A frame membrane for sealing bipolar plates and electrode frames in flow batteries

Abstract

The present invention provides a frame film for sealing bipolar plates and electrode frames in liquid flow batteries. The frame film includes a substrate and a coating located on two opposite surfaces of the substrate. 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). The frame film of the present invention can simultaneously generate a strong bond with the bipolar plate and the electrode frame. 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 in liquid flow batteries.

Description

Technical Field

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

[0002] As a core component of large-scale energy storage systems, the sealing performance of flow batteries directly impacts their cycle life and operational safety. Currently, mainstream sealing technologies rely on mechanical compression of rubber gaskets or hot-melt adhesives for heat-pressing packaging. However, both approaches present significant technical bottlenecks in practical application.

[0003] The structure of a flow battery primarily consists of two major components: the stack module and the electrolyte circulation system. The stack, the core component of the battery, is typically composed of multiple repeating units, each of which contains key components such as bipolar plates, electrodes, proton exchange membranes, and a sealing frame. Relying on rubber gaskets to seal the bipolar plates and electrode frames can lead to a series of problems, including interface deformation and leakage, material aging and failure, and complex assembly processes. Similarly, relying on hot-melt adhesive can lead to adhesive overflow and contamination of the electrochemical interface, damaging components during high-voltage assembly, and the hot-melt adhesive lacks adhesion to the bipolar plates and electrode frames, posing a risk of leakage over long periods of use.

[0004] Furthermore, using silicone gaskets and hot-melt adhesives to achieve sealing is not only costly but also inefficient, making continuous, mechanized production difficult. Furthermore, these rubber gaskets age and lose their sealing function over time, further increasing the cost of maintaining the fuel cell stack. Summary of the Invention

[0005] To address the challenges of existing technologies, the present invention provides a frame film for sealing bipolar plates and electrode frames in flow batteries. This frame film achieves strong adhesion to both the bipolar plates and the electrode frame. Its unique dual-cure system maintains excellent performance even in strong acidic conditions, offering strong corrosion resistance and suitability for long-term use in 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, and 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, the ethylene acrylate maleic anhydride copolymer has an ethylene structural unit content of 81-85% by mass, an acrylate structural unit content of 14-18% by mass, and a maleic anhydride structural unit content of 0.1-0.5% by mass.

[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 herein, the method comprising the following steps:

[0021] (1) uniformly dispersing the raw materials of the coating in a solvent, filtering and degassing to obtain a coating solution;

[0022] (2) applying the coating solution to one surface of the substrate, drying it to obtain a first coating layer, and covering it with a release film as a protective adhesive surface; then applying the coating solution to the other surface of the substrate, drying it to obtain a second coating layer, and covering it with a release film as a protective adhesive surface;

[0023] (3) The obtained double-sided coated substrate is aged.

[0024] In one or more embodiments, the solid content of the chlorinated polypropylene resin is 5 wt% to 30 wt%.

[0025] In one or more embodiments, the ethylene acrylate maleic anhydride copolymer has a solids content of 5 wt% to 30 wt%.

[0026] 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.

[0027] In one or more embodiments, the drying temperature is 80-120°C.

[0028] In one or more embodiments, the aging temperature is 40-60° C., and the aging time is 0.5-3 days.

[0029] A third aspect of the present invention provides a liquid flow battery, comprising a frame membrane for sealing bipolar plates and electrode frames in a liquid flow battery as described in any embodiment herein.

[0030] Beneficial effects of the present invention:

[0031] 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 in liquid flow batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the structure of a flow battery stack using the frame film of the present invention in some embodiments.

[0033] Description of reference numerals:

[0034] Copper plate 1, bipolar plate 2, frame membrane 3, electrode frame 4, electrode 5, silicone pad 6, proton membrane 7. DETAILED DESCRIPTION

[0035] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used herein. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art with respect to the present invention. In the event of conflict, the definitions herein shall prevail.

[0036] 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.

[0037] 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 have been disclosed herein.

[0038] Throughout this document, all features, such as values, amounts, contents, and concentrations, specified in numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to encompass and specifically disclose all possible subranges and individual values ​​within those ranges (including integers and fractions).

[0039] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0040] Herein, when describing embodiments or examples, it should be understood that they are not intended to limit the present invention to these embodiments or examples. On the contrary, all alternatives, modifications and equivalents of the methods and materials described herein are encompassed within the scope defined by the claims.

[0041] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0042] In response to 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 simultaneously produce strong bonding force with the bipolar plates and electrode frames. 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 stacks, greatly reduces production costs and improves production efficiency, and is suitable for long-term use of liquid flow batteries.

[0043] In some embodiments, 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 membrane 3 of the present invention, an electrode frame 4, an electrode 5, a silicone pad 6 and a proton membrane 7, wherein the frame membrane 3 is arranged between the bipolar plate 2 and the electrode frame 4, and the double-sided adhesive of the frame membrane 3 is used 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.

[0044] The frame film of the present invention includes a substrate and coatings located on two opposite surfaces of the substrate.

[0045] 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).

[0046] In the frame film of the present invention, the raw materials of the coating layer 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 layer are composed of chlorinated polypropylene resin, ethylene acrylate maleic anhydride copolymer, initiator, crosslinking agent, binder and anti-hydrolysis agent.

[0047] 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 adhesion with the bipolar plate and the electrode frame; the chlorinated polypropylene resin and the ethylene acrylate maleic anhydride copolymer form a dual-cure system in the coating, producing a synergistic effect, so that the coating can still maintain excellent performance under strong acid conditions, has strong corrosion resistance and strength properties, especially shear strength, and obtains better sealing and service life, making it suitable for long-term use in liquid flow batteries.

[0048] 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).

[0049] 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%.

[0050] In the present invention, acrylate monomers include acrylates (e.g., alkyl acrylates) and methacrylates (e.g., alkyl methacrylates). Suitable acrylate monomers 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, and butyl methacrylate. In some embodiments, the acrylate monomer is butyl acrylate.

[0051] In some embodiments, the ethylene acrylate maleic anhydride copolymer is a copolymer of ethylene, a copolymer of acrylate, and maleic anhydride monomers.

[0052] 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).

[0053] The crosslinking agent suitable for the present invention can be an isocyanate curing agent. Examples of useful crosslinking agents include liquefied MDI, polymeric MDI, Covestro L-75 curing agent, Covestro N3300 HDI, etc. In some embodiments, the crosslinking agent is liquefied MDI. The mass ratio of crosslinking agent to chlorinated polypropylene resin can be (5-10): (20-50).

[0054] Herein, MDI stands for 4,4'-diphenylmethane diisocyanate. Liquefied MDI is a modified form of MDI that has been modified by introducing urethane or carbodiimide groups into 4,4'-diphenylmethane diisocyanate, making it liquid at room temperature. Herein, HDI stands for hexamethylene diisocyanate.

[0055] The binder suitable for use in the present invention may be a tackifying resin. Examples of useful tackifying resins include, but are not limited to, dammar resin, rosin resin, rosin derivative resin, phenolic resin, and the like. In some embodiments, the binder is a dammar resin. The mass ratio of the binder to the chlorinated polypropylene resin may be (10-25): (20-50).

[0056] The anti-hydrolysis agent suitable for use in the present invention can be a carbodiimide anti-hydrolysis agent. Carbodiimides are a class of organic compounds containing a -C=N=C- structural unit. Examples of useful carbodiimide anti-hydrolysis agents include Stabaxol I, Stabaxol P, Stabaxol P200, Stabaxol P400, and the like. 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).

[0057] 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.

[0058] The frame film of the present invention can be produced by dissolving the coating raw materials 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 the solution. 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, followed by drying and aging to produce the frame film.

[0059] In some embodiments, the method of preparing the frame film of the present invention comprises the following steps:

[0060] (1) uniformly mixing a chlorinated polypropylene resin solution, an ethylene acrylate maleic anhydride copolymer solution, an initiator, a cross-linking agent, a natural dammar resin and an anti-hydrolysis agent, filtering and degassing to obtain a coating solution;

[0061] (2) applying the coating solution to one surface of the substrate, drying it to obtain a first coating layer, and covering it with a release film as a protective adhesive surface; then applying the coating solution to the other surface of the substrate, drying it to obtain a second coating layer, and covering it with a release film as a protective adhesive surface;

[0062] (3) The obtained double-sided coated substrate is aged.

[0063] In step (1), the solid content of the chlorinated polypropylene resin solution may be 5 wt% to 30 wt%, preferably 15 wt% to 25 wt%. 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.

[0064] In step (1), the solid content of the ethylene acrylate maleic anhydride copolymer solution may be 5 wt% to 30 wt%, preferably 12 wt% to 22 wt%. 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.

[0065] In some embodiments, in step (1), a chlorinated polypropylene resin can be dissolved in a solvent (e.g., xylene) in a dissolving kettle to obtain a chlorinated polypropylene resin with a suitable solid content, which is then cooled to room temperature for use. An ethylene acrylate maleic anhydride copolymer can be dissolved in a solvent (e.g., 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, which is then cooled to room temperature for use. The first auxiliary agent, initiator, co-crosslinking agent, curing agent, and crosslinking agent are then mixed in a certain proportion with the prepared chlorinated polypropylene resin solution and ethylene acrylate maleic anhydride copolymer solution 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 solution to remove bubbles, and the solution is allowed to stand for use.

[0066] 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 as the description.

[0067] 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.

[0068] In some embodiments, in step (2), the prepared coating solution can be delivered to a coating head using a delivery pump, the coating machine is started, and coating is performed using the coating head. The coating head can be in the form of a micro-dimpled, comma-shaped scraper, a slit, etc. The thickness of the coating can be controlled by controlling the pump delivery speed, scraper height, and casting speed. The frame film coated with the coating is then placed in an oven for drying to evaporate the solvent. The drying temperature can be 80-120°C.

[0069] After drying, cover with a release film to protect the adhesive surface. Then place the double-sided tape in a drying room for curing. The curing temperature is 40-60°C and the curing time is 0.5-3 days.

[0070] 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.

[0071] The present invention will be described below by way 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 starting compounds in the examples can all be purchased from commercial sources.

[0072] The chlorinated polypropylene resin used in the examples and comparative examples was purchased from Shenzhen Jitian Chemical Co., Ltd. with the brand name E0102.

[0073] 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%.

[0074] 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.

[0075] Example 1

[0076] 1) Dissolve chlorinated polypropylene resin (CPP)

[0077] Chlorinated polypropylene resin and xylene were mixed in a mass ratio of 20:80 to obtain a mixture having a solid content of 20%. The mixture was stirred at 80°C and a stirring speed of 600 rpm until the solid particles were completely dissolved, obtaining a translucent chlorinated polypropylene resin solution.

[0078] 2) Dissolve ethylene acrylate maleic anhydride copolymer (EMH)

[0079] The ethylene acrylate maleic anhydride copolymer raw material and a mixed solvent were mixed in a mass ratio of 15:85 to obtain a mixture with a solid content of 15%. The mixed solvent consisted of xylene and N,N-dimethylformamide in a mass ratio of 90:10. The mixture was stirred at 80°C and 600 rpm until the solid particles were completely dissolved, obtaining a translucent ethylene acrylate maleic anhydride copolymer solution.

[0080] 3) Preparation of coating solution

[0081] A chlorinated polypropylene resin solution and an ethylene acrylate maleic anhydride copolymer solution were mixed uniformly in a solute mass ratio of 1:1. Benzoyl peroxide (BPO) as an initiator, liquefied MDI (MDI) as a crosslinker, natural dammar resin E1001, and polycarbodiimide anti-hydrolysis agent (Stabaxol P200) were added, mixed uniformly, filtered, and defoamed to obtain a coating solution. The mass ratios of the chlorinated polypropylene resin, ethylene acrylate maleic anhydride copolymer, benzoyl peroxide (BPO), crosslinker liquefied MDI, natural dammar resin E1001, and Stabaxol P200 were 50:50:3:5:10:5.

[0082] 4) Coating

[0083] The coating solution obtained in step 3 was coated on a 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.

[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] 5) Ripening

[0086] The double-sided tape prepared in step 4) was placed in a 50°C drying room for curing for 48 hours.

[0087] Example 2

[0088] Steps 1) and 2) are the same as in Example 1.

[0089] 3) Preparation of coating solution

[0090] A chlorinated polypropylene resin solution and an ethylene acrylate maleic anhydride copolymer solution were mixed uniformly in a solute mass ratio of 1:1. Benzoyl peroxide (BPO) as an initiator, liquefied MDI (MDI) as a crosslinker, natural dammar resin E1001, and polycarbodiimide anti-hydrolysis agent (Stabaxol 1) were added, mixed uniformly, filtered, and defoamed to obtain a coating solution. The mass ratios of the chlorinated polypropylene resin, ethylene acrylate maleic anhydride copolymer, benzoyl peroxide (BPO), crosslinker liquefied MDI, natural dammar resin E1001, and Stabaxol P200 were 50:50:4:8:10:6.

[0091] 4) Coating

[0092] The coating solution obtained in step 3 was applied to 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.

[0093] 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.

[0094] 5) Ripening

[0095] The prepared double-sided tape was placed in a 50°C drying room for curing.

[0096] Example 3

[0097] Example 3 differs from Example 1 only in that, in step 3), the chlorinated polypropylene resin solution and the ethylene acrylate maleic anhydride copolymer solution are mixed uniformly in a solute mass ratio of 2:8. Benzoyl peroxide (BPO) as an initiator, liquefied MDI (MDI) as a crosslinker, natural dammar resin E1001, and polycarbodiimide anti-hydrolysis agent (Stabaxol P200) are added, mixed uniformly, filtered, and defoamed to obtain a coating solution. The mass ratios of the chlorinated polypropylene resin, ethylene acrylate maleic anhydride copolymer, benzoyl peroxide (BPO), crosslinker liquefied MDI, natural dammar resin E1001, and Stabaxol P200 are 20:80:3:5:10:5.

[0098] The remaining operating conditions and steps are the same as those in Example 1.

[0099] Comparative Example 1

[0100] The commercially available EVA hot melt adhesive 3M™ 3731 was directly applied to the edge of the electrode frame. The curing process conditions were: curing temperature 120°C, curing time 10 minutes.

[0101] Comparative Example 2

[0102] 1) Dissolve ethylene acrylate maleic anhydride copolymer (EMH)

[0103] Same as Example 1.

[0104] 2) Preparation of coating solution

[0105] The ethylene acrylate maleic anhydride copolymer solution obtained in step 1) is mixed evenly with a crosslinking agent, polymeric MDI, natural dammar resin E1001, and a polycarbodiimide anti-hydrolysis agent (Stabaxol 1) in a mass ratio of 100:10:20:5, filtered, and defoamed to obtain a coating solution.

[0106] 3) Coating

[0107] The coating solution obtained in step 3 was applied to 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.

[0108] 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.

[0109] 4) Ripening

[0110] The prepared double-sided tape was placed in a 50°C drying room for curing for 48 hours.

[0111] Comparative Example 3

[0112] 1) Dissolve chlorinated polypropylene resin (CPP)

[0113] Same as Example 1.

[0114] 2) Preparation of coating solution

[0115] 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.

[0116] 3) Coating

[0117] The coating solution obtained in step 3 was applied to 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.

[0118] 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.

[0119] 4) Ripening

[0120] The prepared double-sided tape was placed in a 50°C drying room for curing for 48 hours.

[0121] Test Example 1

[0122] 1. Shear Strength Testing Method for Bipolar Plate Frame Film Adhesion: The frame films of Examples 1-3 and Comparative Examples 1-3 were placed between the flow battery electrode frame and the bipolar plate, cured at 160°C, and subjected to shear testing on a tensile testing machine [referring to the test standard GB / T 7124-2008, Determination of Tensile Shear Strength of Adhesives]. The flow battery electrode frame substrate was 2 cm wide, and the bipolar plate covering was 2 cm long and 2 cm wide. The results are shown in Table 1.

[0123] 2. Acid resistance test method: The frame films of Examples 1-3 and Comparative Examples 1-3 were placed between the electrode frame and the bipolar plate for a 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. After removal, the shear strength was tested [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.

[0124] Table 1. Shear strength test results

[0125]

[0126] Table 2. Acid resistance test results

[0127] .

Claims

1. A frame film 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 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); the ethylene acrylate maleic anhydride copolymer is a copolymer of ethylene, acrylate and maleic anhydride monomers; 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; and the cross-linking agent is selected from isocyanate curing agents.

2. The frame film according to claim 1, wherein: 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, wherein: The thickness of the coating is 10-30 μm.

4. The frame film according to claim 1, wherein: The binder is selected from tackifying resins; and / or 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 to one surface of the substrate, drying it to obtain a first coating layer, and covering it with a release film as a protective adhesive surface; then applying the coating solution to the other surface of the substrate, drying it to obtain a second coating layer, and covering it with a release film as a protective adhesive surface; (3) The obtained double-sided coated substrate is aged.

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

7. The method according to claim 5, wherein 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, wherein The drying temperature is 80-120°C.

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

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

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