A high-stability sulfide solid electrolyte lithium battery and a preparation method thereof

Abstract

This invention discloses a high-stability sulfide solid electrolyte lithium battery and its preparation method. The method involves mixing and drying modified additives with lithium bis(fluorosulfonyl)imide, composite powder, and synergistic powder to obtain an electrolyte membrane. The positive electrode, negative electrode, electrolyte membrane, and battery casing are then assembled to obtain the high-stability sulfide solid electrolyte lithium battery. The main chain of the modified additive is a polysiloxane chain with polyethylene oxide segments. The ether oxygen atoms in its molecular network can coordinate with the lithium salt, dissolving and conducting lithium ions, forming a polymer phase ion transport path. Simultaneously, the flexibility of the polysiloxane segments can facilitate the movement of the copolymer segments, resulting in faster lithium ion migration in the solid electrolyte. The addition of composite powder increases ionic conductivity through the dual doping of bromine and chlorine. The polysiloxane structure and C-F structure of the modified additive enhance the hydrophobic effect of the solid electrolyte, increasing its service life.

Description

Technical Field

[0001] This invention relates to the field of lithium battery manufacturing technology, specifically to a high-stability sulfide solid electrolyte lithium battery and its manufacturing method. Background Technology

[0002] With the rapid increase in energy density and safety demands from electric vehicles, large-scale energy storage, and high-end consumer electronics, traditional lithium-ion batteries using organic liquid electrolytes are approaching their theoretical limits and face inherent risks such as flammability, leakage, and thermal runaway. All-solid-state lithium batteries, which use non-flammable inorganic solid electrolytes instead of liquid electrolytes, are considered a next-generation battery technology that fundamentally solves safety bottlenecks and has the potential to break through the energy density ceiling. Among various solid electrolyte materials, sulfide solid electrolytes have become one of the most popular and fastest-progressing technologies due to their extremely high room-temperature ionic conductivity, excellent mechanical ductility, and low grain boundary resistance. However, sulfide electrolytes are highly reactive to moisture and oxygen. Exposure to air leads to rapid hydrolysis, generating highly toxic and corrosive hydrogen sulfide gas, accompanied by irreversible damage to the electrolyte structure and a sharp drop in ionic conductivity. This places extremely stringent requirements on their production, storage, battery manufacturing, and long-term operating environment. Summary of the Invention

[0003] The purpose of this invention is to provide a high-stability sulfide solid electrolyte lithium battery and its preparation method, which solves the problem that sulfide solid electrolytes are extremely sensitive to moisture in humid environments.

[0004] The objective of this invention can be achieved through the following technical solutions: A method for preparing a high-stability sulfide solid electrolyte lithium battery specifically includes the following steps: Step A1: Lithium dimethylhydrosilylsiloxane and tetrahydrofuran are mixed and protected under nitrogen. Under conditions of 200-300 r / min and 0℃, trifluoropropylmethylcyclotrisiloxane is added while stirring. The temperature is raised to 25-30℃ and the reaction is carried out for 7-9 h. Modified polysiloxane is added and the reaction is continued for 3-5 h to obtain branched polysiloxane. Branched polysiloxane, acrylonitrile, caster catalyst and xylene are mixed and protected under nitrogen. Under conditions of 200-300 r / min and 80-85℃, the reaction is carried out for 6-8 h to obtain modified additive. Step A2: Mix lithium sulfide, phosphorus pentasulfide, lithium bromide and lithium chloride, ball mill evenly and add to a mold. Under pressure of 370-380 MPa, hold pressure for 1-1.5 min, then place in a tube furnace and heat to 580-600℃ at a rate of 1-2℃ / min. Sinter for 8-10 h, then grind into powder to obtain composite powder. Step A3: Mix the modified additive and electrolyte evenly, and keep it at 60-80 r / min and 70-75℃ for 8-10 hours. Then, pulverize and mix with acetone, and centrifuge at 10000 r / min and 20-25℃ for 15 minutes. Remove the supernatant and dry to obtain the enhanced powder. Step A4: Mix the modified additive, lithium bis(fluorosulfonyl)imide salt and acetonitrile, and sonicate them for 1-1.5 hours at a frequency of 30-50 kHz and a temperature of 20-25 ℃. Then add the composite powder and the synergistic powder, sonicate them for 10-12 hours, place them in a mold and dry them to obtain the electrolyte membrane. Assemble the positive electrode, negative electrode, electrolyte membrane and battery case to obtain a high-stability sulfide solid electrolyte lithium battery.

[0005] Furthermore, in step A1, the ratio of the Si-Cl bonds on lithium dimethylhydrosiloxane, trifluoropropylmethylcyclotrisiloxane, and modified polysiloxane is 1:4:1, the molar ratio of the Si-H bonds on the branched polysiloxane to acrylonitrile is 1:1, and the amount of cassiterite catalyst is 0.01% of the mass of acrylonitrile.

[0006] Furthermore, the molar ratio of lithium sulfide, phosphorus pentasulfide, lithium bromide and lithium chloride in step A2 is 5:1:0.7:1.3.

[0007] Furthermore, the mass ratio of the modified additive to the electrolyte in step A3 is 1:50, and the electrolyte is 1M LiPF6 / EC:DMC:EMC.

[0008] Furthermore, the ratio of the modified additive, lithium difluorosulfonyl imide, acetonitrile, composite powder, and synergistic powder used in step A4 is 100 mmol: 10 mmol: 40 mL: 1 g: 1 g.

[0009] Furthermore, the modified polysiloxane is prepared by the following steps: Step B1: Mix octamethylcyclotetrasiloxane, 3-mercaptopropylmethyldimethoxysilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water, purge with nitrogen, and react for 10-12 hours at a speed of 150-200 r / min and a temperature of 90-95℃. Then raise the temperature to 105-110℃ and continue the reaction for 2-3 hours to obtain mercaptopolysiloxane. Step B2: Mix sodium hydride and tetrahydrofuran, purge with argon gas, stir and add allyl alcohol at a speed of 60-80 r / min and a temperature of 0-5℃, heat to 20-25℃ and react for 1-2 h, then cool to -10-0℃, add ethylene oxide, react for 2-4 h, then heat to 20-25℃ and continue reacting for 10-15 h to obtain functionalized polyethylene oxide; Step B3: Mix mercaptopolysiloxane, functionalized polyethylene oxide, benzophenone, and xylene, and purge with nitrogen. React for 30-40 minutes under conditions of 200-300 r / min, 25-30℃, and 365nm ultraviolet light irradiation to obtain pretreated polysiloxane. Mix the pretreated polysiloxane, vinyltrichlorosilane, caster catalyst, and xylene, and purge with nitrogen. React for 6-8 hours under conditions of 200-300 r / min and 80-85℃ to obtain modified polysiloxane.

[0010] Furthermore, the ratio of octamethylcyclotetrasiloxane, 3-mercaptopropylmethyldimethoxysilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water in step B1 is 1 mol: 0.2 mol: 1 mol: 1.5 mol: 20 mL.

[0011] Furthermore, the molar ratio of sodium hydride, allyl alcohol, and ethylene oxide in step B2 is 15:12:500.

[0012] Furthermore, in step B3, the molar ratio of the thiol group on the thiol polysiloxane to the functionalized polyethylene oxide is 1:1, the amount of benzophenone is 0.02% of the mass of the functionalized polyethylene oxide, the molar ratio of the pretreated polysiloxane to vinyltrichlorosilane is 1:2, and the amount of the caster catalyst is 0.01% of the mass of vinyltrichlorosilane.

[0013] The beneficial effects of this invention are as follows: This application discloses a high-stability sulfide solid electrolyte lithium battery, which uses modified additives as raw materials and lithium bis(fluorosulfonyl)imide, composite powder and synergistic powder as raw materials, and then mixes and dries them to obtain an electrolyte membrane. The positive electrode, negative electrode, electrolyte membrane and battery shell are assembled to obtain a high-stability sulfide solid electrolyte lithium battery. The composite powder is made by high-temperature sintering of lithium sulfide, phosphorus pentasulfide, lithium bromide and lithium chloride as raw materials to form chlorobromine double-doped silver sulfide germanium ore type sulfide to obtain composite powder. The synergistic monomer is mixed with modified additives and electrolyte to make the cyano groups on the modified additives undergo in-situ polymerization, then crushed and mixed with acetone, and finally centrifuged and dried to obtain synergistic powder.

[0014] The modified additive uses lithium dimethylcyanosiloxane as an initiator and trifluoropropylmethyldispersible siloxane as a polymerization initiator to form a polysiloxane with lithium siloxane at one end and Si-H bonds at the other end. Then, a modified polysiloxane is added, causing the Si-Cl bonds on the modified polysiloxane to react with the lithium siloxane, yielding a branched polysiloxane. The branched polysiloxane is then reacted with acrylonitrile, causing the Si-H bonds on the branched polysiloxane to react with the double bonds on the acrylonitrile, yielding the modified additive. The modified polysiloxane is obtained by ring-opening octamethylcyclotetrasiloxane as a starting material, followed by hydrolysis with 3-mercaptopropylmethyldimethoxysilane, and then reacting with tetramethyldimethylsiloxane. Thiol-terminated polysiloxanes are prepared by end-capping with siloxanes. Sodium hydride and allyl alcohol are reacted to remove the protons of the hydroxyl groups, forming allyloxy anions. Ethylene oxide is added to open the epoxy ring, forming new oxygen anion active centers, thus forming functionalized polyethylene oxide. The thiol-polysiloxane and functionalized polyethylene oxide are reacted to react the thiol groups on the thiol-polysiloxane and the double bonds on the functionalized polyethylene oxide, thus preparing pretreated polysiloxanes. The pretreated polysiloxane is reacted with vinyltrichlorosilane to react the Si-H bonds on the pretreated polysiloxane and the double bonds on the vinyltrichlorosilane, thus preparing modified polysiloxanes.

[0015] The modified additive has a polysiloxane main chain and polyethylene oxide side chains. The ether oxygen atoms in its molecular network can coordinate with lithium salts, dissolve and conduct lithium ions, forming a polymer phase ion transport pathway. At the same time, the flexibility of the polysiloxane segments can facilitate the movement of copolymer segments, making lithium ions migrate faster in the solid electrolyte. The cyano groups at the molecular ends can polymerize in situ in the electrolyte, firmly locking in the liquid electrolyte components. The integrated structure formed after curing avoids the problem of interface peeling during subsequent cycles. The addition of composite powder increases the ionic conductivity through the dual doping of bromine and chlorine. The polysiloxane and CF structures of the modified additive can improve the hydrophobic effect of the solid electrolyte and increase its service life. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1: A method for preparing a high-stability sulfide solid electrolyte lithium battery, specifically including the following steps: Step A1: Lithium dimethylhydrosilyl alcohol and tetrahydrofuran were mixed and protected with nitrogen. Under the conditions of 200 r / min and 0°C, trifluoropropylmethylcyclotrisiloxane was added while stirring. The mixture was heated to 25°C and reacted for 7 h. Modified polysiloxane was added and the reaction was continued for 3 h to obtain branched polysiloxane. Branched polysiloxane, acrylonitrile, caster catalyst and xylene were mixed and protected with nitrogen. Under the conditions of 200 r / min and 80°C, the mixture was reacted for 6 h to obtain modified additive. Step A2: Mix lithium sulfide, phosphorus pentasulfide, lithium bromide and lithium chloride, ball mill evenly and add to a mold. Under pressure of 370 MPa, hold pressure for 1 min, then place in a tube furnace, heat to 580℃ at a temperature of 1℃ / min, sinter for 8 h, grind into powder, and obtain composite powder. Step A3: Mix the modified additive and electrolyte evenly, keep it at 70°C for 8 hours, pulverize it and mix it with acetone, centrifuge it at 20°C for 15 minutes, remove the supernatant and dry it to obtain the enhanced powder. Step A4: Mix the modified additive, lithium bis(fluorosulfonyl)imide salt and acetonitrile, and sonicate at a frequency of 30 kHz and a temperature of 20 °C for 1 hour. Then add the composite powder and the synergistic powder, sonicate for 10 hours, place in a mold and dry to obtain the electrolyte membrane. Assemble the positive electrode, negative electrode, electrolyte membrane and battery case to obtain a high-stability sulfide solid electrolyte lithium battery.

[0018] In step A1, the ratio of the Si-Cl bonds on lithium dimethylhydrosiloxane, trifluoropropylmethylcyclotrisiloxane, and modified polysiloxane is 1:4:1, the molar ratio of the Si-H bonds on the branched polysiloxane to acrylonitrile is 1:1, and the amount of cassiterite catalyst is 0.01% of the mass of acrylonitrile.

[0019] The molar ratio of lithium sulfide, phosphorus pentasulfide, lithium bromide and lithium chloride in step A2 is 5:1:0.7:1.3.

[0020] The mass ratio of the modified additive to the electrolyte in step A3 is 1:50, and the electrolyte is 1M LiPF6 / EC:DMC:EMC.

[0021] The ratio of the modified additive, lithium difluorosulfonyl imide, acetonitrile, composite powder, and synergistic powder used in step A4 is 100 mmol: 10 mmol: 40 mL: 1 g: 1 g.

[0022] The modified polysiloxane is prepared by the following steps: Step B1: Mix octamethylcyclotetrasiloxane, 3-mercaptopropylmethyldimethoxysilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water, purge with nitrogen, and react at 150 r / min and 90 °C for 10 h. Then raise the temperature to 105 °C and continue the reaction for 2 h to obtain mercaptopolysiloxane. Step B2: Sodium hydride and tetrahydrofuran are mixed and purged with argon gas. Under the conditions of 60 r / min and 0℃, allyl alcohol is added while stirring. The mixture is heated to 20℃ and reacted for 1 h. Then, the mixture is cooled to -10℃, ethylene oxide is added, and the mixture is reacted for 2 h. The mixture is then heated to 20℃ and reacted for another 10 h to obtain functionalized polyethylene oxide. Step B3: Mix mercaptopolysiloxane, functionalized polyethylene oxide, benzophenone and xylene, purify with nitrogen, and react for 30 min at 200 r / min, 25 °C and 365 nm UV irradiation to obtain pretreated polysiloxane. Mix pretreated polysiloxane, vinyltrichlorosilane, caster catalyst and xylene, purify with nitrogen, and react for 6 h at 200 r / min and 80 °C to obtain modified polysiloxane.

[0023] The ratio of octamethylcyclotetrasiloxane, 3-mercaptopropylmethyldimethoxysilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water used in step B1 is 1 mol: 0.2 mol: 1 mol: 1.5 mol: 20 mL.

[0024] The molar ratio of sodium hydride, allyl alcohol, and ethylene oxide in step B2 is 15:12:500.

[0025] In step B3, the molar ratio of thiol groups on the thiol-polysiloxane to functionalized polyethylene oxide is 1:1, the amount of benzophenone is 0.02% of the mass of functionalized polyethylene oxide, the molar ratio of pretreated polysiloxane to vinyltrichlorosilane is 1:2, and the amount of caster catalyst is 0.01% of the mass of vinyltrichlorosilane.

[0026] Example 2: A method for preparing a high-stability sulfide solid electrolyte lithium battery, specifically including the following steps: Step A1: Lithium dimethylhydrosilylsiloxane and tetrahydrofuran were mixed and protected with nitrogen. Under the conditions of 200 r / min and 0°C, trifluoropropylmethylcyclotrisiloxane was added while stirring. The mixture was heated to 30°C and reacted for 8 h. Modified polysiloxane was added and the reaction was continued for 4 h to obtain branched polysiloxane. Branched polysiloxane, acrylonitrile, caster catalyst and xylene were mixed and protected with nitrogen. Under the conditions of 200 r / min and 85°C, the mixture was reacted for 7 h to obtain modified additive. Step A2: Mix lithium sulfide, phosphorus pentasulfide, lithium bromide and lithium chloride, ball mill evenly and add to a mold. Under pressure of 375 MPa, hold pressure for 1.5 min, then place in a tube furnace and heat to 590℃ at a rate of 2℃ / min for sintering for 9 h. Grind into powder to obtain composite powder. Step A3: Mix the modified additive and electrolyte evenly, and keep it at 60 r / min and 75℃ for 9 hours. Then, pulverize it and mix it with acetone. Centrifuge it at 10000 r / min and 20℃ for 15 minutes, remove the supernatant and dry it to obtain the enhanced powder. Step A4: Mix the modified additive, lithium bis(fluorosulfonyl)imide salt and acetonitrile, and sonicate at a frequency of 40 kHz and a temperature of 25 ℃ for 1 h. Then add the composite powder and the synergistic powder, sonicate for 11 h, place in a mold and dry to obtain the electrolyte membrane. Assemble the positive electrode, negative electrode, electrolyte membrane and battery case to obtain a high-stability sulfide solid electrolyte lithium battery.

[0027] In step A1, the ratio of the Si-Cl bonds on lithium dimethylhydrosiloxane, trifluoropropylmethylcyclotrisiloxane, and modified polysiloxane is 1:4:1, the molar ratio of the Si-H bonds on the branched polysiloxane to acrylonitrile is 1:1, and the amount of cassiterite catalyst is 0.01% of the mass of acrylonitrile.

[0028] The molar ratio of lithium sulfide, phosphorus pentasulfide, lithium bromide and lithium chloride in step A2 is 5:1:0.7:1.3.

[0029] The mass ratio of the modified additive to the electrolyte in step A3 is 1:50, and the electrolyte is 1M LiPF6 / EC:DMC:EMC.

[0030] The ratio of the modified additive, lithium difluorosulfonyl imide, acetonitrile, composite powder, and synergistic powder used in step A4 is 100 mmol: 10 mmol: 40 mL: 1 g: 1 g.

[0031] The modified polysiloxane is prepared by the following steps: Step B1: Mix octamethylcyclotetrasiloxane, 3-mercaptopropylmethyldimethoxysilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water, purge with nitrogen, and react for 10 h at a speed of 150 r / min and a temperature of 95 °C. Then raise the temperature to 110 °C and continue the reaction for 2 h to obtain mercaptopolysiloxane. Step B2: Sodium hydride and tetrahydrofuran were mixed and purged with argon gas. Under the conditions of 80 r / min and 0℃, allyl alcohol was added while stirring. The mixture was heated to 25℃ and reacted for 1.5 h. Then, the mixture was cooled to 0℃ and ethylene oxide was added. After reacting for 3 h, the mixture was heated to 20℃ and reacted for another 15 h to obtain functionalized polyethylene oxide. Step B3: Mix mercaptopolysiloxane, functionalized polyethylene oxide, benzophenone and xylene, purify with nitrogen, and react for 35 min at a rotation speed of 200 r / min, a temperature of 30 °C and irradiation with 365 nm ultraviolet light to obtain pretreated polysiloxane. Mix pretreated polysiloxane, vinyltrichlorosilane, caster catalyst and xylene, purify with nitrogen, and react for 7 h at a rotation speed of 300 r / min and a temperature of 80-85 °C to obtain modified polysiloxane.

[0032] The ratio of octamethylcyclotetrasiloxane, 3-mercaptopropylmethyldimethoxysilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water used in step B1 is 1 mol: 0.2 mol: 1 mol: 1.5 mol: 20 mL.

[0033] The molar ratio of sodium hydride, allyl alcohol, and ethylene oxide in step B2 is 15:12:500.

[0034] In step B3, the molar ratio of thiol groups on the thiol-polysiloxane to functionalized polyethylene oxide is 1:1, the amount of benzophenone is 0.02% of the mass of functionalized polyethylene oxide, the molar ratio of pretreated polysiloxane to vinyltrichlorosilane is 1:2, and the amount of caster catalyst is 0.01% of the mass of vinyltrichlorosilane.

[0035] Example 3: A method for preparing a high-stability sulfide solid electrolyte lithium battery, specifically including the following steps: Step A1: Lithium dimethylhydrosilyl alcohol and tetrahydrofuran were mixed and protected with nitrogen. Under the conditions of 300 r / min and 0℃, trifluoropropylmethylcyclotrisiloxane was added while stirring. The temperature was raised to 30℃ and the reaction was carried out for 9 h. Modified polysiloxane was added and the reaction was continued for 5 h to obtain branched polysiloxane. Branched polysiloxane, acrylonitrile, caster catalyst and xylene were mixed and protected with nitrogen. Under the conditions of 300 r / min and 85℃, the reaction was carried out for 8 h to obtain modified additive. Step A2: Mix lithium sulfide, phosphorus pentasulfide, lithium bromide and lithium chloride, ball mill evenly and add to a mold. Under pressure of 380 MPa, hold pressure for 1.5 min, then place in a tube furnace, heat to 600℃ at a temperature of 2℃ / min, sinter for 10 h, grind into powder, and obtain composite powder. Step A3: Mix the modified additive and electrolyte evenly, keep it at 80 r / min and 75℃ for 10 h, then pulverize and mix with acetone. Centrifuge at 10000 r / min and 25℃ for 15 min, remove the supernatant and dry to obtain the enhanced powder. Step A4: Mix the modified additive, lithium bis(fluorosulfonyl)imide salt and acetonitrile, and sonicate at a frequency of 50 kHz and a temperature of 25 °C for 1.5 h. Then add the composite powder and the synergistic powder, sonicate for 12 h, place in a mold and dry to obtain the electrolyte membrane. Assemble the positive electrode, negative electrode, electrolyte membrane and battery case to obtain a high-stability sulfide solid electrolyte lithium battery.

[0036] In step A1, the ratio of the Si-Cl bonds on lithium dimethylhydrosiloxane, trifluoropropylmethylcyclotrisiloxane, and modified polysiloxane is 1:4:1, the molar ratio of the Si-H bonds on the branched polysiloxane to acrylonitrile is 1:1, and the amount of cassiterite catalyst is 0.01% of the mass of acrylonitrile.

[0037] The molar ratio of lithium sulfide, phosphorus pentasulfide, lithium bromide and lithium chloride in step A2 is 5:1:0.7:1.3.

[0038] The mass ratio of the modified additive to the electrolyte in step A3 is 1:50, and the electrolyte is 1M LiPF6 / EC:DMC:EMC.

[0039] The ratio of the modified additive, lithium difluorosulfonyl imide, acetonitrile, composite powder, and synergistic powder used in step A4 is 100 mmol: 10 mmol: 40 mL: 1 g: 1 g.

[0040] The modified polysiloxane is prepared by the following steps: Step B1: Mix octamethylcyclotetrasiloxane, 3-mercaptopropylmethyldimethoxysilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water, purge with nitrogen, and react at 200 r / min and 95°C for 12 h. Then raise the temperature to 110°C and continue the reaction for 3 h to obtain mercaptopolysiloxane. Step B2: Sodium hydride and tetrahydrofuran are mixed and purged with argon gas. Under the conditions of 80 r / min and 5℃, allyl alcohol is added while stirring. The mixture is heated to 25℃ and reacted for 2 hours. Then, the mixture is cooled to 0℃, ethylene oxide is added, and the mixture is reacted for 4 hours. The mixture is then heated to 25℃ and reacted for another 15 hours to obtain functionalized polyethylene oxide. Step B3: Mix mercaptopolysiloxane, functionalized polyethylene oxide, benzophenone and xylene, purge nitrogen, and react for 40 min under the conditions of 300 r / min, 30 °C and 365 nm ultraviolet light irradiation to obtain pretreated polysiloxane. Mix pretreated polysiloxane, vinyltrichlorosilane, caster catalyst and xylene, purge nitrogen, and react for 8 h under the conditions of 300 r / min and 85 °C to obtain modified polysiloxane.

[0041] The ratio of octamethylcyclotetrasiloxane, 3-mercaptopropylmethyldimethoxysilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water used in step B1 is 1 mol: 0.2 mol: 1 mol: 1.5 mol: 20 mL.

[0042] The molar ratio of sodium hydride, allyl alcohol, and ethylene oxide in step B2 is 15:12:500.

[0043] In step B3, the molar ratio of thiol groups on the thiol-polysiloxane to functionalized polyethylene oxide is 1:1, the amount of benzophenone is 0.02% of the mass of functionalized polyethylene oxide, the molar ratio of pretreated polysiloxane to vinyltrichlorosilane is 1:2, and the amount of caster catalyst is 0.01% of the mass of vinyltrichlorosilane.

[0044] Comparative Example 1: This comparative example did not include composite powder compared to Example 1, but the remaining steps were the same.

[0045] Comparative Example 2: This comparative example did not include any synergistic powder compared to Example 1, but the remaining steps were the same.

[0046] Comparative Example 3: This comparative example uses pretreated polysiloxane instead of branched polysiloxane, while the remaining steps are the same as in Example 1.

[0047] The lithium batteries prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to constant voltage AC impedance measurements in the frequency range of 1MHz-1Hz. The ionic conductivity of the electrolyte was obtained by conversion. The electrolyte membrane was placed in an environment with an air humidity of 30% for 24 hours, and its ionic conductivity was measured. The retention rate of ionic conductivity of the electrolyte after exposure to humid air was calculated. The test results are shown in Table 1 below.

[0048] Table 1 Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Ionic conductivity mS / cm 18.7 18.9 19.3 16.1 17.2 16.5 Retention rate % 98.1 98.2 98.4 98.0 97.4 83.5 As shown in Table 1, this application has excellent ionic conductivity and moisture-proof effect.

[0049] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-stability sulfide solid electrolyte lithium battery, characterized in that: Specifically, the steps include the following: Step A1: Lithium dimethylhydrosilyl alcohol and tetrahydrofuran are mixed, nitrogen gas is introduced for protection, and trifluoropropylmethylcyclotrisiloxane is added under stirring to carry out the reaction. Modified polysiloxane is added and the reaction is continued to obtain branched polysiloxane. Branched polysiloxane, acrylonitrile, caster catalyst and xylene are mixed, nitrogen gas is introduced for protection, and the reaction is carried out to obtain modified additive. Step A2: Mix lithium sulfide, phosphorus pentasulfide, lithium bromide and lithium chloride, ball mill evenly and add to a mold. After pressure treatment, place in a tube furnace for sintering treatment, grind into powder, and obtain composite powder. Step A3: After mixing and heat-preserving the modified additive and electrolyte, the mixture is pulverized and mixed with acetone, then centrifuged to remove the supernatant and dried to obtain the synergistic powder. Step A4: Mix the modified additive, lithium bis(fluorosulfonyl)imide salt and acetonitrile, sonicate, add composite powder and synergistic powder, sonicate again, place in a mold and dry to obtain an electrolyte membrane, assemble the positive electrode, negative electrode, electrolyte membrane and battery case to obtain a high-stability sulfide solid electrolyte lithium battery.

2. The method for preparing a high-stability sulfide solid electrolyte lithium battery according to claim 1, characterized in that: The ratio of the Si-Cl bonds on lithium dimethylhydrosiloxane, trifluoropropylmethylcyclotrisiloxane, and modified polysiloxane in step A1 is 1:4:1, and the molar ratio of the Si-H bonds on the branched polysiloxane to acrylonitrile is 1:

1.

3. The method for preparing a high-stability sulfide solid electrolyte lithium battery according to claim 1, characterized in that: The molar ratio of lithium sulfide, phosphorus pentasulfide, lithium bromide and lithium chloride in step A2 is 5:1:0.7:1.

3.

4. The method for preparing a high-stability sulfide solid electrolyte lithium battery according to claim 1, characterized in that: The mass ratio of the modified additive to the electrolyte in step A3 is 1:50, and the electrolyte is 1M LiPF6 / EC:DMC:EMC.

5. The method for preparing a high-stability sulfide solid electrolyte lithium battery according to claim 1, characterized in that: The ratio of the modified additive, lithium difluorosulfonyl imide, acetonitrile, composite powder, and synergistic powder used in step A4 is 100 mmol: 10 mmol: 40 mL: 1 g: 1 g.

6. The method for preparing a high-stability sulfide solid electrolyte lithium battery according to claim 1, characterized in that: The modified polysiloxane is prepared by the following steps: Step B1: Mix octamethylcyclotetrasiloxane, 3-mercaptopropylmethyldimethoxysilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water, purge with nitrogen gas, and react to obtain mercaptopolysiloxane. Step B2: Mix sodium hydride and tetrahydrofuran, purge with argon gas, stir and add allyl alcohol, heat to react, cool and add ethylene oxide to react, and obtain functionalized polyethylene oxide. Step B3: Mix mercaptopolysiloxane, functionalized polyethylene oxide, benzophenone and xylene, purify with nitrogen, and react under ultraviolet light to obtain pretreated polysiloxane. Mix pretreated polysiloxane, vinyltrichlorosilane, castor catalyst and xylene, purify with nitrogen, and react to obtain modified polysiloxane.

7. The method for preparing a high-stability sulfide solid electrolyte lithium battery according to claim 6, characterized in that: The ratio of octamethylcyclotetrasiloxane, 3-mercaptopropylmethyldimethoxysilane, tetramethyldisiloxane, tetramethylammonium hydroxide and deionized water used in step B1 is 1 mol: 0.2 mol: 1 mol: 1.5 mol: 20 mL.

8. The method for preparing a high-stability sulfide solid electrolyte lithium battery according to claim 6, characterized in that: The molar ratio of sodium hydride, allyl alcohol, and ethylene oxide in step B2 is 15:500:

12.

9. The method for preparing a high-stability sulfide solid electrolyte lithium battery according to claim 6, characterized in that: In step B3, the molar ratio of thiol groups on the thiol-based polysiloxane to functionalized polyethylene oxide is 1:1, and the molar ratio of pretreated polysiloxane to vinyltrichlorosilane is 1:

2.

10. A high-stability sulfide solid electrolyte lithium battery, characterized in that: Prepared according to any one of the preparation methods described in claims 1-9.