solid-state batteries

Abstract

This invention aims to realize a solid-state battery that can suppress the migration of components contained in external connection terminals. [Solution] The solid-state battery 1 comprises a power generation element 14, an outer casing 15, and external connection terminals 20 and 30. The outer casing 15 covers the power generation element 14. The external connection terminals 20 and 30 contain Ag, are in contact with the outer casing 15, and are electrically connected to the power generation element 14. The outer casing 15, in contact with the external connection terminals 20 and 30, contains borosilicate glass containing alkali metal elements and alkaline earth metal elements. The borosilicate glass of the outer casing 15 contains more K than Na as alkali metal elements, and the total content of alkali metal elements K and alkaline earth metal elements is 10.0% by mass or more and 16.0% by mass or less.

Description

Technical Field

[0001] The present invention relates to a solid-state battery.

Background Art

[0002] Regarding solid-state batteries, there is known a technique of providing an external electrode on an end face where an internal electrode is exposed of a laminated chip in which a solid electrolyte layer and internal electrodes are alternately laminated and a cover layer of a sintered body is further laminated, and a technique of using Ag (silver) or the like as a main component of the external electrode (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a solid-state battery, due to the influence of moisture in the atmosphere, components such as Ag contained in an external connection terminal may repeatedly dissolve and precipitate and grow as migration. For example, when migration occurring at an external connection terminal on one electrode side of a solid-state battery extends to an external connection terminal on the other electrode side, a short circuit of the solid-state battery is caused.

[0005] On one aspect, an object of the present invention is to realize a solid-state battery capable of suppressing migration of components contained in an external connection terminal.

Means for Solving the Problems

[0006] In one embodiment, a solid-state battery is provided, comprising a power generation element, an outer casing covering the power generation element, and an external connection terminal in contact with the outer casing and electrically connected to the power generation element, the outer casing comprising a borosilicate glass containing an alkali metal element and an alkaline earth metal element, wherein the borosilicate glass contains more K than Na as the alkali metal element, and the total content of K of the alkali metal element and the alkaline earth metal element is 10.0% by mass or more and 16.0% by mass or less. [Effects of the Invention]

[0007] In one respect, it becomes possible to realize a solid-state battery that can suppress the migration of components contained in the external connection terminals. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram illustrating an example of a solid-state battery. [Figure 2] This diagram illustrates the migration of components contained in external connection terminals. [Modes for carrying out the invention]

[0009] Figure 1 illustrates an example of a solid-state battery. Figure 1(A) schematically shows a perspective view of the main part of an example of a solid-state battery. Figures 1(B) and 1(C) schematically show cross-sectional views of the main part of an example of a solid-state battery, respectively. Figure 1(B) is a schematic cross-sectional view taken along line L1 in Figure 1(A). Figure 1(C) is a schematic cross-sectional view taken along line L2 in Figure 1(A).

[0010] The solid-state battery 1 shown in Figures 1(A) to 1(C) is an example of a lithium-ion battery (also referred to as a "lithium-ion secondary battery," "lithium secondary battery," etc.). The solid-state battery 1 includes a battery body 10, external connection terminals 20 and 30.

[0011] As shown in Figures 1(B) and 1(C), the battery body 10 includes a power generation element 14 having electrode layers, namely a positive electrode layer 11 and a negative electrode layer 12, and an electrolyte layer 13 provided at least between them. The positive electrode layer 11, negative electrode layer 12, and electrolyte layer 13 of the power generation element 14 are stacked in a predetermined order in a first direction D1. The positive electrode layer 11 and the negative electrode layer 12 are stacked in the first direction D1 such that they partially overlap via the electrolyte layer 13.

[0012] For convenience, we will use a solid-state battery 1 containing two positive electrode layers 11 and two negative electrode layers 12 as an example. However, the number of positive electrode layers 11 and negative electrode layers 12 is not limited to this example, as long as the positive electrode layers 11 and negative electrode layers 12 are stacked in the first direction D1 via an electrolyte layer 13. Furthermore, the bottom and top layers of the power generation element 14 may be the positive electrode layer 11, the negative electrode layer 12, or the electrolyte layer 13, respectively.

[0013] The battery body 10 further includes an insulating outer casing 15 that covers a predetermined portion of the power generation element 14. As shown in Figures 1(B) and 1(C), the outer casing 15 covers the upper and lower surfaces of the power generation element 14 that face both sides of the first direction D1 (upper and lower sides in Figures 1(B) and 1(C)). As shown in Figure 1(B), the outer casing 15 further covers the end face of the positive electrode layer 11 facing one side of the second direction D2 perpendicular to the first direction D1 (right side in Figure 1(B)), and the end face of the negative electrode layer 12 facing the other side of the second direction D2 (left side in Figure 1(B)). The outer casing 15 further covers the end faces of the positive electrode layer 11, the negative electrode layer 12, and the electrolyte layer 13 facing both sides (right and left sides in Figure 1(C)) of the power generation element 14 in the third direction D3 which is perpendicular to the first direction D1 and the second direction D2, as shown in Figure 1(C).

[0014] As shown in FIG. 1(B), the battery body 10 has a positive electrode lead-out surface 10a where the end surface of the positive electrode layer 11 (the left end surface in FIG. 1(B)) is exposed from the exterior body 15 on both sides in the second direction D2, and a negative electrode lead-out surface 10b where the end surface of the negative electrode layer 12 (the right end surface in FIG. 1(B)) is exposed from the exterior body 15. An external connection terminal 20 and an external connection terminal 30 are provided on the positive electrode lead-out surface 10a and the negative electrode lead-out surface 10b of the battery body 10, respectively.

[0015] The external connection terminal 20 is provided so as to contact a part of the surface of the exterior body 15 continuous from the positive electrode lead-out surface 10a of the battery body 10. The external connection terminal 20 is electrically connected to the end surface of the positive electrode layer 11 exposed on the positive electrode lead-out surface 10a and functions as the positive electrode terminal of the solid-state battery 1. Further, the external connection terminal 30 is provided so as to contact a part of the surface of the exterior body 15 continuous from the negative electrode lead-out surface 10b of the battery body 10. The external connection terminal 30 is electrically connected to the end surface of the negative electrode layer 12 exposed on the negative electrode lead-out surface 10b and functions as the negative electrode terminal of the solid-state battery 1.

[0016] Incidentally, one or both of the positive electrode layer 11 and the negative electrode layer 12 of the power generation element 14 included in the battery body 10 are also referred to as "electrode layers". [[ID=​​​​​​​​​​​

[0018] The positive electrode layer 11 of the power generation element 14 contains a positive electrode active material and a solid electrolyte. As the solid electrolyte of the positive electrode layer 11, an oxide solid electrolyte or a sulfide solid electrolyte, for example, the same type of material as the solid electrolyte used for the electrolyte layer 13 is used. As the positive electrode active material of the positive electrode layer 11, for example, Li2CoP2O7 (cobalt lithium pyrophosphate, also referred to as "LCPO") or the like is used. The positive electrode layer 11 may further contain a conductive aid in addition to the positive electrode active material and the solid electrolyte. As the conductive aid of the positive electrode layer 11, for example, carbon materials such as carbon fiber, carbon black, graphite, graphene, carbon nanotube, and conductive materials such as iron silicide are used.

[0019] The negative electrode layer 12 of the power generation element 14 contains a negative electrode active material and a solid electrolyte. As the solid electrolyte of the negative electrode layer 12, an oxide solid electrolyte or a sulfide solid electrolyte, for example, the same type of material as the solid electrolyte used for the electrolyte layer 13 is used. As the negative electrode active material of the negative electrode layer 12, for example, TiO2 (titanium dioxide), Nb2O5 (niobium pentoxide) or the like is used. In addition, as the negative electrode active material of the negative electrode layer 12, Li3V2(PO4)3 (lithium vanadium phosphate), Li4Ti5O 12 (lithium titanate) or the like may be used. The negative electrode layer 12 may further contain a conductive aid in addition to the negative electrode active material and the solid electrolyte. As the conductive aid of the negative electrode layer 12, for example, carbon materials such as carbon fiber, carbon black, graphite, graphene, carbon nanotube, and conductive materials such as iron silicide are used.

[0020] Incidentally, although not shown here, the positive electrode layer 11 and the negative electrode layer 12 may each be provided with a current collector layer using various conductive materials so as to be in contact with each. Such a current collector layer may contain the above-mentioned conductive aid. When the current collector layer contains a conductive aid, the positive electrode layer 11 and the negative electrode layer 12 may be configured to contain a conductive aid or may be configured not to contain a conductive aid.

[0021] In the solid-state battery 1, during charging, lithium ions are conducted through the electrolyte layer 13 from the positive electrode layer 11 and taken into the negative electrode layer 12, and during discharging, lithium ions are conducted through the electrolyte layer 13 from the negative electrode layer 12 and taken into the positive electrode layer 11. In the solid-state battery 1, such charge and discharge operations are realized by the conduction of lithium ions.

[0022] For the exterior body 15, various insulating materials having insulating properties are used. Note that the insulating property of the insulating material used for the exterior body 15 refers to the property of having no influence or a sufficiently low influence on the lithium ion conduction and electron conduction in the power generation element 14. For example, for the exterior body 15, an insulating material having a lower electron conductivity than the positive electrode layer 11 and the negative electrode layer 12 is used. It is preferable that the exterior body 15 is made of a material having low water and gas permeability and good sealing properties. Among them, it is preferable to use a material having a linear expansion coefficient similar to that of each layer constituting the power generation element 14 or a material having good adhesion to each of these layers for the exterior body 15. As the insulating material for the exterior body 15, for example, glass can be used.

[0023] The external connection terminal 20 is connected to the end face of the positive electrode layer 11 exposed from the exterior body 15 on the positive electrode lead-out surface 10a of the battery body 10. The external connection terminal 30 is connected to the end face of the negative electrode layer 12 exposed from the exterior body 15 on the negative electrode lead-out surface 10b of the battery body 10. For the external connection terminal 20 and the external connection terminal 30, for example, a conductive material containing Ag is used. For example, for the conductive materials of the external connection terminal 20 and the external connection terminal 30, those containing Ag as the main component are used.

[0024] For example, a paste containing a conductive material containing Ag, as well as organic components such as glass and resin, is applied to a part of the positive electrode lead-out surface 10a of the battery body 10 and the surface of the exterior body 15 continuous therefrom. Then, by performing a predetermined heat treatment, the organic components such as resin are removed, and a composite containing Ag and glass is baked on a part of the positive electrode lead-out surface 10a and the surface of the exterior body 15 continuous therefrom, and the external connection terminal 20 is formed.

[0025] Similarly, a conductive material containing Ag, as well as a paste containing organic components such as glass and resin, is applied to the negative electrode lead-out surface 10b of the battery body 10 and a portion of the surface of the casing 15 that is continuous therewith. Then, a predetermined heat treatment is performed to remove the organic components such as resin, and the composite containing Ag and glass is baked onto the negative electrode lead-out surface 10b and a portion of the surface of the casing 15 that is continuous therewith, forming the external connection terminal 30.

[0026] Furthermore, the surface of the layer formed by the application and heat treatment of the above paste may be further coated with various metals such as Ni (nickel) and Sn (tin) using a plating method to form the external connection terminals 20 and 30.

[0027] Incidentally, silver (Ag) is known to be one of the materials that is relatively prone to migration. In solid-state batteries 1, which contain Ag as a component of external connection terminals 20 and 30, migration of the contained Ag may lead to a deterioration in performance.

[0028] Here, Figure 2 illustrates the migration of components contained in the external connection terminal. Figures 2(A) and 2(B) schematically show perspective views of key parts of an example of a solid-state battery in which migration has occurred.

[0029] For example, in a solid-state battery 1 in which Ag is included as a component of external connection terminals 20 and 30, the Ag contained in the positive electrode side external connection terminal 20 may dissolve and leach out due to the influence of moisture in the external environment such as the atmosphere. If the dissolution and leaching of Ag is repeated, Ag may grow as migration 100 on the surface of the outer casing 15, as shown in Figure 2(A) and further in Figure 2(B). If the migration 100 generated from the positive electrode side external connection terminal 20 of the solid-state battery 1 extends to the negative electrode side external connection terminal 30, it will cause a short circuit in the solid-state battery 1.

[0030] Such Ag migration 100 and the resulting short circuits are more likely to occur when the solid battery 1 is operated in a relatively high-temperature, high-humidity environment. Furthermore, even if the external connection terminals 20 and 30 are constructed by coating (plating) the surface of the Ag-containing layer with a metal such as Ni or Sn, if there are insufficient areas in the coating, moisture may penetrate through those areas, and Ag migration 100 may occur.

[0031] Furthermore, the migration described above may occur at the negative terminal 30 as well as the positive terminal 20, depending on the operating conditions and external environment of the solid battery 1. In view of these points, the solid battery 1 employs the following configuration to suppress the migration of Ag, a component contained in the external connection terminals 20 and 30. Specifically, the outer casing 15 of the solid battery 1 that comes into contact with the Ag-containing external connection terminals 20 and 30 is made of glass containing a predetermined element in a predetermined composition, thereby suppressing the migration of Ag, a component contained in the external connection terminals 20 and 30.

[0032] The configuration of the solid-state battery 1 according to this embodiment will be described below. In the solid-state battery 1 according to this embodiment, borosilicate glass is used as the material for its outer casing 15. That is, the outer casing 15 of the solid-state battery 1 contains borosilicate glass. The borosilicate glass of the outer casing 15 contains Si (silicon), B (boron), and O (oxygen) as its constituent elements. The borosilicate glass of the outer casing 15 contains SiO2 (silicon dioxide) and B2O3 (boron oxide) as network-forming oxides that form the main network structure of the glass.

[0033] The borosilicate glass of the outer casing 15 contains alkali metal elements. The borosilicate glass of the outer casing 15 contains at least K (potassium) as an alkali metal element. For example, the borosilicate glass of the outer casing 15 contains Na (sodium) and K as alkali metal elements. The borosilicate glass of the outer casing 15 contains alkali metal oxides as modifying oxides. Modifying oxides do not vitrify on their own but change the properties of the glass. The borosilicate glass of the outer casing 15 contains at least K2O (potassium oxide) as an alkali metal oxide. For example, the borosilicate glass of the outer casing 15 contains Na2O (sodium oxide) and K2O as alkali metal oxides. The borosilicate glass of the outer casing 15 contains more K than Na as an alkali metal element.

[0034] The borosilicate glass of the outer casing 15 contains alkaline earth metal elements. Examples of alkaline earth metal elements that the borosilicate glass of the outer casing 15 may contain include Ca (calcium), Ba (barium), Sr (strontium), and Ra (radium). The borosilicate glass of the outer casing 15 contains an oxide of an alkaline earth metal element, i.e., an alkaline earth metal oxide, as a modifying oxide. The borosilicate glass of the outer casing 15 contains at least one of CaO (calcium oxide), BaO (barium oxide), SrO (strontium oxide), and RaO (radium oxide) as the alkaline earth metal oxide. However, due to the mixed alkali effect, elements with a large ionic radius are effective, and because Ra is a radioactive element, it is desirable that the borosilicate glass of the outer casing 15 contains Ba or Sr as the alkaline earth metal element.

[0035] Here, it is preferable that the borosilicate glass of the outer casing 15 has a total content of alkali metal element K and alkaline earth metal element of 10.0% by mass or more and 16.0% by mass or less. It is preferable that the borosilicate glass of the outer casing 15 has an alkaline earth metal element content of 10.0% by mass or more.

[0036] The borosilicate glass of the outer casing 15 may further contain other metallic elements. Other metallic elements that the borosilicate glass of the outer casing 15 may contain include Al (aluminum), Ti (titanium), Zn (zinc), and Zr (zirconium). The borosilicate glass of the outer casing 15 may contain at least one of Al2O3 (aluminum oxide), TiO2, ZnO (zinc oxide), and ZrO2 (zirconium oxide). These oxides can become intermediate oxides in the borosilicate glass. Intermediate oxides do not vitrify on their own and can enter the glass in relatively large quantities.

[0037] Here, the borosilicate glass of the outer casing 15 either does not contain Zr, or if it does, it contains a relatively small amount of Zr. Preferably, the total content of Na and Zr in the borosilicate glass of the outer casing 15 is 4.3% by mass or less. Preferably, the Zr content in the borosilicate glass of the outer casing 15 is 3.6% by mass or less.

[0038] In the solid-state battery 1 according to this embodiment, a borosilicate glass having the above composition is used as the outer casing 15 that comes into contact with the external connection terminals 20 and 30 containing Ag. This suppresses the migration of Ag, a component contained in the external connection terminals 20 and 30, in the solid-state battery 1.

[0039] Examples and comparative examples are described below.

[0040] [Table 1]

[0041] Solid-state batteries 1 of Examples 1-2 and Comparative Examples 1-3 were fabricated using borosilicate glass containing predetermined elements in the compositions shown in Table 1 as the outer casing 15. The content [mass%] of each element in the borosilicate glass used for the outer casing 15 of each solid-state battery 1 was determined by elemental analysis of the surface of the outer casing 15 using energy dispersive x-ray spectroscopy (EDS).

[0042] In Table 1, "(K)" indicates that the detected fluorescent X-ray is the K-line, and "(L)" indicates that the detected fluorescent X-ray is the L-line. Table 1 shows the results of elemental analysis based on the detected K-line for Na, Al, K, Ca, Ti, and Zn, and elemental analysis based on the detected L-line for Zr and Ba.

[0043] For each solid-state battery 1 of Examples 1-2 and Comparative Examples 1-3, a predetermined charge-discharge cycle operation was performed under conditions of 85°C and 85% relative humidity. After the cycle operation, for each solid-state battery 1 of Examples 1-2 and Comparative Examples 1-3, the migration distance Lx [μm] of Ag extending from the edge of the positive electrode external connection terminal 20 toward the negative electrode external connection terminal 30 on the surface of the outer casing 15, i.e., the migration distance Lx of migration 100 as shown in Figure 2(A) above, was measured.

[0044] Table 1 shows the elemental content [mass%] and migration distance Lx [μm] of the borosilicate glass used in the casing 15 of each solid-state battery 1 in Example 1-2 and Comparative Example 1-3. The configuration of each solid-state battery 1 in Example 1-2 and Comparative Example 1-3, as well as the elemental content and migration distance Lx of the borosilicate glass in each solid-state battery 1, are as follows.

[0045] [Example 1] As the solid battery 1 of Example 1, a solid battery 1 was prepared that included an outer casing 15 made of borosilicate glass containing B, Si, and O, and further containing elements with the composition shown in Table 1 (Example 1). Specifically, as the solid battery 1 of Example 1, a solid battery 1 was prepared that included an outer casing 15 made of borosilicate glass containing 0.56 mass% Na, 8.99 mass% Al, 5.15 mass% K, 1.14 mass% Ti, 2.11 mass% Zn, 0.06 mass% Zr, and 10.41 mass% Ba, with the remainder being B, Si, and O. As shown in Table 1 (Example 1), in the borosilicate glass used for the outer casing 15 of the solid battery 1 of Example 1, Ca was below the detection limit (nd - not detected).

[0046] The migration distance Lx of the solid battery 1 of Example 1 equipped with such an outer casing 15, that is, the migration distance Lx of Ag from the edge of the external connection terminal 20 on the surface of the outer casing 15 after a cycle operation performed under predetermined conditions, was approximately 6 μm, as shown in Table 1 (Example 1).

[0047] [Example 2] As the solid battery 1 of Example 2, a solid battery 1 was prepared that comprises an outer casing 15 made of borosilicate glass containing B, Si, and O, and further containing elements with the composition shown in Table 1 (Example 2). Specifically, as the solid battery 1 of Example 2, a solid battery 1 was prepared that comprises an outer casing 15 made of borosilicate glass containing 0.66 mass% Na, 8.48 mass% Al, 5.44 mass% K, 0.06 mass% Ca, 1.14 mass% Ti, 2.24 mass% Zn, 3.57 mass% Zr, and 10.31 mass% Ba, with the remainder being B, Si, and O.

[0048] The migration distance Lx of the solid battery 1 in Example 2 equipped with such an outer casing 15, that is, the migration distance Lx of Ag from the edge of the external connection terminal 20 on the surface of the outer casing 15 after a cycle operation performed under predetermined conditions, was approximately 14 μm, as shown in Table 1 (Example 2).

[0049] [Comparative Example 1] As a solid-state battery 1 of Comparative Example 1, a solid-state battery 1 was prepared that comprises an outer casing 15 made of borosilicate glass containing B, Si, and O, and further containing elements with the composition shown in Table 1 (Comparative Example 1). Specifically, as a solid-state battery 1 of Comparative Example 1, a solid-state battery 1 was prepared that comprises an outer casing 15 made of borosilicate glass containing 0.45 mass% Na, 7.59 mass% Al, 5.61 mass% K, 0.03 mass% Ca, 1.30 mass% Ti, 2.04 mass% Zn, 4.04 mass% Zr, and 3.98 mass% Ba, with the remainder being B, Si, and O.

[0050] The migration distance Lx of the solid battery 1 of Comparative Example 1 equipped with such an outer casing 15, that is, the migration distance Lx of Ag from the edge of the external connection terminal 20 on the surface of the outer casing 15 after a cycle operation performed under predetermined conditions, was approximately 210 μm, as shown in Table 1 (Comparative Example 1).

[0051] [Comparative Example 2] As a solid battery 1 for Comparative Example 2, a solid battery 1 was prepared that included an outer casing 15 made of borosilicate glass containing B, Si, and O, and further containing elements with the composition shown in Table 1 (Comparative Example 2). Specifically, as a solid battery 1 for Comparative Example 2, a solid battery 1 was prepared that included an outer casing 15 made of borosilicate glass containing 0.64 mass% Na, 7.77 mass% Al, 5.72 mass% K, 0.11 mass% Ca, 1.12 mass% Ti, 2.41 mass% Zn, 4.41 mass% Zr, and 0.17 mass% Ba, with the remainder being B, Si, and O.

[0052] The migration distance Lx of the solid battery 1 of Comparative Example 2 equipped with such an outer casing 15, that is, the migration distance Lx of Ag from the edge of the external connection terminal 20 on the surface of the outer casing 15 after a cycle operation performed under predetermined conditions, was approximately 550 μm, as shown in Table 1 (Comparative Example 2).

[0053] [Comparative Example 3] As Comparative Example 3, a solid-state battery 1 was prepared, comprising an outer casing 15 made of borosilicate glass containing B, Si, and O, and further containing elements with the composition shown in Table 1 (Comparative Example 3). Specifically, as the solid-state battery 1 of Comparative Example 3, a solid-state battery 1 was prepared, comprising an outer casing 15 made of borosilicate glass containing 1.57 mass% Na, 8.53 mass% Al, 0.06 mass% Ca, 1.18 mass% Ti, 2.69 mass% Zn, 5.01 mass% Zr, and 1.26 mass% Ba, with the remainder containing B, Si, and O. As shown in Table 1 (Comparative Example 3), in the borosilicate glass used for the outer casing 15 of the solid-state battery 1 of Comparative Example 3, K was below the detection limit (nd).

[0054] The migration distance Lx of the solid battery 1 of Comparative Example 3, which was equipped with such an outer casing 15, that is, the migration distance Lx of Ag from the edge of the external connection terminal 20 on the surface of the outer casing 15 after a cycle operation performed under predetermined conditions, was approximately 600 μm, as shown in Table 1 (Comparative Example 3).

[0055] <Rating> Regarding the alkali metal elements contained in the borosilicate glass of the outer casing 15, as shown in Table 1, the borosilicate glass of Examples 1-2 and Comparative Example 1-2 had a higher K content than the Na content, while the borosilicate glass of Comparative Example 3 had a lower K content than the Na content. As shown in Table 1, in the solid-state batteries 1 of Examples 1-2 and Comparative Example 1-2, where borosilicate glass with a higher K content than the Na content was used for the outer casing 15, the Ag migration distance Lx was kept smaller compared to the solid-state battery 1 of Comparative Example 3, where borosilicate glass with a lower K content than the Na content was used for the outer casing 15.

[0056] Regarding the alkaline earth metal elements contained in the borosilicate glass of the outer casing 15, as shown in Table 1, the borosilicate glass of Example 1-2 has a relatively high content of Ba, an alkaline earth metal element, or the total content of Ca and Ba, while the borosilicate glass of Comparative Example 1-2 has a relatively low total content of Ca and Ba, both alkaline earth metal elements. As shown in Table 1, in the solid-state battery 1 of Example 1-2, in which a borosilicate glass with a relatively high content of alkaline earth metal elements was used for the outer casing 15, the Ag migration distance Lx was suppressed more effectively than in the solid-state battery 1 of Comparative Example 1-2, in which a borosilicate glass with a relatively low content of alkaline earth metal elements was used for the outer casing 15.

[0057] The specific elemental content of the borosilicate glass in the outer casing 15 of each solid-state battery 1 was as follows: As shown in Table 1, the borosilicate glass of the outer casing 15 of the solid battery 1 of Example 1 had a content of 0.56 mass% of alkali metal element Na, a content of 5.15 mass% of alkali metal element K, a content of 10.41 mass% of alkaline earth metal element Ba, and a total content of alkali metal element K and alkaline earth metal elements (Ca not included) of 15.56 mass%.

[0058] As shown in Table 1, the borosilicate glass of the casing 15 of the solid battery 1 of Example 2 had a content of 0.66 mass% of alkali metal element Na, a content of 5.44 mass% of alkali metal element K, a combined content of alkaline earth metal elements Ca and Ba of 10.37 mass%, and a total content of alkali metal element K and alkaline earth metal elements of 15.81 mass%.

[0059] As shown in Table 1, the borosilicate glass of the casing 15 of the solid battery 1 of Comparative Example 1 had a content of 0.45 mass% of alkali metal element Na, a content of 5.61 mass% of alkali metal element K, a combined content of alkaline earth metal elements Ca and Ba of 4.01 mass%, and a total content of alkali metal element K and alkaline earth metal elements of 9.62 mass%.

[0060] As shown in Table 1, the borosilicate glass of the casing 15 of the solid battery 1 of Comparative Example 2 had a sodium alkali metal content of 0.64 mass%, a potassium alkali metal content of 5.72 mass%, a combined content of calcium and barium alkaline earth metals of 0.28 mass%, and a total content of potassium alkali metals and alkaline earth metals of 6.00 mass.

[0061] As shown in Table 1, the borosilicate glass of the outer casing 15 of the solid battery 1 of Comparative Example 3 had a sodium alkali metal content of 1.57% by mass, a potassium alkali metal content below the detection limit (nd), and a combined content of alkaline earth metal elements Ca and Ba of 1.32% by mass.

[0062] Thus, in the borosilicate glass of the casing 15 of the solid-state battery 1 of Example 1-2, in which the Ag migration distance Lx is effectively suppressed, the content of alkali metal elements is greater for K than for Na, and the total content of alkali metal elements K and alkaline earth metal elements is 10.0% by mass or more and 16.0% by mass or less. Furthermore, the borosilicate glass of the casing 15 of the solid-state battery 1 of Example 1-2 has an alkaline earth metal element content of 10.0% by mass or more.

[0063] It was confirmed that by using a borosilicate glass in which alkali metal elements and alkaline earth metal elements are contained in such a way as to satisfy this relationship, a solid-state battery 1 can be realized that effectively suppresses the migration of Ag from the external connection terminal 20.

[0064] Furthermore, as shown in Table 1, the borosilicate glass of the outer casing 15 of the solid battery 1 of Example 1 had a Na content of 0.56 mass%, a Zr content of 0.06 mass%, and a total Na and Zr content of 0.62 mass%.

[0065] As shown in Table 1, the borosilicate glass of the casing 15 of the solid battery 1 of Example 2 had a Na content of 0.66 mass%, a Zr content of 3.57 mass%, and a total Na and Zr content of 4.23 mass%.

[0066] As shown in Table 1, the borosilicate glass of the outer casing 15 of the solid battery 1 of Comparative Example 1 had a Na content of 0.45 mass%, a Zr content of 4.04 mass%, and a total Na and Zr content of 4.49 mass%.

[0067] As shown in Table 1, the borosilicate glass of the casing 15 of the solid battery 1 of Comparative Example 2 had a Na content of 0.64 mass%, a Zr content of 4.41 mass%, and a total Na and Zr content of 5.05 mass%.

[0068] As shown in Table 1, the borosilicate glass of the casing 15 of the solid battery 1 of Comparative Example 3 had a Na content of 1.57% by mass, a Zr content of 5.01% by mass, and a total Na and Zr content of 6.58% by mass.

[0069] Thus, in the solid-state battery 1 of Example 1-2, where the Ag migration distance Lx is effectively suppressed, the borosilicate glass of the outer casing 15 had a total Na and Zr content of 4.3% by mass or less. Furthermore, the borosilicate glass of the outer casing 15 of the solid-state battery 1 of Example 1-2 had a lower Zr content than the borosilicate glass of the outer casing 15 of the solid-state battery 1 of Comparative Example 1-2, with a Zr content of 3.6% by mass or less. In the solid-state battery 1 of Example 1, where the Zr content in the borosilicate glass of the outer casing 15 was a sufficiently low 0.06% by mass, the Ag migration distance Lx was suppressed even more effectively than in the solid-state battery 1 of Example 2, where the Zr content was higher.

[0070] It was confirmed that by using a borosilicate glass in which Na and Zr are contained such that this relationship is satisfied, a solid-state battery 1 can be realized that effectively suppresses the migration of Ag from the external connection terminal 20.

[0071] In addition, although a borosilicate glass containing Ba was used as an example for the casing 15 in the solid-state battery 1 of Example 1-2, the same effects as those described for the solid-state battery 1 of Example 1-2 can be obtained by using a borosilicate glass in which all or part of the Ba is replaced with Sr. [Explanation of Symbols]

[0072] 1 solid state battery 10 Battery Unit 10a Positive electrode lead side 10b Negative electrode lead surface 11 Positive electrode layer 12 Negative electrode layer 13 Electrolyte layer 14 Power generation elements 15 Exterior 20, 30 External connection terminals 100 migrations Lx migration distance D1 1st direction D2 2nd direction D3 Third direction

Claims

1. Power generation elements, The outer casing covering the power generation element, It is in contact with the outer casing and electrically connected to the power generation element, and includes an external connection terminal containing Ag, It has, The exterior body includes a borosilicate glass containing alkali metal elements and alkaline earth metal elements. The borosilicate glass contains a larger amount of K than Na as the alkali metal element, and the total content of the alkali metal element K and the alkaline earth metal element is 10.0% by mass or more and 16.0% by mass or less, in a solid-state battery.

2. The solid battery according to claim 1, wherein the borosilicate glass contains 10.0% by mass or more of the alkaline earth metal element.

3. The solid battery according to claim 1, wherein the borosilicate glass contains Ba or Sr as the alkaline earth metal element.

4. The solid battery according to claim 1, wherein the borosilicate glass has a total content of 4.3% by mass or less of Na and Zr.

5. The solid battery according to claim 1, wherein the borosilicate glass has a Zr content of 3.6% by mass or less.

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