Solid-state battery and method for producing same

Abstract

This solid-state battery comprises: a battery element that is obtained by alternately laminating positive electrode layers and negative electrode layers with solid electrolyte layers interposed therebetween; insulating layers that are respectively disposed on side surfaces of the battery element, the insulating layers facing each other in parallel with the lamination direction; and a pair of external electrodes that are disposed so as to cover the respective insulating layers. The pair of external electrodes each include lead-out portions that extend so as to penetrate local sections of the insulating layers, are respectively formed in recesses disposed on connection end surfaces of electrode layers of one type selected from the positive electrode layers and the negative electrode layers, and electrically connect the electrode layers of the one type to one of the pair of external electrodes.

Description

Solid-state battery and method of manufacturing the same

[0001] The present disclosure relates to solid-state batteries and methods for manufacturing the same.

[0002] In a conventional solid-state battery including a battery element in which multiple electrode layers (positive and negative electrode layers) are stacked with a solid electrolyte layer interposed therebetween and a pair of external electrodes on the side surfaces of the battery element along the stacking direction, an insulating layer is disposed between the electrode layers and the external electrodes to prevent short circuits between the electrode layers and the external electrodes. For example, in the solid-state battery disclosed in Patent Document 1, the battery element is formed by stacking layers in which such insulating layers are disposed on the same plane as the extending electrode layers. In addition, in the solid-state battery disclosed in Patent Document 2, an insulating layer is partially provided on the side surfaces of the battery element in which the end surfaces of the electrode layers and the solid electrolyte layers are substantially flush with each other.

[0003] International Publication No. WO 2019 / 176940 International Publication No. WO 2023 / 089874

[0004] However, as a result of intensive research, the present inventors have found that the solid state batteries described in Patent Documents 1 and 2 still have room for improvement in terms of increasing the capacity of the solid state battery, as well as the connection stability and contact resistance between the electrode layer and the external electrode.

[0005] The present disclosure has been made in view of the above-mentioned problems, and a main object of the present disclosure is to provide a solid-state battery that has higher capacity, lower resistance, and excellent reliability.

[0006] In order to solve the above problems, a solid-state battery according to one embodiment of the present disclosure includes: a battery element formed by alternately stacking positive electrode layers and negative electrode layers with solid electrolyte layers interposed therebetween; an insulating layer disposed on side surfaces of the battery element that are parallel to the stacking direction and face each other; and a pair of external electrodes disposed so as to cover the insulating layer, wherein the pair of external electrodes each have a lead-out portion that extends to penetrate a local portion of the insulating layer, is formed in a recess that is disposed on a connection end surface of one of the positive electrode layer and the negative electrode layer, and electrically connects the one electrode layer to one of the pair of external electrodes.

[0007] A method for manufacturing a solid-state battery according to another embodiment of the present disclosure is a method for manufacturing the above-mentioned solid-state battery, comprising: forming a through-hole in a local portion of the insulating layer covering the entire end face of the battery element, and a recess connected to the through-hole in a connection end face of one of the electrode layers of the positive electrode layer and the negative electrode layer; and filling the through-hole and the recess with a conductive paste to form an extraction portion.

[0008] The present disclosure can provide a solid-state battery with higher capacity, lower resistance, and excellent reliability.

[0009] FIG. 1A is a perspective view schematically illustrating the configuration of a solid-state battery according to a first embodiment of the present disclosure. FIG. 1B is a cross-sectional view (cross-sectional view A-A in FIG. 1A ) schematically illustrating the configuration of a solid-state battery according to a first embodiment of the present disclosure. FIG. 1C is a cross-sectional view (cross-sectional view B-B in FIG. 1A ) schematically illustrating the configuration of a solid-state battery according to a first embodiment of the present disclosure. FIG. 2 is an enlarged cross-sectional view (enlarged cross-sectional view of portion I in FIG. 1B ) schematically illustrating the configuration of a solid-state battery according to a first embodiment of the present disclosure. FIG. 3A is a process plan view schematically illustrating a manufacturing process of a solid-state battery according to a first embodiment of the present disclosure. FIG. 3B is a process plan view schematically illustrating a manufacturing process of a solid-state battery according to a first embodiment of the present disclosure. FIG. 3C is a process plan view schematically illustrating a manufacturing process of a solid-state battery according to a first embodiment of the present disclosure. FIG. 4 is an enlarged cross-sectional view schematically illustrating the configuration of a solid-state battery according to a second embodiment of the present disclosure. FIG. 5 is a side view schematically illustrating a method for evaluating adhesion in Examples.

[0010] Hereinafter, a solid-state battery and a manufacturing method thereof according to one aspect of the present disclosure will be described in detail with reference to the drawings as necessary. The drawings include schematic illustrations in part to facilitate understanding of the present disclosure, and may not reflect actual dimensions or proportions.

[0011] The terms "plan view" and "plan view shape" used herein are based on a sketch of the object in a direction parallel to the main surfaces of the electrode layer and the solid electrolyte layer when viewed from above (top side) or below (bottom side), or in a direction parallel to the side surface of the battery element when viewed from the side. Furthermore, the term "cross-sectional view" used herein is based on the shape of the cross section formed when the solid-state battery is cut along a plane perpendicular to a pair of opposing side surfaces of the battery element of the solid-state battery and parallel to the Z direction (the definition of the direction will be described later).

[0012] The "upper and lower directions" and "lower and upper directions" used directly or indirectly in this specification correspond to the upper and lower directions and the left and right directions in the drawings, respectively. Unless otherwise specified, the same symbols or signs indicate the same members, parts, or the same meanings. In a preferred embodiment, the vertically downward direction (i.e., the direction in which gravity acts) can be considered to correspond to the "lower direction" / "bottom side (lower surface side)," and the opposite direction can be considered to correspond to the "upper direction" / "top side (upper surface side, top surface side)."

[0013] Furthermore, in this specification, "on" a substrate, layer, etc., includes not only cases where it is in contact with the upper surface of the substrate, layer, etc., but also cases where it is not in contact with the upper surface of the substrate, layer, etc. In other words, "on" a substrate, layer, etc., includes cases where a new film or layer is formed above the substrate or layer, and / or cases where another film or layer is interposed between the substrate or layer. Furthermore, "on" does not necessarily mean the upper side in the vertical direction. "On" merely indicates the relative positional relationship of the substrate, layer, etc.

[0014] When multiple numerical ranges including only one critical value (numerical ranges including only the lower limit or the upper limit) are listed, these numerical ranges can be arbitrarily combined to form a numerical range including both the upper and lower limits. For example, from numerical ranges including only the lower limit such as 1 or more, 3 or more, and 5 or more, and numerical ranges including only the upper limit such as 10 or less, 8 or less, and 6 or less, a numerical range including both the lower and upper limits can be formed as 1 or more and 10 or less.

[0015] In the following embodiments, the positive electrode side will be described as a representative example, and the contents of this description may be applied mutatis mutandis to the negative electrode side.

[0016] First Embodiment: Solid-State Battery The first embodiment relates to a solid-state battery. The solid-state battery according to the first embodiment includes a battery element formed by alternately stacking positive electrode layers and negative electrode layers with solid electrolyte layers interposed therebetween, an insulating layer disposed on side surfaces of the battery element facing each other and parallel to the stacking direction, and a pair of external electrodes disposed to cover the insulating layer, wherein the pair of external electrodes each have a lead-out portion that extends through a local portion of the insulating layer and is formed in a recess disposed on a connection end surface of one of the positive electrode layer and the negative electrode layer, and electrically connects one of the pair of external electrodes to one of the pair of external electrodes.

[0017] In this specification, the term "local portion" refers to a portion of the insulating layer where the lead portion extends to electrically connect the external electrode and the connection end surface of the electrode layer. The portion of the local portion that penetrates the opposing main surfaces of the insulating layer and is filled with the lead portion is called a filled through hole.

[0018] [Mechanism of Action] The solid-state battery according to the first embodiment has higher capacity, lower resistance, and excellent reliability. The reason for this is presumed, without being bound by any particular theory, to be as follows. In the solid-state battery according to the first embodiment, the pair of external electrodes have lead portions that extend from local portions of the insulating layer and are formed within the recesses of the battery element. The lead portions of the external electrodes are firmly connected to the electrode layers of the battery element by an anchor effect. This allows for high electrical connectivity, excellent reliability, and low resistance. Furthermore, the insulating layer is disposed so as to cover the side surfaces of the battery element. The insulating layer is not disposed so as to align with the extension direction of the electrode layers, as in Patent Document 1. Therefore, compared to Patent Document 1, the insulating layer can reduce dead space in the extension direction of the electrode layers, thereby increasing the space for the electrode layers. This allows for a high capacity solid-state battery. From the above, it is believed that the solid-state battery according to the first embodiment has higher capacity, lower resistance, and excellent reliability.

[0019] [Motivation for Proposing the Solid-State Battery According to the First Embodiment] After extensive research into increasing the capacity of the solid-state battery described in Patent Document 1, the present inventors focused on the arrangement of the insulating layers in the solid-state battery described in Patent Document 1. In Patent Document 1, the insulating layers are arranged so as to align with the extension direction of the electrode layers. It was determined that the insulating layers are provided in excess of what is necessary to ensure insulation between the external electrodes and the electrode layers in the extension direction of the electrode layers, and that this excess space could be used as space for the electrode layers. The inventors discovered that the reason for this unnecessary space is that adopting the above-described arrangement conflicts with the processing limits that can be reduced using current manufacturing methods, such as printing. It was also discovered that adopting a special manufacturing method that overcomes such processing limits would significantly increase costs. Based on the technical knowledge that the dead space is caused by the arrangement of the insulating layers, the present inventors conducted extensive research and came up with the idea of ​​reducing the space occupied by the insulating layers in the extension direction of the electrode layers by changing the arrangement so that the insulating layers cover the side surfaces of the battery element.

[0020] Furthermore, the present inventors conducted extensive research into improving the reliability of the solid-state battery described in Patent Document 2 and found that the adhesion between the external electrodes and the electrode layers was low. Therefore, the inventors came up with the idea of ​​providing a through-hole in the insulating layer, providing a recess in the battery element, and forming an extension portion of the external electrode in the through-hole and the recess, thereby improving the adhesion between the extension portion of the external electrode and the electrode layer through an anchor effect and firmly fixing the external electrode to the battery element, thereby further improving the reliability of the solid-state battery. In this way, the inventors have completed the solid-state battery according to the first embodiment.

[0021] Each component of the solid-state battery 100 will be described below. The solid-state battery according to the first embodiment and each component constituting the solid-state battery will be described primarily with reference to FIGS. 1A, 1B, and 1C. FIG. 1A is a perspective view schematically illustrating the configuration of the solid-state battery according to the first embodiment. FIG. 1B is a cross-sectional view (cross-sectional view A-A in FIG. 1) schematically illustrating the configuration of the solid-state battery according to the first embodiment. FIG. 1C is a cross-sectional view (cross-sectional view B-B in FIG. 1) schematically illustrating the configuration of the solid-state battery package according to the first embodiment. Note that FIG. 1C shows a cross section of the side surface 113a of the battery element 110 when cutting the interface between the side surface 113a of the battery element 110 and the insulating layer 120a in the solid-state battery.

[0022] 1A to 1C, the Z direction is the stacking direction of the electrode layer 111 (positive electrode layer 111a and negative electrode layer 111b) and the solid electrolyte layer 112 in the solid-state battery 100. The X direction is perpendicular to the Z direction and is the opposing direction (long axis direction of the solid-state battery) of a pair of opposing side surfaces (first side surface 113a and second side surface 113b) in the stack (battery element 110) of the solid-state battery 100. The Y direction is perpendicular to the Z direction and the X direction (short axis direction of the solid-state battery). The reverse Z direction is the vertically downward direction, and the forward Z direction is the vertically upward direction. This also applies to the other figures below. In addition, the letter "a" attached to the reference numerals in the drawings denotes the positive electrode layer itself and components related to the positive electrode layer, which are mainly arranged on the left side (relatively on the reverse X direction side) in FIG. 1B. The letter b in the reference numerals in the drawings denotes the negative electrode layer itself and components related to the negative electrode layer, which are mainly arranged on the right side (relatively the side in the forward X direction) in FIG. 1B.

[0023] 1A to 1C , a solid-state battery 100 according to the first embodiment includes a battery element 110 having at least a pair of opposing side surfaces 113 a, 113 b, insulating layers (a first insulating layer 120 a and a second insulating layer 120 b) disposed on the side surfaces 113 a, 113 b of the battery element 110, and a pair of external electrodes 130 a, 130 b disposed so as to cover the insulating layers 120 a, 120 b. The solid-state battery 100 is a stacked-type solid-state battery configured such that electrode layers 111 (a positive electrode layer 111 a and a negative electrode layer 111 b) and solid electrolyte layers 112 constituting battery structural units are stacked on top of each other, and these layers are made of, for example, fired bodies.

[0024] In this specification, the term "solid-state battery" refers in a broad sense to a battery whose components are made of solids, and in a narrow sense to an all-solid-state battery whose components (particularly preferably all components) are made of solids. Examples of the solid-state battery 100 include so-called secondary batteries (more specifically, storage batteries) that can be repeatedly charged and discharged, and primary batteries that can only be discharged.

[0025] [Battery Element] The battery element 110 has at least a pair of side surfaces 113a, 113b facing each other, and has, for example, a substantially rectangular parallelepiped shape. The battery element 110 includes a positive electrode layer 111a, a negative electrode layer 111b, and a solid electrolyte layer 112, as well as an outer layer 115 and an outermost layer 116. The battery element 110 is a laminate in which the positive electrode layers 111a and the negative electrode layers 111b are alternately stacked with the solid electrolyte layer 112 interposed therebetween. The outer layer 115 and the outermost layer 116 protect the layers that contribute to power generation and charging of the battery element 110 (the positive electrode layer 111a, the negative electrode layer 111b, and the solid electrolyte layer 112) from the outside and ensure electrical insulation of the layers that contribute to power generation and charging from the outside.

[0026] The battery element 110 has recesses (first recess 114a, second recess 114b) on the side surfaces 113a, 113b. The first recess 114a is provided so that the connection end surface of the positive electrode layer 111a forms the bottom surface of the first recess 114a. The second recess 114b is provided so that the connection end surface of the negative electrode layer 111b forms the bottom surface of the second recess 114b. Referring to FIG. 2, the recesses will be described using the first recess 114a as an example. FIG. 2 is an enlarged cross-sectional view of part I in FIG. 1. The first recess 114a is composed of a bottom surface 114a2 and a side surface 114a1. The bottom surface 114a2 corresponds to the connection end surface 111a1 of the positive electrode layer 111a. The side surface 114a1 is a surface that forms an angle other than 0° and 180° with respect to the X direction (i.e., an inclined surface), and is connected to the side surface of the first local portion 121a of the first insulating layer 120a that is located on the opposite X direction side.

[0027] The first recess 114a has a tapered shape in which the opening width d decreases from the relatively outer side (i.e., the external electrode 130a side in the X direction) of the solid-state battery 100 toward the inner side (i.e., the positive electrode layer 111a side in the X direction). This makes it easier to inject conductive paste, which is the raw material for the first lead portion 131a, into the first recess 114a in the manufacturing method of the solid-state battery 100, and improves the filling rate of the first lead portion 131a. This increases the contact area between the connection end surface 111a1 of the positive electrode layer 111a and the first lead portion 131a of the first external electrode 130a, thereby reducing the connection resistance and improving the connection strength between the connection end surface 111a1 of the positive electrode layer 111a and the first lead portion 131a.

[0028] As shown in Fig. 1C, the first recess 114a has a substantially uniform shape along the depth direction (Y direction) in Fig. 1B. The shape of the first local portion 121a of the first insulating layer 120a is also the same. In other words, the first lead portion 131a has a quadrangular prism shape with the trapezoidal bottom surface shown in Fig. 2.

[0029] The ridge line of the recess exists on at least one of the connection end surface of one of the electrode layers 111, the positive electrode layer 111a and the negative electrode layer 111b, and the end surface of the solid electrolyte layer 112 adjacent to the electrode layer 111. More specifically, as shown in Figures 1B and 1C, the first recess 114a is formed on the end surfaces of the positive electrode layer 111a, the negative electrode layer 111b, and the solid electrolyte layer 112 that constitute the first side surface 113a of the battery element 110, with the ridge line 114a3 of the first recess 114a existing on the connection end surface 111a1 of the positive electrode layer 111a and the end surface of the solid electrolyte layer 112 adjacent to the positive electrode layer 111a. Here, in this specification, taking the first recess 114a as an example, the ridge line of the recess is a line that defines the first opening 121c of the first recess 114a and is a line that connects the first side surface 113a of the battery element 110 and the side surface 114a1 of the first recess 114a. Because the first recess 114a is a location for disposing the first lead portion 131a that electrically connects the first external electrode 130a and the positive electrode layer 111a, the ridge line of the first recess 114a does not exist on the end surface of the negative electrode layer 111b to ensure insulation, as shown in FIG. 1C .

[0030] In a preferred embodiment, in cross-sectional view, the ratio c / d of the depth c of the first recess 114a to the opening width d of the first recess 114a is 0.002 or more and 10 or less, and the opening width d of the first recess 114a is 0.001 mm or more.

[0031] 1A , the cross section of the solid-state battery 100 is a cut surface obtained by cutting the solid-state battery 100 along a ZX plane passing through the intersection of diagonals on the upper surface of the battery element 110 of the solid-state battery 100. In this specification, the opening width d of the recess 114 refers to the opening width in the Z direction of the recess 114a in the above cross section of the solid-state battery 100.

[0032] In this specification, the depth c of the recess is the length in the internal direction (X direction) of the battery element 110 from the side surface 113 to the bottom surface of the battery element 110 in the above-mentioned cross section of the solid-state battery 100. If the bottom surface of the recess 114 is not flat (for example, if the bottom surface of the recess 114 is curved), the depth c of the recess is the longest length from the side surface 113 of the battery element 110 in the internal direction (X direction) of the battery element 110.

[0033] When the ratio c / d is 0.002 or more, the first lead portion 131a can be more firmly fixed to the first recess 114a, further improving the reliability (regarding connection stability) of the solid-state battery 100. When the opening width d of the first recess 114a is 0.001 mm or more and the ratio c / d is 10 or less, the adhesion strength between the first external electrode 130a and the electrode layer 111 (positive electrode layer 111a) increases, further improving the reliability of the solid-state battery 100. Furthermore, the filling rate of the first lead portion 131a in the first recess 114a improves, which reduces the electrical resistance between the first external electrode 130a and the electrode layer 111 (positive electrode layer 111a), thereby improving the adhesion strength.

[0034] In a more preferred embodiment among the above preferred embodiments, the ratio c / d is 0.01 or more and 10 or less. When the ratio c / d is 0.01 or more and 10 or less, the adhesion strength between the external electrode 130 and the electrode layer 111 increases, and the reliability of the solid state battery 100 is further improved.

[0035] (Electrode Layers: Positive Electrode Layer and Negative Electrode Layer) The positive electrode layer 111a contains a positive electrode active material and may further contain at least one selected from the group consisting of a solid electrolyte, a conductive material, and a sintering aid, and may further include a positive electrode current collecting layer. The negative electrode layer 111b contains at least a negative electrode active material and may further contain at least one selected from the group consisting of a solid electrolyte, a conductive material, and a sintering aid, and may further include a negative electrode current collecting layer. The material constituting the negative electrode layer 111b may be the same as the material constituting the positive electrode layer 111a.

[0036] Active Materials Active materials (positive electrode active materials and negative electrode active materials) are materials involved in the transfer of electrons in the solid-state battery 100. Carriers (ions, particularly lithium ions or sodium ions) move (conduct) between the positive electrode layer 111a and the negative electrode layer 111b via the solid electrolyte, transferring electrons to charge and discharge the battery. The electrode layers 111 (positive electrode layer 111a and negative electrode layer 111b) of the positive electrode layer 111a and the negative electrode layer 111b are preferably layers capable of absorbing and releasing lithium ions or sodium ions, in particular. In other words, the solid-state battery 100 is preferably an all-solid-state secondary battery in which lithium ions or sodium ions move between the positive electrode layer 111a and the negative electrode layer 111b via the solid electrolyte layer 112 to charge and discharge the battery.

[0037] Positive Electrode Active Material Positive electrode active materials capable of absorbing and releasing lithium ions include, for example, at least one selected from the group consisting of lithium-containing phosphate compounds having a Nasicon structure, lithium-containing phosphate compounds having an olivine structure, lithium-containing layered oxides, and lithium-containing oxides having a spinel structure. An example of a lithium-containing phosphate compound having a Nasicon structure is Li3V2(PO4)3. An example of a lithium-containing phosphate compound having an olivine structure is Li3Fe2(PO4)3, LiFePO4, and / or LiMnPO4. An example of a lithium-containing layered oxide is LiCoO2 and / or LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 Examples of lithium-containing oxides having a spinel structure include LiMnO and / or LiNi. 0.5 Mn 1.5O4, etc. Examples of lithium compounds include, but are not limited to, lithium transition metal composite oxides and lithium transition metal phosphate compounds. Lithium transition metal composite oxides are oxides containing lithium and one or more transition metal elements as constituent elements. Lithium transition metal phosphate compounds are phosphate compounds containing lithium and one or more transition metal elements as constituent elements. The type of transition metal element is not particularly limited, but examples include cobalt (Co), nickel (Ni), manganese (Mn), and iron (Fe).

[0038] In addition, as the positive electrode active material capable of absorbing and releasing sodium ions, for example, at least one selected from the group consisting of sodium-containing phosphate compounds having a Nasicon structure, sodium-containing phosphate compounds having an olivine structure, sodium-containing layered oxides, and sodium-containing oxides having a spinel structure can be mentioned. ３ V ２ (P.O. ４ ) ３ , NaCoFe ２ (P.O. ４ ) ３ , Na ２ Ni ２ Fe(PO ４ ) ３ , Na ３ Fe ２ (P.O. ４ ) ３ , Na ２ FeP ２ O ７ and Na ４ Fe ３ (P.O. ４ ) ２ (P ２ O ７ ) and NaFeO as a sodium-containing layered oxide ２ At least one selected from the group consisting of:

[0039] Other examples of the positive electrode active material include oxides, disulfides, and conductive polymers. Examples of oxides include titanium oxide, vanadium oxide, and manganese dioxide. Examples of disulfides include titanium disulfide and molybdenum sulfide. Examples of conductive polymers include disulfides, polypyrrole, polyaniline, polythiophene, polyparastyrene, polyacetylene, and polyacene.

[0040] Negative Electrode Active Material Examples of negative electrode active materials capable of absorbing and releasing lithium ions include at least one selected from the group consisting of oxides containing at least one element selected from the group consisting of titanium (Ti), silicon (Si), tin (Sn), chromium (Cr), iron (Fe), niobium (Nb), and molybdenum (Mo), carbon materials such as graphite, graphite-lithium compounds, lithium alloys, lithium-containing phosphate compounds having a Nasicon structure, lithium-containing phosphate compounds having an olivine structure, and lithium-containing oxides having a spinel structure. An example of a lithium alloy is Li-Al. An example of a lithium-containing phosphate compound having a Nasicon structure is Li3V2(PO4)3 and / or LiTi2(PO4)3. An example of a lithium-containing phosphate compound having an olivine structure is Li3Fe2(PO4)3 and / or LiCuPO4. An example of a lithium-containing oxide having a spinel structure is Li4Ti5O. 12 etc.

[0041] In addition, examples of negative electrode active materials capable of absorbing and releasing sodium ions include at least one selected from the group consisting of sodium-containing phosphate compounds having a Nasicon structure, sodium-containing phosphate compounds having an olivine structure, and sodium-containing oxides having a spinel structure.

[0042] The electrode layer 111 and the solid electrolyte layer 112 preferably have high contrast so that each layer can be recognized when viewed from the side surface 113 of the battery element 110. This facilitates the formation of through holes and recesses in localized portions of the insulating layer 120 corresponding to the electrode layer 111 in the manufacturing method of the solid battery 100 described below. Such high contrast can be adjusted, for example, by making the compositions of the layers different from each other.

[0043] -Solid Electrolyte- The solid electrolyte that can be contained in the electrode layer 111 may be made of the same material as the solid electrolyte contained in the solid electrolyte layer 112, which will be described later.

[0044] -Conductive Material- Examples of the conductive material include at least one conductive material selected from the group consisting of metal materials such as silver, palladium, gold, platinum, aluminum, copper, and nickel, and carbon.

[0045] -Sintering Aid- Examples of the sintering aid include at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, boron oxide, silicon oxide, bismuth oxide, and phosphorus oxide.

[0046] Current Collector Layers—The current collector layers (positive electrode current collector layer and negative electrode current collector layer) may each have the form of a foil. Here, if greater importance is placed on improving electronic conductivity through co-firing, reducing the manufacturing cost of the solid-state battery 100, and / or reducing the internal resistance of the solid-state battery 100, the current collector layers may have the form of a sintered body. The positive electrode current collector constituting the positive electrode current collector layer and the negative electrode current collector constituting the negative electrode current collector layer are preferably made of a conductive material with high conductivity. Examples of such conductive materials include at least one selected from the group consisting of silver, palladium, gold, platinum, aluminum, copper, and nickel. The current collectors (positive electrode current collector and negative electrode current collector) may have electrical connection portions for electrical connection with external electrodes and may be configured to be electrically connectable to the external electrodes 130a and 130b. When the current collector layers have the form of a sintered body, they may be made of a sintered body containing a conductive material and a sintering aid. The conductive material contained in the current collecting layer may be selected from, for example, the same materials as the conductive materials that may be contained in the electrode layer 111. The sintering aids contained in the positive electrode current collecting layer and the negative electrode current collecting layer may be selected from, for example, the same materials as the sintering aids that may be contained in the positive electrode layer 111a and the negative electrode layer 111b, respectively.

[0047] The thickness of the positive electrode layer 111a and the negative electrode layer 111b is not particularly limited, but may be, for example, independently 2 μm or more and 200 μm or less, particularly 5 μm or more and 100 μm or less.

[0048] -Solid Electrolyte Layer- The solid electrolyte layer 112 is interposed between the positive electrode layer 111a and the negative electrode layer 111b and is responsible for carrier conduction between these electrode layers. The thickness of the solid electrolyte layer 112 is not particularly limited, but is, for example, 1 μm or more and 500 μm or less, particularly 1 μm or more and 200 μm or less. In this specification, the thickness of the solid electrolyte layer 112 refers to the thickness of the solid electrolyte layer 112 disposed between the positive electrode layer 111a and the negative electrode layer 111b.

[0049] Solid Electrolyte The solid electrolyte layer 112 includes a solid electrolyte and may further include a sintering aid. The solid electrolyte is a material capable of conducting carriers (e.g., lithium ions or sodium ions). In particular, the solid electrolyte layer 112 constituting a battery structural unit in the solid-state battery 100 may form a layer capable of conducting lithium ions between the positive electrode layer 111a and the negative electrode layer 111b. Examples of the solid electrolyte include at least one selected from the group consisting of crystalline solid electrolytes, glass-based solid electrolytes, and glass-ceramic-based solid electrolytes.

[0050] The solid electrolyte capable of conducting lithium ions will be described. Examples of the crystalline solid electrolyte include oxide-based crystalline materials and sulfide-based crystalline materials. Examples of the oxide-based crystalline materials include lithium-containing phosphate compounds having a Nasicon structure, oxides having a perovskite structure, oxides having a garnet structure or a garnet-like structure, and oxide glass ceramic-based lithium ion conductors. Examples of the lithium-containing phosphate compounds having a Nasicon structure include Li ｘ M ｙ (P.O. ４ ) ３ (1≦x≦2, 1≦y≦2, M is at least one selected from the group consisting of titanium (Ti), germanium (Ge), aluminum (Al), gallium (Ga), and zirconium (Zr)). More specifically, Li １．２ Al ０．２ Ti １．８ (P.O. ４ ) ３ Examples of oxides having a perovskite structure include La ０．５５ Li ０．３５ TiO ３ Examples of oxides having a garnet-type or garnet-like structure include Li ７ La ３ Zr ２ O １２ etc.

[0051] In addition, sulfide-based crystal materials include thio-LISICON, for example, Li ３．２５ Ge ０．２５ P ０．７５S ４ and Li １０ GeP ２ S １２ The crystalline solid electrolyte may include a polymer material (for example, polyethylene oxide (PEO)).

[0052] Examples of glass-based solid electrolytes include oxide-based glass materials and sulfide-based glass materials. Examples of oxide-based glass materials include 50Li ４ SiO ４ ・50Li ３ BO ３ Examples of sulfide-based glass materials include 30Li ２ S・26B ２ S ３ ・44LiI, 63Li ２ S・36SiS ２ ・1Li ３ P.O. ４ , 57Li ２ S・38SiS ２ ・5Li ４ SiO ４ , 70Li ２ S・30P ２ S ５ and 50Li ２ S・50GeS ２ Examples include:

[0053] Examples of glass ceramic solid electrolytes include oxide-based glass ceramic materials and sulfide-based glass ceramic materials. Examples of oxide-based glass ceramic materials include a phosphate compound containing lithium, aluminum, and titanium as constituent elements (LATP) and a phosphate compound containing lithium, aluminum, and germanium as constituent elements (LAGP). Examples of LATP include Li, １．０７ Al ０．６９ Ti １．４６ (P.O. ４ ) ３ Examples of LAGP include Li １．５ Al ０．５ Ge １．５ (P.O. ４) and the like. Examples of sulfide-based glass ceramic materials include Li ７ P ３ S １１ and Li ３．２５ P ０．９５ S ４ Examples include:

[0054] In addition, examples of solid electrolytes capable of conducting sodium ions include sodium-containing phosphate compounds having a Nasicon structure, oxides having a perovskite structure, and oxides having a garnet or garnet-like structure. Examples of sodium-containing phosphate compounds having a Nasicon structure include Na x M y (PO4)3 (1≦x≦2, 1≦y≦2, M is at least one selected from the group consisting of Ti, Ge, Al, Ga and Zr).

[0055] - Sintering Aid - The sintering aid contained in the solid electrolyte layer 112 may be, for example, the same material as the sintering aid that may be contained in the electrode layers (positive electrode layer 111a and negative electrode layer 111b).

[0056] [Insulating Layer] The first insulating layer 120a is disposed on the side surfaces 113a of the battery element 110 that are parallel to the stacking direction and face each other. The first insulating layer 120a covers the first side surface 113a of the battery element 110 and is covered by the first external electrode (positive electrode) 130a. In this manner, the first insulating layer 120a is interposed between the first external electrode (positive electrode) 130a and the battery element 110, and insulates the first external electrode 130a from the battery element 110. However, the first external electrode 130a and the electrode layer 111 (positive electrode layer 111a) of the battery element 110 are electrically connected to each other via a first lead portion 131a filled in the first local portion 121a of the first insulating layer 120a.

[0057] As shown in Figures 1B and 2, the first local portion 121a of the first insulating layer 120a has a rectangular shape in the YZ plane view, and exposes the connection end surfaces 111a1 of all the positive electrode layers 111a that constitute the first side surface 113a of the battery element 110 on the first external electrode (positive electrode) 130a side. As shown in Figure 1C, a plurality of first local portions 121a of the first insulating layer 120a are arranged. In the first embodiment, similar to the positive electrode 130a side, the connection end surfaces 111a1 of all the negative electrode layers 111b that constitute the second side surface 113b of the battery element 110 are exposed on the negative electrode 130b side.

[0058] The total light transmittance of the first insulating layer 120a for visible light is, for example, 50% or more, preferably 60% or less, more preferably 70% or less, even more preferably 80% or more, particularly preferably 90% or more, and very particularly preferably 95% or more, from the viewpoint of forming through holes with high positional accuracy in the manufacturing method of the solid-state battery 100 described below. If the total light transmittance is 50% or more, when a through hole is provided in the first local portion 121a of the first insulating layer 120a in the manufacturing method of the solid-state battery 100 and the through hole exposes the connection end surface 111a1 of one of the electrode layers 111 (here, the positive electrode layer 111a), the position of the connection end surface 111a1 of the electrode layer 111 (the positive electrode layer 111a) can be grasped via the first insulating layer 120a (for example, recognized through a monitor image of a through-hole / recess forming device). The total light transmittance of the first insulating layer 120a for visible light can be controlled by the thickness of the first insulating layer 120a (i.e., the optical path length of visible light) and / or the material of the first insulating layer 120a (e.g., resin component).

[0059] This total light transmittance is assumed to be the total light transmittance when the solid-state battery 100 is viewed from the X direction. In other words, in terms of the total light transmittance, the thickness (length in the X direction) of the first insulating layer 120a corresponds to the optical path length of visible light (light having a wavelength of 380 nm or more and 780 nm or less).

[0060] The thickness of the first insulating layer 120a is 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, or 50 μm or less from the viewpoint of improving the total light transmittance of visible light. The thickness of the first insulating layer 120a is 5 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, or 40 μm or more from the viewpoint of ensuring insulation between the external electrode 130 and the battery element 110.

[0061] The first local portions 121a of the insulating layers 120a, 120b are disposed at positions corresponding to the connection end surface 111a1 of the positive electrode layer 111a on the positive electrode 130a side, and at positions corresponding to the connection end surface of the negative electrode layer 111b on the negative electrode 130b side. This positional relationship between the connection end surface of the electrode layer 111 and the local portions will be described in detail later in the manufacturing method of the solid-state battery 100. This can be achieved by forming the insulating layers 120a, 120b on the entire side surface 113 of the battery element 110, and then forming the local portions of the insulating layers 120a, 120b. The formed insulating layers 120a, 120b are preferably transparent. In other words, the insulating layers have a total light transmittance of, for example, 50% or more for visible light (light having a wavelength of 380 nm or more and 780 nm or less). When the insulating layer 120 has a total light transmittance for visible light of 50% or more, it is possible to form a local portion that exposes the connection end surface of the electrode layer 111, for example, through a monitor image of a through-hole / recess forming device, without using expensive and complicated equipment.

[0062] In a preferred embodiment, as shown in Fig. 2, in a filling through-hole that penetrates the first local portion 121a of the insulating layer 120a and is filled with the first lead portion 131a, the first opening width b of the first opening 121c located relatively outside the solid-state battery 100 (i.e., toward the first external electrode 130a in the X direction) is larger than the second opening width d of the second opening 121d located relatively inside the solid-state battery 100 (i.e., toward the positive electrode layer 111a in the X direction) of the first local portion 121a in a cross-sectional view. In a more preferred embodiment, the opening width decreases from the first opening 121c toward the second opening 121d in a cross-sectional view. More specifically, as shown in Fig. 2, the opening width of the first insulating layer 120a decreases from the relatively outside to the relatively inside of the solid-state battery 100 in a cross-sectional view. That is, the inner surface of the first local portion 121a of the first insulating layer 120a is inclined at an angle other than 0° and 180° with respect to the X direction, and the insulating layer 120 has a tapered shape in cross section. As will be described in detail later in the manufacturing method of a solid-state battery, in such a case, it is easy to form the drawn portion 131a.

[0063] In a preferred embodiment, in a cross-sectional view, the ratio a / b of the thickness a of the insulating layer 120 to the first opening width b of the first opening 121c outside the first local portion 121a is 0.01 or more and 100 or less, and the thickness a of the first insulating layer 120a is 0.005 mm or more. When the ratio a / b is 0.01 or more, the first local portion 121a can be processed with high positional accuracy. Furthermore, the filling rate of the conductive paste in the first local portion 121a is improved, and DC resistance can be reduced. Furthermore, when the thickness a of the first insulating layer 120a is 0.005 mm or more and the ratio a / b is 100 or less, the filling rate of the conductive paste in the first local portion 121a is improved, and DC resistance can be reduced.

[0064] In a more preferred embodiment among the above preferred embodiments, the ratio a / b is 0.01 or greater and 10 or less. When the ratio a / b is 0.01 or greater and 10 or less, the filling rate of the first lead portion 131a is further improved, the adhesion strength between the first external electrode 130a and the electrode layer 111 (positive electrode layer 111a) is increased, and the reliability of the solid-state battery 100 is further improved. Furthermore, the DC resistance can be further reduced.

[0065] The first insulating layer 120a contains at least one resin selected from the group consisting of acrylic resin, imide resin, phenolic resin, urea resin, melamine resin, unsaturated polyester resin, epoxy resin, polyurethane resin, silicon resin (e.g., silicone resin), diallyl phthalate resin, and amino resin. Of these resins, the first insulating layer 120a is preferably made of epoxy resin, from the viewpoint of improving the total light transmittance of the first insulating layer 120a.

[0066] [External Electrodes] The pair of external electrodes 130a, 130b each have a lead portion 131a, 131b. The lead portions 131a, 131b extend to penetrate local portions of the insulating layers 120a, 120b, are formed in a recess 114a disposed on the connection end surface of one of the positive electrode layer 111a and the negative electrode layer 111b, and electrically connect one of the electrode layers 111 to one of the pair of external electrodes 130a, 130b. More specifically, the lead portion 131a electrically connects the external electrode 130a to the positive electrode layer 111a. The lead portion 131b electrically connects the external electrode 130b to the negative electrode layer 111b.

[0067] The first lead portion 131a is arranged to fill the first local portion 121a of the first insulating layer 120a and the first recess 114a of the battery element 110. The first lead portion 131a preferably has a male shape corresponding to the female shape formed by the first local portion 121a of the first insulating layer 120a and the first recess 114a of the battery element 110. In other words, the first lead portion 131a is preferably filled to a shape corresponding to the female shape (i.e., the design shape) by, for example, 60% or more, preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, particularly preferably 95% or more, and very particularly preferably 97% or more. Thus, the higher the filling rate, the larger the contact area with the electrode layer 111 (positive electrode layer 111a) and the lower the contact resistance. In addition, the larger the contact area with the side surface 114a1 and bottom surface 114a2 of the first recess 114a and the side surface of the first local portion 121a of the first insulating layer 120, and the improved connection strength between the first extension portion 131a and the connection end surface of the electrode layer 111 (positive electrode layer 111a).

[0068] The lead portion 131 has a generally trapezoidal shape in cross section (ZX cross section). The width (length in the Z direction) of the lead portion 131 has a tapered shape that decreases relatively from the outside to the inside of the solid state battery 100 in cross section.

[0069] The external electrode 130 includes, for example, at least one metal selected from the group consisting of silver, gold, platinum, aluminum, copper, tin, carbon, and nickel.

[0070] [Method for manufacturing solid-state battery] A method for manufacturing the solid-state battery 100 according to the first embodiment includes the steps of: forming a through hole in the insulating layer 120 covering the entire end face of the battery element 110; and forming a recess connected to the through hole in the connection end face of one of the electrode layers 111, the positive electrode layer 111a and the negative electrode layer 111b (through hole / recess formation step); and filling the through hole 121apr and the recess with a conductive paste to form a lead-out portion (lead-out portion formation step).

[0071] One aspect of the manufacturing method for the solid-state battery 100 according to the first embodiment will be described with reference to FIGS. 3A to 3C. FIGS. 3A to 3C are plan views illustrating the manufacturing process of the solid-state battery according to the first embodiment of the present disclosure. The side surface 113a on the positive electrode 130a side is shown in the manufacturing method for the solid-state battery 100. The manufacturing method for the solid-state battery 100 will be described using the positive electrode 130a side as a representative example. The manufacturing of the solid-state battery 100 was performed at room temperature (25°C), atmospheric pressure (1 atm), and in an open system, unless otherwise noted.

[0072] For example, the manufacturing method of the solid state battery 100 further includes preparing the battery element 110 (battery element preparation step), and forming insulating layers 120a, 120b on the end surfaces of the battery element 110 (insulating layer formation step).

[0073] (Battery Element Preparation Step) In the battery element preparation step, the battery element 110 is prepared by, for example, manufacturing or purchasing.

[0074] (Insulating Layer Forming Process) In the insulating layer forming process, a first insulating layer 120a is formed over the entire first side surface 113a of the battery element 110. Specifically, as shown in FIG. 3B , the insulating layer 120 is formed by, for example, a dipping method on the side surfaces 113a and 113b (see FIG. 1A ) of the battery element 110, where the end surfaces of the electrode layer 111 and the solid electrolyte layer 112 are exposed and these end surfaces are substantially flush with each other. Note that in this specification, the positive electrode side will be described as a representative example. The negative electrode side is substantially the same as the positive electrode side except that the lead-out portion is connected to the connection end surface of the negative electrode layer, and therefore a description thereof will be omitted.

[0075] (Through-Hole / Recess Forming Process) In the through-hole / recess forming process, a through-hole is formed in the insulating layer 120 covering the entire side surfaces 113a and 113b of the battery element 110, and a first recess 114a is formed in the connection end surface of one of the electrode layers 111, the positive electrode layer 111a and the negative electrode layer 111b, connecting to the through-hole. Specifically, as shown by the dashed lines in FIG. 3B , the arrangement of the electrode layer 111 (the positive electrode layer 111a and the negative electrode layer 111b) and the solid electrolyte layer 112 can be confirmed through the insulating layer 120 on the side surfaces 113a and 113b of the battery element. In other words, the insulating layer 120 has a certain degree of transparency. In other words, the insulating layer 120 has a total light transmittance of 50% or more for visible light with a wavelength of 380 nm or more and 780 nm or less. Here, the optical path length corresponds to the length (thickness) of the insulating layer 120 in the X direction. Furthermore, the positive electrode layer 111a, the negative electrode layer 111b, and the solid electrolyte layer 112 that constitute the battery element 110 have different constituent components, which can create contrast. Therefore, these layers can be distinguished from one another after the insulating layer formation process. This allows the through-hole 121apr and the first recess 114a to be formed without performing any special processing or using any special equipment.

[0076] 3B , a first external electrode (positive electrode) 130a will be disposed on the insulating layer 120. For this reason, the through-hole in the insulating layer 120 is formed so as to expose the entire connection end surface of the positive electrode layer 111a. This forms a rectangular through-hole 121apr that exposes the entire connection end surface of the positive electrode layer 111a and a portion of the end surface of the solid electrolyte layer 112 corresponding to the peripheral portion of the connection end surface.

[0077] 3C , following the formation of the through-holes, recesses 114 are formed in the end surfaces of the positive electrode layer 111a and the solid electrolyte layer 112 of the battery element 110. This forms the through-holes 121apr and the recesses 114 connected to the through-holes 121apr.

[0078] (Lead Portion Forming Process) In the lead portion forming process, the through hole 121apr and the recess 114 are filled with a conductive paste to form the lead portion 131. More specifically, the through hole 121apr and the first recess 114a are filled with the conductive paste, and a coating film is then formed on the upper surface of the filled portion and on the entire surface of the first insulating layer 120a. The coating film is dried to form the first lead portion 131a and the first external electrode (cathode) 130a. In this manner, the solid state battery 100 according to the first embodiment is manufactured.

[0079] Second Embodiment: Solid-State Battery The solid-state battery according to the second embodiment differs from the solid-state battery 100 according to the first embodiment in that it has a rectangular drawer portion in cross section. This different configuration will be mainly described below. Note that in the second embodiment, the same reference numerals as those in the first embodiment represent the same configuration as in the first embodiment, and therefore, in principle, description thereof will be omitted.

[0080] [Configuration of Solid-State Battery] The configuration of the lead portion will be described with reference to FIG. 4. FIG. 4 is an enlarged cross-sectional view schematically illustrating the configuration of the solid-state battery 100A according to the second embodiment. As shown in FIG. 4, the first lead portion 131Aa has a rectangular shape in cross-sectional view (ZX cross-sectional view). When the first lead portion 131Aa has a rectangular shape in cross-sectional view (ZX cross-sectional view), as shown in FIG. 4, if the width (length in the Z direction) of the lead portion 131Aa is large, the electrical resistance decreases.

[0081] [Method for manufacturing solid-state battery] (Through-hole / recess formation process) The solid-state battery 100A is manufactured in the same manner as in the first embodiment, except that in the through-hole / recess formation process, rectangular through-holes and recesses are formed instead of tapered shapes in cross-section.

[0082] Other Embodiments Although the embodiments of the present disclosure have been described above, the above-described embodiments are merely exemplary examples. Therefore, it will be readily understood by those skilled in the art that the present disclosure is not limited to the above-described embodiments, and that various aspects, such as design modifications and combinations of embodiments, are possible within the scope of the gist of the present disclosure.

[0083] In the first and second embodiments, the first lead portions 131a and 131Aa are in contact with the entire surface of the connection end surface 111a1 of the positive electrode layer 111a, but are not limited to this. For example, the first lead portions 131a and 131Aa may be in contact with only a portion of the connection end surface 111a1 of the positive electrode layer 111a.

[0084] In the first embodiment, the first lead portion 131a has a substantially trapezoidal shape in cross section (ZX cross section). That is, the side surface 114a1 has a tapered shape with a straight line, but this is not limited thereto. For example, part or all of the side surface may be curved. The two side surfaces do not need to be line-symmetrical.

[0085] In the first embodiment, as shown in FIG. 1C , the ridge 114a3 of the first recess 114a exists on the connection end surface 111a1 of the positive electrode layer 111a and on the solid electrolyte layer 112 adjacent to the positive electrode layer 111a. However, this is not limited to this. For example, the ridge 114a3 of the first recess 114a may exist only on the connection end surface 111a1 of the positive electrode layer 111a. These configurations can be used depending on the thickness of the electrode layer 111. For example, the former configuration can be used when the positive electrode layer 111a is not thick enough to provide the first lead portion 131a. Alternatively, the latter configuration can be used when the positive electrode layer 111a is thick enough to provide the first lead portion 131a.

[0086] In the first embodiment, as shown in FIG. 1B , the insulating layer 120 is disposed only on the side surfaces 113 of the battery element 110 that are parallel to the stacking direction and face each other, but is not limited thereto. For example, the insulating layer 120 may be disposed on at least a portion of at least one of the top surface (the upper surface of the uppermost outer layer 116) and the bottom surface (the lower surface of the lowermost outer layer 116) of the battery element 110. More specifically, in one aspect, the insulating layer 120 is disposed on the entire top and / or bottom surfaces of the battery element 110 in addition to the side surfaces 113 of the battery element 110. In another aspect, the insulating layer 120 is disposed on portions of the top and bottom surfaces (both ends thereof) in addition to the side surfaces 113 of the battery element 110, similar to the external electrode 130 in FIG. 1B . Such an aspect is formed by dipping the battery element 110 in a raw material solution for the insulating layer.

[0087] The present disclosure provides a solid-state battery according to the following aspects: <1> A solid-state battery comprising: a battery element formed by alternately stacking positive and negative electrode layers with solid electrolyte layers interposed therebetween; an insulating layer disposed on side surfaces of the battery element facing each other and parallel to the stacking direction; and a pair of external electrodes disposed to cover the insulating layer, wherein the pair of external electrodes extend to penetrate a local portion of the insulating layer, are formed in a recess disposed on a connection end surface of one of the positive and negative electrode layers, and have a lead portion electrically connecting the one electrode layer to one of the pair of external electrodes. <2> The solid-state battery according to <1>, wherein, in a filling through-hole that penetrates the local portion and is filled with the lead portion, a first opening width of a first opening located relatively outside the solid-state battery is larger than a second opening width of a second opening located relatively inside the solid-state battery in the local portion in a cross-sectional view. <3> The solid-state battery according to <2>, wherein the opening width decreases from the first opening to the second opening in a cross-sectional view. <4> The solid-state battery according to any one of <1> to <3>, wherein, in a filling through hole that penetrates the local portion and is filled with the lead-out portion, a first opening width of a first opening that is relatively outside the solid-state battery is substantially the same as a second opening width of a second opening in the local portion that is relatively inside the solid-state battery. <5> The solid-state battery according to <2> and any one of <3> to <4> that cites <2>, wherein, in a cross-sectional view, a ratio a / b of the thickness a of the insulating layer to the first opening width b of the first opening is 0.01 to 100, and the thickness a of the insulating layer is 0.005 mm or more. <6> The solid-state battery according to <5>, wherein the ratio a / b is 0.01 to 10. <7> The solid state battery according to <2> and any one of <3> to <6> citing <2>, wherein, in a cross-sectional view, a ratio c / d of the depth of the recess to the opening width d of the recess is 0.002 to 10, and the opening width d of the recess is 0.001 mm or more. <8> The solid state battery according to <7>, wherein the ratio c / d is 0.01 to 10. <9> The solid state battery according to any one of <1> to <8>, wherein a ridge line of the recess is present on at least one of a connection end surface of one of the electrode layers of the positive electrode layer and the negative electrode layer and an end surface of a solid electrolyte layer adjacent to the electrode layer.<10> The solid-state battery according to any one of <1> to <9>, wherein the insulating layer has a total light transmittance of 50% or more for visible light having a wavelength of 380 nm or more and 780 nm or less. <11> A method for manufacturing the solid-state battery according to any one of <1> to <10>, comprising: forming a through hole in a local portion of the insulating layer covering the entire end face of the battery element, and a recess connected to the through hole in a connection end face of one of the electrode layers of the positive electrode layer and the negative electrode layer, and filling the through hole and the recess with a conductive paste to form a lead-out portion. <12> The method for manufacturing the solid-state battery according to <11>, wherein the through hole is formed so that, in a filled through hole that penetrates the local portion and is filled with the lead-out portion, a first opening width of a first opening that is relatively outside the solid-state battery is larger than a second opening width of a second opening that is relatively inside the solid-state battery in the local portion in a cross-sectional view. <13> The method for manufacturing a solid-state battery according to <11> or <12>, wherein in a filling through hole that penetrates the local portion and is filled with the lead-out portion, a first opening width of a first opening on a relatively outer side of the solid-state battery (i.e., on the external electrode 130a side in the X direction) is substantially the same as a second opening width of a second opening of the local portion on a relatively inner side of the solid-state battery (i.e., on the external electrode 130a side in the X direction) in a cross-sectional view. <14> The method for manufacturing a solid-state battery according to any one of <11> to <13>, wherein the insulating layer has a total light transmittance of 50% or more for visible light having a wavelength of 380 nm or more and 780 nm or less.

[0088] The present disclosure will be described in more detail below with reference to examples and comparative examples, but the present disclosure is not limited to these examples. The production, evaluation, and measurement of the solid-state battery were carried out at room temperature and normal pressure (23°C and atmospheric pressure: 1 atm) in an open system unless otherwise specified.

[0089] 1. Fabrication of Solid-State Battery Example 1 A solid-state battery according to the first embodiment was fabricated according to the manufacturing method described in the first embodiment.

[0090] The solid-state battery of Example 1 had a battery element L dimension (long axis: length in the X direction) of 9 mm, W dimension (short axis: length in the Y direction) of 5 mm, and T dimension (thickness: length in the Z direction) of 5 mm. The external electrodes had a thickness of 0.05 mm. The positive electrode layer had a thickness (length in the Z direction) of 0.04 mm, the negative electrode layer had a thickness (length in the Z direction) of 0.04 mm, the solid electrolyte layer had a thickness (length in the Z direction) of 0.01 mm, the insulating layer had a thickness (length in the X direction) of 0.1 mm, the outer layer had a thickness (length in the Z direction) of 0.04 mm, and the outermost layer had a thickness (length in the Z direction) of 0.08 mm. The positive electrode layer and the negative electrode layer each had a current collector.

[0091] The second opening width d of the second opening relatively inside the local portion of the solid-state battery was 0.03 mm, the first opening width b of the first opening relatively outside was 0.04 mm, the depth c of the recess was 0.05 mm, and the thickness a of the insulating layer was 0.1 mm.

[0092] [Examples 2 to 8 and Comparative Examples] The solid state batteries of Examples 2 to 8 were fabricated in the same manner as the solid state battery of Example 1, except that the dimensions of the recesses described in Table 1 or 2 were changed. The solid state battery of Comparative Example 1 was fabricated in the same manner as the solid state battery of Example 1, except that no recesses were provided.

[0093] <2. Measurement Method> [2-1. Measurement of Recess Length] The recess length was measured from an SEM image of the cut surface of the solid-state battery. Specifically, a cut surface was first formed. A composite was formed by encapsulating the solid-state battery of Example 1 in resin. The composite was cut with a diamond cutter. When the solid-state battery of Example 1 was viewed from the stacking direction of the electrode layer and the solid electrolyte layer, a ZX cut surface passing through the intersection of the diagonals was formed on the rectangular side surface of the solid-state battery.

[0094] Next, an SEM image of the cut surface was taken using a scanning electron microscope ("FlexSEM1000" manufactured by Hitachi High-Technologies Corporation, magnification: 500 times).

[0095] The dimensions of the recess and its surrounding members (thickness a of the insulating layer, first opening width b of the first opening, depth c of the recess, and second opening width d of the second opening) were measured from the obtained SEM image. Each length was measured multiple times (number of measurements n = 5) and the average value was calculated.

[0096] <3. Evaluation Method> [3-1. Adhesion of Solid-State Battery] The adhesion evaluation method was performed with reference to FIG. 5 . FIG. 5 is a side view schematically illustrating the adhesion evaluation method in the examples. As shown in FIG. 5 , the external electrodes of the solid-state battery 100 were bonded to one side of the hexagonal prism-shaped M8 nuts 200 and 300 using an adhesive ("Easy Mix" manufactured by Henkel Japan Co., Ltd.). This resulted in a measurement sample in which the solid-state battery 100 was sandwiched between the M8 nuts 200 and 300. A card ring 400 was hooked onto the M8 nut 200, and the M8 nut 300 was placed in a jig attached to the measurement device and placed on a small benchtop tester (measurement device). A load was applied at a test speed of 20 mm / min, and the solid-state battery was pulled in its longitudinal direction. Stress was applied continuously until the solid-state battery broke, and the stress at the time of breakage was recorded. Three solid-state batteries of each example were prepared, and measurements were performed three times. The average value of the measured stresses was calculated and this average value was taken as the adhesion strength (unit: MPa). The measurement results are shown in Table 1.

[0097] [3-2. Filling Ratio of Lead Portions] 2-1. From the SEM images obtained by measuring the recesses, the designed area of ​​the recesses (hereinafter referred to as the "design area") and the actual area of ​​the recesses (hereinafter referred to as the "actual area") were obtained. In this specification, the filling ratio of the lead portions refers to the ratio (unit: %) of the actual area to the designed area in a cross-sectional view. Here, the "design area" refers to the cross-sectional area of ​​the designed recesses, and in FIG. 2, it is the area of ​​the region surrounded by the surface of the external electrode 130a facing the battery element 110, the side surfaces of the first insulating layer 120a and the solid electrolyte layer 112, and the connection end surface 111a1 of the positive electrode layer 111a. Also, in FIG. 5, it is the area of ​​the region surrounded by the surface of the external electrode 130a facing the battery element 110, the side surfaces of the first insulating layer 120a and the solid electrolyte layer 112, the connection end surface 111a1 of the positive electrode layer 111a, and the bottom surface of the solid electrolyte. From the obtained design area and actual area, the ratio of the actual area to the design area was calculated. The ratio was calculated for three different recesses, and the average value was taken as the filling rate of the lead-out section. The measurement results are shown in Table 2.

[0098] [3-3. Battery Capacity Ratio] Using a charge / discharge evaluation device ("TOSCAT-3000" manufactured by Toyo Systems Co., Ltd.), the battery was charged at 0.05 C until the battery voltage reached 2.5 V, and then, while maintaining the battery voltage at 2.5 V, the battery was charged until the charging current reached 0.01 C. This solid-state battery was discharged at 0.05 C, and the discharge capacity was measured when the battery voltage reached 0.55 V (number of measurements n = 3). The average value of the three measured values ​​was taken as the battery capacity of the solid-state battery. When the capacity in Comparative Example 1 was taken as 100%, the capacity ratio of each Example to the Comparative Example is shown in Table 1.

[0099] [3-4. Electrical Resistance] Using an impedance analyzer ("SI1260" manufactured by Toyo Corporation), an amplitude of 10 mV was swept from 1 Hz to 1 MHz to obtain the electrical resistance of the solid-state battery at a frequency of 1 MHz (number of measurements n = 3). The average value of the three measured values ​​was taken as the electrical resistance of the solid-state battery. The measurement results are shown in Table 2.

[0100] 4. Results and Discussion The evaluation results are summarized in Tables 1 and 2.

[0101]

[0102]

[0103] <Results> The solid-state batteries of Examples 1 to 9 included a battery element, an insulating layer, and a pair of external electrodes. The positive electrode had a lead portion that extended through a local portion of the first insulating layer, was formed in a recess located on the connection end surface of the positive electrode layer, and electrically connected the positive electrode and the positive electrode layer. The negative electrode had a lead portion that extended through a local portion of the second insulating layer, was formed in a recess located on the connection end surface of the negative electrode layer, and electrically connected the negative electrode and the negative electrode layer.

[0104] As shown in Table 1, the solid state batteries of Examples 2 to 4 had a ratio c / d of the recess depth c to the recess opening width d of 0.002 to 10, and the recess opening width d was 0.001 mm (1 μm) or more. Furthermore, as shown in Table 1, the solid state batteries of Examples 3 to 5 had an adhesion strength of 5.3 MPa or more and a battery capacity ratio of more than 99%.

[0105] As shown in Table 1, the solid state batteries of Examples 3 and 4 had a ratio c / d of 0.01 or more and 10 or less. Also, as shown in Table 1, the solid state batteries of Examples 3 and 4 had an adhesion strength of 9.6 MPa or more. On the other hand, the solid state battery of Example 2 had a ratio c / d of 0.01. Also, as shown in Table 1, the solid state battery of Example 2 had an adhesion strength of less than 9.6 MPa.

[0106] As shown in Table 2, the solid state batteries of Examples 5 to 9 had a ratio a / b of the thickness a of the insulating layer to the first opening width b of the first opening outside the local portion of the insulating layer of 0.01 or more and 100 or less, and the thickness a of the insulating layer was 0.005 mm (5 μm) or more. Furthermore, as shown in Table 2, the solid state batteries of Examples 5 to 9 had an electrical resistance of 0.1 Ω or more and 2.4 Ω or less, and a filling factor of 63% or more.

[0107] As shown in Table 2, the solid state batteries of Examples 6 to 9 had a ratio a / b of 0.01 or more and 10 or less. As shown in Table 2, the solid state batteries of Examples 6 to 9 also had an electrical resistance of 0.1 Ω or more and 0.9 Ω or less and a filling factor of 91% or more. On the other hand, as shown in Table 2, the solid state battery of Example 5 had a ratio a / b of more than 10. As shown in Table 2, the solid state battery of Example 5 also had an electrical resistance of more than 0.9 Ω and a filling factor of less than 91%.

[0108] The solid-state battery according to the present disclosure can be used in applications that typically require the use of electrical energy. For example, the solid-state battery according to the present disclosure can be used in various fields where power storage is anticipated. By way of example only, when the solid-state battery according to the present disclosure is a secondary battery, the solid-state battery can be used in the fields of electricity, information, and communications where electric and electronic devices are used (for example, the fields of electric and electronic devices or mobile devices including mobile phones, smartphones, laptop computers, digital cameras, activity monitors, arm computers, electronic paper, wearable devices, and small electronic devices such as RFID tags, card-type electronic money, and smart watches), household and small industrial applications (for example, power tools, golf carts, and household, nursing care, and industrial robots), large industrial applications (for example, forklifts, elevators, and port cranes), transportation systems (for example, hybrid cars, electric cars, buses, trains, electrically assisted bicycles, and electric motorcycles), power system applications (for example, various power generation systems, road conditioners, smart grids, and general household installation-type power storage systems), medical applications (medical devices such as earphones and hearing aids), pharmaceutical applications (dose management systems), as well as the IoT field, and space and deep-sea applications (for example, space probes, submersible research vessels, and the like).

[0109] 100, 100A Solid-state battery 110 Battery element 111 Electrode layer 111a Positive electrode layer 111a1 (Positive electrode layer) connecting end surface 111b Negative electrode layer 112 Solid electrolyte layer 113a First side surface 113b Second side surface 114a First recess 114a1 Side surface 114a2 Bottom surface 114a3 Ridge line 115 Outer layer 116 Outermost layer 120a First insulating layer 120b Second insulating layer 121a First local portion (filling through hole) 121c First opening 121d Second opening 130a First external electrode (positive electrode) 130b Second external electrode (negative electrode) 131a, 131Aa Lead-out portion a Thickness of insulating layer b First opening width of first opening c Depth of recess d Second opening width of the second opening

Claims

1. A solid-state battery comprising: a battery element formed by alternately stacking positive electrode layers and negative electrode layers with solid electrolyte layers interposed therebetween; an insulating layer disposed on side surfaces of the battery element that are parallel to the stacking direction and face each other; and a pair of external electrodes disposed so as to cover the insulating layer, wherein the pair of external electrodes extend so as to penetrate localized portions of the insulating layer, are formed in recesses disposed on the connection end faces of one of the positive electrode layers and the negative electrode layers, and each have lead-out portions that electrically connect the one electrode layer to one of the pair of external electrodes.

2. The solid-state battery according to claim 1, wherein in a filling through-hole that penetrates the local portion and is filled with the lead-out portion, a first opening width of a first opening that is relatively outside the solid-state battery is larger than a second opening width of a second opening that is relatively inside the solid-state battery in the local portion in a cross-sectional view.

3. The solid-state battery according to claim 2, wherein the opening width decreases from the first opening toward the second opening in a cross-sectional view.

4. The solid-state battery according to any one of claims 1 to 3, wherein in a filling through-hole that penetrates the local portion and is filled with the lead-out portion, a first opening width of a first opening that is relatively outside the solid-state battery is substantially the same as a second opening width of a second opening that is relatively inside the solid-state battery in the local portion in a cross-sectional view.

5. The solid-state battery according to claim 2, wherein, in a cross-sectional view, the ratio a / b of the thickness a of the insulating layer to the first opening width b of the first opening is 0.01 or more and 100 or less, and the thickness a of the insulating layer is 0.005 mm or more.

6. The solid-state battery according to claim 5, wherein the ratio a / b is 0.01 or more and 10 or less.

7. The solid-state battery according to claim 2, wherein, in a cross-sectional view, the ratio c / d of the depth c of the recess to the opening width d of the recess is 0.002 or more and 10 or less, and the opening width d of the recess is 0.001 mm or more.

8. The solid-state battery according to claim 7, wherein the ratio c / d is 0.01 or more and 10 or less.

9. The solid-state battery according to any one of claims 1 to 8, wherein the ridge of the recess exists on at least one of the connection end surface of one of the positive electrode layer and the negative electrode layer and the end surface of the solid electrolyte layer adjacent to the electrode layer.

10. The solid-state battery according to any one of claims 1 to 9, wherein the insulating layer has a total light transmittance of 50% or more for visible light having a wavelength of 380 nm or more and 780 nm or less.

11. A method for producing a solid-state battery according to any one of claims 1 to 10, comprising: forming a through-hole in a local portion of the insulating layer covering the entire end face of the battery element; and forming a recess connected to the through-hole in the connecting end face of one of the electrode layers of the positive electrode layer and the negative electrode layer; and filling the through-hole and the recess with a conductive paste to form an extraction portion.

12. A method for manufacturing a solid-state battery according to claim 11, wherein the through hole is formed so that a first opening width of a first opening relatively outside the solid-state battery in a filled through hole that penetrates the local portion and is filled with the lead-out portion is larger than a second opening width of a second opening relatively inside the solid-state battery in the local portion in a cross-sectional view.

13. A method for manufacturing a solid-state battery according to claim 11 or 12, wherein a through hole is formed so that a first opening width of a first opening relatively outside the solid-state battery in a filled through hole that penetrates the local portion and is filled with the lead-out portion is substantially the same as a second opening width of a second opening relatively inside the solid-state battery in the local portion in a cross-sectional view.

14. The method for manufacturing a solid-state battery according to any one of claims 11 to 13, wherein the insulating layer has a total light transmittance of 50% or more for visible light having a wavelength of 380 nm or more and 780 nm or less.

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