WO2024253083A1 - Electrode for solid-state batteries, and solid-state battery - Google Patents

Abstract

An electrode for solid-state batteries according to the present application comprises: an electrode mixture layer that contains an electrode active material and a solid electrolyte; and a current collector. The current collector includes a porous metal base material and a metal foil. The porous metal base material is integrated with the electrode mixture layer. One side of the porous metal base material is exposed from the electrode mixture layer, and the one side of the porous metal base material exposed from the electrode mixture layer is in contact with the metal foil.

Description

Electrode for solid-state battery and solid-state battery

The present invention relates to a solid-state battery that can maintain good internal conductivity and has excellent reliability, and to electrodes that can be used to form the solid-state battery.

In recent years, with the development of portable electronic devices such as mobile phones and notebook personal computers, and the practical application of electric vehicles, there has been a demand for small, lightweight batteries with high capacity and high energy density.

Currently, lithium batteries, particularly lithium ion batteries, that can meet this demand use lithium-containing composite oxides such as lithium cobalt oxide ( _LiCoO2 ) and lithium nickel oxide ( _LiNiO2 ) as the positive electrode active material, graphite or the like as the negative electrode active material, and an organic electrolyte solution containing an organic solvent and a lithium salt as the non-aqueous electrolyte.

As devices that use lithium-ion batteries continue to develop, there is a demand for longer life, higher capacity, and higher energy density lithium-ion batteries, and there is also a high demand for the safety of lithium-ion batteries with longer life, higher capacity, and higher energy density.

However, the organic electrolyte used in lithium-ion batteries contains organic solvents, which are flammable substances, and so there is a possibility that the organic electrolyte may generate abnormal heat if an abnormality such as a short circuit occurs in the battery. Furthermore, with the recent trend toward higher energy density in lithium-ion batteries and an increasing amount of organic solvent in the organic electrolyte, there is an even greater demand for the safety of lithium-ion batteries.

In light of the above, solid-state batteries that use a compact of a solid electrolyte without using organic solvents instead of organic solvent-based electrolytes are being considered. Unlike organic solvent-based electrolytes, solid-state batteries have a high level of safety because their solid electrolytes do not generate abnormal heat. Therefore, there are high expectations for them, especially in product areas that require high-capacity secondary batteries.

In addition to being highly safe, solid-state batteries are also highly reliable and environmentally resistant, and have a long lifespan, making them promising maintenance-free batteries that can contribute to social development while also continuing to contribute to safety and security. Providing solid-state batteries to society can contribute to the achievement of 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) out of the 17 Sustainable Development Goals (SDGs) established by the United Nations.

Furthermore, efforts are being made to further improve the reliability of solid-state batteries. For example, Patent Document 1 proposes disposing a conductive porous material between the electrode stack and the inner bottom surface of the sealed can or the inner bottom surface of the outer can as a current collector for the solid-state battery. In such a solid-state battery, when a compressive force is applied in the thickness direction, for example, the conductive porous material compresses and absorbs the compressive force, thereby preventing cracking of the electrodes due to the compressive force, thereby improving reliability.

International Publication No. 2020/066323

However, further study is needed to determine the structure of the battery that can maintain good conductivity when it is subjected to a strong impact, such as when dropped.

The present invention was made in consideration of the above circumstances, and its purpose is to provide a solid-state battery that can maintain good internal conductivity and has excellent reliability, as well as electrodes that can be used to form the solid-state battery.

The electrode for a solid-state battery of the present invention includes an electrode mixture layer containing an electrode active material and a solid electrolyte, and a current collector, the current collector including a porous metal substrate and a metal foil, the porous metal substrate being integrated with the electrode mixture layer, one side of the porous metal substrate being exposed from the electrode mixture layer, and the one side of the porous metal substrate exposed from the electrode mixture layer being in contact with the metal foil.

The solid-state battery of the present invention includes a battery container and an electrode laminate in which a positive electrode having a current collector and a negative electrode having a current collector face each other via a solid electrolyte layer, and is characterized in that at least one of the positive electrode and the negative electrode has the solid-state battery electrode of the present invention.

The present invention provides a solid-state battery that can maintain good internal conductivity and has excellent reliability, as well as electrodes that can be used to form the solid-state battery.

FIG. 1 is a cross-sectional view that illustrates a schematic diagram of an example of an electrode for a solid-state battery according to the present invention. FIG. 2 is a cross-sectional view illustrating a schematic diagram of another example of an electrode for a solid-state battery according to the present invention. FIG. 1 is a cross-sectional view illustrating a schematic example of a solid-state battery of the present invention.

<Solid battery electrode>

The solid-state battery electrode of the present invention is used as the positive or negative electrode of a solid-state battery (primary or secondary battery).

FIGS. 1 and 2 show cross-sectional views that show a schematic example of an electrode for a solid-state battery. The electrode for a solid-state battery 10 shown in FIG. 1 has an electrode mixture layer 20 on one side of a current collector 30. The current collector 30 has a two-layer structure having a porous metal substrate 31 and a metal foil 32. The electrode mixture layer 20 is integrated with the porous metal substrate 31 of the current collector 30.

In other words, the side of the electrode mixture layer 20 opposite to the side facing the solid electrolyte layer (the lower end in FIG. 1) penetrates into the pores of the porous metal substrate 31 at a certain thickness and is held by the porous metal substrate 31.

The solid-state battery electrode 11 shown in FIG. 2 has electrode mixture layers 20, 20 on both sides of the current collector 30. The current collector 30 has a three-layer structure with porous metal substrates 31, 31 on both sides of the metal foil 32. Each of the two electrode mixture layers 20, 20 is integrated with the porous metal substrates 31, 31 of the current collector 30.

As shown in Figures 1 and 2, the electrode for a solid-state battery of the present invention has a porous metal substrate and a metal foil, and the porous metal substrate, which is present on one or both sides of the metal foil of a current collector in contact with the porous metal substrate and the metal foil, is integrated with an electrode mixture layer containing an electrode active material and a solid electrolyte.

Materials that can be used to make porous metal substrates include aluminum, copper, nickel, magnesium, tin, lead, gold, and alloys of these.

For the porous metal substrate, it is preferable to use a foamed metal porous body. An example of a foamed metal porous body is "Celmet (registered trademark)" by Sumitomo Electric Industries, Ltd. In addition, the thickness of such a porous metal substrate before being used to prepare an electrode (integration with the electrode mixture layer) is usually thicker than the thickness in the electrode (thickness after integration with the electrode mixture layer). For example, the original thickness is preferably 0.1 mm or more, more preferably 0.3 mm or more, and particularly preferably 0.5 mm or more, while it is preferably 3 mm or less, more preferably 2 mm or less, and particularly preferably 1.5 mm or less.

The porosity of the porous metal substrate before being integrated with the electrode mixture layer is preferably 80% or more, more preferably 90% or more, and particularly preferably 95% or more, so that the electrode mixture can be easily filled into the pores of the porous metal substrate in the process of pressurizing the porous metal substrate and the electrode mixture, and the porous metal substrate and the electrode mixture layer can be easily integrated. On the other hand, in order to increase the conductivity by maintaining a certain amount of substrate, the porosity is preferably 99.5% or less, more preferably 99% or less, and particularly preferably 98.5% or less.

In order to reduce the contact resistance with the metal foil when the electrode mixture layer and the porous metal substrate are integrated, one side of the porous metal substrate (the side opposite the electrode mixture layer) should be exposed to the surface, rather than embedding the entire porous metal substrate inside the electrode mixture layer. For example, by overlapping and compressing the electrode mixture and the porous metal substrate, the side of the porous metal substrate opposite the electrode mixture can be exposed to the surface.

In addition, even if one side of the porous metal substrate is exposed on the surface, if there is no metal foil, for example if the exposed porous metal substrate is brought into direct contact with the conductive path on the outer container side, there is a risk of insufficient conductivity if the battery receives a strong impact, and therefore it is necessary to form a current collector from the porous metal substrate and the metal foil to ensure a reliable conductive connection.

The porous metal substrate and the metal foil may simply be in contact with each other, but to reduce contact resistance, it is preferable that they are integrated by crimping or resistance welding.

The constituent materials of the metal foil include aluminum, copper, nickel, titanium and their alloys (various stainless steels (SUS304, SUS316, SUS329J4L, SUS430, SUS444), various nickel alloys (Hastelloy (registered trademark of Haynes Corporation, USA), Inconel (registered trademark of Special Metals Corporation)), titanium alloys, etc.).

In order to increase the mechanical strength of the entire current collector, it is preferable that the metal foil be made of a material with a Vickers hardness (HV) of 200 or more, and preferably 300 or more.

In the solid-state battery electrode of the present invention, the above-mentioned actions of the porous metal substrate and metal foil in the current collector can maintain good internal conductivity in the battery using the electrode (the solid-state battery of the present invention), thereby improving reliability.

The thickness of the porous metal substrate integrated with the electrode mixture layer [when there are two layers of porous metal substrates in contact with the electrode mixture layer as shown in Figure 2, the thickness of each porous metal substrate] is preferably 15 μm or more, and more preferably 20 μm or more, from the viewpoint of better ensuring the effect of suppressing peeling between the current collector and the electrode mixture layer by the porous metal substrate. In addition, the thickness of the porous metal substrate possessed by the current collector is preferably 300 μm or less, and more preferably 150 μm or less.

The thickness of the metal foil (if the current collector has multiple layers of metal foil, the total thickness of those layers. The same applies below.) is preferably 5 μm or more, and more preferably 8 μm or more, from the viewpoint of ensuring a better current collection effect by the metal foil. If the metal foil is too thick, not only will the effect saturate, but the volume occupied by components not involved in power generation in the solid-state battery will increase, so the thickness of the metal foil is preferably 300 μm or less, and more preferably 150 μm or less.

The thickness of the entire current collector is preferably 20 μm or more, more preferably 25 μm or more, and is preferably 600 μm or less, and more preferably 300 μm or less.

When the electrode for solid-state batteries is used as the positive electrode of a solid-state primary battery, the electrode active material contained in the electrode mixture layer can be the same as the positive electrode active material used in conventionally known non-aqueous electrolyte primary batteries.Specific examples of the electrode active material include manganese dioxide; lithium-containing manganese oxides (e.g., LiMn ₃ O ₆ and composite oxides having the same crystal structure as manganese dioxide (β-type, γ-type, or a structure in which β-type and γ-type are mixed, etc.) and a Li content of 3.5% by mass or less, preferably 2% by mass or less, more preferably 1.5% by mass or less, and particularly preferably 1% by mass or less); lithium-containing composite oxides such as Li _a Ti _5/3 O ₄ (4/3≦a<7/3); vanadium oxides; niobium oxides; titanium oxides; sulfides such as iron disulfide; graphite fluoride; silver sulfides such as Ag ₂ S; nickel oxides such as NiO ₂ ; and the like.

When the solid-state battery electrode is used as the positive electrode of a solid-state secondary battery, the electrode active material to be contained in the electrode mixture layer is not particularly limited as long as it is a positive electrode active material used in conventionally known non-aqueous electrolyte secondary batteries, that is, an active material capable of absorbing and releasing Li ions. Specific examples of the positive electrode active material include spinel-type lithium manganese composite oxide represented by _{LiMrMn2 -rO4 (} wherein 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, and 0≦r≦1), _{LirMn (1-s-r) NisMtO (2-u) Fv} a layered compound represented by LiCo 1-r M r O 2 (wherein M is at least one element selected from the group consisting of Co, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Zr, Mo, Sn, Ca, Sr, and W, and 0.8≦r≦1.2, 0<s<0.5, 0≦t≦0.5, u+v<1, -0.1≦u≦0.2, 0≦v≦0.1); a lithium cobalt composite oxide represented by LiCo _1-r M _r O ₂ (wherein 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, and _Ba , and 0≦r≦0.5) _; a lithium nickel composite oxide represented by Li 1+s M 1-r N r PO 4 F s (wherein 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≦r≦0.5); an olivine type composite oxide represented by Li ₂ M _1-r N _r P ₂ O ₇ (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≦ _{r ≦ 0.5} , 0≦ _s ≦ ₁ ); (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≦r≦0.5), and the like. Among these, only one type may be used, or two or more types may be used in combination.

When the solid-state battery electrode is used as the positive electrode of a solid-state secondary battery, the average particle diameter of the electrode active material (positive electrode active material) is preferably 0.1 μm or more, more preferably 0.5 μm or more, and preferably 25 μm or less, more preferably 10 μm or less, from the viewpoint of reducing side reactions that cause capacity degradation of the battery and increasing the density of the electrode. The positive electrode active material may be either primary particles or secondary particles formed by agglomeration of primary particles. When the electrode mixture layer contains a solid electrolyte, using an electrode active material with an average particle diameter in the above range allows for a large interface with the solid electrolyte, thereby further improving the load characteristics of the battery.

The average particle diameter of the electrode active material and the average particle diameter of other particles (such as solid electrolytes) referred to in this specification refer to the 50% diameter value (D50) in the volume-based integrated fraction when the integrated volume is determined from particles with small particle sizes using a particle size distribution measurement device (such as the Microtrack particle size distribution measurement device " _HRA9320 " manufactured by Nikkiso Co., Ltd.).

When the solid-state battery electrode is used as the negative electrode of a solid-state primary battery, examples of the electrode active material contained in the electrode mixture layer include metallic lithium and lithium alloys (lithium-aluminum alloys, lithium-indium alloys, etc.).

In addition, when the solid-state battery electrode is used as the negative electrode of a solid-state secondary battery, the electrode active material to be contained in the electrode mixture layer is not particularly limited as long as it is an active material capable of absorbing and releasing lithium ions that is used in conventionally known non-aqueous electrolyte secondary batteries. For example, as the negative electrode active material, one or a mixture of two or more carbon-based materials capable of absorbing and releasing lithium, such as graphite, pyrolytic carbons, cokes, glassy carbons, baked bodies of organic polymer compounds, mesocarbon microbeads (MCMB), and carbon fibers, is used. The negative electrode active material may be an oxide, and examples thereof include a composite oxide having a monoclinic crystal structure represented by Li _x Nb _y TiM ⁶ _a O _{5y+4/2}+δ (wherein M ⁶ is at least one selected from the group consisting of V, Cr, Mo, Ta, Zr, Mn, Fe, Mg, B, Al, Cu, and Si, and 0≦x≦49, 0.5≦y<24, −5≦δ≦5, 0≦a≦0.3), titanium dioxide having an anatase structure, lithium titanate having a ramsdellite structure represented by Li ₂ Ti ₃ O _7, and a spinel-type lithium titanium composite oxide represented by Li ₄ Ti ₅ O _12. One or more of these may be used. As the negative electrode active material, there can be used simple substances, compounds and alloys thereof containing elements such as Si, Sn, Ge, Bi, Sb, and In; compounds that can be charged and discharged at a low voltage close to that of lithium metal, such as nitrides or lithium-containing oxides containing lithium and transition metals such as Co, Ni, Mn, Fe, Cr, Ti, and W; or metallic lithium and lithium alloys (lithium-aluminum alloy, lithium-indium alloy, and the like).

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

The reaction suppression layer may be made of a material that has ion conductivity and can suppress the reaction between the electrode active material and the solid electrolyte. Examples of materials that can form 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 LiNbO ₃ , Li ₃ PO ₄ , Li ₃ BO ₃ , Li ₄ SiO ₄ , Li ₄ GeO ₄ , LiTiO ₃ , LiZrO ₃ , Li ₂ WO ₄ and the like. The reaction suppression layer may contain only one of these oxides, or may contain two or more of them, and further, a plurality of these oxides may form a composite compound. Among these oxides, it is preferable to use an Nb-containing oxide, and it is more preferable to use LiNbO ₃ .

The reaction suppression layer is preferably present on the surface in an amount of 0.1 to 2.0 parts by mass per 100 parts by mass of electrode active material. This range allows for good suppression of the reaction between the electrode active material and the solid electrolyte.

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

When the solid-state battery electrode is a positive electrode, the content of the electrode active material (positive electrode active material) in the electrode mixture layer is preferably 20 to 95 mass %.

In addition, when the solid-state battery electrode is a negative electrode, the content of the electrode active material (negative electrode active material) in the electrode mixture layer is preferably 30 to 70 mass %.

The electrode mixture layer of the solid-state battery electrode can contain a conductive assistant such as carbon black or graphene, if necessary. When a conductive assistant is contained in the electrode mixture layer, the content of the conductive assistant in the electrode mixture layer is preferably 2 to 10 mass %.

The electrode mixture layer of the solid-state battery electrode can contain a binder. Specific examples include fluororesins such as polyvinylidene fluoride (PVDF) and lithium ion conductive resins in which functional groups have been introduced into the polyethylene oxide skeleton to provide binder functionality. Note that, for example, in cases where the electrode mixture layer contains a sulfide-based solid electrolyte (described below), if good moldability can be ensured in forming the electrode mixture layer without using a binder, the electrode mixture layer does not need to contain a binder.

If a binder is required in the electrode mixture layer, its content is preferably 6 mass% or less, and preferably 0.5 mass% or more. On the other hand, if good moldability can be obtained without the need for a binder, its content is preferably 0.5 mass% or less, more preferably 0.3 mass% or less, and even more preferably 0 mass% (i.e., no binder is contained).

The electrode mixture layer can contain a solid electrolyte. The solid electrolyte used in the electrode mixture layer is not particularly limited as long as it has Li ion conductivity, and examples that can be used include sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes.

Examples of sulfide-based solid electrolytes include glass-based particles such as Li ₂ S-P ₂ S ₅ , Li ₂ S-SiS ₂ , Li ₂ S-P ₂ S ₅ -GeS ₂ , and Li ₂ S- _{B 2} S _{3 . In} addition, thio-LISICON-type electrolytes, which have been attracting attention in recent years for their high Li ion conductivity, are also available. These include Li _{12-12a-b+c+6d-e M 1 3 +} ^a _-b-c-d ^{M 2} _b M ³ _c M ⁴ _d M _{5 12 -e} X _e (where M ¹ is Si, Ge, or Sn, M ^M2 is P or V, ^M3 is Al, Ga, Y or Sb, ^M4 is Zn, Ca or Ba, ^M5 is S or S and O, and X is F, Cl, Br or I, 0≦a<3, 0≦b+c+d≦3, 0≦e≦3] or argyrodite type compounds (such as _Li6PS5Cl , which are represented by Li7 _{-f+gPS6 - xClx +y (} where 0.05≦f≦0.9, -3.0f+1.8≦g≦-3.0f+5.7), or Li7 _{-hPS6 - hCliBrj} (where h=i+j, 0<h≦1.8, 0.1≦i/j≦10.0)) can also be used.

Examples of hydride-based solid electrolytes include LiBH ₄ , solid solutions of LiBH ₄ and the following alkali metal compounds (for example, those in which the molar ratio of LiBH ₄ to the alkali metal compound is 1:1 to 20:1), etc. Examples of the alkali metal compounds in the solid solutions 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.

Examples of halide-based solid electrolytes include monoclinic LiAlCl ₄ , defective spinel or layered structure LiInBr ₄ , and monoclinic Li _6-3m Y _m X ₆ (where Y is yttrium, 0<m<2 and X=Cl or Br). Other known solid electrolytes that can be used include those described in, for example, WO 2020/070958 and WO 2020/070955.

Examples of oxide-based solid electrolytes include Li ₂ O—Al ₂ O ₃ —SiO ₂ —P ₂ O ₅ —TiO ₂ -based glass ceramics, Li ₂ O—Al ₂ O ₃ —SiO ₂ —P ₂ O ₅ —GeO ₂ -based glass ceramics, garnet-type Li ₇ La ₃ Zr ₂ O ₁₂ , NASICON-type Li _1+O Al _1+O Ti _2-O (PO ₄ ) ₃ , Li _1+p Al _1+p Ge _2-p (PO ₄ ) ₃ , and perovskite-type Li _3q La _2/3-q TiO ₃ .

Among these solid electrolytes, sulfide-based solid electrolytes are preferred due to their high Li ion conductivity, sulfide-based solid electrolytes containing Li and P are more preferred, and argyrodite-type sulfide-based solid electrolytes, which have particularly high Li ion conductivity and high chemical stability, are even more preferred.

The average particle size of the solid electrolyte is preferably 0.1 μm or more, and more preferably 0.2 μm or more, from the viewpoint of reducing grain boundary resistance, while it is preferably 10 μm or less, and more preferably 5 μm or less, from the viewpoint of forming a sufficient contact interface between the electrode active material and the solid electrolyte.

When the solid-state battery electrode is a positive electrode, the solid electrolyte content in the electrode mixture layer is preferably 4 to 80 mass %. When the solid-state battery electrode is a negative electrode, the solid electrolyte content in the electrode mixture layer is preferably 4 to 85 mass %.

Electrodes for solid-state batteries can be manufactured, for example, by compressing an electrode mixture prepared by mixing an electrode active material, a solid electrolyte, and a conductive assistant, etc., by pressure molding or the like to form a molded body of the electrode mixture, which is then bonded to a current collector by pressure bonding or the like, or by pressure molding the electrode mixture directly on the surface of the current collector to simultaneously form a molded body of the electrode mixture and bond it to the current collector. In these cases, the electrode mixture layer of the electrode for solid-state batteries is composed of the molded body of the electrode mixture.

Also, the electrode mixture and the solvent may be mixed to prepare an electrode mixture-containing composition, which may be applied to a current collector, dried, and then pressed to bond the current collector and the electrode mixture layer, thereby producing an electrode for a solid battery. Alternatively, the electrode mixture-containing composition may be applied to a solid electrolyte layer that faces the electrode, dried, and then a current collector is placed on top of the composition and pressed to bond the current collector and the electrode mixture layer, thereby producing an electrode for a solid battery.

It is preferable to select a solvent for the electrode mixture-containing composition that does not easily deteriorate the solid electrolyte. In particular, since sulfide-based solid electrolytes and hydride-based solid electrolytes undergo chemical reactions with trace amounts of water, it is preferable to use non-polar aprotic solvents such as hydrocarbon solvents such as hexane, heptane, octane, nonane, decane, decalin, toluene, and xylene. In particular, it is more preferable to use ultra-dehydrated solvents with a water content of 0.001 mass% (10 ppm) or less. In addition, fluorine-based solvents such as "Vertrel (registered trademark)" manufactured by Mitsui DuPont Fluorochemicals, "Zeorolla (registered trademark)" manufactured by Nippon Zeon Co., Ltd., and "Novec (registered trademark)" manufactured by Sumitomo 3M Co., Ltd., as well as non-aqueous organic solvents such as dichloromethane and diethyl ether can also be used.

The thickness of the electrode mixture layer formed by pressure molding of the electrode mixture (if the electrode mixture layer is formed on both sides of the current collector, the thickness per side of the current collector; the same applies below) is usually 100 μm or more, but from the viewpoint of increasing the capacity of batteries that use solid-state battery electrodes, it is preferably 200 μm or more. In addition, the thickness of the electrode mixture layer formed by pressure molding of the electrode mixture is usually 3000 μm or less.

In the case of an electrode for a solid-state battery manufactured by forming an electrode mixture layer on a current collector using an electrode mixture-containing composition that contains a solvent, the thickness of the electrode mixture layer is preferably 10 to 1000 μm.

<Solid-state battery>
The solid-state battery of the present invention includes a battery container, and an electrode laminate in which a positive electrode having a current collector and a negative electrode having a current collector face each other via a solid electrolyte layer, and at least one of the positive electrode and the negative electrode is the electrode for the solid-state battery of the present invention. As for the configuration other than the electrode, various configurations employed in conventionally known solid-state batteries can be applied.

FIG. 3 shows a vertical cross-sectional view that shows a schematic example of a solid-state battery of the present invention. The solid-state battery 100 shown in FIG. 3 has an electrode laminate 110 having a positive electrode 120, a negative electrode 130, and a solid electrolyte layer 140 interposed between them, and this electrode laminate 110 is sealed in a battery container formed of a recessed container 150 and a sealing body 160. At least one of the positive electrode 120 and the negative electrode 130 that constitute the electrode laminate 110 is an electrode for the solid-state battery of the present invention.

The positive electrode 120 has a positive electrode mixture layer 121 and a current collector 122. When the positive electrode 120 is an electrode for a solid-state battery of the present invention, the current collector 122 has a multi-layer structure having a porous metal substrate and a metal foil, but in FIG. 3, it is represented as a single layer to avoid complicating the drawing.

The negative electrode 130 also has a negative electrode mixture layer 131 and a current collector 132. When the negative electrode 130 is an electrode for a solid-state battery of the present invention, the current collector 132 has a multi-layer structure having a porous metal substrate and a metal foil, but in FIG. 3, it is represented as a single layer to avoid complicating the drawing.

The battery container is made up of a concave container 150, which is made up of a bottom portion 151 and a side wall portion 152, and has an opening 153 that opens to the upper side in the figure, with a concave cross section.

The bottom of the recessed container 150 in the figure is provided with connection terminals 180, 190 for electrically connecting the solid-state battery 100 to a device in which it is used. The connection terminal 180 is conductively connected to a conductive path 181 that runs from the inside of the recessed container 150 to the external connection terminal 180. The conductive path 181 is conductively connected to the positive electrode 120 of the electrode stack 110 housed in the recessed container 150, thereby providing electrical continuity between the positive electrode 120 of the electrode stack 110 and the connection terminal 180. In the solid-state battery 100 in FIG. 3, a porous metal layer 200 for thickness adjustment is interposed between the positive electrode 120 of the electrode stack 110 and the conductive path 181.

The solid-state battery 100 shown in FIG. 3 also has an elastic conductive member 170, which presses the electrode laminate 110 downward in the figure. The action of this elastic conductive member 170 can improve the conductivity between the electrode laminate 110 and the porous metal layer 200, and the reliability of the electrical connection between the porous metal layer 200 and the conductive path 181. In addition, if the battery does not have a porous metal layer and the electrode laminate and the conductive path are in direct contact, the elastic conductive member can improve the reliability of the electrical connection between the electrode laminate and the conductive path.

The connection terminal portion 190 is conductively connected to a conductive path 191 that runs from the inside of the recessed container 150 to the external connection terminal portion 190, and this conductive path 191 is disposed at the top of the electrode stack 110 in the figure, and is conductively connected to the negative electrode 130 via an elastic conductive member 170 that contacts the negative electrode 130 of the electrode stack 110. This provides electrical continuity between the negative electrode 130 of the electrode stack 110 and the connection terminal portion 190.

The side wall portion 152 of the concave container 150 has a support portion 154 that supports the elastic conductive member 170. In the solid-state battery 100 shown in FIG. 3, the support portion 154 is formed at the upper end of the inner circumferential surface of the side wall portion 152 and is a protruding portion that protrudes in the radial direction, but the support portion for holding the conductive connection member of the solid-state battery may have another shape as long as it can support the conductive connection member.

The elastic conductive member 170 is formed of, for example, a thin metal plate, and has an engaging portion 171 at its end that corresponds to the support portion 154 of the recessed container 150. In the solid-state battery 100 shown in FIG. 3, the engaging portion 171 on the elastic conductive member 170 is a hook-shaped engaging piece that engages with the support portion 154. More specifically, the engaging portion 171 extends from the edge of the elastic conductive member 170 toward the support portion 154 (downward in the figure), and has a tip that is folded back toward the underside of the support portion 154.

The ends of the conductive path 191 are exposed on the side and bottom surfaces of the support portion 154, and the conductive path 191 and the locking portion 171 of the elastic conductive member 170 are in direct contact with each other, thereby electrically connecting the two. As a result, the elastic conductive member 170 functions as a current collector, and forms part of the conductive path that electrically connects the negative electrode 130 and the connection terminal portion 190.

When the electrode laminate is pressed by the elastic conductive member, the elastic conductive member is pressed against the current collector located on the surface of the electrode laminate on the elastic conductive member side, and the current collector located on the surface of the electrode laminate on the conductive path side (porous metal layer side) is pressed against the conductive path (porous metal layer). In this state, if the battery vibrates, the current collector and the elastic conductive member rub against each other, or the current collector and the conductive path rub against each other, the current collector becomes more likely to be destroyed. However, when the solid battery electrode of the present invention is used, the action of the metal foil constituting the current collector can suppress the destruction of the current collector even in the case of an embodiment having an elastic conductive member pressing the electrode laminate. Therefore, the effect of the present invention is more pronounced in the case of a solid battery having an elastic conductive member pressing the electrode laminate.

3, when installing the elastic conductive member 170, first, the electrode stack 110 is housed inside the recessed container 150, and then the elastic conductive member 170 is placed on the upper surface of the electrode stack 110. Then, with the elastic conductive member 170 placed on the upper surface of the electrode stack 110, the tip of the locking portion 171 is positioned between the upper surface of the electrode stack 110 and the lower surface of the support portion 154 in the axial direction of the electrode stack 110 (the up-down direction in the figure). Then, while pushing the locking portion 171 of the elastic conductive member 170 toward the bottom portion 151 of the recessed container 150, the tip of the locking portion 171 is locked to the lower surface of the support portion 154. At this time, the elastic conductive member 170 has the locking portion 171 pushed downward, so that the elastic conductive member 170 (its recess 172) bends in the opposite direction to the electrode stack 110 while in contact with the electrode stack 110. As a result, the elastic conductive member 170 presses the electrode stack 110 toward the bottom portion 151 of the recessed container 150 by its elastic force. In other words, the elastic conductive member 170 functions as a plate spring.

The elastic conductive member 170 has a recess 172 that contacts the upper surface of the electrode laminate 110, and the bottom surface of the recess 172 is formed in a flat shape so that the electrode laminate 110 can be pressed over a wider area. The elastic conductive member 170 has the function of pressing the electrode laminate 110 against the inner bottom surface of the concave container 150, and since the elastic conductive member 170 has a shape having a flat recess 172, it is possible to press the elastic conductive member 170 and the electrode laminate 110 (its negative electrode 130), and the electrode laminate 110 (its positive electrode 120) and the conductive path 181 (the electrode laminate 110 and the porous metal layer 200, and the porous metal layer 200 and the conductive path 181) over a wider area, and the electrical connection between them can be made over a wider area, which further improves the reliability of the electrical connection between the components in the solid-state battery 100.

As shown in FIG. 3, it is preferable that a gap is formed between the elastic conductive member 170 and the sealing body 160. In other words, it is preferable that the elastic conductive member 170 and the sealing body 160 are not in contact with each other. This makes it possible to avoid contact between the elastic conductive member 170 and the sealing body 160 even if the elastic conductive member 170 is pushed toward the sealing body 160 due to a change in volume of the electrode laminate 110, which is made up of the power generating element.

In the solid-state battery 100 shown in FIG. 3, the electrode stack 110 is arranged so that the positive electrode 120 is located on the inner bottom surface side of the recessed container 150 and the negative electrode 130 is located on the sealing body 160 side (elastic conductive member 170 side), but a solid-state battery can also be constructed by arranging the electrode stack so that the negative electrode is located on the inner bottom surface side of the recessed container and the positive electrode is located on the sealing body side (elastic conductive member side).

(Positive electrode)
The electrode for a solid-state battery of the present invention can be used for the positive electrode of the solid-state battery, but when the negative electrode is the electrode for a solid-state battery of the present invention, a positive electrode other than the electrode for a solid-state battery of the present invention can also be used. Positive electrodes other than the electrode for a solid-state battery of the present invention include those in which the current collector is only a metal foil or only a sheet-shaped conductive porous body (foamed metal porous body, porous carbon sheet, etc.).

(Negative electrode)
The solid-state battery electrode of the present invention can be used as the negative electrode of the solid-state battery, but when the positive electrode is the solid-state battery electrode of the present invention, a negative electrode other than the solid-state battery electrode of the present invention can also be used. Examples of negative electrodes other than the solid-state battery electrode of the present invention include those in which the current collector is only a metal foil or only a sheet-shaped conductive porous body (foamed metal porous body, porous carbon sheet, etc.), and also include negative electrodes having a lithium sheet or a lithium alloy sheet.

In the case of negative electrodes having lithium or lithium alloy sheets, those consisting of these sheets alone or those consisting of these sheets bonded to a current collector are used.

Alloying elements for lithium alloys include aluminum, lead, bismuth, indium, and gallium, with aluminum and indium being preferred. The proportion of alloying elements in the lithium alloy (the total proportion when multiple alloying elements are included) is preferably 50 atomic % or less (in this case, the remainder is lithium and unavoidable impurities).

In the case of a negative electrode having a lithium alloy sheet, a laminate can be used in which a layer containing an alloying element for forming a lithium alloy is laminated on the surface of a lithium layer (layer containing lithium) composed of metallic lithium foil or the like, for example by pressing the layer, and the laminate is brought into contact with a solid electrolyte in a battery to form a lithium alloy on the surface of the lithium layer, thereby forming a negative electrode. In the case of such a negative electrode, a laminate having a layer containing an alloying element on only one side of the lithium layer may be used, or a laminate having layers containing an alloying element on both sides of the lithium layer may be used. The laminate can be formed, for example, by pressing metallic lithium foil and a foil composed of an alloying element.

The current collector can also be used when forming a lithium alloy inside the battery to form the negative electrode. For example, a laminate having a lithium layer on one side of the negative electrode current collector and a layer containing an alloying element on the side of the lithium layer opposite the negative electrode current collector may be used, or a laminate having lithium layers on both sides of the negative electrode current collector and each lithium layer having a layer containing an alloying element on the side opposite the negative electrode current collector may be used. The negative electrode current collector and the lithium layer (metallic lithium foil) may be laminated by crimping or the like.

The layer containing the alloying elements in the laminate to be used as the negative electrode can be, for example, a foil composed of these alloying elements. The thickness of the layer containing the alloying elements is preferably 1 μm or more, more preferably 3 μm or more, and is preferably 20 μm or less, and more preferably 12 μm or less.

The lithium layer of the laminate to be used as the negative electrode can be, for example, metallic lithium foil. The thickness of the lithium layer is preferably 0.1 to 1.5 mm. In addition, the thickness of the sheet for the negative electrode having a lithium or lithium alloy sheet is also preferably 0.1 to 1.5 mm.

In addition, if the negative electrode having a lithium sheet or a lithium alloy sheet has a current collector, the current collector can be any current collector that can be used in the solid-state battery electrode of the present invention.

(Solid electrolyte layer)
The solid electrolyte in the solid electrolyte layer interposed between the positive electrode and the negative electrode can be one or more of the various sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes exemplified above as those usable in electrodes for solid state batteries. However, in order to improve the battery characteristics, it is preferable to contain a sulfide-based solid electrolyte, and it is more preferable to contain an argyrodite-type sulfide-based solid electrolyte. It is even more preferable to contain a sulfide-based solid electrolyte in all of the positive electrode, negative electrode, and solid electrolyte layer, and it is even more preferable to contain an argyrodite-type sulfide-based solid electrolyte.

The solid electrolyte layer may have a porous body such as a resin nonwoven fabric as a support.

The solid electrolyte layer can be formed by compressing the solid electrolyte by pressure molding or the like; by applying a composition for forming the solid electrolyte layer, which is prepared by dispersing the solid electrolyte in a solvent, onto a substrate (including a porous body serving as a support), a positive electrode, or a negative electrode, drying the composition, and, if necessary, performing pressure molding such as pressing.

The solvent used in the composition for forming the solid electrolyte layer should be one that is unlikely to deteriorate the solid electrolyte, and it is preferable to use the same solvents as those exemplified above for the electrode mixture-containing composition.

The thickness of the solid electrolyte layer is preferably 10 to 500 μm.

(Electrode laminate)
The positive electrode and the negative electrode can be used in a battery in the form of an electrode laminate in which a solid electrolyte layer is laminated therebetween, or in the form of a wound electrode body in which this electrode laminate is further wound. In addition, an electrode laminate formed by laminating a positive electrode, a solid electrolyte layer, and a negative electrode can be used as a unit electrode body, and a plurality of unit electrode bodies can be arranged in an exterior body or stacked in the thickness direction of the unit electrode body for use in a solid-state battery. When a plurality of unit electrode bodies are used in a solid-state battery, the unit electrode bodies can be connected in series or in parallel.

When forming the electrode stack, it is preferable to pressure mold the positive electrode, negative electrode, and solid electrolyte layer in a stacked state in order to increase the mechanical strength of the electrode stack.

(Battery container)
The battery container (exterior body) of the solid-state battery may have a structure as shown in Fig. 3, which includes a concave container and a sealing body, the concave container having a conductive path leading from the inside to the outside of the concave container, and the current collectors on the surfaces of the electrodes (positive and negative electrodes) of the electrode stack are brought into contact with the conductive path to electrically connect the electrodes and the conductive path. In such a battery container, the concave container may be made of ceramics or resin. The sealing body may be made of ceramics, resin, or metal (such as an iron-nickel alloy or an iron-based alloy such as an iron-nickel-cobalt alloy).

In the concave container, the connection terminal portion and the conductive path connecting the electrode of the electrode stack and the connection terminal portion can be made of metals such as manganese, cobalt, nickel, copper, molybdenum, silver, palladium, tungsten, platinum, and gold, or alloys containing these metals.

The concave container and the sealing body can be made of an insulating material (resin, ceramics, etc.), in which case they can be sealed by bonding them together with an adhesive. When using a concave container made of an insulating material and a sealing body made of metal, as shown in FIG. 3, a seal ring 210 made of metal (such as an iron-nickel alloy or an iron-based alloy such as an iron-nickel-cobalt alloy) can be placed on the sealing body 160 side (upper side in the figure) of the side wall 152 of the concave container 150, so that the sealing body side of the side wall is made of metal, and the concave container and the sealing body can be welded together to seal.

In addition to the battery containers described above, various types of battery containers used in various conventionally known batteries, such as cylindrical or rectangular metal containers, flat containers with an outer can and a sealing can used in batteries called coin batteries or button batteries, and sheet-like containers made of resin films such as metal laminate films, can be used as battery containers for solid-state batteries.

The shape of the battery container of a solid-state battery in a plan view may be circular or polygonal, such as a quadrilateral (square or rectangle).

<Elastic conductive member>
The elastic conductive member 170 in the solid-state battery 100 shown in Fig. 3 is not particularly limited as long as it has a shape that functions as a leaf spring that presses the electrode stack toward the inner bottom surface of the recessed container. Specifically, for example, as shown in Fig. 3, an elastic conductive member having a cross-sectional shape that has a locking portion 171 shaped according to the support portion 154 of the recessed container 150 and a recess 172 that presses the electrode stack 110 can be used.

The elastic conductive member can be made of a metal plate such as a stainless steel plate or a stainless steel plate plated with nickel. The thickness of the metal plate constituting the elastic conductive member is preferably 0.05 to 0.50 mm. In addition, when the elastic conductive member has a recess for pressing the electrode laminate as shown in Fig. 3, the area of the portion of the recess that contacts the electrode laminate is preferably 3 to 45 ^mm2 from the viewpoint of enabling the elastic conductive member to press the electrode laminate more uniformly at the contact surface with the electrode laminate. The depth of the recess is preferably 0.05 to 0.50 mm.

<Porous Metal Layer>
In the case of a solid-state battery having a battery container as shown in Fig. 3, a porous metal layer can be disposed between the electrode laminate and the inner bottom surface of the concave container related to the battery container, and the porous metal layer can be electrically connected to the conductive path of the concave container. When the porous metal layer is disposed, the electrode on the inner bottom surface side of the concave container in the electrode laminate (positive electrode 120 in the case of the solid-state battery 100 shown in Fig. 3) and the conductive path of the concave container (conductive path 181 in the case of the solid-state battery shown in Fig. 3) are electrically connected via the porous metal layer (porous metal layer 200 in the case of the solid-state battery shown in Fig. 3).

Because the porous metal layer has pores and is made of metal, it can easily undergo plastic deformation by applying a force in the thickness direction. Therefore, when forming a solid-state battery, the electrode laminate can be inserted into the exterior body so as to be pressed against the porous metal layer (the metallic porous body that constitutes it), or the electrode laminate can be pressed against the porous metal layer (the metallic porous body that constitutes it) by the pressing force of an elastic conductive member, thereby compressing and deforming the porous metal layer and improving contact between the electrode on the porous metal layer side of the electrode laminate and the current collector. When a porous metal layer is used in a solid-state battery, these actions make it possible to further reduce internal resistance.

The porous metal layer may be made of a porous material made of a metal that does not adversely affect the characteristics of the solid-state battery within the solid-state battery, but it is preferable to use a foamed metal porous material (such as "Celmet (registered trademark)" manufactured by Sumitomo Electrochemical Industries, Ltd.) because it is relatively easy to cause plastic deformation.

The thickness of the porous metal layer in the solid-state battery is preferably 100 μm or more, and more preferably 150 μm or more, from the viewpoint of ensuring its function better. There is no particular upper limit on the thickness of the porous metal layer in the solid-state battery, but from the viewpoint of suppressing the volume of the members not involved in power generation inside the battery container, it is preferably 1500 μm or less, and more preferably 1000 μm or less.

The thickness of the porous metal layer is determined from the maximum width in the thickness direction in an image of a cross section of the layer observed with a scanning electron microscope (SEM) at a magnification of 50 to 1000 times.

As mentioned above, the porous metal layer is preferably a metal porous body compressed in the thickness direction, and its thickness is preferably 90% or less, and more preferably 80% or less, of the thickness of the metal porous body (such as the foamed metal porous body) used to form the porous metal layer. Therefore, the thickness of the metal porous body (such as the foamed metal porous body) used to form the porous metal layer is preferably 150 to 1000 μm.

The porosity of the metal porous body (such as the foamed metal porous body described above) used to form the porous metal layer is preferably 99.5% or less, more preferably 99% or less, and even more preferably 98.5% or less, from the viewpoint of making it easier to plastically deform when the electrode laminate is pressed against it, and thus better ensuring the effect of reducing the internal resistance of the solid-state battery and the effect of suppressing its variation; from the viewpoint of increasing the capacity of the positive or negative electrode while ensuring sufficient strength for use, the porosity is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more.

The solid-state battery of the present invention can be used in the same applications as conventionally known primary and secondary batteries, but since it has a solid electrolyte instead of an organic electrolyte, it has excellent heat resistance and can be preferably used in applications where it is exposed to high temperatures. The solid-state battery electrode of the present invention can constitute the solid-state battery of the present invention.

The present invention will be described in detail below based on examples. However, the following examples do not limit the present invention.

Example 1
_A negative electrode mixture was prepared by mixing lithium _{titanate (Li4Ti5O12 ,} negative electrode active material) having an average particle size of 2 μm, a sulfide-based solid electrolyte ( _Li6PS5Cl ) having an average _particle size of 0.7 μm, and graphene (conductive additive) in a mass ratio of 50:41:9.

In addition, LiCoO ₂ (positive electrode active material) having an average particle size of 5 μm and having a LiNbO ₃ coating layer formed on its surface, a sulfide-based solid electrolyte (Li ₆ PS ₅ Cl) having an average particle size of 0.7 μm, and graphene were mixed in a mass ratio of 65:30.7:4.3 to prepare a positive electrode mixture.

Next, a powder of sulfide-based solid electrolyte ( _Li6PS5Cl ) having an average particle size of 0.7 μm was placed in a powder molding die, and pressure molding was performed at a surface pressure of 70 _MPa using a press machine to form a provisionally molded layer of the solid electrolyte layer. Furthermore, the negative electrode mixture was placed on the upper surface of the provisionally molded layer of the solid electrolyte layer and pressure molding was performed at a surface pressure of 50 MPa, and a provisionally molded layer of the negative electrode was further formed on the provisionally molded layer of the solid electrolyte layer.

Next, a porous metal substrate made of an aluminum foamed metal porous body (thickness: 1000 μm) and a metal foil made of stainless steel (SUS430, thickness: 10 μm) were cut out as current collectors, and this current collector was placed on the provisionally molded layer of the negative electrode formed on the provisionally molded layer of the solid electrolyte layer so that the porous metal substrate was in contact with the provisionally molded layer of the negative electrode, and the metal foil was placed in contact with the porous metal substrate. Pressure molding was performed at a surface pressure of 300 MPa to form an integrated body of the solid electrolyte layer and the negative electrode (a negative electrode having a negative electrode mixture layer made of a molded body of the negative electrode mixture and a current collector).

Furthermore, after the mold was turned upside down, the positive electrode mixture was placed on the upper surface of the solid electrolyte layer in the mold (the surface opposite to the surface having the negative electrode) and pressure molding was performed with a surface pressure of 50 MPa, forming a provisionally molded layer of the positive electrode on the solid electrolyte layer.

Next, the same porous metal substrate and metal foil used for the negative electrode were cut out as a current collector on top of the provisionally molded layer of the positive electrode formed on the solid electrolyte layer, and the porous metal substrate was placed so that it was in contact with the provisionally molded layer of the positive electrode, and the metal foil was placed so that it was in contact with the porous metal substrate. Pressure molding was performed at a surface pressure of 1400 MPa to obtain an electrode laminate equipped with a positive electrode having a positive electrode mixture layer and a current collector. The thickness of the porous metal substrate integrated with the mixture layers of the positive electrode and negative electrode was 120 μm, and the thickness of the metal foil was 10 μm.

A nickel-made foamed metal porous body cut to a diameter of 7.25 mm was placed on the inner bottom surface of a concave container (ceramic depth 2.5 mm) having a cross-sectional structure similar to that shown in Fig. 3 and made of ceramics, with a seal ring made of an iron-nickel-cobalt alloy arranged on the upper part of the side wall, and the electrode laminate was placed on top of it with the positive electrode facing down. Furthermore, an elastic conductive member (the area of the contact surface with the electrode laminate in the recess is 10 mm2 ⁾ made of a stainless steel plate (thickness 0.3 mm) and having a cross-sectional shape similar to that shown in Fig. 3 was placed on the negative electrode of the electrode laminate so that the bottom surface of the recess was in contact with the negative electrode, and the tip of the engagement part was engaged with the lower surface of the support part of the concave container, so that the recess of the elastic conductive member pressed the electrode laminate against the inner bottom surface of the concave container. Thereafter, a sealing body made of an iron-nickel-cobalt alloy plate (thickness 0.1 mm) was placed on the seal ring of the concave container, and the sealing body and the concave container (seal ring) were welded to seal the battery container, thereby obtaining a solid secondary battery. In the obtained solid secondary battery, as described above, the elastic conductive member presses the electrode laminate toward the inner bottom surface of the concave container, and as a result, the electrode laminate presses the porous metal layer made of the foamed porous metal, and the foamed porous metal is compressed, thereby adjusting the height from the inner bottom surface of the concave container to the upper end of the electrode laminate. In addition, the thickness of the porous metal layer in the solid secondary battery was 200 μm.

(Comparative Example 1)
Except for changing the porous metal substrate of the positive electrode and the negative electrode to a nickel foamed metal porous body having a thickness of 1000 μm and disposing no metal foil on either the positive electrode or the negative electrode, a solid secondary battery was produced in the same manner as in Example 1. The thickness of the porous metal substrate integrated with the mixture layer of the positive electrode and the negative electrode was 124 μm.

(Comparative Example 2)
A solid secondary battery was fabricated in the same manner as in Example 1, except that no porous metal substrate was used for either the positive electrode or the negative electrode, and the mixture layers of the positive electrode and the negative electrode were in direct contact with the stainless steel foil.

(Comparative Example 3)
Except for changing the porous metal substrate of the positive electrode and the negative electrode to a foamed metal porous body made of aluminum having a thickness of 1000 μm and disposing no metal foil on either the positive electrode or the negative electrode, a solid secondary battery was fabricated in the same manner as in Example 1. The thickness of the porous metal substrate integrated with the mixture layer of the positive electrode and the negative electrode was 120 μm.

The following tests were conducted on the solid-state secondary batteries of the examples and comparative examples.

(Charge/discharge test)
The solid secondary batteries of the examples and comparative examples were charged at a constant current of 0.1 C until the voltage reached 2.6 V, and then charged at a constant voltage of 0.01 C while maintaining the voltage at 2.6 V. After the constant voltage charging, the batteries were left without charging or discharging and the open circuit voltage was measured for 10 minutes, and then discharged at a constant current of 0.1 C until the voltage reached 1.0 V. After that, the batteries were similarly charged at a constant current of 0.2 C until the voltage reached 2.6 V, and then charged at a constant voltage while maintaining the voltage at 2.6 V until the current reached 0.01 C, and the initial resistance (impedance at 1 kHz) of the batteries was measured.

(Impact test)
After the charge/discharge test, each battery was subjected to 100 repeated impacts with an acceleration of 19,600 m/ ^s2 in the direction perpendicular to the lamination direction of the electrode laminate (xy direction), and the resistance value (impedance at 1 kHz) thereafter was measured.

The results of each of the above tests are shown in Table 1, along with the material of the current collector used for each electrode.

As shown in Table 1, in the solid secondary battery of Example 1, the resistance value after the impact test was the same as the initial resistance value, indicating excellent reliability, whereas in the battery of Comparative Example 2, which did not use a porous metal substrate and only had the electrode mixture layer in contact with the metal foil, the contact resistance between the electrode mixture layer and the current collector was large, the internal resistance was high from the beginning, and the resistance value after the impact test also increased, indicating poor reliability. In addition, in the batteries of Comparative Examples 1 and 3, in which the electrode mixture layer and the porous metal substrate were integrated but no metal foil was used, although the initial resistance value was low, the resistance value after the impact test increased, indicating poor reliability.

Regarding the embodiments of the present application including the above-mentioned Example 1, the following additional embodiments are disclosed.
(Additional Embodiment 1) A solid-state battery electrode including an electrode mixture layer containing an electrode active material and a solid electrolyte, and a current collector,
The current collector includes a porous metal substrate and a metal foil,
The porous metal substrate is integrated with the electrode mixture layer,
One side of the porous metal substrate is exposed from the electrode mixture layer,
An electrode for a solid-state battery, characterized in that one side of the porous metal substrate exposed from the electrode mixture layer is in contact with the metal foil.
(Additional feature 2) The electrode for a solid state battery according to additional feature 1, wherein the porous metal substrate and the metal foil are integrated together.
(Additional feature 3) The electrode for a solid battery according to additional feature 1 or 2, wherein the porous metal substrate integrated with the electrode mixture layer has a thickness of 15 to 300 μm.
(Additional feature 4) The electrode for a solid battery according to additional feature 1 or 2, wherein the porous metal substrate integrated with the electrode mixture layer has a thickness of 20 to 150 µm.
(Additional Form 5) The electrode for a solid state battery according to any one of Additional Forms 1 to 4, wherein the metal foil has a thickness of 5 to 300 μm.
(Additional Form 6) The electrode for a solid state battery according to any one of Additional Forms 1 to 4, wherein the metal foil has a thickness of 8 to 150 μm.
(Additional Embodiment 7) A solid-state battery including a battery container and an electrode stack in which a positive electrode having a current collector and a negative electrode having a current collector face each other via a solid electrolyte layer,
A solid-state battery comprising the electrode for a solid-state battery according to any one of claims 1 to 6 as at least one of the positive electrode and the negative electrode.
(Additional feature 8) The battery container has a concave container and a sealing body,
the hollow container has a bottom surface portion, a side wall portion, and an opening, and has a conductive path for a positive electrode and a conductive path for a negative electrode that lead from the inside to the outside,
the positive electrode current collector is in conductive connection with the conductive path for the positive electrode, and the negative electrode current collector is in conductive connection with the conductive path for the negative electrode,
8. The solid-state battery according to claim 7, wherein the opening of the hollow container is covered with the sealing body.
(Additional feature 9) An elastic conductive member is disposed between the electrode stack and the inner bottom surface of the sealing body,
9. The solid-state battery according to claim 8, wherein the elastic conductive member is electrically connected to the conductive path for the positive electrode or the conductive path for the negative electrode, and presses the electrode stack toward an inner bottom surface of the hollow container.

This application may be implemented in forms other than those described above. The embodiments disclosed in this application are merely examples and are not intended to be limiting. The scope of this application shall be interpreted in accordance with the appended claims rather than the above description, and all modifications within the scope of the claims are intended to be included in the scope of the claims.

REFERENCE SIGNS LIST 10, 11 Electrode for solid-state battery 20 Electrode mixture layer 30 Current collector 31 Porous metal substrate 32 Metal foil 100 Solid-state battery 110 Electrode laminate 120 Positive electrode 121 Positive electrode mixture layer 122 Positive electrode current collector 130 Negative electrode 131 Negative electrode mixture layer 132 Negative electrode current collector 140 Solid electrolyte layer 150 Concave container 151 Bottom portion 152 Side wall portion 153 Opening 154 Support portion 160 Sealing body 170 Elastic conductive member 171 Locking portion 172 Recess 180 Connection terminal portion 181 Conductive path 190 Connection terminal portion 191 Conductive path 200 Porous metal layer 210 Seal ring

Claims (7)

An electrode for a solid-state battery comprising an electrode mixture layer containing an electrode active material and a solid electrolyte, and a current collector,
The current collector includes a porous metal substrate and a metal foil,
The porous metal substrate is integrated with the electrode mixture layer,
One side of the porous metal substrate is exposed from the electrode mixture layer,
An electrode for a solid-state battery, characterized in that one side of the porous metal substrate exposed from the electrode mixture layer is in contact with the metal foil. The electrode for a solid-state battery according to claim 1, in which the porous metal substrate and the metal foil are integrated. The electrode for a solid-state battery according to claim 1, wherein the thickness of the porous metal substrate integrated with the electrode mixture layer is 15 to 300 μm. The electrode for a solid-state battery according to claim 1, wherein the thickness of the metal foil is 5 to 300 μm. A solid-state battery including a battery container and an electrode stack in which a positive electrode having a current collector and a negative electrode having a current collector face each other via a solid electrolyte layer,
A solid-state battery comprising the electrode for a solid-state battery according to any one of claims 1 to 4 as at least one of the positive electrode and the negative electrode. The battery container has a recessed container and a sealing body,
the hollow container has a bottom surface portion, a side wall portion, and an opening, and has a conductive path for a positive electrode and a conductive path for a negative electrode that lead from the inside to the outside,
the positive electrode current collector is in conductive connection with the conductive path for the positive electrode, and the negative electrode current collector is in conductive connection with the conductive path for the negative electrode,
The solid-state battery according to claim 5 , wherein the opening of the hollow container is covered with the sealing body. an elastic conductive member is disposed between the electrode stack and an inner bottom surface of the sealing body;
7. The solid-state battery according to claim 6, wherein the elastic conductive member is electrically connected to the conductive path for the positive electrode or the conductive path for the negative electrode, and presses the electrode stack against an inner bottom surface of the concave container.

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