Solid-state battery

Abstract

The present invention provides a solid-state battery that is sufficiently exceptional in terms of low temperature densification characteristics and moisture resistance. The present invention relates to a solid-state battery having an exterior part and an insulation part, wherein at least one of the exterior part and the insulation part contains lithium (Li), magnesium (Mg), at least one element (M) selected from the group consisting of group 4 and group 5 elements, and an oxide ceramic that contains bismuth (Bi).

Description

solid state battery

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

[0002] In recent years, the demand for batteries as power sources for portable electronic devices such as mobile phones and portable personal computers has expanded significantly. Batteries used for such applications have traditionally used electrolytes (electrolytic solutions) such as organic solvents as a medium for ion migration. However, batteries with the above-described configurations have the risk of electrolyte leakage. Furthermore, organic solvents and other materials used in the electrolyte solutions are flammable. Therefore, there is a demand for improved battery safety.

[0003] Therefore, in order to improve the safety of batteries, research is being conducted into solid-state batteries that use solid electrolytes instead of electrolytic solutions.

[0004] For example, Patent Documents 1 to 4 propose solid-state batteries having an exterior portion containing oxide ceramics on the outer surface of a battery element including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer therebetween. In the solid-state battery, for example, insulating portions are disposed between the positive electrode layer and the negative electrode-side external electrode, and between the negative electrode layer and the positive electrode-side external electrode, and attempts have been made to include oxide ceramics in such insulating portions.

[0005] WO2019 / 167856 JP 2007-173212 A JP 2003-92092 A WO2019 / 181909

[0006] However, in the conventional solid state batteries described above, when firing (e.g., at 1100°C or higher) is performed during the manufacturing process, the oxide ceramic contained in the exterior part reacts with the solid electrolyte contained in the battery element, causing the solid electrolyte to decompose and generate by-products. This problem is particularly noticeable when a highly reactive solid electrolyte having a garnet-type or LISICON-type crystal structure is used.

[0007] Therefore, if the exterior portion contains an oxide ceramic containing one or more elements (M) selected from the group consisting of Li (lithium), Mg (magnesium), and elements of Groups 4 and 5, the reaction can be prevented to some extent, but the prevention effect is not sufficient. For this reason, attempts have been made to more fully prevent the reaction by firing at a relatively low temperature (for example, 1000°C or lower), but this has resulted in a new problem: the exterior portion does not become sufficiently densified at such a low temperature, which increases the areal porosity and reduces moisture resistance.

[0008] On the other hand, a new problem similar to the reaction between the oxide ceramics contained in the exterior portion and the solid electrolyte contained in the battery element (particularly the solid electrolyte layer) has also arisen between the oxide ceramics contained in the insulating portion and the solid electrolyte contained in the battery element. Therefore, if the insulating portion contains an oxide ceramic containing one or more elements (M) selected from the group consisting of Li (lithium), Mg (magnesium), and Group 4 and Group 5 elements, the reaction can be prevented to some extent, but the prevention effect is insufficient. For this reason, attempts have been made to more fully prevent the reaction by firing at a relatively low temperature (e.g., 1000°C or lower), as in the case where the exterior portion contains oxide ceramics. However, this low temperature does not sufficiently densify the insulating portion, resulting in an increase in areal porosity and a decrease in moisture resistance. Although the insulating portion is not in direct contact with the surrounding environment (e.g., air), air can enter through voids generated in the external electrode and / or between the external electrode and the battery element. Therefore, it is important for the insulating portion to be moisture-resistant. Thus, like the exterior part, the insulating part is also required to be densely fired to improve moisture resistance and to prevent side reactions with the solid electrolyte.

[0009] An object of the present invention is to provide a solid-state battery that is sufficiently superior in low-temperature densification characteristics and moisture resistance.

[0010] Another object of the present invention is to provide a solid-state battery that is more sufficiently superior not only in low-temperature densification characteristics and moisture resistance but also in reactivity resistance.

[0011] The present invention relates to a solid-state battery having an exterior part and an insulating part, wherein at least one of the exterior part and the insulating part comprises an oxide ceramic containing Li (lithium); Mg (magnesium); one or more elements (M) selected from the group consisting of elements of Groups 4 and 5; and Bi (bismuth).

[0012] According to the present invention, a solid-state battery having sufficiently excellent low-temperature densification characteristics and moisture resistance can be provided. Specifically, the solid-state battery of the present invention has an exterior part and / or an insulating part formed with a sufficiently reduced areal porosity even at a relatively low temperature (for example, 1000°C or less (particularly, 800°C or less)), and the water vapor transmission rate (WVTR) is sufficiently reduced even at high temperature and high humidity.

[0013] FIG. 1 is a schematic diagram showing an example of a solid state battery of the present invention, which is a combined perspective view and cross-sectional view. FIG. 2 is a schematic perspective view showing another example of a solid state battery of the present invention. FIG. 3 is an enlarged schematic view of an oxide ceramic for explaining sintered particles constituting an example of the oxide ceramic contained in the exterior portion and / or insulating portion of the solid state battery of the present invention and the structure thereof. FIG. 4 is an SEM photograph of the surface of a sintered body (exterior ceramic single plate) obtained in Example 1. FIG. 5 is an SEM photograph of the surface of a sintered body (exterior ceramic single plate) obtained in Comparative Example 1. FIG. 6 is a TEM photograph of a sintered body (exterior ceramic single plate) obtained in Example 1. FIG. 7 is an EDX mapping image showing the distribution of Bi elements in the TEM photograph shown in FIG. 6. FIG. 8 is a graph showing the results of EDX quantitative analysis of the portion indicated by the arrow in the TEM photograph shown in FIG. 7. FIG. 9 is an SEM photograph of the cross section of a sintered body (exterior ceramic single plate) obtained in Example 2.

[0014] [Solid-State Battery] The present invention provides a solid-state battery. In a broad sense, the term "solid-state battery" refers to a battery whose components (particularly the electrolyte layer) are made of solids, and in a narrow sense, refers to an "all-solid-state battery" whose components (particularly all components) are made of solids. In a preferred embodiment, the solid-state battery of the present invention is a stacked solid-state battery in which the layers constituting the battery units are stacked on top of each other, and preferably each such layer is made of a sintered body. The term "solid-state battery" as used herein encompasses so-called "secondary batteries" that can be repeatedly charged and discharged, and "primary batteries" that can only be discharged. In a preferred embodiment of the present invention, the "solid-state battery" is a "secondary battery." The term "secondary battery" should not be overly constrained by its name and can also encompass electrochemical devices such as "power storage devices." The term "solid electrolyte" as used herein refers to a battery that does not contain a gel or liquid electrolyte (liquid).

[0015] As used herein, the term "plan view" refers to the state of an object viewed from above or below along the thickness direction (top view or bottom view) based on the stacking direction of the layers constituting the solid-state battery (described later). Furthermore, the term "cross-sectional view" refers to the cross-sectional state (cross-sectional view) viewed from a direction approximately perpendicular to the thickness direction based on the stacking direction L of the layers constituting the solid-state battery (described later). The term "side view" refers to the state of a solid-state battery viewed from directly to the side in the thickness (height) direction, and is equivalent to a side view. The placement refers to placement with the largest surface (flat surface) constituting the solid-state battery's exterior facing downward. The terms "vertical direction" and "horizontal direction" used directly or indirectly in this specification correspond to the vertical direction and horizontal direction in the drawings, respectively. Unless otherwise specified, the same symbols or symbols refer to the same components or parts or have the same meaning. In a preferred embodiment, the vertical downward direction (i.e., the direction in which gravity acts) can be considered to correspond to the "downward direction," and the opposite direction can be considered to correspond to the "upward direction."

[0016] The solid-state battery of the present invention may have any shape in plan view, and typically has a rectangular shape, including a square and a rectangle.

[0017] The solid-state battery of the present invention has a layered structure (particularly a laminated structure), for example, as shown in Fig. 1. The solid-state battery of the present invention has a battery element 1 and an exterior part 2 covering the surface of the battery element 1, and usually further has an external electrode 3 for extracting power (particularly current) generated in the battery element to the outside. The insulating part is disposed between the electrode layer (positive electrode layer or negative electrode layer) 1a and the external electrode (negative electrode side or positive electrode side external electrode, respectively) 3, and is a member represented by "1c" in Fig. 1. Fig. 1 is a schematic cross-sectional view showing an example of the solid-state battery of the present invention.

[0018] In the solid-state battery of the present invention, at least one of the exterior and insulating parts contains a specific oxide ceramic. For example, of the exterior and insulating parts, only the exterior may contain the specific oxide ceramic, only the insulating part may contain the specific oxide ceramic, or both may contain the specific oxide ceramic. In the present invention, from the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and reactivity resistance, preferably, at least the exterior contains the specific oxide ceramic, and more preferably, both the exterior and insulating parts contain the specific oxide ceramic. Hereinafter, the solid-state battery of the present invention will be described in detail using a first embodiment and a second embodiment. The present invention includes the first embodiment and the second embodiment.

[0019] <First embodiment> In a solid-state battery according to a first embodiment of the present invention, at least the exterior part contains a specific oxide ceramic out of the exterior part and the insulating part. As will be described in detail later, the insulating part may or may not contain the specific oxide ceramic. In this embodiment, from the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and reactivity resistance, it is preferable that both the exterior part and the insulating part contain the specific oxide ceramic.

[0020] (Exterior Part) The exterior part 2 is a member covering the outside of the battery element 1 and has the function of covering the battery element 1 to prevent moisture from entering the battery element 1. The exterior part 2 typically not only has this function but also the function of electrically, physically, and chemically protecting the battery element 1, and therefore may also be referred to as a protective layer or protective film. The exterior part 2 includes a main surface exterior part 2a (e.g., a set of main surface exterior parts 2a) covering the main surfaces of the battery element 1 and a side surface exterior part 2b (e.g., a set of side surface exterior parts 2b) covering the side surfaces of the battery element 1. The exterior part 2 typically has a layer or film form. The exterior part 2 may be in direct contact with the surface (particularly the main surface and / or side surface) of the battery element 1, or may be in indirect contact via another layer (or film). From the viewpoint of more fully demonstrating the effects of the present invention, it is preferable that the exterior part 2 be in direct contact with the surface (particularly the main surface and / or side surface) of the battery element 1.

[0021] In the solid-state battery of this embodiment, the exterior part 2 contains a specific oxide ceramic. In this embodiment, it is sufficient that at least one of the main surface exterior part and the side surface exterior part contains the specific oxide ceramic. From the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and reactivity resistance, it is preferable that both the main surface exterior part and the side surface exterior part contain the specific oxide ceramic.

[0022] In this specification, low-temperature densification property refers to a property that allows the formation of an exterior part (and / or insulating part) with a sufficiently reduced areal porosity even at a relatively low temperature (for example, 1000°C or less (particularly 800°C or less)). Moisture resistance refers to a property that prevents moisture penetration, and may particularly be a property that sufficiently reduces the water vapor transmission rate (WVTR) even under high temperature and high humidity (for example, water vapor barrier property). Reactivity resistance refers to a property that makes it difficult for the exterior part (and / or insulating part) (particularly the oxide ceramic contained in the exterior part (and / or insulating part)) to react (e.g., undergo a side reaction) with the solid electrolyte contained in the battery element even when fired (for example, fired at 800°C for 5 hours). Reactivity resistance may particularly be a property that makes it difficult for the oxide ceramic and the solid electrolyte to react with each other even when fired together.

[0023] In this embodiment, the oxide ceramic contained in the exterior portion contains Li (lithium); Mg (magnesium); one or more elements (M) selected from the group consisting of elements of Groups 4 and 5; and Bi (bismuth). Specifically, element M is one or more elements selected from the group consisting of Ti (titanium), Zr (zirconium), Hf (hafnium), Ta (tantalum), and Nb (niobium). From the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, element M is preferably at least one element selected from Ti, Ta, and Nb, or two elements, Zr and Ta. In this embodiment, by containing a combination of Li, Mg, element M, and Bi in the oxide ceramic, an exterior portion with excellent low-temperature densification properties and moisture resistance can be obtained. If the oxide ceramic does not contain one or more elements selected from Li, Mg, element M, and Bi, the low-temperature densification properties will be reduced, and as a result, the moisture resistance will also be reduced.

[0024] In the oxide ceramic, the molar ratio Bi / (Mg+M) is not particularly limited, but from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, it is preferably within the following ranges: Bi / (Mg+M) preferably 0<Bi / (Mg+M)≦0.100; more preferably 0.001≦Bi / (Mg+M)≦0.080; even more preferably 0.004≦Bi / (Mg+M)≦0.060; and sufficiently preferably 0.005≦Bi / (Mg+M)≦0.040.

[0025] In the oxide ceramic, the molar ratios Li / M and Mg / M are not particularly limited, but from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, they are preferably within the following ranges: Li / M: preferably 0<Li / M≦5; more preferably 1.0≦Li / M≦4.0; even more preferably 1.5≦Li / M≦3.5; and sufficiently preferably 1.9≦Li / M≦3.0. Mg / M: preferably 0<Mg / M≦9.8; more preferably 0.01≦Mg / M≦7.0; even more preferably 0.05≦Mg / M≦6.0; and sufficiently preferably 0.08≦Mg / M≦4.2.

[0026] The Bi / (Mg+M), Li / M, and Mg / M in the oxide ceramics are values ​​calculated from the contents (or molar ratios) of Li, Mg, M, and Bi measured by a method similar to the analytical method for the chemical composition of oxide ceramics described below.

[0027] The Mg content in the oxide ceramic is usually 0% by mass or more and 58% by mass or less, particularly 1.9% by mass or more and 46% by mass or less, based on the total amount of the oxide ceramic.

[0028] The Mg content is measured by optical emission spectroscopy using high-frequency inductively coupled plasma (ICP) as a light source. For example, ICP-AES (ICP optical emission spectroscopy) or LA-ICP-MS (laser ablation ICP mass spectroscopy) may be used. Specifically, ICP-AES and LA-ICP-MS differ in that metal ions such as Mg are ionized by either solution formation or laser ablation, respectively, but are the same in that these ions are introduced into plasma and excited by the plasma. In particular, LA-ICP-MS contributes to simple measurements in solid-state analysis. In particular, when using LA-ICP-MS, quantitative analysis (composition analysis) may be performed at any 10 or more locations, and the average value may be calculated.

[0029] The oxide ceramic may have any chemical composition as long as it has the above-mentioned molar ratio. From the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, the oxide ceramic preferably has a chemical composition represented by the following general formula (1):

[0030]

[0031] In formula (1), A is one or more elements selected from the group consisting of Na, K, Rb, Ca, Sr, Ba, Sc, Y, Mo, W, Zn, Al, Ga, Ge, Sn, and Sb. M is one or more elements selected from the same group as the above-mentioned element M, and from the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and reactivity resistance, it preferably contains one or more elements selected from the group consisting of Ti, Zr, Nb, and Ta, more preferably at least one element selected from Ti, Ta, and Nb, or two elements selected from Zr and Ta, and even more preferably contains only Ti.

[0032] In formula (1), x / (β+γ), α1 / γ, and β / γ correspond to the molar ratios Bi / (Mg+M), Li / M, and Mg / M, respectively. Therefore, Bi / (Mg+M) satisfies the same range as the molar ratio Bi / (Mg+M), and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, preferably satisfies the preferred range of Bi / (Mg+M), more preferably satisfies the more preferred range of Bi / (Mg+M), even more preferably satisfies the even more preferred range of Bi / (Mg+M), and sufficiently preferably satisfies the sufficiently preferred range of Bi / (Mg+M). α1 / γ satisfies the same range as the molar ratio Li / M described above, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, preferably satisfies the preferred range of Li / M, more preferably satisfies the more preferred range of Li / M, even more preferably satisfies the even more preferred range of Li / M, and sufficiently preferably satisfies the sufficiently preferred range of Li / M. β / γ satisfies the same range as the molar ratio Mg / M described above, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, preferably satisfies the preferred range of Mg / M, more preferably satisfies the more preferred range of Mg / M, even more preferably satisfies the even more preferred range of Mg / M, and sufficiently preferably satisfies the sufficiently preferred range of Mg / M.

[0033] In formula (1), δ satisfies the following formula: δ = {α1 + aα2 + 2β + nγ + bx} / 2 (n is the average valence of M, a is the average valence of A, and b is the average valence of Bi). Specifically, n is the average valence of M. The average valence of M is, for example, when n1 element X with a valence of a+, n2 element Y with a valence of b+, and n3 element Z with a valence of c+ are recognized as M, the value represented by (n1 x a + n2 x b + n3 x c) / (n1 + n2 + n3). a is the average valence of A. The average valence of A is, for example, when n1 element X with a valence of a+, n2 element Y with a valence of b+, and n3 element Z with a valence of c+ are recognized as A, the value represented by (n1 x a + n2 x b + n3 x c) / (n1 + n2 + n3). b is the average valence of Bi, generally taking a value between 3 and 5. Bi typically exists in the grain boundaries (second phase), the main phase (first phase), or both of these phases of oxide ceramics, as described below. When the so-called main phase of sintered particles is referred to as the "first phase," the grain boundaries between adjacent main phases can be referred to as the "second phase." The valence of Bi varies depending on the form (or location) of Bi. Specifically, for example, when Bi exists at grain boundaries, the valence of Bi is often "3." For example, when Bi exists in the main phase, the valence of Bi is often "5." Therefore, the average valence of Bi is the value expressed as (n1 × 3 + n2 × 5) / (n1 + n2) when, for example, n1 Bi atoms are found at grain boundaries with a valence of 3 and n2 Bi atoms are found in the main phase with a valence of 5. The oxygen number δ may deviate by approximately ±10% from the above value. That is, some oxygen vacancies or interstitial oxygen may be present.

[0034] In formula (1), α1 typically satisfies 0 < α1 < 1.0, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, preferably satisfies 0.10 ≦ α1 ≦ 0.80, more preferably 0.20 ≦ α1 ≦ 0.70. α2 typically satisfies 0 ≦ α2 ≦ 1.0, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, preferably satisfies 0 ≦ α2 ≦ 0.5, more preferably satisfies 0 ≦ α2 ≦ 0.1, and even more preferably 0. β typically satisfies 0 < β < 1.0, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, preferably satisfies 0.01 ≦ β ≦ 0.80, more preferably satisfies 0.01 ≦ β ≦ 0.60. γ usually satisfies 0<γ<1.0, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, preferably satisfies 0.05≦γ≦0.50, more preferably satisfies 0.10≦γ≦0.40. x usually satisfies 0<x<1.0, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, preferably satisfies 0.001≦x≦0.050, more preferably satisfies 0.002≦x≦0.030.

[0035] The chemical composition of the oxide ceramic can be determined by ICP analysis (inductively coupled plasma method), LA-ICP-MS (laser ablation ICP-MS), or other analysis. EDX (energy dispersive X-ray spectroscopy) or WDX (wavelength dispersive X-ray spectroscopy) may also be used. When EDX or WDX is used, the chemical composition may be obtained by quantitatively analyzing 100 arbitrary points on each of 100 arbitrary sintered particles and calculating the average value.

[0036] As shown in FIG. 3 , oxide ceramics typically consist of a plurality of sintered grains each composed of a main phase (i.e., a first phase) 21 and a grain boundary (i.e., a second phase) 22 located between two adjacent main phases 21. In such oxide ceramics, the main phase 21 includes a grain boundary vicinity 23 near the grain boundary 22 and an interior 24 located inside the grain boundary vicinity 23. The grain boundary vicinity 23 refers to a region within a distance of 50 nm from a boundary line 20 between the grain boundary 22 and the interior 24 (i.e., the distance from the grain boundary boundary 20 toward the interior 24) (i.e., the grain boundary vicinity region from the boundary line 20 to the dashed line in FIG. 3 ). The grain boundary 22 refers to a region between two adjacent main phases 21. A phase (especially a second phase) does not necessarily have to be present at the grain boundary 22. FIG. 3 shows an enlarged schematic diagram of an oxide ceramic illustrating sintered particles constituting an example of an oxide ceramic contained in the exterior (and / or insulating) portion of the solid-state battery of the present invention, and the structure of the sintered particles. Although only three main phases 21 of sintered grains are shown in FIG. 3, there are usually many other sintered grains around them, forming grain boundaries between adjacent sintered grains.

[0037] In the present invention, in such oxide ceramics, Bi has any one of the following existence forms: (x1) Bi is present only in the grain boundaries (second phase) 22 of the oxide ceramic; in this case, Bi may be present in the main phase (first phase) 21 in an amount below the detection limit of analysis using a predetermined device and conditions; (x2) Bi is present only in the main phase (first phase) 21 of the oxide ceramic; in this case, Bi may be present in the grain boundaries (second phase) 22 in an amount below the detection limit of analysis using a predetermined device and conditions; (x3) Bi is present in both the grain boundaries (second phase) 22 and the main phase (first phase) 21 of the oxide ceramic. From the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, Bi is preferably contained in the oxide ceramic in a form present at least in the grain boundaries (second phase) (for example, the above existence form (x1) or (x3) (particularly existence form (x3))). In one embodiment, Bi is concentrated at grain boundaries and / or in the vicinity of grain boundaries of the oxide ceramic. By "concentrated," we mean that the concentration is higher. For example, the Bi concentration at grain boundaries 22 and / or in the vicinity of grain boundaries 23 of the oxide ceramic is higher than the Bi concentration in the interior 24 located inside the vicinity of grain boundaries 23.

[0038] The presence / absence of Bi at the grain boundaries (second phase) and the main phase (first phase) in such oxide ceramics can be determined based on the distribution of Bi elements in EDX mapping (300,000 to 2,000,000 magnifications) observed by TEM-EDX, as shown in FIG. 7 (described later). FIG. 7 clearly shows that Bi is concentrated at the grain boundaries (or at and near the grain boundaries) of the oxide ceramics. For example, when Bi is detected at the grain boundaries in the distribution of Bi elements, the presence of Bi is confirmed. On the other hand, when Bi is not detected at the grain boundaries in the distribution of Bi elements, the absence of Bi is confirmed. Furthermore, when Bi is detected in the main phase in the distribution of Bi elements, the presence of Bi is confirmed. On the other hand, when Bi is not detected in the main phase in the distribution of Bi elements, the absence of Bi is confirmed. Note that the determination of "presence" or "absence" depends on the resolution of a given analytical method and is not an absolute "presence" or "absence." Therefore, even if a substance is "not present," it is acceptable that it is contained in an amount below the detection limit of analysis using a specified device and conditions.

[0039] ・TEM-EDX TEM equipment: JEOL JEM-F200 EDX detector: EX-24390UBN5T EDX system: Noran system 7 Measurement conditions: Using a sample exfoliated to a thickness of 100 nm or less, EDX is performed at an acceleration voltage of 200 kV, and Bi is detected when measured under conditions where the Mg Kα count is 550,000 or more in the 666 nm field of view.

[0040] For example, when the exterior portion contains not only an oxide ceramic but also a sintering aid, the grain boundaries (second phase) 22 are mainly composed of the sintering aid. For example, when the exterior portion is composed of an oxide ceramic but does not contain a sintering aid, the grain boundaries (second phase) 22 are composed of components leached from the oxide ceramic. In either case, the grain boundaries (second phase) 22 preferably contain, in addition to Bi, at least one element selected from the group consisting of Li, Mg, and M, from the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and reactivity resistance.

[0041] The crystal structure of the oxide ceramic is not particularly limited, and may be, for example, a rock salt crystal structure, a spinel crystal structure, a layered rock salt crystal structure, or a mixed phase structure of these. From the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and reactivity resistance, the oxide ceramic preferably has a rock salt crystal structure or a layered rock salt crystal structure (particularly, only a rock salt crystal structure or a layered rock salt crystal structure), and more preferably has a rock salt crystal structure. Note that the crystal structure may refer to the crystal structure of the main phase.

[0042] The crystal structure can be detected and detected using the following analytical equipment and analytical conditions: X-ray diffractometer Analytical equipment: Bruker D2 PHASER Analytical conditions: Cu Kα, 2θ: 10-60°, step width 0.02° / sec.

[0043] For example, when an oxide ceramic has only a rock-salt crystal structure, it specifically means that the main phase (particularly the interior 24) of the oxide ceramic has only a rock-salt crystal structure, and does not substantially contain any other crystal structure. When the main phase has only a rock-salt crystal structure, it means that "among the peaks detected in the oxide ceramic, substantially no peaks other than those derived from the second phase and the rock-salt crystal structure are observed," i.e., "the oxide ceramic is composed only of the second-phase crystal structure and the rock-salt crystal structure." In this case, when the crystal structure of the oxide ceramic is analyzed using the above-mentioned analytical device and conditions, only the rock-salt crystal structure and the second-phase crystal structure are detected, and no other crystal structures are detected. Note that crystal structures other than these crystal structures may be present in amounts below the detection limit of the analysis using the device and conditions. In this case, the second-phase crystal structure may or may not be detected.

[0044] For example, "an oxide ceramic having only a layered rock-salt crystal structure" means that the main phase (particularly the interior 24) of the oxide ceramic has only a layered rock-salt crystal structure, and does not substantially contain any other crystal structure. "The main phase having only a layered rock-salt crystal structure" means that "among the peaks detected in the oxide ceramic, substantially no peaks other than those attributable to the second phase and the layered rock-salt crystal structure are observed," i.e., "the oxide ceramic is composed only of the second phase crystal structure and the layered rock-salt crystal structure." In this case, when the crystal structure of the oxide ceramic is analyzed using the above-mentioned analytical equipment and conditions, only the layered rock-salt crystal structure and the second phase crystal structure are detected, and no other crystal structures are detected. Note that crystal structures other than these crystal structures may be present in amounts below the detection limit of the analysis using the equipment and conditions. In this case, the second phase crystal structure may or may not be detected.

[0045] The expression "oxide ceramics have a rock-salt type crystal structure" does not simply mean that the oxide ceramics have a "rock-salt type crystal structure," but also encompasses the meaning of "rock-salt type-like crystal structure." Specifically, oxide ceramics have a crystal structure that can be recognized as a rock-salt type or rock-salt type-like crystal structure by those skilled in the art of solid-state batteries in X-ray diffraction. More specifically, in X-ray diffraction, oxide ceramics may exhibit one or more main peaks corresponding to Miller indices specific to the so-called rock-salt type crystal structure diffraction pattern: ICDD Card No. 00-004-0829 at a predetermined angle of incidence, or may exhibit one or more main peaks that differ in angle of incidence (i.e., peak position or diffraction angle) and intensity ratio (i.e., peak intensity or diffraction intensity ratio) from one or more main peaks corresponding to Miller indices specific to the so-called rock-salt type crystal structure due to differences in composition, as a typical diffraction pattern of a rock-salt type-like crystal structure. For example, ICDD Card No. 00-036-0308 and the like.

[0046] The expression "oxide ceramics have a spinel-type crystal structure" does not simply mean that the oxide ceramics have a "spinel-type crystal structure," but also encompasses a "spinel-like crystal structure." Specifically, the oxide ceramics have a crystal structure that can be recognized as a spinel-type or spinel-like crystal structure by those skilled in the art of solid-state batteries in X-ray diffraction. More specifically, the oxide ceramics may exhibit, in X-ray diffraction, one or more main peaks corresponding to Miller indices specific to the so-called spinel-type crystal structure diffraction pattern (ICDD Card No. 01-072-6998) at a predetermined angle of incidence, or may exhibit, as a spinel-like crystal structure, one or more main peaks that differ in angle of incidence (i.e., peak position or diffraction angle) and intensity ratio (i.e., peak intensity or diffraction intensity ratio) from one or more main peaks corresponding to Miller indices specific to the so-called spinel-type crystal structure due to differences in composition.

[0047] The oxide ceramic having a mixed phase structure of a rock salt type crystal structure and a spinel type crystal structure means that the oxide ceramic contains oxide ceramic having both the above-mentioned rock salt type crystal structure and spinel type crystal structure.

[0048] The statement that an oxide ceramic has a layered rock-salt type crystal structure does not simply mean that the oxide ceramic has a "layered rock-salt type crystal structure," but also encompasses a "layered rock-salt type-like crystal structure." Specifically, the oxide ceramic has a crystal structure that can be recognized as a layered rock-salt type or layered rock-salt type-like crystal structure by those skilled in the art of solid-state batteries in X-ray diffraction. More specifically, the oxide ceramic may exhibit, in X-ray diffraction, one or more main peaks corresponding to Miller indices specific to the so-called layered rock-salt type crystal structure diffraction pattern (ICDD Card No. 00-033-0831) at a predetermined angle of incidence, or may exhibit one or more main peaks that differ in angle of incidence (i.e., peak position or diffraction angle) and intensity ratio (i.e., peak intensity or diffraction intensity ratio) from one or more main peaks corresponding to Miller indices specific to the so-called layered rock-salt type crystal structure, due to differences in composition, as a layered rock-salt type-like crystal structure. A typical diffraction pattern of a layered rock salt-like crystal structure is, for example, ICDD Card No. 00-033-0843.

[0049] The oxide ceramics may be produced by any method as long as an oxide ceramics of the desired composition is obtained, and examples thereof include the following methods (1) and (2). Method (1): First, raw materials including a Li source, an Mg source, and an element M source are weighed out so that the desired composition (molar ratio) of the predetermined elements is achieved, and then thoroughly mixed with water and fired (first firing step). Next, the obtained fired product is weighed out together with a Bi-containing firing aid as a Bi source so that the desired composition (molar ratio) of the predetermined elements is achieved, and then thoroughly mixed with alcohol and a binder. The obtained slurry is then formed into a sheet and fired to obtain the oxide ceramics that constitute the exterior portion (second firing step). The Bi-containing firing aid is preferably an oxide containing Bi, and more preferably an oxide containing Bi and Li. Specific examples of the Bi-containing firing aid include LiBiO. ２ and Li ３ Bio ３ etc.

[0050] Method (2): The oxide ceramics can be obtained by weighing raw materials including a Li source, an Mg source, an element M source, and a Bi source so that predetermined elements have a desired composition (molar ratio), thoroughly mixing the mixture with water, and then firing the mixture (firing step).

[0051] The firing temperature in the first firing step in method (1) and the firing step in method (2) is not particularly limited and may be, for example, 800°C or higher and 1200°C or lower (particularly, 850°C or higher and 1100°C or lower). The firing time is not particularly limited and may be, for example, 1 hour or higher and 10 hours or lower (particularly, 3 hours or higher and 7 hours or lower). The firing temperature and firing time in the second firing step in method (1) are the same as those in the "firing step" in the "production method for a solid-state battery" described below.

[0052] Lithium carbonate (Li2CO3), for example, can be used as the Li source. Magnesium oxide (MgO), for example, can be used as the Mg source. Titanium oxide (TiO2), niobium oxide (Nb2O5), zirconium oxide (ZrO2), tantalum oxide (Ta2O5), and hafnium oxide (HfO2) can be used as the M source. Bi, for example, can be used as the Bi source. In producing oxide ceramics, the final composition of the obtained oxide ceramics is determined almost exactly by the ratio of the Li, Mg, and M sources used at the time of charging. Therefore, the molar ratios x / (β + γ), Li / M (α1 / γ), and Mg / M (β / γ) can be controlled by adjusting the ratios of the Li, Mg, M, and Bi sources used.

[0053] In this embodiment, the exterior part 2 may contain other oxide ceramics in addition to the specific oxide ceramics described above. Examples of other oxide ceramics include Li-Bi-O-based oxides, Li-Mg-Bi-O-based oxides, and Bi ２ O ３, Mg—Bi—O-based oxides, Li-M—O-based oxides (wherein M is the same as M in formula (1)), Li-Bi-M—O-based oxides (wherein M is the same as M in formula (1)), MgO, etc. The content of the specific oxide ceramics in the exterior part 2 may typically be an area percentage of 60% to 100%, particularly an area percentage of 90% to 100%. This area percentage can be measured as follows. First, the solid-state battery is fractured so that the fracture surface of the ceramic exterior part is exposed. This fracture surface is polished using a cross-section polisher or the like to obtain a polished surface. EDX analysis is performed on any surface in the exterior part region on the polished surface, and the region where Mg, element M, and element A are detected and Li is detected by TOF-SIMS is considered to be the region of the specific oxide ceramics. From the above, the area percentage of the oxide ceramics relative to the area of ​​the exterior part can be calculated and measured.

[0054] The exterior part 2 may or may not contain a sintering aid. Examples of sintering aids that may be contained in the exterior part include the above-mentioned Bi-containing sintering aid and sintering aids that may be contained in the positive electrode layer and negative electrode layer, which will be described later. From the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and reactivity resistance, it is preferable that the exterior part 2 does not contain any sintering aids other than the Bi-containing sintering aid.

[0055] The thickness of the exterior part 2 is preferably 1 μm or more and 500 μm or less, more preferably 5 μm or more and 100 μm or less, and even more preferably 5 μm or more and 50 μm or less. The thickness of the exterior part 2 is the average thickness of thicknesses at 100 arbitrary positions.

[0056] The relative density of the exterior part 2 is usually 90% or more and 100% or less, and preferably 95% or more and 100% or less. The relative density of the exterior part may be measured using the Archimedes method.

[0057] The exterior part 2 is usually insulating. Insulating means that the exterior part 2 has neither ionic conductivity nor electronic conductivity. For example, the ionic conductivity of the exterior part 2 is usually 1×10 －７ S / cm or less, especially ionic conductivity is 1×10 －１０The ionic conductivity of the exterior part 2 is usually 1×10 －１８ For example, the electronic conductivity of the exterior part 2 is usually 1×10 －７ S / cm or less, especially 1×10 －１０ The electronic conductivity of the exterior part 2 is usually 1×10 －１８ S / cm or more.

[0058] The oxygen permeability in the thickness direction of the exterior part 2 is, for example, 10 －１ cc / m ２ / day / atmospheric pressure or less, especially 10 －３ cc / m ２ / day / atmospheric pressure or less. ２ O permeability is, for example, 10 －２ g / m ２ / day and below, especially 10 －４ g / m ２ / day or less. ２ The O permeability is measured at 25° C. by the cup method, carrier gas method, pressure method, or Ca corrosion method.

[0059] In FIG. 1 , the main surface exterior portion 2a and the side surface exterior portion 2b have the form (or structure) of separate members, but as shown in FIG. 2 , the main surface exterior portion 2a and the side surface exterior portion 2b may have an integrated form (or an integrated structure). FIG. 2 is a schematic perspective view showing another example of a solid-state battery of the present invention. The solid-state battery of FIG. 2 is similar to the solid-state battery of FIG. 1 except that the main surface exterior portion 2a and the side surface exterior portion 2b have the integrated form. In the solid-state battery of FIG. 2 , not only the main surface exterior portion 2a but also the side surface exterior portion 2b can be manufactured using a sheet-attaching method (green sheet method) described below. In particular, manufacturing a solid-state battery (particularly the exterior portion 2) using a sheet in which the sheet corresponding to the main surface exterior portion 2a and the sheet corresponding to the side surface exterior portion 2b are continuous significantly simplifies the manufacture of the solid-state battery (particularly the exterior portion 2). In this case, the oxide ceramic contained in the main surface exterior portion 2a usually has the same chemical composition as the oxide ceramic contained in the side surface exterior portion 2b.

[0060] When the exterior part 2 is in direct contact with the surface (particularly the main surface and / or side surface) of the battery element 1, it is preferable that the exterior part 2 and the surface be sintered together. That is, the exterior part 2 is preferably an integral sintered body formed by sintering the surface (particularly the main surface and / or side surface) of the battery element 1. The exterior part 2 being an integral sintered body formed by sintering the surface of the battery element 1 means that the exterior part 2 and the battery element 1 are joined by sintering. More specifically, the exterior part 2 and the battery element 1 are both sintered bodies, but are sintered together. Note that the exterior part 2 and the battery element 1 do not necessarily have to be strictly integrated in their entirety, and partial integration is also acceptable. It is sufficient that the exterior part 2 and the battery element 1 are integrated as a whole.

[0061] (Battery Element) The battery element 1 is the main body of a solid-state battery covered by an exterior part 2 and includes one or more battery units. A battery unit is the smallest unit capable of performing battery functions, and includes a pair of electrode layers 1a (specifically, one positive electrode layer and one negative electrode layer facing each other) and one solid electrolyte layer 1b disposed between the pair of electrode layers 1a (i.e., between the positive electrode layer and the negative electrode layer). The battery element 1 may have a single cell structure having only one battery unit, or a multi-cell structure in which two or more battery units are stacked along the stacking direction of the layers constituting each battery unit. The electrode layers include a positive electrode layer and a negative electrode layer. The battery element 1 typically has an insulating part 1c to ensure electrical non-contact between one electrode layer and an external electrode for drawing current from the other electrode layer to the outside. For example, the battery element 1 is disposed between the positive electrode layer and an external electrode (i.e., a negative electrode-side external electrode) for drawing current from the negative electrode layer to the outside, and has an insulating portion 1c for ensuring electrical non-contact therebetween. Furthermore, for example, the battery element 1 is disposed between the negative electrode layer and an external electrode (i.e., a positive electrode-side external electrode) for drawing current from the positive electrode layer to the outside, and has an insulating portion 1c for ensuring electrical non-contact therebetween. As shown in FIG. 1 , the battery element typically has solid electrolyte layers 1b in the uppermost and lowermost layers of the battery element.

[0062] The insulating part may or may not contain the specific oxide ceramics described above. In this embodiment, from the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and reactivity resistance, it is preferable that both the exterior part and the insulating part contain the specific oxide ceramics.

[0063] When the insulating part contains the specific oxide ceramic described above, the description of the insulating part may be applied by replacing "external part" with "insulating part" unless otherwise specified. Therefore, the oxide ceramic contained in the insulating part may be selected from the same range as the oxide ceramic contained in the external part described above. The specific oxide ceramic contained in the insulating part and the specific oxide ceramic contained in the external part may each be selected independently. A preferred oxide ceramic contained in the insulating part may be selected from the same range as the preferred oxide ceramic contained in the external part described above.

[0064] The insulating portion usually has a thickness similar to that of the positive electrode layer or the negative electrode layer. The thickness of the insulating portion is preferably 1 μm or more and 500 μm or less, more preferably 5 μm or more and 100 μm or less, and even more preferably 5 μm or more and 50 μm or less. The thickness of the insulating portion is the average thickness of thicknesses at 100 arbitrary locations.

[0065] The relative density of the insulating portion is usually 90% or more and 100% or less, and preferably 95% or more and 100% or less. The relative density of the insulating portion may be measured using the Archimedes method.

[0066] The insulating portion has insulating properties and has neither ionic conductivity nor electronic conductivity. For example, the ionic conductivity of the insulating portion is usually 1×10 －７ S / cm or less, especially 1×10 －１０ The ionic conductivity of the insulating part is usually 1×10 －１８ For example, the electronic conductivity of the insulating portion is usually 1×10 －７ S / cm or less, especially 1×10 －１０ The electronic conductivity of the insulating part is usually 1×10 －１８ S / cm or more.

[0067] The oxygen permeability in the thickness direction of the insulating part is, for example, 10 －１ cc / m ２ / day / atmospheric pressure or less, especially 10 －３ cc / m ２ / day / atmospheric pressure or less. ２ O permeability is, for example, 10 －２ g / m ２ / day and below, especially 10 －４ g / m ２ / day or less. ２ The O permeability is measured at 25° C. by the cup method, carrier gas method, pressure method, or Ca corrosion method.

[0068] When the insulating part does not contain the above-mentioned specific oxide ceramics, the insulating part may be made of any oxide ceramics known in the field of solid-state batteries. For example, the insulating part may be the same as the insulating part described above, except that it is made of the same oxide ceramics as the "other oxide ceramics" described in the explanation of the exterior part.

[0069] The insulating portion includes an insulating portion disposed between the positive electrode layer and the negative electrode-side external electrode, and an insulating portion disposed between the negative electrode layer and the positive electrode-side external electrode. The insulating portion usually has a layer or film form. The insulating portion is disposed between two solid electrolyte layers and may be in direct contact with the surfaces (particularly, parts of the main surfaces) of each of the two solid electrolyte layers, or may be in indirect contact with each of the surfaces (particularly, parts of the main surfaces) via another layer (or film). From the viewpoint of more fully exhibiting the effects of the present invention, it is preferable that the insulating portion be disposed between two solid electrolyte layers and be in direct contact with the surfaces (particularly, parts of the main surfaces) of each of the two solid electrolyte layers.

[0070] When the insulating portion is disposed between two solid electrolyte layers and is in direct contact with the surfaces (particularly, portions of the main surfaces) of the two solid electrolyte layers, it is preferable that the insulating portion be integrally sintered with the surfaces. That is, the insulating portion is preferably an integrally sintered body formed by sintering the surfaces (particularly, portions of the main surfaces) of the two solid electrolyte layers. The insulating portion being integrally sintered with the surfaces of the two solid electrolyte layers means that the insulating portion and the two solid electrolyte layers are joined by sintering. More specifically, the insulating portion and the two solid electrolyte layers are both sintered bodies, but are sintered integrally. Note that the insulating portion does not necessarily have to be integrally integrated with the two solid electrolyte layers, and partial integration is not required. It is sufficient that the insulating portion and the two solid electrolyte layers are integrally integrated as a whole.

[0071] The battery element typically includes a solid electrolyte (hereinafter, sometimes referred to as a first solid electrolyte). The first solid electrolyte included in the battery element may have any crystal structure, such as a garnet-type crystal structure, a LISICON-type crystal structure, a perovskite-type crystal structure, or a mixed phase structure thereof. From the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and reactivity resistance, the first solid electrolyte included in the battery element preferably has a garnet-type crystal structure, a LISICON-type crystal structure, or a mixed phase structure thereof, and more preferably has a garnet-type crystal structure. The reactivity with the oxide ceramic of the exterior increases in the order of solid electrolytes having a perovskite-type crystal structure, solid electrolytes having a LISICON-type crystal structure, and solid electrolytes having a garnet-type crystal structure. This is because even if the battery element contains such a solid electrolyte, the oxide ceramic of the exterior can more sufficiently suppress the reaction with the solid electrolyte.

[0072] When the battery element includes such a first solid electrolyte, the first solid electrolyte may be contained in one or more layers selected from the group consisting of a positive electrode layer, a negative electrode layer, and a solid electrolyte layer. From the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and reactivity resistance, it is preferable that the first solid electrolyte be contained in at least the solid electrolyte layer.

[0073] The term "solid electrolyte having a garnet-type crystal structure" does not simply mean that the solid electrolyte has a "garnet-type crystal structure," but also encompasses a "garnet-like crystal structure." Specifically, the solid electrolyte has a crystal structure that can be recognized as a garnet-type or garnet-like crystal structure by those skilled in the art of solid-state batteries in X-ray diffraction. More specifically, the solid electrolyte may exhibit, in X-ray diffraction, one or more main peaks corresponding to Miller indices specific to the so-called garnet-type crystal structure diffraction pattern (ICDD Card No. 422259) at a predetermined angle of incidence, or may exhibit one or more main peaks that differ in angle of incidence (i.e., peak position or diffraction angle) and intensity ratio (i.e., peak intensity or diffraction intensity ratio) from one or more main peaks corresponding to Miller indices specific to the so-called garnet-like crystal structure due to differences in composition. Representative diffraction patterns of garnet-like crystal structures include, for example, ICDD Card No. 00-045-0109.

[0074] The solid electrolyte having a garnet-type crystal structure may have any chemical composition, for example, a chemical composition represented by the following general formula (2).

[0075]

[0076] In formula (2), A １ indicates a metal element occupying the Li site in the garnet-type crystal structure. １ is usually one or more elements selected from the group consisting of Ga (gallium), Al (aluminum), Mg (magnesium), Zn (zinc) and Sc (scandium). １is preferably one or more elements selected from the group consisting of Ga (gallium) and Al (aluminum), more preferably two elements, Ga and Al, from the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and reactivity resistance.

[0077] In formula (2), B １ indicates a metal element occupying the La site in the garnet-type crystal structure. １ is usually one or more elements selected from the group consisting of Ca (calcium), Sr (strontium), Ba (barium), and lanthanoid elements, such as Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holminium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium).

[0078] In formula (2), D １ indicates a metal element occupying a hexacoordinated site in a garnet-type crystal structure. The hexacoordinated site of a garnet-type crystal structure is, for example, Li ５ La ３ Nb ２ O １２ (ICDD Card No. 00-045-0109) Nb-occupied site, Li ７ La ３ Zr ２ O １２ (ICDD Card. No. 01-078-6708) is the site occupied by Zr. １represents one or more elements selected from the group consisting of transition elements capable of hexacoordination with oxygen and typical elements belonging to groups 12 to 15. Examples of transition elements capable of hexacoordination with oxygen include Sc (scandium), Zr (zirconium), Ti (titanium), Ta (tantalum), Nb (niobium), Hf (hafnium), Mo (molybdenum), W (tungsten), and Te (tellurium). Examples of typical elements belonging to groups 12 to 15 include In (indium), Ge (germanium), Sn (tin), Pb (lead), Sb (antimony), and Bi (bismuth). D １ is usually one or more elements selected from the group consisting of Zr (zirconium), Sn (tin), Sb (antimony), Ti (titanium), Ta (tantalum), Nb (niobium), Hf (hafnium), Mo (molybdenum), W (tungsten) and Te (tellurium), and from the viewpoint of further improving low-temperature densification characteristics, moisture resistance and reactivity resistance, preferably contains one or more elements selected from the group consisting of Zr (zirconium), Ta (tantalum) and Nb (niobium), more preferably contains Zr (zirconium) and Ta (tantalum).

[0079] In formula (2), x satisfies 0≦x≦1.00, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, preferably satisfies 0≦x≦0.70, more preferably 0≦x≦0.40, even more preferably 0≦x≦0.40, and particularly preferably 0≦x≦0.20. y satisfies 0≦y≦0.50, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, preferably satisfies 0≦y≦0.40, more preferably 0≦y≦0.30, and even more preferably 0≦y≦0.20. β satisfies 2.5≦β≦3.5, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, preferably satisfies 2.7≦β≦3.3, more preferably 2.8≦β≦3.2, and even more preferably 2.9≦β≦3.1. z satisfies 0≦z≦2.00, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, preferably satisfies 0≦z≦1.00, more preferably 0≦z≦0.50, and even more preferably 0. γ satisfies 1.5≦γ≦2.5, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, preferably satisfies 1.7≦γ≦2.3, more preferably 1.8≦γ≦2.2, and even more preferably 1.9≦γ≦2.0.

[0080] In formula (2), p usually satisfies 6.0≦p≦7.0, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, it preferably satisfies 6.2≦p≦6.8, and more preferably 6.4≦p≦6.8. １ is the average valence of １ The average valence of A １ For example, when n1 element X with a valence of a+, n2 element Y with a valence of b+, and n3 element Z with a valence of c+ are recognized, it is a value expressed as (n1 x a + n2 x b + n3 x c) / (n1 + n2 + n3). b is B １ is the average valence of B. １ The average valence of B １ For example, when n1 elements X having a valence of a+, n2 elements Y having a valence of b+, and n3 elements Z having a valence of c+ are found, the above-mentioned A １ The same value as the average valence of １ is the average valence of １The average valence of １ For example, when n1 elements X having a valence of a+, n2 elements Y having a valence of b+, and n3 elements Z having a valence of c+ are found, the above-mentioned A １ is the same value as the average valence of δ. δ indicates the amount of oxygen vacancy and may be 0. Usually, δ is sufficient as long as it satisfies 0≦δ<1. The amount of oxygen vacancy δ cannot be quantitatively analyzed even using the latest equipment, so it may be considered to be 0. Note that the molar ratio of each element in the chemical composition of the oxide ceramic of the present invention does not necessarily match, for example, the molar ratio of each element in formula (2), and tends to deviate depending on the analytical method, but the effect of the present invention can be achieved as long as the composition deviation is not so great that it changes the characteristics.

[0081] In the present invention, the chemical composition of the oxide ceramic may be the composition of the entire ceramic material determined using ICP (inductively coupled plasma). It may also be measured and calculated using ICP-AES (inductively coupled plasma atomic emission spectroscopy) or LA-ICP-MS (laser ablation inductively coupled plasma mass spectroscopy). The chemical composition may also be measured and calculated using XPS analysis, or may be determined using TEM-EDX (energy dispersive X-ray spectroscopy) and / or WDX (wavelength dispersive X-ray spectroscopy). Furthermore, the chemical composition may be obtained by quantitatively analyzing 100 arbitrary points on each of 100 arbitrary sintered particles and calculating the average value.

[0082] Specific examples of the garnet-type solid electrolyte represented by the general formula (2) include Li ６．６ La ３ Zr １．６ Ta ０．４ O １２ , Li ６．４ Ga ０．０５ Al ０．１５ La ３ Zr ２ O １２ , Li ６．７５ La ３ Zr １．７５ Nb ０．２５ O １２ , Li ６．５３ La ３ Zr １．５３Ta ０．４ Bi ０．０７ O １２ Examples include:

[0083] The LISICON type crystal structure of the solid electrolyte is Ｉ structure, β ＩＩ Type structure, β ＩＩ 'type structure, T Ｉ Type structure, T ＩＩ Type structure, γ ＩＩ type structure, and γ ０ That is, the LISICON-type solid electrolyte has a β Ｉ structure, β ＩＩ Type structure, β ＩＩ 'type structure, T Ｉ Type structure, T ＩＩ Type structure, γ ＩＩ Type structure, γ ０ The solid electrolyte may contain one or more solid electrolytes having a γ-type structure or a composite structure thereof. The LISICON-type structure of the solid electrolyte is preferably a γ-type structure or a composite structure thereof from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance. ＩＩ A mold structure is preferred.

[0084] The solid electrolyte is γ ＩＩ The term "having a γ-type structure" means that the solid electrolyte ＩＩ It means that the solid-state battery has a γ type crystal structure, and in a broad sense, it is known by those skilled in the art of solid-state batteries as ＩＩ In a narrow sense, a solid electrolyte has a crystal structure that can be recognized as a γ-type crystal structure. ＩＩ The term "having a γ-type structure" means that the solid electrolyte has a γ-type structure in X-ray diffraction. ＩＩ -Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a given angle of incidence. ＩＩ Compounds having this type structure (i.e., solid electrolytes) are described, for example, in the literature "J. Solid State Chem" (A.R.West et al., J. Solid State Chem., 4, 20-28 (1972)), and an example thereof is ICDD Card No. 01-073-2850.

[0085] The solid electrolyte is β Ｉ The term "having a β-type structure" means that the solid electrolyte has a β-type structure. Ｉ In a broad sense, it means that the solid-state battery has a β type crystal structure. Ｉ In a narrow sense, the term "solid electrolyte" refers to a solid electrolyte having a crystal structure that can be recognized as a β-type crystal structure. Ｉ The term "having a β-type structure" means that the solid electrolyte has a β-type structure in X-ray diffraction. Ｉ -Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a given angle of incidence. Ｉ Compounds having the above structure (i.e., solid electrolytes) are described, for example, in the literature "J. Solid State Chem" (A.R. West et al., J. Solid State Chem., 4, 20-28 (1972)). As an example, the XRD data (d-spacing values ​​and corresponding Miller indices) shown in the table below are shown.

[0086]

[0087] The solid electrolyte is β ＩＩ The term "having a β-type structure" means that the solid electrolyte has a β-type structure. ＩＩ In a broad sense, it means that the solid-state battery has a β type crystal structure. ＩＩ In a narrow sense, the term "solid electrolyte" refers to a solid electrolyte having a crystal structure that can be recognized as a β-type crystal structure. ＩＩ The term "having a β-type structure" means that the solid electrolyte has a β-type structure in X-ray diffraction. ＩＩ -Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a given angle of incidence. ＩＩ Compounds having this type structure (i.e., solid electrolytes) are described, for example, in the literature "J. Solid State Chem" (A.R. West et al., J. Solid State Chem., 4, 20-28 (1972)), and an example thereof is ICDD Card No. 00-024-0675.

[0088] The solid electrolyte is β ＩＩ The term "having a β' structure" means that the solid electrolyte has a β ＩＩ It means that the solid-state battery has a β'-type crystal structure, and in a broad sense, it is known by those skilled in the art of solid-state batteries as ＩＩ In a narrow sense, the term refers to a solid electrolyte having a crystal structure that can be recognized as a β'-type crystal structure. ＩＩ The term "having a β' type structure" means that the solid electrolyte has a so-called β' type structure in X-ray diffraction. ＩＩ '-Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a given angle of incidence. ＩＩ Compounds having the '-type structure (i.e., solid electrolytes) are described, for example, in the literature "J. Solid State Chem" (A.R.West et al., J. Solid State Chem., 4, 20-28 (1972)). As an example, the XRD data (d-spacing values ​​and corresponding Miller indices) shown in the table below are shown.

[0089]

[0090] Solid electrolyte is T Ｉ The term "having a T type structure" means that the solid electrolyte has a T type structure. Ｉ It means that the solid-state battery has a crystal structure of T type. Ｉ In a narrow sense, the solid electrolyte has a crystal structure that can be recognized as a T type crystal structure. Ｉ The term "having a type structure" means that the solid electrolyte has a so-called T Ｉ -Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a given angle of incidence. Ｉ Compounds having this type structure (i.e., solid electrolytes) are described, for example, in the literature "J. Solid State Chem" (A.R. West et al., J. Solid State Chem., 4, 20-28 (1972)), and an example thereof is ICDD Card No. 00-024-0668.

[0091] Solid electrolyte is T ＩＩ The term "having a T type structure" means that the solid electrolyte has a T type structure. ＩＩ It means that the solid-state battery has a crystal structure of T type. ＩＩ In a narrow sense, the solid electrolyte has a crystal structure that can be recognized as a T type crystal structure. ＩＩ The term "having a type structure" means that the solid electrolyte has a so-called T ＩＩ -Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a given angle of incidence. ＩＩ Compounds having this type structure (i.e., solid electrolytes) are described, for example, in the literature "J. Solid State Chem" (A.R.West et al., J. Solid State Chem., 4, 20-28 (1972)), and an example thereof is ICDD Card No. 00-024-0669.

[0092] The solid electrolyte is γ ０ The term "having a γ-type structure" means that the solid electrolyte ０ It means that the solid-state battery has a γ type crystal structure, and in a broad sense, it is known by those skilled in the art of solid-state batteries as ０ In a narrow sense, a solid electrolyte has a crystal structure that can be recognized as a γ-type crystal structure. ０ The term "having a γ-type structure" means that the solid electrolyte has a γ-type structure in X-ray diffraction. ０ -Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a given angle of incidence. ０ Compounds having the above structure (i.e., solid electrolytes) are described, for example, in the literature "J. Solid State Chem" (A.R. West et al., J. Solid State Chem., 4, 20-28 (1972)). As an example, the XRD data (d-spacing values ​​and corresponding Miller indices) shown in the table below are shown.

[0093]

[0094] The solid electrolyte having a LISICON-type crystal structure may have any chemical composition, for example, the chemical composition represented by the following general formula (3):

[0095]

[0096] In formula (3), A is one or more elements selected from the group consisting of Na (sodium), K (potassium), Mg (magnesium), Ca (calcium), Al (aluminum), Ga (gallium), Zn (zinc), Fe (iron), Cr (chromium), and Co (cobalt). B is one or more elements selected from the group consisting of Zn (zinc), Al (aluminum), Ga (gallium), Si (silicon), Ge (germanium), Sn (tin), P (phosphorus), As (arsenic), Ti (titanium), Mo (molybdenum), W (tungsten), Fe (iron), Cr (chromium), and Co (cobalt). From the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, B is preferably one or more elements selected from the group consisting of Si (silicon) and P (phosphorus), more preferably Si (silicon) or P (phosphorus). x has the relationship 0≦x≦1.0, particularly 0≦x≦0.2, and preferably has the relationship 0≦x≦0.1 from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance, and is more preferably 0. y has the relationship 0≦y≦1.0, and preferably has the relationship 0≦y≦0.85 from the viewpoint of further improving low-temperature densification properties, moisture resistance, and reactivity resistance. a is the average valence of A. The average valence of A is, for example, when A contains n1 elements X with a valence of a+, n2 elements Y with a valence of b+, and n3 elements Z with a valence of c+, the value is expressed as (n1×a+n2×b+n3×c) / (n1+n2+n3). b is the average valence of B. The average valence of B is the same as the average valence of A described above when, for example, B contains n1 elements X with a valence of a+, n2 elements Y with a valence of b+, and n3 elements Z with a valence of c+.

[0097] Specific examples of the LISICON-type solid electrolyte represented by the general formula (3) include Li ３．２ V０．８ Si ０．２ O ４ , Li ３．５ P ０．５ Si ０．５ O ４ Examples include:

[0098] The term "solid electrolyte having a perovskite crystal structure" does not simply mean that the solid electrolyte has a "perovskite-type crystal structure," but also encompasses a "perovskite-like crystal structure." Specifically, the solid electrolyte has a crystal structure that can be recognized as a perovskite or perovskite-like crystal structure by those skilled in the art of solid-state batteries in X-ray diffraction. More specifically, the solid electrolyte may exhibit, in X-ray diffraction, one or more main peaks corresponding to Miller indices specific to the so-called perovskite crystal structure diffraction pattern (ICDD Card No. 00-046-0465) at a predetermined angle of incidence, or may exhibit, as a perovskite-like crystal structure, one or more main peaks that differ in angle of incidence (i.e., peak position or diffraction angle) and intensity ratio (i.e., peak intensity or diffraction intensity ratio) from one or more main peaks corresponding to Miller indices specific to the so-called perovskite-type crystal structure due to differences in composition. A typical diffraction pattern of a perovskite-like crystal structure is, for example, ICDD Card No. 00-046-0466.

[0099] The solid electrolyte having a perovskite crystal structure may have any chemical composition, for example, a chemical composition represented by the following general formula (3).

[0100] It is preferred that the average chemical composition be expressed as follows:

[0101] In formula (4), x preferably satisfies the relationship 0.09<x<0.167, and more preferably 0.10<x<0.12.

[0102] Specific examples of the perovskite-type solid electrolyte represented by the general formula (4) include Li ０．３５ La ０．５５TiO ３ , Li ０．５ La ０．５ TiO ３ Examples include:

[0103] The chemical composition of the solid electrolyte refers to the average value of the chemical composition of the solid electrolyte in the thickness direction of a layer (e.g., a solid electrolyte layer) containing the solid electrolyte. The chemical composition of the solid electrolyte can be analyzed and measured by breaking the solid-state battery and performing composition analysis by EDX (energy dispersive X-ray spectroscopy) using SEM-EDX in a field of view that includes the entire layer in the thickness direction.

[0104] The solid electrolyte can be obtained by the same method as that for the oxide ceramics described above, except that a raw material compound containing a predetermined metal atom is used, or can be obtained as a commercially available product.

[0105] In order to suppress battery deterioration over a longer period of time, all layers constituting the battery element 1 may be sintered together between two adjacent layers. The phrase "all layers are sintered together between two adjacent layers" means that the two adjacent layers are joined by sintering. Specifically, the two adjacent layers are both sintered bodies, but are sintered together. Note that the two adjacent layers do not necessarily have to be fully integrated, and partial integration is acceptable. It is sufficient that the two adjacent layers are fully integrated. For example, the positive electrode layer 1a, the solid electrolyte layer 1b, and the negative electrode layer 1a may be sintered together in a predetermined stacking order.

[0106] Positive Electrode Layer and Negative Electrode Layer The positive electrode layer is a so-called positive electrode active material layer, and may additionally include a positive electrode current collector layer. When the positive electrode layer includes a positive electrode current collector layer, the positive electrode layer may be provided on one side of the positive electrode current collector layer, or on both sides of the positive electrode current collector layer. The positive electrode layer is formed of a sintered body containing positive electrode active material particles, and may usually be formed of a sintered body containing positive electrode active material particles, electron conductive material particles, and solid electrolyte particles contained in the solid electrolyte layer. The positive electrode layer (particularly the positive electrode active material layer) may include the first solid electrolyte described above.

[0107] The negative electrode layer is a so-called negative electrode active material layer, and may additionally include a negative electrode current collecting layer. When the negative electrode layer includes a negative electrode current collecting layer, the negative electrode layer may be provided on one side of the negative electrode current collecting layer, or on both sides of the negative electrode current collecting layer. The negative electrode layer is formed of a sintered body containing negative electrode active material particles, and may be formed of a sintered body containing negative electrode active material particles, electron conductive material particles, and solid electrolyte particles contained in the solid electrolyte layer. The negative electrode layer (particularly the negative electrode active material layer) may include the first solid electrolyte described above.

[0108] The positive electrode active material contained in the positive electrode layer and the negative electrode active material contained in the negative electrode layer are substances involved in the transfer of electrons in a solid-state battery, and charging and discharging are performed by the transfer of electrons caused by the movement (conduction) of ions contained in the solid electrolyte material constituting the solid electrolyte layer between the positive electrode and the negative electrode. The positive electrode layer and the negative electrode layer may be layers capable of absorbing and releasing lithium ions in particular. In other words, the solid-state battery of the present invention may be a solid-state secondary battery in which lithium ions move between the positive electrode and the negative electrode via the solid electrolyte layer to charge and discharge the battery.

[0109] The positive electrode active material contained in the positive electrode layer is not particularly limited, and for example, at least one selected from the group consisting of a lithium-containing phosphate compound having a Nasicon structure, a lithium-containing phosphate compound having an olivine structure, a lithium-containing layered oxide, and a lithium-containing oxide having a spinel structure can be mentioned. An example of a lithium-containing phosphate compound having a Nasicon structure is Li ３ V ２ (P.O. ４ ) ３ Examples of lithium-containing phosphate compounds having an olivine structure include Li ３ Fe ２ (P.O. ４ ) ３ , LiMnPO ４ An example of a lithium-containing layered oxide is LiCoO ２ , LiCo １／３ Ni １／３ Mn １／３ O ２ An example of a lithium-containing oxide having a spinel structure is LiMn２ O ４ , LiNi ０．５ Mn １．５ O ４ etc.

[0110] The negative electrode active material contained in the negative electrode layer is not particularly limited, and examples thereof include oxides containing at least one element selected from the group consisting of Ti, Si, Sn, Cr, Fe, Nb, and Mo, 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, β-Li ３ VO ４ Type structure, γ-Li ３ VO ４ An example of the lithium alloy is Li-Al. An example of the lithium-containing phosphate compound having a Nasicon structure is Li. ３ V ２ (P.O. ４ ) ３ Examples of lithium-containing phosphate compounds having an olivine structure include Li ３ Fe ２ (P.O. ４ ) ３ Examples of lithium-containing oxides having a spinel structure include Li ４ Ti ５ O １２ β-Li etc. ３ VO ４ As a negative electrode active material having a Li ３ VO ４ γ-Li etc. ３ VO ４ As oxides having the Li type structure, ３．２ V ０．８ Si ０．２ O ４ etc.

[0111] The electron conductive material contained in the positive electrode layer and the negative electrode layer is not particularly limited, and examples thereof include metal materials such as silver, palladium, gold, platinum, aluminum, copper, and nickel; and carbon materials. Carbon is particularly preferred because it is less likely to react with the positive electrode active material, the negative electrode active material, and the solid electrolyte material, and is effective in reducing the internal resistance of the solid-state battery.

[0112] The solid electrolyte material contained in the positive electrode layer and the negative electrode layer may be selected, for example, from the same materials as the solid electrolyte material that can be contained in the solid electrolyte layer described below.

[0113] The positive electrode layer and the negative electrode layer may each independently contain a sintering aid. The sintering aid is not particularly limited and may be, for example, at least one selected from the group consisting of lithium oxide, sodium oxide, potassium oxide, boron oxide, silicon oxide, bismuth oxide, and phosphorus oxide.

[0114] There are no particular limitations on the thickness of the positive electrode layer and the negative electrode layer, and for example, they may each independently be 2 μm or more and 50 μm or less, particularly 5 μm or more and 30 μm or less.

[0115] Solid Electrolyte Layer The solid electrolyte layer 1b may contain a sintering aid. The sintering aid contained in the solid electrolyte layer may be selected from, for example, the same materials as the sintering aids that may be contained in the positive electrode layer and the negative electrode layer.

[0116] In solid electrolyte layer 1b, an end region of the solid electrolyte layer in a cross-sectional view (for example, a portion of the solid electrolyte layer where the positive electrode layer and the negative electrode layer do not face each other in the thickness direction) may contain the specific oxide ceramic described above. The "portion of the solid electrolyte layer where the positive electrode layer and the negative electrode layer do not face each other in the thickness direction" may be a portion of the solid electrolyte layer where the positive electrode layer or the negative electrode layer faces an insulating portion, for example, the portion indicated by "1b'" in FIG. 1.

[0117] The thickness of the solid electrolyte layer is not particularly limited, and may be, for example, 1 μm or more and 15 μm or less, particularly 1 μm or more and 5 μm or less.

[0118] (External Electrode) The external electrode 3 is a member for extracting power (particularly current) generated in the battery element 1 (particularly the electrode layer) to the outside. The external electrode 3 includes a positive electrode side external electrode for extracting power (particularly current) from the positive electrode layer to the outside and a negative electrode side external electrode for extracting power (particularly current) from the negative electrode layer to the outside. The external electrode 3 may be in the form of a sintered body from the viewpoints of reducing the manufacturing cost of the solid-state battery by co-firing and reducing the internal resistance of the solid-state battery.

[0119] When the external electrode 3 has the form of a sintered body, it may be constituted, for example, by a sintered body containing electron-conductive material particles and a sintering aid. The electron-conductive material contained in the external electrode 3 may be selected, for example, from materials similar to the electron-conductive materials that may be contained in the positive electrode layer and the negative electrode layer. The sintering aid contained in the external electrode 3 may be selected, for example, from materials similar to the sintering aids that may be contained in the positive electrode layer and the negative electrode layer.

[0120] Second Embodiment A solid-state battery according to a second embodiment of the present invention contains the specific oxide ceramics described above only in the insulating portion. In this way, the inclusion of the specific oxide ceramics only in the insulating portion can also achieve improved low-temperature densification characteristics, moisture resistance, and reactivity resistance.

[0121] The solid-state battery of this embodiment is similar to the solid-state battery of the first embodiment, except that the insulating portion contains the specific oxide ceramic described above and the exterior portion does not contain the specific oxide ceramic described above.

[0122] In this embodiment, the insulating portion is the same as the insulating portion in the first embodiment "when the insulating portion contains the specific oxide ceramics described above."

[0123] In this embodiment, the exterior may be made of any oxide ceramic known in the field of solid-state batteries, and may be made of, for example, the same oxide ceramic as the "other oxide ceramic" described in the description of the exterior in the first embodiment.

[0124] [Method for manufacturing a solid state battery] The method for manufacturing a solid state battery of the present invention includes the steps of: forming a green laminate; and firing the green laminate.

[0125] (Process for forming unfired laminate) The unfired laminate can be produced by a printing method such as screen printing, a green sheet method using a green sheet, a dipping method, or a combination of these methods, but it is clear that the method is not limited to these.

[0126] For example, the solid electrolyte layer and the main surface exterior part are manufactured by the green sheet method. The electrode layers (positive electrode layer and / or negative electrode layer) and insulating parts are formed on the obtained solid electrolyte layer sheets by a printing method. The solid electrolyte layer sheets and the main surface exterior part sheets on which the electrode layers etc. are printed are stacked in a predetermined order, and then the side exterior parts are formed by a dipping method. Then, the external electrodes are formed by a dipping method. As a result, an unfired laminate is formed.

[0127] (Firing step) The unfired laminate is subjected to firing. Firing is carried out in an oxygen-containing nitrogen gas atmosphere, for example, by removing organic materials at 500°C, followed by heating at 1000°C or less (e.g., 550°C to 1000°C), preferably 700°C to 900°C (particularly, 750°C to 850°C). The firing time may typically be 1 hour to 10 hours (particularly, 3 hours to 7 hours).

[0128] The present invention as described above includes the following preferred embodiments. <1> A solid-state battery having an exterior part and an insulating part, wherein at least one of the exterior part and the insulating part comprises an oxide ceramic containing: Li (lithium); Mg (magnesium); one or more elements (M) selected from the group consisting of Group 4 and Group 5 elements; and Bi (bismuth). <2> The solid-state battery according to <1>, wherein the oxide ceramic has the following molar ratio: 0<Bi / (Mg+M)≦0.100. <3> The solid-state battery according to <1> or <2>, wherein the oxide ceramic has the following molar ratio: 0<Mg / M≦9.8. <4> The solid-state battery according to any one of <1> to <3>, wherein the oxide ceramic has the following molar ratio: 0<Li / M≦5. <5> The solid-state battery according to any one of <1> to <4>, wherein the oxide ceramic has a rock-salt crystal structure, a spinel crystal structure, a layered rock-salt crystal structure, or a mixed phase structure thereof. <6> The solid-state battery according to any one of <1> to <5>, wherein the element (M) is at least one selected from Ti, Zr, Hf, Ta, and Nb. <7> The solid-state battery according to any one of <1> to <6>, wherein the oxide ceramic has a main phase having only a rock-salt crystal structure or a layered rock-salt crystal structure. <8> The solid-state battery according to any one of <1> to <7>, wherein the oxide ceramic has a main phase having only a rock-salt crystal structure or a layered rock-salt crystal structure, wherein the element (M) is at least one selected from Ti, Ta, and Nb, or two elements, Zr and Ta, and wherein the oxide ceramic has the following molar ratio: 0.004≦Bi / (Mg+M)≦0.060. <9> The solid-state battery according to any one of <1> to <8>, wherein the oxide ceramic has grain boundaries, and wherein the grain boundaries contain, in addition to Bi, at least one element selected from the group consisting of Mg and M. <10> The solid-state battery according to any one of <1> to <9>, wherein the oxide ceramic has a grain boundary, and the grain boundary contains the Li in addition to the Bi.<11> The solid-state battery according to any one of <1> to <10>, wherein the oxide ceramic has grain boundaries and grain boundary vicinity portions close to the grain boundaries, and the Bi is concentrated at the grain boundaries and / or the grain boundary vicinity portions. <12> The solid-state battery according to any one of <1> to <11>, wherein the Bi is present at least at the grain boundaries of the oxide ceramic. <13> The solid-state battery according to any one of <1> to <12>, further comprising: a battery element including one or more battery structural units including a positive electrode layer and a negative electrode layer facing each other and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; and positive and negative external electrodes for extracting power generated in the battery element to the outside, wherein the exterior is a member that covers the outside of the battery element, and wherein the insulating portion includes an insulating portion disposed between the positive electrode layer and the negative electrode external electrode, and an insulating portion disposed between the negative electrode layer and the positive electrode external electrode. <14> The solid-state battery according to <13>, wherein one or more layers selected from the positive electrode layer, the negative electrode layer, and the solid electrolyte layer contain at least one solid electrolyte selected from a garnet-type solid electrolyte, a LISICON-type solid electrolyte, and a perovskite-type solid electrolyte. <15> The solid-state battery according to <14>, wherein the one or more layers contain a garnet-type solid electrolyte or a LISICON-type solid electrolyte. <16> The solid-state battery according to <14>, wherein the one or more layers contain a garnet-type solid electrolyte. <17> The solid-state battery according to any one of <13> to <16>, wherein the exterior part and the insulating part have a layered structure. <18> The solid-state battery according to any one of <13> to <17>, wherein the exterior part is in direct contact with a surface of the battery element, and the insulating part is disposed between two solid electrolyte layers and in direct contact with the surface of each of the two solid electrolyte layers. <19> The solid-state battery according to any one of <13> to <18>, wherein the exterior portion is an integral sintered body formed between a surface of the battery element and a sintered body, and the insulating portion is an integral sintered body formed between a surface of each of the two solid electrolyte layers and a sintered body.

[0129] The present invention will be described in more detail below based on specific examples, but the present invention is not limited to the following examples and can be implemented with appropriate modifications within the scope that does not change the gist of the present invention.

[0130] [Experimental Example 1] <Examples and Comparative Examples> [Synthesis of exterior substrate (main phase)] Lithium carbonate (Li ２ CO ３ ), magnesium oxide (MgO), titanium oxide (TiO ２ ), niobium oxide (Nb ２ O ５ ), zirconium oxide (ZrO ２ ), tantalum oxide (Ta ２ O ５ ), hafnium oxide (HfO ２ ), aluminum oxide (Al ２ O ３ ), gallium oxide (Ga ２ O ３ Raw materials containing zinc oxide (ZnO) were weighed out so that the main phase had the composition shown in the table below. Next, water was added, the mixture was sealed in a polyethylene pot, and the pot was rotated at 150 rpm on a pot rack for 16 hours to mix the raw materials. Taking into account Li deficiency during sintering, lithium carbonate, the Li source, was charged in an amount 5% by mass in excess of the target composition. Next, the resulting slurry was dried and then pre-fired at 1050°C for 5 hours. A toluene-acetone mixed solvent was added to the resulting pre-fired material, which was then pulverized in a planetary ball mill for 12 hours and then dried to obtain powders of exterior substrates (oxide ceramics) having the compositions shown in each Example or Comparative Example. Al ２ O ３ The commercially available product was used. ２ O ３ The particles had a particle size of about 1 μm, and were crushed and dried under the same conditions as above to obtain a sample powder.

[0131] [Synthesis of sintering aids] Lithium hydroxide monohydrate (LiOH·H2O), bismuth oxide Bi ２ O ３The raw materials containing the above were weighed out so that the composition of the composite oxide would be as shown in the table below. Next, the weighed raw materials were mixed in an agate mortar. The obtained mixed powder was mixed with N ２ The mixture was calcined in an atmosphere at 600° C. for 5 hours to obtain a calcined powder.

[0132] [Preparation of Sintered Body] The exterior base material powder and sintering aid powder were weighed to obtain the exterior ceramic chemical composition shown in the table and mixed in a mortar to obtain a mixed powder. The obtained mixed powder was kneaded with butyral resin, alcohol, and binder to produce a slurry. The slurry was formed into a sheet on a PET film using a doctor blade method to obtain a sheet. The produced sheet was laminated to a sheet thickness of 200 μm, cut into a 10 cm diameter disk, and fired at 400 °C to remove the butyral resin. After that, the sheet was fired for 10 hours at the temperature shown in the table. The sheet was then cooled to obtain an exterior ceramic veneer. For Example 1 only, a 15 mm square was cut for use in the MA method (water vapor barrier property 2) described below, and the sample was fired under the same conditions as above to produce a sample.

[0133] [Measurement of areal porosity (low-temperature densification characteristics)] The cross section of the obtained exterior ceramic sintered body was processed with a cross-section polisher (CP), and a porcelain structure image was obtained by SEM observation. Then, the areal porosity of the exterior ceramic veneer was calculated using the image processing software "A-zo-kun." ◎: areal porosity < 7% (excellent); ○: 7% ≦ areal porosity < 10% (good); △: 10% ≦ areal porosity < 20% (pass: no practical problems); ×: 20% ≦ areal porosity (fail: practical problems).

[0134] [Evaluation of Water Vapor Barrier Property 1 (Moisture Resistance)] Measurement was carried out using the cup method of Japanese Industrial Standard JIS Z 0208-1976. The water vapor transmission rate (WVTR) 1 was measured at a temperature of 40°C, a relative humidity of 90%, and for 48 hours. The calculation formula for WVTR 1 was as follows: WVTR 1 [g / m 2 / day] = weight increase of CaCl2 [g] / sample area [m 2 ] / Storage time in constant temperature and humidity chamber [days] Criteria ◎: WVTR1<1×10 －１g / m ２ / day (less than the lower limit of measurement) (excellent); ○: 1 × 10 －１ g / m ２ / day≦WVTR1<2×10 －１ g / m ２ / day (good); △: 2 × 10 －１ g / m ２ / day≦WVTR1<1g / m ２ / day (pass: no problem in practical use); ×: 1 g / m ２ / day≦WVTR1 (fail: problematic in practical use).

[0135] [Evaluation of Water Vapor Barrier Property 2 (Moisture Resistance)] For Example 1 only, water vapor barrier property 2 was evaluated by the following method. Using a gas / water vapor permeability measuring device (CELASIS MAT-002), water vapor barrier property evaluation was carried out by the MA (Modified differential pressure method with an Attached support) method. A sample was placed in the device so that the effective permeation diameter was 10 mm in diameter, and water vapor at 60°C and 85% was supplied from the top surface of one side of the sample, and the amount of moisture that permeated the sample was measured using a detector on the opposite side of the sample. Measurement was continued until the permeability became constant, and WVTR2 was measured when it reached a constant value. WVTR2 for Example 1 was 3 x 10 －４ g / m ２ / day.

[0136] [Overall Evaluation of Low-Temperature Densification Properties and Water Vapor Barrier Property 1 (Moisture Resistance)] The lower of the evaluation results for low-temperature densification properties and the evaluation results for water vapor barrier property 1 (moisture resistance) was used as the overall evaluation result.

[0137] [Electronic Conductivity Evaluation] Au electrodes were sputtered on both sides of the obtained single plate. Finally, the cell was sealed in a 2035 size coin cell to prepare an evaluation cell. All of the above operations were carried out in a dry room with a dew point of -40°C or less. At 25°C, 0.5 V was applied to both electrodes, and the transient current was observed. The current that flowed 30 minutes after the voltage application was read as the leakage current. The electronic conductivity was calculated from the leakage current using the following formula: Electronic Conductivity = (I / V) x (L / A) (I: leakage current, V: applied voltage, L: single plate thickness, A: electrode area) As a result, a 1 x 10 －８ It was confirmed that the film exhibited an electronic conductivity of 0.25 S / cm or less and had excellent insulating properties.

[0138] [Evaluation of Resistance to Reactivity with Solid Electrolyte] The exterior substrate (oxide ceramics) obtained in "Synthesis of Exterior Substrate (Main Phase)" was mixed with a garnet-type solid electrolyte, formed into a tablet, and then fired at 800°C for 5 hours. After firing, the crystal phase was analyzed by XRD measurement. The chemical composition of the garnet-type solid electrolyte used in each of the comparative examples and examples was Li ６．６ La ３ Zr １．６ Ta ０．４ O １２ The evaluation was based on the following criteria. Specifically, after firing, the tablets produced in each comparative example or example were pulverized in a mortar to form a powder. The resulting powder was placed in a folder and subjected to XRD measurement using CuKα radiation at a scan rate of 4.0° / min and an angle measurement range of 10° to 60° to evaluate the crystalline phase contained in the tablet. ⊚: "No decomposition" of the solid electrolyte and oxide ceramic (excellent); △: "Partial decomposition" of the solid electrolyte or oxide ceramic (pass: crystalline phase remains) (no practical problem); ×: "Complete decomposition" of the solid electrolyte or oxide ceramic (fail: practical problem).

[0139] "No decomposition" means that in the XRD measurement after firing, all of the peaks originating from the oxide ceramic and the solid electrolyte before firing are clearly observed, and no side reactions between them occur. "Partial decomposition" means that in the XRD measurement after firing, all of the peaks originating from the oxide ceramic and the solid electrolyte before firing are observed, but a third heterogeneous phase is partially formed. "Complete decomposition" means that in the XRD measurement after firing, no peaks originating from at least one of the compounds originating from the oxide ceramic and the solid electrolyte before firing are observed.

[0140] The synthesis method of the solid electrolyte used in the reactivity resistance evaluation is shown below.

[0141] [Synthesis of Garnet-Type Solid Electrolyte] Raw materials including lithium hydroxide monohydrate (LiOH·H2O), lanthanum hydroxide (La(OH)3), zirconium oxide (ZrO2), and tantalum oxide (Ta2O5) were weighed to obtain the desired solid electrolyte composition. Water was then added, the mixture was sealed in a polyethylene pot, and the pot was rotated at 150 rpm for 16 hours on a pot rack to mix the raw materials. Furthermore, the lithium source, lithium hydroxide monohydrate (LiOH·H2O), was added in an amount 3% by mass in excess of the target composition to account for Li deficiency during sintering. The resulting slurry was then dried and calcined at 1000°C for 5 hours to obtain a solid electrolyte powder with the desired composition.

[0142] [Presence of Bi] The presence / absence of Bi in the grain boundaries and main phase was confirmed by TEM-EDX observation and cross-sectional SEM observation, which will be described later, and it was confirmed that Bi existed in one of the following forms: - "Grain boundary": Bi was present only in the grain boundaries (second phase) of the oxide ceramic; - "Main phase": Bi was present only in the main phase (first phase) of the oxide ceramic; - "Both phases": Bi was present in both the grain boundaries (second phase) and the main phase (first phase) of the oxide ceramic; - "Absence": Bi was not present in either the grain boundaries (second phase) or the main phase (first phase) of the oxide ceramic. (TEM-EDX) TEM equipment: JEOL JEM-F200 EDX detector: EX-24390UBN5T EDX system: Noran system 7 Measurement conditions: Using a sample exfoliated to a thickness of 100 nm or less, EDX is performed at an acceleration voltage of 200 kV, and Bi is detected when measured under conditions where the Mg Kα count is 550,000 or more in the 666 nm field of view.

[0143] Specifically, the presence / absence of Bi in the grain boundaries (second phase) and main phase (first phase) of the oxide ceramics was determined based on the distribution of Bi elements in an EDX mapping image (300,000x magnification) obtained by TEM-EDX observation, as shown in FIG. 7 . As a result, for example, when the presence of Bi was confirmed at the grain boundaries, the presence of Bi was confirmed. On the other hand, when the presence of Bi was not confirmed at the grain boundaries in the distribution of Bi elements, the absence of Bi was confirmed. Furthermore, for example, when the presence of Bi was confirmed in the main phase in the distribution of Bi elements, the presence of Bi was confirmed. On the other hand, when the presence of Bi was not confirmed in the main phase in the distribution of Bi elements, the absence of Bi was confirmed. Furthermore, for example, when the presence of Bi was confirmed in both the grain boundaries and the main phase in the distribution of Bi elements, the presence of Bi in "both phases" was confirmed. Furthermore, for example, when the presence of Bi was not confirmed in either the grain boundary or the main phase in the distribution of Bi element, the "absence" of Bi was recognized.

[0144] [Chemical Composition of Exterior Ceramic Veneer] The exterior ceramic veneer was subjected to ICP-AES analysis to obtain the average chemical composition of the exterior ceramic veneer.

[0145] [Mg Content] The average Mg content of the exterior ceramic veneer was determined by ICP-AES analysis.

[0146] [Crystalline structure of exterior ceramic veneer] The crystalline structure of the main phase (particularly the inner portion 24) of the exterior ceramic veneer was analyzed using the following analytical equipment and conditions, and it was confirmed that X-ray diffraction patterns attributable to each crystalline structure could be obtained. X-ray diffractometer: Analytical equipment: Bruker D2 PHASER; Analytical conditions: Cu Kα, 2θ: 10-60°, step width: 0.02° / sec.

[0147]

[0148] [Effect of Bi Addition] Comparing Comparative Examples 1 to 4 and Examples 1 to 4, it was found that when firing was performed at 800°C using only the exterior substrate (oxide ceramics), at which side reactions between the electrode and electrolyte can be suppressed, the areal porosity became very large and densification did not proceed. As a result, it was found that the WVTR became very large and the moisture barrier property, an important property of the exterior material, was significantly reduced. This is thought to be due to moisture permeation through the voids in the exterior. On the other hand, it was found that the inclusion of Bi in the exterior material significantly reduced the areal porosity and significantly promoted densification, even at the same firing temperature. It was also found that the moisture permeation rate was significantly reduced and the moisture barrier property was significantly improved. It was also found that the addition of this auxiliary agent was effective in materials whose exterior crystal structure was rock salt, layered rock salt, spinel, or a mixed phase structure of these. Furthermore, when the WVTR2 of the sample in Example 1 was measured by the MA method, it was found to be 3 × 10 －４ (g / m ２ / day), and it was found that the film had excellent water vapor barrier properties.

[0149] In Comparative Example 6, the composition of the exterior used was Al ２ O ３In the case where the Al alloy was used, the addition of Bi did not result in densification, and the WVTR1 also showed a very large value. Therefore, it can be seen that the effect of the present invention is manifested by the combination of an oxide containing Li, Mg, and M with a Bi-containing oxide (i.e., an embodiment in which the oxide containing Li, Mg, and M further contains Bi). ２ O ３ Although a side reaction occurs with the garnet-type solid electrolyte during firing, the material of this embodiment does not undergo a side reaction with the garnet-type solid electrolyte, and it is therefore clear that this material is promising as an exterior material to be used together with a solid electrolyte.

[0150] From the comparison between Comparative Example 1, Comparative Example 5 and Example 1, it is clear that lithium borate Li, which is known as a sintering aid, ３ BO ３ It was found that when Bi was added, densification did not progress easily. On the other hand, it was found that the addition of Bi was very effective in densifying. This is thought to be because the ease with which liquid phase sintering of the exterior substrate progresses varies greatly depending on the auxiliary element. These results show that Bi is an important additive element in this exterior substrate, promoting densification at low temperatures and exhibiting moisture barrier properties.

[0151] A comparison between Example 1 and Example 5 shows that even if the form in which Bi is added is different, the presence of Bi in the exterior ceramics results in high moisture barrier properties.

[0152]

[0153] [Effect of Bi Amount Added] Examples 6 to 8 show that a wide range of Bi amounts added promotes densification of the exterior material.

[0154] [Effect of Type of Element for M] Examples 9 to 11 show that the effects of the present invention can be obtained even when an element other than Ti is used as M in the exterior substrate.

[0155] [Effect of Type of Element A] Furthermore, from Examples 12 to 14, it can be seen that the effects of the present invention can be obtained even when the exterior substrate contains a constituent element A other than Li, Mg, or M.

[0156] [SEM Observation of Surface] Fig. 4 shows an SEM photograph (10,000 magnification) of the surface of the sintered body (exterior ceramic veneer) obtained in Example 1. Fig. 5 shows an SEM photograph (10,000 magnification) of the surface of the sintered body (exterior ceramic veneer) obtained in Comparative Example 1. Comparing these photographs reveals that the presence of Bi causes the particles of the exterior substrate (oxide ceramic) to densify as they grow.

[0157] [TEM-EDX Observation] The sintered body (exterior ceramic veneer) obtained in Example 1 was observed by TEM-EDX. A TEM photograph (300,000 magnification) of the sintered body (exterior ceramic veneer) obtained in Example 1 is shown in Figure 6. The distribution of Bi elements in the TEM photograph shown in Figure 6 is shown in Figure 7. The results of EDX quantitative analysis of the area indicated by the arrow in the TEM photograph shown in Figure 6 are shown in Figure 8.

[0158] TEM-EDX analysis (particularly Figures 7 and 8) revealed that the Bi component is mainly present at the grain boundaries. Specifically, it was found that Bi is concentrated at the grain boundaries (or at the grain boundaries and in the vicinity of the grain boundaries) of the oxide ceramics. It is believed that the Bi component forms a liquid phase during firing, which promotes liquid phase sintering and promotes densification at low temperatures. It was also found that in addition to Bi, the grain boundary components may also contain some of the constituent elements of the exterior substrate (e.g., M such as Li, Mg, and Ti). Table 1 shows that the presence of Bi component at the grain boundaries does not adversely affect moisture permeability.

[0159] [SEM Observation of Cross Section] Figure 9 shows an SEM photograph (20,000x magnification) of the cross section of the sintered body (exterior ceramic veneer) obtained in Example 2. Depending on the material composition, Bi may not only exist as a second phase at the grain boundaries 12, as shown in Figure 9 (and Figure 7), but may also be solid-dissolved in the exterior substrate (particularly the main phase (first phase) 11). This is thought to be the result of Bi partially diffusing into the exterior substrate during the densification process. In either case, sufficient moisture barrier properties can be obtained. In Figure 9, more specifically, even though Bi is solid-dissolved in the main phase (first phase) 11, it is clear that it is solid-dissolved in the portion of the main phase (first phase) near the grain boundaries (second phase).

[0160] Furthermore, by comparing Examples 1 to 3 and 5 to 14 with Example 4, it was found that if the following condition A1 is satisfied, the low-temperature densification property and moisture resistance are further improved, and the evaluation results for both of these properties are "Good" or better. In this case, moisture resistance and resistance to reactivity with the solid electrolyte are also sufficiently excellent. Condition A1: The main phase in the oxide ceramic has only a rock-salt type crystal structure or a layered rock-salt type crystal structure.

[0161] Furthermore, by comparing Examples 1 to 3, 5, 7 to 8, and 10 to 14 with Examples 4, 6, and 9, it was found that if the following condition A1 is satisfied, the low-temperature densification property and moisture resistance are further improved, and the evaluation results for both of these properties are "Excellent." In this case, moisture resistance and resistance to reactivity with the solid electrolyte are also sufficiently excellent. Condition B1: The main phase in the oxide ceramic has only a rock-salt crystal structure or a layered rock-salt crystal structure; Condition B2: The element (M) is at least one selected from Ti, Ta, and Nb, or two elements, Zr and Ta; Condition B3: The oxide ceramic has the following molar ratio: 0.004≦Bi / (Mg+M)≦0.060

[0162] In Tables 4 and 5, "Chemical composition of exterior ceramic" indicates the final composition. In Tables 4 and 5, "Exterior composition used" indicates the charge ratio (molar ratio) of the raw materials used.

[0163] [Experimental Example 2] In Experimental Example 1, the manufactured exterior substrate (oxide ceramic) and exterior ceramic veneer were used to demonstrate sufficiently excellent low-temperature densification properties and moisture resistance, but these evaluation methods evaluated the oxide ceramic itself or a fired body (veneer) manufactured using the oxide ceramic. Therefore, from Experimental Example 1 and its results, it is clear that the oxide ceramic has sufficiently excellent low-temperature densification properties and moisture resistance even when used in an insulating part.

[0164] In Experimental Example 1, the manufactured exterior substrate (oxide ceramic) and exterior ceramic veneer were also shown to be sufficiently excellent in electronic conductivity (insulation) and reactivity resistance (resistance to reactivity with solid electrolytes), but these evaluation methods evaluated the oxide ceramic itself or a fired body (veneer) manufactured using the oxide ceramic. Therefore, from Experimental Example 1 and its results, it is clear that the oxide ceramic has sufficiently excellent electronic conductivity (insulation) and reactivity resistance (resistance to reactivity with solid electrolytes) even when used in the insulating portion.

[0165] The solid-state battery of the present invention can be used in various fields where battery use or power storage is envisioned. By way of example only, the solid-state battery of the present invention can be used in electronics packaging. The solid state battery according to one embodiment of the present invention can also be used in the electrical, information, and communications fields where mobile devices and the like are used (for example, the electrical and electronic equipment fields or the mobile device fields, including small electronic devices such as mobile phones, smartphones, smart watches, laptops, digital cameras, activity monitors, arm computers, electronic paper, wearable devices, 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 power storage systems), medical applications (medical devices such as earphone hearing aids), pharmaceutical applications (dose management systems), as well as the IoT field, space and deep-sea applications (for example, space probes, submersible research vessels, and the like).

[0166] 1: Battery element 1a: Electrode layer (positive electrode layer and negative electrode layer) 1b: Solid electrolyte layer 1c: Insulating portion 2: Exterior portion 2a: Main surface exterior portion 2b: Side surface exterior portion 3: External electrodes (positive electrode side external electrode and negative electrode side external electrode)

Claims

1. It has an outer casing and an insulating part, At least one of the exterior part and the insulating part, Li (Lithium); Mg (magnesium); One or more elements (M) selected from the group consisting of elements from groups 4 and 5; and Bi (Bismuth) A solid-state battery containing oxide ceramics that contain [a specific substance].

2. The solid battery according to claim 1, wherein the oxide ceramics have the following molar ratios. 0<Bi / (Mg+M)≦0.100

3. The solid battery according to claim 1, wherein the oxide ceramics have the following molar ratios. 0<Mg / M≦9.8

4. The solid battery according to claim 1, wherein the oxide ceramics have the following molar ratios. 0 < Li / M ≤ 5

5. The solid-state battery according to claim 1, wherein the oxide ceramic has a rock salt crystal structure, a spinel crystal structure, a layered rock salt crystal structure, or a multiphase structure thereof.

6. The solid-state battery according to claim 1, wherein the element (M) is at least one selected from Ti, Zr, Hf, Ta, and Nb.

7. The solid battery according to claim 1, wherein the main phase in the oxide ceramic has only a rock salt crystal structure or a layered rock salt crystal structure.

8. The main phase in the aforementioned oxide ceramics has only a rock salt crystal structure or a layered rock salt crystal structure. The element (M) is at least one selected from Ti, Ta, and Nb, or two of Zr and Ta. The solid battery according to claim 1, wherein the oxide ceramics have the following molar ratios. 0.004≦Bi / (Mg+M)≦0.060

9. The oxide ceramics have grain boundaries, The solid-state battery according to claim 1, wherein the grain boundary includes, in addition to Bi, at least one element selected from the group consisting of Mg and M.

10. The oxide ceramics have grain boundaries, The solid-state battery according to claim 1, wherein the grain boundary includes Li in addition to Bi.

11. The oxide ceramic has grain boundaries and a portion near the grain boundaries, The solid-state battery according to claim 1, wherein the Bi is concentrated at the grain boundary and / or near the grain boundary.

12. The solid battery according to claim 1, wherein the Bi is present at least at the grain boundaries of the oxide ceramic.

13. The solid battery further comprises a battery element having one or more battery constituent units including a positive electrode layer and a negative electrode layer facing each other, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, and positive electrode side and negative electrode side external electrodes for drawing out the power generated by the battery element to the outside, The exterior part is a member that covers the outside of the battery element. The solid battery according to claim 1, wherein the insulating portion includes an insulating portion disposed between the positive electrode layer and the negative electrode side external electrode, and an insulating portion disposed between the negative electrode layer and the positive electrode side external electrode.

14. The solid battery according to claim 13, wherein one or more layers selected from the positive electrode layer, the negative electrode layer, and the solid electrolyte layer include at least one solid electrolyte selected from garnet-type solid electrolyte, LISICON-type solid electrolyte, and perovskite-type solid electrolyte.

15. The solid battery according to claim 14, wherein the one or more layers include a garnet-type solid electrolyte or a LISICON-type solid electrolyte.

16. The solid battery according to claim 14, wherein the one or more layers include a garnet-type solid electrolyte.

17. The solid battery according to claim 13, wherein the outer casing and the insulating portion have a layered configuration.

18. The exterior portion is in direct contact with the surface of the battery element. The solid battery according to claim 13, wherein the insulating portion is disposed between two solid electrolyte layers and is in direct contact with the surface of each of the two solid electrolyte layers.

19. The exterior portion is an integral sintered body formed by the surface of the battery element and the sintered bodies themselves. The solid battery according to claim 13, wherein the insulating portion is an integral sintered body formed by the surfaces of each of the two solid electrolyte layers and the sintered bodies themselves.