Carbon fiber graphite composite bipolar plate and preparation method thereof

Abstract

The invention discloses a carbon fiber graphite composite bipolar plate and a preparation method thereof, and the method comprises the following steps: S01, uniformly mixing epoxy resin and short carbon fibers according to a mass ratio of 1: (0.02-0.05) to obtain a mixture; s02, sequentially adding graphite and modified carbon black into the mixture, and uniformly dispersing to obtain a resin mixture; the mass ratio of the short carbon fiber to the graphite to the modified carbon black is (0.5-1): (2-3): (1-2); s03, uniformly coating two side surfaces of the carbon fiber cloth with the resin mixture to obtain a prepreg; s04, arranging conductive layers on two side surfaces of the prepreg to obtain a conductive prepreg; and placing the conductive prepreg in a mold, and pressing to obtain the carbon fiber graphite composite bipolar plate. The preparation method is simple, low in production cost and high in production efficiency. The prepared bipolar plate is low in contact resistance, high in forming efficiency and good in performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and particularly relates to a carbon fiber graphite composite bipolar plate and a preparation method thereof. Background Art

[0002] The bipolar plate of a fuel cell is a core component in the stack. Its main functions are to separate fuel and oxidant, support the membrane electrode, transport gases through the flow field on the surface, and collect and conduct the generated current, heat, water, etc.

[0003] Due to its good thermal conductivity, stability, corrosion resistance and other properties, the carbon fiber graphite composite bipolar plate has great application prospects. Among them, using carbon fiber as the base material can provide high flexural strength for the product.

[0004] However, the bulk resistance of the bipolar plate prepared using carbon fiber fabric and conductive paste is relatively large, resulting in a relatively large contact resistance of the bipolar plate after forming and poor electrical conductivity. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a carbon fiber graphite composite bipolar plate and a preparation method thereof, aiming to solve the problems that the bulk resistance of the bipolar plate prepared using carbon fiber fabric and conductive paste is relatively large, resulting in a relatively large contact resistance of the bipolar plate after forming and poor electrical conductivity. The carbon fiber graphite composite bipolar plate prepared by the present invention can effectively reduce the bulk resistance of the bipolar plate and improve the electrical conductivity of the bipolar plate.

[0006] To achieve the above purpose, on the one hand, an embodiment of the present invention proposes the following technical solution: A preparation method of a carbon fiber graphite composite bipolar plate, comprising the following steps:

[0007] S01. Mix epoxy resin and chopped carbon fiber evenly according to a mass ratio of 1:(0.02 - 0.05) to obtain a mixture;

[0008] S02. Add graphite and modified carbon black to the mixture in step S01 in sequence, disperse evenly to obtain a resin mixture; the mass ratio of the chopped carbon fiber, the graphite and the modified carbon black is (0.5 - 1):(2 - 3):(1 - 2);

[0009] S03. Uniformly coat the resin mixture in step S01 on both sides of the carbon fiber cloth to obtain a prepreg;

[0010] S04. Set a conductive layer on both sides of the prepreg in step S03 to obtain a conductive prepreg; place the conductive prepreg in a mold and press it to obtain a carbon fiber graphite composite bipolar plate.

[0011] As a preferred embodiment, in step S01,

[0012] The length of the chopped carbon fiber is 0.5 mm to 2 mm.

[0013] The chopped carbon fiber is pretreated by the following method: The chopped carbon fiber is placed in concentrated nitric acid for 30 minutes to 60 minutes. By immersing the chopped carbon fiber in concentrated nitric acid, oxidation treatment is carried out on it to improve the surface activity.

[0014] The mixing is carried out by a high-speed shear mixer; the conditions for the mixing are mixing at 2000 rpm to 4000 rpm for 15 minutes to 30 minutes.

[0015] As a preferred embodiment, in step S02,

[0016] The graphite is one or a mixture of at least two of flaky graphite, spherical graphite, tubular graphite or fibrous graphite.

[0017] The modified carbon black is obtained by the following method: adding a silane coupling agent to conductive carbon black and ball milling to obtain modified carbon black; the mass of the silane coupling agent is 0.1% to 0.5% of the mass of the conductive carbon black.

[0018] Preferably, the silane coupling agent is KH-550; the conductive carbon black is EC-600JD or E250G; the ball milling time is 2 hours to 24 hours.

[0019] The dispersion is achieved by ultrasonic waves; the conditions for the ultrasonic waves are ultrasonic dispersion at 40 kHz to 70 kHz for 30 minutes to 60 minutes. Through ultrasonic dispersion, agglomeration can be effectively eliminated.

[0020] As a preferred embodiment, in step S03,

[0021] Based on the total mass of the resin mixture and the carbon fiber cloth being 100%, the coating amount of the resin mixture is 30% to 60%.

[0022] The carbon fiber cloth is at least one of a carbon fiber woven cloth or a unidirectional cloth.

[0023] As a preferred embodiment, in step S04,

[0024] The conductive layer is a conductive layer made of one or a mixture of at least two of expanded graphite, flaky graphite, spherical graphite, tubular graphite or fibrous graphite.

[0025] The thickness of the conductive layer is 0.03 mm to 0.5 mm.

[0026] The setting is achieved by coating or pasting.

[0027] The pressing time is 1 minute to 10 minutes; the pressing temperature is 90°C to 230°C.

[0028] The pressing is achieved by cold pressing, hot pressing or hot stamping. The pressing method is comprehensively selected in combination with the type of resin selected.

[0029] On the other hand, the present application also provides a carbon fiber graphite composite bipolar plate, which is prepared by the above preparation method.

[0030] Compared with the prior art solutions, the present invention has the following beneficial effects:

[0031] In the carbon fiber graphite composite bipolar plate prepared by the present invention, by coating the resin mixture and the conductive layer on both sides of the carbon fiber cloth and pressing it into shape, the conductivity of the carbon fiber graphite composite bipolar plate can be effectively improved, and its conductivity can be increased by 17% to 60%. Through the present application, while effectively improving the conductivity of the carbon fiber graphite composite bipolar plate, the influence of the resin on the conductivity of the bipolar plate can be reduced; by adding a surface treatment process to the bipolar plate, not only the conductivity of the bipolar plate is further improved, but also the corrosion resistance of the bipolar plate is effectively enhanced. The preparation method of the present application is simple, the production cost is low, it is easy to implement, greatly shortens the preparation cycle of the bipolar plate, and has high production efficiency, and can be used for large-scale production of bipolar plates. The prepared carbon fiber graphite composite bipolar plate has a low contact resistance and a high forming efficiency, has good performance, and can meet the use requirements of fuel cells. Detailed Embodiments

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0033] 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 quantity of the indicated technical features. Thus, the features defined with "first", "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 it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions appears to be contradictory or unable to be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0034] At present, the bulk resistance of the existing bipolar plates prepared using carbon fiber fabrics and conductive pastes is relatively large, resulting in a relatively large contact resistance of the bipolar plates after forming and poor electrical conductivity. The embodiments of the present invention provide a carbon fiber graphite composite bipolar plate and a preparation method thereof. The preparation method is simple, the production cost is low, it is easy to implement, greatly shortens the preparation cycle of the bipolar plates, and has a relatively high production efficiency, and can be used for large-scale production of bipolar plates. In the carbon fiber graphite composite bipolar plate prepared by the present invention, by coating a resin mixture and a conductive layer on both sides of the carbon fiber cloth and pressing and forming, the electrical conductivity of the carbon fiber graphite composite bipolar plate can be effectively improved, and its electrical conductivity can be increased by 17% - 60%.

[0035] Through the present application, while effectively improving the electrical conductivity of the carbon fiber graphite composite bipolar plate, the influence of the resin on the electrical conductivity of the bipolar plate can be reduced; by adding a surface treatment process to the bipolar plate, not only the electrical conductivity of the bipolar plate is further improved, but also the corrosion resistance of the bipolar plate is effectively enhanced. The carbon fiber graphite composite bipolar plate prepared by the present application has a low contact resistance and a high forming efficiency, has good performance, and can meet the use requirements of fuel cells. In the embodiments of the present application, the conditions of each step of each preparation method and the composition and dosage ratio of the raw materials can all implement the solution of the present application and obtain good technical effects as long as they are within the above requirements.

[0036] Example 1

[0037] A preparation method of a carbon fiber graphite composite bipolar plate includes the following steps:

[0038] S01. Mix epoxy resin and short-cut carbon fibers evenly according to a mass ratio of 1:0.02 to obtain a mixture;

[0039] S02. Sequentially add graphite and modified carbon black to the mixture in step S01 and disperse evenly to obtain a resin mixture; the mass ratio of the short-cut carbon fibers, the graphite and the modified carbon black is 1:2:1;

[0040] S03. Evenly coat the resin mixture in step S01 on both sides of the carbon fiber cloth to obtain a prepreg;

[0041] S04. Set a conductive layer on both sides of the prepreg in step S03 to obtain a conductive prepreg; place the conductive prepreg in a mold and press to obtain a carbon fiber graphite composite bipolar plate.

[0042] In step S01,

[0043] The length of the short-cut carbon fibers is 0.5 mm.

[0044] The short-cut carbon fibers are pretreated by the following method: placing the short-cut carbon fibers in concentrated nitric acid for 30 minutes.

[0045] The mixing is carried out by a high-speed shearing mixer; the conditions for the mixing are mixing at 2000 rpm for 15 minutes.

[0046] In step S02,

[0047] The graphite is laminated graphite.

[0048] The modified carbon black is obtained by the following method: adding a silane coupling agent to conductive carbon black and ball-milling to obtain modified carbon black; the mass of the silane coupling agent is 0.1% of the mass of the conductive carbon black.

[0049] The silane coupling agent is KH-550; the conductive carbon black is E250G; the ball-milling time is 2 hours.

[0050] The dispersion is achieved by ultrasonic waves; the conditions for the ultrasonic waves are ultrasonic dispersion at 40 kHz for 30 minutes.

[0051] In step S03,

[0052] The coating thickness of the resin mixture is 200 μm.

[0053] The carbon fiber cloth is a carbon fiber woven cloth.

[0054] In step S04,

[0055] The conductive layer is a conductive layer made of expanded graphite.

[0056] The thickness of the conductive layer is 0.05 mm.

[0057] The setting is achieved by coating.

[0058] The pressing time is 5 minutes; the pressing temperature is 120 °C.

[0059] The pressing is achieved by hot pressing.

[0060] After testing, the conductivity of the prepared carbon fiber graphite composite bipolar plate is 17% higher than that of the existing bipolar plate.

[0061] Example 2

[0062] A method for preparing a carbon fiber graphite composite bipolar plate, comprising the following steps:

[0063] S01. Mix epoxy resin and chopped carbon fibers evenly according to a mass ratio of 1:0.05 to obtain a mixture;

[0064] S02, adding graphite and modified carbon black to the mixture of step S01 in sequence and dispersing them evenly to obtain a resin mixture; the mass ratio of the chopped carbon fiber, the graphite and the modified carbon black is 1:2:1;

[0065] S03, evenly coating the resin mixture of step S01 on both sides of the carbon fiber cloth to obtain a prepreg;

[0066] S04. Disposing a conductive layer on both sides of the prepreg in step S03 to obtain a conductive prepreg; placing the conductive prepreg in a mold and pressing it to obtain a carbon fiber graphite composite bipolar plate.

[0067] In step S01,

[0068] The length of the chopped carbon fibers is 0.5 mm.

[0069] The chopped carbon fibers were pretreated by placing the chopped carbon fibers in concentrated nitric acid for 30 minutes.

[0070] The mixing was performed by a high-speed shear mixer; the mixing condition was mixing at 2000 rpm for 15 minutes.

[0071] In step S02,

[0072] The graphite is spherical graphite.

[0073] The modified carbon black is obtained by the following method: adding a silane coupling agent to conductive carbon black, and ball milling to obtain the modified carbon black; the mass of the silane coupling agent is 0.2% of the mass of the conductive carbon black.

[0074] The silane coupling agent is KH-550; the conductive carbon black is EC-600JD; and the ball milling time is 2 hours.

[0075] The dispersion was achieved by ultrasound; the ultrasound conditions were 40 kHz for 30 minutes.

[0076] In step S03,

[0077] The coating thickness of the resin mixture was 210 μm.

[0078] The carbon fiber cloth is unidirectional cloth.

[0079] In step S04,

[0080] The conductive layer is BNB90.

[0081] The thickness of the conductive layer is 0.08 mm.

[0082] The setting is achieved by coating or paving.

[0083] The pressing time is 5 minutes; the pressing temperature is 120 °C.

[0084] After testing, the conductivity of the prepared carbon fiber graphite composite bipolar plate is 25% higher than that of the existing bipolar plate.

[0085] Example 3

[0086] A method for preparing a carbon fiber graphite composite bipolar plate includes the following steps:

[0087] S01. Mix epoxy resin and chopped carbon fibers evenly at a mass ratio of 1:0.05 to obtain a mixture.

[0088] S02. Add graphite and modified carbon black to the mixture in step S01 in sequence and disperse evenly to obtain a resin mixture; the mass ratio of the chopped carbon fibers, the graphite, and the modified carbon black is 0.5:2:1.

[0089] S03. Uniformly coat the resin mixture in step S01 on both sides of a carbon fiber cloth to obtain a prepreg.

[0090] S04. Set conductive layers on both sides of the prepreg in step S03 to obtain a conductive prepreg; place the conductive prepreg in a mold and press to obtain a carbon fiber graphite composite bipolar plate.

[0091] In step S01,

[0092] The length of the chopped carbon fibers is 2 mm.

[0093] The chopped carbon fibers are pretreated by the following method: Place the chopped carbon fibers in concentrated nitric acid for 30 minutes. By immersing the chopped carbon fibers in concentrated nitric acid, oxidation treatment is carried out to improve the surface activity.

[0094] The mixing is carried out by a high-speed shear mixer; the mixing conditions are mixing at 2500 rpm for 15 minutes.

[0095] In step S02,

[0096] The graphite is lamellar graphite.

[0097] The modified carbon black is obtained by the following method: Add a silane coupling agent to conductive carbon black and ball mill to obtain modified carbon black; the mass of the silane coupling agent is 0.2% of the mass of the conductive carbon black.

[0098] The silane coupling agent is KH-550; the conductive carbon black is EC-600JD; the ball milling time is 2.5 hours.

[0099] The dispersion is achieved by ultrasound; the conditions of the ultrasound are ultrasound dispersion at 50 kHz for 40 minutes. Through ultrasound dispersion, agglomeration can be effectively eliminated.

[0100] In step S03,

[0101] The coating thickness of the resin mixture is 200 μm.

[0102] The carbon fiber cloth is a carbon fiber woven cloth.

[0103] In step S04,

[0104] The conductive layer is BNB90.

[0105] The thickness of the conductive layer is 0.1 mm.

[0106] The setting is achieved by coating or pasting.

[0107] The pressing time is 10 minutes; the pressing temperature is 150 °C.

[0108] After testing, the prepared carbon fiber graphite composite bipolar plate has a 30% improvement in conductivity compared to the existing bipolar plate.

[0109] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made using the content of the specification of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A preparation method of a carbon fiber graphite composite bipolar plate, characterized in that It includes the following steps: S01. Mix epoxy resin and chopped carbon fibers evenly at a mass ratio of 1:(0.02 - 0.05) to obtain a mixture; S02. Sequentially add graphite and modified carbon black to the mixture in step S01, and disperse evenly to obtain a resin mixture; the mass ratio of the chopped carbon fibers, the graphite, and the modified carbon black is (0.5 - 1):(2 - 3):(1 - 2); S03. Evenly coat the resin mixture in step S01 on both sides of a carbon fiber cloth to obtain a prepreg; S04. Set conductive layers on both sides of the prepreg in step S03 to obtain a conductive prepreg; place the conductive prepreg in a mold and press it to obtain a carbon fiber graphite composite bipolar plate.

2. The preparation method of the carbon fiber graphite composite bipolar plate according to claim 1, characterized in that, In step S01, the length of the chopped carbon fibers is 0.5 mm - 2 mm; the chopped carbon fibers are pretreated by the following method: place the chopped carbon fibers in concentrated nitric acid for 30 minutes - 60 minutes.

3. The preparation method of the carbon fiber graphite composite bipolar plate according to claim 1, characterized in that, In step S01, the mixing is carried out by a high - speed shear mixer; the mixing conditions are mixing at 2000 rpm - 4000 rpm for 15 minutes - 30 minutes.

4. The preparation method of the carbon fiber graphite composite bipolar plate according to claim 1, characterized in that, In step S02, the graphite is one or a mixture of at least two of lamellar graphite, spherical graphite, tubular graphite, or fibrous graphite; The dispersion is achieved by ultrasonic treatment; the ultrasonic conditions are ultrasonic dispersion at 40 kHz - 70 kHz for 30 minutes - 60 minutes.

5. The preparation method of the carbon fiber graphite composite bipolar plate according to claim 1, wherein In step S02, the modified carbon black is obtained by the following method: add a silane coupling agent to conductive carbon black and ball - mill to obtain modified carbon black; the mass of the silane coupling agent is 0.1% - 0.5% of the mass of the conductive carbon black.

6. The preparation method of the carbon fiber graphite composite bipolar plate according to claim 5, characterized in that, The silane coupling agent is KH - 550; the conductive carbon black is EC - 600JD or E250G; the ball - milling time is 2 hours - 24 hours.

7. The preparation method of the carbon fiber graphite composite bipolar plate according to claim 1, wherein, In step S03, based on the total mass of the resin mixture and the carbon fiber cloth being 100%, the coating amount of the resin mixture is 30% - 60%; The carbon fiber cloth is at least one of carbon fiber woven cloth or unidirectional cloth.

8. The preparation method of the carbon fiber graphite composite bipolar plate according to claim 1, wherein, In step S04, the conductive layer is a conductive layer made of one or a mixture of at least two of expanded graphite, lamellar graphite, spherical graphite, tubular graphite, or fibrous graphite; The thickness of the conductive layer is 0.03 mm - 0.5 mm; the setting is achieved by coating or pasting.

9. The preparation method of the carbon fiber graphite composite bipolar plate according to claim 1, wherein, In step S04, the pressing time is 1 minute - 10 minutes; the pressing temperature is 90°C - 230°C; the pressing is achieved by cold pressing, hot pressing, or hot stamping.

10. A carbon fiber graphite composite bipolar plate, characterized in that, The carbon fiber graphite composite bipolar plate is prepared by the preparation method according to any one of claims 1 to 9.