Positive electrode material, solid battery, method for manufacturing positive electrode material, and method for manufacturing solid battery

Abstract

To provide a positive electrode material having a suppressed initial resistance and a resistance which is not easily increased by repeated charges and discharges.SOLUTION: The positive electrode material according to the present disclosure includes a positive electrode active material composite body and a sulfide solid electrolyte. The positive electrode active material composite body includes a positive electrode active material, a conduction aid covering at least a part of the surface of the positive electrode active material, and a solid electrolyte covering at least a part of the conduction aid. The solid electrolyte contains Li, Ti, X, and F. X is at least one selected from the group of Ca, Mg, Al, Y, and Zr.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a cathode material, a solid-state battery, a method for manufacturing a cathode material, and a method for manufacturing a solid-state battery. [Background technology]

[0002] BACKGROUND ART Conventionally, solid-state batteries have been known as lithium-ion secondary batteries that are excellent in safety. Patent Document 1 discloses a positive electrode material. The positive electrode material specifically disclosed in Patent Document 1 is a first solid electrolyte material (Li 2.6 Ti 0.4 Al 0.6 The cathode active material (Li(Ni, Co, Mn)O2) is surface-coated with P2S5 (Pyrolyzed Li2S-P2S5). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 187391 Summary of the Invention [Problem to be solved by the invention]

[0004] However, a solid-state battery using the positive electrode material specifically disclosed in Patent Document 1 may have a relatively high initial resistance. Also, in a solid-state battery using a positive electrode material in which a conductive additive is added to the positive electrode material specifically disclosed in Patent Document 1 in order to reduce resistance, repeated charging and discharging of the solid-state battery may easily increase the resistance of the solid-state battery.

[0005] The present disclosure has been made in consideration of the above circumstances. An object of one embodiment of the present disclosure is to provide a positive electrode material and a method for manufacturing the positive electrode material, which can provide a solid-state battery in which the initial resistance is suppressed and the resistance is not likely to increase even after repeated charging and discharging. Another embodiment of the present disclosure aims to solve a problem by providing a solid-state battery in which the initial resistance is suppressed and the resistance is less likely to increase even after repeated charging and discharging, and a method for manufacturing the solid-state battery. [Means for solving the problem]

[0006] The means for solving the above problems include the following embodiments. <1> Contains a positive electrode active material composite (A) and a sulfide solid electrolyte (B), The positive electrode active material composite (A) is A positive electrode active material (a), a conductive additive (b) that coats at least a portion of the surface of the positive electrode active material (a); a solid electrolyte (c) that coats at least a portion of the conductive additive (b); and the solid electrolyte (c) contains Li, Ti, X, and F; The positive electrode material, wherein X is at least one selected from the group consisting of Ca, Mg, Al, Y, and Zr. <2> The X includes Al. <1> The positive electrode material according to claim 1. <3> the conductive additive (b) covers the entire surface of the positive electrode active material (a), the solid electrolyte (c) covers the entire conductive additive (b); <1> or <2> The positive electrode material according to claim 1. <4> a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; The positive electrode layer <1> ~ <3> 10. A solid-state battery comprising the positive electrode material according to any one of claims 1 to 9. <5> coating at least a portion of the surface of the positive electrode active material (a) with a conductive additive (b); coating at least a portion of the conductive additive (b) with a solid electrolyte (c) to prepare a positive electrode active material composite (A); kneading the positive electrode active material composite (A) and a sulfide solid electrolyte (B); Including, the solid electrolyte (c) contains Li, Ti, X, and F; A method for producing a positive electrode material, wherein X is at least one selected from the group consisting of Ca, Mg, Al, Y, and Zr. <6> The X includes Al. <5> A method for producing the positive electrode material described in <7> The aforementioned <5> or <6> 2. A method for producing a solid-state battery, comprising the step of producing a positive electrode material by the method for producing a positive electrode material according to claim 1. [Effects of the Invention]

[0007] According to the present disclosure, a positive electrode material and a method for manufacturing the positive electrode material are provided that can produce a solid-state battery in which the initial resistance is suppressed and the resistance is less likely to increase even after repeated charging and discharging. According to the present disclosure, a solid-state battery in which the initial resistance is suppressed and the resistance is unlikely to increase even with repeated charge and discharge, and a method for manufacturing the solid-state battery are provided. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a solid-state battery. [Figure 2] FIG. 2 is a scanning electron microscope (SEM) photograph (magnification: 30,000 times) of the positive electrode active material with a conductive additive of Example 1. [Figure 3] FIG. 3 is an SEM-energy dispersive X-ray analyzer (EDS) image in which the C distribution, F distribution, and Ni distribution of the positive electrode active material composite of Example 1 are superimposed. [Figure 4] FIG. 4 is an SEM-EDS image showing the C distribution of the positive electrode active material composite of Example 1. [Figure 5] FIG. 5 is an SEM-EDS image showing the F distribution of the positive electrode active material composite of Example 1. [Figure 6] FIG. 6 is an SEM-EDS image showing the Ni distribution in the positive electrode active material composite of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the Examples. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, when multiple substances corresponding to each component are present, the amount of each component means the total amount of multiple substances unless otherwise specified. In the present disclosure, the term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0010] (1) Cathode material The cathode material of the present disclosure contains a cathode active material composite (A) and a sulfide solid electrolyte (B). The cathode active material composite (A) includes a cathode active material (a), a conductive additive (b) that coats at least a portion of the surface of the cathode active material (a), and a solid electrolyte (c) that coats at least a portion of the conductive additive (b). The solid electrolyte (c) contains Li (lithium), Ti (titanium), X, and F (fluorine). X is at least one selected from the group consisting of Ca (calcium), Mg (magnesium), Al (aluminum), Y (yttrium), and Zr (zirconium).

[0011] The "cathode active material composite (A)" includes a plurality of particles of a cathode active material composite containing a cathode active material (a), a conductive additive (b), and a solid electrolyte (c). The "sulfide solid electrolyte (B)" includes a plurality of sulfide solid electrolyte (B) particles. The "cathode active material (a)" includes a plurality of cathode active material (a) particles. The "conductive additive (b)" includes a plurality of conductive additive (b) particles. The "solid electrolyte (c)" includes a plurality of solid electrolyte (c) particles. The phrase "having a conductive additive (b) coating at least a portion of the surface of the positive electrode active material (a), and a solid electrolyte (c) coating at least a portion of the conductive additive (b)" may mean that each of the plurality of positive electrode active material composite (A) particles has one positive electrode active material (a) particle, a plurality of conductive additive (b) particles coating at least a portion of the surface of one positive electrode active material (a) particle, and a plurality of solid electrolyte (c) particles coating at least a portion of the plurality of conductive additive (b) particles.

[0012] The positive electrode material of the present disclosure has the above-described configuration, and therefore can provide a solid-state battery in which the initial resistance is suppressed and the resistance is less likely to increase even with repeated charge and discharge. This effect is presumably due to, but not limited to, the following reasons. In the present disclosure, at least a portion of the surface of the positive electrode active material (a) is coated with a conductive additive (b). Therefore, the electronic conductivity and uniformity of the electrochemical reaction throughout the positive electrode layer of a solid-state battery using the positive electrode material of the present disclosure are more likely to be ensured than when the surface of the positive electrode active material (a) is not coated with the conductive additive (b). As a result, it is presumed that the initial resistance of a solid-state battery using the positive electrode material of the present disclosure is suppressed. In a solid-state battery using a positive electrode material containing a conductive additive and a sulfide solid electrolyte, the potential of the conductive additive tends to increase during charging of the solid-state battery. When the conductive additive, which has a high potential, comes into contact with the sulfide solid electrolyte, the sulfide solid electrolyte tends to decompose. As a result, an oxidative decomposition layer that causes interfacial resistance may be formed between the positive electrode active material and the sulfide solid electrolyte. On the other hand, in the present disclosure, the solid electrolyte (c) contains Li, Ti, X, and F. In other words, the solid electrolyte (c) has high oxidation resistance and is not easily decomposed even under high voltage. Furthermore, at least a portion of the conductive additive (b) that coats a portion of the surface of the positive electrode active material (a) is covered with the solid electrolyte (c). In other words, the contact area between the conductive additive (b) coated on the positive electrode active material (a) and the sulfide solid electrolyte (B) is smaller than when the solid electrolyte (c) is not covered by the conductive additive (b). Therefore, even if the potential of the conductive additive (c) increases during charging of the solid battery, the sulfide solid electrolyte (B) is not easily decomposed. In other words, an oxidative decomposition layer that causes interfacial resistance is not easily formed between the positive electrode active material (a) and the sulfide solid electrolyte (B). As a result, it is presumed that the resistance of a solid battery using the positive electrode material of the present disclosure is not easily increased even when the battery is repeatedly charged and discharged.

[0013] The form of the positive electrode material is not particularly limited, and may be a powder or a slurry.

[0014] (1.1) Cathode active material composite (A) The positive electrode material contains a positive electrode active material composite (A).

[0015] The positive electrode active material composite (A) comprises a positive electrode active material (a), a conductive additive (b) that coats at least a portion of the surface of the positive electrode active material (a), and a solid electrolyte (c) that coats at least a portion of the conductive additive (b). The solid electrolyte (c) contains Li, Ti, X, and F. The X is at least one selected from the group consisting of Ca, Mg, Al, Y, and Zr.

[0016] The coverage of the conductive additive (b) is preferably 30% or more, more preferably 60% or more, even more preferably 90% or more, and particularly preferably 100%, from the viewpoint of obtaining a solid battery with reduced initial resistance, etc. The coverage of the conductive additive (b) can be determined from the area ratio obtained by X-ray photoelectron spectroscopy (XPS) measurement. The thickness of the conductive additive (b) covering at least a portion of the surface of the positive electrode active material (a) (hereinafter also referred to as the "first thickness") is not particularly limited, and is preferably 5 nm or more, more preferably 10 nm to 100 nm. If the first thickness is within the above range, the movement of lithium ions is less likely to be hindered. The first thickness is preferably 1% or more of the median diameter of the positive electrode active material (a). This enables the positive electrode material to be a solid battery with a more reduced initial resistance. The method for measuring the median diameter of the positive electrode active material (a) is the same as the measurement method described in the Examples. The first thickness can be measured by SEM observation of a cross section of the positive electrode active material composite (A), measuring the first thickness at any five points, and calculating the average thickness.

[0017] The coverage of the solid electrolyte (c) is preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, and particularly preferably 100%, from the viewpoint of obtaining a solid battery in which the resistance is less likely to increase even with repeated charge and discharge. The coverage of the solid electrolyte (c) can be determined from the area ratio obtained by X-ray photoelectron spectroscopy (XPS) measurement. The thickness of the solid electrolyte (c) that coats at least a portion of the conductive additive (b) that coats at least a portion of the surface of the positive electrode active material (a) (hereinafter also referred to as the "second thickness") is not particularly limited, and is preferably 5 nm or more, more preferably 10 nm to 300 nm. If the second thickness is within the above range, the movement of lithium ions is less likely to be hindered. The second thickness is preferably 1% or more of the median diameter of the positive electrode active material (a). This allows the positive electrode material to be a solid battery whose resistance is less likely to increase even with repeated charge and discharge. The method for measuring the median diameter of the positive electrode active material (a) is the same as the measurement method described in the Examples. The second thickness can be measured by observing the cross section of the positive electrode active material composite (A) with an SEM, measuring the first thickness at any five points, and calculating the average thickness.

[0018] It is preferable that the conductive additive (b) coats the entire surface of the positive electrode active material (a), and the solid electrolyte (c) coats the entire conductive additive (b). In other words, in each of the plurality of positive electrode active material composite (A) particles, it is preferable that the plurality of conductive additive (b) particles coat the entire surface of one positive electrode active material (a), and the plurality of solid electrolytes (c) coat the entire surface of the plurality of conductive additive (b) particles that coat the entire surface of one positive electrode active material (a). This allows the positive electrode material to be a solid battery in which the initial resistance is further suppressed and the resistance is less likely to increase even with repeated charge and discharge.

[0019] (1.1.1) Positive electrode active material (a) The positive electrode active material (a) preferably contains a lithium composite oxide. The lithium composite oxide may contain at least one element selected from the group consisting of F, Cl, N, S, Br, and I. The lithium composite oxide may have a crystal structure belonging to at least one space group selected from the space groups R-3m, Immm, and P63-mmc (also referred to as P63mc or P6 / mmc). The lithium composite oxide may have an O2-type structure in which the transition metal, oxygen, and lithium are primarily arranged.

[0020] Examples of lithium composite oxides having a crystal structure belonging to R-3m include Li x Me y O α X β (Me represents at least one selected from the group consisting of Mn, Co, Ni, Fe, Al, Cu, V, Nb, Mo, Ti, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, Ag, Ru, W, B, Si, and P, and X represents at least one selected from the group consisting of F, Cl, N, S, Br, and I, and satisfy the conditions 0.5≦x≦1.5, 0.5≦y≦1.0, 1≦α<2, and 0<β≦1.)

[0021] Examples of lithium composite oxides having a crystal structure belonging to Immm include Li x1 M 1 A 12 (satisfying 1.5 ≤ x1 ≤ 2.3, M 1 includes at least one selected from the group consisting of Ni, Co, Mn, Cu, and Fe, and A 1 includes at least oxygen, and A 1 the ratio of oxygen in is 85 atomic% or more. ), a composite oxide represented by (specific example: Li2NiO2), Li x1 M 1A 1-x2 M 1B x2 O 2-y A 2 y (0 ≤ x2 ≤ 0.5, 0 ≤ y ≤ 0.3, and at least one of x2 and y is not 0, M 1A represents at least one selected from the group consisting of Ni, Co, Mn, Cu, and Fe, M 1B represents at least one selected from the group consisting of Al, Mg, Sc, Ti, Cr, V, Zn, Ga, Zr, Mo, Nb, Ta, and W, and A2 represents at least one selected from the group consisting of F, Cl, Br, S, and P. ) The composite oxide represented by is mentioned.

[0022] As the lithium composite oxide having a crystal structure belonging to P63 - mmc, for example, M1 x M2 y O2 (M1 represents an alkali metal (at least one of Na and K is preferable), M2 represents a transition metal (at least one selected from the group consisting of Mn, Ni, Co, and Fe is preferable), and x + y satisfies 0 < x + y ≤ 2. ) The composite oxide represented by is mentioned.

[0023] As the lithium composite oxide having an O2 - type structure, for example, Li x [Li α (Mn a Co b M c ) 1-αO2 (where 0.5 < x < 1.1, 0.1 < α < 0.33, 0.17 < a < 0.93, 0.03 < b < 0.50, 0.04 < c < 0.33, and M represents at least one selected from the group consisting of Ni, Mg, Ti, Fe, Sn, Zr, Nb, Mo, W, and Bi). Examples of the composite oxide include, specifically, Li 0.744 [Li 0.145 Mn 0.625 Co 0.115 Ni 0.115 O2 and the like.

[0024] The shape of the positive electrode active material (a) particles is not particularly limited, and examples include spherical (e.g., true spherical, ellipsoidal, etc.), fibrous, and the like. In the present disclosure, "spherical" refers to particles with an aspect ratio of 0.1 to 10, and "fibrous" refers to particles with an aspect ratio exceeding 10. When the shape of the positive electrode active material (a) particles is spherical, the median diameter of the positive electrode active material (a) is preferably 0.05 μm to 50 μm, more preferably 0.1 μm to 20 μm. The measurement method of the median diameter of the positive electrode active material (a) is the same as the measurement method described in the examples.

[0025] (1.1.2) Conductive aid (b) Examples of the conductive aid (b) include carbon materials, metal materials, and conductive polymer materials. Examples of the carbon materials include carbon black (e.g., acetylene black, furnace black, ketjen black, etc.), fibrous carbon (e.g., vapor-phase carbon fiber, carbon nanotube, carbon nanofiber, etc.), graphite, carbon fluoride, and the like. Examples of the metal materials include metal powder (e.g., aluminum powder, etc.), conductive whiskers (e.g., zinc oxide, potassium titanate, etc.), conductive metal oxides (e.g., titanium oxide, etc.), and the like. Examples of the conductive polymer materials include polyaniline, polypyrrole, polythiophene, and the like. The conductive aid (b) may be used alone as only one kind, or two or more kinds may be mixed and used.

[0026] The shape and size of the conductive additive (b) particles are not particularly limited. Examples of the shape of the conductive additive (b) particles include spherical (e.g., spherical, oval, etc.), fibrous, etc. The conductive additive (b) particles are preferably spherical. When the conductive additive (b) particles have a particulate shape, the entire surface of one positive electrode active material (a) particle is easily covered with multiple conductive additive (b) particles.

[0027] When the conductive additive (b) particles are spherical, the median diameter of the conductive additive (b) is preferably smaller than the median diameter of the positive electrode active material (a). The median diameter of the conductive additive (b) is preferably 0.1 times or less, more preferably 0.02 times or less, the median diameter of the positive electrode active material (a). When the median diameter of the conductive additive (b) is 0.1 times or less the median diameter of the positive electrode active material, multiple conductive additive (b) particles tend to cover the entire surface of one positive electrode active material (a) particle. The median diameter of the conductive additive (b) is not particularly limited, but is preferably 5 nm to 1000 nm, more preferably 15 nm to 100 nm. The median diameter of the conductive additive (b) can be measured by the same method as described in the Examples.

[0028] When the conductive assistant (b) particles are fibrous, the conductive assistant (b) particles may have a fiber diameter of 5 nm to 1 μm, and the conductive assistant (b) particles may have an aspect ratio of 20 or more.

[0029] (1.1.3) Solid electrolyte (c) The solid electrolyte (c) contains Li, Ti, X, and F. X is at least one selected from the group consisting of Ca, Mg, Al, Y, and Zr. This provides the solid electrolyte (c) with high lithium ion conductivity and high oxidation resistance.

[0030] The shape of the solid electrolyte (c) particles is not particularly limited, and examples thereof include spherical (for example, circular, elliptical, etc.) and fibrous shapes. When the solid electrolyte (c) particles are spherical, the median diameter of the solid electrolyte (c) is preferably smaller than the median diameter of the positive electrode active material (a). The median diameter of the solid electrolyte (c) is preferably 0.1 times or less, more preferably 0.02 times or less, the median diameter of the positive electrode active material. When the median diameter of the solid electrolyte (c) is 0.1 times or less the median diameter of the positive electrode active material, the plurality of solid electrolyte (c) particles easily cover the entire plurality of conductive additive (b) particles that cover the surface of one positive electrode active material (a) particle. The median diameter of the solid electrolyte (c) is preferably 10 nm to 1000 nm, more preferably 10 nm to 200 nm. The method for measuring the median diameter of the solid electrolyte (c) is the same as the measurement method described in the Examples.

[0031] X more preferably contains Al, and even more preferably is Al. When X contains Al, the lithium conductivity of the solid electrolyte (c) becomes higher than when X does not contain Al. As a result, the positive electrode material can be used to form a solid-state battery with lower resistance.

[0032] When X contains Al, the ratio of the amount of substance of Li to the total amount of substance of Al and Ti may be 1.7 to 4.2.

[0033] When X contains Al, the solid electrolyte (c) preferably contains a material represented by the following composition formula (1), and more preferably consists of a material represented by the following composition formula (1). The material represented by the composition formula (1) may be in a crystalline phase. Formula (1): Li 6-(4-x)b (Ti 1-x M x ) b F6 In formula (1), x is 0 <x<1、bは0<b≦1.5である。 When the solid electrolyte (c) contains a material represented by the following composition formula (1), the lithium conductivity of the solid electrolyte (c) becomes higher, and as a result, the resistance of the solid-state battery becomes lower. In formula (1), X may be in the range of 0.1≦x≦0.9, and b may be in the range of 0.8≦b≦1.2.

[0034] The composition of the solid electrolyte (c) is Li 2.7 Ti 0.3 AI 0.7 Preferably it contains F6, Li 2.7 Ti 0.3 AI 0.7 It is more preferable that the composition of the solid electrolyte (c) is LiF6. 2.7 Ti 0.3 AI 0.7 By including F6, the lithium conductivity of the solid electrolyte (c) is further increased, resulting in a further lower resistance of the solid-state battery.

[0035] (1.2) Sulfide solid electrolyte (B) The positive electrode material contains a sulfide solid electrolyte (B).

[0036] The sulfide solid electrolyte (B) preferably contains sulfur (S) as a main anion element, and more preferably contains, for example, Li, A, and S. The A element is at least one element selected from the group consisting of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In. The sulfide solid electrolyte (B) may further contain at least one of O and a halogen element. Examples of the halogen element (X) include F, Cl, Br, and I. The composition of the sulfide solid electrolyte (B) is not particularly limited, and examples include xLiS·(100-x)P2S5 (70≦x≦80), yLiI·zLiBr·(100-yz)(xLiS·(1-x)P2S5) (0.7≦x≦0.8, 0≦y≦30, 0≦z≦30). The sulfide solid electrolyte (B) may have a composition represented by the following general formula (2). Formula (2): Li 4-x Ge 1-x P x S4(0 <x<1) In formula (2), at least a portion of the Ge may be substituted with at least one selected from the group consisting of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. At least a portion of the P may be substituted with at least one selected from the group consisting of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. At least a portion of the Li may be substituted with at least one selected from the group consisting of Na, K, Mg, Ca, and Zn. At least a portion of the S may be substituted with a halogen. The halogen is at least one of F, Cl, Br, and I.

[0037] The shape of the sulfide solid electrolyte (B) particles is not particularly limited, and examples thereof include spherical (for example, circular, elliptical, etc.) and fibrous shapes. When the sulfide solid electrolyte (B) particles are spherical, the median diameter of the sulfide solid electrolyte (B) is preferably smaller than the median diameter of the positive electrode active material (a). The median diameter of the sulfide solid electrolyte (B) is preferably 0.1 times or less the median diameter of the positive electrode active material. If the median diameter of the sulfide solid electrolyte (B) is 0.1 times or less the median diameter of the positive electrode active material, the initial resistance of the obtained solid battery is further suppressed. The median diameter of the sulfide solid electrolyte (B) is preferably 0.05 μm to 3.0 μm. The method for measuring the median diameter of the sulfide solid electrolyte (B) is the same as the measurement method described in the Examples.

[0038] The blending ratio of the sulfide solid electrolyte (B) is not particularly limited, and is preferably 5 to 70 mass %, more preferably 10 to 45 mass %, relative to the total amount of the positive electrode active material composite (A).

[0039] (1.3) Binder (C) The positive electrode material may or may not contain a binder (C). The binder (C) improves the adhesion between the positive electrode active material composite (A) and the sulfide solid electrolyte (B).

[0040] Examples of the binder (C) include halogenated vinyl resins, rubbers, and polyolefin resins. Examples of halogenated vinyl resins include polyvinylidene fluoride (PVdF) and copolymers of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP). Examples of polyolefin resins include butadiene rubber (BR), acrylate butadiene rubber (ABR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), and butyl rubber (isobutylene-isoprene rubber). Examples of polyolefin resins include polyethylene and polypropylene. The binder (C) may be a diene rubber containing a double bond in the main chain, such as a butadiene rubber in which butadiene accounts for 30 mol % or more of the total.

[0041] When the positive electrode material contains a binder (C), the blending ratio of the binder (C) is not particularly limited and is preferably 0.1 mass % to 20 mass %, more preferably 0.1 mass % to 10 mass %, and even more preferably 0.1 mass % to 5 mass %, relative to the total amount of the positive electrode active material composite (A).

[0042] (1.4) Solvent (D) The positive electrode material may contain a solvent (D) or may not contain a solvent (D). When the positive electrode material contains a solvent (D), the positive electrode material can be in the form of a slurry. The solvent (D) may be any known solvent used in the production of solid-state batteries.

[0043] (1.5) Other ingredients (E) The positive electrode material may or may not contain other components (E), such as oxide solid electrolytes, halide solid electrolytes, thickeners, surfactants, dispersants, wetting agents, and antifoaming agents.

[0044] The positive electrode material may be composed of a positive electrode active material composite (A) and a sulfide solid electrolyte (B). The positive electrode material may be composed of a positive electrode active material composite (A), a sulfide solid electrolyte (B), and a binder (C). The positive electrode material may be composed of a positive electrode active material composite (A), a sulfide solid electrolyte (B), a binder (C), and a solvent (D).

[0045] (2) Solid state battery The solid-state battery of the present disclosure includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer includes the positive electrode material of the present disclosure.

[0046] The solid-state battery according to the present disclosure has the above-described configuration, and therefore the initial resistance is suppressed and the resistance is unlikely to increase even with repeated charge and discharge. This effect is presumed to be due to, but not limited to, the same reasons as those of the positive electrode material according to the present disclosure described above.

[0047] (2.1)Battery structure Solid-state batteries include so-called all-solid-state batteries (in which the electrolyte inside the battery is entirely solid) that use an inorganic solid electrolyte as the electrolyte. The structure of the solid-state battery of the present disclosure may include a positive electrode current collector, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode current collector in this order, for example, as shown in FIG. 1. The solid electrolyte layer B in FIG. 1 may have a two-layer structure. FIG. 1 is a schematic cross-sectional view showing an example of a solid-state battery. The solid-state battery shown in FIG. 1 includes an anode including a negative electrode current collector 113 and a negative electrode layer A, and a positive electrode including a solid electrolyte layer B, a positive electrode current collector 115, and a positive electrode layer C. The negative electrode layer A includes a negative electrode active material 101, a conductive additive 105, a binder 109, and a solid electrolyte 102. The positive electrode layer C includes a positive electrode active material composite 103, a binder 111, and a solid electrolyte 102.

[0048] When a set of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer is defined as a power generation unit, the solid-state battery may have only one power generation unit or may have two or more power generation units. When the solid-state battery has two or more power generation units, the power generation units may be connected in series or in parallel.

[0049] The solid-state battery may be configured by sealing the end faces (side faces) of the stacked structure of the positive electrode layer / solid electrolyte layer / negative electrode layer with resin. The electrode current collector may have a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on the surface. The shape of the solid-state battery is not particularly limited, and may be, for example, a coin type, a cylindrical type, a square type, a sheet type, a button type, a flat type, or a laminate type.

[0050] (2.2) Solid electrolyte layer The solid-state battery includes a solid electrolyte layer, which preferably includes one selected from the group consisting of a sulfide solid electrolyte, an oxide solid electrolyte, and a halide solid electrolyte.

[0051] Examples of the sulfide solid electrolyte include those exemplified as the sulfide solid electrolyte (B). The sulfide solid electrolyte contained in the solid electrolyte layer may be the same as or different from the sulfide solid electrolyte (B).

[0052] The oxide solid electrolyte preferably contains oxygen (O) as the main anion element, and may contain, for example, Li, Q element (Q represents at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, and S), and O. Examples of the oxide solid electrolyte include garnet-type solid electrolytes, perovskite-type solid electrolytes, Nasicon-type solid electrolytes, Li-PO-based solid electrolytes, and Li-BO-based solid electrolytes. Examples of the garnet-type solid electrolyte include Li7La3Zr2O 12 , Li 7-x La3(Zr 2-x Nb x )O 12 (0≦x≦2), Li5La3Nb2O 12Examples include the following. Examples of perovskite-type solid electrolytes include, for example, (Li, La)TiO3, (Li, La)NbO3, (Li, Sr)(Ta, Zr)O3, etc. Examples of NASICON-type solid electrolytes include, for example, Li(Al, Ti)(PO4)3, Li(Al, Ga)(PO4)3, etc. Examples of Li-P-O-based solid electrolytes include Li3PO4, LIPON (a compound in which part of the O in Li3PO4 is replaced by N), and examples of Li-B-O-based solid electrolytes include Li3BO3, a compound in which part of the O in Li3BO3 is replaced by C, etc.

[0053] As the halide solid electrolyte, a solid electrolyte containing Li, M, and X (M represents at least one of Ti, Al, and Y, and X represents F, Cl, or Br) is suitable. Specifically, Li 6-3z Y z X6 (X represents Cl or Br, and z satisfies 0 < z < 2), Li 6-(4-x)b (Ti 1-x Al x ) b F6 (0 < x < 1, 0 < b ≤ 1.5) is preferred. Among Li 6-3z Y z X6, Li3YX6 (X represents Cl or Br) is more preferred in terms of excellent lithium ion conductivity, and further Li3YCl6 is preferred. Also, Li 6-(4-x)b (Ti 1-x Al x ) b F6 (0 < x < 1, 0 < b ≤ 1.5) is preferably included together with a solid electrolyte such as a sulfide solid electrolyte, for example, from the viewpoint of suppressing the oxidative decomposition of the sulfide solid electrolyte.

[0054] The solid electrolyte layer may have a single-layer structure or a multilayer structure of two or more layers.

[0055] The solid electrolyte layer may contain a binder or may not contain a binder. Examples of the binder that can be included in the solid electrolyte layer are the same as those exemplified as the binder (C).

[0056] (2.3) Positive electrode layer The solid-state battery includes a positive electrode layer, which includes the positive electrode material of the present disclosure.

[0057] (2.4) Positive electrode current collector The solid-state battery may further include a positive electrode current collector that collects current from the positive electrode layer and is disposed on the opposite side of the positive electrode layer from the solid electrolyte layer. The positive electrode current collector may be made of, for example, stainless steel, aluminum, copper, nickel, iron, titanium, or carbon, and is preferably an aluminum alloy foil or aluminum foil. The aluminum alloy foil or aluminum foil may be manufactured using powder. The positive electrode current collector may be, for example, in the form of a foil or a mesh. The positive electrode current collector may have a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on the surface thereof.

[0058] (2.5) Negative electrode layer The solid-state battery includes a negative electrode layer. The negative electrode layer contains a negative electrode active material. The negative electrode layer may contain at least one of a negative electrode solid electrolyte, a conductive additive, and a binder, as needed. Examples of the negative electrode active material include Li-based active materials such as metallic lithium, carbon-based active materials such as graphite, oxide-based active materials such as lithium titanate, and Si-based active materials such as elemental Si. Examples of the conductive additive, negative electrode solid electrolyte, and binder used in the negative electrode layer include the same conductive additive, solid electrolyte, and binder (C) as those exemplified in the positive electrode layer and the solid electrolyte and binder (C) contained in the solid electrolyte layer.

[0059] (2.6) Negative electrode current collector The solid-state battery may further include a negative electrode current collector that collects current from the negative electrode layer and is disposed on the opposite side of the negative electrode layer from the solid electrolyte layer. The negative electrode current collector may be made of, for example, stainless steel, aluminum, copper, nickel, iron, titanium, or carbon, with copper being preferred. The negative electrode current collector may be in the form of, for example, a foil or mesh. The negative electrode current collector may have a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on the surface thereof.

[0060] (3) Manufacturing method of positive electrode material The method for producing a positive electrode material of the present disclosure includes coating with a conductive additive (b) (hereinafter also referred to as the "first coating step"), preparing a positive electrode active material composite (A) (hereinafter also referred to as the "second coating step"), and kneading the positive electrode active material composite (A) with a sulfide solid electrolyte (B) (hereinafter also referred to as the "kneading step"). The first coating step, the second coating step, and the kneading step are performed in this order. This results in the positive electrode material of the present disclosure.

[0061] (3.1) First coating process In the first coating step, at least a portion of the surface of each of the positive electrode active materials (a) is coated with a conductive additive (b). This results in a conductive additive-coated positive electrode active material. The conductive additive-coated positive electrode active material includes a plurality of conductive additive-coated positive electrode active material particles. Each conductive additive-coated positive electrode active material particle has one positive electrode active material (a) particle and a plurality of conductive additive (b) particles that coat at least a portion of the surface of one positive electrode active material (a) particle.

[0062] The positive electrode active material (a) in the first coating step may be the same as the positive electrode active material (a) in the positive electrode material. The conductive additive (b) in the first coating step may be the same as the conductive additive (b) in the positive electrode material.

[0063] The method for coating at least a portion of the surface of each of the positive electrode active materials (a) with the conductive additive (b) (hereinafter also referred to as the "first coating method") is not particularly limited, and examples thereof include a method of mixing two materials in a mortar, a method of applying shear force to two materials using a rotating blade, a method of colliding two materials with a jet stream, a physical vapor deposition method (e.g., vacuum deposition, ion plating, sputtering, etc.), a chemical vapor deposition method (e.g., thermal CVD (Chemical Vapor Deposition), plasma CVD, plasma CVD, etc.), a sol-gel method, etc.

[0064] (3.2) Second coating process In the second coating step, at least a part of the conductive additive (b) contained in the conductive additive-containing positive electrode active material is coated with the solid electrolyte (c) to produce a positive electrode active material composite (A).

[0065] The solid electrolyte (c) in the second coating step may be the same as those exemplified as the solid electrolyte (c) of the positive electrode material. That is, the solid electrolyte (c) in the second coating step contains Li, Ti, X, and F. X is at least one selected from the group consisting of Ca, Mg, Al, Y, and Zr.

[0066] X more preferably contains Al, and even more preferably is Al. When X contains Al, the lithium conductivity of the solid electrolyte (c) becomes higher than when X does not contain Al. As a result, a solid-state battery with lower resistance is obtained.

[0067] The method for coating at least a portion of the conductive additive (b) contained in the conductive additive-added positive electrode active material with the solid electrolyte (c) (hereinafter also referred to as the "second coating method") is not particularly limited, and may be the same as the method exemplified as the first coating method. The second coating method may be the same as or different from the first coating method.

[0068] (3.3) Mixing process In the kneading step, the positive electrode active material composite (A) and the sulfide solid electrolyte (B) are kneaded together to obtain a positive electrode material.

[0069] Examples of the sulfide solid electrolyte (B) in the kneading step include the same as those exemplified as the sulfide solid electrolyte (B) of the positive electrode material. When the positive electrode active material composite (A) and the sulfide solid electrolyte (B) are kneaded together, the above-mentioned binder (C), solvent (D) and other components (E) may be added as needed.

[0070] The method for kneading the positive electrode active material composite (A) and the sulfide solid electrolyte (B) is not particularly limited, and examples thereof include a method of kneading using a kneading device, such as an ultrasonic homogenizer, a shaker, a thin film rotary mixer, a dissolver, a homomixer, a kneader, a roll mill, a sand mill, an attritor, a ball mill, a vibrator mill, or a high-speed impeller mill.

[0071] (4) Manufacturing method of solid-state battery The method for producing a solid-state battery according to the present disclosure includes a step of preparing a positive electrode material by the method for producing a positive electrode material according to the present disclosure (hereinafter also referred to as a "first preparation step"), thereby obtaining the solid-state battery according to the present disclosure.

[0072] The method for manufacturing a solid-state battery according to the present disclosure may include a first preparation step, preparing a material for a negative electrode layer (hereinafter also referred to as a "second preparation step"), preparing a material for a solid electrolyte layer (hereinafter also referred to as a "third preparation step"), and fabricating a solid-state battery (hereinafter also referred to as a "lamination step"). The first preparation step, the second preparation step, and the third preparation step are performed before the lamination step is performed. The order in which the first preparation step, the second preparation step, and the third preparation step are performed is not particularly limited.

[0073] (4.1) First preparation step The first preparation step is a step of preparing a positive electrode material by the method for producing a positive electrode material of the present disclosure, thereby obtaining the positive electrode material of the present disclosure.

[0074] (4.2) Second preparation process In the second preparation step, a material for the negative electrode layer is prepared. Examples of the material for the negative electrode layer include those exemplified as materials for the negative electrode layer of the solid-state battery. The method for preparing the material for the negative electrode layer may be a known method.

[0075] (4.3) Third preparation step In the third preparation step, a material for a solid electrolyte layer is prepared. Examples of the material for a solid electrolyte layer include those exemplified as materials for the solid electrolyte layer of a solid-state battery. The method for preparing the material for a solid electrolyte layer may be a known method.

[0076] (4.4) Lamination process In the lamination step, a solid-state battery is fabricated having a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in this order. The positive electrode layer is formed using the positive electrode material of the present disclosure. The solid electrolyte layer is formed using a material for the solid electrolyte layer. The negative electrode layer is formed using a material for the negative electrode layer.

[0077] A method for producing a solid-state battery includes, for example, a pressing method. The order in which the positive electrode layer, solid electrolyte layer, and negative electrode layer are formed is not particularly limited. For example, a solid electrolyte layer may be formed by pressing, and then a positive electrode layer may be formed by pressing on one surface side of the solid electrolyte layer, and then a negative electrode layer may be formed by pressing on the other surface side of the solid electrolyte layer. Two or more layers, i.e., a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, may be formed simultaneously by pressing. A slurry may be used when forming the positive electrode layer, the solid electrolyte layer, and the negative electrode layer. Examples of pressing methods include roll pressing and cold isostatic pressing (CIP).

[0078] The pressure during pressing is preferably 0.1 t / cm 2 More than 0.5t / cm 2 More preferably, 1 t / cm 2 The pressure during pressing is preferably 10 t / cm 2 Less than 8t / cm, preferably 8t / cm 2 Less than 6t / cm, more preferably 2 The following is the result. [Example]

[0079] The present disclosure will be described in more detail below with reference to examples, but the invention of the present disclosure is not limited to these examples.

[0080] [1] Example 1 [1.1] Preparation process The following positive electrode active material (a1), conductive additive (b1), solid electrolyte (c1) (hereinafter also referred to as "LTAF (c1)"), sulfide solid electrolyte (B1), and binder (C1) were prepared.

[0081] [1.1.1] Positive electrode active material (a1) As the positive electrode active material (a1), a powder containing a plurality of core-shell type composite particles (median diameter: 5 μm, density: 4.7 g / cm 3 ) were prepared. The core-shell composite particles had a core made of Li(Ni, Co, Al)O2 and a shell made of LiNbO3. The median diameter of the positive electrode active material (a1) was measured using a laser diffraction particle size distribution analyzer (Shimadzu Corporation, "SALD-2000"). Specifically, the positive electrode active material (a1) was dispersed in a dispersion medium, and the volume-based particle size distribution was measured using the particle size distribution analyzer. The particle size corresponding to 50% of the obtained volume-based cumulative particle size distribution value was taken as the median diameter.

[0082] [1.1.2] Conductive additive (b1) As the conductive additive (b1), a powder consisting of a plurality of acetylene black particles ("Li-435" manufactured by Denka Co., Ltd., average particle size: 23 nm, density: 2.1 g / cm 3 ) was prepared.

[0083] [1.1.3] Solid electrolyte (c1) In a glove box purged with argon gas, LiF, TiF4, and AIF3 were placed in a container in a molar ratio (LiF:TiF4:AIF3) of 2.7:0.3:0.7 to obtain a raw material powder. Next, the raw material powder was milled using a planetary ball mill for 12 hours at a rotation speed of 500 rpm. As a result, a powder consisting of multiple solid electrolyte particles (median diameter: 10 nm to 100 nm, density: 2.7 g / cm3) was obtained as the solid electrolyte (c1). 3 The composition of the solid electrolyte particles was Li 2.7 Ti 0.3 AI 0.7 The median diameter of the solid electrolyte (c1) was calculated by measuring the diameters of multiple solid electrolyte particles using a scanning electron microscope (SEM) image.

[0084] [1.1.4] Sulfide solid electrolyte (B1) As the sulfide solid electrolyte (B1), a powder consisting of multiple LiI-LiBr-LiS-P2S5-based glass ceramic particles (median diameter: 1.0 μm, density: 2.2 g / cm3) was used. 3 The median diameter of the sulfide solid electrolyte (B1) was calculated by measuring the diameters of multiple glass ceramic particles using an SEM image.

[0085] [1.1.5] Binder (C1) As the binder (C1), a butadiene rubber binder (density: 0.9 g / cm 3 ) was dissolved in a dispersion medium (D1) to prepare a solution. The content of the butadiene rubber binder was 5 mass % with respect to the total amount of the solution.

[0086] [1.2] First coating process The positive electrode active material (a1) and the conductive additive (b1) were placed in an agate mortar and kneaded to a mass ratio of positive electrode active material (a1):conductive additive (b1) = 99.5:0.5, thereby obtaining a powder of a plurality of conductive additive-containing positive electrode active material particles as the conductive additive-containing positive electrode active material.

[0087] [1.3] SEM analysis An SEM image (magnification: 30,000 times) of the positive electrode active material particles with conductive additive is shown in Figure 2. A scanning electron microscope (SEM) (Regulus8230 manufactured by Meritachi High-Tech Co., Ltd.) was used to take the SEM image. The accelerating voltage was 1 kV. From the SEM images, it was confirmed that the conductive additive (b1) covered most of the surface of the positive electrode active material (a1). In particular, as shown in Figure 2, it was found that a large amount of the conductive additive (b1) was present in the recesses on the surface of the positive electrode active material (a1).

[0088] [1.4] Second coating process The conductive additive-containing positive electrode active material and LTAF (c1) were placed in a container together with a plurality of zirconia balls (diameter: 3 mm) so that the mass ratio (conductive additive-containing positive electrode active material:LTAF (c1)) was 94:6, to obtain a mixture. The mixture was then kneaded for 6 minutes at a rotation speed of 1200 rpm using a planetary centrifugal mixer (Thinky Corporation, "ARE-310"). This resulted in a powder composed of a plurality of positive electrode active material composite (A1) particles, which served as the positive electrode active material composite (A1).

[0089] [1.5]SEM-EDS surface elemental analysis SEM-EDS images of the same location of the positive electrode active material composite (A1) are shown in Figures 3 to 6. Figure 3 shows the results of mapping in which the C component (corresponding to the conductive additive (b1)), the F component (corresponding to the LTAF (c1)), and the Ni component (corresponding to the positive electrode active material (a1)) are superimposed. Figure 4 shows the results of mapping the C component (corresponding to the conductive additive (b1)). Figure 5 shows the results of mapping the F component (corresponding to the LTAF (c1)). Figure 6 shows the results of mapping the Ni component (corresponding to the positive electrode active material (a1)). In Figures 4 to 6, the light-colored areas indicate the areas coated with the C component, the F component, or the Ni component, respectively. 3 to 6, it was found that the conductive additive (b1) and the solid electrolyte (b1) were uniformly present on the entire surface of the positive electrode active material (a1). In other words, it was found that one positive electrode active material composite (A1) particle has one positive electrode active material (a1) particle, a plurality of conductive additive (b1) particles that cover most of the surface of one positive electrode active material (a1) particle, and a plurality of LTAF (c1) particles that cover almost the entirety of the plurality of conductive additive (b1) particles.

[0090] [1.6] Mixing process The positive electrode active material composite (A1), the sulfide solid electrolyte (B1), and the binder (C1) were weighed out so that the mass ratio (positive electrode active material composite (A1): sulfide solid electrolyte (B1): binder (C1)) was 83.8:15.8:0.4. A dispersion medium (D1) was added to these and kneaded. This resulted in the production of a positive electrode mixture slurry as a positive electrode material.

[0091] [2] Comparative Example 1 [2.1] First coating process The first coating step was not performed.

[0092] [2.2] Second coating process A positive electrode active material composite (X1) was obtained in the same manner as in the second coating step of Example 1, except that a positive electrode active material (a1) was used instead of the positive electrode active material with a conductive additive. The positive electrode active material composite (X1) is composed of a plurality of positive electrode active material composite (X1) particles. One positive electrode active material composite (X1) particle is composed of one positive electrode active material (a1) particle and a plurality of LTAF (c1) particles that coat almost the entire surface of one positive electrode active material (a1) particle.

[0093] [2.3] Mixing process The positive electrode active material composite (X1), the sulfide solid electrolyte (B1), and the binder (C1) were weighed out so that the mass ratio (positive electrode active material composite (X1): sulfide solid electrolyte (B1): binder (C1)) was 83.8:15.8:0.4. A dispersion medium (D1) was added to these and kneaded. This resulted in the production of a positive electrode mixture slurry as a positive electrode material.

[0094] [3] Comparative Example 2 [3.1] First coating process and second coating process In the same manner as in Comparative Example 1, a positive electrode active material composite (X1) was obtained.

[0095] [3.2] Mixing process The positive electrode active material composite (X1), sulfide solid electrolyte (B1), binder (C1), and conductive additive (b1) were weighed out so that the mass ratio (positive electrode active material composite (X1): sulfide solid electrolyte (B1): binder (C1): conductive additive (b1)) was 83.4:15.8:0.4:0.4, and the mixture was kneaded with the addition of a dispersion medium (D1). This produced a positive electrode mixture slurry as a positive electrode material.

[0096] [4] Comparative Example 3 [4.1] First coating process The first powder was obtained in the same manner as in the first coating step of Example 1.

[0097] [4.2] Second coating process A cathode active material composite (X2) was obtained in the same manner as in the second coating step of Example 1, except that the cathode active material with conductive additive and the sulfide solid electrolyte (B1) were placed in a container together with a plurality of zirconia balls (diameter: 3 mm) so that the mass ratio (cathode active material with conductive additive:sulfide solid electrolyte (B1)) was 95:5. The cathode active material composite (X2) was composed of a plurality of cathode active material composite (X2) particles. One cathode active material composite (X2) particle was composed of one cathode active material (a1) particle, a plurality of conductive additive (b1) particles coating most of the surface of the cathode active material (a1) particle, and a plurality of sulfide solid electrolyte (B1) particles coating almost the entire surfaces of the plurality of conductive additive (b1) particles.

[0098] [4.3] Mixing process The positive electrode active material composite (X2), the sulfide solid electrolyte (B1), and the binder (C1) were weighed out so that the mass ratio (positive electrode active material composite (X2):sulfide solid electrolyte (B1):binder (C1)) was 83.7:15.9:0.4, and the dispersion medium (D1) was added and kneaded. As a result, a positive electrode mixture slurry was obtained as a positive electrode material.

[0099] [5] Evaluation Using the positive electrode materials of Example 1 and Comparative Examples 1 to 3, evaluation batteries were fabricated as follows, and the initial resistance and the rate of increase in resistance were evaluated. The evaluation results are shown in Table 1.

[0100] [5.1] Evaluation battery [5.1.1] Positive electrode The positive electrode mixture slurry (positive electrode material) was applied onto a current collector foil and dried at 100°C to obtain a positive electrode. The positive electrode consisted of a current collector foil and a positive electrode mixture layer formed on the current collector foil. The thickness of the positive electrode mixture layer was determined so that the discharge capacity was 2 mAh / cm in the measurement of the initial battery capacity described later. 2 It was adjusted to be.

[0101] [5.1.2] Negative electrode As the negative electrode active material, multiple Li4Ti50 12 Powder consisting of particles (median diameter: 1.1 μm, density: 3.5 g / cm 3 The method for measuring the median diameter of the negative electrode active material was the same as the method for measuring the median diameter of the positive electrode active material. A solution was prepared by dissolving a butadiene rubber binder in a dispersion medium in advance as a binder. The content of the butadiene rubber binder was 1.5% by mass relative to the total amount of the solution. As a conductive additive, carbon fiber ("VGCF-H" manufactured by Showa Denko K.K., average fiber diameter: 0.15 μm, average fiber length: 6 μm, density: 2.1 g / cm) was used. 3 ) was prepared.

[0102] The negative electrode active material, sulfide solid electrolyte, binder, and conductive additive were weighed out so that the mass ratio (negative electrode active material: sulfide solid electrolyte: binder: conductive additive) was 73.8:24.8:0.6:0.8. A dispersion medium (D1) was added to these and kneaded. This produced a negative electrode mixture slurry.

[0103] The negative electrode mixture slurry was applied to a current collector foil and dried at 100°C to obtain a negative electrode. The negative electrode consisted of a current collector foil and a negative electrode mixture layer formed on the current collector foil. The thickness of the negative electrode mixture layer was adjusted so that the first capacity per unit area of the negative electrode was 1.15 times the second capacity per unit area of the positive electrode. The "first capacity per unit area of the negative electrode" refers to the capacity per unit area of the negative electrode when the specific capacity of the negative electrode active material is 175 mAh / g. The "second capacity per unit area of the positive electrode" refers to the initial charge capacity in the initial battery capacity measurement described below.

[0104] [5.1.3] Solid electrolyte layer The solid electrolyte was LiI-LiBr-LiS-P2S5 glass ceramic particles (median diameter: 2.5 μm, density: 2.2 g / cm 3 The median diameter was calculated by measuring the diameter of the solid electrolyte from a scanning electron microscope image of the particles. The solid electrolyte had a median diameter different from that of the sulfide solid electrolyte (B1). A butadiene rubber binder was prepared as a binder by dissolving it in a dispersion medium in advance and using it as a 5% by mass solution.

[0105] The solid electrolyte and the butadiene rubber binder were weighed out so that the mass ratio (solid electrolyte:butadiene rubber binder) was 99.6:0.4, and the dispersion medium (D1) was added thereto and kneaded to obtain a solid electrolyte slurry.

[0106] [5.1.4] Positive electrode laminate The surface of the positive electrode mixture layer was coated with solid electrolyte slurry, dried at 100°C, and then coated with a 2 ton / cm 2 The positive electrode side laminate was obtained by roll pressing at 800° C. The positive electrode side laminate included a positive electrode and a solid electrolyte layer formed on the surface of the positive electrode.

[0107] [5.1.5] Negative electrode laminate The surface of the negative electrode mixture layer was coated with solid electrolyte slurry, dried at 100°C, and then coated with a 2 ton / cm 2The negative electrode side laminate was obtained by roll pressing at 1000 kJ / cm2 at 1000 kJ / cm2. The negative electrode side laminate was provided with a negative electrode and a solid electrolyte layer formed on the surface of the negative electrode.

[0108] 5.1.6 Assembly The positive electrode side laminate and the negative electrode side laminate were each punched. The positive electrode side laminate, an unpressed solid electrolyte layer (the same as the solid electrolyte layer described above), and the negative electrode side laminate were stacked in this order to obtain a laminate. In the laminate, the unpressed solid electrolyte layer was interposed between the solid electrolyte layer of the positive electrode side laminate and the solid electrolyte layer of the negative electrode side laminate. 2 ton / cm at 130℃ 2 The laminate was pressed at 1000 kJ / cm2 to obtain a power generating element. The power generating element had a positive electrode, a solid electrolyte layer formed on the positive electrode, and a negative electrode formed on the solid electrolyte layer. The obtained power generating element was sealed with a laminate and restrained at 0.5 MPa. This resulted in an all-solid-state battery for evaluation.

[0109] [5.2] Measurement of initial resistance The battery was placed in a thermostatic chamber at 25° C. Then, the battery was charged and then discharged (hereinafter also referred to as a "charge-discharge cycle") twice. The battery was charged at a constant current of 1 / 3 C until the battery voltage reached 2.7 V, then at a constant voltage, and was terminated when the charging current reached 0.01 C. The charging rate was set at the design capacity of the battery (capacity per unit area of the positive electrode: 2 mAh / cm). 2 ) was calculated. The battery was discharged at a constant current of 1 / 3C rate until the battery voltage reached 1.5V, and then at a constant voltage, which was terminated when the discharge current reached the equivalent of 0.01C.

[0110] The battery was placed in a thermostatic chamber at 25° C. After charging until the battery voltage reached 2.2 V, the AC impedance of the battery was measured and the battery was discharged. The battery was charged at a constant current of 1 / 3C rate until the battery voltage reached 2.7V, and then at a constant voltage, and was terminated when the charging current reached the equivalent of 0.01C. The AC impedance measurements were performed at an AC amplitude of 10 mV and in the frequency range of 1 MHz to 0.1 Hz. A curve was obtained by circular fitting the waveform of the circular arc portion appearing in the Nyquist diagram obtained from the AC impedance measurements. The difference between the x-axis intercepts on the high-frequency side and the low-frequency side of the obtained curve was taken as the initial resistance. The battery was discharged at a constant current of 1 / 3C rate until the battery voltage reached 1.5V, and then at a constant voltage, until the discharge current reached the equivalent of 0.01C.

[0111] [5.3] Measurement of the rate of increase in resistance The battery was placed in a thermostatic chamber at 60° C. and subjected to a cycle test in which charge / discharge cycles were repeated 150 times. The battery was charged at a constant current of 5C until the battery voltage reached 2.7V, and then at a constant voltage, and was terminated when the charging current reached 1 / 3C. The current was discharged at a constant current of 1C until the battery voltage reached 1.8V.

[0112] The battery was placed in a thermostatic chamber at 25° C. and charged until the battery voltage reached 2.2 V, after which the AC impedance of the battery was measured. The battery was charged at a constant current of 1 / 3C until the battery voltage reached 2.7V, and then at a constant voltage, and was terminated when the charging current reached the equivalent of 0.01C. The AC impedance measurements were performed at an AC amplitude of 10 mV and in the frequency range of 1 MHz to 0.1 Hz. The arc-shaped waveforms appearing in the Nyquist diagram obtained from the AC impedance measurements were circularly fitted to obtain a curve. The difference between the x-axis intercepts on the high-frequency and low-frequency sides of the obtained curve was taken as the resistance after the cycle test. The resistance increase rate was calculated by dividing the resistance after the cycle test by the initial resistance.

[0113] [Table 1]

[0114] In Table 1, "a1 / b1 / LTAF(c1)" denotes a cathode active material composite (A1) having a cathode active material (a1), a conductive additive (b1) that coats the entire surface of the cathode active material (a1), and LTAF (c1) that coats the entire surface of the conductive additive (b1). "LTAF(c1)" denotes a solid electrolyte composed of Li, Ti, Al, and F. "a1 / LTAF(c1)" denotes a cathode active material composite (X1) having a cathode active material (a1) and LTAF (c1) that coats the entire surface of the cathode active material (a1). "a1 / b1 / B1" denotes a cathode active material composite (X2) having a cathode active material (a1), a conductive additive (b1) that coats the entire surface of the cathode active material (a1), and a sulfide solid electrolyte (B1) that coats the entire surface of the conductive additive (b1).

[0115] The positive electrode materials of Comparative Examples 1 to 3 did not contain the positive electrode active material composite (A). Therefore, in Comparative Example 1, the measurement result of the initial resistance was higher than that of Example 1. In Comparative Example 2, the measurement result of the initial resistance was higher than that of Example 1, and the measurement result of the resistance increase rate was also higher than that of Example 1. In Comparative Example 3, the measurement result of the resistance increase rate was higher than that of Example 1. In other words, it was found that the evaluation batteries of Comparative Examples 1 to 3 were not batteries in which the initial resistance was suppressed and the resistance was not resistant to increase even with repeated charge and discharge. As a result, it was found that the positive electrode materials of Comparative Examples 1 to 3 could not be used to form solid state batteries in which the initial resistance was suppressed and the resistance was not resistant to increase even with repeated charge and discharge.

[0116] The positive electrode material of Example 1 contains a positive electrode active material composite (A1) and a sulfide solid electrolyte (B1). The positive electrode active material composite (A1) includes a positive electrode active material (a1), a conductive additive (b1) that coats the entire surface of the positive electrode active material (a1), and an LTAF (c) that coats the entire conductive additive (b1). The LTAF (c) contains Li, Ti, Al, and F. Therefore, the initial resistance of Example 1 is 5.0 Ω, which is smaller than those of Comparative Examples 1 and 2. Furthermore, the resistance increase rate of Example 1 is 0%, which is smaller than those of Comparative Examples 2 and 3. In other words, it was found that the evaluation battery of Example 1 is a battery in which the initial resistance is suppressed and the resistance does not increase easily even with repeated charge and discharge. As a result, it was found that the positive electrode material of Example 1 can be used to form a solid battery in which the initial resistance is suppressed and the resistance does not increase easily even with repeated charge and discharge. [Explanation of symbols]

[0117] A negative electrode active material layer B Solid electrolyte layer C positive electrode active material layer 101 Negative electrode active material 102 Solid electrolyte 103 Cathode active material composite 105 Conductive additives 109,111 binders 113 Negative electrode current collector 115 Positive electrode current collector

Claims

1. Contains a positive electrode active material composite (A) and a sulfide solid electrolyte (B), The positive electrode active material composite (A) is Positive electrode active material (a) particles; Particles of a conductive additive (b) that coat at least a portion of the surface of the particles of the positive electrode active material (a); solid electrolyte (c) particles that cover at least a portion of the surface of the conductive additive (b) particles; and the solid electrolyte (c) particles contain Li, Ti, X, and F; The positive electrode material, wherein X is at least one selected from the group consisting of Ca, Mg, Al, Y, and Zr.

2. 2. The cathode material of claim 1, wherein X comprises Al.

3. the conductive additive (b) particles cover the entire surfaces of the positive electrode active material (a) particles, 2. The positive electrode material according to claim 1, wherein the solid electrolyte (c) particles cover the entire surfaces of the conductive additive (b) particles.

4. a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; A solid-state battery, wherein the positive electrode layer comprises the positive electrode material according to any one of claims 1 to 3.

5. coating at least a portion of the surface of particles of a positive electrode active material (a) with particles of a conductive additive (b); preparing a positive electrode active material composite (A) by coating at least a portion of the surface of the conductive additive (b) particles with solid electrolyte (c) particles; kneading the positive electrode active material composite (A) and a sulfide solid electrolyte (B); Including, the solid electrolyte (c) particles contain Li, Ti, X, and F; The method for producing a positive electrode material, wherein X is at least one selected from the group consisting of Ca, Mg, Al, Y, and Zr.

6. The method for producing a positive electrode material according to claim 5 , wherein X comprises Al.

7. A method for producing a solid-state battery, comprising the step of producing a positive electrode material by the method for producing a positive electrode material according to claim 5 or 6.

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