CN105024094A - Polymer electrolyte containing lithium imide fluorosulfonate and preparing method of polymer electrolyte - Google Patents

Abstract

The invention discloses a polymer electrolyte containing fluorine-containing sulfonylimide lithium salt and a preparation method thereof. The polymer electrolyte prepared by the present invention has the advantages of high normal temperature electrical conductivity, low glass transition temperature and crystallinity, good mechanical strength and film-forming performance, and good compatibility with electrode materials. It is used in lithium (ion) batteries and carbon-based super capacitors. and solar cells have potential application value.

Description

A polymer electrolyte containing fluorine-containing sulfonylimide lithium salt and preparation method thereof

technical field

The invention belongs to the technical field of organic polymer functional materials and electrochemistry, and relates to a polymer electrolyte and a preparation method thereof.

Background technique

Non-aqueous electrolyte is one of the key materials of high specific energy secondary lithium (ion) batteries, and its comprehensive properties (such as chemical and electrochemical stability, safety, etc.) directly affect the performance and safety of batteries. At present, commercial lithium-ion battery electrolytes are mainly composed of liquid organic carbonate, conductive salt (mainly lithium hexafluorophosphate), and necessary functional additives (such as film formers, anti-overshoot additives, flame retardants, lithium hexafluorophosphate stabilizers, etc.) (Chem Rev., 2004, 104, 4303; J. PowerSources, 2006, 162, 1379). However, the liquid electrolyte system has disadvantages such as easy leakage of solvent, easy volatilization, poor high temperature resistance and flammability.

Compared with liquid electrolytes, gel polymer electrolytes (GPEs), which use aprotic small molecule organic solvents as plasticizers, have higher ionic conductivity, but there are still migration, volatilization, and mechanical properties of plasticizers. Poor problems lead to a sharp decline in battery performance (Eur.Polym.J., 2006, 42, 21; Electrochim.Acta, 2011, 57, 4), which cannot be used as a large lithium (ion) battery (such as power and energy storage batteries) ) requirements for safe, leak-free solid polymer electrolytes.

Pure solid polymer electrolytes (SPEs) are considered to be the main alternative electrolyte materials with great potential to solve the safety hazards of existing liquid electrolytes due to their high volume utilization, good film-forming properties, and no leakage (Nature , 2001, 414, 359). Its polymer network framework can effectively inhibit the growth of lithium dendrites, and can be applied to high specific energy secondary lithium batteries with metal lithium as the negative electrode. In particular, Li/LiFePO ₄ polymer batteries (LPB) based on pure SPEs have recently been successfully applied in France as a power source. Electric vehicles have greatly stimulated people's attention to all-solid-state polymer lithium batteries.

Pure SPEs are mainly composed of polymers containing Lewis basic groups such as polyoxyethylene (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF) and conductive lithium salts. mixed composition. In the prior art, the reported conductive salts for pure SPEs mainly include lithium hexafluorophosphate (LiPF ₆ , such as Electrochim.Acta, 2013, 90, 17; CN102117932, etc.), lithium perchlorate (LiClO ₄ , such as SolidStateIonics, 1986, 18-19,295; CN101901938; CN101130587; CN102324561, etc.), lithium tetrafluoroborate (LiBF ₄ , such as Electrochim.Acta, 2005, 50, 3942; CN102324559; CN102318125, etc.), lithium bisoxalate borate (LiBOB, such as CN1031993) , and lithium trifluoromethanesulfonate (LiOSO ₂ CF ₃ , such as Electrochim. Acta, 1998, 43, 1447; CN101735589; CN1396197, etc.), etc.

However, the normal temperature (40-60°C) conductivity of pure SPE _s composed of the above-mentioned lithium salt and polymer is low, only 10 ^-8 -10 ^-7 S cm ^-1 . Studies have shown that when the lithium salt lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) with a sulfonimide (-SO ₂ -N-SO ₂ -) structure is used as a conductive salt, it can significantly reduce the glass density of the polymer electrolyte. Temperature, improve its conductivity at room temperature. However, pure SPEs based on LiTFSI have poor compatibility with electrode materials (Macromolecules, 1994, 27, 7469; J. Electrochem. Soc., 1995, 142, 2118), which greatly limits the application of this type of SPEs.

To sum up, the pure solid polymer electrolytes in the prior art often have problems such as low conductivity at room temperature, insufficient mechanical strength and film-forming performance of the electrolyte, and poor compatibility with electrode materials.

Contents of the invention

The object of the present invention is to provide a polymer electrolyte containing fluorine-sulfonimide lithium salt.

The polymer electrolyte of the fluorine-containing sulfonylimide lithium salt provided by the present invention is composed of a polymer medium, a lithium salt and an additive, and the additive is selected from inorganic nanoparticles;

The solvent described in this method is selected from water, ethanol, methanol, acetone, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, acetic acid, ether, tetrahydrofuran, dimethyl sulfoxide, nitromethane , ethyl acetate, butyl acetate, petroleum ether, and at least one of toluene, preferably acetonitrile; the mass ratio of the solvent to the lithium salt is 20-200:1, preferably 20-100:1; The viscosity of the polymer solution is 1-20:1 Pa·s, preferably 5-10:1 Pa·s;

The polymer is selected from polyoxyethylene (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA) and polyvinyl butyral At least one of aldehydes (PVB), preferably at least one of polyoxyethylene (PEO), polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA); the number average molecular weight of the polymer is 5 ×10 ³ to 5×10 ⁷ g mol ^-1 , preferably the number average molecular weight is 5×10 ⁴ to 5×10 ⁶ g mol ^-1 ; the inorganic nanoparticles are selected from nano titanium dioxide particles, nano alumina particles, nano At least one of magnesium oxide particles, nano-silicon oxide particles, nano-zirconia particles and nano-zinc oxide particles, preferably nano-silicon oxide particles; the structural units of each polymer are respectively:

Described lithium salt is the compound with structure shown in following formula (I):

In formula (I),

R _F is F or CF ₃ ;

When R _F is F, n is an integer of 1-20, preferably n is 1-5; X is O; R _f is C _m F _2m+1 (m=1-8), OCH ₂ CF ₃ and OCH ( One of CF ₃ ) ₂ ;

When R _F is CF ₃ , n is 1; X is N-SO ₂ CF ₃ ; R _f is C _m F _2m+1 (m=1-8), OCH ₂ CF ₃ and OCH(CF ₃ ) ₂ a kind of

The inorganic nanoparticles are selected from at least one of nano-titania particles, nano-alumina particles, nano-magnesia particles, nano-silicon oxide particles, nano-zirconia particles and nano-zinc oxide particles, preferably nano-silicon oxide particles; The particle size of the nanoparticles is 1-500 nanometers, preferably 5-100 nanometers; the molar ratio of the structural unit of the polymer to the lithium salt is 5-30:1, preferably 15-20:1; the The mass ratio of inorganic nanoparticles to the lithium salt is 1:0.5-20, preferably 1:5-10.

Another object of the present invention is to provide a kind of preparation method of the polymer electrolyte containing fluorine sulfonimide lithium salt, and this preparation method comprises the steps:

Dissolving the lithium salt and the polymer in a solvent respectively, adding inorganic nanoparticles into the lithium salt solution, adding the polymer solution into the lithium salt solution, and mixing uniformly to obtain a mixed solution, the mixed solution The uniform method is selected from at least one of conventional stirring and ultrasonic, and the mixing time is 3-30 hours, preferably 10 hours, and the mixed solution is transferred to a flat and smooth substrate, and the flat and smooth surface The matrix can be made of polytetrafluoroethylene, glass or polypropylene material, and vacuum-dried at 60-80°C for 24-50 hours, preferably 48 hours, to obtain a polymer electrolyte containing fluorine-sulfonimide lithium salt;

The solvent described in this method is selected from water, ethanol, methanol, acetone, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, acetic acid, ether, tetrahydrofuran, dimethyl sulfoxide, nitromethane , ethyl acetate, butyl acetate, petroleum ether, and at least one of toluene, preferably acetonitrile; the mass ratio of the solvent to the lithium salt is 20-200:1, preferably 20-100:1; The viscosity of the polymer solution is 1-20:1 Pa·s, preferably 5-10:1 Pa·s;

The lithium salt described in the method is a compound having the structure shown in the above formula (I).

Inorganic nanoparticles described in the method are selected from at least one of nano-titania particles, nano-alumina particles, nano-magnesia particles, nano-silicon oxide particles, nano-zirconia particles and nano-zinc oxide particles, preferably nano-silicon oxide particles The particle diameter of the inorganic nanoparticles is 1 to 500 nanometers, preferably 5 to 100 nanometers; the molar ratio of the structural unit of the polymer to the lithium salt is 5 to 30:1, preferably 15 to 20: 1. The mass ratio of the inorganic nanoparticles to the lithium salt is 1:0.5-20, preferably 1:5-10.

The polymer electrolyte containing fluorine sulfonylimide lithium salt provided by the invention can be used to prepare lithium ion batteries and lithium batteries.

The polymer electrolyte provided by the present invention has the following advantages: (1) due to the strong electron-withdrawing effect of the perfluoroalkyl group, the negative charge density on the N atom is reduced, thereby promoting the increase of the dissociation degree of the sulfonylimide lithium, and the current-carrying The increase in the number of subs is conducive to improving the room temperature conductivity. (2) The unique flexibility of the imine based on the F-SO ₂ -N ^(-) -SO ₂ - structure reduces the crystallinity of the polymer, which is conducive to improving the conductivity of the polymer solid electrolyte. (3) By changing the ratio of lithium salt and polymer, polymer electrolytes with any different lithium salt contents are prepared to achieve the purpose of selecting the polymer electrolyte with the highest conductivity. (4) The polymer electrolyte containing F-SO ₂ -structure has good compatibility with electrode materials such as metal lithium and graphite, which reduces the interface impedance of the battery and improves the cycle efficiency and capacity retention of the battery.

The polymer electrolyte prepared by the present invention has the advantages of high electrical conductivity at room temperature, low glass transition temperature and crystallinity, good mechanical strength and film-forming performance, wide electrochemical window and good thermal stability. It is used in lithium (ion) batteries, carbon-based There are potential applications in supercapacitors and solar cells.

Description of drawings

Figure 1: Film photo of the blended electrolyte (electrolyte 2) of lithium fluorosulfonyl)(pentafluoroethylsulfonyl)imide (LiFPFSI) and polyoxyethylene prepared in Example 2.

Figure 2: The electrical conductivity of the blended electrolyte (electrolyte 2) of lithium fluorosulfonyl) (pentafluoroethylsulfonyl)imide (LiFPFSI) and polyoxyethylene prepared in Example 2 as a function of temperature;

Figure 3: The specific capacity and efficiency of the Li/LiFePO ₄ battery based on the blend electrolyte (electrolyte 2) of lithium fluorosulfonyl) (pentafluoroethylsulfonyl) imide (LiFPFSI) and polyoxyethylene prepared in Example 2. The relationship between the number of cycles.

Detailed ways

The preparation of some compounds involved in the present invention and the performance test results are listed below to further describe the present invention in detail, but are not limited to the listed compounds.

Embodiment 1～6 is the preparation of polymer electrolyte

Example 1: Preparation of a blend electrolyte (electrolyte 1) of (fluorosulfonyl)(trifluoromethylsulfonyl)imide lithium (LiFTFSI) and polyacrylonitrile

Under ultrasonic conditions, 0.5g (2.1mmol) LiFTFSI was added to 5mL of acetone to obtain a colorless homogeneous liquid, and then 2.2g of polyacrylonitrile with a molecular weight of 4×10 ⁵ g mol ^-1 (its structural unit was acrylonitrile , the molar ratio of the structure to lithium ions is 20:1) was added into 80 mL of acetone to obtain a colorless viscous liquid (viscosity of 4.3 Pa·s). The polymer solution was added to the lithium salt solution, and ultrasonicated for 2 hours to obtain a mixed solution; then, the obtained mixed solution was uniformly coated on the surface of a flat polytetrafluoroethylene plate by a spin coating method; the final The polytetrafluoroethylene plate was vacuum-dried at 50° C. for 48 hours to obtain a thin film (electrolyte 1) with a smooth surface, a thickness of 120 μm and a certain mechanical strength.

Example 2: Preparation of a blended electrolyte (electrolyte 2) of lithium (fluorosulfonyl)(pentafluoroethylsulfonyl)imide (LiFPFSI) and polyoxyethylene

Under ultrasonic conditions, 0.5g (1.7mmol) LiFPFSI was added to 5mL of acetonitrile to obtain a colorless homogeneous liquid, and then 1.5g of polyoxyethylene with a molecular weight of 4×10 ⁵ g mol ^-1 (its structural unit was oxyethylene , the molar ratio of this structure to lithium ions is 20:1) was added into 50 mL of acetone to obtain a colorless viscous liquid (viscosity of 9.7 Pa·s). The polymer solution was added to the lithium salt solution, and ultrasonicated for 5 hours to obtain a mixed solution; then, the obtained mixed solution was uniformly coated on the surface of a flat polytetrafluoroethylene plate by a spin coating method; the final The polytetrafluoroethylene plate was vacuum-dried at 50° C. for 24 hours to obtain a film with a smooth surface, a thickness of 150 μm and a certain mechanical strength (electrolyte 2, see FIG. 1 ).

Example 3: Preparation of a blended electrolyte (electrolyte 3) of (fluorosulfonyl) (perfluorobutylsulfonyl) lithium imide (LiFNFSI), nano-silica and polyoxyethylene

Under ultrasonic conditions, 1.2g (3.1mmol) LiFNFSI and 0.3g nano-silicon dioxide (particle size: 100nm) were successively added to 40mL acetone to obtain a uniform suspension, and then 2.2g with a molecular weight of 5×10 ⁵ g mol ^-1 of polyoxyethylene (its structural unit is oxyethylene, and the molar ratio of this structure to lithium ions is 16:1) was added to 100 mL of acetone to obtain a colorless viscous liquid (viscosity of 9.4 Pa·s). Add the polymer solution to the lithium salt and nano-silica solution, and ultrasonicate for 10 hours to obtain a mixed solution; then, use the spin coating method to uniformly coat the obtained mixed solution on a flat polytetrafluoroethylene The surface of the vinyl plate; finally, the polytetrafluoroethylene plate was vacuum-dried at 50° C. for 48 hours to obtain a film (electrolyte 3) with a smooth surface, a thickness of 110 μm and a certain mechanical strength.

Example 4: Preparation of a blend electrolyte (electrolyte 4) of (fluorosulfonyl) (perfluorohexylsulfonyl) lithium imide (LiFHFSI) and polyvinyl alcohol

Under ultrasonic conditions, 2.5g (5.1mmol) LiFHFSI was added to 50mL of ethanol to obtain a colorless homogeneous liquid, and then 2.3g of polyoxyethylene with a molecular weight of 4×10 ⁵ g mol ^-1 (its structural unit was vinyl alcohol , the molar ratio of this structure to lithium ions is 10:1,) was added into 100 mL of acetone to obtain a colorless viscous liquid (viscosity of 7.6 Pa·s). The polymer solution was added to the lithium salt solution, and ultrasonicated for 2 hours to obtain a mixed solution; then, the obtained mixed solution was uniformly coated on the surface of a flat polytetrafluoroethylene plate by a spin coating method; the final The polytetrafluoroethylene plate was vacuum-dried at 50° C. for 48 hours to obtain a thin film (electrolyte 4) with a smooth surface, a thickness of 100 μm and a certain mechanical strength.

Example 5: Preparation of a blended electrolyte (electrolyte 5) of lithium bis(fluorosulfonyl)sulfonyldiimide (LiFSDI) and polyoxyethylene

Under stirring, 0.7g (2.6mmol) LiFSDI was added to 5mL acetonitrile to obtain a colorless homogeneous liquid, and then 2.8g molecular weight was 4×10 ⁵ g mol ^-1 polyoxyethylene (its structural unit was oxyethylene, the The molar ratio of the structure to lithium ions is 24:1,) was added into 100 mL of acetonitrile to obtain a colorless viscous liquid (viscosity of 5.6 Pa·s). Add the polymer solution into the lithium salt solution and stir for 2 hours to obtain a mixed solution; then, use the spin coating method to uniformly coat the obtained mixed solution on the surface of a flat polytetrafluoroethylene plate; The polytetrafluoroethylene plate was vacuum-dried at 50° C. for 48 hours to obtain a thin film (electrolyte 5) with a smooth surface, a thickness of 140 μm and a certain mechanical strength.

Example 6: Preparation of (trifluoromethylsulfonyl) (trifluoromethyl (S-trifluoromethylsulfonimide) sulfonyl) (LiTFIT) and polyoxyethylene blend electrolyte (electrolyte 6)

Under stirring, 0.5g (1.2mmol) ^LiTFIT was added to 5mL of acetonitrile to obtain a colorless homogeneous liquid, and then ^1.1g of polyoxyethylene (its structural unit was oxyethylene, the The molar ratio of the structure to lithium ions is 20:1,) was added into 70 mL of acetonitrile to obtain a colorless viscous liquid (viscosity of 6.4 Pa·s). Add the polymer solution into the lithium salt solution, stir for 4 hours to obtain a mixed solution; then, use the spin coating method to uniformly coat the obtained mixed solution on the surface of a flat polytetrafluoroethylene plate; The polytetrafluoroethylene plate was vacuum-dried at 50° C. for 48 hours to obtain a thin film (electrolyte 6) with a smooth surface, a thickness of 130 μm and a certain mechanical strength.

Example 7: Performance characterization of polymer electrolytes 1-6 containing fluorine-containing sulfonimide lithium salt prepared in Examples 1-6

(1) Measurement of electrical conductivity: In the present invention, Metrohm's electrochemical workstation Autolab PGSTAT302N was used to measure the ionic conductivity of the polymer electrolyte by electrochemical impedance spectroscopy (EIS).

The polymer electrolyte membrane was sandwiched between two stainless steel blocking electrodes of known surface area. In order to ensure good contact between the electrodes and the electrolyte, the measurement system was kept at 60 °C for 2 hours before measurement. The temperature range of the measurement is 20 to 100° C., and the frequency of the measurement is 0.1 to 10 ⁶ Hz. Read the bulk resistance of the polymer electrolyte through the Nyquist diagram of AC impedance, and then calculate the conductivity σ of the polymer electrolyte membrane according to the formula σ=l/AR, where l is the thickness of the membrane, A is the electrode area, and R is the polymerization The bulk resistance of the electrolyte membrane.

(2) Determination of ion migration number: the AC impedance-DC polarization coupling method improved by Bruce et al. (Polymer, 1987, 28, 2324) and Watanabe et al. Determination of lithium ion transfer number. The polymer electrolyte was assembled into a symmetrical model battery Li|SPEs|Li, the test temperature was 60°C, the polarization voltage was 100mV, and the AC impedance test frequency range was 0.01Hz to 1MHz. According to the formula (where I _s and I _o are the steady-state current and the initial-state current (read in the DC polarization diagram) respectively, are the steady-state body resistance and initial-state body resistance (read from the impedance spectrum), respectively, ΔV is the polarization voltage (known, 100mV), Respectively, the initial state interface resistance and the steady state interface resistance (read in the impedance spectrum)), the lithium ion migration number can be calculated.

(3) Electrochemical window measurement: use Metrohm Autolab PGSTAT302N type electrochemical workstation in the present invention, adopt linear sweep voltammetry (LSV) to measure the oxidation and reduction potential of polymer electrolyte, then according to the formula:

EW _s ＝E _anodic -E _cathodic

(where EW _s is the electrochemical window of the polymer electrolyte; E _anodic is the oxidation potential of the polymer electrolyte; E _cathodic is the reduction potential of the polymer electrolyte), and the electrochemical window of the polymer electrolyte can be calculated.

A three-electrode system was used to measure the redox potential; where Pt was the working electrode (electrode area: 7.85×10 ^-3 cm ² ), metal lithium was the reference electrode and counter electrode; the scan rate was 5mV s ^-1 ; the test temperature was 60°C .

The results of the performance tests are listed in Table 1.

Table 1 Performance Test Results of Polymer Electrolytes 1-6 Containing Lithium Fluorine Sulfonylimide Salt (60°C)

Note: The test results of electrolyte 2 are shown in Figure 2.

Example 8: Application of a polymer electrolyte containing fluorine-containing sulfonylimide lithium salt in a lithium battery.

(1) Positive electrode: Electrode sheets respectively using LiCoO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , Li(CoNiMn) _1/3 O ₂ and the like as active materials are the positive electrodes.

(2) Negative electrode: Lithium foil, artificial graphite negative, Li ₄ Ti ₅ O ₁₂ etc. are used as negative electrodes respectively.

(3) Electrolyte: Electrolyte 2 and Electrolyte 5 are polymer electrolytes.

(4) Assembly of polymer battery: In an argon glove box, the above positive electrode, negative electrode and electrolyte were assembled into a polymer battery. The battery cycle performance test was carried out on an automatic charging and discharging instrument controlled by a microcomputer (Land, CT2001A). The test results of this embodiment are shown in Table 2.

Table 2 Performance of secondary lithium batteries based on polymer electrolytes containing fluorine-containing sulfonylimide lithium salts (60°C)

Note: The specific capacity and efficiency of the Li/LiFePO4 battery with electrolyte ₂ as a function of cycle number are shown in Fig. 3.

Claims (10)

1. A polymer electrolyte containing fluorine-containing sulfonylimide lithium salt, consisting of polymer, lithium salt and additive, wherein the additive is selected from inorganic nanoparticles. 2. the polymer electrolyte of fluorine-containing sulfonimide lithium salt according to claim 1, is characterized in that: described polymer is selected from polyoxyethylene (PEO), polyacrylonitrile (PAN), polymethacrylic acid At least one of methyl ester (PMMA), polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB), preferably polyoxyethylene (PEO), polyacrylonitrile (PAN) and at least one of polymethyl methacrylate (PMMA). 3. The polymer electrolyte containing fluorine-containing sulfonylimide lithium salt according to claim 1, 2 or 3, characterized in that: the number average molecular weight of the polymer is 5×10 ³ to 5×10 ⁷ g mol ^-1 , preferably the number average molecular weight is 5×10 ⁴ to 5×10 ⁶ gmol ^-1 . 4. The polymer electrolyte of the fluorine-containing sulfonimide lithium salt according to any one of claims 1 to 3, characterized in that: the lithium salt is a compound having a structure shown in the following formula (I): In formula (I), R _F is F or CF ₃ ; When R _F is F, n is an integer of 1-20, preferably n is 1-5; X is O; R _f is C _m F _2m+1 (m=1-8), OCH ₂ CF ₃ , and OCH One of (CF ₃ ) ₂ ; When R _F is CF ₃ , n is 1; X is N-SO ₂ CF ₃ ; R _f is C _m F _2m + ₁ (m=1-8), OCH ₂ CF ₃ , and OCH(CF ₃ ) ₂ One of. 5. The polymer electrolyte containing fluorine-containing sulfonimide lithium salt according to any one of claims 1 to 4, wherein the inorganic nanoparticles are selected from nano-titanium dioxide particles, nano-alumina particles, and nano-magnesia particles , at least one of nano-silicon oxide particles, nano-zirconia particles and nano-zinc oxide particles, preferably nano-silicon oxide particles. 6. The polymer electrolyte containing fluorine-containing sulfonylimide lithium salt according to any one of claims 1 to 5, characterized in that: the particle diameter of the inorganic nanoparticles is 1 to 500 nanometers, preferably 5 to 100 nanometers The molar ratio of the structural unit of the polymer to the lithium salt is 5 to 30:1, preferably 15 to 20:1; the mass ratio of the inorganic nanoparticles to the lithium salt is 1:0.5 to 20 , preferably 1 _: 5～10. 7. A method for preparing a polymer electrolyte containing fluorine-containing sulfonylimide lithium salt, comprising the steps of: Dissolving the lithium salt and at least one of the polymers polyoxyethylene (PEO), polyacrylonitrile (PAN) or polymethyl methacrylate (PMMA) in a solvent to prepare a lithium salt solution and a polymer solution respectively. Adding inorganic nanoparticles into the lithium salt solution, then adding the polymer solution into the lithium salt solution, and mixing uniformly to obtain a mixed solution, the mixing method is selected from conventional stirring and ultrasonic At least one, the mixing time is 3-30 hours, preferably 10 hours, the mixed solution is transferred to a flat and smooth substrate, and vacuum-dried at 60-80°C for 24-50 hours, preferably 48 hours, to obtain Polymer electrolyte membrane of fluorosulfonimide lithium salt; The solvent described in this method is selected from water, ethanol, methanol, acetone, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, acetic acid, ether, tetrahydrofuran, dimethyl sulfoxide, nitromethane , ethyl acetate, butyl acetate, petroleum ether, and at least one of toluene, preferably acetonitrile; the mass ratio of the solvent to the lithium salt is 20-200:1, preferably 20-100:1; The viscosity of the polymer solution is 1-20:1 Pa·s, preferably 5-10:1 Pa·s; Lithium salt described in this method is the compound with structure shown in general formula (I): In formula (I): R _F is F or CF ₃ ; When R _F is F, n is an integer of 1-20, preferably n is 1-5; X is O; R _f is C _m F _2m+1 (m=1-8), OCH ₂ CF ₃ , and OCH One of (CF ₃ ) ₂ ; When R _F is CF ₃ , n is 1; X is N-SO ₂ CF ₃ ; R _f is C _m F _2m + ₁ (m=1-8), OCH ₂ CF ₃ , and OCH(CF ₃ ) ₂ one of The inorganic nanoparticles are selected from at least one of nano-titania particles, nano-alumina particles, nano-magnesia particles, nano-silicon oxide particles, nano-zirconia particles and nano-zinc oxide particles, preferably nano-silicon oxide particles. 8. The method for preparing a polymer electrolyte containing fluorine-containing sulfonimide lithium salt according to claim 7, wherein the particle diameter of the inorganic nanoparticles is 1 to 500 nanometers, preferably 5 to 100 nanometers; The molar ratio of the structural unit of the polymer to the lithium salt is 5-30:1, preferably 15-20:1; the mass ratio of the inorganic nanoparticles to the lithium salt is 1:0.5-20, Preferably it is 1:5-10. 9. Application of the polymer electrolyte of the fluorine-containing sulfonimide lithium salt described in any one of claims 1 to 6 in lithium ion batteries or lithium batteries. 10. A lithium ion battery or lithium battery, characterized in that it contains the polymer electrolyte of the fluorine-containing sulfonimide lithium salt according to any one of claims 1 to 6.