A method for preparing carbon fiber composite bipolar plate

Abstract

The present invention belongs to the field of fuel cell technology and proposes a method for preparing a carbon fiber composite bipolar plate, comprising the following steps: S01: coating a graphite-containing conductive material on the surface of a carbon fiber prepreg to obtain a coated carbon fiber prepreg; the coating amount of the graphite-containing conductive material is 0.5 g / cm 2 ~2.0g / cm 2 S02: Placing a PTFE membrane on the coated surface of the coated carbon fiber prepreg from step S01 and performing compression molding to obtain a PTFE membrane carbon fiber prepreg with a gas flow field; the thickness of the PTFE membrane is 0.01 mm to 0.5 mm; S03: Curing the PTFE membrane carbon fiber prepreg obtained from step S02 to obtain a carbon fiber composite bipolar plate. The resulting carbon fiber bipolar plate has highly consistent flow channels, resulting in improved airtightness after molding, preventing cracking in the flow channels or ridges during demolding, and effectively improving the surface condition of the bipolar plate after demolding.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cell bipolar plates, and in particular relates to a method for preparing a carbon fiber composite bipolar plate. Background Art

[0002] A fuel cell stack is primarily composed of a catalyst, membrane electrode, gas diffusion layer, bipolar plates, and other structural components such as seals, end plates, and current collecting plates. The bipolar plate is one of the core components of a fuel cell stack. Its primary function is to separate the fuel and oxidant, support the membrane electrode, transport gas through the flow field on its surface, and collect and conduct the current, heat, and water generated during the reaction. Fuel cell bipolar plates are made of a variety of materials, including carbonaceous, metallic, and metal-carbon composites. Carbon fiber materials excel in electrical conductivity, corrosion resistance, and mechanical strength. Composite bipolar plates made from carbon fiber are lightweight, thin, and offer high flexural strength, significantly increasing both the volumetric and gravimetric power densities of a fuel cell stack.

[0003] However, the current existing carbon fiber bipolar plate preparation process has certain technical deficiencies. The flow channel area on the surface of the bipolar plate is prone to glue-rich, resulting in cracks in the flow channel and ridges or inconsistent flow channel heights when the bipolar plate is demolded, and the surface condition of the bipolar plate is poor. Summary of the Invention

[0004] An embodiment of the present invention provides a method for preparing a carbon fiber composite bipolar plate, which aims to solve the technical problems caused by the existing carbon fiber bipolar plate preparation process, such as the easy rich glue in the flow channel area of ​​the bipolar plate, cracking of the flow channel and ridge during demolding, or inconsistent flow channel height.

[0005] In order to achieve the above object, the present invention provides a method for preparing a carbon fiber composite bipolar plate, which is applicable to the technical field of fuel cell bipolar plates, comprising the following steps:

[0006] S01: coating a graphite-containing conductive material on the surface of a carbon fiber prepreg to obtain a coated carbon fiber prepreg; the coating amount of the graphite-containing conductive material is 0.5 g / cm 2 ~2.0g / cm 2 ;

[0007] S02: placing a PTFE membrane on the coated surface of the coated carbon fiber prepreg obtained in step S01 and performing molding to obtain a PTFE membrane carbon fiber prepreg with a gas flow field; the thickness of the PTFE membrane is 0.01 mm to 0.5 mm;

[0008] S03: Curing the PTFE membrane carbon fiber prepreg obtained in step S02 to obtain a carbon fiber composite bipolar plate.

[0009] The coating amount of graphite-containing conductive material can be 0.5g / cm according to actual use needs. 2 , or 1.0g / cm 2 , or 1.5g / cm 2 , or 2.0g / cm 2 Etc., if the coating amount is too high, the surface graphite material will easily fall off and the plate thickness will be thicker; if the coating amount is too low, the conductivity will be poor and the coating will not be uniform.

[0010] As a preferred embodiment, the thickness of the carbon fiber prepreg is 0.15mm to 0.40mm (depending on actual use requirements, it can be 0.15mm, or 0.25mm, or 0.30mm, or 0.4mm, etc.); the thickness of the carbon fiber composite bipolar plate is 0.2mm to 0.6mm (depending on actual use requirements, it can be 0.2mm, or 0.25mm, or 0.45mm, or 0.6mm, etc.). In this way, the plate can be ensured to have appropriate rigidity and flexibility, which is conducive to the production of electrodes, thereby ensuring the good performance of the bipolar plate, making it have good bending, tensile and compressive strength, and also ensuring the specific volume density and specific weight density of the stack.

[0011] As a preferred embodiment, the gas flow field includes a cathode plate flow field and an anode plate flow field; the width of the flow channel of the cathode plate flow field is 0.2 mm to 0.6 mm (depending on actual use requirements, it can be 0.2 mm, or 0.25 mm, or 0.45 mm, or 0.6 mm, etc.); the width of the flow channel of the anode plate flow field is 0.2 mm to 0.6 mm (depending on actual use requirements, it can be 0.2 mm, or 0.25 mm, or 0.45 mm, or 0.6 mm, etc.). This can ensure the stability of the electrode structure under long-term operating conditions.

[0012] The flow channel includes an air channel, a water channel, a sealing groove and a positioning hole.

[0013] As a preferred embodiment, the carbon fiber composite bipolar plate has a bending strength of 50 MPa to 150 MPa and a tensile strength of 80 MPa to 200 MPa.

[0014] As a preferred embodiment, the molding in step S02 is performed by hot pressing or cold pressing, and the molding pressure is 0.1 MPa to 100 MPa.

[0015] As a preferred embodiment, when the pressing method in step S02 is hot pressing, the curing method in step S03 adopts pressure-maintaining curing, or semi-curing demolding in the mold and then secondary curing; the curing temperature is 120°C to 180°C (depending on actual use needs, it can be 120°C, or 140°C, or 160°C, or 180°C, etc.), and the curing time is 0.5 hour to 2 hours (depending on actual use needs, it can be 0.5 hour, or 1 hour, or 1.5 hours, or 2 hours, etc.); in this way, it can be ensured that the electrode plate has appropriate rigidity and flexibility, which is beneficial to the production of the electrode, thereby ensuring the good performance of the bipolar plate, so that it has good bending, tensile and compressive strength.

[0016] When the pressing method in step S02 is cold pressing, the curing method in step S03 is curing after demolding, the curing temperature is 120°C to 180°C (depending on actual use needs, it can be 120°C, or 140°C, or 160°C, or 180°C, etc.), and the curing time is 0.5 hour to 2 hours (depending on actual use needs, it can be 0.5 hour, or 1 hour, or 1.5 hours, or 2 hours, etc.). In this way, it can be ensured that the electrode plate has appropriate rigidity and flexibility, which is conducive to the production of electrodes, thereby ensuring the good performance of the bipolar plate and making it have good bending, tensile and compressive strength.

[0017] In a preferred embodiment, the carbon fiber prepreg is a pre-cut carbon fiber prepreg; the carbon fiber prepreg is a unidirectional carbon fiber prepreg or a woven carbon fiber prepreg; and the carbon fiber prepreg is made from epoxy resin, phenolic resin, or polyimide. This ensures that the plate has appropriate rigidity and flexibility, facilitates electrode fabrication, and thus ensures good bipolar plate performance and the specific volume and weight density of the stack.

[0018] As a preferred embodiment, the graphite-containing conductive material can be a variety of graphite-containing conductive materials; the graphite-containing conductive material can be one or a mixture of at least two of expanded graphite, microcrystalline graphite, flake graphite, natural graphite, artificial graphite, or mesocarbon microbeads; and the graphite-containing conductive material can be in powder, sheet, or slurry form. This ensures that the plate has appropriate rigidity and flexibility, facilitates electrode fabrication, and thus ensures good bipolar plate performance.

[0019] As a preferred embodiment, the graphite-containing conductive material further comprises one or a mixture of at least two of graphene, carbon nanotubes, carbon black, and metal powder. This ensures that the plate has appropriate rigidity and flexibility, facilitates electrode fabrication, and thus ensures good performance of the bipolar plate.

[0020] As a preferred embodiment, in step S01, the covering method is direct coating, spraying, transfer, uniform powdering, direct lamination or mechanical peeling after lamination. In this way, it is possible to ensure that the plate has appropriate rigidity and flexibility while effectively saving raw materials and reducing costs. As a preferred embodiment, the surface of the carbon fiber prepreg is the upper surface of the carbon fiber prepreg and the lower surface of the carbon fiber prepreg; the coated surface is the surface of the carbon fiber prepreg coated with a graphite-containing conductive material; the PTFE membrane covering the upper surface of the coated carbon fiber prepreg and the lower surface of the coated carbon fiber prepreg are the same size, and the PTFE membrane can be of different thicknesses. In this way, the surface state of the carbon fiber prepreg after molding can be effectively improved.

[0021] The present invention coats a carbon fiber prepreg with a graphite-containing conductive material, thereby fully ensuring the contact area between the graphite-containing conductive material and the carbon fiber prepreg, thereby ensuring the stability of the fuel cell plate. By providing a PTFE membrane on the graphite-containing conductive material and forming the plate flow channel on the PTFE membrane, the depth of the flow channel is adjusted by adjusting the thickness of the PTFE membrane. This results in a consistent flow channel height in the prepared carbon fiber composite bipolar plate, effectively improving the surface condition of the carbon fiber prepreg after molding, enhancing its moldability during demolding, and improving the airtightness of the carbon fiber composite bipolar plate after molding, avoiding the possibility of cracking in the flow channel and ridge during demolding, and significantly improving the surface condition of the carbon fiber composite bipolar plate after demolding. DETAILED DESCRIPTION

[0022] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0023] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, top, bottom...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0024] In this application, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0025] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element.

[0026] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features specified as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0027] At present, the existing carbon fiber bipolar plate preparation process can lead to problems such as the bipolar plate flow channel area being prone to glue enrichment, the flow channel and ridge cracking during demolding, or inconsistent flow channel height. In order to solve the above technical problems, the present invention proposes a method for preparing a carbon fiber composite bipolar plate. The present application can be molded in one go, realizing the continuous production of fuel cell bipolar plates, while significantly reducing the weight of the plates, reducing the volume of the fuel cell, reducing production costs, and improving production efficiency. The preparation method of the present invention is simple and easy to batch or large-scale production.

[0028] Example 1

[0029] This embodiment provides a method for preparing a carbon fiber composite bipolar plate, and the specific steps are as follows:

[0030] S01: Tear off the release paper or PE film on the upper and lower surfaces of the carbon fiber prepreg, and stick two pieces of graphite paper with a thickness of 0.05 mm and the same size to the upper and lower surfaces of the carbon fiber prepreg respectively to obtain a coated carbon fiber prepreg;

[0031] The carbon fiber prepreg is cut into a rectangular carbon fiber prepreg with a size of 42.45*14.5 cm;

[0032] S02: Place the PTFE membrane on the coated surface of the coated carbon fiber prepreg obtained in step S01 and then lay it flat in the plate mold. There should be no bulges or wrinkles when laying it flat; mold it in a press to obtain a PTFE membrane carbon fiber prepreg with a gas flow field; the press feed speed is 150r / min, the molding temperature is 150℃, and the pressure is 5MPa.

[0033] S03: Curing the PTFE membrane carbon fiber prepreg obtained in step S02 to obtain the carbon fiber composite bipolar plate. The pressing method in step S02 is hot pressing, and the curing method in step S03 is pressure-maintaining curing. The curing temperature is 120°C and the curing time is 2 hours.

[0034] The thickness of the carbon fiber composite bipolar plate obtained in this embodiment is 0.48 mm, the air surface flow channel depth of the carbon fiber composite bipolar plate is 0.2 mm, and the water surface depth is 0.14 mm; the bending strength of the carbon fiber composite bipolar plate is 120 MPa, and the tensile strength is 150 MPa.

[0035] Example 2

[0036] This embodiment provides a method for preparing a carbon fiber composite bipolar plate, and the specific steps are as follows:

[0037] S01: Tear off the release paper or PE film on the upper and lower surfaces of the carbon fiber prepreg, and stick two pieces of graphite paper with a thickness of 0.05 mm and the same size to the upper and lower surfaces of the carbon fiber prepreg respectively to obtain a coated carbon fiber prepreg;

[0038] The carbon fiber prepreg is cut into a rectangular carbon fiber prepreg with a size of 42.45*14.5 cm;

[0039] S02: Place the PTFE membrane on the coated surface of the coated carbon fiber prepreg obtained in step S01 and then lay it flat in the plate mold. There should be no bulges or wrinkles when laying it flat; mold it in a press to obtain a PTFE membrane carbon fiber prepreg with a gas flow field; the press feed speed is 150r / min, the molding temperature is 150℃, and the pressure is 5MPa.

[0040] S03: Curing the PTFE membrane carbon fiber prepreg obtained in step S02 to obtain the carbon fiber composite bipolar plate. The pressing method in step S02 is hot pressing, and the curing method in step S03 is semi-curing and demolding in the mold followed by secondary curing. The curing temperature is 180°C and the curing time is 0.5 hours.

[0041] The thickness of the carbon fiber composite bipolar plate obtained in this embodiment is 0.5 mm, the air surface flow channel depth of the carbon fiber composite bipolar plate is 0.15 mm, and the water surface depth is 0.14 mm; the bending strength of the carbon fiber composite bipolar plate is 130 MPa, and the tensile strength is 150 MPa.

[0042] Example 3

[0043] This embodiment provides a method for preparing a carbon fiber composite bipolar plate, and the specific steps are as follows:

[0044] S01: Tear off the release paper or PE film on the upper and lower surfaces of the carbon fiber prepreg, and stick two pieces of graphite paper with a thickness of 0.03 mm and the same size to the upper and lower surfaces of the carbon fiber prepreg respectively to obtain a coated carbon fiber prepreg;

[0045] The carbon fiber prepreg is cut into a rectangular carbon fiber prepreg with a size of 42.45*14.5 cm;

[0046] S02: Place the PTFE membrane on the coated surface of the coated carbon fiber prepreg obtained in step S01 and accurately lay it flat in the plate mold without any bulges or wrinkles; mold it in a press to obtain a PTFE membrane carbon fiber prepreg with a gas flow field; the press feed speed is 150r / min, the molding temperature is 150℃, and the pressure is 5MPa.

[0047] S03: Curing the PTFE membrane carbon fiber prepreg obtained in step S04 to obtain the carbon fiber composite bipolar plate. The pressing method in step S02 is hot pressing, and the curing method in step S03 is semi-curing and demolding in the mold followed by secondary curing. The curing temperature is 150°C and the curing time is 1 hour.

[0048] The thickness of the carbon fiber composite bipolar plate obtained in this embodiment is 0.48 mm, the air surface flow channel depth of the carbon fiber composite bipolar plate is 0.2 mm, and the water surface depth is 0.15 mm; the bending strength of the carbon fiber composite bipolar plate is 100 MPa, and the tensile strength is 120 MPa.

[0049] Comparative Example 1

[0050] This embodiment proposes a method for preparing a carbon fiber composite bipolar plate, without using a PTFE membrane, and the remaining steps are the same as those in the first embodiment.

[0051] The carbon fiber composite bipolar plate prepared in Comparative Example 1 was compared with the carbon fiber composite bipolar plate prepared in Example 1. The carbon fiber composite bipolar plate prepared in Comparative Example 1 had inconsistent flow channel depths and slight cracks on the surface ridges of the bipolar plate. The carbon fiber composite bipolar plate prepared in Example 1 with the surface coated with PTFE membrane had a better surface condition and did not have the above problems.

[0052] The present invention coats a carbon fiber prepreg with a graphite-containing conductive material, thereby fully ensuring the contact area between the graphite-containing conductive material and the carbon fiber prepreg, thereby ensuring the stability of the fuel cell plate. By providing a PTFE membrane on the graphite-containing conductive material and forming the plate flow channel on the PTFE membrane, the depth of the flow channel is adjusted by adjusting the thickness of the PTFE membrane. This results in a consistent flow channel height in the prepared carbon fiber composite bipolar plate, effectively improving the surface condition of the carbon fiber prepreg after molding, enhancing its moldability during demolding, and improving the airtightness of the carbon fiber composite bipolar plate after molding, avoiding the possibility of cracking in the flow channel and ridge during demolding, and significantly improving the surface condition of the carbon fiber composite bipolar plate after demolding.

[0053] In this specification, reference to terms such as "one embodiment" or "example" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example.

[0054] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a carbon fiber composite bipolar plate, characterized in that: The following steps are involved: S01: coating a graphite-containing conductive material on the surface of a carbon fiber prepreg to obtain a coated carbon fiber prepreg; the coating amount of the graphite-containing conductive material is 0.5 g / cm 2 ~2.0g / cm 2 ; S02: placing a PTFE membrane on the coated surface of the coated carbon fiber prepreg obtained in step S01 and performing molding to obtain a PTFE membrane carbon fiber prepreg with a gas flow field; the thickness of the PTFE membrane is 0.01 mm to 0.5 mm; S03: Curing the PTFE membrane carbon fiber prepreg obtained in step S02 to obtain a carbon fiber composite bipolar plate.

2. The method for preparing a carbon fiber composite bipolar plate according to claim 1, wherein: The thickness of the carbon fiber prepreg is 0.15 mm to 0.40 mm; the thickness of the carbon fiber composite bipolar plate is 0.2 mm to 0.6 mm.

3. The method for preparing a carbon fiber composite bipolar plate according to claim 1, wherein: The gas flow field includes a cathode plate flow field and an anode plate flow field; the width of the flow channel of the cathode plate flow field is 0.2mm~0.6mm; the width of the flow channel of the anode plate flow field is 0.2mm~0.6mm; the flow channel includes an air channel, a water channel, a sealing groove and a positioning hole.

4. The method for preparing a carbon fiber composite bipolar plate according to claim 1, wherein: The carbon fiber composite bipolar plate has a bending strength of 50 MPa to 150 MPa and a tensile strength of 80 MPa to 200 MPa.

5. The method for preparing a carbon fiber composite bipolar plate according to claim 1, wherein: In step S02, the molding is performed by hot pressing or cold pressing, and the molding pressure is 0.1 MPa to 100 MPa.

6. The method for preparing a carbon fiber composite bipolar plate according to claim 5, wherein: When the molding method is hot pressing, the curing in step S03 is pressure-maintaining curing, or pressure-maintaining semi-curing in the mold followed by demolding and secondary curing. The curing temperature is 120° C. to 180° C., and the curing time is 0.5 to 2 hours. When the pressing method is cold pressing, the curing in step S03 is performed after demoulding and then curing, the curing temperature is 120° C. to 180° C., and the curing time is 0.5 hour to 2 hours.

7. The method for preparing a carbon fiber composite bipolar plate according to claim 1, wherein: In step S01, the carbon fiber prepreg is a cut carbon fiber prepreg; the carbon fiber prepreg is a unidirectional carbon fiber prepreg or a woven carbon fiber prepreg; the carbon fiber prepreg is a prepreg made of epoxy resin, phenolic resin or polyimide; The graphite-containing conductive material contains one or a mixture of at least two of expanded graphite, microcrystalline graphite, flake graphite, natural graphite, artificial graphite or mesophase carbon microspheres; the graphite-containing conductive material is a powdery material, a flaky material or a slurry material.

8. The method for preparing a carbon fiber composite bipolar plate according to claim 7, wherein: The graphite-containing conductive material further contains one or a mixture of at least two of graphene, carbon nanotubes, carbon black and metal powder.

9. The method for preparing a carbon fiber composite bipolar plate according to claim 1, wherein: In step S01, the coating method is direct coating, spraying, transfer printing, uniform powdering, direct lamination or mechanical peeling after lamination.

10. The method for preparing a carbon fiber composite bipolar plate according to claim 1, wherein: The surfaces of the carbon fiber prepreg are the upper surface and the lower surface of the carbon fiber prepreg; the coated surface is the surface of the carbon fiber prepreg coated with the graphite-containing conductive material.