Flow guide frame integrated with graphite felt all-vanadium redox flow battery stack and preparation method thereof

Abstract

The application discloses a kind of flow guide frame and graphite felt integration's all-vanadium redox battery electric pile and preparation method thereof, belong to all-vanadium redox battery energy storage technical field, including sequentially stacked end plate, current collector, bipolar plate, flow guide frame assembly and sealing element, and flow guide frame assembly includes flow guide frame body and graphite felt electrode, wherein, graphite felt electrode is placed in the inner frame cavity of flow guide frame body;Graphite felt electrode is two opposite sides along electrolyte flow direction, and the side edge to be combined is integrally fused with the corresponding side wall of the inner frame of flow guide frame body by injection molding process and forms side edge sealing combination layer;Side edge sealing combination layer is the mechanical interlocking structure formed by the solidification of the porous structure of the molten injection material of flow guide frame body into the side edge to be combined after infiltration. The application solves the problems of traditional interference assembly, such as easy to be washed and deformed graphite felt, easy to produce gap side edge, large invalid flow and high pump consumption.

Description

Technical Field

[0001] This invention relates to the field of vanadium redox flow battery energy storage technology, specifically to a vanadium redox flow battery stack integrating a flow guide frame and graphite felt, and its preparation method. Background Technology

[0002] Vanadium redox flow batteries (VRFBs) have become a core electrochemical energy storage technology for large-scale renewable energy consumption, grid peak shaving, and off-grid power supply due to their advantages such as high safety, long cycle life, power and capacity decoupling, and environmental friendliness. The stack is the core unit of the electrochemical reaction in a VRFB, mainly composed of end plates, current collectors, bipolar plates, a flow guide frame, graphite felt electrodes, and sealing components. The graphite felt serves as the carrier for the electrochemical reaction, and its assembly and sealing with the flow guide frame directly determine the electrolyte flow state, the effective reaction area, and the overall operating efficiency of the battery.

[0003] Currently, the industry generally adopts an interference fit scheme for graphite felt and flow guide frame: that is, the outer size of graphite felt is slightly larger than the inner frame size of flow guide frame. For example, when the inner frame size of flow guide frame is 500mm×1200mm, graphite felt is cut to 502mm×1200mm. The graphite felt is squeezed and embedded into the inner frame of flow guide frame by its own elastic deformation, so that the edge of graphite felt is close to the inner wall of flow guide frame. This eliminates the fit gap between graphite felt and flow guide frame, and forces all electrolyte to flow through the interior of graphite felt to participate in electrochemical reaction, reducing ineffective bypass flow.

[0004] However, during long-term engineering operation, this solution has inherent defects that cannot be overcome: graphite felt is an elastic porous carbonaceous material. Under the combined effects of continuous hydraulic scouring by the electrolyte, high-flow-rate impact, and volume deformation during charging and discharging, the edges of the graphite felt are eroded and deformed, detaching from the guide frame. The original interference fit is gradually lost, and separation gaps appear between the side of the graphite felt and the inner wall of the guide frame. Since the flow resistance of the side gaps is much smaller than the internal resistance of the porous graphite felt, the electrolyte will preferentially flow through the gaps via short-circuiting, causing the gaps to widen and forming a large amount of ineffective flow that does not participate in the electrochemical reaction. On the one hand, this significantly increases the pumping power consumption of the electrolyte circulation pump, increasing the system operating cost; on the other hand, it reduces the effective area of ​​the electrode reaction, leading to a decrease in the voltage efficiency and energy efficiency of the fuel cell stack; in severe cases, it can also cause turbulent flow field distribution, exacerbating the performance degradation of the fuel cell stack and shortening its service life.

[0005] Therefore, developing a fuel cell stack solution that addresses the side gap problem of graphite felt at its structural root and eliminates ineffective electrolyte bypass flow is a key technological requirement for improving the long-term operational stability and economy of vanadium redox flow battery stacks. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a vanadium redox flow battery stack integrating the flow guide frame and graphite felt and its preparation method, so as to solve the problems of easy erosion and deformation of graphite felt, easy gaps on the side, large ineffective flow and high pump consumption in traditional interference fit assembly.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows.

[0008] A vanadium redox flow battery stack integrating a flow guide frame and graphite felt includes end plates, current collectors, bipolar plates, a flow guide frame assembly, and a sealant stacked sequentially. The flow guide frame assembly includes a flow guide frame body and graphite felt electrodes, wherein the graphite felt electrodes are placed in the inner frame cavity of the flow guide frame body. The two opposite sides of the graphite felt electrodes along the electrolyte flow direction are the sides to be joined. The sides to be joined are integrally fused with the corresponding sidewalls of the inner frame of the flow guide frame body through an injection molding process to form a side sealing bonding layer that makes the graphite felt electrodes and the flow guide frame body an inseparable integrated structure. The side sealing bonding layer is a mechanically fitted structure formed by the molten injection molding material of the guide frame body penetrating into the porous structure of the side to be bonded and then curing. It is used to simultaneously achieve the dual functions of mechanical fitting and fixing and flow channel sealing.

[0009] Preferably, the other two opposite sides of the graphite felt electrode are electrolyte inlet and outlet sides, and the electrolyte inlet and outlet sides are in a gap fit with the corresponding side wall of the inner frame of the guide frame body, so that the electrolyte can only enter from one end of the inlet and outlet and flow through the inside of the graphite felt electrode to the other end.

[0010] Preferably, the width of one side of the side sealing bonding layer is 5~20mm.

[0011] Preferably, the material of the guide frame body is a thermoplastic that is resistant to corrosion by vanadium sulfate electrolyte, selected from any one of polypropylene, high-density polyethylene, and polyvinyl chloride.

[0012] Preferably, the graphite felt electrode is a porous carbonaceous reaction carrier, selected from any one of polyacrylonitrile-based graphite felt, pitch-based graphite felt, and viscose-based graphite felt.

[0013] A method for fabricating an all-vanadium redox flow battery stack integrating a flow guide frame and graphite felt includes the following steps: S1. Pretreatment of graphite felt electrode: Cut the graphite felt electrode to the design dimensions; S2. Mold positioning: Place the pretreated graphite felt electrode into the cavity of the guide frame injection mold, and position it so that the two sides of the graphite felt electrode to be joined extend into the forming area of ​​the inner frame side wall of the guide frame body. S3. Mold closing: The upper and lower injection molds are closed. During mold closing, the sealing frame of the mold is used to press the junction of the graphite felt electrode reaction area and the side to be joined, and the air in the pores of the graphite felt electrode in the pressing area is discharged, forming a physical sealing barrier that prevents molten plastic from penetrating into the central reaction area of ​​the graphite felt electrode. S4. Vacuuming the molding area: Open the mold vacuum valve and evacuate the molding area of ​​the guide frame inside the mold to remove the air from the cavity space and the gaps on the side of the graphite felt electrode to be bonded. S5. Injection Molding: Molten guide frame material is injected into the mold, and pressure is maintained to allow the molten plastic to fully penetrate into the porous structure of the side to be joined. After cooling and solidification, the side to be joined is fused with the guide frame body to obtain a guide frame assembly that integrates the guide frame and graphite felt. S6. Stack assembly: Stack the current guide frame assembly, bipolar plate, seal, current collector, and end plate in sequence and tighten them to obtain the vanadium redox flow battery stack.

[0014] Preferably, in step S3, the single-sided pressing width of the sealing frame is 3~8mm, and the compaction surface pressure is set to 5~10MPa.

[0015] Preferably, in step S4, the vacuum degree is -0.06MPa to -0.09MPa.

[0016] Preferably, in step S5, the injection pressure is 60~100MPa, the holding time is 10~30s, and the cooling time is 10~30s.

[0017] Due to the adoption of the above technical solutions, the technical progress achieved by this invention is as follows.

[0018] This invention eliminates bypass gaps at the source, preventing ineffective flow: Through injection molding, the side of the graphite felt electrode is permanently bonded to the side wall of the guide frame, completely solving the problem of long-term deformation and separation gaps caused by electrolyte erosion in traditional interference fits. This completely blocks the side bypass flow path of the electrolyte. Actual measurements show that it can reduce electrolyte circulation pump consumption by 10% to 30%, significantly improving electrolyte utilization and fuel cell stack energy efficiency.

[0019] This invention features high bonding strength and strong long-term operational stability: the side sealing bonding layer forms a mechanical interlocking structure by penetrating the graphite felt pores with plastic, and the bonding force is much greater than the frictional force of interference fit, exhibiting excellent resistance to electrolyte corrosion and water erosion; under long-term operation, there will be no problems such as graphite felt electrode displacement, detachment, or edge erosion, effectively extending the fuel cell stack cycle life and maintenance cycle.

[0020] This invention reduces processing and assembly costs: it eliminates the need for precise control of the interference dimension tolerance of the graphite felt electrode, thus reducing the cutting accuracy requirements of the graphite felt electrode; the integrated component can be directly used for fuel cell stacking, reducing the alignment and calibration process between the graphite felt electrode and the current guide frame body during assembly, improving fuel cell stack assembly efficiency, and reducing manufacturing costs.

[0021] This invention can optimize the uniformity of the flow field and improve the reaction efficiency: the side seal completely avoids the electrolyte from short-circuiting along the gap, ensuring that the electrolyte flows uniformly through the reaction area of ​​the graphite felt electrode, improving the uniformity of the current and flow field distribution inside the graphite felt electrode, and improving the overall reaction efficiency and capacity utilization of the stack. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the fuel cell stack structure of the present invention; Figure 2 This is a schematic diagram of the flow guide frame assembly structure of the present invention.

[0023] Among them: 1. End plate, 2. Current collector, 3. Bipolar plate, 4. Flow guide frame assembly, 41. Flow guide frame body, 42. Graphite felt electrode, 421. Side to be bonded, 422. Electrolyte inlet and outlet side, 43. Side sealing bonding layer, 5. Seal. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0025] A vanadium redox flow battery stack integrating a flow guide frame and graphite felt, combined with Figure 1 As shown, it includes an end plate 1, a current collector 2, a bipolar plate 3, a flow guide frame assembly 4, and a seal 5 stacked in sequence.

[0026] like Figure 2 As shown, the flow guide frame assembly 4 includes a flow guide frame body 41 and a graphite felt electrode 42. The flow guide frame body 41 is made of thermoplastic plastic resistant to corrosion by vanadium sulfate electrolyte, selected from any one of polypropylene (PP), high-density polyethylene (HDPE), and polyvinyl chloride (PVC); the graphite felt electrode 42 is a porous carbonaceous reaction carrier, selected from any one of polyacrylonitrile-based graphite felt, pitch-based graphite felt, and adhesive-based graphite felt.

[0027] The graphite felt electrode 42 is placed in the inner frame cavity of the flow guide frame body 41. The two opposite sides of the graphite felt electrode 42 along the electrolyte flow direction are the sides to be bonded 421. The sides to be bonded 421 and the corresponding sidewalls of the inner frame of the flow guide frame body 41 are integrally fused together by injection molding to form a side sealing bonding layer 43. The side sealing bonding layer 43 makes the graphite felt electrode 42 and the flow guide frame body 41 form an inseparable integrated structure.

[0028] Specifically, the side sealing bonding layer 43 is a mechanically interlocking structure formed by the molten injection molding material of the flow guide frame body 41 penetrating into the porous structure of the side 421 to be bonded and then curing. It is used to simultaneously achieve the dual functions of mechanical interlocking fixation and flow channel sealing. The width of one side of the side sealing bonding layer 43 is 5~20mm.

[0029] The other two opposite sides of the graphite felt electrode 42 are electrolyte inlet and outlet sides 422, and the electrolyte inlet and outlet sides 422 are fitted with the corresponding side walls of the inner frame of the guide frame body 41 with a gap, so that the electrolyte can only enter from one end of the inlet and outlet and flow through the inside of the graphite felt electrode 42 to the other end.

[0030] A method for fabricating an all-vanadium redox flow battery stack integrating a flow guide frame and graphite felt includes the following steps: S1. Pretreatment of graphite felt electrode: Cut the graphite felt electrode 42 according to the design dimensions.

[0031] S2. Mold positioning: Place the pretreated graphite felt electrode 42 into the cavity of the flow guide frame injection mold, and position it so that the two sides 421 of the graphite felt electrode 42 to be joined extend into the forming area of ​​the corresponding flow guide frame sidewall in the mold cavity.

[0032] S3. Mold Closure: The upper and lower injection molds are closed. During mold closure, the sealing frame of the mold presses the junction of the reaction area of ​​the graphite felt electrode 42 and the side 421 to be joined, thereby expelling the air in the pores of the graphite felt electrode 42 in the pressing area and forming a physical sealing barrier that prevents the molten plastic from penetrating into the central reaction area of ​​the graphite felt electrode 42.

[0033] In this step, the single-sided pressing width of the sealing frame is 3~8mm, and the compaction surface pressure is set to 5~10MPa.

[0034] S4. Vacuuming the molding area: Open the mold vacuum valve to evacuate the molding area of ​​the guide frame inside the mold, and expel the air from the cavity space and the gap in the pores of the side 421 of the graphite felt electrode 42 to be joined.

[0035] In this step, the vacuum level is -0.06MPa to -0.09MPa.

[0036] S5. Injection molding: Molten guide frame material is injected into the mold, and pressure is maintained to allow the molten plastic to fully penetrate into the porous structure of the side to be joined 421. After cooling and solidification, the side to be joined 421 and the guide frame body 41 formed after molding are fused together to obtain the guide frame assembly 4, which integrates the guide frame and graphite felt.

[0037] In this step, the injection pressure is 60~100MPa, the holding time is 10~30s, and the cooling time is 10~30s.

[0038] S6. Stack assembly: Stack the current guide frame assembly 4 with the bipolar plate, seal, current collector and end plate in sequence, and then fasten them to obtain the vanadium redox flow battery stack.

[0039] Specifically, this method is also equipped with a special injection mold: the mold is a split structure, including an upper mold and a lower mold. After the mold is closed, a sealing pressure frame is set at the position corresponding to the non-reaction area of ​​the graphite felt electrode 42. When the mold is closed, it can press the intersection of the reaction area of ​​the graphite felt electrode 42 and the side 421 to be combined by 3~8mm, expel the air in the pores, and prevent the molten plastic from penetrating into the reaction area of ​​the graphite felt electrode 42. After the mold closes, the cavity forms a sealed area, which can be connected to an external vacuum system to assist the molten plastic in flowing and filling the molding tank. The mold is equipped with a cooling water tank, and external cooling water can also be connected after the mold closes to cool and solidify the plastic after injection molding.

[0040] Specifically, the vacuum area is the glue-filling area of ​​the mold's flow guide frame groove, and the junction of the graphite felt electrode 42 and the flow guide frame body 41. The reaction area of ​​the graphite felt electrode 42 is sealed by the injection mold sealing frame, which is a non-vacuum area. Example 1

[0041] This embodiment is a 32kW-class vanadium redox flow battery stack. The inner cavity of the flow guide frame body 41 has dimensions of 400mm (width) × 900mm (length), and the electrolyte flows along the 400mm width direction. The flow guide frame body 41 is made of polypropylene (PP), and the electrodes are made of graphite felt with a thickness of 4mm.

[0042] The graphite felt electrode 42 is cut to dimensions of 396mm × 920mm. The two sides along its length, i.e., the sides to be joined 421, are integrally formed with the left and right sidewalls of the inner frame of the guide frame body 41 via injection molding. The joint width on each side is 10mm, forming a 10mm wide side sealing layer 43. The effective reaction area of ​​the graphite felt is 900mm long. The upper and lower electrolyte inlet / outlet sides 422 of the graphite felt electrode are fitted with the upper and lower sidewalls of the inner frame of the guide frame body 41 with a 2mm gap.

[0043] The preparation and assembly process is as follows: S1. Pretreatment of graphite felt electrode: The graphite felt raw material is precisely cut into 396mm×920mm according to the design size, and the edge burrs and free fibers are trimmed to ensure that the straightness of the side meets the molding requirements.

[0044] S2. Mold positioning: Place the cut graphite felt electrode 42 into the corresponding cavity of the lower mold of the flow guide frame injection. Through precise alignment, make the 10mm wide side edges 421 of the graphite felt electrode 42 completely extend into the forming area of ​​the corresponding flow guide frame side wall in the mold cavity.

[0045] S3. Mold Closure: Control the upper and lower molds to close. The sealing frame of the mold presses the junction of the reaction area of ​​the graphite felt electrode 42 and the side 421 to be bonded. The single-sided pressing width is 5mm, and the pressing surface pressure is set to 7MPa. The air in the pores of the graphite felt electrode 42 in the pressing area is discharged by mechanical extrusion, forming a physical sealing barrier that prevents molten plastic from penetrating into the central reaction area of ​​the graphite felt electrode 42.

[0046] S4. Vacuuming in the molding area: Open the mold vacuum valve and evacuate the molding area of ​​the guide frame inside the mold. Control the vacuum level to -0.08MPa. After the air in the cavity space and the gap in the pores of the graphite felt electrode 42 to be joined with the graphite felt electrode 42 is completely discharged, close the vacuum valve.

[0047] S5. Injection Molding: Heat and melt PP granules, control the barrel temperature to 220℃, and inject molten PP material into the mold cavity with an injection pressure of 80MPa. Hold the pressure for 15s to allow the molten plastic to fully penetrate the porous structure of the side 421 to be bonded. After holding the pressure, cool and solidify for 15s. After the material is completely solidified, open the mold to obtain the integrated flow guide frame assembly 4 of the flow guide frame and graphite felt.

[0048] S6. Stack assembly: The prepared current guide frame assembly 4, bipolar plate 3, seal 5, current collector 2, and end plate 1 are assembled in sequence according to the stack stack order. After the bolts are tightened evenly in stages, a 32kW vanadium redox flow battery stack is obtained. Example 2

[0049] The difference from Example 1 is as follows: the width of the side 421 to be joined is 5mm; in step S3, the single-sided pressing width of the sealing frame is 3mm, and the compaction surface pressure is set to 5MPa; in step S4, the vacuum degree is -0.06MPa; in step S5, the injection pressure is 60MPa, the holding time is 10s, and the cooling time is 10s. After 6 months of continuous operation testing, the bypass flow of the fuel cell stack did not increase significantly, and the structural stability was excellent. Example 3

[0050] The difference from Example 1 is as follows: the width of the side 421 to be joined is 20mm; in step S3, the single-sided pressing width of the sealing frame is 8mm, and the compaction surface pressure is set to 10MPa; in step S4, the vacuum degree is -0.09MPa; in step S5, the injection pressure is 100MPa, the holding time is 30s, and the cooling time is 30s. After 6 months of continuous operation testing, the bypass flow of the fuel cell stack did not increase significantly, and the structural stability was excellent. Example 4

[0051] The difference from Example 1 is that the guide frame body is made of HDPE, the graphite felt is asphalt-based graphite felt with a thickness of 4mm, and the width of the side to be bonded 421 is 15mm; the electrolyte inlet / outlet side 422 is in close contact with the guide frame body 41. After 6 months of continuous operation testing, the bypass flow of the fuel cell stack did not increase significantly, and the structural stability was excellent.

[0052] The working principle of this invention is as follows: The core of this invention lies in using an injection molding process to permanently mechanically fit and fix the side of the graphite felt electrode to be joined with the flow guide frame body and seal the flow channel.

[0053] Specifically, in the vanadium redox flow battery stack, the electrolyte is transported from the storage tank to the stack via a circulation pump, flowing into the graphite felt electrode area through the inlet and outlet ports of the guide frame body. During the injection molding process, molten thermoplastic penetrates the three-dimensional porous structure of the graphite felt electrode side to be bonded under pressure. After solidification, it forms a mechanical interlocking structure similar to "anchoring," firmly fixing the graphite felt side to the inside of the guide frame sidewall, forming an inseparable integrated component. This interlocking structure has two functions: first, the mechanical interlocking provides a bonding strength far greater than the frictional force of traditional interference fits, capable of withstanding long-term hydrodynamic erosion of the electrolyte and volume deformation of the graphite felt; second, after the molten plastic penetrates into the pores on the surface of the graphite felt electrode and solidifies, it fills any microscopic gaps that may exist between the graphite felt side and the guide frame sidewall, forming a sealing barrier that completely blocks the path of electrolyte bypass flow from the side.

[0054] The inlet and outlet sides of the graphite felt are fitted with a gap. After the electrolyte enters through the inlet / outlet at one end of the guide frame, it cannot bypass the graphite felt because the left and right sides are completely sealed by the injection-molded bonding layer. Instead, it enters the interior of the graphite felt through the inlet / outlet side, flows along the direction of electrolyte flow through the porous electrode structure, undergoes an electrochemical reaction on the surface of the graphite felt fibers, and then flows out through the inlet / outlet at the other end. This flow path ensures that all the electrolyte effectively flows through the reaction area of ​​the graphite felt, avoiding the generation of ineffective bypass flow.

[0055] During the preparation process, the sealing frame presses the junction between the graphite felt reaction area and the side to be bonded when the mold is closed, forming a physical sealing barrier. This effectively prevents the molten plastic from penetrating excessively into the central reaction area of ​​the graphite felt during injection molding, ensuring the purity of the effective reaction area of ​​the graphite felt. The vacuum system removes air from the cavity and the pores of the graphite felt, which is conducive to the molten plastic fully penetrating into the porous structure of the graphite felt and improving the density of the bonding layer.

Claims

1. A vanadium redox flow battery stack integrating a flow guide frame and graphite felt, comprising an end plate (1), a current collector (2), a bipolar plate (3), a flow guide frame assembly (4), and a sealing element (5) stacked sequentially, wherein the flow guide frame assembly (4) includes a flow guide frame body (41) and a graphite felt electrode (42), characterized in that: The graphite felt electrode (42) is placed in the inner frame cavity of the flow guide frame body (41); the two opposite sides of the graphite felt electrode (42) along the electrolyte flow direction are the sides to be combined (421), and the sides to be combined (421) and the corresponding side walls of the inner frame of the flow guide frame body (41) are integrally fused together by injection molding process to form a side sealing bonding layer (43) that makes the graphite felt electrode (42) and the flow guide frame body (41) an inseparable integrated structure. The side sealing bonding layer (43) is a mechanical bonding structure formed by the molten injection molding material of the guide frame body (41) penetrating into the porous structure of the side to be bonded (421) and then curing. It is used to achieve both mechanical bonding and flow channel sealing.

2. The vanadium redox flow battery stack integrating the flow guide frame and graphite felt according to claim 1, characterized in that: The other two opposite sides of the graphite felt electrode (42) are electrolyte inlet and outlet sides (422), and the electrolyte inlet and outlet sides (422) and the corresponding side wall of the inner frame of the guide frame body (41) are in a gap fit so that the electrolyte can only enter from one end of the inlet and outlet and flow through the inside of the graphite felt electrode (42) to the other end.

3. The vanadium redox flow battery stack integrating the flow guide frame and graphite felt according to claim 1, characterized in that: The width of one side of the side sealing bonding layer (43) is 5~20mm.

4. The vanadium redox flow battery stack integrating the flow guide frame and graphite felt according to claim 1, characterized in that: The material of the guide frame body (41) is a thermoplastic that is resistant to corrosion by vanadium sulfate electrolyte, and is selected from any one of polypropylene, high-density polyethylene, and polyvinyl chloride.

5. The all-vanadium redox flow battery stack integrating the flow guide frame and graphite felt according to claim 1, characterized in that: The graphite felt electrode (42) is a porous carbonaceous reaction carrier, selected from any one of polyacrylonitrile-based graphite felt, pitch-based graphite felt, and viscose-based graphite felt.

6. A method for preparing a vanadium redox flow battery stack integrating a flow guide frame and graphite felt as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Pretreatment of graphite felt electrode: Cut the graphite felt electrode (42) according to the design dimensions; S2. Mold positioning: Place the pretreated graphite felt electrode (42) into the cavity of the flow guide frame injection mold, and position it so that the two sides (421) of the graphite felt electrode (42) to be joined extend into the forming area of ​​the corresponding flow guide frame sidewall in the mold cavity; S3. Mold closing: The upper and lower molds of the injection molding are closed. When the mold is closed, the sealing frame of the mold is used to press the junction of the reaction area of ​​the graphite felt electrode (42) and the side (421) to be combined, and the air in the pores of the graphite felt electrode (42) in the pressing area is discharged, forming a physical sealing barrier that prevents the molten plastic from penetrating into the central reaction area of ​​the graphite felt electrode (42). S4. Vacuuming the molding area: Open the mold vacuum valve and evacuate the molding area of ​​the guide frame inside the mold to remove the air in the cavity space and the gap in the pores of the side (421) of the graphite felt electrode (42) to be joined. S5. Injection molding: Molten guide frame material is injected into the mold, and pressure is maintained so that the molten plastic fully penetrates into the porous structure of the side to be joined (421). After cooling and solidification, the side to be joined (421) and the guide frame body (41) formed after molding are fused together to obtain a guide frame assembly (4) that integrates the guide frame and graphite felt. S6. Stack assembly: Stack the current guide frame assembly (4) with the bipolar plate, seal, current collector and end plate in sequence, and then fasten it to obtain the vanadium redox flow battery stack.

7. The method for preparing a vanadium redox flow battery stack integrating a flow guide frame and graphite felt according to claim 6, characterized in that: In step S3, the single-sided pressing width of the sealing frame is 3~8mm, and the compaction surface pressure is set to 5~10MPa.

8. The method for preparing a vanadium redox flow battery stack integrating a flow guide frame and graphite felt according to claim 6, characterized in that: In step S4, the vacuum level is -0.06MPa to -0.09MPa.

9. The method for preparing a vanadium redox flow battery stack integrating a flow guide frame and graphite felt according to claim 6, characterized in that: In step S5, the injection pressure is 60~100MPa, the holding time is 10~30s, and the cooling time is 10~30s.

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