Negative electrode composite material slurry, negative electrode, and solid-state battery

Abstract

A negative electrode composite material slurry of the present disclosure contains a dispersant (A), an Si-based active material (B), and a sulfide solid electrolyte (C). The dispersant (A) is an acrylic copolymer. The acrylic copolymer has a structural unit (a) that does not have an amino group, and a structural unit (b) that has an amino group. A glass transition temperature of the acrylic copolymer is from -60°C to 50°C. An amine value of a solid content of the acrylic copolymer is within a range of 1.5 mg KOH / g to 130 mg KOH / g.

Description

NEGATIVE ELECTRODE COMPOSITE MATERIAL SLURRY, NEGATIVE ELECTRODE, AND SOLID-STATE BATTERY

[0001] The present disclosure relates to a negative electrode composite material slurry, a negative electrode, and a solid-state battery. Related Art

[0002] Solid-state batteries having a solid electrolyte layer are known as lithium ion secondary batteries having excellent stability.

[0003] Patent Document 1 discloses an all-solid-state secondary battery (hereinafter also called “solid-state battery”). This solid-state battery has a positive electrode, a solid electrolyte layer, and a negative electrode. At least any of the positive electrode, the solid electrolyte layer and the negative electrode contains a graft polymer.

[0004] Japanese Patent Application Laid-Open (JP-A) No. 2011-014387

[0005] However, in the solid-state battery disclosed in Patent Document 1, if the negative electrode contains a graft polymer, there is the concern that the internal resistance of the solid-state battery will be high. Therefore, there is the need for a slurry for a negative electrode that can reduce the internal resistance of a solid-state battery.

[0006] The present disclosure was made in view of the above-described circumstances. A topic that an embodiment of the present disclosure addresses is the provision of a negative electrode composite material slurry and a negative electrode that can reduce the internal resistance of a solid-state battery. A topic that another embodiment of the present disclosure addresses is the provision of a solid-state battery whose internal resistance is reduced. Solution to Problem

[0007] Means for addressing the above topics include the following embodying aspects.

[0008] <1> A negative electrode composite material slurry, including: a dispersant (A); an Si-based active material (B); and a sulfide solid electrolyte (C), wherein: the dispersant (A) is an acrylic copolymer, the acrylic copolymer has a structural unit (a) that does not have an amino group, and a structural unit (b) that has an amino group, a glass transition temperature of the acrylic copolymer is -from -60°C to 50°C, and an amine value of a solid content of the acrylic copolymer is from 1.5 mg KOH / g to 130 mg KOH / g. <2> The negative electrode composite material slurry of above <1>, wherein the structural unit (a) within the acrylic copolymer includes a structural unit expressed by the following formula (a).

[0009]

[0010] In the formula (a), Z represents O or NH, R1represents H or CH3, and R2represents a group selected from hydrocarbyl groups and ether group-containing groups. <3> The negative electrode composite material slurry of above <1> or <2>, having a viscosity of 30 mPa.s to 130 mPa.s at 25°C. <4> The negative electrode composite material slurry of any one of above <1> through <3>, wherein: a number average molecular weight (Mn) of the acrylic copolymer is within a range of 1,000 g / mol to 100,000 g / mol, and a molecular weight distribution (Mw / Mn) of the acrylic copolymer is within a range of 1.05 to 10.00. <5> The negative electrode composite material slurry of any one of above <1> through <4>, wherein the structural unit (b) within the acrylic copolymer includes at least one selected from the group consisting of structural units containing a vinyl group and an amino group and structural units expressed by the following formula (b).

[0011]

[0012] In the formula (b), Z represents O or NH, R1represents H or CH3, R3represents an organic group having 2 to 4 carbon atoms, and R4and R5each independently represent an organic group, and R4and R5may arbitrarily bind together and form a ring structure. <6> The negative electrode composite material slurry of any one of above <1> through <5>, wherein the acrylic copolymer has a block structure. <7> A negative electrode including a negative electrode composite material layer, wherein the negative electrode composite material layer contains a solid content of the negative electrode composite material slurry of any one of above <1> through <6>. <8> A solid-state battery, including the negative electrode of above <7>.

[0013] In accordance with an embodiment of the present disclosure, there are provided a negative electrode composite material slurry and a negative electrode that can reduce the internal resistance of a solid-state battery. In accordance with another embodiment of the present disclosure, there is provided a solid-state battery whose internal resistance is reduced.

[0014] Fig. 1 is a schematic sectional view illustrating an example of a solid-state battery.

[0015] In the present disclosure, numerical value ranges expressed by using “to” mean ranges in which the numerical values listed before and after the “to” are included as the minimum value and maximum value, respectively. In numerical value ranges that are expressed in a stepwise manner in the present disclosure, the maximum value or the minimum value listed in a given numerical value range may be substituted by the maximum value or the minimum value of another numerical value range that is expressed in a stepwise manner. In numerical value ranges mentioned in the present disclosure, the maximum value or the minimum value listed in a given numerical value range may be substituted by a value shown in the Examples. In the present disclosure, combinations of two or more preferable aspects are more preferable aspects. In the present disclosure, in a case in which there are plural types of substances that correspond to a component, the amount of that component means the total amount of the plural types of substances, unless otherwise indicated. In the present disclosure, “step” is not only an independent step and includes steps that, even in a case in which that step cannot be clearly distinguished from another step, achieve the intended object of that step. In the present disclosure, “(meth)acrylic ester” means at least one of acrylic ester and methacrylic ester. “(Meth)acrylic acid” means at least one of acrylic acid and methacrylic acid.

[0016] (1) Negative Electrode Composite Material Slurry The negative electrode composite material slurry of the present disclosure contains a dispersant (A), an Si-based active material (B), and a sulfide solid electrolyte (C). The dispersant (A) is an acrylic copolymer. The acrylic copolymer has a structural unit (a) that does not have amino groups, and a structural unit (b) that has amino groups. The glass transition temperature (hereinafter also called “Tg”) of the acrylic copolymer is from -60°C to 50°C. The amine value of a solid content of the acrylic copolymer is within the range of 1.5 mg KOH / g to 130 mg KOH / g.

[0017] In the present disclosure, “negative electrode composite material slurry” means a slurry used in fabricating a negative electrode composite material layer of a solid-state battery. In the present disclosure, “Si-based active material” means an active material containing Si.

[0018] The negative electrode composite material slurry of the present disclosure has the above-described structure, and therefore can reduce the internal resistance of a solid-state battery. This effect is assumed to be due to the following reasons, but is not limited to this. In the present disclosure, dispersant (A) is an acrylic copolymer. The acrylic copolymer has the structural unit (a) that does not have an amino group, and the structural unit (b) that has an amino group. In addition, the amine value of the solid content of the dispersant (A) is within the range of 1.5 mg KOH / g to 130 mg KOH / g. Due thereto, the solid content of the negative electrode composite material slurry (e.g., the Si-based active material (B) and the sulfide solid electrolyte (C)) can be dispersed better than in a case in which the amine value of the solids is outside of the range of 1.5 mg KOH / g to 130 mg KOH / g. In the present embodiment, Tg of the acrylic copolymer is from -60°C to 50°C. Due thereto, the flexibility of the acrylic copolymers (the dispersant (A)) improves. Therefore, in the negative electrode composite material slurry, resistance that is due to colliding of the solid content of the negative electrode composite material slurry is suppressed. As a result, flocculation of the solids within the negative electrode composite material slurry is suppressed. It is assumed that the negative electrode composite material slurry of the present disclosure can reduce the internal resistance of a solid-state battery due to the above.

[0019] Hereinafter, the structural unit (a) that does not have an amino group is also simply called “the structural unit (a)”. The structural unit (b) that has an amino group is also simply called “the structural unit (b)”.

[0020] The viscosity of the negative electrode composite material slurry at 25°C is not particularly limited, and is preferably from 30 mPa.s to 130 mPa.s. Due thereto, the dispersibility and the dispersion stability of the negative electrode composite material slurry improve, and the surface area of contact between the negative electrode active material and the conduction assistant, and the negative electrode composite material slurry, can be made to be large. The viscosity of the negative electrode composite material slurry at 25°C may be 70 mPa.s or more, or may be 120 mPa.s or more. The viscosity of the negative electrode composite material slurry at 25°C may be 50 mPa.s or less, or may be 30 mPa.s or less. The method of measuring the viscosity of the negative electrode composite material slurry is similar to the method described in the Examples.

[0021] The particle size of the negative electrode composite material slurry is not particularly limited, and may be from 10 micrometres to 100 micrometres, or may be from 60 micrometres to 100 micrometres, or may be from 10 micrometres to 35 micrometres. The method of measuring the particle size of the negative electrode composite material slurry is similar to the method described in the Examples.

[0022] The negative electrode composite material slurry is suitably used to form a negative electrode composite material layer of a lithium ion battery (in particular, a solid-state battery).

[0023] (1.1) Dispersant (A) The negative electrode composite material slurry contains dispersant (A). Dispersant (A) is an acrylic copolymer. The acrylic copolymer may have a block structure (i.e., be a block copolymer), or may have a copolymer produced by simultaneous polymerization of a mixture of two or more components.

[0024] (1.1.1) Properties Tg of the acrylic copolymer is from -60°C to 50°C. If Tg exceeds 50°C, the flexibility of the acrylic copolymers is insufficient, and it is difficult to suppress resistance that is due to collisions between solids. If Tg is less than -60°C, the repulsion due to steric hindrance of the solids is weak, and the dispersibility is poor. From the standpoint of the dispersibility of the slurry, Tg of the acrylic copolymer is preferably from -50°C to 40°C, and is more preferably from -45°C to 20°C, and is even more preferably from -45°C to 0°C.

[0025] The amine value of the solid content of the acrylic copolymer is from 1.5 mg KOH / g to 130 mg KOH / g. From the standpoint of the viscosity of the slurry, the amine value of the solid content of the acrylic copolymer is preferably from 3 mg KOH / g to 120 mg KOH / g, and more preferably from 3 mg KOH / g to 50 mg KOH / g.

[0026] It is preferable that the acrylic copolymer is a block copolymer, and that the amine value of the solid content of the acrylic copolymer is from 1.5 mg KOH / g to 50 mg KOH / g, and that the glass transition temperature of the acrylic copolymer is from -30°C to 0°C. Due thereto, the negative electrode composite material slurry can better reduce the internal resistance of the solid-state battery.

[0027] It is preferable that the acrylic copolymer is a copolymer, and that the amine value of the solid content of the acrylic copolymer is from 20 mg KOH / g to 50 mg KOH / g, and that the glass transition temperature of the acrylic copolymer is from 0°C to 50°C. Due thereto, the negative electrode composite material slurry can better reduce the internal resistance of the solid-state battery.

[0028] (1.1.2) Molecular Weight A number average molecular weight (Mn) of the acrylic copolymer is not particularly limited, and may be from 1,000 g / mol to 100,000 g / mol, or may be from 3,000 g / mol to 50,000 g / mol, or may be from 3,000 g / mol to 30,000 g / mol. The molecular weight distribution (Mw / Mn) of the acrylic copolymer is not particularly limited, and may be from 1.05 to 10.00, or may be from 1.1 to 8.00, or may be from 1.15 to 6.00. The methods of measuring the number average molecular weight (Mn) and the weight average molecular weight (Mw) respectively are similar to the methods described in the Examples.

[0029] The acrylic copolymer preferably satisfies molecular weight conditions. The molecular weight conditions are that the number average molecular weight (Mn) of the acrylic copolymer is within the range of 1,000 g / mol to 100,000 g / mol, and the molecular weight distribution (Mw / Mn) of the acrylic copolymer is within the range of 1.05 to 10.00. Due to the acrylic copolymer satisfying these molecular weight conditions, the solids within the negative electrode composite material slurry of the present disclosure are adsorbed more efficiently than in a case in which the acrylic copolymer does not satisfy these molecular weight conditions. As a result, flocculation of the solids within the negative electrode composite material slurry is suppressed.

[0030] (1.1.3) Structural Units The acrylic copolymer has the structural unit (a) and the structural unit (b). The coupling scheme of the structural unit (a) and the structural unit (b) may be block or may be a copolymer produced by simultaneous polymerization of a mixture of two or more components.

[0031] (1.1.3.1) Structural Unit (a) The structural unit (a) is not particularly limited provided that it is a structural unit that does not have an amino group. It is preferable that the structural unit (a) includes a structural unit expressed by the following formula (a), and it is even more preferable that the structural unit (a) is the structural unit expressed by the following formula (a).

[0032]

[0033] In the formula (a), Z represents O or NH. R1represents H or CH3. R2represents a group selected from hydrocarbyl groups and ether group-containing groups.

[0034] The structural unit (a) is selected from acrylic esters, methacrylic esters, acrylamides and / or methacrylamides that preferably do not have a primary amino group, a secondary amino group, a tertiary amino group or a quaternary amino group.

[0035] Examples of structural unit (a) are: (meth)acrylic esters (a1) of straight-chain aliphatic alcohols, branched-chain aliphatic alcohols or cyclic aliphatic alcohols having 1 to 22 (preferably 1 to 12 , more preferably 1 to 8, and most preferably 1 to 6) carbon atoms; (meth)acrylic esters (a2) having dicyclopentadienyl functionality; aryl(meth)acrylic esters (a3) containing 5 to 12 (preferably 6 to 10) carbon atoms in the aryl ring, and at which there is no possibility of containing other substituents; aralkyl(meth)acrylic esters (a4) containing 6 to 11 (preferably 7 to 11) carbon atoms in the aralkyl radical, and at which there is no possibility of containing other substituents on the aryl radical; (meth)acrylic esters (a5) of mixed polyalkylene glycols having 4 to 80 carbon atoms and having a statistical, a block or a gradient distribution of different monomers along the chain; poly(ethylene glycol) alkyl ether (meth)acrylate (a6) that is a straight-chain alkyl residue or a branched-chain alkyl residue in which the alkyl has 1 to 22 (preferably 1 to 15, more preferably 1 to 12, even more preferably 1 to 8, and most preferably 1 to 4) carbon atoms; and trimethylsilyl (meth)acrylate (a7). Examples of (meth)acrylic esters (a1) are methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, isobutyl (meth)acrylate, isopentyl (meth)acrylate, lauryl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, behenyl (meth)acrylate, isodecyl (meth)acrylate, 2-propylheptyl (meth)acrylate, 3,5,5-trimethyl-1-hexyl (meth)acrylate, nonanyl (meth)acrylate, 2-propylheptyl (meth)acrylate, 2-isopropyl-5-methyl-hexyl (meth)acrylate, tridecyl (meth)acrylate, heptadecyl (meth)acrylate, heneicosanyl (meth)acrylate, and isobornyl (meth)acrylate. Examples of (meth)acrylic esters (a2) are dicyclopentenyloxyethyl acrylate and dicyclopentenyloxyethyl methacrylate. Examples of aryl(meth)acrylic esters (a3) are phenyl acrylate and 4-methylphenyl methacrylate. Examples of aralkyl(meth)acrylic esters (a4) are benzyl methacrylate and the like. Examples of (meth)acrylic esters (a5) are tetrahydrofurfuryl (meth)acrylate, di(ethyleneglycol)methylether (meth)acrylate, furfuryl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, allyloxyethyl (meth)acrylate, 1-ethoxybutyl (meth)acrylate, methyltriglycol (meth)acrylate, ethyltriglycol (meth)acrylate, butyldiglycol (meth)acrylate, and poly(propyleneglycol)methylether (meth)acrylate.

[0036] R2in above the formula (a) is more preferably a branched-chain or a non-branched-chain alkyl residue having 1 to 12 (preferably 1 to 10) carbon atoms, a cycloalkyl residue having 4 to 8 (preferably 6) carbon atoms, or an aromatic aliphatic residue (e.g., a benzyl group) having 7 to 12 carbon atoms.

[0037] (1.1.3.2) Structural Unit (b) The structural unit (b) is not particularly limited provided that it is a structural unit having an amino group, and preferably includes at least one selected from the group consisting of structural units containing a vinyl group and an amino group and structural units expressed by the formula (b).

[0038] Examples of amino group containing monomers that have a vinyl group are 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, and 1-vinylimidazole.

[0039] Structural units expressed by the formula (b) are expressed as follows.

[0040]

[0041] In the formula (b), Z represents O or NH. R1represents H or CH3. R3represents an organic group having 2 to 4 carbon atoms. R4and R5each independently represent an organic group. R4and R5may arbitrarily bind together and form a ring structure.

[0042] Examples of the structural unit (b) are 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 1-vinylimidazole, acryl ester, methacryl ester, acrylamide, and methacryl amide. The hydrogen atoms in the R4residue and R5residue of above the formula (b) may be substituted by a substituent (e.g., tert-amino group). Specific examples of monomer (b) are N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dibutylaminoethyl (meth)acrylate, 2-(2-dimethylaminoethyl(methyl)amino)ethyl (meth)acrylate, 2-(2-dimethylaminoethyloxy)ethyl (meth)acrylate, 2-morpholinoethyl (meth)acrylate, 2-(1-piperidyl)ethyl (meth)acrylate, 2-(N-ethylanilino)ethyl (meth)acrylate, 2-imidazole-1-ylethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, and N,N-dimethylaminoethyl (meth)acrylate. Thereamong, it is preferable that monomer (b) contain N,N-dimethylaminoethyl methacrylate (DMAEMA).

[0043] (1.1.3.3) Block Copolymer The acrylic copolymer may have a block structure (i.e., be a block copolymer).

[0044] The block copolymer preferably has at least one block (a) containing above the structural unit (a).

[0045] The proportion of the structural unit (a) in block (a) is not particularly limited, and preferably exceeds 50 mass%, and more preferably exceeds 70 mass%, and even more preferably exceeds 90 mass%, with respect to the total amount of block (a). The structural unit (a) in block (a) may be a single type, or may be a combination of two or more types.

[0046] The block copolymer preferably has at least one block (b) containing the structural unit (b).

[0047] The structural unit (b) that contains at least one tertiary amino group may be produced by the reaction after the construction of the polymer chain. Oxirane-containing ethyleny unsaturated monomers (e.g., glycidyl methacrylate) are (co)polymerized and can form a polymer block having an oxirane group.

[0048] The structural unit (b) can react with an amine after polymerization. In such a case, the R3residue includes a hydroxyl group. As needed, R4and / or R5may further include a hydroxyl group. A primary amine additionally carry one or more tertiary amino groups, or a secondary amine additionally carry one or more tertiary amino groups, is suitable for this purpose. Specific examples are dialkylamines (e.g., dimethylaminopropylamine, diethylaminoethylamine, diethylamine, dibutylamine and dicyclohexylamine), secondary amines (e.g., N-(2-hydroxyethyl)aniline) having two different types of substituents, secondary amines (e.g., bis(3-dimethylaminopropyl)amine) having at least one tertiary amino group, and dihydroxyalkylamines (e.g., diethanolamine or diisopropanolamine). A secondary amine that additionally carry one or more tertiary amino groups is preferable.

[0049] The proportion of the structural unit (b) in block (b) is not particularly limited, and preferably exceeds 50 mass%, and more preferably exceeds 70 mass%, and even more preferably exceeds 90 mass%, with respect to the total amount of block (b). The proportion of the structural unit (b) in block (b) may be 100 mass%. The structural unit (b) in block (b) may be a single type, or may be a combination of two or more types.

[0050] It is preferable that the acrylic copolymer have at least one block (a) and at least one block (b). The acrylic copolymer may be formed from at least one block (a) and at least one block (b). The mass ratio (block (a) / block (b)) of block (a) and block (b) is not particularly limited and is preferably from 90 / 10 to 25 / 75.

[0051] (1.1.3.4) Copolymer The acrylic copolymer may have a copolymer produced by simultaneous polymerization of a mixture of two or more components (i.e., be a copolymer).

[0052] The acrylic copolymer has the structural unit (a) and the structural unit (b). Each of the plural structural unit (a) and plural structural unit (b) are connected simultaneously.

[0053] The structural unit (a) preferably contains a structural unit expressed by above the formula (a), and more preferably is a structural unit expressed by above the formula (a). The structural unit (b) preferably contains at least one structural unit selected from the group consisting of structural units containing a vinyl group and an amino group and structural units expressed by the formula (b). The structural unit (b) more preferably contains a structural unit containing a vinyl group and an amino group, and a structural unit expressed by the formula (b).

[0054] The mass ratio (the structural unit (a) / the structural unit (b)) of the structural unit (a) and the structural unit (b) is not particularly limited, and is preferably from 90 / 10 to 25 / 75.

[0055] (1.1.4) Content The content of dispersant (A) is not particularly limited, and, with respect to 100 parts by mass of the negative electrode composite material slurry, may be 1 part by mass or more, or may be 3 parts by mass or more, or may be 0.5 parts by mass or less, or may be 0.1 parts by mass or less, or may be from 0.1 parts by mass to 3 parts by mass. The content of dispersant (A) is not particularly limited, and, with respect to 100 parts by mass of the solid content of the negative electrode composite material slurry, may be 2 parts by mass or more, or may be 5 parts by mass or more, or may be 0.5 parts by mass or less, or may be 0.1 parts by mass or less, or may be from 0.1 parts by mass to 5 parts by mass. The content of binder (D) is not particularly limited, and, with respect to a total of 100 parts by mass of the Si-based active material (B) and the sulfide solid electrolyte (C), may be 5 parts by mass or more, or may be 10 parts by mass or more, or may be 0.5 parts by mass or less, or may be 0.1 parts by mass or less, or may be from 0.5 parts by mass to 10 parts by mass.

[0056] (1.2) Si-Based Active Material (B) The negative electrode composite material slurry contains Si-based active material (B).

[0057] Examples of Si-based active materials (B) are Si alone, Si alloys, and silicon oxide (SiO). In the Si alloys, it is preferable that Si is the main component thereof. For example, the proportion of element Si in the Si alloy may be 50 mol% or more, or may be 70 mol% or more, or may be 90 mol% or more. Examples of Si alloys are Si-Al alloys, Si-Sn alloys, Si-In alloys, Si-Ag alloys, Si-Pb alloys, Si-Sb alloys, Si-Bi alloys, Si-Mg alloys, Si-Ca alloys, Si-Ge alloys, and Si-Pb alloys. The Si alloy may be an alloy of two components, or may be a multi-component alloy of three or more components. A single type of the Si-based active material (B) may be used alone, or two or more types may be used by being mixed together.

[0058] The shape of the Si-based active material (B) is usually particle-shaped.

[0059] The median diameter of the Si-based active material (B) may be 0.1 micrometres or more, or may be 1 micrometres or more, or may be 20 micrometres or less. The median average particle diameter of the Si-based active material (B) may be 10 micrometres or less or may be 5 micrometres or less. In the method of measuring the median diameter of the Si-based active material (B), the median diameter can be obtained by dispersing the Si-based active material (B) in a dispersion medium, and measuring the volume-based particle diameter distribution by using a particle diameter distribution measuring device, and calculating the particle diameter (median diameter) at which the value of the volume-based, cumulative particle diameter distribution that was obtained corresponds to 50%.

[0060] The content of the Si-based active material (B) is not particularly limited, and, with respect to 100 parts by mass of the negative electrode composite material slurry, may be 10 parts by mass or more, or may be 30 parts by mass or more, or may be 60 parts by mass or less, or may be 40 parts by mass or less, or may be from 10 parts by mass to 40 parts by mass. The content of the Si-based active material (B) is not particularly limited, and, with respect to 100 parts by mass of the solid content of the negative electrode composite material slurry, may be 30 parts by mass or more, or may be 50 parts by mass or more, or may be 80 parts by mass or less, or may be 60 parts by mass or less, or may be from 30 parts by mass to 60 parts by mass. The content of the Si-based active material (B) is not particularly limited, and, with respect to 100 parts by mass of the sulfide solid electrolyte (C), may be 70 parts by mass or more, or may be 100 parts by mass or more, or may be 130 parts by mass or less, or may be 120 parts by mass or less, or may be from 70 parts by mass to 130 parts by mass.

[0061] (1.3) Sulfide Solid Electrolyte (C) The negative electrode composite material slurry contains sulfide solid electrolyte (C).

[0062] Sulfide solid electrolyte (C) preferably contains sulfur (S) as the main component that is an anion element, and further, preferably contains, for example, the element Li, element A and the element S. Element A is at least one type selected from the group consisting of P, As, Sb, Si, Ge, Sn, B, Al, Ga and In. The sulfide solid electrolyte (C) may further contain at least one of O and a halogen element. Examples of the halogen element (X) are F, Cl, Br and I. The composition of the sulfide solid electrolyte (C) is not particularly limited, and examples are . The sulfide solid electrolyte (C) may have the composition expressed by the following general formula (1). The formula (1): Li4-xGe1-xPxS4(0<x<1) In the formula (1), at least some of the Ge may be substituted by at least one selected from the group consisting of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V and Nb. Further, at least some of the P may be substituted by at least one selected from the group consisting of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V and Nb. Some of the Li may be substituted by at least one selected from the group consisting of Na, K, Mg, Ca and Zn. Some of the S may be substituted by a halogen. The halogen is at least one of F, Cl, Br and I. Only one type of the sulfide solid electrolyte (C) may be used alone, or two or more types may be used by being mixed together.

[0063] The shape of the particles of the sulfide solid electrolyte (C) is not particularly limited, and examples are spherical (e.g., perfect circular, oval) and fiber-shaped.

[0064] The median diameter of sulfide solid electrolyte (C) may be 0.1 micrometres or more, or may be 1 micrometres or more, or may be 20 micrometres or less, or may be 10 micrometres or less, or may be 5 micrometres or less, or may be from 0.1 micrometres to 20 micrometres. The method of measuring the median diameter of sulfide solid electrolyte (C) is similar to the method of measuring the median diameter of the Si-based active material (B).

[0065] The content of the sulfide solid electrolyte (C) is not particularly limited, and, with respect to 100 parts by mass of the negative electrode composite material slurry, may be 10 parts by mass or more, or may be 30 parts by mass or more, or may be 60 parts by mass or less, or may be 40 parts by mass or less, or may be from 10 parts by mass to 40 parts by mass. The content of sulfide solid electrolyte (C) is not particularly limited, and, with respect to 100 parts by mass of the solid content of the negative electrode composite material slurry, may be 30 parts by mass or more, or may be 50 parts by mass or more, or may be 80 parts by mass or less, or may be 60 parts by mass or less, or may be from 30 parts by mass to 60 parts by mass. The content of sulfide solid electrolyte (C) is not particularly limited, and, with respect to 100 parts by mass of the Si-based active material (B), may be 70 parts by mass or more, or may be 100 parts by mass or more, or may be 130 parts by mass or less, or may be 120 parts by mass or less, or may be from 70 parts by mass to 130 parts by mass.

[0066] (1.4) Binder (D) The negative electrode composite material slurry may further contain binder (D), or may not contain binder (D).

[0067] The binder (D) is not particularly limited provided that it is a binder that can be used in lithium ion batteries. Examples thereof are butadiene rubber (BR), butylene rubber (IIR), acrylate-butadiene rubber (ABR), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVdF), and polyvinylidene fluoride (PVdF) - hexafluoropropylene copolymer (PVdF-HFP). One type of the binder (D) may be used alone, or two or more types may be used by being mixed together. Thereamong, the binder (D) preferably includes PVdF-HFP, and more preferably is PVdF-HFP. The PVdF is polarized. Due to the binder (D) containing PVdF-HFP, it is easy for the binder (D) to adsorb at at least one of the active material and the solid electrolyte, and it is easy to make the binding force high.

[0068] If the negative electrode composite material slurry further contains binder (D), the content of binder (D) may be in the following ranges. The content of binder (D) is not particularly limited, and, with respect to 100 parts by mass of the negative electrode composite material slurry, may be 0.1 parts by mass or more, or may be 0.5 parts by mass or more, or may be 2.0 parts by mass or less, or may be 1.0 parts by mass or less, or may be from 0.1 parts by mass to 2.0 parts by mass. The content of binder (D) is not particularly limited, and, with respect to 100 parts by mass of the solid content of the negative electrode composite material slurry, may be 0.2 parts by mass or more, or may be 1.0 parts by mass or more, or may be 4.0 parts by mass or less, or may be 2.0 parts by mass or less, or may be from 0.2 parts by mass to 2.0 parts by mass. The content of binder (D) is not particularly limited, and, with respect to a total of 100 parts by mass of the Si-based active material (B) and the sulfide solid electrolyte (C), may be 0.2 parts by mass or more, or may be 1.0 parts by mass or more, or may be 4.0 parts by mass or less, or may be 2.0 parts by mass or less, or may be from 0.2 parts by mass to 2.0 parts by mass.

[0069] (1.5) Conduction Assistant (E) The negative electrode composite material slurry may contain conduction assistant (E), or may not contain conduction assistant (E).

[0070] Examples of conduction assistant (E) are carbon materials, metal materials, and conductive polymer materials. Examples of carbon materials are fiber-shaped carbon (e.g., vapor grown carbon fibers (VGCF), carbon nanotubes and carbon nanofibers), carbon black (e.g., acetylene black, furnace black and ketjen black), graphite, and fluorocarbons. Examples of metal materials are metal powders (e.g., aluminum powder), conductive whiskers (e.g., zinc oxide and potassium titanate), and conductive metal oxides (e.g., titanium oxide). Examples of conductive polymer materials are polyaniline, polypyrol and polythiophene. One type of the conduction assistant (E) may be used alone, or two or more types may be used by being mixed-together.

[0071] The shape and the size of the conduction assistant (E) are not particularly limited. Examples of the shape of conduction assistant (E) are spherical (e.g., perfect spherical, oval spherical) and fiber-shaped. The shape of the conduction assistant (E) is preferably spherical.

[0072] If the conduction assistant (E) particles are spherical, the median diameter of the conduction assistant (E) is not particularly limited, and is preferably from 5 nm to 1000 nm, and more preferably from 15 nm to 100 nm. The method of measuring the median diameter of conduction assistant (E) is similar to the method of measuring the median diameter of the Si-based active material (B). If the conduction assistant (E) is fiber-shaped, the fiber diameter of the conduction assistant (E) may be from 5 nm to 1 micrometres, and the aspect ratio of the conduction assistant (E) may be 20 or more.

[0073] If the negative electrode composite material slurry further contains conduction assistant (E), the content of the conduction assistant (E) may be within the following ranges. The content of the conduction assistant (E) is not particularly limited, and, with respect to 100 parts by mass of the negative electrode composite material slurry, may be 1.0 parts by mass or more, or may be 2.0 parts by mass or more, or may be 5.0 parts by mass or less, or may be 3.0 parts by mass or less, or may be from 1.0 parts by mass to 5.0 parts by mass. The content of the conduction assistant (E) is not particularly limited, and, with respect to 100 parts by mass of the solid content of the negative electrode composite material slurry, may be 2.0 parts by mass or more, or may be 4.0 parts by mass or more, or may be 10.0 parts by mass or less, or may be 6.0 parts by mass or less, or may be from 2.0 parts by mass to 6.0 parts by mass. The content of the conduction assistant (E) is not particularly limited, and, with respect to a total of 100 parts by mass of the Si-based active material (B) and the sulfide solid electrolyte (C), may be 2.0 parts by mass or more, or may be 4.0 parts by mass or more, or may be 10.0 parts by mass or less, or may be 6.0 parts by mass or less, or may be from 2.0 parts by mass to 6.0 parts by mass.

[0074] (1.6) Solvent (F) The negative electrode composite material slurry may contain solvent (F), or may not contain solvent (F).

[0075] It suffices for solvent (F) to be a known solvent that is used in manufacturing solid-state batteries. Examples of solvent (F) are diisobutyl ketone, butyl acetate, tetralin, decane, dibutyl ether, ethyl acetate, methyl ketone, methyl propyl ketone, xylene, benzene, toluene, heptane, dimethylbutane, methylhexane, tributylamine and allylamine. A single type of the solvent (F) alone may be used, or two or more types may be used by being mixed tougher.

[0076] If the negative electrode composite material slurry further contains solvent (F), the content of the solvent (F) may be within the following range. The content of the solvent (F) is not particularly limited, and, with respect to 100 parts by mass of the negative electrode composite material slurry, may be 20 parts by mass or more, or may be 40 parts by mass or more, or may be 80 parts by mass or less, or may be 60 parts by mass or less, or may be from 20 parts by mass to 80 parts by mass.

[0077] (1.7) Other Components The negative electrode composite material slurry may contain other components as needed, or may not contain other components. Examples of other components are various types of additives. These other components may include known negative electrode active materials that are different than an Si-based active material, and may include solid electrolytes that are different than a sulfide solid electrolyte.

[0078] (2) Negative Electrode The negative electrode of the present disclosure has a negative electrode composite material layer. The negative electrode composite material layer contains the solid content of the negative electrode slurry of the present disclosure.

[0079] The negative electrode of the present disclosure has the above-described structure, and therefore, can reduce the internal resistance of a solid-state battery.

[0080] (2.1) Negative Electrode Collector The negative electrode may further contain a negative electrode collector, in addition to the negative electrode composite material layer. The negative electrode collector carries out power collection of the negative electrode. The negative electrode composite material layer is layered on at least one surface of the negative electrode collector. Examples of the material of the negative electrode collector are stainless steel, aluminum, copper, nickel, iron, titanium and carbon, and copper is preferable. The form of the negative electrode collector is the form of a foil or the form of a mesh, for example. The negative electrode collector may be structured such that a shock-absorbing layer, an elastic layer or a PTC (Positive Temperature Coefficient) thermistor layer is disposed on the surface of the collector.

[0081] (3) Solid-State Battery The solid-state battery of the present disclosure has the negative electrode of the present disclosure.

[0082] The solid-state battery of the present disclosure has the above-described structure, and therefore, the internal resistance thereof is decreased.

[0083] The solid-state battery may further have a positive electrode and a solid electrolyte layer, in addition to the negative electrode. The solid electrolyte layer is disposed between the negative electrode and the positive electrode.

[0084] (3.1) Battery Structure The solid-state battery includes so-called all-solid-state batteries that use an inorganic solid electrolyte as the electrolyte, and the solid electrolyte may contain an electrolyte liquid in an amount of less than 10 mass% with respect to the total amount of the electrolyte. Note that the solid electrolyte may be a complex solid electrolyte containing an inorganic solid electrolyte and a polymer electrolyte. The structure of the solid-state battery may be a structure in which a positive electrode collector, a positive electrode composite material layer, a solid electrolyte layer, a negative electrode composite material layer and a negative electrode collector are layered in that order, and may be the structure illustrated in Fig. 1 for example. Solid electrolyte layer B in Fig. 1 may be a two-layer structure. Fig. 1 is a schematic sectional view illustrating an example of a solid-state battery. The solid-state battery illustrated in Fig. 1 has a negative electrode including a negative electrode collector 113 and a negative electrode composite material layer A, a solid electrolyte layer B, and a positive electrode including a positive electrode collector 115 and a positive electrode composite material layer C. The negative electrode composite material layer A contains a negative electrode active material 101, a conduction assistant 105, a binder 109 and a solid electrolyte 102. The positive electrode composite material layer C contains a positive electrode active material complex 103, a binder 111 and the solid electrolyte 102.

[0085] Given that the set of the positive electrode composite material layer, the solid electrolyte layer and the negative electrode composite material layer is the power generating unit, the solid-state battery may have only one power generating unit or may have two or more power generating units. In a case in which the solid-state battery has two or more power generating units, these power generating units may be connected in series or may be connected in parallel.

[0086] The solid-state battery may be structured such that the layer end surfaces (side surfaces) of a layered structure of a positive electrode composite material layer / a solid electrolyte layer / a negative electrode composite material layer are sealed by a resin. The collector of the electrode may be a structure in which a shock-absorbing layer, an elastic layer or a PTC (Positive Temperature Coefficient) thermistor layer is disposed on the surface of the collector. The shape of the solid-state battery is not particularly limited, and may be, for example, coin-shaped, cylindrical, square, sheet-shaped, button-shaped, flat or layered.

[0087] (3.2) Solid Electrolyte Layer The solid-state battery may include a solid electrolyte layer. It is preferable that the solid electrolyte layer includes one type selected from the group consisting of sulfide solid electrolytes, oxide solid electrolytes and halide solid electrolytes.

[0088] Examples of the sulfide solid electrolyte are similar to those exemplified as the sulfide solid electrolyte (C). The sulfide solid electrolyte that is contained in the solid electrolyte layer may be the same as sulfide solid electrolyte (C) or may be different than sulfide solid electrolyte (C).

[0089] The oxide solid electrolyte preferably contains oxygen (O) as the main component that is an anion element, and, for example, may contain Li, element Q (Q represents at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W and S) and O. Examples of the oxide solid electrolyte are garnet type solid electrolytes, perovskite type solid electrolytes, NASICON type solid electrolytes, Li-P-O solid electrolytes and Li-B-O solid electrolytes. Examples of garnet type solid electrolytes are . Examples of perovskite type solid electrolytes are (Li,La)TiO3, (Li,La)NbO3, and (Li,Sr)(Ta,Zr)O3. Examples of NASICON type solid electrolytes are Li(Al,Ti)(PO4)3and Li(Al,Ga)(PO4)3. Examples of Li-P-O solid electrolytes are Li3PO4and LIPON (compounds in which some of the O in Li3PO4is substituted with N). Examples of Li-B-O solid electrolytes are Li3BO3and compounds in which some of the O in Li3BO3is substituted with C.

[0090] As the halide solid electrolyte, solid electrolytes containing Li, M and X (M represents at least one of Ti, Al and Y, and X represents F, Cl or Br) are suitable. Specifically, Li6-3zYzX6(X represents Cl or Br, and z satisfies 0<z<2) and are preferable. Among Li6-3zYzX6, from the standpoint of having excellent lithium ion conductivity, Li3YX6(X represents Cl or Br) is more preferable, and Li3YCl6is even more preferable. Further, from standpoints such as, for example, suppressing oxidative decomposition of the sulfide solid electrolyte, it is preferable that be contained together with a solid electrolyte such as a sulfide solid electrolyte.

[0091] The solid electrolyte layer may be a single layer structure, or may be a multilayer structure of two or more layers.

[0092] The solid electrolyte layer may contain a binder, or may not contain a binder. Examples of the binder that can be contained in the solid electrolyte layer are similar to those exemplified as the binder (D).

[0093] (3.3) Positive Electrode Composite Material Layer The solid-state battery may have a positive electrode composite material layer. The positive electrode composite material layer contains a positive electrode active material. As needed, the positive electrode composite material layer may contain at least one of a solid electrolyte for the positive electrode, a conduction assistant, and a binder.

[0094] The positive electrode active material preferably includes a lithium composite oxide. The lithium composite oxide may contain at least one type selected from the group consisting of F, Cl, N, S, Br and I. Further, the lithium composite oxide may have a crystal structure belonging to at least one space group selected from space groups R-3m, Immm, and P63-mmc (also called P63mc, P6 / mmc). In the lithium composite oxide, the main sequence of a transition metal, oxygen and lithium may be an O2-type structure.

[0095] Examples of lithium composite oxides having a crystal structure belonging to R-3m are compounds expressed by (Me represents at least one type selected from the group consisting of Mn, Co, Ni, Fe, Al, Cu, V, Nb, Mo, Ti, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, Ag, Ru, W, B, Si and P, and X represents at least one type selected from the group consisting of F, Cl, N, S, Br and I, and are satisfied).

[0096] Examples of lithium composite oxides having a crystal structure belonging to Immm are composite oxides expressed by is satisfied, M1includes at least one type selected from the group consisting of Ni, Co, Mn, Cu and Fe, A1includes at least oxygen, and the ratio of the oxygen contained in A1is greater than or equal to 85 atom%) (a specific example is Li2NiO2), and composite oxides expressed by Lix1M1A1-x2M1Bx2O2-yA2y( , at least one of x2 and y is not 0, M1Arepresents at least one type selected from the group consisting of Ni, Co, Mn, Cu and Fe, M1Brepresents at least one type selected from the group consisting of Al, Mg, Sc, Ti, Cr, V, Zn, Ga, Zr, Mo, Nb, Ta and W, and A2represents at least one type selected from the group consisting of F, Cl, Br, S and P).

[0097] Examples of lithium composite oxides having a crystal structure belonging to P63-mmc are composite oxides expressed by M1xM2yO2(M1 represents an alkali metal (at least one of Na and K is preferable), M2 represents a transition metal (at least one type selected from the group consisting of Mn, Ni, Co and Fe is preferable), and x+y satisfies ).

[0098] Examples of lithium composite oxides having an O2-type structure are composite oxides expressed by and M represents at least one type selected from the group consisting of Ni, Mg, Ti, Fe, Sn, Zr, Nb, Mo, W and Bi). Specific examples are Li0.744[Li0.145Mn0.625Co0.115Ni0.115]O2and the like.

[0099] The solid electrolyte for the positive electrode preferably includes at least one selected from the group consisting of sulfide solid electrolytes, oxide solid electrolytes and halide solid electrolytes. Examples of the sulfide solid electrolytes are similar to those exemplified as the sulfide solid electrolyte (C). Examples of the oxide solid electrolytes are similar to those exemplified as the oxide solid electrolytes that can be contained in the solid electrolyte. Examples of the halide solid electrolytes are similar to those exemplified as the halide solid electrolytes that can be contained in the solid electrolyte.

[0100] Examples of the conduction assistant are similar to those exemplified as the conduction assistant (E). The conduction assistant that is contained in the positive electrode composite material layer may be the same as conduction assistant (E) or may be different than conduction assistant (E).

[0101] (3.4) Positive Electrode Collector The solid-state battery may further have a positive electrode collector. The positive electrode collector carries out power collection of the positive electrode composite material layer. The positive electrode collector is disposed at a position at the side of the positive electrode composite material layer, which side is opposite the side at which the solid electrolyte layer is located. Examples of the positive electrode collector are stainless steel, aluminum, copper, nickel, iron, titanium and carbon. An aluminum alloy foil or an aluminum foil is preferable. The aluminum alloy foil or aluminum foil may be manufactured by using a powder. Examples of the form of the positive electrode collector are the form of a foil and the form of a mesh. The positive electrode collector may be a structure in which a shock-absorbing layer, an elastic layer or a PTC (Positive Temperature Coefficient) thermistor layer is disposed on the surface of the collector.

[0102] The present disclosure will be described in further detail hereinafter by way of Examples, but the invention of the present disclosure is not limited to only these Examples.

[0103] [1] Preparation of Dispersant Diblock copolymers (B-1) through (B-9) and copolymers (R-1) through (R-2) were prepared as dispersant (A) and dispersant (X).

[0104] [1.1] Raw Materials <Monomer> The following raw materials of the negative electrode composite material slurry were readied. MMA: methyl methacrylate (Evonik) BMA: n-butyl methacrylate (Evonik) EHMA: 2-ethylhexyl methacrylate (Evonik) BzMA: benzyl methacrylate (Evonik) ETMA: ethyl triglycol methacrylate (Evonik) LMA: lauryl methacrylate (Tokyo Chemical Industry) DMAEMA: N,N-dimethylaminoethyl methacrylate (Evonik) <Solvent> DIBK: diisobutyl ketone (Tokyo Chemical Industry) <Initiator> MMTP: 1-methoxy-1-(trimethylsiloxy)-2-methylpropene (Sigma-Aldrich) AMBN: 2,2’-azodi(2-methylbutyronitrile) (Akzo Nobel) <Catalyst> catalyst: tetrabutylammonium 3-chlorobenzoate (50% concentration in acetonitrile, refer to US Patent No. 4,588,795)

[0105] DIBK and all of the monomers were stored on a molecular sieve of 3 angstrom for 48 hours before use.

[0106] [1.2] Measuring Methods [1.2.1] Number Average Molecular Weight Mn, Weight Average Molecular Weight Mw, and Molecular Weight Distribution The number average molecular weight Mn, the weight average molecular weight Mw and the molecular weight distribution were determined in accordance with DIN55672-1:2007-08 at 35°C by using a high-speed liquid chromatography pump (Waters 600 HPLC pump) and a differential refractive index detector (Waters 410). A combination of three Styragel columns, whose hole diameters were HR4, HR2 and HR1 and which were manufactured by Waters and were of an inner diameter / column size of and a particle diameter of 5 micrometres, were used as separation columns. The eluent that was used was tetrahydrofuran that contained 1 vol% of dibutylamine and had a dissolution rate of 1 mL / min. Calibration was carried out by a conventional method using a polystyrene reference material.

[0107] [1.2.2] Measurement of Non-Volatile Content (Solid Content) A sample (a test substance of 2.0±0.2g) was precisely measured out into an aluminum dish that had been preliminarily dried. The mixture was dried for 20 minutes at 150°C in a drying cabinet for coatings, and was cooled in a desiccator, and thereafter, was again measured-out. The residue corresponds to the solid content in the sample (ISO3251).

[0108] [1.2.3] Amine Value of Solids 1.5 to 3.0 g of the sample was precisely measured-out into an 80 mL beaker, and was dissolved by using 50 mL of toluene. This solution was neutralization-titrated with a 0.1 mol / L of an HClO4acetic acid solution by using an automatic titration device equipped with a pH electrode. The inflection point of the titration pH curve was used as the titration end point, and the amine value of the solids was obtained by the following formula (i). The formula (i): In the formula (i), f is the factor of the titration agent. V is the titrated amount [mL] at the titration end point. W is the measured mass [g] of the sample. S is the solids concentration [mass%] of the sample.

[0109] [1.2.4] Glass Transition Temperature of Acrylic Copolymer The glass transition temperatures of diblock copolymers (B-1) through (B-9) and copolymers (R-1) through (R-2) that are acrylic copolymers were calculated by using the FOX formula expressed by the following formula (ii). The formula (ii): 1 / Tg = C1 / Tg1+C2 / Tg2+ … + Cn / Tgn In the formula (ii), Tg is the glass transition temperature of the acrylic copolymer. The weight ratios of the structural units 1, 2 … n are C1, C2… Cn, respectively. The glass transition temperatures of the homopolymers of the respective structural units are Tg1, Tg2… Tgn, respectively.

[0110] [1.3] Synthesis [1.3.1] Synthesis of Diblock Copolymer (B-1) 60.00 parts by mass of DIBK (solvent) was placed in an anhydrous reactor. 35.83 parts by mass monomer solution 1 (refer to Table 1) was added dropwise by a dropping funnel over 60 minutes. Immediately after the start of introducing monomer solution 1, 1.12 parts by mass of MMTP (initiator) and 0.04 parts by mass of the above-described catalyst were placed in the reactor. The reaction temperature was maintained at 20°C throughout the reaction. After the addition of monomer solution 1 was finished, 3.24 parts by mass of monomer solution 2 (refer to Table 1) was added by titration over 30 minutes. After the addition of monomer solution 2 was finished, the reaction was continued for 60 minutes. Thereafter, a small amount of 2-methoxypropanol was added in order to stop the reaction. Due thereto, diblock copolymer (B-1) serving as an acrylic copolymer was obtained. The results of measurement of the solids concentration, the amine value of the solids, the glass transition temperature, the molecular weight and the molecular weight distribution of diblock copolymer (B-1) are shown in Table 1.

[0111] [1.3.2] Synthesis of Diblock Copolymers (B-2) through (B-9) Diblock copolymers (B-2) through (B-9) serving as acrylic copolymers were obtained in the same way as in the synthesis of diblock copolymer (B-1) except that the initiator, the catalyst, monomer solution 1 and monomer solution 2 were changed as shown in Table 1 and Table 2. The results of measurement of the solids concentration, the amine value of the solids, the glass transition temperature, the molecular weight and the molecular weight distribution of diblock copolymers (B-2) through (B-9) are shown in Table 1 and Table 2.

[0112] [1.3.3] Synthesis of Copolymer (R-1) 60.00 parts by mass of DIBK was placed in an anhydrous reactor. 38.87 parts by mass of monomer solution 1 (refer to Table 2) was added dropwise by a dropping funnel over 60 minutes. Immediately after the start of introducing monomer solution 1, 1.21 parts by mass of MMTP and 0.05 parts by mass of the above-described catalyst were placed in the reactor. The reaction temperature was maintained at 20°C throughout the reaction. After the addition of monomer solution 1 was finished, the reaction was continued for 60 minutes. Thereafter, a small amount of 2-methoxypropanol was added in order to stop the reaction. Due thereto, copolymer (R-1) serving as an acrylic copolymer was obtained. The results of measurement of the solids concentration, the amine value of the solids, the glass transition temperature, the molecular weight and the molecular weight distribution of copolymer (R-1) are shown in Table 2.

[0113] [1.3.4] Synthesis of Copolymer (R-2) 50.00 parts by mass of DIBK was placed in a reactor, and the temperature was raised to 120°C. An initiator solution, in which 38.29 parts by mass of monomer solution 1 (refer to Table 2) and 1.21 parts by mass of AMBN (initiator) were dissolved in 10.00 parts by mass of DIBK, was added dropwise by a dropping funnel over 60 minutes. After the addition of monomer solution 1 and the above-described initiator solution was finished, the reaction was continued for 60 minutes, and copolymer (R-2) was thereby obtained. The results of measurement of the solids concentration, the amine value of the solids, the glass transition temperature, the molecular weight and the molecular weight distribution of copolymer (R-2) are shown in Table 2.

[0114]

[0115]

[0116] [1.2] Si-Based Active Material (B) An Si-based material was readied as Si-based active material (B1).

[0117] [1.3] Sulfide Solid Electrolyte (C) A sulfide solid electrolyte was readied as sulfide solid electrolyte (C1).

[0118] [1.4] Binder (D) A diisobutyl ketone solution of 5 mass% PVDF-HFP was readied as a solution (hereinafter also called “binder (D1) solution”) containing binder (D1). The “diisobutyl ketone solution of 5 mass% PVDF-HFP” is a mixed solution of polyvinylidene fluoride (PVDF) - hexafluoropropylene copolymer (PVDF-HFP) and diisobutyl ketone, and the content of the PVDF-HFP is 5 mass% with respect to the total amount of the mixed solution.

[0119] [1.5] Conduction Assistant (E) “VGCF-H” was readied as conduction assistant (E1).

[0120] [1.6] Solvent (F) Diisobutyl ketone was readied as solvent (F1).

[0121] [2] Example 1 through Example 8, and Comparative Example 1 through Comparative Example 3 [2.1] Negative Electrode Composite Material Slurry The dispersant (A) and block copolymer (X) listed in Table 3, 0.13 parts by mass of conduction assistant (E1), 1 part by mass of Si active material (B1), 1.2 parts by mass of sulfide solid electrolyte (C1), and 0.8 parts by mass of binder (D1) solution were added to 2.7 parts by mass of solvent (F1), and were dispersed for 10 minutes by ultrasonic waves, and a negative electrode composite material slurry was obtained. In Example 1 through Example 8, the added amount of dispersant (A) was 1.5 parts by mass, and the added amount of dispersant (X) was 0 parts by mass. In Comparative Example 1 through Comparative Example 3, the added amount of dispersant (A) was 0 parts by mass, and the added amount of dispersant (X) was 1.5 parts by mass. The amplitude of the ultrasonic waves was 40 micrometres, and the frequency of the ultrasonic waves was 20 kHz.

[0122] [2.1.1] Measurement of Viscosity The viscosity of the negative electrode composite material slurry was measured by using a modular compact rheometer (“MCR302e” manufactured by Anton Paar). A cone plate (diameter: 50 mm, cone angle: 1°) was used in measuring, the shear rate was 100 / s, and the measurement temperature was 25°C. The results of measurement are shown in Table 3.

[0123] [2.1.2] Measurement of Particle Size The particle size of the negative electrode composite material slurry was measured in accordance with JIS K5600-2-5:1999. The results of measurement are shown in Table 3.

[0124] [2.2] Evaluation As described hereinafter, solid-state batteries were fabricated by using the negative electrode composite material slurries, and the internal resistances of the solid-state batteries were evaluated.

[0125] [2.2.1] Fabrication of Negative Electrode The negative electrode composite material slurry was coated on a roughened Ni foil (negative electrode collector) by using a blade having a 100 micrometres gap. A negative electrode was thereby obtained. The negative electrode was formed from the roughened Ni foil (negative electrode collector), and the solids (negative electrode composite material layer) of the negative electrode composite material slurry that was layered on one surface of the roughened Ni foil.

[0126] [2.2.2] Evaluation of Strength of Negative Electrode Composite Material Layer The peeling strengths of the negative electrodes of Example 1 through Example 5 and Comparative Example 1 through Comparative Example 3 were evaluated. In detail, after the negative electrode was roll-pressed at a linear pressure of 0.25 t / cm, a piece was punched out in a circular form of 1 cm2so as to obtain a sample piece. Double-sided tape was affixed to both surfaces of the sample piece (i.e., the surface at the negative electrode collector side and the surface at the negative electrode composite material layer side), and was pressed at 50 N. Thereafter, the sample piece to which the double-sided tapes were affixed were tensed vertically in the gravitational direction, and the sample piece broke. At the negative electrodes of Example 1 through Example 5 and Comparative Example 1 through Comparative Example 4, it was confirmed that the fracture surface of the sample piece was structured by the negative electrode composite material layer. Namely, it was confirmed that the sample piece broke within the negative electrode composite material layer.

[0127] [2.2.3] Fabrication of Solid Electrolyte Layer 0.4 parts by mass of sulfide solid electrolyte (C1) and 0.05 parts by mass of a heptane solution of 5 mass% ABR were added to 0.8 parts by mass of heptane, and were dispersed for 10 minutes by ultrasonic waves, and a slurry for the solid electrolyte layer was obtained. The “heptane solution of 5 mass% ABR” is a mixed solution of acrylate-butadiene rubber (ABR) and heptane, and the content of the ABR is 5 mass% with respect to the total amount of the mixed solution.

[0128] The slurry for the solid electrolyte layer was coated on a stainless steel foil by using a blade having a 50 micrometres gap. A solid electrolyte layer with a stainless steel foil was thereby obtained. The solid electrolyte layer with a stainless steel foil was formed from the stainless steel foil and the solids (solid electrolyte layer) of the slurry for the solid electrolyte layer that was layered on one surface of the stainless steel foil.

[0129] [2.2.4] Fabrication of Positive Electrode 2 parts by mass of lithium nickel cobalt manganese oxide (NCM), 0.03 parts by mass of VGCF-H, 0.3 parts by mass of a sulfide solid electrolyte, 0.3 parts by mass of a butyl acetate solution of 5 mass% PVDF-HFP were added to 1 part by mass of butyl acetate, and were dispersed for 10 minutes by ultrasonic waves, and a slurry for the positive electrode was obtained. The “butyl acetate solution of 5 mass% PVDF-HFP” is a mixed solution of polyvinylidene fluoride (PVDF) - hexafluoropropylene copolymer (PVDF-HFP) and butyl acetate, and the content of the PVDF-HFP is 5 mass% with respect to the total amount of the mixed solution.

[0130] The slurry for the positive electrode was coated on an aluminum foil (positive electrode collector) by using a blade having a 100 micrometres gap. A positive electrode was thereby obtained. The positive electrode was formed from the aluminum foil (positive electrode collector), and the solids (positive electrode composite material layer) of the slurry for the positive electrode that was layered on one surface of the aluminum foil.

[0131] [2.2.5] Assembling of Solid-State Battery The solid electrolyte layer with a stainless steel foil was superposed on the negative electrode, and a first layered body was obtained. At the first layered body, the negative electrode composite material layer of the negative electrode, and the solid electrolyte layer of the solid electrolyte layer with a stainless steel foil, contacted one another. The first layered body was roll-pressed at room temperature and a linear pressure of 3 t / cm. A piece of 1 cm2was punched out from the first layered body, and the stainless steel foil was peeled-off therefrom, and a first layered piece was obtained.

[0132] The solid electrolyte layer with a stainless steel foil was superposed on the positive electrode, and a second layered body was obtained. At the second layered body, the positive electrode composite material layer of the positive electrode, and the solid electrolyte layer of the solid electrolyte layer with a stainless steel foil, contacted one another. The second layered body was roll-pressed at 170°C and a linear pressure of 4 t / cm. A piece of 1 cm2was punched out from the second layered body, and the stainless steel foil was peeled-off therefrom, and a second layered piece was obtained.

[0133] The first layered piece and the second layered piece were superposed and joined together, and a power generating element was obtained. At the power generating element, the solid electrolyte layer of the first layered piece and the solid electrolyte layer of the second layered piece contacted one another and formed a single solid electrolyte layer. The power generating element had a positive electrode, a solid electrolyte layer formed on the positive electrode, and a negative electrode formed on the solid electrolyte layer. The power generating element was sealed in a laminate exterior body, and bound at 0.5 MPa. A solid-state battery was thereby obtained.

[0134] [2.2.6] Measurement of Internal Resistance The solid-state battery was charged in a constant current constant voltage mode (CCCV) at a rate of 1 / 3C up to 4.35 V, and thereafter, was discharged in CCCV at 1 / 3C to 3.35 V. Thereafter, discharging was further carried out at 7C, and the internal resistance was calculated by the following formula (X) from the change in the voltage during 10 seconds. The results of measurement are shown in Table 3. Allowable internal resistances are less than 63 ohm.cm2. The formula (X): internal resistance = (voltage after 10 seconds - initial voltage) / average current value during 10 seconds and an insoluble component was observed.

[0135]

[0136] The negative electrode composite material slurries of Comparative Example 1 through Comparative Example 3 contained the dispersant (X), the Si-based active material (B) and the sulfide solid electrolyte (C), but did not contain dispersant (A). Therefore, the internal resistances of the solid-state batteries of Comparative Example 1 through Comparative Example 3 were not less than 63 ohm.cm2. From these results, it can be understood that the negative electrode composite material slurries of Comparative Example 1 through Comparative Example 3 are not “negative electrode composite material slurries that can reduce the internal resistance of a solid-state battery”.

[0137] The negative electrode composite material slurries of Example 1 through Example 8 contained the dispersant (A), the Si-based active material (B) and the sulfide solid electrolyte (C). Therefore, the internal resistances of the solid-state batteries of Example 1 through Example 8 were less than 63 ohm.cm2. From these results, it can be understood that the negative electrode composite material slurries of Example 1 through Example 8 are “negative electrode composite material slurries that can reduce the internal resistance of a solid-state battery”.

[0138] A negative electrode composite material layer B solid electrolyte layer C positive electrode composite material layer 101 negative electrode active material 102 solid electrolyte 103 positive electrode active material complex 105 conduction assistant 109, 111 binder 113 negative electrode collector 115 positive electrode collector

Claims

1. A negative electrode composite material slurry, comprising: a dispersant (A); an Si-based active material (B); and a sulfide solid electrolyte (C), wherein: the dispersant (A) is an acrylic copolymer, the acrylic copolymer has a structural unit (a) that does not have an amino group, and a structural unit (b) that has an amino group, a glass transition temperature of the acrylic copolymer is from -60°C to 50°C, and an amine value of a solid content of the acrylic copolymer is within a range of 1.5 mg KOH / g to 130 mg KOH / g.

2. The negative electrode composite material slurry of Claim 1, wherein the structural unit (a) within the acrylic copolymer includes a structural unit expressed by the following formula (a): wherein, in the formula (a), Z represents O or NH, R1represents H or CH3, and R2represents a group selected from hydrocarbyl groups and ether group-containing groups.

3. The negative electrode composite material slurry of Claim 1, having a viscosity of 30 mPa.s to 130 mPa.s at 25°C.

4. The negative electrode composite material slurry of Claim 1, wherein: a number average molecular weight (Mn) of the acrylic copolymer is within a range of 1,000 g / mol to 100,000 g / mol, and a molecular weight distribution (Mw / Mn) of the acrylic copolymer is within a range of 1.05 to 10.00.

5. The negative electrode composite material slurry of Claim 1, wherein the structural unit (b) within the acrylic copolymer includes at least one selected from the group consisting of structural units containing a vinyl group and an amino group and structural units expressed by the following formula (b): wherein, in the formula (b), Z represents O or NH, R1represents H or CH3, R3represents an organic group having 2 to 4 carbon atoms, and R4and R5each independently represent an organic group, and R4and R5may arbitrarily bind together and form a ring structure.

6. The negative electrode composite material slurry of Claim 1, wherein the acrylic copolymer has a block structure.

7. A negative electrode comprising a negative electrode composite material layer, wherein the negative electrode composite material layer contains a solid content of the negative electrode composite material slurry of any one of Claim 1 through Claim 6.

8. A solid-state battery, comprising the negative electrode of Claim 7.

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