Method for producing non-aqueous electrolyte, apparatus for producing non-aqueous electrolyte, and purifier

Abstract

To provide a method for producing a non-aqueous electrolyte capable of reducing desolvation resistance, an apparatus for producing a non-aqueous electrolyte, and a purifier.MEANS FOR SOLVING THE PROBLEM: The method for producing a non-aqueous electrolyte includes a step for bringing an oxide containing at least one of zirconium and lanthanum into contact with a non-aqueous electrolyte, and a step for separating the non-aqueous electrolyte that has been in contact with the oxide from the oxide. The apparatus for producing a non-aqueous electrolyte includes a purifier in which an oxide containing at least one of zirconium and lanthanum is arranged. The purifier has an oxide containing at least one of zirconium and lanthanum placed therein.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for producing a non-aqueous electrolyte, an apparatus for producing a non-aqueous electrolyte, and a purifier. [Background technology]

[0002] In a non-aqueous electrolyte solution in which an electrolyte is dissolved in a non-aqueous solvent, charge carriers (ions) exist in a state coordinated with the solvent molecules. In the prior art disclosed in Patent Document 1, the non-aqueous electrolyte solution contains a solvated ionic liquid, a low-viscosity organic solvent, and a negative electrode interface stabilizer in order to improve the input / output characteristics of an electrochemical device containing the non-aqueous electrolyte solution. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-145054 Summary of the Invention [Problem to be solved by the invention]

[0004] In non-aqueous electrolytes, charge carriers coordinated to solvent molecules desolvate at the electrode interface and move through the electrode. Therefore, there is a need for technology to reduce the desolvation resistance, which affects the input / output characteristics of electrochemical devices.

[0005] The present invention has been made to meet this demand, and an object of the present invention is to provide a method for producing a non-aqueous electrolyte, an apparatus for producing a non-aqueous electrolyte, and a purifier for a non-aqueous electrolyte, which are capable of reducing desolvation resistance. [Means for solving the problem]

[0006] A first aspect for achieving this object is a method for producing a non-aqueous electrolyte, which includes the steps of contacting an oxide containing at least one of zirconium and lanthanum with a non-aqueous electrolyte, and separating the oxide from the non-aqueous electrolyte that has come into contact with the oxide.

[0007] In the second aspect, in the first aspect, the oxide is a solid electrolyte having a garnet-type crystal structure containing lithium, zirconium, and lanthanum.

[0008] In a third embodiment, in the second embodiment, the solid electrolyte further contains magnesium and strontium.

[0009] A fourth aspect is an apparatus for producing a non-aqueous electrolyte, which includes a refiner in which an oxide containing at least one of zirconium and lanthanum is placed.

[0010] In a fifth aspect, in the fourth aspect, the refiner has a liquid permeability that allows the non-aqueous electrolyte to pass through the oxide particles.

[0011] A sixth aspect is a purifier for a non-aqueous electrolyte, in which an oxide containing at least one of zirconium and lanthanum is disposed. [Effects of the Invention]

[0012] According to the method for producing a non-aqueous electrolyte of the present invention, the desolvation resistance can be reduced by bringing an oxide containing at least one of zirconium and lanthanum into contact with the non-aqueous electrolyte and separating the non-aqueous electrolyte from the oxide. The apparatus for producing a non-aqueous electrolyte includes a purifier in which an oxide containing at least one of zirconium and lanthanum is disposed, and the desolvation resistance can be reduced by bringing the oxide into contact with the non-aqueous electrolyte and passing the non-aqueous electrolyte through the purifier. [Brief explanation of the drawings]

[0013] [Figure 1] 1(a) and 1(b) are schematic diagrams of a step of contacting a non-aqueous electrolyte with an oxide, and 1(c) is a schematic diagram of a step of separating the non-aqueous electrolyte from the oxide. [Figure 2] FIG. 1 is a diagram schematically illustrating a garnet-type crystal structure. [Figure 3] FIG. 1 is a schematic diagram of an apparatus according to a first embodiment. [Figure 4] FIG. 10 is a schematic diagram of an apparatus according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a schematic diagram of each step in a method for producing a non-aqueous electrolyte. Figs. 1(a) and 1(b) are schematic diagrams of the step of contacting a non-aqueous electrolyte 11 with an oxide 12. Fig. 2(c) is a schematic diagram of the step of separating the non-aqueous electrolyte 11 from the oxide 12.

[0015] The non-aqueous electrolyte 11 is a medium through which ions (hereinafter referred to as "charge carriers") that contribute to the energy conversion of an electrochemical element (not shown) move. + , Na + , K. + , Mg 2+ , Ca 2+ , Cu + , Ag + Examples of cations include:

[0016] Electrochemical elements are elements that involve the interconversion of chemical energy and electrical energy, and examples thereof include secondary batteries such as lithium ion batteries, sodium ion batteries, potassium ion batteries, magnesium ion batteries, and calcium ion batteries, electrochemical capacitors, and metal-air batteries that use metals such as lithium, zinc, aluminum, magnesium, and iron as the negative electrode active material. Examples of electrochemical capacitors include electric double layer capacitors, redox capacitors that utilize redox reactions of electrodes or redox reactions of ions in a non-aqueous electrolyte, and hybrid capacitors that combine electric double layers and redox reactions, or that combine them with secondary battery materials.

[0017] The nonaqueous electrolyte 11 is a solution in which an electrolyte is dissolved in a nonaqueous solvent. Examples of electrolytes include compounds composed of charge carriers (anions) and cations. Nonaqueous solvents are broadly classified into molecular solvents, which are mostly composed of molecules, and ionic liquids, which are composed of cations and anions. A nonaqueous electrolyte containing a nonaqueous solvent can have a wider potential window than an aqueous electrolyte that uses water as a solvent.

[0018] The molecular solvent is preferably an aprotic solvent to widen the potential window of the nonaqueous electrolyte. Examples of aprotic solvents include cyclic esters, chain esters, aliphatic carboxylic acid esters, phosphate esters, nitriles, amides, sulfur compounds, ketones, ethers, nitro compounds, fluorous solvents, and sulfones. Mixtures of these solvents are also acceptable.

[0019] Examples of cyclic esters include carbonate esters such as propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, vinylethylene carbonate, and fluoroethylene carbonate, and lactones such as β-propiolactone, γ-butyrolactone, δ-valerolactone, α-pyrone, and coumarin. Examples of chain esters include carbonate esters such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Examples of aliphatic carboxylic acid esters include methyl formate, ethyl formate, methyl acetate, ethyl acetate, and ethyl propionate. Examples of phosphate esters include trimethyl phosphate. Examples of nitriles include acetonitrile, propionitrile, butyronitrile, and benzonitrile.

[0020] Examples of amides include formamide, N-methylformamide, dimethylformamide, N-methylacetamide, dimethylacetamide, N-methylpropionamide, hexamethylphosphoramide, and N-methylpyrrolidone. Examples of sulfur compounds include dimethyl sulfoxide, sulfolane, dimethylthioformamide, and N-methylthiopyrrolidone. Examples of ketones include acetone, 4-methyl-2-pentanone, and acetylacetone.

[0021] Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, monoglyme, diglyme, triglyme, and tetraglyme. Examples of nitro compounds include nitromethane and nitrobenzene. Fluorous solvents are compounds in which the hydrogen atoms of hydrocarbons are replaced with fluorine atoms, and derivatives thereof. Examples of sulfones include trimethylene sulfone, tetramethylene sulfone (sulfolane), dimethyl sulfone, ethyl methyl sulfone, and ethyl isopropyl sulfone.

[0022] The reaction in which an electrolyte dissolves in a molecular solvent and dissociates into free ions proceeds more easily as the relative dielectric constant of the solvent increases and as the solvation of ions becomes more likely. Therefore, the relative dielectric constant ε r The solvent with a relatively large r >20) is preferred. Examples of molecular solvents with a relative dielectric constant of greater than 20 include cyclic esters, nitriles, amides, sulfur compounds, acetone, acetylacetone, nitro compounds, and sulfones. It is of course possible to mix a solvent with a relative dielectric constant of greater than 20 with a solvent with a relative dielectric constant of 20 or less in order to adjust the viscosity of the solvent, etc.

[0023] Ionic liquids are compounds consisting of cations and anions, and are liquid at room temperature and normal pressure. If the solvent of a non-aqueous electrolyte is an ionic liquid, the flame retardancy of the non-aqueous electrolyte can be improved. The ionic liquid is preferably one having one or more cation species selected from the group consisting of ammonium, imidazolium, pyrrolidinium, and piperidinium.

[0024] The anion component of the ionic liquid is not particularly limited. The anion component is BF4 - ,N(SO2F)2 - Inorganic anions such as B(C6H5)4 - ,CH3SO3 - ,CF3SO3 - ,N(SO2CF3)2 - ,N(SO2C4F9)2 - Examples of organic anions include:

[0025] The ionic liquid may be a solvated ionic liquid, such as a sulfone-based solvent such as sulfolane or a sulfolane derivative, or a glyme-based solvent such as tetraglyme, in which an electrolyte is dissolved.

[0026] The electrolyte concentration of the nonaqueous electrolyte 11 is 0.2 mol / dm 3 or more, preferably 0.5 mol / dm 3 More preferably, 1.0 mol / dm 3 As the electrolyte concentration increases, the number of solvent molecules coordinated to the charge carriers increases, resulting in fewer uncoordinated solvent molecules, and coordination with counter anions (so-called ionic association) predominates. This suppresses the reductive decomposition of the nonaqueous electrolyte 11, while increasing the oxidation potential and widening the potential window. The electrolyte concentration was 4.0 mol / dm 3 Preferably, it is less than 2.0 mol / dm 3 The electrolyte concentration is 4.0 mol / dm or less. 3 If the temperature exceeds this range, the ionic conductivity tends to decrease significantly due to an increase in the viscosity of the non-aqueous electrolyte.

[0027] As shown in FIG. 1(a), a nonaqueous electrolyte 11 and an oxide 12 are placed in a bottomed container 10 with one end open, and the nonaqueous electrolyte 11 and the oxide 12 are brought into contact with each other. The oxide 12 is an oxide containing at least one of zirconium and lanthanum, and is preferably a basic oxide. In this embodiment, the oxide 12 is in the form of particles. There is no limitation on the size of the particles of the oxide 12, but smaller particles are preferred because they have a larger specific surface area and therefore increase the amount of nonaqueous electrolyte 11 that comes into contact with the particles per unit mass.

[0028] Oxide 12 is a La-based perovskite oxide. 2 / 3-X Li 3X Examples include TiO3, HZr2(PO4)3 and NaZr2(PO4)3 with NASICON-type structures, Zr(HPO4)2·nH2O with a two-dimensional layered structure, and oxides with a garnet-type crystal structure containing Li, Ti, and La. The garnet-type crystal structure is represented by the general formula C3A2B3O 12It is expressed as:

[0029] FIG. 2 is a diagram showing a schematic diagram of a garnet-type crystal structure. In a garnet-type crystal structure, Sc at the C site is dodecahedrally coordinated with an oxygen atom Oa, Sa at the A site is octahedrally coordinated with an oxygen atom Oa, and Sb at the B site is tetrahedrally coordinated with an oxygen atom Oa. In an oxide solid electrolyte, Li can exist in a vacancy V, which is a position where Li is octahedrally coordinated with an oxygen atom Oa in a normal garnet-type crystal structure. The vacancy V is, for example, a position sandwiched between the B site Sb1 and the B site Sb2. The Li present in the vacancy V is octahedrally coordinated with an oxygen atom Oa that constitutes an octahedron including the tetrahedral face Fb1 that forms the B site Sb1 and the tetrahedral face Fb2 that forms the B site Sb2. For example, in Li7La3Zr2O having a garnet-type crystal structure, 12 In the formula, La can occupy the C-site Sc, Zr can occupy the A-site Sa, and Li can occupy the B-site Sb and the vacant V.

[0030] The garnet-type crystal structure can be identified by X-ray diffraction. The garnet-type crystal structure is identified in X-ray diffraction file No. 422259 (Li7La3Zr2O) of the CSD (Cambridge Structural Database). 12 ) has an XRD pattern similar to that of No. 422259. Compared to No. 422259, oxides may differ in the type of constituent elements and Li concentration, so the diffraction angle and intensity ratio may differ. The typical crystal structure of this type is a cubic system (space group Ia-3d (- indicates an overline that indicates a reversal operation), JCPDS: 84-1753).

[0031] Oxides with a garnet-type crystal structure are typically Li7La3Zr2O 12 The oxide is Li7La3Zr2O 12Some of the constituent elements may be substituted with other elements, or a small amount of other elements may be added without substituting the constituent elements. Examples of other elements include at least one element selected from the group consisting of Mg, Al, Si, Ca, Ti, V, Ga, Sr, Y, Nb, Sn, Sb, Ba, Hf, Ta, W, Bi, Rb, and lanthanides (excluding La).

[0032] The oxide is, for example, Li6La3Zr 1.5 W 0.5 O 12 , Li 6.15 La3Zr 1.75 Ta 0.25 Al 0.2 O 12 , Li 6.15 La3Zr 1.75 Ta 0.25 Ga 0.2 O 12 , Li 6.25 La3Zr2Ga 0.25 O 12 , Li 6.4 La3Zr 1.4 Ta 0.6 O 12 , Li 6.5 La3Zr 1.75 Te 0.25 O 12 , Li 6.75 La3Zr 1.75 Nb 0.25 O 12 , Li 6.9 La3Zr 1.675 Ta 0.289 Bi 0.036 O 12 , Li 6.46 Ga 0.23 La3Zr 1.85 Y 0.15 O 12 , Li 6.8 La 2.95 Ca 0.05 Zr 1.75 Nb 0.25 O 12 , Li 7.05 La 3.00 Zr 1.95 Gd 0.05 O 12 , Li 6.20 Ba 0.30La 2.95 Rb 0.05 ZrO 12 Examples include:

[0033] The oxide preferably contains at least one of Mg and element A (A is at least one element selected from the group consisting of Ca, Sr, and Ba) in which the molar ratio of each element satisfies all of the following (1) to (3), or contains both Mg and element A in which the molar ratio of each element satisfies all of the following (4) to (6). Element A is preferably Sr, as it increases the ionic conductivity of the oxide. (1) 1.33≦Li / (La+A)≦3 (2) 0≦Mg / (La+A)≦0.5 (3) 0≦A / (La+A)≦0.67 (4) 2.0≦Li / (La+A)≦2.6 (5) 0.01≦Mg / (La+A)≦0.14 (6) 0.04≦A / (La+A)≦0.17

[0034] 1(b), the non-aqueous electrolyte 11 is stirred or the container 10 is vibrated to create a flow in the non-aqueous electrolyte 11, thereby increasing the frequency of contact between the oxide 12 and the non-aqueous electrolyte 11. If the oxide 12 is in the form of particles, it is preferable because the oxide 12 can be easily dispersed in the non-aqueous electrolyte 11.

[0035] After the oxide 12 and the non-aqueous electrolyte solution 11 have been sufficiently brought into contact with each other, the container 10 is left standing to allow the oxide 12 to settle, as shown in Fig. 1(c), and the oxide 12 can be separated from the non-aqueous electrolyte solution 11 (supernatant). With the oxide 12 dispersed in the non-aqueous electrolyte solution 11 (see Fig. 1(b)), the non-aqueous electrolyte solution 11 and the oxide 12 may be separated by an operation such as filtration or centrifugation.

[0036] The non-aqueous electrolyte 11 separated from the oxide 12 can be used by being interposed between the positive and negative electrodes of an electrochemical element (not shown). It is known that if residual moisture exists in the non-aqueous electrolyte, impurities are generated by hydrolysis of anions and subsequent decomposition reactions. Impurities in the non-aqueous electrolyte have a positive or negative effect on the ionic conductivity of the non-aqueous electrolyte, the interfacial resistance of the electrodes, and low-temperature characteristics. This can have a negative effect. In addition, electrolytes (fluorides) such as LiPF6 can react with residual moisture in the non-aqueous electrolyte to produce hydrofluoric acid (an acidic impurity). Hydrofluoric acid can corrode the container and circuitry of electrochemical devices. Therefore, it is necessary to control the amount of moisture and impurities in the non-aqueous electrolyte.

[0037] When the oxide 12 comes into contact with the nonaqueous electrolyte 11, the amount of water and impurities in the nonaqueous electrolyte 11 is reduced. When the oxide 12 has a garnet-type crystal structure containing Li, Ti, and La, the mechanism by which the water content in the nonaqueous electrolyte 11 is reduced is believed to be that lithium ions in the oxide 12 are exchanged with hydrogen ions, causing a change in the crystal structure of the oxide 12, or that lithium carbonate is produced by a reaction between the oxide 12 and hydroxide ions. The mechanism by which the amount of impurities in the nonaqueous electrolyte 11 is reduced is believed to be that the impurities contained in the nonaqueous electrolyte 11 are decomposed by the basic oxide 12 and adsorbed to the oxide 12 as insoluble or poorly soluble compounds. The amount of water and impurities in the nonaqueous electrolyte 11 can be controlled by the simple operation of contacting the oxide 12 with the nonaqueous electrolyte 11, without requiring special operations such as precision distillation of the nonaqueous solvent.

[0038] In some electrochemical elements having a nonaqueous electrolyte 11 between a positive electrode and a negative electrode, charge carriers in the nonaqueous electrolyte are desolvated at the interface between the negative electrode and the nonaqueous electrolyte during charging, and an intercalation reaction, electrodeposition reaction, or alloying reaction occurs depending on the type of negative electrode. Also, in some electrochemical elements, charge carriers in the nonaqueous electrolyte are desolvated at the interface between the positive electrode and the nonaqueous electrolyte during discharging, and an intercalation reaction, conversion reaction, or the like occurs depending on the type of positive electrode.

[0039] The nonaqueous electrolyte 11, which comes into contact with the oxide 12 and is separated from the oxide 12, contains at least one of 200 wtppb or more of zirconium and 30 wtppb or more of lanthanum. Zirconium and lanthanum are present in the nonaqueous electrolyte 11 in one or more forms of ions, fine particles containing these ions, and oxide particles containing zirconium or lanthanum (hereinafter referred to as "fine particles, etc."). This reduces the desolvation resistance of charge carriers. Since the internal resistance of the electrochemical device during charging and discharging, which is associated with the desolvation resistance of charge carriers, can be reduced, the input / output characteristics of the electrochemical device can be improved.

[0040] The mechanism by which the fine particles and the like present in the non-aqueous electrolyte 11 reduce the desolvation resistance is presumed to be as follows: The fine particles and the like present in the non-aqueous electrolyte 11 are adsorbed to the positive electrode and the negative electrode. Since the oxide 12 containing the fine particles and the like has a relatively high ionic bond, some of the solvent molecules coordinated to the charge carriers preferentially coordinate to the fine particles and the like in the microscopic regions near the fine particles and the like adsorbed to the positive electrode and the negative electrode. This facilitates desolvation of the charge carriers coordinated to some of the solvent molecules, thereby reducing the solvation resistance.

[0041] Furthermore, when the charge carrier is an alkali metal ion and the negative electrode is an alkali metal, zirconium or lanthanum, which precipitates at a potential more noble than the charge carrier ion, serves as an active site for nucleation of crystals, facilitating the precipitation of the charge carrier as a metal, thereby reducing the overvoltage during deposition of the alkali metal at the negative electrode.Furthermore, the product generated by the reaction of the fine particles with the negative electrode acts as a protective film for the negative electrode, thereby reducing the decomposition of the nonaqueous electrolyte at the negative electrode.

[0042] The amount of zirconium and lanthanum present in the non-aqueous electrolyte 11 is preferably 10 wt % or less, respectively, in order to reduce side reactions caused by zirconium and lanthanum.

[0043] The non-aqueous electrolyte 11 may further contain strontium at 10 wt ppb or more, since strontium acts in the same manner as zirconium and lanthanum. The concentrations of zirconium, lanthanum, and strontium can be measured, for example, by inductively coupled plasma mass spectrometry (ICP-MS).

[0044] The non-aqueous electrolyte 11 preferably contains zirconium and lanthanum, and the ratio of the concentration of lanthanum to the concentration of zirconium is preferably 0.2 or more and 0.5 or less, because when the oxide 12 contains zirconium and lanthanum, the non-aqueous electrolyte 11 can be easily produced by contacting the oxide 12 with the non-aqueous electrolyte 11.

[0045] 3 and 4, the devices 20 and 30 for producing the non-aqueous electrolyte solution 11 will be described. The same parts as those described in FIG. 1 are designated by the same reference numerals, and the following description will be omitted.

[0046] 3 is a schematic diagram of the apparatus 20 according to the first embodiment. The apparatus 20 includes a refiner 21. The refiner 21 includes a cylindrical container 22 open at both ends, an oxide 12 packed in the container 22, and a fixture 23 for fixing the oxide 12 in the container 22. The oxide 12 is a collection of particles. The fixture 23 is a liquid-permeable member such as a filter or fiber.

[0047] The nonaqueous electrolyte 11 is supplied to the purifier 21 by a liquid sending device 24 such as a liquid sending pump, passes through the oxides 12, and comes out of the purifier 21. The liquid sending device 24 includes a device that uses the potential energy of the nonaqueous electrolyte 11 to supply the nonaqueous electrolyte 11 to the purifier 21 by allowing the nonaqueous electrolyte 11 to fall naturally. As the nonaqueous electrolyte 11 passes through the purifier 21 while coming into contact with the oxides 12, moisture and impurities contained in the nonaqueous electrolyte 11 are captured by the oxides 12 and purified.

[0048] FIG. 4 is a schematic diagram of an apparatus 30 according to the second embodiment. The apparatus 30 includes a purifier 32 disposed in a first container 31. The first container 31 is cylindrical with both ends open and one end tapered. The purifier 32 may be a filter or mesh in which oxide 12 (particles) are bonded to a liquid-permeable support (not shown), or a porous body of oxide 12 with liquid permeability. The purifier 32 is disposed in the narrowed portion of the first container 31. The second container 33 is connected to the narrowed portion of the first container 31.

[0049] A liquid delivery device 34 such as a pressure reducer is connected to the second container 33 near the connection portion to the first container 31. The liquid delivery device 34 is not limited to one that reduces the pressure in the second container 33, but also includes one that uses the potential energy of the nonaqueous electrolyte 11 to move the nonaqueous electrolyte 11 from the first container 31 to the second container 33 by natural falling of the nonaqueous electrolyte 11.

[0050] When non-aqueous electrolyte 11 is placed on purifier 32 disposed in first container 31 and liquid delivery device 34 is operated, non-aqueous electrolyte 11 passes through purifier 32 and accumulates in second container 33. As non-aqueous electrolyte 11 passes through purifier 32 while in contact with oxide 12, moisture and impurities contained in non-aqueous electrolyte 11 are captured by oxide 12 and purified.

[0051] The oxide 12 that has captured moisture and impurities is heated to around 500°C in an inert atmosphere such as argon or nitrogen gas, thereby restoring its ability to purify the nonaqueous electrolyte 11. Since the purifiers 21 and 32 are replaceable parts, they can be replaced with new ones if their performance deteriorates. [Example]

[0052] The present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples.

[0053] (Preparation of solid electrolyte) Li 6.95 Mg 0.15 La 2.75 Sr 0.25 Zr 2.0 O 12Li2CO3, MgO, La(OH)3, SrCO3, and ZrO2 were weighed out so that the total weight of the raw materials was 100g. An excess amount of Li2CO3 was used to account for the volatilization of Li during firing. The weighed raw materials and ethanol were placed in a nylon pot along with zirconia balls and milled and mixed in a ball mill for 15 hours. The slurry removed from the pot was dried and then fired on an MgO plate at 1100°C for 15 hours. The fired powder was crushed, placed in an MgO sagger, and further fired at 1100°C for 4 hours. The fired powder was crushed in an argon-atmosphere glove box to obtain an oxide-based solid electrolyte (hereinafter referred to as "LLZ"). The garnet-type crystal structure of LLZ was confirmed by powder X-ray diffraction.

[0054] Using a dry jet mill (Aisin Nano Technologies Co., Ltd., Nano Jetmizer (registered trademark) NJ-50 model), the LLZ was milled by passing it through the jet mill twice in a nitrogen atmosphere until the particle size distribution of the LLZ had a median diameter (D50) of 0.8 μm as measured by laser diffraction / scattering. After milling, the LLZ was stored in an argon atmosphere with a dew point of -80°C for at least 7 days. The LLZ after milling and storage is hereinafter referred to as "LLZ powder."

[0055] (Example) A non-aqueous solvent was prepared by mixing lithium battery grade ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a 1:1:1 (volume ratio) ratio, and further mixing 1 wt% vinylene carbonate. The electrolyte LiPF6 was added at 1 mol / dm 3 The nonaqueous electrolyte solution (before treatment) and the LLZ powder were placed in a sealed container under an argon atmosphere in a ratio of 5:1 (mass ratio), and the mixture was stirred intermittently for 1 hour, then allowed to stand for 24 hours, and the supernatant was removed to prepare the nonaqueous electrolyte solution in this example.

[0056] (Comparative Example) The nonaqueous electrolyte (before treatment) was used as the nonaqueous electrolyte in the comparative example.

[0057] (Concentration measurement) The non-aqueous electrolyte solutions in the examples were diluted 10 times with pure water, and the concentrations of zirconium, lanthanum, and strontium in the non-aqueous electrolyte solutions before dilution were measured using an inductively coupled plasma mass spectrometer (iCAP·Q, manufactured by Thermo Fisher Scientific Co., Ltd.). The concentrations of zirconium, lanthanum, and strontium in the non-aqueous electrolyte solutions in the comparative examples were also measured in the same manner.

[0058] (Measurement of electrodeposition resistance) A SUS316 case and cap, an 18 mm diameter synthetic resin separator, a 15 mm diameter lithium metal foil, a gasket, and a 16 mm diameter SUS316 spacer and washer for a CR2032 coin cell were prepared, and the case, gasket, lithium metal foil, separator, spacer, washer, and cap were stacked in this order under an argon atmosphere while the nonaqueous electrolyte solution of the example was poured in to prepare a cell of the example. Similarly, a comparative example cell was also prepared by pouring in the nonaqueous electrolyte solution of the comparative example.

[0059] A constant current of a predetermined volume was applied to the cell to charge it. The average voltage when metallic lithium was deposited in an amount of 1 mAh in the range of potentials less noble than the equilibrium potential was divided by the current value during charging to calculate the value (electrodeposition resistance). When the current density, calculated by dividing the current value by the area of ​​the spacer, was 0.25 mA / cm 2 , 1.0mA / cm 2 , 2.5mA / cm 2 The electrodeposition resistance at each time point was calculated, and the average electrodeposition resistance (n = 3) for the cells in the examples was calculated relative to the average electrodeposition resistance (n = 4) for the cells in the comparative examples, which was set to 100. The concentrations of zirconium, lanthanum, and strontium and the electrodeposition resistance (relative values) are shown in Table 1.

[0060] [Table 1]

[0061] According to Table 1, the concentrations of zirconium, lanthanum, and strontium in the nonaqueous electrolytes in the Examples were higher than those in the nonaqueous electrolytes in the Comparative Examples. The nonaqueous electrolytes in the Examples had zirconium concentrations of 200 wtppb or more, lanthanum concentrations of 30 wtppb or more, and strontium concentrations of 10 wtppb or more. It was estimated that fine particles of LLZ powder may be present in the nonaqueous electrolytes in the Examples.

[0062] According to Table 1, the electrodeposition resistance of the cell in the example was smaller than that of the cell in the comparative example, and the current density was 0.25 mA / cm 2 When the current density was 1.0 mA / cm, the electrodeposition resistance was 80.3% of that of the comparative cell. 2 When the current density was 2.5 mA / cm, the electrodeposition resistance was 91.4% of that of the comparative cell. 2 The electrodeposition resistance was 90.3% of the electrodeposition resistance of the cell in the comparative example. The electrodeposition resistance is the resistance when lithium ions coordinated to the solvent molecules of the nonaqueous electrolyte desolvate and deposit on the lithium metal foil during charging, and therefore corresponds to the desolvation resistance of lithium ions. Therefore, it was revealed that the desolvation resistance of the nonaqueous electrolyte in the example was smaller than the desolvation resistance of the nonaqueous electrolyte in the comparative example. The input / output characteristics, such as charge / discharge rate characteristics, of the cell in the example are expected to be improved compared to the cell in the comparative example.

[0063] According to the examples, it was revealed that the desolvation resistance of the non-aqueous electrolyte can be reduced by the simple procedure of contacting the LLZ powder with the non-aqueous electrolyte and then separating the LLZ powder from the non-aqueous electrolyte that has been in contact with the LLZ powder. LLZ powder reacts with water to produce lithium hydroxide and the like on its surface, and reacts with hydrofluoric acid to produce lithium fluoride and the like on its surface. Therefore, even if the non-aqueous electrolyte contains water or hydrofluoric acid, these are presumably reduced.

[0064] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention.

[0065] In the embodiment, the non-aqueous electrolyte 11 is purified by bringing particles of the oxide 12 into contact with the non-aqueous electrolyte 11, but the present invention is not limited to this. The oxide 12 may have a shape such as a plate, a rod, or a lump, as long as it has a surface area corresponding to the amount of the non-aqueous electrolyte 11.

[0066] In the embodiment, the case where the oxide 12 (particles) is dispersed in the non-aqueous electrolyte 11 placed in the container 10, and then the non-aqueous electrolyte 11 and the oxide 12 are separated by sedimentation, filtration, centrifugation, or other procedures has been described, but the present invention is not necessarily limited to this. It is of course also possible to fix one or more oxides 12 formed into a plate, rod, block, or the like in the container 10, place the non-aqueous electrolyte 11 in the container 10, bring the non-aqueous electrolyte 11 and the oxide 12 into contact with each other, and then discharge only the non-aqueous electrolyte 11 from the container 10 to separate the non-aqueous electrolyte 11 and the oxide 12. [Explanation of symbols]

[0067] 11 Nonaqueous electrolyte 12 Oxides 20,30 equipment 21,32 Purifier

Claims

1. a step of contacting an oxide containing at least one of zirconium and lanthanum with a non-aqueous electrolyte; and separating the nonaqueous electrolyte solution in contact with the oxide from the oxide.

2. 2. The method for producing a non-aqueous electrolyte according to claim 1, wherein the oxide is a solid electrolyte containing lithium, zirconium, and lanthanum and having a garnet-type crystal structure.

3. 3. The method for producing a non-aqueous electrolyte solution according to claim 2, wherein the solid electrolyte further contains magnesium and strontium.

4. An apparatus for producing a non-aqueous electrolyte, comprising a refiner in which an oxide containing at least one of zirconium and lanthanum is disposed.

5. 5. The apparatus according to claim 4, wherein the refiner has a liquid permeability that allows the non-aqueous electrolyte to pass through the gaps between the oxide particles.

6. A non-aqueous electrolyte purifier in which an oxide containing at least one of zirconium and lanthanum is disposed.

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