Solid electrolyte ceramic and solid-state battery

Abstract

The present invention provides a solid electrolyte ceramic that, while having excellent ion conductivity, more sufficiently suppresses increases in electron conductance resulting from operation of a solid-state battery. The present invention relates to a solid electrolyte ceramic having a garnet-type crystal structure. The solid electrolyte ceramic further contains one or more transition metal elements selected from the group consisting of Co, Ni, Mn, and Fe while having a chemical composition represented by a specific general formula. The content X of Li and the content Y of D1, which is one or more elements selected from the group consisting of Ta, Nb, and Bi, are each within a specific range.

Description

Solid electrolyte ceramics and solid-state batteries

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

[0002] In recent years, there has been a significant increase in demand for batteries as power sources for portable electronic devices such as mobile phones and portable personal computers. For such applications, development is underway on sintered solid-state secondary batteries (so-called "solid-state batteries") that use a solid electrolyte as the electrolyte and whose other components are also solid.

[0003] A 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. In particular, the solid electrolyte layer includes a solid electrolyte ceramic and is responsible for ion conduction between the positive electrode layer and the negative electrode layer. Solid electrolyte ceramics are required to have high ionic conductivity and low electronic conductivity. To achieve higher ionic conductivity, attempts have been made to use ceramics obtained by sintering a garnet-type solid electrolyte substituted with Bi (see, for example, Patent Document 1 and Non-Patent Document 1).

[0004] JP 2015-050071 A

[0005] Gao et al., SolidState Ionics, 181 (2010) 1415-1419

[0006] The inventors of the present invention have found that the following problems occur in solid-state batteries using the above-mentioned conventional solid electrolyte ceramics. Specifically, in conventional solid-state batteries using garnet-type solid electrolyte ceramics containing Bi, impurities such as Li—Bi—O-based compounds are likely to be generated at grain boundaries, and these Li—Bi—O-based compounds are reduced during operation of the solid-state battery (i.e., during charging and discharging), resulting in an increase in electronic conductivity. The increase in electronic conductivity can cause the solid-state battery to short-circuit and / or increase in leakage current.

[0007] The inventors of the present invention also found that the inclusion of a transition metal element such as Co is effective from the viewpoint of suppressing the formation of Li—Bi—O-based compounds, but also found that the following new problem arises: Specifically, although the use of a solid electrolyte containing a transition metal element can suppress the formation of Li—Bi—O-based compounds, impurities containing transition metals such as Li—La—Co—O-based compounds that are different from Li—Bi—O-based compounds are newly formed, and these impurities also increase the electronic conductivity during operation of the solid-state battery.

[0008] An object of the present invention is to provide a solid electrolyte ceramic that has excellent ionic conductivity and that more sufficiently suppresses an increase in electronic conductivity due to the operation of a solid-state battery.

[0009] The present invention relates to a compound represented by the following general formula (I): (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 includes at least Li (lithium); B is one or more elements selected from the group consisting of La (lanthanum), Ca (calcium), Sr (strontium), Ba (barium), and lanthanoid elements, and includes at least La (lanthanum); D １ and D ２ is one or more elements selected from the group consisting of transition elements and typical elements belonging to groups 12 to 15 that can form hexacoordinates with oxygen, among which D １ is one or more elements selected from the group consisting of Ta, Nb, and Bi; α satisfies 5.0≦α≦8.0; β satisfies 2.5≦β≦3.5; γ satisfies 1.5≦γ≦2.5; and ω satisfies 11≦ω≦13), 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 the content of Li is X (mol %) when the content of B is 100 mol %, and the content of D is X (mol %) when the content of B is 100 mol %. １A solid electrolyte ceramic having a garnet-type crystal structure, which satisfies the following relational expression when the content of X is Y (mol %): 220<X≦245 and 10≦Y≦70.

[0010] The solid electrolyte ceramic of the present invention has excellent ionic conductivity and also more sufficiently suppresses an increase in electronic conductivity due to the operation of a solid-state battery.

[0011] [Solid Electrolyte Ceramics] The solid electrolyte ceramics of the present invention are composed of a sintered body formed by sintering solid electrolyte particles. The solid electrolyte ceramics of the present invention contain at least Li (lithium), La (lanthanum), and O (oxygen) and have a garnet-type crystal structure. They further contain one or more transition metal elements selected from the group consisting of Co (cobalt), Ni (nickel), Mn (manganese), and Fe (iron) (hereinafter, simply referred to as "predetermined transition metal elements"). Furthermore, the solid electrolyte ceramics of the present invention are ceramics made of a solid electrolyte having a garnet-type crystal structure, and may contain other composite oxides or single oxides as long as the effects of the present invention are not impaired. Furthermore, the solid electrolyte ceramics of the present invention may be a solid electrolyte having a so-called garnet-type crystal structure. Furthermore, the solid electrolyte ceramics of the present invention preferably contain Bi (bismuth) from the viewpoint of superior ionic conductivity. Furthermore, it is sufficient that at least the sintered particles contained in the solid electrolyte ceramics, which are the main component of the present invention, have a garnet-type crystal structure.

[0012] The solid electrolyte ceramic of the present invention preferably has a chemical composition represented by the following general formula (I) and further contains a predetermined transition metal element.

[0013]

[0014] 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 includes at least Li. B is one or more elements selected from the group consisting of La (lanthanum), Ca (calcium), Sr (strontium), Ba (barium), and lanthanoid elements, and includes at least La. Examples of lanthanoid elements include Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holminium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium). D １ and D ２ represents one or more elements (particularly two or more elements) selected from the group consisting of transition elements and typical elements belonging to groups 12 to 15 that can form hexacoordinates with oxygen (hereinafter sometimes referred to as "group P"). １ is one or more elements (particularly two or more elements) selected from the group consisting of Ta, Nb and Bi. ２ may or may not be contained (in the solid electrolyte ceramic), and if contained, it is one or more elements selected from the above group P other than Ta, Nb, and Bi. Examples of transition elements capable of forming 6-coordination with oxygen include Sc (scandium), Zr (zirconium), Ti (titanium), Ta (tantalum), Nb (niobium), Hf (hafnium), Mo (molybdenum), W (tungsten), and Te (tellurium). Examples of typical elements belonging to groups 12 to 15 include In (indium), Ge (germanium), Sn (tin), Pb (lead), Sb (antimony), and Bi (bismuth). D １ From the viewpoint of achieving better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, D preferably contains at least Bi, and more preferably contains at least Bi and Ta. ２In view of better ion conductivity and more sufficient suppression of an increase in electronic conductivity during operation, D may not be contained or may be contained, and when contained, Zr is included. In view of better ion conductivity and more sufficient suppression of an increase in electronic conductivity during operation, in a more preferred embodiment, D １ When contains at least Bi and Ta, D ２ may or may not further contain Zr.

[0015] In formula (I), α, β, γ, and ω satisfy the following relations: 5.0≦α≦8.0, 2.5≦β≦3.5, 1.5≦γ≦2.5, and 11≦ω≦13, respectively. From the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, α preferably satisfies 6.0≦α≦8.0, more preferably 6.5≦α≦7.5, and even more preferably 6.6≦α≦7.4. When A contains multiple elements, it is sufficient that the sum of the values ​​corresponding to α for each of those elements satisfies the above range. From the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, β preferably satisfies 2.6≦β≦3.4, more preferably 2.7≦β≦3.3, and even more preferably 2.8≦β≦3.2. When B contains multiple elements, it is sufficient that the sum of the values ​​corresponding to β for each of those elements satisfies the above range. From the viewpoint of achieving better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, γ preferably satisfies 1.6≦γ≦2.4, more preferably 1.7≦γ≦2.3, and even more preferably 1.8≦γ≦2.2. １ and D ２ The sum of the values ​​corresponding to γ ​​for each of the elements D satisfies the above range. １ and D ２ When each element contains multiple elements, the sum of the values ​​corresponding to γ ​​for each of those elements should satisfy the above range. From the viewpoint of achieving better ionic conductivity and more sufficiently suppressing an increase in electronic conductivity during operation, ω preferably satisfies 11≦ω≦12.5, more preferably 11.5≦ω≦12.5, and even more preferably 11.8≦ω≦12.2.

[0016] D １ When a garnet-type solid electrolyte containing an element (particularly Bi) contains a predetermined transition metal element (Co, Ni, Mn, Fe, etc.), the formation of Li-Bi-O-based compounds is suppressed, while a new impurity Li-La-Co-O-based compound having electronic conductivity is formed. １ By containing a relatively large amount of elements (pentavalent elements including Nb, particularly Ta), it is possible to suppress the formation of Li-La-Co-O compounds even when a relatively large amount of a specific transition metal element is contained. As a result, it is possible to more sufficiently suppress the increase in electronic conductivity while maintaining excellent ionic conductivity. Although the details of the mechanism by which such an effect is obtained are unknown, it is presumed to be as follows. Li and D １ In a system containing a relatively large amount of elements (pentavalent elements including Nb, especially Ta), the catalytic effect (D １ The oxidation promoting effect of elements (pentavalent elements including Nb, especially Bi) is more fully exerted. １ It is believed that the promotion of solid solution of elements (particularly Bi) suppresses the formation of Li-Bi-O based compounds and also more sufficiently suppresses the formation of Li-La-Co-O based compounds.

[0017] From the viewpoint of achieving better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, the specified transition metal element preferably contains one or more elements selected from the group consisting of Co, Ni, and Mn, more preferably contains one or more elements selected from the group consisting of Co and Mn, and even more preferably contains Co.

[0018] In the present invention, Li and D in the solid electrolyte ceramic １ The contents of elements (especially Ta) are 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 taken as 100 mol %, the contents of Li and D are as follows: １When the contents of elements (particularly Ta) are X (mol %) and Y (mol %), respectively, the solid electrolyte ceramic of the present invention satisfies both of the following relational expressions (1) and (2): (1) 220<X≦245 (from the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, preferably 221≦X≦244, more preferably 222≦X≦243); (2) 10≦Y≦70 (from the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, preferably 10≦Y≦50, more preferably 10≦Y≦30).

[0019] Regarding the relational formula (1), if the Li content X is too high, the sinterability decreases, and when used as a solid electrolyte for a solid-state battery, it becomes difficult to sinter. If the Li content X is too low, a different phase (such as an impurity Li—La—Co—O-based compound) appears, and the electronic conductivity increases. Regarding the relational formula (2), D １ If the content Y of the element (especially Ta) is too small, the garnet-type crystal structure will be a tetragonal structure instead of a cubic structure, and therefore the ionic conductivity will be significantly reduced. １ If the content Y of the element (especially Ta) is too high, heterogeneous phases (impurities, tantalum oxide, etc.) appear, resulting in a significant decrease in ionic conductivity.

[0020] The above-mentioned Li contents X and D １ The content Y of an element (especially Ta) is expressed as a ratio (mol%) when the content of B is 100 mol%, but it can also be referred to as a ratio (mol%) when the number of 8-coordinated sites in the garnet-type crystal structure is 100 mol%. For example, in the case of the chemical composition of the general formula (II) described later, the ratio is １ In another specific example, the 8-coordinated site of the garnet-type crystal structure is, for example, a value that can be expressed as a percentage (mol %) when the total number of Li ５ La ３ Nb ２ O １２ (ICDD Card No. 00-045-0109)

[0021] Li content and D １ The content of elements (especially Ta) can be measured by performing inductively coupled plasma (ICP) emission spectroscopy (ICP analysis) on the solid electrolyte ceramic to obtain the average chemical composition of the material. Specifically, the average chemical composition is determined based on the ICP analysis, and the content of Li and D is calculated from the average chemical composition. １ The content of elements (especially Ta) can be calculated as a ratio when the content of B in the general formula (I) is 100 mol %. For example, the number of 8-coordinated sites in the garnet-type crystal structure (for example, the number of La and B in the general formula (II) described later) can be calculated as a ratio when the content of B in the general formula (I) is 100 mol %. １ The total amount of the hydroxyl groups (amount of the hydroxyl groups) can be determined as a percentage relative to 100 mol %. It is also possible to measure and calculate the total amount of the hydroxyl groups using an X-ray photoelectron spectroscopy (XPS).

[0022] The content of the predetermined transition metal element is usually 0.01 mol% to 10 mol% when the content of B is 100 mol%, and from the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, it is preferably 0.01 mol% to 8 mol%, more preferably 0.01 mol% to 5 mol%, even more preferably 0.01 mol% to 3 mol%, and particularly preferably 0.01 mol% to 2 mol%. When two or more types of transition metal elements are contained as the predetermined transition metal element, it is sufficient that the total content thereof is within the above range.

[0023] The content of Bi (bismuth) is usually 40 mol% or less when the content of B is taken as 100 mol%, and from the viewpoint of achieving better ionic conductivity and more sufficiently suppressing an increase in electronic conductivity during operation, the content of Bi is preferably 0.1 mol% or more and 30 mol% or less, more preferably 0.5 mol% or more and 20 mol% or less, even more preferably 0.5 mol% or more and 15 mol% or less, and particularly preferably 1 mol% or more and 10 mol% or less.

[0024] The content of Ta (tantalum) is usually 80 mol% or less when the content of B is taken as 100 mol%, and from the viewpoint of achieving better ionic conductivity and more sufficiently suppressing an increase in electronic conductivity during operation, the content of Ta is preferably 1 mol% or more and 80 mol% or less, more preferably 5 mol% or more and 75 mol% or less, even more preferably 10 mol% or more and 70 mol% or less, and particularly preferably 12 mol% or more and 68 mol% or less.

[0025] The content of Zr (zirconium) is usually 70 mol% or less (particularly 0 mol% or more and 70 mol% or less) when the content of B is 100 mol%, and from the viewpoint of more excellent ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, it is preferably 0 mol% or more and 60 mol% or less, more preferably 0 mol% or more and 55 mol% or less, and even more preferably 0 mol% or more and 50 mol% or less. Note that the content of Zr being 0 mol% means that the solid electrolyte ceramic (particularly D of the general formula (I)) １ or D of general formula (II) １ does not contain Zr.

[0026] The contents of the predetermined transition metal elements, Bi, Ta and Zr, are determined by the above-mentioned Li contents X and D. １ As with the content Y of elements (especially Ta), it can be measured by performing inductively coupled plasma (ICP) emission spectroscopy (ICP analysis) on the solid electrolyte ceramic to obtain the average chemical composition of the material. Specifically, the average chemical composition is determined based on the ICP analysis, and the contents of predetermined transition metal elements, Bi, Ta, and Zr, are calculated from the average chemical composition by subtracting the contents of B in the general formula (I) (for example, La and B in the general formula (II) described later). １ The total amount of the hydroxyl groups (amount of the hydroxyl groups) can be determined as a percentage relative to 100 mol %. It is also possible to measure and calculate the total amount of the hydroxyl groups using an X-ray photoelectron spectroscopy (XPS).

[0027] The form of existence (or inclusion form) of the predetermined transition metal element in the solid electrolyte ceramic of the present invention is not particularly limited, and the predetermined transition metal element may be present, for example, in the crystal lattice or outside the crystal lattice. Specifically, the predetermined transition metal element may be present in the bulk of the solid electrolyte ceramic, in the grain boundaries, or both. The presence of the predetermined transition metal element in the bulk means that the predetermined transition metal element is present at a metal site (lattice site) constituting a garnet-type crystal structure in the solid electrolyte ceramic of the present invention. The metal site may be any metal site, for example, a Li site, a La site, a Bi site, or two or more of these sites. The presence of the predetermined transition metal element at the grain boundary means that, when the solid electrolyte ceramic of the present invention is composed of a plurality of sintered particles, the predetermined transition metal element may be present at the interface between two or more sintered particles.

[0028] In the present invention, the predetermined transition metal element may exist as a single oxide and / or as a composite oxide containing the predetermined transition metal element and one or more metal elements selected from the group consisting of other metal elements capable of constituting the garnet-type solid electrolyte of the present invention. Note that such an oxide of the predetermined transition metal element may exist at the interface between crystal grains of the ceramic having a garnet-type crystal structure, which is the main component of the present invention.

[0029] In the solid electrolyte ceramic of the present invention, the element A (e.g., Li) may generally be present in the bulk, and more specifically, for example, may be present at the Li site as a metal site (lattice site) constituting the garnet-type crystal structure. In this case, a part of the element A may be present at the grain boundary as a composite oxide containing the element A and one or more metal elements selected from the group consisting of other metal elements capable of constituting the garnet-type solid electrolyte of the present invention, and / or as a single oxide.

[0030] In the solid electrolyte ceramic of the present invention, the B element (e.g., La) may generally be present in the bulk, and more specifically, for example, may be present in the La site, which is a metal site (lattice site) constituting the garnet-type crystal structure. In this case, a part of the B element may be present in the grain boundary as a composite oxide containing the B element and one or more metal elements selected from the group consisting of other metal elements capable of constituting the garnet-type solid electrolyte of the present invention, and / or as a single oxide.

[0031] In the solid electrolyte ceramic of the present invention, D １ The elements (e.g., Bi, Ta, Zr) may generally exist in the bulk, and more specifically, as an example, may exist in hexacoordinated sites as metal sites (lattice sites) that constitute the garnet-type crystal structure. １ Some of the elements are １ The element may be present at the grain boundaries as a composite oxide containing the element and one or more metal elements selected from the group consisting of other metal elements capable of constituting the garnet-type solid electrolyte of the present invention, and / or as a single oxide.

[0032] In the present invention, when a solid electrolyte ceramic has a garnet-type crystal structure, it does not simply mean that the solid electrolyte ceramic has a "garnet-type crystal structure," but also means that the solid electrolyte ceramic has 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 of solid-state batteries in X-ray diffraction. More specifically, the solid electrolyte ceramic of the present invention may exhibit, in X-ray diffraction, one or more main peaks corresponding to Miller indices specific to the so-called garnet-type crystal structure diffraction pattern (ICDD Card No. 422259) at a predetermined incident angle, or as a garnet-like crystal structure, it may exhibit one or more main peaks that differ in incident angle (i.e., peak position or diffraction angle) and intensity ratio (i.e., peak intensity or diffraction intensity ratio) from one or more main peaks corresponding to Miller indices specific to the so-called garnet-type crystal structure due to differences in composition. Representative diffraction patterns of a garnet-like crystal structure include, for example, ICDD Card No. 00-045-0109 and the like.

[0033] As a specific embodiment, the solid electrolyte ceramic of the present invention can have a chemical composition represented by general formula (II). More specifically, the solid electrolyte ceramic can have a chemical composition represented by general formula (II) as a whole. In this case, the solid electrolyte ceramic of the present invention has the chemical composition represented by general formula (II) and further contains a predetermined transition metal element as described above.

[0034]

[0035] In formula (II), A １ indicates a metal element occupying the Li site in the garnet-type crystal structure. １ is an element corresponding to A in the general formula (I), and may be one or more elements selected from the group consisting of elements similar to the elements exemplified as A, except for Li. １is usually one or more elements selected from the group consisting of Ga (gallium), Al (aluminum), Mg (magnesium), Zn (zinc) and Sc (scandium). １ is preferably one or more elements selected from the group consisting of Ga (gallium) and Al (aluminum), more preferably two elements, Ga and Al, from the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation.

[0036] In formula (II), B １ indicates a metal element occupying the La site in the garnet-type crystal structure. １ is an element corresponding to B in the general formula (I) and may be one or more elements selected from the group consisting of elements similar to the elements exemplified as B, except for La. １ is usually one or more elements selected from the group consisting of Ca (calcium), Sr (strontium), Ba (barium), and the lanthanoid elements.

[0037] In formula (II), D １ is a 6-coordinated site in the garnet-type crystal structure (Li in the garnet-type crystal structure ７ La ３ Zr ２ O １２ (ICDD Card. No. 01-078-6708)) refers to a metallic element that occupies the site occupied by Zr. １ is D in the general formula (I). １ is an element corresponding to the D １ Among the elements similar to those exemplified above, one or more elements selected from the group consisting of elements other than Bi may be used. １is usually one or more elements selected from the group consisting of Zr (zirconium), Hf (hafnium), Ta (tantalum), Nb (niobium), Mo (molybdenum), W (tungsten) and Te (tellurium), and from the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, preferably contains one or more elements selected from the group consisting of Zr (zirconium) and Ta (tantalum), more preferably contains at least Ta (tantalum).

[0038] In formula (II), x satisfies 0<x≦1.00, and from the viewpoint of superior ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, preferably satisfies 0.01≦x≦0.70, more preferably 0.02≦x≦0.60, even more preferably 0.03≦x≦0.50, particularly preferably 0.03≦x≦0.40, and most preferably 0.04≦x≦0.25. y satisfies 0≦y≦0.50, and from the viewpoint of superior ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, preferably satisfies 0≦y≦0.40, more preferably 0≦y≦0.30, even more preferably 0≦y≦0.20, and particularly preferably 0. １ When B contains a plurality of elements, the sum of the values ​​corresponding to y for each of those elements should satisfy the above range. z satisfies 0≦z≦2.00, and from the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, it preferably satisfies 0≦z≦0.35, more preferably 0≦z≦0.08, even more preferably 0≦z≦0.04, and most preferably 0. １When D contains multiple elements, the sum of the values ​​corresponding to z for each of those elements should satisfy the above range. γ satisfies 1.2≦γ≦3.2, and from the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, it preferably satisfies 1.4≦γ≦3.0, more preferably 1.6≦γ≦2.8, and even more preferably 1.8≦γ≦2.4. "γ-x" satisfies 1.0≦γ-x≦3.0, and from the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, it preferably satisfies 1.2≦γ-x≦2.8, more preferably 1.4≦γ-x≦2.6, and even more preferably 1.6≦γ-x≦2.2. The D １ When contains a plurality of elements, the sum of the values ​​corresponding to "γ-x" for each of those elements should satisfy the above range.

[0039] In formula (II), p satisfies 5.0≦p≦8.0, and from the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, it satisfies 6.0≦p≦8.0, more preferably 6.5≦p≦7.5, and further preferably 6.6≦p≦7.4. １ is the average valence of １ The average valence of １ For example, when n1 element X with a valence of a+, n2 element Y with a valence of b+, and n3 element Z with a valence of c+ are recognized, it is a value expressed as (n1 x a + n2 x b + n3 x c) / (n1 + n2 + n3). b is B １ is the average valence of B １ The average valence of B １ For example, when n1 elements X having a valence of a+, n2 elements Y having a valence of b+, and n3 elements Z having a valence of c+ are found, the above-mentioned A １ The same value as the average valence of １ is the average valence of １ The average valence of １ For example, when n1 elements X having a valence of a+, n2 elements Y having a valence of b+, and n3 elements Z having a valence of c+ are found, the above-mentioned A １ This is the same value as the average valence of the

[0040] In formula (II), q satisfies 2.5≦q≦3.5. From the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, q preferably satisfies 2.6≦q≦3.4, more preferably 2.7≦q≦3.3, and even more preferably 2.8≦q≦3.2. δ indicates the amount of oxygen vacancy and may be 0. Generally, δ only needs to satisfy 0≦δ<1. Since quantitative analysis of the amount of oxygen vacancy δ is impossible even with the latest equipment, it may be considered to be 0. The molar ratio of each element in the chemical composition of the solid electrolyte ceramic of the present invention does not necessarily coincide with the molar ratio of each element in formula (II), for example, and tends to deviate depending on the analytical method. However, the effects of the present invention are achieved as long as the composition deviation is not so great that the properties are changed.

[0041] Even when the solid electrolyte ceramic of the present invention has a chemical composition represented by the general formula (II), the above-mentioned Li content X and D １ It goes without saying that the content Y of each element (especially Ta) satisfies both of the above-mentioned relational expressions (1) and (2). In this case, the contents of the predetermined transition metal elements, Bi, Ta and Zr, may be within the above-mentioned ranges, and are preferably within the above-mentioned ranges. In addition, the reference in expressing these contents, "when the content of B is 100 mol %", is "when the content of La and B is 100 mol %". １ may be read as "when the total number (i.e., total content) of these is taken as 100 mol %."

[0042] In the present invention, the chemical composition of the solid electrolyte ceramic may be the composition of the entire ceramic material determined using ICP (inductively coupled plasma). The chemical composition may also be measured and calculated using XPS analysis, or may be determined using TEM-EDX (energy dispersive X-ray spectroscopy) and / or WDX (wavelength dispersive X-ray spectroscopy). Furthermore, the chemical composition may be obtained by quantitatively analyzing 100 arbitrary points on each of 100 arbitrary sintered particles and calculating the average value.

[0043] The content of a predetermined 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 content of La and B in the general formula (II)] １ The molar ratio when the total number of (a) and (b) is taken as 100 mol % may be calculated by the following method. In the present invention, the chemical composition of the solid electrolyte ceramic can be determined by ICP analysis (inductively coupled plasma method), LA-ICP-MS (laser ablation ICP-mass spectrometry), or the like. Alternatively, the chemical composition may be measured and calculated using XPS analysis, or TEM-EDX (energy dispersive X-ray spectroscopy) or WDX (wavelength dispersive X-ray spectroscopy) may be used. Furthermore, the chemical composition may be obtained by quantitatively analyzing 100 arbitrary points on each of 100 arbitrary sintered particles (composition analysis) and calculating the average value thereof.

[0044] For example, EDX or WDX analysis measures the cross section of a solid-state battery. The cross section of a solid-state battery is a cross section parallel to the stacking direction of the positive electrode layer, solid electrolyte layer, and negative electrode layer. The cross section of a solid-state battery can be exposed by embedding the solid-state battery in resin and then polishing it. The method for polishing the cross section is not particularly limited, but the solid electrolyte layer can be exposed by cutting it with a dicer or the like and then polishing it with abrasive paper, chemical mechanical polishing, ion milling, or the like. Quantitative analysis of the exposed cross section (solid electrolyte layer) using EDX or WDX (wavelength dispersive X-ray fluorescence analyzer) can calculate the molar ratio of each element (e.g., the molar ratio of Co, Ni, Mn, and Fe relative to B).

[0045] In addition, for example, in TEM-EELS measurement, the electrode layer or solid electrolyte layer of a solid battery is exfoliated using a focused ion beam (FIB) or the like, and then the solid electrolyte portion is measured using TEM-EELS (transmission electron microscope-electron energy loss spectroscopy). This allows each element (for example, elements contained in B in the general formula (I), such as Co, Ni, Mn, and Fe) to be detected, and the molar ratio of each element to the B content can be calculated.

[0046] Specific examples of the chemical composition of the solid electrolyte ceramic of the present invention include the following chemical compositions. In the chemical compositions shown below, the transition metal element following the hyphen (-) indicates that the transition metal element may be present in the bulk and / or grain boundaries, as described above. Li ６．７ La ３ Zr １．４ Ta ０．４２ Bi ０．２ O １２ -Co ０．０５ Li ６．７ La ３ Zr ０．８ Ta １ Bi ０．２ O １２ -Co ０．０５ Li ６．７ La ３ Ta １．９５ Bi ０．０５ O １２ -Co ０．０５ Li ６．９ La ３ Zr １．４ Ta ０．４２ Bi ０．２ O １２ -Co ０．０５ Li ６．９ La ３ Zr ０．８ Ta １ Bi ０．２ O １２ -Co ０．０５ Li ６．９ La ３ Ta １．９５ Bi ０．０５ O １２ -Co ０．０５ Li ７．３ La ３ Zr １．４ Ta ０．４２ Bi ０．２ O １２ -Co ０．０５ Li ７．３ La ３ Zr ０．８ Ta １ Bi ０．２ O １２ -Co ０．０５ Li ７．３ La ３ Ta １．９５ Bi ０．０５O １２ -Co ０．０５ Li ６．９ La ３ Zr １．４ Ta ０．４２ Bi ０．２ O １２ -Co ０．００５ Li ６．９ La ３ Zr １．４ Ta ０．４２ Bi ０．２ O １２ -Co ０．００１ Li ６．９ La ３ Zr １．４ Ta ０．４２ Bi ０．２ O １２ -Mn ０．００５ Li ６．９ La ３ Zr １．４ Ta ０．４２ Bi ０．２ O １２ -Mn ０．００１ Li ６．９ La ３ Zr １．４ Ta ０．４２ Bi ０．２ O １２ -Ni ０．００５ Li ６．９ La ３ Zr １．４ Ta ０．４２ Bi ０．２ O １２ -Ni ０．００１

[0047] Among the specific examples of the chemical compositions described above, for example, a chemical composition containing Co as a transition element may be a chemical composition containing Ni, Mn, or Fe instead of Co. Also, for example, a chemical composition containing Mn as a transition element may be a chemical composition containing Co, Ni, or Fe instead of Mn. Also, for example, a chemical composition containing Ni as a transition element may be a chemical composition containing Co, Mn, or Fe instead of Ni.

[0048] [Method for producing solid electrolyte ceramics] The solid electrolyte ceramics of the present invention can be obtained by mixing a compound containing a predetermined metal element (i.e., starting material) with water, drying, and then heat-treating. The compound containing the predetermined metal element is usually a mixture of compounds containing one metal element selected from the group consisting of Li (lithium), La (lanthanum), Bi (bismuth), and a predetermined transition metal element. Examples of the compound containing the predetermined metal element (i.e., starting material) include lithium hydroxide monohydrate (LiOH.H). ２ O, lanthanum hydroxide La(OH) ３ , zirconium oxide ZrO ２ , tantalum oxide Ta ２ O ５ , bismuth oxide Bi ２ O ３ , cobalt oxide Co ３ O ４ , basic nickel carbonate hydrate NiCO ３ 2Ni(OH) ２ ・4H ２ O, manganese carbonate MnCO ３ , iron oxide Fe ２ O ３ , lithium nitrate LiNO ３ , lanthanum nitrate hexahydrate La(NO ３ ) ３ ・6H ２ O, bismuth nitrate pentahydrate Bi(NO ３ ) ３ ・5H ２ O and the like. The mixing ratio of the compound containing the predetermined metal element may be such that the solid electrolyte ceramic of the present invention has the predetermined 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 higher and 1440 minutes or lower, particularly 60 minutes or higher and 600 minutes or lower.

[0049] The solid electrolyte ceramic of the present invention may contain a sintering aid. Any sintering aid known in the field of solid-state batteries can be used as the sintering aid. The composition of such a sintering aid preferably contains at least Li (lithium), B (boron), and O (oxygen), and the molar ratio of Li to B (Li / B) is preferably 2.0 or more. Specific examples of such sintering aids include, for example, Li ３ BO ３ , (Li ２．７ Al ０．３ ) BO ３ , Li ２．８ (B ０．８ C ０．２ ) O ３ , LiBO ２ Examples include:

[0050] The content of the sintering aid is usually preferably 0% to 10%, particularly preferably 0% to 5%, relative to the volume ratio of the garnet-type solid electrolyte.

[0051] [Solid-state battery] In this specification, the term "solid-state battery" refers in a broad sense to a battery whose components (particularly the electrolyte layer) are made of solids, and in a narrow sense to an "all-solid-state battery" whose components (particularly all components) are made of solids. In this specification, the term "solid-state battery" encompasses so-called "secondary batteries" that can be repeatedly charged and discharged, and "primary batteries" that can only be discharged. The term "solid-state battery" is preferably a "secondary battery." The term "secondary battery" should not be overly limited by its name, and can also encompass electrochemical devices such as "power storage devices," for example.

[0052] The solid-state battery of the present invention includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer, and typically has a laminated structure in which the positive electrode layer and the negative electrode layer are stacked with a solid electrolyte layer interposed therebetween. The positive electrode layer and the negative electrode layer may each be stacked in two or more layers, as long as a solid electrolyte layer is provided between them. The solid electrolyte layer is in contact with the positive electrode layer and the negative electrode layer and is sandwiched between them. The positive electrode layer and the solid electrolyte layer may be sintered together as a sintered body, and / or the negative electrode layer and the solid electrolyte layer may be sintered together as a sintered body. "Sintered together as a sintered body" means that two or more adjacent or contacting members (particularly layers) are joined by sintering. Here, the two or more members (particularly layers) may all be sintered bodies but sintered together as a sintered body.

[0053] The solid electrolyte ceramic of the present invention described above is useful as a solid electrolyte for a solid-state battery. Therefore, the solid-state battery of the present invention contains the solid electrolyte ceramic of the present invention described above as a solid electrolyte. Specifically, the solid electrolyte ceramic of the present invention is contained as a solid electrolyte in at least one layer selected from the group consisting of a positive electrode layer, a negative electrode layer, and a solid electrolyte layer. From the viewpoints of achieving superior ionic conductivity in the solid electrolyte layer and more sufficiently suppressing an increase in electronic conductivity during operation, the solid electrolyte ceramic of the present invention is preferably contained in at least the solid electrolyte layer.

[0054] (Positive Electrode Layer) In the solid battery of the present invention, the positive electrode layer is not particularly limited. For example, the positive electrode layer may contain a positive electrode active material and further contain the solid electrolyte ceramic of the present invention. By including the solid electrolyte ceramic of the present invention in the positive electrode layer, it is possible to prevent the solid battery from short-circuiting. The positive electrode layer may be in the form of a sintered body containing positive electrode active material particles and, if desired, the solid electrolyte ceramic of the present invention. The positive electrode layer may be a layer capable of absorbing and releasing ions (particularly lithium ions).

[0055] The positive electrode active material is not particularly limited, and can be used the positive electrode active material known in the field of solid-state batteries.As the positive electrode active material, for example, can be mentioned lithium-containing phosphate compound particles with Nasicon structure, lithium-containing phosphate compound particles with olivine structure, lithium-containing layered oxide particles, lithium-containing oxide particles with spinel structure, etc.The specific example of the lithium-containing phosphate compound with Nasicon structure that is preferably used is Li ３ V ２ (P.O. ４ ) ３ Specific examples of lithium-containing phosphate compounds having an olivine structure that are preferably used include Li ３ Fe ２ (P.O. ４ ) ３ , LiMnPO ４ Specific examples of the lithium-containing layered oxide particles that are preferably used include LiCoO ２ , LiCo １／３ Ni １／３ Mn １／３ O ２ Specific examples of lithium-containing oxides having a spinel structure that are preferably used include LiMn ２ O ４ , LiNi ０．５ Mn １．５ O ４ , Li ４ Ti ５ O １２ From the viewpoint of reactivity during co-sintering with the LISICON type solid electrolyte used in the present invention, LiCoO is used as the positive electrode active material. ２ , LiCo １／３ Ni １／３ Mn １／３ O ２ It is more preferable to use lithium-containing layered oxides such as those mentioned above. Only one type of these positive electrode active material particles may be used, or a mixture of two or more types may be used.

[0056] The positive electrode active material in the positive electrode layer has a Nasicon-type structure, which means that the positive electrode active material (particularly its particles) has a Nasicon-type crystal structure, and in a broad sense, it means that it has a crystal structure that can be recognized as a Nasicon-type crystal structure by those skilled in the art of solid-state batteries. In a narrow sense, the positive electrode active material in the positive electrode layer has a Nasicon-type structure, which means that the positive electrode active material (particularly its particles) shows one or more main peaks in X-ray diffraction at a predetermined incident angle, which correspond to the Miller indices specific to the so-called Nasicon-type crystal structure. The positive electrode active material with a Nasicon-type structure that is preferably used includes the compounds exemplified above.

[0057] The positive electrode active material in the positive electrode layer having an olivine structure means that the positive electrode active material (particularly its particles) has an olivine crystal structure, and in a broad sense, means that the positive electrode active material has a crystal structure that can be recognized as an olivine crystal structure by those skilled in the art of solid-state batteries. In a narrow sense, the positive electrode active material in the positive electrode layer having an olivine structure means that the positive electrode active material (particularly its particles) exhibits one or more main peaks in X-ray diffraction at a predetermined incident angle corresponding to Miller indices specific to the so-called olivine crystal structure. Preferred positive electrode active materials having an olivine structure include the compounds exemplified above.

[0058] The positive electrode active material in the positive electrode layer having a spinel structure means that the positive electrode active material (particularly its particles) has a spinel crystal structure, and in a broad sense, means that the positive electrode active material has a crystal structure that can be recognized as a spinel crystal structure by those skilled in the art of solid-state batteries. In a narrow sense, the positive electrode active material in the positive electrode layer having a spinel structure means that the positive electrode active material (particularly its particles) exhibits one or more main peaks in X-ray diffraction at a predetermined incident angle corresponding to Miller indices specific to the so-called spinel crystal structure. Preferred positive electrode active materials having a spinel structure include the compounds exemplified above.

[0059] The chemical composition of the positive electrode active material may be an average chemical composition. The average chemical composition of the positive electrode active material means an average value of the chemical composition of the positive electrode active material in the thickness direction of the positive electrode layer. The average chemical composition of the positive electrode active material can be analyzed and measured by breaking the solid-state battery and performing composition analysis by EDX (energy dispersive X-ray spectroscopy) using SEM-EDX in a field of view that includes the entire positive electrode layer in the thickness direction.

[0060] The positive electrode active material can be produced, for example, by the following method, or can be obtained as a commercially available product. When producing the positive electrode active material, first, raw material compounds containing predetermined metal atoms are weighed so as to have a predetermined chemical composition, and water is added and mixed to obtain a slurry. The slurry is then dried, calcined at 700°C to 1000°C for 1 hour to 30 hours, and pulverized to obtain the positive electrode active material.

[0061] The chemical composition and crystalline structure of the positive electrode active material in the positive electrode layer may typically change due to elemental diffusion during sintering. The positive electrode active material may have the above-described chemical composition and crystalline structure in the solid-state battery after sintering with the negative electrode layer and the solid electrolyte layer.

[0062] The average particle size of the positive electrode active material is not particularly limited, and may be, for example, 0.01 μm or more and 10 μm or less, particularly 0.05 μm or more and 4 μm or less.

[0063] The average particle size of the positive electrode active material can be determined, for example, by randomly selecting 10 to 100 particles from an SEM image and simply averaging their particle sizes to obtain the average particle size (arithmetic mean). The particle size is the diameter of a spherical particle assuming that the particles are perfectly spherical. Such particle size can be determined, for example, by cutting out a cross section of a solid-state battery, taking a cross-sectional SEM image using an SEM, calculating the cross-sectional area S of the particles using image analysis software (e.g., "A-zo-kun" (manufactured by Asahi Kasei Engineering Co., Ltd.)), and then calculating the particle diameter R using the following formula.

[0064]

[0065] The average particle size of the positive electrode active material in the positive electrode layer can be automatically measured by specifying the positive electrode active material by its composition when measuring the average chemical composition described above.

[0066] The average particle size of the positive electrode active material in the positive electrode layer may typically change due to sintering during the manufacturing process of the solid-state battery. The positive electrode active material may have the above-mentioned average particle size in the solid-state battery after sintering together with the negative electrode layer and the solid electrolyte layer.

[0067] The volume ratio of the positive electrode active material in the positive electrode layer is not particularly limited, and may be, for example, 30% or more and 90% or less, particularly 40% or more and 70% or less.

[0068] The positive electrode layer may contain the solid electrolyte ceramic of the present invention as a solid electrolyte, and / or may contain a solid electrolyte other than the solid electrolyte ceramic of the present invention. The positive electrode layer may further contain a sintering aid and / or a conductive material.

[0069] 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 may generally be 20% or more and 60% or less, particularly 30% or more and 45% or less.

[0070] As the sintering aid in the positive electrode layer, compounds similar to the sintering aids that may be contained in the solid electrolyte ceramics can be used.

[0071] The volume ratio of the sintering aid in the positive electrode layer is not particularly limited, and may be, for example, 0.1% or more and 20% or less, particularly 1% or more and 10% or less.

[0072] The conductive material in the positive electrode layer can be any conductive material known in the field of solid-state batteries. Preferred conductive materials include metal materials such as Ag (silver), Au (gold), Pd (palladium), Pt (platinum), Cu (copper), Sn (tin), and Ni (nickel); and carbon materials such as carbon nanotubes such as acetylene black, Ketjen black, Super P (registered trademark), and VGCF (registered trademark). The shape of the carbon material is not particularly limited, and any shape, such as spherical, plate-like, or fibrous, may be used.

[0073] The volume ratio of the conductive material in the positive electrode layer is not particularly limited, and may be, for example, 10% or more and 50% or less, particularly 20% or more and 40% or less.

[0074] The thickness of the positive electrode layer is usually 0.1 to 30 μm, and preferably 1 to 20 μm, for example. The thickness of the positive electrode layer is the average value of thicknesses measured at any 10 points on the SEM image.

[0075] In the positive electrode layer, the porosity is not particularly limited and may be, for example, 20% or less, usually 15% or less, particularly 10% or less.

[0076] The porosity of the positive electrode layer is a value measured from an SEM image after FIB cross-section processing.

[0077] The positive electrode layer is a layer that can be called a “positive electrode active material layer.” The positive electrode layer may have a so-called positive electrode current collector or positive electrode current collecting layer.

[0078] (Negative electrode layer) In the solid battery of the present invention, the negative electrode layer is not particularly limited. For example, the negative electrode layer may contain a negative electrode active material and further contain the solid electrolyte ceramic of the present invention. By including the solid electrolyte ceramic of the present invention in the negative electrode layer, short-circuiting of the solid battery can be suppressed. The negative electrode layer may be in the form of a sintered body containing negative electrode active material particles and, if desired, the solid electrolyte ceramic of the present invention. The negative electrode layer may be a layer capable of absorbing and releasing ions (particularly lithium ions).

[0079] The negative electrode active material is not particularly limited, and any negative electrode active material known in the field of solid-state batteries can be used. Examples of the negative electrode active material include carbon materials such as graphite, graphite-lithium compounds, lithium metal, lithium alloy particles, phosphate compounds having a Nasicon structure, Li-containing oxides having a spinel structure, β ＩＩ -Li ３ VO ４ Type structure, γ ＩＩ -Li ３ VO ４ The negative electrode active material is an oxide having a lithium metal, β ＩＩ -Li ３ VO ４ Type structure, γＩＩ -Li ３ VO ４ It is preferable to use a Li-containing oxide having a structure of the type ZnO.

[0080] In the negative electrode layer, the oxide is β ＩＩ -Li ３ VO ４ The term "having a β-type structure" means that the oxide (particularly its particles) has a β-type structure. ＩＩ -Li ３ VO ４ In a broad sense, it means that the solid-state battery has a β type crystal structure. ＩＩ -Li ３ VO ４ In a narrow sense, the oxide in the negative electrode layer has a β-type crystal structure. ＩＩ -Li ３ VO ４ The term "having a β-type structure" means that the oxide (particularly its particles) has a so-called β-type structure in X-ray diffraction. ＩＩ -Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a predetermined angle of incidence. ＩＩ -Li ３ VO ４ The Li-containing oxide having the Li-type structure includes Li ３ VO ４ Examples include:

[0081] In the negative electrode layer, the oxide is γ ＩＩ -Li ３ VO ４ The term "having a γ-type structure" means that the oxide (particularly its particles) ＩＩ -Li ３ VO ４ It means that the solid-state battery has a γ type crystal structure, and in a broad sense, it is known by those skilled in the art of solid-state batteries as ＩＩ -Li ３ VO ４ In a narrow sense, the oxide in the negative electrode layer has a γ-type crystal structure. ＩＩ -Li ３ VO ４ The term "having a γ-type structure" means that the oxide (particularly its particles) has a γ-type structure in X-ray diffraction.ＩＩ -Li ３ VO ４ This means that the crystal structure of the type exhibits one or more major peaks corresponding to Miller indices specific to the type at a given angle of incidence (x-axis). ＩＩ -Li ３ VO ４ The Li-containing oxide having the Li-type structure includes Li ３．２ V ０．８ Si ０．２ O ４ Examples include:

[0082] The chemical composition of the negative electrode active material may be an average chemical composition. The average chemical composition of the negative electrode active material means an average value of the chemical composition of the negative electrode active material in the thickness direction of the negative electrode layer. The average chemical composition of the negative electrode active material can be analyzed and measured by breaking the solid-state battery and performing composition analysis by EDX (energy dispersive X-ray spectroscopy) using SEM-EDX in a field of view that includes the entire negative electrode layer in the thickness direction.

[0083] The negative electrode active material can be produced, for example, by the same method as that for the positive electrode active material, or can be obtained as a commercially available product.

[0084] The chemical composition and crystalline structure of the negative electrode active material in the negative electrode layer may typically change due to elemental diffusion during sintering in the manufacturing process of a solid-state battery. The negative electrode active material may have the above-described average chemical composition and crystalline structure in the solid-state battery after sintering together with the positive electrode layer and the solid electrolyte layer.

[0085] The volume ratio of the negative electrode active material in the negative electrode layer is not particularly limited and may be, for example, 50% or more (particularly 50% to 99%), usually 70% to 95%, particularly 80% to 90%.

[0086] The negative electrode layer may contain the solid electrolyte ceramic of the present invention as a solid electrolyte, and / or may contain a solid electrolyte other than the solid electrolyte ceramic of the present invention. The negative electrode layer may further contain a sintering aid and / or a conductive material.

[0087] 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 may generally be 20% or more and 60% or less, particularly 30% or more and 45% or less.

[0088] The sintering aid in the negative electrode layer may be the same compound as the sintering aid in the positive electrode layer, and the conductive material in the negative electrode layer may be the same compound as the conductive material in the positive electrode layer.

[0089] The thickness of the negative electrode layer is usually 0.1 to 30 μm, and preferably 1 to 20 μm, and is the average value of thicknesses measured at 10 arbitrary points on an SEM image.

[0090] In the negative electrode layer, the porosity is not particularly limited and may be, for example, 20% or less, usually 15% or less, particularly 10% or less.

[0091] The porosity of the negative electrode layer is a value measured by the same method as that for the porosity of the positive electrode layer.

[0092] 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.

[0093] (Solid Electrolyte Layer) In the solid battery of the present invention, the solid electrolyte layer preferably contains the above-described solid electrolyte ceramic of the present invention from the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation.

[0094] The volume fraction of the solid electrolyte ceramic of the present invention in the solid electrolyte layer is not particularly limited, and from the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation, it is preferably 10% or more and 100% or less, more preferably 20% or more and 100% or less, and even more preferably 30% or more and 100% or less.

[0095] 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-described chemical composition is present at least in the central portion in the thickness direction of the solid electrolyte layer (particularly, at least 5, preferably at least 8, more preferably at 10 points out of any 10 points therein). This is because the solid electrolyte layer is sandwiched between the positive electrode layer and the negative electrode layer, and sintering during the production process of the solid battery may cause 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.

[0096] The solid electrolyte layer may contain, in addition to the garnet-type solid electrolyte ceramic of the present invention, a solid electrolyte composed of at least Li, Zr, and O, γ-Li ３ VO ４ The solid electrolyte may contain one or more materials selected from a solid electrolyte having a structure, an oxide glass ceramic-based lithium ion conductor, etc. The solid electrolyte may contain at least Li, Zr, and O. ２ ZrO ３ Examples include:

[0097] γ-Li ３ VO ４ Examples of the solid electrolyte having the structure include a solid electrolyte having an average chemical composition represented by the following general formula (III).

[0098]

[0099] In formula (III), A is one or more elements selected from the group consisting of Na, K, Mg, Ca, Al, Ga, Zn, Fe, Cr, and Co. B is one or more elements selected from the group consisting of V and P. D is one or more elements selected from the group consisting of Zn, Al, Ga, Si, Ge, Sn, As, Ti, Mo, W, Fe, Cr, and Co. x satisfies 0≦x≦1.0, particularly 0≦x≦0.2. y satisfies 0≦y≦1.0, particularly 0.20≦y≦0.50. a is the average valence of A. The average valence of A is, for example, when n1 element X with a valence of a+, n2 element Y with a valence of b+, and n3 element Z with a valence of c+ are recognized as A, the value represented by (n1 x a + n2 x b + n3 x c) / (n1 + n2 + n3). c is the average valence of D. When, for example, n1 element X with a valence of a+, n2 element Y with a valence of b+, and n3 element Z with a valence of c+ are recognized as D, the average valence of D is the same value as the average valence of A described above.

[0100] γ-Li ３ VO ４ Specific examples of solid electrolytes having the structure include Li ３．２ (V ０．８ Si ０．２ ) O ４ , Li ３．５ (V ０．５ Ge ０．５ ) O ４ , Li ３．４ (P ０．６ Si0.4)O ４ , Li ３．５ (P ０．５ Ge ０．５ ) O ４ etc.

[0101] Examples of oxide glass ceramic lithium ion conductors that can be used include a phosphate compound containing lithium, aluminum, and titanium as constituent elements (LATP) and a phosphate compound containing lithium, aluminum, and germanium as constituent elements (LAGP).

[0102] The solid electrolyte layer may further contain, in addition to the solid electrolyte, for example, a sintering aid etc. As the sintering aid in the solid electrolyte layer, the same compounds as the sintering aid in the positive electrode layer can be used.

[0103] The volume fraction of the sintering aid in the solid electrolyte layer is not particularly limited, and from the viewpoint of achieving better ionic conductivity and more sufficiently suppressing an increase in electronic conductivity during operation, it is preferably 0% or more and 20% or less, and more preferably 1% or more and 10% or less.

[0104] The thickness of the solid electrolyte layer is usually 0.1 to 30 μm, and preferably 1 to 20 μm from the viewpoint of better ionic conductivity and more sufficient suppression of an increase in electronic conductivity during operation. The thickness of the solid electrolyte layer is the average value of thicknesses measured at arbitrary 10 points on an SEM image.

[0105] In the solid electrolyte layer, the porosity is not particularly limited, and from the viewpoint of achieving better ionic conductivity and more sufficiently suppressing an increase in electronic conductivity during operation, it is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less.

[0106] The porosity of the solid electrolyte layer is a value measured by the same method as for the porosity of the positive electrode layer.

[0107] [Method for Manufacturing Solid-State Battery] A solid-state battery can be manufactured by, for example, the so-called green sheet method, the printing method, or a combination of these methods.

[0108] The green sheet method will be described. First, a paste is prepared by appropriately mixing a solvent, a binder, and the like with a positive electrode active material. The paste is applied to a sheet and dried to form a first green sheet for forming a positive electrode layer. The first green sheet may contain a solid electrolyte, a conductive material, and / or a sintering aid, etc.

[0109] A paste is prepared by appropriately mixing a solvent, a binder, etc. with the negative electrode active material. The paste is applied to a sheet and dried to form a second green sheet for forming the negative electrode layer. The second green sheet may contain a solid electrolyte, a conductive material, and / or a sintering aid, etc.

[0110] A paste is prepared by appropriately mixing a solvent, a binder, etc. with the solid electrolyte. The paste is applied and dried to prepare a third green sheet for forming the solid electrolyte layer. The third green sheet may contain a sintering aid, etc.

[0111] The solvent for producing the first to third green sheets is not particularly limited, and for example, a solvent that can be used in the production of a positive electrode layer, a negative electrode layer, or a solid electrolyte layer in the field of solid state batteries is used. A solvent that can be used with the binder described below is usually used as the solvent. Examples of such solvents include alcohols such as 2-propanol.

[0112] The binder for producing the first to third green sheets is not particularly limited, and may be, for example, a binder that can be used in the production of a positive electrode layer, a negative electrode layer, or a solid electrolyte layer in the field of solid-state batteries. Examples of such binders include butyral resin and acrylic resin.

[0113] Next, the first to third green sheets are appropriately stacked to form a laminate. The laminate may be pressed. A preferred pressing method is hydrostatic pressing. The laminate is then sintered at, for example, 600 to 800°C to obtain a solid-state battery.

[0114] The printing method will now be explained. The printing method is the same as the green sheet method, except for the following points: - Prepare ink for each layer, which has the same composition as the paste for each layer used to obtain the green sheet, except that the blending amounts of solvent and resin are appropriate for use as ink. - Print and laminate using the ink for each layer to create a laminate.

[0115] The present invention as described above includes the following preferred embodiments: <1> A compound represented by the following general formula (I): (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 includes at least Li (lithium); B is one or more elements selected from the group consisting of La (lanthanum), Ca (calcium), Sr (strontium), Ba (barium), and lanthanoid elements, and includes at least La (lanthanum); D １ and D ２ is one or more elements selected from the group consisting of transition elements and typical elements belonging to groups 12 to 15 that can form hexacoordinates with oxygen, among which D １ is one or more elements selected from the group consisting of Ta, Nb, and Bi; α satisfies 5.0≦α≦8.0; β satisfies 2.5≦β≦3.5; γ satisfies 1.5≦γ≦2.5; and ω satisfies 11≦ω≦13), 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 the content of Li is X (mol %) when the content of B is 100 mol %, and the content of D is X (mol %) when the content of B is 100 mol %. １ <2> A solid electrolyte ceramic having a garnet-type crystal structure, which satisfies the following relational expression when the content of D is Y (mol %): 220<X≦245 and 10≦Y≦70. １ The solid electrolyte ceramic according to <1>, wherein the content of Bi is 0.1 mol % or more and 30 mol % or less when the content of B is 100 mol %. １ The solid electrolyte ceramic according to any one of <1> to <3>, wherein the content of the Ta is 1 mol % or more and 80 mol % or less when the content of the B is 100 mol %. <6> The solid electrolyte ceramic according to <4>, wherein the content of the D ２The solid electrolyte ceramic according to any one of <1> to <5>, wherein the content of Zr is 0 mol% or more and 70 mol% or less, when the content of B is taken as 100 mol%. <8> The solid electrolyte ceramic according to any one of <1> to <7>, wherein the content of the one or more transition metal elements is 0.01 mol% or more and 10 mol% or less, when the content of B is taken as 100 mol%. <9> The solid electrolyte ceramic according to any one of <1> to <8>, wherein the one or more transition metal elements include one or more elements selected from the group consisting of Co and Mn. <10> The solid electrolyte ceramic according to any one of <1> to <9>, wherein the one or more transition metal elements include Co. <11> A solid battery comprising the solid electrolyte ceramic according to any one of <1> to <10>. <12> The solid-state battery according to <11>, 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, and the positive electrode layer and the negative electrode layer are layers capable of absorbing and releasing lithium ions. <13> The solid-state battery according to <12>, wherein the solid electrolyte layer is integrally sintered with the positive electrode layer and the negative electrode layer. <14> The solid-state battery according to any one of <11> to <13>, wherein the solid electrolyte ceramic is contained in the solid electrolyte layer of the solid-state battery.

[0116] The present invention will be described in more detail below based on specific examples, but the present invention is not limited to the following examples and can be implemented with appropriate modifications within the scope that does not change the gist of the present invention.

[0117] Examples 1 to 15 and Comparative Examples 1 to 3 [Production of Solid Electrolyte Ceramics] The raw material was lithium hydroxide monohydrate (LiOH.H ２ O, lanthanum hydroxide La(OH) ３ , zirconium oxide ZrO ２ , tantalum oxide Ta ２ O ５ , bismuth oxide Bi ２ O ３ , cobalt oxide Co ３O ４ , basic nickel carbonate hydrate NiCO ３ 2Ni(OH) ２ ・4H ２ O, manganese carbonate MnCO ３ , iron oxide Fe ２ O ３ Each starting material was weighed so that the chemical composition was as shown in Table 1. Water was added, the material was placed in a polyethylene pot, and the pot was rotated at 150 rpm on a pot rack for 16 hours to mix the materials. The resulting slurry was evaporated and dried, and then O ２ The target phase was obtained by calcining for 5 hours at 900°C in a molten metal atmosphere. A toluene-acetone mixed solvent was added to the calcined powder obtained, and the mixture was pulverized for 12 hours in a planetary ball mill. ICP measurement confirmed that the pulverized powder had no compositional deviation. The average particle size of the pulverized powder was 150 nm.

[0118] [Production of Solid Electrolyte Single Plate] As an evaluation sample of solid electrolyte ceramics, a solid electrolyte single plate was produced by the following method.

[0119] The resulting solid electrolyte powder, butyral resin, and alcohol were kneaded in a weight ratio of 200:15:140 to produce a slurry. The slurry was then formed into a sheet on a PET film using a doctor blade method. The resulting sheets were laminated to a thickness of 200 μm, cut into 10 mm x 10 mm squares, and the binder was removed at 400°C. The sheets were then pressure-sintered at 850-950°C for 60-600 minutes under a pressure of 100 MPa to produce solid electrolyte single plates. The porosity of the solid electrolyte single plates was 10% or less, confirming sufficient sintering. The surface of the resulting sintered body was polished to produce a garnet solid electrolyte substrate.

[0120] [Crystalline Structure of Solid Electrolyte Single Plate] In all Examples and Comparative Examples, it was confirmed that X-ray diffraction patterns attributable to a garnet-like crystal structure were obtained by X-ray diffraction of the solid electrolyte single plate (ICDD Card No. 00-045-0109).

[0121] [Chemical Composition of Solid Electrolyte Single Plate] The solid electrolyte single plate was subjected to ICP analysis to obtain the average chemical composition of the solid electrolyte single plate. The contents of Li, La, Ta, Zr, and Bi, and the contents of Co, Mn, Ni, and Fe in the average chemical composition of the entire solid electrolyte single plate were calculated based on the number of 8-coordinated sites in the garnet-type crystal structure (for example, the number of La and B in the general formula (II)). １ The total number of A, B, D in the general formula (I) was calculated as a percentage of 100 mol %, and the percentages were shown in the table. １ , D ２ This value was calculated from the molar ratio and valence of the elements contained in the compound so as to achieve charge neutrality.

[0122] [Electronic Conductivity Measurement] An Au electrode was sputtered onto one side of the obtained single plate to form a working electrode. Li metal with the same area as the Au electrode was attached to the other side. Finally, the cell was sealed in a 2035 size coin cell to form an evaluation cell. All of the above operations were carried out in a dry room with a dew point of -40°C or less. 2 V was applied to the working electrode relative to Li at room temperature, and the transient current was observed. The current that flowed 10 hours after the voltage application was read as the leakage current. The electronic conductivity was calculated from the leakage current using the following formula: Electronic conductivity = (I / V) × (L / A) (I: leakage current, V: applied voltage, L: thickness of solid electrolyte single plate, A: electrode area) ◎: Electronic conductivity < 1.0 × 10 －８ S / cm (excellent); ○; 1.0×10 －８ S / cm≦electronic conductivity<5.0×10 －８ S / cm (good); △; 5.0 x 10 －８ S / cm≦electronic conductivity<1.0×10 －７ S / cm (Acceptable) (No practical problems); ×; 1.0 × 10 －７ S / cm≦electronic conductivity (unacceptable) (problems in practical use).

[0123] [Ionic Conductivity Measurement] A gold (Au) layer was formed on both sides of a solid electrolyte single plate by sputtering to serve as a current collector layer, and then the plate was sandwiched and fixed between SUS current collectors. The sintered tablet 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) to evaluate the ionic conductivity. ◎: Ionic conductivity ≧5.0×10 －４ S / cm (no problem in practical use); ×: ionic conductivity <5.0 × 10 －４ S / cm (unacceptable) (problems in practical use).

[0124] [Overall evaluation] All evaluation results of electronic conductivity and ionic conductivity were evaluated comprehensively. ◎: All evaluation results of electronic conductivity and ionic conductivity were ◎. ○: Of all evaluation results of electronic conductivity and ionic conductivity, the lowest evaluation result was ○. △: Of all evaluation results of electronic conductivity and ionic conductivity, the lowest evaluation result was △. ×: Of all evaluation results of electronic conductivity and ionic conductivity, the lowest evaluation result was ×.

[0125]

[0126]

[0127] From a comparison between Comparative Examples 1 to 3 and Examples 1 to 15, it is clear that when the Li content is 220 mol % or less, the electronic conductivity increases, increasing the risk of short circuiting.

[0128] From a comparison between Examples 1 to 13 and Examples 14 and 15, it is clear that by including one or more elements selected from the group consisting of Co and Mn as one or more transition metal elements in the solid electrolyte ceramic, it is possible to obtain excellent ionic conductivity while more sufficiently suppressing an increase in electronic conductivity.

[0129] From a comparison between Examples 1 to 11 and Examples 12 to 15, it is clear that by including Co as one or more transition metal elements in the solid electrolyte ceramic, excellent ionic conductivity can be obtained while the increase in electronic conductivity can be further sufficiently suppressed.

[0130] A solid-state battery including the solid electrolyte ceramic of the present invention can be used in various fields where battery use or power storage is expected. By way of example only, a solid-state battery according to an embodiment of the present invention can be used in the field of electronics packaging. The solid-state battery according to one embodiment of the present invention can also be used in the fields of electricity, information, and communications where mobile devices and the like are used (for example, the fields of electrical and electronic equipment including small electronic devices such as mobile phones, smartphones, smart watches, laptops, digital cameras, activity monitors, arm computers, electronic paper, wearable devices, RFID tags, card-type electronic money, and smart watches, or the field of mobile devices), household and small industrial applications (for example, the fields of power tools, golf carts, and household, nursing care, and industrial robots), large industrial applications (for example, the fields of forklifts, elevators, and port cranes), transportation systems (for example, the fields of hybrid cars, electric cars, buses, trains, electrically assisted bicycles, and electric motorcycles), power system applications (for example, the fields of various power generation, road conditioners, smart grids, and general household installation-type power storage systems), medical applications (for example, the fields of medical devices such as earphone hearing aids), pharmaceutical applications (for example, the fields of medication management systems), as well as the IoT field, and space and deep-sea applications (for example, the fields of space probes and submersible research vessels).

Claims

1. The following general formula (I): 【Chemistry 1】 (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 includes at least Li (lithium); B is one or more elements selected from the group consisting of La (lanthanum), Ca (calcium), Sr (strontium), Ba (barium), and lanthanoid elements, including at least La (lanthanum); D １ and D. ２ is one or more elements selected from the group consisting of transition elements capable of forming 6-coordination with oxygen and typical elements belonging to groups 12 to 15, among which D １ is one or more elements selected from the group consisting of Ta, Nb, and Bi, including at least 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) and further containing one or more transition metal elements selected from the group consisting of Co (cobalt), Ni (nickel), Mn (manganese) and Fe (iron), The content of Li is X (mol%) when the content of B is 100 mol%, and the content of D is １ A solid electrolyte ceramic having a garnet-type crystal structure, which satisfies the following relational formula when the content of is Y (mol %): In the range of 220<X≦245, 10≦Y≦70.

2. 2. The solid electrolyte ceramic according to claim 1, wherein the content of Bi is 0.1 mol % or more and 30 mol % or less when the content of B is 100 mol %.

3. The above D １ The solid electrolyte ceramic according to claim 1 , wherein the metal oxide comprises Ta (tantalum).

4. 4. The solid electrolyte ceramic according to claim 3, wherein the Ta content is 1 mol % or more and 80 mol % or less when the B content is 100 mol %.

5. The above D ２ The solid electrolyte ceramic according to claim 1 , wherein Zr (zirconium) is contained or not contained.

6. The solid electrolyte ceramic according to claim 5 , wherein the content of Zr is 0 mol % or more and 70 mol % or less when the content of B is 100 mol %.

7. 2. The solid electrolyte ceramic according to claim 1, wherein the content of the one or more transition metal elements is 0.01 mol % or more and 10 mol % or less when the content of B is 100 mol %.

8. 2. The solid electrolyte ceramic according to claim 1, wherein the one or more transition metal elements include one or more elements selected from the group consisting of Co and Mn.

9. The solid electrolyte ceramic according to claim 1 , wherein the one or more transition metal elements include Co.

10. A solid-state battery comprising the solid electrolyte ceramic according to any one of claims 1 to 9.

11. 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 solid-state battery according to claim 10 , wherein the positive electrode layer and the negative electrode layer are layers capable of absorbing and releasing lithium ions.

12. The solid-state battery according to claim 11 , wherein the solid electrolyte layer is integrally sintered with the positive electrode layer and the negative electrode layer.

13. The solid-state battery according to claim 10 , wherein the solid electrolyte ceramic is included in a solid electrolyte layer of the solid-state battery.

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