A fluorinated block comb polymer electrolyte applied to low temperature lithium metal batteries

Abstract

The application 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. A specific preparation method comprises the following steps: using a lithium salt electrolyte, fluorinated propylene acid ester monomers, propylene acid ester cross-linking agent monomers and an initiator, and stirring uniformly to obtain a polymer electrolyte precursor solution; in the process of battery preparation, the polymer electrolyte precursor solution is injected between a polypropylene diaphragm and a lithium metal sheet, and the fluorinated block comb-shaped polymer is obtained by heating polymerization. The fluorinated block comb-shaped polymer electrolyte has a stable local high-concentration solvation structure, effectively provides a lithium ion transmission channel, and significantly improves ion conductivity and lithium ion transference number. Meanwhile, the system can maintain structural dynamic balance in a wide temperature range. When applied to a lithium metal battery, the fluorinated block comb-shaped polymer electrolyte has good high-rate stability performance; under a low-temperature condition, the fluorinated block comb-shaped polymer electrolyte has excellent cycle stability and discharge specific capacity.

Description

Technical Field

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

[0002] Lithium metal batteries (LMBs) are widely used in mobile phones, laptops, cameras, electric vehicles, and energy storage grids due to their high theoretical specific capacity and extremely low electrochemical potential. As their applications continue to expand and operating conditions become increasingly complex and variable, electrical equipment is placing increasingly stringent demands on the environmental adaptability and safety of LMBs. However, challenges such as difficulty charging at low temperatures, low discharge capacity, and short lifespan make them unsuitable for applications in extreme environments.

[0003] To prevent electrolyte leakage and improve safety and stability, solid-state electrolytes have received widespread attention. Among current solid-state electrolyte systems, gel polymer electrolytes (GPEs) are considered promising electrolyte materials due to their good flexibility and processability. However, at low temperatures, the reduced ionic conductivity of polymer electrolytes and the slow lithium ion transport kinetics lead to increased battery polarization and interface deterioration, limiting the application of solid-state batteries in low-temperature environments.

[0004] Therefore, it is urgent to develop a polymer electrolyte system with both good ion conduction properties and interface stability, explore the properties of polymer electrolytes optimized by chain segment group modification, and improve the low-temperature cycle life of batteries through a synergistic strategy of chemical composition optimization-interface engineering-structural design. Summary of the Invention

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

[0006] In order to solve the above technical problems, the present invention specifically provides the following technical solutions:

[0007] The invention discloses 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 lithium salt electrolyte to the fluorinated acrylate monomer is 1:0.002-0.01.

[0008] Preferably, the lithium salt electrolyte comprises a lithium salt, a solvent and an additive.

[0009] Preferably, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalatoborate, and lithium dioxalatoborate.

[0010] 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, methyl ethyl carbonate and methyl propyl carbonate.

[0011] Preferably, the additive is at least one of fluoroethylene carbonate, vinylene carbonate, ethylene sulfate, trimethyl phosphate, propenyl sulfonate and lithium nitrate; the mass ratio of the additive to the solvent is 1g:100-130ml, and the mass ratio of the additive to the lithium salt is 1:40-45.

[0012] Preferably, the fluorinated acrylate monomer is at least one of 2-(perfluoroalkyl)ethyl methacrylate, 2-(perfluorobutyl)ethyl methacrylate and 2-(perfluorooctyl)ethyl methacrylate.

[0013] 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, a methacrylate monomer and N,N'-(1,2-dihydroxyethylene)diacrylamide; the mass ratio of the lithium salt electrolyte to the acrylate crosslinking agent monomer is 1:0.0015-0.01; and the methacrylate monomer is prepared by reacting 2,6-dihydroxyhexanenitrile and methacryloyl chloride.

[0014] The use of the methacrylate monomer and N,N'-(1,2-dihydroxyethylene)diacrylamide as the acrylate crosslinking agent monomer not only can copolymerize with the fluorinated acrylate monomer to form a block structure polymer, reducing the phase separation of the fluorinated acrylate monomer and the lithium salt electrolyte, but also introduces a functional group, which can effectively remove the water that may exist in the lithium salt electrolyte, avoid the corrosion of materials in the battery, and obtain more durable excellent electrochemical performance.

[0015] Preferably, the initiator is azobisisobutyronitrile.

[0016] The application discloses a preparation method of a fluorinated block comb polymer.

[0017] In the battery assembly process, the polymer electrolyte precursor solution is injected between the separator and the lithium metal sheet, and heated at 40-70℃ for 1-24h to obtain the fluorinated block comb polymer.

[0018] The application further discloses application of the fluorinated block comb polymer prepared by the method in preparation of a battery.

[0019] The present invention discloses a method for preparing a polymer electrolyte precursor solution, comprising:

[0020] The solvent and the additive are mixed, and then lithium salt is added and stirred to obtain a lithium salt electrolyte. Fluorinated acrylate monomer and acrylate crosslinker monomer are added to the lithium salt electrolyte, and then an initiator is added and stirred to obtain a polymer electrolyte precursor solution.

[0021] 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.

[0022] Preferably, the additive is at least one of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, trimethyl phosphate, allyl sulfonate and lithium nitrate;

[0023] Preferably, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalatoborate, and lithium dioxalatoborate.

[0024] Preferably, the ratio of the additive to the solvent is 1 g: 100-130 ml.

[0025] Preferably, the mass ratio of the additive to the lithium salt is 1:40-45.

[0026] 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.

[0027] Preferably, the mass ratio of the lithium salt electrolyte to the fluorinated acrylate monomer is 1:0.002-0.01.

[0028] Preferably, the acrylate crosslinker 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)diacrylamide.

[0029] Preferably, the mass ratio of the lithium salt electrolyte to the acrylic ester crosslinking agent monomer is 1:0.0015-0.01.

[0030] Preferably, the initiator is azobisisobutyronitrile

[0031] Preferably, the entire preparation process is carried out under anhydrous and oxygen-free conditions.

[0032] The present invention discloses a method for preparing a fluorinated block comb polymer, comprising:

[0033] During the battery assembly process, the polymer electrolyte precursor solution is injected between the separator and the lithium metal sheet and heated at 40-70°C for 1-24 hours to obtain the fluorinated block comb polymer.

[0034] The present invention discloses a method for preparing a methacrylate monomer, comprising:

[0035] 2,6-dihydroxycapronitrile and triethylamine are added to xylene to obtain a mixed solution, and then methacryloyl chloride is added dropwise to the mixed solution at 0-6°C, followed by reaction at 20-30°C for 15-25 hours. After the reaction is completed, the mixture is filtered and purified, and finally dried to obtain a methacrylate monomer.

[0036] Preferably, the mass ratio of 2,6-dihydroxycapronitrile to triethylamine is 1:0.5-1.

[0037] Preferably, the usage ratio of 2,6-dihydroxycapronitrile to xylene is 1 g:13-18 ml.

[0038] Preferably, the mass ratio of 2,6-dihydroxycapronitrile to methacryloyl chloride is 1:0.7-1.

[0039] More preferably, in the process of preparing the polymer electrolyte precursor solution, on the basis of using methacrylate monomer and N,N'-(1,2-dihydroxyethylene)diacrylamide, flax lignan can also be used for collaborative preparation, thereby introducing more effective functional groups into the polymer electrolyte precursor solution, which is beneficial to further optimize the solvation structure and inhibit the occurrence of side reactions, so that the prepared battery exhibits good electrochemical stability.

[0040] Preferably, the mass ratio of the lithium salt electrolyte to the flax lignan is 1:0.001-0.004.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The application provides a fluorinated block comb-shaped polymer electrolyte applied to a low-temperature lithium metal battery, and first, a lithium salt electrolyte is prepared by stirring a solvent, an additive and a lithium salt; fluorinated propenoate monomers and propenoate crosslinking agent monomers are added into the lithium salt electrolyte, then an initiator is added, and the polymer electrolyte precursor solution is obtained by stirring; the polymer electrolyte precursor solution is injected between a polypropylene diaphragm and a lithium metal sheet in the battery preparation process, and the fluorinated block comb-shaped polymer is obtained by heating polymerization. The fluorinated block comb-shaped polymer prepared as the electrolyte has good ion conductance performance, and the battery prepared has good ion conductance performance; meanwhile, the comb-shaped side chain reduces the interaction with lithium ions through electron-withdrawing effect and volume effect, promotes anions to enter the solvation structure, and further forms a stable interface, effectively inhibits the growth of lithium dendrites, exhibits good electrochemical stability in low-temperature full battery application, and realizes high rate performance of the battery, and exhibits high capacity and cycle performance at low temperature; and the preparation method is efficient and rapid, effectively alleviates the solvent volatilization problem in the preparation of the electrolyte membrane through in-situ polymerization, and has good interface compatibility. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only exemplary, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of the provided drawings.

[0044] Figure 1 It is a scanning electron microscope image of the fluorinated block comb-shaped polymer;

[0045] Figure 2 It is an ion conductivity graph of a lithium-lithium symmetric battery

[0046] Figure 3 It is a lithium ion transference number test result graph of a lithium-lithium symmetric battery;

[0047] Figure 4 It is a Raman spectrum fitting graph of a lithium-lithium symmetric battery;

[0048] Figure 5 It is a time-voltage curve graph of a lithium-lithium symmetric battery;

[0049] Figure 6 It is a charge-discharge cycle graph of a lithium metal full battery;

[0050] Figure 7 It is a charge-discharge cycle graph of a lithium metal full battery at -20 DEG C. DETAILED DESCRIPTION

[0051] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0052] The following first describes the concepts involved in this application with reference to the accompanying drawings. It should be noted that the following description of each concept is intended only to make the content of this application easier to understand and does not limit the scope of protection of this application. At the same time, the embodiments and features in the embodiments of this application can be combined with each other unless there is a conflict. The following detailed description of this application will be made with reference to the accompanying drawings and in conjunction with the embodiments.

[0053] The abbreviations used in the specification and claims have the following meanings:

[0054] Example 1:

[0055] Preparation of polymer electrolyte precursor solution: In anhydrous and oxygen-free conditions, ethylene glycol dimethyl ether and fluoroethylene carbonate were mixed, followed by the addition of lithium bis(fluorosulfonyl)imide and stirring to obtain a lithium salt electrolyte. 2-(Perfluorobutyl)ethyl methacrylate and pentaerythritol triacrylate were added to the lithium salt electrolyte, followed by the addition of azobis(isobutyronitrile) and stirring to obtain a polymer electrolyte precursor solution. The mass ratio of fluoroethylene carbonate to ethylene glycol dimethyl ether was 1 g:115.34 ml, the mass ratio of fluoroethylene carbonate to lithium bis(fluorosulfonyl)imide was 1:42.93, the mass ratio of lithium salt electrolyte to 2-(perfluorobutyl)ethyl methacrylate was 1:0.00561, the mass ratio of lithium salt electrolyte to pentaerythritol triacrylate was 1:0.00441, and the mass ratio of lithium salt electrolyte to azobis(isobutyronitrile) was 1:0.001.

[0056] Preparation of fluorinated block comb polymer: During the battery assembly process, the polymer electrolyte precursor solution was injected between the polypropylene separator and the lithium metal sheet and heated at 50°C for 1.5h to obtain the fluorinated block comb polymer.

[0057] Example 2:

[0058] Preparation of polymer electrolyte precursor solution: The preparation of the polymer electrolyte precursor solution in this embodiment is compared with that in Example 1, except that the mass ratio of the lithium salt electrolyte to 2-(perfluorobutyl)ethyl methacrylate is 1:0.00362, and the mass ratio of the lithium salt electrolyte to pentaerythritol triacrylate is 1:0.00638. Other conditions and parameters are the same as in Example 1.

[0059] Preparation of fluorinated block comb polymer: The preparation of fluorinated block comb polymer in this example is different from that in Example 1 in that the polymer electrolyte precursor solution is prepared in this example, and other conditions and parameters are the same as in Example 1.

[0060] Example 3:

[0061] Preparation of polymer electrolyte precursor solution: The preparation of polymer electrolyte precursor solution in this example is different from that in Example 1 in that the mass ratio of the use amount of lithium salt electrolyte to 2-(perfluorobutyl)ethyl methacrylate is 1:0.00694, the mass ratio of the use amount of lithium salt electrolyte to pentaerythritol triacrylate is 1:0.00306, and other conditions and parameters are the same as in Example 1.

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

[0063] Example 4:

[0064] Preparation of polymer electrolyte precursor solution: The preparation of polymer electrolyte precursor solution in this example is different from that in Example 1 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 use amount of lithium salt electrolyte to 2-(perfluoroalkyl)ethyl methacrylate is 1:0.00647, the mass ratio of the use amount of lithium salt electrolyte to pentaerythritol triacrylate is 1:0.00353, and other conditions and parameters are the same as in Example 1.

[0065] Preparation of fluorinated block comb polymer: The preparation of fluorinated block comb polymer in this example is different from that in Example 1 in that the polymer electrolyte precursor solution is prepared in this example, and other conditions and parameters are the same as in Example 1.

[0066] Example 5:

[0067] Preparation of the polymer electrolyte precursor solution: The preparation of the polymer electrolyte precursor solution in this embodiment is compared with that in Embodiment 1, the difference being that 2-(perfluorobutyl)ethyl methacrylate is replaced by 2-(perfluorooctyl)ethyl methacrylate, the mass ratio of the use amount of the lithium salt electrolyte to 2-(perfluorooctyl)ethyl methacrylate is 1:0.00634, the mass ratio of the use amount of the lithium salt electrolyte to pentaerythritol triacrylate is 1:0.00366, and other conditions and parameters are the same as in Embodiment 1.

[0068] Preparation of the fluorinated block comb polymer: The preparation of the fluorinated block comb polymer in this embodiment is compared with that in Embodiment 1, the difference being that the polymer electrolyte precursor solution is the polymer electrolyte precursor solution prepared in this embodiment, and other conditions and parameters are the same as in Embodiment 1.

[0069] Embodiment 6:

[0070] Preparation of the methacrylate monomer: 2,6-dihydroxyhexanenitrile and triethylamine are added into xylene to obtain a mixed solution, then 3℃, 2,6-dihydroxyhexanenitrile and triethylamine are added into the mixed solution dropwise, followed by reaction at 25℃ for 20h, after the reaction is completed, filtration, purification by resin adsorption, and finally drying to obtain the methacrylate monomer. The mass ratio of the use amount of 2,6-dihydroxyhexanenitrile to triethylamine is 1:0.78, the use amount ratio of 2,6-dihydroxyhexanenitrile to xylene is 1g:15ml, and the mass ratio of the use amount of 2,6-dihydroxyhexanenitrile to methacryloyl chloride is 1:0.81.

[0071] Preparation of the polymer electrolyte precursor solution: Under anhydrous and oxygen-free conditions, ethylene glycol dimethyl ether and fluoroethylene carbonate are mixed uniformly, then lithium bisfluorosulfonimide is added and stirred to obtain a lithium salt electrolyte. 2-(perfluorobutyl)ethyl methacrylate, the methacrylate monomer, and N,N'-(1,2-dihydroxyethylene)diacrylamide are added into the lithium salt electrolyte, followed by addition of azobisisobutyronitrile, and stirring to obtain a polymer electrolyte precursor solution. The use amount ratio of fluoroethylene carbonate to ethylene glycol dimethyl ether is 1g:115.34ml, the mass ratio of the use amount of fluoroethylene carbonate to lithium bisfluorosulfonimide is 1:42.93, the mass ratio of the use amount of the lithium salt electrolyte to 2-(perfluorobutyl)ethyl methacrylate is 1:0.00561, the mass ratio of the use amount of the lithium salt electrolyte to the methacrylate monomer is 1:0.00247, the mass ratio of the use amount of the methacrylate monomer to N,N'-(1,2-dihydroxyethylene)diacrylamide is 1:1, and the mass ratio of the use amount of the lithium salt electrolyte to azobisisobutyronitrile is 1:0.001.

[0072] Preparation of fluorinated block comb polymer: The preparation of fluorinated block comb polymer in this example is different from that in Example 1 in that the polymer electrolyte precursor solution is prepared in this example, and other conditions and parameters are the same as in Example 1.

[0073] Example 7:

[0074] Preparation of methacrylate monomer is the same as in Example 6.

[0075] Preparation of polymer electrolyte precursor solution: The preparation of polymer electrolyte precursor solution in this example is different from that in Example 6 in that the mass ratio of the use amount of lithium salt electrolyte to methacrylate monomer is 1:0.00374, and other conditions and parameters are the same as in Example 6.

[0076] Preparation of fluorinated block comb polymer: The preparation of fluorinated block comb polymer in this example is different from that in Example 6 in that the polymer electrolyte precursor solution is prepared in this example, and other conditions and parameters are the same as in Example 6.

[0077] Example 8:

[0078] Preparation of methacrylate monomer is the same as in Example 6.

[0079] Preparation of polymer electrolyte precursor solution: Under anhydrous and oxygen-free conditions, ethylene glycol dimethyl ether and fluoroethylene carbonate were mixed, then lithium bisfluorosulfonimide was added and stirred to obtain a lithium salt electrolyte. 2-(perfluorobutyl)ethyl methacrylate, methacrylate monomer, N,N'-(1,2-dihydroxyethylene) dipropenamide and linocepon were added to the lithium salt electrolyte, followed by the addition of azobisisobutyronitrile, and stirring to obtain a polymer electrolyte precursor solution. The use amount ratio of fluoroethylene carbonate to ethylene glycol dimethyl ether was 1 g:115.34 ml, the mass ratio of the use amount of fluoroethylene carbonate to lithium bisfluorosulfonimide was 1:42.93, the mass ratio of the use amount of lithium salt electrolyte to 2-(perfluorobutyl)ethyl methacrylate was 1:0.00561, the mass ratio of the use amount of lithium salt electrolyte to methacrylate monomer was 1:0.00247, the mass ratio of the use amount of methacrylate monomer to N,N'-(1,2-dihydroxyethylene) dipropenamide was 1:1, the mass ratio of the use amount of lithium salt electrolyte to linocepon was 1:0.00151, and the mass ratio of the use amount of lithium salt electrolyte to azobisisobutyronitrile was 1:0.001.

[0080] Preparation of fluorinated block comb polymer: The preparation of the fluorinated block comb polymer in this embodiment is compared with that in Example 1, except that the polymer electrolyte precursor solution is the polymer electrolyte precursor solution prepared in this embodiment, and other conditions and parameters are the same as in Example 1.

[0081] Example 9:

[0082] The preparation of methacrylate monomer is the same as in Example 6.

[0083] Preparation of polymer electrolyte precursor solution: The preparation of the polymer electrolyte precursor solution in this embodiment is different from that in Example 8, except that the mass ratio of the lithium salt electrolyte to the flax lignan is 1:0.00233. Other conditions and parameters are the same as in Example 8.

[0084] Preparation of fluorinated block comb polymer: The preparation of fluorinated block comb polymer in this example is compared with that in Example 8, except 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 in Example 8.

[0085] Comparative Example 1:

[0086] Preparation of polymer electrolyte precursor solution: The preparation of the polymer electrolyte precursor solution in this comparative example is compared with that in Example 1, except that 2-(perfluorobutyl)ethyl methacrylate is not used, the mass ratio of the lithium salt electrolyte to pentaerythritol triacrylate is 1:0.01, and other conditions and parameters are the same as in Example 1.

[0087] Preparation of fluorinated block comb polymer: The preparation of the fluorinated block comb polymer in this comparative example is compared with that in Example 1, except 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 in Example 1.

[0088] Comparative Example 2:

[0089] Preparation of polymer electrolyte precursor solution: The preparation of the polymer electrolyte precursor solution in this comparative example is compared with that in Example 8, except that methacrylate monomer and N,N'-(1,2-dihydroxyethylene)diacrylamide are not used. Other conditions and parameters are the same as in Example 8.

[0090] Preparation of fluorinated block comb polymer: The preparation of the fluorinated block comb polymer in this comparative example is compared with that in Example 8, except 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 in Example 8.

[0091] Experimental Example 1:

[0092] The fluorinated block comb polymers prepared in Comparative Example 1, Example 1 and Examples 4-5 were analyzed by scanning electron microscopy. Figure 1 As shown, Figure 1 (a) is a scanning electron microscopy analysis of the fluorinated block comb polymer prepared in Comparative Example 1, exposing the supporting polyethylene diaphragm, indicating that the fluorinated block comb polymer prepared in Comparative Example 1 has poor wettability and interfacial compatibility; Figure 1 (b) is a scanning electron microscopy analysis of the fluorinated block comb polymer prepared in Example 1, which has a smooth and dense electrolyte surface, which is conducive to forming a continuous ion transport path and improving the electrolyte / electrode interface contact; Figure 1 (c) and Figure 1 (d) is a scanning electron microscope analysis of the fluorinated block comb polymers prepared in Example 4 and Example 5, respectively, showing granular and uneven agglomerations and high surface roughness.

[0093] Experimental Example 2:

[0094] Preparation of lithium nickel cobalt manganese oxide positive electrode: LiNi 0.8 Co 0.1 Mn 0.1 O2, Super P, and PVDF-HFP were mixed to obtain a mixture. N-methylpyrrolidone was then added to the mixture and stirred at 1200 r / min for 20 minutes to obtain a positive electrode slurry. The positive electrode slurry was coated on aluminum foil, dried, and then placed in a vacuum dryer to obtain a plate. The plate was cut into 12mm discs with a plate surface loading of 1-11.5mg cm -2 Among them, LiNi 0.8 Co 0.1 Mn 0.1 The mass ratio of O2, Super P and PVDF-HFP used is 8:1:1, and the mass ratio of the mixture to N-methylpyrrolidone used is 1:2.

[0095] Assembly of a lithium-lithium symmetric cell: A lithium metal sheet, polypropylene separator, polymer electrolyte precursor solution, and lithium metal sheet were assembled and packaged in this order, and heated at 50°C for 1.5 hours to produce a button cell, i.e., a lithium-lithium symmetric cell. The polymer electrolyte precursor solution was injected between the polypropylene separator and the lithium metal sheet. The polymer electrolyte precursor solution was the same as that prepared in Examples 1-5 and Comparative Example 1.

[0096] Ionic Conductivity Measurement: Electrochemical impedance spectroscopy was used to measure the ionic conductivity of lithium-lithium symmetrical batteries made from the fluorinated block comb polymers prepared in Examples 1-5 and Comparative Example 1 at 25°C and -30°C, respectively. Ionic conductivity measurements were performed in air, with a test frequency range of 100 Hz to 100,000 Hz and a perturbation voltage of 10 mV. The ionic conductivity was calculated using the following formula:

[0097]

[0098] Where L is the thickness of the fluorinated block comb polymer, A is the surface area of ​​the lithium metal sheet, and R is the impedance value.

[0099] Table 1 Ionic conductivity measurement results

[0100]

[0101] The ionic conductivity of the lithium-lithium symmetrical battery prepared by the fluorinated block comb polymers prepared in Examples 1-3 and Comparative Example 1 at 25°C is as follows: Figure 2 (a) is shown; the ionic conductivity measurement results at -30℃ are shown Figure 2 (b)

[0102] The lithium-lithium symmetric batteries prepared from the fluorinated block comb polymers prepared in Examples 1-5 and Comparative Example 1 have ionic conductivity measurements at 25°C and -30°C as shown in Table 1. Compared with Example 2, Example 1 shows that the amount of 2-(perfluorobutyl)ethyl methacrylate used is low, and the improvement in ionic conductivity is limited; compared with Example 3, Example 1 shows that the amount of 2-(perfluorobutyl)ethyl methacrylate used is too high, and the strong interaction between fluorine atoms reduces the dissociation of lithium salts, resulting in a decrease in ionic conductivity; compared with Example 4, Example 1 shows that the fluorinated side chain of the fluorinated acrylate monomer used is relatively short, and the improvement in ionic conductivity is also limited; compared with Example 5, Example 1 shows that the fluorinated side chain of the fluorinated acrylate monomer used is relatively long, resulting in a decrease in ionic conductivity; compared with Comparative Example 1, Example 1 uses 2-(perfluorobutyl)ethyl methacrylate to prepare a fluorinated block comb polymer, which can effectively improve the ionic conductivity of the prepared lithium-lithium symmetric battery.

[0103] Experimental Example 3:

[0104] The assembly of the lithium-lithium symmetrical battery is the same as that of Experimental Example 2.

[0105] Lithium Ion Transfer Number Test: Lithium-lithium symmetrical batteries made from the fluorinated block comb polymers prepared in Examples 1-5 and Comparative Example 1 were subjected to impedance tests before and after DC constant voltage polarization to calculate the electrolyte ion transfer number. The lithium ion transfer number calculation formula is:

[0106]

[0107] in and are the initial current and steady-state current values ​​of the polarization test, and are the interface impedance values ​​before and after polarization, is the DC polarization voltage, and 0.01 V is used.

[0108] Table 2 Lithium ion migration number measurement results

[0109]

[0110] The lithium ion transference number of the lithium-lithium symmetric battery made of the fluorinated block comb polymer prepared in Example 1 is measured as follows: Figure 3 (a) As shown; The lithium ion migration number of the lithium-lithium symmetric battery made of the fluorinated block comb polymer prepared in Example 2 is measured as shown in Figure 3 (b) As shown; The lithium ion migration number of the lithium-lithium symmetric battery made of the fluorinated block comb polymer prepared in Example 3 is measured as follows Figure 3 (c) As shown; Comparative Example 1 prepared by the fluorinated block comb polymer lithium - lithium symmetric battery made of lithium ion migration number measurement results are as follows Figure 3 (d) shown.

[0111] The results of the lithium ion migration number measurement of the lithium-lithium symmetric battery made of the fluorinated block comb polymer prepared in Examples 1-5 and Comparative Example 1 are shown in Table 2. Compared with Example 2, Example 1 shows that the amount of 2-(perfluorobutyl)ethyl methacrylate used is low, which will reduce the lithium ion migration number; Compared with Example 3, Example 1 shows that the amount of 2-(perfluorobutyl)ethyl methacrylate used is too high, which will also reduce the lithium ion efficiency; Compared with Examples 4 and 5, Example 1 shows that the length of the fluorinated side chain of the fluorinated acrylate monomer used needs to be in an appropriate range, which can effectively reduce the migration activation energy and increase the lithium ion migration number; Compared with Comparative Example 1, the lithium ion migration number of Example 1 is increased by 213%, verifying the decisive role of the fluorinated block in the selective transport of Li⁺.

[0112] Experimental Example 4:

[0113] The assembly of the lithium-lithium symmetrical battery was the same as that of Experimental Example 2. The difference was that the polymer electrolyte precursor solution was the polymer electrolyte precursor solution prepared in Example 1 and Comparative Example 1.

[0114] Raman spectroscopy analysis: Raman spectroscopy analysis was performed on the lithium-lithium symmetric batteries made of 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.

[0115] Table 3 Solvation structure statistics

[0116]

[0117] Raman spectrum of the lithium-lithium symmetric battery made of the fluorinated block comb polymer prepared in Example 1 Figure 4 (a) shows the Raman spectrum of the lithium-lithium symmetric battery made of the fluorinated block comb polymer prepared in Comparative Example 1. Figure 4 (b)

[0118] Table 3 shows the statistical results of the solvation structure of lithium-lithium symmetric batteries made from the fluorinated block comb polymers prepared in Example 1 and Comparative Example 1. Raman peak fitting analysis at 25°C and -20°C for the lithium-lithium symmetric battery made from the fluorinated block comb polymer prepared in Example 1 shows that the proportion of free ions, contact ion pairs, and aggregates varies by less than 5%, indicating that the solvation shell structure of Li⁺ is minimally affected by temperature perturbations, maintaining a highly stable coordination environment. This stability stems from the strong electronegativity and steric hindrance of the fluorinated block. The lithium-lithium symmetric battery made from the fluorinated block comb polymer prepared in Comparative Example 1, which lacks a fluorinated block, exhibits significant temperature sensitivity of the solvation structure. At -20°C, the proportion of CIPs increases by >15%, while the proportion of SSIPs decreases by more than 10%, indicating that solvent molecules more easily form tight ion pairs or even aggregates with Li⁺ at low temperatures, hindering the desolvation process of Li⁺.

[0119] Experimental Example 5:

[0120] The assembly of the lithium-lithium symmetrical battery was the same as that of Experimental Example 2. The difference was that the polymer electrolyte precursor solution was the polymer electrolyte precursor solution prepared in Example 1 and Comparative Example 1.

[0121] Determination of the cycle performance of lithium-lithium symmetrical batteries: The lithium-lithium symmetrical batteries made of the fluorinated block comb polymers prepared in Example 1 and Comparative Example 1 were tested by LAND battery testing system at -20°C, 0.1 mA cm -2 and 0.2 mA cm -2 The time-voltage curve was measured at a current density of 100 nm.

[0122] The results are as follows Figure 5As shown, the lithium-lithium symmetric battery made from the fluorinated block comb polymer prepared in Example 1 can stably cycle for more than 1000 hours 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 hours at -20°C.

[0123] Experimental Example 6:

[0124] The preparation of the lithium nickel cobalt manganese oxide positive electrode is the same as that in Experimental Example 2.

[0125] Preparation of a lithium metal full cell: A polypropylene separator, polymer electrolyte precursor solution, and lithium metal sheet were assembled and packaged in this order, and heated at 50°C for 1.5 hours to produce a button cell, i.e., a lithium metal full cell. The polymer electrolyte precursor solution was injected between the polypropylene separator and the lithium metal sheet. The polymer electrolyte precursor solution was the same as that prepared in Example 1 and Comparative Example 1.

[0126] Rate Performance: The specific capacity of lithium metal full cells made from the fluorinated block comb polymers prepared in Example 1 and Comparative Example 1 was measured using a LAND battery testing system at different rate conditions. The rate performance of the lithium metal full cells was also determined. The test temperature was 25°C and the voltage range was 3.0-4.4V.

[0127] The charge and discharge cycle diagrams of the lithium metal full battery made of the fluorinated block comb polymer prepared in Example 1 and Comparative Example 1 are as follows: Figure 6 As shown, compared with comparative example 1, the specific capacity of embodiment 1 decreases more slowly with the increase of rate, and when the rate returns to 0.1C, the specific capacity remains smooth without attenuation.

[0128] Experimental Example 7:

[0129] The preparation of the lithium nickel cobalt manganese oxide positive electrode is the same as that in Experimental Example 2.

[0130] The preparation of the lithium metal full battery was the same as that of Experimental Example 6. The difference was that the polymer electrolyte precursor solution was the polymer electrolyte precursor solution prepared in Example 1, Examples 6-9, and Comparative Examples 1-2.

[0131] Determination of specific capacity: The specific capacity of the lithium metal full batteries made of the fluorinated block comb polymers prepared in Example 1, Examples 6-9 and Comparative Examples 1-2 was determined using a LAND battery testing system at a rate of 4C and a test temperature of 25°C.

[0132] Table 4 Specific capacity measurement results

[0133]

[0134] The specific capacity of the lithium metal full cell prepared from the fluorinated block comb polymer prepared in Example 1, Example 6-9 and Comparative Example 1-2 was measured, and the results are shown in Table 4. Compared with Example 1 and Example 6, it shows that the use of methacrylate monomer and N,N'-(1,2-dihydroxyethylene) bisacrylamide can further improve the specific capacity of the lithium metal full cell prepared from the fluorinated block comb polymer. Compared with Example 6 and Example 7, it shows that the increase of the amount of methacrylate monomer within a certain range can also improve the specific capacity of the lithium metal full cell prepared from the fluorinated block comb polymer. Compared with Example 6 and Example 8, it shows that on the basis of using methacrylate monomer and N,N'-(1,2-dihydroxyethylene) bisacrylamide, the use of flax lignan can improve the specific capacity of the lithium metal full cell prepared from the fluorinated block comb polymer. Compared with Example 8 and Example 9, it shows that the increase of the amount of flax lignan can also further improve the specific capacity of the lithium metal full cell prepared from the fluorinated block comb polymer. Compared with Example 1 and Comparative Example 1, it shows that the use of 2-(perfluorobutyl) ethyl methacrylate can effectively improve the specific capacity of the lithium metal full cell prepared from the fluorinated block comb polymer. Compared with Example 8 and Comparative Example 2, it shows that flax lignan needs to be used together with methacrylate monomer and N,N'-(1,2-dihydroxyethylene) bisacrylamide, and the use of flax lignan alone has no obvious effect on improving the specific capacity of the lithium metal full cell prepared from the fluorinated block comb polymer.

[0135] Experimental Example 8:

[0136] The lithium metal full cell was assembled as in Experimental Example 6. The difference is that the polymer electrolyte precursor solution is the polymer electrolyte precursor solution prepared in Example 1, Example 6-9 and Comparative Example 1-2.

[0137] The capacity retention rate of the lithium metal full cell prepared from the fluorinated block comb polymer prepared in Example 1, Example 6-9 and Comparative Example 1-2 was measured after 45 cycles, and the test temperature was -20°C, the voltage was 3.0-4.2V, and the current density was 0.1C.

[0138] Table 5 Capacity retention rate measurement results

[0139]

[0140] The charge-discharge cycle diagram of the lithium metal full cell prepared from the fluorinated block comb polymer prepared in Example 1 and Comparative Example 1 is shown in Figure 7 .

[0141] The capacity retention rate of the lithium metal full battery prepared by the fluorinated block comb polymer obtained in Example 1, Examples 6-9 and Comparative Examples 1-2 is shown in Table 5. Compared with Example 1, Example 6 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 prepared by the fluorinated block comb polymer; Compared with Example 7, Example 6 shows that the use of methacrylate monomer within a certain range can also improve the capacity retention rate of the lithium metal full battery prepared by the 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, flax lignan is used. , 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.

[0142] 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 do not impose any form of limitation on the implementation methods of the technology of the present invention. Any person skilled in the art 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.

[0143] 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 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, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of this application, they can also make several improvements, modifications or changes, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution 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 crosslinker monomer, and an initiator; wherein the mass ratio of the lithium salt electrolyte to the fluorinated acrylate monomer is 1:0.002-0.01; The fluorinated acrylate monomer is at least one of 2-(perfluoroalkyl)ethyl methacrylate, 2-(perfluorobutyl)ethyl methacrylate, and 2-(perfluorooctyl)ethyl methacrylate; The acrylic ester crosslinking agent monomer is methacrylate monomer and N,N'-(1,2-dihydroxyethylene)diacrylamide; the mass ratio of the lithium salt electrolyte to the acrylic ester crosslinking agent monomer is 1:0.0015-0.01; the methacrylate monomer is prepared by reacting 2,6-dihydroxyhexanenitrile and methacryloyl chloride.

2. The polymer electrolyte precursor solution according to claim 1, characterized in that: The lithium salt electrolyte includes lithium salt, solvent and additives.

3. The polymer electrolyte precursor solution according to claim 2, characterized in that: The lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalatoborate, and lithium dioxalatoborate.

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

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

7. A method for preparing a fluorinated block comb polymer, comprising: During the battery assembly process, the polymer electrolyte precursor solution according to claim 1 is injected between the separator and the lithium metal sheet and heated at 40-70° C. for 1-24 hours to obtain the fluorinated block comb polymer.

8. Use of the fluorinated block comb polymer prepared by the method of claim 7 in the preparation of batteries.

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