Electrode for solid-state battery and solid-state battery including the same

Abstract

To provide a solid battery electrode capable of improving uniformity of electrode materials and suppressing decomposition of a solid electrolyte and an electrode active material by a binder and a solvent.SOLUTION: A solid battery electrode includes a solid electrolyte made of sulfides and / or oxides, an electrode active material, a binder, and a conductive agent, and at least one of the solid electrolyte and the electrode active material has a surface modified with a surface modifier, and the surface modifier is at least one selected from the group consisting of a carboxylate, a thiocarboxylate, a carboxylic acid, a thiocarboxylic acid, a phosphate, thiophosphates, ketones, nitriles, alcohols, thiols, and ethers.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrode for a solid-state battery and a solid-state battery including the same. [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. Among various types of batteries, there is a high demand for batteries that exhibit high energy density and power output, and the development of even higher performance batteries is anticipated. Solid-state batteries, in particular, are attracting 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 such solid-state batteries, the electrode active material and the solid electrolyte have strong polarity on their surfaces, while the conductive additive has almost no polarity on its surface, 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 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] However, the present applicant has now newly discovered that the electrode active material and the solid electrolyte are decomposed by the binder or the solvent. Therefore, there is a need for an electrode for a solid battery that can improve the uniformity of the electrode material and can suppress the decomposition of the solid electrolyte and the electrode active material caused by the binder or the solvent.

[0007] The present invention has been made in view of the above, and aims to provide an electrode for a solid battery that can improve the uniformity of the electrode material and can suppress decomposition of the solid electrolyte and the electrode active material due to the binder and the solvent, and a solid battery including the electrode. [Means for solving the problem]

[0008] (1) The present invention provides an electrode for a solid battery, comprising a solid electrolyte comprising a sulfide and / or an oxide, an electrode active material, a binder, and a conductive additive, wherein the surface of at least one of the solid electrolyte and the electrode active material is modified with a surface modifier, and the surface modifier is at least one selected from the group consisting of carboxylates, thiocarboxylates, carboxylic acids, thiocarboxylic acids, phosphates, thiophosphates, ketones, nitriles, alcohols, thiols, and ethers.

[0009] (2) In the solid state battery electrode of (1), the surface modifier may have a carbon chain having 1 to 11 carbon atoms.

[0010] (3) In the solid state battery electrode of (1) or (2), the surface modifier may have a carbon chain having 1 to 6 carbon atoms.

[0011] (4) In any one of the solid state battery electrodes (1) to (3), the surface modifier may have a carbon chain with 1 to 4 carbon atoms.

[0012] (5) In any one of the solid state battery electrodes (1) to (4), the surface modifier may be at least one selected from the group consisting of lithium butyrate, lithium isobutyrate, lithium acetate, butyl phosphate, and isobutyronitrile.

[0013] (6) In any one of the solid state battery electrodes (1) to (5), the binder may be a binder that is relatively less polar or non-polar than the solid electrolyte and the electrode active material before their surfaces are modified with the surface modifier.

[0014] (7) In any of the solid-state battery electrodes (1) to (6), the binder may be at least one selected from the group consisting of polyethylene vinyl acetate (PEVA), polymethyl methacrylate (PMMA), styrene butadiene rubber (SBR), hydrogenated nitrile butadiene rubber (HNBR), nitrile butadiene rubber (NBR), and polyisobutene (PIB).

[0015] (8) In any one of the solid state battery electrodes (1) to (7), the solid electrolyte may be a sulfide solid electrolyte having an argyrodite-type crystal structure.

[0016] (9) In the solid state battery electrode of any one of (1) to (8), the electrode active material may be a positive electrode active material, and the solid state battery electrode may be a positive electrode for a solid state battery.

[0017] (10) The present invention also provides a solid-state battery comprising the electrode for a solid-state battery according to any one of (1) to (9). [Effects of the Invention]

[0018] According to the present invention, it is possible to provide an electrode for a solid state battery that can improve the uniformity of the electrode material and can suppress decomposition of the solid electrolyte and electrode active material due to the binder and solvent, and a solid state battery including the electrode. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram showing the configuration of a solid-state battery 10 according to one embodiment of the present invention. [Figure 2] 1 is a chart showing an IR spectrum of a solid electrolyte according to an example of the present invention. [Figure 3] 1 is a chart showing an IR spectrum of a solid electrolyte according to an example of the present invention. [Figure 4] 1 is a chart showing an IR spectrum of a solid electrolyte according to an example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, the electrode for a solid state battery and the method for producing the same of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

[0021] (solid battery) FIG. 1 is a diagram showing an outline of a solid-state battery 10 of the present invention. The solid-state battery 10 of the present invention is constructed in layers and includes a positive electrode current collector 14, a positive electrode layer 11, a negative electrode current collector 15, a negative electrode layer 12, and a solid electrolyte layer 13 interposed between these electrode layers. The battery also includes a positive electrode current collector 14 that collects current from the positive electrode and a negative electrode current collector 15 that collects current from the negative electrode. In the solid electrolyte layer 14, the positive electrode layer 11, and the negative electrode layer 12, the surface of at least one of the solid electrolyte and the electrode active material is modified with a surface modifier. The layers of the solid-state battery of the present invention are configured, for example, from the bottom in FIG. 1 as follows: a negative electrode current collector 15, a negative electrode layer 12, the solid electrolyte layer 13, the positive electrode layer 11, and the positive electrode current collector 14.

[0022] (electrode layer) The electrode layer used in the solid state battery of the present invention is a layer containing at least an electrode active material, a solid electrolyte, a binder, and a surface modifier that modifies the surface of at least one of the electrode active material and the solid electrolyte. The materials described later can be used for each of the electrode active material, the solid electrolyte, the binder, and the surface modifier that modifies the surface of at least one of the electrode active material and the solid electrolyte. In the present invention, the term "electrode layer" collectively refers to the positive electrode layer and the negative electrode layer. Furthermore, the term "electrode active material" collectively refers to the positive electrode active material and the negative electrode active material.

[0023] [Electrode mixture] In the present invention, the electrode mixture contains at least an electrode active material, a solid electrolyte, a binder, a surface modifier that modifies the surface of at least one of the electrode active material and the solid electrolyte, and a solvent. The electrode mixture applicable to the present invention may contain any other components as long as it contains the above materials. The other components are not particularly limited, and may be any components that can be used when producing a solid-state battery. The positive electrode mixture constituting the positive electrode contains at least a positive electrode active material, a solid electrolyte, a binder, a surface modifier for modifying the surface of at least one of the positive electrode active material and the solid electrolyte, and a solvent. Other components, such as a conductive additive, may also be contained. Examples of the positive electrode active material include the materials described below. The negative electrode mixture has the same structure as the positive electrode mixture except that it contains a negative electrode active material instead of the positive electrode active material. Examples of the negative electrode active material include the materials described below.

[0024] (Cathode active material) The positive electrode active material can be the same as that used in the positive electrode active material layer of a general solid-state battery, and is not particularly limited. For example, in the case of a lithium-ion battery, a layered active material containing lithium, a spinel-type active material, an olivine-type active material, etc. can be used. Specific examples of the positive electrode active material include lithium cobalt oxide (LiCoO), lithium nickel oxide (LiNiO), LiNi p Mn q Cor 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).

[0025] The surface of the positive electrode active material is preferably coated with an oxide such as LiNbO3. This further suppresses the positive electrode active material from being decomposed by the binder or solvent. That is, this oxide coating layer such as LiNbO3 functions as a reaction suppression layer that suppresses the reaction between the positive electrode active material and the binder or solvent.

[0026] The coating with the reaction suppression layer is carried out, 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.

[0027] Next, the reaction suppression layer precursor solution is coated onto the positive electrode active material using, for example, a tumbling 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 positive 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 positive electrode active material coated with the precursor of the LiNbO3 reaction inhibitor layer.

[0028] Next, the positive electrode active material coated with the precursor of the LiNbO3 reaction suppression layer is heat-treated in an electric furnace in the atmosphere, to obtain a positive electrode active material coated with the LiNbO3 reaction suppression layer.

[0029] In the positive electrode active material of the present invention, regardless of whether or not it is coated with a reaction suppression layer, it is also preferable that the surface be further modified with a surface modifier described below. More preferably, the positive electrode active material coated with a reaction suppression layer is surface-modified with a surface modifier.

[0030] (Negative electrode active material) The negative electrode active material is not particularly limited as long as it can absorb and release a charge transfer medium. For example, in the case of a lithium ion battery, lithium titanate (Li4Ti5O 12 Examples of the negative electrode active material include lithium transition metal oxides such as LiNbO, transition metal oxides such as TiO, NbO, and WO, metal sulfides, metal nitrides, carbon materials such as graphite, soft carbon, and hard carbon, 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. Similarly to the positive electrode active material, the negative electrode active material is preferably surface-coated with an oxide such as LiNbO. The oxide coating layer on the negative electrode active material is preferably formed by the same method as that for the positive electrode active material. The negative electrode active material of the present invention is preferably surface-modified with a surface modifier described below, regardless of whether or not it is coated with a reaction suppression layer. More preferably, the negative electrode active material coated with a reaction suppression layer is surface-modified with a surface modifier.

[0031] (solid electrolyte) The solid electrolyte material is not particularly limited as long as it has charge transfer medium conductivity, and examples thereof include sulfide solid electrolyte materials, oxide solid electrolyte materials, nitride solid electrolyte materials, and halide solid electrolyte materials. Among these, it is preferable to use an oxide solid electrolyte material or a sulfide solid electrolyte material. More preferably, a sulfide solid electrolyte material can be used. This is because sulfide solid electrolyte materials have higher charge transfer medium conductivity than oxide solid electrolyte materials. In addition, it is also preferable that the surface of the solid electrolyte material of the present invention is modified with a surface modifying substance described below.

[0032] [Oxide solid electrolyte] Examples of oxide solid electrolyte materials for solid-state batteries 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).

[0033] [Sulfide solid electrolyte] The sulfide solid electrolyte typically contains a metal element (M) that becomes a conducting ion, and sulfur (S). Examples of M include Li, Na, K, Mg, and Ca. In this embodiment, where Li ion conductivity is required, M is Li. In particular, the sulfide solid electrolyte of the present invention preferably contains Li, A (A is at least one element selected from the group consisting of P, Si, Ge, Al, and B), and S. Furthermore, A is preferably P (phosphorus). Furthermore, the sulfide solid electrolyte 12 may contain a halogen such as Cl, Br, or I in order to improve ion conductivity. Furthermore, the sulfide solid electrolyte may contain O (oxygen). Furthermore, the sulfide solid electrolyte preferably has an argyrodite-type crystal structure.

[0034] Examples of the sulfide solid electrolyte of the present invention having Li ion conductivity include LiS-P2S5, LiS-P2S5-LiI, LiS-P2S5-LiO, LiS-P2S5-Li2O-LiI, LiS-SiS2, LiS-SiS2-LiI, LiS-SiS2-LiBr, LiS-SiS2-LiCl, LiS-SiS2-B2S3-LiI, LiS-SiS2-P2S5-LiI, LiS-B2S3, and LiS-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 of "Li2S-P2S5" means a sulfide solid electrolyte obtained using a raw material composition containing Li2S and P2S5, and the same applies to other descriptions.

[0035] 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 (ball mill, etc.) 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. The Li ion conductivity of the 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.

[0036] (Surface modification substance) The solid state battery electrode of the present invention includes a surface modifier. The surface modifier is a surface modifier for at least one of the electrode active material and the solid electrolyte contained in the electrode layer of the present invention. By modifying the surface of at least one of the electrode active material and the solid electrolyte with a surface modifier having the following structural formula, at least one of the electrode active material and the solid electrolyte is prevented from being decomposed into the binder or the solvent. Furthermore, this contributes to the homogenization and stabilization of the electrode mixture slurry.

[0037] [kinds] The surface modifier used to modify the surface of at least one of the electrode active material and the solid electrolyte contained in the solid battery electrode of the present invention 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 can be at least one of the compounds represented by the following structural formulas: In the structural formula (1) below, R, R′, and R″ each represent a carbon chain, X represents an oxygen atom or a sulfur atom, and Li represents lithium. These surface modifiers may be used alone or in combination of two or more.

[0038] [ka]

[0039] From the viewpoint that alkyl chains are insulators and do not conduct ions, R, R', and R" preferably have carbon chains with 1 to 11 carbon atoms, and more preferably have carbon chains with 1 to 6 carbon atoms. Even more preferably, R, R', and R" each have a carbon chain with 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 groups, and may be saturated or unsaturated aliphatic groups. Saturated aliphatic groups are preferred. Furthermore, the carbon chain may contain a heteroatom between the carbon-carbon bonds. Furthermore, the carbon chain may or may not have a substituent. When R, R′, and R″ are aromatic groups, they may be either phenyl or naphthyl groups. The aromatic group may contain a heteroatom between the carbon-carbon bonds. The aromatic group may or may not have a substituent.

[0040] The surface modifier 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.

[0041] 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 or 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 is due to intermolecular interactions, such as hydrophobic interactions, π-π stacking, hydrophilic interactions, and electrostatic interactions (hydrogen bonds, van der Waals forces, etc.), acting between the electrode active material or the solid electrolyte and the solvent or binder, resulting in 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 solid electrolyte composition contains a conductive additive, affinity is maintained, resulting in homogenization and stabilization of the electrode mixture slurry and the solid electrolyte slurry.

[0042] [Content] The content of the surface modifier is 3% by mass or less of the electrode mixture after drying. It is preferably 1% by mass or less, and 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 homogenization and stabilization of the electrode mixture slurry.

[0043] (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 cathode 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 due to intermolecular interactions, thereby homogenizing and stabilizing the composition slurry. It is also preferable to use a surface modifier that modifies the surface of at least one of the electrode active material and solid electrolyte as the solvent. 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 and the solid electrolyte.

[0044] (binder) The solid state battery electrode of the present invention contains a binder. The binder functions as a binding agent or a thickener in the electrode layer, homogenizes the electrode mixture slurry, and provides an appropriate viscosity.

[0045] [kinds] The type of binder used in the solid-state battery electrode of the present invention is not particularly limited, and any binder may be used as long as it can be used to bind the electrode active material, solid electrolyte, and other components contained in the electrode mixture, or to bind the components contained in the electrode mixture and the current collector together when forming the electrode layer. Examples include acrylic acid polymers, cellulose polymers, styrene polymers, vinyl acetate polymers, urethane polymers, fluoroethylene polymers, methacrylic acid ester polymers, and acrylic acid ester polymers. Styrene polymers, methacrylic acid ester polymers, and acrylic acid ester polymers are preferred because they are uniformly dispersed in the electrode mixture and provide appropriate viscosity.

[0046] Specific examples of binders include polyvinylidene fluoride (PVdF), polymethyl methacrylate (PMMA), polyisobutene (PIB), styrene butadiene rubber (SBR), polyethylene-vinyl acetate copolymer (PEVA), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), etc. These may be used alone or in combination of two or more. The structural formula of the binder that can be preferably used in the present invention is shown in the following formula (2): In the following formula (2), n and m represent any natural number.

[0047] [ka]

[0048] [Content] The binder content is preferably 5% by mass or less, more preferably 1.0% by mass or less, based on the total electrode mixture after drying. When the content is 5% by mass or less, the electrode active material, solid electrolyte, conductive additive, binder, and current collector are sufficiently strongly bound together. In addition, this is preferable because the electrode mixture slurry has a suitable viscosity and also provides stability and uniformity.

[0049] (Conductive additive) The solid state battery electrode of the present invention contains a conductive additive. As the conductive aid, a conventionally known conductive aid can be used, and specific examples of the conductive aid include acetylene black, natural graphite, and artificial graphite.

[0050] [Content] The content of the conductive additive is preferably 5% by mass or less, more preferably 1% by mass or less, based on the total electrode mixture after drying. When the content is 5% by mass or less, the electrode active material, solid electrolyte, conductive additive, binder, and current collector are sufficiently strongly bonded together. In addition, this is preferable because the electrode mixture slurry has an appropriate viscosity and also provides stability and uniformity.

[0051] (Electrode current collector) The positive electrode current collector 14 is not particularly limited as long as it has the function of collecting current from the positive electrode layer, and examples thereof include aluminum, aluminum alloys, stainless steel, nickel, iron, and titanium, with aluminum, aluminum alloys, and stainless steel being preferred. The shape of the positive electrode current collector 14 may be, for example, a foil, a plate, or a porous shape.

[0052] The negative electrode current collector 15 is not particularly limited as long as it has the function of collecting current from the negative electrode layer 12. Examples of materials for the negative electrode current collector 15 include nickel, copper, and stainless steel. Examples of the shape of the negative electrode current collector 15 include a foil shape, a plate shape, a porous shape, and the like. In the present invention, the electrode current collector collectively refers to the positive electrode current collector and the negative electrode current collector.

[0053] (solid electrolyte layer) The solid electrolyte layer is a layer laminated between the positive electrode layer and the negative electrode layer of a solid-state battery, and contains at least a solid electrolyte material. Charge transfer medium conduction between the positive electrode active material and the negative electrode active material can be achieved via the solid electrolyte material contained in the solid electrolyte layer. The above-mentioned solid electrolyte materials can be suitably used as the solid electrolyte material that can be used for the solid electrolyte layer.

[0054] (Manufacturing method) [Method of manufacturing electrode layer] Positive and negative electrode layers can be produced by disposing a slurry containing an electrode mixture on the surface of a current collector and drying it. The electrode layer can be produced by a conventional method, except that the surface of at least one of the electrode active material and the solid electrolyte is chemically modified with a surface modifier. The electrode layer can be produced by either a wet method or a dry method. The following describes the case where the electrode layer is produced by a wet method.

[0055] The electrode layer is produced 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, thereby surface-modifying the surface of at least one of the electrode active material and the solid electrolyte; mixing the slurry of the electrode mixture surface-modified with the surface modifier obtained in the above step with a binder and a conductive assistant to obtain a slurry solution of the electrode mixture; and coating the slurry solution of the electrode mixture on the surface of an electrode current collector and drying it to form an electrode layer on the surface of the electrode current collector. For example, at least one of an electrode active material and a solid electrolyte and a surface modifier are mixed and dispersed in a solvent to obtain a slurry solution of an electrode mixture in which at least one of an electrode active material and a solid electrolyte is surface-modified with the surface modifier. In this case, the surface modifier can also be used as a solvent. Next, materials for forming the electrode layer, such as a binder and a conductive additive, are mixed and dispersed in the obtained electrode mixture slurry to obtain a slurry solution of the electrode mixture. At this time, if only one of the electrode active material and the solid electrolyte has been surface-modified in the previous step, the remaining one is mixed into the electrode mixture slurry. The electrode active material, solid electrolyte, surface modifier, binder, conductive additive, and solvent can be mixed and dispersed using various mixing and dispersion devices such as an ultrasonic disperser, a shaker, Filmix (registered trademark), etc. The solid content of the electrode mixture slurry solution is not particularly limited.

[0056] The electrode mixture slurry solution thus obtained is applied to the surface of an electrode current collector and dried to form an electrode layer on the surface of the electrode current collector, thereby obtaining an electrode. Here, the solvent used to obtain the electrode mixture slurry in the drying step volatilizes upon drying, or if the solvent is a surface modifier, it modifies the surface of at least one of the electrode active material and the solid electrolyte, so that substantially no solvent remains in the obtained electrode layer. Another application method is, for example, to separately prepare a slurry solution mainly composed of the electrode active material and a slurry solution composed of the solid electrolyte, and then laminate the electrode layers while patterning the components in each solution.

[0057] The method for applying the slurry solution to the surface of the electrode current collector is not particularly limited, and methods such as inkjet printing, screen printing, CVD, and sputtering can be used. In addition, known coating methods such as a doctor blade can also be used. The total thickness of the electrode layer and electrode 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 fabricated through an optional pressing process. The pressure used to press the electrode can be approximately 100 MPa.

[0058] [Method of manufacturing solid electrolyte layer] The solid electrolyte layer can be produced, for example, by pressing a solid electrolyte. Alternatively, the solid electrolyte layer can be produced 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 producing 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. Furthermore, methods commonly used in this technical field can be applied as appropriate to produce the solid electrolyte layer. For mixing and dispersing the solid electrolyte and the solvent, various mixing and dispersing devices can be used, such as an ultrasonic dispersing device, a shaker, Filmix (registered trademark), etc. The solid content of the solid electrolyte slurry solution is not particularly limited.

[0059] Furthermore, when the solid electrolyte layer is produced by a wet method, the means for applying the solid electrolyte slurry solution is not particularly limited, and an inkjet method, a screen printing method, a CVD method, a sputtering method, or the like can be used, or a known application means such as a doctor blade can also be used. In the solid electrolyte layer obtained by the drying step, the solvent used to obtain the solid electrolyte slurry is evaporated by drying, or if the solvent is a surface modifier, it modifies the surface of the solid electrolyte, so that substantially no solvent remains in the obtained solid electrolyte layer. The thickness of the solid electrolyte layer varies greatly depending on the configuration of the battery, but is preferably, for example, 0.1 μm to 1 mm, and more preferably 1 μm to 100 μm. When the surface of at least one of the electrode active material and the solid electrolyte in the electrode layer is chemically modified, the solid electrolyte in the solid electrolyte layer does not necessarily have to be surface-modified.

[0060] [Solid-state battery manufacturing method] A solid state battery including the electrode for a solid state battery of the present invention will be described. The solid-state battery of the present invention is manufactured by stacking the above-mentioned positive electrode current collector, positive electrode layer, solid electrolyte layer, negative electrode layer, and negative electrode current collector in the order shown in Figure 1. After stacking these, they may be optionally pressed to be integrated. In manufacturing the solid-state battery, a commonly used method can be appropriately applied.

[0061] [effect] The electrode for a solid state battery and the solid state battery including the electrode according to the present invention have been described above. The solid state battery electrode and the solid state battery including the electrode of the present invention have the following advantages.

[0062] The present invention provides an electrode for a solid battery, which comprises a solid electrolyte made of a sulfide and / or an oxide, an electrode active material, a binder, and a conductive additive, wherein the surface of at least one of the solid electrolyte and the electrode active material is modified with a surface modifier, and the surface modifier comprises at least one selected from the group consisting of carboxylates, thiocarboxylates, carboxylic acids, thiocarboxylic acids, phosphates, thiophosphates, ketones, nitriles, alcohols, thiols, and ethers. As a result, at least one of the solid electrolyte and the electrode active material has affinity for the binder due to intermolecular interactions, making it less susceptible to decomposition. Furthermore, the inside of the electrode layer is homogenized and stabilized. Therefore, the solid battery electrode and solid battery having the above configuration have reduced electrode resistance and improved battery performance and durability. [Example]

[0063] The electrode of the present invention will be described in detail below using examples. However, Examples 1, 3, 5, 6, 9, 10, and 11 are reference examples.

[0064] Example 1 [Preparation of solid electrolyte] Modification with butyric acid (A-1): In a glove box filled with argon gas, 0.02 g (0.2 mass%) of butyric acid was dissolved in 20 g of butyl butyrate (water concentration <20 ppm). 10 g of Li-PS-Cl-based solid electrolyte was mixed with this solution. After mixing for 12 hours, the butyl butyrate solvent was removed under reduced pressure to obtain the solid electrolyte of Example 1, which was surface-modified with butyric acid.

[0065] Fig. 2 is a chart showing the IR spectrum of the solid electrolyte according to Example 1. As shown in Fig. 2, peaks of carboxylic acid and carboxylate are detected in the IR spectrum, and it is clear that the surface of the solid electrolyte is modified with carboxylic acid and carboxylate.

[0066] [Preparation of positive electrode] 7.0 grams of lithium cobalt oxide (LiCoO2) with a LiNbO3 surface coating was used as the positive electrode active material, 3.0 grams of solid electrolyte, 0.1 grams of acetylene black, and 1 gram of a 10% by weight xylene solution of polymethyl methacrylate were mixed with xylene to prepare a slurry. This slurry was applied to a current collector foil using an automatic bar coater to obtain a positive electrode layer.

[0067] [Preparation of negative electrode] 7.0 g of graphite was used as the negative electrode active material, 3.0 g of solid electrolyte, and 1 g of a 10% by weight xylene solution of polymethyl methacrylate were mixed with xylene to prepare a slurry, which was then applied to a current collector foil using an automatic bar coater to obtain a negative electrode layer.

[0068] [Fabrication of positive electrode half-cell] A compact was prepared by placing 0.1 g of the solid electrolyte prepared above in a ceramic tube with an inner diameter of 10 mm, and the cathode layer prepared above was punched out into a circle with a diameter of 10 mm. The cathode layer and an indium-lithium alloy counter electrode were placed on either side of the compact, and the resultant battery was fabricated by press molding. In this case, the indium-lithium alloy counter electrode served as the anode.

[0069] [Fabrication of negative electrode half-cell] A compact was prepared by placing 0.1 g of the solid electrolyte prepared above in a ceramic tube with an inner diameter of 10 mm, and the anode layer prepared above was punched out into a circle with a diameter of 10 mm. The anode layer and an indium-lithium alloy counter electrode were placed so as to sandwich the compact, and the resultant battery was fabricated by press molding. In this case, the indium-lithium alloy counter electrode served as the positive electrode.

[0070] <Example 2> A positive electrode half-cell and a negative electrode half-cell according to Example 2 were produced in the same manner as in Example 1, except that 0.02 g of lithium butyrate was used instead of 0.02 g of butyric acid when producing the solid electrolyte.

[0071] Example 3 A positive electrode half-cell and a negative electrode half-cell according to Example 3 were produced in the same manner as in Example 1, except that 0.02 g of isobutyric acid was used instead of 0.02 g of butyric acid when preparing the solid electrolyte, and hexane was used as the solvent.

[0072] Example 4 A positive electrode half-cell and a negative electrode half-cell according to Example 4 were produced in the same manner as in Example 1, except that, when producing the solid electrolyte, 0.02 g of lithium isobutyrate was used instead of 0.02 g of butyric acid, and isobutyl isobutyrate was used as the solvent.

[0073] <Example 5> A positive electrode half-cell and a negative electrode half-cell according to Example 5 were produced in the same manner as in Example 1, except that 0.02 g of acetic acid was used instead of 0.02 g of butyric acid when preparing the solid electrolyte.

[0074] Example 6 A positive electrode half-cell and a negative electrode half-cell according to Example 6 were produced in the same manner as in Example 1, except that 0.02 g of lithium acetate was used instead of 0.02 g of butyric acid when preparing the solid electrolyte.

[0075] Example 7 A positive electrode half-cell and a negative electrode half-cell according to Example 7 were produced in the same manner as in Example 1, except that 0.01 g of butyric acid and 0.01 g of lithium butyrate were used instead of 0.02 g of butyric acid when producing the solid electrolyte.

[0076] Fig. 3 is a chart showing the IR spectrum of the solid electrolyte according to Example 7. As shown in Fig. 3, when compared with the IR spectrum of the solid electrolyte alone, peaks of butyric acid and lithium butyrate are detected in the IR spectrum of the solid electrolyte according to Example 7, and it is clear that the surface of the solid electrolyte is modified with butyric acid and lithium butyrate.

[0077] Example 8 A positive electrode half-cell and a negative electrode half-cell according to Example 8 were produced in the same manner as in Example 1, except that 0.02 g of isobutyronitrile was used instead of 0.02 g of butyric acid when preparing the solid electrolyte, and hexane was used as the solvent.

[0078] Fig. 4 is a chart showing the IR spectrum of the solid electrolyte according to Example 8. As shown in Fig. 4, when compared with the IR spectrum of the solid electrolyte alone, a peak of isobutyronitrile is detected in the IR spectrum of the solid electrolyte according to Example 8, and it is clear that the surface of the solid electrolyte is modified with isobutyronitrile.

[0079] Example 9 A positive electrode half-cell and a negative electrode half-cell according to Example 9 were produced in the same manner as in Example 1, except that 0.05 g of tributyl phosphate was used instead of 0.02 g of butyric acid when producing the solid electrolyte, and hexane was used as the solvent.

[0080] Example 10 A positive electrode half-cell and a negative electrode half-cell according to Example 10 were produced in the same manner as in Example 1, except that 0.02 g of anisole was used instead of 0.02 g of butyric acid when producing the solid electrolyte, and hexane was used as the solvent.

[0081] Example 11 A positive electrode half-cell and a negative electrode half-cell according to Example 11 were produced in the same manner as in Example 1, except that 0.02 g of dibutyl ether was used instead of 0.02 g of butyric acid when producing the solid electrolyte, and hexane was used as the solvent.

[0082] <Comparative Example 1> A positive electrode half-cell and a negative electrode half-cell according to Comparative Example 1 were fabricated in the same manner as in Example 1, except that 0.02 g of butyric acid was not added when the solid electrolyte was prepared.

[0083] Battery performance evaluation test Using the positive electrode half-cells and negative electrode half-cells according to Examples 1 to 11 and Comparative Example 1, battery performance evaluation tests were conducted under the following conditions. Charge-discharge cycles were performed at 25°C and a charge-discharge rate of 0.1 c, and the discharge capacities (mAh) at the fifth cycle were taken as the positive electrode capacity and the negative electrode capacity, respectively. The positive electrode capacity and the negative electrode capacity per weight of the electrode active material were calculated. The results are shown in Table 1.

[0084] [Table 1]

[0085] As shown in Table 1, it was confirmed that the positive electrode half-cell and negative electrode half-cell according to the example had higher electrode capacity than the positive electrode half-cell and negative electrode half-cell according to the comparative example. [Explanation of symbols]

[0086] 10 solid state battery 11 Positive electrode layer 12 negative electrode layer 13 Solid electrolyte layer 14 Positive electrode current collector 15 Negative electrode current collector

Claims

1. An electrode for a solid battery comprising a solid electrolyte made of a sulfide and / or an oxide, an electrode active material, a binder, and a conductive additive, the electrode active material has a surface modified with a surface modifier; The solid-state battery electrode, wherein the surface modifier is at least one selected from the group consisting of lithium butyrate, lithium isobutyrate, and isobutyronitrile.

2. 2. The electrode for a solid state battery according to claim 1, wherein the binder is a binder having relatively low polarity or non-polarity compared to the solid electrolyte and the electrode active material before their surfaces are modified with the surface modifier.

3. 3. The electrode for a solid state battery according to claim 1, wherein the binder is at least one selected from the group consisting of polyethylene vinyl acetate (PEVA), polymethyl methacrylate (PMMA), styrene butadiene rubber (SBR), hydrogenated nitrile butadiene rubber (HNBR), nitrile butadiene rubber (NBR), and polyisobutene (PIB).

4. 4. The electrode for a solid state battery according to claim 1, wherein the solid electrolyte is a sulfide solid electrolyte having an argyrodite-type crystal structure.

5. The electrode for a solid battery according to claim 1 , wherein the electrode active material is a positive electrode active material, and the electrode for a solid battery is a positive electrode for a solid battery.

6. A solid-state battery comprising the electrode for a solid-state battery according to claim 1 .

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