Solid electrolyte ceramics and solid-state batteries

Abstract

The present invention provides a solid electrolyte ceramic having excellent ionic conductivity, while being able to more sufficiently suppress an increase in electronic conductivity caused by the operation of a solid battery, and having a higher relative density. The present invention relates to a solid electrolyte ceramic having a garnet-type crystal structure, containing at least Li (lithium), La (lanthanum), and O (oxygen), and further containing one or more transition metal elements selected from the group consisting of Co (cobalt), Ni (nickel), Mn (manganese), and Fe (iron). When the content of Li is set to X (mol%) and the total content of the one or more transition metal elements is set to Y (mol%), any one of the following relational expressions (1) to (3) is satisfied: (1) 0.01 ≤ Y ≤ 4.00 in the range of 221 ≤ X < 227; (2) 0.01 ≤ Y ≤ 6.00 in the range of 227 ≤ X < 237; (3) 0.01 ≤ Y ≤ 8.00 in the range of 237 ≤ X ≤ 250.

Description

Technical Field

[0001] The present invention relates to a solid electrolyte ceramic and a solid battery including the solid electrolyte ceramic. Background Art

[0002] In recent years, the demand for batteries has increased significantly as power sources for portable electronic devices such as mobile phones and portable personal computers. As a battery for such uses, the development of a sintered solid secondary battery (so-called "solid battery") that uses a solid electrolyte as the electrolyte and other constituent elements are also made of solids is underway.

[0003] A solid battery includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer laminated between the positive electrode layer and the negative electrode layer. In particular, the solid electrolyte layer contains a solid electrolyte ceramic and is responsible for ion conduction between the positive electrode layer and the negative electrode layer. The solid electrolyte ceramic is required to have a higher ion conductivity and a lower electron conductivity. As such a solid electrolyte ceramic, from the viewpoint of higher ion conductivity, ceramics obtained by replacing a sintered garnet-type solid electrolyte with Bi have been tried (for example, Patent Document 1 and Non-Patent Document 1).

[0004] In addition, in a solid battery, a solid electrolyte ceramic with a higher relative density is required from the viewpoint of battery capacity.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2015-050071

[0008] Non-Patent Documents

[0009] Non-Patent Document 1: Gao et al., Solid State Ionics, 181(2010)1415-1419 Summary of the Invention

[0010] Technical Problem to be Solved by the Invention

[0011] The inventors of the present invention have found that the following problems occur in a solid battery using the above-mentioned existing solid electrolyte ceramic. Specifically, in an existing solid battery using a garnet-type solid electrolyte ceramic containing Bi, impurities such as Li-Bi-O-based compounds are likely to be generated at grain boundaries, and the Li-Bi-O-based compounds are reduced during the operation of the solid battery (i.e., during charging and discharging), resulting in an increase in electron conductivity. If the electron conductivity increases, a short-circuit phenomenon of the solid battery occurs and / or an increase in leakage current occurs.

[0012] The inventors of the present invention have also found that, from the viewpoint of suppressing the formation of Li-Bi-O-based compounds, it is effective to contain transition metal elements such as Co, but it has also been found that the following new problems will occur. Specifically, if a relatively large amount of transition metal elements is contained, impurities containing transition metals such as Li-La-Co-O-based compounds different from Li-Bi-O-based compounds are generated, and the electron conductivity of these impurities containing transition metals also increases during the operation of the solid battery.

[0013] An object of the present invention is to provide a solid electrolyte ceramic having excellent ionic conductivity, capable of more sufficiently suppressing the increase in electron conductivity caused by the operation of a solid battery, and having a higher relative density.

[0014] Another object of the present invention is to provide a solid electrolyte ceramic that has excellent ionic conductivity even when containing a relatively large amount of transition metal elements, can more sufficiently suppress the increase in electron conductivity caused by the operation of a solid battery, and has a higher relative density.

[0015] Technical solutions for solving technical problems

[0016] The present invention relates to a solid electrolyte ceramic having a garnet-type crystal structure,

[0017] the solid electrolyte ceramic contains at least Li (lithium), La (lanthanum), and O (oxygen), and further contains one or more transition metal elements selected from the group consisting of Co (cobalt), Ni (nickel), Mn (manganese), and Fe (iron),

[0018] the solid electrolyte ceramic has a chemical composition represented by the following general formula (I),

[0019] A α B β D γ O ω (I)

[0020] (In formula (I), A is one or more elements selected from the group consisting of Li (lithium), Ga (gallium), Al (aluminum), Mg (magnesium), Zn (zinc), and Sc (scandium), and at least contains Li (lithium);

[0021] B is one or more elements selected from the group consisting of La (lanthanum), Ca (calcium), Sr (strontium), Ba (barium), and lanthanide elements, and at least contains La (lanthanum);

[0022] D is one or more elements selected from the group consisting of transition elements capable of forming a 6-coordinate with oxygen and main group elements belonging to Groups 12 to 15;

[0023] α satisfies 5.0 ≤ α ≤ 8.0;

[0024] β satisfies 2.5 ≤ β ≤ 3.5;

[0025] γ satisfies 1.5 ≤ γ ≤ 2.5;

[0026] ω satisfies 11 ≤ ω ≤ 13),

[0027] When the content of B is set to 100 mol%, the content of Li is set to X (mol%), and the total content of the above-mentioned one or more transition metal elements is set to Y (mol%), any one of the following relational expressions (1) to (3) is satisfied:

[0028] (1) 0.01 ≤ Y ≤ 4.00 in the range of 221 ≤ X < 227;

[0029] (2) 0.01 ≤ Y ≤ 6.00 in the range of 227 ≤ X < 237;

[0030] (3) 0.01 ≤ Y ≤ 8.00 in the range of 237 ≤ X ≤ 250.

[0031] Effects of the Invention

[0032] The solid electrolyte ceramic of the present invention has excellent ionic conductivity, and at the same time can more sufficiently suppress the increase in electron conductivity caused by the operation of the solid battery.

[0033] The solid electrolyte ceramic of the present invention also has a higher relative density. Detailed Embodiments

[0034] [Solid Electrolyte Ceramic]

[0035] The solid electrolyte ceramic of the present invention is composed of a sintered body formed by sintering solid electrolyte particles. The solid electrolyte ceramic of the present invention is a solid electrolyte ceramic containing at least Li (lithium), La (lanthanum), and O (oxygen), and having a garnet-type crystal structure, and further contains one or more transition metal elements selected from the group consisting of Co (cobalt), Ni (nickel), Mn (manganese), and Fe (iron) (hereinafter sometimes simply referred to as "prescribed transition metal elements"). In addition, the solid electrolyte ceramic of the present invention is a ceramic composed of a solid electrolyte having a garnet-type crystal structure, and within the range not impairing the effects of the present invention, other composite oxides or single oxides may also be included. In addition, from the viewpoint of more excellent ionic conductivity, Bi (bismuth) is preferably included. In addition, it is sufficient that the sintered particles contained in the solid electrolyte ceramic as at least the main component of the present invention have a garnet-type crystal structure.

[0036] The solid electrolyte ceramic of the present invention preferably has a chemical composition represented by the following general formula (I), and further contains a specified transition metal element.

[0037] A α B β D γ O ω (I)

[0038] In formula (I), A is one or more elements selected from the group consisting of Li (lithium), Ga (gallium), Al (aluminum), Mg (magnesium), Zn (zinc), and Sc (scandium), and at least contains Li.

[0039] B is one or more elements selected from the group consisting of La (lanthanum), Ca (calcium), Sr (strontium), Ba (barium), and lanthanide elements, and at least contains La. Examples of lanthanide elements include Ce (cerium), 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).

[0040] D represents one or more elements selected from the group consisting of transition elements capable of forming a 6 - coordinate bond with oxygen and main group elements belonging to Groups 12 - 15. Examples of transition elements capable of forming a 6 - coordinate bond with oxygen include Sc (scandium), Zr (zirconium), Ti (titanium), Ta (tantalum), Nb (niobium), Hf (hafnium), Mo (molybdenum), W (tungsten), and Te (tellurium). Examples of main group elements belonging to Groups 12 - 15 include In (indium), Ge (germanium), Sn (tin), Pb (lead), Sb (antimony), and Bi (bismuth). From the viewpoint of more excellent ionic conductivity, D preferably contains at least Bi.

[0041] In formula (I), α, β, γ, and ω respectively satisfy 5.0 ≤ α ≤ 8.0, 2.5 ≤ β ≤ 3.5, 1.5 ≤ γ ≤ 2.5, and 11 ≤ ω ≤ 13.

[0042] From the viewpoint of more excellent ionic conductivity and more fully suppressing the increase in electron conductivity during operation, α preferably satisfies 6.5 ≤ α ≤ 8.0, more preferably satisfies 6.65 ≤ α ≤ 7.5, further preferably satisfies 6.65 ≤ α ≤ 7.0, and particularly preferably satisfies 6.65 ≤ α ≤ 6.75.

[0043] From the viewpoint of more excellent ionic conductivity and more fully suppressing the increase in electron conductivity during operation, β preferably satisfies 2.5 ≤ β ≤ 3.3, more preferably satisfies 2.5 ≤ β ≤ 3.1, and further preferably satisfies 2.8 ≤ β ≤ 3.0.

[0044] From the viewpoint of more excellent ion conductivity and more fully suppressing the increase in electron conductivity during operation, γ preferably satisfies 1.8 ≤ γ ≤ 2.5, more preferably satisfies 1.8 ≤ γ ≤ 2.3, and still more preferably satisfies 1.9 ≤ γ ≤ 2.3.

[0045] From the viewpoint of more excellent ion conductivity and more fully suppressing the increase in electron conductivity during operation, ω preferably satisfies 11 ≤ ω ≤ 12.5, and more preferably satisfies 11.5 ≤ ω ≤ 12.5.

[0046] In the present invention, the solid electrolyte ceramic contains a relatively large amount of Li within a specific range. Even if a relatively large amount of transition metal elements are contained, it has excellent ion conductivity and more fully suppresses the increase in electron conductivity. In such a solid electrolyte ceramic, if the content of Li is too small, the increase in electron conductivity cannot be sufficiently suppressed. When the content of Li is too large, the relative density decreases.

[0047] In the present invention, the content of Li and the content of a specified transition metal element in the solid electrolyte ceramic are specifically as follows. That is, when the content of B in the general formula (I) representing the chemical composition of the solid electrolyte ceramic of the present invention is set to 100 mol%, and the content of Li is set to X (mol%) and the total content of the specified transition metal element is set to Y (mol%), the solid electrolyte ceramic of the present invention satisfies any one of the following relational expressions (1) to (3):

[0048] (1) In the range of 221 ≤ X < 227 (especially 222 ≤ X ≤ 226), 0.01 ≤ Y ≤ 4.00 (the combined range of 0.01 ≤ Y < 1.40 and 1.40 ≤ Y ≤ 4.00) (from the viewpoints of more excellent ion conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, it is preferably 0.01 ≤ Y ≤ 3.50 (the combined range of 0.01 ≤ Y < 1.50 and 1.50 ≤ Y ≤ 3.50), and more preferably 0.02 ≤ Y ≤ 3.40 (the combined range of 0.02 ≤ Y < 1.60 and 1.60 ≤ Y ≤ 3.40));

[0049] (2) In the range of 227 ≤ X < 237 (especially 227 ≤ X ≤ 235), 0.01 ≤ Y ≤ 6.00 (the combined range of 0.01 ≤ Y < 1.40 and 1.40 ≤ Y ≤ 6.00) (from the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, it is preferably 0.01 ≤ Y ≤ 5.50 (the combined range of 0.01 ≤ Y < 1.50 and 1.50 ≤ Y ≤ 5.50), and more preferably 0.02 ≤ Y ≤ 5.20 (the combined range of 0.02 ≤ Y < 1.60 and 1.60 ≤ Y ≤ 5.20));

[0050] (3) In the range of 237 ≤ X ≤ 250 (especially 237 ≤ X ≤ 245), 0.01 ≤ Y ≤ 8.00 (the combined range of 0.01 ≤ Y < 1.40 and 1.40 ≤ Y ≤ 8.00) (from the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, it is preferably 0.01 ≤ Y ≤ 7.50 (the combined range of 0.01 ≤ Y < 1.50 and 1.50 ≤ Y ≤ 7.50), and more preferably 0.02 ≤ Y ≤ 7.00 (the combined range of 0.02 ≤ Y < 1.60 and 1.60 ≤ Y ≤ 7.00)).

[0051] In each of the relational expressions (1) to (3), if the total content Y of the specified transition metal element exceeds the specified value too much, the increase in electron conductivity cannot be sufficiently suppressed.

[0052] The content X of the above-mentioned Li and the total content Y of the specified transition metal element can be expressed as the ratio (mol%) when the content of B is set to 100 mol%, and can also be expressed as the ratio (mol%) when the number of 8 - coordinate sites in the garnet - type crystal structure is set to 100 mol%. For example, in the case of the chemical composition of the general formula (II) described later, this ratio is a value that can be expressed as the ratio (mol%) when the total of La and B 1 is set to 100 mol%. In other specific examples, the 8 - coordinate sites in the garnet - type crystal structure are, for example, the sites occupied by La in Li5La3Nb2O 12 (ICDD CardNo.00 - 045 - 0109), and are also the sites occupied by La in Li7La3Zr2O 12 (ICDDCard.No01 - 078 - 6708).

[0053] The content of Li and the content of the specified transition metal elements can be determined by performing inductively coupled plasma (ICP) emission spectroscopic analysis (ICP analysis) of the solid electrolyte ceramic to obtain the average chemical composition of the material. Specifically, the average chemical composition can be determined based on the ICP analysis, and from this average chemical composition, the content of Li and the proportions of Co, Mn, Ni, and Fe when the content of B in the general formula (I) is set to 100 mol% can be determined. For example, it is also possible to determine the proportions when the number of 8 - coordinate sites in the garnet - type crystal structure (e.g., the total of La and B 1 in the above - mentioned general formula (II)) is set to 100 mol%.

[0054] It should be noted that it is also possible to measure and calculate using an X - ray photoelectron spectroscopy (XPS) apparatus.

[0055] When the content of B is set to 100 mol%, the content of Bi (bismuth) is usually 33 mol% or less. From the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, it is preferably more than 0 mol% and 23 mol% or less, more preferably 0.3 mol% or more and 13 mol% or less, still more preferably 1 mol% or more and 12 mol% or less, and particularly preferably 5 mol% or more and 10 mol% or less.

[0056] The content of Bi, like the content of the specified transition metal elements, can be determined by performing inductively coupled plasma (ICP) emission spectroscopic analysis (ICP analysis) of the solid electrolyte ceramic to obtain the average chemical composition of the material. Specifically, the average chemical composition can be determined based on the ICP analysis, and from this average chemical composition, the proportion of the content of Bi when the content of B in the general formula (I) (e.g., the total of La and B 1 in the following general formula (II)) is set to 100 mol% can be determined. It should be noted that it is also possible to measure and calculate using an X - ray photoelectron spectroscopy (XPS) apparatus.

[0057] From the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, the solid electrolyte ceramic of the present invention preferably satisfies the above - mentioned relational expression (1) or (2), and more preferably satisfies the above - mentioned relational expression (1).

[0058] The mode of existence (or inclusion mode) of the specified transition metal element in the solid electrolyte ceramic of the present invention is not particularly limited and may exist in the lattice or outside the lattice. For example, the specified transition metal element in the solid electrolyte ceramic may exist in the bulk, in the grain boundary, or in both. As an example of the specified transition metal element existing in the bulk, it means that in the solid electrolyte ceramic of the present invention, the specified transition metal element exists in the metal site (lattice site) constituting the garnet-type crystal structure. The metal site can be any metal site, for example, it can be a Li site, a La site, a Bi site, or two or more of them. The specified transition metal element existing in the grain boundary means that the solid electrolyte ceramic of the present invention is composed of a plurality of sintered particles, and the specified transition metal element can exist at the interface between two or more sintered particles.

[0059] When the solid electrolyte ceramic of the present invention contains Bi, the mode of existence (or inclusion mode) of Bi (bismuth) in the solid electrolyte ceramic of the present invention is not particularly limited. For example, the specified Bi (bismuth) in the solid electrolyte ceramic may exist in the bulk, in the grain boundary, or in both. From the viewpoint of insulation, it is preferred that Bi exists in the bulk. As an example of Bi existing in the bulk, in the solid electrolyte ceramic of the present invention, the Bi may also exist in the metal site (lattice site) constituting the garnet-type crystal structure.

[0060] In the present invention, the specified transition metal and / or Bi (bismuth) may also be contained in the ceramic having a garnet-type crystal structure. In addition, the specified transition metal and / or Bi (bismuth) may exist as a composite oxide and / or a single oxide containing the specified transition metal and / or Bi (bismuth). It should be noted that the oxide may also exist at the interface between the crystal particles of the ceramic having a garnet-type crystal structure as the main component of the present invention.

[0061] Li (lithium) and La (lanthanum) in the solid electrolyte ceramic of the present invention can generally exist in the bulk respectively. Specifically, as an example, in the solid electrolyte ceramic of the present invention, they may also exist in the Li site and the La site which are the metal sites (lattice sites) constituting the garnet-type crystal structure. At this time, Li (lithium) and La (lanthanum) can exist independently in part at the grain boundary.

[0062] From the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, the transition metal element contained in the solid electrolyte ceramic of the present invention is preferably selected from the group consisting of Co, Ni, and Mn, more preferably selected from the group consisting of Co and Mn, and further preferably contains Co.

[0063] In the present invention, that the solid electrolyte ceramic has a garnet-type crystal structure means that the solid electrolyte ceramic may not only have a "garnet-type crystal structure", but also include a case having a "garnet-like crystal structure". Specifically, the solid electrolyte ceramic of the present invention has a crystal structure that can be recognized as a garnet-type or garnet-like crystal structure by those skilled in the art in the field of solid-state batteries in X-ray diffraction. More specifically, the solid electrolyte ceramic of the present invention can show, 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. 422259), or, as a garnet-like crystal structure, can 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) corresponding to the Miller indices inherent in the so-called garnet-type crystal structure due to compositional differences. As a representative diffraction pattern of the garnet-like crystal structure, for example, ICDD Card No. 00-045-0109, etc. can be cited.

[0064] As a specific embodiment, the solid electrolyte ceramic of the present invention can have a chemical composition represented by the general formula (II). Specifically, the solid electrolyte ceramic as a whole can have a chemical composition represented by the general formula (II). It should be noted that at this time, the solid electrolyte ceramic of the present invention has a chemical composition represented by the general formula (II), and at the same time, as described above, it also contains a specified transition metal element.

[0065] (Li p A 1 y )(La β-z B 1 z )(D 1 y-x Bi x )0 12-δ II)

[0066] In the formula (II), A 1 refers to the metal element occupying the Li coordination site in the garnet-type crystal structure. A 1is an element corresponding to A in the general formula (I), and may also be one or more elements selected from the group consisting of elements other than Li among the same elements as those exemplified for A. A 1 is usually one or more elements selected from the group consisting of Ga (gallium), Al (aluminum), Mg (magnesium), Zn (zinc), and Sc (scandium). From the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, A 1 is preferably one or more elements selected from the group consisting of Ga (gallium) and Al (aluminum), and more preferably both elements Ga and Al.

[0067] In formula (II), B 1 refers to the metal element occupying the La site in the garnet-type crystal structure. B 1 is an element corresponding to B in the general formula (I), and may also be one or more elements selected from the group consisting of elements other than La among the same elements as those exemplified for B. B 1 is usually one or more elements selected from the group consisting of Ca (calcium), Sr (strontium), Ba (barium), and lanthanide elements.

[0068] In formula (II), D 1 refers to the metal element occupying the 6-coordination site (the site occupied by Zr in the garnet-type crystal structure Li7La3Zr2O 12 (ICDD Card.No01-078-6708)). D 1 is an element corresponding to D in the general formula (I), and may also be one or more elements selected from the group consisting of elements other than Bi among the same elements as those exemplified for D. D 1 is usually one or more elements selected from the group consisting of Zr (zirconium), Ta (tantalum), Hf (hafnium), Nb (niobium), Mo (molybdenum), W (tungsten), and Te (tellurium). From the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, it is preferably one or more elements selected from the group consisting of Zr (zirconium) and Ta (tantalum), and more preferably contains Zr (zirconium) and Ta (tantalum).

[0069] In formula (II), x satisfies 0 < x ≤ 1.00. From the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, it is preferably 0.01 ≤ x ≤ 0.70, more preferably 0.02 ≤ x ≤ 0.40, further preferably 0.05 ≤ x ≤ 0.40, and particularly preferably 0.05 ≤ x ≤ 0.35.

[0070] y satisfies 0 ≤ y ≤ 0.50. From the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, it is preferably 0 ≤ y ≤ 0.40, more preferably 0 ≤ y ≤ 0.30, further preferably 0 ≤ y ≤ 0.20, and particularly preferably 0.

[0071] β satisfies 2.5 ≤ β ≤ 3.3. From the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, it is preferably 2.5 ≤ β ≤ 3.1, and more preferably 2.8 ≤ β ≤ 3.0.

[0072] z satisfies 0 ≤ z ≤ 2.00. From the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, it is preferably 0 ≤ z ≤ 1.00, more preferably 0 ≤ z ≤ 0.50, and further preferably 0.

[0073] γ satisfies 1.5 ≤ γ ≤ 2.5. From the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, it is preferably 1.8 ≤ γ ≤ 2.5, more preferably 1.8 ≤ γ ≤ 2.3, and further preferably 1.9 ≤ γ ≤ 2.3.

[0074] In formula (II), p satisfies 5.0 ≤ p ≤ 8.0. From the viewpoints of more excellent ionic conductivity and more fully suppressing the increase in electron conductivity during operation, it satisfies 6.5 ≤ p ≤ 8.0, more preferably 6.65 ≤ p ≤ 7.5, further preferably 6.65 ≤ p ≤ 7.0, and particularly preferably 6.65 ≤ p ≤ 6.75. It should be noted that the identification of the existence form of Li is difficult, and it can also be a value calculated based on the composition of the entire ceramic obtained by ICP (inductively coupled plasma method) or XPS analysis.

[0075] a is the average valence number of A 1 As A 1 , for example, when it is considered that there are n1 elements X with valence a+, n2 elements Y with valence b+, and n3 elements Z with valence c+, the average valence number of A 1 is the value represented by (n1 × a + n2 × b + n3 × c) / (n1 + n2 + n3).

[0076] b is the average valence number of B 1 As B 1 , for example, when it is considered that there are n1 elements X with valence a+, n2 elements Y with valence b+, and n3 elements Z with valence c+, B 1The average valence number is the same as that of A above 1 and has the same value as the average valence number of A above.

[0077] c is the average valence number of D 1 . As D 1 , for example, when it is considered that there are n1 elements X with valence a+, n2 elements Y with valence b+, and n3 elements Z with valence c+, the average valence number of D 1 is the same as the average valence number of A above 1 and has the same value as the average valence number of A above.

[0078] δ represents the amount of oxygen deficiency and can be 0. Usually, 0 ≤ δ < 1 is satisfied. Since the amount of oxygen deficiency δ cannot be quantitatively analyzed even with the latest devices, it can be considered to be 0.

[0079] In the present invention, the chemical composition of the solid electrolyte ceramic can be the composition of the entire ceramic material determined by ICP (inductively coupled plasma method). In addition, the chemical composition can be measured and calculated using XPS analysis, or can be determined using TEM-EDX (energy dispersive X-ray spectroscopy) and / or WDX (wavelength dispersive X-ray spectroscopy). Furthermore, the chemical composition can also be obtained by performing quantitative analysis (composition analysis) on 100 arbitrary points of each of 100 arbitrary sintered particles and calculating their average value.

[0080] The content of a specified transition metal element (i.e., Co, Ni, Mn, Fe) in the solid electrolyte ceramic of the present invention [for example, the content of B in the general formula (I) (or the total of La and B in the general formula (II)) 1 when set to 100 mol%) can be calculated by the following method. In the present invention, the chemical composition of the solid electrolyte ceramic can be determined by performing ICP analysis (inductively coupled plasma method), LA-ICP-MS (laser ablation ICP mass spectrometry) analysis, etc. In addition, it can be measured and calculated using XPS analysis, or can be determined using TEM-EDX (energy dispersive X-ray spectroscopy), WDX (wavelength dispersive X-ray spectroscopy). Furthermore, the chemical composition can also be obtained by performing quantitative analysis (composition analysis) on 100 arbitrary points of each of 100 arbitrary sintered particles and calculating their average value.

[0081] For example, the analysis by EDX or WDX is carried out on the cross-section of a solid-state battery. The cross-section of the solid-state battery refers to the cross-section parallel to the lamination direction of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer. The cross-section of the solid-state battery can be exposed by grinding after embedding the solid-state battery in resin. The method of grinding the cross-section is not particularly limited, and after cutting with a cutting machine or the like, grinding can be carried out using abrasive paper, chemical mechanical polishing, ion milling, etc., so as to expose the solid electrolyte layer. By quantitatively analyzing the exposed cross-section (solid electrolyte layer) using EDX or WDX (wavelength-dispersive fluorescent X-ray analyzer), the molar ratio of Co, Ni, Mn, and Fe to B can be calculated.

[0082] In addition, for example, in TEM-EELS measurement, after peeling off the electrode layer or the solid electrolyte layer of the solid-state battery using FIB (focused ion beam) or the like, TEM-EELS (transmission electron microscope - electron energy loss spectroscopy) measurement of the solid electrolyte part is carried out. Thereby, the elements B, Co, Ni, Mn, and Fe contained in B in the general formula (I) are detected, and the molar ratio of Co, Ni, Mn, and Fe to the content of B can be calculated.

[0083] As a specific example showing the chemical composition of the solid electrolyte ceramic of the present invention, the following chemical compositions can be cited. It should be noted that in the chemical compositions shown below, the transition metal elements after the hyphen (-) indicate that the transition metal elements can exist in the bulk and / or grain boundaries as described above.

[0084] Li 6.7 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.05

[0085] Li 6.7 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.1

[0086] Li 6.8 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.05

[0087] Li 6.8 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12-Co0.1

[0088] Li 6.8 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.15

[0089] Li 6.9 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.05

[0090] Li 6.9 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.1

[0091] Li 6.9 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.15

[0092] Li 7.1 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.05

[0093] Li 7.1 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.1

[0094] Li 7.1 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.15

[0095] Li 7.1 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.2

[0096] Li 7.2 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.05

[0097] Li 7.2 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.1

[0098] Li 7.2 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.15

[0099] Li 7.2 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.2

[0100] Li 7.3 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.05

[0101] Li 7.3 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.1

[0102] Li 7.3 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.15

[0103] Li 7.3 La3Zr 1.3 Ta 0.4 Bi 0.24 O 12 -Co0.2

[0104] Specific examples of the above chemical compositions contain Co as a transition element, and may also contain Ni, Mn, or Fe instead of Co.

[0105] [Method for manufacturing a solid electrolyte ceramic]

[0106] The solid electrolyte ceramic of the present invention can be obtained by mixing a compound containing a specified metal element (i.e., starting material) with water, drying it, and then performing heat treatment. The compound containing the specified metal element is usually a mixture of compounds containing one metal element selected from the group consisting of Li (lithium), La (lanthanum), and a specified transition metal element. As the compound containing the specified metal element (i.e., starting material), for example, lithium hydroxide monohydrate LiOH#H2O, lanthanum hydroxide La(OH)3, zirconium oxide ZrO2, tantalum oxide Ta2O5, bismuth oxide Bi2O3, cobalt oxide Co3O4, basic nickel carbonate hydrate NiCO3·2Ni(OH)2·4H2O, manganese carbonate MnCO3, iron oxide Fe2O3, lithium nitrate LiNO3, lanthanum nitrate hexahydrate La(NO3)3·6H2O, bismuth nitrate pentahydrate Bi(NO3)3·5H2O, etc. can be cited. The mixing ratio of the compound containing the specified metal element only needs to be a ratio such that the solid electrolyte ceramic of the present invention has a specified chemical composition after heat treatment. The heat treatment temperature is usually 500 °C or higher and 1200 °C or lower, preferably 600 °C or higher and 1000 °C or lower. The heat treatment time is usually 10 minutes or longer and 1440 minutes or shorter, particularly 60 minutes or longer and 600 minutes or shorter.

[0107] The solid electrolyte ceramic of the present invention may contain a sintering aid. As the sintering aid, all sintering aids known in the field of solid-state batteries can be used. 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 higher. As specific examples of such a sintering aid, for example, Li3BO3, (Li 2.7 Al 0.3 )BO3, Li 2.8 (B 0.8 C 0.2 )O3, LiBO2 can be cited.

[0108] With respect to the volume ratio of the garnet-type solid electrolyte, the content of the sintering aid is usually preferably 0% or higher and 10% or lower, particularly preferably 0% or higher and 5% or lower.

[0109] [Solid State Battery]

[0110] 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 more specifically 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 its name and may include, for example, an electrochemical device such as an "energy storage device".

[0111] 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 positive electrode layer and the negative electrode layer are laminated with the solid electrolyte layer interposed therebetween. 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 so-called integral sintering of sintered bodies means that two or more adjacent or contacting components (especially layers) are joined by sintering. Here, the two or more components (especially layers) are all sintered bodies and can also be integrally sintered.

[0112] The above-mentioned solid electrolyte ceramic of the present invention is useful as the solid electrolyte of the solid-state battery. Therefore, the solid-state battery of the present invention includes the above-mentioned solid electrolyte ceramic of the present invention as the solid electrolyte. Specifically, the solid electrolyte ceramic of the present invention is included as the solid electrolyte in at least one layer selected from the group consisting of the positive electrode layer, the negative electrode layer, and the solid electrolyte layer. From the viewpoints of more excellent ion conductivity in the solid electrolyte layer, more effectively suppressing the increase in the electron conductivity during operation, and further increasing the relative density, the solid electrolyte ceramic of the present invention is preferably included at least in the solid electrolyte layer.

[0113] (Positive electrode layer)

[0114] In the solid-state battery of the present invention, the positive electrode layer is not particularly limited. For example, the positive electrode layer contains a positive electrode active material and may also contain the solid electrolyte ceramic of the present invention. By including the solid electrolyte ceramic of the present invention in the positive electrode layer, short-circuiting of the solid-state battery can be suppressed. The positive electrode layer can be in the form of a sintered body containing positive electrode active material particles. The positive electrode layer can be a layer capable of inserting and extracting ions (especially lithium ions).

[0115] The positive electrode active material is not particularly limited, and positive electrode active materials known in the field of solid-state batteries can be used. As the positive electrode active material, for example, 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, lithium-containing oxide particles having a spinel-type structure, etc. can be cited. As specific examples of the preferably used lithium-containing phosphate compound having a NASICON-type structure, Li3V2(PO4)3 etc. can be cited. As specific examples of the preferably used lithium-containing phosphate compound having an olivine-type structure, Li3Fe2(PO4)3, LiMnPO4 etc. can be cited. As specific examples of the preferably used lithium-containing layered oxide particles, LiCoO2, LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 O2 etc. can be cited. As specific examples of the preferably used lithium-containing oxide having a spinel-type structure, LiMn2O4, LiNi 0.5 Mn 1.5 O4, Li4Ti5O 12 etc. can be cited. From the viewpoint of reactivity during co-sintering with the LISICON-type solid electrolyte used in the present invention, as the positive electrode active material, LiCoO2, LiCo 1 / 3 Ni 1 / 3Mn 1 / 3 O2 etc. of lithium-containing layered oxides are more preferably used. It should be noted that only one of these positive electrode active material particles can be used, or multiple kinds can be used in combination.

[0116] The positive electrode active material having a NASICON-type structure in the positive electrode layer means that the positive electrode active material (especially its particles) has a NASICON-type crystal structure, and in a broad sense, it means having a crystal structure that can be recognized as a NASICON-type crystal structure by those skilled in the art in the field of solid-state batteries. In a narrow sense, the positive electrode active material having a NASICON-type structure in the positive electrode layer means that: the positive electrode active material (especially its particles) shows one or more main peaks corresponding to the Miller indices inherent in the so-called NASICON-type crystal structure in X-ray diffraction at a specified incident angle. As the preferably used positive electrode active material having a NASICON-type structure, the compounds exemplified above can be cited.

[0117] That the positive electrode active material has an olivine-type structure in the positive electrode layer means that the positive electrode active material (especially its particles) has an olivine-type crystal structure. Broadly speaking, it means having a crystal structure that can be recognized as an olivine-type crystal structure by those skilled in the art in the field of solid-state batteries. Narrowly speaking, that the positive electrode active material has an olivine-type structure in the positive electrode layer means that: the positive electrode active material (especially its particles) shows, in X-ray diffraction, one or more main peaks corresponding to the Miller indices inherent in the so-called olivine-type crystal structure at a specified incident angle. As the positive electrode active material preferably used having an olivine-type structure, the compounds exemplified above can be cited.

[0118] That the positive electrode active material has a spinel-type structure in the positive electrode layer means that the positive electrode active material (especially its particles) has a spinel-type crystal structure. Broadly speaking, it means having a crystal structure that can be recognized as a spinel-type crystal structure by those skilled in the art in the field of solid-state batteries. Narrowly speaking, that the positive electrode active material has a spinel-type structure in the positive electrode layer means that: the positive electrode active material (especially its particles) shows, in X-ray diffraction, one or more main peaks corresponding to the Miller indices inherent in the so-called spinel-type crystal structure at a specified incident angle. As the positive electrode active material preferably used having a spinel-type structure, the compounds exemplified above can be cited.

[0119] The chemical composition of the positive electrode active material can also be an 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-state battery, using SEM-EDX (energy-dispersive X-ray spectroscopy), and performing compositional analysis by EDX when the entire thickness direction of the positive electrode layer is within the field of view.

[0120] 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, weigh the raw material compound containing the specified metal atoms, make the chemical composition into the specified chemical composition, add water and mix to obtain a slurry. Then, dry the slurry, pre-burn it at 700 °C or higher and 1000 °C or lower for 1 hour or longer and 30 hours or shorter, and then pulverize it to obtain the positive electrode active material.

[0121] The chemical composition and crystal structure of the positive electrode active material in the positive electrode layer usually change according to the element diffusion during sintering. It can also be that the positive electrode active material has the above chemical composition and crystal structure in the solid-state battery after being sintered together with the negative electrode layer and the solid electrolyte layer.

[0122] The average particle diameter of the positive electrode active material is not particularly limited, and for example, it may be 0.01 μm or more and 10 μm or less, preferably 0.05 μm or more and 4 μm or less.

[0123] 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).

[0124] The particle diameter is the diameter of a spherical particle assuming 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 (such as "Azokun" (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.

[0125] R = 2 × √(S / π) 1 / 2

[0126] It should be noted that the average particle diameter of the positive electrode active material in the positive electrode layer can be automatically measured by determining the positive electrode active material based on the composition during the measurement of the above average chemical composition.

[0127] The average particle diameter of the positive electrode active material in the positive electrode layer usually changes due to sintering during the manufacturing process of the solid battery. It is also possible that the positive electrode active material has the above-mentioned average particle diameter in the solid battery after being sintered together with the negative electrode layer and the solid electrolyte layer.

[0128] The volume ratio of the positive electrode active material in the positive electrode layer is not particularly limited, and for example, it may be 30% or more and 90% or less, especially 40% or more and 70% or less.

[0129] The positive electrode layer may contain the solid electrolyte ceramic of the present invention as a solid electrolyte, and / or may also contain a solid electrolyte other than the solid electrolyte ceramic of the present invention.

[0130] The positive electrode layer may further contain a sintering aid and / or a conductive material, etc.

[0131] When the positive electrode layer contains the solid electrolyte ceramic of the present invention, the volume ratio of the solid electrolyte ceramic of the present invention can usually be 20% or more and 60% or less, especially 30% or more and 45% or less.

[0132] As the sintering aid in the positive electrode layer, the same compounds as those that can be contained in the solid electrolyte ceramic can be used.

[0133] The volume ratio of the sintering aid in the positive electrode layer is not particularly limited, and for example, it is preferably 0.1% or more and 20% or less, more preferably 1% or more and 10% or less.

[0134] The conductive material in the positive electrode layer can use conductive materials known in the field of solid-state batteries. As preferred conductive materials, 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., such as carbon nanotubes. Regarding the shape of the carbon material, there is no particular limitation, and materials of any shape such as spherical, plate-like, fibrous, etc. can be used.

[0135] The volume ratio of the conductive material in the positive electrode layer is not particularly limited. For example, it is preferably 10% or more and 50% or less, more preferably 20% or more and 40% or less.

[0136] The thickness of the positive electrode layer is generally 0.1 to 30 μm, for example, preferably 1 to 20 μm. The thickness of the positive electrode layer uses the average value of the thickness measured at any 10 places in the SEM image.

[0137] In the positive electrode layer, the porosity is not particularly limited, preferably 20% or less, more preferably 15% or less, and further preferably 10% or less.

[0138] The porosity of the positive electrode layer uses the value measured from the SEM image after FIB cross-section processing.

[0139] The positive electrode layer is a layer that can be called the "positive electrode active material layer". The positive electrode layer can have a so-called positive electrode current collector or positive electrode current collecting layer.

[0140] (Negative electrode layer)

[0141] In the solid-state battery of the present invention, the negative electrode layer is not particularly limited. For example, the negative electrode layer contains a negative electrode active material and can also contain the solid electrolyte ceramic of the present invention. By containing the solid electrolyte ceramic of the present invention in the negative electrode layer, short-circuiting of the solid-state battery can be suppressed. The negative electrode layer can have a form including a sintered body of negative electrode active material particles. The negative electrode layer can be a layer capable of inserting and extracting ions (especially lithium ions).

[0142] The negative electrode active material is not particularly limited, and negative electrode active materials known in the field of solid-state 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 NASICON-type structure, Li-containing oxides having a spinel-type structure, having β II -Li3VO4 type structure, γ II -Li3VO4 type structure oxides, etc. are cited. The negative electrode active material is preferably lithium metal, having β II -Li3VO4 type structure, γII - Li-containing oxides with a Li3VO4-type structure.

[0143] The oxide in the negative electrode layer has a β II - The Li3VO4-type structure means that the oxide (especially its particles) has a β II - The Li3VO4-type crystal structure, in a broad sense, refers to a crystal structure that can be recognized by those skilled in the art in the field of solid-state batteries as a β II - Li3VO4-type crystal structure. Narrowly, the oxide in the negative electrode layer has a β II - The Li3VO4-type structure means that: the oxide (especially its particles) shows, in X-ray diffraction, at a specified incident angle, one or more main peaks corresponding to the Miller indices inherent to the so-called β II - Li3VO4-type crystal structure. As a preferably used Li-containing oxide with a β II - Li3VO4-type structure, Li3VO4 can be cited.

[0144] The oxide in the negative electrode layer has a γ II - The Li3VO4-type structure means that the oxide (especially its particles) has a γ II - The Li3VO4-type crystal structure, in a broad sense, refers to a crystal structure that can be recognized by those skilled in the art in the field of solid-state batteries as a γ II - Li3VO4-type crystal structure. Narrowly, the oxide in the negative electrode layer has a γ II - The Li3VO4-type structure means that: the oxide (especially its particles) shows, in X-ray diffraction, at a specified incident angle (x-axis), one or more main peaks corresponding to the Miller indices inherent to the so-called γ II - Li3VO4-type crystal structure. As a preferably used Li-containing oxide with a γ II - Li3VO4-type structure, Li 3.2 V 0.8 Si 0.2 O4.

[0145] The chemical composition of the negative electrode active material can 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-state battery, using SEM-EDX (energy-dispersive X-ray spectroscopy), and performing compositional analysis by EDX when the entire thickness direction of the negative electrode layer is within the field of view.

[0146] 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.

[0147] The chemical composition and crystal structure of the negative electrode active material in the negative electrode layer usually vary according to the element diffusion during sintering in the manufacturing process of the solid battery. Alternatively, the negative electrode active material may have the above-described average chemical composition and crystal structure in the solid battery after being sintered together with the positive electrode layer and the solid electrolyte layer.

[0148] The volume ratio of the negative electrode active material in the negative electrode layer is not particularly limited, and is preferably 50% or more (particularly 50% or more and 99% or less), more preferably 70% or more and 95% or less, and still more preferably 80% or more and 90% or less.

[0149] The negative electrode layer may contain the solid electrolyte ceramic of the present invention as the solid electrolyte, and / or may also contain a solid electrolyte other than the solid electrolyte ceramic of the present invention.

[0150] The negative electrode layer may further contain a sintering aid and / or a conductive material, etc.

[0151] When the negative electrode layer contains the solid electrolyte ceramic of the present invention, the volume ratio of the solid electrolyte ceramic of the present invention can usually be 20% or more and 60% or less, and particularly can be 30% or more and 45% or less.

[0152] As the sintering aid in the negative electrode layer, the same compounds as those in the positive electrode layer can be used.

[0153] As the conductive material in the negative electrode layer, the same compounds as those in the positive electrode layer can be used.

[0154] The thickness of the negative electrode layer is usually 0.1 to 30 μm, preferably 1 to 20 μm. The thickness of the negative electrode layer uses the average value of the thickness measured at any 10 places in the SEM image.

[0155] In the negative electrode layer, the porosity is not particularly limited, and is preferably 20% or less, more preferably 15% or less, and still more preferably 10% or less.

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

[0157] The negative electrode layer is a layer that can be called a "negative electrode active material layer". The negative electrode layer may have a so-called negative electrode current collector or negative electrode current collecting layer.

[0158] (Solid electrolyte layer)

[0159] In the solid battery of the present invention, from the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, the solid electrolyte layer preferably contains the solid electrolyte ceramic of the present invention described above.

[0160] The volume ratio of the solid electrolyte ceramic of the present invention in the solid electrolyte layer is not particularly limited. From the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, it is preferably 10% or more and 100% or less, more preferably 20% or more and 100% or less, and still more preferably 30% or more and 100% or less.

[0161] When the solid electrolyte layer contains the solid electrolyte ceramic of the present invention, it is sufficient that the solid electrolyte ceramic of the present invention having the above chemical composition exists at least in the central portion in the thickness direction of the solid electrolyte layer (particularly 5 or more, preferably 8 or more, and more preferably 10 of any 10 points thereof). This is because the solid electrolyte layer is sandwiched between the positive electrode layer and the negative electrode layer, and due to sintering during the manufacturing process of the solid battery, element diffusion from the positive electrode layer and the negative electrode layer to the solid electrolyte layer and / or element diffusion from the solid electrolyte layer to the positive electrode layer and the negative electrode layer may occur.

[0162] In the solid electrolyte layer, in addition to the garnet-type solid electrolyte ceramic of the present invention, it may further contain one or more materials selected from solid electrolytes composed of at least Li, Zr, and O, solid electrolytes having a γ-Li3VO4 structure, and oxide glass ceramic-based lithium ion conductors. As the solid electrolyte composed of at least Li, Zr, and O, Li2ZrO3 can be cited.

[0163] 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 cited.

[0164] (Li [3-ax+(5-c)(1-y)] A x )(B y D 1-y )O4 (III)

[0165] 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.

[0166] B is one or more elements selected from the group consisting of V and P.

[0167] 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.

[0168] x satisfies 0 ≤ x ≤ 1.0, particularly 0 ≤ x ≤ 0.2.

[0169] y satisfies 0 ≤ y ≤ 1.0, particularly 0.20 ≤ y ≤ 0.50.

[0170] a is the average valence of A. The average valence of A, as A, for example, in the case where it is considered that there are n1 elements X with valence a+, n2 elements Y with valence b+, and n3 elements Z with valence c+, is the value represented by (n1 × a + n2 × b + n3 × c) / (n1 + n2 + n3).

[0171] c is the average valence of D. The average valence of D, as D, for example, in the case where it is considered that there are n1 elements X with valence a+, n2 elements Y with valence b+, and n3 elements Z with valence c+, is the same value as the average valence of A described above.

[0172] 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.

[0173] As the oxide glass-ceramic 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.

[0174] In addition to the solid electrolyte, the solid electrolyte layer may, for example, further contain a sintering aid or the like.

[0175] As the sintering aid in the solid electrolyte layer, the same compounds as those in the sintering aid in the positive electrode layer can be used.

[0176] The volume ratio of the sintering aid in the solid electrolyte layer is not particularly limited. From the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, it is preferably 0% or more and 20% or less, more preferably 1% or more and 10% or less.

[0177] The thickness of the solid electrolyte layer is generally 0.1 to 30 μm. From the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, it is preferably 1 to 20 μm. The thickness of the solid electrolyte layer uses the average value of the thickness measured at any 10 locations in the SEM image.

[0178] In the solid electrolyte layer, the porosity is not particularly limited. From the viewpoints of more excellent ionic conductivity, more fully suppressing the increase in electron conductivity during operation, and further increasing the relative density, it is preferably 20% or less, more preferably 15% or less, and further preferably 10% or less.

[0179] The porosity of the solid electrolyte layer uses the value measured by the same method as the porosity of the positive electrode layer.

[0180] [Manufacturing method of solid battery]

[0181] A solid battery can be manufactured, for example, by a so-called green sheet method, a printing method, or a method combining these methods.

[0182] The green sheet method will be described.

[0183] First, a paste is prepared by appropriately mixing a solvent, a binder, etc. in a positive electrode active material. By coating this paste on a sheet and drying it, a first green sheet for forming a positive electrode layer is formed. The first green sheet may contain a solid electrolyte, a conductive material, and / or a sintering aid, etc.

[0184] A paste is prepared by appropriately mixing a solvent, a binder, etc. in a negative electrode active material. By coating this paste on a sheet and drying it, a second green sheet for forming a negative electrode layer is formed. The second green sheet may contain a solid electrolyte, a conductive material, and / or a sintering aid, etc.

[0185] A paste is prepared by appropriately mixing a solvent, a binder, etc. in a solid electrolyte. By coating this paste and drying it, a third green sheet for forming a solid electrolyte layer is produced. The third green sheet may contain a sintering aid, etc.

[0186] The solvent used for producing the first to third green sheets is not particularly limited. For example, a solvent that can be used in the field of solid-state batteries to manufacture a positive electrode layer, a negative electrode layer, or a solid electrolyte layer can be used. As the solvent, a solvent that can be used with the adhesives described later is generally used. As such a solvent, for example, alcohols such as 2-propanol can be cited.

[0187] The adhesive used for producing the first to third green sheets is not particularly limited. For example, an adhesive that can be used in the field of solid-state batteries to manufacture a positive electrode layer, a negative electrode layer, or a solid electrolyte layer can be used. As such an adhesive, for example, butyral resin, acrylic resin, etc. can be cited.

[0188] Next, a laminate is produced by appropriately laminating the first to third green sheets. The produced laminate can also be pressed. As a preferred pressing method, a hydrostatic pressing method, etc. can be cited.

[0189] Thereafter, a solid-state battery can be obtained by sintering the laminate at, for example, 600 to 800 °C.

[0190] The printing method will be described.

[0191] The printing method is the same as the green sheet method except for the following matters.

[0192] · 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 composition for each layer used to obtain the green sheets are prepared.

[0193] · The inks for each layer are used for printing and laminating to produce a laminate.

[0194] Hereinafter, the present invention will be described in more detail based on specific examples, but the present invention is not limited to any of the following examples and can be appropriately modified and implemented within the scope without changing its gist.

[0195] Examples

[0196] <Examples 1 to 24 and Comparative Examples 1 to 7>

[0197] [Manufacture of Solid Electrolyte Ceramics]

[0198] As raw materials, lithium hydroxide monohydrate LiOH·H2O, lanthanum hydroxide La(OH)3, zirconium oxide ZrO2, tantalum oxide Ta2O5, bismuth oxide Bi2O3, cobalt oxide Co3O4, basic nickel carbonate hydrate NiCO3·2Ni(OH)2·4H2O, manganese carbonate MnCO3, and iron oxide Fe2O3 were used.

[0199] Each starting raw material was weighed so that the chemical composition became each chemical composition in Table 1.

[0200] Water was added, sealed in a polypot made of polyethylene, and rotated at 150 rpm on a can rack for 16 hours to mix the raw materials.

[0201] In addition, considering the Li deficiency during sintering, 3 wt% of lithium hydroxide monohydrate LiOH·H2O as a Li source was added in excess relative to the target composition.

[0202] After evaporating and drying the obtained slurry, it was pre-sintered in O2 at 900 °C for 5 hours to obtain the target phase.

[0203] A mixed solvent of toluene - acetone was added to the obtained pre-sintered powder and pulverized for 12 hours using a planetary ball mill. The pulverized powder was measured by ICP and confirmed to have no compositional deviation. The average particle size of the pulverized powder at this time was 150 nm.

[0204] [Fabrication of Solid Electrolyte Monoliths]

[0205] As a specimen for evaluating the solid electrolyte ceramics, solid electrolyte monoliths were fabricated by the following method.

[0206] The obtained solid electrolyte powder, butyral resin, and alcohol were thoroughly mixed at a weight ratio of 200:15:140, and the alcohol was removed on a heating plate at 80 °C to obtain a powder coated with butyral resin as an adhesive.

[0207] Next, the coated powder was pressed at 90 MPa using a tablet press to form a sheet.

[0208] The sheet was fully covered with the mother powder, degreased at a temperature of 500 °C in an oxygen atmosphere to remove the butyral resin, and then sintered in an oxygen atmosphere at about 1200 °C for 3 hours, and cooled to room temperature to obtain a sintered body of the solid electrolyte.

[0209] By grinding the surface of the obtained sintered body, a garnet solid electrolyte monolith was obtained.

[0210] [Crystal Structure of Solid Electrolyte Monoliths]

[0211] In all the examples and comparative examples, through X-ray diffraction of the solid electrolyte monoliths, it was confirmed that an X-ray diffraction pattern attributable to a garnet-type crystal structure (ICDD Card No. 00-045-0109) could be obtained.

[0212] [Chemical Composition of Solid Electrolyte Monoliths]

[0213] ICP analysis of the solid electrolyte single plate was performed to obtain the average chemical composition of the solid electrolyte single plate. The contents of Co, Mn, Ni, and Fe in the average chemical composition of the entire solid electrolyte single plate were determined as ratios when the content of the above general formula B of the garnet-type crystal structure (for example, the total of La and B in the above general formula (II)) was taken as 100 mol%. It should be noted that O (oxygen) in the chemical composition is a value calculated in such a way that charge neutrality is achieved based on the molar ratio and valence of the elements contained in A, B, and D in the general formula (I). 1 (The sum of the above).

[0214] [Measurement of electronic conductivity]

[0215] An Au electrode was sputtered on one side of the obtained single plate to serve as a working electrode. A Li metal having the same area as the Au electrode was pasted on the other side. Finally, the battery unit was sealed in a 2035-sized coin battery to serve as an evaluation battery unit. All of the above operations were carried out in a drying chamber with a dew point of -40°C or lower.

[0216] A voltage of 2 V relative to Li was applied to the working electrode at room temperature, and the transient current was observed. The current flowing after applying the voltage for 10 hours was read as the leakage current. Based on the leakage current, the electronic conductivity was calculated using the following formula.

[0217] Electronic conductivity = (I / V) × (L / A)

[0218] (I: leakage current, V: applied voltage, L: thickness of the solid electrolyte single plate, A: electrode area)

[0219] ◎: Electronic conductivity < 1.0×10 -8 S / cm (excellent);

[0220] ○: 1.0×10 -8 S / cm ≤ electronic conductivity < 5.0×10 -8 S / cm (good);

[0221] △: 5.0×10 -8 S / cm ≤ electronic conductivity < 1.0×10 -7 S / cm (acceptable) (no problem in practice);

[0222] ×: 1.0×10 -7 S / cm ≤ electronic conductivity (unacceptable) (problem in practice).

[0223] [Measurement of ionic conductivity]

[0224] After forming a gold (Au) layer as a current collector layer on both sides of a single solid electrolyte plate by sputtering, it was sandwiched and fixed with a SUS current collector. The sintered sheet of each solid electrolyte was subjected to AC impedance measurement at room temperature (25 °C) in the range of 10 MHz to 0.1 Hz (±50 mV), and the ionic conductivity was evaluated.

[0225] ◎: 1.3×10 -3 S / cm ≤ ionic conductivity (excellent);

[0226] ○: 1.0×10 -3 S / cm ≤ ionic conductivity < 1.3×10 -3 S / cm (good);

[0227] △: 5.0×10 -4 S / cm ≤ ionic conductivity < 1.0×10 -3 S / cm (acceptable) (no problem in practice);

[0228] ×: ionic conductivity < 5.0×10 -4 S / cm (unacceptable) (problem in practice).

[0229] [Relative density measurement]

[0230] The relative density (%) was calculated by dividing the density calculated from the size and weight of the single solid electrolyte plate by the true density of the solid electrolyte (5.3 g / cm 3 ).

[0231] ◎: 95% ≤ relative density (excellent);

[0232] ○: 93% ≤ relative density < 95% (good);

[0233] △: 90% ≤ relative density < 93% (acceptable) (no problem in practice);

[0234] ×: relative density < 90% (unacceptable) (problem in practice).

[0235] [Comprehensive judgment]

[0236] A comprehensive judgment was made on all the evaluation results of the electronic conductivity, ionic conductivity, and relative density.

[0237] ◎: All the evaluation results of the electronic conductivity, ionic conductivity, and relative density are ◎.

[0238] ○: The lowest evaluation result among all the evaluation results of the electronic conductivity, ionic conductivity, and relative density is ○.

[0239] △: The lowest evaluation result among all the evaluation results of electronic conductivity, ionic conductivity, and relative density is △.

[0240] ×: The lowest evaluation result among all the evaluation results of electronic conductivity, ionic conductivity, and relative density is ×.

[0241] [Table 1]

[0242]

[0243] *: The content when the content of B is 100 mol%.

[0244] [Table 2]

[0245]

[0246] *: The content when the content of B is 100 mol%.

[0247] From the comparison of Comparative Examples 1 and 2 with Examples 1 to 2, it can be seen that when the Li content is less than 221 mol%, the electronic conductivity increases and the risk of short circuit increases.

[0248] From the comparison of Examples 1 to 2 with Comparative Example 3, it can be seen that in the range where the Li content is 221 mol% or more and less than 227 mol%, when the content of the specified transition metal element (especially Co) is more than 4 mol%, the electronic conductivity increases and the risk of short circuit increases.

[0249] From the comparison of Examples 3 to 8 with Comparative Example 4, it can be seen that in the range where the Li content is 227 mol% or more and less than 235 mol%, when the content of the specified transition metal element (especially Co) is more than 6 mol%, the electronic conductivity increases and the risk of short circuit increases.

[0250] From the comparison of Examples 9 to 20 with Comparative Examples 5 and 6, it can be seen that in the range where the Li content is 235 mol% or more and 250 mol% or less, when the content of the specified transition metal element (especially Co) is more than 8%, the electronic conductivity increases and the risk of short circuit increases.

[0251] From the comparison of Examples 9 to 20 with Comparative Example 7, it can be seen that when the Li content is more than 250 mol%, the sinterability deteriorates and the relative density decreases.

[0252] Industrial availability

[0253] The solid battery incorporating the solid electrolyte ceramic of the present invention can be applied to various fields where batteries or electricity storage are envisaged. Although merely by way of example, the solid battery according to one embodiment of the present invention can be applied to 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, and communication fields using mobile devices, etc. (for example, the field of electrical and electronic devices or mobile devices including small electronic devices such as mobile phones, smart phones, smart watches, laptop computers, digital cameras, activity meters, ARM computers, electronic paper, wearable devices, RFID tags, card-type electronic money, smart watches, etc.); household and small industrial uses (for example, the field of power tools, golf carts, household, care, and industrial robots); large industrial 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-installed electricity storage systems, etc.); medical uses (the field of medical devices such as earphone hearing aids, etc.); pharmaceutical uses (the field of medication management systems, etc.); and the IoT field; space and deep sea uses (for example, the fields of space probes, submersible survey ships, etc.), etc.

Claims

1. A solid electrolyte ceramic having a garnet-type crystal structure, The solid electrolyte ceramic contains at least Li (lithium), La (lanthanum), Bi (bismuth), and O (oxygen), and further contains one or more transition metal elements selected from the group consisting of Co (cobalt), Ni (nickel), Mn (manganese), and Fe (iron), and has a chemical composition represented by the following general formula (I), A α B β D γ O ω (I), wherein, In formula (I), A is one or more elements selected from the group consisting of Li (lithium), Ga (gallium), Al (aluminum), Mg (magnesium), Zn (zinc), and Sc (scandium), and at least contains Li (lithium); B is one or more elements selected from the group consisting of La (lanthanum), Ca (calcium), Sr (strontium), Ba (barium), and lanthanide elements, and at least contains La (lanthanum); D is one or more elements selected from the group consisting of transition elements capable of forming a 6 - coordinate bond with oxygen and main group elements belonging to Groups 12 - 15, and at least contains Bi (bismuth); 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, When the content of B is set to 100 mol%, the content of Li is set to X (mol%), and the total content of the one or more transition metal elements is set to Y (mol%), any one of the following relational expressions (1) - (3) is satisfied: (1) 0.03 ≤ Y ≤ 4.00 in the range of 221 ≤ X < 227; (2) 0.02 ≤ Y ≤ 6.00 in the range of 227 ≤ X < 237; (3) 0.03 ≤ Y ≤ 8.00 in the range of 237 ≤ X ≤ 250.

2. The solid electrolyte ceramic according to claim 1, wherein, The solid electrolyte ceramic satisfies the relational expression (1) or (2).

3. The solid electrolyte ceramic according to claim 1, wherein, The solid electrolyte ceramic satisfies the relational expression (1).

4. The solid electrolyte ceramic according to any one of claims 1 to 3, wherein, The one or more transition metal elements include Co.

5. A solid battery, comprising the solid electrolyte ceramic according to any one of claims 1 to 4.

6. The solid battery according to claim 5, wherein, The solid - state battery includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer laminated between the positive electrode layer and the negative electrode layer, The positive electrode layer and the negative electrode layer are layers capable of intercalating and deintercalating lithium ions.

7. The solid battery according to claim 6, wherein, The solid electrolyte layer and the positive electrode layer and the negative electrode layer are integrally sintered with each other to form a sintered body.

8. The solid battery according to any one of claims 5 to 7, wherein, The solid electrolyte ceramic is included in the solid electrolyte layer of the solid - state battery.

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