METHOD FOR COATING AN ELECTRODE PLATE, AN ELECTRODE PLATE AND A FUEL CELL

Abstract

The embodiments of the present disclosure relate to a method for coating an electrode plate, an electrode plate, and a fuel cell. The method (300) for coating an electrode plate comprises the following: providing a metal electrode plate substrate (102), wherein the metal electrode plate substrate (102) comprises several alternately arranged ribs (110) and several grooves (120); coating several internal surfaces in the several grooves (120) with a photoresist; and coating several rib surfaces (112) of the several ribs (110) with a conductive material.In this way, by using a photolithographic process for coating the grooves with a photoresist and by using a metal coating technique for coating the webs with a conductive material, the electrode plate achieves good corrosion resistance in the groove area and good conductivity in the web area, while simultaneously reducing manufacturing costs.

Description

FIELD OF THE INVENTIONThe embodiments of the present disclosure generally relate to the field of batteries, and more specifically relate to electrode plates, fuel cells, and their manufacturing methods.PRIOR ARTIn some batteries, electrode plates are disposed to discharge electric power from the battery. Electrode plates are frequently used, for example, in particular in proton exchange membrane fuel cells (PEMFC). A PEMFC is a type of hydrogen fuel cell and is frequently used in motor vehicles with new energy technology. Multiple fuel cells are typically combined into a fuel cell stack to generate the required power. A fuel cell stack includes a plurality of membrane electrodes (MEA) disposed in the stack and a plurality of bipolar plates (BPP) disposed between the MEAs. The bipolar plates may include the anode side and the cathode side of adjacent fuel cells in the stack to dissipate the electrical energy. An anode gas flow channel on the anode side of the bipolar plate allows the anode gas to flow to the anode side of the MEA. A cathode gas flow channel on the cathode side of the bipolar plate allows the cathode gas to flow to the cathode side of the MEA. The bipolar plate may also include a flow channel for coolant.The bipolar plates are usually made of conductive material such as stainless steel, titanium, aluminum, or polymeric carbon composites so that they can conduct the current generated by the fuel cell from one cell to the next cell and lead it out of the fuel cell stack. The use of metallic bipolar plates in fuel cells offers distinct advantages such as low cost, ease of manufacture, high mechanical strength, and high power density, but the problem of metal corrosion significantly limits the life of the fuel cell.DISCLOSURE OF THE INVENTIONThe embodiments of the present disclosure provide an electrode plate with a heterogeneous coating of photoresist and conductive material and a corresponding manufacturing method.A first aspect of the present disclosure relates to a method for manufacturing an electrode plate. The method includes: providing a metal electrode plate substrate, wherein the metal electrode plate substrate includes a plurality of alternately arranged lands and a plurality of grooves; coating a plurality of inner surfaces in the plurality of grooves with a photoresist; and coating a plurality of land surfaces with a conductive material.A second aspect of the present disclosure relates to a method for manufacturing a fuel cell. The method includes: performing the method described in the first aspect of coating an electrode plate to obtain a plurality of electrode plates; stacking an end plate, a plurality of membrane electrodes, and the plurality of electrode plates into an initial stack, the plurality of membrane electrodes and the plurality of electrode plates being alternately arranged; and processing the initial stack to obtain the fuel cell.A third aspect of the present disclosure relates to an electrode plate. The electrode plate includes: a plurality of lands including a plurality of land surfaces capable of being coupled to a gas diffusion layer; and a plurality of grooves alternately arranged with the plurality of lands and including a plurality of inner surfaces; wherein the plurality of land surfaces are coated with a conductive material and the plurality of inner surfaces are coated with a resist.A fourth aspect of the present disclosure relates to a fuel cell. The fuel cell includes an electrode plate according to the third aspect of the present disclosure.DESCRIPTION OF THE FIGURESBy the following detailed description with reference to the figures, the above-described and other objects, features, and advantages of the embodiments of the present disclosure will be more readily understood. In the figures, several exemplary embodiments of the present disclosure are explained by way of example but not in a limiting manner, wherein the following applies: FIG. 1A is a schematic diagram of a fuel cell according to an exemplary embodiment of the present disclosure; FIG. 1B is an overall schematic diagram of an electrode plate according to an exemplary embodiment of the present disclosure; FIG. 2 is a schematic cross-sectional view of a portion of an electrode plate according to an embodiment of the present disclosure; FIG. 3 is a schematic flow diagram of a method for coating an electrode plate according to an exemplary embodiment of the present disclosure; FIGS. 4A to 4E are schematic diagrams of the process for coating an electrode plate according to an embodiment of the present disclosure; and FIGS. 5A to 5B are schematic diagrams of parameters of the electrode plate according to an embodiment of the present disclosure.DETAILED DESCRIPTION OF THE EMBODIMENTSThe principles of the present disclosure will now be explained on the basis of the various exemplary embodiments shown in the figures. It should be understood that the description of these embodiments is merely intended to provide those skilled in the art with a better understanding of the present disclosure and its implementation, and is not intended to limit the scope of the disclosure in any way. It should be noted that in the figures, similar or identical reference numerals are used as appropriate, and similar or identical reference numerals may mean similar or identical functions. Those skilled in the art will readily appreciate that, based on the following descriptions, alternative embodiments may be used for the structures and methods discussed herein without departing from the principles of the present disclosure described herein.The term "comprising" and its variants used in the present document are to be interpreted as open terms meaning "comprising, but not limited to.". The term "based on" is to be interpreted as being "based at least on a part.". The terms "an exemplary embodiment" and "exemplary embodiments" are to be understood as "at least one exemplary embodiment". The term "other embodiment" is to be understood as "at least one other embodiment.". The terms "first / r / s", "second / r / s", etc. may represent different or same objects. Further explicit and implicit definitions may be included below. Unless explicitly indicated otherwise in the context, the definitions of the terms are uniform throughout the specification.As discussed above, the electrode plate is typically made of metal. The metallic electrode plate forms a natural oxide on its outer surface, by which it becomes corrosion resistant. However, the oxide layer is not conductive, thereby increasing the internal resistance of the fuel cell and decreasing the electrical performance of the fuel cell. Moreover, the oxide layer generally makes the plate more hydrophobic. However, the problem of metal corrosion significantly limits the life of the fuel cell, and therefore a protective coating is essential.In some relevant techniques, currently common coating methods are further based on deposition techniques in a vacuum environment, such as chemical vapor deposition (CVD) and physical vapor deposition (PVD). However, these methods, which are based on a vacuum environment, require a high time and cost, which greatly restricts mass production of metallic electrode plates.In some other relevant techniques, coating solutions that do not require a vacuum system have been proposed. In comparison, these solutions, which are not based on a vacuum system, are distinguished by low costs and short cycle times. However, in such embodiments, only the lands are coated while the grooves remain uncoated. Although such a coating allows contact with the gas diffusion layer and the electrode plate at low interface contact resistance (ICR), the uncoated channels are directly exposed to corrosive media (weakly acidic media), which represents a significant risk of corrosion. This is because dissolved metal ions can reduce proton conductivity and thereby promote decomposition of the membrane.In summary, deposition techniques based on vacuum environments, while being the current standard method for coatings, are not suitable for mass production due to the high time and cost. At the same time, some other coating methods that do not use a vacuum system cannot yet ensure simultaneous conductivity and corrosion resistance with high coating quality.In view of this, the present disclosure proposes a solution for coating electrode plates without a vacuum deposition system. In this solution, the reaction region of the metal electrode plate substrate includes grooves having a certain geometry. The grooves consist of several alternately arranged webs and grooves, the webs being in contact with the electrode and serving to conduct the current generated during the electrode reaction. The grooves serve to distribute target reactants and products of the fuel cell. The surface of the metal electrode plate substrate is provided with a coating containing a resist and intended to prevent corrosion of the metal electrode plate substrate; at the same time, the lands are provided with a coating containing a conductive material and serving to conduct out the current generated in the electrode reaction. In this way, the application of coatings with different materials to the grooves and the lands enables the electrode plate to have good corrosion resistance in the groove region where corrosion resistance is required and at the same time good conductivity in the land region where conductivity is required. The coating with photoresist in the grooves is effected by means of photolithography methods, wherein the method enables a precise coating with photoresist exclusively in the grooves.The coating of the webs with conductive material is effected by means of metal coating methods, whereby time and costs are significantly reduced.Hereinafter, with reference to FIGS. 1 to 5B, the structure and the operation principle of a hearing apparatus according to an exemplary embodiment of the present disclosure will be described in detail.FIG. 1A shows a schematic illustration of a fuel cell 10 according to an exemplary embodiment of the present disclosure. As shown in FIG. 1A, the fuel cell 10 includes a plurality of plate members arranged in a first direction A 1. The plurality of plate members includes an end plate 11- 1 arranged in order, a current collecting plate 12- 1, a plurality of membrane electrodes 13 and bipolar plates 14 arranged alternately, a current collecting plate 12- 2, and an end plate 11- 2. Each plate member extends in a plane parallel to the second direction A 2. The bipolar plate 14- 1 of the plurality of bipolar plates 14 is disposed between the membrane electrode 13- 2 and the membrane electrode 13- 1 of the plurality of membrane electrodes 13. Similarly, the bipolar plate 14- 2 of the plurality of bipolar plates 14 is disposed between the membrane electrode 13- 2 and the membrane electrode 13- 3 of the plurality of membrane electrodes 13, and the bipolar plate 14- 3 of the plurality of bipolar plates 14 is disposed between the membrane electrode 13- 3 and the membrane electrode 13- 4 of the plurality of membrane electrodes 13. Moreover, the fuel cell 10 further includes a monopolar plate 15 disposed between the current collecting plate 12- 1 and the membrane electrode 13- 1. It should be understood that the number of bipolar plates and membrane electrodes shown in FIG. 1A is merely exemplary and the fuel cell may also include more or fewer bipolar plates and membrane electrodes.The membrane electrode 13 is a central member of the proton exchange membrane fuel cell, and is composed of a proton exchange membrane (PEM), a catalyst layer (CL), and a gas diffusion layer (GDL) from the inside to the outside. That is, each membrane electrode 13 includes a proton exchange membrane at the center, catalyst layers arranged symmetrically on both sides of the proton exchange membrane, and a gas diffusion layer on the side of the catalyst layer facing away from the proton exchange membrane, respectively.The proton exchange membrane is a polymer electrolyte membrane and plays an important role in the fuel cell in proton transport as well as in the separation of the cathode and anode reactants; it is the central component of the fuel cell and is a critical component for fuel cell performance, life and cost. In practical applications, the requirements are that the proton exchange membrane must have a high proton conductivity and good chemical and mechanical stability. The catalyst layer may consist, for example, of a Pt / C catalyst and a perfluorosulfonic acid-containing ionomer (polymer). The three phase interface between Pt nanoparticles, ionomer and gas is the active center of the catalyst. The surface of the Pt nanoparticles catalyzes the reaction of hydrogen and oxygen and acts together with the carbon support as an electron conductor, while the ionomer takes over hydrogen proton transport. The main functions of the gas diffusion layer are to serve as a support for the catalyst, support the engine structure, conduct electric current, distribute the gas uniformly, and transport water through the diffusion layer.The bipolar plates 14 and the monopolar plate 15 disposed at the ends may be referred to as electrode plates; the function of the electrode plate is to conduct electrons, distribute reaction gases and assist in the removal of the water formed, wherein the material of the electrode plate must functionally be a good conductor for electricity and heat and have a certain strength and gas tightness; in terms of the stability of the performance, the bipolar plate must be corrosion-resistant in the acidic, high-voltage and hot and moist environment of the fuel cell, be compatible with the other components and materials of the fuel cell and not be contaminating and have a certain hydrophobicity in order to assist in the removal of the water produced by the battery.As shown in FIG. 1A, the individual membrane electrodes 13 of the plurality of membrane electrodes 13 have the same structure, and the individual bipolar plates 14 of the plurality of bipolar plates 14 also have the same structure. Therefore, in the following, for simplicity without limiting generality, the bipolar plate 14- 2 will be explained in more detail. Bipolar plate 14- 2 includes a bipolar plate half 100- 1 and a bipolar plate half 100- 2. The bipolar plate half 100- 1 and the bipolar plate half 100- 2 have the same structure. The side of the bipolar plate half 100- 1 facing the membrane electrode 13- 2 forms the end side and has a plurality of protruding webs and grooves lying between the webs. The side of the bipolar plate half 100- 1 facing the bipolar plate half 100- 2 forms the back side and is coupled to the back side of the bipolar plate half 100- 2 facing the bipolar plate half 100- 1 to form a coupling portion and a coolant flow channel. Moreover, the bipolar plate half 100- 1 and the monopolar plate 15 have the same structure.In the embodiment shown in FIG. 1A, bipolar plate half 100- 1 includes web 110- 1, web 110- 3, web 110- 5, and web 110- 7. A coating of conductive material is applied to the web surfaces of the web 110- 1, the web 110- 3, the web 110- 5, and the web 110- 7, respectively. Web 110- 7. The land 110- 1, the land 110- 3, the land 110- 5, and the land 110- 7 are electrically coupled to the cathode of the membrane electrode 13- 2 via the coating of conductive material. Between the web 110- 1 and the web 110- 3, there are arranged the groove 120- 1, the groove 120- 3, and the groove 120- 5 serving to transport water or oxygen. On the inner surfaces of the inner walls of the groove 120- 1, the groove 120- 3, and the groove 120- 5, resist is applied for corrosion prevention, respectively.Accordingly, bipolar plate half 100- 2 includes land 110- 2, land 110- 4, land 110- 6, and land 110- 8. A coating of conductive material is applied to the web surfaces of the web 110- 2, the web 110- 4, the web 110- 6, and the web 110- 8, respectively. The land 110- 2, the land 110- 4, the land 110- 6, and the land 110- 8 are electrically coupled to the anode of the membrane electrode 13- 3 via the coating of conductive material. Between the web 110- 2 and the web 110- 4, there are disposed the groove 120- 2, the groove 120- 4, and the groove 120- 6 serving to transport hydrogen. On the inner surfaces of the inner walls of the groove 120- 2, the groove 120- 4, and the groove 120- 6, a resist for corrosion prevention is applied, respectively.In some embodiments, the fuel cell may be further manufactured by the following steps. For example, first, the method of manufacturing the electrode plates according to an embodiment of the present disclosure may be performed to obtain a plurality of electrode plates. Here, the plurality of electrode plates may include monopolar plates and bipolar plates. Subsequently, the end plates, the current collecting plates, the plurality of membrane electrodes, and the plurality of electrode plates are stacked to form an initial stack. At this time, the plurality of membrane electrodes and the plurality of electrode plates are alternately arranged. Finally, the initial stack is processed to obtain the fuel cell. Processing may include, for example, compaction operations on the original stack, clamping operations on the compressed stack, tightness testing on the clamped stack, final assembly, activation, and testing.FIG. 1B shows an overall schematic illustration of a bipolar plate 14 according to an exemplary embodiment of the present disclosure. The bipolar plate 14 corresponds to, for example, the bipolar plate 14- 1, the bipolar plate 14- 2, or the bipolar plate 14- 3 in FIG. 1A. The bipolar plate 14 extends, for example, along the second direction A 2 and has, on one side, for example, the end side, a plurality of channels and a plurality of grooves which are arranged alternately along the third direction A 3. FIG. 1B further shows an enlarged fragmentary view of a portion of the bipolar plate 14. It can be seen that the channels and the webs extend curved along the second direction A 2.In the embodiments illustrated in FIGS. 1A and 1B, the bipolar plate 14 is manufactured by, for example, the method of manufacturing an electrode plate described in the present disclosure. By coating the inner surfaces of the grooves 120 with resist, sufficient corrosion resistance can be provided, and by coating the land surfaces with a conductive material, good electrical contact can be made with the gas diffusion layer of the membrane electrode. It should be understood that FIG. 1B shows one half of the bipolar plate 14, which half may correspond to the monopolar plate 15.FIG. 2 shows a schematic cross-sectional view of a part of an electrode plate 100 according to an embodiment of the present disclosure. As shown in FIG. 2, the electrode plate 100 may correspond to, for example, the bipolar plate half 100- 1, the bipolar plate half 100- 2, or the monopolar plate 15 in FIG. 1A. The electrode plate 100 includes a metal electrode plate substrate 102. The metal electrode plate substrate 102 may be made of, for example, SS316L type stainless steel. The metal electrode plate substrate 102 includes a plurality of lands 110 and a plurality of grooves 120. The plurality of ridges 110 includes the ridge 110- 1, the ridge 110- 2, and the ridge 110- 3. Between the land 110- 1 and the land 110- 2, the groove 120- 1 is disposed, and between the land 110- 2 and the land 110- 3, the groove 120- 2 is disposed.The electrode plate 100 is electrically coupled to the gas diffusion layer 200 via the land 110- 1, the land 110- 2, and the land 110- 3. The web 110- 1 includes a web surface 112- 1 facing the gas diffusion layer 200. A coating of conductive material 130- 1 is applied to the web surface 112- 1. Correspondingly, the web 110- 2 comprises a web surface 112- 2 facing the gas diffusion layer 200, and a coating of conductive material 130- 2 is applied to the web surface 112- 2. The web 110- 3 includes a web surface 112- 3 facing the gas diffusion layer 200. A coating of conductive material 130- 3 is applied to the web surface 112- 3.The groove 120- 1 comprises a first side wall 122- 1 extending from the web 110- 1 in a direction facing away from the web 110- 1 parallel to the first direction A 1. The groove 120- 1 further includes a second sidewall 124- 1 extending from the land 110- 2 in a direction away from the land 110- 2 parallel to the first direction A 1. In addition, the groove 120- 1 further includes a bottom 126- 1 bridging over the first sidewall 122- 1 and the second sidewall 124- 1. Accordingly, the groove 120- 2 includes a first sidewall 122- 2 extending from the web 110- 2 in a direction parallel to the first direction A 1. The groove 120- 2 further includes a second sidewall 124- 2 extending from the land 110- 3 in a direction parallel to the first direction A 1. In addition, the groove 120- 2 further includes a bottom 126- 2 bridging over the first sidewall 122- 2 and the second sidewall 124- 2A photoresist coating 140- 1 is applied to the inner surfaces of the groove 120- 1, including the surface of the first side wall 122- 1 facing the second side wall 124- 1, the surface of the second side wall 124- 1 facing the first side wall 122- 1, and the surface of the bottom 126- 1 facing the webs. A photoresist coating 140- 2 is applied in each case to the inner surfaces of the groove 120- 2, including the surface of the first side wall 122- 2 facing the second side wall 124- 2, the surface of the second side wall 124- 2 facing the first side wall 122- 2, and the surface of the base 126- 2 facing the webs.In the embodiment shown in FIG. 2, the coating of conductive material 130- 1 is connected to the photoresist coating 140- 1 at the connection location between the land surface 112- 1 and the first sidewall 122- 1. At the same time, the conductive material coating 130- 2 is bonded to the photoresist coating 140- 1 at the junction between the land surface 112- 2 and the second sidewall 124- 1. In this way, by a similar arrangement, the resist coating and the conductive material coating are connected to each other and collectively cover one side of the metal electrode plate substrate 102 completely. In some embodiments, the back surface of the metal electrode plate substrate 102 may also be provided with respective coatings as needed to provide respective functions such as corrosion resistance or conductivity.In the embodiment shown in FIG. 2, by applying a corrosion-resistant coating to the inner surfaces of the electrode plate grooves, the service life of the electrode plate can be improved, while the coating of conductive material in the contact region between the lands and the gas diffusion layer both reduces the contact resistance between the electrode plate and the membrane electrode and improves the corrosion resistance of the electrode plate.FIG. 3 shows a schematic flow diagram of an example method 300 for manufacturing an electrode plate according to an exemplary embodiment of the present disclosure. For discussion purposes, method 300 will be described with reference to the embodiment illustrated in FIG. 2. The method 300 may be carried out, for example, in a production line or a system for producing electrode plates.As shown in FIG. 3, a metal electrode plate substrate is provided at 302. Here, the metal electrode plate substrate includes a plurality of lands and a plurality of grooves arranged alternately. For example, in the embodiment shown in FIG. 2, a metal electrode plate substrate 102 made of stainless steel which has been stamped and cleaned may be provided. The metal electrode plate substrate 102 includes a plurality of lands 110 and a plurality of grooves 120.At 304, a photoresist is applied to the plurality of inner surfaces of the plurality of grooves 120. For example, in the embodiment shown in FIG. 2, a suitable resist coating process may be used to apply resist to the surfaces of the first sidewall 122- 1, the second sidewall 124- 1, the bottom 126- 1, as well as the first sidewall 122- 2, the second sidewall 124- 2, and the bottom 126- 2.In some embodiments, the coating process may include preparing a first slurry containing photoresist. The photoresist in the first slurry can be present in a concentration or viscosity which corresponds to the respective coating method. Subsequently, the coating process includes applying the first slurry to the entire side surface of the metal electrode plate substrate, which is capable of being coupled to a membrane electrode to form a coating with resist on the entire side surface, the application being performed by one of the following methods: spray coating, dipping, or pouring. The side surface comprises a plurality of web surfaces and a plurality of inner surfaces. Here, a layer of the first slurry may be applied to the entire side surface of the metal electrode plate substrate 102 to be coated by spray coating, dipping, or curtain casting. Finally, the coating process includes removing the coating on the plurality of land surfaces. The coating formed consists essentially of photoresist.For example, in the embodiment shown in FIG. 2, the first slurry may be applied to the land surface 112- 1, the land surface 112- 2, the land surface 112- 3, as well as to the surfaces of the first sidewall 122- 1, the second sidewall 124- 1, the bottom 126- 1, and the first sidewall 122- 2, the second sidewall 124- 2, and the bottom 126- 2. In some embodiments, photoresist may be a positive photoresist or a negative photoresist. A positive photoresist may be, for example, AZ4620 photoresist. A negative photoresist may be the photoresist SU-8.In embodiments, when removing the coating on the multiple web surfaces, the photoresist can be exposed first on the web surfaces using positive photoresist, for example, and the exposed photoresist can then be dissolved using a developer solution. In contrast, in negative photoresist embodiments, the photoresist on the inner surfaces of the grooves outside the land surfaces may be exposed and then the unexposed photoresist on the land surfaces may be dissolved with a developer solution. The developing solution is, for example, an alkaline solution such as potassium hydroxide or potassium carbonate. Since the coating consists essentially of photoresist here, after modification of the photoresist, the coating can be completely removed by the developer solution.At 306, a conductive material is deposited on multiple land surfaces. For example, in the embodiment shown in FIG. 2, conductive material may be applied to the land surface from which the photoresist has been removed by roll coating to form a conductive material coating on the land surface. In some embodiments, the process of applying the conductive material may include preparing a second slurry. The second slurry includes a conductive material, a binder, and a solvent mixed together in a certain ratio. The process of applying the conductive material further includes applying the second slurry to a plurality of land surfaces using one of the following methods to form a coating of conductive material: roller coating, transfer printing, or screen printing.In some embodiments, the roll coating operation may comprise uniformly applying the second slurry to the surface of the roll of a roll coater. The roller coating apparatus may comprise, for example, an upper roller for feeding and a lower roller for uniform application. The roller coating process may further include moving the metal electrode plate substrate so that a plurality of land surfaces come in contact with the roller, thereby coating the plurality of land surfaces with the second slurry so that a second slurry layer is formed. For example, the metal electrode plate substrate coated with photoresist may be placed on a conveyor of the roller coating apparatus to contact the roller by moving over the conveyor. Finally, the roll coating process further comprises drying the second slurry layer to obtain the conductive coating.In some alternative embodiments, the reprinting process may include applying the second slurry to a base sheet to form a second slurry layer. The reprinting process further includes drying the second slurry layer. Finally, the transfer printing process includes transferring the second slurry layer from the base sheet to the plurality of land surfaces.In the exemplary embodiment shown in FIG. 3, the application of the photoresist by means of spray coating, dipping or casting and the application of the conductive material by means of roller coating, transfer printing or screen printing avoid the need to use a coating solution based on a vacuum environment, as a result of which time and costs can be saved to a considerable extent.FIG. 4A shows a schematic diagram of step 400A for providing an electrode plate according to an embodiment of the present disclosure. As shown in FIG. 4A, in step 400A, a metal electrode plate substrate 102 is provided. In some embodiments, the metal electrode plate substrate 102 may be made of, for example, SS316L stainless steel. The metal electrode plate substrate 102 includes a plurality of lands 110 and a plurality of grooves 120. The plurality of ridges 110 includes the ridge 110- 1, the ridge 110- 2, and the ridge 110- 3. Between the land 110- 1 and the land 110- 2, the groove 120- 1 is disposed, and between the land 110- 2 and the land 110- 3, the groove 120- 2 is disposed.The web 110- 1 includes a web surface 112- 1 adapted to be coupled to a gas diffusion layer. The web 110- 2 includes a web surface 112- 2 adapted to be coupled to a gas diffusion layer. The web 110- 3 includes a web surface 112- 3 adapted to be coupled to a gas diffusion layer. The groove 120- 1 includes a first sidewall 122- 1 extending from the web 110- 1 in a direction away from the web 110- 1. The groove 120- 1 further includes a second sidewall 124- 1 extending from the land 110- 2 in a direction away from the land 110- 2. In addition, the groove 120- 1 further includes a bottom 126- 1 bridging over the first sidewall 122- 1 and the second sidewall 124- 1. Accordingly, the groove 120- 2 includes a first side wall 122- 2 extending from the web 110- 2 in a direction away from the web 110- 2. The groove 120- 2 further includes a second sidewall 124- 2 extending from the land 110- 3 in a direction away from the land 110- 3. In addition, the groove 120- 2 further includes a bottom 126- 2 bridging over the first sidewall 122- 2 and the second sidewall 124- 2.In the embodiment shown in FIG. 4A, the metal electrode plate substrate 102 is stamped and cleaned, so that subsequent steps can be performed.FIG. 4B shows a schematic illustration of step 400B for applying a photoresist according to an embodiment of the present disclosure. In step 400B, for example, the metal electrode plate substrate 102 may be placed on a support platform of an electrode plate fabrication system such that a plurality of web surfaces 112 are oriented toward a nozzle that is used for spray coating with photoresist. Then, the metal electrode plate substrate 102 is heated to a predetermined temperature specific to each resist. By heating, evaporation of the solvent of the resist droplets after covering the metal electrode plate substrate 102 can be accelerated, thereby minimizing the flowability of the resist for covering the nozzle facing surface and the curved surface of the metal electrode substrate 102. With the nozzle, the photoresist is uniformly sprayed onto multiple land surfaces and multiple inner surfaces to form a continuous photoresist coating 440. It should be understood that the photoresist coating is the same as and interchangeable with the photoresist-containing coating described above.The photoresist coating 440 formed may have a thickness in the range of 100 nanometers to 100 micrometers, for example. The thickness of the photoresist coating 440 may be, for example, 10 micrometers. Since the grooves are intended to carry water or gas, their most important property is corrosion resistance. The corrosion resistance is again closely related to the thickness of the coating. Therefore, the thickness of the coating should be as thin as possible as long as the requirements for corrosion resistance are satisfied. In this way, a larger volume can be provided for the water guidance.In this step, the nozzle may be caused to scan an S-shaped relative to the land surfaces and inner surfaces of the metal electrode plate substrate 102 to trace all the land surfaces and inner surfaces of the metal electrode plate substrate 102 so that the entire end surface of the metal electrode plate substrate 102 is uniformly covered with resist.In some embodiments, after a first iteration, the angle or trajectory relative to the metal electrode plate substrate 102 may be further changed such that at least one further iteration is performed. Since the inner surfaces have different orientations, after changing the angle or the trajectory, another spray coating operation is performed to fully grasp the end face of the metal electrode plate substrate 102 as well, so that all the orientations can be covered with a sufficiently thick resist coating 440.In some embodiments, after the spray coating operation is completed, baking of the photoresist coating 440 may be additionally performed at a certain temperature to remove most of the solvent contained and solidify the photoresist to form a film of certain hardness.FIG. 4C shows a schematic illustration of step 400C for removing a photoresist according to an embodiment of the present disclosure. In step 400C, the mask 450- 1 is placed on the opening of the groove 120- 1, and the mask 450- 2 is placed on the opening of the groove 120- 2 to form an exposure region 442- 1 on the land surface 112- 1, an exposure region 442- 2 on the land surface 112- 2, and an exposure region 442- 3 on the land surface 112- 3. Subsequently, the exposure region 442- 1, the exposure region 442- 2, and the exposure region 442- 3 are irradiated with ultraviolet light, so that the photoresist in the exposure regions is modified.In contact exposure embodiments, the exposure light source is a mercury lamp or an LED capable of emitting ultraviolet light. Ultraviolet light is subjected to optical path matching and shaping to form a certain region of approximately parallel light, which is then illuminated onto the mask and the exposure region. When ultraviolet light strikes the photoresist coating in the exposure areas, this initiates a photosensitive reaction of the photoresist there.The photosensitive material in the photoresist has the photosensitivity to absorb light energy or other radiation energy. Under the influence of ultraviolet light, electron beams, ion beams or X-rays, the solubility and affinity of the photosensitive resin of the resist change due to the photochemical reaction, and by subsequent treatment with a suitable solvent, the soluble portion is eluted, whereby the desired image can be obtained. Therefore, photoresist in the exposure areas can be removed after irradiation with ultraviolet light.FIG. 4D shows a schematic illustration of step 400D for removing a photoresist according to an embodiment of the present disclosure. In step 400D, the exposed photoresist coating is subjected to a wet chemical treatment in order to selectively remove the photoresist located on the web surface. In the embodiment shown in FIG. 4D, the resist is a positive resist, and the principle of the "developing" process of the resist performed thereby is that after exposure, the dissolution rate of the resist in weakly alkaline solution increases by two to three orders of magnitude. Therefore, the exposed resist on the land surfaces can be quickly dissolved by the weak alkali developing solution, while the dissolution rate of the unexposed resist on the inner surfaces is very low, so that it is maintained on the inner surfaces. After the resist in the exposure regions is removed, the land surface 412- 1, the land surface 412- 2, and the land surface 412- 3 from which the resist has been removed are formed on the lands. At the same time, a resist coating 441- 1 is formed on the inner surfaces in the groove 120- 1, and a resist coating 441- 2 is formed on the inner surfaces in the groove 120- 2.In some embodiments, the "developing process" may be performed by dip developing, spin developing, or bead developing. In some embodiments, after the developing process, baking of the metal electrode plate substrate 102 may be performed to further evaporate remaining solvents and other volatile organics.FIG. 4E shows a schematic diagram of step 400E for depositing a conductive material according to an embodiment of the present disclosure. In step 400E, the metal electrode plate substrate 102 in which the resist has been removed from the land surface 412- 1, the land surface 412- 2, and the land surface 412- 3 is placed on the conveyor of a roll coater. Subsequently, the conveying device is put into operation so that the land surface 412- 1, the land surface 412- 2, and the land surface 412- 3 come into contact with the roller of the roller coating device, thereby coating the land surface 412- 1, the land surface 412- 2, and the land surface 412- 3 with the second slurry on the roller. The second slurry includes, for example, a conductive additive, a binder, and a solvent. After drying, the solvent evaporates completely. The ratio between conductive additive and binder is the decisive parameter for the electrical conductivity of the coating of conductive material. This ratio should be selected such that, while maintaining the structural strength of the conductive material coating, the electrical resistance of the conductive material coating is as low as possible. For example, in some exemplary embodiments, the ratio between conductive additive and binder can be selected such that the contact resistance of the ultimately formed coating of conductive material at a pressure of 1.4 MPa is less than 100 mΩ cm 2 in particular less than 10 mΩ cm 2. As a result, a coating of conductive material 430- 1 is formed on the web surface 412- 1, a coating of conductive material 430- 2 is formed on the web surface 412- 2, and a coating of conductive material 430- 3 is formed on the web surface 412- 3.In the embodiments shown in FIGS. 4A to 4E, both the spray coating process for applying the resist and the roller coating process for applying the conductive material place low demands on the environmental conditions and the equipment for execution, they are suitable for mass production and are characterized by short manufacturing cycles, whereby the manufacturing time and the manufacturing cost can be significantly reduced.FIG. 5A shows a schematic diagram 500A of the contact resistance of an electrode plate as a function of pressure according to an embodiment of the present disclosure. As illustrated in FIG. 5A, the graph 500A includes three curves of contact resistance versus pressure, namely, the curve 510 corresponding to Comparative Example 1, the curve 520 corresponding to Comparative Example 2, and the curve 530 corresponding to a metal electrode plate obtained by the plating method according to an embodiment of the present disclosure. Here, the metal electrode plate in Comparative Example 1 is a completely uncoated electrode plate whose contact resistance starts at 0.6 MPa at about R 3 mΩ cm 2 and decreases with increasing pressure. The metal electrode plate in Comparative Example 2 has a resist coating in the grooves but no coating of conductive material on the lands, and its contact resistance starts at 0.6 MPa slightly below the resistance of Comparative Example 1, but also starts at a resistance of approximately R 3 mΩ cm 2 and decreases with increasing pressure. The contact resistance of the electrode plate according to the embodiment of the present disclosure starts at 0.6 MPa at about R mΩ cm 2 and decreases with increasing pressure.Here, the contact resistance of the electrode plate according to the embodiment of the present disclosure may be lower by up to two orders of magnitude than that of an electrode plate to which the solution of the present disclosure has not been applied. As a result, the conductive coating on the lands can significantly reduce the contact resistance, indicating significantly increased conductivity.FIG. 5B shows a schematic diagram 500B of the current density of an electrode plate as a function of the electrical potential according to an exemplary embodiment of the present disclosure. As illustrated in FIG. 5B, the graph 500B includes three curves of current density depending on electric potential, namely, the curve 540 corresponding to Comparative Example 1, the curve 550 corresponding to Comparative Example 2, and the curve 560 corresponding to a metal electrode plate obtained by the plating method according to an embodiment of the present disclosure. Here, the metal electrode plate in Comparative Example 1 is a completely uncoated electrode plate whose current density is the highest from an electric potential above 0.4 V. The metal electrode plate in Comparative Example 2 has a conductive material coating on the lands but no resist coating in the grooves, and its current density is slightly lower than the current density of Comparative Example 1 from an electric potential higher than 0.4 V. The current density of the electrode plate according to the embodiment of the present disclosure is lowest from an electric potential higher than 0.4 V and is about an order of magnitude among the two examples. As a result, the coating in the grooves can significantly reduce the corrosion current, which indicates a significantly improved corrosion resistance.Although in the present application the claims have been formulated for particular combinations of features, it should be understood that the scope of this disclosure also encompasses all novel features or combinations of features that are explicitly or implicitly disclosed herein or generalized in any way, whether they relate to the same solution as is protected in the presently claimed claims.

Claims

A method (300) of coating an electrode plate, comprising: providing a metal electrode plate substrate (102), wherein the metal electrode plate substrate (102) comprises a plurality of alternately arranged lands (110) and a plurality of grooves (120); coating a plurality of inner surfaces in the plurality of grooves (120) with a photoresist, wherein the grooves each comprise two side walls connected to the lands and a bottom bridging the two side walls, and wherein the inner surfaces comprise the surfaces of the two side walls and the bottom within the respective groove; and coating a plurality of land surfaces (112) of the plurality of lands (110) with a conductive material.The method of claim 1, wherein coating the plurality of inner surfaces in the plurality of grooves (120) with the photoresist comprises: preparing a first slurry containing the photoresist; applying the first slurry to the entire side surface of the metal electrode plate substrate (102) capable of being coupled with a membrane electrode to form a coating with the photoresist, wherein as the application method, one of spray coating, dipping, or casting is used, wherein said side surface comprises the plurality of land surfaces (112) and the plurality of inner surfaces; and removing the coating on the plurality of land surfaces (112).The method of claim 2, wherein applying the first slurry to the side surface by spray coating comprises: fixing the metal electrode plate substrate (102); spraying the first slurry to the side surface to obtain a coating having a predetermined thickness; and drying the coating to solidify the photoresist in the coating.The method of claim 3, wherein the predetermined thickness is 100 nanometers to 100 micrometers.The method of claim 2, wherein removing the coating on the plurality of land surfaces (112) comprises: covering the plurality of openings of the plurality of grooves (120) with a mask to form exposure areas on the plurality of land surfaces; irradiating the exposure areas with ultraviolet light to modify the photoresist on the exposure areas; and dissolving the coating on the exposure areas with developer solution.The method of claim 1, wherein coating the plurality of land surfaces (112) with a conductive material comprises: preparing a second slurry, the second slurry comprising the conductive material, a binder, and a solvent; and applying the second slurry to the plurality of land surfaces (112) using one of the following methods to form a conductive coating: roll coating, transfer printing, or screen printing.The method of claim 6, wherein applying the second slurry to the plurality of land surfaces (112) by roll coating comprises: uniformly applying the second slurry to the surface of a roll of a roll coating apparatus; and moving the metal electrode plate substrate (102) so that the plurality of land surfaces (112) come into contact with the roll, thereby coating the plurality of land surfaces with the second slurry so as to form a second slurry layer; and drying the second slurry layer to obtain the conductive coating.The method of claim 6, wherein applying the second slurry to the plurality of land surfaces (112) by transfer printing comprises: applying the second slurry to a base film to form a second slurry layer; drying the second slurry layer; and transferring the second slurry layer from the base film to the plurality of land surfaces.The method of claim 6, wherein the ratio of conductive material to binder is adjusted such that the conductive coating at 1.4 megapascals is less than 100 milliohms per square centimeterA method for manufacturing a fuel cell, comprising: performing the method (300) of coating an electrode plate according to any one of claims 1 to 9 to obtain a plurality of electrode plates; stacking an end plate, a plurality of membrane electrodes, and the plurality of electrode plates into an initial stack, wherein the plurality of membrane electrodes and the plurality of electrode plates are alternately arranged; and processing the initial stack to obtain the fuel cell.A coated electrode plate (100) comprising: a plurality of lands (110) comprising a plurality of land surfaces (112) adapted to be coupled to a gas diffusion layer; and a plurality of grooves (120) alternately arranged with the plurality of lands (110), comprising a plurality of inner surfaces, and adapted to receive hydrogen, air, or water; wherein the plurality of land surfaces (112) are coated with a conductive material and the plurality of inner surfaces are coated with a photoresist.The electrode plate (100) according to claim 11, wherein the conductive material and the resist are applied by the electrode plate coating method (300) according to any one of claims 1 to 9.A fuel cell comprising the electrode plate (100) according to claim 11.

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