Ion conductive substance, solid electrolyte, and battery

Abstract

One aspect of the present disclosure provides an ion conductive substance which contains an alkali metal element, a divalent metal element D, a trivalent or higher-valent metal element M, and a halogen element, and has a cubic crystal structure, wherein in the X-ray diffraction chart obtained by measurement using CuKα rays at 25°C, the ratio of the peak height of the diffraction peak A to the peak height of the diffraction peak B is 0.80-2.50, where the diffraction peak B is the diffraction peak that has a maximum peak height observed within the 2θ angle range of 45-53°, and the diffraction peak A is the diffraction peak that has a maximum peak height observed within the 2θ angle range of 33-38°.

Description

Ion-conducting material, solid electrolyte, and battery

[0001] The present disclosure relates to ion-conducting materials, solid electrolytes, and batteries.

[0002] In recent years, solid electrolytes have been attracting attention as electrolytes for use in electrochemical devices such as lithium-ion batteries (Patent Documents 1 to 4). Compared with conventional electrolytic solutions, solid electrolytes have superior high-temperature durability, high-voltage resistance, and the like, and are therefore considered useful for improving battery performance such as safety, high capacity, rapid charge / discharge, and pack energy density.

[0003] As described in Patent Documents 1 to 4, solid electrolytes of halides containing lithium and metal elements other than lithium (lithium-based halide-based solid electrolytes) are known as materials used for the solid electrolyte of lithium-ion batteries. Halide-based solid electrolytes are highly flexible and do not require sintering, and they do not contain harmful H ２ It has advantages not found in oxide- or sulfide-based solid electrolytes, such as high safety because it does not release S. In addition to lithium-ion batteries, research is also underway on halide-based solid electrolytes that use other alkali ions, such as sodium and potassium, which are more abundant than lithium.

[0004] International Publication No. 2020 / 070957 International Publication No. 2021 / 024876 International Publication No. 2021 / 024785 International Publication No. 2021 / 024783

[0005] However, there is room for improvement in the stability at low potential, that is, resistance to reduction reactions, of halide-based solid electrolytes.

[0006] The present disclosure has been made in view of the above circumstances, and aims to provide an ion-conductive material with improved reduction resistance, as well as a solid electrolyte and a battery containing the ion-conductive material.

[0007] The present disclosure includes the following exemplary embodiments. [1] An ion-conductive substance containing an alkali metal element, a divalent metal element D, a trivalent or higher valent metal element M, and a halogen element, and having a cubic crystal structure, wherein, in an X-ray diffraction chart obtained by measurement using CuKα radiation at 25°C, the ratio of the peak height of diffraction peak A to the peak height of diffraction peak B is 0.80 to 2.50, where diffraction peak B is the diffraction peak having the largest peak height observed in a 2θ angle range of 45 to 53° and diffraction peak A is the diffraction peak having the largest peak height observed in a 2θ angle range of 33 to 38°. [2] The ion-conductive substance according to [1], wherein the halogen element includes Cl. [3] The ion-conductive substance according to [1] or [2], wherein the halogen element further contains at least one element selected from the group consisting of F, Br, I, and O. [4] The ion-conductive material according to any one of [1] to [3], wherein the divalent metal element D comprises at least one selected from the group consisting of Mg, Ca, Sr, and Ba. [5] The ion-conductive material according to any one of [1] to [4], wherein the metal element M comprises at least one selected from the group consisting of Zr, Nb, In, Bi, and Hf. [6] The ion-conductive material according to any one of [1] to [5], wherein the content of the alkali metal element is 5 to 30 mol %, the content of the metal element D is 1 to 16 mol %, the content of the metal element M is 1 to 18 mol %, and the content of the halogen element is 55 to 78 mol %. [7] The alkali metal element comprises Li, ６ The resonance frequency of the Li nucleus is 44.1 MHz, and the solid state is formed at room temperature under the conditions of magic angle spinning at 10 kHz. ６ When Li-NMR spectrum was measured, ６ The ion-conductive material according to any one of [1] to [6], which has at least one peak having a peak top in the range of -50 to 0.68 ppm, with the chemical shift of LiCl salt being taken as 0 ppm. [8] A solid electrolyte comprising the ion-conductive material according to any one of [1] to [7]. [9] A battery comprising the solid electrolyte according to [8].

[0008] According to the present disclosure, it is possible to provide an ion-conductive material with improved reduction resistance, and also to provide a solid electrolyte and a battery including the ion-conductive material.

[0009] Fig. 1 is an X-ray diffraction chart for each of the ion-conductive materials of Examples 1 to 11 and Comparative Examples 1 and 2. Fig. 2 is a diagram showing the results of cyclic voltammetry measurements for each of the ion-conductive materials of Examples 1 to 4 and Comparative Examples 1 and 2. Fig. 3 is a diagram showing the solid voltammetry measurements for each of the ion-conductive materials of Examples 1, 11, and Comparative Example 1. ６ FIG. 4 is a diagram showing Arrhenius plots measured for the ion-conductive materials of Examples 1 and 2. FIG. 5 is a diagram showing the results of a charge-discharge test for the secondary battery of Example 1. FIG. 6 is a diagram showing the results of a charge-discharge test for the secondary battery of Comparative Example 1. FIG. 7 is a diagram showing the results of a cycle test for each of the secondary batteries of Example 1 and Comparative Example 1.

[0010] An ion-conductive material according to an embodiment of the present disclosure contains an alkali metal element, a divalent metal element D, a trivalent or higher metal element M, and a halogen element. The ion-conductive material according to this embodiment may be a single compound. The ion-conductive material may also contain an alkali metal-containing halide.

[0011] The ion-conductive material has a cubic crystal structure, which can be identified by X-ray diffraction measurement, particularly by Rietveld analysis.

[0012] In an X-ray diffraction chart obtained by measurement at 25°C using CuKα radiation, the ion-conductive substance has a ratio of the peak height of diffraction peak A to the peak height of diffraction peak B of 0.80 to 2.50, where diffraction peak B is the diffraction peak having the largest peak height observed in a 2θ angle range of 45 to 53° and diffraction peak A is the diffraction peak having the largest peak height observed in a 2θ angle range of 33 to 38°.

[0013] For the ion-conductive material according to this embodiment, when the peak height of diffraction peak B, which has the largest peak height observed in the 2θ angle range of 45 to 53° in an X-ray diffraction chart obtained by measurement using CuKα radiation at 25°C, is B, and the peak height of diffraction peak A, which has the largest peak height observed in the 2θ angle range of 33 to 38°, is A, the ratio A / B is 0.80 to 2.50. Note that diffraction peak A is a diffraction peak located in the 33 to 38° range, and diffraction peak B is a diffraction peak located in the 45 to 53° range, both of which correspond to a cubic crystal. In a cubic crystal, alkali metal elements (e.g., Li) are present in three dimensions. Therefore, the diffusion paths of alkali metal ions increase, resulting in increased ionic conductivity.

[0014] The ratio of the heights of the diffraction peaks (value A / B) is related to the crystallinity of the cubic crystal structure. When the ratio is within the above range, it is believed that a highly crystalline and stable cubic crystal structure is formed. The high crystallinity of the ion-conductive material of this embodiment is thought to tend to improve the reduction resistance, which is an effect.

[0015] The ratio of the diffraction peak heights (value A / B) may be, for example, 0.85 to 2.40, 0.90 to 2.30, or 0.95 to 2.20.

[0016] When the target crystal has high crystallinity and high uniformity, the diffraction peak becomes sharper and has a smaller half-width. On the other hand, the half-width of the diffraction peak becomes larger when defects or strain are introduced into the target crystal. In the ion-conductive material according to this embodiment, the half-width of the diffraction peak A may be, for example, 0.1 to 3°, 0.3 to 2°, or 0.5 to 1.5°, from the viewpoint of achieving both reduction resistance and ionic conductivity at an even higher level. Here, the half-width in this specification refers to the full width at half maximum (FWHM) unless otherwise specified.

[0017] In the ion conductive material according to this embodiment, the half width of the diffraction peak B may be, for example, 0.1 to 3°, 0.3 to 2°, or 0.5 to 1.5°, from the viewpoint of achieving both reduction resistance and ionic conductivity at an even higher level.

[0018] The ion-conductive material of this embodiment has a cubic crystal structure, and the lattice constant of the ion-conductive material may be, for example, 10.1 to 10.6 Å, 10.2 to 10.5 Å, or 10.25 to 10.47 Å.

[0019] The alkali metal element may be any of Li, Na, K, Rb, and Cs, but may contain at least one of Li, Na, and K, may contain at least one of Li and Na, may contain Li, or may be Li.

[0020] In the ion-conductive material of this embodiment, the alkali metal element may be one type or two or more types. When the alkali metal element contains two or more types of alkali metal elements, the proportion of one type of alkali metal element among the alkali metal elements contained in the ion-conductive material may be 80 mol% or more, 90 mol% or more, or 95 mol% or more. The one type of alkali metal element (i.e., the alkali metal element contained in the ion-conductive material with the highest molar content) may be any of Li, Na, and K, or may be any of Li and Na, or may be Li.

[0021] The content of the alkali metal element in the ion-conductive material may be, for example, 3 to 33 mol%, 5 to 30 mol%, 10 to 40 mol%, 15 to 30 mol%, or 20 to 30 mol% relative to the total amount of atoms contained in the ion-conductive material.

[0022] The metal element D is a divalent metal element, and examples thereof include alkaline earth metals and Zn. The ion-conductive material may contain one or more elements as the metal element D. The metal element D may contain at least one element selected from Mg, Ca, Sr, and Ba, or may contain at least one element selected from Mg, Sr, and Ba, or may contain Mg.

[0023] The content of the divalent metal element D in the ion-conductive material may be, for example, 0.5 to 20 mol%, 1 to 18 mol%, 1.5 to 16 mol%, 1 to 16 mol%, or 2 to 14 mol% relative to the total amount of atoms contained in the ion-conductive material.

[0024] The metal element M is a metal element having a valence of three or more, and may include a metal element having a valence of three to six, or a metal element having a valence of three to five. The metal element M may include one or more metal elements.

[0025] The trivalent metal element may include at least one selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Al, Ga, In, Sb, and Bi, and may include at least one of In and Bi.

[0026] The tetravalent metal element may include at least one metal element selected from the group consisting of Ti, Zr, and Hf, and may include Zr.

[0027] The pentavalent metal element may include at least one of Nb and Ta, and may include Ta.

[0028] An example of the hexavalent metal element is W.

[0029] The metal element M may include at least one selected from the group consisting of Y, Zr, Nb, In, W, Hf, and Bi, may include at least one selected from the group consisting of Zr, Nb, In, Hf, and Bi, may include at least one selected from the group consisting of Zr, Nb, In, and Hf, may include at least one metal element selected from the group consisting of Zr, Nb, and In, or may include Zr. When the metal element M includes two or more metal elements, the metal element M may include, for example, Zr and at least one selected from the group consisting of Y, Nb, In, W, Hf, and Bi, may include Zr and at least one selected from the group consisting of Nb, In, Hf, and Bi, or may include Zr and at least one selected from the group consisting of Nb, In, and Bi.

[0030] The content of the metal element M in the ion-conductive material may be, for example, 0.5 to 25 mol %, 1 to 20 mol %, 1 to 18 mol %, or 2 to 17 mol % relative to the total amount of atoms contained in the ion-conductive material.

[0031] When the metal element M contained in the ion-conductive material contains two or more metal elements, the content of the metal element having the largest content among the metal elements M may be, for example, 60 mol% or more, 70 mol% or more, 80 mol% or more, 85 mol% or more, or 90 mol% or more, relative to the total amount of the metal elements M. The content of the metal element having the largest content among the metal elements M contained in the ion-conductive material may be 60 to 99.9 mol%, 70 to 99 mol%, 80 to 98 mol%, 85 to 97 mol%, or 85 to 95 mol%, relative to the total amount of the metal elements M. The content of metal elements other than the metal element having the largest content among the metal elements M may be, for example, 30 mol% or less, 20 mol% or less, or 15 mol% or less, relative to the total amount of the metal elements M.

[0032] The "metal element with the highest content" means the metal element with the highest molar content among the metal elements M. The metal element with the highest content may be, for example, Zr, Nb, In, Hf, or Bi, or may be Zr, Nb, or In.

[0033] When the metal element M contained in the ion-conductive material contains two or more metal elements, the content of the metal element M other than the metal element with the largest content may be, for example, 0.5 to 30 mol %, 1 to 20 mol %, or 5 to 15 mol % relative to the total amount of the metal elements M.

[0034] Of the metal elements M contained in the ion-conductive material, the content of Zr may be, for example, 60 mol% or more, 70 mol% or more, 80 mol% or more, 85 mol% or more, or 90 mol% or more, relative to the total amount of metal elements M. Of the metal elements M contained in the ion-conductive material, the content of Zr may be, for example, 60 to 99.9 mol%, 70 to 99 mol%, 80 to 98 mol%, 85 to 97 mol%, or 85 to 95 mol%, relative to the total amount of metal elements M.

[0035] Of the metal elements M contained in the ion-conductive material, the content of metal elements other than Zr may be, for example, 30 mol % or less, 20 mol % or less, or 15 mol % or less, relative to the total amount of metal elements M. Of the metal elements M, the content of metal elements other than Zr may be, for example, 0.5 to 30 mol %, 1 to 20 mol %, or 5 to 15 mol %, relative to the total amount of metal elements M.

[0036] The halogen element contained in the ion-conductive material of this embodiment may be any one of F, Cl, Br, and I, or may contain at least one of Cl, Br, and I, or may contain at least one of Cl and Br, or may contain Cl. The ion-conductive material may contain only one halogen element, or may contain two or more halogen elements.

[0037] The content of halogen elements in the ion-conductive material may be, for example, 45 to 85 mol %, 50 to 80 mol %, or 55 to 78 mol % relative to the total amount of atoms contained in the ion-conductive material.

[0038] The ion-conductive material may contain two or more halogen elements. In this case, the combination of halogen elements contained in the ion-conductive material may be a combination of Cl and at least one halogen element selected from the group consisting of F, Br, and I, a combination of Cl, Br, and I, a combination of Br and I, or a combination of Cl and F.

[0039] When the halogen element contained in the ion-conductive material contains two or more halogen elements, the content of the halogen element having the largest content in the ion-conductive material may be, for example, 50 mol % or more, 60 mol % or more, 70 mol % or more, or 80 mol % or more relative to the total number of halogen atoms contained in the ion-conductive material. Furthermore, the content of the halogen element having the largest content in the ion-conductive material may be, for example, 50 to 85 mol % or 60 to 80 mol % relative to the total number of halogen atoms contained in the ion-conductive material.

[0040] The "halogen element with the highest molar content" refers to the halogen element with the highest molar content among the halogen elements contained in the ion-conductive material. The halogen element with the highest molar content may be Cl or Br, or may be Cl.

[0041] The content of the halogen element other than the halogen element with the largest content may be, for example, 50 mol % or less, 40 mol % or less, 30 mol % or less, or 20 mol % or less, relative to the total number of halogen atoms contained in the ion-conductive material. The content of the halogen element other than the halogen element with the largest content may be, for example, 1 to 40 mol %, 3 to 30 mol %, or 5 to 20 mol %, relative to the total number of halogen atoms contained in the ion-conductive material.

[0042] The Cl content in the ion-conductive material may be, for example, 50 mol % or more, 60 mol % or more, 70 mol % or more, or 80 mol % or more, relative to the total number of halogen atoms contained in the ion-conductive material. The Cl content in the ion-conductive material may be, for example, 50 to 85 mol %, or 60 to 80 mol %, relative to the total number of halogen atoms contained in the ion-conductive material.

[0043] When the ion-conductive material contains Cl, the content of halogen elements other than Cl may be, for example, 50 mol % or less, 40 mol % or less, 30 mol % or less, or 20 mol % or less, relative to the total number of halogen atoms contained in the ion-conductive material. When the ion-conductive material contains Cl, the content of halogen elements other than Cl may be 1 to 40 mol %, 3 to 30 mol %, or 5 to 20 mol %, relative to the total number of halogen atoms contained in the ion-conductive material. The halogen element other than Cl may be F.

[0044] The ion-conductive material of this embodiment may contain oxygen. The content of oxygen in the ion-conductive material may be, for example, 0.5 to 10 mol%, 1.5 to 8 mol%, 2 to 7 mol%, 2 to 6 mol%, or 2.5 to 5 mol% relative to the total amount of atoms contained in the ion-conductive material. The ion-conductive material may not contain oxygen, and the content of oxygen may be, for example, 10 mol% or less, 8 mol% or less, 7 mol% or less, 6 mol% or less, or 5 mol% or less relative to the total amount of atoms contained in the ion-conductive material.

[0045] The ion-conductive material of this embodiment may further contain at least one element selected from the group consisting of F, Br, I, and O. More specifically, the ion-conductive material of this embodiment may contain Cl as a halogen element and may further contain at least one element selected from the group consisting of F, Br, I, and O.

[0046] The ion-conductive material of this embodiment may contain a dopant element X. The dopant element X has a tetrahedral structure XO with four oxygen atoms. ４ and specifically, may include at least one of P and S. The dopant element X may include P.

[0047] The content of the dopant element X in the ion-conductive material may be, for example, 0.05 to 5 mol %, 0.1 to 3 mol %, 0.2 to 2 mol %, or 0.3 to 1.5 mol % relative to the total amount of atoms contained in the ion-conductive material.

[0048] The content of the dopant element X in the ion-conductive material may be 50 mol % or less, 1 to 40 mol %, 5 to 35 mol %, or 10 to 30 mol % of the content of the metal element M. The content of the dopant element X in the ion-conductive material may be 40 mol % or less, 35 mol % or less, 30 mol % or less, or 25 mol % or less of the content of the metal element M.

[0049] The activation energy of the ion-conductive material of this embodiment may be 0.65 eV or less, 0.2 to 0.60 eV, or 0.3 to 0.56 eV.

[0050] The activation energy of an ionically conductive material can be determined by measuring the ionic conductivity σ at five temperatures (25°C, 40°C, 60°C, 80°C, and 100°C) within the temperature range of 25°C to 100°C, and performing curve fitting based on the following formula. Also, a graph (Arrhenius plot) can be created with σ on the vertical axis and 1000 / T (T is absolute temperature) on the horizontal axis. In the formula below, σ represents ionic conductivity (S / cm), T represents absolute temperature (K), A represents frequency factor, and E ａ represents the activation energy, and k ｂ represents the Boltzmann constant. Formula: σT = Aexp(-E ａ / k ｂ T)

[0051] When the ion conductive material of the present embodiment contains Li as the alkali metal element, ６ The resonance frequency of the Li nucleus is 44.1 MHz, and the solid state is formed at room temperature under the conditions of magic angle spinning at 10 kHz. ６ When Li-NMR spectrum was measured, ６ The compound may have at least one peak having a peak top in the range of -50 to 0.68 ppm, -10 to 0.65 ppm, -1 to 0.60 ppm, or 0 to 0.55 ppm, taking the chemical shift of the LiCl salt (solid) as 0 ppm. The number of peaks observed in these ranges may be two or less, or may be one.

[0052] solid ６ Ion-conductive materials in which such a spectrum is observed in the Li-NMR spectrum tend to have better reduction resistance. The reason for this is not entirely clear, but it is possible that the coordination environment of Li affects the reduction resistance. In particular, the presence of a peak at the above peak shift position is thought to be due to the formation of a lithium coordination environment derived from the cubic crystal structure, which improves reduction resistance.

[0053] In this specification, solid ６ The measurement conditions for Li-NMR spectrum are the same as those employed in the examples. The peak top positions may be calculated by performing Lorentzian fitting on the obtained spectrum.

[0054] The ion-conductive material of this embodiment may contain a compound (also referred to as an alkali metal-containing halide) represented by the following composition formula (1), or may be a compound represented by the following composition formula (1). The crystal structure of the compound is a cubic system. α M β X γ D κ Z δ E η O ε ... (1) (In the formula, A is an alkali metal element, M is the above-mentioned tetravalent metal element M, X is the above-mentioned dopant element X, D is the above-mentioned divalent metal element D, Z is a halogen element, and 0.1≦α≦3, 0.01≦β≦1.5, 0≦γ≦0.5, 3≦δ≦6, 0.01≦κ≦1, 0≦ε≦2.)

[0055] In the composition formula (1), α may be, for example, 0.2 to 2.5, 0.3 to 2.3, or 0.5 to 2.2. The upper and lower limits for α can be combined in any desired manner.

[0056] In the above composition formula (1), β may be, for example, 0.05 to 1.2, 0.1 to 1.1, or 0.2 to 1. The upper and lower limits for β can be combined arbitrarily. γ can be 0.01 to 0.3, 0.02 to 0.2, or 0.08 to 0.15. The upper and lower limits for γ can be combined arbitrarily.

[0057] In the above composition formula (1), δ may be, for example, 3.5 to 6, or 4 to 5.8. The upper and lower limits for δ can be combined in any desired manner.

[0058] In the composition formula (1), ε may be, for example, 0.1 to 1.0, or 0.2 to 0.8. The upper and lower limits for ε can be combined in any desired manner.

[0059] In the composition formula (1), κ may be, for example, 0.05 to 1.0, 0.08 to 0.9, or 0.1 to 0.8. The upper and lower limits for κ can be combined in any desired manner.

[0060] In the above composition formula (1), E is an element other than A, M, X, D, Z, and O, and may be an element added or mixed in addition to the essential elements. Examples of E include C, B, and N.

[0061] In the above composition formula (1), η may be, for example, 0 to 0.1, 0 to 0.01, or 0 to 0.001, or may be substantially 0.

[0062] Specific examples of the ion conductive material according to this embodiment include Li ２ Mg ０．２５ Zr ０．７５ Cl ５．５ , Li ２ Mg ０．５ Zr ０．５ Cl ５ , Li ２ Mg ０．２５ Zr ０．７５ Cl ５ F ０．５ , Li １．４ Mg ０．８ Nb ０．２ Cl ４ , Li １．８ Mg ０．８ In ０．２ Cl ４ , Li １．５ Mg ０．７５ Zr ０．２５ Cl ４ , LiMg ０．５ Zr ０．５ Cl ４ , Li ０．５ Mg ０．２５ Zr ０．７５ Cl ４ , Li １．７ Mg ０．８５ Zr ０．１５ Cl ４ , Li １．２ Mg ０．６ Zr ０．４ Cl ４ , Li ０．８ Mg ０．４ Zr ０．６ Cl ４ , Li ０．３ Mg ０．１５ Zr ０．８５ Cl ４ , Li ２ Mg ０．２５ Zr０．７５ Cl ５ O ０．２５ , Li ２ Mg ０．２５ Zr ０．７５ Cl ４．５ O ０．５ , Li ２ Mg ０．２５ In ０．０５ Zr ０．７０ Cl ５．４５ , Li ２ Mg ０．２５ Bi ０．０５ Zr ０．７０ Cl ５．４５ , Li ２ Mg ０．２５ In ０．１ Zr ０．６５ Cl ５．４ , Li ２ Mg ０．２５ Nb ０．０５ Zr ０．７ Cl ５．５５ , Li ２ Mg ０．２５ Nb ０．１ Zr ０．６５ Cl ５．６ , Li １．７ Mg ０．８５ Hf ０．１５ Cl ４ , Li １．２ Mg ０．６ Hf ０．４ Cl ４ , Li ０．８ Mg ０．４ Hf ０．６ Cl ４ , Li １．８５ Mg ０．８５ Y ０．１５ Cl ４ , Li １．５５ Mg ０．８５ Nb ０．１５ Cl ４ , and Li １．４ Mg ０．８５ W ０．１５ Cl ４ Examples of compounds include compounds having the following composition formulas:

[0063] The method for producing the ion-conductive material of this embodiment is not particularly limited, but may be, for example, a production method including a step of subjecting raw materials to ball milling.

[0064] The raw material is not particularly limited, and may be a compound containing any of an alkali metal element, a metal element M, a halogen element, and a metal element D. The raw material may optionally contain an oxygen element, a dopant element X, etc. Examples of the alkali metal source include alkali metal halides, alkali metal oxides, and alkali metal peroxide salts. Examples of the metal element M source include halides of the metal element M. Examples of the metal element D source include halides of the metal element D. Examples of the dopant element X source include XO ４ The raw materials may be compounds such as salts of ions and alkali metals. The raw materials are preferably mixed before being subjected to ball milling, and may be mixed in an inert atmosphere (for example, an Ar atmosphere).

[0065] The above-mentioned manufacturing method may further include a step of annealing the ion-conductive material obtained after ball milling the raw material. The annealing temperature may be, for example, 80°C or higher. The annealing time may be, for example, 1 to 10 hours, or 3 to 6 hours. Annealing may not be performed.

[0066] The ion-conductive material of this embodiment can be used as a material for electrochemical devices such as capacitors and batteries. Examples of such materials include electrolyte materials. The electrolyte may be a solid electrolyte. Examples of batteries include lithium ion batteries and sodium ion batteries, which charge and discharge by the movement of alkali metal ions between a positive electrode and a negative electrode. The ion-conductive material of this embodiment may also be used as an electrode material, and may be contained in the positive electrode or negative electrode of a battery together with an active material.

[0067] The battery of this embodiment will be described below using a lithium ion battery as an example. The lithium ion battery includes a positive electrode, a negative electrode, and an electrolyte (solid electrolyte) disposed between the positive electrode and the negative electrode. The ion-conductive material of this embodiment (an alkali metal-containing halide (a lithium-containing halide in the case of a lithium ion battery)) may be contained in the electrolyte of the lithium ion battery.

[0068] The positive electrode of the lithium ion battery is not particularly limited and may contain a positive electrode active material and, if necessary, a conductive additive, a binder, etc. The positive electrode may be a layer containing these materials formed on a current collector.

[0069] Examples of the positive electrode active material include lithium-containing composite metal oxides containing lithium (Li) and at least one transition metal selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, and Cu. Examples of such lithium composite metal oxides include LiCoO ２ , LiNiO ２ , LiMn ２ O ４ , Li ２ MnO ３ , LiNi ｘ Mn ｙ Co １－ｘ－ｙ O ２ [0<x+y<1]), LiNi ｘ Co ｙ Al １－ｘ－ｙ O ２ [0<x+y<1]), LiCr ０．５ Mn ０．５ O ２ , LiFePO ４ , Li ２ FeP ２ O ７ , LiMnPO ４ , LiFeBO ３ , Li ３ V ２ (P.O. ４ ) ３ , Li ２ CuO ２ , Li ２ FeSiO ４ , and Li ２ MnSiO ４ Examples include:

[0070] The negative electrode of the lithium ion battery is not particularly limited, and may contain a negative electrode active material and, if necessary, a conductive additive, a binder, etc. Examples of the negative electrode active material include simple elements such as Li, Si, P, Sn, Si—Mn, Si—Co, Si—Ni, In, and Au, alloys or composites containing these elements, carbon materials such as graphite, and substances in which lithium ions are inserted between the layers of the carbon materials.

[0071] The material of the current collector is not particularly limited, and may be a simple metal or an alloy of metals such as Mg, Ti, Fe, Co, Ni, Cu, Zn, Pd, Pt, Ag, Au, Al, In, and Ge.

[0072] The electrolyte (solid electrolyte) disposed between the positive electrode and the negative electrode may be in the form of a layer. The solid electrolyte layer may have a plurality of layers. For example, a configuration may be provided in which, in addition to the solid electrolyte layer containing the ion-conductive material of this embodiment, a sulfide solid electrolyte layer containing a sulfide-based electrolyte is included. A configuration may be provided in which a sulfide solid electrolyte layer is included between the solid electrolyte containing the ion-conductive material of this embodiment and the negative electrode.

[0073] The sulfide solid electrolyte is not particularly limited, but for example, Li ６ P.S. ５ Cl, Li ２ S-PS ５ , Li １０ GeP ２ S １２ , Li ９．６ P ３ S １２ , Li ９．５４ Si １．７４ P １．４４ S １１．７ Cl ０．３ , and Li ３ P.S. ４ Examples include:

[0074] (Example 1) Ball mill: In an argon atmosphere having a dew point of −70° C. or less (hereinafter referred to as a dry argon atmosphere), LiCl, MgCl ２ , and ZrCl ４ The above ingredients were weighed out so as to obtain the composition shown in Table 1, and raw materials were prepared.

[0075] The above raw materials were placed in a zirconia pot for a planetary ball mill, and 65 g of zirconia balls with a diameter of 4 mm were added. The mixture was treated for 24 hours at 300 rpm to induce a mechanochemical reaction, yielding a crude composition. Planetary ball mill: PM 400, manufactured by Verder Scientific K.K.

[0076] Annealing The crude composition obtained above was heated in an argon atmosphere at 100° C. for 5 hours to obtain the ion-conductive material of Example 1.

[0077] Example 2 An ion-conductive material was produced in the same manner as in Example 1, except that the compounding ratio of the raw materials was changed so as to obtain the charged composition shown in Table 1.

[0078] (Example 3) As raw materials, LiCl, MgCl ２ , ZrCl ４ An ion-conductive material was produced in the same manner as in Example 1, except that the compounding ratio of the raw materials was changed so as to obtain the charged composition shown in Table 1, using LiF and LiF.

[0079] (Example 4) As raw materials, LiCl, MgCl ２ , and NbCl ５ An ion-conductive material was produced in the same manner as in Example 1, except that the compounding ratio of the raw materials was changed so as to obtain the charged composition shown in Table 1, and annealing was not performed.

[0080] (Example 5) As raw materials, LiCl, MgCl ２ , and InCl ３ An ion-conductive material was produced in the same manner as in Example 1, except that the compounding ratio of the raw materials was changed so as to obtain the charged composition shown in Table 1, and annealing was not performed.

[0081] Examples 6 to 12 Ion-conductive materials were produced in the same manner as in Example 1, except that the compounding ratio of the raw materials was changed to obtain the charged composition shown in Table 1, and that annealing was not performed.

[0082] (Examples 13 and 14) As raw materials, LiCl, MgCl ２ , ZrCl ４ and Li ２An ion-conductive material was produced in the same manner as in Example 1, except that O was used, the compounding ratio of the raw materials was changed so as to obtain the charged composition shown in Table 1, and annealing was not performed.

[0083] (Examples 15 and 17) As raw materials, LiCl, MgCl ２ , ZrCl ４ , and InCl ３ An ion-conductive material was produced in the same manner as in Example 1, except that the compounding ratio of the raw materials was changed so as to obtain the composition shown in Table 1, and annealing was not performed.

[0084] (Example 16) As raw materials, LiCl, MgCl ２ , ZrCl ４ , and BiCl ３ An ion-conductive material was produced in the same manner as in Example 1, except that the compounding ratio of the raw materials was changed so as to obtain the composition shown in Table 1, and annealing was not performed.

[0085] (Examples 18 and 19) As raw materials, LiCl, MgCl ２ , ZrCl ４ , and NbCl ５ An ion-conductive material was produced in the same manner as in Example 1, except that the compounding ratio of the raw materials was changed so as to obtain the composition shown in Table 1, and annealing was not performed.

[0086] (Examples 20 to 22) As raw materials, LiCl, MgCl ２ , and HfCl ４ An ion-conductive material was produced in the same manner as in Example 1, except that the compounding ratio of the raw materials was changed so as to obtain the composition shown in Table 1, and annealing was not performed.

[0087] (Example 23) As raw materials, LiCl, MgCl ２ , and YCl ３ An ion-conductive material was produced in the same manner as in Example 1, except that the compounding ratio of the raw materials was changed so as to obtain the charged composition shown in Table 1, and annealing was not performed.

[0088] (Example 24) As raw materials, LiCl, MgCl ２ , and NbCl ５ An ion-conductive material was produced in the same manner as in Example 1, except that the compounding ratio of the raw materials was changed so as to obtain the charged composition shown in Table 1, and annealing was not performed.

[0089] (Example 25) As raw materials, LiCl, MgCl ２ , and WCl ６ An ion-conductive material was produced in the same manner as in Example 1, except that the compounding ratio of the raw materials was changed so as to obtain the charged composition shown in Table 1, and annealing was not performed.

[0090] Comparative Example 1: LiCl and ZrCl ４ An ion-conductive material was produced in the same manner as in Example 1, except that the compounding ratio of the raw materials was changed to obtain the charged composition shown in Table 1, and annealing was not performed.

[0091] Comparative Example 2 An ion-conductive material was produced in the same manner as in Example 1, except that the compounding ratio of the raw materials was changed to obtain the charged composition shown in Table 1, and that annealing was not performed.

[0092] <Powder X-ray Diffraction> The obtained ion-conductive material was evaluated for diffraction peaks observed by powder X-ray diffraction measurement at 25°C. The results are shown in Table 2. Powder X-ray diffraction measurement was performed under the following conditions. The half-width of the peak was determined by removing the background signal and performing fitting. Measurement device: Ultima IV (manufactured by Rigaku Corporation) X-ray generator: CuKα radiation source, voltage 40 kV, current 40 mA X-ray detector: Scintillation counter or semiconductor detector Measurement range: Diffraction angle 2θ = 5° to 80° Scan speed: 4° / min

[0093] Table 1 shows the crystal structure, the peak height ratio (A / B) of the diffraction peak A observed in the 2θ angle range of 33 to 38° to the diffraction peak B observed in the 2θ angle range of 45 to 53°, and the half-width of the diffraction peak A for each of the ion-conductive materials of the Examples and Comparative Examples. Figure 1 shows the X-ray diffraction charts of the ion-conductive materials of Examples 1 to 11 and Comparative Examples 1 and 2.

[0094] <Preparation of Cell for Cyclic Voltammetry> A cell for cyclic voltammetry was prepared as follows: The preparation of the cell for cyclic voltammetry was carried out in a glove box purged with an inert gas.

[0095] First, 150 mg of the ion-conductive material of Example 1 was placed in an insulating cylinder having an inner diameter of 10 mm. A pressure of 370 MPa was applied to the ion-conductive material to form a solid electrolyte layer (a layer of the ion-conductive material).

[0096] Next, 30 parts by weight of acetylene black and 70 parts by weight of the ion-conductive material of Example 1 were weighed and mixed in an agate mortar, and 30 mg of the mixture was layered on the solid electrolyte layer, and a pressure of 370 MPa was applied to form a working electrode layer.

[0097] Next, 2 mg of Li foil was placed on the surface of the solid electrolyte layer opposite to the surface in contact with the working electrode layer so as to contact and cover the solid electrolyte layer, thereby obtaining a laminate. A pressure of 50 MPa was applied to the laminate, and a reference electrode layer made of Li was formed on the solid electrolyte layer.

[0098] A current collector made of stainless steel was attached to the reference electrode and the working electrode, and then lead wires were attached to the current collector. All components were placed in a sealed desiccator in a glove box. In this way, a cell for cyclic voltammetry was prepared.

[0099] <Cyclic Voltammetry Test> The reference electrode and working electrode of the above-mentioned cyclic voltammetry cell were electrically connected to an impedance analyzer S11260 and a potentiostat S11287A, and a cyclic voltammetry test was carried out under the following conditions: That is, in the cyclic voltammetry test, the sweep rate was set to 1 mV / s, and the reference electrode (Li ＋ The current value flowing when the potential of the working electrode was changed relative to the potential of the electrode (Li).

[0100] First, the potential of the working electrode relative to the reference electrode was increased from the open circuit voltage to 5.5 V, and then turned back and decreased to 0 V.

[0101] Table 1 shows the potential when a current of -100 μA flows (Li ＋ 2 shows the results of cyclic voltammetry measurements of the ion-conductive materials of Examples 1 to 3 and Comparative Examples 1 and 2.

[0102] <NMR Evaluation> The ion-conductive materials obtained in Examples 1, 11, and Comparative Example 1 were subjected to solid NMR analysis under the following conditions. ６ Li-NMR measurement was performed to evaluate the local structural environment of Li. Apparatus: AVANCE300 (manufactured by Bruker) Observation nuclei: ６ Li ( ６ (44.1 MHz as the resonance frequency of Li nucleus) Magic angle spinning (MAS) frequency: 10 kHz Measurement method: Single pulse method (using Bruker's standard pulse sequence zg) Excitation pulse width: π / 4 pulse Waiting time and number of accumulations: 40 seconds, 256 times Measurement temperature: Room temperature (26°C) Reference material: ６ The peak observed for the LiCl salt (solid) was set to 0 ppm.

[0103] FIG. 3 shows the solids obtained for the ion-conductive materials of Examples 1, 11, and Comparative Example 1. ６ The Li-NMR spectrum is shown below. One peak was observed in the range of -50 to 50 ppm, so Lorentzian fitting was performed to calculate the peak top position. The results are shown in Table 2.

[0104] <Evaluation of ionic conductivity> A pressure molding die including a frame, a lower punch, and an upper punch was prepared. The frame was made of insulating polycarbonate. The upper and lower punches were both made of electronically conductive stainless steel and were electrically connected to the terminals of an impedance analyzer (S11260, manufactured by Solatron Analytical).

[0105] Using the above-mentioned pressure molding die, the ionic conductivity of the ion-conductive material was measured by the following method. First, in a dry argon atmosphere, powder of the ion-conductive material was filled onto the lower part of a punch inserted vertically from below into the hollow part of a frame mold. Then, the upper part of the punch was pressed into the hollow part of the frame mold from above, thereby applying a pressure of 370 MPa to the powder of the ion-conductive material inside the pressure molding die. After the pressure was applied, the punch was clamped from above and below with a jig to fix it, and while maintaining a constant pressure, the impedance of the ion-conductive material was measured by electrochemical impedance measurement using the above-mentioned impedance analyzer.

[0106] A Cole-Cole diagram was created from the impedance measurement results. In the Cole-Cole diagram, the real value of the impedance at the measurement point where the absolute value of the phase of the complex impedance was smallest was regarded as the resistance value to the ionic conduction of the ion-conductive material. Using this resistance value, the ionic conductivity was calculated based on the following formula (III). The results are shown in Table 2. σ=(R ＳＥ × S / t) －１ ...(III) where, σ is the ionic conductivity, S is the contact area of ​​the ion-conductive material with the upper part of the punch (equal to the cross-sectional area of ​​the hollow part of the frame), and R ＳＥ is the resistance value of the solid electrolyte material in the impedance measurement, and t is the thickness of the ion-conductive material when pressure is applied.

[0107] Using the above measurement method, measurements were carried out at five temperatures (25°C, 40°C, 60°C, 80°C, and 100°C) within the temperature range of 25°C to 100°C for each ion-conductive material in the Examples and Comparative Examples, and activation energies were determined from Arrhenius plots. ２５℃ ) and activation energy (Ea) are shown in Table 1. FIG. 4 is a diagram showing Arrhenius plots for the ion-conductive materials of Examples 1 and 2.

[0108] <Preparation of Secondary Battery> In a dry argon atmosphere, an ion-conductive material, LiNi １／３ Mn １／３ Co １／３ O ２ 29 parts by mass of cellulose acetate, 67 parts by mass of cellulose acetate, and 4 parts by mass of acetylene black were weighed out and mixed in a mortar to obtain a positive electrode material.

[0109] A laminate was obtained by stacking 100 mg of the ion-conductive material of Example 1 and 15 mg of the above-described positive electrode material in this order in an insulating cylinder having an inner diameter of 10 mm. A pressure of 370 MPa was applied to the laminate to form a first electrode (a layer of the above-described mixture) and a first solid electrolyte layer (a layer of the ion-conductive material of Example 1, 0.5 mm thick).

[0110] Next, the first solid electrolyte layer is formed of a sulfide solid electrolyte Li ６ P.S. ５ 60 mg of Cl was added to the stack so that it was in contact with the electrode, and a laminate was obtained. A pressure of 370 MPa was applied to the stack to form a second solid electrolyte layer (0.3 mm). The first solid electrolyte layer was sandwiched between the first electrode and the second solid electrolyte layer.

[0111] Next, 60 mg of In foil was placed in contact with the second solid electrolyte layer, and 2 mg of Li foil was placed in contact with the In foil to obtain a laminate. A pressure of 370 MPa was applied to the laminate to form a second electrode.

[0112] Current collectors made of stainless steel were attached to the first electrode and the second electrode, and then lead wires were attached to the current collectors. All of the components were placed in a desiccator and sealed, thereby obtaining a secondary battery of Example 1.

[0113] <Charge / Discharge Test> The following charge / discharge tester was used: Charge / discharge tester: Toyo System Co., Ltd. TOSCAT-3100

[0114] At 60°C, the secondary battery was charged at 0.1C (0.19mA / cm ２ ), 0.5C (0.95mA / cm ２ ) and 1C (1.9mA / cm ２ ) Charge-discharge tests were carried out at three different C rates.

[0115] The secondary battery was charged to 3.7 V at a current density corresponding to each C rate using constant current constant voltage (CCCV charging). The secondary battery was discharged to 1.9 V at a current density corresponding to each C rate. Fig. 5 shows the results of the charge / discharge test of the secondary battery of Example 1.

[0116] A secondary battery was fabricated in the same manner as in Example 1, except that the ion-conductive material of Comparative Example 1 was used as the ion-conductive material, and a charge-discharge test was carried out. The C-rate test was carried out at 0.1 C and 1 C. FIG. 6 shows the results of the charge-discharge test of the secondary battery of Comparative Example 1.

[0117] <Cycle Test> Each of the secondary batteries of Example 1 and Comparative Example 1 was subjected to 100 charge / discharge cycles at 60°C and a C rate of 1C, and the discharge capacity at each cycle and the number of cycles were plotted. Fig. 7 is a diagram showing the results of the cycle test for each of the secondary batteries of Example 1 and Comparative Example 1. The capacity retention rate after 100 cycles (the discharge capacity at the 100th cycle relative to the initial discharge capacity) of Example 1 was 91.1%. The capacity retention rate after 100 cycles of Comparative Example 1 was 65.6%.

[0118]

[0119]

Claims

1. An ionically conductive material which contains an alkali metal element, a divalent metal element D, a trivalent or higher metal element M, and a halogen element, has a cubic crystal structure, and in an X-ray diffraction chart obtained by measurement using CuKα radiation at 25°C, when the diffraction peak having the largest peak height observed in a 2θ angle range of 45 to 53° is defined as diffraction peak B, and the diffraction peak having the largest peak height observed in a 2θ angle range of 33 to 38° is defined as diffraction peak A, the ratio of the peak height of diffraction peak A to the peak height of diffraction peak B is 0.80 to 2.

50.

2. The ionically conductive material according to claim 1, wherein the halogen element includes Cl.

3. The ionically conductive material according to claim 2, wherein the halogen element further contains at least one element selected from the group consisting of F, Br, I, and O.

4. The ionically conductive material according to claim 1 or 2, wherein the divalent metal element D includes at least one element selected from the group consisting of Mg, Ca, Sr, and Ba.

5. The ionically conductive material according to claim 1 or 2, wherein the metal element M comprises at least one element selected from the group consisting of Zr, Nb, In, Bi and Hf.

6. The ion-conductive material according to claim 1 or 2, wherein the content of said alkali metal element is 5 to 30 mol %, the content of said metal element D is 1 to 16 mol %, the content of said metal element M is 1 to 18 mol %, and the content of said halogen element is 55 to 78 mol %.

7. The alkali metal element includes Li, ６ The resonance frequency of the Li nucleus is 44.1 MHz, and the solid is ６ When the Li-NMR spectrum was measured, ６ 3. The ion-conductive material according to claim 1, having at least one peak having a peak top in the range of -50 to 0.68 ppm, taking the chemical shift of the LiCl salt as 0 ppm.

8. A solid electrolyte comprising the ion-conductive material according to claim 1 or 2.

9. A battery comprising the solid electrolyte according to claim 8.

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