A metal composite bipolar plate and its processing method and application

Abstract

The present application discloses a metal composite bipolar plate, a processing method, and an application thereof. The metal composite bipolar plate includes an intermediate metal plate layer, wherein the upper and lower surfaces of the intermediate metal plate layer are respectively welded with a bipolar plate structural layer, the intermediate metal plate layer is fully encapsulated in the bipolar plate structural layer, and the intermediate metal plate layer and the bipolar plate structural layer are made of different metal materials; an atomic diffusion layer exists at the interface between the upper and lower surfaces of the intermediate metal plate layer and the bipolar plate structural layer; a plurality of flow channels are formed by stamping on the surface of the bipolar plate structural layer, and the corners at the bottom of the flow channels and the corners at the opening are both configured as chamfered structures. The present application uses titanium / titanium alloy and aluminum / aluminum alloy to form a composite plate combination. By improving the bipolar plate flow channels and adjusting the interface bonding method of the composite layer plates, cracking or warping at the flow channel corners during the stamping process is avoided, while improving the performance of the bipolar plate and reducing production costs.

Description

Technical Field

[0001] The present invention relates to the field of metal composite materials and processing technology, and in particular to a metal composite bipolar plate and a processing method and application thereof. Background Art

[0002] Bipolar plates play a crucial role in proton exchange membrane (PEM) electrolyzer systems. They not only serve as an indispensable conductive bridge between electrolysis units, but also guide the flow of reactants, collect generated gases, and provide necessary structural stability. The design and material selection of bipolar plates in PEM electrolyzers are directly related to electrolysis efficiency, system durability, and overall economic feasibility, and are a key factor in promoting the development of the hydrogen economy. Therefore, developing high-performance and cost-effective bipolar plate technology is of great significance for accelerating the commercialization of PEM electrolyzer technology.

[0003] Traditionally, PEM electrolyzer bipolar plates are made of corrosion-resistant, highly conductive metals or alloys, such as stainless steel, titanium, or their alloys. These materials, with their excellent physical and chemical properties, effectively withstand the harsh electrochemical environment and corrosive challenges encountered during electrolysis. However, high material costs and complex processing, especially in large-scale production, significantly increase bipolar plate manufacturing costs, thereby impacting the market competitiveness of PEM electrolyzer systems. The combination of material costs and precision manufacturing processes has become a significant obstacle to the widespread adoption of PEM electrolyzer technology.

[0004] In recent years, with the continuous advancement of materials science, particularly breakthroughs in composite materials technology, the design and material selection of bipolar plates for PEM electrolyzers have undergone a profound transformation. This presents unprecedented opportunities for reducing system costs and improving electrolysis efficiency. Metal-matrix composites (MMCs), as potential bipolar plate materials, combine the advantageous properties of multiple metals or alloys, such as high strength, high conductivity, and excellent corrosion resistance. While ensuring efficient operation of PEM electrolyzers, they also meet the multiple functional requirements of gas separation, liquid management, and structural support.

[0005] Currently, commercial PEMFC bipolar plates on the market are mainly made of graphite, which has high production costs, resulting in high costs and heavy weight of the bipolar plate stack. Metal bipolar plates have the advantages of light weight, small size and low manufacturing cost, and are the preferred material for hydrogen fuel cell bipolar plates. Currently, the commonly used methods for bipolar plate forming include hydraulic forming, laser engraving and stamping. Among them, the stamping process has high production efficiency, low cost and is easy to achieve large-scale automated production. However, with the increasing requirements for bipolar plate forming, metal bipolar plates tend to be ultra-thin, with complex flow channels and miniaturized, which makes metal bipolar plates prone to cracking or warping when forming at the flow channel corners during the stamping process; therefore, micro-deformation processing and warping control during the stamping process are issues that need to be paid attention to. Summary of the Invention

[0006] In order to overcome the shortcomings of the existing technology, the purpose of this application is to provide a metal composite bipolar plate, which is formed by combining titanium / titanium alloy and aluminum / aluminum alloy to form a composite plate. By improving the bipolar plate flow channel and adjusting the interface bonding method of the composite layer plate, cracking or warping at the flow channel corners during the stamping process is avoided, while improving the performance of the bipolar plate and reducing production costs.

[0007] To solve the above problems, the technical solutions adopted in this application are as follows:

[0008] An embodiment of the present application provides a metal composite bipolar plate, comprising an intermediate metal plate layer, wherein the upper and lower surfaces of the intermediate metal plate layer are respectively welded with bipolar plate structural layers, the intermediate metal plate layer is fully wrapped in the bipolar plate structural layer, the intermediate metal plate layer material is aluminum or an aluminum alloy, and the bipolar plate structural layer material is titanium or a titanium alloy; an atomic diffusion layer exists at the bonding interface between the upper and lower surfaces of the intermediate metal plate layer and the bipolar plate structural layer; a plurality of flow channels are formed by stamping on the surface of the bipolar plate structural layer, and the corners at the bottom of the flow channels and the corners at the opening are both set as chamfered structures.

[0009] As a further preferred solution, the total thickness of the metal composite bipolar plate described in the embodiment of the present application is 2-12 mm, wherein the ratio of the thickness of the bipolar plate structure layer to the thickness of the intermediate metal plate layer is 1:(2-5).

[0010] As a further preferred solution, the average thickness of the atomic diffusion layer described in the embodiment of the present application is 5-20 μm.

[0011] As a further preferred solution, the width of the flow channel described in the embodiment of the present application is 1.2~2.0mm, and the depth is 0.5~0.8mm; the angle formed by the side of the flow channel and the bottom is 135°~175°.

[0012] As a further preferred scheme, the flow channel described in the embodiment of the present application is divided into a gas transition zone, a reaction zone and a drainage transition zone on the surface of the bipolar plate structure layer; wherein, the gas transition zone adopts a multi-branch mesh flow field, the reaction zone adopts a wavy flow field, and the drainage transition zone adopts a point flow field structure.

[0013] As a further preferred scheme, the metal composite bipolar plate described in the embodiment of the present application is provided with a water inlet hole on one side and a water outlet hole on the other side. The water inlet hole and the water outlet hole are located at diagonal positions of the metal composite bipolar plate, and the flow channel connects the water inlet hole and the water outlet hole; the metal composite bipolar plate is also provided with air holes for gas to pass through.

[0014] The present application also provides a method for processing a metal composite bipolar plate. By improving the stamping method, the problem of cracking or warping easily occurring at the flow channel corners during the stamping process is solved. At the same time, welding and annealing are combined to improve the performance of the bipolar plate. The processing method includes the following steps:

[0015] Pretreatment: Cut the intermediate metal sheet and bipolar plate sheet to the appropriate size, clean and ensure that the surface of the metal material is clean and free of pollution;

[0016] Stamping: The bipolar plate sheet is stamped in steps to form flow channels on its surface, so that the corners at the bottom of the flow channel and the intersections at the opening are chamfered to obtain the bipolar plate structure layer;

[0017] Welding composite: Fix the intermediate metal plate, place the bipolar plate structure layers on the upper and lower surfaces of the intermediate metal plate, weld the bipolar plate structure layers and the intermediate metal plate together, and wrap the intermediate metal plate inside the bipolar plate structure layer to obtain a composite metal plate with a bipolar plate structure;

[0018] Annealing treatment: The composite metal plate is subjected to annealing treatment, and after cooling, a metal composite bipolar plate is obtained.

[0019] As a further preferred solution, during the pretreatment process of the processing method, ultrasonic cleaning is used to clean the intermediate metal plate and the bipolar plate, and the cleaning medium is analytical grade anhydrous ethanol.

[0020] As a further preferred embodiment, the stamping forming process of the processing method adopts step-by-step stamping; in the first step, a first punch with a semicircular or arc-shaped end is used to stamp simultaneously on the upper and lower surfaces of the bipolar plate, and the clamping force is set to 300kN~350kN, and the stroke is 40~65SPM; in the second step, a second punch with a first arc chamfered end is used to stamp simultaneously on the upper and lower surfaces of the bipolar plate, and the clamping force is set to 320kN~360kN, and the stroke is 40~65SPM, and the radius r of the first arc chamfer and the width L of the second punch satisfy r1=1 / 4L2; in the third step, a third punch with a second arc chamfered end is used to stamp simultaneously on the upper and lower surfaces of the bipolar plate, and the radius r2 of the second arc chamfer and the width L3 of the third punch satisfy r2=1 / 9L3, the clamping force is set to 320kN~380kN, and the stroke is 40~65SPM.

[0021] As a further preferred solution, the intermediate metal plate described in the processing method is an aluminum or aluminum alloy plate, and the bipolar plate structural layer plate is a titanium or titanium alloy plate; laser welding is adopted in the welding composite, and the welding conditions are: the laser power is 4~6kW, and the spot diameter is 0.18~0.25mm; before welding, the intermediate metal plate and the bipolar plate structural layer plate are preheated, and the preheating temperature is controlled between 350℃~450℃.

[0022] As a further preferred solution, the intermediate metal plate described in the processing method is an aluminum or aluminum alloy plate, and the bipolar plate plate is a titanium or titanium alloy plate; when welding the composite, diffusion welding is adopted, and the welding conditions are: the welding temperature is set to 540~560℃, the pressure is 5.5~7MPa, and the time is 60-90min.

[0023] As a further preferred solution, during the annealing treatment in the processing method, the temperature is set to 490° C. to 520° C., and the duration is 20 min to 30 min.

[0024] The embodiments of the present application also provide an application of a metal composite bipolar plate in the manufacture of a PEM electrolyzer.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. In the metal composite bipolar plates described in the embodiments of the present application, the intermediate metal plate layer and the bipolar plate structural layer are made of different metal materials, which can fully utilize the advantages of their respective materials. The selection of the intermediate metal plate layer material can be adjusted according to the actual application scenario, while the bipolar plate structural layer can be made of corrosion-resistant and easy-to-process materials. This not only improves the overall performance of the bipolar plate, such as conductivity, corrosion resistance, and mechanical strength, but also reduces the cost of the material.

[0027] 2. In the metal composite bipolar plate described in the embodiment of the present application, the intermediate metal plate layer and the bipolar plate structural layer are connected by welding. An atomic diffusion layer exists at the bonding interface between the two, which helps to enhance the bonding strength between the two layers and prevent delamination or falling off due to stress concentration or environmental factors during use.

[0028] 3. In the metal composite bipolar plates described in the embodiments of this application, the bottom corners and opening corners of the multiple flow channels formed by stamping on the surface of the bipolar plate structural layer are chamfered. This design helps optimize fluid flow characteristics, reduces resistance and eddy currents in the flow channels, and improves fluid transmission efficiency. It also prevents cracking or warping at the flow channel corners during stamping. This chamfered structure also reduces erosion and corrosion of the bipolar plate surface by the fluid, extending the service life of the bipolar plate.

[0029] 4. In the processing method of the metal composite bipolar plate described in the embodiment of the present application, flow channels are formed on the surface of the bipolar plate by step-by-step stamping, and the corners at the bottom of the flow channel and the corners at the opening are chamfered. This not only optimizes the flow characteristics of the fluid and reduces the fluid resistance, but also solves the problem of easy cracking and warping at the flow channel corners during the stamping process.

[0030] 5. In the metal composite bipolar plate processing method described in the embodiments of this application, the bipolar plate structural layers and the intermediate metal plate are securely welded together, fully enveloping the intermediate metal plate within the bipolar plate structural layers. This enhances the overall strength and stability of the bipolar plate and ensures its reliability in the intended application environment.

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 This is a schematic structural diagram of the metal composite bipolar plate described in an embodiment of the present application.

[0034] Figure 2 This is a cross-sectional view in the thickness direction of the metal composite bipolar plate described in an embodiment of the present application.

[0035] Figure 3 This is an SEM image of the cross-section of the metal composite bipolar plate described in Example 1 of the present application. DETAILED DESCRIPTION

[0036] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0037] The term "comprising" and other equivalent descriptions in the description and claims of this application are intended to cover non-exclusive inclusions, including both the contents clearly described in the description and claims and the steps or units that are not described in the description and claims but are inherent in the product, method or structure.

[0038] The present invention provides a metal composite bipolar plate comprising an intermediate metal plate layer with bipolar plate structural layers welded to the upper and lower surfaces of the intermediate metal plate layer. The intermediate metal plate layer is made of aluminum or an aluminum alloy, and the bipolar plate structural layer is made of titanium or a titanium alloy. Titanium or a titanium alloy is selected as the bipolar plate structural material due to its excellent corrosion resistance, high strength, and low density. In proton exchange membrane (PEM) electrolyzer applications, titanium exhibits superior corrosion resistance compared to stainless steel and aluminum alloy, helping to extend the service life of the bipolar plate and reduce battery system maintenance costs. Using aluminum or an aluminum alloy as the intermediate metal plate layer increases the overall light spot area of ​​the battery system. The bipolar plate structural layer (titanium or titanium alloy) and the intermediate metal plate layer (aluminum or aluminum alloy) are welded together to form a double-layer structure. This combines the advantages of both materials, ensuring the bipolar plate's lightweight and high strength while also improving its corrosion resistance. The resulting structure offers low density and light weight. The intermediate metal plate layer is fully wrapped in the bipolar plate structural layer, which helps to further enhance the overall strength and stability of the bipolar plate, and can also effectively prevent the intermediate metal plate layer from direct contact with the external environment, thereby reducing its risk of corrosion. An atomic diffusion layer exists at the bonding interface between the upper and lower surfaces of the intermediate metal plate layer and the bipolar plate structural layer. The presence of the atomic diffusion layer can effectively enhance the bonding strength between the intermediate metal plate layer and the bipolar plate structural layer. A number of flow channels are formed on the surface of the bipolar plate structural layer by stamping, and the corners at the bottom of the flow channel and the corners at the opening are both set as chamfered structures; the chamfered structures at the bottom of the flow channel and the opening can optimize the flow characteristics of the fluid, reduce the resistance and eddy currents of the fluid in the flow channel, improve the fluid transmission efficiency, and help improve the performance of the bipolar plate; at the same time, the chamfer can effectively disperse the stress at the corners, reducing the risk of deformation and rupture of the material during the stamping process.

[0039] The thickness of the bipolar plates affects the conduction path and distribution of current. PEM electrolyzers generate heat during operation, and the thickness of the bipolar plates helps conduct and dissipate this heat. Thicker bipolar plates provide better thermal conductivity, helping maintain a stable cell temperature and preventing performance degradation caused by overheating or localized overheating. Bipolar plates used in PEM electrolyzers must withstand the pressure and stress within the cell. A reasonable thickness setting can enhance the mechanical strength of the bipolar plates and improve their resistance to deformation, cracking, and wear, thereby extending the cell's service life. The metal composite bipolar plates described in preferred embodiments of the present application have a total thickness of 2-12 mm, with a preferred thickness of 4-10 mm. To balance corrosion resistance, thermal conductivity, and cost, the thickness of each bipolar plate structural layer relative to the thickness of the intermediate metal plate layer is preferably a ratio of 1:(2-4), with a preferred ratio of 1:4.

[0040] In an embodiment of the present application, the bipolar plate structural layer is welded to the upper and lower surfaces of the intermediate metal layer. During the welding process, an atomic diffusion layer (ADL) forms between the two plates. The ADL acts as a bridge connecting the intermediate metal layer and the bipolar plate structural layer. Its thickness directly affects the bond strength between the two metal layers. A thicker ADL provides a larger contact area and stronger interaction, thereby enhancing bond strength. However, an excessively thick ADL can lead to stress concentration and increased residual stress during welding, which in turn reduces bond strength. Furthermore, because bipolar plates may be subject to various external forces and internal stresses during use, the thickness of the ADL affects the overall stiffness and strength of the bipolar plate, thereby affecting its resistance to deformation. A thicker ADL provides better support and restraint, improving the plate's resistance to deformation. Furthermore, the thickness of the ADL also affects the electrochemical performance of the bipolar plate. A thinner ADL can reduce the resistance to electron transfer between the two metal layers, thereby improving conductivity. However, an excessively thin ADL with defects or pores can disrupt the electron transfer path or increase resistance. During the electrochemical reaction, the thickness of the atomic diffusion layer will also affect the polarization phenomenon of the bipolar plate; a thicker atomic diffusion layer may increase the transmission distance and time of ions and electrons between the two layers of metal plates, thereby increasing the polarization resistance and intensifying the polarization phenomenon. Therefore, when selecting the thickness of the atomic diffusion layer, it is necessary to comprehensively consider factors such as its bonding strength, deformation resistance, fatigue life, conductivity, corrosion resistance and polarization phenomenon. In the embodiment of the present application, the average thickness of the atomic diffusion layer is 5~20μm, which can provide a good balance of mechanical properties and electrochemical properties.

[0041] In the embodiments of the present application, the size of the flow channels provided in the bipolar plate structure has a significant impact on the performance of the bipolar plate. The channel width directly affects the flow velocity and distribution of gas in the flow channels. Wider flow channels not only reduce gas flow resistance and promote uniform gas distribution, allowing gas to flow more smoothly through the flow channels, but also facilitate stamping and molding, improving yield. However, overly wide flow channels may lead to material waste and increased processing difficulty, and also hinder the effective transfer of gas to the membrane electrode. The depth of the flow channels also affects the diffusion efficiency of gas into the diffusion layer and the mass transfer process within the electrolyzer. Deeper flow channels increase the contact area between the gas and the diffusion layer, facilitating better diffusion of gas into the catalytic layer for reaction. However, overly deep flow channels can hinder the effective transfer of gas to the membrane electrode. Therefore, it is important to ensure effective gas flow and distribution in the flow channels to avoid the material waste and increased processing difficulty caused by overly wide flow channels. At the same time, to balance gas diffusion and mass transfer efficiency, the stable performance of the electrolyzer is ensured. In some embodiments of the present application, the flow channels are 1.2-2.0 mm wide and 0.5-0.8 mm deep. The angle between the side of the flow channel and the bottom affects the flow path and resistance of the gas in the flow channel. A larger angle can make the gas flow smoother, reduce flow resistance, and thus improve the performance of the electrolyzer. The size of this angle also affects the structural strength of the bipolar plate. A smaller angle will increase stress concentration at the bottom of the flow channel and reduce the bipolar plate's resistance to deformation. A larger angle helps disperse stress and improve the structural strength of the bipolar plate. Therefore, in some embodiments of the present application, in order to optimize the flow performance and structural strength of the bipolar plate and improve the overall performance and stability of the electrolyzer, the angle formed by the side of the flow channel and the bottom is controlled to be 135° to 175°.

[0042] As a further preferred embodiment, the flow channels described in the embodiments of the present application are divided into a gas transition zone, a reaction zone, and a drainage transition zone on the surface of the bipolar plate structure layer. The gas transition zone utilizes a multi-branch mesh flow field, the reaction zone utilizes a wavy flow field, and the drainage transition zone utilizes a point-like flow field structure. In this embodiment, the multi-branch mesh flow field design in the gas transition zone helps evenly distribute the input gas (such as hydrogen, oxygen, etc.) or liquid (such as water, etc.) throughout the reaction zone, maintaining stable gas flow in the flow channel and preventing gas or liquid accumulation or dead zones in a specific area. It also provides more gas diffusion paths, promoting the diffusion of gas molecules into the electrolyte and catalytic layer, helping to accelerate the reaction rate and improve the overall performance of the electrolyzer. The wavy structure of the reaction zone facilitates uniform heat distribution and transfer, preventing local overheating or overcooling. The point-like flow field structure in the drainage transition zone guides the generated water or electrolyte from the reaction zone to the outlet port, preventing flooding, keeping the reaction zone dry and operating efficiently, and preventing fluid accumulation in the drainage transition zone, helping to maintain the long-term stability and efficiency of the electrolyzer.

[0043] As a further preferred embodiment, the metal composite bipolar plate described in the present application has a water inlet on one side and a water outlet on the other side. The inlet and outlet are located at diagonal positions on the metal composite bipolar plate, and the water inlet and outlet are located diagonally opposite each other. The flow channel connects the inlet and outlet holes, facilitating heat transfer to the entire bipolar plate. The metal composite bipolar plate is also provided with air holes for gas passage.

[0044] The present application also provides a method for processing a metal composite bipolar plate. By improving the stamping method, the problem of cracking or warping easily occurring at the flow channel corners during the stamping process is solved. At the same time, welding and annealing are combined to improve the performance of the bipolar plate. The processing method includes the following steps:

[0045] Pretreatment: Cut the intermediate metal plates and bipolar plates to appropriate sizes, clean them and ensure that the surfaces of the intermediate metal plates and bipolar plates are clean and free of contamination;

[0046] Stamping: The bipolar plate sheet is stamped in steps to form flow channels on its surface, so that the corners at the bottom of the flow channel and the intersections at the opening are chamfered to obtain the bipolar plate structure layer;

[0047] Welding composite: Fix the intermediate metal plate, place the bipolar plate structure layers on the upper and lower surfaces of the intermediate metal plate, weld the bipolar plate structure layers and the intermediate metal plate together, and wrap the intermediate metal plate inside the bipolar plate structure layer to obtain a composite metal plate with a bipolar plate structure;

[0048] Annealing treatment: The composite metal plate is subjected to annealing treatment, and after cooling, a metal composite bipolar plate is obtained.

[0049] As a further preferred solution, during the pretreatment process of the processing method, ultrasonic cleaning is used to clean the intermediate metal plate and the bipolar plate, and the cleaning medium is analytical grade anhydrous ethanol.

[0050] Due to stress concentration and uneven material flow, flow channel corners are prone to cracking and warping. These problems not only affect the appearance quality of the bipolar plate but, more importantly, reduce its structural strength and fluid transport performance. In the embodiments of the present application, a step-by-step stamping design allows for more precise control of material flow and deformation, thus avoiding these problems. In particular, the chamfered design effectively disperses stress at the corners, reducing the risk of material deformation and cracking during the stamping process. It also increases the strength of the flow channel corners and improves the overall structural stability of the bipolar plate. During the stamping process, the plate undergoes continuous and uneven thinning. Locations with significant thinning are prone to developing hazardous cross-sections, increasing the risk of cracking. Therefore, the blank holder force is a critical parameter that requires precise control during the bipolar plate stamping process. The magnitude of the pressure directly affects the plate's degree of plastic deformation and forming quality. If the blank holder force is too low, the plate will not deform sufficiently, resulting in inaccurate or incomplete flow channel shape. Conversely, if the blank holder force is too high, the local stress in the plate may exceed its tensile strength, leading to cracking. Stamping speed is also a significant factor influencing the quality of bipolar plate stamping. The speed directly affects the plate's deformation rate and stress distribution. If the stamping speed is too fast, the plate's deformation rate will increase, potentially leading to stress concentration and an increased risk of cracking. Furthermore, a too fast stamping speed can also cause significant springback during the forming process, impacting the product's dimensional accuracy and performance. Conversely, if the stamping speed is too slow, while reducing the risk of cracking, it will increase production cycle time and costs. Therefore, it is important to select a reasonable stamping speed while ensuring quality. Preferably, the segmented stamping process includes a first stamping step in which a first punch with a semicircular or curved end is simultaneously stamped onto the upper and lower surfaces of the bipolar plate. This step ensures that the plate can begin to plastically deform without inducing excessive stress. Therefore, a moderate blanking force is required. In the embodiment of the present application, the blanking force in the first stamping step is set to 300kN to 350kN. To avoid stress concentration and cracking caused by excessive speed or production efficiency affected by excessive speed, the stroke in this step is 40 to 65 SPM. In the second step, the second punch with a first arc-shaped chamfer at the end is used to punch simultaneously on the upper and lower surfaces of the plate. As the punching progresses, the deformation of the plate increases. Therefore, the clamping force in the second step needs to be appropriately increased. The increase in pressure should be controlled within a certain range to avoid plate rupture. In this step, the clamping force is set to 320kN~360kN; the stroke is 40~65SPM.The third stamping step uses a third punch with a second curved chamfered end to simultaneously stamp the upper and lower surfaces of the plate. Since the plate has already undergone deformation in the first two steps, greater pressure is required to complete the final forming. However, the blank holder force needs to be reasonably controlled while ensuring the forming quality. The stamping speed also needs to be further increased. The increase in stamping speed should avoid excessive springback and dimensional error. In this step, the blank holder force is set to 320kN~380kN, and the stroke is 40~65SPM. The size and shape of the chamfer will directly affect the forming accuracy of the flow channel. After stamping, the plate may rebound. Therefore, in order to obtain a precise flow channel shape, effectively control the amount of springback, and improve the dimensional accuracy of the product, it is necessary to reasonably design the chamfer radius and punch width. Preferably, during the second stamping process, the radius r1 of the first curved chamfer and the second punch width L2 satisfy r1=1 / 4L2. The first curved chamfer radius r1 is relatively large, which helps to reduce the resistance during the stamping process and the risk of plate breakage while ensuring the basic shape and dimensional accuracy of the flow channel. In the third step of stamping, a smaller arc chamfer radius is used to make the corners of the flow channel smoother, reduce the resistance inside the flow channel, and improve the flow efficiency of the fluid; in the third step of stamping, the radius r2 of the second arc chamfer and the width L3 of the third punch satisfy r2=1 / 9L3; in the third step of stamping, it helps to further control the deformation of the plate and ensure the precise forming of the flow channel. Therefore, in the process of partial stamping, by adjusting the stamping steps and parameters, the shape, size and distribution of the flow channel can be flexibly controlled to meet the needs of different application scenarios. During stamping, the corners at the bottom of the flow channel and the corners at the opening are chamfered, which not only optimizes the flow characteristics of the fluid and reduces fluid resistance, but also solves the problem of easy cracking and warping at the flow channel corners in traditional stamping processes; and improves the yield rate of bipolar plate products.

[0051] As a further preferred embodiment, the intermediate metal sheet in the processing method is aluminum or an aluminum alloy, and the bipolar plate structural layer is titanium or a titanium alloy. Laser welding is used for the composite welding. During welding, too low a laser power can result in incomplete weld penetration, while too high a laser power can cause excessive material ablation or defects. The laser power is 4-6 kW, and the spot diameter is 0.18-0.25 mm. Titanium-aluminum alloys are prone to thermal stress during processing, increasing the risk of deformation and cracking. Preheating can reduce thermal stress during processing, thereby reducing the risk of deformation and cracking and ensuring the quality and precision of the titanium-aluminum composite bipolar plate. Proper control of the preheating temperature can significantly improve the material's processing properties, promote the uniform distribution of alloying elements, enhance the quality and strength of the weld joint, optimize the material's microstructure, and improve the material's corrosion resistance. Therefore, in the present embodiment, the intermediate metal sheet and bipolar plate structural layer are preheated before welding, with the preheating temperature controlled between 350°C and 450°C.

[0052] As a further preferred embodiment, the intermediate metal sheet described in the processing method is an aluminum or aluminum alloy sheet, and the bipolar plate sheet is a titanium or titanium alloy sheet. When the welding composite is performed using diffusion welding, an appropriate welding temperature is required to ensure the thickness of the diffusion layer. However, excessively high temperatures may cause excessive grain growth, forming a coarse grain structure, which will adversely affect the mechanical properties of the joint. In an embodiment of the present application, the welding temperature is set to 540-560°C. At this temperature, titanium and aluminum atoms can diffuse sufficiently to form an atomic diffusion layer of a certain thickness. The diffusion layer is the basis of the titanium-aluminum metallurgical bond and helps to enhance the bonding strength of the bipolar plate. Moreover, at this temperature, intermetallic compounds, such as TiAl3, can be controlled within an appropriate range to enhance the hardness and wear resistance of the joint, thereby preventing excessive intermetallic compounds from causing embrittlement of the joint and reducing its plasticity and toughness. Welding pressure is an important factor in determining the strength of the titanium-aluminum interface. A pressure of 5.5-7 MPa helps to achieve close contact between the titanium-aluminum interface, reduce voids and defects at the interface, and thus improve the bonding strength of the joint. At the same time, it can promote diffusion and metallurgical bonding between atoms, further enhance the performance of the joint, and avoid the formation of interface diffusion voids during the welding process. These voids may reduce the mechanical properties and electrical conductivity of the joint. The welding time also affects the firmness of the titanium-aluminum bond. Too short a time may lead to insufficient atomic diffusion, affecting the bonding strength of the joint; while too long a time may lead to grain growth and thickening of intermetallic compounds, reducing the mechanical properties of the joint. In the embodiment of the present application, the welding time is 60-90 minutes. Within this time, the titanium and aluminum atoms can be fully diffused and bonded at the interface, thereby forming a strong metallurgical connection.

[0053] Annealing is a critical step in the processing of metal composite bipolar plates, significantly impacting their performance. Regarding shear strength, when the annealing temperature is high and the holding time is moderate, the shear strength of the titanium-aluminum composite plate gradually increases to a peak; however, if the holding time is too long, the interfacial shear strength begins to decline. Regarding tensile strength and ductility, at high annealing temperatures and for long holding times, the ultimate tensile strength decreases and the ductility decreases. Regarding microstructure, at high annealing temperatures, the grains in the titanium-aluminum composite plate grow, which can affect the mechanical and processing properties of the material. At high annealing temperatures and moderate holding times, the intermediate compound TiAl3 may form in the interface bonding zone. The content of this compound has a significant impact on the microstructure and properties of the bipolar plate interface. Annealing can also improve the mechanical and processing properties of titanium-aluminum alloys, imparting greater strength and toughness. However, improper annealing conditions can lead to a decrease in the material's processing properties. Therefore, in the embodiments of this application, during the annealing process described in the processing method, the annealing shielding gas is 99.99% argon, the annealing temperature is set at 480°C to 520°C, and the duration is 20 minutes to 30 minutes. Under these annealing temperature and time conditions, bipolar plates with excellent mechanical properties can be obtained.

[0054] The embodiments of the present application also provide an application of a metal composite bipolar plate in the manufacture of a PEM electrolyzer.

[0055] The following are some embodiments listed in this application, and the application is further illustrated by the following embodiments.

[0056] Example 1

[0057] like Figure 1 The present embodiment provides a metal composite bipolar plate, comprising an intermediate metal plate layer 10, wherein a bipolar plate structural layer 20 is welded to the upper and lower surfaces of the intermediate metal plate layer, respectively, wherein the intermediate metal plate layer 10 is made of 6061 aluminum alloy, and the bipolar plate structural layer 20 is made of TA1 titanium alloy; the intermediate metal plate layer 10 is fully wrapped in the bipolar plate structural layer 20, and an atomic diffusion layer exists at the bonding interface between the upper and lower surfaces of the intermediate metal plate layer 20 and the bipolar plate structural layer 20, and the average thickness of the atomic diffusion layer is 5.13 μm; a plurality of flow channels 21 are formed by stamping on the surface of the bipolar plate structural layer 20, and the corners at the bottom and the opening of the flow channel 21 are both set to chamfered structures; the width of the flow channel is 2.0 mm and the depth is 0.8 mm; the angle formed by the side of the flow channel and the bottom is 150°.

[0058] The processing method of the metal composite bipolar plate is as follows:

[0059] Pretreatment: Cut the intermediate metal plate and bipolar plate into appropriate sizes, and use ultrasonic cleaning of the intermediate metal plate and bipolar plate. The cleaning medium is analytical pure anhydrous ethanol to make the surface of the metal material clean and free of pollution.

[0060] Stamping: The bipolar plate is stamped in steps to form a flow channel on its surface, so that the corners at the bottom of the flow channel and the intersection of the opening are chamfered to obtain the bipolar plate structure layer; the step-by-step stamping is divided into three steps. In the first step, a first punch with a semicircular or arc-shaped end is used to stamp the upper and lower surfaces of the bipolar plate at the same time. The punching force is set to 300kN and the stroke is 50SPM; in the second step, a second punch with a first arc-shaped chamfered end is used to stamp the upper and lower surfaces of the bipolar plate at the same time. The lower surface is punched simultaneously, the blank holder force is set to 320kN, the stroke is 50SPM, and the relationship between the radius r1 of the first arc chamfer and the width L2 of the second punch satisfies r1=1 / 4L2; the third step of stamping uses a third punch with a second arc chamfer on the end to punch the upper and lower surfaces of the plate simultaneously, the blank holder force is set to 330kN, the stroke is 50SPM, and the relationship between the radius r2 of the second arc chamfer and the width L3 of the third punch satisfies r2=1 / 9L3;

[0061] Welding composite: Fix the intermediate metal sheet, place the bipolar plate structure layers on the upper and lower surfaces of the intermediate metal sheet, and weld the bipolar plate structure layers and the intermediate metal sheet using laser welding. The laser power is 5.5kW and the spot diameter is 0.20mm. The intermediate metal sheet is wrapped inside the bipolar plate structure layer to obtain a composite metal plate with a bipolar plate structure.

[0062] Annealing treatment: the composite metal plate is annealed, the annealing protective gas is 99.99% argon, the annealing temperature is set to 490° C., the duration is 30 minutes, and after cooling, a metal composite bipolar plate is obtained.

[0063] The performance of the metal composite bipolar plate described in Example 1 was tested. The specific test items and the adopted test methods / standards are shown in Table 1 below. Figure 3 This is a cross-sectional SEM image of the metal composite bipolar plate described in this embodiment.

[0064] Table 1: Performance test results of the metal composite bipolar plate of Example 1

[0065] Serial number Test items Test methods / standards Test results 1 Interface bonding strength (MPa) GBT32468-2015 26.96 2 Tensile strength (MPa) GBT32468-2015 144.56 3 Yield strength (MPa) GBT32468-2015 98.28 4 Density (g / cm³) GBT20042.6-2024 3.2 5 Resistance (µΩ·cm) GBT20042.6-2024 17.2 6 Corrosion current density (μA / cm²) GBT20042.6-2024 0.74 7 Elongation (%) GBT32468-2015 12.6%

[0066] On the basis of the above-mentioned Example 1, the influence of the blank holder force in each step on the runner rebound force and the cracking at the corner during the step-by-step stamping was further explored. Different blank holder forces were set, but other conditions remained the same as in Example 1. A scheme using a single stamping process was set as a comparative example (other conditions were the same as in the example, only the stamping process used a single stamping process, and the blank holder force and stamping speed were the same as those in the second step of Example 1). The specific stamping speed settings and comparison results are shown in Table 2.

[0067] Table 2: Effect of stroke on runner stamping results

[0068] Serial number First step blank holding force (kN) Second step blank holding force (kN) Step 3 Blank holding force (kN) Flow channel corner rupture ratio (%) 1 250 300 310 0 2 250 320 320 0 3 250 340 350 0 4 250 360 380 0 5 250 380 400 0.6 6 300 300 310 0 7 300 320 320 0 8 300 340 350 0 9 300 360 380 0 10 300 380 400 0.7 11 320 300 310 0 12 320 320 320 0 13 320 340 350 0 14 320 360 380 0 15 320 380 400 1.7 16 350 300 310 0 17 350 320 320 0 18 350 340 350 0 19 350 360 380 0 20 350 380 400 2.1 21 380 300 310 0.4 22 360 320 320 0.9 23 360 340 350 1.6 24 360 360 380 2.9 25 360 380 400 5.1

[0069] The results in Table 2 show that the fracture rate begins to rise with increasing blank holder force, particularly when the blank holder force reaches 400 kN in the third step, where the fracture rate increases significantly. However, when the blank holder force is within a small range, it is difficult to achieve the desired shape of the bipolar plate structure during stamping.

[0070] Based on Example 1 above, the effect of the stroke of each step on the flow channel rebound force and the cracking at the corner during step-by-step stamping was further explored. Different stroke ranges were set, but other conditions remained the same as in Example 1. Specific stroke settings and comparative results are shown in Table 3.

[0071] Table 3: Effect of stroke on runner stamping effect

[0072] Serial number Stroke (SPM) Corner fracture ratio (%) 1 40 0 2 45 0 3 50 0 4 55 0 5 60 0 6 65 0 7 70 0.3 8 75 0.4 9 80 0.5

[0073] In this experiment, it was found that when the stroke was controlled at less than 40 SPM, the stamping effect could not meet the expected requirements. When the stroke was controlled to exceed 65 SPM, a certain number of the experimental samples broke or cracked to varying degrees at the corners.

[0074] Based on the above Example 1, the effect of annealing temperature on bipolar plate performance was further explored, and different annealing temperatures were set, but other conditions remained the same as in Example 1. Specific welding speed settings and comparative results are shown in Table 4.

[0075] Table 4: Effect of annealing temperature on bipolar plate performance

[0076] Serial number Annealing temperature (℃) Interface bonding strength (MPa) Tensile strength (MPa) Yield strength (MPa) 1 420 19.12 141.64 96.37 2 450 19.97 144.27 97.22 3 480 20.4 140.68 98.20 4 490 26.96 144.56 98.28 5 500 28.84 145.07 99.64 6 520 26.97 144.23 98.73 7 550 21.16 144.30 97.76

[0077] The results in Table 4 above show that the interfacial bonding strength gradually increases from 420°C to 490°C, reaching 26.9 MPa. Then, as the annealing temperature increases to 500°C, the interfacial bonding strength shows an upward trend. At 520°C and 550°C, the interfacial bonding strength decreases significantly, indicating that excessively high annealing temperatures affect the interface microstructure and the types and proportions of intermetallic compounds. The interfacial bonding strength reaches its peak at 500°C, indicating that the material exhibits the strongest interfacial bonding at this temperature. High tensile strength is observed between 490°C and 520°C. Above 520°C, both tensile strength and yield strength show a downward trend. This is likely due to excessively high annealing temperatures causing grain growth within the material, reducing dislocation density, and thus weakening the deformation strengthening effect. The yield strength fluctuates slightly from 420°C to 490°C, but the change is relatively small. The yield strength reaches its maximum at 500°C.

[0078] Based on Example 1 above, the effect of laser welding conditions on bipolar plate performance was further explored. Different laser welding conditions were set, but other conditions remained consistent with Example 1. Specific welding condition settings and performance results are shown in Table 5.

[0079] Table 5: Effect of laser welding conditions on bipolar plate performance

[0080] Serial number Laser power (kW) Spot diameter (mm) Interface bonding strength (MPa) Tensile strength (MPa) Yield strength (MPa) 1 3 0.15 19.01 141.76 96.41 2 3 0.18 19.50 142.05 97.33 3 3 0.20 19.88 142.22 98.20 4 3 0.25 20.59 142.48 98.63 5 3 0.30 19.56 141.31 98.85 6 4 0.15 21.12 142.10 97.00 7 4 0.18 24.45 142.54 98.66 8 4 0.20 27.42 144.54 99.30 9 4 0.25 24.93 144.75 98.75 10 4 0.30 20.69 142.95 97.62 11 5 0.15 20.62 142.62 97.93 12 5 0.18 26.14 144.90 98.18 13 5 0.20 29.23 145.08 99.60 14 5 0.25 26.94 143.76 98.96 15 5 0.30 21.04 141.65 98.12 16 6 0.15 19.02 140.72 96.73 17 6 0.18 26.41 143.21 98.65 18 6 0.20 28.28 144.22 99.54 19 6 0.25 25.74 144.11 98.01 20 6 0.30 21.39 141.86 97.98 21 7 0.15 17.51 14055 95.83 22 7 0.18 20.20 140.41 96.80 23 7 0.20 24.20 141.19 98.02 24 7 0.25 26.32 142.79 98.19 25 7 0.30 22.59 140.02 97.61

[0081] The metal composite bipolar plate described in the embodiments of this application is applied to a proton exchange membrane (PEM) electrolyzer system. According to experimental test results, when the interfacial bonding strength of the metal composite bipolar plate is above 22 MPa, the bipolar plate's performance meets the application requirements. The performance test results in Table 5 above show that, under constant laser power, the relationship between the interfacial bonding strength of the bipolar plate and the spot diameter shows that, within a certain range, the interfacial bonding strength increases with increasing spot diameter. However, when the spot diameter reaches a critical value, the interfacial bonding strength decreases. This may be due to the spot being too large, and the significantly reduced energy density, which may result in incomplete penetration of the titanium-aluminum thin plate. Insufficient element diffusion makes the atomic diffusion layer too thin, resulting in a decrease in interfacial bonding strength. The effect of laser power on the interface bonding strength of the bipolar plate is manifested in that, under the same spot setting, the interface bonding strength roughly increases with the increase of laser power, but there are also abnormal situations. For example, when the laser power reaches 7kW, the spot is between 0.15 and 0.18, showing a smaller interface bonding strength. This may be due to the uneven distribution of welding energy under the conditions of high power and small spot, which affects the microstructure of the metal organization at the bonding interface. For example, insufficient diffusion of metal atoms and grain coarsening affect the interface bonding strength. The results in Table 5 show that when the laser power is in the range of 4-6kW and the spot diameter is in the range of 0.18-0.25mm, the interface bonding strength of the bipolar plate is ≥22MPa, which meets the application requirements. Experiments show that the tensile strength and yield strength of the metal composite bipolar plate obtained in the embodiment of the present application are better in the range of laser power of 4~6kW and spot diameter of 0.18~0.25mm.

[0082] Example 2

[0083] This embodiment provides a metal composite bipolar plate, including an intermediate metal plate layer, wherein the upper and lower surfaces of the intermediate metal plate layer are respectively welded with bipolar plate structural layers, the intermediate metal plate layer material is 6063 aluminum alloy, and the bipolar plate structural layer material is TA1 titanium; the intermediate metal plate layer is fully wrapped in the bipolar plate structural layer, and an atomic diffusion layer exists at the bonding interface between the upper and lower surfaces of the intermediate metal plate layer and the bipolar plate structural layer, and the average thickness of the atomic diffusion layer is 8.62 μm; a plurality of flow channels are formed by stamping on the surface of the bipolar plate structural layer, and the corners at the bottom of the flow channels and the corners at the opening are both set as chamfered structures; the width of the flow channel is 1.6 mm and the depth is 0.8 mm; the angle formed by the side of the flow channel and the bottom is 165°.

[0084] The processing method of the metal composite bipolar plate is as follows:

[0085] Pretreatment: Cut the intermediate metal plate and bipolar plate into appropriate sizes, and use ultrasonic cleaning of the intermediate metal plate and bipolar plate. The cleaning medium is analytical pure anhydrous ethanol to make the surface of the metal material clean and free of pollution.

[0086] Stamping: The bipolar plate is stamped in steps to form a flow channel on its surface, so that the corners at the bottom of the flow channel and the intersection of the opening are chamfered to obtain the bipolar plate structure layer; the step-by-step stamping is divided into three steps. In the first step, the first punch with a semicircular or arc-shaped end is used to stamp the upper and lower surfaces of the bipolar plate at the same time. The punching force is set to 330kN and the stroke is 45SPM; in the second step, the second punch with a first arc-shaped chamfered end is used to stamp the upper and lower surfaces of the bipolar plate at the same time. The lower surface is punched simultaneously, the blank holder force is set to 350kN, the stroke is 45SPM, and the relationship between the radius r1 of the first arc chamfer and the width L2 of the second punch satisfies r1=1 / 4L2; the third step of stamping uses a third punch with a second arc chamfer on the end to punch the upper and lower surfaces of the plate simultaneously, the blank holder force is set to 380kN, the stroke is 45SPM, and the relationship between the radius r2 of the second arc chamfer and the width L3 of the third punch satisfies r2=1 / 9L3;

[0087] Welding composite: Fix the intermediate metal plate, place the bipolar plate structure layer plates on the upper and lower surfaces of the intermediate metal plate, and weld the bipolar plate structure layer plates and the intermediate metal plate using diffusion welding. The welding temperature is set to 550°C, the pressure is 6.0 MPa, and the welding time is 80 minutes. The intermediate metal plate is wrapped inside the bipolar plate structure layer to obtain a composite metal plate with a bipolar plate structure.

[0088] Annealing treatment: the composite metal plate is subjected to annealing treatment, the annealing protective gas is 99.99% argon, the annealing temperature is set to 500° C., the duration is 30 minutes, and after cooling, a metal composite bipolar plate is obtained.

[0089] The performance of the metal composite bipolar plate described in Example 2 was tested. The specific test items and the adopted test methods / standards are shown in Table 6 below.

[0090] Table 6: Performance test results of the metal composite bipolar plate of Example 2

[0091] Serial number Test items Testing methods / standards used Test results 1 Interface bonding strength (MPa) GBT32468-2015 26.4 2 Tensile strength (MPa) GBT32468-2015 147.3 3 Yield strength (MPa) GBT32468-2015 99.3 4 Density (g / cm³) GBT20042.6-2024 3.18 5 Resistance (µΩ·cm) GBT20042.6-2024 24.8 6 Corrosion current density (μA / cm²) GBT20042.6-2024 0.23 7 Elongation (%) GBT32468-2015 12.1%

[0092] Based on Example 2 above, the effect of diffusion welding conditions on bipolar plate performance was further explored, and different diffusion welding conditions were set, while other conditions remained the same as Example 2. Specific welding condition settings and results are shown in Table 7.

[0093] Table 7: Effect of diffusion welding conditions on bipolar plate performance

[0094] Serial number Soldering temperature (℃) Pressure (MPa) Welding time (min) Interface bonding strength (MPa) Tensile strength (MPa) Yield strength (MPa) 1 530 5.0 50 16.91 140.90 95.46 2 530 5.5 60 18.54 140.69 96.15 3 530 6.5 80 19.37 140.10 97.77 4 530 7.0 90 21.92 141.11 97.86 5 530 7.5 100 19.51 141.90 97.29 6 540 5.0 50 20.24 140.47 97.80 7 540 5.5 60 22.73 144.15 98.12 8 540 6.5 80 26.64 144.97 98.72 9 540 7.0 90 25.52 144.60 98.31 10 540 7.5 100 21.26 141.43 98.06 11 550 5.0 50 21.43 142.16 97.78 12 550 5.5 60 25.90 143.33 98.58 13 550 6.5 80 28.03 145.75 99.39 14 550 7.0 90 28.2 145.20 99.65 15 550 7.5 100 24.3 140.41 98.78 16 560 5.0 50 21.82 141.10 97.45 17 560 5.5 60 27.10 144.09 98.35 18 560 6.5 80 28.12 144.88 99.47 19 560 7.0 90 28.33 145.11 99.92 20 560 7.5 100 24.46 141.73 98.29 21 570 5.0 50 20.93 140.13 97.53 22 570 5.5 60 21.21 141.51 98.72 23 570 6.5 80 26.47 143.62 98.77 24 570 7.0 90 25.80 142.78 98.96 25 570 7.5 100 21.91 141.44 97.54

[0095] The results in Table 7 above show that when the welding temperature is set between 540°C and 560°C, the interfacial bonding strength of the bipolar plates is greater than 22 MPa, meeting the application requirements. This is because the diffusion coefficient of titanium and aluminum atoms increases significantly at welding temperatures between 540°C and 560°C, promoting interdiffusion of interfacial elements and thus enabling the formation of a metal atomic diffusion layer with an appropriate thickness. Because the interfacial oxide (Al2O3 / TiO2) fragmentation rate increases at pressures between 5.5 and 6.5 MPa, the interfacial bonding strength can generally be maintained above 22 MPa at welding pressures between 5.5 and 7.0 MPa, while maintaining constant temperature. However, as welding pressure increases, interfacial metal flow intensifies, potentially introducing microcracks. Therefore, after welding pressure exceeds 7.0 MPa, the interfacial bonding strength is affected and shows a downward trend. The results in Table 7 also show that at welding temperatures between 540°C and 560°C, welding pressures between 5.5 and 6.5 MPa, and welding times between 60 and 90 minutes, the tensile strength and yield strength also perform well.

[0096] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A metal composite bipolar plate, characterized in that: It includes an intermediate metal plate layer, the upper and lower surfaces of which are respectively welded with bipolar plate structural layers, the intermediate metal plate layer is fully wrapped in the bipolar plate structural layer, the intermediate metal plate layer is made of aluminum or an aluminum alloy, and the bipolar plate structural layer is made of titanium or a titanium alloy; an atomic diffusion layer exists at the bonding interface between the upper and lower surfaces of the intermediate metal plate layer and the bipolar plate structural layer; a plurality of flow channels are formed by stamping on the surface of the bipolar plate structural layer, and the corners at the bottom of the flow channel and the corners at the opening are both set as chamfered structures; the total thickness of the metal composite bipolar plate is 2~12mm, and the ratio of the thickness of each layer of the bipolar plate structural layer to the thickness of the intermediate metal plate layer is 1:(2~4); the width of the flow channel is 1.2~2.0mm, and the depth is 0.5~0.8mm; the angle formed by the side of the flow channel and the bottom is 135°~175°.

2. The metal composite bipolar plate according to claim 1, characterized in that: The average thickness of the atomic diffusion layer is 5-20 μm.

3. The metal composite bipolar plate according to claim 1 or 2, characterized in that: The flow channel is divided into a gas transition zone, a reaction zone and a drainage transition zone on the surface of the bipolar plate structure layer; among them, the gas transition zone adopts a multi-branch network flow field, the reaction zone adopts a wavy flow field, and the drainage transition zone adopts a point flow field structure.

4. The metal composite bipolar plate according to claim 1 or 2, characterized in that: A water inlet is provided on one side of the metal composite bipolar plate, and a water outlet is provided on the other side. The water inlet and the water outlet are located at diagonal positions of the metal composite bipolar plate, and the flow channel connects the water inlet and the water outlet; the metal composite bipolar plate is also provided with air holes for gas to pass through.

5. A method for processing a metal composite bipolar plate according to any one of claims 1 to 4, characterized in that: The following steps are included: Pretreatment: Cut the intermediate metal sheet and bipolar plate sheet to the appropriate size, clean and ensure the surface of the metal material is clean and free of pollution; Stamping: The bipolar plate is stamped in steps. In the first step, a first punch with a semicircular or arc-shaped end is used to stamp the upper and lower surfaces of the bipolar plate at the same time. The blanking force is set to 300kN~350kN and the stroke is 40~65SPM. In the second step, a second punch with a first arc-shaped chamfered end is used to stamp the upper and lower surfaces of the bipolar plate at the same time. The blanking force is set to 320kN~360kN and the stroke is 40~65SPM. The radius r1 of the first arc-shaped chamfer is the same as The width L2 of the second punch satisfies r1=1 / 4L2; in the third stamping step, a third punch having a second arc-shaped chamfered end is used to stamp simultaneously the upper and lower surfaces of the bipolar plate, and the radius r2 of the second arc-shaped chamfer and the width L3 of the third punch satisfy r2=1 / 9L3. The blank holder force is set to 320kN~380kN, and the stroke is 40~65SPM; a flow channel is formed on the surface of the bipolar plate, and the corners at the bottom of the flow channel and the intersection at the opening are both chamfered to obtain a bipolar plate structure layer; Welding composite: Fix the intermediate metal plate, place the bipolar plate structure layers on the upper and lower surfaces of the intermediate metal plate, weld the bipolar plate structure layers and the intermediate metal plate together, and wrap the intermediate metal plate inside the bipolar plate structure layer to obtain a composite metal plate with a bipolar plate structure; Annealing treatment: the composite metal plate is annealed at a temperature of 490° C. to 520° C. for 20 min to 30 min; after cooling, a metal composite bipolar plate is obtained.

6. The processing method according to claim 5, characterized in that: During the pretreatment process, ultrasonic cleaning is used to clean the intermediate metal plate and bipolar plate, and the cleaning medium is analytical grade anhydrous ethanol.

7. The processing method according to claim 5, characterized in that: The intermediate metal plate is an aluminum or aluminum alloy plate, and the bipolar plate structural layer is a titanium or titanium alloy plate; laser welding is used in the welding composite, and the welding conditions are: laser power of 4~6kW, spot diameter of 0.18~0.25mm; before welding, the intermediate metal plate and the bipolar plate structural layer are preheated, and the preheating temperature is controlled between 350℃ and 450℃.

8. The processing method according to claim 5, characterized in that: The intermediate metal plate is aluminum or an aluminum alloy plate, and the bipolar plate plate is titanium or a titanium alloy plate; when welding the composite, diffusion welding is adopted, and the welding conditions are: the welding temperature is set to 540-560°C, the pressure is 5.5-7MPa, and the time is 60-90min.

9. Use of the metal composite bipolar plate according to any one of claims 1 to 4 in manufacturing a PEM electrolyzer.

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