Metal bipolar plate and air-cooled proton exchange membrane fuel cell

Abstract

The invention relates to a metal bipolar plate for air-cooled proton exchange membrane fuel cell, which comprises an anode plate with hydrogen flow field and a cathode plate with air flow field; the cathode plate is punched from a thin metal plate to form a plurality of support bodies and openings, the support bodies comprise support vertical surfaces and support horizontal surfaces to form a bridge pier structure; the support horizontal surfaces are in contact with the anode plate, and the openings are air channels for electrochemical reaction; the air cooling channels are formed between the cathode plate and the anode plate. The cathode plate of the invention adopts the support bodies with bridge pier structure, the vertical surfaces of the support bodies directly become windward surfaces, the effective heat dissipation area is increased, and the effective heat dissipation efficiency is improved; the openings left on the surface of the cathode plate are in leeward surface, the cooling air is avoided from directly blowing on the membrane electrode, and the stability of the membrane electrode is improved. The bipolar plate is composed of two thin metal plates, the weight is light, the structure of the bipolar plate is simple, the bipolar plate is easy to process, the production cost is reduced, and the bipolar plate is suitable for large-scale popularization and use.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, specifically relating to a bipolar plate for fuel cells suitable for gas-cooled technology. Background Technology

[0002] A fuel cell is a power generation device that directly converts the chemical energy of fuel (such as hydrogen) and oxidant (such as oxygen in the air) into electrical energy. Because it is an electrochemical reaction with no combustion heat release and is not limited by the Carnot cycle, its energy conversion efficiency is much higher than that of ordinary heat engines. In addition, fuel cells have advantages such as being pollution-free, low-noise, and highly reliable, and have a very broad market prospect in transportation, stationary power generation, and portable power generation.

[0003] A fuel cell stack consists of multiple stacked individual cells. Each individual cell includes a cathode plate, an anode plate, and a membrane electrode assembly (MEA). Hydrogen gas is introduced into the anode flow field as fuel, and air is introduced into the cathode flow field as an oxidant. Under load conditions, hydrogen and oxygen react to generate electricity. The energy conversion efficiency of a fuel cell is approximately 50%, with the remaining energy dissipated as heat. Temperature is a critical factor affecting cell performance; if heat cannot be dissipated in time, the cell's lifespan will be reduced. Therefore, during fuel cell operation, a cooling medium is needed to remove the heat generated by the reaction.

[0004] Conventional cooling methods for fuel cells include liquid cooling (water cooling, oil cooling) and air cooling (air cooling, dry cooling). Water-cooled fuel cell stacks use water-cooled flow plates between individual cells, circulating water to cool the stack. This method not only complicates the stack structure but also requires additional operating equipment such as circulating water pumps and cooling fans, resulting in high energy consumption. Air-cooled fuel cell stacks achieve cooling by circulating air through the stack's interior. Currently, there are two types of air-cooled fuel cell cooling: one is open-cathode air cooling, which is the most common method. The cathode flow channel serves as both the reactant gas channel and the cooling channel. While the cathode air-cooled fuel cell stack has a simple structure, the cell control is complex and operation inconvenient. Because the heat capacity of air is much lower than that of water, an airflow rate of 50 to 100 times the stoichiometry is required to remove heat from the stack, as illustrated in patent CN208336384U. Patents include CN210837956U, CN111477915A, CN208722996U, CN113471468A, and CN112103530A. Another method is the cathode-enclosed air-cooled method, where the reaction air and cooling air are introduced into the fuel cell stack in two separate paths, i.e., the reaction gas flow path and the cooling gas flow path are separated. This method results in a larger fuel cell stack volume than the first method, but lower energy consumption and simpler control of fuel cell stack operation, such as patents CN112436163A, CN209344232U, CN 209607843U, and CN110571450A.

[0005] In practice, because the heat capacity of air is much lower than that of water, an airflow rate of 50 to 100 times the stoichiometric ratio is required to remove heat from the fuel cell stack. Air-cooled fuel cell stacks have limitations due to the limited space and small heat dissipation area, resulting in long cooling times and uneven heat dissipation, which affect the performance of the fuel cell stack. Summary of the Invention

[0006] To address the problems of large air volume and high flow rate in commonly used air-cooled proton exchange membrane fuel cells, which lead to membrane dryness, increased membrane resistance, and poor heat dissipation due to the straight-through air cooling channel (flow field), this invention proposes a method to increase the windward heat dissipation surface while protecting the membrane electrode from direct wind blowing, thereby improving the heat dissipation effect and enhancing the performance and stability of the membrane electrode.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] A metal bipolar plate for an air-cooled proton exchange membrane fuel cell, the bipolar plate comprising an anode plate with a hydrogen flow field and a cathode plate with an air flow field; the cathode plate is formed by stamping a thin metal plate into several supports and openings, the supports including a supporting vertical surface and a supporting horizontal surface, forming a bridge-like structure; the supporting horizontal surface is in contact with the anode plate, the openings are air channels for participating in the electrochemical reaction; an air cooling channel is formed between the cathode plate and the anode plate.

[0009] The support body must withstand the self-tightening force of the fuel cell stack while also providing electronic conductivity, and its surface must undergo conductive and corrosion-resistant treatment.

[0010] Based on the above technical solutions, preferably, the supporting surface of the thin metal cathode plate, which is stamped into a support body, is in a windward position, which can increase the effective contact area between the cooling air and the cooling cathode plate and improve the cooling effect; the opening of the air channel participating in the electrochemical reaction is in a leeward position, which can prevent the air from directly drying the membrane electrode.

[0011] Based on the above technical solutions, preferably, the height of the supporting facade of the thin metal cathode plate is 0.3-3mm, and the opening ratio is 25-75%. The opening ratio is the percentage of the total area of ​​all openings left on the plate surface after stamping to the total area of ​​the cathode plate. The facade height determines the thickness of the bipolar plate. If it is too small, the ventilation resistance will increase, the energy consumption will be too high, and it will not achieve the purpose of cooling. If it is too large, it will occupy a lot of space, be bulky, and have a lower volumetric power ratio. The original thickness of the cathode plate is 0.03-2mm, which is selected according to the specific stamping conditions.

[0012] Based on the above technical solutions, preferably, the arrangement of the thin metal cathode plate support can be staggered or arrayed.

[0013] Based on the above technical solutions, preferably, the cathode plate is made of stainless steel, titanium, titanium alloy, aluminum, aluminum alloy, nickel, nickel alloy, or copper.

[0014] Based on the above technical solutions, preferably, the hydrogen flow field of the anode plate is a flexible graphite flow field attached to the surface of the anode plate, a conductive and gas-conducting metal mesh, or is made by stamping the anode plate.

[0015] The present invention also provides a gas-cooled proton exchange membrane fuel cell single cell, including a membrane electrode and a bipolar plate, wherein the membrane electrode is encapsulated between two adjacent metal bipolar plates, and the bipolar plate is the aforementioned metal bipolar plate.

[0016] The present invention also provides an air-cooled proton exchange membrane fuel cell, comprising a stack, a shroud and a fan, wherein the stack is composed of a plurality of the above-mentioned single cells connected in series.

[0017] The beneficial effects of this invention are as follows:

[0018] 1. The cathode plate of this invention transforms the traditional corrugated plate or corrugated plate type straight-through cooling air duct into a bridge pier-type support structure. The vertical surface of the support structure directly becomes the windward surface, which increases the effective heat dissipation area and improves the effective heat dissipation efficiency.

[0019] 2. While the support structure directly faces the wind, the openings on the cathode plate become air channels for participating in the electrochemical reaction. The diffusion layer outside the exposed membrane electrode is on the leeward side, which avoids cooling air blowing directly onto it and improves the stability of the membrane electrode.

[0020] 3. The bipolar plate is composed of only two thin metal plates, which is lightweight and has a high power-to-weight ratio in the fuel cell stack;

[0021] 4. The bipolar plate has a simple structure, is easy to process, reduces production costs, and is suitable for large-scale promotion and use. Attached Figure Description

[0022] Figure 1 The present invention is a cathode plate with staggered support bodies;

[0023] Figure 2 This is a structural diagram of the support body of the present invention;

[0024] Figure 3 This refers to the direction of cooling airflow within the airflow field of the cathode plate in this invention.

[0025] Figure 4 This is a structural diagram of the bipolar plate-film electrode unit of the present invention;

[0026] Figure 5 This is a structural diagram of the gas-cooled proton exchange membrane fuel cell of the present invention;

[0027] Figure 6This is a performance diagram of the gas-cooled proton exchange membrane fuel cell of the present invention;

[0028] The components are: 1. Supporting facade; 2. Supporting plane; 3. Opening; 4. Membrane electrode; 5. Hydrogen flow field; 6. Anode sealing ring; 7. Anode plate; 8. Cathode plate; 9. Cathode sealing gasket; 10. Hydrogen inlet / outlet port; 11. Single cell; 12. Fuel cell stack; 13. Radiator; 14. Fan. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following description of the embodiments is only for the purpose of helping to understand the principles and core ideas of the present invention, and is not intended to limit the scope of protection of the present invention. It should be noted that for those skilled in the art, any obvious modifications, equivalent substitutions, or other improvements made to the present invention without departing from the principles of the present invention also fall within the scope of protection of the claims of the present invention.

[0030] Example 1

[0031] Thin metal sheets are pressed into several supporting bodies and openings to form a bridge pier-like structure, such as... Figure 1 As shown, the support structure is arranged in a crisscross pattern, as shown in the diagram. Figure 2 As shown, the support consists of a support facade 1 and a support plane 2. The support plane 2 is in contact with the anode plate. The height of the support facade 1 is 1 mm. After the cathode plate is stamped, the openings 3 formed on the plate surface become air channels for participating in the electrochemical reaction. The ratio of the total area of ​​all openings to the area of ​​the cathode plate, i.e., the opening ratio, is 38%. An air cooling channel is formed between the cathode plate 8 and the anode plate 7 supported by the support. Figure 3 The arrows indicate the direction of airflow. The supporting surface 1 of the support is positioned in the windward direction, which increases the effective contact area between the cooling air and the cooling cathode plate 8, thus improving the cooling effect. The opening 3 of the air channel participating in the electrochemical reaction is positioned in the leeward direction, which prevents the air from directly drying the membrane electrode, improving the performance and lifespan of the membrane electrode 4. The support must withstand the self-tightening force of the fuel cell stack and also provide electronic conductivity. It is made of stainless steel, titanium, titanium alloy, aluminum, aluminum alloy, nickel, nickel alloy, or copper plates, and its surface undergoes conductive and corrosion-resistant treatment after molding. In this embodiment, 316L stainless steel plate is used, and the surface is silver-plated.

[0032] Figure 4This diagram illustrates the structure of a bipolar plate-membrane electrode unit in a fuel cell stack. Between the two membrane electrodes 4 is a bipolar plate assembly, consisting of a hydrogen flow field 5, an anode sealing ring 6, an anode plate 7, a cathode plate 8, and a cathode sealing gasket 9. An air cooling channel is formed between the anode plate 7 and the cathode plate 8, and an opening 3 on the cathode plate 8 forms an air channel for participating in the electrochemical reaction. The hydrogen flow field 5 can be a flexible graphite flow field attached to the surface of the anode plate, a conductive and gas-conducting metal mesh, or it can be directly stamped from the anode plate 7. It forms a hydrogen transport channel with the membrane electrode 4, providing hydrogen for the electrochemical reaction and simultaneously discharging unreacted hydrogen (participating in the circulation) and reverse osmosis water. The hydrogen inlet / outlet 10 is a vertical through-hole in the fuel cell stack, or a common conduit. Hydrogen enters through the inlet, passes through the anode flow field, and exits through the outlet. For example, if it enters from the left inlet, passes through the cathode flow field, and exits from the right outlet.

[0033] A fuel cell stack 12 is formed by multiple single cells 11 connected in series, with current collectors and end plates added to both sides. A shroud 13 and a fan 14 are installed on the side of the stack, forming an air-cooled proton exchange membrane fuel cell. Figure 5 The fan 14 can operate in either suction or blowing mode. In suction mode, the support surface 1 on the cathode plate 8 should face away from the fan. In blowing mode, the support surface 1 on the cathode plate 8 should face closer to the fan, ensuring that air is directly blown onto the support surface 1, and that the air opening is in a leeward position.

[0034] The anode plate 7 is 0.1mm thick, and its surface is coated with a flexible graphite flow field 5, around which are the flow field and hydrogen inlet / outlet holes 10. The anode plate and cathode flow field plate are made of 316L stainless steel, and their surfaces are silver-plated to improve conductivity and corrosion resistance.

[0035] A gas-cooled proton exchange membrane fuel cell is assembled from 28 individual cells, with each electrode having an active area of ​​100 cm². 2 The hydrogen pressure is 0.5 bar, and air serves as both the cooling medium and the oxidant. Battery performance is as follows: Figure 6 As shown, the maximum output is 1092W.

Claims

1. A metal bipolar plate for use in a gas-cooled proton exchange membrane fuel cell, characterized in that: The bipolar plate includes an anode plate with a hydrogen flow field and a cathode plate with an air flow field. The cathode plate is formed by stamping a thin metal plate into several supports and openings. The supports include a support surface and a support plane, forming a bridge pier structure. The support plane is in contact with the anode plate, and the openings are air channels for participating in the electrochemical reaction. An air cooling channel is formed between the cathode plate and the anode plate. The supporting facade is positioned facing the wind, while the opening is positioned in the leeward direction.

2. The metal bipolar plate for a gas-cooled proton exchange membrane fuel cell according to claim 1, characterized in that: The height of the supporting facade is 0.3-3mm; the total area of ​​the several openings is 25-75% of the total area of ​​the cathode plate.

3. A metal bipolar plate for a gas-cooled proton exchange membrane fuel cell according to claim 1, characterized in that: The arrangement of the supports on the cathode plate is either staggered or arrayed.

4. A metal bipolar plate for a gas-cooled proton exchange membrane fuel cell according to claim 1, characterized in that: The cathode plate is made of stainless steel, titanium, titanium alloy, aluminum, aluminum alloy, nickel, nickel alloy, or copper.

5. A metal bipolar plate for a gas-cooled proton exchange membrane fuel cell according to claim 1, characterized in that: The hydrogen flow field of the anode plate is a flexible graphite flow field attached to the surface of the anode plate, a conductive and gas-conducting metal mesh, or is made by stamping the anode plate.

6. A gas-cooled proton exchange membrane fuel cell single cell, comprising a membrane electrode assembly (MEA), bipolar plates, wherein the MEA is encapsulated between two adjacent metal bipolar plates, characterized in that, The bipolar plate is the metal bipolar plate according to any one of claims 1-5.

7. A gas-cooled proton exchange membrane fuel cell, characterized in that, It includes a fuel cell stack, a shroud, and a fan, wherein the fuel cell stack is composed of several single cells as described in claim 6 connected in series.

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