An epoxy resin-based gel electrolyte, a preparation method and applications thereof

Abstract

The present application relates to an epoxy resin-based gel electrolyte and its preparation method and application, which solves the technical problem of unreasonable pore structure of existing materials, inability to in-situ grow metal organic framework structure materials, and thus poor electrochemical performance of electrolyte, the epoxy resin-based gel electrolyte is provided with a pore structure, the average pore diameter of the pore structure is 17-35 nm; the epoxy resin-based gel electrolyte is in-situ grown with a metal organic framework structure material. The present application also provides its preparation method and application. The present application can be used in the preparation field of electrolyte materials.

Description

Technical Field

[0001] This invention relates to an electrolyte material, and more specifically, to an epoxy resin-based gel electrolyte, its preparation method, and its application. Background Technology

[0002] Lithium metal possesses an extremely high theoretical specific capacity (3860 mAh / g) and an extremely low mass density (0.59 g / cm³). 3 With its extremely low redox potential (-3.04V) compared to the standard hydrogen electrode, lithium metal is an ideal material for the negative electrode of lithium batteries. However, lithium metal is highly reactive with traditional electrolytes, which can lead to uncontrolled growth of lithium dendrites and some safety issues. The requirements for electrolytes in lithium metal batteries include: (1) good lithium-ion conductivity; (2) excellent chemical, electrochemical, and mechanical stability during cycling. Gel electrolytes are the best candidates that combine the above advantages. In addition, gel electrolytes can also solve the disadvantages of liquid electrolytes such as flammability, volatility, and leakage.

[0003] To this end, researchers have devoted considerable effort to developing various gel electrolytes for rechargeable lithium-ion batteries. Among these, epoxy resins have become the best choice for electrolyte matrices due to their low cost, availability, good mechanical properties, excellent chemical stability, and strong structural designability. Furthermore, gel electrolyte systems often require modification to improve electrochemical properties such as ionic conductivity, electrochemical stability window, lithium-ion transference number, and cycle stability. The most common method is to add fillers to the system, such as inorganic ceramic fillers; however, inorganic ceramic fillers are costly to process and lack sufficient thermal stability. To address these issues, replacing inorganic ceramic fillers with metal-organic frameworks (MOFs) is a good alternative. MOFs offer several advantages, including ease of synthesis, high porosity, high specific surface area, easily tunable pore structure, and excellent mechanical and thermal stability.

[0004] Chinese invention patent application CN104335391A discloses a method for manufacturing a diaphragm for a non-aqueous electrolyte storage device comprising an epoxy resin porous membrane. The method includes: a step of preparing an epoxy resin composition containing epoxy resin, a curing agent, and a pore-forming agent; a step of cutting the cured epoxy resin composition into sheets or curing a sheet-shaped form of the epoxy resin composition to obtain an epoxy resin sheet; a step of removing the pore-forming agent from the epoxy resin sheet using a halogen-free solvent to form an epoxy resin porous membrane; a step of irradiating the epoxy resin porous membrane with infrared light to determine the infrared absorption characteristics of the epoxy resin porous membrane; and a step of calculating the membrane thickness and / or average pore size of the epoxy resin porous membrane based on the infrared absorption characteristics.

[0005] Chinese invention patent application CN112421104A discloses an elastomeric epoxy resin-based all-solid-state electrolyte, its preparation method, and its application. It solves the technical problems of existing cross-linked solid polymer electrolytes, such as the introduction of impurities during preparation, the hazards of solvent use, and the narrow operating temperature range of existing thermoplastic polymer solid electrolytes.

[0006] All of the above patents use epoxy resin as the polymer electrolyte matrix, but they have not conducted in-depth research on the regulation of pore structure. Furthermore, the single epoxy resin-based electrolyte membrane does not have a significant effect on suppressing lithium dendrites, and its electrochemical performance still needs to be further improved.

[0007] Chinese invention patent application CN110368823A discloses a method for preparing a metal-organic framework-polyimide composite fiber membrane material. First, ZIF-8 is rapidly prepared in a methanol system at room temperature using a method that allows for subsequent imidization to obtain soluble polyimide 6FDA-BDAF. Then, a simple electrospinning technique is used to prepare a ZIF / PI composite fiber membrane. The resulting membrane material exhibits high thermal stability and mechanical strength, but it is only used as a composite fiber membrane for filtering PM2.5.

[0008] Chinese invention patent application CN110911742A discloses a method for preparing a polymer electrolyte composite membrane for solid-state batteries. The method involves mixing a metal-organic framework (MOF) material and a polymer in an organic solvent, followed by electrospinning to form a polymer / MOF fiber composite membrane. PEO and Li(TFSI) are dissolved in acetonitrile, and a PEO / Li(TFSI) composite film is prepared by solution casting. The PEO / Li(TFSI) composite film, polymer / MOF fiber composite film, and PEO / Li(TFSI) composite film are then sandwiched between or on the surface of a polytetrafluoroethylene (PTFE) membrane, followed by hot pressing and cooling to obtain the polymer electrolyte composite membrane for solid-state batteries. This invention utilizes the good complexing ability of PEO and Li(TFSI), the support sites provided by the polymer / MOF fiber composite membrane, and the ordered lithium-ion conduction channels provided by the microporous structure of MOFs. This allows for the fixation of Li(TFSI) anions within the microporous channels, accelerating cation transport and improving the material's conductivity and high-voltage tolerance. This preparation method produces a multilayer structure, which easily leads to poor interfacial compatibility and increased interfacial impedance.

[0009] Chinese invention patent application CN110085909A discloses a composite solid electrolyte material, its preparation method, and its application. The method involves dispersing a metal-organic framework material and an alkali metal or alkaline earth metal salt in an organic solvent, then adding an ion-conducting polymer solution, stirring until homogeneous, allowing it to stand, and finally pouring it into a mold to dry and solidify. This preparation method tends to result in uneven dispersion of the metal-organic framework material in the system, leading to agglomeration and affecting the overall performance of the electrolyte material.

[0010] These methods have all achieved the combination of MOF and polymer to form composite materials, but no research has yet attempted to grow MOF in situ on the pore walls for structural design. Summary of the Invention

[0011] This invention aims to solve the technical problem of poor electrochemical performance of electrolytes caused by unreasonable pore structure and inability to grow metal-organic framework structures in situ in existing materials. It provides an epoxy resin-based gel electrolyte with reasonable pore structure, in situ growth of metal-organic framework structures, and good electrochemical performance, as well as its preparation method and application.

[0012] Therefore, the present invention provides an epoxy resin-based gel electrolyte, wherein the epoxy resin-based gel electrolyte has a porous structure with an average pore size of 17-35 nm (BET test method); and a metal-organic framework structure material is grown on the epoxy resin-based gel electrolyte at reduction sites.

[0013] Preferably, the epoxy resin is one or more combinations of DGEBA, DGEBF, DGEBS, EPN, ECN, and HBR.

[0014] Preferably, the metal-organic framework material is one or more combinations of Zn(acac)2, Co(NO3)2·6H2O, ZnSO4, Zn(NO3)2·6H2O, Zn(ClO4)2, Zn(CH3COO)2·2H2O, and ZnCl2.

[0015] This invention also provides a method for preparing an epoxy resin-based gel electrolyte, which includes the following steps: (1) preparing a polyvinyl alcohol aqueous solution; (2) uniformly spreading the prepared polyvinyl alcohol aqueous solution on a glass plate, heating to remove moisture, and obtaining a glass plate with a polyvinyl alcohol film coated on the surface; (3) mixing epoxy resin with a pore-forming agent, stirring evenly, and obtaining a solution; (4) adding a curing agent to the solution obtained in step (3), stirring evenly, and then performing degassing treatment; (5) making a film from the solution obtained in step (4), immersing it in a solvent, removing the pore-forming agent, and drying to obtain an electrolyte film; (6) transferring the film obtained in step (5) to a glove box to wet the electrolyte, thereby obtaining a gel electrolyte.

[0016] Preferably, in step (3), epoxy resin is mixed with pore-forming agent, and then metal salt is added and stirred evenly to obtain a solution; between steps (5) and (6), the following step (5a) is also included: the film obtained in step (5) is placed in an organic ligand solution, allowed to stand, washed and dried to obtain a porous epoxy resin film of in-situ grown metal-organic framework structure material, and then step (6) is performed.

[0017] Preferably, in step (3), the metal salt is one or a combination of Zn(acac)2, Co(NO3)2·6H2O, ZnSO4, Zn(NO3)2·6H2O, Zn(ClO4)2, Zn(CH3COO)2·2H2O, and ZnCl2; the mass fraction of the metal salt in the mixture of epoxy resin and the metal salt is 5-25%; in step (5a), the molar ratio of the organic ligand to the metal salt is (2-8):1.

[0018] Preferably, in step (3), the epoxy resin is one or more of DGEBA, DGEBF, DGEBS, EPN, ECN, and HBR; the mass ratio of the epoxy resin to the pore-forming agent is 1:(1-3).

[0019] Preferably, in step (3), the pore-forming agent is one or more combinations of PEG200, PEG400, PEG600, and PEG2000.

[0020] Preferably, in step (4), the curing agent is one or more of PACM, D230, D400, TETA, DDM, and DDS; the epoxy resin and the curing agent are added in equal amounts of active groups, and the curing agent is added in one or more combinations.

[0021] This invention also provides an application of epoxy resin-based gel electrolyte as a battery material.

[0022] The present invention has the following beneficial effects:

[0023] (1) In this invention, the pore structure is controlled by adjusting the proportion of curing agent to obtain electrolyte membranes with micro-mesoporous structure, mesoporous-macroporous coexistence structure and macroporous structure; electrolyte membranes with different pore structures serve as self-supporting skeletons and are used as gel electrolytes after absorbing electrolyte.

[0024] (2) This invention grows metal-organic framework (MOF) materials in situ on the surface and pores of a porous epoxy resin-based electrolyte membrane. Compared to direct physical mixing, it eliminates the need for prior MOF material preparation and dispersion in the casting precursor solution, effectively avoiding the dispersion problem of MOFs. Furthermore, by fixing the MOF in situ onto the surface and pores of the porous epoxy resin-based electrolyte membrane, the microporous structure of the MOF allows small ions to pass through internal pore channels, thereby suppressing large anions. The interaction between surface groups and the electrolyte forms unique pore channels, which can improve the electrochemical window and lithium-ion migration number. The ordered porosity and narrow pore window of the MOF material contribute to uniform lithium-ion deposition, thereby suppressing lithium dendrite formation.

[0025] (3) The preparation process provided by the present invention is simple, no initiator is required during the production and processing, it is environmentally friendly, low cost, and easy to realize industrial production and commercial application. Attached Figure Description

[0026] Figure 1 These are electron microscope images of the pure epoxy resin porous membrane in Embodiment 2 of the present invention, where (a) is the corresponding planar view and (b) is the corresponding cross-sectional view.

[0027] Figure 2 These are electron microscope images of the electrolyte membrane after in-situ growth of MOF in Example 6 of the present invention, where (a) is the corresponding planar view and (b) is the corresponding cross-sectional view;

[0028] Figure 3 These are electrochemical window diagrams of the electrolytes prepared in Examples 2 and 6 of this invention. Detailed Implementation

[0029] The present invention will be further described below with reference to embodiments.

[0030] Example 1

[0031] (1) Prepare a polyvinyl alcohol aqueous solution: Weigh the calculated amount of polyvinyl alcohol, add it to distilled water, stir evenly at 100°C, and prepare a polyvinyl alcohol aqueous solution with a mass fraction of 2%.

[0032] (2) Pour the prepared polyvinyl alcohol aqueous solution onto a clean glass plate. Use a coating rod to spread the solution evenly on the glass plate to form a water film. Then place the glass plate on a hot table at 105°C and heat until the water is removed to obtain a glass plate with a polyvinyl alcohol film coated on the surface.

[0033] (3) Add bisphenol A diglycidyl ether (DGEBA, E51) and pore-forming agent polyethylene glycol (PEG200) (mass ratio of 1:2.75) into a screw-top bottle, stir at 60°C for 1 hour until the mixture is uniform, then add an equivalent amount of curing agent diaminodicyclohexylmethane (PACM), stir evenly using residual heat, and then place in a vacuum dryer for degassing treatment.

[0034] (4) Place gaskets around the prepared glass plate coated with polyvinyl alcohol film, and pour the degassed solution onto the glass plate. Place another glass plate coated with polyvinyl alcohol on the gaskets, forming a sandwich structure between the two glass plates. Clamp the sample with clamps and place it in a forced-air oven. The curing process is to heat at 80°C for 2 hours, and then heat at 120°C for 2 hours to complete the curing.

[0035] (5) After the cured sample has cooled, immerse it in distilled water and slowly separate the epoxy resin film from the glass plate. Since the pore-forming agent PEG200 is miscible with water, the removed epoxy resin film is ultrasonically washed and soaked in distilled water to remove the pore-forming agent. Cut the epoxy resin film into a 16mm diameter circular sheet and dry it to obtain the unactivated electrolyte.

[0036] (6) The unactivated electrolyte described in the previous step was tested using a high-performance fully automated mercury porosimeter, and the average pore size was 8 μm.

[0037] (7) Transfer the film to a glove box and immerse it in an electrolyte solution (the electrolyte solution is a mixed solution of lithium hexafluorophosphate doped with dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate, with a mass ratio of dimethyl carbonate: ethyl methyl carbonate: ethylene carbonate = 1:1:1, concentration 1M) for 24 hours. The final product is the gel polymer electrolyte.

[0038] (8) Assemble the gel polymer electrolyte described in the previous step into a battery in a glove box filled with argon gas.

[0039] (9) Using the AC impedance method, the ionic conductivity of this gel polymer electrolyte was measured to be 0.5 × 10⁻⁶ at 25°C. -3 S / cm.

[0040] Example 2

[0041] (1) Prepare a polyvinyl alcohol aqueous solution: Weigh the calculated amount of polyvinyl alcohol, add it to distilled water, stir evenly at 100°C, and prepare a polyvinyl alcohol aqueous solution with a mass fraction of 2%.

[0042] (2) Pour the prepared polyvinyl alcohol aqueous solution onto a clean glass plate. Use a coating rod to spread the solution evenly on the glass plate to form a water film. Then place the glass plate on a hot table at 105°C and heat until the water is removed to obtain a glass plate with a polyvinyl alcohol film coated on the surface.

[0043] (3) Add bisphenol A diglycidyl ether (DGEBA, E51) and pore-forming agent polyethylene glycol (PEG200) (mass ratio of 1:2.75) to a screw-top bottle, stir at 60°C for 1 hour until the mixture is uniform, and then add equal amounts of curing agent diaminodicyclohexylmethane (PACM) and polyetheramine (D230), wherein PACM:D230 is 7:3. After stirring evenly with residual heat, place in a vacuum dryer for degassing treatment.

[0044] (4) Place gaskets around the prepared glass plate coated with polyvinyl alcohol film, and pour the degassed solution onto the glass plate. Place another glass plate coated with polyvinyl alcohol on the gaskets, forming a sandwich structure between the two glass plates. Clamp the sample with clamps and place it in a forced-air oven. The curing process is to heat at 80°C for 2 hours, and then heat at 120°C for 2 hours to complete the curing.

[0045] (5) After the cured sample has cooled, immerse it in distilled water and slowly separate the epoxy resin film from the glass plate. Since the pore-forming agent PEG200 is miscible with water, the removed epoxy resin film is ultrasonically washed and soaked in distilled water to remove the pore-forming agent. Cut the epoxy resin film into a 16mm diameter circular sheet and dry it to obtain the unactivated electrolyte.

[0046] (6) The unactivated electrolyte described in the previous step was tested using a high-performance fully automatic mercury porosimeter, and the average pore size was 298 nm. BET test was performed, and the average pore size was 24 nm.

[0047] (7) Transfer the film to a glove box and immerse it in an electrolyte solution (the electrolyte solution is a mixed solution of lithium hexafluorophosphate doped with dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate, with a mass ratio of dimethyl carbonate: ethyl methyl carbonate: ethylene carbonate = 1:1:1, concentration 1M) for 24 hours. The final product is the gel polymer electrolyte.

[0048] (8) Assemble the gel polymer electrolyte described in the previous step into a battery in a glove box filled with argon gas.

[0049] (9) Using the AC impedance method, the ionic conductivity of this gel polymer electrolyte was measured to be 1.34 × 10⁻⁶ at 25°C. -3 S / cm.

[0050] Example 3

[0051] (1) Prepare a polyvinyl alcohol aqueous solution: Weigh the calculated amount of polyvinyl alcohol, add it to distilled water, stir evenly at 100°C, and prepare a polyvinyl alcohol aqueous solution with a mass fraction of 2%.

[0052] (2) Pour the prepared polyvinyl alcohol aqueous solution onto a clean glass plate. Use a coating rod to spread the solution evenly on the glass plate to form a water film. Then place the glass plate on a hot table at 105°C and heat until the water is removed to obtain a glass plate with a polyvinyl alcohol film coated on the surface.

[0053] (3) Add bisphenol A diglycidyl ether (DGEBA, E51) and pore-forming agent polyethylene glycol (PEG200) (mass ratio of 1:2.75) to a screw-top bottle, stir at 60°C for 1 hour until the mixture is uniform, and then add equal amounts of curing agent diaminodicyclohexylmethane (PACM) and polyetheramine (D230), wherein PACM:D230 is 5:5. After stirring evenly with residual heat, place in a vacuum dryer for degassing treatment.

[0054] (4) Place gaskets around the prepared glass plate coated with polyvinyl alcohol film, and pour the degassed solution onto the glass plate. Place another glass plate coated with polyvinyl alcohol on the gaskets, forming a sandwich structure between the two glass plates. Clamp the sample with clamps and place it in a forced-air oven. The curing process is to heat at 80°C for 2 hours, and then heat at 120°C for 2 hours to complete the curing.

[0055] (5) After the cured sample has cooled, immerse it in distilled water and slowly separate the epoxy resin film from the glass plate. Since the pore-forming agent PEG200 is miscible with water, the removed epoxy resin film is ultrasonically washed and soaked in distilled water to remove the pore-forming agent. Cut the epoxy resin film into a 16mm diameter circular sheet and dry it to obtain the unactivated electrolyte.

[0056] (6) The unactivated electrolyte described in the previous step was subjected to BET testing, and the average pore size was 35 nm.

[0057] (7) Transfer the film to a glove box and immerse it in an electrolyte solution (the electrolyte solution is a mixed solution of lithium hexafluorophosphate doped with dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate, with a mass ratio of dimethyl carbonate: ethyl methyl carbonate: ethylene carbonate = 1:1:1, concentration 1M) for 24 hours. The final product is the gel polymer electrolyte.

[0058] (8) Assemble the gel polymer electrolyte described in the previous step into a battery in a glove box filled with argon gas.

[0059] (9) Using the AC impedance method, the ionic conductivity of this gel polymer electrolyte was measured to be 0.83 × 10⁻⁶ at 25°C. -3 S / cm.

[0060] Example 4

[0061] (1) Prepare a polyvinyl alcohol aqueous solution: Weigh the calculated amount of polyvinyl alcohol, add it to distilled water, stir evenly at 100°C, and prepare a polyvinyl alcohol aqueous solution with a mass fraction of 2%.

[0062] (2) Pour the prepared polyvinyl alcohol aqueous solution onto a clean glass plate. Use a coating rod to spread the solution evenly on the glass plate to form a water film. Then place the glass plate on a hot table at 105°C and heat until the water is removed to obtain a glass plate with a polyvinyl alcohol film coated on the surface.

[0063] (3) Add bisphenol A diglycidyl ether (DGEBA, E51) and pore-forming agent polyethylene glycol (PEG200) (mass ratio of 1:2.75) to a screw-top bottle, stir at 60°C for 1 hour until the mixture is uniform, then add equal amounts of curing agent diaminodicyclohexylmethane (PACM) and polyetheramine (D230), wherein PACM:D230 is 3:7. After stirring evenly with residual heat, place in a vacuum dryer for degassing treatment.

[0064] (4) Place gaskets around the prepared glass plate coated with polyvinyl alcohol film, and pour the degassed solution onto the glass plate. Place another glass plate coated with polyvinyl alcohol on the gaskets, forming a sandwich structure between the two glass plates. Clamp the sample with clamps and place it in a forced-air oven. The curing process is to heat at 80°C for 2 hours, and then heat at 120°C for 2 hours to complete the curing.

[0065] (5) After the cured sample has cooled, immerse it in distilled water and slowly separate the epoxy resin film from the glass plate. Since the pore-forming agent PEG200 is miscible with water, the removed epoxy resin film is ultrasonically washed and soaked in distilled water to remove the pore-forming agent. Cut the epoxy resin film into a 16mm diameter circular sheet and dry it to obtain the unactivated electrolyte.

[0066] (6) The unactivated electrolyte described in the previous step was subjected to BET testing, and the average pore size was 30 nm.

[0067] (7) Transfer the film to a glove box and immerse it in an electrolyte solution (the electrolyte solution is a mixed solution of lithium hexafluorophosphate doped with dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate, with a mass ratio of dimethyl carbonate: ethyl methyl carbonate: ethylene carbonate = 1:1:1, concentration 1M) for 24 hours. The final product is the gel polymer electrolyte.

[0068] (8) Assemble the gel polymer electrolyte described in the previous step into a battery in a glove box filled with argon gas.

[0069] (9) Using the AC impedance method, the ionic conductivity of this gel polymer electrolyte was measured to be 0.78 × 10⁻⁶ at 25°C. -3 S / cm.

[0070] Example 5

[0071] (1) Prepare a polyvinyl alcohol aqueous solution: Weigh the calculated amount of polyvinyl alcohol, add it to distilled water, stir evenly at 100°C, and prepare a polyvinyl alcohol aqueous solution with a mass fraction of 2%.

[0072] (2) Pour the prepared polyvinyl alcohol aqueous solution onto a clean glass plate. Use a coating rod to spread the solution evenly on the glass plate to form a water film. Then place the glass plate on a hot table at 105°C and heat until the water is removed to obtain a glass plate with a polyvinyl alcohol film coated on the surface.

[0073] (3) Add bisphenol A diglycidyl ether (DGEBA, E51) and pore-forming agent polyethylene glycol (PEG200) (mass ratio of 1:2.75) into a screw bottle, stir at 60°C for 1 hour until the mixture is uniform, then add an equivalent amount of curing agent polyetheramine (D230), stir evenly using residual heat, and then put it into a vacuum dryer for degassing treatment.

[0074] (4) Place gaskets around the prepared glass plate coated with polyvinyl alcohol film, and pour the degassed solution onto the glass plate. Place another glass plate coated with polyvinyl alcohol on the gaskets, forming a sandwich structure between the two glass plates. Clamp the sample with clamps and place it in a forced-air oven. The curing process is to heat at 80°C for 2 hours, and then heat at 120°C for 2 hours to complete the curing.

[0075] (5) After the cured sample has cooled, immerse it in distilled water and slowly separate the epoxy resin film from the glass plate. Since the pore-forming agent PEG200 is miscible with water, the removed epoxy resin film is ultrasonically washed and soaked in distilled water to remove the pore-forming agent. Cut the epoxy resin film into a 16mm diameter circular sheet and dry it to obtain the unactivated electrolyte.

[0076] (6) The unactivated electrolyte described in the previous step was subjected to BET testing, and the average pore size was 17 nm.

[0077] (7) Transfer the film to a glove box and immerse it in an electrolyte solution (the electrolyte solution is a mixed solution of lithium hexafluorophosphate doped with dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate, with a mass ratio of dimethyl carbonate: ethyl methyl carbonate: ethylene carbonate = 1:1:1, concentration 1M) for 24 hours. The final product is the gel polymer electrolyte.

[0078] (8) Assemble the gel polymer electrolyte described in the previous step into a battery in a glove box filled with argon gas.

[0079] (9) Using the AC impedance method, the ionic conductivity of this gel polymer electrolyte was measured to be 0.99 × 10⁻⁶ at 25°C. -3 S / cm.

[0080] Example 6

[0081] (1) Prepare a polyvinyl alcohol aqueous solution: Weigh the calculated amount of polyvinyl alcohol, add it to distilled water, stir evenly at 100°C, and prepare a polyvinyl alcohol aqueous solution with a mass fraction of 2%.

[0082] (2) Pour the prepared polyvinyl alcohol aqueous solution onto a clean glass plate. Use a coating rod to spread the solution evenly on the glass plate to form a water film. Then place the glass plate on a hot table at 105°C and heat until the water is removed to obtain a glass plate with a polyvinyl alcohol film coated on the surface.

[0083] (3) Bisphenol A diglycidyl ether (DGEBA, E51) and pore-forming agent polyethylene glycol (PEG200) (mass ratio of 1:2.75) were added to a screw-top bottle and stirred at 60°C for 1 hour until the mixture was uniform. Then, 5% zinc acetate dihydrate (Zn(CH3COO)2·2H2O) was added and stirred at 60°C for 2 hours. Then, equal amounts of curing agent diaminodicyclohexylmethane (PACM) and polyetheramine (D230) were added, with a PACM:D230 ratio of 7:3. After stirring evenly with residual heat, the mixture was placed in a vacuum dryer for degassing treatment.

[0084] (4) Place gaskets around the glass plate coated with polyvinyl alcohol film prepared in step 2, and pour the degassed solution onto the glass plate. Place another glass plate coated with polyvinyl alcohol on the gaskets, forming a sandwich structure between the two glass plates. Clamp the sample with clamps and place it in a forced-air oven. The curing process is to heat at 80°C for 2 hours, and then heat at 120°C for 2 hours to complete the curing.

[0085] (5) After the cured sample has cooled, immerse it in distilled water and slowly separate the epoxy resin film from the glass plate. Since the pore-forming agent PEG200 is miscible with water, the removed epoxy resin film is ultrasonically washed and soaked in distilled water to remove the pore-forming agent. Cut the epoxy resin film into a 16mm diameter circular sheet and dry it to obtain the unactivated electrolyte.

[0086] (6) Dissolve 2-methylimidazole in anhydrous ethanol and stir magnetically until completely dissolved; then place the porous epoxy resin membrane with zinc acetate dihydrate (Zn(CH3COO)2·2H2O) prepared above into the 2-methylimidazole solution and let it stand for 24 h to allow MOF to grow on the membrane; wash the porous epoxy resin membrane with grown MOF three times with ethanol and dry it in an oven at 60℃ for 10 h to obtain a porous epoxy resin membrane with in-situ grown MOF.

[0087] (7) Transfer the film to a glove box and immerse it in an electrolyte solution (the electrolyte solution is a mixed solution of lithium hexafluorophosphate doped with dimethyl carbonate, ethyl methyl carbonate and ethylene carbonate, with a mass ratio of dimethyl carbonate: ethyl methyl carbonate: ethylene carbonate = 1:1:1, concentration 1M) for 24 hours. The final product is the gel polymer electrolyte.

[0088] (8) Assemble the gel polymer electrolyte described in the previous step into a battery in a glove box filled with argon gas.

[0089] (9) Using the AC impedance method, the ionic conductivity of this gel polymer electrolyte was measured to be 1.7 × 10⁻⁶ at 25 °C. -3 S / cm.

[0090] Comparative Example 1

[0091] Patent CN104335391A discloses a diaphragm for a non-aqueous electrolyte storage device comprising an epoxy resin porous membrane. The process includes: preparing an epoxy resin composition containing epoxy resin, a curing agent, and a pore-forming agent; cutting the cured epoxy resin composition into sheets or curing a sheet-shaped form of the epoxy resin composition to obtain an epoxy resin sheet; removing the pore-forming agent from the epoxy resin sheet using a halogen-free solvent to form the epoxy resin porous membrane; irradiating the epoxy resin porous membrane with infrared light to determine its infrared absorption characteristics; and calculating the membrane thickness and / or average pore size of the epoxy resin porous membrane based on its infrared absorption characteristics.

[0092] Regarding pore size control, patent CN104335391A only yielded micron-sized macropores with a pore size range of 150–400 nm, and a room-temperature ionic conductivity of only 0.3 × 10⁻⁶. -4 ~0.5×10 -3 Within the S / cm range, this single macroporous structure has corresponding limitations. This invention designs the pore structure by adjusting the ratio of two different curing agents, resulting in electrolyte membranes with micro-mesoporous structures, mesoporous-macroporous coexistence structures, and macroporous structures.

[0093] Comparative Example 2

[0094] The patent with publication number CN110085909A describes the preparation of a composite solid electrolyte material. The process involves dispersing a metal-organic framework material and an alkali metal or alkaline earth metal salt in an organic solvent, then adding an ion-conducting polymer solution, stirring until homogeneous, allowing it to stand, and finally pouring it into a mold to dry and solidify.

[0095] Regarding the preparation technology, the preparation method described in patent CN110085909A easily leads to uneven dispersion of the metal-organic framework material in the system, resulting in agglomeration and affecting the overall performance of the electrolyte material. The final room temperature ionic conductivity obtained was 3.16 × 10⁻⁶.-7 S / cm, 3.16×10 -5 S / cm. This invention grows metal-organic framework (MOF) materials in situ on the surface and pores of a porous epoxy resin-based electrolyte membrane. Compared to directly adding embedded MOFs, this eliminates the need for pre-preparation of MOF materials and dispersion in the casting solution, effectively avoiding the dispersion challenges of MOF materials. Furthermore, by in-situ fixing the MOF to the surface and pores of the porous epoxy resin-based electrolyte membrane, the microporous structure of the MOF allows small ions to pass through internal pore channels, thereby suppressing large anions. The interaction between surface groups and the electrolyte improves ionic conductivity, electrochemical window, and lithium-ion transference number. The ordered porosity and narrow pore window of the MOF material contribute to uniform lithium-ion deposition, thus suppressing lithium dendrite formation.

[0096] However, the above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made in accordance with the scope of protection of the present invention should still fall within the scope of the claims of the present invention.

Claims

1. An epoxy resin-based gel electrolyte, characterized in that, The epoxy resin-based gel electrolyte has a porous structure with an average pore size of 17–35 nm; a metal-organic framework structure material is grown at reduction sites on the epoxy resin-based gel electrolyte; the epoxy resin is one or more combinations of DGEBA, DGEBF, DGEBS, EPN, ECN, and HBR; the metal-organic framework structure material is one or more combinations of Zn(acac)2, Co(NO3)2·6H2O, ZnSO4, Zn(NO3)2·6H2O, Zn(ClO4)2, Zn(CH3COO)2·2H2O, and ZnCl2. The epoxy resin-based gel electrolyte is prepared using a method comprising the following steps: (1) Prepare an aqueous solution of polyvinyl alcohol; (2) Spread the prepared polyvinyl alcohol aqueous solution evenly on the glass plate, heat it to remove the water, and obtain a glass plate with a polyvinyl alcohol film coated on the surface. (3) Mix epoxy resin and pore-forming agent, then add metal salt and stir evenly to obtain a solution; the metal salt is one or more combinations of Zn(acac)2, Co(NO3)2·6H2O, ZnSO4, Zn(NO3)2·6H2O, Zn(ClO4)2, Zn(CH3COO)2·2H2O, and ZnCl2; the mass fraction of the metal salt in the mixture of epoxy resin and metal salt is 5-25%; the epoxy resin is one or more combinations of DGEBA, DGEBF, DGEBS, EPN, ECN, and HBR; the mass ratio of epoxy resin to pore-forming agent is 1:(1-3); (4) Add curing agent to the solution obtained in step (3), stir evenly, and then perform degassing treatment; (5) Place a gasket around the glass plate with a polyvinyl alcohol film coated on the surface obtained in step (2), pour the solution obtained in step (4) onto the glass plate with a polyvinyl alcohol film coated on the surface obtained in step (2), place another glass plate coated with polyvinyl alcohol on the gasket, the two glass plates form a sandwich structure, heat and cure to obtain a film; immerse the film in a solvent, remove the pore-forming agent, and dry to obtain an electrolyte membrane; place the obtained electrolyte membrane in an organic ligand solution, let it stand, wash and dry to obtain a porous epoxy resin membrane of in-situ grown metal-organic framework structure material; the molar ratio of the organic ligand to the metal salt is (2~8):1; (6) The porous epoxy resin membrane prepared in step (5) is transferred to a glove box to wet the electrolyte to obtain a gel electrolyte.

2. The epoxy resin-based gel electrolyte according to claim 1, characterized in that, In step (3), the pore-forming agent is one or more combinations of PEG200, PEG400, PEG600, and PEG2000.

3. The epoxy resin-based gel electrolyte according to claim 1, characterized in that, In step (4), the curing agent is one or more combinations of PACM, D230, D400, TETA, DDM, and DDS; The epoxy resin and the curing agent are added in equal amounts to the active groups, and the curing agent is added in one or more combinations.

4. The application of the epoxy resin-based gel electrolyte as described in claim 1 as a battery material.

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