Fluorinated block comb-shaped polymer electrolyte applied to low-temperature lithium metal battery

Abstract

The invention discloses a fluorinated block comb-shaped polymer electrolyte applied to a low-temperature lithium metal battery, and relates to the technical field of lithium electrochemical batteries. The specific preparation method comprises the following steps: uniformly stirring a lithium salt electrolyte, a fluorinated acrylate monomer, an acrylate cross-linking agent monomer and an initiator to obtain a polymer electrolyte precursor solution; the method comprises the following steps: injecting a polymer electrolyte precursor solution between a polypropylene diaphragm and a lithium metal sheet in a battery preparation process, and heating and polymerizing to obtain the fluorinated block comb polymer. The fluorinated block comb-shaped polymer electrolyte has a stable local high-concentration solvation structure, a lithium ion transmission channel is effectively provided, and the ionic conductivity and the lithium ion transference number are remarkably improved. Meanwhile, the system can maintain the dynamic balance of the structure in a wide temperature range. When the material is applied to a lithium metal battery, the material has good high-rate stability; and under a low-temperature condition, the material has excellent cycling stability and specific discharge capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium electrochemical batteries, and particularly to a fluorinated block comb-shaped polymer electrolyte applied to low-temperature lithium metal batteries. Background Art

[0002] Due to their high theoretical specific capacity and extremely low electrochemical potential, lithium metal batteries (LMBs) are widely used in mobile phones, laptops, cameras, electric vehicles, energy storage power grids and other fields. With the continuous expansion of the application scope and the increasingly complex and changeable working conditions, electrical equipment has put forward higher and higher requirements for the environmental adaptability and safety of LMBs. Under low-temperature conditions, problems such as difficult charging, low discharge capacity and short life cannot meet the application requirements of extreme environments.

[0003] In order to prevent electrolyte leakage and improve safety and stability, solid electrolytes have received extensive attention. In the current solid electrolyte system, gel polymer electrolytes (GPEs) are regarded as promising electrolyte materials due to their good flexibility and processing performance. However, at low temperatures, the decrease in the ionic conductivity of polymer electrolytes and the slow lithium-ion transport kinetics lead to an increase in battery polarization and interface deterioration, restricting the application of solid-state batteries in low-temperature environments.

[0004] Therefore, it is urgent to develop a polymer electrolyte system with both good ionic conduction characteristics and interface stability, explore the modification of chain segment groups to optimize the characteristics of polymer electrolytes, and jointly improve the low-temperature cycle life of batteries through the synergistic strategy of chemical composition optimization - interface engineering - structure design. Summary of the Invention

[0005] The purpose of the present invention is to provide a fluorinated block comb-shaped polymer electrolyte applied to low-temperature lithium metal batteries to solve problems such as the instability and short cycle life of existing gel polymer electrolytes.

[0006] To solve the above technical problems, the present invention specifically provides the following technical solutions: The present invention discloses a polymer electrolyte precursor solution, which includes a lithium salt electrolyte solution, a fluorinated acrylate monomer, an acrylate cross-linking agent monomer and an initiator; the mass ratio of the usage amounts of the lithium salt electrolyte solution to the fluorinated acrylate monomer is 1:0.002 - 0.01.

[0007] Preferably, the lithium salt electrolyte solution includes a lithium salt, a solvent and an additive.

[0008] Preferably, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalate borate and lithium dioxalate borate.

[0009] Preferably, the solvent is at least one of ethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 2-methyltetrahydrofuran, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate.

[0010] Preferably, the additive is at least one of fluoroethylene carbonate, vinylene carbonate, ethylene sulfate, trimethyl phosphate, allyl sulfonate, and lithium nitrate; the dosage ratio of the additive to the solvent is 1 g: 100 - 130 ml, and the mass ratio of the additive to the lithium salt is 1: 40 - 45.

[0011] Preferably, the fluorinated acrylate monomer is at least one of 2-(perfluoroalkyl)ethyl methacrylate, 2-(perfluorobutyl)ethyl methacrylate, and 2-(perfluorooctyl)ethyl methacrylate.

[0012] Preferably, the acrylate crosslinking agent monomer is at least one of ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, methacrylate monomer, and N,N'-(1,2-dihydroxyethylene)dipropenamide; the mass ratio of the lithium salt electrolyte to the acrylate crosslinking agent monomer is 1: 0.0015 - 0.01; the methacrylate monomer is prepared by reacting 2,6-dihydroxyhexanenitrile with methacryloyl chloride.

[0013] Using the methacrylate monomer and N,N'-(1,2-dihydroxyethylene)dipropenamide as the acrylate crosslinking agent monomer can not only copolymerize with the fluorinated acrylate monomer to form a block-structured polymer, reduce the phase separation between the fluorinated acrylate monomer and the lithium salt electrolyte, but also introduce functional groups, effectively remove the water that may exist in the lithium salt electrolyte, avoid the corrosion of the materials in the battery, and obtain more durable and excellent electrochemical performance.

[0014] Preferably, the initiator is azobisisobutyronitrile.

[0015] The present invention discloses a method for preparing a fluorinated block comb polymer, comprising: During the battery assembly process, injecting the polymer electrolyte precursor solution between the separator and the lithium metal sheet, and heating at 40 - 70 °C for 1 - 24 h to obtain the fluorinated block comb polymer.

[0016] The present invention also discloses the application of the fluorinated block comb polymer prepared by the above method in the preparation of batteries.

[0017] The present invention discloses a method for preparing a polymer electrolyte precursor solution, comprising: Mix the solvent and the additive evenly, and then add the lithium salt and stir to obtain a lithium salt electrolyte solution. Add a fluorinated acrylate monomer and an acrylate crosslinking monomer to the lithium salt electrolyte solution, and then add an initiator, and stir evenly to obtain a polymer electrolyte precursor solution.

[0018] Preferably, the solvent is at least one of ethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 2-methyltetrahydrofuran, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate.

[0019] Preferably, the additive is at least one of fluoroethylene carbonate, vinylene carbonate, ethylene sulfate, trimethyl phosphate, allyl sulfonate, and lithium nitrate; Preferably, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalate borate, and lithium bis(oxalato)borate.

[0020] Preferably, the dosage ratio of the additive to the solvent is 1 g: 100 - 130 ml.

[0021] Preferably, the mass ratio of the additive to the lithium salt is 1: 40 - 45.

[0022] Preferably, the fluorinated acrylate monomer is at least one of 2-(perfluoroalkyl)ethyl methacrylate, 2-(perfluorobutyl)ethyl methacrylate, and 2-(perfluorooctyl)ethyl methacrylate, and the CAS number of 2-(perfluorobutyl)ethyl methacrylate is 65530-66-7.

[0023] Preferably, the mass ratio of the lithium salt electrolyte solution to the fluorinated acrylate monomer is 1: 0.002 - 0.01.

[0024] Preferably, the acrylate crosslinking monomer is at least one of ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, methacrylate monomer, and N,N'-(1,2-dihydroxyethylene)dipropenamide.

[0025] Preferably, the mass ratio of the lithium salt electrolyte solution to the acrylate crosslinking monomer is 1: 0.0015 - 0.01.

[0026] Preferably, the initiator is azobisisobutyronitrile Preferably, the whole preparation process is carried out under anhydrous and oxygen - isolated conditions.

[0027] The present invention discloses a preparation method of a fluorinated block comb - shaped polymer, comprising: During the battery assembly process, inject the polymer electrolyte precursor solution between the separator and the lithium metal sheet, and heat it at 40 - 70 °C for 1 - 24 h to obtain the fluorinated block comb - shaped polymer.

[0028] The present invention discloses a preparation method of a methacrylate monomer, comprising: Add 2,6 - dihydroxyhexanenitrile and triethylamine into xylene to obtain a mixed solution, then, under the condition of 0 - 6 °C, drop methacryloyl chloride into the mixed solution, and then react at 20 - 30 °C for 15 - 25 h. After the reaction ends, filter and purify, and finally dry to obtain the methacrylate monomer.

[0029] Preferably, the mass ratio of the usage amounts of 2,6 - dihydroxyhexanenitrile and triethylamine is 1:0.5 - 1.

[0030] Preferably, the dosage ratio of 2,6 - dihydroxyhexanenitrile and xylene is 1 g:13 - 18 ml.

[0031] Preferably, the mass ratio of the usage amounts of 2,6 - dihydroxyhexanenitrile and methacryloyl chloride is 1:0.7 - 1.

[0032] More preferably, during the preparation process of the polymer electrolyte precursor solution, on the basis of using the methacrylate monomer and N,N'-(1,2 - dihydroxyethylene)dipropenamide, syringaresinol can also be used for co - preparation, introducing more effective functional groups into the polymer electrolyte precursor solution, which is beneficial to further optimizing the solvation structure and inhibiting the occurrence of side reactions, so that the prepared battery exhibits good electrochemical stability.

[0033] Preferably, the mass ratio of the usage amounts of the lithium salt electrolyte and syringaresinol is 1:0.001 - 0.004.

[0034] The present invention has the following beneficial effects compared with the prior art: The present invention provides a fluorinated block comb-shaped polymer electrolyte for low-temperature lithium metal batteries. First, a lithium salt electrolyte solution is prepared by stirring a solvent, an additive, and a lithium salt. Then, a fluorinated acrylate monomer and an acrylate cross-linking agent monomer are added to the lithium salt electrolyte solution, and then an initiator is added and stirred evenly to obtain a polymer electrolyte precursor solution. During the battery preparation process, the polymer electrolyte precursor solution is injected between a polypropylene separator and a lithium metal sheet and heated to polymerize to obtain a fluorinated block comb-shaped polymer. The fluorinated block comb-shaped polymer prepared by the present invention is used as an electrolyte, and the battery prepared has good ionic conductivity. At the same time, the comb-shaped side chains reduce the interaction with lithium ions through the electron-withdrawing effect and volume effect, promote the entry of anions into the solvation structure, and then form a stable interface, effectively inhibiting the growth of lithium dendrites. It shows good electrochemical stability in the application of low-temperature full batteries, and realizes the high-rate performance of the battery, showing high capacity and cycle performance at low temperature. Moreover, this preparation method is efficient and fast, effectively alleviating the problem of solvent volatilization during the preparation of the electrolyte membrane through in-situ polymerization, and having good interfacial compatibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained according to the provided drawings.

[0036] Figure 1 is the scanning electron microscope image of the fluorinated block comb-shaped polymer; Figure 2 is the ionic conductivity graph of the lithium-lithium symmetric battery Figure 3 is the test result graph of the lithium ion transference number of the lithium-lithium symmetric battery; Figure 4 is the Raman spectrum fitting graph of the lithium-lithium symmetric battery; Figure 5 is the time-voltage curve graph of the lithium-lithium symmetric battery; Figure 6 is the charge-discharge cycle graph of the lithium metal full battery; Figure 7 is the charge-discharge cycle graph of the lithium metal full battery at -20°C. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0038] First, the concepts involved in the present application will be described in conjunction with the accompanying drawings. It should be noted here that the following descriptions of each concept are only for making the content of the present application easier to understand, and do not represent a limitation on the protection scope of the present application; at the same time, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0039] The specific meanings of the abbreviations used in the specification and claims are as follows: Example 1: Preparation of the polymer electrolyte precursor solution: Under anhydrous and oxygen-insulated conditions, ethylene glycol dimethyl ether and vinyl fluorocarbonate are mixed evenly, and then lithium bis(fluorosulfonyl)imide is added and stirred to obtain a lithium salt electrolyte solution. 2-(Perfluorobutyl)ethyl methacrylate and pentaerythritol triacrylate are added to the lithium salt electrolyte solution, and then azobisisobutyronitrile is added and stirred evenly to obtain the polymer electrolyte precursor solution. The dosage ratio of vinyl fluorocarbonate to ethylene glycol dimethyl ether is 1 g:115.34 ml, the mass ratio of vinyl fluorocarbonate to lithium bis(fluorosulfonyl)imide is 1:42.93, the mass ratio of the lithium salt electrolyte solution to 2-(perfluorobutyl)ethyl methacrylate is 1:0.00561, the mass ratio of the lithium salt electrolyte solution to pentaerythritol triacrylate is 1:0.00441, and the mass ratio of the lithium salt electrolyte solution to azobisisobutyronitrile is 1:0.001.

[0040] Preparation of the fluorinated block comb polymer: During the battery assembly process, the polymer electrolyte precursor solution is injected between the polypropylene separator and the lithium metal sheet, and heated at 50 °C for 1.5 h to obtain the fluorinated block comb polymer.

[0041] Example 2: Preparation of the polymer electrolyte precursor solution: In this example, the preparation of the polymer electrolyte precursor solution is different from that in Example 1 in that the mass ratio of the lithium salt electrolyte solution to 2-(perfluorobutyl)ethyl methacrylate is 1:0.00362, and the mass ratio of the lithium salt electrolyte solution to pentaerythritol triacrylate is 1:0.00638. Other conditions and parameters are the same as those in Example 1.

[0042] Preparation of fluorinated block comb polymers: In this example, compared with Example 1, the preparation of the fluorinated block comb polymer is different in that the polymer electrolyte precursor solution is the polymer electrolyte precursor solution prepared in this example, and other conditions and parameters are the same as those in Example 1.

[0043] Example 3: Preparation of polymer electrolyte precursor solution: In this example, compared with Example 1, the preparation of the polymer electrolyte precursor solution is different in that the mass ratio of the lithium salt electrolyte solution to the amount of 2-(perfluorobutyl)ethyl methacrylate used is 1:0.00694, and the mass ratio of the lithium salt electrolyte solution to the amount of pentaerythritol triacrylate used is 1:0.00306, and other conditions and parameters are the same as those in Example 1.

[0044] Preparation of fluorinated block comb polymers: In this example, compared with Example 1, the preparation of the fluorinated block comb polymer is different in that the polymer electrolyte precursor solution is the polymer electrolyte precursor solution prepared in this example, and other conditions and parameters are the same as those in Example 1.

[0045] Example 4: Preparation of polymer electrolyte precursor solution: In this example, compared with Example 1, the preparation of the polymer electrolyte precursor solution is different in that 2-(perfluorobutyl)ethyl methacrylate is replaced by 2-(perfluoroalkyl)ethyl methacrylate, the CAS number of 2-(perfluoroalkyl)ethyl methacrylate is 65530-66-7, the mass ratio of the lithium salt electrolyte solution to the amount of 2-(perfluoroalkyl)ethyl methacrylate used is 1:0.00647, and the mass ratio of the lithium salt electrolyte solution to the amount of pentaerythritol triacrylate used is 1:0.00353, and other conditions and parameters are the same as those in Example 1.

[0046] Preparation of fluorinated block comb polymers: In this example, compared with Example 1, the preparation of the fluorinated block comb polymer is different in that the polymer electrolyte precursor solution is the polymer electrolyte precursor solution prepared in this example, and other conditions and parameters are the same as those in Example 1.

[0047] Example 5: Preparation of polymer electrolyte precursor solution: In this example, compared with Example 1, the preparation of the polymer electrolyte precursor solution is different in that 2-(perfluorobutyl)ethyl methacrylate is replaced by 2-(perfluorooctyl)ethyl methacrylate, the mass ratio of the lithium salt electrolyte solution to the amount of 2-(perfluorooctyl)ethyl methacrylate used is 1:0.00634, and the mass ratio of the lithium salt electrolyte solution to the amount of pentaerythritol triacrylate used is 1:0.00366, and other conditions and parameters are the same as those in Example 1.

[0048] Preparation of fluorinated block comb-shaped polymer: In this example, compared with Example 1, the preparation of the fluorinated block comb-shaped polymer is different in that the polymer electrolyte precursor solution is the polymer electrolyte precursor solution prepared in this example, and other conditions and parameters are the same as those in Example 1.

[0049] Example 6: Preparation of methacrylate monomer: 2,6-dihydroxyhexanenitrile and triethylamine were added to xylene to obtain a mixed solution. Then, at 3 °C, methacryloyl chloride was added dropwise to the mixed solution, and then the reaction was carried out at 25 °C for 20 h. After the reaction, filtration was carried out, purification was carried out by resin adsorption, and finally drying was carried out to obtain the methacrylate monomer. The mass ratio of the usage amounts of 2,6-dihydroxyhexanenitrile and triethylamine is 1:0.78, the usage ratio of 2,6-dihydroxyhexanenitrile and xylene is 1 g:15 ml, and the mass ratio of the usage amounts of 2,6-dihydroxyhexanenitrile and methacryloyl chloride is 1:0.81.

[0050] Preparation of polymer electrolyte precursor solution: Under anhydrous and oxygen-free conditions, ethylene glycol dimethyl ether and vinyl fluorocarbonate were mixed evenly, and then lithium bis(fluorosulfonyl)imide was added and stirred to obtain a lithium salt electrolyte solution. 2-(Perfluorobutyl)ethyl methacrylate, methacrylate monomer and N,N'-(1,2-dihydroxyethylene)dipropenamide were added to the lithium salt electrolyte solution, and then azobisisobutyronitrile was added and stirred evenly to obtain a polymer electrolyte precursor solution. The usage ratio of vinyl fluorocarbonate and ethylene glycol dimethyl ether is 1 g:115.34 ml, the mass ratio of the usage amounts of vinyl fluorocarbonate and lithium bis(fluorosulfonyl)imide is 1:42.93, the mass ratio of the usage amounts of the lithium salt electrolyte solution and 2-(perfluorobutyl)ethyl methacrylate is 1:0.00561, the mass ratio of the usage amounts of the lithium salt electrolyte solution and methacrylate monomer is 1:0.00247, the mass ratio of the usage amounts of methacrylate monomer and N,N'-(1,2-dihydroxyethylene)dipropenamide is 1:1, and the mass ratio of the usage amounts of the lithium salt electrolyte solution and azobisisobutyronitrile is 1:0.001.

[0051] Preparation of fluorinated block comb-shaped polymer: In this example, compared with Example 1, the preparation of the fluorinated block comb-shaped polymer is different in that the polymer electrolyte precursor solution is the polymer electrolyte precursor solution prepared in this example, and other conditions and parameters are the same as those in Example 1.

[0052] Example 7: The preparation of methacrylate monomer is the same as that in Example 6.

[0053] Preparation of polymer electrolyte precursor solution: In this example, compared with Example 6, the preparation of the polymer electrolyte precursor solution is different in that the mass ratio of the lithium salt electrolyte solution to the methacrylate monomer is 1:0.00374, and other conditions and parameters are the same as those in Example 6.

[0054] Preparation of fluorinated block comb polymer: In this example, compared with Example 6, the preparation of the fluorinated block comb polymer is different in that the polymer electrolyte precursor solution is the one prepared in this example, and other conditions and parameters are the same as those in Example 6.

[0055] Example 8: The preparation of the methacrylate monomer is the same as that in Example 6.

[0056] Preparation of polymer electrolyte precursor solution: Under anhydrous and oxygen - isolated conditions, ethylene glycol dimethyl ether and vinyl fluorocarbonate were mixed evenly, and then lithium bis(fluorosulfonyl)imide was added and stirred to obtain the lithium salt electrolyte solution. 2-(Perfluorobutyl)ethyl methacrylate, the methacrylate monomer, N,N'-(1,2 - dihydroxyethylene)dipropenamide and lignan were added to the lithium salt electrolyte solution, and then azobisisobutyronitrile was added and stirred evenly to obtain the polymer electrolyte precursor solution. Among them, the dosage ratio of vinyl fluorocarbonate to ethylene glycol dimethyl ether is 1 g:115.34 ml, the mass ratio of vinyl fluorocarbonate to lithium bis(fluorosulfonyl)imide is 1:42.93, the mass ratio of the lithium salt electrolyte solution to 2-(perfluorobutyl)ethyl methacrylate is 1:0.00561, the mass ratio of the lithium salt electrolyte solution to the methacrylate monomer is 1:0.00247, the mass ratio of the methacrylate monomer to N,N'-(1,2 - dihydroxyethylene)dipropenamide is 1:1, the mass ratio of the lithium salt electrolyte solution to lignan is 1:0.00151, and the mass ratio of the lithium salt electrolyte solution to azobisisobutyronitrile is 1:0.001.

[0057] Preparation of fluorinated block comb polymer: In this example, compared with Example 1, the preparation of the fluorinated block comb polymer is different in that the polymer electrolyte precursor solution is the one prepared in this example, and other conditions and parameters are the same as those in Example 1.

[0058] Example 9: The preparation of the methacrylate monomer is the same as that in Example 6.

[0059] Preparation of polymer electrolyte precursor solution: In this example, compared with Example 8, the preparation of the polymer electrolyte precursor solution is different in that the mass ratio of the lithium salt electrolyte solution to lignan is 1:0.00233, and other conditions and parameters are the same as those in Example 8.

[0060] Preparation of fluorinated block comb-shaped polymer: In this example, the preparation of the fluorinated block comb-shaped polymer is different from that in Example 8 in that the polymer electrolyte precursor solution is the polymer electrolyte precursor solution prepared in this example, and other conditions and parameters are the same as those in Example 8.

[0061] Comparative Example 1: Preparation of polymer electrolyte precursor solution: In this comparative example, the preparation of the polymer electrolyte precursor solution is different from that in Example 1 in that 2-(perfluorobutyl)ethyl methacrylate is not used, and the mass ratio of the lithium salt electrolyte to the amount of trimethylolpropane triacrylate used is 1:0.01, and other conditions and parameters are the same as those in Example 1.

[0062] Preparation of fluorinated block comb-shaped polymer: In this comparative example, the preparation of the fluorinated block comb-shaped polymer is different from that in Example 1 in that the polymer electrolyte precursor solution is the polymer electrolyte precursor solution prepared in this example, and other conditions and parameters are the same as those in Example 1.

[0063] Comparative Example 2: Preparation of polymer electrolyte precursor solution: In this comparative example, the preparation of the polymer electrolyte precursor solution is different from that in Example 8 in that methacrylate monomer and N,N'-(1,2-dihydroxyethylene)dipropenamide are not used, and other conditions and parameters are the same as those in Example 8.

[0064] Preparation of fluorinated block comb-shaped polymer: In this comparative example, the preparation of the fluorinated block comb-shaped polymer is different from that in Example 8 in that the polymer electrolyte precursor solution is the polymer electrolyte precursor solution prepared in this example, and other conditions and parameters are the same as those in Example 8.

[0065] Experimental Example 1: Scanning electron microscopy analysis was performed on the fluorinated block comb-shaped polymers prepared in Comparative Example 1, Example 1, and Examples 4-5. The results are as Figure 1 shown Figure 1 (a) is a scanning electron microscopy analysis diagram of the fluorinated block comb-shaped polymer prepared in Comparative Example 1, exposing the supporting polyethylene separator, indicating that the wettability and interfacial compatibility of the fluorinated block comb-shaped polymer prepared in Comparative Example 1 are poor; Figure 1 (b) is a scanning electron microscopy analysis diagram of the fluorinated block comb-shaped polymer prepared in Example 1, having a smooth and dense electrolyte surface, which is beneficial to the formation of a continuous ion transport path and improves the interfacial contact between the electrolyte and the electrode; Figure 1 (c) and Figure 1 (d) are respectively scanning electron microscopy analysis diagrams of the fluorinated block comb-shaped polymers prepared in Example 4 and Example 5, showing granular and uneven agglomeration and a relatively high surface roughness.

[0066] Experimental Example 2: Preparation of lithium nickel cobalt manganese oxide cathode: Mix LiNi 0.8 Co 0.1 Mn 0.1 O2, Super P, and PVDF-HFP to obtain a mixture, then add N-methylpyrrolidone to the mixture and stir at a speed of 1200 r / min for 20 min to obtain the cathode slurry. Coat the cathode slurry on aluminum foil, dry it in air, and then place it in a vacuum dryer to obtain the electrode sheet. Cut the electrode sheet into 12-mm circular pieces, and the electrode surface loading is 1-11.5 mg cm -2 。Among them, the mass ratio of the usage amounts of LiNi 0.8 Co 0.1 Mn 0.1 O2, Super P, and PVDF-HFP is 8:1:1, and the mass ratio of the usage amounts of the mixture and N-methylpyrrolidone is 1:2.

[0067] Assembly of lithium-lithium symmetric battery: Assemble and encapsulate in the order of lithium metal sheet, polypropylene separator, polymer electrolyte precursor solution, and lithium metal sheet, and heat at 50 °C for 1.5 h to obtain a button battery, that is, a lithium-lithium symmetric battery. Among them, the polymer electrolyte precursor solution is injected between the polypropylene separator and the lithium metal sheet, and the polymer electrolyte precursor solution is the polymer electrolyte precursor solution prepared in Examples 1-5 and Comparative Example 1.

[0068] Ionic conductivity measurement: Using electrochemical impedance spectroscopy, measure the ionic conductivity of the lithium-lithium symmetric batteries made of the fluorinated block comb-shaped polymers prepared in Examples 1-5 and Comparative Example 1 at 25 °C and -30 °C, respectively. The measurement process of the ionic conductivity is carried out in an air atmosphere, the test frequency range is 100 Hz - 100000 Hz, and the perturbation voltage is 10 mV. The ionic conductivity calculation formula is:

[0069] where L is the thickness of the fluorinated block comb-shaped polymer, A is the surface area of the lithium metal sheet, and R is the impedance value.

[0070] Table 1 Ionic conductivity measurement results

[0071] For the lithium-lithium symmetric batteries made of the fluorinated block comb-shaped polymers prepared in Examples 1-3 and Comparative Example 1, the ionic conductivity measurement results at 25 °C are as shown in Figure 2 Figure (a); the ionic conductivity measurement results at -30 °C are as shown in Figure 2 Figure (b).

[0072] The lithium-lithium symmetric batteries prepared from the fluorinated block comb polymers obtained in Examples 1-5 and Comparative Example 1 were measured for ionic conductivity at 25 °C and -30 °C. The results are shown in Table 1. Comparing Example 1 with Example 2, it shows that the amount of 2-(perfluorobutyl)ethyl methacrylate used is relatively low, and the improvement of ionic conductivity is limited. Comparing Example 1 with Example 3, it shows that the amount of 2-(perfluorobutyl)ethyl methacrylate used is too high, and due to the strong intermolecular force between fluorine atoms, the dissociation of lithium salt is reduced, resulting in a decrease in ionic conductivity. Comparing Example 1 with Example 4, it shows that the fluorinated side chain of the fluorinated acrylate monomer used is relatively short, and the improvement of ionic conductivity is also limited. Comparing Example 1 with Example 5, it shows that the fluorinated side chain of the fluorinated acrylate monomer used is relatively long, resulting in a decrease in ionic conductivity. Comparing Example 1 with Comparative Example 1, using 2-(perfluorobutyl)ethyl methacrylate to prepare the fluorinated block comb polymer can effectively improve the ionic conductivity of the prepared lithium-lithium symmetric battery.

[0073] Experimental Example 3: The lithium-lithium symmetric battery was assembled in the same way as in Experimental Example 2.

[0074] Measurement of lithium ion transference number: For the lithium-lithium symmetric batteries prepared from the fluorinated block comb polymers obtained in Examples 1-5 and Comparative Example 1, impedance tests were carried out before and after direct current constant voltage polarization, and the lithium ion transference number of the electrolyte was calculated. The formula for calculating the lithium ion transference number is:

[0075] where and are the initial current and steady-state current values of the polarization test respectively, and are the interfacial impedance values before and after polarization respectively, is the direct current polarization voltage, and 0.01 V is adopted.

[0076] Table 2 Results of lithium ion transference number measurement

[0077] The measurement results of the lithium ion transference number of the lithium-lithium symmetric battery prepared from the fluorinated block comb polymer obtained in Example 1 are as shown in Figure 3 (a); The measurement results of the lithium ion transference number of the lithium-lithium symmetric battery prepared from the fluorinated block comb polymer obtained in Example 2 are as shown in Figure 3 (b); The measurement results of the lithium ion transference number of the lithium-lithium symmetric battery prepared from the fluorinated block comb polymer obtained in Example 3 are as shown in Figure 3 (c); The measurement results of the lithium ion transference number of the lithium-lithium symmetric battery prepared from the fluorinated block comb polymer obtained in Comparative Example 1 are as shown in Figure 3 (d).

[0078] The results of measuring the lithium-ion transference number of the lithium-lithium symmetric batteries made from the fluorinated block comb polymers prepared in Examples 1-5 and Comparative Example 1 are shown in Table 2. Comparing Example 1 with Example 2, it shows that a lower amount of 2-(perfluorobutyl)ethyl methacrylate will reduce the lithium-ion transference number; comparing Example 1 with Example 3, it shows that an excessive amount of 2-(perfluorobutyl)ethyl methacrylate will also reduce the lithium-ion efficiency; comparing Example 1 with Examples 4 and 5, it shows that the length of the fluorinated side chain of the fluorinated acrylate monomer used needs to be in a suitable range, which can effectively reduce the migration activation energy and increase the lithium-ion transference number; comparing Example 1 with Comparative Example 1, the lithium-ion transference number has increased by 213%, verifying the decisive role of the fluorinated block in the selective transport of Li⁺.

[0079] Experimental Example 4: The assembly of the lithium-lithium symmetric battery is the same as that in Experimental Example 2. The difference is that the polymer electrolyte precursor solution is the polymer electrolyte precursor solution prepared in Example 1 and Comparative Example 1.

[0080] Raman spectroscopy measurement and analysis: Raman spectroscopy measurement and analysis were carried out on the lithium-lithium symmetric batteries made from the fluorinated block comb polymers prepared in Example 1 and Comparative Example 1 to study the solvation structure, that is, the interaction between solvent molecules and solute molecules.

[0081] Table 3 Statistical results of solvation structure

[0082] Raman spectrum of the lithium-lithium symmetric battery made from the fluorinated block comb polymer prepared in Example 1 Figure 4 as shown in (a); Raman spectrum of the lithium-lithium symmetric battery made from the fluorinated block comb polymer prepared in Comparative Example 1 Figure 4 as shown in (b).

[0083] The statistical results of the solvation structures of the lithium-lithium symmetric batteries made from the fluorinated block comb polymers prepared in Example 1 and Comparative Example 1 are shown in Table 3. For the lithium-lithium symmetric battery made from the fluorinated block comb polymer prepared in Example 1, the Raman peak fitting analysis at 25 °C and -20 °C shows that the change range of the proportions of free ions, contact ion pairs, and aggregates is less than 5%, indicating that the solvation shell structure of Li⁺ is minimally affected by temperature perturbation and maintains a highly stable coordination environment. This stability stems from the strong electronegativity and steric hindrance effect of the fluorinated block. The fluorinated block comb polymer prepared in Comparative Example 1 has no fluorinated block, and the lithium-lithium symmetric battery made therefrom exhibits significant temperature sensitivity of the solvation structure. The increase in the proportion of CIPs at -20 °C is >15%, while the decrease in the proportion of SSIPs exceeds 10%, indicating that solvent molecules are more likely to form tight ion pairs or even aggregates with Li⁺ at low temperatures, hindering the desolvation process of Li⁺.

[0084] Experimental Example 5: The lithium-lithium symmetric battery was assembled in the same manner as in Experimental Example 2. The difference lies in that the polymer electrolyte precursor solutions were the polymer electrolyte precursor solutions prepared in Example 1 and Comparative Example 1.

[0085] Measurement of the cycling performance of the lithium-lithium symmetric battery: Using the LAND battery test system, the time-voltage curves of the lithium-lithium symmetric batteries made from the fluorinated block comb polymers prepared in Example 1 and Comparative Example 1 were measured at a current density of 0.1 mA cm -2 and 0.2 mA cm -2 at -20 °C.

[0086] The results are as Figure 5 shown. The lithium-lithium symmetric battery made from the fluorinated block comb polymer prepared in Example 1 can stably cycle for more than 1000 h at -20 °C and has good interfacial compatibility at low temperatures. The lithium-lithium symmetric battery made from the fluorinated block comb polymer prepared in Comparative Example 2 can only cycle for about 380 h at -20 °C.

[0087] Experimental Example 6: The preparation of the lithium nickel cobalt manganese oxide cathode was the same as in Experimental Example 2.

[0088] Preparation of the lithium metal full battery: Assembled and encapsulated in the order of a polypropylene separator, a polymer electrolyte precursor solution, and a lithium metal sheet, and heated at 50 °C for 1.5 h to obtain a button battery, i.e., the lithium metal full battery. The polymer electrolyte precursor solution was injected between the polypropylene separator and the lithium metal sheet, and the polymer electrolyte precursor solutions were the polymer electrolyte precursor solutions prepared in Example 1 and Comparative Example 1.

[0089] Measurement of rate performance: Using the LAND battery test system, the specific capacity of the lithium-metal full cells made of the fluorinated block comb polymers prepared in Example 1 and Comparative Example 1 under different rate conditions was measured, and the rate performance of the lithium-metal full cells was determined. The test temperature was 25 °C, and the voltage was 3.0 - 4.4 V.

[0090] The charge-discharge cycle diagrams of the lithium-metal full cells made of the fluorinated block comb polymers prepared in Example 1 and Comparative Example 1 are as Figure 6 shown. Compared with Comparative Example 1, for Example 1, the specific capacity decreased more slowly as the rate increased, and when returning to the 0.1C rate, the specific capacity remained smooth without attenuation.

[0091] Experimental Example 7: The preparation of the lithium nickel cobalt manganese oxide cathode was the same as in Experimental Example 2.

[0092] The preparation of the lithium-metal full cells was the same as in Experimental Example 6. The difference was that the polymer electrolyte precursor solutions were the polymer electrolyte precursor solutions prepared in Example 1, Examples 6 - 9, and Comparative Examples 1 - 2.

[0093] Measurement of specific capacity: Using the LAND battery test system, the specific capacity of the lithium-metal full cells made of the fluorinated block comb polymers prepared in Example 1, Examples 6 - 9, and Comparative Examples 1 - 2 was measured at a rate of 4C and a test temperature of 25 °C.

[0094] Table 4 Results of specific capacity measurement

[0095] The specific capacity measurement results of the lithium metal full battery made of the fluorinated block comb polymer prepared in Example 1, Examples 6-9 and Comparative Examples 1-2 are shown in Table 4. Compared with Example 6, Example 1 shows that the use of methacrylate monomer and N, N'-(1,2-dihydroxyethylene) diacrylamide can further improve the specific capacity of the lithium metal full battery made of the prepared fluorinated block comb polymer; Compared with Example 7, Example 6 shows that the increase in the amount of methacrylate monomer within a certain range can also improve the specific capacity of the lithium metal full battery made of the prepared fluorinated block comb polymer; Compared with Example 8, Example 6 shows that on the basis of using methacrylate monomer and N, N'-(1,2-dihydroxyethylene) diacrylamide, the use of flax phenol Compared with Example 9, Example 8 shows that the increase in the amount of flax lignans used can also further improve the specific capacity of the lithium metal full battery made of the prepared fluorinated block comb polymer; Compared with Comparative Example 1, Example 1 shows that the use of 2-(perfluorobutyl)ethyl methacrylate can effectively improve the specific capacity of the lithium metal full battery made of the prepared fluorinated block comb polymer; Compared with Comparative Example 2, Example 8 shows that flax lignans need to be used together with methacrylate monomers and N,N'-(1,2-dihydroxyethylene)diacrylamide, and the use of flax lignans alone has no obvious effect on improving the specific capacity of the lithium metal full battery made of the prepared fluorinated block comb polymer.

[0096] Experimental Example 8: The assembly of the lithium metal full battery is the same as that of Experimental Example 6. The difference is that the polymer electrolyte precursor solution is the polymer electrolyte precursor solution prepared in Example 1, Examples 6-9 and Comparative Examples 1-2.

[0097] Determination of the cycle performance, the capacity retention rate of the lithium metal full battery made of the fluorinated block comb polymer prepared in Example 1, Examples 6-9 and Comparative Examples 1-2 after 45 cycles was measured, the test temperature was -20°C, the voltage was 3.0-4.2V, and the current density was 0.1C.

[0098] Table 5 Capacity retention rate measurement results

[0099] The charge and discharge cycle diagram of the lithium metal full battery made of the fluorinated block comb polymer prepared in Example 1 and Comparative Example 1 is as follows Figure 7 shown.

[0100] The capacity retention rate of the lithium metal full battery made of the fluorinated block comb polymer prepared in Example 1, Examples 6-9 and Comparative Examples 1-2 is shown in Table 5. Compared with Example 6, Example 1 shows that the use of methacrylate monomer and N, N'-(1,2-dihydroxyethylene) diacrylamide can further improve the capacity retention rate of the lithium metal full battery made of the prepared fluorinated block comb polymer; Compared with Example 7, Example 6 shows that the increase in the amount of methacrylate monomer within a certain range can also improve the capacity retention rate of the lithium metal full battery made of the prepared fluorinated block comb polymer; Compared with Example 8, Example 6 shows that on the basis of using methacrylate monomer and N, N'-(1,2-dihydroxyethylene) diacrylamide, the use of flax lignan , which can improve the capacity retention rate of the lithium metal full battery made of the prepared fluorinated block comb polymer; Example 8, compared with Example 9, shows that the increase in the amount of flax lignan used can also further improve the capacity retention rate of the lithium metal full battery made of the prepared fluorinated block comb polymer; Example 1, compared with Comparative Example 1, shows that the use of 2-(perfluorobutyl)ethyl methacrylate can effectively improve the capacity retention rate of the lithium metal full battery made of the prepared fluorinated block comb polymer; Example 8, compared with Comparative Example 2, shows that flax lignan needs to be used together with methacrylate monomer and N,N'-(1,2-dihydroxyethylene)diacrylamide, and the use of flax lignan alone has no obvious effect on improving the capacity retention rate of the lithium metal full battery made of the prepared fluorinated block comb polymer.

[0101] The embodiments and / or implementation methods described above are only used to illustrate the preferred embodiments and / or implementation methods for realizing the technology of the present invention, and are not intended to limit the implementation methods of the technology of the present invention in any form. Any technical personnel in this field may make slight changes or modifications to other equivalent embodiments without departing from the scope of the technical means disclosed in the content of the present invention, but they should still be regarded as technologies or embodiments that are essentially the same as the present invention.

[0102] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and its core ideas of this application. The above is only the preferred implementation method of this application. It should be pointed out that due to the limitations of textual expression and the objective existence of infinite specific structures, ordinary technicians in this technical field can make several improvements, modifications or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the concept and technical solution of the invention to other occasions without improvement, should be regarded as the scope of protection of this application.

Claims

1. A polymer electrolyte precursor solution, comprising a lithium salt electrolyte, a fluorinated acrylate monomer, an acrylate crosslinking agent monomer, and an initiator; the mass ratio of the usage amount of the lithium salt electrolyte to the fluorinated acrylate monomer is 1:0.002 - 0.

01.

2. The polymer electrolyte precursor solution according to claim 1, wherein: The lithium salt electrolyte comprises a lithium salt, a solvent, and an additive.

3. The polymer electrolyte precursor solution according to claim 2, wherein: The lithium salt comprises at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluoro(oxalato)borate, and lithium bis(oxalato)borate.

4. The polymer electrolyte precursor solution according to claim 2, characterized in that: The solvent is at least one of ethylene glycol dimethyl ether, 1,3 - dioxolane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 2 - methyltetrahydrofuran, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate.

5. A polymer electrolyte precursor solution according to claim 2, characterized in that: The additive is at least one of fluoroethylene carbonate, vinylene carbonate, ethylene sulfate, trimethyl phosphate, allyl sulfonate, and lithium nitrate; the dosage ratio of the additive to the solvent is 1 g:100 - 130 ml, and the mass ratio of the usage amount of the additive to the lithium salt is 1:40 - 45.

6. The polymer electrolyte precursor solution according to claim 1, wherein: The fluorinated acrylate monomer is at least one of 2-(perfluoroalkyl)ethyl methacrylate, 2-(perfluorobutyl)ethyl methacrylate, and 2-(perfluorooctyl)ethyl methacrylate.

7. A polymer electrolyte precursor solution according to claim 1, characterized in that: The acrylate crosslinking agent monomer is at least one of ethylene glycol bis(meth)acrylate, propylene glycol bis(meth)acrylate, butanediol bis(meth)acrylate, hexanediol bis(meth)acrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, a methacrylate monomer, and N,N'-(1,2 - dihydroxyethylene)diacrylamide; the mass ratio of the usage amount of the lithium salt electrolyte to the acrylate crosslinking agent monomer is 1:0.0015 - 0.01; the methacrylate monomer is prepared by reacting 2,6 - dihydroxyhexanenitrile with methacryloyl chloride.

8. A polymer electrolyte precursor solution according to claim 1, characterized in that: The initiator is azobisisobutyronitrile.

9. A method for preparing a fluorinated block comb polymer, comprising: During the battery assembly process, injecting the polymer electrolyte precursor solution between the separator and the lithium metal sheet, and heating at 40 - 70 °C for 1 - 24 h to obtain the fluorinated block comb polymer.

10. Use of the fluorinated block comb polymer prepared by the method according to claim 9 in the preparation of a battery.

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