KR20240029388A - Method for manufacturing submicro-sized sulfide-based solid electrolyte, submicro-sized sulfide-based solid electrolyte prepared thereby, and all-solid-state battery comprising same - Google Patents

Abstract

The present invention relates to a method for producing a fine sulfide-based solid electrolyte, a fine sulfide-based solid electrolyte produced thereby, and an all-solid-state battery containing the same. More specifically, grinding lithium sulfide (Li ₂ S) to produce fine lithium sulfide; Mixing the fine lithium sulfide and sulfur (S), mechanically milling the mixture to prepare a mixture, and adding the mixture to a solvent to prepare a solution containing fine lithium sulfide; After mixing _and stirring the sulfur compound in the solution, lithium sulfide and _{lithium halide} (LiX, Preparing a fine solid electrolyte solution containing b<9, 0<c<2 and X is Cl, Br, I or F); and solvating the solid electrolyte solution, drying it, and then heat-treating it to obtain a fine solid electrolyte. Including, the fine solid electrolyte has reduced inter-particle voids by promoting nucleation by fine Li ₂ S, and an intermediate Disclosed is a method for producing a fine sulfide-based solid electrolyte, characterized in that it is an azirodite-type solid electrolyte with a particle size D50 of 0.5 to 1 ㎛.

Description

Method for manufacturing submicro-sized sulfide-based solid electrolyte, submicro-sized sulfide-based solid electrolyte prepared thereby, and all-solid-state battery containing the same all-solid-state battery comprising same}

The present invention relates to a method for producing a fine sulfide-based solid electrolyte, a fine sulfide-based solid electrolyte produced thereby, and an all-solid-state battery containing the same. More specifically, it relates to a method of manufacturing an ajirodite-type fine solid electrolyte in which voids between particles are reduced by promoting nucleation using fine Li ₂ S with the particle size of lithium sulfide controlled.

Typical solid electrolytes include polymer-based, oxide-based, and sulfide-based electrolytes, and sulfide-based solid electrolytes are attracting attention as commercial solid electrolytes to be applied to electric vehicles. The reason is that both polymer and oxide systems have lower lithium ion conductivity than sulfide systems, and in particular, oxide systems have high interfacial resistance and low ductility, so they are not appropriate. On the other hand, sulfide-based solid electrolytes have the advantage of being able to create a solid electrolyte layer just by forming under pressure. This is due to differences in the mechanical properties of the materials, especially the softness of the particles, and sulfide-based particles can easily adhere to grain boundaries just by applying pressure, resulting in high ionic conductivity.

In order to develop a high-capacity secondary battery using such a solid electrolyte, (1) the low ionic conductivity of the solid electrolyte at room temperature, and (2) the high interfacial resistance at the electrode/electrolyte solid interface must be addressed. In particular, high resistance at the solid electrolyte/electrode interface is a major cause of reduced overall battery performance. The causes of the high interfacial resistance of the solid electrolyte/electrode discovered to date include the low contact area between the solid electrolyte and the electrode, changes in the solid electrolyte/electrode interface pressure (stress) due to volume expansion of the electrode during charging/discharging, and peeling phenomenon. I can hear it. As a way to control the surface of the solid electrode to solve this problem, research is being conducted in the direction of coating a buffer layer on the particle surface in the case of the anode interface or forming an interphase between the solid electrolyte and lithium metal in the case of the cathode interface. there is.

At the solid-solid interface where the solid electrolyte and solid electrode meet, the diffusion of lithium ions and the redox reaction of the active material occur only at the point where the two materials meet, so maintaining the solid-solid contact interface is necessary for effective ion and charge transfer. Therefore, in order to solve the high interfacial resistance of solid electrolyte/electrode, it is necessary to finely control the particle size of the solid electrolyte. In this case, in order to maintain the ionic conductivity of the solid electrolyte, it is required to manufacture the fine solid electrolyte in a reproducible manner so that the fine solid electrolyte does not aggregate and there is no deviation in physical properties.

Meanwhile, sulfide-based solid electrolytes are synthesized through various methods. It is made through melt-quenching and high-energy milling methods, but these methods have the disadvantages of requiring a long reaction time, consuming a lot of energy, and producing a composite with inappropriate particle size and homogeneity, making commercialization difficult. . However, when synthesized on a liquid basis, mass production is possible by simply performing a mixing process at room temperature. However, the solid electrolyte manufactured by this liquid-based synthesis method has heterogeneous, nearly spherical, amorphous particles because the reaction occurs in a solvent. The amorphous solid electrolyte has a small specific surface area and causes the problem that the contact area between the solid electrolyte and the electrode active material in the composite electrode is limited.

Relatedly, in Korean Patent Publication No. 10-2018-0055086, a slurry is prepared by adding lithium sulfide, a sulfide of a group 14 or 15 element, and a solvent, milling it to amorphize the mixture, and then drying the slurry. The step of removing the solvent and crystallizing by heat treatment is disclosed. However, this method has the problem of milling the prepared solid electrolyte slurry to make it amorphous and then going through a heat treatment process, which causes agglomeration of the solid electrolyte and makes it difficult to control the particle size, which reduces reproducibility for mass production.

In addition, the present inventor provides a first solution containing lithium _{polysulfide (} Li ₂ S step; (b) mixing P ₂ S ₅ with the first solution to prepare a second solution containing Li ₃ PS _4+y ; (c) mixing and stirring the second solution and a third solution containing Li ₂ S and LiX (X=Cl, Br or I); and (d) drying and heat-treating the mixed solution to prepare an LPSX compound. However, in this method, lithium polysulfide is prepared by adding sulfur, and lithium polysulfide is Separately from the production of , there was a problem of having to go through a complicated process because a separate solution had to be prepared by mixing and stirring Li ₂ S and lithium salt in a solvent and mixing it again.

Therefore, in order to develop a high-capacity secondary battery using a solid electrolyte, (1) the particle size of the solid electrolyte must be finely controlled to solve the high interfacial resistance of the solid electrolyte/electrode by maintaining the solid-solid contact interface, and (2) one It is necessary to develop a method for producing a fine sulfide-based solid electrolyte with excellent reproducibility and little variation in physical properties while increasing the efficiency of the process by conducting the reaction in batches.

Republic of Korea Patent Publication No. 10-2021-0050469 Republic of Korea Patent Publication No. 10-2018-0055086 Republic of Korea Patent Publication No. 10-2019-0041735

Therefore, in light of the above-mentioned technical needs, the present invention aims to provide a method for producing a fine sulfide-based solid electrolyte as a technical solution.

In addition, the present invention aims to provide a fine sulfide-based solid electrolyte manufactured by the above-described method as another technical problem.

In addition, the present invention aims to provide an all-solid-state battery containing the above-described fine sulfide-based solid electrolyte as another technical problem to be solved.

In order to solve the above-mentioned technical problem, the present invention,

Preparing fine lithium sulfide by grinding lithium sulfide (Li ₂ S);

Mixing the fine lithium sulfide and sulfur (S), then mechanically milling to prepare a mixture, and adding the mixture to a solvent to prepare a solution containing fine lithium sulfide.

After mixing _and stirring the sulfur compound in the solution, lithium sulfide and _{lithium halide} (LiX, Preparing a fine solid electrolyte solution containing b<9, 0<c<2 and X is Cl, Br, I or F);

Including solvating the fine solid electrolyte solution, drying it, and then heat-treating it to obtain a fine solid electrolyte.

Preparation of a fine sulfide-based solid electrolyte, characterized in that the fine solid electrolyte is an ajirodite-type solid electrolyte with reduced inter-particle voids due to acceleration of nucleation by fine Li ₂ S and a median particle size D50 of 0.5 to 1 ㎛. Provides a method.

Preferably, in the present invention, the ionic conductivity of the solid electrolyte is at least 2.0 × 10 ^-3 S/cm.

In addition, in the present invention, the sulfur compound is characterized in that at least one selected from the group consisting of P ₂ S ₃ , P ₂ S ₅ and mixtures thereof.

In addition, in order to solve the above-described other technical problems, the present invention provides an all-solid-state battery containing a fine sulfide-based solid electrolyte manufactured by the above-described method.

In addition, in order to solve another technical problem, the present invention provides an all-solid-state battery containing the above-described fine sulfide-based solid electrolyte.

According to the method for producing a fine sulfide-based solid electrolyte of the present invention, a fine sulfide-based solid electrolyte can be manufactured using fine Li ₂ S. In particular, a liquid-based synthesis reaction is performed in one batch, and the increase in the reaction surface by fine lithium sulfide promotes nucleation during the crystallization process, which has the effect of finely controlling the overall particle size, resulting in excellent Due to reproducibility, it is possible to produce fine sulfide-based solid electrolytes with little variation in physical properties in large quantities and efficiently produce them in one batch.

In addition, the fine sulfide-based solid electrolyte produced by the method of the present invention has reduced inter-particle voids and can maintain sufficient density even when the particle size is reduced, so it can have high ionic conductivity and the solid-solid interface with a fine particle size. As maintenance becomes possible, there is an effect that it can be applied to high capacity secondary batteries.

Figure 1 shows a schematic diagram of the manufacturing process of a fine sulfide-based solid electrolyte according to an embodiment of the present invention, and Figure 2 shows a manufacturing process flow chart.
FIG. 3A schematically shows the production of a fine solid electrolyte by promoting nucleation of fine lithium sulfide according to an embodiment of the present invention, and FIG. 3B schematically shows the production of a solid electrolyte by lithium sulfide.
Figure 4 is a graph showing particle size distribution (individual and cumulative distribution) by fine lithium sulfide particle size according to an embodiment of the present invention.
Figure 5 is a graph showing particle size distribution (individual and cumulative distribution) by size of fine lithium sulfide particles according to a comparative example of the present invention.
Figure 6 is a graph showing the particle size distribution (individual and cumulative distribution) by particle size of the fine sulfide-based solid electrolyte according to an embodiment of the present invention.
Figure 7 is a graph showing the ionic conductivity of a solid electrolyte sample according to an embodiment of the present invention.
Figure 8 is a graph showing the voltage capacity curve of a solid electrolyte sample according to an embodiment of the present invention.
Figure 9 shows the measurement results of cycle characteristics of a solid electrolyte sample according to an embodiment of the present invention.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention. While describing each drawing, similar reference numerals are used for similar components.

The terms used in this application are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

As used herein, the phrase “D50 diameter” or “median diameter (D50)” refers to measurement by microscopy techniques such as, but not limited to, scanning electron microscopy or dynamic light scattering, or other particle size analysis. It refers to the median size in a given size distribution. D50 describes the characteristic particle dimension in which 50% of the particles are smaller than the stated size.

As used herein, the term “argyrodite” or “argyrodite crystal” refers to a crystal structure or crystal bonding arrangement. This crystal structure, or bond arrangement, is based on the crystal structure of the natural mineral agyrhodite, a silver germanium sulfide mineral characterized by the chemical formula Ag ₈ GeS ₆ .

Hereinafter, the present invention will be described in detail with reference to the drawings.

Figure 1 is a schematic diagram showing the manufacturing process of a fine sulfide-based solid electrolyte according to an embodiment of the present invention, and Figure 2 is a flowchart of the manufacturing process of a fine sulfide-based solid electrolyte according to an embodiment of the present invention. The invention relates to a method of manufacturing a fine solid electrolyte that promotes nucleation by finely controlling the particle size of lithium sulfide to grow crystals into a fine solid electrolyte in a liquid-based solid electrolyte synthesis process.

Therefore, according to one aspect of the present invention, the method for producing a fine sulfide-based solid electrolyte of the present invention includes the steps of grinding lithium sulfide (Li ₂ S) to produce fine lithium sulfide; Mixing the fine lithium sulfide and sulfur (S), mechanically milling the mixture to prepare a mixture, and adding the mixture to a solvent to prepare a solution containing fine lithium sulfide; After mixing _and stirring the sulfur compound in the solution, lithium sulfide and _{lithium halide} (LiX, Preparing a fine solid electrolyte solution containing b<9, 0<c<2 and X is Cl, Br, I or F); and solvating the solid electrolyte solution, drying it, and then heat-treating it to obtain a fine solid electrolyte, wherein the fine solid electrolyte has reduced inter-particle voids due to acceleration of nucleation by fine Li ₂ S, and an intermediate It is characterized by being an azyrodite-type solid electrolyte with a particle size D50 of 0.5 to 1㎛.

First, the step of producing the fine lithium sulfide is a step of pulverizing lithium sulfide (Li ₂ S). Figure 3a schematically shows the production of a fine solid electrolyte by promoting the nucleation of fine lithium sulfide. Referring to this, the fine lithium sulfide is formed into crystals by sequentially reacting sulfur, sulfur compounds, lithium salts, and lithium halide. As it grows, a reaction takes place on the surface of lithium sulfide, and the more finely the particle size of lithium sulfide is controlled, the more the reaction surface of lithium sulfide increases. Accordingly, the crystal nucleation reaction is promoted, making it possible to finally synthesize a fine solid electrolyte. On the other hand, as can be seen in Figure 3b, when the particle size is not finely controlled, lithium sulfide has a small reaction surface even when sulfur, sulfur compound, lithium salt, and lithium halide are reacted sequentially, so less crystal nucleation reaction occurs, resulting in less crystal nucleation reaction. A solid electrolyte of crystals is manufactured.

In other words, in order to produce a fine solid electrolyte, the nucleation rate of solid electrolyte crystals is important, and the nucleation rate is determined by the critical nucleus radius. Therefore, referring to (Equation 1) below, when using small Li ₂ S, the surface energy γ decreases and the size of the critical nucleus radius decreases. Also, referring to (Equation 2) below, as supersaturation progresses, the degree of supersaturation S increases, the volumetric free energy decreases, and eventually the size of the critical nucleus radius decreases. thus and By controlling the value, it is possible to accelerate the nucleation reaction and obtain a fine solid electrolyte.

---------------- (Equation 1)

(step, is the critical nuclear radius, is surface energy (interfacial tension), represents the volume free energy)

----------- (Equation 2)

(step, is the volume free energy, is the Boltzmann constant, is the temperature, is the volume of the molecule, indicates supersaturation)

At this time, the method of grinding lithium sulfide in the manufacturing step of fine lithium sulfide is sufficient to use a mechanical milling method capable of applying energy, and may be performed by a grinding means such as grinding. Fine lithium sulfide is produced by finely pulverizing it to submicron size. More preferably, grinding lithium sulfide until it has particles with a D50 particle size of 0.5 ㎛ or less produces a fine solid electrolyte of submicron size.

In one embodiment of the present invention, the material was pulverized using a mortar and pestle for 30 minutes to have a D50 of 0.487㎛, thereby producing a fine solid electrolyte with a D50 of 0.736㎛.

Next, in the step of preparing a solution containing fine lithium sulfide, the fine lithium sulfide and sulfur (S) are mixed, mechanically milled to prepare a mixture, and the mixture is added to a solvent to prepare a fine lithium sulfide solution. do.

At this time, solid sulfur (S ₈ ) may be used, and it is preferable to mix lithium sulfide and sulfur in a 1:2 molar ratio. After mixing the fine lithium sulfide and sulfur, lithium polysulfide is formed through mechanical milling. In the mechanical milling process, fine lithium sulfide whose particle size is finely controlled reacts with sulfur while finely controlling its particle size to form fine lithium polysulfide. In addition, the fine lithium polysulfide promotes the nucleation rate in the process of crystallization into the final solid electrolyte, making it possible to finely control the overall particle size. Preferably, the mechanical milling may be performed by a pulverizing means such as grinding, or may be performed by a method known to those skilled in the art, such as ball milling.

The mixture prepared by mechanical milling of fine lithium sulfide and sulfur is prepared as a solution by adding it to a solvent. At this time, the solvent must be an aprotic solvent with a high dielectric constant and polar characteristics to prevent the generation of impurities and increase ionic conductivity. does not decrease. Therefore, the solvent is acetonitrile, tetrahydrofuran, dimethylformamide, dimethyl carbonate, dimethyl ether, dimethyl sulfoxide, acetone ( acetone) and ethyl acetate.

In one embodiment of the present invention, fine lithium sulfide and solid sulfur were mixed at a molar ratio of 1:2, ground through mechanical mixing in a mortar for 10 minutes, and added to THF solvent to prepare a fine lithium sulfide solution.

Next, in the step of preparing a fine solid electrolyte solution, a sulfur compound is mixed and stirred in the fine lithium sulfide solution, and then lithium sulfide and lithium halide are further added and stirred to prepare a fine solid electrolyte solution.

At this time, when mixing a sulfur compound with the fine lithium sulfide solution, the sulfur compound may be one or more selected from the group consisting of P ₂ S ₃ , P ₂ S ₅ and mixtures thereof, and after mixing, the mixture is heated at 300 to 500 rpm at 60 to 80 ° C. It can be stirred for more than 24 hours. Through the stirring, the sulfur compound is completely dissolved in the solution, and lithium sulfide and the sulfur compound react to produce a solution with the composition Li ₃ PS _4+y (where 0<y≤3). Preferably, y has a value of 2 or more. At this time, if the stirring speed or temperature range is exceeded or below, it is difficult to produce a reactant of the composition Li ₃ PS _4+y (however, 0<y≤3) or the reaction rate is reduced, so it is better to carry out the reaction under the above stirring conditions. desirable.

In addition, when lithium sulfide and lithium halide are further added to the solution of the composition Li ₃ PS _4+y (where 0<y≤3) and stirred, the lithium sulfide and lithium halide react by stirring to form Li _a PS _{b c} (where 5<a<7, 5<b<9, 0<c<2 and X is Cl, Br, I or F) to produce a solid electrolyte. The stirring conditions are preferably 60 to 80°C and 300 to 500 rpm for more than 24 hours. If it exceeds or _falls below the stirring speed or temperature range, the Li _a PS _b This is because it is difficult to produce a solid electrolyte of this composition or the reaction rate is reduced.

In addition, in order to produce a solid electrolyte of _the above Li _{a PS b 4+y} (however, 0<y≤3), and lithium sulfide (Li ₂ S) and lithium halide (LiX, do. In this case, depending on the type of lithium halide, Li ₆ PS ₈ I, Li ₆ PS ₈ Br, Li ₆ PS ₈ F, etc. may be generated.

As an example of the produced solid electrolyte, the overall reaction equation for producing Li ₆ PS ₈ Cl is as follows.

Finally, the step of obtaining a fine solid electrolyte involves evaporating the solvent of the solid electrolyte solution, drying it, and then heat-treating it. The fine solid electrolyte is precipitated by removing the solvent through evaporation and drying of the solvent, and then crystallized by heat treatment. By doing this, a fine solid electrolyte is obtained.

In this step, the solvent can be vaporized at 130 to 190°C while stirring at 300 to 500 rpm, and then vacuum dried at 130 to 190°C for more than 10 hours. If the temperature during solvent vaporization and drying is too low, the drying time may be excessively long and complete removal of the solvent may be difficult, and if it exceeds 190°C, there is a risk of crystallization of the solid electrolyte, so it is preferable to proceed within the above temperature range. . In addition, the solid electrolyte Li _{a PS b} Since the crystallization temperature is at ℃, if the solid electrolyte is crystallized with the remaining solvent without sufficient removal of the solvent, the physical properties of the solid electrolyte may be greatly reduced and the desired lithium ion conductivity may not be secured. Therefore, the solvent inside the solid electrolyte must be removed. It is desirable to perform vacuum drying as described above to ensure complete drying.

In this way, the solid electrolyte precipitated by completely removing the solvent through solvent vaporization and drying is crystallized through heat treatment. Specifically, the crystallization is carried out in the temperature range of 200 to 700 ° C. In this case, in order to prevent the performance of the solid electrolyte from deteriorating due to rapid temperature changes, it is preferable to increase the temperature at a rate of 5 ° C. per minute, and the target temperature for crystallization is reached. After maintaining it for 3 to 4 hours, it crystallizes into ajirodite type.

The solid electrolyte finally obtained through the above steps is a fine solid electrolyte. As described above, the increase in the reaction surface by fine Li ₂ S promotes nucleation during the crystallization process, and the overall particle size is finely controlled. It is characterized by being an azirodite-type solid electrolyte with reduced voids between particles and a median particle size D50 of 0.5 to 1㎛. In addition, as the density of the solid electrolyte is increased by reducing the voids between the particles, high ionic conductivity can be maintained, and the ionic conductivity can be at least 2.0 × 10 ^-3 S/cm.

When the fine solid electrolyte manufactured by the above-described method is applied to a high-capacity secondary battery, the solid electrode and solid-solid contact interface can be maintained by finely controlling the size of the solid electrolyte to the submicron level. In addition, as described above, the efficiency of the process can be increased as the reaction continues in one batch, and by finely controlling the size of lithium sulfide, the raw material for generating crystal nuclei, the particle size can be increased during the crystallization process of the final solid electrolyte. Through this control, it is possible to manufacture a fine sulfide-based solid electrolyte with little variation in physical properties with excellent reproducibility, and can exhibit a high ionic conductivity of at least 2.0 × 10 ^-3 S/cm.

Therefore, the present invention can provide an all-solid-state battery containing a solid electrolyte manufactured by the above manufacturing method, so that it does not need to include a separate fire prevention device, such as electric vehicles, smartphones, and electric kickboards, and can be used in various fields where secondary batteries are used. The scope of application can be expanded to industry.

Hereinafter, the present invention will be described in more detail with reference to an embodiment. However, the following examples are only examples to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

<Example 1> Preparation of fine sulfide-based solid electrolyte

Fine lithium sulfide was prepared by grinding lithium sulfide with a D ₅₀ of 0.487㎛ using a mortar and pestle for 30 minutes, and the particle size distribution of fine lithium sulfide was confirmed using the PSA method. Specifically, a BLUEWAVE device from MICROTRAC MRB was used, and fine lithium sulfide samples ground into xylene solvent were added. The sample measurement settings are the sample refractive index of 1.54, the optical properties of the particles are set to light transmission mode, the particle shape is set to non-spherical, the solvent measurement settings are the solvent refractive index is set to 1.49, and the range of the measured particle size is 0.0107. The particle size distribution was confirmed by setting it to ~2000㎛, and the results are shown in Table 1 and Figure 4 below.

Particle size by particle size distribution (㎛) D ₁₀ D ₂₀ D ₃₀ D ₄₀ D ₅₀ D ₆₀ D ₇₀ D ₈₀ D ₉₀ D ₉₅ 0.125 0.163 0.21 0.299 0.487 0.67 0.865 1.097 1.416 1.734

Referring to Table 1 and Figure 4, it was confirmed that fine lithium sulfide was manufactured at the submicron level with a d50 value of 0.487㎛.

The prepared fine lithium sulfide and sulfur were mixed at a molar ratio of 1:2, mixed by mechanical milling in a mortar for 10 minutes to form lithium polysulfide, and then added to a THF (tetrahydrofuran) solvent. P 2 S 5 was weighed at a molar ratio of 1:3 with lithium polysulfide so that the solution composition was suitable for Li ₃ PS _4+y (y = 3), and then P ₂ S ₅ was added and stirred at 300 rpm for 24 hours at 70°C. Afterwards, Li ₂ S and LiCl were measured and added at a molar ratio of 1:1, and stirred at 300 rpm for 24 hours at 70°C. Afterwards, the lid of the bottle was opened and the solvent was maintained at 140°C while stirring at 300 rpm to evaporate the solvent to precipitate the solid electrolyte, followed by vacuum drying at 140°C for 12 hours to completely remove the solvent inside the solid electrolyte. Finally, the solid electrolyte from which the solvent was removed was heated at a rate of 5°C per minute to 550°C, and after reaching 550°C, the temperature was maintained for 3 hours to heat treat to crystallize the solid electrolyte.

The particle size distribution of the crystallized solid electrolyte was confirmed by the PSA method described above. The results are shown in Table 2 and Figure 5 below.

Particle size by particle size distribution (㎛) D ₁₀ D ₂₀ D ₃₀ D ₄₀ D ₅₀ D ₆₀ D ₇₀ D ₈₀ D ₉₀ D ₉₅ 0.066 0.125 0.211 0.363 0.736 2.616 7.2 14.91 28.6 37.98

Referring to Table 2 and Figure 5, it can be seen that the sulfide-based solid electrolyte prepared in this example was manufactured with the particle size finely controlled to the submicron level with a d50 value of 0.736㎛.

In this way, in this embodiment, fine lithium sulfide was manufactured, and sulfur, sulfur compounds, lithium salts, and lithium halide were sequentially reacted with it and crystallized through heat treatment to prepare a sulfide-based solid electrolyte, and it was confirmed that the size was controlled at the submicron level. I was able to. This is because the reaction occurs from the surface of lithium sulfide, which is the raw material of sulfide-based solid electrolyte, so if the particle size of lithium sulfide is finely controlled, the reaction surface of lithium sulfide increases, and the crystal nucleation reaction is promoted, thereby forming a fine solid electrolyte. It is judged that it can be finally synthesized.

<Comparative Example 1>

In order to compare the particle size distribution and particle size with the solid electrolyte prepared in Example 1, a solid electrolyte prepared by the method described in the present inventor's previous patent, Publication No. 10-2021-0050469, was prepared, and the particle size distribution was was confirmed using the PSA method described above.

The results are shown in Table 3 and Figure 6 below.

Particle size by particle size distribution (㎛) D ₁₀ D ₂₀ D ₃₀ D ₄₀ D ₅₀ D ₆₀ D ₇₀ D ₈₀ D ₉₀ D ₉₅ 11.03 15.44 19.55 23.78 28.36 33.62 40.18 49.66 69.93 103.3

Referring to Table 3 and Figure 6, it can be seen that the sulfide-based solid electrolyte of Comparative Example 1 had a d50 value of 28.36㎛, and the particle size was at the micro level. Compared to Example 1, which has a d50 value of 0.736㎛, the solid electrolyte with d50 value of 1 is about 37 times larger.

<Experimental Example 1>

In order to evaluate the properties of the fine solid electrolyte prepared in Example 1 and the solid electrolyte in Comparative Example 1, ionic conductivity was analyzed. Ion conductivity was measured using VMP3 equipment from Bio logic. The measurement conditions are as follows.

scan from f _i =1.0MHz to f _f =10.0mHz, E Range -10V;10V.

Figure 7 shows the ionic conductivity results. Referring to this, the ionic conductivity was found to be 1.83*10 ^-3 S/cm in Comparative Example 1 and 2.3*10 ³ S/cm in Example 1. That is, it can be confirmed that the fine solid electrolyte prepared in Example 1 of the present invention has an ionic conductivity that is improved by about 25% compared to the solid electrolyte in Comparative Example 1. This is because the solid electrolyte prepared in Example 1 of the present invention is a fine solid electrolyte, and as described above, the increase in the reaction surface by fine Li ₂ S promotes nucleation during the crystallization process, and the overall particle size is finely adjusted. This is because the voids between particles have been reduced through control, which means that sufficient density can be maintained despite a decrease in particle size, resulting in high ionic conductivity.

<Experimental Example 2>

Battery cells were manufactured using the fine solid electrolyte prepared in Example 1 and the solid electrolyte in Comparative Example 1 as electrolytes. The cell consists of a stacked structure of anode (NCM622:SE:SPB)/LPSCl/Li-In powder and was manufactured as a pressed cell, and the electrochemical properties of the manufactured cell were evaluated. Battery characteristics were evaluated for each C-rate (0.1C, 0.2C, 0.5C, 1C, 2C) at 55℃, and the graph evaluating Coulombic efficiency (CE) was conducted at 0.1C and 55℃. It has been done.

Figure 8 shows the voltage capacity curves of the fine solid electrolyte (LPSCl) of Example 1 and the solid electrolyte (LPSCl) of Comparative Example 1, and Figure 9 shows the fine solid electrolyte (LPSCl) of Example 1 and the solid electrolyte of Comparative Example 1. The measurement results of the cycle characteristics of the electrolyte (LPSCl) are shown, and the charging capacity, discharge capacity, and initial coulombic efficiency are summarized in Table 4.

Referring to this, when the fine solid electrolyte of Example 1 was used, the cell test results showed that the charging capacity was 241.59 mAh/g and the discharge capacity was 182.48 mAh/g under 0.5C conditions, compared to the charging capacity of Comparative Example 1 of 211.41 mAh/g. Compared to the discharge capacity of 163.36 mAh/g, it showed excellent performance.

Charging capacity (mAh/g) Discharge capacity (mAh/g) Initial coulombic efficiency (%) Comparative Example 1 211.41 163.36 77.27 Example 1 241.59 182.48 75.53

As can be seen from the results presented in Experimental Example 1, the fine solid electrolyte prepared in Example 1 of the present invention not only has an ionic conductivity that is improved by about 25% compared to the solid electrolyte of Comparative Example 1, but also It is believed that this is because the solid-solid contact interface was better maintained in the battery of Example 1, which was a fine solid electrolyte at the solid-solid interface where the solid electrode meets, resulting in effective ion and charge transfer.

According to the method for producing a fine sulfide-based solid electrolyte of the present invention from the results of the above examples and experimental examples, fine Li ₂ S is manufactured and a fine sulfide-based solid electrolyte can be manufactured through a synthesis reaction and crystallization process using it as a raw material. , a liquid-based synthesis reaction is performed in one batch, but the increase in the reaction surface by fine lithium sulfide promotes nucleation during the crystallization process, allowing fine control of the overall particle size, with excellent reproducibility. It is possible to produce fine sulfide-based solid electrolytes with little variation in physical properties in large quantities and efficiently produce them in one batch.

In addition, the fine sulfide-based solid electrolyte produced by the method of the present invention has reduced inter-particle voids and can maintain sufficient density even when the particle size is reduced, so it can have high ionic conductivity and the solid-solid interface with a fine particle size. As maintenance becomes possible, it can be applied to high-capacity secondary batteries.

As the specific parts of the present invention have been described in detail above, various modifications and variations can be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but are for explanation, and the scope of the technical idea of the present invention is not limited by these examples. The scope of protection of the present invention should be interpreted in accordance with the scope of the patent claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of rights of the present invention.

Claims (5)

Preparing fine lithium sulfide by grinding lithium sulfide (Li ₂ S);
Mixing the fine lithium sulfide and sulfur (S), then mechanically milling to prepare a mixture, and adding the mixture to a solvent to prepare a solution containing fine lithium sulfide.
After mixing _and stirring the sulfur compound in the solution, lithium sulfide and _{lithium halide} (LiX, Preparing a fine solid electrolyte solution containing b<9, 0<c<2 and X is Cl, Br, I or F);
Including the step of solvating the solid electrolyte solution, drying it, and then heat-treating it to obtain a fine solid electrolyte.
Preparation of a fine sulfide-based solid electrolyte, characterized in that the fine solid electrolyte is an ajirodite-type solid electrolyte with reduced inter-particle voids due to acceleration of nucleation by fine Li ₂ S and a median particle size D50 of 0.5 to 1 ㎛. method. According to claim 1,
A method for producing a fine sulfide-based solid electrolyte, characterized in that the ionic conductivity of the solid electrolyte is at least 2.0 × 10 ^-3 S/cm. According to claim 1,
A method for producing a fine sulfide-based solid electrolyte, wherein the sulfur compound is one or more selected from the group consisting of P ₂ S ₃ , P ₂ S ₅ and mixtures thereof. A fine sulfide-based solid electrolyte, characterized in that it is manufactured according to any one of claims 1 to 3. An all-solid-state battery comprising the fine sulfide-based solid electrolyte according to claim 4.