Solid-state battery

Abstract

Provided is a solid-state battery in which an increase in interface resistance and a decrease in discharge capacity, which are caused by use in a high-temperature environment, are more sufficiently suppressed. This solid-state battery is provided with a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, and is characterized in that: the positive electrode layer contains a positive electrode active material having a layered rock salt structure and an oxide having a garnet structure; the positive electrode active material contains Mg (magnesium) and / or Al (aluminum), and the oxide does not contain Al (aluminum).

Description

Technical Field

[0001] The present invention relates to a solid battery. Background Art

[0002] In recent years, as a power source for portable electronic devices such as mobile phones and portable personal computers, the demand for batteries has increased significantly. As a battery for such uses, a sintered solid secondary battery (so-called "solid battery") using a solid electrolyte as an electrolyte and other constituent elements also made of solids is being developed. The solid battery is particularly expected to be used at high temperatures where it is difficult to use in a liquid secondary battery with a liquid electrolyte.

[0003] As a solid battery, for example, a solid battery having a positive electrode layer in which lithium cobalt oxide (LCO) as a positive electrode active material and a garnet-type oxide (for example, Li7La3Zr2O 12 such as so-called LLZ) are combined has been reported (Patent Documents 1 and 2).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: WO18 / 025649

[0007] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2021-174682 Summary of the Invention

[0008] Technical Problem to be Solved by the Invention

[0009] The inventors of the present invention have found that in a solid battery using the existing positive electrode layer as described above, the following problems occur. When the solid battery is placed in a high-temperature environment such as in a high-temperature floating charge test (for example, 60 °C) or when the solid battery is always in a fully charged state, the interfacial resistance between LCO and the garnet-type oxide increases significantly and / or the discharge capacity decreases significantly.

[0010] An object of the present invention is to provide a solid battery that more sufficiently suppresses the increase in interfacial resistance and the decrease in discharge capacity in a high-temperature environment.

[0011] Technical Solution for Solving the Technical Problem

[0012] The present invention is an invention based on in-depth research on the respective compositions of LCO and the garnet-type oxide in the positive electrode layer, and finding a composition that can significantly suppress the deterioration of cell characteristics in a high-temperature environment.

[0013] The present invention relates to a solid battery,

[0014] It includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer.

[0015] The positive electrode layer contains a positive electrode active material having a layered rock salt structure and an oxide having a garnet structure.

[0016] The positive electrode active material contains at least one of Mg (magnesium) or Al (aluminum).

[0017] The oxide substantially does not contain Al (aluminum).

[0018] Effects of the Invention

[0019] The solid battery of the present invention can more sufficiently suppress the reduction of the discharge capacity in a high-temperature environment. Description of the Drawings

[0020] Figure 1 It is a schematic cross-sectional view showing an embodiment of the relationship between the positive electrode active material and the garnet-type oxide in the positive electrode layer of the solid battery according to the present invention.

[0021] Figure 2 It is a graph for explaining the "size of the arc" used to calculate the interface resistance increase rate in the examples.

[0022] Figure 3A It is a TEM photograph (left side) near the interface between the positive electrode active material and the garnet-type oxide and a TEM photograph (right side) of its Mg distribution mapping for the sample of Example 2.

[0023] Figure 3B It shows in Figure 3A In the left TEM photograph, the measurement results when measuring the Mg element from the interface between the positive electrode active material and the garnet-type oxide into the positive electrode active material.

[0024] Figure 4A It is a TEM photograph (left side) near the interface between the positive electrode active material and the garnet-type oxide and a TEM photograph (right side) of its Al distribution mapping for the sample of Example 4.

[0025] Figure 4B It shows in Figure 4A In the left TEM photograph, the measurement results when measuring the Al element from the interface between the positive electrode active material and the garnet-type oxide into the positive electrode active material. Detailed Description of the Invention

[0026] [Solid Battery]

[0027] The present invention provides a solid-state battery. As used in this specification, the "solid-state battery" generally refers to a battery whose constituent elements (especially the electrolyte layer) are composed of solids, and in a narrow sense, it refers to an "all-solid-state battery" whose constituent elements (especially all constituent elements) are composed of solids. The "solid-state battery" as used in this specification includes a so-called "secondary battery" that can be repeatedly charged and discharged and a "primary battery" that can only be discharged. The "solid-state battery" is preferably a "secondary battery". The "secondary battery" is not overly restricted by this name and may also include electrochemical devices such as "energy storage devices".

[0028] The solid-state battery of the present invention includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer, and generally has a laminated structure in which the solid electrolyte layer is disposed between the positive electrode layer and the negative electrode layer. As long as a solid electrolyte layer is provided between the positive electrode layer and the negative electrode layer, two or more layers can be laminated respectively. The solid electrolyte layer is in contact with the positive electrode layer and the negative electrode layer and is sandwiched by them. It is also possible that the positive electrode layer and the solid electrolyte layer form an integral sintering of sintered bodies with each other, and / or the negative electrode layer and the solid electrolyte layer form an integral sintering of sintered bodies with each other. The formation of an integral sintering of sintered bodies with each other means that two or more adjacent or contacting components (especially layers) are joined by sintering. Here, these two or more components (especially layers) are all sintered bodies, but they can also be sintered integrally. 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 form an integral sintering of sintered bodies with each other, and the negative electrode layer and the solid electrolyte layer form an integral sintering between sintered bodies.

[0029] (Positive electrode layer)

[0030] In the solid-state battery of the present invention, specifically, the positive electrode layer includes a positive electrode active material having a layered rock salt-type structure and containing at least one of Mg (magnesium) or Al (aluminum), and an oxide having a garnet-type crystal structure and not containing Al (aluminum). In the present invention, by combining the above-mentioned specific positive electrode active material and specific garnet-type oxide in the positive electrode layer, it is possible to more sufficiently suppress the increase in the interfacial resistance between the positive electrode active material and the garnet-type oxide, and to more sufficiently suppress the reduction in the discharge capacity. The positive electrode layer may also have the form of a sintered body including specific positive electrode active material particles and specific garnet-type oxide particles. The positive electrode layer can be a layer capable of inserting and extracting or intercalating and deintercalating ions (especially lithium ions). As the medium ions of the positive electrode layer, as long as they can be charged and discharged, there is no particular limitation. For example, lithium ions or sodium ions (especially lithium ions) can be cited.

[0031] First, the positive electrode active material and the garnet-type oxide contained in the positive electrode layer will be described in detail in turn.

[0032] The positive electrode active material is a lithium transition metal composite oxide having a layered rock salt-type structure and containing at least one of Mg (magnesium) and Al (aluminum). For example, when a positive electrode active material having a layered rock salt-type structure and not containing both Mg (magnesium) and Al (aluminum) is included in the positive electrode layer instead of such a specific positive electrode active material, an increase in interfacial resistance and a decrease in discharge capacity cannot be sufficiently suppressed. In addition, for example, when a positive electrode active material having another crystal structure (for example, NASICON type structure, olivine type structure, or spinel type structure) is included in the positive electrode layer instead of such a specific positive electrode active material, even if the positive electrode active material contains at least one of Mg or Al, an increase in interfacial resistance and / or a decrease in discharge capacity cannot be sufficiently suppressed.

[0033] That the lithium transition metal composite oxide has a layered rock salt-type structure means that the lithium transition metal composite oxide (especially its particles) has a layered rock salt-type crystal structure, and in a broad sense, it means a crystal structure that can be recognized as a layered rock salt-type by those skilled in the art in the battery field. In a narrow sense, that the positive electrode active material has a layered rock salt-type structure means that the lithium transition metal composite oxide (especially its particles) is identified as having a layered rock salt-type crystal structure by analyzing the X-ray diffraction pattern using Rietveld analysis or the like. More specifically, in X-ray diffraction, this oxide can show one or more main peaks corresponding to the Miller indices inherent to the so-called layered rock salt-type crystal structure (diffraction pattern: ICDD Card No. 01-070-2685) at a specified incident angle. The lithium transition metal composite oxide is a general term for oxides containing lithium and one or two or more transition metal elements (especially Co (cobalt)) as constituent elements.

[0034] That the positive electrode active material contains at least one of Mg (magnesium) and Al (aluminum) means that the lithium transition metal composite oxide as the positive electrode active material contains one of Mg and Al, or contains both. The content of Mg and / or Al is not particularly limited as long as the effects of the present invention can be obtained. For example, when the positive electrode active material is represented by the following general formula (R), it can be a content within the range of γ (especially γ Al ) within the range described later, or it can also be a content within the range of the total concentration C of Mg and Al inside the particles of the positive electrode active material described later. N within the range described later.

[0035] The positive electrode active material (especially the lithium transition metal composite oxide) has, for example, a chemical composition represented by the following general formula (R).

[0036] [Chemical formula 1]

[0037] Liα M1 β M2 γ O ω (R)

[0038] In formula (R), M1 is one or more elements selected from the group consisting of Co (cobalt), Ni (nickel), and Mn (manganese). From the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, Co is preferably contained, and Co alone is more preferably contained.

[0039] M2 contains one or more elements selected from the group consisting of Mg (magnesium) and Al (aluminum). From the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, Al is preferably contained, and both Mg and Al are more preferably contained, and only both Mg and Al are even more preferably contained. In addition to Mg and Al, M1 may contain other elements. Examples of such other elements include Ti (titanium) and the like.

[0040] Alternatively, in formula (R), α satisfies 0.8 ≤ α ≤ 1.5. From the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, 0.8 ≤ α ≤ 1.2 is preferred, 0.9 ≤ α ≤ 1.1 is more preferred, and 1.0 is further preferred.

[0041] β satisfies 0.8 ≤ β ≤ 1.2. From the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, 0.8 ≤ β ≤ 1.1 is preferred, 0.88 ≤ β ≤ 1.0 is more preferred, 0.94 ≤ β ≤ 0.99 is further preferred, 0.94 ≤ β ≤ 0.985 is sufficiently preferred, and 0.975 ≤ β ≤ 0.985 is more sufficiently preferred. When M1 contains multiple elements, as long as the sum of the values corresponding to β for each of these elements satisfies the above range of β. For example, the value corresponding to β for Co is represented as β Co . In addition, for example, the value corresponding to β for Ni is represented as β Ni . In addition, for example, the value corresponding to β for Mn is represented as β Mn .

[0042] γ / β satisfies 0 < γ / β ≤ 0.2. From the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, 0.005 ≤ γ / β ≤ 0.15 is preferred, 0.008 ≤ γ / β ≤ 0.12 is more preferred, 0.015 ≤ γ / β ≤ 0.07 is further preferred, and 0.015 ≤ γ / β ≤ 0.025 is more preferred.

[0043] γ satisfies 0 < γ ≤ 0.24. From the viewpoint of more fully suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 0 < γ ≤ 0.2, more preferably 0 < γ ≤ 0.1, further preferably 0.015 ≤ γ ≤ 0.06, and most preferably 0.015 ≤ γ ≤ 0.025. When M2 contains multiple elements, as long as the sum of the values corresponding to γ for each of these elements satisfies the above range of γ. For example, the value corresponding to γ related to Mg is represented as γ Mg . Additionally, for example, the value corresponding to γ related to Al is represented as γ Al . From the viewpoint of more fully suppressing the increase in interfacial resistance and the decrease in discharge capacity, γ Al is preferably 0.005 ≤ γ Al ≤ 0.2, more preferably 0.008 ≤ γ Al ≤ 0.08, and further preferably 0.008 ≤ γ Al ≤ 0.015. From the viewpoint of more fully suppressing the increase in interfacial resistance and the decrease in discharge capacity, γ Mg is preferably 0.005 ≤ γ Mg ≤ 0.1, more preferably 0.008 ≤ γ Mg ≤ 0.08, and further preferably 0.008 ≤ γ Mg ≤ 0.03.

[0044] "β + γ" generally satisfies 0.8 ≤ β + γ ≤ 1.2. From the viewpoint of more fully suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 0.9 ≤ β + γ ≤ 1.1, and more preferably 1.0.

[0045] ω satisfies 1.8 ≤ ω ≤ 2.2. From the viewpoint of more fully suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 1.9 ≤ ω ≤ 2.1, and more preferably 2.0.

[0046] Specifically, the lithium transition metal composite oxide as the positive electrode active material can be, for example, LiCo 0.99 Mg 0.01 O2, LiCo 0.95 Mg 0.05 O2, LiCo 0.98 Al 0.02 O2, LiCo 0.95 Al 0.05 O2, LiCo 0.9 Al 0.1 O2, LiCo 0.98 Al 0.01 Mg 0.01 O2, LiCo 0.97 Al 0.01Mg 0.01 Ti 0.01 O2 etc.

[0047] The chemical composition of the positive electrode active material may also be the 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 breaking the solid battery, using SEM-EDX (energy dispersive X-ray spectroscopy), and performing EDX-based composition analysis in any field of view including the entire thickness direction of the positive electrode layer. Therefore, the chemical composition of the positive electrode active material is the average chemical composition of the entire "inside of the particles" and "near the grain boundaries".

[0048] The positive electrode active material, for example, as Figure 1 shown, has a concentration gradient with respect to Mg (magnesium) and / or Al (aluminum) between the near-interface portion 11 and the inside of the particles 12 near the interface with the garnet-type oxide 2. Specifically, the near-interface portion 11 in the positive electrode active material is a region where the distance from the interface S with the garnet-type oxide 2 in the positive electrode active material 1 (i.e., the distance from the interface S toward the positive electrode active material 1) is 50 nm or less in a cross-sectional view ( Figure 1 in, the region between the interface S and the dashed line). The near-interface portion 11 is usually arranged at the outer periphery of the positive electrode active material. In a cross-sectional view, the inside of the particles 12 is the inner region surrounded by the near-interface portion 11. Figure 1 is a schematic cross-sectional view showing an embodiment of the relationship between the positive electrode active material and the garnet-type oxide in the positive electrode layer of the solid battery according to the present invention.

[0049] In the positive electrode active material, specifically, the concentration of at least one of Mg (magnesium) or Al (aluminum) in the inside of the particles 12 is greater than the concentration of the at least one in the near-interface portion 11. More specifically, as follows.

[0050] When the positive electrode active material contains only Mg among Mg and Al (hereinafter referred to as case 1), the concentration of Mg in the inside of the particles is greater than the concentration of Mg in the near-interface portion.

[0051] When the positive electrode active material contains only Al among Mg and Al (hereinafter referred to as case 2), the concentration of Al in the inside of the particles is greater than the concentration of Al in the near-interface portion.

[0052] When the positive electrode active material contains both Mg and Al (hereinafter referred to as case 3), the total concentration of Mg and Al in the inside of the particles is greater than the total concentration of Mg and Al in the near-interface portion.

[0053] In any one of the above cases 1 to 3, from the viewpoint of more effectively suppressing the increase in interfacial resistance and the decrease in discharge capacity, the total concentration C of Mg and Al in the particle interior 12 N is greater than the total concentration C of Mg and Al in the vicinity of the interface portion 11 K .

[0054] The total concentration C K The concentration ratio (C N / C K ) with respect to the total concentration C N is generally 0.01 or more and 0.90 or less. From the viewpoint of more effectively suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 0.1 or more and 0.8 or less, more preferably 0.15 or more and 0.60 or less, and further preferably 0.30 or more and 0.60 or less.

[0055] The total concentration C K can generally be 0.1 atomic % or more and 2.0 atomic % or less. From the viewpoint of more effectively suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 0.1 atomic % or more and 1.0 atomic % or less, more preferably 0.2 atomic % or more and 0.8 atomic % or less, further preferably 0.5 atomic % or more and 0.7 atomic % or less, and most preferably 0.55 atomic % or more and 0.7 atomic % or less.

[0056] The total concentration C N can generally be 0.8 atomic % or more and 5.0 atomic % or less. From the viewpoint of more effectively suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 0.8 atomic % or more and 4.0 atomic % or less, more preferably 1.0 atomic % or more and 3.0 atomic % or less, and further preferably 1.0 atomic % or more and 2.0 atomic % or less.

[0057] The total concentration C K is the average value of the values measured by point analysis of TEM-EDX (energy dispersive X-ray spectroscopy) at any 30 points in the vicinity of the interface portion 11.

[0058] The total concentration C N is the average value of the values measured by point analysis of TEM-EDX at any 30 points in the particle interior 12.

[0059] The content of the layered rock salt type positive electrode active material (especially the layered rock salt type lithium transition metal composite oxide) in the positive electrode layer is usually 20% by volume or more, especially 20% by volume or more and 90% by volume or less, based on the whole of the positive electrode layer. From the viewpoint of more sufficiently suppressing the increase in the interfacial resistance and the decrease in the discharge capacity, it is preferably 40% by volume or more and 80% by volume or less, more preferably 45% by volume or more and 70% by volume or less, and particularly preferably 50% by volume. The positive electrode layer may contain two or more kinds of layered rock salt type positive electrode active materials. In this case, as long as their total content is within the above range. Two or more kinds of layered rock salt type positive electrode active materials mean, for example, two or more kinds of layered rock salt type positive electrode active materials in which the types of elements of M1 and / or M2 are different and / or at least one of α, β, or γ is different in the layered rock salt type positive electrode active material represented by the above general formula (R).

[0060] The positive electrode layer may contain a positive electrode active material other than the above-mentioned layered rock salt type positive electrode active material (hereinafter also referred to as "other positive electrode active material"). The content of the positive electrode active material other than the above-mentioned layered rock salt type positive electrode active material is usually 10% by volume or less, based on the whole of the positive electrode layer. From the viewpoint of more sufficiently suppressing the increase in the interfacial resistance and the decrease in the discharge capacity, it is preferably 5% by volume or less, and more preferably 0% by volume. Examples of other positive electrode active materials include lithium-containing phosphate compound particles having a NASICON 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.

[0061] The positive electrode active material can be manufactured, for example, by the following method, or can also be obtained as a commercially available product. In the case of manufacturing the positive electrode active material, first, raw material compounds containing prescribed metal atoms are weighed so that the chemical composition becomes a prescribed chemical composition, water is added and mixed to obtain a slurry. Then, the slurry is dried, pre-fired at 700 °C or higher and 1000 °C or lower for 1 hour or more and 30 hours or less, and pulverized to obtain the positive electrode active material.

[0062] The chemical composition and crystal structure of the positive electrode active material in the positive electrode layer sometimes change due to element diffusion during sintering. The positive electrode active material may have the above-mentioned chemical composition and crystal structure in a solid battery after being sintered together with the negative electrode layer and the solid electrolyte layer.

[0063] The average particle diameter of the positive electrode active material is not particularly limited, and for example, it may be 100 nm or more and 10 μm or less. From the viewpoint of more sufficiently suppressing the increase in interface resistance and the decrease in discharge capacity, it is preferably 500 nm or more and 8 μm or less, more preferably 1 μm or more and 5 μm or less, and most preferably 1 μm or more and 3 μm or less. The average particle diameter of the positive electrode active material is generally larger than the average particle diameter of the garnet-type oxide described later.

[0064] For example, the average particle diameter of the positive electrode active material can be obtained by randomly selecting 10 or more and 100 or less particles from the SEM image and simply averaging their particle diameters (arithmetic mean).

[0065] The particle diameter is the diameter of a spherical particle assuming that the particle is a perfect sphere. Such a particle diameter can be obtained as follows: Cut out the cross-section of the solid battery, take a cross-sectional SEM image using SEM, and after that, use image analysis software (for example, "AZO-KUN" (manufactured by Asahi Kasei Engineering Corporation)) to calculate the cross-sectional area S of the particle, and then obtain the particle diameter R through the following formula.

[0066] [Mathematical formula 1]

[0067] R = 2 × (S / π) 1 / 2

[0068] It should be noted that the average particle diameter of the positive electrode active material in the positive electrode layer can also be measured by determining the positive electrode active material through composition during the measurement of the above chemical composition.

[0069] The average particle diameter of the positive electrode active material in the positive electrode layer sometimes changes due to sintering during the manufacturing process of the solid battery. The positive electrode active material can have the above average particle diameter in the solid battery after sintering together with the negative electrode layer and the solid electrolyte layer.

[0070] The garnet-type oxide is an oxide (especially a metal oxide) having a garnet-type crystal structure and substantially not containing Al (aluminum). For example, when the positive electrode layer contains a garnet-type oxide containing Al instead of such a specific garnet-type oxide, the increase in interface resistance and the decrease in discharge capacity cannot be sufficiently suppressed. In addition, for example, when the positive electrode layer contains an oxide having another crystal structure instead of such a specific garnet-type oxide, even if the oxide does not contain Al, the increase in interface resistance and / or the decrease in discharge capacity cannot be sufficiently suppressed.

[0071] The oxide having a garnet-type crystal structure includes not only that the oxide has only a "garnet-type crystal structure", but also that it has a "crystal structure similar to the garnet-type". Specifically, the oxide has a crystal structure that can be recognized by those skilled in the art of solid-state batteries as a garnet-type or a crystal structure similar to the garnet-type in X-ray diffraction. More specifically, it can be that the oxide shows, in X-ray diffraction, at a specified incident angle, one or more main peaks corresponding to the Miller indices inherent in the so-called garnet-type crystal structure (diffraction pattern: ICDD Card No. 01-080-6142), or it can also be that, as a crystal structure similar to the garnet-type, one or more main peaks corresponding to the Miller indices inherent in the so-called garnet-type crystal structure show one or more main peaks with different incident angles (i.e., peak positions or diffraction angles) and intensity ratios (i.e., peak intensities or diffraction intensity ratios) due to compositional differences. As a representative diffraction pattern of a crystal structure similar to the garnet-type, for example, ICDD Card No. 00-045-0109 etc. can be cited.

[0072] That the garnet-type oxide substantially does not contain Al means that Al can also be contained to the extent that it does not hinder the exertion of the effects of the present invention. For example, relative to the content of La contained in the garnet-type oxide, the content of Al is less than 0.08 (especially less than 0.01). Thereby, side reactions caused by the diffusion of Al from the garnet-type oxide to the positive electrode layer during firing can be suppressed.

[0073] The content ratio of Al to La in the garnet-type oxide is the average value of the values measured by point analysis of TEM-EDX at any 30 points. It should be noted that the content ratio of Al to La is a ratio based on a molar basis (i.e., molar ratio).

[0074] The garnet-type oxide has, for example, a chemical composition represented by the following general formula (I).

[0075] [Chemical formula 2]

[0076] (Li α-p A x )(B I β-y B II y )(D I y-z D II z )O ω (I)

[0077] In formula (I), A is one or more elements that can be solid-dissolved in the Li site of the garnet-type oxide. Specifically, A is one or more elements selected from the group (hereinafter sometimes referred to as "group a") consisting of Mg (magnesium), Ga (gallium), Sc (scandium), and Fe (iron), and does not include Al (aluminum).

[0078] B I is one or more elements selected from the group consisting of elements belonging to Groups 1 to 3 that can form an 8-coordination with oxygen and that can form a valence of 3. Specifically, B I is one or more elements selected from the group (hereinafter sometimes referred to as "group bI") 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). From the viewpoint of more sufficiently suppressing the increase in interface resistance and the decrease in discharge capacity, B I preferably contains La (lanthanum). B I may also contain La (lanthanum) alone.

[0079] B II is one or more elements selected from the group consisting of elements belonging to Groups 1 to 3 that can form an 8-coordination with oxygen and that can form a valence other than 3. Specifically, B II is selected from the group consisting of Ca (calcium), Sr (strontium), Ba (barium) as divalent B II and Ce (cerium) as tetravalent B II hereinafter sometimes referred to as "group bII").

[0080] D I is one or more elements selected from the group consisting of transition elements that can form a 6-coordination with oxygen and typical elements belonging to Groups 12 to 15 and that can form a valence of 4. Specifically, D I is one or more elements selected from the group (hereinafter sometimes referred to as "group dI") consisting of Zr (zirconium), Ti (titanium), Hf (hafnium), Ge (germanium), and Sn (tin). From the viewpoint of more sufficiently suppressing the increase in interface resistance and the decrease in discharge capacity, D I preferably contains Zr (zirconium). D I may also contain Zr (zirconium) alone.

[0081] D IIis one or more elements selected from the group consisting of transition elements capable of forming a 6-coordination with oxygen and typical elements belonging to Groups 12 to 15, which are elements capable of forming a valence other than tetravalent. Specifically, D II is selected from Sc (scandium) as trivalent D II , Ta (tantalum) as pentavalent D II , Nb (niobium), Sb (antimony), Bi (bismuth), and Mo (molybdenum), W (tungsten), and Te (tellurium) as hexavalent D II (hereinafter sometimes referred to as "Group dII"). From the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, D II is preferably one or more elements selected from the group consisting of Bi (bismuth) and Ta (tantalum), more preferably contains Bi (bismuth), and further preferably contains only Bi (bismuth) and Ta (tantalum).

[0082] In formula (I), p is represented by the calculation formula (i):

[0083] p = ax - (3 - b)y + (d - 4)z (i)

[0084] represents.

[0085] In formula (i), a is the average valence of A. Regarding the average valence of A, for example, when it is confirmed that there are n1 elements X with valence r+, n2 elements Y with valence s+, and n3 elements Z with valence t+ as A, it is the value represented by the formula: (n1×r + n2×s + n3×t) / (n1 + n2 + n3).

[0086] b is the average valence of B II . Regarding the average valence of B II , for example, when it is confirmed that there are n1 elements X with valence r+, n2 elements Y with valence s+, and n3 elements Z with valence t+ as B II , it is the value represented by the same formula as the average valence of A described above.

[0087] d is the average valence of D II ; regarding the average valence of D II , for example, when it is confirmed that there are n1 elements X with valence r+, n2 elements Y with valence s+, and n3 elements Z with valence t+ as D II , it is the value represented by the same formula as the average valence of A described above.

[0088] In formula (I), α satisfies 5.0 ≤ α ≤ 8.0. From the perspective of more fully suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 5.5 ≤ α ≤ 7.5, more preferably 5.5 ≤ α ≤ 7.0, further preferably 6.0 ≤ α ≤ 6.8, particularly preferably 6.2 ≤ α ≤ 6.8, and most preferably 6.2 ≤ α ≤ 6.6.

[0089] β satisfies 2.5 ≤ β ≤ 3.5. From the perspective of more fully suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 2.6 ≤ β ≤ 3.4, more preferably 2.7 ≤ β ≤ 3.3, further preferably 2.8 ≤ β ≤ 3.2, particularly preferably 2.9 ≤ β ≤ 3.1, and most preferably 3.0.

[0090] γ satisfies 1.5 ≤ γ ≤ 2.5. From the perspective of more fully suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 1.6 ≤ γ ≤ 2.4, more preferably 1.7 ≤ γ ≤ 2.3, further preferably 1.8 ≤ γ ≤ 2.2, particularly preferably 1.9 ≤ γ ≤ 2.1, and most preferably 2.0.

[0091] ω satisfies 11 ≤ ω ≤ 13. From the perspective of more fully suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 11 ≤ ω ≤ 12.5, more preferably 11.5 ≤ ω ≤ 12.5, and further preferably "12 - δ". δ represents the amount of oxygen deficiency and can also be 0. δ generally satisfies 0 ≤ δ < 1. Since quantitative analysis cannot be performed even with the latest equipment, the amount of oxygen deficiency δ can also be considered 0.

[0092] x satisfies 0 ≤ x ≤ 1.0. From the perspective of more fully suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 0 ≤ x ≤ 0.8, more preferably 0 ≤ x ≤ 0.6, further preferably 0 ≤ x ≤ 0.4, particularly preferably 0 ≤ x ≤ 0.2, and most preferably 0. When A contains multiple elements, as long as the sum of the values corresponding to x for each of these elements satisfies the above range of x.

[0093] y satisfies 0 ≤ y ≤ 1.0. From the perspective of more fully suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 0 ≤ y ≤ 0.8, more preferably 0 ≤ y ≤ 0.6, further preferably 0 ≤ y ≤ 0.4, particularly preferably 0 ≤ y ≤ 0.2, and most preferably 0. In the case of II B containing multiple elements, as long as the sum of the values corresponding to y for each of these elements satisfies the above range of y.

[0094] z satisfies 0.4 ≤ z ≤ 2.2. From the viewpoint of more fully suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 0.4 ≤ y ≤ 1.5, more preferably 0.4 ≤ z ≤ 1.0, still more preferably 0.4 ≤ z ≤ 0.8, particularly preferably 0.5 ≤ z ≤ 0.7, and most preferably 0.6. In D II In the case of containing multiple elements, it is only necessary that the total value of the value equivalent to z related to each of these elements satisfies the above range of z.

[0095] The chemical composition of the garnet-type oxide can also be determined by quantitative analysis (composition analysis) using TEM-EDX (energy-dispersive X-ray spectroscopy). The method for determining the chemical composition of the garnet-type oxide is not particularly limited. For example, TEM-EELS (transmission electron microscopy-electron energy-loss spectroscopy: Electron Energy-Loss Spectroscopy) measurement can be performed.

[0096] From the viewpoint of more fully suppressing the increase in interfacial resistance and the decrease in discharge capacity, the garnet-type oxide preferably has a chemical composition represented by the following general formula (II). Specifically, from the viewpoint of more fully suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferred that the garnet-type oxide has a chemical composition represented by the following general formula (II). It should be noted that the general formula (II) is an embodiment included in the above general formula (I).

[0097] [Chemical formula 3]

[0098] (Li 7-p )(La3)(Zr 2-z D II z )O ω (II)

[0099] In formula (II), D II is the same as D in the general formula (I). II Same.

[0100] z in formula (II) is the same as z in the general formula (I).

[0101] ω in formula (II) is the same as ω in the general formula (I).

[0102] p in formula (II) is represented by p = p(d - 4)z. It should be noted that d is the same as d in formula (i).

[0103] Specifically, the garnet-type oxide can also be, for example, Li 6.4 La3(Zr 1.4 Ta 0.4 Bi 0.2)O 12 etc.

[0104] The average particle diameter of the garnet-type oxide is not particularly limited and can be, for example, 10 nm or more and 5 μm or less. From the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 50 nm or more and 1 μm or less, more preferably 100 nm or more and 800 nm or less, and particularly preferably 500 nm. The average particle diameter of the garnet-type oxide can be measured by the same method as the average particle diameter of the above-described positive electrode active material.

[0105] The content of the garnet-type oxide is usually 10% by volume or more, particularly 20% by volume or more and 80% by volume or less, relative to the entire positive electrode layer. From the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 30% by volume or more and 80% by volume or less, more preferably 30% by volume or more and 70% by volume or less, and particularly preferably 50% by volume. The positive electrode layer may also contain two or more types of garnet-type oxides. In this case, as long as their total content is within the above range. Two or more types of garnet-type oxides mean, for example, two or more types of garnet-type oxides in which the types of elements contained are different and / or at least one of α, β, γ, x, y, z, or p is different in the garnet-type oxide represented by the above general formula (I).

[0106] The garnet-type oxide can be produced by the following method. A raw material compound containing a prescribed metal atom is weighed so that its chemical composition becomes a prescribed chemical composition, water is added and mixed to obtain a slurry. Then, the slurry is dried, pre-fired at 700 °C or more and 1000 °C or less for 1 hour or more and 30 hours or less, and pulverized to obtain the garnet-type oxide.

[0107] The positive electrode layer may also contain a metal oxide other than the garnet-type oxide (for example, a so-called solid electrolyte) (hereinafter referred to as other metal oxide). In this case, the content of the other metal oxide is usually 10% by volume or less relative to the entire positive electrode layer. From the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, it is preferably 5% by volume or less, and more preferably 0% by volume.

[0108] The positive electrode layer may further contain a sintering aid and / or a conductive aid, etc.

[0109] All sintering aids known in the field of solid-state batteries can be used as the sintering aid. The composition of such a sintering aid preferably contains at least Li (lithium), B (boron), and O (oxygen), and the molar ratio of Li to B (Li / B) is 2.0 or more. Specific examples of such a sintering aid include, for example, Li4B2O5, Li3BO3, (Li 2.7Al 0.3 )BO3, Li 2.8 (B 0.8 C 0.2 )O3, LiBO2.

[0110] The content of the sintering aid is not particularly limited. Relative to the whole of the positive electrode layer, it is preferably 0.1% by volume or more and 20% by volume or less, more preferably 1% by volume or more and 10% by volume or less, for example.

[0111] As the conductive aid, those known in the field of solid-state batteries can be used. As the preferably used conductive aids, for example, metal materials such as Ag (silver), Au (gold), Pd (palladium), Pt (platinum), Cu (copper), Sn (tin), Ni (nickel), etc. can be cited; and carbon materials such as acetylene black, Ketjen black, Super P (registered trademark), VGCF (registered trademark), etc. carbon nanotubes, etc. Regarding the shape of the carbon material, there is no particular limitation, and carbon materials of any shape such as spherical, plate-shaped, fibrous, etc. can be used.

[0112] The content of the conductive aid is not particularly limited. Relative to the whole of the positive electrode layer, it is preferably 50% by volume or less (especially 0% by volume or more and 50% by volume or less), more preferably 40% by volume or less (especially 0% by volume or more and 40% by volume or less), for example.

[0113] The thickness of the positive electrode layer is usually 0.1 μm or more and 30 μm or less, preferably 1 μm or more and 20 μm or less, for example. The thickness of the positive electrode layer uses the average value of the thickness measured at any 10 parts in the SEM image.

[0114] In the positive electrode layer, the porosity is not particularly limited, preferably 20% by volume or less, more preferably 15% by volume or less, and further preferably 10% by volume or less.

[0115] The porosity of the positive electrode layer uses the value measured from the SEM image after FIB cross-section processing.

[0116] 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 collecting layer.

[0117] (Negative electrode layer)

[0118] In the solid-state battery of the present invention, the negative electrode layer is not particularly limited. The negative electrode layer usually contains a negative electrode active material. The negative electrode layer may be a layer capable of inserting and extracting or intercalating and deintercalating ions (especially lithium ions). As the medium ions of the negative electrode layer, as long as they can be charged and discharged, there is no particular limitation, and for example, lithium ions or sodium ions (especially lithium ions) can be cited.

[0119] The negative electrode active material is not particularly limited, and negative electrode active materials known in the field of solid batteries can be used. As the negative electrode active material, for example, carbon materials such as graphite, graphite-lithium compounds, lithium metal, lithium alloy particles, phosphoric acid compounds having a NASON type structure, Li-containing oxides having a spinel type structure, and β II -Li3VO4 type structure, γ II -Li3VO4 type structure oxides and the like can be cited. As the negative electrode active material, lithium metal, and oxides having a β II -Li3VO4 type structure and γ II -Li3VO4 type structure Li-containing oxides can also be used.

[0120] In the negative electrode layer, the oxide having a β II -Li3VO4 type structure means that the oxide (especially its particles) has a β II -Li3VO4 type crystal structure. In a broad sense, it means a crystal structure having a crystal structure that can be recognized by those skilled in the art in the field of solid batteries as a β II -Li3VO4 type crystal structure. In a narrow sense, in the negative electrode layer, the oxide having a β II -Li3VO4 type structure means that the oxide (especially its particles) shows one or more main peaks corresponding to the Miller indices inherent in the so-called β II -Li3VO4 type crystal structure at a specified incident angle in X-ray diffraction. As the preferably used Li-containing oxide having a β II -Li3VO4 type structure, Li3VO4 can be cited.

[0121] In the negative electrode layer, the oxide having a γ II -Li3VO4 type structure means that the oxide (especially its particles) has a γ II -Li3VO4 type crystal structure. In a broad sense, it means a crystal structure having a crystal structure that can be recognized by those skilled in the art in the field of solid batteries as a γ II -Li3VO4 type crystal structure. In a narrow sense, in the negative electrode layer, the oxide having a γ II -Li3VO4 type structure means that the oxide (especially its particles) shows one or more main peaks corresponding to the Miller indices inherent in the so-called γ II -Li3VO4 type crystal structure at a specified incident angle (x-axis) in X-ray diffraction. As the preferably used Li-containing oxide having a γ II -Li3VO4 type structure, Li 3.2 V 0.8 Si 0.2 O4 can be cited.

[0122] The chemical composition of the negative electrode active material may also be an 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 breaking the solid battery, using SEM-EDX (energy dispersive X-ray spectroscopy), and performing EDX-based composition analysis in a field of view that includes the entire thickness direction of the negative electrode layer.

[0123] The negative electrode active material can be manufactured, for example, by the same method as the positive electrode active material, or can also be obtained as a commercially available product.

[0124] The chemical composition and crystal structure of the negative electrode active material in the negative electrode layer usually change according to the element diffusion during sintering in the manufacturing process of the solid battery. The negative electrode active material can have the above-mentioned average chemical composition and crystal structure in the solid battery after sintering together with the positive electrode layer and the solid electrolyte layer.

[0125] The content of the negative electrode active material in the negative electrode layer is not particularly limited. For example, relative to the entire negative electrode layer, it is preferably 50% or more (especially 50% or more and 99% or less), more preferably 70% or more and 95% or less, and further preferably 80% or more and 90% or less.

[0126] The negative electrode layer may further contain a so-called solid electrolyte, a sintering aid, and / or a conductive aid, etc.

[0127] The solid electrolyte that can be contained in the negative electrode layer is not particularly limited. For example, the solid electrolytes exemplified as the solid electrolytes constituting the solid electrolyte layer described later can be cited.

[0128] When the negative electrode layer contains a solid electrolyte, the content of the solid electrolyte can usually be 20% by volume or more and 60% by volume or less, especially 30% by volume or more and 45% by volume or less, relative to the entire negative electrode layer.

[0129] As the sintering aid in the negative electrode layer, the same compounds as those in the positive electrode layer can be used.

[0130] As the conductive aid in the negative electrode layer, the same compounds as those in the positive electrode layer can be used.

[0131] The thickness of the negative electrode layer is usually 0.1 μm or more and 30 μm or less, preferably 1 μm or more and 20 μm or less. The thickness of the negative electrode layer is the average value of the thicknesses measured at any 10 positions in the SEM image.

[0132] In the negative electrode layer, the porosity is not particularly limited, preferably 20% or less, more preferably 15% or less, and further preferably 10% or less.

[0133] The porosity of the negative electrode layer uses the value measured by the same method as the porosity of the positive electrode layer.

[0134] The negative electrode layer is a layer that can 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 collecting layer.

[0135] (Solid electrolyte layer)

[0136] In the solid battery of the present invention, the solid electrolyte layer contains a solid electrolyte.

[0137] The solid electrolyte contained in the solid electrolyte layer is not particularly limited and can be all solid electrolytes contained in the solid electrolyte layer in the field of solid batteries. As such a solid electrolyte, for example, it can be an oxide-based material. If exemplified, one or more materials selected from garnet-type oxides contained in the positive electrode layer, solid electrolytes having a Li2ZrO3 or γ-Li3VO4 structure, and oxide glass-ceramic-based lithium ion conductors can be listed. From the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity, the solid electrolyte layer preferably contains a garnet-type oxide contained in the positive electrode layer.

[0138] As the solid electrolyte having a γ-Li3VO4 structure, a solid electrolyte having an average chemical composition represented by the following general formula (III) can be listed.

[0139] [Chemical formula 4]

[0140] (Li [3-ax+(5-c)(1-y) )A x )(B y D 1-y )O4 (III)

[0141] In formula (III), A is one or more elements selected from the group consisting of Na, K, Mg, Ca, Al, Ga, Zn, Fe, Cr, and Co.

[0142] B is one or more elements selected from the group consisting of V and P.

[0143] 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.

[0144] x satisfies 0 ≤ x ≤ 1.0, particularly 0 ≤ x ≤ 0.2.

[0145] y satisfies 0 ≤ y ≤ 1.0, particularly 0.20 ≤ y ≤ 0.50.

[0146] a is the average valence number of A. Regarding the average valence number of A, as A, for example, when it is confirmed that there are n1 elements X with a valence number of a+, n2 elements Y with a valence number of b+, and n3 elements Z with a valence number of c+, it is the value represented by (n1×a + n2×b + n3×c) / (n1 + n2 + n3).

[0147] c is the average valence number of D. Regarding the average valence number of D, as D, for example, when it is confirmed that there are n1 elements X with a valence number of a+, n2 elements Y with a valence number of b+, and n3 elements Z with a valence number of c+, it is the same value as the above-mentioned average valence number of A.

[0148] As a specific example of the solid electrolyte having a γ-Li3VO4 structure, for example, Li 3.2 (V 0.8 Si 0.2 )O4, Li 3.5 (V 0.5 Ge 0.5 )O4, Li 3.4 (P 0.6 Si 0.4 )O4, Li 3.5 (P 0.5 Ge 0.5 )O4, etc.

[0149] As the oxide glass ceramic-based lithium ion conductor, for example, a phosphate compound (LATP) containing lithium, aluminum, and titanium in its constituent elements, and a phosphate compound (LAGP) containing lithium, aluminum, and germanium in its constituent elements can be used.

[0150] The content of the solid electrolyte in the solid electrolyte layer is not particularly limited. For example, relative to the entire solid electrolyte layer, it is preferably 10% by volume or more and 100% by volume or less, more preferably 20% by volume or more and 100% by volume or less, and further preferably 30% by volume or more and 100% by volume or less.

[0151] In addition to the solid electrolyte, the solid electrolyte layer may further contain, for example, a sintering aid, etc.

[0152] As the sintering aid in the solid electrolyte layer, the same compound as the sintering aid in the positive electrode layer can be used.

[0153] The content of the sintering aid in the solid electrolyte layer is not particularly limited. From the viewpoint of more sufficiently suppressing the increase in interface resistance and the decrease in discharge capacity, it is preferably 0% by volume or more and 20% by volume or less, more preferably 1% by volume or more and 10% by volume or less.

[0154] The thickness of the solid electrolyte layer is generally 0.1 μm or more and 30 μm or less, and preferably 1 μm or more and 20 μm or less from the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity. The thickness of the solid electrolyte layer is the average value of the thicknesses measured at any 10 sites in the SEM image.

[0155] In the solid electrolyte layer, the porosity is not particularly limited, and preferably 20% by volume or less, more preferably 15% by volume or less, and still more preferably 10% by volume or less from the viewpoint of more sufficiently suppressing the increase in interfacial resistance and the decrease in discharge capacity.

[0156] The porosity of the solid electrolyte layer uses the value measured by the same method as the porosity of the positive electrode layer.

[0157] [Manufacturing method of solid battery]

[0158] The solid battery can be manufactured, for example, by a so-called green sheet method, a printing method, or a method combining these methods.

[0159] The green sheet method will be described.

[0160] First, a garnet-type oxide, a solvent, a binder, etc. are appropriately mixed in the positive electrode active material to prepare a paste. The paste is coated on a sheet and dried to form a first green sheet for constituting the positive electrode layer. Other so-called solid electrolytes, conductive aids, and / or sintering aids, etc. may also be included in the first green sheet.

[0161] A paste is prepared by appropriately mixing a solvent, a binder, etc. in the negative electrode active material. The paste is coated on a sheet and dried to form a second green sheet for constituting the negative electrode layer. Other so-called solid electrolytes, conductive aids, and / or sintering aids, etc. may also be included in the second green sheet.

[0162] A paste is prepared by appropriately mixing a solvent, a binder, etc. in the solid electrolyte. The paste is coated and dried to prepare a third green sheet for constituting the solid electrolyte layer. Sintering aids, etc. may also be included in the third green sheet.

[0163] The solvent used for producing the first to third green sheets is not particularly limited. For example, all solvents that can be used in the field of solid batteries for manufacturing the positive electrode layer, the negative electrode layer, or the solid electrolyte layer can be used. As the solvent, a solvent that can use the binder described later is usually used. Examples of such a solvent include alcohols such as 2-propanol.

[0164] The binder used for producing the first to third green sheets is not particularly limited. For example, all binders that can be used in the field of solid-state batteries for manufacturing the positive electrode layer, negative electrode layer, or solid electrolyte layer can be used. Examples of such binders include polyvinyl butyral resin, acrylic resin, and the like.

[0165] Next, a laminate is produced by appropriately laminating the first to third green sheets. The produced laminate can also be pressed. Examples of preferred pressing methods include isostatic pressing.

[0166] Then, a solid-state battery can be obtained by sintering the laminate at, for example, 600 °C or higher and 800 °C or lower.

[0167] The printing method will be described.

[0168] The printing method is the same as the green sheet method except for the following matters.

[0169] · In addition to making the blending amounts of the solvent and the resin suitable for use as ink, inks for each layer having the same composition as the paste for each layer used to obtain the green sheet are prepared.

[0170] · The inks for each layer are used for printing and laminating to produce a laminate.

[0171] Hereinafter, the present invention will be described in more detail based on specific examples, but the present invention is not limited by any of the following examples and can be appropriately modified and implemented within the scope without changing its gist.

[0172] The present invention as described above includes the following preferred embodiments.

[0173] <1> A solid-state battery

[0174] 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,

[0175] the positive electrode layer including a positive electrode active material having a layered rock salt structure and an oxide having a garnet structure,

[0176] the positive electrode active material containing at least one of Mg (magnesium) and Al (aluminum),

[0177] the oxide not containing Al (aluminum).

[0178] <2> The solid-state battery according to <1>,

[0179] the oxide containing La,

[0180] the content of Al in the oxide being less than 0.08 with respect to the content of La (Al / La).

[0181] <3>The solid-state battery according to <1> or <2>

[0182] The positive electrode active material has a chemical composition represented by the following general formula (R):

[0183] [Chemical formula 5]

[0184] Li α M1 β M2 γ O ω (R)

[0185] [In formula (R), M1 is one or more elements selected from the group consisting of Co (cobalt), Ni (nickel), and Mn (manganese);

[0186] M2 contains one or more elements selected from the group consisting of Mg (magnesium) and Al (aluminum);

[0187] α satisfies 0.8 ≤ α ≤ 1.5;

[0188] β satisfies 0.8 ≤ β ≤ 1.2;

[0189] γ / β satisfies 0 < γ / β ≤ 0.2;

[0190] ω satisfies 1.8 ≤ ω ≤ 2.2].

[0191] <4>The solid-state battery according to <3>

[0192] The M2 contains Al,

[0193] The value γ corresponding to Al, γ Al satisfies 0.008 ≤ γ Al ≤ 0.08.

[0194] <5>The solid-state battery according to <4>

[0195] The M2 contains only both Mg and Al.

[0196] <6>The solid-state battery according to any one of <1> to <5>

[0197] The positive electrode active material has a vicinity of the interface with the oxide and inside its particles,

[0198] The concentration of at least one of Mg (magnesium) or Al (aluminum) inside the particles is higher than the concentration of the at least one at the vicinity of the interface.

[0199] <7>The solid-state battery according to any one of <1> to <5>

[0200] The positive electrode active material has a near-interface portion and the interior of its particles with respect to the oxide,

[0201] the total concentration C of Mg (magnesium) and Al (aluminum) in the interior of the particles N is higher than the total concentration C of Mg (magnesium) and Al (aluminum) in the near-interface portion K of the interface.

[0202] <8> The solid battery according to <7>,

[0203] the total concentration C K the concentration ratio (C N / C K / C N ) of the total concentration C is 0.01 or more and 0.90 or less.

[0204] <9> The solid battery according to <7> or <8>,

[0205] the total concentration C K is 0.1 atomic % or more and 2.0 atomic % or less,

[0206] the total concentration C N is 0.8 atomic % or more and 5.0 atomic % or less.

[0207] <10> The solid battery according to any one of <1> to <9>,

[0208] the oxide has a chemical composition represented by the following general formula (I).

[0209] [Chemical formula 6]

[0210] (Li α-p A x )(B Iβ-y B II y )(D I y-z D II z )O ω (I)

[0211] In formula (I), A is one or more elements that can be solid-dissolved in the Li site of the oxide having the garnet-type crystal structure, excluding Al (aluminum);

[0212] B I is one or more elements selected from the group consisting of elements belonging to Groups 1 to 3 that can form an 8-coordination with oxygen and that can form a valence of 3;

[0213] B IIis one or more elements selected from the group consisting of elements belonging to Groups 1 to 3 that can form an 8 - coordinate bond with oxygen and that can form a valence other than trivalent;

[0214] D I is one or more elements selected from the group consisting of transition elements that can form a 6 - coordinate bond with oxygen and typical elements belonging to Groups 12 to 15 and that can form a valence of tetravalent;

[0215] D II is one or more elements selected from the group consisting of transition elements that can form a 6 - coordinate bond with oxygen and typical elements belonging to Groups 12 to 15 and that can form a valence other than tetravalent;

[0216] α satisfies 5.0 ≤ α ≤ 8.0;

[0217] β satisfies 2.5 ≤ β ≤ 3.5;

[0218] γ satisfies 1.5 ≤ γ ≤ 2.5;

[0219] ω satisfies 11 ≤ ω ≤ 13;

[0220] x satisfies 0 ≤ x ≤ 1.0;

[0221] y satisfies 0 ≤ y ≤ 1.0;

[0222] z satisfies 0.4 ≤ z ≤ 2.2;

[0223] p is represented by the following calculation formula:

[0224] p = ax-(3 - b)y+(d - 4)z

[0225] (where a is the average valence of A; b is the average valence of B II ; d is the average valence of D II ).

[0226] <11>According to the solid - state battery described in <10>,

[0227] D II contains Bi (bismuth).

[0228] <12>According to the solid - state battery described in any one of <1> to <11>,

[0229] the positive electrode layer and the negative electrode layer are layers capable of intercalating and de - intercalating or inserting and extracting lithium ions.

[0230] <13>According to the solid - state battery described in any one of <1> to <11>,

[0231] The solid electrolyte layer, the positive electrode layer, and the negative electrode layer are integrally sintered with each other to form a sintered body.

[0232] Example

[0233] [Manufacture of positive electrode active material]

[0234] · LiCoO2 (positive electrode active material used in Comparative Example 1)

[0235] The synthesis of LiCoO2 is carried out by synthesizing cobalt oxide Co3O4 and lithium carbonate Li2CO3. Cobalt oxide and lithium carbonate are weighed according to the stoichiometric composition, sealed in a PE bottle together with zirconia beads with a diameter of 1 mm and pure water, and mixed by rotating with a jar mill at 200 rpm for 16 hours. Then, the mixture from which the beads have been removed is dried and pulverized with a mortar. The pulverized material is placed in a crucible and fired in a firing furnace at 800 °C in an air atmosphere for 20 hours. The fired product thus obtained is pulverized with a mortar to obtain LiCoO2.

[0236] · LiCo 0.95 Mg 0.05 O2 (positive electrode active material used in Example 2)

[0237] LiCo 0.95 Mg 0.05 The synthesis of LiCo 0.95 Mg 0.05 O2 is carried out by weighing cobalt oxide Co3O4, lithium carbonate Li2CO3, and MgO according to the stoichiometric composition, sealing them in a PE bottle together with zirconia beads with a diameter of 1 mm and pure water, and mixing by rotating with a jar mill at 200 rpm for 16 hours. Then, the mixture from which the beads have been removed is dried and pulverized with a mortar. The pulverized material is placed in a crucible and fired in a firing furnace at 800 °C in an air atmosphere for 20 hours. The fired product thus obtained is pulverized with a mortar to obtain LiCo

[0238] · Positive electrode active materials other than the above chemical composition (positive electrode active materials used in Example 1, 3 to 7, and Comparative Examples 2 to 4)

[0239] In addition to weighing and using cobalt oxide Co3O4, lithium carbonate Li2CO3, magnesium oxide MgO, aluminum oxide Al2O3, titanium oxide TiO2, iron oxide Fe2O3, and silicon dioxide SiO2 according to the required stoichiometric composition, by the same method as LiCo 0.95 Mg 0.05It is manufactured by the same method as the method for manufacturing O2. For any of the positive electrode active materials, the average particle size is 3 μm. For any of the positive electrode active materials, it is confirmed by XRD measurement that a single phase of a layered rock salt type structure (ICDD card No. 01-070-2685) is obtained. It is confirmed by ICP measurement of the above powder that there is no compositional deviation.

[0240] [Manufacture of Garnet-Type Oxide]

[0241] As raw materials, lithium hydroxide monohydrate LiOH·H2O, lanthanum hydroxide La(OH)3, zirconium oxide ZrO2, tantalum oxide Ta2O5, bismuth oxide Bi2O3, and aluminum oxide Al2O3 are used.

[0242] Weigh each raw material according to the chemical composition shown in Table 1, add water, seal it in a 100 ml polyethylene polyethylene jar, and rotate it at 150 rpm on a jar rack for 16 hours to mix the raw materials. In addition, considering the Li deficiency during sintering, 3 wt% of lithium hydroxide monohydrate LiOH·H2O as the Li source is added in excess relative to the target composition.

[0243] After evaporating and drying the obtained slurry, it is pre-sintered at 900 °C for 5 hours to obtain the target phase.

[0244] Add a mixed solvent of toluene-acetone to the obtained pre-sintered powder and crush it with a planetary ball mill for 6 hours.

[0245] Dry the crushed powder to make a garnet-type oxide powder. It is confirmed by XRD measurement of the above powder that a single garnet-type oxide is obtained. It is confirmed by ICP measurement of the above powder that there is no compositional deviation. The average particle size is 150 nm.

[0246] In each example, without changing the primary particle size of the material, the structure and composition are controlled by the molar ratio of the raw materials and the firing time.

[0247] [Manufacture of Sintering Aid]

[0248] Lithium hydroxide monohydrate LiOH·H2O and boron oxide B2O3 are used. Weigh each starting raw material appropriately so that the chemical composition of the sintering aid is Li4B2O5. After fully mixing in a mortar, it is pre-sintered at 650 °C for 5 hours.

[0249] [Example 1]

[0250] (Manufacture of Positive Electrode Half Cell)

[0251] First, weigh garnet-type oxide, cathode active material powder, and sintering aid powder in a volume ratio of 49:50:1 respectively. Through kneading with alcohol and binder, prepare a cathode layer slurry. Coat the slurry on a sheet and dry it to form a first green sheet for forming the cathode layer.

[0252] In addition, through kneading with the same garnet-type oxide as the garnet-type oxide contained in the first green sheet, alcohol, and binder, prepare a solid electrolyte layer slurry and dry it to form a second green sheet for forming the solid electrolyte layer.

[0253] Fabricate a laminate by appropriately laminating the first and second green sheets. Press the fabricated laminate by the isostatic pressing method and perform appropriate cutting to obtain a laminate of the cathode layer / solid electrolyte layer. After removing the binder at 400 °C, perform pressure sintering at 800 °C under a pressure of 100 MPa for 60 minutes to fabricate a co-fired body of the cathode layer / solid electrolyte layer. The thickness of the sintered cathode layer is 15 μm, and the thickness of the solid electrolyte layer is about 200 μm.

[0254] Then, paste metallic Li on the surface of the solid electrolyte layer on the side opposite to the cathode layer as a counter electrode and reference electrode, and seal it with a 2032-type coin-shaped battery to obtain a solid battery.

[0255] [Examples 2 to 7 and Comparative Examples 1 to 6]

[0256] Except for using the garnet-type oxide and cathode active material shown in Table 1 in combination, a cathode half-cell was fabricated by the same method as in Example 1.

[0257] [Interface Resistance Increase Rate]

[0258] Evaluation was carried out based on the value (increase rate) obtained by normalizing the arc size around 1 kHz at room temperature in the fully charged state after the floating charge test at 60 °C with the arc size around 1 kHz at room temperature in the fully charged state before the floating charge test.

[0259] Specifically, the change rate of the interface resistance between the cathode active material and the solid electrolyte (the size of the arc around 1 kHz in the "cole-cole plot") was confirmed. The arc around 1 kHz was determined from the bode plot (absolute value of resistance vs. frequency, angle (θ) vs. frequency with respect to the real axis of the "cole-cole plot") as the difference between the saddle points of the arc in the real axis direction of the "cole-cole plot" graph. (Refer to Figure 2 )

[0260] ◎◎: Increase rate ≤ 5% (optimal);

[0261] ◎: 5% < growth rate ≤ 10% (excellent);

[0262] ○: 10% < growth rate ≤ 20% (good);

[0263] △: 20% < growth rate ≤ 30% (acceptable) (no problem in practice);

[0264] ×: 30% < growth rate (unacceptable) (problem in practice).

[0265] [Capacity retention rate]

[0266] The capacity retention rate was evaluated based on the value (retention rate) standardized by dividing the discharge capacity at room temperature after the floating charge test at 60°C described below by the discharge capacity at room temperature before the floating charge test.

[0267] ◎◎: 80% ≤ retention rate (optimal);

[0268] ◎: 75% ≤ retention rate < 80% (excellent);

[0269] ○: 65% ≤ retention rate < 75% (good);

[0270] △: 60% ≤ retention rate < 65% (acceptable) (no problem in practice);

[0271] ×: retention rate < 60% (unacceptable) (problem in practice).

[0272] [Comprehensive judgment]

[0273] Based on the judgment results of the interface resistance increase rate and the capacity retention rate, a comprehensive judgment was made.

[0274] ◎◎: All judgment results are ◎◎.

[0275] ◎: Among all the judgment results, the lowest judgment result is ◎.

[0276] ○: Among all the judgment results, the lowest judgment result is ○.

[0277] △: Among all the judgment results, the lowest judgment result is △.

[0278] ×: Among all the judgment results, the lowest judgment result is ×.

[0279] [Floating charge test]

[0280] Charge at a constant current of 0.1C until 4.2V is reached. After reaching 4.2V, charge at a constant voltage until the current decreases to 0.01C. After the charging is completed, make it in an open-circuit state. After standby for 3 hours, perform AC impedance measurement in the frequency range of 0.1Hz to 7MHz with a voltage amplitude of 10mV to obtain a Cole-Cole curve. The conditions for AC impedance are that from the frequency band above 1MHz to the frequency band below 0.1Hz, the voltage amplitude is about 10mV. After the AC impedance measurement, discharge at a constant current of 0.1C until 3V.

[0281] Then, perform constant-current charging at 0.1C in a thermostat at 60°C. After reaching 4.2V, perform constant-voltage charging for 1 week to implement floating charging. After 1 week of floating charging is completed, perform constant-current discharging at 0.1C in the state of 60°C and end the discharging at 3V.

[0282] Take out the battery cell from the 60°C thermostat. At room temperature, under the same conditions as the initial charge-discharge characteristics, confirm the battery characteristics after floating charging. Charge at a constant current of 0.1C until 4.2V is reached. After reaching 4.2V, charge at a constant voltage until the current decreases to 0.01C. After the charging is completed, make it in an open-circuit state. After standby for 3 hours, perform AC impedance measurement. After the AC impedance measurement, discharge at a constant current of 0.1C until 3V.

[0283] [Confirmation of Element Distribution]

[0284] Embed the co-fired laminate of the positive electrode layer / solid electrolyte layer (in the state before pasting metallic Li) with resin, perform delamination to obtain a TEM observation specimen.

[0285] Use TEM-EDX (Energy Dispersive X-ray Spectroscopy) to perform composition analysis based on EDX and perform element distribution mapping near the LCO-LLZ interface.

[0286] Figure 3A It is a specimen of Example 2, showing a TEM photograph (left side) near the LCO-LLZ interface and a TEM photograph (right side) of its Mg distribution mapping.

[0287] Figure 3B Show in Figure 3A In the left TEM photograph, the measurement results when measuring the Mg element from the LCO-LLZ interface into the LCO interior.

[0288] Figure 4A It is a specimen of Example 4, showing a TEM photograph (left side) near the LCO-LLZ interface and a TEM photograph (right side) of its Al distribution mapping.

[0289] Figure 4B Show in Figure 4AMeasurement results of Al element when measuring from the LCO-LLZ interface into the LCO in the TEM image on the left side.

[0290] [Garnet-type crystal structure]

[0291] The garnet-type crystal structure was confirmed by obtaining an X-ray diffraction image attributable to a crystal structure similar to the garnet type from X-ray diffraction (XRD measurement) (ICDD Card No. 00-045-0109).

[0292] [Layered rock salt-type crystal structure]

[0293] The layered rock salt-type crystal structure was confirmed by obtaining an X-ray diffraction image attributable to the layered rock salt-type crystal structure from X-ray diffraction (XRD measurement) (ICDD Card No. 01-070-2685).

[0294] [Chemical composition]

[0295] In the "confirmation of element distribution", the chemical composition was measured by performing EDX-based compositional analysis using TEM-EDX (energy-dispersive X-ray spectroscopy).

[0296] <Measurement of the concentrations of Mg and Al in the vicinity of the interface and inside the particles of the positive electrode active material>

[0297] The positive electrode layer was cut out in two arbitrary directions by FIB processing. In each of their cross-sections (TEM cross-sectional observation), five arbitrary positive electrode active material particles were focused on (a total of ten positive electrode active material particles). Then, in each positive electrode active material particle 1, at ten arbitrary positions in the vicinity of the interface 11 with the adjacent garnet-type oxide 2, the chemical composition was determined by TEM-EDX point analysis to obtain the concentrations of Mg and Al. In addition, in each positive electrode active material particle 1, at ten arbitrary positions inside the particle 12 located inside the vicinity of the interface 11 with the adjacent garnet-type oxide 2, the chemical composition was determined by TEM-EDX point analysis to obtain the concentrations of Mg and Al.

[0298] <Measurement of the Al content in the garnet-type oxide>

[0299] The garnet-type oxide was cut out in two arbitrary directions by FIB processing. In each of their cross-sections (TEM cross-sectional observation), the chemical composition was determined by TEM-EDX point analysis at 30 arbitrary points to measure the concentrations of Al and La, and obtain the ratio of Al to La.

[0300] [Table 1]

[0301]

[0302] When conducting a high-temperature floating charge (60 °C) test starting from Comparative Example 1 using ordinary LCO, a significant increase in interfacial resistance and a decrease in capacity retention rate were confirmed.

[0303] As can be seen from Examples 1 to 7, by containing Al and / or Mg in LCO, there is an effect of significantly suppressing the increase in the above-mentioned interfacial resistance and the decrease in capacity retention rate.

[0304] However, as can be seen from Comparative Examples 2, 3, and 5, when Fe, Si, and Ti are contained in LCO, the characteristics are instead degraded. That is, it can be seen that only specific elements are effective in improving the characteristics of LCO, and these elements are Al and / or Mg.

[0305] From the comparison between Comparative Example 1 and Comparative Example 4, it can be seen that by containing Al in LLZ, the above characteristics deteriorate.

[0306] From the comparison between Comparative Example 6 and Example 4, it can be seen that even when Al is contained in LCO, when Al is contained in LLZ, the effects of the present invention cannot be obtained.

[0307] From the above, in order to fully obtain the effects of the present invention, it is necessary not to contain Al in LLZ and to contain Al and / or Mg in LCO.

[0308] Industrial Applicability

[0309] The solid battery including a solid electrolyte ceramic of the present invention can be applied to various fields where batteries or power storage are envisioned. Although only by way of example, the solid battery according to one embodiment of the present invention can be used in the field of electronic mounting. The solid battery according to one embodiment of the present invention can also be applied to the following fields: the electrical / information / communication field using mobile devices, etc. (for example, the electrical / electronic device field or the mobile device field including small electronic devices such as mobile phones, smartphones, smartwatches, laptop computers, digital cameras, activity meters, wrist-mounted computers, electronic paper, wearable devices, RFID tags, card-type electronic money, smartwatches, etc.); home / small industry uses (for example, the field of power tools, golf carts, home / care / industrial robots); large industry uses (for example, the field of forklifts, elevators, port cranes); transportation system fields (for example, the fields of hybrid vehicles, electric vehicles, buses, trams, electric assist bicycles, electric motorcycles, etc.); power system uses (for example, various power generation, load regulators, smart grids, general household installation-type power storage systems, etc.); and medical uses (the field of medical devices such as earphone hearing aids); pharmaceutical uses (the field of medication management systems); and the IoT field; space / deep sea uses (for example, the fields of space probes, submersible survey ships, etc.).

[0310] Description of reference numerals

[0311] 1: Positive electrode active material; 11: Portion near the interface with the garnet-type oxide in the positive electrode active material; 12: Inner region (inside the particles) of the positive electrode active material; 2: Garnet-type oxide; S: Interface between the positive electrode active material and the garnet-type oxide.

Claims

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

2. The solid battery according to claim 1, wherein the oxide contains La, and the content of Al in the oxide is less than 0.08 relative to the content of La.

3. The solid battery according to claim 1 or 2, wherein the positive electrode active material has a chemical composition represented by the following general formula (R): Li a M1 β M2 γ O ω (R) In formula (R), M1 is one or more elements selected from the group consisting of cobalt (Co), nickel (Ni), and manganese (Mn); M2 contains one or more elements selected from the group consisting of magnesium (Mg) and aluminum (Al); α satisfies 0.8 ≤ α ≤ 1.5; β satisfies 0.8 ≤ β ≤ 1.2; γ / β satisfies 0 < γ / β ≤ 0.2; ω satisfies 1.8 ≤ ω ≤ 2.

2.

4. The solid battery according to claim 3, wherein M2 contains Al, The value of γ equivalent to Al, γ Al satisfies 0.008 ≤ γ Al ≤ 0.

08.

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

6. The solid battery according to any one of claims 1 to 5, wherein the positive electrode active material has an interface vicinity portion with the oxide and inside its particles, and the concentration of at least one of Mg or Al inside the particles is greater than the concentration of the at least one at the interface vicinity portion.

7. The solid battery according to any one of claims 1 to 5, wherein the positive electrode active material has an interface vicinity portion with the oxide and inside its particles, The total concentration C of magnesium (Mg) and aluminum (Al) inside the particle N is greater than the total concentration C of magnesium (Mg) and aluminum (Al) in the vicinity of the interface K .

8. The solid battery according to claim 7, wherein The total concentration C K With respect to the total concentration C N The concentration ratio C K / C N is 0.01 or more and 0.90 or less.

9. The solid battery according to claim 7 or 8, wherein The total concentration C K is 0.1 atomic % or more and 2.0 atomic % or less, The total concentration C N is 0.8 atomic % or more and 5.0 atomic % or less.

10. The solid battery according to any one of claims 1 to 9, wherein the oxide has a chemical composition represented by the following general formula (I): (Li α-p A x )(B I β-y B II y )(D I γ-z D II z )O ω (I) In formula (I), A is one or more elements that can be solid-dissolved in the Li site of the oxide having the garnet-type crystal structure and does not contain aluminum (Al); B I is at least one element selected from the group consisting of elements belonging to Groups 1 to 3 that can form an 8-coordination with oxygen and can form a valence of 3; B II is one or more elements selected from the group consisting of elements belonging to Groups 1 to 3 that can form an 8-coordination with oxygen and that can form a valence other than trivalent; D I is one or more elements selected from the group consisting of transition elements capable of forming a 6-coordination with oxygen and typical elements belonging to Groups 12 to 15, which are elements capable of forming a valence of 4; D II is one or more elements selected from the group consisting of transition elements capable of forming a 6-coordination with oxygen and typical elements belonging to Groups 12 to 15, which are elements capable of forming a valence other than tetravalence; α satisfies 5.0 ≤ α ≤ 8.0; β satisfies 2.5 ≤ β ≤ 3.5; γ satisfies 1.5 ≤ γ ≤ 2.5; ω satisfies 11 ≤ ω ≤ 13; x satisfies 0 ≤ x ≤ 1.0; y satisfies 0 ≤ y ≤ 1.0; z satisfies 0.4 ≤ z ≤ 2.2; p is represented by the following calculation formula: p = ax - (3 - b)y + (d - 4)z Wherein, a is the average valence number of A; b is the average valence number of B II ; d is the average valence number of D II .

11. The solid battery according to claim 10, wherein D II Contains bismuth Bi.

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

13. The solid battery according to any one of claims 1 to 11, wherein the solid electrolyte layer and the positive electrode layer and the negative electrode layer form an integral sintering of sintered bodies with each other.

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