Modified graphite-based composite material as well as preparation method and application thereof

Abstract

The invention provides a modified graphite-based composite material as well as a preparation method and application of the modified graphite-based composite material. Comprising the following raw materials in parts by weight: 100 parts of graphite powder, 20-30 parts of polyethylene dioxythiophene, 10-20 parts of modified graphene, 10-20 parts of carbon nanotubes, 10-20 parts of epoxy resin, 1-5 parts of methyl methacrylate and 0.1-0.5 part of tert-butyl peroxybenzoate. Wherein the modified graphene is polyamide-amine functionalized graphene. The modified graphite-based composite material disclosed by the invention has good conductivity, air tightness and mechanical strength when being used as a bipolar plate of a fuel cell.

Description

Technical Field

[0001] The present invention relates to the technical field of bipolar plate materials for fuel cells, and in particular to a modified graphite-based composite material and a preparation method and application thereof. Background Art

[0002] A fuel cell is a power generation device that directly converts the chemical energy present in fuel and oxidant into electrical energy. Among them, the bipolar plate is one of the core components in the fuel cell. Its main functions are to separate the reaction gas, evenly introduce the reaction gas, collect and conduct current, support the membrane electrode, and realize rapid drainage and heat dissipation of the fuel cell system. Therefore, the bipolar plate should have good electrical conductivity, thermal conductivity, corrosion resistance, gas barrier properties and a certain mechanical strength. Depending on the material, the bipolar plate can be divided into graphite bipolar plates, metal bipolar plates and composite bipolar plates. Graphite has good chemical stability and conductivity, but poor air tightness and low mechanical strength.

[0003] In view of this, it is urgent to propose a modified graphite-based composite material to improve the air tightness and mechanical strength of the graphite bipolar plate while ensuring good electrical conductivity. Summary of the invention

[0004] The object of the present invention is to provide a modified graphite-based composite material to solve the problems in the prior art.

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows:

[0006] A modified graphite-based composite material comprises the following raw materials in parts by weight:

[0007] 100 parts of graphite powder, 20-30 parts of polyethylene dioxythiophene, 10-20 parts of modified graphene, 10-20 parts of carbon nanotubes, 10-20 parts of epoxy resin, 1-5 parts of methyl methacrylate, and 0.1-0.5 parts of tert-butyl perbenzoate;

[0008] Wherein, the modified graphene is polyamide-amine functionalized graphene.

[0009] Preferably, the modified graphite-based composite material further comprises 1-3 parts of acrylamide.

[0010] Preferably, the modified graphite-based composite material further comprises 0.5-1.0 parts of fatty acid diethanolamide.

[0011] Preferably, the modified graphene is polyamide-amine functionalized graphene with terminal amino groups obtained by carboxylating graphene oxide and then reacting with polyamide-amine.

[0012] The present invention also provides a method for preparing a modified graphite-based composite material, comprising the following steps:

[0013] (1) taking graphite powder, polyethylene dioxythiophene, and a solvent, and mixing them uniformly to obtain graphite powder with polyethylene dioxythiophene attached to the surface;

[0014] (2) adding modified graphene, carbon nanotubes, epoxy resin, methyl methacrylate, and tert-butyl perbenzoate to the graphite powder with polyethylenedioxythiophene attached to the surface obtained in step (1), mixing well to obtain a mixed slurry;

[0015] (3) hot pressing the mixed slurry obtained in step (2) to obtain a product.

[0016] Preferably, in step (1), the solvent is N-methylpyrrolidone, and the concentration of the graphite powder in the solvent is 10-20 g / ml.

[0017] Preferably, step (1) is as follows: graphite powder, polyethylene dioxythiophene, solvent, and fatty acid diethanolamide are mixed evenly, stirred at 40-60° C. for 6-48 hours, and filtered to obtain graphite powder with polyethylene dioxythiophene attached to the surface.

[0018] Preferably, in step (3), the hot pressing molding is carried out at a pressure of 10-50 MPa and a temperature of 150-200° C. for 30-60 min.

[0019] Preferably, the modified graphene in step (2) is obtained by the following method:

[0020] a. Take an aqueous solution of graphene oxide, add hydrobromic acid, then add oxalic acid, react, wash and dry to obtain carboxylated graphene oxide;

[0021] The reaction formula is as follows:

[0022]

[0023] b. Add N,N'-dicyclohexylcarbodiimide and polyamide-amine to the carboxylated graphene oxide, mix them evenly, and after reaction, wash and dry to obtain modified graphene.

[0024] The reaction formula is as follows:

[0025]

[0026] Among them, the structural formula of R is as follows:

[0027]

[0028] Preferably, step (2) further comprises the step of adding acrylamide to the graphite powder with polyethylenedioxythiophene attached to the surface obtained in step (1).

[0029] The present invention also provides application of the modified graphite-based composite material in the field of preparing bipolar plates for fuel cells.

[0030] The above solution of the present invention includes at least the following beneficial effects:

[0031] (1) The modified graphite-based composite material of the present invention comprises the following raw materials in parts by weight: 100 parts of graphite powder, 20-30 parts of polyethylene dioxythiophene, 10-20 parts of modified graphene, 10-20 parts of carbon nanotubes, 10-20 parts of epoxy resin, 1-5 parts of methyl methacrylate, and 0.1-0.5 parts of tert-butyl peroxybenzoate; wherein the modified graphene is polyamide-amine functionalized graphene. The modified graphite-based composite material has good electrical conductivity, air tightness and mechanical strength as a bipolar plate of a fuel cell.

[0032] The polyethylenedioxythiophene has good electrical conductivity and can be attached to the outer surface of the graphite powder particles.

[0033] The modified graphene functionalized with polyamide-amine has, on the one hand, a π bond structure, and the polyethylenedioxythiophene has a conjugated structure, and the two can form a π-π interaction, and can be closely compounded with a vertical array of graphene layers without damaging the graphene layer structure, so that it can self-assemble into a structure in which graphite powder and graphene are distributed at intervals; the particles of the graphite powder are connected by the flattened graphene, and the gaps between the graphite powders can also be reduced, thereby improving the conductivity. On the other hand, the modified graphene can increase the interlayer distance of the graphene through the dendritic molecular structure of polyamide-amine, provide a channel for the rapid entry and exit of ions and electrons in the electrochemical cycle process, and the amino group of polyamide-amine can undergo a ring-opening reaction with the epoxy resin to form a three-dimensional cross-linked network structure, so that the composite material has good mechanical strength; during the ring-opening reaction, the resin can more evenly and fully cover the modified graphene and the graphite powder self-assembled with the modified graphene, the bonding strength between the inorganic interfaces is high, the porosity between the inorganic interface and the organic interface is low, and the obtained composite material has good air tightness.

[0034] The carbon nanotubes are one-dimensional structures, filled between the graphite powder particles, and together with the two-dimensional modified graphene and the resin form a three-dimensional structure, further improving the mechanical strength of the composite material.

[0035] The methyl methacrylate undergoes a polymerization reaction under the action of the initiator tert-butyl perbenzoate, and can form an interpenetrating network structure with the epoxy resin during the curing process, thereby reducing the free movement space of the molecular chain, making it difficult for the molecular chain to move and deform significantly, and improving the mechanical strength of the composite material. At the same time, the permeability of the gas can also be significantly reduced, and the air tightness can be improved. In particular, the amount of the epoxy resin can be greatly reduced under the premise of ensuring the mechanical strength of the composite material, and the constraint of the resin on the conductive carrier can be reduced.

[0036] (2) The modified graphite-based composite material of the present invention further comprises 1-5 parts of acrylamide. The acrylamide can synergistically act with the epoxy resin and the methyl methacrylate to adjust the cross-linked network structure and further improve the mechanical properties of the composite material.

[0037] (3) The modified graphite-based composite material of the present invention further comprises 0.5-1.0 parts of fatty acid diethanolamide. The addition of the fatty acid diethanolamide can make the polyethylene dioxythiophene and the graphite powder uniformly dispersed in the solvent. As the solvent evaporates, the amide group of the fatty acid diethanolamide and the polar group thiophene ring of the polyethylene dioxythiophene produce adsorption, and the fatty acid chain of the fatty acid diethanolamide and the graphite powder particles approach each other under the hydrophobic effect, thereby making the polyethylene dioxythiophene more uniformly attached to the outer surface of the graphite powder. DETAILED DESCRIPTION

[0038] In the embodiments of the present invention, if the specific conditions are not specified, the conventional conditions or the conditions recommended by the manufacturer are followed. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially. Raw materials of different manufacturers and models do not affect the implementation of the technical solution of the present invention and the realization of the technical effects.

[0039] In the following embodiments, the modified graphene used is obtained by the following method:

[0040] a. Take an aqueous solution of graphene oxide with a mass concentration of 2.5 mg / ml, add hydrobromic acid, stir and react for 24 hours, then add oxalic acid, stir and react for 24 hours, filter, wash and dry to obtain carboxylated graphene oxide;

[0041] Among them, the mass concentration of the hydrobromic acid is 45wt%, and the volume ratio of the hydrobromic acid to the aqueous solution of graphene oxide is 1:6; the mass ratio of the oxalic acid to the aqueous solution of graphene oxide is 1:18.

[0042] b. Add N,N-dimethylformamide solvent to the carboxylated graphene oxide to make the mass concentration of the carboxylated graphene oxide be 4 mg / ml, then add N,N'-dicyclohexylcarbodiimide (DCC) and polyamide-amine, mix well, stir and react at 110° C. for 24 hours, filter, wash and dry to obtain modified graphene;

[0043] The mass concentration of the N,N'-dicyclohexylcarbodiimide in the N,N-dimethylformamide solvent is 30 mg / ml; the polyamide-amine is 1.0 generation polyamide-amine (1.0PAMAM), and the mass concentration of the polyamide-amine in the N,N-dimethylformamide solvent is 80 mg / ml.

[0044] Example 1

[0045] The modified graphite-based composite material in this embodiment includes the following raw materials in parts by weight:

[0046] 100 parts of graphite powder, 20 parts of polyethylene dioxythiophene, 15 parts of modified graphene, 10 parts of carbon nanotubes, 20 parts of epoxy resin, 5 parts of methyl methacrylate, 0.3 parts of tert-butyl perbenzoate, and 0.5 parts of fatty acid diethanolamide;

[0047] The modified graphene is polyamide-amine functionalized graphene, specifically polyamide-amine functionalized graphene with terminal amino groups obtained by carboxylating graphene oxide and then reacting with polyamide-amine.

[0048] The method for preparing the modified graphite-based composite material described in this embodiment comprises the following steps:

[0049] (1) Graphite powder, polyethylene dioxythiophene, solvent, and fatty acid diethanolamide are mixed evenly, stirred at 50° C. for 6 hours, and filtered to obtain graphite powder with polyethylene dioxythiophene attached to the surface.

[0050] Wherein, the solvent is N-methylpyrrolidone, and the concentration of the graphite powder in the solvent is 15 g / ml.

[0051] (2) adding modified graphene, carbon nanotubes, epoxy resin, methyl methacrylate, and tert-butyl perbenzoate to the graphite powder with polyethylenedioxythiophene attached to the surface obtained in step (1), mixing well to obtain a mixed slurry;

[0052] (3) hot pressing the mixed slurry obtained in step (2) at a pressure of 10 MPa and a temperature of 180° C. for 60 min to obtain a product.

[0053] Example 2

[0054] The modified graphite-based composite material in this embodiment includes the following raw materials in parts by weight:

[0055] 100 parts of graphite powder, 30 parts of polyethylene dioxythiophene, 20 parts of modified graphene, 20 parts of carbon nanotubes, 15 parts of epoxy resin, 1 part of methyl methacrylate, 0.5 parts of tert-butyl perbenzoate, and 1.0 parts of fatty acid diethanolamide;

[0056] The modified graphene is polyamide-amine functionalized graphene, specifically polyamide-amine functionalized graphene with terminal amino groups obtained by carboxylating graphene oxide and then reacting with polyamide-amine.

[0057] The method for preparing the modified graphite-based composite material described in this embodiment comprises the following steps:

[0058] (1) Graphite powder, polyethylene dioxythiophene, solvent, and fatty acid diethanolamide are mixed evenly, stirred at 60° C. for 48 hours, and filtered to obtain graphite powder with polyethylene dioxythiophene attached to the surface.

[0059] Wherein, the solvent is N-methylpyrrolidone, and the concentration of the graphite powder in the solvent is 20 g / ml.

[0060] (2) adding modified graphene, carbon nanotubes, epoxy resin, methyl methacrylate, and tert-butyl perbenzoate to the graphite powder with polyethylenedioxythiophene attached to the surface obtained in step (1), mixing well to obtain a mixed slurry;

[0061] (3) The mixed slurry obtained in step (2) is hot-pressed at a pressure of 50 MPa and a temperature of 200° C. for 45 min to obtain a product.

[0062] Example 3

[0063] The modified graphite-based composite material in this embodiment includes the following raw materials in parts by weight:

[0064] 100 parts of graphite powder, 25 parts of polyethylene dioxythiophene, 10 parts of modified graphene, 15 parts of carbon nanotubes, 10 parts of epoxy resin, 3 parts of methyl methacrylate, 0.1 parts of tert-butyl perbenzoate, and 0.8 parts of fatty acid diethanolamide;

[0065] The modified graphene is polyamide-amine functionalized graphene, specifically polyamide-amine functionalized graphene with terminal amino groups obtained by carboxylating graphene oxide and then reacting with polyamide-amine.

[0066] The method for preparing the modified graphite-based composite material described in this embodiment comprises the following steps:

[0067] (1) Graphite powder, polyethylene dioxythiophene, solvent, and fatty acid diethanolamide are mixed evenly, stirred at 40° C. for 24 hours, and filtered to obtain graphite powder with polyethylene dioxythiophene attached to the surface.

[0068] Wherein, the solvent is N-methylpyrrolidone, and the concentration of the graphite powder in the solvent is 10 g / ml.

[0069] (2) adding modified graphene, carbon nanotubes, epoxy resin, methyl methacrylate, and tert-butyl perbenzoate to the graphite powder with polyethylenedioxythiophene attached to the surface obtained in step (1), mixing well to obtain a mixed slurry;

[0070] (3) The mixed slurry obtained in step (2) is hot-pressed at a pressure of 30 MPa and a temperature of 150° C. for 60 min to obtain a product.

[0071] Example 4

[0072] The modified graphite-based composite material in this embodiment includes the following raw materials in parts by weight:

[0073] 100 parts of graphite powder, 20 parts of polyethylene dioxythiophene, 20 parts of modified graphene, 15 parts of carbon nanotubes, 10 parts of epoxy resin, 1 part of methyl methacrylate, 0.5 parts of tert-butyl perbenzoate, 2 parts of acrylamide, and 1.0 part of fatty acid diethanolamide;

[0074] The modified graphene is polyamide-amine functionalized graphene, specifically polyamide-amine functionalized graphene with terminal amino groups obtained by carboxylating graphene oxide and then reacting with polyamide-amine.

[0075] The method for preparing the modified graphite-based composite material described in this embodiment comprises the following steps:

[0076] (1) Graphite powder, polyethylene dioxythiophene, solvent, and fatty acid diethanolamide are mixed evenly, stirred at 50° C. for 48 hours, and filtered to obtain graphite powder with polyethylene dioxythiophene attached to the surface.

[0077] Wherein, the solvent is N-methylpyrrolidone, and the concentration of the graphite powder in the solvent is 20 g / ml.

[0078] (2) adding modified graphene, carbon nanotubes, epoxy resin, methyl methacrylate, acrylamide, and tert-butyl perbenzoate to the graphite powder with polyethylenedioxythiophene attached to the surface obtained in step (1), mixing well to obtain a mixed slurry;

[0079] (3) hot pressing the mixed slurry obtained in step (2) at a pressure of 50 MPa and a temperature of 200° C. for 60 min to obtain a product.

[0080] Comparative Example 1

[0081] The modified graphite-based composite material of this comparative example is the same as that of Example 4 and is prepared by the same method, except that polyethylene dioxythiophene is not included.

[0082] Comparative Example 2

[0083] The modified graphite-based composite material of this comparative example is the same as that of Example 4 and is prepared by the same method, except that it does not contain fatty acid diethanolamide.

[0084] Comparative Example 3

[0085] The modified graphite-based composite material of this comparative example is the same as that of Example 4 and is prepared by the same method, the only difference being that it does not contain modified graphene.

[0086] Comparative Example 4

[0087] This comparative example is the same as the modified graphite-based composite material of Example 4 and is prepared by the same method, with the only difference being that the modified graphene is replaced by an equal weight of graphene oxide.

[0088] Comparative Example 5

[0089] The modified graphite-based composite material of this comparative example is the same as that of Example 4 and is prepared by the same method, except that methyl methacrylate is not contained.

[0090] Comparative Example 6

[0091] The modified graphite-based composite material of this comparative example is the same as that of Example 4 and is prepared by the same method, except that it does not contain acrylamide.

[0092] Effect experiment example

[0093] In order to verify the technical effect of the modified graphite-based composite material described in the present invention, the following experiments were conducted:

[0094] The modified graphite-based composite materials prepared in Examples 1-4 and Comparative Examples 1-6 were molded into plates with a thickness of 1 mm. The conductivity was measured using a conductivity meter, the bending strength was measured using an electronic universal testing machine, and the hydrogen permeability was measured using a permeation cell and a gas chromatograph.

[0095] After experimentation, the results are as follows:

[0096]

[0097] According to the results of Examples 1-4 and Comparative Examples 1-6, the modified graphite-based composite material of the present invention has good electrical conductivity, mechanical properties and air tightness.

[0098] In the modified graphite-based composite materials of Examples 1-4 and Comparative Example 6, the proportions of the epoxy resin are 11.7%, 8.0%, 6.1%, 5.9% and 6.0%, respectively. According to the results of Examples 1-3 and Comparative Example 6, the electrical conductivity increases with the decrease of the epoxy resin content, and the mechanical properties and air tightness decrease with the decrease of the epoxy resin content. However, in Example 4, by adding the acrylamide, the mechanical properties and air tightness are significantly improved with less epoxy resin and higher conductivity.

[0099] According to the results of Example 4 and Comparative Example 1, the polyethylene dioxythiophene has a significant influence on the electrical conductivity, mechanical properties and air tightness of the obtained modified graphite-based composite material.

[0100] According to the results of Example 4 and Comparative Example 2, the fatty acid diethanolamide has a more obvious effect on the conductivity of the obtained modified graphite-based composite material, but has a weaker effect on the mechanical properties and air tightness.

[0101] According to the results of Example 4 and Comparative Examples 3-4, the modified graphene has a significant effect on the conductivity, mechanical properties and air tightness of the modified graphite-based composite material obtained. The unmodified graphene oxide has a weaker effect on improving the conductivity, mechanical properties and air tightness of the composite material obtained.

[0102] According to the results of Example 4 and Comparative Example 5, the methyl methacrylate has little effect on the electrical conductivity of the modified graphite-based composite material, but has a significant effect on the mechanical properties and air tightness.

[0103] In summary, the addition of polyethylene dioxythiophene, fatty acid diethanolamide, modified graphene, methyl methacrylate, and acrylamide are all beneficial to the obtained modified graphite-based composite material to achieve better conductivity, mechanical properties, and air tightness with less epoxy resin usage to varying degrees. The above raw materials work synergistically to obtain a composite material with better comprehensive performance, especially excellent performance when used in bipolar plate materials for fuel cells.

[0104] It is known from common technical knowledge that the present invention can be implemented by other embodiments that do not deviate from its spirit or essential features. Therefore, the above disclosed embodiments are only illustrative in all respects and are not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are encompassed by the present invention.

Claims

1. A modified graphite-based composite material, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of graphite powder, 20-30 parts of polyethylene dioxythiophene, 10-20 parts of modified graphene, 10-20 parts of carbon nanotubes, 10-20 parts of epoxy resin, 1-5 parts of methyl methacrylate, and 0.1-0.5 parts of tert-butyl perbenzoate; Wherein, the modified graphene is polyamide-amine functionalized graphene.

2. The modified graphite-based composite material according to claim 1, characterized in that: Also included is 1-3 parts of acrylamide.

3. The modified graphite-based composite material according to claim 1, characterized in that: Also included is 0.5-1.0 parts of fatty acid diethanolamide.

4. The modified graphite-based composite material according to claim 1, characterized in that: The modified graphene is a polyamide-amine functionalized graphene with terminal amino groups obtained by carboxylating graphene oxide and then reacting with polyamide-amine.

5. A method for preparing a modified graphite-based composite material, characterized in that: The steps include: (1) taking graphite powder, polyethylene dioxythiophene, and a solvent, and mixing them uniformly to obtain graphite powder with polyethylene dioxythiophene attached to the surface; (2) adding modified graphene, carbon nanotubes, epoxy resin, methyl methacrylate, and tert-butyl perbenzoate to the graphite powder with polyethylenedioxythiophene attached to the surface obtained in step (1), mixing well to obtain a mixed slurry; (3) hot pressing the mixed slurry obtained in step (2) to obtain a product.

6. The method for preparing the modified graphite-based composite material according to claim 5, characterized in that: In step (1), the solvent is N-methylpyrrolidone, and the concentration of the graphite powder in the solvent is 10-20 g / ml.

7. The method for preparing the modified graphite-based composite material according to claim 5, characterized in that: Step (1) is specifically as follows: graphite powder, polyethylene dioxythiophene, solvent, and fatty acid diethanolamide are mixed evenly, stirred at 40-60° C. for 6-48 hours, and filtered to obtain graphite powder with polyethylene dioxythiophene attached to the surface.

8. The method for preparing the modified graphite-based composite material according to claim 5, characterized in that: In step (3), the hot pressing molding is carried out at a pressure of 10-50 MPa and a temperature of 150-200° C. for 30-60 minutes.

9. The method for preparing the modified graphite-based composite material according to claim 5, characterized in that: The modified graphene in step (2) is obtained by the following method: Taking an aqueous solution of graphene oxide, adding hydrobromic acid, and then adding oxalic acid, after reaction, washing, and drying, to obtain carboxylated graphene oxide; N,N'-dicyclohexylcarbodiimide and polyamide-amine are added to the carboxylated graphene oxide, mixed evenly, and after reaction, washed and dried to obtain modified graphene.

10. Use of the modified graphite-based composite material described in claims 1 to 4 or the modified graphite-based composite material obtained by the preparation method of claims 5 to 9 in the field of preparing bipolar plates for fuel cells.

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