Preparation method and application of low-temperature-resistant gel polymer electrolyte

Abstract

The invention relates to a preparation method and application of a low-temperature-resistant gel polymer electrolyte, and belongs to the technical field of polymer electrolytes. The technical problem to be solved by the invention is to provide the preparation method of the low-temperature-resistant gel polymer electrolyte suitable for the lithium metal battery. The method comprises the following steps: uniformly mixing an ether electrolyte, cross-linking agents such as potassium allyltrifluoroborate and pentaerythritol tetraacrylate, and fluoroethylene carbonate to obtain a precursor solution; uniformly mixing azodiisobutyronitrile with the precursor solution to obtain a reaction solution; and heating and reacting to obtain the low-temperature-resistant gel polymer electrolyte. By introducing the anion conductor, the freezing resistance of the electrolyte is remarkably improved, good low-temperature tolerance can be realized, and the low-temperature cycle performance is improved. The electrolyte has high conductivity, and overcomes the defect of low low-temperature ionic conductivity of the conventional polymer electrolyte; the lithium ion transference number is high, and the defect of low Li < + > transference number of the polymer electrolyte is effectively solved.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method and application of a low-temperature-resistant gel polymer electrolyte, and belongs to the technical field of polymer electrolytes. BACKGROUND

[0002] With the in-depth promotion of global energy structure transformation, electric vehicles, aerospace and extreme environment energy storage technologies have ushered in rapid development, and the performance requirements of high-energy-density energy storage devices under harsh working conditions such as low temperature are increasingly stringent. Lithium metal batteries are considered as an ideal choice for the next generation of energy storage technologies due to their extremely high theoretical energy density. However, traditional liquid electrolyte-based lithium metal batteries face severe challenges at low temperatures: the sharp increase in the bulk viscosity of the electrolyte leads to a sharp drop in ionic conductivity, and the slow ion desolvation process at the electrode-electrolyte interface and the sharp increase in charge transfer resistance cause serious kinetic lag. More troublesome is that the unstable interface process at low temperature easily induces uncontrollable growth of lithium dendrites, not only accelerating capacity decay, but also bringing serious safety hazards.

[0003] To overcome the above problems, gel polymer electrolytes have shown great potential due to their perfect combination of the excellent interface wettability of liquid electrolytes and the high safety of solid-state electrolytes. Gel polymer electrolytes can theoretically perfectly combine the excellent interface wettability of liquid electrolytes and the high safety, anti-leakage and other advantages of solid-state electrolytes by anchoring liquid electrolytes in the polymer backbone, and are considered as a potential solution to realize high-safety and high-energy-density lithium metal batteries. However, the performance of conventional gel polymer electrolytes (such as systems based on polyethylene oxide PEO, polyvinylidene fluoride-hexafluoropropylene PVDF-HFP, etc.) at low temperatures is still not satisfactory. The core bottleneck is that as the temperature decreases, the segment motion ability of the polymer matrix decreases significantly, and the molecular chain tends to be "frozen", making it extremely difficult for lithium ions to transport therein, and the ionic conductivity cannot meet the demand of low-temperature large-current operation. For example, the polyvinylidene fluoride-based electrolyte widely used in the prior art, although it exhibits reliable mechanical and electrochemical properties at room temperature, its energy density, power density and cycle life will all decrease significantly at subzero temperatures, greatly limiting its applicability in cold climates.

[0004] In the prior art, researchers have proposed various strategies to improve the low-temperature performance of electrolytes. On the one hand, by designing high-concentration electrolytes (HCE) or locally high-concentration electrolytes (LHCE), the special solvation structure is used to reduce the desolvation energy barrier of lithium ions and improve the bulk stability of the electrolyte. Recent progress has further shown that the introduction of multiple lithium salts to form a high-entropy electrolyte can change the solvation structure and tailor the formation of the interface. However, these in-situ formed SEI layers usually have uncontrollable composition and poor mechanical properties, resulting in short life of lithium metal batteries (LMB) at subzero temperatures. On the other hand, methods such as physical blending of plasticizers, ceramic fillers, etc. can improve the ionic conductivity to some extent, but it is often difficult to simultaneously consider multiple key performance indicators, especially the systematic solution to the "interface compatibility-high efficient ion transport-uniform deposition of metal lithium" optimization problem.

[0005] Specifically, the prior art still faces two major challenges: first, the ion transport efficiency is difficult to balance high Li + transference number (>0.5) and high ionic conductivity (>1.5 mS cm -1 ); second, low temperature will exacerbate the polarization of the electrode, causing lithium ions to tend to deposit unevenly on the electrode surface, forming lithium dendrites, and the unevenness of ion transport and deposition will be amplified at low temperature, further promoting the growth of lithium dendrites, posing a serious threat to the safety and life of the battery.

[0006] Chinese invention patent CN113258145A discloses an elastic low-temperature-resistant solid-state electrolyte and a preparation method thereof, which uses a combination of zwitterions, comonomers, ionic liquids and zinc salts to improve ionic conductivity and improve low-temperature resistance. However, this method relies on ultraviolet light curing process, and the preparation process is relatively complex, and the polymer network structure formed is suitable for flexible zinc ion batteries, and its application in lithium metal batteries still needs to be discussed. SUMMARY

[0007] The technical problem solved by the present application is to provide a preparation method of a low-temperature-resistant gel polymer electrolyte suitable for lithium metal batteries.

[0008] The preparation method of the low-temperature-resistant gel polymer electrolyte of the present application comprises the following steps:

[0009] A. Mixing the ether-based electrolyte with potassium allyl trifluoroborate, a crosslinking agent and fluorinated ethylene carbonate uniformly to obtain a precursor solution;

[0010] B. Mixing azobis isobutyronitrile with the precursor solution uniformly to obtain a reaction solution;

[0011] C. Heating the reaction solution of step B to obtain a low-temperature-resistant gel polymer electrolyte.

[0012] The ether-based electrolyte comprises a lithium salt and an ether solvent; the lithium salt is lithium bistrifluoromethylsulfonylimide, lithium hexafluorophosphate or lithium bisfluorosulfonylimide;

[0013] The crosslinking agent is pentaerythritol tetraacrylate, triethylene glycol dimethacrylate or polyethylene glycol diacrylate.

[0014] The preparation method of the low-temperature-resistant gel polymer electrolyte of the application is initiated by azobisisobutyronitrile, uses pentaerythritol tetraacrylate as a crosslinking agent, initiates a free radical copolymerization reaction containing potassium allyl trifluoroborate, and converts a liquid electrolyte solution into a gel with a three-dimensional network structure. By covalently anchoring the macromolecular anion on the skeleton, selective promotion of lithium ion transmission (high lithium ion transference number) is achieved, the conductivity is improved, and the ether solvent in the ether-based electrolyte and the addition of fluoroethylene carbonate endow the entire electrolyte with excellent low-temperature resistance.

[0015] In an embodiment of the application, the ether-based electrolyte comprises a lithium salt and an ether solvent. The lithium salt is lithium bistrifluoromethylsulfonylimide, lithium hexafluorophosphate or lithium bisfluorosulfonylimide.

[0016] In an embodiment of the application, the concentration of the lithium salt in the ether-based electrolyte is 0.5-2 M. In a specific embodiment, the concentration of the lithium salt in the ether-based electrolyte is 1 M.

[0017] In an embodiment of the application, the ether solvent is at least one of 1,3-dioxolane and 1,2-dimethoxyethane. In a specific embodiment, the ether solvent is 1,3-dioxolane and 1,2-dimethoxyethane. In a more specific embodiment, the volume ratio of 1,3-dioxolane to 1,2-dimethoxyethane is 1:1.

[0018] In an embodiment of the application, in step A, the monomer of potassium allyl trifluoroborate accounts for 0.8-1.2 wt% of the precursor solution; fluoroethylene carbonate accounts for 4-6 wt% of the precursor solution; the molar ratio of potassium allyl trifluoroborate to the crosslinking agent is 1-1.5:1; in step B, azobisisobutyronitrile accounts for 0.5-2 wt% of the precursor solution.

[0019] In a more specific embodiment, in step A, the monomer of potassium allyl trifluoroborate accounts for 1-1.09 wt% of the precursor solution; fluoroethylene carbonate accounts for 5 wt% of the precursor solution; the molar ratio of potassium allyl trifluoroborate to the crosslinking agent is 1.19:1; in step B, azobisisobutyronitrile accounts for 1 wt% of the precursor solution.

[0020] In one embodiment of the present application, in the C step, the temperature-increasing reaction is a reaction at 60 DEG C or higher for at least 5 hours; preferably, the temperature-increasing reaction is a reaction at 60 DEG C to 70 DEG C.

[0021] The second technical problem solved by the present application is to provide a low-temperature-resistant gel polymer electrolyte.

[0022] The low-temperature-resistant gel polymer electrolyte is prepared by the preparation method of the low-temperature-resistant gel polymer electrolyte.

[0023] In one embodiment of the present application, the low-temperature-resistant gel polymer electrolyte has an electrical conductivity of 1.56 mS cm-1 at 25 DEG C. −1 The above.

[0024] The present application also provides the use of the low-temperature-resistant gel polymer electrolyte in a lithium metal battery.

[0025] The low-temperature-resistant gel polymer electrolyte can be used in a lithium metal battery.

[0026] The present application also provides a lithium metal battery.

[0027] The lithium metal battery comprises a positive electrode, a negative electrode and an electrolyte, and the electrolyte is the low-temperature-resistant gel polymer electrolyte.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] 1. The low-temperature-resistant gel polymer electrolyte of the present application significantly improves the freeze resistance of the electrolyte by introducing an anion conductor, achieves good low-temperature resistance, and improves the low-temperature cycle performance.

[0030] 2. The low-temperature-resistant gel polymer electrolyte of the present application has high electrical conductivity, and the electrical conductivity at -20 DEG C is 0.52 mS cm-1. −1 Therefore, the low-temperature-resistant gel polymer electrolyte overcomes the defect of low ion conductivity at low temperature of conventional polymer electrolytes.

[0031] 3. The low-temperature-resistant gel polymer electrolyte of the present application has high lithium ion transference number, and the calculated lithium ion transference number of the low-temperature-resistant gel polymer electrolyte is 0.69, effectively solving the defect of low lithium ion transference number of polymer electrolytes. + 4. The low-temperature-resistant gel polymer electrolyte of the present application has high lithium ion transference number, and the calculated lithium ion transference number of the low-temperature-resistant gel polymer electrolyte is 0.69, effectively solving the defect of low lithium ion transference number of polymer electrolytes. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The photos of the low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application before and after polymerization reaction; wherein the left photo is the photo of the mixed solution before polymerization reaction, and the right photo is the photo of the low-temperature-resistant gel polymer electrolyte after polymerization reaction.

[0033] Figure 2 The Fourier transform infrared (FTIR) spectrum comparison chart of the low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application and PAB, PETEA and precursor solution.

[0034] Figure 3 The Zeta potential chart of the low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application and ether-based electrolyte.

[0035] Figure 4 The Raman spectrum chart of the low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application and ether-based electrolyte at room temperature; wherein a is the Raman spectrum chart of the ether-based electrolyte, and b is the Raman spectrum chart of the low-temperature-resistant gel polymer electrolyte.

[0036] Figure 5 The ion conductivity comparison chart of the low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application and ether-based electrolyte at 25℃ and -20℃.

[0037] Figure 6 The chronoamperometric curve and the alternating current impedance spectrum (insert) of the Li||Li symmetric battery at a polarization voltage of 10 mV of the low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application and ether-based electrolyte; wherein a is the chronoamperometric curve and the alternating current impedance spectrum (insert) of the ether-based electrolyte, b is the chronoamperometric curve and the alternating current impedance spectrum (insert) of the low-temperature-resistant gel polymer electrolyte, c is the chronoamperometric curve and the alternating current impedance spectrum (insert) of the ether-based electrolyte at -20℃, and d is the chronoamperometric curve and the alternating current impedance spectrum (insert) of the low-temperature-resistant gel polymer electrolyte at -20℃.

[0038] Figure 7 The impedance comparison chart of the low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application and ether-based electrolyte.

[0039] Figure 8 The cycle performance comparison chart of the Li||NCM811 full battery at 25℃ of the low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application and ether-based electrolyte.

[0040] Figure 9 The cycle performance comparison chart of the Li||LFP battery at 25℃ of the low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application and ether-based electrolyte.

[0041] Figure 10 The cycle performance comparison chart of the Li||LFP battery at -20℃ of the low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application and ether-based electrolyte. DETAILED DESCRIPTION

[0042] The specific embodiments of the present application are further described in the following non-limiting Examples.

[0043] Example 1

[0044] The raw materials used in this example are as follows:

[0045] Potassium allyl trifluoroborate (PAB); pentaerythritol tetraacrylate (PETEA); fluoroethylene carbonate (FEC); azobisisobutyronitrile (AIBN); lithium bis(trifluoromethylsulfonyl)imide (LiTFSI); 1,2-dimethoxyethane (DME); 1,3-dioxolane (DOL).

[0046] The low-temperature-resistant gel polymer electrolyte was prepared according to the following steps:

[0047] Step 1: 1 wt% (30 mg) of PAB monomer and 2 wt% (60 mg) of PETEA crosslinking agent (molar ratio of PAB:PETEA = 1.19:1) were added to 2.73 g of ether-based electrolyte, and then FEC (150 mg) was added (mass of precursor = 30 mg + 60 mg + 2730 mg + 150 mg = 2970 mg, percentage of PAB monomer in the mass of precursor = 30 / 2970 = 1.01 wt%, and the precursor solution was obtained after uniform stirring; wherein the ether-based electrolyte was obtained by dissolving LiTFSI in DME / DOL solvent, and the concentration of LiTFSI in the ether-based electrolyte was 1 M;

[0048] Step 2: 1 wt% of AIBN thermal polymerization initiator was added to the precursor solution, and the reaction solution was obtained after uniform stirring;

[0049] Step 3: The reaction solution was heated at 70°C for 5h to obtain the low-temperature-resistant gel polymer electrolyte.

[0050] Performance characterization

[0051] 1) Appearance

[0052] The photos of the low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application before and after polymerization reaction are shown in Figure 1 , wherein the left photo is the photo of the mixed solution before polymerization reaction, and the right photo is the photo of the low-temperature-resistant gel polymer electrolyte after polymerization reaction.

[0053] The low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application has the following properties: Figure 1As shown, the low-temperature resistant gel polymer electrolyte is prepared by adding PAB and PETEA to an ether electrolyte, then adding FEC, stirring evenly, and finally adding AIBN and polymerizing at 70℃.

[0054] 2) Infrared characterization

[0055] The low-temperature resistant gel polymer electrolyte prepared in Example 1 was characterized by Fourier transform infrared spectroscopy (FTIR), and the results are shown in the figure. Figure 2 .

[0056] Depend on Figure 2 The polymerization of the precursor solution was verified by Fourier transform infrared spectroscopy in the 1600-1650 cm⁻¹ range. −1 Within the range, C=C bending vibrations and tensile vibrations were observed in PAB and PETEA monomers, respectively. No characteristic C=C peaks were observed in the low-temperature resistant gel polymer electrolyte after polymerization, indicating that the low-temperature resistant gel polymer electrolyte was successfully crosslinked and cured.

[0057] 3) Zeta potential

[0058] The low-temperature resistant gel polymer electrolyte prepared in Example 1 was characterized using a nanoparticle size analyzer and a zeta potential analyzer (DLS). The results are shown in [Figure 1]. Figure 3 .

[0059] Depend on Figure 3 The Zeta potentials of the low-temperature resistant gel polymer electrolyte were observed to be -30.65 mV, while those of the ether electrolyte were -16.24 mV. The low-temperature resistant gel polymer electrolyte exhibited a greater negative potential, resulting in a significant repulsive effect on anions, thereby improving the Li... + The number of migrations.

[0060] 4) Raman spectroscopy

[0061] The low-temperature resistant gel polymer electrolyte prepared in Example 1 was characterized using Raman spectroscopy, and the results are shown in the figure. Figure 4 .

[0062] Depend on Figure 4 Raman spectroscopy was used to study TFSI − Coordination states in low-temperature resistant gel polymer electrolytes and ether electrolytes. Quantitative analysis revealed that the low-temperature resistant gel polymer electrolyte contained a significantly higher proportion of aggregates compared to the ether electrolyte. The high content of aggregates indicates that the introduction of polymers can effectively stabilize these aggregates, thereby reducing the coordination of Li+ with solvent molecules. This increased aggregation is associated with the enhanced formation of inorganic-rich SEI / CEI layers, contributing to improved interfacial stability.

[0063] 5) Ionic conductivity

[0064] The stainless steel symmetric cell assembled by the low-temperature resistant gel polymer electrolyte prepared in Example 1 was tested on a CHI tester with an amplitude voltage of 10 mV and a frequency range of 5 MHz to 1 Hz, and the results are shown in Figure 5 .

[0065] From the comparison chart of the ionic conductivities of Figure 5 , it can be seen that (a) at 25°C, the low-temperature resistant gel polymer electrolyte achieved a high ionic conductivity of 1.56 mS cm −1 , close to that of the ether-based electrolyte (1.79 mS cm −1 ). This shows that the low-temperature resistant gel polymer electrolyte has excellent ionic conductivity; (b) at -20°C, the low-temperature resistant gel polymer electrolyte achieved an ionic conductivity of 0.52 mS cm −1 , higher than that of the ether-based electrolyte (0.33 mS cm −1 ). This shows that the low-temperature resistant gel polymer electrolyte has excellent ionic conductivity at low temperature.

[0066] 6) Electrical performance

[0067] Preparation of Li||Li symmetric cell: Assembled into a Li||Li symmetric cell in the order of negative electrode shell-small lithium piece-electrolyte-pp separator-electrolyte-small lithium piece-gasket-spring piece-positive electrode shell.

[0068] Determination of chronoamperometric curve: The Li||Li symmetric cell assembled by the low-temperature resistant gel polymer electrolyte prepared in Example 1 was tested on the Eclab software using the CA test program, with the program parameters set;

[0069] Determination of AC impedance spectrum: The Li||Li symmetric cell assembled by the low-temperature resistant gel polymer electrolyte prepared in Example 1 was tested on the Eclab software using the EIS test program, with the program parameters set;

[0070] The results are shown in Figure 6 .

[0071] From the chronoamperometric curve of the Li||Li symmetric cell and the AC impedance spectrum before and after polarization (inset) of Figure 6 , it can be seen that (b) the lithium ion transfer number (t Li + =0.69) of the low-temperature resistant gel polymer electrolyte is obviously higher than that (t Li +(d) The low-temperature resistant gel polymer electrolyte has a significantly higher lithium ion transference number (tlit=0.65) than the ether-based electrolyte (tlit=0.23) at -20°C. This significant enhancement is attributed to the anion-rich solvation structure in the low-temperature resistant gel polymer electrolyte that facilitates fast Li + conduction, a variety of Li + coordination groups accelerates the migration of Li + and a high ion transference number at low temperature can prove its low-temperature resistance.

[0072] Measurement of AC impedance spectra at different temperatures: The EIS test program on the Eclab software was used to test the low-temperature resistant gel polymer electrolyte prepared in Example 1 in the Li||Li symmetrical battery assembled at different temperatures;

[0073] The results are shown in Figure 7 .

[0074] From the impedance plots of Figure 7 It can be seen that the impedance of both electrolytes increases with decreasing temperature, but the low-temperature resistant gel polymer electrolyte exhibits lower interfacial impedance than the ether-based electrolyte at all temperatures, indicating that the low-temperature resistant gel polymer electrolyte has better interfacial compatibility and low-temperature resistance.

[0075] 7) Cycle performance

[0076] Preparation of Li||LFP battery: 0.2 g of polyvinylidene fluoride (PVDF) was first added to 6 ml of N-methyl-2-pyrrolidone (NMP), stirred uniformly, then 0.2 g of conductive carbon black was added and stirred for 12 hours, then 1.6 g of LiFePO4 powder was added and stirred for another 12 hours to obtain a slurry with a mass ratio of PVDF: Super P: LiFePO4 of 1:1:8, then the slurry was coated on an aluminum / carbon foil and vacuum dried at 120°C for 12 hours. Finally, the electrode sheet was cut into a disc with a diameter of 12 mm to obtain a LiFePO4 positive electrode sheet. Then the battery was assembled in the order of negative electrode shell-large lithium sheet-electrolyte-pp separator-electrolyte-LiFePO4 positive electrode sheet-gasket-spring- positive electrode shell to obtain a Li||LFP battery.

[0077] Preparation of Li||NCM811 battery: 0.2 g of polyvinylidene fluoride (PVDF) was first added to 6 ml of N-methyl-2-pyrrolidone (NMP), and after stirring uniformly, 0.2 g of conductive carbon black was added, stirred for 12 hours, then 1.6 g of NCM811 powder was added, and stirred for another 12 hours to obtain a slurry (the mass ratio of PVDF: Super P: NCM811 is 1:1:8), then the slurry was coated on an aluminum / carbon foil and dried at 120°C for 12 hours in a vacuum. Finally, the electrode sheet was cut into a disc with a diameter of 12 mm to obtain an NCM811 positive electrode sheet. Then the battery was assembled in the order of negative electrode shell-large lithium sheet-electrolyte-pp separator-electrolyte-NCM811 positive electrode sheet-gasket-spring- positive electrode shell to obtain a Li||NCM811 battery.

[0078] Long cycle test: the assembled Li||LFP full battery and Li||NCM811 full battery were subjected to a long cycle test at 25°C on a new wei tester, and the Li||LFP full battery was subjected to a long cycle test at -20°C in a low temperature box.

[0079] The results are shown in Figures 8-10 . Among them, Figure 8 is a comparison chart of the cycle performance of the Li||NCM811 battery with the ether-based electrolyte and the low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application at 25°C. Figure 9 is a comparison chart of the cycle performance of the Li||LFP battery with the ether-based electrolyte and the low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application at 25°C. Figure 10 is a comparison chart of the cycle performance of the Li||LFP battery with the ether-based electrolyte and the low-temperature-resistant gel polymer electrolyte prepared in Example 1 of the present application at -20°C.

[0080] As can be seen from Figure 8 , the two batteries were subjected to a long cycle test at room temperature 25°C, and it can be seen that the Li||NCM811 battery with the low-temperature-resistant gel polymer electrolyte can be stably cycled more than 300 times, and the capacity retention rate is 82.99%; on the contrary, the cycle performance of the ether-based electrolyte-based Li|NCM811 battery rapidly decays, and the capacity retention rate after 200 cycles is only 73.50%.

[0081] As can be seen from Figure 9 , the two batteries were subjected to a long cycle test at room temperature 25°C, and it can be seen that the Li||LFP battery with the low-temperature-resistant gel polymer electrolyte can be stably cycled more than 1000 times, and the capacity retention rate is 80.86%; on the contrary, the cycle performance of the ether-based electrolyte-based Li|LFP battery is poor, and the capacity retention rate after 900 cycles is only 72.04%.

[0082] As can be seen from Figure 10It can be seen that the two kinds of batteries are tested at low temperature-20℃ for long cycle test, it can be seen that the Li||LFP battery of the low-temperature-resistant gel polymer electrolyte can be stably cycled more than 600 times, and the capacity retention rate is 83.45%; on the contrary, the cycle performance of the ether-based Li||LFP battery is poor, and the capacity retention rate after 600 cycles is only 74.62%. It shows that improving the main structure of the low-temperature-resistant gel polymer electrolyte is beneficial to enhance the low-temperature resistance.

[0083] It can be seen that the low-temperature-resistant gel polymer electrolyte of the application has the advantages of fast Li + Conduction, high ionic conductivity, high lithium ion transference number, low temperature resistance and the like.

[0084] Example 2

[0085] The low-temperature-resistant gel polymer electrolyte is prepared according to the steps of Example 1, the difference is only that: the "2.73 g of ether-based electrolyte" in step 1 is adjusted to "2.76 g of ether-based electrolyte" (the precursor mass = 30 mg + 60 mg + 2760 mg + 150 mg = 3000 mg, and the PAB monomer accounts for 30 / 3000 = 1 wt% of the precursor mass); other steps remain unchanged.

[0086] Example 3

[0087] The low-temperature-resistant gel polymer electrolyte is prepared according to the steps of Example 1, the difference is only that: the "2.73 g of ether-based electrolyte" in step 1 is adjusted to "2.5 g of ether-based electrolyte" (the precursor mass = 30 mg + 60 mg + 2500 mg + 150 mg = 2740 mg, and the PAB monomer accounts for 30 / 2740 = 1.09 wt% of the precursor mass); other steps remain unchanged.

[0088] Example 4

[0089] The low-temperature-resistant gel polymer electrolyte is prepared according to the steps of Example 1, the difference is only that: the "heating the reaction solution at 70℃ for 5 h" in step 3 is adjusted to "heating the reaction solution at 65℃ for 5 h"; other steps remain unchanged.

[0090] Example 5

[0091] The low-temperature-resistant gel polymer electrolyte is prepared according to the steps of Example 1, the difference is only that: the "heating the reaction solution at 70℃ for 5 h" in step 3 is adjusted to "heating the reaction solution at 75℃ for 5 h"; other steps remain unchanged.

[0092] The low-temperature Li +The ion transference number was determined according to the method of Example 1, and the results are shown in Table 1.

[0093] Table 1

[0094] Name Example 2 Example 3 Example 4 Example 5 Ether-based electrolyte -20 °C ion conductivity mS cm −1 ]] 0.50 0.53 0.52 0.52 0.33

[0095] It can be seen that the low-temperature resistant gel polymer electrolyte can improve the freezing resistance of the electrolyte, achieve good low-temperature resistance, and improve the low-temperature cycle performance.

Claims

1. A method for preparing a cryogenically resistant gel polymer electrolyte, characterized by, The method comprises the following steps: A. mixing ether electrolyte, allyl potassium trifluoroborate, crosslinking agent and fluorinated ethylene carbonate to obtain a precursor solution; B. mixing azobisisobutyronitrile with the precursor solution to obtain a reaction solution; C. heating the reaction solution of step B to obtain a low-temperature-resistant gel polymer electrolyte; The ether electrolyte comprises lithium salt and ether solvent; the lithium salt is lithium bistrifluoromethanesulfonylimide, lithium hexafluorophosphate or lithium bisfluorosulfonylimide; The crosslinking agent is pentaerythritol tetraacrylate, triethylene glycol dimethacrylate or polyethylene glycol diacrylate.

2. The preparation method of the low-temperature-resistant gel polymer electrolyte according to claim 1, characterized in that: The concentration of lithium salt in the ether electrolyte is 0.5-2 M.

3. The preparation method of the low-temperature-resistant gel polymer electrolyte according to claim 2, characterized in that: The concentration of lithium salt in the ether electrolyte is 1 M.

4. The preparation method of the low-temperature-resistant gel polymer electrolyte according to claim 1, characterized in that: The ether solvent is 1,3-dioxolane and 1,2-dimethoxyethane with a volume ratio of 1:

1.

5. The preparation method of the low-temperature-resistant gel polymer electrolyte according to claim 1, characterized in that: In step A, the allyl potassium trifluoroborate monomer accounts for 0.8-1.2 wt% of the precursor solution; the fluorinated ethylene carbonate accounts for 4-6 wt% of the precursor solution; the molar ratio of allyl potassium trifluoroborate to crosslinking agent is 1-1.5:1; in step B, the azobisisobutyronitrile accounts for 0.5-2 wt% of the precursor solution; In step C, the heating reaction is carried out at 60°C or above for at least 5 h.

6. The preparation method of the low-temperature-resistant gel polymer electrolyte according to claim 5, characterized in that: In step A, the allyl potassium trifluoroborate monomer accounts for 1-1.09 wt% of the precursor solution; the fluorinated ethylene carbonate accounts for 5 wt% of the precursor solution; the molar ratio of allyl potassium trifluoroborate to crosslinking agent is 1.19:1; in step B, the azobisisobutyronitrile accounts for 1 wt% of the precursor solution; In step C, the heating reaction is carried out at 60-70°C.

7. The low-temperature-resistant gel polymer electrolyte prepared by the method of any one of claims 1-6.

8. The cryogenically resistant gel polymer electrolyte of claim 7, wherein: The low-temperature-resistant gel polymer electrolyte has an electrical conductivity of 0.52 mS cm at -20°C −1 The above.

9. The low-temperature-resistant gel polymer electrolyte of claim 7 for use in a lithium metal battery.

10. A lithium metal battery comprising a positive electrode, a negative electrode, and an electrolyte, characterized in that: The electrolyte is the low-temperature-resistant gel polymer electrolyte of claim 7.

Images