Bipolar plate with low flow resistance and manufacturing method thereof

Abstract

The invention provides a low-flow-resistance bipolar plate and a manufacturing method thereof, the low-flow-resistance bipolar plate comprises a substrate formed by fusing and compounding natural graphite and resin, a reaction flow field is integrally arranged on the substrate, and the low-flow-resistance bipolar plate comprises a flow field unit formed by a combination of nonlinear bulges and recesses or a combination of a plurality of continuous recesses, a reaction flow field integrally arranged on a substrate is a flow field unit formed by the combination of nonlinear bulges and recesses or the combination of a plurality of continuous recesses, and concave turbulent flow riverbeds are uniformly distributed on the surfaces among flow channels, so that an electrolyte flows through a bipolar plate reaction area in the working process of a liquid flow electric pile; the flow resistance is greatly reduced under the action of the flow channel, and the liquid flow can be more uniformly distributed and fully distributed on the whole reaction place without flow velocity difference; the electrolyte on the sunken riverbed is stirred like turbulent flow, and is subjected to effective and sufficient electrochemical reaction with the carbon felt in the reaction place, so that the efficiency is improved, bad polarization factors are eliminated, the stability of the bipolar plate is improved, and the service life of the bipolar plate is prolonged.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of storage batteries, and particularly relates to a low-flow-resistance bipolar plate and a manufacturing method thereof. BACKGROUND

[0002] A flow battery is a kind of energy storage device, which has the characteristics of high capacity, wide application field and long cycle life. The flow battery is composed of a stack unit, electrolyte, electrolyte storage and supply unit, and a management and control unit, and the positive and negative electrolytes exchange at the membrane electrode to realize the mutual conversion between chemical energy and electrical energy, thereby completing the charging and discharging process.

[0003] The bipolar plate forms electrolyte flow fields on both sides, and the design of the flow channel determines the flow state of the reaction liquid in the flow field. Reasonable flow channel design can ensure that the electrochemical reaction can proceed normally and improve the mass transfer efficiency of the reactants, while reducing the resistance of the flow field, reducing the energy consumption of itself, and thus improving the energy efficiency and energy storage efficiency of the battery.

[0004] As disclosed in the patent with the publication number CN223321286U and the patent name of a composite graphite bipolar plate for a flow battery, a composite graphite bipolar plate for a flow battery is disclosed, which comprises a graphite bipolar plate body, the graphite bipolar plate body is composed of a cathode plate, an anode plate and a liquid flow guide plate, the cathode plate and the anode plate are symmetrically attached to the two side surfaces of the liquid flow guide plate, respectively. When the electrolyte flows, the first flow channel, the second flow channel and the third flow channel can effectively increase the flow process of the electrolyte, and the gap generated by the liquid flow guide plate and the cathode plate and the anode plate on both sides when they are stacked can prolong the flow process, so that the graphite bipolar plate body can be more stable when flowing through the electrolyte.

[0005] In the prior art, the reaction area usually adopts a straight-through flow channel form, and the opposite parallel straight flow channels have a simple flow field structure and are easy to process. However, since the flow channel is a straight flow channel, the flow channel length is relatively short, the flow-in and flow-out pressure difference is small, the medium passes through quickly but the reaction area is small and unevenly distributed, the reaction time of the reactants in the straight flow channel is short, the utilization rate is low, and the performance of the flow battery cannot be improved. SUMMARY

[0006] The present application aims to overcome the deficiencies in the prior art and provides a low-flow-resistance bipolar plate and a manufacturing method thereof, which increase the contact reaction time of the electrolyte with the electrode felt and improve the reaction efficiency.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a low flow resistance bipolar plate, comprising a substrate formed by fusing natural graphite and resin, wherein a reaction flow field is integrally disposed on the substrate, comprising flow field units formed by a combination of non-linear protrusions and depressions or a combination of several continuous depressions.

[0008] In the above scheme, the flow channels distributed on the positive and negative surfaces of the substrate are symmetrically arranged or staggeredly embedded, and the depth of the flow channels is 0.30 to 2.5 mm.

[0009] In the above scheme, the substrate and the positive electrode surface, negative electrode surface, and the flow channels respectively provided on the positive electrode surface and negative electrode surface are integrated into a structure. There are no interlayer gaps between them, which can make the resistance extremely low and have excellent conductivity.

[0010] In the above scheme, the flow field unit includes a flow channel formed by several arc-shaped protrusions, and a number of depressions are provided in the flow domain of the flow channel.

[0011] In the above scheme, the interval between the two adjacent arc-shaped protrusions is 10 to 50 mm.

[0012] In the above scheme, a single recess includes a triangle, a polygon, a petal shape, a hemisphere, or a rhombus.

[0013] In the above scheme, the depression includes several woven mesh-like patterns.

[0014] In the above scheme, the depth of the depression is 0.03 to 0.50 mm.

[0015] In the above scheme, the X-direction of the continuous depression within the flow field unit is the inlet and outlet flow channel, and the Y-direction of the continuous depression is the flow path direction.

[0016] A method for manufacturing a low-flow-resistance bipolar plate includes the following steps: Step 1: Prepolymer Production A. Expansion: Natural flake graphite is expanded at high temperature after oxidation and intercalation to obtain expanded graphite worms. The expansion temperature is controlled at 900℃~1200℃. B. Fabric: The prepared expanded graphite worms are sunk into the air-controlled fabric channel and stirred with hot air to control the temperature of the fluffy worms at 20-40℃. C. Mixing: Use dry and pure compressed air to evenly spray the resin onto the graphite worms and mix them evenly; control the resin mass ratio to be 10-50%, and separate the intermediate layer preparation material and the edge layer preparation material. The resin includes thermoplastic resins PP, PE, PR, HDPE, PTFE and fluoropolymers, as well as thermosetting resins PR phenolic, EP epoxy, etc. D. Pre-pressing the material: The uniformly mixed pre-material is laid out in the order of edge layer pre-material, middle layer pre-material, and edge layer pre-material in the largest order, and then pressed by a conveyor-type composite roller press to obtain the prepolymer. Step 2, Shaping: The prepolymer material obtained by the composite is pressed into the designed concave and convex flow channels and regular surface structure of the mold using a special hot press and mold. The molding temperature is controlled at 170℃~250℃, the time is 0.5~10 minutes, and the pressure is >1MPa. Step 3, Shaping: The initial substrate with regular surface shape features of concave and convex flow channels and depressions is quickly solidified and shaped by a special cold pressing machine and mold. The temperature is controlled at 150℃~20℃, the time is 0.25~5 minutes, and the pressure is >1MPa. Step 4: Finishing: Remove waste material from the edges of the molded substrate and finish the surface to remove any residue left after demolding, thus obtaining the finished substrate.

[0017] Compared with the prior art, the present invention has the following beneficial effects: by making the reaction flow field integrally set on the substrate a combination of non-linear protrusions and depressions or a combination of several continuous depressions to form a flow field unit, and the surface between the flow channels is uniformly distributed with a turbulent riverbed with depressions, the electrolyte flows through the bipolar plate reaction zone during the operation of the liquid flow stack. Under the action of the flow channel, the flow resistance is greatly reduced, and the liquid flow can be more uniformly distributed and fill the entire reaction site without flow velocity difference. On the depression riverbed, the electrolyte is stirred up like turbulence, resulting in an effective and sufficient electrochemical reaction with the carbon felt in the reaction site, improving efficiency, eliminating many adverse factors of polarization, and also helping to improve the stability and service life of the bipolar plate. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of Example 1.

[0020] Figure 2 This is a schematic diagram of the structure of Example 2.

[0021] Figure 3 This is a pressure analysis diagram for a typical channelless bipolar plate.

[0022] Figure 4 This is a flow velocity analysis diagram for a typical channelless bipolar plate.

[0023] Figure 5 This is a pressure analysis diagram of a typical DC bipolar plate.

[0024] Figure 6 This is a flow velocity analysis diagram for a typical DC bipolar plate.

[0025] Figure 7 This is a flow velocity-pressure diagram for a low-resistance bipolar plate.

[0026] Figure 8 The flow velocity-pressure curves are for low-resistance bipolar plates.

[0027] Figure 9 This is a flow velocity and direction analysis diagram for a low-resistance bipolar plate. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings.

[0029] The following description is intended to disclose the invention so that those skilled in the art can implement it. The preferred embodiments described below are merely examples, and other obvious modifications will be apparent to those skilled in the art. The basic principles of the invention defined in the following description can be used in other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0030] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or position based on the orientation or positional relationship shown in the accompanying drawings. They are merely simplified descriptions for the convenience of describing this invention and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limitations on this invention.

[0031] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0032] Example 1, see Figure 1 A low flow resistance bipolar plate includes a substrate 1 formed by fusing natural graphite and resin, which has the characteristics of conductivity, high mechanical strength, liquid resistance, and liquid corrosion resistance. A reaction flow field is integrally provided on the substrate 1, including a flow field unit formed by a combination of non-linear protrusions 11 and depressions 12.

[0033] Of course, the symmetrical arrangement or staggered embedding of the flow channels distributed on the positive and negative electrode surfaces of substrate 1 controls the flow channel depth to be 0.30 to 2.5 mm, which is conducive to the formation of eddy currents. The substrate and the flow channels respectively set on the positive and negative electrode surfaces are an integrated structure with no interlayer gaps, which can make the resistance extremely low and have excellent conductivity.

[0034] The non-linear protrusion 11 can be an arc-shaped protrusion, a zigzag protrusion, etc. The interval between two adjacent arc-shaped protrusions 11 is 10 to 50 mm. This interval is used to set the recess 12.

[0035] Each adjacent flow channel distributed on the positive or negative electrode surface serves as an inflow channel for the adjacent one and an outflow channel for the two adjacent ones. A recess 12 is provided on the plane between two adjacent non-linear protrusions 11. The recess is formed by a number of triangles, polygons, petals, hemispheres or rhombuses arranged according to a certain rule, which is conducive to increasing the residence time of the electrolyte in the flow field and making the electrolyte fully contact the electrode felt, such as a honeycomb shape; or the recess 12 is a number of woven mesh shapes.

[0036] Of course, the depth of the depression 12 is 0.03 to 0.50 mm. The X direction of the continuous depression in the flow field unit is the inlet and outlet flow channel, and the Y direction of the continuous depression is the flow path direction. Due to the influence of the non-linear protrusion 11 flow channel, the electrolyte flow is dispersed in the flow channel.

[0037] To achieve the above structure, the manufacturing method of the low flow resistance bipolar plate includes the following steps: Step 1: Prepolymer Production A. Expansion: Natural flake graphite is expanded at high temperature after oxidation and intercalation to obtain expanded graphite worms. The expansion temperature is controlled at 900℃~1200℃. B. Fabric: The prepared expanded graphite worms are sunk into the air-controlled fabric channel and stirred with hot air to control the temperature of the fluffy worms at 20-40℃. C. Mixing: Use dry, pure compressed air to evenly spray the resin onto the graphite worms and mix thoroughly. Control the resin mass ratio to 10-50% and separate the intermediate layer preparation material and the edge layer preparation material. The intermediate layer can be a single structure or a multi-layer composite structure, and the edge layer is used for multi-layer composite structures. Of course, the fusion and composite of natural graphite and resin can be a single-layer graphite and resin uniformly mixed composite, or it can be an edge-intermediate-edge multi-layer combined composite structure. The purpose is to set the advantageous recessed structure in the edge layer. The resins include thermoplastic resins PP, PE, PR, HDPE, PTFE and fluoropolymers, as well as thermosetting resins PR phenolic, EP epoxy, etc. D. Pre-pressing: The uniformly mixed pre-mixed materials are laid out in the order of edge layer pre-mixed materials, middle layer pre-mixed materials, and edge layer pre-mixed materials in the largest order. The prepolymer is then pressed by a conveyor-type composite roller press to obtain the prepolymer. The prepolymer has excellent plasticity and flowability, and is like a sponge. Step 2, Molding: The prepolymer material obtained by the composite is pressed into the designed concave and convex flow channels and regular surface structure of the mold using a special hot press and mold. The molding temperature is controlled at 170℃~250℃, the time is 0.5~10 minutes, and the pressure is >1MPa. Step 3, Shaping: The initial substrate with regular surface shape features of concave and convex flow channels and depressions is quickly solidified and shaped by a special cold pressing machine and mold. The temperature is controlled at 150℃~20℃, the time is 0.25~5 minutes, and the pressure is >1MPa. Step 4: Finishing: Remove waste material from the edges of the molded substrate and finish the surface to remove any residue left after demolding, thus obtaining the finished substrate.

[0038] Example 2: See Figure 2 A low flow resistance bipolar plate is characterized by comprising a substrate 1 formed by fusing natural graphite and resin, wherein a reaction flow field is integrally disposed on the substrate 1, including flow field units formed by a combination of several continuous recesses 12.

[0039] The depressions are formed by a number of triangles, polygons, petals, hemispheres or rhombuses arranged in a certain pattern, which helps to increase the residence time of the electrolyte in the flow area and make the electrolyte fully contact the electrode felt, such as a six-petal flower shape; or the depression 12 is a number of woven mesh shapes.

[0040] Of course, the depth of the depression 12 is 0.03 to 0.50 mm. Since it is not affected by the flow channel, the electrolyte flow is diffusely dispersed in the reaction area. That is, the direction pointed to by the X arrow of the continuous depression in the flow field unit is the direction of liquid inlet and outlet, and the direction pointed to by the Y arrow of the continuous depression is the direction of flow path.

[0041] To achieve the above structure, the manufacturing method of the low flow resistance bipolar plate includes the following steps: Step 1: Prepolymer Production A. Expansion: Natural flake graphite is expanded at high temperature after oxidation and intercalation to obtain expanded graphite worms. The expansion temperature is controlled at 900℃~1200℃. B. Fabric: The prepared expanded graphite worms are sunk into the air-controlled fabric channel and stirred with hot air to control the temperature of the fluffy worms at 20-40℃. C. Mixing: Use dry, pure compressed air to evenly spray the resin onto the graphite worms and mix thoroughly. Control the resin mass ratio to 10-50% and separate the intermediate layer preparation material and the edge layer preparation material. The intermediate layer can be a single structure or a multi-layer composite structure, and the edge layer is used for multi-layer composite structures. Of course, the fusion and composite of natural graphite and resin can be a single-layer graphite and resin uniformly mixed composite, or it can be an edge-intermediate-edge multi-layer combined composite structure. The purpose is to set the advantageous recessed structure in the edge layer. The resins include thermoplastic resins PP, PE, PR, HDPE, PTFE and fluoropolymers, as well as thermosetting resins PR phenolic, EP epoxy, etc. D. Pre-pressing: The uniformly mixed pre-mixed materials are laid out in the order of edge layer pre-mixed materials, middle layer pre-mixed materials, and edge layer pre-mixed materials in the largest order. The prepolymer is then pressed by a conveyor-type composite roller press to obtain the prepolymer. The prepolymer has excellent plasticity and flowability, and is like a sponge. Step 2, Molding: The prepolymer material obtained by the composite is pressed into the recessed structure of the design specifications by a special hot press and mold. The molding temperature is controlled at 170℃~250℃, the time is 0.5~10 minutes, and the pressure is >1MPa. Step 3, Shaping: The initial substrate with regular surface shape features and depressions is quickly solidified and shaped by a special cold pressing machine and mold. The temperature is controlled at 150℃~20℃, the time is 0.25~5 minutes, and the pressure is >1MPa. Step 4: Finishing: Remove waste material from the edges of the molded substrate and finish the surface to remove any residue left after demolding, thus obtaining the finished substrate.

[0042] Through the above embodiments, the edge layer-middle layer-edge layer are integrated into a prepolymer to form a novel composite material with a thermosetting resin on the surface and a thermoplastic resin in the middle. This ensures that the surface has higher erosion resistance and high wear resistance after the subsequent formation of the recessed structure, and is also an advantageous factor for forming low flow resistance.

[0043] The resulting low-flow-resistance bipolar plate not only possesses the advantage of low flow resistance, but also ensures that the electrolyte is evenly distributed throughout the reaction site without any flow rate difference, allowing for an effective and thorough electrochemical reaction with the carbon felt in the reaction site, resulting in a highly efficient reaction.

[0044] See Figures 3 to 9 Therefore, we can conclude that: Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are merely examples and do not limit the present invention. The objectives of the present invention have been fully and effectively achieved. The functions and structural principles of the present invention have been shown and explained in the embodiments, and any modifications or variations of the embodiments of the present invention may be made without departing from the stated principles.

Claims

1. A low-flow-resistance bipolar plate, characterized in that, It includes a substrate (1) formed by fusing natural graphite and resin, and an integrally formed reactive flow field on the substrate (1), including flow field units formed by a combination of non-linear protrusions (11) and depressions (12) or a combination of several continuous depressions (12).

2. The low flow resistance bipolar plate according to claim 1, characterized in that, The flow channels distributed on the positive electrode surface and the negative electrode surface of the substrate (1) are symmetrically arranged or staggeredly embedded, and the depth of the flow channels is 0.30 to 2.5 mm.

3. The low flow resistance bipolar plate according to claim 2, characterized in that, The substrate, the positive electrode surface, the negative electrode surface, and the flow channels respectively provided on the positive electrode surface and the negative electrode surface are integrated into a single structure.

4. The low-flow-resistance bipolar plate according to claim 1, characterized in that, The flow field unit includes a flow channel formed by several arc-shaped protrusions (11), and several depressions (12) are provided in the flow domain of the flow channel.

5. The low flow resistance bipolar plate according to claim 4, characterized in that, The interval between the two adjacent arc-shaped protrusions (11) is 10 to 50 mm.

6. The low-flow-resistance bipolar plate according to claim 1, characterized in that, The individual recess (12) includes triangles, polygons, petals, hemispheres or rhombuses.

7. The low flow resistance bipolar plate according to claim 1, characterized in that, The recess (12) comprises several woven mesh-like shapes.

8. The low-flow-resistance bipolar plate according to any one of claims 6 or 7, characterized in that, The depth of the depression (12) is 0.03 to 0.50 mm.

9. The low-flow-resistance bipolar plate according to claim 6, characterized in that, The X-direction of the continuous depressions within the flow field unit is the inlet and outlet flow channel, and the Y-direction of the continuous depressions is the flow path direction.

10. The method for manufacturing a low-flow-resistance bipolar plate according to claim 1, characterized in that, Includes the following steps: Step 1: Prepolymer Production A. Expansion: Natural flake graphite is expanded at high temperature after oxidation and intercalation to obtain expanded graphite worms. The expansion temperature is controlled at 900℃~1200℃. B. Fabric: The prepared expanded graphite worms are sunk into the air-controlled fabric channel and stirred with hot air to control the temperature of the fluffy worms at 20-40℃. C. Mixing: Use dry and pure compressed air to evenly spray the resin onto the graphite worms and mix them evenly; control the resin mass ratio to be 10-50%, and separate the intermediate layer preparation material and the edge layer preparation material. The resin includes thermoplastic resins PP, PE, PR, HDPE, PTFE and fluoropolymers, as well as thermosetting resins PR phenolic, EP epoxy, etc. D. Pre-pressing the material: The uniformly mixed pre-material is laid out in the order of edge layer pre-material, middle layer pre-material, and edge layer pre-material in the largest order, and then pressed by a conveyor-type composite roller press to obtain the prepolymer. Step 2, Shaping: The prepolymer material obtained by the composite is pressed into the designed concave and convex flow channels and regular surface structure of the mold using a special hot press and mold. The molding temperature is controlled at 170℃~250℃, the time is 0.5~10 minutes, and the pressure is >1MPa. Step 3, Shaping: The initial substrate with regular surface shape features of concave and convex flow channels and depressions is quickly solidified and shaped by a special cold pressing machine and mold. The temperature is controlled at 150℃~20℃, the time is 0.25~5 minutes, and the pressure is >1MPa. Step 4: Finishing: Remove waste material from the edges of the molded substrate and finish the surface to remove any residue left after demolding, thus obtaining the finished substrate.

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