CN114497721B - Composite electrolyte film, preparation method thereof and application thereof in solid-state lithium battery - Google Patents
Composite electrolyte film, preparation method thereof and application thereof in solid-state lithium battery Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
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- H—ELECTRICITY
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- H01M2300/0017—Non-aqueous electrolytes
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Abstract
A composite electrolyte film, a preparation method and application thereof in a solid-state lithium battery relate to the electrolyte film, a preparation method and application thereof. The method aims to solve the technical problem that the electrochemical performance and the mechanical performance of the polymer electrolyte in the existing solid-state lithium battery are poor. The composite electrolyte membrane consists of a porous polymer fiber separator and a filled gel electrolyte. The preparation method comprises the following steps: coating the lithium ion conductor type filler with a surface treating agent, mixing the surface treating agent with a polymer to form an electrostatic spinning solution, and spinning to obtain a porous polymer fiber diaphragm; and (3) scraping gel electrolyte precursor liquid mixed by lithium salt, polymer monomer, plasticizer and initiator on the porous fiber diaphragm, and heating and curing to obtain the composite electrolyte film. And assembling the anode, the composite electrolyte film and the metal lithium cathode in a battery shell, and heating and curing to obtain the solid-state lithium battery. The capacity retention rate of the battery at room temperature in 0.5C circulation 200 circles is 86.4-99.9%, and the battery can be used in the field of lithium batteries.
Description
Technical Field
The invention belongs to the field of solid-state lithium batteries, and particularly relates to a composite electrolyte film, and a preparation method and application thereof.
Background
The solid electrolyte is taken as a core component of the solid lithium battery, and the reasonable design of the composition structure of the solid electrolyte is important for improving the performance of the lithium battery. The polymer electrolyte has the advantages of high flexibility, good interface fit with the electrodes, suitability for roll-to-roll production process and the like, and is widely focused in the field of flexible electronic devices. However, the polymer electrolyte has low room temperature ionic conductivity, poor mechanical strength and electrochemical stability, and still limits its practical application. In addition, the polymer electrolyte typically has a low lithium ion mobility, and concentration polarization caused thereby accelerates non-uniform deposition of lithium, ultimately leading to cell failure.
The addition of lithium ion conductor type fillers in polymer electrolytes is an effective means of improving the ionic conductivity and mechanical strength of the electrolyte. The Lewis acid sites on the surface of the filler not only can fix anions and improve the migration number of lithium ions; the ion rapid transmission channel generated at the interface of the filler and the polymer can obviously improve the lithium ion conduction rate. However, the scattered filler particles in the polymer electrolyte cannot form a continuous seepage structure, and it is difficult to take the advantage of the lithium ion conductor type filler to the maximum extent; and filler particles are easy to settle in the preparation process of the polymer electrolyte film, so that maldistribution is caused. Therefore, in order to construct a high-performance composite solid electrolyte, it is necessary to rationally design the structure of the filler.
Disclosure of Invention
The invention aims to solve the technical problems of poor electrochemical performance and mechanical performance of polymer electrolyte in the existing solid-state lithium battery, and provides a composite electrolyte film, a preparation method thereof and application thereof in the solid-state lithium battery.
The composite electrolyte film consists of a porous polymer fiber diaphragm and a filled gel electrolyte;
the porous polymer fiber diaphragm is formed by electrostatic spinning of a polymer solution containing a surface treatment agent coated lithium ion conductor filler, wherein the mass of the surface treatment agent coated lithium ion conductor filler accounts for 11% -67% of the mass of the polymer;
the gel electrolyte is formed by polymerization and solidification of lithium salt, polymer monomer, initiator and plasticizer; wherein the mass of the lithium salt accounts for 40-70% of the polymer monomer, the mass of the initiator accounts for 0.2-1% of the polymer monomer, and the mass of the plasticizer accounts for 50-100% of the polymer monomer.
Further, the surface treatment agent coated lithium ion conductor filler in the porous polymer fiber diaphragm is obtained by coating the lithium ion conductor filler by taking 3-aminopropyl triethoxysilane as a surface treatment agent; the lithium ion conductor filler is one or more of aluminum-doped titanium lithium phosphate, germanium-doped titanium lithium phosphate, lithium lanthanum titanium oxide, aluminum-doped lithium lanthanum titanium oxide, lithium lanthanum zirconium oxide, tantalum-doped lithium lanthanum zirconium oxide, niobium-doped lithium lanthanum zirconium oxide, lithium thiophosphate and chlorine-doped lithium thiophosphate.
Further, the polymer in the porous fibrous membrane is one or more of polyacrylonitrile, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene chloride and polypropylene carbonate.
Still further, the lithium salt in the gel electrolyte is one or more of lithium bis (trifluoromethanesulfonyl) imide, lithium trifluoromethanesulfonate, lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium perchlorate, and lithium bis (fluorosulfonyl) imide.
Further, the polymer monomer in the gel electrolyte is one or more of vinylene carbonate, methyl methacrylate, butyl acrylate and triethylene glycol diacrylate.
Further, the plasticizer in the gel electrolyte is one or more of fluoroethylene carbonate, triethyl phosphate, succinonitrile, propylene carbonate, dimethyl carbonate, diethyl carbonate and trimethyl phosphate.
Still further, the initiator in the filled gel electrolyte is azobisisobutyronitrile or azobisisoheptonitrile.
Further, the thickness of the porous polymer fiber membrane is 40-70 μm, and the thickness of the composite electrolyte film formed after the gel electrolyte is filled is 40-70 μm.
The preparation method of the composite electrolyte film comprises the following steps:
1. preparing a surface treating agent coated lithium ion conductor filler: the volume ratio of the absolute ethyl alcohol to the deionized water to the glacial acetic acid is 1: (0.04-0.06): (0.02-0.03) mixing and stirring absolute ethyl alcohol, deionized water and glacial acetic acid for 1-5 h to stabilize the pH value, then adding a surface treating agent, and continuously stirring for 2-6 h to obtain a mixed solution; dispersing lithium ion conductor type filler in the mixed solution, and stirring for 10-20 hours at the temperature of 60-80 ℃ to obtain dispersion liquid; sequentially centrifuging and washing the dispersion liquid, and repeating for three times; vacuum drying the solid phase material remained at the bottom after centrifugation to obtain a surface treating agent coated lithium ion conductor filler;
2. preparing an electrostatic spinning solution: weighing surface treating agent coated lithium ion conductor filler, polymer and solvent; wherein the mass of the surface treating agent coated lithium ion conductor filler is 11-67% of the mass of the polymer, and the mass of the solvent is 241-380% of the mass of the polymer; firstly, dissolving a polymer in a solvent, heating to 60-70 ℃ and uniformly stirring, then regulating the mass percentage concentration of the polymer in the solution to 14.9-25.0% by using acetone, then adding a surface treatment agent coated lithium ion conductor filler into the polymer solution, and continuously heating and uniformly stirring to obtain an electrostatic spinning solution;
3. Preparation of porous polymer fiber membrane loaded with surface treatment agent coated lithium ion conductor type filler: extracting the electrostatic spinning solution prepared in the second step into a 5mL injector, regulating the distance between a receiver and a metal needle of the injector to be 10-20 cm, regulating the direct current voltage to be 10-18 kV, and carrying out electrostatic spinning at the liquid injection speed of 0.5-1.2 mL/h to obtain a porous polymer fiber membrane loaded with a surface treatment agent coated lithium ion conductor type filler;
4. preparing gel electrolyte precursor liquid: weighing lithium salt, polymer monomer, initiator and plasticizer; wherein the mass of the lithium salt accounts for 40-70% of the polymer monomer, the mass of the initiator accounts for 0.2-1% of the polymer monomer, and the mass of the plasticizer accounts for 50-100% of the polymer monomer; firstly adding lithium salt into a polymer monomer, stirring for 0.5-1.2 h at room temperature, then adding a plasticizer and an initiator, and stirring uniformly at room temperature to obtain gel electrolyte precursor liquid;
5. preparing a composite electrolyte film: and (3) placing the porous polymer fiber membrane prepared in the step (III) on a flat substrate, uniformly knife-coating the gel electrolyte precursor solution prepared in the step (IV) in the porous polymer fiber membrane, and heating and curing to obtain the composite electrolyte film.
Further, the surface treating agent in the first step is 3-aminopropyl triethoxysilane;
further, the vacuum drying temperature in the first step is 60-80 ℃ and the drying time is 10-20 h;
further, the solvent in the second step is N, N-dimethylformamide, N-methylpyrrolidone or N, N-dimethylacetamide.
Further, the thickness of the porous polymer fiber membrane in the third step is 40-70 μm;
further, the flat substrate in the fifth step is a glass plate, a polytetrafluoroethylene plate or silicone paper.
Further, the heating curing temperature in the fifth step is 60-80 ℃, and the heating curing time is 5-10 h;
further, the thickness of the composite electrolyte film prepared in the fifth step is 40-70 mu m;
the application of the composite electrolyte film is that the composite electrolyte film is used in a solid-state lithium battery.
The method for preparing the solid-state lithium battery by using the composite electrolyte film comprises the following steps:
placing an anode, a composite electrolyte film and a metal lithium cathode in a battery shell, wherein the anode is a lithium iron phosphate anode or a lithium nickel cobalt manganese oxide anode, injecting gel electrolyte precursor liquid between a porous fiber diaphragm and an electrode, packaging the battery, and then heating and curing the battery in an oven with the temperature of 60-80 ℃ for 5-10 hours to obtain an in-situ polymerized solid lithium battery; the gel electrolyte precursor liquid is the same as the gel electrolyte precursor liquid adopted in the preparation process of the composite electrolyte film.
The porous polymer fiber membrane with higher mechanical strength and improved lithium ion transmission efficiency is combined with the gel electrolyte with better interface bonding property, and the composite electrolyte membrane is prepared through an in-situ polymerization curing process. The porous polymer fiber membrane is a three-dimensional porous fiber grid loaded with filler particles prepared by adopting an electrostatic spinning method, and is used as a filler skeleton structure in the composite solid electrolyte, so that the uniform distribution of the filler particles in the polymer electrolyte can be realized, and a long-range continuous lithium ion transmission path can be formed. By adopting the three-dimensional framework structure, the composite electrolyte film formed by in-situ polymerization and solidification of gel electrolyte precursor liquid filled in the three-dimensional framework structure not only has the performance advantage of composite solid electrolyte, but also can obviously promote the fit with an electrode interface. The liquid gel electrolyte precursor can fully infiltrate the inside of the porous electrode, so that continuous ion transmission channels are formed in the electrode and at the electrode/electrolyte interface.
The beneficial effects of the invention are as follows:
(1) According to the composite electrolyte film, the porous polymer fiber diaphragm loaded with the surface treatment agent coated lithium ion conductor type filler can ensure uniform dispersion of the lithium ion conductor type filler in the composite electrolyte, so that the filler sedimentation phenomenon possibly generated in the preparation process of the solid electrolyte film is avoided, and the structural uniformity of the composite electrolyte film composited with the lithium ion conductor type filler is effectively improved.
(2) According to the composite electrolyte film provided by the invention, the porous polymer fiber diaphragm loaded with the surface treatment agent coated lithium ion conductor type filler can enable the surface treatment agent coated lithium ion conductor type filler to be embedded on the fiber instead of being in the gaps between the fiber and the fiber through the hydrogen bond action between the surface treatment agent and the polymer fiber. The porous polymer fiber membrane loaded with the surface treatment agent coated lithium ion conductor type filler has higher porosity (78.6%), better wettability (contact angle=19.4°) to gel electrolyte precursor liquid and higher liquid absorption (386%).
(3) The porous polymer fiber membrane loaded with the surface treatment agent coated lithium ion conductor type filler can remarkably increase the interface contact area of the lithium ion conductor type filler and the gel electrolyte, fully expose Lewis acid sites on the surface of the lithium ion conductor type filler, and greatly exert the fixing effect of the filler on free anion groups in the gel electrolyte. In addition, the surface treating agent coated on the surface of the lithium ion conductor type filler is provided with-NH 3 + Groups, the electropositivity of which can enhance the surface treatment agent coating type lithium ion according to the electrostatic effectThe ionic conductor type filler has the fixing effect on the free anionic groups in the gel electrolyte, so that the dissociation degree of lithium salt in the gel electrolyte is enhanced, and the concentration of movable lithium ions is improved; the lithium ion migration number of the composite electrolyte film can be improved, and concentration polarization caused by movement of anions can be reduced; and a rapid lithium ion transmission channel generated at the interface of the surface treating agent coated lithium ion conductor type filler and the gel electrolyte can form a seepage structure for rapid lithium ion transmission in the electrolyte by means of a three-dimensional polymer fiber grid structure. Such structural advantage enables the composite electrolyte to have high room temperature ionic conductivity (1.06×10 -3 S/cm), up to 0.82, and up to 500 hours of lithium cycling stability.
(4) The electrochemical window of the composite electrolyte film provided by the invention can reach 4.86V, and the composite electrolyte film is prepared by using lithium iron phosphate (LiFePO) 4 ) The solid-state battery with the anode and the cathode of lithium metal has excellent room temperature rate performance and cycle performance (the initial cycle discharge specific capacity of 0.5C is 150.0mAh/g, and the capacity retention rate after 200 cycles is 99.9 percent); in the form of nickel cobalt lithium manganate (LiNi 0.5 Co 0.2 Mn 0.3 O 2 ) The solid-state battery with the anode and the cathode of lithium metal has excellent room temperature rate performance and cycle performance (the initial cycle discharge specific capacity of 0.5C is 144.2mAh/g, and the capacity retention rate after 100 cycles is 86.4%).
(5) The composite electrolyte film provided by the invention is formed by soaking, heating, polymerizing and solidifying gel electrolyte precursor liquid in a porous polymer fiber diaphragm, the thickness of the porous fiber diaphragm can be regulated and controlled by controlling the liquid injection speed and the electrostatic spinning time of an electrostatic spinning process, and the thickness of the prepared composite electrolyte film can be regulated and controlled by combining the effective control of the filling amount of the gel electrolyte precursor liquid. The in-situ polymerization technology can effectively solve the problems of poor contact between the polymer electrolyte and the electrode interface and discontinuous ion transmission inside the electrode. The invention overcomes the disadvantages of low room temperature conductivity, low migration number of lithium ions, poor electrochemical stability, low mechanical strength, poor stability to lithium and the like of polymer electrolyte. The invention has high battery assembly process matching performance with the traditional liquid lithium ion battery, has high practical application and popularization value, and is easy to realize mass production and commercial application of the composite electrolyte film.
Drawings
FIG. 1 is a transmission electron micrograph of polysiloxane coated aluminum-doped lithium titanium phosphate particles of example 1.
FIG. 2 is an X-ray photoelectron spectrum of polysiloxane coated aluminum-doped lithium titanium phosphate particles of example 1.
FIG. 3 is a scanning electron microscope image and a particle size distribution diagram of polysiloxane coated aluminum-doped lithium titanium phosphate particles of example 1.
Fig. 4 is a scanning electron microscope image of a porous polyvinylidene fluoride fiber separator loaded with polysiloxane coated aluminum-doped lithium titanium phosphate in example 1.
Fig. 5 is a photograph showing the contact angle between a porous polyvinylidene fluoride fiber membrane loaded with polysiloxane coated aluminum-doped lithium titanium phosphate and a gel electrolyte precursor in example 1.
Fig. 6 is a fourier infrared spectrum of a gel electrolyte precursor, a porous polyvinylidene fluoride fiber separator loaded with polysiloxane coated aluminum-doped lithium titanium phosphate, and a composite electrolyte film in example 1.
Fig. 7 is a scanning electron microscope image of the composite electrolyte film in example 1.
Fig. 8 is a stress-strain graph of a porous polyvinylidene fluoride fiber separator and a composite electrolyte membrane loaded with polysiloxane coated aluminum-doped lithium titanium phosphate in example 1.
Fig. 9 is an ac impedance spectrum of the composite electrolyte film in example 1.
Fig. 10 is a dc polarization graph of the composite electrolyte film in example 1.
FIG. 11 is a linear sweep voltammogram of the composite electrolyte film of example 1.
Fig. 12 is a graph showing a lithium cycle versus the composite electrolyte film of example 1.
Fig. 13 is a graph showing the rate performance and voltage profile of a lithium iron phosphate solid-state lithium battery prepared using the composite electrolyte membrane in example 1.
Fig. 14 is a graph showing cycle performance and voltage of a lithium iron phosphate solid-state lithium battery prepared using the composite electrolyte thin film in example 1.
Fig. 15 is a graph of rate performance and voltage for a lithium nickel cobalt manganate solid state lithium battery prepared using a composite electrolyte membrane in example 1.
Fig. 16 is a graph showing cycle performance and voltage profile of a lithium nickel cobalt manganese oxide solid-state lithium battery prepared using a composite electrolyte membrane in example 1.
Fig. 17 is a cycle performance chart of a lithium iron phosphate solid-state lithium battery prepared using the composite electrolyte membrane in example 2.
Fig. 18 is a cycle performance chart of a lithium iron phosphate solid-state lithium battery prepared using the composite electrolyte membrane in example 3.
Detailed Description
The following examples are used to demonstrate the benefits of the present invention.
Example 1: the preparation method of the composite electrolyte film of the embodiment comprises the following steps:
1. preparing a surface treating agent coated lithium ion conductor filler: uniformly mixing 45mL of absolute ethyl alcohol, 2.5mL of deionized water and 1.25mL of glacial acetic acid, stirring for 3h to stabilize the pH value, adding 5mL of surface treating agent 3-aminopropyl triethoxysilane, and continuously stirring for 5h to obtain a mixed solution; 1g of lithium ion conductor filler aluminum-doped lithium titanium phosphate (Li) 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 LATP) is dispersed in the mixed solution, and stirred for 10 hours at the temperature of 60 ℃ to obtain a dispersion liquid; sequentially centrifuging and washing the dispersion liquid, and repeating for three times; vacuum drying the solid phase material remained at the bottom after centrifugation for 12 hours at the temperature of 60 ℃ to obtain polysiloxane coated aluminum-doped lithium titanium phosphate particles;
2. preparing an electrostatic spinning solution: dissolving 3.69g of polyvinylidene fluoride in 13.3g of N, N-dimethylformamide, stirring for 5 hours at 60 ℃, adding 4.74g of acetone to form a polymer solution with 17wt% of polymer mass percentage concentration, adding 1.58g of polysiloxane coated aluminum-doped lithium titanium phosphate, and continuing stirring for 7 hours at 60 ℃ to obtain an electrostatic spinning solution;
3. Preparation of porous polymer fiber membrane loaded with surface treatment agent coated lithium ion conductor type filler: extracting 5mL of the electrostatic spinning solution prepared in the second step in a plastic injector, regulating the distance between a receiver and a metal needle of the injector to be 15cm, regulating the direct current voltage to be 15kV, carrying out electrostatic spinning at the injection speed of the injector to be 1mL/h, and obtaining a porous polyvinylidene fluoride fiber diaphragm with the thickness of 50 mu m and loaded with polysiloxane coated aluminum-doped lithium titanium phosphate after electrostatic spinning for 13 h;
4. preparing gel electrolyte precursor liquid: dissolving 0.55g of lithium bistrifluoromethane sulfonyl imide and 0.05g of lithium difluorooxalato borate in 1mL of vinylene carbonate monomer, stirring for 0.5h at room temperature, adding 0.4mL of fluorovinylene carbonate and 0.4mL of triethyl phosphate, stirring for 0.5h at room temperature, uniformly stirring the solution, adding 10mg of azobisisobutyronitrile, and continuing stirring for 0.5h to obtain a clear gel electrolyte precursor solution;
5. preparing a composite electrolyte film: placing the porous polyvinylidene fluoride fiber membrane loaded with the polysiloxane coated aluminum-doped lithium titanium phosphate prepared in the step three on a flat substrate, uniformly scraping the gel electrolyte precursor solution prepared in the step four on the porous polymer fiber membrane, wherein the scraping amount is 20 mu L/cm 2 After the precursor liquid fully infiltrates the fiber diaphragm, the fiber diaphragm is placed in an oven with the temperature of 60 ℃ for heating and curing for 6 hours, and the composite electrolyte film is obtained.
Fig. 1 is a transmission electron microscope image of polysiloxane coated aluminum-doped lithium titanium phosphate particles obtained in step one of example 1. As can be seen from fig. 1 (a) and (b), the polysiloxane coating layer on the surface of the aluminum-doped lithium titanium phosphate particles had a thickness of 7nm. As can be seen from fig. 1 (c), the surface of the polysiloxane coated aluminum-doped lithium titanium phosphate particles, the nitrogen, silicon and titanium elements are uniformly distributed, demonstrating the uniform distribution of the polysiloxane coating on the surface of the aluminum-doped lithium titanium phosphate particles.
FIG. 2 is an X-ray photoelectron spectrum of polysiloxane coated aluminum-doped lithium titanium phosphate particles obtained in example 1. From FIG. 2, it can be dividedPrecipitation, wherein Si-O chemical bonds and-NH exist in the polysiloxane coated aluminum-doped lithium titanium phosphate particles 2 Functional groups further demonstrate the presence of the polysiloxane coating.
FIG. 3 is a scanning electron microscope image and a particle size distribution diagram of polysiloxane coated aluminum-doped lithium titanium phosphate particles in example 1. As can be seen from FIGS. 3 (a) and (b), the particle size distribution of the polysiloxane coated aluminum-doped lithium titanium phosphate particles is 300 to 430nm.
Fig. 4 is a scanning electron microscope image of a porous polyvinylidene fluoride fiber separator loaded with polysiloxane coated aluminum-doped lithium titanium phosphate in example 1. It can be seen that the porous polyvinylidene fluoride fiber membrane loaded with the polysiloxane coated aluminum-doped lithium titanium phosphate, wherein the polysiloxane coated aluminum-doped lithium titanium phosphate particles are embedded on the polyvinylidene fluoride fibers, but not at the gaps among the polyvinylidene fluoride fibers.
The porosity of the porous polyvinylidene fluoride fiber membrane prepared in the embodiment is measured by adopting an n-butanol infiltration method, and the testing process and conditions are as follows:
soaking the porous polyvinylidene fluoride fiber membrane in n-butanol for 24 hours, taking out, and wiping with filter paper until no residual liquid exists on the surface. The porosity of the separator was calculated using the porosity formula:
in the formula (1), m 1 And m 2 Respectively representing the mass of the diaphragm before and after infiltration of n-butanol, ρ B Represents the density of n-butanol (0.81 g/cm) 3 )，V 1 Representing the apparent volume of the porous fibrous separator.
The porous polyvinylidene fluoride fiber membrane prepared in this example was measured for its liquid absorption by gel electrolyte precursor infiltration, and the test procedure and conditions were as follows:
and soaking the porous polyvinylidene fluoride fiber membrane in the gel electrolyte precursor solution for 24 hours, taking out, and wiping with filter paper until the weight of the wet membrane is not changed. Calculating the liquid absorption rate of the diaphragm by using a liquid absorption rate formula:
In the formula (2), m o And m' represents the mass of the separator before and after infiltration of the gel electrolyte precursor solution, respectively.
The porosity and the liquid absorption of the porous polyvinylidene fluoride fiber membrane loaded with polysiloxane coated aluminum-doped lithium titanium phosphate prepared in the step three of the present example 1 are shown in table 1.
Table 1 porosity and wicking of porous polyvinylidene fluoride fiber separator of example 1
Table 1 shows the porosity and the liquid absorption of the porous polyvinylidene fluoride fiber separator loaded with the polysiloxane coated aluminum-doped lithium titanium phosphate in example 1, and fig. 5 shows the contact angle of the porous polyvinylidene fluoride fiber separator to the gel electrolyte precursor in the fourth step. It can be seen that the porous fiber membrane prepared in the embodiment has a porosity of 78.6%, has good wettability to the gel electrolyte precursor solution, has a contact angle of only 19.4 degrees, and has a liquid absorption rate of up to 386%.
Fig. 6 is a fourier infrared spectrum of a gel electrolyte precursor, a porous polyvinylidene fluoride fiber separator loaded with polysiloxane coated aluminum-doped lithium titanium phosphate, and a composite electrolyte film in example 1. As can be seen from fig. 6 (a), no c=c (1562 cm -1 ) And = C-H (3166 cm) -1 ) And at 3019cm -1 Vibration peaks representing C-H appear, which demonstrate successful polymerization of vinylene carbonate monomer in the composite electrolyte film. In addition, as can be seen from FIG. 6 (b), the infrared light of the porous polyvinylidene fluoride fiber membrane loaded with polysiloxane coated aluminum-doped lithium titanium phosphateIn the spectrum, represent-CF 2 The peak of the symmetrical vibration had red shifted to 873cm -1 Is a phenomenon of (2). This is because the polysiloxane coating layer on the surface of the aluminum-doped lithium titanium phosphate particles contains-NH 2 A functional group capable of generating F.NH with fluorine atoms in polyvinylidene fluoride 2 The bonding force between the polysiloxane coated aluminum-doped lithium titanium phosphate particles and the polyvinylidene fluoride fibers is enhanced due to the hydrogen bonding effect.
Fig. 7 is a scanning electron microscope image of the composite electrolyte thin film prepared in example 1. Fig. 7 (a) is a surface view of a composite electrolyte membrane, fig. 7 (b) is a cross-sectional view of a composite electrolyte membrane, it can be seen that the composite electrolyte membrane has a flat and smooth surface morphology, the gel electrolyte can completely fill the pores of the porous fibrous membrane, and the composite electrolyte membrane has a thickness of 50 μm.
Fig. 8 is a stress-strain curve of the porous polyvinylidene fluoride fiber separator and the composite electrolyte membrane loaded with polysiloxane coated aluminum-doped lithium titanium phosphate in example 1. It can be seen that the porous polyvinylidene fluoride fiber membrane loaded with polysiloxane coated aluminum-doped lithium titanium phosphate has a breaking strength of 6.4MPa and a tensile deformation of 51.3%, and after being compounded with the gel electrolyte, the breaking strength of the composite electrolyte film is increased to 15.3MPa, and the tensile deformation is increased to 104.4%. This demonstrates that the even distribution of polysiloxane coated aluminum-doped lithium titanium phosphate particles, the strong hydrogen bonding between the polysiloxane coated aluminum-doped lithium titanium phosphate particles and the polyvinylidene fluoride fibers, and the in situ polymerization curing of the gel polymer electrolyte penetrating the fiber membrane, plays a critical role in enhancing the mechanical properties of the composite electrolyte film. The high mechanical property can effectively inhibit the growth and penetration of lithium dendrites and can relieve the volume change of the electrode in the circulation process.
The ion conductivity of the composite electrolyte membrane prepared in this example 1 was measured by electrochemical ac impedance test using CHI760 e electrochemical workstation by using stainless steel sheet as ion blocking electrode, assembling a symmetrical cell of stainless steel sheet/composite electrolyte membrane/stainless steel sheet structure, and the test procedure and conditions were as follows:
The AC impedance test is at 10 6 In the frequency range of 0.1Hz, the amplitude is 5mV, and the test result of alternating current impedance is fitted by ZView software under the room temperature condition. Calculating the ion conductivity of the composite electrolyte film by using a conductivity formula:
σ＝d/RS (3)
in the formula (3), σ represents the ionic conductivity of the composite electrolyte film, d represents the thickness of the composite electrolyte film, R represents the bulk resistance value of the composite electrolyte film obtained by fitting, and S represents the effective contact area between the stainless steel sheet and the composite electrolyte film.
Fig. 9 is an ac impedance spectrum of the composite electrolyte film of the present example 1, and table 2 is the conductivity of the composite electrolyte film.
TABLE 2 conductivity of composite electrolyte films
As can be seen from the calculation of the formula, the composite electrolyte film prepared in the present example 1 has a thickness of 1.06X10 at room temperature -3 S/cm ion conductivity, and meets the practical standard of a solid-state lithium battery.
The lithium ion migration number of the composite electrolyte film prepared in this example was measured by a dc polarization method and an ac impedance method using a CHI760e electrochemical workstation, and the test procedure and conditions were as follows:
In the DC polarization test, the applied polarization voltage was 20mV, and the change curve of the current with time was recorded. The interface impedance values of the Li/composite electrolyte film/Li battery before and after polarization were tested by an alternating current impedance method. The AC impedance test is at 10 6 In the frequency range of 0.1Hz, the amplitude is 5mV, and the test result of alternating current impedance is fitted by ZView software under the room temperature condition. Calculating the lithium ion migration number of the composite electrolyte film according to the formula:
t Li+ ＝[I ss ×(ΔV-I o R o )]/[I o ×(ΔV-I ss R ss )] (4)
in the formula (4), I o For the initial current value, I ss At steady state current value, R o Represents the interfacial impedance value at the initial state, R ss Represents the interfacial impedance value at steady state, and DeltaV is the polarization voltage.
The lithium ion mobility test curve of the composite electrolyte membrane prepared in example 1 is shown in fig. 10. As can be seen from fig. 10, the current value gradually decreased from the initial 0.0598mA and finally maintained at the steady state value (0.0573 mA) with the increase of the polarization time. The impedance fitting results before and after polarization show that the interface impedance of the lithium-symmetric battery in the initial state and the steady state is 296.7Ω and 303.0 Ω respectively, and the composite electrolyte film has a lithium ion migration number of 0.82 according to calculation.
The electrochemical window of the composite electrolyte film prepared in this example was measured by linear sweep voltammetry using a CHI760 e electrochemical workstation, with assembled Li/composite electrolyte film/stainless steel cell with Li as reference and counter electrode and stainless steel as working electrode. Test conditions: the sweeping speed is 1mV/s in a voltage interval of 2-6V. As can be seen from fig. 11, the composite electrolyte film prepared in example 1 has an oxidative decomposition potential of 4.86V and high electrochemical stability, and can be adapted to high-voltage cathode materials.
The composite electrolyte film prepared in this example was assembled into a lithium symmetric battery (Li/composite electrolyte film/Li), and a test for lithium stability was performed, with constant volume cycling performed by a new CT-4008T multi-channel battery tester at constant current density. Test conditions: the current density is 0.1mA/cm 2 The area of the lithium electrode was 1.78cm 2 Constant capacity of 0.1mAh/cm 2 And (3) carrying out circulation by adopting a mode of charging for 60min and discharging for 60min in each circle of circulation, wherein the test temperature is room temperature. The cycle voltage curve of the resulting symmetric lithium battery is shown in fig. 12. As can be seen from fig. 12, the lithium-symmetric battery assembled based on the composite electrolyte thin film of the present embodiment,has a lower overpotential value (35 mV) at the beginning of the cycle, gradually increases and stabilizes to 45mV at the end of the cycle. The composite electrolyte film prepared by the embodiment has excellent stability to lithium as shown by a stable voltage curve in the circulation process, a lower overpotential value and a circulation life as long as 500 hours.
A solid state lithium battery was prepared using the composite electrolyte film of example 1, and the specific method was as follows: and stacking a disc-shaped positive electrode with the diameter of 12mm, a disc-shaped metal lithium negative electrode with the diameter of 16mm and a disc-shaped metal lithium negative electrode with the diameter of 15mm in a battery shell, wherein the positive electrode is respectively a lithium iron phosphate positive electrode and a lithium nickel cobalt manganese oxide positive electrode, injecting gel electrolyte precursor liquid between a porous fiber diaphragm and an electrode with the injection amount of 40 mu L, packaging after the precursor liquid fully infiltrates the fiber diaphragm and the porous electrode, and heating and curing in an oven with the temperature of 60 ℃ for 6 hours to obtain the in-situ polymerized solid lithium battery. The gel electrolyte precursor liquid is the same as that in the step four of the embodiment 1, and the preparation process is as follows: 0.55g of lithium bistrifluoromethane sulfonyl imide and 0.05g of lithium difluorooxalato borate are dissolved in 1mL of vinylene carbonate monomer, after stirring for 0.5h at room temperature, 0.4mL of fluorovinylene carbonate and 0.4mL of triethyl phosphate are added, after stirring for 0.5h at room temperature, the solution is uniformly stirred, 10mg of azobisisobutyronitrile is added, and stirring is continued for 0.5h, so that a clear gel electrolyte precursor solution is obtained.
As for the solid-state lithium battery of the lithium battery using lithium iron phosphate as the positive electrode and lithium as the negative electrode, constant current charge and discharge cycle tests (1c=170 mAh/g) with different current densities are carried out by a NEWARE CT-4008T multichannel battery tester within a voltage range of 2.5-3.8V, the test temperature is room temperature (25+ -2 ℃), the rate performance of the obtained solid-state lithium battery is shown in fig. 13, and as can be seen from fig. 13 (a), the discharge specific capacities of the solid-state lithium battery at 0.1, 0.2, 0.3, 0.5, 1 and 2℃ rates are 154.9, 153.5, 150.1, 145.1, 137.9 and 124.5mAh/g respectively, and when the current density is recovered to 0.1C, the discharge specific capacities can be recovered to 156.3mAh/g, which indicates that the solid-state lithium battery has excellent rate performance. The corresponding battery charge-discharge cycle voltage curve is shown in fig. 13 (b), and it can be seen that the lithium battery based on the composite electrolyte film prepared in example 1 has a smaller charge-discharge electric polarization overpotential, and the increase of the electric polarization overpotential is smaller with the increase of the current density, which indicates that the composite electrolyte film prepared in example 1 has a higher lithium ion transmission efficiency.
For the solid-state lithium battery of the lithium battery taking lithium iron phosphate as the positive electrode and lithium as the negative electrode, constant current charge and discharge cycle test (1 C=170 mAh/g) under the 0.5C multiplying power is carried out by a NEWARE CT-4008T multichannel battery tester within the voltage range of 2.5-3.8V, the test temperature is room temperature (25+/-2 ℃), the cycle performance of the obtained solid-state lithium battery is shown in fig. 14, and as can be seen from fig. 14 (a), the solid-state lithium battery has the discharge specific capacity of 150.0mAh/g at the first cycle under the 0.5C multiplying power, and the capacity retention rate after 200 cycles can reach 99.9%. Further, it was found from the calculation that the average coulombic efficiency per turn of the battery was 100.0%, and the battery had excellent cycle stability. As can be seen from fig. 14 (b), the solid-state lithium battery has a relatively stable charge-discharge voltage plateau during the cycling process, the charge-discharge electrode overpotential can be maintained stable during the long-term cycling process, and the contact ratio of the charge-discharge voltage curves of the first turn and the 200 th turn is relatively high. Fig. 14 (C) and (d) are results of cycle performance test of solid-state lithium battery at 1C rate, and it can be seen that the first cycle of the battery has a specific discharge capacity of 144.1mAh/g, and the capacity retention rate can be as high as 94.1% after 200 cycles. The average coulombic efficiency value per turn of the cell was found to be 99.7% by calculation. The lithium battery assembled by the composite electrolyte film prepared based on the embodiment has excellent long-term cycling stability as can be known by combining a stable voltage platform and a charge-discharge electrode voltage with smaller amplification in the long-term cycling process of the battery.
For the solid-state lithium battery of the lithium battery taking nickel cobalt lithium manganate as the positive electrode and lithium as the negative electrode, constant current charge and discharge cycle tests (1C=160 mAh/g) with different current densities are carried out by a NEWARE CT-4008T multichannel battery tester within a voltage range of 2.8-4.2V, the test temperature is room temperature (25+/-2 ℃), the obtained solid-state lithium battery has multiplying power performance and corresponding voltage curves as shown in figure 15, and the discharge specific capacities of the solid-state lithium battery at multiplying powers of 0.1, 0.2, 0.3, 0.5, 1 and 2℃ are 170.7, 166.1, 164.1, 156.9, 144.1 and 127.8mAh/g respectively, and when the current density is recovered to 0.1C, the discharge specific capacities can be recovered to 169.0mAh/g, so that the solid-state lithium battery has excellent multiplying power performance is demonstrated.
For a solid-state lithium battery of a lithium battery taking nickel cobalt lithium manganate as a positive electrode and lithium as a negative electrode, a constant current charge and discharge cycle test (1 C=160 mAh/g) under the 0.5C multiplying power is carried out by a NEWARE CT-4008T multichannel battery tester within the voltage range of 2.8-4.2V, the test temperature is room temperature (25+/-2 ℃), the cycle performance and the corresponding voltage curve of the obtained solid-state lithium battery are shown in a graph as shown in fig. 16, and the solid-state lithium battery has the discharge specific capacity of 144.2mAh/g at the first cycle under the 0.5C multiplying power, and the capacity retention rate after 100 cycles can reach 86.4 percent, and has excellent cycle stability.
Example 2: the preparation method of the composite electrolyte film of the embodiment comprises the following steps:
1. preparing a surface treating agent coated lithium ion conductor filler: uniformly mixing 45mL of absolute ethyl alcohol, 2.5mL of deionized water and 1.25mL of glacial acetic acid, and stirring for 3h to stabilize the pH value; adding 5mL of surface treating agent 3-aminopropyl triethoxysilane, and continuously stirring for 5h; 1g of lithium ion conductor filler aluminum-doped lithium titanium phosphate (Li) 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 LATP) is dispersed in the solution, and the solution is heated and stirred for 10 hours at 60 ℃ to form a dispersion; sequentially centrifuging and washing the obtained dispersion liquid, and repeating for three times; sucking out the upper solvent after the third centrifugation, taking out the rest solid phase at the bottom, and vacuum drying at 60 ℃ for 12 hours to obtain polysiloxane coated aluminum-doped lithium titanium phosphate;
2. preparing an electrostatic spinning solution: dissolving 3.69g of polyvinylidene fluoride in 13.3g of N, N-dimethylformamide, stirring for 5 hours at 60 ℃, adding 4.74g of acetone to form a polymer solution with the polymer concentration of 17wt%, adding 1.58g of polysiloxane coated aluminum doped lithium titanium phosphate, and continuing stirring for 7 hours at 60 ℃ to obtain an electrostatic spinning solution;
3. preparation of porous polymer fiber membrane loaded with surface treatment agent coated lithium ion conductor type filler: extracting 5mL of electrostatic spinning solution in a plastic injector, regulating the distance between a metal needle of the injector and a receiving roller to be 15cm, regulating the direct current voltage to be 15kV, and obtaining a porous polyvinylidene fluoride fiber diaphragm with the thickness of 50 mu m and loaded with polysiloxane coated aluminum-doped lithium titanium phosphate after electrostatic spinning for 13h, wherein the injection speed of the injector is 1 mL/h;
4. Preparing gel electrolyte precursor liquid: dissolving 0.6g of lithium hexafluorophosphate in 1mL of vinylene carbonate monomer, stirring for 0.5h at room temperature, adding 0.4mL of dimethyl carbonate and 0.4mL of diethyl carbonate, after stirring for 0.5h, adding 8mg of azodiisobutyronitrile, and continuing stirring for 0.5h to obtain clear gel electrolyte precursor liquid;
5. preparing a composite electrolyte film: uniformly knife-coating the gel electrolyte precursor liquid prepared in the step four on the porous polyvinylidene fluoride fiber diaphragm loaded with the surface treatment agent coated lithium ion conductor type filler prepared in the step three on a flat plate substrate, wherein the knife-coating amount is 20 mu L/cm 2 And after the precursor liquid fully infiltrates the fiber diaphragm, heating and curing for 6 hours at 60 ℃ to obtain the composite electrolyte film.
The solid-state lithium battery was prepared using the composite electrolyte film prepared in this example 2, and the specific method was as follows: and stacking a disc-shaped lithium iron phosphate anode with the diameter of 12mm, a disc-shaped composite electrolyte film with the diameter of 16mm prepared in the example 2 and a disc-shaped metal lithium cathode with the diameter of 15mm in a battery shell, injecting gel electrolyte precursor liquid between a porous fiber diaphragm and an electrode with the injection amount of 40 mu L, and heating and curing for 6 hours at 60 ℃ after the precursor liquid fully infiltrates the fiber diaphragm and the porous electrode to obtain the in-situ polymerized solid-state lithium battery. The gel electrolyte precursor liquid is the same as the gel electrolyte precursor liquid in the step four of the embodiment 2, and the specific preparation method comprises the following steps: 0.6g of lithium hexafluorophosphate is dissolved in 1mL of vinylene carbonate monomer, stirred for 0.5h at room temperature, added with 0.4mL of dimethyl carbonate and 0.4mL of diethyl carbonate, after the solution is stirred for 0.5h uniformly, added with 8mg of azobisisobutyronitrile, and stirred for 0.5h continuously, so as to obtain clear gel electrolyte precursor liquid.
The solid-state lithium battery prepared in this example 2 was subjected to constant current charge and discharge cycle test (1c=170mah/g) at 0.2C rate in a voltage range of 2.5 to 3.8V by a new CT-4008T multi-channel battery tester, the test temperature was room temperature (25±2 ℃), and the cycle performance of the obtained solid-state lithium battery was as shown in fig. 17, and it can be seen that the first-turn discharge specific capacity of the solid-state lithium battery was 149.2mAh/g at 0.2C rate, and the capacity retention rate after 100 cycles was 99.5%.
Example 3: the preparation method of the composite electrolyte film of the embodiment comprises the following steps:
1. preparing a surface treating agent coated lithium ion conductor filler: uniformly mixing 45mL of absolute ethyl alcohol, 2.5mL of deionized water and 1.25mL of glacial acetic acid, and stirring for 3h to stabilize the pH value; then adding 5mL of surface treating agent 3-aminopropyl triethoxysilane, and continuously stirring for 5h; 1g of lithium ion conductor filler aluminum-doped lithium titanium phosphate (Li) 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 LATP) was dispersed in the above solution, and heated and stirred at 60 ℃ for 10 hours to form a dispersion; sequentially centrifuging and washing the obtained dispersion liquid, and repeating for three times; sucking out the upper solvent after the third centrifugation, taking out the rest solid phase at the bottom, and vacuum drying at 60 ℃ for 12 hours to obtain polysiloxane coated aluminum-doped lithium titanium phosphate;
2. Preparing an electrostatic spinning solution: dissolving 3.69g of polyvinylidene fluoride in 13.3g of N, N-dimethylformamide, stirring for 5 hours at 60 ℃, adding 4.74g of acetone to form a polymer solution with the polymer concentration of 17wt%, adding 1.58g of polysiloxane coated aluminum doped lithium titanium phosphate, and continuing stirring for 7 hours at 60 ℃ to obtain an electrostatic spinning solution;
3. preparation of porous polymer fiber membrane loaded with surface treatment agent coated lithium ion conductor type filler: extracting 5mL of electrostatic spinning solution in a plastic injector, regulating the distance between a metal needle of the injector and a receiving roller to be 15cm, regulating the direct current voltage to be 15kV, and obtaining a porous polyvinylidene fluoride fiber diaphragm with the thickness of 50 mu m and loaded with polysiloxane coated aluminum-doped lithium titanium phosphate after electrostatic spinning for 13h, wherein the injection speed of the injector is 1 mL/h;
4. preparing gel electrolyte precursor liquid: dissolving 0.5g of lithium bistrifluoromethane sulfonyl imide and 0.1g of lithium difluorooxalato borate in 1mL of vinylene carbonate monomer, stirring at room temperature for 0.5h, adding 0.7mL of fluorovinylene carbonate and 0.3mL of triethyl phosphate, stirring for 0.5h, uniformly stirring, adding 10mg of azodiisobutyronitrile, and continuing stirring for 0.5h to obtain a clear gel electrolyte precursor solution;
5. Preparation of a composite electrolyte film: uniformly knife-coating the gel electrolyte precursor liquid prepared in the step four on the porous polyvinylidene fluoride fiber diaphragm loaded with the surface treatment agent coated lithium ion conductor type filler prepared in the step three on a flat plate substrate, wherein the knife-coating amount is 20 mu L/cm 2 The method comprises the steps of carrying out a first treatment on the surface of the And after the precursor liquid fully infiltrates the fiber diaphragm, heating and curing for 6 hours at 60 ℃ to obtain the composite electrolyte film.
The preparation of a solid-state lithium battery using the composite electrolyte film obtained in this example 3 was specifically performed according to the following steps: and stacking a disc-shaped lithium iron phosphate anode with the diameter of 12mm, a disc-shaped composite electrolyte film with the diameter of 16mm prepared in the example 3 and a disc-shaped metal lithium cathode with the diameter of 15mm in a battery shell, injecting gel electrolyte precursor liquid between a porous fiber diaphragm and an electrode with the injection amount of 40 mu L, and heating and curing for 6 hours at 60 ℃ after the precursor liquid fully infiltrates the fiber diaphragm and the porous electrode to obtain the in-situ polymerized solid-state lithium battery. The gel electrolyte precursor solution is the same as the gel electrolyte precursor solution in the fourth step of the present embodiment 3, and the specific preparation method is as follows: 0.5g of lithium bistrifluoromethane sulfonyl imide and 0.1g of lithium difluorooxalato borate are dissolved in 1mL of vinylene carbonate monomer, after stirring for 0.5h at room temperature, 0.7mL of fluorovinylene carbonate and 0.3mL of triethyl phosphate are added, after stirring for 0.5h, the solution is uniform, 10mg of azodiisobutyronitrile is added, and stirring is continued for 0.5h, so that a clear gel electrolyte precursor solution is obtained.
The solid-state lithium battery obtained in example 3 was subjected to constant current charge and discharge cycle test (1c=170 mAh/g) in a voltage range of 2.5 to 3.8V by a new CT-4008T multi-channel battery tester at room temperature (25±2 ℃). The cycle performance of the obtained solid lithium battery is shown in fig. 18, and as can be seen from fig. 18 (a), the solid lithium battery has a specific discharge capacity of 144.8mAh/g at the first cycle at 0.5C rate, and the capacity retention rate after 200 cycles is 98.8%. As can be seen from fig. 18 (b), the initial discharge specific capacity can reach 152.8mAh/g at 1C rate, and the capacity retention rate after 100 cycles is 98.8%, with excellent cycle stability.
Claims (7)
1. A composite electrolyte membrane characterized in that the composite electrolyte membrane consists of a porous polymer fiber membrane and a filled gel electrolyte; the porous polymer fiber diaphragm is formed by electrostatic spinning of a polymer solution containing a surface treatment agent coated lithium ion conductor filler, wherein the mass of the surface treatment agent coated lithium ion conductor filler in the porous polymer fiber diaphragm accounts for 11% -67% of the mass of the polymer; the surface treating agent coated lithium ion conductor filler is obtained by coating the lithium ion conductor filler by taking 3-aminopropyl triethoxy silane as a surface treating agent; the lithium ion conductor filler is one or more of aluminum-doped titanium lithium phosphate, germanium-doped titanium lithium phosphate, lithium lanthanum titanium oxide, aluminum-doped lithium lanthanum titanium oxide, lithium lanthanum zirconium oxide, tantalum-doped lithium lanthanum zirconium oxide, niobium-doped lithium lanthanum zirconium oxide, lithium thiophosphate and chlorine-doped lithium thiophosphate; the polymer is one or more of polyacrylonitrile, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene chloride and polypropylene carbonate; the gel electrolyte is formed by gel of lithium salt, polymer monomer, initiator and plasticizer; wherein the mass of the lithium salt accounts for 40-70% of the mass of the polymer monomer, the mass of the initiator accounts for 0.2-1% of the mass of the polymer monomer, and the mass of the plasticizer accounts for 50-100% of the mass of the polymer monomer;
The preparation method of the composite electrolyte film comprises the following steps:
1. preparing a surface treating agent coated lithium ion conductor filler: the volume ratio of the absolute ethyl alcohol to the deionized water to the glacial acetic acid is 1: (0.04-0.06): (0.02-0.03) mixing and stirring absolute ethyl alcohol, deionized water and glacial acetic acid for 1-5 hours to stabilize the pH value, then adding a surface treating agent, and continuously stirring for 2-6 hours to obtain a mixed solution; dispersing lithium ion conductor type filler in the mixed solution, and stirring for 10-20 hours at the temperature of 60-80 ℃ to obtain a dispersion liquid; sequentially centrifuging and washing the dispersion liquid, and repeating for three times; vacuum drying the solid phase material remained at the bottom after centrifugation to obtain a surface treating agent coated lithium ion conductor filler;
2. preparing an electrostatic spinning solution: weighing surface treating agent coated lithium ion conductor filler, polymer and solvent; wherein the mass of the surface treating agent coated lithium ion conductor filler is 11% -67% of the mass of the polymer, and the mass of the solvent is 241% -380% of the mass of the polymer; firstly, dissolving a polymer in a solvent, heating to 60-70 ℃ and uniformly stirring, then regulating the mass percentage concentration of the polymer in the solution to 14.9-25.0% by using acetone, adding a surface treatment agent coated lithium ion conductor filler into the polymer solution, and continuously heating and uniformly stirring to obtain an electrostatic spinning solution;
3. Preparation of porous polymer fiber membrane loaded with surface treatment agent coated lithium ion conductor type filler: extracting the electrostatic spinning solution prepared in the second step into a 5mL injector, adjusting the distance between a receiver and a metal needle of the injector to be 10-20 cm, adjusting the direct current voltage to be 10-18 kV, and performing electrostatic spinning at the liquid injection speed of 0.5-1.2 mL/h to obtain a porous polymer fiber membrane loaded with a surface treatment agent coated lithium ion conductor type filler;
4. preparing gel electrolyte precursor liquid: weighing lithium salt, polymer monomer, initiator and plasticizer; wherein the mass of the lithium salt accounts for 40-70% of the mass of the polymer monomer, the mass of the initiator accounts for 0.2-1% of the mass of the polymer monomer, and the mass of the plasticizer accounts for 50-100% of the mass of the polymer monomer; firstly adding lithium salt into a polymer monomer, stirring at room temperature for 0.5-1.2 h, then adding a plasticizer and an initiator, and stirring at room temperature uniformly to obtain gel electrolyte precursor liquid;
5. preparing a composite electrolyte film: and (3) placing the porous polymer fiber membrane prepared in the step (III) on a flat substrate, uniformly knife-coating the gel electrolyte precursor solution prepared in the step (IV) in the porous polymer fiber membrane, and heating and curing to obtain the composite electrolyte film.
2. The composite electrolyte film according to claim 1, wherein the lithium salt in the gel electrolyte is one or more of lithium bis (trifluoromethanesulfonyl) imide, lithium trifluoromethanesulfonate, lithium hexafluorophosphate, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, lithium perchlorate and lithium bis (fluorosulfonyl) imide.
3. The composite electrolyte film according to claim 1, wherein the polymer monomer in the gel electrolyte is one or more of vinylene carbonate, methyl methacrylate, butyl acrylate and triethylene glycol diacrylate.
4. The composite electrolyte film according to claim 1, wherein the plasticizer in the gel electrolyte is one or more of fluoroethylene carbonate, triethyl phosphate, succinonitrile, propylene carbonate, dimethyl carbonate, diethyl carbonate and trimethyl phosphate.
5. The composite electrolyte film according to claim 1, wherein the initiator in the gel electrolyte is azobisisobutyronitrile or azobisisoheptonitrile.
6. Use of a composite electrolyte membrane according to claim 1, characterized in that the use of the composite electrolyte membrane is in a solid-state lithium battery.
7. The use of a composite electrolyte membrane according to claim 6, characterized in that the method for producing a solid-state lithium battery using the composite electrolyte membrane is carried out by the following steps: placing an anode, a composite electrolyte film and a metal lithium cathode in a battery shell, wherein the anode is a lithium iron phosphate anode or a lithium nickel cobalt manganese oxide anode, injecting gel electrolyte precursor liquid between a porous fiber diaphragm and an electrode, packaging the battery, and then placing the battery in an oven with the temperature of 60-80 ℃ for heating and curing for 5-10 hours to obtain an in-situ polymerized solid lithium battery; the gel electrolyte precursor liquid is the same as the gel electrolyte precursor liquid adopted in the preparation process of the composite electrolyte film.
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