High safety solid-state lithium battery based on ion gel interfacial layer

Abstract

The application discloses a high-safety solid-state lithium battery based on an ionic gel interface layer and belongs to the field of solid-state lithium battery preparation, and specifically comprises a pole core, and the positive pole sheet interface, the negative pole sheet interface and the pores of each layer in the pole core are filled with the ionic gel interface layer. The application is synthesized by adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to a double bond to end-capped synthesis of fluorine-containing flame-retardant bifunctional polyether crosslinking agent, and the crosslinking agent is injected into a dry battery together with a cyclic carbonate-based methacrylate compound and an electrolyte. After vacuum infiltration, in-situ thermal polymerization is initiated to build a three-dimensional crosslinking network to lock free electrolyte, form a conformal ionic gel interface layer, and significantly improve the safety performance and long-cycle performance of the solid-state lithium battery.

Description

Technical Field

[0001] This invention relates to the field of solid-state lithium battery fabrication, and more specifically to a high-safety solid-state lithium battery based on an ion gel interface layer. Background Technology

[0002] High-safety solid-state lithium batteries are an important technological direction for the synergistic evolution of high specific energy and high safety. Currently, they have gradually expanded from single inorganic solid electrolytes or solid polymer electrolytes to composite solid electrolytes, quasi-solid polymer electrolytes, and ion gel interface layer systems. Related studies have shown that liquid carbonate electrolytes have leakage and flammability risks, all-solid polymer systems are limited by the bulk ion conduction capacity, and all-inorganic systems are prone to poor electrode / electrolyte contact, parasitic reactions, and space charge layer-induced interfacial polarization. Based on this, interface engineering paths such as in-situ solidification, buffer layers, ionic liquids, and ion gel interface layers have become important development directions in this field.

[0003] Currently, commonly used materials mainly include polymer matrices such as polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene copolymer, and polyacrylonitrile, as well as inorganic ionic conductors or fillers such as garnet-type lithium lanthanum zirconium oxide, doped lithium lanthanum zirconium oxide, and alumina. Common modification methods include constructing inorganic coating layers such as lithium phosphate and lithium niobate on the electrode surface, introducing inert inorganic particles, plasticizers, flame retardant additives, or ionic liquids into the electrolyte, or using multilayer composite film structures to improve interfacial contact and ion migration. Although the above schemes can adjust local properties, it is still difficult to achieve a unified coordination between interfacial adhesion, flame retardant constraints, structural stability, and ion transport.

[0004] Inside a battery cell composed of electrodes and separators, the combination of pre-fabricated solid electrolyte films, surface coatings, or simple fillers often fails to simultaneously address deep wetting of the core, in-situ interface construction, and continuous adhesion during cycling. This can result in residual micro-gaps in electrode channels and interface regions, further leading to increased interfacial impedance and contact degradation. In addition, the addition of flame-retardant molecules, ionic liquids, or independent functional components may also cause problems such as dilution of the conductive phase, uneven interface distribution, and insufficient long-term stability. Summary of the Invention

[0005] This invention addresses the technical problem that it is difficult to synergistically improve the ionic conductivity, interfacial adhesion, and flame retardant safety of gel electrolytes in high-safety solid-state lithium batteries.

[0006] The objective of this invention can be achieved through the following technical solution: a high-safety solid-state lithium battery based on an ion gel interface layer, comprising an electrode core, wherein the electrode core is formed by alternating stacking of a positive electrode sheet, a negative electrode sheet, and a separator disposed between the positive electrode sheet and the negative electrode sheet;

[0007] The positive electrode interface, negative electrode interface, and pores at each level inside the electrode core are filled with an ion gel interface layer.

[0008] The ion gel interface layer is prepared by in-situ crosslinking polymerization of a precursor solution containing a cyclic carbonate-based methacrylate compound, a phosphorus- and fluorine-containing bifunctional polyether, a liquid electrolyte, and a thermal initiator inside the electrode core.

[0009] The cyclic carbonate-containing methacrylate compound is prepared by reacting glycerol carbonate and isocyanate methacrylate.

[0010] The phosphorus- and fluorine-containing bifunctional polyether is prepared by synthesizing a Schiff base intermediate from p-trifluoromethylbenzaldehyde and polyethylene glycol diamine, followed by sequential addition of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and end-capping reaction with methacryloyl chloride.

[0011] Furthermore, the liquid electrolyte is prepared by mixing 10-15 parts by weight of lithium salt and 85-90 parts by weight of organic solvent. The lithium salt is one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide. The organic solvent is one or more of ethylene carbonate, dimethyl carbonate, and diethyl carbonate. The thermal initiator is one or two of azobisisobutyronitrile or benzoyl peroxide.

[0012] Furthermore, the ion gel interface layer is prepared by the following steps:

[0013] A1. In an inert gas protective glove box, place the liquid electrolyte, methacrylate compound containing cyclic carbonate groups and phosphorus-containing and fluorine-containing bifunctional polyether in a single-necked bottle and stir. Add the thermal initiator and stir for 10-20 minutes in the dark to obtain the precursor solution.

[0014] A2. Inject the precursor solution into the battery casing, let it stand under vacuum for 12-24 hours, seal the battery, and then heat and keep it in a constant temperature chamber at 60-75℃ for 12-24 hours to obtain the ion gel interface layer.

[0015] Furthermore, in step A1, the weight ratio of the liquid electrolyte, the cyclic carbonate-containing methacrylate compound, the phosphorus-containing and fluorine-containing bifunctionalized polyether, and the thermal initiator is 40-65:20-40:10-20:0.5-2.

[0016] Furthermore, in step A2, the vacuum degree under the vacuum conditions is -0.05 to -0.1 MPa, and the battery casing is an aluminum-plastic film soft-pack casing or a metal hard casing.

[0017] Furthermore, the phosphorus- and fluorine-containing bifunctionalized polyether is prepared by the following steps:

[0018] B1. Place p-trifluoromethylbenzaldehyde, polyethylene glycol diamine and ethanol in a reaction vessel under nitrogen atmosphere and stir. Heat the reaction vessel to 75-85℃ and stir for 4-6 hours. Post-process to obtain polyether bis(fluorobenzylamine) intermediate.

[0019] B2. Place the polyether bis(fluorinated benignine) intermediate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and ethanol in a reaction vessel under nitrogen atmosphere and stir. Heat the reaction vessel to 55-65℃ and keep it at the temperature for 4-6 hours. After post-treatment, the fluorinated flame-retardant polyether bisamine intermediate is obtained.

[0020] B3. Place the fluorinated flame-retardant polyether diamine intermediate, triethylamine and dichloromethane in a reaction vessel and stir. Cool the reaction vessel to 0-5℃, slowly add the methacrylamide dichloromethane solution, restore the room temperature and react for 12-16 hours. Post-treatment yields phosphorus- and fluorine-containing bifunctionalized polyether.

[0021] The specific preparation reaction formula is as follows:

[0022]

[0023] In the formula: .

[0024] Further, in step B1, the ratio of p-trifluoromethylbenzaldehyde, polyethylene glycol diamine, and ethanol is 5-7g:6-8g:80-100mL. The post-processing steps include: after the reaction is completed, wait for the reaction system to cool to room temperature, transfer the reaction solution to a rotary evaporator at a temperature of 80-90℃, remove the low-boiling-point solvent by rotary evaporation under reduced pressure, wash the precipitate 2-3 times with hexane in the concentrated solution, transfer the lower layer product to an oven at a temperature of 50-60℃, and dry for 10-12h to obtain the polyether bis(fluorobenzylamine) intermediate.

[0025] Further, in step B2, the ratio of the polyether bis(fluorobenzylamine) intermediate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and ethanol is 3-5g:8-10g:90-110mL. The post-processing steps include: after the reaction is completed, the reaction system is cooled to room temperature, the reaction solution is transferred to a rotary evaporator at 80-90℃, the low-boiling-point solvent is removed by rotary evaporation under reduced pressure, the concentrated crude product is washed and pulped with diethyl ether at 0-5℃, the insoluble matter is collected by filtration, and the product is transferred to a vacuum drying oven at 50-60℃ and vacuum dried for 20-24h to obtain the fluorinated flame-retardant polyether bisamine intermediate.

[0026] Further, in step B3, the ratio of the fluorinated flame-retardant polyether diamine intermediate, triethylamine, dichloromethane, and methacryloyl chloride dichloromethane solution is 2-4g:4-6g:85-95mL:18-22mL. The methacryloyl chloride dichloromethane solution is obtained by uniformly mixing methacryloyl chloride and dichloromethane at a ratio of 1g:2mL. The post-processing steps include: after the reaction is completed, filtration is performed, the filtrate is transferred to a separatory funnel, washed 1-2 times with 50mL of saturated sodium bicarbonate aqueous solution, and then washed 1-3 times with deionized water. The lower organic phase is collected, anhydrous magnesium sulfate is added and dried for 20-30min, the desiccant is removed by filtration, and the filtrate is transferred to a rotary evaporator at 20-30℃ in the dark to remove dichloromethane by rotary evaporation, thereby obtaining a phosphorus- and fluorine-containing bifunctionalized polyether.

[0027] Furthermore, the preparation method of the cyclic carbonate-containing methacrylate compound is as follows: glycerol carbonate, dibutyltin dilaurate, and tetrahydrofuran are placed in a reaction vessel under a nitrogen atmosphere and stirred. Isocyanoethyl methacrylate is added, the reaction vessel is heated to 35-45°C, and the reaction is maintained for 3-5 hours. The cyclic carbonate-containing methacrylate compound is then obtained through post-treatment.

[0028] Furthermore, the ratio of the amount of glyceryl carbonate, dibutyltin dilaurate, tetrahydrofuran, and isocyanate ethyl methacrylate is 10-12g:0.05-0.07g:80-120mL:14-16g. The post-processing steps include: after the reaction is completed, the reaction solution is cooled to room temperature and transferred to a rotary evaporator at a temperature of 35-45℃, and the solution is evaporated under reduced pressure until no liquid is collected, thereby obtaining a methacrylate compound containing cyclic carbonate groups.

[0029] The present invention has the following beneficial effects:

[0030] 1. This invention utilizes a molecular-level synergistic design of methacrylate compounds containing cyclic carbonate groups and phosphorus- and fluorine-containing bifunctional polyethers to couple a hydrogen bond network constructed from urethane bonds with high-dielectric cyclic carbonate groups within the same molecular framework. The hydrogen bond network enhances the mechanical toughness of the gel and the adhesion of the electrode interface, while the high-dielectric groups promote the dissociation of lithium salts to improve ionic conductivity. The two share a molecular skeleton, avoiding performance degradation caused by the migration of functional additives, and forming an ion transport channel that integrates structure and function.

[0031] 2. This invention also integrates the polyether backbone, trifluoromethyl group, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide phosphaphenanthrene group in the crosslinking agent molecule, so that the flexible conformal ability, fluorine-rich interface phase stability and intrinsic flame retardancy work synergistically. The polyether segment reduces crystallinity to improve ion mobility, the trifluoromethyl group promotes the construction of fluorine-rich stable SEI film, and the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide group is introduced into the molecular backbone through PH bond nucleophilic addition to achieve intrinsic flame retardancy. This eliminates the interface degradation caused by flame retardant precipitation or fluoride loss, forming a synergistic strengthening mechanism of flame retardancy, interface and transport.

[0032] 3. This invention also transforms the crosslinking agent and monomer molecular system into a three-dimensional gel network through in-situ injection polymerization. The precursor solution permeates the multi-level pores of the electrode core under vacuum wetting. Thermally initiated polymerization causes crosslinking and copolymerization of the polymerizable double bonds at the ends of the monomer and crosslinking agent, achieving conformal coating and dense adhesion of the gel to the active particles. This gelation mechanism couples the ion dissociation promoted by high dielectric groups, the interface adhesion enhanced by hydrogen bond network, and the intrinsic flame retardancy achieved by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and fluorine synergistically within the same three-dimensional framework, locking the liquid electrolyte in situ and transforming it into an ion gel interface layer, simultaneously reducing interface impedance, inhibiting lithium dendrite nucleation, and preventing thermal runaway. Detailed Implementation

[0033] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0034] The polyethylene glycol dimethacrylate used in this invention was purchased from Jinan Kaichuang Chemical Co., Ltd., with a molecular weight of 400 g / mol, and an appearance of colorless to pale yellow transparent liquid with an acid value ≤0.5 mg KOH / g;

[0035] The polyethylene glycol diamine used in this invention was purchased from Zhiyuan Baimai (Quzhou) New Material Technology Co., Ltd., with a molecular weight of 400-600 g / mol, and an appearance of colorless to pale yellow viscous liquid with a moisture content of ≤0.5%.

[0036] Example 1

[0037] This embodiment provides a method for preparing a methacrylate compound containing a cyclic carbonate group, specifically including the following steps:

[0038] Weigh out 100g of glyceryl carbonate, 0.5g of dibutyltin dilaurate, and 800mL of tetrahydrofuran and place them in a reaction vessel under a nitrogen atmosphere. Stir the mixture and add 140g of isocyanate methyl methacrylate. Heat the reaction vessel to 35°C and maintain the temperature for 3 hours. After the reaction is complete, wait for the reaction solution to cool to room temperature and transfer it to a rotary evaporator at 35°C. Evaporate under reduced pressure until no liquid is collected to obtain a methyl methacrylate compound containing cyclic carbonate groups.

[0039] Using dibutyltin dilaurate as a catalyst, the hydroxyl groups of glycerol carbonate undergo nucleophilic addition with the isocyanate groups of isocyanoethyl methacrylate to construct urethane bonds, yielding methacrylate compounds containing cyclic carbonate groups.

[0040] The urethane bonds form a hydrogen bond network, which enhances the mechanical toughness of the ion gel layer and the adhesion of the electrode interface. The high dielectric cyclic carbonate groups promote the dissociation of lithium salt in the solid electrolyte, improve the room temperature ionic conductivity of the system, and the polymerizable double bonds retained at the ends provide reaction sites for in-situ crosslinking, ensuring the conformal coating and dense adhesion of the gel in the multi-level pores of the electrode core. This molecular configuration synergistically reduces the solid-liquid interface impedance and inhibits lithium dendrite nucleation, ensuring the long-term stable cycling of the battery system.

[0041] Example 2

[0042] This embodiment provides a method for preparing a methacrylate compound containing a cyclic carbonate group, specifically including the following steps:

[0043] Weigh out 110g of glyceryl carbonate, 0.6g of dibutyltin dilaurate, and 1000mL of tetrahydrofuran and place them in a reaction vessel under a nitrogen atmosphere. Stir the mixture and add 150g of isocyanate methacrylate. Heat the reaction vessel to 40℃ and maintain the temperature for 4 hours. After the reaction is complete, wait for the reaction solution to cool to room temperature and transfer it to a rotary evaporator at 40℃. Evaporate under reduced pressure until no liquid is collected to obtain a methacrylate compound containing cyclic carbonate groups.

[0044] Example 3

[0045] This embodiment provides a method for preparing a methacrylate compound containing a cyclic carbonate group, specifically including the following steps:

[0046] Weigh out 120g of glyceryl carbonate, 0.7g of dibutyltin dilaurate, and 1200mL of tetrahydrofuran and place them in a reaction vessel under a nitrogen atmosphere. Stir the mixture and add 160g of isocyanate methacrylate. Heat the reaction vessel to 45℃ and maintain the temperature for 5 hours. After the reaction is complete, wait for the reaction solution to cool to room temperature and transfer it to a rotary evaporator at 45℃. Evaporate under reduced pressure until no liquid is collected to obtain a methacrylate compound containing cyclic carbonate groups.

[0047] Example 4

[0048] This embodiment provides a method for preparing phosphorus- and fluorine-containing bifunctionalized polyethers, specifically including the following steps:

[0049] Step 1: Preparation of polyether bis(fluorobenzylamine) intermediate

[0050] Weigh out 50g of p-trifluoromethylbenzaldehyde, 60g of polyethylene glycol diamine and 800mL of ethanol and place them in a reaction vessel under nitrogen atmosphere protection and stir. Heat the reaction vessel to 75℃ and keep it at this temperature for 4h. After the reaction is completed, wait for the reaction system to cool to room temperature and transfer the reaction solution to a rotary evaporator at 80℃. Remove the low-boiling-point solvent by rotary evaporation under reduced pressure. Heat the concentrated solution with n-hexane to wash the precipitate twice. Transfer the lower product to an oven at 50℃ and dry for 10h to obtain polyether bis(fluorobenzylamine) intermediate.

[0051] Step 2: Preparation of fluorine-containing flame-retardant polyether bisamine intermediate

[0052] Weigh 30g of polyether bis(fluorobenzylamine) intermediate, 80g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 900mL of ethanol and place them in a reaction vessel under nitrogen atmosphere. Stir the mixture and heat it to 55℃. Keep it at this temperature and stir for 4 hours. After the reaction is complete, let the reaction system cool to room temperature. Transfer the reaction solution to a rotary evaporator at 80℃ and remove the low-boiling-point solvent by rotary evaporation under reduced pressure. Wash and slurry the concentrated crude product with diethyl ether at 0℃. Collect the insoluble matter by filtration and transfer it to a vacuum drying oven at 50℃. Dry it under vacuum for 20 hours to obtain the fluorinated flame-retardant polyether bisamine intermediate.

[0053] Step (3): Preparation of phosphorus- and fluorine-containing bifunctionalized polyethers

[0054] Methacrylamide chloride and dichloromethane were mixed evenly at a ratio of 10g:20mL to obtain a methacrylamide chloride-dichloromethane solution for later use.

[0055] Weigh 20g of fluorinated flame-retardant polyether diamine intermediate, 40g of triethylamine, and 850mL of dichloromethane and place them in a reaction vessel and stir. Cool the reaction vessel to 0℃ and slowly add 180mL of methacryloyl chloride dichloromethane solution. Restore the reaction to room temperature for 12h. After the reaction is complete, filter the solution and transfer the filtrate to a separatory funnel. Wash the solution once with 500mL of saturated sodium bicarbonate aqueous solution and then once with deionized water. Collect the lower organic phase, add anhydrous magnesium sulfate and dry for 20min. Filter to remove the desiccant and transfer the filtrate to a rotary evaporator at 20℃ protected from light. Remove the dichloromethane by rotary evaporation to obtain phosphorus- and fluorine-containing bifunctionalized polyether.

[0056] The aldehyde group of p-trifluoromethylbenzaldehyde undergoes dehydration condensation with the primary amino group of polyethylene glycol diamine to construct a Schiff base imine intermediate containing a C=N bond. Next, the active PH bond in 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is used to nucleophilically add a phosphorus-containing flame-retardant group to the molecular backbone, while generating a secondary amine. Finally, using triethylamine as an acid-binding agent, the secondary amine reacts with methacryloyl chloride to introduce a polymerizable double bond at the molecule's end for end capping, ultimately obtaining a phosphorus-containing and fluorine-containing bifunctional polyether.

[0057] The polyether backbone and trifluoromethyl groups impart flexible conformal capability to the interface layer, promoting the construction of a fluorine-rich stable interface phase. Grafting of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide groups achieves intrinsic flame retardancy. Its steric hindrance effect reduces crystallinity to improve ion mobility. The terminal double bonds provide crosslinking sites for in-situ polymerization. By constructing a three-dimensional gel network to lock in the electrolyte, thermal runaway is suppressed and interfacial impedance is reduced.

[0058] Example 5

[0059] This embodiment provides a method for preparing phosphorus- and fluorine-containing bifunctionalized polyethers, specifically including the following steps:

[0060] Step 1: Preparation of polyether bis(fluorobenzylamine) intermediate

[0061] Weigh 60g of p-trifluoromethylbenzaldehyde, 70g of polyethylene glycol diamine, and 900mL of ethanol and place them in a reaction vessel under nitrogen atmosphere. Stir the mixture and heat it to 80℃. Keep the mixture at this temperature and stir for 5 hours. After the reaction is complete, let the reaction system cool to room temperature. Transfer the reaction solution to a rotary evaporator at 85℃ and remove the low-boiling solvent by rotary evaporation under reduced pressure. Heat the concentrated solution with n-hexane to wash the precipitate three times. Transfer the lower layer product to an oven at 55℃ and dry for 11 hours to obtain the polyether bis(fluorobenzylamine) intermediate.

[0062] Step 2: Preparation of fluorine-containing flame-retardant polyether bisamine intermediate

[0063] Weigh 40g of polyether bis(fluorobenzylamine) intermediate, 90g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 1000mL of ethanol and place them in a reaction vessel under nitrogen atmosphere. Stir the mixture and heat it to 60℃. Keep it at this temperature and stir for 5 hours. After the reaction is complete, let the reaction system cool to room temperature. Transfer the reaction solution to a rotary evaporator at 85℃ and remove the low-boiling-point solvent by rotary evaporation under reduced pressure. Wash and slurry the concentrated crude product with diethyl ether at 3℃. Collect the insoluble matter by filtration and transfer it to a vacuum drying oven at 55℃. Dry it under vacuum for 22 hours to obtain the fluorinated flame-retardant polyether bisamine intermediate.

[0064] Step (3): Preparation of phosphorus- and fluorine-containing bifunctionalized polyethers

[0065] Methacrylamide chloride and dichloromethane were mixed evenly at a ratio of 10g:20mL to obtain a methacrylamide chloride-dichloromethane solution for later use.

[0066] Weigh out 30g of fluorinated flame-retardant polyether diamine intermediate, 50g of triethylamine, and 900mL of dichloromethane and place them in a reaction vessel. Stir the vessel and cool it to 3°C. Slowly add 200mL of methacryloyl chloride dichloromethane solution and allow it to return to room temperature for 14 hours. After the reaction is complete, filter the solution and transfer it to a separatory funnel. Wash the solution twice with 500mL of saturated sodium bicarbonate aqueous solution and then twice with deionized water. Collect the lower organic phase and dry it for 25 minutes with anhydrous magnesium sulfate. Filter to remove the desiccant and transfer the solution to a rotary evaporator at 25°C in the dark. Remove the dichloromethane by rotary evaporation to obtain phosphorus- and fluorine-containing bifunctionalized polyether.

[0067] Example 6

[0068] This embodiment provides a method for preparing phosphorus- and fluorine-containing bifunctionalized polyethers, specifically including the following steps:

[0069] Step 1: Preparation of polyether bis(fluorobenzylamine) intermediate

[0070] Weigh 70g of p-trifluoromethylbenzaldehyde, 80g of polyethylene glycol diamine, and 1000mL of ethanol and place them in a reaction vessel under nitrogen atmosphere. Stir the mixture and heat it to 85℃. Keep the mixture at this temperature and stir for 6 hours. After the reaction is complete, let the reaction system cool to room temperature. Transfer the reaction solution to a rotary evaporator at 90℃ and remove the low-boiling solvent by rotary evaporation under reduced pressure. Heat the concentrated solution with n-hexane to wash the precipitate three times. Transfer the lower layer product to an oven at 60℃ and dry for 12 hours to obtain the polyether bis(fluorobenzylamine) intermediate.

[0071] Step 2: Preparation of fluorine-containing flame-retardant polyether bisamine intermediate

[0072] Weigh out 50g of polyether bis(fluorobenzylamine) intermediate, 100g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and 1100mL of ethanol and place them in a reaction vessel under nitrogen atmosphere. Stir the mixture and heat it to 65℃. Keep it at this temperature and stir for 6 hours. After the reaction is complete, let the reaction system cool to room temperature. Transfer the reaction solution to a rotary evaporator at 90℃ and remove the low-boiling-point solvent by rotary evaporation under reduced pressure. Wash and slurry the concentrated crude product with diethyl ether at 5℃. Collect the insoluble matter by filtration and transfer it to a vacuum drying oven at 60℃. Dry it under vacuum for 24 hours to obtain the fluorinated flame-retardant polyether bisamine intermediate.

[0073] Step (3): Preparation of phosphorus- and fluorine-containing bifunctionalized polyethers

[0074] Methacrylamide chloride and dichloromethane were mixed evenly at a ratio of 10g:20mL to obtain a methacrylamide chloride-dichloromethane solution for later use.

[0075] Weigh out 40g of fluorinated flame-retardant polyether diamine intermediate, 60g of triethylamine, and 950mL of dichloromethane and place them in a reaction vessel. Stir the vessel and cool it to 5°C. Slowly add 220mL of methacryloyl chloride dichloromethane solution and allow it to return to room temperature for 16 hours. After the reaction is complete, filter the solution and transfer it to a separatory funnel. Wash the solution twice with 500mL of saturated sodium bicarbonate aqueous solution and then three times with deionized water. Collect the lower organic phase and dry it for 30 minutes with anhydrous magnesium sulfate. Filter to remove the desiccant and transfer the solution to a rotary evaporator at 30°C in the dark. Remove the dichloromethane by rotary evaporation to obtain phosphorus- and fluorine-containing bifunctionalized polyether.

[0076] Example 7

[0077] This embodiment provides a method for preparing a high-safety solid-state lithium battery based on an ion gel interface layer, specifically including the following steps:

[0078] Step ①: Prepare the battery casing

[0079] NCM811, conductive carbon black and polyvinylidene fluoride are mixed evenly in a mass ratio of 8:1:1, and N-methylpyrrolidone is used as a solvent to prepare a uniform slurry. The slurry is coated on an aluminum foil current collector, and then vacuum dried at 60°C, rolled and cut to obtain the positive electrode sheet.

[0080] Graphite, conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber are mixed evenly in a mass ratio of 94:2:2:2, and a uniform slurry is prepared using deionized water as a solvent. The slurry is coated onto a copper foil current collector, and then vacuum dried at 60°C, rolled, and cut to obtain the negative electrode sheet.

[0081] The positive electrode sheet, polyethylene porous separator and negative electrode sheet are stacked alternately and the positive and negative electrode tabs are welded. Then they are put into an aluminum-plastic film soft-pack shell and vacuum baked at 70°C for 10 hours to obtain the battery shell for later use.

[0082] Step 2: Preparation of precursor solution

[0083] Weighing: In an inert gas protected glove box, place 400g of liquid electrolyte, 200g of cyclic carbonate-containing methacrylate compound and 100g of phosphorus- and fluorine-containing bifunctional polyether into a single-necked bottle and stir. Add 5g of azobisisobutyronitrile and stir for 10 minutes in the dark to obtain the precursor solution.

[0084] Step 3: Fabrication of high-safety solid-state lithium batteries

[0085] The precursor solution was injected into the battery casing and left to stand under a vacuum of -0.05 MPa for 12 hours. After sealing the battery, it was placed in a constant temperature chamber at 60°C for 12 hours to form an ion gel interface layer, thus obtaining a high-safety solid-state lithium battery.

[0086] The battery casing is constructed by assembling positive and negative electrodes and a porous separator using conventional coating and stacking processes. Then, a precursor solution is injected, and the electrode core is physically impregnated through vacuum settling. Finally, under heating conditions, the thermal initiator decomposes to generate free radicals, which trigger cross-linking copolymerization reactions between monomers and polymerizable double bonds at the ends of cross-linking agents. A three-dimensional polymer skeleton network is constructed in situ inside the battery, and the liquid electrolyte is solidified in situ and transformed into an ion gel interface layer.

[0087] Vacuum impregnation drives the precursor to deeply penetrate the multi-level pores of the electrode core, eliminating solid-solid physical gaps. In-situ thermal polymerization constructs a three-dimensional cross-linked framework to microscopically lock the electrolyte, completing the liquid-solid configuration transformation. This gelation mechanism achieves conformal coating and dense adhesion between the solid interface layer and the electrode, reducing interface impedance. At the same time, it avoids free liquid leakage and prevents thermal runaway, improving the long-term cycle stability and safety of the system.

[0088] Example 8

[0089] This embodiment provides a method for preparing a high-safety solid-state lithium battery based on an ion gel interface layer, specifically including the following steps:

[0090] Step ①: Prepare the battery casing

[0091] NCM811, conductive carbon black and polyvinylidene fluoride are mixed evenly in a mass ratio of 8:1:1, and N-methylpyrrolidone is used as a solvent to prepare a uniform slurry. The slurry is coated on an aluminum foil current collector, and then vacuum dried at 70°C, rolled and cut to obtain the positive electrode sheet.

[0092] Graphite, conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber are mixed evenly in a mass ratio of 94:2:2:2, and a uniform slurry is prepared using deionized water as a solvent. The slurry is coated onto a copper foil current collector, and then vacuum dried at 70°C, rolled, and cut to obtain the negative electrode sheet.

[0093] The positive electrode sheet, polyethylene porous separator and negative electrode sheet are stacked alternately and the positive and negative electrode tabs are welded. Then, they are put into an aluminum-plastic film soft-pack shell and vacuum baked at 75°C for 11 hours to obtain the battery shell for later use.

[0094] Step 2: Preparation of precursor solution

[0095] Weighing: In an inert gas protected glove box, place 500g of liquid electrolyte, 300g of cyclic carbonate-containing methacrylate compound and 150g of phosphorus- and fluorine-containing bifunctional polyether into a single-necked bottle and stir. Add 12g of azobisisobutyronitrile and stir for 15 minutes in the dark to obtain the precursor solution.

[0096] Step 3: Fabrication of high-safety solid-state lithium batteries

[0097] The precursor solution was injected into the battery casing and left to stand under a vacuum of -0.1 MPa for 18 hours. After sealing the battery, it was placed in a constant temperature chamber at 70°C for 18 hours to form an ion gel interface layer, thus obtaining a high-safety solid-state lithium battery.

[0098] Example 9

[0099] This embodiment provides a method for preparing a high-safety solid-state lithium battery based on an ion gel interface layer, specifically including the following steps:

[0100] Step ①: Prepare the battery casing

[0101] NCM811, conductive carbon black and polyvinylidene fluoride are mixed evenly in a mass ratio of 8:1:1, and N-methylpyrrolidone is used as a solvent to prepare a uniform slurry. The slurry is coated on an aluminum foil current collector, and then vacuum dried at 80°C, rolled and cut to obtain the positive electrode sheet.

[0102] Graphite, conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber are mixed evenly in a mass ratio of 94:2:2:2, and a uniform slurry is prepared using deionized water as a solvent. The slurry is coated onto a copper foil current collector, and then vacuum dried at 80°C, rolled, and cut to obtain the negative electrode sheet.

[0103] The positive electrode sheet, polyethylene porous separator and negative electrode sheet are stacked alternately and the positive and negative electrode tabs are welded. Then they are put into an aluminum-plastic film soft-pack shell and vacuum baked at 80°C for 12 hours to obtain the battery shell for later use.

[0104] Step 2: Preparation of precursor solution

[0105] Weighing: In an inert gas protected glove box, place 650g of liquid electrolyte, 400g of cyclic carbonate-containing methacrylate compound and 200g of phosphorus- and fluorine-containing bifunctional polyether into a single-necked bottle and stir. Add 20g of azobisisobutyronitrile and stir for 20min in the dark to obtain the precursor solution.

[0106] Step 3: Fabrication of high-safety solid-state lithium batteries

[0107] The precursor solution was injected into the battery casing and left to stand under a vacuum of -0.1 MPa for 24 hours. After sealing the battery, it was placed in a constant temperature chamber at 75°C for 24 hours to form an ion gel interface layer, thus obtaining a high-safety solid-state lithium battery.

[0108] Comparative Example 1

[0109] The difference between this comparative example and Example 9 is that, in step ② when preparing the precursor solution, an equal amount of commercially available hydroxyethyl methacrylate is used instead of the methacrylate compound containing cyclic carbonate groups.

[0110] Comparative Example 2

[0111] The difference between this comparative example and Example 9 is that, in step ② when preparing the precursor solution, commercially available polyethylene glycol dimethacrylate is used in an equal amount to replace the phosphorus- and fluorine-containing bifunctionalized polyether.

[0112] Performance testing:

[0113] The precursor solutions used in Examples 7-9 and Comparative Examples 1-2 were injected into PTFE molds and polymerized under the same curing conditions to form gel electrolyte membranes for later use.

[0114] Ionic conductivity: Referring to the test conditions of standard GB / T 31486-2024 "Electrical performance requirements and test methods for power batteries for electric vehicles", the ionic conductivity of the ion gel interface layer was determined by AC impedance spectroscopy. The disc gel electrolyte membranes prepared in Examples 7-9 and Comparative Examples 1-2 were cut into discs with a diameter of 16 mm and sandwiched between stainless steel blocking electrodes. The membrane thickness L and electrode area A were measured in the frequency range of 1 MHz to 0.1 Hz. The bulk resistance Rb was obtained by Nyquist curve, and the ionic conductivity was calculated by formula σ=L / (Rb×A).

[0115] Interfacial impedance: The interfacial impedance of the solid-state lithium batteries prepared in Examples 7-9 and Comparative Examples 1-2 was determined by electrochemical impedance spectroscopy. The test was conducted under environmental conditions of 25℃±2℃ and relative humidity of 25%-85%. After activation by constant current charge-discharge cycle at 0.2C rate for 3 cycles, the solid-state lithium batteries were placed under open circuit voltage for 2 hours. AC impedance scanning was performed using an electrochemical workstation with a frequency range of 100kHz-10mHz and an AC perturbation amplitude of 5mV to obtain the interfacial impedance values.

[0116] Flame retardant performance: The flame retardant rating of the gel electrolyte membranes prepared in Examples 7-9 and Comparative Examples 1-2 was determined by the vertical burning method according to standard GB / T 2408-2021 "Determination of Burning Performance of Plastics - Horizontal and Vertical Methods". The samples were cut into standard strips with a length of 125 mm ± 5 mm and a width of 13.0 mm ± 0.3 mm. The samples were conditioned for 48 h at 23℃ ± 2℃ and relative humidity of 50% ± 5%. The test was conducted using a Bunsen burner flame with the flame height controlled at 20 mm ± 2 mm. The tip of the blue flame core was in contact with the center of the bottom edge of the sample. The flame was applied for 10 s and then removed. The flaming burning time t1 was recorded. If the flaming burning stopped, the flame was applied again for 10 s and the second flaming burning time t2 and the flameless burning time t3 were recorded. At the same time, it was observed and recorded whether the sample burned to the clamping end and whether there were molten drips that ignited the degreased cotton below. The results were expressed as vertical burning ratings (V-0 / V-1 / V-2).

[0117] Electrode interface adhesion strength: Referring to standard GB / T 2792-2014 "Test Method for Peel Strength of Adhesive Tapes", the 180° peel strength between the gel electrolyte membranes prepared in Examples 7-9 and Comparative Examples 1-2 and the positive and negative electrode sheets was determined using a universal testing machine. The gel electrolyte membranes were cut into samples 25mm ± 0.5mm wide and 150mm long. Using the standard floating roller method, these samples were bonded to the surface of the positive electrode sheet (NCM811) after being cleaned and dried with ethanol. The bonding length was controlled to be 100mm. A 2kg standard pressure roller was used to roll the sample back and forth three times at a speed of 300mm / min. After bonding is completed, the specimen is conditioned for 24 hours at 23℃±2℃ and 50%±5% relative humidity. The bonded specimen is then fixed on the fixture of the universal testing machine. The peel angle is controlled at 180° and the peel speed is controlled at 300mm / min. The specimen is continuously peeled for at least 100mm of effective peel length. The peel force-displacement curve is recorded. The data from the first 25mm and the last 25mm are discarded. The average peel force of the middle stable section is taken. The 180° peel strength is calculated according to the formula σ=F / b, where F is the average peel force and b is the specimen width.

[0118] Long-term cycle stability of batteries: The long-term cycle stability of solid-state lithium batteries prepared in Examples 7-9 and Comparative Examples 1-2 was determined using a battery testing system according to standard GB / T 36276-2023 "Lithium-ion Batteries for Power Storage". The tests were conducted under environmental conditions of 25℃±2℃ and relative humidity of 25%-85%. After activation by three constant current charge-discharge cycles at a rate of 0.2C, the solid-state lithium batteries were assembled into lithium symmetric batteries and tested at 0.5mA / cm². 2 Constant current charge-discharge cycles were performed at a current density of 1 mAh / cm³, with the cycle capacity controlled at 1 mAh / cm³. 2Each cycle includes 1 hour of deposition and 1 hour of stripping. The operation is continuous and the overpotential changes are recorded at regular intervals. The overpotential surge or short circuit is used as the basis for determining cycle failure. The number of cycles at the time of cycle failure is recorded as the long cycle life of the lithium symmetric battery. Specific data are shown in Table 1 below.

[0119] Table 1 - Performance Test Data of Samples

[0120]

[0121] Comparative analysis of the data in Table 1 above shows that the ionic conductivity of the gel electrolyte membrane prepared in this invention is 1.58 × 10⁻⁶. -3 With an interface impedance of 66Ω and a cycle life of 1215h, the high-safety solid-state lithium battery prepared by this invention has a flame retardancy rating of V-0 and an electrode interface adhesion strength of 5.6N / mm. All these data are superior to those of the comparative example.

[0122] This invention synthesizes a fluorinated flame-retardant bifunctional polyether crosslinking agent by addition and double bond end-capping of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. This agent, along with a cyclic carbonate-containing methacrylate compound and electrolyte, is injected into a dry cell. After vacuum impregnation, in-situ thermal polymerization is initiated to construct a three-dimensional crosslinked network to lock in the free electrolyte, forming a conformally bonded ion gel interface layer. This significantly improves the safety and long-term cycle performance of solid-state lithium batteries.

[0123] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A high-safety solid-state lithium battery based on an ion gel interface layer, characterized in that, The electrode core is composed of alternating stacks of a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate; The positive electrode interface, negative electrode interface, and pores at each level inside the electrode core are filled with an ion gel interface layer. The ion gel interface layer is prepared by in-situ crosslinking polymerization of a precursor solution containing a cyclic carbonate-based methacrylate compound, a phosphorus- and fluorine-containing bifunctional polyether, a liquid electrolyte, and a thermal initiator inside the electrode core. The cyclic carbonate-containing methacrylate compound is prepared by reacting glycerol carbonate and isocyanate methacrylate. The phosphorus- and fluorine-containing bifunctional polyether is prepared by synthesizing a Schiff base intermediate from p-trifluoromethylbenzaldehyde and polyethylene glycol diamine, followed by sequential addition of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and end-capping reaction with methacryloyl chloride.

2. The high-safety solid-state lithium battery based on an ion gel interface layer according to claim 1, characterized in that, The liquid electrolyte is prepared by mixing 10-15 parts by weight of lithium salt and 85-90 parts by weight of organic solvent. The lithium salt is one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide. The organic solvent is one or more of ethylene carbonate, dimethyl carbonate, and diethyl carbonate. The thermal initiator is one or two of azobisisobutyronitrile or benzoyl peroxide.

3. A high-safety solid-state lithium battery based on an ion gel interface layer according to claim 1, characterized in that, The ion gel interface layer is prepared by the following steps: A1. In an inert gas protective glove box, place the liquid electrolyte, methacrylate compound containing cyclic carbonate groups and phosphorus-containing and fluorine-containing bifunctional polyether in a single-necked bottle and stir. Add the thermal initiator and stir for 10-20 minutes in the dark to obtain the precursor solution. A2. Inject the precursor solution into the battery casing, let it stand under vacuum for 12-24 hours, seal the battery, and then heat and keep it in a constant temperature chamber at 60-75℃ for 12-24 hours to obtain the ion gel interface layer.

4. A high-safety solid-state lithium battery based on an ion gel interface layer according to claim 3, characterized in that, In step A1, the weight ratio of the liquid electrolyte, the cyclic carbonate-containing methacrylate compound, the phosphorus-containing and fluorine-containing bifunctionalized polyether, and the thermal initiator is 40-65:20-40:10-20:0.5-2; in step A2, the vacuum degree under the vacuum conditions is -0.05 to -0.1 MPa, and the battery casing is an aluminum-plastic film soft-pack casing or a metal hard casing.

5. A high-safety solid-state lithium battery based on an ion gel interface layer according to claim 1, characterized in that, The phosphorus- and fluorine-containing bifunctionalized polyether is prepared by the following steps: B1. Place p-trifluoromethylbenzaldehyde, polyethylene glycol diamine and ethanol in a reaction vessel under nitrogen atmosphere and stir. Heat the reaction vessel to 75-85℃ and stir for 4-6 hours. Post-process to obtain polyether bis(fluorobenzylamine) intermediate. B2. Place the polyether bis(fluorinated benignine) intermediate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and ethanol in a reaction vessel under nitrogen atmosphere and stir. Heat the reaction vessel to 55-65℃ and keep it at the temperature for 4-6 hours. After post-treatment, the fluorinated flame-retardant polyether bisamine intermediate is obtained. B3. Place the fluorinated flame-retardant polyether diamine intermediate, triethylamine and dichloromethane in a reaction vessel and stir. Cool the reaction vessel to 0-5℃, slowly add the methacrylamide dichloromethane solution, restore the room temperature and react for 12-16 hours. Post-treatment yields phosphorus- and fluorine-containing bifunctionalized polyether.

6. A high-safety solid-state lithium battery based on an ion gel interface layer according to claim 5, characterized in that, In step B1, the ratio of p-trifluoromethylbenzaldehyde, polyethylene glycol diamine, and ethanol is 5-7 g: 6-8 g: 80-100 mL; in step B2, the ratio of the polyether bis(fluorobenzylamine) intermediate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and ethanol is 3-5 g: 8-10 g: 90-110 mL; in step B3, the ratio of the fluorinated flame-retardant polyether bis-amine intermediate, triethylamine, dichloromethane, and methacryloyl chloride dichloromethane solution is 2-4 g: 4-6 g: 85-95 mL: 18-22 mL, wherein the methacryloyl chloride dichloromethane solution is obtained by uniformly mixing methacryloyl chloride and dichloromethane at a ratio of 1 g: 2 mL.

7. A high-safety solid-state lithium battery based on an ion gel interface layer according to claim 1, characterized in that, The preparation method of the cyclic carbonate-containing methacrylate compound is as follows: glycerol carbonate, dibutyltin dilaurate and tetrahydrofuran are placed in a reaction vessel under nitrogen atmosphere and stirred. Isocyanoethyl methacrylate is added, the reaction vessel is heated to 35-45℃, and the reaction is maintained for 3-5 hours. The cyclic carbonate-containing methacrylate compound is then obtained after post-treatment.

8. A high-safety solid-state lithium battery based on an ion gel interface layer according to claim 7, characterized in that, The ratio of the amounts of glyceryl carbonate, dibutyltin dilaurate, tetrahydrofuran, and isocyanate methyl methacrylate is 10-12g:0.05-0.07g:80-120mL:14-16g.

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