KR20220162084A - Method of preparing sulfur compound-based all-solide-state electrolyte - Google Patents

Abstract

In a manufacturing method of a sulfide-based solid electrolyte according to embodiments, a solvent and a precursor are mixed in a reactor. An open vacuum atmosphere is formed in the reactor. While maintaining the open vacuum atmosphere in the reactor, the mixture inside the reactor is reacted under the conditions of stirring or application of ultrasonic waves. A high-purity sulfide-based solid electrolyte can be manufactured with high efficiency.

Description

Manufacturing method of sulfide-based solid electrolyte {METHOD OF PREPARING SULFUR COMPOUND-BASED ALL-SOLIDE-STATE ELECTROLYTE}

The present invention relates to a method for preparing a sulfide-based solid electrolyte, and more particularly, to a method for preparing a sulfide-based solid electrolyte performed in an open vacuum atmosphere.

The technology of synthesizing an electrolyte by making a precursor into an amorphous phase through a high-energy mechanical milling process and partially crystallizing the electrolyte was started in 1999 by the Tatsumisago group in Japan, and is known as the most common synthesis method for producing an electrolyte to date. However, this method has disadvantages in that it takes a lot of time to amorphize, the amount that can be synthesized in one batch is extremely limited, so productivity is low, and the process cost is very high, so it is not suitable as a technology for mass-producing solid electrolytes.

Then, in 2013, a solution synthesis method that can replace the existing mechanical milling process was reported. The solution synthesis method is a method in which precursor materials are dissolved in an organic solvent such as THF in an inert atmosphere, stirred for about 24 hours, and only the reactants from which the upper layer is removed through centrifugation are dried to form a β-Li ₃ PS ₄ phase. However, there is a limitation that other phases other than the stable phase β-Li ₃ PS ₄ cannot be made. On the other hand, after Li ₆ PS ₅ Cl Arygorodite was synthesized using an organic solvent at Tatsumisago Group in Japan in 2019, several manufacturers are synthesizing solid electrolytes using organic solvents. This solution synthesis method is a relatively more advantageous synthesis method in terms of mass production and solving various problems such as slightly reducing the process time compared to the mechanical milling process method. show difficulties In addition, there is a problem that the performance of the synthesized material is significantly lower than that of the mechanical milling process.

Accordingly, there is a need for a synthesis method capable of synthesizing a compound of high purity with a short reaction time.

One object of the present invention is to provide a method for producing a high-purity and high-efficiency sulfide-based solid electrolyte.

One object of the present invention is to provide a sulfide-based solid electrolyte manufactured with high purity and high efficiency.

One object of the present invention is to provide a sulfide-based all-solid-state battery manufactured with high purity and high efficiency.

The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

A method for preparing a sulfide-based solid electrolyte according to embodiments includes mixing a solvent and a precursor in a reactor; forming an open vacuum atmosphere in the reactor; and reacting the mixture inside the reactor under conditions of stirring or application of ultrasonic waves while maintaining an open vacuum atmosphere in the reactor.

In some embodiments, the reaction of the mixture may be carried out in a state where the temperature is elevated to a temperature below the boiling point of the solvent.

In some embodiments, maintenance of the open vacuum atmosphere may be performed by removing gases generated in the reactor.

In some embodiments, a step of crystallizing a reaction product by heat treatment may be further included.

In some embodiments, bubbles may be continuously generated in the reactor until the reaction of the mixture is complete.

In some embodiments, the reaction of the mixture may be performed in a partially dissolved state of the precursor.

In some embodiments, the precursor may include an alkali metal sulfide, an alkali metal halide and phosphorus pentasulfide.

In some embodiments, the solvent may include a first solvent having low solubility in the alkali metal sulfide and alkali metal halide, and a second solvent at least partially dissolving the alkali metal sulfide and alkali metal halide. .

A sulfide-based solid electrolyte according to embodiments is prepared by the above preparation method and includes A _7-x PS _6-x Ha _x having an azirodite crystalline phase. Among them, A is an alkali metal, Ha is a halogen group element, and x is 0.5 to 2.0.

In some embodiments, the sulfide-based solid electrolyte may exhibit an ion conductivity of 1.0 X 10 ^-3 S/cm to 10 X 10 ^-3 S/cm.

A sulfide-based all-solid-state battery according to embodiments includes a positive electrode, a solid electrolyte layer, and a negative electrode sequentially stacked, and the sulfide-based solid electrolyte may be included in at least one of the positive electrode, the negative electrode, and the solid solid layer. .

According to embodiments, when the reaction mixture reacts under stirring or application of ultrasonic waves while an open vacuum atmosphere is maintained, bubbles may be continuously generated in the mixture during the reaction. Mixing and contact between the reactants are promoted by the generation of bubbles, so that the synthesis rate of the sulfide-based solid electrolyte is improved, and a high-purity sulfide-based solid electrolyte can be obtained.

According to embodiments, a sulfide-based all-solid-state battery having excellent electrical characteristics such as discharge capacity, charge/discharge efficiency, and capacity retention rate can be manufactured with high efficiency using the sulfide-based solid electrolyte prepared according to the above method.

However, the effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

1 is a schematic flow diagram illustrating a method of manufacturing a sulfide-based solid electrolyte according to some embodiments.
2 is a schematic flow diagram illustrating a method of manufacturing a sulfide-based solid electrolyte according to some embodiments.
3 is a photograph showing the color change of the reaction solution according to the reaction time in the method of manufacturing a sulfide-based solid electrolyte of Example.
4 is a graph showing the results of thermogravimetry-differential thermal analysis (TG-DTA) for samples before crystallization.
5 is a graph showing the results of X-ray diffraction crystallography (XRD) for a crystallized sample.
6 is a graph showing the results of measuring the ionic conductivity of the sulfide-based solid electrolyte of Example 1.
7 is an XRD pattern of the sulfide-based solid electrolytes of Examples 9 and 10.
8 is XRD patterns of sulfide-based solid electrolytes of Examples 1 and 11;

Embodiments of the present invention include mixing a solvent and a precursor in a reactor, forming an open vacuum atmosphere in the reactor, and reacting the mixture in the reactor under stirring or ultrasonic application conditions while maintaining the open vacuum atmosphere in the reactor. It provides a method for producing a high-purity sulfide-based solid electrolyte with high efficiency, including the step of doing.

Some embodiments provide a sulfide-based solid electrolyte prepared according to the above method and having high purity and high ionic conductivity and a sulfide-based all-solid-state battery including the same.

The above objects, other objects, features and advantages of the present invention will be easily understood through the following preferred embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content will be thorough and complete and the spirit of the present invention will be sufficiently conveyed to those skilled in the art.

Like reference numerals have been used for like elements throughout the description of each figure. In the accompanying drawings, the dimensions of the structures are shown enlarged than actual for clarity of the present invention. Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this specification, terms such as "include" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof. In addition, when a part such as a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where another part is present in the middle. Conversely, when a part such as a layer, film, region, plate, etc. is said to be "under" another part, this includes not only the case where it is "directly below" the other part, but also the case where another part is in the middle.

Unless otherwise specified, all numbers, values and/or expressions expressing quantities of components, reaction conditions, polymer compositions and formulations used herein refer to the number of factors that such numbers arise, among other things, to obtain such values. Since these are approximations that reflect the various uncertainties of the measurement, they should be understood to be qualified by the term "about" in all cases. Also, when numerical ranges are disclosed herein, such ranges are contiguous and include all values from the minimum value of such range to the maximum value inclusive, unless otherwise indicated. Furthermore, where such ranges refer to integers, all integers from the minimum value to the maximum value inclusive are included unless otherwise indicated.

1 is a schematic flow diagram illustrating a method of manufacturing a sulfide-based solid electrolyte according to some embodiments.

Referring to FIG. 1 , a method for preparing a sulfide-based solid electrolyte according to embodiments includes mixing a solvent and a precursor in a reactor (eg, S100); forming an open vacuum atmosphere in the reactor (eg, S200); and reacting the mixture inside the reactor under conditions of stirring or application of ultrasonic waves while maintaining an open vacuum atmosphere in the reactor (eg, S300).

The step of mixing the solvent and the precursor in the reactor (S100) is performed by first introducing the solvent into the reactor and then introducing the precursor, first introducing the precursor and then introducing the solvent, or mixing the solvent and the precursor and introducing the mixture into the reactor. can

The reactor is capable of forming an open vacuum in a state in which the pressure is lowered in an unsealed state after inputting a reactant including a solvent and a precursor, and the material and shape thereof are not limited. Open vacuum refers to a state in which the internal pressure is lowered in an unenclosed space.

In some embodiments, the precursor may include an alkali metal sulfide (A ₂ S; A is an alkali metal), an alkali metal halide (AX; X is a halogen), and phosphorus pentasulfide (P ₂ S ₅ ). . Alkali metals may include lithium, sodium, potassium or combinations thereof. Halogen may include fluorine, chlorine, bromine, iodine or combinations thereof.

In some embodiments, the alkali metal sulfide, alkali metal halide, and phosphorus pentasulfide may be mixed in a molar ratio of 4.5 to 5.5: 0.5 to 1.5: 1.5 to 2.5. For example, the alkali metal sulfide, alkali metal halide, and phosphorus pentasulfide may react in a stoichiometric molar ratio of 5:1:2.

In some embodiments, the solvent may include a first solvent having low solubility for alkali metal sulfides and alkali metal halides. Optionally, the solvent may further comprise a second solvent that at least partially dissolves the alkali metal sulfide and alkali metal halide.

For example, the first solvent may include a nitrile solvent, an ether solvent, an ester solvent, and the like, and the nitrile solvent may include, for example, acetonitrile.

The second solvent may include an alcohol-based solvent, a carboxylic acid-based solvent, an ester-based solvent, a ketone-based solvent, an amine-based solvent, and a sulfoxide-based solvent. For example, acetic acid, acetyl acetone, 2-aminoethanol, Anisole, benzyl alcohol, 1-butanol, 2-butanol, 2-butanone, t-butyl alcohol, cyclohexanol, cyclohexanone, di-n-butyl phthalate, diethyl glycol, diglyme, dimethoxyethane, Dimethylformamide, dimethyl phthalate, dimethylsulfoxide, dioxane, ethanol, ether, ethyl acetate, ethyl acetoacetate, ethyl benzoate, ethylene glycol, glycerin, 1-heptanol, 1-hexanol, methanol, methyl acetate, methyl t-butyl ether, 1-octanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-pentanone, 3-pentanone, 1-propanol, tetrahydrofuran, and the like. Preferably, the second solvent is acetone, 2-aminoethanol, anisole, benzyl alcohol, 1-butanol, 2-butanol, i-butanol, 2-butanone, t-butyl alcohol containing one oxygen element , cyclohexanol, cyclohexanone, dimethylformamide, ethanol, ether, 1-heptanol, 1-hexanol, methanol, methyl t-butyl ether, 1-octanol, 1-pentanol, 2-pentanol, Including 3-pentanol, 2-pentanone, 3-pentanone, 1-propanol, 2-propanol, tetrahydrofuran, etc., it effectively promotes the reaction of alkali metal sulfides and alkali metal halides with phosphorus pentasulfide, resulting in high purity of can form a sulfide-based solid electrolyte.

In some embodiments, a sulfide-based solid electrolyte may be prepared using only the first solvent without using the second solvent, and in this case, the purity of the sulfide-based solid electrolyte may be improved and ionic conductivity may be increased. have.

In some embodiments, when mixing the precursors, the alkali metal sulfide and the alkali metal halide may be first mixed in a first solvent, and phosphorus pentasulfide may be additionally mixed in a second order.

In some embodiments, the alkali metal sulfide and the alkali metal halide may be pre-stirred in the first solvent during the first mixing. In this case, the alkali metal sulfide and the alkali metal halide are dissolved in the first solvent, so that unreacted substances in the synthesis reaction of the sulfide-based solid electrolyte may be reduced and the purity of the compound may be increased. For example, the pre-stirring may be performed at about 500 rpm, and may be performed for 0.5 to 10 hours, 0.5 to 5 hours, 0.5 to 3 hours, or 0.5 to 2 hours.

In some embodiments, the pre-stirring may be performed at room temperature to 100°C. As the temperature of the pre-stirring increases, the amount of impurities may decrease. Preferably, the pre-stirring may be performed at a temperature that does not exceed the boiling point of the first solvent and/or the second solvent. For example, it may be performed at 50 to 90 °C or 50 to 85 °C.

In some embodiments, when the second solvent is used together with the first solvent, the solubility of the alkali metal sulfide is increased by the second solvent, which is a polar solvent, so that the content of the alkali metal sulfide, which is an impurity, is included in the finally synthesized electrolyte. can reduce However, when the second solvent is used together with the first solvent, oxide-based impurities may be generated, so the second solvent needs to be included in an appropriate amount. For example, the weight of the second solvent included may be 0.005% to 0.03% of the weight of the first solvent.

When the second solvent is used together with the first solvent, the second solvent may be mixed during the first mixing.

Forming an open vacuum atmosphere in the reactor (S200) may be performed by removing gas from the reactor. Removal of gas can be carried out by means of a conventional pressure reducing device. The open vacuum atmosphere may include, for example, a low-pressure atmosphere with an internal gas pressure of -0.1 MPa or less.

The step of reacting the mixture inside the reactor under stirring or applying ultrasonic waves while maintaining an open vacuum atmosphere in the reactor (S300) may be performed while maintaining an internal gas pressure of -0.1 MPa or less.

In some embodiments, maintenance of the open vacuum atmosphere may be performed by removing gases generated in the reactor. For example, the open vacuum atmosphere may be maintained by continuously maintaining a low pressure in the reactor using the pressure reducing device or the like during the reaction of the mixture. In this case, bubbles generated in the mixture by the stirring or application of ultrasonic waves may be continuously generated until the end of the reaction, and bubbles having a large volume may be formed. Mixing and contact between the reactants may be promoted by the bubbles, so that the reaction rate may be increased.

In some embodiments, the agitation rate can be greater than 800 rpm.

In some embodiments, the frequency of the ultrasound may be 1 to 100 kHz. Preferably, the frequency is 1 to 80 kHz, 1 to 70 kHz, 1 to 60 kHz, 5 to 100 kHz, 5 to 80 kHz, 5 to 70 kHz, 5 to 60 kHz, 10 to 100 kHz, 10 to 80 kHz, 10 to 70 kHz, 10 to 60 kHz, 15 to 100 kHz, 15 to 80 kHz, 15 to 70 kHz, 15 to 60 kHz, 20 to 100 kHz, 20 to 80 kHz, 20 to 70 kHz or 20 to 60 kHz. In this case, generation of bubbles may be promoted during the reaction of the mixture, and accordingly, the reaction rate may be increased and the purity of the reactants may be improved.

In Comparative Example, when the open vacuum atmosphere is not maintained during the reaction of the mixture, bubbles may be generated only at the beginning of the reaction, and the bubble generation may be terminated before the end of the reaction. In this case, it is difficult to maintain the increased reaction rate, and it may take, for example, 12 hours or more to complete the reaction.

According to embodiments, as the mixture is stirred or ultrasonic waves are applied while the open vacuum atmosphere is maintained, bubbles may be continuously generated in the reactor until the reaction of the mixture is completed. Accordingly, a reaction for forming a sulfide-based solid electrolyte may be accelerated. For example, the reaction time may be reduced to 4 hours or less, 3 hours or less, 2 hours or less, 1 hour or less, 30 minutes or less, 20 minutes or less, 10 minutes or less, or 5 minutes or less. Specifically, when ultrasonic waves are applied under the condition that an open vacuum atmosphere is maintained during the reaction of the mixture, the reaction time may be shortened to 1 hour or less, 30 minutes or less, 20 minutes or less, 10 minutes or less, or 5 minutes or less.

In some embodiments, the reaction of the mixture may be carried out in a state where the temperature is elevated to a temperature below the boiling point of the solvent. For example, the reaction temperature conditions of the mixture may be below the boiling point of the solvent from room temperature, 25 to 80 ℃, 25 to 70 ℃, 25 to 60 ℃, 30 to 80 ℃, 30 to 70 ℃, 30 to 60 ℃, 35 ℃ to 80 °C, 35 to 70 °C, 35 to 60 °C, 40 to 80 °C, 40 to 70 °C or 40 to 60 °C. In this case, the reaction rate of the reaction of the mixture may increase, and the purity of the sulfide-based solid electrolyte to be produced may increase.

In some embodiments, the reaction of the mixture may be performed in a partially dissolved state of the precursor. Specifically, the precursor is not completely dissolved in the solvent and does not react in the solution phase, but is only partially dissolved in the solvent and reacted through liquid-phase synthesis using the solvent as a catalyst or reaction medium. can

In some embodiments, the inside of the reactor may be maintained in an open vacuum atmosphere even after the reaction of the mixture is completed. Through this, the solvent may be dried from the reactants.

In some embodiments, the method of manufacturing a sulfide-based solid electrolyte may further include heat-treating and crystallizing a reactant resulting from the reaction of the mixture (eg, step S400).

The heat treatment step may be performed at 400 to 800 °C, 400 to 700 °C, 400 to 600 °C, 500 to 800 °C, 500 to 700 °C or 500 to 600 °C.

The heat treatment step may be performed in an open vacuum condition or at a pressure lower than atmospheric pressure, and may be performed for 5 to 30 hours. At the same time as the crystal phase is formed in the heat treatment step, residual solvent may also be additionally removed. The heat treatment step may be performed in an inert gas atmosphere such as argon (Ar) or nitrogen (N ₂ ) gas.

Meanwhile, the heat treatment step may include a first heat treatment and a second heat treatment. A temperature during the second heat treatment may be higher than a temperature during the first heat treatment.

The primary heat treatment additionally induces volatilization of the solvent adsorbed on the surface of the particles that may remain in the reactants, and turns carbon among the elements of the remaining organic solvent into amorphous carbon that has low electrical conductivity and is not involved in synthesis, so that crystalline carbon is electrically By preventing the synthesis of materials having conductivity, it is possible to induce the synthesis of structurally stable azirodite by maintaining a stoichiometric ratio between the precursors. The first heat treatment is preferably performed at 100° C. or higher at which the solvent is sufficiently volatilized and 450° C. or lower at which amorphous carbon is crystallized.

The secondary heat treatment may be performed for 1 hour to 24 hours at a temperature of 450°C or more and 600°C or less under an inert gas atmosphere such as CO, H ₂ , N ₂ , Ar, He, Ne, and the like. A solid electrolyte having a target crystalline phase can be prepared by secondary heat treatment. This secondary heat treatment may be repeated as necessary to enhance crystallinity.

In some embodiments, fabrication of the sulfide-based solid electrolyte may be performed in a glovebox or dry room that is not exposed to moisture and oxygen.

A sulfide-based solid electrolyte according to embodiments is prepared by the above preparation method and includes A _7-x PS _6-x Ha _x having an azirodite crystalline phase. Among them, A is an alkali metal, Ha is a single or multiple halogen group element, and x is 0.5 to 2.0.

In some embodiments, the sulfide-based solid electrolyte may exhibit an ion conductivity of 1.0 X 10 ^-3 S/cm to 10 X 10 ^-3 S/cm. In addition, the sulfide-based solid electrolyte is 1.0 X 10 ^-3 S / cm to 10 X 10 ^-3 S / cm, specifically, 2.0 X 10 ^-3 S / cm to 8.0 X 10 ^-3 S / cm or 2.0 X 10 ^-3 S/cm to 5.0 X 10 ^-3 S/cm of ionic conductivity may be exhibited.

)가 15.5±0.5°, 18.0±0.5°, 25.5±0.5°, 30.0±0.5°, 31.5±0.5°, 40.0±0.5°, 45.5±0.5°, 48.0±0.5°, 53.0±0.5°, 55.0±0.5°, 56.5±0.5°및 59.5±0.5°의 영역에서 회절 피크를 나타내는 것일 수 있다.In some embodiments, the sulfide-based solid electrolyte has a diffraction angle (2

) is 15.5±0.5°, 18.0±0.5°, 25.5±0.5°, 30.0±0.5°, 31.5±0.5°, 40.0±0.5°, 45.5±0.5°, 48.0±0.5°, 53.0±0.5°, 55.0±0.5 °, may represent diffraction peaks in the regions of 56.5 ± 0.5 ° and 59.5 ± 0.5 °.

A sulfide-based all-solid-state battery according to embodiments includes a positive electrode, a solid electrolyte layer, and a negative electrode sequentially stacked, and the sulfide-based solid electrolyte may be included in at least one of the positive electrode, the negative electrode, and the solid solid layer. .

The all-solid lithium battery including the sulfide-based solid electrolyte may include a positive electrode, a solid electrolyte layer, and a negative electrode sequentially stacked. Here, the solid electrolyte layer may include a sulfide-based solid electrolyte, the positive electrode may be a mixture layer of positive electrode active material particles, the sulfide-based solid electrolyte, and conductive particles, and the negative electrode may include negative electrode active material particles, the sulfide-based solid electrolyte and conductive particles. It may be a mixture layer of ash particles.

2 is a schematic flow diagram illustrating a method of manufacturing a sulfide-based solid electrolyte according to some embodiments.

Referring to FIG. 2 , a method for preparing a sulfide-based solid electrolyte according to embodiments includes mixing a solvent and a precursor in a reactor (eg, S100); forming an open vacuum atmosphere in the reactor (eg, S200); reacting the mixture inside the reactor under conditions of stirring or application of ultrasonic waves while maintaining an open vacuum atmosphere within the reactor (eg, S300); additionally mixing the reactants (eg, S350); Crystallizing the reactant by heat treatment (eg, step S400), purifying the crystallized sample and adjusting the particle size (eg, S500); and a drying step (eg, S600) of removing the organic solvent and dissolving the agglomerated sample.

Hereinafter, the same content as shown and described in FIG. 1 will not be repeatedly described, and a step of additionally mixing the reactants (eg, S350), a purification step of purifying the crystallized sample and adjusting the particle size (eg, S500); And a drying step (for example, S600) of removing the organic solvent and dissolving the agglomerated sample will be described.

The step of additionally mixing the reactants (for example, S350) is a step of collecting and additionally mixing the dried reactant powder, and it is possible to make the particle distribution and particle size of the sample adsorbed or aggregated evenly. In addition, by additionally mixing the reactants, residual solvent may be removed and carbon, which is an impurity contained in the solvent, may be removed from the reactants. Therefore, it is possible to induce the synthesis of an electrolyte having a uniform formulation suitable for a stoichiometric ratio during heat treatment.

In one example, further mixing of the reactants may be by wet ball milling. For example, it may be by table ball milling, vertical-ball milling, planetary milling, bead milling, and the like. As another example, further mixing of the reactants may be by stirring, homogenizing, ultra-sonication, and the like.

The solvent used for further mixing of the reactants may be the same as the solvent used when forming the mixture. That is, the solvent used in the additional mixing of the reactants may include a nitrile solvent, an ether solvent, an ester solvent, and the like. As an optional embodiment, an organic solvent that does not contain oxygen, such as heptane, n-heptane, toluene, or the like, may be used as a solvent used when the reactants are additionally mixed.

Such additional mixing of the reactants may be performed for 10 minutes to 2 hours, may be performed multiple times if necessary, or wet mixing and dry mixing may be alternately repeated.

The purification step of purifying the crystallized sample and adjusting the particle size (eg, S500) is a step for further improving the purity of the synthesized sample, and the size and shape of the particles may be adjusted. More specifically, in the purification step, the particle size of the reactants may be finally controlled by mixing the reactants to further remove residual impurities from the reactants, and breaking weak bonds between secondary and tertiary particles with physical force.

The purification step may be performed by ball milling after mixing the reactants and the organic solvent. The particle size of the reactant can be controlled by removing impurities such as carbon on the surface of the reactant and breaking weak bonds between particles by ball milling. A reactant that has undergone the purification step may have high brightness.

Ball milling may include various methods such as table ball milling, vertical-ball milling, planetary milling, and bead milling. As another example, mixing in the purification step may be performed by stirring, homogenizing, ultra-sonication, and the like.

On the other hand, the purification step may be carried out in a wet or dry method, and may include a drying step in the case of a wet method, and may include an additional solution step instead of not including a drying step in the case of a dry method. The drying step may be performed by alternating between dry and wet processes.

The drying step (for example, S600) of removing the organic solvent and dissolving the agglomerated sample is the final step of the synthesis. The organic solvent used in the purification step is dried, and the purified reactant whose particle size is controlled through the purification step is obtained. The sample can be dissolved to prevent re-aggregation by surface energy. To this end, it is necessary to dissolve at the same time as drying at a low temperature below the boiling point of the organic solvent. That is, it may be a method of drying by continuously supplying energy at a low temperature. For example, in the drying step, the purified reactant may be vacuum-dried after centrifugation. Alternatively, a method of drying while applying energy such as blade agitation, and a general drying step such as hot air drying, freeze drying, and spray drying may be performed.

Hereinafter, the present invention will be described in more detail through specific examples. The following examples are merely examples to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example 1: Preparation of sulfide-based solid electrolyte

Li ₆ PS ₅ Cl was synthesized using the precursors Li ₂ S, LiCl and P ₂ S ₅ . The sum of the precursors was carried out in a total of 5 g. Among various organic solvents available, 100 ml of acetonitrile and 0.013 g of isopropanol were used as the solvent.

75 ml of acetonitrile, Li ₂ S, and LiCl were put into the reactor according to the ratio and mixed with isopropanol, followed by pre-stirring at 50° C. for 1 hour, and then 25 ml of P ₂ S ₅ and acetonitrile were added. Li ₂ S, P ₂ S ₅ and LiCl were used in a molar ratio of about 5:1:2.

After the reactor was closed and an open vacuum was gradually formed so that the contents did not boil over, the reactor was placed in an ultrasonic thermostat set at 50° C., which is lower than the boiling point of acetonitrile and isopropanol, while the open vacuum was maintained. Ultrasonic waves of about 40 kHz were applied to the thermostat to maintain open vacuum, temperature, and ultrasonic conditions until the color of the reaction solution turned white.

As a result, bubbles were generated in the mixture solution continuously for 5 minutes during the reaction, and as shown in FIG. 3, the color of the solution gradually changed from blue-green to green and mustard to white. This was similar to the color change over several hours in the existing solution synthesis method. Through this, it was confirmed that the reaction effectively occurs within a short time by the present synthesis method.

After the synthesis was finished (after the color change was finished), the reactant was dried by continuously maintaining an open vacuum system to induce volatilization of the organic solvent. After drying, reactants in the reactor were collected in a glove box under an inert atmosphere, and heat-treated at 550° C. for 12 hours to obtain a crystallized sulfide-based solid electrolyte.

Experimental Example 1: Thermogravimetry-differential thermal analysis (TG-DTA)

Thermogravimetric differential thermal analysis (TG-DTA) was performed on the sample before crystallization of the solid electrolyte synthesized in Example 1.

전후의 흡열반응 이외에 어떠한 반응 피크가 존재하지 않는 것을 확인하였고, Li₃PS₄와 같은 안정한 물질과 관련된 220

부근의 피크가 없음을 확인하였다. 이러한 결과는, 전구체간의 결합이 제대로 이루어졌음을 나타낸다.As shown in FIG. 4, the crystallization temperature of argyrodite electrolyte is 550

It was confirmed that there was no reaction peak other than the endothermic reaction before and after, and 220 related to a stable material such as Li ₃ PS ₄

It was confirmed that there were no nearby peaks. These results indicate that the binding between the precursors was properly performed.

Experimental Example 2: X-ray diffraction crystallography (XRD)

X-ray diffraction analysis (XRD) was performed on the crystallized sample synthesized in Example 1.

)가 15.5±0.5°, 18.0±0.5°, 25.5±0.5°, 30.0±0.5°, 31.5±0.5°, 40.0±0.5°, 45.5±0.5°, 48.0±0.5°, 53.0±0.5°, 55.0±0.5°, 56.5±0.5°및 59.5±0.5°의 영역에서 회절 피크를 나타냈다. 이러한 피크는 고이온전도도를 보이는 Li₆PS₅Cl와 실질적으로 동일한 피크이므로, 상기 실시예1에서 합성된 고체 전해질은 고이온전도성의 입방형 결정 구조를 갖는 아지로다이트 상임을 나타낸다.As shown in FIG. 5, the diffraction angle in the X-ray diffraction spectrum (2

) is 15.5±0.5°, 18.0±0.5°, 25.5±0.5°, 30.0±0.5°, 31.5±0.5°, 40.0±0.5°, 45.5±0.5°, 48.0±0.5°, 53.0±0.5°, 55.0±0.5 °, 56.5 ± 0.5 ° and 59.5 ± 0.5 ° showed diffraction peaks. Since this peak is substantially the same as Li ₆ PS ₅ Cl showing high ionic conductivity, the solid electrolyte synthesized in Example 1 is an azirodite phase having a high ionic conductivity cubic crystal structure.

As a result of Rietveld analysis based on the XRD results, the sulfide-based solid electrolyte of Example 1 had a purity of 97.9% and contained impurities of 1.0% Li ₃ PO ₄ , 1.0% Li ₂ S and 0.1% LiCl It was confirmed that

Experimental Example 3. Measurement of ionic conductivity

In order to measure the ionic conductivity of the solid electrolyte synthesized in Example 1, electrochemical impedance spectroscopy (EIS) was performed.

As shown in FIG. 6, the ionic conductivity of the solid electrolyte synthesized in Example 1 was 3.2Х10 ^-3 S/cm. These results indicate that the solid electrolyte prepared in Example 1 has higher ion conductivity compared to the solid electrolyte prepared by the existing solution synthesis method.

comparative example

A sulfide-based solid electrolyte was prepared in the same manner as in Example, except that an initial open vacuum was formed inside the reactor in which the solvent and the precursor were mixed, and additional vacuum open vacuum was not performed during the reaction of the mixture.

During the manufacturing process of Comparative Example, it was confirmed that before the color change of the reaction mixture was completed, the generation of bubbles suddenly ended or the size of the bubbles significantly decreased, and it took 4 hours to complete the reaction, confirming that the reaction rate was significantly slowed down. It became.

Example 2

A sulfide-based solid electrolyte was prepared in the same manner as in Example 1, except that 2-butanol was used instead of isopropyl alcohol.

It was confirmed that the obtained sulfide-based solid electrolyte had a purity of 97.3% and contained impurities of 1.7% Li ₃ PO ₄ , 0.8% Li ₂ S and 0.1% LiCl.

Example 3

A sulfide-based solid electrolyte was prepared in the same manner as in Example 1, except that isopropyl alcohol was not used.

It was confirmed that the obtained sulfide-based solid electrolyte had a purity of 98.3% and contained impurities of 0.3% Li ₃ PO ₄ , 1.2% Li ₂ S and 0.1% LiCl.

Examples 4 to 6

In Example 1, before adding 25 ml of P ₂ S ₅ and acetonitrile, the mixture of 75 ml of acetonitrile, Li ₂ S, LiCl and isopropanol was not stirred (Example 4), or the temperature was 50 ° C. or higher than 100 A sulfide-based solid electrolyte was prepared in the same manner as in Example 1, except that pre-stirring was performed at less than °C and 800 RPM or more for 1 hour (Example 5) or 24 hours (Example 6).

The sulfide-based solid electrolyte of Example 4 was found to have a purity of 97.4% and contain impurities of 1.0% Li ₃ PO ₄ , 1.0% Li ₂ S and 0.6% LiCl, and the sulfide-based solid electrolyte of Example 5 had a purity of 97.4%. was 97.6%, and it was confirmed to contain impurities of 0.5% Li ₃ PO ₄ , 1.9% Li ₂ S and 0.1% LiCl, and the sulfide-based solid electrolyte of Example 6 had a purity of 93.3% and Li ₃ PO ₄ 3.6 %, Li ₂ S 0.7% and LiCl 2.4%.

Through this, it was confirmed that the amount of Li ₃ PO ₄ and LiCl that reduces the ionic conductivity can be reduced by an appropriate level of pre-stirring, and when the stirring time is excessively increased, rather the amount of Li ₃ PO ₄ and LiCl It was confirmed that this increase

Example 7

A sulfide-based solid electrolyte was prepared in the same manner as in Example 3, except that half of the moles of LiCl was replaced with the same mole of LiBr.

It was confirmed that the obtained sulfide-based solid electrolyte had a purity of 98.2%, contained impurities of 0.7% Li ₃ PO ₄ and 1.0% Li ₂ S, and did not contain LiCl and LiBr. As a result of XRD analysis, XRD of Example 3 An XRD pattern identical to the pattern was confirmed.

Example 8

A sulfide-based solid electrolyte was prepared in the same manner as in Example 3, except that the mixture in the reactor was stirred at a temperature of 80 degrees or less and 800 rpm or more for 12 hours instead of applying ultrasonic waves. In this case, it took 4 hours to complete the color change indicating the end of the reaction.

It was confirmed that the obtained sulfide-based solid electrolyte had a purity of 94.9% and contained impurities of 1.9% Li ₃ PO ₄ , 1.7% Li ₂ S and 1.5% LiCl.

Examples 9 and 10

A sulfide-based solid electrolyte was prepared in the same manner as in Example 1, except that the frequencies of ultrasonic waves were changed to 25 kHz and 59 kHz, respectively.

7 is an XRD pattern of the sulfide-based solid electrolytes of Examples 9 and 10.

Referring to FIG. 7, it was confirmed that a sulfide-based solid electrolyte having the same crystal structure as Example 1 was prepared even when the ultrasonic frequency was changed to 25 kHz and 59 kHz, and when a low-frequency 25 kHz ultrasonic wave was applied, impurities A further decrease was confirmed.

Example 11

설정한 것을 제외하고는, 실시예 1과 동일한 방법으로 황화물계 고체 전해질을 제조하였다.100 of pre-agitation

Except for the settings, a sulfide-based solid electrolyte was prepared in the same manner as in Example 1.

8 is XRD patterns of sulfide-based solid electrolytes of Examples 1 and 11;

Referring to FIG. 8, even in 11 in which the pre-stirring was performed at an elevated temperature, it was confirmed to have the same crystal structure as Example 1, and rather, it was confirmed that the amount of impurities decreased as the pre-stirring temperature increased.

As such, the present invention has been described with reference to one embodiment shown in the drawings, but this is merely exemplary, and those skilled in the art will understand that various modifications and variations of the embodiment are possible therefrom. Therefore, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims.

Claims (11)

mixing a solvent and a precursor in a reactor;
forming an open vacuum atmosphere in the reactor; and
A method for producing a sulfide-based solid electrolyte comprising the step of reacting the mixture inside the reactor under stirring or ultrasonic application conditions while maintaining an open vacuum atmosphere in the reactor. The method of claim 1,
The reaction of the mixture is carried out in a state where the temperature is raised to a temperature below the boiling point of the solvent, a method for producing a sulfide-based solid electrolyte. The method of claim 1,
The maintenance of the open vacuum atmosphere is performed by removing the gas generated in the reactor, a method for producing a sulfide-based solid electrolyte. The method of claim 1,
A method for producing a sulfide-based solid electrolyte, further comprising crystallizing a reactant by heat treatment by the reaction of the mixture. The method of claim 1,
A method for producing a sulfide-based solid electrolyte in which bubbles are continuously generated in the reactor until the reaction of the mixture is completed. The method of claim 1,
The reaction of the mixture is performed in a state in which the precursor is partially dissolved, a method for producing a sulfide-based solid electrolyte. The method of claim 1,
The precursor is a method for producing a sulfide-based solid electrolyte comprising an alkali metal sulfide, an alkali metal halide and phosphorus pentasulfide. The method of claim 7,
The solvent includes a first solvent having low solubility for alkali metal sulfides and alkali metal halides, and a second solvent at least partially dissolving alkali metal sulfides and alkali metal halides. Method for producing a sulfide-based solid electrolyte. It is prepared by the production method of claim 1 and includes A _7-x PS _6-x Ha _x having an azirodite crystal phase, A is an alkali metal, Ha is a halogen group element, and x is a sulfide of 0.5 to 2.0. based solid electrolyte. The method of claim 9,
The sulfide-based solid electrolyte exhibits an ionic conductivity of 1.0 X 10 ^-3 S / cm to 10 X 10 ^-3 S / cm, a sulfide-based solid electrolyte. A sulfide-based all-solid-state battery comprising a positive electrode, a solid electrolyte layer, and a negative electrode sequentially stacked, wherein the sulfide-based solid electrolyte of claim 9 is included in at least one of the positive electrode, the negative electrode, and the solid electrolyte layer.

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