JP7639732B2 - Electrode mixture - Google Patents

Description

This disclosure relates to an electrode mixture.

In recent years, with the rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries to be used as power sources for these devices has become important. In the automotive industry, too, development of high-output, high-capacity batteries for electric and hybrid vehicles is underway.

Patent Document 1 discloses a positive electrode for an all-solid-state battery that includes a conductive material having a specific surface area of the external surface and a total specific surface area including pores (external/total) of less than 0.5, and a conductivity of 1 S/cm or more.

JP 2013-258080 A

In the electrode mixture of an all-solid-state battery, contact between the conductive material and the solid electrolyte may cause the solid electrolyte to decompose, increasing the resistance of the all-solid-state battery and decreasing its durability.

This disclosure has been made in consideration of the above-mentioned circumstances, and has as its main objective the provision of an electrode composite that has an excellent balance between the initial resistance, discharge capacity, and resistance increase rate of an all-solid-state battery.

The electrode mixture of the present disclosure is an electrode mixture for an all-solid-state battery,
The battery includes an active material, a solid electrolyte, and a conductive material,
a conductive load parameter of the conductive material obtained by multiplying an intensity ratio D/G of a peak intensity D at 1350 cm ^-1 to an intensity G of a peak at 1600 cm ^- 1 in a Raman spectrum measurement of the conductive material by a content W (mass%) of the conductive material, dividing the result by a specific surface area Si ( ^m2 /g) of the conductive material, and multiplying the result by 100 is greater than 0.16 and less than 2.29;
The contact interface length (pixel) between the conductive material and the solid electrolyte is greater than 480 and less than 7300.

This disclosure can provide an electrode composite that has an excellent balance between the initial resistance, discharge capacity, and resistance increase rate of an all-solid-state battery.

FIG. 1 is a diagram showing the results of Raman spectrum measurement of the conductive material used in Example 1. FIG. 2 is a diagram showing the measurement results of the sulfur S2p spectrum of the solid electrolyte used in Example 1.

Hereinafter, the embodiments of the present disclosure will be described. Note that matters other than those specifically mentioned in this specification and necessary for implementing the present disclosure (for example, the general configuration and manufacturing process of the electrode mixture that do not characterize the present disclosure) can be understood as design matters of a person skilled in the art based on the prior art in the field. The present disclosure can be implemented based on the contents disclosed in this specification and the technical common sense in the field.
In this specification, the use of "to" indicating a range of values means that the values before and after it are included as the lower limit and upper limit.
Furthermore, any combination of upper and lower limits in a numerical range can be used.

The electrode mixture of the present disclosure is an electrode mixture for an all-solid-state battery,
The battery includes an active material, a solid electrolyte, and a conductive material,
a conductive load parameter of the conductive material obtained by multiplying an intensity ratio D/G of a peak intensity D at 1350 cm ^-1 to an intensity G of a peak at 1600 cm ^- 1 in a Raman spectrum measurement of the conductive material by a content W (mass%) of the conductive material, dividing the result by a specific surface area Si ( ^m2 /g) of the conductive material, and multiplying the result by 100 is greater than 0.16 and less than 2.29;
The contact interface length (pixel) between the conductive material and the solid electrolyte is greater than 480 and less than 7300.

The conductive material forms an electronic path in the solid electrolyte, accelerating the decomposition reaction of the solid electrolyte. Therefore, in the electrode mixture disclosed herein, the decomposition reaction of the solid electrolyte is controlled by controlling the conductive load of the conductive material on the solid electrolyte.

[Electrode mixture]
The electrode mixture of the present disclosure includes an active material, a solid electrolyte, and a conductive material.
The electrode mixture of the present disclosure may be a positive electrode mixture used in a positive electrode layer, or a negative electrode mixture used in a negative electrode layer.
The active material may be a positive electrode active material or a negative electrode active material described below.
As the solid electrolyte, the same ones as those exemplified in the solid electrolyte layer described later can be exemplified.
The solid electrolyte may have a PS4 skeleton of 70% or more and a specific surface area of 5 to 200 m ² /g.
As the conductive material, the same materials as those exemplified in the positive electrode layer described later can be used. The conductive material may be used alone or in combination of two or more kinds.
The specific surface area of the conductive material may be from 5 to 2000 ^{m 2} /g.
The shape of the conductive material is not particularly limited, and may be fibrous, spherical (particulate), or the like.
The mass ratio (mass %) of the active material to the solid electrolyte may be active material:solid electrolyte=65:35 to 85:15.

Conductive Load Parameters
In the electrode mixture of the present disclosure, the conductive material may have a conductive load parameter of more than 0.16 and less than 2.29, and may be 0.19 to 1.15. If the conductive load parameter is 2.29 or more, the initial resistance is high, the solid electrolyte is easily decomposed, and the durability of the all-solid-state battery is reduced. If the conductive load parameter is 0.16 or less, the desired conductivity cannot be obtained.
The conductive load parameter is obtained by multiplying the intensity ratio D/G of the peak intensity D at 1350 cm ^-1 to the peak intensity G at 1600 cm ^-1 in Raman spectrum measurement of the conductive material by the conductive material content W (mass %), dividing the result by the specific surface area Si (m ² /g) of the conductive material, and multiplying the result by 100. The conductive material content is the content in the electrode mixture.
That is, the conductive load parameter can be calculated from the following formula (1).
Equation (1): Conductive load parameter = (D/G) x W÷Si x 100
When two or more conductive materials are used, the conductive load parameter of each conductive material is calculated, and the total value of these should fall within the above range.
The conductive material may have a D/G ratio of 0.01 to 1.

[Contact interface length]
The electrode mixture of the present disclosure may have a contact interface length (pixel) between the conductive material and the solid electrolyte of more than 480 and less than 7,300, and may be 1,800 to 6,700.
The length of the contact interface between the conductive material and the solid electrolyte can be controlled by the timing of adding the conductive material and the solid electrolyte, the kneading time, the type of solvent, and the like when preparing the slurry for the electrode mixture.
The contact interface length [px] between the conductive material and the solid electrolyte is calculated as follows.
Images of carbon (C) as a conductive material and backscattered electron images are acquired by SEM-EDX, and four-value processing is performed using image analysis software (e.g. ImageJ). The ratio of the solid electrolyte component to the carbon component is calculated, and the length of the part where the solid electrolyte component and the carbon component are in contact can be calculated as the contact interface length.

[Intensity ratio B/A]
When the electrode mixture of the present disclosure is used in an all-solid-state battery, the intensity ratio B/A of a peak intensity B near 162 eV to a peak intensity A near 159 to 160 eV in a sulfur S2p spectrum of the solid electrolyte obtained by XPS after initial charge and discharge may be greater than 0.39 and less than 0.85, or may be 0.45 to 0.61. This makes it possible to increase the durability of the all-solid-state battery.

[All-solid-state battery]
The electrode mixture of the present disclosure is an electrode mixture for an all-solid-state battery. The all-solid-state battery of the present disclosure may include a positive electrode, a solid electrolyte layer, and a negative electrode.

[Positive electrode]
The positive electrode has a positive electrode layer, and optionally a positive electrode current collector.

[Positive electrode layer]
The positive electrode layer may be a positive electrode mixture containing a positive electrode active material, a conductive material, and a solid electrolyte, and may optionally contain a binder, etc. The electrode mixture of the present disclosure may be a positive electrode mixture used in the positive electrode layer.

There is no particular limitation on the type of the positive electrode active material, and any material that can be used as an active material for an all-solid-state battery can be used. Examples of the positive electrode active material include lithium alloys, LiCoO ₂ , LiNi _x M _1-x O ₂ (x satisfies 0.5≦x<1, and M is at least one element selected from the group consisting of Co, Mn, and Al), LiMnO ₂ , Li-Mn spinel substituted with a different element, lithium titanate, lithium metal phosphate, LiCoN, Li ₂ SiO ₃ , Li ₄ SiO ₄ , transition metal oxides, TiS ₂ , Si, SiO ₂ , Si alloys, and lithium-storing intermetallic compounds.
_Examples of Li- _{Mn spinels} substituted _with different _{elements include LiMn1.5Ni0.5O4} , _{LiMn1.5Al0.5O4 , LiMn1.5Mg0.5O4 , LiMn1.5Co0.5O4 , LiMn1.5Fe0.5O4 , and LiMn1.5Zn0.5O4 .}
The lithium titanate is, for example, Li ₄ Ti ₅ O ₁₂ .
Examples of lithium metal phosphates include _LiFePO4 , _LiMnPO4 , _LiCoPO4 , and _LiNiPO4 .
Examples of transition metal oxides include _V2O5 and _MoO3 . Examples of _lithium storage intermetallic compounds include _Mg2Sn , _Mg2Ge , _Mg2Sb , and _Cu3Sb .
Examples of lithium alloys include Li-Au, Li-Mg, Li-Sn, Li-Si, Li-Al, Li-B, Li-C, Li-Ca, Li-Ga, Li-Ge, Li-As, Li-Se, Li-Ru, Li-Rh, Li-Pd, Li-Ag, Li-Cd, Li-In, Li-Sb, Li-Ir, Li-Pt, Li-Hg, Li-Pb, Li-Bi, Li-Zn, Li-Tl, Li-Te, and Li-At. Examples of Si alloys include alloys with metals such as Li, and may also be alloys with at least one metal selected from the group consisting of Sn, Ge, and Al.
The shape of the positive electrode active material is not particularly limited, and may be particulate. When the positive electrode active material is particulate, the positive electrode active material may be primary particles or secondary particles.
A coating layer containing a Li ion conductive oxide may be formed on the surface of the positive electrode active material, because this can suppress the reaction between the positive electrode active material and the solid electrolyte.
Examples of Li ion conductive oxides include LiNbO ₃ , Li ₄ Ti ₅ O ₁₂ , and Li ₃ PO ₄ . The thickness of the coating layer is, for example, 0.1 nm or more, and may be 1 nm or more. On the other hand, the thickness of the coating layer is, for example, 100 nm or less, and may be 20 nm or less. The coating layer may cover, for example, 70% or more of the surface of the positive electrode active material, or may cover 90% or more.

The conductive material may be a known material, such as a carbon material, metal particles, etc. The carbon material may be at least one selected from the group consisting of acetylene black (AB), furnace black, VGCF (registered trademark) , carbon nanotubes, and carbon nanofibers. The metal particles may be Ni, Cu, Fe, SUS, or the like.
The content of the conductive material in the positive electrode layer is not particularly limited, and may be 0.4 to 6.0 mass %.

As the solid electrolyte, the same ones as those exemplified in the solid electrolyte layer can be exemplified.
The content of the solid electrolyte in the positive electrode layer is not particularly limited, but may be, for example, within a range of 1 mass % to 80 mass % when the total mass of the positive electrode layer is taken as 100 mass %.

Examples of the binding agent (binder) include polyacrylonitrile, polyacrylic acid, polymethyl ester of acrylic acid, polyethyl ester of acrylic acid, polyhexyl ester of acrylic acid, polymethacrylic acid, polymethyl ester of methacrylic acid, polyethyl ester of methacrylic acid, polyhexyl ester of methacrylic acid, acrylonitrile butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVdF), and styrene butadiene rubber (SBR).
The content of the binder in the positive electrode layer is not particularly limited.

The thickness of the positive electrode layer is not particularly limited, but may be, for example, 10 to 100 μm.

The positive electrode layer can be formed by a conventionally known method.
For example, a positive electrode active material and, if necessary, other components are put into a solvent and stirred to prepare a paste for forming a positive electrode layer, and the paste for forming a positive electrode layer is applied onto one side of a support and dried to obtain a positive electrode layer.
Examples of the solvent include butyl acetate, butyl butyrate, mesitylene, tetralin, heptane, and N-methyl-2-pyrrolidone (NMP).
The method for applying the paste for forming a positive electrode layer onto one surface of the support is not particularly limited, and examples thereof include a doctor blade method, a metal mask printing method, an electrostatic application method, a dip coating method, a spray coating method, a roll coating method, a gravure coating method, and a screen printing method.
The support can be appropriately selected from those having self-supporting properties and is not particularly limited. For example, metal foils such as Cu and Al can be used.

As another method for forming the positive electrode layer, the positive electrode layer may be formed by pressure molding a powder of a positive electrode mixture containing a positive electrode active material and other components as necessary. When the powder of the positive electrode mixture is pressure molded, a surface pressure of 1 MPa to 2000 MPa and a linear pressure of 1 ton/cm to 100 ton/cm are usually applied.
The method of applying pressure is not particularly limited, but examples thereof include a method of applying pressure using a plate press, a roll press, or the like.

[Positive electrode current collector]
The positive electrode current collector may be a known metal that can be used as a current collector for an all-solid-state battery. Examples of such metals include metal materials containing one or more elements selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In. Examples of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon.
The shape of the positive electrode current collector is not particularly limited, and may be in various shapes such as a foil shape, a mesh shape, etc. The thickness of the positive electrode current collector varies depending on the shape, but may be, for example, in the range of 1 μm to 50 μm, or in the range of 5 μm to 20 μm.

[Negative electrode]
The negative electrode has a negative electrode layer, and optionally has a negative electrode current collector.

[Negative electrode layer]
The negative electrode layer may be a negative electrode mixture containing at least a negative electrode active material, a conductive material, and a solid electrolyte, and may optionally contain a binder, etc. The electrode mixture of the present disclosure may be a negative electrode mixture used in the negative electrode layer.
Examples of the negative electrode active material include graphite, mesocarbon microbeads (MCMB), highly oriented pyrolytic graphite (HOPG), hard carbon, soft carbon, lithium alone, lithium alloys, Si alone, Si alloys, and Li ₄ Ti ₅ O _12. As the lithium alloys and Si alloys, the same ones as those exemplified in the positive electrode active material can be used.
The shape of the negative electrode active material is not particularly limited, and examples thereof include a particulate shape, a plate shape, etc. When the negative electrode active material is particulate, the negative electrode active material may be primary particles or secondary particles.
The conductive material and binder used in the negative electrode layer may be the same as those exemplified in the positive electrode layer. The solid electrolyte used in the negative electrode layer may be the same as those exemplified in the solid electrolyte layer.
The thickness of the negative electrode layer is not particularly limited, but may be, for example, 10 to 100 μm.
The content of the negative electrode active material in the negative electrode layer is not particularly limited, but may be, for example, 20% by mass to 90% by mass.
The method for forming the negative electrode layer includes a method of applying a paste for forming the negative electrode layer containing a negative electrode active material onto a support and drying the paste, etc. The support may be the same as those exemplified for the positive electrode layer.

[Negative electrode current collector]
The material of the negative electrode current collector may be a material that does not alloy with Li, and examples of such materials include SUS, copper, and nickel. Examples of the shape of the negative electrode current collector include foil and plate. The planar shape of the negative electrode current collector is not particularly limited, and examples of such shapes include a circle, an ellipse, a rectangle, and any polygon. The thickness of the negative electrode current collector varies depending on the shape, and may be, for example, in the range of 1 μm to 50 μm, or in the range of 5 μm to 20 μm.

[Solid electrolyte layer]
The solid electrolyte layer includes at least a solid electrolyte.
As the solid electrolyte contained in the solid electrolyte layer, a known solid electrolyte that can be used in an all-solid-state battery can be appropriately used, and examples of such inorganic solid electrolytes include a sulfide-based solid electrolyte, an oxide-based solid electrolyte, a hydride-based solid electrolyte, a halide-based solid electrolyte, and a nitride-based solid electrolyte. The sulfide-based solid electrolyte may contain sulfur (S) as a main component of the anion element. The oxide-based solid electrolyte may contain oxygen (O) as a main component of the anion element. The hydride-based solid electrolyte may contain hydrogen (H) as a main component of the anion element. The halide-based solid electrolyte may contain a halogen (X) as a main component of the anion element. The nitride-based solid electrolyte may contain nitrogen (N) as a main component of the anion element.

The sulfide-based solid electrolyte may be a sulfide glass, a crystallized sulfide glass (glass ceramics), or a crystalline material obtained by subjecting a raw material composition to a solid-phase reaction treatment.
The crystalline state of the sulfide-based solid electrolyte can be confirmed, for example, by subjecting the sulfide-based solid electrolyte to powder X-ray diffraction measurement using CuKα radiation.

The sulfide glass can be obtained by subjecting a raw material composition (e.g., _a mixture of _Li2S and _P2S5 ) to an amorphous process. Examples of the amorphous process include mechanical milling.

Glass ceramics can be obtained, for example, by heat treating a sulfide glass.
The heat treatment temperature may be any temperature higher than the crystallization temperature (Tc) of the sulfide glass observed by thermal analysis, and is usually 195° C. or higher. On the other hand, there is no particular upper limit to the heat treatment temperature.
The crystallization temperature (Tc) of the sulfide glass can be measured by differential thermal analysis (DTA).
The heat treatment time is not particularly limited as long as it is a time that can obtain the desired crystallinity of the glass ceramics, but is, for example, in the range of 1 minute to 24 hours, and particularly, in the range of 1 minute to 10 hours.
The method of heat treatment is not particularly limited, but for example, a method using a baking furnace can be mentioned.

Examples of oxide-based solid electrolytes include solid electrolytes containing Li element, Y element (Y is at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, and S), and O element. Specific examples of oxide- _based solid electrolytes include garnet _-type solid _electrolytes such as _Li7La3Zr2O12 , Li7 _{-xLa3 (} Zr2 _{- xNbx} ) _O12 (0≦x≦2), and _Li5La3Nb2O12 ; perovskite-type solid electrolytes such as (Li,La) _TiO3 , (Li,La) _NbO3 , and (Li,Sr)(Ta _, Zr) _{O3 ;} Nasicon-type solid electrolytes such as Li(Al,Ti)( _PO4 ) _{3 and} Li(Al,Ga)( _PO4 ) ₃ ; Li-P-O-based solid electrolytes such as _{Li3PO4 and} LIPON (a compound in which part of the O _{in Li3PO4} is replaced with N); and _{Li3BO 3} , and compounds in which part of O in Li ₃ BO ₃ is replaced with C.
In the present disclosure, the notation "(A, B, C)" in a chemical formula means "at least one selected from the group consisting of A, B, and C."

The hydride-based solid electrolyte contains, for example, Li and a complex anion containing hydrogen, such as (BH ₄ ) ⁻ , (NH ₂ ) ⁻ , (AlH ₄ ) ⁻ , and (AlH ₆ ) ³⁻ .

The halide-based solid electrolyte is, for example, represented by the following composition formula (1).
Li _α M _β X _γ ...Formula (1)
In the composition formula (1), α, β, and γ are each independently a value greater than 0. M includes at least one element selected from the group consisting of metal elements and metalloid elements other than Li. X includes at least one element selected from the group consisting of F, Cl, Br, and I.
In the present disclosure, the term "metalloid elements" refers to B, Si, Ge, As, Sb, and Te. The term "metal elements" refers to all elements contained in Groups 1 to 12 of the periodic table except for hydrogen, and all elements contained in Groups 13 to 16 of the periodic table except for B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. In other words, the term "metalloid elements" or "metal elements" refers to a group of elements that can become cations when forming an inorganic compound with a halogen element.
More specifically, examples of halide-based solid electrolytes include _Li3YX6 , _Li2MgX4 , _Li2FeX4 , _{LiAlX4 , LiGaX4} , _LiInX4 , _Li3AlX6 , _Li3GaX6 , _{and Li3InX6 .} Here, X is at _least one selected from the group consisting of F, Cl, Br, _{and I.}

An example of the nitride-based solid electrolyte is Li ₃ N.

The solid electrolyte may be in the form of particles from the viewpoint of ease of handling.
The average particle size of the solid electrolyte particles is not particularly limited, but may be, for example, 10 nm or more, and may be 100 nm or more, whereas the average particle size of the solid electrolyte particles is, for example, 25 μm or less, and may be 10 μm or less.

In this disclosure, unless otherwise specified, the average particle size of particles is the volume-based median diameter (D50) value measured by laser diffraction/scattering particle size distribution measurement. In addition, in this disclosure, the median diameter (D50) is the diameter (volume average diameter) at which the cumulative volume of particles is half (50%) of the total volume when the particles are arranged in order from smallest to largest particle size.

The solid electrolyte may be used alone or in combination of two or more kinds. When two or more kinds of solid electrolytes are used, the two or more kinds of solid electrolytes may be mixed, or two or more layers of the solid electrolyte may be formed to form a multilayer structure.
The proportion of the solid electrolyte in the solid electrolyte layer is not particularly limited, but is, for example, 50% by mass or more, may be in the range of 60% by mass or more and 100% by mass or less, may be in the range of 70% by mass or more and 100% by mass or less, or may be 100% by mass.

The solid electrolyte layer may contain a binder from the viewpoint of expressing plasticity. Examples of such binders include the materials exemplified as the binders used in the positive electrode layer. However, in order to facilitate high output, the binder may be contained in the solid electrolyte layer in an amount of 5 mass% or less from the viewpoint of preventing excessive aggregation of the solid electrolyte and enabling the formation of a solid electrolyte layer having a uniformly dispersed solid electrolyte.

The thickness of the solid electrolyte layer is not particularly limited, and is usually 0.1 μm or more and 1 mm or less.
The method for forming the solid electrolyte layer includes a method of applying a paste for forming a solid electrolyte layer containing a solid electrolyte onto a support and drying it, and a method of pressurizing a powder of a solid electrolyte material containing a solid electrolyte. The support may be the same as those exemplified for the positive electrode layer. When pressurizing the powder of the solid electrolyte material, a press pressure of about 1 MPa to 2000 MPa is usually applied.
The method of applying pressure is not particularly limited, but may be any of the pressure applying methods exemplified in the formation of the positive electrode layer.

The all-solid-state battery may, as necessary, include an exterior body that houses a laminate including 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, and a restraining member and the like.
The material of the exterior body is not particularly limited as long as it is stable with respect to the solid electrolyte, and examples of the material include polypropylene, polyethylene, and resins such as acrylic resin.
The restraining member may be any known member usable as a battery restraining member as long as it can apply a restraining pressure in the stacking direction to the laminate. For example, a restraining member having a plate-shaped portion that sandwiches both surfaces of the laminate, a rod-shaped portion that connects the two plate-shaped portions, and an adjustment portion that is connected to the rod-shaped portion and adjusts the restraining pressure by a screw structure or the like can be used. The adjustment portion can apply a desired restraining pressure to the laminate.
The restraining pressure is not particularly limited, but may be, for example, 0.1 MPa or more, 1 MPa or more, or 5 MPa or more. By increasing the restraining pressure, there is an advantage that the contact between the layers is easily improved. On the other hand, the restraining pressure may be, for example, 100 MPa or less, 50 MPa or less, or 20 MPa or less. If the restraining pressure is too high, the restraining member is required to have high rigidity, and the restraining member may become large.

The all-solid-state battery may have only one of the laminates, or may be formed by stacking a plurality of the laminates.
The all-solid-state battery may be an all-solid-state lithium-ion secondary battery or the like.
Examples of the shape of the all-solid-state battery include a coin type, a laminate type, a cylindrical type, and a square type.
The use of the all-solid-state battery is not particularly limited, but examples thereof include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. In particular, the all-solid-state battery may be used as a driving power source for hybrid electric vehicles, plug-in hybrid electric vehicles, or electric vehicles. The all-solid-state battery of the present disclosure may also be used as a power source for moving objects other than vehicles (e.g., railways, ships, and aircraft), and may also be used as a power source for electrical products such as information processing devices.

In the manufacturing method of the all-solid-state battery disclosed herein, for example, a solid electrolyte layer is formed by first applying a paste for forming a solid electrolyte layer to a support and drying it. Then, a paste for forming a positive electrode layer containing a positive electrode active material is applied to one side of the solid electrolyte layer and dried to obtain a positive electrode layer. Thereafter, the support is peeled off from the solid electrolyte layer, and a paste for forming an anode layer is applied to the other side of the solid electrolyte layer and dried to form a negative electrode layer. If necessary, a positive electrode current collector is attached to the side of the positive electrode layer opposite the solid electrolyte layer, and a negative electrode current collector is attached to the side of the negative electrode layer opposite the solid electrolyte layer to form an all-solid-state battery.

Example 1
[Preparation of Positive Electrode]
The positive electrode active material ( _{LiNi0.8Co0.15Al0.05O2} , average _particle size _10μm ) _coated with LiNbO3 using a rolling fluidized _granulation coating device, sulfide-based solid electrolyte (10LiI·15LiBr·75 _{( 0.75Li2S} · _0.25P2S5 ) (mol%)), conductive material (VGCF (registered trademark) -H, strength ratio D/G 0.05, specific surface area ^13m2 /g) and a binder (SBR) were weighed out so that the mass ratio of the positive electrode active material: sulfide-based solid electrolyte: conductive material: binder was 69.3: 30.0: 0.5: 0.2, and mixed with a dispersion medium (diisobutyl ketone). The obtained mixture was dispersed with an ultrasonic homogenizer (UH-50, manufactured by SMT Co., Ltd.) to obtain a slurry for forming a positive electrode layer. The obtained slurry for forming a positive electrode layer was applied to an Al foil (thickness 15 μm) by a blade coat method using an applicator, and dried at 100 ° C. for 30 minutes to obtain a positive electrode having a positive electrode layer and an Al foil. The thickness of the positive electrode layer was 100 μm. The positive electrode layer is the electrode mixture of the present disclosure.
Table 1 shows the results of calculating the conductive load parameters of the conductive material and the results of measuring the contact interface length between the conductive material and the solid electrolyte.
FIG. 1 is a diagram showing the results of Raman spectrum measurement of the conductive material used in Example 1.

[Preparation of negative electrode]
A negative electrode active material (Si particles, average particle size 0.5 μm), a sulfide-based solid electrolyte (10LiI.15LiBr.75(0.75Li ₂ S.0.25P ₂ S ₅ ) (mol %), average particle size 0.5 μm), a conductive material (VGCF (registered trademark) -H), and a binder (SBR) were weighed out so that the mass ratio (mass %) of the negative electrode active material:sulfide-based solid electrolyte:conductive material:binder was 47.0:44.6:7.0:1.4, and mixed with a dispersion medium (diisobutyl ketone). The obtained mixture was dispersed with an ultrasonic homogenizer (UH-50, manufactured by SMT Co., Ltd.) to obtain a slurry for forming the negative electrode layer. The obtained negative electrode layer forming slurry was applied onto a negative electrode current collector (Ni foil, thickness 22 μm) by a blade coating method using an applicator, and dried at 100° C. for 30 minutes to obtain a negative electrode having a negative electrode current collector and a negative electrode layer. The thickness of the negative electrode layer was 60 μm.

[Preparation of solid electrolyte layer]
A sulfide-based solid electrolyte (10LiI·15LiBr·75(0.75Li ₂ S·0.25P ₂ S ₅ )(mol%), average particle size 2.0 μm) and a binder (SBR) were weighed out so that the mass ratio of the sulfide-based solid electrolyte:binder was 99.6:0.4, and mixed with a dispersion medium (diisobutyl ketone). The obtained mixture was dispersed with an ultrasonic homogenizer (UH-50, manufactured by SMT Co., Ltd.) to obtain a slurry for forming a solid electrolyte layer. The obtained slurry for forming a solid electrolyte layer was applied to an Al foil (thickness 15 μm) by a blade coat method using an applicator, and dried at 100 ° C. for 30 minutes to obtain a solid electrolyte layer having an Al foil. The thickness of the solid electrolyte layer was 30 μm.
In Examples 1 to 5, the sulfide-based solid electrolyte was heated using a hot plate in an atmosphere with a dew point of -70° C. and 20% oxygen to form a lithium sulfate coating.

[Preparation of all-solid-state lithium-ion secondary battery]
A solid electrolyte layer was placed on the negative electrode layer of the negative electrode, the Al foil was peeled off from the solid electrolyte layer, and a positive electrode was laminated on the solid electrolyte layer such that the positive electrode layer was in contact with the solid electrolyte layer, and pressed at 5 ton/cm at 130° C. This produced an all-solid-state lithium ion secondary battery for evaluation having a positive electrode, a solid electrolyte layer, and a negative electrode in this order.

Example 2
In the above [Preparation of Positive Electrode], except that the ratio of the positive electrode active material:sulfide-based solid electrolyte:conductive material:binder was weighed out to be 68.3:30.0:1.5:0.2, a positive electrode and an all-solid-state lithium ion secondary battery were obtained in the same manner as in Example 1. The conductive load parameters of the conductive material and the contact interface length between the conductive material and the solid electrolyte are shown in Table 1.

Example 3
In the above [Preparation of Positive Electrode], except that the ratio of the positive electrode active material:sulfide-based solid electrolyte:conductive material:binder was weighed to be 67.8:30.0:2.0:0.2, a positive electrode and an all-solid-state lithium ion secondary battery were obtained in the same manner as in Example 1. The conductive load parameters of the conductive material and the contact interface length between the conductive material and the solid electrolyte are shown in Table 1.

Example 4
In the above [Preparation of Positive Electrode], except that the ratio of the positive electrode active material: the sulfide-based solid electrolyte: the conductive material: the binder was weighed out to be 66.8:30.0:3.0:0.2, a positive electrode and an all-solid-state lithium ion secondary battery were obtained in the same manner as in Example 1. The conductive load parameters of the conductive material and the contact interface length between the conductive material and the solid electrolyte are shown in Table 1.

Example 5
A positive electrode and an all-solid-state lithium-ion secondary battery were obtained in the same manner as in Example 1, except that in the above [Preparation of Positive Electrode], VGCF (registered trademark ) -H (intensity ratio D/G 0.05, specific surface area 13 m ² /g) and AB (intensity ratio ^D /G 0.9, specific surface area 120 m 2 /g) were used as the conductive materials and weighed out so that the ratio of positive electrode active material: sulfide-based solid electrolyte: conductive material VGCF (registered trademark)-H: conductive material AB: binder = 67.5:30.0:1.8:0.5:0.2. The conductive load parameters of the conductive materials and the contact interface length between the conductive materials and the solid electrolyte are shown in Table 1.

(Comparative Example 1)
In the above [Preparation of Positive Electrode], except that the ratio of the positive electrode active material:sulfide-based solid electrolyte:conductive material:binder was weighed to be 69.4:30.0:0.4:0.2, a positive electrode and an all-solid-state lithium ion secondary battery were obtained in the same manner as in Example 1. The conductive load parameters of the conductive material and the contact interface length between the conductive material and the solid electrolyte are shown in Table 1.

(Comparative Example 2)
In the above [Preparation of Positive Electrode], except that the ratio of the positive electrode active material:sulfide-based solid electrolyte:conductive material:binder was weighed to be 64.8:30.0:6.0 (5.95):0.2, a positive electrode and an all-solid-state lithium ion secondary battery were obtained in the same manner as in Example 1. The conductive load parameters of the conductive material and the contact interface length between the conductive material and the solid electrolyte are shown in Table 1.

[Charge/discharge test]
Using the evaluation cells of Examples 1 to 5 and Comparative Examples 1 and 2, charge and discharge tests were carried out under the following conditions.
Each evaluation cell was bound to a fixed size under a binding pressure of 5 MPa, and was charged at a constant current-constant voltage (CC-CV) at 0.461 mA to 2.7 V. Then, CC-CV discharge was performed at 0.461 mA to 3.0 V. Then, the all-solid-state lithium-ion secondary battery was charged again. This charge was regarded as the first (initial) charge. Then, the first (initial) discharge was performed, and the discharge capacity (mAh/g) was calculated. The calculation results of the discharge capacity are shown in Table 1. Then, the charge/discharge cycle was performed at 2C up to 300 cycles.

[Intensity ratio B/A]
XPS was performed on each evaluation cell, and the intensity ratio B/A of the peak intensity B near 162 eV to the peak intensity A near 159 to 160 eV in the sulfur S2p spectrum of the solid electrolyte obtained was calculated. The calculated results of the intensity ratio B/A are shown in Table 1.
FIG. 2 is a diagram showing the measurement results of the sulfur S2p spectrum of the solid electrolyte used in Example 1.

[Resistance Evaluation]
The internal resistance of each evaluation cell was evaluated by the impedance method. Specifically, after the initial charge and discharge, each evaluation cell was adjusted to SOC 20%, and the circular hole component value of the impedance was calculated, which was used as the initial resistance. The calculation results of the initial resistance are shown in Table 1.
The resistance after 300 cycles was calculated in the same manner, and the resistance increase rate after 300 cycles was calculated by dividing the resistance after 300 cycles by the initial resistance. The calculation results of the resistance increase rate after 300 cycles are shown in Table 1.

[Evaluation Results]
As shown in Table 1, Examples 1 to 5 have lower initial resistance and higher discharge capacity than Comparative Example 1. Also, Examples 1 to 5 have lower resistance increase rates after 300 cycles than Comparative Example 2. Therefore, it was demonstrated that Examples 1 to 5 have an excellent balance between initial resistance, discharge capacity, and resistance increase rate.

Claims (2)

An electrode mixture for an all-solid-state battery,
The battery includes an active material, a solid electrolyte, and a conductive material,
An electrode mixture, in which the conductive load parameter of the conductive material is obtained by multiplying the intensity ratio D/G of the peak intensity D at 1350 cm ^-1 to the peak intensity G at 1600 cm ^- 1 in Raman spectrum measurement of the conductive material by the content W (mass %) of the conductive material, dividing the result by the specific surface area Si ( ^m2 /g) of the conductive material, and multiplying the result by 100, is greater than 0.16 and less than 0.57 . An all-solid-state battery,
The all-solid-state battery includes the electrode mixture according to claim 1,
An all-solid-state battery in which an intensity ratio B/A of a peak intensity B near 162 eV to a peak intensity A near 159 to 160 eV in a sulfur S2p spectrum of the solid electrolyte obtained by X-ray photoelectron spectroscopy (XPS) after initial charging and discharging of the all-solid-state battery is greater than 0.39 and is 0.51 or less.