A sulfide solid electrolyte membrane and its preparation method and application

Abstract

The present invention discloses a sulfide solid electrolyte membrane, its preparation method, and application, relating to the field of all-solid-state battery technology. This high-performance sulfide solid electrolyte membrane achieves a technological breakthrough through the synergistic modification of polyurethane-modified PTFE, lithium difluorooxalatoborate-coated sulfide electrolyte, and silane crosslinking. First, the PTFE is modified with the active groups (-NHCOO-) in the polyurethane molecules, forming stable bonds between the polar groups and the sulfide particles. Second, the sulfide electrolyte is in situ coated with LiDFOB in ethylene glycol dimethyl ether solvent to construct a stable interface layer to inhibit side reactions. Finally, a silane crosslinker is introduced, and a three-dimensional network structure is formed by hot pressing. The resulting electrolyte membrane exhibits excellent film-forming properties and high ionic conductivity. The preparation process utilizes a dry molding process, free of highly toxic solvents, resulting in a simple and controllable process suitable for large-scale production. This provides a technical solution for the industrialization of sulfide all-solid-state batteries, effectively improving battery cycle stability and rate performance.

Description

Technical Field

[0001] The present invention relates to the technical field of all-solid-state batteries, and in particular to a sulfide solid electrolyte membrane, a preparation method and application thereof, and in particular to a high-performance sulfide solid electrolyte membrane synergistically modified by polyurethane-modified PTFE, lithium difluorooxalatoborate-coated sulfide electrolyte and silane cross-linking, and a preparation process and application thereof. Background Art

[0002] Currently, lithium-ion battery technology faces the dual challenges of energy density and safety. All-solid-state batteries, due to their inherent safety characteristics, have become an important direction for overcoming existing technological bottlenecks. Sulfide-based solid electrolytes, with their ionic conductivity comparable to that of liquid electrolytes and excellent mechanical ductility, are considered the electrolyte system with the greatest practical potential. However, sulfide electrolytes still face three major technical bottlenecks in practical application: First, sulfide materials are extremely sensitive to moisture in the air and transition metal elements in the electrode materials, prone to side reactions that increase interfacial impedance. Second, traditional PTFE binders do not form enough fibers during dry film formation, resulting in poor mechanical strength of the electrolyte membrane and difficulty in reducing its thickness (typically >100μm). Furthermore, traditional PTFE binders have difficulty forming a uniform fiber network structure under mechanical shear, resulting in structural defects in the electrolyte membrane. Furthermore, the interfacial compatibility between sulfide particles and polymer binders is poor, which easily leads to phase separation during film formation. Furthermore, thin-film preparation (<50μm) struggles to achieve both mechanical strength and ionic conductivity, making cracking and fracture more likely.

[0003] Therefore, developing a comprehensive solution that can simultaneously solve the problems of unstable sulfide electrolyte interface, poor film-forming performance, and low ionic conductivity has become a key breakthrough point in promoting the industrialization of sulfide all-solid-state batteries. Summary of the Invention

[0004] In view of this, an object of the present invention is to provide a sulfide solid electrolyte membrane and a preparation method and application thereof.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] <First Aspect>

[0007] The present invention provides a preparation method of a LiDFOB-coated modified sulfide electrolyte, comprising the steps of: performing in-situ coating treatment on a sulfide electrolyte in a LiDFOB / ethylene glycol dimethyl ether solution, and obtaining the coated modified sulfide electrolyte after vacuum drying.

[0008] As an embodiment, the mass ratio of the solute LiDFOB to the solvent ethylene glycol dimethyl ether in the LiDFOB / ethylene glycol dimethyl ether solution is 1:(10~25).

[0009] In some embodiments, the mass ratio of the solute LiDFOB to the solvent ethylene glycol dimethyl ether in the LiDFOB / ethylene glycol dimethyl ether solution is 1:(11.5-19).

[0010] As an embodiment, the mass ratio of LiDFOB to sulfide electrolyte is 1: (8~20).

[0011] In some embodiments, the mass ratio of LiDFOB to sulfide electrolyte is 1:(9-19.02).

[0012] As an embodiment, before the in-situ coating treatment, ethylene glycol dimethyl ether solvent is added to the system and then the in-situ coating treatment is carried out.

[0013] As an embodiment, the mass ratio of the supplemented ethylene glycol dimethyl ether solvent to the sulfide electrolyte is 1: (1.8~2).

[0014] As an embodiment, the sulfide electrolyte is of Li6PS5Cl type.

[0015] As an embodiment, the in-situ coating treatment is carried out by stirring at a speed of 600-1000 rpm for 5-10 hours.

[0016] In some embodiments, the in-situ coating treatment is performed by stirring at a speed of 800 rpm for 5 hours.

[0017] As an embodiment, the parameters of the vacuum drying are: vacuum degree 0.03-0.08 MPa, and heat preservation at 40-80° C. for 5-10 hours.

[0018] In some embodiments, the vacuum drying parameters are: vacuum degree 0.08 MPa, and heat preservation at 60° C. for 10 h.

[0019] <Second Aspect>

[0020] The present invention provides a method for preparing a sulfide solid electrolyte membrane, comprising the following steps:

[0021] S1. uniformly mixing a modified binder, a LiDFOB-coated modified sulfide electrolyte, and a cross-linking agent to obtain a mixture;

[0022] S2. The mixed material is subjected to a hot roller pressing process to obtain the sulfide solid electrolyte membrane.

[0023] As an embodiment, the preparation method of the modified binder is: chemically grafting polytetrafluoroethylene in a polyurethane / acetonitrile solution, then washing with deionized water and vacuum drying to obtain the modified binder.

[0024] As an embodiment, the preparation method of the polyurethane / acetonitrile solution is: adding polyurethane to acetonitrile and mixing uniformly to obtain the polyurethane / acetonitrile solution, wherein the mass ratio of the polyurethane to acetonitrile is (4~9):1.

[0025] As an embodiment, the mass ratio of the polytetrafluoroethylene to the polyurethane / acetonitrile solution is 3: (2.5~10).

[0026] As an embodiment, during the preparation of the modified binder, the chemical grafting modification reaction is promoted by stirring at a speed of 600-1000 rpm, and the reaction time is 4-8 hours.

[0027] In some embodiments, during the preparation of the modified binder, the chemical grafting modification reaction is promoted by stirring at a speed of 800 rpm, and the reaction time is 4 hours.

[0028] As an embodiment, the parameters of the vacuum drying are: vacuum degree 0.03-0.08 MPa, and heat preservation at 40-80° C. for 5-10 hours.

[0029] In some embodiments, the vacuum drying parameters are: vacuum degree 0.08 MPa, and heat preservation at 60° C. for 10 h.

[0030] As an embodiment, the mass ratio of the modified binder, the coated modified sulfide electrolyte, and the cross-linking agent is 98:1:1.

[0031] As an embodiment, the cross-linking agent is a silane coupling agent.

[0032] As an embodiment, the crosslinking agent is methacryloxyalkylsilane.

[0033] In some embodiments, the cross-linking agent is G-570.

[0034] As an embodiment, the parameters of the mixture during preparation are a rotation speed of 5000-8000 rpm and a mixing time of 10-20 min.

[0035] In some embodiments, the mixing parameters during preparation are a rotation speed of 5000 rpm and a mixing time of 10 min.

[0036] As an embodiment, the parameters of the hot roller pressing treatment are: temperature 50-60° C., pressure 5-20 MPa, and film thickness 50-120 μm.

[0037] In some embodiments, the parameters of the hot roller pressing process are: temperature 50° C., pressure 10 MPa, and film thickness 100 μm.

[0038] <Third Aspect>

[0039] The present invention provides a method for preparing a composite positive electrode material, comprising the following steps:

[0040] In an argon environment, a ternary cathode material, a LiDFOB-coated sulfide electrolyte, and a conductive agent are mixed to obtain the composite cathode material.

[0041] As an embodiment, the mass ratio of the ternary cathode material, the LiDFOB-coated sulfide electrolyte, and the conductive agent is 80:15:5.

[0042] As an embodiment, the ternary positive electrode material is selected from one or more of NCM811, NCM622, and NCM523.

[0043] In some embodiments, the ternary positive electrode material is NCM811.

[0044] As an embodiment, the conductive agent is VGCF.

[0045] <Fourth Aspect>

[0046] The present invention provides a method for preparing a composite negative electrode material, comprising the following steps:

[0047] In an argon environment, a silicon negative electrode material, a LiDFOB-coated sulfide electrolyte, and a conductive agent are mixed to obtain the composite negative electrode material.

[0048] As an embodiment, the mass ratio of the silicon negative electrode material, the LiDFOB-coated sulfide electrolyte, and the conductive agent is 6:3:1.

[0049] As an embodiment, the silicon negative electrode material is selected from silicon powder, D 50 =3~8μm.

[0050] In some embodiments, the silicon anode material is D 50 =5μm silicon powder.

[0051] As an embodiment, the conductive agent is VGCF.

[0052] <Fifth Aspect>

[0053] The present invention provides an application of a sulfide solid electrolyte membrane in a sulfide all-solid-state lithium battery.

[0054] As an embodiment, the electrolyte sheet in the battery is formed by pressing the above-mentioned sulfide solid electrolyte membrane.

[0055] As an embodiment, the positive electrode sheet in the battery is formed by pressing the above-mentioned composite positive electrode material.

[0056] As an embodiment, the negative electrode sheet in the battery is formed by pressing the above-mentioned composite negative electrode material.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] (1) The present invention achieves a comprehensive improvement in the performance of the sulfide solid electrolyte membrane through the triple synergistic effect of polyurethane-modified PTFE, LiDFOB-coated sulfide electrolyte, and methacryloxyalkylsilane crosslinking:

[0059] In terms of physical properties, we have successfully produced ultra-thin films that combine toughness with high ionic conductivity;

[0060] In terms of interface stability, a stable interface protection layer is constructed by chemical coating and interface modification of sulfide electrolytes;

[0061] In terms of technology, a fully dry preparation process is adopted, which avoids the use of solvents and has the characteristics of simple process, low cost and environmental friendliness.

[0062] (2) The present invention effectively solves key technical problems such as uneven fiberization, multiple interfacial side reactions and poor film-forming performance in the dry film formation of sulfide electrolytes. In addition, the entire preparation process does not require the use of highly toxic solvents and is fully compatible with large-scale production requirements, providing a practical and feasible technical path for the industrial application of sulfide all-solid-state batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0064] Figure 1 A flow chart of a method for preparing a sulfide solid electrolyte membrane provided by the present invention;

[0065] Figure 2 This is a SEM image of the sulfide solid electrolyte membrane prepared in Example 5 of the present invention. DETAILED DESCRIPTION

[0066] The present invention will be described in detail below with reference to the examples. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that those skilled in the art may make several adjustments and improvements without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0067] For ease of understanding, the abbreviations or nouns mentioned below are first explained:

[0068] PTFE: polytetrafluoroethylene;

[0069] LiDFOB: lithium difluorooxalatoborate;

[0070] Silane coupling agent G-570: γ-methacryloxypropyltrimethoxysilane;

[0071] VGCF: carbon nanofiber conductive agent, VGCF-H, purchased from Kejing Zhida Technology Co., Ltd.;

[0072] This specific embodiment provides a method for preparing a sulfide solid electrolyte membrane, which is based on the synergistic effect of polyurethane grafted modified PTFE, lithium difluorooxalate borate coated sulfide electrolyte and silane crosslinking. Figure 1 As shown, the steps are as follows:

[0073] S1. Dry mixing: Add the modified PTFE, the coated modified sulfide electrolyte, and the silane coupling agent as a cross-linking agent into a mixer and mix them evenly.

[0074] S11, the preparation steps of the modified PTFE are: chemically grafting polytetrafluoroethylene (PTFE) in a polyurethane / acetonitrile solution, then washing with deionized water and vacuum drying to obtain the modified PTFE;

[0075] S12. The preparation steps of the coated modified sulfide electrolyte are as follows: using lithium salt (LiDFOB) to in-situ coat the sulfide electrolyte in ethylene glycol dimethyl ether solvent, and then vacuum drying to obtain the coated modified sulfide electrolyte.

[0076] S2. Hot roller pressing dry film formation: The mixed material is subjected to hot pressing treatment using a roller press, and a three-dimensional network structure is formed during the hot pressing process to obtain a sulfide solid electrolyte membrane with a certain toughness and thickness.

[0077] This specific embodiment also provides a method for preparing a composite positive electrode material using the coated modified sulfide electrolyte prepared in the above step S12.

[0078] This specific embodiment also provides a method for preparing a composite negative electrode material using the coated modified sulfide electrolyte prepared in the above step S12.

[0079] This specific embodiment also provides an all-solid-state battery, which is formed by pressing the sulfide solid electrolyte membrane, composite positive electrode material, composite negative electrode material, positive electrode current collector, and negative electrode current collector prepared above.

[0080] The above methods are specifically introduced below through examples.

[0081] Example 1

[0082] This embodiment provides a method for preparing a LiDFOB-coated modified sulfide electrolyte, comprising the following steps:

[0083] In an argon glove box, 5 g of LiDFOB was added to 95 g of ethylene glycol dimethyl ether and stirred thoroughly to form a homogeneous solution to obtain a LiDFOB / ethylene glycol dimethyl ether solution;

[0084] 10 g of Li6PS5Cl type sulfide solid electrolyte was added to 10.52 g of LiDFOB / ethylene glycol dimethyl ether solution, and then 5 g of ethylene glycol dimethyl ether solvent was added. The mixture was reacted at room temperature with a magnetic stirring rate of 800 rpm for 5 h, and then vacuum dried at 60 ° C for 10 h with a vacuum degree of 0.08 MPa to obtain a lithium salt LiDFOB-coated modified sulfide electrolyte.

[0085] Example 2

[0086] This embodiment provides a method for preparing a LiDFOB-coated modified sulfide electrolyte, comprising the following steps:

[0087] In an argon glove box, 8 g of LiDFOB was added to 92 g of ethylene glycol dimethyl ether and stirred thoroughly to form a homogeneous solution, namely, LiDFOB / ethylene glycol dimethyl ether solution;

[0088] 9 g of Li6PS5Cl type sulfide solid electrolyte was added to 12.5 g of LiDFOB / ethylene glycol dimethyl ether solution, and then 5 g of ethylene glycol dimethyl ether solvent was added. The mixture was reacted at room temperature with a magnetic stirring rate of 800 rpm for 5 h, and then vacuum dried at 60 ° C for 10 h with a vacuum degree of 0.08 MPa to obtain a lithium salt LiDFOB-coated modified sulfide electrolyte.

[0089] Comparative Example 1

[0090] This comparative example provides an uncoated modified sulfide electrolyte, namely, a Li6PS5Cl type sulfide solid electrolyte.

[0091] Comparative Example 2

[0092] This comparative example provides a method for preparing a LiTFSI-coated modified sulfide electrolyte. The steps are basically the same as those in Example 1, except that:

[0093] Replace LiDFOB with LiTFSI.

[0094] Comparative Example 3

[0095] This comparative example provides a method for preparing a sulfide electrolyte using butyl butyrate as a solvent. The steps are basically the same as those in Example 1, except that:

[0096] Ethylene glycol dimethyl ether was replaced by butyl butyrate, and other parameters remained unchanged.

[0097] Example 3

[0098] This embodiment provides a method for preparing modified PTFE, the steps are as follows:

[0099] 10 g of polyurethane was added to 90 g of acetonitrile solvent and stirred thoroughly to form a uniform solution to obtain a polyurethane / acetonitrile solution;

[0100] 3 g of PTFE was added to 10 g of polyurethane / acetonitrile solution, reacted at room temperature with a magnetic stirring rate of 800 rpm for 4 h, then washed with deionized water three times, and vacuum dried at 60°C for 10 h with a vacuum degree of 0.08 MPa to obtain a grafted modified PTFE binder.

[0101] Example 4

[0102] This embodiment provides a method for preparing modified PTFE, the steps are as follows:

[0103] 20 g of polyurethane was added to 80 g of acetonitrile solvent and stirred thoroughly to form a uniform solution, which was named polyurethane / acetonitrile solution;

[0104] 6 g of PTFE was added to 5 g of polyurethane / acetonitrile solution, and then 5 g of acetonitrile solvent was added. The mixture was reacted at room temperature with a magnetic stirring rate of 800 rpm for 4 h, and then washed with deionized water 3 times. The mixture was vacuum dried at 60°C for 10 h with a vacuum degree of 0.08 MPa to obtain a grafted modified PTFE binder.

[0105] Comparative Example 4

[0106] This comparative example provides an unmodified PTFE, that is, commercially available PTFE.

[0107] Example 5

[0108] This embodiment provides a method for preparing a sulfide solid electrolyte membrane, and the steps are as follows:

[0109] S1. 9.8 g of the coated modified sulfide electrolyte (prepared in Example 1), 0.1 g of the modified PTFE binder (prepared in Example 3), and 0.1 g of the silane coupling agent G-570 were added to a mixer and mixed at a mixer speed of 5000 rpm for 10 min to obtain a mixture.

[0110] S2. The mixture obtained in step S1 was hot-pressed in an argon glove box using a roller press. The temperature of the roller press was 50° C., the pressure was 10 MPa, the roller rotation speed was 0.1-3.0 m / min (1.0 m / min in this embodiment), and the roller was pressed 6 times. The film thickness was 100 μm, and an electrolyte membrane was obtained. SEM test showed that Figure 2 shown.

[0111] Example 6

[0112] This embodiment provides a method for preparing a sulfide solid electrolyte membrane, and the steps are as follows:

[0113] S1. 4.9 g of the coated modified sulfide electrolyte (prepared in Example 2), 0.05 g of the modified PTFE binder (prepared in Example 4), and 0.05 g of the silane coupling agent G-570 were added to a mixer and mixed at a mixer speed of 5000 rpm for 10 min to obtain a mixture.

[0114] S2. The mixture obtained in step S1 is hot-pressed using a roller press in an argon glove box. The temperature of the roller press is 50° C., the pressure is 10 MPa, the roller rotation speed is 0.1-3.0 m / min (1.0 m / min in this embodiment), and the roller is pressed 6 times to a film thickness of 100 μm to obtain an electrolyte membrane.

[0115] Comparative Example 5

[0116] This comparative example provides a method for preparing a sulfide solid electrolyte membrane. The steps are basically the same as those in Example 5, except that:

[0117] The modified PTFE prepared in Example 3 was replaced by the unmodified PTFE in Comparative Example 4, and other parameters remained unchanged.

[0118] Comparative Example 6

[0119] This comparative example provides a method for preparing a sulfide solid electrolyte membrane. The steps are basically the same as those in Example 5, except that:

[0120] The coated modified sulfide electrolyte prepared in Example 1 was replaced by the uncoated modified sulfide electrolyte of Comparative Example 1, and other parameters remained unchanged.

[0121] Comparative Example 7

[0122] This comparative example provides a method for preparing a sulfide solid electrolyte membrane. The steps are basically the same as those in Example 5, except that:

[0123] No silane coupling agent was added and other parameters remained unchanged.

[0124] Comparative Example 8

[0125] This comparative example provides a method for preparing a sulfide solid electrolyte membrane. The steps are basically the same as those in Example 5, except that:

[0126] The coated modified sulfide electrolyte prepared in Example 1 was replaced by the LiTFSI coated modified sulfide electrolyte of Comparative Example 2, and other parameters remained unchanged.

[0127] Comparative Example 9

[0128] This comparative example provides a method for preparing a sulfide solid electrolyte membrane. The steps are basically the same as those in Example 5, except that:

[0129] The coated modified sulfide electrolyte prepared in Example 1 was replaced with the sulfide electrolyte prepared in Comparative Example 3 using butyl butyrate as the solvent, and other parameters remained unchanged.

[0130] Example 7

[0131] This embodiment provides a method for preparing a composite positive electrode material, the steps of which are as follows:

[0132] In an argon glove box, 80 mg of NCM811 powder, 15 mg of LiDFOB-coated modified sulfide electrolyte (prepared in Example 1), and 5 mg of conductive agent VGCF powder were placed in a mortar and ground for 30 min to obtain a composite cathode material.

[0133] Example 8

[0134] This embodiment provides a method for preparing a composite positive electrode material, the steps of which are as follows:

[0135] In an argon glove box, 80 mg of NCM811 powder, 15 mg of LiDFOB-coated modified sulfide electrolyte (prepared in Example 2), and 5 mg of conductive agent VGCF powder were placed in a mortar and ground for 30 min to obtain a composite positive electrode material.

[0136] Comparative Example 10

[0137] This comparative example provides a method for preparing a composite positive electrode material. The steps are basically the same as those in Example 7, except that:

[0138] The LiDFOB-coated and modified sulfide electrolyte used in Example 1 was replaced by the uncoated and modified sulfide electrolyte in Comparative Example 1, and other parameters remained unchanged.

[0139] Comparative Example 11

[0140] This comparative example provides a method for preparing a composite positive electrode material. The steps are basically the same as those in Example 7, except that:

[0141] The LiDFOB-coated modified sulfide electrolyte used in Example 1 was replaced by the LiTFSI-coated modified sulfide electrolyte in Comparative Example 2, and other parameters remained unchanged.

[0142] Comparative Example 12

[0143] This comparative example provides a method for preparing a composite positive electrode material. The steps are basically the same as those in Example 7, except that:

[0144] The LiDFOB-coated modified sulfide electrolyte used in Example 1 was replaced by the LiDFOB-coated modified sulfide electrolyte prepared using butyl butyrate as the solvent in Comparative Example 3, and other parameters remained unchanged.

[0145] Example 9

[0146] This embodiment provides a method for preparing a composite negative electrode material, the steps of which are as follows:

[0147] In an argon glove box, 60 mg of silicon powder, 30 mg of LiDFOB-coated modified sulfide electrolyte (prepared in Example 1), and 10 mg of conductive agent VGCF powder were placed in a mortar and ground for 30 minutes to obtain a composite negative electrode material.

[0148] Example 10

[0149] This embodiment provides a method for preparing a composite negative electrode material, the steps of which are as follows:

[0150] In an argon glove box, 60 mg of silicon powder, 30 mg of LiDFOB-coated modified sulfide electrolyte (prepared in Example 2), and 10 mg of conductive agent VGCF powder were placed in a mortar and ground for 30 minutes to obtain a composite negative electrode material.

[0151] Comparative Example 13

[0152] This comparative example provides a method for preparing a composite negative electrode material. The steps are basically the same as those in Example 9, except that:

[0153] The LiDFOB-coated and modified sulfide electrolyte used in Example 1 was replaced by the uncoated and modified sulfide electrolyte in Comparative Example 1, and other parameters remained unchanged.

[0154] Comparative Example 14

[0155] This comparative example provides a method for preparing a composite negative electrode material. The steps are basically the same as those in Example 9, except that:

[0156] The LiDFOB-coated modified sulfide electrolyte used in Example 1 was replaced by the LiTFSI-coated modified sulfide electrolyte in Comparative Example 2, and other parameters remained unchanged.

[0157] Comparative Example 15

[0158] This comparative example provides a method for preparing a composite negative electrode material. The steps are basically the same as those in Example 9, except that:

[0159] The LiDFOB-coated modified sulfide electrolyte used in Example 1 was replaced by the LiDFOB-coated modified sulfide electrolyte prepared using butyl butyrate as the solvent in Comparative Example 3, and other parameters remained unchanged.

[0160] Example 11

[0161] This embodiment provides a method for preparing a sulfide all-solid-state lithium-ion battery, the steps of which are as follows:

[0162] In an argon glove box, the sulfide solid electrolyte membrane prepared in Example 5 was cut and placed in a pressure cell mold with a diameter of 10 mm. The membrane was pressed on a tablet press with a pressure of 1 ton applied and maintained at that pressure for 1 minute to obtain an electrolyte sheet.

[0163] 30 mg of the composite positive electrode material prepared in Example 7 was spread flat on the surface of the electrolyte sheet, and pressed into a sheet by applying a pressure of 1 ton on a tablet press and maintaining the pressure for 1 minute. The positive electrode sheet was covered on one side of the electrolyte sheet.

[0164] 10 mg of the composite negative electrode material prepared in Example 9 was spread flat on the other side of the electrolyte sheet, and pressed into a sheet by applying a pressure of 1 ton on a tablet press and maintaining the pressure for 1 minute. The negative electrode sheet was then covered on the other side of the electrolyte sheet.

[0165] An aluminum foil with a diameter of 10 mm and a thickness of 15 μm is placed on the surface of the positive electrode sheet as the positive electrode current collector, and a copper foil with a thickness of 15 μm is placed on the surface of the negative electrode sheet as the negative electrode current collector. After the assembly is completed, a pressure of 1 ton is applied and the pressure is maintained for 1 minute to obtain a sulfide all-solid-state lithium-ion battery.

[0166] Example 12

[0167] This embodiment provides a method for preparing a sulfide all-solid-state lithium-ion battery, the steps of which are as follows:

[0168] In an argon glove box, the sulfide solid electrolyte membrane prepared in Example 6 was cut and placed in a pressure cell mold with a diameter of 10 mm. The membrane was pressed on a tablet press with a pressure of 1 ton applied and maintained at that pressure for 1 minute to obtain an electrolyte sheet.

[0169] 30 mg of the composite positive electrode material prepared in Example 8 was spread flat on the surface of the electrolyte sheet, and pressed into a sheet by applying a pressure of 1 ton on a tablet press and maintaining the pressure for 1 minute. The positive electrode sheet was covered on one side of the electrolyte sheet.

[0170] 10 mg of the composite negative electrode material prepared in Example 10 was spread flat on the other side of the electrolyte sheet, and pressed into a sheet by applying a pressure of 1 ton on a tablet press and maintaining the pressure for 1 minute. The negative electrode sheet was then covered on the other side of the electrolyte sheet.

[0171] An aluminum foil with a diameter of 10 mm and a thickness of 15 μm is placed on the surface of the positive electrode sheet as the positive electrode current collector, and a copper foil with a thickness of 15 μm is placed on the surface of the negative electrode sheet as the negative electrode current collector. After the assembly is completed, a pressure of 1 ton is applied and the pressure is maintained for 1 minute to obtain a sulfide all-solid-state lithium-ion battery.

[0172] This specific embodiment also provides comparative examples of several methods for preparing sulfide all-solid-state lithium-ion batteries. The steps are basically the same as those in Example 11, with only the selection of various sulfide solid electrolyte membranes, composite positive electrode materials, and composite negative electrode materials being different. See Table 1 for details.

[0173] Table 1

[0174]

[0175] Comparative Example 16

[0176] This comparative example provides a method for preparing a sulfide all-solid-state lithium-ion battery. The steps are basically the same as those in Example 11, except that:

[0177] The sulfide solid electrolyte membrane used in Example 5 was replaced by the electrolyte membrane prepared using unmodified PTFE in Comparative Example 5, and other parameters remained unchanged.

[0178] Comparative Example 17

[0179] This comparative example provides a method for preparing a sulfide all-solid-state lithium-ion battery. The steps are basically the same as those in Example 11, except that:

[0180] The sulfide solid electrolyte membrane used in Example 5 was replaced with an electrolyte membrane prepared with an uncoated modified sulfide electrolyte in Comparative Example 6, the composite positive electrode used in Example 7 was replaced with a composite positive electrode prepared with an uncoated modified sulfide electrolyte in Comparative Example 10, and the composite negative electrode used in Example 9 was replaced with a composite negative electrode prepared with an uncoated modified sulfide electrolyte in Comparative Example 13, while other parameters remained unchanged.

[0181] Comparative Example 18

[0182] This comparative example provides a method for preparing a sulfide all-solid-state lithium-ion battery. The steps are basically the same as those in Example 11, except that:

[0183] The sulfide solid electrolyte membrane used in Example 5 was replaced by the electrolyte membrane prepared using the uncoated modified sulfide electrolyte in Comparative Example 6, and other parameters remained unchanged.

[0184] Comparative Example 19

[0185] This comparative example provides a method for preparing a sulfide all-solid-state lithium-ion battery. The steps are basically the same as those in Example 11, except that:

[0186] The sulfide solid electrolyte membrane used in Example 5 was replaced by the electrolyte membrane prepared without adding a silane coupling agent in Comparative Example 7, and other parameters remained unchanged.

[0187] Comparative Example 20

[0188] This comparative example provides a method for preparing a sulfide all-solid-state lithium-ion battery. The steps are basically the same as those in Example 11, except that:

[0189] The sulfide solid electrolyte membrane used in Example 5 was replaced with an electrolyte membrane prepared by coating a sulfide electrolyte modified by lithium salt LiTFSI in Comparative Example 8, the composite positive electrode used in Example 7 was replaced with a composite positive electrode prepared by coating a sulfide electrolyte modified by lithium salt LiTFSI in Comparative Example 11, and the composite negative electrode used in Example 9 was replaced with a composite negative electrode prepared by coating a sulfide electrolyte modified by lithium salt LiTFSI in Comparative Example 14, and other parameters remained unchanged.

[0190] Comparative Example 21

[0191] This comparative example provides a method for preparing a sulfide all-solid-state lithium-ion battery. The steps are basically the same as those in Example 11, except that:

[0192] The sulfide solid electrolyte membrane used in Example 5 was replaced with an electrolyte membrane prepared by coating a modified sulfide electrolyte with lithium salt LiTFSI in Comparative Example 8, and other parameters remained unchanged.

[0193] Comparative Example 22

[0194] This comparative example provides a method for preparing a sulfide all-solid-state lithium-ion battery. The steps are basically the same as those in Example 11, except that:

[0195] The sulfide solid electrolyte membrane used in Example 5 was replaced with an electrolyte membrane prepared with a sulfide electrolyte modified with butyl butyrate solvent in Comparative Example 9, the composite positive electrode used in Example 7 was replaced with a composite positive electrode prepared with a sulfide electrolyte modified with butyl butyrate solvent in Comparative Example 12, and the composite negative electrode used in Example 9 was replaced with a composite negative electrode prepared with a sulfide electrolyte modified with butyl butyrate solvent in Comparative Example 15, and the other parameters remained unchanged.

[0196] Comparative Example 23

[0197] This comparative example provides a method for preparing a sulfide all-solid-state lithium-ion battery. The steps are basically the same as those in Example 11, except that:

[0198] The sulfide solid electrolyte membrane used in Example 5 was replaced by an electrolyte membrane prepared using a sulfide electrolyte modified with butyl butyrate solvent in Comparative Example 9, and other parameters remained unchanged.

[0199] Detection and Analysis

[0200] The sulfide solid electrolyte membranes prepared in Example 5, Example 6, and Comparative Examples 5 to 9 were cut into small discs with a diameter of 10 mm, loaded into a pressure battery mold, and pressed for 1 min under a pressure of 1 ton. The thickness after pressing corresponded to the data in Table 2. An electrochemical workstation with specification model CHI660E was used to perform AC impedance testing at room temperature. The test results are shown in Table 2.

[0201] Table 2

[0202]

[0203] The all-solid-state batteries prepared in Example 11, Example 12, and Comparative Examples 16 to 23 were subjected to charge and discharge tests using a Xinwei battery testing system with an equipment model of CT-4000. A 0.2C-0.5C rate charge and discharge process was used, the voltage range was 4.3-2.5V, and the temperature was 28°C. The discharge capacity of the sulfide all-solid-state battery was tested, and the test results are shown in Table 3.

[0204] Table 3

[0205]

[0206] As can be seen from Table 2, the ionic conductivities of the sulfide solid electrolyte membranes prepared in Examples 5 and 6 are significantly higher than those in Comparative Examples 5 to 9, and the film-forming properties are better than those in Comparative Examples 5 to 9.

[0207] As can be seen from Table 3, the discharge capacities of the batteries of Examples 11 and 12 at 0.2C and 0.5C are significantly higher than those of Comparative Examples 16 to 23, and the first-cycle coulombic efficiency and 0.5C discharge efficiency are higher than those of several comparative examples. In addition, the cycle stability after 30 cycles is higher than that of each comparative example.

[0208] The sulfide solid-state battery system constructed by the present invention through a multi-dimensional modification strategy achieves a synergistic improvement in interfacial compatibility and electrochemical stability, which is specifically reflected in:

[0209] First, chemically modifying PTFE with active groups (-NHCOO-) within the polyurethane molecule significantly enhances the binder's fibrillation ability. The resulting fiber network increases the effective contact area with the electrolyte particles, thereby improving the film-forming properties of the sulfide electrolyte. Furthermore, the polar groups within the polyurethane molecular chain form stable chemical bonds with the sulfide electrolyte particles, significantly improving interfacial compatibility and resolving the key issue of easy delamination at the electrode / electrolyte interface in sulfide all-solid-state batteries.

[0210] Secondly, LiDFOB was used to in situ coat the sulfide electrolyte in ethylene glycol dimethyl ether solvent, and a stable LiF-rich interface layer was constructed on the surface of the particles. The boric acid groups in the coating layer can effectively inhibit the side reactions between the electrolyte and the electrode material, reduce the interfacial impedance, and improve the interfacial electrochemical stability.

[0211] Furthermore, the introduction of methacryloxyalkylsilane (such as G-570) as a cross-linking agent forms a three-dimensional network structure during the hot pressing process, which significantly improves the film-forming performance of the electrolyte membrane. At the same time, while maintaining high ionic conductivity, this structure effectively improves the cycle stability and rate performance of the sulfide all-solid-state battery.

[0212] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a sulfide solid electrolyte membrane, characterized in that: The following steps are involved: S1, uniformly mixing a modified binder, a LiDFOB-coated modified sulfide electrolyte, and a cross-linking agent to obtain a mixture; S2, subjecting the mixed material to a hot roller pressing process to obtain the sulfide solid electrolyte membrane; The preparation method of the LiDFOB-coated modified sulfide electrolyte comprises: performing an in-situ coating treatment on a sulfide electrolyte in a LiDFOB / ethylene glycol dimethyl ether solution, and vacuum drying to obtain the coated modified sulfide electrolyte; the mass ratio of the solute LiDFOB to the solvent ethylene glycol dimethyl ether in the LiDFOB / ethylene glycol dimethyl ether solution is 1:(10-25); the mass ratio of the LiDFOB to the sulfide electrolyte is 1:(8-20); before the in-situ coating treatment, the system is supplemented with ethylene glycol dimethyl ether solvent, and then the in-situ coating treatment is performed, and the mass ratio of the supplemented ethylene glycol dimethyl ether solvent to the sulfide electrolyte is 1:(1.8-2); The modified binder is prepared by chemically grafting polytetrafluoroethylene in a polyurethane / acetonitrile solution, stirring at a speed of 600-1000 rpm to promote the chemical grafting modification reaction for 4-8 hours, and then washing with deionized water and vacuum drying. The polyurethane / acetonitrile solution is prepared by adding polyurethane to acetonitrile and mixing them uniformly to obtain the polyurethane / acetonitrile solution, wherein the mass ratio of the polyurethane to the acetonitrile is (4-9):1; and the mass ratio of the polytetrafluoroethylene to the polyurethane / acetonitrile solution is 3:(2.5-10); The mass ratio of the modified binder, LiDFOB-coated modified sulfide electrolyte, and cross-linking agent is 98:1:1; The cross-linking agent is methacryloyloxyalkylsilane.

2. The method for preparing an electrolyte membrane according to claim 1, wherein: Also includes at least one of the following technical features: A1. The sulfide electrolyte is of Li6PS5Cl type; B1, the in-situ coating treatment is carried out by stirring at a speed of 600-1000 rpm for 5-10 hours; C1. The vacuum drying parameters are: vacuum degree 0.03-0.08 MPa, heat preservation at 40-80°C for 5-10 hours.

3. The method for preparing an electrolyte membrane according to claim 1, wherein: In the preparation method of the modified binder, the parameters of the vacuum drying are: vacuum degree 0.03-0.08 MPa, and heat preservation at 40-80° C. for 5-10 hours.

4. The method for preparing an electrolyte membrane according to claim 1, wherein: Also includes at least one of the following technical features: A2. The mixing parameters during preparation are a speed of 5000-8000 rpm and a mixing time of 10-20 min; B2. The parameters of the hot roller pressing treatment are: temperature 50-60°C, pressure 5-20 MPa, and film thickness 50-120 μm.

5. A method for preparing a composite positive electrode material, characterized in that: In an argon environment, a ternary cathode material, a LiDFOB-coated sulfide electrolyte, and a conductive agent are mixed to obtain the composite cathode material. The LiDFOB-coated sulfide electrolyte is prepared according to the method according to any one of claims 1 to 4.

6. The method for preparing a composite cathode material according to claim 5, wherein: Also includes at least one of the following technical features: A3, the mass ratio of the ternary cathode material, LiDFOB-coated sulfide electrolyte, and conductive agent is 80:15:5; B3. The ternary positive electrode material is selected from one or more of NCM811, NCM622, and NCM523; C3. The conductive agent is VGCF.

7. A method for preparing a composite negative electrode material, characterized in that: In an argon environment, a silicon negative electrode material, a LiDFOB-coated sulfide electrolyte, and a conductive agent are mixed to obtain the composite negative electrode material. The LiDFOB-coated sulfide electrolyte is prepared according to the method according to any one of claims 1 to 4.

8. The method for preparing a composite negative electrode material according to claim 7, characterized in that: Also includes at least one of the following technical features: A4, the mass ratio of the silicon negative electrode material, the LiDFOB-coated sulfide electrolyte, and the conductive agent is 6:3:1; B4, the silicon negative electrode material is D 50 =3~8μm silicon powder; C4. The conductive agent is VGCF.

9. A sulfide all-solid-state lithium battery, characterized in that: The electrolyte sheet in the battery is pressed from a sulfide solid electrolyte membrane, and the sulfide solid electrolyte membrane is prepared according to the method according to any one of claims 1 to 4; the positive electrode sheet in the battery is pressed from a composite positive electrode material, and the composite positive electrode material is prepared according to the method according to claim 5 or 6; the negative electrode sheet in the battery is pressed from a composite negative electrode material, and the composite negative electrode material is prepared according to the method according to claim 7 or 8.

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