High-conductivity bipolar plate, preparation method therefor, and use thereof

Abstract

The present invention provides a high-conductivity bipolar plate, and a preparation method therefor and a use thereof. Expandable graphite and fluoroplastic micropowder particles are used as raw materials, to prepare a high-conductivity bipolar plate by means of high-temperature expansion, air mixing, degassing, material distribution by a conveyor belt, preliminary extrusion by the belt, roller continuous rolling, trimming, slitting, and hot pressing processes. The high-conductivity bipolar plate shows excellent conductivity, flexibility, liquid resistance, and shear resistance, can be used in a variety of electrochemical-based water-based flow batteries and fuel cells; compared with the prior art, the continuous production between the processes of the present invention improves the production efficiency, shortens the production time, reduces the production cost, and facilitates the implementation of large-scale continuous batch production in industry; the steps are coordinated together, so that the high-conductivity bipolar plate shows excellent conductivity, flexibility, liquid resistance, and shear resistance, the power density of the water-based flow batteries and the power density of the fuel cells are greatly improved, and the service life thereof is prolonged. The present invention relates to the technical field of batteries.

Description

A high-conductivity bipolar plate and its preparation method and application Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a high-conductivity bipolar plate and a preparation method and application thereof. Background Art

[0002] Battery bipolar plates are categorized by material as metal, graphite, and composite materials. Graphite bipolar plates, with their excellent electrical conductivity and corrosion resistance, have been widely used in the battery industry. Expanded graphite is a loose, porous, worm-like substance obtained by intercalating natural graphite flakes, washing them with water, drying them, and then expanding them at high temperatures. In addition to possessing the inherent excellent properties of natural graphite, such as heat and cold resistance, corrosion resistance, and self-lubrication, it also possesses unique properties such as softness, compression resilience, plasticity, adsorption, ecological compatibility, biocompatibility, and radiation resistance. Therefore, it is often used in the production of bipolar plates for energy storage flow batteries and fuel cells.

[0003] Since expanded graphite has poor mechanical strength and anti-leakage performance, it is often necessary to add resin to enhance and improve its performance. Currently, there are two main methods for preparing bipolar plates using expanded graphite and resin as raw materials: wet mixing and dry mixing. Chinese invention patent CN107046140B discloses a fluorine-containing bipolar plate and a preparation method thereof, which uses expandable graphite and fluorine-containing polymer suspension emulsion as raw materials, and obtains a fluorine-containing bipolar plate through mixing, drying, secondary crushing and screening, continuous roller cold pressing, and vacuum hot pressing. This method adopts a wet mixing method to solve the problem of uniform dispersion of fluororesin in graphite and improve the conductivity of the bipolar plate. However, the process flow of this method is complicated and requires a large amount of solvent, which increases the production cost and is not suitable for large-scale continuous production. In addition, the conductivity of the bipolar plate prepared by this method reaches up to 285S / cm, and the conductive performance is limited. Chinese invention patent CN111261893B discloses a highly conductive flexible graphite bipolar plate for flow batteries, as well as its preparation and application. The plate is made from expanded graphite and PVDF powder, which are mixed, pressed, and vacuum hot-pressed or calendered to form the resulting bipolar plate. This method utilizes a dry mixing process, which simplifies the preparation and allows for easy control of the production process. However, the mixing uniformity of the expanded graphite and PVDF powder is limited, which can easily lead to defects such as cracks in the bipolar plate, resulting in poor production quality and a short service life. Furthermore, the bipolar plates produced using this method have a maximum conductivity of 250 S / cm, which is still relatively poor. These issues require urgent resolution. Summary of the Invention

[0004] In order to solve the above technical problems, the technical solution adopted in this application is to provide a high-conductivity bipolar plate and its preparation method and application, so as to solve the technical problems of poor conductivity, poor production quality, high production cost and unsuitability for large-scale continuous production in the existing preparation method of graphene bipolar plates.

[0005] A first aspect of an embodiment of the present application provides a method for preparing a high-conductivity bipolar plate, comprising the following steps:

[0006] (1) Expansion: The expandable graphite is expanded at high temperature to obtain graphite worms;

[0007] (2) Mixing: Graphite worms and fluoroplastic micropowder particles are mixed and degassed to obtain a mixed powder;

[0008] (3) Spreading: Spread the mixed powder to obtain a material strip;

[0009] (4) Forming: The material strip is initially extruded to obtain a blank coil, and then the blank coil is calendered to obtain a finished coil;

[0010] (5) Slitting: cutting the finished coil into product sheets;

[0011] (6) Hot pressing: Hot pressing the product sheet into a highly conductive bipolar plate.

[0012] Preferably, in step (1), the purity of the expandable graphite is 95-99.95%, and the particle size is 32-80 mesh; the temperature of the high-temperature expansion is 500-950° C., and the volume expansion ratio of the expandable graphite is 80-300 times.

[0013] Preferably, in step (2), the fluoroplastic micropowder particles are any one of polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, polytrichlorofluoroethylene, and ethylene-chlorotrifluoroethylene copolymer, and the particle size of the fluoroplastic micropowder particles is 1 to 50 μm.

[0014] Preferably, in step (2), when the fluoroplastic micropowder particles are polyvinylidene fluoride, the amount thereof added is 10 to 20 wt% of the total amount after mixing; when the fluoroplastic micropowder particles are ethylene-tetrafluoroethylene copolymer, the amount thereof added is 11 to 21 wt% of the total amount after mixing; when the fluoroplastic micropowder particles are polytrichlorofluoroethylene, the amount thereof added is 5 to 18 wt% of the total amount after mixing; when the fluoroplastic micropowder particles are ethylene-chlorotrifluoroethylene copolymer, the amount thereof added is 11 to 21 wt% of the total amount after mixing.

[0015] Preferably, in step (2), an air flow is used to mix the graphite worms and the fluoroplastic micropowder particles during mixing, the air flow pressure during feeding is 0.01 to 0.3 MPa, the air flow pressure during mixing is 0.1 to 1 MPa, and the mixing time is 1 to 15 s; after mixing, a cyclone dust collector is used for degassing, and the air flow pressure of the cyclone dust collector is 0.01 to 0.5 MPa.

[0016] Preferably, in step (3), the mixed powder is spread on a conveyor belt to obtain a material belt, the transmission speed of the conveyor belt is 0.1-2 m / min, the thickness of the material belt is 10-50 cm, and the density is 0.1-0.5 g / cm 3 .

[0017] Preferably, in step (4), a belt is used for the initial extrusion, the transmission speed of the belt and the conveyor belt are both 0.1-2 m / min, the extrusion pressure is 1-5 MPa, the thickness of the blank coil is 1-5 cm, and the density is 0.8-1.5 g / cm 3 During calendering, rollers are used for continuous rolling. The roller rotation speed is 0.2-2 m / min, the calendering pressure is 1-8 MPa, the thickness of the finished coil is 0.2-2 mm, and the density is 1.5-1.8 g / cm 3 .

[0018] Preferably, in step (6), when the fluoroplastic micropowder particles are polyvinylidene fluoride, the hot pressing temperature is 170-230°C; when the fluoroplastic micropowder particles are ethylene-tetrafluoroethylene copolymer, the hot pressing temperature is 260-320°C; when the fluoroplastic micropowder particles are polytrichlorofluoroethylene, the hot pressing temperature is 210-270°C; when the fluoroplastic micropowder particles are ethylene-chlorotrifluoroethylene copolymer, the hot pressing temperature is 240-300°C; the hot pressing pressure is 5-25 MPa, and the heat preservation and pressure holding time is 1-4 hours; the thickness of the high conductive bipolar plate is 0.5-1.0 mm, and the density is 1.70-1.85 g / cm 3 .

[0019] A second aspect of the embodiments of the present application provides a highly conductive bipolar plate prepared by any of the preparation methods described above.

[0020] A third aspect of the embodiments of the present application provides applications of highly conductive bipolar plates prepared by any of the preparation methods described above in water-based liquid flow batteries and fuel cells.

[0021] Preferably, the exterior of the high-conductivity bipolar plate presents a smooth gray-black surface with a certain glossiness and good flexibility, and the interior of the high-conductivity bipolar plate is a mesh structure formed by thermally melted fluoroplastic micropowder particles and graphite worms.

[0022] The present invention provides a high-conductivity bipolar plate and its preparation method and application. The high-conductivity bipolar plate is prepared from expandable graphite and fluoroplastic micropowder particles through high-temperature expansion, airflow mixing, degassing, conveyor belt fabrication, initial belt extrusion, roller continuous calendering, trimming, slitting, and hot pressing. The high-conductivity bipolar plate exhibits excellent conductivity, flexibility, liquid resistance and shear resistance, and can be used in various electrochemical water-based flow batteries and fuel cells.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention uses airflow mixing to make fluoroplastic micropowder particles adhere to the surface of graphite worms, achieving highly uniform mixing of raw materials in a short time, improving mixing efficiency, shortening mixing time, and facilitating industrial large-scale production; in addition, the highly uniform mixing of raw materials improves the overall uniformity of the bipolar plate, greatly improving the conductivity, mechanical strength and service life of the bipolar plate, thereby reducing the amount of fluoroplastic micropowder particles added and further improving the conductivity of the bipolar plate;

[0025] (2) The present invention uses a cyclone dust collector to degas the mixed materials, thereby reducing the pressure of the mixed airflow, achieving gas-solid separation at reduced speed, and ensuring the stability of the conveyor belt feeding process. In addition, degassing can also prevent the gas from volatilizing due to heat during the hot pressing process, causing defects such as holes on the surface of the bipolar plate, thereby improving the production quality of the bipolar plate and thus increasing the mechanical strength and service life of the bipolar plate.

[0026] (3) The present invention adopts a two-step forming process of belt preliminary extrusion and roller continuous calendering, connecting the three processes of conveyor belt fabrication, belt preliminary extrusion, and roller continuous calendering. The fabrication, extrusion, and calendering are carried out simultaneously, thereby realizing continuous production, improving production efficiency, and shortening production time.

[0027] (4) The hot pressing process of the present invention sets a heat preservation and pressure holding time of 1 to 4 hours, so that the fluoroplastic micropowder particles melted by heat have sufficient time to flow and fully enter between the layers of graphite and the pores of the graphite worms, thereby achieving sufficient cross-linking and curing of the graphite worms and the fluoroplastic micropowder particles. Under the premise of low addition of fluoroplastic micropowder particles, the conductivity and mechanical strength of the bipolar plate are improved; in addition, sufficient heat preservation and pressure holding time is also conducive to the timely discharge of residual gas in the bipolar plate, avoiding defects on the surface of the bipolar plate, and further improving the mechanical strength, liquid resistance and service life of the bipolar plate;

[0028] (5) The high-temperature puffing furnace, powder feeder, mixing pipe, cyclone dust collector, material distributor, conveyor belt, calender and circular cutter used in the present invention connect the various working steps in sequence to form an assembly line. The continuous production between the various working steps improves the production efficiency, shortens the production time, reduces the production cost, and facilitates the realization of large-scale continuous batch production in industry. The combined effect of the various working steps makes the high-conductivity bipolar plate exhibit excellent conductivity, flexibility, liquid resistance and shear resistance. The conductivity is as high as 423S / cm, the tensile strength is as high as 35MPa, the compressive strength is as high as 42MPa, and the bending strength is as high as 33MPa, which greatly improves the power density and service life of water-based liquid flow batteries and fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0030] FIG1 is an appearance diagram of a high-conductivity bipolar plate prepared by the preparation method of Example 1 of the present application;

[0031] FIG2 is a microstructure diagram of the high-conductivity bipolar plate shown in FIG1 . DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below with reference to the following examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining this application and are not intended to limit this application. The raw materials and devices used in the present invention, unless otherwise specified, are conventional commercially available products; the methods used, unless otherwise specified, are conventional methods.

[0033] In order to verify the reliability of the effects of the present invention, the present invention is described below with reference to examples and comparative examples.

[0034] Examples 1 to 12 are used to illustrate high-conductivity bipolar plates and methods for preparing the same.

[0035] Table 1 Preparation process parameters of high-conductivity bipolar plates of Examples 1 to 12

[0036]

[0037] The method for preparing the high-conductivity bipolar plates of Examples 1 to 12 above comprises the following steps:

[0038] (1) Expansion: Weigh expandable graphite with a purity of 99% and a particle size of 50 mesh according to the addition amounts of Examples 1 to 12 in Table 1, and perform high-temperature expansion on the expandable graphite at 800°C in a high-temperature expansion furnace to obtain graphite worms with a volume expansion ratio of 200 times;

[0039] (2) Mixing: Weigh 30 μm fluoroplastic micropowder particles according to the types and addition amounts of Examples 1 to 12 in Table 1, then use a powder feeder to add graphite worms into a mixing pipe, and add fluoroplastic micropowder particles at the same time. Use airflow in the mixing pipe to mix the graphite worms and fluoroplastic micropowder particles. Set the airflow pressure during feeding to 0.1 MPa, the airflow pressure during mixing to 0.5 MPa, and the mixing time to 2 to 3 s. After mixing, use a cyclone dust collector for degassing, and set the airflow pressure of the cyclone dust collector to 0.2 MPa. After degassing, a mixed powder is obtained.

[0040] (3) Spreading: Use a spreading machine to spread the mixed powder, and spread the mixed powder onto a conveyor belt with a transmission speed of 0.5m / min to obtain a thickness of 10-50cm and a density of 0.1-0.5g / cm 3 Material strip;

[0041] (4) Molding: Use a belt to perform preliminary extrusion on the material strip on the conveyor belt. Set the transmission speed of the belt and conveyor belt to 0.5m / min, the extrusion pressure to 5MPa, and obtain a thickness of 1-5cm and a density of 0.8-1.5g / cm 3 The blank coil is then rolled by a calender using a continuous roller rolling method, with the roller rotation speed set to 0.5 m / min and the rolling pressure to 8 MPa. During the rolling process, a trimming machine is used to trim the edges while rolling to obtain a thickness of 0.2 to 2 mm and a density of 1.5 to 1.8 g / cm 3 Finished coils;

[0042] (5) Cutting: According to the required size of battery bipolar plates, the finished coils are cut into product plates using a circular cutting machine;

[0043] (6) Hot pressing: The product plate is hot pressed according to the hot pressing process of Examples 1 to 12 in Table 1 to obtain a plate with a thickness of 0.5 to 1.0 mm and a density of 1.70 to 1.85 g / cm 3 The high-conductivity bipolar plate is a high-conductivity bipolar plate prepared according to the preparation process parameters of Examples 1 to 12 in Table 1.

[0044] The following performance tests were conducted on the high-conductivity bipolar plates prepared in Examples 1 to 12 and the commercially available bipolar plate of Comparative Example 1, respectively, to test their electrical conductivity, tensile strength, compressive strength, and flexural strength.

[0045] Comparative Example 1: A commercially available fuel cell bipolar plate produced by a manufacturer in Dalian, wherein the raw materials are battery graphite plate and liquid resin.

[0046] Conductivity, tensile strength, compressive strength and flexural strength are tested according to the following methods:

[0047] Conductivity: Tested in accordance with NB / T 42007-2013 "Test Methods for Bipolar Plates for All-Vanadium Redox Flow Batteries";

[0048] Tensile strength: Tested in accordance with JB / T 9141.2-2013 "Flexible graphite sheet - Part 2: Test method for tensile strength";

[0049] Compressive strength: Tested in accordance with GB / T 13465.3-2014 "Test method for compressive strength of impermeable graphite materials";

[0050] Bending strength: Tested in accordance with GB / T 13465.2-2002 "Test method for flexural strength of impermeable graphite materials".

[0051] The performance test results of the high-conductivity bipolar plates of Examples 1 to 12 and the commercially available bipolar plate of Comparative Example 1 are shown in Table 2.

[0052] Table 2 Performance test results of Examples 1 to 12 and Comparative Example 1

[0053]

[0054] From Table 2 we can see that:

[0055] Compared with Comparative Example 1, the electrical conductivity, tensile strength, compressive strength and flexural strength of the high-conductivity bipolar plates prepared in Examples 1 to 12 are all better than those in Comparative Example 1. It can be seen that the high-conductivity bipolar plates prepared in Examples 1 to 12 of the present invention not only maintain the ultra-high conductivity of the hard sintered graphite, but also maintain the excellent flexibility and compressive resistance of the flexible graphite plate. That is, the high-conductivity bipolar plates prepared by the preparation method of the present invention have excellent conductivity, flexibility, liquid resistance and shear resistance, which is determined by the preparation method of the present invention.

[0056] Compared with the fluorine-containing bipolar plate disclosed in Chinese invention patent CN107046140B and the graphite bipolar plate disclosed in Chinese invention patent CN111261893B, the high-conductivity bipolar plate prepared by the preparation method of the present invention has an electrical conductivity of 281 to 423 S / cm, showing excellent high conductivity.

[0057] The high-conductivity bipolar plate prepared by the preparation method of Example 1 was tested, and its appearance was shown in Figure 1. As shown in Figure 1, the high-conductivity bipolar plate of Example 1 has a smooth gray-black surface, a certain glossiness, and good flexibility.

[0058] Microscopic examination of the high-conductivity bipolar plate of Example 1 yielded a microstructure diagram, as shown in Figure 2. As shown in Figure 2, the interior of the high-conductivity bipolar plate is a network structure formed by thermally melted fluoroplastic micropowder particles and graphite worms. This is because the spacing between graphite layers increases during the high-temperature expansion of expandable graphite to form graphite worms, forming a porous, worm-like structure with high porosity. With the addition of fluoroplastic micropowder particles, the thermally melted fluoroplastic micropowder particles fully penetrate between the graphite layers and into the pores of the graphite worms, uniformly mixing the fluoroplastic micropowder particles with the graphite worms. This allows for full crosslinking and solidification of the graphite worms and fluoroplastic micropowder particles, forming a network structure with high strength and high conductivity.

[0059] The high-conductivity bipolar plate prepared by the preparation method of the present invention is used in water-based liquid flow batteries and fuel cells.

[0060] The present invention provides a high-conductivity bipolar plate and its preparation method and application. The high-conductivity bipolar plate is prepared from expandable graphite and fluoroplastic micropowder particles through high-temperature expansion, airflow mixing, degassing, conveyor belt fabrication, initial belt extrusion, roller continuous calendering, trimming, slitting, and hot pressing. The high-conductivity bipolar plate exhibits excellent conductivity, flexibility, liquid resistance and shear resistance, and can be used in various electrochemical water-based flow batteries and fuel cells.

[0061] Compared with the prior art, (1) the present invention uses air flow mixing to make fluoroplastic micropowder particles adhere to the surface of graphite worms, thereby achieving highly uniform mixing of raw materials in a short time, improving mixing efficiency, shortening mixing time, and facilitating industrial large-scale production; in addition, the highly uniform mixing of raw materials improves the overall uniformity of the bipolar plate, greatly increasing the conductivity, mechanical strength and service life of the bipolar plate, thereby reducing the amount of fluoroplastic micropowder particles added and further improving the conductivity of the bipolar plate; (2) the present invention uses a cyclone dust collector to degas the mixed materials, thereby reducing the air flow pressure after mixing, and achieving The gas-solid speed reduction separation is realized to ensure the stability of the conveyor belt feeding process; in addition, after degassing, the gas can be prevented from volatilizing due to heat during the hot pressing process, which causes defects such as holes on the surface of the bipolar plate, thereby improving the production quality of the bipolar plate and thus improving the mechanical strength and service life of the bipolar plate; (3) The present invention adopts a two-step forming process of belt preliminary extrusion and roller continuous calendering to connect the three processes of conveyor belt feeding, belt preliminary extrusion and roller continuous calendering, and realizes continuous production while feeding, extruding and calendering, thereby improving production efficiency and shortening production time; (4) The hot pressing process of the present invention sets a heat preservation and pressure holding time of 1 to 4 hours, The heated and melted fluoroplastic micropowder particles have enough time to flow and fully enter between the layers of graphite and the pores of the graphite worms, thereby achieving full cross-linking and curing of the graphite worms and the fluoroplastic micropowder particles. Under the premise of low addition of fluoroplastic micropowder particles, the conductivity and mechanical strength of the bipolar plate are improved. In addition, sufficient heat preservation and pressure holding time is also conducive to the timely discharge of residual gas in the bipolar plate, avoiding defects on the surface of the bipolar plate, and further improving the mechanical strength, liquid resistance and service life of the bipolar plate. (5) The high-temperature expansion furnace, powder adding machine, mixing pipeline, cyclone dust collector, material distribution machine, conveyor belt, calendering machine used in the present invention The cutting machine and the circular cutting machine connect each process step by step to form an assembly line. The continuous production between each process improves production efficiency, shortens production time, reduces production costs, and facilitates the realization of large-scale continuous batch production in industry. The combined effect of each process step makes the high-conductivity bipolar plate exhibit excellent conductivity, flexibility, liquid resistance and shear resistance. The conductivity is as high as 423S / cm, the tensile strength is as high as 35MPa, the compressive strength is as high as 42MPa, and the bending strength is as high as 33MPa, which greatly improves the power density and service life of water-based liquid flow batteries and fuel cells. It can be widely used in the field of battery technology.

[0062] It should be noted that:

[0063] (1) In the above embodiment, the purity of the expandable graphite is 99% and the particle size is 50 mesh. This is only a preferred embodiment. In actual production, the purity of the expandable graphite can be 95-99.95% and the particle size can be 32-80 mesh. In actual operation, adaptive adjustments should be made according to specific circumstances.

[0064] (2) In the above embodiment, the high-temperature expansion temperature of the expandable graphite is 800°C, and the volume expansion ratio after high-temperature expansion is 200 times. This is only a preferred embodiment. In actual production, the high-temperature expansion temperature can be 500-950°C, and the volume expansion ratio of the expandable graphite can be 80-300 times. Adaptive adjustment is made according to actual conditions.

[0065] (3) In the above embodiment, the particle size of the fluoroplastic micropowder particles is 30 μm. This is only a preferred embodiment. In actual production, the particle size of the fluoroplastic micropowder particles can be 1 to 50 μm.

[0066] (4) In the above embodiment, during the mixing process, the air flow pressure during feeding is 0.1 MPa, the air flow pressure during mixing is 0.5 MPa, the mixing time is 2 to 3 seconds, and the air flow pressure of the cyclone dust collector during degassing is 0.5 MPa. This is only a preferred embodiment. In actual production, the air flow pressure during feeding can be 0.01 to 0.3 MPa, the air flow pressure during mixing can be 0.1 to 1 MPa, the mixing time can be 1 to 15 seconds, and the air flow pressure of the cyclone dust collector during degassing can be 0.01 to 0.5 MPa. Adaptive adjustment is made according to actual conditions.

[0067] (5) In the above embodiment, during the laying process, the transmission speed of the conveyor belt is 0.5 m / min, and during the initial extrusion process, the transmission speeds of the belt and the conveyor belt are both 0.5 m / min, and the extrusion pressure is 5 MPa. This is only a preferred embodiment. In actual production, the transmission speed of the conveyor belt can be 0.1-2 m / min, the transmission speed of the belt can be 0.1-2 m / min, and the extrusion pressure can be 1-5 MPa. Adaptive adjustments can be made according to actual conditions.

[0068] (6) In the above embodiment, during the calendering process, the rotation speed of the roller is 0.5 m / min and the calendering pressure is 8 MPa. This is only a preferred embodiment. In actual production, the rotation speed of the roller can be 0.2 to 2 m / min and the calendering pressure can be 1 to 8 MPa. Adaptive adjustments can be made according to actual conditions.

[0069] (7) The powder feeder used in the above embodiment is the bipolar plate destaticizing powder feeder disclosed in patent CN213010871U, the material distributor used is the graphite powder distributor disclosed in patent CN207618672U, the calender used is the bipolar plate calender disclosed in patent CN207681168U, the trimming machine used is the bipolar plate trimming machine disclosed in patent CN207616102U, and the circular cutting machine used is the bipolar plate circular cutting machine disclosed in patent CN213351006U.

[0070] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A method for preparing a high-conductivity bipolar plate, characterized in that: The following steps are involved: (1) Expansion: The expandable graphite is expanded at high temperature to obtain graphite worms; (2) Mixing: Graphite worms and fluoroplastic micropowder particles are mixed and degassed to obtain a mixed powder; during mixing, air flow is used to mix the graphite worms and fluoroplastic micropowder particles in a mixing pipe, and after mixing, a cyclone dust collector is used to degas; (3) Spreading: Spreading the mixed powder to obtain a material strip; (4) Forming: The material strip is initially extruded to obtain a rough coil, and then the rough coil is calendered to obtain a finished coil; (5) Slitting: Slitting the finished coil into product sheets; (6) Hot pressing: Hot pressing the product sheet into a high-conductivity bipolar plate.

2. The method for preparing a high-conductivity bipolar plate according to claim 1, characterized in that: In step (1), the purity of the expandable graphite is 95-99.95%, and the particle size is 32-80 meshes; the temperature of high-temperature expansion is 500-950° C., and the volume expansion ratio of the expandable graphite is 80-300 times.

3. The method for preparing a high-conductivity bipolar plate according to claim 1, characterized in that: In step (2), the fluoroplastic micropowder particles are any one of polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, polytrichlorofluoroethylene, and ethylene-chlorotrifluoroethylene copolymer, and the particle size of the fluoroplastic micropowder particles is 1 to 50 μm.

4. The method for preparing a high-conductivity bipolar plate according to claim 3, characterized in that: In step (2), when the fluoroplastic micropowder particles are polyvinylidene fluoride, the amount of the added particles is 10 to 20 wt% of the total amount after mixing; When the fluoroplastic micropowder particles are ethylene-tetrafluoroethylene copolymer, the addition amount is 11-21wt% of the total amount after mixing; When the fluoroplastic micropowder particles are polytrichlorofluoroethylene, the amount of addition is 5 to 18 wt% of the total amount after mixing; When the fluoroplastic micropowder particles are ethylene-chlorotrifluoroethylene copolymer, the added amount is 11-21wt% of the total amount after mixing.

5. The method for preparing a high-conductivity bipolar plate according to claim 1, characterized in that: In step (2), the air flow pressure during feeding is 0.01-0.3 MPa, the air flow pressure during mixing is 0.1-1 MPa, and the mixing time is 1-15 s; the air flow pressure of the cyclone dust collector is 0.01-0.5 MPa.

6. The method for preparing a high-conductivity bipolar plate according to claim 1, characterized in that: In step (3), the mixed powder is spread on a conveyor belt to obtain a material belt. The conveying speed of the conveyor belt is 0.1 to 2 m / min, the thickness of the material belt is 10 to 50 cm, and the density is 0.1 to 0.5 g / cm 3 .

7. The method for preparing a high-conductivity bipolar plate according to claim 6, characterized in that: In step (4), a belt is used for initial extrusion, the transmission speed of the belt and the conveyor belt are both 0.1-2 m / min, the extrusion pressure is 1-5 MPa, the thickness of the rough roll is 1-5 cm, and the density is 0.8-1.5 g / cm 3 ; During calendering, rollers are used for continuous rolling. The rotation speed of the rollers is 0.2-2 m / min, the calendering pressure is 1-8 MPa, the thickness of the finished coil is 0.2-2 mm, and the density is 1.5-1.8 g / cm 3 .

8. The method for preparing a high-conductivity bipolar plate according to claim 3, characterized in that: In step (6), when the fluoroplastic micropowder particles are polyvinylidene fluoride, the hot pressing temperature is 170 to 230°C; When the fluoroplastic micropowder particles are ethylene-tetrafluoroethylene copolymer, the hot pressing temperature is 260-320°C; When the fluoroplastic micropowder particles are polytrichlorofluoroethylene, the hot pressing temperature is 210-270°C; When the fluoroplastic micropowder particles are ethylene-chlorotrifluoroethylene copolymer, the hot pressing temperature is 240-300°C; The hot pressing pressure is 5-25MPa, and the heat preservation and pressure holding time is 1-4h; The thickness of the high-conductivity bipolar plate is 0.5-1.0 mm, and the density is 1.70-1.85 g / cm 3 .

9. A high-conductivity bipolar plate prepared by the preparation method according to any one of claims 1 to 8.

10. Application of a high-conductivity bipolar plate prepared by the preparation method according to any one of claims 1 to 8 in water-based liquid flow batteries and fuel cells.

11. The high-conductivity bipolar plate according to claim 9, characterized in that: The high-conductivity bipolar plate has a smooth gray-black surface, a certain glossiness, and good flexibility. The interior of the high-conductivity bipolar plate is a mesh structure formed by fluoroplastic micropowder particles that are melted by heat and graphite worms.

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