Solid state battery

Abstract

The present invention provides a solid battery demonstrating more adequate low temperature densification characteristics and moisture resistance. The present invention relates to a solid-state battery having an exterior part and an insulation part, at least one of the exterior part and the insulation part containing an oxide ceramic containing Li (lithium); Mg (magnesium); one or more elements M I selected from the group consisting of group 4 and group 5 elements; and one or more elements M II selected from the group consisting of transition metal elements.

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] On the other hand, the oxide ceramic contained in the exterior portion is required to have excellent insulating properties.

[0010] 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.

[0011] Another object of the present invention is to provide a solid-state battery that is more sufficiently excellent not only in low-temperature densification characteristics and moisture resistance but also in insulating properties.

[0012] The present invention provides a battery having an exterior part and an insulating part, wherein at least one of the exterior part and the insulating part contains one or more elements M selected from the group consisting of Li (lithium); Mg (magnesium); and elements of Groups 4 and 5. Ｉ and one or more elements M selected from the group consisting of transition metal elements. ＩＩ The present invention relates to a solid-state battery comprising an oxide ceramic containing

[0013] 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.

[0014] 1 is a schematic diagram showing an example of a solid state battery of the present invention, which is a composite diagram of a perspective view and a 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 diagram of an oxide ceramic for explaining sintered particles constituting an example of an oxide ceramic contained in an exterior part and / or an insulating part of a solid state battery of the present invention and the structure thereof. FIG. 4 is an example of a TEM photograph of a sintered body (exterior ceramic single plate). FIG. 5 is an EDX mapping image showing the distribution of Bi elements in the TEM photograph shown in FIG. 4 shows the results of EDX quantitative analysis of the area indicated by the arrow in the TEM photograph shown in FIG.

[0015] [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).

[0016] 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."

[0017] 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.

[0018] 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.

[0019] 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 insulating properties, 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.

[0020] <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 insulating properties, it is preferable that both the exterior part and the insulating part contain the specific oxide ceramic.

[0021] (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.

[0022] 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 insulation properties, it is preferable that both the main surface exterior part and the side surface exterior part contain the specific oxide ceramic.

[0023] In this specification, low-temperature densification property refers to a property that allows an exterior part (and / or insulating part) with a sufficiently reduced areal porosity to be formed 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 from entering, and may be a property that sufficiently reduces the water vapor transmission rate (WVTR) even under high temperature and high humidity conditions (for example, water vapor barrier property). Insulating property refers to a property that makes it difficult for the exterior part (and / or insulating part) (particularly the oxide ceramics contained in the exterior part (and / or insulating part)) to conduct electricity.

[0024] In this embodiment, the oxide ceramic contained in the exterior portion is made of one or more elements M selected from the group consisting of Li (lithium); Mg (magnesium); and elements of Groups 4 and 5. Ｉ and one or more elements M selected from the group consisting of transition metal elementsＩＩ Contains:

[0025] element M Ｉ is, for example, one or more elements selected from the group consisting of Ti (titanium), Zr (zirconium), Hf (hafnium), Ta (tantalum), and Nb (niobium) (particularly the group consisting of Ti, Zr, and Ta). Ｉ is preferably one element selected from the above group (particularly the group consisting of Ti, Zr, Hf, Ta and Nb) or two elements Zr and Ta, more preferably one element selected from the group consisting of Ti, Zr and Ta, or two elements Zr and Ta, and even more preferably Ti, from the viewpoint of further improving low-temperature densification characteristics, moisture resistance and insulating properties.

[0026] element M ＩＩ is, for example, one or more elements selected from the group consisting of Ni (nickel), Mn (manganese), Co (cobalt), Fe (iron) and Ce (cerium). ＩＩ is preferably one element selected from the above group (particularly the group consisting of Ni, Mn, Co, Fe and Ce), and more preferably one element selected from the group consisting of Ni, Mn, Co and Ce, from the viewpoint of further improving low-temperature densification characteristics, moisture resistance and insulating properties.

[0027] In this embodiment, the oxide ceramic contains Li, Mg, and element M. Ｉ and element M ＩＩ By containing a combination of Li, Mg, and the element M, it is possible to obtain an exterior part that is excellent in low-temperature densification property, moisture resistance, and insulation. Ｉ and element M ＩＩ If any one or more of these elements are not contained, the low-temperature densification property will be reduced, and as a result, the moisture resistance will also be reduced.

[0028] In oxide ceramics, the molar ratio M ＩＩ / (Mg+M Ｉ ) is not particularly limited, and is preferably within the following range from the viewpoint of further improving low-temperature densification properties, moisture resistance, and insulating properties. ＩＩ / (Mg+M Ｉ ) Preferably, 0<M ＩＩ / (Mg+M Ｉ )≦0.300; more preferably 0.001≦M ＩＩ / (Mg+M Ｉ )≦0.250; more preferably 0.008≦M ＩＩ / (Mg+M Ｉ )≦0.150; sufficiently preferably 0.008≦M ＩＩ / (Mg+M Ｉ ) ≦0.050.

[0029] The oxide ceramic may or may not further contain Bi (bismuth). From the viewpoint of further improving low-temperature densification properties, moisture resistance, and insulating properties, the oxide ceramic preferably contains Bi.

[0030] In oxide ceramics, the molar ratio Bi / M Ｉ is not particularly limited, but is preferably within the following range from the viewpoint of further improving low-temperature densification properties, moisture resistance, and insulating properties. Ｉ Preferably, 0≦Bi / M Ｉ ≦0.100; more preferably 0<Bi / M Ｉ ≦0.100; more preferably 0.001≦Bi / M Ｉ ≦0.100; sufficiently preferably 0.010≦Bi / M Ｉ ≦0.080; more preferably 0.020≦Bi / M Ｉ ≦0.080.

[0031] In oxide ceramics, the molar ratio Li / M Ｉ and Mg / M Ｉ is not particularly limited, but is preferably within the following range from the viewpoint of further improving low-temperature densification properties, moisture resistance, and insulating properties. Ｉ Preferably, 0<Li / M Ｉ ≦5; more preferably 1.0≦Li / M Ｉ ≦4.0; more preferably 1.5≦Li / M Ｉ ≦3.5; quite preferably 1.9≦Li / M Ｉ ≦2.3. ・Mg / MＩ Preferably, 0<Mg / M Ｉ ≦9.80; more preferably 0.01≦Mg / M Ｉ ≦7.00; more preferably 0.08≦Mg / M Ｉ ≦6.00; sufficiently preferably 2.00≦Mg / M Ｉ ≦5.00.

[0032] Molar ratio in oxide ceramics: M ＩＩ / (Mg+M Ｉ ), Bi / M Ｉ , Li / M Ｉ and Mg / M Ｉ are the amounts of Li, Mg, and M measured by the same method as the analytical method for the chemical composition of oxide ceramics described later. Ｉ , M ＩＩ The value used is calculated from the content (or molar ratio) of M and Bi. ＩＩ The molar ratio for M ＩＩ When M contains two or more elements, it is the molar ratio of the total of the two or more elements. Ｉ The molar ratio for M Ｉ When two or more elements are contained, the molar ratio is the molar ratio of the total of the two or more elements.

[0033] 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.

[0034] 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.

[0035] 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 insulating properties, the oxide ceramic preferably has a chemical composition represented by the following general formula (1):

[0036]

[0037] 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.

[0038] In formula (1), M Ｉ is the above element M Ｉ From the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and insulating properties, it is preferably one element selected from the above group (particularly the group consisting of Ti, Zr, Hf, Ta, and Nb) or two elements, Zr and Ta, more preferably one element selected from the group consisting of Ti, Zr, and Ta, or two elements, Zr and Ta, and even more preferably Ti.

[0039] In formula (1), M ＩＩ is the above element M ＩＩFrom the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and insulating properties, it is preferably one element selected from the above group (particularly the group consisting of Ni, Mn, Co, Fe, and Ce), and more preferably one element selected from the group consisting of Ni, Mn, Co, and Ce.

[0040] In formula (1), γ2 / (β+γ1), x / γ1, α1 / γ1, and β / γ1 are the molar ratios M ＩＩ / (Mg+M Ｉ ), Bi / M Ｉ , Li / M Ｉ and Mg / M Ｉ Therefore, γ2 / (β+γ1) corresponds to the molar ratio M ＩＩ / (Mg+M Ｉ ) and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and insulating properties, preferably M ＩＩ / (Mg+M Ｉ ) and more preferably M ＩＩ / (Mg+M Ｉ ) more preferably satisfies the more preferred range of M ＩＩ / (Mg+M Ｉ ) and satisfies the more preferred range of M ＩＩ / (Mg+M Ｉ ) satisfies the preferred range. Ｉ and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and insulating properties, it is preferable that Bi / M Ｉ and more preferably Bi / M Ｉ and more preferably Bi / M Ｉ and satisfies the more preferred range of Bi / M Ｉ The α1 / γ1 ratio satisfies the above-mentioned preferable range. Ｉ and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and insulating properties, it is preferable that the content of Li / M Ｉ and more preferably Li / M Ｉand more preferably Li / M Ｉ and satisfies the more preferred range of Li / M Ｉ The molar ratio β / γ1 satisfies the above-mentioned preferable range. Ｉ and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and insulating properties, it is preferable that Mg / M Ｉ and more preferably, Mg / M Ｉ and more preferably, Mg / M Ｉ and satisfies the more preferred range of Mg / M Ｉ satisfies the preferred range.

[0041] In formula (1), δ satisfies the following formula: δ = {α1 + aα2 + 2β + nγ1 + mγ2 + bx} / 2 (n is M Ｉ Average valence of, m is M ＩＩ , a is the average valence of A, and b is the average valence of Bi). Ｉ is the average valence of M Ｉ The average valence of M Ｉ 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, m is a value expressed as (n1 x a + n2 x b + n3 x c) / (n1 + n2 + n3). ＩＩ is the average valence of M ＩＩ The average valence of M ＩＩFor 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 present, the value is expressed as (n1 x a + n2 x b + n3 x c) / (n1 + n2 + n3). a is the average valence of A. When, for example, 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 present, the average valence of A is expressed as (n1 x a + n2 x b + n3 x c) / (n1 + n2 + n3). b is the average valence of Bi, and generally takes a value of 3≦b≦5. As will be described later, Bi is usually present in the grain boundaries (second phase), main phase (first phase), or both of these phases of oxide ceramics. When the so-called main phase of a sintered particle is referred to as the "first phase," the grain boundary 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 is present at a grain boundary, the valence of Bi is often "3." Also, for example, when Bi is present in the main phase, the valence of Bi is often "5." Therefore, the average valence of Bi is the value expressed as (n1 x 3 + n2 x 5) / (n1 + n2) when, for example, n1 Bi atoms are found at the grain boundary 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. In other words, some oxygen deficiency or interstitial oxygen may be present.

[0042] In formula (1), α1 typically satisfies 0 < α1 < 1.0, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and insulating properties, preferably satisfies 0.10 ≦ α1 ≦ 0.80, more preferably satisfies 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 insulating properties, preferably satisfies 0 ≦ α2 ≦ 0.5, more preferably satisfies 0 ≦ α2 ≦ 0.1, and even more preferably is 0. β typically satisfies 0 < β < 1.0, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and insulating properties, preferably satisfies 0.01 ≦ β ≦ 0.80, more preferably satisfies 0.01 ≦ β ≦ 0.60. γ1 usually satisfies 0<γ1<1.0, and from the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and insulating properties, preferably satisfies 0.05≦γ1≦0.50, more preferably satisfies 0.10≦γ1≦0.40. γ2 usually satisfies 0<γ2<1.000, and from the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and insulating properties, preferably satisfies 0.001≦γ2≦0.500, more preferably satisfies 0.001≦γ2≦0.200, even more preferably satisfies 0.005≦γ2≦0.100, and sufficiently preferably satisfies 0.005≦γ2≦0.080. x usually satisfies 0≦x<1.0, and from the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and insulating properties, preferably satisfies 0<x≦0.500, more preferably satisfies 0.001≦x≦0.050, and more preferably satisfies 0.002≦x≦0.020.

[0043] 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.

[0044] 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.

[0045] In the present invention, when the oxide ceramic contains Bi, Bi in such an oxide ceramic 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 insulating properties, 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.

[0046] The presence / absence and amount of Bi in the grain boundaries (second phase) and main phase (first phase) of such oxide ceramics can be determined based on the distribution of Bi elements in EDX mapping (300,000 to 2,000,000 magnification) observed by TEM-EDX. For example, a TEM photograph of a sintered body (single ceramic exterior) such as that shown in FIG. 4 can be taken, and EDX mapping images (e.g., FIG. 5) and EDX quantitative analysis results (e.g., FIG. 6) can be obtained from the TEM photograph. In FIG. 5, it is clear that Bi is concentrated at the grain boundaries (or at and near the grain boundaries) of the oxide ceramic. FIG. 4 shows an example of a TEM photograph of a sintered body (single ceramic exterior). FIG. 5 is an EDX mapping image showing the distribution of Bi elements in the TEM photograph shown in FIG. 4. FIG. 6 shows the results of EDX quantitative analysis of the area indicated by the arrow in the TEM photograph shown in FIG. 4.

[0047] For example, when Bi is detected at the grain boundary in the distribution of Bi element, the presence of Bi at the grain boundary is recognized. On the other hand, when Bi is not detected at the grain boundary in the distribution of Bi element, the absence of Bi at the grain boundary is recognized. Also, for example, when Bi is detected in the main phase in the distribution of Bi element, the presence of Bi in the main phase is recognized. On the other hand, when Bi is not detected in the main phase in the distribution of Bi element, the absence of Bi in the main phase is recognized. Note that the determination of "presence" or "absence" depends on the resolution of a specified analytical method and is not an absolute "presence" or "absence." Therefore, even if "absence" occurs, it is acceptable for it to be contained in an amount below the detection limit in analysis using specified equipment and conditions.

[0048] ・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.

[0049] For example, when the exterior portion is made of oxide ceramics and contains a sintering aid, the grain boundary (second phase) 22 is mainly composed of the sintering aid. Also, for example, when the exterior portion is made of oxide ceramics and does not contain a sintering aid, the grain boundary (second phase) 22 is composed of components leached out from the oxide ceramics. In either case, the grain boundary (second phase) 22 contains Li, Mg, M in addition to Bi. Ｉ and M ＩＩ The metal oxide may be composed of at least one element selected from the group consisting of:

[0050] 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 insulating properties, 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.

[0051] 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.

[0052] For example, an oxide ceramic having only a rock-salt crystal structure 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. Having only a rock-salt crystal structure in the main phase means that "among the peaks detected in the oxide ceramic, peaks derived from the second phase, peaks derived from the transition metal-derived phase, and peaks derived from the rock-salt crystal structure are substantially not observed," i.e., "the oxide ceramic is composed only of the second phase crystal structure, the transition metal-derived 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, the second phase crystal structure, and the transition metal-derived 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 and the transition metal-derived phase crystal structure may or may not be detected independently.

[0053] 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, peaks derived from the second phase, peaks derived from the transition metal-derived phase, and peaks derived from the layered rock-salt crystal structure are substantially not observed," i.e., "the oxide ceramic is composed only of the second phase crystal structure, the transition metal-derived 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 device and conditions, only the layered rock-salt crystal structure, the second phase crystal structure, and the transition metal-derived 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 analysis using the device and conditions. In this case, the crystal structure of the second phase and the crystal structure of the phase derived from the transition metal may or may not be detected independently.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] The oxide ceramics may be produced by any method as long as an oxide ceramics of a desired composition can be obtained, and examples thereof include the following methods (1) and (2). Method (1): First, a Li source, an Mg source, and an element M are mixed. Ｉ Source and element M ＩＩRaw materials containing the Bi source are weighed out so that the desired composition (molar ratio) of the specified elements is achieved, thoroughly mixed with water, and fired (first firing step). Next, the resulting fired product is weighed out together with a firing aid (e.g., a Bi-containing firing aid as the Bi source) so that the desired composition (molar ratio) of the specified elements is achieved, and thoroughly mixed with alcohol and a binder. The resulting slurry is then formed into a sheet and fired to obtain the oxide ceramics that constitute the exterior (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 Bi-containing firing aids include LiBiO2 and Li3BiO3.

[0059] Method (2): The oxide ceramic is prepared by adding a Li source, an Mg source, and an element M. Ｉ Source and element M ＩＩ The raw materials containing the source (and optionally the Bi source) are weighed out so that the predetermined elements have a desired composition (molar ratio), thoroughly mixed with water, and then calcined (calcination step).

[0060] 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.

[0061] As the Li source, for example, lithium carbonate (Li2CO3) can be used. As the Mg source, for example, magnesium oxide (MgO) can be used. Ｉ As the source, for example, titanium oxide (TiO2), niobium oxide (Nb2O5), zirconium oxide (ZrO2), tantalum oxide (Ta2O5), and hafnium oxide (HfO2) can be used. ＩＩAs the source, for example, manganese carbonate (MnCO3), nickel oxide (NiO), cobalt oxide (Co3O4), cerium oxide (CeO2), iron oxide (Fe2O3), etc. can be used. As the Bi source, for example, Bi2O3 can be used. In the production of oxide ceramics, the Li source, Mg source, element M, etc. can be used. Ｉ Source and element M ＩＩ The final composition of the oxide ceramics obtained is determined by the ratio of the Li source, Mg source, and element M. Ｉ source, element M ＩＩ By adjusting the charging ratio of the source and the Bi source, the above-mentioned molar ratios γ2 / (β+γ1), x / γ1, α1 / γ1 and β / γ1 can be controlled.

[0062] This embodiment does not preclude the exterior part 2 from containing 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, Bi2O3, Mg-Bi-O-based oxides, and Li-M-O-based oxides (wherein M is M in formula (1)). Ｉ (similar to the formula (1)), Li—Bi—MO-based oxide (wherein M is M in the formula (1) Ｉ (similar to the above), MgO, etc. The content of the specific oxide ceramics in the exterior part 2 may usually be an area percentage of 60% or more and 100% or less, particularly an area percentage of 90% or more and 100% or less. The area percentage can be measured as follows. First, the solid-state battery is broken 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 an arbitrary surface in the exterior part region of the polished surface to determine Mg, element M, etc. Ｉ , element M ＩＩ The region where element A is detected and Li is detected by TOF-SIMS is regarded as the region of the specific oxide ceramic. From the above, the area ratio of the oxide ceramic to the area of ​​the exterior part can be calculated and measured.

[0063] 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 insulating properties, it is preferable that the exterior part 2 does not contain any sintering aids other than the Bi-containing sintering aid.

[0064] 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.

[0065] 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.

[0066] 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 －１０ The ionic conductivity of the exterior part 2 is usually 1×10 －１８ For example, the electronic conductivity of the exterior part 2 is usually 5×10 －７ S / cm or less, especially 3×10 －７ S / cm or less, preferably 1×10 －８ The electronic conductivity of the exterior part 2 is usually 1×10 －１８ S / cm or more.

[0067] 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 The H2O permeability in the thickness direction of the exterior part 2 may be, for example, 1 g / m ２ / day and below, especially 2 x 10 －１ g / m ２ / day or less, preferably 1×10－１ g / m ２ The H2O permeability is measured at 25°C by the cup method, carrier gas method, pressure method, or Ca corrosion method.

[0068] 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.

[0069] 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.

[0070] (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.

[0071] 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 insulating properties, it is preferable that both the exterior part and the insulating part contain the specific oxide ceramics.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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 5×10 －７ S / cm or less, especially 3×10 －７ S / cm or less, preferably 1×10 －８ The electronic conductivity of the insulating part is usually 1×10 －１８ S / cm or more.

[0076] 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 ２The H2O permeability in the thickness direction of the insulating part may be, for example, 1 g / m ２ / day and below, especially 2 x 10 －１ g / m ２ / day or less, preferably 1×10 －１ g / m ２ The H2O permeability is measured at 25°C by the cup method, carrier gas method, pressure method, or Ca corrosion method.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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 insulating properties, 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.

[0081] 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 insulating properties, it is preferable that the first solid electrolyte be contained in at least the solid electrolyte layer.

[0082] 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 the solid electrolyte having 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 incident angle, or may exhibit, as a garnet-like crystal structure, one or more main peaks that differ in incident angle (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-type crystal structure due to differences in composition. Representative diffraction patterns of a garnet-like crystal structure include, for example, the diffraction pattern shown in ICDD Card No. 00-045-0109 and the like.

[0083] 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).

[0084]

[0085] In formula (2), A1 refers to a metal element occupying the Li site in the garnet-type crystal structure. A1 is usually one or more elements selected from the group consisting of Ga (gallium), Al (aluminum), Mg (magnesium), Zn (zinc) and Sc (scandium). From the viewpoint of further improving low-temperature densification characteristics, moisture resistance and insulating properties, A1 is preferably one or more elements selected from the group consisting of Ga (gallium) and Al (aluminum), more preferably two elements, Ga and Al.

[0086] In formula (2), B1 refers to a metal element occupying the La site in the garnet-type crystal structure. B1 is usually one or more elements selected from the group consisting of Ca (calcium), Sr (strontium), Ba (barium), and lanthanoid elements. Examples of lanthanoid elements include 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).

[0087] In formula (2), D1 refers to a metal element occupying a hexacoordinated site in the garnet-type crystal structure. Examples of hexacoordinated sites in a garnet-type crystal structure include the site occupied by Nb in Li5La3Nb2O12 (ICDD Card No. 00-045-0109) having a garnet-type crystal structure, and the site occupied by Zr in Li7La3Zr2O12 (ICDD Card No. 01-078-6708). D1 represents one or more elements selected from the group consisting of transition elements capable of hexacoordinated with oxygen and typical elements belonging to groups 12 to 15. Examples of transition elements capable of hexacoordinated with oxygen include Sc (scandium), Zr (zirconium), Ti (titanium), Ta (tantalum), Nb (niobium), Hf (hafnium), Mo (molybdenum), W (tungsten), and Te (tellurium). Typical elements belonging to Groups 12 to 15 include, for example, In (indium), Ge (germanium), Sn (tin), Pb (lead), Sb (antimony), and Bi (bismuth). D1 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). From the viewpoint of further improving low-temperature densification characteristics, moisture resistance, and insulating properties, D1 preferably contains one or more elements selected from the group consisting of Zr (zirconium), Ta (tantalum), and Nb (niobium), and more preferably contains Zr (zirconium) and Ta (tantalum).

[0088] In formula (2), x satisfies 0≦x≦1.00, and from the viewpoint of further improving low-temperature densification properties, moisture resistance, and insulating properties, 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 insulating properties, 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 insulating properties, 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 insulating properties, 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 insulating properties, preferably satisfies 1.7≦γ≦2.3, more preferably 1.8≦γ≦2.2, and even more preferably 1.9≦γ≦2.0.

[0089] 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 insulating properties, preferably satisfies 6.2≦p≦6.8, more preferably 6.4≦p≦6.8. a is the average valence of A1. The average valence of A1 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 A1, and is a value expressed as (n1×a+n2×b+n3×c) / (n1+n2+n3). b is the average valence of B1. The average valence of B1 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 B1, and is the same value as the average valence of A1 described above. c is the average valence of D1. The average valence of D1 is the same as the average valence of A1 described above when, for example, D1 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+. δ indicates the amount of oxygen vacancy and may be 0. δ generally satisfies 0≦δ<1. Since quantitative analysis of the amount of oxygen vacancy δ is not possible even with the latest equipment, it may be considered to be 0. The molar ratio of each element in the chemical composition of the oxide ceramic of the present invention does not necessarily coincide with the molar ratio of each element in formula (2), for example, and tends to deviate depending on the analytical method. However, the effects of the present invention can be achieved as long as the composition deviation is not so great that it changes the properties.

[0090] 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.

[0091] Specific examples of the garnet-type solid electrolyte represented by the general formula (2) include Li6.6La3Zr1.6Ta0.4O12, Li6.4Ga0.05Al0.15La3Zr2O12, Li6.75La3Zr1.75Nb0.25O12, and Li6.53La3Zr1.53Ta0.4Bi0.07O12.

[0092] The LISICON-type crystal structure of the solid electrolyte includes a βI structure, a βII structure, a βII' structure, a TI structure, a TII structure, a γII structure, and a γ0 structure. That is, the LISICON-type solid electrolyte may include one or more solid electrolytes having a βI structure, a βII structure, a βII' structure, a TI structure, a TII structure, a γII structure, a γ0 structure, or a composite structure thereof. From the viewpoint of further improving low-temperature densification properties, moisture resistance, and insulating properties, the LISICON-type structure of the solid electrolyte is preferably a γII structure.

[0093] A solid electrolyte having a γII structure means that the solid electrolyte has a γII crystal structure, and in a broad sense, means that the solid electrolyte has a crystal structure that can be recognized as a γII crystal structure by those skilled in the art of solid-state batteries. In a narrow sense, a solid electrolyte having a γII structure means that the solid electrolyte exhibits one or more major peaks in X-ray diffraction at a predetermined angle of incidence that correspond to Miller indices specific to the so-called γII-Li3VO4 crystal structure. Compounds having a γII 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.

[0094] "A solid electrolyte having a βI type structure" means that the solid electrolyte has a βI type crystal structure, and in a broad sense, means that the solid electrolyte has a crystal structure that can be recognized as a βI type crystal structure by those skilled in the art of solid state batteries. In a narrow sense, "a solid electrolyte having a βI type structure" means that the solid electrolyte exhibits one or more major peaks in X-ray diffraction at a predetermined angle of incidence that correspond to Miller indices specific to the so-called βI-Li3VO4 type crystal structure. Compounds having a βI 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)). An example of such data is shown in the following table: XRD data (planar spacing d values ​​and corresponding Miller indices):

[0095]

[0096] A solid electrolyte having a βII structure means that the solid electrolyte has a βII crystal structure, and in a broad sense, means that the solid electrolyte has a crystal structure that can be recognized as a βII crystal structure by those skilled in the art of solid-state batteries. In a narrow sense, a solid electrolyte having a βII structure means that the solid electrolyte exhibits one or more major peaks in X-ray diffraction at a predetermined angle of incidence that correspond to Miller indices specific to the so-called βII-Li3VO4 crystal structure. Compounds having a βII 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.

[0097] "A solid electrolyte having a βII'-type structure" means that the solid electrolyte has a βII'-type crystal structure, and in a broad sense, refers to a crystal structure that can be recognized as a βII'-type crystal structure by those skilled in the art of solid-state batteries. In a narrow sense, "a solid electrolyte having a βII'-type structure" means that the solid electrolyte exhibits, in X-ray diffraction, one or more major peaks corresponding to Miller indices specific to the so-called βII'-Li3VO4-type crystal structure at a predetermined angle of incidence. Compounds having a βII'-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)). An example thereof is shown in the XRD data (planar spacing d values ​​and corresponding Miller indices) listed in the table below.

[0098]

[0099] A solid electrolyte having a TI type structure means that the solid electrolyte has a TI type crystal structure, and in a broad sense, means that the solid electrolyte has a crystal structure that can be recognized as a TI type crystal structure by those skilled in the art of solid state batteries. In a narrow sense, a solid electrolyte having a TI type structure means that the solid electrolyte exhibits one or more major peaks in X-ray diffraction at a predetermined angle of incidence that correspond to Miller indices specific to the so-called TI-LiVO type crystal structure. Compounds having a TI 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.

[0100] A solid electrolyte having a TII type structure means that the solid electrolyte has a TII type crystal structure, and in a broad sense, means that the solid electrolyte has a crystal structure that can be recognized as a TII type crystal structure by those skilled in the art of solid-state batteries. In a narrow sense, a solid electrolyte having a TII type structure means that the solid electrolyte exhibits one or more major peaks in X-ray diffraction at a predetermined angle of incidence that correspond to Miller indices specific to the so-called TII-Li3VO4 type crystal structure. Compounds having a TII 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.

[0101] A solid electrolyte having a γ0-type structure means that the solid electrolyte has a γ0-type crystal structure, and in a broad sense, means that the solid electrolyte has a crystal structure that can be recognized as a γ0-type crystal structure by those skilled in the art of solid-state batteries. In a narrow sense, a solid electrolyte having a γ0-type structure means that the solid electrolyte exhibits, in X-ray diffraction, one or more major peaks corresponding to Miller indices specific to the so-called γ0-Li3VO4-type crystal structure at a predetermined angle of incidence. Compounds having a γ0-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)). An example of such data is shown in the following table: XRD data (planar spacing d values ​​and corresponding Miller indices).

[0102]

[0103] 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):

[0104]

[0105] 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 characteristics, moisture resistance, and insulating properties, 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 insulating properties, 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 insulating properties. 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+.

[0106] Specific examples of the LISICON-type solid electrolyte represented by the general formula (3) include Li3.2V0.8Si0.2O4 and Li3.5P0.5Si0.5O4.

[0107] 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.

[0108] The solid electrolyte having a perovskite crystal structure may have any chemical composition, for example, the chemical composition represented by the following general formula (4).

[0109] It is preferred that the average chemical composition be expressed as follows:

[0110] In formula (4), x preferably satisfies the relationship 0.09<x<0.167, and more preferably 0.10<x<0.12.

[0111] Specific examples of the perovskite-type solid electrolyte represented by the general formula (4) include Li0.35La0.55TiO3 and Li0.5La0.5TiO3.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] The positive electrode active material contained in the positive electrode layer is not particularly limited, and may be at least one selected from the group consisting of lithium-containing phosphate compounds having a Nasicon structure, lithium-containing phosphate compounds having an olivine structure, lithium-containing layered oxides, and lithium-containing oxides having a spinel structure. An example of a lithium-containing phosphate compound having a Nasicon structure is Li3V2(PO4)3. An example of a lithium-containing phosphate compound having an olivine structure is Li3Fe2(PO4)3, LiMnPO4, etc. An example of a lithium-containing layered oxide is LiCoO2, LiCo1 / 3Ni1 / 3Mn1 / 3O2, etc. An example of a lithium-containing oxide having a spinel structure is LiMn2O4, LiNi0.5Mn1.5O4, etc.

[0119] The negative electrode active material contained in the negative electrode layer is not particularly limited, and examples thereof include at least one selected from the group consisting of 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, oxides having a β-Li3VO4 structure, and oxides having a γ-Li3VO4 structure. An example of a lithium alloy is Li-Al. An example of a lithium-containing phosphate compound having a Nasicon structure is Li3V2(PO4)3. An example of a lithium-containing phosphate compound having an olivine structure is Li3Fe2(PO4)3. An example of a lithium-containing oxide having a spinel structure is Li4Ti5O12. An example of a negative electrode active material having a β-Li3VO4 structure is Li3VO4. Examples of oxides having a γ-Li3VO4 type structure include Li3.2V0.8Si0.2O4.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] (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.

[0128] 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.

[0129] 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 provide improved low-temperature densification characteristics, moisture resistance, and insulating properties.

[0130] 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.

[0131] 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."

[0132] 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, an oxide ceramic similar to the "other oxide ceramic" described in the description of the exterior in the first embodiment.

[0133] [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.

[0134] (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.

[0135] 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.

[0136] (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).

[0137] The present invention as described above includes the following preferred embodiments: <1> A battery having an exterior part and an insulating part, wherein at least one of the exterior part and the insulating part contains one or more elements M selected from the group consisting of Li (lithium); Mg (magnesium); and elements of Groups 4 and 5. Ｉ and one or more elements M selected from the group consisting of transition metal elements. ＩＩ <2> A solid-state battery comprising an oxide ceramic containing: <1> The solid-state battery according to <1>, wherein the oxide ceramic further contains or does not contain Bi (bismuth), and has the following molar ratio: 0≦Bi / M Ｉ ≦0.100 <3> The element M Ｉ <4> The solid-state battery according to <1> or <2>, wherein the element M is at least one element selected from the group consisting of Ti, Zr, Hf, Ta, and Nb. ＩＩ is at least one element selected from the group consisting of Ni, Mn, Co, Fe, and Ce. <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 oxide ceramic is a solid-state battery according to any one of <1> to <4>, wherein the element M ＩＩ in the following molar ratio: 0<M ＩＩ / (Mg+M Ｉ <7> The solid state battery according to any one of <1> to <6>, wherein the oxide ceramic has the following molar ratio: 0<Mg / M Ｉ ≦9.8 0<M ＩＩ / (Mg+M Ｉ<8> The solid state battery according to any one of <1> to <7>, wherein the oxide ceramic has the following molar ratio: 0<Li / M )≦0.300 Ｉ ≦5 <9> The main phase of the oxide ceramic has only a rock salt type crystal structure or a layered rock salt type crystal structure, and the element M ＩＩ is one element selected from the group consisting of transition metal elements, and the oxide ceramic contains Bi (bismuth) in the following molar ratio: 0<Bi / M Ｉ <10> The solid-state battery according to any one of <1> to <8>, further comprising: <10> a main phase of the oxide ceramic having only a rock-salt type crystal structure or a layered rock-salt type crystal structure; Ｉ is one element selected from the above group, or is two elements, Zr and Ta, and the element M ＩＩ is one element selected from the group consisting of Ni, Mn, Co and Ce, and the oxide ceramic contains the element M ＩＩ in the following molar ratio: 0<M ＩＩ / (Mg+M Ｉ )≦0.300, and the oxide ceramic contains Bi (bismuth) in the following molar ratio: 0<Bi / M Ｉ<10>. The solid-state battery according to any one of <1> to <9>, further comprising a saturation voltage of 0.1 V or less and a saturation voltage of 0.1 V or less and a saturation voltage of 0.1 V or less. <11> The solid-state battery according to any one of <1> to <10>, 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 electrode external electrodes for extracting power generated in the battery element to the outside, wherein the exterior part is a member covering the outside of the battery element, and the insulating part includes an insulating part disposed between the positive electrode layer and the negative electrode external electrode, and an insulating part disposed between the negative electrode layer and the positive electrode external electrode. <12> The solid-state battery according to any one of <11>, wherein the 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. <13> The solid-state battery according to <12>, wherein the one or more layers contain a garnet-type solid electrolyte or a LISICON-type solid electrolyte. <14> The solid-state battery according to <12>, wherein the one or more layers contain a garnet-type solid electrolyte. <15> The solid-state battery according to any one of <11> to <14>, wherein the exterior part and the insulating part have a layered form. <16> The solid-state battery according to any one of <11> to <15>, 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 each surface of the two solid electrolyte layers. <17> The solid-state battery according to any one of <11> to <16>, wherein the exterior part and the sintered part are integrally sintered bodies formed with the surface of the battery element, and the insulating part and the sintered body are integrally sintered bodies formed with the surfaces of the two solid electrolyte layers.

[0138] 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.

[0139] [Experimental Example 1] <Examples and Comparative Examples> [Synthesis of Exterior Substrate (Main Phase)] Raw materials including lithium carbonate (Li2CO3), magnesium oxide (MgO), titanium oxide (TiO2), niobium oxide (Nb2O5), zirconium oxide (ZrO2), tantalum oxide (Ta2O5), hafnium oxide (HfO2), manganese carbonate (MnCO3), nickel oxide (NiO), cobalt oxide (Co3O4), cerium oxide (CeO2), and iron oxide (Fe2O3) were weighed out so that the composition of the main phase would be as shown in the table below. Next, water was added, the mixture was sealed in a polyethylene pot, and the pot was rotated on a pot rack at 150 rpm for 16 hours to mix the raw materials. Note that lithium carbonate, the Li source, was charged in a 5% mass excess relative to the target composition, taking into account Li deficiency during sintering. Next, the resulting slurry was dried and then pre-fired at 1,050°C for 5 hours. A mixed solvent of toluene and acetone was added to the obtained calcined product, and the mixture was pulverized in a planetary ball mill for 12 hours, and then dried to obtain a powder of an exterior substrate (oxide ceramic) having the composition shown in each example or comparative example.

[0140] [Synthesis of Sintering Aid] Raw materials including lithium hydroxide monohydrate (LiOH·H2O) and bismuth oxide (Bi2O3) were weighed out so that the composite oxide had the composition shown in the table below. Next, the weighed raw materials were mixed in an agate mortar. The resulting mixed powder was calcined in a N2 atmosphere at 600°C for 5 hours to obtain a calcined powder.

[0141] [Preparation of Sintered Body] Comparative Examples 1-2 and Examples 1-4: Instead of the "mixed powder" shown below, the powder obtained in [Synthesis of Exterior Substrate (Main Phase)] was used. Comparative Examples 3-7 and Examples 5-18: The exterior substrate 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 a 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. The sheet was then fired for 10 hours at the temperature shown in the table. The resulting sheet was then cooled to obtain an exterior ceramic veneer.

[0142] [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 ≦ 9% (good); △: 9% < areal porosity ≦ 13% (pass: no practical problems); ×: 13% < areal porosity (fail: practical problems).

[0143] [Evaluation of moisture resistance (water vapor barrier property)] Measurement was carried out using the cup method of Japanese Industrial Standard JIS Z 0208-1976. The water vapor transmission rate (WVTR) was measured at a temperature of 40°C and a relative humidity of 90% for 48 hours. The formula for calculating WVTR was as follows: WVTR [g / m2 / day] = Weight increase of CaCl2 [g] / Sample area [m2] / Storage time in constant temperature and humidity chamber [days] Evaluation criteria ⊚: WVTR≦1×10 －１ g / m ２ / day (less than the lower limit of measurement) (excellent); ○: 1 × 10 －１ g / m ２ / day<WVTR≦2×10 －１ g / m ２ / day (good); △: 2 × 10 －１ g / m ２ / day<WVTR≦1g / m ２ / day (pass: no problem in practical use); ×: 1 g / m ２ / day<WVTR (fail: problematic for practical use). Moisture resistance was measured only for the Examples and Comparative Examples listed in Table 6. The evaluation results for moisture resistance were in good agreement with the evaluation results for areal porosity.

[0144] [Evaluation of Insulation (Electronic Conductivity)] 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) ◎: Electronic conductivity ≦ 1 x 10 －８ S / cm (excellent); ○: 1×10 －８ S / cm<electronic conductivity≦3×10 －７ S / cm (good); △: 3 × 10 －７ S / cm<electronic conductivity≦5×10 －７ S / cm (passed: no practical problem); ×: 5 × 10 －７ S / cm<electronic conductivity (fail: problematic for practical use).

[0145] [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.

[0146] [Mg Content] The average Mg content of the exterior ceramic veneer was determined by ICP-AES analysis.

[0147] [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.

[0148]

[0149] As shown in Comparative Examples 1 and 2, Li, Mg, M Ｉ , O is difficult to densify at a firing temperature of 1000°C, and it is not possible to sufficiently ensure low-temperature densification properties (water vapor barrier properties). ＩＩ It was found that by further containing ), sinterability (particularly low-temperature densification characteristics) is improved and sufficient water vapor barrier properties can be ensured.

[0150] M ＩＩ / (Mg+M Ｉ In Example 4, where the transition metal content was 0.2, the electronic conductivity was such that the insulating property was good. This indicates that if the transition metal content is too high, the insulating property decreases.

[0151]

[0152] A comparison between Comparative Example 3 and Example 5 shows that even when the exterior material contains Bi, the inclusion of a transition metal further improves the low-temperature densification characteristics and the water vapor barrier property. Furthermore, even when the type and amount of the transition metal layer were changed, the areal porosity (water vapor barrier property) showed a preferable value.

[0153]

[0154] From the comparison between Comparative Examples 4 to 7 and Examples 15 to 18, it can be seen that the constituent elements of the exterior material are Li, Mg, M Ｉ , O, the transition metal (M ＩＩ ) improves the low-temperature densification properties and sufficiently improves the water vapor barrier properties (moisture resistance), and it can be seen that the effect of containing transition metals can be observed even if the composition is changed.

[0155] Comparing Examples 1, 12, and 17 with Examples 2 to 11, 13 to 16, and 18, it was found that if the following conditions A1 to A3 are satisfied, the low-temperature densification characteristics (and moisture resistance) and insulating properties are further improved, and the evaluation results for all of these characteristics are "Good" or better. Condition A1: The oxide ceramic has only a rock-salt type crystal structure or a layered rock-salt type crystal structure. Condition A2: The element M ＩＩ is one element selected from the group consisting of transition metal elements (particularly, the group consisting of Ni, Mn, Co, Fe, and Ce). Condition A3: The oxide ceramic contains Bi (bismuth) in the following molar ratio: 0<Bi / M Ｉ ≦0.100 and further contained.

[0156] Comparing Examples 1, 4, 5, 8, 12, 13, 15, and 17 with Examples 2, 3, 6, 7, 9-11, 14, 16, and 18, it was found that if the following conditions B1 to B5 are satisfied, the low-temperature densification characteristics (and moisture resistance) and insulating properties are further improved, and the evaluation results for all of these characteristics are "Excellent" or better. Condition B1: The oxide ceramic has only a rock-salt type crystal structure or a layered rock-salt type crystal structure. Condition B2: The element M Ｉ is one element selected from the group consisting of elements of Groups 4 and 5 (particularly, the group consisting of Ti, Zr, Hf, Ta, and Nb), or is two elements, Zr and Ta. Condition B3: Element M ＩＩ is one element selected from the group consisting of Ni, Mn, Co and Ce. Condition B4: The oxide ceramic contains the element M ＩＩ in the following molar ratio: 0.008≦M ＩＩ / (Mg+M Ｉ Condition B5: The oxide ceramic contains Bi (bismuth) in the following molar ratio: 0<Bi / M Ｉ ≦0.100 and further contained.

[0157] In Tables 4 to 6, "Chemical composition of exterior ceramic" indicates the final composition. In Tables 4 to 6, "Exterior substrate" indicates the composition of the oxide ceramic used as a raw material.

[0158] [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.

[0159] In Experimental Example 1, the manufactured exterior substrate (oxide ceramic) and exterior ceramic veneer were also shown to have sufficiently excellent electronic conductivity (insulation), but this evaluation method 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) even when used in an insulating portion.

[0160] 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).

[0161] 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 exterior part and an insulating part, At least one of the exterior part and the insulating part is Li (lithium); Mg (magnesium); one or more elements M selected from the group consisting of elements of Groups 4 and 5; Ｉ and One or more elements M selected from the group consisting of transition metal elements ＩＩ A solid-state battery comprising an oxide ceramic containing

2. 2. The solid-state battery according to claim 1, wherein the oxide ceramic further contains or does not contain Bi (bismuth) and has the following molar ratio: 0≦Bi / M Ｉ ≦0.100

3. The element M Ｉ The solid-state battery according to claim 1 , wherein is at least one selected from the group consisting of Ti, Zr, Hf, Ta, and Nb.

4. The element M ＩＩ The solid-state battery according to claim 1 , wherein is at least one selected from the group consisting of Ni, Mn, Co, Fe, and Ce.

5. 2. 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 mixed phase structure thereof.

6. The oxide ceramic contains the element M ＩＩ in the following molar ratios: 0.008≦M ＩＩ / (Mg+M Ｉ )≦0.150 The solid-state battery according to claim 1 , comprising:

7. 2. The solid-state battery according to claim 1, wherein the oxide ceramic has the following molar ratio: 0<Mg / M Ｉ ≦9.8 0<M ＩＩ / (Mg+M Ｉ )≦0.300

8. 2. The solid-state battery according to claim 1, wherein the oxide ceramic has the following molar ratio: 0<Li / M Ｉ <5

9. a main phase in the oxide ceramic has only a rock salt type crystal structure or a layered rock salt type crystal structure, The element M ＩＩ is an element selected from the group consisting of transition metal elements, The oxide ceramic contains Bi (bismuth) in the following molar ratio: 0<Bi / M Ｉ ≦0.100 10. The solid-state battery of claim 1, further comprising:

10. a main phase in the oxide ceramic has only a rock salt type crystal structure or a layered rock salt type crystal structure, The element M Ｉ is one element selected from the above group, or is two elements, Zr and Ta, The element M ＩＩ is an element selected from the group consisting of Ni, Mn, Co, and Ce, The oxide ceramic contains the element M ＩＩ in the following molar ratios: 0.008≦M ＩＩ / (Mg+M Ｉ )≦0.150 Contains The oxide ceramic contains Bi (bismuth) in the following molar ratio: 0<Bi / M Ｉ ≦0.100 10. The solid-state battery of claim 1, further comprising:

11. the solid-state battery further includes a battery element having 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 electrode external electrodes for extracting power generated in the battery element to the outside; the exterior portion is a member that covers the outside of the battery element, 2. The solid-state 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.

12. 12. The solid-state battery according to claim 11, wherein the 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.

13. 13. The solid-state battery of claim 12, wherein the one or more layers comprise a garnet-type solid electrolyte or a LISICON-type solid electrolyte.

14. 13. The solid-state battery of claim 12, wherein the one or more layers comprise a garnet-type solid electrolyte.

15. The solid-state battery according to claim 11 , wherein the exterior portion and the insulating portion have a layered form.

16. the exterior part is in direct contact with the surface of the battery element, 12. The solid-state battery according to claim 11, wherein the insulating portion is disposed between two solid electrolyte layers and is in direct contact with a surface of each of the two solid electrolyte layers.

17. the exterior portion is an integral sintered body formed by sintering a surface of the battery element and the sintered body, The solid-state battery according to claim 11 , wherein the insulating portion is an integral sintered body formed of a surface of each of the two solid electrolyte layers and a sintered body of the two solid electrolyte layers.