Solid-state polymer electrolyte and preparation method and application thereof

Abstract

The present application relates to solid-state polymer electrolyte and its preparation method and application, belong to lithium metal battery technical field.The technical problem solved by the present application is to provide a kind of preparation method of solid-state polymer electrolyte for efficient transmission lithium ion.The method will polyvinylidene fluoride-hexafluoropropylene, lithium bis (trifluoromethyl sulfone) imide, bis (ethylene sulfone group) methane and tetraacetyl ethylene and N,N-dimethylformamide mix uniformly, then azobisdimethylvaleronitrile is mixed, heated to 40~80 DEG C for 20~60 min, then coated on substrate and dried to obtain.The present application method is simple, easy to operate, can be used for industrialized mass production, the solid-state polymer electrolyte obtained is not easy to burn, has good thermal stability, has high ionic conductivity and high lithium ion migration number, has good mechanical property, and elastic modulus is high, can effectively inhibit lithium dendrite growth, delay battery capacity attenuation.

Description

Technical Field

[0001] This invention relates to solid polymer electrolytes, their preparation methods, and applications, belonging to the field of lithium metal battery technology. Background Technology

[0002] With the rapid development of electric vehicles, large-scale energy storage, and portable electronic devices, the demand for high-energy-density and high-safety rechargeable batteries is becoming increasingly urgent. Lithium metal batteries, due to their use of metallic lithium as the negative electrode, possess extremely high theoretical specific capacity (3860 mAh / g) and the lowest electrochemical potential (-3.04 V vs. standard hydrogen electrode), and are considered an ideal choice for next-generation high-energy-density battery systems. However, traditional lithium-ion batteries use flammable organic liquid electrolytes, posing serious safety hazards such as leakage, combustion, and even explosion. Furthermore, they cannot effectively suppress the growth of lithium dendrites, resulting in short battery cycle life and significant safety risks.

[0003] Solid polymer electrolytes (SPEs) use a solid polymer matrix to replace liquid electrolytes, fundamentally solving the flammability problem and offering higher safety and better machinability, making them one of the key materials for constructing high-safety lithium metal batteries. Among various solid polymer electrolytes, polyethylene oxide (PEO)-based electrolytes are the earliest and most widely studied system. They achieve ion transport through coordination of lithium ions via ether-oxygen bonds (-COC-). However, PEO-based electrolytes also have some inherent drawbacks. For example, at room temperature, the polymer chains of PEO are in a glassy or crystalline state, moving slowly, resulting in extremely low ionic conductivity (typically below 10). -5 S / cm). Therefore, polymer segments need to have sufficient mobility to assist lithium ions (Li). + The transport occurs via "jumping" between chains. Secondly, the solid polymer electrolyte and electrode have a solid-solid contact, unlike a liquid which can perfectly wet the electrode material surface. This results in a small effective contact area and very high interfacial impedance. PEO-based electrolytes have a narrower electrochemical window (oxidative decomposition potential approximately ~3.9V vs. Li). + / Li). It also cannot be matched with high-voltage, high-capacity cathode materials (such as lithium cobalt oxide (LCO), high-nickel NCM, etc., with operating voltages typically >4V). When the voltage increases, the ether oxygen bonds in PEO will be oxidized and decomposed, leading to battery failure. Furthermore, lithium dendrites can still grow along grain boundaries, defects, or channels between polymer chains in the solid polymer electrolyte, potentially causing an internal short circuit in the battery.

[0004] To overcome the limitations of PEO-based electrolytes, researchers have turned their attention to polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP)-based solid polymer electrolytes. PVDF-HFP is a copolymer that combines irregular amorphous hexafluoropropylene (HFP) with the crystalline regions of PVDF chains, exhibiting advantages such as corrosion resistance, high dielectric constant, and good chemical stability. Furthermore, due to the absence of ether groups (-COC-), PVDF-HFP-based solid polymer electrolytes have a wider electrochemical window, making them compatible with high-voltage cathodes. The amorphous phase of the polymer facilitates rapid ion movement, thus contributing to higher ionic conductivity, while the crystalline phase provides mechanical support for the polymer electrolyte. The presence of -CF3 groups in the HFP monomer within the amorphous phase endows HFP with high polarity, enhancing its interaction with lithium salts and promoting lithium ion hopping and transport between polymer chains.

[0005] However, pure PVDF-HFP-based solid polymer electrolytes also face significant challenges. Their room-temperature ionic conductivity is extremely low, typically around 10⁻⁶. -7 ~10 -8 The S / cm ratio is on the order of 1, which is much lower than that of PEO-based electrolytes, resulting in huge internal resistance in the battery and preventing it from functioning properly. In addition, PVDF-HFP films prepared by solution casting often form porous structures, which not only reduces ion transport efficiency but also provides channels for lithium dendrite growth. Furthermore, they have poor compatibility with lithium metal anodes and the interface is unstable.

[0006] In the prior art, numerous attempts have been made to improve the performance of PVDF-HFP based polymer electrolytes. For example, patent CN202111088647.0 introduces L into the polymer matrix... Inorganic additives are used to improve ionic conductivity and suppress lithium dendrite formation. While these methods have made some progress, there is still room for optimization in terms of the overall performance of the electrolyte, such as the balance between mechanical strength, thermal stability, ion transference number, and interfacial stability.

[0007] Therefore, developing a solid polymer electrolyte that combines high ionic conductivity, high lithium-ion transference number, excellent mechanical strength, wide electrochemical window, good thermal stability, and effective lithium dendrite suppression capability is crucial for promoting the practical application of high-safety, high-performance solid lithium metal batteries. Summary of the Invention

[0008] To address the above deficiencies, the technical problem solved by this invention is to provide a method for preparing a solid polymer electrolyte for efficient lithium ion transport.

[0009] The method for preparing the solid polymer electrolyte of the present invention includes the following steps:

[0010] A. Mix polyvinylidene fluoride-hexafluoropropylene, lithium bis(trifluoromethanesulfonylimide), bis(ethylene sulfone)methane, isoprene tetraacrylate, and N,N-dimethylformamide to obtain a precursor solution.

[0011] B. Mix azobisisobutyronitrile with the precursor solution to obtain a reaction solution;

[0012] C. Heat the reaction solution described in step B at 40–80°C for 20–60 min, then coat it onto a substrate and dry it to obtain a solid polymer electrolyte.

[0013] This invention involves adding polyvinylidene fluoride-hexafluoropropylene, lithium bis(trifluoromethanesulfonylimide), bis(vinyl sulfone)methane, and isoprene tetraacrylate to an N,N-dimethylformamide solution and stirring until homogeneous. An initiator is then added, followed by coating and drying to obtain a solid polymer electrolyte. The introduction of a thermally stable copolymerized three-dimensional network polymer significantly improves the electrolyte's stability. This solid polymer electrolyte exhibits high thermal stability, efficient lithium-ion transport, and excellent mechanical strength.

[0014] In one embodiment of the present invention, in step A, the molar ratio of polyvinylidene fluoride-hexafluoropropylene, lithium bis(trifluoromethanesulfonylimide), bis(vinyl sulfone)methane, and isoprene tetraacrylate is 7–8 : 20–21 : 1.5–2.5 : 1. In another embodiment of the present invention, the molar ratio of polyvinylidene fluoride-hexafluoropropylene, lithium bis(trifluoromethanesulfonylimide), bis(vinyl sulfone)methane, and isoprene tetraacrylate is 7.05 : 20.51 : 2.00 : 1.

[0015] In one embodiment of the present invention, the total mass of bis(ethylene sulfonyl)methane and isoprene tetraacrylate accounts for 0.5 to 2 wt% of the precursor solution. In a specific embodiment of the present invention, the total mass of bis(ethylene sulfonyl)methane and isoprene tetraacrylate accounts for 1.5 to 2 wt% of the precursor solution.

[0016] In one embodiment of the present invention, in step B, azobisisobutyronitrile accounts for 0.05 to 0.5 wt% of the precursor solution. In a specific embodiment of the present invention, in step B, azobisisobutyronitrile accounts for 0.1 wt% of the precursor solution.

[0017] In one embodiment of the present invention, in step C, the reaction solution described in step B is heated at 60°C for 30 min.

[0018] In one embodiment of the present invention, in step C, the drying is performed at 60–80°C for 10–20 hours. In a specific embodiment of the present invention, the drying is performed at 70°C for 12 hours.

[0019] The substrates commonly used in this field are all suitable for this invention. In one specific embodiment, the substrate is a glass plate.

[0020] The second technical problem solved by the present invention is to provide a solid polymer electrolyte.

[0021] This invention relates to a solid polymer electrolyte, prepared using the aforementioned method. This solid polymer electrolyte exhibits good thermal stability, non-flammability, and high safety. It also possesses good mechanical properties, a high elastic modulus, and can effectively suppress lithium dendrite growth, thus delaying battery capacity decay. Furthermore, it exhibits high ionic conductivity and a high lithium-ion transference number.

[0022] The present invention also provides the application of the solid polymer electrolyte described herein in lithium metal batteries.

[0023] The solid polymer electrolyte of this invention can be used in lithium metal batteries.

[0024] In one embodiment of the present invention, the lithium metal battery is a Li||NCM811 battery.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. This invention involves adding polyvinylidene fluoride-hexafluoropropylene, lithium bis(trifluoromethanesulfonylimide), bis(ethylene sulfone)methane, and isoprene tetraacrylate to an N,N-dimethylformamide solution and stirring until homogeneous. An initiator is then added, followed by coating and drying to obtain a solid polymer electrolyte. The method is simple, easy to operate, and suitable for large-scale industrial production.

[0027] 2. The solid polymer electrolyte of the present invention is not easily combustible and has good thermal stability.

[0028] 3. The solid polymer electrolyte of the present invention has high ionic conductivity and high lithium-ion transference number, with a lithium-ion transference number of 0.52 or higher at 25°C.

[0029] 4. The solid polymer electrolyte of the present invention has good mechanical properties, with a tensile strength of more than 5.56 MPa and a high elastic modulus of more than 39.67 MPa. It can effectively inhibit the growth of lithium dendrites and delay the capacity decay of the battery. Attached Figure Description

[0030] Figure 1 These are photographs of the solid polymer electrolyte precursor solution prepared in Example 1 of the present invention before and after the polymerization reaction; wherein, a is a photograph of the mixed solution before the polymerization reaction, and b is a photograph of the solid polymer electrolyte precursor solution after the polymerization reaction occurs by heating and stirring at 60°C for 30 min.

[0031] Figure 2 This is a comparison of the Fourier transform infrared (FTIR) spectra of the solid polymer electrolyte PBPL prepared in Example 1 of this invention with those of BVSM and PETEA.

[0032] Figure 3 The stress-strain diagrams are of the PBPL solid polymer electrolyte prepared in Example 1 of the present invention and the PL solid electrolyte membrane prepared in Comparative Example 1.

[0033] Figure 4 The images show combustion test photographs and thermogravimetric analysis (TG) curves of the PBPL solid polymer electrolyte prepared in Example 1 and the PL polymer electrolyte prepared in Comparative Example 1; where a is a combustion test photograph and b is a thermogravimetric analysis (TG) curve.

[0034] Figure 5 The images show the Raman spectra of the PBPL solid polymer electrolyte prepared in Example 1 and the PL polymer electrolyte prepared in Comparative Example 1; where a is the Raman spectrum of the PL polymer electrolyte and b is the Raman spectrum of the PBPL solid polymer electrolyte.

[0035] Figure 6 This is a comparison chart of the ionic conductivity at room temperature of the PBPL solid polymer electrolyte prepared in Example 1 of the present invention and the PL polymer electrolyte prepared in Comparative Example 1.

[0036] Figure 7 The illustrations show the chronoampere curves and AC impedance spectra of the PBPL solid polymer electrolyte prepared in Example 1 and the PL polymer electrolyte prepared in Comparative Example 1 for a Li||Li symmetric cell at a polarization voltage of 10 mV (illustrated); where a is the chronoampere curve and AC impedance spectra of the PL polymer electrolyte before and after polarization (illustrated), and b is the chronoampere curve and AC impedance spectra of the PBPL solid polymer electrolyte before and after polarization (illustrated).

[0037] Figure 8 This is a comparison chart of the cycling performance of Li||LFP batteries at 1C room temperature between the PBPL solid polymer electrolyte prepared in Example 1 of the present invention and the PL polymer electrolyte prepared in Comparative Example 1.

[0038] Figure 9 This is a comparison chart of the cycling performance of Li||NCM811 batteries with PBPL solid polymer electrolyte prepared in Example 1 of the present invention and PL polymer electrolyte prepared in Comparative Example 1 at room temperature at 0.5C. Detailed Implementation

[0039] The specific embodiments of the present invention will be further described below with reference to examples, but the present invention is not limited to the scope of the embodiments described herein.

[0040] Example 1

[0041] The raw materials used are: bis(vinyl sulfone)methane (BVSM); isoprene tetraacrylate (PETEA); azobisisobutyronitrile (AIBN); polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP); lithium bis(trifluoromethanesulfonylimide) (LiTFSI); and N,N-dimethylformamide (DMF).

[0042] The solid polymer electrolyte PBPL was prepared according to the following steps:

[0043] Step 1: Add 12.4 wt% (1000 mg) PVDF-HFP, 15.5 wt% (1250 mg) LiTFSI, 1.03 wt% (83.3 mg) BVSM monomer and 0.93 wt% (74.8 mg) PETEA crosslinking agent (BVSM:PETEA molar ratio of 2:1) to 5.658 g of N,N-dimethylformamide solution (precursor mass = 1000 mg + 1250 mg + 83.3 mg + 74.8 mg + 5658 mg = 8066.1 mg, the percentage of BVSM monomer in the precursor mass is 83.3 / 8066.1 = 1.03 wt%, the percentage of PETEA monomer in the precursor mass is 74.8 / 8066.1 = 0.93 wt%), stir well to obtain the precursor solution;

[0044] Step 2: Add 0.1 wt% of AIBN thermal polymerization initiator to the precursor solution, heat and stir at 60°C for 30 min to obtain the reaction solution; see details. Figure 1 .

[0045] Step 3: Spread the reaction solution evenly onto a glass plate and heat it at 70°C for 12 hours to obtain a solid polymer electrolyte, denoted as PBPL.

[0046] Comparative Example 1: Preparation of PL Electrolyte

[0047] Following the method in Example 1, 1.25 g LiTFSI and 1 g PVDF-HFP were dissolved in 5.658 g N,N-dimethylformamide solution, stirred until homogeneous, and then heated and dried to obtain a solid polymer electrolyte, denoted as PL.

[0048] Performance Characterization

[0049] 1) Appearance

[0050] The photographs of the solid polymer electrolyte precursor solution prepared in Example 1 of this invention before and after the polymerization reaction are shown below. Figure 1Wherein, a is a photograph of the mixed solution before the polymerization reaction, and b is a photograph of the solid polymer electrolyte precursor solution after the polymerization reaction was carried out by heating and stirring at 60°C for 30 min.

[0051] The PBPL solid polymer electrolyte of this invention is prepared by adding PVDF-HFP, LiTFSI, BVSM, and PETEA to an N,N-dimethylformamide solution and stirring until homogeneous. Additionally, AIBN is added at 60°C to initiate the polymerization of BVSM monomers and PETEA crosslinking agent, resulting in a solid polymer electrolyte precursor solution after polymerization. Finally, the polymer electrolyte precursor solution is coated onto a glass plate and dried at 70°C to obtain the PBPL solid polymer electrolyte.

[0052] 2) Infrared characterization

[0053] The PBPL solid polymer electrolyte was validated using Fourier transform infrared spectroscopy (FTIR), and the results are shown in [Figure number missing]. Figure 2 .

[0054] from Figure 2 It can be seen that at 1600-1650 cm -1 Within the range, C=C bending and tensile vibrations were observed in BVSM and PETEA monomers, respectively. No characteristic C=C peaks were observed in the polymerized PBPL solid polymer electrolyte, indicating that the three-dimensional polymer network crosslinking and curing were successful.

[0055] 3) Mechanical properties

[0056] Stress-strain tests were performed on PBPL solid electrolyte membranes and PL solid electrolyte membranes using an electronic universal testing machine. The results are shown in [Figure number missing]. Figure 3 .

[0057] from Figure 3 As can be seen, PBPL solid polymer electrolyte has good mechanical properties, with a tensile strength of over 5.56 MPa and a high elastic modulus of up to 39.67 MPa.

[0058] 4) Combustion experiments and thermogravimetric analysis

[0059] Test method: A lit candle was brought close to the PBPL and PL polymer electrolyte membranes to observe their flammability. Experimental results are shown below. Figure 4 .

[0060] Figure 4 The images show combustion test photographs and thermogravimetric analysis (TG) curves of the solid polymer electrolytes prepared in Example 1 and Comparative Example 1 of this invention; where a is a combustion test photograph and b is a thermogravimetric analysis (TG) curve.

[0061] Depend on Figure 4 Combustion experiments (a) show that, compared to PL electrolyte, PBPL solid polymer electrolyte maintains its non-flammability under continuous exposure to an ignition source. Thermogravimetric analysis (b) reveals that during the pyrolysis of PBPL solid polymer electrolyte and PL polymer electrolyte, the total weight loss rates from room temperature to 400℃ are 40.22% and 36.09%, respectively. This indicates that PBPL solid polymer electrolyte has better thermal stability than PL polymer electrolyte, and the introduction of a three-dimensional network with different molecular structures further delays electrolyte volatilization.

[0062] 5) Raman spectroscopy

[0063] Detection method: Use the standard testing mode, select a 785nm laser wavelength, and test wavenumber range of 500-1000cm. -1 Test three points in an arbitrary region. See the experimental results below. Figure 5 .

[0064] Figure 5 The images show the Raman spectra of the PBPL solid polymer electrolyte prepared in Example 1 and the PL polymer electrolyte prepared in Comparative Example 1; where a is the Raman spectrum of the PL polymer electrolyte and b is the Raman spectrum of the PBPL solid polymer electrolyte.

[0065] Figure 5 Raman spectroscopy was used to study TFSI - Coordination states in PBPL solid polymer electrolyte and PL polymer electrolyte. Quantitative analysis revealed that the PBPL solid polymer electrolyte contained a significantly higher proportion of aggregates and contact ion pairs (aggregates: 6.3%; contact ion pairs: 86.7%) compared to the PL polymer electrolyte (aggregates: 6.12%; contact ion pairs: 84.19%). This increased number of aggregates and contact ion pairs indicates the presence of more lithium-ion hopping sites in the PBPL solid polymer electrolyte, and the increase in hopping sites facilitates faster lithium-ion transport.

[0066] 6) Ionic conductivity

[0067] Detection method: Assemble a stainless steel symmetrical cell and connect it to an electrochemical workstation. Apply a small AC perturbation amplitude (typically 5 mV) and scan over a wide frequency range (1 MHz to 0.1 Hz). The result is a Nyquist plot, also known as a complex plane plot (-Z'' vs. Z'), which typically consists of a semicircle (or arc) in the high-frequency region and a diagonal line in the low-frequency region. The first intersection of the high-frequency region and the real axis: the x-coordinate of this point is the bulk resistance, also known as ohmic resistance. Finally, the ionic conductivity is calculated using the formula σ = L / (R × A). Experimental results are shown below. Figure 5 .

[0068] Figure 6 This is a comparison chart of the ionic conductivity at room temperature between the PBPL solid polymer electrolyte prepared in Example 1 of the present invention and the PL polymer electrolyte prepared in Comparative Example 1.

[0069] Depend on Figure 6 The comparison of ionic conductivity shows that at 25℃, the PBPL solid polymer electrolyte achieved (0.77 mS / cm). -1 The high ionic conductivity of PO4 is close to that of PL polymer electrolyte (1.3 mS / cm). -1 This indicates that the PBPL solid polymer electrolyte has excellent ionic conductivity.

[0070] 7) Lithium-ion transference number

[0071] Preparation of Li||Li symmetric cells: All operations were carried out in an argon atmosphere glove box with water and oxygen contents both below 0.1 ppm (preferably below 0.01 ppm). The cells were assembled using a CR2032 type button cell casing, including a positive electrode casing, a negative electrode casing, a gasket, and a spring sheet, in the following order: negative electrode casing, lithium sheet, polymer electrolyte membrane, lithium sheet, gasket, spring sheet, and positive electrode casing. Finally, the cells were sealed using a battery sealing machine.

[0072] Determination of the chronoamperometry curve: The electrochemical workstation was used for detection, and the time was set to 20 min.

[0073] AC impedance spectroscopy was measured using an electrochemical workstation with a frequency range of 0.1 Hz to 1 MHz and a voltage range of -10 V to 10 V.

[0074] The results are shown in Figure 7 .

[0075] Figure 7The illustrations show the chronoampere curves and AC impedance spectra of the PBPL solid polymer electrolyte and PL polymer electrolyte prepared in Example 1 of this invention at a polarization voltage of 10 mV for a Li||Li symmetric cell (illustrated); where a is the chronoampere curve and AC impedance spectra of the PL polymer electrolyte (illustrated), and b is the chronoampere curve and AC impedance spectra of the PBPL solid polymer electrolyte (illustrated).

[0076] Depend on Figure 7 The chronoampere curves and AC impedance spectra before and after polarization of the Li||Li symmetric cell (illustrated) show that, according to the formula... Calculations were performed to obtain (a) the lithium-ion transfer number (t) of the PBPL solid polymer electrolyte. Li + =0.52) is significantly higher than (b) PL polymer electrolyte (t Li + =0.33) High. This significant enhancement can be attributed to the anion-rich solvation structure in the PBPL solid polymer electrolyte modulating the rapid Li + Conduction, multiple Li + The presence of ligands accelerates the Li + The migration.

[0077] 8) Cyclic performance

[0078] Preparation of Li||LFP batteries: All operations are carried out in an argon atmosphere glove box with water and oxygen content both below 0.1 ppm (preferably below 0.01 ppm). The batteries are assembled in the following order using a CR2025 type button cell, including the positive electrode shell, negative electrode shell, gasket, and spring sheet: negative electrode shell, lithium sheet, polymer electrolyte membrane, LFP electrode, gasket, spring sheet, and positive electrode shell. Finally, the batteries are sealed using a battery sealing machine.

[0079] Preparation of Li||NCM811 batteries: All operations are carried out in an argon atmosphere glove box with water and oxygen content both below 0.1 ppm (preferably below 0.01 ppm). Using a CR2025 type button cell battery case, including positive electrode case, negative electrode case, gasket, and spring sheet, the batteries are assembled in the following order: negative electrode case, lithium sheet, polymer electrolyte membrane, NCM811 electrode, gasket, spring sheet, and positive electrode case. Finally, the batteries are sealed using a battery sealing machine.

[0080] Long-cycle test: In an environment with a temperature of 25℃, use the Xinwei test instrument, clamp the battery and test it. Before starting the long-cycle test, set the program to activate for three cycles.

[0081] See results Figure 8 and Figure 9 .in, Figure 8 This is a comparison chart of the cycling performance of Li||LFP batteries at 1C room temperature between the PBPL solid polymer electrolyte prepared in Example 1 of the present invention and the PL polymer electrolyte prepared in Comparative Example 1. Figure 9 This is a comparison chart of the cycling performance of Li||NCM811 batteries with PBPL solid polymer electrolyte prepared in Example 1 of the present invention and PL polymer electrolyte prepared in Comparative Example 1 at room temperature at 0.5C.

[0082] Depend on Figure 8 It can be seen that, under long-term cycling tests at room temperature and 1C rate, the Li||LFP battery with PBPL solid polymer electrolyte can cycle stably for more than 250 cycles with a capacity retention of 93%; in contrast, the cycling performance of the PL polymer electrolyte-based Li||LFP battery decays rapidly, with a capacity retention of only 78% after 60 cycles.

[0083] Depend on Figure 9 The results show that, under long-term cycling tests at room temperature and a 0.5C rate, the Li|NCM811 battery with PBPL solid polymer electrolyte can stably cycle for over 140 cycles with a capacity retention of 80%. Conversely, the cycling performance of the PL polymer electrolyte-based Li|NCM811 battery degrades rapidly, with a capacity retention of only 55% after 61 cycles. This indicates that physical blending of PVDF-HFP with a three-dimensional polymer network with different molecular structures is beneficial for enhancing battery life.

[0084] The above results demonstrate that this PBPL solid polymer electrolyte exhibits rapid Li-linkage degradation in practical lithium metal batteries. + Significant effects on conductivity, high ionic conductivity, high lithium-ion transference number, and high thermal stability.

[0085] Example 2

[0086] Solid polymer electrolytes were prepared according to the steps of Example 1, with the only difference being that the "5.658 g of N,N-dimethylformamide solution" in step 1 was adjusted to "6.601 g of N,N-dimethylformamide solution" (precursor mass = 1000 mg + 1250 mg + 83.3 mg + 74.8 mg + 6601 mg = 9,009.1 mg, the percentage of BVSM monomer in the precursor mass is 83.3 / 9,009.1 = 0.92 wt%, and the percentage of PETEA monomer in the precursor mass is 74.8 / 9,009.1 = 0.83 wt%); other steps remained unchanged, and electrochemical workstations for Li||Li symmetric batteries were used for testing to obtain AC impedance spectra and chronoamperometric curves, and the calculated lithium-ion transference number was 0.55.

[0087] Example 3

[0088] The solid polymer electrolyte was prepared according to the steps of Example 1, with the only difference being that the "5.658 g of N,N-dimethylformamide solution" in step 1 was adjusted to "7.544 g of N,N-dimethylformamide solution" (precursor mass = 1000 mg + 1250 mg + 83.3 mg + 74.8 mg + 7544 mg = 9952.1 mg, the percentage of BVSM monomer in the precursor mass is 83.3 / 9952.1 = 0.84 wt%, and the percentage of PETEA monomer in the precursor mass is 74.8 / 9952.1 = 0.75 wt%). All other steps remained unchanged. The electrolyte was tested using an electrochemical workstation for Li||Li symmetric cells, and AC impedance spectroscopy and chronoamperometric curves were obtained. The calculated lithium-ion transference number was 0.61.

[0089] Example 4

[0090] The solid polymer electrolyte was prepared according to the steps of Example 1, except that the step of "heating and drying at 70°C for 12 h" in step 3 was changed to "heating and drying at 60°C for 12 h"; the other steps remained the same. The electrolyte was tested using an electrochemical workstation for Li||Li symmetric batteries to obtain AC impedance spectra and chronoamperometric curves. The calculated lithium-ion transference number was 0.58.

[0091] Example 5

[0092] The solid polymer electrolyte was prepared according to the steps of Example 1, except that the step of "heating and drying at 70°C for 12 h" in step 3 was changed to "heating the reaction solution at 80°C for 12 h"; the other steps remained the same. The test was performed using an electrochemical workstation for Li||Li symmetric cells to obtain AC impedance spectra and chronoamperometric curves. The calculated lithium-ion transference number was 0.54.

Claims

1. A method for preparing a solid polymer electrolyte, characterized in that, Includes the following steps: A. Mix polyvinylidene fluoride-hexafluoropropylene, lithium bis(trifluoromethanesulfonylimide), bis(ethylene sulfone)methane, isoprene tetraacrylate, and N,N-dimethylformamide to obtain a precursor solution. B. Mix azobisisobutyronitrile with the precursor solution to obtain a reaction solution; C. Heat the reaction solution described in step B at 40–80°C for 20–60 min, then coat it onto a substrate and dry it to obtain a solid polymer electrolyte; In step A, the molar ratio of polyvinylidene fluoride-hexafluoropropylene, lithium bis(trifluoromethanesulfonylimide), bis(ethylene sulfone)methane, and isoprene tetraacrylate is 7–8 : 20–21 : 1.5–2.5 : 1; the total mass of bis(ethylene sulfone)methane and isoprene tetraacrylate accounts for 0.5–2 wt% of the precursor solution.

2. The method for preparing solid polymer electrolyte according to claim 1, characterized in that: In step B, azobisisobutyronitrile accounts for 0.05–0.15 wt% of the precursor solution.

3. The method for preparing solid polymer electrolyte according to claim 2, characterized in that: In step A, the molar ratio of polyvinylidene fluoride-hexafluoropropylene, lithium bis(trifluoromethanesulfonylimide), bis(ethylene sulfone)methane, and isoprene tetraacrylate is 7.05 : 20.51 : 2.00 : 1; the total mass of bis(ethylene sulfone)methane and isoprene tetraacrylate accounts for 1.5–2 wt% of the precursor solution. In step B, azobisisobutyronitrile accounts for 0.1 wt% of the precursor solution.

4. The method for preparing solid polymer electrolyte according to claim 1, characterized in that: In step C, the reaction solution described in step B is heated at 60°C for 30 min.

5. The method for preparing a solid polymer electrolyte according to claim 1, characterized in that: In step C, the drying process involves drying at 60–80°C for 10–20 hours.

6. The method for preparing a solid polymer electrolyte according to claim 5, characterized in that: In step C, the drying process involves drying at 70°C for 12 hours.

7. The solid polymer electrolyte prepared by the method according to any one of claims 1 to 6.

8. The application of the solid polymer electrolyte according to claim 7 in lithium metal batteries.

9. The application of the solid polymer electrolyte according to claim 8 in lithium metal batteries, characterized in that: The lithium metal battery is a Li||NCM811 battery.

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