Solid-state battery

Abstract

The present invention provides a solid-state battery which sufficiently suppresses an increase in interfacial resistance and a decrease in discharge capacity resulting from the use thereof in high-temperature environments. The solid battery includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer includes a positive-electrode active material having a lamellar rock salt structure and an oxide having a garnet structure, the positive-electrode active material containing magnesium (Mg) and / or aluminum (Al) and the oxide containing no Al (aluminum).

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. Sintered solid-state secondary batteries (so-called "solid-state batteries"), which use a solid electrolyte and also have other solid components, are being developed for such applications. Solid-state batteries are particularly expected to be used at high temperatures, which are difficult for liquid secondary batteries, which use a liquid electrolyte.

[0003] As a solid-state battery, for example, a lithium cobalt oxide (LCO) is used as a positive electrode active material and a garnet-type oxide (e.g., Li ７ La ３ Zr ２ O １２ Solid-state batteries having a positive electrode layer containing a combination of nitrile, nitrile-based polymers, and other polymers (so-called LLZ) have been reported (Patent Documents 1 and 2).

[0004] WO18 / 025649 JP 2021-174682 A

[0005] The inventors of the present invention have found that the following problem occurs in solid-state batteries using the above-described conventional positive electrode layer: When a high-temperature float test (e.g., 60°C) is performed, or when the solid-state battery is placed in a high-temperature environment, such as when the solid-state battery is always kept in a fully charged state, the interfacial resistance between the LCO and the garnet-type oxide increases significantly, and / or the discharge capacity decreases significantly.

[0006] An object of the present invention is to provide a solid-state battery that more sufficiently suppresses an increase in interface resistance and a decrease in discharge capacity in a high-temperature environment.

[0007] The present invention is based on the discovery, through careful investigation of the compositions of the LCO and garnet-type oxide in the positive electrode layer, that there is a composition that can significantly suppress the degradation of cell characteristics in a high-temperature environment.

[0008] The present invention relates to a solid-state battery comprising: a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; the positive electrode layer contains a positive electrode active material having a layered rock salt structure and an oxide having a garnet structure; the positive electrode active material contains at least one of Mg (magnesium) and Al (aluminum); and the oxide does not contain Al (aluminum).

[0009] The solid state battery of the present invention can more sufficiently suppress the decrease in discharge capacity in a high-temperature environment.

[0010] FIG. 1 is a schematic cross-sectional view showing one embodiment of the relationship between the cathode active material and the garnet-type oxide in the cathode layer of a solid-state battery according to the present invention. FIG. 2 is a graph illustrating the "arc size" used to calculate the interfacial resistance increase rate in the examples. FIG. 3A is a TEM photograph (left side) of a sample of Example 2, showing the vicinity of the interface between the cathode active material and the garnet-type oxide, and a TEM photograph (right side) showing Mg distribution mapping thereon. FIG. 3B shows the measurement results of Mg element measurement from the interface between the cathode active material and the garnet-type oxide toward the interior of the cathode active material in the TEM photograph on the left side of FIG. 3A. FIG. 4A is a TEM photograph (left side) of a sample of Example 4, showing the vicinity of the interface between the cathode active material and the garnet-type oxide, and a TEM photograph (right side) showing Al distribution mapping thereon. FIG. 4B shows the measurement results of Al element measurement from the interface between the cathode active material and the garnet-type oxide toward the interior of the cathode active material in the TEM photograph on the left side of FIG. 4A.

[0011] [Solid-State Battery] The present invention provides a solid-state battery. In the present specification, the term "solid-state battery" broadly refers to a battery whose components (particularly the electrolyte layer) are made of solids, and in the narrow sense refers to an "all-solid-state battery" whose components (particularly all components) are made of solids. In the present specification, the term "solid-state battery" encompasses so-called "secondary batteries" that can be repeatedly charged and discharged, and "primary batteries" that can only be discharged. The term "solid-state battery" is preferably a "secondary battery." The term "secondary battery" should not be overly limited by its name, and can also encompass electrochemical devices such as "power storage devices," for example.

[0012] The solid-state battery of the present invention includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer, and typically has a laminated structure in which a solid electrolyte layer is disposed between the positive electrode layer and the negative electrode layer. The positive electrode layer and the negative electrode layer may each be laminated in two or more layers, as long as a solid electrolyte layer is provided between them. The solid electrolyte layer is in contact with the positive electrode layer and the negative electrode layer and is sandwiched between them. The positive electrode layer and the solid electrolyte layer may be sintered together as a sintered body, and / or the negative electrode layer and the solid electrolyte layer may be sintered together as a sintered body. "Sintered together as a sintered body" means that two or more adjacent or contacting members (particularly layers) are joined by sintering. Here, the two or more members (particularly layers) may all be sintered bodies but sintered together as a sintered body. The solid-state battery of the present invention may be referred to as a "sintered solid-state battery" or a "co-sintered solid-state battery" in the sense that the positive electrode layer and the solid electrolyte layer are sintered together as sintered bodies, and the negative electrode layer and the solid electrolyte layer are sintered together as sintered bodies.

[0013] (Positive Electrode Layer) In the solid-state battery of the present invention, specifically, the positive electrode layer includes a positive electrode active material having a layered rock salt structure and containing at least one of Mg (magnesium) and Al (aluminum), and an oxide having a garnet-type crystal structure and not containing Al (aluminum). In the present invention, the positive electrode layer includes a combination of the specific positive electrode active material and the specific garnet-type oxide described above, which can more sufficiently suppress an increase in interfacial resistance between the positive electrode active material and the garnet-type oxide while more sufficiently suppressing a decrease in discharge capacity. The positive electrode layer may be in the form of a sintered body containing specific positive electrode active material particles and specific garnet-type oxide particles. The positive electrode layer may be a layer capable of occluding, desorbing, or inserting / desorbing ions (particularly lithium ions). The mediator ions in the positive electrode layer are not particularly limited as long as they are capable of charging and discharging, and examples thereof include lithium ions or sodium ions (particularly lithium ions).

[0014] First, the positive electrode active material and the garnet-type oxide contained in the positive electrode layer will be described in detail.

[0015] The positive electrode active material is a lithium transition metal composite oxide having a layered rock salt structure and containing at least one of Mg (magnesium) or Al (aluminum).For example, if the positive electrode layer contains a positive electrode active material having a layered rock salt structure and not containing both Mg (magnesium) and Al (aluminum) instead of this specific positive electrode active material, it cannot sufficiently suppress the increase in interfacial resistance and the decrease in discharge capacity.Also, for example, if the positive electrode layer contains a positive electrode active material having other crystalline structures (e.g., Nasicon structure, olivine structure, or spinel structure) instead of this specific positive electrode active material, even if the positive electrode active material contains at least one of Mg and Al, it cannot sufficiently suppress the increase in interfacial resistance and / or the decrease in discharge capacity.

[0016] The statement that a lithium transition metal composite oxide has a layered rock-salt structure means that the lithium transition metal composite oxide (particularly particles thereof) has a layered rock-salt crystal structure. In a broad sense, this means that the lithium transition metal composite oxide has a crystal structure that can be recognized as a layered rock-salt crystal structure by those skilled in the art of batteries. In a narrow sense, the statement that a positive electrode active material has a layered rock-salt structure means that the lithium transition metal composite oxide (particularly particles thereof) is identified as having a layered rock-salt crystal structure by analyzing its X-ray diffraction pattern using Rietveld analysis or the like. More specifically, the oxide may exhibit one or more main peaks corresponding to Miller indices specific to the so-called layered rock-salt crystal structure (diffraction pattern: ICDD Card No. 01-070-2685) at a predetermined angle of incidence in X-ray diffraction. The lithium transition metal composite oxide is a general term for oxides containing lithium and one or more transition metal elements (particularly Co (cobalt)) as constituent elements.

[0017] The positive electrode active material containing at least one of Mg (magnesium) and Al (aluminum) means that the lithium transition metal composite oxide as the positive electrode active material contains either Mg or Al, or both. The content of Mg and / or Al is not particularly limited as long as the effects of the present invention can be obtained. For example, when the positive electrode active material is represented by the general formula (R) described later, γ (particularly γ Ａｌ) may be a content such that the total concentration C of Mg and Al inside the particles of the positive electrode active material described later is within the range described later. Ｎ The content may be within the range described below.

[0018] The positive electrode active material (particularly, the lithium transition metal composite oxide) has, for example, a chemical composition represented by the following general formula (R).

[0019] In formula (R), M1 is one or more elements selected from the group consisting of Co (cobalt), Ni (nickel), and Mn (manganese). From the viewpoint of more fully suppressing an increase in interfacial resistance and a decrease in discharge capacity, it preferably contains Co, more preferably contains Co alone. M2 is one or more elements selected from the group consisting of Mg (magnesium) and Al (aluminum). From the viewpoint of more fully suppressing an increase in interfacial resistance and a decrease in discharge capacity, it preferably contains Al, more preferably contains both Mg and Al, and more preferably contains only both Mg and Al. M1 may contain other elements in addition to Mg and Al. Examples of such other elements include Ti (titanium).

[0020] In formula (R), α satisfies 0.8≦α≦1.5, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, preferably satisfies 0.8≦α≦1.2, more preferably satisfies 0.9≦α≦1.1, and even more preferably may be 1.0. β satisfies 0.8≦β≦1.2, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, preferably satisfies 0.8≦β≦1.1, more preferably satisfies 0.88≦β≦1.0, even more preferably satisfies 0.94≦β≦0.99, sufficiently preferably satisfies 0.94≦β≦0.985, and even more preferably satisfies 0.975≦β≦0.985. When M1 contains multiple elements, the sum of the values ​​corresponding to β for each of those elements may satisfy the above β range. For example, the value corresponding to β for Co is β Ｃｏ For example, the value corresponding to β for Ni is β Ｎｉ For example, the value corresponding to β for Mn is βＭｎ The ratio γ / β satisfies 0<γ / β≦0.2, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, preferably satisfies 0.005≦γ / β≦0.15, more preferably satisfies 0.008≦γ / β≦0.12, even more preferably satisfies 0.015≦γ / β≦0.07, and more preferably satisfies 0.015≦γ / β≦0.025. γ satisfies 0<γ≦0.24, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, preferably satisfies 0<γ≦0.2, more preferably satisfies 0<γ≦0.1, even more preferably satisfies 0.015≦γ≦0.06, and sufficiently preferably satisfies 0.015≦γ≦0.025. When M2 contains multiple elements, the sum of the values ​​corresponding to γ ​​for each of those elements may satisfy the above range of γ. For example, the value corresponding to γ ​​for Mg is γ Ｍｇ For example, the value corresponding to γ ​​for Al is γ Ａｌ It is expressed as γ Ａｌ is preferably 0.005≦γ from the viewpoint of more sufficiently suppressing an increase in interface resistance and a decrease in discharge capacity. Ａｌ ≦0.2, and more preferably 0.008≦γ Ａｌ ≦0.08, and more preferably 0.008≦γ Ａｌ γ≦0.015 Ｍｇ is preferably 0.005≦γ from the viewpoint of more sufficiently suppressing an increase in interface resistance and a decrease in discharge capacity. Ｍｇ ≦0.1, and more preferably 0.008≦γ Ｍｇ ≦0.08, and more preferably 0.008≦γ Ｍｇ ≦0.03. "β + γ" usually satisfies 0.8 ≦ β + γ ≦ 1.2, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, preferably satisfies 0.9 ≦ β + γ ≦ 1.1, and more preferably may be 1.0. ω satisfies 1.8 ≦ ω ≦ 2.2, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, preferably satisfies 1.9 ≦ ω ≦ 2.1, and more preferably may be 2.0.

[0021] Specifically, the lithium transition metal composite oxide used as the positive electrode active material is, for example, LiCo ０．９９ Mg ０．０１ O ２ , LiCo ０．９５ Mg ０．０５ O ２ , LiCo ０．９８ A ｌ０．０２ O ２ , LiCo ０．９５ Al ０．０５ O ２ , LiCo ０．９ Al ０．１ O ２ , LiCo ０．９８ Al ０．０１ Mg ０．０１ O ２ , LiCo ０．９７ Al ０．０１ Mg ０．０１ Ti ０．０１ O ２ etc. may also be used.

[0022] The chemical composition of the positive electrode active material may be an average chemical composition. The average chemical composition of the positive electrode active material means the average value of the chemical composition of the positive electrode active material in the thickness direction of the positive electrode layer. The average chemical composition of the positive electrode active material 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 (scanning electron microscope-EDX) in an arbitrary field of view that includes the entire thickness direction of the positive electrode layer. Therefore, the chemical composition of the positive electrode active material is the average chemical composition of the entire "interior of the particle" and "vicinity of the grain boundary".

[0023] As shown in FIG. 1 , the positive electrode active material has a concentration gradient of Mg (magnesium) and / or Al (aluminum) between a region 11 near the interface with the garnet-type oxide 2 and a particle interior 12. Specifically, the region 11 near the interface in the positive electrode active material 1 is a region (the region between the interface S and the dashed line in FIG. 1 ) where the distance from the interface S with the garnet-type oxide 2 toward the positive electrode active material 1 is 50 nm or less in cross-sectional view. The region 11 near the interface is usually located on the outer periphery of the positive electrode active material. The particle interior 12 is an inner region surrounded by the region near the interface 11 in cross-sectional view. FIG. 1 is a schematic cross-sectional view showing one embodiment of the relationship between the positive electrode active material and the garnet-type oxide in the positive electrode layer of a solid-state battery according to the present invention.

[0024] In the positive electrode active material, specifically, the concentration of at least one of Mg (magnesium) and Al (aluminum) in the particle interior 12 is higher than the concentration of the at least one of the two in the interface vicinity 11. More specifically, this is as follows. When the positive electrode active material contains only Mg of Mg and Al (hereinafter referred to as Case 1), the Mg concentration in the particle interior is higher than the Mg concentration in the interface vicinity. When the positive electrode active material contains only Al of Mg and Al (hereinafter referred to as Case 2), the Al concentration in the particle interior is higher than the Al concentration in the interface vicinity. When the positive electrode active material contains both Mg and Al (hereinafter referred to as Case 3), the total concentration of Mg and Al in the particle interior is higher than the total concentration of Mg and Al in the interface vicinity.

[0025] The total concentration C of Mg and Al in the particle interior 12 Ｎ In any of the above cases 1 to 3, from the viewpoint of more sufficiently suppressing an increase in the interface resistance and a decrease in the discharge capacity, the total concentration C of Mg and Al in the interface vicinity 11 is Ｋ The total concentration C Ｋ The total concentration C Ｎ Concentration ratio (C Ｋ / C Ｎ) is usually 0.01 or more and 0.90 or less, and from the viewpoint of more sufficiently suppressing an increase in interface resistance and a decrease in discharge capacity, it is preferably 0.1 or more and 0.8 or less, more preferably 0.15 or more and 0.60 or less, and even more preferably 0.30 or more and 0.60 or less.

[0026] Total concentration C Ｋ may usually be 0.1 atomic % or more and 2.0 atomic % or less, and from the viewpoint of more sufficiently suppressing an increase in interface resistance and a decrease in discharge capacity, is preferably 0.1 atomic % or more and 1.0 atomic % or less, more preferably 0.2 atomic % or more and 0.8 atomic % or less, even more preferably 0.5 atomic % or more and 0.7 atomic % or less, and sufficiently preferably 0.55 atomic % or more and 0.7 atomic % or less. Ｎ may usually be 0.8 atomic % or more and 5.0 atomic % or less, and from the viewpoint of more sufficiently suppressing an increase in interface resistance and a decrease in discharge capacity, is preferably 0.8 atomic % or more and 4.0 atomic % or less, more preferably 1.0 atomic % or more and 3.0 atomic % or less, and even more preferably 1.0 atomic % or more and 2.0 atomic % or less.

[0027] Total concentration C Ｋ is an average value of values ​​measured by point analysis of TEM-EDX (energy dispersive X-ray spectroscopy) at 30 arbitrary points in the interface vicinity 11. Ｎ is an average value of values ​​measured by point analysis of TEM-EDX at 30 arbitrary points inside the particle 12.

[0028] The content of the layered rock salt type positive electrode active material (particularly, the layered rock salt type lithium transition metal composite oxide) in the positive electrode layer is typically 20 vol% or more, particularly 20 vol% or more and 90 vol% or less, based on the total positive electrode layer. From the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, the content is preferably 40 vol% or more and 80 vol% or less, more preferably 45 vol% or more and 70 vol% or less, and particularly preferably 50 vol%. The positive electrode layer may contain two or more types of layered rock salt type positive electrode active materials, as long as their total content is within the above range. The two or more types of layered rock salt type positive electrode active materials are, for example, two or more types of layered rock salt type positive electrode active materials represented by the above general formula (R), which differ in the type of element M1 and / or M2 and / or differ in at least one of α, β, or γ.

[0029] The positive electrode layer may contain a positive electrode active material other than the layered rock salt type positive electrode active material (hereinafter also referred to as "other positive electrode active material"). The content of the positive electrode active material other than the layered rock salt type positive electrode active material is usually 10% by volume or less relative to the entire positive electrode layer, and from the viewpoint of more fully suppressing the increase in interface resistance and the decrease in discharge capacity, it is preferably 5% by volume or less, more preferably 0% by volume. Examples of other positive electrode active materials include lithium-containing phosphate compound particles having a Nasicon structure, lithium-containing phosphate compound particles having an olivine structure, lithium-containing layered oxide particles, and lithium-containing oxide particles having a spinel structure.

[0030] The positive electrode active material can be produced, for example, by the following method, or can be obtained as a commercially available product. When producing the positive electrode active material, first, raw material compounds containing predetermined metal atoms are weighed so as to have a predetermined chemical composition, and water is added and mixed to obtain a slurry. The slurry is then dried, calcined at 700°C to 1000°C for 1 hour to 30 hours, and pulverized to obtain the positive electrode active material.

[0031] The chemical composition and crystalline structure of the positive electrode active material in the positive electrode layer may typically change due to elemental diffusion during sintering. The positive electrode active material may have the above-described chemical composition and crystalline structure in the solid-state battery after sintering with the negative electrode layer and the solid electrolyte layer.

[0032] The average particle size of the positive electrode active material is not particularly limited and may be, for example, 100 nm or more and 10 μm or less, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, it is preferably 500 nm or more and 8 μm or less, more preferably 1 μm or more and 5 μm or less, and sufficiently preferably 1 μm or more and 3 μm or less. The average particle size of the positive electrode active material is usually larger than the average particle size of the garnet-type oxide described later.

[0033] The average particle size of the positive electrode active material can be determined, for example, by randomly selecting 10 to 100 particles from an SEM image and simply averaging their particle sizes to obtain the average particle size (arithmetic mean). The particle size is the diameter of a spherical particle assuming that the particles are perfectly spherical. Such particle size can be determined, for example, by cutting out a cross section of a solid-state battery, taking a cross-sectional SEM image using an SEM, calculating the cross-sectional area S of the particles using image analysis software (e.g., "A-zo-kun" (manufactured by Asahi Kasei Engineering Co., Ltd.)), and then calculating the particle diameter R using the following formula.

[0034]

[0035] The average particle size of the positive electrode active material in the positive electrode layer may be measured by specifying the positive electrode active material by its composition when measuring the chemical composition described above.

[0036] The average particle size of the positive electrode active material in the positive electrode layer may typically change due to sintering during the manufacturing process of the solid-state battery. The positive electrode active material may have the above-mentioned average particle size in the solid-state battery after sintering together with the negative electrode layer and the solid electrolyte layer.

[0037] A garnet-type oxide is an oxide (particularly a metal oxide) that has a garnet-type crystal structure and is substantially free of aluminum (Al). For example, if the positive electrode layer contains a garnet-type oxide containing Al instead of this specific garnet-type oxide, the increase in interfacial resistance and the decrease in discharge capacity cannot be sufficiently suppressed. Furthermore, if the positive electrode layer contains an oxide having a different crystal structure instead of this specific garnet-type oxide, even if the oxide does not contain Al, the increase in interfacial resistance and / or the decrease in discharge capacity cannot be sufficiently suppressed.

[0038] The expression "an oxide has a garnet-type crystal structure" does not simply mean that the oxide has a "garnet-type crystal structure," but also encompasses the oxide having a "garnet-like crystal structure." Specifically, the oxide 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 oxide may exhibit, in X-ray diffraction, one or more main peaks corresponding to Miller indices specific to a so-called garnet-type crystal structure (diffraction pattern: ICDD Card No. 01-080-6142) at a predetermined angle of incidence, or as a garnet-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 a so-called garnet-type crystal structure due to differences in composition. A typical diffraction pattern of a garnet-like crystal structure is, for example, ICDD Card No. 00-045-0109 and the like.

[0039] The garnet-type oxide being substantially free of Al means that it may contain Al to the extent that it does not impair the effects of the present invention, and means, for example, that the Al content in the garnet-type oxide is less than 0.08 (particularly less than 0.01) relative to the La content, which suppresses side reactions due to diffusion of Al from the garnet-type oxide to the positive electrode layer during firing.

[0040] The content ratio of Al to La in the garnet-type oxide is the average value of values ​​measured by point analysis with TEM-EDX at 30 arbitrary points. The content ratio of Al to La is a ratio based on a molar basis (i.e., a molar ratio).

[0041] The garnet-type oxide has, for example, a chemical composition represented by the following general formula (I).

[0042]

[0043] In formula (I), A represents one or more elements capable of forming a solid solution in the Li site of the garnet-type oxide. Specifically, A represents one or more elements selected from the group consisting of Mg (magnesium), Ga (gallium), Sc (scandium), and Fe (iron) (hereinafter sometimes referred to as "group a"), and does not include Al (aluminum). Ｉ is one or more elements selected from the group consisting of elements that can take a trivalent valence among elements belonging to Groups 1 to 3 that can take an octacoordinated state with oxygen. Ｉ Specifically, B is one or more elements selected from the group consisting of La (lanthanum), Y (yttrium), 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) (hereinafter, sometimes referred to as "group bI"). Ｉ Preferably, B contains La (lanthanum) from the viewpoint of more sufficiently suppressing an increase in interface resistance and a decrease in discharge capacity. Ｉ may contain La (lanthanum) alone. ＩＩ is one or more elements selected from the group consisting of elements belonging to Groups 1 to 3 that can be eight-coordinated with oxygen and can have a valence other than trivalent. ＩＩ For details, divalent B ＩＩ Ca (calcium), Sr (strontium) and Ba (barium) as well as tetravalent B ＩＩand Ce (cerium) as D (hereinafter, sometimes referred to as "Group bII"). Ｉ is one or more elements selected from the group consisting of transition elements that can be hexacoordinated with oxygen and elements that can be tetravalent among the typical elements belonging to groups 12 to 15. Ｉ Specifically, D is one or more elements selected from the group consisting of Zr (zirconium), Ti (titanium), Hf (hafnium), Ge (germanium), and Sn (tin) (hereinafter sometimes referred to as "group dI"). Ｉ Preferably, D contains Zr (zirconium) from the viewpoint of more sufficiently suppressing an increase in interface resistance and a decrease in discharge capacity. Ｉ may contain Zr (zirconium) alone. ＩＩ is one or more elements selected from the group consisting of transition elements that can be hexacoordinated with oxygen and elements that can have a valence other than tetravalent among the typical elements belonging to groups 12 to 15. ＩＩ Specifically, trivalent D ＩＩ Sc (Scandium) as pentavalent D ＩＩ Ta (tantalum), Nb (niobium), Sb (antimony) and Bi (bismuth) as ＩＩ D is one or more elements selected from the group consisting of Mo (molybdenum), W (tungsten), and Te (tellurium) (hereinafter sometimes referred to as "Group dII"). ＩＩ is preferably one or more elements selected from the group consisting of Bi (bismuth) and Ta (tantalum), more preferably contains Bi (bismuth), and even more preferably contains only Bi (bismuth) and Ta (tantalum), from the viewpoint of more sufficiently suppressing an increase in interface resistance and a decrease in discharge capacity.

[0044] In formula (I), p is expressed by calculation formula (i): p=ax-(3-b)y+(d-4)z (i).

[0045] In formula (i), a is the average valence of A. For example, when A contains n1 element X with a valence of r+, n2 element Y with a valence of s+, and n3 element Z with a valence of t+, the average valence of A is a value represented by the formula: (n1 x r + n2 x s + n3 x t) / (n1 + n2 + n3). b is B ＩＩ is the average valence of B. ＩＩ The average valence of B ＩＩ For example, when n1 element X with a valence of r+, n2 element Y with a valence of s+, and n3 element Z with a valence of t+ are found, d is a value expressed by the same formula as the average valence of A described above. ＩＩ is the average valence of ＩＩ The average valence of ＩＩ For example, when n1 element X having a valence of r+, n2 element Y having a valence of s+, and n3 element Z having a valence of t+ are found, the average valence of A is a value expressed by the same formula as the average valence of A described above.

[0046] In formula (I), α satisfies 5.0≦α≦8.0, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, preferably satisfies 5.5≦α≦7.5, more preferably 5.5≦α≦7.0, even more preferably 6.0≦α≦6.8, particularly preferably 6.2≦α≦6.8, and most preferably 6.2≦α≦6.6. β satisfies 2.5≦β≦3.5, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, preferably satisfies 2.6≦β≦3.4, more preferably 2.7≦β≦3.3, even more preferably 2.8≦β≦3.2, particularly preferably 2.9≦β≦3.1, and most preferably 3.0. γ satisfies 1.5≦γ≦2.5, and from the viewpoint of more fully suppressing an increase in interfacial resistance and a decrease in discharge capacity, preferably satisfies 1.6≦γ≦2.4, more preferably 1.7≦γ≦2.3, even more preferably 1.8≦γ≦2.2, particularly preferably 1.9≦γ≦2.1, and most preferably 2.0. ω satisfies 11≦ω≦13, and from the viewpoint of more fully suppressing an increase in interfacial resistance and a decrease in discharge capacity, preferably satisfies 11≦ω≦12.5, more preferably 11.5≦ω≦12.5, and even more preferably "12-δ". δ indicates the amount of oxygen vacancy and may be 0. δ usually satisfies 0≦δ<1. Since the amount of oxygen vacancy δ cannot be quantitatively analyzed even using the latest equipment, it may be considered to be 0. x satisfies 0≦x≦1.0, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, preferably satisfies 0≦x≦0.8, more preferably 0≦x≦0.6, even more preferably 0≦x≦0.4, particularly preferably 0≦x≦0.2, and most preferably 0. When A contains multiple elements, the sum of the values ​​corresponding to x for each of those elements should satisfy the above range of x. y satisfies 0≦y≦1.0, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, preferably satisfies 0≦y≦0.8, more preferably 0≦y≦0.6, even more preferably 0≦y≦0.4, particularly preferably 0≦y≦0.2, and most preferably 0. B ＩＩWhen a plurality of elements are contained, the sum of the values ​​corresponding to y for each of those elements should satisfy the above range of y. From the viewpoint of satisfying 0.4≦z≦2.2, and more preferably satisfying 0.4≦y≦1.5, more preferably 0.4≦z≦1.0, even more preferably 0.4≦z≦0.8, particularly preferably satisfying 0.5≦z≦0.7, and most preferably 0.6. D ＩＩ When a plurality of elements are included, the sum of the values ​​corresponding to z for each of these elements should satisfy the above range of z.

[0047] The chemical composition of the garnet-type oxide may be measured by quantitative analysis (composition analysis) using TEM-EDX (energy dispersive X-ray spectroscopy). The method for measuring the chemical composition of the garnet-type oxide is not particularly limited, but for example, TEM-EELS (transmission microscope-electron energy-loss spectroscopy) measurement may be performed.

[0048] From the viewpoint of more fully suppressing an increase in interfacial resistance and a decrease in discharge capacity, the garnet-type oxide preferably has a chemical composition represented by the following general formula (II): Specifically, from the viewpoint of more fully suppressing an increase in interfacial resistance and a decrease in discharge capacity, the garnet-type oxide preferably has a chemical composition represented by the following general formula (II): General formula (II) is one embodiment included in the above general formula (I).

[0049]

[0050] In formula (II), D ＩＩ is D in general formula (I). ＩＩ In formula (II), z is the same as z in general formula (I). In formula (II), ω is the same as ω in general formula (I). In formula (II), p is expressed as p = (d - 4) z. Note that d is the same as d in formula (i).

[0051] Specifically, the garnet-type oxide is, for example, Li ６．４ La ３ (Zr １．４ Ta０．４ Bi ０．２ ) O １２ etc. may also be used.

[0052] The average particle size of the garnet-type oxide is not particularly limited and may be, for example, 10 nm to 5 μm, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, it is preferably 50 nm to 1 μm, more preferably 100 nm to 800 nm, and particularly preferably 500 nm. The average particle size of the garnet-type oxide can be measured by the same method as that for the average particle size of the positive electrode active material described above.

[0053] The content of the garnet-type oxide is usually 10% by volume or more, particularly 20% by volume or more and 80% by volume or less, based on the entire positive electrode layer. From the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, it is preferably 30% by volume or more and 80% by volume or less, more preferably 30% by volume or more and 70% by volume or less, and particularly preferably 50% by volume. The positive electrode layer may contain two or more types of garnet-type oxides, in which case the total content thereof may be within the above range. The two or more types of garnet-type oxides refer to, for example, two or more types of garnet-type oxides represented by the above general formula (I) that contain different elements and / or differ in at least one of α, β, γ, x, y, z, or p.

[0054] Garnet-type oxides can be produced by the following method: Raw material compounds containing predetermined metal atoms are weighed out so as to have a predetermined chemical composition, and water is added and mixed to obtain a slurry. The slurry is then dried, calcined at 700°C to 1000°C for 1 hour to 30 hours, and pulverized to obtain a garnet-type oxide.

[0055] The positive electrode layer may contain a metal oxide other than a garnet-type oxide (for example, a so-called solid electrolyte) (hereinafter referred to as "other metal oxide"). In this case, the content of the other metal oxide is usually 10% by volume or less, based on the entire positive electrode layer, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, it is preferably 5% by volume or less, and more preferably 0% by volume.

[0056] The positive electrode layer may further contain a sintering aid and / or a conductive aid.

[0057] Any sintering aid known in the field of solid-state batteries can be used as the sintering aid. The composition of such a sintering aid preferably contains at least Li (lithium), B (boron), and O (oxygen), and the molar ratio of Li to B (Li / B) is preferably 2.0 or more. Specific examples of such sintering aids include, for example, Li ４ B ２ O ５ , Li ３ BO ３ , (Li ２．７ Al ０．３ ) BO ３ , Li ２．８ (B ０．８ C ０．２ ) O ３ , LiBO ２ Examples include:

[0058] The content of the sintering aid is not particularly limited, and is preferably, for example, 0.1% by volume to 20% by volume, and more preferably 1% by volume to 10% by volume, based on the entire positive electrode layer.

[0059] The conductive additive may be any conductive additive known in the field of solid-state batteries. Examples of preferred conductive additives include metal materials such as Ag (silver), Au (gold), Pd (palladium), Pt (platinum), Cu (copper), Sn (tin), and Ni (nickel); and carbon materials such as acetylene black, Ketjen black, Super P (registered trademark), and carbon nanotubes such as VGCF (registered trademark). The shape of the carbon material is not particularly limited, and any shape, such as spherical, plate-like, or fibrous, may be used.

[0060] The content of the conductive additive is not particularly limited, and is preferably, for example, 50% by volume or less (particularly, 0% by volume or more and 50% by volume or less) and more preferably 40% by volume or less (particularly, 0% by volume or more and 40% by volume or less) relative to the entire positive electrode layer.

[0061] The thickness of the positive electrode layer is usually 0.1 μm or more and 30 μm or less, for example, preferably 1 μm or more and 20 μm or less. The thickness of the positive electrode layer is the average value of thicknesses measured at any 10 points in the SEM image.

[0062] In the positive electrode layer, the porosity is not particularly limited, but is preferably 20% by volume or less, more preferably 15% by volume or less, and even more preferably 10% by volume or less.

[0063] The porosity of the positive electrode layer is a value measured from an SEM image after FIB cross-section processing.

[0064] The positive electrode layer is a layer that can be called a “positive electrode active material layer.” The positive electrode layer may have a so-called positive electrode current collector or positive electrode current collecting layer.

[0065] (Negative Electrode Layer) In the solid-state battery of the present invention, the negative electrode layer is not particularly limited. The negative electrode layer usually contains a negative electrode active material. The negative electrode layer may be a layer capable of absorbing and releasing ions (particularly lithium ions) or inserting and desorbing ions. The mediator ions in the negative electrode layer are not particularly limited as long as they are capable of charging and discharging, and examples thereof include lithium ions or sodium ions (particularly lithium ions).

[0066] The negative electrode active material is not particularly limited, and any negative electrode active material known in the field of solid-state batteries can be used. Examples of the negative electrode active material include carbon materials such as graphite, graphite-lithium compounds, lithium metal, lithium alloy particles, phosphate compounds having a Nasicon structure, Li-containing oxides having a spinel structure, β ＩＩ -Li ３ VO ４ Type structure, γ ＩＩ -Li ３ VO ４ The negative electrode active material is an oxide having a lithium metal, β ＩＩ -Li ３ VO ４ Type structure, γ ＩＩ -Li ３ VO ４ A Li-containing oxide having a type structure may also be used.

[0067] In the negative electrode layer, the oxide is β ＩＩ -Li ３ VO４ The term "having a β-type structure" means that the oxide (particularly its particles) has a β-type structure. ＩＩ -Li ３ VO ４ In a broad sense, it means that the solid-state battery has a β type crystal structure. ＩＩ -Li ３ VO ４ In a narrow sense, the oxide in the negative electrode layer has a β-type crystal structure. ＩＩ -Li ３ VO ４ The term "having a β-type structure" means that the oxide (particularly its particles) 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 predetermined angle of incidence. ＩＩ -Li ３ VO ４ The Li-containing oxide having the Li-type structure includes Li ３ VO ４ Examples include:

[0068] In the negative electrode layer, the oxide is γ ＩＩ -Li ３ VO ４ The term "having a γ-type structure" means that the oxide (particularly its particles) ＩＩ -Li ３ VO ４ 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 -Li ３ VO ４ In a narrow sense, the oxide in the negative electrode layer has a γ-type crystal structure. ＩＩ -Li ３ VO ４ The term "having a γ-type structure" means that the oxide (particularly its particles) 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 (x-axis). ＩＩ -Li ３VO ４ The Li-containing oxide having the Li-type structure includes Li ３．２ V ０．８ Si ０．２ O ４ Examples include:

[0069] The chemical composition of the negative electrode active material may be an average chemical composition. The average chemical composition of the negative electrode active material means an average value of the chemical composition of the negative electrode active material in the thickness direction of the negative electrode layer. The average chemical composition of the negative electrode active material 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 negative electrode layer in the thickness direction.

[0070] The negative electrode active material can be produced, for example, by the same method as that for the positive electrode active material, or can be obtained as a commercially available product.

[0071] The chemical composition and crystalline structure of the negative electrode active material in the negative electrode layer may typically change due to elemental diffusion during sintering in the manufacturing process of a solid-state battery. The negative electrode active material may have the above-described average chemical composition and crystalline structure in the solid-state battery after sintering together with the positive electrode layer and the solid electrolyte layer.

[0072] The content of the negative electrode active material in the negative electrode layer is not particularly limited, and is, for example, preferably 50% or more (particularly 50% to 99%), more preferably 70% to 95%, and even more preferably 80% to 90% of the total negative electrode layer.

[0073] The negative electrode layer may further contain a so-called solid electrolyte, a sintering aid and / or a conductive aid.

[0074] The solid electrolyte that may be contained in the negative electrode layer is not particularly limited, and examples thereof include the solid electrolytes exemplified as solid electrolytes that constitute the solid electrolyte layer described below.

[0075] When the negative electrode layer contains a solid electrolyte, the content of the solid electrolyte may generally be 20% by volume to 60% by volume, particularly 30% by volume to 45% by volume, based on the total volume of the negative electrode layer.

[0076] The sintering aid in the negative electrode layer may be the same compound as the sintering aid in the positive electrode layer.The conductive aid in the negative electrode layer may be the same compound as the conductive aid in the positive electrode layer.

[0077] The thickness of the negative electrode layer is usually 0.1 μm or more and 30 μm or less, and preferably 1 μm or more and 20 μm or less. The thickness of the negative electrode layer is the average value of thicknesses measured at any 10 points on the SEM image.

[0078] In the negative electrode layer, the porosity is not particularly limited, but is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less.

[0079] The porosity of the negative electrode layer is a value measured by the same method as that for the porosity of the positive electrode layer.

[0080] The negative electrode layer is a layer that can be called a “negative electrode active material layer.” The negative electrode layer may have a so-called negative electrode current collector or negative electrode current collecting layer.

[0081] (Solid Electrolyte Layer) In the solid battery of the present invention, the solid electrolyte layer contains a solid electrolyte.

[0082] The solid electrolyte contained in the solid electrolyte layer is not particularly limited, and may be any solid electrolyte contained in a solid electrolyte layer in the field of solid-state batteries. Such a solid electrolyte may be, for example, an oxide-based solid electrolyte, for example, a garnet-type oxide contained in a positive electrode layer, Li ２ ZrO ３ , γ-Li ３ VO ４ The solid electrolyte layer preferably contains one or more materials selected from the group consisting of a solid electrolyte having a structure and an oxide glass ceramic-based lithium ion conductor. From the viewpoint of more sufficiently suppressing an increase in interface resistance and a decrease in discharge capacity, the solid electrolyte layer preferably contains the garnet-type oxide contained in the positive electrode layer.

[0083] γ-Li ３ VO ４ Examples of the solid electrolyte having the structure include a solid electrolyte having an average chemical composition represented by the following general formula (III).

[0084]

[0085] In formula (III), A is one or more elements selected from the group consisting of Na, K, Mg, Ca, Al, Ga, Zn, Fe, Cr, and Co. B is one or more elements selected from the group consisting of V and P. D is one or more elements selected from the group consisting of Zn, Al, Ga, Si, Ge, Sn, As, Ti, Mo, W, Fe, Cr, and Co. x satisfies 0≦x≦1.0, particularly 0≦x≦0.2. y satisfies 0≦y≦1.0, particularly 0.20≦y≦0.50. a is the average valence of A. The average valence of A is, for example, when n1 element X with a valence of a+, n2 element Y with a valence of b+, and n3 element Z with a valence of c+ are recognized as A, the value represented by (n1 x a + n2 x b + n3 x c) / (n1 + n2 + n3). c is the average valence of D. 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 D, the average valence of D is the same value as the average valence of A described above.

[0086] γ-Li ３ VO ４ Specific examples of solid electrolytes having the structure include Li ３．２ (V ０．８ Si ０．２ ) O ４ , Li ３．５ (V ０．５ Ge ０．５ ) O ４ , Li ３．４ (P ０．６ Si0.4)O ４ , Li ３．５ (P ０．５ Ge ０．５ ) O ４ etc.

[0087] Examples of oxide glass ceramic lithium ion conductors that can be used include a phosphate compound containing lithium, aluminum, and titanium as constituent elements (LATP) and a phosphate compound containing lithium, aluminum, and germanium as constituent elements (LAGP).

[0088] The content of the solid electrolyte in the solid electrolyte layer is not particularly limited, and is, for example, preferably 10% by volume or more and 100% by volume or less, more preferably 20% by volume or more and 100% by volume or less, and even more preferably 30% by volume or more and 100% by volume or less, relative to the entire solid electrolyte layer.

[0089] The solid electrolyte layer may further contain, in addition to the solid electrolyte, for example, a sintering aid etc. As the sintering aid in the solid electrolyte layer, the same compounds as the sintering aid in the positive electrode layer can be used.

[0090] The content of the sintering aid in the solid electrolyte layer is not particularly limited, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, it is preferably 0 vol% or more and 20 vol% or less, and more preferably 1 vol% or more and 10 vol% or less.

[0091] The thickness of the solid electrolyte layer is usually 0.1 μm or more and 30 μm or less, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, preferably 1 μm or more and 20 μm or less. The thickness of the solid electrolyte layer is the average value of thicknesses measured at arbitrary 10 points on an SEM image.

[0092] In the solid electrolyte layer, the porosity is not particularly limited, and from the viewpoint of more sufficiently suppressing an increase in interfacial resistance and a decrease in discharge capacity, it is preferably 20 vol % or less, more preferably 15 vol % or less, and even more preferably 10 vol % or less.

[0093] The porosity of the solid electrolyte layer is a value measured by the same method as for the porosity of the positive electrode layer.

[0094] [Method for Manufacturing Solid-State Battery] A solid-state battery can be manufactured by, for example, the so-called green sheet method, the printing method, or a combination of these methods.

[0095] The green sheet method will be described. First, a paste is prepared by appropriately mixing a garnet-type oxide, a solvent, a binder, etc. with a positive electrode active material. The paste is applied to a sheet and dried to form a first green sheet for forming a positive electrode layer. The first green sheet may also contain other so-called solid electrolytes, conductive additives, and / or sintering additives.

[0096] A paste is prepared by appropriately mixing a solvent, a binder, and the like with the negative electrode active material. The paste is applied to a sheet and dried to form a second green sheet for forming the negative electrode layer. The second green sheet may contain a so-called solid electrolyte, a conductive additive, and / or a sintering additive.

[0097] A paste is prepared by appropriately mixing a solvent, a binder, etc. with the solid electrolyte. The paste is applied and dried to prepare a third green sheet for forming the solid electrolyte layer. The third green sheet may contain a sintering aid, etc.

[0098] The solvent for producing the first to third green sheets is not particularly limited, and any solvent that can be used in the production of a positive electrode layer, a negative electrode layer, or a solid electrolyte layer in the field of solid-state batteries can be used. A solvent that can be used with the binder described below is typically used. Examples of such solvents include alcohols such as 2-propanol.

[0099] The binder for producing the first to third green sheets is not particularly limited, and any binder that can be used in the production of a positive electrode layer, a negative electrode layer, or a solid electrolyte layer in the field of solid-state batteries, such as butyral resin and acrylic resin, can be used.

[0100] Next, the first to third green sheets are appropriately stacked to form a laminate. The laminate may be pressed. A preferred pressing method is hydrostatic pressing. The laminate is then sintered at a temperature of, for example, 600°C to 800°C to obtain a solid-state battery.

[0101] The printing method will now be explained. The printing method is the same as the green sheet method, except for the following points: - Prepare ink for each layer, which has the same composition as the paste for each layer used to obtain the green sheet, except that the blending amounts of solvent and resin are appropriate for use as ink. - Print and laminate using the ink for each layer to create a laminate.

[0102] 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.

[0103] The present invention as described above includes the following preferred embodiments. <1> A solid-state battery comprising: a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer contains a positive electrode active material having a layered rock salt structure and an oxide having a garnet structure, the positive electrode active material containing at least one of Mg (magnesium) and Al (aluminum), and the oxide does not contain Al (aluminum). <2> The solid-state battery according to <1>, wherein the oxide contains La, and the Al content in the oxide relative to the La content (Al / La) is less than 0.08. <3> The solid-state battery according to <1> or <2>, wherein the positive electrode active material has a chemical composition represented by the following general formula (R): [In formula (R), M1 is one or more elements selected from the group consisting of Co (cobalt), Ni (nickel), and Mn (manganese); M2 includes one or more elements selected from the group consisting of Mg (magnesium) and Al (aluminum); α satisfies 0.8≦α≦1.5; β satisfies 0.8≦β≦1.2; γ / β satisfies 0<γ / β≦0.2; and ω satisfies 1.8≦ω≦2.2]. <4> M2 includes Al, and a value γ corresponding to γ ​​related to Al is Ａｌ is 0.008≦γ Ａｌ<3> The solid state battery according to <3>, wherein M2 satisfies the condition of ≦0.08. <5> The solid state battery according to <4>, wherein M2 contains only both Mg and Al. <6> The solid state battery according to any one of <1> to <5>, wherein the positive electrode active material has a portion near the interface with the oxide and an interior of a particle thereof, and wherein the concentration of at least one of Mg (magnesium) and Al (aluminum) in the interior of the particle is higher than the concentration of the at least one of the Mg (magnesium) and Al (aluminum) in the portion near the interface with the oxide. <7> The positive electrode active material has a portion near the interface with the oxide and an interior of the particle thereof, and wherein the total concentration C of Mg (magnesium) and Al (aluminum) in the interior of the particle is Ｎ is the total concentration C of Mg (magnesium) and Al (aluminum) in the vicinity of the interface. Ｋ <8> The solid-state battery according to any one of <1> to <5>, wherein the total concentration C Ｋ The total concentration C Ｎ Concentration ratio (C Ｋ / C Ｎ <9> The solid-state battery according to <7>, wherein the total concentration C Ｋ is 0.1 atomic % or more and 2.0 atomic % or less, and the total concentration C Ｎ <10> The solid-state battery according to any one of <1> to <9>, wherein the oxide has a chemical composition represented by the following general formula (I): [In formula (I), A represents one or more elements capable of forming a solid solution in the Li site of the oxide having a garnet-type crystal structure, and does not include Al (aluminum); B Ｉ is one or more elements selected from the group consisting of elements that can take a trivalent valence among elements belonging to Groups 1 to 3 that can take an eight-coordination with oxygen; B ＩＩ is one or more elements selected from the group consisting of elements belonging to Groups 1 to 3 that can be eight-coordinated with oxygen and can have a valence other than trivalent; D Ｉis one or more elements selected from the group consisting of transition elements capable of forming hexacoordinate bonds with oxygen and elements capable of forming a tetravalent valence among the typical elements belonging to groups 12 to 15; D ＩＩ is one or more elements selected from the group consisting of transition elements capable of hexacoordination with oxygen and elements capable of taking a valence other than tetravalent among typical elements belonging to groups 12 to 15; α satisfies 5.0≦α≦8.0; β satisfies 2.5≦β≦3.5; γ satisfies 1.5≦γ≦2.5; ω satisfies 11≦ω≦13; x satisfies 0≦x≦1.0; y satisfies 0≦y≦1.0; z satisfies 0.4≦z≦2.2; and p is calculated by the following formula: p=ax−(3−b)y+(d−4)z (wherein a is the average valence of A; b is the average valence of B). ＩＩ is the average valence of D ＩＩ <11> D ＩＩ The solid-state battery according to <10>, wherein the positive electrode layer and the negative electrode layer are layers capable of absorbing and releasing lithium ions or inserting and detaching lithium ions. <12> The solid-state battery according to any one of <1> to <11>, wherein the solid electrolyte layer is formed by sintering the positive electrode layer and the negative electrode layer together to form an integral sintered body.

[0104] [Production of positive electrode active material] LiCoO ２ (Positive electrode active material used in Comparative Example 1) LiCoO ２ The synthesis of cobalt oxide Co ３ O ４ and lithium carbonate Li ２ CO ３ Cobalt oxide and lithium carbonate were weighed out in a stoichiometric composition, and then placed in a PE bottle together with 1 mm diameter zirconia beads and pure water. The bottle was then rotated at 200 rpm in a pot mill for 16 hours to mix. The beads were then removed, the mixture was dried, and the mixture was crushed in a mortar. The crushed material was placed in a crucible and fired in a firing furnace at 800°C in an air atmosphere for 20 hours. The fired material thus obtained was crushed in a mortar to obtain LiCoO. ２ obtained.

[0105] ・LiCo ０．９５ Mg ０．０５ O ２ (Positive electrode active material used in Example 2) LiCo ０．９５ Mg ０．０５ O ２ The synthesis of cobalt oxide Co ３ O ４ , lithium carbonate Li ２ CO ３ The stoichiometric composition of LiCo was weighed out, and the mixture was placed in a PE bottle together with 1 mm diameter zirconia beads and pure water. The mixture was mixed by rotating it at 200 rpm in a pot mill for 16 hours. The beads were then removed, the mixture was dried, and the mixture was crushed in a mortar. The crushed material was placed in a crucible and fired in a firing furnace at 800°C in an air atmosphere for 20 hours. The fired material obtained was crushed in a mortar to obtain LiCo. ０．９５ Mg ０．０５ O ２ (Powder) was obtained. The average particle size was 3 μm. XRD measurement of the powder confirmed that a single phase with a layered rock salt structure (ICDD card No. 01-070-2685) was obtained. ICP measurement confirmed that the powder had no composition deviation.

[0106] Positive electrode active materials other than those with the above chemical composition (positive electrode active materials used in Examples 1, 3 to 7 and Comparative Examples 2 to 4): Cobalt oxide Co ３ O ４ , lithium carbonate Li ２ CO ３ , magnesium oxide MgO, aluminum oxide Al ２ O ３ , titanium oxide TiO ２ , iron oxide Fe ２ O ３ , silicon dioxide SiO ２ was used in the desired stoichiometric composition. ０．９５ Mg ０．０５ O ２The positive electrode active materials were manufactured by the same method as in Example 1. The average particle size of each positive electrode active material was 3 μm. XRD measurement confirmed that a single phase with a layered rock salt structure (ICDD card No. 01-070-2685) was obtained for each positive electrode active material. ICP measurement confirmed that the powder had no compositional deviation.

[0107] [Production of Garnet-Type Oxide] The raw material is lithium hydroxide monohydrate (LiOH.H ２ O, lanthanum hydroxide La(OH) ３ , zirconium oxide ZrO ２ , tantalum oxide Ta ２ O ５ , bismuth oxide Bi ２ O ３ , aluminum oxide Al ２ O ３ Each raw material was weighed to have the chemical composition shown in Table 1, water was added, and the raw materials were sealed in a 100 ml polyethylene pot. The pot was rotated on a pot rack at 150 rpm for 16 hours to mix the raw materials. In addition, lithium hydroxide monohydrate (LiOH.H), which is a Li source, ２ Taking into account Li deficiency during sintering, O was charged in an amount 3 wt% in excess of the target composition. The resulting slurry was evaporated and dried, and then calcined at 900°C for 5 hours to obtain the target phase. A toluene-acetone mixed solvent was added to the resulting calcined powder, and it was pulverized in a planetary ball mill for 6 hours. This pulverized powder was dried to obtain garnet-type oxide powder. XRD measurement of the above powder confirmed that a simple garnet-type oxide had been obtained. ICP measurement confirmed that the above powder had no compositional deviation. The average particle size was 150 nm. In each example, the primary particle size of the material was not changed, and the structure and composition were controlled by the molar ratio of the raw materials and the sintering time.

[0108] [Production of sintering aid] Lithium hydroxide monohydrate (LiOH·H2O), boron oxide (B) ２ O ３ The starting materials were used. The chemical composition of the sintering aid was Li ４ B ２ O ５The mixture was thoroughly mixed in a mortar and then calcined at 650° C. for 5 hours.

[0109] Example 1 (Production of a Positive Electrode Half Cell) First, a garnet-type oxide, a positive electrode active material powder, and a sintering aid powder were weighed out in a volume ratio of 49:50:1, respectively, and kneaded with alcohol and a binder to prepare a positive electrode layer slurry. The slurry was then applied to a sheet and dried to form a first green sheet for forming the positive electrode layer. A solid electrolyte layer slurry was also prepared by kneading the same garnet-type oxide as that contained in the first green sheet with alcohol and a binder, and the resulting slurry was dried to form a second green sheet for forming the solid electrolyte layer. A laminate was produced by appropriately stacking the first and second green sheets. The produced laminate was pressurized by isostatic pressing and appropriately cut to obtain a positive electrode layer / solid electrolyte layer laminate. After removing the binder at 400°C, a co-fired positive electrode layer / solid electrolyte layer body was produced by pressure sintering at 800°C for 60 minutes under a pressure of 100 MPa. After sintering, the thickness of the positive electrode layer was 15 μm, and the thickness of the solid electrolyte layer was about 200 μm. Then, metallic Li was attached to the surface of the solid electrolyte layer opposite to the positive electrode layer as a counter electrode and reference electrode, and the resultant was sealed in a 2032-type coin cell to obtain a solid-state battery.

[0110] Examples 2 to 7 and Comparative Examples 1 to 6 Positive electrode half-cells were produced in the same manner as in Example 1, except that the garnet-type oxides and positive electrode active materials shown in Table 1 were used in combination.

[0111] [Interfacial Resistance Increase Rate] Evaluation was performed based on the value (increase rate) obtained by normalizing the arc size around 1 kHz in a fully charged state at room temperature after a float test at 60°C (described later) by the arc size around 1 kHz in a fully charged state at room temperature before the float test. Specifically, the rate of change in the interfacial resistance between the positive electrode active material and the solid electrolyte (the size of the arc around 1 kHz in the "Cole-Cole plot") was confirmed. The arc around 1 kHz was identified from a Bode diagram (absolute value of resistance vs. frequency, angle (θ) with the real axis of the "Cole-Cole plot" vs. frequency), and was taken as the difference between the saddle points of the arc in the real axis direction of the "Cole-Cole plot." (See Figure 2) ⊚: Increase rate ≦ 5% (best); ⊚: 5% < increase rate ≦ 10% (excellent); ○: 10% < increase rate ≦ 20% (good); △: 20% < increase rate ≦ 30% (passable) (no practical problem); ×: 30% < increase rate (unacceptable) (problems in practical use).

[0112] [Capacity Retention Rate] The capacity retention rate was evaluated based on a normalized value (retention rate) obtained by dividing the discharge capacity at room temperature after a float test at 60°C (described later) by the discharge capacity at room temperature before the float test. ⊚: 80%≦retention rate (best); ⊚: 75%≦retention rate<80% (excellent); ◯: 65%≦retention rate<75% (good); Δ: 60%≦retention rate<65% (passive) (no practical problems); ×: retention rate<60% (unacceptable) (problems in practical use).

[0113] [Overall evaluation] An overall evaluation was made based on the evaluation results of the interface resistance increase rate and capacity retention rate. ⊚◎: All evaluation results were ⊚◎. ⊚: Of all evaluation results, the lowest evaluation result was ⊚. ○: Of all evaluation results, the lowest evaluation result was ○. △: Of all evaluation results, the lowest evaluation result was △. ×: Of all evaluation results, the lowest evaluation result was ×.

[0114] [Float Test] The battery was charged to 4.2 V at a constant current of 0.1 C, and after reaching 4.2 V, it was charged at a constant voltage until the current decreased to 0.01 C. After charging was completed, the battery was placed in an open circuit state and waited for 3 hours. Then, AC impedance measurements were performed at a voltage amplitude of 10 mV in a frequency range of 0.1 Hz to 7 MHz, and a Cole-Cole plot was obtained. The AC impedance conditions were from a frequency band of 1 MHz or higher to a frequency band of 0.1 Hz or lower, and the voltage amplitude was approximately 10 mV. After measuring the AC impedance, the battery was discharged to 3 V at a constant current of 0.1 C. Thereafter, a constant current charge of 0.1 C was performed in a thermostatic chamber at 60 ° C. After reaching 4.2 V, constant voltage charging was performed for one week, and float charging was performed. After one week of float charging, a constant current discharge of 0.1 C was performed at 60 ° C., and discharge was completed at 3 V. The cell was removed from the 60°C thermostatic chamber and the battery characteristics after float charging were confirmed at room temperature under the same conditions as the initial charge / discharge characteristics. The cell was charged to 4.2 V at a constant current of 0.1 C, and after reaching 4.2 V, it was charged at a constant voltage until the current decreased to 0.01 C. After charging, the cell was placed in an open circuit state and allowed to stand for 3 hours before measuring the AC impedance. After measuring the AC impedance, the cell was discharged to 3 V at a constant current of 0.1 C.

[0115] [Confirmation of Element Distribution] The co-fired cathode layer / solid electrolyte layer laminate (prior to the attachment of metallic Li) was embedded in resin and exfoliated to prepare a TEM observation sample. EDX (energy dispersive X-ray spectroscopy) was used to perform composition analysis and element distribution mapping near the LCO-LLZ interface. FIG. 3A shows a TEM photograph (left side) of the sample of Example 2 near the LCO-LLZ interface, along with a TEM photograph (right side) showing Mg distribution mapping. FIG. 3B shows the measurement results of Mg elemental analysis from the LCO-LLZ interface toward the interior of the LCO in the TEM photograph on the left side of FIG. 3A. FIG. 4A shows a TEM photograph (left side) of the sample of Example 4 near the LCO-LLZ interface, along with a TEM photograph (right side) showing Al distribution mapping. FIG. 4B shows the measurement results of Al elemental analysis from the LCO-LLZ interface toward the interior of the LCO in the TEM photograph on the left side of FIG. 4A.

[0116] [Garnet-Type Crystal Structure] The garnet-type crystal structure was confirmed by X-ray diffraction (XRD measurement) by obtaining an X-ray diffraction image that could be assigned to a garnet-type-like crystal structure (ICDD Card No. 00-045-0109).

[0117] [Layered Rock Salt Crystal Structure] The layered rock salt crystal structure was confirmed by X-ray diffraction (XRD measurement) by obtaining an X-ray diffraction image that can be assigned to a layered rock salt crystal structure (ICDD Card No. 01-070-2685).

[0118] [Chemical Composition] In the "Confirmation of Element Distribution" step, the chemical composition was measured by EDX composition analysis using TEM-EDX (energy dispersive X-ray spectroscopy).

[0119] <Measurement of Mg and Al Concentrations in the Interface Vicinity and Particle Interior of the Positive Electrode Active Material> The positive electrode layer was cut in two arbitrary directions by FIB processing, and attention was focused on five arbitrary positive electrode active material particles in each of the cross sections (TEM cross-sectional view) (a total of 10 positive electrode active material particles). Next, for each positive electrode active material particle 1, the chemical composition was determined by TEM-EDX point analysis at 10 arbitrary points in the interface vicinity 11 with the adjacent garnet-type oxide 2, and the concentrations of Mg and Al were obtained. Furthermore, for each positive electrode active material particle 1, the chemical composition was determined by TEM-EDX point analysis at 10 arbitrary points in the particle interior 12 located inside the interface vicinity 11 with the adjacent garnet-type oxide 2, and the concentrations of Mg and Al were obtained.

[0120] <Measurement of Al Content in Garnet-Type Oxide> Garnet-type oxides were cut in two arbitrary directions by FIB processing, and the chemical composition was determined by TEM-EDX point analysis at 30 arbitrary points on each of the cross sections (TEM cross-sectional view), and the concentrations of Al and La were measured to obtain the ratio of Al to La.

[0121]

[0122] When a high-temperature float test (60°C) was performed using a conventional LCO from Comparative Example 1, a significant increase in interfacial resistance and a decrease in capacity retention were confirmed. Examples 1 to 7 demonstrated that the inclusion of Al and / or Mg in the LCO significantly suppressed the increase in interfacial resistance and the decrease in capacity retention. However, Comparative Examples 2, 3, and 5 demonstrated that the inclusion of Fe, Si, or Ti in the LCO actually resulted in a decrease in characteristics. In other words, only specific elements were found to be effective in improving the characteristics of the LCO, and these elements were Al and / or Mg. A comparison of Comparative Examples 1 and 4 demonstrated that the inclusion of Al in the LLZ deteriorated the above-described characteristics. A comparison of Comparative Example 6 and Example 4 demonstrated that even if Al was included in the LCO, the effects of the present invention could not be achieved if Al was included in the LLZ. From the above, to fully achieve the effects of the present invention, it is necessary that Al is not included in the LLZ and that Al and / or Mg are included in the LCO.

[0123] A solid-state battery including the solid electrolyte ceramic of the present invention can be used in various fields where battery use or power storage is expected. By way of example only, a solid-state battery according to an embodiment of the present invention can be used in the field of electronics packaging. The solid-state battery according to one embodiment of the present invention can also be used in the fields of electricity, information, and communications where mobile devices and the like are used (for example, the fields of electrical and electronic equipment 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, or the field of mobile devices), household and small industrial applications (for example, the fields of power tools, golf carts, and household, nursing care, and industrial robots), large industrial applications (for example, the fields of forklifts, elevators, and port cranes), transportation systems (for example, the fields of hybrid cars, electric cars, buses, trains, electrically assisted bicycles, and electric motorcycles), power system applications (for example, the fields of various power generation, road conditioners, smart grids, and general household installation-type power storage systems), medical applications (for example, the fields of medical devices such as earphone hearing aids), pharmaceutical applications (for example, the fields of medication management systems), as well as the IoT field, and space and deep-sea applications (for example, the fields of space probes and submersible research vessels).

[0124] 1: Positive electrode active material 11: Portion of positive electrode active material near the interface with the garnet-type oxide 12: Internal region of positive electrode active material (inside particle) 2: Garnet-type oxide S: Interface with the garnet-type oxide in the positive electrode active material

Claims

1. a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer; Equipped with the positive electrode layer contains a positive electrode active material having a layered rock salt structure and an oxide having a garnet structure, the positive electrode active material contains at least one of Mg (magnesium) and Al (aluminum), A solid-state battery, wherein the oxide does not substantially contain Al (aluminum).

2. The oxide contains La, The solid-state battery according to claim 1 , wherein the content of Al relative to the content of La in the oxide is less than 0.

08.

3. The solid state battery according to claim 1, wherein the positive electrode active material has a chemical composition represented by the following general formula (R): 【Chemical 1】 [In formula (R), M1 is one or more elements selected from the group consisting of Co (cobalt), Ni (nickel), and Mn (manganese); M2 includes one or more elements selected from the group consisting of Mg (magnesium) and Al (aluminum); α satisfies 0.8≦α≦1.5; β satisfies 0.8≦β≦1.2; γ / β satisfies 0<γ / β≦0.2; ω satisfies 1.8≦ω≦2.2].

4. M2 contains Al, The value γ corresponding to γ ​​for Al Ａｌ is 0.008≦γ Ａｌ 4. The solid-state battery according to claim 3, wherein the solid-state battery satisfies the following:

5. The solid-state battery according to claim 4 , wherein M2 contains only both Mg and Al.

6. the positive electrode active material has a portion near the interface with the oxide and an interior of the particle thereof, 2. The solid-state battery according to claim 1, wherein a concentration of at least one of Mg (magnesium) and Al (aluminum) inside the particle is higher than a concentration of the at least one in the vicinity of the interface.

7. the positive electrode active material has a portion near the interface with the oxide and an interior of the particle thereof, The total concentration C of Mg (magnesium) and Al (aluminum) inside the particle Ｎ is the total concentration C of Mg (magnesium) and Al (aluminum) in the vicinity of the interface. Ｋ The solid-state battery of claim 1 , wherein

8. The total concentration C Ｋ The total concentration C Ｎ Concentration ratio (C Ｋ / C Ｎ 8. The solid-state battery according to claim 7, wherein σ is 0.01 or more and 0.90 or less.

9. The total concentration C Ｋ is 0.1 atomic % or more and 2.0 atomic % or less, The total concentration C Ｎ The solid-state battery according to claim 7 , wherein the content of the Cr is 0.8 atomic % or more and 5.0 atomic % or less.

10. 2. The solid-state battery according to claim 1, wherein the oxide has a chemical composition represented by the following general formula (I): 【Chemistry 2】 [In formula (I), A represents one or more elements capable of forming a solid solution in the Li site of the oxide having a garnet-type crystal structure, and does not include Al (aluminum); B Ｉ is one or more elements selected from the group consisting of elements that can take a trivalent valence and belong to Groups 1 to 3 and can take an eight-coordination with oxygen; B ＩＩ is one or more elements selected from the group consisting of elements belonging to Groups 1 to 3 that can be eight-coordinated with oxygen and can have a valence other than trivalent; D Ｉ is one or more elements selected from the group consisting of transition elements capable of forming hexacoordinate bonds with oxygen and elements capable of forming a tetravalent valence among the typical elements belonging to Groups 12 to 15; D ＩＩ is one or more elements selected from the group consisting of transition elements capable of forming a hexacoordinate with oxygen and elements capable of forming a valence other than tetravalent among the typical elements belonging to Groups 12 to 15; α satisfies 5.0≦α≦8.0; β satisfies 2.5≦β≦3.5; γ satisfies 1.5≦γ≦2.5; ω satisfies 11≦ω≦13; x satisfies 0≦x≦1.0; y satisfies 0≦y≦1.0; z satisfies 0.4≦z≦2.2; p is calculated using the following formula: p=ax-(3-b)y+(d-4)z (wherein a is the average valence of A; b is the average valence of B ＩＩ is the average valence of D ＩＩ is the average valence of the

11. D ＩＩ The solid-state battery according to claim 10 , wherein includes Bi (bismuth).

12. 12. The solid state battery according to claim 1, wherein the positive electrode layer and the negative electrode layer are layers capable of absorbing and releasing or inserting and desorbing lithium ions.

13. 12. The solid state battery according to claim 1, wherein the solid electrolyte layer is integrally sintered with the positive electrode layer and the negative electrode layer.

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