Preparation method of sulfide-based solid electrolyte and sulfide-based solid electrolyte

Abstract

The present disclosure relates to a method for preparing a sulfide-based solid electrolyte and a sulfide-based solid electrolyte prepared by the preparation method, and more specifically, to a method for preparing a sulfide-based solid electrolyte comprising two or more sulfide-based compounds to improve the atmospheric stability of the solid electrolyte and reduce the generation of toxic gases and a sulfide-based solid electrolyte prepared by the preparation method.

Description

Technical Field

[0001] The present disclosure relates to a method for preparing a sulfide-based solid electrolyte and a sulfide-based solid electrolyte prepared by the preparation method, and more specifically, to a method for preparing a sulfide-based solid electrolyte comprising two or more sulfide-based compounds to improve the atmospheric stability of the solid electrolyte and reduce the generation of toxic gases and a sulfide-based solid electrolyte prepared by the preparation method. Background Art

[0002] Recently, secondary batteries that can be charged and discharged are widely used as large-capacity power storage batteries used in electric vehicles or power storage systems, and small high-performance energy sources for portable electronic devices such as mobile phones, camcorders, notebook computers, and the like.

[0003] A lithium-ion battery, which is a secondary battery, has advantages of high energy density and large capacity per unit area compared to a nickel-manganese battery and a nickel-cadmium battery.

[0004] However, conventional lithium-ion batteries mainly use flammable organic liquid electrolytes as electrolytes, and therefore have safety issues due to overheating. Recently, all-solid-state batteries using non-flammable solid electrolytes have attracted attention.

[0005] For all-solid-state batteries, the movement of lithium ions at the interface between the electrode and the electrolyte has become an important issue. This is because a lithium ion depletion layer is formed at the interface between the sulfide-based solid electrolyte and the oxide-based electrode material, resulting in a large interfacial impedance, which can cause problems such as reduced battery capacity and shortened life.

[0006] Therefore, in order to reduce the interfacial impedance in conventional all-solid-state batteries, a method of coating the surface of the cathode active material with an oxide is proposed. However, there is still a problem that the coating is easily broken by external pressure during the preparation of the battery (including pressing, etc.), or the coating is damaged due to the volume change of the cathode active material during the charge and discharge of the battery.

[0007] In this regard, there is a need for a method for preparing and a structure of a sulfide-based solid electrolyte having reduced interface resistance between an electrode and the solid electrolyte. Summary of the invention

[0008] Therefore, the present disclosure is proposed in view of the problems encountered in the prior art, and an object of the present disclosure is to provide a method for preparing a sulfide-based solid electrolyte and a sulfide-based solid electrolyte prepared by the preparation method, which improves the atmospheric stability of the solid electrolyte and reduces the generation of toxic gases.

[0009] Another object of the present disclosure is to provide a method for preparing a sulfide-based solid electrolyte and a sulfide-based solid electrolyte prepared by the preparation method, wherein the sulfide-based compound complex is crushed into a uniform particle size, thereby reducing the interface impedance of the solid electrolyte, thereby reducing damage to the surface of the solid electrolyte in contact with the atmosphere.

[0010] The present invention provides a method for preparing a sulfide-based solid electrolyte, comprising: preparing lithium sulfide (Li 2 S), a sulfur compound, a first lithium halide and a second lithium halide are dissolved in an organic solvent and then dried to prepare a powder; the powder is heat-treated to prepare a sulfide-based compound composite including two or more sulfide-based compounds; and the sulfide-based compound composite is pulverized.

[0011] In exemplary embodiments, the organic solvent may include any one of dimethylformamide (DMF) and tetrahydrofuran (THF).

[0012] In exemplary embodiments, the sulfur compound may include any one of silicon sulfide, phosphorus sulfide, germanium sulfide, and boron sulfide.

[0013] In an exemplary embodiment, the first lithium halide and the second lithium halide may have a composition of LiX (wherein X includes any one element of Cl, Br, and I).

[0014] In an exemplary embodiment, the sulfide-based compound complex may include a sulfide-based compound having LPS (Li x P y S z ) and LPSX(Li x P y S z X, wherein X includes any one of Cl, Br and I).

[0015] In an exemplary embodiment, the sulfide-based compound composite may be Li 6 PS 5 Cl, Li 6 PS 5 Br, Li 3 PS 4 and Li 7 P 3 S 11A complex of two or more selected from among.

[0016] In an exemplary embodiment, in preparing the powder, the molar ratio of lithium sulfide: sulfur compound: first lithium halide: second lithium halide may be 3:0.5:0.5:0.5, and the lithium sulfide (Li 2 O 2 ) dissolved therein may be dried at a temperature of 80 to 150° C. 2 S), an organic solvent comprising a sulfur compound, a first lithium halide and a second lithium halide.

[0017] In an exemplary embodiment, the heat treatment may include treating the powder at a temperature of 300 to 500° C. for 5 to 24 hours.

[0018] Another embodiment of the present disclosure provides a sulfide-based solid electrolyte, including a sulfide-based compound composite, wherein the sulfide-based compound composite comprises Li 6 PS 5 Cl, Li 6 PS 5 Br, Li 3 PS 4 and Li 7 P 3 S 11 Two or more sulfide-based compounds selected from among

[0019] In an exemplary embodiment, the particle size of the sulfide-based compound composite may be 0.5 to 10 μm.

[0020] According to the present disclosure, a sulfide-based solid electrolyte includes two or more sulfide-based compounds, thereby improving the atmospheric stability of the solid electrolyte and reducing the generation of toxic gases.

[0021] Furthermore, the sulfide-based compound composite is pulverized into a uniform particle size, reducing the interface impedance of the solid electrolyte, thereby reducing damage to the surface of the solid electrolyte in contact with the atmosphere. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flowchart illustrating a method for preparing a sulfide-based solid electrolyte according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0023] The present disclosure will be described in detail with reference to the accompanying drawings. The repetitive description and detailed description of the known functions and configurations that may obscure the subject matter of the present disclosure will be omitted. The embodiments of the present disclosure are provided to more fully describe the present disclosure to those skilled in the art. Therefore, for the sake of clarity, the shapes and sizes of the elements in the drawings, etc. may be exaggerated.

[0024] It should also be understood that when any part is referred to as “including” or “comprising” any element, unless otherwise stated, other elements are not excluded but other elements may be further included.

[0025] The present disclosure will be better understood through the following preferred embodiments, which are provided only to explain the present disclosure more easily and should not be construed as limiting the present disclosure.

[0026] <Method for preparing sulfide-based solid electrolyte>

[0027] Figure 1 is a flowchart illustrating a method for preparing a sulfide-based solid electrolyte according to an embodiment of the present disclosure.

[0028] The method for preparing a sulfide-based solid electrolyte includes: preparing powder (S100); preparing a sulfide-based compound composite (S200); and pulverizing the sulfide-based compound composite (S300).

[0029] The preparation of powder (S100) may include: 2 S) and sulfur compounds are dissolved in an organic solvent; two different lithium halides are dissolved in lithium sulfide (Li 2 S) and a sulfur compound in an organic solvent; and drying the organic solvent to prepare a powder.

[0030] Here, the organic solvent may include any one of dimethylformamide (DMF) and tetrahydrofuran (THF), and the sulfur compound may include any one of silicon sulfide, phosphorus sulfide, germanium sulfide and boron sulfide. In addition, the lithium halide has a composition of LiX (X includes any one element of Cl, Br and I).

[0031] In preparing the powder (S100), lithium sulfide (Li 2 S), the sulfur compound, the first lithium halide and the second lithium halide are dissolved in an organic solvent in a molar ratio of 2:0.1:0.1:0.1 to 4:1:1:1.

[0032] In addition, in the preparation of the powder (S100), lithium sulfide (Li 2 S) and the sulfur compound are completely dissolved in an organic solvent at a molar ratio of 2:0.1 to 4:1, and then the first lithium halide and the second lithium halide can be mixed in the organic solvent at the same molar ratio as the sulfur compound and reacted. Here, the reaction time can be in the range of 12 to 24 hours. If the reaction time is less than 12 hours, the lithium sulfide, the sulfur compound and the lithium halide do not react with each other, thereby making it difficult to generate a sulfide-based compound.

[0033] In drying the organic solvent to prepare the powder, the drying temperature may be in the range of 80 to 150° C. If the drying temperature of the organic solvent is lower than 80° C., the time required to evaporate the solvent may increase. On the other hand, if the drying temperature of the organic solvent is higher than 150° C., sulfur (S) may evaporate together with the solvent, thereby failing to prepare the sulfide-based compound complex.

[0034] According to an exemplary embodiment, in preparing the powder (S100), lithium sulfide (Li 2 S) and phosphorus pentasulfide (P 2 S 5 ) was dissolved in tetrahydrofuran (THF) solvent at a molar ratio of 3:0.5, and then lithium chloride (LiCl) and lithium bromide (LiBr) were mixed at a molar ratio of 0.5:0.5 and reacted for 24 hours. It was then dried at a temperature of 100° C. to prepare a powder.

[0035] In preparing the sulfide-based compound composite ( S200 ), the sulfide prepared in preparing the powder ( S100 ) is heat-treated to prepare a composite including two or more sulfide-based compounds.

[0036] More specifically, in preparing the sulfide-based compound composite ( S200 ), heat treatment is performed at a temperature of 300 to 500° C. for 5 to 24 hours to prepare two or more sulfide-based compounds.

[0037] Here, if the heat treatment temperature and time are less than 350° C. and 5 hours, respectively, the sulfide-based compound may not be synthesized. On the other hand, if the heat treatment temperature and time exceed 500° C. and 24 hours, respectively, the evaporation amount of sulfur (S) may be increased, and thus the phase of the sulfide-based compound may be undesirably transformed into Li 3 PS 4 .

[0038] The sulfide-based compound prepared in the preparation of the sulfide-based compound complex (S200) may be LPS (Li x P y S z ) and LPSX(Li x P y S z X, wherein X includes any one of Cl, Br and I).

[0039] In addition, the sulfide-based compound composite according to the present disclosure includes Li 6 PS 5 Cl, Li 6 PS 5 Br, Li 3 PS 4 and Li7 P 3 S 11 When the powder is heat treated, a sulfide-based compound having Li 6 PS 5 Cl, Li 6 PS 5 Br, Li 3 PS 4 and Li 7 P 3 S 11 A sulfide-based compound of a composition of and preparing a composite structure including the sulfide-based compound. The composite structure can be arranged in the form of a sphere, a core-shell or a stacked body.

[0040] The sulfide-based compound composite according to the present disclosure includes the sulfide-based compound so that the surface of the sulfide-based solid electrolyte in contact with the atmosphere has the sulfide-based compound, thereby improving the atmospheric stability of the solid electrolyte and reducing the generation of toxic gases.

[0041] In the pulverizing of the sulfide-based compound composite ( S300 ), the sulfide-based compound composite is pulverized into a predetermined particle size using a solution dispensing method.

[0042] The solution dispensing method is a method in which the sulfide-based compound complex prepared by S100 and S200 is dispersed in a non-polar solvent, particularly a toluene solvent, and then the sulfide-based compound complex is uniformly pulverized using a grinder.

[0043] In an exemplary embodiment, the grinding machine can be a rotary grinding machine, and the rotary grinding machine can be operated at a speed of 500 to 2000rpm for 5 minutes to 5 hours. If the operating speed and time of the rotary grinding machine are less than 500rpm and 5 minutes respectively, the time required for crushing the sulfide-based compound composite is insufficient, and therefore uniformly dispersed particles may not be obtained. On the other hand, if the operating speed and time of the rotary grinding machine exceed 2000rpm and 5 hours respectively, the crushed particles may gather undesirably.

[0044] <Sulfide-based solid electrolyte>

[0045] According to the present disclosure, the sulfide-based solid electrolyte includes Li 6 PS 5 Cl, Li 6 PS 5 Br, Li 3 PS 4 and Li 7 P 3 S 11A sulfide-based compound complex is a combination of two or more sulfide-based compounds selected therefrom.

[0046] The particle size of the sulfide-based compound composite may be 0.5 to 10 μm, specifically, D10 is 500 nm to 2 μm, D50 is 1 μm to 5 μm, and D90 is 5 μm to 10 μm.

[0047] The sulfide-based solid electrolyte according to the present disclosure includes a sulfide-based compound composite having uniform particles, thereby effectively reducing the interface impedance of the electrolyte.

[0048] Although the preferred embodiments of the present disclosure have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the disclosure as disclosed in the accompanying claims.

Claims

1. A method for preparing a sulfide-based solid electrolyte, comprising: The lithium sulfide (Li2S), the sulfur compound, the first lithium halide and the second lithium halide are dissolved in an organic solvent and then dried to prepare a powder; heat-treating the powder to prepare a sulfide-based compound composite including two or more sulfide-based compounds; and by pulverizing the sulfide-based compound complex using a solution distribution method, wherein the organic solvent in which the lithium sulfide (Li2S), the sulfur compound, the first lithium halide and the second lithium halide are dissolved is dried at a temperature of 80 to 150° C. for 12 to 24 hours, The sulfide-based compound complex comprises LPS, namely Li x P y S z and LPSX, namely Li x P y S z A composite of two or more sulfide-based compounds composed of X, wherein X in the LPSX includes any one element of Cl, Br and I.

2. The method according to claim 1, wherein: The organic solvent includes any one of dimethylformamide (DMF) and tetrahydrofuran (THF).

3. The method according to claim 1, wherein: The sulfur compounds include phosphorus sulfide.

4. The method according to claim 1, wherein: The first lithium halide and the second lithium halide have a composition of LiX, wherein X in the LiX includes any one of Cl, Br and I.

5. The method according to claim 1, wherein: The sulfide-based compound complex is composed of Li6PS5Cl, Li6PS5Br, Li3PS4 and Li7P3S 11 A complex of two or more selected from among.

6. The method according to claim 1, wherein: In the prepared powder, the molar ratio of the lithium sulfide: the sulfur compound: the first lithium halide: the second lithium halide is 3:0.5:0.5:0.

5.

7. The method according to claim 1, wherein: The heat treatment includes treating the powder at a temperature of 300 to 500° C. for 5 to 24 hours.

8. A sulfide-based solid electrolyte prepared by the method of claim 1, comprising: Sulfide-based compound complexes, including Li6PS5Cl, Li6PS5Br, Li3PS4 and Li7P3S 11 Two or more sulfide-based compounds selected from among 9. The sulfide-based solid electrolyte according to claim 8, wherein The particle size of the sulfide-based compound complex is 0.5 to 10 μm.

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