JP2021118038A - Manufacturing method of sulfide-based solid electrolyte - Google Patents

Abstract

To provide a manufacturing method of an LGPS-type sulfide-based solid electrolyte having high ionic conductivity and a small particle size, and an LGPS-type sulfide-based solid electrolyte obtained by the manufacturing method.SOLUTION: There is provided a manufacturing method of an LGPS-type sulfide-based solid electrolyte for all-solid-state lithium battery, which includes the steps of crushing a coarse particulate LGPS type solid electrolyte using a ball mill to obtain a crushed product, and obtaining a pulverized and heat-treated LGPS type solid electrolyte by heat-treating the crushed product, and there is also provided an LGPS type sulfide-based solid electrolyte obtained by the manufacturing method.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a sulfide-based solid electrolyte, and an LGPS-type sulfide-based solid electrolyte obtained by the production method.

In recent years, the demand for lithium ion secondary batteries has been increasing in applications such as personal digital assistants, portable electronic devices, electric vehicles, hybrid electric vehicles, and stationary power storage systems. However, the current lithium ion secondary battery uses a flammable organic solvent as the electrolytic solution, and requires a strong exterior so that the organic solvent does not leak. In addition, in portable personal computers and the like, there are restrictions on the structure of the equipment, such as the need to take a structure to prepare for the risk of leakage of the electrolytic solution.

Furthermore, its use has expanded to mobile objects such as automobiles and airplanes, and a large capacity is required for a stationary lithium ion secondary battery. Under these circumstances, safety tends to be more important than before, and efforts are being focused on the development of all-solid-state lithium-ion secondary batteries that do not use harmful substances such as organic solvents.

For example, it has been studied to use oxides, phosphoric acid compounds, organic polymers, sulfides and the like as solid electrolytes in all-solid-state lithium-ion secondary batteries.
Among these solid electrolytes, sulfide has high ionic conductivity, is relatively soft, and easily forms an interface between solids. It is stable against active materials and is being developed as a practical solid electrolyte.

Particle size is one of the performance requirements for solid electrolytes. The electrode layer in an all-solid-state lithium-ion secondary battery is made by combining an electrode active material and a solid electrolyte, and is a solid having a small particle size for the purpose of forming a good contact interface between the electrode active material and the solid electrolyte. Electrodes are desired. Similarly, in the solid electrolyte layer that separates the positive electrode layer and the negative electrode layer, a solid electrolyte having a small particle size is desired for the purpose of forming a thinner layer. For the above reasons, various methods for pulverizing sulfide-based solid electrolytes have been studied.

Jet mills, bead mills, pin mills, planetary ball mills, and the like are known as methods for pulverizing sulfide-based solid electrolytes. In Patent Document 1, by pulverizing an algyrodite type solid electrolyte with a jet mill or a bead mill, fine particles having a small particle size and high ionic conductivity are obtained. However, the LGPS type solid electrolyte has a problem that the ionic conductivity is lowered when it is similarly pulverized by using a bead mill or a jet mill.

Similarly, Patent Document 2 discloses a method for pulverizing an LGPS type solid electrolyte with a planetary ball mill, but even when a planetary ball mill is used, there is a problem that the ionic conductivity is significantly lowered when the pulverization treatment is performed. rice field.

Japanese Unexamined Patent Publication No. 2019-36536 JP-A-2019-102412

Under such circumstances, it is desired to provide a method for producing an LGPS-type sulfide-based solid electrolyte having high ionic conductivity and a small particle size.

Therefore, the present inventors have conducted diligent research in view of the above problems, and have found that a ball mill is suitable as a method for pulverizing an LGPS type solid electrolyte. A planetary ball mill or a jet mill is generally used as a crushing method for obtaining a powder having a size of several μm. However, when crushing an LGPS type solid electrolyte, the crystal structure of the solid electrolyte is destroyed by strong crushing energy, and eventually ions. The conductivity will decrease. On the other hand, the ball mill has a weaker crushing force than the planetary ball mill and the jet mill, but can suppress the collapse of the crystal structure and the decrease in the ionic conductivity. Furthermore, it has been found that the LGPS type solid electrolyte can be sufficiently miniaturized even with a weak pulverizing force of a ball mill. It is considered that this is because the LGPS type solid electrolyte is softer than other sulfide type solid electrolytes such as algyrodite type. Based on the above findings, the present invention has been completed.

That is, the present invention is as follows.
<1>
A step of crushing a coarse particulate LGPS type solid electrolyte using a ball mill to obtain a crushed product, and
A step of obtaining a pulverized and heat-treated LGPS type solid electrolyte by heat-treating the pulverized product, and
A method for producing an LGPS type solid electrolyte for an all-solid-state lithium battery.
<2>
The method for producing a solid electrolyte for an all-solid-state lithium battery according to <1>, wherein the step of obtaining the pulverized product further comprises adding a solvent to the coarse particulate LGPS type solid electrolyte.
<3>
The method for producing a solid electrolyte for an all-solid-state lithium battery according to <2>, wherein the solvent is added in an amount of 10 wt% or less with respect to the coarse particulate LGPS type solid electrolyte.
<4>
The production of the solid electrolyte for an all-solid-state lithium battery according to <2> or <3>, wherein the solvent is one or more solvents selected from the group consisting of a nitrile solvent, an ether solvent, and a hydrocarbon solvent. Method.
<5>
The method for producing a solid electrolyte for an all-solid-state lithium battery according to <4>, wherein the solvent is selected from the group consisting of acetonitrile, tetrahydrofuran, and heptane.
<6>
The method for producing a solid electrolyte for an all-solid-state lithium battery according to <1> to <5>, wherein the LGPS type solid electrolyte is composed of a sulfur element, a phosphorus element, a silicon element, a chlorine element and a lithium element.
<7>
The crushed and heat-treated solid electrolyte has a decrease in ionic conductivity of 2.0 mS / cm or less and a median diameter of 10 μm or less as compared with the coarse particulate LGPS type solid electrolyte before crushing. 1> The method for producing a solid electrolyte for an all-solid-state lithium battery according to <6>.

According to the present invention, it is possible to provide a method for producing an LGPS-type sulfide-based solid electrolyte having high ionic conductivity and a small particle size.

FIG. 1 is a schematic view showing a crystal structure of a sulfide-based solid electrolyte according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of an all-solid-state battery according to an embodiment of the present invention. FIG. 3 is a graph showing the results of X-ray diffraction measurement of the sulfide-based solid electrolytes obtained in Examples 1 to 5, Comparative Example 2, and Reference Example.

Hereinafter, the present invention will be described in detail. The materials and configurations described below are not limited to the present invention, and can be variously modified within the scope of the gist of the present invention.

In the present specification, the LGPS type solid electrolyte refers to a solid electrolyte having a specific crystal structure including Li, P and S, and is selected from the group consisting of Li, M (M is Ge, Si and Sn), for example. One or more elements), solid electrolytes containing P and S.

As shown in FIG. 1, the crystal structure of the LGPS type solid electrolyte includes an octahedron O composed of Li element and S element, and one or more elements selected from the group consisting of P, Ge, Si, and Sn. It has a tetrahedron T1 composed of S element and a tetrahedron T2 composed of P element and S element, shares the early tetrahedron T1 and the octahedron O ridge, and has the tetrahedron T2 and the octahedron. O is characterized by sharing a vertex.

The LGPS type solid electrolyte has at least 2θ = 20.18 ° ± 0.50 °, 20.44 ° ± 0.50 °, 26.96 ° ± 0 in X-ray diffraction (CuKα: λ = 1.5405 Å). It has peaks at .50 ° and 29.58 ° ± 0.50 °.

1. 1. Production of Coarse Particulate LGPS Type Solid Electrolyte The coarse particulate LGPS type solid electrolyte, which is the target of the method for producing the LGPS type solid electrolyte for an all-solid-state lithium battery of the present invention, is the mechanical milling method described in Japanese Patent No. 5527673. It can be produced by a known method such as the liquid phase synthesis method described in International Publication No. WO2019 / 044517. Hereinafter, the production method will be described using an LGPS-type solid electrolyte containing Li, Si, P, and S as constituent elements as an example, but the embodiments of the present invention are not limited thereto.

Mechanical milling method After mixing the powders of Li ₂ S, P ₂ S ₅ , and Si _{S 2} , the precursor of the LGPS type solid electrolyte is obtained by pulverizing and mixing using a planetary ball mill or the like. Next, by heat-treating the obtained precursor of the LGPS-type solid electrolyte, a coarse-grained LGPS-type solid electrolyte can be obtained. The feature of the mechanical milling method is that the composition is homogenized and amorphized by applying strong mechanical energy.

A solution prepared by dissolving by reacting the Li 2 _S and P ₂ S ₅ in the liquid phase synthesis method acetonitrile or an organic solvent such as tetrahydrofuran, Li 2 _S, and obtain a suspension by adding a powder of SiS ₂ .. Next, the organic solvent is distilled off to obtain a precursor of the LGPS type solid electrolyte. Subsequently, the obtained precursor is heat-treated to obtain a coarse-particulate LGPS-type solid electrolyte. The feature of the liquid phase synthesis method is that a part or all of the raw materials are reacted and dissolved in an organic solvent to make the composition uniform and amorphize.

2. Method for producing LGPS type solid electrolyte for all-solid-state lithium battery of the present invention The present invention is a method for producing a sulfide-based solid electrolyte. Providing a manufacturing method for.

The method for producing an LGPS type solid electrolyte for an all-solid-state lithium battery of the present invention is as follows.
A step of crushing a coarse particulate LGPS type solid electrolyte using a ball mill to obtain a crushed product (hereinafter, also referred to as a "crushing step").
A step of obtaining a pulverized and heat-treated LGPS-type solid electrolyte by heat-treating the pulverized product (hereinafter, also referred to as a “heat treatment step”).
including. In the method of the present invention, by pulverizing the LGPS type sulfide-based solid electrolyte using a ball mill, it is possible to pulverize while suppressing the decrease in ionic conductivity, the ionic conductivity is high, and the particle size is small. It is possible to obtain an LGPS type solid electrolyte for an all-solid-state lithium battery having a small value. Specifically, it is possible to obtain particles of a solid electrolyte having a median diameter of 10 μm or less, particularly 5 μm or less. The median diameter defined in the present invention is the particle diameter at which the cumulative frequency is 50% in the volume-based particle size distribution histogram, and is sometimes called the median diameter, and is expressed as D50. There is also. Examples of the means for measuring the particle size distribution include a laser diffraction / scattering method, a dynamic light scattering method, a sedimentation method, and a sieving method. The median diameter defined in the present invention is a measured value by the laser diffraction / scattering method. Is.

(1) Crushing Step As described above, the method for producing an LGPS type solid electrolyte for an all-solid-state lithium battery of the present invention includes a step of pulverizing a coarse particulate LGPS type solid electrolyte using a ball mill to obtain a pulverized product. .. In the step of obtaining the pulverized product, the pulverization conditions (temperature, rotation speed, etc.) can be appropriately adjusted in consideration of the apparatus to be used, the state of the solid electrolyte, and the like.

The ball mill defined in the present invention is a kind of crusher, and a hard ball such as ceramic and a powder to be crushed are placed in a cylindrical container and rotated to rotate to grind the crushed object. It is a device that produces fine powder.

In one embodiment of the present invention, the step of obtaining the pulverized product can further include adding a solvent to the coarse particulate LGPS type solid electrolyte. That is, in the embodiment of the present invention, the step of obtaining the pulverized product may be carried out by adding a solvent to the coarse particulate LGPS type solid electrolyte, or adding a solvent to the coarse particulate LGPS type solid electrolyte. It may be carried out without any problem. In one embodiment of the present invention, the step of obtaining the pulverized product is carried out by adding a solvent to a coarse particulate LGPS type solid electrolyte. In another embodiment of the present invention, the step of obtaining the pulverized product is carried out without adding a solvent to the coarse particulate LGPS type solid electrolyte. In a preferred embodiment of the present invention, the grinding step can be carried out by adding a solvent.

In one embodiment of the present invention, when a solvent is added and pulverized in the step of obtaining the pulverized product, the solvent can be added in an amount of 10 wt% or less with respect to the coarse particulate LGPS type solid electrolyte. When a solvent is added in the step of obtaining the pulverized product, if the amount of the solvent to be added is within the above range, the coarse particle LGPS type solid electrolyte can be pulverized more finely, and the solid electrolyte can be added to a ball mill container or a ball. Sticking is suppressed and recovery becomes easy. If the amount of the solvent added is more than the above range, the solid electrolyte may be altered and the ionic conductivity may be lowered. Further, if the amount of the solvent to be added is larger than the above range, the solid electrolyte may be strongly adhered to the container or ball of the ball mill, which may make recovery difficult.

In the step of obtaining the pulverized product, the amount of the solvent cannot be unconditionally specified because it depends on the volume of the ball mill container, the type of solvent, etc., but it is more than 0 and 10 wt% or less with respect to the coarse particulate solid electrolyte. Yes, preferably 0.1 or more and 10 wt% or less, and more preferably 0.1 or more and 2 wt% or less.

The solvent that can be used in the step of obtaining the pulverized product is not limited as long as the coarse particle LGPS type solid electrolyte can be pulverized more finely, and is, for example, a nitrile solvent, an ether solvent, and a hydrocarbon solvent. One or more solvents selected from the group consisting of solvents can be used. The above solvent may be used alone or in combination of two or more.

Examples of the nitrile-based solvent include acetonitrile, propionitrile, butyronitrile, isobutylonitrile, valeronitrile, 2-methylbutyronitrile, isovaleronitrile, pivalonitrile, hexanenitrile, heptanenitrile, benzonitrile and the like. However, it is not limited to these. In a preferred embodiment, the nitrile solvent may be acetonitrile.

Examples of the ether solvent include, but are not limited to, tetrahydrofuran, cyclopentyl methyl ether, diisopropyl ether, diethyl ether, dimethyl ether, dioxane and the like. In a preferred embodiment, the ether solvent may be tetrahydrofuran.

Examples of the hydrocarbon solvent include an aliphatic hydrocarbon solvent and an aromatic hydrocarbon solvent. Examples of the aliphatic hydrocarbon solvent include, but are not limited to, saturated aliphatic hydrocarbon solvents having 6 to C11 carbon atoms. Examples of the saturated aliphatic hydrocarbon solvent having 6 to C11 carbon atoms include, but are not limited to, hexane, cyclohexane, heptane, octane, nonane, decane, and undecane. Examples of the aromatic hydrocarbon solvent include, but are not limited to, benzene, toluene, ethylbenzene, xylene, chlorobenzene and the like. In a preferred embodiment, the hydrocarbon solvent may be toluene, n-heptane.

The solvent used preferably has a low water content, preferably has a water content of 1000 ppm or less, more preferably 100 ppm or less, and particularly preferably 10 ppm or less. As the dehydration method, conventional methods such as distillation, purification by a column, and addition of molecular sieves can be used.

Examples of the material of the ball used in the ball mill include, but are not limited to, alumina, zirconia, silicon nitride, and the like. The diameter of the ball is not particularly limited, but is preferably 0.1 mmφ to 30 mmφ, more preferably 0.3 mmφ to 10 mmφ, and particularly preferably 1 mmφ to 5 mmφ.

In the step of obtaining the pulverized product, the ball mill container is preferably filled with an inert gas and sealed. Examples of the inert gas include nitrogen, helium, argon and the like, and argon is particularly preferable. The concentrations of oxygen and water in the inert gas are preferably low, both of which are preferably 1000 ppm or less, more preferably 100 ppm or less, and particularly preferably 10 ppm or less.

The temperature inside the ball mill container is not particularly limited as long as it is a temperature at which the LGPS type solid electrolyte does not thermally decompose and does not grow grains, but is preferably in the range of -10 ° C to 120 ° C, preferably in the range of 0 ° C to 60 ° C. More preferably, the range of 10 ° C. to 40 ° C. is particularly preferable.

The rotation speed of the ball mill container is preferably less than the critical rotation speed, more preferably 50% to 90% of the critical rotation speed, and particularly preferably 60% to 80% of the critical rotation speed. The critical rotation speed is the rotation speed when the contents (balls and objects to be crushed) are crimped to the inner wall of the container by centrifugal force and the contents do not fall. The time of the pulverization treatment is not particularly limited, but is in the range of 1 hour to 96 hours, preferably in the range of 3 hours to 48 hours, and more preferably in the range of 6 hours to 24 hours. If the crushing time is short, the particle size may not be sufficiently small. Further, if the pulverization time is long, the crystal structure of the solid electrolyte may be disrupted and the ionic conductivity may be lowered.

(2) Heat Treatment Step As described above, the method for producing an LGPS-type solid electrolyte for an all-solid-state lithium battery of the present invention includes a step of obtaining a crushed and heat-treated LGPS-type solid electrolyte by heat-treating the pulverized product. .. When the pulverization step is carried out, the crystallinity is lowered and the ionic conductivity is lowered. However, by carrying out the heat treatment step after that, the crystallinity can be restored and the ionic conductivity can be improved.

The heat treatment step is carried out at a temperature at which the pulverized product of the LGPS type solid electrolyte obtained by the pulverization step does not grow grains. In the heat treatment step, the heat treatment conditions can be appropriately adjusted in consideration of the apparatus to be used, the state of the solid electrolyte, and the like. In the heat treatment step, the heat treatment temperature may be in the range of 300 ° C. to 700 ° C., preferably in the range of 350 ° C. to 650 ° C., and more preferably in the range of 400 ° C. to 600 ° C. When the heat treatment temperature is within the above range, desired crystals can be easily obtained. If the temperature is lower than 300 ° C., desired crystals are less likely to be formed, while if the temperature is higher than 700 ° C., crystals other than the desired ones are formed, and the ionic conductivity tends to decrease.

The heat treatment step can be carried out in a vacuum or an atmosphere of an inert gas, preferably in an atmosphere of an inert gas. As the inert gas, nitrogen, helium, argon or the like can be used, but argon is particularly preferable. The concentration of oxygen and water is preferably low, both of which are preferably 1000 ppm or less, more preferably 100 ppm or less, and particularly preferably 10 ppm or less.

3. 3. LGPS-type solid electrolyte for all-solid-state lithium battery obtained by the method of the present invention The LGPS-type solid electrolyte for all-solid-state lithium battery of the present invention obtained as described above is made into a desired molded body by various means and is described below. It can be used for various purposes including all-solid-state batteries. The molding method is not particularly limited. For example, a method similar to the method for molding each layer constituting the all-solid-state battery described in <All-solid-state battery> described later can be used.

<All-solid-state battery>
The sulfide-based solid electrolyte of the present invention can be used, for example, as a solid electrolyte for an all-solid-state battery. Further, according to a further embodiment of the present invention, an all-solid-state battery including the above-mentioned solid electrolyte for an all-solid-state battery is provided.

Here, the "all-solid-state battery" is an all-solid-state lithium-ion secondary battery. FIG. 2 is a schematic cross-sectional view of an all-solid-state battery according to an embodiment of the present invention. The all-solid-state battery 10 has a structure in which the solid electrolyte layer 2 is arranged between the positive electrode layer 1 and the negative electrode layer 3. The all-solid-state battery 10 can be used in various devices such as mobile phones, personal computers, automobiles, and the like.

The sulfide-based solid electrolyte of the present invention may be contained as a solid electrolyte in any one or more of the positive electrode layer 1, the negative electrode layer 3, and the solid electrolyte layer 2. The solid electrolyte may be composed of the sulfide-based solid electrolyte of the present invention alone, or if necessary, an oxide solid electrolyte (for example, Li ₇ La ₃ Zr ₂ O ₁₂ ) and a sulfide-based solid electrolyte (for example, Li 7 La 3 Zr 2 O 12). , Li _{2 SP 2} S ₅ ), other complex hydride solid electrolytes (for example, LiBH ₄ , 3 _{LiBH 4-} LiI) and the like may be used in appropriate combinations. When the positive electrode layer 1 or the negative electrode layer 3 contains the sulfide-based solid electrolyte of the present invention, the sulfide-based solid electrolyte of the present invention is used in combination with a known positive electrode active material or negative electrode active material for a lithium ion secondary battery. do. The amount ratio of the sulfide-based solid electrolyte of the present invention contained in the positive electrode layer 1 or the negative electrode layer 3 is not particularly limited.

The all-solid-state battery is manufactured by molding and laminating each of the above-mentioned layers, but the molding method and laminating method of each layer are not particularly limited.

For example, a method in which a solid electrolyte and / or an electrode active material is dispersed in a solvent to form a slurry is applied by a doctor blade or a spin coat, and the film is formed by rolling the film; vacuum deposition method, ion plating. Vapor deposition method in which film formation and lamination are performed using a method, sputtering method, laser ablation method, etc .; there is a pressure molding method in which powder is molded by hot pressing or cold pressing without applying temperature and then laminated. ..

Since the sulfide-based solid electrolyte of the present invention is relatively soft, it is particularly preferable to form and laminate each layer by a pressure molding method to prepare an all-solid-state battery. As a pressure forming method, there are a hot press performed by heating and a cold press not heated, but a cold press can also be sufficiently formed.

The present invention includes a molded body obtained by heat-molding the sulfide-based solid electrolyte of the present invention. The molded product is suitably used as an all-solid-state battery. The present invention also includes a method for manufacturing an all-solid-state battery, which comprises a step of heat-molding the sulfide-based solid electrolyte of the present invention.

Hereinafter, the present embodiment will be described in more detail with reference to Examples, but the present embodiment is not limited to these Examples.

<X-ray diffraction measurement>
The X-ray diffraction measurement was carried out on the sulfide-based solid electrolyte powder in an Ar atmosphere at room temperature (25 ° C.) using PANalytical's "X'Pert3 Powerer" at CuKα: λ = 1.5405 Å.

<Measurement of lithium ion conductivity>
A sulfide-based solid electrolyte was subjected to uniaxial molding (420 MPa) to obtain a disc having a thickness of about 1 mm and a diameter of 10 mm, and then using an all-solid-state battery evaluation cell (manufactured by Hosen Co., Ltd.) at room temperature (25 ° C.). AC impedance measurement by the four-terminal method (“SI1260 IMPEDANCE / GAIN-PHASE ANALYZER” manufactured by Sulfron) was performed, and the lithium ion conductivity was calculated.

Specifically, the sample was placed in a constant temperature bath set at 25 ° C. and held for 30 minutes, and then the lithium ion conductivity was measured. The measurement frequency range was 0.1 Hz to 1 MHz, and the amplitude was 50 mV.

<Measurement of median diameter>
For the sulfide-based solid electrolyte powder, measure the particle size distribution using a laser diffraction / scattering type particle size distribution measuring device (“MT3300EXII” manufactured by Myctrotrack Bell), and determine the median diameter (D50) on a volume basis. rice field.

Production Example First, a coarse particulate LGPS-type solid electrolyte, which is a target of the method for producing an LGPS-type solid electrolyte for an all-solid-state lithium battery of the present invention, was produced according to the steps exemplified below.

<Solution step 1>
In a glove box under an argon atmosphere _{, 1.42 g of Li 2} S (manufactured by Sigma-Aldrich, purity 99.8%) so as to have a molar ratio of _{Li 2} S: P ₂ S _{5: = 1: 1.} , and _P 2 _{S 5} (sigma Aldrich, purity 99%) was weighed 6.87 g. _{Next, Li 2} S and P ₂ S ₅ were added in this order to 75 g of acetonitrile (manufactured by Wako Pure Chemical Industries, Ltd., ultra-dehydrated grade), and mixed at room temperature for 3 hours. The mixture was gradually dissolved to give a Li-PS homogeneous solution.

<Solution step 2>
In a glove box under an argon _{atmosphere, Li 2 S: SiS 2 =} 0.5: so that a molar ratio, _Li 2 S (Sigma Aldrich, purity 99.8%) and 4g, and SiS ₂ (manufactured by Mitsuwa Chemical Co., Ltd.) was weighed in 16 g. Next, it was added to 610 g of acetonitrile (manufactured by Wako Pure Chemical Industries, Ltd., ultra-dehydrated grade) and mixed at room temperature for 24 hours. The mixture gradually dissolved, but impurities in the raw material remained at this stage.

The obtained solution was filtered using a membrane filter (PTFE, pore size 1.0 μm) to obtain 2.0 g as a filter slag and 578 g as a filtrate (Li-Si—S uniform solution). As a result of ICP analysis of the Li-Si-S uniform solution, the Li / Si (molar ratio) was 50.6 / 49.4. The concentration of (Li ₂ S + SiS ₂ ) was 3.07 wt%.

<Solution mixing process>
A homogeneous mixed solution was prepared by mixing 82.9 g of the Li—P—S homogeneous solution and 233.0 g of the Li—Si—S homogeneous solution so that the molar ratio of Si: P = 1: 1 was obtained. Further, 0.52 g of LiCl (manufactured by Sigma-Aldrich, purity 99.99%) was added with stirring, and the mixture was mixed at room temperature for 3 hours.

<Slurry process>
The homogeneous mixed solution obtained, was added with 6.27g stirring Li 2 _S, to prepare a slurry and mixed at room temperature for 12 hours. A series of operations were carried out in a glove box under an argon atmosphere. The molar ratio of all the raw materials added by the above operation is Li ₂ S: P ₂ S ₅ : SiS ₂ : LiCl = 6.45: 1: 2: 0.40, and the elemental composition is Li _3.33. Si _0.50 P _0.50 S _3.86 Cl _0.10 .

<Drying process>
The solvent was removed by drying the obtained slurry liquid at 180 ° C. for 4 hours under vacuum. The solvent was removed while stirring the solution. Then, it cooled to room temperature to obtain a precursor.

<Heat treatment process>
The obtained precursor was placed in a glass reaction tube in a glove box and placed in an electric tube furnace so that the precursor was not exposed to the atmosphere. Argon (G3 grade) was blown into the reaction tube, the temperature was raised to 475 ° C. over 3 hours, and then calcined at 475 ° C. for 8 hours to obtain an LGPS type solid electrolyte.

Reference Example As a result of X-ray diffraction measurement of the coarse particulate LGPS type solid electrolyte produced by the above production example, 2θ = 19.95 °, 20.16 °, which is attributed to the crystal phase of the LGPS type solid electrolyte, Peaks were observed at 26.70 ° and 29.35 °. The ionic conductivity was 6.1 mS / cm and the median diameter was 69.7 μm.

Example 1
<Crushing process>
1 g of the coarse particulate LGPS type solid electrolyte produced according to the above production example was placed in a 50 cc Duran bottle together with 80 g of zirconia balls having a diameter of 3 mmφ and sealed. The above weighing, adding, and sealing operations were all carried out in a glove box under an argon atmosphere, and all the instruments used were those whose moisture had been removed in advance with a dryer.

This container was pulverized by rotating this container at 120 rpm for 12 hours at room temperature using a ball mill stand (AV-1 type manufactured by Asahi Rika Seisakusho Co., Ltd.). As a result of recovering 0.77 g of the solid electrolyte and measuring the ionic conductivity, the ionic conductivity of the solid electrolyte after the pulverization treatment was 2.7 mS / cm.

<Heat treatment process>
The solid electrolyte after the pulverization treatment was placed in a glass container and heat-treated under argon at 475 ° C. for 4 hours. As a result of X-ray diffraction measurement of the solid electrolyte after the heat treatment, peaks were found at 2θ = 19.97 °, 20.17 °, 26.73 ° and 29.35 °, which are attributed to the crystal phase of the LGPS type solid electrolyte. It was observed. The ionic conductivity was 6.2 mS / cm and the median diameter was 9.4 μm.

Example 2
<Crushing process>
After putting 1 g of the LGPS type solid electrolyte produced by the above production example into a 50 cc duran bottle together with 80 g of zirconia balls having a diameter of 5 mmφ, 18 mg of tetrahydrofuran (manufactured by Wako, ultra-dehydrated grade) was added as a solvent (1 with respect to the solid electrolyte). .8 wt%) The pulverization treatment was carried out in the same manner as in Example 1 except that it was added. The recovered amount of the solid electrolyte was 0.89 g.

<Heat treatment process>
The solid electrolyte after the pulverization treatment was heat-treated in the same manner as in Example 1. As a result of the X-ray diffraction measurement, the crystal phase of the LGPS type solid electrolyte was observed as in Example 1. The ionic conductivity was 6.0 mS / cm and the median diameter was 4.2 μm.

Example 3
<Crushing process>
The pulverization treatment was carried out in the same manner as in Example 2 except that 18 mg of acetonitrile (manufactured by Wako, ultra-dehydrated grade) was added as a solvent instead of tetrahydrofuran. The recovered amount of the solid electrolyte was 0.87 g.

<Heat treatment process>
The solid electrolyte after the pulverization treatment was heat-treated in the same manner as in Example 1. As a result of the X-ray diffraction measurement, the crystal phase of the LGPS type solid electrolyte was observed as in Example 1. The ionic conductivity was 7.4 mS / cm and the median diameter was 8.8 μm.

Example 4
<Crushing process>
The pulverization treatment was carried out in the same manner as in Example 2 except that 18 mg of toluene (manufactured by Wako, ultra-dehydrated grade) was added instead of tetrahydrofuran as a solvent. The recovered amount of the solid electrolyte was 0.83 g.

<Heat treatment process>
The solid electrolyte after the pulverization treatment was heat-treated in the same manner as in Example 1. As a result of the X-ray diffraction measurement, the crystal phase of the LGPS type solid electrolyte was observed as in Example 1. The ionic conductivity was 5.8 mS / cm and the median diameter was 6.3 μm.

Example 5
<Crushing process>
The pulverization treatment was carried out in the same manner as in Example 2 except that tetrahydrofuran (manufactured by Wako, ultra-dehydrated grade) added as a solvent was changed to 90 mg (9.0 wt% with respect to the solid electrolyte). The recovered amount of the solid electrolyte was 1.00 g.

<Heat treatment process>
The solid electrolyte after the pulverization treatment was heat-treated in the same manner as in Example 1. As a result of the X-ray diffraction measurement, the crystal phase of the LGPS type solid electrolyte was observed as in Example 1. The ionic conductivity was 4.5 mS / cm and the median diameter was 4.1 μm.

Comparative Example 1
<Crushing process>
The pulverization treatment was carried out in the same manner as in Example 2 except that tetrahydrofuran (manufactured by Wako, ultra-dehydrated grade) added as a solvent was changed to 180 mg (18.0 wt% with respect to the solid electrolyte). After the pulverization treatment, an attempt was made to recover the solid electrolyte, but the solid electrolyte strongly adhered to the wall surface of the container and the balls, and recovery was difficult.

Comparative Example 2
<Crushing process>
Using a jet mill (manufactured by Aisin Nanotechnology Co., Ltd., NJ-50), 10 g of the LGPS type solid electrolyte produced by the above production example was used at an inlet pressure of 2.0 MPa, a crushing pressure of 1.2 MPa, and a processing speed of 60 g / h. After pulverization, 7.8 g of the pulverized solid electrolyte was recovered.

<Heat treatment process>
The solid electrolyte after the pulverization treatment was heat-treated in the same manner as in Example 1. When X-ray diffraction measurement was performed, in addition to the LGPS type crystal structure, impurity phases attributed to algyrodite were observed at 25.30 ° and 29.80 °. The ionic conductivity was 2.6 mS / cm and the median diameter was 12.4 μm.

Comparative Example 3
<Crushing process>
1.5 g of the LGPS type solid electrolyte produced by the above production example, 53 g of 0.3 mmφ zirconia beads, 4 ml of isobutyronitrile, and 6 ml of toluene were placed in a container for a planetary ball mill having a volume of 45 cc, and the planetary ball mill (manufactured by Fritsch). A pulverization treatment was carried out at a rotation speed of 300 rpm for 15 hours using a P-7 classic line). After pulverization, the zirconia beads were removed to obtain a suspension. The obtained suspension was dried under reduced pressure at 180 ° C. for 2 hours using an evaporator, and 0.51 g of the pulverized solid electrolyte was recovered.

<Heat treatment process>
The solid electrolyte after the pulverization treatment was heat-treated in the same manner as in Example 1. When X-ray diffraction measurement was performed, in addition to the LGPS type crystal structure, impurity phases attributed to algyrodite were observed at 25.25 ° and 29.75 °. The ionic conductivity was 2.5 mS / cm and the median diameter was 1.9 μm.

Table 1 below shows the measurement results of the recovery rate, ionic conductivity, decrease in ionic conductivity compared to before pulverization, and median diameter of the solid electrolytes obtained in Reference Examples, Examples 1 to 5, and Comparative Examples 1 to 3. , The measurement result of the X-ray diffraction pattern is shown in FIG. 3 below.

As described above, according to the present invention, it is possible to provide a method for producing an LGPS-type sulfide-based solid electrolyte having high ionic conductivity and a small particle size. Further, the above-mentioned LGPS type sulfide-based solid electrolyte obtained by the method of the present invention is suitable for an all-solid-state lithium battery.

1 Positive electrode layer 2 Solid electrolyte layer 3 Negative electrode layer 10 All-solid-state battery

Claims (7)

A step of crushing a coarse particulate LGPS type solid electrolyte using a ball mill to obtain a crushed product, and
A step of obtaining a pulverized and heat-treated LGPS type solid electrolyte by heat-treating the pulverized product, and
A method for producing an LGPS type solid electrolyte for an all-solid-state lithium battery. The method for producing a solid electrolyte for an all-solid-state lithium battery according to claim 1, wherein the step of obtaining the pulverized product further comprises adding a solvent to the coarse-particulate LGPS-type solid electrolyte. The method for producing a solid electrolyte for an all-solid-state lithium battery according to claim 2, wherein the solvent is added in an amount of 10 wt% or less with respect to the coarse particulate LGPS type solid electrolyte. The method for producing a solid electrolyte for an all-solid-state lithium battery according to claim 2 or 3, wherein the solvent is one or more solvents selected from the group consisting of a nitrile solvent, an ether solvent, and a hydrocarbon solvent. The method for producing a solid electrolyte for an all-solid-state lithium battery according to claim 4, wherein the solvent is selected from the group consisting of acetonitrile, tetrahydrofuran, and heptane. The method for producing a solid electrolyte for an all-solid-state lithium battery according to claims 1 to 5, wherein the LGPS type solid electrolyte is composed of a sulfur element, a phosphorus element, a silicon element, a chlorine element, and a lithium element. Claimed that the pulverized and heat-treated solid electrolyte has a decrease in ionic conductivity of 2.0 mS / cm or less and a median diameter of 10 μm or less as compared with the coarse particulate LGPS type solid electrolyte before pulverization. Item 6. The method for producing a solid electrolyte for an all-solid-state lithium battery according to Item 1.

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