A method for improving the stability of sulfide electrolytes towards lithium on a large scale

Abstract

The present invention discloses a method for scale-up improving the stability of sulfide electrolyte to lithium, belonging to the field of solid electrolyte materials for lithium metal batteries, and specifically relates to the preparation of electrolyte materials, the preparation of conductive agents, the preparation of composite positive electrode sheets, and the preparation of all-solid-state lithium metal batteries. In the present invention, the sulfide electrolyte is immersed in a liquid inorganic metal halide and then mechanically compounded with the sulfide electrolyte to prepare a composite sulfide electrolyte with high ionic conductivity and high density, which can effectively reduce the lithium deposition overpotential and inhibit the piercing of lithium through the solid electrolyte layer; the glycosylated carbide prepared from cyclohexanehexol hexaphosphate, 2-hydroxymethylimidazole, polyaniline, and glucose is used as a conductive agent, significantly improving the conductivity and critical current density of the composite positive electrode sheet; the prepared all-solid-state lithium metal battery has stable cycling, excellent rate performance and safety, so the present invention has great application potential in fields such as vehicle preparation.

Description

Technical Field

[0001] The present invention belongs to the field of solid electrolyte materials for lithium metal batteries, and particularly relates to a method for large-scale improving the stability of sulfide electrolytes against lithium. Background Art

[0002] As the mainstream technical route of secondary batteries, lithium-ion batteries are widely used in scenarios such as electric vehicles, energy storage of mobile communication devices, and large-scale power energy storage, realizing the development of clean energy. However, due to their limited ultimate energy density, lithium-ion batteries are gradually unable to meet the requirements of the new generation of electronic devices for energy storage systems. In addition, due to the risks of leakage, combustion, and explosion of the organic electrolytes used, the safety of traditional lithium-ion batteries has been widely criticized.

[0003] All-solid-state lithium metal batteries are widely regarded as the most promising technical route to solve the above problems. At present, the solid electrolytes used in all-solid-state lithium batteries can be mainly divided into two categories: inorganic solid electrolytes and polymer solid electrolytes. Among all solid electrolytes, sulfide electrolytes are regarded as one of the electrolyte materials with the most promising industrialization prospects due to their high ionic conductivity and high processability. Currently, all-solid-state lithium metal batteries using sulfide solid electrolytes have become the research focus in the academic and industrial fields. However, the mutual matching between sulfide solid electrolytes and lithium metal is not ideal. During the lithium deposition process, lithium metal will gradually penetrate into the sulfide solid electrolyte, damaging the brittle electrolyte layer, resulting in unsatisfactory battery cycle life and rate capabilities. To solve the above problems, according to the fracture mechanics theory, sulfide solid electrolytes should have high ionic conductivity and high electrical conductivity; the interface formed by the reaction between sulfide solid electrolytes and lithium metal should have high lithium diffusion ability. In addition, considering the problem of interface void generation during the lithium stripping process, the interface formed by the reaction between sulfide solid electrolytes and lithium metal should have high lithiophilicity to reduce the contact loss between phases. However, conventional solid electrolyte modification methods such as doping not only involve a cumbersome trial-and-error process but also are difficult to effectively inhibit the invasion of lithium by simultaneously optimizing the above-mentioned multiple macroscopic properties required.

[0004] Therefore, there is an urgent need to develop a large-scale modification method for sulfide solid electrolytes to optimize the macroscopic properties of sulfide solid electrolytes from multiple dimensions, inhibit the invasion behavior of lithium metal, and thus improve the battery cycle life and rate capabilities. Summary of the Invention

[0005] The object of the present invention is to provide a method for scale-up improving the stability of sulfide electrolyte to lithium. The composite sulfide electrolyte prepared by this method has the characteristics of high ionic conductivity and high density. After reacting with metallic lithium, a self-limiting growth interfacial layer is formed, which can improve the diffusion rate of lithium in the interface. The all-solid-state lithium metal battery prepared has a long cycle life and excellent rate performance.

[0006] The technical solution adopted by the present invention to achieve the above object is as follows:

[0007] A method for scale-up improving the stability of sulfide electrolyte to lithium, comprising: under the protection of inert gas, immersing the sulfide electrolyte in a liquid inorganic metal halide, standing at room temperature until the unreacted metal halide liquid volatilizes, obtaining composite sulfide electrolyte precursor particles, and mechanically compounding the composite sulfide electrolyte precursor particles with the sulfide electrolyte to obtain a composite sulfide electrolyte; wherein, the sulfide electrolyte is Li 6-x-y PS 5-x-y Cl 1+x Br y , 0.3 ≤ x < 0.6, 0.1 ≤ y < 0.7; the liquid inorganic metal halide includes at least one of SnCl4, TiCl4, and TiBr4. The composite sulfide electrolyte combines electrolyte precursor particles with an amorphous metal compound lithium chloride coated on the surface and the sulfide electrolyte. It not only has high ionic conductivity and high density, but also the self-limiting growth interfacial layer formed after reacting with metallic lithium has a lithiumophilic alloy component, which can improve the diffusion rate of lithium in the interface and exhibits extremely high stability to lithium.

[0008] Preferably, the mass ratio of the sulfide electrolyte to the liquid inorganic metal halide is 1-10:3-60.

[0009] Preferably, the mass ratio of the composite sulfide electrolyte precursor particles to the sulfide electrolyte is 1-10:2-50.

[0010] A composite positive electrode sheet is prepared from a sulfide electrolyte, a positive electrode active material, a conductive agent, and a binder. The positive electrode active material includes, but is not limited to, high-nickel ternary NCM83125, ternary NCM532, and LiCoO2; the binder includes, but is not limited to, polytetrafluoroethylene; the conductive agent includes, but is not limited to, acetylene black and glycosyl carbide. The preparation steps of the glycosyl carbide are as follows: Mix aniline and ammonium persulfate to prepare polyaniline; mix cyclohexanehexol hexaphosphate, 2-hydroxymethylimidazole, polyaniline, and glucose to prepare a mixture; carbonize the mixture. Cyclohexanehexol hexaphosphate, 2-hydroxymethylimidazole, polyaniline, and glucose are carbonized together to form a multi-dimensional conductive network structure, which can provide more transmission paths for electrons, reduce the transmission impedance of electrons in the electrode material, accelerate the movement rate of electrons, endow the glycosyl carbide with excellent conductivity, affinity for lithium ions, and the ability to improve the interface performance between the electrode and the electrolyte, thereby effectively enhancing the stability of the sulfide electrolyte to lithium and the overall electrochemical performance of the battery in the all-solid-state lithium metal battery.

[0011] Preferably, the mass ratio of aniline to ammonium persulfate is 1-5:1.6-8.

[0012] Preferably, the mass ratio of cyclohexanehexol hexaphosphate to glucose is 1-12:8-100.

[0013] Preferably, the mass ratio of 2-hydroxymethylimidazole to glucose is 1-15:6-100.

[0014] Preferably, the mass ratio of polyaniline to glucose is 1-15:6-100.

[0015] More preferably, nickel 1,1,1-trifluoroacetylacetonate can be added during the preparation of the glycosyl carbide. The mass ratio of nickel 1,1,1-trifluoroacetylacetonate to glucose is 1-12.5:8-100. Nickel 1,1,1-trifluoroacetylacetonate can act synergistically with cyclohexanehexol hexaphosphate, 2-hydroxymethylimidazole and other substances to change the charge distribution or chemical environment inside the conductive agent, optimize the transmission path of lithium ions, and improve the rate performance of the battery; the formed electrode-electrolyte interface layer can regulate the deposition behavior of lithium ions at the interface, make lithium ions deposit uniformly, inhibit the growth of lithium dendrites, and enhance the stability to lithium.

[0016] An all-solid-state lithium metal battery is composed of an electrolyte material, a composite positive electrode sheet, and a negative electrode material. The electrolyte material is a composite sulfide electrolyte.

[0017] Preferably, the negative electrode material includes, but is not limited to, lithium metal, lithium metal / carbon composite material, and lithium-silicon alloy, and any material suitable for use as a negative electrode material in the art can be used.

[0018] The present invention provides a preparation method of a composite sulfide electrolyte, including:

[0019] Under the protection of inert gas, immerse the sulfide electrolyte in liquid inorganic metal halide, and let it stand at room temperature until the unreacted liquid metal halide volatilizes, obtaining precursor particles of composite sulfide electrolyte. Use high-energy ball milling method to mechanically compound the precursor particles of composite sulfide electrolyte with sulfide electrolyte. The grinding balls are zirconia balls with a diameter of 6 - 10 mm, the ball milling speed is 100 - 150 rpm, and the ball milling time is 3 - 15 min to obtain the composite sulfide electrolyte.

[0020] Preferably, the inert gas is one of argon and nitrogen.

[0021] More preferably, the inert gas is argon.

[0022] Preferably, the sulfide electrolyte is Li 6-x-y PS 5-x-y Cl 1+x Br y , where 0.3 ≤ x < 0.6 and 0.1 ≤ y < 0.7.

[0023] Preferably, the liquid inorganic metal halide is at least one of SnCl4, TiCl4, and TiBr4.

[0024] Preferably, the mass ratio of the sulfide electrolyte to the liquid inorganic metal halide is 1 - 10:3 - 60.

[0025] Preferably, the mass ratio of the precursor particles of composite sulfide electrolyte to the sulfide electrolyte is 1 - 10:2 - 50.

[0026] Preferably, the number - mass ratio of the grinding balls to the sulfide electrolyte is 10 - 100 pieces:1 - 10 g.

[0027] The present invention provides a preparation method of glycosyl carbide, including:

[0028] Dissolve ammonium persulfate in deionized water to obtain an ammonium persulfate solution. Under the condition of an ice - water bath at 0 - 4 °C, dissolve aniline in deionized water to obtain an aniline solution. Under stirring conditions, add the ammonium persulfate solution to the aniline solution, stir and react for 4 - 6 h, then filter, wash the precipitate with deionized water and dry to obtain polyaniline. Mix cyclohexitol hexaphosphate, 2 - hydroxymethylimidazole, polyaniline and glucose, dissolve them in deionized water, stir evenly to form a mixed dispersion liquid, dry and grind evenly at 70 - 90 °C to obtain a mixed powder, heat from room temperature to 550 - 650 °C under the protection of nitrogen gas and hold for 3 - 5 h, then heat to 850 - 950 °C and hold for 1 - 3 h to obtain glycosyl carbide.

[0029] Preferably, in the ammonium persulfate solution, the mass-volume ratio of ammonium persulfate to deionized water is 2-12 g: 2.5-15 mL.

[0030] Preferably, the mass ratio of aniline to ammonium persulfate is 1-5: 1.6-8.

[0031] Preferably, in the aniline solution, the mass-volume ratio of aniline to deionized water is 1-5 g: 24-120 mL.

[0032] Preferably, in the mixed dispersion, the mass ratio of cyclohexanehexol hexaphosphate to glucose is 1-12: 8-100.

[0033] Preferably, in the mixed dispersion, the mass ratio of 2-hydroxymethylimidazole to glucose is 1-15: 6-100.

[0034] Preferably, in the mixed dispersion, the mass ratio of polyaniline to glucose is 1-15: 6-100.

[0035] Preferably, in the mixed dispersion, the mass-volume ratio of glucose to deionized water is 5-50 g: 25-250 mL.

[0036] The present invention provides a method for preparing a composite positive electrode sheet, comprising:

[0037] Mixing a sulfide electrolyte, a positive electrode active material, and a conductive agent uniformly, adding a binder, and applying a shearing force to prepare a composite positive electrode sheet.

[0038] Preferably, the positive electrode active material includes, but is not limited to, high-nickel ternary NCM83125, ternary NCM532, LiCoO2, and any material suitable for use as a positive electrode material in the art can be used.

[0039] Preferably, the conductive agent includes, but is not limited to, acetylene black, glycosyl carbide, and any material suitable for use as a conductive agent in the art can be used.

[0040] Preferably, the binder includes, but is not limited to, polytetrafluoroethylene, and any material suitable for use as an adhesive in the art can be used.

[0041] Preferably, the mass ratio of the sulfide electrolyte to the positive electrode active material is 26-30: 70-74.

[0042] Preferably, the mass ratio of the conductive agent to the positive electrode active material is 1-5: 140-740.

[0043] Preferably, the mass ratio of the adhesive to the positive electrode active material is 1-4: 175-740.

[0044] The present invention provides a method for preparing an all-solid-state lithium metal battery, comprising:

[0045] Press 60 - 100 mg of the composite sulfide electrolyte under a pressure of 500 - 700 MPa to form an electrolyte thin film with a thickness of 0.4 - 0.6 mm. Place the composite positive electrode sheet on one side of the electrolyte thin film, and reapply a pressure of 500 - 700 MPa to ensure sufficient contact between the positive electrode and the electrolyte. Place lithium metal on the other side of the electrolyte thin film to obtain a all-solid-state lithium metal battery.

[0046] Preferably, the negative electrode material includes, but is not limited to, lithium metal, lithium metal / carbon composite materials, and lithium silicon alloys, and any material suitable for use as a negative electrode material in the art can be used.

[0047] Since the present invention uses a composite sulfide electrolyte obtained by liquid-phase immersion and mechanical compounding of a sulfide electrolyte; and a glycosyl carbide formed by carbonization of cyclohexanehexol hexaphosphate, 2-hydroxymethylimidazole, polyaniline, and glucose as a conductive agent, it has the following beneficial effects: The composite sulfide electrolyte has high ionic conductivity and high density, improves the diffusion rate of lithium at the interface, and exhibits extremely high stability to lithium; the glycosyl carbide has excellent conductivity and affinity for lithium ions, can improve the interface performance between the electrode and the electrolyte, and effectively improves the overall electrochemical performance of the battery. Therefore, the present invention is a method for large-scale improving the stability of sulfide electrolyte to lithium with high ionic conductivity, high exchange current density, and long cycle life. Description of the Drawings

[0048] Figure 1 It is a transmission electron microscope schematic diagram of the precursor particles of the composite sulfide electrolyte.

[0049] Figure 2 It is a scanning electron microscope schematic diagram of the electrolyte thin film.

[0050] Figure 3 It is a schematic diagram of the test results of the ionic conductivity of the electrolyte.

[0051] Figure 4 It is a schematic diagram of the test results of the exchange current density of the lithium symmetric battery.

[0052] Figure 5 It is a schematic diagram of the test results of the small-rate charge and discharge cycle test of the all-solid-state lithium battery. Detailed Embodiments

[0053] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0054] First, the concepts involved in this application will be described in conjunction with the accompanying drawings. It should be noted here that the following descriptions of each concept are only for making the content of this application easier to understand and do not represent a limitation on the protection scope of this application; at the same time, without conflict, the embodiments and features in the embodiments of this application can be combined with each other. This application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0055] Example 1:

[0056] Preparation of electrolyte material: Under the protection of argon gas, the sulfide electrolyte is immersed in liquid inorganic metal halide, and left standing at room temperature until the unreacted metal halide liquid volatilizes, obtaining composite sulfide electrolyte precursor particles. The high-energy ball milling method is used to mechanically compound the composite sulfide electrolyte precursor particles with the sulfide electrolyte to obtain a composite sulfide electrolyte. The sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 , the liquid inorganic metal halide is SnCl4, and the mass ratio of Li 5.5 PS 4.5 Cl 1.5 to SnCl4 is 1:4, the mass ratio of the composite sulfide electrolyte precursor particles to Li 5.5 PS 4.5 Cl 1.5 is 1:2, the grinding balls are zirconia balls with a diameter of 8 mm, the ball milling speed is 110 rpm, the ball milling time is 10 min, and the number-mass ratio of the grinding balls to the sulfide electrolyte is 10 pieces: 1 g.

[0057] Preparation of composite positive electrode sheet: The sulfide electrolyte, positive electrode active material and conductive agent are mixed evenly, a binder is added and a shearing force is applied to prepare a composite positive electrode sheet. The sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 , the positive electrode active material is NCM83125, the conductive agent is acetylene black, the binder is polytetrafluoroethylene, the mass ratio of the sulfide electrolyte to the positive electrode active material is 28:72, the mass ratio of acetylene black to the positive electrode active material is 0.5:72, and the mass ratio of polytetrafluoroethylene to the positive electrode active material is 0.4:72.

[0058] Preparation of all-solid-state lithium metal battery: 80 mg of electrolyte material is pressed into an electrolyte thin sheet with a thickness of 0.5 mm under a pressure of 600 MPa. The composite positive electrode sheet is placed on one side of the electrolyte thin sheet, and a pressure of 600 MPa is reapplied to ensure sufficient contact between the positive electrode and the electrolyte. Lithium metal is placed on the other side of the electrolyte thin sheet to obtain an all-solid-state lithium metal battery.

[0059] Example 2: Compared with Example 1, the only difference lies in the preparation of the composite positive electrode sheet.

[0060] Preparation of the glycosyl carbide: Ammonium persulfate is dissolved in deionized water to obtain an ammonium persulfate solution. Under the condition of an ice-water bath at 2 °C, aniline is dissolved in deionized water to obtain an aniline solution. Under stirring conditions, the ammonium persulfate solution is added to the aniline solution. After stirring and reacting for 5 h, filtration is carried out, and the precipitate is washed with deionized water and dried to obtain polyaniline. Cyclohexanehexol hexaphosphate, 2-hydroxymethylimidazole, polyaniline, and glucose are mixed and dissolved in deionized water, and stirred evenly to form a mixed dispersion. It is dried at 80 °C and ground evenly to obtain a mixed powder, which is heated from room temperature to 600 °C under nitrogen gas protection and maintained for 4 h, and then heated to 900 °C and maintained for 2 h to obtain the glycosyl carbide. In the ammonium persulfate solution, the mass-volume ratio of ammonium persulfate to deionized water is 4 g: 5 mL; the mass ratio of aniline to ammonium persulfate is 2.5:4; in the aniline solution, the mass-volume ratio of aniline to deionized water is 2.5 g:60 mL; in the mixed dispersion, the mass ratio of cyclohexanehexol hexaphosphate to glucose is 1.2:10, the mass ratio of 2-hydroxymethylimidazole to glucose is 1.5:10, the mass ratio of polyaniline to glucose is 1.5:10, and the mass-volume ratio of glucose to deionized water is 10 g:50 mL.

[0061] Preparation of the composite positive electrode sheet: The sulfide electrolyte, the positive electrode active material, and the conductive agent are mixed evenly, a binder is added, and a shear force is applied to prepare the composite positive electrode sheet. The sulfide electrolyte is Li 5.5 PS 4.5 Cl 1.5 , the positive electrode active material is NCM83125, the binder is polytetrafluoroethylene, the conductive agent is the glycosyl carbide, the mass ratio of the sulfide electrolyte to the positive electrode active material is 28:72, the mass ratio of the glycosyl carbide to the positive electrode active material is 0.5:72, and the mass ratio of polytetrafluoroethylene to the positive electrode active material is 0.4:72.

[0062] Example 3: Compared with Example 2, the only difference lies in the preparation of the glycosyl carbide.

[0063] Preparation of Glycosyl Carbide: Ammonium persulfate was dissolved in deionized water to obtain an ammonium persulfate solution. Under the condition of an ice-water bath at 2 °C, aniline was dissolved in deionized water to obtain an aniline solution. Under stirring conditions, the ammonium persulfate solution was added to the aniline solution. After stirring and reacting for 5 h, filtration was carried out. The precipitate was washed with deionized water and dried to obtain polyaniline. Cyclohexitol hexaphosphate, 2-hydroxymethylimidazole, polyaniline, and glucose were mixed and dissolved in deionized water. After stirring evenly to form a mixed dispersion, it was dried at 80 °C and ground evenly to obtain a mixed powder. Under the protection of nitrogen gas, it was heated from room temperature to 600 °C and maintained for 4 h, and then heated to 900 °C and maintained for 2 h to obtain glycosyl carbide. In the ammonium persulfate solution, the mass-volume ratio of ammonium persulfate to deionized water was 4 g: 5 mL; the mass ratio of aniline to ammonium persulfate was 2.5:4; in the aniline solution, the mass-volume ratio of aniline to deionized water was 2.5 g:60 mL; in the mixed dispersion, the mass ratio of cyclohexitol hexaphosphate to glucose was 1.8:10, the mass ratio of 2-hydroxymethylimidazole to glucose was 1:10, the mass ratio of polyaniline to glucose was 1.5:10, and the mass-volume ratio of glucose to deionized water was 10 g:50 mL.

[0064] Example 4: The difference between this example and Example 2 lies only in the preparation of glycosyl carbide.

[0065] Preparation of Glycosyl Carbide: Ammonium persulfate was dissolved in deionized water to obtain an ammonium persulfate solution. Under the condition of an ice-water bath at 2 °C, aniline was dissolved in deionized water to obtain an aniline solution. Under stirring conditions, the ammonium persulfate solution was added to the aniline solution. After stirring and reacting for 5 h, filtration was carried out. The precipitate was washed with deionized water and dried to obtain polyaniline. Cyclohexitol hexaphosphate, 2-hydroxymethylimidazole, polyaniline, nickel 1,1,1-trifluoroacetylacetonate, and glucose were mixed and dissolved in deionized water. After stirring evenly to form a mixed dispersion, it was dried at 80 °C and ground evenly to obtain a mixed powder. Under the protection of nitrogen gas, it was heated from room temperature to 600 °C and maintained for 4 h, and then heated to 900 °C and maintained for 2 h to obtain glycosyl carbide. In the ammonium persulfate solution, the mass-volume ratio of ammonium persulfate to deionized water was 4 g: 5 mL; the mass ratio of aniline to ammonium persulfate was 2.5:4; in the aniline solution, the mass-volume ratio of aniline to deionized water was 2.5 g:60 mL; in the mixed dispersion, the mass ratio of cyclohexitol hexaphosphate to glucose was 1.2:10, the mass ratio of 2-hydroxymethylimidazole to glucose was 1.5:10, the mass ratio of polyaniline to glucose was 1.5:10, the mass ratio of nickel 1,1,1-trifluoroacetylacetonate to glucose was 1.25:10, and the mass-volume ratio of glucose to deionized water was 10 g:50 mL.

[0066] Example 5: The difference between this example and Example 2 lies only in the preparation of glycosyl carbide.

[0067] Preparation of Glycosyl Carbide: Ammonium persulfate was dissolved in deionized water to obtain an ammonium persulfate solution. Under the condition of an ice-water bath at 2 °C, aniline was dissolved in deionized water to obtain an aniline solution. Under stirring conditions, the ammonium persulfate solution was added to the aniline solution. After stirring and reacting for 5 h, filtration was carried out, and the precipitate was washed with deionized water and dried to obtain polyaniline. Cyclohexitol hexaphosphate, 2-hydroxymethylimidazole, polyaniline, nickel 1,1,1-trifluoroacetylacetonate, and glucose were mixed and dissolved in deionized water, and stirred evenly to form a mixed dispersion. It was dried at 80 °C and ground evenly to obtain a mixed powder. Under the protection of nitrogen gas, it was heated from room temperature to 600 °C and maintained for 4 h, and then heated to 900 °C and maintained for 2 h to obtain glycosyl carbide. In the ammonium persulfate solution, the mass-volume ratio of ammonium persulfate to deionized water was 4 g: 5 mL; the mass ratio of aniline to ammonium persulfate was 2.5:4; in the aniline solution, the mass-volume ratio of aniline to deionized water was 2.5 g:60 mL; in the mixed dispersion, the mass ratio of cyclohexitol hexaphosphate to glucose was 1.2:10, the mass ratio of 2-hydroxymethylimidazole to glucose was 1.5:10, the mass ratio of polyaniline to glucose was 1.5:10, the mass ratio of nickel 1,1,1-trifluoroacetylacetonate to glucose was 2.5:10, and the mass-volume ratio of glucose to deionized water was 10 g:50 mL.

[0068] Comparative Example 1: This comparative example is different from Example 1 only in the preparation of the electrolyte material.

[0069] Preparation of Electrolyte Material: The sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 was used as the electrolyte material.

[0070] Comparative Example 2: This comparative example is different from Example 1 only in the preparation of the electrolyte material.

[0071] Preparation of Electrolyte Material: Under the protection of argon gas, the sulfide electrolyte was immersed in liquid inorganic metal halide, and left to stand at room temperature until the unreacted metal halide liquid volatilized, obtaining composite sulfide electrolyte precursor particles as the electrolyte material. The sulfide electrolyte was Li 5.5 PS 4.5 Cl 1.5 , and the liquid inorganic metal halide was SnCl4. The mass ratio of Li 5.5 PS 4.5 Cl 1.5 to SnCl4 was 1:4.

[0072] Comparative Example 3: This comparative example is different from Example 2 only in that cyclohexitol hexaphosphate was not used in the preparation of glycosyl carbide.

[0073] Comparative Example 4: This comparative example is the same as Example 2, except that 2-hydroxymethylimidazole was not used in the preparation of the glycosyl carbide.

[0074] Comparative Example 5: This comparative example is the same as Example 2, except that cyclohexanehexol hexaphosphate and 2-hydroxymethylimidazole were not used in the preparation of the glycosyl carbide.

[0075] Test Example 1: Microstructural characterization of the composite sulfide electrolyte precursor particles.

[0076] Test sample: The composite sulfide electrolyte precursor particles prepared in Example 1.

[0077] Test method: The composite sulfide electrolyte precursor particles were scanned by transmission electron microscopy to obtain the microstructural characteristics of the samples.

[0078] The transmission electron micrograph of the composite sulfide electrolyte precursor particles prepared in the present invention is as Figure 1 shown, indicating that the composite sulfide electrolyte precursor particles as shown in the figure were successfully obtained. Figure 1 (a) is the transmission electron micrograph of the composite sulfide electrolyte precursor particles prepared in Example 1; Figure 1 (b) is the sulfur element distribution in the composite sulfide electrolyte precursor particles; Figure 1 (c) is the chlorine element distribution in the composite sulfide electrolyte precursor particles; Figure 1 (d) is the tin element distribution in the composite sulfide electrolyte precursor particles; Figure 1 (e) is the high-resolution transmission electron microscopy observation result of the outer layer of the composite sulfide electrolyte precursor particles.

[0079] Test Example 2: Microstructural characterization of the electrolyte thin film.

[0080] Test samples: The electrolyte materials prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0081] Test method: 150 mg of the electrolyte material prepared in Example 1 was pressed into a thin film of about 1.135 mm under a pressure of 600 MPa, 150 mg of the electrolyte material of Comparative Example 1 was pressed into a thin film of about 1.259 mm under a pressure of 600 MPa, and 150 mg of the electrolyte material of Comparative Example 2 was pressed into a thin film of about 0.936 mm under a pressure of 600 MPa. The surface defect density of the samples was observed by scanning electron microscopy.

[0082] The scanning electron micrograph of the electrolyte thin film prepared in the present invention is as Figure 2 shown. Figure 2 (a), Figure 2 (b), Figure 2 (c) are the results of Example 1, Comparative Example 1, and Comparative Example 2 respectively. FromFigure 2 (b) It can be seen that for the Li in Comparative Example 1 5.5 PS 4.5 Cl 1.5 electrolyte, due to the existence of polycrystalline grain boundaries, the grains are not densely stacked during the cold pressing process, resulting in a large number of defects on its surface; in contrast Figure 2 (c) It can be known that for the electrolyte precursor particles prepared in Comparative Example 2 and subjected to liquid-phase infiltration treatment, since there are a large number of amorphous compounds on the surface, the electrolyte sheet formed by their stacking is very dense, and almost no obvious surface defects can be observed; and from Figure 2 (a) It can be seen that the composite sulfide electrolyte powder material prepared in Example 1 retains the advantages of the electrolyte precursor particles treated by liquid-phase infiltration, and the electrolyte sheet formed by stacking its particles is still dense.

[0083] Test Example 3: Measurement of the ionic conductivity of the electrolyte thin film.

[0084] Test samples: The electrolyte materials prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0085] Test method: Press 150 mg of the electrolyte material prepared in Example 1 into a thin film about 1.135 mm thick under a pressure of 600 MPa, press 150 mg of the electrolyte material of Comparative Example 1 into a thin film about 1.259 mm thick under a pressure of 600 MPa, press 150 mg of the electrolyte material prepared in Comparative Example 2 into a thin film about 0.936 mm thick under a pressure of 600 MPa, fix carbon-coated aluminum foils on both sides of the electrolyte thin film respectively to form a sandwich structure, and obtain its alternating current impedance spectrogram through an electrochemical workstation to calculate and obtain the ionic conductivity.

[0086] The test results of the ionic conductivity of the electrolyte prepared by the present invention are as Figure 3 shown, among which, Figure 3 (a) is the alternating current impedance diagram of the blocking cell of the electrolyte in Example 1, and the ionic conductivity is 6.2 mS / cm; Figure 3 (b) is the alternating current impedance diagram of the blocking cell of the electrolyte in Comparative Example 1, and the ionic conductivity is 7.4 mS / cm; Figure 3 (c) is the alternating current impedance diagram of the blocking cell of the electrolyte in Comparative Example 2, and the ionic conductivity is 4.8 mS / cm. It can be known from the comparison between Example 1 and Comparative Examples 1-2 that the liquid-phase infiltration modification process will significantly reduce the ionic conductivity of the original Li 5.5 PS 4.5 Cl 1.5 electrolyte. After the mechanical compounding step, the high ionic conductivity characteristic of the original Li 5.5 PS 4.5 Cl 1.5 electrolyte is retained in the developed composite sulfide electrolyte.

[0087] Test Example 4: Exchange current density test of lithium symmetric battery

[0088] Test samples: electrolyte materials prepared in Example 1, Comparative Example 1 and Comparative Example 2.

[0089] Test method: 150 mg of electrolyte material was pressed into an electrolyte sheet under a pressure of 600 MPa, lithium metal electrodes were attached to both sides of the electrolyte sheet to obtain a lithium symmetrical battery, and an electrochemical workstation was connected. The frequency range of 10 mHz-1 MHz and the amplitude of 5-10 mV were set to perform AC impedance test to obtain the exchange current density.

[0090] The exchange current density test results of the lithium symmetrical battery prepared by the present invention are as follows: Figure 4 ,Depend on Figure 4 (a) It can be seen that the exchange current density of Example 1 is 1.37 mA / cm 2 ;Depend on Figure 4 (b) It can be seen that the exchange current density of Comparative Example 1 is 1.06 mA / cm 2 ,Depend on Figure 4 (c) It can be seen that the exchange current density of Comparative Example 2 is 0.6 mA / cm 2 Compared with Comparative Examples 1-2, Example 1 shows that although the reaction of the electrolyte modified by liquid phase infiltration with metallic lithium can generate a self-limiting interface containing a lithium-philic alloy, due to the low ionic conductivity of the electrolyte modified by liquid phase infiltration, its symmetric battery exchange current density is lower than that of the original Li 5.5 PS 4.5 Cl 1.5 The symmetric battery exchange current density of the electrolyte is high, and the composite sulfide electrolyte obtained by mechanical compounding can generate a self-limiting interface containing a lithium-philic alloy to increase the diffusion rate of lithium in the interface, and the constructed symmetric battery has a higher lithium symmetric battery exchange current value.

[0091] Experimental Example 5: Critical current density test of lithium symmetric battery.

[0092] Test samples: electrolyte materials prepared in Example 1, Comparative Example 1 and Comparative Example 2.

[0093] Test method: 150 mg of electrolyte material is pressed into an electrolyte sheet under a pressure of 600 MPa, and lithium metal electrodes are attached to both sides of the electrolyte sheet to obtain a lithium symmetrical battery. The battery is connected to an electrochemical workstation, and a cyclic charge and discharge test is performed at a test temperature of 25°C by gradually increasing the constant current density until the battery reaches a critical state of short circuit, and the critical current density is obtained.

[0094] The critical current density of Example 1 is 2.8 mA / cm 2, the critical current density of Comparative Example 1 is 1.0 mA / cm 2 , the critical current density of Comparative Example 2 is 1.8 mA / cm 2 , compared with Comparative Examples 1-2, Example 1 shows that the composite sulfide electrolyte obtained by liquid-phase infiltration and mechanical compounding can exhibit high lithium stability, and the prepared lithium symmetric battery has a high critical current density.

[0095] Test Example 6: Small-rate charge-discharge cycle test of the all-solid-state lithium battery for the full cell.

[0096] Test samples: All-solid-state lithium batteries prepared by the methods of each example and comparative example.

[0097] Test method: Using a charge-discharge tester, the test conditions are a charge-discharge voltage range of 2.5 - 4.25 V, a charge-discharge rate of 0.1 C, and a test temperature of 25°C. Conduct an initial charge-discharge test and calculate the capacity retention rate after 50 cycles.

[0098] The test results of the capacity retention rate of the all-solid-state lithium battery prepared by the present invention are as Figure 5 shown. Among them, the capacity retention rate of Example 1 is 85.2%, the capacity retention rate of Example 2 is 88.8%, the capacity retention rate of Example 3 is 90.0%, the capacity retention rate of Example 4 is 92.1%, and the capacity retention rate of Example 5 is 92.8%. It can be seen from Examples 1-5 that with the optimization of the conductive agent structure and the improvement of the preparation process, the cycle stability of the battery is significantly improved, indicating that the glycosyl carbides used in Examples 2 and 3 can improve the electrode-electrolyte interface performance, reduce capacity loss, and extend the battery cycle life. After adding nickel 1,1,1-trifluoroacetylacetonate in Examples 4 and 5, the capacity retention rate is improved, indicating that its synergistic effect with other substances can effectively inhibit the growth of lithium dendrites, reduce the loss of active substances, and thus improve the cycle stability of the battery. The capacity retention rate of Comparative Example 1 is 70.5%, the capacity retention rate of Comparative Example 2 is 78.7%, the capacity retention rate of Comparative Example 3 is 83.2%, the capacity retention rate of Comparative Example 4 is 84.0%, and the capacity retention rate of Comparative Example 5 is 80.1%, indicating that the preparation method of the composite sulfide electrolyte of the present invention and the mechanical compounding step play an important role in improving the cycle stability of the battery. At the same time, cyclohexanehexol hexaphosphate and 2-hydroxymethylimidazole play an important role in improving the cycle performance of the battery. The lack of them will lead to a decrease in the capacity retention rate of the battery and a deterioration of the cycle stability.

[0099] Test Example 7: Large-rate charge-discharge cycle test of the all-solid-state lithium battery for the full cell.

[0100] Test samples: All-solid-state lithium batteries prepared by the methods of each example and comparative example.

[0101] Test method: Using a charge-discharge tester, the test conditions are a charge-discharge voltage range of 2.5 - 4.25 V, charge-discharge rates of 0.5C and 1C, a test temperature of 25°C. Perform charge-discharge cycle tests and record the capacity retention rate after 1000 cycles at a discharge rate of 0.5C and the capacity retention rate after 2000 cycles at a discharge rate of 1C.

[0102] The test results of the capacity retention rate of the all-solid-state lithium battery prepared by the present invention are shown in Table 1:

[0103] Table 1 Test results of the capacity retention rate of the all-solid-state lithium battery

[0104]

[0105] From the analysis of Example 1, Comparative Example 1, and Comparative Example 2, it can be seen that the composite sulfide electrolyte powder material developed by modifying Example 1 compared with the original Li 5.5 PS 4.5 Cl 1.5 electrolyte and the Li 5.5 PS 4.5 Cl 1.5 electrolyte modified only by liquid phase infiltration all show excellent performance in the high-rate charge-discharge cycle test of the full cell. In particular, the all-solid-state lithium metal battery assembled with the composite sulfide electrolyte developed by modifying Example 1 can cycle more than 2000 times at a rate of 1C, and the capacity retention rate is 93%. The extremely high lithium stability of the composite sulfide electrolyte can be attributed to its multi-dimensional optimized macroscopic characteristics: high ionic conductivity and high density; it has a lithiophilic alloy component after reacting with metallic lithium, which improves the diffusion rate of lithium at the interface. And Examples 2 - 5 optimized the glycosyl carbide. Compared with Example 1, the performance of the full cell in the high-rate charge-discharge cycle test has also been improved. Compared with Comparative Examples 3 - 5, the capacity retention rate has increased more significantly, indicating that with the optimization of the conductive agent structure and the improvement of the preparation process, the prepared electrode can effectively inhibit the growth of lithium dendrites and reduce the loss of active substances, thereby improving the cycle stability of the battery.

[0106] The above-described embodiments and / or implementation manners are only used to illustrate the preferred embodiments and / or implementation manners for realizing the technology of the present invention, and do not impose any form of limitation on the implementation manners of the technology of the present invention. Any person skilled in the art, without departing from the scope of the technical means disclosed in the content of the present invention, may make some changes or modifications to other equivalent embodiments, but should still be regarded as the same technology or embodiment as the present invention in essence.

[0107] In this text, specific examples are used to illustrate the principle and implementation of the present application. The description of the above embodiments is only for helping to understand the method and its core idea of the present application. The above is only the preferred implementation mode of the present application. It should be noted that due to the limitation of literal expression, and objectively there are infinite specific structures. For those of ordinary skill in the art in this technical field, without departing from the principle of the present application, several improvements, refinements or changes can also be made, or the above technical features can be combined in an appropriate manner; these improvements, refinements, changes or combinations, or directly applying the concept and technical solution of the invention to other occasions without improvement, shall all be regarded as the protection scope of the present application.

Claims

1. A method for improving the stability of lithium in all-solid-state lithium metal batteries using sulfide electrolytes on a large scale, comprising: Under the protection of an inert gas, a sulfide electrolyte is immersed in a liquid inorganic metal halide, and allowed to stand at room temperature until the unreacted metal halide liquid evaporates to obtain composite sulfide electrolyte precursor particles, and the composite sulfide electrolyte precursor particles are mechanically composited with the sulfide electrolyte to obtain a composite sulfide electrolyte; wherein the sulfide electrolyte is Li 6-x- y PS 5-x-y Cl 1+x Br y , 0.3≤x<0.6, 0.1≤y<0.7; the liquid inorganic metal halide includes at least one of SnCl4, TiCl4, and TiBr4; and the mechanical compounding is high-energy ball milling.

2. A method for improving the stability of lithium in all-solid-state lithium metal batteries using sulfide electrolytes on a large scale according to claim 1, characterized in that: The mass ratio of the sulfide electrolyte to the liquid inorganic metal halide is 1-10:3-60.

3. The method for improving the stability of lithium in all-solid-state lithium metal batteries by sulfide electrolytes on a large scale according to claim 1, characterized in that: The mass ratio of the composite sulfide electrolyte precursor particles to the sulfide electrolyte is 1-10:2-50.

4. An all-solid-state lithium metal battery, consisting of an electrolyte material, a composite positive electrode plate and a negative electrode material, wherein the electrolyte material is a composite sulfide electrolyte as described in any one of claims 1 to 3, and the negative electrode material comprises lithium metal, a lithium metal / carbon composite material, or a lithium silicon alloy.

5. The all-solid-state lithium metal battery according to claim 4, characterized in that: The composite positive electrode plate is prepared from a sulfide electrolyte, a positive electrode active material, a conductive agent and a binder, wherein the positive electrode active material includes high-nickel ternary NCM83125, ternary NCM532, and LiCoO2; the binder includes polytetrafluoroethylene; the conductive agent includes sugar-based carbide; wherein the preparation steps of the sugar-based carbide are: mixing aniline with ammonium persulfate to prepare polyaniline; mixing cyclohexanehexol hexaphosphate, 2-hydroxymethylimidazole, polyaniline and glucose to prepare a mixture; and carbonizing the mixture to obtain sugar-based carbide.

6. The all-solid-state lithium metal battery according to claim 5, characterized in that: The mass ratio of aniline to ammonium persulfate is 1-5:1.6-8.

7. The all-solid-state lithium metal battery according to claim 5, characterized in that: The mass ratio of cyclohexanehexol hexaphosphate to glucose is 1-12:8-100, the mass ratio of 2-hydroxymethylimidazole to glucose is 1-15:6-100, and the mass ratio of polyaniline to glucose is 1-15:6-100.

8. The all-solid-state lithium metal battery according to claim 5, characterized in that: It is characterized in that The carbonization treatment is carried out at 550-950°C.

9. Use of the all-solid-state lithium metal battery according to claim 4 in the preparation of vehicles.

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