JP7728638B2 - All-solid-state secondary battery, laminated all-solid-state secondary battery and method for manufacturing the same - Google Patents

Description

The present invention relates to an all-solid-state secondary battery, a laminated all-solid-state secondary battery, and a method for manufacturing the same.

In order to improve the energy density of an all-solid-state secondary battery, it is conceivable to use a plurality of all-solid-state secondary batteries stacked one upon the other.
When a plurality of all-solid-state secondary batteries are stacked and used in this manner, in order to improve rate characteristics and improve cycle characteristics by suppressing short circuits, as described in Patent Document 1, it is preferable to use a stacked configuration in which one of a positive electrode layer or a negative electrode layer (hereinafter also referred to as a first electrode layer), solid electrolyte layers respectively disposed on the front and back surfaces of the first electrode layer, and the other of a positive electrode layer or a negative electrode layer (hereinafter also referred to as a second electrode layer) respectively stacked on the outer surface of each solid electrolyte layer, and further reduce unevenness on the surface of each all-solid-state secondary battery to reduce physical influences on adjacent all-solid-state secondary batteries.

In Patent Document 1, therefore, a stack having the above-described configuration is placed on a support plate, laminated, and packed, and pressure is applied in the stacking direction using an isostatic press to produce an all-solid-state secondary battery with even less surface irregularities.

Japanese Patent Application Laid-Open No. 2019-121558

However, the present inventors have noticed that in all-solid-state secondary batteries manufactured by applying pressure in the stacking direction by isostatic pressing as described above, a problem occurs, albeit very rarely, in which the charge/discharge capacity cannot be fully exhibited.
After careful investigation by the inventors, it became clear that the cause of this defect was a crack in part of the current collecting portion, which is a foil-like protruding portion provided to electrically connect the first electrode layer to external wiring, or that the current collecting portion had been cut.

If a crack occurs in the current collecting portion or if the current collecting portion is cut off in this manner, the electrical connection between the first electrode layer and the external wiring is interrupted, which necessitates a step of electrically connecting the current collecting portion to the first electrode layer again, resulting in a problem that the manufacturing process of the all-solid-state secondary battery becomes complicated.
The present invention has been made in view of the above problems, and aims to provide an all-solid-state secondary battery in which the current collecting portion is less likely to crack than before or is less likely to be cut than before, while reducing the unevenness of the surface of the all-solid-state secondary battery, and a method for manufacturing an all-solid-state secondary battery.

That is, the all-solid-state secondary battery according to the present invention is manufactured by the following manufacturing method.
a current collector protection member that protects the current collector and is disposed to wrap the current collector; a laminate manufacturing step of manufacturing a laminate in which solid electrolyte layers are laminated on both sides of the first electrode layer, the second electrode layer is laminated on an outer surface of each of the solid electrolyte layers, foil-shaped current collectors that electrically connect the first electrode layers to external wiring are disposed so as to protrude outward from the first electrode layers, and a current collector protection member that protects the current collectors is disposed so as to wrap the current collectors; a pressurizing step of applying pressure to the laminate in a stacking direction; and a removal step of removing the current collector protection member after the pressurizing step.

With this manufacturing method for an all-solid-state secondary battery, the protruding portions of the current collectors can be protected by being wrapped around them by the current collector protection member while pressure is being applied to the laminate, thereby preventing cracks or breakage of the current collectors due to pressure.

If the laminate further includes an insulating layer arranged to cover the side end surface of the first electrode layer, and the current collector protection member is an excess insulating layer formed integrally with the side end surface of the insulating layer, gaps will not form between the insulating layer and the current collector protection member, further reducing cracking and breakage of the current collector.

If a notch is formed between the surplus insulating layers, it is preferable because it makes it easier to remove only the surplus insulating layer. To make it easier to remove the surplus insulating layer, it is preferable that the notch is formed in a range of 5% to 99% of the thickness of the insulating layer in the stacking direction.

The all-solid-state secondary battery manufactured by the above-described manufacturing method has the following characteristics.
an insulating layer disposed on a side end surface of the first electrode layer; a foil-shaped current collecting portion protruding outward from the first electrode layer through the insulating layer; and a different surface portion having a surface roughness different from that of the other side end surface of the insulating layer, the different surface portion being formed on the side end surface of the insulating layer from which the current collecting portion protrudes.
An example of the different surface portion is a roughened portion that has a rougher surface than the other side end faces of the insulating layer.

More specifically, the different surface portion is formed when excess insulating layer formed on the outer side of the side end face of the insulating layer is removed, and the excess insulating layer encases and protects the protruding portion of the current collecting element before the excess insulating layer is removed.

The height in the stacking direction of the different surface portion formed by removing the excess insulating layer from the insulating layer may be 1% or more and 95% or less of the thickness in the stacking direction of the insulating layer.

A specific embodiment of the present invention is one in which the notch between the insulating layer and the current collector protection member is formed to a depth of 5% to 99% of the thickness of the current collector protection member.

To simplify the manufacturing process, it is preferable that the excess insulating layer and the insulating layer are integrally molded.

In a specific embodiment, it is preferable that the insulating layer is made of resin or contains resin.

If the insulating layer further contains an insulating filler, the insulating filler can improve the adhesion between the materials that form the insulating layer, thereby improving the strength of the insulating layer.

The insulating filler may be one or more substances selected from the group consisting of fibrous resin, resin nonwoven fabric, alumina, magnesium oxide, silica, boehmite, barium titanate, barium carbonate, yttria, manganese oxide, etc.

It is preferable to position part or all of the outer edge of the insulating layer on the side where the current collecting portion protrudes outside the outer edge of the second electrode layer, as this can prevent short circuits due to physical contact between the first electrode layer and the second electrode layer (positive electrode layer and negative electrode layer).

To further prevent short circuits between the first electrode layer and the second electrode layer (positive electrode layer and negative electrode layer), it is preferable that part or all of the outer edge of the second electrode layer be disposed on the insulating layer.

To further improve the structural stability of the entire all-solid-state secondary battery, it is preferable that the first electrode layer be the positive electrode layer.

It is preferable that the solid electrolyte layer of the all-solid-state secondary battery contains a sulfide-based solid electrolyte containing at least lithium, phosphorus, and sulfur, as this can further improve battery performance.

The negative electrode layer preferably contains a negative electrode active material that forms an alloy with lithium and/or a negative electrode active material that forms a compound with lithium, and metallic lithium can be deposited inside the negative electrode layer during charging, with metallic lithium providing 80% or more of the charge capacity of the negative electrode layer.

In a specific embodiment of the present invention, the negative electrode layer may contain one or more elements selected from the group consisting of amorphous carbon, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, and zinc.

According to the present invention, the method for producing an all-solid-state battery includes a pressurizing step, so that unevenness on the surface of the all-solid-state secondary battery can be flattened.
Furthermore, while pressure is being applied, the protruding portion of the current collector is wrapped and protected by the current collector protection member, which makes it possible to further reduce the risk of cracks occurring at the base of the protruding portion of the current collector or the current collector being cut off due to direct pressure being applied to the current collector than in the past.

1 is a cross-sectional view showing a schematic configuration of an all-solid-state secondary battery according to one embodiment of the present invention. FIG. 1 is an enlarged cross-sectional view showing a schematic configuration of an all-solid-state secondary battery according to an embodiment of the present invention. FIG. 1 is an enlarged plan view showing a schematic configuration of an all-solid-state secondary battery according to an embodiment of the present invention. 1A to 1C are schematic diagrams illustrating a method for manufacturing an all-solid-state secondary battery according to an embodiment of the present invention. 1A to 1C are schematic diagrams illustrating a method for manufacturing an all-solid-state secondary battery according to an embodiment of the present invention. 1A to 1C are schematic diagrams illustrating a method for manufacturing an all-solid-state secondary battery according to an embodiment of the present invention. FIG. 2 is a schematic diagram of an excess insulating layer, an insulating layer, and a positive electrode layer of the all-solid-state secondary battery according to the embodiment, viewed from the stacking direction. 5 is a schematic diagram showing a side end surface of an excess insulating layer material. 1A to 1C are schematic diagrams illustrating a method for manufacturing an all-solid-state secondary battery according to an embodiment of the present invention. FIG. 2 is an enlarged view showing a roughened portion of the all-solid-state secondary battery according to the embodiment. 1 is a graph showing the results of charge/discharge evaluation of an all-solid-state secondary battery according to an example of the present invention. 1 is a graph showing cycle characteristics of all-solid-state secondary batteries according to examples of the present invention and comparative examples. 1 is a graph showing the results of charge/discharge evaluation of an all-solid-state secondary battery according to an example of the present invention. 1 is a graph showing the results of charge/discharge evaluation of an all-solid-state secondary battery according to a comparative example of the present invention. 1 is a graph showing the results of charge/discharge evaluation of an all-solid-state secondary battery according to a comparative example of the present invention. 1 is a graph showing cycle characteristics of an all-solid-state secondary battery according to an example of the present invention.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that in this specification and drawings, components having substantially the same functional configuration are designated by the same reference numerals, and redundant explanations will be omitted. Furthermore, each component in the drawings has been enlarged or reduced as appropriate for ease of explanation, and the size and proportions of each component in the drawings may differ from their actual size.

<1. Structure of all-solid-state secondary battery>
First, the configuration of an all-solid-state secondary battery 1 according to an embodiment of the present invention will be described.
The all-solid-state secondary battery 1 according to this embodiment includes a positive electrode layer 10, a negative electrode layer 20, and a solid electrolyte layer 30. More specifically, the all-solid-state lithium secondary battery 1 includes one of the positive electrode layer 10 and the negative electrode layer 20 (hereinafter also referred to as a first electrode layer), solid electrolyte layers 30 laminated on both sides of the first electrode layer, the other of the positive electrode layer 10 and the negative electrode layer 20 (hereinafter also referred to as a second electrode layer) laminated on the outer surface of each solid electrolyte layer, and an insulating layer 13 disposed on a side end surface S of the first electrode layer. In this embodiment, as shown in FIGS. 1 and 2 , a battery in which the first electrode layer is the positive electrode layer 10 and the second electrode layer is the negative electrode layer 20 will be described. Note that the side end surface refers to the peripheral end not in the stacking direction of the layers, but rather the end of each layer in a direction perpendicular to the stacking direction of the layers.

(1-1. Positive electrode layer)
As shown in FIG. 2 , the positive electrode layer 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 .
The positive electrode current collector 11 may be, for example, a plate or foil made of stainless steel, titanium (Ti), nickel (Ni), aluminum (Al), or an alloy thereof.
2, the positive electrode active material layer 12 is disposed on both sides of the positive electrode current collector 11. The positive electrode active material layer 12 contains a positive electrode active material and a solid electrolyte.
The solid electrolyte contained in the positive electrode active material layer 12 may or may not be the same type as the solid electrolyte contained in the solid electrolyte layer 30. Details of the solid electrolyte will be described later in the section on the solid electrolyte layer 30.

The positive electrode active material may be any positive electrode active material capable of reversibly absorbing and releasing lithium ions.

For example, the positive electrode active material may be in powder or granular form and may be formed using lithium salts such as lithium cobalt oxide (hereinafter referred to as LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel aluminum oxide (hereinafter referred to as NCA), lithium nickel cobalt manganese oxide (hereinafter referred to as NCM), lithium manganate, and lithium iron phosphate, as well as nickel sulfide, copper sulfide, sulfur, iron oxide, or vanadium oxide. These positive electrode active materials may be used alone or in combination of two or more.

The positive electrode active material is preferably formed from a lithium salt of a transition metal oxide having a layered rock salt structure, among the lithium salts mentioned above. Here, "layered" refers to a thin sheet-like shape. Furthermore, "rock salt structure" refers to a sodium chloride structure, which is a type of crystalline structure, and specifically refers to a structure in which face-centered cubic lattices formed by cations and anions are offset from each other by half the edge of the unit lattice.

Examples of lithium salts of transition metal oxides having such a layered rock salt structure include lithium salts of ternary transition metal oxides such as LiNi _x Co _y Al _z O ₂ (NCA) or LiNi _x Co _y Mn _z O ₂ (NCM) (where 0<x<1, 0<y<1, 0<z<1, and x+y+z=1).

When the positive electrode active material contains a lithium salt of a ternary transition metal oxide having the layered rock salt structure described above, the energy density and thermal stability of the all-solid-state secondary battery 1 can be improved.

The positive electrode active material may be covered with a coating layer. Here, the coating layer of this embodiment may be any known coating layer for a positive electrode active material of an all-solid-state secondary battery 1. Examples of the coating layer include Li ₂ O—ZrO ₂ .

Furthermore, when the positive electrode active material is formed from a lithium salt of a ternary transition metal oxide such as NCA or NCM and contains nickel (Ni) as the positive electrode active material, the capacity density of the all-solid-state secondary battery 1 can be increased and metal elution from the positive electrode active material in a charged state can be reduced. As a result, the all-solid-state secondary battery 1 according to this embodiment can improve the long-term reliability and cycle characteristics in a charged state.

Here, examples of the shape of the positive electrode active material include particle shapes such as spherical and oval spheres. The particle size of the positive electrode active material is not particularly limited, as long as it is within a range applicable to positive electrode active materials in conventional all-solid-state secondary batteries. The content of the positive electrode active material in the positive electrode layer 10 is also not particularly limited, as long as it is within a range applicable to positive electrode layer 10 in conventional all-solid-state secondary batteries 1.

In addition to the above-mentioned positive electrode active material and solid electrolyte, the positive electrode active material layer 12 may also contain additives such as conductive additives, binders, fillers, dispersants, and ion-conducting additives, as appropriate.

Examples of conductive additives that can be incorporated into the positive electrode active material layer 12 include graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanotubes, graphene, and metal powder. Examples of binders that can be incorporated into the positive electrode active material layer 12 include styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. Furthermore, fillers, dispersants, ion-conducting additives, and the like that can be incorporated into the positive electrode active material layer 12 can be any of the well-known materials commonly used in electrodes for all-solid-state secondary batteries 1.

(1-2. Negative electrode layer)
The negative electrode layer 20 includes, for example, a plate-shaped or foil-shaped negative electrode current collector 21 and a negative electrode active material layer 22 formed on the negative electrode current collector 21, as shown in FIG.
In this embodiment, the negative electrode current collector 21 forms the outermost layer of the all-solid-state secondary battery 1 .
The negative electrode current collector 21 is preferably made of a material that does not react with lithium, that is, that does not form an alloy or compound with lithium.
In addition to stainless steel, examples of materials that can be used to form the negative electrode current collector 21 include copper (Cu), titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni).
The negative electrode current collector 21 may be made of any one of these metals, or may be made of an alloy or clad material of two or more metals.

The negative electrode active material layer 22 contains, for example, at least one of a negative electrode active material that forms an alloy with lithium and a negative electrode active material that forms a compound with lithium. By containing such a negative electrode active material, the negative electrode active material layer 22 may be configured to allow metallic lithium to be deposited on one or both surfaces of the negative electrode active material layer 22, as described below.

Examples of the negative electrode active material include amorphous carbon, gold, platinum, palladium (Pd), silicon (Si), silver, aluminum (Al), bismuth (Bi), tin, antimony, and zinc.
Examples of the amorphous carbon include carbon black such as acetylene black, furnace black, and ketjen black, and graphene.

The shape of the negative electrode active material is not particularly limited, and may be granular or may be a uniform layer such as a plating layer.
In the former case, lithium ions pass through the gaps between the granular negative electrode active material particles, forming a metal layer mainly composed of lithium between the negative electrode active material layer 22 and the negative electrode current collector 21, and some of the lithium exists in the negative electrode active material layer 22 by forming an alloy with the metal elements in the negative electrode active material.
On the other hand, in the latter case, the metal layer is deposited between the negative electrode active material layer 22 and the solid electrolyte layer 30 .

Among the above, it is preferable that the negative electrode active material layer 22 contains, as amorphous carbon, a mixture of low-specific surface area amorphous carbon having a specific surface area of 100 m ² /g or less as measured by nitrogen gas adsorption, and high-specific surface area amorphous carbon having a specific surface area of 300 m ² /g or more as measured by nitrogen gas adsorption.

The negative electrode active material layer 22 may contain only one of these negative electrode active materials, or may contain two or more negative electrode active materials. For example, the negative electrode active material layer 22 may contain only amorphous carbon as the negative electrode active material, or may contain one or more selected from the group consisting of gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, antimony, and zinc. The negative electrode active material layer 22 may also contain a mixture of amorphous carbon and one or more selected from the group consisting of gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, antimony, and zinc.

The mixing ratio (mass ratio) of the mixture of amorphous carbon and the aforementioned metals such as gold is preferably approximately 1:1 to 1:3. By using these substances as the negative electrode active material, the characteristics of the all-solid-state secondary battery 1 are further improved.

When amorphous carbon and one or more elements selected from the group consisting of gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, antimony, and zinc are used as the negative electrode active material, it is preferable that the particle size of these negative electrode active materials be 4 μm or less. In this case, the characteristics of the all-solid-state secondary battery 1 are further improved.

Furthermore, when the negative electrode active material is a material capable of forming an alloy with lithium, such as one or more selected from the group consisting of gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, antimony, and zinc, the negative electrode active material layer 22 may be a layer made of one of these metals. For example, this metal layer may be a plating layer.

The negative electrode active material layer 22 may further contain a binder, if necessary. Examples of binders include styrene butadiene rubber (SBR), polytetrafluoroethylene (PET), polyvinylidene fluoride, and polyethylene oxide. The binder may be composed of one or more of these. By including a binder in the negative electrode active material layer 22 in this manner, it is possible to prevent the negative electrode active material from escaping, particularly when the negative electrode active material is granular. The content of the binder in the negative electrode active material layer 22 is, for example, 0.3% by mass or more and 20.0% by mass or less, preferably 1.0% by mass or more and 15.0% by mass or less, and more preferably 3.0% by mass or more and 15.0% by mass or less, relative to the total mass of the negative electrode active material layer 22.

The negative electrode active material layer 22 may also contain additives used in conventional all-solid-state secondary batteries 1, such as fillers, dispersants, and ion-conducting materials, as appropriate.

When the negative electrode active material layer 22 is granular, the thickness of the negative electrode active material layer 22 is not particularly limited, but is, for example, 1.0 μm to 20.0 μm, preferably 1.0 μm to 10 μm. By setting the thickness in this range, the resistance value of the negative electrode active material layer 22 can be sufficiently reduced while fully obtaining the above-mentioned effects of the negative electrode active material layer 22, and the characteristics of the all-solid-state secondary battery 1 can be sufficiently improved.
On the other hand, when the anode active material layer 22 forms a uniform layer, the thickness of the anode active material layer 22 is, for example, 1.0 nm to 100.0 nm, inclusive. In this case, the upper limit of the thickness of the anode active material layer 22 is preferably 95 nm, more preferably 90 nm, and even more preferably 50 nm.

The present invention is not limited to the above-described embodiment, and the negative electrode active material layer 22 may have any configuration that can be used as the negative electrode active material layer 22 of the all-solid-state secondary battery 1.
For example, the negative electrode active material layer 22 may be a layer containing the above-mentioned negative electrode active material, a solid electrolyte, and a negative electrode layer conductive additive.

In this case, for example, a metal active material or a carbon active material can be used as the negative electrode active material. Examples of the metal active material include metals such as lithium (Li), indium (In), aluminum (Al), tin (Sn), and silicon (Si), as well as alloys thereof. Examples of the carbon active material include artificial graphite, graphite carbon fiber, resin-baked carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-baked carbon, polyacene, pitch-based carbon fiber, vapor-grown carbon fiber, natural graphite, and non-graphitizable carbon. These negative electrode active materials may be used alone or in combination of two or more.

The conductive additive for the negative electrode layer and the solid electrolyte can be the same compounds as the conductive agent and solid electrolyte contained in the positive electrode active material layer 12. Therefore, a description of their composition will be omitted here.

(1-3. Solid electrolyte layer)
The solid electrolyte layer 30 is a layer formed between the positive electrode layer 10 and the negative electrode layer 20, and contains a solid electrolyte.
In this embodiment, the solid electrolyte layer 30 is laminated between the positive electrode layer 10 and the negative electrode layer 20 .
The thickness of the solid electrolyte layer 30 in the completed battery state may be 5 μm to 100 μm, preferably 8 μm to 50 μm, and more preferably 10 μm to 30 μm.

The solid electrolyte is, for example, in powder form, and is made of, for example, a sulfide-based solid electrolyte material.
Examples of the sulfide-based solid electrolyte material include Li ₂ S—P ₂ S ₅ , Li ₂ S—P ₂ S ₅ —LiX (X is a halogen element, for example, I, Br, or Cl), Li ₂ S—P ₂ S ₅ —Li ₂ O, Li ₂ S—P ₂ S ₅ —Li ₂ O—LiI, Li ₂ S—SiS ₂ , Li 2 _S —SiS ₂ —LiI, Li ₂ S—SiS ₂ —LiBr, Li ₂ S—SiS ₂ —LiCl, Li ₂ S—SiS ₂ —B ₂ S ₃ —LiI, Li ₂ S—SiS ₂ —P ₂ S ₅ —LiI, and Li ₂ S—B ₂ S ₃ , Li ₂ S—P ₂ S ₅ -Z _m S _n (m and n are positive numbers, Z is either Ge, Zn or Ga), Li ₂ S—GeS ₂ , Li ₂ S—SiS ₂ —Li ₃ PO ₄ , Li ₂ S—SiS ₂ —Lip _{MO q} (p and q are positive numbers, M is either P, Si, Ge, B, Al, Ga or In), etc. can be mentioned. Here, the sulfide-based solid electrolyte material is produced by treating a starting material (e.g., Li ₂ S, P ₂ S ₅ , etc.) by a melt quenching method, a mechanical milling method, etc. Furthermore, a heat treatment may be further performed after these treatments. The solid electrolyte may be amorphous, crystalline, or a mixture of both.

Furthermore, among the above sulfide-based solid electrolyte materials, it is preferable to use a material containing sulfur and one or more elements selected from the group consisting of silicon, phosphorus, and boron as the solid electrolyte. This improves the lithium conductivity of the solid electrolyte layer 30 and improves the battery characteristics of the all-solid-state secondary battery 1. In particular, it is preferable to use a solid electrolyte containing at least sulfur (S), phosphorus (P), and lithium (Li) as constituent elements, and it is particularly preferable to use _a solid electrolyte containing _Li2S - _P2S5 .

Here, when a sulfide-based solid electrolyte material containing Li ₂ S-P ₂ S ₅ is used to form the solid electrolyte, the mixing molar ratio of Li ₂ S to P ₂ S ₅ may be selected, for example, in the range of Li ₂ S:P ₂ S ₅ = 50:50 to 90:10. The solid electrolyte layer 30 may further contain a binder. Examples of binders contained in the solid electrolyte layer 30 include styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, and polyacrylic acid. The binder contained in the solid electrolyte layer 30 may be the same type as the binder in the positive electrode active material layer 12 and the negative electrode active material layer 22, or may be a different type.

(1-4. Insulating layer)
The insulating layer 13 is disposed in close contact with the side end surface S of the positive electrode layer 10, which is the first electrode layer in this embodiment, so as to cover the entire side end surface S of the positive electrode layer 10. The insulating layer 13 may be formed using an insulating layer material 13A that is an electrically non-conductive material. Examples of materials constituting the insulating layer material 13A include resin films containing resins such as polypropylene, polyethylene, or copolymers thereof. Such resin films can be adhered to the positive electrode layer 10 by pressure molding, such as isostatic pressing, to prevent peeling. It is even more preferable if the insulating layer material 13A is a resin containing an insulating filler or the like. The inclusion of an insulating filler in the insulating layer material 13A improves adhesion between the insulating layer materials 13A, thereby improving the strength of the insulating layer 13 when forming the insulating layer 13 using the insulating layer material 13A and during use. Furthermore, by including an insulating filler in the insulating layer material 13A together with the resin, fine irregularities can be formed by mixing the insulating filler into the surface of the insulating layer 13. This irregular shape on the surface of the insulating layer 13 can also make it more difficult for the solid electrolyte layer 30 to peel off from the insulating layer 13 when the solid electrolyte layer 30 is laminated. The insulating filler can be in various shapes, such as particulate, fibrous, needle-like, or plate-like. Among these, it is preferable to use a fibrous or nonwoven insulating filler, as this particularly produces the above-mentioned effect.
From the viewpoint of suppressing an increase in costs, it is preferable to use, as the insulating filler, one or more substances selected from the group consisting of, for example, fibrous resin, resin nonwoven fabric, alumina, magnesium oxide, silica, boehmite, barium titanate, barium carbonate, yttria, and manganese oxide.

(1-5. Current collecting part)
The positive electrode current collector 11 and the negative electrode current collector 21 are connected to external wiring via current collectors. The current collectors include, for example, a positive electrode current collector 111 that electrically connects the positive electrode current collector 11 to external wiring, and a negative electrode current collector 211 that connects the negative electrode current collector 21 to external wiring, as shown in Figures 2 and 3 .
The positive electrode current collector 111 is, for example, a foil made of the same material as the positive electrode current collector 11. The positive electrode current collector 111 is formed integrally with the positive electrode current collector 11 so as to extend from the positive electrode current collector 11. In each drawing, an imaginary line is drawn between the positive electrode current collector 11 and the positive electrode current collector 111.
In this embodiment, a positive electrode current collecting portion 111 that connects the positive electrode current collector 11 included in the positive electrode layer 10, which is the first electrode layer, to an external wiring is configured to protrude outward through the insulating layer 13. For convenience of explanation, in Figures 1 to 10, the direction in which this positive electrode current collecting portion 111 protrudes is referred to as the protruding direction, and the direction perpendicular to the protruding direction in a plan view of each layer that constitutes the all-solid-state secondary battery 1 when viewed from the stacking direction is referred to as the width direction.
The negative electrode current collector 211 is, for example, a foil made of the same material as the negative electrode current collector 21. The negative electrode current collector 211 is formed integrally with the negative electrode current collector 21 so as to extend from the negative electrode current collector 21. In FIG. 3 , an imaginary line is drawn between the negative electrode current collector 21 and the negative electrode current collector 211.

More specifically, when the all-solid-state secondary battery 1 is in use, the positive electrode current collector 11 is connected to wiring via a positive electrode current collecting part 111 attached to one end of the positive electrode current collector 11 and a terminal (current collecting tab) not shown.
Similarly, when the all-solid-state secondary battery 1 is in use, the negative electrode current collector 21 is connected to wiring via a negative electrode current collecting part 211 attached to one end of the negative electrode current collector 21 and a terminal (current collecting tab) not shown.

The thickness of the positive electrode current collector 111 and the negative electrode current collector 211 can be changed as appropriate depending on the thickness of the positive electrode current collector 11 or the negative electrode current collector 21 formed integrally therewith, but is, for example, 1 μm or more and 50 μm or less, more preferably 5 μm or more and 30 μm or less.

<2. Method for manufacturing all-solid-state secondary battery>
Next, an example of a method and procedure for manufacturing the all-solid-state secondary battery 1 according to this embodiment will be described with reference to FIGS.

The method for manufacturing the all-solid-state secondary battery 1 according to this embodiment includes the following steps.
(2-1. Preparation of Positive Electrode Layer)
Materials constituting the positive electrode active material layer 12 (such as the positive electrode active material and binder) are added to a non-polar solvent to prepare a positive electrode active material layer coating liquid (this positive electrode active material layer coating liquid may be in the form of a slurry or a paste. The same applies to coating liquids used to form other layers). Next, as shown in FIG. 4( a), the obtained positive electrode active material layer coating liquid is applied to both surfaces of the positive electrode current collector 11 and dried, and then the positive electrode current collector 11 and the applied positive electrode active material layer 12 are punched into a rectangular plate using a Thomson blade or the like. The laminate obtained in this manner is called a positive electrode structure. This positive electrode structure is placed on an aluminum plate on which a PET film is laid, and a substantially rectangular ring-shaped insulating layer material 13A that forms the insulating layer 13 is placed around the positive electrode structure. A PET film is then placed on top of the entire structure, and the resulting structure is then laminated and packed and subjected to a pressure treatment using isostatic pressure (isostatic pressing), thereby applying pressure from the stacking direction to produce the pre-cut positive electrode layer 10A shown in FIG. 4( b).

(2-2. Preparation of negative electrode layer)
A coating solution for the negative electrode active material layer 22 is prepared by adding materials (such as a negative electrode active material and a binder) to a polar or nonpolar solvent. Next, as shown in FIG. 5A, the coating solution for the negative electrode active material layer 22 is applied to a negative electrode current collector 21 and dried. The coating solution is punched into a rectangular plate shape using a Thomson blade or the like to prepare the negative electrode layer 20.

(2-3. Preparation of solid electrolyte layer)
The solid electrolyte layer 30 can be made of a solid electrolyte formed from a sulfide-based solid electrolyte material. The method for making the solid electrolyte is as follows.

First, the starting material is treated by melt quenching or mechanical milling.
For example, when using the melt quenching method, a sulfide-based solid electrolyte material can be produced by mixing predetermined amounts of starting materials (e.g., Li ₂ S, P ₂ S ₅ , etc.), forming the pellets, reacting them in a vacuum at a predetermined reaction temperature, and then quenching them. The reaction temperature for the Li ₂ S and P ₂ S ₅ mixture is preferably 400°C to 1000°C, more preferably 800°C to 900°C. The reaction time is preferably 0.1 hours to 12 hours, more preferably 1 hour to 12 hours. The quenching temperature of the reaction product is typically 10°C or lower, preferably 0°C or lower, and the quenching rate is typically about 1°C/sec to 10,000°C/sec, preferably about 1°C/sec to 1000°C/sec.

Furthermore, when mechanical milling is used, a sulfide-based solid electrolyte material can be produced by stirring and reacting starting materials (e.g., _Li2S , _P2S5 , etc.) using a ball mill or the _like . The stirring speed and stirring time in mechanical milling are not particularly limited, but the faster the stirring speed, the faster the production rate of the sulfide-based solid electrolyte material can be, and the longer the stirring time, the higher the conversion rate of the raw materials to the sulfide-based solid electrolyte material can be.

The mixed raw materials obtained by melt quenching or mechanical milling are then heat-treated at a predetermined temperature and pulverized to produce particulate solid electrolytes. If the solid electrolyte has a glass transition point, heat treatment may cause it to change from amorphous to crystalline.

Next, a solid electrolyte layer coating liquid is prepared containing the solid electrolyte obtained by the above method, other additives such as a binder, and a dispersion medium. A general-purpose non-polar solvent such as xylene or diethylbenzene can be used as the dispersion medium. Alternatively, a polar solvent that is relatively unreactive with the solid electrolyte can be used. The concentrations of the solid electrolyte and other additives can be adjusted as appropriate depending on the composition of the solid electrolyte layer 30 to be formed and the viscosity of the liquid composition.

The liquid solid electrolyte composition described above is applied with a blade onto a PET film whose surface has been treated for release, and after drying, a solid electrolyte sheet is produced in which a solid electrolyte layer 30 is formed on the PET film.

(2-4. Lamination process)
As shown in Fig. 5(a), a solid electrolyte sheet punched to have the same shape as or a larger shape than the anode layer 20 is laminated on one side of the anode layer 20 prepared as described above, and these are isostatically pressed to closely adhere and integrate the anode layer 20 and the solid electrolyte layer 30, as shown in Fig. 5(b). If the solid electrolyte layer 30 has a larger shape than the anode layer 20, the portion of the solid electrolyte layer 30 that protrudes outward when laminated on the anode layer 20 can be removed. This laminate will be referred to as an electrolyte anode structure 20A.
Next, as shown in Fig. 6(a), the above-mentioned pre-cut positive electrode layer 10A is laminated so as to be sandwiched between two electrolyte negative electrode structures 20A from both sides. At this time, the electrolyte negative electrode structures 20A are laminated so that the solid electrolyte layers 30 of the electrolyte negative electrode structures 20A contact both sides of the positive electrode layer 10, and the whole is laminate-packed and isostatically pressed to produce an untreated all-solid-state secondary battery 1A, which is a laminate as shown in Fig. 6(b).

In this embodiment, in the lamination step described above, the outer edge 1E of the insulating layer 13 is positioned outside the outer edge 2E of the negative electrode layer 20, as shown in FIGS.
The outer edge 1E of the insulating layer 13 may be disposed so as to be shifted outward from the outer edge 2E of the negative electrode layer 20 by, for example, 1 μm to 2 mm. The range of this shift is preferably 0.05 mm to 1 mm, and more preferably 0.1 mm to 0.5 mm.

More specifically, as shown in FIGS. 2, 3, and 6(b), in this embodiment, the negative electrode layer 20 is laminated so that at least a part of the outer edge 2E is located inside the outer edge 1E of the insulating layer 13 provided around the positive electrode layer 10, and is preferably located on the insulating layer 13.
With this configuration, for example, in the all-solid-state secondary battery 1 shown in FIG. 2 , even if the anode layer 20 is pressed against the cathode layer 10 by external pressure and deformed, it is possible to suppress a physical short circuit between the cathode layer 10 and the anode layer 20.
In the all-solid-state secondary battery 1 shown in FIG. 2 , a physical short circuit is particularly likely to occur between the outer edge 2E of the anode layer 20 and the cathode layer 10 via the cathode current collector 111. Therefore, as shown in FIGS. 2 , 3 , and 6 ( b ), a portion of the outer edge 1E of the insulating layer 13 covering the side end surface S of the cathode layer 10 may be located outside the outer edge 2E of the anode layer 20, at least on the side where the cathode current collector 111 protrudes. This prevents a short circuit between the cathode layer 10 and the anode layer 20 due to contact between the outer edge 2E of the anode current collector 21 or the anode active material layer 22 and the cathode current collector 111. One side or the entire periphery of the outer edge 1E of the insulating layer 13 may be located outside the outer edge 2E of the anode layer 20.

As shown in Figures 2, 3, and 6(b), the outer edge 1E of the insulating layer 13 refers to the outermost edge (outer edge) of the side end surface of the insulating layer 13 in the direction perpendicular to the stacking direction, and more specifically, refers to the outer edge of the insulating layer 13 from which the positive electrode current collector 111 protrudes. Furthermore, the outer edge 2E of the negative electrode layer 20 refers to the outermost edge (outer edge) of the side end surface of the negative electrode layer 20 in the direction perpendicular to the stacking direction, and in this embodiment, for example, refers to the outermost edge of the side end surface of the negative electrode current collector 21 or the negative electrode active material layer 22 in the direction perpendicular to the stacking direction.

(2-5. Isostatic pressing)
The above-mentioned pressure treatment (pressing step) using isostatic pressing will be described below.
The isostatic pressing is performed by placing a support plate 4 such as a stainless steel plate on at least one surface of the laminate. This isostatic pressing allows pressure treatment to be applied from the stacking direction to each laminate that forms the pre-cut positive electrode layer 10A, the electrolyte negative electrode structure 20A, or the untreated all-solid-state secondary battery 1A.
Examples of pressure media for isostatic pressing include liquids such as water and oil, powder, etc. It is more preferable to use a liquid as the pressure media.
The pressure in the isostatic pressing is not particularly limited, but can be, for example, 10 to 1000 MPa, preferably 100 to 500 MPa. The pressing time is also not particularly limited, but can be, for example, 1 to 120 minutes, preferably 5 to 30 minutes. Furthermore, the temperature of the pressure medium during pressing is also not particularly limited, but can be, for example, 20 to 200°C, preferably 50 to 100°C.
During isostatic pressing, the stack constituting the all-solid-state secondary battery 1 is preferably laminated together with the support plate 4 with a resin film or the like to be isolated from the external atmosphere.
Compared to other pressing methods such as roll pressing, isostatic pressing is advantageous from the viewpoint of suppressing cracks in the layers constituting the all-solid-state secondary battery 1 and preventing warping of the all-solid-state secondary battery 1.

(2-6. Features of the manufacturing method of the all-solid-state secondary battery according to the present invention)
A feature of the manufacturing method of the all-solid-state secondary battery 1 according to the present invention is that, at least during the above-described pressurizing step, the entire current collecting part (111 or 211) is covered from both sides with the current collecting part protection member 14 that encases and protects the protruding part of the current collecting part (111 or 211).
In this embodiment, the protruding portion of the positive electrode current collector 111 attached to the positive electrode current collector 11 of the positive electrode layer 10, which is the first electrode layer sandwiched in the center, is covered with the current collector protection member 14.
The shape of the current collector protection member 14 is not particularly limited as long as it has a surface larger than the area of the positive current collector 111 so that it can cover the entire positive current collector 111 without any gaps at least while isostatic pressure is being applied. From the viewpoint of ease of manufacture, the current collector protection member 14 is preferably a rectangular plate-shaped excess insulating layer 14 that is formed integrally with the insulating layer 13, has the same width and thickness as the width of the insulating layer 13, and protrudes from the insulating layer 13 in the same direction as the positive current collector 111, more than the positive current collector 111, as shown in FIG. 7 . Note that an imaginary line is drawn between the insulating layer 13 and the excess insulating layer 14 in each drawing for ease of understanding.
In this embodiment, as shown in FIG. 8, the excess insulating layer 14 is formed by a collector protection member material 14A that is integrally formed on the end of a ring-shaped insulating layer material 13A.
In this embodiment, as shown in Fig. 8, two sheets of excess insulating layer material 13B each including an insulating layer material 13A and a current collector protection member material 14A are prepared, and these two sheets of excess insulating layer material 13B are arranged so that both surfaces of the entire positive current collector 111 are sandwiched between the current collector protection member materials 14A, and then pressure treatment is performed using isostatic pressure, so that the positive current collector 111 is covered with excess insulating layer 14, as shown in Fig. 7. Note that Fig. 8 is a schematic diagram showing a side end surface of excess insulating layer material 13B.
The collector protection member material 14A may be formed independently of the insulating layer material 13A, but from the viewpoint of ease of manufacturing, it is preferable that it be formed integrally with the insulating layer material 13A at the end of the insulating layer material 13A, as shown in Figures 7 and 8.
The thickness of the current collector protection member 14 is, for example, preferably 10 μm to 500 μm, more preferably 50 μm to 300 μm, and particularly preferably 80 μm to 200 μm, for one sheet of the current collector protection member material 14A laminated on one side of the positive current collector 111. This preferred thickness varies depending on the thickness of the positive electrode layer 10, and a thickness close to the thickness of the positive electrode active material layer 12 is suitable. The total thickness of the entire current collector protection member 14 in a state in which the current collector protection member material 14A is laminated on both sides of the positive current collector 111 is preferably 20 μm to 1000 μm, more preferably 100 μm to 600 μm, and particularly preferably 160 μm to 400 μm. As mentioned above, this preferable total thickness also varies depending on the thickness of the positive electrode layer 10, and a thickness close to the total thickness of the two positive electrode active material layers 12 formed on both sides of the positive electrode current collector 11 is suitable.
In this way, by making the thickness of the collector protection member 14 correspond to the thickness of the positive electrode active material layer 12, the difference in level between the collector protection member 14 covering the positive electrode collector 111 and the positive electrode layer 10 is reduced, and cracks or cuts in the positive electrode collector 111 can be more effectively prevented during pressure treatment.
The thicknesses of the two current collector protection member materials 14A, one on each side of the positive current collector 111, may be the same as or different from each other. The thicknesses of the insulating layer 13 and the current collector protection member 14 may be the same as or different from each other.
It is preferable that the collector protection member 14 be made of the same material as the insulating layer 13, as this simplifies the manufacturing process, but the material is not limited to this.

The timing for covering the positive electrode current collector 111 with the current collector protection member 14 is not particularly limited, as long as the positive electrode current collector 111 is covered with the current collector protection member 14 during isostatic pressing. For example, if the current collector protection member material 14A that forms the current collector protection member 14 is not formed integrally with the insulating layer material 13A, the positive electrode current collector 111 may be covered with the current collector protection member 14 before the positive electrode active material layer 12 is laminated on the positive electrode current collector 11.

As described above, isostatic pressure is applied while the positive electrode current collector 111 is covered with the current collector protection member 14, and all layers constituting the all solid state secondary battery 1 are adhered together to form an untreated all solid state secondary battery 1A. Thereafter, as shown in FIG. 9 , a removal step is performed to remove the excess insulating layer 14, which is the current collector protection member 14, from the untreated all solid state secondary battery 1A, thereby completing the all solid state secondary battery 1. Note that in FIG. 9 , FIG. 9( a) shows the untreated all solid state secondary battery 1A, and FIG. 9( b) shows the all solid state secondary battery 1 after the excess insulating layer 14 has been removed. In FIG. 9 , the insulating layer 13 is formed of two sheets of insulating layer material 13A, but these insulating layer materials 13A may be heated and integrated, for example, during initial charging.
The excess insulating layer 14 is cut off by manually pulling it in a direction perpendicular to the stacking direction of the layers constituting the all-solid-state secondary battery 1 so that the positive electrode current collector 111 is exposed. At this time, for example, if a notch 13C is made in the thickness direction between the insulating layer 13 and the excess insulating layer 14, the excess insulating layer 14 can be easily removed. This notch 13C may be made from the positive electrode current collector 111 side toward the outside in the stacking direction, or from the outside in the stacking direction toward the positive electrode current collector 111 side. Furthermore, the notch 13C may be made across the entire width of the excess insulating layer 14, or may be made in the form of a dashed line, for example. Alternatively, the notch 13C may be made only within a predetermined length from one or both ends of the width direction of the excess insulating layer 14 to serve as a trigger for starting the cutting.
The depth of the notch 13C in the thickness direction is preferably in the range of 5% to 99% of the thickness of the insulating layer 13 in the stacking direction of the all-solid-state secondary battery 1. If the notch 13C is formed to a depth of 5% or more of the thickness of the insulating layer, it is preferable because it is easy to cut away excess insulating layer 14. If the notch 13C is formed to a depth of 99% or less of the thickness of the insulating layer 13, it is preferable because it is possible to prevent cracks from occurring in or cut off the positive electrode current collecting portion 111 during the application of isostatic pressure.
The method for removing the excess insulating layer 14 is not limited to the above-described method, and for example, it may be removed by a tool or machine instead of by hand.
3. Characteristics of the all-solid-state secondary battery manufactured by the manufacturing method described in this embodiment

In an all-solid-state secondary battery 1 in which excess insulating layer 14 formed integrally with insulating layer 13 has been removed by manually pulling and cutting it from the insulating layer 13, a different surface portion 13D with a different surface roughness from the other side end surfaces of insulating layer 13 is formed on the side end surface of insulating layer 13 from which the positive electrode current collector 111 protrudes, as shown in Figure 10.

This different surface portion 13D is, for example, an irregular cross-section formed when excess insulating layer 14 is manually pulled and removed from insulating layer 13, resulting in a roughened portion 13D with a rougher surface than the other side end surfaces of insulating layer 13. In this embodiment, excess insulating layer 14 is pulled and torn off, resulting in roughened portion 13D in a burr-like state where the resin has torn at the boundary between excess insulating layer 14 and insulating layer 13. When cut 13C is formed between insulating layer 13 and excess insulating layer 14 as in this embodiment, roughened portion 13D is formed in the area excluding the area where cut 13C was formed, as shown in FIG. 10. FIG. 10 is a schematic diagram of the all-solid-state secondary battery 1 (shown in FIG. 9( b)) after the excess insulating layer 14 has been removed, viewed from the side where the positive electrode current collector 111 protrudes. It shows the insulating layer 13 and positive electrode current collector 111 of the all-solid-state secondary battery in which a cut 13C is formed from the positive electrode current collector 111 outward to about halfway through the thickness of the insulating layer 13. As described above, the location of the different surface portion 13D, such as the roughened portion 13D, varies depending on the location of the cut 13C. The different surface portion 13D may be formed over the entire space between the insulating layer 13 and the excess insulating layer 14, or may be formed only partially. The thickness of the roughened portion 13D in the stacking direction is preferably 1% to 95% of the thickness of the insulating layer, excluding the cut.

4. Effects of the all-solid-state secondary battery and the method for manufacturing the all-solid-state secondary battery according to the present embodiment
Since the all-solid-state secondary battery 1 is formed by solidifying powder to form each layer, if it is manufactured without pressure treatment such as isostatic pressing, there is a risk that small gaps between the powder particles may cause depressions or irregularities on the surface of each layer. According to the manufacturing method of the all-solid-state secondary battery 1 according to this embodiment, the entire battery is molded by isostatic pressing, so that irregularities on the surface of the all-solid-state secondary battery 1 can be minimized. As a result, in a stacked all-solid-state secondary battery in which a plurality of these all-solid-state secondary batteries 1 are stacked, it is possible to avoid current concentration only on the protruding parts of the all-solid-state secondary battery 1.
If it is possible to prevent current from concentrating on only a portion of the surface of the all-solid-state secondary battery 1 in this way, the entire positive electrode layer 10 and the negative electrode layer 20 will contribute to charging and discharging, thereby improving the charging and discharging capacity of the laminated all-solid-state secondary battery.
Furthermore, since the positive electrode layer 10 and the negative electrode layer 20 contribute uniformly to charge and discharge, it is possible to prevent, for example, metallic lithium and the like from being concentrated and deposited in only certain areas, and as a result, it is also possible to prevent short circuits caused by the deposition of metallic lithium.
Furthermore, during isostatic pressing, the entire surface of the positive electrode current collector 111 is covered on both sides by the current collector protection member 14, which prevents cracks from occurring in the positive electrode current collector 111 and prevents the positive electrode current collector 111 from being cut.
As a result, it is possible to manufacture a highly reliable all-solid-state secondary battery 1 and a laminated all-solid-state secondary battery without the need to reconnect the positive electrode current collector 111 to the positive electrode current collector 11 .

<5. Manufacturing method of laminated all-solid-state secondary battery>
A stacked all-solid-state secondary battery is obtained by stacking a plurality of all-solid-state secondary batteries 1 manufactured as described above. When stacking, the negative electrode current collector 21 of one all-solid-state secondary battery 1 is arranged to face the negative electrode current collector 21 of another all-solid-state secondary battery 1 via the insulating layer 13. This makes it possible to manufacture a stacked all-solid-state secondary battery that maintains sufficient cycle characteristics and is less likely to cause short circuits even when a relatively large number of all-solid-state secondary batteries 1, for example, three or four or more, are stacked.

6. Charging and discharging of the all-solid-state secondary battery according to this embodiment
Charging and discharging of the all-solid-state secondary battery 1 according to this embodiment will be described below.
In the all-solid-state secondary battery 1 according to this embodiment, during the initial stage of charging, the negative electrode active material in the negative electrode active material layer 22, which forms an alloy or compound with lithium, forms an alloy or compound with lithium ions, thereby occluding lithium in the negative electrode active material layer 22. After the charge capacity of the negative electrode active material layer 22 is exceeded, metallic lithium is precipitated on one or both surfaces of the negative electrode active material layer 22, forming a metallic lithium layer. Because the metallic lithium is formed by diffusing through the negative electrode active material capable of forming an alloy or compound, it is not dendritic (dendrite-like) but is uniformly formed mainly between the negative electrode active material layer 22 and the negative electrode current collector 21. During discharge, metallic lithium ionizes from the negative electrode active material layer 22 and the metallic lithium layer and migrates toward the positive electrode active material layer 12. Consequently, metallic lithium itself can be used as the negative electrode active material, thereby improving energy density.

Furthermore, when the metallic lithium layer is formed between the anode active material layer 22 and the anode current collector 21, i.e., inside the anode layer 20, the anode active material layer 22 covers the metallic lithium layer. As a result, the anode active material layer 22 functions as a protective layer for the metal layer. This suppresses short circuits and capacity reduction in the all-solid-state secondary battery 1, and ultimately improves the characteristics of the all-solid-state secondary battery 1.

An example of a method for enabling the deposition of metallic lithium in the anode active material layer 22 is to make the charge capacity of the cathode active material layer 12 larger than the charge capacity of the anode active material layer 22. Specifically, the ratio (capacity ratio) of the charge capacity of the cathode active material layer 12 to the charge capacity of the anode active material layer 22 satisfies the requirement of the following mathematical formula (1):
0.002<b/a<0.5 (1)
a: charging capacity (mAh) of the positive electrode active material layer 12
b: charging capacity of the negative electrode active material layer 22 (mAh)

When the capacity ratio represented by the above formula (1) is greater than 0.002, regardless of the configuration of the anode active material layer 22, the anode active material layer 22 can sufficiently mediate the precipitation of metallic lithium from lithium ions, making it easier to properly form a metallic lithium layer. Furthermore, if the metallic lithium layer is formed between the anode active material layer 22 and the anode current collector 21, this is preferable because the anode active material layer 22 can sufficiently function as a protective layer. Therefore, the above capacity ratio is more preferably 0.01 or greater, and even more preferably 0.03 or greater.

Furthermore, when the capacity ratio is less than 0.5, the negative electrode active material layer 22 does not store a large portion of the lithium during charging, making it easier to form a uniform metallic lithium layer regardless of the configuration of the negative electrode active material layer 22. The capacity ratio is more preferably 0.2 or less, and even more preferably 0.1 or less.

It is more preferable that the capacity ratio be greater than 0.01. If the capacity ratio is 0.01 or less, the characteristics of the all-solid-state secondary battery 1 may deteriorate. One reason for this is that the anode active material layer 22 may no longer function adequately as a protective layer. For example, if the thickness of the anode active material layer 22 is very thin, the capacity ratio may be 0.01 or less. In this case, repeated charge and discharge may cause the anode active material layer 22 to collapse, leading to the precipitation and growth of dendrites. This may result in a deterioration in the characteristics of the all-solid-state secondary battery 1. It is also preferable that the capacity ratio be less than 0.5. If the capacity ratio is 0.5 or greater, the amount of lithium precipitation in the anode layer 20 may decrease, potentially reducing the battery capacity. For the same reason, it is more preferable that the capacity ratio be less than 0.25. A capacity ratio of less than 0.25 can also further improve the battery's output characteristics.

The charge capacity of the positive electrode active material layer 12 is calculated by multiplying the specific charge capacity (mAh/g) of the positive electrode active material by the mass of the positive electrode active material in the positive electrode active material layer 12. When multiple types of positive electrode active materials are used, the specific charge capacity x mass value is calculated for each positive electrode active material, and the sum of these values is taken as the charge capacity of the positive electrode active material layer 12. The charge capacity of the negative electrode active material layer 22 is calculated in a similar manner. That is, the charge capacity of the negative electrode active material layer 22 is calculated by multiplying the specific charge capacity (mAh/g) of the negative electrode active material by the mass of the negative electrode active material in the negative electrode active material layer 22. When multiple types of negative electrode active materials are used, the specific charge capacity x mass value is calculated for each negative electrode active material, and the sum of these values is taken as the capacity of the negative electrode active material layer 22. The specific charge capacities of the positive electrode active material and the negative electrode active material are estimated capacities using an all-solid-state half cell using lithium metal as the counter electrode. In practice, the charge capacities of the positive electrode active material layer 12 and the negative electrode active material layer 22 are directly measured using an all-solid-state half cell.

Specific methods for directly measuring the charge capacity include the following. First, the charge capacity of the positive electrode active material layer 12 is measured by fabricating an all-solid-state half-cell using the positive electrode active material layer 12 as the working electrode and Li as the counter electrode, and performing CC-CV charging from the OCV (open circuit voltage) to the upper charge voltage. The upper charge voltage is defined in JIS C 8712:2015, and is 4.25 V for a positive electrode active material layer 12 that uses a lithium cobalt oxide-based positive electrode active material. For a positive electrode active material layer 12 that uses other positive electrode active materials, it refers to the voltage obtained by applying the provisions of JIS C 8712:2015, A.3.2.3 (Safety requirements when applying different upper charge voltages). The charge capacity of the negative electrode active material layer 22 is measured by preparing an all-solid-state half cell using the negative electrode active material layer 22 as the working electrode and Li as the counter electrode, and performing CC-CV charging from the OCV (open circuit voltage) to 0.01 V.

The charge capacity measured in this manner is divided by the mass of each active material to calculate the specific charge capacity. The charge capacity of the positive electrode active material layer 12 may be the initial charge capacity measured during the first charge cycle.

In an embodiment of the present invention, the charge capacity of the positive electrode active material layer 12 is set to be excessive relative to the charge capacity of the negative electrode active material layer 22. As described below, in this embodiment, the all-solid-state secondary battery 1 is charged beyond the charge capacity of the negative electrode active material layer 22. That is, the negative electrode active material layer 22 is overcharged. At the beginning of charging, lithium is absorbed into the negative electrode active material layer 22. That is, the negative electrode active material forms an alloy or compound with lithium ions that have migrated from the positive electrode layer 10. When charging is performed beyond the capacity of the negative electrode active material layer 22, lithium precipitates on the back side of the negative electrode active material layer 22, i.e., between the negative electrode current collector 21 and the negative electrode active material layer 22, and this lithium forms a metallic lithium layer.

This phenomenon occurs when the negative electrode active material is made of a specific substance, namely, a substance that forms an alloy or compound with lithium. During discharge, lithium in the negative electrode active material layer 22 and the metallic lithium layer ionizes and migrates toward the positive electrode layer 10. Therefore, metallic lithium can be used as the negative electrode active material in the all-solid-state secondary battery 1. More specifically, if the charge capacity of the negative electrode layer 20 (the total charge capacity exerted by the negative electrode active material layer 22 and the metallic lithium layer) is taken as 100%, it is preferable that 80% or more of that charge capacity be exerted by the metallic lithium layer.

Furthermore, the negative electrode active material layer 22 coats the aforementioned metallic lithium layer from the side of the solid electrolyte layer 30, and therefore functions as a protective layer for the metallic lithium layer and can suppress the precipitation and growth of dendrites. This more efficiently suppresses short circuits and capacity reduction in the all-solid-state secondary battery 1, thereby improving the characteristics of the all-solid-state secondary battery 1.

7. Other embodiments of the present invention
The all-solid-state secondary battery according to the present invention is not limited to the one described above.
For example, the first electrode layer may be a negative electrode layer, and the second electrode layer may be a positive electrode layer.

In the above embodiment, an insulating layer is disposed on the side end surface of the first polar layer, but an insulating layer may also be provided on the side end surface of the second polar layer.
The solid electrolyte layer 30 provided between the positive electrode layer and the negative electrode layer may be formed by laminating at least one layer, or may be formed by laminating two, three, four or more layers.
In the above-described embodiment, a roughened portion was described as a specific example of a different surface portion formed after removing excess insulating layer from an insulating layer, but depending on the method for forming the insulating layer and the method for removing excess insulating layer, the different surface portion may be smoother than the other surfaces of the insulating layer.
The present invention is not limited to all-solid-state lithium ion secondary batteries, but can be widely applied to all-solid-state secondary batteries that have a foil-shaped current collecting portion and are manufactured by molding using a pressure treatment such as isostatic pressing.

Example 1
Next, examples of the above-described embodiment will be described. In Example 1, an all-solid-state secondary battery 1 was fabricated by the following steps, and the fabricated all-solid-state secondary battery 1 was evaluated.
[Preparation of Positive Electrode Layer]
A ternary powder of LiNi0.8Co0.15Al0.05O2 (NCA) as the positive electrode active material, an amorphous powder of Li2S-P2S5 (80:20 mol %) as the sulfide-based solid electrolyte, and a vapor-grown carbon fiber powder as the positive electrode layer conductive material (conductive additive) were weighed out in a mass % ratio of 60:35:5 and mixed using a planetary centrifugal mixer.
Next, a dehydrated xylene solution in which SBR was dissolved as a binder was added to this mixed powder so that the SBR content was 5.0% by mass relative to the total mass of the mixed powder, thereby preparing a primary mixed liquid.
A suitable amount of dehydrated xylene was added to this primary mixed liquid to adjust the viscosity, thereby preparing a secondary mixed liquid.
Furthermore, in order to improve the dispersibility of the mixed powder, zirconia balls having a diameter of 5 mm were put into the secondary mixed liquid so that the space, mixed powder, and zirconia balls each occupied 1/3 of the total volume of the kneading vessel.
The tertiary mixed liquid thus produced was placed in a planetary mixer and stirred at 3000 rpm for 3 minutes to produce a coating liquid for a positive electrode active material layer.
Next, a 20 μm thick aluminum foil current collector was prepared as the positive electrode current collector 11. The positive electrode current collector 11 was placed in a desktop screen printer, and the positive electrode active material layer coating liquid was applied to the sheet using a 150 μm thick metal mask. The sheet coated with the positive electrode active material layer coating liquid was then dried on a hot plate at 60°C for 30 minutes, after which the coating was applied to the back side, and the sheet was further dried on a hot plate at 60°C for 30 minutes, followed by vacuum drying at 80°C for 12 hours. This was punched into a rectangular plate using a Thomson blade, forming positive electrode active material layers 12 on both sides of the positive electrode current collector 11. The total thickness of the positive electrode current collector 11 and the positive electrode active material layer 12 after drying was approximately 330 μm.
An insulating resin film was punched using a pinnacle die to produce excess insulating layer material 13B, in which current collector protection member material 14A and insulating layer material 13A were integrated. The insulating layer material 13A contained in the excess insulating layer material 13B was ring-shaped, large enough to surround the positive electrode active material layer 12. The insulating resin film used in this example was manufactured by Dai Nippon Printing Co., Ltd. and contained a resin nonwoven fabric as an insulating filler. Between this excess portion (current collector protection member material 14A) and the ring-shaped portion (insulating layer material 13A), a slit was formed through approximately 70% of the film thickness in the film thickness direction, allowing the excess insulating layer 14 formed from current collector protection member material 14A to be easily cut off after pressure molding. The positive electrode current collector 11 and the positive electrode active material layer 12 were placed on a 3 mm thick aluminum plate (support material) with a release-treated surface and a PET film (hereinafter referred to as a release film) attached thereto, and the insulating layer material 13A described above was placed around the positive electrode active material layer 12, and then covered with a release film and a 0.3 mm thick SUS metal plate (support material) of the same shape as the excess insulating layer material 13B. The resulting product, including the support material, was then vacuum laminated and packed. The product was then submerged in a pressurized medium and subjected to hydrostatic pressure treatment at 490 MPa (a compaction process using an isostatic press), whereby the insulating layer material 13A was integrated with the positive electrode current collector 11 and the positive electrode active material layer 12.
This positive electrode current collector 11 has positive electrode active material layers 12 laminated on both sides thereof, and is provided with insulating layer material 13A covering the side surfaces of these positive electrode active material layers 12 in a direction different from the lamination direction. This will be referred to as the pre-cut positive electrode layer 10A.

[Preparation of negative electrode layer]
A 10 μm thick nickel foil current collector was prepared as the negative electrode current collector 21. Furthermore, as the negative electrode active material, Asahi Carbon Co., Ltd.'s CB1 (nitrogen adsorption specific surface area: approximately 339 m ² /g, DBP oil supply amount: approximately 193 ml/100 g), Asahi Carbon Co., Ltd.'s CB2 (nitrogen adsorption specific surface area: approximately 52 m ² /g, DBP oil supply amount: approximately 193 ml/100 g), and silver particles with a particle size of 3 μm were prepared. The particle size of the silver particles can be measured, for example, using a median diameter (so-called D ₅₀ ) measured using a laser particle size distribution system.
Next, 1.5 g of CB1, 1.5 g of CB2, and 1 g of silver particles were placed in a container, and 4 g of an N-methylpyrrolidone (NMP) solution containing 5% by mass of binder (#9300 manufactured by Kureha Corporation) was added thereto. Next, a total of 30 g of NMP was gradually added to this mixed solution while stirring the mixed solution, thereby preparing a negative electrode active material layer coating liquid. This negative electrode active material layer coating liquid was applied to Ni foil using a blade coater and dried in air at 80 ° C for about 20 minutes to form a negative electrode active material layer 22. The resulting laminate was vacuum dried at 100 ° C for about 12 hours and punched with a pinnacle die. Through the above process, a negative electrode layer 20 was prepared.

[Preparation of solid electrolyte layer coating liquid]
A primary mixed slurry was produced by adding an SBR binder dissolved in dehydrated xylene to an amorphous powder of Li2S-P2S5 (80:20 mol%) as a sulfide-based solid electrolyte, at a concentration of 1% by mass relative to the solid electrolyte. Furthermore, a secondary mixed slurry was produced by adding appropriate amounts of dehydrated xylene and dehydrated diethylbenzene to this primary mixed slurry to adjust the viscosity. Furthermore, to improve the dispersibility of the mixed powder, zirconia balls with a diameter of 5 mm were added to the tertiary mixed slurry so that the space, mixed powder, and zirconia balls each occupied 1/3 of the total volume of the kneading vessel. The resulting tertiary mixed liquid was then added to a planetary centrifugal mixer and stirred at 3000 rpm for 3 minutes to produce a solid electrolyte layer coating liquid.

[Fabrication of solid electrolyte sheet]
The prepared solid electrolyte layer coating solution was applied with a blade onto a PET film whose surface had been treated with a release agent, and then dried on a hot plate at 40°C for 10 minutes. The film was then dried in a vacuum at 40°C for 12 hours to obtain a solid electrolyte sheet. The thickness of the solid electrolyte layer after drying was approximately 42 μm. The dried solid electrolyte sheet was punched out with a Thomson blade to a predetermined size.

[Fabrication of Electrolyte Negative Electrode Structure]
A solid electrolyte sheet was placed on the surface of the anode layer 20 so that the solid electrolyte layer 30 and the anode active material layer 22 were in contact with each other, and then the structure was placed on a 3 mm thick aluminum plate (support material) with a release film attached, and vacuum lamination packing was performed including the support material. The structure was submerged in a pressurizing medium and subjected to hydrostatic pressure treatment (a consolidation process using an isostatic press) at 10 MPa, whereby the solid electrolyte layer on the solid electrolyte sheet was integrated with the anode layer 20. This structure is referred to as electrolyte anode structure 20A.

[Fabrication of all-solid-state secondary battery]
The prepared pre-cut positive electrode layer 10A was sandwiched between two electrolyte negative electrode structures 20A such that the outer edge 2E of the electrolyte negative electrode structure 20A on the side where the positive electrode current collector 111 protruded was positioned between the notch 13C and the side end surface S of the positive electrode layer 10.
This laminate was placed on a 3 mm thick aluminum plate (support material) with a release film attached, further covered with a release film, and further covered with a 0.3 mm thick SUS metal plate (support material) of the same shape as the electrolyte negative electrode structure 20A. The laminate, including the support material, was then vacuum laminated and packed. The laminate was then submerged in a pressurized medium and subjected to hydrostatic pressure treatment (consolidation process using an isostatic press) at 490 MPa. The resulting untreated all-solid-state secondary battery 1A was then removed from the laminate pack, and the excess insulating layer 14 was cut out from the notch 13C formed between the insulating layer 13 and the excess insulating layer 14 to produce a single cell (single battery) of the all-solid-state secondary battery 1.
In the examples, an aluminum plate and a stainless steel metal plate are used as the support material, but the material of these support materials is not particularly limited as long as it has the strength to withstand pressure treatment by isostatic pressure.

[Fabrication of laminated all-solid-state secondary battery]
Four single cells of the fabricated all-solid-state secondary battery 1 were stacked, and then an Al metal tab and a Ni metal tab were welded to the positive electrode current collecting portion 111 and the negative electrode current collecting portion 211, respectively, and the resultant was laminate-packed to obtain a stacked all-solid-state secondary battery.

[Evaluation of all-solid-state secondary batteries]
The laminated all-solid-state secondary battery prepared by the above procedure was sandwiched between two metal plates from the outside in the stacking direction, and a screw with a disc spring inserted was passed through a hole previously drilled in the metal plate. The screw was tightened so that the pressure applied to the battery was 1.0 MPa. The battery characteristics were evaluated using a charge/discharge evaluation device TOSCAT-3100 under the following charge/discharge conditions: the laminated all-solid-state secondary battery in the pressurized state as described above was charged at 45 ° C. with a constant current of 0.1 C to an upper limit voltage of 4.25 V, then charged at a constant voltage until the current reached 0.05 C, and discharged at 0.1 C to an end voltage of 2.5 V. The evaluation results are shown in FIG.
Furthermore, for charge/discharge cycle evaluation, the laminated all-solid-state secondary battery in the pressurized state as described above was charged at 45° C. with a constant current of 0.33 C up to an upper limit voltage of 4.25 V and then discharged at 0.33 C down to an end voltage of 2.5 V. The results are shown in FIG.
Furthermore, the total thickness of this laminated all-solid-state secondary battery, including the laminate film, was measured using a film thickness measuring device. Measurements were performed at six different points, and the surface irregularities were evaluated by examining the thickness variations. The results are shown in Table 1.
In the graph of FIG. 11, no overcharging exceeding the theoretical capacity or spike-like charge/discharge curves are observed, which indicates that charging and discharging are performed without any problems, and therefore, no short circuit phenomenon occurs and the positive electrode current collecting portion 111 is not cracked or broken.
Furthermore, it was confirmed from the graph in FIG. 11 that the laminated all-solid-state secondary battery produced in Example 1 was capable of being charged and discharged without short-circuiting.
Furthermore, from the results of FIG. 12, it was confirmed that the laminated all-solid-state secondary battery produced in Example 1 exhibited stable charge-discharge cycle characteristics.

Example 2
In Example 2, an all-solid-state secondary battery 1 and a stacked all-solid-state secondary battery in which these all-solid-state secondary batteries 1 were stacked were produced and evaluated in the same manner as in Example 1, except that two solid electrolyte layers 30 were formed between the positive electrode layer 10 and the negative electrode layer 20. The method for forming two solid electrolyte layers 30 is as follows.
[Fabrication of Electrolyte Positive Electrode Structure]
The two solid electrolyte sheets were sandwiched between the pre-cut positive electrode layer 10A, and then placed on a 3 mm thick aluminum plate (support material) with a release film attached. This was then covered with another release film and further covered with a 0.3 mm thick SUS metal plate (support material) of the same shape as the pre-cut positive electrode layer 10A. The resulting structure, including the support material, was then vacuum laminated and packed. The structure was then submerged in a pressurized medium and subjected to hydrostatic pressure treatment (a compaction process using an isostatic press) at 30 MPa, whereby the electrolyte layer on the electrolyte sheet was integrated with the pre-cut positive electrode layer 10A. This structure is referred to as an electrolyte positive electrode structure.
[Fabrication of all-solid-state secondary battery and laminated all-solid-state secondary battery]
The produced electrolyte positive electrode structure was sandwiched between two electrolyte negative electrode structures 20A, and then an all-solid-state secondary battery 1 and a stacked all-solid-state secondary battery were produced in the same manner as in Example 1.
[Evaluation of all-solid-state secondary batteries]
For the laminated all solid state secondary battery produced in Example 2, a charge/discharge evaluation and a charge/discharge cycle evaluation were performed in the same manner as in Example 1, and the results of the charge/discharge evaluation are shown in Fig. 13 and the results of the charge/discharge cycle evaluation are shown in Fig. 12. From the results in Fig. 13 and Fig. 12, it was confirmed that, similarly to Example 1, when an all solid state secondary battery 1 in which two solid electrolyte layers 30 were laminated between the positive electrode layer 10 and the negative electrode layer 20 was used, the positive electrode current collecting part 111 was not cracked or cut, and no short circuit occurred, allowing stable charge/discharge.

(Comparative Example 1)
An insulating layer material 13A not provided with the notch 13C and the current collector protection member material 14A was used instead of the excess insulating layer material 13B used in Example 1, and otherwise an all-solid-state secondary battery 1 and a laminated all-solid-state secondary battery were fabricated using the same procedures as in Example 1, and charge/discharge evaluation was performed using the same procedures as in Example 1. The evaluation results are shown in Fig. 14 .
In the graph of Fig. 14, spike-shaped charge/discharge curves are observed, which indicates that cracks have occurred or the positive electrode current collector 111 has been cut, and therefore only a charge/discharge capacity significantly below the theoretical capacity has been detected. In the case of the graph of Fig. 14, calculations based on a comparison of the charge/discharge capacity with the theoretical capacity suggest that cracks have occurred or the positive electrode current collector 111 of two or three of the four-layered all-solid-state secondary batteries 1 constituting the laminated all-solid-state secondary battery has been cut.

(Comparative Example 2)
An insulating layer material 13A not provided with the notch 13C and the current collector protection member material 14A was used instead of the excess insulating layer material 13B used in Example 1, and in the [fabrication of positive electrode layer] step and the [fabrication of all-solid-state secondary battery] step, an all-solid-state secondary battery 1 was fabricated using only an aluminum plate as a support material without using the 0.3 mm SUS metal plate used in Example 1. A laminated all-solid-state secondary battery was fabricated in the same manner as in Example 1, and this laminated all-solid-state secondary battery was evaluated.
The overall thickness of this laminated all-solid-state secondary battery, including the laminate film, was measured using a film thickness measuring device in the same manner as in Example 1. Measurements were performed at six different points, and the surface irregularities were evaluated by examining the thickness variations. The results are shown in Table 1.
The results of the charge/discharge evaluation are shown in Fig. 15, and the results of the charge/discharge cycle evaluation are shown in Fig. 12. From the results in Fig. 15, it is considered that the laminated all-solid-state secondary battery produced in Comparative Example 2 was charged to an amount exceeding the theoretical capacity, and therefore, although the positive electrode current collecting part 111 was not cracked or cut, a short circuit occurred.
Furthermore, the results in FIG. 12 show that the charge/discharge capacity is significantly degraded by short circuiting.

Example 3
The all-solid-state secondary battery 1 produced in Example 1 was used as a single cell without being stacked, and an Al metal tab and a Ni metal tab were welded to the positive electrode current collector 11 and the negative electrode current collector 21, respectively, and the battery was subjected to a battery test. The results of the charge-discharge cycle characteristic evaluation performed in the same manner as in Example 1 are shown in FIG.
From these results, good cycle characteristics similar to those of the laminated all-solid-state secondary battery of Example 1 could be observed.
The thickness of the all-solid-state secondary battery 1 of Example 3 was measured at six points through the entire thickness including the laminate film using a film thickness measuring device in the same manner as in Example 1, and the thickness variation was evaluated. The results are shown in Table 1.

(Comparative Example 3)
The all-solid-state secondary battery 1 produced in Comparative Example 2 was laminate-packed as a single cell without being stacked, and the thickness was measured at six points through the entire thickness including the laminate film using a film thickness measuring device to evaluate the thickness variation. The measurement method was the same as in Example 1. The results are shown in Table 1.

From the results in Table 1, when comparing the thickness variations between Example 1 and Comparative Example 2, and Example 3 and Comparative Example 3, it can be seen that in Example 1 and Example 3, in which a 0.3 mm thick SUS metal plate was used when performing the isostatic pressing, the thickness variations are clearly smaller than in Comparative Examples 1 and 3 in which a SUS metal plate was not used when performing the isostatic pressing (in which the support material was placed on only one side of the positive electrode layer 10 or the all-solid-state secondary battery 1 and the pressure treatment was performed), and the surface irregularities are suppressed.
If the surface irregularities can be kept small, the current will not be concentrated only on the protruding parts.
When the current is concentrated in only one part in this way and no current is applied, the positive electrode layer 10 and the negative electrode layer 20 as a whole contribute to charging and discharging, and therefore the charging and discharging capacity of the all-solid-state secondary battery 1 can be improved.
Furthermore, since the positive electrode layer 10 and the negative electrode layer 20 contribute uniformly to charging and discharging over their entirety, it is possible to suppress short circuits caused by, for example, metallic lithium or the like being concentrated and deposited in only a certain location.
As a result, as shown in FIG. 12, it is believed that in Examples 1 and 2, no short circuit occurred and stable charge/discharge cycles were achieved.
As can be seen from the above results, in order to make the surface of the all-solid-state secondary battery 1 flatter as in Example 1 or Example 3, it is preferable to perform a pressure treatment while sandwiching the positive electrode layer 10, the negative electrode layer 20, or the laminate forming the all-solid-state secondary battery 1 between two support materials on both sides in the stacking direction. However, when a pressure treatment such as isostatic pressing is performed while sandwiched between support materials on both sides, the probability of cracks occurring in the current collecting portion or the current collecting portion being cut increases, as can be seen from a comparison between Comparative Example 1 and Comparative Example 2. Therefore, it is considered that the effect of providing the excess insulating layer 14 is more pronounced when the pressure treatment is performed while the all-solid-state secondary battery 1 is sandwiched between support materials on both sides.
When performing a pressure treatment such as isostatic pressing while sandwiched between support materials on both sides in this manner, it is preferable to make the shape of one of the support materials, as viewed from the stacking direction, the same shape as the shape of the laminate that forms the positive electrode layer 10, the negative electrode layer 20, or the all-solid-state secondary battery 1 to be pressure-treated, as viewed from the stacking direction. For example, if a pressure treatment using isostatic pressure is performed while sandwiched between support materials that are larger than the all-solid-state secondary battery 1 and have a different shape, the portion of the support that is not in contact with the positive electrode layer 10, the negative electrode layer 20, or the all-solid-state secondary battery 1 will bend significantly in the stacking direction, making it impossible to reuse the support. Furthermore, the thickness of the all-solid-state secondary battery 1 sandwiched between the support materials creates spaces between the support materials, which can cause the vacuum laminate-packed laminate material to tear during the pressure treatment using isostatic pressure.
In Example 1 and Example 2, a stacked all solid state secondary battery in which four all solid state secondary batteries 1 are stacked was examined, but it can be sufficiently inferred that a stacked all solid state secondary battery in which five or more layers of the all solid state secondary batteries 1 according to the present invention are stacked can also be a stacked all solid state secondary battery in which cracks or breaks do not occur in the positive electrode current collecting portion 111 and short circuits are unlikely to occur.
It goes without saying that the present invention is not limited to these examples.

REFERENCE SIGNS LIST 1 all-solid-state secondary battery 10 positive electrode layer 11 positive electrode current collector 12 positive electrode active material layer 13 insulating layer 14 current collector protection member (excess insulating layer)
20 negative electrode layer 21 negative electrode current collector 22 negative electrode active material layer 30 solid electrolyte layer

Claims (17)

a first electrode layer which is either a positive electrode layer or a negative electrode layer;
a solid electrolyte layer laminated on each of both surfaces of the first electrode layer;
a second electrode layer, which is the other of the positive electrode layer and the negative electrode layer, stacked on an outer surface of each of the solid electrolyte layers;
an insulating layer disposed on a side end surface of the first electrode layer so as to cover the first electrode layer;
a foil-shaped current collecting portion that penetrates the insulating layer from the first electrode layer and protrudes outward,
an insulating layer having a side end surface on the side where the current collecting portion protrudes, the side end surface having a different surface roughness from other side end surfaces of the insulating layer; The all-solid-state secondary battery described in claim 1, characterized in that the different surface portion is a roughened portion whose surface is rougher than the other side end surfaces of the insulating layer. 3. The all-solid-state secondary battery according to claim 1 , wherein the thickness of the different surface portion in the stacking direction is 1% to 95% of the thickness of the insulating layer in the stacking direction. 4. The all-solid-state secondary battery according to claim 1 , wherein the insulating layer contains a resin. 5. The all-solid-state secondary battery according to claim 4 , wherein the insulating layer further contains an insulating filler. 6. The all-solid-state secondary battery according to claim 5, wherein the insulating filler is made of one or more substances selected from the group consisting of fibrous resin, resin nonwoven fabric, alumina, magnesium oxide, silica, boehmite, barium titanate , barium carbonate, yttria, and manganese oxide. 7. The all-solid-state secondary battery according to claim 1 , wherein a part or all of an outer edge of the insulating layer on the side from which the current collecting portion protrudes is located outside an outer edge of the second electrode layer. 8. The all-solid-state secondary battery according to claim 7 , wherein a part or all of the outer edge of the second electrode layer is disposed on the insulating layer. 9. The all-solid-state secondary battery according to claim 1, wherein the first electrode layer is a positive electrode layer. 10. The all-solid-state secondary battery according to claim 1 , wherein the solid electrolyte layer contains a sulfide-based solid electrolyte containing at least lithium, phosphorus, and sulfur. 11. The all-solid-state secondary battery according to claim 1, wherein the anode layer contains an anode active material that forms an alloy with lithium and/or an anode active material that forms a compound with lithium, metallic lithium is capable of being precipitated inside the anode layer during charging, and 80% or more of the charge capacity of the anode layer is exhibited by metallic lithium. 12. The all-solid-state secondary battery according to claim 1, wherein the negative electrode layer contains at least one selected from the group consisting of amorphous carbon, gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, and zinc . A stacked all-solid-state secondary battery, comprising two or more stacked all-solid-state secondary batteries according to any one of claims 1 to 12 . a laminate manufacturing process for manufacturing a laminate in which solid electrolyte layers are laminated on both sides of a first electrode layer, which is one of a positive electrode layer or a negative electrode layer, and a second electrode layer, which is the other of the positive electrode layer or the negative electrode layer, is laminated on an outer surface of each solid electrolyte layer, and a foil-shaped current collector that electrically connects the first electrode layer to an external wiring is disposed so as to protrude outward from the first electrode layer, and a current collector protection member that protects the current collector is disposed so as to wrap the current collector;
a pressurizing step of applying pressure to the laminate in the stacking direction;
a removing step of removing the current collector protection member after the pressurizing step. the laminate further includes an insulating layer disposed so as to cover a side end surface of the first electrode layer,
15. The method for manufacturing an all-solid-state secondary battery according to claim 14 , wherein the current collector protection member is a surplus insulating layer formed integrally with a side end surface of the insulating layer. 16. The method for manufacturing an all-solid-state secondary battery according to claim 15 , further comprising forming a notch between the insulating layer and the excess insulating layer to remove the excess insulating layer. 17. The method for manufacturing an all-solid-state secondary battery according to claim 16 , wherein the cut is formed in a range of 5% to 99% of the thickness of the excess insulating layer.