Frame film for sealing bipolar plate and electrode frame in flow battery

Abstract

The invention provides a frame membrane for sealing a bipolar plate and an electrode frame in a flow battery. The frame film comprises a base material and coatings located on the two opposite surfaces of the base material, and raw materials of the coatings comprise chlorinated polypropylene resin, ethylene acrylate maleic anhydride copolymer, an initiator, a cross-linking agent, a binder and an anti-hydrolysis agent according to the mass ratio of (20-50): (50-80): (1-5): (5-10): (10-25): (5-10). The frame film provided by the invention can simultaneously generate relatively strong bonding force with a bipolar plate and an electrode frame, and due to a specific dual-curing system in the formula, the frame film can still keep excellent performance under a strong acid condition, has relatively strong corrosion resistance and is suitable for long-term use of the flow battery.

Description

Technical Field

[0001] The invention belongs to the field of liquid flow battery packaging materials and relates to a frame film used for sealing a bipolar plate and an electrode frame in a liquid flow battery. Background Art

[0002] As a core component of large-scale energy storage systems, the sealing performance of flow batteries directly affects the cycle life and operational safety of the batteries. The current mainstream sealing technologies mainly use two solutions: mechanical pressing of rubber gaskets or hot-melt adhesive hot-pressing packaging. However, there are significant technical bottlenecks in practical applications.

[0003] The structure of flow battery mainly consists of two parts: the stack module and the electrolyte circulation system. As the core component of the battery, the stack is usually stacked with multiple repeated units. Each unit contains key components such as bipolar plates, electrodes, proton exchange membranes and sealing frames. If the sealing between the bipolar plate and the electrode frame relies on rubber pads, there will be a series of problems such as interface deformation leakage, material aging failure, and complex assembly process. Similarly, if it relies on hot melt adhesive film sealing, there will be overflow of glue to pollute the electrochemical interface, high-voltage assembly will damage the components, and the hot melt adhesive does not actually form adhesion with the bipolar plate and the electrode frame, so there is still a risk of leakage in long-term use.

[0004] Moreover, the use of silicone pads and hot melt adhesives to achieve sealing is not only costly, but also has low production efficiency, making it difficult to achieve continuous and mechanized production. At the same time, the above-mentioned rubber sealing gaskets will age and lose their sealing function as the operating time increases, and the maintenance of the battery stack will increase the cost investment. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a frame film for sealing the bipolar plate and the electrode frame in the liquid flow battery. The frame film of the present invention can achieve strong bonding with the bipolar plate and the electrode frame at the same time. The unique dual-curing system in the formula enables it to maintain excellent performance under strong acid conditions, has strong corrosion resistance, and is suitable for long-term use of liquid flow batteries.

[0006] Specifically, the first aspect of the present invention provides a frame film for sealing bipolar plates and electrode frames in liquid flow batteries, wherein the frame film includes a substrate and a coating located on two opposite surfaces of the substrate, wherein the raw materials of the coating include a chlorinated polypropylene resin, an ethylene acrylate maleic anhydride copolymer, an initiator, a cross-linking agent, a binder and an anti-hydrolysis agent in a mass ratio of (20-50):(50-80):(1-5):(5-10):(10-25):(5-10).

[0007] In one or more embodiments, the material of the substrate is selected from one or more of PP (polypropylene), PEN (polyethylene naphthalate), PPS (polyphenylene sulfide) and PET (polyethylene terephthalate).

[0008] In one or more embodiments, the coating has a thickness of 10-30 μm.

[0009] In one or more embodiments, the ethylene acrylate maleic anhydride copolymer is a copolymer of ethylene, acrylate and maleic anhydride monomers or a copolymer of ethylene, acrylate, maleic anhydride monomers and a functional monomer.

[0010] In one or more embodiments, the functional monomer contains one or more groups selected from epoxy groups, anhydride groups, and carbonyl groups.

[0011] In one or more embodiments, in the ethylene acrylate maleic anhydride copolymer, the mass fraction of ethylene structural units is 81-85%, the mass fraction of acrylate structural units is 14-18%, and the mass fraction of maleic anhydride structural units is 0.1-0.5%.

[0012] In one or more embodiments, the initiator is selected from one or more of a peroxide initiator and an azo initiator.

[0013] In one or more embodiments, the peroxy initiator includes one or more of dibenzoyl peroxide (also known as benzoyl peroxide, BPO), tert-butyl peroxydibenzoate, lauroyl peroxide, di-tert-butyl peroxide, and tert-butyl peroxy-2-ethylhexanoate.

[0014] In one or more embodiments, examples of the azo initiator include one or more of azobisisobutyronitrile, dimethyl azobisisobutyrate, and 2,2′-azobis(2,4-dimethylvaleronitrile).

[0015] In one or more embodiments, the crosslinking agent is selected from isocyanate curing agents.

[0016] In one or more embodiments, the crosslinking agent is selected from one or more of liquefied MDI, polymeric MDI, Covestro L-75 curing agent, and Covestro N3300 HDI.

[0017] In one or more embodiments, the binder is selected from tackifying resins.

[0018] In one or more embodiments, the tackifying resin includes one or more of a dammar resin, a rosin resin, a rosin derivative resin, and a phenolic resin.

[0019] In one or more embodiments, the anti-hydrolysis agent is a carbodiimide anti-hydrolysis agent.

[0020] A second aspect of the present invention provides a method for preparing a frame film as described in any embodiment of the present invention, the method comprising the following steps: (1) uniformly dispersing the raw materials of the coating in a solvent, filtering and degassing to obtain a coating solution; (2) applying the coating solution onto one surface of the substrate, drying to obtain a first coating, and covering the protective adhesive surface with a release film; then applying the coating solution onto the other surface of the substrate, drying to obtain a second coating, and covering the protective adhesive surface with a release film; (3) The obtained double-sided coated substrate is aged.

[0021] In one or more embodiments, the solid content of the chlorinated polypropylene resin is 5 wt % to 30 wt %.

[0022] In one or more embodiments, the ethylene acrylate maleic anhydride copolymer has a solid content of 5 wt% to 30 wt%.

[0023] In one or more embodiments, the solvent is selected from one or more of xylene, N,N-dimethylformamide, toluene, cyclohexane, methyl ethyl ketone, and tetrahydrofuran.

[0024] In one or more embodiments, the drying temperature is 80-120°C.

[0025] In one or more embodiments, the aging temperature is 40-60° C., and the aging time is 0.5-3 days.

[0026] A third aspect of the present invention provides a liquid flow battery, comprising a frame membrane for sealing a bipolar plate and an electrode frame in a liquid flow battery as described in any embodiment of the present invention.

[0027] Beneficial effects of the present invention: The frame film of the present invention can achieve strong bonding with the bipolar plate and the electrode frame through formula design. The unique dual-curing system in the formula enables it to maintain excellent performance under strong acid conditions, has strong corrosion resistance, and is suitable for long-term use of liquid flow batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the structure of a flow battery stack using the frame film of the present invention in some embodiments.

[0029] Description of reference numerals: Copper plate 1, bipolar plate 2, frame membrane 3, electrode frame 4, electrode 5, silicone pad 6, proton membrane 7. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in this article. Unless otherwise specified, all technical and scientific terms used in this article are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definitions in this article shall prevail.

[0031] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0032] Herein, “comprising”, “including”, “containing” and similar terms encompass the meanings of “consisting essentially of” and “consisting of”. For example, when “A comprises B and C” is disclosed herein, “A consists essentially of B and C” and “A consists of B and C” should be deemed to be disclosed herein.

[0033] In this document, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible sub-ranges and individual values ​​within the range (including integers and fractions).

[0034] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0035] Herein, when describing embodiments or examples, it should be understood that they are not used to limit the present invention to these embodiments or examples. On the contrary, all substitutes, improvements and equivalents of the methods and materials described in the present invention can be included in the scope limited by the claims.

[0036] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0037] In view of the defects of the prior art, the present invention provides a frame film for sealing bipolar plates and electrode frames. Through formula design, the frame film can achieve strong bonding with the bipolar plates and electrode frames at the same time. The unique dual-curing system in the formula enables it to maintain excellent performance under strong acid conditions and has strong corrosion resistance. It effectively improves a series of problems such as complex assembly process and leakage risk of battery stack, greatly reduces production costs and improves production efficiency, and is suitable for long-term use of liquid flow batteries.

[0038] In some embodiments, such as Figure 1 As shown, the liquid flow battery stack includes an end plate (such as a copper plate 1), a bipolar plate 2, a frame film 3 of the present invention, an electrode frame 4, an electrode 5, a silicone pad 6 and a proton membrane 7, wherein the frame film 3 is arranged between the bipolar plate 2 and the electrode frame 4, and the frame film 3 is double-sidedly taped to bond and solidify the bipolar plate 2 and the electrode frame 4, so that a bonding force is formed between the bipolar plate 2 and the electrode frame 4 to achieve sealing.

[0039] The frame film of the present invention comprises a substrate and coatings located on two opposite surfaces of the substrate.

[0040] In the frame film of the present invention, the material of the base material can be selected from one or more of PP (polypropylene), PEN (polyethylene naphthalate), PPS (polyphenylene sulfide) and PET (polyethylene terephthalate).

[0041] In the frame film of the present invention, the raw materials of the coating include chlorinated polypropylene resin, ethylene acrylate maleic anhydride copolymer, initiator, crosslinking agent, binder and anti-hydrolysis agent. In some embodiments, the raw materials of the coating consist of chlorinated polypropylene resin, ethylene acrylate maleic anhydride copolymer, initiator, crosslinking agent, binder and anti-hydrolysis agent.

[0042] The present invention finds that, compared with the use of other polymers, the use of chlorinated polypropylene resin and ethylene acrylate maleic anhydride copolymer to prepare the coating of the frame film can improve the corrosion resistance of the glue layer, and the ethylene acrylate maleic anhydride copolymer can enhance the bonding force with the bipolar plate and the electrode frame; the chlorinated polypropylene resin and the ethylene acrylate maleic anhydride copolymer form a dual-curing system in the coating to produce a synergistic effect, so that the coating can still maintain excellent performance under strong acid conditions, has strong corrosion resistance and strength performance, especially shear strength, obtains better sealing performance and service life, and is suitable for long-term use of liquid flow batteries.

[0043] The ethylene acrylate maleic anhydride copolymer suitable for the present invention can be a copolymer of ethylene, acrylate and maleic anhydride monomers. The mass ratio of the ethylene acrylate maleic anhydride copolymer to the chlorinated polypropylene resin can be (20-50): (50-80).

[0044] In the ethylene acrylate maleic anhydride copolymer, the mass fraction of the ethylene structural unit may be 81%-85%; the mass fraction of the acrylate structural unit may be 14%-18%; and the mass fraction of the maleic anhydride monomer structural unit may be 0.1%-0.5%.

[0045] In the present invention, acrylate monomers include acrylates (e.g., alkyl acrylates) and methacrylates (e.g., alkyl methacrylates). Acrylate monomers suitable for use in the present invention include, but are not limited to, one or more selected from methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, etc. In some embodiments, the acrylate monomer is butyl acrylate.

[0046] In some embodiments, the ethylene acrylate maleic anhydride copolymer is a copolymer of ethylene, a copolymer of an acrylate, and maleic anhydride monomers.

[0047] The initiator suitable for the present invention can be a peroxide initiator, an azo initiator or a combination of the two. Examples of available peroxide initiators include dibenzoyl peroxide (also known as benzoyl peroxide, BPO), tert-butyl peroxydibenzoate, lauroyl peroxide, di-tert-butyl peroxide, tert-butyl peroxide 2-ethylhexanoate, etc. Examples of available azo initiators include azobisisobutyronitrile, dimethyl azobisisobutyrate, 2,2'-azobis(2,4-dimethylvaleronitrile), etc. In some embodiments, the initiator is dibenzoyl peroxide. The mass ratio of initiator to chlorinated polypropylene resin can be (1-5): (20-50).

[0048] The crosslinking agent suitable for the present invention can be an isocyanate curing agent. Examples of available crosslinking agents include liquefied MDI, polymerized MDI, Covestro L-75 curing agent, Covestro N3300 HDI, etc. In some embodiments, the crosslinking agent is liquefied MDI. The mass ratio of the crosslinking agent to the chlorinated polypropylene resin can be (5-10): (20-50).

[0049] Herein, MDI is the abbreviation of 4,4'-diphenylmethane diisocyanate. Liquefied MDI is a modified MDI that is made liquid at room temperature by introducing urethane or carbodiimide groups into 4,4'-diphenylmethane diisocyanate. Herein, HDI is the abbreviation of hexamethylene diisocyanate.

[0050] The binder suitable for the present invention can be a tackifying resin. Examples of available tackifying resins include, but are not limited to, dammar resin, rosin resin, rosin derivative resin, phenolic resin, etc. In some embodiments, the binder is dammar resin. The mass ratio of the binder to the chlorinated polypropylene resin can be (10-25): (20-50).

[0051] The anti-hydrolysis agent suitable for the present invention can be a carbodiimide anti-hydrolysis agent. Carbodiimide is a class of organic compounds containing a -C=N=C- structural unit. Examples of available carbodiimide anti-hydrolysis agents include Stabaxol I, Stabaxol P, Stabaxol P200, Stabaxol P400, etc. In some embodiments, the anti-hydrolysis agent is a polycarbodiimide anti-hydrolysis agent, such as Stabaxol I or Stabaxol P200. The mass ratio of the anti-hydrolysis agent to the chlorinated polypropylene resin can be (5-10): (20-50).

[0052] In the frame film of the present invention, the thickness of the two coating layers on the substrate may be 5-25 μm. The thickness of the two coating layers on the substrate may be equal or unequal.

[0053] The frame film of the present invention can be prepared by dissolving the raw materials of the coating in a solvent to obtain a coating solution, applying the coating solution to both surfaces of a substrate film such as a polypropylene film, and drying and aging. For example, a chlorinated polypropylene resin solution, an ethylene acrylate maleic anhydride copolymer solution, an initiator, a crosslinking agent, a binder and an anti-hydrolysis agent can be mixed, and the solution can be coated on a polypropylene film, and then dried and aged to obtain the frame film.

[0054] In some embodiments, the method for preparing the frame film of the present invention comprises the following steps: (1) uniformly mixing a chlorinated polypropylene resin solution, an ethylene acrylate maleic anhydride copolymer solution, an initiator, a crosslinking agent, a natural dammar resin and an anti-hydrolysis agent, filtering and degassing to obtain a coating solution; (2) applying the coating solution onto one surface of the substrate, drying to obtain a first coating, and covering the protective adhesive surface with a release film; then applying the coating solution onto the other surface of the substrate, drying to obtain a second coating, and covering the protective adhesive surface with a release film; (3) The obtained double-sided coated substrate is aged.

[0055] In step (1), the solid content of the chlorinated polypropylene resin solution may be 5wt%-30wt%, preferably 15wt%-25wt%. The solvent in the chlorinated polypropylene resin solution may be selected from one or more of xylene, N,N-dimethylformamide, toluene, cyclohexane, methyl ethyl ketone and tetrahydrofuran. In some embodiments, the solvent in the chlorinated polypropylene resin solution is xylene.

[0056] In step (1), the solid content of the ethylene acrylate maleic anhydride copolymer solution may be 5wt%-30wt%, preferably 12wt%-22wt%. The solvent in the ethylene acrylate maleic anhydride copolymer solution may be selected from one or more of xylene, N,N-dimethylformamide, toluene, cyclohexane, methyl ethyl ketone and tetrahydrofuran. In some embodiments, the solvent in the ethylene acrylate maleic anhydride copolymer solution is xylene and N,N-dimethylformamide.

[0057] In some embodiments, in step (1), the chlorinated polypropylene resin can be dissolved in a solvent (such as xylene) in a dissolving kettle to obtain a chlorinated polypropylene resin with a suitable solid content, and then cooled to room temperature for use. The ethylene acrylate maleic anhydride copolymer is dissolved in a solvent (such as a mixed solvent of xylene and N,N-dimethylformamide) in a dissolving kettle to obtain an ethylene acrylate maleic anhydride copolymer with a suitable solid content, and then cooled to room temperature for use. Then, the first auxiliary agent, initiator, auxiliary cross-linking agent, curing agent and cross-linking agent are mixed with the prepared chlorinated polypropylene resin solution and ethylene acrylate maleic anhydride copolymer solution in a certain proportion to form a uniform solution, the solution in the kettle is filtered through a filter, and the filtered solution is placed in a vacuum degassing kettle to evacuate the air bubbles in the solution, and then allowed to stand for use.

[0058] In step (2), the coating solution is applied to two opposite surfaces of the substrate and dried to obtain the coatings. In the present invention, for the convenience of description, the first coating and the second coating are used.

[0059] In step (2), the coating thickness of the coating solution on the substrate surface can be adjusted according to the target thickness of the coating.

[0060] In some embodiments, in step (2), the prepared coating solution can be delivered to the coating head by a delivery pump, the coating machine is started, and the coating is performed by the coating head. The coating head can be in the form of a micro-dimple, a comma scraper, a slit, etc. The thickness of the coating can be controlled by controlling the pump delivery speed, the scraper height, and the casting speed. Then, the frame film coated with the coating is sent to an oven for drying to evaporate the solvent. The drying temperature can be 80-120°C.

[0061] After drying, cover with release film to protect the adhesive surface. Then put the prepared double-sided adhesive into the drying room for curing. The curing temperature is 40-60℃ and the curing time is 0.5-3 days.

[0062] The present invention also provides a liquid flow battery, which comprises a bipolar plate, an electrode frame, and a frame membrane for sealing the bipolar plate and the electrode frame in the liquid flow battery. The liquid flow battery of the present invention is preferably an all-vanadium liquid flow battery.

[0063] The present invention will be described below in the form of specific examples. It should be understood that these examples are merely illustrative and are not intended to limit the scope of the present invention. The methods, reagents and materials used in the examples are, unless otherwise stated, conventional methods, reagents and materials in the art. The raw material compounds in the examples can all be purchased through commercial routes.

[0064] The chlorinated polypropylene resin used in the examples and comparative examples was purchased from Shenzhen Jitian Chemical Co., Ltd. with the brand name E0102.

[0065] The ethylene acrylate maleic anhydride copolymer used in the examples and comparative examples was purchased from SK of South Korea with the brand name LOTADER® 4403, wherein the mass fraction of the ethylene structural unit is 81.7%, the mass fraction of the acrylate structural unit is 18%, and the mass fraction of the maleic anhydride structural unit is 0.3%.

[0066] The PP films used in the examples and comparative examples were purchased from Dongguan Xuecheng Plastic Products Co., Ltd., with the brand name LDM-010.

[0067] Example 1 1) Dissolve chlorinated polypropylene resin (CPP) Chlorinated polypropylene resin and xylene were mixed at a mass ratio of 20:80 to obtain a mixture with a solid content of 20%. The mixture was stirred at 80° C. and a stirring speed of 600 r / min until the solid particles were completely dissolved to obtain a translucent chlorinated polypropylene resin solution.

[0068] 2) Dissolved ethylene acrylate maleic anhydride copolymer (EMH) The ethylene acrylate maleic anhydride copolymer raw material and the mixed solvent were mixed in a mass ratio of 15:85 to obtain a mixture with a solid content of 15%. The mixed solvent was xylene and N,N-dimethylformamide in a mass ratio of 90:10. The mixture was stirred at 80°C at a stirring speed of 600 r / min until the solid particles were completely dissolved to obtain a translucent ethylene acrylate maleic anhydride copolymer solution.

[0069] 3) Preparation of coating solution The chlorinated polypropylene resin solution and the ethylene acrylate maleic anhydride copolymer solution were mixed evenly in a solute mass ratio of 1:1, and the initiator benzoyl peroxide BPO, the crosslinking agent liquefied MDI, the natural dammar resin E1001 and the polycarbodiimide anti-hydrolysis agent (Stabaxol P200) were added, mixed evenly, filtered, and defoamed to obtain a coating solution. Among them, the mass ratio of the chlorinated polypropylene resin, the ethylene acrylate maleic anhydride copolymer, the benzoyl peroxide BPO, the crosslinking agent liquefied MDI, the natural dammar resin E1001 and the Stabaxol P200 was 50:50:3:5:10:5.

[0070] 4) Coating The coating solution obtained in step 3 was coated on the PP film to obtain a wet coating with a thickness of 250 μm, and the solvent was dried at 80° C. After drying, a PET release film was applied to protect the adhesive surface.

[0071] The coating solution of step 3 was applied to the other side again to obtain a wet coating with a thickness of 250 μm, and the solvent was dried at 80° C. After drying, a PET release film was applied as a protective film.

[0072] 5) Ripening The double-sided adhesive tape prepared in step 4) was placed in a 50°C drying room for curing for 48 hours.

[0073] Example 2 Steps 1) and 2) are the same as in Example 1.

[0074] 3) Preparation of coating solution The chlorinated polypropylene resin solution and the ethylene acrylate maleic anhydride copolymer solution were mixed evenly in a solute mass ratio of 1:1, and an initiator benzoyl peroxide BPO, a crosslinking agent liquefied MDI, a natural dammar resin E1001 and a polycarbodiimide anti-hydrolysis agent (Stabaxol 1) were added, mixed evenly, filtered, and defoamed to obtain a coating solution. Among them, the mass ratio of the chlorinated polypropylene resin, the ethylene acrylate maleic anhydride copolymer, the benzoyl peroxide BPO, the crosslinking agent liquefied MDI, the natural dammar resin E1001 and the Stabaxol P200 was 50:50:4:8:10:6.

[0075] 4) Coating The coating solution obtained in step 3 was coated on the PP material to obtain a wet coating with a thickness of 250 μm, and the solvent was dried at 80° C. After drying, a PET release film was applied to protect the adhesive surface.

[0076] The coating solution of step 3 was applied to the other side again to obtain a wet coating with a thickness of 250 μm, and the solvent was dried at 80° C. After drying, a PET release film was applied as a protective film.

[0077] 5) Ripening The prepared double-sided adhesive was placed in a 50°C drying room for curing.

[0078] Example 3 The difference between Example 3 and Example 1 is that in step 3), the chlorinated polypropylene resin solution and the ethylene acrylate maleic anhydride copolymer solution are mixed evenly at a solute mass ratio of 2:8, and the initiator benzoyl peroxide BPO, the crosslinking agent liquefied MDI, the natural dammar resin E1001 and the polycarbodiimide anti-hydrolysis agent (Stabaxol P200) are added, mixed evenly, filtered, and defoamed to obtain a coating solution. Among them, the mass ratio of the chlorinated polypropylene resin, the ethylene acrylate maleic anhydride copolymer, the benzoyl peroxide BPO, the crosslinking agent liquefied MDI, the natural dammar resin E1001 and the Stabaxol P200 is 20:80:3:5:10:5.

[0079] The remaining operating conditions and steps are the same as those in Example 1.

[0080] Comparative Example 1 The EVA hot melt adhesive 3M™ 3731 hot melt adhesive sold on the market is directly applied to the edge of the electrode frame. The curing process conditions are: curing temperature is 120°C and curing time is 10 minutes.

[0081] Comparative Example 2 1) Dissolved ethylene acrylate maleic anhydride copolymer (EMH) Same as Example 1.

[0082] 2) Preparation of coating solution The ethylene acrylate maleic anhydride copolymer solution obtained in step 1) is mixed evenly with the crosslinking agent polymer MDI, natural dammar resin E1001, and polycarbodiimide anti-hydrolysis agent (Stabaxol 1) in a mass ratio of 100:10:20:5, filtered, and defoamed to obtain a coating solution.

[0083] 3) Coating The coating solution obtained in step 3 was coated on the PP material to obtain a wet coating with a thickness of 250 μm, and the solvent was dried at 80° C. After drying, a PET release film was applied to protect the adhesive surface.

[0084] The coating solution of step 3 was applied to the other side again to obtain a wet coating with a thickness of 250 μm, and the solvent was dried at 80° C. After drying, a PET release film was applied as a protective film.

[0085] 4) Ripening The prepared double-sided adhesive was placed in a 50°C drying room for curing for 48 hours.

[0086] Comparative Example 3 1) Dissolve chlorinated polypropylene resin (CPP) Same as Example 1.

[0087] 2) Preparation of coating solution The chlorinated polypropylene resin solution obtained in step 1) is evenly mixed with initiator benzoyl peroxide BPO, natural dammar resin E1001, and polycarbodiimide anti-hydrolysis agent (Stabaxol 1) in a mass ratio of 100:4:10:6, filtered, and defoamed to obtain a coating solution.

[0088] 3) Coating The coating solution obtained in step 3 was coated on the PP material to obtain a wet coating with a thickness of 250 μm, and the solvent was dried at 80° C. After drying, a PET release film was applied to protect the adhesive surface.

[0089] The coating solution of step 3 was applied to the other side again to obtain a wet coating with a thickness of 250 μm, and the solvent was dried at 80° C. After drying, a PET release film was applied as a protective film.

[0090] 4) Ripening The prepared double-sided adhesive was placed in a 50°C drying room for curing for 48 hours.

[0091] Test Example 1 1. Shear strength test method of bipolar plate frame film adhered to electrode frame: The frame film of Examples 1-3 and Comparative Examples 1-3 was set between the electrode frame for flow battery and the bipolar plate, cured at 160°C, and shear tested on a tensile machine [reference test standard GB∕T 7124-2008 Determination of tensile shear strength of adhesives]. Among them, the electrode frame substrate for flow battery is 2 cm wide, and the covering bipolar plate is 2 cm long and 2 cm wide. The results are shown in Table 1.

[0092] 2. Acid resistance test method: The frame films of Examples 1-3 and Comparative Examples 1-3 were set between the electrode frame and the bipolar plate for the liquid flow battery, cured at 160°C, and then placed in an all-vanadium liquid flow battery electrolyte (vanadium ion concentration of 1.7 mol / L) at 50°C for 0-1000 hours, then taken out and tested for shear strength [same shear test method as in step 1, refer to the test standard GB∕T7124-2008 Determination of tensile shear strength of adhesives]. The results are shown in Table 2.

[0093] Table 1. Shear strength test results

[0094] Table 2. Acid resistance test results .

Claims

1. A frame membrane for sealing bipolar plates and electrode frames in a flow battery, characterized in that: The frame film includes a substrate and a coating located on two opposite surfaces of the substrate, wherein the raw materials of the coating include chlorinated polypropylene resin, ethylene acrylate maleic anhydride copolymer, initiator, crosslinking agent, adhesive and anti-hydrolysis agent in a mass ratio of (20-50):(50-80):(1-5):(5-10):(10-25):(5-10).

2. The frame film according to claim 1, characterized in that: The material of the substrate is selected from one or more of PP, PEN, PPS and PET.

3. The frame film according to claim 1, characterized in that: The coating has a thickness of 10-30 μm.

4. The frame film according to claim 1, characterized in that: The ethylene acrylate maleic anhydride copolymer is a copolymer of ethylene, acrylate and maleic anhydride monomers or a copolymer of ethylene, acrylate, maleic anhydride monomers and functional monomers; the functional monomers contain one or more groups selected from epoxy groups, anhydride groups and carbonyl groups; in the ethylene acrylate maleic anhydride copolymer, the mass fraction of the ethylene structural unit is 81-85%, the mass fraction of the acrylate structural unit is 14-18%, and the mass fraction of the maleic anhydride structural unit is 0.1-0.5%, The initiator is selected from one or more of peroxide initiators and azo initiators; The cross-linking agent is selected from isocyanate curing agents; The binder is selected from tackifying resins; The anti-hydrolysis agent is a carbodiimide anti-hydrolysis agent.

5. A method for preparing the frame film according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: (1) uniformly dispersing the raw materials of the coating in a solvent, filtering and degassing to obtain a coating solution; (2) applying the coating solution onto one surface of the substrate, drying to obtain a first coating, and covering the protective adhesive surface with a release film; then applying the coating solution onto the other surface of the substrate, drying to obtain a second coating, and covering the protective adhesive surface with a release film; (3) The obtained double-sided coated substrate is aged.

6. The method according to claim 5, characterized in that The solid content of the chlorinated polypropylene resin is 5wt%-30wt%; and / or The solid content of the ethylene acrylate maleic anhydride copolymer is 5wt%-30wt%.

7. The method according to claim 5, characterized in that The solvent is selected from one or more of xylene, N,N-dimethylformamide, toluene, cyclohexane, methyl ethyl ketone and tetrahydrofuran.

8. The method according to claim 5, characterized in that The drying temperature is 80-120°C.

9. The method according to claim 5, characterized in that The aging temperature is 40-60° C., and the aging time is 0.5-3 days.

10. A liquid flow battery, characterized in that: The liquid flow battery comprises the frame film for sealing the bipolar plates and electrode frames in the liquid flow battery according to any one of claims 1 to 4.

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