Air-cooled hydrogen fuel cell stack structure based on integrated closed cathode

Abstract

The application discloses a wind-cooled hydrogen fuel cell stack structure based on integrated closed cathodes, which comprises an integrated closed cathode plate based on a porous metal substrate, a membrane electrode, an anode plate and an integrated closed cathode stack, wherein the integrated closed cathode plate is divided into a base plate and a protrusion two-part structure, the protrusion types include three types of straight strip type, curved strip type and wing type, and thus the integrated closed cathode plate is divided into three types of straight strip type protrusion cathode plate, curved strip type protrusion cathode plate and wing type protrusion cathode plate according to different protrusion types. The application can obviously improve the influence of the air flow of the wind-cooled fuel cell on the water balance of the membrane electrode, greatly simplifies the system control difficulty, and only considers the heat dissipation demand factor of the air flow, thereby avoiding the system control complexity caused by simultaneously considering the water balance problem of the membrane electrode, improving the battery performance and stability, and prolonging the battery life.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, specifically to an air-cooled hydrogen fuel cell stack structure based on an integrated closed cathode. Background Technology

[0002] Hydrogen fuel cell stacks can be classified into two types according to their cooling methods: coolant (usually a mixture of water and ethylene glycol) cooling (hereinafter referred to as "water cooling") and air cooling (hereinafter referred to as "air cooling"). Each type has its advantages and disadvantages. Water-cooled stacks have higher heat dissipation efficiency and smaller stack size because the heat capacity of the coolant is much higher than that of air. However, the water-cooling subsystem is relatively complex, including not only the coolant circulation system, but also the plate design, which must consider the compatibility of the coolant, air, and hydrogen flow channels. The design and manufacturing difficulty is greater than that of air cooling, and the cost is higher.

[0003] The advantages of air-cooled fuel cell stacks are that they eliminate the need for a water-cooling circulation system, relying solely on air for heat dissipation. This results in a simpler system with fewer components and lower cost. The disadvantages are that air has a much lower heat capacity than coolant, leading to lower heat dissipation efficiency. A large amount of air is needed to carry away the heat, so the excess air coefficient in the stack's airflow design is often tens to hundreds of times larger than that of water-cooled stacks. To meet the airflow requirements, the cross-sectional area of ​​the cathode plate flow channels in air-cooled stacks is often much larger than that in water-cooled stacks. Furthermore, due to the low heat capacity of air, the channel length is significantly limited to ensure efficient heat dissipation. These factors result in a larger volume of air-cooled cathode plates, leading to a lower volumetric power density in air-cooled fuel cell stacks.

[0004] For the reasons mentioned above, generally speaking, fuel cell stacks with a power of 10KW or more are suitable for water cooling, while small and medium power fuel cell stacks with a power of less than 10KW are suitable for air cooling.

[0005] Currently, most air-cooled hydrogen fuel cell cathode plates on the market adopt a grooved structure, which is mostly made of graphite (carved or molded) or metal plate (stamped). After being stacked into an open cathode stack, the grooved surface is in direct contact with the cathode diffusion layer of the membrane electrode, and the groove and the membrane electrode form an air flow channel.

[0006] In this structure, a large amount of air in the cathode channel directly sweeps the cathode-side diffusion layer (GDL) of the membrane electrode assembly, easily causing excessive evaporation of liquid water in the cathode-side membrane electrode assembly. This leads to a dehydrated proton exchange membrane (membrane dryness), reduced mass transfer capacity, and consequently, decreased fuel cell performance. Therefore, in the actual operation of air-cooled hydrogen fuel cells, airflow is not only constrained by heat dissipation requirements but also by the impact of "membrane dryness," increasing the difficulty of airflow control. In other words, while ensuring the required airflow for heat dissipation, membrane dryness can easily occur, affecting not only fuel cell performance but also significantly reducing its lifespan. Summary of the Invention

[0007] The purpose of this invention is to provide an air-cooled hydrogen fuel cell stack structure based on an integrated closed cathode on a porous metal substrate, so as to solve the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a wind-cooled hydrogen fuel cell stack structure based on an integrated closed cathode, comprising a porous metal integrated closed cathode plate, a membrane electrode assembly (MEA), an anode plate, and an integrated closed cathode stack. The integrated closed cathode plate consists of a cathode plate substrate and two protrusions, which are integrally formed and inseparable. The protrusions are classified into three types: straight strip type, curved strip type, and airfoil type. Therefore, the integrated closed cathode plate is further subdivided into three types: straight strip type protruding cathode plate, curved strip type protruding cathode plate, and airfoil type protruding cathode plate. A MEA is disposed on the upper side of the anode plate, and a porous metal integrated closed cathode plate is disposed on the upper side of the MEA. The upper side of the anode plate is connected to the MEA.

[0009] Preferably, the side of the porous metal integrated closed cathode plate that contacts the cathode-side diffusion layer of the membrane electrode is a plane with micropores on its surface and has undergone metal surface modification treatment. The other side is a raised structure, which can be any one of three types: straight strip, curved strip, and airfoil. The space on both sides of the raised structure is a continuous space, forming an airflow channel.

[0010] Preferably, the average pore size of the porous integrated metal closed cathode plate is between 1 and 500 micrometers, and the porosity is between 10% and 70%.

[0011] Preferably, the substrate material of the porous integrated metal closed cathode plate includes, but is not limited to, stainless steel, titanium, aluminum, nickel, iron, and copper. The porous integrated metal closed cathode plate is composed of two structures: a cathode plate substrate and protrusions. The cathode plate and protrusions are integrally formed and are an inseparable whole. The protrusions include three types: straight strip type, curved strip type, and wing type.

[0012] Preferably, the protruding cross-sectional shape of the porous integrated metal closed cathode plate includes, but is not limited to, three types: straight strip, curved strip, and wing-shaped, and the height of the protrusion is between 0.2-30mm.

[0013] Preferably, the integrated closed cathode stack includes a porous metal integrated closed cathode plate (including three types: straight strip-shaped raised cathode plate, curved strip-shaped raised cathode plate, and wing-shaped raised cathode plate), a membrane electrode, and an anode plate.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] This invention addresses two main issues. Firstly, the porous metal material is a three-dimensional structure with pore sizes ranging from several micrometers to hundreds of micrometers. Under specific porosity and open-pore ratio conditions, it exhibits excellent hydrophilicity and water absorption, while also maintaining good electrical conductivity, thermal conductivity, gas conductivity, and mechanical properties. Upon contact with the material, water is instantly absorbed through capillary action and diffuses along the metal surface between the tiny pores into the porous metal structure. Secondly, the porous metal significantly increases the specific surface area, enhancing the water evaporation rate. This continuously draws liquid water from the cathode-side diffusion layer (GDL) of the membrane electrode assembly (MEA) into the porous metal structure, evaporating it into water vapor, which is then discharged from the fuel cell. Simultaneously, the evaporation of water absorbs a large amount of heat, enhancing the stack's heat dissipation effect. Furthermore, the air in the fuel cell flow channel is generally an unsaturated gas with low relative humidity. In traditional air-cooled fuel cells, a large amount of air directly blows across the surface of the cathode-side diffusion layer of the MEA. Excessive evaporation of water from the proton exchange membrane within the membrane electrode assembly (MEA) can easily lead to a decrease in membrane water content (membrane dryness), thereby reducing the membrane's hydrogen ion transport capacity. The fuel cell structure of this invention avoids direct airflow sweeping of the Cathode-side diffusion layer of the MEA. Instead, air from the cathode channel is indirectly diffused to the MEA catalyst layer via porous metal. Simultaneously, during air diffusion, a large amount of water vapor from the evaporation of liquid water on the porous metal surface is mixed in, humidifying the diffused air. This significantly increases the relative humidity of the air reaching the MEA, slowing down the evaporation rate of water in the MEA and thus providing moisture retention for the proton exchange membrane. Through these three characteristics, the impact of airflow on the MEA water balance in an air-cooled fuel cell can be significantly improved, greatly simplifying system control. Airflow only needs to consider heat dissipation requirements, avoiding the system control complexity caused by simultaneously considering the MEA water balance issue. This improves battery performance and stability and extends battery life. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the assembly structure of an air-cooled integrated closed cathode stack according to an embodiment of the present invention;

[0017] Figure 2 This is a three-dimensional structural diagram of a porous integrated metal closed cathode plate with straight, elongated protrusions according to an embodiment of the present invention.

[0018] Figure 3 This is a three-dimensional structural diagram of a porous integrated metal closed cathode plate with curved elongated protrusions according to an embodiment of the present invention.

[0019] Figure 4 This is a three-dimensional structural diagram of a porous integrated metal closed cathode plate with wing-shaped protrusions according to an embodiment of the present invention.

[0020] Figure 5This is a schematic diagram of a three-dimensional structure of a metal pressure-formed anode plate according to an embodiment of the present invention;

[0021] Figure 6 This is a partial cross-sectional view of an integrated closed cathode stack AA according to an embodiment of the present invention, as well as a diagram showing the flow of water, heat, gas, and current.

[0022] Figure 7 The commonly used air-cooled open cathode plate structure uses solid graphite or graphite composite material.

[0023] Figure 8 A comparative schematic diagram of common air-cooled open cathode fuel cell stack structures on the market;

[0024] Figure 9 This is a partial cross-section of a common example of an air-cooled open cathode fuel cell stack, along with diagrams showing the flow of water, heat, gas, and current.

[0025] In the figure: 1. Straight strip-shaped raised cathode plate; 2. Curved strip-shaped raised cathode plate; 3. Airfoil-shaped raised cathode plate; 4. Cathode plate substrate; 5. Straight strip-shaped protrusion; 6. Curved strip-shaped protrusion; 7. Airfoil-shaped protrusion; 8. Membrane electrode; 9. Anode plate; 10. Integrated closed cathode stack based on straight strip-shaped raised cathode plate; 13. Open cathode stack; 14. Traditional groove structure open cathode plate. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see Figure 1-9A wind-cooled hydrogen fuel cell stack structure based on an integrated closed cathode includes a stack body, which is composed of several single cells stacked based on an integrated closed cathode plate. Each single cell consists of a cathode plate, a membrane electrode assembly (MEA), and an anode plate. The anode plate has grooved channels and is made of graphite, graphite composite material, or a surface-modified metal material. The grooved channels of the anode plate are arranged in an array. The side of the anode plate with the channels is in close contact with the gas diffusion layer (GDL) on the anode side of the MEA under a certain vertical assembly pressure. The cathode plate is made of a porous metal material with a certain degree of hydrophilicity, and one side is a coated plane (containing micropores). This plane is in close contact with the gas diffusion layer (GDL) on the cathode side of the MEA. The cathode gas diffusion layer (GDL) is tightly bonded under a certain vertical assembly pressure, so that the air in the cathode channel does not directly contact the cathode-side gas diffusion layer (GDL) in the membrane electrode assembly, but diffuses to the cathode-side gas diffusion layer (GDL) through the micropores in the cathode plate, forming a so-called closed cathode structure. The other side is provided with multiple sets of protrusions. The shapes of the protrusions include, but are not limited to, traditional straight strips, curved strips, and airfoils. The multiple sets of protrusions are arranged in an array. After several single cells are stacked, they form a stack. In the stack, the top of the cathode plate protrusions and the anode plate back plate are tightly bonded under a certain vertical assembly pressure. At the same time, the groove space between the multiple sets of protrusions of the cathode plate and the anode plate back plate form an open air channel.

[0028] The cathode plate is made of porous metal material with high specific surface area, porosity and open porosity. On the one hand, it exhibits good hydrophilicity, which can instantly absorb water from the gas diffusion layer of the membrane electrode assembly, enhancing the drainage capacity of the gas diffusion layer. On the other hand, it increases the heat dissipation area, enhances the water evaporation rate, and improves the heat dissipation capacity. The third cathode plate isolates the diffusion layer from the air, which can avoid the water imbalance phenomenon (membrane dryness) caused by excessive evaporation of water in the proton exchange membrane due to direct contact between the diffusion layer and the air, and simplifies the control of the stack cooling airflow.

[0029] In a typical closed-cathode air-cooled fuel cell stack, the metal diffusion layer and the airflow channel plate are two separate parts, made of porous metal and metal plate respectively. The cathode plate of this invention is an integrated cathode that combines the functions of a flow channel groove structure and a diffusion layer, prepared using a complex porous metal forming technology. After battery assembly, it is tightly attached to the anode plate backplate to form an airflow channel. This allows the cathode plate to not only have the functions of a traditional gas diffusion layer (GDL) such as water absorption, moisture retention, electrical conductivity, and gas conduction, but also the functions of a traditional cathode plate such as accelerating water evaporation, heat dissipation, and providing support for the airflow channel structure. The stack structure simplifies the difficulty of balancing and controlling the by-product water and heat in the fuel cell reaction, reduces the number of parts, thereby reducing interface resistance and manufacturing costs, and improving the durability and cost-effectiveness of the stack. Therefore, the cathode plate based on porous metal combines the above multiple functions and, together with the membrane electrode assembly and anode plate, forms an integrated closed-cathode air-cooled fuel cell stack structure with good durability and cost-effectiveness.

[0030] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A wind-cooled hydrogen fuel cell stack structure based on an integrated closed cathode, comprising an integrated closed cathode stack (10), characterized in that: The integrated closed cathode stack (10) includes an integrated closed cathode plate based on a porous metal substrate, a membrane electrode (8), and an anode plate (9). The integrated closed cathode plate based on the porous metal substrate is divided into three types: a straight elongated protruding cathode plate (1), a curved elongated protruding cathode plate (2), and a wing-shaped protruding cathode plate (3). The straight elongated protruding cathode plate (1) includes a cathode plate substrate (4) and a straight elongated protrusion (5). The curved elongated protruding cathode plate (2) includes a cathode plate substrate (4) and a curved elongated protrusion (6). The wing-shaped protruding cathode plate (3)... The electrode plate (3) comprises two parts: a cathode substrate (4) and a wing-shaped protrusion (7). A membrane electrode (8) is provided on the upper side of the anode plate (9). An integrated closed cathode plate based on a porous metal substrate is provided on the upper side of the membrane electrode (8). The anode plate (9) is located on the upper side of the integrated closed cathode plate based on the porous metal substrate. The upper side of the anode plate (9) is connected to the membrane electrode (8). The side of the integrated closed cathode plate based on the porous metal substrate that contacts the cathode-side diffusion layer of the membrane electrode (8) is a plane. Furthermore, the portion of the porous metal plane that contacts the cathode-side diffusion layer of the membrane electrode (8) is provided with a metal-modified coating. The coating is discontinuous and porous. The side of the integrated closed cathode plate based on the porous metal substrate that does not contact the membrane electrode (8) is a raised structure. The space on both sides of the raised structure is a continuous space. The average pore size of the porous metal substrate of the integrated closed cathode plate based on the porous metal substrate is between 1 and 500 micrometers, and the porosity is between 10% and 70%. The substrate material of the integrated closed cathode plate based on the porous metal substrate includes stainless steel, titanium, aluminum, nickel, iron, and copper. The cross-sectional shape of the raised part of the integrated closed cathode plate based on the porous metal substrate includes a straight long strip protrusion (5) and a curved long strip protrusion (6). The cathode plate substrate (4) of the integrated closed cathode plate based on porous metal substrate is between 0.2-5mm thick, and the cathode plate substrate (4) and any one of the straight strip protrusion (5), curved strip protrusion (6) and wing protrusion (7) are integrally formed and belong to an inseparable whole part. The anode plate (9) is a traditional groove flow channel, and its substrate material includes metal, graphite and graphite composite material. The groove processing technology includes engraving, etching, pressure forming and molding processing technology.

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