Positive electrode active material and all-solid-state battery

Abstract

The present invention provides an all-solid-state battery in which battery resistance after long-term storage is reduced, a production method for the all-solid-state battery, and a positive electrode active material used in the all-solid-state battery. The present invention relates to: a positive electrode active material for a solid-state battery, the positive electrode active material containing a lithium-containing complex oxide and an additive A that is a compound having a sulfur-oxygen bond; an all-solid-state battery containing a solid electrolyte and a positive electrode that contains the positive electrode active material described above; and a method for manufacturing an all-solid-state battery, the method having a step for obtaining a positive electrode active material for a solid-state battery by mixing together a lithium-containing complex oxide and an additive A that is a compound having a sulfur-oxygen bond, a step for preparing a positive electrode that contains the positive electrode active material for a solid-state battery, and a step for bonding the positive electrode, a negative electrode, and a solid electrolyte such that the solid electrolyte is present between the positive electrode and the negative electrode.

Description

Positive electrode active material and all-solid-state battery

[0001] The present invention relates to a rechargeable all-solid-state battery for use as a power source for portable electronic devices, in-vehicle batteries, and for power storage, etc. This application claims priority based on Japanese Patent Application No. 2023-126539, filed on August 2, 2023, the contents of which are incorporated herein by reference.

[0002] In recent years, lithium secondary batteries have been widely used in electronic devices such as mobile phones and laptop computers, as well as power sources for electric vehicles and power storage. In particular, there has been a rapid increase in demand for batteries with high capacity, high output, and high energy density that can be installed in hybrid and electric vehicles.

[0003] A lithium secondary battery is mainly composed of a positive electrode and a negative electrode containing a material capable of absorbing and releasing lithium, and an electrolyte. The electrolyte may be a non-aqueous electrolyte solution for batteries containing a lithium salt and a non-aqueous solvent, or a solid electrolyte such as a sulfide-based solid electrolyte. A lithium secondary battery using a solid electrolyte as the electrolyte is called an all-solid-state battery.

[0004] In an attempt to improve battery performance, it has been proposed to incorporate various additives into the non-aqueous electrolyte solution, positive electrode, or negative electrode of a battery. For example, it is known that adding a specific cyclic sulfonic acid ester as an additive to the non-aqueous electrolyte solution of a battery can improve the high-temperature storage characteristics of a non-aqueous electrolyte secondary battery (see, for example, Patent Document 1). It is also known that adding a specific chain sulfonic acid ester as an additive to the non-aqueous electrolyte solution of a battery can increase the average discharge voltage of a lithium secondary battery to 4.2 V or more (see, for example, Patent Document 2). It is also known that adding a specific chain sulfonic acid ester as an additive to the non-aqueous electrolyte solution of a battery can suppress swelling of a lithium secondary battery during high-temperature storage (see, for example, Patent Document 3). It is also known that adding a specific cyclic sulfonic acid ester as an additive to the solid electrolyte constituting the negative electrode can suppress a decrease in the Coulombic efficiency during charge-discharge cycles of an all-solid-state battery (see, for example, Patent Document 4).

[0005] JP 2004-185931 A JP 2001-243982 A JP 2003-086249 A JP 2022-076417 A

[0006] Lithium secondary batteries suffer from degradation due to an increase in battery resistance over time, and there is a need to reduce the increase in battery resistance after long-term storage so that lithium secondary batteries can be used stably for a longer period of time.

[0007] An object of the present invention is to provide an all-solid-state battery in which an increase in battery resistance after long-term storage is suppressed, a method for producing the same, and a positive electrode active material or a positive electrode for use in the all-solid-state battery.

[0008] As a result of intensive research aimed at solving the above problems, the present inventors have found that in an all-solid-state battery, an increase in battery resistance after long-term storage can be suppressed by adding a compound having a sulfur-oxygen bond as an additive to a positive electrode active material, and have thus completed the present invention.

[0009] The present invention is as follows: [1] A cathode active material for a solid battery, comprising a lithium-containing composite oxide and an additive A which is a compound having a sulfur-oxygen bond. [2] The cathode active material of [1], wherein the additive A is one or more compounds selected from the group consisting of cyclic sulfate esters, chain sulfate esters, cyclic sulfonate esters, and chain sulfonate esters. [3] The additive A is a compound represented by the following general formulas (A1) to (A4):

[0010]

[0011] [In formula (A1), R １１ and R １２ each independently represents a hydrocarbon group having 1 to 6 carbon atoms. ２１ represents an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, a group represented by general formula (A2-1), or a group represented by general formula (A2-2); in formula (A2-1), R ２２ represents an oxygen atom, an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, or an oxymethylene group; ２３represents an alkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 6 carbon atoms; in formulas (A2-1) and (A2-2), * represents a bonding position. ３１ ~R ３４ each independently represents a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorohydrocarbon group having 1 to 3 carbon atoms. ４１ ~R ４４ each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorohydrocarbon group having 1 to 3 carbon atoms. [4] The positive electrode active material of any of [1] to [3] above, wherein the additive A is one or more selected from the group consisting of 1,3,2-dioxathiolane-2,2-dioxide and dimethyl sulfate. [5] The lithium-containing composite oxide is a compound represented by the following general formula (P1):

[0012]

[0013] [In formula (P1), A is an element other than Li, Ni, Mn, and Co; and a to f are real numbers satisfying 0.8≦a≦1.2, 0≦b≦0.95, 0≦c≦0.5, 0≦d≦1.0, 0.7≦b+c+d≦1.1, 0≦e≦0.1, and 1.8≦f≦2.2.]. [6] The cathode active material of any of [1] to [5] above, wherein at least a part of the surface of the lithium-containing composite oxide is coated with the additive A. [7] A cathode for a solid battery, comprising the cathode active material of any of [1] to [6] above. [8] A cathode for a solid battery, comprising a lithium-containing composite oxide, and an additive A which is a compound having a sulfur-oxygen bond. [9] The positive electrode according to the above [8], wherein the additive A is one or more compounds selected from the group consisting of cyclic sulfate esters, chain sulfate esters, cyclic sulfonate esters, and chain sulfonate esters.

[10] The additive A is a compound represented by the following general formulas (A1) to (A4):

[0014]

[0015] [In formula (A1), R １１and R １２ each independently represents a hydrocarbon group having 1 to 6 carbon atoms. ２１ represents an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, a group represented by general formula (A2-1), or a group represented by general formula (A2-2); in formula (A2-1), R ２２ represents an oxygen atom, an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, or an oxymethylene group; ２３ represents an alkyl group having 1 to 6 carbon atoms or an alkenyl group having 2 to 6 carbon atoms; in formulas (A2-1) and (A2-2), * represents a bonding position. ３１ ~R ３４ each independently represents a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorohydrocarbon group having 1 to 3 carbon atoms. ４１ ~R ４４ each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorohydrocarbon group having 1 to 3 carbon atoms.

[11] The positive electrode of any of [8] to

[10] above, wherein the additive A is one or more selected from the group consisting of 1,3,2-dioxathiolane-2,2-dioxide and dimethyl sulfate.

[12] The lithium-containing composite oxide is a compound represented by the following general formula (P1):

[0016]

[0017] [In formula (P1), A is an element other than Li, Ni, Mn, and Co; and a to f are real numbers satisfying 0.8≦a≦1.2, 0≦b≦0.95, 0≦c≦0.5, 0≦d≦1.0, 0.7≦b+c+d≦1.1, 0≦e≦0.1, and 1.8≦f≦2.2.] The positive electrode of any of [8] to

[11] above, having a composition represented by the following formula.

[13] An all-solid-state battery comprising the positive electrode of any of [7] to

[12] above and a solid electrolyte.

[14] The all-solid-state battery of

[13] above, wherein at least a part of the solid electrolyte is a sulfide-based solid electrolyte.

[15] The all-solid-state battery of

[13] or

[14] above, wherein the solid electrolyte is present between the positive electrode and the negative electrode.

[16] A method for manufacturing an all-solid-state battery, comprising: a step of mixing a lithium-containing composite oxide and an additive A that is a compound having a sulfur-oxygen bond to obtain a cathode active material for a solid state battery, a step of preparing a cathode containing the cathode active material for a solid state battery, and a step of joining the cathode, a negative electrode, and a solid electrolyte so that the solid electrolyte is present between the cathode and the negative electrode.

[17] A method for manufacturing an all-solid-state battery, comprising: a step of preparing a cathode active material containing a lithium-containing composite oxide and an additive A that is a compound having a sulfur-oxygen bond, and a step of joining the cathode, a negative electrode, and a solid electrolyte so that the solid electrolyte is present between the cathode and the negative electrode.

[0018] According to the present invention, it is possible to provide a positive electrode active material for a solid state battery that can reduce an increase in battery resistance after long-term storage, and an all-solid-state battery that uses the positive electrode active material for a solid state battery and has reduced battery resistance after long-term storage.

[0019] In the present invention and this specification, "X to Y (X and Y are real numbers satisfying X<Y)" means a numerical range of "not less than X and not more than Y."

[0020] In the present invention and the present specification, "C ｘ－ｙ (x and y are real numbers satisfying 0≦x<y) means that the number of carbon atoms is x or more and y or less.

[0021] [Cathode active material for solid battery] The cathode active material for solid battery according to the present invention contains a lithium-containing composite oxide and additive A, which is a compound having a sulfur-oxygen bond. By containing additive A, the cathode active material for solid battery according to the present invention can suppress an increase in battery resistance after long-term storage of a solid battery in which additive A is used as the cathode active material. The reason why such an effect of suppressing an increase in battery resistance over time is obtained is not clear, but is presumed as follows.

[0022] During durability tests (storage tests, cycle tests, float tests, etc.) of lithium secondary batteries, there are several factors that can cause an increase in battery resistance, but an increase in the resistance of the positive electrode is one of the main factors. Lithium composite oxides with a layered rock salt structure, such as active materials containing transition metals (Ni, Co, Mn) known as NCM, which are commonly used as positive electrode active materials, lose lithium ions during charging, causing the layered structure to become unstable. At this time, the transition metal atoms move to the sites where the lithium ions have been released, changing the crystal structure, resulting in low lithium ion conductivity and a decrease in the rate at which lithium ions are inserted and removed from the positive electrode active material. This change in crystal structure is one of the reasons for the increase in positive electrode resistance after durability tests.

[0023] The oxygen atom in the sulfur-oxygen bond structure can coordinate to a transition metal atom. In the positive electrode active material for a solid-state battery according to the present invention, Additive A, which is a compound having a sulfur-oxygen bond, coordinates with the transition metal atom through its oxygen atom, thereby stabilizing the transition metal atom in the positive electrode active material. As a result, it is presumed that migration of the transition metal atom is suppressed, the layered rock salt structure is maintained even after lithium ion desorption during charging, and an increase in the positive electrode resistance over time is suppressed.

[0024] The components of the positive electrode active material for a solid battery according to the present invention will be specifically described below.

[0025] <Additive A (Compound Having a Sulfur-Oxygen Bond)> The positive electrode active material for a solid battery according to the present invention contains a compound having a sulfur-oxygen bond (hereinafter, may be referred to as an "S-containing compound"), that is, Additive A. The S-containing compound contained in the positive electrode active material for a solid battery as Additive A may be one type or two or more types.

[0026] The S-containing compound is not particularly limited as long as it has a sulfur-oxygen bond capable of coordinating with a transition metal atom. From the viewpoint of fully exerting the effect of suppressing an increase in positive electrode resistance, the S-containing compound is preferably one or more compounds selected from the group consisting of cyclic sulfate esters, chain sulfate esters, cyclic sulfonate esters, and chain sulfonate esters, and more preferably a compound represented by any of the following general formulas (A1) to (A4).

[0027]

[0028] In general formula (A1), R １１ and R １２ are each independently a hydrocarbon group having 1 to 6 carbon atoms (C １－６ represents a hydrocarbon group). １－６ The hydrocarbon group may be linear or branched. １－６ The hydrocarbon group is an alkenyl group having 2 to 6 carbon atoms (C ２－６ alkenyl group), and alkynyl group having 2 to 6 carbon atoms (C ２－６ alkynyl group), but may be an alkyl group having 1 to 6 carbon atoms (C １－６ C is preferably an alkyl group. １－６ Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a 2-methylbutyl group, a 1-methylpentyl group, a neopentyl group, a 1-ethylpropyl group, a hexyl group, and a 3,3-dimethylbutyl group. ２－６ Specific examples of the alkenyl group include a vinyl group, a propenyl group, a butenyl group, a pentenyl group, and a hexenyl group. ２－６ Specific examples of the alkynyl group include an ethynyl group, a propynyl group, a butynyl group, a pentynyl group, and a hexynyl group.

[0029] The compound represented by general formula (A1) (hereinafter, sometimes referred to as "compound (A1)") includes R １１ and R１２ are each independently a linear or branched C １－３ Preferably, they are alkyl groups, and the same linear or branched C １－３ It is more preferable that they are alkyl groups, and １－３ It is even more preferable that they are alkyl groups, and it is particularly preferable that they are all methyl groups.

[0030]

[0031] In general formula (A2), R ２１ represents an alkylene group having 1 to 6 carbon atoms (C １－６ alkylene group), alkenylene group having 2 to 6 carbon atoms (C ２－６ In general formulas (A2-1) and (A2-2), * indicates a bonding position. That is, the group represented by general formula (A2-1) is a bond marked with * that is bonded to R in general formula (A2). ２１ The group represented by general formula (A2-2) is bonded to the oxygen atom to which R in general formula (A2) is bonded, at the bond marked with *. ２１ It bonds with the oxygen atom to which it is bonded.

[0032] R ２１ is C １－６ When the C is an alkylene group, １－６ The alkylene group may be linear or branched (excluding the group represented by general formula (A2-2)). １－６ Specific examples of the alkylene group include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, a pentylene group, a 2-methylbutylene group, a 1-methylpentylene group, a neopentylene group, a 1-ethylpropylene group, a hexylene group, and a 3,3-dimethylbutylene group.

[0033] The compound represented by general formula (A2) (hereinafter, sometimes referred to as “compound (A2)”) includes R ２１ is C １－６ When the C is an alkylene group, １－６The alkylene group may be a linear C １－６ Preferably, it is an alkylene group, and linear C １－３ An alkylene group is more preferred, and an ethylene group is particularly preferred.

[0034] R ２１ is C ２－６ When the C is an alkenylene group, ２－６ The alkenylene group may be linear or branched. ２－６ Specific examples of the alkenylene group include a vinylene group, a propenylene group, a butenylene group, a pentenylene group, and a hexenylene group.

[0035] Compound (A2) includes R ２１ is C ２－６ When the C is an alkenylene group, ２－６ The alkenylene group may be a linear C ２－６ Alkenylene groups are preferred, and linear C １－３ An alkenylene group is more preferred, and a vinylene group is particularly preferred.

[0036] In general formula (A2-1), R ２２ is an oxygen atom, C １－６ Alkylene group, C ２－６ represents an alkenylene group or an oxymethylene group (bonded to a sultone group via an oxygen atom). １－６ The alkylene group is R ２１ C mentioned in １－６ The same groups as the alkylene group can be mentioned. ２－６ The alkenylene group is R ２１ C mentioned in ２－６ Examples include the same groups as the alkenylene group.

[0037] Compound (A2) includes R ２１ is a group represented by general formula (A2-1), R ２２ is preferably an oxygen atom, a methylene group, an ethylene group, a propylene group, or an oxymethylene group, and more preferably an ethylene group or an oxymethylene group. ２１is an oxymethylene group ([4,4'-bi(1,3,2-dioxathiolane)] 2,2,2',2'-tetraoxide).

[0038] In general formula (A2-2), R ２３ is C １－６ Alkyl group, or C ２－６ represents an alkenyl group. １－６ The alkyl group is R １１ C mentioned in １－６ The same groups as the alkyl group can be mentioned. ２－６ The alkenyl group is R １１ C mentioned in ２－６ Examples include the same groups as alkenyl groups.

[0039] Compound (A2) includes R ２１ is a group represented by general formula (A2-2), R ２３ As the linear C １－６ It is preferably an alkyl group, and a linear C １－３ It is more preferable that the compound (A2) is an alkyl group. ２３ is a propyl group, the compound PEGLST (4-propyl-1,3,2-dioxathiolane-2,2-dioxide) is preferred.

[0040]

[0041] In general formula (A3), R ３１ ~R ３４ are each independently a hydrogen atom, a fluorine atom, or a hydrocarbon group having 1 to 3 carbon atoms (C １－３ hydrocarbon group), or a fluorinated hydrocarbon group having 1 to 3 carbon atoms (C １－３ In general formula (A4), R represents a fluorinated hydrocarbon group. ４１ ~R ４４ are each independently a hydrogen atom, a fluorine atom, or C １－３ Hydrocarbon group, or C １－３ represents a fluorohydrocarbon group. １－３ The fluorohydrocarbon group is C １－３ It is a hydrocarbon group in which one or more hydrogen atoms have been substituted with fluorine atoms.

[0042] R３１ ~R ３４ and R ４１ ~R ４４ is C １－３ When it is a hydrocarbon group, the C １－３ The hydrocarbon group may be linear or branched. １－３ The hydrocarbon group is an alkenyl group having 2 to 3 carbon atoms (C ２－３ alkenyl group). １－３ Specific examples of the hydrocarbon group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a vinyl group, and a propynyl group.

[0043] R ３１ ~R ３４ and R ４１ ~R ４４ is C １－３ When it is a fluorohydrocarbon group, the C １－３ Specific examples of the fluorinated hydrocarbon group include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a perfluoroethyl group, and a perfluoropropyl group.

[0044] The compound represented by general formula (A3) (hereinafter, sometimes referred to as "compound (A3)") is R ３１ ~R ３４ are each independently a hydrogen atom or C １－３ Preferably, R is a hydrocarbon group. ３１ ~R ３３ is a hydrogen atom, and R ３４ is a hydrogen atom or C １－３ A hydrocarbon group is more preferred. In particular, 1,3-propene sultone (PRS), 1-methyl-1,3-propene sultone, 2-methyl-1,3-propene sultone, or 3-methyl-1,3-propene sultone is preferred as compound (A3).

[0045] The compound represented by general formula (A4) (hereinafter, sometimes referred to as “compound (A4)”) includes R ４１ ~R ４４ are each independently a hydrogen atom or C １－３Preferably, R is a hydrocarbon group. ４１ ~R ４３ is a hydrogen atom, and R ４４ is a hydrogen atom or C １－３ A hydrocarbon group is more preferred. In particular, 1,3-propane sultone (PS) is preferred as compound (A3).

[0046] As additive A other than compounds (A1) to (A4), for example, 1,4-butane sultone can also be used.

[0047] The content of additive A in the positive electrode active material for a solid battery according to the present invention (total content when two or more types are used; the same applies hereinafter) is not particularly limited, but from the viewpoint of more effectively achieving the effects of the present invention, it is preferably 0.001% by mass to 10% by mass, more preferably 0.01% by mass to 5% by mass, even more preferably 0.01% by mass to 4% by mass, still more preferably 0.1% by mass to 2% by mass, and particularly preferably 0.1% by mass to 2% by mass.

[0048] In the present specification, the terms "content of additive" and "added amount of additive" both refer to the content of additive relative to the total amount of the positive electrode active material for a solid battery.

[0049] <Lithium-containing composite oxide> In the present invention and this specification, the term "lithium-containing composite oxide" refers to a composite oxide containing lithium (Li) and other atoms. As the lithium-containing composite oxide used in the present invention, various lithium-containing composite oxides used as positive electrode active materials can be used. The lithium-containing composite oxide contained in the positive electrode active material for a solid battery according to the present invention may be one type, or two or more types.

[0050] The lithium-containing composite oxide used in the present invention is preferably a composite oxide containing lithium and a transition metal atom. The lithium-containing composite oxide used in the present invention is preferably a compound containing at least one transition metal atom selected from the group consisting of Co, Ni, and Mn, and may contain atoms other than lithium and these transition metal atoms as necessary. Examples of the other atoms include at least one selected from the group consisting of P, Na, Mg, Ca, Sr, B, Al, Ge, Ti, V, Cr, Fe, Cu, Zr, Nb, Mo, W, Sn, Hf, and Ta (hereinafter also referred to as "additive element").

[0051] When the lithium-containing composite oxide used in the present invention contains Al and Mg as additive elements, it has the advantage that the positive electrode structure is less likely to break. When the lithium-containing composite oxide contains Ca and Mg among the additive elements, the capacity retention rate can be improved by suppressing the decrease in capacity associated with battery cycling without significantly reducing the initial discharge capacity. This is thought to be because calcium ions and magnesium ions that do not contribute to the battery reaction dissolve in the Li site, thereby reducing distortion in the crystal structure change of the lithium-containing composite oxide due to battery cycling. By dissolving in the Li site, Ca acts as a pillar at the Li site and contributes to stabilizing the crystal structure. Mg is thought to contribute to further improvement of cycle characteristics and high durability. Na is thought to have the effect of promoting crystal growth during firing. Other additive elements are also thought to contribute to improvements in the battery's capacity, cycle characteristics, output characteristics, safety, and durability.

[0052] The lithium-containing composite oxide may be a compound that does not contain any of Co, Ni, and Mn. Examples of such compounds include lithium iron phosphate (LiFePO ４ ) are typical examples of lithium transition metal phosphates.

[0053] The lithium-containing composite oxide used in the present invention is preferably a compound having a composition represented by the following general formula (P1) (hereinafter, sometimes referred to as "compound (P1)").

[0054]

[0055] In the general formula (P1), A is an element other than Li, Ni, Mn, and Co. Specific examples include the additive elements described above. A contained in one molecule of the compound (P1) may be one type of atom or two or more types of atoms.

[0056] In general formula (P1), a to f are real numbers that satisfy the following relationship:

[0057] 0.8≦a≦1.2 0≦b≦0.95 0≦c≦0.5 0≦d≦1.0 0.7≦b+c+d≦1.1 0≦e≦0.1 1.8≦f≦2.2

[0058] The compound (P1) preferably has a laminated structure in which a Li layer composed of lithium ions and a transition metal oxide layer containing Ni, Co, and Mn are laminated together. The compound (P1) having such a laminated structure undergoes a relatively small change in lattice volume when lithium is released, and also releases a small amount of oxygen during overcharge.

[0059] The superlattice structure of the compound (P1) can be confirmed by, for example, crystal structure analysis using electron beam diffraction measurement (TEM).

[0060] Compound (P1) is disclosed in Japanese Patent No. 4995444, Japanese Patent No. 5277686, JP 2013-101968, JP 2013-175410, JP 4880936, JP 5271751, JP 5317390, JP 2010-282761, JP 2009-158330, JP It can be produced by the synthesis method described in these publications or a modified method thereof, with reference to known methods described in, for example, Japanese Patent No. 2010-199077, Japanese Patent No. 5365711, Japanese Patent Application Laid-Open No. 2012-252964, Japanese Patent No. 5365711, Japanese Patent Application Laid-Open No. 2012-252964, and Japanese Patent Application Laid-Open No. 2015-176760. For example, lithium hydroxide (LiOH.H ２ O), nickel hydroxide (Ni(OH) ２ ), cobalt hydroxide (Co(OH) ２), and manganese hydroxide (Mn(OH) ２ ) in a mixing ratio such that the desired molar ratio of Li:Ni:Co:Mn is obtained, and the resulting mixed raw material is fired in an oxygen atmosphere (for example, at a temperature of 850 to 1000°C), thereby producing compound (P1).

[0061] The positive electrode active material for a solid battery according to the present invention can be produced by mixing additive A and a lithium-containing composite oxide in a non-aqueous solvent. The non-aqueous solvent is not particularly limited as long as it does not react with additive A and the lithium-containing composite oxide, and ethylene carbonate (EC), dimethyl carbonate (DMC), methyl ethyl carbonate (EMC), etc. can be used, or a mixed solvent of these can be used. Mixing additive A and the lithium-containing composite oxide can be carried out, for example, by reacting them at about 50 to 80°C for 1 to 10 hours.

[0062] The positive electrode active material for a solid battery according to the present invention may contain components other than the additive A and the lithium-containing composite oxide, if necessary. The content of the lithium-containing composite oxide in the positive electrode active material for a solid battery according to the present invention is not particularly limited, but is preferably 70 mass % or more, more preferably 80 mass % or more, and even more preferably 90 mass % or more, based on the entire positive electrode active material for a solid battery.

[0063] In the positive electrode active material for a solid battery according to the present invention, at least a part of the surface of the lithium-containing composite oxide is preferably coated with the additive A. The surface of the active material is an end of the crystal structure, and there are many oxygen atom deficiencies. Therefore, by having the additive A, which has oxygen coordinated to a transition metal atom derived from the lithium-containing composite oxide, present on the surface of the active material, the crystal structure can be further stabilized, and the effect of the additive A in suppressing an increase in the positive electrode resistance can be more fully exhibited.

[0064] The presence of additive A on the surface of the active material can be confirmed, for example, by performing elemental analysis of the active material using SEM-EDS (energy dispersive X-ray spectroscopy). Specifically, if sulfur atoms are detected when SEM-EDS measurement is performed on the surface of the active material, it can be said that additive A is present on the surface of the active material.

[0065] [All-Solid-State Battery] The all-solid-state battery according to the present invention comprises a positive electrode containing a lithium-containing composite oxide and the additive A, and a solid electrolyte. Because the all-solid-state battery according to the present invention has a positive electrode containing the additive A, the battery resistance increases little after long-term storage and has excellent long-term storage stability. The positive electrode may be a positive electrode containing the positive electrode active material according to the present invention (a positive electrode active material containing a lithium-containing composite oxide and the additive A), or may be a positive electrode manufactured using a conventional positive electrode active material (a positive electrode active material containing a lithium-containing composite oxide but not the additive A) and the additive A as raw materials.

[0066] The all-solid-state battery according to the present invention can be manufactured by configuring the battery so that the solid electrolyte is present between the positive electrode and the negative electrode. Specifically, the all-solid-state battery according to the present invention can be manufactured by the steps of: mixing a lithium-containing composite oxide and additive A, which is a compound having a sulfur-oxygen bond, to obtain a positive electrode active material for a solid battery; preparing a positive electrode containing the positive electrode active material for a solid battery; and joining the positive electrode, negative electrode, and solid electrolyte together so that the solid electrolyte is present between the positive electrode and the negative electrode. The all-solid-state battery according to the present invention can also be manufactured by the steps of preparing a positive electrode containing a positive electrode active material containing a lithium-containing composite oxide and additive A, which is a compound having a sulfur-oxygen bond, and joining the positive electrode, negative electrode, and solid electrolyte together so that the solid electrolyte is present between the positive electrode and the negative electrode.

[0067] <Positive electrode> A positive electrode active material layer containing the positive electrode active material according to the present invention can be formed on a current collector to form a positive electrode. The positive electrode active material layer preferably contains a binder in addition to the positive electrode active material, and further preferably contains a solid electrolyte, a conductive additive, a thickener, etc. as necessary. When a positive electrode active material not containing additive A is used, the positive electrode active material layer preferably further contains additive A.

[0068] The positive electrode active material layer can be produced by dry-mixing a positive electrode active material containing a lithium-containing composite oxide, a binder, and (further, if necessary, a solid electrolyte, a conductive aid, an additive A, a thickener, etc.) into a sheet, and pressing the resulting mixture onto a positive electrode current collector. The positive electrode active material layer can also be produced by dissolving or dispersing a positive electrode active material containing a lithium-containing composite oxide, a binder, and (further, if necessary, a solid electrolyte, a conductive aid, an additive A, a thickener, etc.) in a liquid medium to form a slurry, and then applying the resulting slurry to a positive electrode current collector and drying it.

[0069] The content of the positive electrode active material (or the content of the lithium-containing composite oxide) in the positive electrode active material layer is not particularly limited, but is usually 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more, relative to the total amount of the positive electrode active material layer. In addition, the content of the positive electrode active material (or the content of the lithium-containing composite oxide) in the positive electrode active material layer is usually 99% by mass or less, preferably 95% by mass or less, and more preferably 90% by mass or less, from the viewpoint of ionic conductivity of the positive electrode active material layer.

[0070] The binder is not particularly limited, and in the case of a coating method, any material may be used as long as it is stable in the liquid medium used in the production of the electrode. Specific examples of binders include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate (PMMA), polymethyl acrylate (PMA), polyacrylonitrile, polyacrylamide, aromatic polyamide, cellulose, and nitrocellulose; rubber-like polymers such as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers and hydrogenated products thereof, and EPDM (ethylene-propylene-diene ternary copolymer). Examples of suitable polymers include thermoplastic elastomeric polymers such as styrene-ethylene-butadiene-ethylene copolymers, styrene-isoprene-styrene block copolymers, and hydrogenated products thereof; soft resinous polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; and polymer compositions having ionic conductivity for alkali metal ions (particularly lithium ions). These substances may be used alone, or two or more may be used in any combination and ratio.

[0071] The proportion of the binder in the positive electrode active material layer is usually 0.1% by mass or more, preferably 0.3% by mass or more, and more preferably 0.5% by mass or more, from the viewpoint of the mechanical strength of the positive electrode. Also, from the viewpoint of further improving the battery capacity and conductivity, the proportion of the binder in the positive electrode active material layer is usually 50% by mass or less, preferably 30% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0072] The thickener is not particularly limited, and examples thereof include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphated starch, casein, and salts thereof. These substances may be used alone or in any combination and ratio of two or more.

[0073] When the positive electrode active material layer contains a thickener, the proportion of the thickener in the positive electrode active material layer is usually 0.1% by mass or more, preferably 0.3% by mass or more, and more preferably 0.5% by mass or more, from the viewpoint of the stability of the positive electrode slurry. Also, the proportion of the binder in the positive electrode active material layer is usually 50% by mass or less, preferably 30% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, from the viewpoint of further improving the battery capacity and conductivity.

[0074] A solid electrolyte can be contained in the positive electrode active material layer from the viewpoint of ion conductivity. Specific examples of the solid electrolyte include those listed as solid electrolytes constituting the solid electrolyte layer of the all-solid-state battery described below. The solid electrolyte contained in the positive electrode active material layer may be one of the materials described below, or two or more of them may be used in any combination and ratio. The solid electrolyte contained in the positive electrode active material layer may be the same material as the solid electrolyte constituting the solid electrolyte layer of the all-solid-state battery, or may be a different material.

[0075] When the positive electrode active material layer contains a solid electrolyte, the proportion of the solid electrolyte in the positive electrode active material layer is usually 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, from the viewpoint of further improving the conductivity. Also, the proportion of the solid electrolyte in the positive electrode active material layer is usually 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less, from the viewpoint of containing a sufficient amount of the positive electrode active material.

[0076] The positive electrode active material layer can contain a conductive additive to enhance conductivity. There are no particular limitations on the type of conductive additive, but specific examples include metal materials such as copper and nickel; graphite (e.g., natural graphite, artificial graphite), carbon black (e.g., acetylene black), carbon nanotubes, amorphous carbon (e.g., needle coke), and the like. These substances may be used alone, or two or more may be used in any combination and ratio.

[0077] The proportion of the conductive additive in the positive electrode active material layer is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, from the viewpoint of further improving the conductivity. Also, the proportion of the conductive additive in the positive electrode active material layer is usually 50% by mass or less, preferably 30% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, from the viewpoint of further improving the battery capacity.

[0078] As the material for the positive electrode current collector, typically used are metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, and carbon materials such as carbon cloth and carbon paper. Among these, metal materials are preferred, and aluminum is particularly preferred. As for the shape, metal materials include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punched metal, and foam metal, while carbon materials include carbon plate, carbon thin film, and carbon cylinder. Among these, metal thin films are preferred because they are currently used in industrialized products. The thin film may be formed into a mesh shape as appropriate.

[0079] When a thin film is used as the positive electrode current collector, its thickness is not limited, but from the viewpoint of strength, it is usually 1 μm or more, preferably 3 μm or more, and more preferably 5 μm or more. From the viewpoint of handleability, the thickness of the thin film positive electrode current collector is usually 100 mm or less, preferably 1 mm or less, and more preferably 50 μm or less.

[0080] The liquid medium for forming the slurry is not particularly limited as long as it can dissolve or disperse the lithium-containing composite oxide (e.g., powder), binder, and the conductive additive and thickener used as needed. The liquid medium may be either a polar solvent or a non-polar organic solvent. The polar solvent may be a protic polar solvent or an aprotic polar solvent.

[0081] Examples of protic polar solvents include water; alcohol-based polar solvents such as methanol and ethanol; and amine-based polar solvents such as diethylenetriamine and N,N-dimethylaminopropylamine. Examples of aprotic polar solvents include ketone-based polar solvents such as cyclohexanone, N-methylpyrrolidone (NMP), methyl ethyl ketone, and acetone; amide-based polar solvents such as hexamethylphosphalamide, dimethylacetamide, and dimethylformamide; ether-based polar solvents such as tetrahydrofuran (THF), dimethyl ether, and ethylene oxide; sulfoxide compounds such as dimethyl sulfoxide; and ester-based polar solvents such as methyl acrylate and methyl acetate. Examples of nonpolar organic solvents include aromatic-containing nonpolar solvents such as tetralin, anisole (methoxybenzene), benzene, xylene, toluene, methylnaphthalene, quinoline, and pyridine; and aliphatic hydrocarbon-based nonpolar solvents such as hexane. These solvents may be used alone or in any combination and ratio of two or more.

[0082] When a protic polar solvent is used as the liquid medium, a dispersant may be added together with the thickener, and a latex such as SBR may be used to form a slurry.

[0083] When a sulfide-based solid electrolyte is used, the liquid solvent is preferably a non-polar organic solvent, more preferably an aromatic-containing organic solvent, an aliphatic hydrocarbon solvent, or a mixed solvent thereof, and even more preferably an aromatic-containing organic solvent, in order to suppress the effect on the sulfide-based solid electrolyte.

[0084] The thickness of the positive electrode active material layer is usually about 10 μm to 300 μm. The positive electrode active material layer obtained by coating and drying is preferably compacted by a roller press or the like to increase the packing density of the positive electrode active material.

[0085] <Solid Electrolyte> The solid electrolyte contained in the all-solid-state battery according to the present invention is not particularly limited as long as it can conduct ions, and examples thereof include sulfide-based solid electrolytes, oxide-based solid electrolytes, and hydride-based solid electrolytes. Among these, from the viewpoint of high ion conductivity, it is preferable that at least a part of the solid electrolyte is a sulfide-based solid electrolyte. The solid electrolyte may be used alone, or two or more types may be used in any combination and ratio.

[0086] Examples of sulfide solid electrolytes include crystalline, glass, and glass ceramic types. From the viewpoint of high ionic conductivity, crystalline sulfide solid electrolytes are preferred, and among them, argyrodite-type sulfide solid electrolytes are more preferred. The sulfide solid electrolyte can be appropriately selected from various sulfide solid electrolytes described in documents such as Patent Document 1, Patent Document 4, and JP-A-2020-126760. The sulfide solid electrolyte preferably has high ionic conductivity, and for example, Li ２ S-P ２ S ５ , Li ２ S-P ２ S ５ - LiI, Li ２ S-P ２ S ５ -LiCl, Li ２ S-P ２ S ５ - LiBr, Li ２ S-P ２ S ５ -Li ２ O, Li ２ S-P ２ S ５ -Li ２ O-LiI, Li ２ S-P ２ S ５ -Li ３ N., Li. ２ S-SiS ２ , Li２ S-SiS ２ - LiI, Li ２ S-SiS ２ - LiBr, Li ２ S-SiS ２ -LiCl, Li ２ S-SiS ２ -B ２ S ３ - LiI, Li ２ S-SiS ２ -P ２ S ５ - LiI, Li ２ S-B ２ S ３ , Li ２ S-P ２ S ５ -Z ｍ S ２ｎ (where m and n are positive numbers, and Z is Ge, Zn, or Ga.), Li ２ S-GeS ２ , Li ２ S-SiS ２ -Li ３ P.O. ４ , Li ２ S-SiS ２ -Li ｘ MO ｙ (where x and y are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In.), Li １０ GeP ２ S １２ , Li （７-ａ-２） P.S. （６-ａ-ｂ） X ａ (wherein X is at least one of F, Cl, Br, and I, and 0.4≦a≦2.2, −0.9≦b≦(−a+2)) can be mentioned. Among these, from the viewpoint of good ionic conductivity, Li ２ S-P ２ S ５ , Li ２ S-P ２ S ５ - LiI, Li ２ S-P ２ S ５ -LiCl, Li （７-ａ-２） P.S. （６-ａ-ｂ） X ａ(wherein X is at least one of F, Cl, Br, and I, and 0.4≦a≦2.2, −0.9≦b≦(−a+2)) is preferred; ｘ Li ２ S. (100- ｘ ) P ２ S ５ (70≦x≦80), Li （７-ａ-２） P.S. （６-ａ-ｂ） X ａ (wherein X is at least one of F, Cl, Br and I, and 0.4≦a≦2.2, −0.9≦b≦(−a+2)) is more preferred.

[0087] When the solid electrolyte contained in the all-solid-state battery according to the present invention is a solid electrolyte other than a sulfide-based solid electrolyte, the other solid electrolyte can be appropriately selected from the solid electrolytes used in all-solid-state batteries, and specific examples of the other solid electrolyte include oxide-based solid electrolytes, dry polymer electrolytes, gel polymer electrolytes, and quasi-solid electrolytes.

[0088] The lower limit of the average thickness of the solid electrolyte layer in the all-solid-state battery is preferably 1 μm, more preferably 3 μm. The upper limit of the average thickness of the solid electrolyte layer is preferably 50 μm, more preferably 20 μm. By making the average thickness of the solid electrolyte layer equal to or greater than the lower limit, it is possible to reliably insulate the positive electrode and the negative electrode. By making the average thickness of the solid electrolyte layer equal to or less than the upper limit, it is possible to increase the energy density of the all-solid-state battery.

[0089] <Negative Electrode> The negative electrode may be configured by forming a negative electrode active material layer containing a negative electrode active material on a negative electrode current collector. The negative electrode active material layer preferably contains a binder in addition to the negative electrode active material, and further preferably contains a solid electrolyte, a conductive additive, a thickener, etc., as necessary. The binder may be the same as the binder in the positive electrode active material layer described above. The solid electrolyte may be the same as the solid electrolyte in the positive electrode active material layer described above. The conductive additive may be the same as the conductive additive in the positive electrode active material layer described above. The thickener may be the same as the thickener in the positive electrode active material layer described above.

[0090] The negative electrode active material used in the negative electrode of the present invention can be, for example, at least one selected from the group consisting of metallic lithium, lithium-containing alloys, metals or alloys capable of alloying with lithium, oxides capable of doping / dedoping with lithium ions, transition metal nitrides capable of doping / dedoping with lithium ions, and carbon materials capable of doping / dedoping with lithium ions (these may be used alone or as a mixture of two or more of these). Examples of oxides capable of doping / dedoping with lithium ions include silicon oxide, lithium titanate, and the lithium-containing composite oxides listed above for the positive electrode. Examples of metals or alloys capable of alloying with lithium (or lithium ions) include silicon, silicon alloys, tin, and tin alloys. Among these, carbon materials capable of doping / dedoping with lithium ions are preferred. Examples of such carbon materials include carbon black, activated carbon, graphite materials (artificial graphite, natural graphite), amorphous carbon materials, and the like. The carbon materials may be in the form of fibers, spheres, potatoes, or flakes.

[0091] Specific examples of the amorphous carbon material include hard carbon, coke, mesocarbon microbeads (MCMB) fired at 1500°C or less, and mesope pitch carbon fiber (MCF). Examples of the graphite material include natural graphite and artificial graphite. Examples of the artificial graphite include graphitized MCMB and graphitized MCF. Examples of the graphite material that can be used include those containing boron. In addition, graphite materials that can be used include those coated with metals such as gold, platinum, silver, copper, and tin, those coated with amorphous carbon, and those that are a mixture of amorphous carbon and graphite.

[0092] These carbon materials may be used alone or in combination of two or more. As the carbon material, a carbon material having a (002) plane interplanar spacing d(002) of 0.340 nm or less as measured by X-ray analysis is particularly preferred. As the carbon material, graphite having a true density of 1.70 g / cm or more or a highly crystalline carbon material having properties similar to that of graphite is also preferred. The use of such carbon materials can further increase the energy density of the battery.

[0093] The negative electrode active material layer can be formed using a slurry containing a negative electrode active material (and preferably a binder, and further, if necessary, a solid electrolyte, a conductive additive, and a thickener), similar to the above-described positive electrode active material layer. The solvent in the slurry for forming the negative electrode active material layer can be the same as the solvent in the slurry for producing the positive electrode active material layer. The slurry for forming the negative electrode active material layer can also contain a thickener.

[0094] When the above metal or alloy is used as the negative electrode active material, the negative electrode may be configured by forming a negative electrode active material layer made of the negative electrode active material on a current collector by a method such as vapor deposition, sputtering, plating, etc. In this case, the negative electrode active material layer may not contain a binder.

[0095] Examples of materials for the negative electrode current collector include metal materials such as copper, nickel, stainless steel, and nickel-plated steel, with copper being particularly preferred from the standpoints of ease of processing and cost. When the current collector is made of a metal material, the shape of the current collector may be, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punched metal, or a foamed metal. Among these, a metal thin film is preferred, and a copper foil is more preferred. Even more preferred are rolled copper foils produced by a rolling method and electrolytic copper foils produced by an electrolytic method. When the thickness of the copper foil is thinner than 25 μm, a copper alloy (such as phosphor bronze, titanium copper, a Corson alloy, or a Cu—Cr—Zr alloy) that has a higher strength than pure copper can be used as the copper foil material.

[0096] The thickness of the negative electrode active material layer is usually about 10 μm to 300 μm. The positive and negative electrode active material layers obtained by coating and drying are preferably compacted by a roller press or the like to increase the packing density of the negative electrode active material.

[0097] <Battery Configuration> The all-solid-state battery according to the present invention can have various known shapes, such as a cylindrical shape, a coin shape, a square shape, a film shape, or any other shape. However, the basic structure of the battery is the same regardless of the shape, and the design can be modified depending on the purpose.

[0098] The all-solid-state battery according to the present invention may be an all-solid-state battery obtained by charging and discharging an all-solid-state battery (an all-solid-state battery before charging and discharging) including a negative electrode, a positive electrode, and a solid electrolyte layer. That is, the all-solid-state battery according to the present invention may be an all-solid-state battery (a charged and discharged all-solid-state battery) produced by first producing an all-solid-state battery before charging and discharging including a negative electrode, a positive electrode, and a solid electrolyte layer, and then charging and discharging this all-solid-state battery before charging and discharging one or more times.

[0099] The use of the all-solid-state battery according to the present invention is not particularly limited, and it can be used in a wide variety of known applications, including notebook computers, mobile computers, mobile phones, headphone stereos, video camcorders, liquid crystal televisions, handheld vacuum cleaners, electronic organizers, calculators, radios, backup power supplies, motors, automobiles, electric vehicles, motorcycles, electric motorcycles, bicycles, electric bicycles, lighting equipment, game consoles, clocks, power tools, cameras, and the like, regardless of whether they are small portable devices or large devices.

[0100] The present invention will now be described in more detail with reference to examples and reference examples, but the present invention is not limited to the following examples, etc., as long as it does not depart from the gist of the invention.

[0101] Example 1 A positive electrode active material was prepared using 1,3,2-dioxathiolane-2,2-dioxide (DTD) as additive A, and an all-solid-state battery was prepared using the positive electrode active material. ３ LiNCM523 (LiN ０．５ C ０．２ M ０．３ O ２ , nickel / cobalt / lithium manganese oxide = 5 / 2 / 3) was used.

[0102]

[0103] (Production of Positive Electrode Active Material) A mixture of DTD (0.1 g) and dimethyl carbonate (25 g) was added to LiNbO ３ LiNCM523 (LiN ０．５ C ０．２ M ０．３ O ２ , nickel / cobalt / lithium manganate=5 / 2 / 3) (20 g) was added and heated and stored at 60° C. for 6 hours. The resulting mixed slurry was centrifuged, the supernatant was removed, and then the mixture was dried under reduced pressure at 60° C. to prepare a positive electrode active material treated with DTD.

[0104] (Production of Positive Electrode Sheet) The positive electrode active material (82.7 parts by mass), an argyrodite-type sulfide solid electrolyte (average particle size 0.6 μm) (15.4 parts by mass), vapor-grown carbon fiber (VGCF) (1.1 parts by mass), a rubber-based binder (0.8 parts by mass), and a tetralin / anisole mixed solution as a dispersion medium were added and kneaded to obtain a positive electrode composite slurry. The obtained positive electrode composite slurry was applied to an aluminum foil as a positive electrode current collector, and the dispersion medium was removed by vacuum heating and drying to obtain a positive electrode sheet comprising a positive electrode composite layer and a current collector.

[0105] (Production of Negative Electrode Sheet) Graphite (67.5 parts by mass), an argyrodite-type sulfide solid electrolyte (average particle size 0.6 μm) (30.5 parts by mass), a rubber binder (2.0 parts by mass), and a tetralin / anisole mixed solution as a dispersion medium were added and kneaded to obtain a negative electrode composite slurry. The obtained negative electrode composite slurry was applied to a carbon-coated SUS foil as a negative electrode current collector, and the dispersion medium was removed by vacuum heating and drying to obtain a negative electrode sheet comprising a negative electrode composite layer and a current collector.

[0106] (Production of Solid Electrolyte Sheet) An argyrodite-type sulfide solid electrolyte (average particle size 3.7 μm) (97.8 parts by mass), a rubber-based binder (2.2 parts by mass), and a tetralin / anisole mixed solution as a dispersion medium were mixed and kneaded to obtain a solid electrolyte composite slurry. The obtained solid electrolyte composite slurry was applied to a SUS foil as a substrate layer, and the dispersion medium was removed by vacuum heating and drying to obtain a solid electrolyte sheet comprising a solid electrolyte layer and a substrate layer.

[0107] (Production of Solid Electrolyte Layer-Transferred Negative Electrode Sheet) The mixture layer surface of the negative electrode sheet and the mixture layer surface of the solid electrolyte sheet were placed opposite each other, and pressure was applied using a press. Thereafter, the SUS foil serving as the base material of the solid electrolyte sheet was removed, thereby obtaining a solid electrolyte layer-transferred negative electrode sheet including a solid electrolyte layer and a negative electrode sheet.

[0108] (Manufacturing of all-solid-state battery) The composite layer surface of the positive electrode sheet and the composite layer surface of the solid electrolyte layer-transferred negative electrode sheet were placed opposite each other, and the electrode sheets were bonded by isostatic pressing. Leads were connected to the bonded positive and negative electrodes, and the resulting battery cell was then vacuum-sealed in an Al laminate. Both sides of the resulting battery cell were sandwiched between SUS steel plates and screwed (restrained) so that a pressure of 19.6 MPa was applied.

[0109] (Measurement of Initial Resistance of Battery Cell) The initial resistance of the battery cell in the all-solid-state battery obtained above was measured using a constant current / constant voltage charge / discharge (CCCV) method as follows. The battery cell was charged / discharged for three cycles at 25°C with a charge voltage of 4.35 V and a discharge voltage of 3 V at 0.1 C CCCV with a 0.01 C termination, and then charged to 3.685 V at 0.1 C CCCV with a 0.01 C termination. The DC resistance of the charged battery cell was measured for 10 seconds of discharge to determine the initial resistance.

[0110] (Float Test of Battery Cell (High-Temperature Storage)) The high-temperature storage stability of the battery cell was measured by a float test (60°C, charging voltage 4.35V, 0.1C CCCV charging, 168 hours) using the battery cell after initial resistance measurement. The float test is an accelerated test that is widely used to investigate the long-term storage stability of a battery.

[0111] (Measurement of Resistance of Battery Cell After Float Test) The resistance of the battery cell after the float test was measured using the CCCV method as follows. After the float test, the battery cell was discharged to 3 V at 0.1 C CCCV with a 0.01 C termination. After the discharge, the battery cell was charged and discharged for two cycles at 25°C with a charge voltage of 4.35 V and a discharge voltage of 3 V at 0.1 C CCCV with a 0.01 C termination, and then charged to 3.685 V at 0.1 C CCCV with a 0.01 C termination. After the charge, the DC resistance of the battery cell was measured for 10 seconds of discharge to determine the resistance after the float test.

[0112] Example 2 A positive electrode active material was prepared in the same manner as in Example 1, except that dimethyl sulfate (DMS) was used instead of DTD as additive A. An all-solid-state battery was manufactured using the positive electrode active material, and the initial resistance and the resistance after a float test of the obtained all-solid-state battery were measured.

[0113]

[0114] Comparative Example 1 A positive electrode active material was prepared in the same manner as in Example 1, except that Additive A was not contained, and an all-solid-state battery was manufactured using the positive electrode active material. The initial resistance and the resistance after a float test of the obtained all-solid-state battery were measured.

[0115] Comparative Example 2 A positive electrode active material was prepared in the same manner as in Example 1, except that lithium bis(oxalato)borate (BOB) was used instead of DTD as additive A. An all-solid-state battery was manufactured using the positive electrode active material, and the initial resistance and the resistance after a float test of the obtained all-solid-state battery were measured.

[0116] The relative values ​​(%) of the measured values ​​of the battery cell resistance of the all-solid-state battery of Comparative Example 1 were calculated based on the measured value of the all-solid-state batteries of Example 1, Example 2, and Comparative Example 2. The results are shown in Table 1.

[0117]

[0118] Comparative Example 3 A lithium secondary battery was prepared using a non-aqueous electrolyte solution containing no additive A.

[0119] (Preparation of non-aqueous electrolyte solution) Ethylene carbonate (hereinafter "EC"), dimethyl carbonate (hereinafter "DMC"), and ethyl methyl carbonate (hereinafter "EMC") were mixed in a volume ratio of EC:DMC:EMC = 30:35:35. This resulted in a mixed solvent as a non-aqueous solvent. LiPF6 as an electrolyte was dissolved in the resulting mixed solvent so that the concentration in the final non-aqueous electrolyte solution was 1 mol / L, thereby obtaining an electrolyte solution (hereinafter sometimes referred to as a "basic electrolyte solution").

[0120] (Preparation of Positive Electrode) LiNi as Positive Electrode Active Material ０．５ Co ０．２ Mn ０．３ O ２A mixture was obtained by mixing 94% by mass of cellulose acetate, 3% by mass of carbon black as a conductive additive, and 3% by mass of polyvinylidene fluoride (PVdF) as a binder. The resulting mixture was dispersed in an N-methylpyrrolidone solvent to obtain a positive electrode composite slurry. A 20 μm thick aluminum foil was prepared as a positive electrode current collector. The resulting positive electrode composite slurry was applied to aluminum foil, dried, and then rolled using a press to obtain a sheet-shaped positive electrode. The positive electrode consisted of a positive electrode current collector and a positive electrode active material layer.

[0121] (Preparation of Negative Electrode) Graphite (96% by mass) was used as the negative electrode active material, carbon black (1% by mass) was used as a conductive additive, 1% by mass of sodium carboxymethyl cellulose dispersed in pure water as a thickener (solid content), and 2% by mass of styrene-butadiene rubber (SBR) dispersed in pure water as a binder (solid content). A 10 μm thick copper foil was prepared as the negative electrode current collector. The obtained negative electrode mixture slurry was applied to copper foil, dried, and then rolled in a press to obtain a sheet-shaped negative electrode. The negative electrode consisted of a negative electrode current collector and a negative electrode active material layer.

[0122] (Preparation of Separator) A porous polyethylene film was prepared as a separator.

[0123] (Preparation of Lithium Secondary Battery Precursor) The negative electrode, positive electrode, and separator were punched into disc shapes with a diameter of 14 mm, 13 mm, and 17 mm, respectively. This resulted in coin-shaped negative electrodes, coin-shaped positive electrodes, and coin-shaped separators. The resulting coin-shaped negative electrodes, coin-shaped separators, and coin-shaped positive electrodes were stacked in this order in a stainless steel battery can (size: 2032). Next, 28 μL of nonaqueous electrolyte was poured into the battery can, immersing the separator, positive electrode, and negative electrode in the nonaqueous electrolyte. Next, an aluminum plate (thickness 1.2 mm, diameter 16 mm) and a spring were placed on the positive electrode, and the battery can lid was crimped via a polypropylene gasket to seal the battery. This resulted in a coin-shaped lithium secondary battery precursor (i.e., a lithium secondary battery before charging and discharging). The lithium secondary battery precursor had a diameter of 20 mm and a height of 3.2 mm.

[0124] (Fabrication of Lithium Secondary Battery) The lithium secondary battery precursor was charged to 1.5 V to 4.2 V, held for 5 to 50 hours, charged to 4.2 V, and discharged to 2.5 V in this order at a temperature range of 25° C. to 70° C. to obtain a lithium secondary battery.

[0125] (Measurement of Initial Room-Temperature Resistance) The lithium secondary battery was charged at 3.7 V, and then measured in a thermostatic chamber at a temperature of 25°C for each voltage drop (= voltage before discharge start - voltage 10 seconds after discharge start) due to CC10s discharge at discharge rates of 0.1 C to 0.6 C. Here, CC10s discharge refers to discharge performed at a constant current for 10 seconds. Based on the obtained voltage drop and each current value (i.e., each current value corresponding to a discharge rate of 0.1 C to 0.6 C), the DC resistance [Ω] as the initial room-temperature resistance was calculated. The DC resistance [Ω] as the initial room-temperature resistance was also calculated in the same manner for Comparative Example 1 described below.

[0126] (High-Temperature Storage) Next, the lithium secondary battery after measuring the initial room temperature resistance was charged to 4.2 V, and the charged lithium secondary battery was stored in a thermostatic chamber at 60° C. for 14 days (hereinafter referred to as “high-temperature storage”).

[0127] (Measurement of Room Temperature Resistance After High Temperature Storage) The lithium secondary battery after high temperature storage was discharged to 2.5 V, and then the room temperature resistance after high temperature storage was measured in the same manner as in the measurement of the initial room temperature resistance. The DC resistance [Ω] was also determined as the room temperature resistance after high temperature storage for Comparative Example 1 described below.

[0128] (Measurement of Room Temperature Resistance Increase Rate (%) During High Temperature Storage) The room temperature resistance increase rate (%) during high temperature storage was calculated using the following formula: [Room temperature resistance increase rate (%) during high temperature storage] = [Room temperature resistance (Ω) after high temperature storage] / [Initial room temperature resistance (Ω)] × 100 (%)

[0129] Comparative Example 4 A lithium secondary battery was produced in the same manner as in Comparative Example 3, except that a solution obtained by adding DTD as an additive to the base electrolyte solution used in Comparative Example 3 so that the content of DTD relative to the total amount of the finally obtained non-aqueous electrolyte solution was 1.0 mass %, and the room-temperature resistance increase rate of the obtained lithium secondary battery during high-temperature storage was measured.

[0130] Comparative Example 5 A lithium secondary battery was produced in the same manner as in Comparative Example 3, except that a solution obtained by adding BOB as an additive to the base electrolyte solution used in Comparative Example 3 so that the content of BOB relative to the total amount of the finally obtained non-aqueous electrolyte solution was 1.0 mass %, and the room temperature resistance of the obtained lithium secondary battery was measured in the initial state and after high-temperature storage.

[0131] The room temperature resistance increase rate (relative value) of the lithium secondary batteries of Comparative Examples 4 and 5 during high temperature storage was determined, assuming that the room temperature resistance increase rate of the lithium secondary battery of Comparative Example 3 during high temperature storage was 100. The results are shown in Table 2.

[0132]

[0133] As a result, in the all-solid-state batteries of Examples 1 and 2 in which additive A was contained in the positive electrode active material, the relative value of the resistance after the float test was 80% or less compared to the all-solid-state battery of Comparative Example 1 without additive A and Comparative Example 2 in which BOB was contained as an additive, and the increase in internal resistance after high-temperature storage was suppressed.

[0134] The lithium secondary battery of Comparative Example 4, which contained DTD as additive A and used a solution electrolyte rather than a solid electrolyte as the electrolyte, had a relative resistance value after high-temperature storage of 93% compared to the lithium secondary battery of Comparative Example 3 without any additive. The results of Example 1 and Comparative Example 4 demonstrate that the effect of suppressing a rise in battery resistance after long-term storage obtained when DTD is used as additive A is superior in all-solid-state batteries using a solid electrolyte to that obtained when a solution electrolyte is used. Furthermore, the lithium secondary battery of Comparative Example 5, which contained BOB as additive A and used a solution electrolyte rather than a solid electrolyte as the electrolyte, had a relative resistance value after high-temperature storage of 85% compared to the lithium secondary battery of Comparative Example 3 without any additive. The results of Comparative Examples 2 and 5 demonstrate that there is no difference in the effect of suppressing a rise in battery resistance after long-term storage obtained when BOB is used as additive A between a lithium secondary battery using a solution electrolyte and an all-solid-state battery using a solid electrolyte.

[0135] From these results, it is clear that in an all-solid-state battery, by including Additive A in the positive electrode active material, the increase in internal resistance over time can be suppressed, and the battery resistance after long-term storage can be reduced.

Claims

1. Lithium-containing composite oxide and Additive A is a compound having a sulfur-oxygen bond, A positive electrode active material for solid-state batteries that contains the following:

2. The positive electrode active material according to claim 1, wherein the additive A is one or more compounds selected from the group consisting of cyclic sulfate esters, linear sulfate esters, cyclic sulfonic acid esters, and linear sulfonic acid esters.

3. The additive A is the following general formula (A1) to (A4) 【Chemistry 1】 [In formula (A1), R １１ and R １２ Each of these independently represents a hydrocarbon group having 1 to 6 carbon atoms. 【Chemistry 2】 [In formula (A2), R ２１ R represents an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, a group represented by general formula (A2-1), or a group represented by general formula (A2-2); in formula (A2-1), R ２２ R represents an oxygen atom, an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, or an oxymethylene group; in formula (A2-2), R ２３ * represents an alkyl group having 1 to 6 carbon atoms, or an alkenyl group having 2 to 6 carbon atoms; in formulas (A2-1) and (A2-2), * represents a bond position. 【Transformation 3】 [In formula (A3), R ３１ ~R ３４ Each of these independently represents a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorinated hydrocarbon group having 1 to 3 carbon atoms. 【Chemistry 4】 [In formula (A4), R ４１ to R ４４ each independently represents a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorinated hydrocarbon group having 1 to 3 carbon atoms] The positive electrode active material according to claim 1, which is a compound represented by any one of the following.

4. The positive electrode active material according to claim 1, wherein the additive A is one or more selected from the group consisting of 1,3,2-dioxathiolan-2,2-dioxide and dimethyl sulfate.

5. The lithium-containing composite oxide is given by the following general formula (P1) 【Transformation 5】 [In equation (P1), A is an element other than Li, Ni, Mn, and Co; a to f are real numbers satisfying 0.8 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.95, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 1.0, 0.7 ≤ b + c + d ≤ 1.1, 0 ≤ e ≤ 0.1, and 1.8 ≤ f ≤ 2.2.] The positive electrode active material according to claim 1, having a composition represented by the following:

6. The positive electrode active material according to claim 1, wherein at least a portion of the surface of the lithium-containing composite oxide is coated with the additive A.

7. A positive electrode for a solid battery, comprising the positive electrode active material described in any one of claims 1 to 6.

8. Lithium-containing composite oxide and Additive A is a compound having a sulfur-oxygen bond, A positive electrode for solid-state batteries containing [specific ingredient / component].

9. The positive electrode according to claim 8, wherein the additive A is one or more compounds selected from the group consisting of cyclic sulfate esters, linear sulfate esters, cyclic sulfonic acid esters, and linear sulfonic acid esters.

10. The additive A is the following general formula (A1) to (A4) 【Transformation 6】 [In formula (A1), R １１ and R １２ Each of these independently represents a hydrocarbon group having 1 to 6 carbon atoms. 【Transformation 7】 [In formula (A2), R ２１ R represents an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, a group represented by general formula (A2-1), or a group represented by general formula (A2-2); in formula (A2-1), R ２２ R represents an oxygen atom, an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, or an oxymethylene group; in formula (A2-2), R ２３ * represents an alkyl group having 1 to 6 carbon atoms, or an alkenyl group having 2 to 6 carbon atoms; in formulas (A2-1) and (A2-2), * represents a bond position. 【Transformation 8】 [In formula (A3), R ３１ ~R ３４ Each of these independently represents a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorinated hydrocarbon group having 1 to 3 carbon atoms. 【Chemistry 9】 [In formula (A4), R ４１ ~R ４４ Each of these independently represents a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorinated hydrocarbon group having 1 to 3 carbon atoms. The positive electrode according to claim 8, which is a compound represented by any of the following.

11. The positive electrode according to claim 8, wherein the additive A is one or more selected from the group consisting of 1,3,2-dioxathiolan-2,2-dioxide and dimethyl sulfate.

12. The lithium-containing composite oxide is given by the following general formula (P1) 【Chemistry 10】 [In equation (P1), A is an element other than Li, Ni, Mn, and Co; a to f are real numbers satisfying 0.8 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.95, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 1.0, 0.7 ≤ b + c + d ≤ 1.1, 0 ≤ e ≤ 0.1, and 1.8 ≤ f ≤ 2.2.] The positive electrode according to claim 8, having a composition represented by the above.

13. A solid-state battery comprising the positive electrode described in claim 7 and a solid electrolyte.

14. The all-solid-state battery according to claim 13, wherein at least a portion of the solid electrolyte is a sulfide-based solid electrolyte.

15. The all-solid-state battery according to claim 13, wherein the solid electrolyte is present between the positive electrode and the negative electrode.

16. A solid-state battery comprising a positive electrode according to any one of claims 8 to 12 and a solid electrolyte.

17. The all-solid-state battery according to claim 16, wherein at least a portion of the solid electrolyte is a sulfide-based solid electrolyte.

18. The all-solid-state battery according to claim 16, wherein the solid electrolyte is present between the positive electrode and the negative electrode.

19. A step of obtaining a positive electrode active material for a solid-state battery by mixing a lithium-containing composite oxide with additive A, which is a compound having a sulfur-oxygen bond. A step of preparing a positive electrode containing the positive electrode active material for a solid-state battery, A step of joining the positive electrode, the negative electrode, and the solid electrolyte such that the solid electrolyte is present between the positive electrode and the negative electrode, A method for manufacturing an all-solid-state battery.

20. A step of preparing a positive electrode containing a positive electrode active material containing a lithium-containing composite oxide and an additive A which is a compound having a sulfur-oxygen bond, A step of joining the positive electrode, the negative electrode, and the solid electrolyte such that the solid electrolyte is present between the positive electrode and the negative electrode, A method for manufacturing an all-solid-state battery.

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