A degradable film and flow battery stack assembly method

Abstract

The present invention relates to the technical field of liquid flow batteries, and in particular to a degradable film and a method for assembling a liquid flow battery stack. The present invention prepares a degradable film with a highly ordered structure, crystallinity and good tensile properties by adopting a biaxial stretching process; the degradable film can be used in the assembly process of an all-vanadium liquid flow battery stack. The present invention takes the electrode and diaphragm intermediate layer of the first battery cell of the stack as the starting point, and winds the film in an S-shaped manner between the electrode-diaphragm layers of multiple battery cells, ultimately forming an assembly module that can be pre-assembled and modularly assembled; wherein the winding of the film can physically pressurize and tighten the components of the battery cell to prevent them from being dislocated and offset; the pre-assembly and modular assembly methods of assembling into assembly modules can greatly improve the assembly efficiency during stack production, so the present invention has broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to a degradable film and a liquid flow battery stack assembly method. Background Art

[0002] A flow battery stack usually includes end plates on the left and right sides and multiple battery cells. The battery cells are mainly composed of pole frames, electrodes, diaphragms, etc. The two end plates are fixed by screws, and the multiple battery cells are pressed and fixed by physical pressure. During assembly, the lower end plate is usually hoisted into place first, and then the battery cells are hoisted into place, stacked in sequence, and pressed with a large press, and finally the upper end plate is hoisted into place. The number of battery cells also varies with the power of the battery stack, and usually dozens or hundreds of battery cells are required. During installation, manual assembly is required one by one, which is not only inefficient, but also has high requirements for assembly workers. If modularization and pre-assembly can be formed, the assembly efficiency can be greatly improved.

[0003] Currently, there is also an emerging laser welding sealing technology that can weld the upper and lower pole frames of battery cells to form a solid weld point or weld seam, thereby enabling pre-assembly of battery cells. However, this method is prone to weld point deformation or fracture under conditions of large temperature differences, leading to problems such as battery cell position shifting and internal component misalignment. Moreover, this method cannot achieve the overall stacking and welding sealing of the battery stack, and cannot be used for modular assembly.

[0004] For example, patent document CN117855541B proposes a degradable film for liquid flow batteries. This invention can be attached to one or both sides of the surface of the diaphragm layer. It can be punched and positioned to meet assembly requirements, and can also significantly reduce the non-reactive area of ​​the diaphragm layer in the pole frame area, thereby increasing the utilization rate of the diaphragm layer from 60%-75% to 85%-95%. It greatly improves the utilization rate of the diaphragm layer and effectively reduces the generation of additional leakage current, which is of great significance for reducing costs and increasing efficiency of battery stacks and systems.

[0005] However, the structural orderliness, crystallinity and tensile strength of the biodegradable films produced by these existing preparation processes still need to be improved; and the assembly process used in all-vanadium liquid flow battery stacks also needs to be optimized.

[0006] Therefore, based on the above-mentioned related technologies, it is urgent to develop a degradable film and a flow battery stack assembly method. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to propose a degradable film and a liquid flow battery stack assembly method, thereby providing a degradable film with a highly ordered structure, crystallinity and good tensile properties; and an assembly process for an all-vanadium liquid flow battery stack with high assembly efficiency.

[0008] Based on the above objectives, the present invention provides a degradable film and a flow battery stack assembly method.

[0009] A degradable film comprising the following raw materials in parts by weight: 90-130 parts of a degradable resin, 80-100 parts of a degradable filler, 5-30 parts of a plasticizer, 1-3 parts of a lubricant, and 0.5-1 part of an antioxidant;

[0010] The method for preparing the degradable film is as follows:

[0011] Step S1: uniformly mixing a degradable filler and a plasticizer to obtain a thermoplastic elastomer mixture;

[0012] Step S2: feeding the thermoplastic elastomer mixture into a twin-screw extruder for mixing, granulating after cooling, and then drying to obtain thermoplastic elastomer granules;

[0013] Step S3: mixing the thermoplastic elastomer particles, the degradable resin, the lubricant, and the antioxidant, kneading and melting them to obtain a mixed material;

[0014] Step S4: feeding the mixed material into a single screw extruder equipped with a cooling roller, and obtaining a polymer sheet after co-extrusion;

[0015] Step S5: cutting and preheating the polymer sheet, and then biaxially stretching it to obtain a degradable film.

[0016] Preferably, the degradable resin is any one of polybutylene succinate, polylactic acid, terephthalate adipate, polybutylene adipate succinate, carbon dioxide-based plastics, or a combination thereof.

[0017] Preferably, the degradable filler is any one of corn starch, wheat starch, cassava starch, potato starch, rice starch, acetate starch, phosphate starch, oxidized cross-linked starch, or a combination thereof.

[0018] Preferably, the plasticizer is any one of glycerol, ethylene glycol, tung oil anhydride, sorbitol and polyvinyl alcohol, or a combination thereof.

[0019] Preferably, the lubricant is any one of erucamide, oleamide, glyceryl monostearate, stearic acid, polyethylene wax, or a combination thereof.

[0020] Preferably, the antioxidant is any one of 2,6-di-tert-butyl-p-cresol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and n-octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, or a combination thereof.

[0021] Preferably, the weight ratio of the degradable filler to the plasticizer in step S1 is 80-100:5-30;

[0022] During the mixing in step S2, the screw aspect ratio is 40-50:1-1.25, the screw diameter is 20-21 mm, the screw speed is 180-185 rpm, and the temperature is 120-160° C.;

[0023] The drying temperature in step S2 is 45-50° C. and the drying time is 5-8 hours;

[0024] The particle size of the thermoplastic elastomer particles in step S2 is 2.4-2.6 mm;

[0025] The mass ratio of the thermoplastic elastomer particles, the degradable resin, the lubricant and the antioxidant in step S3 is 85-130:90-130:1-3:0.5-1;

[0026] The temperature during mixing and melting in step S3 is 115-155° C. and the screw speed is 180-185 rpm;

[0027] The temperature during co-extrusion in step S4 is 100-155°C;

[0028] The size of the cutting in step S5 is 96-96.2×96-96.2 mm 2 ;

[0029] The preheating temperature in step S5 is 98-90° C. and the preheating time is 60-65 seconds;

[0030] The constant annealing temperature during the biaxial stretching in step S5 is 98-100° C., the stretching ratio is 3.9-4.1×3.9-4.1, the stretching rate is 150-200 mm / s, and the annealing time is 60-65 s.

[0031] Preferably, the thickness of the polymer sheet in step S4 is 0.5-0.55 mm.

[0032] Preferably, the thickness of the degradable film in step S5 is 50-500 μm.

[0033] A method for assembling a flow battery stack, wherein the flow battery stack includes a bipolar plate, a sealing gasket, a pole frame, a sealing gasket, an electrode, a diaphragm and a degradable film;

[0034] The assembly method of the flow battery stack is as follows:

[0035] Step A1: assembling a battery cell in the order of bipolar plates, sealing gaskets, pole frames, sealing gaskets, electrodes, diaphragm layers, electrodes, sealing gaskets, pole frames, and sealing gaskets;

[0036] Step A2: Using a degradable film, starting from the electrode and diaphragm intermediate layer of the first battery cell of the stack, wrap it in an S-shaped manner between the electrode-diaphragm layers of multiple battery cells to form an assembly module. The assembly module is pre-assembled and modularly assembled to obtain a liquid flow battery stack.

[0037] Beneficial effects of the present invention:

[0038] The present invention provides a degradable film and a method for assembling a flow battery stack. The raw materials of the degradable film layer of the present invention are degradable resin, degradable filler, lubricant, plasticizer and antioxidant, all of which are hydrocarbons. They can be degraded during the operation of the flow battery, are environmentally friendly and pollution-free, and have no adverse effects on the electrolyte system of the flow battery. The degradable film of the present invention adopts a biaxial stretching process, which can effectively improve the ordered structure and crystallinity of the film, thereby increasing the tensile strength and meeting the assembly process requirements of the all-vanadium flow battery stack. The degradable film can be used in the assembly process of the all-vanadium flow battery stack. The degradable film of the present invention can be applied to the assembly of all-vanadium liquid flow battery stacks, and multiple battery cells can be assembled into assembly modules by winding them inside and outside. The winding of the film can physically pressurize and tighten the components of the battery cells to prevent them from being dislocated and offset. The pre-assembly and modular assembly methods of assembling into assembly modules can greatly improve the assembly efficiency during the production of the battery stack. The degradable film of the present invention can be attached to one or both sides of the surface of the diaphragm layer when it is internally wound. It can be punched and positioned to meet assembly requirements, and can also greatly reduce the non-reactive area of ​​the diaphragm layer in the pole frame area, greatly improving the utilization rate of the diaphragm layer, and effectively reducing the generation of additional leakage current. After assembly, since the film is degradable, there is no need for additional removal. When the working electrolyte of the battery stack circulates normally, it can gradually degrade into carbon dioxide and water, and has no adverse effects on the electrolyte system of the liquid flow battery. Therefore, the present invention has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1This is an assembly diagram of the flow battery stack of the present invention, wherein 1 is the bipolar plate of the first battery cell; 2 is the first sealing gasket of the first battery cell; 3 is the upper pole frame of the first battery cell; 4 is the second sealing gasket of the first battery cell; 5 is the upper electrode of the first battery cell; 6 is a degradable film; 7 is a diaphragm layer; 8 is the lower electrode of the first battery cell; 9 is the third sealing gasket of the first battery cell; 10 is the lower pole frame of the first battery cell; 11 is the fourth sealing gasket of the first battery cell; 12 is the upper pole frame of the second battery cell;

[0041] Figure 2 This is a comparison chart of the elongation at break of the degradable films prepared in Example 1 of the present invention and Comparative Examples 1 to 12;

[0042] Figure 3 This is a comparison chart of the tensile strength of the degradable films prepared in the embodiment of the present invention and comparative examples 1 to 12. DETAILED DESCRIPTION

[0043] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0044] Example 1: A method for preparing a degradable film and a method for assembling a flow battery stack are as follows:

[0045] S1: 100 g corn starch and 30 g glycerol were mixed to obtain a thermoplastic elastomer mixture;

[0046] S2: The thermoplastic elastomer mixture was fed into a twin-screw extruder, mixed at 120°C with a screw length-to-diameter ratio of 40:1, a screw diameter of 20 mm, and a screw speed of 180 rpm. After cooling to room temperature, the mixture was pelletized and then dried at 50°C for 8 h to obtain thermoplastic elastomer pellets with a particle size of 2.5 mm.

[0047] S3: 130 g of thermoplastic elastomer particles, 130 g of polybutylene succinate, 3 g of erucamide oleamide, and 1 g of 2,6-di-tert-butyl-p-cresol were mixed, and the mixture was kneaded and melted at 115° C. and a screw speed of 180 rpm to obtain a mixture;

[0048] S4: The compounded material was fed into a single screw extruder equipped with a cooling roller and co-extruded at 100°C to obtain a polymer sheet with a thickness of 0.5 mm;

[0049] S5: Cut the polymer sheet into 96×96mm 2 After sizing, the film was preheated at 90°C for 60s, and then biaxially stretched at a constant annealing temperature of 100°C, with a stretching ratio of 4×4 and a stretching rate of 200 mm / s. After annealing for 60s, a biodegradable film with a thickness of 50 μm was obtained.

[0050] S6: Assemble a group of battery cells in the order of bipolar plates, sealing gaskets, pole frames, sealing gaskets, electrodes, diaphragm layers, electrodes, sealing gaskets, pole frames, and sealing gaskets;

[0051] S7: Using a degradable film, starting from the electrode and diaphragm intermediate layer of the first battery cell of the stack, wrap it in an S-shaped manner between the electrode-diaphragm layers of multiple battery cells to form an assembly module. The assembly module is pre-assembled and modularly assembled to obtain a liquid flow battery stack.

[0052] Example 2: A method for preparing a degradable film and a method for assembling a flow battery stack are as follows:

[0053] S1: 90 g of cassava starch and 25 g of tung oil anhydride were mixed to obtain a thermoplastic elastomer mixture;

[0054] S2: The thermoplastic elastomer mixture was fed into a twin-screw extruder, mixed at 140°C with a screw length-to-diameter ratio of 45:1.1, a screw diameter of 20.5 mm, and a screw speed of 185 rpm. After cooling to room temperature, the mixture was pelletized and then dried at 48°C for 6 h to obtain thermoplastic elastomer pellets with a particle size of 2.6 mm.

[0055] S3: 115 g of thermoplastic elastomer particles, 110 g of polybutylene adipate succinate, 2 g of stearic acid, and 0.8 g of n-octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate were mixed, and the mixture was kneaded and melted at 130° C. and a screw speed of 185 rpm to obtain a mixture;

[0056] S4: The compounded material was fed into a single screw extruder equipped with a cooling roller and co-extruded at 130°C to obtain a polymer sheet with a thickness of 0.55 mm;

[0057] S5: Cut the polymer sheet into 96.1×96.1mm 2 After sizing, the film was preheated at 99°C for 65s, and then biaxially stretched at a constant annealing temperature of 99°C, with a stretching ratio of 4.1×4.1 and a stretching rate of 180 mm / s. After annealing for 65s, a biodegradable film with a thickness of 300 μm was obtained.

[0058] S6: Assemble a group of battery cells in the order of bipolar plates, sealing gaskets, pole frames, sealing gaskets, electrodes, diaphragm layers, electrodes, sealing gaskets, pole frames, and sealing gaskets;

[0059] S7: Using a degradable film, starting from the electrode and diaphragm intermediate layer of the first battery cell of the stack, wrap it in an S-shaped manner between the electrode-diaphragm layers of multiple battery cells to form an assembly module. The assembly module is pre-assembled and modularly assembled to obtain a liquid flow battery stack.

[0060] Example 3: A method for preparing a degradable film and a method for assembling a flow battery stack are as follows:

[0061] S1: 30 g corn starch, 20 g rice starch, 20 g acetate starch, 10 g phosphate starch, 10 g oxidized cross-linked starch, 5 g glycerol, 5 g ethylene glycol, 5 g tung oil anhydride, and 5 g polyvinyl alcohol were mixed to obtain a thermoplastic elastomer mixture;

[0062] S2: The thermoplastic elastomer mixture was fed into a twin-screw extruder, mixed at 160°C with a screw length-to-diameter ratio of 50:1.25, a screw diameter of 21 mm, and a screw speed of 185 rpm. After cooling to room temperature, the mixture was pelletized and dried at 45°C for 5 h to obtain thermoplastic elastomer pellets with a particle size of 2.4 mm.

[0063] S3: 110 g of thermoplastic elastomer particles, 30 g of polybutylene succinate, 10 g of butylene terephthalate adipate, 30 g of polybutylene adipate succinate, 30 g of carbon dioxide-based plastic, 1 g of polyethylene wax, 0.2 g of 2,6-di-tert-butyl-p-cresol, and 0.4 g of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] were mixed, and the mixture was kneaded and melted at 115° C. and a screw speed of 185 rpm to obtain a mixture;

[0064] S4: The compounded material was fed into a single screw extruder equipped with a cooling roller and co-extruded at 155°C to obtain a polymer sheet with a thickness of 0.5 mm;

[0065] S5: Cut the polymer sheet into 96.2×96.2mm 2 After sizing, the film was preheated at 98°C for 60s, and then biaxially stretched at a constant annealing temperature of 98°C, with a stretching ratio of 3.9×3.9 and a stretching rate of 150 mm / s. After annealing for 60s, a biodegradable film with a thickness of 500 μm was obtained.

[0066] S6: Assemble a group of battery cells in the order of bipolar plates, sealing gaskets, pole frames, sealing gaskets, electrodes, diaphragm layers, electrodes, sealing gaskets, pole frames, and sealing gaskets;

[0067] S7: Using a degradable film, starting from the electrode and diaphragm intermediate layer of the first battery cell of the stack, wrap it in an S-shaped manner between the electrode-diaphragm layers of multiple battery cells to form an assembly module. The assembly module is pre-assembled and modularly assembled to obtain a liquid flow battery stack.

[0068] Comparative Example 1:

[0069] Compared with Example 1, this comparative example did not stretch the polymer sheet during the preparation process of the degradable film. The remaining steps and parameters were the same and will not be repeated in this comparative example. Finally, a degradable film was obtained.

[0070] Comparative Example 2:

[0071] Compared with Example 1, this comparative example only replaces "annealing for 60 seconds" with "annealing for 0 seconds", and the remaining steps and parameters are the same, which will not be repeated in this comparative example. Finally, a degradable film is obtained;

[0072] Comparative Example 3:

[0073] Compared with Example 1, this comparative example only replaces "annealing for 60 seconds" with "annealing for 180 seconds", and the remaining steps and parameters are the same, which will not be repeated in this comparative example. Finally, a degradable film was obtained;

[0074] Comparative Example 4:

[0075] Compared with Example 1, this comparative example only replaces the "stretching rate of 200 mm / s" with "stretching rate of 25 mm / s", and the remaining steps and parameters are the same, which will not be repeated in this comparative example. Finally, a degradable film is obtained;

[0076] Comparative Example 5:

[0077] Compared with Example 1, this comparative example only replaced the "stretching rate of 200 mm / s" with "stretching rate of 75 mm / s", and the remaining steps and parameters were the same, which will not be repeated in this comparative example. Finally, a degradable film was obtained;

[0078] Comparative Example 6:

[0079] Compared with Example 1, this comparative example only replaces the "stretching rate of 200 mm / s" with "stretching rate of 300 mm / s", and the remaining steps and parameters are the same, which will not be repeated in this comparative example. Finally, a degradable film is obtained;

[0080] Comparative Example 7:

[0081] Compared with Example 1, this comparative example only replaced "biaxial stretching at a stretching rate of 200 mm / s and annealing for 60 seconds" with "biaxial stretching at a stretching rate of 25 mm / s and annealing for 0 seconds", and the remaining steps and parameters were the same, which will not be repeated in this comparative example, and finally a degradable film was obtained;

[0082] Comparative Example 8:

[0083] Compared with Example 1, this comparative example only replaced "biaxial stretching at a stretching rate of 200 mm / s and annealing for 60 seconds" with "biaxial stretching at a stretching rate of 25 mm / s and annealing for 180 seconds", and the remaining steps and parameters were the same, which will not be repeated in this comparative example. Finally, a degradable film was obtained;

[0084] Comparative Example 9:

[0085] Compared with Example 1, this comparative example only replaced "biaxial stretching at a stretching rate of 200 mm / s and annealing for 60 seconds" with "biaxial stretching at a stretching rate of 75 mm / s and annealing for 0 seconds". The remaining steps and parameters were the same and will not be repeated in this comparative example. Finally, a degradable film was obtained.

[0086] Comparative Example 10:

[0087] Compared with Example 1, this comparative example only replaced "biaxial stretching at a stretching rate of 200 mm / s and annealing for 60 seconds" with "biaxial stretching at a stretching rate of 75 mm / s and annealing for 180 seconds". The remaining steps and parameters were the same and will not be repeated in this comparative example. Finally, a degradable film was obtained.

[0088] Comparative Example 11:

[0089] Compared with Example 1, this comparative example only replaced "biaxial stretching at a stretching rate of 200 mm / s and annealing for 60 seconds" with "biaxial stretching at a stretching rate of 300 mm / s and annealing for 0 seconds", and the remaining steps and parameters were the same, which will not be repeated in this comparative example, and finally a degradable film was obtained;

[0090] Comparative Example 12:

[0091] Compared with Example 1, this comparative example only replaced "biaxial stretching at a stretching rate of 200 mm / s and annealing for 60 seconds" with "biaxial stretching at a stretching rate of 300 mm / s and annealing for 180 seconds", and the remaining steps and parameters were the same, which will not be repeated in this comparative example, and finally a degradable film was obtained;

[0092] Performance testing and data analysis:

[0093] Referring to GB / T1040.3-2006 "Test for tensile properties of plastics", a strip specimen with a width of 15 mm and a length of 150 mm and parallel markings with a spacing of 50 mm in the middle was prepared by cutting. The tensile strength (MPa) of the degradable films prepared in Examples 1 to 3 and Comparative Examples 1 to 12 was tested using a universal material testing machine (Instron@6800, Instron) at a speed of 50 mm / min. The test results are shown in FIG. Figure 2 As shown;

[0094] With reference to GB / T1040.3-2006 "Test for tensile properties of plastics", a strip sample with a width of 15 mm and a length of 150 mm and parallel markings of 50 mm intervals in the middle was prepared by cutting. The elongation at break (%) of the degradable films prepared in Examples 1 to 3 and Comparative Examples 1 to 12 was tested using a universal material testing machine (Instron 6800, Instron) at a speed of 50 mm / min. The test results are shown in FIG. Figure 3 As shown;

[0095] Combine Figure 2 and Figure 3 It can be seen that after biaxial stretching, the tensile strength of the biodegradable film prepared in the examples of the present invention increased to a maximum of 210 MPa compared to the unstretched film. However, due to the oriented structure of the polymer chains and the increased crystallinity induced by the biaxial stretching process, the elongation at break of the film decreased to 75%-99.5% compared to the unstretched film. A comparison of various data shows that the optimal stretching rate is 150-200 mm / s, and the optimal annealing time is 60-65 seconds, and all the data are relatively excellent.

[0096] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0097] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for assembling a flow battery stack, characterized in that: The assembly method of the flow battery stack is as follows: Step A1: assembling a battery cell in the order of bipolar plates, sealing gaskets, pole frames, sealing gaskets, electrodes, diaphragms, electrodes, sealing gaskets, pole frames, and sealing gaskets; Step A2: Using a degradable film, starting from the electrode and separator intermediate layer of the first battery cell of the stack, winding in an S-shaped manner between the electrodes and separators of multiple battery cells to form an assembly module, and pre-assembling and modularly assembling the assembly module to obtain a liquid flow battery stack; The degradable film comprises the following raw materials in parts by weight: 90-130 parts of degradable resin, 80-100 parts of degradable filler, 5-30 parts of plasticizer, 1-3 parts of lubricant, and 0.5-1 part of antioxidant; The method for preparing the degradable film is as follows: Step S1: uniformly mixing a degradable filler and a plasticizer to obtain a thermoplastic elastomer mixture; Step S2: feeding the thermoplastic elastomer mixture into a twin-screw extruder for mixing, granulating after cooling, and then drying to obtain thermoplastic elastomer granules; Step S3: mixing the thermoplastic elastomer particles, the degradable resin, the lubricant, and the antioxidant, kneading and melting them to obtain a mixed material; Step S4: feeding the mixed material into a single screw extruder equipped with a cooling roller, and obtaining a polymer sheet after co-extrusion; Step S5: cutting and preheating the polymer sheet, and then biaxially stretching the sheet to obtain a degradable film; The degradable resin is any one of polybutylene succinate, polylactic acid, carbon dioxide-based plastics, or a combination thereof; The degradable filler is any one of corn starch, wheat starch, cassava starch, potato starch, rice starch, acetate starch, phosphate starch, oxidized cross-linked starch, or a combination thereof; The constant annealing temperature during the biaxial stretching in step S5 is 98-100° C., the stretching ratios in both directions are 3.9-4.1, the stretching rate is 150-200 mm / s, and the annealing time is 60-65 s.

2. The method for assembling a flow battery stack according to claim 1, wherein: The plasticizer is any one of glycerol, ethylene glycol, tung oil anhydride, sorbitol, polyvinyl alcohol, or a combination thereof.

3. The assembly method of a flow battery stack according to claim 1, characterized in that: The lubricant is any one of erucamide, oleamide, glyceryl monostearate, stearic acid, polyethylene wax, or a combination thereof.

4. The method for assembling a flow battery stack according to claim 1, wherein: The antioxidant is any one of 2,6-di-tert-butyl-p-cresol, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and n-octadecylβ-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, or a combination thereof.

5. The method for assembling a flow battery stack according to claim 1, wherein: The weight ratio of the degradable filler to the plasticizer in step S1 is 80-100:5-30; The mixing screw in step S2 has an aspect ratio of 40-50:1-1.25, a screw diameter of 20-21 mm, a screw speed of 180-185 rpm, and a temperature of 120-160° C. The drying temperature in step S2 is 45-50° C. and the drying time is 5-8 hours; The particle size of the thermoplastic elastomer particles in step S2 is 2.4-2.6 mm; The mass ratio of the thermoplastic elastomer particles, the degradable resin, the lubricant and the antioxidant in step S3 is 85-130:90-130:1-3:0.5-1; The temperature during mixing and melting in step S3 is 115-155° C. and the screw speed is 180-185 rpm; The temperature during co-extrusion in step S4 is 100-155°C; The size after cutting in step S5 is 96-96.2 mm in length and 96-96.2 mm in width; The preheating temperature in step S5 is 98-90° C., and the preheating time is 60-65 seconds.

6. The method for assembling a flow battery stack according to claim 1, wherein: The thickness of the polymer sheet in step S4 is 0.5-0.55 mm.

7. The method for assembling a flow battery stack according to claim 1, wherein: The thickness of the degradable film in step S5 is 50-500 μm.

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