Electrode mixture slurry, electrode for solid state battery, and solid state battery

Abstract

To provide an electrode mixture material slurry which enables the increase in the evenness of an electrode material and the achievement of a preferred mechanical strength of an electrode layer to be formed in a solid-sate battery.SOLUTION: An electrode mixture material slurry is to be used in manufacturing an electrode for a solid-state battery. The electrode mixture material slurry comprises a solid-state electrolyte, an electrode active substance, a binder, and a solvent. The solid-state electrolyte is at least any of sulfide and oxide, and the binder is a polymer binder containing an unsaturated carbon-carbon bond.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrode mixture slurry, an electrode for a solid state battery, and a solid state battery. [Background technology]

[0002] In recent years, the widespread use of various electrical and electronic devices, including automobiles, personal computers, and mobile phones, has led to a rapid expansion in demand for high-capacity, high-power batteries. The development of even higher-performance batteries is also important from the perspective of continuing and realizing efforts aimed at mitigating or reducing the impact of climate change. Among various types of batteries, solid-state batteries have attracted particular attention due to their superior safety, which is due to the non-flammable solid electrolyte, and their higher energy density.

[0003] In the electrodes of solid-state batteries, the electrode active material and the solid electrolyte have strong polarities on their surfaces, making it difficult to obtain a slurry in which they are uniformly mixed by kneading. Therefore, in order to obtain a slurry in which the electrode materials are uniformly mixed, attempts have been made to suppress the oxidation reaction at the interface between the electrode active material and the solid electrolyte, or to suppress the oxidation of the solid electrolyte by mixing a small amount of oxide into a solid electrolyte made of sulfide.

[0004] Patent Document 1 proposes a technology for improving the output of an all-solid-state secondary battery by adding a surface modifier that functions as a binder, a surface modifier, or a dispersion medium to a solid electrolyte composition in an electrode layer material containing an inorganic solid electrolyte, a surface modifier, and an active material, thereby dispersing the active material and the inorganic solid electrolyte well and uniformly through the interaction of the surface modifier. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 047946 Summary of the Invention [Problem to be solved by the invention]

[0006] While the technology disclosed in Patent Document 1 achieves uniformity of the active material and solid electrolyte, the current situation is that sufficient consideration has not been given to the mechanical strength of the formed electrode layer. Solid-state batteries require sufficient surface pressure to be applied to avoid an increase in interface resistance and a decline in input / output characteristics, so improving the mechanical strength of the electrode layer is important.

[0007] The present invention has been made in view of the above, and aims to provide an electrode mixture slurry that can improve the uniformity of an electrode material in a solid-state battery and obtain a preferable mechanical strength of the formed electrode layer. [Means for solving the problem]

[0008] (1) The present invention relates to an electrode mixture slurry used in the manufacture of an electrode for a solid-state battery, the electrode mixture slurry comprising a solid electrolyte, an electrode active material, a binder, and a solvent, wherein the solid electrolyte is at least one of a sulfide and an oxide, and the binder is at least one of a polymer binder containing an unsaturated carbon-carbon bond and a polymer binder having an electron-donating group.

[0009] (2) The electrode mixture slurry according to (1), further comprising a surface modifier that modifies the surface of at least one of the solid electrolyte and the electrode active material.

[0010] (3) The electrode mixture slurry according to (2), wherein the surface modifier is a copolymer, and the content of repeating units having a predetermined functional group in the copolymer is less than 10 mol %.

[0011] (4) The electrode mixture slurry according to (3), wherein the copolymer is used as the binder.

[0012] (5) The electrode mixture slurry according to (3) or (4), wherein the content of the repeating unit having the predetermined functional group in the copolymer is 1 mol % or more and less than 8 mol %.

[0013] (6) The electrode mixture slurry according to (5), wherein the content of the repeating unit having the predetermined functional group in the copolymer is 2 mol % or more and less than 5 mol %.

[0014] (7) The electrode mixture slurry according to any one of (3) to (6), wherein the predetermined functional group is at least one functional group selected from the group consisting of an ester group, a carboxylate group, a sulfonate group, a nitrile group, an ether group, and a phosphate group.

[0015] (8) The present invention also relates to an electrode for a solid state battery, which has an electrode layer including a solid electrolyte, an electrode active material, and a binder, wherein the binder is at least one of a polymer binder including an unsaturated carbon-carbon bond and a polymer binder having an electron-donating group, the solid electrolyte is at least one of a sulfide and an oxide, and a covalent bond or a coordinate bond is formed between the binder and at least one of the solid electrolyte and the electrode active material.

[0016] (9) A solid-state battery comprising the electrode for a solid-state battery according to (8). [Effects of the Invention]

[0017] According to the present invention, it is possible to provide an electrode mixture slurry that can improve the uniformity of an electrode material in a solid-state battery and can provide a formed electrode layer with a desirable mechanical strength. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a TOF-SIMS image of a positive electrode layer and a solid electrolyte layer formed using an electrode mixture slurry according to an embodiment of the present invention. [Figure 2]FIG. 10 is a diagram showing an IR spectrum when an electrode layer is formed using an electrode mixture slurry according to an example of the present invention. [Figure 3] FIG. 10 is a diagram showing an IR spectrum when an electrode layer is formed using an electrode mixture slurry according to an example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] <Electrode mixture slurry> The electrode mixture slurry according to this embodiment is used in the manufacture of electrodes for solid-state batteries and includes a solid electrolyte, an electrode active material, a binder, and a solvent. The binder is a polymer binder containing unsaturated carbon-carbon bonds, and the inclusion of the polymer binder in the electrode mixture slurry can improve the mechanical strength of the electrode layer formed by the electrode mixture slurry. The electrode mixture slurry also preferably includes a surface modifier, and the surface of the polymer binder is modified by the solvent or the surface modifier. This allows the electrode mixture slurry to be homogenized.

[0020] (solid electrolyte) The solid electrolyte has charge transfer medium conductivity. In this embodiment, the solid electrolyte is either a sulfide solid electrolyte or an oxide solid electrolyte. As the solid electrolyte, a sulfide solid electrolyte is preferable because it has higher charge transfer medium conductivity and can form a chemical bond with a binder, which will be described later. The surface of the solid electrolyte is preferably modified with a surface modifier, which will be described later.

[0021] [Sulfide solid electrolyte] The sulfide solid electrolyte contains, for example, a metal element (M) and sulfur (S). Examples of the metal element (M) include Li, Na, K, Mg, and Ca. Hereinafter, in the present embodiment, the charge transfer medium may be a Li ion, and the metal element (M) may be Li. The sulfide solid electrolyte according to the present embodiment preferably contains, in addition to Li and sulfur (S), an element A (A is at least one selected from the group consisting of P, Si, Ge, Al, and B). The element A is preferably P (phosphorus). Furthermore, the sulfide solid electrolyte may further contain a halogen element such as Cl, Br, or I from the viewpoint of improving Li ion conductivity. Furthermore, the sulfide solid electrolyte may contain O (oxygen). The sulfide solid electrolyte preferably has an argyrodite-type crystal structure.

[0022] Specific examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z. m S n (where m and n are positive numbers. Z is Ge, Zn, or Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is any of P, Si, Ge, B, Al, Ga, and In.) The above description such as "Li2S-P2S5" means a sulfide solid electrolyte obtained using a raw material composition containing Li2S and P2S5. The same applies to other similar descriptions.

[0023] The sulfide solid electrolyte may be sulfide glass or crystallized sulfide glass, or may be a crystalline material obtained by a solid-phase method. Sulfide glass can be obtained, for example, by mechanical milling (such as a ball mill) of a raw material composition. Crystallized sulfide glass can be obtained, for example, by heat treating sulfide glass at a temperature equal to or higher than the crystallization temperature.

[0024] The Li ion conductivity of sulfide solid electrolyte at room temperature is, for example, 1×10 -4 S / cm or more is preferable, and 1×10 -3 It is more preferable that the viscosity is S / cm or more.

[0025] [Oxide solid electrolyte] Examples of oxide solid electrolyte materials include NASICON-type oxides, garnet-type oxides, and perovskite-type oxides. Examples of NASICON-type oxides include oxides containing Li, Al, Ti, P, and O (e.g., Li 1.5 Al 0.5 Ti 1.5 Examples of garnet-type oxides include oxides containing Li, La, Zr, and O (e.g., LiLaZrO 12 Examples of perovskite oxides include oxides containing Li, La, Ti, and O (for example, LiLaTiO3).

[0026] (electrode active material) The electrode active material is a negative electrode active material when the solid battery electrode produced from the electrode mixture slurry is a negative electrode, and similarly, is a positive electrode active material when the solid battery electrode is a positive electrode.

[0027] [Negative electrode active material] The negative electrode active material is not particularly limited as long as it can absorb and release Li ions, which are charge transfer media. For example, lithium titanate (Li4Ti5O 12Examples of the negative electrode active material include lithium transition metal oxides such as TiO2, Nb2O3, and WO3, metal sulfides, metal nitrides, carbon materials such as graphite, soft carbon, and hard carbon, as well as metallic lithium, metallic indium and lithium alloys, silicon oxide, and silicon. The negative electrode active material may be in the form of a powder or a thin film.

[0028] The surface of the negative electrode active material is preferably coated with an oxide such as LiNbO3, which prevents the negative electrode active material from being decomposed by the binder or solvent. The oxide coating layer formed of an oxide such as LiNbO3 functions as a reaction suppression layer that suppresses the reaction between the negative electrode active material and the binder or solvent.

[0029] Coating with the reaction suppression layer is performed, for example, as follows: First, a precursor solution for the reaction suppression layer is prepared. For example, LiOC2H5 is dissolved in an ethanol solvent so that predetermined amounts of ethoxylithium (LiOC2H5) and pentaethoxyniobium (Nb(OC2H5)5) are contained in the ethanol, and then Nb(OC2H5)5 is added and dissolved to prepare a precursor solution for the LiNbO3 reaction suppression layer.

[0030] Next, the precursor solution of the LiNbO3 reaction suppression layer is coated onto the negative electrode active material. This coating is carried out using, for example, a rolling fluidized bed coating device. 1.15 Ni 0.33 Co 0.33 Mn 0.33 O2 particles are placed in a tumbling fluidized bed coating device, and the negative electrode active material is lifted up by dry air and circulated inside the device while the precursor solution is sprayed onto it, resulting in a negative electrode active material coated with the precursor of the LiNbO3 reaction inhibitor layer.

[0031] Next, the negative electrode active material coated with the precursor of the LiNbO3 reaction suppression layer is subjected to heat treatment in the atmosphere in an electric furnace, thereby obtaining a negative electrode active material coated with the LiNbO3 reaction suppression layer.

[0032] Regardless of whether the surface of the negative electrode active material according to this embodiment is coated with a reaction suppression layer, the surface is preferably modified with a surface modifier described below. It is more preferable that the surface of the negative electrode active material coated with a reaction suppression layer is further modified with a surface modifier.

[0033] [Cathode active material] The positive electrode active material is not particularly limited, but examples thereof include a layered active material containing Li, a spinel-type active material, an olivine-type active material, etc. Specific examples of the positive electrode active material include lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), LiNi p Mn q Co r O2(p+q+r=1), LiNi p Al q Co r Examples of suitable Li-Mn spinels include lithium manganese oxide (LiMnO), LiMnO (p+q+r=1), lithium manganese oxide (LiMnO), and heteroelement-substituted Li-Mn spinels represented by LiMnMyO (x+y=2, M=at least one selected from Al, Mg, Co, Fe, Ni, and Zn), and lithium metal phosphate (LiMPO, M=at least one selected from Fe, Mn, Co, and Ni).

[0034] As with the negative electrode active material described above, the positive electrode active material according to this embodiment is preferably surface-coated with an oxide such as LiNbO3 to form a reaction suppression layer. The method for coating the positive electrode active material with the reaction suppression layer is preferably the same as that for the negative electrode active material.

[0035] Regardless of whether the surface of the positive electrode active material according to this embodiment is coated with a reaction suppression layer, the surface is preferably modified with a surface modifier described below. It is more preferable that the surface of the positive electrode active material coated with a reaction suppression layer is further modified with a surface modifier.

[0036] (binder) The binder functions as a binding agent or thickener in the electrode layer. It also homogenizes the slurry of the electrode mixture and provides an appropriate viscosity. The binder is at least one of a polymer binder containing unsaturated carbon-carbon bonds and a polymer binder having electron-donating groups. As a result, when the electrode layer is formed from the electrode mixture, a covalent bond is formed by a chemical reaction between the unsaturated carbon-carbon bond of the polymer binder containing unsaturated carbon-carbon bonds and, for example, sulfur (S) in the solid electrolyte. Alternatively, a covalent bond is formed by a chemical reaction between the electron-donating group of the polymer binder having electron-donating groups and, for example, lithium ions (Li + ) is formed as a coordinate bond. This can improve the mechanical strength of the electrode layer formed from the electrode mixture slurry.

[0037] Examples of polymer binders having unsaturated carbon-carbon bonds include, but are not limited to, styrene-butadiene rubber and styrene-isoprene rubber. Examples of polymer binders having electron-donating groups include, but are not limited to, hydrogenated nitrile-butadiene rubber, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, styrene-methyl methacrylate copolymer, and styrene-n-dodecyl acrylate copolymer. The electron-donating group is preferably at least one functional group selected from the group consisting of an ester group, a carboxylate group, a sulfonate group, a nitrile group, an ether group, and a phosphate group. The polymer binder having an electron-donating group also functions as a surface modifier (copolymer) described below. The above binders can be used alone or in combination.

[0038] The polymer binder having unsaturated carbon-carbon bonds is preferably modified with a solvent or a surface modifier, which will be described later. This improves the affinity between the binder and the solid electrolyte and the electrode active material due to intermolecular interactions, thereby enabling the electrode mixture slurry to be made uniform.

[0039] The binder content is preferably 5% by mass or less, more preferably 1.0% by mass or less, based on the total electrode mixture slurry after drying. When the content is 5% by mass or less, the electrode active material, solid electrolyte, and conductive additive are sufficiently strongly bonded to the binder and current collector. This is also preferable because the electrode mixture slurry has a moderate viscosity and provides stability and uniformity.

[0040] (solvent) The solvent used in the present invention is not particularly limited as long as it is a non-polar, low-polar, or medium-polar organic solvent with a boiling point within the range of 70°C to 220°C. It may be appropriately selected depending on the properties of the electrode active material, solid electrolyte, etc. In this case, non-polarity refers to a Snyder polarity parameter (or Rohrschneider polarity parameter) P' value of -0.2≦P'<1.0, low polarity refers to 1.0≦P'<2.5, and medium polarity refers to 1.0≦P'<5.5. Examples of suitable solvents include aliphatic hydrocarbons, aromatic hydrocarbons, esters, ethers, ketones, and nitriles. These solvents have affinity for the surface modifier and binder based on intermolecular interactions, thereby homogenizing and stabilizing the composition slurry. Furthermore, among the surface modifiers described below, low molecular weight compounds are also preferably used as solvents. In this case, the surface modifier functions as a solvent for dispersing or dissolving the electrode active material, the solid electrolyte, and the binder, and also as a surface modifier for modifying the surface of at least one of the electrode active material, the solid electrolyte, and the binder.

[0041] (Surface modification substance) The electrode mixture slurry according to this embodiment preferably contains a surface modifier. The surface modifier is a substance that modifies the surface of at least one of the electrode active material and the solid electrolyte contained in the electrode mixture slurry. This prevents at least one of the electrode active material and the solid electrolyte from being decomposed into the binder or the solvent. Furthermore, the improved affinity between the electrode active material and the solid electrolyte and the binder and the solvent contributes to the uniformity and stabilization of the electrode mixture slurry.

[0042] [Copolymer] The surface modifier is preferably a copolymer having a predetermined functional group. Using a copolymer as the surface modifier can uniformly distribute the distances between the components constituting the electrode mixture slurry, forming a favorable interface and improving adhesion. The predetermined functional group is preferably at least one functional group selected from the group consisting of an ester group, a carboxylate group, a sulfonate group, a nitrile group, an ether group, and a phosphate group. A polymer binder having an electron-donating group may be used as the copolymer serving as the surface modifier. In other words, in this case, the polymer binder having an electron-donating group also functions as the surface modifier, and these may be the same substance.

[0043] The main chain skeleton of the copolymer is not particularly limited, but examples thereof include copolymers obtained by polymerizing radically polymerizable monomers, such as (meth)acrylic monomers, (meth)acrylamide monomers, styrene monomers, and vinyl monomers.

[0044] The content of the repeating unit having the predetermined functional group in the copolymer is preferably less than 10 mol%. In a situation where a low-polarity group and a polar group are simultaneously present in the copolymer, if the proportion of the repeating unit having the predetermined functional group contained in the copolymer is 10 mol% or more, microphase separation of the copolymer itself may occur. This may reduce the uniformity of the electrode mixture slurry, preventing the production of an electrode mixture slurry with an appropriate viscosity. The above situation can be avoided by setting the content of the repeating unit having the predetermined functional group in the copolymer to less than 10 mol%. The content of the repeating unit having the predetermined functional group in the copolymer is more preferably 1 mol% or more but less than 8 mol%, and even more preferably 2 mol% or more but less than 5 mol%.

[0045] The content of the copolymer is preferably 5% by mass or less, and more preferably 1% by mass or less, based on the total amount of the electrode mixture slurry after drying.

[0046] (Low molecular compound) The surface modifier may contain a low molecular weight compound in addition to the copolymer. The low molecular weight compound is at least one selected from the group consisting of carboxylates, thiocarboxylates, carboxylic acids, thiocarboxylic acids, phosphates, thiophosphates, ketones, nitriles, alcohols, thiols, and ethers. Specifically, the surface modifier (low molecular weight compound) may be at least one of the compounds represented by the following structural formula: In the structural formula (1), R, R', and R" each represent a carbon chain, X represents an oxygen atom or a sulfur atom, and Li represents lithium. These low molecular weight compounds may be used alone or in combination of two or more.

[0047] [ka]

[0048] From the viewpoint that alkyl chains are insulators and do not conduct ions, R, R', and R" preferably have carbon chains containing 1 to 11 carbon atoms, and more preferably have carbon chains containing 1 to 6 carbon atoms. More preferably, R, R', and R" each have carbon chains containing 1 to 4 carbon atoms. When R, R', and R" are aliphatic groups, they are not limited to linear groups, but may be branched or cyclic, and may be saturated or unsaturated aliphatic groups. A saturated aliphatic group is preferred. The carbon chain may contain a heteroatom between the carbon-carbon bond. The carbon chain may or may not have a substituent. When R, R', and R" are aromatic groups, they may be either phenyl groups or naphthyl groups. The aromatic group may contain a heteroatom between the carbon-carbon bond. The aromatic group may or may not have a substituent.

[0049] The surface modifier (low molecular weight compound) selected from the above structural formulas is preferably at least one selected from the group consisting of lithium butyrate, lithium isobutyrate, lithium acetate, butyl phosphate, and isobutyronitrile.

[0050] The content of the surface modifier (low molecular weight compound) is preferably 3% by mass or less of the electrode mixture slurry after drying, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less. A content of 3% by mass or less is preferable because it prevents at least one of the electrode active material and the solid electrolyte from being decomposed into the binder or solvent and contributes to the uniformity and stabilization of the electrode mixture slurry.

[0051] The functional groups possessed by the surface modifier selected from the structural formulas above modify the surface of at least one of the electrode active material and the solid electrolyte, thereby converting the surface of the electrode active material or the solid electrolyte into a surface having carbon chains. This allows at least one of the electrode active material or the solid electrolyte to have affinity for solvents, binders, etc. due to intermolecular interactions, making them less susceptible to decomposition. Furthermore, it is believed that improved affinity due to intermolecular interactions, such as hydrophobic interactions, π-π stacking, hydrophilic interactions, and electrostatic interactions (hydrogen bonds, van der Waals forces, etc.) between the electrode active material or the solid electrolyte and the solvent or binder contributes to the homogenization and stabilization of the electrode mixture slurry and the solid electrolyte slurry. These intermolecular interactions also affect other components applicable to solid-state batteries, such as conductive additives. Therefore, even if the electrode mixture or the solid electrolyte composition contains a conductive additive, the affinity is maintained, resulting in the homogenization and stabilization of the electrode mixture slurry and the solid electrolyte slurry.

[0052] (Other ingredients) The electrode mixture slurry according to this embodiment may optionally contain other known components that can be used when forming an electrode layer of a solid-state battery, as long as the effects of the present invention are not impaired. For example, a conductive additive may be included. Examples of conductive additives include acetylene black, natural graphite, and artificial graphite. Furthermore, as a binder other than the binder having an unsaturated carbon-carbon bond, a known component that functions as a binder or thickener and is used as a binder in a solid-state battery may be included.

[0053] (Method for preparing electrode mixture slurry) The electrode mixture slurry can be obtained, for example, by the steps of dispersing at least one of an electrode active material and a solid electrolyte in a solvent in which a surface modifier is dissolved or dispersed, thereby surface-modifying at least one of the electrode active material and the solid electrolyte, and mixing the mixture obtained in the above step with a binder solution obtained by dispersing a binder in a solvent as needed, and other components such as a conductive additive as needed. In the surface modification step, a surface modifier that is a low molecular weight compound can also be used as the solvent. Various mixing and dispersion devices such as an ultrasonic dispersion device, a shaker, or Filmix (registered trademark) can be used for the above mixing and dispersion.

[0054] <Solid battery electrode> The solid-state battery electrodes (negative and positive electrodes) according to this embodiment are obtained by applying the electrode mixture slurry to the surface of a current collector, drying the slurry, and forming an electrode layer on the current collector. This results in the formation of covalent bonds between the binder contained in the electrode mixture slurry and at least one of the solid electrolyte and the electrode active material.

[0055] (current collector) The positive electrode current collector is not particularly limited, and examples thereof include aluminum, aluminum alloys, stainless steel, nickel, iron, and titanium, among which aluminum, aluminum alloys, and stainless steel are preferred. The shape of the positive electrode current collector may be, for example, a foil, a plate, or a porous shape.

[0056] The negative electrode current collector is not particularly limited, and examples thereof include nickel, copper, stainless steel, etc. The negative electrode current collector may be in the form of, for example, a foil, a plate, or a porous shape.

[0057] (Method for forming electrode layer) The electrode layer can be formed by a known method of applying the electrode mixture slurry to the surface of a current collector and drying it, and either a wet method or a dry method may be used. Hereinafter, the case of forming the electrode layer by the wet method will be described.

[0058] The electrode layer is manufactured by applying an electrode mixture slurry to the surface of a current collector and drying it to form an electrode layer on the surface of the current collector. The method for applying the electrode mixture slurry to the surface of the current collector is not particularly limited, and methods such as inkjet printing, screen printing, CVD, and sputtering can be used. Known coating methods such as a doctor blade can also be used. The total thickness of the electrode layer and current collector after drying (electrode thickness) is not particularly limited, but is preferably 0.1 μm to 1 mm, and more preferably 1 μm to 200 μm, from the viewpoints of energy density and lamination. The electrode may also be manufactured through an optional pressing process. The pressure used to press the electrode can be approximately 100 MPa.

[0059] <Solid battery> A solid-state battery including the solid-state battery electrode includes the negative electrode, the positive electrode, and a solid electrolyte layer. The negative electrode comprises a negative electrode current collector and a negative electrode layer, and the positive electrode comprises a positive electrode current collector and a positive electrode layer. The solid electrolyte layer is disposed between the negative electrode layer and the positive electrode layer. The number of layers of the negative electrode, the positive electrode, and the solid electrolyte layer is not particularly limited, and a plurality of negative electrodes, positive electrodes, and solid electrolyte layers may be stacked. In this case, the layers are disposed so that the solid electrolyte layer is disposed between the negative electrode and the positive electrode.

[0060] (solid electrolyte layer) The solid electrolyte layer is a layer laminated between the anode layer and the cathode layer, and contains at least a solid electrolyte material. Conduction of a charge transfer medium between the anode active material and the cathode active material can be achieved via the solid electrolyte material contained in the solid electrolyte layer. The above-described solid electrolyte materials can be suitably used as the solid electrolyte material for the solid electrolyte layer.

[0061] The solid electrolyte layer can be formed, for example, by pressing the solid electrolyte. Alternatively, the solid electrolyte layer can be formed by applying a slurry solution of the solid electrolyte, prepared by dispersing a solid electrolyte material or the like in a solvent, to the surface of a substrate or an electrode. In manufacturing the solid electrolyte layer, the surface of the solid electrolyte may be chemically modified in a solvent in which a surface modifier is dispersed. In this case, the surface of the solid electrolyte can be chemically modified using the same procedure as for the electrode layer. The thickness of the solid electrolyte layer varies greatly depending on the battery configuration, but is preferably 0.1 μm to 1 mm, and more preferably 1 μm to 100 μm.

[0062] (Solid-state battery manufacturing method) The method for producing a solid-state battery is not particularly limited, and any known method can be applied. For example, a method in which a negative electrode, a solid electrolyte layer, and a positive electrode are stacked in this order and optionally pressed to be integrated can be mentioned.

[0063] The present invention is not limited to the above-described embodiment, and includes modifications and improvements within the scope of achieving the object of the present invention. [Example]

[0064] Next, an example of the present invention will be described, but the present invention is not limited to this example. However, Examples 3, 5, and 6 are reference examples.

[0065] Example 1 (Preparation of binder solution) Styrene-butadiene rubber (A-1, hereinafter chemical formula (2)) as a binder: In a glove box filled with argon gas, styrene-butadiene rubber (butadiene content 90 mol%, water content <20 mass ppm) was dissolved in n-butyl n-butyrate (water concentration <20 ppm) to prepare a 10 mass% binder solution.

[0066] [ka]

[0067] (Preparation of positive electrode) Nickel, manganese, and cobalt ternary positive electrode active material (LiNi 0.8 Mn 0.1 Co 0.1 6.7 grams of O2 was used as the positive electrode active material, 3.0 grams of Li-PS-Cl solid electrolyte, 0.2 grams of acetylene black, and 1 gram of a 10% by mass solution of styrene butadiene rubber binder in n-butyl butyrate were mixed with n-butyl butyrate to prepare a slurry. This slurry was applied to a current collector foil using an automatic bar coater to obtain a positive electrode layer.

[0068] (Preparation of negative electrode) Preparation of negative electrode: 6.9 g of graphite was used as the negative electrode active material, 3.0 g of Li-PS-Cl solid electrolyte, 1 g of a 10% by mass solution of styrene butadiene rubber binder in n-butyl butyrate, and n-butyl butyrate were mixed to prepare a slurry. This slurry was applied to a current collector foil using an automatic bar coater to obtain a negative electrode.

[0069] (Preparation of solid electrolyte layer) 9.9 g of Li-PS-Cl solid electrolyte and 1 g of a 10% by mass solution of styrene butadiene rubber binder in n-butyl butyrate were mixed with n-butyl butyrate to prepare a slurry. This slurry was applied to a PET film using an automatic bar coater, dried, and then the PET film was peeled off to obtain a solid electrolyte layer.

[0070] [TOF-SIMS analysis] The prepared electrode layer and solid electrolyte layer were stacked and analyzed by TOF-SIMS (IONTOF TOFSIMS.5), and the negative ion fragment C2HS - The components were confirmed and it was confirmed that the C=C double bond of the binder had bonded with the sulfur atom of the solid electrolyte. The results are shown in Figure 1.

[0071] <Example 2> A positive electrode layer, a negative electrode layer, and a solid electrolyte layer were produced in the same manner as in Example 1, except that a hydrogenated nitrile butadiene rubber (acrylonitrile content 10 mol %, water content <20 mass ppm) represented by the following chemical formula (3) was used instead of the styrene butadiene rubber of Example 1.

[0072] [ka]

[0073] [IR analysis] The fabricated electrode layer was analyzed by IR (Bruker TENSOR37), and a shift in the C≡N bond in the polymer binder was observed, confirming that the C≡N group coordinated with the lithium ions in the solid electrolyte. The results are shown in Figure 2. The dashed line in Figure 2 shows the IR spectrum before the binder was mixed with the solid electrolyte, and the solid line in Figure 2 shows the IR spectrum after the binder was mixed with the solid electrolyte.

[0074] Example 3 A positive electrode layer, a negative electrode layer, and a solid electrolyte layer were produced in the same manner as in Example 1, except that an ethylene-vinyl acetate copolymer (vinyl acetate content: 12 mol%, water content: <20 mass ppm) represented by the following chemical formula (4) was used instead of the styrene-butadiene rubber of Example 1.

[0075] [ka]

[0076] Example 4 A positive electrode layer, a negative electrode layer, and a solid electrolyte layer were produced in the same manner as in Example 1, except that an ethylene methyl methacrylate copolymer (methyl methacrylate content: 10 mol %, water content: <20 mass ppm) represented by the following chemical formula (5) was used instead of the styrene-butadiene rubber of Example 1.

[0077] [ka]

[0078] [IR analysis] The fabricated electrode layer was analyzed by IR (Bruker TENSOR37), and a shift in the C=O bond in the polymer binder was observed, confirming that the C=O group coordinated with the lithium ions in the solid electrolyte. The results are shown in Figure 3. The dashed line in Figure 3 shows the IR spectrum before the binder was mixed with the solid electrolyte, and the solid line in Figure 3 shows the IR spectrum after the binder was mixed with the solid electrolyte.

[0079] <Example 5> A positive electrode layer, a negative electrode layer, and a solid electrolyte layer were produced in the same manner as in Example 1, except that a styrene-methyl methacrylate copolymer (methyl methacrylate content: 15 mol %, water content: <20 mass ppm) represented by the following chemical formula (6) was used instead of the styrene-butadiene rubber of Example 1.

[0080] [ka]

[0081] Example 6 A positive electrode layer, a negative electrode layer, and a solid electrolyte layer were prepared in the same manner as in Example 1, except that a styrene-acrylic acid n-dodecyl copolymer (n-dodecyl acrylate content: 25 mol %, water content: <20 mass ppm) represented by the following chemical formula (7) was used instead of the styrene-butadiene rubber of Example 1.

[0082] [ka]

[0083] Example 7 A positive electrode layer, a negative electrode layer, and a solid electrolyte layer were produced in the same manner as in Example 1, except that a styrene-dimethyl maleate copolymer (dimethyl maleate content: 5 mol %, water content: <20 mass ppm) represented by the following chemical formula (8) was used instead of the styrene-butadiene rubber of Example 1.

[0084] [ka]

[0085] <Comparative Example 1> A positive electrode layer, a negative electrode layer, and a solid electrolyte layer were produced in the same manner as in Example 1, except that a hydrogenated styrene-butadiene copolymer (styrene content 10 mol %, water content <20 mass ppm) represented by the following chemical formula (9) was used instead of the styrene-butadiene rubber of Example 1.

[0086] [ka]

[0087] <Comparative Example 2> A positive electrode layer, a negative electrode layer, and a solid electrolyte layer were produced in the same manner as in Example 1, except that polyisobutene (water content <20 mass ppm) represented by the following chemical formula (10) was used instead of the styrene-butadiene rubber of Example 1.

[0088] [ka]

[0089] (Fabrication of positive electrode half-cell) Using the positive electrodes and solid electrolyte layers of each Example and Comparative Example, a 10 mm diameter circular positive electrode sheet, a solid electrolyte layer, and an indium-lithium alloy counter electrode were placed in a ceramic tube with an inner diameter of 10 mm and press-molded to fabricate batteries. In this case, the alloy counter electrode served as the negative electrode.

[0090] (Fabrication of negative electrode half-cell) Using the negative electrodes and solid electrolyte layers of each Example and Comparative Example, a battery was fabricated by placing a 10 mm diameter circular punched negative electrode sheet, a solid electrolyte layer, and an indium-lithium alloy counter electrode in a ceramic tube with an inner diameter of 10 mm, and press-molding the tube. In this case, the alloy counter electrode served as the positive electrode.

[0091] [evaluation] The battery capacity was measured using the positive electrode half-cell and negative electrode half-cell prepared in each of the Examples and Comparative Examples. The battery was charged and discharged at 25°C at a charge / discharge rate of 0.1 c. Charge / discharge cycles were repeated, and the discharge capacity in the fifth cycle was recorded as the battery capacity. The battery capacity was divided by the weight of the electrode active material to determine the capacity per unit weight (mAh / g). The results are shown in Table 1.

[0092] [Table 1]

[0093] The results in Table 1 confirm that the solid state batteries according to each Example have higher positive electrode capacity and negative electrode capacity (mAh / g) than the solid state batteries according to each Comparative Example.

Claims

1. An electrode mixture slurry used in the manufacture of an electrode for a solid state battery, a solid electrolyte, an electrode active material, a binder, and a solvent; The solid electrolyte is at least one of a sulfide and an oxide, the binder is at least one of a polymer binder containing an unsaturated carbon-carbon bond and a polymer binder having an electron-donating group; a surface modifier that modifies the surface of at least one of the solid electrolyte and the electrode active material, the surface modifier is a copolymer, The electrode mixture slurry, wherein the content of the repeating unit having the predetermined functional group in the copolymer is less than 10 mol %.

2. The electrode mixture slurry according to claim 1 , wherein the copolymer is used as the binder.

3. 3. The electrode mixture slurry according to claim 1, wherein the content of the repeating unit having the predetermined functional group in the copolymer is 1 mol % or more and less than 8 mol %.

4. 4. The electrode mixture slurry according to claim 3, wherein the content of the repeating unit having the predetermined functional group in the copolymer is 2 mol % or more and less than 5 mol %.

5. The predetermined functional group is at least one functional group selected from the group consisting of an ester group, a carboxylate group, a sulfonate group, a nitrile group, an ether group, and a phosphate group. The electrode mixture slurry according to any one of claims 1 to 4.

6. an electrode layer including a solid electrolyte, an electrode active material, and a binder; the binder is at least one of a polymer binder containing an unsaturated carbon-carbon bond and a polymer binder having an electron-donating group; The solid electrolyte is at least one of a sulfide and an oxide, A covalent bond or a coordinate bond is formed between the binder and at least one of the solid electrolyte and the electrode active material.

7. A solid-state battery comprising the electrode for a solid-state battery according to claim 6.

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