JP7567508B2 - Positive electrode for all-solid-state battery, all-solid-state battery, and method for producing positive electrode for all-solid-state battery - Google Patents

Description

The present invention relates to a positive electrode for an all-solid-state battery, an all-solid-state battery, and a method for manufacturing a positive electrode for an all-solid-state battery.

Lithium ion secondary batteries, due to their high energy density, are widely used in electronic devices such as personal computers and communication terminals, as well as automobiles. The lithium ion secondary battery generally has a pair of electrodes electrically isolated by a separator and a non-aqueous electrolyte interposed between the electrodes, and is configured to charge and discharge by transferring lithium ions between the electrodes. In addition to lithium ion secondary batteries, capacitors such as lithium ion capacitors are also widely used as all-solid-state batteries.

In recent years, in order to improve the safety of non-aqueous electrolyte secondary batteries, all-solid-state batteries have been proposed that use sulfide solid electrolytes as the non-aqueous electrolyte instead of liquid electrolytes such as organic solvents (see Patent Document 1).

JP 2000-340257 A

However, for all-solid-state batteries used in hybrid electric vehicles (hereinafter also referred to as "HEVs") and hybrid industrial machinery (heavy machinery, construction machinery, etc.), there is a demand for improved suppression of the decrease in capacity retention rate after charge-discharge cycles.

The present invention was made based on the above circumstances, and aims to provide a positive electrode for an all-solid-state battery that can suppress the decrease in the capacity retention rate after charge-discharge cycles of the all-solid-state battery.

The positive electrode for an all-solid-state battery according to one aspect of the present invention comprises a positive electrode substrate and a positive electrode mixture layer, the positive electrode mixture layer having a matrix mainly composed of a first sulfide-based solid electrolyte and a positive electrode active material composite dispersed in the matrix, the positive electrode active material composite containing positive electrode active material particles and a second sulfide-based solid electrolyte that directly or indirectly covers at least a portion of the surface of the positive electrode active material particles, and the first sulfide-based solid electrolyte includes a sulfide-based glass solid electrolyte and a sulfide-based crystalline solid electrolyte.

A method for producing a positive electrode for an all-solid-state battery according to another aspect of the present invention includes compounding positive electrode active material particles with a sulfide-based solid electrolyte, and producing a positive electrode mixture containing the positive electrode active material composite obtained by the compounding, a sulfide-based glass solid electrolyte, and a sulfide-based crystalline solid electrolyte.

The positive electrode for an all-solid-state battery according to one aspect of the present invention can suppress the decrease in the capacity retention rate after charge-discharge cycles of the all-solid-state battery.

FIG. 1 is a schematic cross-sectional view of a positive electrode for an all-solid-state battery according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of an all-solid-state battery according to one embodiment of the present invention. FIG. 3 is a schematic diagram showing an electricity storage device formed by assembling a plurality of all-solid-state batteries according to one embodiment of the present invention.

First, an overview of the positive electrode for an all-solid-state battery, the all-solid-state battery, and the method for manufacturing the positive electrode for an all-solid-state battery disclosed in this specification will be provided.

The positive electrode for an all-solid-state battery according to one aspect of the present invention comprises a positive electrode substrate and a positive electrode mixture layer, the positive electrode mixture layer having a matrix mainly composed of a first sulfide-based solid electrolyte and a positive electrode active material composite dispersed in the matrix, the positive electrode active material composite containing positive electrode active material particles and a second sulfide-based solid electrolyte that directly or indirectly covers at least a portion of the surface of the positive electrode active material particles, and the first sulfide-based solid electrolyte includes a sulfide-based glass solid electrolyte and a sulfide-based crystalline solid electrolyte.

The inventors have found that the increase in resistance of an all-solid-state battery accompanying charge-discharge cycles can be suppressed by using a composite of a cathode active material particle and a sulfide-based solid electrolyte, in which at least a portion of the surface of the cathode active material particle is directly or indirectly coated with a specific sulfide-based solid electrolyte. The inventors have come up with the present invention, thinking that the decrease in the capacity retention rate of an all-solid-state battery after charge-discharge cycles can be suppressed by using the above composite in combination with a matrix mainly composed of a specific sulfide-based solid electrolyte as a material for a cathode for an all-solid-state battery. The cathode for an all-solid-state battery can suppress the decrease in the capacity retention rate of an all-solid-state battery after charge-discharge cycles. The reason for this is unclear, but the following reason is presumed. The cathode active material composite is a composite of a cathode active material particle and a second sulfide-based solid electrolyte, and thus a good ion conduction path is formed. Therefore, the ion conductivity at the interface of the cathode active material particles is improved. In addition, since the matrix of the positive electrode mixture layer is mainly composed of a first sulfide-based solid electrolyte that is a combination of a relatively soft sulfide-based glass solid electrolyte and a relatively hard sulfide-based crystalline solid electrolyte, the packing density of the positive electrode mixture can be increased. By increasing the charging density, a good reaction interface is formed, improving the uniformity of the charge/discharge reaction. Therefore, the positive electrode can suppress the decrease in the capacity retention rate after the charge/discharge cycle of the all-solid-state battery.

"Complex" refers to a state in which the positive electrode active material particles and the second sulfide-based solid electrolyte are mechanically combined. The above-mentioned composite is a particle in which the positive electrode active material particles and the second sulfide-based solid electrolyte are present, and means that the positive electrode active material particles and the second sulfide-based solid electrolyte form an aggregated state, and that at least a portion of the surface of the positive electrode active material particles is directly or indirectly covered with the second sulfide-based solid electrolyte. "Main component" means the component with the highest content, for example, a component that is contained in 50 mass% or more of the total mass.

It is preferable that the second sulfide-based solid electrolyte is a sulfide-based crystalline solid electrolyte. By using a sulfide-based crystalline solid electrolyte as the second sulfide-based solid electrolyte, the effect of suppressing the decrease in the capacity retention rate after charge/discharge cycles of the all-solid-state battery can be improved.

It is preferable that the sulfide-based glass solid electrolyte is yLi ₂ S.(1-y)P ₂ S ₅ (where 0.75≦y≦0.77) and the sulfide-based crystalline solid electrolyte has a crystal structure that is cubic, orthorhombic, triclinic, or a combination thereof. By having the sulfide-based glass solid electrolyte be yLi ₂ S.(1-y)P ₂ S ₅ (where 0.75≦y≦0.77) and the sulfide-based crystalline solid electrolyte have a crystal structure that is cubic, orthorhombic, or a combination thereof, the effect of suppressing a decrease in the capacity retention rate after charge-discharge cycles of an all-solid-state battery can be improved.

An all-solid-state battery according to one aspect of the present invention is an all-solid-state battery that includes the positive electrode. Since the all-solid-state battery includes the positive electrode, it is possible to suppress a decrease in the capacity retention rate after charge/discharge cycles.

A method for producing a positive electrode for an all-solid-state battery according to another aspect of the present invention includes compounding positive electrode active material particles with a sulfide-based solid electrolyte, and producing a positive electrode mixture containing the positive electrode active material composite obtained by the compounding, a sulfide-based glass solid electrolyte, and a sulfide-based crystalline solid electrolyte.

The manufacturing method for the positive electrode for an all-solid-state battery includes the above steps, and thus can reliably manufacture a positive electrode for an all-solid-state battery that can suppress a decrease in the capacity retention rate after charge-discharge cycles of the all-solid-state battery.

Here, "composite" means that by applying mechanical energy such as impact, compression, or shear to a mixture of core positive electrode active material particles and sulfide-based solid electrolyte particles that are a different material from the positive electrode active material particles and are smaller than the positive electrode active material particles, at least a portion of the surface of the positive electrode active material particles is directly or indirectly covered with a large number of sulfide-based solid electrolyte particles without using a binder, thereby forming a composite.

The configuration of the positive electrode for an all-solid-state battery according to one embodiment of the present invention, the configuration of the all-solid-state battery, the manufacturing method of the positive electrode for an all-solid-state battery, and other embodiments will be described in detail. Note that the names of the components (each component) used in each embodiment may differ from the names of the components (each component) used in the background art.

<Cathode for all-solid-state batteries>
The positive electrode for an all-solid-state battery according to one embodiment of the present invention includes a positive electrode substrate and a positive electrode mixture layer. In the positive electrode of this embodiment, the positive electrode mixture layer is attached directly to the positive electrode substrate or to an intermediate layer. It is distributed via.

[Positive electrode substrate]
The positive electrode substrate has electrical conductivity. Whether or not the positive electrode substrate has "electrical conductivity" is determined by using a volume resistivity of 107 Ω·cm measured in accordance with JIS-H-0505 (1975) as a threshold value. As the material of the positive electrode substrate, metals such as aluminum, titanium, tantalum, stainless steel, and alloys thereof are used. Among these, aluminum or aluminum alloys are preferred from the viewpoints of potential resistance, high electrical conductivity, and cost. As the positive electrode substrate, foil, vapor deposition film, mesh, porous material, etc. are mentioned, and foil is preferred from the viewpoint of cost. Therefore, aluminum foil or aluminum alloy foil is preferred as the positive electrode substrate. As the aluminum or aluminum alloy, A1085, A3003, A1N30, etc., as specified in JIS-H-4000 (2014) or JIS-H4160 (2006) can be exemplified.

The average thickness of the positive electrode substrate is preferably 3 μm or more and 50 μm or less, more preferably 5 μm or more and 40 μm or less, even more preferably 8 μm or more and 30 μm or less, and particularly preferably 10 μm or more and 25 μm or less. By setting the average thickness of the positive electrode substrate within the above range, it is possible to increase the strength of the positive electrode substrate while increasing the energy density per volume of the secondary battery.

The intermediate layer is a layer disposed between the positive electrode substrate and the positive electrode mixture layer. The intermediate layer contains a conductive agent such as carbon particles to reduce the contact resistance between the positive electrode substrate and the positive electrode mixture layer. The composition of the intermediate layer is not particularly limited, and may include, for example, a binder and a conductive agent.

[Positive electrode mixture layer]
The positive electrode mixture layer has a matrix mainly composed of a first sulfide-based solid electrolyte and a positive electrode active material composite dispersed in the matrix. The positive electrode mixture layer contains optional components such as a conductive agent, a binder, a thickener, and a filler as necessary. FIG. 1 is a schematic cross-sectional view of a positive electrode for an all-solid-state battery according to one embodiment of the present invention. As shown in FIG. 1, the positive electrode for an all-solid-state battery 1 includes a positive electrode substrate 4 and a positive electrode mixture layer 5. The positive electrode mixture layer 5 has a matrix 12 mainly composed of a first sulfide-based solid electrolyte and a positive electrode active material composite 14 dispersed in the matrix 12. The positive electrode active material composite 14 contains a positive electrode active material particle 11 and a second sulfide-based solid electrolyte 13 that directly or indirectly covers at least a part of the surface of the positive electrode active material particle 11.

(matrix)
The matrix 12 is mainly composed of a first sulfide-based solid electrolyte. The first sulfide-based solid electrolyte includes a sulfide-based glass solid electrolyte and a sulfide-based crystalline solid electrolyte. The matrix 12 of the positive electrode mixture layer is mainly composed of the first sulfide-based solid electrolyte, which is a combination of a relatively soft sulfide-based glass solid electrolyte and a relatively hard sulfide-based crystalline solid electrolyte, so that the packing density of the positive electrode mixture can be increased.

Examples of the sulfide-based glass solid electrolyte include Li ₂ S-P ₂ S ₅ , Li ₂ S-P ₂ S ₅ -LiI, Li ₂ S-P ₂ S ₅ -LiCl, Li ₂ S-P ₂ S ₅ -LiBr, etc. Among these, from the viewpoint of improving the effect of suppressing the decrease in the capacity retention rate after charge-discharge cycles of the all-solid-state battery, yLi ₂ S.(1-y)P ₂ S ₅ (where 0.75≦y≦0.77) is preferred, and 0.75Li ₂ S.0.25P ₂ S ₅ is more preferred.

From the viewpoint of improving the effect of suppressing the decrease in the capacity retention rate after charge/discharge cycles of the all-solid-state battery, the sulfide-based crystalline solid electrolyte preferably has a crystal structure that is a cubic system, an orthorhombic system, a triclinic system, or a combination thereof.

Examples of the sulfide-based crystalline solid electrolyte having a cubic crystal structure include Li ₆ PS ₅ Cl and Li ₇ PS ₆ .

Examples of the sulfide-based crystalline solid electrolyte having the orthorhombic crystal structure include β-Li ₃ S ₁₁ , Li _9.6 P ₃ S ₁₂ , Li ₁₀ GeP ₂ S ₁₂ , and Li _9.54 Si _1.74 P _1.44 S _11.7 Cl _0.3 .

An example of the sulfide-based crystalline solid electrolyte having a triclinic crystal structure is Li ₇ P ₃ S ₁₁ .

Among these, the sulfide-based crystalline solid electrolyte is preferably a cubic crystal, an orthorhombic crystal, or a combination of these, from the viewpoint of the effect of suppressing the decrease in the capacity retention rate after charge/discharge cycles.

The shape of the sulfide-based glass solid electrolyte and the sulfide-based crystalline solid electrolyte is not particularly limited, and is usually granular, blocky, etc.

The ratio of the contents of the sulfide-based glass solid electrolyte and the sulfide-based crystalline solid electrolyte in the first sulfide-based solid electrolyte (sulfide-based crystalline solid electrolyte/sulfide-based glass solid electrolyte) is preferably 30/70 or more and 70/30 or less, more preferably 50/50, by mass ratio. By having the ratio of the contents of the sulfide-based glass solid electrolyte and the sulfide-based crystalline solid electrolyte in the above range, the effect of suppressing the decrease in the capacity retention rate after charge/discharge cycles of the all-solid-state battery can be improved.

(Cathode active material composite)
The positive electrode active material composite 14 contains positive electrode active material particles 11 and a second sulfide-based solid electrolyte 13 that directly or indirectly covers at least a portion of the surface of the positive electrode active material particles. Since 14 is a composite of the positive electrode active material particles 11 and the sulfide-based solid electrolyte 13, a good ion conduction path is formed, and the ion conductivity at the interface between the positive electrode active material particles is improved.

The ratio of the content of the positive electrode active material particles 11 and the second sulfide-based solid electrolyte 13 in the positive electrode active material composite 14 (second sulfide-based solid electrolyte 13/positive electrode active material particles 11) is preferably 5/95 or more and 10/90 or less, and more preferably 5/95 or more and 7/93 or less, by mass ratio. By having the ratio of the content of the positive electrode active material particles 11 and the second sulfide-based solid electrolyte 13 in the above range, it is possible to improve ionic conductivity while suppressing a decrease in charge/discharge performance due to an increase in the resistance of the all-solid-state battery.

The content [g] of the second sulfide-based solid electrolyte 13 relative to the total surface area [m ² ] of the positive electrode active material particles 11 in the positive electrode active material composite 14 is preferably 0.75 g/28.5 m ² or more and 1.5 g/5.4 m ² or less, and more preferably 0.75 g/14.25 m ² or more and 0.75 g/8.55 m ² or less. When the content of the second sulfide-based solid electrolyte 13 relative to the total surface area of the positive electrode active material particles 11 is within the above range, it is possible to improve ion conductivity while suppressing a decrease in charge/discharge performance due to an increase in resistance of the all-solid-state battery.

(Positive electrode active material particles)
A material capable of absorbing and releasing lithium ions is usually used as the positive electrode active material particles 11. Examples of the positive electrode active material particles 11 include lithium transition metal composite oxides having an α- _NaFeO2 type crystal structure, lithium transition metal composite oxides having a spinel type crystal structure, polyanion compounds, chalcogen compounds, sulfur, and the like. Examples of lithium transition metal composite oxides having α-NaFeO type ₂ crystal structure include Li[Li _x Ni _(1-x) ]O ₂ (0≦x<0.5), Li[Li _x Ni _γ Co _(1-x-γ) ]O ₂ (0≦x<0.5, 0<γ<1), Li[Li _x Co _(1-x) ]O ₂ (0 ≦x<0.5), Li[Li _x Ni _γ Mn _(1-x-γ) ]O ₂ (0≦x<0.5, 0<γ<1), Li[Li _x Ni _γ Mn _β Co _(1-x-γ-β) ]O ₂ (0≦x<0.5, 0<γ, 0<β, 0.5<γ+β<1), Li[Li _x Ni Examples of the _lithium transition metal composite oxide having a spinel type crystal structure include Li _x Mn ₂ O ₄ and Li _x Ni _γ Mn _{( 2-γ) O 4. Examples} of the polyanion compound include LiFePO ₄ , LiMnPO _{4 ,} LiNiPO ₄ , LiCoPO ₄ , Li ₃ V ₂ (PO ₄ ) ₃ , Li ₂ MnSiO ₄ , and Li ₂ CoPO ₄ F. Examples of the chalcogen compound include titanium disulfide, molybdenum disulfide, and molybdenum dioxide. The atoms or polyanions in these materials may be partially substituted with atoms or anion species of other elements. The surfaces of these materials may be coated with other materials. In the positive electrode active material particles 11, one of these materials may be used alone, or two or more of them may be used in combination.

The average particle size of the positive electrode active material particles 11 is preferably, for example, 0.1 μm or more and 20 μm or less. By setting the average particle size of the positive electrode active material particles 11 to the above lower limit or more, the positive electrode active material particles 11 can be easily manufactured or handled. By setting the average particle size of the positive electrode active material particles 11 to the above upper limit or less, the electronic conductivity of the positive electrode mixture layer 5 is improved. The "average particle size" refers to the value at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2 (2001) is 50% based on the particle size distribution measured by a laser diffraction/scattering method for a diluted solution in which particles are diluted with a solvent in accordance with JIS-Z-8825 (2013).

In order to obtain powder with a specified particle size, a pulverizer or a classifier is used. Examples of pulverizing methods include those using a mortar, ball mill, sand mill, vibrating ball mill, planetary ball mill, jet mill, counter jet mill, swirling airflow type jet mill, or a sieve. Wet pulverization in the presence of water or an organic solvent such as hexane can also be used during pulverization. As for classification methods, sieves and air classifiers are used as necessary for both dry and wet methods.

The positive electrode active material particles 11 preferably have a coating layer. The positive electrode active material particles 11 can suppress side reactions with the sulfide solid electrolyte by having the coating layer. The side reaction is a reaction in which a high resistance layer is formed on the surface of the positive electrode active material particles 11 by reacting with the sulfide solid electrolyte. The formation of the high resistance layer reduces the charge and discharge performance of the all-solid-state battery. The coating material that is the material of the coating layer is not particularly limited, but examples thereof include LiNbO ₃ , LiTaO ₃ , Li ₂ ZrO ₃ , Li _4/3 Ti _5/3 O ₄ , and Li ₂ TiO ₃ .

(Second sulfide solid electrolyte)
The second sulfide-based solid electrolyte 13 is preferably a sulfide-based crystalline solid electrolyte. When the second sulfide-based solid electrolyte 13 is a sulfide-based crystalline solid electrolyte, the charging and discharging of the all-solid-state battery is This can improve the effect of suppressing the decrease in the capacity retention rate after cycling.

The sulfide-based crystalline solid electrolyte used for the second sulfide-based solid electrolyte 13 may be the same as the sulfide-based crystalline solid electrolyte exemplified for the first sulfide-based solid electrolyte. The sulfide-based crystalline solid electrolyte used for the second sulfide-based solid electrolyte 13 may be the same as or different from the sulfide-based crystalline solid electrolyte used for the first sulfide-based solid electrolyte.

The average particle size of the positive electrode active material composite 14 is, for example, preferably 0.1 μm or more and 20 μm or less, and more preferably 3 μm or more and 10 μm or less. By setting the average particle size of the positive electrode active material composite 14 to the above lower limit or more, the positive electrode active material composite 14 becomes easier to manufacture or handle. By setting the average particle size of the positive electrode active material composite 14 to the above upper limit or less, the contact area between the positive electrode active material composite 14 and the matrix 12 increases, and the charge/discharge characteristics of the all-solid-state battery are improved.

The content of the positive electrode active material composite 14 in the positive electrode mixture layer 5 is preferably 70% by mass or more and 90% by mass or less, and more preferably 70% by mass or more and 80% by mass or less. By setting the content of the positive electrode active material composite 14 within the above range, the electrical capacity of the all-solid-state battery can be increased.

(Conductive agent)
The conductive agent is not particularly limited as long as it is a material having electrical conductivity. Examples of such conductive agents include carbonaceous materials, metals, conductive ceramics, and the like. Examples of carbonaceous materials include graphite, non-graphitic carbon, graphene-based carbon, and the like. Examples of non-graphitic carbon include carbon nanofibers, pitch-based carbon fibers, carbon black, and the like. Examples of carbon black include furnace black, acetylene black, ketjen black, and the like. Examples of graphene-based carbon include graphene, carbon nanotubes (CNT), fullerene, and the like. Examples of the shape of the conductive agent include powder and fiber. As the conductive agent, one of these materials may be used alone, or two or more of them may be mixed and used. In addition, these materials may be used in combination. For example, a material in which carbon black and CNT are combined may be used. Among these, carbon black is preferable from the viewpoint of electronic conductivity and coatability, and acetylene black is preferable among them.

The content of the conductive agent in the positive electrode 1 is preferably 1% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 9% by mass or less. By setting the content of the conductive agent in the above range, the electrical capacity of the all-solid-state battery 10 can be increased.

(Binder)
Examples of the binder include thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, polyacrylic, and polyimide; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), and fluororubber; and polysaccharide polymers.

The binder content in the positive electrode 1 is preferably 1% by mass or more and 10% by mass or less, and more preferably 3% by mass or more and 9% by mass or less. By setting the binder content within the above range, the active material can be stably maintained.

(Thickener)
Examples of the thickener include polysaccharide polymers such as carboxymethyl cellulose (CMC), methyl cellulose, etc. When the thickener has a functional group that reacts with lithium or the like, the functional group may be deactivated in advance by methylation or the like.

(Filler)
The filler is not particularly limited. Examples of the filler include polyolefins such as polypropylene and polyethylene, inorganic oxides such as silicon dioxide, alumina, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicates, hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide, carbonates such as calcium carbonate, poorly soluble ion crystals such as calcium fluoride, barium fluoride, and barium sulfate, nitrides such as aluminum nitride and silicon nitride, and mineral resource-derived substances such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica, or artificial products thereof.

The positive electrode mixture layer 5 may contain typical nonmetallic elements such as B, N, P, F, Cl, Br, and I, typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba, and transition metallic elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Nb, and W, as components other than the positive electrode active material, conductive agent, binder, thickener, and filler.

The average thickness of the positive electrode mixture layer 5 is preferably 30 μm or more and 1,000 μm or less, and more preferably 60 μm or more and 500 μm or less. By setting the average thickness of the positive electrode mixture layer 5 to the above lower limit or more, an all-solid-state battery having a high energy density can be obtained. By setting the average thickness of the positive electrode mixture layer to the above upper limit or less, it is possible to miniaturize the all-solid-state battery. The average thickness of the positive electrode mixture layer 5 is the average value of the thicknesses measured at any five points. The same applies to the average thicknesses of the negative electrode mixture layer and the isolation layer described later.

<All-solid-state battery>
An all-solid-state battery according to one embodiment of the present invention will be described. The all-solid-state battery 10 shown in FIG. 2 is a secondary battery in which a positive electrode 1 and a negative electrode 2 are arranged with an isolation layer 3 interposed therebetween. In the all-solid-state battery of this embodiment, the positive electrode 1 has a positive electrode substrate 4 and a positive electrode mixture layer 5, and the positive electrode substrate 4 is the outermost layer of the positive electrode 1. The negative electrode 2 has a negative electrode substrate 7 and a negative electrode mixture layer 6, and the negative electrode substrate 7 is the outermost layer of the negative electrode 2. In the all-solid-state battery 10 shown in FIG. 1, the negative electrode mixture layer 6, the isolation layer 3, the positive electrode 1, and the positive electrode substrate 4 are laminated in this order on the negative electrode substrate 7.

In addition to the first sulfide-based solid electrolyte and the second sulfide-based solid electrolyte, the all-solid-state battery 10 may also use a known general solid electrolyte. Examples of such solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, dry polymer electrolytes, gel polymer electrolytes, and pseudo-solid electrolytes, and sulfide solid electrolytes are preferred. In addition, a single layer in the all-solid-state battery 10 may contain multiple different types of solid electrolytes, or each layer may contain a different solid electrolyte.

Examples of the sulfide solid electrolyte include Li ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₅ -LiI, Li ₂ SP ₂ S ₅ -LiCl, Li ₂ SP ₂ S ₅ -LiBr, Li ₂ S-P ₂ S ₅ -Li ₂ O, Li ₂ S-P ₂ S ₅ -Li ₂ O-LiI, Li ₂ S-P ₂ S ₅ -Li ₃ N, Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -LiI, Li ₂ S-SiS ₂ -LiBr, Li ₂ S-SiS ₂ -LiCl, Li ₂ S-SiS ₂ -B ₂ S ₃ -LiI, Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, Li ₂ S-B ₂ S ₃ , Li ₂ S-P ₂ S ₅ -Z _m S _2n (where m and n are positive numbers, Z is any one of Ge, Zn, and Ga.), Li ₂ S—GeS ₂ , Li ₂ S—SiS ₂ —Li ₃ PO ₄ , Li ₂ S—SiS ₂ —Li _x MO _y (wherein x , y is a positive number, and M is any one of P, Si, Ge, B, Al, Ga, and In. ), Li ₁₀ GeP ₂ S ₁₂ , and the like.

[Positive electrode]
The positive electrode 1 provided in the all-solid-state battery is the positive electrode for an all-solid-state battery according to one embodiment of the present invention described above. Since the all-solid-state battery includes the positive electrode for an all-solid-state battery, the decrease in the capacity retention rate after charge-discharge cycles can be suppressed.

[Negative electrode]
The negative electrode 2 has a negative electrode substrate 7 and a negative electrode mixture layer 6 disposed directly or via an intermediate layer on the negative electrode substrate 7. The configuration of the intermediate layer is not particularly limited and can be selected from the configurations exemplified for the positive electrode for an all-solid-state battery, for example.

(Negative electrode substrate)
The negative electrode substrate 7 has electrical conductivity. Metals such as copper, nickel, stainless steel, nickel-plated steel, and aluminum, or alloys thereof, carbonaceous materials, and the like are used as the material of the negative electrode substrate 7. Among these, copper or copper alloys are preferred. Examples of the negative electrode substrate include foils, vapor deposition films, meshes, and porous materials, and foils are preferred from the viewpoint of cost. Therefore, copper foil or copper alloy foil is preferred as the negative electrode substrate. Examples of copper foil include rolled copper foil and electrolytic copper foil.

The average thickness of the negative electrode substrate is preferably 2 μm or more and 35 μm or less, more preferably 3 μm or more and 30 μm or less, even more preferably 4 μm or more and 25 μm or less, and particularly preferably 5 μm or more and 20 μm or less. By setting the average thickness of the negative electrode substrate within the above range, it is possible to increase the strength of the negative electrode substrate while increasing the energy density per volume of the all-solid-state battery.

The negative electrode mixture layer contains a negative electrode active material. The negative electrode mixture layer contains optional components such as a conductive agent, a binder, a thickener, and a filler as necessary. The optional components such as a conductive agent, a binder, a thickener, and a filler can be selected from the materials exemplified for the positive electrode for the all-solid-state battery above.

The negative electrode mixture layer may contain typical nonmetallic elements such as B, N, P, F, Cl, Br, and I, typical metallic elements such as Li, Na, Mg, Al, K, Ca, Zn, Ga, Ge, Sn, Sr, and Ba, and transition metal elements such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr, Ta, Hf, Nb, and W as components other than the negative electrode active material, conductive agent, binder, thickener, and filler.

The negative electrode active material can be appropriately selected from known negative electrode active materials. As the negative electrode active material, a material capable of absorbing and releasing lithium ions is usually used. Examples of the negative electrode active material include metal Li; metals or semimetals such as Si and Sn; metal oxides or semimetal oxides such as Si oxide, Ti oxide, and Sn oxide; titanium-containing oxides such as Li ₄ Ti ₅ O ₁₂ , LiTiO _{2, and} TiNb ₂ O ₇ ; polyphosphate compounds; silicon carbide; carbon materials such as graphite and non-graphitic carbon (easily graphitized carbon or non-graphitizable carbon). Among these materials, graphite and non-graphitic carbon are preferred. In the negative electrode mixture layer, one of these materials may be used alone, or two or more may be mixed and used.

"Graphite" refers to a carbon material having an average lattice spacing (d ₀₀₂ ) of the (002) plane determined by X-ray diffraction before charging and discharging or in a discharged state of 0.33 nm or more and less than 0.34 nm. Examples of graphite include natural graphite and artificial graphite. Artificial graphite is preferred from the viewpoint of obtaining a material with stable physical properties.

"Non-graphitic carbon" refers to a carbon material having an average lattice spacing ( _d002 ) of 0.34 nm or more and 0.42 nm or less of (002) plane determined by X-ray diffraction before charging and discharging or in a discharged state. Examples of non-graphitic carbon include carbon that is difficult to graphitize and carbon that is easy to graphitize. Examples of non-graphitic carbon include resin-derived materials, petroleum pitch or petroleum pitch-derived materials, petroleum coke or petroleum coke-derived materials, plant-derived materials, and alcohol-derived materials.

Here, the term "discharged state" refers to a state in which the negative electrode active material, the carbon material, is discharged so that lithium ions that can be absorbed and released during charging and discharging are sufficiently released. For example, in a single-electrode battery using a negative electrode containing a carbon material as the negative electrode active material as the working electrode and metallic Li as the counter electrode, this is a state in which the open circuit voltage is 0.7 V or higher.

The term "non-graphitizable carbon" refers to a carbon material having the above _d002 of 0.36 nm or more and 0.42 nm or less.

The term "graphitizable carbon" refers to a carbon material having the above _d002 of 0.34 nm or more and less than 0.36 nm.

The negative electrode active material is usually a particle (powder). The average particle size of the negative electrode active material can be, for example, 1 nm or more and 100 μm or less. When the negative electrode active material is a carbon material, a titanium-containing oxide, or a polyphosphate compound, the average particle size may be 1 μm or more and 100 μm or less. When the negative electrode active material is Si, Sn, Si oxide, Sn oxide, or the like, the average particle size may be 1 nm or more and 1 μm or less. By setting the average particle size of the negative electrode active material to the above lower limit or more, the negative electrode active material can be easily manufactured or handled. By setting the average particle size of the negative electrode active material to the above upper limit or less, the electronic conductivity of the negative electrode mixture layer is improved. In order to obtain powder with a predetermined particle size, a pulverizer, a classifier, or the like is used. The pulverization method and the powder classification method can be selected from, for example, the methods exemplified for the positive electrode. When the negative electrode active material is a metal such as metallic Li, the negative electrode active material may be in the form of a foil.

The content of the negative electrode active material in the negative electrode mixture layer 6 is preferably 60% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 98% by mass or less. By setting the content of the negative electrode active material within the above range, it is possible to achieve both high energy density and manufacturability of the negative electrode mixture layer 6.

When the negative electrode mixture layer 6 contains a solid electrolyte, the content of the solid electrolyte is preferably 1% by mass or more and 40% by mass or less, and more preferably 2% by mass or more and 10% by mass or less. By setting the content of the solid electrolyte within the above range, the electrical capacity of the all-solid-state battery 10 can be increased.

When the negative electrode mixture layer 6 contains a solid electrolyte, it can be a mixture or composite of the above-mentioned negative electrode active material and the solid electrolyte.

The average thickness of the negative electrode mixture layer 6 is preferably 30 μm or more and 1,000 μm or less, and more preferably 60 μm or more and 500 μm or less. By setting the average thickness of the negative electrode mixture layer 6 to the above lower limit or more, an all-solid-state battery 10 having a high energy density can be obtained. By setting the average thickness of the negative electrode mixture layer 6 to the above upper limit or less, it is possible to miniaturize the all-solid-state battery 10.

[Isolation layer]
The isolation layer 3 contains a solid electrolyte. The solid electrolyte contained in the isolation layer 3 is not particularly limited, and the above-mentioned various general solid electrolytes can be used, among which it is preferable to use a sulfide solid electrolyte. The content of the solid electrolyte in the isolation layer 3 is preferably 70% by mass or more, more preferably 90% by mass or more, even more preferably 99% by mass or more, and even more preferably substantially 100% by mass.

The isolation layer 3 may contain optional components such as a binder, a thickener, and a filler. The optional components such as a binder, a thickener, and a filler can be selected from the materials exemplified for the positive electrode for the all-solid-state battery.

The average thickness of the isolation layer 3 is preferably 1 μm or more and 50 μm or less, and more preferably 3 μm or more and 20 μm or less. By making the average thickness of the isolation layer 3 equal to or more than the above lower limit, it is possible to insulate the positive electrode 1 and the negative electrode 2 with high reliability. By making the average thickness of the isolation layer 3 equal to or less than the above upper limit, it is possible to increase the energy density of the all-solid-state battery 10.

[Configuration of Power Storage Device]
The all-solid-state battery of this embodiment can be mounted as a power storage device constituted by assembling a plurality of all-solid-state batteries in a power source for an automobile such as an electric vehicle (EV), a hybrid vehicle (HEV), or a plug-in hybrid vehicle (PHEV), a power source for electronic devices such as a personal computer or a communication terminal, or a power storage power source, etc. In this case, it is sufficient that the technology of the present invention is applied to at least one all-solid-state battery included in the power storage device.
3 shows an example of a power storage device 30 in which a power storage unit 20, which is an assembly of two or more electrically connected all-solid-state batteries 1, is further assembled. The power storage device 30 may include a bus bar (not shown) that electrically connects the two or more all-solid-state batteries 1, a bus bar (not shown) that electrically connects the two or more power storage units 20, and the like. The power storage unit 20 or the power storage device 30 may include a state monitoring device (not shown) that monitors the state of the one or more all-solid-state batteries.

<Method of manufacturing positive electrode for all-solid-state battery>
A method for producing a positive electrode for an all-solid-state battery according to one embodiment of the present invention includes compounding positive electrode active material particles with a sulfide-based solid electrolyte (compounding step), and preparing a positive electrode mixture including the positive electrode active material composite obtained by the compounding, a sulfide-based glass solid electrolyte, and a sulfide-based crystalline solid electrolyte (positive electrode mixture preparation step). The method for producing a positive electrode for an all-solid-state battery may also include a positive electrode substrate preparation step.

(1) Composite step In this step, the positive electrode active material particles and the sulfide-based solid electrolyte are composited. As a composite method, for example, the sulfide-based solid electrolyte is composited on the surface of the positive electrode active material particles by dry composite. By composited with the sulfide-based solid electrolyte on the surface of the positive electrode active material particles, at least a part of the surface of the positive electrode active material particles is directly or indirectly covered with the sulfide-based solid electrolyte.

The dry compounding is carried out, for example, by the following steps. That is, the positive electrode active material particles and the sulfide-based solid electrolyte are put into a dry particle compounding device (e.g., Nobiltamini manufactured by Hosokawa Micron Corporation) in a predetermined mass ratio. Next, the dry particle compounding device is driven at a peripheral speed of 5000 rpm to 9000 rpm and a driving time of 1 minute to 5 minutes. This allows the sulfide-based solid electrolyte to be compounded on the surface of the positive electrode active material particles.
(2) Positive electrode mixture preparation step In this step, a positive electrode mixture for forming a positive electrode mixture layer is prepared. Specifically, in this step, a positive electrode mixture containing the positive electrode active material composite obtained by the above-mentioned compounding, a sulfide-based glass solid electrolyte, and a sulfide-based crystalline solid electrolyte is prepared. The method for preparing the positive electrode mixture is not particularly limited and can be appropriately selected according to the purpose. For example, a stirring and mixing process using a kneader of a positive electrode active material composite, a sulfide-based glass solid electrolyte, a sulfide-based crystalline solid electrolyte, an arbitrary material such as a conductive agent, a binder, and a solvent, a mixture or composite preparation using a mechanical milling method or the like of the material of the positive electrode mixture, compression molding of the material of the positive electrode mixture, and the like can be mentioned.

According to the manufacturing method for the positive electrode for an all-solid-state battery, by including the above steps, it is possible to reliably manufacture a positive electrode for an all-solid-state battery that can suppress a decrease in the capacity retention rate after the charge-discharge cycle of the all-solid-state battery.

<Method of manufacturing all-solid-state battery>
The method for producing an all-solid-state battery according to one embodiment of the present invention can be carried out by a generally known method, except that the method for producing a positive electrode for an all-solid-state battery described above is used as the method for producing a positive electrode. Specifically, the method for producing the all-solid-state battery includes, for example, (1) preparing a positive electrode, (2) preparing an isolation layer, (3) preparing an anode, and (4) stacking the positive electrode, the isolation layer, and the anode. Each step will be described in detail below.

(1) Positive Electrode Preparation Step In this step, the steps of the method for producing the positive electrode for an all-solid-state battery described above are carried out.

(2) Preparation of material for isolating layer In this step, a material for isolating layer for forming an isolating layer is usually prepared. When the all-solid-state battery is a lithium-ion all-solid-state battery, the material for isolating layer can be a solid electrolyte. The solid electrolyte as the material for isolating layer can be prepared by a conventionally known method. For example, it can be obtained by processing a predetermined material by a mechanical milling method. The material for isolating layer may be prepared by heating a predetermined material to a melting temperature or higher by a melt quenching method, melt-mixing the two at a predetermined ratio, and quenching. Other synthesis methods for the material for isolating layer include, for example, a solid-phase method in which the material is sealed under reduced pressure and fired, a liquid-phase method such as dissolution deposition, a gas-phase method (PLD), and firing under an argon atmosphere after mechanical milling.

(3) Negative electrode preparation step In this step, a negative electrode mixture for forming a negative electrode mixture layer is usually prepared. The specific method for preparing the negative electrode mixture is the same as that for the positive electrode mixture. When the negative electrode mixture contains a mixture or composite containing a negative electrode active material and a solid electrolyte, this step may include, for example, mixing the negative electrode active material and the solid electrolyte using a mechanical milling method or the like to prepare a mixture or composite of the negative electrode active material and the solid electrolyte. In addition, this step may include a negative electrode substrate preparation step.

(Lamination process)
In this step, for example, a positive electrode having a positive electrode substrate and a positive electrode mixture layer, an isolation layer, and a negative electrode having a negative electrode substrate and a negative electrode mixture layer are laminated. In this step, the positive electrode, the isolation layer, and the negative electrode may be formed in this order, or vice versa, and the order of formation of each layer is not particularly important. The positive electrode is formed, for example, by pressure molding the positive electrode substrate and the positive electrode mixture, the isolation layer is formed by pressure molding the isolation layer material, and the negative electrode is formed by pressure molding the negative electrode substrate and the negative electrode mixture. The positive electrode, the isolation layer, and the negative electrode may be laminated by pressure molding the positive electrode substrate, the positive electrode mixture, the isolation layer material, the negative electrode mixture, and the negative electrode substrate at once. The positive electrode and the negative electrode may be molded in advance, respectively, and then pressure molded and laminated with the isolation layer.

[Other embodiments]
The present invention is not limited to the above-mentioned embodiment, and can be embodied in various modified and improved forms in addition to the above-mentioned forms. For example, the all-solid-state battery according to the present invention may have layers other than the positive electrode, the separator layer, and the negative electrode, such as an intermediate layer or an adhesive layer. In addition, the all-solid-state battery according to the present invention may contain a liquid in one or more of the layers.

In the above embodiment, the positive electrode mixture layer of the positive electrode is disposed directly on the positive electrode substrate or via an intermediate layer, but this is not limited thereto. For example, the positive electrode mixture layer may be filled into the voids of a sponge-like positive electrode substrate.

The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples.

[Examples 1 to 3, Comparative Examples 1 and 2]
All-solid-state batteries of Examples 1 to 3 and Comparative Examples 1 and 2 were produced as follows.

(Preparation of Positive Electrode Active Material Particles)
Particles of NCM523 ( _{LiNi0.5Co0.2Mn0.3O2 )} shown in Table ₁ were prepared. Next, _LiNbO3 was coated _as a coating layer for the positive electrode active material particles by the following procedure. First, metal Li was dissolved in ultra-dehydrated ethanol, and then niobium ethoxide (Nb( _OC2H5 ) ₅ ) was dissolved to prepare a LiNbO3 precursor solution. Using a rolling fluidized coating device (FD-MP _- 01F) manufactured by Powrex Corporation, the _LiNbO3 precursor was coated on the particle surface of NCM523. The _{LiNbO3 - coated} NCM523 was produced by heat-treating the NCM523 coated with the LiNbO3 precursor at 400°C for 30 minutes. This LiNbO3 _- coated NCM523 was used as the positive electrode active material particles. The coating amount of _LiNbO3 with respect to NCM523 was 0.75 mass%.

(Composite processing step)
A composite process was carried out using the above-mentioned positive electrode active material particles and Li ₆ PS ₅ Cl (cubic argyrodite crystal structure) as the second sulfide-based solid electrolyte to prepare a positive electrode active material composite. The mass ratio in the positive electrode active material composite was positive electrode active material particles: second sulfide-based solid electrolyte = 95 mass%: 5 mass%. Then, the composite was carried out by the following process. That is, the positive electrode active material particles and the second sulfide-based solid electrolyte were put into a Nobiltamini manufactured by Hosokawa Micron Corporation and driven. As a result, a coating of the second sulfide-based solid electrolyte was formed on the surface of the positive electrode active material particles.

(Fabrication of all-solid-state batteries)
The positive electrode active material composite, 75Li ₂ S.25P ₂ S ₅ and Li ₆ PS ₅ Cl listed in Table 1 as the first sulfide-based solid electrolyte, acetylene black as a conductive agent, and SBR as a binder were weighed out to be 80:16:2:2 (mass ratio). First, the positive electrode active material composite, the first sulfide-based solid electrolyte, and the conductive agent were mixed in an agate mortar. Next, butyl acetate as a binder and a solvent was added to this mixture, and the mixture was kneaded with a hybrid mixer to obtain a positive electrode mixture slurry. The obtained positive electrode mixture slurry was applied to an aluminum foil (average thickness 20 μm) as a positive electrode substrate using a YBA type Baker applicator so that the coating amount after drying was 15 mg/cm ² or more and 25 mg/cm ² or less. Next, the positive electrode mixture layer was formed on the positive electrode substrate by drying at normal pressure for 10 minutes in a dryer in an argon atmosphere at 100° C. and then drying under reduced pressure for 10 minutes. The positive electrode mixture layer was then punched out into a circle having a diameter of 10 mm to prepare a positive electrode for evaluation.
Next, 60 mg of Li ₆ PS ₅ Cl, a sulfide-based solid electrolyte, was added as an isolation layer material to a powder molding machine with an inner diameter of 10 mm, and then pressure molding was performed using a hydraulic press to prepare an isolation layer. After pressure release, a positive electrode was placed on one side of the isolation layer so that the positive electrode mixture layer faced the other side, and pressure molding was performed at 360 MPa for 5 minutes. After pressure release, a negative electrode, in which a metal Li foil and a metal In foil, which are negative electrode mixture layers, were previously attached to a stainless steel plate, which is a negative electrode substrate, was placed on the other side of the isolation layer so that the negative electrode mixture layer faced the other side, and pressure molding was performed at 120 MPa for 3 minutes. As a result, a laminate having a diameter of 10 mm and a positive electrode substrate, a positive electrode mixture layer, an isolation layer, a negative electrode mixture layer, and a negative electrode substrate was obtained. A rectangular PTFE plate of about 30 mm square with a through hole of about 10 mm diameter in the center was prepared, and the obtained laminate was placed in this through hole, and sandwiched between two stainless steel foils so as to cover the center of the PTFE plate. This was stored in an exterior body made of an aluminum metal resin composite film, and reduced pressure sealing was performed by heat welding. At this time, each end of the lead terminal made of nickel foil previously attached to each stainless steel foil was led out from the sealing part of the exterior body. Both sides of this exterior body were sandwiched between two PTFE sheets of about 40 mm square, and further, both sides were sandwiched between two stainless steel plates of about 60 mm square, and the stainless steel plates were screwed together under the condition that a pressure of 25 MPa was applied to the laminate. In this way, all-solid-state batteries of Examples 1 to 3, Comparative Example 1 and Comparative Example 2 were obtained.

[Comparative Example 3 and Comparative Example 4]
All-solid-state batteries of Comparative Example 3 and Comparative Example 4 were obtained in the same manner as in Example 1, except that the composite treatment step was not performed, the above-mentioned NCM523 particles were used as the positive electrode active material particles, and the first sulfide-based solid electrolyte was as shown in Table 1.

[evaluation]
(1) Discharge Capacity Confirmation Test A discharge capacity confirmation test was performed on each of the obtained all-solid-state batteries under the following conditions. In a thermostatic chamber at 50° C., the battery was charged at a constant current of 0.05 C up to 3.75 V, and then charged at a constant voltage of 3.75 V. The charge termination condition was that the charge current during constant voltage charging was 0.025 C. After a 10-minute pause after charging, the battery was discharged at a constant current of 0.20 C up to 2.25 V. A 10-minute pause was provided after discharging. This charge and discharge were performed for one cycle. Next, one cycle of charge and discharge was performed under the same conditions except that the discharge current was 0.10 C. Furthermore, one cycle of charge and discharge was performed under the same conditions except that the discharge current was 0.05 C. Then, the discharge capacity [mAh] under each condition was measured. The discharge capacity [mAh] under each condition was divided by the mass of the positive electrode active material contained in the positive electrode, and the result is shown in Table 1 as the discharge capacity [mAh/g] under each condition.
(2) Charge-discharge cycle test Subsequently, a charge-discharge cycle test was performed under the following conditions. At 50° C., charging was performed at a constant current and constant voltage of a current of 0.20 C and a voltage of 3.75 V, and the charge termination condition was that the charging current was 0.05 C. Discharging was performed at a constant current of 0.20 C and a termination voltage of 2.25 V. This charge-discharge cycle was performed for 30 cycles. A rest period of 10 minutes was provided after each charging and discharging.
Next, one cycle of charging and discharging was performed under the same conditions as in the above discharge capacity confirmation test, with a discharge current of 0.20 C. The discharge capacity [mAh] at this time was divided by the mass of the positive electrode active material contained in the positive electrode, and recorded as the discharge capacity [mAh/g] after the charge-discharge cycle test. The percentage of the discharge capacity after the charge-discharge cycle test relative to the discharge capacity at a discharge current of 0.2 C in the above discharge capacity confirmation test discharge is shown in Table 1 as the capacity retention rate [%].

As shown in Table 1, the all-solid-state batteries of Examples 1 to 3 suppressed the decrease in capacity retention rate after charge-discharge cycles at high temperatures (50°C). In contrast, the all-solid-state batteries of Comparative Examples 1 and 2, in which the first sulfide-based solid electrolyte is either a sulfide-based glass solid electrolyte or a sulfide-based crystalline solid electrolyte, and the all-solid-state batteries of Comparative Examples 3 and 4, in which no positive electrode active material composite is used, show a greater decrease in capacity retention rate after charge-discharge cycles than Examples 1 to 3.

The above results show that the positive electrode for an all-solid-state battery can suppress the decrease in the capacity retention rate after charge-discharge cycles of the all-solid-state battery. The positive electrode can be suitably used as a positive electrode for an all-solid-state battery.

Reference Signs List 1 Positive electrode 2 Negative electrode 3 Separator 4 Positive electrode substrate 5 Positive electrode mixture layer 6 Negative electrode mixture layer 7 Negative electrode substrate 10 All-solid-state battery 11 Positive electrode active material particles 12 Matrix mainly composed of first sulfide-based solid electrolyte 13 Second sulfide-based solid electrolyte 14 Positive electrode active material composite 20 Electricity storage unit 30 Electricity storage device

Claims (5)

A positive electrode substrate;
A positive electrode mixture layer;
the positive electrode mixture layer has a matrix mainly composed of a first sulfide-based solid electrolyte and a positive electrode active material composite dispersed in the matrix,
the positive electrode active material composite contains positive electrode active material particles and a second sulfide-based solid electrolyte that directly or indirectly covers at least a portion of a surface of the positive electrode active material particles,
The positive electrode for an all-solid-state battery, wherein the first sulfide-based solid electrolyte includes a sulfide-based glass solid electrolyte and a sulfide-based crystalline solid electrolyte. The positive electrode for an all-solid-state battery according to claim 1, wherein the second sulfide-based solid electrolyte is a sulfide-based crystalline solid electrolyte. The sulfide-based glass solid electrolyte is yLi ₂ S.(1-y)P ₂ S ₅ (where 0.75≦y≦0.77),
3. The positive electrode for an all-solid-state battery according to claim 1, wherein the sulfide-based crystalline solid electrolyte has a crystal structure that is a cubic system, an orthorhombic system, a triclinic system, or a combination thereof. An all-solid-state battery comprising the positive electrode according to claim 1, claim 2 or claim 3. Composite positive electrode active material particles and a sulfide-based solid electrolyte;
and preparing a positive electrode mixture containing the positive electrode active material composite obtained by the above-mentioned compounding, a sulfide-based glass solid electrolyte, and a sulfide-based crystalline solid electrolyte.

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