A gel polymer electrolyte membrane for lithium batteries and a preparation method and application thereof

Abstract

The application discloses a gel polymer electrolyte membrane for lithium batteries and a preparation method and application thereof, and belongs to the polymer electrolyte field. The preparation method provided by the application is that a first prepolymer is obtained by reacting a double-end amino polyethylene glycol with o-phthaldehyde in an inert gas; then tetraethylene glycol dimethyl acrylate and a photoinitiator are added to the first prepolymer to obtain a second prepolymer; a lithium salt is added to the second prepolymer to obtain a precursor slurry; the precursor slurry is subjected to film coating treatment, and the film is subjected to ultraviolet curing treatment and standing treatment in sequence to obtain the gel polymer electrolyte membrane. The dynamic imine bond network is constructed by o-phthaldehyde and the double-end amino polyethylene glycol, the ether oxygen branched chain of the tetraethylene glycol dimethyl acrylate is used to construct a three-dimensional ion transmission channel, and the self-repairing is realized by combining the spontaneous and reversible recombination of the imine bond under the ambient humidity, so that the high ion conductivity of the polymer membrane is ensured to meet the high-frequency charging and discharging requirement.

Description

Technical Field

[0001] This invention relates to the field of polymer electrolyte technology, specifically to a gel polymer electrolyte membrane for lithium batteries, its preparation method, and its application. Background Technology

[0002] With the explosive growth of the electric vehicle and energy storage industries, high-energy-density and high-safety lithium-ion batteries have become a global research focus. However, the mainstream liquid electrolyte system faces a fundamental contradiction: despite its excellent ionic conductivity (10⁻⁶ Ω·cm), it still exhibits high energy density and high safety. -2 While the S / cm ratio and electrode wettability support fast-charging performance, the inherent flammability and volatility of organic solvents result in a persistently high risk of thermal runaway. Overcharging and collisions can easily lead to fires and explosions, posing a primary threat to the safety of new energy vehicles. Furthermore, liquid systems have weak suppression capabilities for lithium dendrites; uncontrolled dendrite growth during cycling not only accelerates capacity decay but can also penetrate the separator, causing short circuits. In high-voltage cathodes (>4.5V), continuous oxidative decomposition of the electrolyte leads to a surge in interfacial impedance and the dissolution of transition metals, severely hindering the commercialization of advanced materials such as high-nickel ternary and lithium-rich manganese-based materials. Despite localized optimization through film-forming additives and flame retardants, a balance between safety and performance has yet to be achieved.

[0003] To overcome the safety constraints of liquid electrolytes, gel polymer electrolytes (GPEs) have opened a third path between solid and liquid states by anchoring the electrolyte within a polymer network. Current mainstream systems such as polyethylene oxide (PEO) and polyvinylidene fluoride (PVDF), while improving thermal stability, face multiple challenges: First, conductivity and mechanical strength are mutually restrictive. Increasing conductivity requires the introduction of large amounts of plasticizers, but this causes mechanical property collapse, resulting in a film strength of less than 1 MPa. Second, repeated expansion and contraction of the electrodes during battery cycling generates microcracks, and traditional cross-linked networks lack self-healing capabilities, leading to interfacial contact failure. Third, poor temperature adaptability; PEO-based electrolytes experience severe crystallization at room temperature, causing a sharp drop in conductivity by two orders of magnitude. While self-healing GPEs (such as those with dynamic disulfide bonds and borate ester bonds) have emerged in recent years, they generally rely on high-temperature activation (>60°C) and severely sacrifice ion transport efficiency. Existing systems still face bottlenecks such as conductivity-strength inversion, irreversible interface damage, and poor temperature adaptability. In particular, they lack a comprehensive solution that simultaneously achieves high-efficiency room-temperature conductivity, mechanical robustness, and interface self-maintenance under real-world operating conditions. To address these challenges, this study innovates from the perspective of molecular topology design, proposing a novel gel electrolyte system that combines dynamic self-healing, high ion transport, and wide-temperature stability. Its core lies in the synergistic assembly of a rigid framework and a branched network, combined with the intelligent regulation of environmentally responsive dynamic bonds, breaking through the performance boundaries of traditional materials and providing a novel solution for high-safety lithium metal batteries. Summary of the Invention

[0004] This invention addresses the triple defects of existing gel polymer electrolytes in lithium-ion battery energy storage, namely, interfacial stress accumulation, ion conduction hysteresis, and uncontrolled cyclic expansion caused by high-frequency charge-discharge. This invention provides a gel polymer electrolyte membrane for lithium-ion batteries, its preparation method, and its applications. This invention innovatively proposes a "rigid support-dynamic self-adaptive" dual-network interpenetrating structure strategy. A rigid cross-linked network is constructed from tetraethylene glycol dimethacrylate (TEGDMA) through photopolymerization to constrain electrode volume deformation. Simultaneously, a dynamic imine bond network formed by o-phthalaldehyde (OPA) and diamine-terminated polyethylene glycol (H2N-PEG-NH2) enables topological restructuring under charge-discharge stress. Furthermore, the continuous phase of polyethylene glycol ether oxygen chains ensures lithium-ion conduction efficiency, thereby addressing the challenge of synergistic optimization of the electrolyte membrane's mechanical stability and electrochemical response.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a gel polymer electrolyte membrane for lithium batteries, comprising:

[0007] The first prepolymer was obtained by reacting diamine-terminated polyethylene glycol with phthalaldehyde in an inert gas atmosphere.

[0008] A second prepolymer is obtained by adding tetraethylene glycol dimethacrylate and a photoinitiator to the first prepolymer and reacting. A lithium salt is then added to the second prepolymer and mixed evenly to obtain a precursor slurry.

[0009] The precursor slurry was coated, and then subjected to UV curing and settling treatments to obtain a gel polymer electrolyte membrane.

[0010] The molecular weight of the diamino-terminated polyethylene glycol is 5,000 to 20,000; the molar ratio of the diamino-terminated polyethylene glycol to phthalaldehyde is 1: (0.8 to 1.2).

[0011] The molar ratio of the diamino-terminated polyethylene glycol to tetraethylene glycol dimethacrylate is 1:(4~6).

[0012] The photoinitiator includes benzoin ether, and the amount of the photoinitiator added is 0.5 to 2 wt% of the total mass of diamino-terminated polyethylene glycol, phthalaldehyde and tetraethylene glycol dimethacrylate.

[0013] The lithium salt includes lithium bis(trifluoromethanesulfonyl)imide or lithium bis(fluoromethanesulfonyl)imide, and the amount of lithium salt added is 38-42% of the total mass of the dual-terminated amino polyethylene glycol and tetraethylene glycol dimethacrylate.

[0014] The double-amino-terminated polyethylene glycol and phthalaldehyde are placed in an inert gas environment and reacted in the dark at 20-30°C to obtain the first prepolymer.

[0015] The first prepolymer is prepared by adding tetraethylene glycol dimethacrylate and a photoinitiator, and then placing it in an inert gas atmosphere and reacting it in the dark at 0-5°C to obtain the second prepolymer.

[0016] The ultraviolet curing process specifically involves irradiating the surface with ultraviolet light of wavelength 200~300 nm.

[0017] The specific static treatment is as follows: stand for 10 to 14 hours in an environment with a temperature of 75 to 85 ℃ and a vacuum degree of ≤ -0.09 MPa; then stand for 12 to 24 hours in an environment with a temperature of 20 to 30 ℃ and a humidity of 50 to 70%RH.

[0018] This invention also provides a gel polymer electrolyte membrane for lithium batteries, prepared according to the above-described method for preparing a gel polymer electrolyte membrane for lithium batteries, wherein the structural formula of the gel polymer in the gel polymer electrolyte membrane is:

[0019] .

[0020] The aforementioned gel polymer electrolyte membrane for lithium batteries is used to prepare semi-solid lithium batteries.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention is based on a functional coupling mechanism of "rigid support - dynamic buffer - high-speed ion transport," achieving performance breakthroughs through molecular-level network interpenetration design. A rigid polyacrylate network formed by TEGDMA photopolymerization provides the structural framework, endowing the electrolyte membrane with high mechanical properties and effectively suppressing the risk of lithium dendrite puncture. Simultaneously, the dynamic imine bond network (-CH=N-) constructed from the aldehyde groups of OPA and the amino groups of H2N-PEG-NH2 undergoes reversible breakage / recombination under charge-discharge thermal effects (60℃), dissipating interfacial stress and repairing microcracks in real time, significantly reducing interfacial impedance growth. Meanwhile, the PEG ether oxygen chains running through the dual networks form continuous ion channels, ensuring the polymer membrane's high ionic conductivity to meet the demands of high-frequency charge-discharge cycles. Ultimately, the rigid network maintains electrode dimensional stability, the dynamic network adapts to volume deformation, and the flexible conductor maintains ion flow continuity; these three elements synergistically provide core material support for high-reliability lithium-ion battery energy storage.

[0023] The polymer electrolyte membrane of this invention exhibits breakthroughs in multiple dimensions: in terms of electrochemical performance, the room temperature ionic conductivity reaches 1.29 × 10⁻⁶. -4The S / cm ratio was controlled by molecular chain entanglement and cross-linking network, maintaining Young's modulus at 160 MPa and elongation at break at 120%. Regarding interface stability, the assembled lithium battery achieved an initial discharge specific capacity of 147 mAh·g at 0.5C rate. -1 This provides a completely new approach for high-safety, long-life semi-solid-state batteries. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram showing the discharge capacity decay of the electrolyte membranes prepared in Example 1 and Comparative Example 1 after 100 cycles.

[0026] Figure 2 This is a schematic diagram of the impedance of the electrolyte membranes prepared in Example 1 and Comparative Example 1 after 100 cycles. Detailed Implementation

[0027] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0028] In this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0029] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0030] It should be understood that in various embodiments of the present invention, the order of the above-mentioned processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0031] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0032] The weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope disclosed in the embodiments of this invention. Specifically, the mass described in the embodiments of this invention can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0033] This invention provides a method for preparing a gel polymer electrolyte membrane for lithium batteries, comprising:

[0034] The first prepolymer was obtained by reacting diamino-terminated polyethylene glycol and phthalaldehyde in an inert gas atmosphere at 20-30°C in the dark.

[0035] Tetraethylene glycol dimethacrylate and a photoinitiator were added to the first prepolymer and placed in an inert gas atmosphere. The reaction was carried out in the dark at 0-5°C to obtain the second prepolymer. Lithium salt was added to the second prepolymer and mixed evenly to obtain the precursor slurry.

[0036] The precursor slurry was coated and then cured with ultraviolet light at a wavelength of 200-300 nm. The mixture was then allowed to stand for 10-14 h at a temperature of 75-85 ℃ and a vacuum degree of ≤-0.09 MPa. Finally, it was allowed to stand for 12-24 h at a temperature of 20-30 ℃ and a humidity of 50-70%RH to obtain the gel polymer electrolyte membrane.

[0037] In some embodiments, the molecular weight of the amino-terminated polyethylene glycol is 5,000 to 20,000; the molar ratio of the amino-terminated polyethylene glycol to phthalaldehyde is 1:(0.8 to 1.2).

[0038] In some embodiments, the molar ratio of diamino-terminated polyethylene glycol to tetraethylene glycol dimethacrylate is 1:(4~6).

[0039] In some embodiments, the photoinitiator includes benzoin ether, and the amount of the photoinitiator added is 0.5 to 2 wt% of the total mass of diamino-terminated polyethylene glycol, phthalaldehyde and tetraethylene glycol dimethacrylate.

[0040] In some embodiments, the lithium salt comprises lithium bis(trifluoromethanesulfonyl)imide or lithium bis(fluoromethanesulfonyl)imide, wherein the amount of lithium salt added is 38 to 42% of the total mass of the diamino-terminated polyethylene glycol and tetraethylene glycol dimethacrylate.

[0041] This invention is based on the synergistic mechanism of dynamic covalent chemistry and photopolymerization. It constructs a flexible adaptive network by forming dynamic imine bonds (-CH=N-) between the primary amine of H2N-PEG-NH2 and the aldehyde group of OPA. Simultaneously, TEGDMA is introduced to form a rigid cross-linked network under photoinitiation. The interpenetration of these two components produces a gel electrolyte membrane that combines rigidity and flexibility. For the first time, this invention combines the reversible breaking / recombining characteristics of dynamic imine bonds (buffering charge / discharge stress) with the mechanical stability of the photopolymer network (suppressing electrode expansion). Through precise formulation of the molar ratio of H2N-PEG-NH2, OPA, and TEGDMA (1:(0.8~1.2):(4~6)) and the addition of lithium salt at 38~42% of the total mass of H2N-PEG-NH2 and TEGDMA, the gel polymer electrolyte membrane exhibits high ionic conductivity, excellent flexible mechanical properties, and good cycle performance when used in lithium-ion battery energy storage systems, thus promoting the development of polymer electrolyte membranes in the field of lithium-ion battery energy storage.

[0042] This invention prepares a self-healing gel polymer electrolyte membrane using the above-described preparation method. The structural formula of the polymer in the self-healing gel polymer electrolyte membrane is shown below:

[0043]

[0044] Applying the self-healing gel polymer electrolyte membrane provided by this invention to semi-solid lithium batteries can significantly improve the discharge specific capacity of semi-solid lithium batteries.

[0045] In the following embodiments, unless otherwise specified, all materials used can be obtained through ordinary channels; the testing methods used are conventional methods in the art.

[0046] Example 1

[0047] 1.0 mmol H2N-PEG-NH2 (molecular weight of H2N-PEG-NH2 is 5000) and 1.0 mmol phthalaldehyde were placed in a nitrogen atmosphere, 25°C, and protected from light. The mixture was magnetically stirred at 500 rpm for 4 hours to generate the first prepolymer.

[0048] Add 4 mmol of TEGDMA and benzoin ether (1 wt% of the total mass of the system) to the first prepolymer and place it in a nitrogen atmosphere at 5°C in the dark. Stir and react for 1 hour to obtain the second prepolymer.

[0049] Lithium bis(trifluoromethanesulfonylimide) (LiTFSI) was added to the second prepolymer. The amount of LiTFSI added was 40% of the total mass of H2N-PEG-NH2 and TEGDMA. The mixture was stirred until it was completely dissolved to obtain the precursor slurry.

[0050] The film was formed by irradiation with 200 nm ultraviolet light for 20 minutes. After film formation, it was kept in an environment of 80℃ and vacuum degree of -0.09 MPa for 12 h. Then it was placed in an environment of 25℃ and 60% RH for 24 h to activate dynamic imine bonds, and a gel polymer electrolyte membrane with a thickness of 35~80 μm was obtained, denoted as DNP-TEG1.

[0051] The DNP-TEG1 prepared in this embodiment was assembled with a positive electrode (lithium iron phosphate) and a negative electrode (lithium metal sheet) into a 2025 model button cell. Performance testing was conducted, and the conductivity at room temperature was measured to be 1.29 × 10⁻⁶. -4 To investigate the application of the gel polymer electrolyte membrane in semi-solid lithium batteries, it was assembled into a LiFePO4 / DNP-TEG1 / Li battery and charged-discharge cycled at 60 °C. The initial discharge specific capacity of the battery at a 0.5 C rate was measured to be 147 mAh·g. -1 .

[0052] Example 2

[0053] 1.0 mmol H2N-PEG-NH2 (molecular weight of H2N-PEG-NH2 is 5000) and 0.6 mmol phthalaldehyde were placed in a nitrogen atmosphere, 25°C, and protected from light. The mixture was magnetically stirred at 500 rpm for 4 hours to generate the first prepolymer.

[0054] Add 4 mmol of TEGDMA and benzoin ether (1 wt% of the total mass of the system) to the first prepolymer and place it in a nitrogen atmosphere at 5°C in the dark. Stir and react for 1 hour to obtain the second prepolymer.

[0055] LiTFSI was added to the second prepolymer at a rate of 40% of the total mass of H2N-PEG-NH2 and TEGDMA. The mixture was stirred until completely dissolved to obtain the precursor slurry.

[0056] The film was formed by irradiation with 200 nm ultraviolet light for 20 minutes. After film formation, it was kept in an environment of 80 °C and vacuum degree of -0.09 MPa for 12 h. Then it was placed in an environment of 25 °C and 60% RH for 24 h to activate dynamic imine bonds, and the gel polymer electrolyte membrane was obtained, denoted as DNP-TEG2.

[0057] Insufficient OPA content resulted in a low density of imine crosslinking points, leading to slightly weaker polymer film strength and edge swelling. The DNP-TEG2 prepared in this example was assembled with a positive electrode (lithium iron phosphate) and a negative electrode (lithium metal sheet) into a 2025-type button cell. Performance testing was conducted, and the conductivity at room temperature was measured to be 1.58 × 10⁻⁶. -4 To investigate the application of the gel polymer electrolyte membrane in semi-solid lithium batteries, it was assembled into a LiFePO4 / DNP-TEG2 / Li battery and charged-discharge cycled at 60 °C. The initial discharge specific capacity of the battery at a 0.5 C rate was measured to be 143 mAh·g. -1 .

[0058] Example 3

[0059] 1.0 mmol H2N-PEG-NH2 (molecular weight of H2N-PEG-NH2 is 5000) and 1.5 mmol phthalaldehyde were placed in a nitrogen atmosphere, 25°C, and protected from light. The mixture was magnetically stirred at 500 rpm for 4 hours to generate the first prepolymer.

[0060] 2 mmol of TEGDMA and benzoin ether (1 wt% of the total mass of the system) were added to the first prepolymer and placed in a nitrogen atmosphere at 5°C in the dark. The mixture was stirred and reacted for 1 hour to obtain the second prepolymer.

[0061] LiTFSI was added to the second prepolymer at a rate of 40% of the total mass of H2N-PEG-NH2 and TEGDMA. The mixture was stirred until completely dissolved to obtain the precursor slurry.

[0062] The film was formed by irradiation with 200 nm ultraviolet light for 20 minutes. After film formation, it was kept in an environment of 80 °C and vacuum degree of -0.09 MPa for 12 h. Then it was placed in an environment of 25 °C and 60% RH for 24 h to activate dynamic imine bonds, and the gel polymer electrolyte membrane was obtained, denoted as DNP-TEG3.

[0063] Excessive OPA content leads to overly dense rigid aromatic ring stacking, resulting in excessively rigid polymer film that is prone to breakage. This makes battery assembly more difficult and hinders battery testing.

[0064] Example 4

[0065] 1.0 mmol H2N-PEG-NH2 (molecular weight of H2N-PEG-NH2 is 5000) and 1.2 mmol phthalaldehyde were placed in a nitrogen atmosphere, 25°C, and protected from light. The mixture was magnetically stirred at 500 rpm for 4 hours to generate the first prepolymer.

[0066] 2 mmol of TEGDMA and benzoin ether (1 wt% of the total mass of the system) were added to the first prepolymer and placed in a nitrogen atmosphere at 5°C in the dark. The mixture was stirred and reacted for 1 hour to obtain the second prepolymer.

[0067] LiTFSI was added to the second prepolymer at a rate of 40% of the total mass of H2N-PEG-NH2 and TEGDMA. The mixture was stirred until completely dissolved to obtain the precursor slurry.

[0068] The film was formed by irradiation with 200 nm ultraviolet light for 20 minutes. After film formation, it was kept in an environment of 80 °C and vacuum degree of -0.09 MPa for 12 h. Then it was placed in an environment of 25 °C and 60% RH for 24 h to activate dynamic imine bonds, and the gel polymer electrolyte membrane was obtained, denoted as DNP-TEG4.

[0069] The DNP-TEG4 prepared in this embodiment was assembled with a positive electrode (lithium iron phosphate) and a negative electrode (lithium metal sheet) into a 2025 model button cell. Performance testing was conducted, and the conductivity at room temperature was measured to be 1.43 × 10⁻⁶. -4 To investigate the application of the gel polymer electrolyte membrane in semi-solid lithium batteries, it was assembled into a LiFePO4 / DNP-TEG4 / Li battery and charged-discharge cycled at 60℃. The initial discharge specific capacity of the battery at a 0.5C rate was measured to be 145 mAh·g. -1 .

[0070] Example 5

[0071] 1.0 mmol H2N-PEG-NH2 (molecular weight of H2N-PEG-NH2 is 5000) and 1.2 mmol phthalaldehyde were placed in a nitrogen atmosphere, 25°C, and protected from light. The mixture was magnetically stirred at 500 rpm for 4 hours to generate the first prepolymer.

[0072] Add 6 mmol of TEGDMA and benzoin ether (1 wt% of the total mass of the system) to the first prepolymer and place it in a nitrogen atmosphere at 5°C in the dark. Stir and react for 1 hour to obtain the second prepolymer.

[0073] LiTFSI was added to the second prepolymer at a concentration of 38% of the total mass of H2N-PEG-NH2 and TEGDMA. The mixture was stirred until completely dissolved to obtain the precursor slurry.

[0074] The film was formed by irradiation with 200 nm ultraviolet light for 20 minutes. After film formation, it was kept in an environment of 80 °C and vacuum degree of -0.09 MPa for 12 h. Then it was placed in an environment of 25 °C and 60% RH for 24 h to activate dynamic imine bonds, and the gel polymer electrolyte membrane was obtained, denoted as DNP-TEG5.

[0075] The DNP-TEG5 prepared in this embodiment was assembled with a positive electrode (lithium iron phosphate) and a negative electrode (lithium metal sheet) into a 2025 model button cell. Performance testing was conducted, and the conductivity at room temperature was measured to be 1.36 × 10⁻⁶. -4 To investigate the application of the gel polymer electrolyte membrane in semi-solid-state batteries, it was assembled into a LiFePO4 / DNP-TEG5 / Li battery and charged-discharge cycled at 60 °C. The initial discharge specific capacity of the battery at a 0.5 C rate was measured to be 144 mAh·g. -1 .

[0076] Example 6

[0077] 1.0 mmol H2N-PEG-NH2 (H2N-PEG-NH2 with a molecular weight of 10000) and 1 mmol o-phthalaldehyde were placed in a nitrogen atmosphere, at 20°C, in the dark, and the mixture was magnetically stirred at 500 rpm for 4 hours to generate the first prepolymer.

[0078] Add 4 mmol of TEGDMA and benzoin ether (0.5 wt% of the total mass of the system) to the first prepolymer and place it in a nitrogen atmosphere, 0°C and dark environment. Stir and react for 1 hour to obtain the second prepolymer.

[0079] Lithium difluoromethanesulfonylimide (LiFSI) was added to the second prepolymer. The amount of LiFSI added was 42% of the total mass of H2N-PEG-NH2 and TEGDMA. The mixture was stirred until completely dissolved to obtain the precursor slurry.

[0080] The film was formed by irradiation with 260 nm ultraviolet light for 20 minutes. After film formation, it was kept in an environment of 75 °C and vacuum degree of -0.08 MPa for 14 h. Then it was placed in an environment of 20 °C and 70% RH for 20 h to activate dynamic imine bonds, and the gel polymer electrolyte membrane was obtained, denoted as DNP-TEG6.

[0081] The DNP-TEG6 prepared in this embodiment was assembled with a positive electrode (lithium iron phosphate) and a negative electrode (lithium metal sheet) into a 2025 model button cell. Performance testing was conducted, and the conductivity at room temperature was measured to be 1.52 × 10⁻⁶. -4To investigate the application of the gel polymer electrolyte membrane in semi-solid lithium batteries, it was assembled into a LiFePO4 / DNP-TEG6 / Li battery and charged-discharge cycled at 60 °C. The initial discharge specific capacity of the battery at a 0.5 C rate was measured to be 141 mAh·g. -1 .

[0082] Example 7

[0083] 1.0 mmol H2N-PEG-NH2 (molecular weight of H2N-PEG-NH2 is 20000) and 1 mmol phthalaldehyde were placed in a nitrogen atmosphere, 30°C, and protected from light. The mixture was magnetically stirred at 500 rpm for 4 hours to generate the first prepolymer.

[0084] Add 4 mmol of TEGDMA and benzoin ether (2 wt% of the total mass of the system) to the first prepolymer and place it in a nitrogen atmosphere at 3°C ​​in the dark. Stir and react for 1 hour to obtain the second prepolymer.

[0085] LiFSI was added to the second prepolymer at a concentration of 42% of the total mass of H2N-PEG-NH2 and TEGDMA. The mixture was stirred until completely dissolved to obtain the precursor slurry.

[0086] The film was formed by irradiation with 300 nm ultraviolet light for 20 minutes. After film formation, it was kept in an environment of 85 °C and vacuum degree of -0.05 MPa for 10 h. Then it was placed in an environment of 30 °C and 50% RH for 12 h to activate dynamic imine bonds, and the gel polymer electrolyte membrane was obtained, denoted as DNP-TEG7.

[0087] The DNP-TEG7 prepared in this embodiment was assembled with a positive electrode (lithium iron phosphate) and a negative electrode (lithium metal sheet) into a 2025 model button cell. Performance testing was conducted, and the conductivity at room temperature was measured to be 1.46 × 10⁻⁶. -4 To investigate the application of the gel polymer electrolyte membrane in semi-solid lithium batteries, it was assembled into a LiFePO4 / DNP-TEG7 / Li battery and charged-discharge cycled at 60 °C. The initial discharge specific capacity of the battery at a 0.5 C rate was measured to be 142 mAh·g. -1 .

[0088] Comparative Example 1

[0089] The specific steps for preparing the polymer electrolyte membrane in Comparative Example 1 are as follows: 1 mmol of polyethylene oxide (PEO) and LiTFSI (1 / 4 of the mass of PEO) were dissolved in 30 ml of acetonitrile (ACN) solution. The resulting solution was poured onto the surface of a polytetrafluoroethylene mold and dried in a vacuum environment at 60 °C for 12 hours to obtain the polymer electrolyte membrane, denoted as PEO@LiTFSI.

[0090] The polymer electrolyte membrane was assembled into a LiFePO4 / PEO@LiTFSI / Li battery, and its charge-discharge cycle performance was tested at 60℃. The conductivity of the polymer electrolyte membrane at room temperature was measured to be 3.68 × 10⁻⁶. -5 The S / cm ratio indicates that the battery's initial discharge specific capacity, measured at a 0.5 C rate, is 117 mAh·g. -1 .

[0091] like Figure 1 As shown, the discharge capacity after 100 cycles of LFP|DNP-TEG1|Li and LFP|PEO@LiTFSI|Li was compared. The efficient ion channels based on the TEGDMA sidechain network enabled it to achieve an initial discharge capacity of 147 mAh g⁻¹. -1 Significantly higher than PEO-based electrolytes (95 mAh g). -1 After 100 cycles, the self-healing function of the dynamic imine bonds in OPA continuously repaired the electrode cracks, maintaining a capacity retention of 95.4% (140.55 mAh / g), while PEO experienced accelerated capacity decay to 90 mAh / g due to intensified crystallization and interfacial side reactions, with a retention rate of 94.7%. This demonstrates that DNP-TEG1 possesses the dual advantages of higher initial capacity and better cycling stability.

[0092] like Figure 2 As shown, the impedance of the LFP|DNP-TEG1|Li battery after 100 cycles (257Ω) is significantly lower than that of the LFP|PEO@LiTFSI|Li (732Ω). This is attributed to the synergistic triple advantages of the DNP-TEG1 electrolyte: dynamic imine bonds repair interfacial cracks in real time during cycling, the TEGDMA branched network maintains the continuity of ion channels, and the ortho-aldehyde group of OPA chelates lithium ions to form a stable SEI film. In contrast, the PEO electrolyte film, lacking self-healing capabilities, suffers from crack propagation, crystallization blocking conduction pathways, and exacerbated interfacial side reactions, ultimately resulting in an interfacial impedance (732Ω) 2.8 times that of Example 1 after 100 cycles.

[0093] As shown in Table 1, Example 2 added 0.8 mmol of OPA. Due to insufficient OPA, the density of imine crosslinking points decreased, resulting in a loose crosslinking network and insufficient rigid aromatic ring support, manifested as a sharp drop in Young's modulus (60 MPa) and excessive elongation (elongation at break >500%). Example 3 added 1.5 mmol of OPA. Due to excessive OPA, the π-π stacking of phthaloyl rings caused stress concentration within the polymer film, resulting in brittle fracture (elongation <15%) and high modulus (400 MPa). For the TEGDMA branched network, Example 4 added 2 mmol of TEGDMA. Due to insufficient addition, the branched crosslinking density was insufficient, and the flexible ether oxygen chain dominated the network, weakening its strength (modulus 120 MPa). Example 5 added 6 mmol of TEGDMA. Due to excessive addition, the entanglement effect of long branches weakened the rigid skeleton, inducing viscoelastic creep (modulus 90 MPa). In Example 1, the molar ratio of OPA to TEGDMA is 1:4. The spatial confinement of the rigid aromatic ring and the flexible buffer of the branch network achieve a dynamic balance. OPA provides 180 MPa of rigid support, and the TEGDMA branches release local stress through covalent grafting (160% elongation at break), ultimately forming a three-dimensional interpenetrating network that combines rigidity and flexibility.

[0094] Table 1. Mechanical performance test results of Examples 1-5

[0095]

[0096] This invention is based on the molecular cooperative design of polymers. Its core mechanism involves locking the polymer network topology through the rigid aromatic ring of orthophthalaldehyde (OPA), while simultaneously constructing a three-dimensional ion transport channel using the ether-oxygen branches of tetraethylene glycol dimethacrylate (TEGDMA). Furthermore, self-repair is achieved through the spontaneous and reversible recombination of imine bonds under ambient humidity. The branched network increases the ionic conductivity to 1.29 × 10⁻⁶. -4 It achieves a high modulus of 180 MPa while maintaining a high S / cm; and creatively utilizes ambient humidity to trigger the self-repair of imine bonds, enabling the battery to have continuous interface regeneration capability under real working conditions, with a capacity retention rate of 95.4% after 100 cycles.

[0097] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0098] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. A gel polymer electrolyte membrane for lithium batteries, characterized in that, The structural formula of the gel polymer in the gel polymer electrolyte membrane is: ； The method for preparing the gel polymer electrolyte membrane for lithium batteries includes: The first prepolymer is obtained by reacting diamine-terminated polyethylene glycol with phthalaldehyde in an inert gas atmosphere; the molar ratio of the diamine-terminated polyethylene glycol to phthalaldehyde is 1:(0.8~1.2). A second prepolymer is obtained by adding tetraethylene glycol dimethacrylate and a photoinitiator to the first prepolymer and reacting. A lithium salt is then added to the second prepolymer and mixed evenly to obtain a precursor slurry. The molar ratio of the diamine-terminated polyethylene glycol to tetraethylene glycol dimethacrylate is 1:(4~6). The precursor slurry is coated, and then subjected to UV curing and settling treatment to obtain a gel polymer electrolyte membrane. The settling treatment is specifically as follows: settling in an environment with a temperature of 75~85 ℃ and a vacuum degree ≤-0.09 MPa for 10~14 h; and then settling in an environment with a temperature of 20~30 ℃ and a humidity of 50~70%RH for 12~24 h.

2. The gel polymer electrolyte membrane for lithium batteries according to claim 1, characterized in that, The molecular weight of the double-amino-terminated polyethylene glycol is 5000~20000.

3. The gel polymer electrolyte membrane for lithium batteries according to claim 1, characterized in that, The photoinitiator includes benzoin ether, and the amount of the photoinitiator added is 0.5 to 2 wt% of the total mass of diamino-terminated polyethylene glycol, phthalaldehyde and tetraethylene glycol dimethacrylate.

4. The gel polymer electrolyte membrane for lithium batteries according to claim 1, characterized in that, The lithium salt includes lithium bis(trifluoromethanesulfonyl)imide or lithium bis(fluoromethanesulfonyl)imide, and the amount of lithium salt added is 38-42% of the total mass of the bi-amino-terminated polyethylene glycol and tetraethylene glycol dimethacrylate.

5. The gel polymer electrolyte membrane for lithium batteries according to claim 1, characterized in that, The first prepolymer is obtained by placing diamino-terminated polyethylene glycol and phthalaldehyde in an inert gas atmosphere and reacting them in the dark at 20-30°C.

6. The gel polymer electrolyte membrane for lithium batteries according to claim 1, characterized in that, The first prepolymer is prepared by adding tetraethylene glycol dimethacrylate and a photoinitiator, and then placing it in an inert gas atmosphere and reacting it in the dark at 0-5°C to obtain the second prepolymer.

7. The gel polymer electrolyte membrane for lithium batteries according to claim 1, characterized in that, The ultraviolet curing process specifically involves irradiation with ultraviolet light of wavelength 200~300 nm.

8. The gel polymer electrolyte membrane for lithium batteries according to any one of claims 1-7 is used to prepare semi-solid lithium batteries.

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