CN111129537A - Composite graphite bipolar plate and preparation method and application thereof - Google Patents
Composite graphite bipolar plate and preparation method and application thereof Download PDFInfo
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- CN111129537A CN111129537A CN201911404942.5A CN201911404942A CN111129537A CN 111129537 A CN111129537 A CN 111129537A CN 201911404942 A CN201911404942 A CN 201911404942A CN 111129537 A CN111129537 A CN 111129537A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0213—Gas-impermeable carbon-containing materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/0258—Collectors; Separators, e.g. bipolar separators; Interconnectors characterised by the configuration of channels, e.g. by the flow field of the reactant or coolant
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
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Abstract
The invention provides a composite graphite bipolar plate and a preparation method and application thereof. The sealing coating forms a layer of compact protection structure on the cathode surface and the anode surface of the graphite bipolar plate, so that the surface defects on the graphite bipolar plate are effectively blocked, the flatness of a fuel field channel on the graphite bipolar plate and the air tightness of the graphite bipolar plate are improved, and the air tightness compensation of the graphite bipolar plate is realized. The composite graphite bipolar plate has simple preparation process and wide industrial application prospect. The fuel cell based on the composite graphite bipolar plate has good cell performance and uniformity, and can fully meet the application requirements of high-performance fuel cells.
Description
Technical Field
The invention belongs to the technical field of fuel cells, and particularly relates to a composite graphite bipolar plate and a preparation method and application thereof.
Background
A fuel cell is a chemical device that directly converts chemical energy of fuel into electric energy, and is also called an electrochemical generator, which is a fourth power generation technology following hydroelectric power generation, thermal power generation, and atomic power generation. The fuel cell converts the Gibbs free energy in the chemical energy of the fuel into electric energy through electrochemical reaction, and is not limited by the Carnot cycle effect, so the power generation efficiency is high. In addition, the fuel cell uses fuel and oxygen as fuel, and has no mechanical transmission part, so that the fuel cell has no noise, and discharges few harmful gases and no pollution. It follows that fuel cells are the most promising power generation technology from the viewpoint of energy conservation and ecological environment conservation.
The proton exchange membrane fuel cell has the advantages of rapid opening/closing function, high specific power and the like, so that the proton exchange membrane fuel cell is widely concerned by researchers, and the proton exchange membrane fuel cell has the potential of being applied to the field of new energy vehicles after years of research and exploration. The bipolar plate is one of the core components of the proton exchange membrane fuel cell, and the functions of the bipolar plate comprise current collection, reaction medium conveying, oxidant and reducing agent separation, mechanical support and the like. The above-mentioned functions require that the bipolar plate material should have the following properties: (1) the gas barrier property is good, and the material has gas impermeability; (2) the corrosion resistance is good, and the corrosion resistance comprises the corrosion resistance under the external atmospheric environment at the temperature of 5-85 ℃ and the internal environment of the battery at the temperature of 65-85 ℃ and under the 200 kPa; (3) high electrical and thermal conductivity; (4) the mechanical property is good; (5) the weight is light; (6) low production and processing cost, suitability for mass production and the like.
At present, a great deal of research work focuses on development of a bipolar plate material, optimization of a bipolar plate structure and a preparation method, for example, CN109921051A discloses an ultrathin flexible graphite bipolar plate and a preparation method thereof, wherein the ultrathin flexible graphite bipolar plate comprises an upper layer of flexible graphite polar plates, a lower layer of flexible graphite polar plates and a graphene film in the middle layer, the graphene film is positioned between the two layers of flexible graphite polar plates, a flexible graphite-based bipolar plate structure with a graphene film sandwich is formed, and the strength and the gas barrier performance of the flexible graphite plate are improved; the ultrathin flexible graphite hydrogen-oxygen polar plate prepared by adopting the die pressing process improves the strength of the bipolar plate, reduces the thickness of the bipolar plate, can improve the specific power density of the galvanic pile and has good practical value under the condition of ensuring the original performance. CN101123313B discloses a metallic bipolar plate for a fuel cell comprising a plate-shaped metal substrate composed of a metal capable of being passivated and a noble metal layer partially coated on the metal substrate, and a fuel cell comprising the same, which has concave-convex portions formed at least in the region facing the electrodes of a membrane electrode assembly, does not have the problem of an increase in resistance due to corrosion of the bipolar plate and the problem of deterioration of the electrolyte due to the evolved ions, and has good cell characteristics. CN110212212A discloses a bipolar plate compounded by a metal plate single face and graphite and a preparation method thereof, wherein the bipolar plate comprises a hydrogen unipolar plate and an oxygen unipolar plate, the unipolar plate is compounded by a metal polar plate and graphite, a conductive layer is arranged on the surface of the metal polar plate, and flexible graphite paper is adhered to one face of the metal polar plate. The bipolar plate improves the corrosion resistance of the bipolar plate and reduces the surface treatment cost of the metal bipolar plate.
The existing bipolar plate for the fuel cell comprises metals, conductive plastics and graphite, the metal bipolar plate has good formability and obvious volume advantage, but the corrosion resistance needs to be further improved, the bipolar plate does not have the prospect of large-scale application temporarily, the contradiction between the conductivity and the mechanical strength of the conductive plastics bipolar plate is difficult to balance, and the bipolar plate is limited in the application of a high-power battery pack. Therefore, the bipolar plate material widely used in proton exchange membrane fuel cells is a non-porous graphite plate, which is mainly manufactured by a powder metallurgy method, and the method causes a plurality of pores on the microstructure, which cannot be distinguished by naked eyes, and the existence of the pores causes the mutual penetration of fuels. Meanwhile, the graphite bipolar plate has lower hardness than metal, and is very easy to be scratched or impacted by sharp objects in the further processing and assembling process of the graphite plate, for example, in the processing process of the graphite plate by using a digital control processing machine, fine processing marks which are difficult to identify by naked eyes are often produced on the graphite plate due to clamping of a clamp and the operations of drilling, groove milling and the like, and the marks are likely to reduce the air tightness of the graphite bipolar plate and have negative influence on the performance of the proton exchange membrane fuel cell manufactured by the graphite bipolar plate.
Therefore, it is an important research in the art to develop a graphite bipolar plate having good gas tightness to improve the uniformity of the performance of the fuel cell.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a composite graphite bipolar plate and a preparation method and application thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a composite graphite bipolar plate comprising a graphite bipolar plate and a seal coat bonded to the cathode and anode faces of the graphite bipolar plate.
In a fuel cell, a graphite bipolar plate is usually prepared by a method of molding graphite powder, and the method can cause a plurality of micro-scale air holes to be formed on the graphite bipolar plate, so that the air tightness of the graphite bipolar plate is reduced, and fuel is penetrated; in addition, the graphite bipolar plate has low hardness, and machining marks are inevitably left in the machining and assembling processes, and the machining marks also influence the air tightness of the graphite bipolar plate, so that the performance of the fuel cell is negatively influenced. Based on the structure, the composite graphite bipolar plate provided by the invention effectively solves the problem of air tightness caused by uneven surface structure and rough surface of the fuel field channel wall of the traditional graphite bipolar plate by arranging the sealing coating on the cathode surface and the anode surface of the traditional graphite bipolar plate, and the sealing coating forms a compact protection structure on the surface of the graphite bipolar plate, so that the surface defects caused in the manufacturing and processing processes of the graphite bipolar plate are effectively blocked, the flatness of the fuel field channel of the bipolar plate and the air tightness of the graphite bipolar plate are improved, and the fuel cell prepared by the composite graphite bipolar plate has uniform and excellent cell performance.
The graphite bipolar plate is obtained by the prior art and is provided with a cathode surface and an anode surface, wherein the cathode surface is an oxygen channel, the anode surface is a hydrogen channel, the channel width of the cathode surface and the channel width of the anode surface are different, and the width of the hydrogen channel of the anode surface is smaller than that of the oxygen channel of the cathode surface.
Preferably, the sealing coating is a polymer resin layer.
Preferably, the polymer resin layer is prepared from one or a combination of at least two of polyvinylidene fluoride, polytetrafluoroethylene, polyaniline, polystyrene amine and epoxy resin, and further preferably polyvinylidene fluoride.
As a preferable technical scheme of the invention, the sealing coating is a polymer resin layer, can effectively fill up rough and uneven structures and air hole defects on the surface of the graphite bipolar plate, and has good mechanical properties and conductivity.
Preferably, the polyvinylidene fluoride has a number average molecular weight of 350 to 600, such as 370, 390, 400, 410, 420, 440, 450, 470, 490, 500, 510, 530, 540, 550, 580, 590, and the like.
Preferably, the sealing coating has a thickness of 1 to 3 μm, such as 1.1 μm, 1.2 μm, 1.3 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.9 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, or 2.9 μm, and specific values therebetween, which are limited to space and for the sake of brevity, the present invention is not exhaustive of the specific values included in the range.
As a preferred technical scheme of the invention, the thickness of the sealing coating is 1-3 μm, if the thickness of the sealing coating is less than the range, the surface defects and covering air holes of the graphite bipolar plate with a flat surface can not be blocked, and if the thickness of the sealing coating is more than the range, the electrical property of the composite graphite bipolar plate can be influenced, so that the battery performance of the fuel battery is reduced.
In another aspect, the present invention provides a method for preparing a composite graphite bipolar plate as described above, comprising the steps of:
(1) mixing and dispersing a polymer and an organic solvent to obtain a sealing coating treating agent;
(2) and (2) respectively coating the sealing coating treating agent obtained in the step (1) on the anode surface and the cathode surface of the graphite bipolar plate, and drying to obtain the composite graphite bipolar plate.
Preferably, the organic solvent in step (1) is selected from any one or a combination of at least two of N-methylpyrrolidone, dimethyl sulfoxide, tetramethylurea, N-dimethylformamide or N, N-dimethylacetamide, and is more preferably N-methylpyrrolidone.
Preferably, the content of the polymer in the seal coat treating agent in the step (1) is 3 to 5% by mass, such as 3.1%, 3.2%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, 4.0%, 4.1%, 4.2%, 4.3%, 4.4%, 4.5%, 4.6%, 4.7%, 4.8% or 4.9%, and the specific values therebetween are limited by space and for brevity, and the invention is not exhaustive.
Preferably, the temperature of the dispersion in step (1) is 60 to 90 ℃, such as 62 ℃, 65 ℃, 68 ℃, 70 ℃, 72 ℃, 75 ℃, 78 ℃, 80 ℃, 82 ℃, 85 ℃, 87 ℃ or 89 ℃.
Preferably, the dispersion of step (1) is carried out under stirring conditions.
Preferably, the dispersing time in step (1) is 4-8 h, such as 4.2h, 4.5h, 4.8h, 5h, 5.2h, 5.5h, 5.8h, 6h, 6.2h, 6.5h, 6.8h, 7h, 7.2h, 7.5h, 7.7h or 7.9h, etc.
Preferably, the coating method in the step (2) is spraying or brushing.
The brush coating is uniform spraying along the direction of the channels on the cathode surface and the anode surface of the graphite bipolar plate.
Preferably, the drying temperature in step (2) is 95-120 ℃, such as 96 ℃, 98 ℃, 100 ℃, 102 ℃, 105 ℃, 107 ℃, 110 ℃, 112 ℃, 115 ℃, 117 ℃ or 119 ℃, and the specific values therebetween are limited by space and for the sake of brevity, and the invention is not exhaustive of the specific values included in the range.
Preferably, the drying time in step (2) is 1 to 5 hours, such as 1.2 hours, 1.5 hours, 1.8 hours, 2 hours, 2.3 hours, 2.5 hours, 2.8 hours, 3 hours, 3.2 hours, 3.5 hours, 3.8 hours, 4 hours, 4.2 hours, 4.5 hours, 4.7 hours or 4.9 hours, and the specific values therebetween are limited by space and for simplicity, and the invention is not exhaustive.
Preferably, the specific method of step (2) is: fixing the graphite bipolar plate by using a clamp, coating the sealing coating treating agent obtained in the step (1) on the anode surface of the graphite bipolar plate, and drying for the first time; and (3) coating the sealing coating treating agent obtained in the step (1) on the cathode surface of the graphite bipolar plate, and performing secondary drying.
Preferably, the temperature of the first drying is 105-120 ℃, such as 106 ℃, 107 ℃, 108 ℃, 109 ℃, 110 ℃, 111 ℃, 112 ℃, 113 ℃, 114 ℃, 115 ℃, 116 ℃, 117 ℃, 118 ℃ or 119 ℃, etc.
Preferably, the time for the first drying is 1 to 2 hours, such as 1.1 hour, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours or 1.9 hours.
Preferably, the temperature of the second drying is 95 to 105 ℃, such as 96 ℃, 97 ℃, 98 ℃, 99 ℃, 100 ℃, 101 ℃, 102 ℃, 103 ℃ or 104 ℃ and the like.
Preferably, the time for the second drying is 0.5-1.5 h, such as 0.6h, 0.7h, 0.8h, 0.9h, 1h, 1.1h, 1.2h, 1.3h or 1.4 h.
According to the preferable technical scheme, in the preparation method of the composite graphite bipolar plate, the sealing coating treating agent is coated on the anode surface of the graphite bipolar plate and dried, and then the sealing coating treating agent is coated on the cathode surface and dried to obtain the composite graphite bipolar plate. Because the width of the hydrogen channel of the anode surface is significantly smaller than that of the oxygen channel of the cathode surface on the graphite bipolar plate, the drying process of the anode surface needs more time, and based on the time cost of mass production, the hydrogen channel of the anode surface is preferably coated in the coating process, and the hydrogen channel of the anode surface is coated and dried and then the cathode surface is coated with the seal coating treatment agent.
Preferably, the preparation method comprises the following steps:
(1) mixing a polymer with an organic solvent, and stirring and dispersing uniformly at 60-90 ℃ to obtain a sealing coating treating agent with the polymer content of 3-5% by mass;
(2) fixing a graphite bipolar plate by using a clamp, brushing the sealing coating treating agent obtained in the step (1) on the anode surface of the graphite bipolar plate, and drying for 1-2 h at 105-120 ℃; after cooling, brushing the sealing coating treating agent obtained in the step (1) on the cathode surface of the graphite bipolar plate, and drying at the temperature of 95-105 ℃ for 0.5-1.5 h; and obtaining the composite graphite bipolar plate.
In another aspect, the present invention provides a fuel cell comprising a composite graphite bipolar plate as described above.
Compared with the prior art, the invention has the following beneficial effects:
the composite graphite bipolar plate provided by the invention forms a layer of compact protection structure on the cathode surface and the anode surface of the graphite bipolar plate through the design of the sealing coating, effectively blocks surface defects on the graphite bipolar plate, improves the flatness of a fuel field channel on the graphite bipolar plate and the air tightness of the graphite bipolar plate, realizes the air tightness compensation of the graphite bipolar plate, and has the air tightness as low as 1.2 multiplied by 10-6～1.8×10-6cm/s, and the resistance value is as low as 0.11-0.19 m omega, so that the method is suitable for preparing a high-performance fuel cell. The composite graphite bipolar plate has simple preparation process and wide industrial application prospect. Based on the inventionThe fuel cell of the composite graphite bipolar plate has good cell performance and uniformity, and can fully meet the application requirement of a high-performance battery pack.
Drawings
Figure 1 is a surface topography map of a composite graphite bipolar plate provided in example 1;
FIG. 2 is an enlarged view of the surface topography of the composite graphite bipolar plate provided in example 1;
figure 3 is a surface topography plot of an untreated graphite bipolar plate of comparative example 1.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
The experimental materials used in the following examples of the present invention include:
(1) graphite bipolar plate: from gasoline liberation Motor Co Ltd;
(2) polyvinylidene fluoride (PVDF) powder, 450 number average molecular weight, was purchased from tetracyclic chemical.
Example 1
The embodiment provides a composite graphite bipolar plate, which is prepared by the following steps:
(1) mixing PVDF and N-methyl pyrrolidone, wherein the mass percentage of the PVDF is 5%; primarily stirring by using a glass rod, heating in a water bath at 75 ℃, and stirring by using a magnetic stirrer at the same time, wherein the stirring speed is 500r/min, and the stirring time is 6 hours, so that PVDF is completely dissolved in N-methylpyrrolidone to form a uniform and stable sealing coating treating agent;
(2) fixing the graphite bipolar plate by using a clamp, enabling the anode surface to face upwards, uniformly brushing the sealing coating treating agent obtained in the step (1) by using a fine brush according to the hydrogen channel trend of the anode surface, repeatedly coating fine parts to ensure uniformity, then transferring the clamp and the graphite bipolar plate into an oven, and drying for 1.5 hours at 110 ℃; taking out and cooling after drying, enabling the cathode surface of the graphite bipolar plate to face upwards, coating the sealing coating treating agent obtained in the step (1) by using a fine hairbrush according to the oxygen channel trend of the cathode surface, putting the coating treating agent into an oven again after coating is finished, and drying the coating treating agent for 1h at the temperature of 100 ℃; and taking out to obtain the composite graphite bipolar plate, wherein the thickness of the sealing coating is 2.6 mu m.
Example 2
The embodiment provides a composite graphite bipolar plate, which is prepared by the following steps:
(1) mixing PVDF and N-methyl pyrrolidone, wherein the mass percentage of the PVDF is 3%; primarily stirring by using a glass rod, heating in a water bath at 60 ℃, and stirring by using a magnetic stirrer at the same time, wherein the stirring speed is 800r/min, and the stirring time is 4h, so that PVDF is completely dissolved in N-methylpyrrolidone to form a uniform and stable sealing coating treating agent;
(2) fixing the graphite bipolar plate by using a clamp, enabling the anode surface to face upwards, uniformly spraying the sealing coating treating agent obtained in the step (1) according to the hydrogen channel trend of the anode surface, repeatedly coating fine parts to ensure uniformity, then transferring the clamp and the graphite bipolar plate into an oven, and drying for 2 hours at 105 ℃; taking out the graphite bipolar plate after drying, cooling the graphite bipolar plate, enabling the cathode surface of the graphite bipolar plate to face upwards, coating the sealing coating treating agent obtained in the step (1) by using a fine hairbrush according to the oxygen channel trend of the cathode surface, placing the coated graphite bipolar plate in a drying oven again after coating, and drying the graphite bipolar plate for 1.5 hours at 95 ℃; and taking out to obtain the composite graphite bipolar plate, wherein the thickness of the sealing coating is 1.2 mu m.
Example 3
The embodiment provides a composite graphite bipolar plate, which is prepared by the following steps:
(1) mixing PVDF and N-methyl pyrrolidone, wherein the mass percentage of the PVDF is 5%; primarily stirring by using a glass rod, heating in a water bath at 90 ℃, and stirring by using a magnetic stirrer at the same time, wherein the stirring speed is 600r/min, and the stirring time is 8 hours, so that PVDF is completely dissolved in N-methylpyrrolidone to form a uniform and stable sealing coating treating agent;
(2) fixing the graphite bipolar plate by using a clamp, enabling the anode surface to face upwards, uniformly spraying the sealing coating treating agent obtained in the step (1) according to the hydrogen channel trend of the anode surface, repeatedly coating fine parts to ensure uniformity, then transferring the clamp and the graphite bipolar plate into an oven, and drying for 1h at 120 ℃; taking out the graphite bipolar plate after drying, cooling the graphite bipolar plate, then enabling the cathode surface of the graphite bipolar plate to face upwards, coating the sealing coating treating agent obtained in the step (1) according to the oxygen channel direction of the cathode surface, placing the graphite bipolar plate in a drying oven again after coating, and drying the graphite bipolar plate for 0.5h at 105 ℃; and taking out to obtain the composite graphite bipolar plate, wherein the thickness of the sealing coating is 3 mu m.
Example 4
The difference between the embodiment and the embodiment 1 is that the mass percentage content of PVDF in the seal coating treating agent in the step (1) is 2.8%, and the thickness of the seal coating of the obtained composite graphite bipolar plate is 0.7 μm. And the air leakage does not meet the standard requirement through single plate air tightness test.
Example 5
The difference between the embodiment and the embodiment 1 is that the mass percentage content of PVDF in the seal coating treating agent in the step (1) is 5.5%, and the thickness of the seal coating of the obtained composite graphite bipolar plate is 3.4 μm. Through single-plate air tightness test, the air leakage amount meets the standard requirement, but the internal resistance is increased in 10 tests.
Example 6
(1) Mixing polyaniline with N-methyl pyrrolidone, wherein the mass percentage of the polyaniline is 4%; primarily stirring by using a glass rod, heating in a water bath at 60 ℃, simultaneously stirring by using a magnetic stirrer at the stirring speed of 800r/min for 4h, and dissolving polyaniline in N-methylpyrrolidone to form a uniform and stable sealing coating treating agent;
(2) fixing the graphite bipolar plate by using a clamp, enabling the anode surface to face upwards, uniformly spraying the sealing coating treating agent obtained in the step (1) according to the hydrogen channel trend of the anode surface, repeatedly coating fine parts to ensure uniformity, then transferring the clamp and the graphite bipolar plate into an oven, and drying for 2 hours at 105 ℃; taking out the graphite bipolar plate after drying, cooling the graphite bipolar plate, enabling the cathode surface of the graphite bipolar plate to face upwards, coating the sealing coating treating agent obtained in the step (1) by using a fine hairbrush according to the oxygen channel trend of the cathode surface, placing the coated graphite bipolar plate in a drying oven again after coating, and drying the graphite bipolar plate for 1.5 hours at 95 ℃; and taking out to obtain the composite graphite bipolar plate, wherein the thickness of the sealing coating is 1.5 mu m.
Comparative example 1
An untreated graphite bipolar plate.
And (3) performance testing:
(1) surface morphology: and testing the surface appearance of the composite graphite bipolar plate by using an optical microscope test.
Fig. 1 and 2 are surface topography diagrams of the composite graphite bipolar plate provided in example 1, and it can be seen from fig. 1 and 2 that field channels on the surface of the composite graphite bipolar plate are relatively flat, and a relatively dense sealing coating is attached to the surface of the composite graphite bipolar plate, so as to effectively block defects generated during the processing of the graphite bipolar plate.
Fig. 3 is a surface topography of an untreated graphite bipolar plate in comparative example 1, and it can be seen from fig. 3 that the surface of the graphite bipolar plate which was not treated with the seal coat had rough and highly uneven fuel field channel walls.
(2) And (3) air tightness test: according to a gas compactness testing method of a 9-bipolar plate component in GB/T20042.6-2011 standard, testing the prepared samples in the embodiments 1-6 and the comparative example 1 to obtain gas compactness values of all samples, wherein the gas compactness values are not more than 2 multiplied by 10 according to the DOE standard-6cm/s is qualified.
(3) And (3) resistance testing: according to the method for testing the resistance of the 15-bipolar plate component in GB/T20042.6-2011, the prepared samples in the embodiments 1-6 and the comparative example 1 are tested, and the resistance value of each sample is obtained, and is qualified according to the standard that the resistance value is not more than 0.21m omega.
TABLE 1
| Composition and thickness of sealing coating | Air tightness | Resistance testing | |
| Example 1 | PVDF 2.6μm | 1.4×10-6cm/s | 0.18mΩ |
| Example 2 | PVDF 1.2μm | 1.8×10-6cm/s | 0.11mΩ |
| Example 3 | PVDF 3μm | 1.3×10-6cm/s | 0.19mΩ |
| Example 4 | PVDF 0.74μm | 2.5×10-6cm/s | 0.05mΩ |
| Example 5 | PVDF 3.4μm | 1.5×10-6cm/s | 0.22mΩ |
| Example 6 | Polyaniline 1.5 μm | 1.2×10-6cm/s | 0.14mΩ |
| Comparative example 1 | Is free of | 2.0×10-6cm/s | 0.10mΩ |
As can be seen from the data in table 1, compared with the conventional graphite bipolar plate used in comparative example 1 without treatment, the composite graphite bipolar plates provided in examples 1 to 3 and 6 according to the present invention have significantly superior gas tightness and battery performance, no gas leakage during the test, and high uniformity of battery performance.
In the composite graphite bipolar plate provided by the invention, the thickness of the sealing coating is preferably 1-3 μm, the sealing effect is poor due to the fact that the thickness of the sealing coating is too low (embodiment 4), the bipolar plate still has an air leakage phenomenon, the uniformity of the battery is low, and the battery performance of the bipolar plate is affected due to the fact that the thickness of the sealing coating is too high (embodiment 5).
The applicant states that the present invention is illustrated by the above examples, but the present invention is not limited to the above process steps, i.e., it is not meant to be dependent upon the above process steps to practice the present invention. It will be apparent to those skilled in the art that any modification of the present invention, equivalent substitutions of selected materials and additions of auxiliary components, selection of specific modes and the like, which are within the scope and disclosure of the present invention, are contemplated by the present invention.
Claims (10)
1. A composite graphite bipolar plate, comprising a graphite bipolar plate, and a seal coating bonded to a cathode face and an anode face of the graphite bipolar plate.
2. The composite graphite bipolar plate of claim 1, wherein said seal coating is a polymer resin layer.
3. The composite graphite bipolar plate of claim 1 or 2, wherein the polymer resin layer is prepared from one or a combination of at least two of polyvinylidene fluoride, polytetrafluoroethylene, polyaniline, polyvinylamine and epoxy resin, preferably polyvinylidene fluoride.
4. The composite graphite bipolar plate of any one of claims 1 to 3, wherein the polyvinylidene fluoride has a number average molecular weight of 350 to 600.
5. The composite graphite bipolar plate of any one of claims 1 to 4, wherein the seal coating layer has a thickness of 1 to 3 μm.
6. A method for preparing the composite graphite bipolar plate as claimed in any one of claims 1 to 5, wherein the method comprises the steps of:
(1) mixing and dispersing a polymer and an organic solvent to obtain a sealing coating treating agent;
(2) and (2) respectively coating the sealing coating treating agent obtained in the step (1) on the anode surface and the cathode surface of the graphite bipolar plate, and drying to obtain the composite graphite bipolar plate.
7. The method according to claim 6, wherein the organic solvent in step (1) is selected from any one or a combination of at least two of N-methylpyrrolidone, dimethyl sulfoxide, tetramethylurea, N-dimethylformamide or N, N-dimethylacetamide, preferably N-methylpyrrolidone;
preferably, the mass percentage of the polymer in the seal coating treating agent in the step (1) is 3-5%;
preferably, the temperature of the dispersion in the step (1) is 60-90 ℃;
preferably, the dispersing time in the step (1) is 4-8 h;
preferably, the dispersion of step (1) is carried out under stirring conditions.
8. The production method according to claim 6 or 7, wherein the coating in step (2) is performed by spraying or brushing;
preferably, the drying temperature in the step (2) is 95-120 ℃;
preferably, the drying time in the step (2) is 1-5 h;
preferably, the specific method of step (2) is: fixing the graphite bipolar plate by using a clamp, coating the sealing coating treating agent obtained in the step (1) on the anode surface of the graphite bipolar plate, and drying for the first time; then coating the sealing coating treating agent obtained in the step (1) on the cathode surface of the graphite bipolar plate, and carrying out secondary drying;
preferably, the temperature of the primary drying is 105-120 ℃;
preferably, the time for the first drying is 1-2 h;
preferably, the temperature of the secondary drying is 95-105 ℃;
preferably, the time of the second drying is 0.5-1.5 h.
9. The method according to any one of claims 6 to 8, characterized by comprising the steps of:
(1) mixing a polymer with an organic solvent, and stirring and dispersing uniformly at 60-90 ℃ to obtain a sealing coating treating agent with the polymer content of 3-5% by mass;
(2) fixing a graphite bipolar plate by using a clamp, brushing the sealing coating treating agent obtained in the step (1) on the anode surface of the graphite bipolar plate, and drying for 1-2 h at 105-120 ℃; after cooling, brushing the sealing coating treating agent obtained in the step (1) on the cathode surface of the graphite bipolar plate, and drying at the temperature of 95-105 ℃ for 0.5-1.5 h; and obtaining the composite graphite bipolar plate.
10. A fuel cell comprising the composite graphite bipolar plate according to any one of claims 1 to 5.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114665102A (en) * | 2022-03-21 | 2022-06-24 | 北京氢沄新能源科技有限公司 | Metal bipolar plate of fuel cell and preparation method thereof |
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| CN1560947A (en) * | 2004-03-12 | 2005-01-05 | 清华大学 | Flexible graphic double polar plate and its preparation method |
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| CN114665102A (en) * | 2022-03-21 | 2022-06-24 | 北京氢沄新能源科技有限公司 | Metal bipolar plate of fuel cell and preparation method thereof |
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