Composite bipolar plate of flow battery and manufacturing method of composite bipolar plate

Abstract

The invention relates to the technical field of flow batteries, in particular to a flow battery composite bipolar plate and a manufacturing method thereof.The flow battery composite bipolar plate comprises an assembly sealing area, a buffer transition area and a reaction activity area which are sequentially connected from the edge to the inner side; the buffer transition area comprises a connecting plate; the upper surface of the inner end of the connecting plate is combined with a first current-conducting channel plate, the lower surface is combined with a second current-conducting channel plate, and the first current-conducting channel plate and the second current-conducting channel plate form a reaction active area; the upper surface of the outer end is combined with a first insulating resin plate, the lower surface of the outer end is combined with a second insulating resin plate, and the first insulating resin plate and the second insulating resin plate are respectively of a frame structure with a set width and form an assembly sealing area; the first current conducting channel plate, the second current conducting channel plate, the first insulating resin plate, the second insulating resin plate and the connecting plate all contain the same thermoplastic resin material. The composite bipolar plate structure has the advantages of high sealing reliability, high assembly operability and the like.

Description

Technical Field

[0001] This invention relates to the field of flow battery technology, specifically to a composite bipolar plate for flow batteries and its manufacturing method. Background Technology

[0002] Vanadium redox flow batteries, as large-scale long-term energy storage terminal application equipment, have four core advantages: high safety, strong scalability, high energy conversion efficiency, and long life. They have achieved good demonstration applications in the field of comprehensive energy utilization, including the efficient utilization of intermittent renewable energy, maintaining grid operation stability, and improving power supply quality.

[0003] Composite bipolar plates are structures that integrate bipolar plates, insulating electrode frames, and flow frames into a single unit. One of their core requirements is to prevent electrolyte leakage from the internal structure of flow batteries, thus achieving stack sealing. Currently, there are two main sealing approaches: one is to add a sealing gasket between the bipolar plate and the insulating electrode frame; the other is to achieve sealing through adhesive bonding.

[0004] To accommodate the multiple functions of the bipolar plate (conductive), the insulating electrode frame (insulating), and the electrolyte flow frame (a channel for containing electrolyte), existing technologies often use resin substrates and conductive fillers of different proportions to form an integrated bipolar plate structure with conductive and insulating regions in the same mold. In addition, some literature proposes to open a weldable resin frame structure on the outer edge of the bipolar plate and use laser welding to achieve a seal between it and the insulating electrode frame, thereby improving the bipolar plate's anti-leakage capability.

[0005] For example, Chinese patent application CN 115548363A uses high-density polyethylene as a resin binder. By mixing or kneading and granulating with carbon-based conductive fillers in different proportions, fillers for the reactive zone and the edge welding zone are prepared respectively. Then, the fillers are laid flat in the corresponding areas of the mold and hot-pressed to prepare an integrated bipolar plate with welded edges. However, the proportion of high-density polyethylene in the reactive zone and the edge welding zone is different. Due to the high resin content in the edge welding zone, internal residual stress concentration is easily generated, resulting in deformation such as edge warping and curling. At the same time, the resin fluidity during heating will blur the boundary between the two zones, causing insufficient structural strength in the overlapping area or uncontrollable performance of the dedicated area (failing to meet the expected indicators). For example, Chinese patent application CN114497614A proposes a method for preparing a composite bipolar plate for flow batteries, comprising a conductive region, an insulating region, and a transition region. This method uses a spreading-hot-pressing-trimming process for different functional regions to form the composite bipolar plate. The multi-step operation of this method results in poor operability, making it unsuitable for mass production. Furthermore, the bonding strength between different regions is insufficient, and stress deformation easily occurs due to differences in material composition and proportion. Another example is Chinese patent application CN118198401A, which discloses a bipolar plate with an integrated shell structure and its preparation method. This method involves first preparing the bipolar plate body, then injecting modified polypropylene around it to form an insulating shell structure at the outer edge of the bipolar plate, achieving integration. This method presents a high risk of shear fracture between the outer edge shell and the plate body. The significant difference in the mechanical properties of the body and the edge shell materials easily leads to strain problems. It is also difficult to accurately control the matching relationship between the spatial position of the material and the bonding strength within the overlapping area (a larger overlapping area results in higher bonding strength, but also compresses the material space), which also becomes a barrier to the implementation of this process.

[0006] Therefore, the industry urgently needs to develop a production process for bipolar plate structures of flow batteries that is simple to manufacture, highly operable, suitable for mass production, and has a stable product structure and reliable performance. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a composite bipolar plate for flow batteries and a method for manufacturing the same. By introducing a connecting plate, an insulating resin plate and a conductive flow channel plate are assembled at both ends of the connecting plate to obtain a multifunctional composite bipolar plate structure for flow batteries with an assembly sealing area, a buffer transition area and a reaction flow channel area. This structure has advantages such as high sealing reliability and high assembly operability, and solves the technical problems of easy delamination, leakage and poor fit between different materials in existing composite bipolar plates.

[0009] (II) Technical Solution

[0010] In a first aspect, the present invention provides a composite bipolar plate for a flow battery, comprising an assembly sealing region, a buffer transition region, and a reactive region connected sequentially from the edge to the inside; the buffer transition region includes a connecting plate; the upper surface of the inner end of the connecting plate is coupled with a first conductive flow channel plate, and the lower surface is coupled with a second conductive flow channel plate, the first conductive flow channel plate and the second conductive flow channel plate forming the reactive region; the upper surface of the outer end is coupled with a first insulating resin plate, and the lower surface is coupled with a second insulating resin plate, the first insulating resin plate and the second insulating resin plate forming the assembly sealing region;

[0011] The first conductive flow channel plate, the second conductive flow channel, the first insulating resin plate, the second insulating resin plate, and the connecting plate all contain the same thermoplastic resin material.

[0012] According to a preferred embodiment of the present invention, the connecting plate is a plate or a frame plate with internal window holes, and the first insulating resin plate and the second insulating resin plate are respectively frame structures with a set width.

[0013] According to a preferred embodiment of the present invention, the plate is a straight plate or an irregularly shaped plate, and the frame plate with internal window holes is a U-shaped frame plate, a circular frame plate, or a square frame plate with internal circular window holes; the inner end of the connecting plate is provided with protrusions, grooves, or through holes for increasing the bonding strength with the reactive zone or the assembly sealing zone. Through holes are preferred, and it is more suitable to use a thermoforming method to firmly bond the insulating resin plate and the conductive flow channel plate to the inner and outer ends of the connecting plate.

[0014] According to a preferred embodiment of the present invention, the inner end of the connecting plate occupies 1 / 2 to 1 / 20 of the overall width of the reactive region; the outer end occupies 1 / 2 to 1 / 10 of the width of the assembly sealing region; and the thickness of the connecting plate is 1 / 3 to 1 / 15 of the overall thickness of the reactive region or the assembly sealing region.

[0015] According to a preferred embodiment of the present invention, the two sides of the connecting plate are provided with guide structures for the alignment and installation of the first conductive flow channel plate and the second conductive flow channel plate or the first insulating resin plate and the second insulating resin plate.

[0016] According to a preferred embodiment of the present invention, the first conductive flow channel plate and the second conductive flow channel plate are obtained by blending, rolling and hot molding of resin material and conductive filler, or by melt vacuum injection molding of resin material and conductive filler, or by mixing, granulation and extrusion injection molding of resin material and conductive filler.

[0017] The first insulating resin board and the second insulating resin board are obtained by blending, rolling and hot molding of resin materials and insulating fillers, or by melt vacuum injection molding of resin materials and insulating fillers, or by mixing, granulation and extrusion injection molding of resin materials and insulating fillers.

[0018] The connecting plate is made by blending, rolling and hot molding of resin materials and inorganic fillers, or by melt vacuum injection molding of resin materials and inorganic fillers, or by mixing, granulation and extrusion injection molding of resin materials and inorganic fillers.

[0019] According to a preferred embodiment of the present invention, the material composition of the first conductive flow channel plate and the second conductive flow channel plate includes: conductive filler, fluoropolymer resin and non-fluorothermoplastic resin. The conductive filler is at least one selected from graphite powder, carbon black, acetylene black, expanded graphite, flake graphite, carbon nanotubes, graphene and carbon fiber. The fluoropolymer resin is at least one selected from PVDF, PCTFE, ETFE and ECTFE. The non-fluorothermoplastic resin is at least one selected from PP, POM, PS, PPS and PES. The conductive filler accounts for 70-90% of the mass of the first conductive flow channel plate and the second conductive flow channel plate. The mass ratio of fluoropolymer resin and non-fluorothermoplastic resin is 1.5:1 to 4:1, and the melting point difference between the fluoropolymer resin and the non-fluorothermoplastic resin is ≤15℃.

[0020] According to a preferred embodiment of the present invention, the material composition of the first insulating resin board and the second insulating resin board includes: insulating filler and non-fluorinated thermoplastic resin, wherein the non-fluorinated thermoplastic resin is the same as the non-fluorinated thermoplastic resin in the first conductive flow channel plate and the second conductive flow channel plate, and the insulating filler is at least one selected from calcium carbonate, glass fiber, basalt fiber, talc powder, and silicon dioxide. Preferably, the mass percentage of insulating filler in the first insulating resin board and the second insulating resin board is 15-45% (preferably 25-35%).

[0021] According to a preferred embodiment of the present invention, the inner end of the connecting plate occupies 1 / 2 to 1 / 20 of the overall width of the reactive region; the outer end occupies 1 / 2 to 1 / 10 of the width of the assembly sealing region; and the thickness of the connecting plate is 1 / 3 to 1 / 15 of the overall thickness of the reactive region or the assembly sealing region.

[0022] According to a preferred embodiment of the present invention, the inner end of the connecting plate is a conductor, and the outer end is an insulator; the connecting plate is an integral structure with an insulator at the outer end and a conductor at the inner end, obtained by hot molding of non-fluorinated thermoplastic resin and conductive / insulating filler in a pressing mold with a pre-embedded surface-treated fiber skeleton; or, the connecting plate is integrally vacuum injection molded in an injection mold with a pre-embedded surface-treated fiber skeleton, wherein the injection melt forming the inner end of the connecting plate contains conductive filler and non-fluorinated thermoplastic resin, and the injection melt forming the outer end of the connecting plate contains insulating filler and non-fluorinated thermoplastic resin; or, the connecting plate is an integral structure with an insulator at the outer end and a conductor at the inner end, obtained by mixing, granulating, and finally co-extruding injection molding of non-fluorinated thermoplastic resin and conductive / insulating filler.

[0023] The non-fluorinated thermoplastic resin in the connecting plate is the same as the non-fluorinated thermoplastic resin in the first conductive flow channel plate and the second conductive flow channel plate; the conductive filler is at least one of graphite powder, carbon black, acetylene black, expanded graphite, flake graphite, carbon nanotubes, graphene and carbon fiber; the insulating filler is at least one of calcium carbonate, glass fiber, basalt fiber, talc powder and silicon dioxide.

[0024] Preferably, the conductive filler content in the inner end of the connecting plate is 20-35% (preferably 25-30%); and the insulating filler content in the outer end of the connecting plate is 10-25% (preferably 15-20%).

[0025] Preferably, the surface-treated fiber skeleton is prepared by pre-treating the fiber skeleton with plasma, coupling agent, or epoxy resin adhesive, etc., in order to increase the bonding strength between the fiber skeleton and the integral injection melt.

[0026] According to a preferred embodiment of the present invention, except for the area separated by the inner end of the connecting plate, the lower surface of the first conductive flow channel plate and the upper surface of the second conductive flow channel plate are fused together to form a pocket-shaped slot between the first conductive flow channel plate and the second conductive flow channel plate. The surface of the inner end of the connecting plate is bonded and fixed to the pocket-shaped slot by adhesive or laser welding. Except for the area separated by the outer end of the connecting plate, the lower surface of the first insulating resin plate and the upper surface of the second insulating resin plate are fused together to form a pocket-shaped slot between the first insulating resin plate and the second insulating resin plate. The surface of the outer end of the connecting plate is bonded and fixed to the pocket-shaped slot by adhesive or laser welding.

[0027] According to a preferred embodiment of the present invention, the edges of the first conductive flow channel plate and the first insulating resin plate are connected, and the edges of the second conductive flow channel plate and the second insulating resin plate are connected, wherein the first joint between the first conductive flow channel plate and the first insulating resin plate and the second joint between the second conductive flow channel plate and the second insulating resin plate are misaligned in a direction perpendicular to the connecting plate.

[0028] It should be noted that, due to the possibility of complete or partial fusion of the seam under hot molding conditions, the "seam" may not be visible from the outside. Therefore, the seam does not necessarily exist; it only refers to the boundary line between the conductive flow channel plate and the insulating resin plate. In this application, the area between the two boundary lines (including the two boundary lines) can be defined as the buffer transition zone of the composite bipolar plate.

[0029] According to a preferred embodiment of the present invention, a first engaging structure is formed on the upper surface of the first insulating resin plate, and a second engaging structure is formed on the lower surface of the second insulating resin plate. The first engaging structure and the second engaging structure can cooperate with each other, thereby enabling multiple composite bipolar plates to be combined and the ion exchange membrane to be fixedly sealed between two composite bipolar plates.

[0030] Secondly, the present invention provides a method for manufacturing a composite bipolar plate for a flow battery, comprising:

[0031] S1. Pre-preparing a connecting plate, a conductive flow channel plate, and an insulating resin plate; the insulating resin plate is a frame structure with a set width; the conductive flow channel plate is a continuous plate with microchannels of topology constructed on its surface.

[0032] S2. Place a conductive flow channel plate on the upper and lower surfaces of the inner end of the connecting plate, and place an insulating resin plate on the upper and lower surfaces of the outer end of the connecting plate.

[0033] S3. The structure obtained in S2 is placed in a hot pressing mold, and then hot pressing or hot pressing combined with laser welding is performed to obtain the finished product of the flow battery composite bipolar plate; wherein, the hot pressing pressure is 15~30MPa; the hot pressing temperature of the conductive flow channel plate area is 165~325℃, and the hot pressing temperature of the other areas is 105~125℃.

[0034] According to a preferred embodiment of the present invention, in S1, the conductive flow channel plate is obtained by blending, rolling, and hot molding of fluororesin, non-fluorothermoplastic resin, and conductive filler, or by melt vacuum injection molding or extrusion injection molding of fluororesin, non-fluorothermoplastic resin, and conductive filler; the fluororesin is at least one of PVDF, PCTFE, ETFE, and ECTFE, and the non-fluorothermoplastic resin is at least one of PP, POM, PS, PPS, and PES; the insulating resin plate is obtained by blending, rolling, and hot molding of the non-fluorothermoplastic resin and insulating filler, or by melt vacuum injection molding or extrusion injection molding of the non-fluorothermoplastic resin and insulating filler;

[0035] The inner end of the connecting plate is a conductor, and the outer end is an insulator. The connecting plate is a one-piece structure with an insulator at the outer end and a conductor at the inner end, obtained by hot molding of non-fluorinated thermoplastic resin and conductive / insulating filler in a pressing mold with a pre-embedded surface-treated fiber skeleton. Alternatively, the connecting plate is obtained by integral vacuum injection molding in an injection mold with a pre-embedded surface-treated fiber skeleton, and the injection melt forming the inner end of the connecting plate contains conductive filler and the same non-fluorinated thermoplastic resin as the conductive flow channel plate, while the injection melt forming the outer end of the connecting plate contains insulating filler and the same non-fluorinated thermoplastic resin as the conductive flow channel plate. Alternatively, the connecting plate is a one-piece structure with an insulator at the outer end and a conductor at the inner end, obtained by mixing, granulating, and finally co-extruding injection molding of non-fluorinated thermoplastic resin and conductive / insulating filler.

[0036] The conductive filler is at least one of graphite powder, carbon black, acetylene black, expanded graphite, flake graphite, carbon nanotubes, graphene, and carbon fiber; the insulating filler is at least one of calcium carbonate, glass fiber, basalt fiber, talc powder, and silicon dioxide.

[0037] According to a preferred embodiment of the present invention, in step S2, a conductive flow channel plate is fixed to the upper and lower surfaces of the inner end of the connecting plate with hot melt adhesive, and an insulating resin plate is fixed to the upper and lower surfaces of the outer end of the connecting plate with hot melt adhesive.

[0038] In step S3, the structure obtained in S2 is placed vertically as a whole in a hot press mold. Resin powder, which is the same as the non-fluorinated thermoplastic resin in the conductive flow channel plate, is sprayed into the hot press mold and vacuum treatment is performed. The resin powder is embedded between the gaps of adjacent plates. Then, the contact interface of the two conductive flow channel plates is fused into one by hot pressing or hot pressing combined with laser welding.

[0039] (III) Beneficial Effects

[0040] The technical effects of the present invention include:

[0041] 1. This invention provides a method for manufacturing a composite bipolar plate for a flow battery. It employs a modular assembly strategy, using a single hot-pressing method or a combination of hot-pressing and laser welding to construct a composite bipolar plate structure with multifunctional regions including an assembly sealing region, a buffer transition region, and a reaction channel region. This structure offers advantages such as a high active area ratio, high sealing reliability, and high assembly operability. The integration stability and process implementability between different functional regions are also strong. The manufacturing process provided by this invention is simple and low-cost. Because the conductive channel plate is prefabricated separately, the conductivity of the reaction channel region is precisely controllable (basically consistent with pre-parameters), meeting the expected conductivity requirements.

[0042] 2. The introduction of the connecting plate can effectively ensure the connection strength between different areas and prevent the conductive flow channel plate in the reaction flow channel area from shearing fracture defects during assembly and use. This transition structure of the connecting plate can avoid stress deformation problems caused by the inherent mechanical properties of materials such as material composition type and composition ratio in different areas from the source. Reliability and practicality are effectively guaranteed. Compared with the existing technology, it can more effectively avoid defects such as poor fit and delamination between different materials, effectively avoid the risk of liquid leakage and seepage of the stack, and significantly extend the service life of the flow battery.

[0043] 3. The composite bipolar plate proposed in this invention has an independently molded insulating resin plate and a conductive flow channel plate, which can effectively improve the assembly accuracy of multiple cells in the flow battery stack, increase the reliability of inter-cell sealing, and at the same time, it can also be designed with a modular sealing area structure (insulating resin plate) to match the functional requirements of electrodes, conductive flow channel plates, etc., and reasonably adjust the electrode compression ratio and the distribution of fluid in the conductive flow channel plate, so that the battery structure and the electrochemical performance of the flow battery are more matched. Attached Figure Description

[0044] Figure 1 This is a partial cross-sectional schematic diagram of the composite bipolar plate of the flow battery of the present invention. Figure 1 .

[0045] Figure 2 This is a top view of the connecting plate.

[0046] Figure 3 This is a top view of a frame plate with internal window openings as the connecting plate.

[0047] Figure 4 This is a top view schematic diagram of the composite bipolar plate structure of a flow battery.

[0048] Figure 5 This is a schematic diagram of the cross-sectional structure of the composite bipolar plate in a flow battery.

[0049] Figure 6 This is a partial cross-sectional schematic diagram of the composite bipolar plate of the flow battery of the present invention. Figure 2 . Detailed Implementation

[0050] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] like Figure 1 The image shown is a partial cross-sectional schematic of the composite bipolar plate of the flow battery of the present invention. Figure 1The composite bipolar plate includes an assembly sealing region 10, a buffer transition region 20, and a reactive region 30 connected sequentially from the edge to the inside. The buffer transition region 20 includes a connecting plate 21. The upper surface of the inner end 211 of the connecting plate 21 is bonded to a first conductive flow channel plate 31 by hot pressing or hot pressing and laser welding, and the lower surface is bonded to a second conductive flow channel plate 32 by hot pressing or hot pressing and laser welding. The first conductive flow channel plate 31 and the second conductive flow channel plate 32 form the reactive region 30. The upper surface of the outer end 212 of the connecting plate 21 is bonded to a first insulating resin plate 11 by hot pressing or hot pressing and laser welding, and the lower surface is bonded to a second insulating resin plate 12 by hot pressing or hot pressing and laser welding. The first insulating resin plate 11 and the second insulating resin plate 12 form the assembly sealing region 10.

[0052] like Figure 2-3 As shown, the connecting plate 21 is a plate or a frame plate with internal window holes. For example... Figure 2 As shown, the connecting plate 21 can be a straight plate (a) or an irregularly shaped plate. The irregularly shaped plate can be any shape, such as an I-beam plate (b), a plate with Y-shaped ends, or a dumbbell-shaped plate (c), preferably a shape that is easy to process. Figure 3 As shown, the connecting plate 21 is a frame plate with internal windows. Specifically, it can be any shape, such as a U-shaped frame plate (e.g., a, where the reactive active region 30 is square), a ring-shaped frame plate (e.g., b, where the reactive active region 30 is circular), or a square outer frame with a circular inner frame (e.g., c, where the reactive active region 30 is circular), depending on the cross-sectional shape of the fuel cell stack and the shape and structure of the reactive active region 30. The inner end of the connecting plate and / or has protrusions, grooves, or through holes to increase the bonding strength with the reactive active region 30 or the assembly sealing region 10, preferably as shown in the figure. Figure 2-3 The through-hole structure 213 shown is more suitable for using a thermoforming method to firmly bond the insulating resin board and the conductive flow channel plate to the inner and outer ends of the connecting plate; for example, during the thermoforming process, the insulating resin board on the upper and lower surfaces of the outer end 212 of the connecting plate 21 may partially melt and fuse together through the through-hole, or the conductive flow channel plate on the upper and lower surfaces of the inner end 211 of the connecting plate 21 may partially melt and fuse together through the through-hole. Figure 6 As shown.

[0053] It should be noted that, Figure 3 The dashed line on the connecting plate 21 is the dividing line between the inner and outer ends. This dividing line does not have to be a clear dividing line, nor does it have to be visible to the naked eye, so it is represented by a dashed line. In addition, in some embodiments, the dashed line may also represent a guide structure for the alignment and installation of the first insulating resin plate and the second insulating resin plate.

[0054] Furthermore, in some embodiments, guide structures may be provided on both sides of the connecting plate 21 for aligning and installing the first conductive flow channel plate 31 and the second conductive flow channel plate 32 or the first insulating resin plate 11 and the second insulating resin plate 12. For example, a depression or recess with a depth of about 1 mm may be formed in the area of ​​the connecting plate 21 corresponding to the fixing of the first conductive flow channel plate 31 and the second conductive flow channel plate 32 (recessed relative to the placement of the first insulating resin plate 11 and the second insulating resin plate 12), or conversely, a recess with a depth of about 1 mm may be formed in the area of ​​the connecting plate 21 corresponding to the placement of the first insulating resin plate 11 and the second insulating resin plate 12. This is beneficial for the rapid assembly of the composite bipolar plate.

[0055] The first conductive flow channel plate 31 and the second conductive flow channel plate 32 are obtained by blending, rolling, and hot molding of resin materials and conductive fillers, or by melt vacuum injection molding of resin materials and conductive fillers, or by mixing, granulation, and extrusion injection molding of resin materials and conductive fillers. The first insulating resin plate 11 and the second insulating resin plate 12 are obtained by blending, rolling, and hot molding of resin materials and insulating fillers, or by melt vacuum injection molding of resin materials and insulating fillers, or by mixing, granulation, and extrusion injection molding of resin materials and insulating fillers. The connecting plate 21 is obtained by blending, rolling, and hot molding of resin materials and inorganic fillers, or by melt vacuum injection molding of resin materials and inorganic fillers, or by mixing, granulation, and extrusion injection molding of resin materials and inorganic fillers. The first conductive flow channel plate 31, the second conductive flow channel 32, the first insulating resin plate 11, the second insulating resin plate 12, and the connecting plate 21 all contain the same thermoplastic resin material. During preparation, the type and addition ratio of conductive filler can be selected according to the conductivity requirements of the reactive zone 30. The first conductive flow channel plate 31 and the second conductive flow channel plate 32 are made into prefabricated plates to avoid technical problems such as the resin fluidity caused by high temperature in the hot press mold, which would reduce the conductivity of the reactive zone 30 and cause poor resistivity of the sealed insulating zone 10.

[0056] The conductive fillers in the first conductive flow channel plate 31 and the second conductive flow channel 32 are at least one selected from graphite powder, carbon black, acetylene black, expanded graphite, flake graphite, carbon nanotubes, graphene, and carbon fiber. The insulating fillers in the first insulating resin plate 11 and the second insulating resin plate 12 are at least one selected from calcium carbonate, glass fiber, basalt fiber, talc powder, and silicon dioxide. The inorganic filler in the connecting plate 21 can be either a conductive filler or an insulating filler. The thermoplastic resin material is at least one selected from PP, POM, PS, PPS, and PES.

[0057] The conductive filler accounts for 70-90% of the mass of the first conductive flow channel plate 31 and the second conductive flow channel plate 32, thereby ensuring that the reactive zone 30 has good comprehensive performance such as conductivity and mechanical properties.

[0058] To increase the electrolyte corrosion resistance of the reactive zone 30, preferably, in addition to the aforementioned thermoplastic resin material, the first conductive flow channel plate 31 and the second conductive flow channel 32 also contain a certain proportion of fluororesin, wherein the fluororesin is at least one of PVDF, PCTFE, ETFE, and ECTFE. The fluororesin enhances the corrosion resistance of the first conductive flow channel plate 31 and the second conductive flow channel 32. Specifically, the material composition of the first conductive flow channel plate 31 and the second conductive flow channel plate 32 includes conductive filler, fluororesin, and non-fluoro thermoplastic resin. The fluororesin is at least one of PVDF, PCTFE, ETFE, and ECTFE, and the non-fluoro thermoplastic resin is at least one of PP, POM, PS, PPS, and PES. To balance the bonding strength, mechanical properties, and corrosion resistance of the first conductive flow channel plate 31 and the second conductive flow channel plate 32 with the connecting plate 21, the mass ratio of fluororesin to non-fluoro thermoplastic resin is 1.5:1 to 4:1. To ensure good compatibility of different types of resins during the processing of conductive flow channel plate 31 (32), the melting point difference between fluorinated resin and non-fluorinated thermoplastic resin is ≤15℃.

[0059] The first insulating resin plate 11 and the second insulating resin plate 12 are composed of insulating filler and non-fluorinated thermoplastic resin. The non-fluorinated thermoplastic resin is the same as the non-fluorinated thermoplastic resin in the first conductive flow channel plate 31 and the second conductive flow channel plate 32. The mass ratio of insulating filler is 15-45% (preferably 25-35%), which can take into account good insulation, mechanical strength and its strong composite with the connecting plate 21.

[0060] To accommodate the different electrical conductivity requirements of the reactive zone 30 and the assembly sealing zone 10, the connecting plate of the buffer transition zone adopts a functional structure, namely, the inner end 211 of the connecting plate 21 is a conductor, and the outer end 212 is an insulator. The inner end 211 is used to connect the reactive zone 30, and the outer end 212 is used to connect the assembly sealing zone 10.

[0061] The connecting plate 21 is an integral structure with an outer end 212 as an insulator and an inner end 211 as a conductor, obtained by hot molding of non-fluorinated thermoplastic resin and conductive / insulating filler in a pressing mold with a pre-embedded surface-treated fiber skeleton; or the connecting plate 21 is integrally vacuum injection molded in an injection mold with a pre-embedded surface-treated fiber skeleton, and the injection melt of the inner end 211 of the connecting plate contains conductive filler and non-fluorinated thermoplastic resin, and the injection melt of the outer end 212 of the connecting plate contains insulating filler and non-fluorinated thermoplastic resin; or the connecting plate 21 is an integral structure with an outer end 212 as an insulator and an inner end 211 as a conductor, obtained by mixing, granulating, and finally co-extruding injection molding of non-fluorinated thermoplastic resin and conductive / insulating filler. Similarly, the non-fluorinated thermoplastic resin used in the connecting plate 21 is the same as the non-fluorinated thermoplastic resin used in the first conductive flow channel plate 31 and the second conductive flow channel plate 32. The conductive filler is at least one of graphite powder, carbon black, acetylene black, expanded graphite, flake graphite, carbon nanotubes, graphene, and carbon fiber, and preferably the same as the conductive filler in the first conductive flow channel plate 31 and the second conductive flow channel plate 32. The insulating filler is at least one of calcium carbonate, glass fiber, basalt fiber, talc powder, and silica, and preferably the same as the insulating filler in the first insulating resin plate 11 and the second insulating resin plate 12. This further reduces the differences in material and mechanical properties between the connecting plate 21 and the reactive zone 30 and the assembly sealing zone 10 at its two ends.

[0062] like Figure 4 and Figure 5 The figures shown are a top view and a cross-sectional view of the composite bipolar plate of a flow battery. When the connecting plate 21 is a frame plate with internal windows, it can specifically be a U-shaped frame plate (e.g.,...). Figure 3 When a), Figure 4The two dashed boxes on the inner and outer sides represent the connecting plates. The reactive zone 30 is attached to the inner end 211 of the connecting plate 21. The reactive zone 30 includes a first conductive flow channel plate 31 and a second conductive flow channel plate 32. The surface of the first conductive flow channel plate 31 or the second conductive flow channel plate 32 can be provided with interconnected electrode liquid channels (microchannels with a topology of 0.2-1 mm depth), such as Z-shaped, W-shaped, or S-shaped channels. The width of the inner end 211 of the connecting plate 21 accounts for 1 / 2 to 1 / 20 of the overall width of the reactive zone 30. The assembly sealing zone 10 is attached to the outer end 212 of the connecting plate 21. The assembly sealing zone 10 includes a first insulating resin plate 11 and a second insulating resin plate 12. The surfaces of the first insulating resin plate 11 and the second insulating resin plate 12 are provided with interlocking structures 111 (121) to facilitate mutual assembly. The conductive flow channel plate in the central region of each connecting plate 21 is connected to the insulating resin plates arranged around it. The width of the outer end 212 of the connecting plate 21 accounts for 1 / 2 to 1 / 10 of the width of the assembly sealing area. Furthermore, the thickness of the connecting plate 21 is only 1 / 3 to 1 / 15 of the overall thickness of the reactive region 30 or the assembly sealing area 10. Therefore, the connecting plate 21 occupies a very small proportion of the entire composite bipolar plate. Thus, although the types of fillers contained in the materials at both ends of the connecting plate 21 are different (one end is conductive filler, the other end is insulating filler), and there are differences in the inherent properties of the materials at both ends, the small overall size and low filler content of the connecting plate 21 mean that the differences in material properties and stress changes between its two ends have a relatively small impact on the entire composite bipolar plate. Alternatively, the connecting plate 21 can be entirely an insulator or a conductor. Since its proportion in the reactive region 30 and the assembly sealing area 10 is small, it will not significantly weaken the overall insulation of the assembly sealing area 10 or the conductivity of the reactive region 30.

[0063] Since the connecting plate 21 is relatively thin, its thickness is only 1 / 3 to 1 / 15 of the overall thickness of the reactive zone 30 or the assembly sealing zone 10. In order to improve the strength of the connecting plate 21 itself, a fiber skeleton material can be set inside the connecting plate 21. The fiber skeleton material can be at least one of carbon fiber mesh, carbon felt, steel wire mesh and glass fiber felt. When the connecting plate 21 is prepared by integral vacuum injection molding or hot molding, it is preferable to first perform surface treatment on the fiber skeleton, such as plasma surface modification, coupling agent surface modification or pre-coating with epoxy resin adhesive, etc. The purpose is to increase the bonding strength between the fiber skeleton and the thermoplastic resin during the melt or hot molding process, and to avoid the separation of the fiber skeleton from the non-fluorinated thermoplastic resin during assembly / use.

[0064] The conductive filler in the inner end 211 of the connecting plate 21 accounts for 20-35 wt%, preferably 25-30 wt%; the insulating filler in the outer end 212 of the connecting plate 21 accounts for 10-25 wt%, preferably 15-20 wt%. This content ratio can take into account the good conductivity / insulation, mechanical strength, good thermoplasticity, and bonding strength with the reactive zone 30 and the assembly sealing zone 10 after hot pressing or laser welding of the connecting plate 21.

[0065] Of the three molding methods for the connecting plate 21, the preferred method is to use co-extrusion to obtain an integral structure with an insulator at the outer end and a conductor at the inner end. This method can integrally mold a high-strength connecting plate 21. The extrusion process can increase the density and mechanical strength of the plate and ensure that the inner end 211 and the outer end 212 are firmly bonded together. For example, PP, calcium carbonate and talc powder (in a mass ratio of 85:9:6), and PP and graphite powder (in a mass ratio of 3:1) are added to a mixer and mixed. Then, the mixture is extruded and granulated to obtain a composite material for injection molding. Finally, the integral connecting plate 21 with an insulator at one end and a conductor at the other end is obtained by co-extrusion injection molding. The composite materials at both ends of the connecting plate 21 are both polypropylene (PP) as the continuous phase. Although the fillers are different, the molten PP molecular chains can diffuse and entangle with each other at the interface, so that the PP matrix forms molecular chain movement in the high-temperature molten state, forming an "interpenetrating network" across the interface, which constitutes a physical anchor point. The steps in the "co-extrusion" molding process are as follows: (1) Melt injection timing control: First inject the high-viscosity melt (insulating end), and when it fills to 70% of the volume, inject the conductive melt simultaneously, and use the thermal effect of the first melt to promote interface fusion. Adjust the barrel temperature (e.g., 200-220°C for the insulating end and 190-210°C for the conductive end) so that the viscosity difference between the two melts at the junction point is <10%, and avoid flow stratification. (2) Pressure holding and cooling optimization: First, force the melt to penetrate into the interface micropores at 80-100MPa (high pressure stage), and then maintain molecular chain diffusion at the medium pressure stage (40-60MPa); (3) Asymmetric cooling: The conductive end is cooled faster (10°C lower mold temperature) to compensate for the shrinkage difference caused by graphite powder and reduce internal stress. (4) Vacuum-assisted exhaust and shear rate control: A vacuum channel is set at the melt junction to remove trapped gas and control the shear rate in the flow channel to ≥5,000 / s, thereby breaking up the packing agglomeration and avoiding the formation of weak interfacial zones.

[0066] like Figure 5 and Figure 6As shown, in the composite bipolar plate, except for the area separated by the inner end of the connecting plate 21, the lower surface of the first conductive channel plate 31 and the upper surface of the second conductive channel plate 32 are fused together to form a pocket-shaped slot between the first conductive channel plate 31 and the second conductive channel plate 32. The surface of the inner end 211 of the connecting plate 21 is bonded and fixed to the inner side of the pocket-shaped slot by adhesive or laser welding. Similarly, except for the area separated by the outer end 212 of the connecting plate 21, the lower surface of the first insulating resin plate 11 and the upper surface of the second insulating resin plate 12 can also be fused together (under higher hot molding temperature and pressure) to form a pocket-shaped slot between the first insulating resin plate 11 and the second insulating resin plate 12. The surface of the outer end 212 of the connecting plate is bonded and fixed to the inner side of the pocket-shaped slot by adhesive or laser welding.

[0067] For example Figure 1 As shown, on the upper side of the connecting plate 21, the edges of the first conductive flow channel plate 31 and the first insulating resin plate 11 are connected, and the edges of the second conductive flow channel plate 32 and the second insulating resin plate 12 are connected. Preferably, the first joint 21A formed between the first conductive flow channel plate 31 and the first insulating resin plate 11 and the second joint 21B between the second conductive flow channel plate 32 and the second insulating resin plate 12 are misaligned in the vertical direction (perpendicular to the connecting plate 21), such as a misalignment of 1-2 cm, to avoid the connecting plate 21 becoming a weak point in the structural strength of the composite bipolar plate when the two joints are aligned, thereby further enhancing the structural strength of the composite bipolar plate. However, since the different plates are fused together by sprayed thermoplastic resin powder after hot molding, even if the "joints" on the upper and lower sides of the connecting plate 21 are aligned, the final composite bipolar plate still has excellent structural strength and stability.

[0068] It should be noted that, due to the possibility of complete or partial fusion of the seams under hot molding conditions, the "seam" may not be visible from the outside. Therefore, the seam here only refers to the boundary line between the current channel plate and the insulating resin plate. In this application, the area between the two boundary lines (including the two boundary lines) can be defined as the buffer transition zone 20 of the composite bipolar plate. In addition, if the first seam 21A and the second seam 21B are not completely fused together, they can also serve as markers for aligning the battery cells during assembly, facilitating the bipolar plate molding and assembly construction, and effectively preventing potential risks such as misalignment and poor overlap.

[0069] To facilitate the assembly of multiple battery cells into a stack structure, such as Figure 1 , Figure 5 and Figure 6As shown, a first engaging structure 111 is formed on the upper surface of the first insulating resin plate 11, and a second engaging structure 121 is formed on the lower surface of the second insulating resin plate 12. The first engaging structure 111 preferably has multiple grooves with spacing between them, and each groove forms a closed loop along the edge of the first insulating resin plate 11. The second engaging structure 121 has multiple protruding ridges with spacing between them, and the ridges form a closed loop along the second insulating resin plate 12. When assembling battery cells into a stack, adjacent battery cells cooperate using the first engaging structure 111 and the second engaging structure 121, thereby fixing and sealing the ion exchange membrane between two adjacent composite bipolar plates. This serves as a limiting assembly for multiple composite bipolar plates, facilitating stacking and assembly during stack production.

[0070] Secondly, the present invention provides a method for manufacturing a composite bipolar plate for a flow battery, comprising:

[0071] S1. Prepare connecting plate 21, conductive flow channel plate, and insulating resin plate. The connecting plate is as follows: Figure 2 The plate structure shown or Figure 3 The diagram shows an internal frame structure with windows. For a fuel cell stack with a predetermined shape, the connecting plate 21 has only one pre-form of a certain size. The insulating resin plate can include two pre-forms of different sizes: one with a narrow frame and multiple grooves on the surface, and the other with a wider frame and multiple raised ridges on the surface. The difference in width between the two frame sizes is the misalignment distance of the upper and lower seams of the connecting plate 21 (if the seam misalignment is not considered, the frame widths can be the same). The conductive channel plate can include two pre-forms of different sizes: one slightly smaller and the other slightly larger. The difference in width between the two conductive channel plates is approximately twice the misalignment distance of the upper and lower seams of the connecting plate 21 (if the seam misalignment is not considered, only one size of pre-form can be produced). The conductive channel plate is a continuous plate structure with microchannels (used as electrolyte channels) on its surface. Of course, the insulating resin plate with the frame structure can also be replaced by four plates that can be spliced ​​into a quadrilateral frame structure.

[0072] S2. Place a conductive flow channel plate on the upper and lower surfaces of the inner end 211 of the connecting plate 21, and place an insulating resin plate (such as...) on the upper and lower surfaces of the outer end 212 of the connecting plate. Figure 4-5 (As shown).

[0073] The conductive flow channel plate with slightly smaller dimensions is installed on the same side surface of the connecting plate 21 in conjunction with the insulating resin plate with a wider frame width; the conductive flow channel plate with slightly larger dimensions is installed on the other side surface of the connecting plate 21 in conjunction with the insulating resin plate with a narrower frame width.

[0074] S3. The structure obtained in S2 is placed in a hot pressing mold, and then hot pressing or hot pressing combined with laser welding is performed to obtain the finished product of the flow battery composite bipolar plate; wherein, the hot pressing pressure is 15~30MPa; the hot pressing temperature of the conductive flow channel plate area is 165~325℃, and the hot pressing temperature of the other areas is 105~125℃.

[0075] In S1, the conductive flow channel plate is obtained by blending, rolling, and hot molding of fluororesin, non-fluorinated thermoplastic resin, and conductive filler; or by melt vacuum injection molding of fluororesin, non-fluorinated thermoplastic resin, and conductive filler; or by mixing, granulation, and extrusion injection molding of fluororesin, non-fluorinated thermoplastic resin, and conductive filler. The insulating resin plate is obtained by blending, rolling, and hot molding of the same non-fluorinated thermoplastic resin and insulating filler as the conductive flow channel plate; or by melt vacuum injection molding of the same non-fluorinated thermoplastic resin and insulating filler as the conductive flow channel plate; or by mixing, granulation, and extrusion injection molding of the same non-fluorinated thermoplastic resin and insulating filler as the conductive flow channel plate. The inner end 211 of the connecting plate 21 is a conductor, and the outer end 212 of the connecting plate 21 is an insulator. The inner end 211 is obtained by blending conductive filler and the same non-fluorinated thermoplastic resin as the conductive flow channel plate, rolling and hot molding. The outer end 212 is obtained by blending insulating filler and the same non-fluorinated thermoplastic resin as the conductive flow channel plate, rolling and hot molding. Alternatively, the connecting plate 21 is integrally vacuum-injected into an injection mold with a pre-embedded surface-treated fiber skeleton. The injection melt forming the inner end 211 of the connecting plate contains conductive filler and the same non-fluorinated thermoplastic resin as the conductive flow channel plate, while the injection melt forming the outer end 212 of the connecting plate contains insulating filler and the same non-fluorinated thermoplastic resin as the conductive flow channel plate. Alternatively, the connecting plate 21 is an integral structure with an outer end 212 as an insulator and an inner end 211 as a conductor, obtained by mixing non-fluorinated thermoplastic resin and conductive / insulating filler, granulating, and finally co-extruding injection molding.

[0076] In step S2, a conductive flow channel plate is fixed to the upper and lower surfaces of the inner end 211 of the connecting plate 21 using hot melt adhesive, and an insulating resin plate is fixed to the upper and lower surfaces of the outer end 212 of the connecting plate 21 using hot melt adhesive. Finally, the structure obtained in S2 is placed vertically as a whole in a hot press mold. Resin powder identical to the non-fluorinated thermoplastic resin in the conductive flow channel plate is sprayed into the hot press mold. The thermoplastic resin powder is embedded between the gaps of adjacent plates. Then, through hot pressing or hot pressing combined with laser welding, the contact interface of the two conductive flow channel plates is fused together. During the spraying of the thermoplastic resin powder, a vacuum process is also performed to embed the thermoplastic resin powder into the gaps, acting as an adhesive. Under the hot press mold, the different plates are bonded together to increase the bonding strength. Simultaneously, the resin powder also increases the roughness of the contact surface.

[0077] The main solution of this invention is to introduce a connecting plate 21 between the reactive zone 30 and the sealed assembly zone 10. The connecting plate 21 is embedded inside both the reactive zone 30 and the sealed assembly zone 10 to improve the connection strength between different zones and effectively prevent the shear fracture defect of the flow channel plate. At the same time, this transition structure design can avoid stress deformation problems caused by the inherent mechanical properties of materials such as material composition type and composition ratio in different zones from the source, and the reliability and practicality are effectively guaranteed.

[0078] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be further described clearly and completely below in conjunction with the embodiments of the present invention. It should be noted that the following embodiments are only for the production of bipolar plate specimens, and each connecting plate 21 is a straight plate (except for Embodiment 5, none have through-hole structures 213); the insulating resin board is illustrated using a composite bipolar plate specimen made with a single-sided frame as an example. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0079] Example 1

[0080] This embodiment provides a composite bipolar plate specimen for a flow battery, the steps of which are as follows:

[0081] (1) A conductive filler composed of expanded graphite and graphene (mass ratio of 10:1) and a composite resin material composed of PVDF and PP (mass ratio of 8:3) are uniformly mixed at a mass ratio of 17:3. The mixture is then rolled and hot-molded at process parameters of 170°C and 23MPa to obtain a square conductive flow channel plate (side length 30cm).

[0082] (2) PP, calcium carbonate and talc powder (mass ratio of 85:9:6) and PP and graphite powder (mass ratio of 3:1) are added to a mixer and mixed. Then, the mixture is extruded and granulated to obtain the composite material for injection molding. Finally, the connecting plate with an insulated outer end and a conductive inner end is obtained by co-extrusion injection molding. The connecting plate is 10mm thick (total thickness of composite bipolar plate is 30mm), 15cm long and 12cm wide. The conductive end (8cm) is the inner end and the non-conductive end (4cm) is the outer end.

[0083] (3) PP, talc powder and glass fiber (mass ratio of 13:2:5) are mixed in an internal mixer, and then extruded and granulated to obtain a composite material for injection molding. The composite material is then produced by extrusion injection molding to obtain an insulating resin board with a uniform frame width but different surface interlocking structures. The frame width is 10cm.

[0084] (4) Apply hot melt adhesive film to the upper and lower surfaces of the connecting plate respectively. Fix an insulating resin plate and a conductive flow channel plate to the upper surface of the connecting plate with hot melt adhesive film. Fix another insulating resin plate and another conductive flow channel plate to the lower surface of the connecting plate with hot melt adhesive film. Place the whole structure in a hot press mold and spray PP resin powder evenly into the mold (with vacuuming to make more PP resin powder embedded in each gap). Then, heat press to obtain the finished product of the flow battery composite bipolar plate.

[0085] The hot-pressing temperature of the conductive flow channel plate area is 172℃, while the hot-pressing temperature of the remaining areas is 108℃, and the hot-pressing pressure is 20MPa. For example... Figure 1 As shown, the hot-pressing temperature of the conductive flow channel plate area is relatively high. At the same time, under the action of pressure, the two conductive flow channel plates 11 and 12 on the upper and lower surfaces of the connecting plate 21 are fused into one piece, and there is no visible connection seam at the contact interface of the two conductive flow channel plates.

[0086] Example 2

[0087] This embodiment provides a composite bipolar plate specimen for a flow battery, the steps of which are as follows:

[0088] (1) A conductive filler composed of flake graphite, carbon black and graphene (mass ratio of 7:2:1) and a composite resin material composed of ECTFE and PS (mass ratio of 3:1) are uniformly mixed at a mass ratio of 4:1, and then hot-molded at 240℃ and 25MPa to obtain a square conductive flow channel plate (side length 30cm).

[0089] (2) PS, talc powder and silica (mass ratio of 80:10:7), and PS, carbon fiber and acetylene black (mass ratio of 30:5:7) are added to a mixer and mixed and granulated to obtain a composite material for injection molding. Finally, a connecting plate is obtained by co-extrusion injection molding. The connecting plate is 10mm thick (total thickness of composite bipolar plate is 30mm), 15cm long and 15cm wide, with the conductive end (10cm) being the inner end and the non-conductive end (5cm) being the outer end.

[0090] (3) PS, calcium carbonate and glass fiber (mass ratio of 12:1:4) are mixed in an internal mixer, and then extruded and granulated by a granulator to obtain a composite material for injection molding. Then, an insulating resin board with a frame width of 10cm is made by extrusion injection molding.

[0091] (4) Apply hot melt adhesive film to the upper and lower surfaces of the connecting plate respectively (the hot melt adhesive film can also be applied to the sides of the insulating resin plate and the conductive flow channel plate). Fix one insulating resin plate and one conductive flow channel plate to the upper surface of the connecting plate with hot melt adhesive film. Fix another insulating resin plate and another conductive flow channel plate to the lower surface of the connecting plate with hot melt adhesive film. Place the whole structure in a hot press mold, spray PS resin powder evenly into the mold (with vacuum treatment), and then hot press to obtain the finished product of the flow battery composite bipolar plate.

[0092] The hot-pressing temperature of the conductive flow channel plate area is 240℃, the hot-pressing temperature of the remaining areas is 108℃, and the hot-pressing pressure is 21MPa.

[0093] Example 3

[0094] This embodiment provides a composite bipolar plate specimen for a flow battery, the steps of which are as follows:

[0095] (1) A conductive graphite material composed of expanded graphite, acetylene black and carbon fiber (mass ratio of 6:2:1) and a composite resin material composed of ETFE and PPS (mass ratio of 2:1) are uniformly mixed at a mass ratio of 13:2. The mixture is then rolled and hot-pressed at process parameters of 280°C and 28 MPa to obtain a square conductive flow channel plate (side length 30cm).

[0096] (2) PPS, talc and silica (mass ratio 79:7:12), and PPS and carbon black (mass ratio 2.5:1) are added to a mixer and mixed and granulated to obtain a composite material for injection molding. Finally, a connecting plate is made by co-extrusion injection molding. The connecting plate is 10mm thick (total thickness of the composite bipolar plate is 30mm), 15cm long, and 15cm wide. The conductive end (10cm) is the inner end, and the non-conductive end (5cm) is the outer end.

[0097] (3) PPS, calcium carbonate and basalt fiber (mass ratio of 13:1:4) are added to a mixer to mix and granulate to obtain a composite material for injection molding. Then, an insulating resin board with a frame width of 10cm is obtained by extrusion injection molding.

[0098] (4) Apply hot melt adhesive film to the upper and lower surfaces of the connecting plate respectively (the hot melt adhesive film can also be applied to the sides of the insulating resin plate and the conductive flow channel plate). Fix one insulating resin plate and one conductive flow channel plate to the upper surface of the connecting plate with hot melt adhesive film. Fix another insulating resin plate and another conductive flow channel plate to the lower surface of the connecting plate with hot melt adhesive film. Place the whole structure in a hot press mold, spray PPS resin powder evenly into the mold (with vacuum treatment), and then heat press and laser weld to obtain the finished product of the flow battery composite bipolar plate.

[0099] The hot-pressing temperature of the conductive flow channel plate area is 280℃, the hot-pressing temperature of the remaining areas is 108℃, and the hot-pressing pressure is 24MPa.

[0100] Example 4

[0101] This embodiment provides a composite bipolar plate specimen for a flow battery, which differs from Embodiment 1 mainly in the fabrication process of the connecting plate, as detailed below:

[0102] PP, calcium carbonate and talc (mass ratio 85:9:6) are uniformly mixed to obtain an insulating composite filler for the outer end of the molding connecting plate, and PP and graphite powder (mass ratio 3:1) are uniformly mixed to obtain a conductive composite filler for the inner end of the molding connecting plate.

[0103] Insulating composite filler is filled into the outer 4cm width section of a 10mm deep hot-molding mold, and conductive composite filler is filled into the inner 8cm width section. The filler is then spread out, ultrasonically vibrated to expel gas, and compacted. Finally, a 0.25mm thick piece with a density of 1.8 g / cm³, slightly smaller than the mold, is placed inside. 3 The carbon fiber mesh (pre-coated with silane coupling agent) is then loaded with composite filler as described above. The filler is then flattened again, ultrasonically vibrated to expel gas from the filler, and compacted. Finally, an integrated connecting plate (specifications see Example 1) is obtained at 172°C and 20MPa. The remaining steps of this example are the same as in Example 1, with laser welding also performed during hot molding.

[0104] Example 5

[0105] The difference between this embodiment and Embodiment 4 is that, in the process of preparing the connecting plate with a conductor at the inner end and an insulator at the outer end using the hot molding method, no carbon fiber mesh skeleton material is laid. However, an island-like structure is set in the hot molding mold, so that the inner and outer ends of the integrated connecting plate formed by hot molding each form two through-hole structures with a diameter of about 1 cm. The remaining steps of this embodiment are the same as those in Embodiment 1, and laser welding is also performed during hot molding.

[0106] To verify the advantages of the connecting plate in improving the performance stability and reliability of the composite bipolar plate, the following comparative examples were designed and tested. The comparative examples are composite bipolar plates prepared by traditional regionalized fillers and molding hard connections.

[0107] Comparative Example 1

[0108] This comparative example illustrates a method for preparing a composite bipolar plate specimen, as detailed below:

[0109] (1) A conductive graphite material composed of expanded graphite and graphene (mass ratio of 10:1) and a composite resin material composed of PVDF and PP (mass ratio of 8:3) are uniformly mixed at a mass ratio of 17:3 to obtain a composite filler for molding reactive zones.

[0110] (2) PP, talc and glass fiber are mixed evenly in a mass ratio of 13:2:5 to obtain a composite filler for the molded sealing assembly area.

[0111] (3) Fill the reactive zone in the center of the mold and the sealing assembly zone at the edge of the mold with the two composite fillers respectively. Spread the fillers flat, use ultrasonic vibration to expel the gas in the fillers, increase the packing density, and then compact them.

[0112] (4) The integrated bipolar plate was hot-pressed at 172℃ and 20MPa process parameters.

[0113] The composition of the two composite fillers is consistent with that of the conductive flow channel plate and the insulating resin plate in Example 1. The hot pressing temperature is taken as the larger value in Example 1, and the hot pressing pressure is consistent with that in Example 1.

[0114] Table 1 shows the test results of various properties of the composite bipolar plates prepared in Examples 1-3 and Comparative Example 1 of the present invention, mainly including the conductivity of the reactive region, the tensile strength between the reactive region and the assembly sealing region, and the resistivity of the assembly sealing region.

[0115] Table 1:

[0116]

[0117] As shown in Table 1, the tensile strengths of the reactive active region and the assembly-sealed region of the composite bipolar plates in Examples 1-5 of the present invention are 33.7 MPa, 35.3 Pa, 38.2 MPa, 38.8 MPa, and 40.6 MPa, respectively. Meanwhile, compared to Comparative Example 1, under the same conditions of adding conductive filler in the reactive active region and insulating filler in the assembly-sealed region, and with identical hot-molding conditions, the conductivity of the reactive active region and the tensile strength between the reactive active region and the assembly-sealed region of the composite bipolar plate prepared in Example 1 are significantly better than those in Comparative Example 1 (14.4 MPa). These two performance parameters directly affect the long-term performance stability and reliability of the flow battery. In Comparative Example 1, the composite filler in the reactive active region and the composite filler in the assembly-sealed region were directly hot-molded in a mold to prepare the bipolar plate. The composite fillers in the two regions flowed and mixed at high temperatures, resulting in a decrease in the conductivity of the reactive active region and the volume resistivity of the assembly-sealed region, and a significant difference in tensile strength.

[0118] It should be noted that the above is a composite bipolar plate specimen structure, only used to illustrate the enhanced tensile strength between the reactive zone and the assembly sealing zone after the two plates are formed using the process of this invention, as well as the conductivity / insulation performance of each region. In actual production, the insulating resin board is usually an integrally molded quadrilateral frame plate, which surrounds the conductive flow channel plate in the inner frame (the conductive flow channel plate is embedded in the insulating resin board of the quadrilateral frame plate structure). At the same time, it is used in conjunction with straight plate-like or integral frame plates with internal windows and holes on the four sides to achieve a reinforced connection. In this case, the tensile strength between the reactive zone and the assembly sealing zone will be significantly improved based on Examples 1-5.

[0119] Therefore, it is evident that the composite bipolar plate prepared by the process of this invention exhibits precisely controllable conductivity in the reaction channel region and insulation in the assembly sealing region (meeting preset conductivity requirements). In particular, the conductivity in the reactive region and the bonding strength between the reactive region and the assembly sealing region are significantly improved, effectively preventing the risk of liquid leakage and extending the lifespan of the flow battery. Furthermore, the composite bipolar plate preparation process of this invention allows for modular design of the sealing region structure to match the functional requirements of the electrodes and conductive channel plates, enabling reasonable adjustment of the electrode compression ratio and fluid distribution within the conductive channel plates, further enhancing the matching degree between the electrochemical performance and battery structure of the flow battery.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. These modifications or substitutions, or combinations of technical features in the above embodiments that do not conflict with each other, can be made in accordance with the manner described in the embodiments. These modifications, substitutions or combinations do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite bipolar plate for a flow battery, characterized in that, It includes an assembly sealing area, a buffer transition area, and a reactive area connected sequentially from the edge to the inside; the buffer transition area includes a connecting plate; the upper surface of the inner end of the connecting plate is connected to a first conductive flow channel plate, and the lower surface is connected to a second conductive flow channel plate, the first conductive flow channel plate and the second conductive flow channel plate forming the reactive area; the upper surface of the outer end is connected to a first insulating resin plate, and the lower surface is connected to a second insulating resin plate, the first insulating resin plate and the second insulating resin plate forming the assembly sealing area; The first conductive flow channel plate, the second conductive flow channel, the first insulating resin plate, the second insulating resin plate, and the connecting plate all contain the same thermoplastic resin material.

2. The composite bipolar plate for a flow battery according to claim 1, characterized in that, The connecting plate is a plate or a frame plate with internal window holes, and the first insulating resin plate and the second insulating resin plate are respectively frame structures with a set width.

3. The composite bipolar plate for a flow battery according to claim 2, characterized in that, The plate is a straight plate or an irregularly shaped plate, and the frame plate with internal window holes is a square frame plate, a circular frame plate, or a square frame plate with internal circular window holes; The inner end of the connecting plate and / or is provided with protrusions, grooves or through holes to increase the bonding strength with the reactive zone or the assembly sealing zone.

4. The composite bipolar plate for a flow battery according to claim 1, characterized in that, The inner end of the connecting plate occupies 1 / 2 to 1 / 20 of the overall width of the reactive zone; the outer end occupies 1 / 2 to 1 / 10 of the width of the assembly sealing zone; the thickness of the connecting plate is 1 / 3 to 1 / 15 of the overall thickness of the reactive zone or the assembly sealing zone.

5. The composite bipolar plate for a flow battery according to claim 1, characterized in that, The two sides of the connecting plate are provided with guide structures for the alignment and installation of the first conductive flow channel plate and the second conductive flow channel plate or the first insulating resin plate and the second insulating resin plate.

6. The composite bipolar plate for a flow battery according to any one of claims 1-5, characterized in that, The first conductive flow channel plate and the second conductive flow channel plate are obtained by blending, rolling and hot molding of resin materials and conductive fillers, or by melt vacuum injection molding of resin materials and conductive fillers, or by mixing, granulation and extrusion injection molding of resin materials and conductive fillers. The first insulating resin board and the second insulating resin board are obtained by blending, rolling and hot molding of resin materials and insulating fillers, or by melt vacuum injection molding of resin materials and insulating fillers, or by mixing, granulation and extrusion injection molding of resin materials and insulating fillers. The connecting plate is made by blending, rolling and hot molding of resin materials and inorganic fillers, or by melt vacuum injection molding of resin materials and inorganic fillers, or by mixing, granulation and extrusion injection molding of resin materials and inorganic fillers.

7. The composite bipolar plate for a flow battery according to claim 6, characterized in that, The first and second conductive flow channel plates are composed of conductive fillers, fluoropolymers, and non-fluorothermoplastic resins. The conductive fillers are at least one of graphite powder, carbon black, acetylene black, expanded graphite, flake graphite, carbon nanotubes, graphene, and carbon fiber. The fluoropolymers are at least one of PVDF, PCTFE, ETFE, and ECTFE. The non-fluorothermoplastic resins are at least one of PP, POM, PS, PPS, and PES. The conductive fillers account for 70-90% of the mass of the first and second conductive flow channel plates. The mass ratio of the fluoropolymers to the non-fluorothermoplastic resins is 1.5:1 to 4:1, and the melting point difference between the fluoropolymers and the non-fluorothermoplastic resins is ≤15℃.

8. The composite bipolar plate for a flow battery according to claim 6, characterized in that, The material composition of the first insulating resin board and the second insulating resin board includes: insulating filler and non-fluorinated thermoplastic resin. The non-fluorinated thermoplastic resin is the same as the non-fluorinated thermoplastic resin in the first conductive flow channel plate and the second conductive flow channel plate. The insulating filler is at least one of calcium carbonate, glass fiber, basalt fiber, talc powder and silicon dioxide. The proportion of insulating filler is 15-45%.

9. The composite bipolar plate for a flow battery according to claim 6, characterized in that, The inner end of the connecting plate is a conductor, and the outer end is an insulator; The connecting plate is an integral structure with an insulator at the outer end and a conductor at the inner end, formed by hot molding non-fluorinated thermoplastic resin and conductive / insulating filler in a pressing mold with a pre-embedded surface-treated fiber skeleton. Alternatively, the connecting plate is integrally vacuum-injected into an injection mold with a pre-embedded surface-treated fiber skeleton. The injection melt at the inner end of the forming connecting plate contains conductive filler and non-fluorinated thermoplastic resin, and the injection melt at the outer end of the forming connecting plate contains insulating filler and non-fluorinated thermoplastic resin. Alternatively, the connecting plate is an integral structure with an outer end as an insulator and an inner end as a conductor, made by mixing non-fluorinated thermoplastic resin and conductive / insulating filler, granulating, and finally co-extruding injection molding. The non-fluorinated thermoplastic resin in the connecting plate is the same as the non-fluorinated thermoplastic resin in the first conductive flow channel plate and the second conductive flow channel plate; the conductive filler is at least one of graphite powder, carbon black, acetylene black, expanded graphite, flake graphite, carbon nanotubes, graphene and carbon fiber; the insulating filler is at least one of calcium carbonate, glass fiber, basalt fiber, talc powder and silicon dioxide.

10. The composite bipolar plate for a flow battery according to claim 1, characterized in that, Except for the area separated by the inner end of the connecting plate, the lower surface of the first conductive flow channel plate and the upper surface of the second conductive flow channel plate are fused together to form a pocket-shaped slot between the first and second conductive flow channel plates. The inner surface of the connecting plate is fixed to the pocket-shaped slot by adhesive or laser welding. Except for the area separated by the outer end of the connecting plate, the lower surface of the first insulating resin plate and the upper surface of the second insulating resin plate are fused together to form a pocket-shaped slot between the first and second insulating resin plates. The outer surface of the connecting plate is fixed to the pocket-shaped slot by adhesive or laser welding.

11. The composite bipolar plate for a flow battery according to claim 1, characterized in that, The edges of the first conductive flow channel plate and the first insulating resin plate are connected, and the edges of the second conductive flow channel plate and the second insulating resin plate are connected, wherein the first joint between the first conductive flow channel plate and the first insulating resin plate and the second joint between the second conductive flow channel plate and the second insulating resin plate are misaligned in a direction perpendicular to the connecting plate.

12. The composite bipolar plate for a flow battery according to claim 1, characterized in that, A first interlocking structure is formed on the upper surface of the first insulating resin plate, and a second interlocking structure is formed on the lower surface of the second insulating resin plate. The first interlocking structure and the second interlocking structure can cooperate with each other, thereby enabling multiple composite bipolar plates to be combined and the ion exchange membrane to be sealed and fixed between two composite bipolar plates.

13. A method for manufacturing a composite bipolar plate for a flow battery, characterized in that, include: S1. Pre-preparing a connecting plate, a conductive flow channel plate, and an insulating resin plate; the insulating resin plate is a frame structure with a set width; the conductive flow channel plate is a continuous plate with microchannels of topology constructed on its surface. S2. Place a conductive flow channel plate on the upper and lower surfaces of the inner end of the connecting plate, and place an insulating resin plate on the upper and lower surfaces of the outer end of the connecting plate. S3. The structure obtained in S2 is placed in a hot pressing mold, and then hot pressing or hot pressing combined with laser welding is performed to obtain the finished product of the flow battery composite bipolar plate; wherein, the hot pressing pressure is 15~30MPa; the hot pressing temperature of the conductive flow channel plate area is 165~325℃, and the hot pressing temperature of the other areas is 105~125℃.

14. The manufacturing method according to claim 13, characterized in that, In S1, The conductive flow channel plate is obtained by blending, rolling, and hot molding of fluororesin, non-fluorinated thermoplastic resin, and conductive filler, or by melt vacuum injection molding or extrusion injection molding of fluororesin, non-fluorinated thermoplastic resin, and conductive filler; the fluororesin is at least one of PVDF, PCTFE, ETFE, and ECTFE, and the non-fluorinated thermoplastic resin is at least one of PP, POM, PS, PPS, and PES; the insulating resin plate is obtained by blending, rolling, and hot molding of the non-fluorinated thermoplastic resin and insulating filler, or by melt vacuum injection molding or extrusion injection molding of the non-fluorinated thermoplastic resin and insulating filler; The inner end of the connecting plate is a conductor, and the outer end is an insulator. The connecting plate is a one-piece structure with an insulator at the outer end and a conductor at the inner end, obtained by hot molding of non-fluorinated thermoplastic resin and conductive / insulating filler in a pressing mold with a pre-embedded surface-treated fiber skeleton. Alternatively, the connecting plate is obtained by integral vacuum injection molding in an injection mold with a pre-embedded surface-treated fiber skeleton, and the injection melt forming the inner end of the connecting plate contains conductive filler and the same non-fluorinated thermoplastic resin as the conductive flow channel plate, while the injection melt forming the outer end of the connecting plate contains insulating filler and the same non-fluorinated thermoplastic resin as the conductive flow channel plate. Alternatively, the connecting plate is a one-piece structure with an insulator at the outer end and a conductor at the inner end, obtained by mixing, granulating, and finally co-extruding injection molding of non-fluorinated thermoplastic resin and conductive / insulating filler. The conductive filler is at least one of graphite powder, carbon black, acetylene black, expanded graphite, flake graphite, carbon nanotubes, graphene, and carbon fiber; the insulating filler is at least one of calcium carbonate, glass fiber, basalt fiber, talc powder, and silicon dioxide.

15. The manufacturing method according to claim 13, characterized in that, In step S2, a conductive flow channel plate is fixed to the upper and lower surfaces of the inner end of the connecting plate with hot melt adhesive, and an insulating resin plate is fixed to the upper and lower surfaces of the outer end of the connecting plate with hot melt adhesive. In step S3, the structure obtained in S2 is placed vertically as a whole in a hot press mold. Resin powder, which is the same as the non-fluorinated thermoplastic resin in the conductive flow channel plate, is sprayed into the hot press mold and vacuum treatment is performed. The resin powder is embedded between the gaps of adjacent plates. Then, the contact interface of the two conductive flow channel plates is fused into one by hot pressing or hot pressing combined with laser welding.

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