A method for preparing a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery

Abstract

The present invention belongs to the technical field of lithium battery materials, and specifically relates to a method for preparing a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery, the preparation method comprising preparing a composite solid electrolyte membrane and assembling a battery. The present invention uses polyvinylidene fluoride-hexafluoropropylene, a lithium salt, and nitrogen-methyl pyrrolidone as raw materials, adds a plasticizer and dendritic mesoporous nano-silica to prepare a composite solid electrolyte membrane, provides more conductive channels for the migration of lithium ions, and increases the capacitance of the electrolyte; the present invention improves the interface compatibility between PVDF-HFP and dendritic mesoporous nano-silica, improves electrochemical performance, reduces PVDF-HFP crystallinity, and avoids short circuits and explosions caused by dendrites piercing the diaphragm; the present invention solves the safety hazards brought by traditional liquid electrolytes, such as leakage, combustion, and explosion, and has a simple preparation method, low cost, and is suitable for industrial large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery materials, and in particular relates to a method for preparing a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery. Background Art

[0002] As the world faces the dual challenges of energy depletion and environmental crisis, optimizing the energy structure and exploring emerging renewable energy sources have become urgent tasks. Lithium-ion batteries, with their excellent energy density, long cycle life, and high discharge voltage, are leading the innovation trend in the new energy field. Currently, organic liquid electrolytes are commonly used in lithium-ion batteries. These electrolytes can effectively wet the electrodes and provide high ion transfer efficiency. However, lithium-ion batteries using liquid electrolytes face multiple potential safety risks such as electrolyte leakage, volatilization, fire, and even explosion. In contrast, solid-state lithium batteries exhibit excellent safety performance due to their solid-state electrolytes. Polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), as a material with high mechanical strength and good electrochemical stability, has become an ideal material for solid-state electrolyte membranes.

[0003] The mechanical properties of PVDF-HFP-based polymer electrolyte membranes rarely surpass those of separators, and manufacturing large-area polymer-based electrolyte membranes free of defects (such as voids) is also extremely difficult. These defects can lead to problems such as internal short circuits in the battery. High-rate charge-discharge performance and low-temperature performance are also poor. The room-temperature ionic conductivity of the electrolyte is several or even dozens of times lower than that of liquid electrolytes. Furthermore, poor interfacial compatibility between the electrolyte and the electrodes is a direct contributor to the battery's poor high-rate charge-discharge and low-temperature performance. Therefore, there is an urgent need to develop a solid-state lithium battery that addresses these issues. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a polyvinylidene fluoride-hexafluoropropylene based solid-state lithium battery.

[0005] The purpose of the present invention is achieved by the following technical solution: a method for preparing a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery, which comprises the following steps:

[0006] S1. Preparation of composite solid electrolyte membrane:

[0007] Polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), a plasticizer, and a lithium salt are mixed, and then nitrogen-methyl pyrrolidone (NMP) is added. The mixture is stirred at a temperature of 40 to 70°C for 10 to 14 hours until the polymer is fully dissolved. Then, a dendritic mesoporous nano-silica solution is added and mixed evenly. The resulting slurry is coated, dried, and cut into pieces to prepare a PVDF-HFP / dendritic mesoporous nano-silica composite solid electrolyte membrane (PHS); wherein the coating thickness is preferably 40 to 1000 μm;

[0008] Wherein, the preparation method of the dendritic mesoporous nano-silica is:

[0009] (1) Preparation of organosilicon nanoparticles: Ammonia water and template are dissolved in a mixed solution of ethanol and deionized water at room temperature to obtain an ammonia precursor solution, and stirred at a temperature of 30-60°C for 0.5-4 hours; the organosilicon source is added twice while maintaining the temperature, and stirring is continued for 1-48 hours each time after addition. After stirring, the mixture is centrifuged to obtain the product benzene-bridged organosilicon nanoparticles;

[0010] (2) Hydrothermal reaction: The benzene-bridged organosilicon nanoparticles are dispersed in water, and the dispersion is placed in a polytetrafluoroethylene-lined hydrothermal reactor for reaction at a temperature of 100 to 180°C for 1 to 5 hours. The reaction product is post-treated to obtain dendritic mesoporous nano-silica.

[0011] S2. Assembling a battery: Assembling the composite solid electrolyte membrane prepared in step S1 into a lithium-ion battery to produce a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery.

[0012] As a preferred technical solution, the plasticizer is at least one of malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile or sebacononitrile.

[0013] As a preferred technical solution, the lithium salt is any one of LiPF6, LiTFSI, LiFSI, LiBOB, LiDFOB, LiBF4, LiClO4 or LiAsF6.

[0014] As a preferred technical solution, the weight ratio of the polyvinylidene fluoride hexafluoropropylene, plasticizer, lithium salt and nitrogen-methyl pyrrolidone is 1-15:1:2.5-20:15-50; the amount of dendritic mesoporous nano-silica added is 0.1-8.0% of the total weight of the solute;

[0015] As a preferred technical solution, the template in step (1) is at least one of cetyltrimethylammonium bromide, sodium lauryl sulfate, cetyltrimethylammonium bromide chloride, polyethylene glycol, polyoxyethylene ether, carbon nanotubes, carbon spheres or polystyrene-b-polyoxyethylene; the organosilicon source is one or two of methoxytrimethylsilane, trimethylsilane, chloromethyltrimethylsilane, triethoxysilylethylene, dimethyloxysilane, silane coupling agent, organosilicon resin, tetraethyl orthosilicate, 1,4-bis(triethoxysilyl)benzene or bistrimethylsilane.

[0016] More preferably, the mass volume ratio of the template to ammonia water is 0.1-2.5 g:0.1-10 mL, the volume ratio of ammonia water, ethanol and deionized water is 1:10-60:15-150, and the volume ratio of ammonia water to the organosilicon source is 1:0.1-2.5; the mass volume ratio of the benzene-bridged organosilicon nanoparticles to water is 0.1-1 mg:1-10 mL.

[0017] As a preferred technical solution, the specific operation of the post-treatment in step (2) is: cooling the reaction product for 24 hours, then washing it with ultrasonic water and ethanol, centrifuging the mixed solution by centrifuge, and dispersing the centrifuged product in a mixed solution of ethanol and hydrochloric acid, wherein the volume ratio of ethanol to hydrochloric acid is 1-50 mL:1-20 μl, stirring at 20-80 ° C and 100-1000 rpm for 1-24 hours, repeating 1-5 times, and then ultrasonically washing it with water, and freeze-drying it in a freeze dryer to obtain dendritic mesoporous nano-silica.

[0018] As a preferred technical solution, the positive electrode sheet of the lithium-ion battery described in step S2 is prepared by the following method: polyvinylidene fluoride and a plasticizer are added to nitrogen-methyl pyrrolidone and stirred overnight to obtain a transparent solution, and lithium iron phosphate and acetylene black are ground and mixed evenly in a grinding mortar, and then the transparent liquid is added to the grinding mortar and continued to grind until the slurry becomes black, shiny and viscous. The ground slurry is coated on aluminum foil, placed in a drying oven at 40-80°C and dried for 10-48 hours, and cut into discs with a cutting machine.

[0019] As a preferred technical solution, the plasticizer is at least one of malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile or sebacate; the weight ratio of the lithium iron phosphate, polyvinylidene fluoride, acetylene black and plasticizer is 7-10:0.1-2:0.1-2:0.1-2; the mass ratio of nitrogen-methyl pyrrolidone to lithium iron phosphate is 1-12 mL:1-5 g.

[0020] As a preferred technical solution, the lithium-ion battery in step S2 is assembled in the order of positive electrode shell, positive electrode sheet, solid electrolyte membrane, negative electrode, stainless steel sheet, spring, and negative electrode shell. The assembled battery is placed on a battery sealing machine and pressurized to 450-650 kg·cm -2 .

[0021] In the present invention, a metal lithium sheet with a diameter of 15.6 mm and a thickness of 0.6 mm is selected as the negative electrode, and the metal lithium sheet is passivated. The passivation treatment can be: dripping a dimethyl sulfoxide solution of phytic acid onto the metal lithium sheet for reaction, then washing with tetrahydrofuran (THF) and drying; or evenly dripping a polydiallyldimethylammonium-bis(trifluoromethanesulfonimide) solution on the surface of the metal lithium sheet and then drying; or soaking the metal lithium sheet in fluoroethylene carbonate.

[0022] In the present invention:

[0023] 1. Using PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene) as the solid electrolyte substrate has the following advantages:

[0024] (1) Long cycle life and strong stability: Compared with liquid electrolytes, solid electrolytes have more stable interactions with electrode materials and better stability to lithium. Fluorine has a high electronegativity, so introducing fluorinated groups into polymers can improve the electrochemical window of polymer solid electrolytes. Fluorine can react with lithium ions in the electrolyte to generate LiF, thereby forming a SEI passivation layer and promoting the uniform transmission and deposition of lithium ions, thereby improving the cycle stability of the battery. In addition, HFP, as an ion conductive plasticizer, can be copolymerized with PVDF to increase the amorphous phase region of the polymer and improve the ionic conductivity.

[0025] (2) Good conductivity and high energy density: PVDF has a high dielectric constant and a strong polar group (-CF-) that promotes the dissolution of lithium salts, thereby forming a high concentration of carriers, so it has a strong affinity for the electrolyte; a larger lithium ion migration number is beneficial to reduce the polarization phenomenon caused by concentration differences during charging and discharging, thereby making the battery have a higher energy density.

[0026] (3) Reduce the growth of lithium dendrites and have high safety: PVDF-HFP has a unique pore structure that can provide additional Li ＋ migration path and can promote the Li ＋ The uniform deposition of lithium ions reduces the excessive growth of lithium dendrites and avoids safety issues such as combustion and explosion caused by contact between the positive and negative electrodes of the battery.

[0027] (4) Low cost: PVDF has excellent flexibility and is easy to process and shape. It can be applied to batteries of various shapes. The processing technology is simple and easy to achieve large-scale production.

[0028] 2. Using dendritic mesoporous nano-silica as filler has the following advantages:

[0029] Nano-silica is categorized into solid silica, mesoporous silica, hollow mesoporous silica, and dendritic mesoporous silica. Dendritic mesoporous silica is a material with a unique three-dimensional, radially oriented pore structure and a hierarchical pore structure, resulting in a large specific surface area, large pore volume, and a narrow pore size distribution. Hollow mesoporous silica nanoparticles, on the other hand, have a simple core-shell structure, with a hollow core and a mesoporous shell. This differs from the dendritic structure of mesoporous silica, which consists of a mesoporous inner layer and a dendritic outer layer.

[0030] In the present invention, the mechanism of action of dendritic mesoporous silica is as follows: plasticizers can reduce the crystallinity of PVDF-HFP, increase the flexibility of the molecular chains, establish a three-dimensional network structure, and improve lithium ion conductivity, but this will reduce the mechanical properties of PVDF-HFP. On this basis, we add dendritic mesoporous silica to significantly improve the mechanical properties of PVDF-HFP. The uniform dispersion of dendritic mesoporous silica can break up the agglomerated and entangled PVDF-HFP molecular chains, further reduce their crystallinity, and improve the flexibility of the molecular chains. The diameter of a lithium ion is about 0.1 nanometer, and the size of dendritic mesoporous silica is about 200 nanometers. Its developed three-dimensional center-radial pores and multi-level pore structure provide more channels for the transmission of lithium ions. The rich Lewis acid centers of dendritic mesoporous silica can effectively fix bis(fluorosulfonyl)imide anions (TFSI-), thereby promoting the release of higher levels of free lithium ions, further increasing the concentration of free lithium ions in the electrolyte, directly improving the ionic conductivity of the electrolyte, and helping to improve battery performance. Immobilized TFSI⁻ may form a space charge layer on the surface of the material, generate an interfacial electric field, trigger the hopping transport of lithium ions under the action of the electric field, and further promote the migration of lithium ions.

[0031] 3. Environmentally friendly: Most of the materials used in solid-state batteries will not cause pollution to the environment, reflecting their environmental friendliness.

[0032] 4. Simple process and low cost: The processing technology of polymer solid electrolyte is simple and easy to achieve large-scale production.

[0033] The present invention has the following advantages:

[0034] (1) PHS prepared with dendritic mesoporous nano-silica nanoparticles as inorganic fillers provides more conductive channels for the migration of lithium ions and has the characteristics of high specific surface area, which can increase the capacitance of the electrolyte.

[0035] (2) The present invention improves the interface compatibility between PVDF-HFP and silica nanoparticles through a unique surface modification technology, ensures seamless integration of the electrolyte and the positive and negative electrode materials, reduces interface resistance, improves electrochemical performance, and enhances interface compatibility.

[0036] (3) By regulating the micropore structure of PHS, multi-level ion transport channels can be established, which helps to improve ionic conductivity and effectively inhibit the growth of lithium dendrites.

[0037] (4) The addition of dendritic mesoporous silica not only provides an additional ion transmission path, but also uses a special composite process to increase the mechanical toughness of the composite material, and can maintain the integrity of the structure even under extreme charge and discharge conditions, significantly extending the cycle life of the battery and enhancing the mechanical properties; the present invention also discloses a new method for preparing dendritic mesoporous silica.

[0038] (5) PHS should have a wide electrochemical stability window, so that the battery can operate stably in a wider voltage range to adapt to different types of electrode materials and broaden the electrochemical stability window. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The scanning electron microscope images of different materials of the present invention are shown, wherein (a) is PVDF-HFP, (b) is PVDF-HFP / plasticizer, (cd) are dendritic mesoporous nano-silica, and (ef) is PHS.

[0040] Figure 2 This is the thermogravimetric curve of PHS.

[0041] Figure 3 These are the EIS graphs of stainless steel sheet | PHS | stainless steel sheet in the temperature range of 30-80°C.

[0042] Figure 4 The charge and discharge curves of LFP|PHS|Li battery at different rates.

[0043] Figure 5 The cycling performance of LFP|PHS|Li battery at 0.5 C rate. DETAILED DESCRIPTION

[0044] The present invention will be further described below with reference to the accompanying drawings and embodiments. The protection scope of the present invention is not limited to the following:

[0045] Example 1: A method for preparing a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery, comprising the following steps:

[0046] S1. Preparation of composite solid electrolyte membrane:

[0047] S11. Preparation method of dendritic mesoporous nano-silica:

[0048] (1) Preparation of organosilicon nanoparticles: Ammonia water and template hexadecyltrimethylammonium bromide salt were dissolved in a mixed solution of ethanol and deionized water at room temperature to obtain an ammonia precursor solution, which was stirred at 30°C for 4 hours; while maintaining the temperature, the organosilicon source methoxytrimethylsilane was added twice, with the first stirring being continued for 1 hour and the second stirring being continued for 48 hours. After the stirring was completed, the mixture was centrifuged to obtain the product benzene-bridged organosilicon nanoparticles; the mass volume ratio of the template to ammonia water was 0.1 g:3 mL, the volume ratio of ammonia water, ethanol and deionized water was 1:10:15, and the volume ratio of ammonia water to the organosilicon source was 1:0.1.

[0049] (2) Hydrothermal reaction: The benzene-bridged organosilicon nanoparticles were dispersed with water, wherein the mass volume ratio of the benzene-bridged organosilicon nanoparticles to water was 0.1 mg:1 mL. The dispersion was placed in a polytetrafluoroethylene-lined hydrothermal reactor for reaction, wherein the reaction temperature was 100°C and the reaction time was 5 h. The reaction product was cooled for 24 h and then ultrasonically washed with water and ethanol. The mixed solution was centrifuged and separated. The centrifuged product was dispersed in a mixed solution of ethanol and hydrochloric acid, wherein the volume ratio of ethanol to hydrochloric acid was 30 mL:10 μL. The mixture was stirred at 20°C and 100 rpm for 24 h, and the mixture was repeated once. The mixture was then ultrasonically washed with water and freeze-dried in a freeze dryer to obtain dendritic mesoporous nano-silica.

[0050] S12. After mixing polyvinylidene fluoride-hexafluoropropylene, plasticizer malononitrile, and lithium salt LiTFSI, add nitrogen-methyl pyrrolidone and stir at 40°C for 14 hours until the polymer is fully dissolved. Then add dendritic mesoporous nano-silica solution and mix evenly. The resulting slurry is transferred to a glass plate for coating, drying, and cutting. The coating thickness is 40 μm to produce PHS. The weight ratio of the polyvinylidene fluoride-hexafluoropropylene, plasticizer, lithium salt, and nitrogen-methyl pyrrolidone is 1:1:2.5:15; the amount of dendritic mesoporous nano-silica added is 0.1% of the total weight of the solute.

[0051] S2. Assemble the battery:

[0052] S21. The positive electrode sheet was prepared using the following method: Lithium iron phosphate (LFP) and acetylene black were ground in an agate mortar to uniformly mix the two powders. Polyvinylidene fluoride and a plasticizer (malononitrile) were added to nitrogen-methyl pyrrolidone (NMP) and stirred overnight to obtain a clear solution. The clear liquid was added to the mortar and mixed with the LFP and acetylene black. Grinding was continued until the slurry became a glossy black viscous slurry. The slurry was coated onto aluminum foil, dried in a drying oven at 40°C for 48 hours, and cut into 12 mm diameter discs using a sheet cutter. The weight ratio of lithium iron phosphate, polyvinylidene fluoride, acetylene black, and plasticizer was 7:0.1:0.1:0.1, and the volume ratio of nitrogen-methyl pyrrolidone to lithium iron phosphate was 1 mL:1 g.

[0053] S22. A lithium metal sheet with a diameter of 15.6 mm and a thickness of 0.6 mm was used as the negative electrode. A phytic acid-dimethyl sulfoxide solution was dripped onto the lithium metal sheet and reacted for 3 h. The sheet was then washed with tetrahydrofuran (THF) and dried.

[0054] S23. Lithium-ion batteries are assembled in the order of positive electrode shell, positive electrode sheet, solid electrolyte membrane, negative electrode, stainless steel sheet, spring, and negative electrode shell. The assembled battery is placed on a battery sealing machine and pressurized to 450 kg·cm -2 .

[0055] Example 2: A method for preparing a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery, comprising the following steps:

[0056] S1. Preparation of composite solid electrolyte membrane:

[0057] S11. Preparation method of dendritic mesoporous nano-silica:

[0058] (1) Preparation of organosilicon nanoparticles: Ammonia water and a template (sodium dodecyl sulfate and hexadecyltrimethylammonium bromide, weight ratio of 1:1) were dissolved in a mixed solution of ethanol and deionized water at room temperature to obtain an ammonia precursor solution, which was stirred at 60°C for 4 h; the organosilicon source was added twice while maintaining the temperature, and stirring was continued for 48 h each time after addition. After stirring, the mixture was centrifuged to obtain the product benzene-bridged organosilicon nanoparticles; the mass volume ratio of the template to ammonia water was 2.5 g:10 mL, the volume ratio of ammonia water, ethanol and deionized water was 1:60:150, and the volume ratio of ammonia water to the organosilicon source was 1:1.5.

[0059] (2) Hydrothermal reaction: The benzene-bridged organosilicon nanoparticles were dispersed with water, wherein the mass volume ratio of the benzene-bridged organosilicon nanoparticles to water was 1 mg:10 mL. The dispersion was placed in a polytetrafluoroethylene-lined hydrothermal reactor for reaction, wherein the reaction temperature was 180°C and the reaction time was 1 h. The reaction product was cooled for 24 h and then ultrasonically washed with water and ethanol. The mixed solution was centrifuged and separated. The centrifuged product was dispersed in a mixed solution of ethanol and hydrochloric acid, wherein the volume ratio of ethanol to hydrochloric acid was 50 mL:20 μL. The mixture was stirred at 80°C and 1000 rpm for 1 h, and the mixture was repeated 5 times. The mixture was then ultrasonically washed with water and freeze-dried in a freeze dryer to obtain dendritic mesoporous nano-silica.

[0060] S12. Mix polyvinylidene fluoride-hexafluoropropylene, plasticizer (succinonitrile and glutaronitrile, volume ratio of 2:1) and lithium salt LiFSI, then add nitrogen-methyl pyrrolidone, stir at 70°C for 10 hours until the polymer is fully dissolved, then add dendritic mesoporous nano-silica solution and mix evenly. Transfer the resulting slurry to a glass plate, coat it, dry it, and cut it into pieces. The coating thickness is 1000μm to produce PHS. The weight ratio of the polyvinylidene fluoride-hexafluoropropylene, plasticizer, lithium salt and nitrogen-methyl pyrrolidone is 15:1:20:50; the amount of dendritic mesoporous nano-silica added is 8.0% of the total weight of the solute.

[0061] S2. Assemble the battery:

[0062] S21. The positive electrode sheet was prepared using the following method: lithium iron phosphate (LFP) and acetylene black were ground in an agate mortar to uniformly mix the two powders. Polyvinylidene fluoride (PVDF) and a plasticizer (glutaronitrile and adiponitrile, in a volume ratio of 2:1) were added to nitrogen-methyl pyrrolidone (NMP) and stirred overnight to obtain a clear solution. The clear solution was added to the mortar and mixed with the LFP and acetylene black. Grinding was continued until the slurry became a glossy black viscous slurry. The slurry was coated onto aluminum foil, dried in a drying oven at 80°C for 10 hours, and cut into 12 mm diameter discs using a sheet cutter. The weight ratio of lithium iron phosphate, polyvinylidene fluoride, acetylene black, and plasticizer was 10:2:2:2. The amount of NMP added was 12 mL:5 g by volume to lithium iron phosphate.

[0063] S22. A lithium metal sheet with a diameter of 15.6 mm and a thickness of 0.6 mm was used as the negative electrode. The lithium metal sheet was passivated by soaking in fluoroethylene carbonate for 5 h.

[0064] S23. Lithium-ion batteries are assembled in the order of positive electrode shell, positive electrode sheet, solid electrolyte membrane, negative electrode, stainless steel sheet, spring, and negative electrode shell. The assembled battery is placed on a battery sealing machine and pressurized to 650 kg·cm -2 .

[0065] Example 3: A method for preparing a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery, comprising the following steps:

[0066] S1. Preparation of composite solid electrolyte membrane:

[0067] S11. Preparation method of dendritic mesoporous nano-silica:

[0068] (4) Preparation of organosilicon nanoparticles: Ammonia water and a template (hexadecyltrimethylammonium bromide, sodium lauryl sulfate and polystyrene-b-polyoxyethylene, weight ratio of 3:2:1) were dissolved in a mixed solution of ethanol and deionized water at room temperature to obtain an ammonia precursor solution, which was stirred at 40°C for 1 hour; while maintaining the temperature, an organosilicon source (tetraethyl orthosilicate and bistrimethylsilane, weight ratio of 1:2) was added twice, and stirring was continued for 12 hours each time after addition. After stirring, the mixture was centrifuged to obtain the product benzene-bridged organosilicon nanoparticles; the mass volume ratio of the template to ammonia water was 1 g:0.1 mL, the volume ratio of ammonia water, ethanol and deionized water was 1:38:100, and the volume ratio of ammonia water to the organosilicon source was 1:0.1.

[0069] (2) Hydrothermal reaction: The benzene-bridged organosilicon nanoparticles were dispersed with water, wherein the mass volume ratio of the benzene-bridged organosilicon nanoparticles to water was 0.4 mg:5 mL. The dispersion was placed in a polytetrafluoroethylene-lined hydrothermal reactor for reaction, wherein the reaction temperature was 130°C and the reaction time was 2 h. The reaction product was cooled for 24 h and then ultrasonically washed with water and ethanol. The mixed solution was centrifuged and separated. The centrifuged product was dispersed in a mixed solution of ethanol and hydrochloric acid, wherein the volume ratio of ethanol to hydrochloric acid was 1 mL:1 μL. The mixture was stirred at 40°C and 500 rpm for 10 h, and the mixture was repeated 3 times. The mixture was then ultrasonically washed with water and freeze-dried in a freeze dryer to obtain dendritic mesoporous nano-silica.

[0070] S12. PVDF / HFP, plasticizers (succinonitrile, glutaronitrile, and adiponitrile, in a volume ratio of 2:2:1), and lithium salt (LiPO2F2) were mixed, and then nitrogen-methyl pyrrolidone was added. The mixture was stirred at 52°C for 12 hours until the polymer was fully dissolved. The dendritic mesoporous nano-silica solution was then added and mixed thoroughly. The resulting slurry was transferred to a glass plate for coating, drying, and cutting. The coating thickness was 450μm to produce PHS. The weight ratio of PVDF / HFP, plasticizer, lithium salt, and nitrogen-methyl pyrrolidone was 5:1:7:20; the amount of dendritic mesoporous nano-silica added was 3wt% of the total weight of the solute.

[0071] S2. Assemble the battery:

[0072] S21. The positive electrode sheet was prepared using the following method: lithium iron phosphate (LFP) and acetylene black were ground in an agate mortar to uniformly mix the two powders. Polyvinylidene fluoride and a plasticizer (adiponitrile, pimelonitrile, and suberonitrile in a volume ratio of 1:2:3) were added to nitrogen-methyl pyrrolidone (NMP) and stirred overnight to obtain a transparent solution. The transparent liquid was added to the mortar and mixed with LFP and acetylene black, and grinding was continued until the slurry became a shiny black viscous slurry. The slurry was coated onto aluminum foil, dried in a drying oven at 70°C for 22 hours, and cut into 12 mm diameter discs using a sheet cutter. The weight ratio of lithium iron phosphate, polyvinylidene fluoride, acetylene black, and plasticizer was 7.5:1.4:1:1, and the amount of nitrogen-methyl pyrrolidone added was 4 mL:4 g by volume to lithium iron phosphate.

[0073] S22. For the negative electrode, use a lithium metal sheet with a diameter of 15.6 mm and a thickness of 0.6 mm. Polydiallyldimethylammonium-bis(trifluoromethanesulfonimide) solution is evenly dripped onto the surface of the lithium metal sheet and dried at 50°C.

[0074] S23. Lithium-ion batteries are assembled in the order of positive electrode shell, positive electrode sheet, solid electrolyte membrane, negative electrode, stainless steel sheet, spring, and negative electrode shell. The assembled battery is placed on a battery sealing machine and pressurized to 500 kg·cm -2 .

[0075] Example 4: A method for preparing a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery, comprising the following steps:

[0076] S1. Preparation of composite solid electrolyte membrane:

[0077] S11. Preparation method of dendritic mesoporous nano-silica:

[0078] (1) Preparation of organosilicon nanoparticles: Ammonia water and a template (hexadecyltrimethylammonium bromide, sodium lauryl sulfate, hexadecyltrimethylammonium bromide and polystyrene microspheres, weight ratio of 1:1:1:2) were dissolved in a mixed solution of ethanol and deionized water at room temperature to obtain an ammonia precursor solution, which was stirred at 50°C for 3.5 hours; the organosilicon source was added twice while maintaining the temperature, and stirring was continued for 40 hours each time after addition. After stirring, the mixture was centrifuged to obtain the product benzene-bridged organosilicon nanoparticles; wherein the mass volume ratio of the template to ammonia water was 0.4 g:8 mL, the volume ratio of ammonia water, ethanol and deionized water was 1:10:15, and the volume ratio of ammonia water to the organosilicon source was 1:2.4.

[0079] (2) Hydrothermal reaction: The benzene-bridged organosilicon nanoparticles were dispersed with water, wherein the mass volume ratio of the benzene-bridged organosilicon nanoparticles to water was 0.8 mg:8 mL. The dispersion was placed in a polytetrafluoroethylene-lined hydrothermal reactor for reaction, wherein the reaction temperature was 170°C and the reaction time was 4 h. The reaction product was cooled for 24 h and then ultrasonically washed with water and ethanol. The mixed solution was centrifuged and separated. The centrifuged product was dispersed in a mixed solution of ethanol and hydrochloric acid, wherein the volume ratio of ethanol to hydrochloric acid was 40 mL:17 μL. The mixture was stirred at 50°C and 800 rpm for 20 h, and the mixture was repeated 4 times. The mixture was then ultrasonically washed with water and freeze-dried in a freeze dryer to obtain dendritic mesoporous nano-silica.

[0080] S12. Polyvinylidene fluoride / hexafluoropropylene, plasticizers (pimelonitrile, suberonitrile, azelaic acid dinitrile, and sebacate in a volume ratio of 1:2:2:1), and lithium salt LiDFOB were mixed, and then nitrogen-methyl pyrrolidone was added. The mixture was stirred at 60°C for 13.5 hours until the polymer was fully dissolved. A dendritic mesoporous nano-silica solution was then added and mixed thoroughly. The resulting slurry was transferred to a glass plate for coating, drying, and cutting. The coating thickness was 200 μm to produce PHS. The weight ratio of the polyvinylidene fluoride / hexafluoropropylene, plasticizer, lithium salt, and nitrogen-methyl pyrrolidone was 14:1:4:35. The amount of dendritic mesoporous nano-silica added was 4% of the total weight of the solute.

[0081] S2. Assemble the battery:

[0082] S21. The positive electrode sheet was prepared using the following method: Lithium iron phosphate (LFP) and acetylene black were ground in an agate mortar to uniformly mix the two powders. Polyvinylidene fluoride (PVDF) and plasticizers (pimelonitrile, suberonitrile, azelaic acid diphosphate, and sebacate in a volume ratio of 1:1:2:2) were added to nitrogen-methyl pyrrolidone (NMP) and stirred overnight to obtain a clear solution. The clear solution was added to the mortar and mixed with the LFP and acetylene black. Grinding was continued until the slurry became a glossy black, viscous slurry. The slurry was coated onto aluminum foil, dried in a drying oven at 75°C for 40 hours, and cut into 12 mm diameter discs using a sheet cutter. The weight ratio of lithium iron phosphate, PVDF, acetylene black, and plasticizer was 9:1.8:1.5:1, and the volume ratio of nitrogen-methyl pyrrolidone to lithium iron phosphate was 7 ml:3 g.

[0083] S22. A lithium metal sheet with a diameter of 15.6 mm and a thickness of 0.6 mm was used as the negative electrode. The lithium metal sheet was passivated by soaking in fluoroethylene carbonate for 5 h.

[0084] S23. Lithium-ion batteries are assembled in the order of positive electrode shell, positive electrode sheet, solid electrolyte membrane, negative electrode, stainless steel sheet, spring, and negative electrode shell. The assembled battery is placed on a battery sealing machine and pressurized to 600 kg·cm-2 .

[0085] The beneficial effects of the present invention are described below by experiments:

[0086] Experimental Example 1: Preparation of PHS:

[0087] Step (1): Dissolve 2 g of CTAB and 7 mL of ammonia water in a flat-bottomed flask containing a 120 mL H2O / 80 mL ethanol solution at room temperature and stir vigorously in an oil bath at 35°C for 1 h. Maintain the temperature, quickly add a 2 mL TEOS / 1.5 mL BTSB mixture to the solution and stir for 24 h. Then, reintroduce the 2 mL TEOS / 1.5 mL BTSB mixture into the system and maintain the temperature and stirring for 24 h.

[0088] Step (2): The mixed solution was placed in a centrifuge and centrifuged at 10,000 rpm for 10 min to obtain the separated product solid silica nanoparticles, which were then ultrasonically washed with water for multiple times.

[0089] Step (3): The solid silica nanoparticles synthesized in the above step are dispersed in a flat-bottom flask filled with deionized water for the following synthesis. The flask is placed in an ultrasonic cleaner and the benzene-bridged organosilicon nanoparticles are completely dispersed by the ultrasonic cleaner until no precipitation is produced after the flat-bottom flask is left to stand for a period of time. The dispersion in the flask is placed in a polytetrafluoroethylene-lined hydrothermal reactor. The polytetrafluoroethylene-lined hydrothermal reactor is placed in an electric constant temperature forced air drying oven, and the drying oven temperature is set to 130°C. After reaching the temperature, the temperature is maintained for 5 hours, and then the power supply of the drying oven is turned off. The reactor is removed after the drying oven is completely cooled for 24 hours.

[0090] Step (4): Place the mixed solution in a centrifuge and centrifuge at 10,000 rpm for 10 min to obtain the separated product. After that, perform ultrasonic water washing once and ethanol washing twice to obtain silica.

[0091] Step (5): Silica was dispersed in a flat-bottom flask containing a magnetron, ethanol, and HCl solution (Vethanol = 30 mL, VHCl = 10 μl) and stirred at 500 rpm for 12 h at 60 °C.

[0092] Step (6): Finally, ultrasonic washing was performed, and the product was centrifuged at 10,000 rpm for 10 min, and freeze-dried in a freeze dryer to obtain dendritic mesoporous nano-silica.

[0093] Step (7): Polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), succinonitrile (SCN), and lithium salt (LiTFSI) were mixed in a mass ratio of 8:1.5:2, and then 7 mL of nitrogen-methylpyrrolidone (NMP) was added. The mixture was placed on a magnetic stirrer and magnetically stirred (580 rpm) at 60 °C for 12 h until the polymer was fully dissolved.

[0094] Step (8): Add 3% of the total weight of the solute to dendritic mesoporous nanosilica and use an ultrasonic cleaner to uniformly disperse the dendritic mesoporous nanosilica in the polymer matrix. The solution is coated on a glass plate to a thickness of 300 μm, then dried and cut into pieces. The diameter of the PHS disc is 19 mm and placed in an argon-filled glove box for 24 hours before use.

[0095] Experimental Example 2: Preparation of PHS:

[0096] Step (1): Synthesize dendritic mesoporous nano-silica using the method in Experimental Example 1.

[0097] Step (2): Polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), succinonitrile (SCN), and lithium salt (LiTFSl) were mixed in a mass ratio of 8:1.5:2, and then 7 mL of nitrogen-methylpyrrolidone (NMP) was added. The mixture was placed on a magnetic stirrer and magnetically stirred (580 rpm) at 60°C for 12 hours until the polymer was fully dissolved.

[0098] Step (3): Add 0.5% of the total weight of the solute to the dendritic mesoporous nano-silica and use an ultrasonic cleaner to uniformly mix the dendritic mesoporous nano-silica in the polymer matrix. The solution is coated on a glass plate to a thickness of 800 μm, then dried and cut into pieces. The diameter of the PHS disc is 19 mm and placed in an argon-filled glove box for 24 hours before use.

[0099] Experimental Example 3: Preparation of PHS:

[0100] Step (1): Synthesize dendritic mesoporous nano-silica using the method in Experimental Example 1.

[0101] Step (2): Polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), succinonitrile (SCN), and lithium salt (LiTFSl) were mixed in a mass ratio of 8:1.5:2, and then 7 mL of nitrogen-methylpyrrolidone (NMP) was added. The mixture was placed on a magnetic stirrer and magnetically stirred (580 rpm) at 60°C for 12 hours until the polymer was fully dissolved.

[0102] Step (3): Add 4% of the total weight of the solute to dendritic mesoporous nanosilica and use an ultrasonic cleaner to uniformly mix the dendritic mesoporous nanosilica in the polymer matrix. The solution is coated on a glass plate to a thickness of 800 μm, then dried and cut into pieces. The diameter of the PHS disc is 19 mm and placed in an argon-filled glove box for 24 hours before use.

[0103] Experimental Example 4: Preparation of PHS:

[0104] Step (1): Synthesize dendritic mesoporous nano-silica using the method in Experimental Example 1.

[0105] Step (2): Polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), succinonitrile (SCN), and lithium salt (LiTFSl) were mixed in a mass ratio of 8:1.5:2, and then 7 mL of nitrogen-methylpyrrolidone (NMP) was added. The mixture was placed on a magnetic stirrer and magnetically stirred (580 rpm) at 60°C for 12 hours until the polymer was fully dissolved.

[0106] Step (3): Add 8.0% of the total weight of the solute to the dendritic mesoporous nano-silica and use an ultrasonic cleaner to uniformly mix the dendritic mesoporous nano-silica in the polymer matrix. The solution is coated on a glass plate to a thickness of 800 μm, then dried and cut into PHS discs with a diameter of 19 mm. Place in an argon-filled glove box for 24 hours before use.

[0107] Experimental Example 5: Preparation of PHS:

[0108] Step (1): Polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), succinonitrile (SCN), and lithium salt (LiTFSI) were mixed in a mass ratio of 8:1.5:2, and then 7 mL of nitrogen-methylpyrrolidone (NMP) was added. The mixture was placed on a magnetic stirrer and magnetically stirred (580 rpm) at 60 °C for 12 hours until the polymer was fully dissolved.

[0109] Step (2): No dendritic mesoporous nanosilica was added. The solution was coated on a glass plate to a thickness of 800 μm, then dried and cut into pieces. The diameter of the PHS disc was 19 mm and placed in an argon-filled glove box for 24 hours.

[0110] Experimental Example 6: Preparation method of lithium iron phosphate positive electrode:

[0111] Weigh lithium iron phosphate (LFP), acetylene black, polyvinylidene fluoride (PVDF), and succinonitrile in a mass ratio of 8:1.5:1:0.5. Grind the lithium iron phosphate (LFP) and acetylene black in an agate mortar until the two powders are evenly mixed. Add PVDF and succinonitrile to nitrogen-methyl pyrrolidone (NMP) and stir overnight to obtain a clear solution. The volume ratio of NMP to lithium iron phosphate is 6 mL:3 g. Add the clear solution to the mortar and mix with the LFP and acetylene black. Continue grinding until the slurry becomes a glossy black, viscous slurry. Coat the slurry onto aluminum foil, dry it in a drying oven at 70°C for 24 hours, and cut it into 12 mm diameter discs using a sheet cutter.

[0112] Experimental Example 7: Assembly of solid-state lithium battery:

[0113] The PHS prepared in Experimental Examples 1-5 and the lithium iron phosphate material positive electrode prepared in Experimental Example 6 were assembled into batteries. The battery assembly must be carried out in a glove box filled with argon. The button battery is assembled in the order of positive electrode shell, positive electrode sheet, solid electrolyte membrane, negative electrode, stainless steel sheet, spring sheet, and negative electrode shell. The positive electrode sheet is the prepared lithium iron phosphate positive electrode, and the negative electrode is the metal lithium sheet with a diameter of 15.6 mm and a thickness of 0.4 mm. The assembled battery is placed on the battery sealing machine and pressurized to 600 kg·cm -2 After standing for 4 hours, the electrochemical workstation and blue electric test system were used to perform electrochemical tests. The nominal specific capacity of lithium iron phosphate was 170 mAh g -1 The working voltage is 2.5-3.8 V. Among them, the negative electrode uses a metal lithium sheet with a diameter of 15.6 mm and a thickness of 0.6 mm. A dimethyl sulfoxide solution of phytic acid is dripped onto the metal lithium sheet for 3 hours, and then washed with tetrahydrofuran (THF) and dried.

[0114] 1. Physical characterization of materials:

[0115] 1. Electron microscopy analysis:

[0116] Scanning electron microscopy (SEM) analysis was performed on PVDF-HFP, PVDF-HFP / plasticizer and PHS (Experimental Example 3), and transmission electron microscopy analysis was performed on dendritic mesoporous nano-silica. Figure 1As shown in the figure, Figure (a) is PVDF-HFP, and Figure (b) is PVDF-HFP / plasticizer. SEM data show that pure PVDF-HFP has a high degree of crystallinity, a dense surface, and fewer continuous pores (Figure (a). In contrast, a porous internet-like structure with uniform pore distribution and pore size was observed in PVDF-HFP / plasticizer, and no agglomeration was observed on the electrolyte surface. The results show that SCN improves the three-dimensional network structure of PVDF-HFP by reducing the crystallinity of PVDF-HFP. Figures (cd) are transmission electron microscopy (TEM) images of dendritic mesoporous nanosilica. Figure c shows that the synthesized dendritic mesoporous nanosilica is uniform in size, evenly dispersed, and has no agglomeration. Figure d shows that the diameter of the dendritic mesoporous nano-silica is about 170 nm, the outer dendritic structure is about 50 nm, and the inner layer is a mesoporous structure of about 75 nm. Figure (ef) is a scanning electron microscope image of PHS. The dendritic mesoporous nano-silica is evenly dispersed in PHS, further reducing the crystallinity of PVDF-HFP, making the porosity of PHS higher, and increasing the transmission channel of lithium ions (Figure (e)). Figure (f) shows the three-dimensional network interconnection of spherical structures with a diameter of about 8µm, and the dendritic mesoporous nano-silica with a diameter of about 170 nm is distributed in the three-dimensional network structure, indicating that a three-dimensional transport channel conducive to lithium ion transfer has been successfully constructed. The well-connected pores in PHS provide sufficient space for ion conduction. The dendritic mesoporous nano-silica further increases the specific surface area, forming a continuous channel conducive to lithium ion transmission.

[0117] 2. Thermogravimetric analysis

[0118] PHS was heated in nitrogen atmosphere at 30~800°C and 10°C min -1 The heating rate test was carried out to obtain the thermogravimetric analysis (TG) and differential thermogravimetric analysis (DTG) data. The experimental results are as follows Figure 2 As shown in FIG, the TGA data show that when the temperature is higher than 284°C, PSH loses 95% of its weight, indicating that PHS (Experimental Example 3) has sufficient thermal stability below 284°C.

[0119] 2. Electrochemical performance test:

[0120] 1. Ionic conductivity test

[0121] Electrochemical performance tests include electrochemical impedance spectroscopy (EIS) and charge-discharge cycle tests. Using a CHI 760E electrochemical workstation, the temperature range was 30-80°C and the 6 -10 2 The EIS data of stainless steel sheet|PHS|stainless steel sheet were obtained with a perturbation of 10 mV in the frequency range of Hz. Figure 3The ionic conductivity of PHS (Experimental Example 3) at different temperatures is given: as the temperature rises, the ionic conductivity gradually increases, and at 80°C the ionic conductivity reaches 4.5×10 -4 S cm -1 .

[0122] 2. Solid-state lithium battery rate performance test:

[0123] The LFP|PHS|Li (passivation) configuration battery was charged and discharged on the LANHE CT3001A blue electricity test system. The test conditions included current rates of 0.1C, 0.2C, 0.5C and 1C. Figure 4 The results show that the solid-state battery assembled by PHS (Experimental Example 3) has an initial discharge capacity of 169.2 mAh g at a rate of 0.1 C. -1 , which is 99% of the theoretical value. As the current density increases, the battery can still provide 167.2, 151.1 and 146.5 mAh·g at current densities of 0.2, 0.5 and 1C. -1 High capacity.

[0124] 3. Solid-state lithium battery charge and discharge cycle performance test

[0125] The PHS prepared in Experimental Examples 1-5 were assembled into batteries, and the first cycle discharge capacity and the capacity retention rate after 200 cycles were tested at a charge and discharge current density of 0.5 C for the solid-state lithium battery. The experimental results are shown in Table 1:

[0126] Table 1: Performance parameters of solid-state lithium batteries in Experimental Examples 1-5 at a charge and discharge current density of 0.5 C

[0127] Experimental example <![CDATA[Initial circle discharge specific capacity (mAh·g -1 )]]> Capacity retention after 200 cycles 1 161.2 97.8% 2 151.3 94.5% 3 159.6 97.2% 4 157.4 96.3% 5 149.5 93.7%

[0128] The battery of LFP|PHS|Li (passivation) configuration (Experimental Example 3) was subjected to 200 charge and discharge cycle tests at room temperature at a current density of 0.5 C. The experimental results are shown in the figure. Figure 5 The results show that the maximum discharge capacity of the battery is 159.6 mAh g at a charge and discharge current density of 0.5 C. -1 The capacity retention rate was 97.2% after 200 cycles. In addition, the solid-state battery also showed a stable coulombic efficiency close to 100% during the cycling process.

[0129] In summary, the method of the present invention has the following advantages:

[0130] 1. Solve the liquid electrolyte problem: Solve the safety hazards brought by traditional liquid electrolytes, such as leakage, combustion and explosion.

[0131] 2. Enhanced thermal stability: The combination of PVDF-HFP polymer matrix and inorganic inert filler dendritic mesoporous nano-silica improves the thermal stability of the electrolyte, effectively inhibits the decomposition of lithium salts at high temperatures, and reduces the risk of combustion.

[0132] 3. Inhibit the growth of lithium dendrites: The addition of dendritic mesoporous nano-silica enhances the mechanical strength of the electrolyte, helps to inhibit the formation of lithium dendrites, and avoids short circuits and explosions caused by dendrites piercing the diaphragm.

[0133] 4. Improve interface compatibility: By optimizing the material composition and improving the surface morphology of the electrolyte membrane, the compatibility of PHS with positive and negative electrode materials is enhanced, and the interface stability between the solid electrolyte and the metal lithium negative electrode is improved, making the ion insertion and extraction on the surface of the metal lithium negative electrode more uniform.

[0134] 5. Improve electrochemical performance: The three-dimensional network structure formed by PHS and the large specific surface area of dendritic mesoporous nano-silica provide more pathways for the transmission of lithium ions and promote the improvement of ionic conductivity. It also has a broad electrochemical stability window and is suitable for high energy density battery systems.

[0135] 6. Reduce the crystallinity of PVDF-HFP: Through the introduction of plasticizers and dendritic mesoporous nano-silica fillers, the PVDF-HFP system undergoes a series of complex microstructural evolution processes, in which the physical barrier effect and the change of the local environment work together to not only significantly inhibit the orderly arrangement of molecular chains, but also induce the formation of amorphous regions, effectively reducing the crystallinity.

[0136] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, and they are all covered by the scope of protection of the present invention.

Claims

1. A method for preparing a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery, characterized in that: It includes the following steps: S1. Preparation of composite solid electrolyte membrane: After mixing polyvinylidene fluoride-hexafluoropropylene, a plasticizer and a lithium salt, nitrogen-methyl pyrrolidone is added, and the mixture is stirred at a temperature of 40 to 70° C. for 10 to 14 hours until the polymer is fully dissolved. Then, a dendritic mesoporous nano-silica solution is added and mixed evenly. The resulting slurry is coated, dried and cut into pieces to prepare a PVDF-HFP / dendritic mesoporous nano-silica composite solid electrolyte membrane; the plasticizer is succinonitrile; the lithium salt is LiTFSI; the weight ratio of the polyvinylidene fluoride-hexafluoropropylene, the plasticizer, the lithium salt and nitrogen-methyl pyrrolidone is 1 to 15:1:2.5 to 20:15 to 50; the amount of the dendritic mesoporous nano-silica added is 0.1 to 8.0% of the total weight of the solute; Wherein, the preparation method of the dendritic mesoporous nano-silica is: (1) Preparation of organosilicon nanoparticles: dissolving ammonia water and a template in a mixed solution of ethanol and deionized water at room temperature to obtain an ammonia precursor solution, stirring at a temperature of 30 to 60°C for 0.5 to 4 hours; adding an organosilicon source twice while maintaining the temperature, stirring continuously for 1 to 48 hours each time after addition, and centrifuging the mixture after the stirring to obtain the product benzene-bridged organosilicon nanoparticles; the template is hexadecyltrimethylammonium bromide; the organosilicon source is tetraethyl orthosilicate and 1,4-bis(triethoxysilyl)benzene; (2) Hydrothermal reaction: The benzene-bridged organosilicon nanoparticles are dispersed in water, and the dispersion is placed in a polytetrafluoroethylene-lined hydrothermal reactor for reaction at a temperature of 100 to 180°C for 1 to 5 hours. The reaction product is post-treated to obtain dendritic mesoporous nano-silica. S2. Assembling a battery: Assembling the composite solid electrolyte membrane prepared in step S1 into a lithium-ion battery to prepare a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery.

2. The method for preparing a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery according to claim 1, characterized in that: The mass volume ratio of the template to ammonia water is 0.1-2.5 g:0.1-10 mL, the volume ratio of ammonia water, ethanol and deionized water is 1:10-60:15-150, and the volume ratio of ammonia water to the organosilicon source is 1:0.1-2.5; the mass volume ratio of the benzene-bridged organosilicon nanoparticles to water is 0.1-1 mg:1-10 mL.

3. The method for preparing a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery according to claim 1, characterized in that: The specific operation of the post-treatment in step (2) is as follows: cooling the reaction product for 24 hours, washing it with ultrasonic water and ethanol, centrifuging the mixed solution by centrifuge, dispersing the centrifuged product in a mixed solution of ethanol and hydrochloric acid, wherein the volume ratio of ethanol to hydrochloric acid is 1-50 mL:1-20 μl, stirring at 20-80° C. and 100-1000 rpm for 1-24 hours, repeating 1-5 times, and then ultrasonically washing it with water, and freeze-drying it in a freeze dryer to obtain dendritic mesoporous nano-silica.

4. The method for preparing a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery according to claim 1, characterized in that: The positive electrode of the lithium-ion battery described in step S2 is prepared by the following method: polyvinylidene fluoride and plasticizer are added to nitrogen-methyl pyrrolidone and stirred overnight to obtain a transparent solution, and lithium iron phosphate and acetylene black are ground and mixed evenly in a grinding mortar, and then the transparent liquid is added to the grinding mortar and continued to grind until the slurry becomes black, shiny and viscous. The ground slurry is coated on aluminum foil, placed in a drying oven at 40-80°C and dried for 10-48 hours, and cut into discs with a cutting machine.

5. The method for preparing a polyvinylidene fluoride-hexafluoropropylene-based solid-state lithium battery according to claim 4, characterized in that: The plasticizer is at least one of malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelaic acid dinitrile or sebacate; the weight ratio of the lithium iron phosphate, polyvinylidene fluoride, acetylene black and plasticizer is 7-10:0.1-2:0.1-2:0.1-2; the volume ratio of nitrogen-methyl pyrrolidone to the mass ratio of lithium iron phosphate is 1-12 mL:1-5 g.

6. The method for preparing a polyvinylidene fluoride-hexafluoropropylene based solid-state lithium battery according to claim 1, wherein: The lithium-ion battery in step S2 is assembled in the order of positive electrode shell, positive electrode sheet, solid electrolyte membrane, negative electrode, stainless steel sheet, spring, and negative electrode shell. The assembled battery is placed on a battery sealing machine and pressurized to 450-650 kg·cm -2 .

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