Wide-temperature-range high-specific-energy fluorinated gel electrolyte, preparation method and application thereof

Abstract

The application provides a wide-temperature-range high-specific-energy fluorinated gel electrolyte and a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. The gel electrolyte comprises a lithium salt, a (methyl) acrylate monomer and a fluorinated sulfonate plasticizer, the molar concentration of the lithium salt in the total volume of the fluorinated sulfonate plasticizer and the (methyl) acrylate monomer is 2-5 mol / L, and the volume ratio of the (methyl) acrylate monomer to the fluorinated sulfonate plasticizer is 2-4:8-6. The gel electrolyte not only has the characteristics of an ionic conductivity at room temperature of more than 2 mS / cm and an electrochemical window of more than 5 V, but also has good stability in matching high-voltage positive electrodes and good stability in matching lithium metal negative electrodes and silicon-carbon negative electrodes, and exhibits good cycle performance at a wide temperature range (-20-60 DEG C).

Description

Technical Field

[0001] This application relates to a wide-temperature-range high-energy-density fluorinated gel electrolyte, its preparation method and application, belonging to the field of lithium-ion battery technology. Background Technology

[0002] Lithium-ion batteries dominate consumer electronics, electric vehicles, and large-scale energy storage due to their high energy density and environmental friendliness. However, as market demands for electrochemical energy storage performance continue to rise, traditional lithium-ion batteries face severe challenges in terms of energy density, safety, and cycle life. Especially in the pursuit of higher energy density, while high-nickel ternary cathode materials offer the advantage of high specific capacity, their poor thermal stability and tendency to release oxygen make them prone to violent side reactions with organic electrolytes, posing serious safety hazards.

[0003] To systematically address the aforementioned problems, using gel electrolytes to replace traditional liquid electrolytes is considered a highly promising technological approach. Gel polymer systems utilize the electrolyte as a plasticizer, swelling it within a three-dimensional polymer network. This effectively suppresses leakage and corrosion, enhancing mechanical strength while maintaining good interfacial wettability, providing a new approach to achieving a synergistic improvement in high energy density and high safety. However, currently reported gel electrolytes still have shortcomings in terms of ionic conductivity, electrochemical window, and flame retardancy. Summary of the Invention

[0004] In view of this, this application firstly provides a wide-temperature-range high-specific-energy fluorinated gel electrolyte, which combines high ionic conductivity, wide electrochemical window and excellent flame retardancy.

[0005] Specifically, this application is implemented through the following scheme:

[0006] A wide-temperature-range, high-specific-energy fluorinated gel electrolyte is obtained by polymerization of a precursor solution, wherein the precursor solution comprises a lithium salt, a (meth)acrylate monomer, and a fluorinated sulfonate plasticizer.

[0007] The structural formula of the (meth)acrylate monomer is:

[0008] R1 is selected from one of -H, -CH3, and -CF3, and R2 is selected from at least one of -H, -CF3, -CHFCF3, and -O-CH3, where m = 0 to 5 and n = 0 to 10.

[0009] The structural formula of the fluorinated sulfonate plasticizer is:

[0010] R3 is selected from -CH3 and -CF3, and R4 is a fluoroalkyl group.

[0011] The applicable temperature range for the above electrolytes is -20 to 60 °C.

[0012] Furthermore, as a preferred option:

[0013] R4 is selected from one of -CH2F, -CH2CF3, -CH2CH2F, -CH2CHF2, -CH2CF2CF3, -CH2CHFCF3, -CH2CF2CF2CF3, and -CH(CF3)2.

[0014] The (meth)acrylate monomer is at least one selected from 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, and 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate.

[0015] The fluorinated sulfonate plasticizer is at least one selected from the following: fluoromethyl trifluoromethanesulfonate, 2-fluoroethyl methanesulfonate, 2,2,2-trifluoroethyl methanesulfonate, 2,2,2-trifluoroethyl trifluoromethanesulfonate, 2,2-difluoroethyl trifluoromethanesulfonate, 1,1,1,3,3,3-hexafluoropropane-2-methanesulfonate, 2,2,3,3,4,4,4-heptafluorobutyl methanesulfonate, and propyl pentafluorotrifluoromethanesulfonate. More preferably, the fluorinated sulfonate plasticizer is a mixture of 2,2,2-trifluoroethyl methanesulfonate and 2,2,2-trifluoroethyl trifluoromethanesulfonate, wherein the volume ratio of 2,2,2-trifluoroethyl methanesulfonate to 2,2,2-trifluoroethyl trifluoromethanesulfonate is 1.5 to 2.5:1.

[0016] The lithium salt includes at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonyl)imide, lithium oxalate borate, lithium difluorooxalate borate, lithium hexafluorophosphate, and lithium tetrafluoroborate.

[0017] Compared to perfluorinated electrolyte systems (Fan et al., Nature Energy, 2019), the perfluorinated gel electrolyte used in this invention combines the high ionic conductivity of traditional liquid electrolytes with the high safety of solid electrolytes, significantly enhancing the flame retardant properties of the electrolyte and achieving a synergistic improvement in electrochemical performance and safety. Compared to recent research results (Xie et al., JACS, 2024, Meng et al., Nature Energy, 2023), this invention uses polarity matching between fluorinated monomers and fluorinated plasticizers to ensure sufficient swelling, thereby improving the uniformity of bulk ion transport. Combined with the synergistic effect of weak coordination / weak solvation of lithium ions by monomers and plasticizers, they jointly reduce the lithium ion migration barrier and desolvation barrier, improve interfacial reaction kinetics, effectively passivate the high-voltage cathode interface, broaden the electrochemical stability window, and suppress side reactions.

[0018] The applicant also provides a method for preparing the above-mentioned wide-temperature-range high-specific-energy fluorinated gel electrolyte, comprising the following steps:

[0019] Step 1: Add the lithium salt to the fluorinated sulfonate plasticizer and stir until completely dissolved;

[0020] Step 2: Add (meth)acrylate monomer to the solution obtained in Step 1 to obtain a homogeneous solution;

[0021] Step 3: Add a cross-linking agent to the homogeneous solution from Step 2;

[0022] Step four: Add an initiator to the solution from step three to obtain the precursor solution.

[0023] Step 5: At a temperature of 50–70 °C, the precursor solution is placed on the matrix to initiate a polymerization reaction, thereby obtaining a gel electrolyte.

[0024] Preferred:

[0025] The molar concentration of the lithium salt relative to the total volume of the fluorinated sulfonate plasticizer and (meth)acrylate monomer is 2-5 mol / L, that is: when the total volume of the fluorinated sulfonate plasticizer and (meth)acrylate monomer is 1 L, the corresponding total amount of lithium salt is 2-5 mol.

[0026] The volume ratio of the (meth)acrylate monomer to the fluorinated sulfonate plasticizer is 2-4:8-6.

[0027] The amount of crosslinking agent added is 3 to 5% of the total volume of the fluorinated sulfonate plasticizer and (meth)acrylate monomer.

[0028] The crosslinking agent includes ethylene glycol dimethacrylate.

[0029] The amount of initiator added is 0.1 to 0.5% of the mass of the (meth)acrylate monomer.

[0030] The initiator is at least one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, dodecyl peroxide, potassium persulfate, or ammonium persulfate.

[0031] The substrate is a positive electrode, a separator, a negative electrode, aluminum foil, or a stainless steel sheet.

[0032] The polymerization reaction takes 10–12 h and is carried out in an inert atmosphere.

[0033] The aforementioned gel electrolyte is a perfluorinated gel electrolyte composed of fluorinated (meth)acrylate monomers and fluorinated sulfonate plasticizers. Compared with traditional liquid and solid electrolytes, the perfluorinated gel electrolyte can achieve synergistic improvements in electrochemical performance and safety, with a room temperature ionic conductivity exceeding 2 × 10⁻⁶. -3 With a S / cm (i.e., exceeding 2 mS / cm) and an electrochemical window exceeding 5 V, the polymer electrolyte also exhibits good stability when matched with high-voltage cathodes and with lithium metal and silicon-carbon anodes. It demonstrates good cycle performance over a wide temperature range (-20 to 60 °C), and therefore can be applied to lithium batteries.

[0034] The lithium battery includes a positive electrode, a separator, a negative electrode, and a gel electrolyte having the above-mentioned characteristics.

[0035] The negative electrode active material of the lithium battery is a lithium metal electrode or a silicon-carbon electrode. More preferably, the lithium battery is a Li / Li symmetric cell, a Li / NCM811 half-cell, a Si-C / NCM811 full cell, or a Si-C / NCM955 full cell.

[0036] Compared with the prior art, the beneficial effects of this application are summarized as follows:

[0037] (1) The present invention provides a perfluorinated gel electrolyte composed of fluorinated (meth)acrylate monomers and fluorinated sulfonate plasticizers. Compared with traditional liquid electrolytes and solid electrolytes, the electrolyte of the present application can achieve synergistic improvement in electrochemical performance and safety.

[0038] (2) The present invention adopts a high-temperature in-situ polymerization preparation method. Compared with polymer electrolyte films, its preparation process is simple and the raw materials are not easily volatilized during the synthesis process, which can greatly improve the safety and efficiency of the synthesis process.

[0039] (3) This invention is used for the assembly of gel electrolytes. The polarity of the (meth)acrylate monomer (especially 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, etc.) and the fluorinated sulfonate plasticizer (such as 2,2,2-trifluoroethyl methanesulfonate and 2,2,2-trifluoroethyl trifluoromethanesulfonate, etc.) is matched. There is a strong interaction between the strongly electronegative fluorinated alkane chain in the monomer and the strongly positive methyl group in the fluorinated sulfonate plasticizer, which allows the plasticizer and monomer to swell fully and the lithium ion bulk phase transport to be more uniform. At the same time, the fluorinated (meth)acrylate monomer serves as the polymer backbone, and the fluorinated groups in it participate in the coordination of lithium ions, thereby weakening the coordination of lithium ions with carbonyl oxygen. The combination of the weak coordination effect of this fluorine-oxygen co-coordination effect on lithium ions and the weak solvation and dilution effect of the fluorinated sulfonate plasticizer on lithium ions can improve the bulk phase ionic conductivity while maintaining high mechanical strength. The above-mentioned gel electrolyte system enables the formation of LiF-rich inorganic electrolyte interfaces at the positive and negative electrodes, which efficiently passivates the electrode interfaces, thereby improving the interfacial ionic conductivity of lithium batteries and broadening the electrochemical window.

[0040] (4) The present invention is used for the assembly of gel electrolytes. The higher degree of fluorinated monomers can improve the thermodynamic stability and oxidation resistance of the polymer skeleton, reduce the occurrence of side reactions, and thus reduce the performance degradation caused by electrolyte decomposition or electrode material degradation during charging and discharging.

[0041] (5) The present invention is used for the assembly of gel electrolytes. The perfluorinated gel electrolyte constructed by fluorinated (meth)acrylate monomers and fluorinated sulfonate plasticizers has good interfacial wettability, which can significantly reduce interfacial impedance and suppress side reactions at the electrolyte-electrode interface. At the same time, the good mechanical strength and coating properties of the gel can suppress the growth and puncture of lithium dendrites and the expansion and cracking of silicon carbon particles in silicon carbon anodes. It is also well compatible with high voltage cathodes, thereby achieving long cycle life and high coulombic efficiency of lithium batteries.

[0042] (6) The present invention is used for the assembly of gel electrolytes. Due to the combined effect of fluorinated (meth)acrylate monomers and fluorinated sulfonate plasticizers, the gel electrolytes are given a wider electrochemical stability window, which enables them to withstand oxidative decomposition under high temperature and high voltage conditions. Furthermore, the chemical inertness inhibits the occurrence of various side reactions, thereby reducing the continuous consumption of electrolytes and the increase in interfacial impedance, and significantly improving the wide temperature range adaptability of the electrolytes.

[0043] (7) The fluorinated gel electrolyte of the present invention has high ionic conductivity (>2 mS / cm), wide electrochemical window (>5 V), wide temperature range adaptability (-20~60 ℃), and is compatible with high voltage positive electrode, lithium metal negative electrode / silicon-carbon negative electrode, and has broad application prospects in future lithium batteries. Attached Figure Description

[0044] Figure 1 The test curves for the Li / Li symmetric cells corresponding to Example 1 and Comparative Example 3 are shown below.

[0045] a) Test curve of Example 1, b) Test curve of Comparative Example 3;

[0046] Figure 2 Cyclic tests of the Li / NCM811 half-cells corresponding to Example 1 and Comparative Example 3 were conducted.

[0047] a) Cycle curve of Example 1, b) Cycle curve of Comparative Example 3;

[0048] Figure 3 Cyclic tests of Li / NCM811 half-cells corresponding to the gel electrolytes in Examples 2, 3, 4, and 5.

[0049] a) Cycle curve of Example 2, b) Cycle curve of Example 3,

[0050] c) Cycle curve of Example 4; d) Cycle curve of Example 5;

[0051] Figure 4 For the cycling tests of the Li / NCM811 half-cells corresponding to the non-fluorinated gel electrolytes of Comparative Examples 1 and 2,

[0052] a) Cyclic curve of Comparative Example 1, b) Cyclic curve of Comparative Example 2;

[0053] Figure 5 Cyclic testing of Si-C / NCM811 full cells corresponding to Example 1 and Comparative Example 3.

[0054] a) Cycle curve of Example 1, b) Cycle curve of Comparative Example 3;

[0055] Figure 6 Cyclic tests of Si-C / NCM955 full cells corresponding to Example 1 and Comparative Example 3 were conducted.

[0056] a) Cycle curve of Example 1, b) Cycle curve of Comparative Example 3. Detailed Implementation

[0057] Example 1

[0058] This embodiment provides a wide-temperature-range high-specific-energy fluorinated gel electrolyte, including lithium difluorosulfonylimide, 2,2,2-trifluoroethyl methanesulfonate and 2,2,2-trifluoroethyl trifluoromethanesulfonate, and 2,2,3,3,4,4,4-heptafluorobutyl methacrylate.

[0059] Its preparation process is as follows:

[0060] Step 1: 2,2,2-Trifluoroethyl methanesulfonate (TM) and 2,2,2-trifluoroethyl trifluoromethanesulfonate (TTMS) are mixed at a volume ratio of 2:1 to obtain a plasticizer. In an argon-atmospheric glove box, lithium difluorosulfonyl imide is slowly dissolved in the plasticizer. Then, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate monomer (7FMA) and crosslinking agent ethylene glycol dimethacrylate (EGDA) are slowly added. The volume ratio of 2,2,3,3,4,4,4-heptafluorobutyl methacrylate monomer to plasticizer is 2:8, and the amount of crosslinking agent added is 5% of the total volume of monomer and plasticizer. Next, the initiator azobisisobutyronitrile (AIBN) is added at an amount of 0.5% of the monomer mass. The mixture is stirred until completely dissolved to obtain the precursor solution.

[0061] Step 2: At 60 °C, the precursor solution is placed on the matrix to initiate a polymerization reaction, thus obtaining the fluorinated gel electrolyte.

[0062] Example 2

[0063] This embodiment has the same setup as Embodiment 1, except that the monomer 7FMA is replaced with 2,2,3,4,4,4-hexafluorobutyl methacrylate (6FMA).

[0064] Example 3

[0065] This embodiment has the same setup as Embodiment 1, except that the monomer 7FMA is replaced with 2,2,3,3,3-pentafluoropropyl methacrylate (5FMA).

[0066] Example 4

[0067] This embodiment has the same setup as Embodiment 1, except that the monomer 7FMA is replaced with 2,2,3,3-tetrafluoropropyl methacrylate (4FMA).

[0068] Example 5

[0069] This embodiment has the same setup as Embodiment 1, except that the monomer 7FMA is replaced with 2,2,2-trifluoroethyl methacrylate (3FMA).

[0070] Comparative Example 1

[0071] The setup for this comparative example is the same as that for Example 1, except that the monomer 7FMA is replaced with methoxyethyl methacrylate (2-MEA).

[0072] Comparative Example 2

[0073] The setup for this comparative example is the same as that for Example 1, except that the monomer 7FMA is replaced with butyl methacrylate (BMA).

[0074] Comparative Example 3

[0075] This comparative example uses a commercially available ester-based electrolyte: a certain amount of LiPF6 was slowly dissolved in a mixture of EC and EMC (volume ratio 1:1) to achieve a LiPF6 concentration of 1 mol / L. The solution was stirred until completely dissolved.

[0076] The electrolytes from the above examples and comparative examples were used for the fabrication and testing of Li / Li, Li / NMC811, Si-C / NCM811, and Si-C / NCM955 batteries, respectively.

[0077] (1) Positive electrode sheet: The active material, binder PVDF and conductive carbon black are added to N-methylpyrrolidone (NMP) in a ratio of 8:1:1 (or 9:0.5:0.5) and mixed evenly to obtain a slurry; then coated onto the aluminum foil current collector, dried at 100°C, rolled and cut into round sheets with a diameter of 12mm by a punching machine.

[0078] (2) Negative electrode sheet: Si, conductive carbon black and CMC electrode slurry are added to N-methylpyrrolidone (NMP) in a ratio of 8:1:1 and ultrasonically dispersed and mixed evenly to obtain a slurry; then coated onto copper foil current collector, dried at 100°C, rolled and cut into round sheets with a diameter of 14 mm by a punching machine.

[0079] (3) Electrolyte: The electrolytes prepared in Examples 1-5 and Comparative Examples 1-3.

[0080] (4) Diaphragm: Cut out polyethylene single-layer diaphragm discs with a diameter of 19 mm using a punching machine.

[0081] (5) Battery assembly: In a glove box (O2<0.1ppm, H2O<0.1ppm), lithium batteries were assembled in the following order: positive electrode shell-positive electrode plate-separator-negative electrode plate-stainless steel plate-spring plate-negative electrode shell. The precursor solutions prepared in Examples 1-5 and Comparative Examples 1-3 were added. Comparative Example 3 was an electrolyte system. After encapsulation, the test battery was obtained directly. Examples 1-5 and Comparative Examples 1 and 2 were gel electrolyte systems. After encapsulation and in-situ polymerization, the test battery was obtained.

[0082] (6) Battery test:

[0083] I. Ionic conductivity

[0084] Table 1: Comparison of Ionic Conductivities of Different Gel Electrolytes

[0085] .

[0086] As shown in Table 1, the perfluorinated gel electrolytes prepared in Examples 1 and 5 all exhibited room-temperature ionic conductivity greater than 2 mS / cm, indicating that the perfluorinated gel electrolytes prepared in these examples possessed high ionic conductivity. In contrast, the non-fluorinated gel electrolytes prepared in Comparative Examples 1 and 2 had room-temperature ionic conductivity lower than 2 mS / cm. This comparison demonstrates that the introduction of fluorine into the polymer monomer can effectively improve the ionic conductivity of the electrolyte.

[0087] Meanwhile, the applicant provides a detailed analysis of the impact of the constituent components and preparation parameters in this scheme:

[0088] 1) Under the same conditions, when the n value of the polymer monomer is larger, that is, when the degree of fluorination of the alkane chain is greater, the improvement effect of ionic conductivity is greater than that of the polymer monomer system with a lower degree of fluorination (see Examples 1 and 5). The reason for this is that, on the one hand, after the degree of monomer fluorination increases, its coordination effect on lithium ions as a polymer backbone is further weakened. Combined with the weak solvation and dilution effect of fluorinated sulfonate plasticizer on lithium ions, the bulk ion transport resistance is reduced and the ionic conductivity is improved. On the other hand, after the degree of monomer fluorination increases, the electronegativity of the monomer fluorinated alkane chain is further enhanced. The interaction between it and the strongly positively charged methyl group in the fluorinated plasticizer is enhanced, resulting in enhanced interaction between monomer and solvent, more uniform and sufficient gel swelling, and more uniform bulk lithium ion transport.

[0089] 2) Under the same conditions, the perfluorinated gel polymer system showed a significantly better improvement in ionic conductivity at -30℃ than the non-fluorinated gel polymer system (see Examples 1 and 5, Comparative Examples 1 and 2). This is because the fluorinated polymer skeleton has high flexibility, which can inhibit the crystallization of electrolyte at low temperature and maintain the smooth flow of lithium ion transport channels.

[0090] II. Cyclic Testing in Li / Li Symmetric Cells

[0091] The perfluorinated gel electrolyte prepared in this study exhibits excellent ability to suppress lithium dendrite growth and compatibility with lithium metal anodes. Taking Example 1 as an example, tests showed that the lithium-lithium (Li / Li) symmetric battery corresponding to the prepared perfluorinated gel electrolyte achieved a speed of 0.2 mA / cm². 2 The current density cycling curve at room temperature (25 °C) shows that it can be stably cycled for more than 2000 h (see [reference]). Figure 1 (See Figure a) in the figure), and there was no obvious overpotential increase or short circuit phenomenon. In contrast, the commercial ester-based electrolyte in Comparative Example 3 showed significant voltage fluctuations under the same cycling conditions (see Figure a). Figure 1 (Figure b)

[0092] III. Cyclic Testing of Li / NCM811 Batteries

[0093] Taking Examples 1, 2, 3, 4, and 5 as examples, the perfluorinated gel polymer batteries prepared therein were tested at room temperature (25 °C) with a 0.2C rate and a voltage range of 2.7–4.5 V. The results were compared with those of Comparative Examples 1, 2, and 3 under the same conditions (see Example 5). Figures 2-4 ).

[0094] from Figure 2 Figure a) in the middle Figure 3 The number of cycles required for each perfluorinated gel polymer system to reduce its capacity to 80% was statistically analyzed. The 3FMA-TM-TTMS, 4FMA-TM-TTMS, 5FMA-TM-TTMS, 6FMA-TM-TTMS, and 7FMA-TM-TTMS systems required 248, 329, 412, 447, and 540 cycles, respectively. This indicates that the cycle stability of the battery improves with increasing fluorination degree of the polymer monomers. Furthermore, the 7FMA-TM-TTMS system achieved an average coulombic efficiency exceeding 99.7%.

[0095] from Figure 4 and Figure 2 Figure b) shows the number of cycles required for each non-fluorinated gel polymer system and conventional commercial ester electrolyte system to decay to 80% of their capacity retention. The 2-MEA-TM-TTMS, BMA-TM-TTMS and commercial ester electrolyte systems correspond to 147, 183 and 146 cycles, respectively, which are far worse than the cycle life in the examples, and the average coulombic efficiency is less than 99.3%.

[0096] Compared to non-fluorinated gel electrolytes or conventional commercial ester-based electrolytes, perfluorinated gel electrolytes exhibit significantly improved cycle capacity retention and coulombic efficiency. This is due to the excellent interfacial wettability of perfluorinated gel electrolytes, which greatly reduces interfacial impedance and suppresses side reactions at the electrolyte-electrode interface. Simultaneously, the good mechanical strength and electrode coating properties of the gel inhibit lithium dendrite growth and puncture, ensuring good compatibility with high-voltage cathodes, thus achieving long cycle life and high coulombic efficiency in lithium batteries. Furthermore, a higher degree of fluorination in the monomers enhances the thermodynamic stability and oxidation resistance of the polymer backbone, reducing the occurrence of side reactions and thereby minimizing performance degradation during charge and discharge due to electrolyte decomposition or electrode material degradation.

[0097] IV. Cyclic Testing in Si-C / NCM811 Batteries

[0098] Taking Example 1 as an example, the test results of the perfluorinated gel polymer battery prepared therein were tested at room temperature (25 °C) at a rate of 0.3C and a voltage range of 2.7–4.3 V (see Example 1). Figure 5 Figure a) in the figure above), and compare it with the test results of Comparative Example 3 under the same conditions (see Figure 3). Figure 5 (Figure b)

[0099] from Figure 5 As shown in Figure a), when using the 7FMA-TM-TTMS perfluorinated gel electrolyte system of this case, the corresponding battery retains more than 86% of its capacity after 500 cycles, and the average coulombic efficiency is as high as 99.8%.

[0100] from Figure 5 As can be seen from Figure b), after 100 cycles, the capacity retention rate of the battery corresponding to the conventional commercial ester-based electrolyte is only 71%, which is far worse than the cycle life in the example, and the average coulombic efficiency is less than 99.4%.

[0101] Compared to conventional commercial ester-based electrolytes, the 7FMA-TM-TTMS perfluorinated gel electrolyte exhibits significantly improved cycle capacity retention and coulombic efficiency. This is due to the excellent coating properties of the perfluorinated gel electrolyte onto the Si-C electrode, which effectively suppresses the expansion and cracking of silicon-carbon particles in the silicon-carbon anode, while also ensuring good compatibility with the high-voltage cathode, thereby achieving long cycle life and high coulombic efficiency in lithium batteries.

[0102] V. Cyclic Testing in Si-C / NCM955 Batteries

[0103] Taking Example 1 as an example, the test results of the perfluorinated gel polymer battery prepared therein were tested at high temperature (60 °C) at a 1C rate and a voltage range of 2.7-4.5 V (see Example 1). Figure 6 Figure a) in the figure above), and compare it with the test results of Comparative Example 3 under the same conditions (see Figure 3). Figure 6 (Figure b)

[0104] from Figure 6 As shown in Figure a), when using the 7FMA-TM-TTMS perfluorinated gel electrolyte system of this case, the corresponding battery retains more than 80% of its capacity after 480 cycles, and the average coulombic efficiency is as high as 99.9%.

[0105] from Figure 6 As can be seen from Figure b), the capacity retention rate of batteries with conventional commercial ester-based electrolytes is less than 80% after 100 cycles, which is far worse than the cycle life in the examples, and the average coulombic efficiency is less than 99.6%.

[0106] Compared to conventional commercial ester-based electrolytes, the 7FMA-TM-TTMS perfluorinated gel electrolyte exhibits significantly improved cycle capacity retention and coulombic efficiency at 60 °C. This is due to the wide electrochemical stability window of the fluorinated polymer monomers and fluorinated plasticizers, which enable them to withstand oxidative decomposition under high temperature and high voltage conditions and suppress various side reactions through chemical inertness, thereby reducing continuous electrolyte consumption and the increase in interfacial impedance.

Claims

1. A wide-temperature-range, high-specific-energy fluorinated gel electrolyte, characterized in that: The wide-temperature-range, high-specific-energy fluorinated gel electrolyte is obtained by polymerization of a precursor solution, which includes lithium salt, (meth)acrylate monomer, and fluorinated sulfonate plasticizer. The (meth)acrylate monomers are 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, and 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate. The structural formula of the fluorinated sulfonate plasticizer is: R3 is selected from -CH3 and -CF3, and R4 is a fluoroalkyl group. The applicable temperature range for the above electrolytes is -20 to 60 °C.

2. The wide-temperature-range, high-specific-energy fluorinated gel electrolyte according to claim 1, characterized in that: R4 is selected from one of -CH2F, -CH2CF3, -CH2CH2F, -CH2CHF2, -CH2CF2CF3, -CH2CHFCF3, -CH2CF2CF2CF3, and -CH(CF3)2.

3. The wide-temperature-range, high-specific-energy fluorinated gel electrolyte according to claim 1, characterized in that: The fluorinated sulfonate plasticizer is at least one selected from the following: fluoromethyl trifluoromethanesulfonate, 2-fluoroethyl methanesulfonate, 2,2,2-trifluoroethyl methanesulfonate, 2,2,2-trifluoroethyl trifluoromethanesulfonate, 2,2-difluoroethyl trifluoromethanesulfonate, 1,1,1,3,3,3-hexafluoropropane-2-methanesulfonate, 2,2,3,3,4,4,4-heptafluorobutyl methanesulfonate, and 2,2,3,3,3-pentafluorotrifluoromethanesulfonate propyl ester.

4. The wide-temperature-range, high-specific-energy fluorinated gel electrolyte according to claim 1, characterized in that: The fluorinated sulfonate plasticizer is a mixture of 2,2,2-trifluoroethyl methanesulfonate and 2,2,2-trifluoroethyl trifluoromethanesulfonate, with a volume ratio of 1.5 to 2.5:

1.

5. The wide-temperature-range, high-specific-energy fluorinated gel electrolyte according to claim 1, characterized in that: The lithium salt includes at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonyl)imide, lithium oxalate borate, lithium difluorooxalate borate, lithium hexafluorophosphate, and lithium tetrafluoroborate.

6. A method for preparing a wide-temperature-range, high-specific-energy fluorinated gel electrolyte according to claim 1, characterized in that: Lithium salt was added to the fluorinated sulfonate plasticizer and stirred until completely dissolved; (meth)acrylate monomer, crosslinking agent, and initiator were added, and polymerization reaction was carried out at 50-70 °C to obtain gel electrolyte.

7. The method for preparing a wide-temperature-range high-specific-energy fluorinated gel electrolyte according to claim 6, characterized in that: The amount of crosslinking agent added is 3 to 5% of the total volume of the fluorinated sulfonate plasticizer and (meth)acrylate monomer.

8. The method for preparing a wide-temperature-range high-specific-energy fluorinated gel electrolyte according to claim 6, characterized in that: The amount of initiator added is 0.1 to 0.5% of the total volume of the fluorinated sulfonate plasticizer and (meth)acrylate monomer.

9. The application of the wide-temperature-range high-energy-density fluorinated gel electrolyte of claim 1 in lithium batteries.

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