A method for preparing a high-conductivity metal-graphite composite bipolar plate

Abstract

The application provides a preparation method of a high-conductivity metal-graphite composite bipolar plate, which comprises the following steps: cutting a titanium plate, titanium plate pretreatment, preparing LDHs material, moulding graphite mixed powder and bipolar plate forming, and utilizes the titanium plate as a base plate material, sets graphite filler on two sides of the titanium plate, greatly enhances the impact strength of the bipolar plate, avoids the disadvantages that the graphite bipolar plate is easy to break and has poor bending strength, and avoids the problem that the metal plate is easy to corrode. The prepared metal-graphite composite bipolar plate is thin in thickness, high in compactness, has excellent bending strength and conductivity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fuel cells, and particularly relates to a preparation method of a high-conductivity metal-graphite composite bipolar plate. BACKGROUND

[0002] The bipolar plate, also known as the current collector plate, is one of the core components of a fuel cell and is also a high-cost component. The bipolar plate serves to separate fuel and oxidant and to collect and conduct electric current, and thus needs to have the characteristics of corrosion resistance, vibration resistance and impact resistance.

[0003] The bipolar plate is generally divided into a metal bipolar plate, a graphite bipolar plate and a composite bipolar plate in terms of material composition. The metal bipolar plate has the characteristics of high conductivity and light weight, but is easily corroded under acidic conditions. The graphite bipolar plate has poor impact resistance and a large volume. The composite bipolar plate has the corrosion resistance of the graphite material and the high strength of the metal material, and can better combine the advantages of the metal bipolar plate and the graphite bipolar plate. However, the traditional composite bipolar plate contains resin fillers, and the resin has poor conductivity, thereby causing poor conductivity of the overall bipolar plate, which needs to be further improved. SUMMARY

[0004] The present application proposes a metal-graphite composite bipolar plate with high conductivity and corrosion resistance to solve the technical problem of poor conductivity of the existing composite bipolar plate.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] A preparation method of a high-conductivity metal-graphite composite bipolar plate, comprising the following steps,

[0007] (1) cutting a titanium plate with a thickness of 0.15-0.3 cm into a shape required by the bipolar plate;

[0008] (2) adding FeCl3·6H2O and Cu(OH)2·6H2O to deionized water, adjusting the pH of the solution to 9-12, washing the precipitate to neutral and drying to obtain Fe-Cu LDHs material;

[0009] (3) dry-mixing graphite fillers, a binder and conductive fillers to obtain a first mixed powder, placing the titanium plate in a molding cavity, uniformly placing a certain amount of the first mixed powder on the titanium plate, and molding;

[0010] (4) co-mixing graphite fillers, a binder and conductive fillers to obtain a second mixed powder, placing the bipolar plate obtained in step (3) in the molding cavity, and arranging the second mixed powder on the other side of the titanium plate, and molding;

[0011] (5) The bipolar plate obtained in step (4) is immersed in a polyacrylic acid resin, and after 24-48 h, the solidification is removed to obtain a shaped composite bipolar plate.

[0012] As preferred, the molar ratio of FeCl3·6H2O to Cu(OH)2·6H2O in step (2) is (1-4):(0.5-1).

[0013] As preferred, the drying temperature in step (2) is 80℃, the drying time is 1-3 h, and after drying, the powder is crushed and passed through a 200-350 mesh screen.

[0014] As preferred, the graphite filler in step (4) and step (5) is one or more of expanded graphite of 150-200 mesh, flake graphite of 100-200 mesh, and microcrystalline graphite of 100-200 mesh.

[0015] As preferred, the binder in step (4) and step (5) is one or more of polybutyl acetate, polypropyl acetate, polymethyl methacrylate, and polybutyl phthalate.

[0016] As preferred, the conductive filler in step (4) and step (5) is one or more of carbon black (XC-72), carbon nanotubes, and metal powder.

[0017] As preferred, the mass ratio of graphite filler, binder, conductive filler, and Fe-Cu LDHs in step (4) is (5-10):(0.1-1):(0.1-3):(1-3).

[0018] As preferred, the mass ratio of graphite filler, binder, and conductive filler in step (5) is (5-10):(0.1-1):(0.1-3).

[0019] As preferred, in step (4) and step (5), the mold pressing pressure is 5-50 MPa, and the mold pressing time is 10-20 min.

[0020] As preferred, in step (6), the solidification temperature is 200-400℃, and the solidification time is 1-3 h.

[0021] As preferred, step (1) further includes a titanium plate pretreatment step, specifically, the cut titanium plate is polished to a bright finish, then immersed in a 40%-60% mass percent NaOH solution, the solution is heated to 60-80℃, and after 1-2 h, washed with deionized water to obtain a titanium plate substrate.

[0022] As preferred, in step (3), after dry mixing by ball milling, the first mixed powder is placed on a vibrating table and vibrated evenly, the vibrating table amplitude is 0.01-100 mm, the frequency is 1-400 times / min, and the vibration time is 3-5 min.

[0023] Compared with the prior art, the application has the advantages and positive effects that:

[0024] The preparation method of the metal graphite composite bipolar plate uses a titanium plate as a base plate material, and graphite fillers are arranged on both sides of the titanium plate, so that the impact strength of the bipolar plate is greatly enhanced, the disadvantages of the fragile graphite bipolar plate and the poor bending strength are avoided, and the problem of easy corrosion of the metal plate is avoided.

[0025] The Fe-Cu LDHs material is added to one side of the composite bipolar plate, the layered double metal hydroxide (LDHs) has high stability and plasticity, and has adsorption capacity for Cu 2+ , Zn 2+ , Fe 3+ , Fe 2+ , Cr 2+ and other metals, so that the corrosion of free metal ions to the proton membrane can be avoided.

[0026] The metal graphite composite bipolar plate has a relatively thin thickness, a relatively high compactness, excellent bending strength and electrical conductivity. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The flow chart of the preparation method of the composite bipolar plate is shown in the figure; DETAILED DESCRIPTION

[0028] In order to better understand the application, the following will be specifically described in combination with the drawings and examples.

[0029] Example 1

[0030] Cut the titanium plate of 50x30x0.2cm, polish the titanium plate with 600 grit sandpaper until the surface of the titanium plate is smooth. Immerse the polished titanium plate in a 50% by mass concentration NaOH solution, and heat the solution to 80℃, and keep for 1h. Then wash the alkali solution with a large amount of deionized water to obtain the titanium plate substrate, dry the titanium plate substrate and store it in vacuum for standby. Add FeCl3·6H2O and Cu(OH)2·6H2O to deionized water according to a molar ratio of 3:1, and titrate with 3mol / L NaOH to pH 12. Filter to obtain the precipitate, wash the precipitate with a large amount of deionized water until it is neutral, then dry at 80℃ for 2h, crush the dried solid after 200 mesh screen to obtain Fe-Cu LDHs material. Weigh 80g of 200 mesh expanded graphite, 5g of polybutyl acetate, 15g of XC-72 carbon black, and 10g of Fe-Cu LDHs material, and ball mill for 2h to obtain a first mixed powder. Place the first mixture on the vibration table and shake evenly, the vibration table amplitude is 50mm, the frequency is 200 times / min, and the vibration time is 5min. Place the vacuum-dried titanium plate in the mold pressing cavity, weigh 40g of the second mixed powder on one side of the titanium plate, and press at 5-45MPa for 5min using 9 pressing sections. Then take out the titanium plate and place it on the other side of the mold pressing cavity.

[0031] Weigh 80g of 200 mesh expanded graphite, 5g of polybutyl acetate, and 15g of XC-72 carbon black, and ball mill for 2h to obtain a second mixed powder. Place the second mixed powder on the vibration table and shake evenly, the vibration table amplitude is 50mm, the frequency is 200 times / min, and the vibration time is 5min. Weigh 40g of the second mixed powder on the titanium plate, and press at 5-45MPa for 5min using 9 pressing sections to obtain a completed composite bipolar plate. Vacuum-immerse the composite graphite plate in polyacrylic acid resin, take it out after 24h and cure at 350℃ for 2h to obtain the final shaped composite bipolar plate, and test its performance.

[0032] Test method:

[0033] (1) Thickness test: Take the composite bipolar plate flow channel area at six different positions, use a thickness gauge to test the thickness, and record the average value.

[0034] (2) Electrical conductivity test: Use RTS-9 type double electrical measurement four-probe tester to measure the electrical conductivity of the composite bipolar plate. In order to eliminate the contact resistance between the metal probe and the sample, the direct current four-probe method is used for testing.

[0035] (3) Bending strength test: use WD-10D universal testing machine, apply three-point bending method to test the bending strength of the composite bipolar plate, the test steps are as follows:

[0036] ① The sample is made into a long strip shape with a width of 10mm;

[0037] 2. Adjust the support span so that the indenter and the support head are perpendicular to the sample axis;

[0038] 3. The indenter applies a load at a uniform and non-impact loading speed of 10 mm / s until the sample breaks, and the breaking load value is read. 2

[0039] The bending strength is calculated according to the following formula:

[0040] δ F = 3PL / 2bh 2 ,

[0041] Wherein, δF: bending strength (MPa), P: breaking load value (N), L: support span (30 mm), B: sample width (mm), h: sample thickness (mm).

[0042] Example 2

[0043] Cut a titanium plate of 50x30x0.3cm, polish the titanium plate with 500 grit sandpaper until the surface of the titanium plate is smooth. Dip the polished titanium plate into a 40% mass percentage NaOH solution, and heat the solution to 80°C for 1h. After that, wash away the alkali solution with a large amount of deionized water to obtain a titanium plate substrate. Dry the titanium plate substrate and store it in a vacuum for later use. Add FeCl3·6H2O and Cu(OH)2·6H2O to deionized water in a molar ratio of 4:1, and then titrate with 2 mol / L ammonia water to pH 11. Filter to obtain a precipitate, wash the precipitate with a large amount of deionized water until it is neutral, and then dry it at 80°C for 1h. Crush the dried solid to pass through a 200 mesh sieve to obtain Fe-Cu LDHs material. Weigh 60g of 150 mesh flaky graphite, 8g of polyacetyl propionate, 10g of multi-walled carbon nanotubes, and 10g of Fe-Cu LDHs material, and ball mill for 2h to obtain a first mixed powder. Place the mixed powder on a vibration table and shake it evenly, with a vibration amplitude of 100mm and a frequency of 300 times / min, and a vibration time of 4min. Place the vacuum-dried titanium plate in a molding cavity, weigh 35g of the composite powder on one side of the titanium plate, and use a 5-45MPa, 9-molding section, and mold for 5min. Then take out the titanium plate and place it on the other side of the molding cavity.

[0044] ​Take 60g 150 mesh flake graphite, 8g polypropyl acetate, 10g multi-walled carbon nanotubes, and ball mill for 2h to obtain a second mixed powder. Place the second mixed powder on a vibration table and vibrate evenly, the vibration table amplitude is 100mm, the frequency is 300 times / min, and the vibration time is 4min. Take 35g of the second mixed powder and place it on one side of the titanium plate, use 5-45MPa, 9 pressing sections, and press for 5min to obtain a completed composite bipolar plate. Vacuum impregnate the composite bipolar plate in polyacrylic acid resin for 48h, take it out and cure at 300℃ for 2h to obtain the final shaped composite bipolar plate, and test the performance.

[0045] Example 3

[0046] Cut a titanium plate of 50x30x0.2cm, polish the titanium plate with 400 grit fine sandpaper until the surface of the titanium plate is smooth. Soak the polished titanium plate in a 60% mass percentage NaOH solution, and heat the solution to 70℃, and keep it at this temperature for 2h. Then wash the alkali solution with a large amount of deionized water to obtain a titanium plate substrate, dry the titanium plate substrate and store it in a vacuum for later use. Add FeCl3·6H2O and Cu(OH)2·6H2O to deionized water in a molar ratio of 3:0.5, and titrate with 2mol / L NaOH to pH 10. Filter to obtain a precipitate, wash the precipitate with a large amount of deionized water until it is neutral, dry it at 80℃ for 1h, crush the dried solid, pass it through a 300 mesh sieve to obtain Fe-Cu LDHs material. Take 75g 150 mesh microcrystalline graphite, 6g polymethyl methacrylate, 20g multi-walled carbon nanotubes, and ball mill for 2h to obtain a first mixed powder. Place the first mixed powder on a vibration table and vibrate evenly. The vibration table amplitude is 100mm, the frequency is 200 times / min, and the vibration time is 5min. Place the vacuum-dried titanium plate substrate in the pressing cavity, take 45g of the composite powder and place it on one side of the titanium plate, use 5-45MPa, 9 pressing sections, and press for 5min. Then take out the titanium plate, and place it in the pressing cavity again.

[0047] Take 75g 150 mesh microcrystalline graphite, 6g polymethyl methacrylate, 20g multi-walled carbon nanotubes, and ball mill for 2h to obtain a second mixed powder. Place the second mixed powder on a vibration table, the vibration table amplitude is 100mm, the frequency is 200 times / min, and the vibration time is 5min. Take 45g of the second mixed powder and place it on one side of the titanium plate, use 5-45MPa, 9 pressing sections, and press for 5min to obtain a completed composite bipolar plate. Vacuum impregnate the composite bipolar plate in polyacrylic acid resin for 36h, take it out and cure at 400℃ for 3h to obtain the final shaped composite bipolar plate, and test the performance.

[0048] Comparative Example 1

[0049] Take 160g 200 mesh expanded graphite, 10g polybutyl acetate, 30g XC-72 carbon black, ball mill mixing 2h, get mixed powder, the composite powder is placed on the vibration table, the vibration table amplitude is 50mm, the frequency is 200 times / min, the vibration time is 5min. Take 80g mixed powder is placed in the mold cavity, using 5-45MPa, 9 mold pressing section, mold pressing 5min, get bipolar plate, the bipolar plate is vacuum impregnated in polyacrylic acid resin for 24h, after taking out with 350℃ curing 2h, get the final shaped bipolar plate, and test performance.

[0050] Comparative example 2

[0051] Take 120g 150 mesh flake graphite, 16g polypropyl acetate, 20g multi-walled carbon nanotube, ball mill mixing 2h, get mixed powder. The mixed powder is placed on the vibration table, the vibration table amplitude is 100mm, the frequency is 300 times / min, the vibration time is 4min. Take 70g mixed powder is placed in the mold cavity, using 5-45MPa, 9 mold pressing section, mold pressing 5min, get bipolar plate, the bipolar plate is vacuum impregnated in polyacrylic acid resin for 48h, after taking out with 300℃ curing 2h, get the final shaped bipolar plate, and test performance.

[0052] Comparative example 3

[0053] Take 150g 150 mesh microcrystalline graphite, 12g polymethyl methacrylate, 40g multi-walled carbon nanotube, ball mill mixing 2h, get mixed powder. The mixed powder is placed on the vibration table, the vibration table amplitude is 100mm, the frequency is 200 times / min, the vibration time is 5min. Take 90g mixed powder is placed in the mold cavity, using 5-45MPa, 9 mold pressing section, mold pressing 5min, get bipolar plate, the bipolar plate is vacuum impregnated in polyacrylic acid resin for 36h, after taking out with 400℃ curing 3h, get the final shaped bipolar plate, and test performance.

[0054] Table 1 is the physical parameter table of the bipolar plate prepared in examples 1-3 and comparative examples 1-3, through comparison, it can be seen that the composite bipolar plate of examples 1-3, the thickness of the bipolar plate is thinner, the compactness is higher. Its conductivity reaches more than 987S / cm, which is obviously improved compared with the comparative example. The bending strength of the composite bipolar plate of examples 1-3 is also obviously improved.

[0055] Table 1 physical parameter table of bipolar plate of examples 1-3 and comparative examples 1-3

[0056]

[0057]

[0058] The preparation method of the metal graphite composite bipolar plate uses a titanium plate as a base plate material, and graphite fillers are arranged on both sides of the titanium plate. The metal titanium plate greatly enhances the impact strength of the bipolar plate, avoids the disadvantages of the fragile graphite bipolar plate and poor bending strength, and avoids the problem of easy corrosion of the metal plate. Fe-Cu LDHs material is added to one side of the composite bipolar plate. Layered double hydroxide (LDHs) has high stability and plasticity. The adsorption capacity of Cu 2+ , Zn 2+ , Fe 3+ , Fe 2+ , Cr 2+ and other metals can avoid the corrosion of free metal ions to the proton membrane. The metal graphite composite bipolar plate has a relatively thin thickness, high density, excellent bending strength and electrical conductivity.

[0059] The above is only a preferred embodiment of the present application, and is not intended to limit the present application in other forms. Any person skilled in the art can use the disclosed technical content to make changes or modifications to equivalent embodiments applied to other fields, but any simple modification, equivalent change and modification made to the above embodiments without departing from the technical solution content of the present application, according to the technical essence of the present application, still belongs to the protection scope of the technical solution of the present application.

Claims

1. A method for preparing a high-conductivity metal-graphite composite bipolar plate, characterized in that: Includes the following steps, (1) Cut titanium plates with a thickness of 0.15~0.3cm into the required shape of the electrode plates; (2) Add FeCl3·6H2O and Cu(OH)2·6H2O to deionized water, adjust the pH of the solution to 9~12, wash the precipitate to neutral and dry to obtain Fe-Cu LDHs material; wherein the molar ratio of FeCl3·6H2O to Cu(OH)2·6H2O is (1~4):(0.5~1); (3) The graphite filler, binder, conductive filler and Fe-Cu LDHs are ball-milled and dry-mixed to obtain the first mixed powder. The titanium plate is placed in the molding cavity, and a certain mass of the first mixed powder is evenly placed on the titanium plate and molded. The mass ratio of graphite filler, binder, conductive filler and Fe-Cu LDHs is (5~10):(0.1~1):(0.1~3):(1~3). (4) The graphite filler, binder and conductive filler are ball-milled and mixed to obtain a second mixed powder. The electrode plate obtained in step (3) is placed in the molding cavity, and the second mixed powder is arranged on the other side of the titanium plate and molded. The mass ratio of graphite filler, binder and conductive filler is (5~10):(0.1~1):(0.1~3). (5) The bipolar plate obtained in step (4) is immersed in polyacrylic acid resin and removed and cured after 24~48h to obtain the shaped composite bipolar plate.

2. The method for preparing a high-conductivity metal-graphite composite bipolar plate according to claim 1, characterized in that: In step (2), the drying temperature is 80℃ and the drying time is 1~3h. After drying, the product is pulverized and passed through a 200~350 mesh sieve.

3. The method for preparing a high-conductivity metal-graphite composite bipolar plate according to claim 1, characterized in that: In steps (3) and (4), the graphite filler is one or more of the following: 150-200 mesh expanded graphite, 100-200 mesh flake graphite, and 100-200 mesh microcrystalline graphite.

4. The method for preparing a high-conductivity metal-graphite composite bipolar plate according to claim 1, characterized in that: The adhesive used in steps (3) and (4) is one or more of polybutyl acetate, polypropyl acetate, polymethyl methacrylate, and polybutyl phthalate.

5. The method for preparing a high-conductivity metal-graphite composite bipolar plate according to claim 1, characterized in that: In steps (3) and (4), the conductive filler is one or more of carbon black, carbon nanotubes, and metal powder.

6. The method for preparing a high-conductivity metal-graphite composite bipolar plate according to claim 1, characterized in that: In steps (3) and (4), the molding pressure is 5~50 MPa and the molding time is 10~20 min.

7. The method for preparing a high-conductivity metal-graphite composite bipolar plate according to claim 1, characterized in that: In step (5), the curing temperature is 200~400℃ and the curing time is 1~3h.

8. The method for preparing a high-conductivity metal-graphite composite bipolar plate according to claim 1, characterized in that: Step (1) also includes a titanium plate pretreatment step, specifically polishing the cut titanium plate to a bright finish, then immersing it in a NaOH solution with a mass percentage concentration of 40%~60%, heating the solution to 60~80℃, washing it with deionized water after 1~2 hours to obtain the titanium plate substrate.

9. The method for preparing a high-conductivity metal-graphite composite bipolar plate according to claim 1, characterized in that: In step (3), after ball milling and dry mixing, the first mixed powder is placed on a vibrating table and vibrated evenly. The amplitude of the vibrating table is 0.01~100 mm, the frequency is 1~400 times / min, and the vibration time is 3~5 min.

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