Graphite-metal composite bipolar plate for fuel cell, and preparation method therefor

Abstract

Disclosed in the present invention are a graphite-metal composite bipolar plate for a fuel cell, and a preparation method therefor. The method comprises the following steps: S01, heating and pressurizing a mixed powder to obtain a formed composite polar plate; S02, at 60-70°C, placing the formed composite polar plate in a first solution, soaking same, then taking same out, and washing same until neutral to obtain a pretreated composite polar plate; at 70-80°C, placing the pretreated composite polar plate in a second solution, soaking same, then taking same out, and washing same with water to obtain a treated composite polar plate; S03, placing the treated composite polar plate in a third solution, soaking same, then taking same out, washing same with water, then placing same in an activation solution for activation, and washing same with water to obtain an activated polar plate; and S04, placing the activated polar plate in a plating solution to perform a metal plating treatment, then washing same with water, and drying same to obtain a graphite-metal composite bipolar plate for a fuel cell. The preparation method of the present application is simple, has low production costs, is easy to implement, has a high production efficiency, and can be used for large-scale production of bipolar plates.

Description

A graphite-metal composite bipolar plate for fuel cells and its preparation method Technical Field

[0001] This invention belongs to the field of fuel cell technology, and particularly relates to a graphite-metal composite bipolar plate for fuel cells and its preparation method. Background Technology

[0002] The bipolar plate (BP) of a fuel cell, also known as a flow field plate, is the "skeleton" of the fuel cell stack. It is stacked with the membrane electrode assembly to form the fuel cell stack. In the fuel cell, it plays a role in supporting, collecting current, providing channels for coolant, and separating oxidant and reductant.

[0003] Currently, common bipolar plates mainly include graphite engraved plates, metal plates, and composite bipolar plates. Among them, graphite plates have advantages such as excellent conductivity and corrosion resistance, but these plates are not easy to make thin and are prone to breakage; while metal plates have advantages such as excellent conductivity, high strength, and can be made thin, but due to the harsh environment inside the fuel cell stack, metal plates are prone to corrosion.

[0004] To address the aforementioned contradictions, composite bipolar plates combine the advantages of both materials, achieving thinner plates while maintaining good corrosion resistance. Existing composite plates are primarily made of graphite and resin composite materials. To ensure strength, a suitable amount of resin is added. However, resin is a non-conductor, leading to poor overall conductivity and high contact resistance in the composite plate, making it difficult to meet the needs of practical production applications. Summary of the Invention

[0005] This invention provides a graphite-metal composite bipolar plate for fuel cells and its preparation method, aiming to solve the technical problems of existing bipolar plates, such as poor conductivity, high contact resistance, and difficulty in meeting practical application requirements.

[0006] To address the aforementioned technical problems, in one aspect, embodiments of the present invention provide a method for preparing a graphite-metal composite bipolar plate for a fuel cell, comprising the following steps:

[0007] S01. The mixed powder is heated and pressurized to obtain a molded composite electrode plate; the heating temperature is 280℃~400℃; the pressurization pressure is 15MPa~25MPa; and the pressurization time is 10min~20min.

[0008] S02. The molded composite electrode plate is immersed in a first solution at 60℃~70℃, then removed and washed until neutral to obtain a pretreated composite electrode plate; the pretreated composite electrode plate is immersed in a second solution at 70℃~80℃, then removed and washed with water to obtain a treated composite electrode plate.

[0009] S03. The treated composite electrode plate is immersed in the third solution, then removed, washed with water, and then placed in the activation solution for activation, washed with water, to obtain the activated electrode plate.

[0010] S04. The activated electrode plate is placed in a plating solution for metal plating treatment, then washed with water and dried to obtain a graphite metal composite bipolar plate for fuel cell (graphite metal composite electrode plate with metal plating on the surface).

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

[0012] The mixed powder is prepared by the following method: the powder body and the resin are dispersed evenly to obtain the mixed powder; the mass ratio of the resin to the powder body is 1:4 to 1:6.

[0013] The powder body is prepared by the following method: 60% to 80% graphite powder, 0.5% to 5% carbon fiber and 20% to 40% metal powder are mixed evenly based on the mass of the powder body as 100% to obtain the powder body.

[0014] The mixing is carried out in a mixing device; the mixing speed is 600 rpm to 800 rpm, and the mixing time is 30 min to 40 min.

[0015] The resin is a thermoplastic resin.

[0016] The thermoplastic resin is preferably one of polystyrene, polyetheretherketone, or polyamide.

[0017] The dispersion speed is 600 rpm to 800 rpm, and the dispersion time is 40 min to 60 min; during the dispersion, the temperature of the powder body and the resin are both <50℃.

[0018] In a preferred embodiment, in step S02,

[0019] The first solution is a sodium hydroxide solution with a concentration of 5 g / L to 10 g / L. Immersion in the first solution can remove oil stains from the surface of the electrode plates.

[0020] The second solution is a mixed solution containing phosphoric acid and chromic acid, wherein the concentration of phosphoric acid is 200 g / L to 300 g / L and the concentration of chromic acid is 100 g / L to 200 g / L.

[0021] In a preferred embodiment, in step S03...

[0022] The third solution is a mixed solution of stannous chloride and hydrochloric acid; the concentration of stannous chloride is 15 g / L to 20 g / L, the amount of concentrated hydrochloric acid added is 30 to 40 ml / L, and the hydrochloric acid is 37% hydrochloric acid (12 mol / L).

[0023] The soaking temperature is 25°C; the soaking time is 8 min to 10 min.

[0024] The activation solution is a mixed solution of palladium chloride and hydrochloric acid; the concentration of palladium chloride is 0.3 g / L to 0.5 g / L, and the concentration of hydrochloric acid is 20 ml / L to 30 ml / L.

[0025] The activation time is 3 to 5 minutes.

[0026] In a preferred embodiment, in step S04,

[0027] The plating solution contains 20 g / L to 30 g / L nickel sulfate, 20 g / L to 30 g / L sodium hypophosphite, 10 g / L to 15 g / L sodium acetate and 10 g / L to 15 g / L sodium citrate.

[0028] The metal plating process is carried out by stirring; the stirring speed is 80 rpm to 100 rpm; and the metal plating time is 40 min to 60 min.

[0029] On the other hand, this application embodiment also provides a graphite metal composite bipolar plate for a fuel cell, which is prepared by the above-described preparation method.

[0030] Compared with the prior art, the technical solution of this invention has the following beneficial effects: By adding metal powder to the powder, this application can effectively improve the conductivity of the composite powder while reducing the influence of resin on the conductivity of the bipolar plate; by adding a surface treatment process to the bipolar plate, not only is the conductivity of the bipolar plate further improved, but its corrosion resistance is also effectively enhanced. The preparation method of this application is simple, has low production cost, is easy to implement, greatly shortens the preparation cycle of the electrode plate, and has high production efficiency, making it suitable for large-scale production of bipolar plates. The prepared graphite-metal composite bipolar plate for fuel cells has low contact resistance, high molding efficiency, and good performance, meeting the needs of fuel cell applications. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0033] Currently, existing bipolar plates suffer from problems such as poor conductivity, high contact resistance, and difficulty in meeting practical application requirements. To address these technical issues, this invention provides a method for preparing a graphite-metal composite bipolar plate for fuel cells, comprising the following steps:

[0034] S01. The mixed powder is heated and pressurized to obtain a molded composite electrode plate; the heating temperature is 280℃~400℃; the pressurization pressure is 15MPa~25MPa; and the pressurization time is 10min~20min.

[0035] S02. The molded composite electrode plate is immersed in a first solution at 60℃~70℃, then removed and washed until neutral to obtain a pretreated composite electrode plate; the pretreated composite electrode plate is immersed in a second solution at 70℃~80℃, then removed and washed with water to obtain a treated composite electrode plate.

[0036] S03. The treated composite electrode plate is immersed in the third solution, then removed, washed with water, and then placed in the activation solution for activation, washed with water, to obtain the activated electrode plate.

[0037] S04. The activated electrode plate is placed in a plating solution for metal plating treatment, then washed with water and dried to obtain a graphite metal composite bipolar plate for fuel cell (graphite metal composite electrode plate with metal plating on the surface).

[0038] In a preferred embodiment, in step S01,

[0039] The mixed powder is prepared by uniformly dispersing the powder matrix and resin to obtain the mixed powder; the mass ratio of the resin to the powder matrix is ​​1:4 to 1:6. By controlling the ratio of the powder matrix and resin, the resulting electrode plate has good hardness, effectively improving the conductivity of the composite powder while reducing the influence of the resin on the conductivity of the bipolar plate. If the resin content is too high, the conductivity of the resulting bipolar plate will be poor; if the resin content is too low, the strength of the electrode plate cannot be guaranteed.

[0040] The powder matrix is ​​prepared by the following method: 60%–80% graphite powder, 0.5%–5% carbon fiber, and 20%–40% metal powder are mixed evenly, based on 100% of the powder matrix's mass, to obtain the powder matrix. By controlling the proportions of graphite powder, carbon fiber, and metal powder, the conductivity of the powder matrix can be effectively improved while reducing the influence of the resin on the conductivity of the bipolar plate.

[0041] The graphite powder is preferably natural graphite powder, artificial graphite powder (such as isostatic graphite powder), or flexible graphite powder.

[0042] The natural graphite powder has a particle size of 10μm to 50μm; the artificial graphite powder has a particle size of 15μm to 45μm; and the flexible graphite powder has a particle size of 20μm to 40μm.

[0043] The carbon fiber has a length of 0.1 mm to 10 mm and a diameter of 5 μm to 10 μm.

[0044] The metal powder is preferably one of stainless steel powder, titanium powder, aluminum powder, or copper powder.

[0045] The stainless steel powder has a particle size of 25μm to 75μm; the titanium powder has a particle size of 30μm to 90μm; the aluminum powder has a particle size of 15μm to 60μm; and the copper powder has a particle size of 10μm to 50μm.

[0046] The mixing is carried out in a mixing device; the mixing speed is 600 rpm to 800 rpm, and the mixing time is 30 min to 40 min. This ensures that the powder is fully mixed.

[0047] The resin is a thermoplastic resin.

[0048] The thermoplastic resin is preferably one of polystyrene, polyetheretherketone, or polyamide.

[0049] The dispersion speed is 600 rpm to 800 rpm, and the dispersion time is 40 min to 60 min. During the dispersion, the temperature of both the powder and the resin is <50℃. This effectively prevents the powder and resin from overheating, which could affect their state and thus the mixing effect.

[0050] In a preferred embodiment, in step S02,

[0051] The first solution is a sodium hydroxide solution with a concentration of 5 g / L to 10 g / L. Immersion in the first solution can remove oil stains from the surface of the electrode plates.

[0052] The soaking time is 10 to 15 minutes.

[0053] The cleaning process involves rinsing with deionized water.

[0054] The second solution is a mixed solution containing phosphoric acid and chromic acid, wherein the concentration of phosphoric acid is 200 g / L to 300 g / L and the concentration of chromic acid is 100 g / L to 200 g / L. By applying a surface treatment process to the bipolar plate using the first and second solutions, not only is the conductivity of the bipolar plate further improved, but its corrosion resistance is also effectively enhanced.

[0055] The water washing is performed using deionized water.

[0056] In this embodiment, the immersion temperature of the second solution is higher than that of the first solution, which allows for better treatment of the electrode surface, enabling better sensitization and activation, and facilitating the formation of palladium particles on the electrode surface.

[0057] In a preferred embodiment, in step S03...

[0058] The third solution is a mixed solution of stannous chloride and hydrochloric acid; the concentration of stannous chloride is 15 g / L to 20 g / L, the amount of concentrated hydrochloric acid added is 30 to 40 ml / L, and the hydrochloric acid is 37% hydrochloric acid (12 mol / L).

[0059] The immersion temperature is 25°C; the immersion time is 8-10 minutes. Immersion sensitizes the electrode, causing tin ions (Sn) to adsorb onto the electrode surface. 2+ ).

[0060] The activation solution is a mixed solution of palladium chloride and hydrochloric acid; the concentration of palladium chloride is 0.3 g / L to 0.5 g / L, and the concentration of hydrochloric acid is 20 ml / L to 30 ml / L.

[0061] The activation time is 3 to 5 minutes. Through activation treatment, palladium particles can be formed on the surface of the electrode, and the palladium particles can serve as catalytic centers for the electrode.

[0062] In a preferred embodiment, in step S04,

[0063] The plating solution contains 20 g / L to 30 g / L nickel sulfate (NiSO4), 20 g / L to 30 g / L sodium hypophosphite (NaH2PO2), 10 g / L to 15 g / L sodium acetate (CH3COONa), and 10 g / L to 15 g / L sodium citrate (C6H5Na3O7).

[0064] In the embodiments of this application, the composition of the plating solution can be adjusted according to actual needs, or it can be replaced with a copper plating solution or the like for copper plating. Through plating solution treatment, the conductivity of the electrode plate can be further improved.

[0065] The pH value of the plating solution is 4.5 to 5.0; the pH value is adjusted by acetic acid or sodium hydroxide.

[0066] The temperature of the plating solution is 80℃~90℃. By controlling the temperature of the plating solution, the quality of the coating can be effectively guaranteed. If the temperature is too low, the coating deposition rate will be too slow, resulting in porosity; if the temperature is too high, the stress on the coating will increase, making it prone to embrittlement and cracking, and the reaction rate will be too fast and difficult to control.

[0067] The metal plating process is carried out under stirring; the stirring speed is 80 rpm to 100 rpm; and the metal plating time is 40 min to 60 min. This ensures the uniformity of the plating solution, resulting in high surface consistency of the electrode plates and thus guaranteeing the stability of the electrode plate performance.

[0068] The water washing process involves cleaning with deionized water.

[0069] The drying temperature is 100℃~120℃.

[0070] In the embodiments of this application, the solution of this application can be achieved as long as the operating conditions are controlled within the above parameter range.

[0071] Example 1

[0072] A method for preparing a graphite-metal composite bipolar plate for a fuel cell includes the following steps:

[0073] S01. The mixed powder is heated and pressurized to obtain a molded composite electrode plate; the heating temperature is 370℃; the pressurization pressure is 25MPa; and the pressurization time is 15min.

[0074] S02. At 70°C, the molded composite electrode plate is immersed in a first solution and then removed and washed until neutral to obtain a pretreated composite electrode plate; at 75°C, the pretreated composite electrode plate is immersed in a second solution and then removed and washed with water to obtain a treated composite electrode plate.

[0075] S03. The treated composite electrode plate is immersed in the third solution, then removed, washed with water, and then placed in the activation solution for activation, washed with water, to obtain the activated electrode plate.

[0076] S04. The activated electrode plate is placed in a plating solution for metal plating treatment, then washed with water and dried to obtain a graphite metal composite bipolar plate for fuel cell (graphite metal composite electrode plate with metal plating on the surface).

[0077] In step S01,

[0078] The mixed powder is prepared by dispersing 100g of powder body and 20g of polyetheretherketone resin evenly to obtain the mixed powder.

[0079] The powder body is prepared by the following method: 78g of natural flake graphite (35μm), 2g of short-cut carbon fiber (0.5mm in length and 5μm in diameter) and 20g of copper powder (20μm) are mixed evenly to obtain the powder body.

[0080] The mixing is carried out in a mixing device; the mixing speed is 800 rpm, and the mixing time is 30 min.

[0081] The dispersion speed is 800 rpm, and the dispersion time is 60 min; during the dispersion, the temperature of both the powder body and the resin is <50℃.

[0082] In step S02,

[0083] The first solution is a 5 g / L sodium hydroxide solution.

[0084] The soaking time is 15 minutes.

[0085] The cleaning process involves rinsing with deionized water.

[0086] The second solution is a mixed solution containing phosphoric acid and chromic acid, wherein the concentration of phosphoric acid is 220 g / L and the concentration of chromic acid is 150 g / L.

[0087] The water washing is performed using deionized water.

[0088] In step S03,

[0089] The third solution is a mixed solution of stannous chloride and hydrochloric acid; the concentration of stannous chloride is 15 g / L, the amount of hydrochloric acid added is 36 ml / L, and the hydrochloric acid is 37% hydrochloric acid (12 mol / L).

[0090] The soaking temperature is 25°C; the soaking time is 10 minutes.

[0091] The activation solution is a mixed solution of palladium chloride and hydrochloric acid; the concentration of palladium chloride is 0.5 g / L, and the concentration of hydrochloric acid is 30 ml / L.

[0092] The activation time is 5 minutes.

[0093] In step S04,

[0094] The plating solution contains 20 g / L nickel sulfate, 20 g / L sodium hypophosphite, 10 g / L sodium acetate and 10 g / L sodium citrate.

[0095] The pH value of the plating solution is 4.5; the pH value is adjusted by acetic acid or sodium hydroxide. The temperature of the plating solution is 80°C.

[0096] The metal plating process is carried out by stirring; the stirring speed is 100 rpm; and the metal plating time is 50 min.

[0097] The washing process involves rinsing with deionized water. The drying temperature is 120°C.

[0098] The prepared graphite-metal composite bipolar plate for fuel cells has a low contact resistance (3.5 mΩ·cm). 2 It has a high molding efficiency and good performance (approximately 3.5-4.5 mm).

[0099] Example 2

[0100] A method for preparing a graphite-metal composite bipolar plate for a fuel cell includes the following steps:

[0101] S01. The mixed powder is heated and pressurized to obtain a molded composite electrode plate; the heating temperature is 370℃; the pressurization pressure is 25MPa; and the pressurization time is 15min.

[0102] S02. At 70°C, the molded composite electrode plate is immersed in a first solution and then removed and washed until neutral to obtain a pretreated composite electrode plate; at 75°C, the pretreated composite electrode plate is immersed in a second solution and then removed and washed with water to obtain a treated composite electrode plate.

[0103] S03. The treated composite electrode plate is immersed in the third solution, then removed, washed with water, and then placed in the activation solution for activation, washed with water, to obtain the activated electrode plate.

[0104] S04. The activated electrode plate is placed in a plating solution for metal plating treatment, then washed with water and dried to obtain a graphite metal composite bipolar plate for fuel cell (graphite metal composite electrode plate with metal plating on the surface).

[0105] In step S01,

[0106] The mixed powder is prepared by dispersing 100g of powder body and 20g of polyetheretherketone resin evenly to obtain the mixed powder.

[0107] The powder body is prepared by the following method: 70g of natural flake graphite (35μm), 2g of short-cut carbon fiber (0.5mm in length and 5μm in diameter) and 28g of copper powder (20μm) are mixed evenly to obtain the powder body.

[0108] The mixing is carried out in a mixing device; the mixing speed is 800 rpm, and the mixing time is 30 min.

[0109] The dispersion speed is 800 rpm, and the dispersion time is 60 min; during the dispersion, the temperature of both the powder body and the resin is <50℃.

[0110] In step S02,

[0111] The first solution is a 5 g / L sodium hydroxide solution.

[0112] The soaking time is 15 minutes.

[0113] The cleaning process involves rinsing with deionized water.

[0114] The second solution is a mixed solution containing phosphoric acid and chromic acid, wherein the concentration of phosphoric acid is 220 g / L and the concentration of chromic acid is 150 g / L.

[0115] The water washing is performed using deionized water.

[0116] In step S03,

[0117] The third solution is a mixture of stannous chloride and concentrated hydrochloric acid; the concentration of stannous chloride is 15 g / L, the amount of concentrated hydrochloric acid added is 36 ml / L, and the concentration of concentrated hydrochloric acid is 37% (12 mol / L).

[0118] The soaking temperature is 25°C; the soaking time is 10 minutes.

[0119] The activation solution is a mixed solution of palladium chloride and hydrochloric acid; the concentration of palladium chloride is 0.5 g / L, and the concentration of hydrochloric acid is 30 ml / L.

[0120] The activation time is 5 minutes.

[0121] In step S04,

[0122] The plating solution contains 20 g / L nickel sulfate, 20 g / L sodium hypophosphite, 10 g / L sodium acetate and 10 g / L sodium citrate.

[0123] The pH value of the plating solution is 4.5; the pH value is adjusted by acetic acid or sodium hydroxide. The temperature of the plating solution is 80°C.

[0124] The metal plating process is carried out by stirring; the stirring speed is 100 rpm; and the metal plating time is 50 min.

[0125] The washing process involves rinsing with deionized water. The drying temperature is 120°C.

[0126] The prepared graphite-metal composite bipolar plate for fuel cells has a low contact resistance (3.5 mΩ·cm). 2 It has a high molding efficiency and good performance (approximately 3.5-4.5 mm).

[0127] Example 3

[0128] A method for preparing a graphite-metal composite bipolar plate for a fuel cell includes the following steps:

[0129] S01. The mixed powder is heated and pressurized to obtain a molded composite electrode plate; the heating temperature is 280℃; the pressurization pressure is 25MPa; and the pressurization time is 15min.

[0130] S02. At 70°C, the molded composite electrode plate is immersed in a first solution and then removed and washed until neutral to obtain a pretreated composite electrode plate; at 75°C, the pretreated composite electrode plate is immersed in a second solution and then removed and washed with water to obtain a treated composite electrode plate.

[0131] S03. The treated composite electrode plate is immersed in the third solution, then removed, washed with water, and then placed in the activation solution for activation, washed with water, to obtain the activated electrode plate.

[0132] S04. The activated electrode plate is placed in a plating solution for metal plating treatment, then washed with water and dried to obtain a graphite metal composite bipolar plate for fuel cell (graphite metal composite electrode plate with metal plating on the surface).

[0133] In step S01,

[0134] The mixed powder is prepared by dispersing 100g of powder body and 20g of polystyrene resin evenly to obtain the mixed powder.

[0135] The powder body is prepared by the following method: 78g of natural flake graphite (35μm), 2g of short-cut carbon fiber (0.5mm in length and 5μm in diameter) and 20g of stainless steel powder (30μm) are mixed evenly to obtain the powder body.

[0136] The mixing is carried out in a mixing device; the mixing speed is 800 rpm, and the mixing time is 30 min.

[0137] The dispersion speed is 800 rpm, and the dispersion time is 60 min; during the dispersion, the temperature of both the powder body and the resin is <50℃.

[0138] In step S02,

[0139] The first solution is a 5 g / L sodium hydroxide solution.

[0140] The soaking time is 15 minutes.

[0141] The cleaning process involves rinsing with deionized water.

[0142] The second solution is a mixed solution containing phosphoric acid and chromic acid, wherein the concentration of phosphoric acid is 220 g / L and the concentration of chromic acid is 150 g / L.

[0143] The water washing is performed using deionized water.

[0144] In step S03,

[0145] The third solution is a mixed solution of stannous chloride and hydrochloric acid; the concentration of stannous chloride is 15 g / L, the amount of hydrochloric acid added is 36 ml / L, and the hydrochloric acid is 37% hydrochloric acid (12 mol / L).

[0146] The soaking temperature is 25°C; the soaking time is 10 minutes.

[0147] The activation solution is a mixed solution of palladium chloride and hydrochloric acid; the concentration of palladium chloride is 0.5 g / L, and the concentration of hydrochloric acid is 30 ml / L.

[0148] The activation time is 5 minutes.

[0149] In step S04,

[0150] The plating solution contains 20 g / L nickel sulfate, 20 g / L sodium hypophosphite, 10 g / L sodium acetate and 10 g / L sodium citrate.

[0151] The pH value of the plating solution is 4.5; the pH value is adjusted by acetic acid or sodium hydroxide. The temperature of the plating solution is 80°C.

[0152] The metal plating process is carried out by stirring; the stirring speed is 100 rpm; and the metal plating time is 50 min.

[0153] The water washing process uses deionized water for cleaning. The drying temperature is 120℃. The prepared fuel cell graphite-metal composite bipolar plate has a low contact resistance (3.5 mΩ·cm). 2 It has a high molding efficiency and good performance (approximately 3.5-4.5 mm).

[0154] 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 within the protection scope of the present invention.

Claims

1. A method for preparing a graphite-metal composite bipolar plate for a fuel cell, characterized in that, Includes the following steps: S01. The mixed powder is heated and pressurized to obtain a molded composite electrode plate; the heating temperature is 280℃~400℃; the pressurization pressure is 15MPa~25MPa; and the pressurization time is 10min~20min. S02. The molded composite electrode plate is immersed in the first solution at 60℃~70℃, then taken out and washed until neutral to obtain the pretreated composite electrode plate. The pretreated composite electrode plate was immersed in the second solution at 70℃~80℃, then removed and washed with water to obtain the treated composite electrode plate. S03. The treated composite electrode plate is immersed in the third solution, then removed, washed with water, and then placed in the activation solution for activation, washed with water, to obtain the activated electrode plate. S04. The activated electrode plate is placed in a plating solution for metal plating treatment, then washed with water and dried to obtain a graphite-metal composite bipolar plate for fuel cell.

2. The method for preparing the graphite-metal composite bipolar plate for a fuel cell according to claim 1, characterized in that, In step S01, the mixed powder is prepared by the following method: the powder body and the resin are dispersed evenly to obtain the mixed powder; the mass ratio of the resin to the powder body is 1:4 to 1:

6.

3. The method for preparing the graphite-metal composite bipolar plate for a fuel cell according to claim 2, characterized in that, The powder body is prepared by the following method: 60% to 80% graphite powder, 0.5% to 5% carbon fiber and 20% to 40% metal powder are mixed evenly based on the mass of the powder body as 100% to obtain the powder body.

4. The method for preparing the graphite-metal composite bipolar plate for a fuel cell according to claim 3, characterized in that, The graphite powder is natural graphite powder, artificial graphite powder, or flexible graphite powder. The metal powder is one of stainless steel powder, titanium powder, aluminum powder, or copper powder.

5. The method for preparing a graphite-metal composite bipolar plate for a fuel cell according to claim 4, characterized in that, The natural graphite powder has a particle size of 10μm to 50μm; the artificial graphite powder has a particle size of 15μm to 45μm; and the flexible graphite powder has a particle size of 20μm to 40μm. The carbon fiber has a length of 0.1 mm to 10 mm and a diameter of 5 μm to 10 μm; The stainless steel powder has a particle size of 25μm to 75μm; the titanium powder has a particle size of 30μm to 90μm; the aluminum powder has a particle size of 15μm to 60μm; and the copper powder has a particle size of 10μm to 50μm. The mixing is carried out in a mixing device; the mixing speed is 600 rpm to 800 rpm, and the mixing time is 30 min to 40 min.

6. The method for preparing a graphite-metal composite bipolar plate for a fuel cell according to claim 2, characterized in that, The resin is a thermoplastic resin; The dispersion speed is 600 rpm to 800 rpm, and the dispersion time is 40 min to 60 min; during the dispersion, the temperature of the powder body and the resin are both <50℃.

7. The method for preparing a graphite-metal composite bipolar plate for a fuel cell according to claim 1, characterized in that, In step S02, The first solution is a sodium hydroxide solution with a concentration of 5 g / L to 10 g / L; The soaking time is 10 to 15 minutes; The second solution is a mixed solution containing phosphoric acid and chromic acid, wherein the concentration of phosphoric acid is 200 g / L to 300 g / L and the concentration of chromic acid is 100 g / L to 200 g / L.

8. The method for preparing a graphite-metal composite bipolar plate for a fuel cell according to claim 1, characterized in that, In step S03, The third solution is a mixed solution of stannous chloride and hydrochloric acid; the concentration of stannous chloride is 15 g / L to 20 g / L, the amount of hydrochloric acid added is 30 to 40 ml / L, and the hydrochloric acid is 37% by mass. The soaking temperature is 25℃; the soaking time is 8 min to 10 min; The activation solution is a mixed solution of palladium chloride and hydrochloric acid; the concentration of palladium chloride is 0.3 g / L to 0.5 g / L, and the concentration of hydrochloric acid is 20 ml / L to 30 ml / L. The activation time is 3 to 5 minutes.

9. The method for preparing a graphite-metal composite bipolar plate for a fuel cell according to claim 1, characterized in that, In step S04, The plating solution contains 20 g / L to 30 g / L nickel sulfate, 20 g / L to 30 g / L sodium hypophosphite, 10 g / L to 15 g / L sodium acetate and 10 g / L to 15 g / L sodium citrate; The pH value of the plating solution is 4.5 to 5.0; the temperature of the plating solution is 80℃ to 90℃. The metal plating process is carried out by stirring; the stirring speed is 80 rpm to 100 rpm; the metal plating time is 40 min to 60 min. The drying temperature is 100℃~120℃.

10. A graphite-metal composite bipolar plate for a fuel cell, characterized in that, The graphite-metal composite bipolar plate of the fuel cell is prepared by the preparation method according to any one of claims 1 to 9.