Flexible graphite polar plate, preparation method and pressing tool

Abstract

The invention discloses a flexible graphite polar plate, a preparation method and a pressing tool. The first flexible graphite flake and the second flexible graphite flake are obtained through cutting, then the cutting faces of the first flexible graphite flake and the second flexible graphite flake are opposite, the area, corresponding to the ridge forming the flow channel, on the second flexible graphite flake and the first flexible graphite flake are pressed into the prefabricated plate, and the area, corresponding to the area forming the flow channel, in the second flexible graphite flake is removed; and further stamping, dipping and curing the prefabricated plate to obtain the flexible graphite polar plate. According to the flexible graphite bipolar plate prepared by the method, the density consistency of a flow field area is improved, so that the compactness of the runner ridge is improved, stamping cracks are eliminated, the mechanical strength of the plate is improved, the service life of the plate is prolonged, and the performance and the service life of a fuel cell are improved. According to the preparation method, related problems are solved through a process, the cost is lower compared with material end modification, and the preparation method is suitable for popularization and application in the field of flexible graphite bipolar plates of fuel cell stacks.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cells, and in particular relates to a flexible graphite plate, a preparation method and a pressing tool. Background Art

[0002] In today's energy field, fuel cells, as an efficient and clean energy conversion device, have received extensive attention and research. Among them, bipolar plates are one of the key components of fuel cells, which play an important role in separating oxidants and reductants, conducting current, and supporting electrodes.

[0003] Traditional bipolar plate materials mainly include metal and graphite. Although metal bipolar plates have good electrical conductivity and mechanical strength, they have problems such as poor corrosion resistance and high cost. Graphite bipolar plates have excellent electrical conductivity, corrosion resistance and chemical stability, but they are usually brittle and difficult to process, and it is difficult to meet the flexibility requirements in some application scenarios. Flexible graphite bipolar plates have the advantages of good electrical conductivity, excellent corrosion resistance, high flexibility, light weight, and relatively low cost.

[0004] At present, the mainstream in the market uses flexible graphite prefabricated plates with high density uniformity to be directly molded, and then impregnated, cured, and bonded to obtain flexible graphite bipolar plates. However, the fluidity of flexible graphite materials is extremely poor. During the molding process, due to the complex structure of the plate, there is a thickness difference of 1 to 2.5 times between the thinnest and thickest parts. The density of the ridges in the flow field area of ​​the plate after stamping is the lowest, and obvious cracks appear; after impregnation and curing, due to the inconsistent density, there are also large differences in the distribution of the impregnation glue content inside the plate. The higher glue content at the ridges of the flow field further increases the surface resistance of the plate. In addition, the plates prepared in this way also have defects such as poor mechanical strength and short service life.

[0005] For example, the patent application with publication number CN114864983A discloses a flexible graphite plate for fuel cells and its preparation method and application. The preparation method of the flexible graphite plate for fuel cells includes the following steps: 1) rolling the flexible graphite blank to obtain a flexible graphite plate; 2) impregnating the flexible graphite plate in a low-viscosity resin, successively impregnating under negative pressure and normal pressure to obtain a sealed plate; 3) using compressed air to clean the resin on the surface of the sealed plate to obtain a plate with no resin residue on the surface; 4) vacuum drying and curing the plate with no resin residue on the surface to obtain a flexible graphite plate for fuel cells. However, it aims to improve production efficiency and reduce production costs, and does not provide solutions to the above problems.

[0006] For example, the patent application with publication number CN112477245A discloses a method for molding and preparing flexible graphite bipolar plates, which includes the following steps: putting graphite into a mold and then closing the mold; evacuating the mold and maintaining the pressure, and then pressing the mold according to the set pressure; introducing gas into the mold to break the vacuum, opening the mold, and taking out the bipolar plate product as a whole; using a laser to cut along the outer surface of the bipolar plate product to remove the scraps, and thus obtaining a finished bipolar plate. However, it is intended to remove product burrs and completely eliminate the problems such as short circuits caused by subsequent plate burrs in the battery stack, and no solutions are provided for the above problems.

[0007] For example, the patent application with publication number CN114566669A discloses a flexible graphite bipolar plate and its preparation method and application. By using a special mold to perform two pressing operations, the second lateral extrusion force parallel to the direction of the graphite bipolar plate can improve the density of the flow channel shoulder part, solve the problem of large difference in density between the flow channel shoulder and the bottom of the bipolar plate, obtain a fuel cell air-cooled stack graphite bipolar plate with uniform density, improve the mechanical strength of the graphite bipolar plate and the density of the flow channel shoulder, and finally obtain a fuel cell air-cooled stack flexible graphite bipolar plate with high flow channel shoulder density, thereby improving the output performance and service life of the fuel cell. However, it is only applicable to air-cooled stacks, and cannot be implemented for the complex structure of water-cooled stack bipolar plates. Summary of the invention

[0008] The present invention aims at the above technical problems existing in the prior art and provides a flexible graphite plate, a preparation method and a pressing tool.

[0009] The present invention first provides a method for preparing a flexible graphite plate. The flexible graphite plate has a flow field area on one or both sides of the surface. The flow field area is provided with flow channels. There are flow channel ridges between adjacent flow channels. The preparation method comprises the following steps:

[0010] (1) cutting the first flexible graphite sponge board along the thickness direction to obtain two first flexible graphite sheets with the same thickness;

[0011] The length and width of the first flexible graphite sponge board are the same as those of the flexible graphite plate, the thickness is 40-120 mm, and the bulk density is 0.1-1.4 g / cm 3 ;

[0012] (2) cutting the second flexible graphite sponge board along the thickness direction to obtain two second flexible graphite sheets with the same thickness;

[0013] The length and width of the second flexible graphite sponge board are the same as the length and width of the flow field area of ​​the flexible graphite plate, the thickness is 40 to 120 mm, and the body density is 0.1 to 1.4 g / cm 3 ;

[0014] (3) pressing the second flexible graphite sheet and the first flexible graphite sheet into a prefabricated plate, wherein the second flexible graphite sheet is aligned with the position on the first flexible graphite sheet for forming the flow field area, and the cut surfaces of the second flexible graphite sheet and the first flexible graphite sheet are in contact with each other; during pressing, the area on the second flexible graphite sheet corresponding to the formation of the flow channel ridge is pressed with the first flexible graphite sheet into the prefabricated plate, and the area on the second flexible graphite sheet corresponding to the formation of the flow channel is removed;

[0015] (4) Punching, impregnating and curing the prefabricated plate obtained in step (3) to obtain the flexible graphite plate.

[0016] Preferably, in step (3), the length, width and thickness of the prefabricated plate obtained after lamination are consistent with those of the first flexible graphite sheet.

[0017] Preferably, in step (3), the pressing pressure is 2 to 10 MPa.

[0018] Preferably, the length of the flexible graphite plate is 300-500 mm, the width is 100-160 mm, and the thickness is 0.6-1.2 mm;

[0019] The flow field area is 260-450 mm long and 80-145 mm wide;

[0020] The flow channel has a depth of 0.15 to 0.4 mm and a width of 1.5 to 4 mm.

[0021] The invention also provides a flexible graphite plate prepared by the preparation method.

[0022] The present invention also provides a material pressing tool suitable for the preparation method, comprising:

[0023] A first lower template, the top surface of which has a first placement groove for placing the first flexible graphite sheet;

[0024] The second lower template is arranged above the first lower template, and has a second placement groove for placing the second flexible graphite sheet on the top surface, and the second placement groove is directly opposite to the middle position of the first placement groove; the bottom surface of the second placement groove has a ridge avoidance opening that penetrates the second lower template, and the number, position and size of the ridge avoidance openings correspond to the number, position and size of the flow channel ridges formed after the second flexible graphite sheet and the first flexible graphite sheet are pressed together;

[0025] The punch is arranged above the second lower template, and the punch is provided with punching sheets whose number, position and size correspond to the back ridge avoidance openings one by one.

[0026] Preferably, a stripping plate is further provided between the second lower template and the punch, and the stripping plate is provided with stripping holes whose number, position and size correspond to those of the punching sheet;

[0027] During the pressing, the punching sheet passes through the stripping hole and acts on the second flexible graphite sheet placed in the second placement groove.

[0028] More preferably, the bottom surface of the second lower template is provided with a first limiting groove having the same length and width as the first placement groove, and the sum of the thickness of the first limiting groove and the first placement groove is the same as the thickness of the first flexible graphite sheet;

[0029] Alternatively, the thickness of the first placement groove is the same as the thickness of the first flexible graphite sheet.

[0030] More preferably, the bottom surface of the stripping plate is provided with a second limiting groove having the same length and width as the second placement groove, and the sum of the thickness of the second limiting groove and the second placement groove is the same as the thickness of the second flexible graphite sheet;

[0031] Alternatively, the thickness of the second placement groove is the same as the thickness of the second flexible graphite sheet.

[0032] More preferably, a vertical guide rod is further provided on the first lower template, and a guide hole for cooperating with the guide rod is respectively provided on the second lower template, the stripping plate and the punch;

[0033] The guide rod is provided with a return spring between the first lower template and the second lower template, between the second lower template and the stripper plate, and between the stripper plate and the punch. The first lower template, the second lower template, the stripper plate and the punch are each provided with an accommodating groove at the corresponding position for accommodating the compressed return spring during pressing.

[0034] Using a reset spring as a reset mechanism can make the second lower template, the stripper plate and the punch automatically reset after pressing once. Of course, other active reset mechanisms can also be used, such as using a cylinder to control the reset of each component. Of course, the reset spring also has another function of controlling the components to play a buffering role when pressing down.

[0035] The accommodating groove can ensure that the second lower template and the first lower template, and the stripper plate and the second lower template can fit better during pressing.

[0036] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0037] (1) The flexible graphite bipolar plate prepared by the present invention improves the regional density consistency of the flow field, thereby not only improving the density of the flow channel ridges and eliminating stamping cracks, but also improving the mechanical strength and service life of the plate, thereby improving the performance and life of the fuel cell.

[0038] (2) The preparation method described in the present invention solves related problems through a process, has lower cost than material-side modification, and is suitable for promotion and application in the field of flexible graphite bipolar plates for fuel cell stacks. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the three-dimensional structure of the flexible graphite electrode.

[0040] Figure 2 for Figure 1 A is a partial enlarged view.

[0041] Figure 3 This is a schematic diagram of the three-dimensional structure of the material pressing tooling of this application.

[0042] Figure 4 This is a schematic diagram of the side view structure of the pressing tooling of this application from the first perspective.

[0043] Figure 5 for Figure 4 Cross-sectional view along direction BB.

[0044] Figure 6 This is a schematic diagram of the side view structure of the pressing tooling of this application from the second viewing angle.

[0045] Figure 7 for Figure 6 Cross-sectional view along CC direction.

[0046] Figure 8 It is a cross-sectional view of the first lower template, the second lower template, and the stripping plate.

[0047] Fig. 9 It is a schematic diagram of the three-dimensional structure of the second lower template.

[0048] Fig.10 It is a schematic diagram of the three-dimensional structure of the stripping plate.

[0049] Fig.11 It is a schematic diagram of the three-dimensional structure of the punch.

[0050] Fig.12 This is an electron microscope image of the flow channel ridge of the flexible graphite plate prepared in Example 1, wherein: Fig.12 A and B in the figure are different magnifications.

[0051] Fig.13 This is an electron microscope image of the flow channel ridge of the flexible graphite plate prepared in Comparative Example 1, wherein: Fig.13 A and B in the figure are different magnifications.

[0052] Reference numerals:

[0053] Flexible graphite plate 1, flow field area 11, flow channel 12, flow channel ridge 13, hydrogen inlet channel 14, hydrogen outlet channel 15, air inlet channel 16, air outlet channel 17, cooling inlet channel 18, cooling outlet channel 19,

[0054] The first flexible graphite sheet 2,

[0055] The second flexible graphite sheet 3,

[0056] The first lower template 4, the first placement groove 41,

[0057] The second lower template 5, the second placement groove 51, the back avoidance opening 52, the first limiting groove 53,

[0058] Stripping plate 6, stripping hole 61, second limiting groove 62,

[0059] Punch 7, punching sheet 71,

[0060] Guide rod 8. DETAILED DESCRIPTION

[0061] like Figure 1 and Figure 2 As shown, the flexible graphite plate 1 prepared by the present invention has a flow field area 11 on one or both sides of the surface, and the flow field area 11 is provided with a flow channel 12, and a flow channel ridge 13 is provided between adjacent flow channels 12. The two ends of the flexible graphite plate 1 are provided with a hydrogen inlet channel 14, a hydrogen outlet channel 15, an air inlet channel 16, an air outlet channel 17, a cooling inlet channel 18 and a cooling outlet channel 19.

[0062] The flexible graphite plate 1 has a length of 300-500 mm, a width of 100-160 mm, and a thickness of 0.6-1.2 mm;

[0063] The flow field area 11 has a length of 260 to 450 mm and a width of 80 to 145 mm;

[0064] The flow channel 12 has a depth of 0.15 to 0.4 mm and a width of 1.5 to 4 mm.

[0065] A method for preparing a flexible graphite plate, the method comprising the following steps:

[0066] (1) Cut the first flexible graphite sponge board along the thickness direction to obtain two first flexible graphite sheets with the same thickness.

[0067] The length and width of the first flexible graphite sponge board are the same as those of the flexible graphite plate, the thickness is 40-120 mm, and the bulk density is 0.1-1.4 g / cm 3 .

[0068] (2) Cut the second flexible graphite sponge board along the thickness direction to obtain two second flexible graphite sheets with the same thickness.

[0069] The length and width of the second flexible graphite sponge board are the same as the length and width of the flow field area of ​​the flexible graphite plate, the thickness is 40 to 120 mm, and the body density is 0.1 to 1.4 g / cm 3 .

[0070] (3) Pressing the second flexible graphite sheet and the first flexible graphite sheet into a prefabricated plate, wherein the second flexible graphite sheet is aligned with the position on the first flexible graphite sheet for forming the flow field area, and the cut surfaces of the second flexible graphite sheet and the first flexible graphite sheet are in contact with each other; during pressing, the area on the second flexible graphite sheet corresponding to the formation of the flow channel ridge is pressed with the first flexible graphite sheet into the prefabricated plate, and the area on the second flexible graphite sheet corresponding to the formation of the flow channel is removed.

[0071] The length, width and thickness of the prefabricated plate obtained after lamination are consistent with those of the first flexible graphite sheet.

[0072] The pressing pressure is 2 to 10 MPa.

[0073] (4) Punching, impregnating and curing the prefabricated plate obtained in step (3) to obtain the flexible graphite plate. The punching, impregnation and curing of the prefabricated plate can be carried out using conventional solutions in the prior art, and no improvements are made in this application.

[0074] In step (1) and step (2), the cutting can be performed using a cutting device. After the cutting device sets upper and lower limits on the flexible graphite sponge board to be cut, it can be cut from the middle using a diamond yarn of φ0.1 mm, so that it can be evenly cut into two flexible graphite sheets in the thickness direction. The flexible graphite sponge board has a low density and is relatively soft, so it can be cut relatively easily. In addition, the flexible graphite sponge board can be directly purchased commercially.

[0075] like Figure 3 to Figure 11 As shown, a pressing tool includes a first lower mold plate 4, a second lower mold plate 5, a stripping plate 6 and a punch 7.

[0076] The top surface of the first lower template 4 has a first placement groove 41 for placing the first flexible graphite sheet 2. The first placement groove 41 limits the first flexible graphite sheet 2, on the one hand ensuring the accuracy of the pressing position, and on the other hand serving as a cavity during pressing.

[0077] The second lower template 5 is arranged above the first lower template 4, and the top surface of the second lower template 5 has a second placement groove 51 for placing the second flexible graphite sheet 3, and the second placement groove 51 is opposite to the middle position of the first placement groove 41; the bottom surface of the second placement groove 1 has a ridge avoidance opening 52 that penetrates the second lower template 5, and the number, position and size of the ridge avoidance opening 52 correspond to the number, position and size of the flow channel ridge 13 formed after the second flexible graphite sheet 3 and the first flexible graphite sheet 2 are pressed together.

[0078] In the structure shown in the figure, the bottom surface of the second lower template 4 is provided with a first limiting groove 53 having the same length and width as the first placement groove 41, and the sum of the thickness of the first limiting groove 53 and the first placement groove 41 is the same as the thickness of the first flexible graphite sheet 2. In another embodiment, the thickness of the first placement groove 41 is the same as the thickness of the first flexible graphite sheet 2, so that there is no need to additionally provide the first limiting groove 53 on the bottom surface of the second lower template 4, and the first flexible graphite sheet 2 can be limited only by the first placement groove 41.

[0079] The punch 7 is disposed above the second lower mold plate 5 , and is provided with punching pieces 71 , the number, position and size of which correspond one to one with the back ridge avoidance openings 52 .

[0080] A stripper plate 6 is provided between the second lower template 5 and the punch 7. The stripper plate 6 is provided with stripper holes 61 whose number, position and size correspond to the punching sheet 71. During pressing, the punching sheet 71 passes through the stripper holes 61 and acts on the second flexible graphite sheet 3 placed in the second placement groove 51.

[0081] In the structure shown in the figure, the bottom surface of the stripping plate 6 is provided with a second limiting groove 62 that is consistent with the length and width of the second placement groove 51, and the sum of the thickness of the second limiting groove 62 and the second placement groove 51 is the same as the thickness of the second flexible graphite sheet 3. In another embodiment, the thickness of the second placement groove 51 is the same as the thickness of the second flexible graphite sheet 3, so that there is no need to additionally set the second limiting groove 62 on the bottom surface of the stripping plate 6, and the second flexible graphite sheet 3 can be limited only by the second placement groove 51.

[0082] The first lower template 4 is also provided with a vertical guide rod 8. In the structure shown in the figure, the guide rod 8 includes four guide rods arranged at four corners, and the second lower template 5, the stripping plate 6 and the punch 7 are respectively provided with a guide hole for cooperating with the guide rod 8.

[0083] The guide rod 8 is provided with a return spring between the first lower template 4 and the second lower template 5, between the second lower template 5 and the stripper plate 6, and between the stripper plate 6 and the punch 7 (the return spring is sleeved on the guide rod 8, and the return spring is not drawn in the figure). Using the return spring as a return mechanism can make the second lower template 5, the stripper plate 6 and the punch 7 automatically return to their original position after being pressed once. Of course, other active return mechanisms can also be used, such as using a cylinder to control the return of each component. Of course, the return spring also has another function of controlling the components to act as a buffer when they are pressed down.

[0084] The first lower template 4, the second lower template 5, the stripper plate 6 and the punch 7 are each provided with a receiving groove (not shown in the figure) for receiving the compressed return spring during pressing. The receiving groove can ensure that the second lower template 5 and the first lower template 4, and the stripper plate 6 and the second lower template 5 can fit better during pressing.

[0085] When the material pressing tool of the present application is used, the cut first flexible graphite sheet 2 is first placed in the first placement groove 41 of the first lower template 4, with the cutting surface facing up during cutting. The cut second flexible graphite sheet 3 is placed in the second placement groove 51 of the second lower template 5, with the cutting surface facing down during cutting. During the stamping process, the punch 7 moves downward, driving the stripping plate 6 and the second lower template 5 to move downward. Finally, the stamping sheet 71 stamps the corresponding part of the second flexible graphite sheet 3 onto the first flexible graphite sheet 2, and compacts it to the same thickness as the first flexible graphite sheet 2 at the beginning, while the second flexible graphite sheet 3 between adjacent stamping sheets 71 is not pressed into the first flexible graphite sheet 2. After the stamping is completed, the body density of the area on the first flexible graphite sheet 2 corresponding to the second flexible graphite sheet 3 pressed in increases, and these areas are subsequently used to form the flow channel ridge when the prefabricated plate is stamped to form a flexible graphite plate.

[0086] Example 1

[0087] Now we want to prepare a flexible graphite plate with double-sided flow channels. The plate length is 400mm, the width is 100mm, the thickness (the thickest part of the plate, that is, the non-flow field area or the flow channel ridge in the flow field area) is 1mm, the thinnest part is 0.4mm, the flow field area length is 320mm, the flow field area width is 85mm, and the average density of the flow field area before impregnation is required to be 1.0g / cm 3 .

[0088] Select the density as 0.1g / cm 3 The graphite preformed plate (the first flexible graphite sponge board) has a length of 400 mm, a width of 100 mm, and a thickness of 81 mm. The cutting device uses a diamond yarn with a diameter of φ0.1 mm to cut it into two new flexible graphite preformed plates (the first flexible graphite sheets) with an average thickness of about 40 mm.

[0089] Select the density as 0.1g / cm 3 The graphite preformed plate (the second flexible graphite sponge board) is 320 mm in length, 85 mm in width and 121 mm in thickness. The cutting device uses a diamond yarn with a diameter of φ0.1 mm to cut it into two new flexible graphite preformed plates (the second flexible graphite sheets) with an average thickness of about 60 mm.

[0090] Use a pressing tool for pressing. Place the cut 40mm thick flexible graphite prefabricated plate (first flexible graphite sheet) into the first placement groove of the first lower template with the cut surface facing upward, and place another cut 60mm thick flexible graphite prefabricated plate (second flexible graphite sheet) into the second placement groove of the second lower template with the cut surface facing downward, and set a pressure of 2Mpa to press into a new flexible graphite prefabricated plate with a thickness of 40mm.

[0091] A stamping, impregnation and curing process was used to prepare a flexible graphite plate with a size of 400 mm in length × 100 mm in width × 1 mm in thickness.

[0092] The performance of the prepared flexible graphite plate was tested, and the contact resistance was 0.6Mpa@3.5mΩ.cm 2 , conductivity 400mΩ.cm, bending strength 22Mpa. The electron microscope image of the flow channel ridge of the flexible graphite plate is as follows Fig.12 shown.

[0093] Example 2

[0094] Now we want to prepare a flexible graphite plate with a single-sided flow channel. The plate length is 400mm, the width is 100mm, the thickness is 0.8mm, the thinnest part is 0.4mm, the flow field area length is 320mm, the flow field area width is 85mm, and the average density of the flow field area before impregnation is required to be 1.0g / cm 3 .

[0095] Select the density as 0.1g / cm 3 The graphite preformed plate (the first flexible graphite sponge board) has a length of 400 mm, a width of 100 mm, and a thickness of 81 mm. The cutting device uses a diamond yarn with a diameter of φ0.1 mm to cut it into two new flexible graphite preformed plates (the first flexible graphite sheets) with an average thickness of about 40 mm.

[0096] Select the density as 0.1g / cm 3 The graphite preformed plate (the second flexible graphite sponge board) is 320 mm in length, 85 mm in width and 81 mm in thickness. The cutting device uses a diamond yarn with a diameter of φ0.1 mm to cut it into two new flexible graphite preformed plates (the second flexible graphite sheets) with an average thickness of about 40 mm.

[0097] Use a pressing tool for pressing. Place the cut 40mm thick flexible graphite prefabricated plate (first flexible graphite sheet) into the first placement groove of the first lower template with the cut surface facing upward, and place another cut 40mm thick flexible graphite prefabricated plate (second flexible graphite sheet) into the second placement groove of the second lower template with the cut surface facing downward, and set a pressure of 2Mpa to press into a new flexible graphite prefabricated plate with a thickness of 40mm.

[0098] The flexible graphite plate with the dimensions of 400mm×100mm×0.8mm was prepared by stamping, impregnation and curing. The contact resistance is 0.6Mpa@2.8mΩ.cm 2 , conductivity 400mΩ.cm, flexural strength 30Mpa.

[0099] Comparative Example 1

[0100] Now we want to prepare a flexible graphite plate with double-sided flow channels. The plate length is 400mm, the width is 100mm, the thickness is 1mm, the thinnest part is 0.4mm, the flow field area length is 320mm, the flow field area width is 85mm, and the average density of the flow field area before impregnation is required to be 1.0g / cm 3 .

[0101] Use a pressing tool for pressing. Select a length of 400mm, a width of 100mm, a thickness of 40mm, and a density of 0.1g / cm 3 The flexible graphite prefabricated plate is placed in the first placement groove of the first lower template, and the length, width, thickness and density of the prefabricated plate are selected to be 320 mm, 85 mm, 60 mm and 0.1 g / cm 3 The flexible graphite prefabricated plate is placed in the second placement groove of the second lower template, and the pressure is set to 2Mpa to press into a new flexible graphite prefabricated plate with a thickness of 40mm.

[0102] A flexible graphite monopolar plate with dimensions of 400 mm in length × 100 mm in width × 1 mm in thickness was prepared using stamping, impregnation and curing processes.

[0103] Compared with Examples 1 and 2, after the flexible graphite plate was immersed in pure water for 7 days, it was found that the plate flow channel position and the two prefabricated plates were separated at the pressing point. Fig.13 shown.

[0104] Comparative Example 2

[0105] Now we want to prepare a flexible graphite plate with a single-sided flow channel. The plate length is 400mm, the width is 100mm, the thickness is 0.8mm, the thinnest part is 0.4mm, the flow field area length is 320mm, the flow field area width is 85mm, and the average density of the flow field area before impregnation is required to be 1.0g / cm 3 .

[0106] Use a pressing tool for pressing. Select a length of 400mm, a width of 100mm, a thickness of 40mm, and a density of 0.1g / cm 3 The flexible graphite prefabricated plate is placed in the first placement groove of the first lower template, and the length, width, thickness and density of the prefabricated plate are selected to be 320 mm, 85 mm, 40 mm and 0.1 g / cm 3 The flexible graphite prefabricated plate is placed in the second placement groove of the second lower template, and the pressure is set to 2Mpa to press into a new flexible graphite prefabricated plate with a thickness of 40mm.

[0107] A stamping, impregnation and curing process was used to prepare a flexible graphite plate with a size of 400 mm in length × 100 mm in width × 0.8 mm in thickness.

[0108] Compared with Examples 1 and 2, after the flexible graphite plate was immersed in pure water for 7 days, separation was found at the plate flow channel and at the joint of the two prefabricated plates.

[0109] Comparative Example 3

[0110] Now we want to prepare a flexible graphite plate with double-sided flow channels. The plate length is 400mm, the width is 100mm, the thickness is 1mm, the thinnest part is 0.4mm, the flow field area length is 320mm, the flow field area width is 85mm, and the average density of the flow field area before impregnation is required to be 1.0g / cm 3 .

[0111] Through dimensional measurement, the surface area ratio of the ridge and the groove in the flow field area is 0.6:0.4, the thickness ratio is 1:0.4, and the length is 400mm, the width is 100mm, the thickness is 62mm, and the density is 0.1g / cm 3 Flexible graphite prefabricated plate.

[0112] A flexible graphite plate with a size of 400 mm×100 mm×1 mm was prepared using a stamping, impregnation and curing process.

[0113] The density of the flexible graphite plate before impregnation is 0.62g / cm 3 , density at groove 1.55g / cm 3 , finished product contact resistance 0.6Mpa@5mΩ.cm 2 , conductivity 330mΩ.cm, flexural strength 18Mpa.

[0114] By comparing with Example 1, it is found that the density uniformity of the electrode plate prepared in Comparative Example 3 is quite different, so that the distribution difference of the amount of impregnation glue is relatively large, so that the contact resistance, conductivity and bending strength are all weaker than those of the electrode plate prepared in Example 1.

[0115] Comparative Example 4

[0116] Now we want to prepare a flexible graphite plate with double-sided flow channels. The plate length is 400mm, the width is 100mm, the thickness is 0.8mm, the thinnest part is 0.4mm, the flow field area length is 320mm, the flow field area width is 85mm, and the average density of the flow field area before impregnation is required to be 1.0g / cm 3 .

[0117] Through dimensional measurement, the area ratio of the flow field ridge to the groove is 0.6:0.4, the thickness ratio is 0.8:0.4, and the length is 400 mm, the width is 100 mm, and the surface density is 58 mg / cm 2 Flexible graphite prefabricated plate.

[0118] A flexible graphite plate with a size of 400 mm×100 mm×1 mm was prepared using a stamping, impregnation and curing process.

[0119] The density of the flexible graphite plate before impregnation is 0.725g / cm 3 , density at groove 1.45g / cm 3 , finished product contact resistance 0.6Mpa@4mΩ.cm 2 , conductivity 350mΩ.cm, flexural strength 22Mpa.

[0120] By comparing with Example 2, it is found that the density uniformity of the electrode plate prepared in Comparative Example 4 is quite different, so that the distribution difference of the amount of impregnation glue is relatively large, so that the contact resistance, conductivity and bending strength are all weaker than those of the electrode plate prepared in Example 2.

Claims

1. A method for preparing a flexible graphite plate, wherein one side or both sides of the flexible graphite plate have a flow field area, the flow field area is provided with flow channels, and there are flow channel ridges between adjacent flow channels, characterized in that: The preparation method comprises the following steps: (1) cutting the first flexible graphite sponge board along the thickness direction to obtain two first flexible graphite sheets with the same thickness; The length and width of the first flexible graphite sponge board are the same as those of the flexible graphite plate, the thickness is 40-120 mm, and the bulk density is 0.1-1.4 g / cm 3 ; (2) cutting the second flexible graphite sponge board along the thickness direction to obtain two second flexible graphite sheets with the same thickness; The length and width of the second flexible graphite sponge board are the same as the length and width of the flow field area of ​​the flexible graphite plate, the thickness is 40 to 120 mm, and the body density is 0.1 to 1.4 g / cm 3 ; (3) pressing the second flexible graphite sheet and the first flexible graphite sheet into a prefabricated plate, wherein the second flexible graphite sheet is aligned with the position on the first flexible graphite sheet for forming the flow field area, and the cut surfaces of the second flexible graphite sheet and the first flexible graphite sheet are in contact with each other; during pressing, the area on the second flexible graphite sheet corresponding to the formation of the flow channel ridge is pressed with the first flexible graphite sheet into the prefabricated plate, and the area on the second flexible graphite sheet corresponding to the formation of the flow channel is removed; (4) Punching, impregnating and curing the prefabricated plate obtained in step (3) to obtain the flexible graphite plate.

2. The method for preparing the flexible graphite plate according to claim 1, characterized in that: In step (3), the length, width and thickness of the prefabricated plate obtained after pressing are consistent with those of the first flexible graphite sheet.

3. The method for preparing the flexible graphite plate according to claim 1, characterized in that: In step (3), the pressing pressure is 2 to 10 MPa.

4. The method for preparing the flexible graphite plate according to claim 1, characterized in that: The flexible graphite plate has a length of 300-500 mm, a width of 100-160 mm, and a thickness of 0.6-1.2 mm; The flow field area is 260-450 mm long and 80-145 mm wide; The flow channel has a depth of 0.15 to 0.4 mm and a width of 1.5 to 4 mm.

5. The flexible graphite plate prepared by the preparation method according to any one of claims 1 to 4.

6. A material pressing tool suitable for the preparation method according to any one of claims 1 to 4, characterized in that: include: A first lower template, the top surface of which has a first placement groove for placing the first flexible graphite sheet; The second lower template is arranged above the first lower template, and has a second placement groove for placing the second flexible graphite sheet on the top surface, and the second placement groove is directly opposite to the middle position of the first placement groove; the bottom surface of the second placement groove has a ridge avoidance opening that penetrates the second lower template, and the number, position and size of the ridge avoidance openings correspond to the number, position and size of the flow channel ridges formed after the second flexible graphite sheet and the first flexible graphite sheet are pressed together; The punch is arranged above the second lower template, and the punch is provided with punching sheets whose number, position and size correspond to the back ridge avoidance openings one by one.

7. The material pressing tool according to claim 6, characterized in that: A stripping plate is also provided between the second lower template and the punch, and the stripping plate is provided with stripping holes whose number, position and size correspond to those of the punching sheet; During the pressing, the punching sheet passes through the stripping hole and acts on the second flexible graphite sheet placed in the second placement groove.

8. The material pressing tool according to claim 7, characterized in that: The bottom surface of the second lower template is provided with a first limiting groove having the same length and width as the first placement groove, and the sum of the thickness of the first limiting groove and the first placement groove is the same as the thickness of the first flexible graphite sheet; Alternatively, the thickness of the first placement groove is the same as the thickness of the first flexible graphite sheet.

9. The material pressing tool according to claim 7, characterized in that: The bottom surface of the stripping plate is provided with a second limiting groove having the same length and width as the second placement groove, and the sum of the thickness of the second limiting groove and the second placement groove is the same as the thickness of the second flexible graphite sheet; Alternatively, the thickness of the second placement groove is the same as the thickness of the second flexible graphite sheet.

10. The material pressing tool according to claim 7, characterized in that: The first lower template is also provided with a vertical guide rod, and the second lower template, the stripper plate and the punch are each provided with a guide hole for cooperating with the guide rod; The guide rod is provided with a return spring between the first lower template and the second lower template, between the second lower template and the stripper plate, and between the stripper plate and the punch. The first lower template, the second lower template, the stripper plate and the punch are each provided with an accommodating groove at the corresponding position for accommodating the compressed return spring during pressing.

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