Fluorosilicone polymer composite electrolyte with high ionic conductivity and good adaptability to high-voltage positive electrode and preparation method thereof

Abstract

The present invention belongs to the technical field of solid electrolyte material preparation, and specifically relates to a fluorosilicone polymer composite electrolyte with high ionic conductivity and good adaptability to high-voltage positive electrodes and a preparation method thereof. A fluorosilicone polymer is prepared by copolymerizing a monomer containing fluorine atoms with a monomer containing siloxane, and is used as one of the components for preparing a solid electrolyte, thereby improving the adaptability and safety performance of the solid electrolyte to high-voltage positive electrodes. At the same time, lithium salts and inorganic nanomaterials are added to the system to give the composite electrolyte high ionic conductivity. The present invention produces a composite solid electrolyte material that can match high-voltage positive electrode materials and has high ionic conductivity, which can be applied to various energy storage systems such as electronic terminal equipment and smart grids.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid electrolyte material preparation, and specifically relates to a fluorosilicone polymer composite electrolyte with high ionic conductivity and good adaptability to high-voltage positive electrodes, and a preparation method thereof. Background Art

[0002] At present, the main method to improve the energy density of lithium secondary batteries is to use high specific capacity negative electrode materials and high voltage positive electrode materials for lithium ion batteries. In recent years, lithium ion positive electrode materials such as LiCoPO4, Li2CoPO4F, LiNi 0.5 Mn 1.5 O4 and lithium-rich positive electrode materials such as xLi2MnO3-(1-x)LiMO2 (M=Ni, Co, Mn) have developed rapidly in recent years due to their high specific capacity, operating voltage platform and good rate performance.

[0003] Currently, commercial lithium-ion battery electrolytes are mainly organic carbonate-based electrolytes, which have a working voltage of 4.5V (vs.Li + / Li) or above, a violent oxidative decomposition reaction will occur, which will prevent the lithium battery from inserting and removing lithium normally. This makes it difficult for high-voltage electrode materials to take advantage of their high specific capacity and high voltage platform. Moreover, organic carbonate electrolytes have safety issues such as easy leakage, easy combustion, and easy explosion, which limit the further application of this type of electrolyte. Therefore, in order to solve the problems of low voltage platform and poor safety performance of electrolytes, it is urgent to develop a safer polymer electrolyte system with a higher voltage platform to replace the liquid carbonate electrolyte and separator in traditional lithium-ion batteries, thereby constructing a high-voltage polymer lithium metal battery with only three components: a high-voltage positive electrode, a lithium negative electrode, and a polymer electrolyte.

[0004] In recent years, reports on polysiloxane electrolytes have gradually increased. Studies have found that polysiloxane polymer electrolytes have the advantages of being non-toxic, biocompatible, having a low glass transition temperature, good molecular flexibility, and high chemical stability. They also have high thermal stability, making polysiloxane electrolytes stable and non-flammable at high temperatures, which greatly improves the safety performance of lithium-ion batteries. Moreover, the ether groups in the siloxane backbone have good lithium ion transfer capabilities, which makes them have high conductivity at room temperature (>10 -4 S / cm). However, the electrochemical window of polysiloxane electrolytes is difficult to exceed 5V (vs. Li + / Li), it is difficult to match high voltage positive electrode materials, and in terms of ionic conductivity, it has not yet broken through the ionic conductivity of more than 10 at room temperature. -3 The S / cm threshold means that polysiloxane polymer electrolytes are still unable to compete with liquid electrolytes in terms of ionic conductivity.

[0005] In order to improve this problem, the introduction of fluorine atoms into siloxane polymers is expected to solve the problems of narrow voltage window, low ionic conductivity and safety hazards in polymer electrolytes. Fluorine atoms have the characteristics of high electronegativity, small atomic radius and low polarizability, so the introduction of -F bonds into the compound can enhance the electron-withdrawing ability of the compound, thereby making the fluorinated compound have the advantages of high electrochemical stability and non-flammability. Moreover, the introduction of fluorine atoms also helps to form a passivation film (i.e., solid electrolyte interface film SEI) on the electrode surface, the main components of which are compounds containing CF bonds and LiF, among which LiF has a large band gap and low Li + The diffusion energy barrier and high surface energy enable the fluorinated SEI film to effectively block the penetration of electrons and promote the + The rapid diffusion of ions reduces the side reactions between the electrodes and the electrolyte. However, the polymer has a high degree of crystallinity at room temperature and the molecular chain mobility is poor, so the ionic conductivity of a single polymer electrolyte at room temperature is not ideal.

[0006] Currently, there are two theories regarding the improvement of the ionic conductivity of polymer electrolytes by inorganic fillers. Wzorek proposes that the functional groups of inorganic fillers can complex with anions in the electrolyte through Lewis acid-base interactions, promoting the dissociation of lithium salts and thereby increasing the number of free lithium ions in the system. Croce proposes that inorganic fillers hinder the local recombination of polymer chain segments and promote chain motion by reducing the adjustment of polymer crystallinity. In addition to increasing the conductivity of polymer electrolytes, the incorporation of inorganic fillers can broaden the electrochemical window of the polymer through interactions between the polymers and increase mechanical strength. Large particle size or agglomeration can block lithium ion transport pathways, while nanosized fillers have a higher specific surface area and are therefore more conducive to improving the ionic conductivity of composite electrolytes. While composite solid electrolytes combine the advantages of organic and inorganic materials, traditional inorganic fillers still have disadvantages such as high doping ratios, complex preparation processes, and low ionic conductivity. Furthermore, with increasing energy density requirements, many electrolytes have poor oxidation resistance, making them incompatible with high-voltage cathodes. In addition, the poor compatibility between the solid electrolyte and the electrode can easily cause the growth of lithium dendrites and increase the interface impedance, seriously affecting the charge and discharge performance and cycle life of the battery. Summary of the Invention

[0007] In response to the shortcomings of the existing technology, the present invention proposes a fluorosilicone polymer composite solid electrolyte with high ionic conductivity at room temperature and good adaptability to high-voltage positive electrode materials, and a preparation method thereof. This not only solves the safety hazards of liquid electrolytes such as volatility and leakage, but also improves the operating voltage platform of the electrolyte, making it more adaptable to high-voltage positive electrode materials. At the same time, during the preparation process, lithium salts and nanofiber materials are added, so that the prepared fluorosilicone polymer composite solid electrolyte solves the problem of unsatisfactory ionic conductivity caused by the high crystallinity of a single polymer at room temperature, achieving high ionic conductivity at room temperature, and is low-cost, pollution-free, highly efficient and environmentally friendly, and has a high energy density. It can be widely used in electronic terminal equipment, high-efficiency energy storage, new energy vehicles and other fields.

[0008] The present invention adopts the following technical solutions:

[0009] The fluorosilicone polymer composite solid electrolyte with high ionic conductivity and high voltage resistance is prepared by the step-by-step polymerization of a fluorine-containing bifunctional polyol monomer and a siloxane-containing monomer, followed by the addition of lithium salts and inorganic active materials. The reaction equation is:

[0010] ,

[0011] + Lithium salt + Inorganic materials / nanofibers → Fluorosilicone polymer composites

[0012] Where: R1=

[0013]

[0014] R2=CH3 or C3H6X, X= one of Cl, Br, I; n=8-15.

[0015] The specific preparation method steps of the fluorosilicone polymer composite electrolyte with high ionic conductivity and good adaptability to high voltage positive electrodes are as follows:

[0016] (1) A fluorine-containing bifunctional polyol and a siloxane-containing monomer are mixed and dissolved in an organic solvent. Then, a p-toluenesulfonic acid catalyst is added and the mixture is reacted at a reflux temperature of 80-90°C for 15 hours to obtain a fluorine-containing siloxane polymer F-1.

[0017] Among them, the polyol containing a fluorine atom bifunctional group is one of 2,2'-[oxybis[(1,1,2,2-tetrafluoro-2,1-ethanediyl)oxy]]bis[2,2-difluoroethanol], hexafluoroglutaric acid, and 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol; the siloxane-containing monomer is halopropyltrimethoxysilane or methyltrimethoxysilane, wherein the halogen element is one of Cl, Br, and I.

[0018] The molar ratio of the fluorine-containing bifunctional polyol to the siloxane-containing monomer is 3:1.

[0019] The amount of the catalyst p-toluenesulfonic acid used is 0.40 wt% of the mass of the silicone-containing monomer.

[0020] The organic solvent is one of NN-dimethylformamide and N-methylpyrrolidone.

[0021] (2) adding the lithium salt and F-1 in step (1) into the solvent in a certain mass ratio, and magnetically stirring the system at 40-50° C. for 20-30 minutes to mix them evenly, thereby preparing a fluorosilicone polymer composite material F-2 containing lithium salt;

[0022] The lithium salt is one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO4), and lithium hexafluorophosphate (LiPF6), and the mass ratio of the lithium salt to F-1 is 1-2:7.

[0023] The solvent is one of methanol, ethanol, acetone and acetonitrile.

[0024] (3) adding an inorganic active material having high ionic conductivity and F-2 in step (2) to a solvent in a certain mass ratio, and mechanically stirring the system at 40-50° C. for 20-30 min to uniformly mix the mixture, thereby obtaining a fluorosilicone polymer composite material F-3 containing lithium and an inorganic active material;

[0025] The inorganic active material is Li 6.4 La3Zr 1.4 Ta o.6 O 12 (LLZTO), Li 1.5 Al 0.5 Ge 1.5 One of (PO4)3(LAGP) and 70Li2S-29P2S5-1P2O5(LPOS), wherein the mass ratio of LPOS to F-2 is 1-4:9.

[0026] The solvent is one of methanol, ethanol, acetone and acetonitrile.

[0027] (4) Nanofibers with certain mechanical properties and F-3 in step (3) are added to the solvent in a certain mass ratio, and the system is mechanically stirred at 40-50°C for 20-30 minutes to mix them evenly, thereby obtaining a fluorosilicone polymer composite material F-4 containing nanofibers.

[0028] The solvent is one of copper ammonia, copper ethylenediamine and calcium thiocyanate.

[0029] The nanofiber is one of carboxymethyl cellulose (CMC), polyaniline nanofiber and polypyrrole nanofiber, and the mass ratio of the nanofiber to F-3 is 1-4:9.

[0030] (5) The prepared F-4 is formed into a film to obtain an electrolyte membrane.

[0031] The method for obtaining the electrolyte membrane is one of a solution casting method, a spin coating method, and a cast method. Beneficial effects

[0032] (1) The polymer obtained by the ester exchange reaction of fluorine / silicon monomers works synergistically with lithium salts and inorganic active materials, which can not only achieve high ionic conductivity at room temperature, but also better adapt to high-voltage positive electrode materials, greatly improving the matching of electrolyte and electrode.

[0033] (2) The introduction of fluorine-containing groups improves the antioxidant properties of the electrolyte and increases its electrochemical window to 5.3V, which fully meets the requirements of high-voltage systems.

[0034] (3) Further improve the antioxidant and mechanical properties of the electrolyte by introducing inorganic materials.

[0035] (4) Nanofibers have a higher specific surface area, which is more conducive to improving the ion conductivity of the composite electrolyte, thereby avoiding the low ion conductivity caused by limiting the mobility of anions and further improving the safety performance of secondary batteries in use.

[0036] (5) The thermal decomposition temperature of the solid electrolyte membrane prepared by the present invention reaches above 300°C, and it can work well at high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the LSV test diagram of Example 1.

[0038] Figure 2 This is the LSV test chart of control example 2.

[0039] Figure 3 This is the thermogravimetric analysis curve of the solid electrolyte membrane prepared in Example 1.

[0040] Figure 4 This is the thermogravimetric analysis curve of the solid electrolyte membrane prepared in Control Example 1.

[0041] FIG5 shows the calculated lithium ion migration number of the lithium-lithium battery prepared in Example 1 and Comparative Example 2, wherein: Figure 5.a For control example 2, Figure 5.b This is Example 1.

[0042] Figure 6This is a cycle capacity diagram of the NCM622 lithium metal battery prepared in Example 1 and Control Example 1. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Example

[0044] 6.00 g of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol was added to a 50 ml three-necked flask equipped with a thermometer, a stirrer, a dropping funnel, a condenser and vacuumed and nitrogen-filled for three times, 1.00 g of chloropropyltrimethoxysilane dissolved in 20 ml of NN-dimethylformamide was added, and 0.004 g of p-toluenesulfonic acid catalyst was added. The reflux temperature was controlled at 85 ° C for 15 hours to obtain a fluorosilicone polymer F-1; 1.00 g of lithium bistrifluoromethanesulfonyl imide dissolved in 10 ml of acetonitrile solution was added to F-1 (3.50 g) and stirred at 50 ° C for 30 minutes to obtain a fluorosilicone polymer composite material F-2 containing lithium salt; Li dissolved in 15 ml of acetonitrile solution was added. 6.4 La3Zr 1.4 Ta o.6 O 12 (2g) powder was added to F-2 and stirred at 50°C for 30 minutes to obtain a fluorosilicone polymer composite material F-3 containing lithium and inorganic active materials; carboxymethyl cellulose (3g) dissolved in 10ml of copper ammonia solution was added to F-3 and stirred at 50°C for 30 minutes to obtain a fluorosilicone polymer composite material F-4 containing nanofibers; F-4 was cast onto a polytetrafluoroethylene plate and vacuum dried in a glove box at 65°C for 24 hours until no solvent remained to obtain an electrolyte membrane.

[0045] Table 1 Ionic conductivity at different temperatures Example 2

[0046] 6.00 g of hexafluoroglutaric acid was added to a 50 ml three-necked flask equipped with a thermometer, a stirrer, a dropping funnel, a condenser and vacuumed and nitrogen-filled for three times. 1.00 g of chloropropyltrimethoxysilane dissolved in 20 ml of NN-dimethylformamide was added, and then 0.004 g of p-toluenesulfonic acid catalyst was added. The reflux temperature was controlled at 85 ° C for 15 hours to obtain a fluorosilicone polymer F-1. 1.00 g of lithium bis(trifluoromethanesulfonyl)imide dissolved in 10 ml of acetonitrile solution was added to F-1 (3.50 g) and stirred at 50 ° C for 30 minutes to obtain a fluorosilicone polymer composite material F-2 containing a lithium salt. Li dissolved in 15 ml of acetonitrile solution was added. 6.4 La3Zr 1.4Ta o.6 O 12 (2g) powder was added to F-2 and stirred at 50°C for 30 minutes to obtain a fluorosilicone polymer composite material F-3 containing lithium and inorganic ceramic materials; carboxymethyl cellulose (3g) dissolved in 10ml of cuprammonium solution was added to F-3 and stirred at 50°C for 30 minutes to obtain a fluorosilicone polymer composite material F-4 containing nanofibers; F-4 was cast onto a polytetrafluoroethylene plate and vacuum dried in a glove box at 65°C for 24 hours until no solvent remained to obtain an electrolyte membrane. Example 3

[0047] 6.00 g of 2,2'-[oxybis[(1,1,2,2-tetrafluoro-2,1-ethanediyl)oxy]]bis[2,2-difluoroethanol] was added to a 50 ml three-necked flask equipped with a thermometer, a stirrer, a dropping funnel, a condenser and vacuumed and nitrogen-filled for three times. 1.00 g of chloropropyltrimethoxysilane dissolved in 20 ml of NN-dimethylformamide was added, and then 0.004 g of p-toluenesulfonic acid catalyst was added. The reflux temperature was controlled at 85 ° C for 15 h to obtain a fluorosilicone polymer F-1. 1.00 g of lithium bistrifluoromethanesulfonyl imide dissolved in 10 ml of acetonitrile solution was added to F-1 (3.50 g) and stirred at 50 ° C for 30 min to obtain a fluorosilicone polymer composite material F-2 containing lithium salt. Li dissolved in 15 ml of acetonitrile solution was added. 6.4 La3Zr 1.4 Ta o.6 O 12 (2g) powder was added to F-2 and stirred at 50°C for 30 minutes to obtain a fluorosilicone polymer composite material F-3 containing lithium and inorganic ceramic materials; carboxymethyl cellulose (3g) dissolved in 10ml of cuprammonium solution was added to F-3 and stirred at 50°C for 30 minutes to obtain a fluorosilicone polymer composite material F-4 containing nanofibers; F-4 was cast onto a polytetrafluoroethylene plate and vacuum dried in a glove box at 65°C for 24 hours until no solvent remained to obtain an electrolyte membrane. Example 4

[0048] 6.00 g of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol was added to a 50 ml three-necked flask equipped with a thermometer, a stirrer, a dropping funnel, a condenser and vacuumed and nitrogen-filled for three times, 1.00 g of chloropropyltrimethoxysilane dissolved in 20 ml of NN-dimethylformamide was added, and 0.004 g of p-toluenesulfonic acid catalyst was added. The reflux temperature was controlled at 85 ° C for 15 hours to obtain a fluorosilicone polymer F-1; 1.00 g of lithium bistrifluoromethanesulfonyl imide dissolved in 10 ml of acetonitrile solution was added to F-1 (3.50 g) and stirred at 50 ° C for 30 minutes to obtain a fluorosilicone polymer composite material F-2 containing lithium salt; Li dissolved in 15 ml of acetonitrile solution was added. 1.5 Al 0.5 Ge 1.5 (PO4)3 (2g) powder was added to F-2 and stirred at 50°C for 30 minutes to obtain a fluorosilicone polymer composite material F-3 containing lithium and inorganic ceramic materials; carboxymethyl cellulose (3g) dissolved in 10ml of copper ammonia solution was added to F-3 and stirred at 50°C for 30 minutes to obtain a fluorosilicone polymer composite material F-4 containing nanofibers; F-4 was cast onto a polytetrafluoroethylene plate and vacuum dried in a glove box at 65°C for 24 hours until no solvent remained to obtain an electrolyte membrane. Example 5

[0049] 6.00 g of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol was added to a 50 ml three-necked flask equipped with a thermometer, a stirrer, a dropping funnel, a condenser and vacuumed and nitrogen-filled for three times. 1.00 g of chloropropyltrimethoxysilane dissolved in 20 ml of NN-dimethylformamide was added, and then 0.004 g of p-toluenesulfonic acid catalyst was added. The reflux temperature was controlled at 85 ° C for 15 h to obtain a fluorosilicone polymer F-1. 1.00 g of lithium bistrifluoromethanesulfonyl imide dissolved in 10 ml of acetonitrile solution was added to F-1 (3.50 g) and stirred at 50 ° C for 30 min to obtain a fluorosilicone polymer composite material F-2 containing lithium salt. 70Li2S-29P dissolved in 15 ml of acetonitrile solution was added. 2S5-1P2O5 (2 g) powder was added to F-2 and stirred at 50°C for 30 min to obtain a fluorosilicone polymer composite material F-3 containing lithium and inorganic ceramic materials; carboxymethyl cellulose (3 g) dissolved in 10 ml of copper ammonia solution was added to F-3 and stirred at 50°C for 30 min to obtain a fluorosilicone polymer composite material F-4 containing nanofibers; F-4 was cast onto a polytetrafluoroethylene plate and vacuum dried in a glove box at 65°C for 24 hours until no solvent remained to obtain an electrolyte membrane. Example 6

[0050] 6.00 g of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol was added to a 50 ml three-necked flask equipped with a thermometer, a stirrer, a dropping funnel, a condenser and vacuumed and nitrogen-filled for three times, 1.00 g of chloropropyltrimethoxysilane dissolved in 20 ml of NN-dimethylformamide was added, and 0.004 g of p-toluenesulfonic acid catalyst was added. The reflux temperature was controlled at 85 ° C for 15 hours to obtain a fluorosilicone polymer F-1; 1.00 g of lithium bistrifluoromethanesulfonyl imide dissolved in 10 ml of acetonitrile solution was added to F-1 (3.50 g) and stirred at 50 ° C for 30 minutes to obtain a fluorosilicone polymer composite material F-2 containing lithium salt; Li dissolved in 15 ml of acetonitrile solution was added. 6.4 La3Zr 1.4 Ta o.6 O 12 (2g) powder was added to F-2 and stirred at 50°C for 30 minutes to obtain a fluorosilicone polymer composite material F-3 containing lithium and inorganic ceramic materials; polyaniline nanofibers (3g) dissolved in 10ml of cuprammonium solution were added to F-3 and stirred at 50°C for 30 minutes to obtain a fluorosilicone polymer composite material F-4 containing nanofibers; F-4 was cast onto a polytetrafluoroethylene plate and vacuum dried in a glove box at 65°C for 24 hours until no solvent remained to obtain an electrolyte membrane. Example 7

[0051] 6.00 g of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol was added to a 50 ml three-necked flask equipped with a thermometer, a stirrer, a dropping funnel, a condenser and vacuumed and nitrogen-filled for three times, 1.00 g of chloropropyltrimethoxysilane dissolved in 20 ml of NN-dimethylformamide was added, and 0.004 g of p-toluenesulfonic acid catalyst was added. The reflux temperature was controlled at 85 ° C for 15 hours to obtain a fluorosilicone polymer F-1; 1.00 g of lithium bistrifluoromethanesulfonyl imide dissolved in 10 ml of acetonitrile solution was added to F-1 (3.50 g) and stirred at 50 ° C for 30 minutes to obtain a fluorosilicone polymer composite material F-2 containing lithium salt; Li dissolved in 15 ml of acetonitrile solution was added. 6.4 La3Zr 1.4 Ta o.6 O 12 (3g) powder was added to F-2 and stirred at 50°C for 30 minutes to obtain a fluorosilicone polymer composite material F-3 containing lithium and inorganic active materials; carboxymethyl cellulose (3g) dissolved in 10ml of copper ammonia solution was added to F-3 and stirred at 50°C for 30 minutes to obtain a fluorosilicone polymer composite material F-4 containing nanofibers; F-4 was cast onto a polytetrafluoroethylene plate and vacuum dried in a glove box at 65°C for 24 hours until no solvent remained to obtain an electrolyte membrane. Example 8

[0052] 6.00 g of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol was added to a 50 ml three-necked flask equipped with a thermometer, a stirrer, a dropping funnel, a condenser and vacuumed and nitrogen-filled for three times, 1.00 g of chloropropyltrimethoxysilane dissolved in 20 ml of NN-dimethylformamide was added, and 0.004 g of p-toluenesulfonic acid catalyst was added. The reflux temperature was controlled at 85 ° C for 15 hours to obtain a fluorosilicone polymer F-1; 1.00 g of lithium bistrifluoromethanesulfonyl imide dissolved in 10 ml of acetonitrile solution was added to F-1 (3.50 g) and stirred at 50 ° C for 30 minutes to obtain a fluorosilicone polymer composite material F-2 containing lithium salt; Li dissolved in 15 ml of acetonitrile solution was added. 6.4 La3Zr 1.4 Ta o.6 O 12 (2g) powder was added to F-2 and stirred at 50°C for 30 minutes to obtain a fluorosilicone polymer composite material F-3 containing lithium and inorganic active materials; carboxymethyl cellulose (2g) dissolved in 10ml of copper ammonia solution was added to F-3 and stirred at 50°C for 30 minutes to obtain a fluorosilicone polymer composite material F-4 containing nanofibers; F-4 was cast onto a polytetrafluoroethylene plate and vacuum dried in a glove box at 65°C for 24 hours until no solvent remained to obtain an electrolyte membrane. Comparative Example 1

[0053] Take 6.00g of 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol and add it to a 50ml three-necked flask equipped with a thermometer, a stirrer, a dropping funnel, a condenser and vacuumed and nitrogen-filled for three times, then add 20ml of 1.00g of chloropropyltrimethoxysilane was added to NN-dimethylformamide, and then 0.004g of p-toluenesulfonic acid catalyst was added. The reflux temperature was controlled to react at 85°C for 15h to obtain a fluorosilicone polymer F-1; 1.00g of lithium bis(trifluoromethanesulfonyl)imide dissolved in 10ml of acetonitrile solution was added to F-1 (3.50g), and stirred at 50°C for 30min to obtain a fluorosilicone polymer composite material F-2 containing lithium salt; carboxymethyl cellulose (3g) dissolved in 10ml of copper ammonia solution was added to F-2, and stirred at 50°C for 30min to obtain a fluorosilicone polymer composite material F-3 containing nanofibers; F-3 was cast onto a polytetrafluoroethylene plate and vacuum dried in a glove box at 65°C for 24h until no solvent remained to obtain an electrolyte membrane. Comparative Example 2

[0054] 1.00g of chloropropyltrimethoxysilane was added to a 50ml three-necked flask equipped with a thermometer, stirrer, dropping funnel, and condenser, and vacuumed and nitrogen-filled for three times. 20ml of NN-dimethylformamide was added. 1.00g of lithium bis(trifluoromethanesulfonyl)imide dissolved in 10ml of acetonitrile was added to the flask (3.50g) and stirred at 50°C for 30min to prepare a siloxane electrolyte containing lithium salt. Li dissolved in 15ml of acetonitrile was added to the flask. 6.4 La3Zr 1.4 Ta o.6 O 12 (2g) powder was added to a flask and stirred at 50°C for 30 minutes to obtain a siloxane electrolyte containing inorganic ceramic material; carboxymethyl cellulose (3g) dissolved in 10ml of cuprammonium solution was added to the flask and stirred at 50°C for 30 minutes to obtain a fluorine-free siloxane polymer composite material containing nanofibers; the composite material was cast onto a polytetrafluoroethylene plate and vacuum dried in a glove box at 65°C for 24 hours until no solvent remained to obtain an electrolyte membrane.

[0055] Table 2 Ionic conductivity of different electrolytes at room temperature

[0056]

[0057] Table 3 Antioxidant properties of different electrolytes

[0058]

[0059] Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing a fluorosilicone polymer composite electrolyte with high ionic conductivity and good adaptability to high-voltage positive electrodes, characterized by: The preparation method comprises the following steps: (1) A fluorine-containing bifunctional polyol and a siloxane-containing monomer were mixed and dissolved in an organic solvent, p-toluenesulfonic acid catalyst was added, and the mixture was refluxed at 80-90°C for 15 hours to obtain a fluorine-containing siloxane polymer F-1; The general structural formula of fluorinated silicone polymer is as follows: ， Where R1= or , R2=CH3 or C3H6X; X= one of Cl, Br, I; n=8-15; (2) adding the lithium salt and F-1 in step (1) into the solvent in a mass ratio, and magnetically stirring the system at 40-50° C. for 20-30 minutes to mix them evenly, thereby preparing a fluorosilicone polymer composite material F-2 containing a lithium salt; (3) adding an inorganic active material having high ionic conductivity and F-2 in step (2) into a solvent in a mass ratio, and mechanically stirring the system at 40-50° C. for 20-30 min to uniformly mix the mixture, thereby obtaining a fluorosilicone polymer composite material F-3 containing lithium and an inorganic active material; (4) adding the nanofibers and the F-3 prepared in step (3) into the solvent in a mass ratio, and mechanically stirring the system at 40-50° C. for 20-30 min to uniformly mix the nanofibers to obtain a fluorosilicone polymer composite material F-4; The nanofiber is one of carboxymethyl cellulose CMC, polyaniline nanofiber, and polypyrrole nanofiber; (5) The prepared F-4 is prepared into a solid electrolyte film.

2. The method for preparing a fluorosilicone polymer composite electrolyte having high ionic conductivity and good adaptability to high-voltage positive electrodes according to claim 1, characterized in that: The fluorine-containing bifunctional polyol in step (1) is one of hexafluoroglutaric acid and 2,2,3,3,4,4,5,5-octafluoro-1,1-pentanediol; the siloxane-containing monomer is halopropyltrimethoxysilane or methyltrimethoxysilane, and the halogen element is one of Cl, Br, and I.

3. The method for preparing a fluorosilicone polymer composite electrolyte having high ionic conductivity and good adaptability to high-voltage positive electrodes according to claim 1, characterized in that: In step (1), the molar ratio of the fluorine-containing bifunctional polyol to the siloxane-containing monomer is 3:1; the organic solvent is one of NN-dimethylformamide and N-methylpyrrolidone; and the amount of the catalyst p-toluenesulfonic acid used is 0.40 wt% of the mass of the siloxane-containing monomer.

4. The method for preparing a fluorosilicone polymer composite electrolyte having high ionic conductivity and good adaptability to high-voltage positive electrodes according to claim 1, characterized in that: The lithium salt in step (2) is one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO4), and lithium hexafluorophosphate (LiPF6), and the mass ratio of the lithium salt to F-1 is 1-2:

7.

5. The method for preparing a fluorosilicone polymer composite electrolyte having high ionic conductivity and good adaptability to high-voltage positive electrodes according to claim 1, characterized in that: The solvent in step (2) and step (3) is one of methanol, ethanol, acetone and acetonitrile.

6. The method for preparing a fluorosilicone polymer composite electrolyte having high ionic conductivity and good adaptability to high-voltage positive electrodes according to claim 1, characterized in that: The inorganic active material in step (3) is Li 6.4 La3Zr 1.4 Ta o.6 O 12 LLZTO, Li 1.5 Al 0.5 Ge 1.5 One of (PO4)3LAGP and 70Li2S-29P2S5-1P2O5LPOS, wherein the mass ratio of the inorganic active material to F-2 is 1-4:

9.

7. The method for preparing a fluorosilicone polymer composite electrolyte having high ionic conductivity and good adaptability to high-voltage positive electrodes according to claim 1, characterized in that: The solvent in step (4) is one of cuprammonium, copper ethylenediamine, and calcium thiocyanate; and the mass ratio of nanofiber to F-3 is 1-4:

9.

8. The method for preparing a fluorosilicone polymer composite electrolyte having high ionic conductivity and good adaptability to high-voltage positive electrodes according to claim 1, characterized in that: The method for preparing the solid electrolyte film in step (5) is one of solution casting, spin coating and flow casting.

9. A fluorosilicone polymer electrolyte prepared by the method according to any one of claims 1 to 8.

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