CN104810549A - Method for preparing porous gel polymer electrolyte doped with composite nanoparticles - Google Patents

Abstract

The invention discloses a method for preparing a porous gel polymer electrolyte doped with composite nanoparticles, which is applied to a polymer lithium ion battery. First, the organic nanoparticles of methyl methacrylate copolymerized lithium maleate copolymer were obtained by aqueous phase dispersion polymerization, and then the surface was coated with silica by sol-gel method to obtain composite nanoparticles with core-shell morphology, and then Dispersed in N'N-dimethylformamide solution of PVDF, the PVDF-based composite porous membrane was prepared by immersion precipitation method, which was heated and dried in vacuum, and then adsorbed with liquid electrolyte to obtain a composite gel polymer electrolyte membrane. The film obtained by the invention has a thickness of 30-50 μm, an ion conductivity of 6.31×10 ^-3 Scm ^-1 at 30°C, and an electrochemical window of 5.4V, and its performance is better than that of conventional ordinary gel polymer electrolytes.

Description

Preparation method of porous gel polymer electrolyte doped with composite nanoparticles

technical field

The invention discloses a preparation method of a porous gel polymer electrolyte doped with composite nano particles, which is applied to a polymer lithium ion battery.

Background technique

As environmental problems become more and more prominent, the use of conventional fossil energy causes serious air pollution, and the demand for new environmentally friendly new energy sources such as new lithium-ion batteries and fuel cells is increasingly strong. Polymer lithium-ion batteries have attracted widespread attention due to their high energy density and recyclable use. As an important part of polymer lithium-ion batteries, polymer electrolytes have an important decisive influence on the safety, reliability, charge and discharge performance of lithium-ion batteries.

Previous studies have focused on the direct doping of inorganic nanoparticles into organic phase polymers to prepare composite polymer electrolytes. Due to the small size of inorganic nanoparticles, nanoclusters are prone to occur when dispersed in the polymer matrix, which makes it impossible to achieve the effect of uniform dispersion of nanoparticles. Prepare core-shell nanoparticles by chemical modification, and analyze its influence on the performance of composite polymer electrolytes. nanophase. Tests have found that polymethyl methacrylate cannot uniformly coat the surface of inorganic nanoparticles, and the grafting rate is relatively low, so it is impossible to truly realize the synthesis of nanoparticles with uniform core-shell morphology. It is necessary to design a new synthesis method to prepare a composite nanoparticle with uniform core-shell morphology and dope it into the polymer matrix to effectively dope the composite polymer electrolyte and effectively improve its various properties .

Contents of the invention

The object of the present invention is to overcome the defects of the above-mentioned prior art, and provide a method for preparing a porous gel polymer electrolyte doped with composite nanoparticles, which is applied to a polymer lithium ion battery. The method is to first synthesize a new type of core-shell morphology composite nanoparticle of methyl methacrylate copolymerized lithium maleate whose shell is a silicon dioxide core layer, and then dope and disperse it into polyvinylidene fluoride polymer In the solution, the composite polyvinylidene fluoride porous membrane is prepared by immersion precipitation, and after the membrane absorbs the liquid electrolyte and gels, a composite gel polymer electrolyte with porous morphology is obtained.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A preparation method of a porous gel polymer electrolyte doped with composite nanoparticles, comprising the steps of:

Step 1. Mix the mixed monomers methyl methacrylate and maleic anhydride in a molar ratio of 1:1 to 100:1, and then add 3-10wt% dispersant, the mixture is dispersed in deionized water under high-speed stirring, the mass ratio of the total amount of monomers to deionized water is 5-20wt%, and 1-3wt% of dispersant is added relative to the mass of mixed monomers Potassium sulfate, the temperature rise range of the reaction system is 60-100°C, the reaction time is controlled at 6-24 hours, after the reaction is completed, it is lowered to 25°C, and lithium hydroxide, which is twice the molar amount of maleic anhydride, is added to the reaction system. reacting for 6 to 10 hours to obtain organic nanoparticles of methyl methacrylate copolymerized lithium maleate dispersed in the water phase, and freeze-drying to obtain organic nanometer particles of methyl methacrylate copolymerized lithium maleate;

Step 2. Disperse the organic nano-powder of methyl methacrylate copolymerized lithium maleate obtained in step 1 in ethanol, control its concentration at 0.01g/ml～0.5g/ml, ultrasonically disperse for 0.5h, and normalize according to the mass ratio Ethyl silicate: organic nano powder of methyl methacrylate copolymerized lithium maleate is 10:1～1:10, add orthosilicate ethyl ester, drop ammonia water to control the pH value of the adjustment system between 8～11, React at room temperature at 25°C for 6 to 24 hours to obtain core-shell morphology composite nanoparticles of methyl methacrylate copolymerized lithium maleate whose shell is silicon dioxide;

Step 3: Dissolve and disperse polyvinylidene fluoride powder in N,N-dimethylformamide solution at room temperature, control the concentration of the polymer solution at 0.1-5g/ml, stir for 6-12 hours, and then obtain in step 2 The composite nanoparticles with core-shell morphology are added according to 0.01-10wt% of the doping amount of polyvinylidene fluoride powder and dispersed therein by ultrasonication for 0.1-1h, and then stirred at room temperature for 12-24h; The spatula is evenly coated on the glass plate, soaked in the water phase, and the composite porous film with core-shell morphology composite nanoparticles doped with polyvinylidene fluoride is prepared by immersion precipitation method;

Step 4: Vacuum-dry the composite porous film of core-shell morphology composite nanoparticles doped polyvinylidene fluoride obtained in step 3 at a temperature of 40°C to 80°C for 8 to 24 hours, and then soak the liquid in a glove box Electrolyte for 0.5-1 hour to obtain a composite gel polymer electrolyte membrane with a porous structure in which the absorbed liquid electrolyte component accounts for 40-70 wt% of the total mass.

The above-mentioned thin film has a thickness of 30 μm to 50 μm.

The molar ratio of methyl methacrylate to maleic anhydride described in the above step 1 is preferably 5:1-20:1.

The dispersant described in the above step 1 is polyvinylpyrrolidone, the model is PVP-K30.

The mass ratio of ethyl orthosilicate and methyl methacrylate copolymerized lithium maleate described in the above step 2 is preferably 5:1˜1:2.

The molecular weight of the polyvinylidene fluoride described in the above step 3 is M _n =4×10 ⁵ -5×10 ⁵ .

The doping amount of the composite nanoparticles with core-shell morphology in the above step 3 relative to the polyvinylidene fluoride powder is preferably 1-10 wt%.

The liquid electrolyte described in the above step 4 is a 1M lithium hexafluorophosphate carbonate electrolyte. The 1M lithium hexafluorophosphate carbonate electrolyte is a mixed solution composed of lithium hexafluorophosphate mixed with dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate, and its mass ratio is dimethyl carbonate:methyl carbonate Ethyl ester: ethylene carbonate = 1:1:1.

The beneficial effect of the preparation method of the porous gel polymer electrolyte doped with composite nanoparticles of the present invention is:

The traditional research on composite polymer electrolytes is to directly dope the inorganic phase into the organic phase to prepare composite polymer electrolytes. However, the inorganic phase does not contribute to the conduction of lithium ions, although it plays a role in the interface between the organic phase and the inorganic phase. general effect, but its effect is not obvious. In the present invention, the added core-shell structure nanoparticles, on the one hand, play a role in reducing the crystallinity of the polyvinylidene fluoride matrix, making it more conducive to the conduction of lithium ions, and due to the existence of the inorganic phase, to a certain extent It reduces the decrease in strength due to the decrease in crystallinity; on the other hand, the added polymer lithium salt has a greater affinity for the electrolyte and plays a better role in ion conduction; give full play to the composite two-phase composite polymer electrolyte characteristics; finally, the composite effect is beneficial to the gel polymer electrolyte system obtained after adding the liquid electrolyte to maintain good mechanical properties.

The research proves that the composite two phases are continuous phases, the phase domain size is small, the mixing is relatively uniform, and the system performance is stable. The room temperature ion conductivity of the modified nanocomposite porous gel polymer electrolyte of the invention reaches the order of 10 ^-3 Scm ^-1 , and the electrochemical stability window reaches 5.3V. It meets the actual requirements for the use of polymer lithium-ion batteries.

Description of drawings

Fig. 1 is the optical microscope picture of the core-shell nanoparticle-doped polyvinylidene fluoride composite polymer electrolyte film prepared in Example 1 of the present invention;

Fig. 2 is the electrochemical stability window result of the core-shell nanoparticle-doped polyvinylidene fluoride composite polymer electrolyte film prepared in Example 1 of the present invention;

Fig. 3 is the AC impedance spectrum curve at different temperatures of different proportions of core-shell structure nanoparticles doped polyvinylidene fluoride composite polymer electrolyte film prepared in Example 1 of the present invention;

Fig. 4 is the relationship curve of the ionic conductivity of the core-shell nanoparticle-doped polyvinylidene fluoride composite polymer electrolyte film prepared in Example 1-4 of the present invention as a function of temperature;

Detailed ways

Below through specific embodiment, can better understand the present invention. However, those skilled in the art can easily understand that the content described in the embodiments is only for illustrating the present invention, and should not and will not limit the content described in the claims of the present invention.

Example 1

(1) First, 4g methyl methacrylate and 0.196g maleic anhydride are mixed according to a molar ratio of 20:1, and the mixture is dispersed in deionized water under high-speed stirring. The mass ratio is 10wt%, that is, the mass of water is 41.96g, and then 0.21g of polyvinylpyrrolidone PVP-K30 relative to the mass of methyl methacrylate and maleic anhydride is added as a dispersant, with a mass fraction of 3 % that is, 0.126g of potassium persulfate is used as an initiator, the temperature is raised to 75°C, and the reaction is performed for 24 hours. After the reaction is completed, it is lowered to 25°C, and 0.096g of lithium hydroxide, which is twice the molar amount of maleic anhydride, is added to the reaction system. , reacted for 8 hours, and freeze-dried the product to obtain organic nanometer powder of methyl methacrylate copolymerized lithium maleate.

(2) Disperse 0.3 g of organic nano-powder methyl methacrylate copolymerized lithium maleate in 25 ml of absolute ethanol, control the mass ratio at 0.012 g/ml, ultrasonically disperse for 0.5 h, add tetraethyl orthosilicate, Among them, the mass ratio of ethyl orthosilicate and methyl methacrylate copolymerized lithium maleate is 5:1, that is, the quality of ethyl orthosilicate is 1.5g, and ammonia water is added dropwise to control the pH value of the adjustment system at about 11, and the room temperature is 25 The reaction was carried out at ℃ for 24 hours to obtain core-shell morphology composite nanoparticles whose shell layer is silicon dioxide and whose core layer is methyl methacrylate copolymerized lithium maleate.

(3) Dissolve and disperse polyvinylidene fluoride powder with a molecular weight of 4×10 ⁵ in N,N-dimethylformamide solution at room temperature, control the concentration range of the polymer solution at 1 g/ml, stir for 8 hours, and then Add core-shell composite nanoparticles into it and disperse them, wherein the doping amount of core-shell composite nanoparticles relative to polyvinylidene fluoride is 1%wt%, first ultrasonic 0.4h, and then stir at room temperature for 20h to completely disperse uniform. After the polymer solution was left standing to remove air bubbles, it was evenly coated on a glass plate with a spatula, soaked in the water phase, and a composite porous membrane doped with composite nanoparticles doped with polyvinylidene fluoride was prepared by the immersion precipitation method. The thickness of the film was about is 30 μm.

(4) The obtained composite nanoparticle-doped polyvinylidene fluoride composite porous film was vacuum-dried at a temperature of 40° C. for 20 hours, and then soaked in a liquid electrolyte (made from lithium hexafluorophosphate mixed with dimethyl carbonate) in a glove box. , the concentration that ethyl methyl carbonate and ethylene carbonate are formed is the mixed solution of 1M, and it forms by mass ratio dimethyl carbonate: ethyl methyl carbonate: ethylene carbonate=1:1:1.) 0.5 hour, By controlling the immersion time, the adsorbed liquid electrolyte component in the composition accounts for 40wt% of the total mass, and the final composite gel polymer electrolyte film with a porous structure is obtained, and the film thickness is about 30 μm.

Figure 1 is an optical microscope image of the core-shell structure nanoparticle-doped polyvinylidene fluoride composite polymer electrolyte film prepared in Example 1; the nanoparticles are uniformly dispersed on the polyvinylidene fluoride matrix, no clusters are found, and the size of the holes is uniform. evenly distributed.

Fig. 2 is the test result of the linear sweep voltammetry curve of the composite gel polymer electrolyte film prepared in Example 1 at room temperature (with stainless steel as the working positive electrode, metal lithium as the negative electrode and reference electrode, the composite gel polymer electrolyte film Sandwiched during), its electrochemical stability window is 5.4V.

Fig. 3 is the AC spectrum curve obtained by sandwiching the polyvinylidene fluoride composite polymer electrolyte film doped with core-shell structure nanoparticles in different proportions prepared in Example 1 between stainless steel electrodes and tested at different temperatures. Because the stainless steel blocking electrode is used, there is no electrochemical reaction, so the arc part representing the electrochemical reaction in the impedance spectrum can be regarded as an infinite diameter, which is shown as an approximate straight line in the figure. Calculate the resistance R _b of the polymer electrolyte according to the point where the Nyquist curve in the AC impedance spectrum intersects with the real axis on the impedance spectrum, and use the calculation test Calculate the ionic conductivity (σ) of the polymer electrolyte membrane, and its ionic conductivity at room temperature (25°C) reaches 6.31×10 ^-3 Scm ^-1 .

Example 2

(1) First, 4g of methyl methacrylate and 0.392g of maleic anhydride are mixed in a molar ratio of 10:1, and the mixture is dispersed in deionized water under high-speed stirring. The mass ratio is 5wt%, the mass of water is 87.84g, and then 0.132g of polyvinylpyrrolidone PVP-K30 relative to the mass of methyl methacrylate and maleic anhydride is added as a dispersant, with a mass fraction of 2.5% That is, 0.11g of potassium persulfate is used as an initiator, the temperature is raised to 85°C, and the reaction is carried out for 6 hours. After the reaction is completed, it is lowered to 25°C, and 0.192g of lithium hydroxide, which is twice the molar amount of maleic anhydride, is added to the reaction system. After reacting for 6 hours, the product was freeze-dried to obtain organic nanometer powder of methyl methacrylate copolymerized lithium maleate.

(2) Disperse 0.25 g of organic nano-powder methyl methacrylate copolylithium maleate in 25 ml of absolute ethanol, control the mass ratio at 0.01 g/ml, ultrasonically disperse for 0.5 h, add tetraethyl orthosilicate, Among them, the mass ratio of ethyl orthosilicate to lithium maleate copolymerized with methyl methacrylate is 3:1, that is, the quality of ethyl orthosilicate is 0.75g, and ammonia water is added dropwise to control the pH value of the adjustment system at about 9, and the room temperature is 25 The reaction is carried out at ℃ for 20 hours to obtain core-shell morphology composite nanoparticles whose shell layer is silicon dioxide and whose core layer is methyl methacrylate copolymerized lithium maleate.

(3) Dissolve and disperse polyvinylidene fluoride powder with a molecular weight of 4.5×10 ⁵ in N,N-dimethylformamide solution at room temperature, control the concentration range of the polymer solution at 5 g/ml, stir for 12 hours, and then Add and disperse the composite nanoparticles with core-shell morphology, wherein the doping amount of the composite nanoparticles relative to polyvinylidene fluoride is 0.01wt%, ultrasonication for 0.1h, and then stirring at room temperature for 12h to completely disperse uniformly. After the polymer solution was left standing to remove air bubbles, it was evenly coated on a glass plate with a spatula, soaked in the water phase, and a composite porous membrane doped with composite nanoparticles doped with polyvinylidene fluoride was prepared by the immersion precipitation method. The thickness of the film was about is 50 μm.

(4) The obtained composite nanoparticle-doped polyvinylidene fluoride composite porous film was vacuum-dried at a temperature of 80° C. for 8 hours, and then soaked in a liquid electrolyte (mixed with dimethyl carbonate by lithium hexafluorophosphate) in a glove box. , the concentration that ethyl methyl carbonate and ethylene carbonate are formed is the mixed solution of 1M, and it forms by mass ratio dimethyl carbonate: ethyl methyl carbonate: ethylene carbonate=1:1:1.) 1 hour, By controlling the immersion time, the adsorbed liquid electrolyte component in the composition accounts for 70wt% of the total mass, and the final composite gel polymer electrolyte film with a porous structure is obtained, and the film thickness is about 50 μm.

Example 3

(1) First, 5g methyl methacrylate and 0.98g maleic anhydride are mixed according to a molar ratio of 5:1, and the mixture is dispersed in deionized water under high-speed stirring. The mass ratio is 20wt%, that is, the mass of water is 29.9g, and then 0.598g of polyvinylpyrrolidone PVP-K30 is added as a dispersant relative to the mass of methyl methacrylate and maleic anhydride, with a mass fraction of 1 % that is 0.0598g potassium persulfate is the initiator, heat up 100 ° C, react for 10 hours, drop to 25 ° C after the end of the reaction, add lithium hydroxide that is 0.48 g of 2 times the relative maleic anhydride molar weight to the reaction system, After reacting for 24 hours, the product was freeze-dried to obtain organic nanometer powder of methyl methacrylate copolymerized lithium maleate.

(2) Disperse 12.5 g of organic nano-powder methyl methacrylate copolymerized lithium maleate in 25 ml of absolute ethanol, control the mass ratio at 0.5 g/ml, ultrasonically disperse for 0.5 h, add tetraethyl orthosilicate, Among them, the mass ratio of ethyl orthosilicate to lithium maleate copolymerized with methyl methacrylate is 1:2, that is, the mass of ethyl orthosilicate is 6.25g, and ammonia water is added dropwise to control the pH value of the adjustment system at about 8, and the room temperature is 25 React at ℃ for 6 hours to obtain core-shell morphology composite nanoparticles whose shell layer is silicon dioxide (SiO ₂ ) and whose core layer is methyl methacrylate copolymerized lithium maleate.

(3) Dissolve and disperse polyvinylidene fluoride powder with a molecular weight of 5×10 ⁵ in N,N-dimethylformamide (N,N-dimethylformamide) solution at room temperature, and the concentration range of the polymer solution is controlled After stirring at 0.1g/ml for 6 hours, the composite nanoparticles with core-shell morphology were added and dispersed in it, wherein the doping amount of the composite nanoparticles relative to polyvinylidene fluoride was 10wt%. Stir for 24h so that it is completely dispersed. After the polymer solution is left standing to remove air bubbles, it is evenly coated on a glass plate with a spatula, soaked in the water phase, and a composite porous membrane doped with composite nanoparticles and polyvinylidene fluoride is prepared by an immersion precipitation method.

(4) The obtained composite nanoparticle-doped polyvinylidene fluoride composite porous film was vacuum-dried at a temperature of 60° C. for 24 hours, and then soaked in a liquid electrolyte (mixed with dimethyl carbonate by lithium hexafluorophosphate) in a glove box. , the concentration that ethyl methyl carbonate and ethylene carbonate are formed is the mixed solution of 1M, and it forms by mass ratio dimethyl carbonate: ethyl methyl carbonate: ethylene carbonate=1:1:1.) 0.7 hour, By controlling the immersion time, the adsorbed liquid electrolyte component in the composition accounts for 60 wt% of the total mass, and the final composite gel polymer electrolyte film with a porous structure is obtained, and the film thickness is about 40 μm.

Example 4

(1) First, 8g methyl methacrylate and 0.98g maleic anhydride are mixed according to a molar ratio of 8:1, and the mixture is dispersed in deionized water under high-speed stirring. The mass ratio is 15wt%, that is, the mass of water is 59.9g, and then 0.539g of polyvinylpyrrolidone PVP-K30 relative to the mass of methyl methacrylate and maleic anhydride is added as a dispersant, with a mass fraction of 1.5 % that is 0.135g potassium persulfate is the initiator, heat up 100 ° C, react for 10 hours, drop to 25 ° C after the end of the reaction, add lithium hydroxide that is 0.48 g of 2 times the relative maleic anhydride molar weight to the reaction system, After reacting for 20 hours, the product was freeze-dried to obtain organic nanometer powder of methyl methacrylate copolymerized lithium maleate.

(2) Disperse 2.5 g of organic nano-powder methyl methacrylate copolymerized lithium maleate in 25 ml of absolute ethanol, control the mass ratio at 0.1 g/ml, ultrasonically disperse for 0.5 h, add ethyl orthosilicate, Among them, the mass ratio of ethyl orthosilicate to lithium maleate copolymerized with methyl methacrylate is 1:1, that is, the quality of ethyl orthosilicate is 2.5g, and ammonia water is added dropwise to control the pH value of the adjustment system at about 10, and the room temperature is 25 The reaction was carried out at ℃ for 15 hours to obtain composite nanoparticles whose shell layer was silicon dioxide and core layer was methyl methacrylate copolymerized lithium maleate.

(3) Dissolve and disperse polyvinylidene fluoride powder with a molecular weight of 4.5×10 ⁵ in N,N-dimethylformamide (N,N-dimethylformamide) solution at room temperature, and the concentration range of the polymer solution is controlled After stirring at 0.5g/ml for 10 hours, the composite nanoparticles with core-shell morphology were added and dispersed therein, wherein the doping amount of the composite nanoparticles with core-shell morphology relative to polyvinylidene fluoride was 2wt%, and ultrasonic 0.8 h, and then stirred at room temperature for 20 h so as to completely disperse evenly. After the polymer solution is left standing to remove air bubbles, it is evenly coated on a glass plate with a spatula, soaked in the water phase, and a composite porous membrane doped with composite nanoparticles and polyvinylidene fluoride is prepared by an immersion precipitation method.

(4) The obtained composite nanoparticle-doped polyvinylidene fluoride composite porous film was vacuum-dried at a temperature of 50° C. for 18 hours, and then soaked in a liquid electrolyte (mixed with dimethyl carbonate by lithium hexafluorophosphate) in a glove box. , the concentration that ethyl methyl carbonate and ethylene carbonate are formed is the mixed solution of 1M, and it forms by mass ratio dimethyl carbonate: ethyl methyl carbonate: ethylene carbonate=1:1:1.) 0.9 hours, By controlling the immersion time, the adsorbed liquid electrolyte component in the composition accounts for 65wt% of the total mass, and the final composite gel polymer electrolyte film with a porous structure is obtained, and the film thickness is about 45 μm.

Fig. 4 is the change of ion conductivity with temperature of the core-shell nanoparticle-doped polyvinylidene fluoride composite polymer electrolyte film in Example 1-4. The linear relationship shows that the ionic conductivity of the composite gel polymer electrolyte film conforms to the experimental Arrhenius equation and the general law of ionic conduction in the gel polymer electrolyte film. Conductive ion carriers are transported through the gel phase in the system and the liquid phase adsorbed in it. The folding of the polymer chain around the lithium ion helps it to separate from the large anion, and the peristalsis of the polymer chain can promote the lithium ion in it. transmission. The volume of the material expands with the rise of temperature, which makes the space free volume for ion conduction expand, and the energy of ion movement also increases with the rise of temperature. These factors all promote the movement of conductive ion carriers. Therefore, as the temperature increases, _Rb decreases.

Claims (9)

1. A preparation method of a porous gel polymer electrolyte doped with composite nanoparticles, characterized in that the steps are as follows: Step 1. Mix the mixed monomers methyl methacrylate and maleic anhydride in a molar ratio of 1:1 to 100:1, and then add 3-10wt% dispersant, the mixture is dispersed in deionized water under high-speed stirring, the mass ratio of the total amount of monomers to deionized water is 5-20wt%, and 1-3wt% of dispersant is added relative to the mass of mixed monomers Potassium sulfate, the temperature rise range of the reaction system is 60-100°C, the reaction time is controlled at 6-24 hours, after the reaction is completed, it is lowered to 25°C, and lithium hydroxide, which is twice the molar amount of maleic anhydride, is added to the reaction system. reacting for 6 to 10 hours to obtain organic nanoparticles of methyl methacrylate copolymerized lithium maleate dispersed in the water phase, and freeze-drying to obtain organic nanometer particles of methyl methacrylate copolymerized lithium maleate; Step 2. Disperse the organic nano-powder of methyl methacrylate copolymerized lithium maleate obtained in step 1 in ethanol, control its concentration at 0.01g/ml～0.5g/ml, ultrasonically disperse for 0.5h, and normalize according to the mass ratio Ethyl silicate: organic nano powder of methyl methacrylate copolymerized lithium maleate is 10:1～1:10, add orthosilicate ethyl ester, drop ammonia water to control the pH value of the adjustment system between 8～11, React at room temperature at 25°C for 6 to 24 hours to obtain core-shell morphology composite nanoparticles of methyl methacrylate copolymerized lithium maleate whose shell is silicon dioxide; Step 3: Dissolve and disperse polyvinylidene fluoride powder in N,N-dimethylformamide solution at room temperature, control the concentration of the polymer solution at 0.1-5g/ml, stir for 6-12 hours, and then obtain in step 2 The composite nanoparticles with core-shell morphology are added according to 0.01-10wt% of the doping amount of polyvinylidene fluoride powder and dispersed therein by ultrasonication for 0.1-1h, and then stirred at room temperature for 12-24h; The spatula is evenly coated on the glass plate, soaked in the water phase, and the composite porous film with core-shell morphology composite nanoparticles doped with polyvinylidene fluoride is prepared by immersion precipitation method; Step 4: Vacuum-dry the composite porous film of core-shell morphology composite nanoparticles doped polyvinylidene fluoride obtained in step 3 at a temperature of 40°C to 80°C for 8 to 24 hours, and then soak the liquid in a glove box Electrolyte for 0.5-1 hour to obtain a composite gel polymer electrolyte membrane with a porous structure in which the absorbed liquid electrolyte component accounts for 40-70 wt% of the total mass. 2 . The method for preparing a porous gel polymer electrolyte doped with composite nanoparticles according to claim 1 , wherein the thickness of the film is 30 μm˜50 μm. 3. according to the preparation method of the porous gel polymer electrolyte of a kind of doping composite nanoparticle according to claim 1, it is characterized in that, the mole of methyl methacrylate and maleic anhydride described in step 1 The ratio is preferably 5:1-20:1. 4. The method for preparing a porous gel polymer electrolyte doped with composite nanoparticles according to claim 1, wherein the dispersant in step 1 is polyvinylpyrrolidone, and the model is PVP-K30. 5. according to the preparation method of the porous gel polymer electrolyte of a kind of doping composite nanoparticle according to claim 1, it is characterized in that, tetraethyl orthosilicate described in step 2 and methyl methacrylate copolymerization The mass ratio of lithium formate is preferably 5:1˜1:2. 6. The method for preparing a porous gel polymer electrolyte doped with composite nanoparticles according to claim 1, wherein the molecular weight of the polyvinylidene fluoride described in step 3 is _Mn =4×10 ⁵ to 5×10 ⁵ . 7. according to the preparation method of the porous gel polymer electrolyte of a kind of doping composite nanoparticle according to claim 1, it is characterized in that, the composite nanoparticle of core-shell morphology described in step 3 is relative to polyvinylidene fluoride The doping amount of the powder is preferably 1 to 10 wt%. 8 . The method for preparing a porous gel polymer electrolyte doped with composite nanoparticles according to claim 1 , wherein the liquid electrolyte in step 4 is a 1M lithium hexafluorophosphate electrolyte. 9. according to the preparation method of the porous gel polymer electrolyte of a kind of doping composite nanoparticle according to claim 8, it is characterized in that, described 1M lithium hexafluorophosphate carbonate electrolyte is made of lithium hexafluorophosphate Add a mixed solution composed of dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate, the mass ratio of which is dimethyl carbonate:ethyl methyl carbonate:ethylene carbonate=1:1:1.