Polyvinyl chloride composite solid electrolyte and preparation method thereof

Abstract

The invention belongs to the technical field of solid electrolyte, and particularly relates to polyvinyl chloride composite solid electrolyte and a preparation method thereof. The polyvinyl chloride composite solid electrolyte is prepared from the following raw materials in parts by weight: 30 to 50 parts of polyvinyl chloride resin, 45 to 65 parts of PCL-based compound, 3 to 8 parts of modified CePO4, 20 to 35 parts of LiTFSI and 3 to 6 parts of propylene carbonate, the added modified CePO4 realizes uniform dispersion of an inorganic filler in a polymer matrix, so that the mechanical property of the electrolyte membrane is enhanced, and a stable channel is provided for lithium ion transmission; the PCL-based compound not only relieves the brittleness defect of a polyvinyl chloride matrix, but also improves the free lithium ion concentration through the interaction of a coordinate bond and a lithium salt, and optimizes the ion conduction efficiency. And the step-by-step curing process promotes the system to form a stable dual cross-linked network, so that the electrochemical stability and long-term cycle reliability of the electrolyte are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolyte technology, specifically relating to a polyvinyl chloride composite solid electrolyte and its preparation method. Background Technology

[0002] Solid-state batteries, as a core development direction of next-generation energy storage technology, have broad application prospects in new energy vehicles, energy storage devices, and other fields due to their higher energy density and safety. Among them, polymer-based solid electrolytes have become one of the key routes for current industrialization exploration due to their advantages such as good flexibility and good contact with the electrode interface. Polyvinyl chloride (PVC), as a low-cost polymer material with strong chemical stability and a wide electrochemical window, has attracted much attention in the field of solid electrolyte matrix. However, pure PVC-based solid electrolytes have inherent defects: the high crystallinity of the matrix limits the lithium-ion transport efficiency, and the interfacial compatibility with inorganic fillers and electrode materials is poor, which seriously affects the cycle stability and safety of the battery.

[0003] To address these issues, existing technologies often employ physical blending of inorganic fillers or composites with other polymers for modification. However, simple physical mixing often results in the inability to simultaneously optimize the electrolyte's mechanical properties and ion conduction efficiency. Polycaprolactone (PCL) is a commonly used flexible polymer component, but PCL itself lacks sufficient mechanical strength and has limited compatibility with the PVC matrix, making direct blending prone to phase separation. Furthermore, traditional PCL-based modification systems struggle to balance the electrolyte's structural stability and interfacial compatibility. Therefore, developing a PVC-based composite solid electrolyte that achieves molecular-level interfacial fusion between the inorganic filler and the polymer matrix, while simultaneously ensuring both mechanical properties and ion conduction efficiency, has become a pressing technical challenge in this field. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a polyvinyl chloride (PVC) composite solid electrolyte and its preparation method. This invention modifies CePO4 by silanization to enable polymerization, preparing a PCL-based composite containing dynamic coordination bonds. These two components are then synergistically composited with a PVC matrix using a stepwise crosslinking process involving humidity-induced silane hydrolysis condensation and UV curing, constructing a dual network structure of covalent crosslinking and dynamic coordination. The modified CePO4 achieves molecular-level interfacial bonding with the matrix through double-bond polymerization, enhancing the electrolyte's mechanical strength to suppress lithium dendrite formation and providing stable ion transport channels. The PCL-based composite imparts good flexibility and self-healing properties to the electrolyte, reducing the crystallinity of PVC. The composite solid electrolyte prepared by this invention achieves simultaneous optimization of mechanical properties, ion conduction efficiency, and electrochemical stability, solving the core problems of traditional PVC electrolytes, such as limited performance and poor interfacial compatibility. It is suitable for high-performance energy storage devices and possesses significant practical value and industrialization prospects.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: This invention provides a polyvinyl chloride composite solid electrolyte, comprising the following raw materials in parts by weight: 30-50 parts polyvinyl chloride resin, 45-65 parts PCL-based composite, 3-8 parts modified CePO4, 20-35 parts lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), 3-6 parts propylene carbonate, and 0.2-0.8 parts photoinitiator; Preferably, the photoinitiator is one of Irgacure 184, Irgacure 1173, and Darocur 2959.

[0006] The PCL-based composite comprises raw materials in the following mass ratio: hydroxyl-terminated PCL: itaconic anhydride: zinc trifluoromethanesulfonate: 3-isocyanate-propyltriethoxysilane (IPTES): dibutyltin dilaurate = 8-12: 2.2: 0.9: 4.8: 0.1; The preparation method of the PCL-based complex includes the following steps: (1) In a dry three-necked flask, add terminal hydroxyl PCL and anhydrous tetrahydrofuran. The ratio of terminal hydroxyl PCL to anhydrous tetrahydrofuran is 1g:10-20mL. Stir at 60℃ until completely dissolved. Add itaconic anhydride and continue the reaction for 12 hours. Pour the reaction solution into cold diethyl ether to precipitate. The ratio of terminal hydroxyl PCL to anhydrous tetrahydrofuran is 1g:10-20mL. Filter and dry for 24 hours to obtain a white waxy solid. (2) Dissolve the white waxy solid in anhydrous tetrahydrofuran. The ratio of the white waxy solid to anhydrous tetrahydrofuran is 1g:10-15mL. Add IPTES and dibutyltin dilaurate. Stir the reaction at room temperature for 8 hours. Then add zinc trifluoromethanesulfonate and continue stirring for 4 hours. Add the reaction solution dropwise to petroleum ether and stir vigorously to precipitate. Filter to collect the precipitate, wash, and dry for 24 hours to obtain the PCL-based complex.

[0007] The modified CePO4 comprises raw materials in the following mass ratio: CePO4:KH-570 = 1:3; The method for preparing the modified CePO4 includes the following steps: CePO4 was placed in a muffle furnace and calcined at 300℃ for 2 hours. After removal, it was quickly placed in a desiccator for cooling to obtain activated CePO4. The activated CePO4 was added to a mixed solvent at a ratio of 1 g to 15 mL. The mixed solvent was composed of anhydrous ethanol and deionized water at a volume ratio of 95:5. The mixture was ultrasonically dispersed for 30 minutes, KH-570 was added, and the pH was adjusted to 4-5 with acetic acid. The mixture was transferred to a round-bottom flask, a condenser was installed, and the mixture was magnetically stirred and refluxed in an oil bath at 78℃ for 6 hours. After the reaction was completed, the mixture was centrifuged, washed, dried for 12 hours, ground, and passed through a 400-mesh sieve to obtain modified CePO4.

[0008] This invention also provides a method for preparing a polyvinyl chloride composite solid electrolyte, specifically including the following steps: S1. In a glove box filled with high-purity argon, weigh polyvinyl chloride resin and add it to a wide-mouth bottle containing anhydrous cyclohexanone. The ratio of polyvinyl chloride resin to anhydrous cyclohexanone is 1g:5-10mL. Place the bottle on a 60℃ hot plate and stir magnetically for 6 hours until completely dissolved to obtain a polyvinyl chloride solution. Keep the temperature at 60℃ and add PCL-based composite to the polyvinyl chloride solution. Stir for 2 hours, then add modified CePO4 and ultrasonically disperse for 1 hour. Continue stirring for 1 hour to obtain a mixture. S2, add LiTFSI to the mixture and stir for 2 hours, then add propylene carbonate and stir for 1 hour, then add photoinitiator and stir for 30 minutes to obtain a mixture, and then stir at 60 °C for 24-48 hours to obtain a casting solution; S3. Allow the casting solution to stand for 30 minutes to degas. Using a precision doctor blade, cast the solution onto a clean polyimide film to obtain a wet film. Control the thickness of the wet film to 300 micrometers. Then, perform stepwise curing according to the following procedure: Place the wet film horizontally in a constant temperature and humidity chamber, set the temperature to 40℃ and the relative humidity to 30%, and let it stand for 8 hours to allow the solvent to slowly evaporate, obtaining a semi-dry film. At the same time, the moisture in the air initiates the hydrolysis and condensation reaction of the triethoxysilane groups in the PCL-based composite. Transfer the semi-dry film to a nitrogen-atmosphere UV curing chamber and cure it at a wavelength of 365nm and a light intensity of 10mW / cm². 2 Under these conditions, both sides are irradiated for 5 minutes each. Ultraviolet light initiates the polymerization of methacrylate double bonds on the surface of modified CePO4, and at the same time initiates free radical reactions in the system. S4. Transfer the membrane to a vacuum drying oven and dry for 24 hours. Turn off the heating and allow it to cool naturally to room temperature under vacuum. In a glove box, carefully peel the cured membrane off the polyimide substrate and cut it into round pieces using a precision mold with a diameter of 15-20 mm. Place the cut membrane on a 40°C constant temperature plate and let it stand for 2 hours to obtain a polyvinyl chloride composite solid electrolyte.

[0009] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention utilizes chemical modification and stepwise composite processes to create interfacial interactions and a synergistic network effect, resulting in a high-performance polyvinyl chloride (PVC) composite solid electrolyte. Modified CePO4, through surface-grafted unsaturated double bonds, forms covalent bonds with polymerizable components in the system, resolving issues such as uneven dispersion and interfacial voids. The modified CePO4 not only achieves uniform dispersion within the PVC system but also constructs a continuous interfacial network. This network enhances the mechanical strength of the electrolyte membrane by leveraging the rigidity of the inorganic filler, suppressing the risk of lithium dendrite penetration. Furthermore, the polar sites on the modified CePO4 surface promote lithium salt dissociation, providing a stable channel for lithium-ion transport. The dynamic coordination bonds introduced by the PCL-based composite impart excellent flexibility and self-healing potential to the system, mitigating the film brittleness caused by excessive rigidity in the PVC matrix. Simultaneously, the interaction between the coordination bonds and lithium salt ions further promotes lithium salt dissociation, increasing the concentration of free lithium ions. In addition, the introduction of PCL-based composites can reduce the crystallinity of polyvinyl chloride, increase the mobility of polymer chain segments, and form a dual ion transport pathway with the inorganic channel constructed by modified CePO4, thus significantly optimizing ion conduction efficiency.

[0010] In the stepwise curing process, humidity-induced silane hydrolysis and condensation and UV-induced free radical polymerization occur in stages, forming a dual network structure: the initial hydrolysis and condensation achieves a tight bond between the inorganic filler and the polymer matrix, improving membrane uniformity; the subsequent UV curing further enhances network stability through the polymerization reaction of modified CePO4 surface double bonds, while simultaneously fixing ion transport channels. This stepwise crosslinking strategy avoids network defects caused by single curing methods and achieves controlled solvent evaporation, reducing membrane porosity and residual solvent, thus improving the electrochemical stability and long-term cycling reliability of the electrolyte. Compared to the current single-function polyvinyl chloride electrolytes, this system significantly expands the application scenarios of polyvinyl chloride composite solid electrolytes, especially suitable for energy storage devices with high stability and safety requirements, possessing significant technological breakthrough value. Attached Figure Description

[0011] Figure 1 Cyclic data diagram of the lithium battery assembled with the polyvinyl chloride composite solid electrolyte prepared in this invention; Figure 2 The polyvinyl chloride composite solid electrolyte prepared according to this invention is at 0.3 mA / cm². -2 The following is a diagram of a lithium stripping / electroplating experiment. Detailed Implementation

[0012] To enable those skilled in the art to better understand the technical solutions of the present invention and to make the above-mentioned features, objectives, and advantages of the present invention clearer and easier to understand, the present invention will be further described below with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0013] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0014] Unless otherwise specified, all methods used in the following examples are conventional. Unless otherwise specified, all materials used in the following examples are new materials purchased from the market. Polyvinyl chloride was purchased from Yantai Wanhua Company, and hydroxyl-terminated PCL was purchased from Aladdin Reagent (Shanghai) Co., Ltd.

[0015] Example 1: This example provides a polyvinyl chloride composite solid electrolyte, comprising the following raw materials in parts by weight: 30 parts polyvinyl chloride resin, 45 parts PCL-based composite, 3 parts modified CePO4, 20 parts LiTFSI, 3 parts propylene carbonate, and 0.2 parts Irgacure 1173; The PCL-based composite comprises raw materials in the following mass ratio: itaconic anhydride: zinc trifluoromethanesulfonate: IPTES: dibutyltin dilaurate = 8:2.2:0.9:4.8:0.1; The preparation method of the PCL-based complex includes the following steps: (1) In a dry three-necked flask, add terminal hydroxyl PCL and anhydrous tetrahydrofuran. The ratio of terminal hydroxyl PCL to anhydrous tetrahydrofuran is 1 g: 10 mL. Stir at 60 °C until completely dissolved. Add itaconic anhydride and continue the reaction for 12 hours. Pour the reaction solution into cold diethyl ether to precipitate. The ratio of terminal hydroxyl PCL to anhydrous tetrahydrofuran is 1 g: 10 mL. Filter and dry under vacuum at 40 °C for 24 hours to obtain a white waxy solid. (2) Dissolve the white waxy solid again in anhydrous tetrahydrofuran. The ratio of the white waxy solid to anhydrous tetrahydrofuran is 1 g: 10 mL. Add IPTES and dibutyltin dilaurate. Stir the reaction at room temperature for 8 hours. Then add zinc trifluoromethanesulfonate and continue stirring for 4 hours. Add the reaction solution dropwise to petroleum ether. The volume ratio of the reaction solution to petroleum ether is 1:20. Stir vigorously to precipitate the solution. Filter and collect the precipitate. Wash the precipitate three times with petroleum ether and dry it in a vacuum drying oven at 40 °C for 24 hours to obtain a pale yellow elastic solid PCL-based complex.

[0016] The modified CePO4 comprises raw materials in the following mass ratio: CePO4:KH-570 = 1:3; The method for preparing the modified CePO4 includes the following steps: CePO4 was placed in a muffle furnace and calcined at 300℃ for 2 hours. After removal, it was quickly placed in a desiccator for cooling to obtain activated CePO4. The activated CePO4 was added to a mixed solvent at a ratio of 1 g to 15 mL. The mixed solvent was composed of anhydrous ethanol and deionized water at a volume ratio of 95:5. The mixture was ultrasonically dispersed for 30 minutes at a power of 300 W. KH-570 was added, and the pH was adjusted to 4 with acetic acid. The mixture was transferred to a round-bottom flask, a condenser was installed, and the mixture was magnetically stirred and refluxed in an oil bath at 78℃ for 6 hours. After the reaction was completed, the mixture was centrifuged at 10,000 rpm for 10 minutes. The precipitate was washed three times with anhydrous ethanol and placed in a vacuum drying oven at 80℃ for 12 hours. After grinding, the precipitate was passed through a 400-mesh sieve to obtain modified CePO4.

[0017] This embodiment also provides a method for preparing a polyvinyl chloride composite solid electrolyte, which specifically includes the following steps: S1. In a glove box filled with high-purity argon, weigh polyvinyl chloride resin and add it to a wide-mouth bottle containing anhydrous cyclohexanone. The ratio of polyvinyl chloride resin to anhydrous cyclohexanone is 1g:5mL. Place the bottle on a 60℃ hot plate and stir magnetically for 6 hours until completely dissolved to obtain a polyvinyl chloride solution. Keep the temperature at 60℃ and add PCL-based composite to the polyvinyl chloride solution. Stir for 2 hours, then add modified CePO4 and ultrasonically disperse for 1 hour at a power of 300W. Continue stirring for 1 hour to obtain a mixture. S2, add LiTFSI to the mixture and stir for 2 hours, then add propylene carbonate and stir for 1 hour, then add Irgacure 1173 and stir for 30 minutes to obtain a mixture, and then stir at 60 °C for 24 hours to obtain a uniform, high-viscosity casting solution with a slightly milky white luster. S3. Allow the casting solution to stand for 30 minutes to degas. Using a precision doctor blade, cast the solution onto a clean polyimide film to obtain a wet film. Control the thickness of the wet film to 300 micrometers. Then, perform stepwise curing according to the following procedure: Place the wet film horizontally in a constant temperature and humidity chamber, set the temperature to 40℃ and the relative humidity to 30%, and let it stand for 8 hours to allow the solvent to slowly evaporate, obtaining a semi-dry film. At the same time, the moisture in the air initiates the hydrolysis and condensation reaction of the triethoxysilane groups in the PCL-based composite. Transfer the semi-dry film to a nitrogen-atmosphere UV curing chamber and cure it at a wavelength of 365nm and a light intensity of 10mW / cm². 2 Under these conditions, both sides are irradiated for 5 minutes each. Ultraviolet light initiates the polymerization of methacrylate double bonds on the surface of modified CePO4, and at the same time initiates free radical reactions in the system. S4. Transfer the membrane to a vacuum drying oven and dry it at 60°C and -0.095MPa vacuum for 24 hours. Turn off the heating and allow it to cool naturally to room temperature under vacuum. In a glove box, carefully peel the cured membrane off the polyimide substrate and cut it into round pieces using a precision die with a diameter of 15mm. Place the cut membrane on a constant temperature plate at 40°C and let it stand for 2 hours to obtain a polyvinyl chloride composite solid electrolyte.

[0018] Example 2: This example provides a polyvinyl chloride composite solid electrolyte, comprising the following raw materials in parts by weight: 40 parts polyvinyl chloride resin, 55 parts PCL-based composite, 5 parts modified CePO4, 25 parts LiTFSI, 4 parts propylene carbonate, and 0.5 parts Irgacure 184. The PCL-based composite comprises raw materials in the following mass ratio: hydroxyl-terminated PCL: itaconic anhydride: zinc trifluoromethanesulfonate: IPTES: dibutyltin dilaurate = 10:2.2:0.9:4.8:0.1; The preparation method of the PCL-based complex includes the following steps: (1) In a dry three-necked flask, add terminal hydroxyl PCL and anhydrous tetrahydrofuran. The ratio of terminal hydroxyl PCL to anhydrous tetrahydrofuran is 1 g: 15 mL. Stir at 60 °C until completely dissolved. Add itaconic anhydride and continue the reaction for 12 hours. Pour the reaction solution into cold diethyl ether to precipitate. The ratio of terminal hydroxyl PCL to anhydrous tetrahydrofuran is 1 g: 18 mL. Filter and dry under vacuum at 40 °C for 24 hours to obtain a white waxy solid. (2) Dissolve the white waxy solid again in anhydrous tetrahydrofuran. The ratio of the white waxy solid to anhydrous tetrahydrofuran is 1 g: 12 mL. Add IPTES and dibutyltin dilaurate. Stir the reaction at room temperature for 8 hours. Then add zinc trifluoromethanesulfonate and continue stirring for 4 hours. Add the reaction solution dropwise to petroleum ether. The volume ratio of the reaction solution to petroleum ether is 1:20. Stir vigorously to precipitate the precipitate. Filter and collect the precipitate. Wash it three times with petroleum ether. Dry it in a vacuum drying oven at 40 °C for 24 hours to obtain a pale yellow elastic solid PCL-based complex.

[0019] The modified CePO4 comprises raw materials in the following mass ratio: CePO4:KH-570 = 1:3; The method for preparing the modified CePO4 includes the following steps: CePO4 was placed in a muffle furnace and calcined at 300℃ for 2 hours. After removal, it was quickly placed in a desiccator for cooling to obtain activated CePO4. The activated CePO4 was added to a mixed solvent at a ratio of 1 g to 15 mL. The mixed solvent was composed of anhydrous ethanol and deionized water at a volume ratio of 95:5. The mixture was ultrasonically dispersed for 30 minutes at a power of 300 W. KH-570 was added, and the pH was adjusted to 4.5 with acetic acid. The mixture was transferred to a round-bottom flask, a condenser was installed, and the mixture was magnetically stirred and refluxed in an oil bath at 78℃ for 6 hours. After the reaction was completed, the mixture was centrifuged at 10,000 rpm for 10 minutes. The precipitate was washed three times with anhydrous ethanol and placed in a vacuum drying oven at 80℃ for 12 hours. After grinding, the precipitate was passed through a 400-mesh sieve to obtain modified CePO4.

[0020] This embodiment also provides a method for preparing a polyvinyl chloride composite solid electrolyte, which specifically includes the following steps: S1. In a glove box filled with high-purity argon, weigh polyvinyl chloride resin and add it to a wide-mouth bottle containing anhydrous cyclohexanone. The ratio of polyvinyl chloride resin to anhydrous cyclohexanone is 1g:8mL. Place the bottle on a 60℃ hot plate and stir magnetically for 6 hours until completely dissolved to obtain a polyvinyl chloride solution. Keep the temperature at 60℃ and add PCL-based composite to the polyvinyl chloride solution. Stir for 2 hours, then add modified CePO4 and ultrasonically disperse for 1 hour at a power of 300W. Continue stirring for 1 hour to obtain a mixture. S2, add LiTFSI to the mixture and stir for 2 hours, then add propylene carbonate and stir for 1 hour, then add Irgacure 184 and stir for 30 minutes to obtain a mixture, and then stir at 60 °C for 36 hours to obtain a uniform, high-viscosity casting solution with a slightly milky white luster. S3. Allow the casting solution to stand for 30 minutes to degas. Using a precision doctor blade, cast the solution onto a clean polyimide film to obtain a wet film. Control the thickness of the wet film to 300 micrometers. Then, perform stepwise curing according to the following procedure: Place the wet film horizontally in a constant temperature and humidity chamber, set the temperature to 40℃ and the relative humidity to 30%, and let it stand for 8 hours to allow the solvent to slowly evaporate, obtaining a semi-dry film. At the same time, the moisture in the air initiates the hydrolysis and condensation reaction of the triethoxysilane groups in the PCL-based composite. Transfer the semi-dry film to a nitrogen-atmosphere UV curing chamber and cure it at a wavelength of 365nm and a light intensity of 10mW / cm². 2 Under these conditions, both sides are irradiated for 5 minutes each. Ultraviolet light initiates the polymerization of methacrylate double bonds on the surface of modified CePO4, and at the same time initiates free radical reactions in the system. S4. Transfer the membrane to a vacuum drying oven and dry it at 60°C and -0.08MPa vacuum for 24 hours. Turn off the heating and allow it to cool naturally to room temperature under vacuum. In a glove box, carefully peel the cured membrane off the polyimide substrate and cut it into round pieces using a precision die with a diameter of 16mm. Place the cut membrane on a constant temperature plate at 40°C and let it stand for 2 hours to obtain a polyvinyl chloride composite solid electrolyte.

[0021] Example 3: This example provides a polyvinyl chloride composite solid electrolyte, comprising the following raw materials in parts by weight: 50 parts polyvinyl chloride resin, 65 parts PCL-based composite, 8 parts modified CePO4, 35 parts LiTFSI, 6 parts propylene carbonate, and 0.8 parts Darocur 2959. The PCL-based composite comprises raw materials in the following mass ratio: hydroxyl-terminated PCL: itaconic anhydride: zinc trifluoromethanesulfonate: IPTES: dibutyltin dilaurate = 12:2.2:0.9:4.8:0.1; The preparation method of the PCL-based complex includes the following steps: (1) In a dry three-necked flask, add terminal hydroxyl PCL and anhydrous tetrahydrofuran. The ratio of terminal hydroxyl PCL to anhydrous tetrahydrofuran is 1 g: 20 mL. Stir at 60 °C until completely dissolved. Add itaconic anhydride and continue the reaction for 12 hours. Pour the reaction solution into cold diethyl ether to precipitate. The ratio of terminal hydroxyl PCL to anhydrous tetrahydrofuran is 1 g: 20 mL. Filter and dry under vacuum at 40 °C for 24 hours to obtain a white waxy solid. (2) Dissolve the white waxy solid again in anhydrous tetrahydrofuran. The ratio of the white waxy solid to anhydrous tetrahydrofuran is 1 g: 15 mL. Add IPTES and dibutyltin dilaurate. Stir the reaction at room temperature for 8 hours. Then add zinc trifluoromethanesulfonate and continue stirring for 4 hours. Add the reaction solution dropwise to petroleum ether. The volume ratio of the reaction solution to petroleum ether is 1:20. Stir vigorously to precipitate the precipitate. Filter and collect the precipitate. Wash it three times with petroleum ether and dry it in a vacuum drying oven at 40 °C for 24 hours to obtain a pale yellow elastic solid PCL-based complex.

[0022] The modified CePO4 comprises raw materials in the following mass ratio: CePO4:KH-570 = 1:3; The method for preparing the modified CePO4 includes the following steps: CePO4 was placed in a muffle furnace and calcined at 300℃ for 2 hours. After removal, it was quickly placed in a desiccator for cooling to obtain activated CePO4. The activated CePO4 was added to a mixed solvent at a ratio of 1 g to 15 mL. The mixed solvent was composed of anhydrous ethanol and deionized water at a volume ratio of 95:5. The mixture was ultrasonically dispersed for 30 minutes at a power of 300 W. KH-570 was added, and the pH was adjusted to 5 with acetic acid. The mixture was transferred to a round-bottom flask, a condenser was installed, and the mixture was magnetically stirred and refluxed in an oil bath at 78℃ for 6 hours. After the reaction was completed, the mixture was centrifuged at 10,000 rpm for 10 minutes. The precipitate was washed three times with anhydrous ethanol and placed in a vacuum drying oven at 80℃ for 12 hours. After grinding, the precipitate was passed through a 400-mesh sieve to obtain modified CePO4.

[0023] This embodiment also provides a method for preparing a polyvinyl chloride composite solid electrolyte, which specifically includes the following steps: S1. In a glove box filled with high-purity argon, weigh polyvinyl chloride resin and add it to a wide-mouth bottle containing anhydrous cyclohexanone. The ratio of polyvinyl chloride resin to anhydrous cyclohexanone is 1g:10mL. Place the bottle on a 60℃ hot plate and stir magnetically for 6 hours until completely dissolved to obtain a polyvinyl chloride solution. Keep the temperature at 60℃ and add PCL-based composite to the polyvinyl chloride solution. Stir for 2 hours, then add 0.6g of modified CePO4 and ultrasonically disperse for 1 hour at a power of 300W. Continue stirring for 1 hour to obtain a mixture. S2, add LiTFSI to the mixture and stir for 2 hours, then add propylene carbonate and stir for 1 hour, then add Darocur 2959 and stir for 30 minutes to obtain a mixture, then stir at 60 °C for 48 hours to obtain a uniform, high-viscosity casting solution with a slightly milky white luster. S3. Allow the casting solution to stand for 30 minutes to degas. Using a precision doctor blade, cast the solution onto a clean polyimide film to obtain a wet film. Control the thickness of the wet film to 300 micrometers. Then, perform stepwise curing according to the following procedure: Place the wet film horizontally in a constant temperature and humidity chamber, set the temperature to 40℃ and the relative humidity to 30%, and let it stand for 8 hours to allow the solvent to slowly evaporate, obtaining a semi-dry film. At the same time, the moisture in the air initiates the hydrolysis and condensation reaction of the triethoxysilane groups in the PCL-based composite. Transfer the semi-dry film to a nitrogen-atmosphere UV curing chamber and cure it at a wavelength of 365nm and a light intensity of 10mW / cm². 2 Under these conditions, both sides are irradiated for 5 minutes each. Ultraviolet light initiates the polymerization of methacrylate double bonds on the surface of modified CePO4, and at the same time initiates free radical reactions in the system. S4. Transfer the membrane to a vacuum drying oven and dry it at 60°C and -0.095MPa vacuum for 24 hours. Turn off the heating and allow it to cool naturally to room temperature under vacuum. In a glove box, carefully peel the cured membrane off the polyimide substrate and cut it into round pieces using a precision die with a diameter of 20mm. Place the cut membrane on a constant temperature plate at 40°C and let it stand for 2 hours to obtain a polyvinyl chloride composite solid electrolyte.

[0024] The difference between Comparative Example 1 and Example 2 is that no PCL-based complex was added; the rest of the parts are exactly the same as Example 2.

[0025] The difference between Comparative Example 2 and Example 2 is that no modified CePO4 is added; the rest is exactly the same as Example 2.

[0026] The difference between Comparative Example 3 and Example 2 is that itaconic anhydride is not added; the rest is exactly the same as Example 2.

[0027] Experimental example: 1. Ionic conductivity: The polyvinyl chloride composite solid electrolytes prepared in Examples 1-3 and Comparative Examples 1-3 of this invention were used as samples, and the conductivity was measured by electrochemical impedance spectroscopy (EIS). Specifically, a blocked symmetric cell of stainless steel (SS) | quasi-solid electrolyte | SS was assembled. The assembled stainless steel symmetric cell was placed in a constant temperature oven, and the bulk impedance of the cell at -10-80℃ was tested using an electrochemical workstation. The test parameters were: 0.1 Hz-100 kHz, amplitude of 5 mV. The ionic conductivity of the electrolyte was calculated using the following formula, and the ion transport activation energy was calculated using the Arrhenius equation: σ=l / (R b ×S), where σ is the ionic conductivity, and R is the ionic conductivity. b This is the bulk resistance of a stainless steel symmetrical cell with a quasi-solid-state electrolyte, where S represents the effective contact area between the solid electrolyte and the stainless steel sheet, and l represents the thickness of the solid electrolyte. σ = (A / T)e -Ea / kt In the formula, A is the pre-exponential factor, T is the absolute temperature, k is the Boltzmann gas constant, and E is the absolute temperature. a Assuming the activation energy for ion transport, the slope of the linear relationship between Log(σ) and 1000 / T was obtained by fitting the equation, thus yielding the E values ​​for different quasi-solid-state electrolytes. a The calculated ionic conductivity results are recorded in Table 1.

[0028] 2. Lithium-ion transport number: Using the polyvinyl chloride composite solid electrolytes prepared in Examples 1-3 and Comparative Examples 1-3 as samples, Li|quasi-solid electrolyte|Li symmetric cells were prepared in a glove box. EIS tests were performed on the cells at room temperature (frequency 0.1 Hz-100 kHz, amplitude 5 mV) to obtain the initial impedance of the quasi-solid electrolyte. Then, a polarization voltage of 10 mV (ΔV) was applied to the cell, and the initial response current and steady-state response current Iss were recorded. Finally, the cell was subjected to EIS tests again to obtain the impedance Rss of the quasi-solid electrolyte after polarization. Lithium-ion transport number (t) Li+ ) Calculated using the Bruce & Vincent method: t Li+ =I SS (△V-I0R0)\I0(△VI SS R SS The results are recorded in Table 1.

[0029] 3. Electrochemical stability window: Using the polyvinyl chloride composite solid electrolytes prepared in Examples 1-3 and Comparative Examples 1-3 of this invention as samples, the electrochemical stability window of the solid electrolytes was measured by linear scanning voltammetry. First, SS|quasi-solid electrolyte|Li cells were assembled in a glove box, and the tests were conducted in an electrochemical workstation at a scan rate of 1 mV / s and a voltage range of 2.5-6V. The results are recorded in Table 1.

[0030] Table 1: Performance Test Results of the Polyvinyl Chloride Composite Solid Electrolyte of the Present Invention

[0031] As shown in Table 1, the ionic conductivity and ion transport number of Examples 1-3 of this invention are higher than those of Comparative Examples 1-3. Comparative Example 1, however, shows a significant decrease in ionic conductivity and transport number due to the lack of a PCL-based complex, the absence of a dynamic coordination network and flexible components, and an excessively rigid system with poor interfacial compatibility, resulting in a narrowed electrochemical stability window. Comparative Example 2, compared to the examples, demonstrates that modified CePO4 effectively suppresses the oxidative decomposition of the electrolyte under high voltage, significantly improving the high-voltage stability of the system and making it suitable for high-energy-density battery systems. The results of Comparative Example 3 indicate that the addition of itaconic anhydride further optimizes the polymer network structure and ion transport kinetics.

[0032] Figure 1 To assemble lithium metal coin batteries using the polyvinyl chloride composite solid electrolyte prepared in this invention, tests were conducted at 45 °C and 2C (1C = 170 mAh·g). -1 The current long-cycle charge-discharge test, such as Figure 1 As shown, it still retains 92.2% capacity retention and 146.2 mAh·g after 600 cycles. -1The discharge specific capacity indicates that the polyvinyl chloride composite solid electrolyte prepared in this invention has an excellent effect on improving battery cycle performance. Figure 2 For Li / / polyvinyl chloride composite solid electrolyte / / Li battery at 0.3 mAcm -2 The figure shows the results of a long-term lithium stripping / electroplating experiment. As can be seen from the figure, lithium ion stripping / electroplating can be carried out stably, maintaining stable cycling for up to 1200 h and maintaining low electrochemical polarization.

[0033] In summary, this invention successfully prepared a high-performance polyvinyl chloride (PVC) composite solid electrolyte through precisely designed material modification, component synergy, and stepwise curing processes. This electrolyte uses modified CePO4 as a functional filler, leveraging its surface unsaturated double bonds to covalently connect with the polymerizable components of the system. This achieves uniform dispersion of the inorganic filler in the polymer matrix, constructing a continuous interfacial network. This enhances the mechanical properties of the electrolyte membrane to inhibit lithium dendrite penetration and promotes lithium salt dissociation through the polar sites on the filler surface, providing a stable channel for lithium ion transport. The PCL-based composite containing dynamic coordination bonds serves as the flexible ion-conducting component, not only alleviating the brittleness of the PVC matrix and endowing the electrolyte with good flexibility and self-healing potential, but also increasing the free lithium ion concentration through the interaction of coordination bonds with the lithium salt, while simultaneously reducing the crystallinity of the PVC matrix and optimizing ion conduction efficiency. Furthermore, the stepwise curing process combines humidity-induced silane hydrolysis and condensation with UV-induced free radical polymerization in an orderly manner, promoting the formation of a stable double cross-linked network in the system. This not only achieves controllable solvent evaporation and uniform regulation of the membrane structure, but also strengthens the interfacial bonding between components, reduces membrane porosity and residual solvent, and significantly improves the electrochemical stability and long-term cycling reliability of the electrolyte.

[0034] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A polyvinyl chloride composite solid electrolyte, characterized in that, The raw materials include the following parts by weight: 30-50 parts polyvinyl chloride resin, 45-65 parts PCL-based composite, 3-8 parts modified CePO4, 20-35 parts LiTFSI, 3-6 parts propylene carbonate, and 0.2-0.8 parts photoinitiator; The photoinitiator is one of Irgacure 184, Irgacure 1173, and Darocur 2959; The PCL-based composite comprises raw materials in the following mass ratio: hydroxyl-terminated PCL: itaconic anhydride: zinc trifluoromethanesulfonate: IPTES: dibutyltin dilaurate = 8-12: 2.2: 0.9: 4.8: 0.1; The preparation method of the PCL-based complex includes the following steps: (1) Take the terminal hydroxyl PCL and add it to anhydrous tetrahydrofuran. Stir until dissolved, add itaconic anhydride to obtain a reaction solution. Pour the reaction solution into cold diethyl ether to precipitate, filter, and dry to obtain a white waxy solid. (2) Dissolve the white waxy solid in anhydrous tetrahydrofuran, add IPTES and dibutyltin dilaurate, stir, then add zinc trifluoromethanesulfonate, continue stirring, then drop it into petroleum ether, stir vigorously to precipitate, filter to collect the precipitate, wash, dry, and obtain PCL-based complex.

2. The polyvinyl chloride composite solid electrolyte according to claim 1, characterized in that, In step (1), the ratio of the terminal hydroxyl PCL to anhydrous tetrahydrofuran is 1g:10-20mL; the volume ratio of the cold diethyl ether to the reaction solution is 5:

1. In step (2), the ratio of the white waxy solid to anhydrous tetrahydrofuran is 1g:10-15mL.

3. The polyvinyl chloride composite solid electrolyte according to claim 1, characterized in that, The modified CePO4 comprises raw materials in the following mass ratio: CePO4:KH-570 = 1:3; The method for preparing the modified CePO4 includes the following steps: CePO4 was calcined and cooled to obtain activated CePO4. The activated CePO4 was added to a mixed solvent, ultrasonically dispersed, KH-570 was added, the pH was adjusted, and the mixture was heated under reflux. Then, it was centrifuged, washed, dried, ground, and sieved to obtain modified CePO4.

4. The polyvinyl chloride composite solid electrolyte according to claim 3, characterized in that, The ratio of activated CePO4 to the mixed solvent is 1g:15mL; the mixed solvent is composed of anhydrous ethanol and deionized water in a volume ratio of 95:

5.

5. A method for preparing a polyvinyl chloride composite solid electrolyte according to any one of claims 1-4, characterized in that, Specifically, the following steps are included: S1, Under inert gas protection, weigh polyvinyl chloride resin and add it to anhydrous cyclohexanone, heat and stir to obtain polyvinyl chloride solution, then add PCL-based composite to it, stir, then add modified CePO4 to it, and ultrasonically disperse to obtain a mixture; S2, add LiTFSI to the mixture, stir, then add propylene carbonate, stir, then add photoinitiator, and continue stirring under heating conditions to obtain casting solution; S3, allow the casting solution to stand to remove bubbles, then cast it into a wet film, followed by stepwise curing to obtain a cured film: S4. The cured film is vacuum dried, cooled to room temperature, peeled off, and punched to obtain a polyvinyl chloride composite solid electrolyte.

6. The method for preparing a polyvinyl chloride composite solid electrolyte according to claim 5, characterized in that, In step S1, the ratio of polyvinyl chloride resin to anhydrous cyclohexanone is 1g:5-10mL.

7. The method for preparing a polyvinyl chloride composite solid electrolyte according to claim 5, characterized in that, In step S3, the stepwise curing process is as follows: the wet film is allowed to evaporate the solvent under constant temperature and humidity conditions, which are set at a temperature of 40°C and a relative humidity of 30%, and left to stand for 8 hours to obtain a semi-dry film. Subsequently, it is cured with ultraviolet light under a nitrogen atmosphere at a wavelength of 365nm and a light intensity of 10mW / cm². 2 Irradiate both sides for 5 minutes each to obtain a cured film.

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