All-solid-state battery and method for manufacturing same

Abstract

The present invention provides an all-solid-state battery which has excellent reliability, and a method for manufacturing the same.　An all-solid-state battery according to the present invention has an electrode body formed by stacking a positive electrode and a negative electrode with a solid electrolyte layer interposed therebetween. The solid electrolyte layer is characterized by being a multilayer body of a solid electrolyte layer (I) which has a porous base material and a portion that protrudes from the end of the positive electrode and the end of the negative electrode when viewed in plan, a solid electrolyte layer (II) which is bonded to the positive electrode and has a smaller area than the solid electrolyte layer (I) when viewed in plan, and a solid electrolyte layer (III) which is bonded to the negative electrode and has a smaller area than the solid electrolyte layer (I) when viewed in plan.

Description

All-solid-state battery and method for manufacturing the same

[0001] The present invention relates to a highly reliable all-solid-state battery and a manufacturing method thereof.

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

[0003] Currently, lithium batteries, especially lithium ion batteries, that can meet this requirement use lithium cobalt oxide (LiCoO ２ ), lithium nickel oxide (LiNiO ２ ), graphite or the like is used as the negative electrode active material, and an organic electrolyte solution containing an organic solvent and a lithium salt is used as the non-aqueous electrolyte.

[0004] Furthermore, with the further development of devices that use lithium-ion batteries, there is a demand for lithium-ion batteries with longer life, higher capacity, and higher energy density, as well as a high demand for the reliability of lithium-ion batteries with longer life, higher capacity, and higher energy density.

[0005] However, the organic electrolyte used in lithium-ion batteries contains flammable organic solvents, which can cause the organic electrolyte to generate excessive heat in the event of an abnormality such as a short circuit. 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 a growing demand for greater reliability in lithium-ion batteries.

[0006] In light of the above, all-solid-state lithium batteries (all-solid-state batteries) that do not use organic solvents are also being considered. All-solid-state lithium batteries use a molded body of a solid electrolyte that does not use an organic solvent instead of the conventional organic solvent-based electrolyte, and are highly reliable without the risk of abnormal heat generation of the solid electrolyte. Therefore, there are high expectations for them, especially in product fields that require high-capacity secondary batteries.

[0007] Furthermore, because all-solid-state batteries are not only highly safe but also highly reliable, environmentally resistant, and have a long lifespan, they are expected to be maintenance-free batteries that can continue to contribute to social development while also contributing to safety and security. Providing all-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 inclusive, safe, resilient, and sustainable cities and human settlements), and Goal 12 (Ensure sustainable consumption and production patterns) out of the 17 Sustainable Development Goals (SDGs) established by the United Nations.

[0008] Various studies have also been conducted on all-solid-state batteries. For example, Patent Document 1 proposes a secondary battery structure in which an insulating layer interposed between a positive electrode layer and a negative electrode layer is composed of an electrolyte layer and a polymer-rich layer having a larger amount of polymer than the electrolyte layer, in order to solve problems such as short circuits caused by the development of adhesiveness in a secondary battery having an electrolyte with low fluidity, such as a solid electrolyte. The electrolyte layer is disposed on the positive electrode layer and negative electrode layer side.

[0009] Furthermore, Patent Documents 2 to 5 propose that a solid electrolyte sheet having both lithium ion conductivity and strength is obtained by filling pores in a substrate made of a porous substrate such as a nonwoven fabric with a solid electrolyte, and that this solid electrolyte sheet is used to construct an all-solid-state secondary battery.

[0010] Of these, Patent Document 5 discloses that by making the thickness of the porous substrate 70% or more of the thickness of the entire solid electrolyte sheet, the mechanical strength of the solid electrolyte sheet can be improved, and even if the area of ​​the solid electrolyte sheet is increased, damage to the solid electrolyte and separation of the solid electrolyte from the porous substrate can be prevented.

[0011] JP 2019-16573 A JP 2015-153460 A JP 2016-139482 A International Publication No. 2019 / 208347 International Publication No. 2020 / 054081

[0012] The technology described in Patent Document 5, for example, makes it possible to increase the size of an all-solid-state battery, thereby achieving a higher capacity. However, when a positive electrode having a positive electrode mixture layer containing a positive electrode active material or a negative electrode having a negative electrode mixture layer containing a negative electrode active material is integrated with a solid electrolyte sheet having a porous substrate by, for example, pressure molding, cracks may occur in the solid electrolyte sheet, causing a short circuit in the battery, or the solid electrolyte sheet may become insufficiently bonded to the positive electrode or negative electrode, causing the solid electrolyte sheet to peel off from the positive electrode or negative electrode. Therefore, in all-solid-state batteries having a solid electrolyte sheet as a solid electrolyte layer, there is a need to develop a technology that suppresses the occurrence of such problems and improves reliability.

[0013] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an all-solid-state battery with excellent reliability and a method for manufacturing the same.

[0014] The all-solid-state battery of the present invention has an electrode body in which a positive electrode and a negative electrode are stacked with a solid electrolyte layer interposed therebetween, and the solid electrolyte layer is a laminate of a solid electrolyte layer (I) having a porous substrate and portions protruding from ends of the positive electrode and the negative electrode in a planar view, a solid electrolyte layer (II) joined to the positive electrode and having a smaller area in a planar view than the solid electrolyte layer (I), and a solid electrolyte layer (III) joined to the negative electrode and having a smaller area in a planar view than the solid electrolyte layer (I).

[0015] Further, a method for producing an all-solid-state battery of the present invention is a method for producing an all-solid-state battery having an electrode assembly in which a positive electrode and a negative electrode are stacked with a solid electrolyte layer interposed therebetween, the solid electrolyte layer being a laminate of a solid electrolyte layer (I) having a porous substrate, a solid electrolyte layer (II) bonded to the positive electrode, and a solid electrolyte layer (III) bonded to the negative electrode, the method comprising the steps of: preparing a solid electrolyte sheet having a porous substrate and a solid electrolyte held on the porous substrate; preparing a positive electrode coated on one side with a solid electrolyte; preparing a negative electrode coated on one side with a solid electrolyte; bonding the positive electrode to one side of the solid electrolyte sheet such that the solid electrolyte covering the positive electrode is in contact with the solid electrolyte; and bonding the negative electrode to the other side of the solid electrolyte sheet such that the solid electrolyte covering the negative electrode is in contact with the solid electrolyte; and the solid electrolyte layer is formed by pressurizing the solid electrolyte sheet, the solid electrolyte covering the positive electrode, and the solid electrolyte covering the negative electrode.

[0016] According to the present invention, it is possible to provide an all-solid-state battery with excellent reliability and a method for manufacturing the same.

[0017] FIG. 1 is a cross-sectional view schematically illustrating an example of an all-solid-state battery of the present invention.

[0018] The all-solid-state battery of the present invention has an electrode assembly in which a positive electrode and a negative electrode are stacked with a solid electrolyte layer interposed therebetween. The solid electrolyte layer includes the following three layers: solid electrolyte layer (I), solid electrolyte layer (II), and solid electrolyte layer (III), and these three layers are stacked together.

[0019] The solid electrolyte layer (I) has a porous substrate and has portions that protrude from the ends of the positive electrode and the negative electrode in plan view. The solid electrolyte layer (II) is bonded to the positive electrode and has a smaller area in plan view than the solid electrolyte layer (I). The solid electrolyte layer (III) is bonded to the negative electrode and has a smaller area in plan view than the solid electrolyte layer (I).

[0020] A cross-sectional view schematically illustrating an example of an all-solid-state battery of the present invention is shown in Fig. 1. The all-solid-state battery 10 shown in Fig. 1 includes an exterior body formed of an exterior can 50, a sealing can 60, and a resin gasket 70 interposed between them, and encapsulates a positive electrode 20, a negative electrode 30, and a solid electrolyte layer 40 interposed between the positive electrode 20 and the negative electrode 30.

[0021] The sealing can 60 is fitted into the opening of the outer can 50 via a gasket 70, and the open end of the outer can 50 is tightened inward, causing the gasket 70 to abut against the sealing can 60, thereby sealing the opening of the outer can 50 and creating an airtight structure inside the battery.

[0022] The outer can and the sealing can can be made of stainless steel or the like. The gasket can be made of polypropylene, nylon, or the like. If heat resistance is required for the battery's intended use, heat-resistant resins with melting points exceeding 240°C, such as fluororesins such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyphenylene ether (PPE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), polyphenylene sulfide (PPS), and polyetheretherketone (PEEK), can also be used. If the battery is used in an application requiring heat resistance, a glass hermetic seal can be used for sealing.

[0023] The solid electrolyte layer 40 includes a solid electrolyte layer (I) 41 having a porous substrate, a solid electrolyte layer (II) 42 joined to the positive electrode 20, and a solid electrolyte layer (III) 43 joined to the negative electrode 30.

[0024] As described above, when an electrode body is formed using a solid electrolyte sheet having a porous substrate, if the solid electrolyte sheet is bonded to a positive electrode or a negative electrode by pressure molding, the bonding between the positive electrode (a compact of a positive electrode mixture containing a positive electrode active material or a positive electrode mixture layer) and the negative electrode (a compact of a negative electrode mixture containing a negative electrode active material or a negative electrode mixture layer) may be insufficient, or cracks may occur in the solid electrolyte sheet.

[0025] However, as shown in Figure 1, when the solid electrolyte layer of the electrode assembly is configured to have a solid electrolyte layer (I) containing a porous substrate and solid electrolyte layers (II) and (III) disposed on both sides of the solid electrolyte layer (I), for example, a positive electrode having a solid electrolyte coating layer pre-formed on the surface of a positive electrode mixture compact (positive electrode mixture layer) facing the solid electrolyte layer (I), and a negative electrode having a solid electrolyte coating layer pre-formed on the surface of a negative electrode mixture compact (negative electrode mixture layer) facing the solid electrolyte layer (I), the electrode assembly can be formed by pressure molding these coating layers on the solid electrolyte layer (I) side. In this way, the solid electrolyte layers (II) and (III) are well bonded to the solid electrolyte layer (I), and excessive pressure on the solid electrolyte layer (I) (solid electrolyte sheet) can be avoided when applying pressure during electrode assembly formation. Therefore, it is possible to effectively suppress the deterioration of battery characteristics due to peeling of the solid electrolyte layer from the positive electrode and the negative electrode during the manufacture or use of the all-solid-state battery, and the occurrence of short circuits due to cracking of the solid electrolyte layer (solid electrolyte sheet), thereby providing the all-solid-state battery of the present invention with excellent reliability and also enabling increased productivity.

[0026] As shown in FIG. 1, the solid electrolyte layer of the all-solid-state battery preferably has a solid electrolyte layer (I) whose outer periphery extends beyond the ends of the positive and negative electrodes in a plan view of the electrode body (when viewed from above or below in FIG. 1), and the solid electrolyte layers (II) and (III) have a smaller area than the solid electrolyte layer (I) in a plan view. This configuration allows the solid electrolyte layer (II) to have an area equivalent to that of the positive electrode mixture compact (positive electrode mixture layer) of the positive electrode, and the solid electrolyte layer (III) to have an area equivalent to that of the negative electrode mixture compact (negative electrode mixture layer) of the negative electrode. That is, the size of the solid electrolyte layer (II) can be the same as that of the positive electrode (positive electrode mixture layer), and the size of the solid electrolyte layer (III) can be the same as that of the negative electrode (negative electrode mixture layer). Therefore, for example, the positive electrode mixture compact (positive electrode mixture layer) and the solid electrolyte layer (II), and the negative electrode mixture compact (negative electrode mixture layer) and the solid electrolyte layer (III) can be formed using a common mold (such as a metal mold), while the large-area solid electrolyte layer (I) can effectively prevent contact between the positive electrode and the negative electrode even if they are misaligned during assembly. Therefore, this action also makes it possible for the all-solid-state battery of the present invention to improve productivity and reliability. Note that it is preferable that the outer periphery of the solid electrolyte layer (I) protrudes from the ends of the positive electrode and the negative electrode over the entire periphery. That is, it is preferable that the portions of the solid electrolyte layer (I) protruding from the ends of the positive electrode and the negative electrode are formed in an annular shape.

[0027] Next, each component of the all-solid-state battery of the present invention will be described in detail. The all-solid-state battery of the present invention includes a primary battery and a secondary battery.

[0028] <Solid Electrolyte Layer> [Solid Electrolyte Layer (I)] The solid electrolyte layer (I) has a porous substrate, and at least a part of the solid electrolyte constituting the solid electrolyte layer (I) is present in a state of being held inside the porous substrate.

[0029] The solid electrolyte layer (I) can be formed by using a solid electrolyte sheet obtained by filling the inside of a porous substrate with a solid electrolyte.

[0030] The porous substrate of the solid electrolyte sheet may be made of a fibrous material, and for example, a woven fabric, a nonwoven fabric, a mesh, or the like is preferred, with the nonwoven fabric being particularly preferred.

[0031] The fiber diameter of the fibrous material constituting the porous substrate is preferably 5 μm or less, and is preferably 0.5 μm or more.

[0032] The material of the fibrous material is not particularly limited as long as it does not react with metallic lithium and has insulating properties. For example, resins such as polyolefins such as polypropylene and polyethylene; polystyrene; aramid; polyamideimide; polyimide; nylon; polyesters such as polyethylene terephthalate (PET); polyarylate; cellulose or modified cellulose; etc. may be used. Inorganic materials such as glass, alumina, silica, and zirconia may also be used. A preferred material is polyarylate. The fibrous material may be composed of one or more of the above-mentioned materials. The porous substrate may be composed of only fibrous materials of the same material, or may be composed of a combination of two or more fibrous materials made of different materials.

[0033] The basis weight of the porous substrate is 10 g / m so as to be able to hold a sufficient amount of solid electrolyte to ensure good lithium ion conductivity and to ensure good lithium dendrite growth suppression function. ２ Preferably, it is 8 g / m or less. ２ It is more preferable that the thickness is 3 g / m or less, and from the viewpoint of ensuring sufficient strength, ２ It is preferable that the content is 4 g / m or more. ２ More preferably, it is equal to or greater than this.

[0034] The solid electrolyte contained in the solid electrolyte sheet is not particularly limited as long as it has lithium ion conductivity, and for example, a sulfide-based solid electrolyte, a hydride-based solid electrolyte, a halide-based solid electrolyte, an oxide-based solid electrolyte, etc. can be used.

[0035] The sulfide-based solid electrolyte is Li ２ S-P ２ S５ , Li ２ S-SiS ２ , Li ２ S-P ２ S ５ -GeS ２ , Li ２ S-B ２ S ３ In addition to particles such as glass particles, thio-LISICON type particles [Li １０ GeP ２ S １２ , Li ９．５４ Si １．７４ P １．４４ S １１．７ Cl ０．３ Li12-12a-b+c+6d-eM, etc. １ ３＋ａ－ｂ－ｃ－ｄ M ２ ｂ M ３ ｃ M ４ ｄ 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, and X is F, Cl, Br or I, 0≦a<3, 0≦b+c+d≦3, 0≦e≦3], or argyrodite type [Li ６ P.S. ５ Li, such as Cl ７－ｋ P.S. ６－ｋ X ｋ (wherein X represents one or more halogen elements, and 0.2<k<2.0), Li ７－ｆ＋ｇ P.S. ６－ｆ Cl ｆ＋ｇ (wherein 0.05≦g≦0.9, −3.0f+1.8≦g≦−3.0f+5.7), Li ７－ｈ P.S. ６－ｈ Cl ｉ Br ｊ(where h=i+j, 0<h≦1.8, 0.1≦i / j≦10.0) can also be used.

[0036] Examples of hydride-based solid electrolytes include LiBH ４ , LiBH ４ and a solid solution of the following alkali metal compound (e.g., LiBH ４ and the alkali metal compound in a molar ratio of 1:1 to 20:1. The alkali metal compound in the solid solution may be 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.

[0037] Examples of halide-based solid electrolytes include monoclinic LiAlCl ４ , defect spinel type or layer structure LiInBr ４ , monoclinic Li ６－３ｍ Y ｍ X ６ (wherein 0 < m < 2 and X = Cl or Br), and other known compounds described in, for example, WO 2020 / 070958 and WO 2020 / 070955 can also be used.

[0038] As the oxide-based solid electrolyte, for example, garnet-type Li ７ La ３ Zr ２ O １２ , NASICON type Li １＋Ｏ Al １＋Ｏ Ti ２－Ｏ (P.O. ４ ) ３ , Li １＋ｐ Al １＋ｐ Ge ２－ｐ (P.O. ４ ) ３ , perovskite-type Li ３ｑ La ２／３－ｑ TiO ３ Examples include:

[0039] The solid electrolyte may be one of the above-mentioned examples, or two or more of them may be used in combination. Among these solid electrolytes, sulfide-based solid electrolytes are preferred because of their high lithium ion conductivity, sulfide-based solid electrolytes containing Li and P are more preferred, and sulfide-based solid electrolytes having an argyrodite structure, which have particularly high lithium ion conductivity and high chemical stability, are even more preferred.

[0040] The solid electrolyte is preferably in the form of particles, and the size thereof is preferably 5 μm or less, more preferably 2 μm or less, on the basis of improving the filling of the pores of the porous substrate and ensuring good lithium ion conductivity. However, if the size of the solid electrolyte particles is too small, there is a risk of reduced handleability. Furthermore, as will be described later, the solid electrolyte particles are preferably bound using a binder to ensure good retention within the pores of the porous substrate and good adhesion to the surface of the porous substrate. In this case, however, a larger amount of binder is required, which may result in an increase in resistance. Therefore, the average particle size of the solid electrolyte particles is preferably 0.3 μm or more, more preferably 0.5 μm or more.

[0041] The average particle diameter of the solid electrolyte particles and other particles (positive electrode active material, negative electrode active material, etc.) referred to in this specification is the 50% diameter value (D) in the volume-based integrated fraction when the integrated volume is calculated from particles with small particle sizes using a particle size distribution measuring device (e.g., a Microtrac particle size distribution measuring device "HRA9320" manufactured by Nikkiso Co., Ltd.). ５０ ) means

[0042] The edges of the porous substrate may be exposed on the surface of the solid electrolyte sheet, but in this case, it is desirable that the solid electrolyte be exposed along with the edges of the porous substrate in order to facilitate smoother movement of lithium ions between the positive electrode and the negative electrode. Alternatively, the surface of the solid electrolyte sheet and its vicinity may be free of the porous substrate and may be composed only of the solid electrolyte (and a binder, etc., as described below).

[0043] In the solid electrolyte sheet, it is preferable to use a binder to bind the solid electrolyte, by favorably retaining the solid electrolyte in the pores of the porous substrate and improving the adhesion of the solid electrolyte covering the surface of the porous substrate to the porous substrate, thereby increasing the shape retention of the solid electrolyte sheet and improving the adhesion to the solid electrolyte layer (II) and the solid electrolyte layer (III).

[0044] The binder for the solid electrolyte sheet is preferably one that does not react with the solid electrolyte, and at least one resin selected from the group consisting of butyl rubber, chloroprene rubber, acrylic resin, and fluororesin is preferably used.

[0045] The thickness of the solid electrolyte sheet is preferably 5 μm or more, more preferably 10 μm or more, from the viewpoint of optimizing the distance between the positive electrode and the negative electrode of a battery using the solid electrolyte sheet and suppressing the occurrence of a short circuit or an increase in resistance, and is preferably 50 μm or less, more preferably 30 μm or less.

[0046] In the solid electrolyte sheet, the thickness of the porous substrate is preferably 85% or less, and more preferably 80% or less, of the thickness of the solid electrolyte sheet, from the viewpoint of ensuring smooth movement of lithium ions on the positive electrode side and smooth movement of lithium ions on the negative electrode side, and also of better ensuring the effect of suppressing precipitation of lithium dendrites that cause charging abnormalities, with the solid electrolyte covering the surface of the porous substrate having the above-mentioned thickness.

[0047] The porous substrate serves as a component for enhancing the shape retention of the solid electrolyte sheet, but if the thickness ratio of the porous substrate to the solid electrolyte sheet is too small, the shape retention of the solid electrolyte sheet may be reduced. Furthermore, if the thickness ratio of the porous substrate to the solid electrolyte sheet is relatively large, the effect of smoothing the movement of lithium ions on the positive electrode side and the negative electrode side, as well as suppressing metal precipitation that causes charging abnormalities, becomes more pronounced. For these reasons, the thickness of the porous substrate is preferably 30% or more, and more preferably 50% or more, of the thickness of the solid electrolyte sheet.

[0048] Specifically, the thickness of the porous substrate is, for example, preferably 3 μm or more, more preferably 8 μm or more, and preferably 45 μm or less, more preferably 25 μm or less.

[0049] The proportion of the porous substrate in the solid electrolyte sheet (the proportion of the actual volume excluding the pores) is preferably 30% by volume or less, and more preferably 25% by volume or less, from the viewpoint of ensuring good lithium ion conductivity. However, if the proportion of the porous substrate in the solid electrolyte sheet is too small, the effect of improving the shape retention of the solid electrolyte sheet may be reduced. Therefore, from the viewpoint of further increasing the strength of the solid electrolyte sheet, the proportion of the porous substrate in the solid electrolyte sheet is preferably 5% by volume or more, and more preferably 10% by volume or more.

[0050] Furthermore, from the viewpoint of further enhancing the shape retention of the solid electrolyte sheet, the content of the binder in the solid electrolyte sheet is preferably 0.5 mass % or more, and preferably 1 mass % or more, of the total amount of the solid electrolyte and the binder. Furthermore, from the viewpoint of restricting the amount of the binder to some extent and suppressing a decrease in lithium ion conductivity, the content of the binder is preferably 5 mass % or less, and preferably 3 mass % or less.

[0051] Although there are no particular limitations on the method for producing a solid electrolyte sheet, it is preferable to produce it by a method including a step of dispersing a solid electrolyte and an optional binder in a solvent to prepare a slurry for forming a solid electrolyte layer, and then wet-filling the voids of a porous substrate with the slurry (filling step). Furthermore, when the surface portion of the solid electrolyte sheet is composed only of the solid electrolyte (and binder, etc.) without the presence of a porous substrate, the filling step may involve filling the voids of the porous substrate with the slurries while forming coatings of the slurries on the surface of the porous substrate. This method improves the strength of the solid electrolyte sheet and facilitates the production of large-area solid electrolyte sheets.

[0052] As a method for filling the voids of the porous substrate with a slurry containing a solid electrolyte, or for forming a coating film of the slurry on the surface of the porous substrate, coating methods such as screen printing, doctor blade method, and dipping method can be used.

[0053] The slurry is prepared by adding a solid electrolyte and, if necessary, a binder to a solvent and mixing them. It is preferable to select a solvent for the slurry that is less likely to deteriorate the solid electrolyte. In particular, sulfide-based solid electrolytes and hydride-based solid electrolytes undergo chemical reactions with trace amounts of water, so it is preferable to use nonpolar aprotic solvents, such as hydrocarbon solvents such as hexane, heptane, octane, nonane, decane, decalin, toluene, and xylene. It is particularly preferable to use an ultra-dehydrated solvent with a water content of 0.001% by mass (10 ppm) or less. Fluorine-based solvents such as "Vertrel (registered trademark)" manufactured by DuPont-Mitsui Fluorochemicals, "Zeorolla (registered trademark)" manufactured by Nippon Zeon Co., Ltd., and "Novec (registered trademark)" manufactured by Sumitomo 3M Company, Ltd., as well as nonaqueous organic solvents such as dichloromethane and diethyl ether can also be used.

[0054] After filling the voids in the porous substrate with the slurry or forming a coating of the slurry on the surface of the porous substrate as described above, the solvent in the slurry is removed by drying, and pressure molding is performed as necessary to obtain a solid electrolyte sheet.

[0055] As mentioned above, the manufacturing method of the solid electrolyte sheet is not limited to the wet method. For example, when filling the pores of the porous substrate with the solid electrolyte (and a binder used as needed), the solid electrolyte or a mixture of the solid electrolyte and the binder may be dry-filled, followed by pressure molding. In addition, when covering the surface of the porous substrate with the solid electrolyte, a sheet obtained by molding a mixture of the solid electrolyte and the binder may be attached to the surface of a sheet of the porous substrate in which the pores are filled with the solid electrolyte.

[0056] The solid electrolyte layer (I) produced using the solid electrolyte sheet preferably has its outer periphery protruding from the positive electrode [the compact of the positive electrode mixture (positive electrode mixture layer)] and the negative electrode [the compact of the negative electrode mixture (negative electrode mixture layer)] in a plan view, and the width of the protruding portion [the length of the shortest distance from the end of the compact of the positive electrode mixture (positive electrode mixture layer) and the compact of the negative electrode mixture (negative electrode mixture layer) to the end of the solid electrolyte layer (I)] can be, for example, 1 μm to 1 mm.

[0057] [Solid Electrolyte Layer (II) and Solid Electrolyte Layer (III)] The solid electrolyte layer (II) and the solid electrolyte layer (III) contain a solid electrolyte, and specific examples of the solid electrolyte include the same sulfide-based solid electrolytes, hydride-based solid electrolytes, halide-based solid electrolytes, and oxide-based solid electrolytes as those exemplified above for constituting the solid electrolyte layer (I).

[0058] The solid electrolyte of the solid electrolyte layer (II) and the solid electrolyte layer (III) may be one of the above-mentioned examples, or two or more of them may be used in combination. Among these solid electrolytes, sulfide-based solid electrolytes are preferred because of their high lithium ion conductivity, sulfide-based solid electrolytes containing Li and P are more preferred, and sulfide-based solid electrolytes having an argyrodite structure, which have particularly high lithium ion conductivity and high chemical stability, are even more preferred.

[0059] The solid electrolyte contained in the solid electrolyte layer (I), the solid electrolyte contained in the solid electrolyte layer (II), and the solid electrolyte contained in the solid electrolyte layer (III) may be the same type in all layers, or the same type may be used in two of the three layers and a different type may be used in the remaining layer, or different types may be used in each layer. For example, the solid electrolyte contained in at least one of the solid electrolyte layer (II) and the solid electrolyte layer (III) may be a different type from the solid electrolyte contained in the solid electrolyte layer (I).

[0060] The solid electrolyte layer (II) and the solid electrolyte layer (III) may contain a binder. The binder contained in the solid electrolyte layer (II) and the solid electrolyte layer (III) may be the same as the binders exemplified above as those that may be contained in the solid electrolyte layer (I).

[0061] When the solid electrolyte layer (II) and the solid electrolyte layer (III) contain a binder, the content is preferably 2 to 10 mass % (the remainder can be solid electrolyte). In the solid electrolyte layer (II) and the solid electrolyte layer (III), if good formability can be ensured without containing a binder, the solid electrolyte layer (II) and the solid electrolyte layer (III) may not contain a binder, and may be formed, for example, from a solid electrolyte alone (the binder content may be 0 mass %). Note that it is also possible for only one of the solid electrolyte layer (II) and the solid electrolyte layer (III) to contain no binder, and the other to contain a binder.

[0062] The thickness of each of the solid electrolyte layer (II) and the solid electrolyte layer (III) is preferably 1 to 10 μm. The thickness of the solid electrolyte layer (II) and the thickness of the solid electrolyte layer (III) may be the same or different.

[0063] The areas of the solid electrolyte layer (II) and the solid electrolyte layer (III) in a planar view can be smaller than the area of ​​the solid electrolyte layer (I) in a planar view, and can be the same as, for example, the area of ​​the compact of the positive electrode mixture (positive electrode mixture layer) and the area of ​​the compact of the negative electrode mixture (negative electrode mixture layer).

[0064] The solid electrolyte layer (II) and the solid electrolyte layer (III) can be formed by arranging a solid electrolyte or the like in a layer on the surface of the solid electrolyte sheet, and then pressure-molding the layer in a state in which it is overlapped with a molded body of a positive electrode mixture (positive electrode mixture layer) or a molded body of a negative electrode mixture (negative electrode mixture layer). However, it is preferable to use a previously formed molded body of a positive electrode mixture (positive electrode mixture layer) or a molded body of a negative electrode mixture (negative electrode mixture layer) as a base material, arrange a solid electrolyte or the like in a layer on one surface of the base material to coat one side with the solid electrolyte, and then pressure-molde the layer in a state in which it is overlapped with the solid electrolyte sheet.

[0065] (Total Thickness of Solid Electrolyte Layer) The total thickness of the solid electrolyte layer [total thickness of the solid electrolyte layer (I), the solid electrolyte layer (II), and the solid electrolyte layer (III)] is preferably 5 μm or more, more preferably 20 μm or more, and is preferably 100 μm or less, more preferably 50 μm or less, from the viewpoint of optimizing the distance between the positive electrode and the negative electrode of the battery and suppressing the occurrence of a short circuit or an increase in resistance.

[0066] <Positive Electrode> Examples of the positive electrode of the all-solid-state battery include a structure in which a layer (positive electrode mixture layer) made of a compact of a positive electrode mixture containing a positive electrode active material and a solid electrolyte is formed on a current collector, a structure in which only a compact of a positive electrode mixture (pellets, etc.) is formed, and a structure in which a positive electrode mixture containing a positive electrode active material and a solid electrolyte is filled into the pores of a conductive porous substrate.

[0067] When the all-solid-state battery is a primary battery, the positive electrode active material can be the same as the positive electrode active material used in conventionally known non-aqueous electrolyte primary batteries. Specifically, for example, manganese dioxide, lithium-containing manganese oxide (e.g., LiMn ３ O ６or a composite oxide having the same crystal structure as manganese dioxide (e.g., β-type, γ-type, or a mixed structure of β-type and γ-type) 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, particularly preferably 1% by mass or less); ａ Ti ５／３ O ４ (4 / 3≦a<7 / 3) and other lithium-containing composite oxides; vanadium oxide; niobium oxide; titanium oxide; sulfides such as iron disulfide; graphite fluoride; Ag ２ Silver sulfides such as S; NiO ２ Nickel oxides such as:

[0068] In addition, when the all-solid-state battery is used as the positive electrode of the secondary battery, the same positive electrode active material as that used in conventionally known non-aqueous electrolyte secondary batteries can be used. ｒ Mn ２－ｒ O ４ (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), a spinel-type lithium manganese composite oxide represented by Li ｒ Mn （１－ｓ－ｒ） Ni ｓ M ｔ O （２－ｕ） F ｖ (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 layered compound represented by 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), lithium cobalt composite oxide represented by LiNi １－ｒ M ｒ O２ (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), a lithium nickel composite oxide represented by Li １＋ｓ M １－ｒ N ｒ P.O. ４ F 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≦r≦0.5, 0≦s≦1), 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)

[0069] When the all-solid-state battery is a secondary battery, the average particle size of the positive electrode active material is preferably 1 μm or more, more preferably 2 μm or more, and preferably 10 μm or less, more preferably 8 μm or less. The positive electrode active material may be primary particles or secondary particles formed by aggregation of primary particles. When a positive electrode active material having an average particle size within the above range is used, a large interface with the solid electrolyte contained in the positive electrode can be secured, thereby further improving the output characteristics of the battery.

[0070] When the all-solid-state battery is a secondary battery, the positive electrode active material preferably has a reaction suppression layer on its surface to suppress reaction with the solid electrolyte contained in the positive electrode.

[0071] If the positive electrode active material and the solid electrolyte come into direct contact in the positive electrode, the solid electrolyte may oxidize to form a resistance layer, which may reduce ionic conductivity in the positive electrode. By providing a reaction suppression layer on the surface of the positive electrode active material that suppresses reaction with the solid electrolyte and preventing direct contact between the positive electrode active material and the solid electrolyte, it is possible to suppress the reduction in ionic conductivity in the positive electrode due to oxidation of the solid electrolyte.

[0072] The reaction suppression layer may be made of a material that has ion conductivity and can suppress the reaction between the particles of the electrode active material (positive 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, LiNbO ３ Nb-containing oxides such as Li ３ P.O. ４ , Li ３ BO ３ , Li ２ SO ４ , Li ４ SiO ４ , Li ４ GeO ４ , LiTiO ３ , LiZrO ３ , Li ２ WO ４ The reaction suppression layer may contain only one of these oxides, or may contain two or more of them, or may contain a composite compound of two or more of these oxides. Among these oxides, it is preferable to use an Nb-containing oxide, such as LiNbO ３ It is more preferable to use

[0073] The reaction suppression layer is preferably present on the surface in an amount of 0.1 to 1.0 part by mass per 100 parts by mass of the positive electrode active material, which allows for effective suppression of the reaction between the positive electrode active material and the solid electrolyte.

[0074] Examples of methods for forming a reaction suppression layer on the surface of a positive electrode active material include the sol-gel method, mechanofusion method, CVD method, PVD method, and ALD method.

[0075] The content of the positive electrode active material in the positive electrode mixture is preferably 60 to 85 mass % from the viewpoint of increasing the energy density of the all-solid-state battery.

[0076] The positive electrode mixture may contain a conductive additive. Specific examples thereof include carbon materials such as graphite (natural graphite, artificial graphite), graphene, carbon black, carbon nanofibers, and carbon nanotubes. ２ When S is used, conductive Ag is generated during the discharge reaction, so the conductive additive does not need to be contained. When the conductive additive is contained in the positive electrode mixture, the content thereof is preferably 1.0 part by mass or more, preferably 7.0 parts by mass or less, and more preferably 6.5 parts by mass or less, relative to 100 parts by mass of the positive electrode active material.

[0077] The positive electrode mixture may contain a binder. Specific examples include fluororesins such as polyvinylidene fluoride (PVDF). Note that, for example, when a sulfide-based solid electrolyte is contained in the positive electrode mixture (described later), the positive electrode mixture may not contain a binder if good moldability can be ensured in forming the positive electrode without using a binder.

[0078] When a binder is required in the positive electrode mixture, the content thereof is preferably 15% by mass or less, and preferably 0.5% by mass or more. On the other hand, when moldability can be obtained in the positive electrode mixture without a binder, the content thereof 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 contained).

[0079] The positive electrode mixture may contain a solid electrolyte.

[0080] The solid electrolyte contained in the positive electrode mixture is not particularly limited as long as it has lithium ion conductivity. For example, the sulfide-based solid electrolyte, hydride-based solid electrolyte, halide-based solid electrolyte, oxide-based solid electrolyte, and the like, which are exemplified above as those usable for the solid electrolyte layer of the solid electrolyte sheet, can be used.

[0081] 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 active material and the solid electrolyte.

[0082] From the viewpoint of further increasing ionic conductivity in the positive electrode and further improving the output characteristics of the all-solid-state battery, the content of the solid electrolyte in the positive electrode mixture is preferably 10 parts by mass or more, and more preferably 15 parts by mass or more, when the content of the positive electrode active material is 100 parts by mass. However, if the amount of solid electrolyte in the positive electrode mixture is too large, the amounts of other components may be reduced, and the effects of these components may be reduced. Therefore, the content of solid electrolyte in the positive electrode mixture is preferably 65 parts by mass or less, and more preferably 60 parts by mass or less, when the content of the positive electrode active material is 100 parts by mass.

[0083] When a current collector is used for the positive electrode, the current collector can be a metal foil such as aluminum or stainless steel; a sheet-like conductive porous substrate such as punched metal, mesh, expanded metal, or foamed metal; or a carbon sheet. The sheet-like conductive porous substrate is preferably a foamed metal porous body. Specific examples of foamed metal porous bodies include "Celmet (registered trademark)" from Sumitomo Electric Industries, Ltd.

[0084] The positive electrode can be produced by a method in which a positive electrode mixture-containing composition (paste, slurry, etc.) obtained by dispersing a positive electrode active material, a solid electrolyte, and optionally added conductive additives, binders, etc. in a solvent is applied to a current collector, dried, and then pressure-molded, as required, by calendaring or the like, to form a molded body of the positive electrode mixture (positive electrode mixture layer) on the surface of the current collector.

[0085] As the solvent for the positive electrode mixture-containing composition, water or an organic solvent such as N-methyl-2-pyrrolidone (NMP) can be used. However, when a solid electrolyte that is highly reactive to water is used, it is desirable to select a solvent that is unlikely to deteriorate the solid electrolyte. It is preferable to use the same solvents as those exemplified above as the solvent for the slurry for forming the solid electrolyte sheet.

[0086] In addition to the above-mentioned method, the compact of the positive electrode mixture may be formed by compressing a positive electrode mixture prepared by mixing a positive electrode active material and a solid electrolyte with a conductive additive, a binder, etc., which are added as needed, by pressure molding, etc. As described above, the compact of the positive electrode mixture obtained by such a method can be used as a positive electrode as it is, or it can also be used as a positive electrode after being bonded to a current collector by pressure bonding, etc.

[0087] The thickness of the positive electrode mixture compact (positive electrode mixture layer) formed using the solvent-containing positive electrode mixture-containing composition (when a current collector is included, the thickness per one surface of the current collector) is preferably 10 to 1000 μm. The thickness of the positive electrode mixture compact obtained by pressure molding is preferably 0.15 to 4 mm.

[0088] The thickness of the positive electrode current collector is preferably 0.01 to 0.1 mm.

[0089] Furthermore, when a conductive porous substrate is used for the positive electrode current collector, the positive electrode can be produced, for example, by filling the pores of the conductive porous substrate with the positive electrode mixture-containing composition, drying the composition, and then, if necessary, performing pressure molding such as calendaring.

[0090] Furthermore, instead of the above-described positive electrode mixture-containing composition, a positive electrode mixture containing a positive electrode active material, a solid electrolyte, and further a conductive additive and a binder, etc., but not containing a solvent, may be dry-filled into the pores of a conductive porous substrate, and the resulting mixture may be subjected to pressure molding such as calendaring as necessary, to produce a positive electrode.

[0091] In the case of a positive electrode obtained by filling the pores of a conductive porous substrate with a positive electrode mixture-containing composition or a positive electrode mixture, the thickness is preferably 30 to 4000 μm.

[0092] The negative electrode of the all-solid-state battery has, for example, a molded body of a negative electrode mixture containing a negative electrode active material, a lithium sheet, or a lithium alloy sheet. Alternatively, a conductive porous substrate having pores filled with a negative electrode mixture containing a negative electrode active material can also be used as the negative electrode.

[0093] When the negative electrode is a molded body of a negative electrode mixture containing a negative electrode active material, examples of the negative electrode include a structure in which a layer (negative electrode mixture layer) made of a molded body of the negative electrode mixture is formed on a current collector, and a structure in which only a molded body (pellet, etc.) made of a molded negative electrode mixture is formed.

[0094] Examples of the negative electrode active material include carbon materials such as graphite, lithium titanium oxides (lithium titanate, etc.), simple substances containing elements such as Si and Sn, compounds (oxides, etc.), and alloys thereof. Lithium metal and lithium alloys (lithium-aluminum alloys, lithium-indium alloys, etc.) can also be used as the negative electrode active material.

[0095] The content of the negative electrode active material in the negative electrode mixture is preferably 40 to 80 mass % from the viewpoint of increasing the energy density of the battery.

[0096] The negative electrode mixture may contain a conductive additive. Specific examples include the same conductive additives as those exemplified above as the conductive additives that may be contained in the positive electrode mixture. The content of the conductive additive in the negative electrode mixture is preferably 10 to 30 parts by mass, relative to 100 parts by mass of the negative electrode active material.

[0097] The negative electrode mixture may contain a binder. Specific examples thereof include the same binders as those exemplified above as binders that may be contained in the positive electrode mixture. Note that, for example, when a sulfide-based solid electrolyte is contained in the negative electrode mixture (described later), if good moldability can be ensured in forming the negative electrode mixture layer without using a binder, the negative electrode mixture need not contain a binder.

[0098] When a binder is required in the negative electrode mixture, the content thereof is preferably 15% by mass or less, and preferably 0.5% by mass or more. On the other hand, when the negative electrode mixture can be molded without a binder, the content thereof 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 contained).

[0099] The negative electrode mixture can contain a solid electrolyte. Specific examples include the same solid electrolytes as those exemplified above as those that can be contained in the positive electrode mixture. Among the solid electrolytes exemplified above, sulfide-based solid electrolytes are preferred because they have high lithium ion conductivity and also have the function of improving the formability of the negative electrode mixture. Sulfide-based solid electrolytes having an argyrodite-type crystal structure are more preferred.

[0100] For the same reasons as in the case of the positive electrode mixture, the average particle size of the solid electrolyte in the negative electrode mixture is preferably 0.1 μm or more, more preferably 0.2 μm or more, and is preferably 10 μm or less, more preferably 5 μm or less.

[0101] From the viewpoint of further increasing ionic conductivity in the negative electrode and further improving the output characteristics of the all-solid-state battery, the content of the solid electrolyte in the negative electrode mixture is preferably 30 parts by mass or more, and more preferably 35 parts by mass or more, when the content of the negative electrode active material is 100 parts by mass. However, if the amount of solid electrolyte in the negative electrode mixture is too large, the amounts of other components may be reduced, and the effects of these components may be reduced. Therefore, the content of solid electrolyte in the negative electrode mixture is preferably 130 parts by mass or less, and more preferably 110 parts by mass or less, when the content of the negative electrode active material is 100 parts by mass.

[0102] When a current collector is used for a negative electrode having a molded body of a negative electrode mixture, the current collector can be a sheet-like conductive porous substrate such as copper or nickel foil, punched metal, mesh, expanded metal, or foamed metal; a carbon sheet; or the like. As the sheet-like conductive porous substrate, a foamed metal porous body is preferably used. A specific example of a foamed metal porous body is "Celmet (registered trademark)" from Sumitomo Electric Industries, Ltd.

[0103] The negative electrode can be produced by a method in which a negative electrode mixture-containing composition (paste, slurry, etc.) in which a negative electrode active material, and optionally a conductive additive, a solid electrolyte, a binder, etc. are dispersed in a solvent is applied to a current collector, dried, and then pressure-molded, as required, by calendaring or the like, to form a molded body of the negative electrode mixture (negative electrode mixture layer) on the surface of the current collector.

[0104] As the solvent for the anode mixture-containing composition, an organic solvent such as water or NMP can be used. However, when the anode mixture-containing composition also contains a solid electrolyte, it is desirable to select a solvent that is unlikely to deteriorate the solid electrolyte. It is preferable to use the same solvents as those exemplified above as the solvent for the slurry for forming the solid electrolyte sheet.

[0105] In addition to the above-mentioned method, the molded body of the negative electrode mixture may be formed by compressing, by pressure molding, an negative electrode mixture prepared by mixing the negative electrode active material and, if necessary, a conductive additive, a solid electrolyte, a binder, etc. As described above, the molded body of the negative electrode mixture obtained by such a method can be used as the negative electrode as it is, or it can be used as the negative electrode after being bonded to a current collector by, for example, pressure bonding.

[0106] The thickness of the negative electrode mixture compact (negative electrode mixture layer) formed using the solvent-containing negative electrode mixture-containing composition (thickness per one surface of the current collector when a current collector is used) is preferably 10 to 1000 μm. The thickness of the negative electrode mixture compact obtained by pressure molding is preferably 0.15 to 4 mm.

[0107] The thickness of the negative electrode current collector is preferably 0.01 to 0.1 mm.

[0108] Furthermore, when a conductive porous substrate such as a punched metal is used as the negative electrode current collector, the negative electrode can be produced, for example, by filling the pores of the conductive porous substrate with the above-mentioned negative electrode mixture-containing composition, drying it, and then, if necessary, performing pressure molding such as calendaring. A negative electrode produced by such a method can ensure high strength, and therefore can hold a solid electrolyte sheet with a larger area.

[0109] Furthermore, instead of the above-described negative electrode mixture-containing composition, a negative electrode mixture containing a negative electrode active material, a solid electrolyte, a binder, a conductive additive, and the like, but not containing a solvent, may be dry-filled into the pores of a conductive porous substrate, and the resulting mixture may be subjected to pressure molding such as calendaring as necessary, to produce a negative electrode.

[0110] In the case of a negative electrode obtained by filling the pores of a conductive porous substrate with a negative electrode mixture-containing composition or a negative electrode mixture, the thickness is preferably 30 to 4000 μm.

[0111] In the case of a negative electrode having a lithium sheet or a lithium alloy sheet, one consisting of only this sheet or one consisting of this sheet stuck to a current collector is used.

[0112] Examples of 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 of alloying elements when multiple alloying elements are included) is preferably 50 atomic % or less (in this case, the remainder is lithium and inevitable impurities).

[0113] In addition, 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 (a layer containing lithium) composed of a metal lithium foil or the like by pressure bonding, and this 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 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 a layer containing an alloying element on both sides of the lithium layer may be used. The laminate can be formed, for example, by pressure bonding a metal lithium foil and a foil composed of an alloying element.

[0114] The current collector can also be used when a lithium alloy is formed in a battery to form a 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 a layer containing an alloying element on the side of each lithium layer 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 compression bonding or the like.

[0115] 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, more preferably 12 μm or less.

[0116] The lithium layer of the laminate for forming the negative electrode can be, for example, a metallic lithium foil. The thickness of the lithium layer is preferably 0.1 to 1.5 mm. 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.

[0117] When a negative electrode having a lithium sheet or a lithium alloy sheet has a current collector, the same current collectors as those exemplified above as those usable for a negative electrode having a molded body of a negative electrode mixture can be used for the current collector.

[0118] <Electrode Assembly> The positive electrode and the negative electrode can be used in a battery in the form of a laminated electrode assembly in which the positive electrode and the negative electrode are laminated with a solid electrolyte layer interposed therebetween, or in the form of a wound electrode assembly in which this laminated electrode assembly is wound.

[0119] When forming an electrode assembly, a method can be employed in which a positive electrode having a solid electrolyte coating layer formed on the surface of a compact of a positive electrode mixture (positive electrode mixture layer) and a negative electrode having a solid electrolyte coating layer formed on the surface of a compact of a negative electrode mixture (negative electrode mixture layer) are used, and these are then stacked and pressure-molded onto a solid electrolyte sheet for forming the solid electrolyte layer (I) so that the solid electrolyte coating layers formed on the surfaces of the compact of the positive electrode mixture and the compact of the negative electrode mixture face the solid electrolyte sheet. This can suppress the occurrence of short circuits due to peeling between the solid electrolyte layer and the positive and negative electrodes and cracking of the solid electrolyte layer during electrode assembly formation and after completion of the battery, thereby improving the reliability and productivity of the battery. The coating layer may be formed to a thickness of, for example, 5 to 30 μm.

[0120] <Battery Configuration> The configuration of the all-solid-state battery is not limited to one having an exterior body composed of an exterior can, a sealing can, and a gasket as shown in FIG. 1 , that is, one generally referred to as a coin-type battery or a button-type battery. For example, the all-solid-state battery may have an exterior body composed of a resin film or a metal-resin laminate film, an exterior body having a metallic, bottomed, tubular (cylindrical or rectangular) exterior can and a sealing structure that seals the opening of the metal, or a box-shaped exterior body made of ceramics.

[0121] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0122] (Example 1) Using xylene ("ultra-dehydrated" grade) with a water content of 0.001% by mass (10 ppm) or less, a sulfide-based solid electrolyte (Li ６ P.S. ５ Cl), an acrylic resin binder, and a dispersant were mixed in a mass ratio of 100:3:1 so that the solid content was 40%, and the mixture was stirred for 10 minutes in a Thinky mixer to prepare a uniform slurry.

[0123] As a porous substrate, thickness: 40 μm, basis weight: 8 g / m ２ A PET nonwoven fabric was used, and the nonwoven fabric was immersed in the slurry and pulled up, followed by vacuum drying at 120° C. for 1 hour to prepare a solid electrolyte sheet having a thickness of 42 μm.

[0124] The solid electrolyte sheet was punched into a circle and used to assemble an all-solid-state battery.

[0125] Lithium titanate (Li) having an average particle size of 2 μm ４ Ti ５ O １２ , negative electrode active material) and a sulfide-based solid electrolyte (Li ６ P.S. ５ Cl) and graphene (conductive additive) were mixed in a mass ratio of 50:41:9 to prepare a negative electrode mixture.

[0126] Next, the negative electrode mixture was placed in a powder molding die and subjected to pressure molding using a press to prepare a negative electrode compact. ６ P.S. ５ Cl) was placed on the substrate, and pressure molding was performed at a surface pressure of 70 MPa using a press to form a preformed layer (coating layer) of the solid electrolyte having a thickness of 10 μm.

[0127] In addition, LiNbO ３ LiCoO having an average particle size of 5 μm on which a coating layer of ２ (positive electrode active material) and a sulfide-based solid electrolyte (Li ６ P.S. ５ Cl) and graphene were mixed in a mass ratio of 65:30.7:4.3 to prepare a positive electrode mixture.

[0128] Next, the positive electrode mixture was placed in a powder molding die and subjected to pressure molding using a press to prepare a positive electrode compact. ６ P.S. ５ Cl) was placed on the substrate, and pressure molding was performed at a surface pressure of 70 MPa using a press to form a preformed layer (coating layer) of the solid electrolyte having a thickness of 10 μm.

[0129] Next, the negative electrode and the positive electrode were stacked on a solid electrolyte sheet with the preformed layer of the solid electrolyte facing the solid electrolyte sheet side, and the whole was pressed together to obtain an electrode body in which the positive electrode and the negative electrode were stacked via the solid electrolyte layer. The solid electrolyte layer (II) bonded to the positive electrode was the same size as the positive electrode in a plan view, and the solid electrolyte layer (III) bonded to the negative electrode was the same size as the negative electrode in a plan view, and the solid electrolyte sheet [solid electrolyte layer (I)] was sized to extend 2 mm around the positive electrode and the negative electrode. The total thickness of the solid electrolyte layer was 31 μm, and the thicknesses of the solid electrolyte layers (I), (II), and (III) were 25 μm, 3 μm, and 3 μm, respectively.

[0130] The electrode assembly was sealed in a battery container consisting of an outer can and a sealing can to produce an all-solid-state battery, with graphite sheets interposed between the electrode assembly and the outer can and between the electrode assembly and the sealing can.

[0131] Comparative Example 1 An electrode body was produced in the same manner as in Example 1, except that no preformed solid electrolyte layer (coating layer) was formed on the positive electrode and the negative electrode, and the negative electrode molded body and the positive electrode molded body were in direct contact with the solid electrolyte sheet.

[0132] An all-solid-state battery was fabricated in the same manner as in Example 1 using the electrode body.

[0133] After charging and discharging the batteries of Example 1 and Comparative Example 1, the AC impedance was measured at 1 kHz with an applied voltage of 10 mV. The results are shown in Table 1.

[0134]

[0135] As shown in Table 1, in Example 1, the bonding between the positive electrode and the negative electrode in the electrode body and the solid electrolyte layer was good, and the internal resistance of the battery was low, but in Comparative Example 1, the bonding between the positive electrode and the negative electrode in the electrode body and the solid electrolyte layer was insufficient, and the internal resistance of the battery was high.

[0136] The present invention can be implemented in other forms without departing from the spirit of the present invention. The embodiments disclosed in this application are merely examples, and the present invention is not limited to these embodiments. The scope of the present invention shall be interpreted in accordance with the appended claims rather than the description in the above specification, and all modifications within the scope of the claims are included in the scope of the claims.

[0137] The all-solid-state battery of the present invention can be used in the same applications as conventionally known primary batteries and secondary batteries, but since it has a solid electrolyte instead of an organic electrolyte solution, it has excellent heat resistance and can be preferably used in applications where it is exposed to high temperatures.

[0138] REFERENCE SIGNS LIST 10 All-solid-state battery 20 Positive electrode 30 Negative electrode 40 Solid electrolyte layer 41 Solid electrolyte layer (I) 42 Solid electrolyte layer (II) 43 Solid electrolyte layer (III) 50 Outer can 60 Sealing can 70 Gasket

Claims

1. An all-solid-state battery having an electrode assembly in which a positive electrode and a negative electrode are stacked with a solid electrolyte layer interposed therebetween, The solid electrolyte layer is A solid electrolyte layer (I) having a porous substrate and having portions protruding from the ends of the positive electrode and the negative electrode in a planar view; a solid electrolyte layer (II) joined to the positive electrode and having a smaller area in a plan view than the solid electrolyte layer (I); a laminate of the negative electrode and a solid electrolyte layer (III) having a smaller area in a plan view than the solid electrolyte layer (I), At least one of the solid electrolyte of the solid electrolyte layer (II) and the solid electrolyte of the solid electrolyte layer (III) does not contain a binder, The all-solid-state battery is characterized in that the width of the portion of the solid electrolyte (I) that protrudes from the ends of the positive electrode and the negative electrode is 1 μm to 1 mm.

2. 2. The all-solid-state battery according to claim 1, wherein the total thickness of the solid electrolyte layer is 5 to 100 μm.

3. 2. The all-solid-state battery according to claim 1, wherein the solid electrolyte layer (II) is formed to have the same size as the positive electrode.

4. 2. The all-solid-state battery according to claim 1, wherein the solid electrolyte layer (III) is formed to have the same size as the negative electrode.

5. 2. The all-solid-state battery according to claim 1, wherein the portions of the solid electrolyte layer (I) that protrude from the ends of the positive electrode and the negative electrode are formed in an annular shape.

6. 2. The all-solid-state battery according to claim 1, wherein at least one of the solid electrolyte of the solid electrolyte layer (II) and the solid electrolyte of the solid electrolyte layer (III) is different from the solid electrolyte of the solid electrolyte layer (I).

7. A method for producing an all-solid-state battery having an electrode assembly in which a positive electrode and a negative electrode are stacked with a solid electrolyte layer interposed therebetween, comprising: the solid electrolyte layer is a laminate of a solid electrolyte layer (I) having a porous substrate, a solid electrolyte layer (II) joined to the positive electrode, and a solid electrolyte layer (III) joined to the negative electrode, preparing a solid electrolyte sheet having a porous substrate and a solid electrolyte supported on the porous substrate; preparing a positive electrode having one side coated with a solid electrolyte; preparing a negative electrode having one side coated with a solid electrolyte; a step of attaching the positive electrode to one surface of the solid electrolyte sheet so that the solid electrolyte covering the positive electrode is in contact with the surface of the solid electrolyte sheet; and attaching the negative electrode to the other surface of the solid electrolyte sheet so that the solid electrolyte covering the negative electrode is in contact with the other surface of the solid electrolyte sheet, a solid electrolyte sheet, a solid electrolyte covering the positive electrode, and a solid electrolyte covering the negative electrode, thereby forming the solid electrolyte layer;

8. 8. The method for manufacturing an all-solid-state battery according to claim 7, wherein the step of attaching the positive electrode and the step of attaching the negative electrode are performed so that the solid electrolyte sheet protrudes from ends of the positive electrode and the negative electrode in a plan view.