Solid electrolyte material and battery using the same

Abstract

The present disclosure relates to a solid electrolyte material containing Li, Zr, and F. Here, the molar ratio of Li to Zr is 3.5 or more, and in the X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα rays of the solid electrolyte material, the value of the full width at half maximum of the peak having the highest intensity in the range of diffraction angle 2θ of 42.5° or more and 44.7° or less is greater than 1.19 with respect to the value of the full width at half maximum of the peak corresponding to the (111) plane of Si measured under the same conditions.

Description

Technical Field

[0001] The present disclosure relates to a solid electrolyte material and a battery using the solid electrolyte material. Background Art

[0002] A all-solid-state battery using a sulfide solid electrolyte is disclosed in Patent Document 1.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-129312 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] An object of the present disclosure is to provide a solid electrolyte material having a high lithium ion conductivity.

[0008] Means for Solving the Problems

[0009] The present disclosure relates to a solid electrolyte material, wherein

[0010] it contains Li, Zr, and F,

[0011] here, the molar ratio of Li to Zr is 3.5 or more, and

[0012] in the X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα rays of the solid electrolyte material, the value of the full width at half maximum of the peak having the highest intensity in the range of diffraction angle 2θ of 42.5° or more and 44.7° or less, and the ratio of the value of the full width at half maximum of the peak corresponding to the (111) plane of Si measured under the same conditions is greater than 1.19.

[0013] Effects of the Invention

[0014] The present disclosure provides a solid electrolyte material having a high lithium ion conductivity. Brief Description of the Drawings

[0015] Figure 1 A cross-sectional view showing the battery 1000 of the second embodiment.

[0016] Figure 2 A cross-sectional view showing the battery 2000 of the second embodiment.

[0017] Figure 3 A graph showing the X-ray diffraction patterns of the solid electrolyte materials of Examples 1 to 9 and Comparative Example 1.

[0018] Figure 4 It represents Figure 3 a graph of the transformed spectrum of the solid electrolyte material of Example 1 obtained by transforming the horizontal axis of the graph of 2θ to q.

[0019] Figure 5 It is a schematic diagram of the compression molding die 300 used to evaluate the ionic conductivity of the solid electrolyte material.

[0020] Figure 6 It is a graph of the Cole-Cole plot obtained by impedance measurement of the solid electrolyte material of Example 1.

[0021] Figure 7 It is a graph showing the initial discharge characteristics of the batteries of Example 1 and Comparative Example 1. Detailed implementation mode

[0022] Hereinafter, the implementation modes of the present disclosure will be described with reference to the accompanying drawings.

[0023] (First implementation mode)

[0024] The solid electrolyte material of the first implementation mode contains Li, Zr, and F. Here, the molar ratio of Li to Zr is 3.5 or more. In the X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα rays for the solid electrolyte material of the first implementation mode, the value of the full width at half maximum of the peak having the highest intensity in the range of diffraction angle 2θ of 42.5° or more and 44.7° or less, and the ratio of the value of the full width at half maximum of the peak corresponding to the (111) plane of Si measured under the same conditions is greater than 1.19. Hereinafter, in the X-ray diffraction pattern obtained by X-ray diffraction measurement of the solid electrolyte material, the full width at half maximum of the peak having the highest intensity in the range of diffraction angle 2θ of 42.5° or more and 44.7° or less is referred to as "FWHM". In addition, the full width at half maximum of the peak corresponding to the (111) plane of Si is referred to as "FWHM Si ". Here, as Si measured under the same conditions as the X-ray diffraction measurement of the solid electrolyte material of the first implementation mode, a Si standard sample can be used. As the Si standard sample, for example, a standard Si powder manufactured by NIST can be used.

[0025] In the solid electrolyte material of the first implementation mode, by satisfying the above "FWHM relative to FWHM SiWhen the condition of "ratio greater than 1.19" is met, the lattice constants of the crystalline phase become uneven. As a result, in the solid electrolyte material of the first embodiment, regions with broad lattices are generated, making it easier to conduct lithium ions. Therefore, the solid electrolyte material of the first embodiment has a high lithium ion conductivity. Here, the so-called high lithium ion conductivity is, for example, 1×10 -9 S / cm or more. That is to say, the solid electrolyte material of the first embodiment can have, for example, an ionic conductivity of 1×10 -9 S / cm or more.

[0026] The solid electrolyte material of the first embodiment is not specified by the value of FWHM, but by the ratio of FWHM to FWHM Si So, when specifying the solid electrolyte material of the first embodiment, the measurement error due to the measuring device can also be not considered.

[0027] In the X-ray diffraction pattern of the solid electrolyte material of the first embodiment, the peak with the highest intensity in a single peak exists in the range of diffraction angle 2θ of 42.5° or more and 44.7° or less. By using such a peak, the value of FWHM can be correctly evaluated. Therefore, the ratio of FWHM to FWHM Si can be correctly evaluated. Furthermore, the so-called single peak refers to a peak that does not overlap with other peaks.

[0028] The solid electrolyte material of 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 can be a primary battery or a secondary battery.

[0029] The solid electrolyte material of the first embodiment preferably contains substantially no sulfur. The fact that the solid electrolyte material of the first embodiment contains substantially no sulfur means that this solid electrolyte material contains no sulfur as a constituent element except for sulfur inevitably mixed in as an impurity. In this case, the sulfur mixed in as an impurity in the solid electrolyte material is, for example, 1 mol% or less. From the perspective of safety, it is preferred that the solid electrolyte material of the first embodiment contains no sulfur. The sulfur-free solid electrolyte material has excellent safety because hydrogen sulfide does not occur even when exposed to the atmosphere. The sulfide solid electrolyte disclosed in Patent Document 1 can generate hydrogen sulfide when exposed to the atmosphere.

[0030] Since the solid electrolyte material of the first embodiment contains F, it can have high oxidation resistance. This is because F has a high redox potential.

[0031] The solid electrolyte material of the first embodiment may also substantially consist of Li, Zr, and F. Here, the statement that "the solid electrolyte material of the first embodiment substantially consists of Li, Zr, and F" means that the total molar ratio (i.e., mole fraction) of the amounts of Li, Zr, and F relative to the total amount of all elements constituting the solid electrolyte material of the first embodiment is 90% or more. As an example, this molar ratio (i.e., mole fraction) may also be 95% or more. The solid electrolyte material of the first embodiment may also consist only of Li, Zr, and F.

[0032] The solid electrolyte material of the first embodiment may also contain elements 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.

[0033] In the transformed spectrum where the horizontal axis of the X-ray diffraction pattern of the solid electrolyte material of the first embodiment is transformed from the diffraction angle 2θ to q, the value of the full width at half maximum of the peak having the highest intensity in the range of q of 2.96 or more and 3.10 or less, and the ratio of this value to the value of the full width at half maximum of the peak corresponding to the (111) plane of Si measured under the same conditions may also be greater than 1.19. Here, q satisfies the mathematical formula: q = 4πsinθ / λ. λ represents the wavelength of the X-ray used in the X-ray diffraction measurement.

[0034] In other words, in the above-mentioned transformed spectrum, for the value of the full width at half maximum of the peak having the highest intensity in the range of q of 2.96 or more and 3.10 or less, and the ratio of this value to the value of the full width at half maximum of the peak corresponding to the (111) plane of Si measured under the same conditions having a value greater than 1.19 and a solid electrolyte material containing Li, Zr, and F, it can be regarded as a solid electrolyte material containing Li, Zr, and F and satisfying FWHM / FWHM Si > 1.19. Therefore, regarding a solid electrolyte material containing Li, Zr, and F, the measurement results obtained using radiation other than X-rays (e.g., electron rays) can be transformed by using the mathematical formula: q = 4πsinθ / λ' (λ' represents the wavelength of this radiation) to obtain a transformed spectrum. In the transformed spectrum thus obtained, when the condition "the value of the full width at half maximum of the peak having the highest intensity in the range of q of 2.96 or more and 3.10 or less, and the ratio of this value to the value of the full width at half maximum of the peak corresponding to the (111) plane of Si measured under the same conditions is greater than 1.19" is satisfied, this solid electrolyte material can be regarded as the solid electrolyte material of the first embodiment.

[0035] In the solid electrolyte material of the first embodiment, FWHM relative to FWHM SiThe ratio can also be less than 5.0. Thus, a crystal structure with high ionic conductivity can be maintained. To improve the ionic conductivity of the solid electrolyte material, the FWHM relative to the FWHM Si The ratio can also be 1.25 or more and 3.88 or less.

[0036] The solid electrolyte material of the first embodiment may also contain a crystalline phase represented by the following compositional formula (1).

[0037] Li x ZrF 4+x Formula (1)

[0038] In formula (1), the mathematical formula: 3.5 ≤ x can be satisfied. The solid electrolyte material containing such a crystalline phase has a high ionic conductivity.

[0039] To improve the ionic conductivity of the solid electrolyte material, in formula (1), the mathematical formula: 3.5 ≤ x ≤ 4.5 can also be satisfied. It is also preferably satisfied with the mathematical formula: 3.8 ≤ x ≤ 4.5.

[0040] The upper limit value and the lower limit value of the range of x in formula (1) can be defined by any combination of values selected from 3.5, 3.8, 4, 4.2, and 4.5.

[0041] The shape of the solid electrolyte material of the first embodiment is not limited. Examples of the shape are needle-like, spherical, or ellipsoidal. The solid electrolyte material of the first embodiment may also be particles. The solid electrolyte material of the first embodiment may also be formed in the shape of a pellet or a plate.

[0042] When the shape of the solid electrolyte material of the first embodiment is, for example, granular (e.g., spherical), the solid electrolyte material may also have a median particle diameter of 0.1 μm or more and 100 μm or less. The median particle diameter means the particle diameter when the cumulative volume in the volume-based particle size distribution is 50%. The volume-based particle size distribution can be measured, for example, by a laser diffraction type measuring device or an image analysis device.

[0043] The solid electrolyte material of the first embodiment may also have a median particle diameter of 0.5 μm or more and 10 μm or less. Thus, the solid electrolyte material has higher conductivity. In addition, when the solid electrolyte material of the first embodiment is mixed with other materials such as an active material, the dispersion state of the solid electrolyte material and the other materials becomes good.

[0044] <Manufacturing method of solid electrolyte material>

[0045] The solid electrolyte material of the first embodiment can be manufactured, for example, by the following method.

[0046] Prepare the raw material powder and mix it in a manner to achieve the target composition. The raw material powder can also be a halide, for example.

[0047] As an example, when the target composition is Li4ZrF8, mix LiF and ZrF4 as the raw material powder at a molar ratio of about 4.0∶1.0. In order to offset the possible compositional changes during the synthesis process, the raw material powder can also be mixed at a pre-adjusted molar ratio.

[0048] React the raw material powders with each other in a mechanochemical manner (i.e., using the method of mechanochemical grinding) in a mixing device such as a planetary ball mill to obtain a reaction product. The reaction product can also be heat-treated in a vacuum or an inert atmosphere. Alternatively, the mixture of the raw material powders can also be heat-treated in a vacuum or an inert atmosphere. The heat treatment can be carried out, for example, at 100°C or higher and 400°C or lower for 1 hour or more. In order to suppress the compositional changes during the heat treatment, the raw material powders or the reaction product can also be heat-treated in a sealed container such as a quartz tube.

[0049] If the heat treatment temperature is increased or the time is extended, the value of FWHM of the obtained solid electrolyte material may decrease.

[0050] Through these methods, the solid electrolyte material of the first embodiment can be obtained.

[0051] The composition of the solid electrolyte material can be determined, for example, by ICP emission spectrometry, ion chromatography, inert gas fusion-infrared absorption method, or EPMA (Electron Probe Micro Analyzer) method. For example, the compositions of Li and Zr can be determined by ICP emission spectrometry, and the composition of F can be determined by ion chromatography.

[0052] (Second Embodiment)

[0053] Hereinafter, the second embodiment will be described. The matters described in the first embodiment can be omitted.

[0054] The battery of the second embodiment includes a positive electrode, a negative electrode, and an electrolyte layer. The electrolyte layer is provided between the positive electrode and the negative electrode. At least one selected from the positive electrode, the electrolyte layer, and the negative electrode contains the solid electrolyte material of the first embodiment. Since the battery of the second embodiment contains the solid electrolyte material of the first embodiment, it has excellent charge and discharge characteristics. This battery can also be an all-solid-state battery.

[0055] Figure 1 A cross-sectional view showing the battery 1000 of the second embodiment.

[0056] The battery 1000 of the second embodiment includes 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.

[0057] The positive electrode 201 contains positive electrode active material particles 204 and solid electrolyte particles 100.

[0058] The electrolyte layer 202 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte material.

[0059] The negative electrode 203 contains negative electrode active material particles 205 and solid electrolyte particles 100.

[0060] The solid electrolyte particles 100 are particles containing the solid electrolyte material of the first embodiment. The solid electrolyte particles 100 may also be particles composed of the solid electrolyte material of the first embodiment or particles containing the solid electrolyte material of the first embodiment as a main component. Here, the particles containing the solid electrolyte material of the first embodiment as a main component mean particles in which the component contained in the largest amount by molar ratio is the solid electrolyte material of the first embodiment.

[0061] The positive electrode 201 contains a material into which metal ions (such as lithium ions) can be inserted and extracted. This material is, for example, a positive electrode active material (such as positive electrode active material particles 204).

[0062] Examples of the positive electrode active material include lithium-containing transition metal oxides, transition metal fluorides, polyanion materials, fluorinated polyanion materials, transition metal sulfides, transition metal sulfur oxides, or transition metal nitrides. Examples of the lithium-containing transition metal oxides are Li(Ni, Co, Al)O2, Li(Ni, Co, Mn)O2, or LiCoO2. In the present disclosure, the notation “(Ni, Co, Al)” in the chemical formula represents at least one element selected from the group of elements within the parentheses. That is, “(Ni, Co, Al)” is synonymous with “at least one selected from Ni, Co, and Al”. The same applies to other elements.

[0063] The positive electrode active material particles 204 may have a median particle size of 0.1 μm or more and 100 μm or less. When the positive electrode active material particles 204 have a median particle size of 0.1 μm or more, the dispersion state of the positive electrode active material particles 204 and the solid electrolyte particles 100 in the positive electrode 201 becomes good. As a result, the charge and discharge characteristics of the battery are improved. When the positive electrode active material particles 204 have a median particle size of 100 μm or less, the lithium diffusion rate within the positive electrode active material particles 204 is increased. As a result, the battery can operate at a high output power.

[0064] The positive electrode active material particles 204 may also have a median particle size larger than that of the solid electrolyte particles 100. As a result, in the positive electrode 201, the dispersion state of the positive electrode active material particles 204 and the solid electrolyte particles 100 becomes good.

[0065] From the viewpoints of the energy density and output power of the battery, in the positive electrode 201, the ratio of the volume of the positive electrode active material particles 204 to the total volume of the positive electrode active material particles 204 and the solid electrolyte particles 100 may also be 0.30 or more and 0.95 or less.

[0066] A coating layer may also be formed on at least a part of the surface of the positive electrode active material particles 204. The coating layer may be formed on the surface of the positive electrode active material particles 204, for example, before mixing with the conductive assistant and the binder. Examples of the coating material contained in the coating layer include a sulfide solid electrolyte, an oxide solid electrolyte, or a halide solid electrolyte. When the solid electrolyte particles 100 contain a sulfide solid electrolyte, in order to suppress the oxidative decomposition of the sulfide solid electrolyte, the coating material may also contain the solid electrolyte material of the first embodiment. When the solid electrolyte particles 100 contain the solid electrolyte material of the first embodiment, in order to suppress the oxidative decomposition of the solid electrolyte material, the coating material may also contain an oxide solid electrolyte. As the oxide solid electrolyte, lithium niobate having excellent stability at high potentials may also be used. By suppressing the oxidative decomposition, an increase in the overvoltage of the battery can be suppressed.

[0067] From the viewpoints of the energy density and output power of the battery, the positive electrode 201 may also have a thickness of 10 μm or more and 500 μm or less.

[0068] The electrolyte layer 202 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte material. The electrolyte layer 202 may also be a solid electrolyte layer.

[0069] The electrolyte layer 202 may also contain the solid electrolyte material of the first embodiment. The electrolyte layer 202 may also be composed only of the solid electrolyte material of the first embodiment. The electrolyte layer 202 may also be composed only of a solid electrolyte material different from the solid electrolyte material of the first embodiment. Examples of the solid electrolyte material different from the solid electrolyte material of the first embodiment include Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, Li3(Al, Ga, In)X6, or LiI. Here, X is at least one selected from F, Cl, Br, and I.

[0070] Hereinafter, the solid electrolyte material of the first embodiment will be referred to as the first solid electrolyte material. The solid electrolyte material different from the solid electrolyte material of the first embodiment will be referred to as the second solid electrolyte material.

[0071] The electrolyte layer 202 contains not only the first solid electrolyte material but may also contain 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. Layers formed of the first solid electrolyte material and layers formed of the second solid electrolyte material may also be stacked along the stacking direction of the battery 1000.

[0072] Figure 2 A cross-sectional view showing the battery 2000 of the second embodiment.

[0073] As Figure 2 shown, the battery 2000 may also include a positive electrode 201, a first electrolyte layer 212, a second electrolyte layer 222, and a negative electrode 203. That is, the electrolyte layer 202 may include the first electrolyte layer 212 and the second electrolyte layer 222. The first electrolyte layer 212 is disposed between the positive electrode 201 and the negative electrode 203. The second electrolyte layer 222 is disposed between the first electrolyte layer 212 and the negative electrode 203.

[0074] In the battery 2000, the first electrolyte layer 212 may contain the solid electrolyte material of the first embodiment. Since the solid electrolyte material of the first embodiment has high oxidation resistance, the solid electrolyte material contained in the second electrolyte layer 222 can be used without being oxidized. As a result, the charge and discharge efficiency of the battery can be improved.

[0075] In the battery 2000, the solid electrolyte material contained in the second electrolyte layer 222 may have a lower reduction potential than the solid electrolyte material contained in the first electrolyte layer 212. Thereby, the solid electrolyte material contained in the first electrolyte layer 212 can be used without being reduced. As a result, the charge and discharge efficiency of the battery can be improved. For example, when the first electrolyte layer 212 contains the solid electrolyte material of the first embodiment, in order to suppress the reduction decomposition of the solid electrolyte material, the second electrolyte layer 222 may contain a sulfide solid electrolyte.

[0076] From the viewpoints of the energy density and output power of the battery, the electrolyte layer 202 may have a thickness of 1 μm or more and 1000 μm or less.

[0077] The negative electrode 203 contains a material capable of inserting and extracting metal ions (such as lithium ions). This material is, for example, a negative electrode active material (such as negative electrode active material particles 205).

[0078] Examples of the negative electrode active material include metal materials, carbon materials, oxides, nitrides, tin compounds, or silicon compounds. The metal material may be a single metal or may also be an alloy. Examples of the metal material are lithium metal or a lithium alloy. Examples of the carbon material include natural graphite, coke, graphitizable carbon, carbon fiber, spherical carbon, artificial graphite, or amorphous carbon. From the viewpoint of the capacity density, suitable examples of the negative electrode active material are silicon (i.e., Si), tin (i.e., Sn), a silicon compound, or a tin compound.

[0079] The negative electrode active material can also be selected in consideration of the reducibility resistance of the solid electrolyte material contained in the negative electrode 203. For example, when the negative electrode 203 contains the solid electrolyte material of the first embodiment, the negative electrode active material can also be a material that can intercalate and deintercalate lithium ions at 0.27 V or more relative to lithium. Examples of such a negative electrode active material are titanium oxide, indium metal, or a lithium alloy. Examples of the titanium oxide are Li4Ti5O 12 , LiTi2O4, or TiO2. By using the above negative electrode active material, the reduction decomposition of the solid electrolyte material of the first embodiment contained in the negative electrode 203 can be suppressed. As a result, the charge and discharge efficiency of the battery can be improved.

[0080] The negative electrode active material particles 205 can also have a median particle size of 0.1 μm or more and 100 μm or less. When the negative electrode active material particles 205 have a median particle size of 0.1 μm or more, in the negative electrode 203, the dispersion state of the negative electrode active material particles 205 and the solid electrolyte particles 100 becomes good. Thereby, the charge and discharge characteristics of the battery are improved. When the negative electrode active material particles 205 have a median particle size of 100 μm or less, the lithium diffusion rate in the negative electrode active material particles 205 is increased. Thereby, the battery can operate at a high output power.

[0081] The negative electrode active material particles 205 can also have a median particle size larger than that of the solid electrolyte particles 100. Thereby, in the negative electrode 203, the dispersion state of the negative electrode active material particles 205 and the solid electrolyte particles 100 becomes good.

[0082] From the viewpoints of the energy density and output power of the battery, in the negative electrode 203, the ratio of the volume of the negative electrode active material particles 205 to the total volume of the negative electrode active material particles 205 and the solid electrolyte particles 100 can also be 0.30 or more and 0.95 or less.

[0083] From the viewpoints of the energy density and output power of the battery, the negative electrode 203 can also have a thickness of 10 μm or more and 500 μm or less.

[0084] At least one selected from the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may also contain a second solid electrolyte material for the purpose of improving ionic conductivity, chemical stability, and electrochemical stability. Examples of the second solid electrolyte material include sulfide solid electrolytes, oxide solid electrolytes, halide solid electrolytes, or organic polymer solid electrolytes.

[0085] In the present disclosure, "sulfide solid electrolyte" means a solid electrolyte containing sulfur. "Oxide solid electrolyte" means a solid electrolyte containing oxygen. The oxide solid electrolyte may also contain anions other than oxygen (excluding sulfur anions and halogen anions). "Halide solid electrolyte" means a solid electrolyte containing a halogen element and not containing sulfur. The halide solid electrolyte may contain not only a halogen element but also oxygen.

[0086] The second solid electrolyte material may also be a sulfide solid electrolyte.

[0087] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, Li 3.25 Ge 0.25 P 0.75 S4 or Li 10 GeP2S 12 。

[0088] When the electrolyte layer 202 contains the solid electrolyte material of the first embodiment, in order to suppress the reductive decomposition of the solid electrolyte material, the negative electrode 203 may also contain a sulfide solid electrolyte. By coating the negative electrode active material with an electrochemically stable sulfide solid electrolyte, contact between the solid electrolyte material of the first embodiment and the negative electrode active material can be suppressed. As a result, the internal resistance of the battery can be reduced.

[0089] The second solid electrolyte material may also be an oxide solid electrolyte.

[0090] Examples of oxide solid electrolytes include:

[0091] (i) NASICON-type solid electrolytes such as LiTi2(PO4)3 or its elemental substitution products,

[0092] (ii) perovskite-type solid electrolytes such as (LaLi)TiO3,

[0093] (iii) LISICON-type solid electrolytes such as Li 14 ZnGe4O 16 , Li4SiO4, LiGeO4, or their elemental substitution products,

[0094] (iv) Li7La3Zr2O 12 a garnet-type solid electrolyte such as its elemental substitution product, or (v) Li3PO4 or its N substitution product.

[0095] As described above, the second solid electrolyte material may also be a halide solid electrolyte.

[0096] Examples of the halide solid electrolyte include Li2MgX4, Li2FeX4, Li(Al, Ga, In)X4, Li3(Al, Ga, In)X6, or LiI. Here, X is at least one selected from F, Cl, Br, and I.

[0097] Other examples of the halide solid electrolyte material are compounds represented by Li a Me b Y c X6. Here, a + mb + 3c = 6 and c > 0 are satisfied. Me is at least one selected from metal elements and semi-metal elements other than Li and Y. m represents the valence of Me. The so-called "semi-metal element" is B, Si, Ge, As, Sb, and Te. The so-called "metal element" is all elements contained in Groups 1 to 12 of the periodic table (excluding hydrogen) and all elements contained in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0098] In order to improve the ionic conductivity of the halide solid electrolyte material, Me may also be at least one selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb. The halide solid electrolyte may also be Li3YCl6 or Li3YBr6.

[0099] The second solid electrolyte material may also be an organic polymer solid electrolyte.

[0100] Examples of the organic polymer solid electrolyte are high molecular compounds and lithium salt compounds.

[0101] The high molecular compound may also have an ethylene oxide structure. The high molecular compound having an ethylene oxide structure can contain more lithium salts, and thus can further improve the ionic conductivity.

[0102] Examples of the lithium salt include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. One kind of lithium salt selected therefrom may be used alone. Alternatively, a mixture of two or more kinds of lithium salts selected therefrom may be used.

[0103] At least one selected from the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a non-aqueous 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.

[0104] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent.

[0105] Examples of the non-aqueous solvent include a cyclic carbonate solvent, a linear carbonate solvent, a cyclic ether solvent, a linear ether solvent, a cyclic ester solvent, a linear ester solvent, or a fluorine solvent. Examples of the cyclic carbonate solvent include ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of the linear carbonate solvent include dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. Examples of the cyclic ether solvent include tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. Examples of the linear ether solvent are 1,2-dimethoxyethane or 1,2-diethoxyethane. Examples of the cyclic ester solvent are γ-butyrolactone. Examples of the linear ester solvent are methyl acetate. Examples of the fluorine solvent include fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, ethyl methyl fluorocarbonate, or dimethylene fluorocarbonate. One kind of non-aqueous solvent selected therefrom may be used alone. Alternatively, a combination of two or more kinds of non-aqueous solvents selected therefrom may be used.

[0106] Examples of the lithium salt include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), or LiC(SO2CF3)3. One kind of lithium salt selected therefrom may be used alone. Alternatively, a mixture of two or more kinds of lithium salts selected therefrom 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.

[0107] As the gel electrolyte, a polymer material impregnated with a non-aqueous electrolyte solution can be used. Examples of the polymer material include polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or a polymer having a polyethylene oxide bond.

[0108] Examples of the cation contained in the ionic liquid include:

[0109] (i) aliphatic chain quaternary salts such as tetraalkylammonium or tetraalkylphosphonium,

[0110] (ii) aliphatic cyclic ammonium such as pyrrolidinium, morpholinium, imidazolinium, tetrahydropyrimidinium, piperazinium or piperidinium, or

[0111] (iii) nitrogen-containing heteroaromatic cations such as pyridinium or imidazolium.

[0112] Examples of anions contained in the ionic liquid are PF6 - , BF4 - , SbF6 - , AsF6 - , SO3CF3 - , N(SO2CF3)2 - , N(SO2C2F5)2 - , N(SO2CF3)(SO2C4F9) - or C(SO2CF3)3 - .

[0113] The ionic liquid may also contain a lithium salt.

[0114] 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.

[0115] Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aromatic polyamide resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, methyl polyacrylate, ethyl polyacrylate, hexyl polyacrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, polyhexafluoropropylene, styrene-butadiene rubber, or carboxymethyl cellulose. In addition, a copolymer can also be used as the binder. Examples of such a binder include copolymers of two or more materials selected from 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 therefrom can also be used as the binder.

[0116] At least one of the positive electrode 201 and the negative electrode 203 may contain a conductive additive to reduce the electron resistance.

[0117] Examples of the conductive additive include:

[0118] (i) graphites such as natural graphite or artificial graphite,

[0119] (ii) carbon blacks such as acetylene black or Ketjen black,

[0120] (iii) Conductive fiber materials such as carbon fiber or metal fiber,

[0121] (iv) Carbon fluoride,

[0122] (v) Metal powder materials such as aluminum,

[0123] (vi) Conductive whisker materials such as zinc oxide or potassium titanate,

[0124] (vii) Conductive metal oxides such as titanium oxide, or

[0125] (viii) Conductive polymer compounds such as polyaniline, polypyrrole or polythiophene.

[0126] For cost reduction, the conductive aids of the above (i) or (ii) can also be used.

[0127] Examples of the shape of the battery of the second embodiment include coin type, cylindrical type, square type, sheet type, button type, flat type or laminated type.

[0128] The battery of the second embodiment can also 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 manufacturing a laminate in which a positive electrode, an electrolyte layer, and a negative electrode are sequentially arranged by a known method.

[0129] Examples

[0130] Hereinafter, the present disclosure will be described in more detail with reference to examples and comparative examples.

[0131] <Example 1>

[0132] (Production of solid electrolyte material)

[0133] In an argon atmosphere with a dew point of -60°C or lower (hereinafter referred to as "dry argon atmosphere"), LiF and ZrF4 were prepared as raw material powders so as to achieve a molar ratio of LiF:ZrF4 = 4.0:1.0. These raw material powders were pulverized and mixed in a mortar. Using a planetary ball mill, the obtained mixed powder was ground at 500 rpm for 12 hours. In this way, the powder of the solid electrolyte material of Example 1 was obtained. The solid electrolyte material of Example 1 has a composition represented by Li4ZrF8.

[0134] (Evaluation of full width at half maximum)

[0135] Figure 3 It is a graph showing the X-ray diffraction pattern of the solid electrolyte material of Example 1.

[0136] In a dry environment with a dew point below -50°C, using an X-ray diffractometer (MiniFlex600 manufactured by Rigaku Corporation), the X-ray diffraction pattern of the solid electrolyte material of Example 1 was measured. As the X-ray source, Cu-Kα rays (wavelength and ) were used, and the measurement was performed by the θ-2θ method. The measurement angle interval was 0.01°. The divergence angle of the divergence slit was 0.25°. The slit width of the length limiting slit was 5 mm.

[0137] The value of the diffraction angle 2θ of the peak having the highest intensity in the range of the diffraction angle 2θ of 42.5° or more and 44.7° or less was set as 2θ top , and the intensity of this peak was set as I top . The intensity at the diffraction angle 2θ of 44.7° was set as I bg . That is, I bg represents the intensity of the baseline. The half value I top of I htop was set as [(I top -I bg ) / 2 + I bg .

[0138] The diffraction angle 2θ that reaches the intensity closest to I top in the range of the diffraction angle 2θ of 42.5° or more and 2θ htop or less was set as 2θ L . The diffraction angle 2θ that reaches the intensity closest to I top in the range of 2θ htop or more and 44.7° or less was set as 2θ H . FWHM is the difference between 2θ H and 2θ L . The FWHM of the solid electrolyte material of Example 1 was 0.6 deg.

[0139] Next, X-ray diffraction measurement was performed on the Si crystal powder under the same conditions as the solid electrolyte material of Example 1. The value of the diffraction angle 2θ of the peak having the highest intensity in the range of the diffraction angle 2θ of 28.0° or more and 28.6° or less was set as 2θ top , and the intensity of this peak was set as I top . The intensity at the diffraction angle 2θ of 28.0° was set as I bg . As a result, the FWHM Si of the Si crystal powder was 0.16 deg. Furthermore, the Si crystal powder used was the Si standard sample "SRM 640d (NIST)".

[0140] (Change of the horizontal axis of the X-ray diffraction pattern)

[0141] The Figure 3 horizontal axis of the X-ray diffraction pattern of the solid electrolyte material of Example 1 shown is transformed from the diffraction angle 2θ to q. Here, the equation: q = 4πsinθ / λ is satisfied. λ is the wavelength of the X-ray used in the X-ray diffraction measurement. Thus, the transformed pattern of the solid electrolyte material of Example 1 is obtained. Figure 4 It is a graph showing Figure 3 the transformed pattern of the solid electrolyte material of Example 1 obtained by transforming the horizontal axis of the graph from 2θ to q.

[0142] (Evaluation of ionic conductivity)

[0143] Figure 5 The schematic diagram of the compression molding die 300 used for evaluating the ionic conductivity of the solid electrolyte material is shown.

[0144] The compression molding die 300 includes an upper punch 301, a frame die 302, and a lower punch 303. The frame die 302 is formed of insulating polycarbonate. The upper punch 301 and the lower punch 303 are formed of electronically conductive stainless steel.

[0145] Using Figure 5 the compression molding die 300 shown, the ionic conductivity of the solid electrolyte material of Example 1 was evaluated by the following method.

[0146] In a dry atmosphere with a dew point of -30°C or lower, the powder of the solid electrolyte material of Example 1 was filled inside the compression molding die 300. Inside the compression molding die 300, a pressure of 400 MPa was applied to the solid electrolyte material of Example 1 using the upper punch 301 and the lower punch 303.

[0147] While maintaining the pressure applied, the upper punch 301 and the lower punch 303 were connected to a potentiostat (Versa STAT4 manufactured by Princeton Applied Research) equipped with a frequency response analyzer. The upper punch 301 was connected to the working electrode and the potential measurement terminal. The lower punch 303 was connected to the counter electrode and the reference electrode. At room temperature, the impedance of the solid electrolyte material was measured by electrochemical impedance spectroscopy.

[0148] Figure 6 It is a graph showing the Cole-Cole plot of the solid electrolyte material of Example 1 obtained by impedance measurement.

[0149] Figure 6Among them, the real value of the impedance at the measurement point with the smallest absolute value of the phase of the complex impedance is regarded as the resistance value of the solid electrolyte material for ion conduction. Regarding this real value, refer to Figure 6 the arrow R shown in SE . Using this resistance value, based on the following mathematical formula (2), the ionic conductivity was calculated.

[0150] σ = (R SE ×S / t) -1 (2)

[0151] Here, σ represents the ionic conductivity. S represents the contact area between the solid electrolyte material and the upper part 301 of the punch ( Figure 5 in, equal to the cross-sectional area of the hollow part of the frame mold 302). R SE represents the resistance value of the solid electrolyte material in the impedance measurement. t represents the thickness of the solid electrolyte material (i.e., Figure 5 the thickness of the layer formed by the powder 101 of the solid electrolyte material in

[0152] The ionic conductivity of the solid electrolyte material of Example 1 measured at 25 °C was 1.39×10 -7 S / cm.

[0153] (Fabrication of Battery)

[0154] In a dry argon atmosphere, the solid electrolyte material of Example 1 and LiCoO2 as the active material were prepared in a volume ratio of 30:70. These materials were mixed in an agate mortar. In this way, a positive electrode mixture was obtained.

[0155] Next, LiCl and YCl3 were prepared in a molar ratio of LiCl:YCl3 = 3:1. These materials were pulverized and mixed in a mortar. Using a planetary ball mill, the obtained mixture was ground at 500 rpm for 12 hours. In this way, a halide solid electrolyte having a composition represented by Li3YCl6 (hereinafter referred to as "LYC") was obtained.

[0156] In an insulating cylinder with an inner diameter of 9.5 mm, LYC (70 mg), the solid electrolyte material of Example 1 (33 mg), and the above positive electrode mixture (9.1 mg) were stacked in this order. A pressure of 300 MPa was applied to the obtained laminate to form a second electrolyte layer formed of LYC, a first electrolyte layer formed of the solid electrolyte material of Example 1, and a positive electrode. That is, the first electrolyte layer formed of the solid electrolyte material of Example 1 is sandwiched between the second electrolyte layer and the positive electrode. The thicknesses of the second electrolyte layer and the first electrolyte layer are 450 μm and 150 μm, respectively.

[0157] Next, a metal In (thickness: 200 μm) was laminated on the second electrolyte layer. A pressure of 80 MPa was applied to the obtained laminate to form a negative electrode.

[0158] Next, a current collector formed of stainless steel was attached to the positive electrode and the negative electrode, and a current collecting lead was attached to the current collector.

[0159] Finally, an insulating hoop was used to block the inside and outside atmospheres of the insulating cylinder and seal the inside of the cylinder. In this way, the battery of Example 1 was obtained.

[0160] (Charge and discharge test)

[0161] Figure 7 It is a graph showing the initial discharge characteristics of the battery of Example 1. The initial charge and discharge characteristics were measured by the following method.

[0162] The battery of Example 1 was placed in a thermostat at 85°C.

[0163] At a current density of 27 μA / cm 2 , the battery of Example 1 was charged until a voltage of 3.6 V was reached. This current density corresponds to a 0.02 C rate.

[0164] Next, at a current density of 27 μA / cm 2 , the battery of Example 1 was discharged until a voltage of 1.9 V was reached.

[0165] The results of the charge and discharge test showed that the battery of Example 1 had an initial discharge capacity of 778 μAh.

[0166] <Examples 2 to 9>

[0167] (Production of solid electrolyte material)

[0168] In Examples 2 to 5, LiF and ZrF4 were prepared as raw material powders so as to achieve a molar ratio of LiF:ZrF4 = x:1. Except for the above matters, the solid electrolyte materials of Examples 2 to 5 were obtained in the same manner as in Example 1. The values of x are shown in Table 1.

[0169] In Examples 6 to 9, LiF and ZrF4 were prepared as raw material powders so as to achieve a molar ratio of LiF:ZrF4 = x:1. After the mixed powder of the raw materials was ground, heat treatment was performed for 1 hour. Except for the above matters, the solid electrolyte materials of Examples 6 to 9 were obtained in the same manner as in Example 1.

[0170] The values of x for Examples 2 to 9 and the heat treatment temperatures for Examples 6 to 9 are shown in Table 1 respectively. In Table 1, "BM" indicates grinding treatment using a planetary ball mill.

[0171] (Evaluation of full width at half maximum)

[0172] In the same manner as in Example 1, the FWHM of the solid electrolyte materials of Examples 2 to 9 was calculated. The FWHM and the value of FWHM / FWHM are shown in Table 1. Si value

[0173] (Evaluation of ionic conductivity)

[0174] In the same manner as in Example 1, the ionic conductivities of the solid electrolyte materials of Examples 2 to 9 were measured. The measurement results are shown in Table 1.

[0175] (Fabrication of battery)

[0176] Using the solid electrolyte materials of Examples 2 to 9, the batteries of Examples 2 to 9 were obtained in the same manner as in Example 1.

[0177] (Charge-discharge test)

[0178] The charge-discharge tests were carried out on the batteries of Examples 2 to 9 in the same manner as in Example 1. The batteries of Examples 2 to 9, like those of Example 1, could be charged and discharged well.

[0179] <Comparative Example 1>

[0180] In a dry argon atmosphere, LiF and ZrF4 were prepared as raw material powders so that LiF∶ZrF4 = 4∶1. After mixing the raw material powders in a mortar, they were formed into a pellet shape. The obtained pellet-shaped mixed powder was heat-treated at 500 °C for 5 hours. In this way, the powder of the solid electrolyte material of Comparative Example 1 was obtained.

[0181] In the same manner as in Example 1, the FWHM of the solid electrolyte material of Comparative Example 1 was calculated. The results are shown in Table 1.

[0182] In the same manner as in Example 1, the ionic conductivity of the solid electrolyte material of Comparative Example 1 was measured. The results are shown in Table 1.

[0183] Using the solid electrolyte material of Comparative Example 1, the battery of Comparative Example 1 was obtained in the same manner as in Example 1. The charge-discharge test was carried out on the battery of Comparative Example 1 in the same manner as in Example 1. As a result, the battery of Comparative Example 1 had an initial discharge capacity of 0.01 μAh or less. That is, the battery of Comparative Example 1 could not be charged and discharged.

[0184] Table 1

[0185]

[0186] <Discussion>

[0187] The solid electrolyte materials of Examples 1 to 9 have a relatively high ionic conductivity of 1×10 -9 S / cm or more at room temperature.

[0188] The comparison between Examples 1 and 3 to 5 and Example 2 shows that as long as the value of x is 3.8 or more and 4.5 or less, the solid electrolyte material has higher ionic conductivity.

[0189] The batteries of Examples 1 to 9 can be charged and discharged at 85°C. On the other hand, the battery of Comparative Example 1 cannot be charged and discharged.

[0190] The solid electrolyte materials of Examples 1 to 9 do not generate hydrogen sulfide because they do not contain sulfur.

[0191] As described above, the solid electrolyte material of the present disclosure is suitable for providing a battery having a relatively high lithium ion conductivity and capable of being charged and discharged well.

[0192] Industrial applicability

[0193] The solid electrolyte material of the present disclosure can be used, for example, in all-solid-state lithium ion secondary batteries.

Claims

1. A solid electrolyte material, wherein, It contains a crystalline phase represented by the following compositional formula (1), Li x ZrF 4+x (1) where 3.5 ≤ x is satisfied, and in the X-ray diffraction pattern obtained by X-ray diffraction measurement using Cu-Kα rays of the solid electrolyte material, the value of the full width at half maximum of the peak having the highest intensity in the range of diffraction angle 2θ of 42.5° or more and 44.7° or less is greater than 1.19 with respect to the value of the full width at half maximum of the peak corresponding to the (111) plane of Si measured under the same conditions.

2. The solid electrolyte material according to claim 1, wherein, In the transformed spectrum obtained by transforming the horizontal axis of the X-ray diffraction pattern from the diffraction angle 2θ to q, the value of the full width at half maximum of the peak having the highest intensity in the range of q of 2.96 or more and 3.10 or less, relative to the value of the full width at half maximum of the peak corresponding to the (111) plane of Si measured under the same conditions, is greater than 1.

19. Here, q = 4πsinθ / λ, λ represents the wavelength of the X-ray used in the X-ray diffraction measurement.

3. The solid electrolyte material according to claim 1 or 2, wherein, 3.5 ≤ x ≤ 4.5 is satisfied.

4. A battery, comprising: a positive electrode, a negative electrode, and an electrolyte layer provided between the positive electrode and the negative electrode; At least one selected from the positive electrode, the negative electrode, and the electrolyte layer contains the solid electrolyte material according to any one of claims 1 to 3.

5. The battery according to claim 4, wherein, The electrolyte layer includes a first electrolyte layer and a second electrolyte layer, the first electrolyte layer is disposed between the positive electrode and the negative electrode, the second electrolyte layer is disposed between the first electrolyte layer and the negative electrode, and the first electrolyte layer contains the solid electrolyte material.

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