Electrodes for all-solid-state batteries, method for manufacturing the same, and all-solid-state batteries

Abstract

Provided are an electrode with which an all-solid-state battery having a low internal resistance can be configured, a method for producing the electrode, and an all-solid-state battery having a low internal resistance.　This electrode for an all-solid-state battery is characterized by including a molded electrode-mix object comprising a solid electrolyte (B) and a composite obtained by press-molding a mix comprising an active material and a solid electrolyte (A), the solid electrolyte (B) being the same as or different from the solid electrolyte (A), the molded electrode-mix object having a porosity of 10% or less and an area larger than 1.8 cm2. This all-solid-state battery includes a power generation element comprising a positive electrode, a negative electrode, and a solid electrolyte layer, and is characterized in that the positive electrode and / or the negative electrode is the aforementioned electrode for an all-solid-state battery.

Description

[Technical Field]

[0001] This invention relates to an electrode capable of forming an all-solid-state battery with low internal resistance, a method for manufacturing the same, and an all-solid-state battery with low internal resistance. [Background technology]

[0002] In recent years, with the development of portable electronic devices such as mobile phones and notebook computers, and the practical application of electric vehicles, there has been a growing need for batteries that are small, lightweight, and yet possess high capacity and high energy density.

[0003] Currently, lithium batteries, particularly lithium-ion batteries, that can meet this requirement use lithium-containing composite oxides such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2) as the positive electrode active material, graphite as the negative electrode active material, and an organic electrolyte containing an organic solvent and a lithium salt as the non-aqueous electrolyte.

[0004] Furthermore, with the continued development of devices utilizing lithium-ion batteries, there is a growing demand for even longer lifespans, higher capacity, and higher energy density lithium-ion batteries, as well as for greater reliability of these long-life, high-capacity, and high-energy-density lithium-ion batteries.

[0005] However, because the organic electrolyte used in lithium-ion batteries contains organic solvents, which are flammable substances, there is a possibility that the organic electrolyte may overheat if an abnormal situation such as a short circuit occurs in the battery. Furthermore, with the recent trend towards higher energy density in lithium-ion batteries and an increase in the amount of organic solvents in the organic electrolyte, there is an even greater demand for the reliability of lithium-ion batteries.

[0006] In light of the above circumstances, all-solid-state lithium batteries that do not use organic solvents are also being considered. All-solid-state lithium batteries use a molded solid electrolyte that does not use organic solvents instead of conventional organic solvent-based electrolytes, eliminating the risk of abnormal heat generation from the solid electrolyte and offering high reliability. Therefore, there are high expectations for them, especially in product fields that require high-capacity secondary batteries.

[0007] Furthermore, solid-state batteries are expected to contribute to the development of society while simultaneously providing peace of mind and safety, as they possess not only high safety but also high reliability, high environmental resistance, and a long lifespan, making them maintenance-free batteries. By providing solid-state batteries to society, it is possible to contribute to achieving three of the 17 Sustainable Development Goals (SDGs) established by the United Nations: Goal 3 (Ensure healthy lives and promote well-being for all at all ages), Goal 7 (Ensure access to affordable, reliable, sustainable, and modern energy for all), Goal 11 (Make cities and human settlements inclusive, safe, resilient and sustainable), and Goal 12 (Ensure sustainable consumption and production patterns).

[0008] Incidentally, in all-solid-state batteries, electrodes are typically made of a molded body formed by pressure molding a powdered electrode mixture containing an active material (positive electrode active material or negative electrode active material) and a solid electrolyte. In order to increase the capacity of such all-solid-state batteries, it is conceivable to increase the surface area of ​​the electrodes and increase the density of the molded electrode mixture. However, in this case, it is necessary to pressure-molde the molded electrode mixture at a higher pressure than in conventional methods.

[0009] For example, the area in plan view is 1.8 cm². 2 For molded electrode mixtures up to a certain degree, it is relatively easy to obtain high-density ones by molding at a pressure of about 800 to 2000 MPa (Patent Document 1, etc.). However, to increase the area of ​​the molded electrode mixture layer, 1.8 cm 2Obtaining a density as close as possible to that of the following small-area materials requires the use of special equipment that enables higher pressure pressing, which presents challenges to productivity. Furthermore, even with such special equipment, there are limits to the area over which a high-density electrode mixture layer can be formed. Additionally, a decrease in the density of the molded electrode mixture leads to problems such as an increase in the internal resistance of the electrode and, consequently, the internal resistance of the all-solid-state battery using it.

[0010] Although not intended to increase the density of the electrode mixture molded body, Patent Document 2 proposes a method in which a sulfide-based inorganic solid electrolyte powder and an electrode active material powder are pressure-molded, then crushed to produce a granulated powder with an average particle size of 10 to 50 μm, and this granulated powder is pressure-molded again to obtain a molded electrode mixture. According to Patent Document 2, the particle shape of the sulfide-based inorganic solid electrolyte disappears and forms a sea-island structure, causing the sulfide-based inorganic solid electrolyte and the electrode active material to bond and improving the ion conduction path at the interface between the two materials. Therefore, it is thought that the density of the electrode mixture molded body may also be improved. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2021-163582 (paragraphs

[0078] ,

[0079] , etc.) [Patent Document 2] Japanese Patent Publication No. 2014-192061 (Claims, paragraph

[0010] , etc.) [Overview of the Initiative] [Problems that the invention aims to solve]

[0012] However, even if the molding pressure used to produce the granulated powder is increased in the method described in Patent Document 2 to produce a high-density granulated powder, the particle size of the granulated powder remains small, at 50 μm or less. Therefore, when the granulated powder is repressurized on its own to form a large-area molded body of the electrode mixture, the porosity of the formed molded body becomes high, making it difficult to increase the density. For these reasons, even with the method described in Patent Document 2, it is difficult to reduce the internal resistance of the molded body of the electrode mixture to below a certain level.

[0013] The present invention has been made in view of the above circumstances, and its object is to provide an electrode capable of constituting an all-solid-state battery with low internal resistance, a method for manufacturing the same, and an all-solid-state battery with low internal resistance. [Means for solving the problem]

[0014] The electrode for an all-solid-state battery of the present invention comprises a composite formed by pressure molding a mixture containing an active material and a solid electrolyte (A), and a molded body of the electrode mixture containing the same or different solid electrolyte (B) as the solid electrolyte (A), wherein the molded body of the electrode mixture has a porosity of 10% or less and a width of 1.8 cm. 2 It is characterized by having a larger area.

[0015] Furthermore, the present invention provides a method for manufacturing electrodes for all-solid-state batteries, comprising: (a) a step of pressurizing a mixture 1 containing an active material and a solid electrolyte (A) at a pressure of 800 MPa or higher to form a composite; (b) a step of mixing the composite with a solid electrolyte (B) that is the same as or different from the solid electrolyte (A) to prepare a mixture 2; and a step of applying a predetermined thickness of 1.8 cm. 2 The present invention is characterized by comprising the step (c) of forming a layered material of the mixture 2 having a larger surface area, and pressurizing it at a predetermined pressure of less than 800 MPa to form a molded body of the electrode mixture.

[0016] Furthermore, the all-solid-state battery of the present invention is characterized in that a power generation element comprising a positive electrode having a molded body of a positive electrode mixture, a solid electrolyte layer, and a negative electrode having a molded body of a negative electrode mixture is sealed inside an outer casing, and at least one of the positive electrode and the negative electrode is an electrode for the all-solid-state battery of the present invention. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide an electrode capable of constituting an all-solid-state battery with low internal resistance, a method for manufacturing the same, and an all-solid-state battery with low internal resistance. [Brief explanation of the drawing]

[0018] [Figure 1] This is a schematic cross-sectional view showing an example of the all-solid-state battery of the present invention. [Figure 2] This is a schematic cross-sectional view showing another example of the all-solid-state battery of the present invention. [Modes for carrying out the invention]

[0019] <Electrodes for all-solid-state batteries and methods for manufacturing the same> The electrode for an all-solid-state battery of the present invention has a molded body of an electrode mixture containing an active material and a solid electrolyte, and is used as the positive or negative electrode of an all-solid-state battery. Its forms include those composed solely of a molded body of the electrode mixture, and those in which a layer (electrode mixture layer) made of a molded body of the electrode mixture is formed on a current collector.

[0020] The molded body of the electrode mixture comprises a composite [a molded body (pressure-molded body) of the mixture] formed by pressure molding a mixture containing an active material and a solid electrolyte (A), and a solid electrolyte (B) that is present between the composite (for example, its granular material) and is the same as or different from the solid electrolyte (A), with a porosity of 10% or less and a width of 1.8 cm. 2 It has a larger area.

[0021] The lower limit of the porosity is not limited, and it is possible to achieve a porosity close to 0% by using a highly flexible material for the solid electrolyte (A) and / or solid electrolyte (B).

[0022] The present invention provides a method for manufacturing electrodes for all-solid-state batteries, comprising: (a) pressurizing a mixture 1 containing an active material and a solid electrolyte (A) at a pressure of 800 MPa or higher to form a composite; (b) mixing the composite with a solid electrolyte (B) that is the same as or different from the solid electrolyte (A) to prepare a mixture 2; and applying a predetermined thickness of 1.8 cm. 2 The method includes step (c) forming a layered material of the mixture 2 having a larger surface area, and pressurizing it at a predetermined pressure of less than 800 MPa to form a molded body of the electrode mixture. By this manufacturing method, electrodes for all-solid-state batteries of the present invention can be manufactured.

[0023] In step (a), the mixture 1, which contains the active material and solid electrolyte that make up the molded body of the electrode mixture, is pressurized at a pressure of 800 MPa or higher to form a composite. In this case, the size is smaller than the molded body of the electrode mixture to be finally produced, for example, 1.8 cm. 2 Since the mixture 1 is molded into a composite (molded body) by pressure molding over the following area, it is possible to mold the mixture 1 into a high-density molded body (for example, a molded body with a porosity of 8% or less) by applying a pressure of 800 MPa or more using a conventional pressure molding method with conventional equipment.

[0024] However, the composite of mixture 1, which has been molded into a body, is either used as is or crushed into granules and then pressurized to 1.8 cm 2 Even when attempting to form a molded electrode mixture with a larger surface area, the poor fluidity of the composite leaves some voids between the composites. Therefore, it is not possible to increase the density of the molded electrode mixture using conventional pressure molding methods with equipment that has an upper limit of force that can be applied of about 100-200 kN.

[0025] Therefore, in the method for manufacturing an electrode for an all-solid-state battery of the present invention, in step (b), the agent 1 formed into a composite through step (a) [or the granular material obtained by pulverizing the agent 1 formed into a composite through step (a) in the subsequent pulverizing step] is mixed with a solid electrolyte (B) that is the same as or different from the solid electrolyte (A) of the agent 1 to form an agent 2, and this is formed into a layered product having an area larger than 1.8 cm in a predetermined thickness in step (c), and then pressed at a predetermined pressure of less than 800 MPa to form a molded body of the electrode agent. In this case, due to the action of the solid electrolyte (B) used together with the agent 1 that has undergone step (a), the molded body of the electrode agent can be made to have a high density, and the ionic conductivity can be improved to reduce the internal resistance. For this reason, in the method for manufacturing an electrode for an all-solid-state battery of the present invention, a molded body of the electrode agent having an area larger than 1.8 cm in plan view can be formed with a high density (for example, the porosity of the molded body calculated from the true density and composition ratio of each material constituting the molded body of the electrode agent, and the mass and volume of the molded body is 10% or less) without using a special device. Therefore, according to the manufacturing method of the present invention, it is possible to manufacture an electrode for an all-solid-state battery of the present invention with a low internal resistance while increasing the area in plan view of the molded body of the electrode agent as described above. 2 After that, a layered product having an area larger than 1.8 cm was formed, and then pressed at a predetermined pressure of less than 800 MPa to form a molded body of the electrode agent. In this case, due to the action of the solid electrolyte (B) used together with the agent 1 that has undergone step (a), the molded body of the electrode agent can be made to have a high density, and the ionic conductivity can be improved to reduce the internal resistance. For this reason, in the method for manufacturing an electrode for an all-solid-state battery of the present invention, a molded body of the electrode agent having an area larger than 1.8 cm in plan view can be formed with a high density (for example, the porosity of the molded body calculated from the true density and composition ratio of each material constituting the molded body of the electrode agent, and the mass and volume of the molded body is 10% or less) without using a special device. 2 Therefore, according to the manufacturing method of the present invention, it is possible to manufacture an electrode for an all-solid-state battery of the present invention with a low internal resistance while increasing the area in plan view of the molded body of the electrode agent as described above.

[0026] First, the electrode for an all-solid-state battery will be described below, and then each step of the method for manufacturing the electrode for an all-solid-state battery will be described.

[0027] Examples of the active material used in the electrode for an all-solid-state battery include the following.

[0028] When the electrode for the all-solid-state battery is a positive electrode and is used in an all-solid-state primary battery, the active material (positive electrode active material) can be the same as the positive electrode active material used in a conventionally known non-aqueous electrolyte primary battery. Specifically, for example, manganese dioxide, lithium-containing manganese oxide [e.g., LiMn3O6 and composite oxides having the same crystal structure as manganese dioxide (such as β-type, γ-type, or a structure in which β-type and γ-type are mixed), and the content of Li is 3.5 mass% or less, preferably 2 mass% or less, more preferably 1.5 mass% or less, and particularly preferably 1 mass% or less], Li a Ti 5 / 3 Lithium-containing composite oxides such as O4 (4 / 3 ≦ a < 7 / 3); vanadium oxides; niobium oxides; titanium oxides; sulfides such as iron disulfide; graphite fluoride; silver sulfides such as Ag2S; nickel oxides such as NiO2: and the like can be mentioned.

[0029] When the electrode for the all-solid-state battery is a positive electrode and is used in an all-solid-state secondary battery, the active material (positive electrode active material) can be the same as the positive electrode active material used in a conventionally known non-aqueous electrolyte secondary battery, that is, the same as an active material capable of occluding and releasing Li (lithium) ions. Specifically, Li 1-x M r Mn 2-r O4 (where M is at least one element selected from the group consisting of Li, Na, K, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Zr, Fe, Co, Ni, Cu, Zn, Al, Sn, Sb, In, Nb, Ta, Mo, W, Y, Ru, and Rh, 0 ≦ x ≦ 1, 0 ≦ r ≦ 1), spinel-type lithium manganese composite oxide represented by Li r Mn (1-s-t) Ni s ​​​​​​​​​​​r Lithium cobalt composite oxide represented as O2 (where M is at least one element selected from the group consisting of Al, Mg, Ti, V, Cr, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, Ba, Mn, Bi, Ca, F, P, Sr, W, Si, Ta, K, S, Er, and Na, with 0 ≤ x ≤ 1 and 0 ≤ r ≤ 0.5), Li 1-x Ni 1-r M r Lithium nickel composite oxide represented by O2 (where M is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0 ≤ x ≤ 1, 0 ≤ r ≤ 0.5), Li 1+s-x M 1-r N r PO4F s (wherein M is at least one element selected from the group consisting of Fe, Mn, and Co, and N is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, V, and Ba, and 0≦x≦1, 0≦r≦0.5, 0≦s≦1) Li is an olivine-type composite oxide. 2-x M 1-r N r Examples include pyrophosphate compounds represented by P2O7 (where M is at least one element selected from the group consisting of Fe, Mn, and Co, and N is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, V, and Ba, with 0≦x≦2 and 0≦r≦0.5). Only one of these may be used, or two or more may be used in combination.

[0030] When electrodes for all-solid-state batteries are used as the positive electrode of an all-solid-state secondary battery, the average particle size of the positive electrode active material contained therein is preferably 1 μm or more, more preferably 2 μm or more, preferably 10 μm or less, and more preferably 8 μm or less. The positive electrode active material may be primary particles or secondary particles formed by aggregation of primary particles. Using a positive electrode active material with an average particle size within the above range allows for a larger interface with the solid electrolyte contained in the positive electrode, thereby improving the output characteristics of the battery.

[0031] In this specification, the average particle diameter of various particles (such as positive electrode active material and solid electrolyte) is the 50% diameter value in the volume-based integrated fraction when determining the integrated volume from the smallest particles using a particle size distribution analyzer (such as the Microtrac particle size distribution analyzer "HRA9320" manufactured by Nikkiso Co., Ltd.). 50 ) means.

[0032] When the electrode for an all-solid-state battery is the negative electrode and it is used in an all-solid-state primary battery, examples of the active material (negative electrode active material) include metallic lithium and lithium alloys (lithium-aluminum alloy, lithium-indium alloy, etc.).

[0033] When the electrode for an all-solid-state battery is the negative electrode and it is used in an all-solid-state secondary battery, there are no particular restrictions on the active material (negative electrode active material) as long as it is an active material that can intercept and release Li ions and is conventionally used in lithium secondary batteries. For example, as the negative electrode active material, one or more carbon-based materials capable of intercepting and releasing lithium, such as graphite, pyrolytic carbons, cokes, glassy carbons, calcined organic polymer compounds, mesocarbon microbeads (MCMB), and carbon fibers, can be used. Oxides may also be used as the negative electrode active material, for example, Li x Nb y TiM 6 a O {5y+4 / 2}+δ (However, M 6This is at least one selected from the group consisting of V, Cr, Mo, Ta, Zr, Mn, Fe, Mg, B, Al, Cu, and Si, and is a composite oxide having a monoclinic crystal structure represented by 0≦x≦49, 0.5≦y<24, -5≦δ≦5, 0≦a≦0.3), titanium dioxide having an anatase structure, lithium titanate having a ramsdelite structure represented by Li2Ti3O7, Li4Ti5O 12 Examples include spinel-type lithium titanium composite oxides represented by [formula], and one or more of these can be used. Elements such as Si, Sn, Ge, Bi, Sb, and In, as well as their compounds and alloys; nitrides or lithium-containing oxides containing transition metals such as Co, Ni, Mn, Fe, Cr, Ti, and W, which can be charged and discharged at low voltages close to lithium metal; or metallic lithium or lithium alloys (such as lithium-aluminum alloys and lithium-indium alloys) can also be used as negative electrode active materials.

[0034] The active material may have a reaction-suppressing layer on its surface to inhibit the reaction between the active material and the solid electrolyte. In particular, when the electrode for an all-solid-state battery is the positive electrode, it is preferable that a reaction-suppressing layer is provided on the surface of the active material (positive electrode active material).

[0035] The reaction suppression layer may be composed of a material that has ionic conductivity and can suppress the reaction between the active material and the solid electrolyte. Examples of materials that can constitute the reaction suppression layer include oxides containing Li and at least one element selected from the group consisting of Nb, P, B, Si, Ge, Ti, Zr, Ta, and W, more specifically, Nb-containing oxides such as LiNbO3, Li3PO4, Li3BO3, Li4SiO4, Li4GeO4, LiTiO3, LiZrO3, Li2WO4, etc. The reaction suppression layer may contain only one of these oxides, or it may contain two or more, and furthermore, multiple of these oxides may form a composite compound. Among these oxides, it is preferable to use an Nb-containing oxide, and more preferable to use LiNbO3.

[0036] The reaction-inhibiting layer is preferably present on the surface in an amount of 0.1 to 1.0 parts by mass per 100 parts by mass of the active material (matrix particles forming the reaction-inhibiting layer). Within this range, the reaction between the active material and the solid electrolyte can be effectively suppressed.

[0037] Methods for forming a reaction-inhibiting layer on the surface of an active material include the sol-gel method, mechanofusion method, CVD method, PVD method, and ALD method.

[0038] When electrodes for all-solid-state batteries are used as the positive electrode of an all-solid-state battery, the content of the active material in the molded electrode mixture is preferably 60 to 98% by mass, from the viewpoint of increasing the energy density of the all-solid-state battery.

[0039] When an electrode for an all-solid-state battery is used as the negative electrode of an all-solid-state battery, the content of the active material in the molded electrode mixture is preferably 40 to 99% by mass, from the viewpoint of increasing the energy density of the all-solid-state battery.

[0040] The solid electrolyte in electrodes for all-solid-state batteries is not particularly limited as long as it has lithium-ion conductivity, and for example, sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, oxide-based solid electrolytes, etc., can be used.

[0041] Examples of sulfide-based solid electrolytes include particles such as Li2S-P2S5, Li2S-SiS2, Li2S-P2S5-GeS2, and Li2S-B2S3 glass, as well as thio-LISICON type electrolytes, which have recently attracted attention for their high Li ion conductivity. 10 GeP2S 12 Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 such as, 12-12a-b+c+6d-e M 1 3+a-b-c-d M 2 b M 3 c M 4d M 5 12-e X e (However, M 1 is Si, Ge or Sn, M 2 is P or V, M 3 is Al, Ga, Y or Sb, M 4 is Zn, Ca, or Ba, M 5 is either S or S and O, X is F, Cl, Br or I, 0 ≦ a < 3, 0 ≦ b + c + d ≦ 3, 0 ≦ e ≦ 3), and those having an al-dilothite-type crystal structure can also be used.

[0042] Examples of the hydride-based solid electrolyte include LiBH4, a solid solution of LiBH4 and the following alkali metal compound (for example, those having a molar ratio of LiBH4 to the alkali metal compound of 1:1 to 20:1). Examples of the alkali metal compound in the solid solution include at least one selected from the group consisting of lithium halides (LiI, LiBr, LiF, LiCl, etc.), rubidium halides (RbI, RbBr, RbF, RbCl, etc.), cesium halides (CsI, CsBr, CsF, CsCl, etc.), lithium amide, rubidium amide, and cesium amide.

[0043] Examples of the halide-based solid electrolyte include monoclinic LiAlCl4, defective spinel-type or layered-structured LiInBr4, monoclinic Li 6-3m Y m X6 (where 0 < m < 2 and X = Cl or Br), etc. In addition, for example, known ones described in International Publication No. 2020 / 070958 and International Publication No. 2020 / 070955 can also be used.

[0044] Examples of the oxide-based solid electrolyte include garnet-type Li7La3Zr2O 12 , NASICON-type Li 1+O Al 1+O Ti 2-O (PO4)3, Li 1+p Al 1+p Ge 2-p (PO4)3, perovskite-type Li3q La 2 / 3-q Examples include TiO3.

[0045] Among these solid electrolytes, sulfide-based solid electrolytes are preferred due to their high lithium ion conductivity, sulfide-based solid electrolytes containing Li and P are more preferred, and sulfide-based solid electrolytes having an argyrodite crystal structure are even more preferred due to their higher lithium ion conductivity and chemical stability.

[0046] Furthermore, sulfide-based solid electrolytes are also preferred because they contribute to improving the moldability of the electrode mixture molded body. The electrode for an all-solid-state battery contains a solid electrolyte (A) that forms a complex with the active material, and a solid electrolyte (B) that exists between the complexes, separate from the solid electrolyte (A). The solid electrolyte (B), which contributes to the moldability of the electrode mixture molded body, is preferably a sulfide-based solid electrolyte with excellent moldability, and it is even more preferable that both solid electrolyte (A) and solid electrolyte (B) are sulfide-based solid electrolytes.

[0047] As sulfide-based solid electrolytes having an argyrodite-type crystal structure, those represented by the following general composition formulas (1), (2), or (3), such as Li6PS5Cl, are particularly preferred.

[0048] Li 7-k PS 6-k X k (1)

[0049] In the above general composition formula (1), X represents one or more halogen elements, and 0.2 <k<2.0または0.2<k<1.8である。

[0050] Li 7-x+y PS 6-x Cl x+y (2)

[0051] In the general composition formula (2) above, 0.05 ≤ y ≤ 0.9 and -3.0x + 1.8 ≤ y ≤ -3.0x + 5.7.

[0052] Li 7-a PS 6-a Cl b Br c (3)

[0053] In the above general composition formula (3), a = b + c, 0 <a≦1.8、0.1≦b / c≦10.0である。

[0054] The average particle size of the solid electrolyte is preferably 0.1 μm or larger, and more preferably 0.2 μm or larger, from the viewpoint of reducing grain boundary resistance. On the other hand, from the viewpoint of forming a sufficient contact interface between the active material and the solid electrolyte, it is preferably 10 μm or smaller, and more preferably 5 μm or smaller.

[0055] When an electrode for an all-solid-state battery is used as the positive electrode of an all-solid-state battery, the content of the solid electrolyte in the molded body of the electrode mixture is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and particularly preferably 50 parts by mass or more, when the content of the positive electrode active material is 100 parts by mass. This is from the viewpoint of further improving the ionic conductivity within the positive electrode and further improving the output characteristics of the all-solid-state battery. However, if the amount of solid electrolyte in the molded body of the electrode mixture is too high, the amount of other components will decrease, and the effects of those components may be reduced. Therefore, the content of the solid electrolyte in the molded body of the electrode mixture is preferably 90 parts by mass or less, more preferably 80 parts by mass or less, and particularly preferably 70 parts by mass or less, when the content of the positive electrode active material is 100 parts by mass or more.

[0056] When an electrode for an all-solid-state battery is used as the negative electrode of an all-solid-state battery, the solid electrolyte content in the molded body of the electrode mixture is preferably 30 parts by mass or more, and more preferably 35 parts by mass or more, when the negative electrode active material content is 100 parts by mass, from the viewpoint of further improving the ionic conductivity within the negative electrode and further improving the output characteristics of the all-solid-state battery. However, if the amount of solid electrolyte in the molded body of the electrode mixture is too high, the amount of other components will decrease, and the effects of those components may be reduced. Therefore, the solid electrolyte content in the molded body of the electrode mixture is preferably 130 parts by mass or less, and more preferably 110 parts by mass or less, when the negative electrode active material content is 100 parts by mass.

[0057] The molded electrode mixture for all-solid-state batteries may contain conductive additives. Examples of such conductive additives include highly crystalline carbon materials such as graphite (natural graphite, artificial graphite), graphene (single-layer graphene, multi-layer graphene), and carbon nanotubes; and low-crystalline carbon materials such as carbon black. One or more of these can be used.

[0058] When the electrode for all-solid-state batteries is used as the positive electrode of an all-solid-state battery, the content of the conductive additive in the molded electrode mixture is preferably 1 to 10% by mass. Furthermore, when the electrode for all-solid-state batteries is used as the negative electrode of an all-solid-state battery, the content of the conductive additive in the molded electrode mixture is preferably 5 to 15% by mass.

[0059] A binder can be included in the molded body of the electrode mixture for all-solid-state batteries. Specific examples include fluororesins such as polyvinylidene fluoride (PVDF). However, if good moldability can be ensured in forming the molded body of the electrode mixture without using a binder, such as when a sulfide-based solid electrolyte is included in the molded body of the electrode mixture, then the binder does not need to be included in the molded body of the electrode mixture.

[0060] In the molded article of the electrode mixture, if a binder is required, its content is preferably 15% by mass or less, and more preferably 0.5% by mass or more. On the other hand, in the molded article of the electrode mixture, if moldability can be obtained without the need for a binder, its content is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and even more preferably 0% by mass (i.e., no binder is included).

[0061] The thickness of the molded electrode mixture is preferably 500 to 3000 μm.

[0062] There are no particular restrictions on the shape of the molded electrode mixture; it can be in the form of circular or polygonal pellets (flat plates) when viewed from above.

[0063] Current collectors can be used for electrodes in solid-state batteries. When the electrode is used as the positive electrode of a solid-state battery, examples of current collectors include metal foils such as aluminum or stainless steel, perforated metal, mesh, expanded metal, foamed metal, and carbon sheets. When the electrode is used as the negative electrode of a solid-state battery, examples of current collectors include copper or nickel foils, perforated metal, mesh, expanded metal, foamed metal, and carbon sheets. The thickness of the current collector is preferably 30 to 100 μm.

[0064] In step (a) of the method for manufacturing electrodes for all-solid-state batteries, a mixture 1 containing an active material and a solid electrolyte (A) is pressurized to form a composite.

[0065] There are no particular restrictions on the preparation method of compound 1; the active material and solid electrolyte (A), etc., can be mixed using known methods.

[0066] When a conductive aid or a binder is contained in the formed body of the electrode mixture, they can be added during the preparation of the mixture 1. Further, as described later, when the mixture 1 formed into a composite is pulverized into granular materials with adjusted sizes after the step (a) and then the mixture 2 is prepared in the step (b), the conductive aid or the binder may be added during the preparation of the mixture 2.

[0067] There is no particular limitation on the means of pressure molding when the mixture 1 is made into a composite, and a known device capable of pressure molding the powder may be used. However, the pressure applied is 800 MPa or more, preferably 1000 MPa or more, more preferably 1200 MPa or more. Thereby, the density of the composite of the mixture 1 is increased, and the combined action of this and the action of the solid electrolyte used in the subsequent process makes it possible to increase the density of the finally obtained formed body of the electrode mixture and reduce the internal resistance. The upper limit value of the pressure applied when the mixture 1 is made into a composite is usually about 2000 MPa.

[0068] There is no particular limitation on the shape of the composite of the mixture 1 obtained by pressure, and it can be made into a pellet shape (flat plate shape) such as circular or polygonal, spherical, etc. in plan view. Further, as the size of the composite of the mixture 1, the area in plan view is, for example, 1.8 cm 2 It is preferable to be the following, 1.5 cm 2 It is more preferable to be the following, 1 cm 2 It is particularly preferable to be the following. On the other hand, in order to improve productivity, the area of the composite in plan view is preferably 0.1 cm 2 or more, more preferably 0.2 cm 2 or more, and particularly preferably 0.5 cm 2 or more.

[0069] Further, the thickness of the composite is not particularly limited when it is pulverized and the size is adjusted for use. When it is used for the formation of the mixture 2 in the shape at the time of pressure molding, it may be adjusted in consideration of the thickness of the formed body of the electrode mixture to be produced.

[0070] In step (b) of the method for manufacturing electrodes for all-solid-state batteries, the composite of mixture 1 obtained in step (a) is mixed with solid electrolyte (B) to prepare mixture 2.

[0071] In preparing mixture 2, mixture 1 may be used as is, as the composite obtained in step (a), or a step of crushing the composite of mixture 1 may be added prior to step (b), and the mixture may be used in the form of granules obtained in this step. By using mixture 2 prepared after crushing the composite of mixture 1 into granules, the uniformity of the distribution of each component in the molded body of the resulting electrode mixture is further improved, resulting in better characteristics for the electrode for the all-solid-state battery and the all-solid-state battery obtained using this electrode.

[0072] When the composite of mixture 1 is crushed to form granules, in order to facilitate the molding of the electrode mixture at a higher density, the size of the granules is preferably, for example, larger than 50 μm, and more preferably larger than 100 μm. On the other hand, in order to set the thickness of the electrode mixture molded body within a suitable range, it is appropriate for the average particle size of the granules to be 1 mm or less. The average particle size of the granules referred to here is determined by the same method as the method for measuring the average particle size of the positive electrode active material, etc. 50 That is the case.

[0073] When preparing compound 2, it is preferable to use 20 to 60 parts by mass of solid electrolyte (B) per 100 parts by mass of the composite obtained in step (a). Therefore, the amount of solid electrolyte (A) used in the preparation of compound 1 in step (a) should be determined considering the amount used in step (b).

[0074] Furthermore, as described above, when preparing mixture 2 using granular material obtained by crushing the composite obtained in step (a), a conductive additive or a binder may be added to mixture 2.

[0075] There are no particular restrictions on the method of preparing combination 2; the various components to be included in combination 2 can be mixed using known methods.

[0076] In step (c) of the method for manufacturing electrodes for all-solid-state batteries, the mixture 2 is spread to a predetermined thickness of 1.8 cm. 2 After forming a layered material with a larger surface area, it is pressed to form a molded body of the electrode mixture.

[0077] There are no particular restrictions on the means of pressure molding; any known apparatus capable of pressure molding strip-shaped films, powders, or pellets may be used. However, the pressure applied should be adjusted according to the area of ​​the layered material of the mixture 2 so that the total pressure is within the range that can be applied by a general molding apparatus (for example, up to about 200 kN). For example, if the area of ​​the layered material of the mixture 2 is 5 cm² 2 In this case, the maximum pressure can be set to approximately 400 MPa. This makes it easy to increase the density of the molded electrode mixture, thereby reducing the internal resistance of electrodes for all-solid-state batteries.

[0078] Furthermore, in order to increase the density of the molded body of the electrode mixture, the pressure applied to the layered material is preferably 200 MPa or higher, and more preferably 300 MPa or higher.

[0079] The molded electrode mixture can be used as an electrode for an all-solid-state battery as is. However, if it is to be used as an electrode for an all-solid-state battery that also includes a current collector, it can be obtained, for example, by pressurizing the mixture 2 on the current collector in step (c) to form a molded electrode mixture.

[0080] Furthermore, by preparing a solid electrolyte layer in advance and forming a molded electrode mixture on this solid electrolyte layer by step (c), the solid electrolyte layer and the electrodes for the all-solid-state battery can be joined. Moreover, by forming a molded positive electrode mixture (or a molded negative electrode mixture) on one side of the solid electrolyte layer by step (c), and further forming a molded negative electrode mixture (or a molded positive electrode mixture) on the other side of the solid electrolyte layer by step (c), a power generation element can be obtained in which electrodes for the all-solid-state battery are formed on both sides of the solid electrolyte layer.

[0081] In the molded electrode mixture for an all-solid-state battery obtained by the manufacturing method of the present invention, the area in plan view is 1.8 cm².2 If it is a larger value, there is no particular limitation. When using a general hydraulic press or a mold, it can be formed with an area similar to that of the conventionally adopted electrodes (for example, in the case of a coin-shaped battery, ~3 cm 2 or so). However, by pressure molding using a roll press or the like, it is also possible to make it larger than 10 cm 2 or more, and it can also correspond to a battery that requires a wider electrode area. Even in such a case, it is possible to obtain an electrode for an all-solid-state battery that has a small internal resistance and good characteristics.

[0082] <All-solid-state battery> In the all-solid-state battery of the present invention, a power generation element in which a positive electrode having a molded body of a positive electrode mixture, a solid electrolyte layer, and a negative electrode having a molded body of a negative electrode mixture are laminated is enclosed in an exterior body, and at least one of the positive electrode and the negative electrode is an electrode for an all-solid-state battery of the present invention.

[0083] That is, in the all-solid-state battery of the present invention, since at least one of the positive electrode and the negative electrode has an electrode for an all-solid-state battery with a low internal resistance, the internal resistance is reduced.

[0084] In the all-solid-state battery of the present invention, it is sufficient that only one of the positive electrode and the negative electrode is an electrode for an all-solid-state battery of the present invention, but it is preferable that both the positive electrode and the negative electrode are electrodes for an all-solid-state battery of the present invention.

[0085] In an all-solid-state battery, when only the positive electrode is an electrode for an all-solid-state battery of the present invention, as the negative electrode, without going through steps (a) and (b), a negative electrode mixture in which constituent materials such as a negative electrode active material and a solid electrolyte are mixed, and a negative electrode having a molded body of the negative electrode mixture obtained by molding in the same manner as in step (c); a negative electrode composed only of various alloys (such as lithium alloys such as lithium-aluminum alloy and lithium-indium alloy) or a foil of metallic lithium that function as a negative electrode active material, or a negative electrode in which the foil is laminated as an active material layer on a current collector; etc. can be used.

[0086] In an all-solid-state battery, when only the negative electrode is the electrode for the all-solid-state battery of the present invention, the positive electrode can be the positive electrode having a molded body of a positive electrode mixture obtained by mixing constituent materials such as a positive electrode active material and a solid electrolyte, and molding it using the same method as in step (c), without going through steps (a) and (b).

[0087] Specific examples of solid electrolytes constituting the solid electrolyte layer in a power generation element for an all-solid-state battery include the same solid electrolytes as those previously exemplified for use in electrodes for all-solid-state batteries. Among the solid electrolytes exemplified above, sulfide-based solid electrolytes are preferred because they have high lithium-ion conductivity and the ability to improve moldability. Sulfide-based solid electrolytes having an argyrodite-type crystal structure are preferred, and those represented by the general composition formula (1), general composition formula (2), or general composition formula (3) are even more preferred.

[0088] The solid electrolyte layer may have a porous material, such as a resin nonwoven fabric, as a support.

[0089] The thickness of the solid electrolyte layer is preferably 10 to 200 μm.

[0090] All-solid-state batteries are manufactured by forming a power generation element by manufacturing at least one of the positive electrode and negative electrode using the method for manufacturing electrodes for all-solid-state batteries of the present invention, and then enclosing this element in an outer casing.

[0091] Figure 1 shows a schematic longitudinal cross-sectional view of an example of the all-solid-state battery of the present invention. The all-solid-state battery 10 shown in Figure 1 has a power generation element 20 having a positive electrode 21, a negative electrode 22, and a solid electrolyte layer 23 interposed between them, and this power generation element 20 is enclosed within an outer casing formed by an outer container 60 and a lid 70.

[0092] External terminals 80 and 90 are provided on the lower surface of the outer casing 60 in the figure for electrically connecting to the equipment to which the all-solid-state battery 10 is applied. External terminal 80 is electrically connected to the positive electrode 21 of the power generation element 20 via a conductive path 81. Furthermore, external terminal 90 is electrically connected to the negative electrode 22 of the power generation element 20 via a lead 40 and a conductive path 91.

[0093] The positive electrode 21 constituting the power generation element 20 has a positive electrode mixture layer (molded body of positive electrode mixture) 211 and a current collector 212. The negative electrode 22 constituting the power generation element 20 has a negative electrode mixture layer (molded body of negative electrode mixture) 221 and a current collector 222.

[0094] Furthermore, a conductive sheet (such as a metal foil or a foamed porous metal) 30 is placed on the surface of the current collector 212 of the positive electrode 21 (the surface opposite to the positive electrode mixture layer 211), and the positive electrode 21 makes electrical contact with the conductive sheet 30 when it comes into contact with the current collector 212, and this conductive sheet 30 is electrically connected to the conductive path 81.

[0095] Furthermore, in the all-solid-state battery 10 shown in Figure 1, a spacer 50 is placed between the lead 40 and the cover 70, which has the effect of pressing the power generation element 20 toward the conductive sheet 30. Due to the action of this spacer 50, the electrical connection between the lead 40 and the negative electrode 22 and the conductive path 91, the electrical connection between the positive electrode 21 and the conductive sheet 30, and the electrical connection between the conductive sheet 30 and the conductive path 81 are improved.

[0096] Figure 2 also shows a schematic longitudinal cross-sectional view of another example of the all-solid-state battery of the present invention. The all-solid-state battery 11 shown in Figure 2 has a power generation element 20 enclosed within an outer casing formed by an outer casing 100, a sealing casing 110, and a resin gasket 120 interposed between them, with a positive electrode 21, a solid electrolyte layer 23, and a negative electrode 22 stacked on top of each other.

[0097] The sealing can 110 is fitted into the opening of the outer can 100 via a gasket 120. The opening end of the outer can 100 is tightened inward, causing the gasket 120 to contact the sealing can 110, thereby sealing the opening of the outer can 100 and creating a sealed structure inside the battery.

[0098] A current collector 130 is interposed between the positive electrode 21 and the outer casing 100, and the outer casing 100 also serves as the positive electrode terminal by electrically connecting to the positive electrode 21 via the current collector 130 on its inner surface. Similarly, a current collector 131 is interposed between the negative electrode 22 and the sealing casing 110, and the sealing casing 110 also serves as the negative electrode terminal by electrically connecting to the negative electrode 22 via the current collector 131 on its inner surface. Depending on the battery's application, the outer casing can also serve as the negative electrode terminal and the sealing casing can also serve as the positive electrode terminal.

[0099] As shown in Figure 2, all-solid-state batteries can also use a current collector for the positive electrode that is separate from the positive electrode, and a current collector for the negative electrode that is separate from the negative electrode. Furthermore, the positive and negative electrodes may be in direct contact with the inner surface of the outer casing or the inner surface of the sealing casing, without the need for a current collector.

[0100] A power generation element can be manufactured, for example, by bonding a positive electrode, a solid electrolyte layer, and a negative electrode. In this case, for example, a solid electrolyte layer can be formed by first pressure molding a solid electrolyte, an electrode for the all-solid-state battery of the present invention (positive or negative electrode) can be provided on one side thereof, and then an electrode for the all-solid-state battery of the present invention (negative or positive electrode) can be provided on the other side of the solid electrolyte layer, or an electrode other than the electrode for the all-solid-state battery of the present invention (negative or positive electrode) can be bonded to it. When providing the electrode for the all-solid-state battery of the present invention on the solid electrolyte layer, a method such as bonding a separately manufactured electrode for the all-solid-state battery to the solid electrolyte layer can be employed, but as described above, the electrode for the all-solid-state battery can also be manufactured directly on the solid electrolyte layer.

[0101] The resulting power generation element is then sealed inside an outer casing to obtain an all-solid-state battery. As the outer casing for the all-solid-state battery, the following can be used: a battery container having an outer casing and a lid as shown in Figure 1; a flat-shaped (coin-shaped, button-shaped, etc.) battery container having an outer can and a sealing can as shown in Figure 2; a sheet-shaped battery container made of resin film or resin-metal laminate film; and so on.

[0102] In the case of a battery container having an outer casing and a lid as shown in Figure 1, the outer casing can be made of ceramics or resin. The lid can be made of ceramics, resin, or metal (such as iron-nickel alloys or iron-nickel-cobalt alloys). Furthermore, in the outer casing, the external terminals and the conductive paths connecting the electrodes of the electrode stack to the external terminals can be made of metals such as manganese, cobalt, nickel, copper, molybdenum, silver, palladium, tungsten, platinum, gold, or alloys containing these metals.

[0103] The outer container and the lid can be sealed by bonding them together with adhesive. Alternatively, if a metal lid is used, the side wall of the recess in the outer container that faces the lid can be made of metal (such as an iron-nickel alloy or an iron-nickel-cobalt alloy), and then welded to the lid to seal it.

[0104] In the case of a battery container having an outer can and a sealing can as shown in Figure 2, stainless steel or similar materials can be used for the outer can and the sealing can. Furthermore, a resin adhesive or a method of crimping with a gasket interposed can be used to seal the outer can and the sealing can. For the gasket material, polypropylene, nylon, etc., can be used. If heat resistance is required due to the battery's application, heat-resistant resins with melting points exceeding 240°C, such as fluororesins like tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyphenylene ether (PPE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), polyphenylene sulfide (PPS), and polyetheretherketone (PEEK), can also be used. Additionally, if the battery is applied to an application requiring heat resistance, a glass hermetic seal can be used for sealing. [Examples]

[0105] The present invention will be described in detail below based on examples. However, the following examples are not intended to limit the present invention.

[0106] (Example 1) <Fabrication of the positive electrode> LiCo with an average particle size of 5 μm and a LiNbO3 coating layer formed on its surface. 0.98 Al 0.01 Mg 0.01 O2 (positive electrode active material): 83 parts by mass, and a sulfide-based solid electrolyte (Li) with an average particle size of 0.7 μm. 5.8 PS 4.4 Cl 1.2 ): 14 parts by mass, average particle diameter: 8 μm, thickness: 10-20 nm, BET specific surface area: 24 m² 2 Mixture 1 was obtained by mixing 3 parts by mass of graphene (conductive additive) at a concentration of / g.

[0107] Next, the mixture 1 is placed in a powder molding die and pressure molding is performed using a press machine at a surface pressure of 1400 MPa (total pressure is 110 kN, the upper limit of the press machine used), resulting in a composite with a circular shape in plan view (diameter: 1 cm, area: 0.79 cm²). 2A sample with a void ratio of 4% was prepared.

[0108] Furthermore, the composite was crushed to obtain granular material with an average particle size of approximately 300 μm. Then, 65 parts by mass of the granular material, 32 parts by mass of the same sulfide-based solid electrolyte, and 3 parts by mass of the same graphene were mixed to obtain mixture 2.

[0109] This mixture 2 is placed in a powder molding die, and pressure molding is performed using the same press machine as above at a surface pressure of 350 MPa (total pressure is 110 kN, the upper limit of the press machine used), resulting in a molded body of positive electrode mixture with a circular shape in plan view (diameter: 2 cm, area: 3.14 cm²). 2 A positive electrode was fabricated with a thickness of 0.96 mm and a porosity of 7%. The ratio of positive electrode active material, solid electrolyte, and conductive additive contained in the entire positive electrode mixture was 54:41:5 (by mass).

[0110] <Battery assembly> Lithium titanate (Li4Ti5O) with an average particle size of 2 μm 12 A negative electrode mixture was prepared by mixing the negative electrode active material, the same sulfide-based solid electrolyte used in the positive electrode, and the same graphene (conductive additive) used in the positive electrode, in a mass ratio of 50:41:9.

[0111] A sulfide-based solid electrolyte, the same as that used for the positive electrode, was placed on top of the molded body that would become the positive electrode in a powder molding die, and pressure molding was performed using a press machine at a surface pressure of 70 MPa to form a preliminary molded layer of the solid electrolyte. Furthermore, the negative electrode mixture was placed on the upper surface of the preliminary molded layer of the solid electrolyte and pressure molding was performed at a surface pressure of 50 MPa to form another preliminary molded layer of the negative electrode on top of the preliminary molded layer of the solid electrolyte. Then, the entire assembly was pressure molded at a surface pressure of 350 MPa (total pressure was 110 kN, the upper limit of the press machine used), thereby fabricating a power generation element in which the positive electrode, a solid electrolyte layer with a thickness of 0.1 mm, and a negative electrode consisting of a molded body with a thickness of 1.4 mm were laminated together.

[0112] Flexible graphite sheet "PERMA-FOIL" (product name) manufactured by Toyo Tanso Co., Ltd. (thickness: 0.1 mm, apparent density: 1.1 g / cm³)3 Two pieces of graphite sheet were prepared, each punched to the same size as the power generation element. One of these pieces was placed on the inner bottom surface of a stainless steel sealed can fitted with a polyphenylene sulfide annular gasket. The power generation element was then placed on top of the graphite sheet, with the negative electrode facing the graphite sheet. The remaining graphite sheet was then placed on the positive electrode of the molded body. After covering it with the stainless steel outer can, the open end of the outer can was crimped inward to seal it, thereby creating an all-solid-state secondary battery (coin-type all-solid-state secondary battery) with the structure shown in Figure 2.

[0113] (Example 2) Mixture 2 was prepared in the same manner as in Example 1, except that the composite of mixture 1 was pulverized to obtain granules with an average particle size of approximately 30 μm. Furthermore, a molded body of the positive electrode mixture (diameter: 2 cm, area: 3.14 cm²) was prepared using mixture 2. 2 A coin-type all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that a positive electrode consisting of a thickness of 0.98 mm and a porosity of 9% was prepared.

[0114] Comparative Example 1 A positive electrode mixture was prepared by mixing the same positive electrode active material, solid electrolyte, and conductive additive used in Example 1 in a ratio of 54:41:5 (mass ratio). Next, the positive electrode mixture was placed in a powder molding die and pressure-molded using a press machine at a surface pressure of 350 MPa (total pressure was 110 kN, the upper limit of the press machine used) to form a molded body of the positive electrode mixture with a circular shape in plan view (diameter: 2 cm, area: 3.14 cm²). 2 A positive electrode consisting of a thickness of 0.96 mm and a porosity of 17% was fabricated.

[0115] Then, a coin-type all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that a power generation element was fabricated using the aforementioned positive electrode.

[0116] Comparative Example 2 Compound 1 was prepared by mixing the same positive electrode active material, solid electrolyte, and conductive additive used in Example 1 in a ratio of 54:41:5 (mass ratio).

[0117] Next, the mixture 1 was placed in a powder molding die, and pressure molding was performed using a press machine at a surface pressure of 1400 MPa (total pressure was 110 kN, the upper limit of the press machine used) to produce a composite with a circular shape in plan view (diameter: 1 cm, porosity: 5%).

[0118] Furthermore, the composite material was crushed to obtain granules with an average particle size of approximately 30 μm. These granules were then placed into a powder molding die and pressure-molded using a press machine at a surface pressure of 350 MPa (total pressure was 110 kN, the upper limit of the press machine used), resulting in a molded body of positive electrode composite material with a circular shape in plan view (diameter: 2 cm, area: 3.14 cm²). 2 A positive electrode consisting of a thickness of 0.96 mm and a porosity of 12% was fabricated.

[0119] Then, a coin-type all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that a power generation element was fabricated using the aforementioned positive electrode.

[0120] [Internal resistance evaluation] Ten all-solid-state secondary batteries each for the examples and comparative examples were subjected to a chemical treatment combining constant-current charging (at a current of 0.5C until the battery voltage reached 2.6V) and constant-voltage charging (at a voltage of 2.6V until the current reached 0.01C). Furthermore, a constant-current discharge treatment was performed at a current of 0.05C until the battery voltage reached 1.0V. After the chemical treatment, a 1kHz AC current was applied to each battery to measure its internal resistance, and the average value for all ten batteries was calculated. The results are shown in Table 1 as relative values, with the internal resistance of the battery in Example 1 set to 100.

[0121] Since the negative electrode and solid electrolyte layer are common to both the example and comparative example batteries, the difference in the internal resistance of the batteries is considered to directly reflect the difference in the internal resistance of the positive electrode. Therefore, the internal resistance of the battery obtained by this measurement can be used to evaluate the internal resistance of the positive electrode.

[0122] [Table 1]

[0123] As shown in Table 1, the all-solid-state secondary batteries of Examples 1 and 2, in which a mixture containing the active material and solid electrolyte was first pressurized to a pressure of 800 MPa or higher to form a high-density composite, and then mixed with the solid electrolyte to form the positive electrode mixture, had lower internal resistance compared to the all-solid-state secondary battery of Comparative Example 1, in which the positive electrode mixture was formed without forming the composite, and the all-solid-state secondary battery of Comparative Example 2, in which the positive electrode mixture was formed using only the composite without mixing it with the solid electrolyte, even if the composite was formed. Therefore, the internal resistance of the positive electrode could be reduced.

[0124] The present invention can also be implemented in forms other than those described herein, without departing from its spirit. The embodiments disclosed herein are examples, and the present invention is not limited to these embodiments. The scope of the present invention shall be interpreted in accordance with the claims attached, which take precedence over the description herein, and all modifications within the scope equivalent to the claims are included in the claims. [Industrial applicability]

[0125] The all-solid-state battery of the present invention can be applied to the same applications as conventionally known all-solid-state batteries (all-solid-state primary batteries or all-solid-state secondary batteries). Furthermore, the electrodes for the all-solid-state battery of the present invention can constitute the all-solid-state battery of the present invention. [Explanation of Symbols]

[0126] 10, 11 All-solid-state battery 20 Power generation geometry 21 Positive electrode 211 Cathode mixture layer (molded body of cathode mixture) 212 Current collector 22 Negative electrode 221 Negative electrode mixture layer (molded body of negative electrode mixture) 222 Current collector 23 Solid electrolyte layer 30 Conductive Sheets 40 Lead 50 Spacer 80, 90 External terminals 81, 91 Conduction Path 100 Outer cans 110 Sealed cans 120 Gasket 130, 131 Current collector

Claims

1. The present invention comprises a composite, which is a molded body of a mixture containing an active material and a solid electrolyte (A), and a molded body of an electrode mixture containing the same or a different solid electrolyte (B) as the solid electrolyte (A), The composite is a granular material with an average particle size of 30 μm or more. The molded body of the electrode mixture has a porosity of 10% or less and is 1.8 cm ２ An electrode for all-solid-state batteries, characterized by having a larger surface area.

2. The electrode for an all-solid-state battery according to claim 1, wherein the composite is granular material with an average particle size greater than 50 μm.

3. The electrode for an all-solid-state battery according to claim 1, wherein the solid electrolyte (A) and the solid electrolyte (B) are sulfide-based solid electrolytes.

4. A method for manufacturing an electrode for an all-solid-state battery, having a molded body of an electrode mixture having a porosity of 10% or less and an area greater than 1.8 cm², A step (a) of forming a composite by pressurizing a mixture 1 containing an active material and a solid electrolyte (A) at a pressure of 800 MPa or more, (b) A step of preparing a composite agent 2 by mixing the composite agent with a solid electrolyte (B) that is the same as or different from the solid electrolyte (A), 1.8 cm with a specified thickness ２ A method for manufacturing an electrode for an all-solid-state battery, comprising the steps of (c) forming a layered material of the mixture 2 having a larger surface area, and pressurizing it at a predetermined pressure of less than 800 MPa to form a molded body of the electrode mixture.

5. The method for manufacturing an electrode for an all-solid-state battery according to claim 4, further comprising a step of crushing the composite to adjust its size between step (a) and step (b).

6. A method for manufacturing an electrode for an all-solid-state battery according to claim 4 or 5, wherein the solid electrolyte (A) and the solid electrolyte (B) are sulfide-based solid electrolytes.

7. A fully solid-state battery comprising a power generation element in which a positive electrode having a molded body of a positive electrode mixture, a solid electrolyte layer, and a negative electrode having a molded body of a negative electrode mixture are stacked, and the power generation element is enclosed within an outer casing, An all-solid-state battery characterized in that at least one of the positive electrode and the negative electrode is an electrode for an all-solid-state battery according to any one of claims 1 to 3.

8. The all-solid-state battery according to claim 7, wherein at least one of the molded body of the positive electrode mixture, the solid electrolyte layer, and the molded body of the negative electrode mixture contains a sulfide-based solid electrolyte.

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