Nonaqueous alkali metal power storage element and method for producing same

Abstract

Provided is a nonaqueous lithium power storage element precursor which is a nonaqueous alkali metal power storage element precursor comprising a positive electrode precursor, a negative electrode precursor, a separator, and an exterior material, wherein: the negative electrode precursor contains, as a negative electrode active material, a material that stores and releases alkali metal ions; the positive electrode precursor has a positive electrode active material layer which includes a positive electrode active material that stores and releases alkali metal ions; and an alkali metal carbonate or a pre-doped material is included in the positive electrode active material layer and / or an arbitrary intermediate layer between the positive electrode active material layer and the separator.

Description

Nonaqueous alkali metal storage element and method for manufacturing same

[0001] The present invention relates to an alkali metal storage element, a precursor thereof, and a manufacturing method thereof.

[0002] In recent years, from the perspective of protecting the global environment and effectively utilizing energy to conserve resources, attention has been drawn to wind power generation power smoothing systems or late-night power storage systems, distributed home energy storage systems based on solar power generation technology, and energy storage systems for electric vehicles.

[0003] For the alkali metal ion secondary batteries used in these power storage systems, technological development is being actively pursued to achieve both high capacity density and durability.

[0004] Conventionally, alkali metal ion secondary batteries have had the problem that alkali metal ions equivalent to the initial irreversible capacity of the negative electrode are trapped at the solid electrolyte interface (SEI) or the like during the initial charge, resulting in a loss of capacity equivalent to the irreversible capacity in the discharge capacity of the full cell.

[0005] On the other hand, a pre-doping technique is known as a technique for improving the capacity density of alkali metal ion secondary batteries.

[0006] By using the pre-doping technique, it is possible to compensate for the capacity loss equivalent to the initial irreversible capacity of the negative electrode. Techniques using alkali metal carbonate as a pre-doping source are disclosed in Patent Document 1 and Patent Document 2. However, these techniques have the following problems remaining: the decomposition efficiency of alkali metal carbonate is insufficient, there is a problem of a decrease in the effective utilization rate of the positive electrode, the effect of pre-doping has not been obtained for negative electrodes with small irreversible capacity, there is room for improvement in reducing resistance, and gas generation occurs when used at 40°C. The development of countermeasures to these problems has been desired.

[0007] By using the pre-doping technique, the capacity loss corresponding to the initial irreversible capacity of the negative electrode is compensated for, thereby increasing the capacity density of the battery. Patent Documents 3 and 4 disclose a technique in which a positive electrode active material layer includes a positive electrode active material and a pre-dope material, and the pre-dope material has a higher capacity density and a larger irreversible capacity than the positive electrode active material. ５ FeO ４ In addition, Patent Document 5 discloses a method for doping Li as a pre-dope material. ４ TiO ４ , Li ２ TiO ３ In Patent Document 6, Li is used as a pre-dopant. １．２ (Ti ０．５ Fe ０．５ ) ０．８ O ２ However, in these prior arts, the influence on charge-discharge cycle durability that occurs when a pre-dope material is introduced into a positive electrode active material layer has not been fully investigated.

[0008] Furthermore, in the prior art described in Patent Documents 3 to 6, the influence on high temperature durability was not fully considered.

[0009] International Publication No. 2017 / 126682 International Publication No. 2020 / 017515 JP 2014-157653 A International Publication No. 2014 / 118834 JP 2019-87590 A Japanese Patent Application Laid-Open No. 2020-167187

[0010] A first object of the present invention is to decompose an alkali metal carbonate at a relatively low decomposition voltage when used as a pre-dope source for an alkali metal storage element, thereby increasing doping efficiency, improving positive electrode utilization, reducing resistance, and suppressing gas generation under storage conditions at 40° C. A second object of the present invention is to improve the durability of an alkali metal storage element in which a material having a higher capacity density than the positive electrode active material is introduced into the positive electrode active material layer as a pre-dope material. A third object of the present invention is to improve the high-temperature durability of a lithium-ion secondary battery.

[0011] Examples of embodiments of the present disclosure are listed below: (1) A nonaqueous alkali metal electric storage element precursor including a positive electrode precursor, a negative electrode precursor, a separator, and an exterior material, wherein the negative electrode precursor includes a material that occludes and releases alkali metal ions as a negative electrode active material, and the positive electrode precursor has a positive electrode active material layer including a positive electrode active material that occludes and releases alkali metal ions, and an alkali metal carbonate or a pre-dope material 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. (2) A nonaqueous alkali metal electric storage element including a positive electrode including a positive electrode active material layer, a negative electrode, a separator, and an exterior material, wherein the negative electrode includes a material that occludes and releases alkali metal ions as a negative electrode active material. (3) A method for producing a nonaqueous alkali metal electric storage element using a nonaqueous alkali metal electric storage element precursor including a positive electrode precursor, a negative electrode precursor, a separator, and an exterior material, wherein the negative electrode precursor contains, as a negative electrode active material, a material that inserts and desorbs alkali metal ions, and the positive electrode precursor has a positive electrode active material layer containing a positive electrode active material that occludes and releases alkali metal ions, and wherein an alkali metal carbonate or a pre-dope material 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 of them, wherein the nonaqueous alkali metal electric storage element precursor has a nonaqueous electrolytic solution containing an electrolyte containing alkali metal ions, and the method for producing a nonaqueous alkali metal electric storage element includes applying a voltage between the positive electrode precursor and the negative electrode precursor to dope the alkali metal ions into the negative electrode active material.(4) The nonaqueous alkali metal storage element precursor according to item 1, wherein 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 both, and a carbon material is contained in the positive electrode active material layer, the intermediate layer, or both, wherein the amount of oxygen atoms X calculated from carbon monoxide and / or carbon dioxide when the carbon material is measured by temperature programmed desorption-mass spectrometry (TPDMS) is 0.1 mmol / g or more per mass of the carbon material, and the amount of the carbon material in the layer containing the carbon material among the positive electrode active material layer and the intermediate layer, if present, is 0.3 mass% or more and 15 mass% or less, based on the total mass of the layer containing the carbon material. (5) The nonaqueous alkali metal storage element precursor according to item 1 or 4, wherein the positive electrode active material layer contains the alkali metal carbonate in an amount of 0.2 to 15 mass%. (6) The nonaqueous alkali metal storage element precursor according to item 1, 4, or 5, wherein the intermediate layer contains 20 to 95 mass % of the alkali metal carbonate. (7) The carbon material has a BET specific surface area of ​​100 m. ２ / g or more 1800m ２ / g or less. (8) The nonaqueous alkali metal storage element precursor according to any one of items 1 and 4 to 7, wherein the negative electrode active material includes at least one of an alloy-based negative electrode material that forms an alloy with an alkali metal and an amorphous carbon material. (9) The nonaqueous alkali metal storage element according to item 2, comprising a positive electrode including a positive electrode active material layer, a negative electrode, a separator, and an exterior material, wherein the negative electrode includes a material that inserts and releases alkali metal ions as a negative electrode active material, the effective utilization rate of the positive electrode active material is 85 to 99.5%, and the negative electrode active material includes at least one of an alloy-based negative electrode material that forms an alloy with an alkali metal and an amorphous carbon material. (10) The nonaqueous alkali metal storage element according to item 2 or 9, wherein the positive electrode active material layer includes an alkali metal carbonate in an amount of 0.02 wt % to 12 wt %, based on the weight of the positive electrode active material layer. (11) The effective utilization rate of the positive electrode active material is 85 to 99.5%, and the negative electrode reversible capacity (mAh / cm ２) to the negative electrode irreversible capacity (mAh / cm ２ (12) The nonaqueous alkali metal storage element according to item 2 or 11, wherein the positive electrode active material layer contains an alkali metal carbonate in an amount of 0.02 wt % to 12 wt % based on the weight of the positive electrode active material layer. (13) The nonaqueous lithium storage element according to any one of items 2 and 9 to 12, wherein a carbon material is provided in the positive electrode active material layer or between the positive electrode active material layer and the separator, wherein the amount of oxygen atoms X calculated from carbon monoxide and / or carbon dioxide obtained when the carbon material is measured by temperature programmed desorption-mass spectrometry (TPDMS) is 0.1 mmol / g or more per mass of the carbon material, and the effective utilization rate of the positive electrode active material contained in the positive electrode active material layer is 85 to 99.5%. (14) The nonaqueous lithium storage element according to any one of items 2 and 9 to 12, wherein the BET specific surface area of ​​the carbon material is 100 m ２ / g or more 1800m ２ / g or less. (15) The nonaqueous lithium storage element according to item 13, wherein the negative electrode active material includes at least one of an alloy-based negative electrode material that forms an alloy with lithium and an amorphous carbon material. (16) The nonaqueous alkali metal storage element according to item 13, wherein the positive electrode active material layer includes an alkali metal carbonate in an amount of 0.02 wt % or more and 12 wt % or less based on the weight of the positive electrode active material layer. (17) A method for producing a nonaqueous alkali metal storage element using a nonaqueous alkali metal storage element precursor including a positive electrode precursor, a negative electrode precursor, a separator, a nonaqueous electrolyte, and an exterior material, wherein the negative electrode precursor includes a material that occludes and releases alkali metal ions as a negative electrode active material, the positive electrode precursor has a positive electrode active material layer including a positive electrode active material that occludes and releases alkali metal ions, the nonaqueous alkali metal 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 in both, and contains a carbon material in the positive electrode active material layer, or in the intermediate layer, or in both, and the carbon material has an oxygen atomic weight X calculated from carbon monoxide and / or carbon dioxide obtained when the carbon material is measured by temperature programmed desorption-mass spectrometry (TPDMS) is 0.1 mmol / g or more per mass of the carbon material, The amount of the carbon material in the layer containing the carbon material in the positive electrode active material layer and, if present, in the intermediate layer is 0.3 mass % or more and 15 mass % or less based on the total mass of the layer containing the carbon material, the non-aqueous electrolytic solution contains an electrolyte containing an alkali metal ion, and the potential of the positive electrode precursor is 4.15 to 4.75 V (vs. Li / Li) relative to the non-aqueous alkali metal electric storage element precursor. ＋a voltage is applied between the positive electrode precursor and the negative electrode precursor so that the negative electrode active material is doped with alkali metal ions. (18) A method for producing a nonaqueous lithium storage element, wherein the nonaqueous alkali metal storage element is a nonaqueous lithium storage element, and the method uses a nonaqueous lithium storage element precursor including a positive electrode precursor, a negative electrode precursor, a separator, a nonaqueous electrolyte, and an exterior material, wherein the nonaqueous lithium storage element precursor includes: the negative electrode precursor including a material that absorbs and releases lithium ions as a negative electrode active material; the positive electrode precursor has a positive electrode active material layer including a positive electrode active material that absorbs and releases lithium ions; lithium 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 of them; and a carbon material is contained in the positive electrode active material layer, or in the intermediate layer, or in both of them; and an oxygen atomic weight X calculated from carbon monoxide and / or carbon dioxide obtained when the carbon material is measured by temperature programmed desorption-mass spectrometry (TPDMS) is 0.1 mmol / g or more per mass of the carbon material; 4. The method according to item 3, wherein the amount of the carbon material in the layer containing the carbon material in the positive electrode active material layer and the intermediate layer, if present, is 0.3 mass % or more and 15 mass % or less based on the total mass of the layer containing the carbon material, the nonaqueous electrolytic solution includes an electrolyte containing lithium ions, and the nonaqueous lithium storage element precursor is doped with lithium ions by applying a voltage of 4.1 V or more and 4.6 V or less between the positive electrode precursor and the negative electrode precursor.(19) A method for producing a non-aqueous lithium storage element precursor including a positive electrode precursor, a negative electrode precursor, a separator, a non-aqueous electrolyte solution, and an exterior material, wherein the non-aqueous alkali metal storage element precursor has the following configuration: (a) the negative electrode precursor has a negative electrode active material layer containing a negative electrode active material including a material that absorbs and releases lithium ions, and (b) the positive electrode precursor has a positive electrode active material layer containing a positive electrode active material that contains a positive electrode active material that absorbs and releases lithium ions, and (c) the positive electrode active material layer contains lithium carbonate, and (d) the positive electrode active material layer contains 0.30 mass% or more and 15.00 mass% or less of a carbon material, and (e) the carbon material has an oxygen atomic weight X calculated from carbon monoxide and / or carbon dioxide obtained by temperature programmed desorption-mass spectrometry (TPDMS) of 0.10 mmol / g or more and 5.00 mmol / g or less per mass of the carbon material, and (f) A method for producing a nonaqueous lithium storage element precursor, wherein the nonaqueous electrolytic solution contains an electrolyte containing lithium ions, and the method comprises applying a voltage of 4.1 V or more and 4.45 V or less between the positive electrode precursor and the negative electrode precursor to dope the lithium ions into the nonaqueous lithium storage element precursor.(20) A method for producing a nonaqueous sodium storage element, wherein the nonaqueous alkali metal storage element is a nonaqueous sodium storage element, using a nonaqueous sodium storage element precursor including a positive electrode precursor, a negative electrode precursor, a separator, a nonaqueous electrolyte, and an exterior material, wherein the nonaqueous sodium storage element precursor includes: the negative electrode precursor including a material that occludes and releases sodium ions as a negative electrode active material; the positive electrode precursor has a positive electrode active material layer including a positive electrode active material that occludes and releases sodium ions; sodium 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 of them; and a carbon material is contained in the positive electrode active material layer, or in the intermediate layer, or in both of them; and an oxygen atomic weight X calculated from carbon monoxide and / or carbon dioxide obtained when the carbon material is measured by temperature programmed desorption-mass spectrometry (TPDMS) is 0.1 mmol / g or more per mass of the carbon material; 4. The method according to item 3, wherein the amount of the carbon material in the layer containing the carbon material in the positive electrode active material layer and, if present, in the intermediate layer, is 0.3 mass % or more and 15 mass % or less based on the total mass of the layer containing the carbon material, the nonaqueous electrolytic solution contains an electrolyte containing sodium ions, and the nonaqueous sodium storage element precursor is doped with sodium ions by applying a voltage of 3.8 V or more and 4.3 V or less between the positive electrode precursor and the negative electrode precursor.(21) The nonaqueous alkali metal electric storage element precursor according to any one of items 1 and 4 to 8 is a nonaqueous lithium electric storage element precursor, and the nonaqueous lithium electric storage element precursor includes a positive electrode active material layer, wherein the positive electrode active material layer contains a pre-dope material and a positive electrode active material, and the positive electrode active material contains a positive electrode active material that absorbs and releases lithium ions, and when the initial charge capacity density of the positive electrode active material is A1 (mAh / g), the D50 of the positive electrode active material is R1 (μm), the initial charge capacity density of the pre-dope material is A2 (mAh / g), the initial discharge capacity of the pre-dope material is B2 (mAh / g), and the D50 of the pre-dope material is R2 (μm), the following formulas are satisfied: A2 / A1>1.2, B2 / A2<0.3, and (22) A positive electrode precursor, which satisfies the following condition: 0.25<(R1×A1) / (R2×A2)<2. (22) The pre-dopant is Li. ６ CoO ４ , Li ５ FeO ４ , Li ２ NiO ４ , Li ６ MnO ４ , and Li １．２ (Ti ０．５ Fe ０．５ ) ０．８ O ２(23) The positive electrode precursor according to item 21 or 22, which further satisfies the following formula: R2<9 μm. (24) A lithium ion secondary battery obtained by pre-doping a nonaqueous lithium storage element precursor having the positive electrode precursor according to any one of items 21 to 23. (25) The lithium ion secondary battery according to item 24, wherein the volume resistivity of the positive electrode active material layer after pre-doping is 10 Ω cm or less. (26) The lithium ion secondary battery according to item 24 or 25, wherein the negative electrode active material included in the lithium ion secondary battery contains an alloy-based negative electrode material that forms an alloy with lithium. (27) A method for producing a lithium ion secondary battery, comprising the steps of applying a voltage between the positive electrode precursor according to any one of items 21 to 23 and a negative electrode precursor, decomposing the pre-dope material to release lithium ions, and pre-doping the negative electrode active material with lithium ions. (28) The nonaqueous alkali metal storage element precursor according to any one of items 1 and 4 to 8 is a lithium storage element precursor having a positive electrode precursor, a negative electrode precursor, and a separator, wherein the positive electrode precursor contains a positive electrode active material that absorbs and releases lithium ions, and a pre-dope material layer containing a pre-dope material is provided at the interface between the positive electrode precursor and the separator, and the lithium storage element precursor satisfies the following formulae: B2 / A2<0.3, A2 / A1>1.2, and 0.2≦R2≦15, where A1 (mAh / g) is the initial charge capacity density of the positive electrode active material, A2 (mAh / g) is the initial charge capacity density of the pre-dope material, B2 (mAh / g) is the initial discharge capacity density of the pre-dope material, and R2 (μm) is the D50 of the pre-dope material. (29) The lithium storage element precursor is a lithium storage element precursor having a positive electrode precursor, a negative electrode precursor, and a pre-dope material layer containing a pre-dope material at the interface between the positive electrode precursor and the separator, and the pre-dope material satisfies the following formulae: B2 / A2<0.3, A2 / A1>1.2, and 0.2≦R2≦15. ６ CoO ４ , Li ５ FeO ４ , Li ２ NiO ４ , Li ６ MnO ４ , and Li １．２ (Ti ０．５ Fe ０．５ ) ０．８ O ２(30) The lithium storage element precursor according to item 28 or 29, wherein the pre-dope material layer contains a conductive material. (31) The lithium storage element precursor according to any one of items 28 to 30, further satisfying the following formula: R2≦5 μm. (32) The lithium storage element precursor according to any one of items 28 to 31, wherein the negative electrode active material contained in the negative electrode precursor includes an alloy-based negative electrode material that forms an alloy with lithium. (33) A lithium ion secondary battery obtained by pre-doping the lithium storage element precursor according to any one of items 28 to 32. (34) A method for producing a lithium ion secondary battery, comprising: a step of applying a voltage between the positive electrode precursor and the negative electrode precursor of the lithium storage element precursor according to any one of items 28 to 33; a step of decomposing the pre-dope material to release lithium ions; and a step of pre-doping lithium ions into a negative electrode active material contained in the negative electrode precursor.

[0012] According to the present disclosure, it is possible to decompose alkali metal carbonate at a relatively low decomposition voltage, increase doping efficiency, improve positive electrode utilization, reduce positive electrode active material loss, reduce resistance, and further suppress gas generation under storage conditions at 40° C. As another effect, according to the present disclosure, it is possible to improve the durability in charge / discharge cycles of an alkali metal storage element in which a material having a higher capacity density than the positive electrode active material is introduced into the positive electrode active material layer as a pre-dope material. As a further effect, according to the present disclosure, it is possible to improve the high-temperature durability of a lithium-ion secondary battery.

[0013] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail, but the present invention is not limited to this embodiment. The upper and lower limits of each numerical range in this embodiment can be arbitrarily combined to form any numerical range.

[0014] In this embodiment, the alkali metal storage element before pre-doping described below is defined as a "nonaqueous alkali metal storage element precursor," the positive electrode before pre-doping described below is defined as a "positive electrode precursor," the negative electrode before pre-doping described below is defined as a "negative electrode precursor," the alkali metal storage element after pre-doping is defined as a "nonaqueous alkali metal storage element," the positive electrode after pre-doping is defined as a "positive electrode," and the negative electrode after pre-doping is defined as a "negative electrode."

[0015] In this embodiment, the alkali metal is selected from one or more of lithium, sodium, potassium, rubidium, cesium, and francium. The alkali metal ion is selected from one or more of lithium ion, sodium ion, potassium ion, rubidium ion, cesium ion, and francium ion. Among these, lithium, sodium, and potassium are preferred from the viewpoints of energy density, resource amount, and the like, and lithium is particularly preferred.

[0016] In a first embodiment, the nonaqueous alkali metal storage element precursor includes a positive electrode including a positive electrode active material layer disposed on a positive electrode current collector, a negative electrode including a negative electrode active material layer disposed on a negative electrode current collector, a separator, and optionally an outer casing. A nonaqueous electrolyte solution containing alkali metal ions is also included. The positive electrode active material layer includes a positive electrode active material capable of absorbing and desorbing alkali metal ions. Known materials used in known nonaqueous alkali metal storage elements can be used as the positive electrode active material capable of absorbing and desorbing alkali metal ions. For example, a material containing an alkali metal and at least one transition metal is preferred. Examples of such compounds include alkali metal-containing transition metal oxides and alkali metal-containing transition metal phosphate compounds. The nonaqueous alkali metal storage element precursor includes an alkali metal carbonate in the positive electrode active material layer, an optional intermediate layer between the positive electrode active material layer and the separator, or both, and a carbon material in the positive electrode active material layer, the intermediate layer, or both. That is, the first embodiment includes at least the following aspects: (i) an aspect in which the positive electrode active material layer contains both an alkali metal carbonate and a carbon material; (ii) an aspect in which the positive electrode active material layer contains both an alkali metal carbonate and a carbon material, and an intermediate layer is present between the positive electrode active material layer and the separator, the intermediate layer containing a carbon material; (iii) an aspect in which the positive electrode active material layer contains both an alkali metal carbonate and a carbon material, and an intermediate layer is present between the positive electrode active material layer and the separator, the intermediate layer containing an alkali metal carbonate; (iv) an aspect in which the positive electrode active material layer contains an alkali metal carbonate, and an intermediate layer is present between the positive electrode active material layer and the separator, the intermediate layer containing both an alkali metal carbonate and a carbon material; (v) an aspect in which the positive electrode active material layer contains a carbon material, and an intermediate layer is present between the positive electrode active material layer and the separator, the intermediate layer containing both an alkali metal carbonate and a carbon material. (vi) An embodiment in which the positive electrode active material layer contains an alkali metal carbonate, and an intermediate layer is present between the positive electrode active material layer and the separator, the intermediate layer containing a carbon material. (vii) An embodiment in which the positive electrode active material layer contains a carbon material, and an intermediate layer is present between the positive electrode active material layer and the separator, the intermediate layer containing an alkali metal carbonate.(viii) An embodiment in which an intermediate layer is present between the positive electrode active material layer and the separator, and the intermediate layer contains both an alkali metal carbonate and a carbon material. (ix) An embodiment in which the positive electrode active material layer contains both an alkali metal carbonate and a carbon material, and an intermediate layer is present between the positive electrode active material layer and the separator, and the intermediate layer contains both an alkali metal carbonate and a carbon material.

[0017] The carbon material has an oxygen atomic weight X calculated from carbon monoxide and / or carbon dioxide when measured by temperature programmed desorption-mass spectrometry (hereinafter also simply referred to as "TPDMS") of 0.1 mmol / g or more per mass of the carbon material. The amount of carbon material in the layer containing the carbon material, of the positive electrode active material layer and the intermediate layer (if present), is 0.3 mass% or more and 15 mass% or less, based on the total mass of the layers containing the carbon material. When both the positive electrode active material layer and the intermediate layer contain the carbon material, it is preferable that the positive electrode active material layer and the intermediate layer each satisfy the above-mentioned range of the carbon material content.

[0018] In a second embodiment, there are provided a positive electrode precursor including a positive electrode active material layer, a non-aqueous lithium storage element precursor including the positive electrode precursor, a doping method for the non-aqueous lithium storage element precursor, a lithium ion secondary battery using the same, and a method for manufacturing a lithium ion secondary battery.

[0019] In a third embodiment, there are provided a lithium storage element precursor, a doping method for the lithium storage element precursor using the same, and a lithium ion secondary battery and a manufacturing method for the lithium ion secondary battery using the same. In the third embodiment, the state of the electrode body before pre-doping described below is defined as a "lithium ion secondary battery precursor", and the state after pre-doping is defined as a "lithium ion secondary battery".

[0020] The configurations of the first, second, and third embodiments are interchangeable or can be combined. Preferred configurations and common configurations of the first, second, and third embodiments will be described below.

[0021] <Positive electrode and positive electrode precursor> The positive electrode in the first embodiment is formed by pre-doping a negative electrode precursor with alkali metal ions in a non-aqueous alkali metal energy storage element precursor containing a positive electrode precursor, in the production of an energy storage element described later. As a pre-doping method in this embodiment, it is preferable to assemble an energy storage element precursor using a positive electrode precursor, a negative electrode precursor, a separator, and a non-aqueous electrolyte solution, and then apply a voltage between the positive electrode precursor and the negative electrode precursor.

[0022] The positive electrode in the second embodiment is formed by pre-doping a negative electrode precursor with lithium ions in a positive electrode precursor containing a positive electrode active material and a pre-dope material, as described below, during the production of an energy storage device. As a pre-doping method in the second embodiment, a positive electrode precursor, a negative electrode precursor, a separator, and a non-aqueous electrolyte are preferably used to assemble an energy storage device precursor, and then a voltage is applied between the positive electrode precursor and the negative electrode precursor. From the viewpoint of pre-doping reaction efficiency, it is preferable that the pre-dope material be contained in a state where it is mixed with the positive electrode active material in a positive electrode active material layer formed on the positive electrode current collector of the positive electrode precursor.

[0023] The positive electrode in the third embodiment is formed by pre-doping a negative electrode precursor with lithium ions during the production of an energy storage device, as described below. As a pre-doping method in the third embodiment, it is preferable to assemble an energy storage device precursor using a positive electrode precursor, a negative electrode precursor, a separator, and a non-aqueous electrolyte solution, and then apply a voltage between the positive electrode precursor and the negative electrode precursor.

[0024] The positive electrode precursor according to the first embodiment has a positive electrode active material layer containing a positive electrode active material. The positive electrode precursor may include an alkali metal carbonate and a carbon material in the positive electrode active material layer or in an intermediate layer between the positive electrode active material layer and the separator. Preferably, the positive electrode precursor includes the carbon material and the alkali metal carbonate in the positive electrode active material layer.

[0025] The positive electrode precursor in the first embodiment may have a positive electrode current collector and a positive electrode active material layer present on one or both sides thereof so as to constitute a positive electrode of an alkali metal ion secondary battery. The positive electrode precursor of the first embodiment constitutes a positive electrode after assembling an electric storage device and pre-doping. As described below, in this embodiment, it is preferable to pre-dope alkali metal ions from an alkali metal carbonate into an anode precursor in the manufacturing process of the electric storage device. A preferred pre-doping method is to assemble an electric storage device precursor using the positive electrode precursor of the first embodiment, an anode precursor, a separator, an outer casing, and a non-aqueous electrolyte solution, and then apply a voltage between the positive electrode precursor and the anode precursor and charge the precursor to a voltage at which an oxidation reaction of the alkali metal carbonate occurs.

[0026] The positive electrode precursor in the second embodiment has a positive electrode active material layer containing a positive electrode active material and a pre-dope material other than the positive electrode active material. The positive electrode precursor in the second embodiment may have a positive electrode current collector and a positive electrode active material layer present on one or both sides thereof so as to form a positive electrode of an alkali metal ion secondary battery. The positive electrode precursor in the second embodiment forms a positive electrode after assembling an energy storage device and pre-doping. As described below, in the second embodiment, it is preferable to pre-dope the negative electrode precursor with alkali metal ions from the pre-dope material during the manufacturing process of the energy storage device. A preferred pre-doping method is to assemble an energy storage device precursor using the positive electrode precursor of the second embodiment, a negative electrode precursor, a separator, an outer casing, and a non-aqueous electrolyte solution, and then apply a voltage between the positive electrode precursor and the negative electrode precursor and charge the precursor to a voltage at which an oxidation reaction of the pre-dope material occurs.

[0027] The positive electrode precursor in the third embodiment has a positive electrode active material layer containing a positive electrode active material. 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. In the third embodiment, in the manufacturing process of the energy storage device, it is preferable to pre-dope the negative electrode precursor with alkali metal ions from the pre-dope material contained in the pre-dope material layer. As a pre-doping method, a method is desirable in which a energy storage device precursor is assembled using the positive electrode precursor of the third embodiment, a negative electrode precursor, a separator, a pre-dope material layer present between the positive electrode and the separator, an outer casing, and a non-aqueous electrolyte solution, and then a voltage is applied between the positive electrode precursor and the negative electrode precursor, and charging is performed up to a voltage at which an oxidation reaction of the pre-dope material occurs.

[0028] (Positive Electrode Active Material Layer) The positive electrode active material layer contains a positive electrode active material that occludes and releases alkali metal ions, and may further contain optional components such as a conductive filler, a binder, and a dispersion stabilizer, as necessary.

[0029] The positive electrode active material layer in the first embodiment may contain a carbon material and an alkali metal carbonate, which will be described later.

[0030] The positive electrode active material layer in the second embodiment contains a pre-dope material other than the positive electrode active material.

[0031] (Positive electrode active material) The positive electrode active material in the first, second, or third embodiment absorbs and releases alkali metal ions. Known materials used in known non-aqueous alkali metal storage elements can be used as the positive electrode active material that absorbs and releases alkali metal ions. For example, a material containing an alkali metal and at least one transition metal is preferred. Particularly preferred examples of such compounds include alkali metal-containing transition metal oxides and alkali metal-containing transition metal phosphate compounds. Two types of positive electrode active materials may be mixed and used.

[0032] The positive electrode active material is not particularly limited. Positive electrode active materials used in known alkali metal storage elements can be used. Examples of positive electrode active materials containing an alkali metal and at least one transition metal include materials containing at least one element selected from the group consisting of cobalt, nickel, manganese, iron, vanadium, and chromium.

[0033] Specifically, when the alkali metal is lithium, for example, Li ｘ CoO ２ , Li ｘ NiO ２ , Li ｘ Ni ｙ M （１－ｙ） O ２ (M is at least one element selected from the group consisting of Co, Mn, Al, Fe, Mg, and Ti, and y satisfies 0.2<y<0.97), Li ｘ Ni １／３ Co １／３ Mn １／３ O ２ , Li ｘ MnO ２ , α-Li ｘ FeO ２ , Li ｘ VO ２ , Li ｘ CrO ２ , Li ｘ FePO ４ , LiMn ｘ Fe １－ｘ P.O. ４ , Li ｘ Mn ２ O ４ , Li ｘ M ｙ Mn （２－ｙ） O ４ (M is at least one element selected from the group consisting of Co, Mn, Al, Fe, Mg, and Ti, and y satisfies 0.2<y<0.97), Li ｘ Ni ａ Co ｂ Al （１－ａ－ｂ） O ２ (a and b satisfy 0.2<a<0.97, 0.2<b<0.97), Li ｘ Ni ｃ Co ｄ Mn（１－ｃ－ｄ） O ２ (c and d satisfy 0.2<c<0.97, 0.2<d<0.97) (x satisfies 0≦x≦1) etc. Specific representative examples include LiCoO ２ (LCO), LiFePO ４ (LFP), LiMn ０．６ Fe ０．４ P.O. ４ (LMFP), LiNi １／３ Co １／３ Mn １／３ O ２ (NCM111), LiNi ０．８ Co ０．１５ Al ０．０５ O ２ (NCA), LiMn ２ O ４ (LMO), etc. can be suitably used.

[0034] Specifically, when the alkali metal is sodium, other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may be used. These materials may include sodium transition metal oxides, polyanion compounds, and Prussian blue compounds. In the sodium transition metal oxides, the transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The sodium transition metal oxide may be, for example, Na ｘ MO ２ where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr, and Cu, and 0<x≦1. The polyanionic compound contains sodium ions, transition metal ions, and tetrahedral (YO ４ ) ｎ － The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y may be at least one of P, S, and Si, and n may be any of (YO ４ ) ｎ － The polyanionic compound also contains sodium ions, transition metal ions, tetrahedral ions (YO ４ )ｎ－ The anionic unit may be a compound such as a halogen anion. The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y may be at least one of P, S, and Si, and n may be (YO ４ ) ｎ － The halogen may be at least one of F, Cl, and Br. The polyanionic compound also contains sodium ions, tetrahedral (YO ４ ) ｎ － Anionic unit, polyhedral unit (ZO ｙ ) ｍ ＋ and a compound having a selectable halogen anion. Y may be at least one of P, S, and Si, and n may be (YO ４ ) ｎ－ Z represents a transition metal and may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, and m represents a valence of (ZO ｙ ) ｍ ＋ The halogen may be at least one of F, Cl, and Br. The polyanion compound is, for example, NaFePO ４ , Na ３ V ２ (P.O. ４ ) ３ , NaM'PO ４ F (wherein M' is one or more of V, Fe, Mn, and Ni) and Na ３ (VO ｙ ) ２ (P.O. ４ ) ２ F ３ － ２ ｙ (wherein 0≦y≦1). The Prussian blue compound is at least one of sodium ions, transition metal ions, and cyanide ions (CN －The transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The Prussian blue compound may be, for example, a compound having Na ａ Me ｂ Me' ｃ (CN) ６ wherein Me and Me′ are each independently at least one of Ni, Cu, Fe, Mn, Co, and Zn, and 0<a≦2, 0<b<1, and 0<c<1.

[0035] In addition, in the first embodiment, the alkali metal carbonate serves as a dopant source for the alkali metal during pre-doping, allowing the negative electrode to be pre-doped. Therefore, even if the transition metal compound does not already contain an alkali metal (i.e., even if x = 0), the element can be used as a non-aqueous alkali metal type storage element for electrochemical charging and discharging.

[0036] 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 therefore the capacity per electrode volume tends to be high. When the average particle diameter of the positive electrode active material is small, durability may be reduced, but when the average particle diameter is 0.1 μm or more, durability is less likely to be reduced. When the average particle diameter of the positive electrode active material is 20 μm or less, it tends to be more suitable for high-speed charging and discharging. The average particle diameter of the positive electrode active material is more preferably 1 to 15 μm, and even more preferably 1 to 10 μm.

[0037] The content of the positive electrode active material in the positive electrode active material layer is preferably 35% by mass or more and 98% by mass or less, based on the total mass of the positive electrode active material layer in the positive electrode precursor. The lower limit of the content of the positive electrode active material is more preferably 45% by mass or more, and even more preferably 55% by mass or more. The upper limit of the content of the positive electrode active material is even more preferably 95% by mass or less. By having the content of the positive electrode active material in the positive electrode active material layer be 35% by mass or more and 95% by mass or less, favorable charge / discharge characteristics are exhibited.

[0038] (Stable operating potential of positive electrode and stable operating voltage of battery according to positive electrode active material) The potential region of a positive electrode in which a positive electrode active material can be stably used is called the "stable operating potential", and the voltage region of a battery (full cell) in which a positive electrode active material can be stably used is called the "stable operating voltage". The "upper limit of stable operating potential" and the "upper limit of stable operating voltage" vary depending on the type of positive electrode active material, but generally, the potential and voltage ranges in which a positive electrode active material can be stably used are determined by performing a charge / discharge cycle of a non-aqueous alkali metal storage element. The "lower limit of stable operating potential" and the "lower limit of stable operating voltage" are the potential and voltage at which the alkali metal ions are fully loaded in the positive electrode and almost no further discharge capacity is obtained. Below, the upper limits of the stable operating potential and stable operating voltage are shown for preferred specific examples of positive electrode active materials. LiCoO ２ (LCO): Upper limit of stable operating potential 4.3 V (vs. Li / Li ＋ ), the upper limit of stable operating voltage is 4.2V LiFePO ４ (LFP): Upper limit of stable operating potential 3.7 V (vs. Li / Li ＋ ), the upper limit of stable operating voltage is 3.6V LiMn ０．６ Fe ０．４ P.O. ４ : Upper limit of stable operating potential 4.3 V (vs. Li / Li ＋ ), the upper limit of stable operating voltage is 4.2V LiNi １／３ Co １／３ Mn １／３ O ２ (NCM111): Upper limit of stable operating potential 4.3 V (vs. Li / Li ＋ ), the upper limit of stable operating voltage is 4.2V LiNi ０．８ Co ０．１５ Al ０．０５ O ２ (NCA): Upper limit of stable operating potential 4.3 V (vs. Li / Li ＋ ), the upper limit of stable operating voltage is 4.2V LiMn ２ O ４ (LMO): Upper limit of stable operating potential 4.3 V (vs. Li / Li ＋ ), the upper limit of stable operating voltage is 4.2V NaFe １／３ Ni １／３ Mn １／３ O ２ : Upper limit of stable operating potential 4.0 V (vs. Na / Na＋ ), the upper limit of stable operating voltage is 3.9V

[0039] The upper limits of the stable operating potential and stable operating voltage for a positive electrode active material are not particularly limited, but can be determined, for example, by the following method. A battery containing a positive electrode half-cell containing an unknown positive electrode active material as the working electrode, an alkali metal as the counter electrode and reference electrode, and an electrolyte described below is charged at a constant current (cc) equivalent to 0.1 C until the potential of the positive electrode half-cell reaches a predetermined upper limit potential. At this voltage, the battery is charged at a constant voltage (CV) until the current reaches 0.03 C, and then discharged at a constant current (cc) to a lower limit potential. This cycle test is performed for 10 cycles. The upper limit of the stable operating potential is determined as the upper limit of the stable operating potential, at which the discharge capacity of the positive electrode half-cell reaches a specific value (e.g., 95%) of the initial discharge capacity. The upper limit of the stable operating voltage is determined by subtracting the operating potential of the negative electrode used in the full cell. The electrolyte for a nonaqueous alkali metal storage element can be an electrolyte commonly used in alkali metal ion batteries or alkali metal ion capacitors. The non-aqueous electrolyte preferably contains an alkali metal salt as an electrolyte in an amount of 0.5 mol / L or more based on the total amount of the non-aqueous electrolyte. As the alkali metal salt of the electrolyte, an electrolyte generally used in non-aqueous alkali metal storage elements can be used. When the alkali metal is lithium, LiFSI, LiBFq ４ , LiPF ６ , LiCiO ４ , LiTFSI, etc. can be used alone or in combination of two or more. When the alkali metal is sodium, Na(SO ２ CF ３ ) ２ , NaN(SO ２ F) ２ , NaN(C ２ F ５ SO ２ ) ２ , NaCF ３ SO ３ , NaC(CF ３ SO ２ ) ３ , NaPF ６, NaBF ４ , NaClO ４ , NaAsF ６ , NaAlCl ４ These may be used alone or in combination of two or more.

[0040] The stable operating potential and the lower limit of the stable operating voltage for each of the preferred specific examples of the positive electrode active material are shown below. ２ (LCO): Lower limit of stable operating potential 3.1 V, lower limit of stable operating voltage 3.0 V LiFePO ４ (LFP): Lower limit of stable operating potential 2.5V, lower limit of stable operating voltage 2.4V LiMn ０．６ Fe ０．４ P.O. ４ (LMFP): Lower limit of stable operating potential 2.5V, lower limit of stable operating voltage 2.4V LiNi １／３ Co １／３ Mn １／３ O ２ (NCM111): Lower limit of stable operating potential 3.1V, lower limit of stable operating voltage 3.0V LiNi ０．８ Co ０．１５ Al ０．０５ O ２ (NCA): Lower limit of stable operating potential 3.1 V, lower limit of stable operating voltage 3.0 V LiMn ２ O ４ (LMO): Lower limit of stable operating potential 3.1 V, lower limit of stable operating voltage 3.0 V NaFe １／３ Ni １／３ Mn １／３ O ２ : Lower limit of stable operating potential 2.0 V (vs. Na / Na ＋ ), the upper limit of stable operating voltage is 1.9V

[0041] (Particle size D50) The average particle diameter of the positive electrode active material and pre-dope material in the second and third embodiments refers to the particle diameter at the point where the cumulative curve is 50% when the particle size distribution is measured using a particle size distribution measurement device and the cumulative curve is calculated assuming the total volume to be 100% (i.e., 50% diameter (median diameter)). This average particle diameter can be measured using a commercially available laser diffraction particle size distribution measurement device. When determining the average particle diameter of the positive electrode active material and pre-dope material formed into an electrode in this embodiment, multiple fields of view of the surface and / or cross section of the obtained electrode are photographed using an electron microscope, and the active material and pre-dope material are selected using energy dispersive X-ray analysis (SEM-EDX) or the like. The particle diameters of approximately 2,000 to 3,000 particles of the positive electrode active material and pre-dope material in those fields of view are measured using a fully automatic image processing device or the like, and the arithmetic average value of these is determined as the average particle diameter.

[0042] (A1, A2, B2, R1, R2) In the second embodiment, when the initial charge capacity density of the active material is A1 (mAh / g), D50 of the positive electrode active material is R1 (μm), the initial charge capacity density of the pre-dope material is A2 (mAh / g), the initial discharge capacity density of the pre-dope material is B2 (mAh / g), and D50 of the pre-dope material is R2 (μm), the following formulas are satisfied: A2 / A1>1.2, B2 / A2<0.3, and 0.25<(R1×A1) / (R2×A2)<2.

[0043] When B2 / A2<0.3, the pre-dope material has a large irreversible capacity and therefore functions effectively as a pre-dope material. When A2 / A1>1.2, the capacity density of the pre-dope material is sufficiently higher than that of the positive electrode active material, so by using the pre-dope material, the capacity density of the lithium ion secondary battery can be increased while compensating for the irreversible capacity of the negative electrode. A more preferable lower limit of A2 / A1 is 1.44. However, when a pre-dope material having a higher capacity density than the positive electrode active material is used, the charge-discharge cycle durability is insufficient.

[0044] In the second embodiment, (R1×A1) / (R2×A2) is greater than 0.25 and less than 2. More preferably, the lower limit is greater than 0.4 and the upper limit is less than 1.5. Under these conditions, the battery exhibits good charge-discharge cycle durability.

[0045] Without being bound by theory, the pre-dope material is generally used in an amount sufficient to compensate for the irreversible capacity of the negative electrode, and therefore its presence ratio in the positive electrode composite is generally designed to be low. The negative electrode portion opposite the portion where the pre-dope material particles are present in the positive electrode receives excess lithium compared to the portion opposite the portion where the pre-dope material particles are not present, resulting in localized unevenness in the doping amount of the negative electrode. The inventors speculate that this causes localized lithium deposition during cycle testing and accelerates degradation. Therefore, the inventors discovered that if (R1 × A1) / (R2 × A2) is greater than 0.25, the particle size of the pre-dope material becomes smaller depending on the relative capacity density with the positive electrode active material, thereby reducing localized lithium concentration differences. Reducing localized lithium concentration differences makes the in-plane load of the negative electrode more uniform, resulting in good cycle durability. If (R1×A1) / (R2×A2) is greater than 2, the particle size is too small, so the pre-dope material is distributed throughout the positive electrode active material layer, and therefore, vacancies are generated throughout the positive electrode active material layer due to the decomposition reaction of the pre-dope material during initial charging. As a result, the positive electrode is likely to become embrittled due to expansion and contraction during charging and discharging, and in this case, durability is reduced.

[0046] The particle size R2 of the pre-dope material is preferably 9 μm or less, since this tends to make it difficult to impede electrical conduction between the positive electrode active materials, and therefore is desirable because it can reduce the volume resistivity of the active material layer.

[0047] (Initial Charge Capacity Density A1 and Initial Discharge Capacity Density B1 of Positive Electrode Active Material) The initial charge capacity A1 of this embodiment is obtained by measuring the charge capacity when a half cell consisting of a positive electrode active material, a binder, and a conductive material prepared using a known electrode preparation process for alkali metal ion secondary batteries, an alkali metal counter electrode, and a known separator is charged at a constant current of 0.1 C rate to the upper limit of the stable operating potential at a 25°C environment, and then constant voltage charging is performed until the current converges to a 0.03 C rate. The initial discharge capacity B2 of the positive electrode active material of this embodiment is obtained by measuring the discharge capacity when a constant current discharge is performed at a 0.1 C rate to the lower limit of the stable operating potential after a 10-minute pause following the completion of the constant voltage charge at the upper limit of the stable operating voltage. The positive electrode single-electrode capacity densities A1 and B1 (mAh / g) can be obtained by further dividing the obtained charge capacity and discharge capacity by the mass of the positive electrode active material used.

[0048] The upper limit of the stable operating potential and the upper limit of the stable operating voltage vary depending on the positive electrode active material, but may be a commonly known potential or voltage. For example, the upper limit of the stable operating potential may be measured using 3.7 V vs. lithium for LFP, 4.3 V for LCO, 4.3 V for NCM111, 4.3 V for NCA, or 4.3 V for LMO.

[0049] In the first embodiment, the alkali metal carbonate is contained in the positive electrode active material layer of the positive electrode precursor or in the intermediate layer between the positive electrode active material layer and the separator of the nonaqueous alkali metal electric storage element precursor. The alkali metal carbonate decomposes in the nonaqueous alkali metal electric storage element precursor to release alkali metal ions, which can be reduced at the negative electrode to perform pre-doping.

[0050] When the positive electrode active material layer contains an alkali metal carbonate, the content is preferably 0.2% by mass or more and 15% by mass or less. The lower limit is more preferably 0.5% by mass, and even more preferably 2% by mass or more. The upper limit is more preferably 10% by mass or less, and even more preferably 8% by mass or less. If the content is 0.2% by mass or more, the effect of pre-doping can be obtained, and if it is 15% by mass or less, the decrease in the density of the active material in the positive electrode active material layer can be suppressed, and the doping efficiency (mAh / cc) is excellent.

[0051] When the alkali metal carbonate is contained in the intermediate layer between the positive electrode active material layer and the separator, the content is preferably 20% by mass or more and 95% by mass or less, which can obtain the effect of pre-doping without impairing the energy density of the energy storage element and can provide excellent doping efficiency (mAh / cc).

[0052] (Pre-dope material) In the second embodiment, when the initial charge capacity density of the positive electrode active material is A1 (mAh / g), the D50 of the positive electrode active material is R1 (μm), the initial charge capacity density of the pre-dope material is A2 (mAh / g), the initial discharge capacity density of the pre-dope material is B2 (mAh / g), and the D50 of the pre-dope material is R2 (μm), a material that satisfies A2 / A1>1.2 and B2 / A2<0.3 is used as the pre-dope material.

[0053] For example, Li ｘ AO ｙ (wherein x / y>0.5, A is at least one element selected from the group consisting of Fe, Mn, Co, Ni, and Cu). ５ FeO ４ , Li ６ CoO ４ , Li ２ NiO ４ , Li ６ MnO ４ and the like are preferably used. ｃ TiO ｄ (In the formula, 1.5≦c≦2.3, 2.7≦d≦3.5), Li ｅ TiO ｆ (wherein 3.5≦e≦4.5, 3.7≦f≦4.8) ４ TiO ４ , Li２ TiO ３ can be used. １＋ｘ (Ti １－ｙ Fe ｙ ) １－ｘ O ２ [wherein x satisfies 0<x≦0.25, and y satisfies 0.4<y≦0.9]. １．２ (Ti ０．５ Fe ０．５ ) ０．８ O ２ etc. can be used.

[0054] In the pre-doping step, the pre-dope material decomposes in the positive electrode precursor to release alkali metal ions, and the alkali metal ions can be doped into the negative electrode precursor. The pre-dope material is preferably present in the positive electrode active material layer at 0.3 mass% to 10 mass%. Within this range, the pre-dope material can compensate for the irreversible capacity of the negative electrode, and the capacity density of the alkali metal ion secondary battery can be easily improved.

[0055] The particle size of the pre-dope material can be adjusted by various methods, for example, by using a grinder such as a ball mill, a bead mill, a ring mill, a jet mill, or a rod mill.

[0056] The average particle size of the pre-dope material is preferably 0.1 μm or more and 9 μm or less. If it is 0.1 μm or more, it has excellent dispersibility in the positive electrode precursor. If it is 9 μm or less, the pre-dope reaction proceeds efficiently.

[0057] (Initial charge capacity density A2 and initial discharge capacity density B2 of the pre-dope material) The initial charge capacity density A2 of the pre-dope material of this embodiment is obtained by preparing a positive electrode precursor consisting of a pre-dope material, a binder, and a conductive material using a known electrode preparation process for alkali metal ion secondary batteries, and then charging a half cell consisting of an alkali metal counter electrode and a known separator at a constant current of 0.1 C rate to the upper limit of the operating potential in a 25 ° C environment, and then measuring the charge capacity when constant voltage charging is performed until the current converges to a 0.03 C rate. The initial discharge capacity B2 of the pre-dope material of this embodiment is obtained by measuring the discharge capacity when constant current discharging is performed at a 0.1 C rate to 3.0 V after a 10-minute pause after the completion of the constant voltage charging at the upper limit of the operating potential. Furthermore, the pre-dope material capacity densities A2 and B2 (mAh / g) can be obtained by dividing the obtained charge capacity and discharge capacity by the mass of the pre-dope material used.

[0058] In the present disclosure, the potential region where the pre-dope material decomposes and releases alkali metal ions produces a reaction capacity is referred to as the "operating potential" of the pre-dope material. The "lower limit of the operating potential" is the potential at which the release of alkali metal ions begins, and the "upper limit of the operating potential" is the potential at which the release of alkali metal ions ends (no reaction capacity is produced). Note that the upper limit of the operating potential of the capacity recovery material is measured up to the potential region where no reaction capacity is produced, and therefore varies depending on the type of capacity recovery material. Below, the upper limit of the operating potential of preferred specific examples of capacity recovery materials is shown. Li ５ FeO ４ : Upper limit of operating potential 4.2V, upper limit of operating voltage 4.1V Li ６ CoO ４ : Upper limit of operating potential 4.3V, upper limit of operating voltage 4.2V Li ２ NiO ４ : Upper limit of operating potential 4.5V, upper limit of operating voltage 4.4V Li ６ MnO ４ : Upper limit of operating potential 4.8V, upper limit of operating voltage 4.7V Li １．２ (Ti ０．５ Fe ０．５ ) ０．８ O ２ So, the upper limit of the operating potential is 4.3V, and the upper limit of the operating voltage is 4.2V.４ TiO ４ : Upper limit of operating potential 4.0 V, upper limit of operating voltage 3.9 V Li ２ TiO ３ : Upper limit of operating potential 4.0 V, upper limit of operating voltage 3.9 V

[0059] (Method for Identifying Pre-Dope Material) The qualitative analysis method for the pre-dope material contained in the positive electrode active material layer can be a known analytical method, and is not particularly limited, but can be identified by, for example, the following method. For example, general methods such as SEM-EDX, X-ray photoelectric spectroscopy (XPS), and X-ray diffraction (XRD) can be used.

[0060] The amount of alkali metal carbonate in the positive electrode active material layer and the intermediate layer can be measured by ion chromatography.

[0061] (Carbon Material) In a first embodiment, the carbon material contains a carbon material having an oxygen atomic weight X calculated from carbon monoxide and / or carbon dioxide when measured by temperature-programmed desorption-mass spectrometry (TPDMS), of 0.1 mmol / g or more per mass of the carbon material. When an alkali metal carbonate is added to a system containing an alkali metal transition metal oxide as the primary active material to carry out a decomposition reaction, a high overvoltage is typically required. This requires a high voltage of over 4.7 V to be applied between the positive electrode precursor and the negative electrode. This can lead to problems such as damage to the electrolyte, increased resistance, gas generation during high-temperature storage, and destruction of the structure of the alkali metal transition metal oxide positive electrode active material, resulting in a reduction in the positive electrode utilization rate. Furthermore, due to the low decomposition efficiency of alkali metal carbonate, it is difficult to obtain the effect of pre-doping for negative electrodes using active materials with low irreversible capacity (e.g., graphite). The inventors have discovered that by adding the specific carbon material, the decomposition overvoltage of the alkali metal carbonate can be lowered, and the decomposition reaction can be favorably promoted even at a relatively low voltage. Without being limited by theory, it is speculated that these carbon materials have high electrical conductivity, which is a characteristic of carbon materials, and contain many oxygen atoms at the edges of the graphite, which increases the reactivity of the electrolyte, etc., and reduces the decomposition overvoltage of alkali metal carbonate. It has been found that this is highly effective even for negative electrodes using active materials with small irreversible capacity (e.g., graphite).

[0062] Examples of a method for adjusting the oxygen atom amount X calculated from carbon monoxide and carbon dioxide when measuring a carbon material with TPDMS to 0.1 mmol / g or more per mass of the carbon material include a method using a highly amorphous carbon material with a high oxygen atom content (e.g., Knobel manufactured by Toyo Tanso) and a method for adjusting the oxygen content by subjecting a known carbon material to an acid treatment.

[0063] The composition ratio of the carbon material having a carbon atom content X of 0.1 mmol / g or more per mass of the carbon material in the positive electrode active material layer is preferably 0.3 mass% or more and 15 mass% or less, based on the total mass of the layer containing the carbon material. The lower limit is more preferably 1 mass%, and even more preferably 2 mass% or more. The upper limit is more preferably 10 mass% or less, and even more preferably 6 mass% or less. When the carbon material having a carbon atom content of 0.1 mmol / g or more is 0.3 mass% or more and 15 mass% or less, the doping reaction can proceed under relatively mild conditions of a cell voltage of 4.6 V or less, and the amount of carbon material added is not too large, thereby improving the doping efficiency per volume and the positive electrode utilization rate described below. Furthermore, since pre-doping is possible under mild conditions, low resistance and cell swelling during storage at 40°C can be suppressed.

[0064] Without being limited by theory, it is speculated that carbon materials containing a specified amount of oxygen have high conductivity and contain an appropriate amount of oxygen atoms at the edges of the graphite, which increases the reactivity of electrolytes and reduces the decomposition overvoltage of alkali metal carbonates, thereby accelerating the decomposition reaction of alkali metal carbonates at relatively low voltages. Therefore, since there is no need to apply a high voltage during pre-doping, it is believed that damage to the positive electrode and electrolyte is reduced, the effective utilization rate of the positive electrode active material is increased, initial resistance is reduced, and gas generation at high temperatures is suppressed. Furthermore, because the decomposition efficiency of alkali metal carbonates and the like is increased, the effect can be obtained even with a negative electrode that uses only graphite as the active material, which has a low irreversible capacity.

[0065] The composition ratio of the carbon material having X of 0.1 mmol / g or more per mass of the carbon material in the intermediate layer between the positive electrode active material layer and the separator is preferably 0.3 mass% or more and 15 mass% or less, based on the total mass of the layers containing the carbon material. The lower limit is more preferably 1 mass%, and even more preferably 2 mass% or more. The upper limit is more preferably 10 mass% or less, and even more preferably 6 mass% or less. When the carbon material having X of 0.1 mmol / g or more is 0.3 mass% or more and 15 mass% or less, the doping reaction can proceed under relatively mild conditions of a cell voltage of 4.6 V or less, and the amount of carbon material added is not too large, thereby improving the doping efficiency per volume and the positive electrode utilization rate described below. Furthermore, since pre-doping is possible under mild conditions, low resistance and cell swelling during high-temperature storage can be suppressed.

[0066] The carbon material in which X is 0.1 mmol / g or more per mass of the carbon material is preferably contained in the same layer as the alkali metal carbonate from the viewpoint of promoting the pre-doping reaction.

[0067] The specific surface area of ​​a carbon material in which X is 0.1 mmol / g or more per mass of the carbon material, as determined by the BET multipoint method, is ２ / g or more 1800m ２ Within this range, the increase in volume caused by adding a carbon material in which X is 0.1 mmol / g or more per mass of the carbon material can be kept small, and the pre-doping volumetric efficiency can be increased.

[0068] (TPDMS Measurement of Carbon Material) In the TPDMS measurement, the carbon material is heated in a heating furnace at a constant temperature increase rate, and the desorbed gas derived from the generated functional groups is flowed as a carrier gas and qualitatively and quantitatively analyzed by GC / MS. In this embodiment, the carbon material is heated from 50°C to 1000°C at a temperature increase rate of 20°C / min using helium as a carrier gas, and CO desorbed from the carbon material is analyzed. ２ The amount of CO was quantitatively analyzed. This was converted into the number of oxygen atoms, and used as an index of the amount of oxygen contained in the carbon material, based on the mass of the carbon material sample. Generally, residual moisture and H derived from the carboxyl group of the carbon material are included. ２Although O gas is also desorbed, the amount of residual moisture varies greatly depending on the state of the carbon material, making it difficult to distinguish it from oxygen derived from carboxyl groups. Therefore, in this embodiment, O gas is excluded from the oxygen content of the carbon material. Among carbons having the above characteristics, activated carbon, carbon black, Ketjenblack, and Knobel are preferred from the viewpoints of handling and production costs.

[0069] (Isolation of Carbon Material from Non-Aqueous Alkali Metal Energy Storage Element) To isolate a carbon material from a non-aqueous alkali metal energy storage element, known separation techniques can be used. For example, an active material layer or an alkali metal carbonate layer can be scraped off from a current collector foil or separator substrate, subjected to ultrasonic cleaning or the like in a solvent to separate as many constituent particles as possible, and then separated by specific gravity by centrifugation or the like. The isolated carbon material may be subjected to the above-mentioned TPDMS measurement.

[0070] (Optional Components) The positive electrode active material layer in this embodiment may contain optional components such as a conductive filler and a binder, as needed.

[0071] The conductive filler in this embodiment is not particularly limited, and examples thereof include carbon black, acetylene black, ketjen black, vapor-grown carbon fiber, graphite, carbon nanotubes, and mixtures thereof. The amount of conductive filler used is preferably more than 0 parts by mass and less than 30 parts by mass, more preferably more than 0 parts by mass and less than 25 parts by mass, and even more preferably 1 part by mass and less than 20 parts by mass, relative to 100 parts by mass of the positive electrode active material. A mixed amount of 30 parts by mass or less increases the content of the positive electrode active material in the positive electrode active material layer, thereby ensuring a high energy density per volume of the positive electrode active material layer. In the first embodiment, a carbon material having an oxygen atomic weight X calculated from carbon monoxide and carbon dioxide when measured with TPDMS, as described above, of 0.1 mmol / g or more per mass of the carbon material can also be used as the conductive filler. This eliminates the need to add extra components to the positive electrode active material layer, which is preferable from the perspective of energy density.

[0072] The binder in this embodiment is not particularly limited, and examples thereof include PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, and acrylic copolymer. The amount of binder used is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 1 part by mass or more and 15 parts by mass or less, and even more preferably 1 part by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the positive electrode active material. If the amount of binder is 1% by mass or more, sufficient electrode strength is achieved. On the other hand, if the amount of binder is 30 parts by mass or less, the ingress and egress of ions into and diffusion from the positive electrode active material are not hindered, and high input / output characteristics are achieved.

[0073] (Positive electrode current collector) The material for the positive electrode current collector in this embodiment is not particularly limited as long as it has high electronic conductivity and is not susceptible to deterioration due to elution in the electrolytic solution or reaction with the electrolyte or ions, etc., but metal foil is preferred. Aluminum foil is particularly preferred as the positive electrode current collector for the nonaqueous alkali metal energy storage element of this embodiment.

[0074] The metal foil may be a normal metal foil without irregularities or through holes, or may be a metal foil with irregularities that has been subjected to embossing, chemical etching, electrolytic deposition, blasting, or the like, or may be a metal foil with through holes such as expanded metal, punched metal, or etched foil.

[0075] The thickness of the positive electrode current collector is not particularly limited as long as it can sufficiently maintain the shape and strength of the positive electrode, but is preferably 1 to 100 μm, for example.

[0076] (Production of Positive Electrode Precursor) The positive electrode precursor has a positive electrode active material layer on one or both surfaces of a positive electrode current collector. Typically, the positive electrode active material layer is fixed to one or both surfaces of the positive electrode current collector.

[0077] In the first embodiment, the positive electrode precursor can be manufactured using known electrode manufacturing techniques for alkali metal ion batteries, electric double layer capacitors, and the like to form a positive electrode. For example, when the positive electrode precursor contains a positive electrode active material, the alkali metal carbonate, and a carbon material, the alkali metal carbonate and the carbon material, as well as other optional components used as needed, are dispersed or dissolved in water or an organic solvent to prepare a slurry coating liquid. This coating liquid is then applied to one or both sides of a positive electrode current collector to form a coating film, which is then dried to obtain a positive electrode precursor. The resulting positive electrode precursor may be pressed to adjust the film thickness and bulk density of the positive electrode active material layer. Alternatively, when the positive electrode precursor contains a positive electrode active material, the alkali metal carbonate, and the carbon material, without using a solvent, the alkali metal carbonate and the carbon material, as well as other optional components used as needed, may be dry-mixed, press-molded, and then attached to the positive electrode current collector using a conductive adhesive.

[0078] In the second and third embodiments, the positive electrode precursor can be manufactured using known electrode manufacturing techniques for lithium ion batteries, electric double layer capacitors, etc. to form a positive electrode. For example, a positive electrode active material, a pre-dope material as needed, and other optional components used as needed are dispersed or dissolved in water or an organic solvent to prepare a slurry coating liquid, and this coating liquid is applied to one or both sides of a positive electrode current collector to form a coating film, which is then dried to obtain a positive electrode precursor. The obtained positive electrode precursor may be pressed to adjust the film thickness and bulk density of the positive electrode active material layer. Alternatively, a method is also possible in which the positive electrode active material, the pre-dope material, and other optional components used as needed are dry mixed without using a solvent, the resulting mixture is press-molded, and then attached to the positive electrode current collector using a conductive adhesive.

[0079] In the present embodiment, the formation of the coating film of the positive electrode precursor is not particularly limited, but it is preferable to use a coating machine such as a die coater, a comma coater, a knife coater, a gravure coater, etc. The coating film may be formed by single-layer coating or multi-layer coating.

[0080] The method for drying the coating film of the positive electrode precursor is not particularly limited, but preferably, a drying method such as hot air drying or infrared (IR) drying can be used.

[0081] The method for pressing the positive electrode precursor is not particularly limited, but it is preferable to use a press such as a hydraulic press, a vacuum press, etc. The film thickness, bulk density, and electrode strength of the positive electrode active material layer can be adjusted by the pressing pressure, gap, and surface temperature of the pressing part.

[0082] The thickness of the positive electrode active material layer per side of the positive electrode current collector is preferably 20 μm to 200 μm, more preferably 25 μm to 150 μm, and even more preferably 30 μm to 100 μm. A positive electrode active material layer thickness of 20 μm or more can exhibit sufficient charge / discharge capacity. A positive electrode active material layer thickness of 200 μm or less can maintain low ion diffusion resistance within the electrode. Therefore, sufficient output characteristics can be obtained, and the cell volume can be reduced, thereby increasing the energy density. Note that when the current collector has through-holes or irregularities, the thickness of the positive electrode active material layer refers to the average thickness per side of the current collector in the portion not having through-holes or irregularities.

[0083] <Positive electrode> (Alkali metal carbonate of positive electrode) The positive electrode after pre-doping preferably contains 0.02 wt% or more and 12 wt% or less of alkali metal carbonate in terms of weight ratio per weight of the active material layer of the positive electrode. The lower limit of the weight ratio is more preferably 0.1 wt% or more, and even more preferably 1 wt% or more. The upper limit of the weight ratio is more preferably 10 wt% or less, and even more preferably 7 wt% or less. Within this range, although not limited by theory, by-products generated when the alkali metal carbonate decomposes during doping are adsorbed onto the remaining alkali metal carbonate, thereby preventing deterioration of the initial resistance and storage gas characteristics at 40 ° C.

[0084] (Measurement of alkali metal carbonate in positive electrode) There are no particular limitations on the method for measuring alkali metal carbonate in the positive electrode, but it can be measured, for example, by ion chromatography as shown below. Specifically, the battery whose voltage has been adjusted is disassembled, the positive electrode is removed, and then the positive electrode is measured by ion chromatography.

[0085] 1. Battery voltage adjustment Before disassembly, the battery is adjusted to the lowest stable operating voltage. The specific method is described below. ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ When LiFePO is used as the positive electrode active material, the completed nonaqueous alkali metal storage element is charged at a constant current of 0.1 C in a thermostatic chamber set at 25° C. until the stable operating voltage upper limit, i.e., 4.2 V, is reached, followed by 30 minutes of constant voltage charging with a constant voltage of 4.2 V applied. Thereafter, the element is discharged at a constant current of 0.1 C until the stable operating voltage lower limit, i.e., 3.0 V, is reached, followed by 30 minutes of constant voltage discharge with a constant voltage of 3.0 V applied. ４ When NaFe is used as the positive electrode active material, the alkali metal ion secondary battery is charged in a thermostatic chamber set at 25°C at a constant current of 0.1 C until the stable operating voltage upper limit, i.e., 3.6 V, is reached, followed by 30 minutes of constant voltage charging with a constant voltage of 3.6 V applied. Thereafter, the battery is discharged at a constant current of 0.1 C until the stable operating voltage lower limit, i.e., 2.4 V, is reached, followed by 30 minutes of constant voltage discharge with a constant voltage of 2.4 V applied. １／３ Ni １／３ Mn １／３ O ２ When using as the positive electrode active material, an alkali metal ion secondary battery is charged in a thermostatic chamber set at 25° C. at a constant current of 0.1 C until the stable operating voltage upper limit, i.e., 3.9 V, is reached, followed by 30 minutes of constant voltage charging with a constant voltage of 3.9 V applied. Thereafter, the battery is discharged at a constant current of 0.1 C until the stable operating voltage lower limit, i.e., 1.9 V, is reached, followed by 30 minutes of constant voltage discharge with a constant voltage of 1.9 V applied.

[0086] 2. Disassembly of the Battery and Removal of the Positive Electrode The battery was disassembled in an Ar box with a dew point of -70°C or lower. In the case of a laminate, the positive electrode was cut out at a location located at 1 / 4 and 3 / 4 of the four quarters of the stacking direction, and also including the center position within the electrode surface. In the case of a flat wound body, the positive electrode was cut out at a location located at 1 / 4 and 3 / 4 of the four quarters of the number of windings, at a flat portion avoiding the bent portion, and including the center position within the electrode surface. In the case of a cylindrical wound body, the positive electrode was cut out at a location located at 1 / 2 of the cylinder's radial direction from the center and including a location located at 1 / 2 of the two quarters of the cylinder's height direction. The removed positive electrode was immersed and washed in methyl ethyl carbonate in an Ar box with a dew point of -70°C or lower, and then vacuum dried at room temperature in the Ar box to remove volatile components of the electrolyte and cleaning solvent.

[0087] 3. Quantitative analysis by ion chromatography: Approximately 5 cm ２The positive electrode active material layer is scraped off from the positive electrode, placed in a vial, and weighed. 2 mL of distilled water is added so that the scraped active material layer is completely submerged, and the current collector is immersed and extracted for three days. Extraction can be performed without peeling off the active material layer. In this case, the active material layer is removed after extraction is completed, and the current collector is weighed. This weight is subtracted from the weight of the positive electrode to calculate the weight of the active material layer. The supernatant of the extract is appropriately diluted with distilled water, and carbonate ions derived from alkali metal carbonates are measured by ion chromatography. For quantification, alkali metal carbonates are used as standards. The alkali metal carbonates are dissolved and diluted with distilled water, and ion chromatography is performed under the same conditions as for the positive electrode active material layer extract, and a calibration curve for alkali metal carbonates is created. Using this calibration curve, the concentration of alkali metal carbonates in the extract is quantified, and the weight ratio of alkali metal carbonates per weight of active material layer is calculated. Note that because carbonate ions can be contaminated from the environment, a blank value is subtracted to calculate the weight ratio of alkali metal carbonates per weight of active material layer. The ion chromatography measurement conditions are as follows: <Ion chromatography measurement conditions> Apparatus: IC-2001 manufactured by Tosoh Corporation Column: TSKgel-SCX (4.6 mm x 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

[0088] <Intermediate layer> The nonaqueous alkali metal storage element precursor of the first embodiment may include an intermediate layer containing an alkali metal carbonate, a carbon material, or both, between the positive electrode active material layer and the separator. The method for forming the intermediate layer is not particularly limited, but examples include a method in which the intermediate layer is formed by a conventional coating method on the surface of the positive electrode active material layer or on the surface of the separator that contacts the positive electrode, and then disposed between the positive electrode and the separator during formation of the electrode assembly.

[0089] The intermediate layer may contain optional components in addition to the alkali metal carbonate, such as a binder component for maintaining the shape and a conductive material for ensuring conductivity.

[0090] The alkali metal carbonate contained in the intermediate layer is preferably decomposed in a pre-doping step described below, and the negative electrode precursor is doped with alkali metal ions.

[0091] The thickness of the intermediate layer is preferably 0.3 μm or more and 10 μm or less, more preferably 0.5 μm or more and 5 μm or less per side. 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, and the cell volume can be reduced, thereby increasing the energy density.

[0092] (Method of Forming Intermediate Layer) The intermediate layer is formed between the positive electrode and the separator, and is typically fixed to the surface of the positive electrode active material layer or the surface of the separator that comes into contact with the positive electrode.

[0093] The intermediate layer can be formed on the surface of the positive electrode active material layer or the separator surface by known manufacturing techniques for electrodes or separator coating layers in alkali metal ion batteries, electric double layer capacitors, etc.

[0094] For example, when forming it 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 coating liquid, and this coating liquid is applied to one or both sides of the positive electrode active material layer to form a coating film, which can be obtained by drying. The obtained integrated product of the positive electrode active material layer and the intermediate layer may be pressed to adjust the film thickness and bulk density. Alternatively, a method is also possible in which, without using a solvent, the pre-dope material and other optional components used as needed are dry mixed, the resulting mixture is press-molded, and then attached to the positive electrode active material layer using a conductive adhesive or the like.

[0095] For example, when forming the intermediate layer on the separator surface, the alkali metal carbonate and other optional components used as needed are dispersed or dissolved in water or an organic solvent to prepare a slurry coating solution, and this coating solution is applied to the surface of the separator that contacts the positive electrode to form a coating film, which can be obtained by drying. The resulting integrated product of the separator and intermediate layer may be pressed to adjust the film thickness and bulk density. Alternatively, a method is also possible in which the alkali metal carbonate and other optional components used as needed are dry mixed without using a solvent, the resulting mixture is press-molded, and then attached to the separator using a conductive adhesive or the like.

[0096] The formation of the coating film of the intermediate layer is not particularly limited, but coating methods and coating devices such as die coating, gravure coating, comma coating, knife coating, etc. can be suitably used. The coating film may be formed by single-layer coating or multi-layer coating.

[0097] There are no particular limitations on the method for drying the coating film of the pre-dope material layer, but it is preferable to use a drying method such as hot air drying or infrared (IR) drying.

[0098] The pressing of the intermediate layer is not particularly limited, but a pressing machine such as a hydraulic press, a vacuum press, etc. can be preferably 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.

[0099] (Measurement of Alkali Metal Carbonate in Intermediate Layer) Measurement can be performed by applying the method described in (Measurement of Alkali Metal Carbonate in Positive Electrode) to the intermediate layer.

[0100] (Optional Components) The intermediate layer in this embodiment may contain optional components such as a conductive filler, a binder, and an inorganic filler, as needed.

[0101] The conductive filler is not particularly limited, and examples thereof include acetylene black, ketjen black, vapor-grown carbon fiber, graphite, carbon nanotubes, and mixtures thereof. The amount of conductive filler used is preferably 0 to 30, more preferably 1 to 25, and even more preferably 5 to 20, relative to the total mass of the intermediate layer being 100. If it is 20 or less, the content of the pre-dope material in the pre-dope material layer increases, and the alkali metal density per volume that can be extracted from the intermediate layer can be ensured.

[0102] The binder is not particularly limited, but examples thereof include PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, and acrylic copolymer. The amount of binder used is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 1 part by mass or more and 15 parts by mass or less, and even more preferably 1 part by mass or more and 10 parts by mass or less, per 100 parts by mass of the intermediate layer. If the amount of binder is 1% by mass or more, sufficient strength of the intermediate layer is exhibited. On the other hand, if the amount of binder is 30 parts by mass or less, the ingress and egress of the electrolyte into and diffusion into the intermediate layer are not hindered, and pre-doping is facilitated.

[0103] Examples of inorganic fillers include oxide ceramics such as alumina, silica (silicon oxide), titania, zirconia, magnesia, ceria, yttria, zinc oxide, and iron oxide; nitride ceramics such as silicon nitride, titanium nitride, and boron nitride; ceramics such as silicon carbide, calcium carbonate, aluminum sulfate, aluminum hydroxide, potassium titanate, talc, kaolin clay, kaolinite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amesite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and silica sand; and glass fiber. By mixing an inorganic filler, the pre-dope material layer can further exhibit a safety-improving effect.

[0104] <Method for Identifying Alkali Metal Carbonate> The method for identifying the alkali metal carbonate contained in the positive electrode active material layer or the intermediate layer is not particularly limited, and can be identified, for example, by the following method. The alkali metal carbonate is preferably identified by combining the following analytical techniques. In ion chromatography, which will be described later, anions can be identified by analyzing the water obtained after washing the positive electrode precursor with distilled water.

[0105] (Microscopic Raman Spectroscopy) The alkali metal carbonate and the positive electrode active material can be identified by Raman imaging of carbonate ions on the surface of the positive electrode active material layer or intermediate layer, measured at a magnification of 1000 to 4000 times. Measurement conditions include an excitation light of 532 nm, an excitation light intensity of 1%, a long working distance of the objective lens of 50 times, a diffraction grating of 1800 gr / mm, a point scanning mapping method (slit 65 mm, binning 5 pix), 1 mm steps, an exposure time per point of 3 seconds, an accumulation count of 1, and a noise filter. The measured Raman spectrum showed a peak intensity of 1071 to 1104 cm. －１ A linear baseline is set in the range, and the area is calculated assuming that positive values ​​from the baseline are carbonate ion peaks, and the frequency is integrated. At this time, the frequency for the carbonate ion peak area, which is approximated by a Gaussian function for noise components, is subtracted from the carbonate ion frequency distribution.

[0106] (X-ray Photoelectron Spectroscopy (XPS)) The bonding state of lithium can be determined by analyzing the electronic state using XPS. Measurement conditions can be exemplified as follows: monochromatic AlKα X-ray source, X-ray beam diameter 100 μmφ (25 W, 15 kV), narrow scan pass energy: 58.70 eV, charge neutralization, narrow scan sweep count: 10 times (carbon, oxygen), 20 times (fluorine), 30 times (phosphorus), 40 times (alkali metal element), 50 times (silicon), and narrow scan energy step: 0.25 eV. It is preferable to clean the surface of the positive electrode by sputtering before XPS measurement. For example, sputtering conditions include an acceleration voltage of 1.0 kV, a 2 mm x 2 mm area, and 1 minute (SiO ２The surface of the positive electrode active material layer or intermediate layer can be cleaned under the condition of a rate of 1.25 nm / min (equivalent to 1.25 nm / min). ２ or Li-C bond, the peak at 55 to 60 eV is LiF, Li ２ CO ３ , Li ｘ P.O. ｙ F ｚ (wherein x, y, and z are integers of 1 to 6); the C1s bond energy peak of 285 eV corresponds to a C—C bond, the peak of 286 eV corresponds to a C—O bond, the peak of 288 eV corresponds to a COO bond, and the peak of 290 to 292 eV corresponds to a CO ３ ２－ , C—F bond; O1s bond energy peak of 527 to 530 eV ２－ (Li ２ O), the peak at 531-532 eV is CO, CO ３ , OH, PO ｘ (wherein x is an integer of 1 to 4), SiO ｘ (wherein x is an integer of 1 to 4), and the peak at 533 eV is C—O, SiO ｘ (wherein x is an integer of 1 to 4); the peak at 685 eV of F1s bond energy corresponds to LiF, the peak at 687 eV corresponds to C—F bond, and Li ｘ P.O. ｙ F ｚ (wherein x, y, and z are integers of 1 to 6), PF ６ － For the P2p binding energy, the peak at 133 eV is PO ｘ (wherein x is an integer of 1 to 4), and the peak at 134 to 136 eV is PF ｘ (wherein x is an integer of 1 to 6); the peak at the Si2p binding energy of 99 eV is Si silicide, and the peak at 101 to 107 eV is Si ｘ O ｙ (where x and y are any integers). When peaks overlap in the obtained spectrum, it is preferable to separate the peaks by assuming a Gaussian function or a Lorentzian function and assign the spectrum. The lithium compounds present can be identified from the obtained results of measuring the electronic state and the results of the ratios of the elements present.

[0107] (Energy Dispersive X-ray Analysis (SEM-EDX)) The elements contained can be quantified by SEM-EDX analysis of the surface of the positive electrode active material layer or intermediate layer measured at a magnification of 1000 to 4000 times. As an example of measuring an SEM-EDX image, the measurement can be performed at an acceleration voltage of 10 kV, an emission current of 1 μA, a measurement pixel count of 256 × 256 pixels, and an accumulation count of 50. In order to prevent the sample from becoming charged, the surface can also be treated with gold, platinum, osmium, or the like by a method such as vacuum deposition or sputtering.

[0108] (Ion Chromatography) The positive electrode active material layer or intermediate layer is washed with distilled water, and the resulting water is analyzed by ion chromatography to identify the anion species eluted in the water. Ion exchange, ion exclusion, and reversed-phase ion-pair columns can be used. Detectors that can be used include electrical conductivity detectors, ultraviolet-visible absorbance detectors, and electrochemical detectors. Suppressor-based detectors, in which a suppressor is installed before the detector, and non-suppressor-based detectors, in which a low-conductivity solution is used as the eluent without a suppressor, can also be used. Measurements can also be performed in combination with a mass spectrometer or a charged particle detector. Therefore, it is preferable to combine an appropriate column and detector based on the alkali metal compounds identified from the analytical results of SEM-EDX, Raman spectroscopy, and XPS.

[0109] (Method for Quantifying Alkali Metals: ICP-MS) The positive electrode active material layer or intermediate layer is subjected to acid decomposition using a strong acid such as concentrated nitric acid, concentrated hydrochloric acid, or aqua regia, and the resulting solution is diluted with pure water to an acid concentration of 2% to 3%. The acid decomposition can also be carried out by heating or pressurizing as appropriate. The resulting diluted solution is analyzed by ICP-MS, but it is preferable to add a known amount of alkali metal as an internal standard. If the alkali metal to be measured exceeds the upper limit of measurement concentration, it is preferable to further dilute the diluted solution while maintaining the acid concentration. The alkali metal can be quantified based on the obtained measurement results and a calibration curve created in advance using a standard solution for chemical analysis.

[0110] <Pre-dope material layer> (Pre-dope material layer) The lithium storage element precursor of the third embodiment contains a pre-dope material layer containing a pre-dope material at the interface between the positive electrode precursor and the separator. That is, the lithium ion secondary battery of the present embodiment has a pre-dope material layer containing a pre-dope material between the positive electrode and the separator. The method for forming the pre-dope material layer is not particularly limited, but examples include a method in which the pre-dope material layer is formed by an existing coating method on the surface of the positive electrode active material layer or the surface of the separator that contacts the positive electrode precursor, and then disposed between the positive electrode precursor and the separator when forming the electrode body.

[0111] The pre-dope material layer may contain optional components in addition to the pre-dope material, such as a binder component for maintaining the shape and a conductive material for ensuring conductivity.

[0112] It is preferable that the pre-dope material contained in the pre-dope material layer is decomposed in a pre-doping step described below, and lithium ions are doped into the negative electrode precursor.

[0113] In this embodiment, high-temperature durability can be improved by placing the pre-dope material between the positive electrode and the separator and adjusting each value to satisfy various conditions. Although the theory is not entirely clear, in conventional lithium-ion secondary batteries, a smaller positive electrode is placed opposite the negative electrode, and the battery is initially charged and activated. Therefore, lithium is not absorbed into the negative electrode at a position that does not face the positive electrode (i.e., the non-negative electrode facing portion). However, when a completed lithium-ion secondary battery is used, lithium is gradually absorbed into the non-negative electrode facing portion, which can cause capacity degradation. When the pre-dope material is placed between the positive electrode and the separator, i.e., closer to the negative electrode, lithium doping into the non-negative electrode facing portion is more likely to proceed, and the lithium concentration difference between the non-negative electrode facing portion and the negative electrode facing portion at the time of battery completion is reduced compared to normal. Therefore, it is speculated that lithium absorption from the negative electrode facing portion to the non-negative electrode facing portion during high-temperature floating can be prevented, preventing capacity degradation.

[0114] The thickness of the pre-dope material layer is preferably 0.1 μm or more and 10 μm or less, more preferably 0.5 μm or more and 5 μm or less per side. If the thickness of the pre-dope material layer is 0.1 μm or more, the effect of pre-doping can be obtained. If the thickness is 5 μm or less, sufficient output characteristics can be obtained, and the cell volume can be reduced, thereby increasing the energy density.

[0115] (Pre-dope material) In the third embodiment, when the initial charge capacity density of the positive electrode active material is A1 (mAh / g), the initial charge capacity density of the pre-dope material is A2 (mAh / g), the initial discharge capacity density of the pre-dope material is B2 (mAh / g), and D50 of the pre-dope material is R2 (μm), a material that satisfies the following formulae: A2 / A1>1.2, B2 / A2<0.3, and 0.2≦R2≦15 is used as the pre-dope material.

[0116] The pre-dope material may be, for example, LixAOy (x / y>0.5, A is at least one element selected from the group consisting of Fe, Mn, Co, Ni, and Cu). ５ FeO ４ , Li ６ CoO ４ , Li ２ NiO ４ , Li ６ MnO ４ etc. are preferably used.

[0117] Further, examples of the pre-dope material include compounds represented by LicTiOd (1.5≦c≦2.3, 2.7≦d≦3.5) and LieTiOf (3.5≦e≦4.5, 3.7≦f≦4.8). ４ TiO ４ , Li ２ TiO ３ is available.

[0118] The pre-dope material is Li １＋ｘ (Ti １－ｙ Fe ｙ ) １－ｘ O ２[wherein x satisfies 0<x≦0.25, and y satisfies 0.4<y≦0.9]. １．２ (Ti ０．５ Fe ０．５ ) ０．８ O ２ etc. can be used.

[0119] In the pre-doping step, the pre-dope material decomposes in the pre-dope material layer to release lithium ions, and the lithium ions can be doped into the negative electrode precursor. The proportion of the pre-dope material in the pre-dope material layer is preferably 60% by mass or more and 98% by mass or less. Within this range, the effect of compensating for the irreversible capacity of the negative electrode by the pre-dope material can be obtained, and the effect of improving the capacity density of the lithium ion secondary battery can be easily obtained.

[0120] The particle size (D50) of the pre-dope material can be adjusted by various methods, for example, by using a grinder such as a ball mill, a bead mill, a ring mill, a jet mill, or a rod mill.

[0121] The average particle diameter D2 of the pre-dope material is preferably 0.1 μm or more and 15 μm or less. If it is 0.1 μm or more, the dispersibility of the slurry prepared when forming the pre-dope material layer is excellent. If it is 15 μm or less, the pre-dope reaction proceeds efficiently.

[0122] (Initial charge capacity density A2 and initial discharge capacity density B2 of the pre-doped material) The initial charge capacity density A2 of the pre-doped material of the third embodiment is obtained by preparing a positive electrode consisting of a pre-dope material, a binder, and a conductive material using a known lithium ion secondary battery electrode preparation process, and then measuring the charge capacity density when a half cell consisting of a lithium counter electrode and a known separator is subjected to constant current charging at a 0.1 C rate to the upper limit of the operating potential in a 25 ° C environment, followed by constant voltage charging until the current converges to a 0.03 C rate. The initial discharge capacity density B2 of the pre-doped material of this embodiment is obtained by measuring the discharge capacity density when constant current discharging is performed at a 0.1 C rate to 3.0 V after a 10-minute pause following completion of the constant voltage charging at the upper limit of the operating potential. Furthermore, the capacity densities A2 and B2 (mAh / g) of the pre-doped material can be obtained by dividing the obtained charge capacity density and discharge capacity density by the mass of the pre-dope material used.

[0123] In the present disclosure, the potential region where the pre-dope material decomposes and releases lithium ions produces a reaction capacity is referred to as the "operating potential" of the pre-dope material. The "lower limit of the operating potential" is the potential at which the release of lithium ions begins, and the "upper limit of the operating potential" is the potential at which the release of lithium ions ends (no reaction capacity is produced). Note that the upper limit of the operating potential of the capacity recovery material is measured up to the potential region where no reaction capacity is produced, and therefore varies depending on the type of capacity recovery material. Below, the upper limit of the operating potential of preferred specific examples of capacity recovery materials is shown. Li ５ FeO ４ : Upper limit of operating potential 4.2V, upper limit of operating voltage 4.1V Li ６ CoO ４ : Upper limit of operating potential 4.3V, upper limit of operating voltage 4.2V Li ２ NiO ４ : Upper limit of operating potential 4.5V, upper limit of operating voltage 4.4V Li ６ MnO ４ : Upper limit of operating potential 4.8V, upper limit of operating voltage 4.7V Li １．２ (Ti ０．５ Fe ０．５ ) ０．８ O ２ : Upper limit of operating potential 4.3V, upper limit of operating voltage 4.2V Li４ TiO ４ : Upper limit of operating potential 4.0 V, upper limit of operating voltage 3.9 V Li ２ TiO ３ : Upper limit of operating potential 4.0 V, upper limit of operating voltage 3.9 V

[0124] (Method for Identifying Pre-Dope Material) The pre-dope material contained in the pre-dope layer can be qualitatively analyzed using known analytical techniques, and is not particularly limited, but can be identified by the following method, for example: For example, common techniques such as SEM-EDX, X-ray photoelectric spectroscopy (XPS), and X-ray diffraction (XRD) can be used.

[0125] (A1, A2, B2, R2) When the initial charge capacity density of the positive electrode active material is A1 (mAh / g), D50 of the positive electrode active material is R1 (μm), the initial charge capacity density of the pre-dope material is A2 (mAh / g), the initial discharge capacity density of the pre-dope material is B2 (mAh / g), and D50 of the pre-dope material is R2 (μm), high temperature durability can be improved when the pre-dope material is contained in a pre-dope material layer formed between the positive electrode (or positive electrode precursor) and the separator and the following formulae are satisfied: B2 / A2<0.3, A2 / A1>1.2, and 0.2≦R2≦15.

[0126] Without being limited by theory, in this embodiment, the pre-dope material is supported within the above-mentioned specific range between the positive electrode (or positive electrode precursor) and the separator, i.e., at a position closer to the negative electrode, compared to when the pre-dope material is supported on the positive electrode mixture, it is thought that doping of lithium ions also progresses more easily in the negative electrode non-facing portion that does not face the positive electrode. In float charging, deterioration may occur due to diffusion of lithium ions to the non-facing portion, but this can be suppressed.

[0127] When B2 / A2<0.3, the pre-dope material has a large irreversible capacity and therefore functions effectively as a pre-dope material. When A2 / A1>1.2, the capacity density of the pre-dope material is sufficiently larger than that of the positive electrode active material, so that the use of the pre-dope material can increase the capacity density of the lithium ion secondary battery while compensating for the irreversible capacity of the negative electrode. A more preferable lower limit of A2 / A1 is 1.44.

[0128] If R2 is 0.2 or more (preferably, greater than 0.2), it is easy to prepare a slurry when forming the pre-dope material layer, and if R2 is 15 or less (preferably, less than 15), surface unevenness of the pre-dope material layer can be prevented, so that a pre-dope material layer with good contact with the positive electrode is formed, and doping proceeds smoothly.

[0129] (Method for forming a pre-dope material layer) The pre-dope material layer is formed between the positive electrode (or positive electrode precursor) and the separator. Typically, it is fixed to the surface of the positive electrode active material layer or the surface of the separator that contacts the positive electrode. As a method for forming the pre-dope material layer, it is possible to form it on the surface of the positive electrode active material layer or the surface of the separator by a known manufacturing technique for electrodes or separator coating layers in lithium ion batteries, electric double layer capacitors, etc.

[0130] For example, when forming on the surface of the positive electrode active material layer, the pre-dope material and other optional components used as needed are dispersed or dissolved in water or an organic solvent to prepare a slurry coating liquid, and this coating liquid is applied to one or both sides of the positive electrode active material layer to form a coating film, which can be obtained by drying. The obtained integrated product of the positive electrode active material layer and the pre-dope material layer may be pressed to adjust the film thickness or bulk density. Alternatively, a method is also possible in which the pre-dope material and other optional components used as needed are dry mixed without using a solvent, the resulting mixture is press-molded, and then attached to the positive electrode active material layer using a conductive adhesive or the like.

[0131] For example, when forming on the separator surface, the pre-dope material and other optional components used as needed are dispersed or dissolved in water or an organic solvent to prepare a slurry coating liquid, and this coating liquid is applied to the surface of the separator that contacts the positive electrode to form a coating film, which can be obtained by drying. The obtained separator and pre-dope material layer may be laminated together and pressed to adjust the film thickness or bulk density. Alternatively, a method is also possible in which the pre-dope material and other optional components used as needed are dry mixed without using a solvent, the resulting mixture is press-molded, and then attached to the separator using a conductive adhesive or the like.

[0132] The method for forming the coating film of the pre-dope material layer is not particularly limited, but it is possible to use a coating method and a coating device such as a die coating method, a gravure coating method, a comma coating method, a knife coating method, etc. The coating film may be formed by single-layer coating or multi-layer coating.

[0133] There are no particular limitations on the method for drying the coating film of the pre-dope material layer, but it is preferable to use a drying method such as hot air drying or infrared (IR) drying.

[0134] The method for pressing the pre-dope material layer is not particularly limited, but it is preferable to use a press such as a hydraulic press, a vacuum press, etc. The film thickness, bulk density, and electrode strength of the positive electrode active material layer can be adjusted by the pressing pressure, gap, and surface temperature of the pressing part.

[0135] (Optional Components) The pre-dope material layer in the third embodiment may contain optional components such as a conductive filler, a binder, and an inorganic filler, as needed.

[0136] The conductive filler is not particularly limited, and examples thereof include acetylene black, ketjen black, vapor-grown carbon fiber, graphite, carbon nanotubes, and mixtures thereof. The amount of the conductive filler used is preferably 0 to 30, more preferably 1 to 25, and even more preferably 5 to 20, relative to the total mass of the pre-dope material layer being 100. If it is 20 or less, the content of the pre-dope material in the pre-dope material layer increases, and the lithium density per volume that can be extracted from the pre-dope material layer can be ensured.

[0137] The binder is not particularly limited, and examples thereof include PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, and acrylic copolymer. The amount of binder used is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 1 part by mass or more and 15 parts by mass or less, and even more preferably 1 part by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the pre-dope material layer. If the amount of binder is 1 part by mass or more, sufficient strength of the pre-dope material layer is exhibited. On the other hand, if the amount of binder is 30 parts by mass or less, the ingress and egress of the electrolyte into and diffusion from the pre-dope material layer are not hindered, and pre-doping is facilitated.

[0138] Examples of inorganic fillers include oxide ceramics such as alumina, silica (silicon oxide), titania, zirconia, magnesia, ceria, yttria, zinc oxide, and iron oxide; nitride ceramics such as silicon nitride, titanium nitride, and boron nitride; ceramics such as silicon carbide, calcium carbonate, aluminum sulfate, aluminum hydroxide, potassium titanate, talc, kaolin clay, kaolinite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amesite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and silica sand; and glass fiber. By mixing an inorganic filler, the pre-dope material layer can further exhibit a safety-improving effect.

[0139] The negative electrode and the negative electrode precursor may have a common configuration, except for the configuration related to the amount of alkali metal ions doped.

[0140] (Negative Electrode Active Material Layer) The negative electrode active material layer contains a negative electrode active material capable of absorbing and releasing alkali metal ions, and may contain optional components such as a conductive filler, a binder, and a dispersion stabilizer, as necessary.

[0141] (Negative electrode active material) The negative electrode active material may be a material capable of absorbing and releasing alkali metal ions such as lithium ions. Specific examples of the negative electrode active material include carbon materials, alkali metals, alloys containing alkali metals, titanium oxides, silicon, silicon oxides, silicon alloys, silicon compounds, tin, and tin compounds.

[0142] The content of the negative electrode active material in the negative electrode active material layer of the negative electrode is preferably 70 mass % or more, and more preferably 80 mass % or more, based on the total mass of the negative electrode active material layer.

[0143] (Carbon Material) As the carbon material, known materials for alkali metal ion secondary batteries can be used. Examples include non-graphitizable carbon materials (hard carbon), easily graphitizable carbon materials (soft carbon), carbon black, carbon nanoparticles, activated carbon, artificial graphite, natural graphite, graphitized mesophase carbon microspheres, graphite whiskers, amorphous carbonaceous materials such as polyacene-based substances, carbonaceous materials obtained by heat-treating carbonaceous material precursors such as petroleum-based pitch, coal-based pitch, mesocarbon microbeads, coke, and synthetic resins (e.g., phenolic resins), pyrolysates of furfuryl alcohol resins or novolac resins, fullerenes, carbon nanophones, and composite carbon materials thereof.

[0144] According to the present disclosure, when an amorphous carbon material is used as a negative electrode active material, it is preferable because it can reduce the loss of the positive electrode active material. Hard carbon and soft carbon are particularly preferable. Furthermore, when the alkali metal is sodium, hard carbon is preferably used from the viewpoint of achieving a good doped state or exhibiting a high capacity.

[0145] (Alloy-based negative electrode material) The negative electrode active material may be a material that forms an alloy with an alkali metal (hereinafter also referred to as "alloy-based negative electrode material"), and preferably contains at least one selected from the group consisting of silicon, silicon compounds, tin, tin compounds, and composite materials of these with carbon or a carbonaceous material. The silicon compound is preferably SiC or silicon oxide, and SiO ｘIt is more preferable that (0.01≦x≦1). According to the present disclosure, when used as a negative electrode active material in an alloy-based negative electrode material, it is possible to reduce positive electrode active material loss, and therefore, silicon and / or a silicon compound are particularly preferable.

[0146] The composite material is preferably a material obtained by combining, by heat treatment or the like, at least one substrate selected from the group consisting of silicon, silicon compounds, tin, and tin compounds with at least one type of carbon or carbonaceous material selected from the group consisting of: non-graphitizable carbon materials; graphitizable carbon materials; carbon black; carbon nanoparticles; activated carbon; artificial graphite; natural graphite; graphitized mesophase carbon microspheres; graphite whiskers; amorphous carbonaceous materials such as polyacene-based substances; carbonaceous materials obtained by heat treating carbonaceous material precursors such as petroleum-based pitch, coal-based pitch, mesocarbon microbeads, coke, and synthetic resins (e.g., phenolic resins); pyrolysates of furfuryl alcohol resins or novolac resins; fullerenes; and carbon nanophones.

[0147] Among these, composite materials that can be obtained by heat treating one or more of the above-mentioned base materials together with petroleum-based pitch or coal-based pitch in the presence of each other are particularly preferred. Before the heat treatment, the base material and pitch may be mixed at a temperature higher than the melting point of the pitch. The heat treatment temperature may be any temperature at which the components generated by volatilization or thermal decomposition of the pitch used become carbonaceous materials, and is preferably 400°C or higher and 2500°C or lower, more preferably 500°C or higher and 2000°C or lower, and even more preferably 550°C or higher and 1500°C or lower. The atmosphere in which the heat treatment is performed is not particularly limited, but a non-oxidizing atmosphere is preferred.

[0148] (Average particle diameter of negative electrode active material) The average particle diameter of the negative electrode active material is preferably 0.01 μm or more and 30 μm or less, with the lower limit being more preferably 2 μm or more, even more preferably 2.5 μm or more, and the upper limit being more preferably 6 μm or less, even more preferably 4 μm or less. If the average particle diameter is 0.01 μm or more, the contact area with the nonaqueous electrolyte increases, thereby reducing the resistance of the alkali metal ion secondary battery. If the average particle diameter of the negative electrode active material is 30 μm or less, the negative electrode active material layer can be made sufficiently thin, thereby improving the energy density of the alkali metal ion secondary battery.

[0149] The average particle size of the negative electrode active material can be adjusted by pulverizing it using a wet or dry jet mill with a built-in classifier, an agitation ball mill, etc. The pulverizer is equipped with a centrifugal classifier, and the fine particles pulverized in an inert gas environment such as nitrogen or argon can be collected with a cyclone or a dust collector.

[0150] The average particle diameter in the present disclosure is determined by the following method. First, the primary particle diameter of the active material is measured by the following method. If the primary particle diameter is smaller than 1 μm, the primary particle diameter is taken as the average particle diameter. If the primary particle diameter is 1 μm or greater, the particle size distribution of the active material powder is measured using a particle size distribution measuring device, a cumulative curve is calculated assuming the total volume to be 100%, and the particle diameter at the point where the cumulative curve is 50% (i.e., the 50% diameter (median diameter)) is taken as the average particle diameter. An example of a particle size distribution measuring device is a laser diffraction particle size distribution measuring device. The primary particle diameter of the active material in the present disclosure is determined by the following method. 1) A method in which several fields of view of the active material powder are photographed using an electron microscope, and the particle diameters of approximately 2,000 to 3,000 particles in those fields of view are measured using a fully automatic image processing device or the like, and the arithmetic average of these values ​​is taken as the primary particle diameter. 2) The surface and / or cross section of the obtained electrode is photographed in several fields using an electron microscope, and the arithmetic average is calculated using the method described above.

[0151] The primary particle diameter of the active material incorporated in the alkali metal ion secondary battery can be measured by disassembling the alkali metal ion secondary battery, removing the electrodes, and then measuring the diameter by the above-mentioned method 2); or by removing components other than the active material from the removed electrodes and then measuring the diameter by the above-mentioned method 1).

[0152] The operation of disassembling the alkali metal ion secondary battery and removing the electrodes is preferably carried out in an inert atmosphere such as argon.

[0153] Components other than the active material can be removed from the electrode by, for example, the following method. First, the removed electrode is immersed in ethyl methyl carbonate or dimethyl carbonate to remove the nonaqueous electrolyte, alkali metal salt, etc., and then air-dried. Next, it is immersed in a mixed solvent of methanol and isopropanol to deactivate the alkali metal ions occluded in the active material, and then air-dried again. Next, to remove the binder contained in the active material layer, the electrode with deactivated alkali metal ions is immersed in distilled water or NMP. Next, if necessary, the active material is peeled off with a spatula or the like, and then ultrasonically irradiated to slide the active material off the current collector, and the active material is recovered by suction filtration. If necessary, the obtained active material may be immersed again in distilled water or NMP, ultrasonically irradiated, and then suction-filtered several times. Finally, the obtained active material is vacuum-dried at 170°C to obtain an active material powder.

[0154] (Optional Components) In addition to the negative electrode active material, the negative electrode active material layer in this embodiment may contain optional components such as a conductive filler, a binder, and a dispersion stabilizer, as needed.

[0155] The type of conductive filler is not particularly limited, and examples thereof include acetylene black, ketjen black, vapor-grown carbon fiber, etc. The amount of the conductive filler used is preferably more than 0 parts by mass and not more than 30 parts by mass, more preferably more than 0 parts by mass and not more than 20 parts by mass, and even more preferably more than 0 parts by mass and not more than 15 parts by mass, relative to 100 parts by mass of the negative electrode active material.

[0156] The binder is not particularly limited, but examples thereof include PVdF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), polyimide, latex, styrene-butadiene copolymer, fluororubber, and acrylic copolymer. The amount of binder used is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 2 parts by mass or more and 27 parts by mass or less, and even more preferably 3 parts by mass or more and 25 parts by mass or less, relative to 100 parts by mass of the negative electrode active material. If the amount of binder is 1% by mass or more, sufficient electrode strength is exhibited. If the amount of binder is 30 parts by mass or less, the ingress and egress of alkali metal ions such as lithium ions into and from the negative electrode active material is not inhibited, and high input / output characteristics are exhibited.

[0157] (Negative electrode current collector) In this embodiment, the material constituting the negative electrode current collector is preferably a metal foil that has high electronic conductivity and is resistant to degradation due to elution in a non-aqueous electrolyte solution and reaction with an electrolyte or ions. Such metal foils are not particularly limited, and examples thereof include aluminum foil, copper foil, nickel foil, and stainless steel foil. Copper foil is preferred as the negative electrode current collector in the lithium ion secondary battery of this embodiment. When the alkali metal is sodium, aluminum foil is particularly preferred as the negative electrode current collector from the viewpoint of cost, etc.

[0158] The metal foil may be a normal metal foil without irregularities or through holes, or may be a metal foil with irregularities that has been subjected to embossing, chemical etching, electrolytic deposition, blasting, or the like, or may be a metal foil with through holes such as expanded metal, punched metal, or etched foil.

[0159] The thickness of the negative electrode current collector is not particularly limited as long as it can sufficiently maintain the shape and strength of the negative electrode, but is preferably 1 to 100 μm, for example.

[0160] (Production of Negative Electrode) The negative electrode has a negative electrode active material layer on one or both surfaces of a negative electrode current collector. Typically, the negative electrode active material layer is fixed to one or both surfaces of the negative electrode current collector.

[0161] The negative electrode can be manufactured using known electrode manufacturing techniques for alkali metal ion secondary batteries, electric double layer capacitors, and the like. For example, various materials including the negative electrode active material are dispersed or dissolved in water or an organic solvent to prepare a slurry-like negative electrode coating liquid. This negative electrode coating liquid is applied to one or both sides of a negative electrode current collector to form a coating film, which is then dried to obtain a negative electrode. The obtained negative electrode may be pressed to adjust the film thickness, bulk density, etc. of the negative electrode active material layer. Alternatively, various materials including the negative electrode active material may be dry-mixed without using a solvent, the resulting mixture is press-molded, and then attached to the negative electrode current collector using a conductive adhesive.

[0162] The negative electrode coating fluid may be prepared by dry-blending some or all of various material powders including the negative electrode active material, and then adding water or an organic solvent and / or a liquid or slurry substance in which a binder and a dispersion stabilizer are dissolved or dispersed therein. Alternatively, the negative electrode coating fluid may be prepared by adding various material powders including the negative electrode active material to a liquid or slurry substance in which a binder and a dispersion stabilizer are dissolved or dispersed in water or an organic solvent.

[0163] The dissolving or dispersing method is not particularly limited, but preferably, a dispersing machine such as a homodisper, a multi-axis dispersing machine, a planetary mixer, or a thin film rotating high-speed mixer can be used.

[0164] The method for forming the coating film is not particularly limited, but it is preferable to use a coating machine such as a die coater, a comma coater, a knife coater, a gravure coater, etc. The coating film may be formed by single-layer coating or multi-layer coating.

[0165] The method for drying the coating film is not particularly limited, but preferably, hot air drying, infrared (IR) drying, or the like can be used. The coating film may be dried at a single temperature, or may be dried at a temperature that is changed in multiple stages. Alternatively, a combination of multiple drying methods may be used.

[0166] The method for pressing the negative electrode is not particularly limited, but a press such as a hydraulic press or a vacuum press can be suitably used. The thickness of the negative electrode active material layer is preferably 20 μm or more and 200 μm or less per side of the negative electrode current collector. The lower limit of the thickness of the negative electrode active material layer is more preferably 25 μm or more, and even more preferably 30 μm or more. The upper limit of the thickness of the negative electrode active material layer is more preferably 150 μm or less, and even more preferably 100 μm or less. When the thickness of the negative electrode active material layer is 20 μm or more, streaks are less likely to occur when the negative electrode active material layer is applied, resulting in excellent coatability. When the thickness of the negative electrode active material layer is 200 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 thickness of the negative electrode active material layer per side in the portion of the negative electrode current collector that does not have irregularities.

[0167] (Manufacturing of Negative Electrodes Using Alloy-Based Negative Electrode Materials) 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. 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 including the negative electrode active material are dispersed or dissolved in water or an organic solvent to prepare a slurry coating liquid, and this coating liquid is applied to one or both sides of the negative electrode current collector to form a coating film, which is then dried to obtain a negative electrode. The obtained negative electrode may then be pressed to adjust the film thickness and bulk density of the negative electrode active material layer. 2) A negative electrode can also be obtained by dry-mixing various materials including 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 the 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.

[0168] Among the above-mentioned methods for producing a negative electrode, method 1) is preferred from the viewpoint of mass productivity.

[0169] The thickness of the negative electrode active material layer per side is preferably 20 μm or more and 200 μm or less, with the lower limit being more preferably 25 μm or more, and even more preferably 30 μm or more. The upper limit is more preferably 150 μm or less, and even more preferably 100 μm or less. If the thickness of the negative electrode active material layer is 10 μm or more, the electric capacity of the positive electrode can be fully utilized, and 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 the through hole portion of punched metal, expanded metal, etched foil, etc.

[0170] (Irreversible Capacity Rate of Negative Electrode or Negative Electrode Precursor) This embodiment can supply lithium from the alkali metal carbonate or pre-dope material instead of the positive electrode active material, and is therefore suitable for use with negative electrode precursors or negative electrodes with a large irreversible capacity rate. The irreversible capacity rate of the negative electrode precursor or negative electrode is preferably 5% or more and 50% or less. If the irreversible capacity rate is 5% or more and 50% or less, the alkali metal that cannot be effectively used for charging and discharging the energy storage element due to the irreversible capacity of the negative electrode precursor or negative electrode can be supplied from the alkali metal carbonate or pre-dope material, thereby reducing the initial resistance.

[0171] Examples of methods for preparing a negative electrode with an irreversible capacity of 5% or more and 50% or less include a method of using a material with a high irreversible capacity ratio as an active material; a method of mixing a material with a high irreversible capacity ratio with a material with a low irreversible capacity ratio and adjusting the mixing ratio. Examples of materials with a high irreversible capacity ratio include the alloy-based negative electrode materials described in <Negative electrode, negative electrode precursor> (alloy-based negative electrode material) and the carbon materials described in <Negative electrode, negative electrode precursor> (carbon material), such as carbon black; carbon nanoparticles; activated carbon; graphitized mesophase carbon microspheres; graphite whiskers; amorphous carbonaceous materials such as polyacene-based substances; carbonaceous materials obtained by heat-treating carbonaceous material precursors such as petroleum-based pitch, coal-based pitch, mesocarbon microbeads, coke, and synthetic resins (e.g., phenolic resins); pyrolysis products of furfuryl alcohol resins or novolac resins; fullerenes; carbon nanophones; and composite carbon materials thereof. Examples of materials with low irreversible capacity include artificial graphite and natural graphite among the carbon materials described in the section <Negative electrode, negative electrode precursor> (carbon material).

[0172] (Calculation of Irreversible Capacity Rate of Negative Electrode Precursor) The irreversible capacity rate of the negative electrode precursor of this embodiment is determined by the following method. A single-sided negative electrode comprising a negative electrode active material, a binder, and optionally a conductive material is produced using a known process for producing electrodes for alkali metal ion secondary batteries. A negative electrode half-cell comprising an alkali metal counter electrode, an alkali metal reference electrode, an electrolyte solution described below, and a known separator is discharged at a constant current of 0.1 C rate to 0.01 V relative to the alkali metal reference electrode in a 25°C environment, and then discharged at a constant voltage of 0.02 C rate until the current converges. The discharge capacity (mAh) is measured, and the area (cm2) of the coated portion of the single-sided negative electrode precursor is calculated. ２ ) to obtain the initial storage capacity of the alkali metal (H1 (mAh / cm ２ After the completion of the constant voltage discharge at 0.01 V, a 10-minute pause was allowed, and then the battery was charged at a constant current of 0.1 C rate up to 2.5 V. The charge capacity (mAh) was measured, and the area of ​​the coated portion of the single-sided negative electrode precursor (cm ２ ) to obtain the initial release capacity of the alkali metal H (mAh / cm ２The irreversible capacity rate Q (%) of the negative electrode precursor is obtained by the following formula: Q = (H1 - H2) / H1 × 100

[0173] (Calculation of Irreversible Capacity Rate of Negative Electrode) The irreversible capacity rate of the negative electrode of this embodiment is determined by the following method (1) or (2).

[0174] (1) Method of calculation from negative electrode precursor The negative electrode is the negative electrode of an alkali metal storage element that has been completed through an initial charging step. However, when a negative electrode before the initial charging step, i.e., a negative electrode precursor, is obtained, it can be measured by the method described above (Calculation of irreversible capacity rate of negative electrode precursor).

[0175] (2) Method of Calculation from the Negative Electrode: The completed alkali metal storage element after the initial charging process is charged at a constant current of 0.1 C in a thermostatic chamber set at 25 ° C until the stable operating voltage upper limit is reached, followed by 30 minutes of constant voltage charging at a constant voltage equal to the stable operating voltage upper limit. The storage element is then disassembled in an argon box, the negative electrode is removed, and in the case of a double-sided negative electrode, the active material layer on one side is removed using a spatula or the like to create a single-sided negative electrode, which is then reassembled into a negative electrode half cell using an alkali metal counter electrode, an alkali metal reference electrode, and a glass filter separator. Based on the capacity of the negative electrode half cell, the cell is charged at a constant current of 0.1 C to 2.5 V, then, after a 10-minute pause, discharged at a constant current of 0.1 C to 0.01 V relative to the alkali metal reference electrode, and then discharged at a constant voltage until the current converges to a rate of 0.02 C. After that, after a 10-minute rest, the battery was charged at a constant current of 0.1 C up to 2.5 V, and the charge capacity (mAh) was measured. The area of ​​the coated part of the negative electrode on one side (cm ２ ) to obtain the reversible release capacity H1 (mAh / cm ２ ) is obtained.

[0176] Meanwhile, the completed alkali metal storage element after the initial charging process is subjected to constant-current charging at a current value of 0.1 C in a thermostatic chamber set at 25°C until the stable operating voltage upper limit is reached, followed by 30 minutes of constant-voltage charging at a constant voltage equal to the stable operating voltage upper limit. The storage element is then disassembled in an argon box, the negative electrode is removed, and in the case of a double-sided negative electrode, the active material layer on one side is peeled off using a spatula or the like to create a single-sided negative electrode, which is then reassembled into a negative electrode half-cell using an alkali metal counter electrode, an alkali metal reference electrode, and a glass filter as a separator. Based on the capacity of the negative electrode half-cell, the negative electrode half-cell is then disassembled in an argon box, and the negative electrode is removed. The procedure of "immersing the negative electrode in an electrolyte for alkali metal storage elements, minus the electrolyte and additives, i.e., the electrolyte solvent alone, and then removing the washing solvent" is repeated three times. The negative electrode is then immersed in an electrolyte solution for alkali metal storage elements, minus the electrolyte and additives, i.e., the electrolyte solvent alone. The negative electrode is then removed and vacuum dried at 25°C for 12 hours. This results in a negative electrode in which the alkali metal ions in the electrolyte solution have been removed, while the alkali metal equivalent to the irreversible capacity remains in the negative electrode. The negative electrode active material layer is then scraped off, and the negative electrode is subjected to acid decomposition using a strong acid, such as concentrated nitric acid, concentrated hydrochloric acid, or aqua regia. The resulting solution is diluted with pure water to an acid concentration of 2% to 3%. Acid decomposition can also be performed by heating and pressurization as appropriate. The resulting diluted solution is analyzed by ICP-MS, but it is preferable to add a known amount of alkali metal as an internal standard. If the alkali metal concentration to be measured exceeds the upper limit of measurement, it is preferable to further dilute the diluted solution while maintaining the acid concentration. The amount of alkali metal (g) is quantified based on a calibration curve prepared in advance using a standard solution for chemical analysis, and the amount of alkali metal M (g / cm) equivalent to the irreversible capacity contained per coated area of ​​the single-sided negative electrode is calculated. ２ The irreversible capacity H2 (mAh / cm2) contained per coated area of ​​the single-sided negative electrode is calculated using the atomic weight m of the alkali metal. ２ ) is calculated by H2 = M ÷ m × 1000 ÷ 3600. In this case, the irreversible capacity rate Q (%) of the negative electrode is obtained by the following formula: Q = H2 / (H1 + H2) × 100

[0177] <Separator> The positive electrode precursor and the negative electrode are generally stacked or wound with a separator interposed therebetween to form an electrode stack or an electrode wound body having the positive electrode precursor, the negative electrode, and the separator.

[0178] The separator may be a known separator used in alkali metal ion secondary batteries. For example, a polyethylene microporous membrane or a polypropylene microporous membrane, or a cellulose nonwoven paper used in electric double layer capacitors may be used. A membrane composed of organic or inorganic fine particles may be laminated on one or both sides of the separator. Furthermore, the separator may contain organic or inorganic fine particles.

[0179] The thickness of the separator is preferably 5 μm or more and 35 μm or less. A separator thickness of 5 μm or more is preferred because it tends to reduce self-discharge due to internal micro-short circuits. A separator thickness of 35 μm or less is preferred because it tends to improve the output characteristics of non-aqueous alkali metal type energy storage devices such as lithium ion secondary batteries and sodium ion secondary batteries.

[0180] The thickness of the film made of organic or inorganic fine particles is preferably 1 μm or more and 10 μm or less. A film made of organic or inorganic fine particles having a thickness of 1 μm or more is preferred because it tends to reduce self-discharge due to internal micro-short circuits. A film made of organic or inorganic fine particles having a thickness of 10 μm or less is preferred because it tends to improve the output characteristics of non-aqueous alkaline metal storage batteries such as lithium ion secondary batteries and sodium ion secondary batteries. The film made of organic or inorganic fine particles may be the same layer as the intermediate layer of the first embodiment, or may be a different layer. The film made of organic or inorganic fine particles may be the same layer as the pre-dope material layer of the third embodiment, or may be a different layer.

[0181] In an embodiment of the alkali metal ion secondary battery (or alkali metal storage element precursor) of the present disclosure, the separator may contain an organic polymer that swells upon penetration of a non-aqueous electrolyte solution, or an organic polymer may be used alone as a substitute for the separator. The organic polymer is not particularly limited, but is preferably one that has good affinity with the non-aqueous electrolyte solution and gels upon penetration and swelling of the electrolyte solution. Suitable organic polymers include, for example, polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, and mixtures thereof, which exhibit high alkali metal ion conductivity when gelled.

[0182] The organic polymer can contain the electrolyte solution within the organic polymer, which is advantageous from the viewpoint of safety because it has the effect of preventing the electrolyte solution from leaking out of the alkali metal ion secondary battery when the exterior body is damaged.

[0183] <Solid Electrolyte> In another embodiment, the alkali metal ion secondary battery can include a solid electrolyte in addition to the positive electrode and negative electrode.

[0184] When a solid electrolyte is used, the positive electrode precursor and the negative electrode are stacked with the solid electrolyte interposed therebetween, and it is important to ensure an alkali metal ion conduction path. The method for this is not particularly limited, but for example, in the case of an inorganic solid electrolyte, a solid interface with the active material particles can be appropriately constructed by adding a solid electrolyte layer to the positive electrode precursor and the negative electrode.

[0185] The material used for the solid electrolyte is not particularly limited as long as it functions as a solid electrolyte material, and the same materials as those used in general solid alkali metal ion secondary batteries can be used. Examples of inorganic solid electrolytes include LiN, LISICONs, Thio-LISICONs, and LaN having a perovskite structure. ０．５１ Li ０．３４ TiO ２．９４ , Li having a NASICON structure １．３ Al ０．３ Ti １．７ P ３ O １２, Li having a garnet structure ７ La ３ Zr ２ O １２ and Li ２ S-P ２ S ５ System, LiI-Li ２ S-P ２ S ５ system, Li ３ P.O. ４ -Li ２ S-Si ２ S series, Li １０ GeP ２ S １２ However, inorganic solid electrolytes containing one or more inorganic oxides and inorganic sulfides having alkali metal ion conductivity are preferred.

[0186] <Method for Manufacturing Alkali Metal Ion Secondary Battery> The alkali metal ion secondary battery in this embodiment can be manufactured by the following method using the positive electrode precursor and negative electrode formed as described above: (1) housing a laminate composed of a positive electrode precursor, a negative electrode, and a separator in an exterior body (cell assembly), (2) injecting a non-aqueous electrolyte solution into the exterior body (electrolyte solution injection), and (3) applying a voltage between the positive electrode precursor and the negative electrode to decompose the alkali metal compound (pre-doping), in the order described above.

[0187] (Assembly) In cell assembly, a positive electrode terminal and a negative electrode terminal are connected to a laminate formed by stacking a positive electrode precursor and a negative electrode cut into a sheet shape with a separator interposed therebetween to produce an electrode laminate. Alternatively, a positive electrode terminal and a negative electrode terminal are connected to a wound body formed by winding a positive electrode precursor and a negative electrode with a separator interposed therebetween to produce an electrode wound body. The shape of the electrode wound body may be cylindrical or flat. The method for connecting the positive electrode terminal and the negative electrode terminal is not particularly limited, and can be performed by methods such as resistance welding or ultrasonic welding.

[0188] (Exterior Body) As the exterior body, a metal can, a laminated packaging material, etc. can be used. As the metal can, one made of aluminum is preferred. As the laminated packaging material, a film in which a metal foil and a resin film are laminated is preferred, and an example is a laminated packaging material composed of three layers: an outer layer resin film / a metal foil / an interior resin film. The outer layer resin film is intended to prevent damage to the metal foil due to contact, etc., and a resin such as nylon or polyester can be suitably used. The metal foil is intended to prevent permeation of moisture and gas, and a foil of copper, aluminum, stainless steel, etc. can be suitably used. Furthermore, the interior resin film is intended to protect the metal foil from the electrolyte solution stored inside and to melt-seal the exterior body when it is heat-sealed, and a polyolefin, an acid-modified polyolefin, etc. can be suitably used.

[0189] (Storage in packaging material) The electrode laminate or electrode wound body is preferably stored in a packaging material such as a metal can or a laminate packaging material, and the opening is preferably sealed except for one side. The method for sealing the packaging material is not particularly limited, but when a laminate packaging material is used, methods such as heat sealing or impulse sealing can be used.

[0190] (Drying) The electrode is preferably dried to remove any remaining electrode slurry solvent and moisture. The drying method is not limited, but can be vacuum drying or the like. The remaining solvent and moisture are preferably 1.5 mass% or less based on the mass of the positive electrode active material layer or the negative electrode active material layer. Residual solvent exceeding 1.5 mass% is undesirable because the solvent remains in the system, which may deteriorate the self-discharge characteristics and cycle characteristics. Drying may be performed in any step. For example, drying may be performed in the state of the electrode, in the state of an electrode stack or electrode winding, or after being housed in an outer casing.

[0191] (Non-aqueous electrolyte) The electrolyte in this embodiment can be a known electrolyte for alkali metal ion batteries. It is a non-aqueous electrolyte containing alkali metal ions such as lithium ions and sodium ions. That is, this non-aqueous electrolyte contains a non-aqueous solvent, which will be described later. The non-aqueous electrolyte preferably contains 0.5 mol / L or more of an alkali metal salt, such as a lithium salt or a sodium salt, based on the total volume of the non-aqueous electrolyte. That is, the non-aqueous electrolyte contains alkali metal ions, such as lithium ions and sodium ions, as an electrolyte. Lithium salts and sodium salts are preferably used as the alkali metal salt used as the electrolyte.

[0192] Examples of lithium salts include LiN(SO ２ F) ２ , LiN(SO ２ CF ３ ) ２ , LiN(SO ２ C ２ F ５ ) ２ , LiN(SO ２ CF ３ ) (SO ２ C ２ F ５ ), LiN(SO ２ CF ３ ) (SO ２ C ２ F ４ H), LiC(SO ２ F) ３ , LiC(SO ２ CF ３ ) ３ , LiC(SO ２ C ２ F ５ ) ３ , LiCF ３ SO ３ , LiC ４ F ９ SO ３ , LiPF ６ , and LiBF ４ These may be used alone or in combination of two or more. The lithium salt LiPF ６ and / or LiN(SO ２ F)２ It is preferred that the compound contains:

[0193] Examples of sodium salts include Na(SO ２ CF ３ ) ２ , NaN(SO ２ F) ２ , NaN(C ２ F ５ SO ２ ) ２ , NaCF ３ SO ３ , NaC(CF ３ SO ２ ) ３ , NaPF ６ , NaBF ４ , NaClO ４ , NaAsF ６ , NaAlCl ４ These can be used alone or in combination of two or more. For example, NaClO ４ , NaPF ６ and / or NaN(SO ２ CF ３ ) ２ It is preferred that the compound contains:

[0194] The alkali metal salt concentration in the non-aqueous electrolyte is preferably 0.5 mol / L or more, more preferably in the range of 0.5 to 2.0 mol / L. If the alkali metal salt concentration is 0.5 mol / L or more, sufficient ions are present, allowing the battery capacity to be sufficiently high. If the alkali metal salt concentration is 2.0 mol / L or less, this is preferable because it can prevent undissolved alkali metal salt from precipitating in the non-aqueous electrolyte and the viscosity of the non-aqueous electrolyte from becoming too high, making it difficult for the conductivity to decrease and the output characteristics to decrease.

[0195] The non-aqueous electrolyte solution in this embodiment preferably contains a cyclic carbonate and a chain carbonate as a non-aqueous solvent. The non-aqueous electrolyte solution containing a cyclic carbonate and a chain carbonate is advantageous in that it can dissolve an alkali metal salt at a desired concentration and exhibit high ionic conductivity. Examples of cyclic carbonates include alkylene carbonate compounds such as ethylene carbonate, propylene carbonate, and butylene carbonate. The alkylene carbonate compound is typically unsubstituted. Examples of chain carbonates include dialkyl carbonate compounds such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, and dibutyl carbonate. The dialkyl carbonate compound is typically unsubstituted.

[0196] The total content of the cyclic carbonate and the chain carbonate is preferably 50% by mass or more, more preferably 65% ​​by mass or more, even more preferably 95% by mass or less, and even more preferably 90% by mass or less, based on the total mass of the non-aqueous electrolyte solution. If the total content of the cyclic carbonate and the chain carbonate is 50% by mass or more, it is possible to dissolve the alkali metal salt at a desired concentration, and high ionic conductivity can be exhibited. If the total concentration of the cyclic carbonate and the chain carbonate is 95% by mass or less, the electrolyte solution can further contain the additives described below.

[0197] The nonaqueous electrolyte solution in this embodiment may further contain an additive. The additive is not particularly limited, but examples thereof include sultone compounds, cyclic phosphazenes, acyclic fluorine-containing ethers, fluorine-containing cyclic carbonates, cyclic carbonates such as vinylene carbonate, cyclic carboxylic acid esters, and cyclic acid anhydrides. These may be used alone or in combination of two or more.

[0198] (Injection) After assembly, a non-aqueous electrolyte solution is injected into the electrode laminate housed in the exterior housing. After the injection, it is desirable to further impregnate the positive electrode, negative electrode, and separator so that they are thoroughly soaked in the non-aqueous electrolyte solution. The impregnation method is not particularly limited, but for example, after the non-aqueous electrolyte solution is injected, the electrode laminate is placed in a reduced-pressure chamber with the exterior housing open, and a vacuum pump is used to reduce the pressure inside the chamber, and the pressure is then returned to atmospheric pressure. After the impregnation, the electrode laminate can be sealed while reducing the pressure while the exterior housing is open.

[0199] (Pre-doping) In the first embodiment, the alkali metal carbonate functions as a doping source of alkali metal ions into the negative electrode active material. In the pre-doping, a voltage is applied between the positive electrode precursor and the negative electrode to decompose the alkali metal carbonate and release the alkali metal ions, and the alkali metal ions are pre-doped into the negative electrode active material. Pre-doping may be performed in the initial charging step.

[0200] In the first embodiment, the ultimate potential of the positive electrode precursor is 4.15 to 4.75 V (vs. Li / Li ＋ In this range, the alkali metal carbonate can be decomposed and the alkali metal ions can be doped into the negative electrode active material while minimizing damage to the positive electrode and the electrolyte, thereby suppressing the loss of the positive electrode active material due to irreversible capacity and increasing the effective utilization rate of the positive electrode active material.

[0201] In the method for producing an alkali metal ion secondary battery of the present disclosure, when the alkali metal is lithium, the voltage applied between the positive electrode precursor and the negative electrode precursor during pre-doping can be appropriately adjusted taking into consideration the voltage tolerance of the electrolyte solution and the positive electrode active material used, and is preferably 4.1 V or more and 4.6 V or less. The lower limit of the applied voltage is more preferably 4.2 V or more, and even more preferably 4.3 V or more, and the upper limit of the applied voltage is more preferably 4.5 V or less, and even more preferably 4.45 V or less.

[0202] When the alkali metal is lithium, applying a voltage of 4.1 V or more and 4.6 V or less between the positive electrode precursor and the negative electrode precursor can obtain the pre-doping effect while avoiding damage to the positive electrode active material and the electrolyte, which is preferable from the viewpoints of positive electrode utilization rate and resistance, gas generation during high-temperature storage, etc. In this embodiment, the use of the specific carbon material described above makes it possible to decompose lithium carbonate at such a relatively low voltage.

[0203] Further, from the same viewpoint as above, the present invention provides a battery having the following configurations (a) to (f): (a) the negative electrode precursor has a negative electrode active material layer containing a negative electrode active material including a material that absorbs and releases lithium ions, and (b) the positive electrode precursor has a positive electrode active material layer containing a positive electrode active material that contains a positive electrode active material that absorbs and releases lithium ions, and (c) the positive electrode active material layer contains lithium carbonate, and (d) the positive electrode active material layer contains 0.30 mass % or more and 15.00 mass % or less of a carbon material, and (e) the carbon material has an oxygen atomic weight X calculated from carbon monoxide and / or carbon dioxide obtained when measured by temperature programmed desorption-mass spectrometry (TPDMS) of 0.10 mmol / g or more and 5.00 mmol / g or less per mass of the carbon material, and (f) the non-aqueous electrolyte solution includes an electrolyte containing lithium ions, Another aspect of the present disclosure is a method for producing a nonaqueous lithium storage element precursor or a doping method, or a method for producing a nonaqueous lithium storage element, in which a nonaqueous lithium storage element precursor having the formula (I) is doped with lithium ions by applying a voltage of 4.1 V or more and 4.45 V or less between a positive electrode precursor and a negative electrode precursor. The above-mentioned production method or doping method makes the effects of the present disclosure more pronounced.

[0204] When the alkali metal is lithium, the method of voltage application is not particularly limited, and examples that can be used include a method of charging to a voltage of 4.1 V or higher using a charge / discharge device, a power source, or the like (constant current charging and constant voltage charging may be used in combination); a method of superimposing a pulse voltage while applying a constant voltage of 4.1 V or higher; and a method of performing a charge / discharge cycle using a charge / discharge device within a voltage range that includes a voltage of 4.1 V or higher.

[0205] In the method for producing an alkali metal ion secondary battery of the present disclosure, when the alkali metal is sodium, the voltage applied between the positive electrode precursor and the negative electrode during pre-doping can be appropriately adjusted taking into consideration the voltage tolerance of the electrolyte solution and the positive electrode active material used, and is preferably 3.8 V or more and 4.3 V or less. The lower limit of the applied voltage is more preferably 3.9 V or more, and even more preferably 4.0 V or more, and the upper limit of the applied voltage is more preferably 4.2 V or less, and even more preferably 4.15 V or less.

[0206] When the alkali metal is sodium, applying a voltage of 3.8 V or more and 4.3 V or less between the positive electrode precursor and the negative electrode can obtain the pre-doping effect while avoiding damage to the positive electrode active material and the electrolyte, which is preferable from the viewpoints of positive electrode utilization rate and resistance, gas generation during high-temperature storage, etc. In the first embodiment, the use of the specific carbon material described above enables decomposition of the alkali metal carbonate at such a relatively low voltage.

[0207] When the alkali metal is sodium, the method of voltage application is not particularly limited, and examples that can be used include a method of charging to a voltage of 3.8 V or higher using a charge / discharge device, a power source, or the like (constant current charging and constant voltage charging may be used in combination); a method of superimposing a pulse voltage while applying a constant voltage of 3.8 V or higher; and a method of performing a charge / discharge cycle using a charge / discharge device within a voltage range that includes a voltage of 3.8 V or higher.

[0208] The amount of doping from the alkali metal carbonate can be controlled by adjusting the temperature, voltage, current, time, etc. during pre-doping.

[0209] (Measurement of the potential of the positive electrode precursor) The positive electrode potential (vs. Li / Li ＋) is measured by the following method. An electrode assembly consisting of a positive electrode precursor, a negative electrode precursor, and a separator, and an alkali metal reference electrode are sealed in a laminate to prepare a nonaqueous lithium storage element precursor before injection. The alkali metal reference electrode and the electrode assembly are positioned close to each other so that the potential difference between the positive electrode precursor and the alkali metal reference electrode can be measured. If necessary, it is preferable to wrap the alkali metal reference electrode in a separator and bring the separator into contact with the electrode assembly to ensure that the electrolyte passes between the alkali metal reference electrode and the electrode assembly. After the electrolyte is injected, the laminate is sealed. During the initial charging process, a voltage is applied between the positive electrode precursor and the negative electrode precursor, and simultaneously the potential difference between the positive electrode and the alkali metal reference electrode is measured, and the potential of the positive electrode precursor relative to the alkali metal is measured.

[0210] When the alkali metal is lithium, the potential difference X between the positive electrode and the alkali metal reference electrode obtained by the measurement is the positive electrode potential (vs Li / Li ＋ ) and the maximum positive electrode potential during the initial charge is taken as the reached potential.

[0211] When the alkali metal is an alkali metal M other than lithium, the maximum potential difference X (vs M / M) between the positive electrode and the alkali metal reference electrode during the initial charge ＋ For example, when the alkali metal is sodium, the difference in the standard electrode potential between sodium and lithium is 0.33 V, so by adding 0.33 V to the potential difference X obtained against sodium, the positive electrode potential (vs Li / Li ＋ ) is obtained as

[0212] (Pre-doping in the second and third embodiments) In the second and third embodiments, the pre-dope material functions as a dopant source of alkali metal ions to the negative electrode active material. In the pre-doping, it is preferable to apply a voltage between the positive electrode precursor and the negative electrode to decompose the pre-dope material to release alkali metal ions, and pre-dope the alkali metal ions into the negative electrode active material.

[0213] In the manufacturing method of the alkali metal ion secondary battery of the second and third embodiments, the voltage applied between the positive electrode precursor and the negative electrode during pre-doping is appropriately set depending on the pre-dope material and the negative electrode material. When using a general graphite negative electrode and lithium as the alkali metal, the potential of the negative electrode is around 0.1 V relative to lithium. The upper limit of the operating potential of the pre-dope material is as follows relative to lithium: Li ５ FeO ４ So, 4.2V Li ６ CoO ４ So, 4.3V Li ２ NiO ４ So, 4.5V Li ６ MnO ４ So, 4.8V Li １．２ (Ti ０．５ Fe ０．５ ) ０．８ O ２ So, 4.3V Li ４ TiO ４ So, 4.0V Li ２ TiO ３ So it is 4.0V.

[0214] The working potential voltage of the full cell is as follows: ５ FeO ４ So, 4.1V Li ６ CoO ４ So, 4.2V Li ２ NiO ４ So, 4.4V Li ６ MnO ４ So, 4.7V Li １．２ (Ti ０．５ Fe ０．５ ) ０．８ O ２ So, 4.2V Li ４ TiO ４ So, 3.9V Li ２ TiO ３ So it's 3.9V.

[0215] However, these potentials or voltages can be appropriately adjusted taking into consideration the voltage resistance of the electrolyte solution used, etc.

[0216] The method of voltage application is not particularly limited, and examples that can be used include a method of applying a constant voltage of 4.2 V or higher using a charge / discharge device, a power source, or the like (constant current charging and constant voltage charging may be used in combination); a method of superimposing a pulse voltage while applying a constant voltage of 4.2 V or higher; and a method of performing a charge / discharge cycle using a charge / discharge device in a voltage range that includes a voltage of 4.2 V or higher.

[0217] In this embodiment, in the pre-doping operation, CO ２ , O ２ Gases such as argon, argon, and argon may be generated. Therefore, when applying a voltage, it is preferable to take measures to release the generated gas to the outside of the "electrode laminate, or electrode wound body, or exterior body." Examples of such measures include a method of applying a voltage with a part of the exterior body opened; a method of applying a voltage with an appropriate gas release means such as a gas vent valve or a gas permeable film previously installed in a part of the exterior body; and a method of storing gas in the excess part of the laminate and removing the generated gas together with the excess part of the laminate in a subsequent step such as degassing.

[0218] (Aging) After the pre-doping, the electrode laminate is preferably subjected to aging, in which the solvent in the nonaqueous electrolyte solution is decomposed at the negative electrode, and a solid polymer coating film permeable to alkali metal ions is formed on the surface of the negative electrode.

[0219] The aging method is not particularly limited, but for example, a method of reacting the solvent in the electrolyte in a high-temperature environment can be used.

[0220] (Gassing) After aging, it is preferable to perform further gassing to completely remove any remaining gas in the electrolyte, the positive electrode, and the negative electrode. If gas remains in at least part of the electrolyte, the positive electrode, and the negative electrode, ion conduction is inhibited, resulting in an increase in the resistance of the resulting nonaqueous alkali metal storage element.

[0221] The degassing method is not particularly limited, and may be, for example, a method in which the electrode laminate is placed in a reduced pressure chamber with the exterior body open and the chamber is reduced in pressure using a vacuum pump, etc. After degassing, the exterior body is sealed to hermetically close the exterior body, and a nonaqueous alkali metal type storage element can be produced.

[0222] <Alkali Metal Ion Secondary Battery> An alkali metal ion secondary battery can be manufactured by the above method. This alkali metal ion secondary battery includes a positive electrode having a positive electrode active material layer in which the alkali metal carbonate or pre-dope material contained in the positive electrode precursor has been decomposed, or an intermediate layer in which the alkali metal carbonate contained in the intermediate layer has been decomposed, or a negative electrode having a negative electrode active material layer in which the pre-dope material contained in the pre-dope material layer has been decomposed or the pre-dope material layer is doped with an alkali metal. The positive electrode active material layer, the intermediate layer, or the pre-dope material layer may contain the alkali metal carbonate or pre-dope material that was not decomposed during pre-doping.

[0223] In the alkali metal ion secondary battery of the first embodiment, the negative electrode is doped with an alkali metal from an alkali metal carbonate as a pre-doping source, and therefore the positive electrode active material can be more effectively utilized, which in the past could not function effectively due to the irreversible capacity of the negative electrode. Specifically, the effective utilization rate of the positive electrode active material described below can be increased to 85% or more and 99.5% or less, or 95% or more and 99.5% or less. Therefore, by reducing the amount of positive electrode active material used, it is possible to reduce the cost of the battery.

[0224] (Volume Resistivity of Positive Electrode Active Material Layer) In the second embodiment, the volume resistivity (Ωcm) of the positive electrode active material layer of the positive electrode after pre-doping is preferably 10 or less. If it is 10 Ωcm or less, the electrical resistance in the composite is low, so that the charge / discharge reaction during the cycle test proceeds uniformly, and the cycle capacity retention rate is likely to be improved.

[0225] The method for measuring the volume resistivity of the positive electrode active material layer is not particularly limited, and measurement can be performed, for example, using an electrode resistance measurement system (an electrode resistance measuring device for positive electrode sheets and negative electrode sheets of alkali metal ion secondary batteries) manufactured by Hioki E.E. Corp. A measurement probe is brought into contact with the surface of the positive electrode active material layer of the positive electrode precursor at normal pressure, a constant current is passed through the surface of the positive electrode active material layer, and the potential distribution generated on the surface is measured at multiple points, thereby calculating the volume resistivity of the positive electrode active material layer in the positive electrode precursor.

[0226] <Characteristics Evaluation of Alkali Metal Ion Secondary Batteries> The characteristics of alkali metal ion secondary batteries according to the present disclosure are shown below, but because the operating voltage varies depending on the combination of positive electrode active material and negative electrode active material, it is necessary to change the set values ​​for the charge and discharge voltages depending on the alkali metal ion secondary battery. The charge and discharge voltages in the following exemplary characteristic evaluations are not particularly limited to these.

[0227] (Discharge capacity Q, full cell capacity density P per mass of positive electrode active material full In the present disclosure, the capacity Q (Ah) is a value obtained by the following method: ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ When using as the positive electrode active material, the alkali metal ion secondary battery is charged at a constant current of 0.1 C in a thermostatic chamber set at 25° C. until the stable operating voltage upper limit, i.e., 4.2 V, is reached, and then constant voltage charging is performed for 30 minutes by applying a constant voltage of 4.2 V. Thereafter, the battery is discharged at a constant current of 0.1 C to the stable operating voltage lower limit, i.e., 3.0 V, and the electric capacity when this is discharged is defined as Q (Ah).

[0228] LiFePO ４When using as the positive electrode active material, the alkali metal ion secondary battery is charged in a thermostatic chamber set at 25° C. at a constant current of 0.1 C until the stable operating voltage upper limit, i.e., 3.6 V, is reached, and then constant voltage charging is performed for 30 minutes by applying a constant voltage of 3.6 V. Thereafter, the battery is discharged at a constant current of 0.1 C to the stable operating voltage lower limit, i.e., 2.4 V, and the electric capacity when this is discharged is defined as Q (Ah).

[0229] By dividing Q by the mass of the positive electrode active material used, the full cell capacity density P per mass of the positive electrode active material is obtained. full (mAh / g) can be obtained.

[0230] NaFe １／３ Ni １／３ Mn １／３ O ２ When using as the positive electrode active material, the alkali metal ion secondary battery is charged at a constant current of 0.1 C in a thermostatic chamber set at 25°C until the stable operating voltage upper limit, i.e., 3.9 V, is reached, followed by 30 minutes of constant voltage charging at a constant voltage of 3.9 V. The electric capacity when the battery is then discharged at a constant current of 0.1 C to the stable operating voltage lower limit, i.e., 1.9 V, is defined as Q (Ah). The full cell capacity density P per mass of the positive electrode active material is calculated by dividing Q by the mass of the positive electrode active material used. full (mAh / g) can be obtained.

[0231] (Effective utilization rate of positive electrode active material) The above-mentioned "full cell discharge capacity density P per mass of positive electrode active material" ｆｕｌｌ The effective utilization rate of the positive electrode active material can be determined by dividing "(mAh / g)" by "initial discharge capacity density B1 per mass of positive electrode active material." By performing pre-doping using an alkali metal carbonate or a pre-dope material, the alkali metal lost in the irreversible capacity of the negative electrode can be compensated for, thereby increasing the effective utilization rate of the positive electrode active material.

[0232] The effective utilization rate of the positive electrode active material of the nonaqueous alkali metal storage element is preferably 85 to 99.5%. When the effective utilization rate of the positive electrode active material is in this range, loss of the positive electrode active material can be reduced, and the amount of positive electrode active material used can be reduced, which is preferable from the viewpoint of production costs.

[0233] (Reduction in Positive Electrode Active Material Loss) In the first embodiment, the effect of reducing the loss of positive electrode active material due to the irreversible capacity of the negative electrode is achieved. The effective utilization rate a (%) of the positive electrode active material of the alkali metal storage element of the first embodiment is calculated. A separate alkali metal storage element, which has the same basis weight of positive electrode active material and negative electrode active material as the alkali metal storage element of the first embodiment and does not contain carbonate, is initially charged at the upper limit voltage of the "stable operating voltage" corresponding to the positive electrode active material described in (Stable operating potential of positive electrode and stable operating voltage of battery corresponding to positive electrode active material), to produce an alkali metal storage element, and the effective utilization rate b (%) of the positive electrode active material is measured. The reduction in positive electrode active material loss X (%) is calculated by X = a - b. A reduction in positive electrode active material loss of 2% or more is preferable because it reduces the loss of the costly positive electrode active material in the alkali metal storage element. The reduction in the loss of the positive electrode active material is more preferably 10% or more, and particularly preferably 18% or more.

[0234] (DC Resistance R) In the present disclosure, 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 according to the positive electrode active material. That is, it is a value obtained by the following method.

[0235] LiCoO ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ When using this as the positive electrode active material, the alkali metal ion secondary battery is charged in a thermostatic chamber set at 25°C at a constant current of 0.1 C until the stable operating voltage upper limit, i.e., 4.2 V, is reached, and then constant voltage charging is performed by applying a constant voltage of 4.2 V for 30 minutes. １Ｃ (A) The voltage V after 10 seconds when constant current discharge is performed １０秒 (V). The resistance R (Ω) is calculated using the following formula: R = (4.2 - V １０秒 ) ÷ I１Ｃ It is calculated as follows.

[0236] LiFePO ４ When using this as the positive electrode active material, the alkali metal ion secondary battery is charged in a thermostatic chamber set at 25°C at a constant current of 0.1 C until the stable operating voltage upper limit, i.e., 3.6 V, is reached, and then constant voltage charging is performed by applying a constant voltage of 3.6 V for 30 minutes. １Ｃ (A) The voltage V after 10 seconds when constant current discharge is performed １０秒 (V). The resistance R (Ω) is calculated using the following formula: R = (3.6 - V １０秒 ) ÷ I １Ｃ It is calculated as follows.

[0237] NaFe １／３ Ni １／３ Mn １／３ O ２ When using this as the positive electrode active material, the alkali metal ion secondary battery is charged in a thermostatic chamber set at 25°C at a constant current of 0.1 C until the stable operating voltage upper limit, i.e., 3.9 V, is reached, and then constant voltage charging is performed by applying a constant voltage of 3.9 V for 30 minutes. １Ｃ (A) The voltage V after 10 seconds when constant current discharge is performed １０秒 (V). The resistance R (Ω) is calculated using the following formula: R = (3.9 - V １０秒 ) ÷ I １Ｃ It is calculated as follows.

[0238] (Amount of Negative Electrode Doped, Volume Difference, Pre-Doping Volumetric Efficiency) <When Alkali Metal Carbonate and Carbon Material Are Contained in Positive Electrode Active Material Layer> In the present disclosure, the pre-doping volumetric efficiency when the positive electrode active material layer contains an alkali metal carbonate and a carbon material is obtained by the following method. Positive electrode precursor 1 contains an active material, and optionally contains conductive carbon black Super C65 and a binder, but does not contain an alkali metal carbonate. 炭酸Ｌｉなし On the other hand, a positive electrode precursor 2 containing an active material, a conductive material, a binder as optional components, an alkali metal carbonate, and a carbon material is prepared. 炭酸Ｌｉあり At this time, the slurry composition and basis weight are adjusted so that the basis weight of the active material is the same.炭酸Ｌｉなし Thickness t1 (μm), positive electrode precursor 2 炭酸Ｌｉあり The thickness t2 (μm) of the positive electrode precursor 1 is measured. 炭酸Ｌｉなし and positive electrode precursor 2 炭酸Ｌｉあり Area S (cm ２ ) is used and combined with a negative electrode and separator common to No. 1 and No. 2 to prepare nonaqueous alkali metal electricity storage element precursors No. 1 and No. 2. The volume difference V (cc / cell) of the nonaqueous alkali metal electricity storage element precursor due to the introduction of the alkali metal carbonate and the carbon material is calculated by the following formula: V = (t2 - t1) × S ÷ 10000.

[0239] Positive electrode precursor 1 炭酸Liなし The non-aqueous alkali metal storage element precursor 1 using 炭酸Liあり For the non-aqueous alkali metal storage element precursor 2 using the above, pre-doping is performed in the initial charging process (initial charging is performed under the same conditions for both storage element precursors 1 and 2), thereby producing non-aqueous alkali metal storage elements 1 (without alkali metal carbonate) and 2 (with alkali metal carbonate), respectively.

[0240] LiCoO ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４When using as the positive electrode active material, the completed nonaqueous alkali metal storage elements 1 and 2 are charged at a constant current of 0.1 C in a thermostatic chamber set at 25 °C until the stable operating voltage upper limit, i.e., 4.2 V, is reached, followed by 30 minutes of constant voltage charging at a constant voltage of 4.2 V. The storage elements are then disassembled in an argon box, the negative electrodes are removed, and reassembled into negative electrode half cells using a lithium counter electrode and a glass filter separator. Using the capacity of the negative electrode half cell as a reference, the negative electrode doping amounts Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 4.2 V are measured by desorbing lithium from the negative electrode through constant current charging at a current of 0.1 C to 2.5 V.

[0241] LiFePO ４ When using as the positive electrode active material, the alkali metal ion secondary battery is charged at a constant current of 0.1 C in a thermostatic chamber set at 25 °C until the stable operating voltage upper limit, i.e., 3.6 V, is reached, followed by 30 minutes of constant voltage charging at a constant voltage of 3.6 V. The storage element is then disassembled in an argon box, the negative electrode is removed, and reassembled into a negative electrode half cell using a lithium counter electrode and a glass filter separator. Using the capacity of the negative electrode half cell as a reference, the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 3.6 V is measured by desorbing lithium from the negative electrode by constant current charging at a current of 0.1 C to 2.5 V.

[0242] NaFe １／３ Ni １／３ Mn １／３ O ２When using as the positive electrode active material, the alkali metal ion secondary battery was charged at a constant current of 0.1 C in a thermostatic chamber set at 25 °C until the stable operating voltage limit, i.e., 3.9 V, was reached, followed by 30 minutes of constant voltage charging at a constant voltage of 3.9 V. The storage element was then disassembled in an argon box, the negative electrode removed, and reassembled into a negative electrode half cell using a sodium counter electrode and a glass filter separator. Using the capacity of the negative electrode half cell as a reference, the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 3.9 V was measured by desorbing sodium from the negative electrode through constant current charging at a current of 0.1 C to 2.5 V.

[0243] The pre-doping volumetric efficiency E (mAh / cc) can be calculated by the following formula: E = (Q2 - Q1) ÷ V That is, it is an index obtained by dividing the amount of alkali metal carbonate decomposed and doped into the negative electrode by the volume increased by mixing the alkali metal carbonate and the carbon material for pre-doping, and the higher this is, the more efficiently the pre-doping can be performed by suppressing the trade-off of the volume increase.

[0244] <When an alkali metal carbonate and a carbon material are contained in an intermediate layer between a positive electrode active material layer and a separator> In the present disclosure, the pre-doping volumetric efficiency when an alkali metal carbonate and a carbon material are contained in an intermediate layer between a positive electrode active material layer and a separator is obtained by the following method.

[0245] A positive electrode precursor containing an active material and, as optional components, conductive carbon black Super C65 and a binder, but not containing an alkali metal carbonate. 炭酸Ｌｉなし and combine it with the separator and the negative electrode to form a positive electrode precursor with an area S (cm ２ ) is used to form a non-aqueous alkali metal electricity storage element precursor 1.

[0246] Separator surface or positive electrode precursor 炭酸Liなし a positive electrode precursor in which an intermediate layer containing an alkali metal carbonate and a carbon material, and further containing a conductive material and a binder as optional components, is formed on the surface of the active material layer by the method described in the section on the method for forming the intermediate layer; 炭酸Liなし , separator, and negative electrode are combined, and the positive electrode precursor is placed on a substrate with an area of ​​S (cm２ ) to form a non-aqueous alkali metal electricity storage element precursor 2. The thickness of the intermediate layer at this time is designated as t2 (μm).

[0247] The volume difference V (cc / cell) of the nonaqueous alkali metal electricity storage element precursor due to the introduction of the alkali metal carbonate and the carbon material can be calculated by the following formula: V=(t2)×S÷10000.

[0248] Non-aqueous alkali metal storage element precursor 1, which does not contain an alkali metal carbonate, is subjected to initial charging, and non-aqueous alkali metal storage element precursor 2, which does contain an alkali metal carbonate, is subjected to pre-doping in the initial charging process (initial charging is performed under the same conditions for both storage element precursors 1 and 2), thereby producing non-aqueous alkali metal storage elements 1 (without alkali metal carbonate) and 2 (with alkali metal carbonate), respectively.

[0249] LiCoO ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ When using as the positive electrode active material, the completed nonaqueous alkali metal storage element 1, 2 is placed in a thermostatic chamber set at 25 ° C. and subjected to constant current charging at a current value of 0.1 C until the stable operating voltage upper limit, i.e., 4.2 V, is reached. Subsequently, a constant voltage charge of 4.2 V is applied for 30 minutes. The storage element is then disassembled in an argon box, the negative electrode is removed, and reassembled into a negative electrode half cell using a lithium counter electrode and a glass filter as a separator. Using the capacity of the negative electrode half cell as a reference, the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 4.2 V are measured by desorbing lithium from the negative electrode through constant current charging at a current value of 0.1 C to 2.5 V.

[0250] LiFePO ４When using as the positive electrode active material, the alkali metal ion secondary battery is charged at a constant current of 0.1 C in a thermostatic chamber set at 25 °C until the stable operating voltage upper limit, i.e., 3.6 V, is reached, followed by 30 minutes of constant voltage charging at a constant voltage of 3.6 V. The storage element is then disassembled in an argon box, the negative electrode is removed, and reassembled into a negative electrode half cell using a lithium counter electrode and a glass filter separator. Using the capacity of the negative electrode half cell as a reference, the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 3.6 V are measured by desorbing lithium from the negative electrode by constant current charging at a current of 0.1 C to 2.5 V.

[0251] NaFe １／３ Ni １／３ Mn １／３ O ２ When using as the positive electrode active material, the alkali metal ion secondary battery is charged at a constant current of 0.1 C in a thermostatic chamber set at 25 °C until the stable operating voltage upper limit, i.e., 3.9 V, is reached, followed by 30 minutes of constant voltage charging at a constant voltage of 3.9 V. The storage element is then disassembled in an argon box, the negative electrode is removed, and reassembled into a negative electrode half cell using a sodium counter electrode and a glass filter separator. Using the capacity of the negative electrode half cell as a reference, the negative electrode doping amount Q1 (without alkali metal carbonate) and Q2 (with alkali metal carbonate) (mAh / cell) at 3.9 V are measured by desorbing sodium from the negative electrode by constant current charging at a current of 0.1 C to 2.5 V.

[0252] The pre-doping volumetric efficiency E (mAh / cc) can be calculated by the following formula: E = (Q2 - Q1) ÷ V That is, it is an index obtained by dividing the amount of alkali metal carbonate decomposed and doped into the negative electrode by the volume increased by mixing the alkali metal carbonate and the carbon material for pre-doping, and the higher this is, the more efficiently the pre-doping can be performed by suppressing the trade-off of the volume increase.

[0253] (Gas Measurement at 40° C. Storage) In the present disclosure, the amount of gas generated in a 40° C. storage test is measured by the following method.

[0254] LiCoO２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ When using as the positive electrode active material, the nonaqueous alkali metal storage element is charged in a thermostatic chamber set at 40°C at a constant current of 0.1 C until the stable operating voltage upper limit, i.e., 4.2 V, is reached, followed by 30 minutes of constant voltage charging with a constant voltage of 4.2 V applied. The cell is then stored in a 40°C environment, and every week, the cell is recharged to the stable operating voltage upper limit, i.e., 4.2 V, using the above-mentioned charging procedure in a 40°C environment. The cell volume Va (cc) before the start of storage and the cell volume Vb (cc) after 6 weeks of storage are measured using the Archimedes method. Vb - Va is the amount of gas generated (cc). The unit "cc" is a unit of "cm ３ ' can be converted to

[0255] LiFePO ４ When using as the positive electrode active material, the nonaqueous alkali metal storage element is charged in a thermostatic chamber set at 40°C at a constant current of 0.1 C until the stable operating voltage, i.e., 3.6 V, is reached, followed by 30 minutes of constant voltage charging with a constant voltage of 3.6 V applied. The cell is then stored in a 40°C environment, and every week, the cell voltage is recharged to the upper stable operating voltage limit, i.e., 3.6 V, using the aforementioned charging procedure in a 40°C environment. The cell volume Va (cc) before the start of storage and the cell volume Vb (cc) after 6 weeks of storage testing are measured using the Archimedes method. Vb - Va is the amount of gas generated (cc).

[0256] NaFe １／３ Ni １／３ Mn １／３ O ２When using as the positive electrode active material, the nonaqueous alkali metal storage element is charged in a thermostatic chamber set at 40°C at a constant current of 0.1 C until the stable operating voltage, i.e., 3.9 V, is reached, followed by 30 minutes of constant voltage charging with a constant voltage of 3.9 V applied. The cell is then stored in a 40°C environment, and every week, the cell voltage is recharged to the upper stable operating voltage limit, i.e., 3.9 V, using the aforementioned charging procedure in a 40°C environment. The cell volume Va (cc) before the start of storage and the cell volume Vb (cc) after 6 weeks of storage testing are measured using the Archimedes method. Vb - Va is the amount of gas generated (cc).

[0257] (Capacity Retention Rate After 100 Cycles) In the present disclosure, the cycle capacity retention rate (%) after 100 cycles is a value obtained by the following method: That is, this value can be measured by performing charge-discharge cycles at a current value of 1 C.

[0258] LiCoO ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ When using as the positive electrode active material, first, the discharge capacity Q1 (Ah) of the lithium-ion secondary battery before the cycle test is measured using the method described above. Next, in a thermostatic chamber set at 40°C, constant current charging is performed at a current value of 1 C until the voltage reaches 4.2 V, followed by constant voltage charging at a constant voltage of 4.2 V for 30 minutes. Subsequently, constant current discharging is performed at a current value of 1 C until the voltage reaches 3.0 V, and this cycle is repeated for 100 cycles. Furthermore, the discharge capacity Q2 (Ah) after 100 cycles is measured using the method described above. The capacity retention rate after 100 cycles is calculated as (Q2 / Q1) × 100.

[0259] LiFePO ４When using as a positive electrode active material, first, the discharge capacity Q1 (Ah) of the lithium-ion secondary battery before cycle testing is measured using the method described above. Next, in a thermostatic chamber set at 40°C, constant current charging is performed at a current value of 1 C until the voltage reaches 3.6 V, followed by constant voltage charging at a constant voltage of 3.6 V for 30 minutes. Subsequently, constant current discharging is performed at a current value of 1 C until the voltage reaches 2.4 V, and this cycle is repeated for 100 cycles. Furthermore, the discharge capacity Q2 (Ah) after 100 cycles is measured using the method described above. The capacity retention rate after 100 cycles is calculated as (Q2 / Q1) × 100.

[0260] (Float Capacity Maintenance Rate After 1000 Hours) In the present disclosure, the float capacity maintenance rate (%) after 1000 hours is a value obtained by the following method.

[0261] First, the discharge capacity Q1 (Ah) of the lithium ion secondary battery before the cycle test is measured by the above-mentioned method.

[0262] A float test is carried out in which constant voltage charging at a stable operating potential is continued for 1000 hours in a 40°C environment. ２ , LiMn ０．６ Fe ０．４ P.O. ４ , LiNi １／３ Co １／３ Mn １／３ O ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ is used as the positive electrode active material, 4.2 V, LiFePO ４ When used as a positive electrode active material, the test is carried out at 3.6V.

[0263] Furthermore, the discharge capacity Q2 (Ah) after 1000 hours is measured by the method described above, and the capacity retention rate after 1000 hours is calculated by (Q2 / Q1)×100.

[0264] Examples and comparative examples of the present embodiment will be shown below, but the present invention is not limited to these examples and comparative examples.

[0265] <Examples according to the first embodiment>

[0266] (TPDMS Measurement of Carbon Material) Approximately 3 mg of carbon material was precisely weighed out in an EcoCup (manufactured by Frontier Labs). The precisely weighed carbon material was set in a mass spectrometer equipped with a heating device. The cup containing the carbon material was set in a heating furnace at 50°C, and the inside of the heating furnace was purged with carrier gas (helium) for 5 minutes before measurement. The sample was heated to 1000°C at 20°C / min, and the amount of gas desorbed from the sample during heating up to 1000°C was quantified. CO ２ The monitor ion for CO was m / z 44, and the monitor ion for CO was m / z 28. Calcium oxalate monohydrate was used as a standard substance for quantification. Calcium oxalate monohydrate was subjected to TPDMS measurement under the same conditions, and the amount of CO and CO generated was determined to be equimolar to the amount of calcium oxalate monohydrate used in the measurement. ２ Using this calibration curve, the CO and CO generated from the carbon material were ２ was quantified.

[0267] The carbon mass used in the measurement is M 炭素 (g) CO obtained in the above analysis ２ , the quantitative value of CO M ＣＯ２ (g), M ＣＯ２ (g) Desorbed CO per mass of carbon material ２ Quantity C ＣＯ２ (mmol / g), desorbed CO amount C ＣＯ (mmol / g) using the following two equations: ＣＯ２ (mmol / g)=M ＣＯ２ (g) / 44×1000 / M 炭素 (g) C ＣＯ (mmol / g)=M ＣＯ (g) / 28×1000 / M 炭素 (g) was calculated and further converted to oxygen concentration X (mmol / g) by the following formula: X (mmol / g) = C ＣＯ２ (mmol / g)×2+C ＣＯ (mmol / g) The TPDMS measurement conditions are as follows:

[0268] <TPDMS measurement conditions> Heating conditions Heating device: FRONTIER Lab Py3030D manufactured by Frontier Labs Heating atmosphere: Helium Heating conditions: After holding at 50°C for 20 minutes, heat to 1000°C at 20°C / min, and hold at 1000°C for 30 minutes GC conditions GC device: Agilent 8890 manufactured by Agilent Technologies Carrier gas: Helium Flow rate: 1 mL / min Injection port temperature: 250°C Split ratio: 1 / 10 Column: Agilent FS Deactivated manufactured by Agilent Technologies Oven temperature: Constant 250°C MS conditions MS device: JEOL JMS Q1500 Interface temperature: 250°C Ionization: EI method Scan range: m / z 10 to 300 Ion source temperature: 230°C

[0269] (Preparation of Carbon Material) Crushed coconut shell carbonized product was carbonized in a small carbonization furnace at 600°C in nitrogen. Then, instead of nitrogen, 1 kg / h of steam was preheated in the furnace and introduced into the furnace. The temperature was raised to 900°C over 12 hours, then removed and cooled under a nitrogen atmosphere to obtain activated carbon. The obtained activated carbon was washed with water for 10 hours and then drained. It was then dried for 10 hours in an electric dryer maintained at 115°C, pulverized for 60 minutes in a ball mill, immersed in 5% sulfuric acid for 1 hour, washed with distilled water until the sulfuric acid was removed, and then vacuum dried for 12 hours to remove moisture, obtaining steam-activated activated carbon 1. The specific surface area measured by the BET multipoint method was 2100 m. ２ The oxygen content obtained by the above TPDMS was 2.4 mmol / g.

[0270] The crushed coconut shell carbonized product was carbonized in a small carbonization furnace at 600°C in nitrogen. Then, instead of nitrogen, 1 kg / h of steam was preheated in the furnace and introduced into the furnace. The temperature was raised to 900°C over 6 hours, then removed and cooled under a nitrogen atmosphere to obtain activated carbon. The obtained activated carbon was washed with water for 10 hours and then drained. It was then dried for 10 hours in an electric dryer maintained at 115°C, pulverized for 30 minutes in a ball mill, immersed in 5% sulfuric acid for 1 hour, washed with distilled water until the sulfuric acid was removed, and then vacuum dried for 12 hours to remove moisture, obtaining steam-activated activated carbon 2. The specific surface area measured by the BET multipoint method was 1700 m ２ The amount of oxygen atoms obtained by the above TPDMS was 0.9 mmol / g.

[0271] The phenolic resin was carbonized in a calcination furnace under a nitrogen atmosphere at 700°C for 2 hours. The carbonized product was then pulverized in a ball mill for 4 hours. The carbonized product was mixed with KOH in a mass ratio of 1:4, and the mixture was heated in a calcination furnace under a nitrogen atmosphere at 800°C for 1 hour for activation. The product was then washed with dilute hydrochloric acid adjusted to 2 mol / L under stirring for 1 hour, then boiled and washed with distilled water until the pH stabilized between 5 and 6, and then dried. The product was then immersed in 5% sulfuric acid for 1 hour, washed with distilled water until the sulfuric acid was removed, and then vacuum dried for 12 hours to remove moisture, producing an alkali-activated activated carbon. The specific surface area measured by the BET multipoint method was 2,400 m. ２ The amount of oxygen atoms obtained by the above TPDMS was 0.15 mmol / g.

[0272] Carbon black manufactured by Lion Specialty Chemicals was used as carbon black 1. The specific surface area obtained by the BET multipoint method was 1,400 m ２ The amount of oxygen atoms obtained by the above TPDMS was 0.19 mmol / g.

[0273] The porous carbon used was Knobel manufactured by Toyo Tanso. The specific surface area obtained by the BET multipoint method was 1450 m ２ The amount of oxygen atoms obtained by the above TPDMS was 3.5 mmol / g.

[0274] Acetylene black manufactured by Denka was used as carbon black 2. The specific surface area obtained by the BET multipoint method was 70 m ２ The amount of oxygen atoms obtained by the above TPDMS was 0.04 mmol / g.

[0275] Carbon black manufactured by Imerys was used as carbon black 3. The specific surface area obtained by the BET multipoint method was 60 m ２ The amount of oxygen atoms obtained by the above TPDMS was 0.01 mmol / g.

[0276] The crushed coconut shell carbonized product was carbonized in a small carbonization furnace at 600°C in nitrogen. Then, instead of nitrogen, 1 kg / h of steam was preheated in the furnace and introduced into the furnace. The temperature was raised to 900°C over 6 hours, then removed and cooled under a nitrogen atmosphere to obtain activated carbon. The obtained activated carbon was washed with water for 10 hours and then drained. It was then dried for 10 hours in an electric dryer maintained at 115°C and pulverized for 30 minutes in a ball mill to obtain steam-activated activated carbon 3, which was then used. The specific surface area measured by the BET multipoint method was 1600 m ２ The amount of oxygen atoms obtained by the above TPDMS was 0.09 mmol / g.

[0277] The phenolic resin was carbonized in a nitrogen atmosphere in a calcination furnace at 700°C for 2 hours. The carbonized product was then pulverized in a ball mill for 4 hours, mixed with KOH in a mass ratio of 1:4, and activated by heating the mixture in a calcination furnace at 700°C for 1 hour under a nitrogen atmosphere. The mixture was then washed with dilute hydrochloric acid adjusted to 2 mol / L under stirring for 1 hour, and then boiled and washed with distilled water until the pH stabilized between 5 and 6, followed by drying, to produce alkali-activated activated carbon 2. The specific surface area obtained by the BET multipoint method was 1850 m ２ The amount of oxygen atoms obtained by the above TPDMS was 0.05 mmol / g.

[0278] Example 1-1 (Alkali Metal, Alkali Metal Carbonate) In this example, lithium was used as the alkali metal, and lithium carbonate was used as the alkali metal carbonate. (Measurement of Initial Charge Capacity A1 and Initial Discharge Capacity B1 of Positive Electrode Active Material) LiCoO was used as the positive electrode active material.２ 91% by mass of the powder, 4% by mass of carbon black 3, 5% by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) were mixed to a solids concentration of 45% by mass to obtain a positive electrode slurry for a positive electrode half cell used to measure the initial charge capacity of the positive electrode active material. The obtained slurry was applied at 100 g / m to one side of a 15 μm-thick anchor aluminum foil serving as a positive electrode current collector. ２ The coated layer was dried and pressed to obtain a positive electrode for a positive electrode half cell to be used for measuring the initial charge capacity of the positive electrode active material.

[0279] The obtained single-sided positive electrode was punched out to a coated area of ​​2 cm x 2 cm, and the positive electrode terminal was connected by ultrasonic welding. The negative electrode terminal was connected by ultrasonic welding to a Li counter electrode in which Li was attached to copper foil. This was combined with a polypropylene separator and a glass filter to obtain a positive electrode half-cell electrode laminate. This electrode laminate was housed in an exterior body made of aluminum laminate packaging, and three sides of the exterior body, including the electrode terminal portion and the bottom portion, were heat-sealed at a temperature of 180°C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. The electrode laminate was vacuum-dried at a temperature of 50°C, a pressure of 50 Pa, and a drying time of 25 hours. As the electrolyte, 1.0 M LiPF in an EC:MEC mixed solvent (volume ratio 1:2) was used. ６ An electrolyte solution containing 1% by mass of vinylene carbonate was prepared.

[0280] 2 g of the nonaqueous electrolyte solution was injected into the electrode laminate housed in the aluminum laminate packaging material under atmospheric pressure, a temperature of 25°C, and a dry air environment with a dew point of -40°C or less. Subsequently, this was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -87 kPa, and then the pressure was returned to atmospheric pressure, allowing for impregnation. Thereafter, the electrode laminate housed in the aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed at 180°C for 10 seconds at a pressure of 0.1 MPa under a reduced pressure of -95 kPa, to produce a positive electrode half cell.

[0281] The initial charge capacity density A1 and the initial discharge capacity density B1 of the positive electrode active material were determined by the method described above (initial charge capacity density A1 and initial discharge capacity density B1 of the positive electrode active material). The initial charge capacity density A1 and initial discharge capacity density B1 of the positive electrode active material were obtained. The obtained A1 and B1 are shown in the table below.

[0282] (Fabrication of alkali metal storage element) (Fabrication of positive electrode precursor) LiCoO as positive electrode active material ２ A positive electrode precursor slurry was prepared using lithium carbonate as an alkali metal carbonate, steam-activated activated carbon 1 as a carbon material, and PVdF (polyvinylidene fluoride) as a binder in the composition shown in the table below, and then NMP (N-methylpyrrolidone) was mixed in. The resulting positive electrode precursor slurry was applied to one side of a 15 μm-thick aluminum foil in the basis weight shown in the table below, and pressed to obtain a positive electrode precursor.

[0283] In order to calculate the volume difference described above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), the film thickness t2 of the positive electrode precursor containing lithium carbonate was measured.

[0284] (Preparation of Negative Electrode Precursor) 91.0 parts by mass of artificial graphite, 5.0 parts by mass of silicon monoxide, 2.0 parts by mass of styrene-butadiene rubber, 2.0 parts by mass of carboxymethyl cellulose (CMC), and water were mixed to obtain a negative electrode precursor slurry. The obtained negative electrode precursor slurry was applied to one side of a 10 μm thick electrolytic copper foil at a basis weight shown in the table below, and pressed to obtain a negative electrode precursor.

[0285] (Evaluation of Negative Electrode Irreversible Capacity Rate) In this example, the negative electrode precursor was used to evaluate the negative electrode irreversible capacity rate. Specifically, a negative electrode half-cell was fabricated from the obtained negative electrode precursor, and the irreversible capacity rate was calculated according to the method described in (Calculation of the Irreversible Capacity Rate of the Negative Electrode Precursor). The results are shown in the table below. The electrolyte was a 1.0 M LiPF in an EC:MEC mixed solvent (volume ratio 1:2). ６ An electrolyte solution containing 1% by mass of vinylene carbonate was used.

[0286] (Assembly) The resulting positive electrode precursor was cut to a coated area of ​​2 cm x 2 cm, and the resulting negative electrode precursor was cut to a coated area of ​​2.2 cm x 2.2 cm. A 15 μm thick microporous membrane separator was sandwiched between the positive electrode precursor and the negative electrode precursor and laminated. Then, a negative electrode terminal and a positive electrode terminal were connected to the negative electrode precursor and the positive electrode precursor, respectively, by ultrasonic welding to form an electrode laminate. This electrode laminate and a lithium reference electrode, which was press-bonded to SUS foil and wrapped in a microporous separator, were housed in an exterior body made of aluminum laminate packaging, and the three sides of the exterior body, including the electrode terminal portion and the bottom portion, were heat-sealed at a temperature of 180 ° C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. Vacuum drying was performed at a temperature of 50 ° C, a pressure of 50 Pa, and a drying time of 25 hours.

[0287] (Injection of electrolyte) 1.0 M LiPF in EC:MEC mixed solvent (volume ratio 1:2) was used as the electrolyte. ６ An electrolyte solution containing 1% by mass of vinylene carbonate was prepared.

[0288] 2 g of the above non-aqueous electrolyte solution was injected into the electrode laminate housed in the aluminum laminate packaging material under atmospheric pressure, a temperature of 25°C, and a dry air environment with a dew point of -40°C or less. Subsequently, this was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -87 kPa, and then the pressure was returned to atmospheric pressure for impregnation. Thereafter, the electrode laminate housed in the aluminum laminate packaging material and impregnated with the non-aqueous electrolyte solution was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed by sealing at 180°C for 10 seconds at a pressure of 0.1 MPa under a reduced pressure of -95 kPa.

[0289] (Initial charge pre-doping) The obtained injected battery was subjected to constant current charging at a 0.2C rate under a 45 ° C. environment using a charge / discharge device (TOSCAT-3100U) manufactured by Toyo Systems Co., Ltd. until a voltage of 4.7 V was reached, followed by initial charging by performing a 4.7 V constant voltage charge for 5 hours, and pre-doping was performed on the negative electrode precursor. At this time, the positive electrode final potential was measured using the method described in (Measurement of the potential of the positive electrode precursor) and was listed in the table below.

[0290] (Gassing) After pre-doping, the lithium ion secondary battery was placed in a dry air environment at a temperature of 25°C and a dew point of -40°C, and a portion of the aluminum laminate packaging material was opened. Subsequently, the lithium ion secondary battery was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -80 kPa over 3 minutes, and then the pressure was returned to atmospheric pressure over 3 minutes. Thereafter, the lithium ion secondary battery was placed in a vacuum sealing machine, and the pressure was reduced to -90 kPa. The aluminum laminate packaging material was sealed by sealing at 200°C for 10 seconds at a pressure of 0.1 MPa, and a lithium ion secondary battery was obtained.

[0291] (Amount of Negative Electrode Dope) The amount of negative electrode dope Q2 (mAh / cell) was measured according to the method described above in the section (Amount of Negative Electrode Dope, Volume Difference, Pre-Doping Volumetric Efficiency).

[0292] (Effective utilization rate of positive electrode active material) The above (discharge capacity Q, full cell capacity density P per mass of positive electrode active material) ｆｕｌｌ The discharge capacity Q (mAh) of the cell was measured by the method described in the section 1. ｆｕｌｌ (mAh / g) was obtained using the following formula: Effective utilization rate of positive electrode active material = P ｆｕｌｌ The effective utilization rate of the positive electrode active material was calculated by the following formula: ÷ B1 × 100. The results are shown in the table below.

[0293] (Calculation of Reduction in Positive Electrode Active Material Loss) Calculations were made according to the method described in the section (Reduction in Positive Electrode Active Material Loss), and the results are shown in the table below. Note that, for comparison in the calculations, an alkali metal storage element was used, which had the same basis weights of the positive electrode active material and the negative electrode active material as those in Example 1-1, contained no carbonate, and was initially charged at the upper limit voltage of the stable operating voltage according to the positive electrode active material, and the reduction in positive electrode active material loss was calculated using the results of Reference Example 1-9.

[0294] (Initial Resistance) The DC resistance was measured by the method described above in the section (DC Resistance R) to determine the initial resistance. The results are summarized in the table below.

[0295] (Pre-doping volumetric efficiency) According to the method described in the above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), pre-doping volumetric efficiency was obtained. Reference example 1-1 described later was used as a comparison object for calculating negative electrode doping amount and volume difference.

[0296] (Gas Amount at 40° C. during Storage) The gas amount after 6 weeks of storage at 40° C. was measured using the method described above in the section (Gas Measurement at 40° C. during Storage). The results are summarized in the table below.

[0297] <Examples 1-2 to 1-73, Comparative Examples 1-1 to 1-42> Evaluations were carried out in the same manner as in Example 1-1 except for the conditions shown in Tables 1 and 2. The results are shown in Tables 1 and 2.

[0298] <Reference Example 1-1> Except as shown in Tables 1 and 2, a prototype was prepared and evaluated in the same manner as in Example 1-1. A positive electrode precursor was obtained that had the same active material basis weight as in Example 1-1 and did not contain lithium carbonate. The thickness t1 (μm) of this positive electrode precursor was measured. The negative electrode doping amount Q1 (mAh / cell) was measured according to the method described above in the section (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), and was used to calculate the pre-doping volumetric efficiency of the examples and comparative examples.

[0299] <Reference Examples 1-2 to 1-28> Except as shown in Tables 1 and 2, the samples were prepared and evaluated in the same manner as in Reference Example 1-1. The thickness t1 (μm) of this positive electrode precursor was measured. The negative electrode doping amount Q1 (mAh / cell) was measured according to the method described above in the section (negative electrode doping amount, volume difference, pre-doping volumetric efficiency). This was used to calculate the pre-doping volumetric efficiency of the examples and comparative examples and the reduction in positive electrode active material loss.

[0300] Example 2-1 (Alkali Metal, Alkali Metal Carbonate) In this example, lithium was used as the alkali metal, and lithium carbonate was used as the alkali metal carbonate.

[0301] (Measurement of initial charge capacity A1 and initial discharge capacity B1 of positive electrode active material) ２ The initial charge capacity density A1 and the initial discharge capacity density B1 were obtained. The obtained A1 and B1 are shown in Tables 1 and 2 below.

[0302] (Fabrication of alkali metal storage element) (Fabrication of positive electrode precursor) LiCoO as positive electrode active material ２ , lithium carbonate, carbon black 3 as a carbon material, and PVdF (polyvinylidene fluoride) as a binder were prepared according to the compositions shown in Tables 1 and 2 below, and NMP (N-methylpyrrolidone) was further mixed therewith to obtain a positive electrode precursor slurry. The obtained positive electrode precursor slurry was applied to one side of an aluminum foil having a thickness of 15 μm at a basis weight shown in Tables 1 and 2 below, and pressed to obtain a positive electrode precursor.

[0303] (Preparation of Negative Electrode Precursor) 91.0 parts by mass of artificial graphite, 5.0 parts by mass of silicon monoxide, 2.0 parts by mass of styrene-butadiene rubber, 2.0 parts by mass of carboxymethyl cellulose (CMC), and water were mixed to obtain a negative electrode precursor slurry. The obtained negative electrode precursor slurry was applied to one side of a 10 μm-thick electrolytic copper foil at a basis weight shown in Tables 1 and 2 below, and pressed to obtain a negative electrode precursor.

[0304] (Evaluation of Negative Electrode Irreversible Capacity Rate) In this example, the negative electrode precursor was used to evaluate the negative electrode irreversible capacity rate. Specifically, a negative electrode half-cell was fabricated from the obtained negative electrode precursor, and the irreversible capacity rate was calculated according to the method described in (Calculation of the Irreversible Capacity Rate of the Negative Electrode Precursor). The results are shown in the table below. The electrolyte was a 1.0 M LiPF in an EC:MEC mixed solvent (volume ratio 1:2). ６ An electrolyte solution containing 1% by mass of vinylene carbonate was used.

[0305] (Preparation of Intermediate Layer) Lithium carbonate, steam-activated activated carbon 1 as a conductive material, acrylic latex as a binder, and carboxymethyl cellulose as a thickener were prepared according to the composition shown in the table below, and water was further mixed therein to obtain an intermediate layer slurry. The obtained intermediate layer slurry was hand-coated with a doctor blade onto one side of a 15 μm-thick microporous membrane separator to the single-side basis weight shown in Table 1 below, to form an intermediate layer.

[0306] In order to calculate the volume difference described above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), the thickness t2 of the intermediate layer was measured.

[0307] (Assembly) The resulting positive electrode precursor was cut to a coated area of ​​2 cm x 2 cm, and the resulting negative electrode precursor was cut to a coated area of ​​2.2 cm x 2.2 cm. A microporous membrane separator with an intermediate layer formed thereon was sandwiched between the positive electrode precursor and the negative electrode precursor, with the intermediate layer facing the active material layer of the positive electrode precursor, and the resulting laminate was then stacked. A negative electrode terminal and a positive electrode terminal were then ultrasonically welded to the negative electrode precursor and the positive electrode precursor, respectively, to form an electrode laminate. This electrode laminate and a lithium reference electrode, composed of lithium pressed onto SUS foil and wrapped in a microporous separator, were then housed in an exterior package made of aluminum laminate packaging, and the three sides of the exterior package, including the electrode terminal and bottom portion, were heat-sealed at a temperature of 180 °C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. Vacuum drying was performed at a temperature of 50 °C, a pressure of 50 Pa, and a drying time of 25 hours.

[0308] (Injection of electrolyte) 1.0 M LiPF in EC:MEC mixed solvent (volume ratio 1:2) was used as the electrolyte. ６ An electrolyte solution containing 1% by mass of vinylene carbonate was prepared. 2 g of the nonaqueous electrolyte solution was injected into an electrode laminate housed in an aluminum laminate packaging material under atmospheric pressure, a temperature of 25°C, and a dry air environment with a dew point of -40°C or less. This was then placed in a vacuum chamber, the pressure reduced from atmospheric pressure to -87 kPa, and then returned to atmospheric pressure for impregnation. The electrode laminate housed in the aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was then placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed by sealing at 180°C for 10 seconds at a pressure of 0.1 MPa under a reduced pressure of -95 kPa.

[0309] (Initial charge pre-doping) The obtained injected battery was subjected to constant current charging at a 0.2C rate under a 45 ° C. environment using a charge / discharge device (TOSCAT-3100U) manufactured by Toyo Systems Co., Ltd. until a voltage of 4.4 V was reached, followed by initial charging by performing a 4.4 V constant voltage charge for 5 hours, and pre-doping was performed on the negative electrode precursor. At this time, the positive electrode final potential was measured using the method described in (Measurement of the potential of the positive electrode precursor) and was listed in the table below.

[0310] (Gassing) After pre-doping, the lithium ion secondary battery was placed in a dry air environment at a temperature of 25°C and a dew point of -40°C, and a portion of the aluminum laminate packaging material was opened. Subsequently, the lithium ion secondary battery was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -80 kPa over 3 minutes, and then the pressure was returned to atmospheric pressure over 3 minutes. Thereafter, the lithium ion secondary battery was placed in a vacuum sealing machine, and the pressure was reduced to -90 kPa. The aluminum laminate packaging material was sealed by sealing at 200°C for 10 seconds at a pressure of 0.1 MPa, and a lithium ion secondary battery was obtained.

[0311] (Amount of Negative Electrode Dope) The amount of negative electrode dope Q2 (mAh / cell) was measured according to the method described above in the section (Amount of Negative Electrode Dope, Volume Difference, Pre-Doping Volumetric Efficiency).

[0312] (Effective utilization rate of positive electrode active material) The above (discharge capacity Q, full cell capacity density P per mass of positive electrode active material) ｆｕｌｌ The discharge capacity Q (mAh) of the cell was measured by the method described in the section 1. ｆｕｌｌ (mAh / g) was obtained using the following formula: Effective utilization rate of positive electrode active material = P ｆｕｌｌ The effective utilization rate of the positive electrode active material was calculated by the following formula: ÷ B1 × 100. The results are shown in the table below.

[0313] (Calculation of Reduction in Positive Electrode Active Material Loss) Calculations were made according to the method described in the section (Reduction in Positive Electrode Active Material Loss), and the results are shown in the table below. For comparison in the calculations, an alkali metal storage element was used, which had the same basis weights of the positive electrode active material and the negative electrode active material as those in Example 2-1, contained no carbonate, and was initially charged at the upper limit voltage of the stable operating voltage according to the positive electrode active material, and the reduction in positive electrode active material loss was calculated using the results of Reference Example 2-2.

[0314] (Initial Resistance) The DC resistance was measured by the method described above in the section (DC Resistance R) to determine the initial resistance. The results are summarized in the table below.

[0315] (Pre-doping volumetric efficiency) According to the method described in the above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), pre-doping volumetric efficiency was obtained. Reference example 2-1 described later was used as a comparison object for calculating negative electrode doping amount and volume difference.

[0316] (Gas Amount at 40° C. during Storage) The gas amount after 6 weeks of storage at 40° C. was measured using the method described above in the section (Gas Measurement at 40° C. during Storage). The results are summarized in the table below.

[0317] <Examples 2-2 to 2-12, Comparative Examples 2-1 to 2-4> Evaluations were carried out in the same manner as in Example 2-1 except for the conditions shown in Tables 1 and 2. The results are shown in Tables 1 and 2.

[0318] <Reference Examples 2-1, 2-2> Except for the fact that no intermediate layer was provided and the fact that it is shown in Tables 1 and 2, the same trial production and evaluation were carried out as in Example 2-1. According to the method described in the above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), the negative electrode doping amount Q1 (mAh / cell) was measured, and used to calculate the pre-doping volumetric efficiency of Examples and Comparative Examples and the reduction amount of positive electrode active material loss.

[0319]

[0320]

[0321]

[0322]

[0323]

[0324]

[0325]

[0326]

[0327]

[0328]

[0329]

[0330]

[0331]

[0332]

[0333]

[0334]

[0335]

[0336]

[0337]

[0338]

[0339]

[0340]

[0341]

[0342]

[0343]

[0344]

[0345]

[0346]

[0347]

[0348]

[0349]

[0350]

[0351]

[0352]

[0353]

[0354]

[0355]

[0356]

[0357]

[0358] Example 3-1 (Alkali Metal, Alkali Metal Carbonate) In this example, sodium was used as the alkali metal, and sodium carbonate was used as the alkali metal carbonate.

[0359] (Measurement of initial charge capacity A1 and initial discharge capacity B1 of positive electrode active material) NaFe was used as the positive electrode active material. １／３ Ni １／３ Mn １／３ O ２ 91% by mass of the powder, 4% by mass of carbon black 3, 5% by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) were mixed to a solids concentration of 45% by mass to obtain a positive electrode slurry for a positive electrode half cell used to measure the initial charge capacity of the positive electrode active material. The obtained slurry was applied at 100 g / m to one side of a 15 μm-thick anchor aluminum foil serving as a positive electrode current collector. ２ The coated layer was dried and pressed to obtain a positive electrode for a positive electrode half cell to be used for measuring the initial charge capacity of the positive electrode active material.

[0360] The obtained single-sided positive electrode was punched out to a coated area of ​​2 cm x 2 cm, and the positive electrode terminal was connected by ultrasonic welding. The negative electrode terminal was connected by ultrasonic welding to a Na counter electrode with Na attached to copper foil. This was combined with a polypropylene separator and a glass filter to obtain a positive half-cell electrode laminate. This electrode laminate was housed in an exterior body made of aluminum laminate packaging, and three sides of the exterior body, including the electrode terminal portion and the bottom portion, were heat-sealed at a temperature of 180°C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. The electrode laminate was vacuum-dried at a temperature of 50°C, a pressure of 50 Pa, and a drying time of 25 hours. As the electrolyte, 1.0 M NaPF in a PC:DMC mixed solvent (volume ratio 1:2) was used. ６ An electrolyte solution containing 1% by mass of fluoroethylene carbonate was prepared.

[0361] 2 g of the nonaqueous electrolyte solution was injected into the electrode laminate housed in the aluminum laminate packaging material under atmospheric pressure, a temperature of 25°C, and a dry air environment with a dew point of -40°C or less. Subsequently, this was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -87 kPa, and then the pressure was returned to atmospheric pressure, allowing for impregnation. Thereafter, the electrode laminate housed in the aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed at 180°C for 10 seconds at a pressure of 0.1 MPa under a reduced pressure of -95 kPa, to produce a positive electrode half cell.

[0362] The initial charge capacity density A1 and the initial discharge capacity density B1 of the positive electrode active material were determined by the method described above (initial charge capacity density A1 and initial discharge capacity density B1 of the positive electrode active material). The initial charge capacity density A1 and initial discharge capacity density B1 of the positive electrode active material were obtained. The obtained A1 and B1 are shown in the table below.

[0363] (Preparation of alkali metal storage element) (Preparation of positive electrode precursor) NaFe as positive electrode active material １／３ Ni １／３ Mn １／３ O ２ A positive electrode precursor slurry was prepared using sodium carbonate as an alkali metal carbonate, steam-activated activated carbon 1 as a carbon material, and PVdF (polyvinylidene fluoride) as a binder according to the composition shown in Table 1 below, and NMP (N-methylpyrrolidone) was further mixed therewith. The resulting positive electrode precursor slurry was applied to one side of a 15 μm-thick aluminum foil at a basis weight shown in Tables 3 and 4 below, and pressed to obtain a positive electrode precursor.

[0364] In order to calculate the volume difference described above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), the film thickness t2 of the positive electrode precursor containing sodium carbonate was measured.

[0365] (Preparation of Negative Electrode Precursor) 90.0 parts by mass of hard carbon, 5.0 parts by mass of carbon black 3 as a conductive material, 2.5 parts by mass of styrene-butadiene rubber, 2.5 parts by mass of carboxymethyl cellulose (CMC), and water were mixed to obtain a negative electrode precursor slurry. The obtained negative electrode precursor slurry was applied to one side of a 15 μm thick aluminum foil at a basis weight shown in Tables 3 and 4 below, and pressed to obtain a negative electrode precursor.

[0366] (Evaluation of Negative Electrode Irreversible Capacity Rate) In this example, the negative electrode precursor was used to evaluate the negative electrode irreversible capacity rate. Specifically, a negative electrode half-cell was fabricated from the obtained negative electrode precursor, and the irreversible capacity rate was calculated according to the method described in (Calculation of Irreversible Capacity Rate of Negative Electrode Precursor). The results are shown in Tables 3 and 4 below. The electrolyte was a PC:DMC mixed solvent (volume ratio 1:2) containing 1.0 M NaPF ６ An electrolyte solution containing 1% by mass of fluoroethylene carbonate was used.

[0367] (Assembly) The resulting positive electrode precursor was cut to a coated area of ​​2 cm x 2 cm, and the resulting negative electrode precursor was cut to a coated area of ​​2.2 cm x 2.2 cm. A 15 μm thick microporous membrane separator was sandwiched between the positive electrode precursor and the negative electrode precursor, and the resulting electrodes were laminated. Then, a negative electrode terminal and a positive electrode terminal were connected to the negative electrode precursor and the positive electrode precursor, respectively, by ultrasonic welding to form an electrode laminate. This electrode laminate and a sodium reference electrode, which was press-bonded to SUS foil and wrapped in a microporous separator, were housed in an exterior body made of aluminum laminate packaging, and the three sides of the exterior body, including the electrode terminal portion and the bottom portion, were heat-sealed at a temperature of 180 ° C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. Vacuum drying was performed at a temperature of 50 ° C, a pressure of 50 Pa, and a drying time of 25 hours.

[0368] (Injection solution) As the electrolyte, 1.0 M NaPF in a PC:DMC mixed solvent (volume ratio 1:2) was used. ６ An electrolyte solution containing 1% by mass of fluoroethylene carbonate was prepared.

[0369] 2 g of the nonaqueous electrolyte solution was injected into the electrode laminate housed in the aluminum laminate packaging material under atmospheric pressure, a temperature of 25°C, and a dry air environment with a dew point of -40°C or less. Subsequently, this was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -87 kPa, and then the pressure was returned to atmospheric pressure and impregnated. Thereafter, the electrode laminate housed in the aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed by sealing at 180°C for 10 seconds at a pressure of 0.1 MPa under a reduced pressure of -95 kPa.

[0370] (Initial charge pre-doping) The obtained injected battery was subjected to constant current charging at a 0.2C rate under a 45 ° C. environment until a voltage of 4.4 V was reached using a charge / discharge device (TOSCAT-3100U) manufactured by Toyo Systems Co., Ltd., followed by initial charging by performing 4.4V constant voltage charging for 5 hours, and pre-doping was performed on the negative electrode precursor. At this time, the positive electrode final potential was measured using the method described in (Measurement of the potential of the positive electrode precursor) and was listed in Tables 3 and 4 below.

[0371] (Gassing) After pre-doping, the sodium ion secondary battery was placed in a dry air environment at a temperature of 25°C and a dew point of -40°C, and a portion of the aluminum laminate packaging material was opened. Subsequently, the lithium ion secondary battery was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -80 kPa over 3 minutes, and then the pressure was returned to atmospheric pressure over 3 minutes. Thereafter, the lithium ion secondary battery was placed in a vacuum sealing machine, and the pressure was reduced to -90 kPa. The aluminum laminate packaging material was sealed by sealing at 200°C for 10 seconds at a pressure of 0.1 MPa, and a sodium ion secondary battery was obtained.

[0372] (Amount of Negative Electrode Dope) The amount of negative electrode dope Q2 (mAh / cell) was measured according to the method described above in the section (Amount of Negative Electrode Dope, Volume Difference, Pre-Doping Volumetric Efficiency).

[0373] (Effective utilization rate of positive electrode active material) The above (discharge capacity Q, full cell capacity density P per mass of positive electrode active material) ｆｕｌｌ The discharge capacity Q (mAh) of the cell was measured by the method described in the section 1. ｆｕｌｌ(mAh / g) was obtained using the following formula: Effective utilization rate of positive electrode active material = P ｆｕｌｌ The effective utilization rate of the positive electrode active material was calculated by the following formula: ÷ B1 × 100. The results are shown in the table below.

[0374] (Calculation of Reduction in Positive Electrode Active Material Loss) Calculations were made according to the method described in the section (Reduction in Positive Electrode Active Material Loss), and the results are shown in Tables 3 and 4. Note that, for comparison in the calculations, an alkali metal storage element was used, which had the same basis weights of the positive electrode active material and the negative electrode active material as those in Example 3-1, contained no carbonate, and was initially charged at the upper limit voltage of the stable operating voltage according to the positive electrode active material, and the reduction in positive electrode active material loss was calculated using the results of Reference Example 1-9.

[0375] (Initial Resistance) The DC resistance was measured by the method described above in the section (DC Resistance R) to determine the initial resistance. The results are summarized in Tables 3 and 4 below.

[0376] (Pre-doping volumetric efficiency) According to the method described in the above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), pre-doping volumetric efficiency was obtained. Reference example 3-1 described later was used as a comparison object for calculating negative electrode doping amount and volume difference.

[0377] (Gas Amount at 40° C. during Storage) The gas amount after 6 weeks of storage at 40° C. was measured using the method described above in the section (Gas Measurement at 40° C. during Storage). The results are summarized in the table below.

[0378] <Examples 3-2 to 3-35, Comparative Examples 3-1 to 3-28> Evaluations were carried out in the same manner as in Example 3-1 except for the conditions shown in Tables 3 and 4. The results are shown in Tables 3 and 4 below.

[0379] <Reference Example 3-1> Except as shown in Tables 3 and 4, a prototype was prepared and evaluated in the same manner as in Example 3-1. A positive electrode precursor was obtained that had the same active material basis weight as in Example 3-1 and did not contain lithium carbonate. The thickness t1 (μm) of this positive electrode precursor was measured. According to the method described above in the section (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), the negative electrode doping amount Q1 (mAh / cell) was measured and used to calculate the pre-doping volumetric efficiency of the examples and comparative examples.

[0380] <Reference Examples 3-2 to 3-8> Except as shown in Tables 3 and 4, the same prototypes and evaluations were carried out as in Reference Example 3-1. The thickness t1 (μm) of this positive electrode precursor was measured. The negative electrode doping amount Q1 (mAh / cell) was measured according to the method described above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency). This was used to calculate the pre-doping volumetric efficiency of the examples and comparative examples and the reduction in positive electrode active material loss.

[0381]

[0382]

[0383]

[0384]

[0385]

[0386]

[0387]

[0388]

[0389]

[0390]

[0391]

[0392]

[0393]

[0394]

[0395]

[0396]

[0397]

[0398]

[0399]

[0400]

[0401]

[0402]

[0403]

[0404]

[0405] Example 4-1 (Alkali Metal, Alkali Metal Carbonate) In this example, sodium was used as the alkali metal, and sodium carbonate was used as the alkali metal carbonate.

[0406] (Measurement of initial charge capacity A1 and initial discharge capacity B1 of positive electrode active material) In the same manner as in Example 3-1, NaFe １／３ Ni １／３ Mn １／３ O ２ The initial charge capacity density A1 and the initial discharge capacity density B1 were obtained. The obtained A1 and B1 are shown in Table 5 below.

[0407] (Preparation of alkali metal storage element) (Preparation of positive electrode precursor) NaFe as positive electrode active material １／３ Ni １／３ Mn １／３ O ２ A positive electrode precursor slurry was prepared using sodium carbonate as an alkali metal carbonate, steam-activated activated carbon 1 as a carbon material, and PVdF (polyvinylidene fluoride) as a binder according to the composition shown in Table 5 below, and NMP (N-methylpyrrolidone) was further mixed therewith. The resulting positive electrode precursor slurry was applied to one side of a 15 μm-thick aluminum foil at a basis weight shown in Table 5 below, and pressed to obtain a positive electrode precursor.

[0408] (Preparation of Negative Electrode Precursor) 90.0 parts by mass of hard carbon, 5.0 parts by mass of carbon black 3 as a conductive material, 2.5 parts by mass of styrene-butadiene rubber, 2.5 parts by mass of carboxymethyl cellulose (CMC), and water were mixed to obtain a negative electrode precursor slurry. The obtained negative electrode precursor slurry was applied to one side of a 15 μm thick aluminum foil at a basis weight shown in Table 5 below, and pressed to obtain a negative electrode precursor.

[0409] (Evaluation of Negative Electrode Irreversible Capacity Rate) In this example, the negative electrode precursor was used to evaluate the negative electrode irreversible capacity rate. Specifically, a negative electrode half-cell was fabricated from the obtained negative electrode precursor, and the irreversible capacity rate was calculated according to the method described in (Calculation of the Irreversible Capacity Rate of the Negative Electrode Precursor). The results are shown in Table 5. The electrolyte was a PC:DMC mixed solvent (volume ratio 1:2) containing 1.0 M NaPF ６ An electrolyte solution containing 1% by mass of fluoroethylene carbonate was used.

[0410] (Preparation of Intermediate Layer) Sodium carbonate, steam-activated activated carbon 1 as a conductive material, acrylic latex as a binder, and carboxymethyl cellulose as a thickener were prepared according to the composition shown in Table 5 below, and water was further mixed therein to obtain a slurry for an intermediate layer. The obtained slurry for an intermediate layer was manually coated with a doctor blade onto one side of a 15 μm-thick microporous membrane separator in the single-side basis weight shown in Table 5 to form an intermediate layer.

[0411] In order to calculate the volume difference described above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), the thickness t2 of the intermediate layer was measured.

[0412] (Assembly) The resulting positive electrode precursor was cut to a coated area of ​​2 cm x 2 cm, and the resulting negative electrode precursor was cut to a coated area of ​​2.2 cm x 2.2 cm. A microporous membrane separator with an intermediate layer formed thereon was sandwiched between the positive electrode precursor and the negative electrode precursor, with the intermediate layer facing the active material layer of the positive electrode precursor, and the resulting laminate was then stacked. A negative electrode terminal and a positive electrode terminal were then ultrasonically welded to the negative electrode precursor and the positive electrode precursor, respectively, to form an electrode laminate. This electrode laminate and a sodium reference electrode, which was press-bonded to SUS foil and wrapped in a microporous separator, were then housed in an exterior package made of aluminum laminate packaging, and the three sides of the exterior package, including the electrode terminal portion and the bottom portion, were heat-sealed at a temperature of 180°C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. Vacuum drying was performed at a temperature of 50°C, a pressure of 50 Pa, and a drying time of 25 hours.

[0413] (Injection solution) As the electrolyte, 1.0 M NaPF in a PC:DMC mixed solvent (volume ratio 1:2) was used. ６An electrolyte solution containing 1% by mass of fluoroethylene carbonate was prepared. 2 g of the above nonaqueous electrolyte solution was injected into an electrode laminate housed in an aluminum laminate packaging material under atmospheric pressure, a temperature of 25°C, and a dry air environment with a dew point of -40°C or less. This was then placed in a vacuum chamber, the pressure was reduced from atmospheric pressure to -87 kPa, and the pressure was then returned to atmospheric pressure for impregnation. The electrode laminate housed in the aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was then placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed by sealing at 180°C for 10 seconds at a pressure of 0.1 MPa under a reduced pressure of -95 kPa.

[0414] (Initial charge pre-doping) The obtained injected battery was subjected to constant current charging at a 0.2C rate under a 45 ° C. environment until a voltage of 4.1 V was reached using a charge / discharge device (TOSCAT-3100U) manufactured by Toyo Systems Co., Ltd., followed by initial charging by performing a 4.1V constant voltage charge for 5 hours, and pre-doping was performed on the negative electrode precursor. At this time, the positive electrode final potential was measured using the method described in (Measurement of the potential of the positive electrode precursor) and listed in Table 5.

[0415] (Gassing) After pre-doping, the sodium ion secondary battery was placed in a dry air environment at a temperature of 25°C and a dew point of -40°C, and a portion of the aluminum laminate packaging material was opened. Subsequently, the lithium ion secondary battery was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -80 kPa over 3 minutes, and then the pressure was returned to atmospheric pressure over 3 minutes. Thereafter, the sodium ion secondary battery was placed in a vacuum sealing machine, and the pressure was reduced to -90 kPa. The aluminum laminate packaging material was sealed by sealing at 200°C for 10 seconds at a pressure of 0.1 MPa, and a sodium ion secondary battery was obtained.

[0416] (Amount of Negative Electrode Dope) The amount of negative electrode dope Q2 (mAh / cell) was measured according to the method described above in the section (Amount of Negative Electrode Dope, Volume Difference, Pre-Doping Volumetric Efficiency).

[0417] (Effective utilization rate of positive electrode active material) The above (discharge capacity Q, full cell capacity density P per mass of positive electrode active material) ｆｕｌｌ The discharge capacity Q (mAh) of the cell was measured by the method described in the section 1.ｆｕｌｌ (mAh / g) was obtained using the following formula: Effective utilization rate of positive electrode active material = P ｆｕｌｌ The effective utilization rate of the positive electrode active material was calculated by the following equation: ÷ B1 × 100. The results are shown in Table 5. (Calculation of Reduction in Positive Electrode Active Material Loss) Calculations were made according to the method described in the section (Reduction in Positive Electrode Active Material Loss), and the results are shown in Table 5. Note that, for comparison in the calculations, an alkali metal storage element was used, which had the same basis weights of the positive electrode active material and the negative electrode active material as those in Example 4-1, did not contain carbonate, and was initially charged at the upper limit voltage of the stable operating voltage corresponding to the positive electrode active material, and the reduction in positive electrode active material loss was calculated using the results of Reference Example 4-2.

[0418] (Initial Resistance) The DC resistance was measured by the method described above in the section (DC Resistance R) to determine the initial resistance. The results are summarized in Table 5.

[0419] (Pre-doping volumetric efficiency) According to the method described in the above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), pre-doping volumetric efficiency was obtained. Use reference example 4-1 described later as a comparison object for calculating negative electrode doping amount and volume difference.

[0420] (Gas Amount at 40° C. Storage) The gas amount after 6 weeks of storage at 40° C. was measured by the method described above in the section (Gas Measurement at 40° C. Storage).

[0421] <Examples 4-2 to 4-5, Comparative Examples 4-1 to 4-4> Evaluations were carried out in the same manner as in Example 4-1 except for the conditions shown in Tables 5 and 6. The results are shown in Table 5.

[0422] <Reference Examples 4-1, 4-2> Except for the fact that no intermediate layer was provided and the fact that it is shown in Table 5, the same trial production and evaluation were carried out as in Example 4-1. According to the method described in the above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), the negative electrode doping amount Q1 (mAh / cell) was measured, and used to calculate the pre-doping volumetric efficiency of Examples and Comparative Examples and the reduction amount of positive electrode active material loss.

[0423]

[0424]

[0425]

[0426] Example 5-1 (Alkali Metal, Alkali Metal Carbonate) In this example, lithium was used as the alkali metal, and lithium carbonate was used as the alkali metal carbonate.

[0427] (Measurement of initial charge capacity A1 and initial discharge capacity B1 of positive electrode active material) ２ 91% by mass of the powder, 4% by mass of carbon black 3, 5% by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) were mixed to a solids concentration of 45% by mass to obtain a positive electrode slurry for a positive electrode half cell used to measure the initial charge capacity of the positive electrode active material. The obtained slurry was applied at 100 g / m to one side of a 15 μm-thick anchor aluminum foil serving as a positive electrode current collector. ２ The coated layer was dried and pressed to obtain a positive electrode for a positive electrode half cell to be used for measuring the initial charge capacity of the positive electrode active material.

[0428] The obtained single-sided positive electrode was punched out to a coated area of ​​2 cm x 2 cm, and the positive electrode terminal was connected by ultrasonic welding. The negative electrode terminal was connected by ultrasonic welding to a Li counter electrode in which Li was attached to copper foil. This was combined with a polypropylene separator and a glass filter to obtain a positive electrode half-cell electrode laminate. This electrode laminate was housed in an exterior body made of aluminum laminate packaging, and three sides of the exterior body, including the electrode terminal portion and the bottom portion, were heat-sealed at a temperature of 180°C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. The electrode laminate was vacuum-dried at a temperature of 50°C, a pressure of 50 Pa, and a drying time of 25 hours. As the electrolyte, 1.0 M LiPF in an EC:MEC mixed solvent (volume ratio 1:2) was used. ６ An electrolyte solution containing 1% by mass of vinylene carbonate was prepared.

[0429] 2 g of the nonaqueous electrolyte solution was injected into the electrode laminate housed in the aluminum laminate packaging material under atmospheric pressure, a temperature of 25°C, and a dry air environment with a dew point of -40°C or less. Subsequently, this was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -87 kPa, and then the pressure was returned to atmospheric pressure, allowing for impregnation. Thereafter, the electrode laminate housed in the aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed at 180°C for 10 seconds at a pressure of 0.1 MPa under a reduced pressure of -95 kPa, to produce a positive electrode half cell.

[0430] The upper limit of the stable operating potential of the positive electrode active material was set by the method described above (initial charge capacity density A1, initial discharge capacity density B1 of the positive electrode active material), and the initial charge capacity density A1 and initial discharge capacity density B1 of the positive electrode active material were obtained. The obtained A1 and B1 are shown in Tables 6 to 8 below.

[0431] (Fabrication of alkali metal storage element) (Fabrication of positive electrode precursor) LiCoO as positive electrode active material ２ Lithium carbonate as an alkali metal carbonate, porous carbon as a carbon material, and PVdF (polyvinylidene fluoride) as a binder were prepared according to the compositions shown in Tables 6 to 8 below, and NMP (N-methylpyrrolidone) was further mixed therewith to obtain a positive electrode precursor slurry. The obtained positive electrode precursor slurry was applied to one side of a 15 μm-thick aluminum foil at a basis weight shown in Tables 6 to 8 below, and pressed to obtain a positive electrode precursor.

[0432] In order to calculate the volume difference described above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), the film thickness t2 of the positive electrode precursor containing lithium carbonate was measured.

[0433] (Preparation of Negative Electrode Precursor) 13.0 parts by mass of artificial graphite, 79.38 parts by mass of silicon monoxide, 3.81 parts by mass of styrene-butadiene rubber, 3.81 parts by mass of carboxymethyl cellulose (CMC), and water were mixed to obtain a negative electrode precursor slurry. The obtained negative electrode precursor slurry was coated on one side of a 10 μm thick electrolytic copper foil at a basis weight shown in Tables 6 to 8 below, and pressed to obtain a negative electrode precursor.

[0434] (Evaluation of Negative Electrode Irreversible Capacity Rate) In this example, the negative electrode precursor was used to evaluate the negative electrode irreversible capacity rate. Specifically, a negative electrode half-cell was fabricated from the obtained negative electrode precursor, and the irreversible capacity rate was calculated according to the method described in (Calculation of Irreversible Capacity Rate of Negative Electrode Precursor). The results are shown in Tables 6 to 8. The electrolyte was a 1.0 M LiPF solution in an EC:MEC mixed solvent (volume ratio 1:2). ６ An electrolyte solution containing 1% by mass of vinylene carbonate was used.

[0435] (Assembly) The resulting positive electrode precursor was cut to a coated area of ​​2 cm x 2 cm, and the resulting negative electrode precursor was cut to a coated area of ​​2.2 cm x 2.2 cm. A 15 μm thick microporous membrane separator was sandwiched between the positive electrode precursor and the negative electrode precursor and laminated. Then, a negative electrode terminal and a positive electrode terminal were connected to the negative electrode precursor and the positive electrode precursor, respectively, by ultrasonic welding to form an electrode laminate. This electrode laminate and a lithium reference electrode, which was press-bonded to SUS foil and wrapped in a microporous separator, were housed in an exterior body made of aluminum laminate packaging, and the three sides of the exterior body, including the electrode terminal portion and the bottom portion, were heat-sealed at a temperature of 180 ° C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. Vacuum drying was performed at a temperature of 50 ° C, a pressure of 50 Pa, and a drying time of 25 hours.

[0436] (Injection of electrolyte) 1.0 M LiPF in EC:MEC mixed solvent (volume ratio 1:2) was used as the electrolyte. ６ An electrolyte solution containing 1% by mass of vinylene carbonate was prepared.

[0437] 2 g of the nonaqueous electrolyte solution was injected into the electrode laminate housed in the aluminum laminate packaging material under atmospheric pressure, a temperature of 25°C, and a dry air environment with a dew point of -40°C or less. Subsequently, this was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -87 kPa, and then the pressure was returned to atmospheric pressure and impregnated. Thereafter, the electrode laminate housed in the aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed by sealing at 180°C for 10 seconds at a pressure of 0.1 MPa under a reduced pressure of -95 kPa.

[0438] (Initial charge pre-doping) The obtained injected battery was subjected to constant current charging at a 0.2C rate under a 45 ° C. environment until a voltage of 4.4 V was reached using a charge / discharge device (TOSCAT-3100U) manufactured by Toyo Systems Co., Ltd., followed by initial charging by performing 4.4V constant voltage charging for 200 hours, and pre-doping was performed on the negative electrode precursor. At this time, the positive electrode final potential was measured using the method described in (Measurement of the potential of the positive electrode precursor) and listed in Tables 6 to 8.

[0439] (Gassing) After pre-doping, the lithium ion secondary battery was placed in a dry air environment at a temperature of 25°C and a dew point of -40°C, and a portion of the aluminum laminate packaging material was opened. Subsequently, the lithium ion secondary battery was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -80 kPa over 3 minutes, and then the pressure was returned to atmospheric pressure over 3 minutes. Thereafter, the lithium ion secondary battery was placed in a vacuum sealing machine, and the pressure was reduced to -90 kPa. The aluminum laminate packaging material was sealed by sealing at 200°C for 10 seconds at a pressure of 0.1 MPa, and a lithium ion secondary battery was obtained.

[0440] (Amount of Negative Electrode Dope) The amount of negative electrode dope Q2 (mAh / cell) was measured according to the method described above in the section (Amount of Negative Electrode Dope, Volume Difference, Pre-Doping Volumetric Efficiency).

[0441] (Effective utilization rate of positive electrode active material) The above (discharge capacity Q, full cell capacity density P per mass of positive electrode active material) ｆｕｌｌ The discharge capacity Q (mAh) of the cell was measured by the method described in the section 1. ｆｕｌｌ (mAh / g) was obtained using the following formula: Effective utilization rate of positive electrode active material = P ｆｕｌｌ The effective utilization rate of the positive electrode active material was calculated by the following formula: ÷ B1 × 100. The results are shown in Tables 6 to 8 below.

[0442] (Calculation of Reduction in Positive Electrode Active Material Loss) Calculations were made according to the method described in the section (Reduction in Positive Electrode Active Material Loss), and the results are shown in Tables 6 to 8. Note that, for comparison in the calculations, an alkali metal storage element was used, which had the same basis weights of the positive electrode active material and the negative electrode active material as those in Example 5-1, contained no carbonate, and was initially charged at the upper limit voltage of the stable operating voltage according to the positive electrode active material, and the reduction in positive electrode active material loss was calculated using the results of Reference Example 5-2.

[0443] (Initial Resistance) The DC resistance was measured by the method described above in the section (DC Resistance R) to determine the initial resistance. The results are summarized in Tables 6 to 8 below.

[0444] (Pre-doping volumetric efficiency) According to the method described in the above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), pre-doping volumetric efficiency was obtained. Use reference example 5-1 described later as a comparison object for calculating negative electrode doping amount and volume difference.

[0445] (Gas Amount at 40° C. Storage) The gas amount after 6 weeks of storage at 40° C. was measured using the method described above in the section (Gas Measurement at 40° C. Storage). The results are summarized in Tables 6 to 8 below.

[0446] (Quantitative Determination of Alkali Metal Carbonate) Measurement was carried out by the method described above in the section (Measurement of Alkali Metal Carbonate in Positive Electrode), and the results are summarized in Tables 6 to 8.

[0447] <Examples 5-2 to 5-30, Comparative Examples 5-1 to 5-8> Evaluations were carried out in the same manner as in Example 5-1 except for the conditions shown in Tables 6 to 8. The results are shown in Tables 6 to 8.

[0448] <Reference Example 5-1> Except as shown in Tables 6 to 8, a prototype was prepared and evaluated in the same manner as in Example 5-1. A positive electrode precursor was obtained that had the same active material basis weight as in Example 5-1 and did not contain lithium carbonate. The thickness t1 (μm) of this positive electrode precursor was measured. The negative electrode doping amount Q1 (mAh / cell) was measured according to the method described above in the section (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), and was used to calculate the pre-doping volumetric efficiency of the examples and comparative examples.

[0449] <Reference Examples 5-2 to 5-4> Except for the details shown in Tables 6 to 8, the samples were prepared and evaluated in the same manner as in Reference Example 5-1. The thickness t1 (μm) of this positive electrode precursor was measured. The negative electrode doping amount Q1 (mAh / cell) was measured according to the method described above in the section (negative electrode doping amount, volume difference, pre-doping volumetric efficiency). This was used to calculate the pre-doping volumetric efficiency of the examples and comparative examples and the reduction in positive electrode active material loss.

[0450] Example 5-31 (Alkali Metal, Alkali Metal Carbonate) In this example, sodium was used as the alkali metal, and sodium carbonate was used as the alkali metal carbonate.

[0451] (Measurement of initial charge capacity A1 and initial discharge capacity B1 of positive electrode active material) NaFe was used as the positive electrode active material. １／３ Ni １／３ Mn １／３ O ２ 91% by mass of the powder, 4% by mass of carbon black 3, 5% by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) were mixed to a solids concentration of 45% by mass to obtain a positive electrode slurry for a positive electrode half cell used to measure the initial charge capacity of the positive electrode active material. The obtained slurry was applied at 100 g / m to one side of a 15 μm-thick anchor aluminum foil serving as a positive electrode current collector. ２ The coated layer was dried and pressed to obtain a positive electrode for a positive electrode half cell to be used for measuring the initial charge capacity of the positive electrode active material.

[0452] The obtained single-sided positive electrode was punched out to a coated area of ​​2 cm x 2 cm, and the positive electrode terminal was connected by ultrasonic welding. The negative electrode terminal was connected by ultrasonic welding to a Na counter electrode with Na attached to copper foil. This was combined with a polypropylene separator and a glass filter to obtain a positive half-cell electrode laminate. This electrode laminate was housed in an exterior body made of aluminum laminate packaging, and three sides of the exterior body, including the electrode terminal portion and the bottom portion, were heat-sealed at a temperature of 180°C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. The electrode laminate was vacuum-dried at a temperature of 50°C, a pressure of 50 Pa, and a drying time of 25 hours. As the electrolyte, 1.0 M NaPF in an EC:MEC mixed solvent (volume ratio 1:2) was used. ６An electrolyte solution containing 1% by mass of fluoroethylene carbonate was prepared.

[0453] 2 g of the nonaqueous electrolyte solution was injected into the electrode laminate housed in an aluminum laminate packaging material under atmospheric pressure, a temperature of 25 ° C., and a dry air environment with a dew point of -40 ° C. or less. Subsequently, this was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -87 kPa, then returned to atmospheric pressure, and the material was allowed to stand for 5 minutes. After that, the operation of reducing the pressure from atmospheric pressure to -87 kPa and then returning to atmospheric pressure was repeated four times, and the material was allowed to stand for 15 minutes, and the nonaqueous electrolyte solution was impregnated into the electrode laminate. Thereafter, the electrode laminate housed in the aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed by sealing at a pressure of 0.1 MPa at 180 ° C. for 10 seconds in a state where the pressure was reduced to -95 kPa, to prepare a positive electrode half cell.

[0454] The upper limit of the stable operating potential of the positive electrode active material was set by the method described above (initial charge capacity density A1, initial discharge capacity density B1 of the positive electrode active material), and the initial charge capacity density A1 and initial discharge capacity density B1 of the positive electrode active material were obtained. The obtained A1 and B1 are shown in Tables 6 to 8 below.

[0455] (Preparation of alkali metal storage element) (Preparation of positive electrode precursor) NaFe as positive electrode active material １／３ Ni １／３ Mn １／３ O ２ Sodium carbonate as an alkali metal carbonate, porous carbon as a carbon material, and PVdF (polyvinylidene fluoride) as a binder were prepared according to the compositions shown in Tables 6 to 8 below, and NMP (N-methylpyrrolidone) was further mixed therewith to obtain a positive electrode precursor slurry. The obtained positive electrode precursor slurry was applied to one side of a 15 μm-thick aluminum foil at a basis weight shown in Tables 6 to 8 below, and pressed to obtain a positive electrode precursor.

[0456] In order to calculate the volume difference described above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), the film thickness t2 of the positive electrode precursor containing sodium carbonate was measured.

[0457] (Preparation of Negative Electrode Precursor) 90.0 parts by mass of hard carbon, 5.0 parts by mass of carbon black 3 as a conductive material, 2.5 parts by mass of styrene-butadiene rubber, 2.5 parts by mass of carboxymethyl cellulose (CMC), and water were mixed to obtain a negative electrode precursor slurry. The obtained negative electrode precursor slurry was applied to one side of a 15 μm thick aluminum foil at a basis weight shown in Tables 6 to 8 below, and pressed to obtain a negative electrode precursor.

[0458] (Evaluation of Negative Electrode Irreversible Capacity Rate) In this example, the negative electrode precursor was used to evaluate the negative electrode irreversible capacity rate. Specifically, a negative electrode half-cell was fabricated from the obtained negative electrode precursor, and the irreversible capacity rate was calculated according to the method described in (Calculation of Irreversible Capacity Rate of Negative Electrode Precursor). The results are shown in Tables 6 to 8. The electrolyte solution was a PC:DMC mixed solvent (volume ratio 1:2) with 1.0 M NaPF ６ An electrolyte solution containing 1% by mass of fluoroethylene carbonate was used.

[0459] (Assembly) The resulting positive electrode precursor was cut to a coated area of ​​2 cm x 2 cm, and the resulting negative electrode precursor was cut to a coated area of ​​2.2 cm x 2.2 cm. A 15 μm thick microporous membrane separator was sandwiched between the positive electrode precursor and the negative electrode precursor, and the resulting electrodes were laminated. Then, a negative electrode terminal and a positive electrode terminal were connected to the negative electrode precursor and the positive electrode precursor, respectively, by ultrasonic welding to form an electrode laminate. This electrode laminate and a sodium reference electrode, which was press-bonded to SUS foil and wrapped in a microporous separator, were housed in an exterior body made of aluminum laminate packaging, and the three sides of the exterior body, including the electrode terminal portion and the bottom portion, were heat-sealed at a temperature of 180 ° C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. Vacuum drying was performed at a temperature of 50 ° C, a pressure of 50 Pa, and a drying time of 25 hours.

[0460] (Injection solution) As the electrolyte, 1.0 M NaPF in a PC:DMC mixed solvent (volume ratio 1:2) was used. ６ An electrolyte solution containing 1% by mass of fluoroethylene carbonate was prepared.

[0461] 2 g of the nonaqueous electrolyte solution was injected into the electrode laminate housed in the aluminum laminate packaging material under atmospheric pressure, a temperature of 25°C, and a dry air environment with a dew point of -40°C or less. Subsequently, this was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -87 kPa, and then the pressure was returned to atmospheric pressure and impregnated. Thereafter, the electrode laminate housed in the aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed by sealing at 180°C for 10 seconds at a pressure of 0.1 MPa under a reduced pressure of -95 kPa.

[0462] (Initial charge pre-doping) The obtained injected battery was subjected to constant current charging at a 0.2C rate under a 45 ° C. environment using a charge / discharge device (TOSCAT-3100U) manufactured by Toyo Systems Co., Ltd. until a voltage of 4.1 V was reached, followed by initial charging by performing a 4.1 V constant voltage charge for 200 hours, and pre-doping was performed on the negative electrode precursor. At this time, the positive electrode final potential was measured using the method described in (Measurement of the potential of the positive electrode precursor) and was listed in Tables 6 to 8.

[0463] (Gassing) After pre-doping, the sodium ion secondary battery was placed in a dry air environment at a temperature of 25°C and a dew point of -40°C, and a portion of the aluminum laminate packaging material was opened. Subsequently, the lithium ion secondary battery was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -80 kPa over 3 minutes, and then the pressure was returned to atmospheric pressure over 3 minutes. Thereafter, the lithium ion secondary battery was placed in a vacuum sealing machine, and the pressure was reduced to -90 kPa. The aluminum laminate packaging material was sealed by sealing at 200°C for 10 seconds at a pressure of 0.1 MPa, and a sodium ion secondary battery was obtained.

[0464] (Amount of Negative Electrode Dope) The amount of negative electrode dope Q2 (mAh / cell) was measured according to the method described above in the section (Amount of Negative Electrode Dope, Volume Difference, Pre-Doping Volumetric Efficiency).

[0465] (Effective utilization rate of positive electrode active material) The above (discharge capacity Q, full cell capacity density P per mass of positive electrode active material) ｆｕｌｌ The discharge capacity Q (mAh) of the cell was measured by the method described in the section 1. ｆｕｌｌ(mAh / g) was obtained using the following formula: Effective utilization rate of positive electrode active material = P ｆｕｌｌ The effective utilization rate of the positive electrode active material was calculated by the following formula: ÷ B1 × 100. The results are shown in Tables 6 to 8 below. (Calculation of Reduction in Positive Electrode Active Material Loss) Calculations were made according to the method described in the section (Reduction in Positive Electrode Active Material Loss), and the results are shown in Tables 6 to 8. Note that, for comparison in the calculations, an alkali metal storage element was used, which had the same basis weights of the positive electrode active material and the negative electrode active material as those in Example 5-31, did not contain carbonate, and was initially charged at the upper limit voltage of the stable operating voltage corresponding to the positive electrode active material, and the reduction in positive electrode active material loss was calculated using the results of Reference Example 5-2.

[0466] (Initial Resistance) The DC resistance was measured by the method described above in the section (DC Resistance R) to determine the initial resistance. The results are summarized in Tables 6 to 8 below.

[0467] (Pre-doping volumetric efficiency) According to the method described in the above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), pre-doping volumetric efficiency was obtained. Use reference example 5-5 described later as a comparison object for calculating negative electrode doping amount and volume difference.

[0468] (Gas Amount at 40°C Storage) The gas amount after 6 weeks of storage at 40°C was measured using the method described above in the section (Gas Measurement at 40°C Storage), and the results are summarized in Tables 6 to 8. (Quantitative Amount of Alkali Metal Carbonate) The gas amount was measured using the method described above in the section (Measurement of Alkali Metal Carbonate in Positive Electrode), and the results are summarized in Tables 6 to 8.

[0469] <Examples 5-32 to 5-45, Comparative Examples 5-9 to 5-12> Evaluations were performed in the same manner as in Example 5-31 except for the conditions shown in Tables 6 to 8. The results are shown in Tables 6 to 8.

[0470] <Reference Example 5-5> Except as shown in Tables 6 to 8, a prototype was prepared and evaluated in the same manner as in Example 5-31. A positive electrode precursor was obtained that had the same active material basis weight as Example 5-31 and did not contain lithium carbonate. The thickness t1 (μm) of this positive electrode precursor was measured. According to the method described above in the section (negative electrode doping amount, volume difference, pre-doping volumetric efficiency), the negative electrode doping amount Q1 (mAh / cell) was measured and used to calculate the pre-doping volumetric efficiency of the examples and comparative examples.

[0471] <Reference Example 5-6> Except for the conditions shown in Tables 6 to 8, the same prototypes and evaluations were carried out as in Reference Example 5-5. The thickness t1 (μm) of this positive electrode precursor was measured. The negative electrode doping amount Q1 (mAh / cell) was measured according to the method described above (negative electrode doping amount, volume difference, pre-doping volumetric efficiency). This was used to calculate the pre-doping volumetric efficiency of the examples and comparative examples and the reduction in positive electrode active material loss.

[0472]

[0473]

[0474]

[0475]

[0476]

[0477]

[0478]

[0479]

[0480]

[0481] From Tables 1 to 8, it has become clear that a high pre-doping volumetric efficiency can be obtained for a non-aqueous alkali metal storage element precursor in which the oxygen atomic weight X calculated from carbon monoxide and / or carbon dioxide obtained when measuring the carbon material with TPDMS is 0.1 mmol / g or more per mass of the carbon material, and the amount of carbon material in the layer containing the carbon material among the positive electrode active material layer and the intermediate layer, if present, is 0.3 mass% or more and 15 mass% or less based on the total mass of the layers containing the carbon material.

[0482] It was also revealed that non-aqueous alkali metal storage elements, in which the effective utilization rate of the positive electrode active material is 80 to 99.5% and the negative electrode active material contains at least one of an alloy-based negative electrode material that forms an alloy with an alkali metal and an amorphous carbon material, have a significant effect in reducing the loss of the positive electrode active material.

[0483] In addition, the potential of the positive electrode precursor is 4.15 to 4.75 V (vs. Li / Li＋ or, when the alkali metal is lithium, a voltage of 4.1 V or more and 4.6 V or less is applied between the positive electrode precursor and the negative electrode precursor to dope the negative electrode active material with alkali metal ions, or, when the alkali metal is lithium, a voltage of 3.8 V or more and 4.3 V or less is applied between the positive electrode precursor and the negative electrode precursor to dope the negative electrode active material with lithium ions, or, when the alkali metal is sodium, a voltage of 3.8 V or more and 4.3 V or less is applied between the positive electrode precursor and the negative electrode precursor to dope the negative electrode active material with lithium ions, it has been revealed that a nonaqueous alkaline storage element can be obtained, and that the initial resistance can be suppressed and the amount of gas generated during storage at 40°C can be reduced.

[0484] <Examples according to the second embodiment>

[0485] Example 6-1 (Preparation of Positive Electrode Active Material and Pre-Dope Material) LiCoO ２ The D50 of the Li powder used as a pre-dopant was adjusted to the particle size shown in the table below using a bead mill. ５ FeO ４ The D50 was adjusted to the particle size shown in the table below using a bead mill.

[0486] (Measurement of initial charge capacity A1 density and initial discharge capacity B1 density of positive electrode active material) ２ 91% by mass of the powder, 4% by mass of carbon black, 5% by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) were mixed to a solids concentration of 45% by mass to obtain a positive electrode slurry for a positive electrode half cell used for measuring the initial charge capacity of the positive electrode active material. The obtained slurry was applied at 100 g / m to one side of a 15 μm-thick anchor aluminum foil serving as a positive electrode current collector. ２ The coated layer was dried and pressed to obtain a positive electrode for a positive electrode half cell to be used for measuring the initial charge capacity density of the positive electrode active material.

[0487] The obtained single-sided positive electrode was punched out to a coated area of ​​2 cm x 2 cm, and the positive electrode terminal was connected by ultrasonic welding. The negative electrode terminal was connected by ultrasonic welding to a Li counter electrode in which Li was attached to copper foil. This was combined with a polypropylene separator and a glass filter to obtain a positive electrode half-cell electrode laminate. This electrode laminate was housed in an exterior body made of aluminum laminate packaging, and three sides of the exterior body, including the electrode terminal portion and the bottom portion, were heat-sealed at a temperature of 180°C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. The electrode laminate was vacuum-dried at a temperature of 50°C, a pressure of 50 Pa, and a drying time of 25 hours. As the electrolyte, 1.0 M LiPF in an EC:MEC mixed solvent (volume ratio 1:2) was used. ６ An electrolyte solution containing 1% by mass of vinylene carbonate was prepared.

[0488] 2 g of the nonaqueous electrolyte solution was injected into the electrode laminate housed in an aluminum laminate packaging material under atmospheric pressure, a temperature of 25 ° C., and a dry air environment with a dew point of -40 ° C. or less. Subsequently, this was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -87 kPa, then returned to atmospheric pressure, and the material was allowed to stand for 5 minutes. After that, the operation of reducing the pressure from atmospheric pressure to -87 kPa and then returning to atmospheric pressure was repeated four times, and the material was allowed to stand for 15 minutes, and the nonaqueous electrolyte solution was impregnated into the electrode laminate. Thereafter, the electrode laminate housed in the aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed by sealing at a pressure of 0.1 MPa at 180 ° C. for 10 seconds in a state where the pressure was reduced to -95 kPa, to prepare a positive electrode half cell.

[0489] The initial charge capacity density and the initial discharge capacity density were obtained by setting the upper limit of the stable operating potential of the positive electrode active material using the method described above (initial charge capacity density A1 and initial discharge capacity density B1 of the positive electrode active material). The results are shown in the table below.

[0490] (Measurement of initial charge capacity density A2 and initial discharge capacity density B2 of pre-doped material) ５ FeO ４91% by mass of the powder, 4% by mass of carbon black, 5% by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) were mixed to a solids concentration of 45% by mass to obtain a positive electrode slurry for a positive electrode half cell used for measuring the initial charge capacity of the positive electrode active material. The obtained slurry was applied at 100 g / m to one side of a 15 μm-thick anchor aluminum foil serving as a positive electrode current collector. ２ The coated material was dried and pressed to obtain a positive electrode for a positive electrode half cell to be used for measuring the initial charge and initial discharge capacity density of the pre-dope material.

[0491] The obtained single-sided positive electrode was punched out to a coated area of ​​2 cm x 2 cm, and the positive electrode terminal was connected by ultrasonic welding. The negative electrode terminal was connected by ultrasonic welding to a Li counter electrode, which had Li attached to copper foil. This was combined with a polypropylene separator and a glass filter to obtain a positive half-cell electrode laminate. This electrode laminate was housed in an exterior body made of aluminum laminate packaging, and three sides of the exterior body, including the electrode terminal portion and the bottom portion, were heat-sealed at a temperature of 180°C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. The electrode laminate was vacuum-dried at a temperature of 50°C, a pressure of 50 Pa, and a drying time of 25 hours. As the electrolyte, 1.0 M LiPF in an EC:MEC mixed solvent (volume ratio 1:2) was used. ６ An electrolyte solution containing 1% by mass of vinylene carbonate was prepared.

[0492] 2 g of the nonaqueous electrolyte solution was injected into the electrode laminate housed in the aluminum laminate packaging material under atmospheric pressure, a temperature of 25°C, and a dry air environment with a dew point of -40°C or less. Subsequently, this was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -87 kPa, and then the pressure was returned to atmospheric pressure, allowing for impregnation. Thereafter, the electrode laminate housed in the aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed at 180°C for 10 seconds at a pressure of 0.1 MPa under a reduced pressure of -95 kPa, to produce a positive electrode half cell.

[0493] Using the method described above (initial charge capacity density A2 and initial discharge capacity density B2 of the pre-dope material), the initial charge capacity and initial discharge capacity were measured by setting the upper limit of the operating potential of the pre-dope material to the values ​​shown in the table below and the lower limit of the operating potential to 3.0 V. The initial charge capacity density A2 and initial discharge capacity density B2 per mass of the pre-dope material obtained by dividing by the amount of the pre-dope material are shown in the table below.

[0494] (Calculation of parameters) From the above, A2 / A1, B2 / A2, and (R1×A1) / (R2×A2) were calculated. The results are shown in the table below.

[0495] (Fabrication of Lithium Ion Secondary Battery) (Fabrication of Positive Electrode Precursor) LiCoO ２ As a pre-dopant, Li ５ FeO ４ The resulting slurry for the positive electrode precursor was applied to one side of a 15 μm-thick aluminum foil in an amount of 97 g / m². ２ and pressed to obtain a positive electrode precursor.

[0496] (Preparation of Negative Electrode Precursor) 91.0 parts by mass of artificial graphite, 5.0 parts by mass of silicon monoxide, 2.0 parts by mass of styrene-butadiene rubber, 2.0 parts by mass of carboxymethyl cellulose (CMC), and water were mixed to obtain a slurry for a negative electrode precursor. The obtained slurry for a negative electrode precursor was applied to one side of a 10 μm-thick electrolytic copper foil with a one-side basis weight of 40 g / m. ２ and pressed to obtain a negative electrode.

[0497] (Assembly) The resulting positive electrode precursor was cut to a coated area of ​​2 cm x 2 cm, and the resulting negative electrode precursor was cut to a coated area of ​​2.2 cm x 2.2 cm. A 15 μm thick microporous membrane separator was sandwiched between the positive electrode precursor and the negative electrode, and the resulting laminate was then stacked. The negative electrode precursor and the positive electrode precursor were then connected to a negative electrode terminal and a positive electrode terminal, respectively, by ultrasonic welding to form an electrode laminate. This electrode laminate was then housed in an exterior body made of aluminum laminate packaging, and the three sides of the exterior body, including the electrode terminal portion and the bottom portion, were heat-sealed at a temperature of 180°C, a sealing time of 20 seconds, and a sealing pressure of 1.0 MPa. The laminate was then vacuum-dried at a temperature of 50°C, a pressure of 50 Pa, and a drying time of 25 hours.

[0498] (Injection of electrolyte) 1.0 M LiPF in EC:MEC mixed solvent (volume ratio 1:2) was used as the electrolyte. ６ An electrolyte solution containing 1% by mass of vinylene carbonate was prepared. 2 g of the nonaqueous electrolyte solution was injected into an electrode laminate housed in an aluminum laminate packaging material under atmospheric pressure, a temperature of 25°C, and a dry air environment with a dew point of -40°C or less. This was then placed in a vacuum chamber, the pressure reduced from atmospheric pressure to -87 kPa, and then returned to atmospheric pressure for impregnation. The electrode laminate housed in the aluminum laminate packaging material and impregnated with the nonaqueous electrolyte solution was then placed in a vacuum sealing machine, and the aluminum laminate packaging material was sealed by sealing at 180°C for 10 seconds at a pressure of 0.1 MPa under a reduced pressure of -95 kPa.

[0499] (Pre-doping) The obtained injected battery was subjected to constant current charging at a rate of 0.2 C under a 25 ° C. environment using a charge / discharge device (TOSCAT-3100U) manufactured by Toyo Systems Co., Ltd. until the voltage reached 4.2 V, and then to initial charging by continuously performing 4.2 V constant voltage charging for 5 hours, thereby pre-doping the negative electrode precursor.

[0500] (Gassing) After pre-doping, the lithium ion secondary battery was placed in a dry air environment at a temperature of 25°C and a dew point of -40°C, and a portion of the aluminum laminate packaging material was opened. Subsequently, the lithium ion secondary battery was placed in a vacuum chamber, and the pressure was reduced from atmospheric pressure to -80 kPa over 3 minutes, and then the pressure was returned to atmospheric pressure over 3 minutes. Thereafter, the lithium ion secondary battery was placed in a vacuum sealing machine, and the pressure was reduced to -90 kPa. The aluminum laminate packaging material was sealed by sealing at 200°C for 10 seconds at a pressure of 0.1 MPa, and a lithium ion secondary battery was obtained.

[0501] (Measurement of volume resistivity of positive electrode) The obtained lithium ion secondary battery was adjusted to 2.4 V, and then disassembled in an argon box. The removed positive electrode was immersed and washed in dimethyl carbonate and air-dried. Using an electrode resistance measurement system RM2610 manufactured by Hioki E.E. Corporation, a measurement probe was brought into contact with the surface of the positive electrode active material layer of the positive electrode at normal pressure, and a constant current (1 mA) was passed through the surface of the positive electrode active material layer. The potential distribution generated on the surface was measured at multiple points, and the volume resistivity of the positive electrode active material layer in the positive electrode was calculated. The results are shown in the table below.

[0502] (Initial characteristic evaluation) The above (discharge capacity Q, full cell capacity density P per mass of positive electrode active material) full The discharge capacity of the cell was measured by the method described in the section full The results are shown in the table below.

[0503] (Capacity Retention Rate After 100 Cycles) The capacity retention rate after 100 cycles was measured by the method described above, and the results are summarized in the table below.

[0504] Examples 6-2 to 33, Comparative Examples 6-1 to 33 Evaluations were carried out in the same manner as in Example 6-1 except as shown in the table below. The results are shown in the table below.

[0505]

[0506]

[0507]

[0508]

[0509]

[0510]

[0511]

[0512]

[0513]

[0514] From the above table, when the initial charge capacity density A1 (mAh / g) of the positive electrode active material, the D50 of the positive electrode active material is R1 (μm), the initial charge capacity density A2 (mAh / g) of the pre-doped material, the initial discharge capacity density B2 (mAh / g) of the pre-doped material, and the D50 of the pre-doped material is R2 (μm), when A2 / A1 > 1.2, B2 / A2 < 0.3, and 0.2 < (R1 × A1) / (R2 × A2) < 2, it is clear that the pre-doped material functions effectively, and at the same time, it can increase the effective utilization rate of the positive electrode and exhibit a high cycle capacity retention rate. Furthermore, it is clear that when the volume resistivity of the positive electrode precursor is below 10 Ω cm, it exhibits a particularly good cycle capacity retention rate.

[0515] Without being limited by theory, the pre-dope material is typically used in an amount sufficient to compensate for the irreversible capacity of the negative electrode, so its presence in the positive electrode composite is generally low. The negative electrode portion opposite the portion where the pre-dope material particles are present in the positive electrode receives excess lithium compared to the portion opposite the portion where the pre-dope material particles are not present, resulting in localized unevenness in the doping amount of the negative electrode. The inventors speculate that this causes localized lithium deposition during cycle testing and accelerates degradation. Therefore, the inventors discovered that if (R1 × A1) / (R2 × A2) is greater than 0.25, the particle size of the pre-dope material decreases depending on the relative capacity density with the positive electrode active material, thereby reducing localized lithium concentration differences. Reducing localized lithium concentration differences results in more uniform in-plane load on the negative electrode, resulting in good cycle durability. If (R1 x A1) / (R2 x A2) is greater than 2, the particle size is too small, and the pre-dope material is distributed throughout the positive electrode active material layer. Therefore, the decomposition reaction of the pre-dope material during initial charging generates voids throughout the positive electrode active material layer, and the positive electrode is prone to embrittlement due to expansion and contraction during charging and discharging, resulting in reduced durability. Furthermore, if the volume resistivity of the positive electrode is 10 Ω cm or less, the electrical resistance within the composite is low, and therefore the charge-discharge reaction during cycle testing proceeds uniformly, and it is thought that the cycle capacity retention rate in particular is likely to be improved.

[0516] <Examples according to the third embodiment>

[0517] Example 7-1 (Preparation of Positive Electrode Active Material and Pre-Dope Material) LiCoO ２ The D50 of the Li powder used as a pre-dopant was adjusted to the particle size shown in the table below using a bead mill. ５ FeO ４ The D50 was adjusted to the particle size shown in the table below using a bead mill.

[0518] (Measurement of initial charge capacity density A1 of positive electrode active material) ２91% by mass of the powder, 4% by mass of carbon black, 5% by mass of PVdF (polyvinylidene fluoride), and NMP (N-methylpyrrolidone) were mixed to a solids concentration of 45% by mass to obtain a positive electrode slurry for a positive electrode half cell used to measure the initial charge capacity density of the positive electrode active material. The obtained slurry was applied at 100 g / m to one side of a 15 μm-thick anchor aluminum foil serving as a positive electrode current collector. ２ The coated layer was dried and pressed to obtain a positive electrode for a positive electrode half cell to be used for measuring the initial charge capacity density of the positive electrode active material.

[0519] The obtained single-sided positive electrode was punched out to a coated area of ​​2 cm x 2 cm, and the positive electrode terminal was connected by ultrasonic welding. The negative electrode terminal was connected by ultrasonic welding to a Li counter electrode in which Li was attached to copper foil. This was combined with a polypropylene separator and a glass filter to obtain a positive e...

Claims

1. A non-aqueous alkali metal electricity storage element precursor comprising a positive electrode precursor, a negative electrode precursor, a separator, and an exterior material, wherein the negative electrode precursor comprises a material that occludes and releases alkali metal ions as a negative electrode active material, the positive electrode precursor has a positive electrode active material layer containing a positive electrode active material that occludes and releases alkali metal ions, and the non-aqueous alkali metal electricity storage element precursor contains an alkali metal carbonate or a pre-dope material in the positive electrode active material layer, or in any intermediate layer between the positive electrode active material layer and the separator, or in both of them.

2. A non-aqueous alkali metal storage element comprising a positive electrode including a positive electrode active material layer, a negative electrode, a separator, and an exterior material, wherein the negative electrode comprises a material that occludes and releases alkali metal ions as the negative electrode active material.

3. A method for producing a nonaqueous alkali metal electric storage element using a nonaqueous alkali metal electric storage element precursor comprising a positive electrode precursor, a negative electrode precursor, a separator, and an exterior material, wherein the negative electrode precursor comprises, as a negative electrode active material, a material that inserts and desorbs alkali metal ions, and the positive electrode precursor has a positive electrode active material layer containing a positive electrode active material that occludes and releases alkali metal ions, and wherein an alkali metal carbonate or a pre-dope material 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, wherein the nonaqueous alkali metal electric storage element precursor comprises a nonaqueous electrolytic solution containing an electrolyte containing alkali metal ions, and the method for producing a nonaqueous alkali metal electric storage element comprises applying a voltage between the positive electrode precursor and the negative electrode precursor to dope the alkali metal ions into the negative electrode active material.

4. The nonaqueous alkali metal storage element precursor according to claim 1, wherein the nonaqueous alkali metal storage element precursor contains the 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 contains a carbon material in the positive electrode active material layer, the intermediate layer, or both, wherein the amount of oxygen atoms X calculated from carbon monoxide and / or carbon dioxide when the carbon material is measured by temperature programmed desorption-mass spectrometry (TPDMS) is 0.1 mmol / g or more per mass of the carbon material, and wherein the amount of the carbon material in the layer containing the carbon material in the positive electrode active material layer and, if present, the intermediate layer, is 0.3 mass% or more and 15 mass% or less, based on the total mass of the layers containing the carbon material.

5. The non-aqueous alkali metal electric storage element precursor according to claim 1 or 4, wherein the positive electrode active material layer contains 0.2 to 15 mass % of the alkali metal carbonate.

6. The non-aqueous alkali metal electric storage element precursor according to claim 1 or 4, wherein the intermediate layer contains 20 to 95 mass % of the alkali metal carbonate.

7. The BET specific surface area of ​​the carbon material is 100 m ２ / g or more 1800m ２ The non-aqueous alkali metal capacitor element precursor according to claim 4, wherein the SiO 2 content is 1 / g or less.

8. The non-aqueous alkali metal storage element precursor according to claim 1 or 4, wherein the negative electrode active material comprises at least one of an alloy-based negative electrode material that forms an alloy with an alkali metal and an amorphous carbon material.

9. A non-aqueous alkali metal storage element according to claim 2, comprising a positive electrode including a positive electrode active material layer, a negative electrode, a separator, and an exterior material, wherein the negative electrode includes a material that inserts and releases alkali metal ions as a negative electrode active material, the effective utilization rate of the positive electrode active material is 85 to 99.5%, and the negative electrode active material includes at least one of an alloy-based negative electrode material that forms an alloy with an alkali metal and an amorphous carbon material.

10. The nonaqueous alkali metal storage element according to claim 2 or 9, wherein the positive electrode active material layer contains 0.02% by weight or more and 12% by weight or less of an alkali metal carbonate, based on the weight of the positive electrode active material layer.

11. The effective utilization rate of the positive electrode active material is 85 to 99.5%, and the negative electrode reversible capacity (mAh / cm ２ ) to the negative electrode irreversible capacity (mAh / cm ２ 3. The nonaqueous alkali metal storage element according to claim 2, wherein the irreversible capacity ratio, which is the ratio of the total capacity of the nonaqueous alkali metal to the total capacity of the nonaqueous alkali metal, is 5% or more and 50% or less.

12. The nonaqueous alkali metal storage element according to claim 2 or 11, wherein the positive electrode active material layer contains 0.02% by weight or more and 12% by weight or less of an alkali metal carbonate, based on the weight of the positive electrode active material layer.

13. The nonaqueous lithium storage element according to claim 2, wherein a carbon material is provided in the positive electrode active material layer or between the positive electrode active material layer and the separator, wherein the amount of oxygen atoms X calculated from carbon monoxide and / or carbon dioxide obtained when the carbon material is measured by temperature programmed desorption-mass spectrometry (TPDMS) is 0.1 mmol / g or more per mass of the carbon material, and wherein the effective utilization rate of the positive electrode active material contained in the positive electrode active material layer is 85 to 99.5%.

14. The BET specific surface area of ​​the carbon material is 100 m ２ / g or more 1800m ２ The non-aqueous lithium storage element according to claim 13, wherein the SiO 2 content is 1 / g or less.

15. The nonaqueous lithium storage element according to claim 13, wherein the negative electrode active material includes at least one of an alloy-based negative electrode material that forms an alloy with lithium and an amorphous carbon material.

16. The nonaqueous alkali metal storage element according to claim 13, wherein the positive electrode active material layer contains 0.02% by weight or more and 12% by weight or less of an alkali metal carbonate, based on the weight of the positive electrode active material layer.

17. A method for manufacturing a nonaqueous alkali metal storage element using a nonaqueous alkali metal storage element precursor including a positive electrode precursor, a negative electrode precursor, a separator, a nonaqueous electrolyte, and an exterior material, wherein the negative electrode precursor includes a material that occludes and releases alkali metal ions as a negative electrode active material, the positive electrode precursor has a positive electrode active material layer including a positive electrode active material that occludes and releases alkali metal ions, the nonaqueous alkali metal 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 in both, and contains a carbon material in the positive electrode active material layer, or in the intermediate layer, or in both, and the carbon material has an oxygen atomic weight X calculated from carbon monoxide and / or carbon dioxide when the carbon material is measured by temperature programmed desorption-mass spectrometry (TPDMS) of 0.1 mmol / g or more per mass of the carbon material, The amount of the carbon material in the layer containing the carbon material in the positive electrode active material layer and, if present, in the intermediate layer is 0.3 mass % or more and 15 mass % or less based on the total mass of the layer containing the carbon material, the non-aqueous electrolytic solution contains an electrolyte containing an alkali metal ion, and the potential of the positive electrode precursor is 4.15 to 4.75 V (vs. Li / Li) relative to the non-aqueous alkali metal electric storage element precursor. ＋ a voltage is applied between the positive electrode precursor and the negative electrode precursor so that the negative electrode active material is doped with alkali metal ions.

18. A method for producing a non-aqueous lithium storage element, wherein the non-aqueous alkali metal storage element is a non-aqueous lithium storage element, and the method uses a non-aqueous lithium storage element precursor including a positive electrode precursor, a negative electrode precursor, a separator, a non-aqueous electrolyte, and an exterior material, wherein the non-aqueous lithium storage element precursor comprises: the negative electrode precursor including a material that absorbs and releases lithium ions as a negative electrode active material; the positive electrode precursor having a positive electrode active material layer including a positive electrode active material that absorbs and releases lithium ions; lithium 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; and a carbon material is contained in the positive electrode active material layer, or in the intermediate layer, or in both; when the carbon material is measured by temperature programmed desorption-mass spectrometry (TPDMS), the oxygen atomic weight X calculated from carbon monoxide and / or carbon dioxide is 0.1 mmol / g or more per mass of the carbon material; 4. The method of manufacturing a lithium-ion battery according to claim 3, wherein the amount of the carbon material in the layer containing the carbon material in the positive electrode active material layer and, if present, in the intermediate layer, is 0.3 mass % or more and 15 mass % or less, based on the total mass of the layer containing the carbon material; the nonaqueous electrolytic solution includes an electrolyte containing lithium ions; and a voltage of 4.1 V or more and 4.6 V or less is applied between the positive electrode precursor and the negative electrode precursor for the nonaqueous lithium energy storage element precursor to dope the negative electrode active material with lithium ions.

19. A method for producing a non-aqueous lithium storage element precursor including a positive electrode precursor, a negative electrode precursor, a separator, a non-aqueous electrolyte, and an exterior material, wherein the non-aqueous alkali metal storage element precursor has the following configuration: (a) the negative electrode precursor has a negative electrode active material layer containing a negative electrode active material including a material that absorbs and releases lithium ions, and (b) the positive electrode precursor has a positive electrode active material layer containing a positive electrode active material that contains a positive electrode active material that absorbs and releases lithium ions, and (c) the positive electrode active material layer contains lithium carbonate, and (d) the positive electrode active material layer contains 0.30 mass% or more and 15.00 mass% or less of a carbon material, and (e) the carbon material has an oxygen atomic weight X calculated from carbon monoxide and / or carbon dioxide obtained by temperature programmed desorption-mass spectrometry (TPDMS) of 0.10 mmol / g or more and 5.00 mmol / g or less per mass of the carbon material, and (f) A method for producing a nonaqueous lithium storage element precursor, wherein the nonaqueous electrolytic solution contains an electrolyte containing lithium ions, and the method comprises applying a voltage of 4.1 V or more and 4.45 V or less between the positive electrode precursor and the negative electrode precursor to dope the lithium ions into the nonaqueous lithium storage element precursor.

20. A method for producing a non-aqueous sodium storage element, wherein the non-aqueous alkali metal storage element is a non-aqueous sodium storage element, and the method uses a non-aqueous sodium storage element precursor including a positive electrode precursor, a negative electrode precursor, a separator, a non-aqueous electrolyte, and an exterior material, wherein the non-aqueous sodium storage element precursor comprises: the negative electrode precursor including a material that occludes and releases sodium ions as a negative electrode active material; the positive electrode precursor has a positive electrode active material layer including a positive electrode active material that occludes and releases sodium ions; sodium 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; and a carbon material is contained in the positive electrode active material layer, or in the intermediate layer, or in both; when the carbon material is measured by temperature programmed desorption-mass spectrometry (TPDMS), the oxygen atomic weight X calculated from carbon monoxide and / or carbon dioxide is 0.1 mmol / g or more per mass of the carbon material; the amount of the carbon material in the layer containing the carbon material in the positive electrode active material layer and, if present, in the intermediate layer, is 0.3 mass % or more and 15 mass % or less, based on the total mass of the layer containing the carbon material; the nonaqueous electrolytic solution includes an electrolyte containing sodium ions; and the nonaqueous sodium storage element precursor is doped with sodium ions by applying a voltage of 3.8 V or more and 4.3 V or less between the positive electrode precursor and the negative electrode precursor.

21. A positive electrode precursor for a non-aqueous alkali metal electric storage element according to claim 1, which is a non-aqueous lithium electric storage element precursor, comprising a positive electrode active material layer for the non-aqueous lithium electric storage element precursor, wherein the positive electrode active material layer contains a pre-dope material and a positive electrode active material, and the positive electrode active material contains a positive electrode active material that absorbs and releases lithium ions, and wherein, when the initial charge capacity density of the positive electrode active material is A1 (mAh / g), the D50 of the positive electrode active material is R1 (μm), the initial charge capacity density of the pre-dope material is A2 (mAh / g), the initial discharge capacity of the pre-dope material is B2 (mAh / g), and the D50 of the pre-dope material is R2 (μm), the positive electrode precursor satisfies the following formulas: A2 / A1>1.2, B2 / A2<0.3, and 0.25<(R1×A1) / (R2×A2)<2.

22. The pre-dopant is Li ６ CoO ４ , Li ５ FeO ４ , Li ２ NiO ４ , Li ６ MnO ４ , and Li １．２ (Ti ０．５ Fe ０．５ ) ０．８ O ２ 22. The positive electrode precursor of claim 21, wherein the positive electrode precursor is at least one selected from the group consisting of:

23. The positive electrode precursor according to claim 21, further satisfying the following formula: R2<9 μm.

24. A lithium ion secondary battery obtained by pre-doping a non-aqueous lithium storage element precursor having the positive electrode precursor according to claim 21.

25. The lithium ion secondary battery according to claim 24, wherein the volume resistivity of the positive electrode active material layer after pre-doping is 10 Ωcm or less.

26. The lithium ion secondary battery according to claim 24, wherein the negative electrode active material contained in the lithium ion secondary battery includes an alloy-based negative electrode material that forms an alloy with lithium.

27. A method for producing a lithium ion secondary battery, comprising the steps of: applying a voltage between the positive electrode precursor according to claim 21 and a negative electrode precursor; decomposing the pre-dope material to release lithium ions; and pre-doping the negative electrode active material with lithium ions.

28. The non-aqueous alkali metal electric storage element precursor according to claim 1 is a lithium electric storage element precursor having a positive electrode precursor, a negative electrode precursor, and a separator, wherein the positive electrode precursor contains a positive electrode active material that absorbs and releases lithium ions, and a pre-dope material layer containing a pre-dope material is present at the interface between the positive electrode precursor and the separator, and when the initial charge capacity density of the positive electrode active material is A1 (mAh / g), the initial charge capacity density of the pre-dope material is A2 (mAh / g), the initial discharge capacity density of the pre-dope material is B2 (mAh / g), and the D50 of the pre-dope material is R2 (μm), the lithium electric storage element precursor satisfies the following formulas: B2 / A2<0.3, A2 / A1>1.2, and 0.2≦R2≦15.

29. The pre-dopant is Li ６ CoO ４ , Li ５ FeO ４ , Li ２ NiO ４ , Li ６ MnO ４ , and Li １．２ (Ti ０．５ Fe ０．５ ) ０．８ O ２ The lithium storage element precursor according to claim 28, which is at least one selected from the group consisting of:

30. A lithium storage element precursor according to claim 28, wherein the pre-dope material layer contains a conductive material.

31. The lithium storage element precursor according to claim 28, further satisfying the following formula: R2≦5 μm.

32. A lithium storage element precursor according to claim 28, wherein the negative electrode active material contained in the negative electrode precursor comprises an alloy-based negative electrode material that forms an alloy with lithium.

33. A lithium ion secondary battery obtained by pre-doping the lithium storage element precursor according to claim 28.

34. A method for manufacturing a lithium ion secondary battery, comprising the steps of: applying a voltage between the positive electrode precursor and the negative electrode precursor of the lithium storage element precursor described in claim 28; decomposing the pre-dope material to release lithium ions; and pre-doping the negative electrode active material contained in the negative electrode precursor with lithium ions.

Images