A fluorine-containing compound-modified cellulose-based polymer electrolyte, and a preparation method and applications thereof

Abstract

The present application relates to the technical field of lithium metal battery electrolyte material, and provides a fluorine-containing compound modified cellulose-based polymer electrolyte and a preparation method and application thereof.The fluorine-containing compound in the polymer electrolyte can weaken the ability of lithium ions and anions through dipole interaction with lithium salt anions, promote the rapid conduction of ions, and form a fluorinated interface on the lithium metal negative electrode during lithium deposition, thereby playing a role in stabilizing the lithium metal negative electrode; the butanedinitrile in the structure can act as a plasticizer to improve the ionic conductivity of the polymer electrolyte, and also can improve the ion conduction rate through dipole interaction with lithium salt anions.Compared with traditional polymer electrolytes, the present application can effectively overcome the shortcomings of slow ion conduction rate and poor interface stability of traditional electrolytes, the formed fluorinated artificial solid electrolyte interface film can inhibit the side reaction of lithium metal, improve the interface stability, and realize the long-time cycle stability of lithium metal batteries.

Description

Technical Field

[0001] This invention relates to the field of polymer electrolyte materials for lithium metal batteries, and more specifically, to a fluorinated compound-modified cellulose-based polymer electrolyte, its preparation method, and its application. Background Technology

[0002] Although graphite has been widely used as a negative electrode material for lithium-ion batteries, its inherent specific capacity (372 mAh g⁻¹) remains a concern. −1 This significantly limits the improvement of battery energy density, making it difficult to meet the high energy density requirements of advanced energy storage systems. In contrast, lithium metal, with its ultra-high theoretical capacity (3860 mAh g⁻¹), offers superior performance. −1 Lithium metal (LiMe) batteries, with their lowest electrochemical potential (-3.04 V vs. SHE), are considered ideal anode choices for constructing high-energy-density battery systems. However, persistent side reactions between lithium metal and liquid electrolytes can induce the formation of an unstable solid electrolyte interface (SEI), leading to lithium dendrite growth, "dead lithium" accumulation, and irreversible capacity decay. Furthermore, conventional carbonate electrolytes tend to form porous SEI layers with weak mechanical properties, while ether-based systems are limited by a narrow electrochemical stability window (most oxidation potentials < 4.0 V). These defects not only severely restrict cycle stability but also hinder the effective utilization of high-voltage cathode materials, ultimately reducing the actual energy density and application range of lithium metal batteries. Therefore, developing novel electrolyte systems with a wide electrochemical stability window and achieving effective control over lithium metal deposition behavior is crucial for advancing high-performance lithium metal battery technology.

[0003] Polymer electrolytes, composed of a polymer matrix and lithium salts, significantly improve the safety performance of lithium-ion batteries due to the absence of organic electrolytes. However, the low ionic conductivity and poor interfacial stability of polymer electrolytes limit their commercial application due to the crystallinity of polymer molecular chains and the poor compatibility between solid electrolytes and electrode materials. Therefore, designing and preparing polymer electrolyte materials with high ionic conductivity and excellent interfacial properties is of great significance for the development of high-performance lithium-ion battery technology.

[0004] Cellulose, as a natural and renewable polymer material, possesses excellent biodegradability and low toxicity. Furthermore, its structure contains numerous hydroxyl groups, allowing for functional modification through chemical synthesis to enhance its performance. Compared to polyolefin membranes, cellulose-based electrolytes significantly improve electrolyte wettability and absorption rate; however, the large amount of liquid electrolyte within them still poses serious safety risks. In addition, side reactions between the liquid electrolyte and the lithium metal anode can easily form a brittle SEI film, which is a key factor affecting the electrochemical performance of lithium-ion batteries. Therefore, developing cellulose-based electrolyte systems with good electrochemical performance to optimize the structure and composition of the SEI film is crucial. Summary of the Invention

[0005] This invention provides a fluorinated compound-modified cellulose-based polymer electrolyte, its preparation method, and its application. By improving the key structure and related composition of this polymer electrolyte (especially the key monomer structure design), as well as the reaction conditions of each step in the corresponding preparation method, a fluorinated compound-modified cellulose-based polymer electrolyte is formed.

[0006] In a first aspect, the present invention provides a fluorinated compound-modified cellulose-based polymer electrolyte, the polymer electrolyte comprising fluorinated compound-modified cellulose acetate, succinate, and lithium salt, the chemical structural formula of the fluorinated compound-modified cellulose acetate being as follows: ; The structure of the fluorine-containing compound is as follows: ; The molecular structure of the cellulose acetate is as follows: .

[0007] Preferably, the polymer electrolyte further includes a lithium salt, which includes one or more of lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium perchlorate, lithium hexafluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide.

[0008] Preferably, the polymer electrolyte is in the form of a film, and the thickness of the polymer electrolyte is 50~300μm.

[0009] Secondly, the present invention provides a method for preparing a fluorinated compound-modified cellulose-based polymer electrolyte, comprising the following steps: 1) Dissolve pentafluoropropanol, epichlorohydrin and sodium hydroxide in a first solvent. After the resulting solution is reacted under stirring, the solvent is removed by rotary evaporation. The fraction at 108~112℃ is collected by distillation to obtain the fluorinated compound PFEE. 2) The obtained PFEE, cellulose acetate, triphenylphosphine, and second solvent were mixed evenly. Under stirring conditions, the product was washed three times with diethyl ether and dried to obtain fluorinated cellulose acetate. 3) Mix equimolar amounts of N-ethylimidazolium and 1-bromobutane with ethyl acetate and stir until homogeneous. After heating and reflux reaction, obtain the organic layer using a separatory funnel. Wash the product three times with ethyl acetate and dry the product to obtain 1-ethyl-3-methylimidazolium bromide ionic liquid. 4) Fluorine-modified cellulose acetate, 1-ethyl-3-methylimidazolium bromide ionic liquid, succinate, and lithium salt are mixed in a third solvent and stirred to form a homogeneous solution. The resulting solution is then poured onto a mold and dried under vacuum to obtain a cellulose-based polymer electrolyte membrane.

[0010] Preferably, in step 1), the reaction temperature is 30~80℃ and the reaction time is 4~10h; the molar ratio of pentafluoropropanol to epichlorohydrin is 1-5:1; the first solvent includes one or more of ethanol, ethyl acetate, deionized water, and acetonitrile.

[0011] Preferably, in step 2), the reaction temperature is 30~150℃, the reaction time is 4~10h; the molar ratio of PFEE to cellulose acetate is 1-10:1; the amount of triphenylphosphine added is 1%~10% of the mass of cellulose acetate; the second solvent includes one or more of N-methylpyrrolidone, methanol, deionized water, and acetonitrile.

[0012] Preferably, in step 3), the reaction temperature is 50~100℃ and the reaction time is 10~24h.

[0013] Preferably, in step 4), the weight ratio of the fluorinated cellulose acetate modified with the ionic liquid is 1-4:1; and the weight ratio of the fluorinated cellulose acetate modified with the succinic acid is 1-5:1.

[0014] Preferably, in step 4), the weight of the lithium salt is 5% to 30% of the total weight of the electrolyte; the third solvent includes one or more of tetrahydrofuran, N,N-dimethylformamide, and N-methylpyrrolidone.

[0015] Thirdly, the present invention provides an application of a fluorinated compound-modified cellulose-based polymer electrolyte in lithium metal batteries.

[0016] In summary, the present invention has the following beneficial effects: This invention provides a method for preparing a fluorinated cellulose-based polymer electrolyte. The fluorinated compound in the polymer electrolyte weakens the interaction between lithium ions and anions through a dipole interaction with lithium salt anions, thus promoting rapid ion conduction. During lithium deposition, it forms a fluorinated interface at the lithium metal anode, stabilizing the anode. The succinic anionizer in the structure acts as a plasticizer to improve the ionic conductivity of the polymer electrolyte and also enhances the ion conduction rate through its dipole interaction with lithium salt anions. Compared to traditional polymer electrolytes, this invention effectively overcomes the shortcomings of slow ion conduction rates and poor interfacial stability. The formed fluorinated lithium-ionized artificial SEI film effectively suppresses side reactions of lithium metal, improves the cycle stability of lithium metal batteries, and solves the technical problems of low ionic conductivity and poor interfacial stability with the lithium metal anode in existing polymer electrolytes.

[0017] 2. This invention first synthesizes a fluorinated compound PFEE by reacting pentafluoropropanol and epichlorohydrin. Then, it uses the epoxy group in the structure of the fluorinated compound PFEE to perform a ring-opening reaction with the hydroxyl group of cellulose acetate to modify the fluorinated compound into cellulose acetate. Finally, the fluorinated compound-modified cellulose acetate is blended with an ionic liquid, succinate, and lithium salt to prepare a fluorinated compound-modified cellulose-based polymer electrolyte.

[0018] 3. The introduction of fluorinated compounds in this invention can improve the electrochemical stability of the polymer electrolyte. At the same time, it can form a lithium fluoride-rich SEI film on the surface of the lithium metal anode during cycling, thereby improving the interfacial stability between the electrolyte and the anode. This method of improving interfacial stability by modifying cellulose with fluorinated compounds has not been reported before.

[0019] 4. The fluorinated compound of the present invention can weaken the affinity between lithium ions and anions through a dipole interaction with lithium salt anions, thereby promoting rapid ion conduction. Succinitriles can be used as plasticizers to improve the ionic conductivity of polymer electrolytes. Similarly, they can also improve the ion conduction rate and thus the ionic conductivity of polymer electrolytes through a dipole interaction with lithium salt anions.

[0020] 5. The present invention can obtain a polymer electrolyte by blending fluorinated cellulose acetate modified with ionic liquid, succinic acid and lithium salt. The preparation process is simple and the raw materials are readily available, making it suitable for large-scale production of cellulose-based polymer electrolyte materials.

[0021] 6. The fluorinated compound-modified cellulose-based polymer electrolyte prepared by this invention can be used as an electrolyte material to assemble lithium metal batteries, and its excellent performance can improve the electrochemical performance of lithium metal batteries.

[0022] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the scope of protection of the present invention. Attached Figure Description

[0023] Figure 1 This is the nuclear magnetic resonance spectrum of the fluorine-containing compound prepared in Example 1 of this invention; Figure 2 This is an appearance diagram of the polymer electrolyte membrane prepared in Example 1 of the present invention; Figure 3 This is a polarization curve of a symmetrical battery assembled with the polymer electrolyte prepared in Example 1 of this invention. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments can be obtained from commercially available sources.

[0025] Example Example 1 A method for preparing a fluorinated compound-modified cellulose-based polymer electrolyte includes the following steps: 3.0 g of pentafluoropropanol, 9.2 g of epichlorohydrin, 1.2 g of sodium hydroxide, and 0.35 g of deionized water were stirred until homogeneous and reacted at 70 °C for 10 hours to obtain the initial product. The product was purified by distillation, and the fraction collected at 108–112 °C yielded the fluorinated compound PFEE. The structure of the fluorinated compound PFEE synthesized in this example was confirmed by nuclear magnetic resonance spectroscopy, as shown in the spectrum below. Figure 1 As shown.

[0026] 1.0 g of fluorinated compound PFEE, 1.67 g of cellulose acetate, and 50 mg of triphenylphosphine were dissolved in 20 mL of N-methylpyrrolidone. The mixture was heated to 100 °C and reacted for 10 hours to obtain a solid product. The solid product was washed three times with diethyl ether and dried under vacuum at 70 °C for 24 hours to obtain fluorinated compound-modified cellulose acetate.

[0027] 2.0 g of N-methylimidazolium and 3.3 g of 1-bromobutane were dissolved in 20 mL of ethyl acetate and magnetically stirred at 85 °C for 18 hours. After the reaction was completed, the mixture was separated into liquid and liquid layers. The ionic liquid layer was washed three times with ethyl acetate, and the product was dried to obtain the ionic liquid 1-ethyl-3-methylimidazolium bromide.

[0028] 1.0 g of fluorinated cellulose acetate, 0.3 g of ionic liquid, 0.3 g of succinic acid, and 0.4 g of lithium perchlorate were dissolved in N-methylpyrrolidone and stirred into a homogeneous solution. The resulting solution was then poured into a mold and dried under vacuum to obtain a fluorinated cellulose-based polymer electrolyte. Figure 2 This is an appearance image of the polymer electrolyte prepared according to an embodiment of the present invention, showing that the electrolyte has good structural stability. The electrolyte membrane was assembled into a Li||Li symmetric battery for cycle testing. Figure 3 This is the polarization curve of the symmetrical battery. The stable polarization curve observed after 220 hours of cycling at a current density of 0.5 mA cm⁻² indicates that the polymer electrolyte prepared in this embodiment of the invention exhibits good interfacial stability with the lithium metal anode.

[0029] Example 2 A method for preparing a fluorinated compound-modified cellulose-based polymer electrolyte includes the following steps: 3.0 g pentafluoropropanol, 18.5 g epichlorohydrin, 1.2 g sodium hydroxide, and 0.35 g ethanol were stirred until homogeneous and reacted at 30 °C for 4 hours to obtain the primary product. The product was purified by distillation, and the fraction collected at 108–112 °C yielded the fluorinated compound PFEE.

[0030] 1.0 g of fluorinated compound PFEE, 22.8 g of cellulose acetate, and 228 mg of triphenylphosphine were dissolved in 20 mL of methanol, heated to 30 °C, and reacted for 4 hours to obtain a solid product. The solid product was washed three times with diethyl ether and dried under vacuum at 70 °C for 24 hours to obtain fluorinated compound-modified cellulose acetate.

[0031] 2.0 g of N-methylimidazolium and 3.3 g of 1-bromobutane were dissolved in 20 mL of ethyl acetate and magnetically stirred at 50 °C for 10 hours. After the reaction was completed, the mixture was separated into liquid and liquid layers. The ionic liquid layer was washed three times with ethyl acetate, and the product was dried to obtain the ionic liquid 1-ethyl-3-methylimidazolium bromide.

[0032] 1.0 g of fluorinated cellulose acetate, 0.25 g of ionic liquid, 0.2 g of succinic acid, and 0.07 g of lithium tetrafluoroborate were dissolved in tetrahydrofuran and stirred to form a homogeneous solution. The resulting solution was then poured into a mold and dried under vacuum to obtain a fluorinated cellulose-based polymer electrolyte.

[0033] Example 3 A method for preparing a fluorinated compound-modified cellulose-based polymer electrolyte includes the following steps: 3.0 g pentafluoropropanol, 0.37 g epichlorohydrin, 1.2 g sodium hydroxide, and 0.35 g ethyl acetate were stirred until homogeneous and reacted at 80 °C for 10 hours to obtain the primary product. The product was purified by distillation, and the fraction collected at 108–112 °C yielded the fluorinated compound PFEE.

[0034] 1.0 g of fluorinated compound PFEE, 2.28 g of cellulose acetate, and 22.8 mg of triphenylphosphine were dissolved in 20 mL of deionized water, heated to 150 °C, and reacted for 10 hours to obtain a solid product. The solid product was washed three times with diethyl ether and dried under vacuum at 70 °C for 24 hours to obtain fluorinated compound-modified cellulose acetate.

[0035] 2.0 g of N-methylimidazolium and 3.3 g of 1-bromobutane were dissolved in 20 mL of ethyl acetate and magnetically stirred at 100 °C for 10 hours. After the reaction was completed, the mixture was separated into liquid and liquid layers. The ionic liquid layer was washed three times with ethyl acetate, and the product was dried to obtain the ionic liquid 1-ethyl-3-methylimidazolium bromide.

[0036] 1.0 g of fluorinated cellulose acetate, 4.0 g of ionic liquid, 5.0 g of succinic acid, and 3.0 g of lithium bis(oxalato)borate were dissolved in N,N-dimethylformamide and stirred to form a homogeneous solution. The resulting solution was then poured into a mold and dried under vacuum to obtain a fluorinated cellulose-based polymer electrolyte.

[0037] Example 4 A method for preparing a fluorinated compound-modified cellulose-based polymer electrolyte includes the following steps: 3.0 g of pentafluoropropanol, 0.5 g of epichlorohydrin, 1.2 g of sodium hydroxide, and 0.35 g of acetonitrile were stirred until homogeneous and reacted at 50 °C for 8 hours to obtain the initial product. The product was purified by distillation, and the fraction collected at 108–112 °C yielded the fluorinated compound PFEE.

[0038] 1.0 g of fluorinated compound PFEE, 2.0 g of cellulose acetate, and 20 mg of triphenylphosphine were dissolved in 20 mL of acetonitrile and heated to 50 °C for 6 hours to obtain a solid product. The solid product was washed three times with diethyl ether and dried under vacuum at 70 °C for 24 hours to obtain fluorinated compound-modified cellulose acetate.

[0039] 2.0 g of N-methylimidazolium and 3.3 g of 1-bromobutane were dissolved in 20 mL of ethyl acetate and magnetically stirred at 70 °C for 6 hours. After the reaction was completed, the mixture was separated into liquid and liquid layers. The ionic liquid layer was washed three times with ethyl acetate, and the product was dried to obtain the ionic liquid 1-ethyl-3-methylimidazolium bromide.

[0040] 1.0 g of fluorinated cellulose acetate, 0.9 g of ionic liquid, 0.5 g of succinic acid, and 0.8 g of lithium bis(trifluoromethanesulfonyl)imide were dissolved in tetrahydrofuran and stirred to form a homogeneous solution. The resulting solution was then poured into a mold and dried under vacuum to obtain a fluorinated cellulose-based polymer electrolyte.

[0041] Example 5 A method for preparing a fluorinated compound-modified cellulose-based polymer electrolyte includes the following steps: 3.0 g of pentafluoropropanol, 12.5 g of epichlorohydrin, 1.2 g of sodium hydroxide, and 0.35 g of deionized water were stirred until homogeneous and reacted at 60 °C for 5 hours to obtain the initial product. The product was purified by distillation, and the fraction collected at 108–112 °C yielded the fluorinated compound PFEE.

[0042] 1.0 g of fluorinated compound PFEE, 5.2 g of cellulose acetate, and 52 mg of triphenylphosphine were dissolved in 20 mL of N-methylpyrrolidone. The mixture was heated to 120 °C and reacted for 8 hours to obtain a solid product. The solid product was washed three times with diethyl ether and dried under vacuum at 70 °C for 24 hours to obtain fluorinated compound-modified cellulose acetate.

[0043] 2.0 g of N-methylimidazolium and 3.3 g of 1-bromobutane were dissolved in 20 mL of ethyl acetate and magnetically stirred at 90 °C for 12 hours. After the reaction was completed, the mixture was separated into liquid and liquid layers. The ionic liquid layer was washed three times with ethyl acetate, and the product was dried to obtain the ionic liquid 1-ethyl-3-methylimidazolium bromide.

[0044] 1.0 g of fluorinated cellulose acetate, 0.2 g of ionic liquid, 0.8 g of succinic acid, and 0.9 g of lithium perchlorate were dissolved in N-methylpyrrolidone and stirred into a homogeneous solution. The resulting solution was then poured into a mold and dried under vacuum to obtain a fluorinated cellulose-based polymer electrolyte.

[0045] Example 6 A method for preparing a fluorinated compound-modified cellulose-based polymer electrolyte includes the following steps: 3.0 g of pentafluoropropanol, 12.5 g of epichlorohydrin, 1.2 g of sodium hydroxide, and 0.35 g of deionized water were stirred until homogeneous and reacted at 50 °C for 10 hours to obtain the initial product. The product was purified by distillation, and the fraction collected at 108–112 °C yielded the fluorinated compound PFEE.

[0046] 1.0 g of fluorinated compound PFEE, 15.2 g of cellulose acetate, and 152 mg of triphenylphosphine were dissolved in 20 mL of acetonitrile and heated to 120 °C for 12 hours to obtain a solid product. The solid product was washed three times with diethyl ether and dried under vacuum at 70 °C for 24 hours to obtain fluorinated compound-modified cellulose acetate.

[0047] 2.0 g of N-methylimidazolium and 3.3 g of 1-bromobutane were dissolved in 20 mL of ethyl acetate and magnetically stirred at 90 °C for 24 hours. After the reaction was completed, the mixture was separated into liquid and liquid layers. The ionic liquid layer was washed three times with ethyl acetate, and the product was dried to obtain the ionic liquid 1-ethyl-3-methylimidazolium bromide.

[0048] 1.0 g of fluorinated cellulose acetate, 2.4 g of ionic liquid, 0.5 g of succinic acid, and 1.0 g of lithium perchlorate were dissolved in tetrahydrofuran and stirred to form a homogeneous solution. The resulting solution was then poured into a mold and dried under vacuum to obtain a fluorinated cellulose-based polymer electrolyte.

[0049] Example 7 A method for preparing a fluorinated compound-modified cellulose-based polymer electrolyte includes the following steps: 3.0 g of pentafluoropropanol, 4.3 g of epichlorohydrin, 1.2 g of sodium hydroxide, and 0.35 g of deionized water were stirred until homogeneous and reacted at 40 °C for 10 hours to obtain the initial product. The product was purified by distillation, and the fraction collected at 108–112 °C yielded the fluorinated compound PFEE.

[0050] 1.0 g of fluorinated compound PFEE, 1.35 g of cellulose acetate, and 13.5 mg of triphenylphosphine were dissolved in 20 mL of N-methylpyrrolidone, heated to 80 °C, and reacted for 10 hours to obtain a solid product. The solid product was washed three times with diethyl ether and dried under vacuum at 70 °C for 24 hours to obtain fluorinated compound-modified cellulose acetate.

[0051] 2.0 g of N-methylimidazolium and 3.3 g of 1-bromobutane were dissolved in 20 mL of ethyl acetate and magnetically stirred at 60 °C for 12 hours. After the reaction was completed, the mixture was separated into liquid and liquid layers. The ionic liquid layer was washed three times with ethyl acetate, and the product was dried to obtain the ionic liquid 1-ethyl-3-methylimidazolium bromide.

[0052] 1.0 g of fluorinated cellulose acetate, 0.3 g of ionic liquid, 0.3 g of succinic acid, and 0.4 g of lithium perchlorate were dissolved in N-methylpyrrolidone and stirred into a homogeneous solution. The resulting solution was then poured into a mold and dried under vacuum to obtain a fluorinated cellulose-based polymer electrolyte.

[0053] Example 8 A method for preparing a fluorinated compound-modified cellulose-based polymer electrolyte includes the following steps: 3.0 g pentafluoropropanol, 2.3 g epichlorohydrin, 1.2 g sodium hydroxide, and 0.35 g ethanol were stirred until homogeneous and reacted at 60 °C for 6 hours to obtain the primary product. The product was purified by distillation, and the fraction collected at 108–112 °C yielded the fluorinated compound PFEE.

[0054] 1.0 g of fluorinated compound PFEE, 3.8 g of cellulose acetate, and 38 mg of triphenylphosphine were dissolved in 20 mL of N-methylpyrrolidone. The mixture was heated to 70 °C and reacted for 8 hours to obtain a solid product. The solid product was washed three times with diethyl ether and dried under vacuum at 70 °C for 24 hours to obtain fluorinated compound-modified cellulose acetate.

[0055] 2.0 g of N-methylimidazolium and 3.3 g of 1-bromobutane were dissolved in 20 mL of ethyl acetate and magnetically stirred at 100 °C for 9 hours. After the reaction was completed, the mixture was separated into liquid and liquid layers. The ionic liquid layer was washed three times with ethyl acetate, and the product was dried to obtain the ionic liquid 1-ethyl-3-methylimidazolium bromide.

[0056] 1.0 g of fluorinated cellulose acetate, 0.1 g of ionic liquid, 0.8 g of succinic acid, and 0.8 g of lithium perchlorate were dissolved in N-methylpyrrolidone and stirred into a homogeneous solution. The resulting solution was then poured into a mold and dried under vacuum to obtain a fluorinated cellulose-based polymer electrolyte.

[0057] The above description is merely an exemplary embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A cellulose-based polymer electrolyte modified with a fluorinated compound, characterized in that, The polymer electrolyte comprises fluorinated cellulose acetate, succinate, and lithium salt, and the chemical structural formula of the fluorinated cellulose acetate is as follows: ； The structure of the fluorine-containing compound is as follows: ； The molecular structure of the cellulose acetate is as follows: 。 2. The fluorinated compound-modified cellulose-based polymer electrolyte according to claim 1, characterized in that, The polymer electrolyte further includes a lithium salt, which includes one or more of lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium perchlorate, lithium hexafluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide.

3. The fluorinated compound-modified cellulose-based polymer electrolyte according to claim 1, characterized in that, The polymer electrolyte is in the form of a film, and the thickness of the polymer electrolyte is 50~300μm.

4. The method for preparing the fluorinated compound-modified cellulose-based polymer electrolyte according to any one of claims 1-3, characterized in that, Includes the following steps: 1) Dissolve pentafluoropropanol, epichlorohydrin and sodium hydroxide in a first solvent. After the resulting solution is reacted under stirring, the solvent is removed by rotary evaporation. The fraction at 108~112℃ is collected by distillation to obtain the fluorinated compound PFEE. 2) The obtained PFEE, cellulose acetate, triphenylphosphine, and second solvent were mixed evenly. Under stirring conditions, the product was washed three times with diethyl ether and dried to obtain fluorinated cellulose acetate. 3) Mix equimolar amounts of N-ethylimidazolium and 1-bromobutane with ethyl acetate and stir until homogeneous. After heating and reflux reaction, obtain the organic layer using a separatory funnel. Wash the product three times with ethyl acetate and dry the product to obtain 1-ethyl-3-methylimidazolium bromide ionic liquid. 4) Fluorine-modified cellulose acetate, 1-ethyl-3-methylimidazolium bromide ionic liquid, succinate, and lithium salt are mixed in a third solvent and stirred to form a homogeneous solution. The resulting solution is then poured onto a mold and dried under vacuum to obtain a cellulose-based polymer electrolyte membrane.

5. The method for preparing the fluorinated compound-modified cellulose-based polymer electrolyte according to claim 4, characterized in that, In step 1), the reaction temperature is 30~80℃ and the reaction time is 4~10h; the molar ratio of pentafluoropropanol to epichlorohydrin is 1-5:1; the first solvent includes one or more of ethanol, ethyl acetate, deionized water, and acetonitrile.

6. The method for preparing the fluorinated compound-modified cellulose-based polymer electrolyte according to claim 4, characterized in that, In step 2), the reaction temperature is 30~150℃ and the reaction time is 4~10h; the molar ratio of PFEE to cellulose acetate is 1-10:1; the amount of triphenylphosphine added is 1%~10% of the mass of cellulose acetate; the second solvent includes one or more of N-methylpyrrolidone, methanol, deionized water, and acetonitrile.

7. The method for preparing the fluorinated compound-modified cellulose-based polymer electrolyte according to claim 4, characterized in that, In step 3), the reaction temperature is 50~100℃ and the reaction time is 10~24h.

8. The method for preparing the fluorinated compound-modified cellulose-based polymer electrolyte according to claim 4, characterized in that, In step 4), the weight ratio of the fluorinated cellulose acetate modified with the ionic liquid is 1-4:1; the weight ratio of the fluorinated cellulose acetate modified with the succinic acid is 1-5:

1.

9. The method for preparing the fluorinated compound-modified cellulose-based polymer electrolyte according to claim 4, characterized in that, In step 4), the weight of the lithium salt is 5% to 30% of the total weight of the electrolyte; the third solvent includes one or more of tetrahydrofuran, N,N-dimethylformamide, and N-methylpyrrolidone.

10. The application of the fluorinated compound-modified cellulose-based polymer electrolyte according to any one of claims 1-3, characterized in that, Application of the fluorinated compound-modified cellulose-based polymer electrolyte in lithium metal batteries.

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