Non-aqueous alkali metal energy storage element and method for manufacturing the same

Abstract

The object of the invention of the first embodiment of the present disclosure is to enable alkali metal carbonate decomposition at a relatively low decomposition voltage when using alkali metal carbonate as a predoping source for non-aqueous alkali metal energy storage elements, thereby increasing the volumetric efficiency of the predoping. [Solution] The non-aqueous alkali metal energy storage element of this disclosure comprises a positive electrode, a negative electrode, a separator, an outer casing, and a non-aqueous electrolyte containing alkali metal ions. The negative electrode contains a material that intercepts and releases alkali metal ions as a negative electrode active material, the positive electrode has a positive electrode active material layer containing the positive electrode active material that intercepts and releases alkali metal ions, and the non-aqueous electrolyte further contains a carbonate decomposition accelerator. The oxidation initiation potential of the carbonate decomposition accelerator is 3.8V (vs Li / Li + ) Above 4.7V (vs Li / Li + ) or less, and the effective utilization rate of the positive electrode active material is 85-99.5%.

Description

[Technical Field]

[0001] This disclosure relates to non-aqueous alkali metal energy storage elements such as lithium-ion secondary batteries, their precursors, a method for manufacturing a non-aqueous alkali metal energy storage element with restored capacity, and a non-aqueous alkali metal energy storage element with recoverable capacity. [Background technology]

[0002] In recent years, from the perspective of protecting the global environment and promoting the efficient use of energy to conserve resources, wind power generation power smoothing systems or off-peak electricity storage systems, distributed household energy storage systems based on solar power generation technology, and energy storage systems for electric vehicles have attracted attention. As a promising candidate for high-energy-density batteries that can meet these demands, the development of non-aqueous alkali metal energy storage elements, such as lithium-ion secondary batteries (hereinafter referred to as LiBs), is being vigorously pursued.

[0003] In the non-aqueous alkali metal energy storage elements used in these energy storage systems, vigorous technological development is underway to achieve both high capacity density and durability.

[0004] Conventionally, in non-aqueous alkali metal energy storage devices, alkali metal ions equivalent to the initial irreversible capacity of the negative electrode are trapped at the solid electrolyte interface (SEI) during the initial charge. This results in a loss of capacity equivalent to the irreversible capacity of the full cell's discharge capacity.

[0005] One technique for improving the capacity density of non-aqueous alkali metal energy storage elements is pre-doping. By using pre-doping, it is possible to compensate for the capacity loss equivalent to the initial irreversible capacity of the negative electrode. For example, a technique in which alkali metal carbonate is contained in the positive electrode and used as a pre-doping source by charging is disclosed in Patent Documents 1 and 2. However, these techniques had the following problems. Specifically, charging at a high voltage is required to sufficiently decompose the alkali metal carbonate, which increases resistance, while charging at a low voltage does not sufficiently decompose the alkali metal carbonate. In addition, there were other issues such as the effective utilization rate of the positive electrode active material, capacity density, gas amount when stored at 40°C, positive electrode active material loss, capacity retention rate after cycle testing, and minor short circuits.

[0006] On the other hand, in recent years, demand for LiBs has been rapidly expanding, particularly for electric vehicle applications. This has created resource supply risks for LiBs (e.g., cobalt), leading to increased adoption of lithium transition metal compounds such as lithium iron phosphate, which have lower resource risks. While lithium transition metal compounds have stable crystal structures and offer the potential for long lifespan among LiB cathode materials, they have lower energy density. Furthermore, lithium transition metal compounds are inexpensive, and the recycling process, which involves decomposing used LiBs and regenerating them as materials (cathode materials or various elements), is complex, making it difficult to achieve economic viability through recycling.

[0007] Generally, lithium-ion batteries (LiBs) experience capacity degradation and a shortened lifespan due to charge-discharge cycles and use in high-temperature environments. Therefore, research and development to improve the durability of LiBs through improvements in battery materials and battery design is being actively pursued, and various technologies have been disclosed (Patent Documents 3-6).

[0008] Patent Document 3 describes a lithium-ion battery (LiB) containing an additive in the electrolyte or cathode that has an oxidation potential exceeding the nominal voltage of the LiB and below the decomposition potential of the electrolyte, and that can be oxidized at the cathode. After degradation, the battery capacity of this LiB can be restored by charging it at a potential higher than the oxidation potential of the additive.

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

[0010] Patent document 5 describes a technology 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 technique for restoring the capacity of a degraded LiB by over-discharging it, thereby reactivating the inert lithium incorporated into the negative electrode SEI (Solid Electrolyte Interphase) and the non-opposing part of the negative electrode.

[0012] In this 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. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] International Publication No. 2017 / 126682 [Patent Document 2] International Publication No. 2020 / 017515 [Patent Document 3] Japanese Patent Publication No. 2012-174437 [Patent Document 4] International Publication No. 2017 / 126682 [Patent Document 5] International Publication No. 2019 / 098197 [Patent Document 6] International Publication No. 2022 / 196114 [Non-patent literature]

[0014] [Non-Patent Document 1] EP Barrett, LG Joyner, and P. Halenda, "The Determination of Pore Volume and Area Distributions in Porous Substances", J.Am.Chem.Soc., (1951), 73, pp.373-380 [Non-Patent Document 2] BCLippens, and JHde Boer, "Studies on pore Systems in Catalysis V. The t Method", J.Catalysis,(1965), 4, pp.319-323 [Non-Patent Document 3] RSMikhail, S.Brunauer, and EEBodor, "Investigations of a Complete Pore Structure Analysis", J.Colloid Interface Sci.,(1968), 26, pp.45-53 [Overview of the project] [Problems that the invention aims to solve]

[0015] The object of the invention of the first embodiment of this disclosure is to enable alkali metal carbonate decomposition at a relatively low decomposition voltage when using alkali metal carbonate as a predoping source for non-aqueous alkali metal energy storage elements, thereby increasing the volumetric efficiency of the predoping. In one aspect of this disclosure, the effective utilization rate, capacity density, and capacity retention rate of the positive electrode active material are improved, and resistance, gas amount at 40°C storage, positive electrode active material loss, and minor short circuits after cycle testing are suppressed.

[0016] The 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 carbonates, suppress the decomposition of alkali metal carbonates from the manufacture of the energy storage element to its use, and restore the capacity of the energy storage element by decomposing the alkali metal carbonates in the energy storage element after degradation through a simple electrochemical operation. [Means for solving the problem]

[0017] Examples of embodiments of this disclosure are listed below. [1] A non-aqueous alkali metal energy storage element precursor having a positive electrode precursor, a negative electrode precursor, a separator, an outer casing, and a non-aqueous electrolyte containing alkali metal ions, The anode precursor contains a material that intercepts and deintercepts alkali metal ions as the anode active material, The positive electrode precursor has a positive electrode active material layer containing a positive electrode active material that intercepts and releases alkali metal ions, The 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 thereof. The aforementioned non-aqueous electrolyte further contains a carbonate decomposition accelerator, The oxidation initiation potential of the carbonate decomposition accelerator is 3.8V (vs Li / Li + ) Above 4.7V (vs Li / Li + ) Non-aqueous alkali metal energy storage element precursors. [2] The initial charge capacity per unit area of ​​the positive electrode active material is A1 (Ah / cm²). 2 ), the theoretical volume per unit area of ​​the alkali metal carbonate is B1 (Ah / cm³). 2 ), the initial charge capacity per unit area of ​​the negative electrode active material is C1 (Ah / cm²). 2 ) When that is the case, (A1 + 0.3 × B1) / C1 ≤ 0.98 A non-aqueous alkali metal energy storage element precursor as described in item 1, which satisfies the requirements. [3] The non-aqueous alkali metal energy 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 non-aqueous alkali metal energy storage element precursor according to item 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] The non-aqueous alkali metal energy storage element precursor according to item 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 non-aqueous alkali metal energy 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 non-aqueous alkali metal energy 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, 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 unit area of ​​the positive electrode precursor is D1 (mAh / cm²). 2 ), the irreversible capacity per unit area of ​​the negative electrode precursor is set to E1 (mAh / cm²). 2 ) When that is the case, 1.05 <E1 / D1 A non-aqueous alkali metal energy storage element precursor that satisfies any one of items 1 to 7. [9] The positive electrode precursor comprises a positive electrode active material layer containing 0.2 to 15% by mass of the alkali metal carbonate based on the total mass of the positive electrode active material layer, as described in any one of items 1 to 8, for a non-aqueous alkali metal energy storage element precursor.

[10] The intermediate layer contains 20 to 95% by mass of the alkali metal carbonate based on the total mass of the intermediate layer, and is a non-aqueous alkali metal energy storage element precursor according to any one of items 1 to 9.

[11] The non-aqueous electrolyte contains the carbonate decomposition accelerator at a concentration of 0.0001 mol / L to 1.5 mol / L based on the total mass of the non-aqueous electrolyte, and is a non-aqueous alkali metal energy storage element precursor according to any one of items 1 to 10.

[12] 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, as described in any one of items 1 to 11, for a non-aqueous alkali metal energy storage element precursor.

[13] The negative electrode active material includes 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 carbonaceous materials. The non-aqueous alkali metal storage element precursor according to any one of items 1 to 12.

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

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

[16] The non-aqueous 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 non-aqueous 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 non-aqueous alkali metal energy storage element according to item 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 non-aqueous alkali metal energy 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 non-aqueous alkali metal energy 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. [twenty one] The excess capacity per unit area of ​​the positive electrode is F1 (mAh / cm²). 2 ), the irreversible capacity per unit area of ​​the negative electrode is G1 (mAh / cm²). 2 ) When that is the case, 0.01 <F1 / G1<0.9 A non-aqueous alkali metal energy storage element described in any one of items 14 to 20, which satisfies the requirements. [twenty two] The positive electrode active material layer further contains an alkali metal carbonate in an amount of 0.02 to 1.5% by mass, based on the total mass of the positive electrode active material layer, as described in any one of items 14 to 21. [twenty three] The non-aqueous alkali metal energy storage element further comprises an optional intermediate layer between the positive electrode active material layer and the separator, wherein the intermediate layer contains an alkali metal carbonate in an amount of 0.2 to 9.5% by mass based on the total mass of the intermediate layer, as described in any one of items 14 to 22. [twenty four] A non-aqueous alkali metal energy storage element according to any one of items 14 to 23, wherein the carbonate decomposition accelerator is contained in the non-aqueous electrolyte at a concentration of 0.0001 mol / L to 1.5 mol / L. [twenty five] The non-aqueous alkali metal energy 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 ion, and an amorphous carbon material.

[26] The non-aqueous alkali metal energy storage element according to any one of items 14 to 25, wherein the negative electrode active material includes an alloying negative electrode material that forms an alloy with the alkali metal of the alkali metal ion, and the alloying 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 carbonaceous materials.

[27] A method for manufacturing a non-aqueous alkali metal energy storage element, wherein the method is: The present invention relates to a non-aqueous alkali metal energy storage element precursor having a positive electrode precursor, a negative electrode precursor, a separator, an outer casing, and a non-aqueous electrolyte containing alkali metal ions, and includes applying a voltage between the positive electrode precursor and the negative electrode precursor to dope the negative electrode active material of the negative electrode precursor with alkali metal ions. The negative electrode precursor contains a material that intercepts and deintercepts 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 intercepts and releases alkali metal ions, The 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 thereof. The aforementioned non-aqueous electrolyte further contains a carbonate decomposition accelerator, The oxidation initiation potential of the carbonate decomposition accelerator is 3.8V (vs Li / Li + ) Above 4.7V (vs Li / Li + The method is as follows:

[28] The potential of the positive electrode precursor is 4.15~4.75V (vs Li / Li + The method according to item 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 item 27, wherein the alkali metal ion is a lithium ion, and the method comprises applying a voltage of 4.1V to 4.6V between the positive electrode precursor and the negative electrode precursor to dope the negative electrode active material with the lithium ion.

[30] The method according to item 27, wherein the alkali metal ion is a lithium ion, and the method comprises applying a voltage of 4.2V or more and less than 4.5V between the positive electrode precursor and the negative electrode precursor to dope the negative electrode active material with the lithium ion.

[31] The method according to item 27, wherein the alkali metal ion is a sodium ion, a voltage of 3.8V to 4.3V is applied between the positive electrode precursor and the negative electrode precursor, and the negative electrode active material is doped with the sodium ion.

[32] The initial charge capacity per unit area of ​​the positive electrode active material is A1 (Ah / cm²). 2 ), the theoretical volume per unit area of ​​the alkali metal carbonate is B1 (Ah / cm³). 2 ), the initial charge capacity per unit area of ​​the negative electrode active material is C1 (Ah / cm²). 2 ) When that is the case, (A1 + 0.3 × B1) / C1 ≤ 0.98 A method described in any one of items 27 to 31 that satisfies the requirements.

[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 comprises 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 comprises 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] The irreversible capacity per unit area of ​​the positive electrode precursor is D1 (Ah / cm²). 2 ), the irreversible capacity per unit area of ​​the negative electrode precursor is set to E1 (Ah / cm²). 2 ) When that is the case, 1.05 × D1 <E1 A method described in any one of items 27 to 37 that satisfies the requirements.

[39] A method for manufacturing a non-aqueous alkali metal energy storage element with restored capacity, wherein the non-aqueous alkali metal energy 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 containing alkali metal ions, wherein the positive electrode active material layer includes a positive electrode active material that absorbs and releases alkali metals, The non-aqueous alkali metal energy storage element before capacity recovery contains 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 initiation potential of the carbonate decomposition accelerator is between the stable operating potential of the positive electrode active material and 4.7V (vs Li / Li+). The method includes restoring the capacity of a non-aqueous alkali metal energy storage element by raising the potential of the positive electrode of the non-aqueous alkali metal energy storage element before capacity recovery to a level above the stable operating potential of the positive electrode active material.

[40] The theoretical volume per unit area of ​​the alkali metal carbonate is B1 (Ah / cm²). 2 ), the excess capacity per unit area of ​​the negative electrode active material is J1 (Ah / cm²). 2 ), the total volume per unit area of ​​the negative electrode active material is J2 (Ah / cm²). 2 ) When that is the case, 0.1 ≤ J1 / J2 ≤ 0.5, and, 0.03 ≤ 0.3 × B1 / J1 ≤ 0.98 Satisfying the conditions, The method according to item 39, further comprising suppressing the decomposition of the alkali metal carbonate of the non-aqueous alkali metal energy storage element until the potential of the positive electrode of the non-aqueous alkali metal energy storage element before capacity recovery is raised to or above the stable operating 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 according to any one of items 39 to 45, comprising recovering 2% or more of the capacity of the non-aqueous alkali metal energy storage element before capacity recovery, which has a capacity of 95% or less based on the initial capacity P1 (mAh) of the non-aqueous alkali metal energy storage element.

[47] The method according to any one of items 39 to 46, comprising restoring the capacity of the non-aqueous alkali metal energy storage element by raising the voltage of the non-aqueous alkali metal energy storage element to an upper limit of the stable operating voltage of the positive electrode active material.

[48] The method according to any one of items 39 to 47, wherein the positive electrode active material layer further contains the alkali metal carbonate, and when the mass ratio of the alkali metal carbonate is X3 (mass%) based on the total mass of the positive electrode active material layer, X3 is 0.3 or more and 20.0 or less.

[49] The method according to any one of items 39 to 48, wherein the non-aqueous alkali metal energy storage element before capacity recovery further comprises the intermediate layer containing the alkali metal carbonate, and when the mass ratio of the alkali metal carbonate is X4 (mass%) based on the total mass of the intermediate layer, X4 is 20 or more and 95 or less.

[50] The non-aqueous alkali metal energy storage element before capacity recovery is the method according to any one of items 39 to 49, wherein when the mass ratio of the positive electrode active material is X2 (mass%) based on the total mass of the positive electrode active material layer, X2 is 60 or more and 97 or less.

[51] The discharge capacity of a positive electrode half-cell using a positive electrode extracted from a non-aqueous alkali metal energy storage element before capacity recovery, or using the positive electrode and intermediate layer if an intermediate layer is present, in the potential region of the stable operating potential of the positive electrode active material, is K1 (mAh / cm²). 2 ) and the discharge capacity of the negative electrode half-cell of the negative electrode taken from the non-aqueous alkali metal energy storage element before capacity recovery is set to K3 (mAh / cm²). 2 The method described in any one of items 39 to 50, where 0.80 ≤ K1 / K3 ≤ 1.2.

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

[53] The non-aqueous alkali metal energy storage element before capacity recovery is in the form of a battery pack formed by combining multiple single cells of the non-aqueous alkali metal energy storage element before capacity recovery, and the method according to any one of items 39 to 52, wherein the battery pack is not disassembled into the single cells, and the capacity of the battery pack is recovered.

[54] A method for restoring the capacity of the aforementioned non-aqueous alkali metal energy storage element, comprising restoring the capacity multiple times, according to any one of items 39 to 53.

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

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

[57] A non-aqueous alkali metal energy 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, The positive electrode active material layer includes a positive electrode active material that intercepts and deintercepts alkali metals, The non-aqueous alkali metal energy 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 initiation potential of the carbonate decomposition accelerator is 4.7V (vs Li / Li) or higher than the stable operating potential of the positive electrode active material. + ) Non-aqueous alkali metal energy storage elements.

[58] The theoretical volume per unit area of ​​the alkali metal carbonate is B1 (Ah / cm²). 2 ), the excess capacity per unit area of ​​the negative electrode active material is J1 (Ah / cm²). 2 ), the total volume per unit area of ​​the negative electrode active material is F2 (Ah / cm²). 2 ) When that is the case, 0.1 ≤ J1 / J2 ≤ 0.5, and, 0.03 ≤ 0.3 × B1 / J1 ≤ 0.98 A non-aqueous alkali metal energy storage element as described in item 57, which satisfies the requirements.

[59] The non-aqueous alkali metal energy 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-containing organic compounds, TEMPO derivatives, pyridine-N-oxide derivatives, and cyclohexylbenzene derivatives.

[60] The non-aqueous alkali metal energy 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-containing organic compounds.

[61] The non-aqueous alkali metal energy 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-containing organic compounds excluding biphenyl.

[62] The non-aqueous alkali metal energy 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 non-aqueous alkali metal energy 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 when the mass ratio of the alkali metal carbonate is X3 (mass%) based on the total mass of the positive electrode active material layer, X3 is 0.3 or more and 20.0 or less, the non-aqueous alkali metal energy storage element according to any one of items 57 to 63.

[65] The non-aqueous alkali metal energy storage element further comprises the intermediate layer containing the alkali metal carbonate, wherein when the mass ratio of the alkali metal carbonate is X4 (mass%) based on the total mass of the intermediate layer, X4 is 20 or more and 95 or less, as described in any one of items 57 to 64.

[66] The non-aqueous alkali metal energy storage element according to any one of items 57 to 65, wherein the outer casing of the non-aqueous alkali metal energy storage element has a gas permeation mechanism.

[67] The non-aqueous alkali metal energy storage element described in any one of items 57 to 66 is used to restore the capacity by 2% or more when the capacity has deteriorated to 95% or less of the initial capacity P1 (mAh) by raising the potential of the positive electrode to a level above the oxidative decomposition potential of the alkali metal carbonate.

[68] The non-aqueous alkali metal energy storage element described in any one of items 57 to 67, wherein when the capacity deteriorates, the non-aqueous alkali metal energy storage element is used to restore the capacity by raising the voltage of the non-aqueous alkali metal energy storage element to an upper limit of the stable operating voltage of the positive electrode active material.

[69] A non-aqueous alkali metal energy storage element according to any one of items 57 to 68, comprising the carbonate decomposition accelerator in an electrolyte solution at a concentration of 0.0001 mol / L to 1.5 mol / L.

[70] A battery pack comprising a combination of multiple non-aqueous alkali metal energy storage elements described in any one of items 57 to 69. [Effects of the Invention]

[0018] According to the first embodiment, alkali metal carbonate decomposition at a relatively low decomposition voltage is possible in a non-aqueous alkali metal energy storage element precursor or non-aqueous alkali metal energy storage element, thereby increasing the volumetric efficiency of the pre-doping. Furthermore, the effective utilization rate of the positive electrode active material, capacity density, and capacity retention rate after cycle testing can be improved, and resistance, gas amount during storage at 40°C, positive electrode active material loss, and minor short circuits after cycle testing can be suppressed. According to the second embodiment of this disclosure, a technique is provided that allows the capacity of the energy storage element to be restored by a simple electrochemical operation. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic diagram of a positive electrode, negative electrode, separator, lithium (Li) reference electrode, and Li reference electrode with separator according to one aspect of the present disclosure. [Figure 2] This is a schematic perspective view illustrating the positional relationship between an electrode stack and a Li reference electrode according to one aspect of the present disclosure. [Figure 3] In one embodiment of this disclosure, the graph shows the positive electrode potential (V vs Li / Li+) plotted against the capacity per unit weight of positive electrode active material (mAh / g of positive electrode active material) in the case of an accelerator (curve 1) and the case of no accelerator (curve 2). [Figure 4]Figure 3 shows the difference curve (curve 1-2) at the same positive electrode potential, and a graph illustrating the oxidation initiation potential of the accelerator, using method A (measurement of the oxidation initiation potential of the accelerator). [Figure 5] In another embodiment of this disclosure, the graph shows the positive electrode potential (V vs Li / Li+) plotted against the capacity per unit weight of positive electrode active material (mAh / g of positive electrode active material) in the case of an accelerator (curve 1) and the case of no accelerator (curve 2). [Figure 6] In Figure 5, the difference curve (curve 1-2) at the same positive electrode potential, and a graph illustrating the oxidation initiation potential of the accelerator, are shown using method B (measurement of the oxidation initiation potential of the accelerator). [Figure 7] Figure 7 is a schematic diagram of a battery pack in which four single cells are connected in series. [Modes for carrying out the invention]

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

[0021] In this embodiment, the alkali metal energy storage element before pre-doping, described later, is defined as a "non-aqueous alkali metal energy storage element precursor," the positive electrode before pre-doping, described later, is defined as a "positive electrode precursor," the negative electrode before pre-doping, described later, is defined as a "negative electrode precursor," the alkali metal energy storage element after pre-doping is defined as a "non-aqueous alkali metal energy 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 energy storage element precursor comprises 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 containing alkali metal ions, wherein the positive electrode active material layer contains a positive electrode active material that intercepts and releases alkali metal ions. The non-aqueous alkali metal energy storage element precursor contains 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 both thereof, and the non-aqueous electrolyte further contains a carbonate decomposition accelerator (also simply called an "accelerator"), and the oxidation initiation potential of the accelerator is 3.8V (vs Li / Li + ) Above 4.7V (vs Li / Li + ) are as follows:

[0023] In another embodiment, the non-aqueous alkali metal energy storage element 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, an outer casing, and a non-aqueous electrolyte containing alkali metal ions, wherein the positive electrode active material layer contains a positive electrode active material that intercepts and deintercepts alkali metal ions. The non-aqueous alkali metal energy 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 both, and the non-aqueous electrolyte further contains an accelerator, the oxidation initiation potential of the accelerator is 3.8V (vs Li / Li + ) Above 4.8V (vs Li / Li + The values ​​are below ), and the effective utilization rate of the positive electrode active material is 85-99.5%.

[0024] In another embodiment, the method for manufacturing a non-aqueous alkali metal energy storage element includes applying a voltage between the positive electrode precursor and the negative electrode precursor to a non-aqueous alkali metal energy storage element precursor having a positive electrode precursor, a negative electrode precursor, a separator, an outer casing, and a non-aqueous electrolyte containing alkali metal ions, thereby doping the negative electrode active material of the negative electrode precursor with alkali metal ions. The negative electrode precursor contains a material that intercepts and deintercepts 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 intercepts and deintercepts alkali metal ions. Furthermore, the non-aqueous alkali metal energy storage element precursor 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 both, and the non-aqueous electrolyte further contains an accelerator, the oxidation initiation potential of the accelerator is 3.8V (vs Li / Li + ) Above 4.7V (vs Li / Li + ) are as follows:

[0025] Non-aqueous alkali metal energy storage elements generally experience capacity degradation mainly due to the deactivation of some alkali metal ions through repeated charge-discharge cycles, causing a shift in the usable range of the positive and negative electrodes. The inventors conceived of restoring capacity by pre-containing alkali metal carbonates in non-aqueous alkali metal energy storage elements and, after capacity degradation, decomposing the alkali metal carbonates by electrochemical operation to generate alkali metal ions, thereby compensating for the total amount of deactivated alkali metal ions. Furthermore, by further containing a specific accelerator in the electrolyte, the alkali metal carbonates can be efficiently decomposed at a potential higher than the voltage range during normal use of the non-aqueous alkali metal energy storage element, and alkali metal ions can be replenished in the negative electrode of the degraded energy storage element. Therefore, the capacity of the energy storage element can be restored while maintaining the battery state (i.e., without decomposing the energy storage element) by a simple operation of raising the potential of the positive electrode above the stable operating potential of the positive electrode active material. Furthermore, since the electrolyte accelerator promotes the decomposition of alkali metal carbonates, there is no need to add a catalyst to the positive electrode to promote the decomposition of alkali metal carbonates, thus avoiding a decrease in the initial capacity density of the energy storage element.

[0026] Therefore, even non-aqueous lithium energy storage elements using inexpensive lithium transition metal compounds such as lithium iron phosphate, which were previously impossible to recycle from an economic standpoint, can now be recycled while maintaining economic viability.

[0027] A second embodiment of this disclosure provides a non-aqueous alkali metal energy storage element (hereinafter also referred to as the "pre-capacity recovery battery") suitable for the capacity recovery method of this disclosure. In this disclosure, the term "pre-capacity recovery non-aqueous alkali metal energy storage element" encompasses all non-aqueous alkali metal energy storage elements from those immediately after the initial charging process to (unused) non-aqueous alkali metal energy storage elements that have undergone the aging process and degassing process, as well as non-aqueous alkali metal energy storage elements whose capacity has deteriorated due to use. The degree of capacity deterioration is not limited, and it may be a non-aqueous alkali metal energy storage element in any deteriorated state.

[0028] The non-aqueous alkali metal energy storage element before capacity recovery according to this disclosure is a non-aqueous alkali metal energy 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. The positive electrode active material layer contains a positive electrode active material that intercalates and deintercalates alkali metals. The non-aqueous alkali metal energy 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. The non-aqueous electrolyte further contains an accelerator, the oxidation initiation potential of the accelerator being between the stable operating potential of the positive electrode active material and 4.7V (vs Li / Li+). When a system containing a positive electrode active material that intercalates and deintercalates alkali metals is further enriched with alkali metal carbonates and the capacity recovery process described later is performed, the oxidative decomposition reaction of the alkali metal carbonates may not proceed sufficiently, resulting in insufficient replenishment of alkali metals to the negative electrode and inability to recover capacity. The accelerator contained in the electrolyte promotes the oxidative decomposition reaction of alkali metal carbonates, thereby achieving a capacity recovery effect. Furthermore, it eliminates the need to add a catalyst for decomposing alkali metal carbonates 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 non-aqueous alkali metal energy storage element with restored capacity includes restoring the capacity of the non-aqueous alkali metal energy storage element by raising the potential of the positive electrode of the non-aqueous alkali metal energy storage element before the capacity restoration described above to a level above the stable operating potential of the positive electrode active material.

[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 ions, sodium ions, potassium ions, rubidium ions, cesium ions, and francium ions. Among these, lithium, sodium, and potassium are preferred from the viewpoint of energy density, resource availability, etc., and lithium is particularly preferred.

[0031] <Positive electrode, positive electrode precursor> In the first embodiment, the positive electrode is formed by pre-doping the negative electrode precursor with alkali metal ions in a non-aqueous alkali metal energy storage element precursor containing a positive electrode precursor, as described later in the manufacturing of the energy storage element. The positive electrode precursor includes a positive electrode active material layer containing a positive electrode active material that intercepts and deintercepts alkali metal ions. In this embodiment, it is preferable to apply a voltage between the positive electrode precursor and the negative electrode precursor after assembling the energy storage element precursor using the positive electrode precursor, the negative electrode precursor, a separator, and a non-aqueous electrolyte as the pre-doping method.

[0032] In the 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 non-aqueous alkali metal energy storage element precursor, or in both. The alkali metal carbonate can be pre-doped by decomposing in the non-aqueous alkali metal energy storage element precursor to release alkali metal ions, which are then reduced at the negative electrode.

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

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

[0035] A second embodiment of the present disclosure provides a positive electrode for use in a battery before capacity recovery, suitable for the capacity recovery 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 includes a positive electrode active material that intercepts and deintercepts alkali metal ions, and 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 a separator, or both.

[0036] Insofar as the battery obtained in the initial energy storage element manufacturing process exhibits a 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 energy storage element manufacturing process.

[0037] Alkali metal carbonates may be included in the positive electrode in any manner, for example, at the interface with the positive electrode current collector within the positive electrode active material layer, or on the surface of the positive electrode active material layer. From the viewpoint of the reactivity of alkali metal compounds in the capacity recovery process, it is preferable that alkali metal carbonates are dispersed in the positive electrode active material layer in particulate form. Alkali metal carbonates may be present in the positive electrode active material layer, in any intermediate layer between the positive electrode active material layer and the separator, or in both.

[0038] The coating liquid used for manufacturing the positive electrode is called the "positive electrode coating liquid." The positive electrode coating liquid may include not only known coating liquid forms, but also known suspensions, dispersions, emulsions, compositions, or mixtures. The positive electrode coating liquid is sometimes simply called a slurry, coating liquid, etc.

[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 contain an alkali metal carbonate in the positive electrode active material layer, in the intermediate layer between the positive electrode active material layer and the separator, or 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 be able to constitute the positive electrode of a non-aqueous alkali metal energy storage element. The positive electrode precursor constitutes the positive electrode after the energy storage element is assembled and pre-doped. As described later, in this embodiment, it is preferable to pre-dope the negative electrode precursor with alkali metal ions from alkali metal carbonate in the manufacturing process of the energy storage element. As a pre-doping method, it is desirable to assemble the energy storage element precursor using the positive electrode precursor, negative electrode precursor, separator, outer casing, and non-aqueous electrolyte, and then apply a voltage between the positive electrode precursor and the negative electrode precursor to charge up to a voltage at which the oxidation reaction of alkali metal carbonate occurs.

[0041] (Cathode active material layer) The positive electrode active material layer of the first or second embodiment includes the positive electrode active material described later, and may also include optional components such as conductive fillers, binders, and dispersion stabilizers, dispersants, and pH adjusters as needed.

[0042] The positive electrode active material layer may contain alkali metal carbonates, as described later. In the second embodiment, the positive electrode active material layer can be subjected to an electrochemical operation to restore capacity after its capacity has deteriorated, thereby achieving a capacity recovery effect.

[0043] (Cathode active material) The cathode active material in the first embodiment or the second embodiment stores and releases alkali metal ions. As the cathode active material for storing and releasing alkali metal ions, known materials used in known non-aqueous alkali metal storage elements can be used. For example, substances containing an alkali metal and at least one transition metal are preferred. Such compounds are particularly preferably alkali metal-containing transition metal oxides, alkali metal-containing transition metal phosphate compounds, etc. Also, two kinds of active materials may be mixed and used.

[0044] There is no particular limitation on the cathode active material. The cathode active material used in known alkali metal storage elements can be used. Examples of the cathode active material 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 CoO2, Li x NiO2, Li x Ni y M (1-y) O2 (where 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 O2, Li x MnO2, α-Li x FeO2, Li x VO2, Li x CrO2, Li x FePO4, LiMn x Fe 1-x PO4, Li x Mn2O4, Li x M y Mn (2-y) O4 (where 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 Cob Al (1-a-b) O₂ (where 0.2 < a < 0.97 and 0.2 < b < 0.97), Li x Ni c Co d Mn (1-c-d) O₂ (where 0.2 < c < 0.97 and 0.2 < d < 0.97) (however, throughout the entire formula, 0 ≤ x ≤ 1) and the like can be mentioned.

[0046] Specific representative examples include LiCoO₂ (LCO), LiFePO₄ (LFP), LiMn 0.6 Fe 0.4 PO₄ (LMFP), LiNi 1 / 3 Co 1 / 3 Mn[[ID=2৪]] 1 / 3 O₂ (NCM111), LiNi 0.8 Co 0.15 Al 0.05 O₂ (NCA), LiMn₂O₄ (LMO), and the like can be preferably used.

[0047] Specifically, when the alkali metal is sodium, other conventionally known materials that can be used as the positive electrode active material of a sodium-ion battery may be used. It may contain sodium transition metal oxides, polyanion compounds, and Prussian blue compounds. In the sodium transition metal oxide, 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 is, for example, Na x MO₂, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0 < x ≤ 1. The polyanion compound may be a compound having sodium ions, transition metal ions, and a tetrahedral (YO₄) n- anion unit. 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 represents the valence of (YO₄) n- The polyanion compound may also be a compound having sodium ions, transition metal ions, and a tetrahedral (YO₄) 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 is (YO4) n- The valency is expressed, and the halogen may be at least one of F, Cl, and Br. Polyanionic compounds also contain sodium ions, tetrahedral (YO4) n- Anion unit, polyhedral unit (ZO y ) m+ and may be compounds having selectable halogen anions. Y may be at least one of P, S and Si, and n is (YO4) n- The valency of is represented, Z represents a transition metal, which may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m is (ZO y ) m+ The valency is expressed, and the halogen may be at least one of F, Cl, and Br. Examples of polyanionic compounds include NaFePO4, Na3V2(PO4)3, NaM'PO4F (wherein M' is one or more of V, Fe, Mn, and Ni) and Na3(VO y )2(PO4)2F 3-2y (wherein the formula, at least one of 0≦y≦1) is present. Prussian blue compounds are sodium ions, transition metal ions and cyanide ions (CN - The compound may have ). 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, Na a Me b Me' c (CN)6 may also be, where Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 <a≦2、0<b<1、0<c<1である。

[0048] In the first embodiment, since the alkali metal carbonate serves as a doping source of the alkali metal and / or the alkali metal carbonate for pre-doping and can be pre-doped into the negative electrode, even if the transition metal compound does not contain an alkali metal in advance (that is, even if x = 0 in the above formula), it is possible to perform electrochemical charge and discharge as a non-aqueous alkali metal type storage element.

[0049] In the second embodiment, it is preferable that the charge-discharge capacity is shown below the decomposition voltage of the alkali metal carbonate described later, and further, the structure has stability at a voltage higher than the decomposition voltage. As the alkali metal transition metal compound, preferably, lithium iron phosphate Li x FePO4 (LFP), lithium manganese iron phosphate LiMn x Fe 1-x PO4 (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. When 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 thus the capacity per electrode volume tends to increase. When the average particle diameter of the positive electrode active material is small, the durability may decrease, but if the average particle diameter is 0.1 μm or more, the durability is less likely to decrease. When the average particle diameter of the positive electrode active material is 20 μm or less, it tends to be more suitable for high-rate charge and discharge. 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 ratio 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. As the lower limit of the content ratio of the positive electrode active material, it is more preferably 45% by mass or more, and even more preferably 55% by mass or more. As the upper limit of the content ratio of the positive electrode active material, it is more preferably 98% by mass or less, and even more preferably 96% by mass or less. By setting the content ratio of the positive electrode active material in the positive electrode active material layer to be from 35% by mass to 99% by mass, suitable charge-discharge characteristics can be exhibited.

[0052] In the second embodiment, the mass percentage X2 (mass%) of alkali metal transition metal compounds in the positive electrode active material layer is preferably 60% by mass or more and 99% by mass or less, based on the total mass of the positive electrode active material layer. The lower limit of X2 (mass%) is more preferably 70% by mass or more, and even more preferably 80% by mass or more. The upper limit of X2 (mass%) is more preferably 98% by mass or less, even more preferably 97% by mass or less, even more preferably 96% by mass or less, and particularly preferably 92% by mass or less.

[0053] The primary cause of capacity degradation in non-aqueous alkali metal energy storage elements is the shift in the usable range of the positive and negative electrodes due to the loss of alkali metal ions that contribute to charging and discharging. Therefore, by oxidatively decomposing alkali metal carbonates and replenishing alkali metal ions in the negative electrode, the shift in the usable range can be eliminated, resulting in a significant capacity recovery effect.

[0054] If the mass percentage X2 of the alkali metal transition metal compound is between 60.0% and 99.0% by mass, both initial capacity density and capacity recovery effect after degradation can be achieved. If the mass percentage X2 of the alkali metal transition metal compound is 60.0% or more by mass, excellent capacity density is achieved. If it is 99.0% or less by mass, alkali metal carbonates can be introduced into the positive electrode active material layer, and conductivity and electrolyte retention can be sufficiently increased. Therefore, in the capacity recovery process described later, the decomposition of alkali metal carbonates proceeds easily, promoting the replenishment of alkali metals to the negative electrode and facilitating the recovery of battery capacity. One method for controlling the mass percentage of the alkali metal transition metal compound is to adjust the composition of the positive electrode coating solution.

[0055] (Stable operating potential of the positive electrode and stable operating voltage of the battery, depending on the positive electrode active material) The potential range of the positive electrode where the positive electrode active material can be used stably is called the "stable operating potential", and the voltage range of the battery (full cell) where the positive electrode active material can be used stably is called the "stable operating voltage". The "upper limit of the stable operating potential" and the "upper limit of the stable operating voltage" vary depending on the type of positive electrode active material. Generally, the charge-discharge cycle of a non-aqueous alkali metal energy storage element is performed to determine the potential and voltage ranges where the positive electrode active material can be used stably. The "lower limit of the stable operating potential" and the "lower limit of the stable operating voltage" are the potential and voltage at which alkali metal ions are completely inserted into the positive electrode and almost no more discharge capacity can be obtained. Although not particularly limited to the following numerical values, specific preferred examples of the positive electrode active material are shown with their upper limits of the stable operating potential and the stable operating voltage. LiCoO2 (LCO): The upper limit of the stable operating potential is 4.3 V (vs. Li / Li + ) and the upper limit of the stable operating voltage is 4.2 V (There are also those with high stable operating potential and stable operating voltage in LCO by techniques such as doping with different elements). LiFePO4 (LFP): The upper limit of the stable operating potential is 3.7 V (vs. Li / Li + ) and the upper limit of the stable operating voltage is 3.6 V LiMn 0.6 Fe 0.4 PO4: The upper limit of the stable operating potential is 4.3 V (vs. Li / Li + ) and the upper limit of the stable operating voltage is 4.2 V LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM111): The upper limit of the stable operating potential is 4.3 V (vs. Li / Li + ) and the upper limit of the stable operating voltage is 4.2 V LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811): The upper limit of the stable operating potential is 4.3 V (vs. Li / Li + ) and the upper limit of the stable operating voltage is 4.2 V LiNi 0.8 Co 0.15 Al 0.05 O2 (NCA): The upper limit of the stable operating potential is 4.3 V (vs. Li / Li + ) and the upper limit of the stable operating voltage is 4.2 V LiMn2O4 (LMO): Upper limit of stable operating potential 4.3V (vs. Li / Li + ), upper limit of stable operating voltage: 4.2V NaFe 1 / 3 Ni 1 / 3 Mn 1 / 3 O2: Upper limit of stable operating potential 4.0V (vs. Na / Na) + ), upper limit of stable operating voltage: 3.9V

[0056] For positive electrode active materials with unknown upper limits for stable operating potential and stable operating voltage, there are no particular restrictions, but they can be determined, for example, by the following method. A battery containing the following electrolyte is used, with a positive electrode half-cell containing the unknown positive electrode active material as the working electrode, an alkali metal as the counter electrode and reference electrode, and charged with a constant current (cc) at a current value equivalent to 0.1C until the potential of the positive electrode half-cell reaches a predetermined upper limit potential, then charged with a constant voltage (cv) at this voltage until the current value reaches 0.03C, and then discharged with a constant current (cc) to the lower limit potential. This cycle test is performed for various different upper limit potentials. The upper limit potential at which the discharge capacity of the positive electrode half-cell reaches a specific value (e.g., 95%) relative to the initial discharge capacity is defined 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. For the electrolyte of non-aqueous alkali metal energy storage elements, electrolytes generally used in alkali metal ion batteries or alkali metal ion capacitors can be used. The non-aqueous electrolyte preferably contains 0.5 mol / L or more of an alkali metal salt as the electrolyte, based on the total amount of the non-aqueous electrolyte. As the alkali metal salt of the electrolyte, electrolytes commonly used in non-aqueous alkali metal energy storage elements can be used. When the alkali metal is lithium, LiFSI, LiBF4, LiPF6, LiCiO4, LiTFSI, etc. can be used individually, or two or more may be used in mixture. When the alkali metal is sodium, Na(SO2CF3)2, NaN(SO2F)2, NaN(C2F5SO2)2, NaCF3SO3, NaC(CF3SO2)3, NaPF6, NaBF4, NaClO4, NaAsF6, NaAlCl4, etc. can be used individually, or two or more may be used in mixture.

[0057] As a lower limit for the stable operating voltage of a battery, it is preferable to apply an appropriate lower limit for the stable operating potential and stable operating voltage depending on the positive electrode active material used. The following values ​​are not particularly restrictive, but preferred specific examples of positive electrode active materials are shown below, along with their stable operating potential and stable operating voltage lower limits. LiCoO2 (LCO): Lower limit of stable operating potential 3.1V, lower limit of stable operating voltage 3.0V LiFePO4 (LFP): Lower limit of stable operating potential 2.5V, lower limit of stable operating voltage 2.4V LiMn 0.6 Fe 0.4 PO4(LMFP): Lower limit of stable operating potential 2.5V (vs.Li / Li + ), lower limit of stable operating voltage is 2.4V LiRing 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM111): Lower limit of stable operating potential 3.1V (vs. Li / Li + ), lower limit of stable operating voltage is 3.0V LiRing 0.8 Co 0.1 Mn 0.1 O2 (NCM811): Lower limit of stable operating potential 3.1V (vs. Li / Li + ), lower limit of stable operating voltage is 3.0V LiRing 0.8 Co 0.15 Al 0.05 O2(NCA): Lower limit of stable operating potential 3.1V (vs.Li / Li + ), lower limit of stable operating voltage is 3.0V LiMn2O4 (LMO): Lower limit of stable operating potential is 3.1V (vs. Li / Li + ), lower limit of stable operating voltage is 3.0V NaFe 1 / 3 Ni 1 / 3 Mn 1 / 3 O2: Lower limit of stable operating potential 2.0V (vs. Na / Na) + ), upper limit of stable operating voltage is 1.9V

[0058] (C-rate) In this specification, the C rate for a positive electrode half-cell is defined as the current (A) required to discharge from the upper limit to the lower limit of the stable operating potential in one hour, with 1C being the value obtained by proportional conversion based on the current value (A) equivalent to 1C. For example, 10C is defined as a current value 10 times the current value equivalent to 1C, and 0.1C is defined as a current value 0.1 times the current value equivalent to 1C.

[0059] In this specification, the C rate for a full cell is defined as the current (A) required to discharge from the upper limit to the lower limit of the stable operating voltage in one hour, with 1C being the value obtained by proportional conversion based on the current value (A) equivalent to 1C. For example, 10C is defined as a current value 10 times the current value equivalent to 1C, and 0.1C is defined as a current value 0.1 times the current value equivalent to 1C.

[0060] (Initial charge capacity density L1 and initial discharge capacity density L2 of the positive electrode active material) The initial charge capacity density L1 (mAh / g) of the positive electrode active material is obtained by measuring the charge capacity when a half-cell consisting of a positive electrode made of positive electrode active material, binder, and conductive material, fabricated using a known electrode fabrication process for non-aqueous alkali metal energy storage elements, an alkali metal counter electrode, and a known separator is charged at a constant current at a rate of 0.1C up to the stable operating upper limit potential in a 25°C environment, and then charged at a constant voltage until the current converges to a rate of 0.03C. The initial discharge capacity density L2 (mAh / g) of the positive electrode active material is obtained by measuring the discharge capacity when, after a 10-minute pause following the completion of constant voltage charging at the stable operating upper limit potential, the discharge is performed at a constant current at a rate of 0.1C up to the stable operating lower limit potential. Furthermore, the capacity densities L1 and L2 (mAh / g) can be obtained by dividing the obtained charge capacity and discharge capacity by the mass of the positive electrode active material used.

[0061] (Alkali metal carbonates) 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 non-aqueous alkali metal energy storage element precursor, or in both. In the first embodiment, the alkali metal carbonate can be pre-doped by decomposing in the non-aqueous alkali metal energy storage element precursor to release alkali metal ions, which are then reduced at the negative electrode. In the second embodiment, after capacity degradation, the capacity can be restored by decomposing the alkali metal carbonate by electrochemical operation to generate alkali metal ions, thereby compensating for the total amount of deactivated alkali metal ions.

[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 carbonates at the positive electrode) There are no particular restrictions on the method for measuring alkali metal carbonates in the positive electrode, but for example, it can be measured by ion chromatography as shown below. Specifically, a battery with adjusted voltage is disassembled, the positive electrode is removed, and then measured by ion chromatography.

[0064] 1. Adjusting the battery voltage Before disassembly, adjust the battery to the lower limit of its stable operating voltage. Specific methods are described below. (LiCoO2, LiMn) 0.6 Fe 0.4 PO4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiLiLi 0.8 Co 0.15 Al 0.05When using O2 or LiMn2O4 as the positive electrode active material, the completed non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, i.e., 4.2V, followed by constant voltage charging at 4.2V for 30 minutes. After that, it is discharged with a constant current of 0.1C until it reaches the lower limit of the stable operating voltage, i.e., 3.0V, followed by constant voltage discharge at 3.0V for 30 minutes. When using LiFePO4 as the positive electrode active material, the non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, i.e., 3.6V, followed by constant voltage charging at 3.6V for 30 minutes. Subsequently, constant current discharge is performed at a current value of 0.1C until the lower limit of the stable operating voltage, i.e., 2.4V, is reached, followed by constant voltage discharge at a constant voltage of 2.4V for 30 minutes. 1 / 3 Ni 1 / 3 Mn 1 / 3 When using O2 as the positive electrode active material, a non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, i.e., 3.9V. This is followed by constant voltage charging at 3.9V for 30 minutes. After that, a constant current discharge is performed with a current of 0.1C until it reaches the lower limit of the stable operating voltage, i.e., 1.9V. This is followed by constant voltage discharge at 1.9V for 30 minutes.

[0065] 2. Disassembling the battery and removing the positive electrode. The battery was disassembled inside an Ar box with a dew point below -70°C. In the case of a laminate, for the 1 / 4 and 3 / 4 positions out of the four divisions in the lamination direction, and at a location including the center position within the electrode plane, the positive electrode is cut out. In the case of a flat wound body, for the 1 / 4 and 3 / 4 positions out of the four divisions of the number of windings, at a flat part avoiding the bent part, and at a location including the center position within the electrode plane, the positive electrode is cut out. In the case of a cylindrical wound body, in the radial direction of the cylinder, at a location at 1 / 2 from the center of the cylinder, and including the location at 1 / 2 of the two divisions in the cylinder height direction, the positive electrode is cut out. The extracted positive electrode is immersed and washed with methyl ethyl carbonate inside an Ar box with a dew point below -70°C, and then normal temperature vacuum drying is performed inside the Ar box to remove the volatile components of the electrolytic solution and the washing solvent.

[0066] 3. Quantification by ion chromatography Approximately 5 cm 2 Scrape off the positive electrode active material layer from the positive electrode of about 5 cm and put it into a vial for weighing. Pour 2 mL of distilled water so that the scraped active material layer is completely immersed, and perform immersion extraction for 3 days. During extraction, it is also possible to extract without peeling off the active material layer. In that case, after completion of extraction, remove the active material layer and weigh the current collector, and subtract from the positive electrode weight to calculate the active material layer weight. Appropriately dilute the supernatant of the extraction solution with distilled water, and measure carbonate ions derived from alkali metal carbonate by ion chromatography. For quantification, use an alkali metal carbonate as a standard substance. Dissolve and dilute the alkali metal carbonate with distilled water, perform ion chromatography measurement under the same conditions as the positive electrode active material layer extraction solution, and create a calibration curve for the alkali metal carbonate. Using that calibration curve, quantify the concentration of alkali metal carbonate in the extraction solution, and further calculate the weight ratio of alkali metal carbonate per active material layer weight. Since carbonate ions can be mixed in from the environment, subtract the operation blank value to calculate the weight ratio of alkali metal carbonate per active material layer weight. The ion chromatography measurement conditions are as follows. <Ion chromatography measurement conditions> Apparatus: IC-2001 manufactured by Tosoh Corporation Column: TSKgel-SCX (4.6 mm × 150 mm) manufactured by Tosoh Corporation Eluent: 0.1 mmol / L phosphoric acid Flow rate: 0.6 mL / min Detection: Electrical 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 value is more preferably 0.5% by mass, and even more preferably 2% by mass or more. The upper limit value 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 alkali metal doping into the negative electrode due to the decomposition of the alkali metal carbonate proceeds sufficiently, and if it is 15% by mass or less, the ratio of the alkali metal carbonate in the positive electrode active material layer is low, and the doping promotion effect by the accelerator 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 volume efficiency can be increased, which 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. If 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, when the mass ratio of the alkali metal carbonate is X4 (% by mass) based on the total mass of the intermediate layer, X4 is preferably 20.0% by mass or more and 95.0% by mass or less. If X4 is 20.0% by mass or more, a high capacity recovery effect can be obtained, and if it is 95.0% by mass or less, the initial capacity density can be maintained high. The upper limit value of X4 is more preferably 90% by mass or less, and even more preferably 85% by mass or less, and the lower limit value is more preferably 30% by mass or more, and even more preferably 50% by mass or more.

[0070] In the second embodiment, when the mass ratio of alkali metal carbonate in the positive electrode active material layer is X3 (mass%), it is preferable that X3 is 0.3 mass% or more and 20.0 mass% or less. If X3 is 20.0 mass% or less, it is preferable because it can increase the initial capacity volume density of the non-aqueous alkali metal energy storage element. If X3 is 0.3 mass% or more, a higher battery capacity recovery effect can be obtained during the capacity recovery operation described later. The lower limit of X3 is more preferably 1 mass% or more, even more preferably 3 mass% or more, and particularly preferably 5 mass% or more. The upper limit of X3 is more preferably 15 mass% or less, and even more preferably 10 mass% or less.

[0071] It is preferable that the alkali metal compound maintains the decomposition reactivity of alkali metal carbonates in each of the following processes: the initial charging process, the aging process, and the battery usage process before capacity recovery (where capacity degradation progresses), as described later. This allows the decomposition reaction of alkali metal carbonates to proceed in the capacity recovery process, replenishing alkali metals to the negative electrode and achieving 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. If a voltage exceeding the upper limit of the stable operating voltage is applied before the capacity recovery process, the decomposition reaction of the alkali metal carbonate will proceed, causing some or all of the alkali metal carbonate to disappear, which may reduce or eliminate the capacity recovery effect in the capacity recovery process. Also, if a voltage exceeding the upper limit of the stable operating voltage is applied before the capacity recovery process, acids such as HF generated by side reactions of the electrolyte will deactivate the reactivity of the alkali metal carbonate surface, which may reduce or eliminate the capacity recovery effect in the capacity recovery process. However, there may be situations where a voltage exceeding the upper limit of the stable operating voltage is applied before the capacity recovery process, as long as the capacity recovery effect is demonstrated in the capacity recovery process of this disclosure. 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 between 0.1 μm and 10 μm. An average particle size of 0.1 μm or more provides excellent dispersibility in the cathode. An average particle size of 10 μm or less increases the surface area of ​​the alkali metal carbonate, allowing for efficient decomposition reactions of the alkali metal carbonate during pre-doping and volume 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 alkali metal transition metal compounds and alkali metal carbonates in the positive electrode active material layer can be quantified by the measurement methods described in the examples below.

[0075] (optional ingredient) In the first and second embodiments, the positive electrode active material layer may contain, as necessary, optional components such as conductive fillers, binders, dispersion stabilizers, dispersants, and pH adjusters, in addition to alkali metal transition metal compounds and alkali metal compounds.

[0076] In the first and second embodiments, the conductive filler is not particularly limited, but examples include conductive carbonaceous materials with higher conductivity than the positive electrode active material. Such conductive fillers are not particularly limited, but for example, carbon black, acetylene black, Ketjen black, vapor-grown carbon fibers, graphite, flake graphite, carbon nanotubes, graphene, and mixtures thereof can be used. The amount of conductive filler used is preferably more than 0 parts by mass and 30 parts by mass or less, more preferably more than 0 parts by mass and 25 parts by mass or less, and even more preferably 1 part by mass or more and 20 parts by mass or less, per 100 parts by mass of positive electrode active material. If the mixing amount is 30 parts by mass or less, the content ratio of positive electrode active material in the positive electrode active material layer will be high, and the energy density per unit volume of the positive electrode active material layer can be secured. 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 for example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer, etc. can be used. The amount of binder used is preferably 1 to 30 parts by mass per 100 parts by mass of positive electrode active material. If the amount of binder is 1% by mass or more, sufficient electrode strength will be achieved. On the other hand, if the amount of binder is 30 parts by mass or less, it will not hinder the entry and exit and diffusion of ions to and from the positive electrode active material, and high input / output characteristics will be 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 for example, PVP (polyvinylpyrrolidone) and PVA (polyvinyl alcohol) can be used. The amount of dispersion stabilizer used is preferably 0 to 10 parts by mass per 100 parts by mass of positive electrode active material. If the amount of dispersion stabilizer is 10 parts by mass or less, it does not hinder the entry and exit and diffusion of ions into and out of the positive electrode active material, and the input / output characteristics are improved.

[0079] In the first and second embodiments, the dispersant is not particularly limited, but for example, at least one selected from the group consisting of carboxymethylcellulose, methylcellulose, ethylcellulose, cellulose acetate phthalate, hydroxymethylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose phthalate, polyvinylpyrrolidone, polyvinyl alcohol, and polyvinyl acetal can be used. The amount of dispersant used is preferably 0 to 10 parts by mass, more preferably more than 0 parts by mass and 10 parts by mass, per 100 parts by mass of positive electrode active material. If the amount of dispersant is 10 parts by mass or less, it does not hinder the entry and exit and diffusion of ions to and from the positive electrode active material, and the input / output characteristics are improved.

[0080] In the first and second embodiments, water, N-methyl-2-pyrrolidone, and mixtures thereof can be used as the dispersion solvent for the positive electrode coating solution. When water is used as the solvent for the coating solution, the coating solution may become alkaline by adding an alkali metal compound, so a pH adjuster may be added to the coating solution as needed. The pH adjuster is not particularly limited, but examples of pH adjusters that can be used 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 constituting the positive electrode current collector in this embodiment is not particularly limited as long as it has high electronic conductivity and is resistant to degradation due to dissolution into the electrolyte and reaction with electrolytes or ions, but metal foil is preferred. In the first and second embodiments, aluminum foil is particularly preferred as the positive electrode current collector for a non-aqueous alkali metal type energy storage element.

[0082] In the positive electrode current collectors according to the first and second embodiments of this disclosure, an undercoat layer may be provided on the metal foil, and more specifically, a conductive anchor coat layer (for example, an undercoat layer made of a conductive material such as graphite, flake graphite, carbon nanotubes, graphene, carbon black, or vapor-grown carbon fibers) may be provided on the surface of the positive electrode current collector. Providing an 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 ordinary metal foil without irregularities or through holes, or it may be metal foil with irregularities achieved by embossing, chemical etching, electrolytic etching, blasting, etc., or it may be metal foil with through holes such as expanded metal, perforated metal, or etched foil.

[0084] The thickness of the positive electrode current collector is not particularly limited as long as the shape and strength of the positive electrode can be sufficiently maintained. For example, 1 to 100 μm is preferable.

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

[0086] In the first embodiment, the positive electrode precursor can be manufactured by the manufacturing techniques of electrodes in known alkali metal ion batteries, electric double layer capacitors, etc. to form the positive electrode. For example, a positive electrode active material, an alkali metal carbonate, and other optional components used as necessary are dispersed or dissolved in water or an organic solvent to prepare a slurry-like coating solution. This coating solution is applied to one or both sides of the positive electrode current collector to form a coating film, and the positive electrode precursor can be obtained by drying this. Pressing may be applied to the obtained positive electrode precursor to adjust the film thickness and bulk density of the positive electrode active material layer. Alternatively, without using a solvent, a positive electrode active material, an alkali metal carbonate, and other optional components used as necessary are dry-mixed, and after the obtained mixture is press-molded, it can also be attached to the positive electrode current collector using a conductive adhesive.

[0087] The formation of the coating film of the positive electrode precursor is not particularly limited, but preferably a coating machine such as a die coater, comma coater, knife coater, gravure coater, etc. can be used. The coating film may be formed by single-layer coating or multi-layer coating.

[0088] The drying of 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 pressing of the positive electrode precursor is not particularly limited, but preferably a press machine such as a hydraulic press or a vacuum press can be used. 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] <Manufacturing of positive electrode> The positive electrode of the non-aqueous alkali metal energy storage element of the second embodiment can be manufactured using known electrode manufacturing techniques for alkali metal ion batteries, electric double-layer capacitors, etc. For example, the coating liquid can be prepared as described above, and this coating liquid can be applied to one or both sides of the positive electrode current collector to form a coating film, which can then be dried to obtain the positive electrode. The obtained positive electrode may be further pressed to adjust the thickness or bulk density of the positive electrode active material layer. Alternatively, the positive electrode active material and alkali metal carbonate, along with other optional components used as needed, can be dry-mixed without the use of solvents, the resulting mixture can be press-molded, and then attached to the positive electrode current collector using a conductive adhesive, or the resulting mixture can be heat-pressed onto the positive electrode current collector to form the positive electrode active material layer.

[0091] There are no particular limitations on the method of forming the coating on the positive electrode, but preferably a die coater, comma coater, knife coater, gravure coating machine, or other coating machine can be used. The coating may be formed by single-layer coating or by multi-layer coating. When coating the positive electrode current collector, multi-strand coating may be used, intermittent coating may be used, or multi-strand intermittent coating may be used. Alternatively, sequential coating may be performed, where the coating is applied to one side of the positive electrode current collector and dried, and then the other side is coated and dried, or simultaneous coating may be performed, where the coating liquid is applied to both sides of the positive electrode current collector at the same time and dried.

[0092] For pressing the positive electrode, a press machine such as a hydraulic press or a vacuum press can preferably be used. 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 area.

[0093] When the positive electrode is coated with multiple strips, it is preferable to slit it before pressing. By slitting and pressing the multi-strip coated positive electrode, stress is applied to the current collector portion where the positive electrode active material layer is not coated, preventing wrinkles from forming. Alternatively, the positive electrode can be slit again after pressing.

[0094] The thickness of the positive electrode active material layer in the first and second embodiments is preferably 20 μm to 200 μm, more preferably 25 μm to 100 μm, and even more preferably 30 μm to 80 μm per side of the positive electrode current collector. If the thickness of the positive electrode active material layer per side of the positive electrode current collector is 20 μm or more, sufficient charge and discharge capacity can be achieved. If the thickness of the positive electrode active material layer per side of the positive electrode current collector is 200 μm or less, the ion diffusion resistance within the electrode can be kept low. Therefore, sufficient output characteristics can be obtained, the cell volume can be reduced, and thus the energy density can be increased. 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 portion of the current collector that does not have through holes or irregularities.

[0095] <Middle class> The non-aqueous alkali metal energy storage element precursors of the first and second embodiments may include an intermediate layer containing an alkali metal carbonate between the positive electrode active material layer and the separator. There are no particular limitations on the method of forming the intermediate layer, but examples include forming it on the surface of the positive electrode active material layer or the surface of the separator that is in contact with the positive electrode using an existing coating method, and then placing it between the positive electrode and the separator during electrode formation.

[0096] In the second embodiment, the alkali metal carbonate that may be contained in the intermediate layer is decomposed in the capacity recovery process described later, and alkali metal ions are replenished and doped into the negative electrode, thereby restoring the capacity of the non-aqueous alkali metal energy storage element. Details are as described above in the section on the positive electrode.

[0097] The intermediate layer may contain optional components in addition to alkali metal carbonates. For example, binder components for maintaining shape and conductive materials for ensuring conductivity are examples of optional components.

[0098] In the first embodiment, it is preferable to decompose the alkali metal carbonate contained in the intermediate layer in a pre-doping step described later, and to dope the negative electrode precursor 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 effect of pre-doping can be obtained. If the thickness of the intermediate layer is 10 μm or less, sufficient output characteristics can be obtained, the cell volume can be reduced, and therefore the energy density can be increased.

[0100] (Method for forming the intermediate layer) In the first and second embodiments, the intermediate layer is formed between the positive electrode and the separator. Typically, it is fixed to the surface of the positive electrode active material layer or to the surface of the separator that is in contact with 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 separator surface using known manufacturing techniques for electrodes and separator coatings 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 is in contact with the positive electrode.

[0102] In the first and second embodiments, for example, when forming on the surface of the 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-like coating solution. This coating solution is then applied to one or both sides of the positive electrode active material layer to form a coating film, which is then dried. The resulting integral, formed by laminating 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 a pre-doping material and other optional components used as needed are dry-mixed without the use of a solvent, 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 a coating on the separator surface, 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 solution. This coating solution is then applied to the surface of the separator that contacts the positive electrode to form a coating film, which is then dried. The resulting integral, formed by laminating the separator and the intermediate layer, may be pressed to adjust the film thickness and bulk density. Alternatively, the alkali metal carbonate and other optional components used as needed are mixed dry without the use of 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 intermediate layer coating is not particularly limited, but preferably coating methods and equipment such as die coating, gravure coating, comma coating, and knife coating can be used. The coating may be formed by single-layer coating or by multi-layer coating.

[0105] In the first embodiment, the drying of the intermediate layer coating is not particularly limited, but preferably drying methods 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 preferably a press such as a hydraulic press or a vacuum press can be used. The 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 pressed area.

[0107] (optional ingredient) The intermediate layer in the first and second embodiments may optionally contain optional components such as conductive fillers, binders, and inorganic fillers.

[0108] The conductive filler is not particularly limited, but for example, acetylene black, Ketjen black, vapor-grown carbon fibers, graphite, carbon nanotubes, mixtures thereof, etc., can be used. 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 a total mass of 100 parts by 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-doped material in the intermediate layer increases, and the alkali metal density per unit volume that can be extracted from the intermediate layer can be secured. 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, and the alkali metal density per unit volume that can be extracted from the intermediate layer can be secured.

[0109] The binder is not particularly limited, but for example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer, etc. can be used. The amount of binder used is preferably 1 to 30 parts by mass, more preferably 1 to 15 parts by mass, and even more preferably 1 to 10 parts by mass, per 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 will be achieved. On the other hand, in the first embodiment, if the amount of binder used is 30 parts by mass or less, it does not hinder the entry and exit and diffusion of the electrolyte into and out of the intermediate layer, and pre-doping proceeds easily. 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 increases, and the alkali metal density per unit volume that can be extracted from the intermediate layer can be secured.

[0110] Examples of inorganic fillers include oxide-based ceramics such as alumina, silica (silicon oxide), titania, zirconia, magnesia, ceria, yttria, zinc oxide, and iron oxide; nitride-based 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, amethyst, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and silica sand; and glass fibers. By mixing inorganic fillers, the intermediate layer of the first embodiment can further exhibit safety-enhancing effects.

[0111] (Measurement of alkali metal carbonates in the intermediate layer) The measurement can be performed by applying the method described in (Measurement of alkali metal carbonates in the positive electrode) to the intermediate layer.

[0112] <Method for identifying alkali metal carbonates> In the first and second embodiments, the method for identifying alkali metal carbonates contained in the positive electrode active material layer or intermediate layer is not particularly limited, but they can be identified by, for example, the method described below. For the identification of alkali metal carbonates, it is preferable to combine the multiple analytical methods described below.

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

[0114] (Micro-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 1000x to 4000x. As an example of measurement conditions, measurements can be taken with an excitation light of 532 nm, an excitation light intensity of 1%, an objective lens working length of 50x, a diffraction grating of 1800 gr / mm, a mapping method of point scanning (slit 65 mm, binning 5 pixels), a 1 mm step, an exposure time of 3 seconds per point, one integration, and with a noise filter. The measured Raman spectrum is 1071-1104 cm⁻¹. -1 A linear baseline is set within a certain range, and the area of ​​the carbonate ion peak is calculated for values ​​positive from the baseline. The frequency is then integrated, but at this time, the frequency of the carbonate ion peak area, approximated by a Gaussian function for the noise component, is subtracted from the carbonate ion frequency distribution.

[0115] (X-ray photoelectric spectroscopy (XPS)) In the first and second embodiments, the bonding state of alkali metals can be determined by analyzing the electronic state using XPS. As an example of measurement conditions, the X-ray source can be monochromatized AlKα, the X-ray beam diameter can be 100 μmφ (25 W, 15 kV), the pass energy can be narrow scan: 58.70 eV, charge neutralization can be enabled, the number of sweeps can be narrow scan: 10 times (carbon, oxygen), 20 times (fluorine), 30 times (phosphorus), 40 times (alkali metal elements), 50 times (silicon), and the energy step can be narrow scan: 0.25 eV. It is preferable to clean the surface of the positive electrode by sputtering before XPS measurement. As sputtering conditions, for example, the surface of the positive electrode active material layer or intermediate layer can be cleaned under the conditions of an acceleration voltage of 1.0 kV and a 2 mm × 2 mm area for 1 minute (1.25 nm / min in terms of SiO2). In the obtained XPS spectrum, the peaks at Li1s binding energies of 50-54 eV represent LiO2 or Li-C bonds, and the peaks at 55-60 eV represent LiF, Li2CO3, and Li x PO y F z(In the formula, x, y, and z are integers from 1 to 6); the peak at 285 eV of the C1s bond energy represents the CC bond, the peak at 286 eV represents the CO bond, the peak at 288 eV represents the COO bond, and the peak at 290-292 eV represents the CO3 bond. 2- , CF bond; O1s bond energy peaks at 527-530 eV 2- (Li2O), peaks of 531-532 eV are associated with CO, CO3, OH, and PO x (wherein x is an integer from 1 to 4), SiO x (In the formula, x is an integer from 1 to 4), the peak at 533 eV is CO, SiO x (In the formula, x is an integer from 1 to 4); the peak at the 685eV bond energy of F1s is LiF, the peak at 687eV is CF bond, Li x PO y F z (In the formula, x, y, and z are integers from 1 to 6), PF6 - Regarding the P2p bond energy, the peak at 133 eV is PO x (In the formula, x is an integer from 1 to 4), the peak of 134 to 136 eV is PF x (In the formula, x is an integer from 1 to 6); the peak at 99 eV of the Si2p bond energy is Si, the peak at 101 to 107 eV is Si x O y The spectrum can be assigned as follows (where x and y are arbitrary integers). If the peaks in the obtained spectrum overlap, it is preferable to separate the peaks by assuming a Gaussian or Lorentz function and then assign the spectrum. The alkali metal compounds present can be identified from the measured electronic states and the ratio of elements present.

[0116] (Energy-dispersive X-ray spectroscopy (SEM-EDX)) In the first and second embodiments, the elements contained can be quantified by SEM-EDX analysis of the positive electrode active material layer or intermediate layer surface measured at an observation magnification of 1000x to 4000x. As an example of SEM-EDX image measurement, measurements can be taken with an acceleration voltage of 10kV, an emission current of 1μA, a measurement pixel count of 256×256 pixels, and 50 integration cycles. To prevent the sample from becoming charged, the surface can be treated with gold, platinum, osmium, etc., by methods 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 anion species eluted into the water can be identified by analyzing the water after washing with ion chromatography. Ion exchange type, ion exclusion type, and reversed-phase ion pair type columns can be used. Electrical conductivity detectors, UV-Vis absorbance detectors, electrochemical detectors, etc., can be used as detectors, and either a suppressor system, in which a suppressor is placed in front of the detector, or a non-suppressor system, in which a solution with low electrical conductivity is used as the eluent without placing a suppressor, can be used. Furthermore, since measurements can also be taken in combination with a mass spectrometer or charged particle detector, it is preferable to combine an appropriate column and detector based on the alkali metal compounds identified from the analysis results of SEM-EDX, Raman spectroscopy, and XPS.

[0118] (Method for determining alkali metal carbonates) In the first and second embodiments, alkali metal carbonates contained in the positive electrode active material layer or intermediate layer are preferably measured by the method described in (Measurement of alkali metal carbonates in the positive electrode) or (Measurement of alkali metal carbonates in the intermediate layer) from the viewpoint of accuracy, but another quantitative method is described below. The alkali metal carbonates can be quantified by washing the positive electrode precursor with distilled water and observing 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, 5 cm² is recommended. 2 More than 200cm 2 Preferably, it is less than 25 cm, and more preferably 25 cm2 More than 150cm 2 The following applies: The measurement area of ​​the positive electrode precursor is 5 cm². 2 The reproducibility of the measurement is ensured if the measurement area of ​​the positive electrode precursor is 200 cm². 2 The following conditions offer superior sample handling capabilities.

[0119] The following describes a method for quantifying 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 operations may be performed while the material is fixed to the positive electrode current collector foil or separator. Measure the mass of the cut positive electrode active material layer or intermediate layer and define it as M0 [g]. Immerse the positive electrode active material layer or intermediate layer in distilled water at 100 times its mass (100M0 [g]) for at least 3 days at a 25°C environment to dissolve the alkali metal carbonates into the water. At this time, it is preferable to take measures such as covering the container to prevent the distilled water from evaporating. After immersion for at least 3 days, remove the positive electrode active material layer or intermediate layer from the distilled water (if measuring ion chromatography, adjust the liquid volume so that the amount of distilled water is 100M0 [g]), and vacuum dry it. For vacuum drying, it is preferable to have conditions such as a temperature of 100-200°C, a pressure of 0-10kPa, and a time of 5-20 hours, such that the residual moisture content in the positive electrode active material layer or intermediate layer is 1% by mass or less. The residual moisture content can be quantified by the Karl Fischer method. Let M1 [g] be the mass of the positive electrode active material layer or intermediate layer after vacuum drying. Subsequently, in order to measure the mass of the carrier (current collector foil or separator) of the obtained positive electrode active material layer or intermediate layer, the positive electrode active material layer or intermediate layer is removed using a spatula, brush, or the like. If M2 [g] is the mass of the obtained current collector foil or separator, the mass ratio X [mass%] of alkali metal carbonates such as lithium carbonate contained in the positive electrode active material layer or intermediate layer can be calculated using the following formula 1. X = 100 × (M0 - M1) / (M0 - M2) (Equation 1)

[0120] (Method for determining alkali metals: ICP-MS) In the first and second embodiments, the positive electrode active material layer or intermediate layer is acid-decomposed 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%. Acid decomposition can also be carried out by heating and pressurizing as appropriate. The resulting diluted solution is analyzed by ICP-MS, and 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 limit of the measurement, it is preferable to further dilute the solution while maintaining the acid concentration. Based on the obtained measurement results, the alkali metal can be quantified using a calibration curve prepared in advance using standard solutions for chemical analysis.

[0121] <Negative electrode, negative electrode precursor> In the first and second embodiments, the negative electrode in this embodiment comprises a negative electrode current collector and a negative electrode active material layer containing negative electrode active material provided on one or both sides thereof. The negative electrode and the negative electrode precursor may have common configurations, except for the configuration relating to the amount of alkali metal ion doping.

[0122] (Negative electrode active material layer) In the first and second embodiments, the negative electrode active material layer includes a negative electrode active material capable of adsorbing and releasing alkali metal ions, and may optionally include optional components such as conductive fillers, binders, and dispersant stabilizers.

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

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

[0125] (Carbon materials) In the first and second embodiments, known non-aqueous alkali metal energy storage element materials can be used as the carbon material. Examples include: poorly graphitizable carbon materials (hard carbon); easily graphitizable carbon materials (soft carbon); carbon black; carbon nanoparticles; activated carbon; artificial graphite; natural graphite; graphitized mesophase carbon spheres; graphite whiskers; amorphous carbonaceous materials such as polyacene-based materials; 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 resin); thermal decomposition products of furfuryl alcohol resin or novolac resin; fullerenes; carbon nanophones; and composite carbon materials thereof. Among these, from the viewpoint of intercalation 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] Preferably, the carbon material content relative to the total amount of negative electrode active material is 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 good effects from the combined use of other materials (such as alloy-based negative electrode materials described later), it is preferable, for example, to be 95% by mass or less, and may also be 90% by mass or less. The upper and lower limits of the carbon material content range can be arbitrarily combined.

[0127] According to this disclosure, using an amorphous carbon material as the negative electrode active material is preferable because it can reduce positive electrode active material loss. Hard carbon and soft carbon are particularly preferred. Furthermore, when the alkali metal is sodium, hard carbon is preferably used among these materials because it can achieve a good doping state or exhibit 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 includes at least one selected from the group consisting of silicon, silicon compounds, tin, tin compounds, and composite materials of these with carbon or carbonaceous materials. Furthermore, the silicon compound is preferably SiC or silicon oxide, and SiO x (wherein the formula, 0.01 ≤ x ≤ 1 is more preferable.) According to this disclosure, when used as an alloy-based negative electrode material as a negative electrode active material, the loss of positive electrode active material can be reduced, and therefore silicon and / or silicon compounds are preferred.

[0129] The composite material is a material obtained by heat treatment or the like, which combines at least one base material selected from the group consisting of silicon, silicon compounds, tin, and tin compounds with at least one carbon or carbonaceous material selected from the group consisting of poorly graphitizable carbon materials; easily graphitizable carbon materials; carbon black; carbon nanoparticles; activated carbon; artificial graphite; natural graphite; graphitized mesophase carbon spheres; graphite whiskers; amorphous carbonaceous materials such as polyacene-based materials; carbonaceous materials obtained by heat treatment of carbonaceous material precursors such as petroleum-based pitch, coal-based pitch, mesocarbon microbeads, coke, and synthetic resins (e.g., phenolic resin); thermal decomposition products of furfuryl alcohol resin or novolac resin; fullerene; and carbon nanophones.

[0130] Among these, composite materials that can be obtained by heat-treating one or more of the above-mentioned base materials with petroleum-based pitch or coal-based pitch are particularly preferred. Before heat treatment, the base materials and pitch may be mixed at a temperature higher than the melting point of the pitch. The heat treatment temperature should be such that the components generated by the volatilization or thermal decomposition of the pitch used become carbonaceous materials, but preferably it is 400°C to 2500°C, more preferably 500°C to 2000°C, and even more preferably 550°C to 1500°C. There are no particular restrictions on the atmosphere for heat treatment, but a non-oxidizing atmosphere is preferred.

[0131] (Average particle size of the 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, more preferably 2 μm or more, even more preferably 2.5 μm or more, and 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 non-aqueous electrolyte increases, which can lower the resistance of the non-aqueous alkali metal energy 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 sufficiently thinned, which can improve the energy density of the non-aqueous alkali metal energy storage element. Furthermore, if the particle diameter is 30 μm or less, the swelling and contraction of the negative electrode caused by doping and dedoping of alkali metal ions to the negative electrode during charging and discharging is reduced, and the strength of the negative electrode is maintained.

[0132] The average particle size of the negative electrode active material can be adjusted or reduced to fine particles by grinding using wet and dry jet mills, agitated ball mills, etc., which have built-in classifiers. The grinder is equipped with a centrifugal classifier, and the fine particles ground in an inert gas environment such as nitrogen or argon can be collected by a cyclone or dust collector.

[0133] The average particle diameters of the positive 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 method described below. If the primary particle diameter is less 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 analyzer, and a cumulative curve is obtained with the total volume set to 100%. The particle diameter at the point where the cumulative curve reaches 50% (i.e., the 50% diameter (median diameter)) is taken as the average particle diameter. Examples of particle size distribution analyzers include laser diffraction particle size distribution analyzers.

[0134] The primary particle size of the active material in the first and second embodiments is determined by the following method. 1) A method in which the active material powder is photographed in several fields using an electron microscope, the particle size of approximately 2,000 to 3,000 particles in those fields is measured using a fully automated image processing device, and the arithmetic mean of these measurements is taken as the primary particle size. 2) A method in which the surface and / or cross-section of the obtained electrodes are photographed in several fields using an electron microscope, and the result is obtained by arithmetic mean using the method described above.

[0135] The primary particle size of the active material incorporated into a non-aqueous alkali metal energy storage element can be measured by disassembling the non-aqueous alkali metal energy storage element, removing the electrodes, and using method 2) above; or by removing components other than the active material from the removed electrodes and using method 1) above.

[0136] The dismantling of a non-aqueous alkali metal energy storage element and the removal of its electrodes is preferably carried out under an inert atmosphere such as argon.

[0137] To remove components other than the active material from the electrode, the following method can be used, for example. First, the removed electrode is immersed in ethyl methyl carbonate or dimethyl carbonate to remove non-aqueous electrolytes, alkali metal salts, etc., and then air-dried. Next, it is immersed in a mixed solvent consisting of methanol and isopropanol to deactivate alkali metal ions adsorbed in the active material and air-dried again. Next, in order to remove the binder contained in the active material layer, the electrode from which the alkali metal ions have been deactivated is immersed in distilled water or NMP. Then, if necessary, the active material is scraped off with a spatula or the like, and then ultrasonic waves are irradiated to make the active material slide off the current collector, and the active material is recovered by suction filtration. Furthermore, if necessary, the obtained active material may be immersed in distilled water or NMP again, irradiated with ultrasonic waves, and then suction filtration, and this process may be repeated several times. Finally, the obtained active material can be obtained as powder by vacuum drying at 170°C.

[0138] (optional ingredient) In the first and second embodiments, the negative electrode active material layer may contain, as necessary, optional components such as conductive fillers, binders, and dispersant stabilizers, in addition to the negative electrode active material.

[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 fibers, graphite, carbon nanotubes, and mixtures thereof. Furthermore, it is preferable that the conductive filler consists of a conductive carbonaceous material with higher conductivity than the negative electrode active material. The amount of conductive filler used is preferably more than 0 parts by mass and 30 parts by mass or less, more preferably more than 0 parts by mass and 20 parts by mass or less, and even more preferably more than 0 parts by mass and 15 parts by mass or less, per 100 parts by mass of negative electrode active material. From the viewpoint of high input, it is preferable to mix the conductive filler in the negative electrode active material layer in an amount greater than 0 parts by mass. When the mixing amount is 20 parts by mass or less, the content of the negative electrode active material in the negative electrode active material layer increases, which is preferable because it improves the energy density per unit volume.

[0140] In the first and second embodiments, the binder is not particularly limited, but for example, PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, acrylic copolymer, etc. can be used. The amount of binder used is preferably more than 0 parts by mass and 30 parts by mass or less per 100 parts by mass of the negative electrode active material. If the amount of binder used is more than 0 parts by mass, sufficient electrode strength is achieved. If 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 with high electronic conductivity and that is resistant to degradation due to elution into non-aqueous electrolytes and reactions with electrolytes or ions. There are no particular limitations on such metal foils, and examples include aluminum foil, copper foil, nickel foil, and stainless steel foil. Copper foil is preferred as the negative electrode current collector in non-aqueous alkali metal energy storage elements. When the alkali metal is sodium, aluminum foil is particularly preferred as the negative electrode current collector from the viewpoint of cost and other factors.

[0142] The metal foil may be ordinary metal foil without irregularities or through holes, or it may be metal foil with irregularities achieved by embossing, chemical etching, electrolytic etching, blasting, etc., or it may be metal foil with through holes such as expanded metal, perforated metal, or etched foil. 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 the shape and strength of the negative electrode are sufficiently maintained, but for example, 1 to 100 μm is preferred.

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

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

[0146] In the first and second embodiments, the coating solution for the negative electrode may be prepared by dry blending some or all of the various material powders containing the negative electrode active material, and then adding water or an organic solvent and / or a liquid or slurry-like substance in which a binder and a dispersion stabilizer are dissolved or dispersed. Alternatively, the coating solution for the negative electrode may be prepared by adding various material powders containing the negative electrode active material to a liquid or slurry-like 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 dissolution or dispersion method is not particularly limited, but preferably, a homodisperser, a multi-axis disperser, a planetary mixer, a thin-film swirling high-speed mixer, or the like can be used.

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

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

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

[0151] In the first and second embodiments, the thickness of the negative electrode active material layer is preferably 5 μm to 100 μm 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. If 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 coated, and the coating performance is excellent. If 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 when the negative electrode current collector has irregularities, the thickness of the negative electrode active material layer refers to the average value of the thickness of the negative electrode active material layer per side in the portion of the negative electrode current collector that does not have irregularities.

[0152] (Manufacturing of anodes using alloy-based anode materials) In the first embodiment, the negative electrode has a negative electrode active material layer on one or both sides of the 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, etc. For example: 1) Various materials containing the negative electrode active material are dispersed or dissolved in water or an organic solvent to prepare a slurry-like coating solution. This coating solution is then applied to one or both sides of the negative electrode current collector to form a coating film, which is then dried to obtain the negative electrode. Furthermore, the obtained negative electrode may be pressed to adjust the thickness and bulk density of the negative electrode active material layer. 2) A negative electrode can be obtained by dry mixing various materials containing the negative electrode active material without using a solvent, press-molding the resulting mixture, and then attaching it to the negative electrode current collector using a conductive adhesive; 3) A negative electrode can 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 methods for manufacturing the negative electrode described above, method 1) is preferred from the viewpoint of mass production.

[0155] In the first embodiment, the thickness of the negative electrode active material layer is preferably 10 μm to 75 μm per side of the negative electrode current collector, 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 is more preferably 70 μm or less, even more preferably 65 μm or less, and even more preferably 60 μm or less. If the thickness of the negative electrode active material layer is 10 μm or more, the capacitance of the positive electrode can be fully utilized, and if 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 through holes include through-holes in perforated metal, expanded metal, etched foil, etc.

[0156] (Amount of alkali metal in the negative electrode composite) The amount of alkali metal in the negative electrode mixture is preferably 0.06 mmol / g or less. Doping negative electrode mixtures using alkali metal carbonates has presented challenges in terms of resistance and gas blistering during high-temperature storage. However, with the manufacturing method disclosed herein, although not limited to theory, the amount of alkali metal in the negative electrode mixture can be controlled, and if the amount of alkali metal in the negative electrode mixture is 0.06 mmol / g or less, resistance and gas blistering during high-temperature storage can be improved. This can be controlled by adjusting (A1 + 0.3 × B1) or by adjusting the doping voltage.

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

[0158] (1) Adjustment of the energy storage element before dismantling (1-1) When the alkali metal is lithium, LiCoO2, LiMn 0.6 Fe 0.4 PO4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiLiLi 0.8 Co 0.15 Al 0.05 When using O2 or LiMn2O4 as the positive electrode active material, the completed non-aqueous alkali metal energy storage element is subjected to constant current discharge at a current value of 0.1C in a constant temperature bath set to 25°C until it reaches the lower limit of the stable operating voltage, for example, 3.0V, followed by constant voltage discharge at a constant voltage of 3.0V for 30 minutes. When using LiFePO4 as the positive electrode active material, the completed non-aqueous alkali metal energy storage element is subjected to constant current discharge at a current value of 0.1C in a constant temperature bath set to 25°C until it reaches the lower limit of the stable operating voltage, for example, 2.5V, followed by constant voltage discharge at a constant voltage of 2.5V for 30 minutes.

[0159] (1-2) When the alkali metal is sodium, a representative example of sodium active material is added. NaFe 1 / 3 Ni 1 / 3 Mn 1 / 3 When using O2 as the positive electrode active material, the completed non-aqueous alkali metal energy storage element is subjected to constant current discharge at a current value of 0.1C in a constant temperature bath set to 25°C until it reaches the lower limit of the stable operating voltage, for example, 1.9V, followed by constant voltage discharge at a constant voltage of 1.9V for 30 minutes.

[0160] (2) Disassembly of alkali metal energy storage element Subsequently, the energy storage element is disassembled in an argon box with a dew point of -60°C or lower, and the negative electrode is removed. The negative electrode is sampled according to the shape of the assembly as follows: In the case of a laminate, the negative electrode is cut out at locations that are 1 / 4 and 3 / 4 of the way through when the lamination direction is divided into four parts, and that include the center position within the electrode surface. In the case of a flat wound body, the negative electrode is cut out at locations that are 1 / 4 and 3 / 4 of the way through when the number of turns is divided into four parts, on a flat part avoiding the bends, and that includes the center position within the electrode plane. In the case of a cylindrical wound body, the negative electrode is cut out at a location that is 1 / 2 of the way from the center of the cylinder in the radial direction of the cylinder, and that includes a location that is 1 / 2 of the way through when the cylinder height direction is divided into two parts. The negative electrode composite layer is scraped off from the current collector foil, and the negative electrode composite is sampled.

[0161] (3) Determination of alkali metals Alkali metals in the negative electrode composite are measured using solid-state NMR (nuclear magnetic resonance). For quantitative analysis, alkali metal salts are used as standard substances. The alkali metal salts are dissolved and diluted with distilled water. Negative electrode powder (Underlined section: Match the description of the sampling method) Perform NMR measurements with the same signal amplification factor (receiver gain) as the receiver, and create a calibration curve for alkali metal salts. Using that calibration curve, Negative electrode powder The alkali metals in the material are quantified, and the weight ratio of alkali metals per unit weight of the active material layer is calculated. When quantifying alkali metals, it is desirable to position the NMR observation center close to the location where the alkali metal peak appears, and it should be noted that the excitation efficiency of the alkali metal peak location is 90% of the excitation efficiency of the observation center.

[0162] (3-1) When the alkali metal is lithium, LiCl is used as the alkali metal salt to be used as the quantitative standard substance as described above. The NMR measurement conditions are as follows. Equipment: JEOL ECA 700 Probe: 3.2mm probe Observed nuclei: 7 Li Observation frequency: 272.1MHz Measurement method: Single pulse method Pulse angle: 45° Pulse width: 1.0 μs Waiting time: 10s Total number of times: 256 MAS rotation speed: 7kHz Measurement temperature: Room temperature (approx. 25℃) Chemical shift reference: LiCl aqueous solution (external standard, 0 ppm) Broadening factor: 20Hz The lithium metal content is quantified based on peaks with peak tops in the 255 ppm to 270 ppm range. After correcting using a straight line connecting points on the spectrum at 220 ppm and 340 ppm as a baseline, the peak integral value is calculated in the 220 ppm to 340 ppm range.

[0163] (3-2) When the alkali metal is sodium, NaCl is used as the alkali metal salt to be used as the quantitative standard substance as described above. The NMR measurement conditions are as follows. Equipment: Bruker Japan AVANCE500 Probe: 4mm probe Observed nuclei: 23 Na Observation frequency: 132.3MHz Measurement method: Single pulse method (pulse program zg) Pulse width: 1.0 μs Waiting time: 5s Total number of times: 256 MAS rotation speed: 7kHz Measurement temperature: Room temperature (approx. 25℃) Chemical shift reference: NaCl aqueous solution (external standard, 0 ppm) Broadening factor: 30Hz The sodium metal content is quantified based on peaks with peak tops in the range of 1110 ppm to 1150 ppm. After correcting using a straight line connecting 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 alkali metal content in negative electrode composite The alkali metal content (mmol / g) in the negative electrode mixture is calculated by dividing the alkali metal content (mmol) obtained from the NMR measurement described above by the sample weight (g) of the negative electrode mixture used in the NMR measurement.

[0165] (Irreversible capacity ratio of the negative electrode or negative electrode precursor) This embodiment allows lithium to be supplied from alkali metal carbonate or pre-doped material instead of positive electrode active material, making it suitable for use as a negative electrode precursor or negative electrode with a high irreversible capacity ratio. Preferably, the irreversible capacity ratio of the negative electrode precursor or negative electrode is 5% or more and 50% or less. If the irreversible capacity ratio is 5% or more and 50% or less, the initial resistance can be reduced by supplying 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 from alkali metal carbonate or pre-doped material.

[0166] Methods for preparing a negative electrode with an irreversible capacity of 5% to 50% include using a material with a high ratio of irreversible capacity as the active material, and using a mixture of a material with a high ratio of irreversible capacity and a material with a low ratio of irreversible capacity as the active material and adjusting the ratio of the mixture. Examples of materials with a high ratio of irreversible capacity include alloy negative electrode materials described in <Negative Electrode, Negative Electrode Precursor> (Alloy-based Negative Electrode Materials) and carbon materials described in the section <Negative Electrode, Negative Electrode Precursor> (Carbon Materials), such as amorphous carbonaceous materials like carbon black, carbon nanoparticles, activated carbon, graphitized mesophase carbon spheres, graphite whiskers, and polyacene-based materials; 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 resin); thermal decomposition products of furfuryl alcohol resin or novolac resin; 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 listed in the section on <negative electrode, negative electrode precursor> (carbon materials).

[0167] (Calculation of irreversible capacity ratio and irreversible capacity G1 of the negative electrode precursor) The irreversible capacitance of the negative electrode precursor is determined by the following method. A single-sided negative electrode consisting of a negative electrode active material, a binder, and a conductive material if necessary is fabricated using a known electrode fabrication process for non-aqueous alkali metal energy storage elements. A negative electrode half-cell consisting of an alkali metal counter electrode, an alkali metal reference electrode, an electrolyte (described later), and a known separator is discharged at a constant current to 0.01V against the alkali metal reference electrode at a rate of 0.1C in a 25°C environment, and then discharged at a constant voltage until the current converges to a rate of 0.02C. The discharge capacity (mAh) is measured, and the coated area (cm²) of the single-sided negative electrode precursor is determined. 2 By dividing by ), the initial storage capacity H1 (mAh / cm³) of alkali metals can be calculated. 2 ) is obtained. After the constant voltage discharge at 0.01V described above, a 10-minute rest period is observed, and then the charging capacity (mAh) is measured when constant current charging is performed up to 2.5V at a rate of 0.1C, and the coating area (cm²) of the single-sided negative electrode precursor is obtained. 2 By dividing by ), the initial release capacity of alkali metals H2 (mAh / cm³) can be calculated. 2 The irreversible capacity ratio Q (%) of the negative electrode precursor is obtained by the following formula: Q = (H1 - H2) / H1 × 100 Irreversible capacitance G1 (mAh / cm²) of the negative electrode precursor 2 ) can be obtained from the following formula. G1 = H1 - H2

[0168] (Calculation of negative electrode irreversible capacity ratio and negative electrode irreversible capacity G1) The irreversible capacitance ratio of the negative electrode can be determined by the following method (1) or (2).

[0169] (1) Method for calculation from the negative electrode precursor The negative electrode is the negative electrode of the alkali metal energy storage element completed after the initial charging process. However, if the negative electrode before the initial charging process, i.e., the negative electrode precursor, is available, the irreversible capacity Q (%) and irreversible capacity G1 (mAh / cm²) can be calculated using the method described above in (Calculation of irreversible capacity ratio of negative electrode precursor). 2 It is possible to calculate ).

[0170] (2) Method of calculation from the negative electrode After the initial charging process, the completed alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage. This is followed by 30 minutes of constant voltage charging at the upper limit of the stable operating voltage. After that, the energy storage element is 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 similar tool to create a single-sided negative electrode. This 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, it is charged with a constant current of 0.1C up to 2.5V, followed by a 10-minute pause. After that, it is discharged with a constant current of 0.1C against the alkali metal reference electrode to 0.01V, and then discharged with a constant voltage until the current converges to a 0.02C rate. After a 10-minute pause, the charging capacity (mAh) was measured when the battery was charged with a constant current of 0.1C up to 2.5V, and the coating area (cm²) of the negative electrode on one side was measured. 2 By dividing by ), the reversible emission capacity of alkali metals H1 (mAh / cm²) can be calculated. 2 ) obtain.

[0171] On the other hand, the alkali metal energy storage element, completed after the initial charging process, is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, and then charged with a constant voltage of the upper limit of the stable operating voltage for 30 minutes. After that, the energy storage element is 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 make it a single-sided negative electrode, and then it is 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, it is charged with a constant current of 0.1C up to 2.5V, then the negative electrode half cell is disassembled in an argon box and the negative electrode is removed. The operation of "immersing the negative electrode in the electrolyte for alkali metal energy storage elements with the electrolyte and additives removed, i.e., only the solvent of the electrolyte, and removing the washing solvent" is performed three times. Furthermore, the negative electrode is immersed in an electrolyte solution for alkali metal energy storage elements, but with the electrolyte and additives removed, i.e., only the solvent of the electrolyte solution. After that, the negative electrode is removed and vacuum-dried at 25°C for 12 hours. This results in a negative electrode in which alkali metals equivalent to the irreversible capacity remain, while alkali metal ions in the electrolyte are removed. Next, the negative electrode active material layer is scraped off and acid-decomposed 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 pressurizing as appropriate. The resulting diluted solution is analyzed by ICP-MS, and 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 limit of the measurement, it is preferable to further dilute the diluted solution while maintaining the acid concentration. Based on the obtained measurement results, the amount of alkali metal (g) is quantified using a calibration curve prepared in advance with standard solutions for chemical analysis, and the amount of alkali metal M (g / cm³) equivalent to the irreversible capacity contained per unit area of ​​the coated part of the single-sided negative electrode is determined. 2 The irreversible capacity G1 (mAh / cm³) contained per unit area of ​​the coated part of the single-sided negative electrode is obtained using the atomic weight m of the alkali metal. 2 ) is calculated by G1 = M ÷ m × 1000 ÷ 3600. And the irreversible capacitance ratio Q (%) of the negative electrode in this case is obtained by the following formula: Q = G1 / (H1 + G1) × 100

[0172] <Separator> In the first embodiment, the positive electrode precursor and the negative electrode are generally stacked or wound with a separator in between to form an electrode stack or electrode winding 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 in between to form an electrode stack or electrode winding having the positive electrode, the negative electrode and the separator.

[0173] In the first and second embodiments, known separators used in non-aqueous alkali metal energy storage elements can be used as separators. For example, a microporous membrane made of polyethylene or polypropylene, or a cellulose nonwoven fabric used in electric double-layer capacitors can be used. A film made of organic or inorganic fine particles may be laminated on one or both sides of these separators. Organic or inorganic fine particles may also be contained inside the separator.

[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 preferable because it tends to reduce self-discharge due to internal micro-shorts. A separator thickness of 35 μm or less is preferable because it tends to improve the output characteristics of the non-aqueous alkali metal type energy storage element.

[0175] In the first and second embodiments, the thickness of the film composed of organic or inorganic fine particles is preferably 1 μm or more and 10 μm or less. A film thickness of 1 μm or more is preferable because it tends to reduce self-discharge due to internal micro-shorts. A film thickness of 10 μm or less is preferable because it tends to improve the output characteristics of non-aqueous alkali metal type rechargeable batteries. The film composed of organic or inorganic fine particles may be the same layer as the intermediate layer in the first and second embodiments, or it 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, or an organic polymer may be used alone as a substitute for the separator. There are no particular restrictions on the organic polymer, but those that have good affinity with non-aqueous electrolytes and gel when permeated with the electrolyte and swell are preferred. Examples of organic polymers include polyethylene oxide, polyacrylonitrile, polypyrinidene fluoride, polymethyl methacrylate, and mixtures thereof, which can exhibit high alkali metal ion conductivity when gelled and are therefore preferably used.

[0177] Organic polymers can encapsulate the electrolyte within themselves. Therefore, when the outer casing is damaged, they have the effect of preventing the electrolyte from leaking out of the non-aqueous alkali metal energy storage element, which is preferable from a safety standpoint.

[0178] (Middle class) In the first and second embodiments, the aforementioned intermediate layer may be located on the surface of the separator facing the positive electrode. The detailed features are as described in the section on "Intermediate Layer".

[0179] <K1 / K3> In the second embodiment, the discharge capacity of a positive electrode half-cell using a positive electrode taken from a battery before capacity recovery, or using the positive electrode and intermediate layer if an intermediate layer is present, in the potential region of the stable operating potential of the positive electrode active material is K1 (mAh / cm²). 2 ) is defined as the discharge capacity of the negative electrode half-cell of the negative electrode taken from the battery before capacity recovery, and K3 (mAh / cm²) is defined as the discharge capacity of the negative electrode half-cell. 2 When this is the case, preferably 0.80 ≤ K1 / K3 ≤ 1.2, and more preferably 0.85 ≤ K1 / K3 ≤ 1.2. If 0.80 ≤ K1 / K3 ≤ 1.2, a high capacity recovery effect and a high initial capacity density of the non-aqueous alkali metal energy storage element can be obtained. Here, the voltage of the negative electrode half cell is obtained with the alkali metal as the reference.

[0180] <Non-aqueous electrolyte> The non-aqueous electrolyte contains an accelerator. By including an accelerator in the non-aqueous electrolyte, the decomposition reaction of alkali metal carbonates contained in the positive electrode active material layer, 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 in the capacity recovery step of the second embodiment. Although not necessarily limited to theory, it is thought that the accelerator promotes the decomposition of alkali metal carbonates, which have extremely low conductivity, by mediating electron conduction between the positive electrode active material and the alkali metal carbonates of the alkali metal ion battery. In the second embodiment, the timing of introducing the accelerator into the battery before capacity recovery may be in the electrolyte injection step before the initial charging step, or the battery may be used before capacity recovery, and after degradation, the outer casing may be opened before the capacity recovery step and the accelerator or the non-aqueous electrolyte containing the accelerator may be added into the battery.

[0181] (Oxidation initiation potential of accelerator) In the first embodiment of this disclosure, the oxidation initiation potential of the accelerator is 3.8V or more and 4.8V or less (vsLi / Li + ) is a characteristic feature. This allows the reaction in which alkali metal carbonates contained in the positive electrode active material layer or the intermediate layer between the positive electrode active material layer and the separator are decomposed in the pre-doping process to proceed efficiently. If the oxidation initiation potential of the accelerator is 3.8V or higher, the initial charging process of the alkali metal ion battery can proceed smoothly, and the decomposition of alkali metal carbonates proceeds effectively, which is preferable as it allows for the manufacture of non-aqueous alkali metal energy storage elements such as alkali metal ion batteries without problems. On the other hand, if the oxidation initiation potential of the accelerator is less than 3.8V, the voltage of the alkali metal ion battery may not rise sufficiently in the initial charging process, making it impossible to manufacture the battery, or the decomposition reaction of alkali metal carbonates may not proceed sufficiently in the initial charging process, which is undesirable. The oxidation initiation potential of the accelerator is 4.8V or lower (vsLi / Li + This is preferable because it allows the decomposition of alkali metal carbonates and the doping reaction to the negative electrode to proceed even if the voltage during the initial charge is lowered.

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

[0183] (Oxidation initiation potential of accelerator) The oxidation initiation potential of the accelerator in the second embodiment is above the stable operating potential of the positive electrode active material and below 4.8V (vs Li / Li + This allows the decomposition reaction of alkali metal carbonates contained in the positive electrode active material layer, any intermediate layer between the positive electrode active material layer and the separator, or both, to proceed efficiently during the capacity recovery process.

[0184] If the oxidation initiation potential of the accelerator is greater than or equal to the stable operating potential of the positive electrode active material, then even if the alkali metal ion battery is used below the stable operating voltage of the positive electrode active material after initial manufacturing, the decomposition of alkali metal carbonate can be suppressed, thereby enhancing the capacity recovery effect. On the other hand, if the oxidation initiation potential of the accelerator is less than the stable operating potential of the positive electrode active material, then during the initial charging process and when using the alkali metal ion battery, when the potential of the positive electrode reaches a level greater than or equal to the oxidation initiation potential of the accelerator but less than the stable operating potential of the positive electrode active material, the alkali metal carbonate may decompose, and the recovery effect in the capacity recovery process may not be fully obtained. + If the value is below this, the alkali metal carbonate can be sufficiently decomposed in the capacity recovery process, and a high capacity recovery effect can be obtained. The lower limit of the oxidation initiation potential of the accelerator is preferably 0.3V or higher above the stable operating potential of the positive electrode active material, more preferably 0.2V or higher above the stable operating potential of the positive electrode active material, and particularly preferably 0.1V or higher above the stable operating potential of the positive electrode active material. The upper limit of the oxidation initiation potential of the accelerator is preferably 4.7V (vs Li / Li + ) or less, more preferably 4.6V (vs Li / Li + ) are as follows:

[0185] (Measurement of oxidation initiation potential of accelerator) The oxidation initiation potential of the accelerator in 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 it using the positive electrode of a non-aqueous alkali metal energy storage element in which the accelerator is actually used. For details, it is preferable to measure it using the method described in the examples. In this disclosure, the oxidation initiation potential of the accelerator is the potential (V vs Li / Li+) relative to a lithium reference electrode measured by the following method.

[0186] In this specification, the oxidation initiation potential of the accelerators of the first and second embodiments is obtained by the following method: A positive electrode precursor 1 comprising an active material and optionally comprising conductive carbon black and a binder, but not containing alkali metal carbonates. 炭酸Liなし To make a positive electrode precursor 1, as illustrated in Figures 1 and 2. 炭酸Liなし The painted area (the black painted area in Figure 1) has an area S (cm²) 2 It is used as a component and combined with a negative electrode (2), a separator (3), and a lithium reference electrode (4), and sealed in a laminate to fabricate pre-aqueous non-aqueous alkali metal energy storage element precursors 1 and 2.

[0187] A non-aqueous alkali metal energy storage element precursor 1 containing an accelerator is injected into the non-aqueous alkali metal energy storage element precursor 1 before injection, and a non-aqueous electrolyte 2 without an accelerator is injected into the non-aqueous alkali metal energy storage element precursor 2 before injection. The laminate is then sealed to obtain non-aqueous alkali metal energy storage element precursors 1 and 2. This is then charged with a constant current of 0.1C in a constant temperature bath set to 45°C until the voltage reaches 4.8V. At the same time, the positive electrode potential relative to the lithium reference electrode is measured. Based on these measurements, the positive electrode potential (V vs Li / Li) is determined for the non-aqueous alkali metal energy storage element precursors 1 and 2 in relation to the capacity per unit weight of positive electrode active material (mAh / g of positive electrode active material). + Obtain curves 1 and 2 plotting the following. Next, calculate the oxidation initiation potential using method A or B below.

[0188] A. When the positive electrode potential of the non-aqueous alkali metal energy storage element precursor 1 is charged to a region of 3.7V or higher. The starting point for calculating capacity (0 mAh / g of positive electrode active material) is set when the positive electrode potential reaches 3.7 V. Curves 1 and 2 are shifted in parallel, and the difference in positive electrode active material weight capacity at the same positive electrode potential (curve 1 - curve 2) is calculated. The positive electrode potential at which the capacity difference between curves 1 and 2 exceeds 5 mAh / g is defined as the oxidation initiation potential of the accelerator. Figures 3 and 4 illustrate the graphs for calculating the difference curve (curve 1 - curve 2) and the oxidation initiation potential of the accelerator at the same positive electrode potential using method A.

[0189] B. When the positive electrode potential of the non-aqueous alkali metal energy storage element precursor 1 is charged to a region of 3.7V or higher. The charging start point is set as the capacity calculation starting point (0 mAh / g of positive electrode active material), and curves 1 and 2 are shifted in parallel. Then, the difference in positive electrode active material weight capacity at the same positive electrode potential (curve 1 - curve 2) is calculated. The positive electrode potential at which the capacity difference between curves 1 and 2 exceeds 5 mAh / g is taken as the oxidation start potential of the accelerator. Figures 5 and 6 illustrate graphs for calculating the difference curve (curve 1 - curve 2) and the oxidation start potential of the accelerator at the same positive electrode potential using method B.

[0190] (Types of accelerators) The non-aqueous electrolyte preferably contains, as an accelerator, at least one selected from the group consisting of methoxybenzene derivatives, phenyl-containing organic compounds, TEMPO derivatives, pyridine-N-oxide derivatives, and cyclohexylbenzene derivatives. The inclusion of these accelerators in the electrolyte allows for efficient decomposition of alkali metal carbonates contained in the positive electrode active material layer, or any intermediate layer between the positive electrode active material layer and the separator, during the pre-doping step of the first embodiment of this disclosure, or during the capacity recovery step of the second embodiment of this disclosure. As described above, the oxidation initiation potential of the accelerator in the first embodiment of this disclosure is between the stable operating potential of the positive electrode active material and 4.8V (vs Li / Li + ) is preferable. The oxidation initiation potential of the accelerator in the second embodiment of this disclosure is 4.8V or less (vs Li / Li) above the stable operating potential of the positive electrode active material. + ) is preferable.

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

[0192] There are no particular limitations on methoxybenzene derivatives, but examples 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, and 2,5-ditert-butyl-1,4-dimethoxybenzene (also known as 1,4-ditert-butyl-2,5-dimethoxybenzene).

[0193] The phenyl-containing organic compound is not particularly limited, but examples include biphenyl, cyclohexylbenzene, hexamethylbenzene, and tert-butylphenyl carbonate. In one embodiment, it is preferable that the phenyl-containing organic compound is something other than biphenyl.

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

[0195] The pyridine-N-oxide derivative is not particularly limited, but examples 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] (Content of accelerator) 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 alkali metal carbonate decomposition acceleration effect can be obtained in the first and second embodiments. In the second embodiment, a volume recovery effect due to alkali metal carbonate decomposition can be obtained. If the accelerator content is 1.5 mol / L or less, the ionic conductivity of the electrolyte can be kept low, so the overpotential during pre-doping can be reduced. In the first embodiment, a sufficient alkali metal carbonate decomposition acceleration effect and a high effective utilization rate of the positive electrode active material can be obtained, which is also preferable in terms of resistance and gas bloating during high-temperature storage. In the second embodiment, a sufficient alkali metal carbonate decomposition volume recovery effect can be obtained. In addition, a accelerating effect and a high effective utilization rate of the positive electrode active material can be obtained, which is also preferable.

[0197] The lower limit of the accelerator content is preferably 0.01 mol / L or more, more preferably 0.05 mol / L or more. The upper limit of the accelerator 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 accelerator may be injected together with the insoluble components, as the insoluble components may dissolve and function when the accelerator is consumed during pre-doping in the first embodiment or during volume recovery in the second embodiment.

[0199] (Qualitative and quantitative analysis of accelerators) In the first and second embodiments, the accelerator contained in the electrolyte of the non-aqueous alkali metal energy storage element can be identified and quantified by taking the electrolyte from the completed energy storage element and using known qualitative and quantitative analysis (e.g., 1H-NMR).

[0200] In the first and second embodiments, the measurement of the oxidation initiation potential of the accelerator, as described above, can be performed separately by the method described above (measurement of oxidation initiation potential of accelerator) after identifying and quantifying the accelerator, which may be present in the completed non-aqueous alkali metal energy storage element, using known qualitative and quantitative analysis (e.g., H-NMR).

[0201] (Electrolytes, solvents, additives) In the first and second embodiments, the electrolyte, other than the accelerator, can be any known electrolyte for alkali metal ion batteries, and is a non-aqueous electrolyte containing alkali metal ions such as alkali metal ions. That is, this non-aqueous electrolyte contains a non-aqueous solvent, which will be described later. Preferably, the non-aqueous electrolyte contains alkali metal salts such as alkali metal salts 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. Lithium salts, sodium salts, etc., are preferably used as the alkali metal salts used as the electrolyte.

[0202] In the first and second embodiments, examples of lithium salts include (LiN(SO2F)2), LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C2F5), LiN(SO2CF3)(SO2C2F4H), LiC(SO2F)3, LiC(SO2CF3)3, LiC(SO2C2F5)3, LiCF3SO3, LiC4F9SO3, LiPF6, LiCiO4, and LiBF4, which can be used individually or in mixtures of two or more. Because high conductivity can be achieved, the alkali metal salt preferably contains LiPF6, and may further contain LiN(SO2F)2.

[0203] In the first and second embodiments, the sodium salt can be, for example, Na(SO2CF3)2, NaN(SO2F)2, NaN(C2F5SO2)2, NaCF3SO3, NaC(CF3SO2)3, NaPF6, NaBF4, NaClO4, NaAsF6, NaAlCl4, etc., used individually or in combination of two or more. For example, it is preferable to include NaClO4, NaPF6 and / or NaN(SO2CF3)2 because they can exhibit high conductivity.

[0204] In the first and second embodiments, the alkali metal salt concentration in the non-aqueous electrolyte is preferably 0.5 mol / L or higher, 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 higher, there is a sufficient amount of anions, so the battery capacity can be sufficiently high. If the alkali metal salt concentration is 2.0 mol / L or lower, it is preferable because it prevents undissolved alkali metal salts from precipitation in the non-aqueous electrolyte and prevents the viscosity of the non-aqueous electrolyte from becoming too high, thus preventing a decrease in conductivity and a decrease in output characteristics.

[0205] The non-aqueous electrolytes in the first and second embodiments may contain a carbonate solvent as the non-aqueous solvent, preferably containing a cyclic carbonate and a linear carbonate. The inclusion of cyclic carbonates and linear carbonates in the non-aqueous electrolyte is advantageous in that it dissolves alkali metal salts at a desired concentration and exhibits high ionic conductivity. Examples of cyclic carbonates include alkylene carbonate compounds such as ethylene carbonate, propylene carbonate, and butylene carbonate. Alkylene carbonate compounds are typically unsubstituted. Examples of linear carbonates include dialkyl carbonate compounds such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, and dibutyl carbonate. Dialkyl carbonate compounds are typically unsubstituted. The solvent may be used alone or mixed in any proportion of two or more solvents.

[0206] In the first and second embodiments, the total content of cyclic carbonates and linear carbonates is 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, based on the total mass of the non-aqueous electrolyte. If the total content of cyclic carbonates and linear carbonates is 50% by mass or more, it is possible to dissolve alkali metal salts at a desired concentration and to exhibit high ionic conductivity. If the total concentration of cyclic carbonates and linear carbonates is 95% by mass or less, the electrolyte may further contain additives described later.

[0207] The non-aqueous electrolytes in the first and second embodiments may further contain additives. The additives are not particularly limited, but examples include sultone compounds, cyclic phosphazenes, acyclic fluorine-containing ethers, fluorine-containing cyclic carbonates, cyclic carbonate esters such as vinylene carbonate, cyclic carboxylic acid esters, and cyclic acid anhydrides. These can be used individually or in combination of two or more. These additives form a good film on the positive or negative electrode, improving the durability of the alkali metal ion battery.

[0208] <Gas permeation mechanism> In the second embodiment, during the capacity recovery process described later, gases such as CO2 may be generated due to the oxidative decomposition of alkali metal compounds, such as alkali metal carbonates, in the positive electrode. Therefore, it is preferable that the casing of the non-aqueous alkali metal energy storage element be equipped with a gas permeability mechanism that can release the gas generated when voltage is applied during the capacity recovery process to the outside of the casing. By removing the gas generated due to the oxidative decomposition of alkali metal compounds through the gas permeability mechanism, the capacity recovery effect can be further enhanced.

[0209] In the second embodiment, the gas permeation mechanism may include, for example, a mechanism that opens a part of the outer casing and reseals it after the capacity recovery process; or appropriate gas release means such as a gas vent valve, a gas permeable film, gas permeable rubber, or a gas check valve (a valve that allows gas to pass in only one direction, from the inside to the outside of the non-aqueous alkali metal energy storage element) pre-installed on a part of the outer casing. The gas release means such as the gas vent valve, gas permeable film, gas permeable rubber, and 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 is preferable because it allows the capacity recovery process described later to be performed without excessively disassembling the battery pack of non-aqueous alkali metal energy storage elements, and even in general environments that are not low dew point environments, thus simplifying the design of the capacity recovery process.

[0210] <Manufacturing method> <Manufacturing method for non-aqueous alkali metal energy storage elements> The non-aqueous alkali metal energy storage element in the first embodiment of this embodiment can be manufactured using the positive electrode precursor and negative electrode formed as described above by the following method: (1) A laminate consisting of a positive electrode precursor, a negative electrode, and a separator is housed in an outer casing (cell assembly), (2) Injecting a non-aqueous electrolyte into the outer casing (electrolyte injection), (3) Applying a voltage between the positive electrode precursor and the negative electrode to decompose the alkali metal compound (pre-doping) This includes the items listed above in that order.

[0211] The method for manufacturing a non-aqueous alkali metal energy storage element (pre-capacity recovery battery) before capacity recovery according to the second embodiment of this disclosure includes the steps of: preparing a positive electrode coating solution; obtaining a positive electrode; manufacturing a negative electrode; manufacturing an electrode stack or electrode winding from the positive electrode and the negative electrode; housing the electrode stack or electrode winding in an outer casing and injecting a non-aqueous electrolyte; and an initial charging step. The method for manufacturing a pre-capacity recovery battery may optionally include an aging step and a degassing step. The steps for obtaining a positive electrode and manufacturing a negative electrode are described in separate sections of this specification.

[0212] (assembly) In the cell assembly of the first embodiment, an electrode laminate is produced by connecting the positive electrode terminals and negative electrode terminals to a laminate formed by stacking a positive electrode precursor and a negative electrode cut into a single-leaf shape with a separator in between. Alternatively, an electrode winding body is produced by connecting the positive electrode terminals and negative electrode terminals to a winding body formed by stacking and winding a positive electrode precursor and a negative electrode with a separator in between. The shape of the electrode winding body may be cylindrical or flattened. Furthermore, in the assembly process of the second embodiment, for example, an electrode laminate can be produced by connecting the positive electrode terminals and negative electrode terminals to a laminate formed by stacking a positive electrode and a negative electrode cut into a single-leaf shape with a separator in between. Alternatively, an electrode winding body may be produced by connecting the positive electrode terminals and negative electrode terminals to a winding body formed by stacking and winding a positive electrode and a negative electrode with a separator in between. The shape of the electrode winding body may be cylindrical or flattened.

[0213] In the first and second embodiments, the method of connecting the positive and negative terminals is not particularly limited, but can be done by methods such as resistance welding or ultrasonic welding.

[0214] (Drying of electrodes) In the first and second embodiments, it is preferable to remove residual solvent by drying the electrode state before assembly or the electrode body (electrode stack or electrode winding) after assembly. Drying may also be performed after housing in the outer casing described later. The drying method is not limited, but drying can be done by vacuum drying or the like. The residual solvent and moisture are preferably 1.5% by mass or less, based on the mass of the positive electrode active material layer or the negative electrode active material layer. If the residual solvent is greater than 1.5% by mass, the solvent will remain in the system, which may worsen the self-discharge characteristics and cycle characteristics, so this is undesirable.

[0215] (Exterior) In the first and second embodiments, metal cans, laminate packaging materials, etc., can be used as the outer casing. Aluminum cans are preferred as the metal cans. Metal cans may be in shapes such as square, round, or cylindrical. As the laminate packaging material, a film made by laminating metal foil and a resin film is preferred, and an example of laminate packaging material consisting of three layers: outer resin film / metal foil / inner resin film is provided. The outer resin film is for preventing damage to the metal foil due to contact, etc., and resins such as nylon or polyester can be suitably used. The metal foil is for preventing the permeation of moisture and gas, and foils such as copper, aluminum, and stainless steel can be suitably used. The inner resin film protects the metal foil from the electrolyte stored inside and is for melt sealing during heat sealing of the outer casing, and polyolefins, acid-modified polyolefins, etc., can be suitably used.

[0216] (Storage in the outer casing) In the first and second embodiments, the dried electrode laminate or electrode winding is preferably housed in an outer casing, such as a metal can or laminate packaging, in a dry environment with a dew point of -40°C or lower, and sealed, leaving only one opening for pouring the non-aqueous electrolyte. A dew point of -40°C or lower is preferable because it prevents moisture from adhering to the electrode and preventing water from remaining in the system, thereby improving the self-discharge characteristics. The method of sealing the outer casing is not particularly limited, but when using laminate packaging, methods such as heat sealing or impulse sealing can be used.

[0217] (Drying) In the first and second embodiments, it is preferable to remove any remaining electrode slurry solvent and moisture from the electrode laminate or electrode winding housed in the outer casing by drying. The drying method is not limited, but it can be dried by vacuum drying or the like. The amount of remaining solvent and moisture is preferably 1.5% by mass or less, based on the mass of the positive electrode active material layer or the negative electrode active material layer. If the amount of remaining solvent is greater than 1.5% by mass, the solvent will remain in the system, which may worsen the self-discharge characteristics and cycle characteristics, so this is undesirable.

[0218] (Injection, impregnation, sealing) In the first and second embodiments, after assembly, a non-aqueous electrolyte is poured into the electrode stack housed in the outer casing. After pouring, it is desirable to further impregnate the electrode, negative electrode, and separator to thoroughly immerse them in the non-aqueous electrolyte. The impregnation method is not particularly limited, but for example, after pouring the non-aqueous electrolyte, the electrode stack can be placed in a vacuum chamber with the outer casing open, the chamber can be depressurized using a vacuum pump, and then returned to atmospheric pressure. After impregnation, the electrode stack can be sealed by depressurizing it with the outer casing open. In the first embodiment, if at least a portion of the positive electrode, negative electrode, and separator are not immersed in the non-aqueous electrolyte, the pre-doping process described later will proceed unevenly, resulting in an increase in the resistance of the resulting non-aqueous alkali metal energy storage element and a decrease in durability.

[0219] (Pre-dope) In the first embodiment, the alkali metal carbonate functions as a doping source for alkali metal ions into the negative electrode active material. In pre-doping, it is preferable to apply a voltage between the positive electrode precursor and the negative electrode to decompose the alkali metal carbonate and release alkali metal ions, thereby pre-doping the negative electrode active material with alkali metal ions. Pre-doping can be performed at any step from liquid injection to degassing, but it is preferable to perform it during the initial charge from the viewpoint of manufacturing process efficiency.

[0220] In the first embodiment, the target potential of the positive electrode precursor is 4.15~4.75V (vsLi / Li + It is preferable to apply 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 the following occurs: Within this range, alkali metal carbonates can be decomposed and alkali metal ions can be doped into the negative electrode active material while minimizing damage to the positive electrode and electrolyte. This suppresses loss of the positive electrode active material due to irreversible capacitance and thus increases the effective utilization rate of the positive electrode active material.

[0221] In the method for manufacturing a non-aqueous alkali metal energy storage element according to the first embodiment of this 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 4.1V or more and 4.6V or less. The applied voltage can be appropriately adjusted taking into consideration the electrolyte used and the voltage tolerance of the positive electrode active material, and is more preferably 4.2V or more and less than 4.5V.

[0222] When the alkali metal is lithium, applying a voltage of 4.1V to 4.6V between the positive electrode precursor and the negative electrode precursor of the non-aqueous alkali metal energy storage element precursor allows for pre-doping while avoiding damage to the positive electrode active material and electrolyte, which is preferable in terms of positive electrode utilization rate, resistance, and gases during high-temperature storage. In this embodiment, the decomposition of alkali metal carbonates at such a relatively low voltage is made possible by using an electrolyte containing the aforementioned accelerator.

[0223] When the alkali metal is lithium, there are no particular restrictions on the method of applying voltage. Methods such as charging to a voltage of 4.1V or higher using a charge / discharge device or power supply, superimposing a pulse voltage when applying a constant voltage of 4.1V or higher, or performing a charge / discharge cycle within a voltage range including a voltage of 4.1V or higher using a charge / discharge device can be used.

[0224] In the method for manufacturing a non-aqueous alkali metal energy storage element according to this 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 electrolyte used and the voltage tolerance of the positive electrode active material, and is preferably 3.8V or more and 4.3V or less. The lower limit of the applied voltage is more preferably 3.9V or more, and even more preferably 4.0V or more, and the upper limit of the applied voltage is more preferably 4.2V or less, and even more preferably 4.15V or less.

[0225] When the alkali metal is sodium, applying a voltage of 3.8V to 4.3V between the positive electrode precursor and the negative electrode is preferable in terms of positive electrode utilization rate, resistance, and gases during high-temperature storage, as it allows for pre-doping while avoiding damage to the positive electrode active material and electrolyte. In the first embodiment, the decomposition of alkali metal carbonates at such relatively low voltages is made possible by using the specific accelerator described above.

[0226] When the alkali metal is sodium, there are no particular restrictions on the method of applying voltage. Methods such as charging to a voltage of 3.8V or higher using a charge / discharge device, power supply, etc. (constant current charging and constant voltage charging may be used in combination); superimposing a pulse voltage when applying a constant voltage of 3.8V or higher; or performing a charge / discharge cycle within a voltage range including a voltage of 3.8V or higher using a charge / discharge device can be used.

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

[0228] (Measurement of the potential of the positive electrode precursor) The positive electrode potential (vsLi / Li) of the non-aqueous alkali metal energy storage element disclosed herein. +The measurement of the potential is performed 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 non-aqueous lithium energy storage element precursor before electrolyte injection. The alkali metal reference electrode and the electrode assembly are placed in close proximity so that the potential difference between the positive electrode precursor and the alkali metal reference electrode can be measured. If necessary, the alkali metal reference electrode is wrapped in a separator and the separator is brought into contact with the electrode assembly, and it is preferable to ensure that the alkali metal reference electrode and the electrode assembly are connected by the electrolyte. After the electrolyte is injected, the laminate is sealed. In the initial charging process, a voltage is applied between the positive electrode precursor and the negative electrode precursor, and at the same time, the potential difference between the positive electrode and the alkali metal reference electrode is measured to measure the potential of the positive electrode precursor with respect to alkali metal.

[0229] When the alkali metal is lithium, the potential difference X between the positive electrode and the alkali metal reference electrode obtained in the measurement is the positive electrode potential (vsLi / Li + The maximum positive electrode potential during the initial charge is defined as the target potential.

[0230] If the alkali metal is an alkali metal M other than lithium, the maximum potential difference X(vsM / M) between the positive electrode and the alkali metal reference electrode during initial charging is + The potential difference between sodium and lithium is calculated by converting from the standard electrode potential. For example, if the alkali metal is sodium, the difference between the standard electrode potentials of sodium and lithium is 0.33V, so by adding 0.33V to the potential difference X obtained with sodium, the positive electrode potential (vsLi / Li) can be calculated. + ) is obtained as follows.

[0231] During the pre-doping operation, gases such as CO2 and O2 may be generated due to the oxidative decomposition of alkali metal carbonates in the positive electrode precursor and intermediate layer. Therefore, when applying voltage, it is preferable to take measures to release the generated gas to the outside of the "electrode laminate, electrode winding, or outer casing." Examples of such measures include: applying voltage with a part of the outer casing open; applying voltage with appropriate gas release means such as a gas release valve or gas permeable film installed in advance on a part of the outer casing; accumulating gas in the excess portion of the laminate and removing the generated gas along with the excess portion of the laminate in a subsequent degassing process; and so on.

[0232] (Initial charging process) In the initial charging process, a voltage is applied between the positive and negative electrodes 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 to dope the negative electrode active material layer with alkali metal ions, thereby forming SEI at the negative electrode.

[0233] To maintain the decomposition reactivity of alkali metal compounds, it is preferable not to apply a cell voltage above the upper limit of the stable operating voltage during the initial charging process. This allows alkali metal ions generated by the decomposition reaction of alkali metal compounds to be replenished to the negative electrode during the capacity recovery process, resulting in a high capacity recovery effect. Applying a voltage above the upper limit of the stable operating voltage during the initial charging process will cause the decomposition reaction of alkali metal compounds to proceed, resulting in the disappearance of some or all of the alkali metal compounds, which may reduce or eliminate the capacity recovery effect during the capacity recovery process. However, there may be situations where the voltage is applied above the upper limit of the stable operating voltage during the initial charging process, as long as the capacity recovery effect is observed in the capacity recovery process of this disclosure. The temperature during the initial charging process is not particularly limited. Initial discharge may be performed after the initial charging process.

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

[0235] There are no particular restrictions on the aging method, but for example, a method of reacting the solvent in the electrolyte under high temperature conditions can be used.

[0236] (Aging of the second embodiment) In the first embodiment, it is preferable to perform aging on the battery before capacity recovery after the initial charge. In the aging process, the solvent in the electrolyte decomposes at the negative electrode, and an alkali metal ion-permeable solid polymer film is formed on the negative electrode surface. The aging method is not particularly limited, but for example, a method of reacting the solvent in the electrolyte under 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 above 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. If a voltage above the upper limit of the stable operating voltage is applied during the aging process, the decomposition reaction of the alkali metal compound will proceed, causing some or all of the alkali metal compound to disappear, which may reduce or eliminate the capacity recovery effect during the capacity recovery process. However, there may be situations in which a voltage above the upper limit of the stable operating voltage is applied during the aging process, as long as the capacity recovery effect is observed in the capacity recovery process of this disclosure. The temperature during the aging process is not particularly limited.

[0238] (Release gas) It is preferable to perform further degassing after aging to ensure that any remaining gas in the electrolyte, positive electrode, and negative electrode is completely removed. If gas remains in at least a portion of the electrolyte, positive electrode, and negative electrode, ion conduction will be inhibited, causing the resistance of the non-aqueous alkali metal type energy storage element obtained in the first embodiment to increase. Furthermore, it is possible to prevent the resistance of the battery before capacity recovery obtained in the second embodiment from increasing.

[0239] The method of degassing is not particularly limited, but for example, one method can be used in which the electrode stack is placed in a reduced pressure chamber with the outer casing open and the inside of the chamber is reduced in pressure using a vacuum pump. After degassing, the outer casing is sealed to create a non-aqueous alkali metal type energy storage element of the first embodiment, or a battery before capacity recovery of the second embodiment.

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

[0241] Non-aqueous alkali metal energy storage elements dope the negative electrode with alkali metal from alkali metal carbonate, which is the pre-doping source. This allows for more efficient utilization of the positive electrode active material, which conventionally could not function effectively due to the irreversible capacitance of the negative electrode. Specifically, the utilization rate of the positive electrode active material, as described later, 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 lower the cost of the battery. The lower limit of the utilization rate of the positive electrode active material is preferably 95% or more.

[0242] In addition, the pre-charge battery of the second 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 contain an alkali metal carbonate that did not decompose during pre-doping.

[0243] <Properties of the alkali metal storage element precursor> (Irreversible capacity ratio E1 / D1 and its calculation) For the alkali metal storage element precursor of the first embodiment, when the irreversible capacity per unit area of the positive electrode is D1 (mAh / cm 2 ), and the irreversible capacity per unit area of the negative electrode is E1 (mAh / cm 2 ), it is preferably 1.05 < E1 / D1. More preferably, 1.10 < E1 / D1. Thereby, high effects can be obtained from the viewpoints of reducing the positive electrode loss, maintaining the cycle capacity ratio, suppressing micro short-circuits after cycling, and the capacity density per unit volume. The irreversible capacity E1 (mAh / cm 2 ) per unit area of the negative electrode is obtained by the method described in (Negative electrode irreversible capacity ratio and calculation of negative electrode irreversible capacity G1). The irreversible capacity D1 (mAh / cm 2 ) per unit area of the positive electrode is obtained by the following method. The initial irreversible capacity (mAh / g) of the positive electrode active material, which is obtained by subtracting the initial discharge capacity density L2 (mAh / g) from the initial charge capacity density L1 (mAh / g) calculated by the method described in (Initial charge capacity density L1 and initial discharge capacity density L2 of the positive electrode active material), is multiplied by the basis weight (g / m 2 ) of the positive electrode active material and divided by 10000. E1 / D1 is calculated from these values.

[0244] (Capacity ratio (A1 + 0.3×B1) / C1 and its calculation) For the alkali metal storage element precursor of the first embodiment, the initial charge capacity per unit area of the positive electrode active material is A1 (Ah / cm 2 ), and the theoretical capacity per unit area of the alkali metal carbonate is B1 (Ah / cm 2), the initial charge capacity per unit area of ​​the negative electrode active material is C1 (Ah / cm²). 2 When this is the case, it is preferable that (A1 + 0.3 × B1) / C1 ≤ 0.98. More preferably, 0.85 ≤ (A1 + 0.3 × B1) / C1 ≤ 0.98. This results in high effectiveness in doping efficiency per unit volume, positive electrode utilization rate, resistance, reduction of high-temperature storage gas blister, reduction of positive electrode loss, cycle capacity maintenance rate, suppression of minor short circuits after cycling, and energy density per unit volume. Initial charge capacity per unit area of ​​positive electrode active material A1 (Ah / cm²) 2 The initial charge capacity density (mAh / g) of the positive electrode active material, obtained by the method described in (Initial charge capacity density L1, initial discharge capacity density L2 of the positive electrode active material), can be used to calculate the weight (g / m²) of the positive electrode active material. 2 It is obtained by multiplying by ) and then dividing by 10,000,000 and converting the units. Initial charge capacity C1 (Ah / cm²) per unit area of ​​negative electrode active material 2 The initial storage capacity H1 (mAh / cm³) of the alkali metal, as described in (Calculation of irreversible capacity ratio and irreversible capacity G1 of the negative electrode precursor), can be calculated using the following method. 2 The theoretical capacity per unit area of ​​alkali metal carbonate B1 (Ah / cm³) is calculated using the same method as above and obtained by converting the units. 2 The theoretical capacity (mAh / g) of alkali metal carbonates can be calculated using the following method. Calculate the theoretical capacity (mAh / g) of alkali metal carbonates assuming the oxidative decomposition reaction of alkali metal carbonates 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. Add the weight (g / m²) of the alkali metal carbonate to this. 2 By multiplying by ) and then dividing by 10,000,000, and converting the units, the theoretical capacity per unit area of ​​alkali metal carbonate B1 (Ah / cm³) can be obtained. 2 ) can be calculated. From these values, calculate (A1 + 0.3 × B1) / C1.

[0245] <Characteristics of Alkali Metal Energy Storage Elements> (Ratio of excess capacity of positive electrode to irreversible capacity of negative electrode F1 / G1) The alkali metal energy storage element of the first embodiment has a excess capacity per unit area of ​​the positive electrode F1 (mAh / cm²). 2)、When the irreversible capacity per unit area of the negative electrode is G1 (mAh / cm 2 ), it is preferable that 0.01 < F1 / G1 < 0.9. Thereby, effects such as a reduction effect of the positive electrode loss reduction amount, an improvement effect of the cycle capacity retention rate, a short-circuit suppression effect after the cycle test, and an improvement effect of the capacity density per unit volume can be obtained. The upper limit value is more preferably 0.8, and even more preferably 0.6. It can be adjusted by E1 / D1 of the precursor, (A1 + 0.3×B1) / C1, the amount of alkali metal carbonate, the voltage at the time of pre-doping, etc.

[0246] (Excess capacity F1 of the positive electrode) The excess capacity per unit area of the positive electrode is F1 (mAh / cm 2 ) and is measured by the following method. The completed alkali metal storage element is placed in a thermostatic bath set at 25°C, and constant current discharge is performed at a current value of 0.1C until the lower limit of the stable operating voltage is reached, and then constant voltage discharge with the lower limit of the stable operating voltage applied is performed for 30 minutes. Thereafter, the storage element is disassembled in an argon box, the positive electrode is taken out, and in the case of a double-sided positive electrode, one-sided active material layer is peeled off using a spatula or the like to make a single-sided positive electrode, and then it is recombined into a positive electrode half-cell using a glass filter for the alkali metal counter electrode, alkali metal reference electrode, and separator. Based on the capacity of the positive electrode half-cell, when discharging at a current value of 0.1C to the lower limit potential of the stable operating potential of the positive electrode active material, the discharge capacity (mAh) is measured and divided by the coated area (cm 2 ) of the single-sided positive electrode to obtain the excess capacity F1 (mAh / cm 2 ) of the positive electrode. Note that for the lower limit of the stable operating voltage and the lower limit of the stable operating potential, the specific values corresponding to the active material described in (the stable operating potential of the positive electrode and the stable operating voltage of the battery corresponding to the positive electrode active material) can be used.

[0247] (Irreversible capacity G1 of the negative electrode) The irreversible capacity G1 of the negative electrode is measured by the method described in (negative electrode irreversible capacity rate and calculation of negative electrode irreversible capacity G1).

[0248] <Characteristic Evaluation of Non-Aqueous Alkali Metal Storage Element of the First Embodiment> The characteristics evaluation of a non-aqueous alkali metal energy storage element in the first embodiment of this disclosure is shown below. However, since the operating voltage changes depending on the combination of positive electrode active material and negative electrode active material, the set value for charge and discharge voltage needs to be changed depending on the non-aqueous alkali metal energy storage element. The charge and discharge voltages for the characteristics evaluation exemplified below are not particularly limited to those shown.

[0249] (Discharge capacity Q, full cell capacity density P per unit mass of positive electrode active material) full ) In this specification, the capacity Q(Ah) is a value obtained by the following method. LiCoO2, LiMn 0.6 Fe 0.4 PO4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiLiLi 0.8 Co 0.15 Al 0.05 When using O2 or LiMn2O4 as the positive electrode active material, a non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, for example, 4.2V. This is followed by constant voltage charging at 4.2V for 30 minutes. After that, the capacitance when a constant current discharge is performed with a current of 0.1C until it reaches the lower limit of the stable operating voltage, i.e., 3.0V, is defined as Q (Ah). Dividing Q by the mass of the positive electrode active material gives the full cell capacity density P per unit mass of positive electrode active material. full (mAh / g) can be obtained.

[0250] When using LiFePO4 as the positive electrode active material, a non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, for example, 3.6V. This is followed by constant voltage charging at 3.6V for 30 minutes. After that, the capacitance when a constant current discharge is performed with a current of 0.1C down to the lower limit of the stable operating voltage, i.e., 2.4V, is defined as Q(Ah).

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

[0252] NaFe 1 / 3 Ni 1 / 3 Mn 1 / 3 When using O2 as the positive electrode active material, a non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, i.e., 3.9V. This is followed by constant voltage charging at 3.9V for 30 minutes. After that, the capacitance when a constant current discharge is performed with a current of 0.1C until it reaches the lower limit of the stable operating voltage, i.e., 1.9V, is defined as Q (Ah). Dividing Q by the mass of the positive electrode active material gives the full cell capacity density P per unit mass of positive electrode active material. full (mAh / g) can be obtained.

[0253] (Effective utilization rate of positive electrode active material) The aforementioned "full cell discharge capacity density P per unit mass of positive electrode active material" full The effective utilization rate of the positive electrode active material can be determined by dividing the "(mAh / g)" by the "initial discharge capacity density L2 per unit mass of positive electrode active material". Pre-doping with alkali metal carbonates can compensate for the alkali metal lost due to the irreversible capacity of the negative electrode, thereby increasing the effective utilization rate of the positive electrode active material. The effective utilization rate of the positive electrode active material in non-aqueous alkali metal energy storage elements is preferably 85% to 99.5%. 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 suppressed, thus reducing the amount of positive electrode active material used, which is preferable from the viewpoint of manufacturing costs. An effective utilization rate of 93% or more is more preferable, and 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 obtained. The effective utilization rate a (%) of the positive electrode active material of the alkali metal energy storage element of the first embodiment is calculated. Another alkali metal energy storage element, with the same basis weight of positive electrode active material and negative electrode active material as the alkali metal energy storage element of the first embodiment, and without carbonate, is initially charged at the upper limit voltage of the "stable operating voltage" corresponding to the positive electrode active material, as described in (Stable operating potential of the positive electrode and stable operating voltage of the battery according to the positive electrode active material), to fabricate an alkali metal energy storage element, and the effective utilization rate b (%) of its positive electrode active material is measured. The reduction amount X (%) of positive electrode active material loss is calculated as X = ab. A reduction amount of positive electrode active material loss of 2% or more is preferable because it reduces the loss of the high-cost positive electrode active material in alkali metal energy storage elements. A reduction amount of positive electrode active material loss of 12% or more is more preferable, and 18% or more is particularly preferable.

[0255] (capacity density) In the first embodiment, the capacity density is measured by the following method: First, the discharge capacity is (discharge capacity Q, full cell capacity density P per unit mass of positive electrode active material) full The volume is then measured using the method described above. The volume is then obtained using the following method: LiCoO2, LiMn 0.6 Fe 0.4 PO4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiLiLi 0.8 Co 0.15 Al 0.05When using O2 or LiMn2O4 as the positive electrode active material, the completed non-aqueous alkali metal energy storage elements 1 and 2 are charged with a constant current of 0.1C in a constant temperature bath set to 25°C until the upper limit of the stable operating voltage, for example, 4.2V, is reached, followed by constant voltage charging at 4.2V for 30 minutes. After that, the energy storage elements are disassembled in an argon box and the electrode assembly is removed. When using LiFePO4 as the positive electrode active material, the non-aqueous alkali metal energy storage elements are charged with a constant current of 0.1C in a constant temperature bath set to 25°C until the upper limit of the stable operating voltage, for example, 3.6V, is reached, followed by constant voltage charging at 3.6V for 30 minutes. After that, the energy storage elements are disassembled in an argon box and the electrode assembly is removed. If the electrode assembly is a laminate, the volume of the electrode assembly is obtained by multiplying the area S, which is based on the coated portion of the positive electrode, by the measured thickness of the laminate. If the electrode assembly is a cylindrical winding, the volume of the electrode assembly is obtained by multiplying the area of ​​the circle obtained from the measured radius of the cylinder by the cylindrical height based on the coated portion of the positive electrode. If the electrode assembly is a flat winding, the volume of the electrode assembly is obtained by calculating the cross-sectional area from the measured length and width of the flat winding and the radius of the semicircular portion, and multiplying this by the measured thickness of the flat winding. The volumetric capacity density (mAh / cc) is obtained by dividing the discharge capacity by the volume of the electrode assembly.

[0256] (Percentage improvement in capacity density) The capacity density a (mAh / cc) of the alkali metal energy storage element of the first embodiment is calculated. Another alkali metal energy storage element, with the same basis weight of positive electrode active material and negative electrode active material as the alkali metal energy storage element of the first embodiment, and without carbonate, is initially charged at the upper limit voltage of the "stable operating voltage" corresponding to the positive electrode active material, as described in (Stable operating potential of the positive electrode according to the positive electrode active material and stable operating voltage of the battery according to the positive electrode active material), to fabricate an alkali metal energy storage element, and its capacity density b (mAh / cc) is measured. The capacity density improvement rate X (%) is calculated as X = (ab) / b × 100. A capacity density improvement rate of 1% or more is preferable because it improves the capacity density of the alkali metal energy storage element. A rate of improvement of 4% or more is more preferable, and a rate of improvement of 7% or more is particularly preferable.

[0257] (DC resistance R) In this specification, the discharge resistance R (Ω) is calculated from the voltage drop 10 seconds after discharge from the upper limit of the stable operating voltage of the battery, depending on the positive electrode active material. That is, it is the value obtained by the following method: LiCoO2, LiMn 0.6 Fe 0.4 PO4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiLiLi 0.8 Co 0.15 Al 0.05 When using O2 or LiMn2O4 as the positive electrode active material, the non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until the stable operating voltage upper limit, for example, 4.2V, is reached, followed by constant voltage charging at 4.2V for 30 minutes. After that, a current of 1C is applied. 1C (A) Voltage V after 10 seconds when constant current discharge is performed 10秒 Measure (V). Calculate the resistance R(Ω) using the following formula. R=(4.2―V 10秒 )÷I 1C

[0258] When using LiFePO4 as the positive electrode active material, the non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until the stable operating voltage upper limit, for example, 3.6V, is reached, followed by constant voltage charging at 3.6V for 30 minutes. After that, a current of 1C is applied. 1C (A) Voltage V after 10 seconds when constant current discharge is performed 10秒 Measure (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 / 3When using O2 as the positive electrode active material, the non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, i.e., 3.9V. Then, constant voltage charging is performed for 30 minutes with a constant voltage of 3.9V applied. After that, the current value 1C is applied. 1C (A) Voltage V after 10 seconds when constant current discharge is performed 10秒 Measure (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 embodiment, a discharge resistance R of 2.5 mΩ or less is preferable because it provides low resistance and enables high rate characteristics. A discharge resistance R of 2.0 mΩ or less is more preferable, and a discharge resistance of 1.5 mΩ or less is particularly preferable.

[0261] (Negative electrode doping amount, volume difference, pre-doped volume efficiency) <When the positive electrode active material layer contains alkali metal carbonates> In this specification, the pre-doped volume efficiency when the positive electrode active material layer contains an alkali metal carbonate is obtained by the following method.

[0262] A positive electrode precursor 1 containing an active material, and optionally containing conductive material carbon black SuperC65 and a binder, but not containing alkali metal carbonates. 炭酸Liなし To create a cathode precursor 2 containing an active material, and optionally containing a conductive material, a binder, and an alkali metal carbonate. 炭酸Liあり To prepare the positive electrode precursor 1 炭酸Liなし and positive electrode precursor 2 炭酸Liあり The slurry composition and basis weight are adjusted so that the basis weight of the active material, conductive material, and binder are equivalent. Furthermore, the positive electrode precursor 1 炭酸Liなし Thickness t1 (μm), positive electrode precursor 2 炭酸Liあり Measure the thickness t2 (μm). Positive electrode precursor 1 炭酸Liなし and positive electrode precursor 2 炭酸Liあり Area S(cm²) 2Using this, non-aqueous alkali metal energy storage element precursors 1 and 2 are fabricated by combining them with a common negative electrode and separator for positive electrode precursor 1 and positive electrode precursor 2. The volume difference V (cc / cell) of the non-aqueous alkali metal energy storage element precursor due to the introduction of alkali metal carbonate is calculated using the following formula. V = (t² - t¹) × S ÷ 10000

[0263] Cathode precursor 1 炭酸Liなし Non-aqueous alkali metal energy storage element precursor and positive electrode precursor 2 using 炭酸Liあり By performing initial charging under the same conditions on non-aqueous alkali metal energy storage element precursors using the above method, non-aqueous alkali metal energy storage elements 1 (without alkali metal carbonate) and 2 (with alkali metal carbonate) are fabricated, respectively. As a result, pre-doping with alkali metal carbonate is performed on energy storage element 2.

[0264] LiCoO2, LiMn 0.6 Fe 0.4 PO4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiLiLi 0.8 Co 0.15 Al 0.05 When using O2 or LiMn2O4 as the positive electrode active material, the completed non-aqueous alkali metal energy storage elements 1 and 2 are charged with a constant current of 0.1C in a constant temperature bath set to 25°C until the stable operating voltage upper limit, for example, 4.2V, is reached, followed by constant voltage charging at 4.2V for 30 minutes. After that, the energy storage elements are disassembled in an argon box, the negative electrode is removed, and it is reassembled into a negative electrode half-cell using lithium as the counter electrode and a glass filter as the separator. Using the capacity of the negative electrode half-cell as a reference, lithium is desorbed from the negative electrode by constant current charging at a current of 0.1C down to 2.5V, and the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 4.2V are measured.

[0265] When using LiFePO4 as the positive electrode active material, a non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, for example, 3.6V. Subsequently, a constant voltage charge of 3.6V is applied for 30 minutes. After that, the energy storage element is disassembled in an argon box, the negative electrode is removed, and it is reassembled into a negative electrode half-cell using lithium as the counter electrode and a glass filter as the separator. Using the capacity of the negative electrode half-cell as a reference, lithium is desorbed from the negative electrode by constant current charging at a current of 0.1C down to 2.5V, and the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 3.6V are measured. The pre-doping volumetric efficiency E (mAh / cc) can be calculated using the following formula. E = (Q2 - Q1) ÷ V In other words, it is an index obtained by dividing the amount that alkali metal carbonate decomposed and doped into the negative electrode by the volume increased by mixing alkali metal carbonate for pre-doping. A higher value indicates that the trade-off for volume increase was suppressed and pre-doping was performed efficiently. A pre-doping volume efficiency of 400 mAh / cc or higher is preferable because it suppresses the trade-off for volume increase and allows for efficient pre-doping in alkali metal energy storage elements. A pre-doping volume efficiency of 600 mAh / cc or higher is more preferable, and 700 mAh / cc or higher is particularly preferable.

[0266] NaFe 1 / 3 Ni 1 / 3 Mn 1 / 3 When using O2 as the positive electrode active material, a non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, i.e., 3.9V. This is followed by constant voltage charging at 3.9V for 30 minutes. After that, the energy storage element is disassembled in an argon box, the negative electrode is removed, and it is reassembled into a negative electrode half-cell using sodium as the counter electrode and a glass filter as the separator. Using the capacity of the negative electrode half-cell as a reference, the sodium is removed from the negative electrode by constant current charging at a current of 0.1C down to 2.5V, and the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 3.9V are measured.

[0267] <When alkali metal carbonate is included in the intermediate layer between the positive electrode active material layer and the separator> In this specification, the pre-doped 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 cathode precursor containing an active material, and optionally containing conductive carbon black SuperC65 and a binder, but free of alkali metal carbonates. 炭酸Liなし This creates a positive electrode precursor with an area S(cm²) of the separator and negative electrode. 2 A non-aqueous alkali metal energy storage element precursor 1 is formed using only ). Separator surface or positive electrode precursor 炭酸Liなし A positive electrode precursor is formed on the surface of the active material layer by the method described in the section on the method of forming the intermediate layer, which contains an alkali metal carbonate and optionally includes a conductive material and a binder. 炭酸Liなし Combine the separator and negative electrode, and the positive electrode precursor is formed over an area S (cm²). 2 A non-aqueous alkali metal energy storage element precursor 2 is formed using only ). The thickness of the intermediate layer at this time is denoted as t2 (μm).

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

[0270] Non-aqueous alkali metal energy storage element precursor 1, which does not contain alkali metal carbonate, is subjected to initial charging, while non-aqueous alkali metal energy storage element precursor 2, which contains alkali metal carbonate, is subjected to pre-doping during the initial charging process. This process is used to fabricate non-aqueous alkali metal energy storage elements 1 (without alkali metal carbonate) and 2 (with alkali metal carbonate), respectively.

[0271] LiCoO2, LiMn 0.6 Fe 0.4 PO4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2, LiLiLi 0.8 Co 0.15 Al 0.05 When using O2 or LiMn2O4 as the positive electrode active material, the completed non-aqueous alkali metal energy storage elements 1 and 2 are charged with a constant current of 0.1C in a constant temperature bath set to 25°C until the stable operating voltage upper limit, for example, 4.2V, is reached, followed by constant voltage charging at 4.2V for 30 minutes. After that, the energy storage elements are disassembled in an argon box, the negative electrode is removed, and it is reassembled into a negative electrode half-cell using lithium as the counter electrode and a glass filter as the separator. Using the capacity of the negative electrode half-cell as a reference, lithium is desorbed from the negative electrode by constant current charging at a current of 0.1C down to 2.5V, and the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 4.2V are measured.

[0272] When using LiFePO4 as the positive electrode active material, a non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, for example, 3.6V. This is followed by constant voltage charging at 3.6V for 30 minutes. After that, the energy storage element is disassembled in an argon box, the negative electrode is removed, and it is reassembled into a negative electrode half-cell using lithium as the counter electrode and a glass filter as the separator. Using the capacity of the negative electrode half-cell as a reference, lithium is desorbed from the negative electrode by constant current charging at a current of 0.1C down to 2.5V, and the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 3.6V are measured.

[0273] NaFe 1 / 3 Ni 1 / 3 Mn 1 / 3When using O2 as the positive electrode active material, a non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, i.e., 3.9V. This is followed by constant voltage charging at 3.9V for 30 minutes. After that, the energy storage element is disassembled in an argon box, the negative electrode is removed, and it is reassembled into a negative electrode half-cell using sodium as the counter electrode and a glass filter as the separator. Using the capacity of the negative electrode half-cell as a reference, the sodium is removed from the negative electrode by constant current charging at a current of 0.1C down to 2.5V, and the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 3.9V are measured.

[0274] The pre-doped volumetric efficiency E (mAh / cc) can be calculated using the following formula. E = (Q2 - Q1) ÷ V In other words, it is an index obtained by dividing the amount of alkali metal carbonate that decomposed and doped the negative electrode by the volume increase caused by providing an intermediate layer for pre-doping. A higher value indicates that the trade-off with volume increase was suppressed and pre-doping was performed efficiently.

[0275] (Gas measurement when stored at 40°C) In this specification, the amount of gas generated during the 40°C storage test is measured by the following method. LiCoO2, LiMn 0.6 Fe 0.4 PO4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiLiLi 0.8 Co 0.15 Al 0.05When using O2 or LiMn2O4 as the positive electrode active material, the non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 40°C until it reaches the upper limit of the stable operating voltage, e.g., 4.2V, followed by constant voltage charging at 4.2V for 30 minutes. After that, the cell is stored in a 40°C environment, and every week in a 40°C environment, the cell voltage is recharged to the upper limit of the stable operating voltage, e.g., 4.2V, using the aforementioned charging procedure. The cell volume Va (cc) before storage and the cell volume Vb (cc) after 6 weeks of storage are measured by the Archimedes method. Vb - Va is taken as the amount of gas generated (cc).

[0276] When using LiFePO4 as the positive electrode active material, a non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 40°C until it reaches a stable operating voltage of 3.6V, and then a constant voltage of 3.6V is applied for 30 minutes. After that, the cell is stored in a 40°C environment, and every week in a 40°C environment, the cell voltage is recharged to the upper limit of the stable operating voltage, i.e., 3.6V, using the aforementioned charging procedure. The cell volume Va (cc) before storage and the cell volume Vb (cc) after 6 weeks of storage are measured by the Archimedes method. Vb - Va is taken as the amount of gas generated (cc).

[0277] NaFe 1 / 3 Ni 1 / 3 Mn 1 / 3 When using O2 as the positive electrode active material, a non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 40°C until it reaches a stable operating voltage of 3.9V, and then a constant voltage charge of 3.9V is applied for 30 minutes. After that, the cell is stored in a 40°C environment, and every week in a 40°C environment, the cell voltage is recharged to the upper limit of the stable operating voltage, i.e., 3.9V, using the aforementioned charging procedure. The cell volume Va (cc) before storage and the cell volume Vb (cc) after 6 weeks of storage are measured by the Archimedes method. Vb - Va is taken as the amount of gas generated (cc).

[0278] In the battery configuration of the example, a storage gas volume of 1.0 cc or less at 40°C is preferable because it can suppress swelling of the battery when the alkali metal energy storage element is stored in a high-temperature environment. A storage gas volume of 0.6 cc or less at 40°C is more preferable, and 0.2 cc or less is particularly preferable. (Cycle testing) For the non-aqueous alkali metal energy storage element of the first embodiment, the cycle test is performed by the following method: LiCoO2, LiMn 0.6 Fe 0.4 PO4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiLiLi 0.8 Co 0.15 Al 0.05 When using O2 or LiMn2O4 as the positive electrode active material, a non-aqueous alkali metal energy storage element was subjected to constant current charging at a current value of 0.5C in a constant temperature bath set to 25°C until it reached the upper limit of the stable operating voltage of the battery corresponding to the positive electrode active material, i.e., 4.2V. Subsequently, constant voltage charging was performed by applying a constant voltage of the same voltage until the current value reached 0.03C. After a 10-minute pause, constant current discharge was performed at a current value of 0.5C until it reached the lower limit of the stable operating voltage, i.e., 3.0V, followed by a 10-minute pause. This constituted one cycle, and 500 charge-discharge cycles were performed. When LiFePO4 was used as the positive electrode active material, a non-aqueous alkali metal energy storage element was charged with a constant current of 0.5C in a constant temperature bath set to 25°C until it reached the upper limit of the stable operating voltage of the battery corresponding to the positive electrode active material, i.e., 3.6V. Subsequently, constant voltage charging was performed by applying a constant voltage of the same voltage until the current value reached 0.03C. After a 10-minute pause, constant current discharge was performed with a current value of 0.5C until it reached the lower limit of the stable operating voltage, i.e., 2.4V, followed by a 10-minute pause. This constituted one cycle, and 500 charge-discharge cycles were performed. 1 / 3 Ni 1 / 3 Mn 1 / 3When using O2 as the positive electrode active material, a non-aqueous alkali metal energy storage element was charged with a constant current of 0.5C in a constant temperature bath set to 25°C until it reached the upper limit of the stable operating voltage of the battery corresponding to the positive electrode active material, i.e., 3.9V. Subsequently, constant voltage charging was performed by applying a constant voltage of the same voltage until the current value reached 0.03C. After a 10-minute pause, constant current discharge was performed with a current value of 0.5C until it reached the lower limit of the stable operating voltage, i.e., 1.9V, followed by a 10-minute pause. This constituted one cycle, and 500 charge-discharge cycles were performed.

[0279] (Capacity retention rate after cycle testing) Capacity measurements were performed before and after the cycle test described above using the method described in the section on (discharge capacity Q, full cell capacity density Pfull per unit mass of positive electrode active material). 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 of 80% or more after the cycle test is preferable because it minimizes capacity degradation even with repeated charging and discharging of the alkali metal energy storage element. A capacity retention rate of 85% or more after the cycle test is more preferable, and 90% or more is particularly preferable.

[0280] (Self-discharge failure rate after cycle testing) For the non-aqueous alkali metal energy storage element of the first embodiment, the self-discharge failure rate after cycle testing is calculated by the following method. Prepare 20 cells of the non-aqueous alkali metal energy storage element after cycle testing. LiCoO2, LiMn 0.6 Fe 0.4 PO4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiLiLi 0.8 Co 0.15 Al 0.05When using O2 or LiMn2O4 as the positive electrode active material, a non-aqueous alkali metal energy storage element is discharged at a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the lower limit of the stable operating voltage, i.e., 3.0V, followed by a constant voltage discharge of 3.0V for 30 minutes. After that, the cells are stored in a 25°C environment, and the cell voltage is measured after one week. The number of cells whose voltage falls below 3.0V is considered the number of self-discharge failure cells, and the self-discharge failure rate is calculated by dividing this by 20. When using LiFePO4 as the positive electrode active material, a non-aqueous alkali metal energy storage element is discharged at a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the lower limit of the stable operating voltage, i.e., 2.4V, followed by a constant voltage discharge of 2.4V for 30 minutes. Subsequently, the cells were stored in a 25°C environment, and after one week, the cell voltage was measured. The number of cells with a voltage below 2.4V was defined as the number of self-discharge-defective cells, and this was divided by 20 to determine the self-discharge-defect rate. 1 / 3 Ni 1 / 3 Mn 1 / 3 When using O2 as the positive electrode active material, a non-aqueous alkali metal energy storage element is discharged at a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the lower limit of the stable operating voltage, i.e., 1.9V. This is followed by a constant voltage discharge of 1.9V for 30 minutes. After that, the cells are stored in a 25°C environment, and the cell voltage is measured after one week. The number of cells whose voltage falls below 2.4V is considered the number of self-discharge failure cells, and this is divided by 20 to obtain the self-discharge failure rate. A self-discharge failure rate of 30% or less after the cycle test is preferable because it increases the likelihood that the alkali metal energy storage element can be used without problems for a long period of time. A rate of 15% or less is more preferable, and a rate of 5% or less is particularly preferable.

[0281] <Evaluation of the characteristics of the alkali metal energy storage element in the second embodiment> The second embodiment will be described below.

[0282] (capacity, capacity density) The upper and lower limits of the stable operating voltage of the battery, corresponding to the positive electrode active material of the non-aqueous alkali metal energy storage element in the second embodiment, are determined by the following method: The non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set at 25°C until the upper limit of the stable operating voltage of the battery corresponding to the positive electrode active material is reached. Subsequently, constant voltage charging is performed by applying 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 reaches 0.03C. After that, the capacity when constant current discharge is performed with a current of 0.1C until the lower limit of the stable operating voltage is reached is defined as Q(mAh).

[0283] Initial capacitance density Q of the non-aqueous alkali metal energy storage element of the second embodiment v (mAh / cc) is calculated when V1 (cc) is the total volume of the positive electrode coating (foil + positive electrode active material layer) contained in a non-aqueous alkali metal energy storage element, V2 (cc) is the total volume of the negative electrode coating (foil + negative electrode active material layer), V3 (cc) is the total volume of the separator, V4 (cc) is the total volume of the intermediate layer (if present), and Q (mAh) is the initial capacity obtained by capacity measurement. v The answer can be calculated as =Q÷(V1+V2+V3+V4)÷10000). Here, the uncoated parts of the positive and negative electrodes are not included in the volume calculation.

[0284] (Constant current cycle) For the non-aqueous alkali metal energy storage element of the second embodiment, a constant current cycle was performed in a constant temperature bath set to 25°C using the following method: Constant current charging was performed at a current value of 1C until the upper limit of the stable operating voltage of the battery corresponding to the positive electrode active material was reached, followed by constant voltage charging by applying a constant voltage of that voltage until the current value reached 0.03C, a 10-minute pause was followed by constant current discharge at a current value of 1C until the lower limit of the stable operating voltage was reached, and a 10-minute pause was repeated. This constituted one cycle, and 300 cycles were performed.

[0285] (Capacity retention rate after constant current cycle) After the constant current cycle test in the second embodiment, capacity measurements were performed using the method described in the section on <Capacity, Capacity Density> above. The capacity retention rate after the constant current cycle was calculated by dividing the capacity after the cycle test by the capacity before the cycle test.

[0286] <Use of non-aqueous alkali metal energy storage elements before capacity recovery> A second embodiment of this disclosure provides the use of a non-aqueous alkali metal energy storage element (pre-capacity recovery battery) before capacity recovery. The pre-capacity recovery battery can be used by charging and discharging it in the same way as a normal alkali metal ion battery. For example, it can be used in common methods such as cycling and float charging.

[0287] The battery before capacity recovery of the second embodiment is preferably used as a battery pack. The battery before capacity recovery can be used in an energy storage system, which is at least one selected from the group consisting of, for example, a power regeneration assist system in a hybrid drive system of an automobile, a power load leveling system in a microgrid or natural power generation system such as solar power generation or wind power generation, an uninterruptible power supply system in a factory production facility, a contactless power supply system for the purpose of leveling voltage fluctuations and storing energy such as microwave power transmission or electrolytic resonance, an energy harvesting system for the purpose of utilizing electricity generated by vibration power generation, a solar power 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 fast charging system, and a smart grid system.

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

[0289] To maintain the decomposition reactivity of alkali metal compounds, it is preferable not to apply a cell voltage above the upper limit of the stable operating voltage when using a battery before capacity recovery. This allows alkali metal ions generated by the decomposition reaction of alkali metal compounds to be replenished to the negative electrode during the capacity recovery process, resulting in a high capacity recovery effect. If a voltage above the upper limit of the stable operating voltage is applied when using a battery before capacity recovery, the decomposition reaction of alkali metal compounds will proceed, causing some or all of the alkali metal compounds to disappear, which may reduce or eliminate the capacity recovery effect during the capacity recovery process. However, as long as the capacity recovery effect is demonstrated in the capacity recovery process of this disclosure, there may be situations where a voltage above the upper limit of the stable operating voltage is applied when using a battery before capacity recovery.

[0290] <Method for recovering capacity and method for manufacturing a non-aqueous alkali metal energy storage element with recovered capacity> (Capacity recovery process) A second embodiment of this disclosure provides a method for restoring the capacity of a non-aqueous alkali metal energy storage element, that is, a method for manufacturing a non-aqueous alkali metal energy storage element with restored capacity (hereinafter also referred to as a "restored battery"). The battery before capacity restoration used in the method for manufacturing the restored battery 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 containing alkali metal ions. 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, or in any intermediate layer between the positive electrode active material layer and the separator, or in both. The non-aqueous electrolyte contains an accelerator. The method for manufacturing the restored battery includes restoring the capacity by raising the potential of the positive electrode of the non-aqueous alkali metal energy storage element before capacity restoration to above the stable operating potential of the positive electrode active material (capacity restoration step). For details on the configuration of the non-aqueous alkali metal energy storage element before capacity recovery, please refer to the section above titled "Non-aqueous alkali metal energy storage element before capacity recovery."

[0291] Furthermore, as a modification of the method for manufacturing a battery after capacity recovery according to the second embodiment of this disclosure, the alkali metal compound may be contained in other components of the non-aqueous alkali metal energy storage element, provided that the alkali metal compound can be oxidized and 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 separator surface in contact with the positive electrode active material layer, in the electrolyte, in the negative electrode, on the inner surface of the outer casing, and in the terminals of the positive and negative electrodes. It may be included in advance during the manufacturing of the non-aqueous alkali metal energy storage element before capacity recovery, or it may be mixed with the electrolyte or the like into the non-aqueous alkali metal energy storage element and introduced into the battery after battery degradation and before the capacity recovery process.

[0292] In the capacity recovery step of the second embodiment, it is preferable to recover the capacity of the non-aqueous alkali metal energy storage element by raising the voltage of the non-aqueous alkali metal energy storage element to an 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 in which the positive electrode active material can be used stably is as described above.

[0293] More specifically in the second embodiment, in an LFP where the upper limit of the stable operating voltage is approximately 3.6V, it is preferable to restore the capacity of the non-aqueous alkali metal energy storage element by raising the voltage, preferably to 4.0V or higher, more preferably to 4.1V or higher, even more preferably to 4.2V or higher, even more preferably to 4.3V or higher, and particularly preferably to 4.4V or higher. The upper limit of the voltage is not particularly limited, but from the viewpoint of suppressing the formation of excessive SEI film, it is preferably 4.6V or lower.

[0294] In the second embodiment, for LCO, LMFP, NCM111, NCM811, NCA, and LMO, where the upper limit of the stable operating voltage is approximately 4.2V, it is preferable to restore the capacity of the non-aqueous alkali metal energy storage element by raising the voltage to preferably 4.3V or higher, and particularly preferably 4.4V or higher. The upper limit of the voltage is not particularly limited, but from the viewpoint of suppressing the formation of excessive SEI film and avoiding damage to the positive electrode active material structure while obtaining the capacity recovery effect, it is preferably 4.6V or lower.

[0295] The specific charge and discharge operations in the capacity recovery process of the second embodiment are not particularly limited as long as the voltage of the non-aqueous alkali metal energy storage element can be raised to a voltage above the oxidative decomposition potential of the alkali metal compound. For example, constant current charging may be performed at a constant current value until an arbitrary voltage above the oxidative decomposition potential of the alkali metal compound is reached, and then constant voltage charging may be performed for a while while maintaining that voltage. More specifically, it is preferable to perform constant current charging until the voltage reaches an arbitrary voltage between the upper limit of the stable operating voltage corresponding to the positive electrode active material and 4.6V or less, and then constant voltage charging may be performed 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 an arbitrary voltage suitable for use of the non-aqueous alkali metal energy storage element is reached. The capacity recovery process may consist of multiple cycles, with one charge-discharge cycle being one cycle. For example, the capacity recovery process may consist of 2 to 10 cycles, more preferably 3 to 9 cycles, and even more preferably 4 to 8 cycles. Furthermore, the capacity recovery process is not limited to a single step; it may be performed multiple times, such as by performing the capacity recovery process, then using a non-aqueous alkali metal energy storage element to allow for further degradation, and then performing the capacity recovery process again.

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

[0297] In the capacity recovery process of the second embodiment, the temperature of the non-aqueous alkali metal energy storage element can be at room temperature, but it is preferably maintained at 35°C or higher, more preferably at 45°C or higher. This promotes the decomposition reaction of the alkali metal compound and effectively replenishes the alkali metal to the negative electrode, thereby achieving a high capacity recovery effect. On the other hand, the temperature of the non-aqueous alkali metal energy storage element in the capacity recovery process is preferably 70°C or lower in order to suppress the formation of resistive components such as coatings due to side reactions.

[0298] The degree of capacity degradation and recovery of the battery before capacity recovery in the second embodiment is not particularly limited. For example, by performing the capacity recovery process on a battery before capacity recovery that has a capacity of 95% or less based on the initial capacity P1 (mAh) of the battery before capacity recovery, the capacity can be recovered by 2% or more. Preferably, the capacity of a battery before capacity recovery with a capacity of 95% or less can be recovered by 3% or more, more preferably by 5% or more, even more preferably by 10% or more, the capacity of a battery before capacity recovery with a capacity of 90% or less can be recovered by 20% or more, and particularly preferably by 30% or more, the capacity of a battery before capacity recovery with a capacity of 70% or less can be recovered.

[0299] (Capacity recovery in battery packs) In the second embodiment, the non-aqueous alkali metal energy storage element whose capacity is to be restored may be in the form of a single cell or in the form of a battery pack made up of multiple single cells. When the non-aqueous alkali metal energy storage element is in the form of a battery pack, it is preferable to restore the capacity of the battery pack as a whole without disassembling it into single cells. Alternatively, when the battery pack is composed of multiple modules (which are also "battery packs") made up of multiple single cells, it is preferable to disassemble it down to the module unit and perform capacity restoration on a module-by-module basis without disassembling it down to the single cells. Furthermore, even with capacity restoration in a battery pack, the capacity restoration process is not limited to just one step; it may be performed multiple times, such as performing the capacity restoration process, then degrading it again using a non-aqueous alkali metal energy storage element, and then performing the capacity restoration process again.

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

[0301] In the second embodiment, it is preferable that some or all of the individual cells be equipped with a gas permeation mechanism in order to perform capacity recovery while the battery pack remains intact. When a gas venting mechanism is provided, gas generated during the capacity recovery process can be vented, and the effectiveness of capacity recovery is enhanced. Furthermore, by providing a gas venting mechanism to the individual cells, the capacity recovery process can be performed at a location close to the end-use location, such as the place where the non-aqueous alkali metal energy storage element is used or a primary collection location, without disassembling the individual cells. This is preferable because it reduces the costs of collection and transportation, as well as the carbon dioxide emissions associated with them. The place where the non-aqueous alkali metal energy storage element is used refers to, for example, the place where the ESS is installed in the case of an ESS, or a parking lot in the case of an electric vehicle, or any other place where the end user of the battery uses the battery. The primary collection location refers to, for example, a place where products are collected from the end user of the battery, such as a dealership in the case of an electric vehicle.

[0302] (Deterioration confirmation process) In the second embodiment, before performing the capacity recovery process, the degree of capacity degradation of the battery before capacity recovery may be optionally determined, and the capacity recovery process may be performed according to the degree of degradation. For example, the capacity of the degraded battery before capacity recovery (degraded capacity) P2 (mAh) may be measured and compared with the capacity of the undegraded battery before capacity recovery (initial capacity) P1 (mAh) to confirm the degree of capacity degradation. By confirming the degree of capacity degradation, the specific conditions for the charge and discharge operation in the capacity recovery process may be determined. Examples of charge and discharge operation conditions include charge capacity, cell temperature, C rate, voltage, duration, and number of cycles.

[0303] (J1 / J2) In the second embodiment, the non-aqueous alkali metal energy storage element performing the capacity recovery process has a remaining capacity per unit area of ​​the negative electrode active material J1 (Ah / cm²).2 ), the total volume per unit area of ​​the negative electrode active material is J2 (Ah / cm²). 2 When J1 / J2 is set to 0.1 ≤ J1 / J2 ≤ 0.5, it is preferable that J1 / J2 ≤ 0.5. Within this range, alkali metal can be supplied from alkali metal carbonate to the negative electrode during the capacity recovery process, and a high capacity recovery effect can be obtained. J1 / J2 may vary depending on the operating conditions of the non-aqueous alkali metal energy storage element. The excess capacity per unit area of ​​the negative electrode active material is J1 (Ah / cm²). 2 ), and the total volume per unit area of ​​the negative electrode active material is J2 (Ah / cm²). 2 ) is measured by the following method.

[0304] 1. Voltage adjustment LiCoO2, LiMn 0.6 Fe 0.4 PO4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiLiLi 0.8 Co 0.15 Al 0.05 When using O2 or LiMn2O4 as the positive electrode active material, the non-aqueous alkali metal energy storage element, which has deteriorated with use and before capacity recovery, should be charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, for example, 4.2V, followed by constant voltage charging of 4.2V for 30 minutes. When using LiFePO4 as the positive electrode active material, the non-aqueous alkali metal energy storage element should be charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, for example, 3.6V, followed by constant voltage charging of 3.6V for 30 minutes. 1 / 3 Ni 1 / 3 Mn 1 / 3 When using O2 as the positive electrode active material, the non-aqueous alkali metal energy storage element is charged with a constant current of 0.1C in a constant temperature bath set to 25°C until it reaches the upper limit of the stable operating voltage, i.e., 3.9V, and then charged with a constant voltage of 3.9V for 30 minutes.

[0305] 2. Measurement of negative electrode capacitance Subsequently, the energy storage element is disassembled in an argon box, the negative electrode is removed, and it is reassembled into a negative electrode half-cell using lithium as the counter electrode and a glass filter as the separator. Using the capacity of the negative electrode half-cell as a reference, constant current charging is performed up to 2.5V at a current value of 0.1C to desorb lithium from the negative electrode, and the negative electrode doping amount O (Ah / cell) at 4.2V before capacity recovery is measured after degradation. The coating area (cm²) of the negative electrode half-cell is measured. 2 By dividing by ), the negative electrode doping amount O1 (Ah / cm²) 2 ) is obtained. Subsequently, after constant current discharge down to 0.01V, the discharge capacity (Ah / cell) is measured when constant voltage discharge is performed until the current converges to a rate of 0.02C, and the coated area (cm²) of the single-sided negative electrode precursor is obtained. 2 By dividing by ), the coating area of ​​the negative electrode half cell (cm²) can be calculated. 2 By dividing by ), the total volume per unit area of ​​the negative electrode active material is J2 (Ah / cm²). 2 ) is obtained. The excess capacity per unit area of ​​the negative electrode active material J1 (Ah / cm²) 2 ) is obtained by J1 = J2 - O1.

[0306] (B1 / J1) In the second embodiment, the non-aqueous alkali metal energy storage element performing the capacity recovery process has a theoretical capacity per unit area of ​​alkali metal carbonate B1 (Ah / cm²). 2 ), the excess capacity per unit area of ​​the negative electrode active material is J1 (Ah / cm²). 2 When this is the case, it is preferable that 0.03 ≤ 0.3 × B1 / J1 ≤ 0.98. Within this range, alkali metal can be supplied to the negative electrode from alkali metal carbonate during the capacity recovery process, and a high capacity recovery effect can be obtained. B1 / J1 may vary depending on the usage conditions of the non-aqueous alkali metal energy storage element and the amount of alkali metal carbonate contained in the non-aqueous alkali metal energy storage element before capacity recovery. Excess capacity J1 (Ah / cm²) per unit area of ​​the negative electrode active material 2 )teeth, <j1 j2>It can be measured using the method described above. Theoretical capacity per unit area of ​​alkali metal carbonate B1 (Ah / cm³) 2 The theoretical capacity (mAh / g) of alkali metal carbonates is calculated by assuming that the oxidative decomposition reaction of alkali metal carbonates 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. Then, the weight (g / cm³) of the alkali metal carbonate is added to this. 2 By multiplying by ) and dividing by 1000, the theoretical capacity per unit area of ​​alkali metal carbonate B1 (Ah / cm³) can be obtained. 2 ) is required.

[0307] (Re-gassing process) In the second embodiment, it is preferable to further degass the electrolyte, positive electrode, and negative electrode after the capacity recovery process to remove any remaining gas. This prevents the resistance of the resulting non-aqueous alkali metal energy storage element from increasing due to gas remaining in at least a portion of the electrolyte, positive electrode, and negative electrode inhibiting ion conduction. The method of degassing is not particularly limited, but for example, one method can be used in which the electrode stack is placed in a reduced pressure chamber with the outer casing open and the inside of the chamber is reduced in pressure using a vacuum pump. After degassing, the outer casing can be sealed to create a non-aqueous alkali metal energy storage element (battery after capacity recovery).

[0308] <Non-aqueous alkali metal energy storage element with restored capacity> A second embodiment of this disclosure provides a non-aqueous alkali metal energy storage element with restored capacity (also referred to as a "restored battery"). The restored battery of this disclosure can be obtained by raising the potential of the positive electrode of the battery before capacity recovery to above the oxidative decomposition potential of the alkali metal compound (capacity recovery method). For details of the configuration of the battery before capacity recovery and the capacity recovery method, please refer to the sections above titled "Non-aqueous alkali metal energy storage element before capacity recovery" and "Capacity recovery method and method for manufacturing a restored non-aqueous alkali metal energy storage element."

[0309] In the second embodiment, the battery after capacity recovery includes a positive electrode containing a positive electrode active material layer disposed on a positive electrode current collector, a negative electrode containing 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 an alkali metal transition metal compound. The positive electrode active material layer or intermediate layer may optionally contain alkali metal compounds that remain undivided during capacity recovery, or may not contain alkali metal compounds. If the initial capacity of the battery before capacity recovery is P1 (mAh), the capacity after degradation is P2 (mAh), and the capacity of the battery after capacity recovery is P3 (mAh), then the capacity recovery rate calculated by (P3-P2)÷P1×100 is 2% or more. The capacity recovery rate is preferably 3% or more, more preferably 5% or more, even more preferably 10% or more, even more preferably 20% or more, and particularly preferably 30% or more.

[0310] In the second embodiment, the battery after capacity recovery is obtained by subjecting a capacity recovery process to a non-aqueous alkali metal energy storage element that had deteriorated to some extent before capacity recovery. Therefore, the configuration of the battery after capacity recovery is basically the same as that of the battery before capacity recovery, except that the amount of alkali metal compound in the positive electrode active material layer is reduced and the charge / discharge capacity is recovered. Therefore, details regarding the positive electrode, negative electrode, separator, non-aqueous electrolyte, and the casing and gas vent valve of the battery after capacity recovery can be found by referring to the description in the section on "Non-aqueous alkali metal energy storage element before capacity recovery" above.

[0311] In the second embodiment, the battery after capacity recovery is a non-aqueous alkali metal energy storage element that has undergone a capacity recovery process before capacity recovery, which contains a certain amount of alkali metal that has deteriorated to some extent, i.e., deactivated alkali metal. It is assumed that this deactivated alkali metal remains in the battery even after capacity recovery according to this disclosure. Therefore, although not limited to these, the battery after capacity recovery can have a high capacity (capacity recovery rate) despite containing a certain amount of the deactivated alkali metal.

[0312] <Use of non-aqueous alkali metal energy storage elements with restored capacity> A second embodiment of this disclosure provides the use of a non-aqueous alkali metal energy storage element (recovered battery) with restored capacity. The recovered battery of this disclosure may be reused for the same purpose as before the capacity recovery, or for a different purpose. It is preferable to select an appropriate reuse destination according to the capacity recovery rate. For example, the recovered battery of this disclosure can be suitably used in energy storage systems, which are at least one selected from the group consisting of: power regeneration assist systems in hybrid drive systems of automobiles, 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, contactless power supply systems for the purpose of leveling voltage fluctuations and storing energy such as microwave power transmission and electrolytic resonance, energy harvesting systems for the purpose of utilizing electricity generated by vibration power generation, solar power 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, rapid charging systems, and smart grid systems.

[0313] In the second embodiment, when the degree of capacity degradation is not uniform among a group of degraded non-aqueous alkali metal energy storage elements, the voltage, temperature, and charging current capacity of the capacity recovery process of this 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 less capacity degradation, thereby uniformly adjusting the recovered capacity. This is thought to improve the residual value by standardizing the capacity quality among batteries when reusing degraded non-aqueous alkali metal energy storage elements.

[0314] The capacity recovery method of the second embodiment of this disclosure can recover the capacity of each of a group of degraded non-aqueous alkali metal energy storage elements (a group of non-aqueous alkali metal energy storage elements). If there is variation in the capacities of the group of non-aqueous alkali metal energy storage elements, that is, if at least two of the group of non-aqueous alkali metal energy 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 positive electrode potential (battery voltage), temperature, and charging current capacity during capacity recovery. If the non-aqueous alkali metal energy storage elements originally had equivalent capacities before degradation, but variation in capacity occurs due to degradation, the difference in capacity may be reduced by reducing the difference in capacity retention rates.

[0315] In the second embodiment, in a battery pack composed of multiple single non-aqueous alkali metal energy storage elements, if there is variation in the capacity of the individual cells, the smaller capacity will determine the overall capacity of the battery pack. Therefore, when reusing alkali metal energy storage elements, it is preferable to reduce the variation in capacity. It is preferable to reduce the variation in capacity among the single cells constituting the battery pack before capacity recovery by controlling the capacity recovery effect of the capacity recovery process of this disclosure. The control method is not particularly limited, but at least one selected from the group consisting of positive electrode potential (battery voltage), temperature, and charging current capacity is mentioned. It is also preferable to control the capacity recovery conditions based on the amount of degradation during primary use.

[0316] The battery after capacity recovery according to the second embodiment of this disclosure can be suitably used in the form of an energy storage module connected in series or parallel with a lead-acid battery, a nickel-metal hydride battery, a non-aqueous alkali metal energy storage element (including the battery before capacity recovery according to this disclosure and other non-aqueous alkali metal energy storage elements), or a fuel cell. The energy storage module including the non-aqueous alkali metal energy storage element after capacity recovery may be reused for the same purpose as before capacity recovery, or for a different purpose. It is preferable to select an appropriate reuse destination according to the capacity recovery rate. [Examples]

[0317] I. Examples relating to the first embodiment Examples and comparative examples of the first embodiment are shown below. However, this disclosure is not limited in any way by the following examples and comparative examples. In addition, multiple batteries of the same standard were created because the test included destructive testing involving disassembly.

[0318] (Measurement of oxidation potential of accelerator) (i) When LFP is used as the positive electrode active material and 1,4-dimethoxybenzene is used as the accelerator. • Cathode fabrication A slurry for the positive electrode was prepared by mixing 91.4% by mass of LiFePO4 powder, 3.23% by mass of carbon black, 5.38% by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) as the positive electrode active material, adjusting the viscosity. The obtained slurry was then applied at a density of 100 g / m² to one side of a 15 μm thick anchor-coated aluminum foil, which served as the positive electrode current collector. 2 By coating and drying the material with a specified basis and then pressing it, a positive electrode for a full cell used to measure the oxidation potential of the accelerator was obtained.

[0319] • Negative electrode fabrication A slurry for the negative electrode was obtained by mixing 96.0 parts by mass of artificial graphite, 2.0 parts by mass of styrene-butadiene rubber, 2.0 parts by mass of carboxymethylcellulose (CMC), and water. The obtained slurry for the negative electrode was applied to one side of a 10 μm thick electrolytic copper foil at a density of 100 g / m². 2 By coating and drying the material with a specified basis and then pressing it, a negative electrode for a full cell used to measure the oxidation potential of the accelerator was obtained.

[0320] ·assembly As shown in Figure 1, the obtained positive electrode (1) was cut so that the coated area size was 5 cm × 10 cm, leaving the exposed terminal portion (10) of the current collector foil for tab welding (Figure 1). The obtained negative electrode (2) was cut so that the coated area size was 5.2 cm × 10.2 cm, leaving the terminal portion with the exposed current collector foil for tab welding (Figure 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 film separator (3) measuring 5.5 cm × 10.5 cm (Figure 1) was laminated between the positive electrode (1) and the negative electrode (2). Then, the negative electrode terminal (31) and positive electrode terminal (11) were connected to the exposed current collector foil terminals (10) of the negative electrode (2) and positive electrode (1) respectively by ultrasonic welding to form an electrode laminate. A lithium reference electrode (412) was placed 1 cm from the electrode laminate, with a lithium foil (5) wrapped around a SUS foil (6) and then wrapped in a 20 μm thick microporous film separator (12) measuring 5.5 cm × 5.5 cm, and a Ni terminal (7) with a resin tape (9) for removal from the laminate being welded to the end of the SUS foil (6) by ultrasonic welding, and the lithium reference electrode (412) was placed 1 cm from the electrode laminate to create a liquid junction with 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 Figure 2. This electrode stack was housed in an outer casing made of aluminum laminate packaging material, and the electrode terminals and bottom of the outer casing were heat-sealed on three sides under the conditions of a temperature of 180°C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa to obtain two full cells (full cell 1, full cell 2) for measuring the accelerating potential before liquid injection.

[0322] • Injection Electrolyte 1 was prepared by dissolving 1.0 M LiPF6 and 1% by mass of vinylene carbonate, and 0.1 mol / L of 1,4-dimethoxybenzene in an EC:MEC mixed solvent (volume ratio 1:2).

[0323] On the other hand, electrolyte solution 2 was prepared by dissolving 1.0 M LiPF6 and 1% by mass of vinylene carbonate in an EC:MEC mixed solvent (volume ratio 1:2).

[0324] Under atmospheric pressure, at a temperature of 25°C and in a dry air environment with a dew point of -40°C or lower, 2g of electrolyte 1 was injected into full cell 1 and 2g of electrolyte 2 into full cell 2. Subsequently, these were placed in a vacuum chamber, the pressure was reduced from atmospheric pressure to -87kPa, then returned to atmospheric pressure, and left to stand for 5 minutes. After that, the process of reducing the pressure from atmospheric pressure to -87kPa and returning to atmospheric pressure was repeated four times, and then left to stand for 15 minutes to impregnate the electrode stack with the non-aqueous electrolyte. Then, the electrode stack, which was housed in an aluminum laminate packaging and impregnated with the non-aqueous electrolyte, was placed in a vacuum sealing machine, and the aluminum laminate packaging was sealed by sealing at a pressure of 0.1MPa for 10 seconds at 180°C under a reduced pressure of -95kPa, thereby obtaining full cells 1 and 2 for oxidation potential measurement before the first charge after electrolyte injection.

[0325] ·First charge As described in the section above (Measurement of Oxidation Initiation Potential of Accelerator), the oxidation potential was measured under the following conditions: Constant current charging was performed in a constant temperature bath set to 45°C with a current value of 0.1C until the voltage reached 4.8V. At the same time, the positive electrode potential relative to the lithium reference electrode was measured. Based on the above measurements, as shown in Figure 3, for full cells 1 and 2, the positive electrode potential (V vs Li / Li) was obtained relative to the capacity per unit weight of positive electrode active material (mAh / g of positive electrode active material). + We obtained curves 1 and 2 by plotting the curves.

[0326] In this test, the positive electrode potential was charged to a region of 3.7V or higher, so the oxidation initiation potential was calculated using method A above (measurement of oxidation initiation potential of accelerator). Specifically, the point at which the positive electrode potential reached 3.7V was set as the starting point for capacity calculation (0mAh / g of positive electrode active material), and as shown in Figure 3, curves 1 and 2 were obtained by shifting them in parallel. Then, as shown in Figure 4, the difference in weight-capacity of the positive electrode active material at the same positive electrode potential (curve 1 - curve 2) was calculated, and 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. + A difference curve (curve 1-2) was obtained by plotting the values. The positive electrode potential of 4.03V, where the capacitance of the difference curve exceeded 5mAh / g, was defined as the oxidation initiation potential of the accelerator.

[0327] (ii) When LFP is used as the positive electrode active material and N,N,N',N'-tetramethyl-p-phenylenediamine is used as the accelerator. The preparation of the positive electrode, negative electrode, and assembly were carried out in the same manner as described in "(i) When LFP is used as the positive electrode active material and 1,4-dimethoxybenzene is used as the accelerator" above.

[0328] • Injection Electrolyte 1 was prepared by dissolving 1.0 M LiPF6 and 1% by mass of vinylene carbonate, and 0.1 mol / L of N,N,N',N'-tetramethyl-p-phenylenediamine in an EC:MEC mixed solvent (volume ratio 1:2).

[0329] On the other hand, electrolyte solution 2 was prepared by dissolving 1.0 M LiPF6 and 1% by mass of vinylene carbonate in an EC:MEC mixed solvent (volume ratio 1:2).

[0330] Under atmospheric pressure, at a temperature of 25°C and in a dry air environment with a dew point of -40°C or lower, 2g of electrolyte 1 was injected into full cell 1 and 2g of electrolyte 2 into full cell 2. Subsequently, these were placed in a vacuum chamber, the pressure was reduced from atmospheric pressure to -87kPa, then returned to atmospheric pressure, and left to stand for 5 minutes. After that, the process of reducing the pressure from atmospheric pressure to -87kPa and returning to atmospheric pressure was repeated four times, and then left to stand for 15 minutes to impregnate the electrode stack with the non-aqueous electrolyte. Then, the electrode stack, which was housed in an aluminum laminate packaging and impregnated with the non-aqueous electrolyte, was placed in a vacuum sealing machine, and the aluminum laminate packaging was sealed by sealing at a pressure of 0.1MPa for 10 seconds at 180°C under a reduced pressure of -95kPa, thereby obtaining full cells 1 and 2 for oxidation potential measurement before the first charge after electrolyte injection.

[0331] ·First charge As described in the section above (Measurement of Oxidation Initiation Potential of Accelerator), the oxidation potential was measured under the following conditions: Constant current charging was performed in a constant temperature bath set to 45°C with a current value of 0.1C until the voltage reached 4.8V. At the same time, the positive electrode potential relative to the lithium reference electrode was measured. Based on the above measurements, as shown in Figure 5, for full cells 1 and 2, the positive electrode potential (V vs Li / Li) was determined as follows: Capacity per unit weight of positive electrode active material (mAh / g of positive electrode active material). + Curves 1 and 2 were obtained by plotting the values. However, since the cell voltage did not rise to 4.8V in full cell 1, the measurement was stopped without waiting for it to reach 4.8V.

[0332] In this test, when constant current charging was performed, the cell voltage of full cell 1 did not rise to 4.8V, and the positive electrode potential did not reach the region of 3.7V or higher. Therefore, the oxidation initiation potential was calculated using method B above (measurement of oxidation initiation potential of accelerator). Specifically, the charging start point was set as the starting point of capacity calculation (0mAh / g of positive electrode active material), and as shown in Figures 5 and 6, curves 1 and 2 were shifted in parallel, and the difference curve (curve 1 - curve 2) at the same positive electrode potential was calculated. A positive electrode potential of 3.46V, where the capacity difference between curves 1 and 2 exceeded 5mAh / g, was taken as the oxidation initiation potential of the accelerator.

[0333] (iii) When LFP and various accelerators are used as the positive electrode active material Table 1 shows the results of measuring the oxidation potential of other accelerators in the same manner as the oxidation initiation potential calculation method described above.

[0334] (iv) Measurement of oxidation potential of accelerators when LCO, NCM811, and NCA are used as active materials Except for changing the cathode active material during cathode fabrication, the oxidation potential of the accelerator was measured in the same manner as when LFP was used as the cathode active material. The results are shown in Tables 2-4.

[0335] (v) Active material: NaFe 1 / 3 Ni 1 / 3Mn 1 / 3 Measurement of the oxidation potential of accelerators when using O2 (abbreviated as "NFNMO" in the table). By changing the positive electrode active material during positive electrode fabrication, In the fabrication of the negative electrode, hard carbon is used as the negative electrode active material. During assembly, a sodium reference electrode is used. For the injection solution, an electrolyte solution prepared by dissolving 1% by mass of 1.0 M NaPF6 and fluoroethylene carbonate in a PC:DMC mixed solvent (volume ratio 1:2) was used. During the initial charge, the battery was charged with a constant current up to a voltage of 4.5V. 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 same method as (measurement of the positive electrode precursor potential) was used for converting the sodium reference potential to the lithium reference potential. The results are shown in Table 5.

[0336] <Example 1-1> (Measurement of initial charge capacity density L1 and initial discharge capacity density L2 of the positive electrode active material) A positive electrode slurry for a positive electrode half-cell used for measuring the initial charge capacity of the positive electrode active material was obtained by mixing 91% by mass of LiFePO4 powder, 4% by mass of carbon black, 5% by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) as the positive electrode active material, and adjusting the solid content concentration to 45% by mass. The obtained slurry was applied at a rate of 100 g / m² to one side of a 15 μm thick anchor-coated aluminum foil, which was to be used as the positive electrode current collector. 2 By coating and drying the material with a specified basis and then pressing it, a positive electrode for a positive electrode half-cell used for measuring the initial charge capacity of the positive electrode active material was obtained.

[0337] The obtained single-sided positive electrode was punched out so that the coated area was 2 cm x 2 cm, and vacuum dried at 200°C for 24 hours. The positive electrode terminals were connected by ultrasonic welding. The negative electrode terminals were connected by ultrasonic welding to the Li counter electrode, which had lithium (Li) attached to copper foil. A positive electrode half-cell electrode laminate was obtained by combining it with a polypropylene separator and a glass filter. This electrode laminate was housed in an outer casing made of aluminum laminate packaging material, and the three sides of the outer casing, including the electrode terminals and the bottom, 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, an electrolyte solution was prepared by dissolving 1.0 M LiPF6 and 1 mass% vinylene carbonate in an EC:MEC mixed solvent (volume ratio 1:2).

[0338] Two grams of the above-mentioned non-aqueous electrolyte were injected into an electrode laminate housed in an aluminum laminate packaging under atmospheric pressure, a temperature of 25°C, and a dry air environment with a dew point of -40°C or lower. Subsequently, this was placed in a vacuum chamber, the pressure was reduced from atmospheric pressure to -87 kPa, then returned to atmospheric pressure, and left to stand for 5 minutes. After that, the process of reducing the pressure from atmospheric pressure to -87 kPa and returning to atmospheric pressure was repeated four times, and then left to stand for 15 minutes to impregnate the electrode laminate with the non-aqueous electrolyte. After that, the electrode laminate housed in the aluminum laminate packaging and impregnated with the non-aqueous electrolyte was placed in a vacuum sealing machine, and the aluminum laminate packaging was sealed at a pressure of 0.1 MPa for 10 seconds at 180°C under a reduced pressure of -95 kPa to produce a positive electrode half-cell.

[0339] Using the method described above (initial charge capacity density L1 and initial discharge capacity density L2 of the positive electrode active material), the upper limit of the stable operating potential of the positive electrode active material was set, and the initial charge capacity density L1 and initial discharge capacity density L2 of the positive electrode active material were obtained. The obtained L1 and L2 are shown in Table 6 below.

[0340] (Fabrication of non-aqueous alkali metal energy storage elements) (Preparation of positive electrode precursor) LiFePO4 as the positive electrode active material, lithium carbonate, carbon black as the conductive material, and PVdF (polyvinylidene fluoride) as the binder were prepared in the compositions shown in Table 6 below. NMP (N-methylpyrrolidone) was then mixed in to obtain a slurry for the positive electrode precursor. The obtained slurry for the positive electrode precursor was coated onto one side of a 15 μm thick anchor-coated aluminum foil with the basis weight shown in Table 6 below, and pressed to obtain the positive electrode precursor. To calculate the volume difference mentioned above (negative electrode doping amount, volume difference, pre-doping volume efficiency), the thickness t2 of the positive electrode precursor containing lithium carbonate was measured as the film thickness of this positive electrode precursor.

[0341] (Preparation of negative electrode precursor) A slurry for the negative electrode precursor was obtained by mixing 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 carboxymethylcellulose (CMC), and water. The obtained slurry for the negative electrode precursor was coated onto one side of a 10 μm thick electrolytic copper foil with the basis weight shown in Table 6 below, and then pressed to obtain the negative electrode precursor.

[0342] (assembly) The obtained positive electrode precursor was cut to a coated area size of 2 cm x 2 cm, and the obtained negative electrode precursor was cut to a coated area size of 2.2 cm x 2.2 cm. A microporous film separator with a thickness of 15 μm was sandwiched between the positive and negative electrode precursors and laminated. Then, the negative electrode terminals and positive electrode terminals were connected to the negative electrode precursor and positive electrode precursor, respectively, by ultrasonic welding to form an electrode laminate. This electrode laminate and a lithium reference electrode, which was lithium pressed onto SUS foil and wrapped in a microporous separator, were housed in an outer casing made of alumin...

Claims

1. A non-aqueous alkali metal energy storage element comprising a positive electrode, a negative electrode, a separator, an outer casing, and a non-aqueous electrolyte containing alkali metal ions, The negative electrode contains a material that intercepts and deintercepts 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 intercepts and releases alkali metal ions, The aforementioned non-aqueous electrolyte further contains a carbonate decomposition accelerator, The oxidation initiation potential of the carbonate decomposition accelerator is 3.8 V (vs Li / Li ＋ ) or more 4.7V (vs Li / Li ＋ ) less than or equal to and A non-aqueous alkali metal energy storage element in which the effective utilization rate of the positive electrode active material is 85 to 99.5%.

2. The non-aqueous alkali metal energy storage element according to claim 1, wherein the amount of alkali metal measured by solid-state NMR is 0.06 mmol / g or less per negative electrode active material layer.

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

4. The non-aqueous alkali metal energy storage element 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. The non-aqueous alkali metal energy storage element 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 non-aqueous alkali metal energy storage element 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 non-aqueous alkali metal energy storage element 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 excess capacitance per unit area of ​​the positive electrode is F. １ (mAh / cm ２ ), the irreversible capacitance per unit area of ​​the negative electrode is G １ (mAh / cm ２ ) When that is the case, 0.01<F １ / G １ <0.9 A non-aqueous alkali metal energy storage element according to claim 1 or 2, satisfying the requirements.

9. The non-aqueous alkali metal energy storage element according to claim 1 or 2, wherein the positive electrode active material layer further contains an alkali metal carbonate in an amount of 0.02 to 1.5% by mass, based on the total mass of the positive electrode active material layer.

10. The non-aqueous alkali metal energy storage element according to claim 1 or 2, further comprising an optional intermediate layer between the positive electrode active material layer and the separator, wherein the intermediate layer contains an alkali metal carbonate in an amount of 0.2 to 9.5% by mass based on the total mass of the intermediate layer.

11. The non-aqueous alkali metal energy storage element according to claim 1 or 2, wherein the carbonate decomposition accelerator is contained in the non-aqueous electrolyte at a concentration of 0.0001 mol / L to 1.5 mol / L.

12. The non-aqueous alkali metal energy storage element 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 non-aqueous alkali metal energy storage element according to claim 1 or 2, wherein the negative electrode active material includes 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 carbonaceous materials.

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