Negative electrode protective film for solid-state battery, negative electrode layer for solid-state battery, and solid-state battery

Abstract

The objective of the present invention is to provide a protective layer that separates a solid electrolyte layer from an active material layer to prevent corrosion and deterioration of an inorganic solid electrolyte caused by contact between the inorganic solid electrolyte and a negative electrode active material such as metallic lithium. It was found that a negative electrode protective film containing at least a polyether copolymer and a lithium salt compound according to the present invention does not reduce ion conductivity, prevents contact between an inorganic solid electrolyte and a negative electrode active material, and does not deteriorate the inorganic solid electrolyte even when the negative electrode protective film is in contact with the inorganic solid electrolyte.

Description

Negative electrode protective film for solid-state batteries, negative electrode layer for solid-state batteries, solid-state batteries

[0001] The present invention relates to an anode protective film for a solid state battery, an anode layer for a solid state battery, and a solid state battery.

[0002] Lithium-ion secondary batteries are used in a wide variety of applications, large and small, across a wide range of industries. Liquid-type lithium-ion secondary batteries, the most common type today, are becoming increasingly compact and lightweight, resulting in improved performance for devices like mobile phones. However, they face challenges such as declining energy density and capacity loss due to repeated charging and discharging. Furthermore, large lithium-ion batteries used in hybrid vehicles and other vehicles pose a risk of fire due to electrolyte leakage. To address these challenges, active research has been conducted in recent years on the development of materials for all-solid-state lithium-ion batteries.

[0003] Therefore, while all-solid-state lithium-ion batteries do not use electrolyte solutions and therefore do not have to worry about leakage, there is a problem in that contact between inorganic solid electrolytes such as sulfide solid electrolytes and oxide solid electrolytes and negative electrode active materials such as metallic lithium causes a reaction and degradation of the electrolyte. Patent Document 1 discloses an all-solid-state lithium-ion battery in which 0.1 to 25 volume % of a halide-based solid electrolyte is added to a sulfide solid electrolyte, and the halide-based solid electrolyte reacts with the negative electrode active material to produce a halogen compound such as lithium chloride, which forms a film on the surface of the negative electrode active material, thereby reducing side reactions between the sulfide solid electrolyte and the negative electrode active material and suppressing capacity loss.

[0004] Japanese Patent Application Laid-Open No. 2023-112694

[0005] The halide-based solid electrolyte having a coating formed thereon as disclosed in Patent Document 1 does not reliably prevent contact between the sulfide solid electrolyte and the negative electrode active material, and there remains a problem in that there is a concern about short circuits and deterioration.

[0006] As a result of extensive investigations aimed at solving the above problems, the present inventors have found that an anode protective film containing at least a polyether copolymer and a lithium salt compound prevents contact between an inorganic solid electrolyte and an anode active material, and further, that the anode protective film of the present invention does not deteriorate the inorganic solid electrolyte even when it comes into contact with the inorganic solid electrolyte. The present invention was completed based on this finding and through further investigations.

[0007] That is, the present invention provides the following configuration: Item 1. An anode protective film for a solid battery, comprising at least a polyether copolymer containing at least a structural unit (A) derived from an epoxy compound represented by the following formula (1) and a structural unit (B) derived from ethylene oxide represented by the following formula (2), and a lithium salt compound, wherein the composition ratio of the polyether copolymer is 30 to 99 mol % for (A) and 1 to 70 mol % for (B). [In the formula, R １ is an alkyl group, a cycloalkyl group, or an aryl group having 1 to 12 carbon atoms. Item 2. The solid state battery anode protective film according to Item 1, wherein the polyether contains 0.1 to 20 mol % of a structural unit derived from a compound having an ethylenically unsaturated bond represented by the following formula (3): [In the formula, R ２ is a group having an ethylenically unsaturated bond.] Item 3. An anode layer for a solid battery comprising at least the anode protective film for a solid battery and a current collector foil according to Item 1 or 2. Item 4. A solid battery comprising at least the anode layer for a solid battery according to Item 3, a solid electrolyte layer, and a cathode layer.

[0008] According to the present invention, contact between the inorganic solid electrolyte and the negative electrode active material is prevented, and furthermore, even if the negative electrode protective film of the present invention comes into contact with the inorganic solid electrolyte, the inorganic solid electrolyte is not deteriorated.

[0009] <Anode Protective Film for Solid Battery> The anode protective film for a solid battery of the present invention (also simply referred to as anode protective film) has a configuration including at least a polyether copolymer (also referred to as the polyether copolymer of the present invention) containing at least a structural unit derived from an epoxy compound represented by the following formula (1) and a structural unit derived from ethylene oxide represented by the following formula (2), and a lithium salt compound. This prevents contact between the inorganic solid electrolyte and the anode active material, and further prevents deterioration of the inorganic solid electrolyte even when the anode protective film of the present invention comes into contact with the inorganic solid electrolyte. [In the formula, R １ is an alkyl group, a cycloalkyl group, or an aryl group having 1 to 12 carbon atoms.

[0010] The reason why the above-mentioned effect is obtained in the present invention is not clear, but is presumed as follows. The anode protective film for a solid battery of the present invention, like other protective films, can be provided between an inorganic solid electrolyte and an anode active material, thereby physically preventing contact between the inorganic solid electrolyte and the anode active material. On the other hand, with the polymer used in the conventional anode protective film for a solid battery, there is a risk that contact between the polymer and the inorganic solid electrolyte will cause a reaction and deterioration of the inorganic solid electrolyte. On the other hand, the anode protective film for a solid battery of the present invention is a polymer containing R, a structural unit derived from an epoxy compound represented by the above formula (1), １ The presence of the polymer main chain can prevent contact between the polymer main chain and the inorganic solid electrolyte, thereby reducing or suppressing deterioration of the inorganic solid electrolyte.

[0011] Polyether copolymer As a structural unit derived from an epoxy compound represented by formula (1), a side chain (R １ ) is, for example, preferably an alkyl group, a cycloalkyl group, or an aryl group having 1 to 12 carbon atoms, and more preferably an alkyl group having 1 to 12 carbon atoms. The structural unit derived from the epoxy compound represented by the above formula (1) may be used alone or in combination of two or more types.

[0012] The alkyl group having 1 to 12 carbon atoms preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, even more preferably 1 to 6 carbon atoms, particularly preferably 1 to 4 carbon atoms, and most preferably 1 or 2 carbon atoms.

[0013] The alkyl group may be branched or linear, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, etc. Among these, a methyl group, an ethyl group, an n-propyl group, and an n-butyl group are preferred, a methyl group and an ethyl group are more preferred, and a methyl group is even more preferred.

[0014] The cycloalkyl group preferably has 3 to 12 carbon atoms, more preferably 3 to 8 carbon atoms, and even more preferably 4 to 8 carbon atoms.

[0015] Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a norbornyl group, an isobornyl group, etc. Of these, a cyclohexyl group is preferred.

[0016] The aryl group preferably has 6 to 14 carbon atoms, more preferably 6 to 12 carbon atoms, and even more preferably 6 to 10 carbon atoms.

[0017] Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, an anthracenyl group, etc. Among these, a phenyl group and a naphthyl group are preferred.

[0018] Examples of the epoxy resin having an alkyl group having 1 to 12 carbon atoms in the side chain include propylene oxide, butylene oxide, 1,2-epoxypentane, 1,2-epoxyhexane, 1,2-epoxyheptane, 1,2-epoxyoctane, 1,2-epoxydecane, 1,2-epoxydodecane, etc. Among these, propylene oxide, butylene oxide, 1,2-epoxypentane, and 1,2-epoxyhexane are preferred, and propylene oxide and butylene oxide are more preferred. These may be used alone or in combination of two or more.

[0019] In 100 mol% of the polyether copolymer of the present invention, the content of the structural unit derived from the epoxy compound represented by formula (1) is preferably 30 mol% or more as a lower limit, more preferably 32 mol% or more, even more preferably 35 mol% or more, and particularly preferably 40 mol% or more. The upper limit is preferably 99 mol% or less, more preferably 90 mol% or less, even more preferably 80 mol% or less, particularly preferably 70 mol% or less, and most preferably 60 mol% or less. By being within these ranges, the inorganic solid electrolyte is stable and does not undergo a deterioration reaction even when it comes into contact with the anode protective film.

[0020] The compound of formula (2) is ethylene oxide. The compound of formula (2) is a basic chemical product and is readily available commercially.

[0021] In 100 mol% of the polyether copolymer of the present invention, the content of the ethylene oxide-derived structural unit represented by formula (2) is preferably 1 mol% or more as a lower limit, more preferably 10 mol% or more, even more preferably 20 mol% or more, particularly preferably 30 mol% or more, and most preferably 40 mol% or more. The upper limit is preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 60 mol% or less. By being within these ranges, the ionic conductivity required for the anode protective film can be ensured.

[0022] In 100 mol % of the polyether copolymer of the present invention, the total content of the structural units derived from the epoxy compound represented by formula (1) and the structural units derived from ethylene oxide represented by formula (2) is preferably 31 mol % or more, more preferably 70 mol % or more, even more preferably 80 mol % or more, particularly preferably 90 mol % or more, most preferably 99 mol % or more, and may be 100 mol %.

[0023] The polyether copolymer used in the negative electrode protective film of the present invention is produced by a polymerization reaction from a repeating unit derived from a monomer of formula (1): (A): [In the formula, R １ is an alkyl group, a cycloalkyl group, or an aryl group having 1 to 12 carbon atoms, and R １ and (B): a repeating unit derived from a monomer of formula (2). Includes:

[0024] Furthermore, as other structural units, a structural unit derived from a compound having an ethylenically unsaturated bond represented by the following formula (3) can be included. The structural unit derived from a compound having an ethylenically unsaturated bond represented by the following formula (3) has an ethylenically unsaturated bond, and therefore can be crosslinked. Therefore, R in formula (3) ２ is not particularly limited as long as it has an ethylenically unsaturated bond. The structural unit derived from a compound having an ethylenically unsaturated bond represented by the following formula (3) may be used alone or in combination of two or more types. [In the formula, R ２ is a group having an ethylenically unsaturated bond.

[0025] In the structural unit derived from a compound having an ethylenically unsaturated bond represented by formula (3), R ２ Examples of the alkyl group are not particularly limited as long as they have an ethylenically unsaturated bond, but may be hydrocarbon groups having a double bond, particularly cyclic hydrocarbon groups having a double bond, or CH ２ = CH-A １ - (A １ may be a direct bond or a hydrocarbon group having 1 to 30 carbon atoms which may have a heteroatom, such as an alkylene group.

[0026] When the polyether copolymer of the present invention contains a structural unit derived from a compound having an ethylenically unsaturated bond represented by formula (3), in addition to the above (A) and (B), (C): a repeating unit derived from a monomer of formula (3) [In the formula, R ２ is a group having an ethylenically unsaturated bond, and R in formula (3) ２The same applies to the above.]

[0027] Examples of the structural unit derived from the compound having an ethylenically unsaturated bond represented by formula (3) include allyl glycidyl ether, 4-vinylcyclohexyl glycidyl ether, α-terpinyl glycidyl ether, cyclohexenylmethyl glycidyl ether, p-vinylbenzyl glycidyl ether, allylphenyl glycidyl ether, vinyl glycidyl ether, 3,4-epoxy-1-butene, 3,4-epoxy-1-pentene, 4,5-epoxy-2-pentene, 1,2-epoxy-5,9-cyclododecadiene, 3,4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5-cyclooctene, glycidyl acrylate, glycidyl methacrylate, glycidyl sorbate, glycidyl cinnamate, glycidyl crotonate, and glycidyl-4-hexenoate. Of these, allyl glycidyl ether, vinyl glycidyl ether, glycidyl acrylate, and glycidyl methacrylate are preferred.

[0028] In 100 mol% of the polyether copolymer of the present invention, the content of the structural unit derived from the compound having an ethylenically unsaturated bond represented by formula (3) is preferably 0.1 mol% or more as a lower limit, more preferably 0.5 mol% or more, and even more preferably 1 mol% or more. The upper limit is preferably 20 mol% or less, more preferably 15 mol% or less, even more preferably 10 mol% or less, and particularly preferably 5 mol% or less. Within these ranges, the strength of the polyether copolymer after crosslinking is increased, and it becomes easier to maintain the shape as a negative electrode protective film.

[0029] In 100 mol % of the polyether copolymer of the present invention, the total content of the structural units derived from the epoxy compound represented by formula (1), the structural units derived from ethylene oxide represented by formula (2), and the structural units derived from the compound having an ethylenically unsaturated bond represented by formula (3) is preferably 31.1 mol % or more, more preferably 75 mol % or more, even more preferably 85 mol % or more, particularly preferably 95 mol % or more, most preferably 99 mol % or more, and may be 100 mol %.

[0030] The molar ratio of the polymerization composition of the polyether copolymer is １ The integral value of each unit is determined by H-NMR, and the composition can be determined from the calculation results.

[0031] The polyether copolymer may be either a block copolymer or a random copolymer, with the random copolymer being preferred since it has a greater effect of reducing the crystallinity of polyethylene oxide.

[0032] Regarding the weight-average molecular weight of the polyether copolymer, the lower limit of the weight-average molecular weight is preferably 100,000 or more, more preferably 150,000 or more, and even more preferably 300,000 or more, and the upper limit of the weight-average molecular weight is preferably 3,000,000 or less, more preferably 2,700,000 or less, and even more preferably 2,500,000 or less. The molecular weight of the polyether copolymer was measured by gel permeation chromatography (GPC), and the weight-average molecular weight was calculated in terms of standard polystyrene. DMF (N,N-dimethylformamide) was used as the solvent.

[0033] The polyether copolymer of the present invention can be synthesized as follows: As a ring-opening polymerization catalyst, a coordinated anion initiator such as an organoaluminum-based catalyst system, an organozinc-based catalyst system, or an organotin-phosphate ester condensate catalyst system, or a catalyst containing K as a counter ion, is used. ＋A polyether copolymer can be obtained by reacting the monomers with an anionic initiator such as potassium alkoxide containing the above-mentioned compound, diphenylmethyl potassium, or potassium hydroxide, in the presence or absence of a solvent, at a reaction temperature of 10 to 120°C, with stirring. From the viewpoints of the degree of polymerization and the properties of the resulting copolymer, a coordinated anionic initiator is preferred, and among these, an organotin-phosphate ester condensate catalyst system is particularly preferred because of its ease of handling.

[0034] The content of the polyether copolymer in 100 parts by mass of the anode protective film of the present invention is preferably 35 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 45 parts by mass or more, and particularly preferably 50 parts by mass or more, as a lower limit. The content is preferably 95 parts by mass or less, more preferably 90 parts by mass or less, even more preferably 85 parts by mass or less, and particularly preferably 80 parts by mass or less, as an upper limit. These ranges are preferred in that the strength of the anode protective film is sufficiently maintained and penetration due to dendrite precipitation can be suppressed.

[0035] The anode protective film of the present invention may contain a polyether copolymer other than the polyether copolymer of the present invention. However, the content of the polyether copolymer of the present invention in 100 parts by mass of the polyether copolymer contained in the anode protective film of the present invention is, as a lower limit, preferably 85 parts by mass or more, more preferably 90 parts by mass or more, even more preferably 95 parts by mass or more, particularly preferably 98 parts by mass or more, and may be 100 parts by mass.

[0036] The lithium salt compound contained in the anode protective film of the present invention is a lithium salt compound having a wide potential window, such as those commonly used in lithium ion batteries. For example, LiBF ４ , LiPF ６ , LiClO ４ , LiCF ３ SO ３ , LiN(FSO ２ ) ２ , LiN(CF ３ SO ２ ) ２, LiN(C ２ F ５ SO ２ ) ２ , LiN[CF ３ SC (C ２ F ５ SO ２ ) ３ ] ２ These may be used alone or in combination of two or more.

[0037] The content of the lithium salt compound in 100 parts by mass of the anode protective film of the present invention is preferably 5 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more, as a lower limit. The upper limit is preferably 50 parts by mass or less, preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less. If the content is too low, sufficient ionic conductivity cannot be ensured, adversely affecting the cycle characteristics of a solid-state battery. If the content is too high, the mechanical strength of the anode protective film decreases, which can lead to dendrite precipitation and cause short-circuiting.

[0038] The lower limit of the total content of the polyether copolymer and the lithium salt compound in 100 parts by mass of the anode protective film of the present invention is preferably 70 parts by mass or more, more preferably 80 parts by mass or more, even more preferably 90 parts by mass or more, and particularly preferably 98 parts by mass or more, and may be 100 parts by mass.

[0039] Method for Forming the Anode Protective Film The method for forming the anode protective layer is not particularly limited. Depending on the desired film thickness, any anode protective film can be formed from a composition containing a polyether copolymer and a lithium salt compound (anode protective film composition for solid batteries) by wet forming methods such as doctor blade, silk screen, or spray coating, or by dry forming methods such as compression pressing using a mold or roll pressing. Furthermore, if the anode protective film composition for solid batteries has a high viscosity, it can be dissolved in a solvent such as water or an organic solvent, and the solution can be applied by the above-mentioned method and then dried to form an anode protective film. Drying equipment such as heaters, hot air dryers, infrared radiation dryers, and vacuum dryers can be used to dry the solvent after application. Excess solvent can be removed by drying, for example, at 50 to 150°C (particularly at 80°C) under normal pressure or in a vacuum.

[0040] The solvent for dissolving the polyether copolymer and the lithium salt compound is not limited as long as it dissolves the polyether copolymer, and can be selected from, for example, water, alcohol, acetone, acetonitrile, methyl ethyl ketone, tetrahydrofuran, and N-methyl-2-pyrrolidone. These solvents may be used alone or in combination of two or more.

[0041] The concentration of the polyether copolymer in the solution is not particularly limited, but is preferably 0.05 to 30% by weight, and more preferably 0.1 to 20% by weight.

[0042] The thickness of the anode protective film for a solid battery of the present invention is preferably 0.5 μm or more as a lower limit, more preferably 0.75 μm or more, and even more preferably 1 μm or more. The upper limit is preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 60 μm or less. If the thickness is less than the lower limit, the protective film effect cannot be obtained, and if the thickness is more than the upper limit, there is a concern that the film will function as a resistor.

[0043] When the polyether copolymer of the present invention contains a structural unit derived from a compound having an ethylenically unsaturated bond represented by formula (3), the negative electrode protective film may be formed into a crosslinked product by applying heat or irradiating with active energy rays such as ultraviolet light, and a photoinitiator or a thermal polymerization initiator is preferably used. Furthermore, a crosslinking aid may also be added as needed.

[0044] Examples of photoinitiators that can be used in the present invention include alkylphenones, benzophenones, acylphosphine oxides, titanocenes, triazines, bisimidazoles, and oxime esters. Preferably, alkylphenones, benzophenones, and acylphosphine oxides are used. Two or more of the above-mentioned compounds can be used in combination as the photoinitiator.

[0045] Examples of thermal polymerization initiators that can be used in the present invention include radical initiators selected from organic peroxides, azo compounds, etc. Preferably, the organic peroxides include ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters, etc., and the azo compounds include azonitrile compounds, azoamide compounds, azoamidine compounds, etc. More preferably, organic peroxide initiators are used, and two or more of these compounds can be used in combination.

[0046] The amount of the photoreaction initiator or thermal polymerization initiator used in the present invention is preferably within a range of 0.1 to 10 parts by mass, more preferably 0.1 to 4.0 parts by mass, per 100 parts by mass of the polyether copolymer.

[0047] In the present invention, a crosslinking aid may be used in combination with a photoinitiator or a thermal polymerization initiator. The crosslinking aid is usually a polyfunctional compound (e.g., CH ２ =CH-, CH ２ =CH-CH ２ -, CF ２ ═CF—).

[0048] The amount of the crosslinking aid used in the present invention is preferably within a range of 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, per 100 parts by mass of the polyether copolymer.

[0049] The active energy rays used to crosslink the polyether copolymer used in the present invention may be ultraviolet light, visible light, electron beams, etc. Among these, ultraviolet light is particularly preferred in view of the cost of the equipment and ease of control.

[0050] <Anode Layer for Solid Battery> The anode layer for a solid battery of the present invention comprises at least the anode protective film for a solid battery of the present invention and a current collecting foil.

[0051] Current Collector Foil The current collector foil used in the present invention may have a lithium metal layer formed on it by charging, and may be any current collector foil that does not react with lithium when the lithium metal layer is formed. For example, metals, carbon, conductive polymers, etc. can be used, with metals being preferred. Metals typically used for current collector foils include aluminum, platinum, nickel, tantalum, titanium, stainless steel, copper, and other alloys. Among these, metal foils such as copper foil are preferred in terms of conductivity and voltage resistance.

[0052] The thickness of the current collector foil is not particularly limited, but may be, for example, about 5 to 50 μm, and preferably about 10 to 20 μm.

[0053] The negative electrode layer for a solid-state battery of the present invention may contain a negative electrode active material as needed. Carbon materials (natural graphite, artificial graphite, amorphous carbon, etc.) having a structure (porous structure) capable of absorbing and releasing lithium ions, or silicon-based compounds, can be used. The particle size is preferably 10 nm to 100 μm, more preferably 20 nm to 20 μm.

[0054] Examples of carbon materials include graphite, low-crystalline carbon (soft carbon, hard carbon), carbon black (ketjen black, acetylene black, channel black, lamp black, oil furnace black, thermal black, etc.), fullerene, carbon nanotube, carbon nanofiber, carbon nanohorn, carbon fibril, coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fiber, phenolic resin baked body, polyacrylonitrile-based carbon fiber, and the like, and graphite is preferred.

[0055] The silicon-based compounds include elemental Si, alloys with Si, oxides containing Si, carbides containing Si, etc. ４ , SiB ６ , Mg ２ Si, Ni ２ Si, TiSi ２ , MoSi ２ , CoSi ２ , NiSi ２ , CaSi ２ , CrSi ２ , Cu ５ Si, FeSi ２ , MnSi ２ , NbSi ２ , TaSi ２ , VSi ２ , WSi ２ , ZnSi ２ , SiC, Si ３ N ４ , Si ２ N ２ O, SiO ｘ (0<x≦2), SnSiO ｘ , LiSiO, and SiO ｘ (0<x≦2) is preferred, and examples thereof include silicon monoxide (SiO).

[0056] In addition, when a lithium ion battery is produced using the dissolution and deposition of lithium, metallic lithium or a lithium alloy capable of absorbing and releasing lithium can be used.

[0057] Examples of lithium alloys include lithium-aluminum alloys, lithium-tin alloys, lithium-indium alloys, lithium-silver alloys, lithium-gold alloys, lithium-zinc alloys, lithium-germanium alloys, lithium-silicon alloys, etc. Any other alloy that can be alloyed with lithium using a known alloying method can also be used.

[0058] When a carbon material or a silicon-based compound is used as the negative electrode active material, they may be used alone or in combination. When a carbon material and a silicon-based compound are used in combination, they are preferably contained as follows.

[0059] The lower limit of the content of the carbon material relative to the total amount (100% by mass) of the negative electrode active material is preferably 20% by mass or more, more preferably 40% by mass or more, particularly preferably 60% by mass or more, and may be 70% by mass or more, and the upper limit is preferably 99% by mass or less, more preferably 98% by mass or less, particularly preferably 96% by mass or less.

[0060] The lower limit of the content of the silicon-based compound relative to the total amount (100% by mass) of the negative electrode active material is preferably 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 4% by mass or more, and the upper limit is preferably 80% by mass or less, more preferably 60% by mass or less, particularly preferably 40% by mass or less, and may be 30% by mass or less.

[0061] When a conductive additive is used, a known conductive additive can be used, and examples thereof include conductive carbon black such as graphite, furnace black, acetylene black, and ketjen black, carbon fibers such as carbon nanotubes (CNT), and metal powders. These conductive additives may be used alone or in combination of two or more.

[0062] When a conductive additive is used, the content of the conductive additive is not particularly limited, but is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, relative to 100 parts by mass of the negative electrode active material. The lower limit of the content of the conductive additive is usually 0.05 parts by mass or more, 0.1 parts by mass or more, 0.2 parts by mass or more, or 0.5 parts by mass or more, for example.

[0063] Method for Producing Anode Layer for Solid Battery The anode layer for a solid battery of the present invention is obtained by laminating and bonding the anode protective film for a solid battery of the present invention onto a current collector foil, as described above.

[0064] The method for producing the anode layer for a solid battery is not particularly limited, and a general method can be used, for example, by laminating a previously produced anode protective layer and a current collector foil as described above, or by uniformly applying the anode protective film composition for a solid battery to an appropriate thickness on the surface of the current collector by a doctor blade method, an applicator method, a silk screen method, or the like.

[0065] When a previously prepared anode protective layer is attached, the anode layer for a solid battery is produced by press molding using a press machine.

[0066] For example, in the doctor blade method, the solid-state battery anode protective film composition is applied to a current collector foil, and then uniformly applied to an appropriate thickness using a blade with a predetermined slit width. After application, the coating is dried, for example, with hot air at 100°C or in a vacuum at 80°C. After drying, the coating is pressed using a press to produce a solid-state battery anode layer. After pressing, the coating may be heat-treated again to remove excess components.

[0067] <Solid State Battery> The solid state battery of the present invention is characterized by comprising the solid state battery anode layer of the present invention, a cathode layer serving as a counter electrode, and an inorganic solid electrolyte layer.

[0068] <Positive Electrode Layer> The positive electrode layer of the solid state battery of the present invention includes at least a current collector and a positive electrode active material.

[0069] Positive Electrode A known current collector can be used for the positive electrode used in the present invention. Specifically, metals such as aluminum, nickel, stainless steel, gold, platinum, and titanium are used for the positive electrode.

[0070] The positive electrode active material used in the solid state battery of the present invention is AMO. ２ , A.M. ２ O ４ , A ２ MO ３ , AMBO ４ The alkali metal-containing composite oxide has any one of the following compositions. A is an alkali metal, and M is a single or two or more transition metals, some of which may contain non-transition metals. B is P, Si, or a mixture thereof. The positive electrode active material is preferably a powder, and the particle size is preferably 50 microns or less, more preferably 20 microns or less. These positive electrode active materials have an electromotive force of 3 V (vs. Li / Li+) or more.

[0071] Preferable examples of the positive electrode active material used in the solid state battery include Li ｘ CoO ２ , Li ｘ NiO ２ , Li ｘ MnO ２ , Li ｘ CrO ２ , Li ｘ FeO ２ , Li ｘ Co ａ Mn １－ａ O ２ , Li ｘ Co ａ Ni １－ａ O ２ , Li ｘ Co ａ Cr １－ａ O ２ , Li ｘ Co ａ Fe １－ａ O ２ , Li ｘ Co ａ Ti １－ａ O ２ , Li ｘ Mn ａ Ni １－ａ O ２ , Li ｘ Mn ａ Cr １－ａ O ２ , Li ｘ Mn ａ Fe１－ａ O ２ 、 ｘ Mn ａ Ti １－ａ O ２ 、 ｘ Ni ａ Cr １－ａ O ２ 、 ｘ Ni ａ Fe １－ａ O ２ 、 ｘ Ni ａ Ti １－ａ O ２ 、 ｘ Cr ａ Fe １－ａ O ２ 、 ｘ Cr ａ Ti １－ａ O ２ 、 ｘ Fe ａ Ti １－ａ O ２ 、 ｘ Co ｂ Mn ｃ Ni １－ｂ－ｃ O ２ 、 ｘ Ni ａ Co ｂ Al ｃ O ２ 、 ｘ Cr ｂ Mn ｃ Ni １－ｂ－ｃ O ２ 、 ｘ Fe ｂ Mn ｃ Ni １－ｂ－ｃ O ２ 、 ｘ Ti ｂ Mn ｃ Ni １－ｂ－ｃ O ２ 、 ｘ Mn ２ O ４ 、 ｘ Mn ｄ Co ２－ｄ O ４ 、 ｘ Mn ｄ Ni ２－ｄ O ４ 、 ｘMn ｄ Cr ２－ｄ O ４ 、Li ｘ Mn ｄ Fe ２－ｄ O ４ 、Li ｘ Mn ｄ Today ２－ｄ O ４ 、Li ｙ Mnｯ ３ 、Li ｙ Mn ｅ Yes １－ｅ O ３ 、Li ｙ Mn ｅ N １－ｅ O ３ 、Li ｙ Mn ｅ Fe １－ｅ O ３ 、Li ｙ Mn ｅ Today １－ｅ O ３ 、Li ｘ BoPO ４ 、Li ｘ MnPO ４ 、Li ｘ NiPO ４ 、Li ｘ FePO ４ 、Li ｘ Yes ｆ Mn １－ｆ PO ４ 、Li ｘ Yes ｆ N １－ｆ PO ４ 、Li ｘ Yes ｆ Fe １－ｆ PO ４ 、Li ｘ Mn ｆ N １－ｆ PO ４ 、Li ｘ Mn ｆ Fe １－ｆ PO ４ 、Li ｘ N ｆ Fe １－ｆ PO ４ ,Li ｙ Copt ４ 、Li ｙ MnSiｯ ４、 ｙ &-SiOO ４ 、 ｙ FeSiOO ４ 、 ｙ Co ｇ Mn １－ｇ SiO ４ 、 ｙ Co ｇ Ni １－ｇ SiO ４ 、 ｙ Co ｇ Fe １－ｇ SiO ４ 、 ｙ Mn ｇ Ni １－ｇ SiO ４ 、 ｙ Mn ｇ Fe １－ｇ SiO ４ 、 ｙ Ni ｇ Fe １－ｇ SiO ４ 、 ｙ CoP ｈ Si １－ｈ O ４ 、 ｙ MnP ｈ Si １－ｈ O ４ 、 ｙ NiP ｈ Si １－ｈ O ４ 、 ｙ FeP ｈ Si １－ｈ O ４ 、 ｙ Co ｇ Mn １－ｇ P ｈ Si １－ｈ O ４ 、 ｙ Co ｇ Ni １－ｇ P ｈ Si １－ｈ O ４ 、 ｙ Co ｇ Fe １－ｇ P ｈ Si １－ｈ O ４ 、 ｙ Mn ｇ Ni １－ｇ Pｈ Si １－ｈ O ４ , Li ｙ Mn ｇ Fe １－ｇ P ｈ Si １－ｈ O ４ , Li ｙ Ni ｇ Fe １－ｇ P ｈ Si １－ｈ O ４ (wherein x = 0.01 to 1.2, y = 0.01 to 2.2, a = 0.01 to 0.99, b = 0.01 to 0.98, c = 0.01 to 0.98, proviso that b + c = 0.02 to 0.99, d = 1.49 to 1.99, e = 0.01 to 0.99, f = 0.01 to 0.99, g = 0.01 to 0.99, and h = 0.01 to 0.99.)

[0072] Among the above-mentioned preferred positive electrode active materials for use in solid-state batteries, more preferred positive electrode active materials are, specifically, Li ｘ CoO ２ , Li ｘ NiO ２ , Li ｘ MnO ２ , Li ｘ CrO ２ , Li ｘ Co ａ Ni １－ａ O ２ , Li ｘ Mn ａ Ni １－ａ O ２ , Li ｘ Co ｂ Mn ｃ Ni １－ｂ－ｃ O ２ , Li ｘ Ni ａ Co ｂ Al ｃ O ２ , Li ｘ Mn ２ O ４ , Li ｙ MnO ３ , Li ｙ Mn ｅ Fe １－ｅ O ３ , Liｙ Mn ｅ Ti １－ｅ O ３ , Li ｘ CoPO ４ , Li ｘ MnPO ４ , Li ｘ NiPO ４ , Li ｘ FePO ４ , Li ｘ Mn ｆ Fe １－ｆ P.O. ４ (Here, x = 0.01 to 1.2, y = 0.01 to 2.2, a = 0.01 to 0.99, b = 0.01 to 0.98, c = 0.01 to 0.98, provided that b + c = 0.02 to 0.99, d = 1.49 to 1.99, e = 0.01 to 0.99, and f = 0.01 to 0.99. Note that the values ​​of x and y increase or decrease with charge and discharge.)

[0073] In order to improve the binding strength between the current collector and the positive electrode active material, a binder may be contained, and any known binder used for a positive electrode can be used. Specifically, fluorine-based resins such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, polytetrafluoroethylene, and fluorine rubber, hydrocarbon elastomers such as styrene-butadiene copolymer and ethylene-propylene copolymer, polysaccharides such as carboxymethyl cellulose, alginic acid, and sodium alginate, and polyimides can be used.

[0074] The material constituting the positive electrode layer may contain an organic solvent and water to form a slurry. The water is not particularly limited, and commonly used water can be used. Specific examples include tap water, distilled water, ion-exchanged water, and ultrapure water. Among these, distilled water, ion-exchanged water, and ultrapure water are preferred.

[0075] When the material constituting the positive electrode is used in the form of a slurry, the solid content of the slurry is preferably 10 to 90 mass %, more preferably 20 to 85 mass %, and particularly preferably 20 to 80 mass %.

[0076] The preparation method is not particularly limited, and the binder, conductive additive, water, etc. may be dispersed using a conventional stirrer, disperser, kneader, planetary ball mill, homogenizer, etc. To increase the efficiency of dispersion, the material may be heated within a range that does not affect the material.

[0077] The method for producing the positive electrode layer is not particularly limited, and a common method can be used. The positive electrode layer is produced by uniformly applying the positive electrode material to an appropriate thickness on the surface of the current collector using a doctor blade method, an applicator method, a silk screen method, or the like.

[0078] For example, in the doctor blade method, a slurry of the positive electrode material is applied to a metal electrode substrate, and then uniformly applied to an appropriate thickness using a blade with a predetermined slit width. After the active material is applied to the electrode, the electrode is dried, for example, with hot air at 100°C or in a vacuum at 80°C to remove excess organic solvent or water. The dried electrode is press-molded using a press device to produce an electrode material. After pressing, the electrode may be heat-treated again to remove water, solvent, emulsifier, etc.

[0079] <Inorganic Solid Electrolyte Layer> Examples of the inorganic solid electrolyte layer include an oxide solid electrolyte and a sulfide solid electrolyte. An inorganic solid electrolyte is generally an aggregate of inorganic solid particles that constitute the electrolyte.

[0080] The oxide solid electrolyte is not particularly limited as long as it contains oxygen, has the ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, and has electronic insulation properties.

[0081] Specific compounds constituting the oxide solid electrolyte include Li ｘ La ｙ TiO ３ [x=0.3~0.7, y=0.3~0.7] (LLT), Li ｘ La ｙ Zr ｚ M ｍO ｎ (M is at least one element selected from Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, and Sn, x satisfies 5≦x≦10, y satisfies 1≦y≦4, z satisfies 1≦z≦4, m satisfies 0≦m≦2, and n satisfies 5≦n≦20.) Li ｘ B ｙ M ｚ O ｎ (wherein M is at least one element selected from C, S, Al, Si, Ga, Ge, In, and Sn, x satisfies 0≦x≦5, y satisfies 0≦y≦1, z satisfies 0≦z≦1, and n satisfies 0≦n≦6), Li ｘ (Al, Ga) ｙ (Ti, Ge) ｚ Si ａ P ｍ O ｎ (wherein 1≦x≦3, 0≦y≦1, 0≦z≦2, 0≦a≦1, 1≦m≦7, 3≦n≦13), Li （３－２ｘ） M ｘ DO (x represents a number of 0 or more and 0.1 or less, M represents a divalent metal atom, and D represents a halogen atom or a combination of two or more halogen atoms), Li ｘ Si ｙ O ｚ (1≦x≦5, 0<y≦3, 1≦z≦10), Li ｘ S ｙ O ｚ (1≦x≦3, 0<y≦2, 1≦z≦10), Li ３ BO ３ -Li ２ SO ４ , Li ２ Alumni ２ O ３ -P ２ O ５ , Li ２ O—SiO ２ , Li ６ BaLa ２ Ta ２ O １２ , Li ３ P.O. （４－３／２ｗ） N ｗ (w is w<1), Li having a LISICON (Lithium super ionic conductor) type crystal structure ３．５ Zn ０．２５GeO ４ , La having a perovskite crystal structure ０．５５ Li ０．３５ TiO ３ , LiTi having a NASICON (sodium super ionic conductor) type crystal structure ２ P ３ O １２ , Li （１＋ｘ＋ｙ） (Al, Ga) ｘ (Ti, Ge) （２－ｘ） Si ｙ P （３－ｙ） O １２ (where 0≦x≦1, 0≦y≦1), Li having a garnet-type crystal structure ７ La ３ Zr ２ O １２ Also preferred are phosphorus compounds containing Li, P, and O. For example, lithium phosphate (Li ３ P.O. ４ and LiPON and LiPOD (where D is at least one selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Ag, Ta, W, Pt, Au, etc.), in which part of the oxygen in lithium phosphate has been substituted with nitrogen. Also preferably used are LiAON (where A is at least one selected from Si, B, Ge, Al, C, Ga, etc.).

[0082] Among them, Li ｘ La ｙ TiO ３ [x=0.3~0.7, y=0.3~0.7] (LLT), Li ｘ La ｙ Zr ｚ M ｍ O ｎ (M is at least one element selected from Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, and Sn, x satisfies 5≦x≦10, y satisfies 1≦y≦4, z satisfies 1≦z≦4, m satisfies 0≦m≦2, and n satisfies 5≦n≦20.), Li ７ La ３ Zr ２ O １２ (LLZ), Li ３ BO ３ , Li３ BO ３ -Li ２ SO ４ , Li ３ BO ３ -Li ２ CO ３ , Li ｘ (Al, Ga) ｙ (Ti, Ge) ｚ Si ａ P ｍ O ｎ (wherein 1≦x≦3, 0≦y≦1, 0≦z≦2, 0≦a≦1, 1≦m≦7, 3≦n≦13) are preferred. These may be used alone or in combination of two or more.

[0083] The sulfide solid electrolyte is not particularly limited as long as it contains sulfur, has the ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, and has electronic insulation. For example, a lithium ion conductive solid electrolyte having a composition represented by the following formula can be used.

[0084] Li ａ M ｂ P ｃ S ｄ A ｅ

[0085] In the formula, M represents an element selected from B, Zn, Sn, Si, Cu, Ga, Sb, Al, and Ge. Among them, B, Sn, Si, Al, and Ge are preferred, and Sn, Al, and Ge are more preferred. A represents I, Br, Cl, and F, with I and Br being preferred, and I being particularly preferred. a to e represent the composition ratio of each element, and a:b:c:d:e satisfies the ratio of 1-12:0-1:1:2-12:0-5. a is more preferably 1-9, and more preferably 1.5-4. b is preferably 0-0.5. d is more preferably 3-7, and more preferably 3.25-4.5. e is more preferably 0-3, and more preferably 0-2.

[0086] In the formula, the composition ratio of Li, M, P, S, and A is preferably such that b and e are 0, more preferably b=0, e=0, and the ratio of a, c, and d (a:c:d) is a:c:d=1-9:1:3-7, and even more preferably b=0, e=0, and a:c:d=1.5-4:1:3.25-4.5.

[0087] When the inorganic solid electrolyte is in the form of particles, the particle size is, for example, 0.01 to 100 μm, preferably 0.1 to 20 μm.

[0088] For the purpose of improving the binding strength between the inorganic solid particles, a binder may be contained, and a known binder can be used. Specifically, fluororesin binders such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, and polytetrafluoroethylene, rubber binders such as fluororubber, styrene-butadiene rubber, and ethylene-propylene rubber, polysaccharides such as carboxymethyl cellulose, alginic acid, and sodium alginate, and polyimides can be used.

[0089] The method for producing an inorganic solid electrolyte layer is not particularly limited, and a general method can be used. The inorganic solid electrolyte layer can be obtained by producing pellets of inorganic solid particles and then molding them into a desired shape using a press molding machine or the like. Alternatively, the inorganic solid particles can be dispersed in water, an organic solvent, or the like, and a slurry solution is then uniformly applied to an appropriate thickness using a doctor blade method, an applicator method, a silk screen method, or the like.

[0090] The water and organic solvent used to prepare the slurry solution are not particularly limited, and commonly used water can be used. Specific examples include tap water, distilled water, ion-exchanged water, and ultrapure water. Among these, distilled water, ion-exchanged water, and ultrapure water are preferred. Examples of organic solvents include alcohol, acetone, acetonitrile, methyl ethyl ketone, toluene, tetrahydrofuran, and N-methyl-2-pyrrolidone.

[0091] The solid content concentration in the slurry is preferably 10 to 90% by mass, more preferably 20 to 85% by mass, and particularly preferably 20 to 80% by mass.

[0092] The preparation method is not particularly limited, and the binder, conductive additive, water, etc. may be dispersed using a conventional stirrer, disperser, kneader, planetary ball mill, homogenizer, etc. To increase the efficiency of dispersion, the material may be heated within a range that does not affect the material.

[0093] The method for manufacturing a solid-state battery of the present invention is not particularly limited, and the battery can be manufactured by a known method using a positive electrode layer, a negative electrode layer for a solid-state battery, and an inorganic solid electrolyte layer. For example, in the case of a coin-shaped battery, a positive electrode layer, an inorganic solid electrolyte layer, and a negative electrode layer are formed in this order on an outer can, stacked, and then pressed together under high confining pressure to obtain a solid-state battery. The shape of the solid-state battery is not limited, and examples include a coin-shaped, cylindrical, and sheet-shaped battery.

[0094] The present invention will be described in more detail in the following examples, but the present invention is not limited to these examples.

[0095] [Synthesis Example] (Production of Polymerization Catalyst) 10 parts by mass of tributyltin chloride and 35 parts by mass of tributylphosphate were placed in a three-necked flask equipped with a stirrer, a thermometer, and a distillation apparatus, and heated at 250°C for 20 minutes with stirring under a nitrogen stream to remove the distillate, thereby obtaining a solid condensation product as a residue, which was used as a polymerization catalyst in the following polymerization examples.

[0096] [Polymerization Example 1] (Production of Polyether Copolymer 1) The interior of a 3 L four-necked glass flask was purged with nitrogen, and 3.3 parts by mass of the polymerization catalyst produced in Synthesis Example, 58 parts by mass of ethylene oxide, 190 parts by mass of propylene oxide, 0.4 parts by mass of tert-butanol, and 1,000 parts by mass of n-hexane as a solvent were charged. While monitoring the polymerization rate by gas chromatography, 86 parts by mass of ethylene oxide was gradually added. The polymerization temperature was 20°C, and the reaction was carried out for 10 hours. The polymerization reaction was terminated by adding methanol. Polyether Copolymer 1 was removed by decantation and then dried at 25°C under normal pressure for 24 hours and then at 40°C under reduced pressure for 10 hours to obtain 317 parts by mass of Polyether Copolymer 1. The weight average molecular weight and copolymer composition of the obtained Polyether Copolymer 1 were measured as follows. The results are shown in Table 1. It was a copolymer of ethylene oxide and propylene oxide and had a weight average molecular weight of 760,000.

[0097] [Weight-average molecular weight of polyether copolymer] Gel permeation chromatography (GPC) was performed to calculate the weight-average molecular weight in terms of standard polystyrene. The GPC measurement was performed at 60°C using RID-6A manufactured by Shimadzu Corporation, and Showdex KD-807, KD-806, KD-806M, and KD-803 columns manufactured by Showa Denko K.K., and DMF as a solvent.

[0098] [Copolymerization Composition of Polyether Copolymer] The polyether copolymer was dissolved in deuterated chloroform, and the integral value of each unit was determined by H-NMR, and the composition ratio was calculated from the result. The apparatus used was a JNM ECZS-400 model manufactured by JEOL Ltd.

[0099] [Polymerization Example 2] (Production of Polyether Copolymer 2) The interior of a 3 L four-necked glass flask was purged with nitrogen, and 3.3 parts by mass of the polymerization catalyst produced in Synthesis Example, 56 parts by mass of ethylene oxide adjusted to a water content of 10 ppm or less, 179 parts by mass of propylene oxide, 18 parts by mass of allyl glycidyl ether, 0.4 parts by mass of tert-butanol, and 1000 parts by mass of n-hexane as a solvent were charged, and 80 parts by mass of ethylene oxide was added successively while monitoring the polymerization rate by gas chromatography. The polymerization temperature at this time was 20 ° C., and the reaction was carried out for 10 hours. The polymerization reaction was terminated by adding methanol. Polyether copolymer 2 was removed by decantation and then dried at 25 ° C. under normal pressure for 24 hours and then at 40 ° C. under reduced pressure for 10 hours to obtain 317 parts by mass of polyether copolymer 2. The resulting polyether copolymer 2 was tested as described above, and the resulting polymer was a copolymer of ethylene oxide, propylene oxide, and allyl glycidyl ether, and had a weight average molecular weight of 1,370,000.

[0100] [Polymerization Example 3] (Production of Polyether Copolymer 3) The interior of a 3 L four-necked glass flask was purged with nitrogen, and 3.3 parts by mass of the polymerization catalyst produced in Synthesis Example, 56 parts by mass of ethylene oxide adjusted to a water content of 10 ppm or less, 197 parts by mass of butylene oxide, 16 parts by mass of allyl glycidyl ether, 0.7 parts by mass of tert-butanol, and 1000 parts by mass of n-hexane as a solvent were charged. While monitoring the polymerization rate by gas chromatography, 64 parts by mass of ethylene oxide was gradually added. The polymerization temperature was 28 ° C., and the reaction was carried out for 8 hours. The polymerization reaction was terminated by adding methanol. Polyether copolymer 3 was removed by decantation and then dried at 25 ° C. under normal pressure for 24 hours, and then at 40 ° C. under reduced pressure for 10 hours to obtain 300 parts by mass of polyether copolymer 3. The resulting polyether copolymer 3 was tested as described above, and the resulting polymer was a copolymer of ethylene oxide, butylene oxide, and allyl glycidyl ether, and had a weight average molecular weight of 1,020,000.

[0101] [Polymerization Example 4] (Production of Polyether Copolymer 4) The interior of a 3 L four-necked glass flask was purged with nitrogen, and 3.3 parts by mass of a polymerization catalyst, 106 parts by mass of ethylene oxide, 120 parts by mass of propylene oxide, 0.4 parts by mass of tert-butanol, and 1,000 parts by mass of n-hexane as a solvent were charged. While monitoring the polymerization rate by gas chromatography, 107 parts by mass of ethylene oxide was gradually added. The polymerization temperature was 20°C, and the reaction was carried out for 10 hours. The polymerization reaction was terminated by adding methanol. Polyether copolymer 4 was removed by decantation and then dried at 25°C under normal pressure for 24 hours and then at 40°C under reduced pressure for 10 hours to obtain 317 parts by mass of polyether copolymer 3. The obtained polyether copolymer 4 was a copolymer of ethylene oxide and propylene oxide and had a weight-average molecular weight of 610,000.

[0102] [Polymerization Example 5] (Production of Polyether Copolymer 5) The interior of a 3 L four-necked glass flask was purged with nitrogen, and 2.5 parts by mass of a polymerization catalyst, 87 parts by mass of ethylene oxide, 32 parts by mass of propylene oxide, and 1,000 parts by mass of n-hexane as a solvent were charged. While monitoring the polymerization rate by gas chromatography, 131 parts by mass of ethylene oxide was gradually added. The polymerization temperature was 20°C, and the reaction was carried out for 10 hours. The polymerization reaction was terminated by adding methanol. Polyether Copolymer 5 was removed by decantation and then dried at 25°C under normal pressure for 24 hours and then at 45°C under reduced pressure for 10 hours, yielding 238 parts by mass of Polyether Copolymer 5. The resulting Polyether Copolymer 4 was a copolymer of ethylene oxide and propylene oxide and had a weight-average molecular weight of 4,040,000.

[0103] Example 1 74.6 parts by mass of the polyether copolymer 1 obtained in Polymerization Example 1 and LiN(FSO ２ ) ２A solid battery anode protective film composition was prepared by dissolving 25.4 parts by mass of the above in 600 parts by mass of tetrahydrofuran as a dispersion medium. The solid battery anode protective film composition was then applied to a PET film to a predetermined thickness and dried to prepare a solid battery anode protective film (protective film thickness: 50 μm), thereby preparing anode protective film 1. The following tests were performed to evaluate the solid battery anode protective film.

[0104] [Evaluation of Deterioration of Sulfide Solid Electrolyte] An argyrodite-type sulfide solid electrolyte (manufactured by NEI, Li ６ P.S. ５ A slurry solution containing HCl) and a rubber-based binder was applied to a PET film, and the dispersion medium was removed by vacuum heating and drying to prepare an inorganic solid electrolyte layer. This was then attached to the anode protective film for a solid battery prepared in Example 1, and a load of 100 MPa or more was applied using a flat press to prepare a composite of the anode protective film and the inorganic solid electrolyte layer having a thickness of 500 to 2000 μm. Thereafter, a heat treatment was performed at 60° C. for one week, and the inorganic solid electrolyte and the ３１ P-NMR studies were carried out.

[0105] ３１ P-NMR test: In a glove box under an argon atmosphere, the composite after the heat treatment was ground in a mortar and thoroughly mixed, and then sealed in a solid-state NMR sample tube (probe diameter: 4.0 mm), and measurements were carried out using a single pulse method with an NMR device (device name: Agilent NMR System 400WB). NMR measurements were also carried out on an argyrodite-type sulfide solid electrolyte using the same procedure, and this was used as a comparison. The evaluation method included measuring the PS content of the argyrodite-type sulfide solid electrolyte before heating. ４ ３－ Unit-derived spectra and P ２ S ７ ４－ Ratio of spectra derived from units and PS contained in sulfide solid electrolyte after heat treatment ４ ３－ The spectrum of the unit and the P generated by the reaction with the polymer ２ S ７ ４－The difference in the ratio change of the spectrum originating from the unit was evaluated. The test temperature was 25°C. An 85% aqueous solution of phosphoric acid was used as a reference substance showing a chemical shift of 0 ppm. ４ ３－ Unit-derived spectra and P ２ S ７ ４－ The ratio with the spectrum derived from the unit was 96% and 4%. Sample rotation speed: 20 kHz, number of measurements accumulated: 16, relaxation time: 2000 seconds

[0106] [Example 2] Polyether copolymer 1 was changed to polyether copolymer 2, and a composition for a solid battery anode protective film was prepared by dissolving 74.6 parts by mass of polyether copolymer 2 and 25.4 parts by mass of LiN(FSO2)2 in 600 parts by mass of tetrahydrofuran. The composition was used to prepare a solid battery anode protective film 2, and evaluation was performed as described in Example 1, except that evaluation was performed.

[0107] [Example 3] Polyether copolymer 1 was changed to polyether copolymer 3, and a composition for a solid battery anode protective film was prepared by dissolving 74.6 parts by mass of polyether copolymer 3 and 25.4 parts by mass of LiN(FSO2)2 in 600 parts by mass of tetrahydrofuran. The composition was used to prepare a solid battery anode protective film 3, and evaluation was performed as described in Example 1, except that the composition was used to prepare a solid battery anode protective film 3.

[0108] Comparative Example 1 Polyether copolymer 1 obtained in Polymerization Example 1 was changed to polyether copolymer 4, and a composition for a solid battery anode protective film was prepared by dissolving 73.5 parts by mass of polyether copolymer 3 and 26.5 parts by mass of LiN(FSO2)2 in 600 parts by mass of tetrahydrofuran. The composition was used to prepare a solid battery anode protective film 4, and evaluation was performed as described in Example 1.

[0109] Comparative Example 2 The polyether copolymer 1 obtained in Polymerization Example 1 was changed to polyether copolymer 5, and a composition for a solid battery anode protective film was prepared by dissolving 72.5 parts by mass of polyether copolymer 4 and 27.5 parts by mass of LiN(FSO2)2 in 600 parts by mass of tetrahydrofuran. The composition was used to prepare a solid battery anode protective film 5, and evaluation was performed as described in Example 1, except that the composition was changed to polyether copolymer 5.

[0110]

[0111] From the results of the sulfide resistance test for Example 1, Example 2, Comparative Example 1, and Comparative Example 2, it can be seen that Example 1 and Example 2, which used the anode protective film of the present invention, have a low sulfide resistance. ２ S ７ ４－ Therefore, it can be seen that the anode protective film of the present invention, which contains at least a polyether copolymer including specific amounts of the structural unit (A) derived from the epoxy compound represented by formula (1) above and the structural unit (B) derived from ethylene oxide represented by formula (2) above, and a lithium salt compound, suppresses deterioration of the inorganic solid electrolyte and the reaction between the polymer and the sulfide solid electrolyte.

[0112] The inorganic solid electrolyte secondary battery containing the polyether electrolyte of the present invention functions as a negative electrode protective film without causing deterioration of the inorganic solid electrolyte, and can be used to fabricate a solid electrolyte secondary battery having a high energy density negative electrode active material such as metallic lithium. Furthermore, this battery is suitable for use in vehicles such as electric vehicles and hybrid electric vehicles, and for large-scale battery applications such as storage batteries for home power storage.

Claims

1. An anode protective film for a solid-state battery, comprising at least a polyether copolymer containing at least a structural unit (A) derived from an epoxy compound represented by the following formula (1) and a structural unit (B) derived from ethylene oxide represented by the following formula (2), and a lithium salt compound, wherein the composition ratio of the polyether copolymer is 30 to 99 mol % for (A) and 1 to 70 mol % for (B). [In the formula, R １ is an alkyl group, a cycloalkyl group, or an aryl group having 1 to 12 carbon atoms.

2. The negative electrode protective film for a solid battery according to claim 1, wherein the polyether contains 0.1 to 20 mol % of a structural unit derived from a compound having an ethylenically unsaturated bond represented by the following formula (3): [In the formula, R ２ is a group having an ethylenically unsaturated bond.

3. An anode layer for a solid-state battery comprising at least the anode protective film for a solid-state battery according to claim 1 or 2 and a current collecting foil.

4. A solid-state battery comprising at least the anode layer for a solid-state battery according to claim 3, a solid electrolyte layer, and a cathode layer.

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