Solid state battery

Abstract

The present invention provides a solid state battery that has sufficiently excellent fixing strength between an exterior part and an external electrode. The present invention is a solid state battery including: a battery element; an exterior part present on an outer surface of the battery element; and an external electrode in contact with the exterior part. The exterior part includes oxide ceramic that contains one or more elements (M) selected from the group consisting of Li (lithium), Mg (magnesium), and group 4 and group 5 elements. Bi (bismuth) is present between the exterior part and the external electrode.

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.

[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 by-products to be generated, which has been a problem.

[0007] Therefore, when the exterior portion includes 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 with the solid electrolyte can be prevented to some extent, but the following new problem arises.

[0008] Specifically, silica-based additives are generally used in the external electrodes that are placed in contact with the exterior part to ensure bonding, but using only silica-based additives causes side reactions with the exterior part, resulting in defects in the exterior part. More specifically, cracks occurred at the corners of the exterior part. On the other hand, when no additive is added to the external electrode, a bonding layer is not formed at the interface between the external electrode and the exterior part, and sufficient bonding strength cannot be obtained between them.

[0009] An object of the present invention is to provide a solid-state battery having a sufficiently excellent bonding strength between an exterior part and an external electrode.

[0010] Another object of the present invention is to provide a solid-state battery that has a sufficiently excellent adhesive strength between the exterior and the external electrode, even if the external electrode does not contain an additive (for example, a silica-based additive).

[0011] The present invention relates to a solid-state battery having a battery element, an exterior covering the surface of the battery element, and an external electrode in direct contact with the exterior covering for extracting electric power generated in the battery element to the outside, wherein the exterior covering comprises an oxide ceramic containing Li (lithium); Mg (magnesium); and one or more elements (M) selected from the group consisting of elements of Groups 4 and 5, and Bi (bismuth) is present between the exterior covering and the external electrode.

[0012] The solid state battery of the present invention is sufficiently excellent in the adhesive strength between the exterior part and the external electrode.

[0013]

[0023] FIG. 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.

[0024] FIG. 2 is a schematic perspective view showing another example of a solid state battery of the present invention.

[0025] FIG. 3 is a schematic cross-sectional view illustrating an interface region between an oxide ceramic that constitutes a housing and a material that constitutes an external electrode.

[0026] FIG. 4 is another schematic cross-sectional view illustrating an interface region between an oxide ceramic that constitutes a housing and a material that constitutes an external electrode.

[0027] FIG. 5 is a schematic diagram of a TEM photograph showing the presence of Bi atoms when the interface region between an oxide ceramic that constitutes a housing and a material that constitutes an external electrode is observed by TEM-EDX (energy dispersive X-ray spectroscopy).

[0028] FIG. 6 is a schematic diagram of a TEM photograph showing the presence of Bi atoms when the interface region between an oxide ceramic that constitutes a housing and a material that constitutes an external electrode is observed by TEM-EDX.

[0029] FIG. 7 is a schematic diagram of a TEM photograph showing the presence of Bi atoms when the interface region between an oxide ceramic that constitutes a housing and a material that constitutes an external electrode is observed by TEM-EDX. 1 is a schematic diagram of an example of a TEM photograph showing the presence of Bi atoms when the interface region between the oxide ceramic constituting the exterior portion and the material constituting the external electrode is observed by TEM-EDX. 2 is a plan view for explaining a method for measuring adhesion strength in the examples, which is a schematic plan view of a lateral push test. 3 is a side view for explaining a method for measuring adhesion strength in the examples, which is a schematic side view of a lateral push test.

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

[0015] As used herein, the term "planar 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 T based on the stacking direction of the layers constituting the solid-state battery (described later). The term "side view" refers to the state of a solid-state battery placed and viewed from directly to the side in the thickness (height) direction T, and is equivalent to a side view. The placement refers to placement with the largest surface (flat surface) constituting the solid-state battery's exterior facing downward. The terms "vertical direction" and "horizontal direction" used directly or indirectly in this specification correspond to the vertical direction and horizontal direction in the drawings, respectively. Unless otherwise specified, the same symbols or symbols refer to the same components or parts or have the same meaning. In a preferred embodiment, the vertical downward direction (i.e., the direction in which gravity acts) can be considered to correspond to the "downward direction," and the opposite direction can be considered to correspond to the "upward direction."

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

[0017] The solid-state battery of the present invention has a layered structure (particularly a laminated structure), for example, as shown in Fig. 1. The solid-state battery of the present invention has a battery element 1 and an exterior part 2 covering the surface of the battery element 1, and usually further has an external electrode 3 for extracting power (particularly current) generated in the battery element to the outside. Fig. 1 is a schematic cross-sectional view showing an example of the solid-state battery of the present invention. In Fig. 1, L, W, and T respectively refer to the longitudinal direction, width direction, and thickness direction of the solid-state battery.

[0018] The exterior portion 2 is present on the outer surface of the battery element 1 and includes a main surface exterior portion 2a (e.g., a set of main surface exterior portions 2a) covering the main surface of the battery element 1 and a side surface exterior portion 2b (e.g., a set of side surface exterior portions 2b) covering the side surfaces of the battery element 1. 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.

[0019] In the solid-state battery of the present invention, Bi is present between the exterior casing 2 and the external electrode 3. Specifically, Bi is present in the interface region between the oxide ceramic that constitutes the exterior casing 2 and the material that constitutes the external electrode 3 (e.g., a conductive material containing Ag (silver)). The presence of Bi between the exterior casing 2 and the external electrode 3 (particularly in the interface region) more sufficiently improves the bonding strength between the exterior casing 2 and the external electrode 3 (hereinafter, simply referred to as "bonding strength"). The details of the mechanism by which the presence of Bi (particularly its uneven distribution in the interface region) more sufficiently improves the bonding strength are not clear, but it is thought to be based on the following phenomenon. When the external electrode is baked, Bi becomes liquid and wets the interface between the external electrode and the exterior without reacting with the exterior material, and the Bi layer functions as a bonding layer. Absence of Bi between the exterior casing 2 and the external electrode 3 reduces the bonding strength between the exterior casing 2 and the external electrode 3.

[0020] The "interface region" where Bi is present refers to the boundary region between the oxide ceramic and the external electrode material. The interface between them is not necessarily clearly defined (or observed). For example, when the interface is clearly defined (or observed), as shown in FIG. 3A , the interface region 5 is the boundary region between the oxide ceramic 20 and the external electrode material 30, and is a region in which the interface 50 is located and which includes two adjacent boundary regions located adjacent to each other on either side of the interface 50. Alternatively, when the interface is not clearly defined (or observed), as shown in FIG. 3B , the interface region 5 is a region in which, if an interface 51 were to exist, it would be inferred to exist based on the attributes (particularly the chemical composition) of the surrounding region. The existence of such an interface 51 can be inferred by analyzing the chemical composition at several analysis points in the surrounding regions of the oxide ceramic 20 and the external electrode material 30 and based on the differences in composition at each analysis point ( FIG. 3B ). The width p of the interface region 5 (see FIGS. 3A and 3B) is not particularly limited and is usually 1 to 100 nm, and from the viewpoint of further improving the bonding strength, it is preferably 2 to 80 nm, more preferably 3 to 60 nm, and particularly preferably 5 to 50 nm.

[0021] In a preferred embodiment of the solid-state battery of the present invention, as shown in FIGS. 4A to 4D , Bi is concentratedly segregated in the interface region 5 between the oxide ceramic 20 constituting the exterior and the material (e.g., Ag (silver)) 30 constituting the external electrode. This region (portion) where Bi is segregated may be defined as the "interface region." Therefore, the width p of the interface region may correspond to the width of the region (portion) where Bi is segregated. FIGS. 4A to 4D are schematic TEM photographs showing the presence of Bi atoms when a cross section of the interface region between the oxide ceramic constituting the exterior and the material constituting the external electrode is milled by FIB ion milling and then observed by TEM-EDX (energy dispersive X-ray spectroscopy) at a magnification of 1,000,000 times. In these schematic diagrams, black dots indicate the presence of Bi. "Concentrated" refers to a denser distribution. For example, Bi is present in the interface region 5 more densely than in the surrounding region. Furthermore, for example, Bi is more concentrated in the interface region than in the surrounding region. The term "segregation" refers to the phenomenon in which Bi is precipitated (or present) unevenly in the interface region 5 as described above.

[0022] From another perspective, when the interface region is observed by TEM-EDX at a magnification of, for example, 1,000,000 times, Bi is present in the form of bands or layers between the oxide ceramic 20 that constitutes the exterior portion and the material 30 that constitutes the external electrode. The reason why Bi is observed to be present in the form of bands or layers is that Bi is "more densely present" (or "more concentrated") in the interface region 5. Bi is usually more densely present in the interface region 5 having the width p described above than in the surrounding region, resulting in Bi being more concentrated. For example, the Bi concentration ratio, expressed as the ratio of "concentration in the interface region / concentration in the surrounding region," may be 1.05 or more.

[0023] In detail, for example, FIG. 4A shows that when the interface is not clearly defined (or observed), Bi is segregated intensively between the oxide ceramic 20 constituting the exterior part and the material (e.g., Ag (silver)) 30 constituting the external electrode.

[0024] 4B shows that when the interface 50 is clearly defined (or observed), Bi is segregated in a concentrated manner between the oxide ceramic 20 constituting the exterior portion and the material (e.g., a conductive material containing Ag (silver)) 30 constituting the external electrode. Specifically, as shown in FIG. 4B , Bi may be present in a concentrated manner in a region in the oxide ceramic 20 region near the external electrode material 30. Therefore, in this case, the interface region 5 where Bi is present can be positioned as an altered layer on the surface of the oxide ceramic 20.

[0025] 4C shows, for example, that when the interface 50 is clearly defined (or observed), Bi is segregated in a concentrated manner between the oxide ceramic 20 constituting the exterior portion and the material (e.g., Ag (silver)) 30 constituting the external electrode. Specifically, as shown in FIG. 4C , Bi may be present in a concentrated manner in both the region close to the external electrode constituent material 30 within the oxide ceramic 20 region and the region close to the oxide ceramic 20 within the external electrode constituent material 30 region. Therefore, in this case, the interface region 5 where Bi is present can be positioned as a composite altered layer of the altered layer on the surface of the oxide ceramic 20 and the altered layer on the surface of the external electrode constituent material 30.

[0026] 4D shows that when the interface 50 is clearly defined (or observed), Bi is segregated in a concentrated manner between the oxide ceramic 20 constituting the exterior portion and the material (e.g., a conductive material containing Ag (silver)) 30 constituting the external electrode. Specifically, as shown in FIG. 4D , Bi may be present in a concentrated manner in a region close to the oxide ceramic 20 within the region of the external electrode-constituting material 30. Therefore, in this case, the interface region 5 where Bi is present can be positioned as an altered layer on the surface of the external electrode-constituting material 30.

[0027] The presence of Bi between the exterior part 2 and the external electrode 3 (particularly concentrated segregation of Bi in the interface region) can be achieved, for example, by the following embodiments: Embodiment (1): Forming a Bi-containing layer as a bonding layer on at least the region of the exterior part surface where the external electrode is to be formed; Embodiment (2): Using an oxide ceramic containing Bi as at least a part of the oxide ceramic that constitutes the exterior part; Embodiment (3): Using a sintering aid containing Bi as the material that constitutes the external electrode; Embodiment (4): Using an oxide ceramic containing Bi as at least a part of the oxide ceramic that constitutes the battery element; Embodiment (5): Using a combination of two or more of the above-mentioned embodiments (1) to (4).

[0028] The presence of Bi between the exterior part 2 and the external electrode 3 (particularly concentrated segregation of Bi in the interface region) is preferably achieved by at least mode (1) (particularly mode (1) only) from the viewpoint of further improving the bonding strength.

[0029] In aspect (1), a Bi-containing layer is formed as a bonding layer on at least the region of the exterior surface where the external electrode is to be formed. The Bi-containing layer is an oxide layer (or oxide film) containing Bi. Examples of Bi sources include bismuth nitrate (or its hydrate), bismuth oxide, and bismuth alkoxide. The Bi-containing layer can be formed, for example, by applying an alcohol solution containing the Bi source to the exterior surface, drying it, and then firing it. The alcohol is not particularly limited as long as it can dissolve the Bi source, and examples include 2-ethoxyethanol. The drying temperature is not particularly limited and may be, for example, 50 to 150°C (particularly 80 to 120°C). The firing temperature is not particularly limited and may be, for example, 300 to 500°C (particularly 350 to 450°C). In aspect (1), when a Bi-containing layer is formed on at least the region of the exterior surface where the external electrode is to be formed, the external electrode may be indirectly in contact with the exterior in a solid-state battery via the Bi-containing layer.

[0030] In a preferred embodiment of aspect (1), the Bi-containing layer is preferably an oxide layer containing not only Bi but also Li and / or Mg, and more preferably an oxide layer containing Bi and Li, from the viewpoint of further improving bonding strength. The Bi-containing layer may further contain Mg and / or Si. Examples of Li sources include lithium nitrate and lithium hydroxide. Examples of Mg sources include magnesium ethoxide and magnesium hydroxide. Examples of Si sources include silicon tetraethoxide. The Li source and Mg source are contained in an alcohol solution together with the Bi source. The alcohol solution may contain ethyl acetoacetate to more uniformly disperse bismuth in the solution.

[0031] In the embodiment (1), the Bi-containing layer is made of an oxide ceramic and has, for example, a chemical composition represented by the following general formula (A).

[0032]

[0033] In formula (A), A １ is one or more elements selected from the group consisting of Na, K, Rb, Ca, Sr, Ba, Sc, Y, Mo, W, Zn, Al, Ga, Ge, Sn, and Sb. M is one or more elements selected from the same group as element M described below, and from the viewpoint of further improving moisture resistance, it preferably contains one or more elements selected from the group consisting of Ti, Zr, Hf, Nb, and Ta, more preferably contains Ti, and even more preferably contains only Ti, or contains Ti and Zr or Ta.

[0034] In formula (A), x7 = {x1 + ax2 + dx3 + 2x4 + 4x5 + nx6} / 2 (n is the average valence of M, a is A １ where d is the valence of Bi and is 3 or 5. Specifically, n is the average valence of M. For example, when M has 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 average valence of M is １ a is the same value as the average valence of A １is the average valence of １ The average valence of A １ For example, when n1 element X with a valence of a+, n2 element Y with a valence of b+, and n3 element Z with a valence of c+ are recognized, the value represented by (n1 x a + n2 x b + n3 x c) / (n1 + n2 + n3) is used. Note that the number of oxygen atoms x may deviate from the above value by about ±10%. In other words, some oxygen vacancies or interstitial oxygen may be included.

[0035] In formula (A), x1 usually satisfies 0<x1≦1.0, and from the viewpoint of further improving the fixing strength, moisture resistance, and reactivity resistance, preferably satisfies 0.3≦x1≦1.0, more preferably 0.5≦x1≦1.0. x2 usually satisfies 0≦x2≦1.0, and from the viewpoint of further improving the fixing strength, moisture resistance, and reactivity resistance, preferably satisfies 0≦x2≦0.5, more preferably 0. x3 usually satisfies 0<x3≦1.0, and from the viewpoint of further improving the fixing strength, moisture resistance, and reactivity resistance, preferably satisfies 0.1≦x3≦0.7, more preferably satisfies 0.2≦x3≦0.5. x4 usually satisfies 0≦x4≦1.0, and from the viewpoint of further improving the fixing strength, moisture resistance, and reactivity resistance, preferably satisfies 0≦x4≦0.5, more preferably satisfies 0≦x4≦0.3, even more preferably satisfies 0.01≦x4≦0.3. x5 usually satisfies 0≦x5≦1.0, and from the viewpoint of further improving the adhesive strength, moisture resistance, and reactivity resistance, preferably satisfies 0≦x5≦0.5, more preferably satisfies 0≦x5≦0.3. x6 usually satisfies 0≦x6<1.0, and from the viewpoint of further improving the adhesive strength, moisture resistance, and reactivity resistance, preferably satisfies 0≦x6<0.35, more preferably 0.

[0036] The chemical composition of the oxide ceramic can be determined by ICP analysis (inductively coupled plasma) or LA-ICP-MS (laser ablation ICP-MS). EDX (energy dispersive X-ray spectroscopy) or WDX (wavelength dispersive X-ray spectroscopy) may also be used. 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.

[0037] In aspect (1), the thickness of the Bi-containing layer is not particularly limited and may be equal to the width p of the interface region 5 described above. From the viewpoint of further improving the bonding strength, the thickness is preferably 1 nm or more and 200 nm or less, more preferably 10 nm or more and 100 nm or less.

[0038] In aspect (1), by forming a Bi-containing layer as a bonding layer on at least the region of the exterior part surface where the external electrode is formed, Bi is present between the exterior part 2 and the external electrode 3, and Bi segregates intensively, particularly in the interface region.

[0039] In aspect (1), the explanations of the "exterior part," the "battery element," the "external electrode," and the "manufacturing method for a solid-state battery" are the same as those of the "exterior part," the "battery element," the "external electrode," and the "manufacturing method for a solid-state battery" described later, except that a Bi-containing layer is formed as a bonding layer in at least a region of the exterior part surface where the external electrode is formed.

[0040] In aspect (2), an oxide ceramic containing Bi is used as at least a part of the oxide ceramic constituting the exterior portion. The oxide ceramic containing Bi has a chemical composition represented by the same general formula as general formula (1) described below, except that A contains Bi and α2 is within the following range. α2 usually satisfies 0 < α2 ≦ 1.0, and from the viewpoint of further improving the bonding strength, preferably satisfies 0.001 ≦ α2 ≦ 0.050, and more preferably satisfies 0.002 ≦ α2 ≦ 0.030.

[0041] In aspect (2), by using an oxide ceramic having the above chemical composition to form the exterior part, Bi is present between the exterior part 2 and the external electrode 3, and Bi segregates intensively, particularly in the interface region.

[0042] In aspect (2), the explanations of the "exterior part," "battery element," "external electrode," and "manufacturing method for a solid-state battery" are the same as those of the "exterior part," "battery element," "external electrode," and "manufacturing method for a solid-state battery" described later, except that an oxide ceramic having the above chemical composition is used to form the exterior part.

[0043] In the third aspect, the external electrodes are made of an electron conductive material and a sintering aid containing Bi, such as bismuth-containing glass (e.g., B—Si—Bi—O glass).

[0044] In aspect (3), by using a sintering aid containing Bi in forming the external electrode, Bi is present between the exterior part 2 and the external electrode 3, and Bi segregates intensively, particularly in the interface region.

[0045] In aspect (3), the explanations of the "exterior part," the "battery element," the "external electrode," and the "manufacturing method for a solid-state battery" are the same as those of the "exterior part," the "battery element," the "external electrode," and the "manufacturing method for a solid-state battery" described later, except that a sintering aid containing Bi is used to form the external electrode.

[0046] In aspect (4), a Bi-containing oxide ceramic is used as at least a part of the oxide ceramic constituting the battery element. Examples of the Bi-containing oxide ceramic include a garnet-type solid electrolyte having a chemical composition represented by the general formula (2) described below. Such a Bi-containing oxide ceramic may be contained in one or more layers selected from the positive electrode layer, the negative electrode layer, and the solid electrolyte layer of the battery element.

[0047] In aspect (4), by using an oxide ceramic containing Bi to form the battery element, Bi is present between the exterior part 2 and the external electrode 3, and Bi segregates intensively, particularly in the interface region. Even if materials containing Bi (e.g., an oxide ceramic containing Bi and a sintering aid containing Bi) are not used to form the exterior part 2 and the external electrode 3, if an oxide ceramic containing Bi is used to form the battery element, Bi will migrate and Bi will be present between the exterior part 2 and the external electrode 3, and Bi will segregate intensively, particularly in the interface region.

[0048] In aspect (4), the explanations of the "exterior part," the "battery element," the "external electrode," and the "manufacturing method for a solid-state battery" are the same as those of the "exterior part," the "battery element," the "external electrode," and the "manufacturing method for a solid-state battery" described later, except that an oxide ceramic containing Bi is used to form the battery element.

[0049] (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 surface 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 surface 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 of the battery element 1 (particularly the main surface and / or side surface) or 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 of the battery element 1 (particularly the main surface and / or side surface). A portion of the exterior part 2 is in direct contact with the external electrode 3, which will be described later.

[0050] In the solid-state battery of the present invention, the exterior part 2 contains a specific oxide ceramic. In the present invention, 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 the bonding strength, moisture resistance, and reactivity resistance, it is preferable that both the main surface exterior part and the side surface exterior part contain the specific oxide ceramic.

[0051] In the present invention, the oxide ceramic contained in the exterior portion contains one or more elements (M) selected from the group consisting of Li (lithium); Mg (magnesium); and elements of Groups 4 and 5. Specifically, element M is one or more elements selected from the group consisting of Ti (titanium), Zr (zirconium), Hf (hafnium), Ta (tantalum), and Nb (niobium). From the viewpoint of further improving moisture resistance, element M preferably contains Ti, and more preferably contains only Ti, or Ti and Zr or Ta. In the present invention, when the oxide ceramic contains a combination of Li, Mg, and element M, an exterior portion with excellent moisture resistance and reactivity resistance can be obtained. When the oxide ceramic does not contain Li, Mg, or element M, at least one of the properties of moisture resistance and reactivity resistance is reduced.

[0052] In this specification, moisture resistance refers to the property of preventing moisture penetration, and may particularly refer to the property of being less susceptible to the effects of moisture even under high temperature and high humidity conditions (e.g., the property of being less susceptible to moisture absorption). Unless otherwise specified, reactivity resistance refers to the property of the exterior (e.g., the oxide ceramic contained in the exterior) being less likely to react (e.g., undergo a side reaction) with the solid electrolyte contained in the battery element even when fired (e.g., at 800°C for 5 hours). Reactivity resistance may particularly refer to the property of the oxide ceramic and the solid electrolyte being less likely to react with each other even when fired together.

[0053] In the oxide ceramic, the molar ratios Li / M and Mg / M are not particularly limited, but from the viewpoint of further improving bonding strength, moisture resistance, and reactivity resistance, they are preferably within the following ranges: Li / M: preferably 0<Li / M≦5, more preferably 0.8≦Li / M≦4.2, and even more preferably 0.8≦Li / M≦2.1. Mg / M: preferably 0.1≦Mg / M≦9.8, more preferably 0.3≦Mg / M≦9.8, and even more preferably 0.8≦Mg / M≦4.2.

[0054] The Li / M and Mg / M in the oxide ceramics are values ​​calculated from the contents (or molar ratios) of Li, Mg, and M measured by a method similar to the analytical method for the chemical composition of oxide ceramics described below.

[0055] The Mg content in the oxide ceramic is usually 0 mass% or more and 58 mass% or less, particularly 1 mass% or more and 58 mass% or less, preferably 10 mass% or more and 55 mass% or less, and more preferably 20 mass% or more and 50 mass% or less, based on the total amount of the oxide ceramic.

[0056] 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.

[0057] The oxide ceramic may have any chemical composition as long as it has the above molar ratio. From the viewpoint of further improving bonding strength, moisture resistance, and reactivity resistance, the oxide ceramic preferably has a chemical composition represented by the following general formula (1):

[0058]

[0059] 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, Sb, and Bi. M is one or more elements selected from the same group as the element M described above, and from the viewpoint of further improving moisture resistance, it preferably contains one or more elements selected from the group consisting of Ti, Zr, Hf, Nb, and Ta, more preferably contains Ti, and even more preferably contains only Ti, or contains Ti and Zr or Ta.

[0060] In formula (1), α1 / γ and β / γ correspond to the molar ratios Li / M and Mg / M, respectively. Therefore, α1 / γ satisfies the same range as the molar ratio Li / M, and from the viewpoint of further improving the bonding strength, moisture resistance, and reactivity resistance, preferably satisfies the preferred range of Li / M, more preferably satisfies the more preferred range of Li / M, and even more preferably satisfies the more preferred range of Li / M. β / γ satisfies the same range as the molar ratio Mg / M, and from the viewpoint of further improving the bonding strength, moisture resistance, and reactivity resistance, preferably satisfies the preferred range of Mg / M, more preferably satisfies the more preferred range of Mg / M, and even more preferably satisfies the more preferred range of Mg / M. δ = {α1 + aα2 + 2β + nγ} / 2 (n is the average valence of M, a is the average valence of A). Specifically, n is the average valence of M. The average valence of M is, for example, when n1 element X with a valence of a+, n2 element Y with a valence of b+, and n3 element Z with a valence of c+ are recognized as M, the average valence of M is the same value as the average valence of A described below. 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 recognized as A, the average valence of A is the value expressed as (n1 x a + n2 x b + n3 x c) / (n1 + n2 + n3). Note that the oxygen number δ may deviate by about ±10% from the above value. In other words, some oxygen vacancies or interstitial oxygen may be included.

[0061] In formula (1), α1 typically satisfies 0 < α1 < 1.0, and from the viewpoint of further improving the adhesion strength, moisture resistance, and reactivity resistance, preferably satisfies 0.15 < α1 < 0.70, and more preferably satisfies 0.29 ≦ α1 ≦ 0.50. α2 typically satisfies 0 ≦ α2 ≦ 1.0, and from the viewpoint of further improving the adhesion strength, moisture resistance, and reactivity resistance, preferably satisfies 0 ≦ α2 ≦ 0.5, and more preferably is 0. β typically satisfies 0 < β < 1.0, and from the viewpoint of further improving the adhesion strength, moisture resistance, and reactivity resistance, preferably satisfies 0.03 ≦ β < 0.85, and more preferably satisfies 0.25 ≦ β ≦ 0.60. γ typically satisfies 0 < γ < 1.0, and from the viewpoint of further improving the adhesion strength, moisture resistance, and reactivity resistance, preferably satisfies 0.05 < γ < 0.35, and more preferably satisfies 0.14 ≦ γ ≦ 0.26.

[0062] In particular, in the embodiment (2), as described above, a Bi-containing oxide ceramic having a chemical composition represented by the same general formula as the above general formula (1) is used, except that A contains Bi and α2 is within the above range.

[0063] The chemical composition of the oxide ceramic can be determined by ICP analysis (inductively coupled plasma) or LA-ICP-MS (laser ablation ICP-MS). EDX (energy dispersive X-ray spectroscopy) or WDX (wavelength dispersive X-ray spectroscopy) may also be used. 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.

[0064] 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 thereof. From the viewpoint of further improving bonding strength, moisture resistance, and reactivity resistance, the oxide ceramic preferably has a rock salt crystal structure and / or a spinel crystal structure (particularly a rock salt crystal structure or a mixed phase structure of a rock salt crystal structure and a spinel crystal structure), and more preferably has a rock salt crystal structure.

[0065] 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.

[0066] 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.

[0067] 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 rock salt type crystal structure and the spinel type crystal structure described above.

[0068] 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.

[0069] Oxide ceramics may be produced by any method that produces an oxide ceramic of the desired composition. For example, oxide ceramics can be obtained by weighing raw materials containing a Li source, an Mg source, and an M source to achieve the desired composition, thoroughly mixing them with water, and then firing the mixture. The firing temperature is not particularly limited and may be, for example, 800°C to 1200°C (particularly, 850°C to 1100°C). The firing time is not particularly limited and may be, for example, 1 hour to 10 hours (particularly, 3 hours to 7 hours). For example, lithium carbonate (Li2CO3) can be used as the Li source. For example, magnesium oxide (MgO) can be used as the M source. For example, titanium oxide (TiO2), niobium oxide (Nb2O5), zirconium oxide (ZrO2), tantalum oxide (Ta2O5), and hafnium oxide (HfO2) can be used as the M source. In the production of oxide ceramics, the final composition of the oxide ceramics is determined by the ratio of the Li source, Mg source, and element M source at the time of charging. Therefore, the molar ratios Li / M and Mg / M can be controlled by adjusting the ratio of the Li source, Mg source, and element M source.

[0070] The present invention 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 oxides containing Bi. For example, Li-Bi-O-based oxides, Li-Mg-Bi-O-based oxides, and Bi ２ O ３, Mg—Bi—O-based oxides, etc. The content of the above-mentioned specific oxide ceramics in the exterior portion 2 may typically be an area percentage of 60% or more and 100% or less, particularly an area percentage of 90% or more and 100% or less. This area percentage can be measured as follows. First, the solid-state battery is fractured so that the fracture surface of the ceramic exterior portion is exposed. This fracture surface is polished using a cross-section polisher or the like to obtain a polished surface. EDX analysis is performed on any surface in the exterior portion region of the polished surface, and the region where Mg, element M, and element A are detected and Li is detected by TOF-SIMS is considered to be the region of the above-mentioned specific oxide ceramics. From the above, the area percentage of the oxide ceramics relative to the area of ​​the exterior portion can be calculated and measured.

[0071] 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.

[0072] 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.

[0073] 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 1×10 －７ S / cm or less, especially 1×10 －１０ The electronic conductivity of the exterior part 2 is usually 1×10 －１８ S / cm or more.

[0074] The oxygen permeability in the thickness direction of the exterior part 2 is, for example, 10 －１ cc / m ２ / day / atmospheric pressure or less, especially 10－３ cc / m ２ / day / atmospheric pressure or less. ２ O permeability is, for example, 10 －２ g / m ２ / day and below, especially 10 －４ g / m ２ / day or less. ２ The O permeability is measured at 25° C. by the cup method, carrier gas method, pressure method, or Ca corrosion method.

[0075] 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.

[0076] 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.

[0077] (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 has an insulating portion 1c for ensuring electrical non-contact between the positive electrode layer and an external electrode (i.e., external negative electrode) for drawing current from the negative electrode layer to the outside. Also, for example, the battery element 1 has an insulating portion 1c for ensuring electrical non-contact between the negative electrode layer and an external electrode (i.e., external negative electrode) for drawing current from the positive electrode layer to the outside. The battery element usually has solid electrolyte layers 1b on the top and bottom layers of the battery element, as shown in Figure 1.

[0078] 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 adhesion strength, moisture resistance, and reactivity resistance, the first solid electrolyte included in the battery element preferably has a garnet-type crystal structure, a LISICON-type crystal structure, or a mixed phase structure thereof, and more preferably has a garnet-type crystal structure.

[0079] 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 adhesion strength, moisture resistance, and reactivity resistance, it is preferable that the first solid electrolyte be contained in at least the solid electrolyte layer.

[0080] 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.

[0081] 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).

[0082]

[0083] In formula (2), A １ indicates a metal element occupying the Li site in the garnet-type crystal structure. １ is usually one or more elements selected from the group consisting of Ga (gallium), Al (aluminum), Mg (magnesium), Zn (zinc) and Sc (scandium). １ is preferably one or more elements selected from the group consisting of Ga (gallium) and Al (aluminum), more preferably two elements of Ga and Al, from the viewpoint of further improving adhesive strength, moisture resistance, and reactivity resistance.

[0084] In formula (2), B １ indicates a metal element occupying the La site in the garnet-type crystal structure. １ is usually one or more elements selected from the group consisting of Ca (calcium), Sr (strontium), Ba (barium), and lanthanoid elements, such as Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holminium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium).

[0085] In formula (2), D １ indicates a metal element occupying a hexacoordinated site in a garnet-type crystal structure. The hexacoordinated site of a garnet-type crystal structure is, for example, Li ５ La ３ Nb ２ O １２ (ICDD Card No. 00-045-0109) Nb-occupied site, Li ７ La ３ Zr ２ O１２ (ICDD Card. No. 01-078-6708) is the site occupied by Zr. １ represents one or more elements selected from the group consisting of transition elements capable of hexacoordination with oxygen and typical elements belonging to groups 12 to 15. Examples of transition elements capable of hexacoordination with oxygen include Sc (scandium), Zr (zirconium), Ti (titanium), Ta (tantalum), Nb (niobium), Hf (hafnium), Mo (molybdenum), W (tungsten), and Te (tellurium). Examples of typical elements belonging to groups 12 to 15 include In (indium), Ge (germanium), Sn (tin), Pb (lead), Sb (antimony), and Bi (bismuth). D １ is usually one or more elements selected from the group consisting of Zr (zirconium), Sn (tin), Sb (antimony), Ti (titanium), Ta (tantalum), Nb (niobium), Hf (hafnium), Mo (molybdenum), W (tungsten) and Te (tellurium), and from the viewpoint of further improving the bonding strength, moisture resistance and reactivity resistance, it 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).

[0086] In formula (2), x satisfies 0≦x≦1.00, and from the viewpoint of further improving the fixing strength, moisture resistance, and reactivity resistance, preferably satisfies 0≦x≦0.70, more preferably 0≦x≦0.40, even more preferably 0≦x≦0.40, and particularly preferably 0≦x≦0.20. y satisfies 0≦y≦0.50, and from the viewpoint of further improving the fixing strength, moisture resistance, and reactivity resistance, preferably satisfies 0≦y≦0.40, more preferably 0≦y≦0.30, and even more preferably 0≦y≦0.20. β satisfies 2.5≦β≦3.5, and from the viewpoint of further improving the fixing strength, moisture resistance, and reactivity resistance, preferably satisfies 2.7≦β≦3.3, more preferably 2.8≦β≦3.2, and even more preferably 2.9≦β≦3.1. z satisfies 0≦z≦2.00, and from the viewpoint of further improving the adhesive strength, moisture resistance, and reactivity resistance, preferably satisfies 0≦z≦1.00, more preferably 0≦z≦0.50, and even more preferably 0. γ satisfies 1.5≦γ≦2.5, and from the viewpoint of further improving the adhesive strength, moisture resistance, and reactivity resistance, preferably satisfies 1.7≦γ≦2.3, more preferably 1.8≦γ≦2.2, and even more preferably 1.9≦γ≦2.0.

[0087] In formula (2), p usually satisfies 6.0≦p≦7.0, and from the viewpoint of further improving the adhesive strength, moisture resistance, and reactivity resistance, it preferably satisfies 6.0≦p≦6.6, and more preferably 6.25≦p≦6.55. １ is the average valence of １ The average valence of A １ For example, when n1 element X with a valence of a+, n2 element Y with a valence of b+, and n3 element Z with a valence of c+ are recognized, it is a value expressed as (n1 x a + n2 x b + n3 x c) / (n1 + n2 + n3). b is B １ is the average valence of B １ The average valence of B １ For example, when n1 elements X having a valence of a+, n2 elements Y having a valence of b+, and n3 elements Z having a valence of c+ are found, the above-mentioned A １ The same value as the average valence of １ is the average valence of １ The average valence of１ For example, when n1 elements X having a valence of a+, n2 elements Y having a valence of b+, and n3 elements Z having a valence of c+ are found, the above-mentioned A １ is the same value as the average valence of δ. δ indicates the amount of oxygen vacancy and may be 0. Usually, δ is sufficient as long as it satisfies 0≦δ<1. The amount of oxygen vacancy δ cannot be quantitatively analyzed even using the latest equipment, so it may be considered to be 0. Note that the molar ratio of each element in the chemical composition of the solid electrolyte ceramic of the present invention does not necessarily match, for example, the molar ratio of each element in formula (2), and tends to deviate depending on the analytical method, but the effect of the present invention can be achieved as long as the composition deviation is not so great that the characteristics change.

[0088] In the present invention, the chemical composition of the solid electrolyte 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 performing quantitative analysis (composition analysis) of 100 arbitrary points on each of 100 arbitrary sintered particles and calculating the average value.

[0089] Specific examples of the garnet-type solid electrolyte represented by the general formula (2) include Li ６．６ La ３ Zr １．６ Ta ０．４ O １２ , Li ６．４ Ga ０．０５ Al ０．１５ La ３ Zr ２ O １２ , Li ６．７５ La ３ Zr １．７５ Nb ０．２５ O １２ , Li ６．５３ La ３ Zr １．５３ Ta０．４ Bi ０．０７ O １２ Examples include:

[0090] The LISICON type crystal structure of the solid electrolyte is Ｉ structure, β ＩＩ Type structure, β ＩＩ 'type structure, T Ｉ Type structure, T ＩＩ Type structure, γ ＩＩ type structure, and γ ０ That is, the LISICON-type solid electrolyte has a β Ｉ structure, β ＩＩ Type structure, β ＩＩ 'type structure, T Ｉ Type structure, T ＩＩ Type structure, γ ＩＩ Type structure, γ ０ The solid electrolyte may contain one or more solid electrolytes having a γ-type structure or a composite structure thereof. The LISICON-type structure of the solid electrolyte is preferably a γ-type structure or a composite structure thereof from the viewpoint of further improving adhesion strength, moisture resistance, and reactivity resistance. ＩＩ A mold structure is preferred.

[0091] The solid electrolyte is γ ＩＩ The term "having a γ-type structure" means that the solid electrolyte ＩＩ It means that the solid-state battery has a γ type crystal structure, and in a broad sense, it is known by those skilled in the art of solid-state batteries as ＩＩ In a narrow sense, a solid electrolyte has a crystal structure that can be recognized as a γ-type crystal structure. ＩＩ The term "having a γ-type structure" means that the solid electrolyte has a γ-type structure in X-ray diffraction. ＩＩ -Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a given angle of incidence. ＩＩ Compounds having this type structure (i.e., solid electrolytes) are described, for example, in the literature "J. Solid State Chem" (A.R.West et al., J. Solid State Chem., 4, 20-28 (1972)), and an example thereof is ICDD Card No. 01-073-2850.

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

[0093]

[0094] The solid electrolyte is β ＩＩ The term "having a β-type structure" means that the solid electrolyte has a β-type structure. ＩＩ In a broad sense, it means that the solid-state battery has a β type crystal structure. ＩＩ In a narrow sense, the term "solid electrolyte" refers to a solid electrolyte having a crystal structure that can be recognized as a β-type crystal structure. ＩＩ The term "having a β-type structure" means that the solid electrolyte has a β-type structure in X-ray diffraction. ＩＩ -Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a given angle of incidence. ＩＩ Compounds having this type structure (i.e., solid electrolytes) are described, for example, in the literature "J. Solid State Chem" (A.R. West et al., J. Solid State Chem., 4, 20-28 (1972)), and an example thereof is ICDD Card No. 00-024-0675.

[0095] The solid electrolyte is βＩＩ The term "having a β' structure" means that the solid electrolyte has a β ＩＩ It means that the solid-state battery has a β'-type crystal structure, and in a broad sense, it is known by those skilled in the art of solid-state batteries as ＩＩ In a narrow sense, the term refers to a solid electrolyte having a crystal structure that can be recognized as a β'-type crystal structure. ＩＩ The term "having a β' type structure" means that the solid electrolyte has a so-called β' type structure in X-ray diffraction. ＩＩ '-Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a given angle of incidence. ＩＩ Compounds having the '-type structure (i.e., solid electrolytes) are described, for example, in the literature "J. Solid State Chem" (A.R.West et al., J. Solid State Chem., 4, 20-28 (1972)). As an example, the XRD data (d-spacing values ​​and corresponding Miller indices) shown in the table below are shown.

[0096]

[0097] Solid electrolyte is T Ｉ The term "having a T type structure" means that the solid electrolyte has a T type structure. Ｉ It means that the solid-state battery has a crystal structure of T type. Ｉ In a narrow sense, the solid electrolyte has a crystal structure that can be recognized as a T type crystal structure. Ｉ The term "having a type structure" means that the solid electrolyte has a so-called T Ｉ -Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a given angle of incidence. Ｉ Compounds having this type structure (i.e., solid electrolytes) are described, for example, in the literature "J. Solid State Chem" (A.R. West et al., J. Solid State Chem., 4, 20-28 (1972)), and an example thereof is ICDD Card No. 00-024-0668.

[0098] Solid electrolyte is T ＩＩ The term "having a T type structure" means that the solid electrolyte has a T type structure. ＩＩ It means that the solid-state battery has a crystal structure of T type. ＩＩ In a narrow sense, the solid electrolyte has a crystal structure that can be recognized as a T type crystal structure. ＩＩ The term "having a type structure" means that the solid electrolyte has a so-called T ＩＩ -Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a given angle of incidence. ＩＩ Compounds having this type structure (i.e., solid electrolytes) are described, for example, in the literature "J. Solid State Chem" (A.R.West et al., J. Solid State Chem., 4, 20-28 (1972)), and an example thereof is ICDD Card No. 00-024-0669.

[0099] The solid electrolyte is γ ０ The term "having a γ-type structure" means that the solid electrolyte ０ It means that the solid-state battery has a γ type crystal structure, and in a broad sense, it is known by those skilled in the art of solid-state batteries as ０ In a narrow sense, a solid electrolyte has a crystal structure that can be recognized as a γ-type crystal structure. ０ The term "having a γ-type structure" means that the solid electrolyte has a γ-type structure in X-ray diffraction. ０ -Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a given angle of incidence. ０ Compounds having the above structure (i.e., solid electrolytes) are described, for example, in the literature "J. Solid State Chem" (A.R. West et al., J. Solid State Chem., 4, 20-28 (1972)). As an example, the XRD data (d-spacing values ​​and corresponding Miller indices) shown in the table below are shown.

[0100]

[0101] 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):

[0102]

[0103] 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), and from the viewpoint of further improving the bonding strength, moisture resistance, and reactivity resistance, it 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 a relationship of 0≦x≦1.0, particularly 0≦x≦0.2, and preferably has a relationship of 0≦x≦0.1 from the viewpoint of further improving adhesive strength, moisture resistance, and reactivity resistance, and is more preferably 0. y has a relationship of 0≦y≦1.0, and preferably has a relationship of 0≦y≦0.85 from the viewpoint of further improving adhesive strength, moisture resistance, and reactivity resistance. a is the average valence of A. The average valence of A is, for example, when A contains n1 elements X with a valence of a+, n2 elements Y with a valence of b+, and n3 elements Z with a valence of c+, the value is expressed as (n1×a+n2×b+n3×c) / (n1+n2+n3). b is the average valence of B. The average valence of B is the same as the average valence of A described above when, for example, B contains n1 elements X with a valence of a+, n2 elements Y with a valence of b+, and n3 elements Z with a valence of c+.

[0104] Specific examples of the LISICON-type solid electrolyte represented by the general formula (3) include Li ３．２ V ０．８ Si０．２ O ４ , Li ３．５ P ０．５ Si ０．５ O ４ Examples include:

[0105] 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.

[0106] The solid electrolyte having a perovskite crystal structure may have any chemical composition, for example, a chemical composition represented by the following general formula (3).

[0107] It is preferred that the average chemical composition be expressed as follows:

[0108] In formula (4), x preferably satisfies the relationship 0.09<x<0.167, and more preferably 0.10<x<0.12.

[0109] Specific examples of the perovskite-type solid electrolyte represented by the general formula (4) include Li ０．３５ La ０．５５ TiO ３, Li ０．５ La ０．５ TiO ３ Examples include:

[0110] 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.

[0111] 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.

[0112] From the viewpoint of suppressing battery deterioration over a long period of time, it is preferable that all layers constituting the battery element 1 are 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. It is not necessary that the two adjacent layers are strictly integrated, and only a portion of the layers may be unintegrated. It is sufficient that the two adjacent layers are integrated as a whole. For example, it is preferable that the positive electrode layer 1a, the solid electrolyte layer 1b, and the negative electrode layer 1a are sintered together in a predetermined stacking order.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] The positive electrode active material contained in the positive electrode layer is not particularly limited, and for example, at least one selected from the group consisting of a lithium-containing phosphate compound having a Nasicon structure, a lithium-containing phosphate compound having an olivine structure, a lithium-containing layered oxide, and a lithium-containing oxide having a spinel structure can be mentioned. An example of a lithium-containing phosphate compound having a Nasicon structure is Li ３ V ２ (P.O. ４ ) ３ Examples of lithium-containing phosphate compounds having an olivine structure include Li ３ Fe ２ (P.O. ４ ) ３ , LiMnPO ４ An example of a lithium-containing layered oxide is LiCoO ２ , LiCo １／３ Ni １／３ Mn １／３ O ２ An example of a lithium-containing oxide having a spinel structure is LiMn２ O ４ , LiNi ０．５ Mn １．５ O ４ etc.

[0117] The negative electrode active material contained in the negative electrode layer is not particularly limited, and examples thereof include oxides containing at least one element selected from the group consisting of Ti, Si, Sn, Cr, Fe, Nb, and Mo, graphite-lithium compounds, lithium alloys, lithium-containing phosphate compounds having a Nasicon structure, lithium-containing phosphate compounds having an olivine structure, and lithium-containing oxides having a spinel structure, β-Li ３ VO ４ Type structure, γ-Li ３ VO ４ An example of the lithium alloy is Li-Al. An example of the lithium-containing phosphate compound having a Nasicon structure is Li. ３ V ２ (P.O. ４ ) ３ Examples of lithium-containing phosphate compounds having an olivine structure include Li ３ Fe ２ (P.O. ４ ) ３ Examples of lithium-containing oxides having a spinel structure include Li ４ Ti ５ O １２ β-Li etc. ３ VO ４ As a negative electrode active material having a Li ３ VO ４ γ-Li etc. ３ VO ４ As oxides having the Li type structure, ３．２ V ０．８ Si ０．２ O ４ etc.

[0118] 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.

[0119] 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.

[0120] The positive electrode layer and the negative electrode layer may each independently contain a sintering aid. The sintering aid contained in the positive electrode layer and the negative electrode layer 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. In particular, in embodiments (1) to (3), the sintering aid contained in the positive electrode layer and the negative electrode layer may contain a bismuth-containing sintering aid. The bismuth-containing sintering aid may be selected from the same bismuth-containing sintering aid as the bismuth-containing sintering aid contained in the external electrode in embodiment (3) described above.

[0121] 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.

[0122] Solid Electrolyte Layer The solid electrolyte layer may contain a sintering aid. The sintering aid contained in the solid electrolyte layer may be selected, for example, from the same materials as the sintering aids that may be contained in the positive electrode layer and the negative electrode layer. In particular, in aspects (1) to (3), the sintering aid contained in the solid electrolyte layer may contain a bismuth-containing sintering aid. The bismuth-containing sintering aid may be selected from the same bismuth-containing sintering aids as the bismuth-containing sintering aid contained in the external electrodes in aspect (3) described above.

[0123] 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.

[0124] (External Electrode) The external electrode 3 is a member for extracting power (particularly current) generated in the battery element 1 to the outside. The external electrode 3 includes a positive external electrode and a negative external electrode, and may be in direct contact with the surface (particularly a part thereof) of the exterior part 2. In the above-described embodiment (1), when a Bi-containing layer is formed as a bonding layer on at least the region of the exterior part surface where the external electrode is formed, the external electrode 3 may be indirectly in contact with the surface (particularly a part thereof) of the exterior part 2 via the Bi-containing layer. In this case, the Bi-containing layer is in direct contact with the exterior part and the external electrode on one side and the other side, respectively. The external electrode 3 preferably has 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.

[0125] When the external electrode 3 has the form of a sintered body, it may be composed of, for example, 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 from, for example, materials similar to the electron-conductive materials that may be contained in the positive electrode layer and the negative electrode layer. From the viewpoint of further improving the bonding strength between the exterior and the external electrode, moisture resistance, and reactivity resistance, the electron-conductive material of the external electrode is preferably a metal material (particularly silver, copper, palladium, or an alloy thereof (particularly Ag-Pd)), more preferably silver. The sintering aid contained in the external electrode 3 may be selected from, for example, materials similar to the sintering aids that may be contained in the positive electrode layer and the negative electrode layer. In particular, in aspect (3), the sintering aid contained in the external electrode includes a bismuth-containing sintering aid. The bismuth-containing sintering aid contained in the external electrode in aspect (3) is the bismuth-containing sintering aid described above in the description of aspect (3). In aspects (1) and (2), the sintering aid contained in the external electrode may include a bismuth-containing sintering aid. In the embodiments (1) and (2), the bismuth-containing sintering aid contained in the external electrodes may be selected from the same bismuth-containing sintering aids as the bismuth-containing sintering aid contained in the external electrodes in the above-described embodiment (3).

[0126] In aspects (1) and (2), the electronically conductive material of the external electrode 3 preferably contains Ag (silver), and more preferably consists of Ag alone, from the viewpoints of further improving bonding strength and more sufficiently preventing reaction between the exterior portion (particularly oxide ceramics) and the external electrode. The electronically conductive material of the external electrode 3 consisting of Ag alone means that it does not contain any electronically conductive material other than Ag. In aspects (1) and (2), the content of electronically conductive material other than Ag in the electronically conductive material of the external electrode 3 is 2 vol% or less, and more preferably 0.5 vol% or less, relative to the total amount of the external electrode. In particular, from the viewpoint of further improving bonding strength, the external electrode 3 preferably contains a sintering aid. The content of the sintering aid in the external electrode 3 is 1 vol% or less, and more preferably 0.1 vol% or less, relative to the total amount of the external electrode, from the viewpoint of more sufficiently preventing reaction between the exterior portion (particularly oxide ceramics) and the external electrode.

[0127] In aspect (3), the external electrodes 3 contain the above-mentioned electron conductive material and a sintering aid (particularly bismuth-containing glass (e.g., B-Si-Bi-O glass)), and from the viewpoints of further improving bonding strength and more sufficiently preventing reaction between the exterior parts (e.g., oxide ceramics) and the external electrodes, preferably contain Ag (silver) and a sintering aid (particularly bismuth-containing glass (e.g., B-Si-Bi-O glass)). In aspect (3), the content of the sintering aid in the external electrodes 3 is usually 1% by volume or more relative to the total amount of the external electrodes, and from the viewpoints of further improving bonding strength and more sufficiently preventing reaction between the exterior parts (e.g., oxide ceramics) and the external electrodes, it is preferably 10% by volume or more, and more preferably 15% by volume or more.

[0128] The total content (volume %) of sintering aid in the external electrode 3 can be measured and calculated by the following method. A solid-state battery with an external electrode formed thereon was processed using a cross-section polisher (CP), and a ceramic structure image was obtained by SEM observation. EDX analysis was then performed, and the areas where Ag was detected were designated as the external electrode locations, and the areas where Bi or Si was detected were designated as the sintering aid locations. By calculating the area ratio of the above locations, it is possible to measure the area ratio of the sintering aid in the external electrode. The image processing software "A-zo-kun" was used to calculate the area ratio.

[0129] [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.

[0130] (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.

[0131] 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.

[0132] (Firing Step) The unfired laminate is subjected to firing, for example, by removing organic materials at 500°C in a nitrogen gas atmosphere containing oxygen gas, and then heating at 550°C or higher and 1300°C or lower.

[0133] The present invention as described above includes the following preferred embodiments. <1> A solid-state battery having a battery element, an exterior portion on the outer surface of the battery element, and an external electrode in contact with the exterior portion, wherein the exterior portion contains an oxide ceramic containing Li (lithium); Mg (magnesium); and one or more elements (M) selected from the group consisting of Group 4 and Group 5 elements, and Bi (bismuth) is present between the exterior portion and the external electrode. <2> The solid-state battery according to <1>, wherein the external electrode contains Ag (silver). <3> The solid-state battery according to <1> or <2>, wherein the external electrode is composed only of Ag. <4> The solid-state battery according to any one of <1> to <3>, wherein the oxide ceramic has a rock-salt crystal structure. <5> The solid-state battery according to any one of <1> to <4>, wherein the exterior portion has a layered structure. <6> The solid-state battery according to any one of <1> to <5>, wherein the exterior portion is in direct contact with the surface of the battery element. <7> The solid-state battery according to any one of <1> to <6>, wherein the battery element includes a garnet-type solid electrolyte. <8> The solid-state battery according to <7>, wherein the battery element includes 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 the solid electrolyte is contained in one or more layers selected from the positive electrode layer, the negative electrode layer, and the solid electrolyte layer. <9> The solid-state battery according to any one of <1> to <8>, wherein the Bi (bismuth) segregates between the exterior part and the external electrode. <10> The solid-state battery according to <9>, wherein the width of the portion where the Bi (bismuth) segregates is 1 to 100 nm.

[0134] 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.

[0135] Examples 1 to 4 and Comparative Examples 1 to 3 Example 1 includes Examples 1-1 to 1-3, and the chemical compositions and thicknesses of the Bi-containing layers are different from each other (see Table 4). Example 2 includes Examples 2-1 to 2-3, and the chemical compositions and thicknesses of the Bi-containing layers are different from each other (see Table 4). Example 3 includes Examples 3-1 to 3-3, and the chemical compositions and thicknesses of the Bi-containing layers are different from each other (see Table 4). Note that the chemical composition of the Bi-containing layer shown in Table 4 is not the chemical composition of the Bi-containing layer formed during the manufacturing process of the solid-state battery, but rather the chemical composition of the portion where Bi is segregated in TEM-EDX observation, as described below. Furthermore, the thickness of the Bi-containing layer shown in Table 4 is not the thickness of the Bi-containing layer formed during the manufacturing process of the solid-state battery, but rather the width of the portion where Bi is segregated in TEM-EDX observation, as described below.

[0136] [Production of exterior ceramics] The raw materials used were lithium carbonate Li2CO3, magnesium oxide MgO, titanium oxide TiO2, and manganese carbonate MnCO3. Each starting material was weighed to have the chemical composition shown in Table 1. Water was added, the material was sealed in a polyethylene pot, and the pot was rotated at 150 rpm on a pot rack for 16 hours to mix the raw materials. In addition, lithium carbonate Li2CO3, the Li source, was charged in an amount 12.5 wt% in excess of the target composition, taking into account Li deficiency during sintering. The obtained slurry was evaporated and dried, and then O ２ The target compound was obtained by calcining for 5 hours at 1030°C in a molten metal atmosphere. A toluene-acetone mixed solvent was added to the calcined powder obtained, and the mixture was pulverized for 12 hours in a planetary ball mill. ICP measurement confirmed that the pulverized powder had no compositional deviation. The average particle size of the pulverized powder was 150 nm.

[0137] [Production of exterior veneer] Exterior veneers were produced as evaluation samples for exterior ceramics using the following method. The resulting pulverized powder was kneaded with butyral resin, alcohol, and a binder to produce a slurry. The slurry was then formed into a sheet on a PET film using a doctor blade method. The produced sheets were stacked until the sheet thickness reached 200 μm, after which the binder was removed at 400°C and sintered at 1280°C for 120 minutes to produce exterior veneers. The porosity of the exterior veneer was 10% or less, confirming that sintering had progressed sufficiently.

[0138] Formation of the Bonding Layer (Bi-Containing Layer) In Examples 1 to 4, the bonding layer was formed using the following method. In Comparative Examples 1 to 3, no bonding layer was formed. Specifically, in Examples 1 to 4, a solution was prepared by dissolving metal raw materials selected from lithium nitrate LiNO3, magnesium ethoxide Mg(OC2H5)5, bismuth nitrate pentahydrate Bi(NO3)3·5H2O, and silicon tetraethoxide (Si(OC2H5)4), and ethyl acetoacetate in 2-methoxyethanol. The bonding layer composition was weighed to achieve the chemical composition described in each example below. Both sides of the WT side of the exterior veneer were dipped in this solution and then dried at 100°C. The bonding layer was then formed by heat treatment at 400°C. The bonding layers in Examples 1 to 4 are listed in Table 4. The WT side of the exterior material refers to the surface that includes the W and T directions of the exterior portion. In this example, it is the surface of the exterior veneer described above.

[0139] [Formation of Terminal Electrode (External Electrode)] In Examples 1 and 2 and Comparative Examples 1 and 2, the external electrodes were manufactured by the following method. A conductive paste made by kneading Ag powder, ethyl cellulose resin, and an organic solvent was applied to the exterior veneer. After application, the paste was dried in an oven at 150°C for 20 minutes to volatilize the solvent in the conductive paste, resulting in a dried film. After application and drying, the terminal electrode was baked at 750°C for 10 minutes to form a dense terminal electrode on the exterior veneer. In Examples 1 and 2, a bonding layer (Bi-containing layer) was interposed between the exterior veneer and the terminal electrode.

[0140] In Examples 3 and 4 and Comparative Example 3, external electrodes were manufactured using the following method. A conductive paste containing Ag powder, the glass powder listed in Table 4, an ethyl cellulose-based resin, and an organic solvent was applied to a veneer. After application, the paste was dried in an oven at 150°C for 20 minutes to volatilize the solvent in the conductive paste, resulting in a dried film. After application and drying, the terminal electrode was fired at 750°C for 10 minutes to form a dense terminal electrode on the veneer. In Examples 3 and 4, a bonding layer (Bi-containing layer) was interposed between the veneer and the terminal electrode. The glass powder content was 1% by volume or more, preferably 10% by volume or more, and more preferably 15% by volume or more, of the total amount of the fired terminal electrode.

[0141] [Adhesion Strength Test] A simulated adhesion strength test between the exterior and terminal electrodes was conducted using an exterior veneer bonded to the terminal electrode via the above-described bonding layer. Specifically, a NiCr layer was sputtered onto the terminal electrode surface of the exterior veneer, a NiCu layer was sputtered onto the NiCr layer, and an Ag layer was sputtered onto the NiCu layer. A Sn-Ag-Cu solder paste (M705-GRN360-K2-V) was applied to the surface of a substrate (FR-4), and a solid-state battery with sputtered layers (NiCr layer, NiCu layer, and Ag layer) was placed on top. The substrate on which the solid-state battery was placed was heated to thermally cure the solder paste. The exterior veneer with the terminal electrode formed in this manner was then mounted on the substrate. The adhesive strength of each sample prepared in this manner was measured using a DAGE-SERIES-5000PXY (P6J2) bond tester manufactured by DAGE Corporation. The exterior veneer adhered to the substrate surface was pressed with a shear tool in a direction parallel to the substrate surface (horizontal direction) at a speed of 100 μm / s, as shown in Figures 5A and 5B, and the strength (breaking strength) was measured when the bonded surface between the exterior veneer and the substrate broke. The height of the shear tool from the substrate surface was set to 0.15 mm. The adhesive strengths of the comparative examples and examples were measured at n10 and the average values ​​were used.

[0142] [TEM-EDX Observation] In the TEM-EDX analysis method described below, a cross section between the oxide ceramics constituting the exterior veneer and the material constituting the terminal electrode (external electrode) (particularly near the interface region between them) was milled by FIB ion milling and then observed by TEM-EDX (energy dispersive X-ray spectroscopy). In Examples 1 to 4, as shown in FIG. 4A , Bi atoms segregated intensively between the oxide ceramics 20 constituting the exterior veneer and the material 30 constituting the terminal electrode (external electrode) (particularly in the interface region between them), and were present in band-like or layer-like form in the interface region. In particular, in Example 4, Bi atoms were observed in the region of the material 30 constituting the terminal electrode (external electrode), but the Bi atoms also segregated intensively between the oxide ceramics 20 constituting the exterior veneer and the material 30 constituting the terminal electrode (external electrode) (particularly in the interface region between them), and were present in band-like or layer-like form in the interface region. The width of the area where Bi atoms segregate intensively was measured from the TEM-EDX mapping image, and this length is shown as the thickness of the Bi-containing layer in Table 4. The chemical composition of the area where Bi atoms segregate intensively can be determined from the TEM-EDX mapping image. In Comparative Examples 1 to 3, Bi atoms were not present in either the region of oxide ceramic 20 that constitutes the exterior veneer or the region of material 30 that constitutes the terminal electrode (external electrode), much less intensively segregated between these regions (particularly in or near the interface region between them), nor were they present in band-like or layer-like form in or near the interface region.

[0143] [TEM-EDX analysis] After processing the exterior veneer / terminal electrode interface into a thin slice using FIB treatment, the element distribution at the exterior veneer / terminal electrode interface was measured using TEM-EDX (energy dispersive X-ray spectroscopy). 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 100nm or less, EDX was performed at an acceleration voltage of 200kV, and Bi was detected when measured under conditions where the Mg Kα count was 550,000 or more in the 666nm field of view.

[0144] [Chemical Composition of Exterior Veneer] The exterior veneer was analyzed by ICP-AES to obtain the average chemical composition of the exterior veneer.

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

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

[0147]

[0148] Examples 1 to 3 correspond to the above-mentioned mode (1). Example 4 corresponds to the above-mentioned mode (5) (more specifically, a mode that combines mode (1) and mode (3)).

[0149] 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 the field of electronics packaging. The solid-state battery 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 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 installation-type power storage systems), medical applications (medical devices such as earphone hearing aids), pharmaceutical applications (dose management systems), as well as the IoT field, and space and deep-sea applications (for example, space probes, submersible research vessels, and the like).

[0150] 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 (external positive electrode and external negative electrode) 5: Interface region 20: Oxide ceramic 30: External electrode constituent material 50: Clear interface 51: Indistinct interface

Claims

1. A solid-state battery having a battery element, an exterior part present on the outer surface of the battery element, and an external electrode in contact with the exterior part, wherein the exterior part includes an oxide ceramic containing Li (lithium); Mg (magnesium); and one or more elements (M) selected from the group consisting of elements of groups 4 and 5, and Bi (bismuth) is present between the exterior part and the external electrode.

2. The solid-state battery of claim 1, wherein the external electrodes comprise Ag (silver).

3. The solid-state battery according to claim 1 or 2, wherein the external electrodes are made of Ag only.

4. The solid-state battery according to any one of claims 1 to 3, wherein the oxide ceramic has a rock-salt crystal structure.

5. The solid-state battery according to any one of claims 1 to 4, wherein the exterior portion has a layered form.

6. The solid-state battery according to any one of claims 1 to 5, wherein the exterior portion is in direct contact with the surface of the battery element.

7. The solid-state battery according to any one of claims 1 to 6, wherein the battery element contains a garnet-type solid electrolyte.

8. The solid-state battery according to claim 7, wherein the battery element comprises one or more battery constituent units including a positive electrode layer and a negative electrode layer facing each other and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, and the solid electrolyte is contained in one or more layers selected from the positive electrode layer, the negative electrode layer and the solid electrolyte layer.

9. The solid-state battery according to any one of claims 1 to 8, wherein the Bi (bismuth) is segregated between the exterior portion and the external electrode.

10. The solid-state battery according to claim 9, wherein the width of the portion where Bi (bismuth) is segregated is 1 to 100 nm.

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