Solid state battery

Abstract

The present invention provides a solid state battery that has more sufficiently suitable float characteristics and cycle characteristics. The present invention relates to a solid state battery comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer that is disposed between the positive electrode layer and the negative electrode layer, wherein the positive electrode layer contains a positive electrode active material, a solid electrolyte which has a LISICON-type crystal structure, and an oxide ceramic which has a higher Young's modulus than the solid electrolyte.

Description

solid state battery

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

[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 for liquid-electrolyte rechargeable batteries. Therefore, solid batteries require float properties related to heat resistance at high temperatures.

[0003] As a solid-state battery, for example, a solid-state battery is disclosed that includes a solid electrolyte having a LISICON-type crystal structure in the positive electrode layer (Patent Document 1).

[0004] WO2023-181536

[0005] The inventors of the present invention have found that the following problems occur in conventional solid-state batteries using the above-described positive electrode layer. Conventional solid-state batteries have excellent float characteristics, but their cycle characteristics are reduced. Specifically, due to the expansion and contraction of the active material during charging and discharging, cracks occur within the positive electrode, at the interface between the active material and the LISICON solid electrolyte, or within the LISICON solid electrolyte, resulting in reduced cycle characteristics.

[0006] The present invention aims to provide a solid-state battery that exhibits sufficiently superior characteristics in both float and cycle performance.

[0007] 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, wherein the positive electrode layer includes a positive electrode active material, a solid electrolyte having a LISICON-type crystal structure, and an oxide ceramic having a Young's modulus higher than that of the solid electrolyte.

[0008] The solid-state battery of the present invention exhibits excellent characteristics in both float and cycle performance.

[0009] [Solid-state 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 in a narrow sense 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".

[0010] 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.

[0011] (Positive Electrode Layer) In the solid-state battery of the present invention, the positive electrode layer includes a positive electrode active material (sometimes referred to as "component A"), a solid electrolyte having a LISICON-type crystal structure (sometimes referred to as "component B"), and an oxide ceramic having a Young's modulus higher than that of the solid electrolyte (sometimes referred to as "component C"). In the present invention, by including the positive electrode active material in the positive electrode layer in combination with a solid electrolyte having a LISICON-type crystal structure and an oxide ceramic having a Young's modulus higher than that of the solid electrolyte, both the float characteristics and the cycle characteristics are more significantly improved. Specifically, since the oxide ceramic has a Young's modulus higher than that of the LISICON-type solid electrolyte, including the oxide ceramic in the positive electrode layer improves the overall mechanical strength of the positive electrode layer. Therefore, while exhibiting the excellent float characteristics of the LISICON-type solid electrolyte, deformation of the LISICON-type solid electrolyte due to expansion and contraction can be suppressed, and as a result, a decrease in cycle characteristics due to crack generation can be suppressed. If the positive electrode layer does not contain component B, the float characteristics will decrease. If the positive electrode layer does not contain a carbon component, the cycle characteristics will deteriorate. The positive electrode layer may have the form of a sintered body comprising positive electrode active material particles, solid electrolyte particles having a LISICON-type crystal structure, and oxide ceramic particles having a Young's modulus higher than that of the solid electrolyte particles. The positive electrode layer may be a layer capable of intercalating and deintercalating ions (particularly lithium ions). The mediating ions for 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).

[0012] The positive electrode active material contained in the positive electrode layer can be any material that has been conventionally used as a positive electrode active material for solid-state batteries, for example, a material having a rock salt crystal structure may be used. Preferably, the positive electrode active material contains a positive electrode active material having a rock salt crystal structure. From the viewpoint of further improving float characteristics and cycle characteristics, the content of the positive electrode active material having a rock salt crystal structure is preferably 50 volume% or more (particularly 50 volume% to 100 volume%), more preferably 70 volume% or more (particularly 70 volume% to 100 volume%), even more preferably 90 volume% or more (particularly 90 volume% to 100 volume%), sufficiently preferably 95 volume% or more (particularly 95 volume% to 100 volume%), and more very preferably 100 volume%, based on the total amount of positive electrode active material.

[0013] The statement that a positive electrode active material has a rock salt crystal structure means that the positive electrode active material (especially its particles) has a rock salt crystal structure. In a broad sense, it means that it has a crystal structure that can be recognized as a 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 rock salt structure means that the positive electrode active material (especially its particles) is identified as having a rock salt crystal structure by analyzing the X-ray diffraction pattern using Rietveld analysis or the like. More specifically, the positive electrode active material may, in X-ray diffraction, exhibit one or more major peaks corresponding to Miller indices specific to a so-called rock salt crystal structure (diffraction pattern: ICDD Card No. 00-001-1241) at a predetermined angle of incidence.

[0014] The positive electrode active material (particularly a positive electrode active material having a rock salt type crystal structure) has, for example, a chemical composition represented by the following general formula (1).

[0015]

[0016] In formula (1), 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 further improving float and cycle characteristics. M2 contains one or more elements selected from the group consisting of Mg (magnesium), Al (aluminum), and Ti (titanium), and preferably contains Al, more preferably contains both Mg and Al, and more preferably contains only both Mg and Al, from the viewpoint of further improving float and cycle characteristics.

[0017] In formula (1), α satisfies 0.8 ≤ α ≤ 1.5, preferably 0.8 ≤ α ≤ 1.2, more preferably 0.9 ≤ α ≤ 1.1, and even more preferably 1.0 from the viewpoint of further improving float and cycle characteristics. β satisfies 0.8 ≤ α ≤ 1.5, preferably 0.8 ≤ α ≤ 1.2, more preferably 0.9 ≤ α ≤ 1.1, and even more preferably 1.0 from the viewpoint of further improving float and cycle characteristics. γ satisfies 0 ≤ γ ≤ 0.24, preferably 0 ≤ γ ≤ 0.2, more preferably 0 ≤ γ ≤ 0.1, and even more preferably 0 from the viewpoint of further improving float and cycle characteristics. ω satisfies 1.8 ≤ ω ≤ 2.2, preferably 1.9 ≤ ω ≤ 2.1, and even more preferably 2.0 from the viewpoint of further improving float and cycle characteristics.

[0018] Specifically, the positive electrode active material is, for example, LiCoO ２ You can also use these.

[0019] 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 EDX compositional analysis using SEM-EDX (energy-dispersive X-ray spectroscopy) in any field of view that encompasses the entire thickness direction of the positive electrode layer.

[0020] The content of the positive electrode active material (particularly a positive electrode active material having a rock salt crystal structure) 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 further improving float characteristics and cycle characteristics, it is preferably 40% by volume or more and 80% by volume or less, more preferably 40% by volume or more and 60% by volume or less, and particularly preferably 45% by volume or more and 55% by volume or less. The positive electrode layer may contain two or more types of positive electrode active materials (particularly positive electrode active materials having a rock salt crystal structure), in which case their total content should be within the above range. Two or more types of rock salt positive electrode active materials refer to, for example, two or more positive electrode active materials represented by the above general formula (1) 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.

[0021] When the positive electrode layer contains the positive electrode active material described above (particularly a positive electrode active material having a rock salt crystal structure), it may further contain positive electrode active materials other than the rock salt type positive electrode active material (hereinafter also referred to as "other positive electrode active materials"). The content of positive electrode active materials other than the rock salt type positive electrode active material described above 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 further improving float characteristics and cycle characteristics. 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.

[0022] 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. Next, the slurry is dried, calcined at 700°C to 1000°C for 1 hour to 30 hours, and then pulverized to obtain the positive electrode active material. The calcination may be carried out in two stages. The first and second calcination stages may be called "pre-calcination" and "final calcination," respectively. The calcination conditions for the first and second stages may be independently within the range of the calcination temperature and calcination time described above.

[0023] The chemical composition and crystal structure of the positive electrode active material in the positive electrode layer may change due to elemental diffusion during sintering. Preferably, the positive electrode active material has the above-described chemical composition and crystal structure in the solid-state battery after sintering together with the negative electrode layer and the solid electrolyte layer.

[0024] 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. From the viewpoint of further improving the float characteristics and cycle characteristics, it is preferably 500 nm or more and 8 μm or less, more preferably 1 μm or more and 5 μm or less, and very preferably 1 μm or more and 3 μm or less.

[0025] 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 that the particle 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 an SEM, calculating the cross-sectional area S of the particle using image analysis software (for example, "A-Image-kun" (manufactured by Asahi Kasei Engineering Co., Ltd.)), and then determining the particle diameter R using the following formula.

[0026]

[0027] 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.

[0028] The average particle diameter of the positive electrode active material in the positive electrode layer usually may change due to sintering during the manufacturing process of a solid battery. The positive electrode active material may have the above-described average particle diameter in the solid battery after being sintered together with the negative electrode layer and the solid electrolyte layer.

[0029] The positive electrode layer contains a solid electrolyte (component B) having a LISICON-type crystal structure. The solid electrolyte (component B) having a LISICON-type crystal structure is β Ｉ structure, β ＩＩ -type structure, β ＩＩ '-type structure, T Ｉ -type structure, T ＩＩ -type structure, γ ＩＩ -type structure, and γ ０ -type structure, which is a solid electrolyte having one or more crystal structures selected from the group consisting of the above. The solid electrolyte having a LISICON-type crystal structure has β Ｉ structure, β ＩＩ -type structure, β ＩＩ '-type structure, T Ｉ -type structure, T ＩＩ -type structure, γ ＩＩ -type structure, γ ０ -type structure or a composite structure thereof, and contains one or more solid electrolytes having any of the above. From the viewpoint of further improving float characteristics and cycle characteristics, the solid electrolyte having a LISICON-type crystal structure preferably contains a solid electrolyte having a γ ＩＩ -type structure.

[0030] When a solid electrolyte has a γ ＩＩ -type structure, it means that the solid electrolyte has a γ ＩＩ -type crystal structure. In a broad sense, it means that the solid electrolyte has a crystal structure that can be recognized as a γ ＩＩ -type crystal structure by those skilled in the art of solid batteries. In a narrow sense, when a solid electrolyte has a γ ＩＩ -type structure, it means that in X-ray diffraction, the solid electrolyte exhibits one or more main peaks corresponding to Miller indices specific to a so-called γ ＩＩ -Li ３ VO ４ -type crystal structure at a predetermined incident angle. γ ＩＩCompounds with a solid-state structure (i.e., solid electrolytes) are described, for example, in the literature "J. solid state chem" (ARWest et al., J. solid state chem., 4, 20-28 (1972)), and one example is ICDD Card No. 01-073-2850.

[0031] Solid electrolyte is β Ｉ Having a type structure means that the solid electrolyte is β Ｉ This means having a crystal structure of type β, and in a broader sense, according to those skilled in the field of solid-state batteries, β Ｉ This refers to having a crystal structure that can be recognized as a β-type crystal structure. In a narrower sense, it refers to a solid electrolyte that is β-type. Ｉ Having a type structure means that the solid electrolyte exhibits a so-called β-type structure in X-ray diffraction. Ｉ -Li ３ VO ４ This means that at a given angle of incidence, one or more major peaks corresponding to Miller indices specific to the crystal structure of type β are shown. Ｉ Compounds with a solid-state structure (i.e., solid electrolytes) are described, for example, in the literature "J. solid state chem" (ARWest et al., J. solid state chem., 4, 20-28 (1972)). As an example, the following table shows XRD data (interplanar spacing d value and corresponding Miller index).

[0032]

[0033] Solid electrolyte is β ＩＩ Having a type structure means that the solid electrolyte is β ＩＩ This means having a crystal structure of type β, and in a broader sense, according to those skilled in the field of solid-state batteries, β ＩＩ This refers to having a crystal structure that can be recognized as a β-type crystal structure. In a narrower sense, it refers to a solid electrolyte that is β-type. ＩＩ Having a type structure means that the solid electrolyte exhibits a so-called β-type structure in X-ray diffraction. ＩＩ -Li ３ VO ４ This means that at a given angle of incidence, one or more major peaks corresponding to Miller indices specific to the crystal structure of type β are shown. ＩＩCompounds with a solid-state structure (i.e., solid electrolytes) are described, for example, in the literature "J. solid state chem" (ARWest et al., J. solid state chem., 4, 20-28 (1972)), and one example is ICDD Card No. 00-024-0675.

[0034] Solid electrolyte is β ＩＩ Having a 'type structure' means that the solid electrolyte is β ＩＩ 'It means having a crystal structure of type β, and in a broader sense, according to those skilled in the field of solid-state batteries ＩＩ This refers to having a crystal structure that can be recognized as a 'type crystal structure'. In a narrower sense, it refers to a solid electrolyte that is β ＩＩ Having a 'type structure' means that the solid electrolyte exhibits a so-called β-type structure in X-ray diffraction. ＩＩ '-Li ３ VO ４ This means that at a given angle of incidence, one or more major peaks corresponding to Miller indices specific to the crystal structure of type β are shown. ＩＩ Compounds with a '-type structure (i.e., solid electrolytes) are described, for example, in the literature "J. solid state chem" (ARWest et al., J. solid state chem., 4, 20-28 (1972)), and as an example, the XRD data (interplanar spacing d value and corresponding Miller index) shown in the table below is presented.

[0035]

[0036] Solid electrolyte is T Ｉ Having a type structure means that the solid electrolyte is T Ｉ This means having a crystal structure of type T, and in a broader sense, by those skilled in the field of solid-state batteries. Ｉ This refers to having a crystal structure that can be recognized as a T-type crystal structure. In a narrower sense, it refers to a solid electrolyte having a T-type crystal structure. Ｉ Having a type structure means that the solid electrolyte exhibits a so-called T-type structure in X-ray diffraction. Ｉ -Li ３ VO ４ This means that one or more major peaks corresponding to the Miller indices specific to the crystal structure of type T are shown at a given angle of incidence.Ｉ Compounds with a solid-state structure (i.e., solid electrolytes) are described, for example, in the literature "J. solid state chem" (ARWest et al., J. solid state chem., 4, 20-28 (1972)), and one example is ICDD Card No. 00-024-0668.

[0037] Solid electrolyte is T ＩＩ Having a type structure means that the solid electrolyte is T ＩＩ This means having a crystal structure of type T, and in a broader sense, by those skilled in the field of solid-state batteries. ＩＩ This refers to having a crystal structure that can be recognized as a T-type crystal structure. In a narrower sense, it refers to a solid electrolyte having a T-type crystal structure. ＩＩ Having a type structure means that the solid electrolyte exhibits a so-called T-type structure in X-ray diffraction. ＩＩ -Li ３ VO ４ This means that one or more major peaks corresponding to the Miller indices specific to the crystal structure of type T are shown at a given angle of incidence. ＩＩ Compounds with a solid-state structure (i.e., solid electrolytes) are described, for example, in the literature "J. solid state chem" (ARWest et al., J. solid state chem., 4, 20-28 (1972)), and one example is ICDD Card No. 00-024-0669.

[0038] Solid electrolyte is γ ０ Having a type structure means that the solid electrolyte is γ ０ This means having a crystal structure of type γ, and in a broader sense, according to those skilled in the field of solid-state batteries, γ ０ This refers to having a crystal structure that can be recognized as a γ-type crystal structure. In a narrower sense, the solid electrolyte is γ ０ Having a type structure means that the solid electrolyte exhibits a so-called γ-type structure in X-ray diffraction. ０ -Li ３ VO ４ This means that at a given angle of incidence, one or more major peaks corresponding to Miller indices specific to the crystal structure of the type γ are shown. ０Compounds with a solid-state structure (i.e., solid electrolytes) are described, for example, in the literature "J. solid state chem" (ARWest et al., J. solid state chem., 4, 20-28 (1972)). As an example, the following table shows XRD data (interplanar spacing d value and corresponding Miller index).

[0039]

[0040] Solid electrolytes having a LISICON-type crystal structure typically have a chemical composition represented by general formula (2), and it is preferable that they contain V (vanadium) from the viewpoint of further improving float properties and cycling properties.

[0041]

[0042] In formula (2), A is one or more elements selected from the group consisting of Na (sodium), K (potassium), Mg (magnesium), Ca (calcium), Al (aluminum), Ga (gallium), Zn (zinc), Fe (iron), Cr (chromium), and Co (cobalt). B is one or more elements selected from the group consisting of Zn (zinc), Al (aluminum), Ga (gallium), Si (silicon), Ge (germanium), Sn (tin), P (phosphorus), As (arsenic), Ti (titanium), Mo (molybdenum), W (tungsten), Fe (iron), Cr (chromium), and Co (cobalt), and preferably one or more elements selected from the group consisting of Si (silicon), Ge (germanium), and P (phosphorus) from the viewpoint of further improving float characteristics and cycle characteristics. x has the relationship 0 ≤ x ≤ 1.0, preferably 0 ≤ x ≤ 0.2, and more preferably 0, from the viewpoint of further improving float and cycle characteristics. y has the relationship 0 ≤ y ≤ 1.0, preferably 0 < y ≤ 1.0, more preferably 0 < y ≤ 0.65, even more preferably 0.1 ≤ y ≤ 0.65, and sufficiently preferably 0.15 ≤ y ≤ 0.62, from the viewpoint of further improving float and cycle characteristics. 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 is, for example, n1 elements X with valence a+, n2 elements Y with valence b+, and n3 elements Z with valence c+. b is the average valence of B. The average valency of B is the same value as the average valency of A described above, for example, if B consists of n1 elements X with valency a+, n2 elements Y with valency b+, and n3 elements Z with valency c+.

[0043] A specific example of a solid electrolyte having a LISICON-type crystal structure is, for example, Li ３．２ V ０．８ Si ０．２ O ４ Li ３．３ V ０．７ Si ０．３ O ４ Li ３．４ V０．６ Si ０．４ O ４ , Li ３．５ V ０．５ Si ０．５ O ４ , Li ３．２ V ０．８ Ge ０．２ O ４ , Li ３．５ V ０．５ Ge ０．５ O ４ , Li ３．８ V ０．２ Ge ０．８ O ４ , Li ３．５ Ge ０．５ P ０．５ O ４ and the like.

[0044] The chemical composition of the solid electrolyte having a LISICON-type crystal structure (component B) means the average value of the chemical composition of said solid electrolyte in the thickness direction of the positive electrode layer (average chemical composition). The average chemical composition of the solid electrolyte (component B) can be analyzed and measured by breaking the solid battery and performing composition analysis by EDX using SEM-EDX (energy dispersive X-ray spectroscopy) in a field of view that covers the entire thickness direction of the positive electrode layer.

[0045] In the positive electrode layer, the chemical composition of component B (particularly a solid electrolyte having a LISICON-type crystal structure) and the chemical composition of component C (for example, a solid electrolyte having a garnet-type crystal structure), as described below, can be automatically distinguished and measured based on their compositions in the above compositional analysis. Specifically, when component B is a solid electrolyte with a LISICON-type structure containing V and / or Ge, and component C is an LLZ-type solid electrolyte, an LLT-type solid electrolyte, a La-free Li-containing oxide ceramic, or a Li-free oxide ceramic, the parts of component B can be identified by detection of V and / or Ge, and the parts of component C can be identified by one or more elements selected from the group consisting of La, Zr, Ti, and Sn, using SEM-EDX analysis. For example, if component B is a solid electrolyte with a LISICON-type structure containing V, and component C is an LLZ-type solid electrolyte having a garnet-type crystal structure, then SEM-EDX analysis can separate and distinguish the parts of component B by detection of V, and the parts of component C by identification using La and / or Zr. Also, for example, if component B is a solid electrolyte with a LISICON-type structure containing Ge, and component C is an LLZ-type solid electrolyte, then SEM-EDX analysis can separate and distinguish the parts of component B by detection of Ge, and the parts of component C by identification using La and / or Zr. Furthermore, for example, if component B is a solid electrolyte with a LISICON-type structure containing V, and component C is an LLT-type solid electrolyte, then SEM-EDX analysis can separate and distinguish the parts of component B by detection of V, and the parts of component C by identification using La and / or Ti. For example, if component B is a solid electrolyte with a LISICON-type structure containing V, and component C is a La-free Li-containing oxide ceramic containing Zr and / or Sn, then SEM-EDX analysis can separate and distinguish the parts of component B by identifying V, and the parts of component C by identifying Zr and / or Sn.For example, if component B is a solid electrolyte with a LISICON-type structure containing V, and component C is a Li-free oxide ceramic containing Zr, then SEM-EDX analysis can separate and distinguish the parts of component B by detecting V, and the parts of component C by identifying Zr.

[0046] Component B of the positive electrode layer can be obtained by the same method as the positive electrode active material, except that a raw material compound containing a predetermined metal atom is used, or it can be obtained as a commercially available product.

[0047] The chemical composition and crystal structure of component B in the positive electrode layer may normally change due to elemental diffusion during sintering. Preferably, component B has the above-described chemical composition and crystal structure in the solid-state battery after sintering together with the negative electrode layer and the solid electrolyte layer.

[0048] The content of component B in the positive electrode layer is not particularly limited, but from the viewpoint of further improving the float characteristics and cycle characteristics, it is preferably 5 to 120 volumes, more preferably 5 to 95 volumes, even more preferably 30 to 95 volumes, sufficiently preferably 40 to 95 volumes, and more preferably 40 to 60 volumes per 100 volumes of positive electrode active material.

[0049] The content of component B in the positive electrode layer can be measured by known methods. For example, the content of component B in the positive electrode layer can be measured by processing the positive electrode layer with an ion beam to expose the cross-section, and then calculating the area ratio of the area where V and Si are detected by SEM-EDX analysis within a predetermined range of the cross-section to that range. For example, the image processing software "A-Image-kun" can be used to calculate the area ratio.

[0050] The volume ratio of component B to component C (described later) in the positive electrode layer is usually 5 / 95 or more and 95 / 5 or less. From the viewpoint of further improving float characteristics and cycle characteristics, it is preferably 30 / 70 or more and 95 / 5 or less, more preferably 40 / 60 or more and 95 / 5 or less, and even more preferably 40 / 60 or more and 60 / 40 or less.

[0051] The average particle size of component B is not particularly limited and may be, for example, 100 nm to 3 μm. From the viewpoint of further improving float characteristics and cycle characteristics, it is preferably 110 nm to 1 μm, and more preferably 120 nm to 500 nm.

[0052] The average particle size of component B can be determined, for example, by the same method as the method for measuring the average particle size of the positive electrode active material as component A. Alternatively, the average particle size of component B in the positive electrode layer may be determined by identifying component B based on its composition during the chemical composition measurement described above.

[0053] The average particle size of component B in the positive electrode layer may change due to sintering during the manufacturing process of the solid-state battery. Component B 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.

[0054] The positive electrode layer also contains an oxide ceramic (component C) having a Young's modulus higher than that of component B. More specifically, component C is an oxide ceramic having a Young's modulus higher than that of component B, and may be an ionic conductive oxide ceramic (especially a solid electrolyte), an ionic non-conductive oxide ceramic, or a mixture thereof. From the viewpoint of further improving float and cycle characteristics, it is preferable that component C contains an ionic conductive oxide ceramic (especially a solid electrolyte).

[0055] Oxide ceramics are said to be ionic conductive if, when their resistance is measured by the AC impedance method at 25°C, their ionic conductivity is 1.0 × 10⁻⁶. －８ This refers to exhibiting a value of S / cm or greater. In this specification, oxide ceramics having such ionic conductivity are referred to as "solid electrolytes." On the other hand, oxide ceramics are said not to have ionic conductivity if, when the resistance of the oxide ceramic is measured by the AC impedance method at 25°C, the ionic conductivity is 1.0 × 10⁻⁶. －８ This refers to a value less than S / cm.

[0056] When the Young's moduli of component C and component B are denoted as "Yc (GPA)" and "Yb (GPA)", respectively, "Yc - Yb" is usually 10 GPa or more, preferably 30 GPa or more, more preferably 50 GPa or more, even more preferably 70 GPa or more, and very preferably 80 GPa or more, from the viewpoint of further improving float and cycle characteristics. The upper limit of "Yc - Yb" is not particularly limited, and "Yc - Yb" is usually 300 GPa or less, particularly 220 GPa or less, preferably 190 GPa or less, more preferably 170 GPa or less, and even more preferably 150 GPa or less, from the viewpoint of further improving float and cycle characteristics.

[0057] The Young's modulus Yc of component C is usually greater than 50 GPa, and from the viewpoint of further improving float and cycle characteristics, it is preferably 70 GPa or more, more preferably 90 GPa or more, even more preferably 100 GPa or more, sufficiently preferably 110 GPa or more, even more certainly preferably 120 GPa or more, and particularly preferably 130 GPa or more. The upper limit of the Young's modulus Yc of component C is not particularly limited, and the Young's modulus Yc of component C is usually 220 GPa or less, preferably 190 GPa or less, more preferably 170 GPa or less, and even more preferably 150 GPa or less. With respect to such a Young's modulus of component C, the aforementioned component B usually has a Young's modulus (Yb) of 50 GPa or less (particularly a Young's modulus of 10 GPa or more and 50 GPa or less).

[0058] In this invention, the Young's modulus is measured using the following method. First, a rectangular or cylindrical sample of predetermined dimensions is prepared, and the initial length L of the sample in the tensile direction is measured. ０ The cross-sectional area Z of the sample perpendicular to the tensile direction is measured. Next, when a tensile force (F) is applied to the sample at a constant speed using a tensile testing machine, the displacement (ΔL) of the sample's length in the tensile direction is measured. Here, the tension is applied along the direction in which the sample dimensions are longest; for example, in the case of a rectangular parallelepiped, it is applied along the longest side of the rectangular parallelepiped. The measured initial length L ０ And the strain ε can be calculated using ΔL (ε = ΔL / L ０). Furthermore, the stress σ applied to the sample can be calculated using the tensile force F and the cross-sectional area Z (σ = F / Z). Young's modulus (E) can be determined from the stress-strain curve (σ-ε curve) obtained by changing the tensile force F. In this case, the formula used is "E = σ / ε". That is, in the stress-strain curve, the slope of the linear region in which the strain ε changes in proportion to the stress σ is used as the value of Young's modulus.

[0059] Specific examples of component C include LLZ-based solid electrolytes, LLT-based solid electrolytes, La-free Li-containing oxide ceramics, and Li-free oxide ceramics. From the viewpoint of further improving float characteristics and cycle characteristics, component C is preferably selected from the group consisting of LLZ-based solid electrolytes, LLT-based solid electrolytes, and La-free Li-containing oxide ceramics, and more preferably selected from the group consisting of LLZ-based solid electrolytes.

[0060] LLZ-type solid electrolytes are oxide ceramics (particularly solid electrolytes) containing Li, La, and Zr in their chemical composition, and possess the aforementioned ionic conductivity. For example, LLZ-type solid electrolytes have a chemical composition represented by the following general formula (3-1).

[0061]

[0062] In formula (3-1), A is one or more elements that can be dissolved in the Li site of the LLZ solid electrolyte. More 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"). 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 relationship with oxygen and can have a valency of 3. ＩMore 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). Ｉ From the viewpoint of further improving float characteristics and cycle characteristics, it preferably includes La (lanthanum). Ｉ This may include La (lantern) on its own. B ＩＩ B 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 relationship 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 a component. Ｉ D is 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. Ｉ More specifically, it is one or more elements selected from the group consisting of Zr (zirconium), Hf (hafnium), Ge (germanium), and Sn (tin). Ｉ From the viewpoint of further improving float characteristics and cycle characteristics, it preferably contains Zr (zirconium). Ｉ It may contain Zr (zirconium) alone. ＩＩ D is 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 valencies other than four. ＩＩ For more details, see trivalent D ＩＩ Sc (scandium) as a pentavalent D ＩＩTa (tantalum), Nb (niobium), Sb (antimony), and Bi (bismuth) as hexavalent D ＩＩ It is one or more elements selected from the group consisting of Mo (molybdenum), W (tungsten), and Te (tellurium). ＩＩ From the viewpoint of further improving float characteristics and cycle characteristics, it is preferably one or more elements selected from the group consisting of Ta (tantalum), Nb (niobium), and W (tungsten).

[0063] In equation (3-1), p is expressed by the calculation formula (i): p = ax - (3-b)y + (d-4)z (i).

[0064] 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 is, 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 is the value that can be expressed by the same formula as the average valence of A described above. d is D ＩＩ The average valence of; D ＩＩ The average price is D ＩＩ For example, if there are n1 elements X with valence r+, n2 elements Y with valence s+, and n3 elements Z with valence t+, then this value is expressed by the same formula as the average valence of A described above.

[0065] In equation (3-1), α satisfies 5.0 ≤ α ≤ 8.0, preferably 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, 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, preferably 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, 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. Normally, δ should satisfy 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 from the viewpoint of further improving float and cycle characteristics, preferably 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. 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 further improving float and cycle characteristics, 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. B ＩＩIf the mixture contains multiple elements, the sum of the values ​​corresponding to y for each of those elements should satisfy the above range of y. z satisfies 0.2 ≤ z ≤ 2.2, and from the viewpoint of further improving float and cycle characteristics, preferably 0.2 ≤ y ≤ 1.8, more preferably 0.2 ≤ z ≤ 1.4, even more preferably 0.2 ≤ z ≤ 1.2, and particularly preferably 0.4 ≤ z ≤ 1.0. ＩＩ If the formula contains multiple elements, the sum of the values ​​corresponding to z for each of those elements must satisfy the above range of z.

[0066] From the viewpoint of further improving float characteristics and cycling characteristics, the LLZ-type solid electrolyte preferably has a chemical composition represented by the following general formula (3-1-1). Note that general formula (3-1-1) is one embodiment included in the above general formula (3-1).

[0067]

[0068] In formula (3-1-1), D ＩＩ D in general formula (3-1) ＩＩ It is the same as above. z in equation (3-1-1) is the same as z in general equation (3-1). ω in equation (3-1-1) is the same as ω in general equation (3-1). p in equation (3-1-1) is expressed as p = (d-4)z. Note that d is the same as d in equation (i).

[0069] LLZ-type solid electrolytes include, for example, Li ６．６ La ３ Zr １．６ Ta ０．４ O １２ Li ６．６ La ３ Zr １．６ Nb ０．４ O １２ Li ６．４ La ３ Zr １．６ Wa ０．４ O １２ Li ６ La ３ ZrTaO １２ These are some examples.

[0070] The crystal structure of the LLZ-based solid electrolyte is not particularly limited. For example, from the viewpoint of further improving float characteristics and cycle characteristics, it is preferable that the LLZ-based solid electrolyte has a garnet-type crystal structure. The statement that the LLZ-based solid electrolyte has a garnet-type crystal structure includes not only the case that the LLZ-based solid electrolyte has a "garnet-type crystal structure," but also the case that it has a "garnet-type similar crystal structure." More specifically, the LLZ-based solid electrolyte has a crystal structure that can be recognized as a garnet-type or garnet-type similar crystal structure by those skilled in the field of solid-state batteries in X-ray diffraction. More specifically, LLZ-based solid electrolytes may, in X-ray diffraction, exhibit one or more major peaks corresponding to the Miller indices specific 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-type similar crystal structure, may exhibit one or more major peaks that differ from the one or more major peaks corresponding to the Miller indices specific 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 for a garnet-type similar crystal structure is, for example, ICDD Card No. 00-045-0109.

[0071] LLT-type solid electrolytes are oxide ceramics (particularly solid electrolytes) containing Li, La, and Ti in their chemical composition, and possess the ionic conductivity described above. For example, LLT-type solid electrolytes have a chemical composition represented by the following general formula (3-2).

[0072]

[0073] In equation (3-2), x has the relationship 0.2 ≤ x ≤ 0.4, and from the viewpoint of further improving the float characteristics and cycle characteristics, it preferably has the relationship 0.22 ≤ x ≤ 0.38, more preferably 0.24 ≤ x ≤ 0.36, even more preferably 0.26 ≤ x ≤ 0.34, sufficiently preferably 0.28 ≤ x ≤ 0.32, and even more sufficiently preferably 0.29. y has the relationship y = 2 / 3 - x / 3.

[0074] The crystal structure of the LLT-based solid electrolyte is not particularly limited. For example, from the viewpoint of further improving float characteristics and cycle characteristics, it is preferable that the LLT-based solid electrolyte has a perovskite-type crystal structure. The statement that the LLT-based solid electrolyte has a perovskite-type crystal structure includes not only the case that the LLT-based solid electrolyte has a "perovskite-type crystal structure," but also the case that it has a "perovskite-like crystal structure." More specifically, the LLT-based solid electrolyte has a crystal structure that can be recognized as a perovskite-type or perovskite-like crystal structure by those skilled in the field of solid-state batteries in X-ray diffraction. More specifically, LLT-type solid electrolytes may, in X-ray diffraction, exhibit one or more major peaks corresponding to the Miller indices inherent in so-called perovskite-type crystal structures at a predetermined incident angle, or, as a perovskite-like crystal structure, may exhibit one or more major peaks that differ from the one or more major peaks corresponding to the Miller indices inherent in so-called perovskite-type crystal structures 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. Known diffraction patterns are representative diffraction patterns of perovskite-like crystal structures.

[0075] La-free Li-containing oxide ceramics are oxide ceramics that contain Li in their chemical composition but do not contain La, and do not possess the ionic conductivity described above. For example, La-free Li-containing oxide ceramics have a chemical composition represented by the following general formula (3-3).

[0076]

[0077] In formula (3-3), B ＩＩＩ B is 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. ＩＩＩ More specifically, it is one or more elements selected from the group consisting of Zr (zirconium), Hf (hafnium), and Sn (tin). ＩＩＩFrom the viewpoint of further improving float characteristics and cycle characteristics, it preferably contains one or more elements selected from the group consisting of Zr (zirconium) and Sn (tin). ＩＩＩ This may contain either Zr (zirconium) or Sn (tin) alone. ＩＩＩ If the substance contains multiple elements, the sum of the values ​​corresponding to the content of each of those elements must be 1.

[0078] A specific example of a La-free Li-containing oxide ceramic is, for example, Li ２ ZrO ３ Li ２ SnO ３ These are some examples.

[0079] The crystal structure of the La-free Li-containing oxide ceramic is not particularly limited. For example, from the viewpoint of further improving float properties and cycle properties, it is preferable that the La-free Li-containing oxide ceramic has a rock salt crystal structure. The statement that the La-free Li-containing oxide ceramic has a rock salt crystal structure includes not only the case that it has a "rock salt crystal structure," but also the case that it has a "rock salt-like crystal structure." More specifically, the La-free Li-containing oxide ceramic has a crystal structure that, in X-ray diffraction, can be recognized as a rock salt type or a rock salt-like crystal structure by those skilled in the field of solid-state batteries. More specifically, La-free Li-containing oxide ceramics may, in X-ray diffraction, exhibit one or more major peaks corresponding to Miller indices specific to so-called rock salt crystal structures at a predetermined incident angle, or, as a rock salt-like crystal structure, may exhibit one or more major peaks that differ from the one or more major peaks corresponding to Miller indices specific to so-called rock salt crystal structures 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. Known diffraction patterns are representative diffraction patterns of rock salt-like crystal structures.

[0080] Li-free oxide ceramics are oxide ceramics that do not contain Li in their chemical composition and do not possess the ionic conductivity described above. Li-free oxide ceramics have, for example, a chemical composition represented by the following general formula (3-4).

[0081]

[0082] In formula (3-4), D ＩＩＩ D is 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. ＩＩＩ More specifically, it is one or more elements selected from the group consisting of Zr (zirconium), Hf (hafnium), and Sn (tin). ＩＩＩ From the viewpoint of further improving float characteristics and cycle characteristics, it preferably contains Zr (zirconium). ＩＩＩ It may contain Zr (zirconium) alone. ＩＩＩ If the substance contains multiple elements, the sum of the values ​​corresponding to the content of each of those elements must be 1.

[0083] Specific examples of Li-free oxide ceramics include ZrO ２ , SnO ２ These are some examples.

[0084] The crystalline structure of the Li-free oxide ceramic is not particularly limited; for example, it may have any known crystalline structure, or it may not have any crystalline structure at all.

[0085] The chemical composition of component C refers to the average value (average chemical composition) of the chemical composition of component C in the thickness direction of the positive electrode layer. The chemical composition of component C can be analyzed and measured by fracturing the solid-state battery and performing EDX compositional analysis using SEM-EDX (energy-dispersive X-ray spectroscopy) in a field of view that covers the entire thickness direction of the positive electrode layer.

[0086] The chemical composition and crystal structure of the carbon (C) component in the positive electrode layer may change due to elemental diffusion during sintering. Preferably, the carbon component has the above-described chemical composition and crystal structure in the solid-state battery after sintering together with the negative electrode layer and the solid electrolyte layer.

[0087] The average particle size of component C is not particularly limited and may be, for example, 10 nm to 5 μm. From the viewpoint of further improving float characteristics and cycle characteristics, 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 component C can be measured by the same method as the average particle size of the positive electrode active material described above.

[0088] The average particle size of component C can be determined, for example, by the same method as the method for measuring the average particle size of the positive electrode active material as component A. Alternatively, the average particle size of component C in the positive electrode layer may be determined by identifying component C based on its composition during the chemical composition measurement described above.

[0089] The average particle size of the carbon (C) component in the positive electrode layer may change due to sintering during the manufacturing process of the solid-state battery. The carbon (C) component 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.

[0090] The carbon (C) component of the positive electrode layer can be obtained by the same method as for the positive electrode active material, except that a raw material compound containing a predetermined metal atom is used, or it can be obtained as a commercially available product.

[0091] The content of component C in the positive electrode layer is not particularly limited, but from the viewpoint of further improving float characteristics and cycle characteristics, it is preferably 5 to 95 parts by volume, preferably 5 to 70 parts by volume, more preferably 5 to 60 parts by volume, and even more preferably 40 to 60 parts by volume, per 100 parts by volume of positive electrode active material.

[0092] The carbon content in the positive electrode layer can be measured by known methods. For example, the carbon content in the positive electrode layer can be measured by processing the positive electrode layer with an ion beam to expose the cross-section, and then calculating the area ratio between the area where the constituent elements of carbon are detected by SEM-EDX analysis within a predetermined range of the cross-section and the area within that range. For example, the image processing software "A-Image-kun" can be used to calculate the area ratio.

[0093] The positive electrode layer may further contain sintering aids and / or conductive additives, etc.

[0094] Any sintering aid known in the field of solid-state batteries can be used as a sintering aid. 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. A specific example of such a sintering aid is, 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 These are some examples.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] The positive electrode layer may further contain metal oxides other than the above-mentioned components A, B, C and sintering aids (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 further improving float characteristics and cycle characteristics.

[0099] 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.

[0100] 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.

[0101] The porosity of the positive electrode layer is based on values ​​measured from SEM images after FIB cross-sectional processing.

[0102] 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.

[0103] (Negative electrode layer) The negative electrode layer in the solid-state battery of the present invention 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 in 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).

[0104] 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 -Li ３ VO ４ Type structure, γ ＩＩ -Li ３ VO ４ Examples include oxides having a specific structure. The negative electrode active material is lithium metal, β ＩＩ -Li ３ VO ４ Type structure, γ ＩＩ -Li ３ VO ４ Li-containing oxides having a specific structure may also be used.

[0105] In the negative electrode layer, the oxide is β ＩＩ -Li ３ VO ４ Having a type structure means that the oxide (especially its particles) is β ＩＩ -Li ３ VO ４ This means having a crystal structure of type β, and in a broader sense, according to those skilled in the field of solid-state batteries, β ＩＩ -Li ３ VO ４ This refers to having a crystal structure that can be recognized as a β-type crystal structure. In a narrower sense, in the negative electrode layer, the oxide is β ＩＩ -Li ３ VO ４ Having a type structure means that the oxide (especially its particles) exhibits a so-called β-type structure in X-ray diffraction. ＩＩ -Li ３ VO ４ This means that one or more major peaks corresponding to the Miller indices specific to the crystal structure of the type are shown at a given angle of incidence. Preferably used β ＩＩ -Li ３ VO ４ Li-containing oxides having a type structure include Li ３ VO ４ These are some examples.

[0106] In the negative electrode layer, the oxide is γ ＩＩ -Li３ VO ４ Having a type structure means that the oxide (especially its particles) has a γ ＩＩ -Li ３ VO ４ This means having a crystal structure of type γ, and in a broader sense, according to those skilled in the field of solid-state batteries, γ ＩＩ -Li ３ VO ４ This refers to having a crystal structure that can be recognized as a type of crystal structure. In a narrower sense, in the negative electrode layer, the oxide is γ ＩＩ -Li ３ VO ４ Having a type structure means that the oxide (especially its particles) exhibits a so-called γ structure in X-ray diffraction. ＩＩ -Li ３ VO ４ This means that one or more major peaks corresponding to the Miller indices specific to the crystal structure of the type are shown at a predetermined angle of incidence (x-axis). Preferably used γ ＩＩ -Li ３ VO ４ Li-containing oxides having a type structure include Li ３．２ V ０．８ Si ０．２ O ４ These are some examples.

[0107] 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 EDX 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.

[0108] The negative electrode active material can be obtained by the same method as the positive electrode active material, except that a raw material compound containing a predetermined metal atom is used, or it can be obtained as a commercially available product.

[0109] 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 chemical composition and crystal structure in the solid-state battery after sintering together with the positive electrode layer and the solid electrolyte layer.

[0110] 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%.

[0111] The negative electrode layer may further contain a so-called solid electrolyte, a sintering aid, and / or a conductive aid.

[0112] 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.

[0113] 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.

[0114] 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 conductive additive in the negative electrode layer, the same compounds as those used for the conductive additive in the positive electrode layer can be used.

[0115] 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.

[0116] 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.

[0117] The porosity of the negative electrode layer is measured using the same method as the porosity of the positive electrode layer.

[0118] 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.

[0119] (Solid Electrolyte Layer) In the solid battery of the present invention, the solid electrolyte layer includes a solid electrolyte.

[0120] The solid electrolyte contained in the solid electrolyte layer is not particularly limited and may be any solid electrolyte contained in the solid electrolyte layer in the field of solid-state batteries. Such solid electrolytes may be oxide systems, for example, garnet-type oxides contained in the positive electrode layer, Li ２ ZrO ３ γ-Li ３ VO ４ Examples include one or more materials selected from solid electrolytes with a structure and oxide glass ceramic lithium ion conductors. From the viewpoint of further improving float characteristics and cycle characteristics, it is preferable that the solid electrolyte layer contains the C component (especially LLZ-type solid electrolyte) contained in the positive electrode layer.

[0121] γ-Li ３ VO ４ Examples of solid electrolytes having a structure include solid electrolytes having an average chemical composition represented by the following general formula (I).

[0122]

[0123] In formula (I), 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, in particular 0 ≤ x ≤ 0.2. y satisfies 0 ≤ y ≤ 1.0, in particular 0.20 ≤ y ≤ 0.50. a is the average valency 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 of element X with valence a+, n2 elements of element Y with valence b+, and n3 elements of element 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 when D consists of, for example, 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+.

[0124] γ-Li ３ VO ４ A specific example of a solid electrolyte with a structure is, for example, 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 Si 0.4) O ４ Li ３．５ (P ０．５ Ge ０．５ ) O ４ These are some examples.

[0125] 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).

[0126] 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.

[0127] The solid electrolyte layer may further contain, for example, a sintering aid in addition to the solid electrolyte. The same compounds used as the sintering aid in the positive electrode layer can be used as the sintering aid in the solid electrolyte layer.

[0128] The content of the sintering aid in the solid electrolyte layer is not particularly limited, but from the viewpoint of further improving float characteristics and cycle characteristics, it is preferably 0% to 20% by volume, and more preferably 1% to 10% by volume.

[0129] 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 further improving float and cycle characteristics. The thickness of the solid electrolyte layer is determined using the average value of thicknesses measured at 10 arbitrary locations in the SEM image.

[0130] In the solid electrolyte layer, the porosity is not particularly limited, but from the viewpoint of further improving the float characteristics and cycle characteristics, it is preferably 20% by volume or less, more preferably 15% by volume or less, and even more preferably 10% by volume or less.

[0131] The porosity of the solid electrolyte layer is measured using the same method as the porosity of the positive electrode layer.

[0132] [Method for manufacturing 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.

[0133] The green sheet method will now be explained. First, a paste is prepared by appropriately mixing components B and C, a solvent, a binder, etc., with the positive electrode active material (component A). This paste is 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 metal oxides, conductive additives and / or sintering aids.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] Next, a laminate is prepared by appropriately stacking the first to third green sheets. The prepared laminate may be pressed. Preferred pressing methods include hydrostatic pressing. After that, a solid battery can be obtained by sintering the laminate at, for example, 600°C to 1000°C.

[0139] The printing method will now be explained. The printing method is the same as the green sheet method, except for the following: - Prepare inks for each layer that have the same composition as the pastes for each layer used to obtain the green sheet, except that the solvent and resin amounts are suitable for use as inks. - Print and laminate using the inks for each layer to create a laminate.

[0140] 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.

[0141] The present invention, as described above, encompasses 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 comprises a positive electrode active material, a solid electrolyte having a LISICON-type crystal structure, and an oxide ceramic having a Young's modulus higher than that of the solid electrolyte. <2> The solid-state battery according to <1>, wherein the volume ratio of the solid electrolyte to the oxide ceramic is 5 / 95 or more and 95 / 5 or less. <3> The solid-state battery according to <2>, wherein the volume ratio of the solid electrolyte to the oxide ceramic is 30 / 70 or more and 95 / 5 or less. <4> The solid-state battery according to any one of <1> to <3>, wherein the content of the solid electrolyte is 5 to 120 volumes per 100 volumes of the positive electrode active material, and the content of the oxide ceramic is 5 to 95 volumes per 100 volumes of the positive electrode active material. <5> The solid battery according to <4>, wherein the content of the solid electrolyte is 30 to 95 volumes per 100 volumes of the positive electrode active material, and the content of the oxide ceramics is 5 to 70 volumes per 100 volumes of the positive electrode active material. <6> The solid battery according to any one of <1> to <5>, wherein the positive electrode active material includes a positive electrode active material having a rock salt type structure. <7> The solid battery according to <6>, wherein the positive electrode active material has a chemical composition represented by general formula (1): [In formula (1), 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), Al (aluminum), and Ti (titanium); α satisfies 0.8 ≤ α ≤ 1.5; β satisfies 0.8 ≤ β ≤ 1.5; γ satisfies 0 ≤ γ ≤ 0.24; ω satisfies 1.8 ≤ ω ≤ 2.2]. <8> The solid electrolyte is given by the following general formula (2): (In formula (2), A is one or more elements selected from the group consisting of Na (sodium), K (potassium), Mg (magnesium), Ca (calcium), Al (aluminum), Ga (gallium), Zn (zinc), Fe (iron), Cr (chromium), and Co (cobalt); B is one or more elements selected from the group consisting of Zn (zinc), Al (aluminum), Ga (gallium), Si (silicon), Ge (germanium), Sn (tin), P (phosphorus), As (arsenic), Ti (titanium), Mo (molybdenum), W (tungsten), Fe (iron), Cr (chromium), and Co (cobalt); x has the relationship 0 ≤ x ≤ 1.0; y has the relationship 0 ≤ y ≤ 1.0; a is the average valence of A; b is the average valence of B) A solid battery according to any one of <1> to <7>, comprising a solid electrolyte having an average chemical composition represented by . <9> A solid battery according to any one of <1> to <8>, wherein the oxide ceramic is either an ion-conductive solid electrolyte or an oxide ceramic that does not have ion conductivity. <10> A solid battery according to any one of <1> to <9>, wherein the oxide ceramic is selected from the group consisting of LLZ-type solid electrolyte, LLT-type solid electrolyte, La-free Li-containing oxide ceramic, and Li-free oxide ceramic. <11> A solid battery according to any one of <1> to <10>, wherein the volume ratio of the solid electrolyte to the oxide ceramic is 30 / 70 or more and 95 / 5 or less, the solid electrolyte comprises a solid electrolyte containing V (vanadium), and the oxide ceramic is selected from the group consisting of LLZ-type solid electrolyte, LLT-type solid electrolyte, and the La-free Li-containing oxide ceramic. <12> The volume ratio of the solid electrolyte to the oxide ceramics is 30 / 70 or more and 95 / 5 or less, and the solid electrolyte is given by the following general formula (2): The solid electrolyte has an average chemical composition represented by formula (2), where A is one or more elements selected from the group consisting of Na (sodium), K (potassium), Mg (magnesium), Ca (calcium), Al (aluminum), Ga (gallium), Zn (zinc), Fe (iron), Cr (chromium), and Co (cobalt); B is one or more elements selected from the group consisting of Zn (zinc), Al (aluminum), Ga (gallium), Si (silicon), Ge (germanium), Sn (tin), P (phosphorus), As (arsenic), Ti (titanium), Mo (molybdenum), W (tungsten), Fe (iron), Cr (chromium), and Co (cobalt); x has the relationship 0 ≤ x ≤ 1.0; y has the relationship 0 < y ≤ 0.65; a is the average valence of A; b is the average valence of B) The solid battery according to any one of <1> to <10>, wherein the oxide ceramic is selected from the group consisting of LLZ-based solid electrolytes. <13> The solid battery according to any one of <1> to <12>, wherein the positive electrode layer and the negative electrode layer are layers capable of intercalating and deintercalating lithium ions. <14> The solid battery according to any one of <1> to <13>, wherein the solid electrolyte layer is integrally sintered with the positive electrode layer and the negative electrode layer as sintered bodies. <15> The solid battery according to any one of <1> to <14>, wherein the oxide ceramic has a Young's modulus greater than 50 GPa.

[0142] [Manufacturing of positive electrode active material] ・LiCoO ２ LiCoO ２ Cobalt oxide Co ３ O ４ and lithium carbonate Li ２ CO ３ It was synthesized from the following: 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. 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 crushed in a mortar to obtain LiCoO ２The average particle size was 2 μm. The positive electrode active material also had the same average particle size in the positive electrode half-cell described later.

[0143] [Production of LISICON-type solid electrolyte] The LISICON-type solid electrolyte used in the examples and comparative examples was produced as follows. The raw material was lithium hydroxide monohydrate LiOH·H. ２ O, Vanadium pentoxide V ２ O ５ silicon dioxide (SiO₂) ２ Germanium oxide (GeO) ２ Phosphorus oxidized P ２ O ５ The following was used. Each raw material was weighed appropriately so that its chemical composition was the predetermined chemical composition, water was added, and the mixture was sealed in a 100 ml polyethylene poly pot and rotated on a pot rack at 150 rpm for 16 hours to mix the raw materials. After the obtained slurry was evaporated and dried, it was calcined in air at 800°C for 5 hours. Alcohol was added to the obtained calcined powder, and it was again sealed in a 100 ml polyethylene poly pot and rotated on a pot rack at 150 rpm for 16 hours to pulverize it. The pulverized powder was then calcined again at 900°C for 5 hours. After that, a toluene-acetone mixed solvent was added to the obtained calcined powder, and it was pulverized in a planetary ball mill for 6 hours and dried to obtain the LISICON type solid electrolyte (powder). The above powder was confirmed to have no compositional deviation by ICP measurement. All of the LISICON type solid electrolytes used in the examples and comparative examples were found to have a γ ion by XRD measurement. ＩＩ It had a specific structure. The average particle size was 150 nm. The LISICON-type solid electrolyte also had this average particle size in the positive electrode half-cell described later.

[0144] [Preparation of LLZ-based solid electrolytes] The LLZ-based solid electrolytes used in the examples and comparative examples were prepared as follows. The raw material was lithium hydroxide monohydrate LiOH·H ２ O, lanthanum hydroxide La(OH) ３ Zirconium oxide (ZrO) ２ Tantalum oxide Ta ２ O ５ Niobium oxide (Nb) ２ O ５、Tungsten oxide WO ３ The following was used. Each raw material was weighed to achieve the specified chemical composition, water was added, and the mixture was sealed in a 100 ml polyethylene poly pot and rotated on a pot stand at 150 rpm for 16 hours to mix the raw materials. In addition, lithium hydroxide monohydrate LiOH·H was used as the Li source. ２ O was added in a 3 wt% excess relative to the target composition, taking into account Li deficiencies during sintering. 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 ground in a planetary ball mill for 6 hours. This ground powder was dried to obtain a garnet-type oxide powder. XRD measurement of the above powder confirmed that a single garnet-type oxide was obtained. ICP measurement confirmed that there was no compositional deviation in the above powder. The average particle size was 150 nm. The LLZ-based solid electrolyte also had the same average particle size in the positive electrode half-cell described later.

[0145] [Production of LLT-based solid electrolytes] LLTO was synthesized by the sol-gel method. Isopropoxytitanium Ti[OCH(CH ３ ) ２ ] ４ Lanthanum acetate La(CH ３ COO) ３ ・xH ２ O, and lithium acetate Li(CH) ３ COO) ２ ・H ２ O was used as a precursor. In addition, lactic acid CH was used as a peptizing agent. ３CH(OH)COOH was used, and distilled water was used as the solvent. A titanium dioxide sol was prepared using these. To improve the stability of the titanium sol, the ratios of isopropoxytitanium to lactic acid and isopropoxytitanium to water were set at 2% and 3% molar ratios, respectively. The aqueous solution of lactic acid was stirred at 85°C for 15 minutes. Then, isopropoxytitanium was carefully and quickly added to the mixture, taking care to prevent hydrolysis of isopropoxytitanium. The resulting mixture was stirred continuously at 85°C for 72 hours until a completely transparent sol was obtained. Next, lanthanum and lithium acetate were dissolved in distilled water, and this solution was mixed with the titanium dioxide sol obtained in the appropriate stoichiometric ratio. This mixture was stirred for 2 hours and then dried at 60°C for 96 hours. The recovered translucent gel was crushed using an agate mortar and then heat-treated in air at different temperatures. The average particle size was 150 nm. The LLT-type solid electrolyte also possessed the same average particle size in the positive electrode half-cell, as described later.

[0146] [Li ２ ZrO ３ [Manufacturing] The raw materials include lithium hydroxide monohydrate LiOH·H ２ O, Zirconium oxide (ZrO) ２ The following was used. Each raw material was weighed to achieve the desired chemical composition, water was added, and the mixture was sealed in a 100 ml polyethylene poly pot and rotated on a pot stand at 150 rpm for 16 hours to mix the raw materials. After evaporating and drying the resulting slurry, the target phase was obtained by calcining at 800°C for 12 hours. A toluene-acetone mixed solvent was added to the resulting calcined powder and it was ground in a planetary ball mill for 6 hours. This ground powder was dried to obtain a garnet-type oxide powder. XRD measurement of the above powder confirmed that a single garnet-type oxide had been obtained. ICP measurement of the above powder confirmed that there was no compositional deviation. The average particle size was 150 nm. Li ２ ZrO ３ The same average particle size was also present in the positive electrode half-cell, as described later.

[0147] [Li ２ SnO ３[Manufacturing] The raw materials include lithium hydroxide monohydrate LiOH·H ２ O, tin oxide (SnO) ２ The following was used. Each raw material was weighed to achieve the desired chemical composition, water was added, and the mixture was sealed in a 100 ml polyethylene poly pot and rotated on a pot stand at 150 rpm for 16 hours to mix the raw materials. After evaporating and drying the resulting slurry, the target phase was obtained by calcining at 800°C for 12 hours. A toluene-acetone mixed solvent was added to the resulting calcined powder and it was ground in a planetary ball mill for 6 hours. This ground powder was dried and Li ２ SnO ３ It was processed into a powder. The average particle size was 150 nm. Li ２ SnO ３ The same average particle size was also present in the positive electrode half-cell, as described later.

[0148] [ZrO ２ [Manufacturing of] Commercially available ZrO ２ (Manufactured by High Purity Chemicals Co., Ltd.) was used after being crushed. The average particle size was 150 nm. ZrO ２ The same average particle size was also present in the positive electrode half-cell, as described later.

[0149] [Manufacturing of sintering aids] Lithium hydroxide monohydrate LiOH・H2O, Boron oxide B ２ O ３ The chemical composition of each starting material and sintering aid was Li ４ B ２ O ５ The ingredients were weighed appropriately, mixed thoroughly in a mortar, and then baked at 650°C for 5 hours.

[0150] [Manufacturing of Positive Electrode Half Cells] (Examples 1-19 and Comparative Examples 1-2) The solid-state batteries of each example or comparative example were manufactured as follows. First, as shown in Tables 4-7, a mixed powder was obtained by weighing and mixing predetermined amounts of component B (e.g., LISICON-type solid electrolyte powder), component C (e.g., LLZ-type solid electrolyte powder), and sintering aid powder with 100 volumes of positive electrode active material powder as component A. The amount of sintering aid was equivalent to "0.064 × x" when the amount of component B relative to 100 volumes of component A was x (volume). A positive electrode layer slurry was prepared by kneading the mixed powder with alcohol and a binder, and a first green sheet for forming the positive electrode layer was formed by applying the slurry onto a sheet and drying it. Similarly, a solid electrolyte layer slurry was prepared by kneading garnet-type solid electrolyte powder with alcohol and a binder, and a second green sheet for forming the solid electrolyte layer was formed by drying it. 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 positive electrode layer and a solid electrolyte layer. After removing the binder at 400°C, the positive electrode layer and solid electrolyte layer were co-fired by pressurized sintering at 800°C for 60 minutes under a pressure of 100 MPa. After sintering, the thickness of the positive electrode layer was approximately 15 μm, and the thickness of the solid electrolyte layer was approximately 200 μm. Subsequently, metallic Li was attached to the surface of the solid electrolyte layer opposite the positive electrode layer as a counter electrode and reference electrode, and sealed with a 2032 type coin cell to obtain a solid battery.

[0151] [Evaluation 1: Float Characteristics (85°C Float Test)] The fabricated positive electrode half-cell was charged using a constant current charge-discharge test at a current density equivalent to 0.2C at 25°C until it reached an upper voltage limit of 4.2V (vs. Li / Li+). It was then discharged at a current density equivalent to 0.2C at 25°C until it reached a lower voltage limit of 3.0V (vs. Li / Li+). This initial discharge capacity was defined as 100%. A float test was performed for one week at 3.93V (vs. Li / Li+) in an 85°C environment. A float test is a test in which the charging voltage of the battery is maintained at a constant value using an external DC power supply. After the float test was completed, the coin cell was cooled to 25°C and then discharged at a current density equivalent to 0.2C until it reached a lower voltage limit of 3.0V (vs. Li / Li+). The battery was charged at a current density equivalent to 25°C and 0.2C until it reached an upper voltage limit of 4.2V (vs. Li / Li+). It was then discharged at a current density equivalent to 25°C and 0.2C until it reached a lower voltage limit of 3.0V (vs. Li / Li+). The discharge capacity at this point was used as the discharge capacity after 85°C float, and the discharge capacity retention rate after 85°C float was calculated by comparing it with the initial discharge capacity.

[0152] ◎: 95% or less capacity retention rate (Excellent); ○: 90% or less capacity retention rate < 95% (Good); △: 80% or less capacity retention rate < 90% (Acceptable) (No practical problems); ×: Capacity retention rate < 80% (Unacceptable) (Practical problems exist).

[0153] [Evaluation 2: Cycle Characteristics (25°C Cycle Test)] The fabricated positive electrode half-cell was charged using a constant current charge-discharge test at a current density equivalent to 25°C and 1C until it reached an upper voltage limit of 4.2V (vs. Li / Li+). It was then discharged at a current density equivalent to 25°C and 1C until it reached a lower voltage limit of 3.0V (vs. Li / Li+). This was considered one cycle, and the same charge-discharge process was repeated 100 times. The capacity retention rate after 100 cycles at 25°C was calculated by comparing the initial discharge capacity (set as 100%) with the discharge capacity after 100 cycles.

[0154] ◎: 88% ≤ Capacity retention rate (Excellent); ○: 81% ≤ Capacity retention rate < 88% (Good); △: 80% ≤ Capacity retention rate < 81% (Acceptable) (No practical problems); ×: Capacity retention rate < 80% (Unacceptable) (Practical problems exist).

[0155] [Overall Judgment] An overall judgment was made based on the results of the float characteristics and cycle characteristics. ◎: All judgment results were ◎. ○: The lowest judgment result among all judgment results was ○. △: The lowest judgment result among all judgment results was △. ×: The lowest judgment result among all judgment results was ×.

[0156] [Measurement of Young's Modulus] First, a rectangular parallelepiped sample with dimensions of 40 mm × 5 mm × 1 mm was prepared. More specifically, a rectangular parallelepiped sample was manufactured using the predetermined material to be measured under the same conditions as for the preparation of the positive electrode half-cell described above. More specifically, a sample slurry was prepared by kneading only the predetermined material (component A, component B, or component C) with alcohol and a binder. This sample slurry was then applied to a sheet and dried to form a sample green sheet for the composition of the sample. A sample precursor was prepared by laminating the sample green sheets as appropriate. The prepared sample precursor was pressurized using a hydrostatic press method and cut as appropriate to obtain a sample laminate. The binder was removed from the sample laminate at 400°C, and then the sample (fired body) was manufactured by pressurizing and sintering at 800°C for 60 minutes under a pressure of 100 MPa. For the obtained sample, the initial length L of the sample in the tensile direction was measured. ０ The cross-sectional area Z of the sample perpendicular to the tensile direction was measured. Next, when a tensile force (F) was applied to the sample at a constant speed using a tensile testing machine, the displacement (ΔL) of the sample's length in the tensile direction was measured. Here, the tension was applied along the direction of the longest dimension of the sample; for example, in the case of a rectangular parallelepiped, it was applied along the longest side of the rectangular parallelepiped. The measured initial length L ０ The strain ε was calculated using ΔL (ε = ΔL / L ０). Furthermore, the stress σ applied to the sample was calculated using the tensile force F and the cross-sectional area Z (σ = F / Z). Young's modulus (E) was determined from the stress-strain curve (σ-ε curve) obtained by changing the tensile force F. The formula used in this case was "E = σ / ε". That is, the slope of the linear region in the stress-strain curve where the strain ε changes in proportion to the stress σ was used as the value of Young's modulus. The Young's modulus of the positive electrode active material manufactured as component A was 370 GPa. The Young's modulus of each of the LISICON-type solid electrolytes manufactured as component B was less than 50 GPa.

[0157] [Rock Salt Crystal Structure] The positive electrode active material used in the examples was confirmed to have a rock salt crystal structure. Specifically, the rock salt crystal structure was confirmed by obtaining an X-ray diffraction pattern that can be attributed to a rock salt crystal structure from X-ray diffraction (XRD measurement) (ICDD Card No. 00-001-1241). The C component used in Examples 17 and 18 was also confirmed to have a rock salt crystal structure, similar to the positive electrode active material described above.

[0158] [LISICON-type crystal structure] It was confirmed that component B used in the examples has a LISICON-type crystal structure. Specifically, the LISICON-type crystal structure was confirmed by obtaining an X-ray diffraction pattern that can be attributed to a LISICON-type crystal structure from X-ray diffraction (XRD measurement).

[0159] [Garnet-type crystal structure] The LLZ-based solid electrolyte used in the examples was confirmed to have a garnet-type crystal structure. Specifically, the garnet-type crystal structure was confirmed by obtaining an X-ray diffraction pattern that can be attributed to a garnet-like crystal structure from X-ray diffraction (XRD measurement) (ICDD Card No. 00-045-0109).

[0160] [Perovskite-type crystal structure] It was confirmed that the C component used in Example 16 has a perovskite-type crystal structure.

[0161]

[0162] Comparative Example 1 showed that the system using only a Garnet-type solid electrolyte in the cathode layer exhibited excellent cycle characteristics, but suffered significant capacity degradation after 85°C float. Comparative Example 2 showed that the system using only a LISICON-type solid electrolyte in the cathode layer had high 85°C float resistance, but suffered significant cycle degradation. Examples 1 to 5 showed that the system using both a LISICON-type solid electrolyte and a Garnet-type solid electrolyte in the cathode layer exhibited high float resistance and suppressed cycle degradation.

[0163]

[0164] Examples 6 to 12 showed that systems using LISICON-type solid electrolytes and Garnet-type solid electrolytes in the positive electrode layer exhibited high float resistance and suppressed cycle degradation. The effects of the present invention were obtained with any composition of LISICON.

[0165]

[0166] Examples 13 to 15 showed that systems using a LISICON-type solid electrolyte and a Garnet-type solid electrolyte in the positive electrode layer exhibited high float resistance and suppressed cycle degradation. The effects of the present invention were also obtained with any Garnet-type solid electrolyte composition.

[0167]

[0168] From Example 16, it was found that by adding a LISICON-type solid electrolyte and a solid electrolyte other than a Garnet-type solid electrolyte as fillers to the cathode layer, float resistance was increased and cycle degradation was suppressed. This suppression of cycle degradation is thought to be due to an improvement in the mechanical strength of the cathode layer. From Examples 17, 18, and 19, it was found that by adding a LISICON-type solid electrolyte and an inorganic material other than a solid electrolyte (oxide ceramics) as fillers to the cathode layer, float resistance was increased and cycle degradation was suppressed. This suppression of cycle degradation is thought to be due to an improvement in the mechanical strength of the cathode layer.

[0169] The solid-state battery of the present invention can be used in various fields where battery use or energy storage is anticipated. While this is merely an example, 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 fields such as earphones and hearing aids), pharmaceutical applications (fields such as medication management systems), as well as IoT fields and space and deep-sea applications (for example, space probes and submersible research vessels, etc.).

Claims

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 comprises a positive electrode active material, a solid electrolyte having a LISICON-type crystal structure, and an oxide ceramic having a Young's modulus higher than that of the solid electrolyte.

2. The solid battery according to claim 1, wherein the volume ratio of the solid electrolyte to the oxide ceramics is 5 / 95 or more and 95 / 5 or less.

3. The solid battery according to claim 2, wherein the volume ratio of the solid electrolyte to the oxide ceramics is 30 / 70 or more and 95 / 5 or less.

4. The solid battery according to any one of claims 1 to 3, wherein the content of the solid electrolyte is 5 to 120 volumes per 100 volumes of the positive electrode active material, and the content of the oxide ceramics is 5 to 95 volumes per 100 volumes of the positive electrode active material.

5. The solid battery according to claim 4, wherein the content of the solid electrolyte is 30 to 95 volumes per 100 volumes of the positive electrode active material, and the content of the oxide ceramics is 5 to 70 volumes per 100 volumes of the positive electrode active material.

6. The solid battery according to any one of claims 1 to 5, wherein the positive electrode active material includes a positive electrode active material having a rock salt type structure.

7. The solid battery according to claim 6, wherein the positive electrode active material has a chemical composition represented by the following general formula (1): [In formula (1), 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), Al (aluminum), and Ti (titanium); α satisfies 0.8 ≤ α ≤ 1.5; β satisfies 0.8 ≤ β ≤ 1.5; γ satisfies 0 ≤ γ ≤ 0.24; ω satisfies 1.8 ≤ ω ≤ 2.2].

8. The solid electrolyte is given by the following general formula (2): (In formula (2), A is one or more elements selected from the group consisting of Na (sodium), K (potassium), Mg (magnesium), Ca (calcium), Al (aluminum), Ga (gallium), Zn (zinc), Fe (iron), Cr (chromium), and Co (cobalt); B is one or more elements selected from the group consisting of Zn (zinc), Al (aluminum), Ga (gallium), Si (silicon), Ge (germanium), Sn (tin), P (phosphorus), As (arsenic), Ti (titanium), Mo (molybdenum), W (tungsten), Fe (iron), Cr (chromium), and Co (cobalt); x has the relationship 0 ≤ x ≤ 1.0; y has the relationship 0 ≤ y ≤ 1.0; a is the average valence of A; b is the average valence of B) A solid battery according to any one of claims 1 to 7, comprising a solid electrolyte having an average chemical composition represented by [the formula shown].

9. The solid battery according to any one of claims 1 to 8, wherein the oxide ceramic is either a solid electrolyte having ion conductivity or an oxide ceramic that does not have ion conductivity.

10. The solid battery according to any one of claims 1 to 9, wherein the oxide ceramic is selected from the group consisting of LLZ-type solid electrolyte, LLT-type solid electrolyte, La-free Li-containing oxide ceramic, and Li-free oxide ceramic.

11. The solid battery according to any one of claims 1 to 10, wherein the volume ratio of the solid electrolyte to the oxide ceramics is 30 / 70 or more and 95 / 5 or less, the solid electrolyte includes a solid electrolyte containing V (vanadium), and the oxide ceramics are selected from the group consisting of LLZ-type solid electrolytes, LLT-type solid electrolytes, and the La-free Li-containing oxide ceramics.

12. The volume ratio of the solid electrolyte to the oxide ceramics is 30 / 70 or more and 95 / 5 or less, and the solid electrolyte is given by the following general formula (2): The solid electrolyte comprises an average chemical composition represented by formula (2), where A is one or more elements selected from the group consisting of Na (sodium), K (potassium), Mg (magnesium), Ca (calcium), Al (aluminum), Ga (gallium), Zn (zinc), Fe (iron), Cr (chromium), and Co (cobalt); B is one or more elements selected from the group consisting of Zn (zinc), Al (aluminum), Ga (gallium), Si (silicon), Ge (germanium), Sn (tin), P (phosphorus), As (arsenic), Ti (titanium), Mo (molybdenum), W (tungsten), Fe (iron), Cr (chromium), and Co (cobalt); x has the relationship 0 ≤ x ≤ 1.0; y has the relationship 0 < y ≤ 0.65; a is the average valence of A; b is the average valence of B. The solid battery according to any one of claims 1 to 10, wherein the oxide ceramic is selected from the group consisting of LLZ-based solid electrolytes.

13. The solid-state battery according to any one of claims 1 to 12, wherein the positive electrode layer and the negative electrode layer are layers capable of intercalating and deintercalating lithium ions.

14. The solid-state battery according to any one of claims 1 to 13, wherein the solid electrolyte layer is integrally sintered with the positive electrode layer and the negative electrode layer as sintered bodies.

15. The solid-state battery according to any one of claims 1 to 14, wherein the oxide ceramic has a Young's modulus of more than 50 GPa.

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