Solid electrolyte laminate sheet, all-solid-state secondary battery, and method for manufacturing all-solid-state secondary battery

Abstract

Provided are: a solid electrolyte layered sheet which has a sheet-like porous support including therein an inorganic solid electrolyte, and a solid electrolyte layer containing an inorganic solid electrolyte, and in which the porosity of the porous support is 20% or more, and the porosity of the solid electrolyte layer is smaller than the porosity of the porous support; a method for producing an all solid secondary battery through compression while adjusting the porosity of the sold electrolyte layer and the porous support by using said solid electrolyte layered sheet; and an all solid secondary battery.

Description

[Technical Field]

[0001] The present invention relates to a solid electrolyte laminate sheet, an all-solid-state secondary battery, and a method for manufacturing an all-solid-state secondary battery. [Background technology]

[0002] Secondary batteries such as lithium-ion secondary batteries have a negative electrode, a positive electrode, and an electrolyte sandwiched between the negative and positive electrodes. They are storage batteries that can be charged and discharged by moving ions of metals (hereinafter simply referred to as metals) belonging to Group 1 or Group 2 of the periodic table back and forth between the two electrodes. Traditionally, organic electrolyte solutions have been used as electrolytes in secondary batteries. However, organic electrolyte solutions are prone to leakage, and there is also the risk of short circuits occurring inside the battery due to overcharging and overdischarging. Therefore, further improvements in reliability and safety are required. Under these circumstances, development of all-solid-state secondary batteries using non-flammable inorganic solid electrolytes instead of organic electrolyte solutions is underway. All-solid-state secondary batteries have a negative electrode, electrolyte, and positive electrode all made of solids, which is expected to significantly improve the safety and reliability that are issues with batteries using organic electrolyte solutions, and also enable longer life.

[0003] During charging, electrons move from the positive electrode to the negative electrode. At the same time, metal ions are released from the active material that makes up the positive electrode. These metal ions pass through the electrolyte and reach the negative electrode, where they are stored. Some of the metal ions stored in the negative electrode then absorb electrons and precipitate as metal. If these metal precipitates grow into dendrites through repeated charge and discharge cycles, they eventually reach the positive electrode, causing an internal short circuit and preventing the secondary battery from functioning properly. In particular, lithium-ion secondary batteries, which move lithium ions back and forth, are prone to the significant generation and growth of metallic lithium dendrites, which can lead to internal short circuits. Therefore, even in all-solid-state secondary batteries, preventing metal dendrites (sometimes simply referred to as dendrites) from reaching the positive electrode is important for extending the battery's lifespan.

[0004] In order to address the problem of internal short circuits caused by dendrites, a technique has been proposed in which the solid electrolyte layer constituting the all-solid-state secondary battery has a multi-layer structure. For example, Patent Document 1 describes "a solid electrolyte laminate sheet in which a solid electrolyte layer containing particles of an inorganic solid electrolyte and having a porosity of 10% or less is laminated with a fragile layer containing particles of an inorganic solid electrolyte and having a porosity of 15% or more," and an all-solid-state secondary battery including this solid electrolyte laminate sheet. Patent Document 2 describes "a laminate sheet for a negative electrode, the laminate sheet having an electron ion conductive layer containing a lithium ion conductive inorganic solid electrolyte and electron conductive particles, adjacent to a negative electrode current collector, the electron ion conductive layer having a porosity of 20% or more, and an ion conductive layer containing a lithium ion conductive inorganic solid electrolyte and a porosity of 20% or more, on the side of the electron ion conductive layer opposite the negative electrode current collector." The same document also describes an all-solid-state secondary battery using the laminate sheet for a negative electrode, the all-solid-state lithium ion secondary battery having "an electron ion conductive layer containing a lithium ion conductive inorganic solid electrolyte and electron conductive particles, adjacent to a negative electrode current collector, the ion conductive layer containing a lithium ion conductive inorganic solid electrolyte and a porosity of 15% or more, an ion conductive layer opposite the negative electrode current collector, the electron ion conductive layer having a porosity of 10% or less, and a positive electrode active material layer adjacent to the ion conductive layer on the side opposite the electron ion conductive layer, wherein in a charged state, at least the electron ion conductive layer contains a negative electrode active material, and the negative electrode active material is metallic lithium." Furthermore, Patent Document 3 describes a lithium battery using, as a negative electrode, an electrode body for a lithium battery having, in this order, a collector electrode, a negative electrode active material, a wet sand-like electrolyte layer impregnated with a room-temperature molten salt electrolyte of a plurality of particles, and an inorganic solid electrolyte layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-107594 [Patent Document 2] International Publication No. 2020-196040 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-058250 Summary of the Invention [Problem to be solved by the invention]

[0006] Generally, when an all-solid-state secondary battery is charged, metal deposition and dissolution occur repeatedly during charging and discharging, causing the negative electrode active material layer to undergo volumetric fluctuations (expansion and contraction). In particular, in all-solid-state secondary batteries that utilize metal ions generated in the positive electrode active material layer during charging, which are then reduced and deposited on the negative electrode side, the volumetric fluctuations become significant due to metal deposition and dissolution occurring between the adjacent negative electrode current collector and solid electrolyte layer. These volumetric fluctuations gradually form voids within or between layers, and if the metal becomes isolated within these voids and no longer comes into contact with the negative electrode current collector or solid electrolyte layer (formation of isolated metal), the metal can no longer be dissolved (ionized). The formation of such isolated metal is thought to gradually reduce the discharge capacity (due to a gradual decrease in the amount of metal that can be ionized), degrade cycle characteristics, and ultimately render the battery unable to discharge. Moreover, the formation of the voids promotes the growth of dendrites that progress along the grain boundaries, accelerating the occurrence of internal short circuits.

[0007] Patent Document 3 does not fully consider preventing the occurrence of such internal short circuits and suppressing the deterioration of cycle characteristics. On the other hand, it is expected that the techniques described in Patent Documents 1 and 2 can suppress the occurrence of internal short circuits and the deterioration of cycle characteristics in all-solid-state secondary batteries to some extent. However, in recent years, development toward the practical use of all-solid-state secondary batteries has progressed rapidly, and in addition to further improving battery performance such as cycle characteristics, it is desired to highly suppress the occurrence of internal short circuits and achieve high reliability (safety).

[0008] An object of the present invention is to provide a solid electrolyte laminate sheet that suppresses the occurrence of an internal short circuit in an all-solid-state secondary battery and further improves the cycle characteristics even when the all-solid-state secondary battery incorporated therein is repeatedly charged and discharged. Another object of the present invention is to provide an all-solid-state secondary battery that suppresses the occurrence of an internal short circuit and has excellent cycle characteristics, and a method for producing the same. [Means for solving the problem]

[0009] After various studies, the present inventors came up with the idea that by making the solid electrolyte layer incorporated in the all-solid-state secondary battery have a multi-layer structure, and by configuring one of the layers as a layer that allows metal deposition without a large volume change and the other as a dense layer with few voids, it is possible to suppress the occurrence of internal short circuits and also to suppress the deterioration of cycle characteristics. Based on this idea, the inventors conducted further detailed studies and found that in an all-solid-state secondary battery, the layer that enables metal deposition is not simply provided with many voids to accommodate the deposited metal (simply increasing the porosity), but is composed of a layer that incorporates a support that serves as a basic skeleton to increase the porosity while being resistant to defects (cracks, breaks, fractures, etc.) caused by metal deposition and dissolution, thereby making it possible to accommodate the deposited metal without isolating it during dissolution while suppressing volume fluctuations caused by metal deposition and dissolution. Furthermore, by overlapping this layer with a dense layer, it is possible to prevent stress caused by volume fluctuations caused by metal deposition and dissolution from propagating to the dense layer, thereby preventing defects in the dense layer and, as a result, effectively inhibiting dendrite penetration into the positive electrode. Furthermore, the inventors have found that, in producing the above-mentioned all-solid-state secondary battery, a layer that allows deposition of the metal and a dense layer can be formed by using a sheet in which a porous support that incorporates an inorganic solid electrolyte and has a predetermined porosity and a solid electrolyte layer that has a porosity smaller than that of the porous support are laminated, and by pressing this laminated sheet. The present invention has been completed as a result of further investigations based on these findings.

[0010] That is, the above problems were solved by the following means. <1> A solid electrolyte laminated sheet comprising: a sheet-like porous support incorporating an inorganic solid electrolyte having ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table; and a solid electrolyte layer on one surface of the porous support, the solid electrolyte layer containing an inorganic solid electrolyte having ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, A solid electrolyte laminate sheet, wherein the porosity of the porous support is 20% or more, and the porosity of the solid electrolyte layer is smaller than the porosity of the porous support. <2> The inorganic solid electrolyte contained in the porous support is made of particles smaller than the opening diameter of the porous support. <1> The solid electrolyte laminate sheet according to claim 1. <3> the inorganic solid electrolyte contained in the solid electrolyte layer contains particles larger than the opening diameter of the porous support and particles smaller than the opening diameter of the porous support; <1> or <2> The solid electrolyte laminate sheet according to claim 1. <4> a negative electrode current collector on the other surface of the porous support; <1> ~ <3> 10. The solid electrolyte laminate sheet according to claim 9, wherein the first and second electrodes are made of a polyimide. <5> the above <1> ~ <4> An all-solid-state secondary battery using the solid electrolyte laminate sheet according to any one of the above items, a layer structure in which a negative electrode current collector, a porous support of a solid electrolyte laminate sheet, a solid electrolyte layer, and a positive electrode active material layer are laminated and pressed together in this order; The porosity of the porous support after lamination and compression bonding is 15% or more, An all-solid-state secondary battery in which the porosity of the solid electrolyte layer after lamination and compression bonding is 10% or less. <6> a negative electrode active material layer between the negative electrode current collector and the porous support; <5> The all-solid-state secondary battery according to claim 1. <7> The negative electrode active material layer is a metallic lithium foil. <6> The all-solid-state secondary battery according to claim 1. <8> In a charged state of the all-solid-state secondary battery, at least the porous support contains a negative electrode active material. <5> The all-solid-state secondary battery according to claim 1. <9> the inorganic solid electrolyte contained in the porous support after lamination and compression bonding is made of particles smaller than the opening diameter of the porous support; <5> ~ <8> 10. The all-solid-state secondary battery according to any one of the above. <10> the inorganic solid electrolyte contained in the solid electrolyte layer after lamination and compression bonding contains particles larger than the opening diameter of the porous support and particles smaller than the opening diameter of the porous support; <5> ~ <9> 10. The all-solid-state secondary battery according to any one of the above. <11> the above <1> ~ <4> A method for producing an all-solid-state secondary battery using the solid electrolyte laminate sheet according to any one of the above items, A method for manufacturing an all-solid-state secondary battery, comprising a step of pressurizing a solid electrolyte laminate sheet until the porosity of the solid electrolyte layer becomes 10% or less, while restricting the porosity of the porous support of the solid electrolyte laminate sheet to 15% or more. <12> forming a negative electrode active material layer between a negative electrode current collector and a porous support; <11> A method for producing the all-solid-state secondary battery according to claim 1. <13> the step of forming the negative electrode active material layer is a step of forming a film of a negative electrode composition containing a negative electrode active material or a step of laminating a metallic lithium foil; <12> A method for producing the all-solid-state secondary battery according to claim 1. <14> the step of forming the negative electrode active material layer is a step of charging the all-solid-state secondary battery after the pressurizing step to deposit the negative electrode active material at least in the porous support; <12> A method for producing the all-solid-state secondary battery according to claim 1. [Effects of the Invention]

[0011] The all-solid-state secondary battery of the present invention is suppressed from occurring an internal short circuit and has excellent cycle characteristics. Furthermore, the method for producing an all-solid-state secondary battery of the present invention can easily produce an all-solid-state secondary battery that is suppressed from occurring an internal short circuit and has excellent cycle characteristics. Furthermore, by using the solid electrolyte laminate sheet of the present invention in the production of an all-solid-state secondary battery, an all-solid-state secondary battery having the above-mentioned excellent characteristics can be realized. The above and other features and advantages of the present invention will become more apparent from the following description, taken in conjunction with the accompanying drawings where appropriate. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a longitudinal sectional view schematically showing a preferred embodiment of the all-solid-state secondary battery of the present invention. [Figure 2]FIG. 2 is a longitudinal sectional view schematically showing a preferred embodiment of the solid electrolyte laminate sheet of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] In the description of the present invention, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the lower and upper limits. In the description of the present invention, when multiple numerical ranges are set for the content of a component, physical properties, etc., the upper and lower limits forming the numerical range are not limited to a specific combination of upper and lower limits, and can be any numerical range obtained by appropriately combining the upper and lower limits of each numerical range.

[0014] [All-solid-state secondary battery] First, the all-solid-state secondary battery of the present invention will be described by way of preferred embodiments with reference to the drawings. The all-solid-state secondary battery of the present invention is an all-solid-state secondary battery manufactured using the solid electrolyte laminate sheet of the present invention, and has a layered structure in which an anode current collector, a porous support of the solid electrolyte laminate sheet, a solid electrolyte layer of the solid electrolyte laminate sheet, and a cathode active material layer are laminated and pressed together in this order. This layered structure includes, on the anode current collector, a porous support (hereinafter also referred to as the internal battery porous support) on which the porous support of the solid electrolyte laminate sheet is laminated and pressed together, a solid electrolyte layer (hereinafter also referred to as the internal battery solid electrolyte layer) on which the solid electrolyte layer of the solid electrolyte laminate sheet is laminated and pressed together, and a cathode active material layer, in this order. In other words, this layered structure includes an anode current collector on the surface of the internal battery porous support opposite the internal battery solid electrolyte layer, and a cathode active material layer on the surface of the internal battery solid electrolyte layer opposite the internal battery porous support.

[0015] In the present invention, unless otherwise specified, the all-solid-state secondary battery includes a configuration having a pre-formed (disposed) negative electrode active material layer (sometimes referred to as a configuration in which a negative electrode active material layer is pre-formed), and a configuration in which a negative electrode active material layer is not pre-formed, and metal ions generated in a positive electrode active material layer by charging are reduced and precipitated on the negative electrode side to form a metal (layer) as the negative electrode active material layer (sometimes referred to as a configuration in which a negative electrode active material layer is not pre-formed. An all-solid-state secondary battery of this configuration is sometimes referred to as a self-forming negative electrode type all-solid-state secondary battery). In a self-forming negative electrode type all-solid-state secondary battery, the metal (preferably metallic lithium) needs to be precipitated at least within the porous support (usually within the pores) in the battery, and may also be appropriately precipitated on the surface of the negative electrode current collector (the interface between the porous support and the negative electrode current collector in the battery), the interface between the porous support and the solid electrolyte layer in the battery, or even within the battery solid electrolyte layer. When metallic lithium is used as the deposited metal, it has a theoretical capacity that is more than 10 times that of graphite, which is commonly used as the negative electrode active material in conventional all-solid-state secondary batteries.In addition, since the battery can be made thinner because the negative electrode active material layer is not formed in advance, self-forming negative electrode type all-solid-state secondary batteries can achieve high energy density.

[0016] Thus, the self-forming anode type all-solid-state secondary battery includes both an uncharged state (a state in which the metal constituting the anode active material layer is not precipitated) and a charged state (a state in which the metal constituting the anode active material layer is precipitated). Note that "no metal precipitated" includes not only a state in which the metal is completely ionized and dissolved, but also a state in which some metal remains to the extent that the effects of the present invention are not impaired. In the present invention, "charged" refers to a state in which charging is completed as well as a state in which charging is in progress, and "uncharged" refers to a state in which discharging is completed. In the present invention, the self-forming anode type all-solid-state secondary battery simply means that the anode active material layer is not formed in the layer formation step in the battery production, and as described above, the anode active material layer is formed by charging.

[0017] In the layer structure, other layers described later may be interposed between the layers, or the layers may be adjacent to each other. The porous support body in the battery and the solid electrolyte layer in the battery may have a dendrite penetration blocking layer described later interposed between them, but they are preferably adjacent to each other. The solid electrolyte layer in the battery and the positive electrode active material layer are preferably adjacent to each other. On the other hand, the preferred stacking state of the negative electrode current collector and the porous support body in the battery varies depending on the form of the all-solid-state secondary battery. For example, in a form in which the negative electrode active material layer is formed in advance, it is preferable that the negative electrode active material layer is interposed between the negative electrode current collector and the porous support body in the battery, and that the three layers are adjacent to each other. On the other hand, in a form in which the negative electrode active material layer is not formed in advance, it is preferable that the negative electrode current collector and the porous support body in the battery are adjacent to each other. In the present invention, adjacent layers mean that the surfaces of the layers are arranged (formed) in contact with each other.

[0018] In the all-solid-state secondary battery having the above-mentioned layer structure, the porosity of the porous support in the battery is 15% or more, and the porosity of the solid electrolyte layer in the battery is 10% or less, thereby improving cycle characteristics and preventing short circuits. The porosity of each layer is measured by the following method. That is, an arbitrary cross section of each layer is observed with a scanning electron microscope (SEM) at a magnification of 30,000 times, and the (total) area of ​​voids in a field of view of 3 μm × 2.5 μm is calculated from the SEM photograph obtained. This area is then divided into the field of view (7.5 μm 2 ) and calculate the area ratio (percentage).

[0019] In the present invention, each layer constituting the all-solid-state secondary battery may have a single layer structure or a multi-layer structure, as long as it exhibits a specific function. The all-solid-state secondary battery of the present invention is not particularly limited in configuration as long as it has the above-described layer structure, and any known configuration related to all-solid-state secondary batteries can be used. For example, the all-solid-state secondary battery of the present invention preferably has a film of a metal capable of forming an alloy with lithium on the surface of the porous support body in the battery opposite to the solid electrolyte layer in the battery. Also, a known dendrite penetration blocking layer can be disposed between the porous support body in the battery and the solid electrolyte layer in the battery.

[0020] 1 is a cross-sectional view showing a schematic representation of the stacked state (layer structure) of the constituent layers constituting a self-forming anode type all-solid-state secondary battery (uncharged state) according to one embodiment of the present invention. The self-forming anode type all-solid-state secondary battery 10 of this embodiment has a layered structure in which, as viewed from the anode side, an anode current collector 1, an internal porous support 2, an internal solid electrolyte layer 3, a cathode active material layer 4, and a cathode current collector 5 are stacked in this order, with the stacked layers being in direct contact with each other. In a self-forming anode type all-solid-state secondary battery with such a layer structure, electrons (e - ) is supplied to the negative electrode, and at the same time, the alkali metal or alkaline earth metal that constitutes the positive electrode active material is ionized, passes through (conducts) the solid electrolyte layer 3 in the battery, moves to the porous support 2 in the battery, and combines with electrons (is reduced) to precipitate the alkali metal or alkaline earth metal. For example, in the case of a lithium ion secondary battery, lithium ions (Li + In this way, the alkali metal or alkaline earth metal deposited at least in the porous support 2 in the battery functions as a negative electrode active material layer. On the other hand, during discharge, the precipitated alkali metal or alkaline earth metal generates metal ions and electrons. The metal ions pass through (conduct) the solid electrolyte layer 3 in the battery and are returned (migrated) to the positive electrode active material layer side, and the electrons are supplied to the operating part 6 and reach the positive electrode current collector 5. In the example of the self-forming negative electrode type all-solid-state secondary battery 10 shown in the figure, a light bulb is used as the operating part 6, and this is designed to light up when the battery is discharged.

[0021] In an all-solid-state secondary battery having a configuration in which the negative electrode active material layer is formed in advance, as described above, the negative electrode active material layer (not shown in FIG. 1 ) is disposed between the negative electrode current collector 1 and the battery internal porous support 2. The operation of this configuration of the all-solid-state secondary battery is basically the same as that of the self-forming negative electrode type all-solid-state secondary battery 10, except that the negative electrode active material layer does not disappear during discharge.

[0022] The all-solid-state secondary battery of the present invention having the above layer structure is preferably produced using the solid electrolyte laminate sheet of the present invention by the method for producing an all-solid-state secondary battery of the present invention described below. The all-solid-state secondary battery of the present invention highly suppresses the occurrence of internal short circuits (over many cycles), and exhibits excellent cycle characteristics by suppressing the decrease in discharge capacity even after many cycles of charge and discharge.

[0023] The details of the reason for this are not yet clear, but it is thought to be as follows. The all-solid-state secondary battery of the present invention has, on a negative electrode current collector, an internal porous support body having a porosity of 15% or more and an internal solid electrolyte layer having a porosity of 10% or less. As described below, this porous support in a battery incorporates (contains) an inorganic solid electrolyte within the porous support (the pores contain the inorganic solid electrolyte) and has pores sufficient to accommodate the deposited alkali metal or alkaline earth metal (sometimes simply referred to as metal). This allows the metal to deposit and accumulate within the porous support (pores) in the battery while suppressing volumetric fluctuations. Furthermore, a porous support in a battery, which is constructed using the porous support as a basic framework, is less susceptible to defects (cracks, breaks, fractures, etc.) caused by metal deposition and dissolution (is less susceptible to self-destruction). In such a porous support in a battery, the metal deposits in contact with the inorganic solid electrolyte incorporated within the porous support (inside the pores) or with the already deposited metal (a state in which the inorganic solid electrolyte is appropriately positioned to establish an ion conduction path). Therefore, even without the use of an electronic conductive material as in Patent Document 2, the ion conduction path established within the porous support in the battery is maintained during dissolution, allowing the metal to be sequentially ionized and preventing the isolation of undissolved metal. It is believed that this metal deposition and dissolution will not be impaired even when the all-solid-state secondary battery is repeatedly charged and discharged. On the other hand, the solid electrolyte layer in the battery has a small porosity, which can prevent dendrites from growing (penetrating) toward the positive electrode. Moreover, even when the all-solid-state secondary battery is repeatedly charged and discharged, the porous support in the battery accommodates the deposited metal, effectively suppressing volume fluctuations while also being less likely to develop defects. Therefore, stress caused by volume fluctuations and even defect generation (self-destruction) is not transmitted to the solid electrolyte layer in the battery. Therefore, although a dense solid electrolyte layer with a small porosity is generally prone to defects, the solid electrolyte layer in the battery highly suppresses the generation of defects even when the all-solid-state secondary battery is repeatedly charged and discharged, effectively preventing dendrites from penetrating into the positive electrode. It is believed that the cooperation of the above-mentioned functions of the porous support body in the battery and the solid electrolyte layer in the battery can effectively suppress the deterioration of cycle characteristics (maintain excellent charge / discharge efficiency) even after repeated charge / discharge, and can also effectively suppress the occurrence of internal short circuits.

[0024] <Negative electrode current collector> The negative electrode current collector 1 can be made of an electron conductor. The material for forming the negative electrode current collector is not particularly limited, but examples thereof include metal materials such as aluminum, copper, copper alloys, stainless steel, nickel, and titanium, and nickel, copper, copper alloys, and stainless steel are preferred. Furthermore, these metal materials may also be used with their surfaces treated with carbon, nickel, titanium, or silver (thin films formed thereon). The negative electrode current collector is usually in the form of a film sheet, but net, punched, lath, porous, foamed, or fibrous molded body can also be used. The thickness of the negative electrode current collector (including the above thin film) is not particularly limited, but is preferably 1 to 500 μm. It is also preferable to make the surface of the negative electrode current collector uneven by surface treatment. In the present invention, both the negative electrode current collector and the positive electrode current collector described below may be collectively referred to as the current collector.

[0025] <Porous support in battery> The porous support in the battery is constructed using a sheet-like porous support as a basic skeleton (base) and contains an inorganic solid electrolyte inside the pores that is conductive to ions of a metal belonging to Group 1 or Group 2 of the periodic table (usually attached to the pore surface). The porous support has a porosity of 15% or more and is a layer that can accommodate metals that precipitate inside (usually in the pores). Therefore, this porous support in the battery can accumulate metals in the pores while suppressing volume fluctuations and even self-destruction due to charge and discharge. This porous support in the battery differs in characteristics and function from the "easily destructible layer" of Patent Document 1, which actively self-destructs, in that it is less susceptible to volume fluctuations and dendrite growth.

[0026] In the all-solid-state secondary battery of the present invention, when the porosity of the porous support in the battery is 15% or more, the deposited metal can be accommodated while suppressing volume fluctuation, and high cycle characteristics can be achieved. From the viewpoint of further improving cycle characteristics, the porosity of the porous support in the battery is preferably 20% or more. The porosity can be set even higher by taking advantage of the breakage-resistant properties of the porous support in the battery, for example, 30% or more, and more preferably 35% or more. The upper limit of the porosity is appropriately determined depending on the amount of metal deposited in the all-solid-state secondary battery, and is, for example, preferably 80% or less, more preferably 60% or less, and even more preferably 50% or less. The porosity of the porous support in the battery is a value calculated as an area ratio by the above-mentioned method.

[0027] The thickness of the porous support in the battery is not particularly limited and can be appropriately determined depending on the battery capacity (amount of metal deposition), porosity, etc. For example, it can be 1 to 100 μm, and preferably 3 to 80 μm. The porous support in the battery is preferably a compressed body of the porous support in the sheet described below.

[0028] The porous support in the battery preferably exhibits metal ion conductivity, although this depends on the charge level of the inorganic solid electrolyte. The metal ion conductivity of the porous support in the battery is not particularly limited and can be appropriately set within a range that does not impair the conduction (transfer) of metal ions generated from the metal (a range that allows the support to function as a constituent layer of the secondary battery). The metal ion conductivity can be adjusted by the type and content of the inorganic solid electrolyte contained. On the other hand, the porous support in the battery does not exhibit electronic conductivity (is electronically insulating) in the discharged state of the all-solid-state secondary battery. The electronic insulation of the porous support in the battery is not limited to a conductivity of 0 (S / m), but also includes a property of exhibiting conductivity that does not allow electrons to be conducted (transferred) through the porous support in the battery to two layers adjacent to the porous support in the battery (electronic insulation that does not short-circuit the all-solid-state secondary battery).

[0029] When the all-solid-state secondary battery is a self-forming anode type all-solid-state secondary battery, the porous support in the battery contains a metal deposited as a negative electrode active material when the all-solid-state secondary battery is in a charged state. The metal contained in the porous support in the battery varies depending on the capacity of the positive electrode active material layer and is not uniquely determined.

[0030] The porous support constituting the porous support in the battery means a support having many micrometer-order pores (holes opening on the surface, through-holes, etc.), and any known sheet-like porous material can be used without any particular limitation. Examples of the porous material include a sponge-like molded body, a sheet-like molded body having many through-holes, and a nonwoven fabric, and a sheet-like molded body or a nonwoven fabric having many through-holes is preferred. The material forming the porous support is not particularly limited and may be, for example, various resins, ceramics, fibers, etc., with resins and fibers being preferred. Examples of resins include natural fiber / polyethylene terephthalate (PET) / acrylic resin-coated composite resins, fluorine-containing resins, hydrocarbon-based thermoplastic resins, acrylic resins, polyurethane resins, polyurea resins, polyamide resins, polyimide resins, polyester resins, polyether resins, polycarbonate resins, and cellulose derivative resins, while examples of fibers include natural fibers and composite resin fibers. Among these, the above-mentioned composite resins are preferred in that they exhibit appropriate strength (to the extent that they do not collapse or compress significantly) against the applied pressure during the production of all-solid-state secondary batteries. The porous support is preferably the above-mentioned resin sheet-like molded product or nonwoven fabric, since the porosity can be adjusted by compressing it under pressure during the production of an all-solid-state secondary battery.

[0031] The porosity of the porous support itself (porosity as a material) is appropriately determined depending on the material, the pressure applied during production of the all-solid-state secondary battery, and the amount of metal precipitated in the all-solid-state secondary battery. For example, in order to easily set the porosity of the porous support in the sheet described below and the porous support in the battery within a predetermined range, the porosity can be 50 to 99%, preferably 60 to 97%, and more preferably 70 to 95%. The opening diameter of the porous support itself is appropriately determined taking into consideration the ease of filling with the inorganic solid electrolyte, etc. For example, the opening diameter measured by the following measurement method is preferably 0.1 to 50 μm, more preferably 1 to 20 μm. The opening diameter is determined by arbitrarily selecting 10 openings in a 1 mm × 1 mm area in an SEM photograph obtained by observing an arbitrary surface of the porous support with an SEM at a magnification of 30,000, and determining the circle-equivalent diameter of each opening, and then calculating the arithmetic mean value of these. The thickness of the porous support itself is not particularly limited and is determined appropriately depending on the battery capacity (amount of metal deposition), porosity, etc., and is, for example, preferably 1 μm or more and 1 mm or less, more preferably 3 to 300 μm, even more preferably 10 to 200 μm, and particularly preferably 20 to 100 μm.

[0032] The porous support can be produced by any known method without any particular limitation, and examples thereof include a method in which a sheet-like molded body is produced and then perforated, a photoresist method as described in the examples below, and a conventional nonwoven fabric production method.

[0033] The inorganic solid electrolyte may be contained in the form of a film that covers the pore surfaces of the porous support, but is usually contained (adhered) to the pore surfaces as particles. The content (filling amount) of the inorganic solid electrolyte contained in the porous support is not particularly limited and is determined appropriately taking into consideration the porosity of the porous support and the porosity of the porous support itself. For example, a content that reduces the porosity of the porous support itself by 5 to 80% is preferred, and a content that reduces the porosity of the porous support itself by 10 to 70% is more preferred. The inorganic solid electrolyte contained in the porous support in particulate form is, as will be described later, typically smaller than the opening size of the porous support. This can be confirmed by observation during porosity measurement. The specific particle size (also referred to as particle diameter) is appropriately determined taking into consideration the opening size, porosity, content (filling amount), etc., but is preferably, for example, 0.01 to 5 μm, more preferably 0.05 to 3 μm, and even more preferably 0.1 to 2 μm. The difference between the opening size and the particle size is also appropriately determined, but is preferably, for example, 0.1 to 10 μm, more preferably 0.5 to 8 μm, and even more preferably 0.8 to 5 μm, in order to ensure uniform distribution of the inorganic solid electrolyte within the porous support. The particle size of the inorganic solid electrolyte is determined by arbitrarily selecting 10 particles of the inorganic solid electrolyte present in voids in a predetermined region (for example, a 1 mm × 1 mm region) in an SEM photograph obtained by observing an arbitrary cross section of the porous support with an SEM, determining the circle-equivalent diameter of each particle, and taking the arithmetic mean value of these. The inorganic solid electrolyte contained in the porous support in the battery may be one type or two or more types.

[0034] - Inorganic solid electrolyte - In the present invention, an inorganic solid electrolyte refers to an inorganic solid electrolyte, and a solid electrolyte is a solid electrolyte capable of transferring ions therein. Because inorganic solid electrolytes do not contain organic substances as the primary ion-conducting material, they are clearly distinguished from organic solid electrolytes (polymer electrolytes such as polyethylene oxide (PEO) and organic electrolyte salts such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)). Furthermore, inorganic solid electrolytes are solid in the steady state and are generally not dissociated or liberated into cations and anions. In this respect, they are also clearly distinguished from electrolyte solutions or inorganic electrolyte salts (e.g., LiPF, LiBF, lithium bis(fluorosulfonyl)imide (LiFSI), LiCl) that are dissociated or liberated into cations and anions in a polymer. The inorganic solid electrolyte is not particularly limited as long as it has ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, but generally does not have electronic conductivity.

[0035] The inorganic solid electrolyte contained in the porous support in the battery can be selected from solid electrolyte materials typically used in all-solid-state secondary batteries. Examples of inorganic solid electrolytes include (i) sulfide-based inorganic solid electrolytes, (ii) oxide-based inorganic solid electrolytes, (iii) halide-based inorganic solid electrolytes, and (iv) hydride-based inorganic solid electrolytes. Sulfide-based inorganic solid electrolytes are preferred because they can form a better interface between the active material and the inorganic solid electrolyte. When the all-solid-state secondary battery of the present invention is a lithium-ion battery, the inorganic solid electrolyte preferably has ionic conductivity for lithium ions.

[0036] (i) Sulfide-based inorganic solid electrolyte The sulfide-based inorganic solid electrolyte preferably contains sulfur atoms, has the ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, and has electronic insulation. The sulfide-based inorganic solid electrolyte preferably contains at least Li, S, and P as elements and has lithium ion conductivity, but may contain elements other than Li, S, and P as appropriate.

[0037] An example of the sulfide-based inorganic solid electrolyte is a lithium ion conductive inorganic solid electrolyte that satisfies the composition represented by the following formula (1). L a1 M b1 P c1 S d1 A e1 (1) In the formula, L represents an element selected from Li, Na, and K, and Li is preferred. M represents an element selected from B, Zn, Sn, Si, Cu, Ga, Sb, Al, and Ge. A represents an element selected from I, Br, Cl, and F. a1 to e1 represent the composition ratio of each element, and a1:b1:c1:d1:e1 satisfies the ratio 1-12:0-5:1:2-12:0-10. a1 is preferably 1-9, and more preferably 1.5-7.5. b1 is preferably 0-3, and more preferably 0-1. d1 is preferably 2.5-10, and more preferably 3.0-8.5. e1 is preferably 0-5, and more preferably 0-3.

[0038] The composition ratio of each element can be controlled by adjusting the blending amounts of raw material compounds when producing the sulfide-based inorganic solid electrolyte, as described below.

[0039] The sulfide-based inorganic solid electrolyte may be amorphous (glass) or crystallized (glass-ceramic), or may be only partially crystallized. For example, a Li-PS-based glass containing Li, P, and S, or a Li-PS-based glass-ceramic containing Li, P, and S may be used. The sulfide-based inorganic solid electrolyte can be produced by reacting at least two or more raw materials selected from the group consisting of lithium sulfide (LiS), phosphorus sulfide (e.g., diphosphorus pentasulfide (PS)), elemental phosphorus, elemental sulfur, sodium sulfide, hydrogen sulfide, lithium halides (e.g., LiI, LiBr, LiCl), and sulfides of the elements represented by M above (e.g., SiS, SnS, GeS).

[0040] In the Li-PS glass and Li-PS glass ceramics, the ratio of Li2S to P2S5 is preferably 60:40 to 90:10, more preferably 68:32 to 78:22, in terms of the molar ratio of Li2S:P2S5. By setting the ratio of Li2S to P2S5 within this range, the lithium ion conductivity can be increased. Specifically, the lithium ion conductivity is preferably 1×10 -4 S / cm or more, preferably 1×10 -3 S / cm or more. There is no upper limit, but it is 1×10 -1 It is practical to have a value of S / cm or less.

[0041] Specific examples of sulfide-based inorganic solid electrolytes, including combinations of raw materials, are shown below: Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-P2S5-H2S, Li2S-P2S5-H2S-LiCl, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SiS2-LiCl, Li2S-P2S5-SnS, and Li2S-P2S5-Al2S3 , Li2S-GeS2, Li2S-GeS2-ZnS, Li2S-Ga2S3, Li2S-GeS2-Ga2S3, Li2S-GeS2-P2S5, Li2S-GeS2-Sb2S5, Li2S-GeS2-Al2S3, Li2S-SiS2, L i2S-Al2S3, Li2S-SiS2-Al2S3, Li2S-SiS2-P2S5, Li2S-SiS2-P2S5-LiI, Li2S-SiS2-LiI, Li2S-SiS2-Li4SiO4, Li2S-SiS2-Li3PO4, Li 10 GeP2S 12 However, the mixing ratio of each raw material is not important. As a method for synthesizing a sulfide-based inorganic solid electrolyte material using such a raw material composition, for example, an amorphization method can be mentioned. Examples of the amorphization method include a mechanical milling method, a solution method, and a melt quenching method. This is because processing at room temperature becomes possible, and the manufacturing process can be simplified.

[0042] (ii) Oxide-based inorganic solid electrolyte The oxide-based inorganic solid electrolyte preferably contains oxygen atoms, has ionic conductivity of metal ions belonging to Group 1 or Group 2 of the periodic table, and has electron insulation properties. The oxide-based inorganic solid electrolyte has an ionic conductivity of preferably 1×10 -6 S / cm or more, more preferably 5×10 -6 S / cm or more, and particularly preferably 1×10 -5 S / cm or more. The upper limit is not particularly limited, but it is practical that it is 1×10 -1 S / cm or less.

[0043] Specific compound examples include, for example, Li xa La ya TiO3 [xa = 0.3 to 0.7, ya = 0.3 to 0.7] (LLT), Li xb La yb Zr[[ID=2色]] zb [[ID=色]] bb mb O nb (M bb is at least one element of Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, Sn, xb satisfies 5 ≤ xb ≤ 10, yb satisfies 1 ≤ yb ≤ 4, zb satisfies 1 ≤ zb ≤ 4, mb satisfies 0 ≤ mb ≤ 2, and nb satisfies 5 ≤ nb ≤ 20. ), Li<( xc B yc M色々 cc zc O nc (M cc is at least one element of C, S, Al, Si, Ga, Ge, In, Sn, xc satisfies 0 < xc ≤ 5, yc satisfies 0 < yc ≤ 1, zc satisfies 0 < zc ≤ 1, and nc satisfies 0 < nc ≤ 6. ), Li xd (Al,Ga) yd (Ti,Ge) zd Si ad P md O nd(where 1≦xd≦3, 0≦yd≦1, 0≦zd≦2, 0≦ad≦1, 1≦md≦7, 3≦nd≦13), Li (3-2xe) M ee xe D ee O(xe represents a number between 0 and 0.1, and M ee represents a divalent metal atom. ee represents a halogen atom or a combination of two or more halogen atoms.) Li xf Si yf O zf (1≦xf≦5, 0 <yf≦3、1≦zf≦10)、Li xg S yg O zg (1≦xg≦3, 0 <yg≦2、1≦zg≦10)、Li3BO3-Li2SO4、Li2O-B2O3-P2O5、Li2O-SiO2、Li6BaLa2Ta2O 12 , LiPO (4-3 / 2w) N w (w<1), Li with LISICON (Lithium super ionic conductor) type crystal structure 3.5 Zn 0.25 GeO4, La with perovskite crystal structure 0.55 Li 0.35 TiO3, LiTi2P3O with NASICON (sodium super ionic conductor) type crystal structure 12 , Li 1+xh+yh (Al,Ga) xh (Ti,Ge) 2-xh Si yh P 3-yh O 12 (where 0≦xh≦1, 0≦yh≦1), Li7La3Zr2O with a garnet-type crystal structure 12 (LLZ) and others. Also desirable are phosphorus compounds containing Li, P, and O. For example, lithium phosphate (Li3PO4), LiPON, LiPOD, etc., in which some of the oxygen atoms in lithium phosphate are replaced with nitrogen atoms. 1 (D 1 is at least one selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Ag, Ta, W, Pt, Au, etc. Furthermore, LiA 1 ON(A 1 is at least one selected from Si, B, Ge, Al, C, Ga, etc.) can also be preferably used.

[0044] (iii) Halide-based inorganic solid electrolytes The halide-based inorganic solid electrolyte is preferably a compound that contains a halogen atom, has ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, and has electronic insulation properties. The halide-based inorganic solid electrolyte is not particularly limited, but examples thereof include LiCl, LiBr, LiI, and compounds such as Li3YBr6 and Li3YCl6 described in ADVANCED MATERIALS, 2018, 30, 1803075. Of these, Li3YBr6 and Li3YCl6 are preferred.

[0045] (iv) Hydride-based inorganic solid electrolytes The hydride-based inorganic solid electrolyte is preferably a compound that contains hydrogen atoms, has the ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, and has electronic insulation properties. The hydride-based inorganic solid electrolyte is not particularly limited, but examples thereof include LiBH4, Li4(BH4)3I, 3LiBH4-LiCl, and the like.

[0046] The inorganic solid electrolyte contained in the porous support in the battery is preferably in the form of particles. In this case, the particle size (volume average particle size) is not particularly limited, but is preferably in the same range as the particle size of the inorganic solid electrolyte contained in the porous support in particulate form.

[0047] In addition to the inorganic solid electrolyte, the porous support in the battery may preferably contain a binder described below and, as appropriate, one or more other components. The porous support in the battery does not usually contain a positive electrode active material or a negative electrode active material (excluding metals consisting of ions derived from the positive electrode active material layer), but contains a metal (negative electrode active material) in the charged state.

[0048] - Binder - The binder contained in the porous support in the battery is not particularly limited, and may be an organic polymer, such as a fluorine-containing resin, a hydrocarbon thermoplastic resin, an acrylic resin, a polyurethane resin, a polyurea resin, a polyamide resin, a polyimide resin, a polyester resin, a polyether resin, a polycarbonate resin, or a cellulose derivative resin.

[0049] - Other ingredients - Other components include, but are not limited to, various additives. Examples include thickeners, antifoaming agents, leveling agents, dehydrating agents, and antioxidants. Other examples include inorganic solid electrolyte particles having metallic lithium on their surfaces, conductive particles such as carbon, and particles of metals capable of forming an alloy with lithium, as described in Patent Document 1. For each of the above components described in Patent Document 1, the contents of Patent Document 1 can be referenced as appropriate, and the contents thereof are incorporated herein by reference. Furthermore, the porous support in the battery may contain the electronically conductive particles described in Patent Document 2, but as described above, the all-solid-state secondary battery of the present invention does not necessarily contain electronically conductive particles because an ion conduction path is established (maintained) within the porous support in the battery during charge and discharge. The phrase "not necessarily containing" includes an embodiment in which the content of the components incorporated in the porous support in the battery is 0% by mass, as well as an embodiment in which the content is less than 1% by mass.

[0050] The contents of the inorganic solid electrolyte, binder, and other components incorporated in the porous support in the battery are not particularly limited, but are usually the same as the contents in 100% by mass of the solid content of the composition for porous support described below. Note that the total mass of each component incorporated in the porous support in the battery is synonymous with 100% by mass of the solid content of the composition for porous support.

[0051] The porous support in the battery can be produced by compressing the porous support in the sheet in the stacking direction (thickness direction) by applying pressure to the solid electrolyte laminate sheet of the present invention, thereby adjusting (reducing) the porosity to a predetermined range.

[0052] <Solid electrolyte layer in battery> The solid electrolyte layer in the battery is disposed (laminated) on one surface (main surface) of the porous support in the battery directly or via another layer. This solid electrolyte layer in the battery is composed of an inorganic solid electrolyte, usually particles, that has ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table. The inorganic solid electrolyte particles have voids with a porosity of 10% or less, making it a denser layer than the porous support in the battery. When the porosity of the solid electrolyte layer in the battery is 10% or less, it is possible to prevent dendrites growing in the porous support in the battery from penetrating into the positive electrode active material layer, thereby suppressing the occurrence of internal short circuits. In terms of effectively suppressing the occurrence of internal short circuits, the porosity of the solid electrolyte layer in the battery is preferably 8% or less, more preferably 7% or less. The lower limit of the porosity is not particularly limited, but in practice it is 0.1% or more, and for example, 1% or more is preferred. The difference between the porosity of the porous support in the battery and the porosity of the solid electrolyte layer in the battery is not particularly limited, but can be, for example, 5% or more, preferably 5 to 40%, and more preferably 5 to 30%. The porosity of the solid electrolyte layer in the battery is a value calculated as an area ratio by the above method. The thickness of the solid electrolyte layer in the battery is not particularly limited and can be determined appropriately. For example, in order to effectively prevent penetration of dendrites, the thickness is preferably 10 to 1000 μm, more preferably 20 to 500 μm, and even more preferably 20 to 100 μm. The solid electrolyte layer in the battery is preferably a compressed body of the solid electrolyte layer in the sheet, which will be described later.

[0053] The solid electrolyte layer in the battery, like the porous support in the battery, exhibits metal ion conductivity but does not exhibit electronic conductivity, and functions as a separator for both electrodes.

[0054] The inorganic solid electrolyte constituting the solid electrolyte layer in the battery is as described above, and may be the same or different from the inorganic solid electrolyte contained in the porous support in the battery, but is preferably the same type. The inorganic solid electrolyte constituting the solid electrolyte layer in the battery is usually in the form of particles. The particle size of the inorganic solid electrolyte is not particularly limited, but is preferably 0.01 μm or more, more preferably 0.1 μm or more. The upper limit is preferably 100 μm or less, more preferably 50 μm or less. The particle size of the inorganic solid electrolyte particles is a value measured in the same manner as the particle size of the inorganic solid electrolyte in the porous support. The particle size (volume-average particle size) of inorganic solid electrolyte particles used in the manufacture of all-solid-state secondary batteries or solid electrolyte laminate sheets is not particularly limited, but can be within the particle size range of the inorganic solid electrolyte in the porous support or solid electrolyte layer within the battery, depending on the porous support or solid electrolyte layer within the battery to be incorporated. The particle size of the inorganic solid electrolyte particles used in the manufacture is measured using the following procedure. The inorganic solid electrolyte particles are diluted with water (or heptane for water-unstable substances) in a 20 mL sample bottle to prepare a 1 mass% dispersion. The diluted dispersion sample is irradiated with 1 kHz ultrasound for 10 minutes and then immediately used for testing. This dispersion sample is used with a laser diffraction / scattering particle size analyzer LA-920 (product name, manufactured by HORIBA) to acquire data 50 times at 25°C using a quartz cell for measurement, and the volume-average particle size is determined. For other detailed conditions, please refer to the description of Japanese Industrial Standards (JIS) Z 8828:2013, "Particle Size Analysis - Dynamic Light Scattering Method," as necessary. Five samples are prepared for each level and the average value is used.

[0055] The solid electrolyte layer in the battery may contain one or more inorganic solid electrolytes, but preferably contains two or more inorganic solid electrolytes with different average particle sizes, one of which is preferably particles with an average particle size larger than the opening diameter of the porous support in the battery, and another of which is preferably particles with an average particle size smaller than the opening diameter of the porous support in the battery. This allows the porosity of the solid electrolyte layer in the battery to be set to a small value within the above range. This can be confirmed by observation during porosity measurement. The average particle size larger than the opening size is appropriately determined from the above range depending on the opening size of the porous support in the battery. For example, from the viewpoint of preventing solid electrolytes having an average particle size smaller than the opening size from falling into the pores of the porous support and further from the viewpoint of ion conductivity, it is preferably, for example, 1 to 20 μm, more preferably 2 to 15 μm, and even more preferably 5 to 12 μm. On the other hand, the average particle size smaller than the opening size is appropriately determined depending on the opening size of the porous support in the battery. For example, from the viewpoint of reducing porosity by penetrating between solid electrolytes having an average particle size larger than the opening size, it is preferably, for example, 0.01 to 10 μm, more preferably 0.05 to 5 μm, and even more preferably 1 to 3 μm. The difference between the larger and smaller average particle sizes is, for example, preferably 0.1 to 15 μm, more preferably 0.3 to 12 μm, and even more preferably 0.5 to 10 μm, from the viewpoint of porosity. Furthermore, the ratio of the larger average particle diameter to the smaller average particle diameter [larger average particle diameter / smaller average particle diameter] is, for example, preferably more than 1 and not more than 20, more preferably 1.5 to 15, and even more preferably 2 to 10, in terms of porosity.

[0056] The total content of inorganic solid electrolytes in the solid electrolyte layer in a battery is not particularly limited, but from the viewpoint of establishing an ion conduction path, it is preferably the same as the content in 100% by mass of the solid content of the composition for solid electrolyte in a sheet described below. When the solid electrolyte layer in a battery contains two or more inorganic solid electrolytes, the content of each inorganic solid electrolyte is preferably the same as the content in 100% by mass of the solid content of the composition for solid electrolyte in a sheet described below. Note that 100% by mass of the solid content of the composition for solid electrolyte in a sheet is synonymous with the total mass of the solid electrolyte layer in a battery, and further, the total mass of the components constituting the solid electrolyte layer in a battery in an uncharged all-solid-state secondary battery.

[0057] The solid electrolyte layer in the battery contains an inorganic solid electrolyte, preferably the binder, and may further contain one or more of the other components described above as appropriate. The solid electrolyte layer in the battery usually does not contain a positive electrode active material or a negative electrode active material, but metal may precipitate in the layer in a charged state. The binder used in the solid electrolyte layer in the battery is appropriately selected from those mentioned above, but the binders contained in the porous support in the battery and the solid electrolyte layer in the battery may be the same or different. The content of the binder and other components in the solid electrolyte layer in the battery is not particularly limited, but is usually the same as the content in 100 mass % of the solid content of the solid electrolyte composition in the sheet, which will be described later. The solid electrolyte layer in the battery does not usually contain other components such as inorganic solid electrolyte particles having metallic lithium on the surface as described in Patent Document 1, conductive particles such as carbon, or particles of metals capable of forming an alloy with lithium.

[0058] The solid electrolyte layer can be formed by a conventional method using an inorganic solid electrolyte. The solid electrolyte layer in the battery can be produced by compressing the solid electrolyte laminate sheet of the present invention in the lamination direction (thickness direction) to reduce the porosity to a predetermined range.

[0059] <Cathode active material layer> The positive electrode active material layer contains a positive electrode active material and has the function of generating metal ions upon charging and supplying them to the porous support body within the battery. The thickness of the positive electrode active material is determined appropriately depending on the amount of lithium ions to be supplied, and is, for example, preferably 10 to 1000 μm, more preferably 20 to 500 μm.

[0060] The positive electrode active material layer preferably contains an inorganic solid electrolyte having ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, a conductive additive, a binder, and other components to the extent that the effects of the present invention are not impaired. In addition, in an uncharged state of the all-solid-state secondary battery, one preferred embodiment contains the negative electrode active material precursor described in Patent Document 1. The inorganic solid electrolyte, binder, and other components contained in the positive electrode active material layer are the same as those described for the porous support in the battery. Regarding the negative electrode active material precursor and its function, the contents of Patent Document 1 can be appropriately referenced, and the contents thereof are incorporated herein as is.

[0061] - Cathode active material - The positive electrode active material may be any active material capable of inserting and releasing ions of a metal belonging to Group 1 or 2 of the periodic table, and is preferably one capable of reversibly inserting and releasing lithium ions. The material is not particularly limited as long as it has the above-mentioned properties, and examples thereof include transition metal oxides, organic substances, elements that can be composited with Li, such as sulfur, and composites of sulfur and metals.

[0062] Among these, it is preferable to use a transition metal oxide as the positive electrode active material, and a transition metal element M a A transition metal oxide containing at least one element selected from Co, Ni, Fe, Mn, Cu, and V is more preferred. b (Elements of Group 1 (Ia) of the periodic table other than lithium, elements of Group 2 (IIa), Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Si, P, B, etc.) may be mixed. The amount of the mixed element is determined by the following formula: aThe amount of Li / M is preferably 0 to 30 mol % relative to the amount of Li (100 mol %). a More preferably, the compounds are synthesized by mixing them so that the molar ratio is 0.3 to 2.2. Specific examples of transition metal oxides include (MA) transition metal oxides having a layered rock salt structure, (MB) transition metal oxides having a spinel structure, (MC) lithium-containing transition metal phosphate compounds, (MD) lithium-containing transition metal halide phosphate compounds, and (ME) lithium-containing transition metal silicate compounds.

[0063] (MA) Specific examples of transition metal oxides with a layered rock salt structure include LiCoO2 (lithium cobalt oxide [LCO]), LiNi2O2 (lithium nickel oxide), and LiNi 0.85 Co 0.10 Al 0.05 O2 (nickel cobalt lithium aluminate [NCA]), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (lithium nickel manganese cobalt oxide [NMC]) and LiNi 0.5 Mn 0.5 O2 (lithium manganese nickel oxide). (MB) Specific examples of transition metal oxides having a spinel structure include LiMn2O4 (LMO), LiCoMnO4, Li2FeMn3O8, Li2CuMn3O8, Li2CrMn3O8, and Li2NiMn3O8. (MC) Examples of lithium-containing transition metal phosphate compounds include olivine-type iron phosphates such as LiFePO4 and Li3Fe2(PO4)3, iron pyrophosphates such as LiFeP2O7, cobalt phosphates such as LiCoPO4, and monoclinic Nasicon-type vanadium phosphates such as Li3V2(PO4)3 (lithium vanadium phosphate). (MD) Examples of lithium-containing transition metal halide phosphate compounds include iron fluorophosphates such as Li2FePO4F, manganese fluorophosphates such as Li2MnPO4F, and cobalt fluorophosphates such as Li2CoPO4F. (ME) Examples of lithium-containing transition metal silicate compounds include Li2FeSiO4, Li2MnSiO4, and Li2CoSiO4. In the present invention, transition metal oxides having a layered rock salt structure (MA) are preferred, and LCO or NMC are more preferred.

[0064] The shape of the positive electrode active material is not particularly limited, but a particulate form is preferred. The particle size (volume average particle size) of the positive electrode active material is not particularly limited. For example, it can be 0.1 to 50 μm. A conventional grinder or classifier can be used to adjust the positive electrode active material to a predetermined particle size. The positive electrode active material obtained by the firing method may be used after washing with water, an acidic aqueous solution, an alkaline aqueous solution, or an organic solvent. The average particle size of the positive electrode active material particles can be measured using a method similar to the method for measuring the average particle size of the inorganic solid electrolyte described above.

[0065] The surface of the positive electrode active material may be coated with another metal oxide. Examples of the surface coating agent include metal oxides containing Ti, Nb, Ta, W, Zr, Al, Si, or Li. Specific examples include titanate spinel, tantalum-based oxides, niobium-based oxides, and lithium niobate-based compounds, such as Li4Ti5O 12 , Li2Ti2O5, LiTaO3, LiNbO3, LiAlO2, Li2ZrO3, Li2WO4, Li2TiO3, Li2B4O7, Li3PO4, Li2MoO4, Li3BO3, LiBO2, Li2CO3, Li2SiO3, SiO2, TiO2, ZrO2, Al2O3, B2O3, etc. The surface of the electrode containing the positive electrode active material may be surface-treated with sulfur or phosphorus. Furthermore, the particle surfaces of the positive electrode active material may be subjected to a surface treatment with actinic rays or an active gas (plasma, etc.) before or after the above surface coating.

[0066] The positive electrode active material layer may contain one type or two or more types of positive electrode active materials.

[0067] - Conductive additive - The conductive additive preferably contained in the positive electrode active material layer is not particularly limited, and can be a commonly known conductive additive.For example, it can be an electron conductive material, such as graphites (e.g., natural graphite, artificial graphite), carbon blacks (e.g., acetylene black, ketjen black, furnace black), amorphous carbon (e.g., needle coke), carbon fibers (e.g., vapor-grown carbon fiber or carbon nanotube), carbonaceous materials (e.g., graphene or fullerene), metal powders (e.g., copper, nickel), metal fibers, or conductive polymers (e.g., polyaniline, polypyrrole, polythiophene, polyacetylene, polyphenylene derivatives). In the present invention, when a positive electrode active material and a conductive additive are used in combination, the conductive additive is one among the above-mentioned conductive additives that does not insert or release ions of metals belonging to Group 1 or Group 2 of the periodic table (preferably Li ions) during charging and discharging of the battery and does not function as a positive electrode active material. Therefore, among conductive additives, one that can function as a positive electrode active material in the positive electrode active material layer during charging and discharging of the battery is classified as a positive electrode active material rather than a conductive additive. Whether or not a conductive additive functions as a positive electrode active material during charging and discharging of the battery is not uniquely determined, but is determined by the combination with the conductive additive.

[0068] The shape of the conductive additive is not particularly limited, but is preferably particulate. The particle size is not particularly limited, but is preferably 0.05 to 10 μm, and more preferably 0.1 to 5 μm. The particle size is a value measured in the same manner as the particle size of the inorganic solid electrolyte described above. The conductive additive may contain one kind or two or more kinds.

[0069] The content of each component (positive electrode active material, inorganic solid electrolyte, conductive additive, binder, negative electrode active material precursor, and other components) in the positive electrode active material layer is not particularly limited, but is usually the same as the content in 100% by mass of the solid components in the positive electrode composition described below. Note that 100% by mass of the solid components of the positive electrode composition is synonymous with the total mass of all components constituting the positive electrode active material layer.

[0070] <Negative electrode active material layer> When the all-solid-state secondary battery of the present invention is in a form in which the negative electrode active material layer is formed in advance, the negative electrode active material layer is present between the negative electrode current collector and the porous support body in the battery even in an uncharged state. The thickness of the negative electrode active material is determined appropriately and is, for example, preferably 10 to 1000 μm, more preferably 20 to 500 μm. When a layer made of the negative electrode active material described below is used as the negative electrode active material layer, its thickness can be set to, for example, 0.01 to 100 μm, regardless of the thickness described above. Note that the thickness of the negative electrode active material layer formed in a configuration in which the negative electrode active material layer is not formed in advance cannot be uniquely determined because it varies depending on the amount of metal deposited by charging and the amount formed in the porous support body in the battery.

[0071] The negative electrode active material layer may be any layer containing a negative electrode active material, and examples thereof include a layer made of a negative electrode active material and a layer formed from a negative electrode composition described below. The layer made of the negative electrode active material is preferably a thin metal film, and more preferably a thin metal lithium film (metal lithium foil) that enables realization of high capacity all-solid-state secondary batteries. Examples of the thin metal film include a layer formed by depositing or molding a metal powder, a metal foil, a metal vapor deposition film, etc. The layer formed from the negative electrode composition may include a layer containing a negative electrode active material, an inorganic solid electrolyte preferably having ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, a conductive additive, a binder, and further other components within the range not impairing the effects of the present invention. The inorganic solid electrolyte, binder, and other components contained in the negative electrode active material layer are the same as those described in the porous support body in the battery, and the conductive additive is the same as those described in the positive electrode active material layer.

[0072] - Anode active material - The negative electrode active material is an active material capable of inserting and releasing ions of a metal belonging to Group 1 or 2 of the periodic table, and is preferably one capable of reversibly inserting and releasing lithium ions. The material is not particularly limited as long as it has the above-mentioned properties, and examples thereof include carbonaceous materials, metal oxides, metal composite oxides, lithium alone, lithium alloys, and negative electrode active materials capable of forming an alloy (alloyable) with lithium. Among these, carbonaceous materials, metal composite oxides, and lithium alone are preferably used from the viewpoint of reliability. Active materials capable of forming an alloy with lithium are preferred in terms of enabling an increase in the capacity of all-solid-state secondary batteries. Using a negative electrode active material capable of forming an alloy with lithium as the negative electrode active material enables an increase in the capacity of all-solid-state secondary batteries and a longer battery life.

[0073] The carbonaceous material used as the negative electrode active material is a material essentially composed of carbon. Examples include carbon black such as petroleum pitch and acetylene black (AB), graphite (natural graphite, artificial graphite such as vapor-grown graphite, etc.), and carbonaceous materials obtained by calcining various synthetic resins such as PAN (polyacrylonitrile)-based resins and furfuryl alcohol resins. Further examples include various carbon fibers such as PAN-based carbon fiber, cellulose-based carbon fiber, pitch-based carbon fiber, vapor-grown carbon fiber, dehydrated PVA (polyvinyl alcohol)-based carbon fiber, lignin carbon fiber, glassy carbon fiber, and activated carbon fiber, as well as mesophase microspheres, graphite whiskers, and tabular graphite. These carbonaceous materials can be divided into non-graphitizable carbonaceous materials (also called hard carbon) and graphite-based carbonaceous materials depending on the degree of graphitization. Furthermore, the carbonaceous material preferably has the interplanar spacing, density, and crystallite size described in JP-A-62-22066, JP-A-2-6856, and JP-A-3-45473. The carbonaceous material does not need to be a single material, and a mixture of natural graphite and artificial graphite described in JP-A-5-90844, graphite with a coating layer described in JP-A-6-4516, and the like can also be used. As the carbonaceous material, hard carbon or graphite is preferably used, and graphite is more preferably used.

[0074] The oxide of a metal or metalloid element used as the negative electrode active material is not particularly limited as long as it is an oxide capable of absorbing and releasing lithium, and examples thereof include oxides of metal elements (metal oxides), composite oxides of metal elements, or composite oxides of metal elements and metalloid elements (collectively referred to as metal composite oxides), and oxides of metalloid elements (metalloid oxides). Amorphous oxides are preferred as these oxides, and chalcogenides, which are reaction products of metal elements and elements of Group 16 of the periodic table, are also preferred. In the present invention, the term "metalloid element" refers to an element exhibiting properties intermediate between metal elements and non-metalloid elements, and typically includes six elements: boron, silicon, germanium, arsenic, antimony, and tellurium, and three elements: selenium, polonium, and astatine. Furthermore, "amorphous" refers to an element that exhibits a broad scattering band with a peak in the 2θ range of 20° to 40° in an X-ray diffraction method using CuKα radiation, and may also have crystalline diffraction lines. The strongest intensity of the crystalline diffraction lines seen at 2θ values ​​of 40° to 70° is preferably 100 times or less, more preferably 5 times or less, the diffraction line intensity at the apex of the broad scattering band seen at 2θ values ​​of 20° to 40°, and it is particularly preferable that there are no crystalline diffraction lines.

[0075] Among the compounds consisting of the amorphous oxides and chalcogenides, amorphous oxides or chalcogenides of metalloid elements are more preferred, and (composite) oxides or chalcogenides consisting of one or a combination of two or more elements selected from the elements of Groups 13 (IIIB) to 15 (VB) of the Periodic Table (e.g., Al, Ga, Si, Sn, Ge, Pb, Sb, and Bi) are particularly preferred. Specific examples of preferred amorphous oxides and chalcogenides include Ga2O3, GeO, PbO, PbO2, Pb2O3, Pb2O4, Pb3O4, Sb2O3, Sb2O4, Sb2O8Bi2O3, Sb2O8Si2O3, Sb2O5, Bi2O3, Bi2O4, GeS, PbS, PbS2, Sb2S3, and Sb2S5. Suitable examples of negative electrode active materials that can be used in combination with amorphous oxides mainly containing Sn, Si, or Ge include carbonaceous materials that can occlude and / or release lithium ions or metallic lithium, lithium alone, lithium alloys, and negative electrode active materials that can be alloyed with lithium.

[0076] From the viewpoint of high current density charge / discharge characteristics, it is preferable that the oxides of metal or semi-metal elements, particularly the metal (composite) oxides and the chalcogenides contain at least one of titanium and lithium as a constituent component. Examples of lithium-containing metal composite oxides (lithium composite metal oxides) include composite oxides of lithium oxide and the metal (composite) oxides or the chalcogenides, more specifically Li2SnO2. The negative electrode active material, for example, a metal oxide, preferably contains titanium element (titanium oxide). Specifically, Li4Ti5O 12 Lithium titanate (LTO) is preferred because it has small volume fluctuations when absorbing and releasing lithium ions, has excellent rapid charge and discharge characteristics, suppresses electrode deterioration, and can improve the life of lithium ion secondary batteries.

[0077] The lithium alloy used as the negative electrode active material is not particularly limited as long as it is an alloy that is commonly used as a negative electrode active material for secondary batteries, and examples thereof include lithium-aluminum alloys, specifically lithium-aluminum alloys having lithium as the base metal and 10 mass % of aluminum added thereto.

[0078] The negative electrode active material capable of forming an alloy with lithium is not particularly limited as long as it is one that is commonly used as a negative electrode active material for secondary batteries. Such active materials undergo significant expansion and contraction during charging and discharging of all-solid-state secondary batteries. Examples of such active materials include (negative electrode) active materials (alloys, etc.) containing silicon or tin, and metals such as Al and In. A negative electrode active material containing silicon (silicon-containing active material) that enables higher battery capacity is preferred, and a silicon-containing active material with a silicon content of 50 mol % or more of all constituent elements is more preferred. Generally, negative electrodes containing these negative electrode active materials (for example, Si negative electrodes containing silicon element-containing active materials, Sn negative electrodes containing active materials having tin elements, etc.) can occlude more Li ions than carbon negative electrodes (such as graphite and acetylene black). That is, the amount of Li ions occluded per unit mass increases. Therefore, the battery capacity (energy density) can be increased. As a result, there is an advantage that the battery driving time can be lengthened. Examples of the silicon element-containing active material include silicon materials such as Si and SiOx (0 < x ≤ 1), and further, silicon-containing alloys containing titanium, vanadium, chromium, manganese, nickel, copper, lanthanum, etc. (for example, LaSi2, VSi2, La-Si, Gd-Si, Ni-Si), or organized active materials (for example, LaSi2 / Si). In addition, active materials containing silicon elements and tin elements such as SnSiO3 and SnSiS3 can also be mentioned. Note that SiOx can be used as a negative electrode active material (semimetal oxide) itself, and can also be used as a negative electrode active material (its precursor material) that can be alloyed with lithium because Si is generated by the operation of the all-solid-state secondary battery. Examples of the negative electrode active material having a tin element include Sn, SnO, SnO2, SnS, SnS2, and further, active materials containing the above silicon element and tin element. In addition, composite oxides with lithium oxide, for example, Li2SnO2 can also be mentioned.

[0079] In the present invention, the above-mentioned negative electrode active materials can be used without particular limitation, but in terms of battery capacity, a negative electrode active material that can be alloyed with lithium is a preferred embodiment as the negative electrode active material. Among them, the above silicon material or silicon-containing alloy (alloy containing silicon element) is more preferred, and it is even more preferred to include silicon (Si) or a silicon-containing alloy. Examples of the alloy containing a silicon element include LaSi2, VSi2, La-Si, Gd-Si, and Ni-Si.

[0080] The shape of the negative electrode active material is not particularly limited, but is preferably particulate. The average particle size (volume average particle size) of the negative electrode active material is not particularly limited, but is preferably 0.1 to 60 μm. The average particle size of the negative electrode active material particles can be measured in the same manner as the average particle size of the inorganic solid electrolyte. To achieve a predetermined particle size, a conventional grinder or classifier is used, as with the positive electrode active material. For example, a mortar, ball mill, sand mill, vibration ball mill, satellite ball mill, planetary ball mill, swirling airflow jet mill, sieve, etc. are preferably used. Wet grinding in the presence of water or an organic solvent such as methanol can also be performed during grinding. Classification is preferably performed to achieve a desired particle size. The classification method is not particularly limited, and a sieve, air classifier, etc. can be used. Classification can be performed using either a dry method or a wet method.

[0081] In the present invention, the chemical formula of the compound obtained by the calcination method can be measured by inductively coupled plasma (ICP) emission spectroscopy, or simply calculated from the difference in mass of the powder before and after calcination. The surface of the negative electrode active material may be coated with another metal oxide.

[0082] The negative electrode active material layer may contain one or more types of negative electrode active materials.

[0083] The content of each component (negative electrode active material, inorganic solid electrolyte, conductive additive, binder, and other components) in the negative electrode active material layer is not particularly limited, but is usually the same as the content in 100% by mass of the solid components in the negative electrode composition described below. Note that 100% by mass of the solid components of the negative electrode composition is synonymous with the total mass of all components constituting the negative electrode active material layer formed from the negative electrode composition.

[0084] The all-solid-state secondary battery of the present invention has the above-described layers, and preferably or appropriately has the following constituent layers. <Positive electrode current collector> The all-solid-state secondary battery of the present invention preferably has a positive electrode current collector. The positive electrode current collector can be made of an electron conductor. The material for forming the positive electrode current collector is not particularly limited, but in addition to aluminum, aluminum alloys, stainless steel, nickel, and titanium, aluminum or stainless steel surfaces treated with carbon, nickel, titanium, or silver (thin films formed thereon) are preferred, and among these, aluminum and aluminum alloys are more preferred. The positive electrode current collector is usually in the form of a film sheet, but net, punched, lath, porous, foamed, or fibrous molded body can also be used. The thickness of the positive electrode current collector (including the above thin film) is not particularly limited, but is preferably 1 to 500 μm. It is also preferable to make the surface of the current collector uneven by surface treatment.

[0085] In the present invention, a functional layer or member may be appropriately interposed or disposed between or on the outside of each of the negative electrode current collector, negative electrode active material layer, solid electrolyte layer, positive electrode active material layer, and positive electrode current collector. Each layer may be composed of a single layer or multiple layers.

[0086] <Metal film that can form an alloy with lithium> The all-solid-state secondary battery of the present invention may have a metal film capable of forming an alloy with lithium between the negative electrode current collector and the porous support in the battery. This metal film is usually provided and disposed on the surface of the negative electrode current collector (the surface disposed on the porous support side in the battery) or on the surface of the porous support in the battery (the surface disposed on the negative electrode current collector side). The film of a metal capable of forming an alloy with lithium is not particularly limited as long as it is a metal film formed of a metal capable of forming an alloy with lithium. Examples of the metal capable of forming an alloy with lithium include Sn, Al, In, etc., which are described above in the negative electrode active material, as well as metals such as Zn, Bi, and Mg. Among these, Zn, Bi, etc. are preferred. The thickness of this metal film is not particularly limited, but is preferably 300 nm or less, more preferably 20 to 100 nm, and even more preferably 30 to 50 nm. By incorporating the above-mentioned metal film into an all-solid-state secondary battery, the state of precipitation of metallic lithium due to charging can be effectively controlled, and the occurrence of short circuits can be more effectively suppressed (the time until a short circuit occurs can be extended (the number of charge / discharge cycles can be extended)). For details of this metal film and the method of forming it, the contents of Patent Document 1 can be referred to as appropriate, and the contents thereof are incorporated as is into this specification as part of the description.

[0087] <Dendrite penetration prevention layer> The all-solid-state secondary battery of the present invention also preferably has a dendrite penetration blocking layer between the porous support and the positive electrode active material layer in the battery, preferably between the porous support and the solid electrolyte layer in the battery. The dendrite penetration blocking layer can be a known layer (film) or can be prepared as appropriate. Known layers include layers formed from an oxide-based inorganic solid electrolyte, such as LiPON, as described below, and layers formed by the method described in Patent Document 1 (shearing treatment or heat treatment). The porosity of a dendrite penetration blocking layer prepared by the method described in Patent Document 1 is preferably 3% or less, more preferably 1% or less. The dendrite penetration blocking layer is usually formed as a thin layer, and although there are no particular limitations on the thickness thereof, it is preferably 0.001 to 100 μm, and more preferably 0.01 to 10 μm. For details of a preferred dendrite penetration blocking layer and a method for producing it, the contents of Patent Document 1 can be referred to as appropriate, and the contents thereof are incorporated as is into this specification as part of the description.

[0088] <Case> Depending on the application, the all-solid-state secondary battery of the present invention may be used as an all-solid-state secondary battery with the above-mentioned layer structure as it is, but it is also preferable to further encapsulate it in an appropriate casing to make it into a form such as a dry cell. The casing may be made of metal or resin (plastic). When a metallic casing is used, examples include those made of aluminum alloy and stainless steel. The metallic casing is preferably divided into a positive electrode casing and a negative electrode casing, and is electrically connected to the positive electrode current collector and the negative electrode current collector, respectively. The positive electrode casing and the negative electrode casing are preferably joined and integrated via a gasket to prevent short circuits.

[0089] <Applications of all-solid-state secondary batteries> The all-solid-state secondary battery of the present invention can be used in a variety of applications. While there are no particular limitations on the application, examples of applications include electronic devices such as notebook computers, pen-input PCs, mobile PCs, electronic book players, mobile phones, cordless phone handsets, pagers, handheld terminals, portable fax machines, portable copiers, portable printers, headphone stereos, video camcorders, LCD televisions, handheld vacuum cleaners, portable CD players, mini-discs, electric shavers, transceivers, electronic organizers, calculators, portable tape recorders, radios, backup power supplies, and memory cards. Other consumer applications include automobiles (e.g., electric vehicles), electric vehicles, motors, lighting fixtures, toys, game consoles, road conditioners, clocks, flash devices, cameras, and medical devices (e.g., pacemakers, hearing aids, and shoulder massagers). Furthermore, the battery can be used for various military and space applications. It can also be combined with solar cells.

[0090] [Solid electrolyte laminated sheet] The solid electrolyte laminate sheet of the present invention is a sheet-like molded article that is suitably used in the method for producing an all-solid-state secondary battery of the present invention described below, and that constitutes an internal porous support body and an internal solid electrolyte layer in the all-solid-state secondary battery of the present invention. The solid electrolyte laminate sheet of the present invention comprises a sheet-like porous support (hereinafter also referred to as an intra-sheet porous support) incorporating an inorganic solid electrolyte having ion conductivity of a metal belonging to Group 1 or 2 of the periodic table, and a solid electrolyte layer (hereinafter also referred to as an intra-sheet solid electrolyte layer) disposed on one surface of the intra-sheet porous support and containing an inorganic solid electrolyte having ion conductivity of a metal belonging to Group 1 or 2 of the periodic table. The porosity of the intra-sheet porous support is 20% or more, and the porosity of the intra-sheet solid electrolyte layer is set to be smaller than the porosity of the intra-sheet porous support. The porosity of each layer is measured by the above-mentioned measurement method.

[0091] In the solid electrolyte laminate sheet, the above-mentioned other layers may be interposed between the in-sheet porous support and the in-sheet solid electrolyte layer, but it is preferable that the in-sheet porous support and the in-sheet solid electrolyte layer are adjacent to each other. The in-sheet porous support may have various functional layers on the side opposite to the in-sheet solid electrolyte layer. Different layers are arranged as this functional layer depending on the form of the all-solid-state secondary battery to be manufactured. For example, in a form in which the negative electrode active material layer is formed in advance, the negative electrode active material layer and further the substrate (preferably the negative electrode current collector) are laminated, and it is preferable that these are adjacent to each other. On the other hand, in a form in which the negative electrode active material layer is not formed in advance, it is preferable that the substrate (preferably the negative electrode current collector) is laminated, and both layers are adjacent to each other. In addition to the above layers, functional layers also include protective layers (release sheets), coating layers, etc. The substrate is not particularly limited as long as it can support the solid electrolyte laminate sheet, and examples thereof include sheets (plates) of the materials described above for the negative electrode or positive electrode current collector, organic materials, and inorganic materials. Examples of organic materials include various polymers, specifically polyethylene terephthalate, polypropylene, polyethylene, and cellulose. Examples of inorganic materials include glass and ceramics.

[0092] In the present invention, each layer constituting the solid electrolyte laminate sheet may have a single layer structure or a multi-layer structure, as long as it exhibits a specific function. The solid electrolyte laminate sheet of the present invention is not particularly limited in its configuration as long as it has the above-described laminate structure, and any known configuration related to solid electrolyte laminate sheets can be used. For example, the solid electrolyte laminate sheet of the present invention preferably has a film of a metal capable of forming an alloy with lithium on the surface of the intra-sheet porous support opposite the intra-sheet solid electrolyte layer. A known dendrite penetration blocking layer can also be disposed between the intra-sheet porous support and the intra-sheet solid electrolyte layer. Furthermore, the intra-sheet solid electrolyte layer may have a positive electrode active material layer and further a positive electrode current collector on the surface opposite the intra-sheet porous support.

[0093] The solid electrolyte laminate sheet of the present invention is preferably used in combination with a positive electrode sheet described later (as a sheet to be laminated by pressure bonding to the positive electrode sheet) in the method for producing an all-solid-state secondary battery of the present invention to form an all-solid-state secondary battery.

[0094] 2 is a cross-sectional view showing a schematic diagram of the stacking state of the constituent layers constituting one embodiment of a solid electrolyte laminate sheet suitable for use in a self-forming anode-type all-solid-state secondary battery of the present invention. This solid electrolyte laminate sheet 11 has a layer structure in which an anode current collector 1, an intra-sheet porous support 8, and an intra-sheet solid electrolyte layer 9 are stacked in this order, with the stacked layers being in direct contact with each other. When used in the manufacture of an all-solid-state secondary battery in a form in which the negative electrode active material layer is formed in advance, as described above, the negative electrode active material layer (not shown in FIG. 2) is disposed between the negative electrode current collector 1 and the intra-sheet porous support 8. The solid electrolyte laminate sheet of the present invention is suitably used in the method for producing an all-solid-state secondary battery of the present invention described below, and by applying pressure to the solid electrolyte laminate sheet, the above-mentioned porous support body and solid electrolyte layer in the battery are formed, thereby contributing to suppressing the occurrence of internal short circuits and improving the cycle characteristics of the all-solid-state secondary battery.

[0095] The solid electrolyte laminate sheet of the present invention is usually in a sheet form, but also includes a laminate sheet material cut into a predetermined shape when producing the all-solid-state secondary battery of the present invention. For example, a plate-shaped or disk-shaped laminate sheet material can be mentioned depending on the shape of the all-solid-state secondary battery.

[0096] <Negative electrode current collector> The negative electrode current collector preferably applied to the solid electrolyte laminate sheet of the present invention is as explained (same meaning) for the negative electrode current collector in the above-mentioned all-solid-state secondary battery.

[0097] <Porous support inside the sheet> The intra-sheet porous support provided in the solid electrolyte laminate sheet of the present invention is a sheet-like porous support incorporating an inorganic solid electrolyte having ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table. This intra-sheet porous support is a layer that is incorporated into an all-solid-state secondary battery to become the intra-battery porous support. Therefore, the intra-sheet porous support is the same as the above-mentioned intra-battery porous support, except that it is a porous support before being compressed under pressure and has a porosity of 20% or more. When the porosity of the porous support within the sheet is 20% or more, even when pressure is applied during the production of an all-solid-state secondary battery, the porosity of the porous support within the battery can be prevented from decreasing to less than 15% (excessive compression of the porous support within the sheet), and a porous support within the battery with a predetermined porosity can be formed by pressure application. The porosity of the porous support within the sheet cannot be uniquely determined because the range within which the porosity of the porous support within the battery can be achieved varies depending on the pressure applied, the porosity of the solid electrolyte layer within the sheet (described below), and the like. As an example of the porosity of the porous support within the sheet that allows the above porosity of the porous support within the battery, it is preferably 40% or more, more preferably 50% or more. The upper limit of the porosity can be determined appropriately, and is, for example, preferably 99% or less, more preferably 95% or less, and even more preferably 90% or less.

[0098] The thickness of the porous support in the sheet is not particularly limited, and since the amount of compression (thickness) varies depending on the pressure, it can be appropriately determined taking into consideration the amount of compression required to form a porous support in the battery, etc. For example, it can be 1 to 100 μm, and preferably 3 to 80 μm.

[0099] The components (compounds) and their contents contained in the porous support within the sheet are the same as those contained in the porous support within the battery, but the content is based on the total mass of the components contained in the porous support within the sheet, and this total mass is equivalent to 100 mass% of the solid content of the composition because the inorganic solid electrolyte and the like are contained in the porous support within the sheet.

[0100] <Solid electrolyte layer inside the sheet> The in-sheet solid electrolyte layer is disposed (laminated) on one surface (main surface) of the in-sheet porous support, either directly or via another layer. This in-sheet solid electrolyte layer is composed of an inorganic solid electrolyte, usually containing particles thereof, that has ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table. This in-sheet solid electrolyte layer is a layer that is incorporated into an all-solid-state secondary battery to become the in-cell solid electrolyte layer. Thus, the in-sheet solid electrolyte layer is a solid electrolyte layer before being compressed, and has a smaller porosity than the in-sheet porous support. Except for the fact that it is not specifically specified, it is the same as the in-cell porous support described above. If the porosity of the in-sheet solid electrolyte layer is smaller than the porosity of the in-sheet porous support, combined with the fact that the in-sheet porous support has a porous support as a basic skeleton, the in-battery porous support and in-battery solid electrolyte layer having porosities within the above-mentioned predetermined range can be formed by simultaneously pressurizing both layers. As described above, the porosity of the solid electrolyte layer within the sheet may be smaller than that of the porous support within the sheet, but the porosity of the solid electrolyte layer within the sheet cannot be uniquely determined because the range within which the porosity of the solid electrolyte layer within the battery can be set varies depending on the pressure, the porosity of the porous support within the sheet, etc. An example of the porosity of the solid electrolyte layer within the sheet is preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more, from the viewpoints of easily setting the porosities of the porous support within the battery and the solid electrolyte layer within the battery within the above range, and furthermore, of realizing strong adhesion with the positive electrode active material layer (reduced interlayer resistance) when the positive electrode active material layer is also pressurized and bonded to the solid electrolyte layer. The difference between the porosity of the porous support in the sheet and the porosity (filling amount) of the solid electrolyte layer in the sheet is not particularly limited, but is preferably, for example, 5 to 90%, more preferably 10 to 50%.

[0101] The thickness of the solid electrolyte layer in the sheet is not particularly limited, and since the amount of compression (thickness) varies depending on the pressure, it can be appropriately determined taking into consideration the amount of compression required to form a solid electrolyte layer in the battery, etc. For example, it can be 1 to 150 μm, and preferably 3 to 100 μm.

[0102] The components (compounds) and their contents in the in-sheet solid electrolyte layer are the same as those in the in-battery solid electrolyte layer, but the content is based on the total mass of the in-sheet solid electrolyte layer, which is synonymous with the sum of the mass of the components constituting the in-sheet solid electrolyte layer, and further with 100% by mass of the solid content of the composition forming the in-sheet solid electrolyte layer.

[0103] <Method for producing solid electrolyte laminated sheet> The method for producing the solid electrolyte laminated sheet of the present invention is not particularly limited, and the sheet can be produced, for example, by a method in which a porous support composition containing an inorganic solid electrolyte (a composition for incorporating an inorganic solid electrolyte or the like into an intra-sheet porous support) is applied to and impregnated into a porous support to form an intra-sheet porous support, and then a composition for an intra-sheet solid electrolyte layer containing an inorganic solid electrolyte (a composition for forming an intra-sheet solid electrolyte layer) is formed on this intra-sheet porous support. The porous support and the solid electrolyte layer within the sheet may be formed individually, sequentially, or collectively as a laminate.

[0104] (Preparation of Composition) In producing the solid electrolyte laminate sheet, a porous support composition and an in-sheet solid electrolyte composition are prepared. The porous support constituting the in-sheet porous support is as described above. The composition for a porous support and the composition for a solid electrolyte in a sheet (sometimes referred to as each composition) each contain an inorganic solid electrolyte, and preferably contain a binder, a dispersion medium, and may further contain other components as appropriate. The components other than the dispersion medium contained in each composition are as described above.

[0105] - Dispersion medium - The dispersion medium used in preparing each composition may be any medium capable of dispersing (dissolving) each of the above-mentioned components contained in each composition. In the present invention, the dispersion medium is preferably a non-aqueous dispersion medium that does not contain water, and is usually selected from organic solvents. In the present invention, the dispersion medium not containing water includes an embodiment in which the water content is 0% by mass, as well as an embodiment in which the water content is 0.1% by mass or less. However, the water content in each composition is preferably within the above range (non-aqueous composition). The organic solvent is not particularly limited, but examples thereof include organic solvents such as alcohol compounds, ether compounds, amide compounds, amine compounds, ketone compounds, aromatic compounds, aliphatic compounds, nitrile compounds, and ester compounds. The dispersion medium contained in each composition may be one type or two or more types.

[0106] Each composition is preferably a non-aqueous composition. In the present invention, the term "non-aqueous composition" encompasses not only an embodiment that does not contain water, but also an embodiment in which the water content (also referred to as water content) is 200 ppm or less. The water content of the composition is preferably 150 ppm or less, more preferably 100 ppm or less, and even more preferably 50 ppm or less. The water content indicates the amount of water contained in the composition (mass ratio relative to the composition). The water content can be determined by filtering the composition through a 0.45 μm membrane filter and subjecting it to Karl Fischer titration.

[0107] - Content of each component - The content of the inorganic solid electrolyte in each composition is not particularly limited, but from the viewpoint of binding property, it is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on 100% by mass of the solid content. From the same viewpoint, the upper limit is preferably 99.9% by mass or less, more preferably 99.5% by mass or less, and particularly preferably 99% by mass or less. When the solid electrolyte composition in a sheet contains two or more of the inorganic solid electrolytes described above, the content of each inorganic solid electrolyte is appropriately determined in consideration of the total content and the porosity. For example, at 100% by mass of solid content, the content of the large particle size (average particle size) is preferably 0.1 to 90% by mass, more preferably 0.1 to 80% by mass, and can also be 1 to 50% by mass. The lower limit of the content of the large particle size can also be 60% or 70% by mass. On the other hand, the content of the small particle size (average particle size) is preferably 0.1 to 50% by mass, more preferably 5 to 25% by mass, and can also be 5 to 10% by mass. The difference in content between the large average particle size and the small average particle size is, for example, preferably 0.1 to 90% by mass, more preferably 10 to 90% by mass, and even more preferably 50 to 85% by mass. The ratio of the content of large average particle diameter to the content of small average particle diameter [content of large average particle diameter / content of small average particle diameter] is, for example, preferably more than 1 and 20 or less, and more preferably 2 to 10.

[0108] The content of the binder in each composition is not particularly limited, and from the viewpoints of strengthening the binding property of the solid particles and further adjusting the porosity, for example, it is preferably 0.1 to 10 mass%, more preferably 1 to 10 mass%, and even more preferably 2 to 6 mass%, based on 100 mass% of the solid content. The contents of other components in each composition are not particularly limited and may be set appropriately. The content of the composition is based on 100 parts by mass of the solid content of the composition. In the present invention, the solid content (solid components) refers to components that do not volatilize or vaporize when the composition is dried at 130°C for 6 hours under a nitrogen atmosphere at an atmospheric pressure of 1 mmHg. Typically, this refers to components other than the dispersion medium.

[0109] The solids concentration of the composition for a porous support is not particularly limited, but should not be excessively high so as to enable each component in the composition, particularly the inorganic solid electrolyte, to be filled (penetrated, attached, or arranged) in the pores of the porous support. For example, the solids concentration is preferably 20 to 70 mass %, more preferably 30 to 65 mass %, and even more preferably 35 to 50 mass %. On the other hand, the solid content concentration of the in-sheet solid electrolyte composition is not particularly limited, but is preferably high so as not to fill the pores of the porous support with the components in the composition, for example, 40 to 80 mass % is preferable, and 50 to 80 mass % is more preferable. With this solid content concentration, when the in-sheet solid electrolyte composition contains particles larger and smaller than the opening diameter of the porous support, even the small particles can be prevented from penetrating the pores of the porous support, and a solid electrolyte layer can be formed on the in-sheet porous support together with the large particles.

[0110] - Preparation method of each composition - Each composition can be prepared, for example, as a solid mixture or a slurry, by mixing the above-mentioned components in, for example, any of various commonly used mixers. The mixing method is not particularly limited, and can be carried out using a known mixer such as a ball mill, a bead mill, or a disk mill. The mixing conditions are also not particularly limited. The mixing atmosphere may be any of air, dry air (dew point -20°C or lower), and inert gas (e.g., argon gas, helium gas, or nitrogen gas). Since inorganic solid electrolytes react with moisture, mixing is preferably carried out in dry air or inert gas.

[0111] (Support Forming Method and Film Forming Method) The porous support composition and the in-sheet solid electrolyte composition are applied (impregnated) and dried to form a membrane, thereby forming an in-sheet porous support and an in-sheet solid electrolyte layer. The method for applying the composition for a porous support and the composition for an in-sheet solid electrolyte can be any of various application methods, such as spray coating, spin coating, dip coating, slit coating, stripe coating, bar coating, and application using a Baker applicator, without any particular limitations. When forming an in-sheet porous support, it is preferable to allow the composition for a porous support applied to the porous support to stand still and allow it to impregnate (penetrate into the pores of) the porous support. The impregnation time is not particularly limited and can be determined appropriately. The application temperature and impregnation temperature for each composition are not particularly limited, and are preferably performed without heating, for example, at a temperature of 0 to 50°C. The drying temperature for both compositions is not particularly limited, but the lower limit is preferably 30°C or higher, more preferably 60°C or higher, and even more preferably 80°C or higher. The upper limit of the drying temperature is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower. Heating within this temperature range removes the dispersion medium, converts the composition for a porous support into a solid state (impregnated and dried state), and allows it to adhere (fill) into the pores of the porous support, and also converts the composition for an in-sheet solid electrolyte layer into a solid state (coated and dried layer). The drying time is not particularly limited, but is, for example, 0.3 to 5 hours. The coated and dried layer formed from the composition for an in-sheet solid electrolyte layer can also be pressurized. The pressing method is not particularly limited, but pressurization (e.g., pressurization using a hydraulic cylinder press) is preferred. The pressure is not particularly limited, but is set to a pressure such that the porosity after pressing is not smaller than the porosity of the in-sheet porous support, and can be, for example, 10 to 200 MPa. Heating can be performed simultaneously with pressing the coated and dried layer. The temperature at this time is not particularly limited, but is preferably 10 to 100°C, for example. The support formation method and film formation method are preferably carried out in an atmosphere in which the above-mentioned compositions are mixed.

[0112] - Formation of porous support within the sheet - By employing the above-mentioned method, conditions, etc., the porous support composition can be applied to the porous support, impregnated, and then dried to form a porous support in a sheet having a predetermined porosity. In this case, it is preferable to place (place) the porous support on the surface of a substrate. The porosity of the porous support within the sheet can be appropriately set by the porosity of the porous support itself, the solids concentration (viscosity) of the composition for a porous support, the particle size of each component contained in the composition for a porous support, particularly the inorganic solid electrolyte, the impregnation time, and, if pressurized, the applied pressure, etc. For example, the porosity tends to decrease when the solids concentration is reduced, when the particle size of each component is reduced, or when the impregnation time is extended.

[0113] - Formation of solid electrolyte layer inside the sheet - Alternatively, after forming an intra-sheet porous support, the intra-sheet solid electrolyte layer composition can be formed on the intra-sheet porous support by forming a membrane using the above-mentioned method, conditions, etc., to form an intra-sheet solid electrolyte layer. The porosity of the intra-sheet solid electrolyte layer can be appropriately set by the solid content (viscosity) of the porous support composition, the components contained in the porous support composition, particularly the particle size of the inorganic solid electrolyte, and, if pressurized, the applied pressure, etc. For example, the porosity tends to decrease when the solid content concentration is reduced, when the particle size of each component is reduced, or when two or more inorganic solid electrolytes with different particle sizes are used. In forming an in-sheet solid electrolyte layer, when a composition for an in-sheet solid electrolyte layer containing an inorganic solid electrolyte having a particle size smaller than the opening size of the in-sheet porous support is used, the solids concentration of the composition for an in-sheet solid electrolyte layer, the coexistence of an inorganic solid electrolyte having a particle size larger than the opening size, etc., can prevent the inorganic solid electrolyte having a small particle size from falling into the pores of the porous support, and most of the inorganic solid electrolyte having a small particle size can be used to form the in-sheet solid electrolyte layer.

[0114] Another method for producing an in-sheet solid electrolyte layer includes, for example, forming a film (coating and drying) of a composition for an in-sheet solid electrolyte layer on a substrate, or press-molding the composition for an in-sheet solid electrolyte layer to form a solid electrolyte layer, and then providing the solid electrolyte layer on an in-sheet porous support (press-laminating or pasting). The substrate used is not particularly limited, but examples include sheets (plates) made of organic or inorganic materials. Examples of organic materials include various polymers, specifically polyethylene terephthalate, polypropylene, polyethylene, cellulose, etc. Examples of inorganic materials include glass and ceramic. The method and conditions for forming a film of the composition for an in-sheet solid electrolyte layer are the same as those for the above-mentioned coating and drying method. The conditions for press-lamination may be any conditions that allow press-lamination of the solid electrolyte layer formed on the in-sheet porous support, such as a pressure of 1 to 100 MPa and preferably 10 to 100°C. The atmosphere for press-lamination is the same as the mixing atmosphere used when preparing the above-mentioned compositions.

[0115] (Pressure process) In the preparation of the solid electrolyte laminate sheet, after preparing the laminate of the porous support and the solid electrolyte layer in the sheet as described above, the laminate may be pressurized. The pressurizing method and pressure are not particularly limited, but are the same as those for the coated and dried layer.

[0116] In this way, a solid electrolyte laminate sheet having an in-sheet porous support and an in-sheet solid electrolyte layer can be produced. The in-sheet porous support and the in-sheet solid electrolyte layer of the produced solid electrolyte laminate sheet may contain (remain) the dispersion medium used in preparing each composition, as long as the effects of the present invention are not impaired. The remaining amount can be, for example, 3 mass% or less in the layer.

[0117] [Method of manufacturing the all-solid-state secondary battery of the present invention] Next, a method for producing an all-solid-state secondary battery of the present invention (hereinafter sometimes referred to as the production method of the present invention) will be described. The manufacturing method of the present invention is a method for manufacturing an all-solid-state secondary battery using the solid electrolyte laminate sheet of the present invention, and includes a step of pressurizing the solid electrolyte laminate sheet until the porosity of the solid electrolyte layer becomes 10% or less, while restricting the porosity of the porous support of the solid electrolyte laminate sheet to 15% or more. This makes it possible to manufacture an all-solid-state secondary battery that is suppressed from causing internal short circuits and has excellent cycle characteristics by a simple method called pressure lamination. In this pressurizing step, it is preferable to pressurize and compress the solid electrolyte laminate sheet onto the negative electrode current collector or the positive electrode active material layer (pressure compression, compression lamination), rather than using the solid electrolyte laminate sheet alone. It is more preferable to pressurize and compress the positive electrode active material layer, since this allows the layer structure essential for an all-solid-state secondary battery to be produced in the pressurizing step and enables strong adhesion with the positive electrode active material layer (reduction in interface resistance).

[0118] When the cathode active material layer is laminated with the solid electrolyte laminate sheet of the present invention by pressure bonding, a cathode sheet comprising a cathode active material layer can be used as the cathode active material layer, but it is preferable to use a cathode sheet having a cathode current collector and a cathode active material layer. The cathode active material layer and cathode current collector constituting the cathode sheet are the same as those in the above-mentioned all-solid-state secondary battery. However, since the cathode active material layer of the cathode sheet may be thinned by the above-mentioned pressure bonding lamination, the thickness is determined so that even when thinned, it remains the thickness required for the cathode active material layer of the all-solid-state secondary battery. This cathode sheet may have other layers and functional layers described for the solid electrolyte laminate sheet. The positive electrode sheet is usually in a sheet form, similar to the solid electrolyte laminate sheet, but it may also be cut into a predetermined shape (positive electrode sheet material) for use in the manufacturing method of the present invention.

[0119] - Preparation of positive electrode sheet - The positive electrode sheet can be produced by various known methods. For example, the positive electrode sheet can be produced by forming a positive electrode active material layer on the surface of a substrate, preferably a positive electrode current collector. In this production method, first, a composition (positive electrode composition) for forming the positive electrode active material layer is prepared. The positive electrode composition contains a positive electrode active material, preferably an inorganic solid electrolyte, a conductive additive, a binder, a dispersion medium, and optionally other components. The components contained in the positive electrode composition are as described above.

[0120] The content of the positive electrode active material in the positive electrode composition is not particularly limited, and is preferably 10 to 95 mass %, more preferably 30 to 90 mass %, still more preferably 50 to 85 mass %, and particularly preferably 55 to 80 mass %, based on 100 mass % of the solid content. When the positive electrode composition contains an inorganic solid electrolyte, the content of the inorganic solid electrolyte in the positive electrode composition is not particularly limited, but the total content of the positive electrode active material and the inorganic solid electrolyte is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 50% by mass or more, particularly preferably 70% by mass or more, and most preferably 90% by mass or more, based on 100% by mass of the solid content. The upper limit is not particularly limited, and is, for example, preferably 99.9% by mass or less, more preferably 99.5% by mass or less, and even more preferably 99% by mass or less, based on 100% by mass of the solid content. The content of the conductive auxiliary in the positive electrode composition is not particularly limited, and is preferably 0.1 to 20 mass %, more preferably 0.5 to 10 mass %, relative to 100 mass % of the solid content. The content of the binder in the positive electrode composition is not particularly limited, and from the viewpoints of strengthening the binding property of the solid particles and further adjusting the porosity, for example, the content is preferably 0.1 to 10 mass%, more preferably 1 to 10 mass%, and even more preferably 2 to 6 mass%, relative to 100 mass% of the solid content. The content of the dispersion medium in the positive electrode composition is not particularly limited, but is preferably 20 to 80 mass %, more preferably 30 to 70 mass %, and particularly preferably 40 to 60 mass %. The positive electrode composition is preferably a non-aqueous composition.

[0121] (Preparation of Positive Electrode Composition) The positive electrode composition can be prepared, for example, as a solid mixture or a slurry by mixing the above-mentioned components, for example, using various commonly used mixers. The mixing method and mixing conditions are the same as those for preparing the above-mentioned porous support composition.

[0122] (Formation of positive electrode active material layer) The positive electrode active material layer is not particularly limited, and can be produced by a coating and drying method in which a positive electrode composition (slurry) is applied to the surface of a substrate, preferably a positive electrode current collector, and then dried, or a molding method in which the positive electrode composition is pressure-molded, or the like. In either method, the atmosphere during production is not particularly limited, and may be a mixture atmosphere of the above-mentioned compositions. The method for forming the positive electrode active material layer is the same as the method for forming the in-sheet solid electrolyte layer, except for the composition used and the surface to be formed, except that the porosity does not need to be actively adjusted when forming the positive electrode active material layer.

[0123] The positive electrode sheet can also be produced by forming a positive electrode active material layer on a substrate instead of the positive electrode current collector and then providing the film on the positive electrode current collector (by pressure lamination or pasting). The substrate, pressure lamination conditions, etc. used in this method are the same as those used in other methods for producing a solid electrolyte layer in a solid electrolyte laminate sheet.

[0124] As described above, a positive electrode sheet having a positive electrode active material layer preferably on a positive electrode current collector can be produced.

[0125] <Compression lamination process> In the manufacturing method of the present invention, a fabricated or prepared solid electrolyte laminate sheet and a positive electrode sheet are laminated together by pressure bonding through the following sequential steps of overlapping and pressing. Specifically, the manufacturing method of the present invention uses a solid electrolyte laminate sheet having an intra-sheet porous support and an intra-sheet solid electrolyte layer. The laminate sheet is pressurized and integrated with a positive electrode active material layer to compress the intra-sheet porous support and the intra-sheet solid electrolyte layer to a predetermined porosity, thereby forming an intra-battery porous support and an intra-battery solid electrolyte layer with reduced porosity. This ensures space for metal deposition within the intra-battery porous support and densifies the intra-battery solid electrolyte layer. Furthermore, the interlayer adhesion between the intra-battery solid electrolyte layer and the intra-battery positive electrode active material layer can be strengthened.

[0126] The overlapping step: overlapping the solid electrolyte laminate sheet and the positive electrode sheet with the solid electrolyte layer of the solid electrolyte laminate sheet facing the positive electrode active material layer of the positive electrode sheet. Pressurizing step: Pressurizing the stacked solid electrolyte laminate sheet and the positive electrode sheet in the stacking direction until the porosity of the solid electrolyte layer becomes 10% or less, while keeping the porosity of the porous support at 15% or more.

[0127] In the present invention, "performing steps in order" means the temporal order in which one step is performed relative to another step, and also includes a mode in which another step (including a pause step) is performed between one step and another step. Furthermore, the mode in which one step is performed relative to another step also includes a mode in which the time, place, or performer is changed as appropriate.

[0128] - Layering process - The overlapping step can be carried out by stacking (stacking) both sheets in a conventional manner, and this step results in the solid electrolyte layer and the positive electrode active material layer in the sheets being in contact (adjacent) with each other.

[0129] - Pressurizing process - Next, while maintaining this overlapping state, the overlapped solid electrolyte laminate sheet and the positive electrode sheet are pressed (compressed) in the overlapping direction. The pressure applied at this time is set to a pressure that keeps the porosity of the porous support (intra-battery porous support) after pressurization at 15% or more (maintains 15% or more, i.e., does not decrease to 15% or less), and also makes the porosity of the solid electrolyte layer (intra-battery solid electrolyte layer) after pressurization 10% or less. That is, in the pressurizing step, both sheets are pressed to set the porosity of the intra-battery porous support to 15% or more and the porosity of the intra-battery solid electrolyte layer to less than 10%.

[0130] In the manufacturing method of the present invention, the porosity of the porous support in the battery after pressurization is not limited to less than 15%, and is set to the above-mentioned porosity of the porous support in the battery. The reduction in porosity due to pressurization (porosity of the porous support in the sheet before pressurization - porosity after pressurization) is not particularly limited, but is preferably 5 to 40%, and more preferably 5 to 30%, for example. On the other hand, the porosity of the solid electrolyte layer in the battery after pressurization may be less than 10%, and is set to the above-mentioned porosity of the solid electrolyte layer in the battery. The amount of porosity reduction by pressurization (porosity of the solid electrolyte layer in the sheet before pressurization - porosity after pressurization) is not particularly limited, but is preferably 10 to 60%, and more preferably 20 to 50%, for example.

[0131] The method of applying pressure is not particularly limited, and various known pressure applying methods can be applied, with press pressing (for example, press pressing using a hydraulic cylinder press) being preferred. The pressure in the pressurizing step may be any pressure that results in the porosity of the porous support in the battery and the solid electrolyte layer in the battery falling within the above range, but cannot be uniquely determined because it varies depending on the porosity of the porous support in the sheet and the solid electrolyte layer in the sheet, the porosity after pressurization, etc. The pressure can be, for example, 100 to 1000 MPa, preferably 200 to 800 MPa, and more preferably 350 to 800 MPa. The pressurizing time can be set appropriately. The pressurizing step may be performed under heating, but is preferably performed without heating. For example, pressure lamination at an ambient temperature of 0 to 50°C is preferred. When pressurizing under heating, the heating temperature is not particularly limited, but is generally in the range of 30 to 300°C.

[0132] By pressing (pressing) the above-mentioned solid electrolyte laminate sheet against the positive electrode active material layer, the porous support in the sheet is not compressed until the porosity becomes less than 15%, and the solid electrolyte layer in the sheet is compressed until the porosity becomes 10% or less.

[0133] As described above, by compressing the solid electrolyte layer in the sheet (solid electrolyte layer in the battery) until the porosity of the solid electrolyte layer in the sheet after pressing is 10% or less, the solid electrolyte layer is densified, preventing dendrites from growing to the positive electrode active material layer. This improves the ionic conductivity of the solid electrolyte layer in the battery, and also ensures good bonding (strong adhesion (compression)) of the contact interface between the solid electrolyte layer in the battery and the positive electrode active material layer, thereby reducing the interfacial resistance. By making the porosity of the porous support within the sheet (porous support within the battery) after pressurization at least 15%, voids are left in the electronic ion conductive layer within the battery, allowing the deposited metal to be accommodated and accumulated while suppressing volume fluctuations.

[0134] As described above, the solid electrolyte laminate sheet and the positive electrode sheet are integrated by compressing the porous support and the solid electrolyte layer in the sheet to a porosity of 15% or more and 10% or less, respectively. In this way, it is possible to manufacture a self-forming anode type all-solid-state secondary battery (discharged state) having a layer structure in which at least a porous support body in the battery, a solid electrolyte layer in the battery, and a positive electrode active material are stacked in this order, preferably a layer structure in which a negative electrode current collector, a porous support body in the battery, a solid electrolyte layer in the battery, a positive electrode active material, and a positive electrode current collector are stacked in this order. In the self-forming anode type all-solid-state secondary battery, after the pressurizing step, a charging step described later is carried out to deposit a metal (anode active material) in the porous support in the battery, and further between the anode current collector and the porous support in the battery, thereby forming an anode active material layer.

[0135] On the other hand, in an all-solid-state secondary battery in which the negative electrode active material layer is formed in advance, a step of forming the negative electrode active material layer between the negative electrode current collector and the porous support is carried out. The process of forming the negative electrode active material layer can be performed during the manufacture of an all-solid-state secondary battery by using a solid electrolyte laminate sheet that does not include a negative electrode current collector, and then, before, after, or simultaneously with the positive electrode sheet being pressed and laminated to the negative electrode active material layer and the negative electrode current collector. In this process, a negative electrode active material layer formed by the following formation method can be pressed and laminated; however, lamination or press-bonding of a layer made of the above-described negative electrode active material, particularly a metallic lithium foil, is preferred. Another example of the process of forming the negative electrode active material layer is the process of forming the negative electrode active material layer between the negative electrode current collector and the porous support within the sheet during the manufacture of the solid electrolyte laminate sheet. The method for forming the negative electrode active material layer used in this process is not particularly limited, but, like the positive electrode active material layer, it can be prepared by a method of forming a film of a negative electrode composition (slurry) on the surface of a substrate, preferably the negative electrode current collector, using a coating and drying method in which the negative electrode composition is applied and then dried, or by a molding method in which the negative electrode composition is pressure-molded. The atmosphere in which the step of forming the negative electrode active material layer is carried out is not particularly limited, and may be an atmosphere in which the above-mentioned compositions are mixed.

[0136] The negative electrode composition forming the negative electrode active material layer contains a negative electrode active material, and preferably an inorganic solid electrolyte, a conductive additive, a binder, a dispersion medium, and optionally other components. The components contained in the negative electrode composition are as described above. The content of the negative electrode active material in the negative electrode composition is not particularly limited, and is preferably 100% by mass or less, more preferably 10 to 90% by mass, more preferably 20 to 85% by mass, even more preferably 30 to 80% by mass, and still more preferably 40 to 75% by mass, based on 100% by mass of the solid content. When the negative electrode composition contains an inorganic solid electrolyte, the content of the inorganic solid electrolyte in the negative electrode composition is not particularly limited, but the total content of the negative electrode active material and the inorganic solid electrolyte is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 50% by mass or more, particularly preferably 70% by mass or more, and most preferably 90% by mass or more, relative to 100% by mass of the solid content. The upper limit is not particularly limited, and is, for example, preferably 99.9% by mass or less, more preferably 99.5% by mass or less, and even more preferably 99% by mass or less, relative to 100% by mass of the solid content. The content of the conductive auxiliary in the negative electrode composition is not particularly limited, and is preferably 0.1 to 20 mass %, more preferably 0.5 to 10 mass %, relative to 100 mass % of the solid content. The content of the binder in the negative electrode composition is not particularly limited, and from the viewpoints of strengthening the binding property of the solid particles and further adjusting the porosity, for example, it is preferably 0.1 to 10 mass%, more preferably 1 to 10 mass%, and even more preferably 2 to 6 mass%, relative to 100 mass% of the solid content. The content of the dispersion medium in the negative electrode composition is not particularly limited, but is preferably 20 to 80 mass %, more preferably 30 to 70 mass %, and particularly preferably 40 to 60 mass %. The negative electrode composition is preferably a non-aqueous composition. The negative electrode composition can be prepared, for example, as a solid mixture or a slurry by mixing the above-mentioned components, for example, in a commonly used mixer. The mixing method and conditions are the same as those for preparing the above-mentioned porous support composition.

[0137] By forming the anode active material layer between the anode current collector and the porous support in the battery as described above, it is possible to manufacture an all-solid-state secondary battery having a layer structure in which the anode current collector, the anode active material layer, the porous support in the battery, the solid electrolyte layer in the battery, and the cathode active material, preferably the cathode current collector, are stacked in this order.

[0138] <Pressure restraint> The all-solid-state secondary battery manufactured as described above is preferably pressurized and constrained in the stacking direction when it is initialized or used. The constraining force is not particularly limited, but is preferably 0.05 MPa or more, more preferably 1 MPa. The upper limit is, for example, preferably less than 10 MPa, more preferably 8 MPa or less.

[0139] <Initialization> The production method of the present invention may include a step of initializing the all-solid-state secondary battery (discharged state) obtained above, or may include a step of charging the battery. Initialization is usually performed after the production of the all-solid-state secondary battery and before use, and involves performing a charging step and a discharging step at least once each.

[0140] - Charging process - The charging step allows metal ions to be supplied from the positive electrode active material layer to at least the porous support (usually within the pores) within the battery, and in particular, in a self-forming negative electrode type all-solid-state secondary battery, the supplied metal ions are precipitated to form a negative electrode active material layer (to form an all-solid-state secondary battery in a charged state). The charging conditions are not particularly limited, but examples include the following conditions. Current: 0.05~30mA / cm 2 Voltage: 4.0~4.5V Charging time: 0.1 to 100 hours Temperature: 0~80℃ The charging step is preferably carried out by pressurizing and restraining the all-solid-state secondary battery (discharged state) in the stacking direction. This makes it possible to suppress expansion of the all-solid-state secondary battery. The restraining pressure at this time is as described above.

[0141] - Discharge process - The discharging step ionizes the metal deposited on the porous support in the battery and allows it to migrate to the positive electrode active material layer. The discharge conditions are not particularly limited, and examples thereof include the following conditions. Current: 0.05~30mA / cm 2 Voltage: 4.0~4.5V Charging time: 0.1 to 100 hours Temperature: 0~80℃ The discharging step is preferably carried out by pressurizing and restraining the all-solid-state secondary battery (charged state) in the stacking direction. The restraining pressure at this time is as described above, and may be the same as or different from the restraining pressure in the charging step.

[0142] In this way, by carrying out each step and further performing initialization as appropriate, the all-solid-state secondary battery of the present invention can be manufactured. As described above, this all-solid-state secondary battery effectively suppresses the occurrence of internal short circuits and has excellent cycle characteristics. Furthermore, an increase in interface resistance is also suppressed. [Example]

[0143] The present invention will be described in more detail below based on examples. However, the present invention is not to be construed as being limited thereto. In the following examples, "parts" and "%" representing compositions are by mass unless otherwise specified.

[0144] <Synthesis Example 1: Synthesis of sulfide-based inorganic solid electrolyte Li-PS-based glass> For the sulfide-based inorganic solid electrolyte, Li-PS-based glass was synthesized with reference to the non-patent literature of T. Ohtomo, A. Hayashi, M. Tatsumisago, Y. Tsuchida, S. Hama, K. Kawamoto, Journal of Power Sources, 233, (2013), pp. 231-235, and A. Hayashi, S. Hama, H. Morimoto, M. Tatsumisago, T. Minami, Chem. Lett., (2001), pp. 872-873.

[0145] Specifically, in a glove box under an argon atmosphere (dew point -70°C), 2.42 g of lithium sulfide (Li2S, Aldrich, purity >99.98%) and 3.90 g of diphosphorus pentasulfide (P2S5, Aldrich, purity >99%) were weighed out, placed in an agate mortar, and mixed for 5 minutes using an agate pestle. The molar ratio of Li2S to P2S5 was Li2S:P2S5 = 75:25. 66 g of 5 mm diameter zirconia beads were placed in a 45 mL zirconia container (manufactured by Fritsch), and the entire lithium sulfide and diphosphorus pentasulfide mixture was added. The container was then completely sealed under an argon atmosphere. The container was then placed in a planetary ball mill P-7 (trade name, manufactured by Fritsch) and mechanically milled at 25 °C and 450 rpm for 20 hours to obtain 6.20 g of a yellow sulfide-based inorganic solid electrolyte (1) (Li-PS glass, hereinafter sometimes referred to as LPS (1)). The average particle size measured by the above method was 10 μm.

[0146] <Synthesis Examples 2 and 3: Synthesis of LPS (2) and (3)> LPS (1) synthesized in Synthesis Example 1 above was wet dispersed under the following conditions to adjust the particle size, and LPS (2) and (3) were synthesized. Specifically, 300 zirconia beads with a diameter of 3 mm were placed in a 45 mL zirconia container (manufactured by Fritsch), and 4.0 g of the synthesized LPS (1) and 6.0 g of diisobutyl ketone as a dispersion medium were added. The container was then placed in a planetary ball mill P-7 and subjected to wet dispersion for 60 minutes under the following conditions 1 or 2. As a result, LPS (2) and (3) with the average particle sizes shown below were obtained. Condition 1: Rotation speed 300 rpm, LPS (2): average particle size 2 μm Condition 2: Rotation speed 400 rpm, LPS (3): average particle diameter 1 μm The average particle diameters of LPS (1) to (3) were measured as volume-average particle diameters by the above-mentioned measurement method, except that a dispersion medium (diisobutyl ketone) was added to the dispersions obtained in the above-mentioned synthesis examples to prepare dispersions for measurement with a solid content of 1% by mass.

[0147] <Support Preparation Example 1: Preparation of Porous Support 1> Porous support 1 was prepared using a negative photosensitive polyimide resin as follows. First, a polyimide precursor was synthesized. The atmosphere in a flask equipped with a stirrer and thermometer was replaced with nitrogen gas. Then, 12.86 g of 3,3'-diaminobenzidine and 200 g of N-methyl-2-pyrrolidone were added to the flask. While maintaining the temperature of the mixture in the flask below 10°C, 18.60 g of isocyanatoethyl methacrylate was added and the mixture was stirred at room temperature for 3 hours. Next, 6.00 g of 4,4'-diaminodiphenyl ether and 2.49 g of 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane were added to the flask, followed by the addition of 32.22 g of 3,3'-benzophenonetetracarboxylic acid and 4,4'-benzophenonetetracarboxylic dianhydride, while cooling the reaction mixture so that it did not exceed 40°C. After the addition was complete, the mixture in the flask was stirred at room temperature for 10 hours to obtain a polyimide precursor. To 100 parts by mass of the synthesized polyimide precursor, 5 parts by mass of a photosensitizer and a photopolymerization initiator were added, and an organic solvent (N-methyl-2-pyrrolidone) was added appropriately until a coatable viscosity was achieved to obtain a resin composition.

[0148] Next, the obtained resin composition was applied by a casting method onto a smooth glass substrate that had been subjected to a release treatment so that the thickness of the dry film (film after drying) would be 50 μm, and then dried at a temperature of 180° C. for 2 hours. Thereafter, a negative mask having a pattern in which circular holes with a diameter of 5 μm were arranged at an arrangement pitch of 1 μm at 1 μm intervals (in each arrangement direction) was attached to the surface of the dry film, and a high-pressure mercury lamp was used to apply 3000 mJ / cm 2 The sample was irradiated with ultraviolet light so that the cumulative irradiation amount was 1000 .mu.m. After UV irradiation, the negative mask was peeled off, development was carried out using an aqueous sodium hydroxide solution, and the dry film was thoroughly dried for 30 minutes with hot air at 80°C. The dry film was then heated at 300°C for 3 hours to promote the imidization reaction, yielding a patterned porous support made of polyimide resin (thickness 50 μm, porosity 70% as measured by the above method).

[0149] <Support Preparation Example 2: Preparation of Porous Support 2> A nonwoven fabric (natural fiber / polyethylene terephthalate (PET) / acrylic resin coated type, manufactured by Asahi Kasei Chemicals Corporation, Silky Fine, WS7R02-14, thickness 50 μm, porosity measured by the above method 70%) was prepared as the porous support 2.

[0150] <Support Preparation Example 3: Preparation of Porous Support 3> A nonwoven fabric (natural fiber / PET / acrylic resin coated type, manufactured by Asahi Kasei Chemicals Corporation, Silky Fine, WS7R02-06, thickness 30 μm, porosity measured by the above-mentioned method 80%) was prepared as the porous support 3.

[0151] <Example 1: Preparation of solid electrolyte laminate sheet> (Example 1-1: Preparation of solid electrolyte laminate sheet A-1) - Preparation of solid electrolyte composition 1 - LPS (3) with an average particle size adjusted to 1 μm and the following binder B-1 were mixed in a mass ratio of 98:2 (solid content equivalent), and placed in a 45 mL zirconia container (manufactured by Fritsch), and 20 g of zirconia beads with a diameter of 3 mm and diisobutyl ketone as a dispersion medium were added to adjust the solid content concentration to 45 mass%. Then, this container was set in a planetary ball mill P-7 and stirred at a temperature of 25 ° C and a rotation speed of 100 rpm for 1 hour to prepare solid electrolyte composition 1 (slurry) as a composition for a porous support. Binder B-1: Copolymer of vinylidene fluoride and hexafluoropropylene (PVdF-HFP, PVdF:HFP = 8:2 (mass ratio) (Arkema)) - Preparation of solid electrolyte composition 2 - Solid electrolyte composition 2 was prepared as a composition for an in-sheet solid electrolyte layer in the same manner as in the preparation of solid electrolyte composition 1, except that in the preparation of solid electrolyte composition 1, LPS (3) was changed to LPS (1) having an average particle size of 10 μm and the rotation speed during stirring was changed to 50 rpm.

[0152] - Preparation of solid electrolyte laminate sheet A-1 - The porous support 1 was fixed on a polyphenylene sulfide (PPS) film (TORELINA 3000, manufactured by Toray Industries, Inc.), and the solid electrolyte composition 1 was applied to the porous support 1 without heating using a bar coater (SA-201, manufactured by Tester Sangyo Co., Ltd.) In this way, the solid electrolyte composition 1 was impregnated (penetrated) into the porous support 1 (into the pores), and then the porous support was dried by heating at 100°C for 1 hour to prepare an in-sheet porous support. Next, solid electrolyte composition 2 was applied to the surface of the intra-sheet porous support without heating using a Baker-type applicator, and then heated and dried at 100°C for 1 hour. In this way, an intra-sheet solid electrolyte layer having a thickness of 100 µm was formed on the surface of the intra-sheet porous support. The thickness of the intra-sheet solid electrolyte layer is the thickness of the layer formed on the surface of the intra-sheet solid electrolyte layer. In this way, a solid electrolyte laminate sheet A-1 was produced on the PPS film, and was peeled off from the PPS film to obtain a solid electrolyte laminate sheet A-1.

[0153] (Example 1-2: Preparation of solid electrolyte laminate sheet A-2) Solid electrolyte composition 3 was prepared as a composition for a porous support in the same manner as in the preparation of solid electrolyte composition 1, except that in the preparation of solid electrolyte composition 1, LPS (3) was changed to LPS (2) adjusted to an average particle diameter of 2 μm. Next, a solid electrolyte laminate sheet A-2 was produced in the same manner as in the production of the solid electrolyte laminate sheet A-1, except that solid electrolyte composition 3 was used instead of solid electrolyte composition 1 in the production of the solid electrolyte laminate sheet A-1.

[0154] (Example 1-3: Preparation of solid electrolyte laminate sheet A-3) Solid electrolyte composition 4 was prepared as a composition for an in-sheet solid electrolyte layer in the same manner as in the preparation of solid electrolyte composition 2, except that in the preparation of solid electrolyte composition 2, LPS (1) having an average particle size of 10 μm was changed to LPS (1) having an average particle size of 10 μm and LPS (3) having an average particle size of 1 μm in a mass ratio of 9:1. Next, a solid electrolyte laminate sheet A-3 was produced in the same manner as in the production of the solid electrolyte laminate sheet 1, except that solid electrolyte composition 4 was used instead of solid electrolyte composition 2.

[0155] (Example 1-4: Preparation of solid electrolyte laminate sheet A-4) Solid electrolyte composition 5 was prepared as a composition for an in-sheet solid electrolyte layer in the same manner as in the preparation of solid electrolyte composition 2, except that in the preparation of solid electrolyte composition 2, LPS (1) having an average particle size of 10 μm was changed to LPS (1) having an average particle size of 10 μm and LPS (3) having an average particle size of 1 μm in a mass ratio of 8:2. Next, a solid electrolyte laminate sheet A-4 was produced in the same manner as in the production of the solid electrolyte laminate sheet 1, except that solid electrolyte composition 5 was used instead of solid electrolyte composition 2.

[0156] (Example 1-5: Preparation of solid electrolyte laminate sheet A-5) The porous support 1 was fixed on a 20 μm thick stainless steel (SUS) foil, and the solid electrolyte composition 1 was applied onto the porous support 1 using a bar coater without heating. After the solid electrolyte composition 1 was impregnated (penetrated) into the porous support 1 (pores), the porous support was dried by heating at 100° C. for 1 hour to prepare an in-sheet porous support. Next, solid electrolyte composition 4 was applied to the surface of the porous support without heating using a Baker applicator, and then heated and dried at 100°C for 1 hour. In this way, a 100µm-thick solid electrolyte layer was formed on the surface of the porous support. The thickness of the solid electrolyte layer is the thickness of the layer formed on the surface of the solid electrolyte layer.

[0157] (Example 1-6: Preparation of solid electrolyte laminate sheet A-6) Solid electrolyte composition 6 was prepared as a composition for an in-sheet solid electrolyte layer in the same manner as in the preparation of solid electrolyte composition 2, except that in the preparation of solid electrolyte composition 2, LPS (1) having an average particle size of 10 μm was changed to LPS (1) having an average particle size of 10 μm and LPS (3) having an average particle size of 1 μm in a mass ratio of 9:1, and the solid content concentration was changed from 45 mass% to 50 mass%. The porous support 2 was fixed on a 20 μm thick stainless steel (SUS) foil, and the solid electrolyte composition 1 was applied onto the porous support 2 using a bar coater without heating. After the solid electrolyte composition 1 was impregnated (penetrated) into the porous support 2 (pores) in this way, it was heated and dried at 100° C. for 1 hour to produce an in-sheet porous support. Next, solid electrolyte composition 6 was applied to the surface of the intra-sheet porous support without heating using a Baker-type applicator, and then heated and dried for 1 hour at 100° C. In this way, an intra-sheet solid electrolyte layer having a thickness of 100 μm was formed on the surface of the intra-sheet porous support.

[0158] (Example 1-7: Preparation of solid electrolyte laminate sheet A-7) A solid electrolyte laminate sheet A-7 was produced in the same manner as in the production of the solid electrolyte laminate sheet A-6, except that solid electrolyte composition 3 was used instead of solid electrolyte composition 1 and solid electrolyte composition 4 was used instead of solid electrolyte composition 6.

[0159] (Example 1-8: Preparation of solid electrolyte laminate sheet A-8) A solid electrolyte laminate sheet A-8 was produced in the same manner as in the production of the solid electrolyte laminate sheet A-6, except that the porous support 3 was used instead of the porous support 2 in the production of the solid electrolyte laminate sheet A-6.

[0160] (Example 1-9: Preparation of solid electrolyte laminate sheet A-9) Solid electrolyte composition 7 was prepared as a composition for a porous support in the same manner as in the preparation of solid electrolyte composition 1, except that the solid content concentration was changed from 45% by mass to 40% by mass. Next, a solid electrolyte laminate sheet A-9 was produced in the same manner as in the production of the solid electrolyte laminate sheet A-8, except that solid electrolyte composition 7 was used instead of solid electrolyte composition 1 in the production of the solid electrolyte laminate sheet A-8.

[0161] (Example 1-10: Preparation of solid electrolyte laminate sheet A-10) Solid electrolyte composition 8 was prepared as a composition for a porous support in the same manner as in the preparation of solid electrolyte composition 1, except that the solid content concentration was changed from 45% by mass to 35% by mass. Next, a solid electrolyte laminate sheet A-10 was produced in the same manner as in the production of the solid electrolyte laminate sheet A-8, except that solid electrolyte composition 8 was used instead of solid electrolyte composition 1 in the production of the solid electrolyte laminate sheet A-8.

[0162] (Comparative Example 1-1: Preparation of solid electrolyte laminate sheet B-1) Solid electrolyte composition 9 was prepared as a composition for a porous support in the same manner as in the preparation of solid electrolyte composition 1, except that the solid content concentration was changed from 45% by mass to 30% by mass. Next, a solid electrolyte laminate sheet B-1 was produced in the same manner as in the production of the solid electrolyte laminate sheet A-1, except that solid electrolyte composition 9 was used instead of solid electrolyte composition 1 in the production of the solid electrolyte laminate sheet A-1.

[0163] (Comparative Example 1-2: Preparation of solid electrolyte laminate sheet B-2) A solid electrolyte laminate sheet B-2 was produced in the same manner as in the production of the solid electrolyte laminate sheet A-3, except that solid electrolyte composition 9 was used instead of solid electrolyte composition 1 in the production of the solid electrolyte laminate sheet A-3.

[0164] (Comparative Example 1-3: Preparation of solid electrolyte laminate sheet B-3) A solid electrolyte laminate sheet B-3 was produced in the same manner as in the production of the solid electrolyte laminate sheet A-1, except that the solid electrolyte layer within the sheet was not formed using solid electrolyte composition 2.

[0165] (Comparative Example 1-4: Preparation of solid electrolyte laminate sheet B-4) A solid electrolyte laminate sheet B-4 was produced in the same manner as in the production of the solid electrolyte laminate sheet B-1, except that the solid electrolyte layer within the sheet was not formed using solid electrolyte composition 2.

[0166] (Comparative Example 1-5: Preparation of solid electrolyte laminate sheet B-5) A solid electrolyte laminate sheet B-5 was produced in the same manner as in the production of the solid electrolyte laminate sheet A-5, except that the solid electrolyte composition 1 was changed to the solid electrolyte composition 9.

[0167] (Comparative Example 1-6: Preparation of solid electrolyte laminate sheet B-6) A solid electrolyte laminate sheet B-6 was produced in the same manner as in the production of the solid electrolyte laminate sheet A-6, except that the solid electrolyte composition 1 was changed to the solid electrolyte composition 9.

[0168] (Comparative Example 1-7: Preparation of solid electrolyte laminate sheet B-7) A solid electrolyte laminate sheet B-7 was produced in the same manner as in the production of the solid electrolyte laminate sheet A-6, except that the solid electrolyte layer within the sheet was not formed using the solid electrolyte composition 6.

[0169] (Comparative Example 1-8: Preparation of solid electrolyte laminate sheet B-8) A solid electrolyte laminate sheet B-8 was produced in the same manner as in the production of the solid electrolyte laminate sheet B-6, except that the solid electrolyte layer within the sheet was not formed using the solid electrolyte composition 6.

[0170] <Measurement of porosity and opening diameter> For the prepared solid electrolyte laminate sheets A-1 to A-10 and B-1 to B-8, the porosities (measured by the above-mentioned measurement method) of the porous supports 1 to 3 used in the preparation, the porous supports within the sheets, and the solid electrolyte layers within the sheets are shown in Table 1. Note that in measuring the porosity, any cross section was a longitudinal cross section (vertical cross section). Furthermore, the opening diameters measured by the above-mentioned measurement method for the porous supports 1 to 3 are shown in Table 1. Table 1 shows the thickness of the porous support used, the particle size of the inorganic solid electrolyte, the thickness of the solid electrolyte layer within the sheet, and the amount of inorganic solid electrolyte filled into Porous Supports 1 to 3 (the difference in porosity between Porous Supports 1 to 3 and the porous support within the sheet). The particle size of the inorganic solid electrolyte was measured on a longitudinal cross section (vertical cross section) of an arbitrary cross section, and the results were nearly consistent with the volume average particle size of LPS (1) to (3). Note that the thickness of the porous support within each laminate sheet is the same as the thickness of the porous support used in the fabrication, so it is not included in Table 1. When the porosity, etc. cannot be measured or when a solid electrolyte layer is not provided in the sheet, the symbol "-" is indicated in the corresponding column.

[0171] In Table 1, when a porous support formed on a SUS foil is used, the "Porous support" column in Table 1 indicates "SUS / porous support X" (X is the porous support number). In addition, when multiple LPSs are used to form the solid electrolyte layer in the sheet, they are listed together in the "Inorganic solid electrolyte" and "Particle size" columns of Table 1 using " / ". The units for porosity, opening diameter, filling amount, and thickness are "%", "μm", "%", and "μm", respectively, but these are omitted in Table 1. "Particle size" in Table 1 indicates "average particle size", and the unit "μm" is omitted. In Table 1, the support (negative electrode current collector), solid electrolyte layer B, and solid electrolyte layer A of the all-solid-state secondary battery produced in Reference Example 1 described later are shown in the "intra-sheet porous support" column and the "intra-sheet solid electrolyte layer" column, respectively.

[0172] [Table 1]

[0173] Supports 1 to 3: Porous supports 1 to 3 prepared or produced in the above Support Production Examples 1 to 3 SUS: Stainless steel foil LPS(1) to LPS(3): LPS synthesized in Synthesis Examples 1 to 3

[0174] <Example 2: Production of all-solid-state secondary battery> An all-solid-state secondary battery was manufactured as follows, and its characteristics were evaluated. In producing an all-solid-state secondary battery, a positive electrode sheet was produced as follows.

[0175] (Preparation Example 1: Preparation of Positive Electrode Sheet) - Preparation of positive electrode composition - As the positive electrode active material, nickel manganese cobalt oxide lithium (average particle size 0.5 μm, manufactured by Aldrich), LPS (2) adjusted to an average particle size of 2 μm, acetylene black (average particle size 0.1 μm, manufactured by Denka) as a conductive additive, and the binder B-1 shown below were mixed in a mass ratio (solid content equivalent) of 70:27:2:1, and added to a 45 mL zirconia container (manufactured by Fritsch), 20 g of zirconia beads with a diameter of 3 mm and diisobutyl ketone as a dispersion solvent, and the solid content concentration was adjusted to 45% by mass. Then, this container was set in a planetary ball mill P-7, and stirred at a temperature of 25 ° C. and a rotation speed of 100 rpm for 1 hour to prepare a positive electrode composition (slurry). B-1: Copolymer of vinylidene fluoride and hexafluoropropylene (PVdF-HFP, PVdF:HFP = 8:2 (mass ratio) (Arkema)) - Formation of positive electrode active material layer - The obtained positive electrode composition was applied to the surface of a carbon-coated aluminum foil (positive electrode current collector) having a thickness of 20 μm using a Baker-type applicator (product name: SA-201), and the applied composition was dried by heating at 100°C for 1 hour to prepare a positive electrode sheet having a positive electrode active material layer (coated and dried layer) having a thickness of 150 μm.

[0176] (Examples 2-1 to 2-4: Production of all-solid-state secondary batteries 1 to 4) The prepared positive electrode sheet was punched into a disk with a diameter of 1 cm to obtain a disk-shaped positive electrode sheet. In addition, the solid electrolyte laminate sheet shown in the "Solid electrolyte laminate sheet No." column in Table 2 was punched into a disk with a diameter of 1.2 cm to obtain a disk-shaped solid electrolyte laminate sheet (laminate sheet material). The positive electrode active material layer of the disk-shaped positive electrode sheet and the solid electrolyte layer within the disk-shaped solid electrolyte laminate sheet were placed opposite each other and overlapped so that the disk-shaped positive electrode sheet did not protrude from the disk-shaped solid electrolyte laminate sheet. In this state, the disc-shaped positive electrode sheet and the disc-shaped solid electrolyte laminate sheet were pressed in the overlapping direction at a pressure of 500 MPa for 1 minute. This pressure compressed the porous support and the solid electrolyte layer within the sheet, forming a porous support and a solid electrolyte layer within the battery with the thickness and porosity shown in Table 2. In this way, pressure-bonded laminates of the solid electrolyte laminate sheet and the positive electrode sheet were obtained. Next, a 50 μm thick lithium metal foil was punched out into a disk shape with a diameter of 1.1 cm and placed on the center of the surface of the porous support within the sheet of the pressure-bonded laminate (so that the punched out lithium metal foil into a disk shape did not protrude from the disk-shaped solid electrolyte laminate sheet), and was restrained from both sides in the stacking direction with 1.5 cm diameter SUS rods at a restraining pressure of 5 MPa in the stacking direction. In this way, all solid state secondary batteries 1 to 4 in an uncharged state were produced. All-solid-state secondary batteries 1 to 4 have a laminated structure shown in Fig. 1, which is composed of a negative electrode current collector (SUS rod), a negative electrode active material layer (metallic lithium foil), a porous support body in the battery, a solid electrolyte layer in the battery, a positive electrode active material layer, and a positive electrode current collector (aluminum foil). The thickness of the positive electrode active material layer was 80 µm.

[0177] (Examples 2-5 to 2-10: Production of all-solid-state secondary batteries 5 to 10) In the production of the all-solid-state secondary battery 1 of Example 2-1, pressure-bonded laminates of a solid electrolyte laminate sheet and a positive electrode sheet were obtained in the same manner as in the production of the all-solid-state secondary battery 1 of Example 2-1, except that the solid electrolyte laminate sheet A-1 was changed to the solid electrolyte laminate sheet shown in the "Solid electrolyte laminate sheet No." column in Table 2. In these pressure-bonded laminates, an internal-battery porous support and an internal-battery solid electrolyte layer having the thickness and porosity shown in Table 2 were formed. Next, each pressed laminate was restrained from both sides in the lamination direction with a SUS rod having a diameter of 1.5 cm at a restraining pressure of 5 MPa in the lamination direction. In this way, all solid state secondary batteries 5 to 10 in an uncharged state were produced. The all-solid-state secondary batteries 5 to 10 each have a laminated structure consisting of a negative electrode current collector (SUS rod and SUS foil), a porous support body in the battery, a solid electrolyte layer in the battery, a positive electrode active material layer, and a positive electrode current collector (aluminum foil). The thickness of the positive electrode active material layer was 80 μm.

[0178] (Comparative Examples 2-1 to 2-4: Production of All-Solid State Secondary Batteries C1 to C4) All solid state secondary batteries C1 to C4 were produced in the same manner as in the production of the all solid state secondary battery 1 of Example 2-1, except that the solid electrolyte laminate sheet A-1 was changed to the solid electrolyte laminate sheet shown in the "Solid electrolyte laminate sheet No." column of Table 2.

[0179] (Comparative Examples 2-5 to 2-8: Production of All-Solid State Secondary Batteries C5 to C8) All solid state secondary batteries C5 to C8 were produced in the same manner as in the production of the all solid state secondary battery 5 of Example 2-5, except that in the production of the all solid state secondary battery 5 of Example 2-5, the solid electrolyte laminate sheet A-5 was changed to the solid electrolyte laminate sheet shown in the "Solid electrolyte laminate sheet No." column in Table 2.

[0180] (Comparative Examples 2-9 and 2-10: Production of all-solid-state secondary batteries C9 and C10) All solid state secondary batteries C9 and C10 were produced in the same manner as in the production of the all solid state secondary battery 1 of Example 2-1, except that in the production of the all solid state secondary battery 1 of Example 2-1, the pressure applied when pressing the overlapping disc-shaped positive electrode sheet and disc-shaped solid electrolyte laminate sheet was changed from 500 MPa to 300 MPa (Comparative Example 2-9) or 1000 MPa (Comparative Example 2-10). The thicknesses of the positive electrode active material layers of the all solid state secondary batteries C9 and C10 were 85 μm and 75 μm.

[0181] (Reference Example 1: Manufacturing of all-solid-state secondary battery R) The positive electrode sheet was punched into a 1 cm diameter disk, and the resulting disk-shaped positive electrode sheet was placed in a 10 mm diameter polyethylene terephthalate (PET) cylinder. 30 mg of LPS (1) with an average particle size of 10 μm was placed on the positive electrode active material layer inside the cylinder, and 10 mm diameter SUS rods were inserted into both sides of the cylinder. Next, a pressure of 350 MPa was applied axially from the aluminum foil side and the LPS (1) side of the disk-shaped positive electrode sheet using the SUS rods. In this way, a solid electrolyte layer A consisting of LPS (1) was formed. The SUS rod on the solid electrolyte layer A side was temporarily removed, and 5 mg of LPS (3) with an average particle size adjusted to 1 μm was placed on top of the solid electrolyte layer A. A disk-shaped SUS foil punched into a 1 cm diameter disk was then inserted and placed on top of it. The removed SUS rod was then reinserted into the cylinder, and a pressure of 10 MPa was applied axially, followed by a pressure of 5 MPa. In this way, the solid electrolyte layer B was formed on the solid electrolyte layer A, and an all-solid-state secondary battery R having a two-layer structure of solid electrolyte layers A and B was manufactured. The all-solid-state secondary battery R has a laminated structure consisting of a negative electrode current collector (SUS rod and SUS foil), a solid electrolyte layer B, a solid electrolyte layer A, a positive electrode active material layer, and a positive electrode current collector (aluminum foil). The thickness of the positive electrode active material layer was 80 μm.

[0182] <Porosity measurement> For each of the produced all-solid-state secondary batteries, the porosity (measured by the above-mentioned measurement method) of the porous support in the battery, the solid electrolyte layer in the battery, and the solid electrolyte layers A and B is shown in Table 2. The thicknesses of the porous support body in the battery, the solid electrolyte layer in the battery, and the solid electrolyte layers A and B are shown in Table 2. The units for porosity and thickness are "%" and "μm," respectively, but are omitted in Table 2.

[0183] <Measurement of particle size of inorganic solid electrolyte particles> The particle sizes of the inorganic solid electrolytes contained in the porous support body in the battery formed by pressing and the inorganic solid electrolytes constituting the solid electrolyte layer in the battery were measured by the above-mentioned measurement method, and the results are shown in Table 2. The unit of particle size is "μm", but this is omitted in Table 2.

[0184] (initialization) For each of the manufactured all-solid-state secondary batteries, 0.05 mA / cm 2 After charging to 4.25 V with 2 Then I discharged it down to 2.5V and initialized it. In this way, initialized all-solid-state secondary batteries 1 to 10, C1 to C10 and R were obtained, respectively. In each of the all-solid-state secondary batteries, metallic lithium is deposited in the pores of the porous support body in the battery during charging, and in all-solid-state secondary batteries 5 to 10 and C5 to C8, the deposited metallic lithium functions as a negative electrode active material layer.

[0185] <Evaluation: Charge / Discharge Cycle Characteristics Test> For each all-solid-state secondary battery after initialization, the current density was 0.5 mA / cm 2 After charging to 4.25V, the 2 A charge-discharge cycle in which the battery was charged at 100 V and discharged to 2.5 V was defined as one cycle, and this cycle was repeated 100 times. The charge-discharge cycle characteristics were evaluated based on the discharge capacity retention rate and the occurrence of internal short circuits according to the following criteria. The results are shown in Table 2. The discharge capacity retention rate was evaluated by calculating the ratio (percentage) of the discharge capacity after 100 cycles to the discharge capacity at the first cycle. Furthermore, when a sudden voltage drop occurred during charging while repeatedly performing charge-discharge cycles, it was determined that an internal short circuit had occurred, and the subsequent charge-discharge cycle characteristic test was stopped, and the internal short circuit was evaluated based on the number of charge-discharge cycles at which the internal short circuit occurred.

[0186] [Table 2]

[0187] Li foil: metallic lithium foil NMC: Lithium nickel manganese cobalt oxide

[0188] The results shown in Tables 1 and 2 reveal the following. The all-solid-state secondary batteries C1 and C2 were manufactured using solid electrolyte laminate sheets B-1 and B-2, which had porous supports within the sheets with too small a porosity. These all-solid-state secondary batteries developed internal short circuits after several cycles. This is thought to be because the porosity of the porous supports within the batteries was too small compared to the range specified in the present invention, resulting in large volume fluctuations during charging and discharging, and damage to the solid electrolyte layer within the batteries. All-solid-state secondary batteries C3, C4, C7, and C8 were manufactured using solid electrolyte laminate sheets B-3, B-4, B-7, and B-8, each of which had only an intra-sheet porous support. These all-solid-state secondary batteries developed internal short circuits after only one or two cycles. This is thought to be because the batteries did not have an internal solid electrolyte layer, and therefore could not prevent dendrites from reaching the positive electrode active material layer. The all-solid-state secondary batteries C5 and C6 are self-forming anode type all-solid-state secondary batteries manufactured using the solid electrolyte laminate sheets B-5 and B-6 having an intra-sheet porous support with too small a porosity. Therefore, like the all-solid-state secondary batteries C1 and C2, internal short circuits occur, but the number of charge / discharge cycles is smaller. In the case of all-solid-state secondary battery C9, even though the solid electrolyte laminate sheet specified in the present invention was used, the pressure applied during production was too weak, resulting in a porosity of the solid electrolyte layer in the battery exceeding 10%, making it impossible to prevent dendrites from reaching the positive electrode active material layer, resulting in a short circuit after 20 cycles.On the other hand, in the case of all-solid-state secondary battery C10, even though the solid electrolyte laminate sheet specified in the present invention was used, the pressure applied during production was too strong, resulting in a porosity of the porous support in the battery of less than 15%, making it impossible to absorb (offset) the stress due to volume fluctuations, resulting in a short circuit.

[0189] In the reference example, the cycle characteristics were evaluated for an all-solid-state secondary battery R that employs a two-layer solid electrolyte layer structure in which a highly porosity solid electrolyte layer B is laminated on a solid electrolyte layer A (corresponding to the solid electrolyte layer in the battery) instead of a porous support in the battery. This all-solid-state secondary battery R can prevent the occurrence of short circuits up to 100 cycles because the solid electrolyte layer B has a porosity of 40% and the solid electrolyte layer A has a porosity of 10%, but because a porous support is not incorporated in the solid electrolyte layer B, the discharge capacity retention rate is 20%, which is not sufficient for recent all-solid-state secondary batteries that require even higher reliability.

[0190] In contrast, all of the all-solid-state secondary batteries 1 to 10 of the present invention, which are manufactured by laminating the solid electrolyte laminate sheet specified in the present invention by pressure bonding to a positive electrode sheet so that the porous support body in the battery and the solid electrolyte layer in the battery satisfy the porosity specified in the present invention, can prevent the occurrence of an internal short circuit up to 100 cycles, and furthermore, the discharge capacity retention rate after 100 cycles is 60% or more, showing excellent cycle characteristics. In particular, all-solid-state secondary batteries 1 to 4, which use metallic lithium foil as the negative electrode active material layer, exhibit excellent cycle characteristics, with a discharge capacity retention rate of 72% after 100 cycles. On the other hand, all-solid-state secondary batteries 5 to 10 with self-forming negative electrode can suppress volume fluctuation and isolation of metallic lithium even after repeated deposition and dissolution of metallic lithium, and exhibit excellent cycle characteristics while increasing battery capacity. That is, the all-solid-state secondary battery of the present invention, whether it is an all-solid-state secondary battery in an embodiment in which the negative electrode active material layer is formed in advance (particularly a high-capacity all-solid-state secondary battery employing a metallic lithium foil as the negative electrode active material layer) or a self-forming negative electrode type all-solid-state secondary battery, exhibits excellent cycle characteristics and operates (drives) stably while highly preventing the occurrence of internal short circuits. Therefore, it can achieve a higher level of reliability than has been demanded of recent all-solid-state secondary batteries.

[0191] While the present invention has been described in connection with embodiments thereof, we do not intend to limit our invention to any of the details of the description unless otherwise specified, and believe that the claims should be construed broadly without departing from the spirit and scope of the invention as set forth in the appended claims.

[0192] This application claims priority based on Japanese Patent Application No. 2021-053904, filed in Japan on March 26, 2021, the contents of which are incorporated herein by reference as part of the present specification. [Explanation of symbols]

[0193] 1 Negative electrode current collector 2 (Inside the battery) Porous support 3 (Inside the battery) Solid electrolyte layer 4 Cathode active material layer 5 Positive electrode current collector 6. Operating parts 8 (inside the sheet) porous support 9 (Inside the sheet) solid electrolyte layer 10 All-solid-state secondary battery 11. Laminated sheet for negative electrode

Claims

1. A solid electrolyte laminated sheet comprising: a sheet-like porous support incorporating an inorganic solid electrolyte having ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table; and a solid electrolyte layer on one surface of the porous support, the solid electrolyte layer containing an inorganic solid electrolyte having ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, A solid electrolyte laminate sheet, wherein the porosity of the porous support is 20% or more, and the porosity of the solid electrolyte layer is smaller than the porosity of the porous support.

2. 2. The solid electrolyte laminate sheet according to claim 1, wherein the inorganic solid electrolyte contained in the porous support is in the form of particles smaller than the opening diameter of the porous support.

3. 3. The solid electrolyte laminate sheet according to claim 1, wherein the inorganic solid electrolyte contained in the solid electrolyte layer includes particles larger than an opening diameter of the porous support and particles smaller than an opening diameter of the porous support.

4. 4. The solid electrolyte laminate sheet according to claim 1, further comprising a negative electrode current collector on the other surface of said porous support.

5. An all-solid-state secondary battery using the solid electrolyte laminate sheet according to any one of claims 1 to 4, a layer structure in which a negative electrode current collector, the porous support of the solid electrolyte laminate sheet, the solid electrolyte layer, and a positive electrode active material layer are laminated and pressure-bonded in this order, The porosity of the porous support after lamination and compression bonding is 15% or more, An all-solid-state secondary battery, in which the porosity of the solid electrolyte layer after lamination and compression bonding is 10% or less.

6. The all-solid-state secondary battery according to claim 5 , further comprising a negative electrode active material layer between the negative electrode current collector and the porous support.

7. The all-solid-state secondary battery according to claim 6 , wherein the negative electrode active material layer is a metallic lithium foil.

8. The all-solid-state secondary battery according to claim 5 , wherein, in a charged state of the all-solid-state secondary battery, at least the porous support contains a negative electrode active material.

9. The all-solid-state secondary battery according to any one of claims 5 to 8, wherein the inorganic solid electrolyte contained in the porous support after lamination and compression bonding is in the form of particles smaller than the opening diameter of the porous support.

10. The all-solid-state secondary battery according to any one of claims 5 to 9, wherein the inorganic solid electrolyte contained in the solid electrolyte layer after lamination and compression bonding contains particles larger than the opening diameter of the porous support and particles smaller than the opening diameter of the porous support.

11. A method for producing an all-solid-state secondary battery using the solid electrolyte laminate sheet according to any one of claims 1 to 4, comprising: a step of pressurizing the solid electrolyte laminate sheet until the porosity of the solid electrolyte layer becomes 10% or less, while restricting the porosity of the porous support of the solid electrolyte laminate sheet to 15% or more.

12. The method for producing an all-solid-state secondary battery according to claim 11 , further comprising a step of forming a negative electrode active material layer between the negative electrode current collector and the porous support.

13. The method for producing an all-solid-state secondary battery according to claim 12 , wherein the step of forming the negative electrode active material layer is a step of forming a film of a negative electrode composition containing a negative electrode active material or a step of laminating a metallic lithium foil.

14. 13. The method for producing an all-solid-state secondary battery according to claim 12, wherein the step of forming the negative electrode active material layer is a step of charging the all-solid-state secondary battery after the pressurizing step to deposit the negative electrode active material at least in the porous support.

Images