, a compound having Na ａ Me ｂ Me' ｃ (CN) ６ wherein Me and Me′ are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, and 0<a≦2, 0<b<1, and 0<c<1.

[0048] Furthermore, in the first embodiment, the alkali metal carbonate can be pre-doped into the negative electrode, with the alkali metal compound and / or alkali metal carbonate acting as a dopant source for the alkali metal. Therefore, even if the transition metal compound does not already contain an alkali metal (i.e., even if x = 0 in the above formula), the element can be electrochemically charged and discharged as a non-aqueous alkali metal type storage element.

[0049] In the second embodiment, it is preferable that the battery exhibits charge / discharge capacity at a voltage equal to or lower than the decomposition voltage of the alkali metal carbonate described later, and has structural stability at a voltage equal to or higher than the decomposition voltage. The alkali metal transition metal compound is preferably lithium iron phosphate Li ｘ FePO ４ (LFP), lithium iron manganese phosphate LiMn ｘ Fe １－ｘ P.O. ４ (LMFP).

[0050] In the first and second embodiments, the average particle diameter of the positive electrode active material is preferably 0.1 to 20 μm. If the average particle diameter of the positive electrode active material is 0.1 μm or more, the density of the positive electrode active material layer is high, and therefore the capacity per electrode volume tends to be high. If the average particle diameter of the positive electrode active material is small, durability may be reduced, but if the average particle diameter is 0.1 μm or more, durability is less likely to be reduced. If the average particle diameter of the positive electrode active material is 20 μm or less, it tends to be more suitable for high-speed charging and discharging. The average particle diameter of the positive electrode active material is more preferably 1 to 15 μm, and even more preferably 1 to 10 μm.

[0051] In the first embodiment, the content of the positive electrode active material in the positive electrode active material layer is preferably 35% by mass or more and 99% by mass or less, based on the total mass of the positive electrode active material layer in the positive electrode precursor. The lower limit of the content of the positive electrode active material is more preferably 45% by mass or more, and even more preferably 55% by mass or more. The upper limit of the content of the positive electrode active material is more preferably 98% by mass or less, and even more preferably 96% by mass or less. When the content of the positive electrode active material in the positive electrode active material layer is 35% by mass or more and 99% by mass or less, favorable charge / discharge characteristics are exhibited.

[0052] In the second embodiment, the mass ratio X of the alkali metal transition metal compound in the positive electrode active material layer is ２ (mass %) is preferably 60 mass % or more and 99 mass % or less based on the total mass of the positive electrode active material layer. ２ The lower limit of (mass%) is more preferably 70 mass% or more, and even more preferably 80 mass% or more. ２ The upper limit of (mass %) is more preferably 98 mass % or less, even more preferably 97 mass % or less, still more preferably 96 mass % or less, and particularly preferably 92 mass % or less.

[0053] The main cause of capacity degradation in non-aqueous alkali metal storage elements is the shift in the utilization range of the positive and negative electrodes due to the loss of alkali metal ions that contribute to charge and discharge. Therefore, by oxidatively decomposing alkali metal carbonate and replenishing and inserting alkali metal ions into the negative electrode, the shift in utilization range can be eliminated, resulting in a significant capacity recovery effect.

[0054] Mass ratio X of alkali metal transition metal compound ２ When the mass ratio X of the alkali metal transition metal compound is 60.0 mass % or more and 99.0 mass % or less, both the initial capacity density and the capacity recovery effect after degradation can be achieved. ２ When the mass ratio of the alkali metal transition metal compound is 60.0% by mass or more, the capacity density is excellent. When the mass ratio is 99.0% by mass or less, the alkali metal carbonate can be introduced into the positive electrode active material layer, and the electrical conductivity and electrolyte retention can be sufficiently increased, which facilitates decomposition of the alkali metal carbonate in the capacity recovery step described below, promotes replenishment of the alkali metal to the negative electrode, and facilitates recovery of the battery capacity. One method for controlling the mass ratio of the alkali metal transition metal compound is to adjust the composition of the positive electrode coating solution.

[0055] (Stable operating potential of positive electrode and stable operating voltage of battery according to positive electrode active material) The potential range of a positive electrode in which a positive electrode active material can be stably used is called the "stable operating potential", and the voltage range of a battery (full cell) in which a positive electrode active material can be stably used is called the "stable operating voltage". The "upper limit of stable operating potential" and the "upper limit of stable operating voltage" vary depending on the type of positive electrode active material, but generally, the potential and voltage range in which the positive electrode active material can be stably used are determined by performing a charge / discharge cycle of a non-aqueous alkali metal storage element. The "lower limit of stable operating potential" and the "lower limit of stable operating voltage" are the potential and voltage at which the alkali metal ions are fully loaded in the positive electrode and almost no further discharge capacity is obtained. Although not particularly limited to the following numerical values, the upper limits of the stable operating potential and stable operating voltage are shown for preferred specific examples of positive electrode active materials. LiCoO ２ (LCO): Upper limit of stable operating potential 4.3 V (vs. Li / Li ＋ ), and the upper limit of stable operating voltage is 4.2V (LCOs with higher stable operating potential and stable operating voltage exist using technology such as doping with other elements). ４ (LFP): Upper limit of stable operating potential 3.7 V (vs. Li / Li ＋ ), the upper limit of stable operating voltage is 3.6V LiMn ０．６ Fe ０．４ P.O. ４ : Upper limit of stable operating potential 4.3 V (vs. Li / Li ＋ ), the upper limit of stable operating voltage is 4.2V LiNi１／３ Co １／３ Mn １／３ O ２ (NCM111): Upper limit of stable operating potential 4.3 V (vs. Li / Li ＋ ), the upper limit of stable operating voltage is 4.2V LiNi ０．８ Co ０．１ Mn ０．１ O ２ (NCM811): Upper limit of stable operating potential 4.3 V (vs. Li / Li ＋ ), the upper limit of stable operating voltage is 4.2V LiNi ０．８ Co ０．１５ Al ０．０５ O ２ (NCA): Upper limit of stable operating potential 4.3 V (vs. Li / Li ＋ ), the upper limit of stable operating voltage is 4.2V LiMn ２ O ４ (LMO): Upper limit of stable operating potential 4.3 V (vs. Li / Li ＋ ), the upper limit of stable operating voltage is 4.2V NaFe １／３ Ni １／３ Mn １／３ O ２ : Upper limit of stable operating potential 4.0 V (vs. Na / Na ＋ ), the upper limit of stable operating voltage is 3.9V

[0056] The upper limits of the stable operating potential and stable operating voltage for a positive electrode active material are not particularly limited, but can be determined, for example, by the following method. A battery containing a positive electrode half cell containing an unknown positive electrode active material as the positive electrode active material, an alkali metal as the counter electrode and reference electrode, and the following electrolyte is used. The battery is charged at a constant current (cc) corresponding to 0.1 C until the potential of the positive electrode half cell reaches a predetermined upper limit potential. At this voltage, the battery is charged at a constant voltage (cv) until the current reaches 0.03 C, and then discharged at a constant current (cc) to a lower limit potential. This cycle test is performed for various different upper limit potentials. The upper limit of the stable operating potential is determined as the upper limit of the stable operating potential. The upper limit of the stable operating voltage is determined by subtracting the operating potential of the negative electrode used in the full cell. The electrolyte for the nonaqueous alkali metal storage element can be an electrolyte commonly used in alkali metal ion batteries or alkali metal ion capacitors. The non-aqueous electrolyte preferably contains an alkali metal salt as an electrolyte at a concentration of 0.5 mol / L or more based on the total amount of the non-aqueous electrolyte. As the alkali metal salt of the electrolyte, an electrolyte generally used in non-aqueous alkali metal storage elements can be used. When the alkali metal is lithium, LiFSI, LiBF ４ , LiPF ６ , LiCiO ４ , LiTFSI, etc. can be used alone or in combination of two or more. When the alkali metal is sodium, Na(SO ２ CF ３ ) ２ , NaN(SO ２ F) ２ , NaN(C ２ F ５ SO ２ ) ２ , NaCF ３ SO ３ , NaC(CF ３ SO ２ ) ３ , NaPF ６ , NaBF ４ , NaClO ４ , NaAsF ６, NaAlCl ４ These may be used alone or in combination of two or more.

[0057] As the lower limit of the stable operating voltage of the battery, it is preferable to apply an appropriate lower limit of the stable operating potential and stable operating voltage depending on the positive electrode active material used. Although not particularly limited to the following numerical values, the lower limits of the stable operating potential and stable operating voltage are shown for preferred specific examples of the positive electrode active material. ２ (LCO): Lower limit of stable operating potential 3.1 V, lower limit of stable operating voltage 3.0 V LiFePO ４ (LFP): Lower limit of stable operating potential 2.5V, lower limit of stable operating voltage 2.4V LiMn ０．６ Fe ０．４ P.O. ４ (LMFP): Lower limit of stable operating potential 2.5 V (vs. Li / Li ＋ ), the lower limit of stable operating voltage is 2.4V LiNi １／３ Co １／３ Mn １／３ O ２ (NCM111): Lower limit of stable operating potential 3.1 V (vs. Li / Li ＋ ), the lower limit of stable operating voltage is 3.0V LiNi ０．８ Co ０．１ Mn ０．１ O ２ (NCM811): Lower limit of stable operating potential 3.1 V (vs. Li / Li ＋ ), the lower limit of stable operating voltage is 3.0V LiNi ０．８ Co ０．１５ Al ０．０５ O ２ (NCA): Lower limit of stable operating potential 3.1 V (vs. Li / Li ＋ ), the lower limit of stable operating voltage is 3.0V LiMn ２ O ４ (LMO): Lower limit of stable operating potential 3.1 V (vs. Li / Li ＋ ), the lower limit of stable operating voltage is 3.0V NaFe １／３ Ni １／３ Mn １／３ O ２ : Lower limit of stable operating potential 2.0 V (vs. Na / Na ＋ ), the upper limit of stable operating voltage is 1.9V

[0058] (C Rate) In this specification, the C rate is defined as the current (A) required for one hour of constant current discharge from the upper limit to the lower limit of the stable operating potential in the case of a positive electrode half cell, and is a value proportionally converted based on the current value (A) corresponding to 1 C. For example, a current value 10 times the current value corresponding to 1 C is defined as 10 C, and a current value 0.1 times the current value corresponding to 1 C is defined as 0.1 C.

[0059] In this specification, the C rate is a value proportionally converted based on the current value (A) corresponding to 1 C, where 1 C is the current (A) required for one hour of constant current discharge from the upper limit to the lower limit of the stable operating voltage in the case of a full cell. For example, 10 times the current value corresponding to 1 C is defined as 10 C, and 0.1 times the current value corresponding to 1 C is defined as 0.1 C.

[0060] (The initial charge capacity density L of the positive electrode active material １ , initial discharge capacity density L ２ ) Initial charge capacity density L of the positive electrode active material １ The initial discharge capacity density L (mAh / g) is obtained by preparing a positive electrode comprising a positive electrode active material, a binder, and a conductive material using a known process for preparing an electrode for a non-aqueous alkali metal storage element, and then charging a half cell comprising an alkali metal counter electrode and a known separator at a constant current of 0.1 C rate up to the upper limit potential for stable operation in a 25°C environment, followed by constant voltage charging until the current converges to a rate of 0.03 C, and measuring the charge capacity. ２ The capacity density L (mAh / g) can be obtained by measuring the discharge capacity when the battery is discharged at a constant current of 0.1 C rate to the lower limit of the stable operating potential after a 10-minute pause following the completion of the constant voltage charge at the upper limit of the stable operating potential. The capacity density L １ , L ２ (mAh / g) can be obtained.

[0061] (Alkali Metal Carbonate) In this embodiment, the alkali metal carbonate is contained in the positive electrode active material layer of the positive electrode precursor, in the intermediate layer between the positive electrode active material layer and the separator of the nonaqueous alkali metal energy storage element precursor, or in both. In a first embodiment, the alkali metal carbonate can be pre-doped by decomposing in the nonaqueous alkali metal energy storage element precursor to release alkali metal ions, which are then reduced at the negative electrode. In a second embodiment, after capacity degradation, the alkali metal carbonate can be decomposed by electrochemical operation to generate alkali metal ions, thereby compensating for the total amount of deactivated alkali metal ions and thereby recovering capacity.

[0062] The amount of alkali metal carbonate in the positive electrode active material layer and the intermediate layer can be measured by ion chromatography.

[0063] (Measurement of alkali metal carbonate in positive electrode) There are no particular limitations on the method for measuring alkali metal carbonate in the positive electrode, but it can be measured, for example, by ion chromatography as shown below. Specifically, the battery whose voltage has been adjusted is disassembled, the positive electrode is removed, and then the positive electrode is measured by ion chromatography.

[0064] 1. Battery voltage adjustment Before disassembly, the battery is adjusted to the lowest stable operating voltage. The specific method is described below. ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ When LiFePO is used as the positive electrode active material, the completed nonaqueous alkali metal storage element is charged at a constant current of 0.1 C in a thermostatic chamber set at 25° C. until the stable operating voltage upper limit, i.e., 4.2 V, is reached, followed by 30 minutes of constant voltage charging with a constant voltage of 4.2 V applied. Thereafter, the element is discharged at a constant current of 0.1 C until the stable operating voltage lower limit, i.e., 3.0 V, is reached, followed by 30 minutes of constant voltage discharge with a constant voltage of 3.0 V applied.４ When NaFe is used as the positive electrode active material, the nonaqueous alkali metal storage element is charged in a thermostatic chamber set at 25°C at a constant current of 0.1 C until the stable operating voltage upper limit, i.e., 3.6 V, is reached, followed by 30 minutes of constant voltage charging with a constant voltage of 3.6 V applied. Thereafter, the element is discharged at a constant current of 0.1 C until the stable operating voltage lower limit, i.e., 2.4 V, is reached, followed by 30 minutes of constant voltage discharge with a constant voltage of 2.4 V applied. １／３ Ni １／３ Mn １／３ O ２ When the positive electrode active material is used, the nonaqueous alkali metal storage element is charged in a thermostatic chamber set at 25° C. at a constant current of 0.1 C until the stable operating voltage upper limit, i.e., 3.9 V, is reached, followed by 30 minutes of constant voltage charging with a constant voltage of 3.9 V applied. Thereafter, the element is discharged at a constant current of 0.1 C until the stable operating voltage lower limit, i.e., 1.9 V, is reached, followed by 30 minutes of constant voltage discharge with a constant voltage of 1.9 V applied.

[0065] 2. Disassembly of the Battery and Removal of the Positive Electrode The battery was disassembled in an Ar box with a dew point of -70°C or lower. In the case of a laminate, the positive electrode was cut out at a location located at 1 / 4 and 3 / 4 of the four quarters of the stacking direction, and also including the center position within the electrode surface. In the case of a flat wound body, the positive electrode was cut out at a location located at 1 / 4 and 3 / 4 of the four quarters of the number of windings, at a flat portion avoiding the bent portion, and including the center position within the electrode surface. In the case of a cylindrical wound body, the positive electrode was cut out at a location located at 1 / 2 from the center of the cylinder in the radial direction of the cylinder, and also including a location located at 1 / 2 of the two quarters of the cylinder height direction. The removed positive electrode was immersed and washed in methyl ethyl carbonate in an Ar box with a dew point of -70°C or lower, and then vacuum dried at room temperature in the Ar box to remove volatile components of the electrolyte and cleaning solvent.

[0066] 3. Quantitative analysis by ion chromatography (approx. 5 cm) ２The positive electrode active material layer is scraped off from the positive electrode, placed in a vial, and weighed. 2 mL of distilled water is added so that the scraped active material layer is completely submerged, and the current collector is immersed and extracted for three days. Extraction can be performed without peeling off the active material layer. In this case, the active material layer is removed after extraction is completed, and the current collector is weighed. This weight is subtracted from the weight of the positive electrode to calculate the weight of the active material layer. The supernatant of the extract is appropriately diluted with distilled water, and carbonate ions derived from alkali metal carbonates are measured by ion chromatography. For quantification, alkali metal carbonates are used as standards. The alkali metal carbonates are dissolved and diluted with distilled water, and ion chromatography is performed under the same conditions as for the positive electrode active material layer extract, and a calibration curve for alkali metal carbonates is created. Using this calibration curve, the concentration of alkali metal carbonates in the extract is quantified, and the weight ratio of alkali metal carbonates per weight of active material layer is calculated. Note that because carbonate ions can be contaminated from the environment, a blank value is subtracted to calculate the weight ratio of alkali metal carbonates per weight of active material layer. The ion chromatography measurement conditions are as follows: <Ion chromatography measurement conditions> Apparatus: Tosoh Corporation, IC-2001 Column: Tosoh Corporation, TSKgel-SCX (4.6 mm x 150 mm) Eluent: 0.1 mmol / L phosphoric acid Flow rate: 0.6 mL / min Detection: Electric conductivity Column temperature: 40°C Injection volume: 30 μL

[0067] In the first embodiment, when an alkali metal carbonate is contained in the positive electrode active material layer of the positive electrode precursor, the content of the alkali metal carbonate is preferably 0.2% by mass or more and 15% by mass or less. The lower limit is more preferably 0.5% by mass, and even more preferably 2% by mass or more. The upper limit is more preferably 10% by mass or less, and even more preferably 8% by mass or less. If the content of the alkali metal carbonate is 0.2% by mass or more, the doping of the alkali metal into the negative electrode due to decomposition of the alkali metal carbonate proceeds sufficiently. If the content is 15% by mass or less, the proportion of alkali metal carbonate in the positive electrode active material layer is low, and the doping promotion effect of the promoter is sufficiently maintained. Therefore, if the content of the alkali metal carbonate in the positive electrode active material layer of the positive electrode precursor is 0.2% by mass or more and 15% by mass or less, the pre-doping volumetric efficiency can be increased, and this is also preferable from the viewpoints of resistance and gas swelling during high-temperature storage.

[0068] In the first embodiment, when an alkali metal carbonate is contained in the intermediate layer between the positive electrode active material layer of the positive electrode precursor and the separator, the content of the alkali metal carbonate is preferably 20% by mass or more and 95% by mass or less. When the content of the alkali metal carbonate is 20% by mass or more and 95% by mass or less, the effect of pre-doping can be obtained without impairing the energy density of the energy storage element.

[0069] In the second embodiment, when the intermediate layer contains an alkali metal carbonate, the mass ratio of the alkali metal carbonate is X based on the total mass of the intermediate layer. ４ (mass%), X ４ is preferably 20.0% by mass or more and 95.0% by mass or less. ４ When X is 20.0 mass % or more, a high capacity recovery effect can be obtained, and when X is 95.0 mass % or less, the initial capacity density can be maintained high. ４ The upper limit is more preferably 90% by mass or less, and even more preferably 85% by mass or less, and the lower limit is more preferably 30% by mass or more, and even more preferably 50% by mass or more.

[0070] In the second embodiment, the mass ratio of the alkali metal carbonate in the positive electrode active material layer is X ３ (mass%), X ３ is preferably 0.3 mass % or more and 20.0 mass % or less. ３ However, if the content is 20.0 mass % or less, the initial capacity volume density of the nonaqueous alkali metal storage element can be increased, which is preferable. ３ However, if the content of X is 0.3 mass % or more, a higher battery capacity recovery effect can be obtained during the capacity recovery operation described below. ３ The lower limit of X is more preferably 1% by mass or more, even more preferably 3% by mass or more, and particularly preferably 5% by mass or more. ３ The upper limit is more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0071] The alkali metal compound preferably maintains the decomposition reactivity of the alkali metal carbonate in each of the steps of the initial charging step, the aging step, and the step of using the battery before capacity recovery (when capacity deterioration progresses), which will be described later. This allows the decomposition reaction of the alkali metal carbonate to progress in the capacity recovery step, replenish the alkali metal to the negative electrode, and achieve a high capacity recovery effect.

[0072] Specifically, it is preferable not to apply a cell voltage in a heated state that exceeds the upper limit of the stable operating voltage corresponding to the positive electrode active material. Applying a voltage above the upper limit of the stable operating voltage before the capacity recovery process promotes the decomposition reaction of the alkali metal carbonate, resulting in partial or complete loss of the alkali metal carbonate, which may reduce or eliminate the capacity recovery effect in the capacity recovery process. Furthermore, applying a voltage above the upper limit of the stable operating voltage before the capacity recovery process may reduce or eliminate the capacity recovery effect in the capacity recovery process, due to the acid, such as HF, generated by a side reaction of the electrolyte deactivating the surface reactivity of the alkali metal carbonate. However, as long as the capacity recovery effect is exhibited in the capacity recovery process of the present disclosure, there may be situations in which the voltage is applied above the upper limit of the stable operating voltage before the capacity recovery process. The upper limit of the stable operating voltage corresponding to the positive electrode active material is as described above.

[0073] The average particle size of the alkali metal carbonate is preferably 0.1 μm or more and 10 μm or less. If the average particle size is 0.1 μm or more, the dispersibility in the positive electrode is excellent. If the average particle size is 10 μm or less, the surface area of ​​the alkali metal carbonate increases, allowing the decomposition reaction of the alkali metal carbonate to proceed efficiently in the pre-doping and capacity recovery processes. Various grinding methods can be used to adjust the particle size of the alkali metal carbonate.

[0074] In the first and second embodiments, the amounts of the alkali metal transition metal compound and alkali metal carbonate in the positive electrode active material layer can be quantified by the measurement method described in the examples below.

[0075] (Optional Components) In addition to the alkali metal transition metal compound and the alkali metal compound, the positive electrode active material layer in the first and second embodiments may contain optional components such as a conductive filler, a binder, a dispersion stabilizer, a dispersant, and a pH adjuster, as needed.

[0076] In the first and second embodiments, the conductive filler is not particularly limited, but examples thereof include conductive carbonaceous materials having higher conductivity than the positive electrode active material. Examples of such conductive fillers include, but are not limited to, carbon black, acetylene black, ketjen black, vapor-grown carbon fiber, graphite, flake graphite, carbon nanotubes, graphene, and mixtures thereof. The amount of conductive filler used is preferably more than 0 parts by mass and not more than 30 parts by mass, more preferably more than 0 parts by mass and not more than 25 parts by mass, and even more preferably 1 part by mass to 20 parts by mass, per 100 parts by mass of the positive electrode active material. When the amount is 30 parts by mass or less, the content of the positive electrode active material in the positive electrode active material layer is increased, thereby ensuring a high energy density per volume of the positive electrode active material layer. The upper limit is more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less.

[0077] In the first and second embodiments, the binder is not particularly limited, but examples thereof include PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, and acrylic copolymer. The amount of binder used is preferably 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of the positive electrode active material. If the amount of binder is 1% by mass or more, sufficient electrode strength is achieved. On the other hand, if the amount of binder is 30 parts by mass or less, the ingress and egress of ions into and diffusion from the positive electrode active material are not hindered, and high input / output characteristics are achieved. The upper limit is preferably 25 parts by mass or less, more preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. The lower limit is preferably 1 part by mass or more.

[0078] In the first and second embodiments, the dispersion stabilizer is not particularly limited, but examples thereof include PVP (polyvinylpyrrolidone) and PVA (polyvinyl alcohol). The amount of the dispersion stabilizer used is preferably 0 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the positive electrode active material. When the amount of the dispersion stabilizer is 10 parts by mass or less, the ingress and egress of ions into and from the positive electrode active material and the diffusion thereof are not inhibited, and the input / output characteristics are improved.

[0079] In the first and second embodiments, the dispersant is not particularly limited, but may be at least one selected from the group consisting of carboxymethyl cellulose, methyl cellulose, ethyl cellulose, cellulose acetate phthalate, hydroxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose phthalate, polyvinyl pyrrolidone, polyvinyl alcohol, and polyvinyl acetal. The amount of dispersant used is preferably 0 to 10 parts by mass, more preferably 0 to 10 parts by mass, per 100 parts by mass of the positive electrode active material. When the amount of dispersant is 10 parts by mass or less, the ingress and egress of ions into and diffusion from the positive electrode active material are not inhibited, improving input / output characteristics.

[0080] In the first and second embodiments, water, N-methyl-2-pyrrolidone, a mixture thereof, or the like can be used as the dispersion solvent for the positive electrode coating liquid. When water is used as the solvent for the coating liquid, adding an alkali metal compound can make the coating liquid alkaline, so a pH adjuster may be added to the coating liquid as needed. The pH adjuster is not particularly limited, but examples include hydrogen halides such as hydrogen fluoride, hydrogen chloride, and hydrogen bromide; halogen oxoacids such as hypochlorous acid, chlorous acid, and chloric acid; carboxylic acids such as formic acid, acetic acid, citric acid, oxalic acid, lactic acid, maleic acid, and fumaric acid; sulfonic acids such as methanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid; and acids such as nitric acid, sulfuric acid, phosphoric acid, boric acid, and carbon dioxide.

[0081] (Positive electrode current collector) The material for the positive electrode current collector in this embodiment is not particularly limited as long as it has high electronic conductivity and is not susceptible to deterioration due to elution in the electrolytic solution or reaction with the electrolyte or ions, etc., but metal foil is preferred. In the first and second embodiments, aluminum foil is particularly preferred as the positive electrode current collector for the nonaqueous alkali metal energy storage element.

[0082] In the positive electrode current collectors according to the first and second embodiments of the present disclosure, an undercoat layer may be provided on the metal foil, more specifically, a conductive anchor coat layer (e.g., an undercoat layer made of a conductive material such as graphite, flake graphite, carbon nanotubes, graphene, carbon black, or vapor-grown carbon fiber) may be provided on the surface of the positive electrode current collector. Providing the anchor layer improves electrical conductivity between the positive electrode current collector and the positive electrode active material layer, thereby reducing resistance. The thickness of the anchor layer is preferably 0.1 μm or more and 5 μm or less per side of the positive electrode current collector.

[0083] The metal foil may be a normal metal foil without irregularities or through holes, or may be a metal foil with irregularities that has been subjected to embossing, chemical etching, electrolytic deposition, blasting, or the like, or may be a metal foil with through holes such as expanded metal, punched metal, or etched foil.

[0084] The thickness of the positive electrode current collector is not particularly limited as long as it can sufficiently maintain the shape and strength of the positive electrode, but is preferably 1 to 100 μm, for example.

[0085] (Production of Positive Electrode Precursor) In the first embodiment, the positive electrode precursor has a positive electrode active material layer on one or both surfaces of a positive electrode current collector. Typically, the positive electrode active material layer is fixed to one or both surfaces of the positive electrode current collector.

[0086] In the first embodiment, the positive electrode precursor can be manufactured using known electrode manufacturing techniques for alkali metal ion batteries, electric double layer capacitors, and the like to form a positive electrode. For example, a positive electrode active material, an alkali metal carbonate, and other optional components used as needed are dispersed or dissolved in water or an organic solvent to prepare a slurry-like coating liquid, and this coating liquid is applied to one or both sides of a positive electrode current collector to form a coating film, which is then dried to obtain a positive electrode precursor. The obtained positive electrode precursor may be pressed to adjust the film thickness and bulk density of the positive electrode active material layer. Alternatively, a method is also possible in which the positive electrode active material, the alkali metal carbonate, and other optional components used as needed are dry-mixed without using a solvent, the resulting mixture is press-molded, and then attached to the positive electrode current collector using a conductive adhesive.

[0087] The method for forming the coating film of the positive electrode precursor is not particularly limited, but it is preferable to use a coating machine such as a die coater, a comma coater, a knife coater, a gravure coater, etc. The coating film may be formed by single-layer coating or multi-layer coating.

[0088] The method for drying the coating film of the positive electrode precursor is not particularly limited, but preferably, a drying method such as hot air drying or infrared (IR) drying can be used.

[0089] The method for pressing the positive electrode precursor is not particularly limited, but it is preferable to use a press such as a hydraulic press, a vacuum press, etc. The film thickness, bulk density, and electrode strength of the positive electrode active material layer can be adjusted by the pressing pressure, gap, and surface temperature of the pressing part.

[0090] <Production of Positive Electrode> The positive electrode of the nonaqueous alkali metal storage element of the second embodiment can be produced by known electrode production techniques for alkali metal ion batteries, electric double layer capacitors, and the like. For example, a positive electrode can be obtained by preparing a coating liquid as described above, applying the coating liquid to one or both sides of a positive electrode current collector to form a coating film, and drying the coating film. The resulting positive electrode may then be pressed to adjust the film thickness or bulk density of the positive electrode active material layer. Alternatively, a method is also possible in which the positive electrode active material, alkali metal carbonate, and other optional components used as needed are dry-mixed without using a solvent, the resulting mixture is press-molded, and then attached to the positive electrode current collector using a conductive adhesive, or the resulting mixture is hot-pressed onto the positive electrode current collector to form the positive electrode active material layer.

[0091] The coating film on the positive electrode is not particularly limited, but a coating machine such as a die coater, comma coater, knife coater, or gravure coater can be suitably used. The coating film may be formed by single-layer coating or multi-layer coating. When applying the coating film to the positive electrode current collector, multi-line coating, intermittent coating, or multi-line intermittent coating may be used. Sequential coating may be performed by coating one side of the positive electrode current collector and drying, and then coating the other side and drying. Simultaneous double-sided coating may be performed by simultaneously coating both sides of the positive electrode current collector with the coating liquid and drying the coating liquid.

[0092] The positive electrode can be pressed using a press such as a hydraulic press, a vacuum press, etc. The thickness, bulk density, and electrode strength of the positive electrode active material layer can be adjusted by the press pressure, the gap between the press rolls, and the surface temperature of the press part.

[0093] When the positive electrode is multi-line coated, it is preferable to slit it before pressing. By slitting and pressing the multi-line coated positive electrode, stress is applied to the current collector portion not coated with the positive electrode active material layer, which can prevent wrinkles from occurring. Alternatively, the positive electrode can be slit again after pressing.

[0094] In the first and second embodiments, the thickness of the positive electrode active material layer per side of the positive electrode current collector is preferably 20 μm to 200 μm, more preferably 25 μm to 100 μm, and even more preferably 30 μm to 80 μm. When the thickness of the positive electrode active material layer per side of the positive electrode current collector is 20 μm or more, sufficient charge / discharge capacity can be achieved. When the thickness of the positive electrode active material layer per side of the positive electrode current collector is 200 μm or less, low ion diffusion resistance within the electrode can be maintained. Therefore, sufficient output characteristics can be obtained, and the cell volume can be reduced, thereby increasing the energy density. Note that when the current collector has through-holes or irregularities, the thickness of the positive electrode active material layer refers to the average thickness per side of the current collector in the portion not having through-holes or irregularities.

[0095] <Intermediate layer> The nonaqueous alkali metal storage element precursor of the first and second embodiments may have an intermediate layer containing an alkali metal carbonate between the positive electrode active material layer and the separator. The method for forming the intermediate layer is not particularly limited, but examples include a method in which the intermediate layer is formed on the surface of the positive electrode active material layer or the surface of the separator that contacts the positive electrode by an existing coating method, and then disposed between the positive electrode and the separator during formation of the electrode assembly.

[0096] In the second embodiment, the alkali metal carbonate that may be contained in the intermediate layer is decomposed in the capacity recovery step described below, and the negative electrode is doped with replenished alkali metal ions, thereby recovering the capacity of the nonaqueous alkali metal storage element. Details are as described above in the section on <Positive Electrode>.

[0097] The intermediate layer may contain optional components in addition to the alkali metal carbonate, such as a binder component for maintaining the shape and a conductive material for ensuring conductivity.

[0098] In the first embodiment, it is preferable that the alkali metal carbonate contained in the intermediate layer is decomposed in a pre-doping step described below, and the negative electrode precursor is doped with alkali metal ions.

[0099] In the first and second embodiments, the thickness of the intermediate layer is preferably 0.3 μm to 10 μm, more preferably 0.5 μm to 5 μm, per side of the positive electrode current collector or separator. If the thickness of the intermediate layer is 0.3 μm or more, the pre-doping effect can be obtained. If the thickness of the intermediate layer is 10 μm or less, sufficient output characteristics can be obtained, and the cell volume can be reduced, thereby increasing the energy density.

[0100] (Method of Forming Intermediate Layer) In the first and second embodiments, the intermediate layer is formed between the positive electrode and the separator. Typically, the intermediate layer is fixed to the surface of the positive electrode active material layer or the surface of the separator that contacts the positive electrode.

[0101] In the first and second embodiments, the intermediate layer can be formed on the surface of the positive electrode active material layer or the surface of the separator by known manufacturing techniques for electrodes or separator coating layers in alkali metal ion batteries, electric double layer capacitors, etc. After forming the positive electrode active material layer, the intermediate layer may be formed on the positive electrode active material layer, or the intermediate layer may be formed on the surface of the separator that comes into contact with the positive electrode.

[0102] In the first and second embodiments, for example, when forming a coating on the surface of a positive electrode active material layer, an alkali metal carbonate and other optional components used as needed are dispersed or dissolved in water or an organic solvent to prepare a slurry coating liquid, and this coating liquid is applied to one or both sides of the positive electrode active material layer to form a coating film, which can be obtained by drying. The obtained integrated product of the positive electrode active material layer and the intermediate layer may be pressed to adjust the film thickness and bulk density. Alternatively, a method is also possible in which, without using a solvent, the pre-dope material and other optional components used as needed are dry mixed, the resulting mixture is press-molded, and then attached to the positive electrode active material layer using a conductive adhesive or the like.

[0103] In the first and second embodiments, for example, when forming the intermediate layer on the separator surface, the alkali metal carbonate and other optional components used as needed are dispersed or dissolved in water or an organic solvent to prepare a slurry coating liquid, and this coating liquid is applied to the surface of the separator that contacts the positive electrode to form a coating film, which can be obtained by drying. The obtained integrated product of the separator and intermediate layer may be pressed to adjust the film thickness and bulk density. Alternatively, a method is also possible in which the alkali metal carbonate and other optional components used as needed are dry mixed without using a solvent, the resulting mixture is press-molded, and then attached to the separator using a conductive adhesive or the like.

[0104] In the first and second embodiments, the formation of the coating film of the intermediate layer is not particularly limited, but it is possible to use a coating method and a coating device such as die coating, gravure coating, comma coating, knife coating, etc. The coating film may be formed by single-layer coating or multi-layer coating.

[0105] In the first embodiment, the drying method of the coating film of the intermediate layer is not particularly limited, but preferably, a drying method such as hot air drying or infrared (IR) drying can be used.

[0106] In the first and second embodiments, the pressing of the intermediate layer is not particularly limited, but it is preferable to use a press such as a hydraulic press, a vacuum press, etc. The film thickness, bulk density, and electrode strength of the positive electrode active material layer can be adjusted by the pressing pressure, gap, and surface temperature of the pressing part.

[0107] (Optional Components) The intermediate layer in the first and second embodiments may contain optional components such as a conductive filler, a binder, and an inorganic filler, as needed.

[0108] The conductive filler is not particularly limited, and examples thereof include acetylene black, ketjen black, vapor-grown carbon fiber, graphite, carbon nanotubes, and mixtures thereof. The amount of conductive filler used is preferably 0 to 30 parts by mass, more preferably 1 to 25 parts by mass, and even more preferably 5 to 20 parts by mass, based on 100 parts by mass of the total mass of the intermediate layer. In the first embodiment, if the amount of conductive filler used is 30 parts by mass or less, the content of the pre-dope material in the intermediate layer increases, thereby ensuring a high alkali metal density per volume that can be extracted from the intermediate layer. In the second embodiment, if the amount of conductive filler used is 30% by mass or less, the content of the alkali metal carbonate in the intermediate layer increases, thereby ensuring a high alkali metal density per volume that can be extracted from the intermediate layer.

[0109] The binder is not particularly limited, and examples thereof include PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, and acrylic copolymer. The amount of binder used is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 1 part by mass or more and 15 parts by mass or less, and even more preferably 1 part by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the intermediate layer. If the amount of binder used is 1% by mass or more, sufficient strength of the intermediate layer is achieved. On the other hand, in the first embodiment, if the amount of binder used is 30 parts by mass or less, the ingress and egress of the electrolyte into and diffusion from the intermediate layer are not hindered, and pre-doping is facilitated. Furthermore, in the second embodiment, if the amount of conductive filler used is 30% by mass or less, the content of alkali metal carbonate in the intermediate layer is increased, and the alkali metal density per volume that can be extracted from the intermediate layer can be ensured.

[0110] Examples of inorganic fillers include oxide ceramics such as alumina, silica (silicon oxide), titania, zirconia, magnesia, ceria, yttria, zinc oxide, and iron oxide; nitride ceramics such as silicon nitride, titanium nitride, and boron nitride; ceramics such as silicon carbide, calcium carbonate, aluminum sulfate, aluminum hydroxide, potassium titanate, talc, kaolin clay, kaolinite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amesite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and silica sand; and glass fiber. By incorporating an inorganic filler, the intermediate layer of the first embodiment and the intermediate layer of the first embodiment can further exhibit a safety-improving effect.

[0111] (Measurement of Alkali Metal Carbonate in Intermediate Layer) Measurement can be performed by applying the method described in (Measurement of Alkali Metal Carbonate in Positive Electrode) to the intermediate layer.

[0112] <Method for Identifying Alkali Metal Carbonate> In the first and second embodiments, the method for identifying the alkali metal carbonate contained in the positive electrode active material layer or the intermediate layer is not particularly limited, but can be, for example, identified by the following method. The alkali metal carbonate is preferably identified by a combination of the following analytical techniques.

[0113] In ion chromatography, which will be described later, anions can be identified by analyzing the water obtained after washing the positive electrode precursor with distilled water.

[0114] (Microscopic Raman Spectroscopy) In the first and second embodiments, lithium carbonate and the positive electrode active material can be distinguished by Raman imaging of carbonate ions on the surface of the positive electrode active material layer or intermediate layer, measured at an observation magnification of 1000 to 4000 times. Measurement conditions include, for example, excitation light of 532 nm, excitation light intensity of 1%, objective lens long-range operation of 50 times, diffraction grating of 1800 gr / mm, mapping method of point scanning (slit 65 mm, binning 5 pix), 1 mm step, exposure time per point of 3 seconds, number of integrations of 1, and noise filter. The measured Raman spectrum was measured at 1071 to 1104 cm.－１ A linear baseline is set in the range, and the area is calculated assuming that positive values ​​from the baseline are carbonate ion peaks, and the frequency is integrated. At this time, the frequency for the carbonate ion peak area, which is approximated by a Gaussian function for noise components, is subtracted from the carbonate ion frequency distribution.

[0115] (X-ray Photoelectron Spectroscopy (XPS)) In the first and second embodiments, the bonding state of the alkali metal can be determined by analyzing the electronic state using XPS. Measurement can be performed under the following conditions, for example: a monochromatic AlKα X-ray source, an X-ray beam diameter of 100 μmφ (25 W, 15 kV), narrow scan pass energy of 58.70 eV, charge neutralization, narrow scan sweep count of 10 (carbon, oxygen), 20 (fluorine), 30 (phosphorus), 40 (alkali metal element), 50 (silicon), and narrow scan energy step of 0.25 eV. It is preferable to clean the surface of the positive electrode by sputtering before XPS measurement. For example, sputtering conditions include an acceleration voltage of 1.0 kV, a 2 mm x 2 mm area, and 1 minute of sputtering (SiO ２ The surface of the positive electrode active material layer or intermediate layer can be cleaned under the condition of a rate of 1.25 nm / min (equivalent to 1.25 nm / min). ２ or Li-C bond, the peak at 55 to 60 eV is LiF, Li ２ CO ３ , Li ｘ P.O. ｙ F ｚ (wherein x, y, and z are integers of 1 to 6); the C1s bond energy peak of 285 eV corresponds to a C—C bond, the peak of 286 eV corresponds to a C—O bond, the peak of 288 eV corresponds to a COO bond, and the peak of 290 to 292 eV corresponds to a CO ３ ２－ , C—F bond; O1s bond energy peak of 527 to 530 eV ２－ (Li ２ O), the peak at 531-532 eV is CO, CO ３ , OH, PO ｘ (wherein x is an integer of 1 to 4), SiO ｘ (wherein x is an integer of 1 to 4), and the peak at 533 eV is C—O, SiOｘ (wherein x is an integer of 1 to 4); the peak at 685 eV of F1s bond energy corresponds to LiF, the peak at 687 eV corresponds to C—F bond, and Li ｘ P.O. ｙ F ｚ (wherein x, y, and z are integers of 1 to 6), PF ６ － For the P2p binding energy, the peak at 133 eV is PO ｘ (wherein x is an integer of 1 to 4), and the peak at 134 to 136 eV is PF ｘ (wherein x is an integer of 1 to 6); the peak at the Si2p binding energy of 99 eV is Si silicide, and the peak at 101 to 107 eV is Si ｘ O ｙ (where x and y are any integers). When peaks overlap in the obtained spectrum, it is preferable to separate the peaks by assuming a Gaussian function or a Lorentzian function and assign the spectrum. The alkali metal compounds present can be identified from the obtained results of measuring the electronic state and the results of the ratio of elements present.

[0116] (Energy Dispersive X-ray Analysis (SEM-EDX)) In the first and second embodiments, the elements contained can be quantified by SEM-EDX analysis of the surface of the positive electrode active material layer or intermediate layer measured at an observation magnification of 1000 to 4000 times. As an example of measuring an SEM-EDX image, measurement can be performed at an acceleration voltage of 10 kV, an emission current of 1 μA, a measurement pixel count of 256 × 256 pixels, and an accumulation count of 50. In order to prevent the sample from becoming charged, the surface can also be treated with gold, platinum, osmium, or the like by a method such as vacuum deposition or sputtering.

[0117] (Ion Chromatography) In the first and second embodiments, the positive electrode active material layer or intermediate layer is washed with distilled water, and the resulting water is analyzed by ion chromatography to identify the anion species eluted in the water. Ion exchange, ion exclusion, and reversed-phase ion pair columns can be used. Detectors that can be used include electrical conductivity detectors, ultraviolet-visible absorbance detectors, and electrochemical detectors. A suppressor system in which a suppressor is installed before the detector, or a non-suppressor system in which a low-electrical conductivity solution is used as the eluent without a suppressor, can be used. Furthermore, since measurements can be performed in combination with a mass spectrometer or a charged particle detector, it is preferable to combine an appropriate column and detector based on the alkali metal compounds identified from the analytical results of SEM-EDX, Raman spectroscopy, and XPS.

[0118] (Method for quantifying alkali metal carbonate) In the first and second embodiments, the alkali metal carbonate contained in the positive electrode active material layer or intermediate layer is preferably measured by the method described in (Measurement of alkali metal carbonate in positive electrode) or (Measurement of alkali metal carbonate in intermediate layer) from the viewpoint of accuracy, but another quantification method will be described below. The positive electrode precursor is washed with distilled water, and the alkali metal carbonate can be quantified from the change in mass before and after washing with distilled water. The area of ​​the positive electrode precursor to be measured is not particularly limited, but from the viewpoint of reducing measurement variability, it is preferable to measure an area of ​​5 cm ２ More than 200cm ２ Preferably it is less than 25 cm ２ More than 150cm ２ The measurement area of ​​the positive electrode precursor is 5 cm or less. ２ If the measurement area of ​​the positive electrode precursor is 200 cm or more, the reproducibility of the measurement is ensured. ２ If the value is less than this, the sample is easy to handle.

[0119] The following describes a method for quantifying the amount of alkali metal carbonates, such as lithium carbonate, in the positive electrode active material layer or intermediate layer. Depending on the ease of analysis, the following procedure may be performed in a state where the layer is attached to the positive electrode current collector foil or separator. The mass of the cut positive electrode active material layer or intermediate layer is measured, and the M０ In a 25°C environment, the mass of the positive electrode active material layer or the intermediate layer is 100 times (100M ０ The positive electrode active material layer or intermediate layer is then thoroughly immersed in distilled water (100 mL / min. of distilled water) for at least three days to allow the alkali metal carbonate to elute into the water. At this time, it is preferable to take measures such as covering the container to prevent the distilled water from volatilizing. After immersion for at least three days, the positive electrode active material layer or intermediate layer is removed from the distilled water (when measuring by ion chromatography, the amount of distilled water is 100 mL / min. of distilled water). ０ The amount of liquid is adjusted so that the total mass of the positive electrode active material layer or intermediate layer is 100 to 200°C, the pressure is 0 to 10 kPa, and the time is 5 to 20 hours. The vacuum drying conditions are preferably, for example, in the range of temperature: 100 to 200°C, pressure: 0 to 10 kPa, and time: 5 to 20 hours, under which the residual moisture content in the positive electrode active material layer or intermediate layer is 1 mass % or less. The residual moisture content can be quantified by the Karl Fischer method. The mass of the positive electrode active material layer or intermediate layer after vacuum drying is M １ [g], and then, to measure the mass of the obtained support (current collector foil or separator) for the positive electrode active material layer or intermediate layer, the positive electrode active material layer or intermediate layer is removed using a spatula, brush, paintbrush, etc. The mass of the obtained current collector foil or separator is M ２ [g], the mass ratio X [mass %] of the alkali metal carbonate such as lithium carbonate contained in the positive electrode active material layer or the intermediate layer can be calculated by the following formula 1: X = 100 × (M ０ -M １ ) / (M ０ -M ２ ) (Equation 1)

[0120] (Method for Quantifying Alkali Metals by ICP-MS) In the first and second embodiments, the positive electrode active material layer or intermediate layer is subjected to acid decomposition using a strong acid such as concentrated nitric acid, concentrated hydrochloric acid, or aqua regia, and the resulting solution is diluted with pure water to an acid concentration of 2% to 3%. The acid decomposition can also be carried out by heating or pressurizing as appropriate. The resulting diluted solution is analyzed by ICP-MS, but it is preferable to add a known amount of alkali metal as an internal standard at this time. If the alkali metal to be measured exceeds the upper measurement limit concentration, it is preferable to further dilute the diluted solution while maintaining the acid concentration. The alkali metal can be quantified based on the obtained measurement results and a calibration curve created in advance using a standard solution for chemical analysis.

[0121] <Negative electrode, negative electrode precursor> In the first and second embodiments, the negative electrode in the present embodiments has a negative electrode current collector and a negative electrode active material layer containing a negative electrode active material provided on one or both surfaces of the negative electrode current collector. The negative electrode and the negative electrode precursor may have a common configuration except for the configuration related to the amount of alkali metal ions doped.

[0122] (Negative electrode active material layer) In the first and second embodiments, the negative electrode active material layer contains a negative electrode active material capable of absorbing and releasing alkali metal ions, and may contain optional components such as a conductive filler, a binder, and a dispersion stabilizer, as necessary.

[0123] (Negative Electrode Active Material) In the first and second embodiments, the negative electrode active material may be a material capable of absorbing and releasing alkali metal ions, such as alkali metal ions. Specific examples of the negative electrode active material include carbon materials, titanium oxides, silicon, silicon oxides, silicon alloys, silicon compounds, tin, and tin compounds, and these may be used in combination.

[0124] The content of the negative electrode active material in the negative electrode active material layer of the negative electrode is preferably 50 mass % or more, more preferably 70 mass % or more, and even more preferably 80 mass % or more, based on the total mass of the negative electrode active material layer.

[0125] (Carbon Material) In the first and second embodiments, known materials for non-aqueous alkali metal storage elements can be used as the carbon material. Examples include: non-graphitizable carbon materials (hard carbon); easily graphitizable carbon materials (soft carbon); carbon black; carbon nanoparticles; activated carbon; artificial graphite; natural graphite; graphitized mesophase carbon microspheres; graphite whiskers; amorphous carbonaceous materials such as polyacene-based substances; carbonaceous materials obtained by heat-treating carbonaceous material precursors such as petroleum-based pitch, coal-based pitch, mesocarbon microbeads, coke, and synthetic resins (e.g., phenolic resins); pyrolyzates of furfuryl alcohol resins or novolac resins; fullerenes; carbon nanohorns; and composite carbon materials thereof. Among these, from the viewpoint of occlusion and release of alkali metal ions, it is preferable that the negative electrode precursor or negative electrode contains graphite as the negative electrode active material.

[0126] The carbon material content relative to the total amount of the negative electrode active material is preferably 50% by mass or more, more preferably 70% by mass or more, and most preferably 80% by mass or more. The carbon material content may be 100% by mass, but from the viewpoint of obtaining the effect of the combined use of other materials (such as the alloy-based negative electrode material described later), it is preferably 95% by mass or less, and may be 90% by mass or less. The upper and lower limits of the range of the carbon material content can be combined arbitrarily.

[0127] According to the present disclosure, when an amorphous carbon material is used as a negative electrode active material, it is preferable because it can reduce the loss of the positive electrode active material. Hard carbon and soft carbon are particularly preferable. Furthermore, when the alkali metal is sodium, hard carbon is preferably used from the viewpoint of achieving a good doped state or exhibiting a high capacity.

[0128] (Alloy-based negative electrode material) In the first and second embodiments, the negative electrode active material may be a material that forms an alloy with an alkali metal (hereinafter also referred to as "alloy-based negative electrode material"), and preferably contains at least one selected from the group consisting of silicon, silicon compounds, tin, tin compounds, and composite materials of these with carbon or a carbonaceous material. The silicon compound is preferably SiC or silicon oxide, and SiO ｘ (wherein, 0.01≦x≦1) is more preferable. According to the present disclosure, when used as a negative electrode active material in an alloy-based negative electrode material, it is possible to reduce the loss of positive electrode active material, and therefore, silicon and / or a silicon compound are particularly preferable.

[0129] The composite material is preferably a material obtained by combining, by heat treatment or the like, at least one substrate selected from the group consisting of silicon, silicon compounds, tin, and tin compounds with at least one type of carbon or carbonaceous material selected from the group consisting of: non-graphitizable carbon materials; graphitizable carbon materials; carbon black; carbon nanoparticles; activated carbon; artificial graphite; natural graphite; graphitized mesophase carbon microspheres; graphite whiskers; amorphous carbonaceous materials such as polyacene-based substances; carbonaceous materials obtained by heat treating carbonaceous material precursors such as petroleum-based pitch, coal-based pitch, mesocarbon microbeads, coke, and synthetic resins (e.g., phenolic resins); pyrolysates of furfuryl alcohol resins or novolac resins; fullerenes; and carbon nanophones.

[0130] Among these, composite materials that can be obtained by heat treating one or more of the above-mentioned base materials together with petroleum-based pitch or coal-based pitch in the presence of each other are particularly preferred. Before the heat treatment, the base material and pitch may be mixed at a temperature higher than the melting point of the pitch. The heat treatment temperature may be any temperature at which the components generated by volatilization or thermal decomposition of the pitch used become carbonaceous materials, and is preferably 400°C or higher and 2500°C or lower, more preferably 500°C or higher and 2000°C or lower, and even more preferably 550°C or higher and 1500°C or lower. The atmosphere in which the heat treatment is performed is not particularly limited, but a non-oxidizing atmosphere is preferred.

[0131] (Average Particle Diameter of Negative Electrode Active Material) In the first and second embodiments, the negative electrode active material is preferably particulate. The average particle diameter of the negative electrode active material is preferably 0.01 μm or more and 30 μm or less, with the lower limit being more preferably 2 μm or more, even more preferably 2.5 μm or more, and the upper limit being more preferably 6 μm or less, even more preferably 4 μm or less. If the average particle diameter of the negative electrode active material is 0.01 μm or more, the contact area with the nonaqueous electrolyte increases, thereby reducing the resistance of the nonaqueous alkali metal storage element. If the average particle diameter of the negative electrode active material is 30 μm or less, the negative electrode active material layer can be made sufficiently thin, thereby improving the energy density of the nonaqueous alkali metal storage element. Furthermore, if the particle diameter is 30 μm or less, swelling and shrinkage of the negative electrode caused by doping and dedoping of alkali metal ions into the negative electrode during charge and discharge are reduced, thereby maintaining the strength of the negative electrode.

[0132] The average particle size of the negative electrode active material can be adjusted or made into fine particles by pulverizing using a wet or dry jet mill with a built-in classifier, an agitation ball mill, etc. The pulverizer is equipped with a centrifugal classifier, and the fine particles pulverized in an inert gas environment such as nitrogen or argon can be collected with a cyclone or a dust collector.

[0133] The average particle diameters of the positive electrode and negative electrode active materials in the first and second embodiments are determined by the following method. First, the primary particle diameter of the active material is measured by the following method. If the primary particle diameter is smaller than 1 μm, the primary particle diameter is taken as the average particle diameter. If the primary particle diameter is 1 μm or greater, the particle size distribution of the active material powder is measured using a particle size distribution measuring device, a cumulative curve is determined with the total volume being 100%, and the particle diameter at the point where the cumulative curve is 50% (i.e., the 50% diameter (median diameter)) is taken as the average particle diameter. An example of a particle size distribution measuring device is a laser diffraction particle size distribution measuring device.

[0134] The primary particle diameter of the active material in the first and second embodiments can be determined by the following methods: 1) A method in which several fields of view of the powder of the active material are photographed with an electron microscope, and the particle diameters of approximately 2,000 to 3,000 particles in those fields of view are measured using a fully automatic image processing device or the like, and the arithmetic average of these values ​​is used as the primary particle diameter; 2) A method in which several fields of view of the surface and / or cross section of the obtained electrode are photographed with an electron microscope, and the arithmetic average is determined using the above method.

[0135] The primary particle diameter of the active material incorporated in the nonaqueous alkali metal storage element can be measured by disassembling the nonaqueous alkali metal storage element, removing the electrodes, and then measuring the primary particle diameter using the above-mentioned method 2); or by removing components other than the active material from the removed electrodes and then measuring the primary particle diameter using the above-mentioned method 1).

[0136] The operation of disassembling the nonaqueous alkali metal electricity storage element and removing the electrodes is preferably carried out in an inert atmosphere such as argon.

[0137] Components other than the active material can be removed from the electrode by, for example, the following method. First, the removed electrode is immersed in ethyl methyl carbonate or dimethyl carbonate to remove the nonaqueous electrolyte, alkali metal salt, etc., and then air-dried. Next, it is immersed in a mixed solvent of methanol and isopropanol to deactivate the alkali metal ions occluded in the active material, and then air-dried again. Next, to remove the binder contained in the active material layer, the electrode with deactivated alkali metal ions is immersed in distilled water or NMP. Next, if necessary, the active material is peeled off with a spatula or the like, and then ultrasonically irradiated to slide the active material off the current collector, and the active material is recovered by suction filtration. If necessary, the obtained active material may be immersed again in distilled water or NMP, ultrasonically irradiated, and then suction-filtered several times. Finally, the obtained active material is vacuum-dried at 170°C to obtain an active material powder.

[0138] (Optional Components) In addition to the negative electrode active material, the negative electrode active material layer in the first and second embodiments may contain optional components such as a conductive filler, a binder, and a dispersion stabilizer, as needed.

[0139] In the first and second embodiments, the type of conductive filler is not particularly limited, but examples include acetylene black, carbon black, ketjen black, vapor-grown carbon fiber, graphite, carbon nanotubes, and mixtures thereof. The conductive filler is preferably made of a conductive carbonaceous material having higher conductivity than the negative electrode active material. The amount of conductive filler used is preferably more than 0 parts by mass and not more than 30 parts by mass, more preferably more than 0 parts by mass and not more than 20 parts by mass, and even more preferably more than 0 parts by mass and not more than 15 parts by mass, per 100 parts by mass of the negative electrode active material. From the viewpoint of high input power, it is preferable to mix more than 0 parts by mass of the conductive filler into the negative electrode active material layer. A mixed amount of 20 parts by mass or less is preferable because the content of the negative electrode active material in the negative electrode active material layer is increased, thereby improving the energy density per volume.

[0140] In the first and second embodiments, the binder is not particularly limited, but examples thereof include PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, and acrylic copolymer. The amount of binder used is preferably more than 0 parts by mass and not more than 30 parts by mass relative to 100 parts by mass of the negative electrode active material. When the amount of binder used is more than 0 parts by mass, sufficient electrode strength is achieved. When the amount of binder used is 30 parts by mass or less, the movement of alkali metal ions, such as alkali metal ions, into and out of the negative electrode active material is not inhibited, and high input / output characteristics are achieved. The lower limit is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more. The upper limit is preferably 25 parts by mass or less.

[0141] (Negative electrode current collector) In the first and second embodiments, the material constituting the negative electrode current collector is preferably a metal foil that has high electronic conductivity and is resistant to degradation due to elution in a non-aqueous electrolyte solution and reaction with an electrolyte or ions. Such metal foils are not particularly limited, and examples thereof include aluminum foil, copper foil, nickel foil, and stainless steel foil. Copper foil is preferred as the negative electrode current collector in a non-aqueous alkali metal energy storage element. When the alkali metal is sodium, aluminum foil is particularly preferred as the negative electrode current collector from the viewpoint of cost, etc.

[0142] The metal foil may be a normal metal foil without irregularities or through holes, or may be a metal foil with irregularities obtained by embossing, chemical etching, electrolytic deposition, blasting, or the like, or may be a metal foil with through holes such as expanded metal, punched metal, etched foil, etc. The negative electrode current collector is preferably a non-porous copper foil.

[0143] The thickness of the negative electrode current collector is not particularly limited as long as it can sufficiently maintain the shape and strength of the negative electrode, but is preferably 1 to 100 μm, for example.

[0144] (Production of Negative Electrode) In the first and second embodiments, the negative electrode has a negative electrode active material layer on one or both surfaces of a negative electrode current collector. Typically, the negative electrode active material layer is fixed to one or both surfaces of the negative electrode current collector.

[0145] In the first and second embodiments, the negative electrode can be manufactured by known electrode manufacturing techniques for nonaqueous alkali metal storage elements, electric double layer capacitors, and the like. For example, various materials including a negative electrode active material are dispersed or dissolved in water or an organic solvent to prepare a slurry negative electrode coating liquid. This negative electrode coating liquid is applied to one or both sides of a negative electrode current collector to form a coating film, which is then dried to obtain a negative electrode. The obtained negative electrode may be pressed to adjust the film thickness, bulk density, etc. of the negative electrode active material layer. Alternatively, various materials including the negative electrode active material may be dry-mixed without using a solvent, the resulting mixture is press-molded, and then attached to the negative electrode current collector using a conductive adhesive.

[0146] In the first and second embodiments, the negative electrode coating fluid may be prepared by dry-blending some or all of various material powders including the negative electrode active material, and then adding water or an organic solvent and / or a liquid or slurry substance in which a binder and a dispersion stabilizer are dissolved or dispersed therein. Alternatively, the negative electrode coating fluid may be prepared by adding various material powders including the negative electrode active material to a liquid or slurry substance in which a binder and a dispersion stabilizer are dissolved or dispersed in water or an organic solvent.

[0147] In the first and second embodiments, the dissolving or dispersing method is not particularly limited, but preferably, a dispersing machine such as a homodisper, a multi-axis dispersing machine, a planetary mixer, or a thin film rotating high-speed mixer can be used.

[0148] In the first and second embodiments, the method for forming the coating film is not particularly limited, but it is preferable to use a coating machine such as a die coater, a comma coater, a knife coater, a gravure coater, etc. The coating film may be formed by single-layer coating or multi-layer coating.

[0149] In the first and second embodiments, the method for drying the coating film is not particularly limited, but drying methods such as hot air drying and infrared (IR) drying can be preferably used. The coating film may be dried at a single temperature, or may be dried at a temperature that is changed in multiple stages. Furthermore, a combination of multiple drying methods may be used.

[0150] In the first and second embodiments, the method for pressing the negative electrode is not particularly limited, but a press such as a hydraulic press or a vacuum press can be preferably used.

[0151] In the first and second embodiments, the thickness of the negative electrode active material layer is preferably 5 μm or more and 100 μm or less per side of the negative electrode current collector. The lower limit of the thickness of the negative electrode active material layer is more preferably 7 μm or more, and even more preferably 10 μm or more. The upper limit of the thickness of the negative electrode active material layer is more preferably 80 μm or less, and even more preferably 60 μm or less. When the thickness of the negative electrode active material layer is 5 μm or more, streaks and the like are less likely to occur when the negative electrode active material layer is applied, and the coating properties are excellent. When the thickness of the negative electrode active material layer is 100 μm or less, a high energy density can be achieved by reducing the cell volume. Note that the thickness of the negative electrode active material layer when the negative electrode current collector has irregularities refers to the average thickness of the negative electrode active material layer per side in a portion of the negative electrode current collector that does not have irregularities.

[0152] (Production of negative electrode using alloy-based negative electrode material) In the first embodiment, the negative electrode has a negative electrode active material layer on one or both sides of a negative electrode current collector. Typically, the negative electrode active material layer is fixed to one or both sides of the negative electrode current collector.

[0153] In the first embodiment, the negative electrode can be manufactured using known electrode manufacturing techniques for alkali metal ion batteries, electric double layer capacitors, and the like. For example: 1) Various materials including a negative electrode active material are dispersed or dissolved in water or an organic solvent to prepare a slurry coating liquid, and this coating liquid is applied to one or both sides of a negative electrode current collector to form a coating film, which is then dried to obtain a negative electrode. The resulting negative electrode may be pressed to adjust the film thickness and bulk density of the negative electrode active material layer; 2) Various materials including a negative electrode active material may be dry-mixed without using a solvent, the resulting mixture may be press-molded, and then attached to the negative electrode current collector using a conductive adhesive to obtain a negative electrode; 3) A negative electrode may also be obtained by forming a negative electrode active material layer on a negative electrode current collector. Suitable film formation methods include electroless plating, electrolytic plating, chemical reduction, vacuum deposition, ion plating, sputtering, chemical vapor deposition (CVD), laser ablation, and thermal spraying.

[0154] Among the above-mentioned methods for producing a negative electrode, method 1) is preferred from the viewpoint of mass productivity.

[0155] In the first embodiment, the thickness of the negative electrode active material layer per side of the negative electrode current collector is preferably 10 μm or more and 75 μm or less, with the lower limit being more preferably 13 μm or more, even more preferably 15 μm or more, and even more preferably 20 μm or more, and the upper limit being more preferably 70 μm or less, even more preferably 65 μm or less, and even more preferably 60 μm or less. When the thickness of the negative electrode active material layer is 10 μm or more, the electric capacity of the positive electrode can be fully utilized, and when it is 75 μm or less, a high energy density can be achieved by reducing the cell volume. When the negative electrode current collector has through holes or irregularities, the thickness of the negative electrode active material layer refers to the average thickness per side of the portion of the negative electrode current collector that does not have through holes or irregularities. In this case, examples of the through holes include the through-hole portions of punched metal, expanded metal, etched foil, etc.

[0156] (Amount of alkali metal in negative electrode composite) The amount of alkali metal contained in the negative electrode composite is preferably 0.06 mmol / g or less. Doping the negative electrode composite with an alkali metal carbonate has caused problems with resistance and gas swelling during high-temperature storage. However, in the manufacturing method of the present disclosure, while not limited by theory, if the amount of alkali metal in the negative electrode composite is controlled so that the amount of alkali metal in the negative electrode composite is 0.06 mmol / g or less, resistance and gas swelling during high-temperature storage are improved. (A １ +0.3 x B １ ) and can be controlled by adjusting the doping voltage.

[0157] (Measurement of the amount of alkali metal in the negative electrode composite) To quantify the amount of alkali metal in the negative electrode composite, first, the alkali metal storage element is adjusted in advance to the lowest stable operating voltage limit. Next, the alkali metal storage element is disassembled in a low dew point environment in an argon box, and the negative electrode is removed. It is preferable to sample the negative electrode from an average position within the storage element. Alkali metal solid-state NMR can be used to quantify the amount of alkali metal in the negative electrode composite. A specific measurement method is disclosed below.

[0158] (1) Adjustment of the storage element before disassembly (1-1) When the alkali metal is lithium, LiCoO ２ , LiMn ０．６ Fe０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ When LiFePO is used as the positive electrode active material, the completed non-aqueous alkali metal storage element is subjected to constant current discharge at a current value of 0.1 C in a thermostatic chamber set at 25° C. until the stable operating voltage reaches the lower limit, for example, 3.0 V, and then subjected to constant voltage discharge at a constant voltage of 3.0 V for 30 minutes. ４ When the positive electrode active material is used, the completed nonaqueous alkali metal storage element is placed in a thermostatic chamber set at 25°C and subjected to constant current discharge at a current value of 0.1 C until the stable operating voltage reaches a lower limit, for example, 2.5 V, followed by constant voltage discharge at a constant voltage of 2.5 V for 30 minutes.

[0159] (1-2) When the alkali metal is sodium, a representative example of a sodium active material is listed below. １／３ Ni １／３ Mn １／３ O ２ When the positive electrode active material is used, the completed nonaqueous alkali metal storage element is placed in a thermostatic chamber set at 25°C and subjected to constant current discharge at a current value of 0.1 C until the stable operating voltage lower limit, for example, 1.9 V, is reached, followed by constant voltage discharge at a constant voltage of 1.9 V for 30 minutes.

[0160] (2) Disassembly of the Alkali Metal Storage Element The storage element is then disassembled in an argon box with a dew point of -60°C or less, and the negative electrode is removed. Sampling of the negative electrode is performed as follows depending on the shape of the assembly. In the case of a laminate, the negative electrode is cut out at locations located at 1 / 4 and 3 / 4 of the four sections of the stacking direction, and also so as to include the center position within the electrode surface. In the case of a flat wound body, the negative electrode is cut out at locations located at 1 / 4 and 3 / 4 of the four sections of the winding number, at a flat portion avoiding bent portions, and also so as to include the center position within the electrode surface. In the case of a cylindrical wound body, the negative electrode is cut out at a location located at 1 / 2 from the center of the cylinder in the radial direction of the cylinder, and also so as to include a location located at 1 / 2 of the two sections of the cylinder height direction. The negative electrode composite layer is scraped off from the current collector foil, and the negative electrode composite is sampled.

[0161] (3) Quantification of Alkali Metals: The alkali metals in the negative electrode composite are measured by solid-state NMR (nuclear magnetic resonance). For quantification, alkali metal salts are used as standard substances. The alkali metal salts are dissolved and diluted with distilled water, and NMR measurements are performed with the same receiver gain as the negative electrode powder (underlined: match the description of the sampling method). A calibration curve for the alkali metal salts is then created. The alkali metals in the negative electrode powder are quantified using this calibration curve, and the weight ratio of the alkali metals per weight of the active material layer is calculated. When quantifying the alkali metals, it is desirable to position the NMR observation center close to the position where the alkali metal peak appears. It should be noted that the excitation efficiency at the alkali metal peak appears is 90% of the excitation efficiency at the observation center.

[0162] (3-1) When the alkali metal is lithium, LiCl is used as the alkali metal salt used as the standard substance for quantification. The NMR measurement conditions are as follows: Apparatus: JEOL ECA 700 Probe: 3.2 mm probe Observation nucleus: ７Li Observation frequency: 272.1 MHz Measurement method: Single pulse method Pulse angle: 45° Pulse width: 1.0 μs Waiting time: 10 s Number of accumulations: 256 MAS rotation speed: 7 kHz Measurement temperature: Room temperature (approximately 25°C) Chemical shift reference: LiCl aqueous solution (external standard, 0 ppm) Broadening factor: 20 Hz Quantitative determination of lithium metal is performed based on the peak with a peak top in the range of 255 ppm to 270 ppm. After correction using the straight line connecting the points on the spectrum at 220 ppm and 340 ppm as the baseline, the peak integral value is calculated in the range of 220 ppm to 340 ppm.

[0163] (3-2) When the alkali metal is sodium, NaCl is used as the alkali metal salt used as the standard substance for quantification. The NMR measurement conditions are as follows: Apparatus: AVANCE 500 manufactured by Bruker Japan Co., Ltd. Probe: 4 mm probe Observation nucleus: ２３ Na Observation frequency: 132.3 MHz Measurement method: Single pulse method (pulse program zg) Pulse width: 1.0 μs Waiting time: 5 s Number of accumulations: 256 times MAS rotation speed: 7 kHz Measurement temperature: Room temperature (approximately 25°C) Chemical shift reference: NaCl aqueous solution (external standard, 0 ppm) Broadening factor: 30 Hz Sodium metal is quantified based on the peak with a peak top in the range of 1110 ppm to 1150 ppm. After correction using the straight line connecting the points on the spectrum at 1090 ppm and 1170 ppm as the baseline, the peak integral value is calculated in the range of 1090 ppm to 1170 ppm.

[0164] (4) Calculation of the Amount of Alkali Metal in the Negative Electrode Composite The amount of alkali metal (mmol) obtained by the above-described NMR measurement is divided by the sample weight (g) of the negative electrode composite used in the NMR measurement to calculate the amount of alkali metal (mmol / g) in the negative electrode composite.

[0165] (Irreversible Capacity Rate of Negative Electrode or Negative Electrode Precursor) This embodiment can supply lithium from the alkali metal carbonate or pre-dope material instead of the positive electrode active material, and is therefore suitable for use with negative electrode precursors or negative electrodes with a large irreversible capacity rate. The irreversible capacity rate of the negative electrode precursor or negative electrode is preferably 5% or more and 50% or less. If the irreversible capacity rate is 5% or more and 50% or less, the alkali metal that cannot be effectively used for charging and discharging the energy storage element due to the irreversible capacity of the negative electrode precursor or negative electrode can be supplied from the alkali metal carbonate or pre-dope material, thereby reducing the initial resistance.

[0166] Examples of methods for preparing a negative electrode with an irreversible capacity of 5% or more and 50% or less include a method of using a material with a high irreversible capacity ratio as an active material; a method of mixing a material with a high irreversible capacity ratio with a material with a low irreversible capacity ratio and adjusting the mixing ratio. Examples of materials with a high irreversible capacity ratio include the alloy-based negative electrode materials described in <Negative electrode, negative electrode precursor> (alloy-based negative electrode material) and the carbon materials described in <Negative electrode, negative electrode precursor> (carbon material), such as carbon black; carbon nanoparticles; activated carbon; graphitized mesophase carbon microspheres; graphite whiskers; amorphous carbonaceous materials such as polyacene-based substances; carbonaceous materials obtained by heat-treating carbonaceous material precursors such as petroleum-based pitch, coal-based pitch, mesocarbon microbeads, coke, and synthetic resins (e.g., phenolic resins); pyrolysis products of furfuryl alcohol resins or novolac resins; fullerenes; carbon nanophones; and composite carbon materials thereof. Examples of materials with low irreversible capacity include artificial graphite and natural graphite among the carbon materials described in the section <Negative electrode, negative electrode precursor> (carbon material).

[0167] (Irreversible capacity rate and irreversible capacity G of negative electrode precursor １The irreversible capacity rate of the negative electrode precursor is determined by the following method. A single-sided negative electrode comprising a negative electrode active material, a binder, and, if necessary, a conductive material is produced using a known process for producing an electrode for a non-aqueous alkali metal storage element. A negative electrode half-cell comprising an alkali metal counter electrode, an alkali metal reference electrode, an electrolyte solution described below, and a known separator is discharged at a constant current of 0.1 C rate to 0.01 V relative to the alkali metal reference electrode in a 25°C environment, and then discharged at a constant voltage of 0.02 C rate until the current converges. The discharge capacity (mAh) is measured, and the area (cm2) of the coated portion of the single-sided negative electrode precursor is calculated. ２ ) to obtain the initial storage capacity H of the alkali metal. １ (mAh / cm ２ After the completion of the constant voltage discharge at 0.01 V, a 10-minute pause was allowed, and then the battery was charged at a constant current of 0.1 C rate up to 2.5 V. The charge capacity (mAh) was measured, and the area of ​​the coated portion of the single-sided negative electrode precursor (cm ２ ) to obtain the initial release capacity H of the alkali metal. ２ (mAh / cm ２ The irreversible capacity rate Q (%) of the negative electrode precursor is obtained by the following formula: Q = (H １ -H ２ ) / H1 × 100 Irreversible capacity G of negative electrode precursor １ (mAh / cm ２ ) is obtained from the following formula: １ = H １ -H ２

[0168] (Negative electrode irreversible capacity rate and negative electrode irreversible capacity G １ The irreversible capacity rate of the negative electrode can be calculated by the following method (1) or (2).

[0169] (1) Method of calculation from negative electrode precursor The negative electrode is the negative electrode of an alkali metal storage element completed through an initial charging step. However, when a negative electrode before the initial charging step, i.e., a negative electrode precursor, is obtained, the irreversible capacity Q (%) and the irreversible capacity G are calculated by the method described above (Calculation of the irreversible capacity rate of the negative electrode precursor). １ (mAh / cm ２ ) can be calculated.

[0170] (2) Method of calculating from the negative electrode: The completed alkali metal storage element after the initial charging process is charged at a constant current of 0.1 C in a thermostatic chamber set at 25 ° C until the stable operating voltage upper limit is reached, followed by 30 minutes of constant voltage charging at a constant voltage equal to the stable operating voltage upper limit. The storage element is then disassembled in an argon box, the negative electrode is removed, and in the case of a double-sided negative electrode, the active material layer on one side is removed using a spatula or the like to create a single-sided negative electrode, which is then reassembled into a negative electrode half cell using an alkali metal counter electrode, an alkali metal reference electrode, and a glass filter separator. Based on the capacity of the negative electrode half cell, the cell is charged at a constant current of 0.1 C to 2.5 V, then, after a 10-minute pause, discharged at a constant current of 0.1 C to 0.01 V relative to the alkali metal reference electrode, and then discharged at a constant voltage until the current converges to a rate of 0.02 C. After that, after a 10-minute rest, the battery was charged at a constant current of 0.1 C up to 2.5 V, and the charge capacity (mAh) was measured. The area of ​​the coated part of the negative electrode on one side (cm ２ ) to obtain the reversible release capacity H1 (mAh / cm ２ ) is obtained.

[0171] Meanwhile, the completed alkali metal storage element after the initial charging process is subjected to constant-current charging at a current value of 0.1 C in a thermostatic chamber set at 25°C until the stable operating voltage upper limit is reached, followed by 30 minutes of constant-voltage charging at a constant voltage equal to the stable operating voltage upper limit. The storage element is then disassembled in an argon box, the negative electrode is removed, and in the case of a double-sided negative electrode, the active material layer on one side is peeled off using a spatula or the like to create a single-sided negative electrode, which is then reassembled into a negative electrode half-cell using an alkali metal counter electrode, an alkali metal reference electrode, and a glass filter as a separator. Based on the capacity of the negative electrode half-cell, the negative electrode half-cell is then disassembled in an argon box, and the negative electrode is removed. The procedure of "immersing the negative electrode in an electrolyte for alkali metal storage elements, minus the electrolyte and additives, i.e., the electrolyte solvent alone, and then removing the washing solvent" is repeated three times. The negative electrode is then immersed in an electrolyte solution for alkali metal storage elements, minus the electrolyte and additives, i.e., the electrolyte solvent alone. The negative electrode is then removed and vacuum dried at 25°C for 12 hours. This results in a negative electrode in which the alkali metal ions in the electrolyte solution have been removed, while the alkali metal equivalent to the irreversible capacity remains in the negative electrode. The negative electrode active material layer is then scraped off, and the negative electrode is subjected to acid decomposition using a strong acid, such as concentrated nitric acid, concentrated hydrochloric acid, or aqua regia. The resulting solution is diluted with pure water to an acid concentration of 2% to 3%. Acid decomposition can also be performed by heating and pressurization as appropriate. The resulting diluted solution is analyzed by ICP-MS, but it is preferable to add a known amount of alkali metal as an internal standard. If the alkali metal concentration to be measured exceeds the upper limit of measurement, it is preferable to further dilute the diluted solution while maintaining the acid concentration. The amount of alkali metal (g) is quantified based on a calibration curve prepared in advance using a standard solution for chemical analysis, and the amount of alkali metal M (g / cm) equivalent to the irreversible capacity contained per coated area of ​​the single-sided negative electrode is calculated. ２ The irreversible capacity G contained per coated area of ​​the single-sided negative electrode is calculated using the atomic weight m of the alkali metal. １ (mAh / cm ２ ) is G １ In this case, the irreversible capacity rate Q (%) of the negative electrode is calculated by the following formula: Q=G １ / (H１ +G １ ) x 100

[0172] <Separator> In the first embodiment, the positive electrode precursor and the negative electrode are generally stacked or wound with a separator interposed therebetween to form an electrode laminate or an electrode wound body having the positive electrode precursor, the negative electrode, and the separator. In the second embodiment, the positive electrode and the negative electrode are stacked or wound with a separator interposed therebetween to form an electrode laminate or an electrode wound body having the positive electrode, the negative electrode, and the separator.

[0173] In the first and second embodiments, the separator may be a known separator used in nonaqueous alkali metal storage elements. For example, a polyethylene microporous membrane or a polypropylene microporous membrane, or a cellulose nonwoven paper used in electric double layer capacitors, etc., may be used. A membrane composed of organic or inorganic fine particles may be laminated on one or both sides of these separators. Furthermore, the separator may contain organic or inorganic fine particles.

[0174] In the first and second embodiments, the thickness of the separator is not particularly limited, but is preferably 5 μm or more and 35 μm or less. A separator thickness of 5 μm or more is preferred because it tends to reduce self-discharge due to internal micro-short circuits. A separator thickness of 35 μm or less is preferred because it tends to improve the output characteristics of the nonaqueous alkali metal type energy storage element.

[0175] In the first and second embodiments, the thickness of the film made of organic or inorganic fine particles is preferably 1 μm or more and 10 μm or less. A film made of organic or inorganic fine particles having a thickness of 1 μm or more is preferred because it tends to reduce self-discharge due to internal micro-short circuits. A film made of organic or inorganic fine particles having a thickness of 10 μm or less is preferred because it tends to improve the output characteristics of a non-aqueous alkaline metal storage battery. The film made of organic or inorganic fine particles may be the same layer as the intermediate layer in the first and second embodiments, or may be a different layer.

[0176] In the first and second embodiments, the separator may contain an organic polymer that swells upon penetration of a non-aqueous electrolyte solution, or an organic polymer may be used alone as a separator. The organic polymer is not particularly limited, but is preferably one that has good affinity with a non-aqueous electrolyte solution and gels upon penetration and swelling of the electrolyte solution. Suitable organic polymers include, for example, polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, and mixtures thereof, which exhibit high alkali metal ion conductivity upon gelation.

[0177] The organic polymer can encapsulate the electrolyte solution within the organic polymer, which is advantageous from the viewpoint of safety because it has the effect of preventing the electrolyte solution from leaking out of the nonaqueous alkali metal storage element when the exterior body is damaged.

[0178] (Intermediate layer) In the first and second embodiments, the separator may have the intermediate layer on the surface facing the positive electrode. Detailed features are as described in the section on intermediate layer.

[0179] <K １ / K ３ In the second embodiment, the discharge capacity of a positive electrode half cell using a positive electrode removed from a battery before capacity recovery, or using a positive electrode and an intermediate layer if an intermediate layer is present, is calculated as K １ (mAh / cm ２ ) and the discharge capacity of the negative electrode half-cell taken out from the battery before capacity recovery was K ３ (mAh / cm ２ ), preferably 0.80≦K １ / K ３ ≦1.2, more preferably 0.85≦K １ / K ３ ≦1.2. 0.80≦K １ / K ３ If the ratio is ≦1.2, a high capacity recovery effect and a high capacity density of the initial non-aqueous alkali metal storage element can be obtained. Here, the voltage of the negative electrode half cell is obtained based on the alkali metal.

[0180] <Non-aqueous Electrolyte> The non-aqueous electrolyte solution contains an accelerator. By including an accelerator in the non-aqueous electrolyte solution, the decomposition reaction of the alkali metal carbonate contained in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or both, proceeds efficiently in the pre-doping step of the first embodiment and the capacity recovery step of the second embodiment. While not necessarily limited by theory, it is believed that the accelerator mediates electronic conduction between the positive electrode active material of the alkali metal ion battery and the alkali metal carbonate, thereby promoting the decomposition of the alkali metal carbonate, which has extremely low electrical conductivity, in the alkali metal ion battery. In the second embodiment, the accelerator may be introduced into the battery before capacity recovery during a liquid injection step before the initial charging step. Alternatively, after using and deteriorating the battery before capacity recovery, the exterior may be opened and the accelerator or a non-aqueous electrolyte solution containing the accelerator may be added to the battery before the capacity recovery step.

[0181] (Oxidation Onset Potential of Accelerator) In the first embodiment of the present disclosure, the oxidation onset potential of the accelerator is 3.8 V or more and 4.8 V or less (vs. Li / Li ＋ ). This allows the decomposition reaction of the alkali metal carbonate contained in the positive electrode active material layer or the intermediate layer between the positive electrode active material layer and the separator to proceed efficiently in the pre-doping step. If the oxidation onset potential of the accelerator is 3.8 V or higher, the initial charging step of the alkali metal ion battery can proceed smoothly, and the decomposition of the alkali metal carbonate proceeds effectively, which is preferable in that a non-aqueous alkali metal storage element such as an alkali metal ion battery can be manufactured without any problems. On the other hand, if the oxidation onset potential of the accelerator is less than 3.8 V, the voltage of the alkali metal ion battery does not increase sufficiently in the initial charging step, making it impossible to manufacture the battery, or the decomposition reaction of the alkali metal carbonate does not proceed sufficiently in the initial charging step, which is not preferable. The oxidation onset potential of the accelerator is 4.8 V or lower (vs. Li / Li ＋ ) is preferable because it is possible to proceed with the decomposition of the alkali metal carbonate and the doping reaction to the negative electrode even if the voltage at the time of initial charge is lowered.

[0182] The lower limit of the oxidation onset potential is preferably 3.9 V, more preferably 4.0 V. The upper limit of the oxidation onset potential is preferably 4.7 V, more preferably 4.6 V.

[0183] (Oxidation onset potential of accelerator) The oxidation onset potential of the accelerator of the second embodiment is equal to or higher than the stable operating potential of the positive electrode active material and equal to or lower than 4.8 V (vs. Li / Li ＋ This allows the decomposition reaction of the alkali metal carbonate contained in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or in both of them, to proceed efficiently in the capacity recovery step.

[0184] If the oxidation onset potential of the accelerator is equal to or higher than the stable operating potential of the positive electrode active material, the decomposition of the alkali metal carbonate can be suppressed even when the alkali metal ion battery is used at a stable operating voltage or lower of the positive electrode active material after the initial manufacture, thereby enhancing the capacity recovery effect. On the other hand, if the oxidation onset potential of the accelerator is lower than the stable operating potential of the positive electrode active material, the alkali metal carbonate may decompose during the initial charging step and during use of the alkali metal ion battery when the potential of the positive electrode reaches a value equal to or higher than the oxidation onset potential of the accelerator but lower than the stable operating potential of the positive electrode active material, and the recovery effect in the capacity recovery step may not be sufficiently obtained. If the oxidation onset potential of the accelerator is 4.8 V (vs. Li / Li ＋ ) or less, the alkali metal carbonate is sufficiently decomposed in the capacity recovery step, and a high capacity recovery effect can be obtained. The lower limit of the oxidation onset potential of the promoter is preferably 0.3 V or more of the stable operating potential of the positive electrode active material, more preferably 0.2 V or more of the stable operating potential of the positive electrode active material, and particularly preferably 0.1 V or more of the stable operating potential of the positive electrode active material. The upper limit of the oxidation onset potential of the promoter is preferably 4.7 V (vs Li / Li ＋ ) or less, more preferably 4.6 V (vs Li / Li ＋ ) below.

[0185] (Measurement of Oxidation Onset Potential of Accelerator) The oxidation onset potential of the accelerator of the first and second embodiments may vary depending on the positive electrode active material layer used in the alkali metal ion battery. Therefore, it is preferable to measure the oxidation onset potential using a positive electrode of a nonaqueous alkali metal storage element that actually uses the accelerator. For details, it is preferable to measure the oxidation onset potential using the method described in the Examples. In the present disclosure, the oxidation onset potential of the accelerator is the potential relative to a lithium reference electrode (V vs. Li / Li+) measured by the following method.

[0186] In this specification, the oxidation onset potential of the accelerator of the first and second embodiments is obtained by the following method. A positive electrode precursor 1 containing an active material and, as optional components, a conductive material carbon black and a binder, but not containing an alkali metal carbonate, is prepared. 炭酸Ｌｉなし As illustrated in FIGS. 1 and 2, a positive electrode precursor 1 炭酸Ｌｉなし The coated area (black area in Figure 1) is defined as the area S (cm ２ ) and combined with a negative electrode (2), a separator (3) and a lithium reference electrode (4), and sealed in a laminate to prepare non-aqueous alkali metal storage element precursors 1 and 2 before injection.

[0187] Non-aqueous electrolyte solution 1 containing an accelerator is injected into non-aqueous alkali metal storage element precursor 1 before injection, and non-aqueous electrolyte solution 2 not containing an accelerator is injected into non-aqueous alkali metal storage element precursor 2 before injection, and the laminate is sealed to obtain non-aqueous alkali metal storage element precursors 1 and 2. This is then charged at a constant current of 0.1 C in a thermostatic chamber set at 45°C until a voltage of 4.8 V is reached. At this time, the positive electrode potential relative to the lithium reference electrode is simultaneously measured. From the above measurements, the positive electrode potential (V vs Li / Li) relative to the capacity per weight of positive electrode active material (mAh / g of positive electrode active material) for non-aqueous alkali metal storage element precursors 1 and 2 is ＋ ) are plotted to obtain curves 1 and 2. Next, the oxidation onset potential is calculated using the following method A or B.

[0188] A. When the positive electrode potential of the nonaqueous alkali metal storage element precursor 1 is charged to a range of 3.7 V or higher, the point at which the positive electrode potential reaches 3.7 V is set as the starting point for calculating the capacity (0 mAh / g of positive electrode active material), and curves 1 and 2 are shifted in parallel to calculate the difference in capacity by weight of the positive electrode active material (curve 1 - curve 2) at the same positive electrode potential. The positive electrode potential at which the capacity difference between curves 1 and 2 exceeds 5 mAh / g is determined to be the oxidation onset potential of the accelerator. Graphs for calculating the difference curve (curve 1 - curve 2) at the same positive electrode potential and the oxidation onset potential of the accelerator using method A are shown in FIGS. 3 and 4.

[0189] B. When the positive electrode potential of the nonaqueous alkali metal storage element precursor 1 is charged to a range of 3.7 V or higher, the starting point of charge is set as the starting point for calculating the capacity (0 mAh / g of positive electrode active material), and curves 1 and 2 are shifted in parallel to calculate the difference in capacity by weight of the positive electrode active material (curve 1 - curve 2) at the same positive electrode potential. The positive electrode potential at which the capacity difference between curves 1 and 2 exceeds 5 mAh / g is determined to be the oxidation onset potential of the accelerator. Graphs for calculating the difference curve (curve 1 - curve 2) at the same positive electrode potential and the oxidation onset potential of the accelerator using method B are shown in FIGS. 5 and 6.

[0190] (Type of Accelerator) The non-aqueous electrolyte preferably contains at least one accelerator selected from the group consisting of methoxybenzene derivatives, phenyl-containing organic compounds, TEMPO derivatives, pyridine-N-oxide derivatives, and cyclohexylbenzene derivatives. When the electrolyte contains these accelerators, the decomposition reaction of the alkali metal carbonate contained in the positive electrode active material layer or in any intermediate layer between the positive electrode active material layer and the separator proceeds efficiently in the pre-doping step of the first embodiment of the present disclosure or the capacity recovery step of the second embodiment of the present disclosure. As described above, the oxidation onset potential of the accelerator of the first embodiment of the present disclosure is equal to or higher than the stable operating potential of the positive electrode active material and equal to or lower than 4.8 V (vs Li / Li ＋ The oxidation onset potential of the accelerator according to the second embodiment of the present disclosure is preferably equal to or higher than the stable operating potential of the positive electrode active material and equal to or lower than 4.8 V (vs. Li / Li ＋ ) is preferred.

[0191] From the viewpoint of the decomposition efficiency of the alkali metal carbonate, the accelerator is preferably a methoxybenzene derivative and / or a phenyl group-containing organic compound.

[0192] The methoxybenzene derivative is not particularly limited, but examples thereof include anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene (also known as 1,4-ditert-butyl-2,5-dimethoxybenzene), and the like.

[0193] The phenyl group-containing organic compound is not particularly limited, but examples thereof include biphenyl, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, etc. In one embodiment, the phenyl group-containing organic compound is preferably one other than biphenyl.

[0194] The TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl) derivative is not particularly limited, but examples thereof include TEMPO, 4-methoxy-TEMPO, and 4-oxo-TEMPO.

[0195] The pyridine-N-oxide derivative is not particularly limited, but examples thereof include pyridine-N-oxide, 4-picoline-N-oxide (also known as 4-methylpyridine N-oxide), and 4-tert-butylpyridine-N-oxide, with pyridine-N-oxide and 4-picoline-N-oxide being particularly preferred.

[0196] (Accelerator Content) The accelerator content is preferably 0.1 mmol / L (0.0001 mol / L) or more and 1.5 mol / L or less, based on the volume of the non-aqueous electrolyte. If the accelerator content is 0.1 mmol / L or more, the decomposition promotion effect of the alkali metal carbonate is obtained in the first and second embodiments. Furthermore, in the second embodiment, a capacity recovery effect due to the decomposition of the alkali metal carbonate is obtained. If the accelerator content is 1.5 mol / L or less, the ionic conductivity of the electrolyte can be kept low, thereby reducing the overvoltage during pre-doping. In the first embodiment, a sufficient alkali metal carbonate decomposition promotion effect and a high effective utilization rate of the positive electrode active material are obtained, which is preferable from the viewpoints of resistance and gas swelling during high-temperature storage. Furthermore, in the second embodiment, a capacity recovery effect due to the decomposition of the alkali metal carbonate is obtained. Furthermore, a promotion effect and a high effective utilization rate of the positive electrode active material are obtained, which is preferable.

[0197] The lower limit of the promoter content is preferably 0.01 mol / L or more, more preferably 0.05 mol / L or more, and the upper limit of the promoter content is preferably 0.5 mol / L or less, more preferably 0.3 mol / L or less.

[0198] Furthermore, if the desired concentration cannot be completely dissolved in the electrolyte, the insoluble matter may dissolve and function when the promoter is consumed in the pre-doping of the first embodiment or the capacity recovery of the second embodiment, so the promoter may be injected together with the insoluble matter.

[0199] (Qualitative and quantitative analysis of accelerator) In the first and second embodiments, the accelerator contained in the electrolyte solution of the nonaqueous alkali metal energy storage element can be identified and quantified by extracting the electrolyte solution from the completed energy storage element and using known qualitative and quantitative analysis (e.g., H-NMR).

[0200] In the first and second embodiments, the oxidation onset potential of the accelerator can be measured by identifying and quantifying the accelerator, which may be contained in the completed nonaqueous alkali metal energy storage element, using a known qualitative and quantitative analysis (e.g., H-NMR), and then separately measuring the oxidation onset potential by the method described above (Measurement of the oxidation onset potential of the accelerator).

[0201] (Electrolyte, Solvent, Additive) The electrolyte in the first and second embodiments is a non-aqueous electrolyte containing alkali metal ions such as alkali metal ions, and any known electrolyte for alkali metal ion batteries can be used for materials other than the accelerator. That is, this non-aqueous electrolyte contains a non-aqueous solvent described below. The non-aqueous electrolyte preferably contains an alkali metal salt such as an alkali metal salt at a concentration of 0.5 mol / L or more based on the total volume of the non-aqueous electrolyte. Therefore, the non-aqueous electrolyte contains alkali metal ions such as alkali metal ions as an electrolyte. The alkali metal salt used as the electrolyte is preferably a lithium salt, a sodium salt, or the like.

[0202] In the first and second embodiments, the lithium salt may be, for example, (LiN(SO ２ F) ２ ), LiN(SO ２ CF ３ ) ２ , LiN(SO ２ C ２ F ５ ) ２ , LiN(SO ２ CF ３ ) (SO ２ C ２ F ５ ), LiN(SO ２ CF ３ ) (SO ２ C ２ F ４ H), LiC(SO ２ F) ３ , LiC(SO ２ CF ３ ) ３ , LiC(SO ２ C ２ F ５ ) ３ , LiCF ３ SO ３ , LiC ４ F ９ SO ３ , LiPF ６ , LiCiO4 and LiBF ４ These can be used alone or in combination of two or more. The alkali metal salt LiPF６ and preferably further contains LiN(SO ２ F) ２ may include:

[0203] In the first and second embodiments, examples of sodium salts include Na(SO ２ CF ３ ) ２ , NaN(SO ２ F) ２ , NaN(C ２ F ５ SO ２ ) ２ , NaCF ３ SO ３ , NaC(CF ３ SO ２ ) ３ , NaPF ６ , NaBF ４ , NaClO ４ , NaAsF ６ , NaAlCl ４ These can be used alone or in combination of two or more. For example, NaClO ４ , NaPF ６ and / or NaN(SO ２ CF ３ ) ２ It is preferred that the compound contains:

[0204] In the first and second embodiments, the alkali metal salt concentration in the nonaqueous electrolyte is preferably 0.5 mol / L or more, and more preferably in the range of 0.5 to 2.0 mol / L. If the alkali metal salt concentration is 0.5 mol / L or more, sufficient anions are present, allowing the battery capacity to be sufficiently high. If the alkali metal salt concentration is 2.0 mol / L or less, this is preferable because it can prevent undissolved alkali metal salt from precipitating in the nonaqueous electrolyte and the viscosity of the nonaqueous electrolyte from becoming too high, making it difficult for the conductivity to decrease and the output characteristics to decrease.

[0205] The nonaqueous electrolyte solution in the first and second embodiments can contain a carbonate solvent as a nonaqueous solvent, and preferably contains a cyclic carbonate and a chain carbonate. The nonaqueous electrolyte solution containing a cyclic carbonate and a chain carbonate is advantageous in that it can dissolve an alkali metal salt at a desired concentration and exhibit high ionic conductivity. Examples of cyclic carbonates include alkylene carbonate compounds such as ethylene carbonate, propylene carbonate, and butylene carbonate. The alkylene carbonate compound is typically unsubstituted. Examples of chain carbonates include dialkyl carbonate compounds such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, and dibutyl carbonate. The dialkyl carbonate compound is typically unsubstituted. The solvent may be used alone, or two or more may be mixed in any ratio.

[0206] In the first and second embodiments, the total content of the cyclic carbonate and the chain carbonate is, based on the total mass of the non-aqueous electrolyte solution, preferably 50% by mass or more, more preferably 65% ​​by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less. If the total content of the cyclic carbonate and the chain carbonate is 50% by mass or more, it is possible to dissolve the alkali metal salt at a desired concentration, and high ionic conductivity can be achieved. If the total concentration of the cyclic carbonate and the chain carbonate is 95% by mass or less, the electrolyte solution can further contain the additives described below.

[0207] The nonaqueous electrolyte solution in the first and second embodiments may further contain an additive. The additive is not particularly limited, but examples thereof include sultone compounds, cyclic phosphazenes, acyclic fluorine-containing ethers, fluorine-containing cyclic carbonates, cyclic carbonates such as vinylene carbonate, cyclic carboxylic acid esters, and cyclic acid anhydrides. These additives may be used alone or in combination of two or more. These additives form a good coating on the positive electrode or negative electrode, improving the durability of the alkali metal ion battery.

[0208] <Gas Permeation Mechanism> In the second embodiment, in the capacity recovery process described later, CO ２ Therefore, it is preferable that the exterior body of the nonaqueous alkali metal storage element is provided with a gas permeation mechanism that can release the gas generated when a voltage is applied in the capacity recovery step to the outside of the exterior body. The gas permeation mechanism allows gas generated by the oxidative decomposition of the alkali metal compound to escape, thereby further enhancing the capacity recovery effect.

[0209] In the second embodiment, examples of the gas permeation mechanism include a mechanism that allows a portion of the exterior body to be opened and resealed after the capacity recovery process; a gas vent valve, a gas permeable film, a gas-permeable rubber, a gas check valve (a valve that allows gas to pass only in one direction from the inside to the outside of the nonaqueous alkali metal energy storage element), or other appropriate gas release means that are pre-installed in a portion of the exterior body. The gas release means, such as the gas vent valve, the gas permeable film, the gas-permeable rubber, and the gas check valve, are not particularly limited, and known gas permeation mechanisms can be used. Having a gas permeation mechanism such as a gas check valve enables the capacity recovery process, described below, to be performed in a general environment, not a low-dew-point environment, without excessive disassembly of the battery pack of the nonaqueous alkali metal energy storage element, and is therefore preferred from the perspective of ease of designing the capacity recovery process.

[0210] <Manufacturing Method> <Manufacturing Method for Non-Aqueous Alkali Metal Storage Element> The non-aqueous alkali metal storage element in the first embodiment of the present invention can be manufactured by the following method using the positive electrode precursor and negative electrode formed as described above: (1) housing a laminate composed of a positive electrode precursor, a negative electrode, and a separator in an outer casing (cell assembly), (2) injecting a non-aqueous electrolyte solution into the outer casing (electrolyte solution injection), and (3) applying a voltage between the positive electrode precursor and the negative electrode to decompose the alkali metal compound (pre-doping), in the order described above.

[0211] A method for producing a nonaqueous alkali metal storage element (pre-capacity-restored battery) according to a second embodiment of the present disclosure includes the steps of preparing a positive electrode coating liquid; obtaining a positive electrode; producing a negative electrode; fabricating an electrode stack or an electrode wound body from the positive electrode and the negative electrode; housing the electrode stack or the electrode wound body in an outer casing and injecting a nonaqueous electrolyte solution; and an initial charging step. The method for producing a pre-capacity-restored battery may optionally include an aging step and a degassing step. The steps of obtaining a positive electrode and producing a negative electrode are described elsewhere in this specification.

[0212] (Assembly) In the cell assembly of the first embodiment, a positive electrode terminal and a negative electrode terminal are connected to a laminate formed by stacking a positive electrode precursor and a negative electrode cut into a sheet shape with a separator interposed therebetween to produce an electrode laminate. Alternatively, a positive electrode terminal and a negative electrode terminal are connected to a wound body formed by stacking and winding a positive electrode precursor and a negative electrode with a separator interposed therebetween to produce an electrode wound body. The electrode wound body may be cylindrical or flat. In the assembly process of the second embodiment, for example, an electrode laminate may be produced by connecting a positive electrode terminal and a negative electrode terminal to a laminate formed by stacking a positive electrode and a negative electrode cut into a sheet shape with a separator interposed therebetween. Alternatively, an electrode wound body may be produced by connecting a positive electrode terminal and a negative electrode terminal to a wound body formed by stacking and winding a positive electrode and a negative electrode with a separator interposed therebetween. The electrode wound body may be cylindrical or flat.

[0213] In the first and second embodiments, the method for connecting the positive electrode terminal and the negative electrode terminal is not particularly limited, but can be performed by resistance welding, ultrasonic welding, or the like.

[0214] (Drying of Electrodes) In the first and second embodiments, it is preferable to remove the remaining solvent by drying the electrode state before assembly or the electrode body (electrode stack or electrode wound body) after assembly. Drying may also be performed after housing in an outer casing, which will be described later. The drying method is not limited, and drying by vacuum drying or the like is possible. The remaining solvent and moisture content is preferably 1.5 mass % or less based on the mass of the positive electrode active material layer or the negative electrode active material layer. If the remaining solvent content is more than 1.5 mass %, the solvent will remain in the system, which may deteriorate the self-discharge characteristics and cycle characteristics, and is therefore not preferable.

[0215] (Exterior Body) In the first and second embodiments, a metal can, a laminated packaging material, or the like can be used as the exterior body. The metal can is preferably made of aluminum. The metal can may be, for example, rectangular, round, or cylindrical. The laminated packaging material is preferably a film formed by laminating a metal foil and a resin film, and an example of such a laminated packaging material is a three-layer structure consisting of an outer resin film, a metal foil, and an interior resin film. The outer resin film is intended to prevent damage to the metal foil due to contact or the like, and resins such as nylon or polyester can be suitably used. The metal foil is intended to prevent permeation of moisture and gas, and foils such as copper, aluminum, and stainless steel can be suitably used. The interior resin film protects the metal foil from the electrolyte solution stored therein and melt-seals the exterior body when it is heat-sealed, and polyolefins, acid-modified polyolefins, and the like can be suitably used.

[0216] (Storage in an Exterior Body) In the first and second embodiments, the dried electrode stack or electrode wound body is preferably stored in an exterior body, such as a metal can or a laminate packaging material, in a dry environment, preferably with a dew point of −40° C. or less, and is preferably sealed except for one opening for injecting a non-aqueous electrolyte solution. A dew point of −40° C. or less is preferable because it can prevent moisture from adhering to the electrode body and remaining in the system, thereby improving self-discharge characteristics. There are no particular limitations on the method for sealing the exterior body, but when a laminate packaging material is used, methods such as heat sealing or impulse sealing can be used.

[0217] (Drying) In the first and second embodiments, the electrode stack or electrode wound body housed in the outer casing is preferably dried to remove any remaining electrode slurry solvent and moisture. The drying method is not limited, but vacuum drying or the like can be used. The amount of residual solvent and moisture is preferably 1.5 mass % or less, based on the mass of the positive electrode active material layer or the negative electrode active material layer. Residual solvent exceeding 1.5 mass % is undesirable because the solvent remains in the system, which may deteriorate the self-discharge characteristics and cycle characteristics.

[0218] (Injection, Impregnation, Sealing) In the first and second embodiments, after assembly, a non-aqueous electrolyte solution is injected into the electrode stack housed in the outer casing. After the injection, it is desirable to further perform impregnation so that the positive electrode, negative electrode, and separator are sufficiently immersed in the non-aqueous electrolyte solution. The impregnation method is not particularly limited, and for example, after the non-aqueous electrolyte solution is injected, the electrode stack is placed in a decompression chamber with the outer casing open, and the pressure in the chamber is reduced using a vacuum pump, and then returned to atmospheric pressure. After the impregnation, the electrode stack can be sealed by decompressing the electrode stack with the outer casing open. In the first embodiment, if at least a portion of the positive electrode, negative electrode, and separator is not immersed in the non-aqueous electrolyte solution, the pre-doping described below will proceed unevenly, resulting in increased resistance and reduced durability of the resulting non-aqueous alkali metal storage element.

[0219] (Pre-doping) In the first embodiment, the alkali metal carbonate functions as a doping source of alkali metal ions into the negative electrode active material. In the pre-doping, a voltage is applied between the positive electrode precursor and the negative electrode to decompose the alkali metal carbonate and release alkali metal ions, and the alkali metal ions are pre-doped into the negative electrode active material. The pre-doping can be performed at any step from the injection step to the step before degassing, and is preferably performed during the initial charge step from the viewpoint of the efficiency of the manufacturing process.

[0220] In the first embodiment, the ultimate potential of the positive electrode precursor is 4.15 to 4.75 V (vs. Li / Li ＋In this range, the alkali metal carbonate can be decomposed and the alkali metal ions can be doped into the negative electrode active material while minimizing damage to the positive electrode and the electrolyte, thereby suppressing the loss of the positive electrode active material due to irreversible capacity and increasing the effective utilization rate of the positive electrode active material.

[0221] In the method for producing a nonaqueous alkali metal storage element according to the first embodiment of the present disclosure, when the alkali metal is lithium, the voltage applied between the positive electrode precursor and the negative electrode precursor during pre-doping is preferably 4.1 V or more and 4.6 V or less. The applied voltage can be appropriately adjusted taking into consideration the voltage tolerance of the electrolyte solution and the positive electrode active material used, and is more preferably 4.2 V or more and less than 4.5 V.

[0222] When the alkali metal is lithium, applying a voltage of 4.1 V or more and 4.6 V or less between the positive electrode precursor and the negative electrode precursor of the nonaqueous alkali metal storage element precursor can obtain the pre-doping effect while avoiding damage to the positive electrode active material and the electrolyte, which is preferable from the viewpoints of positive electrode utilization rate and resistance, gas generation during high-temperature storage, etc. In this embodiment, the use of an electrolyte containing the above-mentioned accelerator makes it possible to decompose the alkali metal carbonate at such a relatively low voltage.

[0223] When the alkali metal is lithium, the method of voltage application is not particularly limited, and examples that can be used include a method of charging to a voltage of 4.1 V or higher using a charge / discharge device, a power source, or the like; a method of superimposing a pulse voltage while applying a constant voltage of 4.1 V or higher; and a method of performing a charge / discharge cycle using a charge / discharge device within a voltage range that includes a voltage of 4.1 V or higher.

[0224] In the manufacturing method of the nonaqueous alkali metal storage element of the present disclosure, when the alkali metal is sodium, the voltage applied between the positive electrode precursor and the negative electrode during pre-doping can be appropriately adjusted taking into consideration the voltage tolerance of the electrolyte solution and the positive electrode active material used, and is preferably 3.8 V or more and 4.3 V or less. The lower limit of the applied voltage is more preferably 3.9 V or more, and even more preferably 4.0 V or more, and the upper limit of the applied voltage is more preferably 4.2 V or less, and even more preferably 4.15 V or less.

[0225] When the alkali metal is sodium, applying a voltage of 3.8 V or more and 4.3 V or less between the positive electrode precursor and the negative electrode can obtain the pre-doping effect while avoiding damage to the positive electrode active material and the electrolyte, which is preferable from the viewpoints of positive electrode utilization rate and resistance, gas generation during high-temperature storage, etc. In the first embodiment, the use of the specific accelerator described above enables decomposition of the alkali metal carbonate at such a relatively low voltage.

[0226] When the alkali metal is sodium, the method of voltage application is not particularly limited, and examples that can be used include a method of charging to a voltage of 3.8 V or higher using a charge / discharge device, a power source, or the like (constant current charging and constant voltage charging may be used in combination); a method of superimposing a pulse voltage while applying a constant voltage of 3.8 V or higher; and a method of performing a charge / discharge cycle using a charge / discharge device within a voltage range that includes a voltage of 3.8 V or higher.

[0227] In the first and second embodiments, the amount of doping from the alkali metal carbonate can be controlled by the temperature, voltage, current, time, etc. during initial charge. In the second embodiment, the decomposition of the alkali metal carbonate during initial charge is suppressed, and the alkali metal carbonate is used as a lithium replenishment source for capacity recovery after deterioration, thereby achieving a capacity recovery effect.

[0228] (Measurement of Potential of Positive Electrode Precursor) The positive electrode potential (vs. Li / Li ＋) is measured by the following method. An electrode assembly consisting of a positive electrode precursor, a negative electrode precursor, and a separator, and an alkali metal reference electrode are sealed in a laminate to prepare a nonaqueous lithium storage element precursor before injection. The alkali metal reference electrode and the electrode assembly are positioned close to each other so that the potential difference between the positive electrode precursor and the alkali metal reference electrode can be measured. If necessary, it is preferable to wrap the alkali metal reference electrode in a separator and bring the separator into contact with the electrode assembly to ensure that the electrolyte passes between the alkali metal reference electrode and the electrode assembly. After the electrolyte is injected, the laminate is sealed. During the initial charging process, a voltage is applied between the positive electrode precursor and the negative electrode precursor, and simultaneously the potential difference between the positive electrode and the alkali metal reference electrode is measured, and the potential of the positive electrode precursor relative to the alkali metal is measured.

[0229] When the alkali metal is lithium, the potential difference X between the positive electrode and the alkali metal reference electrode obtained by the measurement is the positive electrode potential (vs Li / Li ＋ ) and the maximum positive electrode potential during the initial charge is taken as the reached potential.

[0230] When the alkali metal is an alkali metal M other than lithium, the maximum potential difference X (vs M / M) between the positive electrode and the alkali metal reference electrode during the initial charge ＋ For example, when the alkali metal is sodium, the difference in the standard electrode potential between sodium and lithium is 0.33 V, so by adding 0.33 V to the potential difference X obtained against sodium, the positive electrode potential (vs Li / Li ＋ ) is obtained as

[0231] During the pre-doping operation, CO ２ , O ２Gases such as these may be generated. Therefore, when applying a voltage, it is preferable to take measures to release the generated gas to the outside of the "electrode laminate, or electrode wound body, or exterior body." Examples of such measures include a method of applying a voltage with a part of the exterior body opened; a method of applying a voltage with an appropriate gas release means such as a gas vent valve or a gas permeable film previously installed in a part of the exterior body; and a method of storing gas in the excess part of the laminate and then removing the generated gas together with the excess part of the laminate in a subsequent step such as degassing.

[0232] (Initial Charging Step) In the initial charging step, a voltage is applied between the positive electrode and the negative electrode to release alkali metal ions from the alkali metal transition metal compound in the positive electrode, and the alkali metal ions are reduced at the negative electrode, thereby doping the alkali metal ions into the negative electrode active material layer and forming an SEI in the negative electrode.

[0233] In order to maintain the decomposition reactivity of the alkali metal compound, it is preferable not to apply a cell voltage higher than the upper limit of the stable operating voltage in the initial charging step. This allows alkali metal ions generated by the decomposition reaction of the alkali metal compound to be replenished to the negative electrode in the capacity recovery step, resulting in a high capacity recovery effect. If a voltage higher than the upper limit of the stable operating voltage is applied in the initial charging step, the decomposition reaction of the alkali metal compound will proceed, resulting in partial or complete loss of the alkali metal compound, thereby reducing or eliminating the capacity recovery effect in the capacity recovery step. However, as long as the capacity recovery effect is exhibited in the capacity recovery step of the present disclosure, there may be situations in which a voltage higher than the upper limit of the stable operating voltage is applied in the initial charging step. The temperature in the initial charging step is not particularly limited. An initial discharge may be performed after the initial charging step.

[0234] (Aging in First Embodiment) In the first embodiment, it is preferable to perform aging on the electrode laminate after pre-doping. In the aging, the solvent in the nonaqueous electrolyte solution is decomposed at the negative electrode, and an alkali metal ion-permeable solid polymer coating is formed on the surface of the negative electrode.

[0235] The aging method is not particularly limited, but for example, a method of reacting the solvent in the electrolyte in a high-temperature environment can be used.

[0236] (Aging in Second Embodiment) In the first embodiment, after the initial charge, it is preferable to perform aging on the battery before capacity recovery. In the aging step, the solvent in the electrolyte solution decomposes at the negative electrode, and an alkali metal ion-permeable solid polymer coating is formed on the surface of the negative electrode. The aging method is not particularly limited, and for example, a method of reacting the solvent in the electrolyte solution in a high-temperature environment can be used.

[0237] In the second embodiment, in order to maintain the decomposition reactivity of the alkali metal compound, it is preferable not to apply a cell voltage higher than the upper limit of the stable operating voltage during the aging process. This allows alkali metal ions generated by the decomposition reaction of the alkali metal compound to be replenished to the negative electrode during the capacity recovery process, resulting in a high capacity recovery effect. Applying a voltage higher than the upper limit of the stable operating voltage during the aging process accelerates the decomposition reaction of the alkali metal compound, resulting in partial or complete loss of the alkali metal compound, which may reduce or eliminate the capacity recovery effect during the capacity recovery process. However, as long as the capacity recovery effect is exhibited during the capacity recovery process of the present disclosure, there may be situations in which the voltage applied during the aging process is higher than the upper limit of the stable operating voltage. The temperature during the aging process is not particularly limited.

[0238] (Gassing) After aging, it is preferable to perform further gassing to completely remove any remaining gas in the electrolyte, positive electrode, and negative electrode. If gas remains in at least a portion of the electrolyte, positive electrode, and negative electrode, ion conduction is inhibited, resulting in an increase in the resistance of the nonaqueous alkali metal storage element obtained in the first embodiment. Furthermore, an increase in the resistance of the battery before capacity recovery obtained in the second embodiment can be prevented.

[0239] The degassing method is not particularly limited, and may be, for example, a method in which the electrode stack is placed in a decompression chamber with the exterior body open and the chamber is decompressed using a vacuum pump, etc. After degassing, the exterior body is sealed to hermetically close the exterior body, and the nonaqueous alkali metal energy storage element of the first embodiment or the pre-capacity-recovery battery of the second embodiment can be produced.

[0240] <Non-aqueous alkali metal storage element> The non-aqueous alkali metal storage element of the first embodiment can be manufactured by the above method. This non-aqueous alkali metal storage element includes a positive electrode having a positive electrode active material layer in which the alkali metal carbonate contained in the positive electrode precursor has been decomposed, or an intermediate layer in which the alkali metal carbonate has been decomposed, and a negative electrode having an alkali metal-doped negative electrode active material layer. The positive electrode active material layer and / or the intermediate layer may contain alkali metal carbonate that has not been decomposed during pre-doping.

[0241] In nonaqueous alkali metal storage elements, alkali metal is doped into the negative electrode from an alkali metal carbonate as a pre-doping source, enabling more effective utilization of the positive electrode active material, which previously could not function effectively due to the irreversible capacity of the negative electrode. Specifically, the effective utilization rate of the positive electrode active material described below can be increased to 85% or more and 99.5% or less. Therefore, by reducing the amount of positive electrode active material used, it is possible to reduce the cost of the battery. The lower limit of the effective utilization rate of the positive electrode active material is preferably 95% or more.

[0242] The above method can also be used to manufacture a pre-capacity-recovery battery according to the second embodiment. This nonaqueous alkali metal storage element includes a positive electrode having a positive electrode active material layer formed by decomposing the alkali metal carbonate contained in the positive electrode precursor, or an intermediate layer formed by decomposing the alkali metal carbonate, and a negative electrode having an alkali metal-doped negative electrode active material layer. The positive electrode active material layer and / or the intermediate layer contains the alkali metal carbonate that was not decomposed during pre-doping.

[0243] <Various characteristics of alkali metal storage element precursor> (irreversible capacity ratio E １ / D １ and its calculation) The alkali metal storage element precursor of the first embodiment has an irreversible capacity per area of ​​the positive electrode of D １ (mAh / cm ２ ), the irreversible capacity per area of ​​the negative electrode is E １ (mAh / cm ２ ), 1.05<E １ / D １ It is more preferable that 1.10<E１ / D １ This provides a significant effect in terms of reducing the positive electrode loss, maintaining the cycle capacity, preventing micro-short circuits after cycling, and increasing the capacity density per volume. １ (mAh / cm ２ ) is the negative electrode irreversible capacity rate and the negative electrode irreversible capacity G １ The irreversible capacity per area of ​​the positive electrode, D １ (mAh / cm ２ ) can be determined by the following method. １ , initial discharge capacity density L ２ ) The initial charge capacity density L １ (mAh / g) to the initial discharge capacity density L ２ The initial irreversible capacity (mAh / g) of the positive electrode active material is calculated by subtracting the weight (g / m) of the positive electrode active material from the initial irreversible capacity (mAh / g) of the positive electrode active material. ２ ) and divide by 10,000. １ / D １ Calculate.

[0244] (Capacity ratio (A １ +0.3 x B １ ) / C １ and its calculation) The alkali metal storage element precursor of the first embodiment has an initial charge capacity per area of ​​the positive electrode active material of A １ (Ah / cm ２ ), the theoretical capacity per area of ​​the alkali metal carbonate is B １ (Ah / cm ２ ), the initial charge capacity per area of ​​the negative electrode active material is C １ (Ah / cm ２ ), then (A １ +0.3 x B １ ) / C １ It is preferable that the ratio is 0.85≦(A １ +0.3 x B １ ) / C １≦0.98. This provides high effects in terms of doping efficiency per volume, positive electrode utilization rate, resistance, gas swelling during high-temperature storage, reduction of positive electrode loss, cycle capacity retention rate, suppression of micro-short circuiting after cycling, and energy density per volume. Initial charge capacity A per area of ​​the positive electrode active material １ (Ah / cm ２ ) can be calculated by the following method. １ , initial discharge capacity density L ２ ) The initial charge capacity density (mAh / g) of the positive electrode active material obtained by the method described in ) is multiplied by the basis weight (g / m ２ ) and then divided by 10,000,000 to convert the units. １ (Ah / cm ２ ) can be calculated by the following method. １ The initial storage capacity H of the alkali metal described in １ (mAh / cm ２ ) and convert the units to obtain the theoretical capacity B per unit area of ​​alkali metal carbonate. １ (Ah / cm ２ ) can be calculated by the following method. The theoretical capacity (mAh / g) of the alkali metal carbonate is calculated assuming that the oxidative decomposition reaction of the alkali metal carbonate is a two-electron reaction. For example, the theoretical capacity of lithium carbonate is 725 mAh / g, and that of sodium carbonate is 506 mAh / g. The basis weight (g / m) of the alkali metal carbonate is then calculated. ２ ) and then divided by 10,000,000 to convert the units to obtain the theoretical capacity B per area of ​​the alkali metal carbonate. １ (Ah / cm ２ ) can be calculated from these values. １ +0.3 x B １ ) / C １ Calculate.

[0245] <Characteristics of alkali metal storage elements> (Ratio of the positive electrode residual capacity to the negative electrode irreversible capacity F １ / G １ In the alkali metal storage element of the first embodiment, the excess capacity per area of ​​the positive electrode is F １(mAh / cm ２ ), the irreversible capacity per area of ​​the negative electrode is G １ (mAh / cm ２ ) when 0.01<F １ / G １ It is preferable that the E of the precursor is less than 0.9. This provides the effect of reducing the amount of positive electrode loss, the effect of improving the cycle capacity retention rate, the effect of suppressing micro-short circuits after cycle testing, and the effect of improving the capacity density per volume. The upper limit is more preferably 0.8, and even more preferably 0.6. １ / D １ , and (A １ +0.3 x B １ ) / C １ The amount of alkali metal carbonate, the voltage during pre-doping, etc. can be adjusted.

[0246] (Positive electrode excess capacity F １ ) The remaining capacity per area of ​​the positive electrode is F １ (mAh / cm ２ ) is measured by the following method. The completed alkali metal storage element is placed in a thermostatic chamber set at 25°C, and subjected to constant-current discharge at a current value of 0.1 C until the stable operating voltage lower limit is reached. Subsequently, a constant voltage discharge is performed for 30 minutes, applying a constant voltage equal to the stable operating voltage lower limit. The storage element is then disassembled in an argon box, and the positive electrode is removed. In the case of a double-sided positive electrode, the active material layer on one side is peeled off using a spatula or the like to leave a single-sided positive electrode. This is then reassembled into a positive electrode half cell using an alkali metal counter electrode, an alkali metal reference electrode, and a glass filter as a separator. The discharge capacity (mAh) is measured when the element is discharged at a constant current value of 0.1 C until the stable operating voltage lower limit of the positive electrode active material is reached. The area (cm2) of the coated portion of the single-sided positive electrode is then measured. ２ ) to obtain the remaining capacity F of the positive electrode. １ (mAh / cm ２ ) is obtained. As for the lower limit of the stable operating voltage and the lower limit of the stable operating potential, the specific values ​​according to the active material described in (Stable operating potential of the positive electrode and stable operating voltage of the battery according to the positive electrode active material) can be used.

[0247] (Irreversible Capacity G1 of Negative Electrode) The irreversible capacity G1 of the negative electrode is measured by the method described in (Calculation of Negative Electrode Irreversible Capacity Rate and Negative Electrode Irreversible Capacity G1).

[0248] <Characteristics Evaluation of the Non-Aqueous Alkali Metal Energy Storage Element of the First Embodiment> The characteristics of the non-aqueous alkali metal energy storage element of the first embodiment of the present disclosure are evaluated below, but because the operating voltage varies depending on the combination of the positive electrode active material and the negative electrode active material, it is necessary to change the set values ​​for the charge / discharge voltage depending on the non-aqueous alkali metal energy storage element. The charge / discharge voltages in the characteristic evaluation exemplified below are not particularly limited to these.

[0249] (Discharge capacity Q, full cell capacity density P per mass of positive electrode active material ｆｕｌｌ In this specification, the capacity Q (Ah) is a value obtained by the following method: ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ When using as the positive electrode active material, the nonaqueous alkali metal storage element is charged at a constant current of 0.1 C in a thermostatic chamber set at 25°C until the stable operating voltage upper limit, for example, 4.2 V, is reached, followed by 30 minutes of constant voltage charging at a constant voltage of 4.2 V. The electrical capacity when the element is then discharged at a constant current of 0.1 C to the stable operating voltage lower limit, i.e., 3.0 V, is taken as Q (Ah). The full cell capacity density P per mass of the positive electrode active material is calculated by dividing Q by the mass of the positive electrode active material used. ｆｕｌｌ (mAh / g) can be obtained.

[0250] LiFePO ４When the positive electrode active material is used, the nonaqueous alkali metal storage element is charged at a constant current of 0.1 C in a thermostatic chamber set at 25° C. until the stable operating voltage upper limit, for example, 3.6 V, is reached, and then constant voltage charging is performed for 30 minutes by applying a constant voltage of 3.6 V. Thereafter, the element is discharged at a constant current of 0.1 C to the stable operating voltage lower limit, i.e., 2.4 V, and the electric capacity when this is discharged is defined as Q (Ah).

[0251] By dividing Q by the mass of the positive electrode active material used, the full cell capacity density P per mass of the positive electrode active material is obtained. ｆｕｌｌ (mAh / g) can be obtained.

[0252] NaFe １／３ Ni １／３ Mn １／３ O ２ When using as the positive electrode active material, the nonaqueous alkali metal storage element is charged at a constant current of 0.1 C in a thermostatic chamber set at 25°C until the stable operating voltage upper limit, i.e., 3.9 V, is reached, followed by 30 minutes of constant voltage charging at a constant voltage of 3.9 V. The electrical capacity when the element is subsequently discharged at a constant current of 0.1 C to the stable operating voltage lower limit, i.e., 1.9 V, is defined as Q (Ah). The full cell capacity density P per mass of the positive electrode active material is calculated by dividing Q by the mass of the positive electrode active material used. ｆｕｌｌ (mAh / g) can be obtained.

[0253] (Effective utilization rate of positive electrode active material) The above-mentioned "full cell discharge capacity density P per mass of positive electrode active material" ｆｕｌｌ (mAh / g)" is expressed as "initial discharge capacity density L per mass of positive electrode active material" ２ ", the effective utilization rate of the positive electrode active material can be determined. When pre-doping is performed using an alkali metal carbonate, the alkali metal lost due to the irreversible capacity of the negative electrode can be compensated for, thereby increasing the effective utilization rate of the positive electrode active material. The effective utilization rate of the positive electrode active material of a non-aqueous alkali metal storage element is preferably 85% or more and 99.5% or less. When the effective utilization rate of the positive electrode active material is within this range, the loss of the positive electrode active material can be reduced, and the amount of positive electrode active material used can be reduced, which is preferable from the perspective of manufacturing costs. An effective utilization rate of the positive electrode active material of 93% or more is more preferable, and an effective utilization rate of 97% or more is particularly preferable.

[0254] (Reduction in Positive Electrode Active Material Loss) In the first embodiment, the effect of reducing the loss of positive electrode active material due to the irreversible capacity of the negative electrode is achieved. The effective utilization rate a (%) of the positive electrode active material of the alkali metal storage element of the first embodiment is calculated. A separate alkali metal storage element, which has the same basis weight of positive electrode active material and negative electrode active material as the alkali metal storage element of the first embodiment and does not contain carbonate, is initially charged at the upper limit voltage of the "stable operating voltage" corresponding to the positive electrode active material described in (Stable operating potential of positive electrode and stable operating voltage of battery corresponding to positive electrode active material), to produce an alkali metal storage element, and the effective utilization rate b (%) of the positive electrode active material is measured. The reduction in positive electrode active material loss X (%) is calculated by X = a - b. A reduction in positive electrode active material loss of 2% or more is preferable because it reduces the loss of the costly positive electrode active material in the alkali metal storage element. The reduction in the loss of the positive electrode active material is more preferably 12% or more, and particularly preferably 18% or more.

[0255] (Capacity Density) In the first embodiment, the capacity density is measured by the following method. First, the discharge capacity (Q) is calculated as the full cell capacity density P per mass of the positive electrode active material. ｆｕｌｌ The volume is then obtained as follows: ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ When LiFePO is used as the positive electrode active material, the completed nonaqueous alkali metal storage elements 1 and 2 are charged in a thermostatic chamber set at 25°C at a constant current of 0.1 C until the stable operating voltage reaches an upper limit, for example, 4.2 V, and then a constant voltage of 4.2 V is applied for 30 minutes. Thereafter, the storage elements are disassembled in an argon box, and the electrode assemblies are removed. ４When using as the positive electrode active material, the nonaqueous alkali metal storage element is subjected to constant current charging at a current value of 0.1 C in a thermostatic chamber set at 25°C until the stable operating voltage upper limit, for example, 3.6 V, is reached, followed by constant voltage charging at a constant voltage of 3.6 V for 30 minutes. The storage element is then disassembled in an argon box, and the electrode assembly is removed. When the electrode assembly is a laminate, the volume of the electrode assembly is obtained by multiplying the area S based on the coated portion of the positive electrode by the measured thickness of the laminate. When the electrode assembly is a cylindrically wound body, the volume of the electrode assembly is obtained by multiplying the area of ​​a circle obtained from the measured radius of the cylinder by the height of the cylinder based on the coated portion of the positive electrode. When the electrode assembly is a flat wound body, the cross-sectional area is calculated from the measured vertical and horizontal lengths of the flat wound body and the radius of the semicircular portion, and the cross-sectional area is then multiplied by the measured thickness of the flat wound body to obtain the volume of the electrode assembly. The volumetric capacity density (mAh / cc) is obtained by dividing the discharge capacity by the volume of the electrode assembly.

[0256] (Improvement Rate of Capacity Density) The capacity density a (mAh / cc) of the alkali metal storage element of the first embodiment is calculated. A separate alkali metal storage element, which has the same basis weight of positive electrode active material and negative electrode active material as the alkali metal storage element of the first embodiment and does not contain carbonate, is initially charged at the upper limit voltage of the "stable operating voltage" corresponding to the positive electrode active material described in (Stable operating potential of positive electrode and stable operating voltage of battery corresponding to positive electrode active material), to produce an alkali metal storage element, and its capacity density b (mAh / cc) is measured. The improvement rate X (%) of capacity density is calculated by X = (a - b) / b × 100. A capacity density improvement rate of 1% or more is preferable because it improves the capacity density of the alkali metal storage element. 4% or more is more preferable, and 7% or more is particularly preferable.

[0257] (DC Resistance R) In this specification, the discharge resistance R (Ω) is calculated from the voltage drop after 10 seconds of discharge from the upper limit of the stable operating voltage of the battery according to the positive electrode active material. That is, it is a value obtained by the following method. ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ When using this as the positive electrode active material, the nonaqueous alkali metal storage element is charged in a thermostatic chamber set at 25°C at a constant current of 0.1 C until the stable operating voltage reaches an upper limit, for example, 4.2 V, and then a constant voltage of 4.2 V is applied for 30 minutes. １Ｃ (A) The voltage V after 10 seconds when constant current discharge is performed １０秒 Measure the resistance (V). Calculate the resistance R (Ω) using the following formula: R = (4.2 - V １０秒 ) ÷ I １Ｃ

[0258] LiFePO ４ When using this as the positive electrode active material, the nonaqueous alkali metal storage element is charged in a thermostatic chamber set at 25°C at a constant current of 0.1 C until the stable operating voltage reaches an upper limit, for example, 3.6 V, and then a constant voltage charge of 3.6 V is applied for 30 minutes. １Ｃ (A) The voltage V after 10 seconds when constant current discharge is performed １０秒 Measure the resistance (V). Calculate the resistance R (Ω) using the following formula: R = (3.6 - V １０秒 ) ÷ I １Ｃ

[0259] NaFe １／３ Ni １／３ Mn １／３ O ２ When using this as the positive electrode active material, the nonaqueous alkali metal storage element is charged in a thermostatic chamber set at 25°C at a constant current of 0.1 C until the stable operating voltage upper limit, i.e., 3.9 V, is reached, and then constant voltage charging is performed by applying a constant voltage of 3.9 V for 30 minutes. １Ｃ (A) The voltage V after 10 seconds when constant current discharge is performed １０秒 Measure the resistance (V). Calculate the resistance R (Ω) using the following formula: R = (3.9 - V １０秒 ) ÷ I １Ｃ

[0260] In the battery configuration of the example, the discharge resistance R is preferably 2.5 mΩ or less because the resistance is low and high rate characteristics can be achieved. The discharge resistance R is more preferably 2.0 mΩ or less, and particularly preferably 1.5 mΩ or less.

[0261] (Negative Electrode Doping Amount, Volume Difference, Pre-Doping Volumetric Efficiency) <When Alkali Metal Carbonate is Contained in Positive Electrode Active Material Layer> In this specification, the pre-doping volumetric efficiency when an alkali metal carbonate is contained in the positive electrode active material layer is obtained by the following method.

[0262] Positive electrode precursor 1 containing an active material and, as optional components, conductive carbon black Super C65 and a binder, but not containing an alkali metal carbonate. 炭酸Ｌｉなし On the other hand, a positive electrode precursor 2 containing an active material, a conductive material, a binder as optional components, and an alkali metal carbonate is prepared. 炭酸Ｌｉあり At this time, positive electrode precursor 1 炭酸Ｌｉなし and cathode precursor 2 炭酸Ｌｉあり The slurry composition and basis weight are adjusted so that the basis weights of the active material, conductive material, and binder are the same. 炭酸Ｌｉなし Thickness t1 (μm), positive electrode precursor 2 炭酸Ｌｉあり The thickness t2 (μm) of the positive electrode precursor 1 is measured. 炭酸Ｌｉなし and positive electrode precursor 2 炭酸Ｌｉあり Area S (cm ２ ) is used and combined with a negative electrode and separator common to positive electrode precursor 1 and positive electrode precursor 2 to prepare nonaqueous alkali metal energy storage element precursors 1 and 2. The volume difference V (cc / cell) of the nonaqueous alkali metal energy storage element precursor due to the introduction of the alkali metal carbonate is calculated using the following formula: V = (t2 - t1) × S ÷ 10,000

[0263] Positive electrode precursor 1 炭酸Ｌｉなし A non-aqueous alkali metal capacitor precursor and a positive electrode precursor 2 炭酸Ｌｉあり The nonaqueous alkali metal storage element precursors using the above materials were initially charged under the same conditions to produce nonaqueous alkali metal storage elements 1 (without alkali metal carbonate) and 2 (with alkali metal carbonate). As a result, pre-doping was performed on storage element 2 using alkali metal carbonate.

[0264] LiCoO ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ When using as the positive electrode active material, the completed nonaqueous alkali metal storage element 1, 2 is placed in a thermostatic chamber set at 25 ° C. and subjected to constant current charging at a current value of 0.1 C until the stable operating voltage upper limit, for example, 4.2 V, is reached. Subsequently, a constant voltage charge of 4.2 V is applied for 30 minutes. The storage element is then disassembled in an argon box, the negative electrode is removed, and reassembled into a negative electrode half cell using a lithium counter electrode and a glass filter as a separator. Using the capacity of the negative electrode half cell as a reference, the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 4.2 V is measured by desorbing lithium from the negative electrode by constant current charging at a current value of 0.1 C to 2.5 V.

[0265] LiFePO ４When used as a positive electrode active material, the non-aqueous alkali metal storage element is placed in a thermostatic chamber set at 25 ° C., and a constant current charge is performed at a current value of 0.1 C until the stable operating voltage upper limit, for example, 3.6 V, is reached. Subsequently, a constant voltage charge of 3.6 V is applied for 30 minutes. The storage element is then disassembled in an argon box, the negative electrode is removed, and the negative electrode half cell is reassembled using a lithium counter electrode and a glass filter separator. Using the capacity of the negative electrode half cell as a reference, the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 3.6 V is measured by desorbing lithium from the negative electrode by constant current charging at a current value of 0.1 C to 2.5 V. The pre-doping volumetric efficiency E (mAh / cc) is calculated using the following formula: E = (Q2 - Q1) ÷ V That is, it is an index obtained by dividing the amount of alkali metal carbonate decomposed and doped into the negative electrode by the volume increased by mixing the alkali metal carbonate for pre-doping, and the higher the index, the more efficiently pre-doping was performed by suppressing the trade-off of volume increase. If the pre-doping volumetric efficiency is 400 mAh / cc or more, it is preferable because it can suppress the trade-off of volume increase in the alkali metal storage element and perform pre-doping efficiently. If the pre-doping volumetric efficiency is 600 mAh / cc or more, it is more preferable, and if it is 700 mAh / cc or more, it is particularly preferable.

[0266] NaFe １／３ Ni １／３ Mn １／３ O ２ When using as the positive electrode active material, the nonaqueous alkali metal storage element is placed in a thermostatic chamber set at 25 °C and subjected to constant current charging at a current value of 0.1 C until the stable operating voltage upper limit, i.e., 3.9 V, is reached. Subsequently, a constant voltage charge of 3.9 V is applied for 30 minutes. The storage element is then disassembled in an argon box, the negative electrode is removed, and reassembled into a negative electrode half cell using a sodium counter electrode and a glass filter separator. Using the capacity of the negative electrode half cell as a reference, the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 3.9 V are measured by desorbing sodium from the negative electrode by constant current charging at a current value of 0.1 C to 2.5 V.

[0267] <When an alkali metal carbonate is contained in the intermediate layer between the positive electrode active material layer and the separator> In this specification, the pre-doping volumetric efficiency when an alkali metal carbonate is contained in the intermediate layer between the positive electrode active material layer and the separator is obtained by the following method.

[0268] A positive electrode precursor containing an active material and, as optional components, conductive carbon black Super C65 and a binder, but not containing an alkali metal carbonate. 炭酸Ｌｉなし and combine it with the separator and the negative electrode to form a positive electrode precursor with an area S (cm ２ ) is used to form a non-aqueous alkali metal capacitor element precursor 1. 炭酸Ｌｉなし a positive electrode precursor in which an intermediate layer containing an alkali metal carbonate and, as optional components, a conductive material and a binder is formed on the surface of the active material layer by the method described in the section on the method for forming the intermediate layer; 炭酸Ｌｉなし , separator, and negative electrode are combined, and the positive electrode precursor is placed on a substrate with an area of ​​S (cm ２ ) to form a non-aqueous alkali metal electricity storage element precursor 2. The thickness of the intermediate layer at this time is designated as t2 (μm).

[0269] The volume difference V (cc / cell) of the nonaqueous alkali metal energy storage element precursor due to the introduction of the alkali metal carbonate is calculated using the following formula: V = (t2) × S ÷ 10000

[0270] Non-aqueous alkali metal storage element precursor 1, which does not contain alkali metal carbonate, is subjected to initial charging, and non-aqueous alkali metal storage element precursor 2, which contains alkali metal carbonate, is subjected to pre-doping in the initial charging step, thereby producing non-aqueous alkali metal storage elements 1 (without alkali metal carbonate) and 2 (with alkali metal carbonate), respectively.

[0271] LiCoO ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２, LiMn ２ O ４ When using as the positive electrode active material, the completed nonaqueous alkali metal storage element 1, 2 is placed in a thermostatic chamber set at 25 ° C. and subjected to constant current charging at a current value of 0.1 C until the stable operating voltage upper limit, for example, 4.2 V, is reached. Subsequently, a constant voltage charge of 4.2 V is applied for 30 minutes. The storage element is then disassembled in an argon box, the negative electrode is removed, and reassembled into a negative electrode half cell using a lithium counter electrode and a glass filter as a separator. Using the capacity of the negative electrode half cell as a reference, the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 4.2 V is measured by desorbing lithium from the negative electrode by constant current charging at a current value of 0.1 C to 2.5 V.

[0272] LiFePO ４ When using as the positive electrode active material, the nonaqueous alkali metal storage element is charged at a constant current of 0.1 C in a thermostatic chamber set at 25 ° C. until the stable operating voltage upper limit, for example, 3.6 V, is reached, followed by 30 minutes of constant voltage charging at a constant voltage of 3.6 V. The storage element is then disassembled in an argon box, the negative electrode is removed, and reassembled into a negative electrode half cell using a lithium counter electrode and a glass filter as a separator. Using the capacity of the negative electrode half cell as a reference, the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 3.6 V are measured by desorbing lithium from the negative electrode by constant current charging at a current of 0.1 C to 2.5 V.

[0273] NaFe １／３ Ni １／３ Mn １／３ O ２When using as the positive electrode active material, the nonaqueous alkali metal storage element is placed in a thermostatic chamber set at 25 °C and subjected to constant current charging at a current value of 0.1 C until the stable operating voltage upper limit, i.e., 3.9 V, is reached. Subsequently, a constant voltage charge of 3.9 V is applied for 30 minutes. The storage element is then disassembled in an argon box, the negative electrode is removed, and reassembled into a negative electrode half cell using a sodium counter electrode and a glass filter separator. Using the capacity of the negative electrode half cell as a reference, the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 3.9 V are measured by desorbing sodium from the negative electrode by constant current charging at a current value of 0.1 C to 2.5 V.

[0274] The pre-doping volumetric efficiency E (mAh / cc) can be calculated by the following formula: E = (Q2 - Q1) ÷ V That is, it is an index obtained by dividing the amount of alkali metal carbonate decomposed and doped into the negative electrode by the volume increased by providing the intermediate layer for pre-doping, and the higher this is, the more efficiently the pre-doping can be performed by suppressing the trade-off of the volume increase.

[0275] (Gas Measurement During Storage at 40°C) In this specification, the amount of gas generated during a storage test at 40°C is measured by the following method. ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４When using as the positive electrode active material, the nonaqueous alkali metal storage element is charged in a thermostatic chamber set at 40°C at a constant current of 0.1 C until the stable operating voltage upper limit, for example, 4.2 V, is reached, followed by 30 minutes of constant voltage charging with a constant voltage of 4.2 V applied. The cell is then stored in a 40°C environment, and every week, the cell voltage is recharged to the stable operating voltage upper limit, for example, 4.2 V, using the aforementioned charging procedure in a 40°C environment. The cell volume Va (cc) before the start of storage and the cell volume Vb (cc) after 6 weeks of storage testing are measured using the Archimedes method. Vb - Va is the amount of gas generated (cc).

[0276] LiFePO ４ When using as the positive electrode active material, the nonaqueous alkali metal storage element is charged in a thermostatic chamber set at 40°C at a constant current of 0.1 C until the stable operating voltage, i.e., 3.6 V, is reached, followed by 30 minutes of constant voltage charging with a constant voltage of 3.6 V applied. The cell is then stored in a 40°C environment, and every week, the cell voltage is recharged to the upper stable operating voltage limit, i.e., 3.6 V, using the aforementioned charging procedure in a 40°C environment. The cell volume Va (cc) before the start of storage and the cell volume Vb (cc) after 6 weeks of storage testing are measured using the Archimedes method. Vb - Va is the amount of gas generated (cc).

[0277] NaFe １／３ Ni １／３ Mn １／３ O ２ When using as the positive electrode active material, the nonaqueous alkali metal storage element is charged in a thermostatic chamber set at 40°C at a constant current of 0.1 C until the stable operating voltage, i.e., 3.9 V, is reached, followed by 30 minutes of constant voltage charging with a constant voltage of 3.9 V applied. The cell is then stored in a 40°C environment, and every week, the cell voltage is recharged to the upper stable operating voltage limit, i.e., 3.9 V, using the aforementioned charging procedure in a 40°C environment. The cell volume Va (cc) before the start of storage and the cell volume Vb (cc) after 6 weeks of storage testing are measured using the Archimedes method. Vb - Va is the amount of gas generated (cc).

[0278] In the battery configuration of the example, the storage gas volume at 40°C is preferably 1.0 cc or less, since this can prevent the battery from swelling when the alkali metal storage element is stored in a high-temperature environment. The storage gas volume at 40°C is more preferably 0.6 cc or less, and particularly preferably 0.2 cc or less. (Cycle Test) The cycle test for the nonaqueous alkali metal storage element of the first embodiment is performed in the following manner. LiCoO ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ When LiFePO was used as the positive electrode active material, the nonaqueous alkali metal storage element was placed in a thermostatic chamber set at 25°C and subjected to constant current charging at a current value of 0.5 C until the battery reached the upper limit of stable operating voltage according to the positive electrode active material, i.e., 4.2 V, followed by constant voltage charging at the same voltage until the current value reached 0.03 C, followed by a 10-minute pause, followed by constant current discharging at a current value of 0.5 C until the lower limit of stable operating voltage, i.e., 3.0 V, followed by a 10-minute pause, and 500 charge-discharge cycles were performed. ４ When NaFe was used as the positive electrode active material, the nonaqueous alkali metal storage element was placed in a thermostatic chamber set at 25°C and subjected to constant current charging at a current value of 0.5 C until the battery reached the upper limit of stable operating voltage according to the positive electrode active material, i.e., 3.6 V, followed by constant voltage charging at the same voltage until the current value reached 0.03 C. After a 10-minute pause, constant current discharging was performed at a current value of 0.5 C until the lower limit of stable operating voltage, i.e., 2.4 V, followed by a 10-minute pause. Five hundred charge-discharge cycles were performed, with each cycle consisting of one cycle being NaFe. １／３ Ni １／３ Mn １／３ O ２When the positive electrode active material was used, the nonaqueous alkali metal storage element was placed in a thermostatic chamber set at 25°C and subjected to constant-current charging at a current value of 0.5 C until the battery reached the upper limit of stable operating voltage corresponding to the positive electrode active material, i.e., 3.9 V, followed by constant-voltage charging at the same voltage until the current value reached 0.03 C. After a 10-minute pause, the battery was discharged at a constant current value of 0.5 C until the lower limit of stable operating voltage, i.e., 1.9 V, followed by a 10-minute pause, and 500 charge-discharge cycles were performed.

[0279] (Capacity Retention Rate After Cycle Test) Before and after the above-described cycle test, capacity measurements were performed using the method described above in the section (Discharge Capacity Q, Full Cell Capacity Density Pfull per Mass of Positive Electrode Active Material), and the capacity retention rate after the cycle test was calculated by dividing the discharge capacity Q after the cycle test by the capacity Q before the cycle test. A capacity retention rate after the cycle test of 80% or more is preferable because it can reduce capacity degradation even when the alkali metal storage element is repeatedly charged and discharged. A capacity retention rate after the cycle test of 85% or more is more preferable, and a capacity retention rate of 90% or more is particularly preferable.

[0280] (Self-discharge defect rate after cycle test) For the nonaqueous alkali metal storage element of the first embodiment, the self-discharge defect rate after cycle test is calculated by the following method. Twenty nonaqueous alkali metal storage elements after cycle test are prepared. ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４When LiFePO is used as the positive electrode active material, the nonaqueous alkali metal storage element is placed in a thermostatic chamber set at 25°C and discharged at a constant current of 0.1 C until the stable operating voltage reaches the lower limit, i.e., 3.0 V, followed by a constant voltage discharge of 3.0 V for 30 minutes. The cell is then stored in a 25°C environment, and the cell voltage is measured after one week. The number of cells that fell below 3.0 V is taken as the number of self-discharge defective cells, and this is divided by 20 to determine the self-discharge defect rate. ４ When NaFe is used as the positive electrode active material, the nonaqueous alkali metal storage element is placed in a thermostatic chamber set at 25°C and discharged at a constant current of 0.1 C until the stable operating voltage reaches the lower limit, i.e., 2.4 V. Subsequently, a constant voltage discharge of 2.4 V is applied for 30 minutes. The cell is then stored in a 25°C environment, and the cell voltage is measured after one week. The number of cells that fell below 2.4 V is taken as the number of self-discharge defective cells, and this is divided by 20 to obtain the self-discharge defect rate. １／３ Ni １／３ Mn １／３ O ２ When used as the positive electrode active material, the nonaqueous alkali metal storage element is placed in a thermostatic chamber set at 25°C, and discharged at a constant current of 0.1 C until the stable operating voltage reaches its lower limit, i.e., 1.9 V. A constant voltage of 1.9 V is then applied and a constant voltage discharge is performed for 30 minutes. The cell is then stored in a 25°C environment, and the cell voltage is measured after one week. The number of cells that dropped below 2.4 V is taken as the number of self-discharge defective cells, and this is divided by 20 to determine the self-discharge defect rate. A self-discharge defect rate of 30% or less after the cycle test is preferred because it increases the likelihood that the alkali metal storage element can be used for a long period of time without any problems. A self-discharge defect rate of 15% or less is more preferred, and a self-discharge defect rate of 5% or less is particularly preferred.

[0281] <Evaluation of Characteristics of Alkali Metal Storage Element of Second Embodiment> Hereinafter, the second embodiment will be described.

[0282] (Capacity, Capacity Density) The capacity Q (mAh) between the upper limit and lower limit of the stable operating voltage of the battery corresponding to the positive electrode active material of the nonaqueous alkali metal storage element of the second embodiment is determined by the following method. The nonaqueous alkali metal storage element is placed in a thermostatic chamber set at 25°C and subjected to constant current charging at a current value of 0.1 C until the upper limit of the stable operating voltage of the battery corresponding to the positive electrode active material is reached, followed by constant voltage charging at a constant voltage corresponding to the upper limit of the stable operating voltage of the battery corresponding to the positive electrode active material until the current value reaches 0.03 C. The capacity Q (mAh) is then determined by constant current discharge at a current value of 0.1 C down to the lower limit of the stable operating voltage.

[0283] Initial capacity density Q of the nonaqueous alkali metal storage element of the second embodiment ｖ (mAh / cc) is the total volume of the positive electrode coating portion (foil + positive electrode active material layer) contained in the non-aqueous alkali metal storage element, V １ (cc), the total volume of the negative electrode coating part (foil + negative electrode active material layer) is V ２ (cc), the total volume of the separator is V ３ (cc), the total volume of the intermediate layer (if any) is V ４ (cc), when the initial capacity obtained by capacity measurement is Q (mAh), Q ｖ = Q ÷ (V １ +V ２ +V ３ +V ４ ) ÷ 10000) where the volume is calculated so that the uncoated portions of the positive and negative electrodes are not included in the volume.

[0284] (Constant Current Cycle) The nonaqueous alkali metal storage element of the second embodiment was subjected to constant current cycling in a thermostatic chamber set at 25° C. by the following method: constant current charging was performed at a current value of 1 C until the battery reached the upper limit of the stable operating voltage corresponding to the positive electrode active material, followed by constant voltage charging in which a constant voltage of the same voltage was applied until the current value reached 0.03 C, followed by a 10-minute pause, followed by constant current discharging at a current value of 1 C until the lower limit of the stable operating voltage, followed by a 10-minute pause. A 300-cycle test was performed.

[0285] (Capacity Retention Rate After Constant Current Cycle) After the constant current cycle test of the second embodiment, the capacity was measured by the method described above in the section <Capacity, Capacity Density>, and the capacity after the cycle test was divided by the capacity before the cycle test to calculate the capacity retention rate after the constant current cycle.

[0286] <Use of nonaqueous alkali metal storage element before capacity recovery> A second embodiment of the present disclosure provides use of a nonaqueous alkali metal storage element before capacity recovery (a battery before capacity recovery). The battery before capacity recovery can be charged and discharged and used in the same way as a normal alkali metal ion battery. For example, it can be used in a general manner such as cycle charging or float charging.

[0287] The pre-capacity-recovery battery of the second embodiment is preferably used as a battery pack. The pre-capacity-recovery battery can be used in at least one power storage system selected from the group consisting of a power regeneration assist system in an automobile hybrid drive system, a power load leveling system for natural power generation such as solar power generation and wind power generation and a microgrid, an uninterruptible power supply system in a factory production facility, a contactless power supply system for leveling voltage fluctuations and storing energy such as microwave power transmission and electrolytic resonance, an energy harvesting system for utilizing power generated by vibration power generation, a solar power generation and storage system, an electric power steering system, an emergency power supply system, an in-wheel motor system, an idling stop system, an electric vehicle, a plug-in hybrid vehicle, a hybrid vehicle, an electric motorcycle, a quick charging system, and a smart grid system.

[0288] The pre-capacity-restored battery of the second embodiment of the present disclosure can be suitably used in the form of a storage module connected in series or parallel to a lead battery, a nickel-metal hydride battery, a non-aqueous alkali metal storage element (including the post-capacity-restored battery of the present disclosure and other non-aqueous alkali metal storage elements), or a fuel cell.

[0289] In order to maintain the decomposition reactivity of the alkali metal compound, it is preferable not to apply a cell voltage higher than the upper limit of the stable operating voltage when using the battery before capacity recovery. This allows alkali metal ions generated by the decomposition reaction of the alkali metal compound to be replenished to the negative electrode during the capacity recovery process, resulting in a high capacity recovery effect. Applying a voltage higher than the upper limit of the stable operating voltage when using the battery before capacity recovery can cause the decomposition reaction of the alkali metal compound to proceed, resulting in partial or complete loss of the alkali metal compound, thereby reducing or eliminating the capacity recovery effect during the capacity recovery process. However, as long as the capacity recovery effect is demonstrated during the capacity recovery process of the present disclosure, applying a voltage higher than the upper limit of the stable operating voltage when using the battery before capacity recovery may be acceptable.

[0290] <Capacity Recovery Method and Manufacturing Method of Capacity-Recovered Non-Aqueous Alkali Metal Storage Element> (Capacity Recovery Step) A second embodiment of the present disclosure provides a capacity recovery method for a non-aqueous alkali metal storage element, i.e., a method for manufacturing a capacity-recovered non-aqueous alkali metal storage element (hereinafter also referred to as a "capacity-recovered battery"). The pre-capacity-recovered battery used in the manufacturing method of the capacity-recovered battery includes a positive electrode including a positive electrode active material layer disposed on a positive electrode current collector, a negative electrode including a negative electrode active material layer disposed on a negative electrode current collector, a separator, and a non-aqueous electrolyte solution containing alkali metal ions, where the positive electrode active material layer contains an alkali metal transition metal compound, and an alkali metal carbonate is contained in the positive electrode active material layer, an optional intermediate layer between the positive electrode active material layer and the separator, or both. The non-aqueous electrolyte solution contains a promoter. The method for manufacturing a capacity-restored battery includes restoring the capacity by increasing the potential of the positive electrode of the nonaqueous alkali metal storage element before capacity restoration to a stable operating potential of the positive electrode active material or higher (capacity restoration step). For details about the configuration of the nonaqueous alkali metal storage element before capacity restoration, see the above section "Nonaqueous alkali metal storage element before capacity restoration."

[0291] In a modified example of the method for manufacturing a capacity-restored battery according to the second embodiment of the present disclosure, the alkali metal compound may be contained in other components of the nonaqueous alkali metal storage element, as long as the alkali metal compound can be oxidatively decomposed. The alkali metal compound may be contained, for example, in the separator, between the positive electrode current collector and the positive electrode active material layer, on the surface of the positive electrode active material layer, on the surface of the separator in contact with the positive electrode active material layer, in the electrolyte, the negative electrode, the inner surface of the exterior body, or in the terminals of the positive and negative electrodes. The alkali metal compound may be contained in advance during the manufacturing of the nonaqueous alkali metal storage element before capacity restoration, or may be mixed with the electrolyte or the like in the nonaqueous alkali metal storage element after battery deterioration and before the capacity restoration step, and then introduced into the battery.

[0292] In the capacity recovery step of the second embodiment, the capacity of the nonaqueous alkali metal storage element is preferably recovered by increasing the voltage of the nonaqueous alkali metal storage element to or above the upper limit of the stable operating voltage corresponding to the positive electrode active material. The upper limit of the stable operating voltage of a battery that can stably use the positive electrode active material is as described above.

[0293] In more detail in the second embodiment, in an LFP whose upper limit of stable operating voltage is about 3.6 V, it is preferable to recover the capacity of the nonaqueous alkali metal storage element by increasing the voltage to preferably 4.0 V or higher, more preferably 4.1 V or higher, even more preferably 4.2 V or higher, still more preferably 4.3 V or higher, and particularly preferably 4.4 V or higher. The upper limit of the voltage is not particularly limited, but is preferably 4.6 V or lower from the viewpoint of suppressing the formation of an excessive SEI coating.

[0294] In the second embodiment, for LCO, LMFP, NCM111, NCM811, NCA, and LMO, whose upper limit of stable operating voltage is about 4.2 V, it is preferable to recover the capacity of the nonaqueous alkali metal storage element by increasing the voltage preferably to 4.3 V or more, particularly preferably to 4.4 V or more. The upper limit of the voltage is not particularly limited, but from the viewpoint of suppressing the formation of an excessive SEI film and from the viewpoint of obtaining a capacity recovery effect while avoiding damage to the positive electrode active material structure, it is preferably 4.6 V or less.

[0295] The specific charge / discharge operation in the capacity recovery step of the second embodiment is not particularly limited as long as it can raise the voltage of the nonaqueous alkali metal storage element to or above the oxidative decomposition potential of the alkali metal compound. For example, constant-current charging may be performed at a constant current value until a desired voltage equal to or higher than the oxidative decomposition potential of the alkali metal compound is reached, and then constant-voltage charging may be performed while maintaining that voltage for a while. More specifically, it is preferable to perform constant-current charging until the voltage reaches a desired voltage equal to or higher than the upper limit of the stable operating voltage corresponding to the positive electrode active material and 4.6 V or less, and then perform constant-voltage charging while maintaining that voltage. The duration of constant-voltage charging is not limited, but is preferably 10 minutes to 5 hours. After constant-voltage charging, constant-current discharge may be performed at a constant current value until the desired voltage is reached that is suitable for use of the nonaqueous alkali metal storage element. The capacity recovery step may be performed multiple times, with one charge-discharge cycle considered to be one cycle. For example, the capacity recovery step may be performed for preferably 2 to 10 cycles, more preferably 3 to 9 cycles, and even more preferably 4 to 8 cycles. Furthermore, the capacity recovery process does not necessarily have to be carried out once, but may be carried out multiple times, such as by performing the capacity recovery process, then using the nonaqueous alkali metal storage element to cause re-deterioration, and then performing the capacity recovery process again.

[0296] In the second embodiment, the C-rate of the current value at the stage where the decomposition reaction of the alkali metal carbonate occurs, for example, at the stage of constant current charging, is preferably 0.10 C or more and 5.0 C or less. If the current value is 0.10 C or more, the time the cell is exposed to high voltage is short, thereby suppressing side reactions and enabling efficient capacity recovery. If the current value is 5.0 C or less, heat generation in the cell is suppressed, thereby suppressing side reactions and enabling efficient capacity recovery.

[0297] In the capacity recovery step of the second embodiment, the temperature of the nonaqueous alkali metal storage element is maintained at room temperature, but is preferably maintained at 35°C or higher, and more preferably 45°C or higher. This promotes the decomposition reaction of the alkali metal compound and effectively replenishes the alkali metal to the negative electrode, resulting in a high capacity recovery effect. On the other hand, the temperature of the nonaqueous alkali metal storage element in the capacity recovery step is preferably maintained at 70°C or lower to suppress the formation of resistance components such as coatings due to side reactions.

[0298] The degree of capacity deterioration and recovery of the battery before capacity recovery in the second embodiment is not particularly limited. For example, １ By performing the capacity recovery process on a pre-capacity-recovery battery having a capacity of 95% or less based on the standard (mAh), it is possible to recover 2% or more of the capacity. Preferably, the capacity of a pre-capacity-recovery battery having a capacity of 95% or less is recovered by 3% or more, more preferably, the capacity of a pre-capacity-recovery battery having a capacity of 95% or less is recovered by 5% or more, even more preferably, the capacity of a pre-capacity-recovery battery having a capacity of 90% or less is recovered by 10% or more, still more preferably, the capacity of a pre-capacity-recovery battery having a capacity of 80% or less is recovered by 20% or more, and particularly preferably, the capacity of a pre-capacity-recovery battery having a capacity of 70% or less is recovered by 30% or more.

[0299] (Capacity Recovery in a Battery Assembly) In the second embodiment, the nonaqueous alkali metal storage element whose capacity is recovered may be in the form of a single cell or a battery assembly formed by combining a plurality of single cells. When the nonaqueous alkali metal storage element is in the form of a battery assembly, a method of recovering the capacity of the battery assembly as it is without disassembling the battery assembly into single cells is preferred. Alternatively, when the battery assembly is composed of a plurality of modules (which are also "battery assembly") each consisting of a plurality of combined single cells, a method of disassembling the battery assembly into modules without disassembling the battery assembly into single cells is preferred, and capacity recovery is performed on each module. Furthermore, with regard to capacity recovery in a battery assembly, the capacity recovery process is not limited to one time, and may be performed multiple times, for example, by performing the capacity recovery process, then using the nonaqueous alkali metal storage element to re-degrade the battery, and then performing the capacity recovery process again.

[0300] In the second embodiment, capacity recovery is performed with minimal disassembly, which is preferable because it eliminates the need to transport the nonaqueous alkali metal storage element to a dedicated battery disassembly and capacity recovery location (such as a factory), disassemble the battery pack, and perform capacity recovery processing on the individual cells.

[0301] In the second embodiment, in order to perform capacity recovery on the battery pack itself, it is preferable that some or all of the cells are provided with a gas permeation mechanism. The provision of a gas venting mechanism allows gas generated during the capacity recovery process to be vented, thereby enhancing the capacity recovery effect. Furthermore, providing the cells with a gas venting mechanism allows the capacity recovery process to be performed at a location close to the final use site, such as the place where the nonaqueous alkali metal storage element is used or a primary collection site, without disassembling the cells. This is preferable because it reduces the costs of collection and transportation and the carbon dioxide emissions associated with such collection. The use site of the nonaqueous alkali metal storage element refers to, for example, the location where the ESS is installed in the case of an energy storage system (ESS), and to the location where the battery is used by the end user, such as a parking lot, in the case of an electric vehicle. The primary collection site refers to, for example, the location where products from the end user of the battery are collected in the case of an electric vehicle, such as a dealer's factory.

[0302] (Deterioration Confirmation Step) In the second embodiment, before the capacity restoration step is performed, the degree of capacity deterioration of the battery before capacity restoration may be determined arbitrarily, and the capacity restoration step may be performed according to the degree of deterioration. For example, the capacity of the deteriorated battery before capacity restoration (post-deterioration capacity) P ２ (mAh) was measured, and this was taken as the capacity (initial capacity) P of the undegraded battery before capacity recovery. １ The degree of capacity deterioration may be confirmed by comparing the measured value (mAh) with the actual value (mAh). By confirming the degree of capacity deterioration, specific conditions for charge / discharge operations in the capacity recovery process may be determined. The conditions for charge / discharge operations include charge capacity, cell temperature, C rate, voltage, duration, and number of cycles.

[0303] (J １ / J ２ In the second embodiment, the non-aqueous alkali metal storage element undergoing the capacity recovery process has a residual capacity per area of ​​the negative electrode active material of J １ (Ah / cm ２ ), the total capacity per area of ​​the negative electrode active material is J ２ (Ah / cm ２ ), then 0.1≦J １ / J ２If the ratio is within this range, the alkali metal can be supplied from the alkali metal carbonate to the negative electrode in the capacity recovery step, and a high capacity recovery effect can be obtained. １ / J ２ The residual capacity per area of ​​the negative electrode active material is defined as J. １ (Ah / cm ２ ), and the total capacity per area of ​​the negative electrode active material is J ２ (Ah / cm ２ ) is measured by the following method.

[0304] 1. Voltage adjustment LiCoO ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ When LiFePO is used as the positive electrode active material, a nonaqueous alkali metal storage element that has deteriorated with use and is not yet undergoing capacity recovery is subjected to constant current charging at a current value of 0.1 C in a thermostatic chamber set at 25°C until the stable operating voltage upper limit, for example, 4.2 V, is reached, and then constant voltage charging is performed for 30 minutes by applying a constant voltage of 4.2 V. ４ When NaFe is used as the positive electrode active material, the nonaqueous alkali metal storage element is charged in a thermostatic chamber set at 25°C at a constant current of 0.1 C until the stable operating voltage upper limit, for example, 3.6 V, is reached, and then constant voltage charging is performed by applying a constant voltage of 3.6 V for 30 minutes. １／３ Ni １／３ Mn １／３ O ２ When the positive electrode active material is used, the nonaqueous alkali metal storage element is subjected to constant current charging at a current value of 0.1 C in a thermostatic chamber set at 25°C until the stable operating voltage upper limit, i.e., 3.9 V, is reached, and then constant voltage charging is performed by applying a constant voltage of 3.9 V for 30 minutes.

[0305] 2. Measurement of negative electrode capacity: The storage element is then disassembled in an argon box, the negative electrode is removed, and reassembled into a negative electrode half cell using a lithium counter electrode and a glass filter as a separator. Using the capacity of the negative electrode half cell as a reference, the negative electrode is desorbed from the negative electrode by constant current charging at a current value of 0.1 C up to 2.5 V, and the negative electrode doping amount O (Ah / cell) at 4.2 V before capacity recovery is measured. The coated area (cm) of the negative electrode half cell is then measured. ２ ) to obtain the negative electrode doping amount O １ (Ah / cm ２ Subsequently, the battery was discharged at a constant current to 0.01 V, and then discharged at a constant voltage until the current converged to a 0.02 C rate. The discharge capacity (Ah / cell) was measured, and the coated area (cm ) of the single-sided negative electrode precursor was calculated. ２ ) to obtain the coated area (cm ) of the negative electrode half-cell. ２ ) to obtain the total capacity J per area of ​​the negative electrode active material. ２ (Ah / cm ２ The remaining capacity J per area of ​​the negative electrode active material is obtained. １ (Ah / cm ２ ) is J １ =J ２ -O １ and get.

[0306] (B １ / J １ In the second embodiment, the non-aqueous alkali metal storage element undergoing the capacity recovery process has a theoretical capacity per area of ​​the alkali metal carbonate of B １ (Ah / cm ２ ), the remaining capacity per area of ​​the negative electrode active material is J １ (Ah / cm ２ ) 0.03≦0.3×B １ / J １ Within this range, the alkali metal can be supplied from the alkali metal carbonate to the negative electrode in the capacity recovery step, and a high capacity recovery effect can be obtained. １ / J １ The residual capacity J per area of ​​the negative electrode active material may vary depending on the conditions under which the nonaqueous alkali metal storage element is used, the amount of alkali metal carbonate contained in the nonaqueous alkali metal storage element before capacity recovery, and other factors.１ (Ah / cm ２ ) is <J １ / J ２ The theoretical capacity per area of ​​alkali metal carbonate B can be measured by the method described above. １ (Ah / cm ２ ) is calculated by the following method. The theoretical capacity (mAh / g) of the alkali metal carbonate is calculated assuming that the oxidative decomposition reaction of the alkali metal carbonate is a two-electron reaction. For example, the theoretical capacity of lithium carbonate is 725 mAh / g, and that of sodium carbonate is 506 mAh / g. The basis weight (g / cm) of the alkali metal carbonate is then calculated. ２ ) and divide by 1000 to obtain the theoretical capacity B per area of ​​the alkali metal carbonate. １ (Ah / cm ２ ) is required.

[0307] (Re-venting process) In the second embodiment, after the capacity recovery process, it is preferable to further vent the gas to remove gas remaining in the electrolyte, the positive electrode, and the negative electrode. Gas remaining in at least a portion of the electrolyte, the positive electrode, and the negative electrode inhibits ionic conduction, which can prevent an increase in the resistance of the resulting capacity-recovered nonaqueous alkali metal storage element. The venting method is not particularly limited, and can be, for example, a method in which the electrode stack is placed in a reduced pressure chamber with the outer casing open and the chamber is reduced pressure using a vacuum pump. After venting, the outer casing is sealed to hermetically seal the outer casing, and a nonaqueous alkali metal storage element (capacity-recovered battery) can be produced.

[0308] <Capacity-Restored Non-Aqueous Alkali Metal Energy Storage Element> A second embodiment of the present disclosure provides a capacity-restored non-aqueous alkali metal energy storage element (also referred to as a "capacity-restored battery"). The capacity-restored battery of the present disclosure can be obtained by increasing the potential of the positive electrode of the pre-capacity-restored battery of the present disclosure to or above the oxidative decomposition potential of the alkali metal compound (capacity recovery method). For details about the configuration of the pre-capacity-restored battery and the capacity recovery method, please refer to the above sections "Non-Aqueous Alkali Metal Energy Storage Element Before Capacity Recovery" and "Capacity Recovery Method and Manufacturing Method for Capacity-Restored Non-Aqueous Alkali Metal Energy Storage Element."

[0309] In a second embodiment, the battery after capacity recovery includes a positive electrode including a positive electrode active material layer disposed on a positive electrode current collector, a negative electrode including a negative electrode active material layer disposed on a negative electrode current collector, a separator, and a non-aqueous electrolyte solution containing alkali metal ions, and the positive electrode active material layer includes an alkali metal transition metal compound. The positive electrode active material layer or the intermediate layer may optionally include an alkali metal compound remaining without being divided by the capacity recovery, or may not include an alkali metal compound. Then, the initial capacity of the battery before capacity recovery is P １ (mAh), and the capacity after degradation is P ２ (mAh), and the capacity of the battery after capacity recovery is P ３ (mAh), then (P ３ -P ２ ) ÷ P １ × 100 is 2% or more. The capacity recovery rate is preferably 3% or more, more preferably 5% or more, even more preferably 10% or more, still more preferably 20% or more, and particularly preferably 30% or more.

[0310] In the second embodiment, the capacity-restored battery is a non-aqueous alkali metal storage element that has undergone a capacity restoration process and has a certain degree of capacity degradation before capacity restoration. Therefore, the configuration of the capacity-restored battery is basically the same as that of the battery before capacity restoration, except that the amount of alkali metal compound in the positive electrode active material layer is reduced compared to the battery before capacity restoration, and the charge / discharge capacity is restored. Therefore, for details of the positive electrode, negative electrode, separator, non-aqueous electrolyte, outer casing, gas vent valve, etc. of the capacity-restored battery, the descriptions in the above section "Non-aqueous alkali metal storage element before capacity restoration" can be cited.

[0311] In the second embodiment, the capacity-restored battery is a nonaqueous alkali metal storage element that has undergone a capacity restoration process and that contains a certain amount of deactivated alkali metal, and it is believed that the deactivated alkali metal remains in the battery even after capacity restoration according to the present disclosure. Thus, although not limited thereto, the capacity-restored battery can have a high restored capacity (capacity recovery rate) despite containing a certain amount of deactivated alkali metal.

[0312] <Use of Capacity-Restored Non-Aqueous Alkali Metal Energy Storage Element> A second embodiment of the present disclosure provides a use of a capacity-restored non-aqueous alkali metal energy storage element (capacity-restored battery). The capacity-restored battery of the present disclosure may be reused for the same purpose as the purpose before capacity restoration, or for a purpose different from the purpose before capacity restoration. It is preferable to select an appropriate reuse destination depending on the capacity restoration rate. For example, the capacity-restored battery of the present disclosure can be suitably used in at least one energy storage system selected from the group consisting of power regeneration assist systems in automobile hybrid drive systems and the like, power load leveling systems in natural power generation such as solar power generation and wind power generation and microgrids, uninterruptible power supply systems in factory production facilities and the like, contactless power supply systems intended to level voltage fluctuations such as microwave power transmission and electrolytic resonance and to store energy, energy harvesting systems intended to utilize power generated by vibration power generation and the like, solar power generation and storage systems, electric power steering systems, emergency power supply systems, in-wheel motor systems, idling stop systems, electric vehicles, plug-in hybrid vehicles, hybrid vehicles, electric motorcycles, quick charging systems, and smart grid systems.

[0313] In the second embodiment, when the degree of capacity degradation is not uniform among the batteries in a group of degraded nonaqueous alkali metal energy storage elements, the voltage, temperature, and charging current capacity of the capacity recovery process of the present disclosure can be controlled to increase the capacity recovery rate for batteries with severe capacity degradation and decrease the capacity recovery rate for batteries with little capacity degradation, thereby making the restored capacities uniform. This can be considered to make the capacity quality uniform among the batteries when reusing degraded nonaqueous alkali metal energy storage elements and improve the residual value.

[0314] The capacity recovery method of the second embodiment of the present disclosure can recover the respective capacities of a plurality of nonaqueous alkali metal storage elements (a group of nonaqueous alkali metal storage elements) after degradation. When there is variation in the capacities of the plurality of nonaqueous alkali metal storage elements, i.e., when at least two of the plurality of nonaqueous alkali metal storage elements have different capacities, it is preferable to reduce the difference in capacity by controlling at least one selected from the group consisting of the positive electrode potential (battery voltage), temperature, and charge current capacity during capacity recovery. When the nonaqueous alkali metal storage elements originally had the same capacity before degradation but have now experienced capacity variation due to degradation, the difference in capacity may be reduced by reducing the difference in capacity retention rate.

[0315] In the second embodiment, in a battery assembly comprising a plurality of nonaqueous alkali metal storage element cells, if the individual cells vary in capacity, the cell with the smallest capacity will determine the capacity of the battery assembly. Therefore, when reusing alkali metal storage elements, it is preferable to reduce the capacity variation. By controlling the capacity recovery effect of the capacity recovery process of the present disclosure, it is preferable to reduce the capacity variation among the cells constituting the battery assembly before capacity recovery. The control method is not particularly limited, but may include at least one selected from the group consisting of the positive electrode potential (battery voltage), temperature, and charging current capacity. It is also preferable to control the capacity recovery conditions based on the amount of deterioration during primary use.

[0316] The capacity-restored battery of the second embodiment of the present disclosure can be suitably used in the form of a storage module connected in series or parallel with a lead battery, a nickel-metal hydride battery, a nonaqueous alkali metal storage element (including the pre-capacity-restored battery of the present disclosure and other nonaqueous alkali metal storage elements), or a fuel cell. The storage module including the capacity-restored nonaqueous alkali metal storage element may be reused for the same purpose as before the capacity restoration, or for a different purpose than before the capacity restoration. It is preferable to select an appropriate reuse destination depending on the capacity restoration rate.

[0317] I. Examples According to the First Embodiment Examples and Comparative Examples according to the first embodiment are shown below. However, the present disclosure is not limited to the following Examples and Comparative Examples. In addition, since the present disclosure includes a destructive test involving disassembly, multiple batteries of the same standard were produced.

[0318] (Measurement of oxidation potential of accelerator) (i) When LFP was used as the positive electrode active material and 1,4-dimethoxybenzene was used as the accelerator, LiFePO was used as the positive electrode active material. ４ 91.4 mass% of the powder, 3.23 mass% of carbon black, 5.38 mass% of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) were mixed to adjust the viscosity, and a positive electrode slurry was obtained. The obtained slurry was applied at 100 g / m to one side of a 15 μm thick anchor-coated aluminum foil as a positive electrode current collector. ２ The coating was dried and pressed to obtain a positive electrode for a full cell to be used for measuring the oxidation potential of the accelerator.

[0319] Negative Electrode Preparation: 96.0 parts by mass of artificial graphite, 2.0 parts by mass of styrene-butadiene rubber, 2.0 parts by mass of carboxymethyl cellulose (CMC), and water were mixed to obtain a negative electrode slurry. The obtained negative electrode slurry was applied to one side of a 10 μm-thick electrolytic copper foil in an amount of 100 g / m. ２ The coating was dried and pressed to obtain a full-cell negative electrode to be used for measuring the oxidation potential of the accelerator.

[0320] As shown in assembly diagram 1, the obtained positive electrode (1) was cut so that the coated area was 5 cm x 10 cm, leaving the terminal portion (10) of the current collector foil exposed for tab welding (Fig. 1). The obtained negative electrode (2) was cut so that the coated area was 5.2 cm x 10.2 cm, leaving the terminal portion (10) of the current collector foil exposed for tab welding (Fig. 1). Both the positive electrode (1) and the negative electrode (2) were vacuum dried at a temperature of 120°C for 24 hours (h).

[0321] As shown in Figures 1 and 2, a 20 μm thick microporous membrane separator (3) measuring 5.5 cm x 10.5 cm (Figure 1) was sandwiched between the positive electrode (1) and the negative electrode (2). The negative electrode terminal (31) and the positive electrode terminal (11) were then ultrasonically welded to the exposed terminals (10) of the current collector foils of the negative electrode (2) and the positive electrode (1), respectively, to form an electrode laminate. The SUS foil (6) wrapped around the lithium foil (5) was wrapped in a 20 μm thick microporous membrane separator (12) measuring 5.5 cm x 5.5 cm. A Ni terminal (7) with a resin tape (9) for external connection to the SUS foil (6) was ultrasonically welded to the end of the SUS foil (6). A lithium reference electrode (412) was positioned 1 cm from the electrode laminate, and was connected to the electrode laminate via the separator. A schematic perspective view illustrating the positional relationship between the electrode laminate and the Li reference electrode is shown in Fig. 2. This electrode laminate was housed in an exterior body made of an aluminum laminate packaging material, and three sides of the exterior body, including the electrode terminal portion and the bottom portion, were heat-sealed under conditions of a temperature of 180°C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa, thereby obtaining two full cells (full cell 1 and full cell 2) for measuring the accelerated potential before injection.

[0322] Injection: 1.0 M LiPF in EC:MEC mixed solvent (volume ratio 1:2) ６ An electrolyte solution 1 was prepared by dissolving 1 mass % of vinylene carbonate and 0.1 mol / L of 1,4-dimethoxybenzene.

[0323] On the other hand, 1.0 M LiPF in EC:MEC mixed solvent (volume ratio 1:2) ６ Electrolyte solution 2 was prepared by dissolving 1% by mass of vinylene carbonate.

[0324] Under atmospheric pressure, a temperature of 25 ° C., and a dry air environment with a dew point of -40 ° C. or less, 2 g of electrolyte solution 1 was injected into full cell 1, and 2 g of electrolyte solution 2 was injected into full cell 2. Subsequently, this was placed in a reduced pressure chamber, and the pressure was reduced from atmospheric pressure to -87 kPa, then returned to atmospheric pressure, and the cell was allowed to stand for 5 minutes. Thereafter, the operation of reducing the pressure from atmospheric pressure to -87 kPa and then returning to atmospheric pressure was repeated four times, and the cell was allowed to stand for 15 minutes, thereby impregnating the electrode laminate with the nonaqueous electrolyte solution. Thereafter, the electrode laminate housed in an aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was placed in a reduced pressure sealing machine, and the aluminum laminate packaging material was sealed by sealing at a pressure of 0.1 MPa at 180 ° C. for 10 seconds in a state where the pressure was reduced to -95 kPa. Full cells 1 and 2 for measuring the oxidation potential after injection and before the first charge were obtained.

[0325] As described above in the section (Measurement of Oxidation Onset Potential of Accelerator), the oxidation potential was measured under the following conditions. In a thermostatic chamber set at 45°C, constant current charging was performed at a current value of 0.1 C until the voltage reached 4.8 V. At this time, the positive electrode potential was measured against the lithium reference electrode. From the above measurements, as shown in Figure 3, the positive electrode potential (V vs Li / Li) was calculated for full cells 1 and 2 relative to the capacity per weight of the positive electrode active material (mAh / g of positive electrode active material). ＋ ) were plotted to obtain curves 1 and 2.

[0326] In this test, the positive electrode was charged to a potential of 3.7 V or higher, so the oxidation onset potential was calculated by the method A described above (Measurement of the oxidation onset potential of the accelerator). That is, the starting point of the capacity (0 mAh / g of positive electrode active material) was set when the positive electrode potential reached 3.7 V. As shown in FIG. 3, a curve was obtained by shifting Curves 1 and 2 in parallel. Then, as shown in FIG. 4, the difference in the capacity by weight of the positive electrode active material at the same positive electrode potential (Curve 1 - Curve 2) was calculated, whereby the reaction capacity (mAh / g) derived from the accelerator was plotted on the horizontal axis and the positive electrode potential (V vs. Li / Li) was plotted on the vertical axis. ＋ ) was plotted to obtain a differential curve (Curve 1-2). The positive electrode potential of 4.03 V, at which the capacity of the differential curve exceeded 5 mAh / g, was determined as the oxidation starting potential of the accelerator.

[0327] (ii) When LFP was used as the positive electrode active material and N,N,N',N'-tetramethyl-p-phenylenediamine was used as the accelerator, the positive electrode and negative electrode were prepared and assembled in the same manner as in "(i) When LFP was used as the positive electrode active material and 1,4-dimethoxybenzene was used as the accelerator" above.

[0328] Injection: 1.0 M LiPF in EC:MEC mixed solvent (volume ratio 1:2) ６ An electrolyte solution 1 was prepared by dissolving 1 mass % of vinylene carbonate and 0.1 mol / L of N,N,N',N'-tetramethyl-p-phenylenediamine.

[0329] On the other hand, 1.0 M LiPF in EC:MEC mixed solvent (volume ratio 1:2) ６ Electrolyte solution 2 was prepared by dissolving 1% by mass of vinylene carbonate.

[0330] Under atmospheric pressure, a temperature of 25 ° C., and a dry air environment with a dew point of -40 ° C. or less, 2 g of electrolyte solution 1 was injected into full cell 1, and 2 g of electrolyte solution 2 was injected into full cell 2. Subsequently, this was placed in a reduced pressure chamber, and the pressure was reduced from atmospheric pressure to -87 kPa, then returned to atmospheric pressure, and the cell was allowed to stand for 5 minutes. Thereafter, the operation of reducing the pressure from atmospheric pressure to -87 kPa and then returning to atmospheric pressure was repeated four times, and the cell was allowed to stand for 15 minutes, thereby impregnating the electrode laminate with the nonaqueous electrolyte solution. Thereafter, the electrode laminate housed in an aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was placed in a reduced pressure sealing machine, and the aluminum laminate packaging material was sealed by sealing at a pressure of 0.1 MPa at 180 ° C. for 10 seconds in a state where the pressure was reduced to -95 kPa. Full cells 1 and 2 for measuring the oxidation potential after injection and before the first charge were obtained.

[0331] As described above in the section (Measurement of Oxidation Onset Potential of Accelerator), the oxidation potential was measured under the following conditions. In a thermostatic chamber set at 45°C, constant current charging was performed at a current value of 0.1 C until the voltage reached 4.8 V. At this time, the positive electrode potential was measured against the lithium reference electrode. From the above measurements, as shown in Figure 5, the positive electrode potential (V vs Li / Li) was calculated for full cells 1 and 2 relative to the capacity per weight of the positive electrode active material (mAh / g of positive electrode active material). ＋) were plotted to obtain curves 1 and 2. However, in the case of full cell 1, the cell voltage did not rise to 4.8 V, so the measurement was stopped before reaching 4.8 V.

[0332] In this test, when constant-current charging was performed, the cell voltage of full cell 1 did not rise to 4.8 V, and the positive electrode potential was not charged to a range of 3.7 V or higher. Therefore, the oxidation onset potential was calculated using method B (Measurement of Oxidation Onset Potential of Accelerator) above. That is, the charge start point was set as the starting point for calculating the capacity (0 mAh / g of positive electrode active material), and as shown in Figures 5 and 6, curves 1 and 2 were shifted in parallel, and a difference curve (curve 1 - curve 2) at the same positive electrode potential was calculated. The positive electrode potential of 3.46 V, at which the capacity difference between curves 1 and 2 exceeded 5 mAh / g, was defined as the oxidation onset potential of the accelerator.

[0333] (iii) When LFP and various accelerators were used as the positive electrode active material The oxidation potentials of other accelerators were measured in the same manner as in the calculation of the oxidation onset potential described above. The results are shown in Table 1.

[0334] (iv) Measurement of the oxidation potential of the accelerator when LCO, NCM811, or NCA was used as the active material The oxidation potential of the accelerator was measured in the same manner as when LFP was used as the positive electrode active material, except that the positive electrode active material was changed in the preparation of the positive electrode. The results are shown in Tables 2 to 4.

[0335] (v) NaFe as the active material １／３ Ni １／ 3Mn １／３ O ２ (abbreviated as "NFNMO" in the table) was used. The cathode active material was changed in the positive electrode preparation, hard carbon was used as the negative electrode active material in the negative electrode preparation, a sodium reference electrode was used in the assembly, and a 1.0 M electrolyte solution containing 1% by mass of 1.0 M NaPF6 and fluoroethylene carbonate dissolved in a PC:DMC mixed solvent (volume ratio 1:2) was used as the electrolyte in the injection. The initial charge was performed at a constant current up to a voltage of 4.5 V, and the oxidation potential of the accelerator was measured in the same manner as when LFP was used as the positive electrode active material, except that the sodium reference potential was converted to the lithium reference potential in the same manner as in the measurement of the potential of the positive electrode precursor. The results are shown in Table 5.

[0336] Example 1-1 (Initial charge capacity density L of positive electrode active material) １ Measurement of initial discharge capacity density L ２ Measurement of the positive electrode active material: LiFePO ４ 91% by mass of the powder, 4% by mass of carbon black, 5% by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) were mixed to a solids concentration of 45% by mass to obtain a positive electrode slurry for a positive electrode half cell used for measuring the initial charge capacity of the positive electrode active material. The obtained slurry was applied at 100 g / m to one side of a 15 μm thick anchor-coated aluminum foil serving as a positive electrode current collector. ２ The coated layer was dried and pressed to obtain a positive electrode for a positive electrode half cell to be used for measuring the initial charge capacity of the positive electrode active material.

[0337] The obtained single-sided positive electrode was punched out to a coated area of ​​2 cm x 2 cm and vacuum dried at 200°C for 24 hours. The positive electrode terminal was connected by ultrasonic welding. The negative electrode terminal was connected by ultrasonic welding to a Li counter electrode, which was made of copper foil with lithium (Li) attached. This was combined with a polypropylene separator and a glass filter to obtain a positive electrode half-cell electrode laminate. This electrode laminate was placed in an exterior body made of aluminum laminate packaging, and the three sides of the exterior body, including the electrode terminal portion and the bottom portion, were heat-sealed at a temperature of 180°C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. As the electrolyte, 1.0 M LiPF in an EC:MEC mixed solvent (volume ratio 1:2) was used. ６ An electrolyte solution containing 1% by mass of vinylene carbonate was prepared.

[0338] 2 g of the nonaqueous electrolyte solution was injected into the electrode laminate housed in an aluminum laminate packaging material under atmospheric pressure, a temperature of 25 ° C., and a dry air environment with a dew point of -40 ° C. or less. Subsequently, this was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -87 kPa, then returned to atmospheric pressure, and the material was allowed to stand for 5 minutes. Thereafter, the operation of reducing the pressure from atmospheric pressure to -87 kPa and then returning to atmospheric pressure was repeated four times, and the material was allowed to stand for 15 minutes, thereby impregnating the electrode laminate with the nonaqueous electrolyte solution. Thereafter, the electrode laminate housed in the aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed by sealing at a pressure of 0.1 MPa at 180 ° C. for 10 seconds in a state where the pressure was reduced to -95 kPa, to prepare a positive electrode half cell.

[0339] The initial charge capacity density L of the positive electrode active material １ , initial discharge capacity density L ２ ) by setting the upper limit of the stable operating potential of the positive electrode active material, and the initial charge capacity density L １ , initial discharge capacity density L ２ The obtained L １ and L ２ is shown in Table 6 below.

[0340] (Preparation of non-aqueous alkali metal storage element) (Preparation of positive electrode precursor) LiFePO as positive electrode active material ４ , lithium carbonate, carbon black as a conductive material, and PVdF (polyvinylidene fluoride) as a binder were prepared in the composition shown in Table 6 below, and NMP (N-methylpyrrolidone) was further mixed to obtain a positive electrode precursor slurry. The obtained positive electrode precursor slurry was applied to one side of a 15 μm thick anchor-coated aluminum foil with the basis weight shown in Table 6 below, and pressed to obtain a positive electrode precursor. In order to calculate the volume difference described above (negative electrode dope amount, volume difference, pre-doping volume efficiency), the thickness t2 of this positive electrode precursor was measured as the film thickness of the positive electrode precursor containing lithium carbonate.

[0341] (Preparation of Negative Electrode Precursor) 91.0 parts by mass of artificial graphite, 5.0 parts by mass of silicon monoxide (SiO), 2.0 parts by mass of styrene-butadiene rubber, 2.0 parts by mass of carboxymethyl cellulose (CMC), and water were mixed to obtain a negative electrode precursor slurry. The obtained negative electrode precursor slurry was applied to one side of a 10 μm-thick electrolytic copper foil at a basis weight shown in Table 6 below, and pressed to obtain a negative electrode precursor.

[0342] (Assembly) The resulting positive electrode precursor was cut to a coated area of ​​2 cm x 2 cm, and the resulting negative electrode precursor was cut to a coated area of ​​2.2 cm x 2.2 cm. A 15 μm thick microporous membrane separator was sandwiched between the positive electrode precursor and the negative electrode precursor and laminated. Then, a negative electrode terminal and a positive electrode terminal were connected to the negative electrode precursor and the positive electrode precursor, respectively, by ultrasonic welding to form an electrode laminate. This electrode laminate and a lithium reference electrode, which was press-bonded to SUS foil and wrapped in a microporous separator, were housed in an exterior body made of aluminum laminate packaging, and the three sides of the exterior body, including the electrode terminal portion and the bottom portion, were heat-sealed at a temperature of 180 ° C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. Vacuum drying was performed at a temperature of 50 ° C, a pressure of 50 Pa, and a drying time of 25 hours.

[0343] (Injection of electrolyte) 1.0 M LiPF in EC:MEC mixed solvent (volume ratio 1:2) was used as the electrolyte. ６ An electrolyte solution was prepared by dissolving 1 mass % of vinylene carbonate and 0.1 mol / L of 1,4-dimethoxybenzene.

[0344] 2 g of the nonaqueous electrolyte solution was injected into the electrode laminate housed in an aluminum laminate packaging material under atmospheric pressure, a temperature of 25 ° C., and a dry air environment with a dew point of -40 ° C. or less. Subsequently, this was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -87 kPa, then returned to atmospheric pressure, and the material was allowed to stand for 5 minutes. After that, the operation of reducing the pressure from atmospheric pressure to -87 kPa and then returning to atmospheric pressure was repeated four times, and the material was allowed to stand for 15 minutes, and the nonaqueous electrolyte solution was impregnated into the electrode laminate. Thereafter, the electrode laminate housed in the aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed by sealing at a pressure of 0.1 MPa for 10 seconds at 180 ° C. in a state where the pressure was reduced to -95 kPa.

[0345] ((A １ +0.3 x B １ ) / C １ ) (capacity ratio (A １ +0.3 x B １ ) / C １ According to the method described in (A) １ +0.3 x B １ ) / C １ was calculated.

[0346] (E １ / D １ ) (irreversible capacity ratio E １ / D １ and its calculation) according to the method described in １ / D １ was calculated.

[0347] (Initial charge pre-doping) The obtained injected battery was subjected to constant current charging at a 0.1C rate using a charge / discharge device (TOSCAT-3100U) manufactured by Toyo Systems Co., Ltd., in a 45 ° C. environment until a voltage of 4.7 V was reached, followed by a 4.7V constant voltage charge for 30 minutes to perform initial charging, and pre-doping was performed on the negative electrode precursor. A constant current discharge was performed at a 0.1C rate to 2.4V, the lower limit of stable operating voltage. At this time, the positive electrode final potential was measured using the method described in (Measurement of the potential of the positive electrode precursor) and is listed in the table below.

[0348] (Gassing) After pre-doping, the aluminum laminate packaging material of the nonaqueous alkali metal storage element was partially opened in a dry air environment at a temperature of 25°C and a dew point of -40°C. Subsequently, the nonaqueous alkali metal storage element was placed in a reduced pressure chamber, and the pressure was reduced from atmospheric pressure to -80 kPa over 3 minutes, and then the pressure was returned to atmospheric pressure over 3 minutes. Thereafter, the nonaqueous alkali metal storage element was placed in a reduced pressure sealing machine, and the pressure was reduced to -90 kPa. The aluminum laminate packaging material was sealed by sealing at 200°C for 10 seconds at a pressure of 0.1 MPa, and a nonaqueous alkali metal storage element was obtained.

[0349] (Weight ratio of alkali metal carbonate per positive electrode mixture layer) According to the method described above (Measurement of alkali metal carbonate in positive electrode), the weight ratio of alkali metal carbonate per positive electrode mixture layer was measured, and the results are shown in the table.

[0350] (Amount of Lithium Metal in Negative Electrode) The amount of alkali metal in the negative electrode mixture was measured according to the method described above (Measurement of Amount of Alkali Metal in Negative Electrode Mixture), and the results are shown in the table.

[0351] (Amount of Negative Electrode Dope) The amount of negative electrode dope Q2 (mAh / cell) was measured according to the method described above in the section (Amount of Negative Electrode Dope, Volume Difference, Pre-Doping Volumetric Efficiency).

[0352] (Effective utilization rate of positive electrode active material) The above (discharge capacity Q, full cell capacity density P per mass of positive electrode active material) ｆｕｌｌ The discharge capacity Q (mAh) of the cell was measured by the method described in ...

Claims

1. A non-aqueous alkali metal storage element precursor having a positive electrode precursor, a negative electrode precursor, a separator, an outer casing, and a non-aqueous electrolyte solution containing alkali metal ions, wherein the negative electrode precursor contains a material that occludes and releases alkali metal ions as a negative electrode active material, the positive electrode precursor has a positive electrode active material layer containing a positive electrode active material that occludes and releases alkali metal ions, an alkali metal carbonate is contained in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or in both, the non-aqueous electrolyte solution further contains a carbonate decomposition accelerator, and the oxidation onset potential of the carbonate decomposition accelerator is 3.8 V (vs. Li / Li ＋ ) or more 4.7V (vs Li / Li ＋ ) or less.

2. The initial charge capacity per area of ​​the positive electrode active material is A １ (Ah / cm ２ ), the theoretical capacity per area of ​​the alkali metal carbonate is B １ (Ah / cm ２ ), the initial charge capacity per area of ​​the negative electrode active material is C １ (Ah / cm ２ ) and then (A １ +0.3 x B １ ) / C １ The non-aqueous alkali metal storage element precursor according to claim 1 , wherein the non-aqueous alkali metal storage element precursor satisfies the following condition:

3. The nonaqueous alkali metal storage element precursor according to claim 1 or 2, wherein the carbonate decomposition accelerator contains at least one selected from the group consisting of methoxybenzene derivatives, phenyl group-containing organic compounds, 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) derivatives, pyridine-N-oxide derivatives, and cyclohexylbenzene derivatives.

4. The non-aqueous alkali metal storage element precursor according to claim 1 or 2, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds.

5. A non-aqueous alkali metal storage element precursor according to claim 1 or 2, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds excluding biphenyl.

6. The nonaqueous alkali metal electricity storage element precursor according to claim 1 or 2, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, biphenyl, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, 4-picoline-N-oxide, and 4-tert-butylpyridine-N-oxide.

7. The nonaqueous alkali metal electricity storage element precursor according to claim 1 or 2, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, and 4-picoline-N-oxide.

8. The irreversible capacity per area of ​​the positive electrode precursor is D １ (mAh / cm ２ ), the irreversible capacity per area of ​​the negative electrode precursor is E １ (mAh / cm ２ ) , 1.05<E １ / D １ The non-aqueous alkali metal storage element precursor according to claim 1 or 2, which satisfies the above.

9. The nonaqueous alkali metal energy storage element precursor according to claim 1 or 2, wherein the positive electrode active material layer of the positive electrode precursor contains the alkali metal carbonate in an amount of 0.2 to 15 mass % based on the total mass of the positive electrode active material layer.

10. The non-aqueous alkali metal storage element precursor according to claim 1 or 2, wherein the intermediate layer contains 20 to 95 mass % of the alkali metal carbonate based on the total mass of the intermediate layer.

11. The nonaqueous alkali metal storage element precursor according to claim 1 or 2, wherein the nonaqueous electrolyte solution contains the carbonate decomposition accelerator in an amount of 0.0001 mol / L to 1.5 mol / L based on the total mass of the nonaqueous electrolyte solution.

12. The nonaqueous alkali metal storage element precursor according to claim 1 or 2, wherein the negative electrode active material comprises at least one selected from the group consisting of an alloy-based negative electrode material that forms an alloy with the alkali metal of the alkali metal ion, and an amorphous carbon material.

13. The nonaqueous alkali metal storage element precursor according to claim 1 or 2, wherein the negative electrode active material comprises an alloy-based negative electrode material that forms an alloy with the alkali metal of the alkali metal ion, and the alloy-based negative electrode material is at least one selected from the group consisting of silicon, silicon compounds, tin, tin compounds, and composite materials of these with carbon or a carbonaceous material.

14. A non-aqueous alkali metal storage element comprising a positive electrode, a negative electrode, a separator, an exterior body, and a non-aqueous electrolyte solution containing alkali metal ions, wherein the negative electrode contains a material that occludes and releases the alkali metal ions as a negative electrode active material, the positive electrode has a positive electrode active material layer containing a positive electrode active material that occludes and releases the alkali metal ions, the non-aqueous electrolyte solution further contains a carbonate decomposition accelerator, and the oxidation onset potential of the carbonate decomposition accelerator is 3.8 V (vs. Li / Li ＋ ) or more 4.7V (vs Li / Li ＋ ) or less, and the effective utilization rate of the positive electrode active material is 85 to 99.5%.

15. The nonaqueous alkali metal storage element according to claim 14, wherein the amount of alkali metal per negative electrode active material layer as measured by solid-state NMR is 0.06 mmol / g or less.

16. The nonaqueous alkali metal storage element according to claim 14 or 15, wherein the carbonate decomposition accelerator contains at least one selected from the group consisting of methoxybenzene derivatives, phenyl group-containing organic compounds, TEMPO derivatives, pyridine-N-oxide derivatives, and cyclohexylbenzene derivatives.

17. The non-aqueous alkali metal storage element according to claim 14 or 15, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds.

18. A non-aqueous alkali metal storage element according to claim 14 or 15, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds excluding biphenyl.

19. The nonaqueous alkali metal electricity storage element according to claim 14 or 15, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, biphenyl, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, 4-picoline-N-oxide, and 4-tert-butylpyridine-N-oxide.

20. The nonaqueous alkali metal electricity storage element according to claim 14 or 15, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, and 4-picoline-N-oxide.

21. The remaining capacity per area of ​​the positive electrode is F １ (mAh / cm ２ ), the irreversible capacity per area of ​​the negative electrode is G １ (mAh / cm ２ ) and 0.01<F １ / G １ The nonaqueous alkali metal storage element according to claim 14 or 15, wherein the above-mentioned relationship satisfies <0.

9.

22. The nonaqueous alkali metal storage element according to claim 14 or 15, wherein the positive electrode active material layer further contains an alkali metal carbonate in an amount of 0.02 to 1.5 mass % based on the total mass of the positive electrode active material layer.

23. The nonaqueous alkali metal storage element according to claim 14 or 15, further comprising an optional intermediate layer between the positive electrode active material layer and the separator, the intermediate layer containing an alkali metal carbonate in an amount of 0.2 to 9.5 mass % based on the total mass of the intermediate layer.

24. The nonaqueous alkali metal storage element according to claim 14 or 15, wherein the carbonate decomposition accelerator is contained in the nonaqueous electrolyte solution in an amount of 0.0001 mol / L to 1.5 mol / L.

25. The nonaqueous alkali metal storage element according to claim 14 or 15, wherein the negative electrode active material comprises at least one selected from the group consisting of an alloy-based negative electrode material that forms an alloy with the alkali metal of the alkali metal ions, and an amorphous carbon material.

26. The nonaqueous alkali metal storage element according to claim 14 or 15, wherein the negative electrode active material comprises an alloy-based negative electrode material that forms an alloy with the alkali metal of the alkali metal ions, and the alloy-based negative electrode material is at least one selected from the group consisting of silicon, silicon compounds, tin, tin compounds, and composite materials of these with carbon or a carbonaceous material.

27. A method for manufacturing a non-aqueous alkali metal storage element, the method comprising: applying a voltage between a positive electrode precursor and a negative electrode precursor to a non-aqueous alkali metal storage element precursor having a positive electrode precursor, a negative electrode precursor, a separator, an outer casing, and a non-aqueous electrolyte solution containing alkali metal ions, thereby doping alkali metal ions into a negative electrode active material of the negative electrode precursor; the negative electrode precursor contains a material that occludes and releases alkali metal ions as the negative electrode active material; the positive electrode precursor has a positive electrode active material layer containing a positive electrode active material that occludes and releases alkali metal ions; an alkali metal carbonate is contained in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or in both; the non-aqueous electrolyte solution further contains a carbonate decomposition accelerator; and the carbonate decomposition accelerator has an oxidation onset potential of 3.8 V (vs. Li / Li ＋ ) or more 4.7V (vs Li / Li ＋ ) A method as follows.

28. The potential of the positive electrode precursor is 4.15 to 4.75 V (vs Li / Li ＋ 28. The method of claim 27, comprising applying a voltage between the positive electrode precursor and the negative electrode precursor to dope the negative electrode active material with alkali metal ions such that:

29. The method according to claim 27, wherein the alkali metal ions are lithium ions, and the method comprises applying a voltage of 4.1 V or more and 4.6 V or less between the positive electrode precursor and the negative electrode precursor to dope the lithium ions into the negative electrode active material.

30. The method according to claim 27, wherein the alkali metal ions are lithium ions, and the method comprises applying a voltage of 4.2 V or more and less than 4.5 V between the positive electrode precursor and the negative electrode precursor to dope the lithium ions into the negative electrode active material.

31. The method according to claim 27, wherein the alkali metal ions are sodium ions, and a voltage of 3.8 V or more and 4.3 V or less is applied between the positive electrode precursor and the negative electrode precursor to dope the negative electrode active material with the sodium ions.

32. The initial charge capacity per area of ​​the positive electrode active material is A １ (Ah / cm ２ ), the theoretical capacity per area of ​​the alkali metal carbonate is B １ (Ah / cm ２ ), the initial charge capacity per area of ​​the negative electrode active material is C １ (Ah / cm ２ ) and then (A １ +0.3 x B １ ) / C １ The method according to claim 27 or 28, wherein the inequality satisfies ≦0.

98.

33. The method according to claim 27 or 28, wherein the carbonate decomposition accelerator contains at least one selected from the group consisting of methoxybenzene derivatives, phenyl-containing organic compounds, 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) derivatives, pyridine-N-oxide derivatives, and cyclohexylbenzene derivatives.

34. The method according to claim 27 or 28, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds.

35. The method according to claim 27 or 28, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds excluding biphenyl.

36. The method of claim 27 or 28, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, biphenyl, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, 4-picoline-N-oxide, and 4-tert-butylpyridine-N-oxide.

37. The method of claim 27 or 28, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, and 4-picoline-N-oxide.

38. The irreversible capacity per area of ​​the positive electrode precursor is D １ (Ah / cm ２ ), the irreversible capacity per area of ​​the negative electrode precursor is E １ (Ah / cm ２ ) 1.05 × D １ <E １ 29. The method according to claim 27 or 28, wherein 39. A method for manufacturing a capacity-restored non-aqueous alkali metal storage element, wherein the non-aqueous alkali metal storage element before capacity restoration comprises: a positive electrode including a positive electrode active material layer disposed on a positive electrode current collector; a negative electrode including a negative electrode active material layer disposed on a negative electrode current collector; a separator; and a non-aqueous electrolyte solution containing alkali metal ions, wherein the positive electrode active material layer comprises a positive electrode active material that absorbs and releases alkali metal ions; the non-aqueous alkali metal storage element before capacity restoration contains an alkali metal carbonate in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or in both; the non-aqueous electrolyte solution further contains a carbonate decomposition accelerator, and the oxidation onset potential of the carbonate decomposition accelerator is equal to or higher than the stable operating potential of the positive electrode active material and equal to or lower than 4.7 V (vs. Li / Li+); The method includes recovering the capacity of the nonaqueous alkali metal storage element by increasing the potential of the positive electrode of the nonaqueous alkali metal storage element before the capacity recovery to a stable working potential of the positive electrode active material or higher.

40. The theoretical capacity per area of ​​the alkali metal carbonate is B １ (Ah / cm ２ ), the remaining capacity per area of ​​the negative electrode active material is J １ (Ah / cm ２ ), the total capacity per area of ​​the negative electrode active material is J ２ (Ah / cm ２ ) , 0.1≦J １ / J ２ ≦0.5, and 0.03≦0.3×B １ / J １ 40. The method of claim 39, wherein the relationship between the capacity recovery potential and the positive electrode potential satisfies the condition of ≦0.98, and the method further comprises suppressing decomposition of the alkali metal carbonate in the nonaqueous alkali metal electricity storage element before the potential of the positive electrode of the nonaqueous alkali metal electricity storage element before the capacity recovery is increased to or above a stable working potential of the positive electrode active material.

41. The method of claim 39 or 40, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives, phenyl-containing organic compounds, TEMPO derivatives, pyridine-N-oxide derivatives, and cyclohexylbenzene derivatives.

42. The method according to claim 39 or 40, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds.

43. The method according to claim 39 or 40, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds excluding biphenyl.

44. The method of claim 39 or 40, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, biphenyl, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, 4-picoline-N-oxide, and 4-tert-butylpyridine-N-oxide.

45. The method of claim 39 or 40, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, and 4-picoline-N-oxide.

46. ​​The method includes determining the initial capacity P of the nonaqueous alkali metal storage element. １ 41. The method of claim 39 or 40, comprising recovering the capacity of the nonaqueous alkali metal capacitor element before capacity recovery by 2% or more, the nonaqueous alkali metal capacitor element having a capacity of 95% or less based on (mAh).

47. The method of claim 39 or 40, wherein the method comprises restoring the capacity of the nonaqueous alkali metal storage element by increasing the voltage of the nonaqueous alkali metal storage element to or above the upper limit of the stable operating voltage of the positive electrode active material.

48. The positive electrode active material layer further contains the alkali metal carbonate, and the mass ratio of the alkali metal carbonate based on the total mass of the positive electrode active material layer is X ３ (mass%), X ３ 41. The method of claim 39 or 40, wherein is greater than or equal to 0.3 and less than or equal to 20.

0.

49. The nonaqueous alkali metal storage element before capacity recovery further comprises an intermediate layer containing the alkali metal carbonate, and the mass ratio of the alkali metal carbonate based on the total mass of the intermediate layer is X. ４ (mass%), X ４ The method of claim 39 or 40, wherein is 20 or more and 95 or less.

50. In the nonaqueous alkali metal storage element before capacity recovery, the mass ratio of the positive electrode active material is X based on the total mass of the positive electrode active material layer. ２ (mass%), X ２ The method of claim 39 or 40, wherein is 60 or more and 99 or less.

51. The discharge capacity of a positive electrode half cell using the positive electrode removed from the nonaqueous alkali metal storage element before capacity recovery, or using the positive electrode and the intermediate layer if an intermediate layer is present, in the potential region of the stable operating potential of the positive electrode active material is calculated as K １ (mAh / cm ２ ) and the discharge capacity of the negative electrode half-cell of the negative electrode taken out from the nonaqueous alkali metal storage element before the capacity recovery was K ３ (mAh / cm ２ ) and 0.80≦K １ / K ３ 41. The method of claim 39 or 40, wherein ≦1.

2.

52. The method according to claim 39 or 40, wherein the voltage applied to the nonaqueous alkali metal storage element during capacity recovery is equal to or higher than the upper limit of the stable operating voltage of the positive electrode active material and is equal to or lower than 4.6 V.

53. The method according to claim 39 or 40, wherein the nonaqueous alkali metal storage element before capacity recovery is in the form of a battery pack comprising a plurality of unit cells of the nonaqueous alkali metal storage element before capacity recovery, and the capacity of the battery pack is recovered without disassembling the unit cells.

54. The method of claim 39 or 40 for restoring the capacity of the non-aqueous alkali metal capacitor element, comprising restoring the capacity multiple times.

55. The method of claim 39 or 40, comprising restoring the capacities of a plurality of non-aqueous alkali metal storage elements, at least two of the plurality of non-aqueous alkali metal storage elements having different capacities from each other, and restoring the capacities of the plurality of non-aqueous alkali metal storage elements and reducing the difference in capacity by controlling at least one selected from the group consisting of the potential, temperature, and charge current capacity of the positive electrode.

56. The method according to claim 39 or 40, wherein the carbonate decomposition accelerator is contained in the electrolyte at 0.0001 mol / L to 1.5 mol / L.

57. A non-aqueous alkali metal storage element comprising: a positive electrode including a positive electrode active material layer disposed on a positive electrode current collector; a negative electrode including a negative electrode active material layer disposed on a negative electrode current collector; a separator; and a non-aqueous electrolyte containing alkali metal ions, wherein the positive electrode active material layer contains a positive electrode active material that absorbs and releases alkali metals; the non-aqueous alkali metal storage element contains an alkali metal carbonate in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or in both; the non-aqueous electrolyte further contains a carbonate decomposition accelerator, and the oxidation onset potential of the carbonate decomposition accelerator is 4.7 V (vs. Li / Li) or higher than the stable operating potential of the positive electrode active material. ＋ ) or less.

58. The theoretical capacity per area of ​​the alkali metal carbonate is B １ (Ah / cm ２ ), the remaining capacity per area of ​​the negative electrode active material is J １ (Ah / cm ２ ), the total capacity per area of ​​the negative electrode active material is F ２ (Ah / cm ２ ) , 0.1≦J １ / J ２ ≦0.5, and 0.03≦0.3×B １ / J １ 58. The nonaqueous alkali metal storage element according to claim 57, wherein the nonaqueous alkali metal storage element satisfies the following condition: ≦0.

98.

59. The nonaqueous alkali metal storage element according to claim 57 or 58, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives, phenyl group-containing organic compounds, TEMPO derivatives, pyridine-N-oxide derivatives, and cyclohexylbenzene derivatives.

60. A non-aqueous alkali metal storage element according to claim 57 or 58, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds.

61. A non-aqueous alkali metal storage element according to claim 57 or 58, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of methoxybenzene derivatives and phenyl-containing organic compounds excluding biphenyl.

62. The nonaqueous alkali metal electricity storage element according to claim 57 or 58, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, biphenyl, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, 4-picoline-N-oxide, and 4-tert-butylpyridine-N-oxide.

63. The nonaqueous alkali metal electricity storage element according to claim 57 or 58, wherein the carbonate decomposition accelerator comprises at least one selected from the group consisting of anisole, 4-bromoanisole, 2-bromo-4-fluoroanisole, 2,4,6-tribromoanisole, 1,4-dimethoxybenzene, 2-bromo-1,4-dimethoxybenzene, 1,4-dibromo-2,5-dimethoxybenzene, 2,5-ditert-butyl-1,4-dimethoxybenzene, cyclohexylbenzene, hexamethylbenzene, tert-butylphenyl carbonate, TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, pyridine-N-oxide, and 4-picoline-N-oxide.

64. The positive electrode active material layer further contains the alkali metal carbonate, and the mass ratio of the alkali metal carbonate based on the total mass of the positive electrode active material layer is X ３ (mass%), X ３ 59. The nonaqueous alkali metal storage element according to claim 57 or 58, wherein the value of is 0.3 or more and 20.0 or less.

65. The nonaqueous alkali metal storage element further includes an intermediate layer containing the alkali metal carbonate, and the mass ratio of the alkali metal carbonate based on the total mass of the intermediate layer is X. ４ (mass%), X ４ 59. The nonaqueous alkali metal storage element according to claim 57 or 58, wherein the value of σ is 20 or more and 95 or less.

66. A nonaqueous alkali metal storage element according to claim 57 or 58, wherein the exterior of the nonaqueous alkali metal storage element has a gas permeability mechanism.

67. The nonaqueous alkali metal storage element has an initial capacity P １ 59. The nonaqueous alkali metal storage element according to claim 57 or 58, wherein when the capacity has deteriorated to 95% or less based on the capacity (mAh), the potential of the positive electrode is increased to an oxidative decomposition potential of the alkali metal carbonate or higher to recover 2% or more of the capacity.

68. A nonaqueous alkali metal storage element as described in claim 57 or 58, which is used to restore capacity when capacity has deteriorated by increasing the voltage of the nonaqueous alkali metal storage element to or above the upper limit of the stable operating voltage of the positive electrode active material.

69. The nonaqueous alkali metal storage element according to claim 57 or 58, wherein the carbonate decomposition accelerator is contained in the electrolyte at 0.0001 mol / L to 1.5 mol / L.

70. A battery pack comprising a plurality of the non-aqueous alkali metal storage elements according to claim 57 or 58.

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