Metal graphite composite bipolar plate and preparation method thereof

Abstract

The application provides a metal graphite composite bipolar plate and a preparation method thereof, and solves the technical problems of complex manufacturing process and insufficient overall rigidity in the prior art; the bipolar plate is provided with a graphite layer, an intermediate layer and a base layer, and the bipolar plate is sequentially metallurgically connected from top to bottom with the graphite layer, the intermediate layer and the base layer, wherein the graphite layer is a flexible graphite paper, the intermediate layer is a copper-nickel laminated foil, the copper-nickel laminated foil is sequentially a copper plate, a nickel plate from top to bottom, and the base layer is a titanium thin plate; the preparation method of the bipolar plate comprises the following steps: S1, pretreating the flexible graphite paper, S2, cleaning the surfaces of the copper plate, the nickel plate and the titanium thin plate; S3, stacking and die forming the flexible graphite paper after the pretreatment of step S1, and the copper plate, the nickel plate and the titanium thin plate after the surface cleaning treatment of step S2 from top to bottom, keeping the mold closed and heating to 800-850 DEG C, the mold closing pressure is 5-10 MPa, after keeping the pressure for a period of time, a metal graphite composite bipolar plate is obtained; and the metal graphite composite bipolar plate can be widely applied in the field of fuel cell bipolar plate precision manufacturing technology.

Description

Technical Field

[0001] The present application relates to the technical field of precision manufacturing of fuel cell bipolar plates, and in particular to a metal-graphite composite bipolar plate and a preparation method thereof. Background Art

[0002] With the development of hydrogen energy technology, fuel cells, as a clean energy technology, have garnered widespread attention and application. In fuel cell systems, bipolar plates, as a core component, perform multiple functions, including electrical conductivity, thermal conductivity, and gas distribution. The material properties of bipolar plates directly impact the efficiency, lifespan, and cost of fuel cells. Bipolar plate materials must be corrosion-resistant, electrically conductive, possess good mechanical strength, be inexpensive, and easily mass-produced.

[0003] Currently, commonly used bipolar plate materials mainly include graphite, metal, and composite materials. Graphite bipolar plates are widely used in medium- and low-temperature fuel cells due to their excellent electrical conductivity, good corrosion resistance, and high mechanical strength. A Chinese invention patent, publication number CN109755603 A, discloses an ultra-thin metal sheet sandwich flexible graphite bipolar plate and its preparation method. By adding a metal sheet to the raw material of the flexible graphite plate, an ultra-thin flexible graphite hydrogen-oxygen plate is prepared by molding. While maintaining the performance of the original flexible graphite plate, the strength of the bipolar plate is improved and the thickness of the bipolar plate is reduced. However, this method still has inherent problems with graphite bipolar plates, such as a complex manufacturing process and insufficient overall rigidity. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies of the above-mentioned technology and provide a metal-graphite composite bipolar plate and a preparation method thereof, so as to simplify the manufacturing process and improve the strength of the metal-graphite composite bipolar plate.

[0005] To this end, the present invention provides a metal-graphite composite bipolar plate, which is provided with a graphite layer, an intermediate layer and a base layer; the bipolar plate is provided with a graphite layer, an intermediate layer and a base layer metallurgically connected from top to bottom; wherein the graphite layer is flexible graphite paper; the intermediate layer is a copper-nickel composite foil, and the copper-nickel composite foil is copper plate and nickel plate from top to bottom; and the base layer is a titanium thin plate.

[0006] The method for preparing the metal-graphite composite bipolar plate as described above comprises the following steps:

[0007] Step S1. The flexible graphite paper is pretreated and set aside;

[0008] Step S2. Clean the surfaces of the copper plate, nickel plate, and titanium plate and set aside;

[0009] Step S3. The flexible graphite paper pretreated in step S1 and the copper plate, nickel plate, and titanium sheet surface-cleaned in step S2 are stacked from top to bottom and compression molded. The mold is kept closed and heated to 800-850°C with a clamping pressure of 5-10 MPa. After maintaining the pressure for a period of time, a metal-graphite composite bipolar plate is obtained.

[0010] Preferably, in step S3, the forming device used is provided with an upper mold mechanism and a lower mold mechanism, the upper mold mechanism is provided with an upper mold base plate and an upper mold plate, and micro-protrusions are provided below the lower surface of the upper mold plate; the lower mold mechanism is provided with a lower mold base plate and a lower mold plate, and micro-grooves are provided on the upper surface of the lower mold plate. The upper mold plate and the lower mold plate are arranged relative to each other up and down, and after the mold is closed, the micro-protrusions and micro-grooves are matched to form a microchannel.

[0011] The forming device is also provided with a stepped punch mechanism, which is provided with a pad and multiple punch assemblies; each punch assembly is provided with a segmented punch, a pressure rod, a first spring, and a second spring; the lower part of the segmented punch is provided with a micro-protrusion, and the upper part of the segmented punch is provided with a first blind hole with an opening facing upward; the opening of the first blind hole is provided with a hole edge extending inward, and a first spring is installed in the first blind hole.

[0012] The upper template is provided with a plurality of longitudinal through holes spaced apart from left to right, and each longitudinal through hole is correspondingly installed with a punch assembly; the segmented punch is arranged in the longitudinal through hole, and the two are slidably connected; the pad covers the longitudinal through hole, and the top end of the pressure rod is provided with a first stop, and the rod body of the pressure rod passes downward through the second spring and the pad and then enters the longitudinal through hole, and the bottom end of the pressure rod is provided with a second stop, and the second stop is connected to the first spring. Under the action of the elastic force of the first spring, the second stop is movably engaged in the edge of the hole.

[0013] The lengths of the rods of the plurality of pressure rods exposed from the pad are distributed in a step-down manner from left to right.

[0014] The present invention provides a metal-graphite composite bipolar plate and a preparation method thereof, which have the following beneficial effects:

[0015] (1) Copper-nickel composite foil is used as the intermediate layer to connect the flexible graphite paper and the substrate. Through high-temperature pressure treatment, metallurgical connections such as carbides and metal compounds are formed between the flexible graphite paper and the copper plate, and between the nickel plate and the titanium sheet, which significantly enhances the connection strength between the graphite paper and the metal substrate.

[0016] (2) Copper-nickel composite foil is used as the intermediate layer. The electrode potential of the copper layer is higher than that of the carbon electrode, which will hinder the occurrence of galvanic corrosion.

[0017] (3) When the cathode plate of the bipolar plate is in an oxygen-rich environment, copper is prone to oxidative corrosion. At this time, the protective layer formed by the nickel plate can effectively prevent the further expansion of corrosion and fully protect the substrate surface.

[0018] (5) The flexible graphite paper does not need to be bonded with the intermediate layer before forming, which reduces the risk of breakage of the flexible graphite paper during the forming process, and the preparation of the metal-graphite composite bipolar plate can be completed in one set of mold and one process, thereby reducing the preparation process and improving the production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0020] Figure 1 FIG. 1 is a cross-sectional structure diagram of the metal-graphite composite bipolar plate of the present application;

[0021] Figure 2 FIG. 2 is a structure diagram of the enlarged view of part A shown in FIG. 1; Figure 1

[0022] Figure 3 FIG. 3 is a structure diagram of the enlarged view of part B shown in FIG. 1;

[0023] Figure 4 FIG. 4 is a structure diagram of the enlarged view of part C shown in FIG. 1; Figure 3

[0024] Figure 5 FIG. 5 is a structure diagram of the enlarged view of part D shown in FIG. 1; Figure 3

[0025] Figure 6 FIG. 6 is a structure diagram of the partial cross-sectional view of the mold pressing forming device in the mold opening state of the present application;

[0026] Figure 7 FIG. 7 is a structure diagram of the partial cross-sectional view of the mold pressing forming device in the mold closing process of the present application;

[0027] Figure 8 FIG. 8 is a structure diagram of the partial cross-sectional view of the mold pressing forming device in the mold closing state of the present application.

[0028] ​​​Markings in the figure: 1. Upper die base plate, 2. Upper die plate, 3. Micro-protrusion, 4. Lower die base plate, 5. Lower die plate, 6. Micro-groove, 7. Pad, 8. Punch assembly, 9. Segmented punch, 10. Press rod, 11. First spring, 12. Second spring, 13. First blind hole, 14. Hole edge, 15. Longitudinal through hole, 16. First stop, 17. Second stop, 18. First guide post, 19. Position limiting support device, 20. Position limiting support rod, 21. Second blind hole, 22. Third spring, 23. Third stop, 24. Sheet workpiece, 25. Flexible graphite paper, 26. Copper-nickel composite foil, 27. Titanium sheet, 261. Copper plate, 262. Nickel plate. DETAILED DESCRIPTION

[0029] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining this application and are not intended to limit this application. The methods used in this invention are conventional methods unless otherwise specified; the raw materials and devices used are conventional commercially available products unless otherwise specified.

[0030] Example 1

[0031] Depend on Figure 1 、 Figure 2 As shown, the present invention provides a metal-graphite composite bipolar plate, which is provided with a graphite layer, an intermediate layer and a base layer; the characteristic is that the bipolar plate is metallurgically connected with a graphite layer, an intermediate layer and a base layer in sequence from top to bottom; wherein the graphite layer is a flexible graphite paper 25; the intermediate layer is a copper-nickel composite foil 26, and the copper-nickel composite foil 26 is copper plate 261 and nickel plate 262 in sequence from top to bottom; and the base layer is a titanium thin plate 27.

[0032] On the one hand, copper-nickel composite foil 26 is used as an intermediate layer to connect the flexible graphite paper 25 and the substrate. Metallurgical connections such as carbides and metal compounds are formed between the flexible graphite paper 25 and the copper plate 261, and between the nickel plate 262 and the titanium sheet 27, which significantly enhances the connection strength between the graphite paper and the metal substrate.

[0033] On the other hand, when the copper-nickel clad foil 26 is used as the intermediate layer, the electrode potential of the copper layer is higher than that of the carbon electrode, which will hinder the occurrence of galvanic corrosion.

[0034] Third, when the cathode plate of the bipolar plate is in an oxygen-rich environment, copper is prone to oxidative corrosion. At this time, the protective layer formed by the nickel plate 262 can effectively prevent the further expansion of corrosion and fully protect the substrate surface.

[0035] Fourth, there is no adhesive layer between the flexible graphite paper 25 and the intermediate layer, as in conventional techniques. This reduces the risk of the flexible graphite paper 25 breaking during the forming process. For example, prior art publication CN 110212212 A discloses a bipolar plate with graphite composited on one side of a metal plate and a preparation method. However, bonding the flexible graphite paper 25 to the metal plate before compression molding can easily lead to breakage of the flexible graphite paper 25 during the forming process, affecting its conductivity and corrosion resistance.

[0036] Preferably, the thickness of the flexible graphite paper 25 is 0.02 to 0.05 mm, the thickness of the copper-nickel clad foil 26 is 0.05 to 0.15 mm, and the thickness of the titanium sheet 27 is 0.08 to 0.1 mm. The use of the extremely thin flexible graphite paper 25 and the extremely thin metal intermediate layer of copper-nickel clad foil 26 increases the thickness by only 0.1 to 0.15 mm compared to the prior art, significantly improving the corrosion resistance of the metal bipolar plate, eliminating the need for a conductive, corrosion-resistant coating on the metal surface, and reducing the surface treatment cost of the metal bipolar plate.

[0037] Example 2

[0038] The present invention provides a method for preparing the metal-graphite composite bipolar plate described in Example 1, comprising the following steps:

[0039] Step S1. The flexible graphite paper 25 is pretreated and set aside;

[0040] Step S2. Clean the surfaces of the copper plate 261, the nickel plate 262, and the titanium plate 27 and set aside;

[0041] Step S3. The flexible graphite paper 25 pretreated in step S1 and the copper plate 261, nickel plate 262, and titanium sheet 27 surface-cleaned in step S2 are stacked from top to bottom and compression molded. The mold is kept closed and heated to 800-850°C. The mold closing pressure is 5-10 MPa to ensure sufficient contact between the flexible graphite paper 25 and the copper plate 261 as well as the titanium sheet 27 and the nickel plate 262. After maintaining the pressure for a period of time, a metal-graphite composite bipolar plate is obtained.

[0042] In step S1, the pretreatment method for the flexible graphite paper 25 preferably includes: vacuum immersing the flexible graphite paper 25 in a treatment solution, fully immersing it, and then drying and curing it; the treatment solution is any one of phenolic resin, epoxy resin, and acrylate, diluted with water to a viscosity of 300mPa.s to 600mPa.s. Furthermore, preferably, the flexible graphite paper 25 is immersed in a vacuum tank containing the treatment solution and fully immersed at a vacuum of 133Pa; then, the soaked flexible graphite paper 25 is placed in a drying oven under an inert gas atmosphere and cured at the curing temperature of the treatment solution. The curing temperatures for phenolic resin, epoxy resin, and acrylate are 130-150°C, 60-80°C, and 60-80°C, respectively. The curing time is generally 2 hours, which can be adjusted based on actual conditions. This solves the technical problem of prior art where the resin bonding between the graphite paper and the bipolar plate is insufficiently strong and easily detaches from the metal surface during long-term fuel cell operating temperature cycles.

[0043] In step S2, the surface cleaning treatment of the copper plate 261 and the nickel plate 262 preferably includes: thoroughly immersing the copper plate 261 and the nickel plate 262 in a 0.5-0.6 mol / L dilute hydrochloric acid solution, while simultaneously applying ultrasonic vibration. The immersion time is typically 10-20 minutes, which can be adjusted according to actual conditions.

[0044] In step S2, the surface cleaning treatment of the titanium thin plate 27 preferably includes: polishing the surface of the titanium thin plate 27, typically using sandpaper (1000 grit sandpaper, or other grit sandpaper depending on the actual situation); then immersing the surface of the titanium thin plate 27 in a 6.0-6.5 mol / L dilute nitric acid solution while applying ultrasonic vibration. The immersion time is typically 10-20 minutes, which can be adjusted depending on the actual situation.

[0045] The present invention provides a method for preparing the metal-graphite composite bipolar plate described in Example 1. On the one hand, the present invention uses a copper-nickel composite foil 26 as an intermediate layer to connect the flexible graphite paper 25 and the substrate. Through high-temperature pressure treatment, metallurgical connections such as carbides and metal compounds are formed between the flexible graphite paper 25 and the copper plate 261, and between the nickel plate 262 and the titanium thin plate 27, thereby significantly enhancing the connection strength between the graphite paper and the metal substrate. On the other hand, the flexible graphite paper 25 does not need to be bonded to the intermediate layer before forming, thereby reducing the risk of the flexible graphite paper 25 breaking during the forming process. The preparation of the metal-graphite composite bipolar plate can be completed in a set of molds and a single process, thereby reducing the preparation process and improving production efficiency.

[0046] Example 3

[0047] Depend on Figure 3 、 Figure 4 As shown, the molding device used to prepare the metal-graphite composite bipolar plate described in Example 1, or the molding device used for molding in step S3 of Example 2, includes an upper mold mechanism and a lower mold mechanism. The upper mold mechanism is provided with an upper mold base plate 1 and an upper mold plate 2, and a micro-protrusion 3 is provided below the lower surface of the upper mold plate 2; the lower mold mechanism is provided with a lower mold base plate 4 and a lower mold plate 5, and a micro-groove 6 is provided on the upper surface of the lower mold plate 5. The upper mold plate 2 and the lower mold plate 5 are arranged opposite to each other in the upper and lower directions. After the mold is closed, the micro-protrusion 3 matches the micro-groove 6 to form a microchannel.

[0048] The forming device is also provided with a stepped punch mechanism, which is provided with a pad 7 and multiple punch assemblies 8; each punch assembly 8 is provided with a segmented punch 9, a pressure rod 10, a first spring 11, and a second spring 12. The lower part of the segmented punch 9 is provided with a micro-protrusion 3, and the upper part of the segmented punch 9 is provided with a first blind hole 13 with an opening facing upward. The opening of the first blind hole 13 is provided with a hole edge 14 extending inward, and a first spring 11 is installed in the first blind hole 13.

[0049] The upper template 2 is provided with a plurality of longitudinal through holes 15 spaced apart from left to right, and each longitudinal through hole 15 is correspondingly installed with a punch assembly 8; the segmented punch 9 is arranged in the longitudinal through hole 15, and the two are slidably connected; the pad 7 covers the longitudinal through hole 15, and the top end of the pressure rod 10 is provided with a first stop 16, and the rod body of the pressure rod 10 passes downward through the second spring 12 and the pad 7 and then enters the longitudinal through hole 15, and the bottom end of the pressure rod 10 is provided with a second stop 17, and the second stop 17 is connected to the first spring 11. Under the action of the elastic force of the first spring 11, the second stop 17 is movably engaged in the hole edge 14.

[0050] The lengths of the rods of the plurality of pressure rods 10 exposed from the pad 7 are distributed in a stepped manner from left to right.

[0051] When the present invention is used, the upper mold base plate 1 and the lower mold base plate 4 are fixed on the hydraulic press respectively, wherein the upper mold base plate 1 is fixedly connected to the crossbeam of the hydraulic press, and the lower mold base plate 4 is fixed on the base of the hydraulic press. The downward pressure of the upper mold base plate 1 is controlled by controlling the displacement of the crossbeam of the hydraulic press; first, the plate workpiece 24 to be formed is placed in the forming area on the lower template 5, and the plate workpiece 24 is the metal-graphite composite plate to be formed in Example 1.

[0052] The specific forming process is as follows: the hydraulic press is started, the upper die base plate 1 moves downward, first touching the first punch assembly 8 on the left, pushing the pressure rod 10 of the punch assembly 8 downward, so that the first spring 11 and the second spring 12 are compressed, driving the segment punch 9 to move downward, and the micro protrusion 3 at the bottom of the segment punch 9 matches the micro groove 6 located directly below it, forming the micro channel of the plate workpiece 24 on the far left, as shown in FIG. Figure 3 、 Figure 4 、 Figure 6 shown.

[0053] As the upper die base plate 1 continues to move downward, it touches the second punch assembly 8 on the left, compressing the second pressure rod 10 on the left to move downward, so that the first spring 11 and the second spring 12 are compressed, driving the segment punch 9 to move downward, causing the sheet workpiece 24 to flow to the left to form the second microchannel on the left, as shown in FIG. Figure 6 、 Figure 7 shown.

[0054] As the upper die plate 1 continues to move downward, the segmented punches 9 of the five punch assemblies 8 form the microchannels from left to right. Finally, the entire upper die plate 2 is driven downward to complete the final mold closing process, and then heated and pressurized to complete the preparation of the metal-graphite composite bipolar plate. Figure 8 shown.

[0055] During the entire process, the formation of the microchannels of the metal-graphite composite bipolar plate relies on the flow of the flexible graphite paper from right to left, rather than the overall stamping deformation of the existing technology, which effectively avoids the breakage of the flexible graphite paper and ensures that the flexible graphite paper is intact.

[0056] In some embodiments, Figure 4 As shown, the first spring 11 is preferably a force transmission spring that maintains a constant elastic force within a corresponding stroke.

[0057] In some embodiments, Figure 4 As shown, the second spring 12 is preferably a compression spring for resisting compression force or storing energy.

[0058] In some embodiments, Figure 3 As shown, the forming device is preferably also provided with a first guide column 18 for guiding and positioning, and the two ends of the first guide column 18 are respectively connected to the upper mold base plate 1 and the lower mold base plate 4, and the first guide column 18 is respectively slidably connected through the upper mold base plate 1, the upper mold plate 2, and the lower mold plate 5.

[0059] In some embodiments, Figure 4 As shown, the longitudinal through hole 15 of the upper template 2 is preferably a square hole with good stability.

[0060] In some embodiments, Figure 3 、 Figure 5As shown, the forming device is preferably further provided with a limit support device 19, which is provided with a limit support rod 20. A second blind hole 21 opening downward is provided on the lower surface of the upper template 2, and a third spring 22 is installed in the second blind hole 21. The bottom end of the limit support rod 20 is installed on the lower template 5, and the top end of the limit support rod 20 is connected to the third spring 22. When the forming device is closing the mold, the third spring 22 is compressed, and the top end of the limit support rod 20 gradually enters the second blind hole 21. The third spring 22 is continuously compressed, and the mold closing is finally completed. When the forming device is opening the mold, the elastic force of the third spring 22 is released, pushing the upper template 2 upward, so that the upper template 2 and the lower template 5 are completely separated.

[0061] In some embodiments, preferably, a third stop 23 is provided at the top of the limiting support rod 20, the third stop 23 is connected to the third spring 22, and the third stop 23 is slidingly connected to the inner wall of the second blind hole 21, so that the upper template 2 rises or falls more stably and reliably.

[0062] In some embodiments, the third spring 22 is preferably a limit spring, which uses the elasticity of the spring to limit the range of the moving part.

[0063] It should be noted that:

[0064] (1) During the process of opening or closing the mold of the hydraulic press, under the action of the spring force of the first spring 11 and the second spring 12, the punch assembly 8 rises or falls in the longitudinal through hole 15; intuitively, the pressure rod 10 drives the segment punch 9 to rise or fall.

[0065] (2) During the mold opening process after the hydraulic press closes the mold, the working state of the present invention is as follows Figure 8 、 Figure 7 、 Figure 6 、 Figure 3 order.

[0066] (3) By Figure 3 As shown, the lengths of the rods 10 exposed from the backing plate 7 are distributed in a stepped manner from left to right, preferably in an arithmetic progression, and the length difference between the rods of two adjacent rods 10 exposed from the backing plate 7 is equal to the height of the microfluidic channel. The operator can adjust the length of the rods 10 according to actual conditions.

[0067] In the description of the present invention, it should be understood that the terms "left", "right", "up", "down", "top", "bottom", "front", "back", "inside", "outside", "back", "middle", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0068] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A metal-graphite composite bipolar plate, comprising a graphite layer, an intermediate layer, and a base layer; characterized in that: The bipolar plate is metallurgically connected in sequence from top to bottom with the graphite layer, the intermediate layer, and the base layer; wherein the graphite layer is a flexible graphite paper (25); the intermediate layer is a copper-nickel composite foil (26); the copper-nickel composite foil (26) is a copper plate (261) and a nickel plate (262) in sequence from top to bottom; and the base layer is a titanium thin plate (27); The thickness of the flexible graphite paper (25) is 0.02-0.05 mm, the thickness of the copper-nickel composite foil (26) is 0.05-0.15 mm, and the thickness of the titanium sheet (27) is 0.08-0.1 mm.

2. The method for preparing a metal-graphite composite bipolar plate according to claim 1, characterized in that: The steps are as follows: Step S1. pre-treating the flexible graphite paper (25) for standby use; Step S2. Cleaning the surfaces of the copper plate (261), the nickel plate (262), and the titanium sheet (27) for later use; Step S3. The flexible graphite paper (25) pretreated in step S1 and the copper plate (261), nickel plate (262), and titanium sheet (27) surface-cleaned in step S2 are stacked from top to bottom for compression molding, the mold is kept closed and heated to 800-850° C., the mold pressure is 5-10 MPa, and after maintaining the pressure for a period of time, the metal-graphite composite bipolar plate is obtained.

3. The method according to claim 2, characterized in that In step S1, the pretreatment method of the flexible graphite paper (25) includes: vacuum immersing the flexible graphite paper (25) in a treatment liquid, fully immersing it, and then drying and curing it; the treatment liquid is any one of phenolic resin, epoxy resin, and acrylate diluted with water to a viscosity of 300mPa.s to 600mPa.s.

4. The method according to claim 3, characterized in that The flexible graphite paper (25) is immersed in a vacuum tank containing the treatment liquid and fully immersed at a vacuum degree of 133 Pa; then the soaked flexible graphite paper (25) is placed in a drying furnace and cured at the curing temperature of the treatment liquid under the protection of an inert gas.

5. The method according to claim 2, characterized in that In step S2, the method for cleaning the surfaces of the copper plate (261) and the nickel plate (262) comprises: fully immersing the copper plate (261) and the nickel plate (262) in a 0.5-0.6 mol / L dilute hydrochloric acid solution, and applying ultrasonic vibration.

6. The method according to claim 2, characterized in that In step S2, the method for cleaning the surface of the titanium thin plate (27) includes: polishing the surface of the titanium thin plate (27), then fully immersing it in a 6.0-6.5 mol / L dilute nitric acid solution, and applying ultrasonic vibration at the same time.

7. The method according to claim 2, characterized in that In step S3, the forming device used is provided with an upper mold mechanism and a lower mold mechanism, the upper mold mechanism is provided with an upper mold base plate (1) and an upper mold plate (2), and a micro protrusion (3) is provided below the lower surface of the upper mold plate (2); the lower mold mechanism is provided with a lower mold base plate (4) and a lower mold plate (5), and a micro groove (6) is provided on the upper surface of the lower mold plate (5), and the upper mold plate (2) and the lower mold plate (5) are arranged relative to each other in the upper and lower directions, and after the molds are closed, the micro protrusion (3) and the micro groove (6) are matched to form a micro channel; The forming device is further provided with a stepped punch mechanism, the stepped punch mechanism being provided with a pad (7) and a plurality of punch assemblies (8); each of the punch assemblies (8) being provided with a segmented punch (9), a pressure rod (10), a first spring (11), and a second spring (12); a micro protrusion (3) being provided at the lower portion of the segmented punch (9); a first blind hole (13) opening upward is provided at the upper portion of the segmented punch (9); a hole edge (14) extending inward is provided at the opening of the first blind hole (13); and a first spring (11) is installed in the first blind hole (13); The upper template (2) is provided with a plurality of longitudinal through holes (15) spaced from left to right, and each longitudinal through hole (15) is correspondingly provided with a punch assembly (8); the segmented punch (9) is arranged in the longitudinal through hole (15), and the two are slidably connected; the pad (7) covers the longitudinal through hole (15), and the top end of the pressure rod (10) is provided with a first stopper (16), and the rod body of the pressure rod (10) passes through the second spring (12) and the pad (7) downward and enters the longitudinal through hole (15), and the bottom end of the pressure rod (10) is provided with a second stopper (17), and the second stopper (17) is connected to the first spring (11), and under the action of the elastic force of the first spring (11), the second stopper (17) is movably engaged in the hole edge (14); The lengths of the rod bodies of the plurality of pressure rods (10) exposed from the pad (7) are distributed in a stepped manner from left to right.

8. The method according to claim 7, characterized in that The first spring (11) is a force transmission spring, and the second spring (12) is a compression spring.

9. The method according to claim 7, characterized in that The forming device is further provided with a limit support device (19), the limit support device (19) is provided with a limit support rod (20), a second blind hole (21) opening downward is provided on the lower surface of the upper template (2), a third spring (22) is installed in the second blind hole (21), the bottom end of the limit support rod (20) is installed on the lower template (5), and the top end of the limit support rod (20) is connected to the third spring (22).

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