阅读说明：本技术 固体电解质材料和使用它的电池 (Solid electrolyte material and battery using the same ) 是由 长岭健太 酒井章裕 于 2019-09-12 设计创作，主要内容包括：本公开提供一种在微粒化过程中能够维持高的锂离子传导率的固体电解质材料。本公开的固体电解质材料由Li、M和X构成,M是选自除Li以外的金属元素和半金属元素中的至少一种元素,X是选自F、Cl、Br和I中的至少一种元素,满足式子FWHM/2θ-p≤0.015,FWHM表示在通过使用Cu-Kα射线进行的固体电解质材料的X射线衍射测定而得到的X射线衍射图中,在衍射角为25°以上且35°以下的衍射角2θ的范围内具有最高强度的X射线衍射峰的半值宽度,2θ-p表示X射线衍射峰的中心的衍射角,Li和M的平均离子半径除以X的平均离子半径得到的值大于0.424,并且固体电解质材料包含属于六方晶的结晶相。(The present disclosure provides a solid electrolyte material capable of maintaining a high lithium ion conductivity during micronization. The solid electrolyte material of the present disclosure is composed of Li, M and X, M being at least one element selected from metal elements other than Li and semimetal elements, X being at least one element selected from F, Cl, Br and I, satisfying the formula FWHM/2 θ p 0.015 or less, wherein FWHM is a half-value width of an X-ray diffraction peak having the highest intensity in a diffraction angle 2 theta range of 25 DEG or more and 35 DEG or less in an X-ray diffraction pattern obtained by X-ray diffraction measurement of the solid electrolyte material using Cu-K alpha rays, and 2 theta is represented by p A diffraction angle representing the center of an X-ray diffraction peak, a value obtained by dividing the average ionic radius of Li and M by the average ionic radius of X is larger than 0.424, and the solid electrolyte material contains a crystalline phase belonging to hexagonal crystals.)

1. A solid electrolyte material is composed of Li, M and X,

m is at least one element selected from the group consisting of metal elements other than Li and semimetal elements,

x is at least one element selected from the group consisting of F, Cl, Br and I,

satisfies the following formula (I),

FWHM/2θ_p≤0.015 (I)

wherein FWHM represents a half-value width of an X-ray diffraction peak having a highest intensity in a diffraction angle 2 theta range of 25 DEG to 35 DEG in an X-ray diffraction pattern obtained by X-ray diffraction measurement of the solid electrolyte material using Cu-Ka rays,

2θ_prepresents a diffraction angle of the center of the X-ray diffraction peak,

the average ionic radius of Li and M divided by the average ionic radius of X is greater than 0.424, and

the solid electrolyte material contains a crystalline phase belonging to hexagonal crystal.

2. The solid electrolyte material according to claim 1,

m contains a metal element having a valence of 3.

3. The solid electrolyte material according to claim 1 or 2,

m contains a rare earth element.

4. The solid electrolyte material according to any one of claims 1 to 3,

m contains at least one element selected from Y and Gd.

5. The solid electrolyte material according to any one of claims 1 to 4,

m comprises a group 2 element.

6. The solid electrolyte material according to claim 5,

the group 2 element is Ca.

7. The solid electrolyte material according to any one of claims 1 to 6,

x is at least one element selected from Cl and Br.

8. The solid electrolyte material according to claim 7,

x is Cl and Br.

9. The solid electrolyte material according to any one of claims 1 to 8,

the molar ratio Li/X of Li to X is 0.3 to 0.6.

10. A battery comprising a positive electrode, a negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode,

at least one selected from the group consisting of the positive electrode, the negative electrode and the electrolyte layer, containing the solid electrolyte material according to any one of claims 1 to 9.

Technical Field

The present disclosure relates to a solid electrolyte material and a battery using the same.

Background

Patent document 1 discloses an all-solid battery using a sulfide solid electrolyte material.

Prior art documents

Patent document 1: japanese patent laid-open publication No. 2011-129312

Disclosure of Invention

Problems to be solved by the invention

An object of the present disclosure is to provide a solid electrolyte material capable of maintaining a high ionic conductivity even when micronized.

Means for solving the problems

The solid electrolyte material of the present disclosure is composed of Li, M, and X,

m is at least one element selected from the group consisting of metal elements other than Li and semimetal elements,

x is at least one element selected from the group consisting of F, Cl, Br and I,

satisfies the following formula (I),

FWHM/2θ_p≤0.015 (I)

wherein the content of the first and second substances,

the FWHM represents a half-value width of an X-ray diffraction peak having the highest intensity in a diffraction angle 2 θ range of 25 ° or more and 35 ° or less in a diffraction pattern obtained by X-ray diffraction measurement of the solid electrolyte material using Cu — K α rays,

2θ_prepresents a diffraction angle of the center of the X-ray diffraction peak,

the average ionic radius of Li and M divided by the average ionic radius of X is greater than 0.424, and

the solid electrolyte material contains a crystalline phase belonging to hexagonal crystal.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present disclosure, a solid electrolyte material capable of maintaining a high lithium ion conductivity even when micronized can be provided.

Drawings

Fig. 1 shows a cross-sectional view of a battery 1000 according to embodiment 2.

Fig. 2 shows a schematic view of a pressure forming die 300 for evaluating the ion conductivity of a solid electrolyte material.

Fig. 3 is a graph showing the initial discharge characteristics of the battery of example 1.

Fig. 4 is a graph showing X-ray diffraction patterns of the solid electrolyte materials of example 5A, example 5B, comparative example 4A, and comparative example 4B.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

(embodiment 1)

The solid electrolyte material of embodiment 1 is composed of Li, M and X,

m is at least one element selected from the group consisting of metal elements other than Li and semimetal elements,

x is at least one element selected from the group consisting of F, Cl, Br and I,

satisfies the following formula (I),

FWHM/2θ_p≤0.015 (I)

wherein the content of the first and second substances,

the FWHM represents a half-value width of an X-ray diffraction peak having the highest intensity in a diffraction angle 2 θ range of 25 ° or more and 35 ° or less in a diffraction pattern obtained by X-ray diffraction measurement of the solid electrolyte material using Cu — K α rays,

2θ_prepresents a diffraction angle of the center of the X-ray diffraction peak,

the average ionic radius of Li and M divided by the average ionic radius of X is greater than 0.424, and

the solid electrolyte material contains a crystalline phase belonging to hexagonal crystal.

"semimetallic elements" means B, Si, Ge, As, Sb and Te.

The "metal element" means:

(i) all elements contained in groups 1 to 12 of the periodic table except hydrogen, and

(ii) all elements contained in groups 13 to 16 of the periodic table except for B, Si, Ge, As, Sb, Te, C, N, P, O, S and Se.

The solid electrolyte material according to embodiment 1 can maintain high lithium ion conductivity even when micronized. That is, in the process of manufacturing a battery (for example, an all-solid secondary battery) using the solid electrolyte material of embodiment 1, even in the case where the solid electrolyte material is pulverized by pulverization, a decrease in the ion conductivity of the solid electrolyte material can be suppressed. This makes it possible to obtain a battery having excellent charge/discharge characteristics.

The solid electrolyte material of embodiment 1 contains no sulfur, and therefore does not generate hydrogen sulfide even when exposed to the atmosphere. Therefore, the solid electrolyte material of embodiment 1 is excellent in safety.

The "ionic radius" in the present disclosure is based on a defined value described in "Shannon et al, ActaA32(1976) 751".

The average ionic radii of Li and M contained in the solid electrolyte material of embodiment 1 are calculated based on the following formula.

Σ(r_C·R_C)/ΣR_C

Wherein r is_CRepresents the ionic radius of an element (i.e., cation) contained in Li and M. R_CIndicates the amount of substance of the element contained in Li and M.

The average ionic radius of X contained in the solid electrolyte material of embodiment 1 is calculated based on the following formula.

Σ(r_A·R_A)/ΣR_A

Wherein r is_ARepresents the ionic radius of the element (i.e., anion) contained in X. R_AIndicates the amount of substance of the element contained in X.

If the value obtained by dividing the average ionic radius of Li and M by the average ionic radius of X (hereinafter also referred to as "average ionic radius ratio") is larger than 0.424, a crystal phase belonging to hexagonal crystals is precipitated. Since the crystal structure of the crystal phase belonging to hexagonal crystal is maintained even when the particles are made fine, the decrease in ion conductivity is suppressed.

The phrase "crystal phase belonging to hexagonal crystal" in the present disclosure means a crystal having Li equivalent to that disclosed in ICSD (inorganic Crystal Structure database) #01-087-₃ErCl₆A similar crystal structure and a crystalline phase having an X-ray diffraction pattern characteristic of the crystal structure. Therefore, the presence or absence of a crystalline phase belonging to hexagonal crystals contained in the solid electrolyte material is judged based on the X-ray diffraction pattern. At this time, the diffraction angle and/or the peak intensity ratio of the diffraction pattern vary from Li depending on the kind of the element contained in the solid electrolyte material₃ErCl₆A change occurs. Therefore, regarding the presence or absence of "a crystal phase belonging to hexagonal crystal", not only does it existThe diffraction angle of the diffraction peak is determined based on a pattern of 3 or more diffraction peaks having high intensity.

The solid electrolyte material of embodiment 1 may contain 30 vol% or more of a crystal phase belonging to hexagonal crystals. The solid electrolyte material according to embodiment 1 may contain 50 vol% or more of a crystal phase belonging to hexagonal crystals. The solid electrolyte material of embodiment 1 may also be substantially composed of a crystal phase belonging to hexagonal crystal. Here, "the solid electrolyte material of embodiment 1 is substantially composed of a crystal phase belonging to hexagonal crystal" means that the solid electrolyte material of embodiment 1 contains 90 vol% or more of a crystal phase belonging to hexagonal crystal. The solid electrolyte material of embodiment 1 may be composed of only a crystal phase belonging to hexagonal crystal.

The solid electrolyte material of embodiment 1 may be substantially composed of Li, M, and X. Here, "the solid electrolyte material of embodiment 1 substantially consists of Li, M, and X" means that, in the solid electrolyte material of embodiment 1, the molar ratio of the amounts of substances of Li, M, and X contained in the solid electrolyte material to the total amount of substances of all elements constituting the solid electrolyte material is 90% or more. The molar ratio may be 95% or more. The solid electrolyte material of embodiment 1 may be composed of only Li, M, and X.

In order to maintain the lithium ion conductivity at a higher maintenance rate even when micronized, M may contain a metal element having a valence of 3. In the case where M contains an element having a valence of 3, the solid electrolyte material of embodiment 1 is capable of forming a solid solution in a wider composition region.

In order to maintain lithium ion conductivity with higher maintenance even by microparticulation, M may contain a rare earth element.

In order to maintain the lithium ion conductivity with a higher maintenance ratio even when micronized, M may contain at least one element selected from Y (i.e., yttrium) and Gd (i.e., gadolinium).

In order to maintain lithium ion conductivity at a higher maintenance rate even when micronized, M may contain a group 2 element.

In order to maintain lithium ion conductivity at a higher maintenance rate even when micronized, M may contain Ca (i.e., calcium).

In order to maintain the lithium ion conductivity at a higher maintenance rate even if micronized, X may be at least one element selected from Cl and Br.

In order to maintain the lithium ion conductivity at a higher maintenance rate even if micronized, X may be Cl and Br.

In order to maintain lithium ion conductivity with higher maintenance rate even if micronized, the average ionic radius ratio may be greater than 0.424 and 0.460 or less. The average ionic radius ratio may be greater than 0424 and 0.455 or less. The average ionic radius ratio may be greater than 0424 and 0.450 or less. The average ionic radius ratio may be greater than 0.424 and less than 0.442. The average ionic radius ratio may be greater than 0.426 and 0.442 or less. The average ionic radius ratio may be 0.427 or more and 0.442 or less.

In order to maintain the lithium ion conductivity at a higher maintenance ratio even when micronized, the molar ratio Li/X of Li to X may be 0.3 or more and 0.6 or less. The molar ratio Li/X may be 0.33 or more and 0.6 or less. The molar ratio Li/X may be 0.37 or more and 0.55 or less.

The solid electrolyte material of embodiment 1 may contain an amorphous phase.

The shape of the solid electrolyte material of embodiment 1 is not limited. Examples of the shape of the solid electrolyte material of embodiment 1 include a needle shape, a spherical shape, an oval spherical shape, or a fibrous shape. For example, the solid electrolyte material of embodiment 1 may be particles. The solid electrolyte material of embodiment 1 may be formed to have a particle or plate shape.

In order to further improve the ion conductivity and to form a good dispersion state with other materials such as an active material, for example, in the case where the solid electrolyte material of embodiment 1 is in a particulate form (for example, spherical), the median particle diameter of the solid electrolyte material of embodiment 1 may be 0.1 μm or more and 100 μm or less. The median particle diameter may be 0.5 to 10 micrometers. The median particle diameter refers to a particle diameter at which the cumulative volume in the volume-based particle size distribution is equal to 50%. The volume-based particle size distribution can be measured by a laser diffraction measuring apparatus or an image analyzing apparatus.

In order to form a good dispersion state of the solid electrolyte material and the active material, in the case where the solid electrolyte material of embodiment 1 is in a particulate (for example, spherical) shape, the median particle diameter of the solid electrolyte material may be smaller than that of the active material.

The solid electrolyte material of embodiment 1 can be produced, for example, by the following method.

Raw material powders were prepared in a compounding ratio of the target composition. The raw powder may be, for example, a halide. For example, in the production of Li₃GdBr₂Cl₄In the case of (2), LiBr, LiCl and GdCl are added₃Prepared at a molar ratio of 2.0:1.0: 1.0. In order to counteract the compositional changes that may occur during the synthesis, the raw meal may be mixed in a molar ratio that is pre-adjusted.

The raw powder is not limited to the above. For example, LiBr, LiCl and GdBr are mentioned₃Combinations of (a) and (b). LiBr can be used_0.5Cl_0.5Such a complex anionic compound is used as the raw material powder. Mixtures of oxygen-containing raw meal (e.g. oxides, hydroxides, sulfates or nitrates) and halides (e.g. ammonium halides) can be used.

The raw material powders were thoroughly mixed using a mortar and pestle, a ball mill, or a stirrer to obtain a mixed powder. Then, the mixed powder is fired in vacuum or in an inert atmosphere. The firing may be performed, for example, in the range of 100 ℃ to 650 ℃ for 1 hour or more.

Thus, the solid electrolyte material of embodiment 1 is obtained.

(embodiment 2)

Hereinafter, embodiment 2 of the present disclosure will be described. The matters already described in embodiment 1 will be omitted.

The battery of embodiment 2 includes a positive electrode, a negative electrode, and an electrolyte layer. The electrolyte layer is disposed between the positive electrode and the negative electrode.

At least one selected from the group consisting of a positive electrode, an electrolyte layer, and a negative electrode contains the solid electrolyte material according to embodiment 1.

The battery of embodiment 2 contains the solid electrolyte material of embodiment 1, and therefore the charge-discharge characteristics of the battery of embodiment 2 can be improved.

A specific example of the battery of embodiment 2 will be described below.

Fig. 1 shows a cross-sectional view of a battery 1000 according to embodiment 2.

The battery 1000 includes a positive electrode 201, an electrolyte layer 202, and a negative electrode 203.

The positive electrode 201 includes positive electrode active material particles 204 and solid electrolyte particles 100.

The electrolyte layer 202 is disposed between the positive electrode 201 and the negative electrode 203.

The electrolyte layer 202 contains an electrolyte material (e.g., a solid electrolyte material).

The negative electrode 203 contains negative electrode active material particles 205 and solid electrolyte particles 100.

The solid electrolyte particles 100 are particles composed of the solid electrolyte material of embodiment 1, or particles containing the solid electrolyte material of embodiment 1 as a main component. Here, the particles containing the solid electrolyte material of embodiment 1 as a main component refer to particles containing the solid electrolyte material of embodiment 1 as the largest component.

(Positive electrode 201)

The positive electrode 201 contains a material capable of occluding and releasing metal ions (e.g., lithium ions). The positive electrode 201 contains, for example, a positive electrode active material (for example, positive electrode active material particles 204).

Examples of the positive electrode active material are lithium-containing transition metal oxides, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal oxyfluorides, transition metal oxysulfides, or transition metal oxynitrides. Examples of lithium-containing transition metal oxides are Li (NiCoMn) O₂、Li(NiCoAl)O₂Or LiCoO₂。

The median diameter of the positive electrode active material particles 204 may be 0.1 μm or more and 100 μm or less. When the median diameter of the positive electrode active material particles 204 is 0.1 μm or more, the positive electrode active material particles 204 and the solid electrolyte particles 100 can be dispersed well in the positive electrode. This improves the charge/discharge characteristics of the battery. When the median diameter of the positive electrode active material particles 204 is 100 μm or less, the lithium diffusion rate in the positive electrode active material particles 204 increases. Thereby, the battery can operate with high output.

The median particle diameter of the positive electrode active material particles 204 may be larger than the solid electrolyte particles 100. This enables the positive electrode active material particles 204 and the solid electrolyte particles 100 to be dispersed well.

From the viewpoint of the energy density and output of the battery, in the positive electrode 201, the ratio of the volume Vca1 of the positive electrode active material particles 204 to the total of the volume Vca1 of the positive electrode active material particles 204 and the volume Vce1 of the solid electrolyte particles 100 may be 0.30 or more and 0.95 or less. That is, the ratio of (Vca1)/(Vca1+ Vce1) may be 0.30 or more and 0.95 or less.

The thickness of the positive electrode 201 may be 10 micrometers or more and 500 micrometers or less from the viewpoint of energy density and output of the battery.

(electrolyte layer 202)

The electrolyte layer 202 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte material. That is, the electrolyte layer 202 may be a solid electrolyte layer. The solid electrolyte material contained in the electrolyte layer 202 may contain the solid electrolyte material of embodiment 1.

In order to improve the charge-discharge characteristics of the battery, the electrolyte layer 202 may contain the solid electrolyte material of embodiment 1 as a main component. For example, in the electrolyte layer 202, the mass ratio of the solid electrolyte material of embodiment 1 to the entire electrolyte layer 202 may be 50% or more.

The mass ratio may be 70% or more in order to improve the charge-discharge characteristics of the battery.

The electrolyte layer 202 may contain not only the solid electrolyte material of embodiment 1 but also inevitable impurities. As the unreacted material in the electrolyte layer 202, a starting material of a solid electrolyte material may be contained. The electrolyte layer 202 may contain a by-product generated at the time of synthesis of the solid electrolyte material. The electrolyte layer 202 may contain a decomposition product generated by decomposition of the solid electrolyte material.

The mass ratio may be 100% (except for inevitable impurities) in order to improve the charge-discharge characteristics of the battery. That is, the electrolyte layer 202 may be composed of only the solid electrolyte material of embodiment 1.

The electrolyte layer 202 may be formed only of a solid electrolyte material different from that of embodiment 1. As a solid electrolyte material different from that of embodiment 1, for example, Li can be used₂MgX₄、Li₂FeX₄、Li(Al,Ga,In)X₄、Li₃(Al,Ga,In)X₆Or LiI (wherein X is at least one selected from F, Cl, Br, and I).

The electrolyte layer 202 may contain both the solid electrolyte material of embodiment 1 and a solid electrolyte material different from the solid electrolyte material of embodiment 1. At this time, both can be uniformly dispersed. The layer made of the solid electrolyte material according to embodiment 1 and the layer made of a solid electrolyte material different from the solid electrolyte material according to embodiment 1 may be arranged in this order with respect to the stacking direction of the battery.

The thickness of the electrolyte layer 202 may be 1 μm or more and 100 μm or less. When the thickness of the electrolyte layer 202 is 1 μm or more, the positive electrode 201 and the negative electrode 203 are less likely to be short-circuited. When the thickness of the electrolyte layer 202 is 100 μm or less, the battery can operate at high output.

(cathode 203)

The anode 203 contains a material capable of occluding and releasing metal ions (e.g., lithium ions). The negative electrode 203 contains, for example, a negative electrode active material (for example, negative electrode active material particles 205).

Examples of the negative electrode active material include a metal material, a carbon material, an oxide, a nitride, a tin compound, or a silicon compound. The metal material may be a simple metal or an alloy. Examples of the metallic material are lithium metal or lithium alloy. Examples of carbon materials are natural graphite, coke, carbon in graphitized carbon, carbon fibers, spherical carbon, artificial graphite or amorphous carbon. Preferable examples of the negative electrode active material include silicon (i.e., Si), tin (i.e., Sn), a silicon compound, and a tin compound from the viewpoint of capacity density.

The median diameter of the negative electrode active material particles 205 may be 0.1 μm or more and 100 μm or less. When the median diameter of the negative electrode active material particles 205 is 0.1 μm or more, the negative electrode active material particles 205 and the solid electrolyte particles 100 can be dispersed well in the negative electrode 203. This improves the charge/discharge characteristics of the battery. When the median diameter of the negative electrode active material particles 205 is 100 μm or less, the lithium diffusion rate in the negative electrode active material particles 205 increases. Thereby, the battery can operate with high output.

The median particle diameter of the anode active material particles 205 may be larger than that of the solid electrolyte particles 100. This enables the negative electrode active material particles 205 and the solid electrolyte particles 100 to be dispersed well.

From the viewpoint of the energy density and output of the battery, in the anode 203, the ratio of the volume vaa1 of the anode active material particles 205 to the total of the volume vaa1 of the anode active material particles 205 and the volume vae1 of the solid electrolyte particles 100 may be 0.30 or more and 0.95 or less. That is, the ratio of (vaa1)/(vaa1+ vae1) may be 0.30 or more and 0.95 or less.

The thickness of the negative electrode 203 may be 10 micrometers or more and 500 micrometers or less from the viewpoint of energy and output of the battery.

At least one selected from the cathode 201, the electrolyte layer 202, and the anode 203 may include a solid electrolyte material different from that of embodiment 1 for the purpose of improving ion conductivity, chemical stability, and electrochemical stability. Examples of the solid electrolyte material different from the solid electrolyte material of embodiment 1 are a sulfide solid electrolyte material, an oxide solid electrolyte material, a halide solid electrolyte material, or an organic polymer solid electrolyte.

An example of the sulfide solid electrolyte material is Li₂S-P₂S₅、Li₂S-SiS₂、Li₂S-B₂S₃、Li₂S-GeS₂、Li_3.25Ge_0.25P_0.75S₄Or Li₁₀GeP₂S₁₂。

Examples of oxide solid electrolyte materials are:

(i)LiTi₂(PO₄)₃or an element substitution body thereof,

(ii)(LaLi)TiO₃a perovskite-type solid electrolyte of the series,

(iii)Li₁₄ZnGe₄O₁₆、Li₄SiO₄、LiGeO₄or an element substitution body thereof,

(iv)Li₇La₃Zr₂O₁₂or an elemental substitution thereof, or

(v)Li₃PO₄Or an N-substitution thereof.

The halide solid electrolyte may be, for example, a solid electrolyte represented by the formula Li_aMe_bY_cX₆The compound represented (where a + mb +3c ═ 6 and c > 0 are satisfied, Me is at least one selected from metallic elements and semimetallic elements other than Li and Y, and the value of m represents the valence of Me.

Examples of the organic polymer solid electrolyte include a polymer compound and a lithium salt compound. The polymer compound may have an ethylene oxide structure. Since the polymer compound having an ethylene oxide structure can contain a large amount of lithium salt, the ionic conductivity can be further improved.

An example of the lithium salt is LiPF₆、LiBF₄、LiSbF₆、LiAsF₆、LiSO₃CF₃、LiN(SO₂CF₃)₂、LiN(SO₂C₂F₅)₂、LiN(SO₂CF₃)(SO₂C₄F₉) Or LiC (SO)₂CF₃)₃. A lithium salt selected from these may be used alone. Alternatively, a mixture of two or more lithium salts selected from these may also be used.

At least one selected from the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a nonaqueous electrolyte solution, a gel electrolyte, or an ionic liquid for the purpose of facilitating the transfer of lithium ions and improving the output characteristics of the battery.

The nonaqueous electrolytic solution contains a nonaqueous solvent and a lithium salt dissolved in the nonaqueous solvent.

Examples of the nonaqueous solvent include a cyclic carbonate solvent, a chain carbonate solvent, a cyclic ether solvent, a chain ether solvent, a cyclic ester solvent, a chain ester solvent, or a fluorine solvent.

Examples of the cyclic carbonate solvent are ethylene carbonate, propylene carbonate or butylene carbonate.

Examples of the chain carbonate solvent are dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate.

Examples of cyclic ether solvents are tetrahydrofuran, 1, 4-dioxane or 1, 3-dioxolane.

Examples of the chain ether solvent are 1, 2-dimethoxyethane or 1, 2-diethoxyethane.

An example of a cyclic ester solvent is gamma-butyrolactone.

An example of the chain ester solvent is methyl acetate.

Examples of fluorosolvents are fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate or dimethyl fluorocarbonate.

A nonaqueous solvent selected from these may be used alone. Alternatively, a mixture of two or more nonaqueous solvents selected from these may also be used.

An example of the lithium salt is LiPF₆、LiBF₄、LiSbF₆、LiAsF₆、LiSO₃CF₃、LiN(SO₂CF₃)₂、LiN(SO₂C₂F₅)₂、LiN(SO₂CF₃)(SO₂C₄F₉) Or LiC (SO)₂CF₃)₃。

A lithium salt selected from these may be used alone. Alternatively, a mixture of two or more lithium salts selected from these may also be used.

The concentration of the lithium salt may be, for example, 0.5 mol/liter or more and 2 mol/liter or less.

As the gel electrolyte, a polymer material impregnated with a nonaqueous electrolytic solution can be used. Examples of polymeric materials are polyoxyethylene, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or polymers with ethylene oxide groups.

Examples of cations contained in ionic liquids are:

(i) aliphatic linear quaternary salts such as tetraalkyl amines or tetraalkyl phosphonium,

(ii) aliphatic cyclic ammonium such as pyrrolidinium, morpholinium, imidazolinium, tetrahydropyrimidinium, piperazinium or piperidinium, or

(iii) Nitrogen-containing heterocyclic aromatic cations such as pyridinium or imidazolium.

An example of the anion contained in the ionic liquid is PF₆ ^-、BF₄ ^-、SbF₆ ^-、AsF₆ ^-、SO₃CF₃ ^-、N(SO₂CF₃)₂ ^-、N(SO₂C₂F₅)₂ ^-、N(SO₂CF₃)(SO₂C₄F₉)^-Or C (SO)₂CF₃)₃ ^-. The ionic liquid may contain a lithium salt.

At least one selected from the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a binder for the purpose of improving the adhesion between particles.

Examples of binders are polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resins, polyamides, polyimides, polyamideimides, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexamethylene acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexamethylene methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropropylene, styrene-butadiene rubber or carboxymethylcellulose.

The copolymers may also be used as binders. Examples of such binders are copolymers of at least two materials selected from the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene.

A mixture of two or more selected from the above materials may also be used as the binder.

At least one selected from the positive electrode 201 and the negative electrode 203 may contain a conductive assistant for the purpose of improving electron conductivity.

Examples of the conductive assistant are:

(i) graphites such as natural graphites and artificial graphites,

(ii) carbon blacks such as acetylene black and ketjen black,

(iii) conductive fibers such as carbon fibers or metal fibers,

(iv) the carbon fluoride is used as a raw material,

(v) the class of metal powders such as aluminum and the like,

(vi) conductive whiskers such as zinc oxide and potassium titanate,

(vii) a conductive metal oxide such as titanium oxide, or

(viii) And a conductive polymer compound such as polyaniline, polypyrrole, or polythiophene.

In order to reduce the cost, the conductive additive (i) or (ii) can be used.

The battery according to embodiment 2 has a shape of a coin-type battery, a cylindrical battery, a rectangular battery, a sheet-type battery, a button-type battery, a flat-type battery, or a laminated battery.

(examples)

Hereinafter, the present disclosure will be described in more detail with reference to examples.

< example 1 >

[ production of solid electrolyte Material ]

In an argon atmosphere having a dew point of-60 ℃ or lower (hereinafter referred to as "dry argon atmosphere"), LiBr LiCl CaBr was used as a raw material powder₂:YCl₃LiBr, LiCl, CaBr were prepared at a molar ratio of 1.8:1.0:0.1:1.0₂And YCl₃. These raw material powders were pulverized and mixed in a mortar to obtain a mixed powder. Then, the obtained mixed powder was fired in an electric furnace at 500 ℃ for 3 hours to make coarse particles and obtain a fired product. Then, the fired product (i.e., coarse grains) was divided into two groups. One set of the coarse particles was pulverized for 1 minute using a pestle and mortar, and a powder of the solid electrolyte material of example 1A was obtained. The remaining coarse particles were pulverized for 6 minutes to obtain a powder of the solid electrolyte material of example 1B. That is, the solid electrolyte material of example 1A was a solid electrolyte material before pulverization, that is, without being micronized. The solid electrolyte material of example 1B was a pulverized, i.e., micronized, solid electrolyte material.

[ evaluation of the ion conductivity maintenance ratio of the solid electrolyte material after pulverization ]

Fig. 2 shows a schematic view of a pressure forming die 300 for evaluating the ion conductivity of a solid electrolyte material.

The press mold 300 includes a frame 301, a punch lower portion 302, and a punch upper portion 303. The frame 301 is made of insulating polycarbonate. Punch upper 303 and punch lower 302 are both formed of an electronically conductive stainless steel.

The ion conductivity was measured by the following method using a press mold 300 shown in fig. 2.

The powder 101 of the solid electrolyte material of example 1 was filled in the inside of the press mold 300 in a dry atmosphere having a dew point of-30 ℃ or lower. Inside the pressure molding die 300, a pressure of 400MPa was applied to the solid electrolyte material of example 1 using a punch lower portion 302 and a punch upper portion 303.

The resistance of the solid electrolyte material of example 1 was measured at room temperature (25 degrees celsius ± 3 degrees celsius) by an electrochemical resistance measurement method using a potentiostat (product name "VersaSTAT 4" manufactured by princetonated Research) through a punch lower portion 302 and a punch upper portion 303 in a state where pressure was applied.

The real part value of the impedance at the measurement point at which the absolute value of the phase of the complex impedance is smallest is regarded as the resistance value of the solid electrolyte material with respect to ion conduction.

The ion conductivity was calculated based on the following formula (2) using the resistance value of the solid electrolyte material.

σ＝(R_SE×S/t)^-1···(2)

Wherein the content of the first and second substances,

sigma is the ionic conductivity of the metal oxide particles,

s is the contact area of the solid electrolyte material with the punch upper portion 303 (in fig. 2, equal to the cross-sectional area of the hollow portion of the frame 301),

R_SEis the resistance value of the solid electrolyte material in the impedance measurement, and

t is the thickness of the solid electrolyte material to which pressure is applied (in fig. 2, equal to the thickness of the layer formed by the solid electrolyte particles 100).

Not only the ion conductivity of the solid electrolyte material of example 1A (i.e., the solid electrolyte material that was not micronized) but also the ion conductivity of the solid electrolyte material of example 1B (i.e., the micronized solid electrolyte material) was measured. A value of a quotient obtained by dividing the ion conductivity of the solid electrolyte material of example 1B by the ion conductivity of the solid electrolyte material of example 1A by a percentage was calculated as "the ion conductivity maintenance ratio of the solid electrolyte material after pulverization". Table 1 shows "the ion conductivity maintenance ratio of the solid electrolyte material after pulverization" of the solid electrolyte material of example 1.

[ analysis of Crystal Structure ]

The crystal structure of the solid electrolyte material of example 1 was analyzed. The solid electrolyte material of example 1 was measured for its X-ray diffraction in a dry atmosphere having a dew point of-45 ℃ or lower using an X-ray diffraction apparatus (rig aku, MiniFlex600)Figure (a). As the X-ray source, Cu-Ka rays were used. That is, an X-ray diffraction pattern was measured by the theta-2 theta method using Cu-Ka rays (wavelength: 0.15405 nm and 0.15444 nm) as X-rays. The X-ray diffraction pattern of the solid electrolyte material of example 1 was compared with the X-ray diffraction pattern of ICSD loading, for 3 or more diffraction peaks having high intensity. For example, with Li₃ErCl₆In similar hexagonal crystals, strong diffraction peaks were observed at4 diffraction angles of approximately 15.3 °, approximately 16.7 °, approximately 30.5 °, and approximately 39.6 °. As mentioned above, in the crystallization with Li₃ErCl₆In a different case, at least one of the diffraction angle of the diffraction peak and the intensity ratio of the diffraction peak is different from that of Li₃ErCl₆The difference in (c). Taking into account diffraction peaks and comparatively weak peaks having diffraction angles slightly different from the above-mentioned diffraction angles, with Li₃ErCl₆When the X-ray diffraction patterns of (A) and (B) are similar, the crystal structure is judged to be hexagonal. Table 1 shows the crystal structure of the solid electrolyte material of example 1.

In the X-ray diffraction pattern of the solid electrolyte material in example 1, the full width at half maximum of the peak having the highest intensity in the range where the value of the diffraction angle 2 θ is 25 ° or more and 35 ° or less is FWHM, and the diffraction angle at the center of the peak is 2 θ_pAt, FWHM/2 θ_p≤0.015。

[ molar ratio of Li to X Li/X ]

The molar ratio Li/X of Li to X in the solid electrolyte material of example 1 was determined. The molar ratio Li/X is determined from the molar ratio of Li to X contained in the raw material powder. Table 1 shows the molar ratio Li/X of the solid electrolyte material of example 1.

[ average ionic radius ratio ]

The average ionic radius ratio of the solid electrolyte material of example 1 was calculated based on the above formula.

The solid electrolyte material of example 1 contains Li, Ca, and Y as cations and Cl and Br as anions. The ionic radii of Li, Ca, Y, Cl and Br were 0.76, 1.00, 0.90, 1.81 and 1.96, respectively. The amounts of Li, Ca, Y, Cl and Br were 2.800, 0.100, 1.000 and 4.00 respectively0 and 2.000. Thus, the average ionic radius r of the cation_CThe value was 0.8020 by calculation (2.800X 0.76+ 0.100X 1.00+ 1.000X 0.90)/(2.800+0.100+ 1.000). Average ionic radius r of anion_AIt was calculated to be (4.000X 1.81+ 2.000X 1.96)/(4.000+2.000) to be 1.860. Thus, the average ionic radius ratio is calculated by calculating r_C/r_AThe value was calculated to be 0.431.

[ production of Secondary Battery ]

The solid electrolyte material of example 1B and Li (Ni, Co, Mn) O were mixed in a dry argon atmosphere₂Prepared at a volume ratio of 50: 50. These prepared materials were mixed with an agate mortar, thereby obtaining a positive electrode mixture. Li (Ni, Co, Mn) O₂And functions as a positive electrode active material.

In an insulating cylinder having an inner diameter of 9.5 mm, a sulfide solid electrolyte Li was charged₆PS₅Cl (60mg), the solid electrolyte material of example 1B (20mg, equal to a thickness of 700 μm), and the positive electrode mixture (9.6mg) were sequentially stacked to obtain a stacked body. A pressure of 720MPa was applied to the laminate to form the 1 st electrode and the solid electrolyte layer.

Next, metal InLi was laminated on the solid electrolyte layer. A pressure of 80MPa was applied to the laminate to form a 2 nd electrode. The thickness of the 2 nd electrode after pressing was 600 μm. Thus, a laminate of the 1 st electrode, the solid electrolyte layer, and the 2 nd electrode was produced. The 1 st electrode is a positive electrode and the 2 nd electrode is a negative electrode.

Current collectors formed of stainless steel were mounted to the 1 st and 2 nd electrodes, and then current collecting leads were mounted to the current collectors. Finally, the inside of the insulating cylinder is sealed by isolating the inside of the insulating cylinder from the outside atmosphere using an insulating sleeve.

Thus, a secondary battery of example 1 was produced.

[ Charge/discharge test ]

Fig. 3 is a graph showing the initial discharge characteristics of the secondary battery of example 1.

The initial discharge characteristics shown in fig. 3 were measured by the following method.

The secondary electricity of example 1 was chargedThe cell was placed in a thermostatic bath at 25 ℃. At 0.1mA/cm²Until a voltage of 3.7V is reached. Then, at 0.1mA/cm²Until a voltage of 1.9V is reached. This current density corresponds to a 0.05C rate.

As a result of the above measurement, the secondary battery of example 1 had an initial discharge capacity of 1.2 mAh.

< example 2 >

[ production of solid electrolyte Material ]

As raw material powder, LiBr LiCl CaBr₂:YCl₃LiBr, LiCl and CaBr were prepared in a molar ratio of 1.7:1.0:0.15:1.0₂And YCl₃。

In the same manner as in example 1 except for the above, the solid electrolyte material of example 2A (i.e., the solid electrolyte material before pulverization) and the solid electrolyte material of example 2B (i.e., the solid electrolyte material after pulverization) were obtained.

[ evaluation of the ion conductivity maintenance ratio of the solid electrolyte material after pulverization ]

The ion conductivity maintenance factor of the pulverized solid electrolyte material of example 2 was measured in the same manner as in example 1.

Table 1 shows "the ionic conductivity maintenance ratio of the solid electrolyte material after pulverization" of example 2.

[ analysis of Crystal Structure ]

The crystal structure of the solid electrolyte material of example 2 was analyzed in the same manner as in example 1. Table 1 shows the crystal structure of the solid electrolyte material of example 2.

[ molar ratio of Li to X Li/X ]

In example 2, the molar ratio Li/X of Li to X was determined in the same manner as in example 1. Table 1 shows the molar ratio Li/X of the solid electrolyte material of example 2.

[ average ionic radius ratio ]

In example 2, the average ionic radius ratio was calculated in the same manner as in example 1. The calculated values are shown in table 1.

< example 3 >

As the raw material powder, LiBr CaBr₂:YCl₃LiBr, LiCl and CaBr were prepared in a molar ratio of 2.2:0.4:1.0₂And YCl₃。

In the same manner as in example 1 except for the above, the solid electrolyte material of example 3A (i.e., the solid electrolyte material before pulverization) and the solid electrolyte material of example 3B (i.e., the solid electrolyte material after pulverization) were obtained.

[ evaluation of the ion conductivity maintenance ratio of the solid electrolyte material after pulverization ]

The ion conductivity maintenance factor of the pulverized solid electrolyte material of example 3 was measured in the same manner as in example 1.

Table 1 shows "the ionic conductivity maintenance ratio of the solid electrolyte material after pulverization" of example 3.

[ analysis of Crystal Structure ]

The crystal structure of the solid electrolyte material of example 3 was analyzed in the same manner as in example 1. Table 1 shows the crystal structure of the solid electrolyte material of example 3.

[ molar ratio of Li to X Li/X ]

In example 3, the molar ratio Li/X of Li to X was determined in the same manner as in example 1. Table 1 shows the molar ratio Li/X of the solid electrolyte material of example 3.

[ average ionic radius ratio ]

In example 3, the average ionic radius ratio was calculated in the same manner as in example 1. The calculated values are shown in table 1.

< example 4 >

As the raw material powder, LiBr LiCl: GdCl₃:YCl₃LiBr, LiCl, and GdCl were prepared at a molar ratio of 2.0:1.0:0.5:0.5₃And YCl₃。

In the same manner as in example 1 except for the above, the solid electrolyte material of example 4A (i.e., the solid electrolyte material before pulverization) and the solid electrolyte material of example 4B (i.e., the solid electrolyte material after pulverization) were obtained.

[ evaluation of the ion conductivity maintenance ratio of the solid electrolyte material after pulverization ]

The ion conductivity maintenance factor of the pulverized solid electrolyte material of example 4 was measured in the same manner as in example 1.

Table 1 shows "the ionic conductivity maintenance ratio of the solid electrolyte material after pulverization" of example 4.

[ analysis of Crystal Structure ]

The crystal structure of the solid electrolyte material of example 4 was analyzed in the same manner as in example 1. Table 1 shows the crystal structure of the solid electrolyte material of example 4.

[ molar ratio of Li to X Li/X ]

In example 4, the molar ratio Li/X of Li to X was determined in the same manner as in example 1. Table 1 shows the molar ratio Li/X of the solid electrolyte material of example 4.

[ average ionic radius ratio ]

In example 4, the average ionic radius ratio was calculated in the same manner as in example 1. The calculated values are shown in table 1.

< example 5 >

As the raw material powder, LiBr LiCl: GdCl₃:YCl₃LiBr, LiCl, and GdCl were prepared at a molar ratio of 2.0:1.0:0.9:0.1₃And YCl₃。

In the same manner as in example 1 except for the above, the solid electrolyte material of example 5A (i.e., the solid electrolyte material before pulverization) and the solid electrolyte material of example 5B (i.e., the solid electrolyte material after pulverization) were obtained.

[ evaluation of the ion conductivity maintenance ratio of the solid electrolyte material after pulverization ]

The ion conductivity maintenance factor of the pulverized solid electrolyte material of example 5 was measured in the same manner as in example 1.

Table 1 shows "the ionic conductivity maintenance ratio of the solid electrolyte material after pulverization" of example 5.

[ analysis of Crystal Structure ]

The crystal structure of the solid electrolyte material of example 5 was analyzed in the same manner as in example 1. Table 1 shows the crystal structure of the solid electrolyte material of example 5. Fig. 4 shows an X-ray diffraction pattern of the solid electrolyte materials of examples 5A and 5B.

[ molar ratio of Li to X Li/X ]

In example 5, the molar ratio Li/X of Li to X was determined in the same manner as in example 1. Table 1 shows the molar ratio Li/X of the solid electrolyte material of example 5.

[ average ionic radius ratio ]

In example 5, the average ionic radius ratio was calculated in the same manner as in example 1. The calculated values are shown in table 1.

< example 6 >

As the raw material powder, LiBr LiCl: GdCl₃LiBr, LiCl and GdCl were prepared at a molar ratio of 2.0:1.0:1.0₃。

In the same manner as in example 1 except for the above, the solid electrolyte material of example 6A (i.e., the solid electrolyte material before pulverization) and the solid electrolyte material of example 6B (i.e., the solid electrolyte material after pulverization) were obtained.

[ evaluation of the ion conductivity maintenance ratio of the solid electrolyte material after pulverization ]

The ion conductivity maintenance factor of the pulverized solid electrolyte material of example 6 was measured in the same manner as in example 1.

Table 1 shows "the ionic conductivity maintenance ratio of the solid electrolyte material after pulverization" of example 6.

[ analysis of Crystal Structure ]

The crystal structure of the solid electrolyte material of example 6 was analyzed in the same manner as in example 1. Table 1 shows the crystal structure of the solid electrolyte material of example 6.

[ molar ratio of Li to X Li/X ]

In example 6, the molar ratio Li/X of Li to X was determined in the same manner as in example 1. Table 1 shows the molar ratio Li/X of the solid electrolyte material of example 6.

[ average ionic radius ratio ]

In example 6, the average ionic radius ratio was calculated in the same manner as in example 1. The calculated values are shown in table 1.

< comparative example 1 >

LiBr YCl is used as raw material powder₃LiBr and YCl were prepared at a molar ratio of 3.0:1.0₃。

In the same manner as in example 1 except for the above, the solid electrolyte material of comparative example 1A (i.e., the solid electrolyte material before pulverization) and the solid electrolyte material of comparative example 1B (i.e., the solid electrolyte material after pulverization) were obtained.

[ evaluation of the ion conductivity maintenance ratio of the solid electrolyte material after pulverization ]

The ion conductivity maintenance ratio of the pulverized solid electrolyte material of comparative example 1 was measured in the same manner as in example 1.

Table 1 shows "the ionic conductivity maintenance ratio of the solid electrolyte material after pulverization" of comparative example 1.

[ analysis of Crystal Structure ]

The crystal structure of the solid electrolyte material of comparative example 1 was analyzed in the same manner as in example 1. Table 1 shows the crystal structure of the solid electrolyte material of comparative example 1.

[ molar ratio of Li to X Li/X ]

In comparative example 1, the molar ratio Li/X of Li to X was determined in the same manner as in example 1. Table 1 shows the molar ratio Li/X of the solid electrolyte material of comparative example 1.

[ average ionic radius ratio ]

In comparative example 1, the average ionic radius ratio was calculated in the same manner as in example 1. The calculated values are shown in table 1.

< comparative example 2 >

As the raw material powder, LiBr CaBr₂:YCl₃LiBr and CaBr were prepared at a molar ratio of 2.9:0.05:1.0₂And YCl₃。

In the same manner as in example 1 except for the above, the solid electrolyte material of comparative example 2A (i.e., the solid electrolyte material before pulverization) and the solid electrolyte material of comparative example 2B (i.e., the solid electrolyte material after pulverization) were obtained.

[ evaluation of the ion conductivity maintenance ratio of the solid electrolyte material after pulverization ]

The ion conductivity maintenance rate of the pulverized solid electrolyte material of comparative example 2 was measured in the same manner as in example 1.

Table 1 shows "the ionic conductivity maintenance ratio of the solid electrolyte material after pulverization" of comparative example 2.

[ analysis of Crystal Structure ]

The crystal structure of the solid electrolyte material of comparative example 2 was analyzed in the same manner as in example 1. Table 1 shows the crystal structure of the solid electrolyte material of comparative example 2.

[ molar ratio of Li to X Li/X ]

In comparative example 2, the molar ratio Li/X of Li to X was determined in the same manner as in example 1. Table 1 shows the molar ratio Li/X of the solid electrolyte material of comparative example 2.

[ average ionic radius ratio ]

In comparative example 2, the average ionic radius ratio was calculated in the same manner as in example 1. The calculated values are shown in table 1.

< comparative example 3 >

As the raw material powder, LiBr: GdCl₃:GdBr₃LiBr and GdCl were prepared at a molar ratio of 3.0:0.667:0.333₃And GdBr₃。

In the same manner as in example 1 except for the above, the solid electrolyte material of comparative example 3A (i.e., the solid electrolyte material before pulverization) and the solid electrolyte material of comparative example 3B (i.e., the solid electrolyte material after pulverization) were obtained.

[ evaluation of the ion conductivity maintenance ratio of the solid electrolyte material after pulverization ]

The ion conductivity maintenance rate of the pulverized solid electrolyte material of comparative example 3 was measured in the same manner as in example 1.

Table 1 shows "the ionic conductivity maintenance ratio of the solid electrolyte material after pulverization" of comparative example 3.

[ analysis of Crystal Structure ]

The crystal structure of the solid electrolyte material of comparative example 3 was analyzed in the same manner as in example 1. Table 1 shows the crystal structure of the solid electrolyte material of comparative example 3.

[ molar ratio of Li to X Li/X ]

In comparative example 3, the molar ratio Li/X of Li to X was determined in the same manner as in example 1. Table 1 shows the molar ratio Li/X of the solid electrolyte material of comparative example 3.

[ average ionic radius ratio ]

In comparative example 3, the average ionic radius ratio was calculated in the same manner as in example 1. The calculated values are shown in table 1.

< comparative example 4 >

As the raw material powder, LiBr: GdCl₃:GdBr₃:YCl₃LiBr and GdCl were prepared in a molar ratio of 3:0.567:0.333:0.1₃、GdBr₃And YCl₃。

In the same manner as in example 1 except for the above, the solid electrolyte material of comparative example 4A (i.e., the solid electrolyte material before pulverization) and the solid electrolyte material of comparative example 4B (i.e., the solid electrolyte material after pulverization) were obtained.

[ evaluation of the ion conductivity maintenance ratio of the solid electrolyte material after pulverization ]

The ion conductivity maintenance factor of the pulverized solid electrolyte material of comparative example 4 was measured in the same manner as in example 1.

Table 1 shows "the ionic conductivity maintenance ratio of the solid electrolyte material after pulverization" of comparative example 4.

[ analysis of Crystal Structure ]

The crystal structure of the solid electrolyte material of comparative example 4 was analyzed in the same manner as in example 1. Table 1 shows the crystal structure of the solid electrolyte material of comparative example 4. Fig. 4 shows X-ray diffraction patterns of the solid electrolyte materials of comparative examples 4A and 4B.

[ molar ratio of Li to X Li/X ]

In comparative example 4, the molar ratio Li/X of Li to X was determined in the same manner as in example 1. Table 1 shows the molar ratio Li/X of the solid electrolyte material of comparative example 4.

[ average ionic radius ratio ]

In comparative example 4, the average ionic radius ratio was calculated in the same manner as in example 1. The calculated values are shown in table 1.

TABLE 1

Comparing the solid electrolyte materials of examples 1 to 6 with the solid electrolyte materials of comparative examples 1 to 4, it is understood that, in the case where the solid electrolyte material composed of Li, M, and X (where M is at least one element selected from metal elements other than Li and semimetal elements, and X is at least one element selected from F, Cl, Br, and I) contains a crystal phase belonging to hexagonal crystal, the solid electrolyte material has good ion conductivity retention even when micronized.

Since the retention rate of the ion conductivity is good, when the solid electrolyte material is subjected to micronization such as pulverization, the ion conductivity of the solid electrolyte material containing hexagonal crystals is less likely to be reduced than the ion conductivity of a solid electrolyte material composed of only monoclinic crystals.

When the X-ray diffraction measurement was performed using Cu — K α rays, the crystallinity of the monoclinic solid electrolyte material pulverized for 6 minutes was greatly reduced as compared with that of the monoclinic solid electrolyte material pulverized for 1 minute. On the other hand, in the solid electrolyte material containing hexagonal crystals, the decrease in crystallinity due to pulverization is small. Since the change in the crystal structure of the crystal phase belonging to hexagonal crystal due to pulverization is smaller than that in a single crystal, the ion conductivity maintenance rate of the solid electrolyte material containing the crystal phase belonging to hexagonal crystal is good even after pulverization such as pulverization.

As a result of the investigation by the present inventors, it was clarified that the average ionic radius ratio is related to the determination of the crystal structure. As shown in table 1, if the value of the average ionic radius ratio is greater than 0.424, a crystal phase belonging to hexagonal crystals is precipitated.

As is clear from table 1, if the molar ratio Li/X is 0.37 or more and 0.50 or less, good ion conductivity can be obtained.

The solid electrolyte materials of examples 1 to 6 do not contain sulfur, and therefore do not generate hydrogen sulfide.

Industrial applicability

The solid electrolyte material of the present disclosure is useful, for example, for an all-solid lithium ion secondary battery.

Description of the reference numerals

100 solid electrolyte plasmid

101 powder of solid electrolyte material

201 positive electrode

202 electrolyte layer

203 negative electrode

204 positive electrode active material particle

205 negative electrode active material particle

300 compression molding die

301 framework

Lower part of 302 punch press

303 upper part of punch press

1000 cell