Graphite polar plate, preparation method thereof and fuel cell

Abstract

The invention discloses a graphite polar plate, a preparation method thereof and a fuel cell, and the preparation method of the graphite polar plate comprises the following steps: (1) graphitizing carbon black to obtain a graphite cage; (2) mixing and pressing the graphite cage and graphite to obtain a graphite substrate; then carrying out compression molding on the graphite substrate to obtain a molded pole plate; and (3) carrying out resin dipping treatment on the molded polar plate to obtain the graphite polar plate. The conductivity of the high-conductivity graphite cage doped flexible molded graphite pole plate is greatly improved, and the current transmission capability is greatly enhanced; meanwhile, by adding the high-conductivity graphite cage, the conductivity difference of the molded graphite polar plate in the forming direction and the direction perpendicular to the polar plate forming direction can be greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to a graphite plate and a preparation method thereof, and a fuel cell. Background Art

[0002] The fuel cell system includes key components such as catalysts, bipolar plates, proton exchange membranes, and gas diffusion layers. As one of the key components of fuel cells, the cost of bipolar plates accounts for about 30% of the battery stack and the mass accounts for about 70% of the battery stack. Fuel cell bipolar plates are in an acidic environment for a long time, and their main functions are to collect and conduct current, conduct heat, support membrane electrodes, and block gases. Therefore, bipolar plates need to have good electrical conductivity, thermal conductivity, corrosion resistance, mechanical properties, and airtightness.

[0003] In order to enhance the mechanical properties of bipolar plates, polymer resins are usually added to form resin / carbon composite materials to achieve this purpose. However, resins with extremely high resistance will also damage the conductivity of the bipolar plates and increase the resistance of the bipolar plates while enhancing the mechanical properties. The resistance of a bipolar plate is mainly composed of the interface contact resistance and its own volume resistance. During the preparation of bipolar plates, resins are easily enriched on the surface of the bipolar plates, increasing the contact resistance of the bipolar plates. In addition, the resins hinder the formation of a conductive network inside the composite material, increasing the volume resistance of the composite material. Therefore, reducing the volume resistance and contact resistance of the bipolar plates becomes the key to enhancing conductivity.

[0004] Molded graphite plates are formed by upper and lower molds. During the molding process, the graphite substrate will be oriented along the molding direction. At the same time, the conductivity of the graphite material along the crystal crystallization direction and the direction perpendicular to the crystal crystallization direction is quite different. This leads to a huge difference in the conductivity of the graphite plate along the molding direction and the direction perpendicular to the molding direction, which is extremely unfavorable for the graphite plate to transmit the current generated by the fuel cell. Summary of the invention

[0005] The present invention is based on the inventor's discovery and understanding of the following facts and problems: Resins with extremely high resistance can enhance mechanical properties while also damaging the conductivity of bipolar plates and increasing the resistance of bipolar plates. Therefore, reducing the volume resistance and contact resistance of bipolar plates is the key to enhancing conductivity. In addition, the conductivity of graphite plates along the molding direction and perpendicular to the molding direction is very different.

[0006] At present, in the related technology, researchers improve the conductivity of materials by adding a second carbon material such as graphene, carbon nanotubes, and carbon microspheres as a conductive additive. However, graphene and carbon nanotubes are both nanomaterials, which are very difficult to prepare and expensive. Adding them to graphite plates is not conducive to reducing the production cost of graphite plates, and is not conducive to the large-scale promotion and application of graphite plates. In addition, graphene is in the form of sheets, and carbon nanotubes are in the form of long tubes with a relatively large aspect ratio. During the molding process, it is easy to be oriented along the molding direction under pressure, which is helpful for improving the conductivity along the molding direction, and it is difficult to improve the conductivity in the vertical molding direction. Carbon microspheres are micron-sized carbon spheres prepared by asphalt. The particle size of non-hollow carbon microsphere materials is large, and the distance of electron transmission is long, which is not conducive to a substantial improvement in conductivity. In addition, carbon microspheres with micron particle sizes are difficult to achieve perfect dispersion in the graphite substrate, which is not conducive to improving the conductivity of graphite plates.

[0007] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the embodiments of the present invention provide a graphite plate and a preparation method thereof, and a fuel cell. The conductivity of the flexible molded graphite plate doped with highly conductive graphite cages is greatly improved, and the current transmission capacity is greatly enhanced; at the same time, the addition of highly conductive graphite cages can greatly improve the conductivity difference of the molded graphite plate along the forming direction and the perpendicular plate forming direction. The preparation method of the present invention is simple and easy to implement, and is easy to process on a large scale, and has good application prospects for large-scale preparation of flexible molded graphite plates.

[0008] The embodiment of the present invention provides a method for preparing a graphite plate, comprising the following steps:

[0009] (1) graphitizing carbon black to obtain a graphite cage;

[0010] (2) mixing and pressing the graphite cage and graphite to obtain a graphite substrate; and then molding the graphite substrate to obtain a molded electrode plate;

[0011] (3) The molded plate is impregnated with resin to obtain a graphite plate.

[0012] Advantages and technical effects brought by the method for preparing the graphite plate of the embodiment of the present invention: a highly conductive graphite cage is prepared by graphitizing carbon black, and the highly conductive graphite cage and graphite are prepared into a substrate, and then molded and resin impregnated to strengthen to prepare a highly conductive flexible graphite plate. The highly conductive graphite cage has a hollow ultra-thin rigid graphite crystal cage structure, a complete graphite crystal structure, fewer crystal defects, and high crystallinity. At the same time, the electron transmission distance of the thin-walled graphite structure is short, so it has ultra-high conductivity. When the ultra-high conductive graphite cage is added to the graphite plate, the ultra-high conductivity of the graphite cage itself will greatly improve the conductivity of the substrate; on the other hand, the thin-walled rigid cage structure of the graphite cage can better fill the gaps between the large-particle graphite matrix, overlap and stack with the graphite, produce a synergistic conductive effect, and further improve the conductivity of the graphite plate; therefore, the conductivity of the graphite plate is greatly improved, greatly enhancing the current transmission capacity of the battery. At the same time, the structure of the graphite cage is a thin-walled graphite spherical crystal structure, which shows typical isotropy in conductivity, which is significantly different from anisotropic structures such as graphene and carbon nanotubes. Therefore, the addition of highly conductive graphite cages can greatly improve the conductivity difference of molded graphite plates along the forming direction and perpendicular to the plate forming direction, and better meet the large current conductivity requirements of fuel cell plates. The preparation method of the present invention is simple and easy to implement, easy to process on a large scale, and has good application prospects for large-scale preparation of flexible molded graphite plates.

[0013] In some embodiments, in step (1), the temperature of the graphitization treatment is 1800-2800°C;

[0014] And / or, the graphitization treatment time is 0.5-10h.

[0015] In some embodiments, in step (1), the particle size of the carbon black is 1 nm-10 μm;

[0016] And / or, the particle size of the graphite cage is 1 nm-10 μm;

[0017] And / or, the graphite cage has a hollow cage morphology of a crystalline graphite structure.

[0018] In some embodiments, in step (2), the graphite includes at least one of expanded graphite, artificial graphite, and natural graphite;

[0019] And / or, the mass ratio of the graphite cage to graphite is (0.01-50):100;

[0020] And / or, the pressing method includes at least one of rolling or molding;

[0021] And / or, the thickness of the graphite substrate is greater than 0.1 mm.

[0022] In some embodiments, in the step (2), the compression molding is performed by vacuum compression molding;

[0023] And / or, the compression molding pressure is 20MPa-6GPa;

[0024] And / or, the compression molding temperature is 20-120°C;

[0025] And / or, the thickness of the molded plate is greater than 0.1 mm.

[0026] In some embodiments, in step (3), the resin includes at least one of acrylate resin, polyphenylene sulfide, polypropylene, polyvinylidene fluoride, epoxy resin, phenolic resin or vinyl resin.

[0027] In some embodiments, in step (3), subjecting the molded plate to resin impregnation treatment includes immersing the molded plate in a liquid containing resin;

[0028] And / or, the temperature of the resin impregnation treatment is 20-150°C;

[0029] And / or, the resin impregnation treatment time is 1-30min;

[0030] And / or, the resin impregnation process adopts vacuum impregnation.

[0031] The embodiment of the present invention provides a graphite plate, which is prepared by the preparation method described in the embodiment of the present invention. In the embodiment of the present invention, the conductivity of the flexible molded graphite plate doped with high-conductive graphite cages is greatly improved, and the current transmission capacity is greatly enhanced; at the same time, the addition of high-conductive graphite cages can greatly improve the conductivity difference of the molded graphite plate along the plate forming direction and perpendicular to the plate forming direction.

[0032] In some embodiments, the thickness of the graphite plate is greater than 0.1 mm;

[0033] And / or, the conductivity of the graphite plate along its thickness direction is not less than 40S / cm;

[0034] And / or, the conductivity of the graphite plate in a direction perpendicular to its thickness is not less than 200 S / cm;

[0035] And / or, the contact resistance of the graphite plate is not higher than 5mΩ / cm 2 .

[0036] The present invention provides a fuel cell, including the graphite plate described in the present invention. In the present invention, the conductivity of the graphite plate is greatly improved, which greatly enhances the current transmission capacity of the fuel cell and better meets the high current conductivity requirements of the fuel cell plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a flow chart of the method for preparing the graphite plate of the present invention.

[0038] Figure 2 It is the XRD pattern and transmission electron microscope image of the carbon black particles in Example 1 of the present invention.

[0039] Figure 3 It is the XRD pattern and transmission electron microscope image of the graphite cage in Example 1 of the present invention.

[0040] Figure 4 It is a cross-sectional view of the flow field of the graphite electrode plate with 5% graphite cage added in Example 4 of the present invention. DETAILED DESCRIPTION

[0041] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0042] like Figure 1 As shown, a method for preparing a graphite plate according to an embodiment of the present invention comprises the following steps:

[0043] (1) graphitizing carbon black to obtain a graphite cage;

[0044] (2) mixing and pressing the graphite cage and graphite to obtain a graphite substrate; and then molding the graphite substrate to obtain a molded electrode plate;

[0045] (3) The molded plate is impregnated with resin to obtain a graphite plate.

[0046] The method for preparing the graphite plate of the embodiment of the present invention is to prepare a highly conductive graphite cage by graphitizing carbon black, prepare the highly conductive graphite cage and graphite into a substrate, and then prepare a highly conductive flexible graphite plate after molding and resin impregnation reinforcement. The highly conductive graphite cage has a hollow ultra-thin rigid graphite crystalline cage structure, the graphite crystal structure is complete, the crystal defects are relatively few, the crystallinity is high, and the electron transmission distance of the thin-walled graphite structure is short, so it has ultra-high conductivity. When the ultra-high conductive graphite cage is added to the graphite plate, the ultra-high conductivity of the graphite cage itself will greatly improve the conductivity of the substrate; on the other hand, the thin-walled rigid cage structure of the graphite cage can better fill the gaps between the large-particle graphite matrix, overlap and stack with the graphite, produce a synergistic conductive effect, and further improve the conductivity of the graphite plate; therefore, the conductivity of the graphite plate is greatly improved, greatly enhancing the current transmission capacity of the battery. At the same time, the structure of graphite cages is a thin-walled graphite spherical crystal structure, which shows typical isotropy in conductivity, which is significantly different from anisotropic structures such as graphene and carbon nanotubes. Therefore, the addition of highly conductive graphite cages can greatly improve the conductivity difference of molded graphite plates along the forming direction and perpendicular to the forming direction of the plates, and better meet the large current conductivity requirements of fuel cell plates.

[0047] In the embodiment of the present invention, the pores in the graphite plate can be blocked by resin impregnation treatment, gas penetration can be prevented, and the airtightness performance can be improved. The method of directly mixing and pressing the resin, graphite, and graphite cage is difficult to achieve uniform dispersion of the resin in the pores of the graphite graphite cage, which can easily cause uneven dispersion of the resin and graphite inside the plate, resulting in conductivity differences and gas penetration. Compared with the method of directly mixing and pressing the resin, graphite, and graphite cage, the resin impregnation treatment is conducive to the resin being evenly filled into the graphite pores of the pressed graphite plate, achieving the purpose of blocking the pores, while not affecting the construction of a conductive path between the graphite and the graphite cage. The preparation method of the present invention is simple and easy to operate, easy to process on a large scale, and has good application prospects for large-scale preparation of flexible molded graphite plates.

[0048] In some embodiments, in step (1), there is no particular limitation on the type and source of carbon black; the particle size of the carbon black is 1 nm-10 μm, specifically, for example, 1 nm, 5 nm, 10 nm, 20 nm, 50 nm, 70 nm, 90 nm, 100 nm, 200 nm, 500 nm, 1 μm, 5 μm, 10 μm; optionally, the carbon black is spherical or quasi-spherical.

[0049] In some embodiments, in step (1), the temperature of the graphitization treatment is 1800-2800°C, specifically, for example, 1800°C, 2000°C, 2200°C, 2400°C, 2500°C, 2600°C, 2800°C; the time of the graphitization treatment is 0.5-10h, specifically, for example, 0.5h, 1h, 2h, 4h, 6h, 8h, 10h. In the embodiment of the present invention, the temperature of the graphitization treatment is 1800-2800°C, which can realize the transformation of carbon black into a crystalline graphite cage structure. If the temperature is too low, the graphite cage structure formed has a low degree of crystallinity and poor conductivity; if the temperature is too high, the equipment manufacturing is more difficult.

[0050] In some embodiments, in step (1), the particle size of the graphite cage is 1nm-10μm, specifically, for example, 1nm, 5nm, 10nm, 20nm, 50nm, 70nm, 90nm, 100nm, 200nm, 500nm, 1μm, 5μm, 10μm; the graphite cage has a hollow cage morphology of a crystalline graphite structure; optionally, the graphite cage is spherical or quasi-spherical.

[0051] In some embodiments, in step (2), the graphite includes at least one of expanded graphite, artificial graphite, and natural graphite.

[0052] In some embodiments, in step (2), the mass ratio of the graphite cage to the graphite is (0.01-50):100, specifically, for example, 0.01:100, 0.5:100, 1:100, 5:100, 10:100, 20:100, 30:100, 40:100, 50:100. In the embodiment of the present invention, the mass ratio of the graphite cage to the graphite is (0.01-50):100, which is conducive to the synergistic conductivity of the graphite cage and the graphite matrix. Too high a content of graphite cages can easily cause insufficient impregnation of the graphite plate resin, and there is a certain risk of gas permeation; too low a content of graphite cages can only increase the conductivity of the graphite plate to a limited extent.

[0053] In some embodiments, in step (2), the pressing method includes at least one of rolling or molding. Optionally, the pressing temperature is 20-80°C, the pressing time is 10s-10min, and the pressing pressure is 10MPa-1GPa.

[0054] In some embodiments, in step (2), the thickness of the graphite substrate is greater than 0.1 mm, specifically, for example, 0.1 mm, 0.5 mm, 0.9 mm, 1 mm, 2 mm, 4 mm, 5 mm, 10 mm.

[0055] In some embodiments, in the step (2), the graphite substrate is compression molded to obtain a molded plate; optionally, the compression molding adopts vacuum molding; optionally, the compression molding pressure is 20MPa-6GPa; optionally, the compression molding temperature is 20-120°C, specifically, for example, 20°C, 25°C, 30°C, 50°C, 80°C, 100°C, 120°C; optionally, the compression molding time is 10s-10min, specifically, for example, 10s, 20s, 30s, 1min, 3min, 5min, 10min; optionally, the thickness of the molded plate is 0.1mm or more, specifically, for example, 0.1mm, 0.5mm, 0.9mm, 1mm, 2mm, 4mm, 5mm, 10mm;

[0056] Optionally, the compression molding includes placing the graphite substrate into a vacuum mold and pressing it by a large-tonnage compression molding machine; the large-tonnage compression molding machine has a tonnage of 10-1000 tons;

[0057] Optionally, the molded plate has a flow channel, that is, the molded plate has a flow channel feature.

[0058] In the embodiment of the present invention, compression molding is beneficial for pressing the electrode plate to a desired thickness, and the flow field characteristics of the surface can be obtained by molding as required.

[0059] In some embodiments, in step (3), the resin includes at least one of acrylate resin, polyphenylene sulfide, polypropylene, polyvinylidene fluoride, epoxy resin, phenolic resin or vinyl resin.

[0060] In some embodiments, in step (3), the molded plate is subjected to resin impregnation treatment; optionally, the molded plate is subjected to resin impregnation treatment including immersing the molded plate in a liquid containing resin;

[0061] There is no particular limitation on the specific form of the resin-containing liquid, and the impregnation can be performed in the form of a liquid. For example, the resin-containing liquid includes at least one of a molten resin, a liquid resin, a resin solution, a resin emulsion, and a resin-containing adhesive. There is no particular limitation on the resin content of the resin-containing liquid, for example, the viscosity of the resin-containing liquid is 5-15 cP (25° C.);

[0062] Optionally, the temperature of the resin impregnation treatment is 20-150°C, specifically, for example, 20°C, 25°C, 30°C, 50°C, 80°C, 100°C, 120°C, 150°C; Optionally, the time of the resin impregnation treatment is 1min-30min, specifically, for example, 1min, 3min, 5min, 10min, 20min, 30min;

[0063] Optionally, the resin impregnation treatment adopts vacuum impregnation; the vacuum degree of the impregnation treatment is -0.05--0.1MPa;

[0064] Optionally, the resin impregnation treatment includes first performing vacuum impregnation and then performing pressure impregnation under pressure; the pressure of the pressure impregnation is 0.5-1 MPa;

[0065] Optionally, the resin impregnation treatment is followed by drying and / or curing. Optionally, the drying and / or curing is carried out by water bath heating or drying. Optionally, the drying and / or curing temperature is 80-100°C, specifically, for example, 80°C, 90°C, 100°C; the drying and / or curing time is 3min-2h, specifically, for example, 3min, 10min, 20min, 30min, 1h, 2h.

[0066] In the embodiment of the present invention, the pores in the graphite plate can be blocked by resin impregnation treatment, gas penetration can be prevented, and airtightness can be improved. Compared with the method of directly mixing and pressing the resin, graphite, and graphite cage, the resin impregnation treatment is conducive to the resin being evenly filled into the graphite pores of the pressed graphite plate, thereby achieving the purpose of blocking the pores, while not affecting the construction of a conductive path between the graphite and the graphite cage. By adjusting the impregnation process, it is conducive to adjusting the composition of the resin, graphite, and graphite cage, and achieving the best performance of the plate.

[0067] A graphite electrode plate according to an embodiment of the present invention is prepared by the preparation method according to an embodiment of the present invention.

[0068] In the embodiment of the present invention, the conductivity of the flexible molded graphite plate doped with highly conductive graphite cages is greatly improved, greatly enhancing the current transmission capacity; at the same time, the addition of highly conductive graphite cages can greatly improve the conductivity difference of the molded graphite plate along the plate forming direction and perpendicular to the plate forming direction.

[0069] In some embodiments, the graphite plate includes graphite, graphite cages and resin; optionally, graphite, graphite cages and resin are uniformly dispersed in the graphite plate; optionally, in the graphite plate, graphite and graphite cages form a conductive path; optionally, in the graphite plate, the mass percentage of graphite is 10-40%, specifically, for example, 10%, 20%, 30%, 40%; the mass percentage of graphite cages is 0.01-50%, specifically, for example, 0.01%, 1%, 2%, 5%, 10%, 20%, 30%, 40%, 50%; the mass percentage of the resin is 10-90%, specifically, for example, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%.

[0070] In some embodiments, the thickness of the graphite plate is greater than 0.1 mm, specifically, for example, 0.1 mm, 0.5 mm, 0.9 mm, 1 mm, 2 mm, 4 mm, 5 mm, 10 mm.

[0071] In some embodiments, the conductivity of the graphite plate along its thickness direction (vertical to the forming direction) is not less than 40S / cm; and / or, the conductivity of the graphite plate along the direction perpendicular to its thickness (along the forming direction) is not less than 200S / cm; and / or, the contact resistance of the graphite plate is not higher than 5mΩ / cm 2 .

[0072] In some embodiments, the graphite plate is a monopolar plate. Optionally, a bipolar plate is obtained by bonding two graphite plates together.

[0073] A fuel cell according to an embodiment of the present invention comprises the graphite plate according to an embodiment of the present invention. In the embodiment of the present invention, the conductivity of the graphite plate is greatly improved, which greatly enhances the current transmission capacity of the fuel cell and better meets the large current conductivity requirements of the fuel cell plate.

[0074] The present invention is described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0075] Example 1

[0076] A method for preparing a graphite plate comprises the following steps:

[0077] (1) Use carbon black particles with a particle size of 70 nm (such as Figure 2 As shown in the figure, it can be seen that the morphology is spherical particles. From its XRD spectrum, it can be seen that carbon black shows an amorphous peak at about 26°, indicating that it is an amorphous carbon material. The carbon black is graphitized at 2500℃ for 1h to obtain a highly conductive graphite cage material, which has a nano-hollow graphite cage structure, as shown in the figure. Figure 3 As shown, its XRD spectrum shows a sharp peak at 26°, indicating that the carbon black has been completely transformed into graphite material;

[0078] (2) mixing the graphite cage material and the expanded graphite material in a mass ratio of 0.5:100, and pressing the mixed material into a graphite substrate with a thickness of 5 mm by roller pressing;

[0079] (3) A 5 mm graphite substrate was placed in a vacuum molding press, pressed into a 1 mm plate at 50 MPa and 25°C, and impregnated with an acrylic resin (5-15 cP) at 70°C for 20 min, and then dried at 90°C for 60 min to obtain a highly conductive flexible graphite plate. The highly conductive flexible graphite plate was tested for conductivity along the plate thickness direction and perpendicular to the thickness direction using a four-probe resistance meter, and for contact resistance using a resistance meter to test performance changes.

[0080] Example 2

[0081] A method for preparing a graphite plate comprises the following steps:

[0082] (1) Using carbon black particles with a particle size of 70 nm, the carbon black is graphitized at 2000° C. for 1 h to obtain a highly conductive graphite cage material having a nano-hollow graphite cage structure;

[0083] (2) mixing the graphite cage material and the expanded graphite material in a mass ratio of 1:100, and pressing the mixed material into a graphite substrate with a thickness of 5 mm by roller pressing;

[0084] (3) A 5 mm graphite substrate was placed in a vacuum molding machine and pressed into a 0.9 mm electrode at 70 MPa and 30°C. The electrode was then impregnated with an acrylic resin (5-15 cP) at 70°C for 20 min and then dried at 90°C for 60 min to obtain a highly conductive flexible graphite electrode.

[0085] Example 3

[0086] A method for preparing a graphite plate comprises the following steps:

[0087] (1) Using carbon black particles with a particle size of 70 nm, the carbon black is graphitized at 2500° C. for 1 h to obtain a highly conductive graphite cage material having a nano-hollow graphite cage structure;

[0088] (2) mixing the graphite cage material and the expanded graphite material in a mass ratio of 3:100, and pressing the mixed material into a graphite substrate with a thickness of 5 mm by roller pressing;

[0089] (3) A 5 mm graphite substrate was placed in a vacuum molding machine and pressed into a 0.9 mm electrode at 70 MPa and 30°C. The electrode was then impregnated with an acrylic resin (5-15 cP) at 70°C for 20 min and then dried at 90°C for 60 min to obtain a highly conductive flexible graphite electrode.

[0090] Example 4

[0091] A method for preparing a graphite plate comprises the following steps:

[0092] (1) Using carbon black particles with a particle size of 70 nm, the carbon black is graphitized at 2500° C. for 1 h to obtain a highly conductive graphite cage material having a nano-hollow graphite cage structure;

[0093] (2) mixing the graphite cage material and the expanded graphite material in a mass ratio of 5:100, and pressing the mixed material into a graphite substrate with a thickness of 5 mm by roller pressing;

[0094] (3) A 5 mm graphite substrate was placed in a vacuum molding press and pressed into a 1 mm plate at 50 MPa and 30°C. The plate was then impregnated with an acrylic resin (5-15 cP) at 70°C for 20 min and then dried at 90°C for 60 min to obtain a highly conductive flexible graphite plate. The cross-sectional view of the obtained graphite plate is shown in FIG. Figure 4 As shown, it can be seen that graphite and graphite cages are effectively mixed and overlapped together to form a conductive path.

[0095] Comparative Example 1

[0096] A method for preparing a carbon black-doped flexible molded graphite plate is the same as the preparation method in Example 1, except that in step (2), the graphite cage material is replaced by the carbon black particles in step (1) of Example 1.

[0097] Comparative Example 2

[0098] A method for preparing a flexible molded graphite plate doped with carbon microspheres is the same as the preparation method in Example 1, except that in step (2), the graphite cage material is replaced by 5 μm carbon microspheres; wherein the mesophase asphalt is dissolved in an organic solvent, a surfactant and water are used to form a suspension and vigorously stirred to make the mesophase asphalt into balls, and then the organic solvent is removed by heating, and the mesophase carbon microspheres, i.e. carbon microspheres, are obtained after cooling, filtration, pre-oxidation and carbonization.

[0099] Comparative Example 3

[0100] A method for preparing a graphene-doped flexible molded graphite plate is the same as the preparation method in Example 1, except that in step (2), the graphite cage material is replaced by graphene.

[0101] Comparative Example 4

[0102] A method for preparing a carbon nanotube-doped flexible molded graphite plate is the same as the preparation method in Example 1, except that in step (2), the graphite cage material is replaced by carbon nanotubes.

[0103] Comparative Example 5

[0104] The preparation method is the same as that in Example 1, except that the graphite cage in step (1) and step (2) is omitted, that is, in step (2), the expanded graphite material is directly rolled into a graphite substrate with a thickness of 5 mm, and step (3) is the same as that in Example 1.

[0105] Table 1

[0106]

[0107] As can be seen from Table 1, compared with the graphite plate of Comparative Example 5, the conductivity of the highly conductive graphite cage-doped flexible molded graphite plates in Examples 1-4 along the thickness and perpendicular to the thickness is significantly improved, and the contact resistance is increased from 8.62 mΩ / cm 2 Reduced to 4.52mΩ / cm 2 , which greatly enhances the current transmission capacity and improves the conductivity of the graphite plate along its thickness and perpendicular to its thickness.

[0108] Compared with the graphite plate of comparative example 5, the addition of carbon black, carbon microspheres, graphene or carbon nanotubes to the flexible molded graphite plates in comparative examples 1-4 can improve the conductivity of the graphite plates along their thickness and in a direction perpendicular to their thickness, while reducing the contact resistance. However, the electrical conductivity of the flexible molded graphite plates in Comparative Examples 1-4 is lower than that of the flexible molded graphite plates in Example 1, and the contact resistance is higher than that of the flexible molded graphite plates in Example 1. This is because the highly conductive graphite cage of the present invention has a hollow ultra-thin rigid graphite crystalline cage structure, the graphite crystal structure is complete, the crystal defects are relatively few, the crystallinity is high, and the electron transmission distance of the thin-walled graphite structure is short, so it has ultra-high conductivity, which can greatly improve the conductivity of the substrate; the thin-walled rigid cage structure of the graphite cage can better fill the gaps between the large particles of the graphite matrix, overlap and stack with the graphite, produce a synergistic conductive effect, and further improve the conductivity of the graphite plate; at the same time, the structure of the graphite cage is a thin-walled graphite spherical crystal structure, which shows typical isotropy in conductivity, which is significantly different from anisotropic structures such as graphene and carbon nanotubes. The addition of highly conductive graphite cages can greatly improve the conductivity difference of the molded graphite plate along its thickness and in the direction perpendicular to its thickness, and better meet the large current conductivity requirements of the fuel cell plate.

[0109] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0110] Although the above embodiments have been shown and described, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those of ordinary skill in the art are all within the scope of protection of the present invention.

Claims

1. A method for preparing a graphite plate, characterized in that: The following steps are involved: (1) graphitizing carbon black to obtain a graphite cage; (2) mixing and pressing the graphite cage and graphite to obtain a graphite substrate; and then molding the graphite substrate to obtain a molded electrode plate; (3) The molded plate is impregnated with resin to obtain a graphite plate.

2. The method for preparing a graphite plate according to claim 1, wherein: In the step (1), the temperature of the graphitization treatment is 1800-2800°C; And / or, the graphitization treatment time is 0.5-10h.

3. The method for preparing a graphite plate according to claim 1, characterized in that: In the step (1), the particle size of the carbon black is 1 nm-10 μm; And / or, the particle size of the graphite cage is 1 nm-10 μm; And / or, the graphite cage has a hollow cage morphology of a crystalline graphite structure.

4. The method for preparing a graphite plate according to claim 1, characterized in that: In the step (2), the graphite includes at least one of expanded graphite, artificial graphite, and natural graphite; And / or, the mass ratio of the graphite cage to graphite is (0.01-50):100; And / or, the pressing method includes at least one of rolling or molding; And / or, the thickness of the graphite substrate is greater than 0.1 mm.

5. The method for preparing a graphite plate according to claim 1, characterized in that: In the step (2), the compression molding is performed by vacuum compression molding; And / or, the compression molding pressure is 20MPa-6GPa; And / or, the compression molding temperature is 20-120°C; And / or, the thickness of the molded plate is greater than 0.1 mm.

6. The method for preparing a graphite plate according to claim 1, characterized in that: In the step (3), the resin includes at least one of acrylate resin, polyphenylene sulfide, polypropylene, polyvinylidene fluoride, epoxy resin, phenolic resin or vinyl resin.

7. The method for preparing a graphite plate according to claim 1, characterized in that: In the step (3), subjecting the molded plate to resin impregnation treatment includes immersing the molded plate in a liquid containing resin; And / or, the temperature of the resin impregnation treatment is 20-150°C; And / or, the resin impregnation treatment time is 1-30min; And / or, the resin impregnation process adopts vacuum impregnation.

8. A graphite plate, characterized in that: The graphite plate is prepared by the preparation method described in any one of claims 1 to 7.

9. The graphite plate according to claim 8, characterized in that: The thickness of the graphite plate is greater than 0.1 mm; And / or, the conductivity of the graphite plate along its thickness direction is not less than 40S / cm; And / or, the conductivity of the graphite plate in a direction perpendicular to its thickness is not less than 200 S / cm; And / or, the contact resistance of the graphite plate is not higher than 5mΩ / cm 2 .

10. A fuel cell, characterized in that: Comprising the graphite electrode plate as described in claim 8 or 9.

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