solid-state batteries

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

[Technical Field]

[0001] This invention relates to a solid-state battery. [Background technology]

[0002] In recent years, the demand for batteries has expanded significantly as power sources for portable electronic devices such as mobile phones and portable personal computers. For these applications, development is progressing on sintered solid-state rechargeable batteries (so-called "solid batteries"), which use a solid electrolyte and other solid components. Solid batteries are particularly expected to be used at high temperatures, which are difficult to achieve with liquid-electrolyte rechargeable batteries.

[0003] As a solid-state battery, for example, lithium cobalt oxide (LCO) is used as the positive electrode active material and garnet-type oxide (e.g., Li7La3Zr2O) is used as the solid electrolyte. 12 Solid-state batteries having a positive electrode layer containing a combination of so-called LLZs such as the above have been reported (Patent Documents 1, 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] WO18 / 025649 [Patent Document 2] Japanese Patent Publication No. 2021-174682 [Overview of the Initiative] [Problems that the invention aims to solve]

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

[0006] The present invention aims to provide a solid-state battery that more effectively suppresses the increase in interfacial resistance and the decrease in discharge capacity under high-temperature conditions. [Means for solving the problem]

[0007] This invention is based on the discovery, through diligent investigation of the compositions of LCO and garnet-type oxides in the positive electrode layer, that there is a composition that can significantly suppress the degradation of cell characteristics under high-temperature conditions.

[0008] The present invention 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 comprises a positive electrode active material having a layered rock salt type structure and an oxide having a garnet type structure. The positive electrode active material contains at least one of Mg (magnesium) or Al (aluminum), The aforementioned oxide does not contain Al (aluminum), solid battery Regarding. [Effects of the Invention]

[0009] The solid-state battery of the present invention can more effectively suppress the decrease in discharge capacity under high-temperature conditions. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 shows a schematic cross-sectional view illustrating one embodiment of the relationship between the positive electrode active material and the garnet-type oxide in the positive electrode layer of the solid-state battery according to the present invention. [Figure 2] Figure 2 is a graph illustrating the "arc size" used to calculate the interfacial resistance increase rate in the example. [Figure 3A] Figure 3A shows a TEM image (left) of the vicinity of the interface between the positive electrode active material and the garnet-type oxide for the sample of Example 2, and a TEM image (right) showing its Mg distribution mapping. [Figure 3B] Figure 3B shows the measurement results when the Mg element was measured from the interface between the positive electrode active material and the garnet-type oxide toward the interior of the positive electrode active material, as seen in the left-hand TEM image of Figure 3A. [Figure 4A] Figure 4A shows a TEM image (left) of the vicinity of the interface between the positive electrode active material and the garnet-type oxide for the sample of Example 4, and a TEM image (right) showing its Al distribution mapping. [Figure 4B] Figure 4B shows the measurement results when the Al element was measured from the interface between the positive electrode active material and the garnet-type oxide toward the interior of the positive electrode active material, as seen in the left-hand TEM image of Figure 4A. [Modes for carrying out the invention]

[0011] [Solid battery] The present invention provides a solid-state battery. In this specification, "solid-state battery" broadly refers to a battery whose components (especially the electrolyte layer) are made of solids, and narrowly refers to an "all-solid-state battery" whose components (especially all components) are made of solids. In this specification, "solid-state battery" includes so-called "secondary batteries" that can be repeatedly charged and discharged, and "primary batteries" that can only be discharged. The "solid-state battery" is preferably a "secondary battery." The term "secondary battery" is not overly restrictive and may also include electrochemical devices such as "energy storage devices."

[0012] The solid-state battery of the present invention comprises a positive electrode layer, a negative electrode layer, and a solid electrolyte layer, and typically has a laminated structure in which the 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 and sandwiched between the positive electrode layer and the negative electrode layer. The positive electrode layer and the solid electrolyte layer may be integrally sintered as sintered bodies, and / or the negative electrode layer and the solid electrolyte layer may be integrally sintered as sintered bodies. Integral sintering of sintered bodies means that two or more adjacent or contacting members (especially layers) are joined by sintering. Here, the two or more members (especially layers) may all be sintered bodies, but may be integrally sintered. The solid-state battery of the present invention can be called 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 integrally sintered as sintered bodies, and the negative electrode layer and the solid electrolyte layer are integrally sintered as sintered bodies.

[0013] (Positive electrode layer) In the solid-state battery of the present invention, more specifically, the positive electrode layer comprises a positive electrode active material having a layered rock salt structure and containing at least one of Mg (magnesium) or Al (aluminum), and an oxide having a garnet-type crystal structure and not containing Al (aluminum). In the present invention, by comprising the above-mentioned specific positive electrode active material and a specific garnet-type oxide in combination in the positive electrode layer, the decrease in discharge capacity can be suppressed more effectively while more effectively suppressing the increase in interfacial resistance between the positive electrode active material and the garnet-type oxide. The positive electrode layer may have 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 intercalating and deintercalating ions (particularly lithium ions). The mediating ions of the positive electrode layer are not particularly limited as long as they can be charged and discharged, and examples include lithium ions or sodium ions (particularly lithium ions).

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

[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 but not containing both Mg (magnesium) and Al (aluminum) instead of such a specific positive electrode active material, the increase in interfacial resistance and the decrease in discharge capacity cannot be sufficiently suppressed. Also, for example, if the positive electrode layer contains a positive electrode active material having a different crystal structure (e.g., a Nasicone-type structure, an olivine-type structure, or a spinel-type structure) instead of such a specific positive electrode active material, even if the positive electrode active material contains at least one of Mg or Al, the increase in interfacial resistance and / or the decrease in discharge capacity cannot be sufficiently suppressed.

[0016] The statement that a lithium transition metal composite oxide has a layered rock salt structure means that the lithium transition metal composite oxide (especially its particles) has a layered rock salt crystal structure. In a broad sense, it means that it has a crystal structure that can be recognized as a layered rock salt crystal structure by a person skilled in the field 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 (especially its particles) is identified as having a layered rock salt crystal structure by analyzing the X-ray diffraction pattern using Rietveld analysis or the like. More specifically, the oxide may, in X-ray diffraction, show one or more major 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 given angle of incidence. Lithium transition metal composite oxides are a general term for oxides that contain lithium and one or more transition metal elements (especially Co (cobalt)) as constituent elements.

[0017] The statement that the positive electrode active material contains at least one of Mg (magnesium) or Al (aluminum) means that the lithium transition metal composite oxide used 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 are obtained. For example, when the positive electrode active material is represented by the general formula (R) described later, γ (especially γ) Al The content may be such that it is within the range described below, or the total concentration of Mg and Al inside the particles of the positive electrode active material described below C N The content may be within the range described below.

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

[0019] In formula (R), M1 is one or more elements selected from the group consisting of Co (cobalt), Ni (nickel), and Mn (manganese), and preferably contains Co, and more preferably contains Co alone, from the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity. M2 comprises one or more elements selected from the group consisting of Mg (magnesium) and Al (aluminum), and preferably contains Al, more preferably contains both Mg and Al, and more preferably contains only both Mg and Al, from the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity. M1 may contain elements other than 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 the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 0.8 ≤ α ≤ 1.2, more preferably 0.9 ≤ α ≤ 1.1, and even more preferably 1.0. β satisfies 0.8 ≤ β ≤ 1.2, and preferably satisfies 0.8 ≤ β ≤ 1.1, more preferably satisfies 0.88 ≤ β ≤ 1.0, still more preferably satisfies 0.94 ≤ β ≤ 0.99, most preferably satisfies 0.94 ≤ β ≤ 0.985, and even more preferably satisfies 0.975 ≤ β ≤ 0.985, from the viewpoint of more sufficiently suppressing the increase in interface resistance and the decrease in discharge capacity. When M1 contains a plurality of elements, the sum of the values corresponding to β for each of those elements only needs to satisfy the above range of β. For example, the value corresponding to β for Co is represented as β Co and so on. Also, for example, the value corresponding to β for Ni is represented as β Ni and so on. Also, for example, the value corresponding to β for Mn is represented as β Mn and so on. γ / β satisfies 0 < γ / β ≤ 0.2, and preferably satisfies 0.005 ≤ γ / β ≤ 0.15, more preferably satisfies 0.008 ≤ γ / β ≤ 0.12, still more preferably satisfies 0.015 ≤ γ / β ≤ 0.07, and more preferably satisfies 0.015 ≤ γ / β ≤ 0.025, from the viewpoint of more sufficiently suppressing the increase in interface resistance and the decrease in discharge capacity. γ satisfies 0 < γ ≤ 0.24, and preferably satisfies 0 < γ ≤ 0.2, more preferably satisfies 0 < γ ≤ 0.1, still more preferably satisfies 0.015 ≤ γ ≤ 0.06, and most preferably satisfies 0.015 ≤ γ ≤ 0.025, from the viewpoint of more sufficiently suppressing the increase in interface resistance and the decrease in discharge capacity. When M2 contains a plurality of elements, the sum of the values corresponding to γ for each of those elements only needs to satisfy the above range of γ. For example, the value corresponding to γ for Mg is represented as γ Mg and so on. Also, for example, the value corresponding to γ for Al is represented as γ Al and so on. γ Al preferably satisfies 0.005 ≤ γ Al ≤ 0.2, more preferably satisfies 0.008 ≤ γ Al ≤ 0.08, still more preferably satisfies 0.008 ≤ γ Al ≤ 0.015, from the viewpoint of more sufficiently suppressing the increase in interface resistance and the decrease in discharge capacity. γ Mg preferably satisfies 0.005 ≤ γMg Satisfying ≤0.1, and more preferably 0.008 ≤ γ Mg Satisfying ≤0.08, and more preferably 0.008 ≤ γ Mg It satisfies ≤ 0.03. "β+γ" usually satisfies 0.8 ≤ β+γ ≤ 1.2, and from the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it 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 the increase in interfacial resistance and the decrease in discharge capacity, it preferably satisfies 1.9 ≤ ω ≤ 2.1, and more preferably may be 2.0.

[0021] Specifically, lithium transition metal composite oxides used as positive electrode active materials include, for example, LiCo 0.99 Mg 0.01 O2, LiCo 0.95 Mg 0.05 O2, LiCo 0.98 A l0.02 O2, LiCo 0.95 Al 0.05 O2, LiCo 0.9 Al 0.1 O2, LiCo 0.98 Al 0.01 Mg 0.01 O2, LiCo 0.97 Al 0.01 Mg 0.01 Ti 0.01 O2, etc.

[0022] The chemical composition of the positive electrode active material may be its average chemical composition. The average chemical composition of the positive electrode active material refers to 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 fracturing the solid-state battery and performing compositional analysis by EDX (energy-dispersive X-ray spectroscopy) in any field of view that encompasses 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 "inside of the particle" and "near the grain boundary".

[0023] The positive electrode active material has a concentration gradient of Mg (magnesium) and / or Al (aluminum) between the interface vicinity 11 with the garnet-type oxide 2 and the interior of the particle 12, as shown in Figure 1, for example. The interface vicinity 11 in the positive electrode active material is, more specifically, the region in cross-sectional view where the distance from the interface S with the garnet-type oxide 2 in the positive electrode active material 1 (i.e., the distance from the interface S toward the positive electrode active material 1) is 50 nm or less (the region between the interface S and the dashed line in Figure 1). The interface vicinity 11 is usually located on the outer edge of the positive electrode active material. The interior of the particle 12 is the inner region surrounded by the interface vicinity 11 in cross-sectional view. Figure 1 shows a schematic cross-sectional view illustrating 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, more specifically, the concentration of at least one of Mg (magnesium) or Al (aluminum) in the interior 12 of the particle is greater than the concentration of the at least one in the vicinity 11 of the interface. More specifically, it is as follows. When the positive electrode active material contains only Mg among Mg and Al (hereinafter referred to as Case 1), the concentration of Mg inside the particles is greater than the concentration of Mg near the interface. When the positive electrode active material contains only Al among Mg and Al (hereinafter referred to as Case 2), the concentration of Al inside the particles is greater than the concentration of Al near the interface. When the positive electrode active material contains both Mg and Al (hereinafter referred to as Case 3), the total concentration of Mg and Al inside the particle is greater than the total concentration of Mg and Al near the interface.

[0025] Total concentration of Mg and Al inside particle 12 C N In all of the above cases 1 to 3, from the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, the total concentration of Mg and Al in the vicinity of the interface 11 is C K It is larger than that. Total concentration C K Total of C N The concentration ratio (C) K / CN The interfacial resistance is usually between 0.01 and 0.90, and from the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably between 0.1 and 0.8, more preferably between 0.15 and 0.60, and even more preferably between 0.30 and 0.60.

[0026] Total concentration C K The amount of the atom is usually 0.1 atomic% to 2.0 atomic%, and from the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 0.1 atomic% to 1.0 atomic%, more preferably 0.2 atomic% to 0.8 atomic%, even more preferably 0.5 atomic% to 0.7 atomic%, and very preferably 0.55 atomic% to 0.7 atomic%. Total concentration C N The amount of the substrate is usually between 0.8 atomic% and 5.0 atomic%, and from the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably between 0.8 atomic% and 4.0 atomic%, more preferably between 1.0 atomic% and 3.0 atomic%, and even more preferably between 1.0 atomic% and 2.0 atomic%.

[0027] Total concentration C K This uses the average value obtained by point analysis using TEM-EDX (energy-dispersive X-ray spectroscopy) at any 30 points in the vicinity of the interface 11. Total concentration C N This uses the average value of measurements taken by TEM-EDX point analysis at any 30 points within the particle interior 12.

[0028] The content of layered rock salt type positive electrode active material (especially layered rock salt type lithium transition metal composite oxide) in the positive electrode layer is usually 20% by volume or more, particularly 20% by volume or more and 90% by volume or less, relative to the total positive electrode layer. From the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 40% by volume or more and 80% by volume or less, more preferably 45% 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 layered rock salt type positive electrode active material, in which case their total content should be within the above range. Two or more types of layered rock salt type positive electrode active material refer to, for example, two or more layered rock salt type positive electrode active materials represented by the above general formula (R) in which the types of elements of M1 and / or M2 are different, and / or in which at least one of α, β or γ is different.

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

[0030] The positive electrode active material can be manufactured, for example, by the following method, or it can be obtained as a commercially available product. When manufacturing the positive electrode active material, first, a raw material compound containing a predetermined metal atom is weighed so that its chemical composition is predetermined, and water is added and mixed to obtain a slurry. Then, the slurry is dried, calcined at 700°C to 1000°C for 1 to 30 hours, and pulverized to obtain the positive electrode active material.

[0031] The chemical composition and crystal structure of the positive electrode active material in the positive electrode layer may normally change due to elemental diffusion during sintering. The positive electrode active material may have the above-described chemical composition and crystal structure in a solid-state battery after sintering together 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 to 10 μm. From the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 500 nm to 8 μm, more preferably 1 μm to 5 μm, and very preferably 1 μm to 3 μm. 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 defined as the diameter of a spherical particle assuming it is perfectly spherical. Such a particle size can be determined, for example, by cutting a cross-section of a solid-state battery, taking a cross-sectional SEM image using a scanning electron microscope (SEM), calculating the particle's cross-sectional area S using image analysis software (e.g., "A-Image-kun" (manufactured by Asahi Kasei Engineering Co., Ltd.)), and then determining the particle diameter R using the following formula.

[0034]

number

[0035] Furthermore, the average particle size of the positive electrode active material in the positive electrode layer may be determined by identifying the positive electrode active material based on its composition during the measurement of the chemical composition described above.

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

[0037] Garnet-type oxides are oxides (especially metal oxides) that have a garnet-type crystal structure and do not substantially contain Al (aluminum). For example, if the positive electrode layer contains an Al-containing garnet-type oxide instead of such a specific garnet-type oxide, it is not possible to sufficiently suppress the increase in interfacial resistance and the decrease in discharge capacity. Also, for example, if the positive electrode layer contains an oxide with a different crystal structure instead of such a specific garnet-type oxide, it is not possible to sufficiently suppress the increase in interfacial resistance and / or the decrease in discharge capacity, even if the oxide does not contain Al.

[0038] The statement that an oxide has a garnet-type crystal structure means not only that the oxide has a "garnet-type crystal structure," but also that it has a "garnet-like crystal structure." More specifically, the oxide has a crystal structure that can be recognized as a garnet-type or garnet-like crystal structure by a person skilled in the field of solid-state batteries in X-ray diffraction. More specifically, the oxide may, in X-ray diffraction, show one or more major peaks corresponding to the Miller indices unique to a so-called garnet-type crystal structure (diffraction pattern: ICDD Card No. 01-080-6142) at a predetermined incident angle, or, as a garnet-like crystal structure, may show one or more major peaks that differ from the one or more major peaks corresponding to the Miller indices unique to a so-called garnet-type crystal structure in terms of incident angle (i.e., peak position or diffraction angle) and intensity ratio (i.e., peak intensity or diffraction intensity ratio) due to differences in composition. A typical diffraction pattern of a garnet-like crystal structure is, for example, ICDD Card No. 00-045-0109.

[0039] The statement that a garnet-type oxide is substantially free of Al means that it may contain Al to an extent that does not hinder the performance of the effects of the present invention. For example, it means that the Al content is less than 0.08 (particularly less than 0.01) relative to the La content in the garnet-type oxide. This suppresses side reactions caused by the diffusion of Al from the garnet-type oxide to the cathode layer during firing.

[0040] The Al-to-La content ratio in garnet-type oxides is calculated using the average value obtained by TEM-EDX point analysis at 30 arbitrary points. Note that the Al-to-La content ratio is based on a molar basis (i.e., a molar ratio).

[0041] Garnet-type oxides have a chemical composition represented by the following general formula (I), for example.

[0042] [ka]

[0043] In formula (I), A is one or more elements that can be dissolved in the Li site of a garnet-type oxide. Specifically, A is 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). B I B is one or more elements selected from the group consisting of elements belonging to Groups 1 to 3 that can form an 8-coordinate with oxygen and can have a valency of 3. I More specifically, it 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 (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium) (hereinafter sometimes referred to as "group bI"). I From the viewpoint of more effectively suppressing the increase in interfacial resistance and the decrease in discharge capacity, it preferably contains La (lanthanum). I It may also include La (lantern) on its own. B IIB is one or more elements selected from the group consisting of elements belonging to Groups 1 to 3 that can coordinate with oxygen in an 8-degree configuration and can have a valency other than 3. II For more details, see divalent B II Ca (calcium), Sr (strontium), and Ba (barium) as tetravalent B II It is one or more elements selected from the group consisting of Ce (cerium) as such (hereinafter sometimes referred to as "group bII"). D I D is one or more elements selected from the group consisting of transition elements that can coordinate with oxygen to 6 and main group elements belonging to groups 12 to 15 that can have a valency of 4. I More specifically, it 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 From the viewpoint of more effectively suppressing the increase in interfacial resistance and the decrease in discharge capacity, it preferably contains Zr (zirconium). I It may contain Zr (zirconium) alone. D II D is one or more elements selected from the group consisting of transition elements that can coordinate with oxygen to 6 and main group elements belonging to groups 12 to 15 that can have valencies other than 4. II For more details, see trivalent D II Sc (scandium) as a pentavalent D II As such, Ta (tantalum), Nb (niobium), Sb (antimony), and Bi (bismuth), as well as hexavalent D II It 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"). IIFrom the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably one or more elements selected from the group consisting of Bi (bismuth) and Ta (tantalum), more preferably containing Bi (bismuth), and even more preferably containing only Bi (bismuth) and Ta (tantalum).

[0044] In equation (I), p is calculated using equation (i): p = ax - (3 - b)y + (d - 4)z (i) It is represented as follows.

[0045] In equation (i), a is the average valence of A. The average valence of A is the value expressed by the equation: (n1 × r + n2 × s + n3 × t) / (n1 + n2 + n3) when A consists of, for example, n1 elements of element X with valence r+, n2 elements of element Y with valence s+, and n3 elements of element Z with valence t+. b is B II This is the average value of B. II The average price is B II For example, if there are n1 elements of element X with valence r+, n2 elements of element Y with valence s+, and n3 elements of element Z with valence t+, then this value is expressed by the same formula as the average valence of A described above. d is D II The average value of; D II The average price is D II For example, if there are n1 elements of element X with valence r+, n2 elements of element Y with valence s+, and n3 elements of element Z with valence t+, then this value is expressed by the same formula as the average valence of A described above.

[0046] In equation (I), α satisfies 5.0 ≤ α ≤ 8.0, and from the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it 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 the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 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 sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it 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 sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 11 ≤ ω ≤ 12.5, more preferably 11.5 ≤ ω ≤ 12.5, and even more preferably "12-δ". δ represents the oxygen deficiency and may be 0. Usually, it is sufficient that δ satisfies 0 ≤ δ < 1. Since the oxygen deficiency δ cannot be quantitatively analyzed even with the latest equipment, it may be considered to be 0. x satisfies 0 ≤ x ≤ 1.0, and more 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, from the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity. If 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 the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 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. II If the expression contains multiple elements, the sum of the values ​​corresponding to y for each of those elements must satisfy the above range of y. z satisfies 0.4 ≤ z ≤ 2.2, and from the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 0.4 ≤ y ≤ 1.5, more preferably 0.4 ≤ z ≤ 1.0, even more preferably 0.4 ≤ z ≤ 0.8, particularly preferably 0.5 ≤ z ≤ 0.7, and most preferably 0.6. II If the expression contains multiple elements, the sum of the values ​​corresponding to z for each of those elements must satisfy the above range of z.

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

[0048] Garnet-type oxides are preferably given a chemical composition represented by the following general formula (II) from the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity. Specifically, garnet-type oxides are preferably given a chemical composition represented by the following general formula (II) from the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity. Note that general formula (II) is one embodiment included in the above general formula (I).

[0049] [ka]

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

[0051] Specifically, garnet-type oxides include, for example, Li 6.4 La3(Zr 1.4 Ta 0.4 Bi 0.2 )O 12 You can also use these.

[0052] The average particle size of the garnet-type oxide is not particularly limited and may be, for example, 10 nm to 5 μm. From the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the 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 the average particle size of the positive electrode active material described above.

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

[0054] Garnet-type oxides can be produced by the following method: A raw material compound containing a predetermined metal atom is weighed to achieve 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 to 30 hours, and pulverized to obtain a garnet-type oxide.

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

[0056] The positive electrode layer may further contain sintering aids and / or conductive additives, etc.

[0057] Any sintering aid known in the field of solid-state batteries can be used. The composition of such a sintering aid preferably includes at least Li (lithium), B (boron), and O (oxygen), with a molar ratio of Li to B (Li / B) of 2.0 or higher. Specific examples of such sintering aids include, for example, Li4B2O5, Li3BO3, (Li 2.7 Al 0.3 )BO3, Li 2.8 (B 0.8 C 0.2 Examples include O3 and LiBO2.

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

[0059] Conductive additives that are known in the field of solid-state batteries can be used. Preferred conductive additives include, for example, metallic materials such as Ag (silver), Au (gold), Pd (palladium), Pt (platinum), Cu (copper), Sn (tin), and Ni (nickel); and carbon materials such as carbon nanotubes such as acetylene black, Ketjenblack, Super P®, and VGCF®. The shape of the carbon material is not particularly limited, and any shape such as spherical, plate-shaped, or fibrous may be used.

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

[0061] The thickness of the positive electrode layer is typically between 0.1 μm and 30 μm, preferably between 1 μm and 20 μm. The thickness of the positive electrode layer is determined using the average value of thicknesses measured at 10 arbitrary locations 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 based on values ​​measured from SEM images after FIB cross-sectional processing.

[0064] The positive electrode layer is a layer that can be called the "positive electrode active material layer." The positive electrode layer may have a so-called positive electrode current collector or positive electrode current collector 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 intercalating and deintercalating ions (particularly lithium ions). The mediating ions of the negative electrode layer are not particularly limited as long as they can be charged and discharged, and examples 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 negative electrode active materials include carbon materials such as graphite, graphite-lithium compounds, lithium metals, lithium alloy particles, phosphate compounds having a NASCON-type structure, Li-containing oxides having a spinel-type structure, and β II -Li3VO4 type structure, γ II Examples include oxides having a -Li3VO4 type structure. The negative electrode active material is lithium metal, β II -Li3VO4 type structure, γII - A Li-containing oxide having a Li3VO4-type structure may be used.

[0067] In the negative electrode layer, the oxide is β II - Having a Li3VO4-type structure means that the oxide (especially its particles) is β II - Having a Li3VO4-type crystal structure, in a broad sense, it means having a crystal structure that can be recognized as a β-Li3VO4-type crystal structure by those skilled in the art of solid-state batteries. II - In a narrow sense, having a Li3VO4-type structure means that in the negative electrode layer, the oxide is β II - Having a Li3VO4-type structure means that the oxide (especially its particles) shows, at a predetermined incident angle in X-ray diffraction, one or more main peaks corresponding to the Miller indices specific to the so-called β-Li3VO4-type crystal structure. II - The preferably used Li-containing oxide having a Li3VO4-type structure includes Li3VO4. II - As the Li-containing oxide having a Li3VO4-type structure, Li3VO4 is mentioned.

[0068] In the negative electrode layer, the oxide is γ II - Having a Li3VO4-type structure means that the oxide (especially its particles) is γ II - Having a Li3VO4-type crystal structure, in a broad sense, it means having a crystal structure that can be recognized as a γ-Li3VO4-type crystal structure by those skilled in the art of solid-state batteries. II - In a narrow sense, having a Li3VO4-type structure means that in the negative electrode layer, the oxide is γ II - Having a Li3VO4-type structure means that the oxide (especially its particles) shows, at a predetermined incident angle (x-axis) in X-ray diffraction, one or more main peaks corresponding to the Miller indices specific to the so-called γ-Li3VO4-type crystal structure. II - The preferably used Li-containing oxide having a Li3VO4-type structure includes Li II V 3.2 V 0.8 Si 0.2 O4 is mentioned.

[0069] The chemical composition of the negative electrode active material may be its average chemical composition. The average chemical composition of the negative electrode active material refers to the 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 fracturing the solid-state battery and performing a compositional analysis using SEM-EDX (energy-dispersive X-ray spectroscopy) in a field of view that covers the entire thickness direction of the negative electrode layer.

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

[0071] The chemical composition and crystal structure of the negative electrode active material in the negative electrode layer may normally change due to elemental diffusion during sintering in the manufacturing process of solid-state batteries. The negative electrode active material may have the above-described average chemical composition and crystal 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, but for example, it is preferably 50% or more (particularly 50% to 99%) of the total negative electrode layer, more preferably 70% to 95%, and even more preferably 80% to 90%.

[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 included in the negative electrode layer is not particularly limited, and examples include the solid electrolytes exemplified as solid electrolytes constituting the solid electrolyte layer described later.

[0075] If the negative electrode layer contains a solid electrolyte, the solid electrolyte content is usually 20% to 60% by volume, and particularly 30% to 45% by volume, relative to the entire negative electrode layer.

[0076] For the sintering aid in the negative electrode layer, the same compounds as those used for the sintering aid in the positive electrode layer can be used. For the negative electrode layer, the same compounds as those used for the positive electrode layer can be used as conductive additives.

[0077] The thickness of the negative electrode layer is typically between 0.1 μm and 30 μm, preferably between 1 μm and 20 μm. The thickness of the negative electrode layer is determined using the average value of thicknesses measured at 10 arbitrary locations in 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 measured using the same method as the porosity of the positive electrode layer.

[0080] The negative electrode layer is a layer that may be called the "negative electrode active material layer." The negative electrode layer may have a so-called negative electrode current collector or negative electrode current collector layer.

[0081] (Solid electrolyte layer) In the solid-state battery of the present invention, the solid electrolyte layer includes 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. Examples of such solid electrolytes include oxide-based materials, and examples include one or more materials selected from garnet-type oxides contained in the positive electrode layer, Li2ZrO3, solid electrolytes having a γ-Li3VO4 structure, and oxide glass ceramic lithium-ion conductors. From the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferable that the solid electrolyte layer contains a garnet-type oxide contained in the positive electrode layer.

[0083] Examples of solid electrolytes having a γ-Li3VO4 structure include solid electrolytes having an average chemical composition represented by the following general formula (III).

[0084] [ka]

[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, and in particular 0 ≤ x ≤ 0.2. y satisfies 0 ≤ y ≤ 1.0, and in particular 0.20 ≤ y ≤ 0.50. a is the average valence of A. The average valence of A is the value expressed as (n1 × a + n2 × b + n3 × c) / (n1 + n2 + n3) when A consists of, for example, n1 elements X with valence a+, n2 elements Y with valence b+, and n3 elements Z with valence c+. c is the average valence of D. The average valence of D is the same value as the average valence of A described above, for example, if D consists of n1 elements of element X with valence a+, n2 elements of element Y with valence b+, and n3 elements of element Z with valence c+.

[0086] A specific example of a solid electrolyte having a γ-Li3VO4 structure is, for example, Li 3.2 (V 0.8 Si 0.2 )O4, Li 3.5 (V 0.5 Ge 0.5 )O4, Li 3.4 (P 0.6 Si0.4)O4, Li 3.5 (P 0.5 Ge 0.5 Examples include O4, etc.

[0087] Examples of oxide glass ceramic lithium ion conductors include phosphate compounds containing lithium, aluminum, and titanium as constituent elements (LATP), and phosphate compounds containing lithium, aluminum, and germanium as constituent elements (LAGP).

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

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

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

[0091] The thickness of the solid electrolyte layer is typically between 0.1 μm and 30 μm, and preferably between 1 μm and 20 μm, from the viewpoint of more effectively suppressing the increase in interfacial resistance and the decrease in discharge capacity. The thickness of the solid electrolyte layer is determined using the average value of the thickness measured at 10 arbitrary locations in the SEM image.

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

[0093] The porosity of the solid electrolyte layer is measured using the same method as the porosity of the positive electrode layer.

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

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

[0096] A paste is prepared by appropriately mixing a solvent, binder, etc., with the negative electrode active material. A second green sheet for forming the negative electrode layer is formed by applying the paste onto a sheet and drying it. The second green sheet may contain a so-called solid electrolyte, a conductive additive, and / or a sintering aid.

[0097] A paste is prepared by appropriately mixing a solvent, binder, etc., with a solid electrolyte. A third green sheet for forming the solid electrolyte layer is produced by applying the paste and drying it. The third green sheet may contain a sintering aid or the like.

[0098] The solvents used to produce the first to third green sheets are not particularly limited, and any solvent that can be used, for example, in the field of solid-state batteries for the manufacture of positive electrode layers, negative electrode layers, or solid electrolyte layers may be used. Typically, solvents that can be used with the binders described below are used. Examples of such solvents include alcohols such as 2-propanol.

[0099] The binder used to produce the first to third green sheets is not particularly limited, and any binder that can be used, for example, in the field of solid-state batteries to manufacture the positive electrode layer, negative electrode layer, or solid electrolyte layer may be used. Examples of such binders include butyral resin and acrylic resin.

[0100] Next, a laminate is created by appropriately stacking the first to third green sheets. The created laminate may be pressed. Preferred pressing methods include hydrostatic pressing. Subsequently, a solid-state battery can be obtained by sintering the laminate at, for example, a temperature between 600°C and 800°C.

[0101] I will explain the printing method. The printing method is the same as the green sheet method, except for the following: Aside from ensuring that the solvent and resin are blended in amounts suitable for use as an ink, each layer of ink is prepared having the same composition as the paste of each layer used to obtain the green sheet. • Printing and lamination are performed using inks from 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 in any way to the following examples and can be implemented with appropriate modifications without changing the gist of the invention.

[0103] The present invention, as described above, encompasses the following preferred embodiments. <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 comprises a positive electrode active material having a layered rock salt type structure and an oxide having a garnet type structure. The positive electrode active material contains at least one of Mg (magnesium) or Al (aluminum), The aforementioned oxide does not contain Al (aluminum), and is a solid-state battery. <2> The aforementioned oxide contains La, The Al content in the aforementioned oxide is less than (Al / La) 0.08 relative to the La content. <1> Solid-state batteries as described above. <3> The positive electrode active material has a chemical composition represented by the following general formula (R): <1> or <2> Solid batteries as described: [ka] [In formula (R), M1 is one or more elements selected from the group consisting of Co (cobalt), Ni (nickel), and Mn (manganese); M2 contains 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> The aforementioned M2 contains Al, γ is the value equivalent to γ ​​for Al. Al 0.008≦γ Al Satisfying ≤ 0.08, <3> Solid-state batteries as described above. <5> The aforementioned M2 contains only Mg and Al. <4> Solid-state batteries as described above. <6> The positive electrode active material has a portion near the interface with the oxide and the interior of its particles, The concentration of at least one of Mg (magnesium) or Al (aluminum) inside the particle is greater than the concentration of at least one of them near the interface. <1> ~ <5> A solid-state battery as described in any of the following. <7> The positive electrode active material has a portion near the interface with the oxide and the interior of its particles, The total concentration C of Mg (magnesium) and Al (aluminum) inside the particle. N This refers to the total concentration C of Mg (magnesium) and Al (aluminum) in the vicinity of the interface. K Larger than, <1> ~ <5> A solid-state battery as described in any of the following. <8> Said total concentration CK The total concentration C N The concentration ratio (C) K / C N ) is between 0.01 and 0.90. <7> Solid-state batteries as described above. <9> Said total concentration C K It is between 0.1 atomic percent and 2.0 atomic percent. Said total concentration C N It is between 0.8 atomic percent and 5.0 atomic percent. <7> or <8> Solid-state batteries as described above. <10> The aforementioned oxide has a chemical composition represented by the following general formula (I): <1> ~ <9> A solid-state battery as described in any of the following. [ka] [In formula (I), A is one or more elements that can be dissolved in the Li site of the oxide having the garnet-type crystal structure, and does not contain Al (aluminum); B I It is one or more elements selected from the group consisting of elements belonging to Groups 1 to 3 that can coordinate with oxygen in an 8-degree configuration and that can have a valency of 3; B II It is one or more elements selected from the group consisting of elements belonging to Groups 1 to 3 that can coordinate with oxygen in an 8-degree configuration and can have a valency other than 3; D I It is one or more elements selected from the group consisting of transition elements that can coordinate with oxygen to 6 and main group elements belonging to groups 12 to 15 that can have a valency of 4; D II It is one or more elements selected from the group consisting of transition elements that can coordinate with oxygen to 6 and main group elements belonging to groups 12 to 15 that can have a valency other than 4; 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 (In the formula, a is the average valence of A; b is B II The average value of is; d is D II [It is represented by the average value of ] <11> D II It contains Bi (bismuth), <10> Solid-state batteries as described above. <12> The positive electrode layer and the negative electrode layer are layers capable of intercepting and deintercepting lithium ions. <1> ~ <11> A solid-state battery as described in any of the following. <13> The solid electrolyte layer is integrally sintered with the positive electrode layer and the negative electrode layer, forming a sintered body structure. <1> ~ <11> A solid-state battery as described in any of the following. [Examples]

[0104] [Manufacturing of positive electrode active material] • LiCoO2 (the positive electrode active material used in Comparative Example 1) LiCoO2 was synthesized from cobalt oxide (Co3O4) and lithium carbonate (Li2CO3). Cobalt oxide and lithium carbonate were weighed in stoichiometric proportions, sealed in a PE bottle with 1 mm diameter zirconia beads and pure water, and mixed in a pot mill at 200 rpm for 16 hours. The mixture was then dried after removing the beads and crushed in a mortar. The crushed material was placed in a crucible and calcined in a furnace at 800°C in an air atmosphere for 20 hours. The resulting calcined material was then crushed in a mortar to obtain LiCoO2.

[0105] ·LiCo 0.95 Mg 0.05 O2 (the positive electrode active material used in Example 2) Lisco 0.95 Mg 0.05O2 was synthesized by weighing cobalt oxide (Co3O4), lithium carbonate (Li2CO3), and MgO in stoichiometric proportions, sealing them in a PE bottle with 1mm diameter zirconia beads and pure water, and mixing them in a pot mill at 200 rpm for 16 hours. After removing the beads, the mixture was dried and crushed in a mortar. The crushed material was placed in a crucible and calcined in a furnace at 800°C in an air atmosphere for 20 hours. The resulting calcined material was then crushed in a mortar to produce LiCo 0.95 Mg 0.05 O2 (powder) was obtained. The average particle size was 3 μm. XRD measurement of the above powder confirmed that a single phase with a layered rock salt structure (ICDD card No. 01-070-2685) was obtained. ICP measurement confirmed that there was no compositional deviation in the above powder.

[0106] • Positive electrode active materials other than those listed above (positive electrode active materials used in Examples 1, 3-7 and Comparative Examples 2-4) Except for the fact that cobalt oxide (Co3O4), lithium carbonate (Li2CO3), magnesium oxide (MgO), aluminum oxide (Al2O3), titanium oxide (TiO2), iron oxide (Fe2O3), and silicon dioxide (SiO2) were weighed and used in the desired stoichiometric composition, LiCo 0.95 Mg 0.05 The materials were manufactured using the same method as for O2. The average particle size of all positive electrode active materials was 3 μm. XRD measurements confirmed that all positive electrode active materials exhibited a single phase with a layered rock salt structure (ICDD card No. 01-070-2685). ICP measurements confirmed that the powders were free from compositional deviations.

[0107] [Production of garnet-type oxides] The raw materials used were lithium hydroxide monohydrate (LiOH·H2O), lanthanum hydroxide (La(OH)3), zirconium oxide (ZrO2), tantalum oxide (Ta2O5), bismuth oxide (Bi2O3), and aluminum oxide (Al2O3). Each raw material was weighed to achieve the chemical composition shown in Table 1, water was added, and the mixture was sealed in 100 ml polyethylene poly pots and rotated on a pot rack at 150 rpm for 16 hours to mix the raw materials. In addition, lithium hydroxide monohydrate LiOH·H2O, which is the Li source, was charged in an excess of 3 wt% relative to the target composition, taking into account Li loss during sintering. The obtained slurry was evaporated and dried, and then calcined at 900°C for 5 hours to obtain the target phase. The resulting calcined powder was mixed with a toluene-acetone solvent and ground in a planetary ball mill for 6 hours. This pulverized powder was dried to obtain a garnet-type oxide powder. XRD measurement of the powder confirmed that a single garnet-type oxide was obtained. ICP measurement confirmed that there was no compositional deviation in the powder. The average particle size was 150 nm. In each embodiment, the primary particle size of the material was kept constant, and the structure and composition were controlled by the molar ratio of the raw materials and the firing time.

[0108] [Manufacturing of sintering aids] Lithium hydroxide monohydrate (LiOH·H2O) and boron oxide (B2O3) were used. Each starting material was weighed appropriately so that the chemical composition of the sintering aid was Li4B2O5, thoroughly mixed in a mortar, and then calcined at 650°C for 5 hours.

[0109] [Example 1] (Manufacturing of positive electrode half-cells) First, garnet-type oxide, cathode active material powder, and sintering aid powder were weighed in a volume ratio of 49:50:1, respectively, and mixed with alcohol and a binder to prepare a cathode layer slurry. This slurry was then applied to a sheet and dried to form a first green sheet for the cathode layer. Furthermore, a solid electrolyte layer slurry was prepared by kneading the garnet-type oxide, alcohol, and binder similar to those contained in the first green sheet, and a second green sheet for forming the solid electrolyte layer was formed by drying the slurry. A laminate was fabricated by appropriately stacking the first and second green sheets. The fabricated laminate was pressurized using a hydrostatic press method and cut as needed to obtain a laminate of a cathode layer / solid electrolyte layer. After removing the binder at 400°C, the cathode layer / solid electrolyte layer was co-fired by pressurized sintering at 800°C for 60 minutes under a pressure of 100 MPa. After sintering, the thickness of the cathode layer was approximately 15 μm, and the thickness of the solid electrolyte layer was approximately 200 μm. Subsequently, metallic lithium was attached to the surface of the solid electrolyte layer opposite the positive electrode layer as a counter electrode and reference electrode, and the cell was sealed with a 2032 type coin cell to obtain a solid-state battery.

[0110] [Examples 2-7 and Comparative Examples 1-6] A cathode half-cell was manufactured in the same manner as in Example 1, except that a combination of garnet-type oxide and cathode active material shown in Table 1 was used.

[0111] [Interfacial resistance increase rate] The arc size around 1 kHz in a fully charged state at room temperature after the float test at 60°C, as described later, was evaluated based on a value (increase rate) normalized by the arc size around 1 kHz in a fully charged state at room temperature before the float test. For more details, we examined 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"). The arc around 1 kHz was identified from a Bode plot (absolute value of resistance vs. frequency, angle with the real axis (θ) vs. frequency in the "cole-cole plot") and was defined as the difference between the saddle points of the arc in the real axis direction of the "cole-cole plot" diagram. (See Figure 2) ◎◎: Growth rate ≤ 5% (best); ◎: 5% < Growth Rate ≤ 10% (Excellent); ○; 10% < Growth Rate ≤ 20% (Good); △; 20% < Increase rate ≤ 30% (acceptable) (no practical problems); ×; 30% < Increase rate (not possible) (problematic in practice).

[0112] [Capacity maintenance rate] The capacity retention rate was evaluated based on a value (retention rate) normalized by dividing the discharge capacity at room temperature after the 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); △; Maintenance rate < 65% (acceptable) (no practical problems); ×; Maintenance rate < 60% (unacceptable) (problematic in practice).

[0113] [Overall assessment] The overall determination was made based on the results of the interfacial resistance increase rate and capacity retention rate assessments. ◎◎: All evaluation results were ◎◎. ◎: Of all the evaluation results, the lowest evaluation result was ◎. ○: Of all the judgment results, the lowest result was ○. △: Of all the evaluation results, △ was the lowest evaluation result. ×: Of all the judgment results, the lowest result was ×.

[0114] [Float test] The battery was charged to 4.2V with a constant current of 0.1C, and after reaching 4.2V, charging was continued at a constant voltage until the current decreased to 0.01C. After charging was complete, the circuit was left open for 3 hours, and then AC impedance measurements were performed with a voltage amplitude of 10mV in the frequency range from 0.1Hz to 7MHz, and a Cole-Cole plot was obtained. The AC impedance conditions were set from the frequency band above 1MHz to the frequency band below 0.1Hz, with a voltage amplitude of approximately 10mV. After the AC impedance measurement, the battery was discharged to 3V with a constant current of 0.1C. Subsequently, constant current charging was performed at 0.1C in a 60°C constant temperature bath. After reaching 4.2V, constant voltage charging was performed for one week, followed by float charging. After one week of float charging, constant current discharge was performed at 0.1C while maintaining the 60°C temperature, and the discharge was terminated when it reached 3V. The cells were removed from the 60°C constant temperature bath, and the initial charge-discharge characteristics were checked at room temperature under the same conditions, followed by the battery characteristics after float charging. The cells were charged to 4.2V with a constant current of 0.1C, and after reaching 4.2V, charging was continued at a constant voltage until the current decreased to 0.01C. After charging was complete, the circuit was left open for 3 hours, and then the AC impedance was measured. After the AC impedance measurement, the cells were discharged to 3V with a constant current of 0.1C.

[0115] [Checking elemental distribution] A laminate of co-fired cathode layer / solid electrolyte layer (before metallic Li was attached) was embedded in resin, then exfoliated to prepare a TEM observation sample. Using TEM-EDX (energy-dispersive X-ray spectroscopy), we performed EDX-based compositional analysis and mapped the elemental distribution near the LCO-LLZ interface. Figure 3A shows a TEM image of the sample from Example 2 near the LCO-LLZ interface (left) and a TEM image showing its Mg distribution mapping (right). Figure 3B shows the measurement results when the Mg element was measured from the LCO-LLZ interface toward the interior of the LCO in the left-hand TEM image of Figure 3A. Figure 4A shows a TEM image of the vicinity of the LCO-LLZ interface (left) and a TEM image showing the Al distribution mapping (right) for the sample of Example 4. Figure 4B shows the measurement results when the Al element was measured from the LCO-LLZ interface toward the interior of the LCO in the left-hand TEM image of Figure 4A.

[0116] [Garnet-type crystal structure] The garnet-type crystal structure was confirmed by obtaining an X-ray diffraction pattern that can be attributed to a garnet-like crystal structure using X-ray diffraction (XRD measurement) (ICDD Card No. 00-045-0109).

[0117] [Layered rock salt crystal structure] The layered rock salt crystal structure was confirmed by obtaining an X-ray diffraction pattern that can be attributed to the layered rock salt crystal structure using X-ray diffraction (XRD measurement) (ICDD Card No. 01-070-2685).

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

[0119] <Measurement of Mg and Al concentrations near the interface and inside particles in positive electrode active material> The positive electrode layer was cut in two arbitrary directions by FIB processing, and five arbitrary positive electrode active material particles were focused on in each of these cross-sections (TEM cross-sectional view) (a total of 10 positive electrode active material particles). Next, the chemical composition of each positive electrode active material particle 1 was determined by TEM-EDX point analysis at 10 arbitrary locations near the interface 11 with the adjacent garnet-type oxide 2, and the concentrations of Mg and Al were obtained. Furthermore, the chemical composition of each positive electrode active material particle 1 was determined by TEM-EDX point analysis at 10 arbitrary locations inside the particle 12 located inside the interface 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 oxides> Garnet-type oxides were cut in any two directions by FIB processing, and the chemical composition was determined by TEM-EDX point analysis at any 30 points on each of these cross-sections (TEM cross-sectional view). The concentrations of Al and La were measured, and the ratio of Al to La was obtained.

[0121] [Table 1]

[0122] When a high-temperature float (60°C) test was performed using a standard LCO as in Comparative Example 1, a significant increase in interfacial resistance and a decrease in capacity retention were observed. Examples 1 to 7 show that the inclusion of Al and / or Mg in LCO significantly suppresses the increase in interfacial resistance and the decrease in capacity retention. However, comparative examples 2, 3, and 5 showed that when Fe, Si, and Ti were included in LCO, the properties actually deteriorated. In other words, it was found that only specific elements were effective in improving the properties of LCO, and those elements were Al and / or Mg. A comparison of Comparative Examples 1 and 4 revealed that the above properties deteriorate when Al is included in LLZ. From a comparison of Comparative Example 6 and Example 4, it was found that even if Al is contained in LCO, the effects of the present invention cannot be obtained if Al is contained in LLZ. Therefore, in order to fully obtain the effects of the present invention, it is necessary that LLZ does not contain Al, and that LCO contains Al and / or Mg. [Industrial applicability]

[0123] The solid-state battery containing the solid electrolyte ceramic of the present invention can be used in various fields where battery use or energy storage is anticipated. While this is merely illustrative, a solid-state battery according to one embodiment of the present invention can be used in the field of electronics packaging. A solid battery according to one embodiment of the present invention can also be used in the electrical, information and communication fields where mobile devices are used (for example, the electrical and electronic equipment field or mobile device field including small electronic devices such as mobile phones, smartphones, smartwatches, laptops, digital cameras, activity trackers, ARM computers, electronic paper, wearable devices, RFID tags, card-type electronic money, and smartwatches), household and small industrial applications (for example, power tools, golf carts, household, caregiving and industrial robots), large industrial applications (for example, forklifts, elevators, and port cranes), transportation systems (for example, hybrid vehicles, electric vehicles, buses, trains, electric assist bicycles, electric motorcycles, etc.), power grid applications (for example, various power generation, road conditioners, smart grids, and general household energy storage systems), medical applications (medical equipment such as earphones and hearing aids), pharmaceutical applications (medication management systems, etc.), as well as IoT fields and space and deep-sea applications (for example, space probes and submersible research vessels, etc.). [Explanation of symbols]

[0124] 1: Positive electrode active material 11: Near the interface with garnet-type oxide in the positive electrode active material 12: Internal region of the positive electrode active material (inside the particle) 2: Garnet-type oxides S: Interface with 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 comprises a positive electrode active material having a layered rock salt type structure and an oxide having a garnet type structure. The positive electrode active material contains at least one of Mg (magnesium) or Al (aluminum), The aforementioned oxide contains La and substantially does not contain Al (aluminum). A solid-state battery in which the Al content in the oxide is less than 0.08 in molar ratio to the La content.

2. The positive electrode active material has a chemical composition represented by the following general formula (R), the solid battery according to claim 1: 【Chemistry 1】 [In formula (R), M1 is one or more elements selected from the group consisting of Co (cobalt), Ni (nickel), and Mn (manganese); M2 contains 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.

3. The aforementioned M2 contains Al, The value corresponding to γ ​​for Al Ａｌ 0.008 ≤ γ Ａｌ A solid-state battery according to claim 2, satisfying ≤ 0.

08.

4. The solid battery according to claim 3, wherein M2 comprises only both Mg and Al.

5. The positive electrode active material has a portion near the interface with the oxide and the interior of its particles, The solid battery according to claim 1, wherein the concentration of at least one of Mg (magnesium) or Al (aluminum) inside the particle is greater than the concentration of at least one near the interface.

6. The positive electrode active material has a portion near the interface with the oxide and the interior of its particles, The total concentration C of Mg (magnesium) and Al (aluminum) inside the particle. Ｎ This is the total concentration C of Mg (magnesium) and Al (aluminum) in the vicinity of the interface. Ｋ A solid battery according to claim 1, which is larger than the one described above.

7. Said total concentration C Ｋ The total concentration C Ｎ Socket ratio (C) Ｋ / C Ｎ The solid battery according to claim 6, wherein the value is 0.01 or more and 0.90 or less.

8. The total concentration C Ｋ is 0.1 atomic % or more and 2.0 atomic % or less, Said total concentration C Ｎ The solid battery according to claim 6, wherein the amount is 0.8 atomic percent or more and 5.0 atomic percent or less.

9. The solid 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 is one or more elements that can be dissolved in the Li site of the oxide having the garnet-type crystal structure, and does not include Al (aluminum); B Ｉ It is one or more elements selected from the group consisting of elements belonging to Groups 1 to 3 that can coordinate with oxygen in an 8-degree configuration and can have a trivalent valency; B ＩＩ This refers to one or more elements selected from the group consisting of elements belonging to Groups 1 to 3 that can coordinate with oxygen in an 8-degree relationship and that can have a valency other than 3; D Ｉ This refers to one or more elements selected from the group consisting of transition elements that can coordinate with oxygen to six and main group elements belonging to groups 12 to 15 that can have a valency of four; D ＩＩ This refers to one or more elements selected from the group consisting of transition elements that can coordinate to oxygen in 6-degree inclination and main group elements belonging to groups 12 to 15 that can have valencies other than 4; 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 (In the formula, a is the average valence of A; b is B ＩＩ The average valence of is; d is D ＩＩ [It is expressed as the average value of ]

10. D ＩＩ The solid battery according to claim 9, wherein the solid battery contains Bi (bismuth).

11. The solid battery according to any one of claims 1 to 10, wherein the positive electrode layer and the negative electrode layer are layers capable of intercalating and deintercalating lithium ions.

12. The solid battery according to any one of claims 1 to 10, wherein the solid electrolyte layer is integrally sintered with the positive electrode layer and the negative electrode layer as sintered bodies.

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