All-solid-state secondary battery

Abstract

The present invention provides an all-solid-state secondary battery which is provided with: a multilayer body that is obtained by stacking a positive electrode layer that contains a positive electrode active material and a negative electrode layer that contains a negative electrode active material, with a solid electrolyte layer being interposed therebetween; a positive electrode external terminal which is bonded to the positive electrode layer at a first surface among the lateral surfaces of the multilayer body; and a negative electrode external terminal which is bonded to the negative electrode layer at a second surface that is different from the first surface. With respect to this all-solid-state secondary battery, the positive electrode layer expands in a direction from the first surface toward the second surface; the negative electrode layer expands in a direction from the second surface toward the first surface; and the multilayer body is provided with a void in at least one region that is selected from among a region that is surrounded by the positive electrode layer and the first surface, a region that is surrounded by the positive electrode layer, the solid electrolyte layer and the first surface, a region that is surrounded by the negative electrode layer and the second surface, and a region that is surrounded by the negative electrode layer, the solid electrolyte layer and the second surface.

Description

All-solid-state secondary battery

[0001] The present invention relates to an all-solid-state secondary battery. This application claims priority to Japanese Patent Application No. 2022-105471, filed on June 30, 2022, the contents of which are incorporated herein by reference.

[0002] In recent years, electronics technology has made remarkable advances, leading to efforts to make portable electronic devices smaller, lighter, thinner, and more multifunctional. Accordingly, there is a strong demand for smaller, lighter, thinner, and more reliable batteries, which serve as the power source for such electronic devices. Currently, commonly used lithium-ion secondary batteries have traditionally used electrolytes (electrolytic solutions), such as organic solvents, as a medium for ion migration. However, lithium-ion secondary batteries that use electrolyte solutions have the risk of electrolyte leakage. Furthermore, because organic solvents and other materials used in electrolyte solutions are flammable, safer batteries are in demand.

[0003] Therefore, as one measure to improve the safety of batteries, so-called all-solid-state secondary batteries that use a solid electrolyte instead of an electrolytic solution have been proposed (e.g., Patent Documents 1 and 2). The all-solid-state secondary batteries of Patent Documents 1 and 2 include a stack in which positive electrode layers including positive electrode active material layers and negative electrode layers including negative electrode active material layers are alternately stacked with a solid electrolyte layer interposed therebetween, and a pair of external electrodes that are arranged in contact with and face each other on the side surfaces of the stack.

[0004] In an all-solid-state secondary battery, there is a concern that peeling of electrode layers such as a positive electrode layer and a negative electrode layer may result in a deterioration in cycle characteristics. Specifically, in an all-solid-state secondary battery, a positive electrode current collector and a negative electrode current collector are connected to a positive electrode external terminal and a negative electrode external terminal, respectively, and there is a concern that peeling of the positive electrode current collector from the positive electrode external terminal or peeling of the negative electrode current collector from the negative electrode external terminal due to expansion and contraction during charge and discharge may result in a deterioration in cycle characteristics.

[0005] In the all-solid-state secondary battery of Patent Document 2, in order to prevent the positive electrode current collector and the negative electrode current collector from peeling off from the external terminals, it is proposed to increase the thickness of the portions of the positive electrode current collector and the negative electrode current collector that are bonded to the external terminals, and to increase the area of ​​the regions where the positive electrode current collector and the negative electrode current collector are bonded to the external terminals.

[0006] JP 2021-108258 A International Publication No. 2020 / 105662

[0007] However, the all-solid-state secondary batteries disclosed in Patent Documents 1 and 2 were unable to sufficiently prevent short circuits caused by expansion and contraction of the electrode layers during charging and discharging.

[0008] Specifically, the all-solid-state secondary battery of Patent Document 1 aims to improve the adhesion between materials of the same type and to increase the energy density, but does not include any means for buffering the stress caused by the expansion and contraction of the electrode layer. As a result, the expansion and contraction of the electrode layer may cause the current collector to peel off from the external electrode terminal, or cracks may occur in the solid electrolyte layer, resulting in a short circuit.

[0009] In the all-solid-state secondary battery of Patent Document 2, expansion and contraction of the electrode active material during charging and discharging causes stress in the solid electrolyte layer from the end of the electrode layer on the side not joined to the external electrode terminal, causing cracks to form from the end through the solid electrolyte layer toward an electrode layer having a polarity opposite to that of the electrode layer, which can result in a short circuit.

[0010] The present invention has been made in consideration of the above circumstances, and aims to suppress the occurrence of cracks extending from the end toward an electrode layer having a polarity different from that of the electrode layer due to the influence of expansion and contraction of the electrode active material during charging and discharging.

[0011] (1) An all-solid-state secondary battery according to a first aspect of the present invention comprises: a laminate in which a cathode layer containing a cathode active material and an anode layer containing an anode active material are stacked with a solid electrolyte layer interposed therebetween; a cathode external terminal joined to the cathode layer on a first surface of a side surface of the laminate; and a cathode external terminal joined to the anode layer on a second surface of a side surface of the laminate different from the first surface, wherein the cathode layer extends in a direction from the first surface to the second surface, and the anode layer extends in a direction from the second surface to the first surface; and the laminate has voids formed in at least one of a region surrounded by the cathode layer and the first surface, a region surrounded by the cathode layer, the solid electrolyte layer, and the first surface, a region surrounded by the anode layer and the second surface, and a region surrounded by the anode layer, the solid electrolyte layer, and the second surface.

[0012] (2) In the all-solid-state secondary battery of (1), a ratio of the length of the void to the distance between the negative electrode layer and the first surface in an in-plane direction of the negative electrode layer may be 20% to 100%, and a ratio of the length of the void to the distance between the positive electrode layer and the second surface in an in-plane direction of the positive electrode layer may be 20% to 100%.

[0013] (3) In the all-solid-state secondary battery of (1) or (2) above, the angle formed by the two layers defining the void may be 30° or less.

[0014] (4) In the all-solid-state secondary batteries of (1) to (3), the laminate may include a plurality of cathode layers including an outermost cathode layer located at an end in the stacking direction, a plurality of anode layers including an outermost anode layer located at an end in the stacking direction, and a plurality of solid electrolyte layers, and the laminate may have voids formed in at least one of a region surrounded by the outermost cathode layer and the first surface, a region surrounded by the outermost cathode layer, the solid electrolyte layer, and the first surface, a region surrounded by the outermost anode layer and the second surface, and a region surrounded by the outermost anode layer, the solid electrolyte layer, and the second surface.

[0015] (5) In the all-solid-state secondary batteries according to (1) to (4), the laminate may include a plurality of positive electrode layers and a plurality of negative electrode layers, and the ratio of the sum of the number of positive electrode layers in contact with the voids and the number of negative electrode layers in contact with the voids to the total number of the positive electrode layers and the negative electrode layers may be 10% or more.

[0016] (6) In the all-solid-state secondary batteries according to any one of (1) to (5), the positive electrode layer may include a positive electrode current collector and a positive electrode active material layer, the negative electrode layer may include a negative electrode current collector and a negative electrode active material layer, and the void may be in contact with the positive electrode active material layer or the negative electrode active material layer.

[0017] (7) In the all-solid-state secondary batteries described in (1) to (6) above, at least one of the positive electrode active material and the negative electrode active material may be AgPd.

[0018] According to the present invention, it is possible to suppress the occurrence of cracks that extend from the end portion through the solid electrolyte layer toward an electrode layer having a polarity different from that of the electrode layer or an external terminal having a polarity different from that of the electrode layer, due to the influence of expansion and contraction of the electrode active material during charge and discharge.

[0019] Fig. 2 is a cross-sectional view of an all-solid-state secondary battery according to one embodiment of the present invention. Fig. 3 is a cross-sectional view showing a modified example of the all-solid-state secondary battery of Fig. 1. Fig. 4 is a cross-sectional view showing another modified example of the all-solid-state secondary battery of Fig. 1. Fig. 5 is a cross-sectional view showing another modified example of the all-solid-state secondary battery of Fig. 1. Fig. 6 is a cross-sectional view showing another modified example of the all-solid-state secondary battery of Fig. 1. Fig. 7 is a cross-sectional view showing another modified example of the all-solid-state secondary battery of Fig. 1.

[0020] An example of an embodiment of the present invention will be described in detail below with reference to the drawings. Note that the drawings used in the following description may show characteristic parts enlarged for the sake of convenience in order to make the features of the present invention easier to understand. Therefore, the dimensional ratios of each component may differ from the actual ones.

[0021] [All-solid-state secondary battery] Fig. 1 is a cross-sectional view of an all-solid-state secondary battery according to one embodiment of the present invention. The all-solid-state secondary battery 100A shown in Fig. 1 includes a laminate 1A in which a positive electrode layer 10A and a negative electrode layer 20A are laminated with a solid electrolyte layer 30 interposed therebetween, and a positive electrode external terminal 2 and a negative electrode external terminal 3 joined to the laminate 1A.

[0022] In this embodiment, in FIG. 1 , the stacking direction of the positive electrode layer 10A and the negative electrode layer 20A in the laminate 1A is defined as the z direction, the direction perpendicular to the z direction and in which the positive electrode layer 10A and the negative electrode layer 20A in FIG. 1 extend is defined as the x direction, and the direction perpendicular to the x direction and the z direction is defined as the y direction.

[0023] [Laminate] The laminate 1A is a substantially hexahedron having an upper surface St and a lower surface Sb, which are end surfaces in the stacking direction, and four side surfaces parallel to the stacking direction. Of the side surfaces of the laminate 1A, the end surface that joins with the positive electrode layer 10A is referred to as a first surface S1, and the end surface that joins with the negative electrode layer 20A is referred to as a second surface S2. In the laminate 1A, the first surface S1 and the second surface S2 are end surfaces in the x direction.

[0024] The laminate provided in the all-solid-state secondary battery according to this embodiment has voids in at least one of the regions surrounded by the positive electrode layer 10 and the first surface S1, the region surrounded by the positive electrode layer 10, the solid electrolyte layer 30, and the first surface S1, the region surrounded by the negative electrode layer 20 and the second surface S2, and the region surrounded by the negative electrode layer 20, the solid electrolyte layer 30, and the second surface S2.

[0025] The laminate 1A shown in FIG. 1 has a void 50a in the region surrounded by the positive electrode layer 10 and the first surface S1, and a void 50b in the region surrounded by the negative electrode layer 20 and the second surface S2.

[0026] <Positive Electrode Layer> The positive electrode layer 10A includes a positive electrode active material. The positive electrode layer 10A includes, for example, a positive electrode current collector 11A and a positive electrode active material layer 12A provided on at least one of the main surfaces of the positive electrode current collector 11A.

[0027] The positive electrode layer 10A is joined to the external positive electrode terminal 2 at the first surface S1. The positive electrode layer 10A extends in a direction from the first surface S1 toward the second surface S2. The positive electrode layer 10A does not extend to the second surface S2. In this embodiment, of the ends of the positive electrode layer 10A in the x direction, the end on the first surface S1 side, i.e., the end in the −x direction, is referred to as an end extending laterally, and the end opposite to the extending end, i.e., the end in the +x direction, is referred to as an end not extending laterally.

[0028] (Positive Electrode Current Collector) The positive electrode current collector 11A is made of, for example, a material with high conductivity. The positive electrode current collector 11A is made of, for example, a metal or alloy containing at least one metal element selected from silver (Ag), palladium (Pd), gold (Au), platinum (Pt), aluminum (Al), copper (Cu), and nickel (Ni), or a non-metal such as carbon (C). An example of such an alloy is AgPd.

[0029] The positive electrode current collector 11A has, for example, a flat portion 11Ap that extends in a direction intersecting the stacking direction and has a substantially flat shape, and a curved portion 11Aw that is located closer to the positive electrode external terminal 2 than the flat portion 11Ap and curves in the stacking direction. The curved portion 11Aw is joined to the positive electrode external terminal 2. The angle formed between the curved portion 11Aw of the positive electrode current collector 11A and the positive electrode external terminal 2 is, for example, 45° to 90°, or may be 60° to 90°. The curved portion 11Aw has a shape that moves away from the positive electrode active material layer 12A in the stacking direction as it approaches the positive electrode external terminal 2 in the x direction, and may be linear, or a shape that approaches the positive electrode current collector 11A in the stacking direction as it approaches the positive electrode external terminal 2 in the x direction.

[0030] When the positive electrode layer 10A is composed of a flat portion 11Ap and a curved portion 11Aw of the current collector and a flat portion 12Ap of the active material layer, the curved portion 11Aw of the current collector and the flat portion 12Ap of the active material layer are spaced apart from each other. That is, the positive electrode layer 10A has an opening on one end side thereof.

[0031] The angle of the curved portion 11Aw with respect to the flat portion 11Ap is, for example, greater than 0° and equal to or less than 45°, and preferably greater than 0° and equal to or less than 30°.

[0032] (Positive Electrode Active Material Layer) The positive electrode active material layer 12A is made of a positive electrode active material layer flat portion 12Ap that extends in a direction intersecting the stacking direction and has a substantially flat shape. The flat portion 12Ap is joined to the positive electrode external terminal 2. For example, one extending end of the flat portion 12Ap forms an angle of 80° to 90° with the positive electrode external terminal 2.

[0033] The positive electrode active material layer 12A contains, as a positive electrode active material, a known compound capable of absorbing and releasing at least lithium ions. The positive electrode active material is, for example, a compound exhibiting a more noble potential than the negative electrode active material. The positive electrode active material layer 12A may also contain a conductive additive or an ion-conducting additive. It is preferable that the positive electrode active material be capable of efficiently inserting and desorbing lithium ions.

[0034] Such a positive electrode active material is, for example, a transition metal oxide or a transition metal composite oxide. Specific examples of the positive electrode active material include lithium manganese composite oxide Li ２Mn ａ Ma １－ａ O ３ (0.8≦a≦1, Ma=Co, Ni), lithium cobalt oxide (LiCoO ２ (LCO)), lithium nickel oxide (LiNiO ２ ), lithium manganese oxide (LiMn) having a spinel structure ２ O ４ ), general formula: LiNi ｘ Co ｙ Mn ｚ O ２ a composite metal oxide represented by (x+y+z=1, 0≦x≦1, 0≦y≦1, 0≦z≦1), a lithium vanadium compound (LiV ２ O ５ ), olivine-type LiMbPO ４ (wherein Mb is one or more elements selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, and Zr), lithium vanadium phosphate (Li ３ V ２ (P.O. ４ ) ３ (LVP) or LiVOPO ４ ), Li ２ MnO ３ -LiMcO ２ Lithium-excess solid solution cathode represented by (Mc=Mn, Co, Ni), lithium titanate (Li ４ Ti ５ O １２ ), titanium oxide (TiO ２ ), Li ｓ Ni ｔ Co ｕ Al ｖ O ２ (0.9<s<1.3, 0.9<t+u+v<1.1), and the like.

[0035] Furthermore, in these positive electrode active materials, some of the elements may be substituted with different elements, and the composition may be changed from the stoichiometric composition.

[0036] Examples of the conductive aid include carbon materials such as carbon black, acetylene black, ketjen black, carbon nanotubes, graphite, graphene, and activated carbon, and metal materials such as gold, silver, palladium, platinum, copper, and tin.

[0037] The ion-conducting aid is, for example, a solid electrolyte. Specifically, the solid electrolyte may be the same material as that used for the solid electrolyte layer 30.

[0038] When a solid electrolyte is used as the ion-conducting aid, it is preferable that the ion-conducting aid and the solid electrolyte used in the solid electrolyte layer 30 are made of the same material.

[0039] <Negative Electrode Layer> The negative electrode layer 20A includes a negative electrode active material. The negative electrode layer 20A has, for example, a negative electrode current collector 21A and a negative electrode active material layer 22A provided on at least one of the main surfaces of the negative electrode current collector 21A. The negative electrode active material layer 22A is located, for example, on the inner side of the negative electrode current collector 21A in the stacking direction.

[0040] The negative electrode layer 20A is joined to the negative electrode external terminal 3 at the second surface S2. The negative electrode layer 20A extends in a direction from the second surface S2 toward the first surface S1. The negative electrode layer 20A does not extend to the first surface S1. In this embodiment, of the ends of the negative electrode layer 20A in the x direction, the end on the second surface S2 side, i.e., the end in the +x direction, is referred to as an end extending laterally, and the end opposite to the extending end, i.e., the end in the −x direction, is referred to as an end not extending laterally.

[0041] The negative electrode current collector 21A includes, for example, a flat portion 21Ap that extends in a direction intersecting the stacking direction and has a substantially flat shape. The negative electrode active material layer 22A includes, for example, a flat portion 22Ap that extends in a direction intersecting the stacking direction and has a substantially flat shape, and a curved portion 22Aw that is positioned closer to the negative electrode external terminal 3 than the flat portion 22Ap and is curved in the stacking direction.

[0042] The curved portion 22Aw is joined to the negative electrode external terminal 3. The angle formed between the curved portion 22Aw of the negative electrode active material layer 22A and the negative electrode external terminal 3 is, for example, 45° to 90°, and may be 60° to 90°. The curved portion 22Aw has a shape that moves away from the negative electrode current collector 21A in the stacking direction as it approaches the negative electrode external terminal 3 in the x direction, and may have a linear shape or a shape that moves closer to the negative electrode current collector 21A in the stacking direction as it approaches the negative electrode external terminal 3 in the x direction.

[0043] When the anode layer 20A is composed of the flat portion 21Ap, the flat portion 22Ap, and the curved portion 22Aw, the flat portion 21Ap and the curved portion 22Aw are spaced apart from each other. That is, the anode layer 20A has an opening at one end thereof.

[0044] The angle of the curved portion 22Aw with respect to the flat portion 21Ap is, for example, 45° or less, and preferably 30° or less.

[0045] (Negative Electrode Current Collector) The negative electrode current collector 21A is made of, for example, a material with high conductivity. For example, the same material as that of the positive electrode current collector 11A can be used for the negative electrode current collector 21A.

[0046] (Negative Electrode Active Material Layer) The negative electrode active material layer 22A contains, as the negative electrode active material, a known compound capable of absorbing and releasing at least lithium ions. The negative electrode active material is, for example, a compound that exhibits a lower potential than the positive electrode active material. The negative electrode active material layer 22A may contain, in addition to the negative electrode active material, a conductive additive or an ion-conducting additive. It is preferable that the negative electrode active material be capable of efficiently inserting and desorbing lithium ions.

[0047] <Solid Electrolyte Layer> The solid electrolyte layer 30 includes, for example, an interlayer solid electrolyte layer 31 located between the positive electrode layer 10A and the negative electrode layer 20A, and margin layers 32 arranged next to each of the positive electrode layer 10A and the negative electrode layer 20A. In this embodiment, a layer of the solid electrolyte located outside the outermost electrode layer in the stacking direction may also be referred to as an interlayer solid electrolyte layer.

[0048] The solid electrolyte layer 30 is preferably made of a material having low electron conductivity and high lithium ion conductivity. For example, the solid electrolyte layer 30 is made of La ０．５ Li ０．５ TiO ３ Perovskite compounds such as Li １４ Zn(GeO ４ ) ４ Lithium-type compounds such as Li ７ La ３ Zr ２ O １２ Garnet-type compounds such as LiZr ２ (P.O. ４ ) ３, Li １＋ｘ Al ｘ Ti ２－ｘ (P.O. ４ ) ３ ; LATP(Li １．３ Al ０．３ Ti １．７ (P.O. ４ ) ３ , Li １．５ Al ０．５ Ge １．５ (P.O. ４ ) ３ ) and other Nasicon-type compounds, Li ３．２５ Ge ０．２５ P ０．７５ S ４ and Li ３ P.S. ４ Thiolisicon-type compounds such as Li ２ S-P ２ S ５ and Li ２ O-V ２ O ５ -SiO ２ Glass compounds such as Li ３ P.O. ４ and Li ３．５ Si ０．５ P ０．５ O ４ (LSPO) and Li ２．９ P.O. ３．３ N ０．４６ and the like.

[0049] The thickness of the interlayer solid electrolyte layer 31 is preferably, for example, in the range of 0.5 μm to 20.0 μm. Increasing the thickness of the interlayer solid electrolyte layer 31 makes it easier to obtain the effect of suppressing short circuits between the positive electrode layer 10A and the negative electrode layer 20A that sandwich the interlayer solid electrolyte layer 31. Furthermore, setting the thickness of the interlayer solid electrolyte layer 31 to 20.0 μm or less shortens the migration distance of lithium ions, making it easier to reduce internal resistance.

[0050] 1, the laminate 1A may include a solid electrolyte and may also include margin layers 32 disposed adjacent to the positive electrode layer 10A and the negative electrode layer 20A. The margin layers 32 may be considered to be part of the solid electrolyte layer 30.

[0051] The margin layer 32 is provided to eliminate, for example, a step between the non-extending end of the positive electrode layer 10A and the interlayer solid electrolyte layer 31, and a step between the non-extending end of the negative electrode layer 20A and the interlayer solid electrolyte layer 31. Therefore, the margin layer 32 is formed, for example, on the main surface of the interlayer solid electrolyte layer 31 at the non-extending end of each electrode layer, at approximately the same height as the positive electrode layer 10A or the negative electrode layer 20A (i.e., so as to be arranged alongside the positive electrode layer 10A and the negative electrode layer 20A, respectively). The margin layer 32 eliminates the steps between the interlayer solid electrolyte layer 31 and the positive electrode layer 10A, and between the interlayer solid electrolyte layer 31 and the negative electrode layer 20A, thereby increasing the density of the solid electrolyte layer 30 and each electrode layer at the non-extending end of each electrode layer. Even when processing is performed to form voids, as described below, delamination due to firing of the all-solid-state secondary battery and unintended warping at the non-extending end are less likely to occur. The distance between the end of the positive electrode layer 10A and the second surface S2 at the non-extending end and the distance between the end of the negative electrode layer 20A and the first surface S1 are, for example, the same. FIG. 1 shows an all-solid-state secondary battery 100A in which the distance between the end of the positive electrode layer 10A and the second surface S2 at the non-extending end and the distance between the end of the negative electrode layer 20A and the first surface S1 are the same, and these distances are indicated by the symbol L ３２ Shown in.

[0052] <Void> Because the positive electrode layer 10A has the open-mouth structure described above at one extending end, a void 50a is formed between the positive electrode layer 10A and the first surface S1. The void 50a is defined by the positive electrode layer 10A and the first surface S1. More specifically, the void 50a is defined by the current collector flat portion 11Ap, the curved portion 12Aw, and the first surface S1. The void 50a has a length L50a in the x direction and a length (height) h50a in the z direction.

[0053] The angle θ of the gap 50a is the angle formed by the gap 50a of two layers that defines the gap 50a. ５０ａis, for example, 45° or less, and preferably 30° or less. In the example shown in FIG. 1 , the two layers that define the corner of the void 50a are the positive electrode current collector 11A and the positive electrode active material layer 12A, more specifically, the positive electrode current collector flat portion 11Ap and the curved portion 12w. The angle of the void 50a can be calculated, for example, based on the length L50a and the height h50a. That is, assuming that the shape of the void 50a is a right-angled triangle in which the positive electrode active material layer 12A and the first surface S1 are perpendicular to each other, the angle of the void 50a can be calculated, for example, based on the length L50a and the height h50a. In other words, the shape of the void 50a is considered to be a right-angled triangle in which the positive electrode active material layer 12A and the first surface S1 are perpendicular to each other, and the angle of the void 50a can be calculated, for example, based on the ratio (height h50a / length L50a). ２ is 1 / 3 or less, the angle θ between the curved portion 11Aw of the positive electrode current collector 11A and the flat portion 12Ap of the positive electrode active material layer with the gap 50a in between ５０ａ Similarly, the shape of the void 50b is considered to be a right triangle in which the negative electrode current collector 21A and the second surface S2 are perpendicular to each other, and the angle between the negative electrode current collector 21A and the second surface S2 is determined as, for example, (height h50b / length L50b) ２ is 1 / 3 or less, the angle θ between the curved portion 22Aw of the negative electrode active material layer 22A and the gap 50b of the negative electrode current collector 21A is ５０ｂ It is confirmed that the angle is 30° or less.

[0054] As described above, in the in-plane direction of the positive electrode layer 10A, the distance between the negative electrode layer 20A and the first surface S1 and the distance between the positive electrode layer 10A and the second surface S2 are, for example, approximately equal. ３２ The length L ３２ The length L of the gaps 50a and 50b ５０ａ , L ５０ｂ The ratio (L ５０ａ / L ３２ ), (L ５０ｂ / L ３２ ) is, for example, 5 to 150, preferably 20 to 100%, and more preferably 50% to 100%. ５０ａ / L ３２ ) is 20 or more, the stress caused by the expansion and contraction of the electrode active material layer during charge and discharge can be further alleviated. ５０ａ / L ３２ ), (L ５０ｂ / L ３２ ) is 100% or less, the voids become excessively large and the movement of carriers and electrons is less likely to be hindered.

[0055] [Method for manufacturing all-solid-state secondary battery] The all-solid-state secondary battery 100A can be manufactured, for example, by a procedure using the following co-firing method. The co-firing method is a method for manufacturing a laminate by simultaneously firing different materials that are the base materials of the laminate. When the co-firing method is used, the number of work steps for the all-solid-state secondary battery 100 can be reduced. Furthermore, when the co-firing method is used, the resulting laminate 1A becomes denser. Below, an example of using the co-firing method will be described.

[0056] The method for manufacturing the all-solid-state secondary battery according to this embodiment includes, for example, a pasting step of preparing a paste of each material constituting the laminate, a solid electrolyte layer sheet fabrication step of applying and drying the paste for the solid electrolyte to fabricate a solid electrolyte layer sheet, an electrode unit fabrication step of forming a positive electrode layer and a negative electrode layer on the solid electrolyte layer sheet to fabricate a positive electrode unit and a negative electrode unit, a stacking step of alternately stacking the positive electrode units and negative electrode units to fabricate a base material for the laminate, and a firing step of co-firing the fabricated base material for the laminate. Each step will be described in more detail below.

[0057] (Paste-Making Process) First, the materials for the positive electrode current collector 11A, the positive electrode active material layer 12A, the solid electrolyte layer 30, the negative electrode current collector 21A, and the negative electrode active material layer 22A are paste-made. The paste-making method is not particularly limited. For example, the paste can be obtained by mixing powders of the materials with a vehicle. Here, the term vehicle is a general term for a medium in a liquid phase. The vehicle includes a solvent and a binder. The binder contained in the paste is not particularly limited, but polyvinyl acetal resin, cellulose resin, acrylic resin, urethane resin, vinyl acetate resin, polyvinyl alcohol resin, etc. can be used. Using this method, a paste for the positive electrode current collector, a paste for the positive electrode active material layer, a paste for the solid electrolyte layer, a paste for the negative electrode active material layer, and a paste for the negative electrode current collector are prepared. A void-forming resin paste is also prepared separately using a similar method. The resin paste contains only resin as a solid component, and these components become voids after firing. The resin may be, for example, ethyl cellulose, acrylic, or the like, as long as it melts when heated to a high temperature of, for example, 400° C. or higher, and then vaporizes and is eliminated from the laminate.

[0058] (Solid electrolyte layer forming step) Next, a solid electrolyte paste is applied and dried to form a solid electrolyte layer sheet. For example, the solid electrolyte paste is formed into a sheet on a PET film by a doctor blade method, and then dried to form a solid electrolyte layer sheet.

[0059] (Electrode Unit Fabrication Process) Next, a positive electrode layer and a negative electrode layer are formed on the solid electrolyte layer sheet, respectively, to fabricate a positive electrode unit and a negative electrode unit, respectively. The solid electrolyte layer sheet is, for example, a solid electrolyte layer sheet that will become the interlayer solid electrolyte layer 31 after lamination and firing. For example, first, a paste for a positive electrode active material layer is formed on the solid electrolyte layer sheet. The paste for the positive electrode active material layer is printed, for example, by screen printing and then dried. Next, a resin portion is formed on one end of the substrate for the positive electrode active material layer in the in-plane direction by applying a resin paste, for example, by screen printing. Next, for example, a paste for a positive electrode current collector is screen-printed and then dried. The paste for the positive electrode current collector is screen-printed, for example, so as to overlap the resin portion and the substrate for the positive electrode active material layer, and then dried. Then, a margin layer paste is screen-printed on an area of ​​the solid electrolyte layer sheet other than the positive electrode layer, and then dried to form a margin layer substrate having approximately the same height as the substrate for the positive electrode layer. The paste for the margin layer is, for example, the same material as the paste for the solid electrolyte layer. Next, the PET film is peeled off. In this way, a positive electrode current collector is formed on the substrate of the solid electrolyte layer, and a resin part and a substrate of the positive electrode active material layer are formed thereon to produce a positive electrode unit. The negative electrode unit is produced using the same procedure as the positive electrode unit.

[0060] (Lamination process) Next, the active material layers of the positive electrode units and the negative electrode units are alternately stacked with the solid electrolyte layer sheets interposed therebetween, and are stacked with offsetting so that one end of each does not overlap, to produce a substrate for the laminate. For example, solid electrolyte layer sheets are formed on the outer sides of the positive electrode units and the negative electrode units in the stacking direction. Here, when producing a series-type all-solid-state secondary battery instead of a parallel-type all-solid-state secondary battery, the above-described offsetting is not performed, and the positive electrode units may be stacked without offsetting so that one end of the substrate for the positive electrode layer and one end of the substrate for the negative electrode layer overlap.

[0061] The substrates for the laminate can be pressed together using a mold press, hot isostatic press (WIP), cold isostatic press (CIP), isostatic press, etc. to enhance adhesion. Pressurization is preferably performed while heating, and can be performed at, for example, 40 to 95°C. The substrates for the laminate are cut and shaped using, for example, a dicing device.

[0062] Next, the base material of the laminate produced by the above procedure is fired to produce the laminate 1 A. Note that, before firing the laminate, it is preferable to carry out a binder removal step (binder removal step).

[0063] (Binder Removal Process) By carrying out a binder removal process and thermally decomposing the binder components contained in the laminate substrate before firing, excessive and rapid decomposition of the binder components during the firing process can be suppressed. The binder removal process can be carried out by placing the prepared laminate substrate on a ceramic setter for a base, for example, in a nitrogen atmosphere at a temperature range of 300°C to 800°C for 0.1 to 10 hours. If a reducing atmosphere is used, the binder removal process may be carried out in, for example, an argon atmosphere or a nitrogen / hydrogen mixed atmosphere instead of a nitrogen atmosphere. Furthermore, a reducing atmosphere containing a small amount of oxygen may be used as long as the metal current collector does not oxidize.

[0064] (Firing Step) Next, the substrate for the laminate is heat-treated in a temperature range of 600°C to 1000°C under a nitrogen atmosphere to obtain the laminate 1A. The firing time is, for example, 0.1 to 3 hours. If a reducing atmosphere is used, firing may be performed in, for example, an argon atmosphere or a nitrogen / hydrogen mixed atmosphere instead of a nitrogen atmosphere.

[0065] In the manufacturing method of the all-solid-state secondary battery 100A according to this embodiment, in order to manufacture an all-solid-state secondary battery having a curved portion in a part of the electrode layer and a gap formed between the electrode layer and the side surface of the laminate joined to the electrode layer, the above-mentioned resin is used, and then a device having a base, a lid, and a stand can be used in the firing process. For example, a base and a lid sandwiching the base material of the laminate from both sides in the stacking direction, and a stand disposed between the base and the lid and in the in-plane direction of the base material of the laminate are used. Specifically, the all-solid-state secondary battery 100A can be manufactured using a ceramic setter or the like as follows.

[0066] In the firing process, in order to produce a laminate 1A having a desired warpage, taking advantage of the fact that warpage is likely to occur when firing is performed rapidly, the height of the side of the laminate before firing (the height h of the side of the laminate from the ceramic setter for the base) is ０ ) to the height position h obtained by adding the increase in height Δh corresponding to the desired warpage angle after firing. １A method can be used in which a ceramic setter for the lid is placed on the base to control the amount of warpage and prevent further warpage of the laminate. This method involves providing a gap between the ceramic setter for the lid and the laminate to form the desired warpage angle. The height position of the ceramic setter for the lid can be easily adjusted by placing height-adjusting laminates and height-adjusting ceramic plates at the four corners of the ceramic setter for the base. For example, if a gap of 10 μm is desired between the pre-fired laminate and the ceramic setter for the lid, a height-adjusting laminate consisting of a 10 μm-thick ceramic plate for height adjustment placed on top of the pre-fired laminate can be placed at the four corners of the ceramic setter for the base. Rapid firing refers to firing at a temperature rise rate of 1000°C / hour or more. Furthermore, smooth ceramic setters are preferred for the ceramic setters used for the base and lid in order to better control warpage. For example, ceramic setters with polished main surfaces can be used. Furthermore, the ceramic setter may be a dense substrate or a porous substrate having holes. The material is preferably a material with a sintering temperature higher than the firing temperature of the laminate, such as zirconia or alumina. In this manner, the laminate 1A can be produced.

[0067] As another method, the all-solid-state secondary battery 100A having the voids 50 a, 50 b can be manufactured by printing the resin portion so as to form the voids of a desired shape using a 3D printer or the like. In the above method, the resin portion is formed so that the thickness increases toward the electrode terminal, for example.

[0068] (Terminal Formation) Next, a positive electrode external terminal 2 and a negative electrode external terminal 3 are formed on each of the first surface S1 and the second surface S2 of the side surfaces of the fired laminate 1A. The positive electrode external terminal 2 and the negative electrode external terminal 3 are formed so as to bond to the positive electrode layer 10A and the negative electrode layer 20A, respectively. The positive electrode external terminal 2 and the negative electrode external terminal 3 can be formed on the positive electrode layer 10A and the negative electrode layer 20A exposed from the side surfaces of the laminate 1A by known means such as sputtering, dip coating, screen printing, spray coating, etc. When the positive electrode external terminal 2 and the negative electrode external terminal 3 are formed so as to bond only to predetermined portions, they can be formed after, for example, applying masking with tape or the like.

[0069] The all-solid-state secondary battery 100A according to this embodiment has a void 50a in the region surrounded by the positive electrode current collector 11A, the positive electrode active material layer 12A, and the first surface S1, and a void 50b in the region surrounded by the negative electrode active material layer 22A, the negative electrode current collector 21A, and the second surface S2. This allows the voids 50a, 50b in contact with the positive electrode active material layer 12A and the negative electrode active material layer 22A, respectively, to relieve stress acting on the solid electrolyte layer 30 when the positive electrode active material and the negative electrode active material expand and contract during charge and discharge. This prevents cracks from occurring in the solid electrolyte layer 30 that extend from the non-extending end of the positive electrode active material layer 12A toward the negative electrode layer 20A or the negative electrode external terminal 3, or that extend from the non-extending end of the negative electrode active material layer 22A toward the positive electrode layer 10A or the positive electrode external terminal 2. This prevents short circuits from occurring in the all-solid-state secondary battery 100A. The all-solid-state secondary battery 100A has voids 50 a, 50 b at positions in contact with the electrode active material layers, which makes it easier to relieve stress from the electrode active material layers. The first surface S1 and the second surface S2 correspond to, for example, the inner surfaces of the positive electrode external terminal 2 and the negative electrode external terminal 3, respectively.

[0070] [Modifications] The all-solid-state secondary battery according to this embodiment is not limited to the all-solid-state secondary battery 100A shown in Fig. 1, and various modifications are possible within the scope of the claims. For example, the all-solid-state secondary battery according to this embodiment may be an all-solid-state secondary battery as shown in Figs. 2 to 4. In the all-solid-state secondary batteries according to the modifications, the same components as those in the all-solid-state secondary battery 100A are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0071] Fig. 2 is a cross-sectional view showing a modified example of the all-solid-state secondary battery of Fig. 1. The all-solid-state secondary battery 100B shown in Fig. 2 differs from the all-solid-state secondary battery 100A shown in Fig. 1 in the shape of a void 50c formed in the region surrounded by the positive electrode layer 10B and the first surface S1 and a void 50d formed in the region surrounded by the negative electrode layer 20B and the second surface S2.

[0072] The all-solid-state secondary battery 100B includes a laminate 1B in which a positive electrode layer 10B and a negative electrode layer 20B are laminated with a solid electrolyte layer 30 interposed therebetween.

[0073] The positive electrode layer 10B includes, for example, a positive electrode current collector 11B and a positive electrode active material layer 12A provided on an inner main surface of the positive electrode current collector 11B in the stacking direction. The positive electrode current collector 11B has a flat portion 11Bp and an extending portion 12Bx that is located closer to the positive electrode external terminal 2 than the flat portion 11Bp and joins to the positive electrode external terminal 2. The extending portion 11Bx is, for example, a region that is thinner than the flat portion 11Bp and has a generally rectangular shape in cross section, and contacts the solid electrolyte layer 30. In the positive electrode layer 10B, a void 50c is formed in a region surrounded by the extending portion 12Bx, the flat portion 12Bp, the positive electrode active material layer 12A, and the first surface S1.

[0074] The anode layer 20B includes, for example, a anode current collector 21A and an anode active material layer 22B provided on an inner main surface of the anode current collector 21A in the stacking direction. The anode active material layer 22B has a flat portion 22Bp and an extending portion 22Bx that is located closer to the anode external terminal 3 than the flat portion 22Bp and joins to the anode external terminal 3. The extending portion 22Bx is, for example, a region that is thinner than the flat portion 21Bp and has a generally rectangular shape in cross section, and contacts the solid electrolyte layer 30. In the anode layer 20B, a void 50d is formed in a region surrounded by the extending portion 22Bx, the flat portion 22Bp, the anode current collector 21A, and the second surface S2.

[0075] 2, the angle formed by the gaps 50c, 50d between the two layers (the positive electrode current collector 11B and the positive electrode active material layer 12B, and the negative electrode current collector 21A and the negative electrode active material layer 22B) that define the gaps 50c, 50d is, for example, 0°. The height of the gaps 50c, 50d in the stacking direction is approximately constant from the end in the +x direction to the end in the −x direction.

[0076] The all-solid-state secondary battery 100B can be manufactured by changing the conditions of the firing process from those in the manufacturing method of the all-solid-state secondary battery 100A, while keeping the other conditions the same. When manufacturing the all-solid-state secondary battery 100B having the gaps 50c and 50d with a substantially rectangular cross-sectional shape, the height of the side surface of the laminate before firing (the height h of the side surface of the laminate from the ceramic setter for the base) is ０ ) to prevent the base material of the laminate from warping. In this method, a gap for forming a desired warpage angle is not provided between the ceramic setter for the lid and the laminate. Furthermore, when manufacturing the all-solid-state secondary battery 100B, rapid firing is not necessarily required, and a gradual temperature rise rate may be used.

[0077] Even in the all-solid-state secondary battery 100B, the gaps 50c and 50d can alleviate stress caused by expansion and contraction of the electrode active material during charging and discharging, and cracks can be prevented from occurring in the solid electrolyte layer 30 from the non-extending end of the electrode layer toward an electrode layer having a polarity different from that of the electrode layer or toward the electrode external terminal.

[0078] FIG. 3 is a cross-sectional view showing another modified example of the all-solid-state secondary battery of FIG. 1 . The all-solid-state secondary battery 100C shown in FIG. 3 has a void 50e in a region surrounded by the positive electrode layer 10C, the solid electrolyte layer 30, and the first surface S1, and a void 50f in a region surrounded by the negative electrode layer 20C, the solid electrolyte layer 30, and the second surface S2. The two adjacent layers that define the corner of the void 50f are the negative electrode current collector 21C and the solid electrolyte layer 31, more specifically, the negative electrode current collector curved portion 21Cw and the solid electrolyte layer curved portion 31Cw. The angle of the void 50f is calculated, for example, based on the length L50f and the height h50f. The solid electrolyte layer curved portion 31Cw is a region of the solid electrolyte layer that overlaps with the curved portion 21Cw in the stacking direction and sandwiches the void 50f together with the curved portion 21Cw. The curved portion 31Cw of the solid electrolyte layer is peeled off from the negative electrode current collector 21C.

[0079] The positive electrode layer 10C includes, for example, a positive electrode current collector 11C including a flat portion 11Cp and a positive electrode active material layer 12A including a flat portion 11Ap and disposed on the inner side of the positive electrode current collector 11C in the stacking direction. Near one extending end of the positive electrode layer 10C, the interlayer solid electrolyte layer 31 is missing, forming a curved portion. The negative electrode layer 20C includes, for example, a negative electrode active material layer 22A and a negative electrode current collector 21C including a flat portion 21Cp and a curved portion 21Cw. The negative electrode current collector 21C includes, for example, a flat portion 21Cp that extends in a direction intersecting the stacking direction and has a substantially flat shape, and a curved portion 21Cw that is positioned closer to the negative electrode external terminal 3 than the flat portion 21Cp and curves in the stacking direction.

[0080] The all-solid-state secondary battery 100C can be manufactured by changing the conditions of the firing process from those of the all-solid-state secondary battery 100A, while maintaining the other conditions the same. To form the void 50e in the region surrounded by the positive electrode layer 10C, the solid electrolyte layer 30, and the first surface S1, for example, when forming the positive electrode unit, after applying the paste for the solid electrolyte layer, a resin paste is applied to one end in the in-plane direction to form a resin portion, and then a paste for the positive electrode active material layer and a paste for the positive electrode current collector are printed and dried in that order so as to overlap with the resin portion. To form the void 50f in the region surrounded by the negative electrode layer 20, the solid electrolyte layer 30, and the second surface S2, for example, after applying the paste for the solid electrolyte layer, a resin paste is applied to one end in the in-plane direction to form a resin portion, and then a paste for the negative electrode current collector and a paste for the negative electrode current collector are printed and dried in that order so as to overlap with the resin portion, and then the unit is fired.

[0081] In addition, when manufacturing an all-solid-state secondary battery 100C including a laminate 1C including a positive electrode layer 10C having a flat portion and a negative electrode layer 20C having a curved portion as shown in FIG. 3, the cover of the ceramic setter on one end side from which the positive electrode extends is set so that the height h of the side surface of the laminate from the ceramic setter for the base does not cause warping of the positive electrode layer 10C. ０ The lid on the end where the negative electrode extends is arranged to have a height h ０ The lid may be placed at a higher position than the baking step.

[0082] The all-solid-state secondary battery 100C can also provide the same effects as the all-solid-state secondary batteries 100A and 100B.

[0083] Fig. 4 is a cross-sectional view showing another modified example of the all-solid-state secondary battery of Fig. 1. A laminate 1D of an all-solid-state secondary battery 100D shown in Fig. 4 includes a plurality of positive electrode layers 10A, 10D, and 10E and a plurality of negative electrode layers 20D, 20E, and 20F. In the all-solid-state secondary battery 100D, the positive electrode layers 10 and the negative electrode layers 20 are alternately stacked with the solid electrolyte layer 30 interposed therebetween. The laminate 1D has voids 50a and 50g in a region surrounded by the positive electrode layer 10A and the first surface S1 and in a region surrounded by the negative electrode layer 20E, the solid electrolyte layer 30, and the second surface S2.

[0084] Among the electrode layers, each of which includes a plurality of positive electrode layers 10A, 10D, and 10E and a plurality of negative electrode layers 20D, 20E, and 20F, the positive electrode layer 10A and the negative electrode layer 20F located at the ends in the stacking direction are, for example, composed of a current collector and an active material layer provided on the inner side of the current collector in the stacking direction. Of the electrode layers, the remaining electrode layers, excluding the positive electrode layer 10A and the negative electrode layer 20F located at the ends in the stacking direction, include, for example, a current collector and an active material layer provided on both of the main surfaces of the current collector. For example, the positive electrode layers 10D and 10E include a positive electrode current collector 11 and a positive electrode active material layer 12 provided on both of the main surfaces of the positive electrode current collector 11. The negative electrode layer 20D includes a negative electrode current collector 21 and a negative electrode active material layer 22 provided on both of the main surfaces of the negative electrode current collector 21. The negative electrode layer 20E includes a negative electrode current collector and negative electrode active material layers 22Ew1 and 22Ew2 provided on both sides of the negative electrode current collector's main surface. The negative electrode layer 20E includes, for example, a negative electrode current collector having a flat portion 21Ep extending in a direction intersecting the stacking direction and having a substantially flat shape, and a curved portion 21Ew located closer to the negative electrode external terminal 3 than the flat portion 21Bp and curved in the stacking direction, and negative electrode active material layers 22Ew1 and 22Ew2 having a flat portion 22Ep extending in a direction intersecting the stacking direction and having a substantially flat shape, and a curved portion 22Ew located closer to the negative electrode external terminal 3 than the flat portion 22Bp and curved in the stacking direction. Furthermore, a region of the solid electrolyte layer that overlaps with the curved portion 22Ew in the stacking direction and that sandwiches a gap 50g between the curved portion 22Ew and the solid electrolyte layer curved portion 31Ew is referred to as the solid electrolyte layer curved portion 31Ew. The curved portion 31Ew of the solid electrolyte layer is peeled off from the negative electrode active material layer 22E. The void 50g has, for example, a length L50g in the x direction and a height h50g in the z direction. The angle between the two adjacent layers that define the void 50g, that is, the negative electrode active material layer 22Ew2 and the interlayer solid electrolyte layer 31, is calculated based on, for example, the length L50g and the height h50g.

[0085] In the all-solid-state secondary battery 100D, one of the four outermost positive electrode layers and outermost negative electrode layers located at the ends in the stacking direction among the plurality of positive electrode layers and negative electrode layers is in contact with the void 50a. The contact of the outermost positive electrode layer and the outermost negative electrode layer with the void makes it easier to obtain the effect of suppressing cracks.

[0086] In an all-solid-state secondary battery including a plurality of positive electrode layers and a plurality of negative electrode layers, such as the all-solid-state secondary battery 100D, the ratio of the sum of the number of positive electrode layers in contact with voids and the number of negative electrode layers in contact with the voids to the total number of the plurality of positive electrode layers 10A, 10D, and 10E and the plurality of negative electrode layers 20D, 20E, and 20F is preferably 10% or more, more preferably 15% or more, and more preferably 20% or more. When the ratio of electrode layers in contact with voids to the total number of the plurality of positive electrode layers and negative electrode layers is within the above range, an all-solid-state secondary battery having a plurality of positive electrode layers and negative electrode layers has electrode active materials that expand and contract during charge and discharge and serve as origins of stress at various positions, which may result in cracks occurring at various positions in the laminate. However, in the laminate 1D, the ratio of electrode layers in contact with voids is 10% or more, so that the stress on the solid electrolyte layer 30 due to the expansion and contraction of the active materials during charge and discharge can be alleviated at various positions in the laminate 1D, making it easier to achieve the effect of suppressing cracks.

[0087] Fig. 5 is a cross-sectional view showing another modified example of the all-solid-state secondary battery of Fig. 1. The all-solid-state secondary battery 100E shown in Fig. 4 includes a positive electrode layer composed of a positive electrode current collector 11F and a positive electrode active material layer 12F, and a negative electrode layer composed of a negative electrode current collector 21F and a negative electrode active material layer 22F.

[0088] The positive electrode current collector 11F has a flat portion 11Fp having a substantially flat shape and a curved portion 11Fw that is curved in the stacking direction and is located closer to the positive electrode external terminal 2 than the flat portion 11Fp. The positive electrode active material layer 12F has a flat portion 12Fp having a substantially flat shape and a curved portion 12Fw that is located closer to the positive electrode external terminal 2 than the flat portion 12Fp and is curved in the stacking direction.

[0089] 5, in the all solid state secondary battery according to this embodiment, the positive electrode current collector 11F and the positive electrode active material layer 12F constituting the positive electrode layer 10F, and the negative electrode current collector 21F and the negative electrode active material layer 22F constituting the negative electrode layer 20F all have a shape that is convex in the −z direction. Even with this all solid state secondary battery 100E, the same effects as those of the all solid state secondary battery according to the above embodiments can be obtained.

[0090] FIG. 6 is a cross-sectional view showing another modified example of the all-solid-state secondary battery of FIG. 1 . In the all-solid-state secondary battery 100F shown in FIG. 6 , at least one of the electrode layers included in the positive electrode layer and the negative electrode layer contains a material that functions as both an electrode active material and an electrode current collector. In the example shown in FIG. 6 , the negative electrode layer 20F contains a material that functions as both an negative electrode active material and a negative electrode current collector, and is, for example, composed of this material. Of the positive electrode layer and the negative electrode layer, an electrode layer that contains a material that functions as both an electrode active material and an electrode current collector may be referred to as an integrated layer. In an integrated layer, it can be said that the electrode active material layer and the electrode current collector layer are integrated.

[0091] An example of a material that functions as both the negative electrode active material and the negative electrode current collector is AgPd, but it may also be a Si alloy, a Sn alloy, etc. The negative electrode layer 20F may contain AgPd or the like and be composed of an AgPd alloy, for example.

[0092] 6, the integral layer has, for example, a flat portion 20Fp and a curved portion 20Fw. The integral layer has, for example, the flat portion 20Fp that extends in a direction intersecting the stacking direction and has a substantially flat shape, and the curved portion 20Fw that is positioned closer to the negative electrode external terminal 3 than the flat portion 20Fp and curves in the stacking direction.

[0093] The angle between the curved portion 20Fw and the negative electrode external terminal 3, the shape of the curved portion 20Fw, and the angle between the flat portion 20Fp and the curved portion 20Fw can be the same as in the above embodiment. The void 50f is defined by the negative electrode layer 20F, the solid electrolyte layer 31, and the second surface S2. The angle, length L50f, and height h50f of the void 50f are the same as in the above embodiment and are calculated by the same method.

[0094] Although an example in which the negative electrode layer is an integral layer is shown in Fig. 6, the positive electrode layer may also be an integral layer. Also, although an example in which the negative electrode layer 20F has a flat portion 20Fp and a curved portion 20Fw is shown in Fig. 6, the negative electrode layer 20F may also be configured to have the flat portion 20Fp.

[0095] In this embodiment, the outermost positive electrode layer and the outermost negative electrode layer refer to the positive electrode layer and the negative electrode layer located at the outermost positions in the stacking direction, respectively. An all-solid-state secondary battery having two or more positive electrode layers and two or more negative electrode layers has two or more outermost positive electrode layers and two or more outermost negative electrode layers. In an all-solid-state secondary battery having one positive electrode layer and one negative electrode layer as shown in Figures 1 to 3 and 5, both electrode layers correspond to the outermost positive electrode layer or the outermost negative electrode layer. The voids 50a to 50h formed in the stack may be formed continuously in the y direction or may be formed partially in the y direction.

[0096] The all-solid-state secondary batteries 100A, 100B, 100C, 100D, and 100E according to the above embodiments can be implemented by appropriately combining their characteristic configurations. The all-solid-state secondary batteries according to the above embodiments may be implemented by swapping the shapes of the positive electrode and the negative electrode.

[0097] In the above embodiment, the margin layer 32 is included in the solid electrolyte layer 30, but the margin layer 32 may contain a compound other than the solid electrolyte in addition to the solid electrolyte. The solid electrolyte contained in the margin layer 32 may be different from the solid electrolyte contained in the interlayer solid electrolyte layer 31. The interlayer solid electrolyte layer 31 includes not only the solid electrolyte layer provided between the positive electrode layer 10 and the negative electrode layer 20, but also a solid electrolyte layer located outside the outermost electrode layer in the stacking direction.

[0098] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0099] Example 1 In Example 1, an all-solid-state secondary battery was fabricated having a laminate in which 10 positive electrode layers and 10 negative electrode layers were alternately provided with solid electrolyte layers interposed therebetween, and its characteristics were evaluated.

[0100] <Preparation of Stack> In Example 1, an all-solid-state secondary battery including a stack having 20 electrode layers in which four electrode layers are in contact with a void was prepared by the following procedure.

[0101] (Preparation of Paste for Solid Electrolyte Layer) Li １．３ Al ０．３ Ti １．７(P.O. ４ ) ３ To 100 parts of the powder, 100 parts of ethanol and 200 parts of toluene were added as a solvent, and the mixture was wet-mixed in a ball mill. Then, 16 parts of a polyvinyl butyral binder and 4.8 parts of benzyl butyl phthalate as a plasticizer were further added and mixed to prepare an outermost solid electrolyte layer paste. This solid electrolyte layer paste was formed into sheets using a doctor blade method with a PET film as a substrate, to obtain an outermost solid electrolyte layer sheet and an interlayer solid electrolyte layer sheet. The thicknesses of the outermost solid electrolyte layer sheet and the interlayer solid electrolyte layer sheet were both 20 μm.

[0102] (Preparation of Positive Electrode Active Material Layer Paste and Negative Electrode Active Material Layer Paste) The positive electrode active material layer paste and the negative electrode active material layer paste were prepared by adding Li ３ V ２ (P.O. ４ ) ３ To 100 parts of the powder, 15 parts of ethyl cellulose as a binder and 65 parts of dihydroterpineol as a solvent were added, and the mixture was mixed and dispersed to prepare a paste for a positive electrode active material layer and a paste for a negative electrode active material layer.

[0103] (Preparation of Positive Electrode Current Collector Paste and Negative Electrode Current Collector Paste) A positive electrode current collector paste and a negative electrode current collector paste were prepared by adding 100 parts of Cu as a current collector, 10 parts of ethyl cellulose as a binder, and 50 parts of dihydroterpineol as a solvent, mixing and dispersing the mixture.

[0104] (Preparation of void-forming resin paste) A void-forming resin paste was prepared by mixing and dispersing 10 parts of ethyl cellulose as a binder and void-forming resin and 50 parts of dihydroterpineol as a solvent.

[0105] (Fabrication of Electrode Units) A positive electrode unit and a negative electrode unit were fabricated as follows. An active material layer paste was printed on the interlayer solid electrolyte layer sheet to a thickness of 5 μm by screen printing. Next, the printed active material layer paste was dried, and a current collector paste was printed thereon to a thickness of 5 μm by screen printing. Next, the printed current collector paste was dried, and another active material layer paste was printed thereon to a thickness of 5 μm by screen printing. The printed active material layer paste was dried, and then the PET film was peeled off. In this way, an electrode unit sheet was obtained in which the active material layer paste, current collector paste, and active material layer paste were printed and dried in this order on the interlayer solid electrolyte layer sheet.

[0106] (Fabrication of Electrode Units in Contact with Voids) In Example 1, electrode units with electrode layers not in contact with voids were fabricated using the above procedure, and electrode units with electrode layers in contact with voids were fabricated using the following procedure. To fabricate electrode units with electrode layers in contact with voids, ethyl cellulose was used as a resin when fabricating positive electrode units and negative electrode units. In Example 1, a region surrounded by a positive electrode layer and a first surface, which is the side surface of the laminate that is bonded to the positive electrode layer, was defined as a first region; a region surrounded by a positive electrode layer, a solid electrolyte layer, and the first surface was defined as a second region; a region surrounded by a negative electrode layer and a second surface, which is the side surface of the laminate that is bonded to the negative electrode layer, was defined as a third region; and a region surrounded by a negative electrode layer, a solid electrolyte layer, and the second surface was defined as a fourth region. The following procedure was performed to fabricate a laminate having voids in the first and third regions.

[0107] The positive electrode unit, which becomes a positive electrode layer having a void in the first region, was formed by applying a paste for a positive electrode current collector, and then applying a resin paste to one end of the paste for the positive electrode current collector in the in-plane direction by screen printing to form a resin part with a thickness of 2 μm. Next, a paste for a positive electrode active material layer was screen-printed on the surface of the resin part and the paste for the positive electrode current collector, and then drying.

[0108] The positive electrode unit, which becomes a positive electrode layer having a void in the second region, was formed by applying a paste for a solid electrolyte layer onto a PET film and drying it, then forming a resin portion having a thickness of 2 μm at one end of the paste for the solid electrolyte in the in-plane direction by screen printing, screen-printing a paste for a positive electrode active material layer so as to overlap the resin portion and an area of ​​the paste for the solid electrolyte that did not overlap with the resin portion, followed by drying, and then screen-printing and drying a paste for a positive electrode current collector and a paste for a positive electrode active material in that order.

[0109] The negative electrode units, which were to become negative electrode layers having voids in the third and fourth regions, were formed by the same procedures as those for the positive electrode unit having voids in the first region and the positive electrode unit having voids in the second region, respectively.

[0110] (Fabrication of Laminate) An outermost solid electrolyte layer sheet was stacked, and 20 electrode units (10 positive electrode units and 10 negative electrode units) were alternately stacked on top of it with the interlayer solid electrolyte layer 31 interposed therebetween. At this time, each unit was stacked with a shift so that the current collector paste layer of the odd-numbered electrode units extended only to one end surface, and the current collector paste layer of the even-numbered electrode units extended only to the opposite end surface. A solid electrolyte layer sheet for the outermost solid electrolyte layer was stacked on top of these stacked units. This was then molded by thermocompression bonding and cut to produce a laminate. The laminate size was 5 mm, 4 mm, and 1 mm in the x, y, and z directions, respectively. Here, the size of the laminate in the z direction before firing was the height h in the above embodiment. ０ That is, in Example 1, h ０ = 1 mm.

[0111] Next, the pre-fired laminate is placed on a ceramic setter for a base, and then height-adjusting laminates are placed on the four corners of the ceramic setter for a base, thereby adjusting the height h of the side of the pre-fired laminate. ０ A ceramic setter for a lid was placed at the same height as the stacked bodies, and then co-fired to obtain a laminate. The co-fired body was heated to a firing temperature of 840°C at a rate of 100°C / hour in a nitrogen atmosphere, and held at that temperature for 2 hours. After firing, the laminated body was allowed to cool naturally.

[0112] (Formation of External Electrode Terminals) Of the side surfaces of the laminate, an external electrode paste was applied to the first surface and the second surface on which the current collector was exposed, and thermally cured at 150°C for 30 minutes to form a positive electrode external terminal and a negative electrode external terminal.

[0113] (Evaluation of Voids) The cross section of the fired laminate of Example 1 was observed with a scanning electron microscope to evaluate the position and shape of voids formed in the laminate. The cross section was prepared on a plane passing through the center of the laminate in the y direction. In the laminate of Example 1, the first region, the second region, the third region, and the fourth region were confirmed to be located in the first positive electrode layer, the tenth positive electrode layer, the first negative electrode layer, and the tenth negative electrode layer from the bottom side, respectively. That is, in the all-solid-state secondary battery of Example 1, the ratio of the sum of the number of positive electrode layers in contact with voids and the number of negative electrode layers in contact with voids to the total number of positive electrode layers and negative electrode layers was 20%. In addition, in the all-solid-state secondary battery of Example 1, all of the outermost positive electrode layers and outermost negative electrode layers located at the ends in the stacking direction were in contact with voids. In addition, all of the voids formed in Example 1 were approximately rectangular, and the angle formed by the voids between two adjacent layers in the laminate defining the voids (edge ​​void angle) was 0°.

[0114] In the all-solid-state secondary battery of Example 1, the distance between the negative electrode layer and the first surface in the in-plane direction of the negative electrode layer, the distance between the positive electrode layer and the second surface in the in-plane direction of the positive electrode layer, and the length of the void were measured, and the ratio thereof (void length / distance between the negative electrode layer and the first surface or the distance between the positive electrode layer and the second surface), i.e., (L ５０ａ / L ３２ ) or (L ５０ｂ / L ３２ The length was calculated as the average value of all five positions in the stacking direction of a given electrode layer in a scanning electron microscope image. As a result, the ratio was 1 for all voids.

[0115] [Short-Circuit Resistance Test] 1,000 all-solid-state secondary batteries identical to those in Example 1 were prepared. Each all-solid-state secondary battery was sandwiched between spring probes so that the positive and negative external terminals faced each other, and a charge-discharge test was performed to measure the initial discharge capacity and the short-circuit occurrence rate after 1,000 cycles of the all-solid-state secondary batteries. The measurement conditions were a constant current charge (CC charge) at a 25°C environment at a constant current of 1 C rate until the battery voltage reached 1.6 V, and then discharge at a constant current of 1 C rate until the battery voltage reached 0 V (CC discharge). This charge and discharge constituted one cycle, and the short-circuit occurrence rate was calculated from the number of all-solid-state secondary batteries that were short-circuited among 100 all-solid-state secondary batteries that were repeatedly cycled up to 1,000 times. A short circuit was determined when the voltage suddenly dropped during CC charge and then stopped increasing. As a result, of the 1,000 all-solid-state secondary batteries, 8 all-solid-state secondary batteries were short-circuited after 1,000 cycles. That is, the rate of occurrence of short circuits after 1000 cycles of the all-solid-state secondary battery of Example 1 was 0.8%.

[0116] [Examples 2 to 5] All-solid-state secondary batteries were fabricated under the same conditions as in Example 1, except that the area in which the resin portion was formed was increased and the (gap length / distance between the anode layer and the first surface or the cathode layer and the second surface) was changed for all voids. In Examples 2, 3, 4, and 5, the size of the void from the end in the in-plane direction was changed so that (gap length / distance between the anode layer and the first surface or the cathode layer and the second surface) × 100 (%) was 10%, 50%, 80%, and 150%, respectively. The lengths of the multiple voids provided in one all-solid-state secondary battery were controlled to be approximately the same.

[0117] [Examples 6 to 9] When performing the firing process, a height-adjusting ceramic plate with a height Δh was used, and the height h of the ceramic setter for the lid was adjusted. １ All-solid-state secondary batteries were fabricated under the same conditions as in Example 1, except that the height (Δh) of the height-adjusting ceramic plate was changed to 0.004 mm, 0.034 mm, 0.100 mm, and 0.142 mm in Examples 6, 7, 8, and 9, respectively.

[0118] [Example 10] An all-solid-state secondary battery was produced in the same manner as in Example 1, except that the positions at which the voids were formed in the laminate were changed. In Example 10, the first region and the second region were adjusted to be provided in the fourth and fifth positive electrode layers from the bottom out of 10 positive electrode layers, respectively, and the third region and the fourth region were adjusted to be provided in the fifth and sixth negative electrode layers from the bottom out of 10 negative electrode layers, respectively. In this way, in Example 10, a laminate was produced in which the outermost positive electrode layer and the outermost negative electrode layer were not in contact with any voids.

[0119] [Examples 11 to 14] All-solid-state secondary batteries were fabricated in the same manner as in Example 1, except that the number and position of voids were changed. In Example 11, an all-solid-state secondary battery was fabricated that included a laminate having voids in a first region of the first positive electrode layer from the bottom out of 10 positive electrode layers and 10 negative electrode layers. In Example 12, an all-solid-state secondary battery was fabricated that included a laminate having voids in a first region of the first positive electrode layer from the bottom out of 10 positive electrode layers and in a third region of the first negative electrode layer from the bottom out of 10 negative electrode layers. In Example 13, an all-solid-state secondary battery was fabricated including a laminate adjusted so that voids were provided in first regions of the first, third, fifth, seventh, and tenth positive electrode layers from the bottom side among ten positive electrode layers, and in third regions of the first, second, fourth, sixth, eighth, and tenth negative electrode layers from the bottom side among ten negative electrode layers. In Example 14, an all-solid-state secondary battery was fabricated so that all electrode layers were in contact with voids.

[0120] Comparative Example 1 An all-solid-state secondary battery was produced in the same manner as in Example 1, except that no resin part was used and paste for an electrode layer or a solid electrolyte layer was used in the places where a resin part would have been used.

[0121] The all-solid-state secondary batteries produced in Examples 2 to 13 and Comparative Example 1 were evaluated in the same manner as in Example 1. The results are shown in Table 1. In each of Examples 2 to 14 and Comparative Example 1, in examples in which a plurality of voids were formed, the plurality of voids had approximately the same shape.

[0122]

[0123] When the cross sections were observed using a scanning electron microscope, it was confirmed that in Examples 1 to 14, the number of cracks extending from the non-extending end of the electrode layer toward the electrode active material layer having a polarity opposite to that of the electrode layer was smaller and the length of the cracks was shorter than in Comparative Example 1. Furthermore, in Examples 2 to 5 and 10 to 14, no curved portions were observed, and all voids were approximately flat, as in Example 1. On the other hand, in Examples 6, 7, 8, and 9, curved portions were observed in at least one of the electrode layer and the solid electrolyte layer, and the angles formed by the voids between the two layers that defined the voids were 1°, 10°, 30°, and 45°, respectively.

[0124] When Examples 1 to 14 are compared with Comparative Example 1, the incidence of short circuits is reduced in all Examples compared to Comparative Example 1. Therefore, it was confirmed that the formation of voids in the laminate in at least one region surrounded by the electrode layer and the electrode active material layer, and in the region surrounded by the electrode layer, the solid electrolyte layer, and the electrode active material layer, suppresses the occurrence of cracks and reduces the incidence of short circuits. Comparing Examples 1 to 5, it was confirmed that the ratio in the in-plane direction (length of void / distance between the negative electrode layer and the first surface, or the distance between the positive electrode layer and the second surface) × 100 (%) is greater than 10% and less than 150%, thereby further suppressing the incidence of short circuits, and that the ratio is 50% or more and 100% or less, thereby further suppressing the incidence of short circuits. It is believed that the reason the incidence of short circuits increases when the ratio is equal to or greater than a predetermined value compared to when it is within a predetermined range is that cracks are more likely to occur toward the voids. Comparing Example 1 with Examples 6 to 9, it was confirmed that when the angle between the two layers defining the void in the laminate was 30° or less, the incidence of short circuits was reduced compared to when the angle was 45°. This is thought to be due to the increased movement in the z-direction during expansion and contraction due to charging and discharging, making cracks more likely to occur. Comparing Example 1 with Example 10, in which the outermost electrode layer and the void were in contact, showed a lower incidence of short circuits compared to Example 10, in which the outermost electrode layer and the void were not in contact. This confirmed the effectiveness of providing a void in contact with the outermost electrode layer in improving cycle characteristics. Comparing Examples 1, 11, 12, 13, and 14, the incidence of short circuits decreased in the order of the percentage of electrode layers in contact with the void (100%, 50%, 20%), confirming the effectiveness of forming a void in contact with the electrode layer.

[0125] [Example 15] An all-solid-state secondary battery was fabricated in the same manner as in Example 1, except that the materials for the solid electrolyte, the positive electrode layer, and the negative electrode layer were changed. In Example 15, when fabricating the solid electrolyte layer, LATP in the solid electrolyte paste was replaced with Li ３．５ Si ０．５ P ０．５ O ４The procedure was the same as in Example 1, except that the LVP in the paste for the positive electrode active material layer was changed to LiCoO ２ The same procedure as in Example 1 was carried out except that the LVP in the paste for the negative electrode active material layer was changed to (LCO) and Cu in the paste for the positive electrode current collector was changed to AgPd. The same procedure as in Example 1 was carried out to produce a negative electrode unit except that the LVP in the paste for the negative electrode active material layer was changed to AgPd and Cu in the paste for the negative electrode current collector was changed to AgPd.

[0126] Except for using the above paste, the all-solid-state secondary battery of Example 15 was fabricated in the same manner as in Example 1. That is, in Example 15, the negative electrode layer was an integrated layer in which the negative electrode current collector and the negative electrode active material layer were integrated.

[0127] [Examples 16 to 19] All-solid-state secondary batteries of Examples 16 to 19 were produced in the same manner as in Examples 2 to 5, except that the materials for the solid electrolyte, the positive electrode layer, and the negative electrode layer were changed in the same manner as in Example 15. Examples 16 to 19 were all the same in conditions other than (gap length / distance between the negative electrode layer and the first surface or the positive electrode layer and the second surface).

[0128] [Examples 20 to 23] All-solid-state secondary batteries of Examples 20 to 23 were fabricated in the same manner as in Examples 6 to 9, except that the materials for the solid electrolyte, the positive electrode layer, and the negative electrode layer were changed in the same manner as in Example 15. In Examples 20 to 23, the conditions were the same except for the angle of the voids.

[0129] [Examples 24 to 28] All-solid-state secondary batteries of Examples 24 to 28 were fabricated in the same manner as in Examples 10 to 14, except that the materials for the solid electrolyte, the positive electrode layer, and the negative electrode layer were changed in the same manner as in Example 15. Examples 24 to 28 were the same in conditions other than the number and arrangement of voids.

[0130] [Examples 29 to 32] All-solid-state secondary batteries were fabricated in the same manner as in Example 15, except that the thickness of the active material layer paste printed by screen printing on the interlayer solid electrolyte layer sheet and the thickness of the active material layer paste printed on the dried current collector paste were changed. Examples 29 to 32 had the same conditions except for the thickness of the active material layer paste.

[0131] [Comparative Examples 2 to 5] All-solid-state secondary batteries were fabricated in the same manner as in Example 1, except that no resin part was used and paste for the electrode layer or solid electrolyte layer was used in the places where the resin part would have been used.

[0132] [Evaluation] The all-solid-state secondary batteries produced in Examples 15 to 32 and Comparative Examples 2 to 5 were evaluated in the same manner as in Example 1. The results are shown in Table 2. In each of Examples 15 to 32 and Comparative Examples 2 to 5, in examples in which a plurality of voids were formed, the plurality of voids had approximately the same shape.

[0133]

[0134] When the cross sections were observed using a scanning electron microscope, it was confirmed that in Examples 15 to 32, the number of cracks extending from the non-extending end of the electrode layer toward the electrode active material layer having a polarity opposite to that of the electrode layer was smaller and the length of the cracks was shorter than in Comparative Examples 2 to 5. Furthermore, in Examples 16 to 29 and 24 to 32, similar to Example 1, no curved portions were observed, and all voids were substantially flat. On the other hand, in Examples 20, 21, 23, and 24, curved portions were observed in at least one of the electrode layer and the solid electrolyte layer, and the angles formed by the gap between the two layers defining the void were 1°, 10°, 30°, and 45°, respectively. Comparing Examples 15 to 32 with Comparative Example 3, the incidence of short circuits was reduced in all Examples compared to Comparative Example 3. Therefore, it was confirmed that the formation of voids in the laminate in at least one region surrounded by the electrode layer and the electrode active material layer, and in the region surrounded by the electrode layer, the solid electrolyte layer, and the electrode active material layer, suppresses the occurrence of cracks and reduces the incidence of short circuits. Furthermore, by comparing Example 29, Example 1, Examples 30 to 32, and Comparative Examples 2 to 5, it was confirmed that the short circuit occurrence rate differs significantly depending on the presence or absence of voids, even in all-solid-state secondary batteries having the same thickness of the active material.

[0135] Furthermore, a comparison between Comparative Example 3 and Comparative Example 1 confirmed that the short circuit occurrence rate was particularly high when the electrode layer contained AgPd. Furthermore, a comparison between Examples 1 to 14 and Examples 15 to 28 confirmed that when the electrode layer contained AgPd, the effect of suppressing the short circuit occurrence rate was particularly high when voids were provided.

[0136] Example 33 An all-solid-state secondary battery was produced in the same manner as in Example 1, except that LATP in the paste for the solid electrolyte layer was changed to LSPO.

[0137] Example 34 An all-solid-state secondary battery was produced in the same manner as in Example 1, except that LATP in the paste for the solid electrolyte layer was changed to LSPO, Cu in the paste for the negative electrode current collector was changed to AgPd, and LVP in the paste for the negative electrode active material layer was changed to AgPd.

[0138] Example 35 An all-solid-state secondary battery was produced in the same manner as in Example 1, except that the LVP in the paste for the positive electrode active material layer was changed to LCO, the Cu in the paste for the positive electrode current collector was changed to AgPd, the LVP in the paste for the negative electrode active material layer was changed to AgPd, and the Cu in the paste for the negative electrode current collector was changed to AgPd.

[0139] Example 36 An all-solid-state secondary battery was produced in the same manner as in Example 1, except that LVP in the paste for the positive electrode active material layer was changed to LCO and Cu in the paste for the positive electrode current collector was changed to AgPd.

[0140] [Evaluation] The all-solid-state secondary batteries of Examples 33 to 36 were evaluated in the same manner as the all-solid-state secondary battery of Example 1. The results are shown in Table 3. In Examples 33 to 36, in which a plurality of voids were formed, the plurality of voids had approximately the same shape. It was confirmed that the incidence of short circuits could be suppressed in all Examples compared to Comparative Examples 1 to 5.

[0141]

[0142] 1A, 1B, 1C, 1D, 1E: Laminated body, 2: Positive electrode external terminal, 3: Negative electrode external terminal, 10A, 10B, 10C, 10D, 10E, 10F: Positive electrode layer, 11, 11A, 11B, 11C: Positive electrode current collector, 11Aw: Curved portion (positive electrode current collector curved portion), 11Ap, 11Bp, 11Cp: Flat portion (positive electrode current collector flat portion), 11Bx: Extended portion (positive electrode current collector extended portion), 12, 12A: Positive electrode active material layer, 12Ap: Flat portion (positive electrode active material layer flat portion), 20A, 20B, 20C, 20D, 20E, 20F: Negative electrode layer, 21, 21A, 21C, 21E: Negative electrode current collector, 21Cp, 21 Ep: Flat portion (flat portion of negative electrode current collector), 21Cw, 21Ew, 21Fw: Curved portion (curved portion of negative electrode current collector), 22, 22A, 22B, 22Ew1, 22Ew2: Negative electrode active material layer, 22Ew1, 22Ew2, 22Fw: Curved portion (curved portion of negative electrode active material layer), 30: Solid electrolyte layer, 31: Interlayer solid electrolyte layer, 32: Masking layer, 50a, 50b, 50c, 50d, 50e, 50f, 50g: Gap, E10, E20, E20D: Extended end, S1: First surface, S2: Second surface, St: Top surface, Sb: Bottom surface, 100A, 100B, 100C, 100D: All-solid-state secondary battery

Claims

1. a laminate in which a positive electrode layer including a positive electrode active material and a negative electrode layer including a negative electrode active material are laminated with a solid electrolyte layer interposed therebetween; a positive electrode external terminal that is joined to the positive electrode layer on a first surface of the side surfaces of the laminate, and a negative electrode external terminal that is joined to the negative electrode layer on a second surface of the side surfaces of the laminate that is different from the first surface; Equipped with The positive electrode layer extends in a direction from the first surface to the second surface, the negative electrode layer extends in a direction from the second surface toward the first surface, The laminate comprises: A region surrounded by the positive electrode layer and the first surface; a region surrounded by the positive electrode layer, the solid electrolyte layer, and the first surface; a region surrounded by the negative electrode layer and the second surface; a region surrounded by the negative electrode layer, the solid electrolyte layer, and the second surface; A void is formed in at least one region of the all-solid-state secondary battery.

2. In an in-plane direction of the negative electrode layer, a ratio of a length of the gap to a distance between the negative electrode layer and the first surface is 20% to 100%, 2. The all-solid-state secondary battery according to claim 1, wherein a ratio of the length of the void to the distance between the positive electrode layer and the second surface in an in-plane direction of the positive electrode layer is 20% to 100%.

3. 2. The all-solid-state secondary battery according to claim 1, wherein an angle between the two layers defining the void is 30° or less.

4. the laminate comprises a plurality of positive electrode layers including an outermost positive electrode layer located at an end in a stacking direction, a plurality of negative electrode layers including an outermost negative electrode layer located at an end in a stacking direction, and a plurality of solid electrolyte layers; The laminate comprises: a region surrounded by the outermost positive electrode layer and the first surface; a region surrounded by the outermost positive electrode layer, the solid electrolyte layer, and the first surface; a region surrounded by the outermost negative electrode layer and the second surface; a region surrounded by the outermost negative electrode layer, the solid electrolyte layer, and the second surface; The all-solid-state secondary battery according to claim 1 , wherein a void is formed in at least one of the regions.

5. The laminate includes a plurality of positive electrode layers and a plurality of negative electrode layers, 2. The all-solid-state secondary battery according to claim 1, wherein a ratio of a sum of a number of the positive electrode layers in contact with the gap and a number of the negative electrode layers in contact with the gap to a total number of the plurality of positive electrode layers and the plurality of negative electrode layers is 10% or more.

6. the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer, the negative electrode layer includes a negative electrode current collector and a negative electrode active material layer, The all-solid-state secondary battery according to claim 1 , wherein the void is in contact with the positive electrode active material layer or the negative electrode active material layer.

7. 2. The all-solid-state secondary battery according to claim 1, wherein at least one of the positive electrode active material and the negative electrode active material is AgPd.