Solid electrolyte materials and batteries using the same

Abstract

A solid electrolyte material according to the present disclosure includes a crystal phase that includes Li, Zr, Al and F. In an X-ray diffraction pattern for the solid electrolyte material obtained by X-ray structural analysis using Cu–Kα rays, has: at least two peaks in a first range of diffraction angles 2θ between 21.2° and 23.5°; at least two peaks in a second range of diffraction angles 2θ between 29.3° and 31.8°; and at least two peaks in a third range of diffraction angles 2θ between 37° and 40.3°.

Description

【Technical Field】 【0001】 The present disclosure relates to a solid electrolyte material and a battery using the same. 【Background Art】 【0002】 Patent Document 1 discloses an all-solid-state battery using a sulfide solid electrolyte. 【0003】 Patent Document 2 discloses LiBF4 as a fluoride solid electrolyte material. 【Prior Art Documents】 【Non-Patent Documents】 【0004】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2011-129312 【Patent Document 2】 Japanese Patent Application Laid-Open No. 2008-277170 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 An object of the present disclosure is to provide a solid electrolyte material with improved heat resistance. 【Means for Solving the Problems】 【0006】 The solid electrolyte material of the present disclosure is a solid electrolyte material containing a crystal phase containing Li, Zr, Al, and F, in the X-ray diffraction pattern of the solid electrolyte material obtained by X-ray structure analysis using Cu-Kα rays, at least two peaks are present in the first range of diffraction angle 2θ from 21.2° to 23.5°, at least two peaks are present in the second range of diffraction angle 2θ from 29.3° to 31.8°, and at least two peaks are present in the third range of diffraction angle 2θ from 37° to 40.3°. [Effect of the Invention] 【0007】 The present disclosure provides a solid electrolyte material with improved heat resistance. [Brief Description of the Drawings] 【0008】 [Figure 1] FIG. 1 shows a cross-sectional view of the battery 1000 according to the second embodiment. [Figure 2] FIG. 2 is a diagram showing the X-ray diffraction patterns of the solid electrolyte materials according to Examples 1 to 3 and Comparative Example 1. [Figure 3] FIG. 3 shows a schematic diagram of the compression molding die 300 used to evaluate the ionic conductivity of the solid electrolyte material. [Figure 4] FIG. 4 is a graph showing the Cole-Cole plot obtained by impedance measurement of the solid electrolyte material according to Example 1. [Figure 5] FIG. 5 is a graph showing the conductivity retention rates of the solid electrolyte materials according to Examples 1 to 3 and Comparative Example 1 after heat treatment. [Figure 6] FIG. 6 is a graph showing the initial discharge characteristics of the batteries according to Example 1 and Comparative Example 1. [Modes for Carrying Out the Invention] 【0009】 Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. 【0010】 (First Embodiment) The solid electrolyte material according to the first embodiment includes a crystal phase containing Li, Zr, Al, and F. In the X-ray diffraction pattern of the solid electrolyte material according to the first embodiment obtained by X-ray structure analysis using Cu-Kα rays, at least two peaks exist in the first range of diffraction angle 2θ from 21.2° to 23.5°, at least two peaks exist in the second range of diffraction angle 2θ from 29.3° to 31.8°, and at least two peaks exist in the third range of diffraction angle 2θ from 37° to 40.3°. 【0011】 With the above configuration, the solid electrolyte material according to the first embodiment has high heat resistance. 【0012】 The solid electrolyte material according to the first embodiment has high heat resistance due to containing the above-mentioned crystalline phase. 【0013】 In this disclosure, "at least two peaks exist within a predetermined range (for example, the first range described above)" means "there are two peaks within a predetermined range that are clearly separable from each other." Here, "clearly separable from each other" means that, if the peak positions of the two peaks are 2θ1 and 2θ2, and the full width at half maximum of each peak is 2Δθ1 and 2Δθ2, then at least |2θ2-2θ1|>(2Δθ1+2Δθ2) is satisfied. 【0014】 The peak angle is the angle that indicates the maximum intensity of the peak-shaped portion where the signal-to-noise ratio (SNR) is 1.5 or higher and the full width at half maximum (FWHM) is 3° or less. FWHM is the angle that indicates the maximum intensity of the peak. MAX When the intensity is I MAX The width is represented by the difference between two diffraction angles that are half the value of the given value. The signal-to-noise ratio (SNR) is the ratio of the signal S to the background noise N. 【0015】 The above crystalline phases are not limited to a specific crystalline structure, but examples of crystalline structures include the following. 【0016】 In the first embodiment, more than half of the cations other than Li that constitute the solid electrolyte material may have an anion coordination number of 6 in the crystal structure. That is, more than half of the cations other than Li that constitute the solid electrolyte material in the first embodiment may have an anion coordination number of 6. It can be determined, for example, by Rietveld analysis based on X-ray diffraction profiles that more than half of the cations other than Li in the crystal structure have an anion coordination number of 6. 【0017】 All cations other than Li that constitute the solid electrolyte material according to the first embodiment may have an anion coordination number of 6 in the crystal structure. 【0018】 An example of such a crystal structure is a material having the composition represented by Li3AlF6. Hereinafter, the crystal structure of Li3AlF6 will be referred to as the "LAF structure" or "Li3AlF6 structure". The LAF structure can be classified as a Zn4Ta2O9 structure belonging to the space group C2 / c. Its detailed atomic arrangement is listed in the Inorganic Crystal Structure Database (ICSD) (ICSD No. 25226). 【0019】 The solid electrolyte material according to the first embodiment may include a heterocrystalline phase having a different crystal structure from the above-mentioned crystalline phase. 【0020】 In the solid electrolyte material according to the first embodiment, the coexistence of multiple ions with different ionic radii, such as Zr and Al, in the crystal structure can introduce strain into the structure. As a result, it is thought that regions where the potential of Li becomes unstable are created. This forms pathways for the diffusion of lithium ions. Furthermore, the inclusion of Zr with a high valence results in a composition where Li is deficient, creating unoccupied sites and making it easier for lithium ions to conduct. Therefore, lithium ion conductivity can be further improved. 【0021】 The process of manufacturing all-solid-state batteries using solid electrolyte materials often involves steps that apply heat. Specifically, these include steps such as drying the coated slurry or heating and pressing to improve contact between particles. Therefore, it is desirable that the solid electrolyte material according to the first embodiment be stable up to about 250°C. By forming a crystalline structure such as the crystalline phase described above, the structure becomes more robust, and its thermal stability can be improved. 【0022】 The solid electrolyte material according to the first embodiment can be used to obtain a battery with excellent charge-discharge characteristics. An example of such a battery is an all-solid-state battery. The all-solid-state battery may be a primary battery or a secondary battery. 【0023】 The solid electrolyte material according to the first embodiment is preferably sulfur-free. Sulfur-free solid electrolyte materials do not generate hydrogen sulfide when exposed to the atmosphere, thus offering superior safety. The sulfide solid electrolyte disclosed in Patent Document 1 may generate hydrogen sulfide when exposed to the atmosphere. 【0024】 The solid electrolyte material according to the first embodiment may have high oxidation resistance because it contains F. This is because F has a high oxidation-reduction potential. On the other hand, because F has high electronegativity, it has a relatively strong bond with Li. As a result, the lithium ion conductivity of solid electrolyte materials containing Li and F is usually low. For example, LiBF4 disclosed in Patent Document 2 has a conductivity of 6.67 × 10⁻⁶. -9 It has a low ionic conductivity of S / cm. In contrast, the solid electrolyte material according to Embodiment 1 further includes Zr and Al in addition to Li and F, for example, 7 × 10 -9 It can have an ionic conductivity of S / cm or higher. 【0025】 The X-ray diffraction pattern of the solid electrolyte material according to the first embodiment can be obtained by X-ray diffraction measurement using the θ-2θ method with Cu-Kα rays (wavelengths 1.5405 Å and 1.5444 Å, i.e., wavelengths 0.15405 nm and 0.15444 nm). 【0026】 In the X-ray diffraction pattern of the solid electrolyte material according to the first embodiment, at least two peaks may be present in the fourth range of the diffraction angle 2θ from 15° to 20°. A solid electrolyte material having such a crystalline phase has even higher heat resistance. 【0027】 The crystalline phase contained in the solid electrolyte material according to the first embodiment may have a Li3AlF6 structure or a structure in which the Li3AlF6 structure is distorted. A structure in which the Li3AlF6 structure is distorted refers to a structure in which the arrangement of anions is disordered, for example, due to the mixing of cations with different ionic radii. 【0028】 To enhance the ionic conductivity of the solid electrolyte material, the solid electrolyte material according to the first embodiment may contain anions other than F. Examples of such anions are Cl, Br, I, O, or Se. 【0029】 To improve the oxidation resistance of the solid electrolyte material, the ratio of the amount of substance of F to the total amount of substance of the anions constituting the solid electrolyte material according to the first embodiment may be 0.50 or more and 1.0 or less. 【0030】 The solid electrolyte material according to the first embodiment may consist substantially of Li, Zr, Al, and F. Here, "the solid electrolyte material according to the first embodiment consists substantially of Li, Zr, Al, and F" means that the ratio (i.e., mole fraction) of the total amount of substance of Li, Zr, Al, and F to the total amount of substance of all elements constituting the solid electrolyte material according to the first embodiment is 90% or more. For example, this ratio (i.e., mole fraction) may be 95% or more. The solid electrolyte material according to the first embodiment may consist only of Li, Zr, Al, and F. 【0031】 The solid electrolyte material according to the first embodiment may contain elements that are inevitably mixed in. Examples of such elements are hydrogen, oxygen, or nitrogen. Such elements may be present in the raw material powder of the solid electrolyte material or in the atmosphere used for manufacturing or storing the solid electrolyte material. 【0032】 To further enhance the ionic conductivity of the solid electrolyte material, in the solid electrolyte material according to the first embodiment, the ratio of the amount of Li to the total amount of Zr and Al may be 1.12 or more and 5.07 or less. 【0033】 The solid electrolyte material according to the first embodiment may contain a crystal phase represented by the following compositional formula (1). 【0034】 Li 6-(4-x)b (Zr 1-x Al x ) b F6···(1) In formula (1), 0 < x < 1 and 0 < b ≤ 1.5 are satisfied. The solid electrolyte material containing such a crystal phase has high ionic conductivity. 【0035】 In order to enhance the ionic conductivity of the solid electrolyte material, in formula (1), 0.01 ≤ x ≤ 0.99 may be satisfied, 0.2 ≤ x ≤ 0.95 may be satisfied, 0.4 ≤ x ≤ 0.95 may be satisfied, or 0.5 ≤ x ≤ 0.9 may be satisfied. 【0036】 The upper and lower limit values of the range of x in formula (1) may be defined by any combination selected from the numerical values of 0.01, 0.2, 0.4, {0.5}, 0.5, 0.7, 0.8, 0.95, and 0.99. 【0037】 In order to enhance the ionic conductivity of the solid electrolyte material, in formula (1), 0.7 ≤ b ≤ 1.3 may be satisfied, or 0.9 ≤ b ≤ 1.04 may be satisfied. 【0038】 The upper and lower limit values of the range of b in formula (1) may be defined by any combination selected from the numerical values of 0.7, 0.8, 0.9, 0.96, 1, 1.04, 1.1, 1.2, and 1.3. 【0039】 The solid electrolyte material according to the first embodiment may be Li 2.5 Zr 0.5 Al 0.5 F6, Li 2.8 Zr 0.2 Al 0.8 F6, or Li 2.9 Zr 0.1 Al 0.9 F6. (Zr Note: There seems to be a duplicate entry for "Zr" in the original text which might be a formatting error. I've translated it as it is. Also, there was an extra closing bracket in the original text which I've removed in the translation for better readability. If this is not correct, please provide more context or clarify the issue.【0040】 The shape of the solid electrolyte material according to the first embodiment is not limited. Examples of such shapes include needle-shaped, spherical, or ellipsoidal. The solid electrolyte material according to the first embodiment may be particles. The solid electrolyte material according to the first embodiment may have the shape of pellets or plates. 【0041】 If the solid electrolyte material according to the first embodiment is particulate (e.g., spherical), the solid electrolyte material may have a median diameter of 0.1 μm or more and 100 μm or less, or a median diameter of 0.5 μm or more and 10 μm or less. This allows the solid electrolyte material according to the first embodiment and other materials (e.g., active material) to be well dispersed. The median diameter refers to the particle size at which the cumulative deposition in the volume-based particle size distribution reaches 50%. The volume-based particle size distribution is measured, for example, by a laser diffraction measuring device or an image analysis device. 【0042】 <Method for manufacturing solid electrolyte materials> The solid electrolyte material according to the first embodiment is manufactured, for example, by the following method. 【0043】 Multiple halide raw material powders, weighed to have the desired composition, are mixed with an organic solvent in a mixing apparatus. 【0044】 For example, if the target composition is Li 2.8 Zr 0.2 Al 0.8 For F6, LiF, ZrF4, and AlF3 are prepared in a molar ratio of approximately 2.8:0.2:0.8. The raw material powders may be prepared in a pre-adjusted molar ratio to compensate for any compositional changes that may occur during the synthesis process. The raw material powders and organic solvents are introduced into a mixing device such as a planetary ball mill and mixed while being pulverized. In other words, the process is carried out using a wet ball mill. The raw material powders may be mixed before being introduced into the mixing device. 【0045】 After mixing, the balls are separated, and the resulting slurry containing dispersed particles is dried at a temperature corresponding to the boiling point of the organic solvent used. The resulting solid is then ground in a mortar to obtain the reaction product. 【0046】 The reactants may be calcined in a vacuum or an inert atmosphere. Calcination is carried out, for example, at a temperature of 100°C or higher and 300°C or lower for at least one hour. To suppress compositional changes during calcination, calcination may be carried out in a sealed container such as a quartz tube. 【0047】 As described above, a solid electrolyte material according to the first embodiment can be obtained by processing a mixture containing a raw material composition containing the constituent components of the solid electrolyte material and a solvent in a wet ball mill. 【0048】 The solvent used in the wet ball mill may be at least one selected from the group consisting of γ-butyrolactone, propylene carbonate, butyl acetate, ethanol, dimethyl sulfoxide, and tetralin. From the viewpoint of the dielectric constant of the solvent, N-methyl-2-pyrrolidone (NMP) may be used as the solvent. 【0049】 (Second Embodiment) The second embodiment will now be described. Matters described in the first embodiment will be omitted as appropriate. 【0050】 The battery according to the second embodiment comprises a positive electrode, an electrolyte layer, and a negative electrode. The electrolyte layer is located between the positive electrode and the negative electrode. 【0051】 At least one selected from the group consisting of a positive electrode, an electrolyte layer, and a negative electrode contains a solid electrolyte material according to the first embodiment. 【0052】 The battery according to the second embodiment contains the solid electrolyte material according to the first embodiment, and therefore has excellent charge and discharge characteristics. 【0053】 Figure 1 shows a cross-sectional view of the battery 1000 according to the second embodiment. 【0054】 The battery 1000 according to the second embodiment comprises a positive electrode 201, an electrolyte layer 202, and a negative electrode 203. The electrolyte layer 202 is provided between the positive electrode 201 and the negative electrode 203. 【0055】 The positive electrode 201 contains a positive electrode active material 204 and a solid electrolyte 100. 【0056】 The electrolyte layer 202 contains an electrolyte material. 【0057】 The negative electrode 203 contains a negative electrode active material 205 and a solid electrolyte 100. 【0058】 The solid electrolyte 100 includes, for example, the solid electrolyte material according to the first embodiment. The solid electrolyte 100 may also be particles containing the solid electrolyte material according to the first embodiment as the main component. Particles containing the solid electrolyte material according to the first embodiment as the main component mean particles in which the most abundant component in terms of molar ratio is the solid electrolyte material according to the first embodiment. The solid electrolyte 100 may also be particles made of the solid electrolyte material according to the first embodiment. 【0059】 The positive electrode 201 contains a material capable of intercalating and releasing metal ions (e.g., lithium ions). This material is, for example, the positive electrode active material 204. 【0060】 Examples of positive electrode active material 204 include lithium-containing transition metal oxides, transition metal fluorides, polyanions, fluorinated polyanion materials, transition metal sulfides, transition metal oxyfluorides, transition metal oxysulfides, or transition metal oxynitrides. Examples of lithium-containing transition metal oxides include Li(Ni,Co,Mn)O2, Li(Ni,Co,Al)O2, or LiCoO2. 【0061】 In this disclosure, "(A, B, C)" means "at least one selected from the group consisting of A, B, and C." 【0062】 The shape of the positive electrode active material 204 is not limited to a specific shape. The positive electrode active material 204 may be particles. The positive electrode active material 204 may have a median diameter of 0.1 μm or more and 100 μm or less. When the positive electrode active material 204 has a median diameter of 0.1 μm or more, the positive electrode active material 204 and the solid electrolyte 100 can be well dispersed in the positive electrode 201. This improves the charge and discharge characteristics of the battery 1000. When the positive electrode active material 204 has a median diameter of 100 μm or less, the lithium diffusion rate within the positive electrode active material 204 is improved. This allows the battery 1000 to operate at high power. 【0063】 The positive electrode active material 204 may have a median diameter larger than that of the solid electrolyte 100. This allows the positive electrode active material 204 and the solid electrolyte 100 to be well dispersed in the positive electrode 201. 【0064】 In order to improve the energy density and output of the battery 1000, the ratio of the volume of the positive electrode active material 204 to the sum of the volume of the positive electrode active material 204 and the volume of the solid electrolyte 100 in the positive electrode 201 may be 0.30 or more and 0.95 or less. 【0065】 A coating layer may be formed on at least a portion of the surface of the positive electrode active material 204. The coating layer can be formed on the surface of the positive electrode active material 204, for example, before mixing with a conductive additive and a binder. Examples of coating materials included in the coating layer are sulfide solid electrolytes, oxide solid electrolytes, or halide solid electrolytes. If the solid electrolyte 100 contains a sulfide solid electrolyte, the coating material may contain the solid electrolyte material according to the first embodiment in order to suppress the oxidative decomposition of the sulfide solid electrolyte. If the solid electrolyte 100 contains the solid electrolyte material according to the first embodiment, the coating material may contain an oxide solid electrolyte in order to suppress the oxidative decomposition of the solid electrolyte material. As the oxide solid electrolyte, lithium niobate, which has excellent stability at high potentials, may be used. By suppressing oxidative decomposition, the overvoltage rise of the battery 1000 can be suppressed. 【0066】 To improve the energy density and output of battery 1000, the positive electrode 201 may have a thickness of 10 μm or more and 500 μm or less. 【0067】 The electrolyte layer 202 contains an electrolyte material. This electrolyte material is, for example, a solid electrolyte material. This solid electrolyte material may include the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may also be a solid electrolyte layer. 【0068】 The electrolyte layer 202 may contain 50% by mass or more of the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may contain 70% by mass or more of the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may contain 90% by mass or more of the solid electrolyte material according to the first embodiment. The electrolyte layer 202 may consist only of the solid electrolyte material according to the first embodiment. 【0069】 Hereinafter, the solid electrolyte material according to the first embodiment will be referred to as the first solid electrolyte material. A solid electrolyte material different from the first solid electrolyte material will be referred to as the second solid electrolyte material. 【0070】 The electrolyte layer 202 may contain not only a first solid electrolyte material but also a second solid electrolyte material. In the electrolyte layer 202, the first solid electrolyte material and the second solid electrolyte material may be uniformly dispersed. The layer made of the first solid electrolyte material and the layer made of the second solid electrolyte material may be stacked along the stacking direction of the battery 1000. 【0071】 The battery according to the second embodiment may comprise a positive electrode 201, a second electrolyte layer, a first electrolyte layer, and a negative electrode 203 in this order. Here, the solid electrolyte material contained in the first electrolyte layer may have a lower reduction potential than the solid electrolyte material contained in the second electrolyte layer. This allows the solid electrolyte material contained in the second electrolyte layer to be used without reduction. As a result, the charge and discharge efficiency of the battery 1000 can be improved. For example, if the second electrolyte layer contains the first solid electrolyte material, the first electrolyte layer may contain a sulfide solid electrolyte to suppress the reductive decomposition of the solid electrolyte material. This improves the charge and discharge efficiency of the battery 1000. The second electrolyte layer may also contain the first solid electrolyte material. Since the first solid electrolyte material has high oxidation resistance, a battery with excellent charge and discharge characteristics can be realized. 【0072】 The electrolyte layer 202 may consist solely of the second solid electrolyte material. 【0073】 The electrolyte layer 202 may have a thickness of 1 μm or more and 1000 μm or less. If the electrolyte layer 202 has a thickness of 1 μm or more, the positive electrode 201 and the negative electrode 203 are less likely to short-circuit. If the electrolyte layer 202 has a thickness of 1000 μm or less, the battery 1000 can operate at high output. 【0074】 Examples of second solid electrolyte materials are Li2MgX4, Li2FeX4, Li(Al,Ga,In)X4, Li3(Al,Ga,In)X6, or LiI, where X is at least one selected from the group consisting of F, Cl, Br, and I. 【0075】 To improve the energy density and output of the battery 1000, the electrolyte layer 202 may have a thickness of 1 μm or more and 1000 μm or less. 【0076】 The negative electrode 203 contains a material capable of intercalating and releasing metal ions (e.g., lithium ions). This material is, for example, the negative electrode active material 205. 【0077】 Examples of negative electrode active materials 205 are metallic materials, carbon materials, oxides, nitrides, tin compounds, or silicon compounds. Metallic materials may be elemental metals or alloys. Examples of metallic materials are lithium metal or lithium alloys. Examples of carbon materials are natural graphite, coke, carbon in the process of graphitization, carbon fibers, spheroidal carbon, artificial graphite, or amorphous carbon. From the viewpoint of capacity density, preferred examples of negative electrode active materials are silicon (i.e., Si), tin (i.e., Sn), silicon compounds, or tin compounds. 【0078】 The negative electrode active material 205 may be selected considering the reduction resistance of the solid electrolyte material contained in the negative electrode 203. For example, if the negative electrode 203 contains a first solid electrolyte material, the negative electrode active material 205 may be a material capable of intercalating and releasing lithium ions at a voltage of 0.27 V or higher relative to lithium. Examples of such negative electrode active materials are titanium oxide, indium metal, or lithium alloy. An example of titanium oxide is Li4Ti5O 12 The negative electrode active material is either LiTi2O4 or TiO2. By using the above negative electrode active material, the reductive decomposition of the first solid electrolyte material contained in the negative electrode 203 can be suppressed. As a result, the charge and discharge efficiency of the battery 1000 can be improved. 【0079】 The shape of the negative electrode active material 205 is not limited to a specific shape. The negative electrode active material 205 may be particles. The negative electrode active material 205 may have a median diameter of 0.1 μm or more and 100 μm or less. When the negative electrode active material 205 has a median diameter of 0.1 μm or more, the negative electrode active material 205 and the solid electrolyte 100 can be well dispersed in the negative electrode 203. This improves the charge and discharge characteristics of the battery 1000. When the negative electrode active material 205 has a median diameter of 100 μm or less, the lithium diffusion rate within the negative electrode active material 205 is improved. This allows the battery 1000 to operate at high power. 【0080】 The negative electrode active material 205 may have a larger median diameter than the solid electrolyte 100. This allows the negative electrode active material 205 and the solid electrolyte 100 to be well dispersed in the negative electrode 203. 【0081】 In order to improve the energy density and output of the battery 1000, the ratio of the volume of the negative electrode active material 205 to the sum of the volume of the negative electrode active material 205 and the volume of the solid electrolyte 100 in the negative electrode 203 may be 0.30 or more and 0.95 or less. 【0082】 To improve the energy density and output of the battery 1000, the negative electrode 203 may have a thickness of 10 μm or more and 500 μm or less. 【0083】 At least one selected from the group consisting of a positive electrode 201, an electrolyte layer 202, and a negative electrode 203 may contain a second solid electrolyte material for the purpose of enhancing ionic conductivity, chemical stability, and electrochemical stability. 【0084】 The second solid electrolyte material may be a sulfide solid electrolyte. 【0085】 Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge 0.25 P 0.75 S4, or Li 10 GeP2S 12 That is the case. 【0086】 If the electrolyte layer 202 contains a first solid electrolyte material, the negative electrode 203 may contain a sulfide solid electrolyte to suppress the reductive decomposition of the solid electrolyte material. By covering the negative electrode active material with an electrochemically stable sulfide solid electrolyte, contact between the first solid electrolyte material and the negative electrode active material can be suppressed. As a result, the internal resistance of the battery 1000 can be reduced. 【0087】 The second solid electrolyte material may be an oxide solid electrolyte. 【0088】 Examples of oxide solid electrolytes are: (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 or its elemental substitutions, (ii) Perovskite-type solid electrolytes such as (LaLi)TiO3, (iii) Li 14 ZnGe4O 16 , LISICON-type solid electrolytes such as Li4SiO4, LiGeO4 or their elementally substituted counterparts, (iv)Li7La3Zr2O 12 or a garnet-type solid electrolyte such as an elemental substitution thereof, (v) Li3PO4 or its N-substituted derivatives, That is the case. 【0089】 As described above, the second solid electrolyte material may be a halide solid electrolyte. 【0090】 Examples of halide solid electrolytes are Li2MgX4, Li2FeX4, Li(Al,Ga,In)X4, Li3(Al,Ga,In)X6, or LiI, where X is at least one selected from the group consisting of F, Cl, Br, and I. 【0091】 Other examples of halide solid electrolytes include Li a Me b Y c This is a compound represented by Z6. Here, a+mb+3c=6 and c>0 are satisfied. Me is at least one selected from the group consisting of metallic elements other than Li and Y and metalloid elements. Z is at least one selected from the group consisting of F, Cl, Br, and I. m represents the valence of Me. "Metalloid elements" are B, Si, Ge, As, Sb, and Te. "Metallic elements" are all elements in groups 1 through 12 of the periodic table (except hydrogen), and all elements in groups 13 through 16 of the periodic table (except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se). 【0092】 To improve the ionic conductivity of the halide solid electrolyte, Me may be at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb. 【0093】 The halide solid electrolyte may be Li3YCl6 or Li3YBr6. 【0094】 The second solid electrolyte material may be an organic polymer solid electrolyte. 【0095】 Examples of organic polymer solid electrolytes include polymer compounds and lithium salt compounds. 【0096】 Polymer compounds may have an ethylene oxide structure. Polymer compounds having an ethylene oxide structure can contain a large amount of lithium salt, and therefore their ionic conductivity can be further increased. 【0097】 Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. One lithium salt selected from these may be used alone, or a mixture of two or more lithium salts selected from these may be used. 【0098】 At least one selected from the group consisting of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a non-aqueous electrolyte, a gel electrolyte, or an ionic liquid to facilitate the transfer of lithium ions and improve the output characteristics of the battery. 【0099】 The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent. 【0100】 Examples of non-aqueous solvents include cyclic carbonate solvents, linear carbonate solvents, cyclic ether solvents, linear ether solvents, cyclic ester solvents, linear ester solvents, or fluorinated solvents. Examples of cyclic carbonate solvents are ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of linear carbonate solvents are dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of cyclic ether solvents are tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Linear ether solvents are 1,2-dimethoxyethane or 1,2-diethoxyethane. An example of a cyclic ester solvent is γ-butyrolactone. An example of a linear ester solvent is methyl acetate. Examples of fluorinated solvents are fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, fluoroethyl methyl carbonate, or fluorodimethylene carbonate. One non-aqueous solvent selected from these may be used alone, or a combination of two or more non-aqueous solvents selected from these may be used. 【0101】 Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. One lithium salt selected from these may be used alone, or a mixture of two or more lithium salts selected from these may be used. The concentration of the lithium salt is, for example, in the range of 0.5 mol / L or more and 2 mol / L or less. 【0102】 Polymer materials impregnated with a non-aqueous electrolyte can be used as the gel electrolyte. Examples of polymer materials include polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or polymers having ethylene oxide bonds. 【0103】 Examples of cations contained in ionic liquids are: (i) aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium, (ii) Aliphatic cyclic ammonium compounds such as pyrrolidiniums, morpholiniums, imidazoliniums, tetrahydropyrimidiniums, piperadiniums, or piperidiniums, (iii) Nitrogen-containing heterocyclic aromatic cations such as pyridinium or imidazolium That is the case. 【0104】 An example of anion contained in an ionic liquid is PF6. - BF4 - SbF6 - AsF6 - , SO3CF3 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9) - , or C(SO2CF3)3 - That is the case. 【0105】 The ionic liquid may contain lithium salts. 【0106】 At least one selected from the group consisting of a positive electrode 201, an electrolyte layer 202, and a negative electrode 203 may contain a binder to improve the adhesion between particles. 【0107】 Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resins, polyamides, polyimides, polyamide-imides, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyethers, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, or carboxymethylcellulose. Copolymers can also be used as binders. Examples of such binders are copolymers of two or more 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 materials selected from these may also be used as a binder. 【0108】 At least one of the positive electrode 201 and the negative electrode 203 may contain a conductive additive to improve electronic conductivity. 【0109】 Examples of conductive additives are: (i) Graphites such as natural graphite or artificial graphite, (ii) Carbon blacks such as acetylene black or Ketjen black, (iii) Conductive fibers such as carbon fibers or metal fibers, (iv) Carbon fluoride, (v) Metal powders such as aluminum, (vi) Conductive whiskers such as zinc oxide or potassium titanate, (vii) conductive metal oxides such as titanium oxide, or (viii) Conductive polymer compounds such as polyaniline, polypyrrole, or polythiophene, Therefore, to reduce costs, the conductive additives described in (i) or (ii) above may be used. 【0110】 Examples of battery shapes according to the second embodiment include coin-shaped, cylindrical, prismatic, sheet-shaped, button-shaped, flat, or stacked types. 【0111】 The battery according to the second embodiment may be manufactured, for example, by preparing a material for forming a positive electrode, a material for forming an electrolyte layer, and a material for forming a negative electrode, and then fabricating a laminate in which the positive electrode, electrolyte layer, and negative electrode are arranged in that order by a known method. [Examples] 【0112】 The present disclosure will be described in more detail below with reference to examples and comparative examples. 【0113】 <Example 1> (Preparation of solid electrolyte materials) In an argon atmosphere with a dew point of -60°C or lower (hereinafter referred to as a "dry argon atmosphere"), LiF, ZrF4, and AlF3 were prepared as raw material powders in a molar ratio of LiF:ZrF4:AlF3 = 2.5:0.5:0.5. These raw material powders, along with 1 mmΦ balls (25 g), were placed in a 45 cc pod for a planetary ball mill. γ-butyrolactone (GBL) was added dropwise to the pod as an organic solvent to achieve a solid content ratio of 30%. Here, the solid content ratio is calculated as {(mass of raw materials) / (mass of raw materials + mass of solvent)} × 100. Milling was performed using a planetary ball mill at 500 rpm for 12 hours. After milling, the balls were separated to obtain a slurry. The obtained slurry was dried at 200°C for 1 hour under a nitrogen flow using a mantle heater. The obtained solid material was ground in a mortar to obtain the powder of the solid electrolyte material according to Example 1. The solid electrolyte material according to Example 1 is Li 2.5 Zr 0.5 Al 0.5 It had a composition represented by F6. 【0114】 (Analysis of crystal structure) Figure 2 is a graph showing the X-ray diffraction pattern of the solid electrolyte material according to Example 1. The results shown in Figure 2 were measured by the following method. 【0115】 The X-ray diffraction patterns of the solid electrolyte material according to Example 1 were measured using an X-ray diffractometer (RIGAKU, MiniFlex600) in a dry atmosphere with a dew point of -45°C or lower. Cu-Kα rays (wavelengths 1.5405 Å and 1.5444 Å) were used as the X-ray source. X-ray diffraction was measured using the θ-2θ method. 【0116】 In the X-ray diffraction patterns of the solid electrolyte material according to Example 1, relatively high-intensity peaks were observed at 21.5°, 22.71°, 29.84°, 31.1°, 37.86°, and 39.43°. 【0117】 These peaks roughly coincided with the peak locations of some of the X-ray diffraction patterns observed from the LAF structure. 【0118】 (Evaluation of ionic conductivity) Figure 3 shows a schematic diagram of a pressure-molding die 300 used to evaluate the ionic conductivity of a solid electrolyte material. 【0119】 The pressure forming die 300 comprised a punch upper section 301, a frame 302, and a punch lower section 303. The frame 302 was formed from insulating polycarbonate. The punch upper section 301 and the punch lower section 303 were formed from electronically conductive stainless steel. 【0120】 Using the pressure molding die 300 shown in Figure 3, the ionic conductivity of the solid electrolyte material according to Example 1 was evaluated by the following method. 【0121】 In a dry atmosphere having a dew point of -30°C or lower, the powder of the solid electrolyte material according to Example 1 was filled into the inside of a pressure molding die 300. Inside the pressure molding die 300, a pressure of 400 MPa was applied to the solid electrolyte material according to Example 1 using the upper part of the punch 301 and the lower part of the punch 303. 【0122】 With pressure still applied, the upper part 301 and lower part 303 of the punch were connected to a potentiostat (BioLogic, VSP300) equipped with a frequency response analyzer. The upper part 301 of the punch was connected to the working electrode and potential measurement terminals. The lower part 303 of the punch was connected to the counter electrode and reference electrode. The impedance of the solid electrolyte material was measured at room temperature using electrochemical impedance measurement. 【0123】 Figure 4 is a graph showing the Cole-Cole plot obtained by impedance measurement of the solid electrolyte material according to Example 1. 【0124】 In Figure 4, the real value of the impedance at the measurement point where the absolute value of the phase of the complex impedance is smallest was considered to be the resistance value to ion conduction of the solid electrolyte material. This real value is indicated by the arrow R in Figure 4. SE Refer to [reference]. Using the resistance value, the ionic conductivity was calculated based on the following formula (2). 【0125】 σ=(R SE ×S / t) -1 ...(2) Here, σ represents the ionic conductivity. S represents the contact area between the solid electrolyte material and the upper part 301 of the punch (equal to the cross-sectional area of ​​the hollow part of the frame mold 302 in Figure 3). SE represents the resistance value of the solid electrolyte material in impedance measurement. t represents the thickness of the solid electrolyte material (i.e., the thickness of the layer formed from the powder 101 of the solid electrolyte material in Figure 3). 【0126】 The ionic conductivity of the solid electrolyte material according to Example 1, measured at 25°C, was 7.88 × 10⁻⁶. -8The value was S / cm. 【0127】 (Evaluation of heat resistance) In a dry argon atmosphere, the solid electrolyte material according to Example 1 was placed in each of two alumina crucibles. One was heat-treated at 200°C for 1 hour, and the other at 250°C for 1 hour. The solid material obtained after heat treatment was crushed in a mortar as needed to obtain a powder sample. The ionic conductivity of the obtained powder sample was evaluated in the same manner as described in (Evaluation of Ionic Conductivity) above. Next, the retention rate of ionic conductivity after heat treatment was calculated based on the formula {(Ionic conductivity after heat treatment) / (Ionic conductivity before heat treatment)} × 100. Figure 5 is a graph showing the conductivity retention rate of the solid electrolyte material according to Example 1 after heat treatment. 【0128】 As a result, the ionic conductivity retention rates of the solid electrolyte material according to Example 1 after heat treatment at 200°C and 250°C were 104.2% and 87.5%, respectively. 【0129】 (Battery construction) In a dry argon atmosphere, the solid electrolyte material and the active material LiCoO2 according to Example 1 were prepared in a volume ratio of 30:70. These materials were mixed in an agate mortar. In this way, a cathode mixture was obtained. 【0130】 In an insulating cylinder with an inner diameter of 9.5 mm, Li3PS4 (57.41 mg), the solid electrolyte material according to Example 1 (26 mg), and the above-mentioned positive electrode mixture (9.1 mg) were layered in this order. A pressure of 300 MPa was applied to the resulting laminate to form a first electrolyte layer, a second electrolyte layer, and a positive electrode. That is, the second electrolyte layer formed from the solid electrolyte material according to Example 1 was sandwiched between the first electrolyte layer and the positive electrode. The thicknesses of the first and second electrolyte layers were 450 μm and 150 μm, respectively. 【0131】 Next, metallic Li (thickness: 200 μm) was laminated onto the first electrolyte layer. A pressure of 80 MPa was applied to the resulting laminate to form a negative electrode. 【0132】 Next, current collectors made of stainless steel were attached to the positive and negative electrodes, and current collector leads were attached to the current collectors. 【0133】 Finally, an insulating ferrule was used to isolate the inside of the insulating cylinder from the outside atmosphere, thereby sealing the inside of the cylinder. In this way, the battery according to Example 1 was obtained. 【0134】 (Charge / Discharge Test) Figure 6 is a graph showing the initial discharge characteristics of the battery according to Example 1. The initial charge-discharge characteristics were measured by the following method. 【0135】 The battery according to Example 1 was placed in a constant temperature bath at 85°C. 【0136】 13.5 μA / cm 2 The battery according to Example 1 was charged to a voltage of 4.2V at a current density of 0.01C. 【0137】 Next, 13.5 μA / cm 2 The battery according to Example 1 was discharged until it reached a voltage of 2.5V at the given current density. 【0138】 The charge-discharge test results showed that the battery according to Example 1 had an initial discharge capacity of 865 μAh. 【0139】 <Examples 2 and 3> (Preparation of solid electrolyte materials) In Example 2, LiF, ZrF4, and AlF3 were prepared as raw material powders in a molar ratio of LiF:ZrF4:AlF3 = 2.8:0.2:0.8. 【0140】 In Example 3, LiF, ZrF4, and AlF3 were prepared as raw material powders in a molar ratio of LiF:ZrF4:AlF3 = 2.9:0.1:0.9. 【0141】 Except for the matters mentioned above, the solid electrolyte materials according to Examples 2 and 3 were obtained in the same manner as in Example 1. 【0142】 (Analysis of crystal structure) The X-ray diffraction patterns of the solid electrolyte materials in Examples 2 and 3 were measured in the same manner as in Example 1. The results are shown in Figure 2 and Table 2. 【0143】 The X-ray diffraction patterns of the solid electrolyte materials from Examples 2 and 3 were in close agreement with the peaks originating from the LAF structure. 【0144】 (Evaluation of ionic conductivity) The ionic conductivity of the solid electrolyte materials in Examples 2 and 3 was measured in the same manner as in Example 1. The results are shown in Table 1. 【0145】 (Evaluation of heat resistance) The heat resistance of the solid electrolyte materials in Examples 2 and 3 was evaluated in the same manner as in Example 1. The ionic conductivity retention rates of the solid electrolyte materials in Examples 2 and 3 are shown in Table 1. Figure 5 is a graph showing the conductivity retention rates of the solid electrolyte materials in Examples 2 and 3 after heat treatment. 【0146】 (Charge / Discharge Test) Using the solid electrolyte materials from Examples 2 and 3, batteries according to Examples 2 and 3 were obtained in the same manner as in Example 1. 【0147】 A charge-discharge test was performed using the batteries from Examples 2 and 3 in the same manner as in Example 1. As a result, the batteries from Examples 2 and 3 charged and discharged successfully. 【0148】 <Reference example 1> In a dry argon atmosphere, LiF, ZrF4, and AlF3 were prepared as raw material powders in a molar ratio of LiF:ZrF4:AlF3 = 2.5:0.5:0.5. These raw material powders were ground and mixed in a mortar. The resulting mixture was milled using a planetary ball mill at 500 rpm for 12 hours. In this way, the solid electrolyte material according to Reference Example 1 was obtained. 【0149】 As described above, the solid electrolyte material according to Reference Example 1 was prepared using a dry ball mill without the use of organic solvents. 【0150】 The ionic conductivity of the solid electrolyte material according to Reference Example 1 was measured in the same manner as in Example 1. As a result, the ionic conductivity measured at 25°C was 8.86 × 10⁻⁶. -7 The value was S / cm. 【0151】 Using the solid electrolyte material according to Reference Example 1, the crystal structure was analyzed and the heat resistance was evaluated in the same manner as in Example 1. 【0152】 From the X-ray diffraction pattern of the solid electrolyte material according to Reference Example 1, it was found that the solid electrolyte material according to Reference Example 1 mainly had an amorphous phase, and no peaks consistent with the LAF structure were observed. In other words, the X-ray diffraction pattern of the solid electrolyte material according to Reference Example 1 did not have the characteristics of "at least two peaks in the first range of diffraction angle 2θ from 21.2° to 23.5°, at least two peaks in the second range of diffraction angle 2θ from 29.3° to 31.8°, and at least two peaks in the third range of diffraction angle 2θ from 37° to 40.3°." 【0153】 Figure 5 is a graph showing the conductivity retention rate after heat treatment of the solid electrolyte material according to Reference Example 1. The ionic conductivity retention rates after heat treatment at 200°C and 250°C were 3.7% and 2.4%, respectively. 【0154】 <Comparative Example 1> LiBF4 was used as the solid electrolyte material, and the ionic conductivity was measured in the same manner as in Example 1. As a result, the ionic conductivity measured at 25°C was 6.67 × 10⁻⁶. -9 The value was S / cm. 【0155】 A battery according to Comparative Example 1 was obtained in the same manner as in Example 1, except that the solid electrolyte material from Comparative Example 1 was used as the solid electrolyte for the positive electrode mixture and the electrolyte layer. 【0156】 A charge-discharge test was performed using the battery from Comparative Example 1 in the same manner as in Example 1. Figure 6 is a graph showing the initial discharge characteristics of the battery from Comparative Example 1. As a result, the initial discharge capacity of the battery from Comparative Example 1 was 0.01 μAh or less. In other words, the battery from Comparative Example 1 neither charged nor discharged. 【0157】 [Table 1] 【0158】 [Table 2] 【0159】 <Consideration> The solid electrolyte materials according to Examples 1 to 3 have a capacitance of 7 × 10 at room temperature. -9 It has ionic conductivity of S / cm or higher. 【0160】 Compared to Reference Example 1, which is an amorphous phase, the solid electrolyte materials of Examples 1 to 3 exhibited a high ionic conductivity retention rate. In other words, the solid electrolyte materials of Examples 1 to 3 had high heat resistance. 【0161】 The solid electrolyte materials according to Examples 1 and 2, which have at least two peaks in the diffraction angle range of 15° to 20° in the X-ray diffraction pattern, have higher heat resistance than the solid electrolyte material according to Example 3, which does not have two peaks in that range. 【0162】 The batteries from Examples 1 to 3 were all charged and discharged at 85°C. On the other hand, the battery from Comparative Example 1 was neither charged nor discharged. 【0163】 The solid electrolyte materials according to Examples 1 to 3 do not contain sulfur, and therefore do not generate hydrogen sulfide. 【0164】 As described above, the solid electrolyte material according to this disclosure has high lithium-ion conductivity and sufficient heat resistance to be expected to be stable against the heat generated during the battery manufacturing process, making it suitable for providing a battery that can be charged and discharged well. [Industrial applicability] 【0165】 The solid electrolyte material of this disclosure can be used, for example, in all-solid-state lithium-ion secondary batteries. [Explanation of Symbols] 【0166】 100 solid electrolyte particles 101 Powder of solid electrolyte material 201 Positive electrode 202 Electrolyte layer 203 Negative electrode 204 Cathode active material 205 Anode active material 300 pressure molding dies 301 Punch Top 302 Frame type 303 Punch bottom 1000 batteries

Claims

[Claim 1] A solid electrolyte material comprising a crystalline phase containing Li, Zr, Al, and F, In the X-ray diffraction pattern of the solid electrolyte material obtained by X-ray structural analysis using Cu-Kα rays, At least two peaks exist in the first range of diffraction angles 2θ from 21.2° to 23.5°. At least two peaks exist in the second range of diffraction angle 2θ from 29.3° to 31.8°. and, At least two peaks exist in the third range of diffraction angle 2θ from 37° to 40.3°. The aforementioned crystalline phase is represented by the following compositional formula (1): Li 6-(4-x)b (Zr 1-x Al x ) b F 6 ... (1) Here, the conditions 0 < x < 1 and 0 < b ≤ 1.5 are satisfied. Solid electrolyte material. [Claim 2] More than half of the cations other than Li that constitute the solid electrolyte material have an anion coordination number of 6 in the crystal structure. The solid electrolyte material according to claim 1. [Claim 3] The crystalline phase is Li 3 AlF 6 Structure, or Li 3 AlF 6 The solid electrolyte material according to claim 1, having a distorted structure. [Claim 4] In the above compositional formula (1), 0.5 ≤ x ≤ 0.9 is satisfied. The solid electrolyte material according to claim 1. [Claim 5] In the aforementioned X-ray diffraction pattern, At least two peaks exist in the fourth range of diffraction angles 2θ from 15° to 20°. The solid electrolyte material according to claim 1. [Claim 6] positive electrode, Negative electrode, and An electrolyte layer provided between the positive electrode and the negative electrode, Equipped with, At least one selected from the group consisting of the positive electrode, the negative electrode, and the electrolyte layer contains the solid electrolyte material described in any one of claims 1 to 5. battery.