Solid electrolyte ceramics and solid batteries

Abstract

The present invention provides solid electrolyte ceramics that more sufficiently suppress an increase in the electron conductance resulting from operation of a solid-state battery while still having excellent ion conductivity. The present invention is a solid electrolyte ceramic that has a garnet-type crystal structure, the solid electrolyte ceramic having a chemical composition that is represented by the general formula AαBβDγOω (in the formula: A is one or more elements selected from the group consisting of Li, Ga, Al, Mg, An, and Sc, and includes at least Li; B is one or more elements selected from the group consisting of La, Ca, Sr, Ba, and lanthanides, and includes at least La; and D is one or more elements selected from the group consisting of a transition element that is capable of a 6-coordinate bond with oxygen, and a typical element that belongs to groups 12–15), while further including one or more transition metal elements selected from the group consisting of Co, Ni, Mn, and Fe. When the solid electrolyte ceramic contains 100 mol% of D in the formula, X (mol%) of Li, and Y (mol%) of B, the following relationship is satisfied: in the range of 330<X≤370, 139≤Y<150.

Description

[Technical Field]

[0001] The present invention relates to solid electrolyte ceramics and solid-state batteries containing said solid electrolyte ceramics. [Background technology]

[0002] In recent years, the demand for batteries has expanded significantly as power sources for portable electronic devices such as mobile phones and portable personal computers. For use in such applications, development is progressing on sintered solid-state rechargeable batteries (so-called "solid batteries") that use a solid 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 and negative electrode layers. In particular, the solid electrolyte layer includes a solid electrolyte ceramic and is responsible for ion conduction between the positive and negative electrode layers. The solid electrolyte ceramic is required to have higher ionic conductivity and lower electronic conductivity. As such a solid electrolyte ceramic, attempts have been made to use ceramics obtained by sintering a Bi-substituted garnet-type solid electrolyte (for example, Patent Document 1 and Non-Patent Document 1) from the viewpoint of higher ionic conductivity. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-050071 [Non-patent literature]

[0005] [Non-Patent Document 1] Gao et al., SolidState Ionics, 181 (2010) 1415-1419 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The inventors of the present invention have found that the following problems occur in conventional solid-state batteries using the above-described solid electrolyte ceramics. Specifically, in conventional solid-state batteries using garnet-type solid electrolyte ceramics containing Bi, impurities such as Li-Bi-O compounds tend to form at grain boundaries. These Li-Bi-O compounds are reduced during the operation of the solid-state battery (i.e., during charging and discharging), increasing the electronic conductivity. This increase in electronic conductivity can lead to short circuits in the solid-state battery and / or an increase in leakage current.

[0007] The inventors of the present invention also found that including transition metal elements such as Co is effective in suppressing the formation of Li-Bi-O compounds, but they also found that the following new problems arise. Specifically, while using a solid electrolyte containing transition metal elements can suppress the formation of Li-Bi-O compounds, it also generates new impurities containing transition metals, such as Li-La-Co-O compounds, which are different from Li-Bi-O compounds, and these impurities also increase the electronic conductivity when the solid battery is in operation.

[0008] The present invention aims to provide a solid electrolyte ceramic that has excellent ionic conductivity while more effectively suppressing the increase in electronic conductivity caused by the operation of a solid-state battery. [Means for solving the problem]

[0009] The present invention The following general formula (I): [ka] (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 contains at least La (lanthanum); D is one or more elements selected from the group consisting of transition elements capable of six-coordinating with oxygen and typical elements belonging to Groups 12 to 15; 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 containing one or more transition metal elements selected from the group consisting of Co (cobalt), Ni (nickel), Mn (manganese), and Fe (iron), Regarding a solid electrolyte ceramic having a garnet-type crystal structure, when the content of D is 100 mol%, and the content of Li is X (mol%) and the content of B is Y (mol%), the following relational expression is satisfied: 139 ≤ Y < 150 in the range of 330 < X ≤ 370.

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.

Embodiments 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 O (oxygen), and is a solid electrolyte ceramic having a garnet-type crystal structure, and further contains one or more transition metal elements selected from the group consisting of Co (cobalt), Ni (nickel), Mn (manganese), and Fe (iron) (hereinafter sometimes simply referred to as "a predetermined transition metal element"). 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 to the extent that it does not impair the effects of the present invention. Furthermore, the solid electrolyte ceramic of the present invention may be a solid electrolyte having a so-called garnet-type crystal structure. Furthermore, from the viewpoint of better ionic conductivity, the solid electrolyte ceramic of the present invention preferably contains Bi (bismuth). In addition, 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 ceramics of the present invention preferably have a chemical composition represented by the following general formula (I) and further contain 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 lanthanide elements, and contains at least La. Examples of lanthanide elements include Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium). D represents one or more elements selected from the group consisting of transition elements capable of 6-coordinate with oxygen and main group elements belonging to groups 12 to 15. Examples of transition elements capable of 6-coordinate with oxygen include Sc (scandium), Zr (zirconium), Ti (titanium), Ta (tantalum), Nb (niobium), Hf (hafnium), Mo (molybdenum), W (tungsten), and Te (tellurium). Examples of main group elements belonging to groups 12 to 15 include In (indium), Ge (germanium), Sn (tin), Pb (lead), Sb (antimony), and Bi (bismuth). From the viewpoint of better ionic conductivity and more sufficient suppression of the increase in electronic conductivity during operation, D preferably contains at least Bi, and more preferably contains at least Bi, Ta, and Zr.

[0015] In equation (I), α, β, γ, and ω satisfy 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 the 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. If A contains multiple elements, the sum of the values ​​corresponding to α for each of those elements should satisfy the above range. From the viewpoint of better ionic conductivity and more sufficient suppression of the increase in electronic conductivity during operation, β preferably satisfies 2.6 ≤ β ≤ 3.3, more preferably 2.6 ≤ β ≤ 3.1, and even more preferably 2.7 ≤ β ≤ 3.0. If B contains multiple elements, the sum of the values ​​corresponding to β for each of those elements should satisfy the above range. From the viewpoint of better ionic conductivity and more sufficient suppression of the 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. If D 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 better ionic conductivity and more sufficient suppression of the 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] In garnet-type solid electrolytes containing element D (especially Bi), the presence of a predetermined transition metal element (Co, Ni, Mn, Fe, etc.) suppresses the formation of Li-Bi-O compounds, while simultaneously generating a new impurity Li-La-Co-O compound with electronic conductivity. In contrast, the solid electrolyte ceramics of the present invention contain a relatively large amount of Li, and element B (especially La) is deficient and / or substituted within a specific range. This suppresses the formation of Li-La-Co-O compounds even when containing a relatively large amount of the predetermined transition metal element. As a result, it is possible to suppress the increase in electronic conductivity more effectively while maintaining excellent ionic conductivity. The details of the mechanism by which such an effect is obtained are unknown, but it is presumed to be as follows: In a system containing a relatively large amount of Li and element B (especially La) being deficient and / or substituted within a specific range, the catalytic effect of the predetermined transition metal element (oxidation-promoting effect of element D (especially Bi)) is more fully exhibited. This is thought to promote the solid solution of element D (especially Bi) in LLZ, suppressing the formation of Li-Bi-O compounds, and also to reduce the activity of element B (especially La) (8-coordinate sites), thereby more effectively suppressing the formation of Li-La-Co-O systems. The absence of element B (especially La) means that in the garnet-type crystal structure, some of the sites originally occupied by element B (especially La) (e.g., La sites) are vacancies. Substitution of element B (especially La) means that in the garnet-type crystal structure, some of the sites originally occupied by element B (especially La) (e.g., La sites) are replaced by other metallic elements (e.g., B in general formula (II) described later). 1 This refers to the fact that it has been replaced by ).

[0017] 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, the contents of Li and B elements (especially La) in the solid electrolyte ceramics are as follows in detail. That is, when the content of D in the general formula (I) representing the chemical composition of the solid electrolyte ceramics of the present invention is set to 100 mol%, and the contents of Li and B elements (especially La) are 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) 330 < X ≦ 370 (from the viewpoint of more excellent ionic conductivity and more sufficient suppression of the increase in electronic conductivity during operation, preferably 335 ≦ X ≦ 370, more preferably 335 ≦ X ≦ 365); (2) 139 ≦ Y < 150 (from the viewpoint of more excellent ionic conductivity and more sufficient suppression of the increase in electronic conductivity during operation, preferably 139 ≦ Y ≦ 149, more preferably 139 ≦ Y ≦ 147).

[0019] Regarding the relational expression (1), if the content X of Li is too large, the sinterability deteriorates and the ionic conductivity decreases. Further, 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) is generated and the electronic conductivity becomes high. Regarding the relational expression (2), if the content Y of the B element (especially La) is too small, a heterogeneous phase (such as an impurity Li-Zr-O-based compound) appears and the garnet-type crystal structure cannot be maintained. Therefore, the ionic conductivity significantly decreases. If the content Y of the B element (especially La) is too large, a heterogeneous phase (such as an impurity Li-La-Co-O-based compound) appears and the electronic conductivity becomes high.

[0020] The above-described content X of Li and the content Y of the B element (especially La) are expressed as ratios (mol%) when the content of D is 100 mol%, but can also be referred to as ratios (mol%) when the number of 6-coordination 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 Bi and D 1This is a value that can be expressed as a percentage (mol%) when the total number is set to 100 mol%. In other specific examples, the 6-coordinate sites of a garnet-type crystal structure are, for example, Li5La3Nb2O, which has a garnet-type crystal structure. 12 The sites occupied by Nb in (ICDD Card No. 00-045-0109), also in the garnet-type crystal structure Li7La3Zr2O 12 This refers to the site occupied by Zr in (ICDD Card.No01-078-6708).

[0021] The content of Li and element B (especially La) 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 can be determined from the ICP analysis, and from this average chemical composition, the content of Li and element B (especially La) can be determined as a percentage when the content of D in the general formula (I) is set to 100 mol%. For example, the number of 6-coordination sites in the garnet-type crystal structure (e.g., Bi and D in the general formula (II) described later) 1 It can be calculated as a percentage when the total number of ( ) is set to 100 mol%. Alternatively, it may be measured and calculated using X-ray photoelectron spectroscopy (XPS).

[0022] The content of the specified transition metal element is usually 0.01 mol% to 10 mol% when the content of D is set to 100 mol%, and from the viewpoint of better ionic conductivity and more sufficient suppression of the increase in electronic conductivity during operation, it is preferably 0.01 mol% to 8 mol%, more preferably 0.1 mol% to 5 mol%, even more preferably 0.3 mol% to 5 mol%, very preferably 0.5 mol% to 5 mol%, very preferably 1 mol% to 5 mol%, and particularly preferably 1.5 mol% to 3.5 mol%. If the specified transition metal element includes two or more types of transition metal elements, their total content should be within the above range.

[0023] The bismuth content is usually 40 mol% or less when the D content is set to 100 mol%, and from the viewpoint of better ionic conductivity and more sufficient suppression of the increase in electronic conductivity during operation, it is preferably 1 mol% to 30 mol%, more preferably 2 mol% to 20 mol%, even more preferably 5 mol% to 15 mol%, and particularly preferably 8 mol% to 12 mol%.

[0024] The tantalum (Ta) content is usually 60 mol% or less when the D content is set to 100 mol%, and from the viewpoint of better ionic conductivity and more sufficient suppression of the increase in electronic conductivity during operation, it is preferably 10 mol% to 60 mol%, more preferably 11 mol% to 60 mol%, even more preferably 10 mol% to 30 mol%, and particularly preferably 15 mol% to 25 mol%.

[0025] The zirconium (Zr) content is usually 80 mol% or less when the content of D is set to 100 mol%, and from the viewpoint of better ionic conductivity and more sufficient suppression of the increase in electronic conductivity during operation, it is preferably 10 mol% to 80 mol%, more preferably 20 mol% to 80 mol%, even more preferably 30 mol% to 80 mol%, particularly preferably 60 mol% to 80 mol%, and very preferably 65 mol% to 75 mol%.

[0026] The content of predetermined transition metal elements, Bi, Ta, and Zr 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, similar to the content of Li X and the content of element B (especially La) Y described above. Specifically, the average chemical composition is determined based on the ICP analysis, and from this average chemical composition, the content of predetermined transition metal elements, Bi, Ta, and Zr is determined by the content of D in the general formula (I) (for example, Bi and D in the general formula (II) described later). 1 It can be calculated as a percentage when the total number of ( ) is set to 100 mol%. Alternatively, it may be measured and calculated using X-ray photoelectron spectroscopy (XPS).

[0027] The mode of existence (or inclusion mode) of a predetermined transition metal element in the solid electrolyte ceramic of the present invention is not particularly limited, and the predetermined transition metal element may, for example, be present in the crystal lattice or outside the crystal lattice. More specifically, the predetermined transition metal element may be present in the bulk, at grain boundaries, or both in the solid electrolyte ceramic. The presence of the predetermined transition metal element in the bulk means that in the solid electrolyte ceramic of the present invention, the predetermined transition metal element is present at metal sites (lattice sites) constituting the garnet-type crystal structure. The metal sites may be any metal sites, for example, Li sites, La sites, Bi sites, or two or more of these sites. The presence of the predetermined transition metal element at grain boundaries means that, in the solid electrolyte ceramic of the present invention, which 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, a predetermined transition metal element and / or Bi (bismuth) may exist as a composite oxide comprising the predetermined transition metal element and / or Bi (bismuth) 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, and / or as a single oxide. Such oxides of the predetermined transition metal element and / or Bi (bismuth) may exist at the interface between crystal grains of ceramics having a garnet-type crystal structure, which is the main component of the present invention.

[0029] In the solid electrolyte ceramics of the present invention, element A (e.g., Li) may normally be present in bulk, and more specifically, as an example, may be present in Li sites as metal sites (lattice sites) constituting a garnet-type crystal structure. In this case, a portion of element A may be present at grain boundaries as a composite oxide and / or as a single oxide, comprising element A 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.

[0030] In the solid electrolyte ceramics of the present invention, element B (e.g., La) may normally be present in bulk, and more specifically, as an example, may be present in La sites as metal sites (lattice sites) constituting a garnet-type crystal structure. In this case, a portion of element B may be present at grain boundaries as a composite oxide and / or as a single oxide, comprising element B 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.

[0031] In the solid electrolyte ceramics of the present invention, element D (e.g., Bi, Ta, Zr) may normally be present in the bulk, and more specifically, as an example, may be present in Zr sites as metal sites (lattice sites) constituting a garnet-type crystal structure. In this case, a portion of element D may be present at grain boundaries as a composite oxide and / or as a single oxide, comprising element D 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.

[0032] In the present invention, the statement that a solid electrolyte ceramic has a garnet-type crystal structure means not only that the solid electrolyte ceramic has a "garnet-type crystal structure," but also that it has a "garnet-type-like crystal structure." More specifically, the solid electrolyte ceramic of the present invention has a crystal structure that can be recognized as a garnet-type or garnet-type-like crystal structure by those skilled in the field of solid-state batteries in X-ray diffraction. More specifically, the solid electrolyte ceramic of the present invention may, in X-ray diffraction, show one or more major peaks corresponding to the Miller indices unique to the so-called garnet-type crystal structure diffraction pattern (ICDD Card No. 422259) at a predetermined incident angle, or, as a garnet-type-like crystal structure, may show 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 the one or more major peaks corresponding to the Miller indices unique to the so-called garnet-type crystal structure due to differences in composition. Examples of typical diffraction patterns of garnet-type-like crystal structures include ICDD Card No. 00-045-0109.

[0033] In one specific embodiment, the solid electrolyte ceramic of the present invention may have a chemical composition represented by general formula (II). More specifically, the solid electrolyte ceramic as a whole may have the chemical composition represented by general formula (II). 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 This refers to the metallic element occupying the Li site in a 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 other than Li among the elements similar to the elements exemplified as A. A 1 is usually one or more elements selected from the group consisting of Ga (gallium), Al (aluminum), Mg (magnesium), Zn (zinc) and Sc (scandium). A 1 From the viewpoints of more excellent ion conductivity and more sufficient suppression of the increase in electron conductivity during operation, it is preferably one or more elements selected from the group consisting of Ga (gallium) and Al (aluminum), and more preferably two elements of Ga and Al.

[0036] In formula (II), B 1 refers to a metal element occupying the La site in the garnet crystal structure. B 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 other than La among the elements similar to the elements exemplified as B. B 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 refers to a metal element occupying the 6-coordinate site in the garnet crystal structure (the site occupied by Zr in the garnet crystal structure Li7La3Zr2O 12 (ICDD Card.No01-078-6708)). D 1 is an element corresponding to D in the general formula (I), and may be one or more elements selected from the group consisting of elements other than Bi among the elements similar to the elements exemplified as D. D 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 perspective 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 Zr (zirconium) and Ta (tantalum).

[0038] In formula (II), x satisfies 0 < x ≤ 1.00. From the perspective 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 0.05 ≤ x ≤ 0.50, particularly preferably 0.10 ≤ x ≤ 0.40, and most preferably 0.15 ≤ x ≤ 0.25. y satisfies 0 ≤ y ≤ 0.50. From the perspective 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 these elements only needs to satisfy the above range. z satisfies 0 ≤ z ≤ 2.00. From the perspective 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 these elements only needs to satisfy the above range. γ satisfies 1.2 ≤ γ ≤ 3.2. From the perspective 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 the 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 If the formula contains multiple elements, the sum of the values ​​corresponding to "γ-x" for each of those elements must satisfy the above range.

[0039] In equation (II), p satisfies 5.0 ≤ p ≤ 8.0, and more preferably 6.0 ≤ p ≤ 8.0, more preferably 6.5 ≤ p ≤ 7.5, and even more preferably 6.6 ≤ p ≤ 7.4, from the viewpoint of better ionic conductivity and more sufficient suppression of the increase in electronic conductivity during operation. a is A 1 This is the average value of A 1 The average price is A 1 For example, if there are n1 elements X with valence a+, n2 elements Y with valence b+, and n3 elements Z with valence c+, then the value is expressed as (n1 × a + n2 × b + n3 × c) / (n1 + n2 + n3). b is B 1 This is the average value of B. 1 The average price is B 1 For example, if there are n1 elements X with valence a+, n2 elements Y with valence b+, and n3 elements Z with valence c+, then the above A 1 This refers to a value similar to the average value of [something]. c is D 1 This is the average value of D 1 The average price is D 1 For example, if there are n1 elements X with valence a+, n2 elements Y with valence b+, and n3 elements Z with valence c+, then the above A 1 This refers to a value similar to the average value of [something].

[0040] In equation (II), q satisfies 2.5 ≤ q ≤ 3.5, and preferably satisfies 2.6 ≤ q ≤ 3.3, more preferably 2.6 ≤ q ≤ 3.1, and even more preferably 2.7 ≤ q ≤ 3.0, from the viewpoint of better ionic conductivity and more sufficient suppression of the increase in electronic conductivity during operation. δ represents the oxygen deficiency and may be 0. Typically, δ only needs to satisfy 0 ≤ δ < 1. Since the oxygen deficiency δ cannot be quantitatively analyzed even with the latest equipment, it may be considered to be 0. Furthermore, the molar ratios of each element in the chemical composition of the solid electrolyte ceramics of the present invention do not necessarily match, for example, the molar ratios of each element in formula (II), and tend to deviate from this depending on the analytical method. However, as long as the compositional deviation is not so large as to change the properties, the effects of the present invention will be achieved.

[0041] Even when the solid electrolyte ceramic of the present invention has a chemical composition represented by the above general formula (II), it goes without saying that, as in the case where it has a chemical composition represented by the above general formula (I), the above-mentioned Li content X and the B element (especially La) content Y satisfy both of the above-mentioned relational formulas (1) and (2). In this case, the content of the predetermined transition metal elements, Bi, Ta, and Zr may be within the above-mentioned range, and preferably within the above-mentioned range. Note that in the notation of these contents, the standard "when the content of D is set to 100 mol%" means "the Bi and D 1 This can also be rephrased as, "When the total number (i.e., total content) is set to 100 mol%."

[0042] In the present invention, the chemical composition of the solid electrolyte ceramic may be the overall composition of the ceramic material determined using ICP (inductively coupled plasma spectroscopy). Alternatively, this chemical composition may 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, this chemical composition may be obtained by performing quantitative analysis (composition analysis) on 100 arbitrary points of each of 100 arbitrary sintered particles and calculating their 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 D in the general formula (I) (or Bi and D in the general formula (II)] 1 The molar ratio when the total number of particles is set to 100 mol% may be calculated by the following method. In this 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), etc. It may also be measured and calculated using XPS analysis, or by using TEM-EDX (energy-dispersive X-ray spectroscopy) or WDX (wavelength-dispersive X-ray spectroscopy). Furthermore, the chemical composition may be obtained by performing quantitative analysis (composition analysis) of any 100 points on each of any 100 sintered particles and calculating the average value.

[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 the 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 polishing after the solid-state battery is embedded in resin. There are no particular limitations on the method of polishing the cross-section, but the solid electrolyte layer can be exposed by cutting with a dicer and then polishing with abrasive paper, chemical mechanical polishing, ion milling, etc. By quantitatively analyzing the exposed cross-section (solid electrolyte layer) with EDX or WDX (wavelength dispersive X-ray fluorescence spectrometer), the molar ratio of each element (for example, the molar ratio of Co, Ni, Mn, and Fe to D) can be calculated.

[0045] For example, in TEM-EELS measurement, the electrode layer or solid electrolyte layer of a solid-state battery is exfoliated using FIB (Focused Ion Beam) or the like, and then TEM-EELS (Electron Energy-Loss Spectroscopy) measurement is performed on the solid electrolyte portion. This allows for the detection of each element (for example, the elements contained in D in the general formula (I), Co, Ni, Mn, Fe), and the molar ratio of each element to the D content can be calculated.

[0046] The following chemical compositions are specific examples of the chemical compositions representing the solid electrolyte ceramics of the present invention. In the chemical compositions shown below, the transition metal elements after the hyphen (-) indicate that the transition metal elements may be present in the bulk and / or at grain boundaries as described above. Li 6.7 La 2.95 Zr 1.4 Ta 0.4 Bi 0.2 O 12 -Co 0.05 Li 6.8 La 2.95 Zr 1.4 Ta 0.4 Bi 0.2 O 12 -Co 0.05 Li 7.1 La 2.95 Zr 1.4 Ta 0.4 Bi 0.2 O 12 -Co 0.05 Li 7.3 La 2.95 Zr 1.4 Ta 0.4 Bi 0.2 O 12 -Co 0.05 Li 6.7 La 2.9 Zr 1.4 Ta 0.4 Bi 0.2 O 12 -Co 0.05 Li 6.8 La 2.9 Zr 1.4 Ta 0.4 Bi 0.2 O 12 -Co 0.05 Li 6.9 La 2.9 Zr 1.4 Ta 0.4 Bi 0.2 O 12 -Co 0.05 Li7.1 Day 2.9 Zr 1.4 Dad 0.4 Bi 0.2 O 12 -Co 0.05 Li 7.3 Day 2.9 Zr 1.4 Dad 0.4 Bi 0.2 O 12 -Co 0.05 Li 6.7 Day 2.8 Zr 1.4 Dad 0.4 Bi 0.2 O 12 -Co 0.05 Li 6.8 Day 2.8 Zr 1.4 Dad 0.4 Bi 0.2 O 12 -Co 0.05 Li 7.1 Day 2.8 Zr 1.4 Dad 0.4 Bi 0.2 O 12 -Co 0.05 Li 7.3 Day 2.8 Zr 1.4 Dad 0.4 Bi 0.2 O 12 -Co 0.05 Li 6.9 Day 2.9 Zr 1.1 Dad 0.7 Bi 0.2 O 12 -Co 0.05 Li 6.9 Day 2.9 Zr 0.8 Ta1Bi 0.2 O 12 -Co 0.05 Li 6.9 Day 2.9 Zr 1.4 Dad 0.4 Bi 0.2O 12 -Co 0.005 Li 6.9 Day 2.9 Zr 1.1 Dad 0.7 Bi 0.2 O 12 -Co 0.005 Li 6.9 Day 2.9 Zr 0.8 Ta1Bi 0.2 O 12 -Co 0.005 Li 6.9 Day 2.9 Zr 1.4 Dad 0.4 Bi 0.2 O 12 -Co 0.001 Li 6.9 Day 2.9 Zr 1.1 Dad 0.7 Bi 0.2 O 12 -Co 0.001 Li 6.9 Day 2.9 Zr 0.8 Ta1Bi 0.2 O 12 -Co 0.001 Li 6.9 Day 2.9 Zr 1.4 Dad 0.4 Bi 0.2 O 12 - Mr 0.001 Li 6.9 Day 2.9 Zr 1.1 Dad 0.7 Bi 0.2 O 12 - Mr 0.001 Li 6.9 Day 2.9 Zr 0.8 Ta1Bi 0.2 O 12 - Mr 0.001 Li 6.9 Day 2.9 Zr 1.4 Dad0.4 Bi 0.2 O 12 -N 0.001 Li 6.9 La 2.9 Zr 1.1 Ta 0.7 Bi 0.2 O 12 -N 0.001 Li 6.9 La 2.9 Zr 0.8 Ta1Bi 0.2 O 12 -N 0.001

[0047] Among the specific examples of chemical compositions described above, for example, a chemical composition containing Co as a transition element may also contain Ni, Mn, or Fe instead of Co. Similarly, a chemical composition containing Mn as a transition element may also contain Co, Ni, or Fe instead of Mn. Furthermore, a chemical composition containing Ni as a transition element may also contain 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., a starting material) with water, drying it, and then heat-treating it. 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 compounds containing the predetermined metal element (i.e., starting materials) 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, bismuth nitrate pentahydrate Bi(NO3)3·5H2O, and the like. The mixing ratio of the compound containing the predetermined metal element is 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 to 1200°C, preferably 600°C to 1000°C. The heat treatment time is usually 10 minutes to 1440 minutes, particularly 60 minutes to 600 minutes.

[0049] The solid electrolyte ceramics of the present invention may contain a sintering aid. Any sintering aid known in the field of solid-state batteries can be used. The composition of such a sintering aid preferably includes at least Li (lithium), B (boron), and O (oxygen), with a molar ratio of Li to B (Li / B) of 2.0 or 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 Examples include O3 and LiBO2.

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

[0051] [Solid battery] In this specification, "solid-state battery" broadly refers to a battery whose components (especially the electrolyte layer) are made of solids, and narrowly refers to an "all-solid-state battery" whose components (especially all components) are made of solids. In this specification, "solid-state battery" includes so-called "secondary batteries" that can be repeatedly charged and discharged, and "primary batteries" that can only be discharged. A "solid-state battery" is preferably a "secondary battery." The term "secondary battery" is not overly restrictive and may also include electrochemical devices such as "energy storage devices."

[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 the solid electrolyte layer in between. The positive electrode layer and the negative electrode layer may each be laminated in two or more layers, as long as a solid electrolyte layer is provided between them. The solid electrolyte layer is in contact with and sandwiched between the positive electrode layer and the negative electrode layer. The positive electrode layer and the solid electrolyte layer may be integrally sintered as sintered bodies, and / or the negative electrode layer and the solid electrolyte layer may be integrally sintered as sintered bodies. Integral sintering of sintered bodies means that two or more adjacent or contacting members (especially layers) are joined by sintering. Here, the two or more members (especially layers) may all be sintered bodies, but may be integrally sintered.

[0053] The solid electrolyte ceramics of the present invention described above are useful as solid electrolytes for solid-state batteries. Therefore, the solid-state battery of the present invention includes the solid electrolyte ceramics of the present invention described above as a solid electrolyte. More specifically, the solid electrolyte ceramics of the present invention are included 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 viewpoint of better ionic conductivity in the solid electrolyte layer and more sufficient suppression of the increase in electronic conductivity during operation, it is preferable that the solid electrolyte ceramics of the present invention be included in at least the solid electrolyte layer.

[0054] (Positive electrode layer) The positive electrode layer in the solid-state battery of the present invention 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 circuits in the solid-state battery can be suppressed. The positive electrode layer may have the form of a sintered body containing positive electrode active material particles and optionally the solid electrolyte ceramic of the present invention. The positive electrode layer may be a layer capable of intercalating and deintercalating ions (especially lithium ions).

[0055] The positive electrode active material is not particularly limited, and any positive electrode active material known in the field of solid-state batteries can be used. Examples of positive electrode active materials include lithium-containing phosphate compound particles having a NASICON-type structure, lithium-containing phosphate compound particles having an olivine-type structure, lithium-containing layered oxide particles, and lithium-containing oxide particles having a spinel-type structure. Specific examples of lithium-containing phosphate compounds having a NASICON-type structure that are preferably used include Li3V2(PO4)3. Specific examples of lithium-containing phosphate compounds having an olivine-type structure that are preferably used include Li3Fe2(PO4)3 and LiMnPO4. Specific examples of lithium-containing layered oxide particles that are preferably used include LiCoO2 and LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 Examples include O2. Specific examples of lithium-containing oxides having a spinel-type structure that are preferably used include LiMn2O4 and LiNi 0.5 Mn 1.5 O4, Li4Ti5O 12 Examples include LiCoO2, LiCo 1 / 3 Ni 1 / 3 Mn 1 / 3 Lithium-containing layered oxides such as O2 are more preferably used. Note that only one type of these positive electrode active material particles may be used, or a mixture of multiple types may be used.

[0056] In the positive electrode layer, the positive electrode active material having a NASICON-type structure means that the positive electrode active material (especially its particles) has a NASICON-type crystal structure; in a broad sense, it means having a crystal structure that can be recognized as a NASICON-type crystal structure by those skilled in the field of solid-state batteries. In a narrow sense, the positive electrode active material having a NASICON-type structure in the positive electrode layer means that the positive electrode active material (especially its particles) exhibits one or more major peaks corresponding to the Miller indices characteristic of the so-called NASICON-type crystal structure at a predetermined angle of incidence in X-ray diffraction. Examples of positive electrode active materials having a NASICON-type structure that are preferably used include the compounds exemplified above.

[0057] In the positive electrode layer, the positive electrode active material having an olivine-type structure means that the positive electrode active material (especially its particles) has an olivine-type crystal structure. In a broad sense, it means having a crystal structure that can be recognized as an olivine-type crystal structure by those skilled in the field of solid-state batteries. In a narrow sense, the positive electrode active material having an olivine-type structure in the positive electrode layer means that the positive electrode active material (especially its particles) exhibits one or more major peaks corresponding to Miller indices characteristic of so-called olivine-type crystal structures at a given angle of incidence in X-ray diffraction. Examples of positive electrode active materials having an olivine-type structure that are preferably used include the compounds exemplified above.

[0058] In the positive electrode layer, the positive electrode active material having a spinel-type structure means that the positive electrode active material (especially its particles) has a spinel-type crystal structure. In a broad sense, it means having a crystal structure that can be recognized as a spinel-type crystal structure by those skilled in the field of solid-state batteries. In a narrow sense, the positive electrode active material having a spinel-type structure in the positive electrode layer means that the positive electrode active material (especially its particles) exhibits one or more major peaks corresponding to Miller indices characteristic of so-called spinel-type crystal structures at a given angle of incidence in X-ray diffraction. Examples of positive electrode active materials having a spinel-type structure that are preferably used include the compounds exemplified above.

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

[0060] The positive electrode active material can be manufactured, for example, by the following method, or it can be obtained as a commercially available product. When manufacturing the positive electrode active material, first, a raw material compound containing a predetermined metal atom is weighed so that its chemical composition is predetermined, and water is added and mixed to obtain a slurry. Then, the slurry is dried, calcined at 700°C to 1000°C for 1 to 30 hours, and pulverized to obtain the positive electrode active material.

[0061] The chemical composition and crystal structure of the positive electrode active material in the positive electrode layer may normally change due to elemental diffusion during sintering. The positive electrode active material may have the above-described chemical composition and crystal structure in a solid-state battery after sintering together 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, and 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 between 10 and 100 particles from an SEM image and simply averaging their particle sizes to obtain the average particle size (arithmetic mean). The particle size is defined as the diameter of a spherical particle assuming it is perfectly spherical. Such a particle size can be determined, for example, by cutting a cross-section of a solid-state battery, taking a cross-sectional SEM image using a scanning electron microscope (SEM), calculating the particle's cross-sectional area S using image analysis software (e.g., "A-Image-kun" (manufactured by Asahi Kasei Engineering Co., Ltd.)), and then determining the particle diameter R using the following formula.

[0064]

number

[0065] Furthermore, the average particle size of the positive electrode active material in the positive electrode layer can be automatically measured by identifying the positive electrode active material based on its composition during the measurement of the average chemical composition described above.

[0066] The average particle size of the positive electrode active material in the positive electrode layer can usually change due to sintering during the manufacturing process of solid-state batteries. The positive electrode active material may have the above-mentioned average particle size in a 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% to 90%, and especially 40% to 70%.

[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 sintering aids and / or conductive materials, etc.

[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 is usually 20% to 60%, and particularly 30% to 45%.

[0070] For the sintering aid in the positive electrode layer, compounds similar to those used as sintering aids in solid electrolyte ceramics can be used.

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

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

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

[0074] The thickness of the positive electrode layer is typically 0.1 to 30 μm, but may also be, for example, 1 to 20 μm. The thickness of the positive electrode layer is determined using the average value of thicknesses measured at 10 arbitrary locations in the SEM image.

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

[0076] The porosity of the positive electrode layer is based on values ​​measured from SEM images after FIB cross-sectional processing.

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

[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 circuits in the solid-state battery can be suppressed. The negative electrode layer may have the form of a sintered body containing negative electrode active material particles and optionally the solid electrolyte ceramic of the present invention. The negative electrode layer may be a layer capable of intercalating and deintercalating ions (especially 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 negative electrode active materials include carbon materials such as graphite, graphite-lithium compounds, lithium metals, lithium alloy particles, phosphate compounds having a NASCON-type structure, Li-containing oxides having a spinel-type structure, and β II -Li3VO4 type structure, γ II Examples include oxides having a -Li3VO4 type structure. The negative electrode active material is lithium metal, β II -Li3VO4 type structure, γ II -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 -Having a Li3VO4 type structure means that the oxide (especially its particles) is β II - This means that it has a Li3VO4 type crystal structure, and in a broader sense, by those skilled in the field of solid-state batteries β II - This refers to having a crystal structure that can be recognized as a Li3VO4 type crystal structure. In a narrower sense, the oxide in the negative electrode layer is β II -Having a Li3VO4 type structure means that the oxide (especially its particles) exhibits so-called β-type diffraction in X-ray diffraction. II - This means that at a given angle of incidence, one or more major peaks corresponding to Miller indices specific to the Li3VO4 type crystal structure are shown. Preferably, β 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-Having a Li3VO4 type structure means that the oxide (especially its particles) is γ II - This means that it has a Li3VO4 type crystal structure, and in a broader sense, according to those skilled in the field of solid-state batteries, γ II - This refers to having a crystal structure that can be recognized as a Li3VO4 type crystal structure. In a narrower sense, the oxide in the negative electrode layer is γ II -Having a Li3VO4 type structure means that the oxide (especially its particles) exhibits a so-called γ-ray diffraction pattern in X-ray diffraction. II - This means that one or more major peaks corresponding to the Miller indices specific to the Li3VO4 type crystal structure are shown at a predetermined angle of incidence (x axis). Preferably used γ II Li-containing oxides having a -Li3VO4 type structure include Li 3.2 V 0.8 Si 0.2 O4 is one example.

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

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

[0084] The chemical composition and crystal structure of the negative electrode active material in the negative electrode layer may normally change due to elemental diffusion during sintering in the manufacturing process of solid-state batteries. The negative electrode active material may have the above-described average chemical composition and crystal structure in a 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; for example, it may be 50% or more (particularly 50% to 99%), particularly 70% to 95%, and preferably 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, etc.

[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 is usually 20% to 60%, and particularly 30% to 45%.

[0088] For the sintering aid in the negative electrode layer, the same compounds as those used for the sintering aid in the positive electrode layer can be used. For the negative electrode layer, the same compounds as those used for the positive electrode layer can be used as the conductive material.

[0089] The thickness of the negative electrode layer is typically 0.1 to 30 μm, but may also be, for example, 1 to 20 μm. The thickness of the negative electrode layer is determined using the average value of thicknesses measured at 10 arbitrary locations in the SEM image.

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

[0091] The porosity of the negative electrode layer is measured using the same method as the porosity of the positive electrode layer.

[0092] The negative electrode layer is a layer that may be called the "negative electrode active material layer." The negative electrode layer may have a so-called negative electrode current collector or negative electrode current collector layer.

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

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

[0095] If the solid electrolyte layer contains the solid electrolyte ceramic of the present invention, it is sufficient that the solid electrolyte ceramic having the above-described chemical composition is present in at least the central part of the thickness direction of the solid electrolyte layer (particularly at 5 or more points, preferably 8 or more points, and more preferably 10 points, out of any 10 points thereon). This is because the solid electrolyte layer is sandwiched between the positive electrode layer and the negative electrode layer, and elemental diffusion from the positive electrode layer and the negative electrode layer to the solid electrolyte layer and / or from the solid electrolyte layer to the positive electrode layer and the negative electrode layer may occur due to sintering during the manufacturing process of the solid-state battery.

[0096] In addition to the garnet-type solid electrolyte ceramic of the present invention, the solid electrolyte layer may also 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 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. y satisfies 0 ≤ y ≤ 1.0, and in particular 0.20 ≤ y ≤ 0.50. a is the average valence of A. The average valence of A is the value expressed as (n1 × a + n2 × b + n3 × c) / (n1 + n2 + n3) when A consists of, for example, n1 elements X with valence a+, n2 elements Y with valence b+, and n3 elements Z with valence c+. c is the average valence of D. The average valence of D is the same value as the average valence of A described above, for example, if D consists of n1 elements X with valence a+, n2 elements Y with valence b+, and n3 elements Z with valence c+.

[0100] A specific example of a solid electrolyte having a γ-Li3VO4 structure is, for example, Li 3.2 (V 0.8 Si 0.2 )O4, Li 3.5 (V 0.5 Ge 0.5 )O4, Li 3.4 (P 0.6 Si 0.4 )O4, Li 3.5 (P 0.5 Ge 0.5 Examples include O4, etc.

[0101] Examples of oxide glass ceramic lithium ion conductors include phosphate compounds containing lithium, aluminum, and titanium as constituent elements (LATP), and phosphate compounds containing lithium, aluminum, and germanium as constituent elements (LAGP).

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

[0103] The volume ratio of the sintering aid in the solid electrolyte layer is not particularly limited, but from the viewpoint of better ionic conductivity and more sufficient suppression of the increase in electronic conductivity during operation, it is preferably 0% to 20%, and more preferably 1% to 10%.

[0104] The thickness of the solid electrolyte layer is typically 0.1 to 30 μm, but is preferably 1 to 20 μm from the viewpoint of better ionic conductivity and more sufficient suppression of the increase in electronic conductivity during operation. The thickness of the solid electrolyte layer is determined using the average value of the thickness measured at any 10 locations in the 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 the 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 measured using the same method as the porosity of the positive electrode layer.

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

[0108] Let me explain the Green Sheet method. First, a paste is prepared by appropriately mixing a solvent, binder, etc., with the positive electrode active material. The paste is then applied to a sheet and dried to form a first green sheet for 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 a solvent, binder, etc., with the negative electrode active material. A second green sheet for forming the negative electrode layer is formed by applying the paste onto a sheet and drying it. The second green sheet may contain a solid electrolyte, a conductive material, and / or a sintering aid.

[0110] A paste is prepared by appropriately mixing a solvent, binder, etc., with a solid electrolyte. A third green sheet for forming the solid electrolyte layer is produced by applying the paste and drying it. The third green sheet may contain a sintering aid or the like.

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

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

[0113] Next, a laminate is created by appropriately stacking the first to third green sheets. The created laminate may be pressed. Preferred pressing methods include hydrostatic pressing. Subsequently, a solid-state battery can be obtained by sintering the laminate at, for example, 600-800°C.

[0114] I will explain the printing method. The printing method is the same as the green sheet method, except for the following: Prepare inks for each layer having the same composition as the paste for each layer for obtaining a green sheet, except that the amounts of the solvent and the resin are set to amounts suitable for use as an ink. Print and laminate using the inks for each layer to produce a laminate.

[0115] The present invention as described above includes the following preferred embodiments. <1> The following general formula (I):

Chemical formula

[0116] The present invention will be described in more detail below based on specific examples, but the present invention is not limited in any way to the following examples and can be implemented with appropriate modifications without changing the gist of the invention. [Examples]

[0117] <Examples 1-27 and Comparative Examples 1-3> [Manufacturing of 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 its chemical composition matched the chemical composition shown in Table 1. Water was added, the mixture was sealed in polyethylene poly pots, and rotated on a pot rack at 150 rpm for 16 hours to mix the raw materials. The obtained 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 obtained calcined powder, and it was ground in a planetary ball mill for 12 hours. The composition of this ground powder was confirmed to be consistent by ICP measurement. The average particle size of the ground powder at this time was 150 nm.

[0118] [Manufacturing of solid electrolyte sheets] Solid electrolyte single sheets were manufactured as evaluation samples for solid electrolyte ceramics using the following method.

[0119] A slurry was prepared by kneading the obtained solid electrolyte powder, butyral resin, and alcohol in a weight ratio of 200:15:140. A slurry was formed into a sheet on a PET film using the doctor blade method to obtain a sheet. The fabricated sheets were stacked until the sheet thickness reached 200 μm, then cut into 10 mm x 10 mm squares. After removing the binder at 400°C, the sheets were pressure-sintered at 850-950°C for 60-600 minutes under a pressure of 100 MPa to produce a solid electrolyte veneer. The porosity of the solid electrolyte veneer 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 plates] In all examples and comparative examples, it was confirmed that X-ray diffraction patterns attributable to a garnet-like crystal structure could be obtained from the solid electrolyte single plate (ICDD Card No. 00-045-0109).

[0121] [Chemical composition of solid electrolyte sheet] ICP analysis was performed on the solid electrolyte single sheet to obtain the average chemical composition of the solid electrolyte single sheet. The content of Li, La, Ta, Zr, and Bi, as well as the content of Co, Mn, Ni, and Fe in the average chemical composition of this entire solid electrolyte single sheet, was determined by the number of 6-coordination sites in the garnet-type crystal structure (for example, Bi and D in the general formula (II) above). 1 The percentage was calculated by setting the total number of elements to 100 mol%. The value of O (oxygen) in the chemical composition was calculated based on the molar ratios and valencies of the elements contained in A, B, and D in general formula (I), ensuring charge neutrality.

[0122] [Electron conductivity measurement] An Au electrode was sputtered onto one side of the obtained single plate to serve as the working electrode. A Li metal with the same surface area as the Au electrode was attached to the other side. Finally, the cell was sealed in a 2035-size coin cell to serve as the evaluation cell. All of the above operations were performed in a dry room with a dew point of -40°C or lower. At room temperature, a voltage of 2V was applied to the working electrode relative to Li, and the transient current was observed. The current that flowed 10 hours after the voltage was applied was read as the leakage current. From the leakage current, the electronic conductivity was calculated using the following formula. Electronic conductivity = (I / V) × (L / A) (I: Leakage current, V: Applied voltage, L: Thickness of solid electrolyte sheet, A: Electrode area) ◎◎: Electronic conductivity < 6.5 × 10 -9 S / cm (best); ◎: 6.5 × 10 -9 S / cm ≤ Electronic conductivity < 1.0 × 10⁻⁶ -8 S / cm(excellent); ○; 1.0 × 10 -8 S / cm ≤ Electronic conductivity < 5.0 × 10⁻⁶ -8 S / cm (Good); △; 5.0 × 10 -8 S / cm ≤ Electronic conductivity < 1.0 × 10⁻⁶ -7 S / cm (acceptable) (no practical problems); ×; 1.0 × 10 -7 S / cm ≤ Electronic conductivity (not acceptable) (problematic in practical applications).

[0123] [Ionic conductivity measurement] Gold (Au) layers, which serve as current collector layers, were formed on both sides of a solid electrolyte single sheet by sputtering, and then sandwiched and fixed with 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 ionic conductivity. Note that all measurements were 5.0 × 10⁻⁶. -4 I confirmed that it was S / cm. ◎; Ionic conductivity ≥ 5.0 × 10 -4 S / cm (No practical problems); ×; Ionic conductivity < 5.0 × 10 -4 S / cm (Not acceptable) (This poses practical problems).

[0124] [Overall assessment] All evaluation results for electronic conductivity and ionic conductivity were comprehensively assessed. ◎: All evaluation results for electronic conductivity and ionic conductivity were ◎. ○: The lowest evaluation result among all evaluation results for electronic conductivity and ionic conductivity was ○. △: The lowest evaluation result among all evaluation results for electronic conductivity and ionic conductivity was △. ×: The lowest evaluation result among all evaluation results for electronic conductivity and ionic conductivity was ×.

[0125] [Table 1]

[0126] [Table 2]

[0127] From a comparison of Comparative Examples 1-3 and Examples 1-27, it is clear that when the Li content is 330 mol% or less, the electronic conductivity increases, and the risk of short circuits increases.

[0128] A comparison of Examples 1-24 and Examples 25-27 reveals that by including one or more transition metal elements selected from the group consisting of Co and Mn in the solid electrolyte ceramic, excellent ionic conductivity can be obtained while more effectively suppressing the increase in electronic conductivity.

[0129] A comparison of Examples 1-21 and Examples 22-27 reveals that by including Co as one or more transition metal elements in the solid electrolyte ceramics, excellent ionic conductivity can be obtained while further sufficiently suppressing the increase in electronic conductivity.

[0130] A comparison of Examples 5-13 with Examples 1-4 and 14-27 reveals that by satisfying the following conditions, the solid electrolyte ceramic can achieve excellent ionic conductivity while further suppressing the increase in electronic conductivity: • Contains one or more transition metal elements, including Co; • D contains Ta (tantalum); The content of B, Y (mol%), is between 139 mol% and 147 mol%; • The content of one or more transition metal elements is between 1 mol% and 5 mol%; The Ta content is between 10 mol% and 30 mol%. [Industrial applicability]

[0131] The solid-state battery containing the solid electrolyte ceramic of the present invention can be used in various fields where battery use or energy storage is anticipated. While this is merely illustrative, a solid-state battery according to one embodiment of the present invention can be used in the field of electronics packaging. A solid battery according to one embodiment of the present invention can also be used in the electrical, information and communication fields where mobile devices are used (for example, the electrical and electronic equipment field or mobile device field including small electronic devices such as mobile phones, smartphones, smartwatches, laptops, digital cameras, activity trackers, ARM computers, electronic paper, wearable devices, RFID tags, card-type electronic money, and smartwatches), household and small industrial applications (for example, power tools, golf carts, household, caregiving and industrial robots), large industrial applications (for example, forklifts, elevators, and port cranes), transportation systems (for example, hybrid vehicles, electric vehicles, buses, trains, electric assist bicycles, electric motorcycles, etc.), power grid applications (for example, various power generation, road conditioners, smart grids, and general household energy storage systems), medical applications (medical equipment such as earphones and hearing aids), pharmaceutical applications (medication management systems, etc.), as well as IoT fields and space and deep-sea applications (for example, space probes and submersible research vessels, etc.).

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 lanthanide elements, and includes at least La (lanthanum); D is one or more elements selected from the group consisting of transition elements capable of coordinating with oxygen to six and main group elements belonging to groups 12 to 15, 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) Having a chemical composition represented by [formula], and containing one or more transition metal elements selected from the group consisting of Co (cobalt), Ni (nickel), and Mn (manganese) Furthermore, When the content of D is 100 mol%, and the content of Li is X (mol%), and the content of B is Y (mol%), a solid electrolyte ceramic having a garnet-type crystal structure satisfies the following relationship: Within the range 330 < X ​​≤ 370, 139 ≤ Y < 150.

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

3. The solid electrolyte ceramic according to claim 1, wherein D includes Ta (tantalum).

4. The solid electrolyte ceramic according to claim 3, wherein the content of Ta is 10 mol% or more and 60 mol% or less, when the content of D is 100 mol%.

5. The solid electrolyte ceramic according to claim 1, wherein D contains Zr (zirconium).

6. The solid electrolyte ceramic according to claim 5, wherein the content of Zr is 20 mol% or more and 80 mol% or less when the content of D is 100 mol%.

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

8. 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. The aforementioned one or more transition metal elements include Co, The aforementioned D includes Ta (tantalum), When the content of D is set to 100 mol%, The content Y (mol%) of B is 139 mol% or more and 147 mol% or less. The content of one or more transition metal elements is 1 mol% or more and 5 mol% or less. The solid electrolyte ceramic according to claim 1, wherein the Ta content is 10 mol% or more and 30 mol% or less.

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

12. The solid battery includes a positive electrode layer, a negative electrode layer, and a solid electrolyte layer laminated between the positive electrode layer and the negative electrode layer. The solid-state battery according to claim 11, wherein the positive electrode layer and the negative electrode layer are layers capable of intercalating and deintercalating lithium ions.

13. The solid battery according to claim 12, wherein the solid electrolyte layer is integrally sintered with the positive electrode layer and the negative electrode layer as sintered bodies.

14. The solid battery according to claim 11, wherein the solid electrolyte ceramic is included in the solid electrolyte layer of the solid battery.

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