JP7071899B2 - Method for manufacturing solid electrolyte - Google Patents

Description

The present invention relates to a method for producing a solid electrolyte.

With the development of mobile communication and information electronic devices in recent years, the demand for high-capacity and lightweight lithium-ion batteries tends to increase. Most of the electrolytes showing high lithium ion conductivity at room temperature are liquids, and most of the commercially available lithium ion batteries use organic electrolytes. Lithium-ion batteries using an organic electrolytic solution have a risk of leakage, ignition and explosion, so a battery with higher safety is desired. In response to the above demand, an all-solid-state battery using a solid electrolyte such as a sulfide solid electrolyte has been developed.

As a method for producing a solid electrolyte, a method of reacting while pulverizing a raw material by using a ball mill, a vibration mill or the like is known. Recently, a method for synthesizing a solid electrolyte in a polar solvent has been developed. Furthermore, new solid electrolytes are being actively developed by controlling morphology, such as crystal control and particle size control.

For example, in Non-Patent Document 1, after reacting Li ₂ S and P ₂ S ₅ in a tetrahydrofuran (THF) solvent, THF is heated from the reaction solution to evaporate and the reaction product is dried to dryness. It is described that crystal Li ₃ PS ₄ can be synthesized.
In Non-Patent Document ₂ , the starting materials Li 2S, LiBr and Li ₃ PS ₄ are dissolved in ethanol, reacted in a solution, and then the solvent is distilled off to synthesize crystals of Li ₆ PS ₅ Br. It states that it can be done.
Patent Documents 1 and 2 disclose that a solid electrolyte containing a specific crystal structure can be synthesized by heat-treating a raw material.
Further, Patent Document 3 discloses a method for producing particles, and Patent Document 4 discloses the synthesis of a fine particle solid electrolyte using a bead mill.

JP-A-2015-179649 Special Table 2010-540396 Gazette Japanese Unexamined Patent Publication No. 2017-18872 Japanese Unexamined Patent Publication No. 2012-134133

J.Am.Chem.Soc., 135,975 (2013) J.Jpn.Soc.Color Mater., 89 [9], 300-305 (2016)

In Patent Documents 1 and 2 and Non-Patent Documents 1 and 2, in either method, a solid electrolyte or a precursor thereof is synthesized by a solution reaction, a mechanical milling reaction, or the like, and then the solvent is removed from the obtained product. , The solid electrolyte is synthesized by heat-treating the precursor. That is, at least two steps, a reaction step and a solvent removal step and a heat treatment step, are required.
In Patent Document 4, when synthesizing a fine-grained solid electrolyte, a solid electrolyte is prepared by using raw materials such as Li ₂ S and P ₂ S ₅ , and then the obtained solid electrolyte is atomized to form fine particles. Obtaining a solid electrolyte. This method also requires at least two steps, a synthesis step and an atomization step.

In general, the synthesis of solid electrolyte fine particles including a crystal structure requires at least three steps of a synthesis step, a crystallization step, and an atomization step, and the production step is complicated. Therefore, it is required to improve productivity by simplifying the manufacturing process.
One of the objects of the present invention is to provide a method capable of efficiently producing solid electrolyte fine particles containing a crystal structure.

According to one embodiment of the present invention, it is a method for producing a solid electrolyte containing an argyrodite type crystal structure (hereinafter, may be referred to as an argyrodite type solid electrolyte), and is a solid electrolyte raw material containing lithium, phosphorus, sulfur and chlorine. The solid electrolyte raw material-containing liquid containing the above and the solvent is supplied to a medium which is a liquid or gas at a temperature higher than the boiling point of the solvent to evaporate the solvent and react with the solid electrolyte raw material to form an argylodite type. A method for producing a solid electrolyte, which comprises precipitating a crystal structure, is provided.

According to the present invention, solid electrolyte fine particles containing a crystal structure can be efficiently produced.

It is a particle size distribution of the solid electrolyte obtained in Examples 1 and 2. It is a particle size distribution of the solid electrolyte obtained in Examples 3-1 and 4 and 5.

In the method for producing a solid electrolyte according to an embodiment of the present invention, a liquid containing a solid electrolyte raw material containing a solid electrolyte raw material containing lithium, phosphorus, sulfur and chlorine and a solvent is heated to a temperature higher than the boiling point of the solvent. The solvent is evaporated by supplying the medium to a medium which is a liquid or a gas, and the solid electrolyte raw material is reacted to precipitate (form) an algyrodite type crystal structure. By supplying the solid electrolyte raw material-containing liquid to a high-temperature medium, the synthesis and atomization of the argilodite-type solid electrolyte can be carried out in one step, so that this embodiment has higher productivity than the conventional manufacturing method. The solid electrolyte raw material-containing liquid may be a solution in which the solid electrolyte raw material is dissolved in a solvent, or may be a mixed liquid in which a part or all of the solid electrolyte raw material is dispersed and mixed without being dissolved. When the medium is a liquid, the contained liquid can be supplied to the medium by injection, dropping or the like, and when the medium is a gas, it can be supplied by spraying or the like.

As the solid electrolyte raw material, an element containing the target solid electrolyte, for example, lithium, phosphorus, sulfur and chlorine, and a compound containing any element as a constituent element or a simple substance can be used. A mixture obtained by combining two or more substances selected from a compound and a simple substance, or a reaction product obtained from this mixture can be used.

Examples of the lithium-containing compound include lithium sulfide (Li ₂ S), lithium oxide (Li ₂ O), lithium carbonate (Li ₂ CO ₃ ), lithium hydrohydrate (Li SH), and lithium trithiocarbonate (Li ₂ CS). ₃ ), lithium polysulfide (Li ₂ S _x : x is 2 to 100) can be mentioned. Of these, lithium sulfide is preferable.
Lithium sulfide can be used without particular limitation, but high-purity lithium sulfide is preferable.

Examples of the phosphorus-containing compound include phosphorus sulfide such as diphosphorus trisulfide (P ₂ S ₃ ) and diphosphorus pentasulfide (P ₂ S ₅ ), sodium phosphate (Na ₃ PO ₄ ), and PSX ₃ (. X is an element selected from F, Cl, Br and I) and the like. Among these, phosphorus sulfide is preferable, and _{P2 S 5 is} more preferable.

Examples of the compound containing chlorine include compounds represented by the general formula (M _l − X _m ).

In the formula, M is sodium (Na), lithium (Li), boron (B), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), germanium (Ge), arsenic (As). , Serene (Se), tin (Sn), antimony (Sb), tellurium (Te), lead (Pb), bismuth (Bi), or these elements combined with an oxygen element or a sulfur element, Li or P is preferable, and Li is more preferable.
X is a halogen element selected from F, Cl, Br and I, and at least one of X is Cl.
Further, l is an integer of 1 or 2, and m is an integer of 1 to 10. When m is an integer of 2 to 10, that is, when there are a plurality of Xs, Xs may be the same or different. For example, SiBrCl ₃ , which will be described later, has m of 4, and X is composed of different elements, Br and Cl.

Specific examples of the compound represented by the above formula include NaCl, LiClBCl ₃ , AlCl ₃ , NaCl ₄ , SiCl ₃ , Si ₂ Cl ₆ , SiBrCl ₃ , SiBr ₂ Cl ₂ , PCl ₃ , PCl ₅ , and POCl ₃ . , P ₂ Cl ₄ , SCl ₂ , S ₂ Cl ₂ , GeCl ₄ , GeCl ₂ , AsCl ₃ , SeCl ₂ , SeCl ₄ , SnCl ₄ , SnCl ₂ , SbCl ₃ , SbCl ₅ , TeCl ₂ , _{TeCl 4} , P. Examples thereof include PbCl ₂ and BiCl ₃ .

Above all, LiCl is preferable.
As the compound containing chlorine, one of the above compounds may be used alone, or two or more of them may be used in combination.

In one embodiment of the invention, the solid electrolyte raw material preferably contains Cl and other halogens. In this case, other halogen-containing compounds may be used in addition to the chlorine-containing compounds described above. Specifically, sodium halides such as NaI, NaF, NaBr; lithium halides such as LiF, LiBr, LiI; boron halides such as BBr ₃ , BI ₃ ; halogenation of AlF ₃ , AlBr ₃ , AlI ₃ , etc. Aluminum; Halogenated silicon such as SiF ₄ , SiBr ₄ , _{SiI 4} ; Halogenated phosphorus such as PF ₃ , PF ₅ , PBr ₃ , POBr ₃ , PI ₃ , P2 I ₄ ; SF ₂ , SF ₄ , SF ₆ , Halogenated sulfur such as S ₂ F ₁₀ , S ₂ Br ₂ ; Halogenated germanium such as GeF ₄ , GeBr ₄ , GeI ₄ , GeF ₂ , GeBr ₂ , GeI ₂ ; AsF ₃ , AsBr ₃ , AsI ₃ , AsF ₅ , etc. Halogenated arsenic; Halogenated selenium such as SeF ₄ , SeF ₆ , Se ₂ Br ₂ , SeBr ₄ , etc .; Halogenated tin such as SnF ₄ , SnBr ₄ , SnI ₄ , SnF ₂ , SnBr ₂ , SnI _{2 ,} etc. Halogenated antimonies such as SbBr ₃ , SbI ₃ , SbF ₅ ; Halogenated telluriums such as TeF ₄ , Te ₂ F ₁₀ , TeF ₆ , TeBr ₂ , TeBr ₄ , TeI ₄ ; PbF ₄ , PbF ₂ , _{PbBr 2} Halogenated lead, etc .; examples thereof include halogenated bismuth, such as BiF _{3, BiBr 3 ,} and BiI ₃ .

Among them, lithium halide or phosphorus halide is preferable, LiBr, LiI or PBr ₃ is more preferable, LiBr or LiI is further preferable, and LiBr is most preferable.
As the halogen compound, one of the above compounds may be used alone, or two or more of them may be used in combination.

Elemental substances that can be used as a raw material include elemental phosphorus such as lithium metal and elemental phosphorus such as red phosphorus, or elemental sulfur. It may be effective to use elemental sulfur as a raw material as a dissolution aid.

The above-mentioned compounds and simple substances can be used without particular limitation as long as they are industrially manufactured and sold. The compounds and simple substances are preferably of high purity.

The elemental composition of the solid electrolyte raw material is adjusted by mixing the above compounds and the like. A combination of the above compounds and two or more substances selected from simple substances may be used as a raw material for a solid electrolyte, and in advance, such as Li ₃ PS ₄ , Li ₂ P ₂ S ₆ , Li ₇ P ₃ S ₁₁ , etc. A compound obtained by reacting the above substances may be used as a raw material for a solid electrolyte.
In one embodiment of the present invention, it is preferable to react lithium sulfide with phosphorus sulfide in a solvent to obtain a solid electrolyte raw material-containing liquid.

In one embodiment of the present invention, the solid electrolyte raw material is a mixture containing a lithium compound, a phosphorus compound and a compound containing chlorine, and it is preferable that at least one of the lithium compound and the phosphorus compound contains a sulfur element. A combination of Li 2S, phosphorus sulfide and LiCl is more preferable, and a combination of Li _{2S, P2S 5 and LiCl} is even _more preferable. Further, a combination of Li ₂ S, P ₂ S ₅ , Li Cl, and Li Br is also preferable.
In addition, in order to improve the solubility of the raw material, LiSH, Li ₂ CS ₃ , Li ₂ S _x or the like may be used instead of Li ₂ S.
In one embodiment of the present invention, the solid electrolyte raw material is phosphorus sulfide, elemental phosphorus, phosphorus chloride, PSX ₃ (X is a halogen element selected from F, Cl, Br and I, and at least one of X is. Cl.), Li ₃ PS ₄ , Li ₂ P ₂ S ₆ and Li ₇ P ₃ S ₁₁ are preferably contained. Further, the solid electrolyte raw material preferably contains lithium sulfide.
Further, it is preferable that at least one of the compounds or simple substances contained in the solid electrolyte raw material is soluble in the solvent. In addition, soluble means that a part or all of a compound or a simple substance is dissolved in a liquid.

When Li ₂ S, P ₂ S ₅ and Li Cl are used as raw materials for the argylodite type solid electrolyte, the molar ratio of the compound is set to Li ₂ S: P ₂ S ₅ : LiCl = 30-60: 10-25 :. It can be 15 to 50. Li ₂ S: P ₂ S ₅ : LiCl = 45 to 55:10 to 15:30 to 50, and more preferably Li ₂ S: P ₂ S ₅ : LiCl = 45 to 50: 11 to 14. : 35 to 45, more preferably Li ₂ S: P ₂ S ₅ : LiCl = 46 to 49: 11 to 13: 38 to 42.
When other lithium halides are used as a part of LiCl, the above molar ratio is the sum of LiCl and other lithium halides.

Examples of the solvent in which the solid electrolyte raw material is dissolved or dispersed and used as the contained liquid include polar solvents. Specifically, ketones such as nitrile compounds, acetone and methyl ethyl ketone, ethers such as tetrahydrofuran, dimethoxyethane and diethyl ether, carbonates such as dimethyl carbonate, esters such as ethyl acetate, alcohols such as ethanol and butanol, Examples thereof include amines such as pyridine, aniline, hydrazine, triethylamine, diethylamine, monoethylamine and ammonia, and amides of N-methylformamide and N-methyl-2-pyrrolidone (NMP). Ethers or amines are preferable, and amines are most preferable. Of these, pyridine is preferable. When ethers are used, it is preferable to provide a step of blowing hydrogen sulfide into the contained liquid. By treating with hydrogen sulfide, the production of lithium phosphate in the obtained solid electrolyte can be suppressed. As a result, the ionic conductivity of the solid electrolyte is increased.

Examples of the medium to which the solid electrolyte raw material-containing liquid is supplied include a liquid or gas that is stable even at a temperature higher than the boiling point of the above-mentioned solvent.
As the liquid, a liquid having an insoluble algyrodite-type crystal structure and a high boiling point, which is the target product, can be preferably used. The fact that the crystal structure is insoluble means that part or all of the crystal structure is not dissolved in the liquid and precipitates as a solid. Specifically, hydrocarbons having a high boiling point can be used. Examples thereof include saturated hydrocarbons such as tridecane and tetradecane, and aromatic hydrocarbons such as diaryl ethers, alkylaryls and aryl halides.
The boiling point of the liquid is preferably 150 ° C. or higher and 500 ° C. or lower, and more preferably 180 ° C. or higher and 400 ° C. or lower, because the solvent injected into the medium can be easily volatilized and removed and the decomposition of the solvent and the medium can be suppressed.

As the gas, an inert gas can be used. Examples of the inert gas include nitrogen and argon. In some cases, hydrogen sulfide can be used. Hydrogen sulfide may be used alone, or hydrogen sulfide and an inert gas may be mixed and used. By using hydrogen sulfide, it may be possible to reduce the mixing of impurities such as oxygen components. The temperature of the gas is preferably 150 ° C. or higher and 700 ° C. or lower.

When a liquid is used as a medium, it is preferable that the liquid is filled in a container and used in a stirred state.
When a gas is used as a medium, it is preferable that the gas is circulated as in a spray dryer, a slurry dryer, or the like.

In the present embodiment, the solid electrolyte raw material-containing liquid is supplied into a high-temperature medium. Upon contact with a hot medium, the solid electrolyte raw material-containing liquid is rapidly heated. As a result, the solvent is vaporized and fine particle solid components are deposited. The solid component is an argylodite-type solid electrolyte produced by the reaction of raw materials or a precursor thereof. The solid component is then crystallized by heating in a hot medium. As a result, argilodite type solid electrolyte fine particles can be obtained.

When the medium is a liquid, the contained liquid can be supplied to the medium by injection, dropping or the like, and when the medium is a gas, it can be supplied by spraying or the like.
In order to atomize and homogenize the solid electrolyte, it is preferable that the supply amount of the solid electrolyte raw material-containing liquid is a constant amount little by little. The supply amount needs to be appropriately adjusted depending on the medium used, the temperature, and the like. For example, a tube pump or a microspray can be used to supply the solid electrolyte raw material-containing liquid.

By recovering the solid component from the medium, solid electrolyte fine particles can be obtained. In the present embodiment, heat treatment (crystallization treatment) and atomization treatment are performed at the time of recovery from the medium. Further, additional heat treatment may be performed in addition to this operation. By this heat treatment, it may be possible to reduce the volatile content, improve the crystallinity, or improve the ionic conductivity.

The fact that the recovered solid electrolyte contains an algyrodite-type crystal structure means that the diffraction peaks are 2θ = 25.2 ± 0.5 deg and 29.7 ± 0.5 deg in the powder X-ray diffraction measurement using CuKα beam. It can be confirmed by having. The diffraction peaks of 2θ = 25.2 ± 0.5 deg and 29.7 ± 0.5 deg are peaks derived from the algyrodite type crystal structure. The diffraction peaks of the algyrodite type crystal structure are, for example, 2θ = 15.3 ± 0.5 deg, 17.7 ± 0.5 deg, 31.1 ± 0.5 deg, 44.9 ± 0.5 deg, 47.7 ± 0. It may also appear in .5deg.

Examples of the algyrodite-type crystal structure include the crystal structure disclosed in JP-A-2010-540396. Examples of the composition formula include Li ₆ PS ₅ X, Li _7-x PS _6-x X _x (X = Cl, Br, I, x = 0.0 to 1.8) and the like.

In the present embodiment, as long as the solid electrolyte has an algyrodite type crystal structure, an amorphous (glass) component may be contained in a part thereof. The amorphous component shows a halo pattern in the powder X-ray diffraction measurement. Further, the solid electrolyte may contain a crystal structure other than the algyrodite type crystal structure, and the raw material may remain.

The solid electrolyte obtained in the present embodiment preferably has a volume-based average particle diameter (D ₅₀ ) of 200 μm or less from the viewpoint of being used as a battery material. It is preferably 0.1 μm or more and 100 μm or less, more preferably 0.1 μm or more and 50 μm or less, and further preferably 0.1 μm or more and 20 μm or less. Details of the measurement of _D50 will be described in Examples described later.

Hereinafter, the present invention will be described in more detail with reference to Examples.
The evaluation method is as follows.
(1) Powder X-ray diffraction (XRD) measurement The solid electrolyte powder produced in each example was filled in a groove having a diameter of 20 mm and a depth of 0.2 mm and leveled with glass to prepare a sample. This sample was measured with a Kapton film for XRD without contact with air. The 2θ position of the diffraction peak was determined by Le Ball analysis using the XRD analysis program RIETAN-FP.
It was carried out under the following conditions using the powder X-ray diffraction measuring device D2 PHASER of BRUKER Co., Ltd.
Tube voltage: 30kV
Tube current: 10mA
X-ray wavelength: Cu-Kα ray (1.5418 Å)
Optical system: Concentrated method Slit configuration: Solar slit 4 °, divergence slit 1 mm, Kβ filter (Ni plate) used Detector: Semiconductor detector Measurement range: 2θ = 10-60deg
Step width, scan speed: 0.05 deg, 0.05 deg / sec
In the analysis of the peak position for confirming the existence of the crystal structure from the measurement result, the baseline was corrected by the 11th-order Legendre orthogonal polynomial using the XRD analysis program RIETAN-FP, and the peak position was obtained.

(2) Ion Conductivity Measurement A solid electrolyte was filled in a tablet molding machine, and a pressure of 407 MPa was applied to obtain a molded product. Carbon was placed on both sides of the molded body as an electrode, and pressure was applied again with a tablet molding machine to prepare a molded body (diameter: about 10 mm, thickness: 0.1 to 0.2 cm) for measurement. The ionic conductivity of this molded product was measured by AC impedance measurement. As the value of conductivity, the value at 25 ° C. was adopted.

(3) Volume-based average particle diameter (D ₅₀ )
The measurement was performed with a laser diffraction / scattering type particle size distribution measuring device (LA-950V2 model LA-950W2 manufactured by HORIBA).
A mixture of dehydrated toluene (manufactured by Wako Pure Chemical Industries, Ltd., special grade) and tert-butyl alcohol (manufactured by Wako Pure Chemical Industries, Ltd., special grade) at a weight ratio of 93.8: 6.2 was used as a dispersion medium. After injecting 50 ml (milliliter) of the dispersion medium into the flow cell of the apparatus and circulating it, the measurement target was added and ultrasonic treatment was performed, and then the particle size distribution was measured. The amount of addition to be measured is 80 to 90% for the red light transmittance (R) and 70 to 90% for the blue light transmittance (B) corresponding to the particle concentration on the measurement screen specified by the device. Adjusted to fit. Further, as the calculation conditions, 2.16 was used as the value of the refractive index of the measurement target, and 1.49 was used as the value of the refractive index of the dispersion medium. In setting the distribution form, the particle size was calculated by fixing the number of repetitions to 15 times.

Production Example 1
(Manufacturing of lithium sulfide (Li _2S ))
It was produced by the method described in Example 1 of WO2016 / 098351.
Specifically, lithium hydroxide anhydrous dried under an inert gas in a 500 ml separable flask equipped with an anchor stirring blade (manufactured by Honjo Chemical Co., Ltd., particle size range: 0.1 mm or more and 1.5 mm or less, 200 g of water content (1 wt% or less) was charged. The temperature was raised under a nitrogen stream while stirring at 200 rpm, and the internal temperature (powder) was maintained at 200 ° C. using an oil bath. At the same time, the upper part of the separable flask was held at 100 ° C. with a ribbon heater. The nitrogen gas was switched to hydrogen sulfide gas (manufactured by Sumitomo Seika Co., Ltd.), the flow rate was 500 ml / min, and the lithium hydroxide anhydride and hydrogen sulfide were reacted while stirring with an anchor blade.

The water generated by the reaction was condensed and recovered by a condenser. When the reaction was carried out for 6 hours, 144 ml of water was recovered. Further, hydrogen sulfide was maintained at 500 ml / min and the reaction was continued for 3 hours, but no water was generated. In addition, no adhesion of the product to the separable flask or the like was observed.
Subsequently, while the temperature was maintained at 200 ° C., the hydrogen sulfide gas was switched to nitrogen gas, the nitrogen gas was aerated for 20 minutes, and the hydrogen sulfide gas in the flask was replaced with nitrogen gas. The internal temperature was lowered while nitrogen gas was flowing, and the product powder (Li _2S ) was recovered. As a result of potentiometric titration, the purity of Li _{2S was 98.5 wt%, and the amount of LiOH in Li 2 S} was 0.1 wt% or less.

Example 1
(Preparation of liquid containing solid electrolyte raw material)
As raw materials, 6.763 g of Li ₃ PS ₄ , 0.690 g of Li ₂ S manufactured in Production Example 1 and 2.547 g of LiCl (manufactured by Sigma-Aldrich) are weighed in a nitrogen gas atmosphere and have a capacity of 500 ml. It was put into a container. 120 ml of dehydrated ethanol was added to the container to prepare a solid electrolyte raw material-containing liquid.
In addition, Li ₃ PS ₄ (glass) was synthesized by the method described in Example 4 of JP-A-2012-134133. Specifically, 30.62 g of Li ₂ S and 49.38 g of P ₂ S ₅ (manufactured by Sigma-Aldrich) manufactured in Production Example 1 are placed in a 500 ml alumina container containing 175 alumina balls having a diameter of 10 mm and sealed. bottom. The molar ratio of Li ₂ S and P ₂ S ₅ (Li ₂ S: P ₂ S ₅ ) is 75:25. The alumina container was mounted on a planetary ball mill (manufactured by Fritsch, model number P-5), and the composition was performed by processing (mechanical milling) at a rotation speed of 250 rpm for 36 hours.

(Adjustment of high temperature medium)
480 ml of tridecane was placed in a 500 ml separable flask equipped with a stirrer and a condenser, and the inside of the flask was replaced with _N2 gas. The temperature of tridecane was raised to 210 ° C. and maintained.

(Injection of liquid containing solid electrolyte raw material)
Using a tube pump, the solid electrolyte raw material-containing liquid was poured into the separable flask over about 1 hour. Ethanol volatilized at the same time as the injection of the solid electrolyte raw material-containing liquid. The vaporized ethanol was liquefied by a condenser and recovered. At the same time as vaporization, solid content was precipitated in tridecane to form a slurry. After the injection of the solid electrolyte raw material-containing liquid was completed, stirring was continued for 30 minutes.

(Recovery of product)
After cooling the slurry consisting of tridecane and the solid content (product) to 100 ° C., the solid content was separated by decantation. The separated solid content was washed with toluene three times. After washing, it was vacuum dried at 150 ° C. to recover the solid content.

As a result of XRD measurement of the recovered solid content, it was confirmed that it contained an algyrodite type crystal structure. The ionic conductivity was 6 × 10 ^-5 S / cm. D ₅₀ was 16 μm. The particle size distribution of the solid electrolyte is shown in FIG.

(Heat treatment)
The solid electrolyte obtained in Example 1 was set in a gas flow furnace and heat-treated at 430 ° C. for 8 hours under a hydrogen sulfide stream.
As a result of XRD measurement, diffraction peaks derived from argylodite-type crystal structure and impurities lithium phosphate and lithium chloride were observed. The ionic conductivity was 2 mS / cm. D ₅₀ was 37 μm.

Example 2
Regarding the preparation of the solid electrolyte raw material-containing liquid, _3.179 g of Li 2S as a raw material and 7.701 g of elemental sulfur as a dissolution aid (manufactured by Aldrich) were weighed in a nitrogen gas atmosphere, and a container of 500 ml was used. I put it in. 120 ml of tetrahydrofuran (THF: dehydrated product) was added to the container to prepare a solution. Subsequently, 4.174 g of P2S ₅ and _2.547 g of LiCl were added and dissolved to prepare a solid electrolyte raw material-containing liquid.
Other than that, a solid electrolyte was prepared in the same manner as in Example 1 and heat-treated.
As a result of XRD measurement of the solid electrolyte (before heat treatment), it was confirmed that it contained an algyrodite type crystal structure. The ionic conductivity was 6 × 10 ^-5 S / cm. D ₅₀ was 15 μm. The particle size distribution of the solid electrolyte is shown in FIG.
The ionic conductivity after the heat treatment was 0.05 mS / cm. As a result of XRD measurement, a diffraction peak derived from an algyrodite type crystal structure and an impurity lithium phosphate was observed.

Example 3-1
(Preparation of liquid containing solid electrolyte raw material)
As raw materials, 3.279 g of Li 2S, _2.547 g of LiCl (manufactured by Sigma-Aldrich) and 4.174 g of P2 S5 ₍ manufactured by Sigma _- Aldrich) manufactured in Production Example 1 were weighed in a nitrogen gas atmosphere. It was put into a container having a capacity of 500 ml. Under ice-cooling, 120 ml of dehydrated pyridine was added to the container with stirring. After returning to room temperature for 20 hours, the mixture was heated to 80 ° C. and reacted for 5 hours.
Since the mixture was viscous after the reaction was completed, 20 ml of pyridine was added, and hydrogen sulfide was further blown into the reaction mixture at 100 ml / min for 1 hour to contain a solid electrolyte raw material (solvent: pyridine, with hydrogen sulfide treatment). Was prepared.
Others performed the same operations as in Example 1.
As a result of XRD measurement of the recovered solid content, it was confirmed that it contained an algyrodite type crystal structure. The ionic conductivity was 3.29 × ^10-6 S / cm. D ₅₀ was 78 μm. The particle size distribution of the solid electrolyte is shown in FIG.

(Heat treatment)
The solid electrolyte obtained in Example 3-1 was set in a gas flow furnace and heat-treated at 430 ° C. for 8 hours under a hydrogen sulfide stream. As a result of the heat treatment, an algyrodite type crystal structure was observed as a main component by XRD measurement. The ionic conductivity was 7.08 mS / cm.

Example 3-2
A solid electrolyte was prepared and heat-treated in the same manner as in Example 3-1 except that hydrogen sulfide was not blown into the solid electrolyte raw material-containing liquid.
As a result of XRD measurement of the solid electrolyte (before heat treatment), it was confirmed that it contained an algyrodite type crystal structure. The ionic conductivity was 3 × 10 ^-6 S / cm.
The ionic conductivity after the heat treatment was 8.5 mS / cm. An algyrodite-type crystal structure was observed as a main component by XRD measurement.
From Examples 3-1 and 3-2, when pyridine is used as the solvent, the ionic conductivity of the solid electrolyte can be significantly improved by the heat treatment regardless of the presence or absence of hydrogen sulfide treatment of the solid electrolyte raw material-containing liquid. You can check.

Example 4
A solid electrolyte raw material-containing liquid (solvent: THF, with hydrogen sulfide treatment) was prepared using dehydrated THF instead of dehydrated pyridine, and a solid electrolyte was prepared and heat-treated in the same manner as in Example 3-1.
As a result of XRD measurement of the solid electrolyte (before heat treatment), it was confirmed that it contained an algyrodite type crystal structure. The ionic conductivity was 6.60 × ^10-5 S / cm. D ₅₀ was 29 μm. The particle size distribution of the solid electrolyte is shown in FIG.
After the heat treatment, an algyrodite type crystal structure was observed as a main component by XRD measurement. The ionic conductivity was 4.47 mS / cm.
When THF, which is an ether, was used as the solvent, the ionic conductivity of the solid electrolyte of Example 4 was significantly improved by the heat treatment as compared with Example 2 in which the solid electrolyte raw material-containing liquid in which hydrogen sulfide was not blown was used. It can be confirmed that it will be done.

Example 5
(Spraying of liquid containing solid electrolyte raw material)
The solid electrolyte raw material-containing liquid (solvent: pyridine, with hydrogen sulfide treatment) prepared in Example 3-1 was spray-dried (micro mist spray dryer Labo MDL-015 (C) MH, Fujisaki Electric Co., Ltd.). By treating with, a solid electrolyte was prepared. Nitrogen at 300 ° C. was used as the high temperature medium (dry gas).
As a result of XRD measurement of the solid electrolyte, it was confirmed that it contained an algyrodite type crystal structure. The ionic conductivity was 2.32 × 10 ^-4 S / cm. D ₅₀ was 9 μm. The particle size distribution of the solid electrolyte is shown in FIG.

(Heat treatment)
The solid electrolyte obtained in Example 5 was set in a gas flow furnace and heat-treated at 430 ° C. for 8 hours under a hydrogen sulfide stream.
As a result of XRD measurement, an algyrodite type crystal structure and a diffraction peak of the β crystal of Li ₃ PS ₄ were observed. The ionic conductivity was 2 mS / cm.

Comparative Example 1
The solid electrolyte raw material-containing liquid (solvent: ethanol) prepared in the same manner as in Example 1 is heated in an oil bath at 150 ° C. for 3 hours while stirring under vacuum to remove ethanol and dry to remove solid content. Collected.
As a result of XRD measurement of the solid content, no diffraction peak derived from the algyrodite type crystal structure was observed.

Comparative Example 2
The solid electrolyte raw material-containing liquid (solvent: THF) prepared in the same manner as in Example 2 is heated in an oil bath at 150 ° C. for 3 hours while stirring under vacuum to remove THF and dry to remove solid content. Collected.
As a result of XRD measurement of the solid content, no diffraction peak derived from the algyrodite type crystal structure was observed.

Comparative Example 3
The solid content was recovered in the same manner as in Comparative Example 2 except that the solid electrolyte raw material-containing liquid (solvent: THF, with hydrogen sulfide treatment) prepared in the same manner as in Example 4 was used.
As a result of XRD measurement of the solid content, no diffraction peak derived from the algyrodite type crystal structure was observed.

Comparative Example 4
The solid electrolyte raw material-containing liquid (solvent: pyridine) prepared in the same manner as in Example 3-2 is heated in an oil bath at 150 ° C. for 3 hours while stirring under vacuum to remove pyridine, dry, and solidify. The minutes were collected.
As a result of XRD measurement of the solid content, no diffraction peak derived from the algyrodite type crystal structure was observed.

Comparative Example 5
The solid content was recovered in the same manner as in Comparative Example 4, except that the solid electrolyte raw material-containing liquid (solvent: pyridine, with hydrogen sulfide treatment) prepared in the same manner as in Example 3-1 was used.
As a result of XRD measurement of the solid content, no diffraction peak derived from the algyrodite type crystal structure was observed.

Claims (15)

A solid electrolyte raw material-containing liquid containing a solid electrolyte raw material containing lithium, phosphorus, sulfur and chlorine and a solvent is supplied to a medium which is a liquid or gas at a temperature higher than the boiling point of the solvent and is supplied with the solvent. A method for producing a solid electrolyte, which comprises reacting the solid electrolyte raw material with the solid electrolyte raw material to precipitate an algyrodite type crystal structure. The method for producing a solid electrolyte according to claim 1, wherein the solvent is amines or ethers. The method for producing a solid electrolyte according to claim 2, wherein the amines are pyridine. The solvent is ethers,
The method for producing a solid electrolyte according to claim 1 or 2, which comprises blowing hydrogen sulfide into the solid electrolyte raw material -containing liquid. The method for producing a solid electrolyte according to any one of claims 1 to 4, wherein the medium is a liquid and the algyrodite-type crystal structure is insoluble in the liquid. The method for producing a solid electrolyte according to any one of claims 1 to 5, wherein the medium is a liquid, and the solid electrolyte raw material-containing liquid is injected or dropped into the liquid. The method for producing a solid electrolyte according to any one of claims 1 to 4, wherein the medium is a gas and the solid electrolyte raw material-containing liquid is sprayed onto the gas. The method for producing a solid electrolyte according to any one of claims 1 to 7, wherein the solid electrolyte raw material contains a compound or a simple substance containing one or more elements selected from lithium, phosphorus, sulfur and chlorine. The method for producing a solid electrolyte according to any one of claims 1 to 8, wherein the solid electrolyte raw material contains lithium chloride. The solid electrolyte raw material is phosphorus sulfide, elemental phosphorus, phosphorus chloride, PSX ₃ (X is one or more selected from F, Cl, Br and I, and represents a halogen element containing at least Cl), Li. ₃ The method for producing a solid electrolyte according to any one of claims 1 to 9, which comprises one or more selected from PS ₄ , Li ₂ P ₂ S ₆ and Li ₇ P ₃ S ₁₁ . The method for producing a solid electrolyte according to any one of claims 1 to 10, wherein the solid electrolyte raw material contains lithium sulfide. The method for producing a solid electrolyte according to any one of claims 1 to 11, wherein lithium sulfide and phosphorus sulfide are reacted in the solvent to obtain the solid electrolyte raw material-containing liquid. The method for producing a solid electrolyte according to any one of claims 1 to 12, wherein the volume-based average particle diameter (D ₅₀ ) of the solid electrolyte is 200 μm or less. The method for producing a solid electrolyte according to any one of claims 1 to 13, wherein at least one of the compounds or simple substances contained in the solid electrolyte raw material is soluble in the solvent. The method for producing a solid electrolyte according to any one of claims 1 to 14, wherein the medium is a saturated hydrocarbon or an aromatic hydrocarbon.

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