Solid electrolyte material and battery using the same

Abstract

A solid electrolyte material contains Li, Ti, Al, M, and F. Among them, M is at least one selected from Zr and Mg.

Description

Technical Field

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

[0002] Patent Document 1 discloses an all-solid battery using a sulfide solid electrolyte. Patent Document 2 discloses LiBF 4 as a fluoride solid electrolyte material.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2011-129312

[0006] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2008-277170 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] An object of the present disclosure is to provide a solid electrolyte material having a high lithium ion conductivity (also referred to as lithium ion electric conductivity, lithium ion conductivity).

[0009] Means for Solving the Problems

[0010] The solid electrolyte material of the present disclosure contains Li, Ti, Al, M, and F, where M is at least one selected from Zr and Mg.

[0011] Effects of the Invention

[0012] The present disclosure provides a solid electrolyte material having a high lithium ion conductivity. Brief Description of the Drawings

[0013] Figure 1 A cross-sectional view of the battery 1000 showing the second embodiment is shown.

[0014] Figure 2 A cross-sectional view of the battery 2000 showing the second embodiment is shown.

[0015] Figure 3 A schematic diagram of the pressure forming die 300 for evaluating the ion conductivity of the solid electrolyte material is shown.

[0016] Figure 4 A graph showing a Cole-Cole plot obtained by impedance measurement of the solid electrolyte material of Example 1 is shown.

[0017] Figure 5It is a graph showing the initial discharge characteristics of the batteries of Example 1 and Comparative Example 1. Detailed Description

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0019] (First Embodiment)

[0020] The solid electrolyte material of the first embodiment contains Li, Ti, Al, M, and F. M is at least one selected from Zr and Mg. 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 -8 S / cm or more. That is, the solid electrolyte material of the first embodiment may have, for example, an ion conductivity of 1×10 -8 S / cm or more.

[0021] The solid electrolyte material of the first embodiment can be used to obtain a battery with excellent charge and 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.

[0022] The solid electrolyte material of the first embodiment preferably does not contain sulfur. Since the solid electrolyte material that does not contain sulfur does not generate hydrogen sulfide even when exposed to the atmosphere, it has excellent safety. If the sulfide solid electrolyte disclosed in Patent Document 1 is exposed to the atmosphere, hydrogen sulfide can be generated.

[0023] 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. On the other hand, since F has a high electronegativity, its bond with Li is relatively strong. As a result, generally, the lithium ion conductivity of a solid electrolyte material containing Li and F will decrease. For example, LiBF disclosed in Patent Document 2 4 has a low ion conductivity of 6.67×10 -9 S / cm. Furthermore, LiBF 4 is the solid electrolyte material used in Comparative Example 1 described later. In contrast, the solid electrolyte material of the first embodiment can have a high ion conductivity of, for example, 1×10 -8 S / cm or more by containing Ti, Al, and M in addition to Li and F.

[0024] In order to improve the ion conductivity of the solid electrolyte material, the solid electrolyte material of the first embodiment may also contain anions other than F. Examples of such anions are Cl, Br, I, O, S, or Se.

[0025] The solid electrolyte material of the first embodiment may also be substantially made of Li, Ti, Al, M, and F. Herein, the statement that "the solid electrolyte material of the first embodiment is substantially made of Li, Ti, Al, M, and F" means that the molar ratio (i.e., mole fraction) of the sum of the amounts of substances of Li, Ti, Al, M, and F to the sum of the amounts of substances of all elements constituting the solid electrolyte material of the first embodiment is 90% or more. As an example, this molar ratio may also be 95% or more. The solid electrolyte material of the first embodiment may also be made only of Li, Ti, Al, M, and F.

[0026] The solid electrolyte material of the first embodiment may also contain unavoidably mixed-in elements. 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.

[0027] In order to further improve the ionic conductivity of the solid electrolyte material, in the solid electrolyte material of the first embodiment, the ratio of the amount of substance of Li to the sum of the amounts of substances of Ti, Al, and M may also be 1.33 or more and 3.79 or less.

[0028] In order to improve the ionic conductivity of the solid electrolyte material, M may also be Zr.

[0029] The solid electrolyte material of the first embodiment may also be represented by the following compositional formula (1).

[0030] Li 6-(4-x-(4-a)y)b (Ti 1-x-y Al x M y ) b F 6 Formula (1)

[0031] In formula (1), a represents the valence of M, satisfying the mathematical formulas: 0 < x < 1, 0 < y < 1, 0 < (x + y) < 1, and 0 < b ≤ 1.5. The solid electrolyte material having such a composition has a high ionic conductivity.

[0032] In order to improve the ionic conductivity of the solid electrolyte material, in formula (1), the mathematical formula: 0.05 ≤ x ≤ 0.9 may also be satisfied.

[0033] When M is Mg, in order to improve the ionic conductivity of the solid electrolyte material, in formula (1), the mathematical formula: 0.33 ≤ x ≤ 0.7 may also be satisfied.

[0034] The upper limit value and the lower limit value of the range of x in formula (1) may be defined by any combination selected from the values of 0.05, 0.1, 0.33, 0.37, 0.5, 0.6, 0.7, and 0.9.

[0035] In order to improve the ionic conductivity of the solid electrolyte material, in formula (1), the mathematical formula 0.05 ≤ y ≤ 0.9 can also be satisfied.

[0036] When M is Mg, in order to improve the ionic conductivity of the solid electrolyte material, in formula (1), the mathematical formula 0.1 ≤ y ≤ 0.33 can also be satisfied.

[0037] The upper limit value and the lower limit value of the range of y in formula (1) can be defined by any combination selected from the values of 0.05, 0.1, 0.2, 0.26, 0.33, 0.5, 0.8, and 0.9.

[0038] In order to improve the ionic conductivity of the solid electrolyte material, in formula (1), the mathematical formula 0.8 ≤ b ≤ 1.2 can also be satisfied.

[0039] The upper limit value and the lower limit value of the range of b in formula (1) can be defined by any combination selected from the values of 0.8, 0.9, 1.0, 1.1, and 1.2.

[0040] The solid electrolyte material of the first embodiment may be crystalline or may be amorphous.

[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 a shape having particles or plates.

[0042] When the shape of the solid electrolyte material of the first embodiment is, for example, particulate (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 at which the cumulative volume in the particle size distribution based on volume is equal to 50%. The particle size distribution based on volume is 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. Thereby, 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 raw material powders and mix them in a manner that aims to form a composition. The raw material powders can also be halides, for example.

[0047] As an example, when the composition to be formed is Li 3.07 Ti 0.27 Al 0.27 Zr 0.27 F 6 When it is, mix LiF, TiF 4 , AlF 3 , ZrF 4 at a molar ratio of about 3.07:0.27:0.27:0.27. It is also possible to mix the raw material powders at a molar ratio that has been pre-adjusted in a manner that can offset the compositional changes that may occur during the synthesis process.

[0048] React the raw material powders mechanochemically (i.e., using the method of mechanochemical grinding) with each other in a mixing device such as a planetary ball mill to obtain a reaction product. It is also possible to sinter the reaction product in a vacuum or an inert atmosphere. Or, it is also possible to obtain a reaction product by sintering a mixture of the raw material powders in a vacuum or an inert atmosphere. The sintering is preferably carried out at 100 °C or higher and 300 °C or lower for 1 hour or more. In order to suppress compositional changes during sintering, it is preferable to sinter the raw material powders in a sealed container such as a quartz tube.

[0049] By these methods, the solid electrolyte material of the first embodiment is obtained.

[0050] (Second Embodiment)

[0051] Hereinafter, the second embodiment will be described. Matters described in the first embodiment will be omitted.

[0052] The battery of the second embodiment includes a positive electrode, a negative electrode, and an electrolyte layer. The electrolyte layer is disposed between the positive electrode and the negative electrode. At least one selected from the 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.

[0053] Figure 1 A cross-sectional view of the battery 1000 of the second embodiment is shown.

[0054] 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 disposed between the positive electrode 201 and the negative electrode 203.

[0055] The positive electrode 201 contains positive electrode active material particles 204 and solid electrolyte particles 100.

[0056] The electrolyte layer 202 contains an electrolyte material. The electrolyte material is, for example, a solid electrolyte material.

[0057] The negative electrode 203 contains negative electrode active material particles 205 and solid electrolyte particles 100.

[0058] The solid electrolyte particles 100 are particles made 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 mass ratio is the solid electrolyte material of the first embodiment.

[0059] The positive electrode 201 contains a material capable of inserting and extracting metal ions (such as lithium ions). This material is, for example, a positive electrode active material (such as positive electrode active material particles 204).

[0060] Examples of the positive electrode active material are lithium-containing transition metal oxides, transition metal fluorides, polyanion materials, fluorinated polyanion materials, transition metal sulfides, transition metal sulfur oxides, or transition metal nitrogen oxides. Examples of the lithium-containing transition metal oxides are Li(Ni, Co, Al)O 2 , Li(Ni, Co, Mn)O 2 or LiCoO 2 . In the present disclosure, the notation “(Ni, Co, Al)” in the chemical formula means at least one element selected from the group of elements within the parentheses. That is, “(Ni, Co, Al)” is synonymous with at least one of “Ni, Co, and Al”. The same applies to other elements.

[0061] The positive electrode active material particles 204 may also 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, in the positive electrode 201, the dispersion state of the positive electrode active material particles 204 and the solid electrolyte particles 100 becomes good. Thereby, the charge-discharge characteristics of the battery 1000 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. Thereby, the battery 1000 can operate at high power.

[0062] The positive electrode active material particles 204 may also have a larger median particle size than the solid electrolyte particles 100. Thereby, in the positive electrode 201, the dispersion state of the positive electrode active material particles 204 and the solid electrolyte particles 100 becomes good.

[0063] In order to increase the energy density and power of the battery, in the positive electrode 201, the ratio of the volume of the positive electrode active material particles 204 to the sum of the volume of the positive electrode active material particles 204 and the volume of the solid electrolyte particles 100 may also be 0.30 or more and 0.95 or less.

[0064] 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 are sulfide solid electrolyte, oxide solid electrolyte, or 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 with excellent stability at high potentials may also be used. By suppressing the oxidative decomposition of the solid electrolyte material, an increase in the overvoltage of the battery can be suppressed.

[0065] In order to increase the energy density and power of the battery, the positive electrode 201 may also have a thickness of 10 μm or more and 500 μm or less.

[0066] 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.

[0067] The electrolyte layer 202 may also be composed only of the solid electrolyte material of the first embodiment. Alternatively, it 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 are Li 2 MgX 4 、Li 2 FeX 4 、Li(Al, Ga, In)X 4 、Li 3 (Al, Ga, In)X 6 or LiI. Herein, X is at least one selected from F, Cl, Br, and I.

[0068] 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.

[0069] 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. The layer formed of the first solid electrolyte material and the layer formed of the second solid electrolyte material may be stacked along the stacking direction of the battery 1000.

[0070] Figure 2 A cross-sectional view of the battery 2000 showing the second embodiment is presented.

[0071] 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.

[0072] 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-discharge efficiency of the battery can be improved.

[0073] 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-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.

[0074] In order to improve the energy density and power of the battery, the electrolyte layer 202 may have a thickness of 1 μm or more and 1000 μm or less.

[0075] 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).

[0076] Examples of the negative electrode active material are a metal material, a carbon material, an oxide, a nitride, a tin compound, or a silicon compound. 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 are natural graphite, coke, carbon during graphitization, carbon fiber, spherical carbon, artificial graphite, or amorphous carbon. From the viewpoint of capacity density, preferred examples of the negative electrode active material are silicon (i.e., Si), tin (i.e., Sn), a silicon compound, or a tin compound.

[0077] The negative electrode active material can also be selected in consideration of the reduction 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 capable of inserting and extracting lithium ions at 0.27 V or more with respect 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 Li 4 Ti 5 O 12 、LiTi 2 O 4 or TiO 2 。 By using the above negative electrode active material, 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-discharge efficiency of the battery can be improved.

[0078] 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, the dispersion state of the negative electrode active material particles 205 and the solid electrolyte particles 100 in the negative electrode 203 becomes good. Thereby, the charge-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 inside the negative electrode active material particles 205 is increased. Thereby, the battery can operate at high power.

[0079] The negative electrode active material particles 205 can also have a larger median particle size than the solid electrolyte particles 100. Thereby, the dispersion state of the negative electrode active material particles 205 and the solid electrolyte particles 100 in the negative electrode 203 becomes good.

[0080] In order to improve the energy density and power of the battery, the ratio of the volume of the negative electrode active material particles 205 to the sum of the volume of the negative electrode active material particles 205 and the volume of the solid electrolyte particles 100 in the negative electrode 203 can also be 0.30 or more and 0.95 or less.

[0081] In order to improve the energy density and power of the battery, the negative electrode 203 can also have a thickness of 10 μm or more and 500 μm or less.

[0082] 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 ion conductivity, chemical stability, and electrochemical stability.

[0083] The second solid electrolyte material may also be a sulfide solid electrolyte.

[0084] Examples of the sulfide solid electrolyte are Li 2 S-P 2 S 5 、Li 2 S-SiS 2 、Li 2 S-B 2 S 3 、Li 2 S-GeS 2 、Li 3.25 Ge 0.25 P 0.75 S 4 、or Li 10 GeP 2 S 12 。

[0085] 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. Coating the negative electrode active material with an electrochemically stable sulfide solid electrolyte can inhibit the contact between the solid electrolyte material of the first embodiment and the negative electrode active material. As a result, the internal resistance of the battery can be reduced.

[0086] The second solid electrolyte material may also be an oxide solid electrolyte.

[0087] Examples of the oxide solid electrolyte are:

[0088] (i) NASICON-type solid electrolytes such as LiTi 2 (PO 4 ) 3 or its element substitution products,

[0089] (ii) Perovskite-type solid electrolytes such as (LaLi)TiO 3 ,

[0090] (iii) LISICON-type solid electrolytes such as Li 14 ZnGe 4 O 16 、Li 4 SiO 4 、LiGeO 4 or its element substitution products,

[0091] (iv) Li 7 La 3 Zr 2 O 12 a garnet-type solid electrolyte such as or its elemental substitute, or

[0092] (v) Li 3 PO 4 or its N-substitute.

[0093] As described above, the second solid electrolyte material may also be a halide solid electrolyte.

[0094] Examples of the halide solid electrolyte are Li 2 MgX 4 , Li 2 FeX 4 , Li(Al, Ga, In)X 4 , Li 3 (Al, Ga, In)X 6 or LiI. Among them, X is at least one selected from F, Cl, Br, and I.

[0095] Other examples of the halide solid electrolyte material are compounds represented by Li a Me b Y c X 6 . Among them, 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 included in Groups 1 to 12 of the periodic table (excluding hydrogen) and all elements included in Groups 13 to 16 of the periodic table (excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se).

[0096] 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 Li 3 YCl 6 or Li 3 YBr 6 .

[0097] The second solid electrolyte material may also be an organic polymer solid electrolyte.

[0098] Examples of the organic polymer solid electrolyte are compounds of a high molecular compound and a lithium salt.

[0099] The polymer compound may also have an ethylene oxide structure. Since the polymer compound having an ethylene oxide structure contains a relatively large amount of lithium salt, the ionic conductivity can be further improved.

[0100] Examples of the lithium salt are LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiSO 3 CF 3 , LiN(SO 2 CF 3 ), 2 , LiN(SO 2 C 2 F 5 ), 2 , LiN(SO 2 CF 3 )(SO 2 C 4 F 9 ), or LiC(SO 2 CF 3 ). 3 One kind of lithium salt selected from the above may be used alone. Alternatively, a mixture of two or more lithium salts selected from the above may be used.

[0101] 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 power characteristics of the battery.

[0102] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt dissolved in the non-aqueous solvent.

[0103] Examples of the non-aqueous solvent are a cyclic carbonate solvent, a chain carbonate solvent, a cyclic ether solvent, a chain ether solvent, a cyclic ester solvent, a chain ester solvent, or a fluorine solvent. Examples of the cyclic carbonate solvent are ethylene carbonate, propylene carbonate, or butylene carbonate. Examples of the chain carbonate solvent are dimethyl carbonate, methyl ethyl carbonate, or diethyl carbonate. Examples of the cyclic ether solvent are tetrahydrofuran, 1,4-dioxane, or 1,3-dioxolane. The chain ether solvent is 1,2-dimethoxyethane or 1,2-diethoxyethane. Examples of the cyclic ester solvent are γ-butyrolactone. Examples of the chain ester solvent are methyl acetate. Examples of the fluorine solvent are fluoroethylene carbonate, methyl fluoropropionate, fluorobenzene, methyl ethyl fluorocarbonate, or dimethyl fluorocarbonate. One kind of non-aqueous solvent selected from the above may be used alone. Alternatively, a combination of two or more non-aqueous solvents selected from the above may be used.

[0104] Examples of the lithium salt are LiPF 6 、LiBF 4 、LiSbF 6 、LiAsF 6 、LiSO 3 CF 3 、LiN(SO 2 CF 3 ) 2 、LiN(SO 2 C 2 F 5 ) 2 、LiN(SO 2 CF 3 )(SO 2 C 4 F 9 ) or LiC(SO 2 CF 3 ) 3 . One kind of lithium salt selected from the above can also be used alone. Alternatively, a mixture of two or more lithium salts selected from the above can also 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.

[0105] As the gel electrolyte, a polymer material impregnated with a non-aqueous electrolyte can be used. Examples of the polymer material are polyethylene oxide, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, or a polymer having an ethylene oxide bond.

[0106] Examples of the cations contained in the ionic liquid are:

[0107] (i) aliphatic chain-like quaternary salts (quaternary salts) such as tetraalkylammonium or tetraalkylphosphonium,

[0108] (ii) aliphatic cyclic ammonium such as pyrrolidinium, morpholinium, imidazolinium, tetrahydropyrimidinium, piperazinium, or piperidinium, or

[0109] (iii) nitrogen-containing heterocyclic aromatic cations such as pyridinium or imidazolium.

[0110] Examples of the anions contained in the ionic liquid are PF 6 -, BF 4 -, SbF 6 - 、AsF 6 - 、SO 3 CF 3 - 、N(SO 2 CF 3 ) 2- , N(SO 2 C 2 F 5 ) 2 - , N(SO 2 CF 3 )(SO 2 C 4 F 9 )- or C(SO 2 CF 3 ) 3 - .

[0111] The ionic liquid may also contain a lithium salt.

[0112] At least one selected from the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may also contain a binder for the purpose of improving the adhesion between particles.

[0113] Examples of the binder are 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, hexafluoropropylene, styrene-butadiene rubber, or carboxymethyl cellulose. Copolymers can also be used as the binder. Examples of such binders are 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 from these can also be used as the binder.

[0114] To reduce the resistance, at least one of the positive electrode 201 and the negative electrode 203 may also contain a conductive additive.

[0115] Examples of the conductive additive are:

[0116] (i) Graphite-based materials such as natural graphite or artificial graphite,

[0117] (ii) Carbon black-based materials such as acetylene black or Ketjen black,

[0118] (iii) Conductive fiber-based materials such as carbon fiber or metal fiber,

[0119] (iv) Carbon fluoride,

[0120] (v) Metal powder-based materials such as aluminum,

[0121] (vi) Conductive whiskers such as zinc oxide or potassium titanate,

[0122] (vii) Conductive metal oxides such as titanium oxide, or

[0123] (viii) Conductive polymer compounds such as polyaniline, polypyrrole or polythiophene.

[0124] For cost reduction, the conductive aids of the above (i) or (ii) may also be used.

[0125] Examples of the shape of the battery of the second embodiment are coin type, cylindrical type, square type, thin plate type, button type, flat type or laminated type.

[0126] The battery of the second embodiment can also be manufactured, for example, by the following method: Prepare a material for forming a positive electrode, a material for forming an electrolyte layer, and a material for forming a negative electrode, and fabricate a laminate in which the positive electrode, the electrolyte layer, and the negative electrode are sequentially arranged by a known method.

[0127] Examples

[0128] Hereinafter, the present disclosure will be described in more detail with reference to examples and comparative examples.

[0129] <Example 1>

[0130] (Production of solid electrolyte material)

[0131] In an argon atmosphere having a dew point of -60°C or lower (hereinafter referred to as "dry argon atmosphere"), LiF, TiF 4 : AlF 3 : ZrF 4 = 3.07: 0.27: 0.27: 0.27 in terms of molar ratio were prepared. LiF, TiF 4 , AlF 3 and ZrF 4 . These materials were pulverized and mixed in a mortar. The obtained mixture was ground for 12 hours at 500 rpm using a planetary ball mill. By operating 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 Li 3.07 Ti 0.27 Al 0.27 Zr 0.27 F 6 .

[0132] (Evaluation of ionic conductivity)

[0133] Figure 3 The schematic diagram of the compression molding die 300 for evaluating the ionic conductivity of the solid electrolyte material is shown.

[0134] 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 electroconductive stainless steel.

[0135] Using Figure 3 the compression molding die 300 shown below, the ionic conductivity of the solid electrolyte material of Example 1 was evaluated by the following method.

[0136] In a dry atmosphere having 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.

[0137] With the pressure applied, the upper punch 301 and the lower punch 303 were connected to a potentiostat (Princeton Applied Research Corporation, Versa STAT4) 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 measurement method.

[0138] Figure 4 is a graph showing the Cole-Cole plot obtained by impedance measurement of the solid electrolyte material of Example 1.

[0139] Figure 4 In, the real value of the impedance at the measurement point where the absolute value of the phase of the complex impedance is the smallest is regarded as the resistance value for ionic conduction of the solid electrolyte material. Regarding this real value, refer to Figure 4 the arrow R shown in SE . Using this resistance value, the ionic conductivity was calculated based on the following mathematical formula (2).

[0140] σ = (R SE ×S / t) -1 (2)

[0141] where σ represents the ionic conductivity. S represents the contact area between the solid electrolyte material and the upper punch 301 ( Figure 3 in, equal to the cross-sectional area of the hollow portion of the frame die 302). R SE represents the resistance value of the solid electrolyte material during impedance measurement. t represents the thickness of the solid electrolyte material (i.e., Figure 3 in, the thickness of the layer formed by the powder 101 of the solid electrolyte material).

[0142] The ionic conductivity of the solid electrolyte material of Example 1 measured at 25 °C was 2.23×10 -6 S / cm.

[0143] (Fabrication of the battery)

[0144] In a dry argon atmosphere, the solid electrolyte material of Example 1 and the active material, i.e., LiCoO, were prepared in a volume ratio of 30:70. 2 These materials were mixed in an agate mortar. By operating in this way, a positive electrode mixture was obtained.

[0145] Next, LiCl and YCl were prepared in a molar ratio of LiCl:YCl 3 = 3:1. 3 These materials were pulverized and mixed in a mortar. The resulting mixture was milled using a planetary ball mill at 500 rpm for 12 hours. By operating in this way, a halide solid electrolyte (hereinafter referred to as "LYC") having a composition represented by Li 3 YCl 6 was obtained.

[0146] In an insulating cylinder having an inner diameter of 9.5 mm, 60 mg of LYC, 26 mg of the solid electrolyte material of Example 1, and 9.1 mg of the above positive electrode mixture were stacked in this order. A pressure of 300 MPa was applied to the resulting stack to form a second electrolyte layer, a first electrolyte layer, and a positive electrode. That is, the first electrolyte layer formed of the solid electrolyte material of Example 1 was sandwiched between the second electrolyte layer and the positive electrode. The thicknesses of the second electrolyte layer and the first electrolyte layer were 450 μm and 150 μm, respectively.

[0147] Next, metallic In (thickness: 200 μm) was stacked on the second electrolyte layer. A pressure of 80 MPa was applied to the resulting stack to form a negative electrode.

[0148] Next, current collectors made of stainless steel were attached to the positive electrode and the negative electrode, and current collecting leads were attached to these current collectors.

[0149] Finally, an insulating sleeve was used to isolate the inside of the insulating cylinder from the external atmosphere, and the inside of the cylinder was sealed. By operating in this way, the battery of Example 1 was obtained.

[0150] (Charge-discharge test)

[0151] Figure 5 is a graph showing the initial discharge characteristics of the battery of Example 1. The initial charge-discharge characteristics were measured by the following method.

[0152] The battery of Example 1 was placed in a thermostat at 85°C.

[0153] The battery of Example 1 was charged at a current density of 27 μA / cm 2 to a voltage of 3.6 V. This current density corresponds to a 0.02 C rate.

[0154] Next, the battery of Example 1 was discharged at a current density of 27 μA / cm 2 to a voltage of 1.9 V.

[0155] As a result of the charge-discharge test, the battery of Example 1 had an initial discharge capacity of 698 μAh.

[0156] <Examples 2 to 20>

[0157] (Production of Solid Electrolyte Material)

[0158] In Examples 2 to 15, LiF, TiF 4 : AlF 3 : ZrF 4 ={6-(4-x)b}:(1-x-y)b:xb:yb in terms of molar ratio were prepared as raw material powders for LiF, TiF 4 , AlF 3 and ZrF 4 .

[0159] In Examples 16 to 20, LiF, TiF 4 : AlF 3 : MgF 2 ={6-(4-x-2y)b}:(1-x-y)b:xb:yb in terms of molar ratio were prepared as raw material powders for LiF, TiF 4 , AlF 3 and MgF 2 .

[0160] Except for the above matters, the solid electrolyte materials of Examples 2 to 20 were obtained by operating in the same manner as in Example 1.

[0161] Regarding the solid electrolyte materials of Examples 2 to 20, the values of x, y, b, and the Li / (Ti+Al+M) molar ratio are shown in Table 1.

[0162] (Evaluation of Ionic Conductivity)

[0163] The ionic conductivities of the solid electrolyte materials of Examples 2 to 20 were measured in the same manner as in Example 1. The measurement results are shown in Table 1.

[0164] (Charge-Discharge Test)

[0165] Using the solid electrolyte materials of Examples 2 to 20, batteries of Examples 2 to 21 were obtained by operating in the same manner as in Example 1.

[0166] For the batteries of Examples 2 to 20, charge-discharge tests were conducted by operating in the same manner as in Example 1. The batteries of Examples 2 to 20 were charged and discharged well in the same manner as the battery of Example 1.

[0167] <Comparative Example 1>

[0168] As the solid electrolyte material, LiBF 4 was used to replace Li 3.07 Ti 0.27 Al 0.27 Zr 0.27 F 6 .

[0169] The ionic conductivity of LiBF 4 was measured by operating in the same manner as in Example 1. The ionic conductivity measured at 25 °C was 6.67×10- 9 S / cm.

[0170] Using LiBF 4 as the solid electrolyte material, a battery of Comparative Example 1 was obtained by operating in the same manner as in Example 1.

[0171] For the battery of Comparative Example 1, a charge-discharge test was conducted by operating 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 was neither charged nor discharged.

[0172] Table 1 shows the solid electrolyte materials and the respective evaluation results in Examples 1 to 20 and Comparative Example 1.

[0173] Table 1

[0174]

[0175] <Discussion>

[0176] The solid electrolyte materials of Examples 1 to 20 had a high ionic conductivity of 1×10 -8 S / cm or more at room temperature. On the other hand, the solid electrolyte material of the comparative example had a low ionic conductivity of less than 1×10 -8 S / cm.

[0177] By comparing Example 2, 4, 5, and 6 with Example 16, 17, 18, and 19 respectively, it was found that the ionic conductivity of the solid electrolyte material was further improved when M was Zr compared to when M was Mg.

[0178] The batteries of Examples 1 to 20 were charged and discharged at 85°C. On the other hand, the battery of Comparative Example 1 was neither charged nor discharged.

[0179] Since the solid electrolyte materials of Examples 1 to 20 do not contain sulfur, hydrogen sulfide is not generated.

[0180] As described above, the solid electrolyte material of the present disclosure is suitable for providing a battery having a high lithium ion conductivity and capable of being charged and discharged well.

[0181] Industrial applicability

[0182] The solid electrolyte material of the present disclosure can be used, for example, in all-solid-state lithium ion secondary batteries.

[0183] Symbol description

[0184] 100: Solid electrolyte particles

[0185] 101: Powder of solid electrolyte material

[0186] 201: Positive electrode

[0187] 202: Electrolyte layer

[0188] 212: First electrolyte layer

[0189] 222: Second electrolyte layer

[0190] 203: Negative electrode

[0191] 204: Positive electrode active material particles

[0192] 205: Negative electrode active material particles

[0193] 300: Pressing die

[0194] 301: Upper part of punch

[0195] 302: Frame die

[0196] 303: Lower part of punch

[0197] 1000: Battery

[0198] 2000: Battery

Claims

1. A solid electrolyte material is substantially made of Li, Ti, Al, M and F, wherein, M is at least one selected from Zr and Mg, the solid electrolyte material is represented by the following compositional formula (1), Li 6-(4-x-(4-a)y)b (Ti 1-x-y Al x M y ) b F 6 Formula (1) wherein, a represents the valence of M, satisfying 0 < x < 1, 0 < y < 1, 0 < (x + y) < 1 and 0.8 ≤ b ≤ 1.

5.

2. A solid electrolyte material contains Li, Ti, Al, M and F, wherein, M is at least one selected from Zr and Mg, the ratio of the amount of substance of Li to the total amount of substance of Ti, Al and M is 1.33 or more and 3.79 or less, the solid electrolyte material is represented by the following compositional formula (1), Li 6-(4-x-(4-a)y)b (Ti 1-x-y Al x M y ) b F 6 Formula (1) wherein, a represents the valence of M, satisfying 0 < x < 1, 0 < y < 1, 0 < (x + y) < 1 and 0.8 ≤ b ≤ 1.

5.

3. The solid electrolyte material according to claim 1 or 2, wherein, it satisfies the mathematical formula: 0.05 ≤ x ≤ 0.

9.

4. The solid electrolyte material according to claim 1 or 2, wherein, it satisfies the mathematical formula: 0.05 ≤ y ≤ 0.

9.

5. The solid electrolyte material according to claim 1 or 2, wherein, M is Mg, and it satisfies the mathematical formula: 0.33 ≤ x ≤ 0.

7.

6. The solid electrolyte material according to claim 1 or 2, wherein, M is Mg, and it satisfies the mathematical formula: 0.1 ≤ y ≤ 0.

33.

7. The solid electrolyte material according to claim 1 or 2, wherein, it satisfies the mathematical formula: 0.8 ≤ b ≤ 1.

2.

8. A battery includes: a positive electrode; a negative electrode; and an electrolyte layer disposed between the positive electrode and the negative electrode, wherein, 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 7.

9. The battery according to claim 8, 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, the first electrolyte layer contains the solid electrolyte material.

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