WO2023097587A1 - Method for preparing bipolar plate for electrochemical fuel cell - Google Patents

Abstract

The present application provides a bipolar plate for a fuel cell. The bipolar plate is formed by laminating a substrate. The substrate is made of a soft graphite plate. The soft graphite plate has a density of 0.8-1.3 g/cm³, a carbon content of greater than 98% and an ash content of less than 2%; and based on the thickness of the substrate before lamination, the thickness compression ratio of the bipolar plate is 40-50%.

Description

Electrochemical fuel cell bipolar plate preparation method technical field

Embodiments of the present invention relate to fuel cells, and in particular to bipolar plates for fuel cells.

Background technique

With the growth of population and the development of industry, human's demand for energy has also skyrocketed. For a long time, fossil fuels have been heavily relied on as the main source of energy. The use of petroleum has driven the progress of transportation, technology and civilization, but it has also caused air pollution and triggered environmental crises in various places. Due to the dual pressure of energy and the environment, the development of fuel cells has received more and more attention and support from governments.

Proton Exchange Membrane Fuel Cell (PEMFC) is a relatively mature one among various fuel cells at present. Proton exchange membrane fuel cells convert the chemical energy in fuel and air directly and continuously into electrical energy. Its basic principle is to pass fuel (such as hydrogen or methanol, etc.) on the anode side and oxidant (oxygen or air, etc.) on the cathode side, and make them electrochemically react under the action of the catalyst to generate water and electrical energy.

The bipolar plate (anode plate, cathode plate) in the proton exchange membrane fuel cell is mainly responsible for transporting the reaction gas to the catalyst reaction area for electrochemical reaction, and making the reaction gas evenly distributed on the membrane electrode group, and at the same time conducting the electrochemical reaction. In addition, in the battery stack, the bipolar plate also has the function of heat dissipation. When the proton exchange membrane fuel cell is in operation, its internal working temperature is between 60 and 80°C, the internal relative humidity is usually 100%, and due to the hydrogen protons generated by the electrochemical reaction, the internal is an acidic environment (pH=2 ~3). Based on the above points, it can be known that the material of the bipolar plate must have high electrical conductivity, good thermal conductivity and better corrosion resistance. In addition, considering the processing of the flow channel on the bipolar plate, it is also necessary to select the material of the bipolar plate. Consider its processing characteristics.

At present, the most commonly used bipolar plate material is graphite, because its material properties meet the above characteristics, but its disadvantages are high material cost, poor mechanical strength, brittleness and limited processability. Due to the mechanical properties of graphite, most manufacturers use CNC (Computer Numerical Control) milling machines to process graphite bipolar plates. The processed graphite bipolar plates are thick, bulky, and heavy (the weight of traditional graphite plates accounts for about 50% to 60% heavy) and other shortcomings, it is difficult to be used as a bipolar plate material for future miniaturization and lightweight fuel cells. In addition, due to the complex machining process of CNC milling machines and the long machining cycle, it is difficult to reduce the machining cost of graphite bipolar plates.

Metal materials also have high electrical conductivity and good thermal conductivity, and its excellent ductility enables it to be formed by stamping or hydraulic pressure, so that the thickness of the plate can be effectively reduced, so the use of metal bipolar plates can further reduce the battery stack The volume and weight of the battery stack can increase the power density per unit volume and unit weight. In addition, metal bipolar plates have good shock resistance, which can increase the competitiveness of fuel cell power systems applied to vehicles in the future. In addition to the advantages brought by the above better mechanical properties, the cost of metal is also lower than that of graphite, and the stamping method can also greatly shorten the production time of bipolar plates, thus reducing the cost of batteries in the mass production stage. However, the disadvantage of metal bipolar plates is low corrosion resistance. Under high temperature, high humidity and acidic fuel cell environments, the metal surface is prone to form a passivation layer due to corrosion and oxidation reactions, which in turn increases the contact resistance and reduces the power generation efficiency of the fuel cell. , On the other hand, metal ions may also damage the performance of MEA.

Therefore, the current development technology of bipolar plates still faces many problems. How to provide durable bipolar plates in a low-cost and high-efficiency manner is still an urgent problem to be solved in the industry.

Contents of the invention

An embodiment of the present invention provides a bipolar plate for a fuel cell, which is formed by laminating substrates, wherein the substrate is formed of a flexible graphite plate, the density of the flexible graphite plate is 0.8-1.3g/cm ³ , and the carbon content> 98% and ash content<2%, and based on the thickness of the substrate before pressing, the thickness compression rate of the bipolar plate is 40-50%.

In some embodiments, based on the thickness of the substrate before lamination, the thickness deformation of the bipolar plate is 0.5-1 mm.

In some embodiments, the flexible graphite plate has a sulfur content of <1000 ppm and a chlorine content of <50 ppm.

In some embodiments, the density of the bipolar plates is 1-3 g/cm ³ .

In some embodiments, the flow channel depth of the bipolar plate is <1 mm.

In some embodiments, the flow channel of the bipolar plate is a convoluted flow channel, a serpentine flow channel, an interdigitated flow channel, a grid-like flow channel or a parallel flow channel.

The embodiment of the present invention also provides a fuel cell, comprising: a proton exchange membrane; a pair of catalyst layers, respectively arranged on both sides of the proton exchange membrane; a pair of bipolar plates, respectively arranged on the outside of the catalyst layer, the proton exchange membrane And the catalyst layer is clamped in the middle, wherein the bipolar plate is the bipolar plate of any example in the above-mentioned embodiments.

An embodiment of the present invention further provides a method for manufacturing a bipolar plate for a fuel cell, including: a die cutting step, cutting the soft graphite plate into a substrate; a matching step, placing the substrate in a mold; pressing step, pressing the mold on which the substrate is placed; and a demolding step, separating the pressed substrate from the mold to obtain a bipolar plate, wherein the density of the soft graphite plate is 0.8-1.3g/cm ³ , carbon The content is >98% and the ash content is <2%, and based on the thickness of the substrate before lamination, the thickness compression rate of the bipolar plate is 40-50%.

In some embodiments, the mold has a draft angle of 1-10°.

In some embodiments, the pressing weight of the pressing step is 300-1500 kg/cm ² .

In some embodiments, the pressing step is performed at room temperature.

In some embodiments, the duration of the pressing step is 0.05-3 minutes.

Description of drawings

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, in accordance with standard practice in the art, the various features are not drawn to scale and are used for illustrative purposes only. In fact, the dimensions of the elements may be arbitrarily expanded or reduced to clearly illustrate the features of the embodiments of the invention.

1A-1E are partial schematic diagrams illustrating flow channels of a bipolar plate, according to some embodiments.

FIG. 2 is a partial schematic diagram illustrating a fuel cell, according to some embodiments.

FIG. 3A is a schematic diagram illustrating a substrate placed in a mold and pressed together, according to some embodiments.

FIG. 3B is a schematic diagram illustrating a bipolar plate obtained after demolding, according to some embodiments.

4A-4B are partial side views illustrating a mold, according to some embodiments.

reference sign

10: bipolar plate;

10a: anode plate;

10b: cathode plate;

12: runner;

12a: runner;

12b: runner;

13: runner;

13a: runner;

13b: runner;

14: Runner entrance;

16: runner outlet;

20: proton exchange membrane;

30a: anode catalyst layer;

30b: cathode catalyst layer;

50: substrate;

100: fuel cell;

300: mold;

d1: thickness;

d2: thickness

Detailed ways

The following disclosure provides a number of embodiments or examples for implementing different elements of the provided object. Specific examples of each element and its configuration are described below to simplify the description of the embodiments of the present invention. Of course, these are just examples, not intended to limit the embodiments of the present invention. For example, if the description mentions that a first element is formed on a second element, it may include an embodiment in which the first and second elements are in direct contact, or may include an additional element formed between the first and second elements , so that they are not in direct contact with the example. In addition, the embodiments of the present invention may repeat reference numerals or letters in various examples. This repetition is for the purpose of brevity and clarity and not to show the relationship between the different embodiments or configurations discussed.

Furthermore, words relative to space may be used, such as "below", "below", "lower", "above", "higher" and similar words, for the convenience of description The relationship between one component or feature(s) and another component(s) or feature(s) in the drawings. Spatially relative terms are intended to encompass different orientations of the device in use or operation, as well as the orientations depicted in the figures. When the device is turned to a different orientation (rotated 90 degrees or otherwise), the spatially relative adjectives used therein shall also be interpreted in accordance with the turned orientation.

The disclosure provides a bipolar plate for a fuel cell, the main feature of which is that the bipolar plate is formed by direct pressing of a soft graphite plate, which can provide high-durability fuel in a low-cost and high-efficiency manner Battery bipolar plates.

The "soft graphite plate" referred to in this case refers to a graphite plate with a density of 0.8-1.3 g/cm ³ , a tensile strength of 40-50 kg/cm ² , a carbon content >98%, and an ash content <2%. According to some embodiments, the flexible graphite plate may be made of expanded graphite material, for example. According to some embodiments, the expanded graphite material can be, for example, made of natural flake graphite through intercalation treatment, water washing, drying, and high-temperature expansion. The special structure and characteristics of expanded graphite make it not only have the properties of natural graphite, but also have other excellent properties, such as: high pressure resistance, flexibility, plasticity and self-lubrication; high resistance to high temperature, low temperature, corrosion resistance, radiation resistance Characteristics; high shock resistance; high electrical conductivity; high anti-aging, anti-distortion characteristics, etc. According to some embodiments, the flexible graphite plate has a density of about 0.8-1.3 g/cm ³ (eg, 0.9-1 g/cm ³ , 0.95-1.2 g/cm ³ ). According to some embodiments, the flexible graphite plate has a carbon content >98% (eg >98.5%, >99%, >99.5%) and an ash content <2% (eg <1.5%, <1%, <0.5%). In this case, the high carbon content of the flexible graphite plate achieves high thermal conductivity and electrical conductivity, so as to meet the needs of the electrochemical reaction of the fuel cell.

According to some embodiments, the flexible graphite sheet is cut to form the substrate. According to some embodiments, the flexible graphite plate does not contain resin, so the bipolar plate formed by directly pressing the cut substrates can maintain the characteristic of high electrical conductivity. According to some embodiments, the tensile strength of the flexible graphite sheet is about 40-50 kg/cm ² (eg, 42-45 kg/cm ² , 43-48 kg/cm ² ). According to some embodiments, the compressibility of the flexible graphite sheet is >40% (eg >50%, >60%).

According to some embodiments, based on the thickness of the substrate before lamination, the thickness compression rate of the bipolar plate is 40-50% (such as 42-45%, 43-48%), that is, based on the thickness of the substrate before lamination As a comparison basis, the thickness of the bipolar plate formed after pressing is reduced by 40-50%. Wherein, the thickness of the substrate is the maximum thickness of the entire substrate, and the thickness of the bipolar plate is the maximum thickness of the entire bipolar plate. According to some embodiments, based on the thickness of the substrate before lamination, the thickness deformation of the bipolar plate is 0.5-1 mm (eg, 0.6-0.9 mm, 0.7-0.8 mm). Generally speaking, soft graphite needs to be impregnated with resin to obtain higher mechanical strength. However, in this case, the soft graphite can be formed by controlling the thickness compressibility of the bipolar plate and/or the thickness deformation of the bipolar plate. Under the premise of obtaining sufficient rigidity, the bipolar plate remains unbroken. If the thickness compressibility of the bipolar plate is too low, the strength of the bipolar plate will be too low and the impedance value will be too high. If the thickness compression rate of the bipolar plate is too high, it will increase the difficulty of demolding the bipolar plate, and it is easy to break during the compression process. According to some embodiments, the density of the bipolar plates is about 1-3 g/cm ³ (eg, 1.2-2.5 g/cm ³ , 1.6-2 g/cm ³ ).

According to some embodiments, the sulfur content of the flexible graphite plate<1000ppm and the chlorine content<50ppm, by controlling the sulfur content and the chlorine content in the flexible graphite plate, the impact on the catalyst in the fuel cell can be suppressed, thereby improving fuel efficiency. battery durability.

Bipolar plates with different flow channels can be obtained according to different mold designs. Referring to FIGS. 1A-1E , according to some embodiments, a bipolar plate 10 has flow channels 12 , flow channel inlets 14 , flow channel outlets 16 , and the like. The flow channel 12 can be, for example, a convoluted flow channel (as shown in Figure 1A), a serpentine flow channel (as shown in Figure 1B), an interdigitated flow channel (as shown in Figure 1C), a grid-shaped flow channel (as shown in Figure 1D) or a parallel flow channel Road (as shown in Figure 1E) and so on. According to some embodiments, the channel depth of the bipolar plate 10 is about <1 mm (eg <0.8 mm, <0.5 mm).

According to some embodiments, the bipolar plate of the present application can be used as a bipolar plate (anode plate and/or cathode plate) of a fuel cell. According to some embodiments, the flow channels on the bipolar plate of the present invention can be used as gas flow channels (such as hydrogen, air, etc.) and/or liquid flow channels (such as cooling liquid or methanol, etc.). According to some embodiments, bipolar plates may have flow channels on both sides. According to some embodiments, a bipolar plate may have flow channels on a single face.

Referring to FIG. 2 , according to some embodiments, FIG. 2 is a partial schematic diagram of a fuel cell 100 using a bipolar plate of the present invention. According to some embodiments, the fuel cell 100 may be composed of multiple single cells connected in series. According to some embodiments, fuel cell 100 includes proton exchange membrane 20 . According to some embodiments, the fuel cell 100 includes a pair of catalyst layers (an anode catalyst layer 30 a and a cathode catalyst layer 30 b ), respectively disposed on two sides of the proton exchange membrane 20 . According to some embodiments, the fuel cell 100 includes a pair of bipolar plates (anode plate 10a and cathode plate 10b), which are respectively arranged on the outside of the anode catalyst layer 30a and the cathode catalyst layer 30b, and the proton exchange membrane 20, the anode catalyst layer 30a And the cathode catalyst layer 30b is sandwiched in the middle. According to some embodiments, the hydrogen enters the channel 12a from the gas inlet of the anode plate 10a, and diffuses to the anode catalyst layer 30a through the gas diffusion layer (not shown). According to some embodiments, the air enters the channel 12b from the air inlet of the cathode plate 10b, and diffuses to the cathode catalyst layer 30b through a gas diffusion layer (not shown). Through the action of the anode catalyst layer 30a, the hydrogen atoms at the anode are decomposed into two hydrogen protons and two electrons, among which the protons are "attracted" to the other side of the proton exchange membrane 20, and the electrons reach the cathode through an external circuit to form a current . Under the action of the cathode catalyst layer 30b, hydrogen protons, oxygen and electrons react to form water molecules. According to some embodiments, the anode catalyst layer 30a may include, for example, Pt, Ru, Ni, or the like. According to some embodiments, the cathode catalyst layer 30b may include, for example, Pt, Ni, or the like. According to some embodiments, the anode plate 10a and the cathode plate 10b of the fuel cell 100 may further have a flow channel 13a and a flow channel 13b respectively. According to some embodiments, the flow channel 13a and the flow channel 13b are cooling liquid flow channels. Although fuel cells have better transfer efficiency than conventional internal combustion engines, about 50% of the energy is still dissipated as waste heat. Therefore, the flow channels 13a and 13b can make the flow distribution of the cooling liquid on the surface of the anode plate 10a and the cathode plate 10b respectively uniform, so as to achieve the effect of uniform heat dissipation. It should be understood that the fuel cell 100 may further include collector plates, end plates, sealing layers and other existing components, which are not described in detail here for simplicity.

Hereinafter, the manufacturing method of the bipolar plate will be further described.

According to some embodiments, the fabrication of the bipolar plates includes a die cutting step, cutting the flexible graphite plates into substrates. As the soft graphite plate, a commercially available soft graphite plate can be directly used. According to some embodiments, the size of the flexible graphite plate before cutting can be, for example, about 20-40 cm long (for example, about 23-35 cm, 25-30 cm), and about 20-40 cm wide (for example, about 23-35 cm, 25-30 cm ), about 0.3-3cm high (for example about 1-2.8cm, 1.5-2.5cm). The size of the cut substrate can be set according to requirements, for example, it can be about 3-30cm long (for example, about 10-28cm, 15-20cm), and about 3-30cm wide (for example, about 10-28cm, 15-20cm) , about 0.3-3cm in height (for example about 1-2.8cm, 1.5-2.5cm). In addition, the runner outlet and runner inlet (gas outlet and inlet and/or coolant outlet and inlet) can be cut out, and the position and location of the cut runner outlet and runner inlet can be set according to actual product requirements. size.

According to some embodiments, a matching step is performed after the die cutting step. As shown in FIG. 3A , the substrate 50 is placed in the mold 300 , wherein the thickness of the substrate 50 is d1 . According to some embodiments, a suitable mold 300 can be manufactured and selected according to requirements. By setting the texture on the mold 300, the shape of the flow path of the bipolar plate formed after lamination can be determined, and the bipolar plate can be set by the outer frame of the mold. board size.

According to some embodiments, a pressing step is performed after the matching step, and the mold 300 on which the substrate 50 is placed is subjected to pressing. Through the application of pressure, the substrate 50 is deformed along with the pattern of the mold 300 to form a shape with a specific flow channel. According to some embodiments, the pressing weight of the pressing step is about 300-1500 kg/cm ² (eg, 500-1300 kg/cm ² , 650-1200 kg/cm ² , 700-1000 kg/cm ² ). By controlling the pressing weight within this range, the thickness compressibility and/or thickness deformation of the bipolar plate can be controlled, so that the bipolar plate has sufficient rigidity. According to some embodiments, the pressing step is performed at normal temperature and the duration of the pressing step is about 0.05-3 minutes (eg, 1-2.5 minutes, 1.5-2.3 minutes).

According to some embodiments, the demoulding step is performed after the pressing step, and the pressed substrate 50 is separated from the mold 300 by vigorously hitting the demoulding base downward, so as to obtain the bipolar plate 10 having the flow channel 12 and the flow channel 13 , as shown in FIG. 3B , wherein the maximum thickness of the bipolar plate 10 as a whole is d2. According to some embodiments, based on the thickness d1 of the substrate 50 before lamination, the thickness compression rate of the bipolar plate 10 is 40-50%, ie (d2/d1)×100%=40-50%. According to some embodiments, the entire manufacturing process takes no more than 5 minutes (such as 1-4 minutes, 2-3 minutes), which greatly shortens the processing time of the bipolar plate.

According to some embodiments, the combined pressure in pounds and the thickness deformation of the bipolar plate have a relationship as shown in Table 1. Wherein, the substrate used in the embodiment has a length of about 5-25 cm, a width of about 5-25 cm, and a height of about 0.5-2 cm, and the pressing time is 1-2 min.

Table 1

Total output force of hydraulic cylinder (kgf)	Pressing pounds (kg/cm 2 )	Thickness deformation (mm)
0	0	0
5,000	312.5	0.803
10,000	625	0.919
15,000	937.5	0.946
20,000	1,250	0.989

According to some embodiments, the mold has a draft angle of 1-10°. According to some embodiments, the mold has a lead/rounded design. The draft angle is the slope of the mold, which is the slope designed on both sides of the cavity for the convenience of mold release. In order to allow the molded product to be ejected from the mold smoothly, the draft angle must be set on the wall in the same direction as the opening and closing of the mold to facilitate demoulding. Since the soft graphite plate is easier to stick to the mold, by setting the draft angle of the mold in the range of 1-10°, the friction force during demolding can be reduced, and the bipolar plate can be completely separated. The mold with traditional right-angle design does not have a draft angle, which makes it difficult to demould later. 4A to 4B are referred to below. Figure 4A is a partial side view of mold 300, according to some embodiments. The angle between the side wall of the mold 300 and its vertical direction is the draft angle s. The mold 300 with the draft angle s can reduce the friction between the mold and the material to be pressed in the vertical direction during demoulding, so that the material to be pressed can be released from the mold more easily. According to some embodiments, the draft angle s may be about 1° to about 10° (eg, about 2° to 8°, about 3° to 6°). According to some embodiments, in addition to the draft angle, the mold 300 also has a lead/round corner design, as shown in FIG. 4B , which further reduces friction.

According to some embodiments, after demoulding, various physical inspections can be performed to confirm that the finished specification of the bipolar plate meets the requirements of the product. For example, a thickness gauge can be used to detect the thickness of the bipolar plate; a depth gauge can be used to detect the depth of the flow channel of the bipolar plate; a caliper can be used to detect the length of the bipolar plate. According to some embodiments, bipolar plates may be bonded for gas leak detection. According to some embodiments, an impedance test and an electrical test may be performed on the bipolar plate.

Due to the fragility of graphite, the processing of bipolar plates made of graphite is difficult and takes a long time. A piece of pure graphite bipolar plate requires several hours of processing time. In contrast, the soft graphite plate in this case has high plasticity, and the processing of the bipolar plate can be completed only by short-term pressing at room temperature (for example, <5min), which greatly reduces the processing time of the bipolar plate And cost, saving at least 90% of the processing time, 90.2% of the processing cost. Moreover, due to the flexibility of the soft graphite plate, compared with the graphite material, it has better shock resistance, and is more suitable for use on vehicles such as electric vehicles. In addition, the price of graphite is relatively high. The material cost of a pure graphite bipolar plate costs thousands of yuan, while the material cost of a bipolar plate made of soft graphite plate is only tens of yuan, saving at least 90% of the material. cost. In addition, the bipolar plate made of flexible graphite plate in this case can pass the airtight test and electrical test to prove that its material will not affect the performance of the fuel cell. That is to say, the bipolar plate formed by pressing the soft graphite plate in this application can save the manufacturing cost and shorten the manufacturing time without reducing the performance of the fuel cell.

Although the metal bipolar plate can be processed quickly through the stamping process, and the cost of the metal is lower than that of graphite, but in the environment of high temperature, high humidity and acidity of the fuel, the metal bipolar plate is prone to oxidation, and additional processing is required ( Plating) anti-oxidation surface treatment, so its durability is low. However, the soft graphite plate used in this case will not have the problem of oxidation, and is more suitable for long-term use products.

In summary, the bipolar plate made of soft graphite plate in this case has the advantages of low cost, fast processing, and good durability.

The components of several embodiments are summarized above so that those skilled in the art can understand the viewpoints of the embodiments of the present invention more easily. Those skilled in the art should understand that they can design or modify other processes and structures based on the embodiments of the present invention, so as to achieve the same purpose or advantages as the embodiments introduced here. Those skilled in the art should also understand that such equivalent processes and structures do not depart from the spirit and scope of the present invention, and they can make various changes without departing from the spirit and scope of the present invention , Replace and Replace.

Although objects have been described in language specific to structural features or methodological acts, it is to be understood that objects of claimed scope are not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing at least some of the claimed scope.

Claims (12)

1. A bipolar plate for a fuel cell, formed by pressing a substrate, characterized in that the substrate is formed of a flexible graphite plate, and the density of the flexible graphite plate is 0.8 to 1.3 g/cm ^3. The carbon content is >98% and the ash content is <2%, and based on the thickness of the substrate before lamination, the thickness compressibility of the bipolar plate is 40-50%.
2. The bipolar plate according to claim 1, characterized in that, based on the thickness of the substrate before lamination, the thickness deformation of the bipolar plate is 0.5-1 mm.
3. The bipolar plate according to claim 1, characterized in that the sulfur content of the flexible graphite plate is <1000ppm and the chlorine content is <50ppm.
4. The bipolar plate according to claim 1, characterized in that, the density of the bipolar plate is 1˜3 g/cm ³ .
5. The bipolar plate according to claim 1, characterized in that, the flow channel depth of the bipolar plate is <1 mm.
6. The bipolar plate according to claim 1, wherein the flow channel of the bipolar plate is a convoluted flow channel, a serpentine flow channel, an interdigitated flow channel, a grid-like flow channel or a parallel flow channel .
7. A fuel cell, characterized in that it comprises:

   Proton exchange membrane;

   A pair of catalyst layers are respectively arranged on both sides of the proton exchange membrane;

   A pair of bipolar plates are respectively arranged on the outside of the pair of catalyst layers, sandwiching the proton exchange membrane and the pair of catalyst layers in the middle, wherein the pair of bipolar plates are right Any bipolar plate from 1 to 6 is required.
8. A method for preparing a bipolar plate for a fuel cell, characterized in that it comprises:

   Die cutting step, cutting the soft graphite plate into a substrate;

   Matching step, placing the substrate in the mold;

   A pressing step of pressing the mold on which the substrate is placed; and

   The demolding step is to separate the laminated substrate from the mold to obtain the bipolar plate, wherein the flexible graphite plate has a density of 0.8-1.3 g/cm ³ and a carbon content of >98 % and the ash content <2%, and based on the thickness of the substrate before lamination, the thickness compressibility of the bipolar plate is 40-50%.
9. The method for preparing a bipolar plate according to claim 8, wherein the mold has a draft angle of 1-10°.
10. The preparation method of the bipolar plate according to claim 8, characterized in that, the pressing weight of the pressing step is 300-1500 kg/cm ² .
11. The preparation method of the bipolar plate according to claim 8, characterized in that, the pressing step is carried out at normal temperature.
12. The method for preparing a bipolar plate according to claim 11, characterized in that the duration of the pressing step is 0.05-3 minutes.

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