All-solid-state batteries

Abstract

The purpose of the present invention is to provide an all-solid-state battery of a lithium deposition type, which is excellent in resistance during charging, cycle characteristics, and short-circuiting rate during charging. The present invention provides an all-solid-state battery, which comprises a power-generating element comprising: a positive electrode which has a positive electrode active material layer containing a positive electrode active material; a negative electrode which has a negative electrode current collector on which lithium metal is deposited during charging; a solid electrolyte layer which is disposed between the positive electrode and the negative electrode and contains a solid electrolyte; and a negative electrode intermediate layer that is adjacent to a negative electrode current collector-side surface of the solid electrolyte layer and contains a binder and at least one kind selected from the group consisting of metal materials capable of alloying with lithium and carbon materials capable of absorbing lithium ions, wherein the negative electrode intermediate layer has a porosity of 10% to 70%.

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state battery. [Background technology]

[0002] In recent years, research and development on all-solid-state batteries using oxide- or sulfide-based solid electrolytes has been actively conducted. Solid electrolytes are materials primarily composed of ionic conductors that can conduct ions in a solid state. Therefore, all-solid-state batteries have the advantage that, in principle, they do not encounter the various problems associated with flammable organic electrolytes, as occurs in conventional liquid-based batteries that use nonaqueous electrolytes.

[0003] One type of all-solid-state secondary battery is known as a lithium deposition type, in which lithium metal is deposited on a negative electrode current collector during charging. In such lithium deposition type all-solid-state secondary batteries, the lithium metal deposited during charging ionizes during discharging, creating voids in the lithium metal, which can lead to a decrease in discharge capacity. Therefore, in order to prevent the formation of such voids, a restraining pressure is generally applied in the stacking direction of the battery in lithium deposition type all-solid-state secondary batteries.

[0004] As a means of suppressing the generation of voids during discharge without applying high restraining pressure, Japanese Patent Application Laid-Open No. 2020-191202 discloses a technology in which an Ag-containing anode active material layer (anode intermediate layer) is provided between the anode current collector and the solid electrolyte layer. With this configuration, Li precipitates as a Li(Ag) alloy containing Ag in solid solution during the charging process. Then, during the discharging process, only Li dissolves from the Li(Ag) alloy, leaving the Ag in solid solution, which is believed to suppress the generation of voids. Summary of the Invention

[0005] However, the inventors have conducted research and found that even in the lithium deposition type all-solid-state battery having the negative electrode intermediate layer described in JP 2020-191202 A, the resistance during charging, cycle characteristics, or short circuit rate during charging may be insufficient.

[0006] Therefore, an object of the present invention is to provide a lithium deposition-type all-solid-state battery that is excellent in resistance during charging, cycle characteristics, and short-circuit rate during charging.

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result, have found that in an all-solid-state battery including a lithium deposition-type power generating element, the above-mentioned problems can be solved by providing a negative electrode intermediate layer between a negative electrode current collector and a solid electrolyte layer, the negative electrode intermediate layer including a metal material capable of alloying with lithium or a carbon material capable of absorbing lithium ions, and a binder, and by controlling the porosity of the negative electrode intermediate layer within a specific range, thereby completing the present invention.

[0008] That is, one embodiment of the present invention is an all-solid-state battery including a power generating element including: a positive electrode having a positive electrode active material layer containing a positive electrode active material; a negative electrode having a negative electrode current collector, on which lithium metal is deposited during charging; a solid electrolyte layer interposed between the positive electrode and the negative electrode and containing a solid electrolyte; and a negative electrode intermediate layer present adjacent to a surface of the solid electrolyte layer facing the negative electrode current collector, the negative electrode intermediate layer containing at least one material selected from the group consisting of a metal material capable of alloying with lithium and a carbon material capable of absorbing lithium ions, and a binder, wherein the porosity of the negative electrode intermediate layer is 10% or more and 70% or less. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating the overall structure of a stacked-type (internal parallel connection type) all-solid-state lithium secondary battery (stacked-type secondary battery) according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] One embodiment of the present invention is an all-solid-state battery including a power generating element including: a positive electrode having a positive electrode active material layer containing a positive electrode active material; a negative electrode having a negative electrode current collector on which lithium metal is deposited during charging; a solid electrolyte layer interposed between the positive electrode and the negative electrode and containing a solid electrolyte; and a negative electrode intermediate layer adjacent to the surface of the solid electrolyte layer facing the negative electrode current collector and containing at least one material selected from the group consisting of a metal material capable of alloying with lithium and a carbon material capable of absorbing lithium ions, and a binder, wherein the porosity of the negative electrode intermediate layer is 10% to 70%. The all-solid-state battery according to this embodiment can provide an all-solid-state battery with excellent charging resistance, cycle characteristics, and charging short-circuit rate in a lithium deposition-type all-solid-state battery.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate explanations will be omitted. Furthermore, the dimensional proportions in the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0012] FIG. 1 is a cross-sectional view schematically illustrating the overall structure of a stacked-type (internal parallel connection type) all-solid-state lithium secondary battery (hereinafter also simply referred to as a "stacked-type secondary battery") according to one embodiment of the present invention. FIG. 1 shows a cross section of the stacked-type secondary battery during charging. The stacked-type secondary battery 10a shown in FIG. 1 has a structure in which a substantially rectangular power generating element 21, where charge and discharge reactions actually proceed, is sealed inside a laminate film 29, which is a battery exterior. The power generating element 21 has a structure in which a negative electrode, a solid electrolyte layer 17, and a positive electrode are stacked. The negative electrode has a structure in which a negative electrode current collector 11′ and a negative electrode active material layer 13 made of lithium metal deposited on the surface of the negative electrode current collector 11′ are stacked. A negative electrode intermediate layer 14 is disposed adjacent to the surface of the negative electrode active material layer 13 facing the solid electrolyte layer 17. The positive electrode has a structure in which a positive electrode active material layer 15 is disposed on the surface of a positive electrode current collector 11". The negative electrode, solid electrolyte layer, and positive electrode are laminated in this order, with the negative electrode intermediate layer 14 and the positive electrode active material layer 15 facing each other with the solid electrolyte layer 17 interposed therebetween. As a result, adjacent negative electrodes, solid electrolyte layers, and positive electrodes constitute one unit cell layer 19. Therefore, the stacked secondary battery 10a shown in FIG. 1 can be said to have a structure in which a plurality of unit cell layers 19 are laminated and electrically connected in parallel. A negative electrode current collector 25 and a positive electrode current collector 27, which are electrically connected to the respective electrodes (negative electrode and positive electrode), are attached to the negative electrode current collector 11' and the positive electrode current collector 11", respectively, and are structured so as to be sandwiched between the ends of the laminate film 29 and extended to the outside of the laminate film 29. A constraining pressure is applied to the stacked secondary battery 10a in the stacking direction of the power generating element 21 by a pressure member (not shown). Therefore, the volume of the power generating element 21 is kept constant.

[0013] The main components of the all-solid-state battery according to this embodiment will be described below.

[0014] [Current collector] The current collectors (negative electrode current collector, positive electrode current collector) function to mediate the transfer of electrons from the electrode active material layers (negative electrode active material layer, positive electrode active material layer). There are no particular limitations on the material that constitutes the current collectors. Examples of materials that can be used for the current collectors include metals such as aluminum, nickel, iron, stainless steel, titanium, and copper, as well as conductive resins. There are also no particular limitations on the thickness of the current collectors, but an example is 10 to 100 μm.

[0015] [Negative electrode active material layer] The all-solid-state battery according to the present embodiment is a so-called lithium deposition type battery in which lithium metal is deposited on the negative electrode current collector during charging. The layer of lithium metal deposited on the negative electrode current collector during charging is the negative electrode active material layer of the all-solid-state battery according to the present embodiment. Therefore, the thickness of the negative electrode active material layer increases as the charging process progresses, and decreases as the discharging process progresses. The negative electrode active material layer does not need to be present during full discharge, but in some cases, a negative electrode active material layer consisting of a certain amount of lithium metal may be present during full discharge. The thickness of the negative electrode active material layer (lithium metal layer) during full charge is not particularly limited, but is typically 0.1 to 1000 μm.

[0016] [Negative electrode intermediate layer] The negative electrode intermediate layer is a layer adjacent to the surface of the solid electrolyte layer facing the negative electrode current collector, and contains at least one material selected from the group consisting of a metal material capable of alloying with lithium and a carbon material capable of absorbing lithium ions, and a binder. The negative electrode intermediate layer is preferably electrically conductive as a whole. The volume resistivity of the negative electrode intermediate layer is not particularly limited, but is preferably 10 2 The volume resistivity of the negative electrode intermediate layer is preferably 10 Ω·cm or less, and more preferably 10 Ω·cm or less. In this specification, the volume resistivity of the negative electrode intermediate layer is a value measured using an electrode resistance measurement system (manufactured by Hioki E.E. Corporation, product name: RM2610).

[0017] The negative electrode intermediate layer preferably contains at least one metal material selected from the group consisting of metal materials that can be alloyed with lithium. By including a metal material that can be alloyed with lithium in the negative electrode intermediate layer, lithium metal can be more uniformly deposited on the current collector surface. Specific examples of metal materials that can be alloyed with lithium include indium (In), aluminum (Al), silicon (Si), tin (Sn), magnesium (Mg), gold (Au), silver (Ag), zinc (Zn), and alloys containing at least one of these. Among these, the metal material preferably contains at least one metal selected from the group consisting of In, Al, Si, Sn, Mg, Au, Ag, and Zn, more preferably at least one metal selected from the group consisting of Ag, Mg, Zn, and Al, even more preferably at least one metal selected from the group consisting of Ag, Mg, and Zn, and particularly preferably Ag.

[0018] The negative electrode intermediate layer preferably contains at least one selected from the group consisting of carbon materials capable of absorbing lithium ions, instead of or in addition to containing at least one selected from the group consisting of metal materials capable of alloying with lithium. The presence of a carbon material capable of absorbing lithium ions in the negative electrode intermediate layer can suppress the precipitation and growth of lithium dendrites. Specific examples of carbon materials capable of absorbing lithium ions include carbon black (specifically, acetylene black, Ketjen Black (registered trademark), furnace black, channel black, thermal lamp black, etc.), carbon nanotubes (CNTs), graphite, hard carbon, etc. Among these, the carbon material preferably contains at least one selected from the group consisting of carbon black, and more preferably contains at least one selected from the group consisting of acetylene black, Ketjen Black (registered trademark), furnace black, channel black, and thermal lamp black.

[0019] The negative electrode intermediate layer may further contain a metal material other than the metal material capable of alloying with lithium (a metal material that does not alloy with lithium) in addition to at least one selected from the group consisting of a metal material capable of alloying with lithium and a carbon material capable of absorbing lithium ions. Examples of metal materials that do not alloy with lithium include nickel (Ni) and copper (Cu). According to one embodiment, the negative electrode intermediate layer contains at least one selected from the group consisting of a carbon material capable of absorbing lithium ions and a metal material that does not alloy with lithium.

[0020] According to a preferred embodiment, the negative electrode intermediate layer contains at least one type of metal particles containing the aforementioned metal material capable of forming an alloy with lithium and / or at least one type of carbon particles containing the aforementioned carbon material capable of absorbing lithium ions. This makes it easier to control the porosity of the negative electrode intermediate layer to a predetermined value. Furthermore, the effects of the present invention can be more pronounced. According to a preferred embodiment, the negative electrode intermediate layer contains at least one type of metal particles containing the aforementioned metal material capable of forming an alloy with lithium and at least one type of carbon particles containing the aforementioned carbon material capable of absorbing lithium ions. By using both metal particles and carbon particles to form the negative electrode intermediate layer, an all-solid-state battery with even better charging resistance, cycle characteristics, and charging short-circuit rate can be obtained.

[0021] The average primary particle diameter of the metal particles is, for example, 500 nm or less, preferably 300 nm or less, more preferably 200 nm or less, even more preferably 100 nm or less, and particularly preferably 80 nm or less. The lower limit of the average primary particle diameter of the metal particles is not particularly limited, but is, for example, 10 nm or more, preferably 20 nm or more, even more preferably 30 nm or more, and even more preferably 40 nm or more. The average primary particle diameter of the carbon particles is, for example, 200 nm or less, preferably 150 nm or less, more preferably 100 nm or less, even more preferably 80 nm or less, even more preferably 60 nm or less, even more preferably 50 nm or less, and particularly preferably 45 nm or less. The lower limit of the average primary particle diameter of the carbon particles is not particularly limited, but is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 25 nm or more. When the average primary particle diameter of the metal particles and the average primary particle diameter of the carbon particles are within the above ranges, it becomes easy to control the porosity of the negative electrode intermediate layer, described later, within a predetermined range. In this specification, the average primary particle diameter of particles refers to the 50% cumulative diameter (D50) of particle diameters of the particles observed in several to several tens of fields of view when the cross section of a layer containing the particles is observed with a scanning electron microscope (SEM) (the maximum distance between any two points on the outline of the observed particles).

[0022] When both carbon particles and metal particles are used, the mass ratio of the carbon particles to the metal particles (carbon particles:metal particles) is preferably 10:1 to 1:1, more preferably 5:1 to 2:1, and even more preferably 4:1 to 2.5:1. The volume ratio of the carbon particles to the metal particles (carbon particles:metal particles) is preferably 99:1 to 70:30, more preferably 95:5 to 75:25. When the blending ratio (mass ratio or volume ratio) of the carbon particles to the metal particles is within the above range, an all-solid-state battery with better charging resistance, cycle characteristics, and charge short circuit rate can be obtained. Furthermore, metal particles may undergo a significant volume change (expansion) when alloyed with lithium. Therefore, when both carbon particles and metal particles are used, it is preferable that the ratio of the mass of the carbon particles to the mass of the metal particles contained in the negative electrode intermediate layer (mass of carbon particles / mass of metal particles) exceeds 1. This makes it easier to maintain a predetermined porosity, and an all-solid-state battery with better cycle characteristics and charge short circuit rate can be obtained.

[0023] From the same viewpoint, the average primary particle size of the carbon particles is preferably smaller than the average primary particle size of the metal particles. The ratio of the average primary particle size of carbon atoms to the average primary particle size of the metal particles (average primary particle size of carbon particles / average primary particle size of metal particles) is preferably less than 1, more preferably 0.9 or less, even more preferably 0.8 or less, and even more preferably 0.7 or less. This makes it easier to maintain a predetermined porosity, and an all-solid-state battery with even better cycle characteristics and short-circuit rate during charging can be obtained. Furthermore, from the viewpoint of easily controlling the porosity within a predetermined range, the ratio of the primary particle size of carbon particles to the average primary particle size of the metal particles is, for example, 0.3 or more, more preferably 0.4 or more, and even more preferably 0.5 or more.

[0024] According to a preferred embodiment, the ratio of the mass of carbon particles to the mass of metal particles contained in the negative electrode intermediate layer (mass of carbon particles / mass of metal particles) exceeds 1, and the ratio of the average primary particle diameter of carbon atoms to the average primary particle diameter of metal particles (average primary particle diameter of carbon particles / average primary particle diameter of metal particles) is less than 1. This makes it easier to maintain a predetermined porosity, and an all-solid-state battery with even better cycle characteristics and short-circuit rate during charging can be obtained.

[0025] The negative electrode intermediate layer further contains a binder. The type of binder is not particularly limited, and binders known in the art can be appropriately used. Examples of binders include polyvinylidene fluoride (PVDF), compounds in which hydrogen atoms of PVDF are substituted with other halogen elements, polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC). Among these, from the viewpoint of easily controlling the porosity and thickness of the negative electrode intermediate layer (described later) within a predetermined range, it is preferable that the binder contains polyvinylidene fluoride (PVDF), and more preferably polyvinylidene fluoride (PVDF).

[0026] The content of the binder in the negative electrode intermediate layer is, for example, 8% by mass or more, preferably 10% by mass or more, and more preferably 12% by mass or more, relative to the total mass of the metal material (e.g., metal particles), carbon material (e.g., carbon particles), and binder (100% by mass). When the binder content is within this range, it becomes easy to control the porosity of the negative electrode intermediate layer (described later) within a predetermined range. There is no particular upper limit for the binder content, but from the viewpoint of suppressing an increase in resistance, it is preferably 20% by mass or less, more preferably 18% by mass or less, and even more preferably 16% by mass or less.

[0027] The ratio of the total surface area of ​​at least one kind of metal particles containing a metal material capable of alloying with lithium and at least one kind of carbon particles containing a carbon material capable of absorbing lithium ions to the mass of the binder contained in the negative electrode intermediate layer (total surface area of ​​metal particles and carbon particles / mass of binder) is 800 m 2It is preferable that the above value (total surface area of ​​metal particles and carbon particles / mass of binder) is 800m 2 / g or less, a sufficient amount of binder is present on the surfaces of the metal particles and carbon particles, thereby enhancing the adhesive strength between these particles. As a result, it is easy to reduce the porosity of the negative electrode intermediate layer, and it is easy to control the porosity of the negative electrode intermediate layer within the range of 10 to 70%. The above value (total surface area of ​​metal particles and carbon particles / mass of binder) is 700m 2 / g or less is more preferable, and 600m 2 / g or less is more preferable, and 2 / g or less, and more preferably 450m 2 It is particularly preferable that the above value (total surface area of ​​metal particles and carbon particles / mass of binder) is 10 m 2 / g or more, preferably 100m 2 / g or more, more preferably 200m 2 / g or more, and even more preferably 300m 2 / g or more. This range can improve the energy density of the all-solid-state battery. The above value (total surface area of ​​metal particles and carbon particles / mass of binder) is calculated as follows: for each type of particle, the volume per particle is calculated as a spherical particle having a radius equal to half the average primary particle diameter. The number of particles contained in the negative electrode intermediate layer per unit mass is calculated using this and the blending ratio of each component contained in the negative electrode intermediate layer. This is then multiplied by the surface area per particle of the spherical particles to obtain the total surface area for each particle type. The total surface areas for each particle type are then added together to obtain the total surface area, which is then divided by the mass of the binder contained in the negative electrode intermediate layer per unit mass to obtain the above value (total surface area of ​​metal particles and carbon particles / mass of binder). Specifically, this can be determined by the method described in the Examples below.

[0028] In a preferred embodiment, the average primary particle size of the metal particles or carbon particles contained in the negative electrode intermediate layer may be 30 nm or more, and the binder content may be 10 parts by mass or more per 100 parts by mass of the total of the metal particles, carbon particles, and binder.

[0029] When the negative electrode intermediate layer contains the metal particles but not the carbon particles, the above (total surface area of ​​the metal particles and the carbon particles / mass of the binder) means (total surface area of ​​the metal particles / mass of the binder). Similarly, when the negative electrode intermediate layer contains the carbon particles but not the metal particles, the above (total surface area of ​​the metal particles and the carbon particles / mass of the binder) means (total surface area of ​​the carbon particles / mass of the binder).

[0030] The proportion of the total mass of the metal material, carbon material, and binder relative to the total mass of the negative electrode intermediate layer is preferably 90 mass% or more, more preferably 95 mass% or more, even more preferably 98 mass% or more, particularly preferably 99 mass% or more, and most preferably 100 mass%.

[0031] The all-solid-state battery according to this embodiment is characterized in that the porosity of the negative electrode intermediate layer is 10% or more and 70% or less. In a lithium deposition-type all-solid-state battery, lithium ions are supplied from the positive electrode side during charging, and lithium metal is deposited between the negative electrode current collector and the negative electrode intermediate layer to form a negative electrode active material layer. However, the lithium metal may also deposit in the pores of the negative electrode intermediate layer and partially contact the solid electrolyte layer. When the porosity of the negative electrode intermediate layer exceeds 70%, lithium metal is more likely to deposit in the pores of the negative electrode intermediate layer, and the lithium metal deposited in the pores of the negative electrode active material layer and the solid electrolyte layer are more likely to come into contact with each other. As a result, the deposited lithium metal may grow through the pores in the solid electrolyte layer and come into contact with the positive electrode active material layer, which may lead to a short circuit in the battery.

[0032] Furthermore, if the porosity of the negative electrode intermediate layer exceeds 70%, the solid electrolyte contained in the solid electrolyte layer may penetrate close to the negative electrode active material layer (lithium metal deposited on the negative electrode current collector), and the deposited lithium metal may cause the solid electrolyte to undergo reductive decomposition and degradation. Furthermore, if the porosity of the negative electrode intermediate layer exceeds 70%, the strength of the negative electrode intermediate layer may decrease. As a result, repeated deposition and disappearance of lithium metal with the charge / discharge cycle of the battery may destroy the structure of the negative electrode intermediate layer due to stress caused by the lithium metal during deposition, and the conductive path may be destroyed. Furthermore, the strength may further decrease with the charge / discharge cycle of the battery, causing cracks in the negative electrode intermediate layer. As a result, even if a short circuit does not occur, the cycle durability of the battery may decrease. Furthermore, the small contact area between the negative electrode intermediate layer and the solid electrolyte layer may increase resistance during charging.

[0033] On the other hand, if the porosity of the negative electrode intermediate layer is less than 10%, the current density during charging will be high, which may promote the formation of lithium dendrites and cause a short circuit. Even if a short circuit does not occur, the current density will be high during charging, which may increase the cell resistance during charging.

[0034] The porosity of the negative electrode intermediate layer is preferably 65% ​​or less, more preferably 60% or less, and even more preferably 55% or less. The porosity of the negative electrode intermediate layer is preferably 15% or more, more preferably 20% or more, and even more preferably 25% or more. According to a preferred embodiment of the present invention, the porosity of the negative electrode intermediate layer is 10% or more and 60% or less. This can further improve the resistance during charging and the cycle durability. According to a more preferred embodiment of the present invention, the porosity of the negative electrode intermediate layer is 20% or more and 60% or less. This can further improve the resistance during charging and the cycle durability. In this specification, the porosity of the negative electrode intermediate layer is a value measured by the method described in the Examples below.

[0035] The method for controlling the porosity of the negative electrode intermediate layer within a predetermined range is not particularly limited. For example, a two-stage pressing process may be employed in the production of an all-solid-state battery. This involves pressing the solid electrolyte layer at a predetermined pressure, and then laminating the solid electrolyte layer and the negative electrode intermediate layer together and pressing them at a predetermined pressure. More specifically, a solid electrolyte slurry containing a solid electrolyte is applied to the surface of a support (e.g., a metal foil) and the resulting coating is dried to obtain a solid electrolyte layer formed on the surface of the support. The solid electrolyte layer formed on the surface of the support is then pressed at a predetermined pressure (first pressing step). This improves the alignment of the solid electrolyte particles on the surface of the solid electrolyte layer adjacent to the support, thereby reducing unevenness. After peeling off the support used to form the solid electrolyte layer, pressing may be performed using another metal foil or the like. Alternatively, prior to the first pressing step, the exposed surface of a separately prepared positive electrode active material layer may be placed on the exposed surface of the solid electrolyte layer, and the first pressing step may be performed with the solid electrolyte layer and the positive electrode active material layer stacked together. That is, according to a preferred embodiment of the present invention, prior to the first pressing step, the exposed surface of a separately prepared positive electrode active material layer is placed on the exposed surface of the solid electrolyte layer, and the first pressing step is performed with the solid electrolyte layer and the positive electrode active material layer stacked together. Meanwhile, a negative electrode intermediate layer slurry containing the materials contained in the negative electrode intermediate layer (metal particles and / or carbon particles and a binder) is applied to the surface of a negative electrode current collector (e.g., stainless steel foil), and the coating is dried to obtain a negative electrode intermediate layer formed on the surface of the negative electrode current collector. The support (metal foil) used in the first pressing step is then peeled off to expose the solid electrolyte layer. The exposed surfaces of the solid electrolyte layer and the negative electrode intermediate layer are then stacked so that they face each other, and pressed at a predetermined pressure (second pressing step). The porosity of the negative electrode intermediate layer can be adjusted by adjusting the pressing pressure, pressing temperature, and pressing time of the second pressing step. The porosity of the negative electrode intermediate layer can be more appropriately adjusted by further adjusting the amount of metal particles and / or carbon particles contained in the negative electrode intermediate layer, their average primary particle diameters, and the amount of binder. Specifically, as described above, the ratio of the total surface area of ​​the metal particles and carbon particles to the mass of the binder contained in the negative electrode intermediate layer is 800 m 2 / g or less, the porosity can be easily controlled within a predetermined range. Furthermore, this is preferable because the porosity achieved by the pressing process can be maintained even after the pressing pressure is released. Note that cold isostatic pressing (CIP) is suitable for the first and second pressing steps, but is not limited thereto.

[0036] In the above manufacturing method, it is preferable not to perform a press treatment on only the negative electrode intermediate layer before the second press step, because performing a press treatment on only the negative electrode intermediate layer may result in the porosity of the negative electrode intermediate layer being lower than a predetermined value.

[0037] The pressing pressure in the first pressing step varies depending on the material contained in the solid electrolyte layer, and when the first pressing step is performed with the solid electrolyte layer and the positive electrode active material layer stacked together, it also varies depending on the materials contained in the solid electrolyte layer and the positive electrode active material layer. This pressure can be appropriately set by those skilled in the art. For example, the pressing pressure in the first pressing step is preferably 300 MPa or more and 1000 MPa or less, more preferably 300 MPa or more and 800 MPa or less, and even more preferably 500 MPa or more and 700 MPa or less. The pressing temperature in the first pressing step is also not particularly limited, but is, for example, 20 to 80°C, preferably 20 to 40°C. The pressing time in the first pressing step is also not particularly limited, but is, for example, 10 seconds to 30 minutes, preferably 10 seconds to 10 minutes.

[0038] The pressure in the second pressing step varies depending on the material contained in the negative electrode intermediate layer and the desired porosity, and can be appropriately set by those skilled in the art. For example, the pressure in the second pressing step is preferably 100 MPa or more and 700 MPa or less, more preferably 300 MPa or more and 700 MPa or less, and even more preferably 500 MPa or more and 700 MPa or less. Within the above range, the porosity of the negative electrode intermediate layer can be easily controlled to a predetermined value.

[0039] The pressing temperature in the second pressing step varies depending on the material contained in the negative electrode intermediate layer and the desired porosity, and can be appropriately set by those skilled in the art. For example, the pressing temperature in the second pressing step is preferably 20 to 90°C, and more preferably 25 to 80°C. Within this range, the porosity of the negative electrode intermediate layer can be easily controlled to a predetermined value.

[0040] The pressing time of the second pressing step varies depending on the material contained in the negative electrode intermediate layer and the desired porosity, and can be appropriately set by those skilled in the art. For example, the pressing time of the second pressing step is preferably 10 seconds to 30 minutes, more preferably 1 to 10 minutes. Within this range, the porosity of the negative electrode intermediate layer can be easily controlled to a predetermined value.

[0041] The thickness of the negative electrode intermediate layer is not particularly limited, but is preferably 10 μm or less, more preferably 7 μm or less, and even more preferably 6 μm or less. When the thickness of the negative electrode intermediate layer is 10 μm or less, the path of lithium ions moving through the negative electrode intermediate layer during charging is not too long, and therefore the resistance during charging can be kept low. In addition, the energy density of the all-solid-state battery can be improved. The lower limit of the thickness of the negative electrode intermediate layer is not particularly limited, but from the viewpoint of ensuring the strength of the negative electrode intermediate layer, it is, for example, 1 μm or more, preferably 1.5 μm or more, and more preferably 2 μm or more. In this specification, the thickness of the negative electrode intermediate layer is a value measured by the method described in the Examples below.

[0042] [Solid electrolyte layer] The solid electrolyte layer is interposed between the negative electrode and the positive electrode and contains a solid electrolyte (usually as a main component). The solid electrolyte contained in the solid electrolyte layer is not particularly limited, and any known solid electrolyte in the art can be appropriately adopted, including sulfide solid electrolytes and oxide solid electrolytes. Because this solid electrolyte exhibits excellent lithium ion conductivity, it is preferably a sulfide solid electrolyte containing the element S, more preferably a sulfide solid electrolyte containing the element Li, the element M, and the element S, where the element M contains at least one element selected from the group consisting of P, Si, Ge, Sn, Ti, Zr, Nb, Al, Sb, Br, Cl, and I, and even more preferably a sulfide solid electrolyte containing the element S, the element Li, and the element P. Examples include LPS (Li2S-P2S5), Li6PS5X (where X is Cl, Br, or I), and Li7PS 11 , Li 3.2 P 0.96 Examples of suitable sulfide solid electrolytes include sulfide solid electrolytes such as S and Li3PS4. These sulfide solid electrolytes are preferably used because they have excellent lithium ion conductivity.

[0043] The ionic conductivity (e.g., Li ion conductivity) of a solid electrolyte (e.g., sulfide solid electrolyte) at room temperature (25°C) is, for example, 1 × 10 -5 S / cm or more is preferable, and 1×10 -4 It is more preferable that the ionic conductivity is S / cm or more. The ionic conductivity value of the solid electrolyte can be measured by an AC impedance method.

[0044] The shape of the solid electrolyte may be, for example, particulate such as a spherical or oval sphere, thin film, etc. When the solid electrolyte is particulate, its average particle size (D50) is not particularly limited, but is preferably 0.01 μm or more and 40 μm or less, more preferably 0.1 μm or more and 20 μm or less, and even more preferably 0.5 μm or more and 10 μm or less.

[0045] The content of the solid electrolyte in the solid electrolyte layer is preferably 50 to 100 mass %, more preferably 90 to 100 mass %.

[0046] The solid electrolyte layer may further contain a binder in addition to the solid electrolyte. The binder is not particularly limited, and known binders can be used as appropriate. For example, the binders described above for the negative electrode intermediate layer can be similarly employed. The content of the binder in the solid electrolyte layer is not particularly limited, and is, for example, 1 to 10 mass %.

[0047] The thickness of the solid electrolyte layer varies depending on the configuration of the intended all-solid-state battery, but is usually 0.1 to 1000 μm, and preferably 10 to 100 μm.

[0048] [Cathode active material layer] The positive electrode active material layer essentially contains a positive electrode active material, and may contain a solid electrolyte, a binder, and a conductive additive as needed.

[0049] The type of positive electrode active material contained in the positive electrode active material layer is not particularly limited, but may be layered rock salt active materials such as LiCoO2, LiMnO2, LiNiO2, LiVO2, and Li(Ni-Mn-Co)O2; LiMn2O4, LiNi 0.5 Mn 1.5 Examples of oxide active materials include spinel-type active materials such as LiFePO4 and LiMnPO4, olivine-type active materials such as LiFeSiO4 and LiMnSiO4, and Si-containing active materials such as LiFeSiO4 and LiMnSiO4. 12 Among these, Li(Ni-Mn-Co)O2 and those in which part of the transition metals is replaced with other elements (hereinafter also simply referred to as "NMC composite oxides") are preferably used as the positive electrode active material.

[0050] In another preferred embodiment, a sulfur-based positive electrode active material is used. Examples of the sulfur-based positive electrode active material include particles or thin films of organic sulfur compounds or inorganic sulfur compounds, and any material can be used as long as it can release lithium ions during charging and absorb lithium ions during discharging by utilizing the oxidation-reduction reaction of sulfur.

[0051] The content of the positive electrode active material in the positive electrode active material layer is not particularly limited, but is, for example, preferably 30 to 99 mass %, more preferably 40 to 90 mass %, and even more preferably 45 to 80 mass %.

[0052] The positive electrode active material layer preferably further contains a solid electrolyte. Specific forms of the solid electrolyte contained in the positive electrode active material layer may be the same as those described in the solid electrolyte layer section. A sulfide solid electrolyte is preferably used because it has excellent lithium ion conductivity and a low bulk modulus, allowing it to follow the volumetric changes of the positive electrode active material that accompany charge and discharge. The content of the solid electrolyte in the positive electrode active material layer is not particularly limited, but is, for example, 1 to 70 mass %, preferably 10 to 60 mass %, and more preferably 20 to 55 mass %.

[0053] The binder used in the positive electrode active material layer is not particularly limited, and known binders can be used as appropriate. For example, the binders described above for the negative electrode intermediate layer can be used. The content of the binder in the positive electrode active material layer is not particularly limited, and is, for example, 1 to 10 mass%.

[0054] The conductive additive used in the positive electrode active material layer is not particularly limited, and may be, for example, carbon such as carbon black (specifically, acetylene black, Ketjen Black (registered trademark), furnace black, channel black, thermal lamp black, etc.). The content of the conductive additive in the positive electrode active material layer is not particularly limited, and is, for example, 10 to 30 mass %.

[0055] The thickness of the positive electrode active material layer varies depending on the intended configuration of the all-solid-state battery, but is usually 0.1 to 1000 μm, and preferably 10 to 300 μm.

[0056] Although one embodiment of the all-solid-state battery of the present invention has been described above, the present invention is not limited to the configuration described in the above embodiment, and can be modified as appropriate based on the claims.

[0057] The present invention encompasses the following aspects and configurations: 1. A positive electrode having a positive electrode active material layer containing a positive electrode active material; a negative electrode having a negative electrode current collector on which lithium metal is deposited during charging; a solid electrolyte layer interposed between the positive electrode and the negative electrode and containing a solid electrolyte; a negative electrode intermediate layer located adjacent to a surface of the solid electrolyte layer facing the negative electrode current collector, the negative electrode intermediate layer containing at least one material selected from the group consisting of a metal material capable of alloying with lithium and a carbon material capable of absorbing lithium ions, and a binder; An all-solid-state battery comprising a power generating element having an all-solid-state battery, wherein the porosity of the negative electrode intermediate layer is 10% or more and 70% or less; 2. The all-solid-state battery according to 1 above, wherein the porosity of the negative electrode intermediate layer is 10% or more and 60% or less; 3. The all-solid-state battery according to 1. or 2. above, wherein the porosity of the negative electrode intermediate layer is 20% or more and 60% or less; 4. The all-solid-state battery according to any one of 1. to 3. above, wherein the thickness of the negative electrode intermediate layer is 10 μm or less; 5. The all-solid-state battery according to any one of 1. to 4., wherein the negative electrode intermediate layer contains at least one kind of metal particles containing a metal material capable of alloying with lithium and / or at least one kind of carbon particles containing a carbon material capable of absorbing lithium ions; 6. The all-solid-state battery according to any one of 1. to 5., wherein the negative electrode intermediate layer contains at least one kind of metal particles containing a metal material capable of alloying with lithium and at least one kind of carbon particles containing a carbon material capable of absorbing lithium ions; 7. The ratio of the total surface area of ​​the at least one metal particle containing a metal material capable of alloying with lithium and the at least one carbon particle containing a carbon material capable of absorbing lithium ions to the mass of the binder contained in the negative electrode intermediate layer is 800 m 2 7. The all-solid-state battery according to 5. or 6., wherein the ionic current density is 0. / g or less. [Example]

[0058] The present invention will be described in more detail below with reference to examples. However, the technical scope of the present invention is not limited to the following examples. Note that the following operations were performed in a glove box. Furthermore, the instruments and devices used in the glove box were thoroughly dried beforehand.

[0059] <Example of evaluation cell production> [Example 1] (Preparation of positive electrode) First, as the constituent material of the positive electrode active material layer, the positive electrode active material NMC composite oxide (composition = LiNi 0.8 Mn 0.1 Co 0.1 O2), an argyrodite-type sulfide solid electrolyte (Li6PS5Cl) as a solid electrolyte, acetylene black as a conductive additive, and styrene-butadiene rubber (SBR) as a binder were prepared.

[0060] Of these, NMC composite oxide, solid electrolyte, and acetylene black were weighed out in a mass ratio of 50:30:20 and mixed in an agate mortar in a glove box. The mixture was then further mixed and stirred in a planetary ball mill. Two parts by mass of styrene-butadiene rubber (SBR) were added to 100 parts by mass of the resulting mixed powder, and xylene was added as a solvent to prepare a positive electrode active material slurry. The positive electrode active material slurry was then applied to the surface of a carbon-coated aluminum foil serving as a positive electrode current collector and dried to form a positive electrode active material layer (200 μm thick). This produced a positive electrode.

[0061] (Preparation of solid electrolyte layer) In a glove box with an argon atmosphere and a dew point of -68°C or less, an argyrodite-type sulfide solid electrolyte (Li6PS5Cl) as the solid electrolyte and SBR as the binder were mixed in a mass ratio of 95:5, and an appropriate amount of xylene was added as a solvent and mixed to prepare a solid electrolyte slurry. The solid electrolyte slurry was applied to one surface of a stainless steel foil support and dried to obtain a solid electrolyte layer (thickness 80 μm).

[0062] (Fabrication of the negative electrode intermediate layer) Acetylene black (average primary particle size (D50): 35 nm) and silver nanoparticles (average primary particle size (D50): 60 nm) were weighed and mixed to a mass ratio of acetylene black (AB):Ag = 3:1. 14 parts by mass of polyvinylidene fluoride (PVDF) as a binder was added to 86 parts by mass of the resulting mixture, and N-methylpyrrolidone was added as a solvent and mixed to prepare a negative electrode intermediate layer slurry. The negative electrode intermediate layer slurry was applied to the surface of stainless steel foil as a negative electrode current collector and dried to obtain a negative electrode intermediate layer (thickness before pressing: 10 μm).

[0063] (Preparation of evaluation cells) The positive electrode active material layer formed on the surface of an aluminum foil (positive electrode current collector) and the solid electrolyte layer formed on the surface of a stainless steel foil were stacked so that the exposed surface of the positive electrode active material layer and the exposed surface of the solid electrolyte layer faced each other, and then pressed by cold isostatic pressing (CIP) at 700 MPa and 25°C for 1 minute (first pressing step). After peeling off the stainless steel foil adjacent to the solid electrolyte layer, the solid electrolyte layer and the negative electrode intermediate layer formed on the surface of the stainless steel foil (negative electrode current collector) were stacked so that the exposed surface of the solid electrolyte layer and the exposed surface of the negative electrode intermediate layer faced each other, and then pressed by cold isostatic pressing (CIP) at 500 MPa and 80°C for 1 minute (second pressing step). This transferred the negative electrode intermediate layer to the exposed surface of the solid electrolyte layer and adjusted the porosity of the negative electrode intermediate layer. Finally, an aluminum positive electrode tab and a nickel negative electrode tab were bonded to the aluminum foil (positive electrode current collector) and the stainless steel foil (negative electrode current collector), respectively, using an ultrasonic welding machine, and the resulting laminate was placed inside an aluminum laminate film and vacuum-sealed, thereby obtaining an evaluation cell, which is the lithium deposition-type all-solid-state battery of this example.

[0064] [Example 2] The evaluation cell of this example was produced in the same manner as in Example 1, except that in the above (production of evaluation cell), the pressing temperature in the second pressing step was changed to 25°C.

[0065] [Example 3] The evaluation cell of this example was produced in the same manner as in Example 1, except that in the above (production of evaluation cell), the pressing pressure in the second pressing step was changed to 700 MPa and the pressing temperature was changed to 25°C.

[0066] [Example 4] The evaluation cell of this example was produced in the same manner as in Example 1, except that in the above (production of evaluation cell), the pressing pressure in the second pressing step was changed to 700 MPa and the pressing time was changed to 10 minutes.

[0067] [Example 5] The evaluation cell of this example was produced in the same manner as in Example 1, except that in the above (production of evaluation cell), the pressing pressure in the second pressing step was changed to 100 MPa and the pressing temperature was changed to 25°C.

[0068] [Comparative Example 1] In the above (preparation of evaluation cell), after the first pressing step and before the second pressing step, the negative electrode intermediate layer formed on the surface of the stainless steel foil (negative electrode current collector) was subjected to a roll pressing treatment at 25°C with a linear pressure of 3.0 kN / cm, and the pressing pressure in the second pressing step was changed to 700 MPa and the pressing time to 10 minutes. An evaluation cell for this comparative example was prepared in the same manner as in Example 1, except for this.

[0069] Comparative Example 2 The evaluation cell of this comparative example was produced in the same manner as in Example 1, except that the second pressing step was not carried out in the above (production of the evaluation cell).

[0070] Comparative Example 3 In the above (production of the negative electrode intermediate layer), the acetylene black was changed to acetylene black with an average primary particle diameter (D50) of 12 nm. Then, 12 parts by mass of polyvinylidene fluoride (PVDF) as a binder was added to 88 parts by mass of a mixture mixed so as to have a mass ratio of AB:Ag = 3:1. Furthermore, in the above (production of the evaluation cell), the pressing temperature in the second pressing step was changed to 25°C, and the pressing time was changed to 30 minutes. Except for the above, the evaluation cell of this comparative example was produced in the same manner as in Example 1.

[0071] Comparative Example 4 In the above (production of the negative electrode intermediate layer), the acetylene black was changed to acetylene black with an average primary particle diameter (D50) of 38 nm. Then, 4 parts by mass of polyvinylidene fluoride (PVDF) as a binder was added to 96 parts by mass of a mixture mixed so as to have a mass ratio of AB:Ag = 3:1. Furthermore, in the above (production of the evaluation cell), the pressing temperature in the second pressing step was changed to 25°C, and the pressing time was changed to 30 minutes. Except for the above, the evaluation cell of this comparative example was produced in the same manner as in Example 1.

[0072] Comparative Example 5 In the above (production of the negative electrode intermediate layer), the acetylene black was changed to acetylene black with an average primary particle diameter (D50) of 30 nm. Then, 8 parts by mass of polyvinylidene fluoride (PVDF) as a binder was added to 92 parts by mass of a mixture mixed so as to have a mass ratio of AB:Ag = 3:1. Furthermore, in the above (production of the evaluation cell), the pressing temperature in the second pressing step was changed to 25°C, and the pressing time was changed to 30 minutes. Except for the above, the evaluation cell of this comparative example was produced in the same manner as in Example 1.

[0073] <Measurement of porosity and thickness of the negative electrode intermediate layer> The porosity of the negative electrode intermediate layer is a value calculated from the negative electrode intermediate layer in a discharged state, which is calculated after the all-solid-state battery is completely discharged, the cell is released from restraints, and the outer casing is removed, and can be calculated using 3D-SEM.

[0074] Specifically, the power generating element was removed from the evaluation cell after full discharge, and a cross section perpendicular to the surface direction (laminated cross section) was exposed by ion milling. Using a Hitachi High-Tech Science Corporation focused ion beam scanning electron microscope (FIB-SEM), a SEM photograph of the surface portion of the negative electrode intermediate layer (5 μm × 5 μm size photograph) was taken, which was a front view of the laminated cross section of the power generating element. The surface of the negative electrode intermediate layer was then irradiated with an ion beam to excavate the surface of the negative electrode intermediate layer, and another photograph of the surface of the negative electrode intermediate layer was taken. The excavation of the negative electrode intermediate layer surface by ion beam irradiation and the photographing of the negative electrode intermediate layer surface were repeated to obtain a group of 2D photographs of the surface of the negative electrode intermediate layer. Each 2D region in the obtained group of 2D photographs was then identified, the area of ​​voids present in the 2D region was calculated, and the area was integrated to calculate the volume of voids in the 3D region. The porosity was then calculated by calculating the volume of voids relative to the volume of the entire 3D region.

[0075] The lithium metal in the negative electrode intermediate layer is considered to be voids. Specifically, if lithium metal remains in the voids in the evaluation cell after discharge, the lithium metal is counted as voids in the calculation of the area. The lithium metal is identified by high-sensitivity EDS, and the identified lithium metal is identified by its contrast, and its area is calculated.

[0076] The cross section was also observed with an SEM, and the thickness was measured at several to several tens of different locations on the negative electrode intermediate layer, and the arithmetic mean value of these measurements was taken as the thickness of the negative electrode intermediate layer.

[0077] In this example, the evaluation cells after the charge-discharge test described below were fully discharged and then the porosity and thickness of the negative electrode intermediate layer were measured. However, similar values ​​for the porosity and thickness of the negative electrode intermediate layer were also obtained for the evaluation cells before the first charge.

[0078] <Proportion of the total surface area of ​​silver nanoparticles and acetylene black particles to the mass of the binder contained in the negative electrode intermediate layer> The ratio of the total surface area of ​​silver nanoparticles and acetylene black particles to the mass of the binder contained in the negative electrode intermediate layer (m 2 / g) was determined by the following procedure.

[0079] (1) Determine the masses of acetylene black particles, silver nanoparticles, and binder per unit mass of the negative electrode intermediate layer, as well as their specific gravities. (2) Determine the average primary particle size of acetylene black particles and silver nanoparticles. (3) From (1) and (2) above, the number of acetylene black particles and the number of silver nanoparticles per unit mass of the negative electrode intermediate layer are calculated, assuming that each particle is spherical. 2 Using the formula × number of particles (where r is the average primary particle size of the acetylene black particles or silver nanoparticles / 2), calculate the total surface area of ​​the acetylene black particles and the total surface area of ​​the silver nanoparticles, add them together, and divide this by the mass of the binder per unit mass of the negative electrode intermediate layer.

[0080] Here, the specific gravity of the acetylene black particles, silver nanoparticles, and binder is 2.01 g / cm 3 , 11.23g / cm 3 , and 1.89 g / cm 3 The results are shown in Table 1 below.

[0081] <Evaluation of the presence or absence of a short circuit> A positive electrode lead and a negative electrode lead were connected to the positive electrode current collector and negative electrode current collector, respectively, of the evaluation cell (before the first charge). A confining pressure of 3 MPa was applied to the evaluation cell in the stacking direction using a pressure member. The evaluation cell was charged from 0% SOC at a charge rate of 0.5C in a thermostatic chamber at 60°C. The evaluation cell was then examined for short-circuiting within 30 minutes. A short-circuit was determined to have occurred if the evaluation cell's voltage dropped during the charging process. Furthermore, the evaluation cells that were determined to have short-circuited were disassembled and the interior of the cells was inspected. The formation of lithium metal dendrites was confirmed in all cases. The results are shown in Table 1 below.

[0082] <Cycle test> A positive electrode lead and a negative electrode lead were connected to the positive electrode current collector and the negative electrode current collector, respectively, of the evaluation cell (before the first charge) prepared above, and a cycle test was performed while applying a restraining pressure of 3 MPa in the stacking direction of the evaluation cell using a pressure member. The cycle test was performed at 60°C, with a cell voltage ranging from 3.0 V to 4.3 V, and 200 cycles of charge and discharge at a charge / discharge rate of 0.5 C (charge CCCV mode (0.01 C cutoff), discharge CC mode). The ratio of the 200th discharge capacity to the first discharge capacity was calculated, and this was defined as the discharge capacity retention rate (capacity retention rate) (%). The results are shown in Table 1 below. It should be noted that the discharge capacity retention rates of the evaluation cells of Comparative Examples 1 and 2 could not be measured due to short circuits.

[0083] <Measurement of resistance during charging> A positive electrode lead and a negative electrode lead were connected to the positive electrode current collector and the negative electrode current collector, respectively, of the evaluation cell (before the first charge) prepared above, and the evaluation cell was charged to an SOC of 50% while applying a restraining pressure of 3 MPa in the stacking direction of the evaluation cell using a pressure member. Thereafter, charging was repeated in the order of (1) to (7) below, and the relationship between the amount of current and the voltage increase was plotted. The resistance during charging was calculated from the slope of this plotted graph. Note that all of (1) to (7) below were performed at a temperature of 60°C. The resistance during charging of each evaluation cell is shown in Table 1 below as a relative value when the resistance during charging of the evaluation cell of Example 1 is set to 100. Note that the resistance during charging of the batteries of Comparative Examples 1 and 2 could not be measured due to short circuits.

[0084] (1)0.05C CC charging 15sec (2) Two-hour break (3)0.1C CC charging 15sec (4) Two-hour break (5)0.2C CC charging 15sec (6) Two-hour break (7)0.5C CC charging 15sec.

[0085] [Table 1]

[0086] The results in Table 1 show that the evaluation cells of Examples 1 to 5, which contained a predetermined metal material (metal particles), carbon material (carbon particles), and binder and had a negative electrode intermediate layer with a porosity of 10 to 70%, all exhibited good resistance during charging, cycle characteristics, and short-circuit rate during charging. In contrast, the evaluation cells of Comparative Examples 1 and 2, in which the porosity of the negative electrode intermediate layer was outside the above range, exhibited short-circuits during charging. Similarly, the evaluation cells of Comparative Examples 3 to 5, in which the porosity of the negative electrode intermediate layer was outside the above range, did not exhibit short-circuits, but had low cycle durability, and it was not possible to obtain batteries that exhibited good performance in terms of resistance during charging, cycle characteristics, and short-circuit rate during charging.

[0087] This application is based on Japanese Patent Application No. 2022-172093, filed on October 27, 2022, the disclosure of which is incorporated herein by reference in its entirety. [Explanation of symbols]

[0088] 10a stacked secondary battery, 11' negative electrode current collector, 11” positive electrode current collector, 13 negative electrode active material layer, 14 negative electrode intermediate layer, 15 positive electrode active material layer, 17 solid electrolyte layer, 19 cell layer, 21 power generation elements, 25 negative current collector plate, 27 positive current collector plate, 29 Laminating film.

Claims

1. a positive electrode having a positive electrode active material layer containing a positive electrode active material; a negative electrode having a negative electrode current collector on which lithium metal is deposited during charging; a solid electrolyte layer interposed between the positive electrode and the negative electrode and containing a solid electrolyte; a negative electrode intermediate layer located adjacent to a surface of the solid electrolyte layer facing the negative electrode current collector, the negative electrode intermediate layer including at least one kind of metal particles containing a metal material capable of alloying with lithium, at least one kind of carbon particles containing a carbon material capable of absorbing lithium ions, and a binder; An all-solid-state battery comprising a power generating element having the negative electrode intermediate layer is composed of a single layer, The porosity of the negative electrode intermediate layer is 10% or more and 70% or less.

2. The all-solid-state battery according to claim 1 , wherein the porosity of the negative electrode intermediate layer is 10% or more and 60% or less.

3. The all-solid-state battery according to claim 1 , wherein the porosity of the negative electrode intermediate layer is 20% or more and 60% or less.

4. 3. The all-solid-state battery according to claim 1, wherein the negative electrode intermediate layer has a thickness of 10 μm or less.

5. the ratio of the total surface area of ​​the at least one metal particle containing a metal material capable of alloying with lithium and the at least one carbon particle containing a carbon material capable of absorbing lithium ions to the mass of the binder contained in the negative electrode intermediate layer is 800 m ２ The all-solid-state battery according to claim 1 or 2, wherein the surface area of ​​the all-solid-state battery is 1 / g or less.

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