Preparation method for constructing root-soil interlocking structure composite solid electrolyte based on Janus particles

Abstract

The invention belongs to the field of lithium ion solid electrolyte manufacturing, and particularly relates to a preparation method for constructing a root-soil interlocking structure composite solid electrolyte based on Janus particles. The method comprises the following preparation steps: 1) surface modification of SiO2 particles; 2) preparing a PVDF latex seed solution; (3) preparing SiO2 coated PVDF core-shell composite particles; (4) preparing the Fe3O4 / SiO2 coated PVDF (Polyvinylidene Fluoride); (5) modifying the LLZO ceramic electrolytic sheet; (6) preparing an LLZO ceramic electrolytic sheet; and (6) preparing the LLZO / Fe3O4 / SiO2 coated PVDF composite solid electrolyte material. The preparation method disclosed by the invention has the technical advantages that (1) a multifunctional partitioned Janus modified material Fe3O4 / SiO2 coated PVDF is synthesized and forms a firm root-soil interlocking structure with LLZO, so that strong interaction among LLZO, Janus and PVDF is realized; and 2) the Janus modified material Fe3O4 / SiO2 coated PVDF optimizes the contact between the LLZO material and an electrolyte or an electrode through two different interface properties of hydrophilicity and hydrophobicity, improves the ion migration efficiency and the interface stability, and overcomes the limitation of the traditional LLZO material in the aspect of interface contact.

Description

Technical Field

[0001] The invention belongs to the field of lithium ion solid electrolyte manufacturing, and specifically relates to a preparation method of a composite solid electrolyte with a root-soil interlocking structure constructed based on Janus particles. Background Art

[0002] Traditional energy sources such as coal, oil and natural gas support global energy demand, but as environmental and resource depletion issues become more prominent, people are turning to clean and sustainable energy. Electric energy, due to its renewable and environmentally friendly characteristics, has become a key energy conversion and storage medium. As a type of energy storage technology, lithium-ion batteries are widely used in portable electronic devices, electric vehicles and grid energy storage due to their high energy density, long life and low self-discharge rate.

[0003] The performance of lithium-ion batteries is mainly reflected in their high energy density, which means that they can store more electrical energy in a smaller volume and weight (LI M, WANG C, CHEN Z, et al. New Concepts in Electrolytes [J]. Chemical Reviews, 2020, 120(14): 6783-819). In addition, they have high charge and discharge efficiency and long cycle life, which makes them more economical and environmentally friendly in long-term use. However, due to the extremely high chemical reactivity of lithium metal anodes, lithium metal anodes react with liquid electrolytes, resulting in uneven lithium deposition and safety issues such as combustion or explosion, which limits the commercial application of lithium metal batteries by many safety issues (AXK, BYW, CLD, et al. Cell failures of all-solid-state lithium metal batteries with inorganic solid electrolytes: Lithiumdendrites [J]. Energy Storage Materials, 2020, 33: 309-28). Therefore, designing highly safe solid-state lithium metal batteries is crucial for practical applications.

[0004] Inorganic solid electrolytes have fewer side reactions with metal negative electrodes and have a series of advantages such as high safety, long life, and no leakage. They can fundamentally solve safety hazards. The assembled solid-state lithium batteries are expected to achieve a higher energy density (>300 Wh / kg) (LU Z, YANG Z, LI C, et al. Modulating nano-inhomogeneity atelectrode-solid electrolyte interfaces for dendrite-proof solid-state batteries and long-life memristors [J]. 2020). However, inorganic solid electrolytes lack fluidity, and the electrolyte-metal lithium interface formed by solid-solid contact has a small contact area, resulting in slow ion transfer and high impedance. This interface problem has become a bottleneck restricting the development of inorganic solid electrolytes.

[0005] Research found that LLZO (solid electrolyte lithium lanthanum zirconium oxide Li7La3Zr2O 12 ) has a series of advantages such as high lithium ion conductivity, stability to metal lithium electrodes, stable electrochemical performance, and miniaturization. However, the interface between LLZO and lithium metal may react during long-term use, resulting in lithium dendrite growth or electrolyte failure, and LLZO materials have large mechanical brittleness and are prone to breakage or cracks. In particular, the expansion and contraction of lithium batteries during charging and discharging may cause the electrolyte to rupture. This has an adverse effect on the stability and life of the battery. This problem affects the long-term stability of LLZO and the cycle performance of the battery.

[0006] The present invention proposes to construct a root-soil interlocking structure by designing a multifunctional partitioned organic-inorganic composite Janus material to self-orientate and arrange between ceramic and polymer electrolyte, thereby ensuring good and uniform dispersion of ceramic and improving the interface stability of polymer / ceramic, which is beneficial to Li + and the extended amorphous region provide a continuous path for 3D interconnection, which is a promising approach for achieving long-period Li + Transmission stability provides important guarantee. Summary of the invention

[0007] The purpose of the present invention is to provide a method for preparing a composite solid electrolyte with a root-soil interlocking structure constructed based on Janus particles in order to solve the technical problems existing in the background technology.

[0008] The present invention designs and synthesizes a multifunctional partitioned Janus material Fe3O4 / SiO2@PVDF, wherein the silicon oxide end forms a coordination bond with N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole (DI) to the surface of the LLZO material, and the polymer end spontaneously constructs a strong root-soil interlocking structure toward the PVDF polymer electrolyte, thereby achieving a strong interaction between LLZO, Janus and PVDF and improving the interface stability of the polymer / ceramic.

[0009] The technical solution adopted to achieve the purpose of the present invention is: a preparation method of a composite solid electrolyte with a root-soil interlocking structure constructed based on Janus particles, comprising the following preparation steps: 1) Surface modification of SiO2 particles Dispersing SiO2 particles in a mixed solution of ethanol and deionized water, using ultrasonic treatment to make the SiO2 particles uniformly dispersed, and preparing a SiO2 particle solution; mixing the SiO2 particle solution with a coupling agent, 3-aminopropyltriethoxysilane, and centrifuging and washing after the reaction is completed; 2) Preparation of PVDF latex seed solution Using water as a continuous phase, adding a surfactant, sodium dodecyl sulfate, an initiator, potassium persulfate, and a polymerizable monomer, vinyl fluoride, to emulsify the polymerizable monomer, vinyl fluoride, to form an oil / water emulsion, and heating to initiate polymerization to form nano-scale PVDF latex particles, thereby obtaining a PVDF latex seed solution; 3) Preparation of SiO2@PVDF core-shell composite particles The surface-modified SiO2 particles in step 1) are ultrasonically dispersed in the PVDF latex seed solution obtained in step 2), and the SiO2 particles are anchored on the surface of the PVDF latex particles by electrostatic adsorption to obtain seed particles, and then the polymerization monomer vinyl fluoride is continuously added, and the reaction temperature is controlled to continue to initiate polymerization, so that the polymerization monomer vinyl fluoride grows on the surface of the seed particles to form SiO2@PVDF core-shell composite particles. After the reaction is completed, the terminator carbon disulfide is added to terminate the polymerization reaction, and the obtained SiO2@PVDF core-shell composite particles are centrifugally washed with deionized water and ethanol, and finally the SiO2@PVDF core-shell composite particles are obtained after vacuum drying; 4) Preparation of Fe3O4 / SiO2@PVDF The SiO2@PVDF core-shell composite particles prepared in step 3) are ultrasonically dispersed in distilled water, mechanically stirred and introduced with argon, and then anhydrous ferric chloride and ferrous sulfate heptahydrate are added, and ammonia water is added dropwise to adjust the pH to alkaline, and stirred for sufficient reaction; the product is centrifugally washed with ethanol and deionized water, and then vacuum freeze-dried with a freeze dryer to obtain the final product Fe3O4 / SiO2@PVDF; 5) Modification of LLZO ceramic electrolyte The LLZO ceramic electrolytic sheet is immersed in a NaOH solution for pretreatment, and then the NaOH solution on the surface of the LLZO ceramic electrolytic sheet is washed away with ethanol to obtain a pretreated LLZO ceramic electrolytic sheet; ethanol, water and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole are mixed in proportion to obtain a mixed solution; the pretreated LLZO ceramic electrolytic sheet is added into the mixed solution for ultrasonic dispersion, and then a condensation reflux reaction is performed; 6) Preparation of LLZO / Fe3O4 / SiO2@PVDF composite solid electrolyte materials N,N-dimethylamide, matrix polyvinylidene fluoride and Fe3O4 / SiO2@PVDF prepared in step 4) are mixed and stirred evenly, then spread on the surface of the LLZO ceramic electrolyte sheet and baked in a vacuum oven to obtain LLZO / Fe3O4 / SiO2@PVDF composite solid electrolyte material, that is, a composite solid electrolyte with a root-soil interlocking structure constructed based on Janus particles.

[0010] Preferably, the particle size of the SiO2 particles in step 1) of the present invention is 15 nm, the mass volume ratio of the SiO2 particles to the mixed solution is (1-2) g:10 mL, the mixed solution is prepared from ethanol and deionized water in a volume ratio of 9:1, and the ultrasonic treatment time is 30-60 min; the mass volume ratio of the SiO2 particle solution to the coupling agent 3-aminopropyltriethoxysilane is 20:(3-5).

[0011] Preferably, the mass ratio of the surfactant sodium dodecyl sulfate to the polymerizable monomer vinyl fluoride in step 2) of the present invention is (0.18-0.3):(10-14); the mass ratio of the initiator potassium persulfate to the polymerizable monomer vinyl fluoride is (0.12-0.28):(10-14).

[0012] Preferably, in step 3) of the present invention, the mass volume ratio of the polymerizable monomer vinyl fluoride to the terminator carbon disulfide is 1 g: (0.01-0.03) mL, and the reaction temperature for initiating the polymerization is controlled at 60° C.-80° C.

[0013] Preferably, in step 4) of the present invention, the mass volume ratio of the SiO2@PVDF core-shell composite particles to distilled water is 1 g:20 mL, and the mass ratio of the SiO2@PVDF core-shell composite particles to anhydrous ferric chloride and ferrous sulfate heptahydrate is 10:(3-5):(2-3).

[0014] Preferably, the volume ratio of ethanol, water and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole in step 5) of the present invention is 9:2.5:1.

[0015] Preferably, the LLZO ceramic electrolyte sheet pretreated in step 5) of the present invention is added to the mixed solution for ultrasonic dispersion for 30-60 minutes, and then refluxed in an oil bath at 75° C. with a rotor stirring and a spherical condenser for 24 hours.

[0016] Preferably, the volume mass ratio of N,N-dimethylamide, polyvinylidene fluoride and Fe3O4 / SiO2@PVDF in step 6) of the present invention is (5-8) mL: (1-1.6) g: (0.1-0.5) g.

[0017] Preferably, in step 6) of the present invention, the temperature of the vacuum oven is 80° C. and the baking time is 24 hours.

[0018] Compared with the prior art, the technical advantages of the present invention are: 1) The present invention synthesized a multifunctional partitioned Janus modified material Fe3O4 / SiO2@PVDF, which formed a strong root-soil interlocking structure with LLZO, thereby achieving a strong interaction among LLZO, Janus and PVDF.

[0019] 2) The Janus modified material Fe3O4 / SiO2@PVDF of the present invention optimizes the contact between the LLZO material and the electrolyte or electrode through two different interface properties, hydrophilic and hydrophobic, improves the ion migration efficiency and interface stability, and overcomes the limitations of traditional LLZO materials in interface contact.

[0020] 3) The introduction of PVDF in the present invention enables the Janus modified material Fe3O4 / SiO2@PVDF to have better mechanical strength and flexibility while maintaining a relatively high electrical conductivity, and can better adapt to the high stress environment of lithium batteries. Due to the optimized performance of the material, the Fe3O4 / SiO2@PVDF modified LLZO material also has obvious advantages in improving battery performance, especially under extreme working conditions such as high temperature and high voltage, it can maintain high conductivity and stability, and reduce safety issues caused by material deformation or degradation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The figure is a schematic diagram of the interface bridging between the Janus organic-inorganic composite electrolyte and the electrode surface of the present invention.

[0022] Figure 2 This is a microstructure diagram of the LLZO / 0.3Fe3O4 / SiO2@PVDF sample synthesized in Example 3 of the present invention.

[0023] Figure 3 This is a cross-sectional view of the LLZO / 0.3Fe3O4 / SiO2@PVDF sample synthesized in Example 3 of the present invention.

[0024] Figure 4 The AC impedance spectra of the LLZO / xFe3O4 / SiO2@PVDF (x=0.1, 0.3, 0.5) synthesized in Examples 1, 3, and 5 of the present invention and the LLZO / SiO2@PVDF ceramic samples synthesized in Comparative Example 2.

[0025] Figure 5 The samples synthesized and assembled into button cells LFP / LLZO / xFe3O4 / SiO2@PVDF / Li (x=0.1, 0.3, 0.5) in Examples 1, 3, 5 of the present invention and Comparative Example 2, and their cycle performance at 0.1C. DETAILED DESCRIPTION

[0026] The present invention is further described below with reference to Examples and Comparative Examples. Embodiment 1:

[0027] 1) Surface modification of SiO2 particles: 2 g of commercially available SiO2 particles (particle size 15 nm) were dispersed in 20 mL of a mixed solution of ethanol and deionized water, wherein the volume ratio of ethanol to deionized water was 9:1. Ultrasonic treatment was used for about 30 min to ensure that the SiO2 particles were evenly dispersed to obtain a SiO2 particle solution. The SiO2 particle solution was mixed with 3 mL of a silane coupling agent, 3-aminopropyltriethoxysilane (APTES), and the reaction was carried out for 2 hours to modify the surface of the SiO2 particles. Finally, the excess silane coupling agent was removed by centrifugation and washed.

[0028] 2) Preparation of PVDF latex seed solution With water as the continuous phase, 0.18 g of surfactant sodium dodecyl sulfate, 0.12 g of initiator potassium persulfate and 10 g of polymerization monomer vinyl fluoride were added, the polymerization monomer vinyl fluoride was emulsified to form an oil / water emulsion, the temperature was raised to 60°C to initiate polymerization, nano-scale PVDF latex particles were formed, and a PVDF latex seed solution was prepared.

[0029] 3) Preparation of SiO2@PVDF core-shell composite particles The surface-modified SiO2 particles of step 1) are ultrasonically dispersed in the PVDF latex seed solution prepared in step 2), and the SiO2 particles are anchored on the surface of the PVDF latex particles by electrostatic adsorption to obtain seed particles. Subsequently, 5 g of the polymerization monomer vinyl fluoride is added, and the reaction temperature is controlled at 60°C to continue to initiate polymerization for 4 hours, so that the polymerization monomer vinyl fluoride grows on the surface of the seed particles to form SiO2@PVDF core-shell composite particles. After the reaction, 0.05 mL of the terminator carbon disulfide is added to terminate the polymerization reaction, and the unreacted polymerization monomer vinyl fluoride and the initiator potassium persulfate are removed by centrifugation. The obtained SiO2@PVDF core-shell composite particles are washed by centrifugation multiple times with deionized water and ethanol to remove residual reactants and surfactant sodium dodecyl sulfate. Finally, the washed SiO2@PVDF core-shell composite particles can be dried in a vacuum drying oven at 60°C for 12 hours to normal weight.

[0030] 4) Preparation of Fe3O4 / SiO2@PVDF 10g SiO2@PVDF core-shell composite particles were added to a three-necked flask and ultrasonically dispersed in 200 mL distilled water. The mixture was mechanically stirred and argon was introduced. Then, 3g anhydrous ferric chloride and 2g ferrous sulfate heptahydrate were added. Ammonia water was added dropwise to adjust the pH to alkaline (pH=8). The mixture was stirred for 2h for full reaction to obtain the product. The product was washed by centrifugation with ethanol and deionized water several times, and then freeze-dried in a freeze dryer at -50°C for about 24 hours to obtain the final product Fe3O4 / SiO2@PVDF.

[0031] 5) Modification of LLZO ceramic electrolyte The LLZO ceramic electrolyte sheet was pretreated by immersing it in a 20% by mass NaOH solution for 30 minutes, and then the NaOH solution on the surface of the LLZO ceramic electrolyte sheet was washed away with ethanol to obtain a pretreated LLZO ceramic electrolyte sheet; ethanol, water and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole were mixed in a volume ratio of V 乙醇 :V 水 :V DI =9:2.5:1 ratio solution was added to a two-necked flask to prepare a mixed solution; the pretreated LLZO ceramic electrolyte sheet was added to the mixed solution for ultrasonic dispersion for 30 minutes, and then refluxed in an oil bath at 75°C with a rotor added for stirring and a spherical condenser for reaction for 24 hours; The LLZO ceramic electrolyte sheet is prepared by the following method: a garnet-type LLZO electrolyte conductor material is prepared by a solid phase synthesis method (refer to the existing patent application CN113363562 A), and an LLZO ceramic sheet with a diameter of 10 mm and a thickness of 1 mm is prepared by pre-sintering and debinding, and finally sintering in a muffle furnace.

[0032] 6) Preparation of LLZO / Fe3O4 / SiO2@PVDF composite solid electrolyte materials 5 mL of N,N-dimethylamide, 1 g of matrix polyvinylidene fluoride and 0.1 g of Fe3O4 / SiO2@PVDF prepared in step 4) were placed in a glass reagent bottle, and a magnetic stirrer was added for 24 hours to mix and stir evenly. The mixture was then spread on the surface of the LLZO ceramic electrolyte sheet and baked in a vacuum oven at 80°C for 24 hours to obtain a LLZO / 0.1Fe3O4 / SiO2@PVDF composite solid electrolyte material. Embodiment 2:

[0033] 1) Surface modification of SiO2 particles: 3 g of commercially available SiO2 particles (particle size 15 nm) were dispersed in 20 mL of a mixed solution of ethanol and deionized water, wherein the volume ratio of ethanol to deionized water was 9:1, and ultrasonic treatment was performed for about 45 min to ensure that the SiO2 particles were evenly dispersed to obtain a SiO2 particle solution; the SiO2 particle solution was mixed with 4 mL of a silane coupling agent, 3-aminopropyltriethoxysilane (APTES), and the reaction was performed for 3 hours to modify the surface of the SiO2 particles. Finally, the excess silane coupling agent was removed by centrifugation and washed.

[0034] 2) Preparation of PVDF latex seed solution With water as the continuous phase, 0.24 g of surfactant sodium dodecyl sulfate, 0.15 g of initiator potassium persulfate and 12 g of polymerization monomer vinyl fluoride were added, the polymerization monomer vinyl fluoride was emulsified to form an oil / water emulsion, the temperature was raised to initiate polymerization, nano-scale PVDF latex particles were formed, and a PVDF latex seed solution was prepared.

[0035] 3) Preparation of SiO2@PVDF core-shell composite particles The surface-modified SiO2 particles in step 1) are ultrasonically dispersed in the PVDF latex seed solution obtained in step 2), and the SiO2 is anchored on the surface of the PVDF particles by electrostatic adsorption to obtain seed particles. Subsequently, 5 g of the polymerization monomer vinyl fluoride is added, and the reaction temperature is controlled at 80°C to continue initiating polymerization. During the polymerization process, the polymerization monomer vinyl fluoride molecules will combine with the seed particles in the emulsion. The polymerization reaction time is 5 hours, so that the polymerization monomer grows on the surface of the seed particles to form SiO2@PVDF core-shell composite particles. After the reaction is completed, 0.1 mL of the terminator carbon disulfide is added to terminate the polymerization reaction, and the unreacted polymerization monomer vinyl fluoride and initiator potassium persulfate are removed by centrifugation. The obtained SiO2@PVDF core-shell composite particles are washed by centrifugation multiple times with deionized water and ethanol to remove residual reactants and surfactant sodium dodecyl sulfate. Finally, the washed SiO2@PVDF core-shell composite particles can be dried in a vacuum drying oven at 60°C for 12 hours to normal weight.

[0036] 4) Preparation of Fe3O4 / SiO2@PVDF 10g SiO2@PVDF Janus core-shell composite particles were added to a three-necked flask and ultrasonically dispersed in 200 mL distilled water. The mixture was mechanically stirred and argon was introduced. Then, 3g anhydrous ferric chloride and 3g ferrous sulfate heptahydrate were added, and ammonia water was added dropwise to adjust the pH to alkaline (pH=8). The mixture was stirred for 2h for full reaction to obtain the product. The product was washed by centrifugation with ethanol and deionized water several times, and then freeze-dried in a freeze dryer at -50°C in a vacuum freeze dryer for about 24 hours to obtain the final product Fe3O4 / SiO2@PVDF.

[0037] 5) Modification of LLZO ceramic electrolyte The LLZO ceramic electrolyte sheet (same as in Example 1) was pretreated by immersing it in a 20% by mass NaOH solution for 30 minutes, and then the NaOH solution on the surface of the LLZO ceramic electrolyte sheet was washed away with ethanol to obtain a pretreated LLZO ceramic electrolyte sheet; ethanol, water and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole were mixed in a volume ratio of V 乙醇 :V 水 :V DI =9:2.5:1 ratio of the solution is added to a two-necked flask to prepare a mixed solution; the pretreated LLZO ceramic electrolyte sheet is added to the mixed solution for ultrasonic dispersion for 30 minutes, and then refluxed in an oil bath at 75 ° C with a rotor stirring and a spherical condenser for 24 hours.

[0038] 6) Preparation of LLZO / Fe3O4 / SiO2@PVDF composite solid electrolyte materials 7 mL of N,N-dimethylamide, 1.5 g of matrix polyvinylidene fluoride and 0.2 g of Fe3O4 / SiO2@PVDF prepared in step 4) were placed in a glass reagent bottle, and a magnetic stirrer was added for 24 hours to mix and stir evenly. The mixture was then spread on the surface of the LLZO ceramic electrolyte sheet and baked in a vacuum oven at 80°C for 24 hours to obtain a LLZO / 0.2Fe3O4 / SiO2@PVDF composite solid electrolyte material. Embodiment 3:

[0039] 1) Surface modification of SiO2 particles: 4 g of commercially available SiO2 particles (particle size 15 nm) were dispersed in 20 mL of a mixed solution of ethanol and deionized water, wherein the volume ratio of ethanol to deionized water was 9:1. Ultrasonic treatment was used for about 60 min to ensure that the SiO2 particles were evenly dispersed to obtain a SiO2 particle solution. The SiO2 particle solution was mixed with 5 mL of a silane coupling agent, 3-aminopropyltriethoxysilane (APTES), and the reaction was carried out for 3 hours to modify the surface of the SiO2 particles. Finally, the excess silane coupling agent was removed by centrifugation and washed.

[0040] 2) Preparation of PVDF latex seed solution With water as the continuous phase, 0.18 g of surfactant sodium dodecyl sulfate, 0.12 g of initiator potassium persulfate and 10 g of polymerization monomer vinyl fluoride were added, the polymerization monomer vinyl fluoride was emulsified to form an oil / water emulsion, the temperature was raised to initiate polymerization, nano-scale PVDF latex particles were formed, and a PVDF latex seed solution was prepared.

[0041] 3) Preparation of SiO2@PVDF core-shell composite particles The surface-modified SiO2 particles in step 1) are ultrasonically dispersed in the PVDF latex seed solution prepared in step 2), and the SiO2 is anchored on the surface of the PVDF particles by electrostatic adsorption to obtain seed particles. Subsequently, 5 g of the polymerization monomer vinyl fluoride is added, and the reaction temperature is controlled at 80°C to continue initiating polymerization. During the polymerization process, the polymerization monomer vinyl fluoride molecules will combine with the seed particles in the emulsion. The polymerization reaction time is 5 hours, so that the polymerization monomer grows on the surface of the seed particles to form SiO2@PVDF core-shell composite particles. After the reaction is completed, 0.15 mL of the terminator carbon disulfide is added to terminate the polymerization reaction, and the unreacted polymerization monomer vinyl fluoride and initiator potassium persulfate are removed by centrifugation. The obtained SiO2@PVDF core-shell composite particles are washed by centrifugation multiple times with deionized water and ethanol to remove residual reactants and surfactant sodium dodecyl sulfate. Finally, the washed SiO2@PVDF core-shell composite particles can be dried in a vacuum drying oven at 60°C for 12 hours to normal weight.

[0042] 4) Preparation of Fe3O4 / SiO2@PVDF 10g SiO2@PVDF core-shell composite particles were added to a three-necked flask and ultrasonically dispersed in 200 mL distilled water. The mixture was mechanically stirred and argon was introduced. Then, 5g anhydrous ferric chloride and 3g ferrous sulfate heptahydrate were added, and ammonia water was added dropwise to adjust the pH to alkaline (pH=8). The mixture was stirred for 2h for full reaction to obtain the product. The product was washed by centrifugation with ethanol and deionized water several times, and then freeze-dried in a freeze dryer at -50°C in a vacuum freeze dryer for about 24 hours to obtain the final product Fe3O4 / SiO2@PVDF.

[0043] 5) Modification of LLZO ceramic electrolyte The LLZO ceramic electrolyte sheet (same as in Example 1) was pretreated by immersing it in a 20% by mass NaOH solution for 30 minutes, and then the NaOH solution on the surface of the LLZO ceramic electrolyte sheet was washed away with ethanol to obtain a pretreated LLZO ceramic electrolyte sheet; ethanol, water and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole were mixed in a volume ratio of V 乙醇 :V 水 :V DI =9:2.5:1 ratio of the solution is added to a two-necked flask to prepare a mixed solution; the pretreated LLZO ceramic electrolyte sheet is added to the mixed solution for ultrasonic dispersion for 30 minutes, and then refluxed in an oil bath at 75 ° C with a rotor stirring and a spherical condenser for 24 hours.

[0044] 6) Preparation of LLZO / Fe3O4 / SiO2@PVDF composite solid electrolyte materials 7 mL of N,N-dimethylamide, 1.5 g of matrix polyvinylidene fluoride and 0.3 g of Fe3O4 / SiO2@PVDF prepared in step 4) were placed in a glass reagent bottle, and a magnetic stirrer was added for 24 hours to mix and stir evenly. The mixture was then spread on the surface of the LLZO ceramic electrolyte sheet and baked in a vacuum oven at 80°C for 24 hours to obtain a LLZO / 0.3Fe3O4 / SiO2@PVDF composite solid electrolyte material. Figure 2 and Figure 3 Microstructure and cross-sectional diagram of the LLZO / 0.3Fe3O4 / SiO2@PVDF sample synthesized in this example. Embodiment 4:

[0045] 1) Surface modification of SiO2 particles: 3 g of commercially available SiO2 particles (particle size 15 nm) were dispersed in 20 mL of a mixed solution of ethanol and deionized water, wherein the volume ratio of ethanol to deionized water was 9:1. Ultrasonic treatment was used for about 30 min to ensure that the SiO2 particles were evenly dispersed to obtain a SiO2 particle solution. The SiO2 particle solution was mixed with 4 mL of a silane coupling agent, 3-aminopropyltriethoxysilane (APTES), and the reaction was carried out for 3 hours to modify the surface of the SiO2 particles. Finally, the excess silane coupling agent was removed by centrifugation and washed.

[0046] 2) Preparation of PVDF latex seed solution With water as the continuous phase, 0.18 g of surfactant sodium dodecyl sulfate, 0.12 g of initiator potassium persulfate and 10 g of polymerization monomer vinyl fluoride were added, the polymerization monomer vinyl fluoride was emulsified to form an oil / water emulsion, the temperature was raised to initiate polymerization, nano-scale PVDF latex particles were formed, and a PVDF latex seed solution was prepared.

[0047] 3) Preparation of SiO2@PVDF core-shell composite particles The surface-modified SiO2 particles in step 1) are ultrasonically dispersed in the PVDF latex seed solution obtained in step 2), and the SiO2 is anchored on the surface of the PVDF particles by electrostatic adsorption to obtain seed particles. Subsequently, 5 g of the polymerization monomer vinyl fluoride is added, and the reaction temperature is controlled at 80°C to continue initiating polymerization. During the polymerization process, the polymerization monomer vinyl fluoride molecules will combine with the seed particles in the emulsion. The polymerization reaction time is 5 hours, so that the polymerization monomer grows on the surface of the seed particles to form SiO2@PVDF core-shell composite particles. After the reaction is completed, 0.1 mL of the terminator carbon disulfide is added to terminate the polymerization reaction, and the unreacted polymerization monomer vinyl fluoride and initiator potassium persulfate are removed by centrifugation. The obtained SiO2@PVDF core-shell composite particles are washed by centrifugation multiple times with deionized water and ethanol to remove residual reactants and surfactant sodium dodecyl sulfate. Finally, the washed SiO2@PVDF core-shell composite particles can be dried in a vacuum drying oven at 60°C for 12 hours to normal weight.

[0048] 4) Preparation of Fe3O4 / SiO2@PVDF 10 g SiO2@PVDF core-shell composite particles were added to a three-necked flask and ultrasonically dispersed in 200 mL distilled water. The mixture was mechanically stirred and argon was introduced. Then 4 g anhydrous ferric chloride and 2 g ferrous sulfate heptahydrate were added, and ammonia water was added dropwise to adjust the pH to alkaline (pH=8). The mixture was stirred for 2 h for full reaction to obtain the product. The product was washed by centrifugation with ethanol and deionized water several times, and then freeze-dried in a freeze dryer at -50 °C for about 24 hours to obtain the final product Fe3O4 / SiO2@PVDF.

[0049] 5) Modification of LLZO ceramic electrolyte The LLZO ceramic electrolyte sheet (same as in Example 1) was pretreated by immersing it in a 20% by mass NaOH solution for 30 minutes, and then the NaOH solution on the surface of the LLZO ceramic electrolyte sheet was washed away with ethanol to obtain a pretreated LLZO ceramic electrolyte sheet; ethanol, water and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole were mixed in a volume ratio of V 乙醇 :V 水 :V DI =9:2.5:1 ratio of the solution was added to a two-necked flask to prepare a mixed solution; the pretreated LLZO ceramic electrolyte sheet was added to the mixed solution for ultrasonic dispersion for 60 minutes, and then refluxed in an oil bath at 75 ° C with a rotor stirring and a spherical condenser for 24 hours.

[0050] 6) Preparation of LLZO / Fe3O4 / SiO2@PVDF composite solid electrolyte materials 7 mL of N,N-dimethylamide, 1.4 g of matrix polyvinylidene fluoride and 0.4 g of Fe3O4 / SiO2@PVDF prepared in step 4) were placed in a glass reagent bottle, stirred with a magnetic stirrer for 24 hours, mixed and stirred evenly, and then spread on the surface of the LLZO ceramic electrolyte sheet and baked in a vacuum oven at 80°C for 24 hours to obtain LLZO / 0.4Fe3O4 / SiO2@PVDF composite solid electrolyte material. Embodiment 5:

[0051] 1) Surface modification of SiO2 particles: 4 g of commercially available SiO2 particles (particle size 15 nm) were dispersed in 20 mL of a mixed solution of ethanol and deionized water, wherein the volume ratio of ethanol to deionized water was 9:1. Ultrasonic treatment was used for about 30 min to ensure that the SiO2 particles were evenly dispersed to obtain a SiO2 particle solution. The SiO2 particle solution was mixed with 5 mL of a silane coupling agent, 3-aminopropyltriethoxysilane (APTES), and the reaction was carried out for 3 hours to modify the surface of the SiO2 particles. Finally, the excess silane coupling agent was removed by centrifugation and washed.

[0052] 2) Preparation of PVDF latex seed solution With water as the continuous phase, 0.3 g of surfactant sodium dodecyl sulfate, 0.28 g of initiator potassium persulfate and 14 g of polymerization monomer vinyl fluoride were added, the polymerization monomer vinyl fluoride was emulsified to form an oil / water emulsion, the temperature was raised to initiate polymerization, nano-scale PVDF latex particles were formed, and a PVDF latex seed solution was prepared.

[0053] 3) Preparation of SiO2@PVDF core-shell composite particles The surface-modified SiO2 particles in step 1) are ultrasonically dispersed in the PVDF latex seed solution obtained in step 2), and the SiO2 is anchored on the surface of the PVDF particles by electrostatic adsorption to obtain seed particles. Subsequently, 5 g of the polymerization monomer vinyl fluoride is added, and the reaction temperature is controlled at 80°C to continue initiating polymerization. During the polymerization process, the polymerization monomer vinyl fluoride molecules will combine with the seed particles in the emulsion. The polymerization reaction time is 5 hours, so that the polymerization monomer grows on the surface of the seed particles to form SiO2@PVDF core-shell composite particles. After the reaction is completed, 0.15 mL of the terminator carbon disulfide is added to terminate the polymerization reaction, and the unreacted polymerization monomer vinyl fluoride and initiator potassium persulfate are removed by centrifugation. The obtained SiO2@PVDF core-shell composite particles are washed by centrifugation multiple times with deionized water and ethanol to remove residual reactants and surfactant sodium dodecyl sulfate. Finally, the washed SiO2@PVDF core-shell composite particles can be dried in a vacuum drying oven at 60°C for 12 hours to normal weight.

[0054] 4) Preparation of Fe3O4 / SiO2@PVDF 10g SiO2@PVDF core-shell composite particles were added to a three-necked flask and ultrasonically dispersed in 200mL distilled water. The mixture was mechanically stirred and argon was introduced. Then, 5g anhydrous ferric chloride and 2g ferrous sulfate heptahydrate were added. Ammonia water was added dropwise to adjust the pH to alkaline (pH=8). The mixture was stirred for 2h for full reaction to obtain the product. The product was washed by centrifugation with ethanol and deionized water several times, and then freeze-dried in a freeze dryer at -50°C for about 24 hours to obtain the final product Fe3O4 / SiO2@PVDF.

[0055] 5) Modification of LLZO ceramic electrolyte The LLZO ceramic electrolyte sheet (same as in Example 1) was pretreated by immersing it in a 20% by mass NaOH solution for 30 minutes, and then the NaOH solution on the surface of the LLZO ceramic electrolyte sheet was washed away with ethanol to obtain a pretreated LLZO ceramic electrolyte sheet; ethanol, water and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole were mixed in a volume ratio of V 乙醇 :V 水 :V DI =9:2.5:1 ratio of the solution was added to a two-necked flask to prepare a mixed solution; the pretreated LLZO ceramic electrolyte sheet was added to the mixed solution for ultrasonic dispersion for 40 minutes, and then refluxed in an oil bath at 75 ° C with a rotor stirring and a spherical condenser for 24 hours.

[0056] 6) Preparation of LLZO / Fe3O4 / SiO2@PVDF composite solid electrolyte materials 8 mL of N,N-dimethylamide, 1.6 g of matrix polyvinylidene fluoride and 0.5 g of Fe3O4 / SiO2@PVDF prepared in step 4) were placed in a glass reagent bottle, and a magnetic stirrer was added for 24 hours to mix and stir evenly. The mixture was then spread on the surface of the LLZO ceramic electrolyte sheet and baked in a vacuum oven at 80°C for 24 hours to obtain a LLZO / 0.5Fe3O4 / SiO2@PVDF composite solid electrolyte material. Embodiment 6:

[0057] 1) Surface modification of SiO2 particles: 2 g of commercially available SiO2 particles (particle size 15 nm) were dispersed in 20 mL of a mixed solution of ethanol and deionized water, wherein the volume ratio of ethanol to deionized water was 9:1. Ultrasonic treatment was used for about 50 min to ensure that the SiO2 particles were evenly dispersed to obtain a SiO2 particle solution. The SiO2 particle solution was mixed with 3 mL of a silane coupling agent, 3-aminopropyltriethoxysilane (APTES), and the reaction was carried out for 2.5 hours to modify the surface of the SiO2 particles. Finally, the excess silane coupling agent was removed by centrifugation and washed.

[0058] 2) Preparation of PVDF latex seed solution With water as the continuous phase, 0.24 g of surfactant sodium dodecyl sulfate, 0.15 g of initiator potassium persulfate and 12 g of polymerization monomer vinyl fluoride were added, the polymerization monomer vinyl fluoride was emulsified to form an oil / water emulsion, the temperature was raised to initiate polymerization, nano-scale PVDF latex particles were formed, and a PVDF latex seed solution was prepared.

[0059] 3) Preparation of SiO2@PVDF core-shell composite particles The surface-modified SiO2 particles in step 1) are ultrasonically dispersed in the PVDF latex seed solution obtained in step 2), and the SiO2 is anchored on the surface of the PVDF particles by electrostatic adsorption to obtain seed particles. Subsequently, 5 g of the polymerization monomer vinyl fluoride is added, and the reaction temperature is controlled at 80°C to continue initiating polymerization. During the polymerization process, the polymerization monomer vinyl fluoride molecules will combine with the seed particles in the emulsion. The polymerization reaction time is 5 hours, so that the polymerization monomer grows on the surface of the seed particles to form SiO2@PVDF core-shell composite particles. After the reaction is completed, 0.05 mL of the terminator carbon disulfide is added to terminate the polymerization reaction, and the unreacted polymerization monomer vinyl fluoride, solvent and initiator potassium persulfate are removed by centrifugation. The obtained SiO2@PVDF core-shell composite particles are washed by centrifugation multiple times with deionized water and ethanol to remove residual reactants and surfactant sodium dodecyl sulfate. Finally, the washed SiO2@PVDF core-shell composite particles can be dried in a vacuum drying oven at 60°C for 12 hours to normal weight.

[0060] 4) Preparation of Fe3O4 / SiO2@PVDF 10 g of SiO2@PVDF core-shell composite particles were added to a three-necked flask and ultrasonically dispersed in 200 mL of distilled water. The mixture was mechanically stirred and argon was introduced. Then, 4 g of anhydrous ferric chloride and 3 g of ferrous sulfate heptahydrate were added, and ammonia water was added dropwise to adjust the pH to alkaline (pH=8). The mixture was stirred for 2 h for full reaction to obtain the product. The product was washed by centrifugation with ethanol and deionized water several times, and then freeze-dried in a freeze dryer at -50 °C in a vacuum freeze dryer for about 24 hours to obtain the final product Fe3O4 / SiO2@PVDF.

[0061] 5) Modification of LLZO ceramic electrolyte The LLZO ceramic electrolyte sheet (same as in Example 1) was pretreated by immersing it in a 20% by mass NaOH solution for 30 minutes, and then the NaOH solution on the surface of the LLZO ceramic electrolyte sheet was washed away with ethanol to obtain a pretreated LLZO ceramic electrolyte sheet; ethanol, water and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole were mixed in a volume ratio of V 乙醇 :V 水 :V DI=9:2.5:1 ratio of the solution was added to a two-necked flask to prepare a mixed solution; the pretreated LLZO ceramic electrolyte sheet was added to the mixed solution for ultrasonic dispersion for 45 minutes, and then refluxed in an oil bath at 75 ° C with a rotor stirring and a spherical condenser for 24 hours.

[0062] 6) Preparation of LLZO / Fe3O4 / SiO2@PVDF composite solid electrolyte materials Place 7 mL of N,N-dimethylamide, 1.4 g of matrix polyvinylidene fluoride and 0.25 g of Fe3O4 / SiO2@PVDF prepared in step 4) in a glass reagent bottle, add a magnetic stirrer for 24 hours, mix and stir evenly, then spread on the surface of the LLZO ceramic electrolyte sheet and bake in a vacuum oven at 80°C for 24 hours to obtain LLZO / 0.25Fe3O4 / SiO2@PVDF composite solid electrolyte material. Embodiment 7:

[0063] 1) Surface modification of SiO2 particles: 2 g of commercially available SiO2 particles (particle size 15 nm) were dispersed in 20 mL of a mixed solution of ethanol and deionized water, wherein the volume ratio of ethanol to deionized water was 9:1, and ultrasonic treatment was performed for about 50 min to ensure that the SiO2 particles were evenly dispersed to obtain a SiO2 particle solution; the SiO2 particle solution was mixed with 3 mL of a silane coupling agent 3-aminopropyltriethoxysilane (APTES), and the reaction was performed for 2.5 hours to modify the surface of the SiO2 particles. Finally, the excess silane coupling agent was removed by centrifugation and washed.

[0064] 2) Preparation of PVDF latex seed solution With water as the continuous phase, 0.18 g of surfactant sodium dodecyl sulfate, 0.12 g of initiator potassium persulfate and 10 g of polymerization monomer vinyl fluoride were added, the polymerization monomer vinyl fluoride was emulsified to form an oil / water emulsion, the temperature was raised to initiate polymerization, nano-scale PVDF latex particles were formed, and a PVDF latex seed solution was prepared.

[0065] 3) Preparation of SiO2@PVDF core-shell composite particles The surface-modified SiO2 particles in step 1) are ultrasonically dispersed in the PVDF latex seed solution obtained in step 2), and the SiO2 is anchored on the surface of the PVDF particles by electrostatic adsorption to obtain seed particles. Subsequently, 5 g of the polymerization monomer vinyl fluoride is added, and the reaction temperature is controlled at 60°C to continue initiating polymerization. During the polymerization process, the polymerization monomer vinyl fluoride molecules will combine with the seed particles in the emulsion. The polymerization reaction time is 5 hours, so that the polymerization monomer grows on the surface of the seed particles to form SiO2@PVDF core-shell composite particles. After the reaction is completed, 0.05 mL of the terminator carbon disulfide is added to terminate the polymerization reaction, and the unreacted polymerization monomer vinyl fluoride and the initiator potassium persulfate are removed by centrifugation. The obtained SiO2@PVDF core-shell composite particles are washed by centrifugation multiple times with deionized water and ethanol to remove residual reactants and surfactant sodium dodecyl sulfate. Finally, the washed SiO2@PVDF core-shell composite particles can be dried in a vacuum drying oven at 60°C for 12 hours to normal weight.

[0066] 4) Preparation of Fe3O4 / SiO2@PVDF 10g SiO2@PVDF core-shell composite particles were added to a three-necked flask and ultrasonically dispersed in 200mL distilled water. The mixture was mechanically stirred and argon was introduced. Then, 3g anhydrous ferric chloride and 2g ferrous sulfate heptahydrate were added. Ammonia water was added dropwise to adjust the pH to alkaline (pH=8). The mixture was stirred for 2h for full reaction to obtain the product. The product was washed by centrifugation with ethanol and deionized water several times, and then freeze-dried in a freeze dryer at -50°C for about 24 hours to obtain the final product Fe3O4 / SiO2@PVDF.

[0067] 5) Modification of LLZO ceramic electrolyte The LLZO ceramic electrolyte sheet (same as in Example 1) was pretreated by immersing it in a 20% by mass NaOH solution for 30 minutes, and then the NaOH solution on the surface of the LLZO ceramic electrolyte sheet was washed away with ethanol to obtain a pretreated LLZO ceramic electrolyte sheet; ethanol, water and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole were mixed in a volume ratio of V 乙醇 :V 水 :V DI =9:2.5:1 ratio of the solution was added to a two-necked flask to prepare a mixed solution; the pretreated LLZO ceramic electrolyte sheet was added to the mixed solution for ultrasonic dispersion for 60 minutes, and then refluxed in an oil bath at 75 ° C with a rotor stirring and a spherical condenser for 24 hours.

[0068] 6) Preparation of LLZO / Fe3O4 / SiO2@PVDF composite solid electrolyte materials Place 5 mL of N,N-dimethylamide, 1 g of matrix polyvinylidene fluoride and 0.35 g of Fe3O4 / SiO2@PVDF prepared in step 4) in a glass reagent bottle, add a magnetic stirrer for 24 hours, mix and stir evenly, then spread on the surface of the LLZO ceramic electrolyte sheet and bake in a vacuum oven at 80°C for 24 hours to obtain LLZO / 0.35Fe3O4 / SiO2@PVDF composite solid electrolyte material.

[0069] Comparative Example 1:

[0070] In step (5) of modifying the LLZO ceramic electrolyte sheet, DI modification is not performed, and the rest is the same as in Example 3.

[0071] Comparative Example 2:

[0072] Step (4) of the preparation of Fe3O4 / SiO2@PVDF was omitted, and the rest was the same as in Example 3.

[0073] Comparative Example 3:

[0074] Step (4) preparation of Fe3O4 / SiO2@PVDF was omitted, and in step (5) modification of LLZO ceramic electrolyte sheet, DI modification was not performed. The rest was the same as in Example 3.

[0075] Comparative Example 4:

[0076] In step (2) of preparing the latex seed solution, PEO is selected to replace PVDF, and the rest is the same as in Example 3.

[0077] The preparation process of the latex seed solution is as follows: 10 mg of PEO-based copolymer (PEO-PLA) is dissolved in 2 mL of organic solvent THF, 20 mL of deionized water is measured, poured into a 50 mL beaker, pre-stirred (500 rpm), 2 mL of copolymer / THF solution is slowly added to the aqueous phase at a rate of 1 mL / min using a syringe, and stirred (1000 rpm) for 2 hours to evaporate THF. The solution is transferred to a dialysis bag (MWCO 3.5 kDa), dialyzed against deionized water for 24 hours (changing the water 3-4 times) to remove residual solvents and free molecules, and finally centrifuged to obtain a PEO latex seed solution.

[0078] The room temperature conductivity of each component sample of LLZO / xFe3O4 / SiO2@PVDF (0<x≤0.5) composite solid electrolyte material was determined by Archimedes drainage method and the calculation formula of ionic conductivity σ=L / RS, where L represents the thickness of the sample and S represents the area of ​​the electrode, and is shown in Tables 1 and 2.

[0079] Table 1 shows the shrinkage, density and conductivity of LLZO / xFe3O4 / SiO2@PVDF (0<x≤0.5) system at 30℃

[0080] Table 2 shows the shrinkage, density and conductivity of LLZO / xFe3O4 / SiO2@PVDF (x=0, 0.3) system at 30℃

[0081] As shown in Table 1, with the increase of the content of Fe3O4 / SiO2@PVDF modified LLZO ceramic electrolyte, the density, shrinkage and conductivity of LLZO / xFe3O4 / SiO2@PVDF (0<x≤0.5) composite solid electrolyte materials gradually increase, among which the density, shrinkage and ionic conductivity of LLZO / 0.3Fe3O4 / SiO2@PVDF reach the highest, which are 96%, 9.7% and 5.09×10 -4 S / cm, while excessive Fe3O4 particles will aggregate on the surface or inside of LLZO to form a discontinuous particle layer, which will hinder the transmission path of lithium ions in LLZO, increase the resistance to ion migration, and thus reduce the ionic conductivity. Figure 1 The paper describes how the imidazole group of LLZO-DI coordinates with the Janus material, thereby achieving the interface bonding between the electrode and the composite electrolyte. The improved LLZO / Janus / PVDF interface can ensure fast Li + The formation of conductive tunnels provides a new approach for the design of new all-solid composite electrolytes.

[0082] As shown in Table 2, when the composite electrolyte was not modified by DI in the operation of Comparative Example 1, good physical and electrochemical properties were not exhibited. This is because the imidazole group in LLZO-DI is missing, which will coordinate with the Janus material, so as to achieve the interface bonding between the electrode and the composite electrolyte and achieve the purpose of modifying the interface. In Comparative Examples 2 and 3, Fe3O4 nanoparticles are missing, resulting in poor electrochemical performance. Fe3O4 nanoparticles can improve the ionic conductivity of the interface and reduce the interface impedance by improving the interface compatibility. In Comparative Example 4, PEO was used instead of PVDF, but it did not show good performance because PEO's rigidity and flexibility are not as good as PVDF, and the ionic conductivity of PEO depends on temperature. PEO is easily oxidized and decomposed under high voltage (>4V), which limits its application in high energy density batteries. Figure 4The AC impedance spectra of the LLZO / xFe3O4 / SiO2@PVDF (x=0.1, 0.3, 0.5) synthesized in Examples 1, 3, and 5 of the present invention and the LLZO / SiO2@PVDF ceramic samples synthesized in Comparative Example 2. Figure 5 The samples synthesized and assembled into button cells LFP / LLZO / xFe3O4 / SiO2@PVDF / Li (x=0.1, 0.3, 0.5) in Examples 1, 3, 5 of the present invention and Comparative Example 2, and their cycle performance at 0.1C.

Claims

1. A method for preparing a composite solid electrolyte with a root-soil interlocking structure based on Janus particles, characterized in that: The preparation steps include: 1) Surface modification of SiO2 particles Dispersing SiO2 particles in a mixed solution of ethanol and deionized water, using ultrasonic treatment to make the SiO2 particles uniformly dispersed, and preparing a SiO2 particle solution; mixing the SiO2 particle solution with a coupling agent, 3-aminopropyltriethoxysilane, and centrifuging and washing after the reaction is completed; 2) Preparation of PVDF latex seed solution Using water as a continuous phase, adding a surfactant, sodium dodecyl sulfate, an initiator, potassium persulfate, and a polymerizable monomer, vinyl fluoride, to emulsify the polymerizable monomer, vinyl fluoride, to form an oil / water emulsion, and heating to initiate polymerization to form nano-scale PVDF latex particles, thereby obtaining a PVDF latex seed solution; 3) Preparation of SiO2@PVDF core-shell composite particles The surface-modified SiO2 particles in step 1) are ultrasonically dispersed in the PVDF latex seed solution obtained in step 2), and the SiO2 particles are anchored on the surface of the PVDF latex particles by electrostatic adsorption to obtain seed particles, and then the polymerization monomer vinyl fluoride is continuously added, and the reaction temperature is controlled to continue to initiate polymerization, so that the polymerization monomer vinyl fluoride grows on the surface of the seed particles to form SiO2@PVDF core-shell composite particles. After the reaction is completed, the terminator carbon disulfide is added to terminate the polymerization reaction, and the obtained SiO2@PVDF core-shell composite particles are washed by centrifugation with deionized water and ethanol, and finally the SiO2@PVDF core-shell composite particles are obtained after vacuum drying; 4) Preparation of Fe3O4 / SiO2@PVDF The SiO2@PVDF core-shell composite particles prepared in step 3) are ultrasonically dispersed in distilled water, mechanically stirred and introduced with argon, and then anhydrous ferric chloride and ferrous sulfate heptahydrate are added, and ammonia water is added dropwise to adjust the pH to alkaline, and stirred for sufficient reaction; the product is centrifugally washed with ethanol and deionized water, and then vacuum freeze-dried with a freeze dryer to obtain the final product Fe3O4 / SiO2@PVDF; 5) Modification of LLZO ceramic electrolyte The LLZO ceramic electrolytic sheet is immersed in a NaOH solution for pretreatment, and then the NaOH solution on the surface of the LLZO ceramic electrolytic sheet is washed away with ethanol to obtain a pretreated LLZO ceramic electrolytic sheet; ethanol, water and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole are mixed in proportion to obtain a mixed solution; the pretreated LLZO ceramic electrolytic sheet is added into the mixed solution for ultrasonic dispersion, and then a condensation reflux reaction is performed; 6) Preparation of LLZO / Fe3O4 / SiO2@PVDF composite solid electrolyte materials N,N-dimethylamide, matrix polyvinylidene fluoride and Fe3O4 / SiO2@PVDF prepared in step 4) are mixed and stirred evenly, then spread on the surface of the LLZO ceramic electrolyte sheet and baked in a vacuum oven to obtain LLZO / Fe3O4 / SiO2@PVDF composite solid electrolyte material, that is, a composite solid electrolyte with a root-soil interlocking structure constructed based on Janus particles.

2. The preparation method according to claim 1, characterized in that: The particle size of the SiO2 particles in step 1) is 15 nm, the mass volume ratio of the SiO2 particles to the mixed solution is (1-2) g:10 mL, the mixed solution is prepared by ethanol and deionized water in a volume ratio of 9:1, and the ultrasonic treatment time is 30-60 min; the mass volume ratio of the SiO2 particle solution to the coupling agent 3-aminopropyltriethoxysilane is 20:(3-5).

3. The preparation method according to claim 1, characterized in that: The mass ratio of the surfactant sodium dodecyl sulfate to the polymerized monomer vinyl fluoride in step 2) is (0.18-0.3):(10-14); the mass ratio of the initiator potassium persulfate to the polymerized monomer vinyl fluoride is (0.12-0.28):(10-14).

4. The preparation method according to claim 1, characterized in that: In step 3), the mass volume ratio of the polymerized monomer vinyl fluoride to the terminator carbon disulfide is 1 g: (0.01-0.03) mL, and the reaction temperature for initiating the polymerization is controlled at 60°C-80°C.

5. The preparation method according to claim 1, characterized in that: In step 4), the mass volume ratio of the SiO2@PVDF core-shell composite particles to distilled water is 1 g:20 mL, and the mass ratio of the SiO2@PVDF core-shell composite particles to anhydrous ferric chloride and ferrous sulfate heptahydrate is 10:(3-5):(2-3).

6. The preparation method according to claim 1, characterized in that: The volume ratio of ethanol, water and N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole in step 5) is 9:2.5:

1.

7. The preparation method according to claim 6, characterized in that: The LLZO ceramic electrolyte sheet pretreated in step 5) is added to the mixed solution for ultrasonic dispersion for 30-60 minutes, and then refluxed in an oil bath at 75°C with a rotor for stirring and a spherical condenser for reaction for 24 hours.

8. The preparation method according to claim 1, characterized in that: The volume mass ratio of N,N-dimethylamide, polyvinylidene fluoride and Fe3O4 / SiO2@PVDF in step 6) is (5-8) mL: (1-1.6) g: (0.1-0.5) g.

9. The preparation method according to claim 8, characterized in that: In step 6), the temperature of the vacuum oven is 80° C. and the baking time is 24 h.

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