Solid electrolyte ceramics and solid-state batteries

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

[Technical Field]

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

[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 batteries used in such applications, development is underway of 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. As such solid electrolyte ceramics, attempts have been made to use ceramics obtained by sintering a garnet-type solid electrolyte substituted with Bi from the viewpoint of higher ionic conductivity (e.g., Patent Document 1 and Non-Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-050071 [Non-patent literature]

[0005] [Non-Patent Document 1] Gao et al., SolidState Ionics, 181 (2010) 1415-1419 Summary of the Invention [Problem to be solved by the invention]

[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 compounds are likely to be generated at grain boundaries, and these Li-Bi-O 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 in suppressing the formation of Li-Bi-O 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 compounds, it also generates new impurities containing transition metals, such as Li-La-Co-O compounds that are different from Li-Bi-O compounds, 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. [Means for solving the problem]

[0009] The present invention provides The following general formula (I): [ka] (In formula (I), A represents 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 contains 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 a six - coordinate bond with oxygen and typical elements belonging to Groups 12 to 15, and among these, 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; ω satisfies 11 ≤ ω ≤ 13) while having a chemical composition represented by, 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 B is taken as 100 mol%, the content of Li is X (mol%) and the content of D 1 is Y (mol%), a solid electrolyte ceramic having a garnet - type crystal structure that satisfies the following relational expression: 10 ≤ Y ≤ 70 in the range of 220 < X ≤ 245.

Advantages of the Invention

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

Modes for Carrying Out the Invention

[0011] [Solid Electrolyte Ceramic] 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 contains at least Li (lithium), La (lanthanum), and oxygen (oxygen) and has a garnet-type crystal structure. It further contains 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 ceramic of the present invention is a ceramic 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 ceramic of the present invention may be a solid electrolyte having a so-called garnet-type crystal structure. Furthermore, the solid electrolyte ceramic of the present invention preferably contains Bi (bismuth) from the viewpoint of superior ionic conductivity. Furthermore, it is sufficient that at least the sintered particles contained in the solid electrolyte ceramic, which is 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] [ka]

[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, including 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"). Among these, D 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 or may not 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 relationships: 5.0≦α≦8.0, 2.5≦β≦3.5, 1.5≦γ≦2.5, and 11≦ω≦13, respectively. From the viewpoint of achieving better ionic conductivity and more sufficiently suppressing 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 achieving better ionic conductivity and more sufficiently suppressing 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 of them contains a plurality of elements, the sum of the values ​​corresponding to γ ​​for each of those elements should fall within 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 elements (especially 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. In contrast, in the solid electrolyte ceramics of the present invention, the formation of Li and D 1 By containing a relatively large amount of elements (pentavalent elements including Nb, especially 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. The details of the mechanism by which this effect is obtained are unknown, but it is presumed to be as follows. Li and D 1 In systems containing relatively large amounts 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. This allows the D 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 includes one or more elements selected from the group consisting of Co, Ni, and Mn, more preferably includes one or more elements selected from the group consisting of Co and Mn, and even more preferably includes Co.

[0018] In the present invention, Li and D in the solid electrolyte ceramics 1The content of the element (especially Ta) is as follows in detail. That is, when the content of B in the general formula (I) representing the chemical composition of the solid electrolyte ceramics of the present invention is 100 mol%, Li and D 1 When the content of the element (especially Ta) is X (mol%) and Y (mol%) respectively, the solid electrolyte ceramics of the present invention satisfy both of the following relational expressions (1) and (2): (1) 220 < X ≦ 245 (preferably 221 ≦ X ≦ 244, more preferably 222 ≦ X ≦ 243) from the viewpoint of more excellent ionic conductivity and more sufficient suppression of the increase in electronic conductivity during operation; (2) 10 ≦ Y ≦ 70 (preferably 10 ≦ Y ≦ 50, more preferably 10 ≦ Y ≦ 30) from the viewpoint of more excellent ionic conductivity and more sufficient suppression of the increase in electronic conductivity during operation).

[0019] Regarding the relational expression (1), if the content X of Li is too large, the sinterability decreases, and when used as a solid electrolyte of a solid battery, it becomes difficult to sinter. If the content X of Li is too small, a heterogeneous phase (such as an impurity Li-La-Co-O-based compound) appears and the electronic conductivity increases. Regarding the relational expression (2), D 1 If the content Y of the element (especially Ta) is too small, the garnet-type crystal structure is not cubic but tetragonal, and therefore, the ionic conductivity decreases significantly. D 1 If the content Y of the element (especially Ta) is too large, a heterogeneous phase (such as an impurity and tantalum oxide) appears and the ionic conductivity decreases significantly.

[0020] The above-mentioned content X of Li and D 1 The content Y of the 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-coordinate sites of 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 La and B 1The total number of the 8-coordinated sites is 100 mol %. In another specific example, the 8-coordinated sites of the garnet-type crystal structure are, for example, Li5La3Nb2O 12 (ICDD Card No. 00-045-0109) refers to the site occupied by La.

[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 taken as 100 mol %. For example, the number of 8-coordinated sites in the garnet-type crystal structure (for example, the ratio of La and B in the general formula (II) described later) can be calculated as a ratio. 1 The total number of the elements (compounds) can be calculated as a percentage of the total number of the elements (compounds) taken as 100 mol %. Alternatively, the amount of the elements (compounds) may be calculated by measuring with 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 taken as 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, the total content thereof may be 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 better ionic conductivity and more sufficient suppression of 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 better ionic conductivity and more sufficient suppression of 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. 1As with the element (particularly Ta) content Y, this 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 the 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 number of the elements (compounds) can be calculated as a percentage of the total number of the elements (compounds) taken as 100 mol %. Alternatively, the amount of the elements (compounds) may be calculated by measuring with 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 that can constitute 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 that 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 in 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 in 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 as 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, for 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 boundary 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, the solid electrolyte ceramic having a garnet-type crystal structure 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 major 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 may exhibit one or more major 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 major peaks corresponding to Miller indices specific to the so-called garnet-like crystal structure due to differences in composition. A representative diffraction pattern of a garnet-like crystal structure is, for example, ICDD Card No. 00-045-0109.

[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] [ka]

[0035] In formula (II), A 1 A indicates a metal element that occupies the Li site in the garnet-type crystal structure. 1is 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. 1 is 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 that occupies 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 lanthanoid elements.

[0037] In formula (II), D 1 is a 6-coordinated site in the garnet-type crystal structure (Garnet-type crystal structure Li7La3Zr2O 12 (ICDD Card. No. 01-078-6708)) refers to the metallic element that occupies the site occupied by Zr. 1 is D in the general formula (I). 1 The element corresponding to D 1 Among the elements similar to those exemplified above, one or more elements may be selected from the group consisting of elements other than Bi. 1is usually at least one element selected from the group consisting of Zr (zirconium), Hf (hafnium), Ta (tantalum), Nb (niobium), Mo (molybdenum), W (tungsten) and Te (tellurium). From the viewpoint of more excellent ion conductivity and more sufficient suppression of the increase in electron conductivity during operation, it preferably contains at least one element selected from the group consisting of Zr (zirconium) and Ta (tantalum), and more preferably contains at least Ta (tantalum).

[0038] In formula (II), x satisfies 0 < x ≤ 1.00. From the viewpoint of more excellent ion conductivity and more sufficient suppression of the increase in electron conductivity during operation, it preferably satisfies 0.01 ≤ x ≤ 0.70, more preferably 0.02 ≤ x ≤ 0.60, still 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. From the viewpoint of more excellent ion conductivity and more sufficient suppression of the increase in electron conductivity during operation, it preferably satisfies 0 ≤ y ≤ 0.40, more preferably 0 ≤ y ≤ 0.30, still more preferably 0 ≤ y ≤ 0.20, and particularly preferably 0. When the A 1 contains a plurality of elements, the sum of the values corresponding to y for each of those elements only needs to satisfy the above range. z satisfies 0 ≤ z ≤ 2.00. From the viewpoint of more excellent ion conductivity and more sufficient suppression of the increase in electron conductivity during operation, it preferably satisfies 0 ≤ z ≤ 0.35, more preferably 0 ≤ z ≤ 0.08, still more preferably 0 ≤ z ≤ 0.04, and most preferably 0. When the B 1 contains a plurality of elements, the sum of the values corresponding to z for each of those elements only needs to satisfy the above range. γ satisfies 1.2 ≤ γ ≤ 3.2. From the viewpoint of more excellent ion conductivity and more sufficient suppression of the increase in electron conductivity during operation, it preferably satisfies 1.4 ≤ γ ≤ 3.0, more preferably 1.6 ≤ γ ≤ 2.8, and still 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. 1 When includes 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 even more preferably 6.6≦p≦7.4. a is A 1 is the average valence of A 1 The average valence of is A 1 For example, if there are n1 elements X with a valence of a+, n2 elements Y with a valence of b+, and n3 elements Z with a valence of c+, then the value is (n1×a+n2×b+n3×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 with a valence of a+, n2 elements Y with a valence of b+, and n3 elements Z with a valence of c+ are recognized, the above-mentioned A 1 This is the same value as the average valence of the c is D 1 is the average valence of D 1 The average valence of 1 For example, when n1 elements X with a valence of a+, n2 elements Y with a valence of b+, and n3 elements Z with a valence of c+ are recognized, 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, and from the viewpoint of achieving better ionic conductivity and more sufficiently suppressing 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. δ usually satisfies 0≦δ<1. The amount of oxygen vacancy δ cannot be quantitatively analyzed even with the latest equipment, so 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, for example, the molar ratio of each element in formula (II), and tends to deviate from that depending on the analytical method. However, as long as the deviation in composition is not so great as to change the characteristics, the effects of the present invention can be achieved.

[0041] Even when the solid electrolyte ceramic of the present invention has a chemical composition represented by the general formula (II) above, the above-mentioned Li content X and D 1 It goes without saying that the content Y of elements (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 is "when the content of B is 100 mol%" and "when the content of La and B is 100 mol%." 1 may be read as "when the total number (i.e., total content) 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 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 performing quantitative analysis (composition analysis) on 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 (amount of) 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-MS) analysis, or the like. Alternatively, it may be measured and calculated using XPS analysis, or TEM-EDX (energy dispersive X-ray spectroscopy) or WDX (wavelength dispersive X-ray spectroscopy). Furthermore, the chemical composition may be obtained by quantitatively analyzing (compositionally analyzing) 100 arbitrary points on each of 100 arbitrary sintered particles and calculating the average value.

[0044] For example, EDX or WDX analysis involves measuring 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. There are no particular limitations on the method for polishing the cross section, 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-state battery is exfoliated using a focused ion beam (FIB) or the like, and then the solid electrolyte portion is subjected to TEM-EELS (transmission electron microscope-electron energy loss spectroscopy) measurement. This allows each element (e.g., the elements contained in B in the general formula (I), i.e., 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 La3Zr 1.4 Ta 0.42 Bi 0.2 O 12 -Co 0.05 Li 6.7 La3Zr 0.8 Ta1Bi 0.2 O 12 -Co 0.05 Li 6.7 La3Ta 1.95 Bi 0.05 O 12 -Co 0.05 Li 6.9 La3Zr 1.4 Ta 0.42 Bi 0.2 O 12 -Co 0.05 Li 6.9 La3Zr 0.8 Ta1Bi 0.2 O 12 -Co 0.05 Li 6.9 La3Ta 1.95 Bi 0.05 O 12 -Co 0.05 Li 7.3 La3Zr1.4 Ta 0.42 Bi 0.2 O 12 -Co 0.05 Li 7.3 La3Zr 0.8 Ta1Bi 0.2 O 12 -Co 0.05 Li 7.3 La3Ta 1.95 Bi 0.05 O 12 -Co 0.05 Li 6.9 La3Zr 1.4 Ta 0.42 Bi 0.2 O 12 -Co 0.005 Li 6.9 La3Zr 1.4 Ta 0.42 Bi 0.2 O 12 -Co 0.001 Li 6.9 La3Zr 1.4 Ta 0.42 Bi 0.2 O 12 -Mn 0.005 Li 6.9 La3Zr 1.4 Ta 0.42 Bi 0.2 O 12 -Mn 0.001 Li 6.9 La3Zr 1.4 Ta 0.42 Bi 0.2 O 12 -Ni 0.005 Li 6.9 La3Zr 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 manufacturing 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 heat-treating. The compound containing the predetermined metal element is typically a mixture of compounds containing one metal element selected from the group consisting of lithium (Li), lanthanum (La), bismuth (Bi), and a predetermined transition metal element. Examples of compounds containing the predetermined metal element (i.e., starting material) include 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), and bismuth nitrate pentahydrate (Bi(NO3)3·5H2O). The mixing ratio of the compounds containing the predetermined metal elements 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, Li3BO3, (Li 2.7 Al 0.3 )BO3, Li 2.8 (B 0.8 C 0.2 )O3, LiBO2.

[0050] The content of the sintering aid is usually preferably 0% or more and 10% or less, particularly preferably 0% or more and 5% or less, based on the volume ratio of the garnet-type solid electrolyte.

[0051] [Solid 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 laminated with a solid electrolyte layer interposed therebetween. The positive electrode layer and the negative electrode layer may each be laminated in two or more layers, as long as a solid electrolyte layer is provided between them. The solid electrolyte layer is in contact with 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 single sintered body, and / or the negative electrode layer and the solid electrolyte layer may be sintered together as a single sintered body. "Sintered together as a single 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 single sintered body.

[0053] The solid electrolyte ceramic of the present invention described above is useful as a solid electrolyte for solid-state batteries. 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 superior ionic conductivity in the solid electrolyte layer and more sufficient suppression of 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-state 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, short-circuiting of the solid-state battery can be suppressed. 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 positive electrode active materials known in the field of solid-state batteries can be used. Examples of the positive electrode active material include lithium-containing phosphate compound particles having a Nasicon structure, lithium-containing phosphate compound particles having an olivine structure, lithium-containing layered oxide particles, and lithium-containing oxide particles having a spinel structure. Specific examples of lithium-containing phosphate compounds having a Nasicon structure that are preferably used include Li3V2(PO4)3, etc. Specific examples of lithium-containing phosphate compounds having an olivine structure that are preferably used include Li3Fe2(PO4)3, LiMnPO4, etc. Specific examples of lithium-containing layered oxide particles that are preferably used include LiCoO2, LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 Specific examples of lithium-containing oxides having a spinel structure that are preferably used include LiMnO, LiNi 0.5 Mn 1.5 O4, Li4Ti5O 12 From the viewpoint of reactivity when co-sintered with the LISICON-type solid electrolyte used in the present invention, LiCoO2, LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 It is more preferable to use a lithium-containing layered oxide such as O2. 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 having a Nasicon structure means that the positive electrode active material (particularly its particles) has a Nasicon crystal structure, and in a broad sense, it means that the positive electrode active material has a crystal structure that can be recognized as a Nasicon 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 Nasicon structure 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 Miller indices specific to the so-called Nasicon crystal structure. Preferred examples of positive electrode active materials having a Nasicon structure include 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 particles thereof) 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 field 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 particles thereof) exhibits, in X-ray diffraction, one or more main peaks corresponding to Miller indices specific to the so-called olivine crystal structure at a predetermined angle of incidence. 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 field 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 corresponding to Miller indices specific to the so-called spinel crystal structure at a predetermined incident angle in X-ray diffraction. 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 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 and performing EDX composition analysis using SEM-EDX (energy dispersive X-ray spectroscopy) 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 commercially. To produce the positive electrode active material, raw material compounds containing predetermined metal atoms are first weighed out so as to achieve a predetermined chemical composition, and water is added and mixed to obtain a slurry. The slurry is then dried, calcined at 700°C to 1000°C for 1 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 (arithmetic mean) of the positive electrode active material can be determined by, for example, randomly selecting 10 to 100 particles from an SEM image and simply averaging their particle sizes. The particle diameter is the diameter of a spherical particle when the particle is assumed to be perfectly spherical. Such particle diameter 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 particle 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]

number

[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 include 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. Examples of 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, including 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 was 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) The negative electrode layer in the solid-state battery of the present invention 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-state 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 -Li3VO4 type structure, γ II The negative electrode active material is an oxide having a lithium metal, β II -Li3VO4 type structure, γII It is preferable to use a Li-containing oxide having a -Li3VO4 type structure.

[0080] In the negative electrode layer, the oxide is β II -Li3VO4 type structure means that the oxide (particularly its particles) has a β II -Li3VO4 type crystal structure, and in a broad sense, it is known by those skilled in the art of solid-state batteries as II In a narrow sense, the oxide in the negative electrode layer has a β-LiVO4 type crystal structure. II -Li3VO4 type structure means that the oxide (particularly its particles) has a so-called β II This means that the β exhibits one or more major peaks corresponding to Miller indices specific to the Li3VO4 type crystal structure at a given angle of incidence. II An example of a Li-containing oxide having a -Li3VO4 type structure is Li3VO4.

[0081] In the negative electrode layer, the oxide is γ II -Li3VO4 type structure means that the oxide (particularly its particles) II -Li3VO4 type crystal structure, and in a broad sense, it is known by those skilled in the art of solid-state batteries as γ II In a narrow sense, the oxide in the negative electrode layer is γ-LiVO4 type. II -Li3VO4 type structure means that the oxide (particularly its particles) has a so-called γ II This means that the crystal structure exhibits one or more major peaks corresponding to Miller indices specific to the Li3VO4 type crystal structure at a given angle of incidence (x-axis). II As the Li-containing oxide having the -Li3VO4 type structure, Li 3.2 V 0.8 Si 0.2 O4 is an example.

[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 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 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 include 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] As the sintering aid in the negative electrode layer, the same compounds as the sintering aid in the positive electrode layer can be used. As the conductive material for the negative electrode layer, the same compounds as the conductive material for the positive electrode layer can be used.

[0089] The thickness of the negative electrode layer is usually 0.1 to 30 μm, and preferably 1 to 20 μm. The thickness of the negative electrode layer is the average value of thicknesses measured at any 10 points on the 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, and 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 state 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 superior 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 center of the solid electrolyte layer in the thickness direction (particularly at 5 or more points out of any 10 points, preferably 8 or more points, more preferably 10 points). 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-state 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] In addition to the garnet-type solid electrolyte ceramic of the present invention, the solid electrolyte layer may contain one or more materials selected from a solid electrolyte composed of at least Li, Zr, and O, a solid electrolyte having a γ-Li3VO4 structure, and an oxide glass ceramic-based lithium ion conductor. An example of a solid electrolyte composed of at least Li, Zr, and O is Li2ZrO3.

[0097] Examples of solid electrolytes having a γ-Li3VO4 structure include solid electrolytes having an average chemical composition represented by the following general formula (III).

[0098] [ka]

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

[0100] Specific examples of solid electrolytes having a γ-Li3VO4 structure include 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.

[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. 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 better ionic conductivity and more sufficient suppression of 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, but from the viewpoint of better ionic conductivity and more sufficient suppression of 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] [Solid-state battery manufacturing method] The 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 now be described. First, a paste is prepared by appropriately mixing a solvent, binder, etc. with the positive electrode active material. The paste is applied to a sheet and dried to form a first green sheet for forming the positive electrode layer. The first green sheet may contain a solid electrolyte, a conductive material, and / or a sintering aid.

[0109] A paste is prepared by appropriately mixing the negative electrode active material with a solvent, binder, etc. 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 can be used. handIn general, a solvent that can be used with the binder described below is used. Examples of such a solvent include alcohols such as 2-propanol.

[0112] The binder for producing the first to third green sheets is not particularly limited, and 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 can be used. Examples of such binders include butyral resin and acrylic resin.

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

[0114] The printing method will be explained. The printing method is similar to the green sheet method except for the following points. Ink for each layer is prepared having the same composition as the paste for each layer used to obtain the green sheet, except that the solvent and resin are blended in amounts suitable for use as an ink. · Each layer is printed using ink and laminated to create a laminate.

[0115] The present invention as described above includes the following preferred embodiments. <1> The following general formula (I): [ka] (In formula (I), A represents 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 contains at least La (lanthanum); D 1 and D 2 and D is one or more elements selected from the group consisting of transition elements capable of six-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; 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) while having a chemical composition represented by the formula, and further contains 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 B is taken as 100 mol%, and the content of Li is X (mol%) and the content of D 1 is Y (mol%), a solid electrolyte ceramic having a garnet-type crystal structure that satisfies the following relational expression: 10 ≤ Y ≤ 70 in the range of 220 < X ≤ 245. <2> The solid electrolyte ceramic according to <1>, wherein the D 1 contains Bi (bismuth). <3> The solid electrolyte ceramic according to <2>, wherein the content of Bi is 0.1 mol% or more and 30 mol% or less when the content of B is taken as 100 mol%. <4> The solid electrolyte ceramic according to any one of <1> to <3>, wherein the D 1 contains Ta (tantalum). <5> The solid electrolyte ceramic according to <4>, wherein the content of Ta is 1 mol% or more and 80 mol% or less when the content of B is taken as 100 mol%. <6> The D 2may or may not contain Zr (zirconium), <1> ~ <5> 10. The solid electrolyte ceramic according to claim 9, wherein the solid electrolyte ceramic is a ceramic material. <7> The content of Zr is 0 mol% or more and 70 mol% or less when the content of B is 100 mol%. <6> The solid electrolyte ceramic according to claim 1. <8> 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%. <1> ~ <7> 10. The solid electrolyte ceramic according to claim 9, wherein the solid electrolyte ceramic is a ceramic material. <9> The one or more transition metal elements include one or more elements selected from the group consisting of Co and Mn. <1> ~ <8> 10. The solid electrolyte ceramic according to claim 9, wherein the solid electrolyte ceramic is a ceramic material. <10> The one or more transition metal elements include Co; <1> ~ <9> 10. The solid electrolyte ceramic according to claim 9, wherein the solid electrolyte ceramic is a ceramic material. <11> <1> ~ <10> A solid-state battery comprising the solid electrolyte ceramic according to any one of claims 1 to 4. <12> the solid-state battery includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer stacked between the positive electrode layer and the negative electrode layer; The positive electrode layer and the negative electrode layer are layers capable of absorbing and releasing lithium ions. <11> The solid-state battery according to claim 1. <13> the solid electrolyte layer is integrally sintered with the positive electrode layer and the negative electrode layer; <12> The solid-state battery according to claim 1. <14> the solid electrolyte ceramic is contained in a solid electrolyte layer of the solid-state battery; <11> ~ <13> 1. The solid-state battery according to claim 1 ,

[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. [Example]

[0117] <Examples 1 to 15 and Comparative Examples 1 to 3> [Manufacturing solid electrolyte ceramics] The raw materials used were 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). Each starting material was weighed so that the chemical composition was as shown in Table 1. Water was added, the mixture was sealed in a polyethylene pot, and the mixture was rotated on a pot rack at 150 rpm for 16 hours to mix the raw materials. The resulting slurry was evaporated and dried, and then calcined in O2 at 900°C for 5 hours to obtain the target phase. A toluene-acetone mixed solvent was added to the calcined powder and pulverized in a planetary ball mill for 12 hours. ICP measurement confirmed that the pulverized powder had no compositional deviation. The average particle size of the pulverized powder was 150 nm.

[0118] [Manufacturing solid electrolyte single plate] As an evaluation sample of the solid electrolyte ceramic, a solid electrolyte single plate was produced by the following method.

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

[0120] [Crystal 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 could be 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, as well as 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 above 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] [Electron conductivity measurement] An Au electrode was sputtered onto one side of the resulting single plate to form the 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 the evaluation cell. All of the above procedures were carried out in a dry room with a dew point of -40°C or below. 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 that flowed 10 hours after the voltage application was measured was taken as the leakage current. The electronic conductivity was calculated from the leakage current using the following formula: Electronic conductivity = (I / V) x (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≦Electron conductivity<5.0×10 -8 S / cm (good); △;5.0×10 -8S / cm≦Electron 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 the solid electrolyte single plate by sputtering to serve as a current collector, and then the plate was sandwiched and fixed between SUS current collectors. The sintered tablets of each solid electrolyte were subjected to AC impedance measurements at room temperature (25°C) in the range of 10 MHz to 0.1 Hz (±50 mV) to evaluate the ionic conductivity. ◎: Ion conductivity ≥ 5.0 × 10 -4 S / cm (no practical problems); ×; ionic conductivity <5.0 × 10 -4 S / cm (not possible) (problems in practical use).

[0124] [Overall Judgment] All evaluation results of electronic conductivity and ionic conductivity were evaluated comprehensively. ⊚: All evaluation results for electronic conductivity and ionic conductivity were ⊚. ◯: The lowest evaluation result of all the evaluation results of electronic conductivity and ionic conductivity was ◯. △: The lowest evaluation result among all evaluation results of electronic conductivity and ionic conductivity was △. ×: The lowest evaluation result of all the evaluation results of electronic conductivity and ionic conductivity was ×.

[0125] [Table 1]

[0126] [Table 2]

[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] A comparison between Examples 1 to 13 and Examples 14 to 15 reveals 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] A comparison between Examples 1 to 11 and Examples 12 to 15 reveals 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. [Industrial Applicability]

[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 one 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 electrical, information, and communications fields where mobile devices and the like are used (e.g., electrical and electronic devices 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 mobile device field), household and small industrial applications (e.g., power tools, golf carts, and household, nursing care, and industrial robots), large industrial applications (e.g., forklifts, elevators, and harbor cranes), transportation systems (e.g., hybrid cars, electric cars, buses, trains, electrically assisted bicycles, and electric motorcycles), power system applications (e.g., various power generation systems, road conditioners, smart grids, and general household energy storage systems), medical applications (medical devices such as earphones and hearing aids), pharmaceutical applications (medical management systems), as well as the IoT field, and space and deep-sea applications (e.g., space probes, submersible research vessels, and the like).

Claims

1. The following general formula (I): 【Chemistry 1】 (In formula (I), A represents 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, and includes 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), When the content of B is 100 mol%, the content of Li is X (mol%), and the content of D is １ A solid electrolyte ceramic having a garnet-type crystal structure, which satisfies the following relational expression when the content of Y (mol %) is Y: 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 taken as 100 mol %.

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

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

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

6. 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 taken as 100 mol %.

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