Membrane electrode structure and air-cooled fuel cell

Abstract

The application provides a membrane electrode structure, which comprises a cathode gas diffusion layer, a CCM unit and an anode gas diffusion layer, the CCM unit is arranged between the cathode gas diffusion layer and the anode gas diffusion layer, the cathode gas diffusion layer is arranged close to the cathode side of the CCM unit, and the anode gas diffusion layer is arranged close to the anode side of the CCM unit; the cathode gas diffusion layer is a multilayer foam metal gas diffusion layer; and the porosity of the multilayer foam metal gas diffusion layer is 50%-90%. The application also provides an air-cooled fuel cell. The cathode gas diffusion layer of the application has better thermal conductivity, which is more conducive to transferring the heat generated by chemical reaction to the cathode flow channel so as to take away the heat and is conducive to discharging the reaction water. The air-cooled fuel cell of the application has good moisturizing capacity, and can effectively avoid the phenomenon that the battery performance is reduced and the service life is rapidly attenuated due to insufficient wetting of the membrane electrode.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a membrane electrode structure and an air-cooled fuel cell. Background Technology

[0002] Hydrogen fuel cells offer advantages such as being clean, environmentally friendly, and structurally simple. With ongoing research into hydrogen fuel cells, they have become integrated into our daily lives, including various vehicle systems (hydrogen fuel cell buses, logistics vehicles, heavy-duty trucks, sanitation vehicles, etc.), backup power supplies, and home energy storage devices. A single fuel cell typically consists of plates and a membrane electrode assembly (MEA). Multiple cells are connected in series to form a fuel cell, enabling high-voltage output. The required voltage and power output constitutes a fuel cell stack.

[0003] Fuel cells are generally classified into liquid-cooled fuel cells and air-cooled fuel cells. Air-cooled fuel cells are widely used in low-power applications such as small two-wheeled vehicles, three-wheeled vehicles, drones, and emergency power supplies due to their advantages of fewer auxiliary components, simpler structure, and easier control. However, because the cathode of an air-cooled fuel cell uses a fully open flow channel, temperature and humidity coupling is difficult. When the fan speed is high, although it can reduce the temperature of the fuel cell stack, the membrane electrode assembly (MEA) dries out; when the fan speed is low, although it can maintain the humidity of the MEA, it is difficult to maintain the stack temperature within the ideal range. Therefore, air-cooled fuel cells suffer from uneven heat dissipation and difficulties in temperature and humidity coupling. Summary of the Invention

[0004] Based on this, embodiments of the present invention provide a membrane electrode structure and an air-cooled fuel cell, aiming to solve the problems of uneven heat dissipation and difficulty in temperature and humidity coupling in existing air-cooled fuel cells.

[0005] To achieve the above objectives, in one aspect, embodiments of the present invention provide a membrane electrode structure, including a cathode gas diffusion layer, a CCM unit, and an anode gas diffusion layer. The CCM unit is disposed between the cathode gas diffusion layer and the anode gas diffusion layer. The cathode gas diffusion layer is disposed on the cathode side near the CCM unit, and the anode gas diffusion layer is disposed on the anode side near the CCM unit.

[0006] The cathode gas diffusion layer is a multilayer foamed metal gas diffusion layer; the porosity of the multilayer foamed metal gas diffusion layer is 50% to 90%.

[0007] In a preferred embodiment, the multilayer foamed metal gas diffusion layer includes at least a first diffusion layer and a second diffusion layer stacked together, with the first diffusion layer disposed close to the CCM unit.

[0008] In a preferred embodiment, the multilayer foamed metal gas diffusion layer is prepared by the following method: the first diffusion layer and the second diffusion layer are stacked and dried to obtain a shaped plate; the shaped plate is placed at 800℃~1200℃ for 20min~30min and cooled to obtain the multilayer foamed metal gas diffusion layer.

[0009] As a preferred embodiment.

[0010] The drying temperature is 40℃~80℃.

[0011] The insulation is carried out in a non-oxidizing environment. The first and second spherical foaming agents decompose and release gas during heating, forming spherical cellular pores of different sizes.

[0012] In a preferred embodiment, the first diffusion layer is prepared by the following method: mixing a first metal powder and a first spherical foaming agent at a mass ratio of 70:30 to 90:10 to obtain a first mixture; hot-pressing the first mixture to obtain the first diffusion layer; the hot-pressing temperature is 150℃ to 350℃, the time is 30s to 3min, and the pressure is 0.2MPa to 1MPa.

[0013] As a preferred embodiment.

[0014] The first metal powder is dehydrogenated titanium powder.

[0015] The porosity of the first diffusion layer is 40% to 65%.

[0016] The first spherical foaming agent is NaCl or K2CO3.

[0017] The mixing is achieved by a planetary ball mill or a two-roll internal mixer.

[0018] The hot pressing is achieved using a press.

[0019] In a preferred embodiment, the second diffusion layer is prepared by the following method: mixing the second metal powder and the second spherical foaming agent at a mass ratio of 60:40 to 80:20 to obtain a second mixture; hot-pressing the second mixture to obtain a pre-pressed second diffusion layer; and then sintering the pre-pressed second diffusion layer at 250°C to 500°C and a pressure of 0.2 MPa to 1 MPa for 30 seconds to 5 minutes to obtain the second diffusion layer.

[0020] As a preferred embodiment.

[0021] The second metal powder is copper powder or aluminum powder.

[0022] The porosity of the second diffusion layer is 60%–95%.

[0023] The second spherical foaming agent is polystyrene (EPS).

[0024] The mixing is achieved by a planetary ball mill or a two-roll internal mixer.

[0025] The hot pressing is achieved using a press.

[0026] In this embodiment, the cathode gas diffusion layer is prepared using a multilayer foamed metal material. Compared to carbon-based gas diffusion layers, the cathode gas diffusion layer of this application has superior thermal conductivity, which is more conducive to transferring the heat generated by the chemical reaction to the cathode channel for heat removal. Moreover, the foamed metal gas diffusion layer has sufficient porosity, which is beneficial for the drainage of water generated in the reaction. In particular, composite gas diffusion layers with different porosities can be made according to the requirements of drainage and moisture retention.

[0027] On the other hand, embodiments of this application provide an air-cooled fuel cell, which is fabricated from the membrane electrode structure.

[0028] In a preferred embodiment, the air-cooled fuel cell includes an electrode body and a membrane electrode structure; one side of the electrode body is configured as a cathode surface and the other side as an anode surface; the membrane electrode structure is disposed between the cathode surface and the anode surface, with the cathode gas diffusion layer of the membrane electrode structure disposed close to the cathode surface and the anode gas diffusion layer of the membrane electrode structure disposed close to the anode surface.

[0029] In a preferred embodiment, a cathode flow channel is provided on the cathode surface, and the inlet of the cathode flow channel is arranged in a C-shape. This creates a semi-open flow field structure at the inlet side of the cathode flow channel, facilitating the entry of external cold air into the cathode flow channel to remove the heat generated by the reaction and the water produced by the cathode membrane electrode reaction, effectively preventing flooding on the cathode side. Furthermore, the anode of this application has a closed structure, while the cathode has an open structure, which reduces the number of system BOP accessories and requirements.

[0030] Compared with the prior art, the specific technical effects of this application are as follows:

[0031] (1) This application uses a multilayer foamed metal material to prepare the cathode gas diffusion layer of the membrane electrode structure. Compared with carbon-based gas diffusion layers, the cathode gas diffusion layer of this application has better thermal conductivity, which is more conducive to transferring the heat generated by the chemical reaction to the cathode channel to remove the heat. Moreover, the foamed metal gas diffusion layer has sufficient composite porosity, which is conducive to the drainage of water generated by the reaction. Foamed metal gas diffusion layers with different porosities can be made according to the requirements of drainage, moisture retention, different power levels, or environmental conditions (for example, the porosity and resistivity of the gas diffusion layer can be adjusted to meet the requirements of moisture retention by adjusting the composition formula).

[0032] (2) The cathode of the air-cooled fuel cell of this application adopts a semi-open flow field, which has good moisturizing ability and can effectively avoid the phenomenon of battery performance degradation and rapid life decay caused by insufficient wetting of membrane electrode due to excessive dryness. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0034] Figure 1 This is a partial cross-sectional structural diagram of a membrane electrode according to an embodiment of the present invention;

[0035] Figure 2 for Figure 1 A three-dimensional structural diagram of the cathode gas diffusion layer in a membrane electrode structure;

[0036] Figure 3 This is a schematic diagram of the overall structure of an air-cooled fuel cell according to another embodiment of this application;

[0037] Figure 4 for Figure 3 A schematic diagram of the cross-sectional structure;

[0038] Figure 5 This is a schematic diagram of air entering the cathode channel;

[0039] Figure 6 for Figure 3 The result of surface humidity detection for an air-cooled fuel cell.

[0040] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0041] 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 a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, top, bottom, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0043] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0044] It should be noted that when a component is described as "fixed to" or "set on" another component, it can be directly on the other component or there may be an intervening component. When a component is described as "connected to" another component, it can be directly connected to the other component or there may be an intervening component.

[0045] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0046] Currently, existing technologies have the following drawbacks:

[0047] 1) Existing air-cooled fuel cell plates are mostly open cathode structures, which presents the problem of difficulty in coupling the two phases of moisture retention and heat dissipation;

[0048] 2) Existing membrane electrodes generally use thick carbon paper or carbon cloth as a gas diffusion layer. Protons pass through the fluorosulfonic acid proton membrane to generate water, while liquid water is mostly formed in porous layers or flow field channels.

[0049] 3) Existing gas diffusion layers (such as carbon cloth and carbon paper) have limited water retention capacity due to their fibrous structure. When a large flow of air passes through the open cathode flow field, the carbon paper (carbon cloth) on the cathode side of the membrane electrode is easily dried out, making it impossible to wet and humidify the polymer electrolyte.

[0050] Based on this, embodiments of this application provide a membrane electrode structure and an air-cooled fuel cell to solve the above-mentioned technical problems.

[0051] Specifically, such as Figures 1 to 2 As shown, an embodiment of the present invention provides a membrane electrode structure, including a cathode gas diffusion layer 10, a CCM unit 20, and an anode gas diffusion layer 30. The CCM unit 20 is disposed between the cathode gas diffusion layer 10 and the anode gas diffusion layer 30. The cathode gas diffusion layer 10 is disposed near the cathode side of the CCM unit 20, and the anode gas diffusion layer 30 is disposed near the anode side of the CCM unit 20.

[0052] The cathode gas diffusion layer 10 is a multilayer foamed metal gas diffusion layer; the porosity of the multilayer foamed metal gas diffusion layer is 50% to 90%.

[0053] In this application, depending on the requirements of drainage, moisture retention, different power levels, or environmental conditions, the porosity and resistivity of the multilayer foamed metal gas diffusion layer can be adjusted to meet the moisture retention requirements, thus creating multilayer foamed metal gas diffusion layers with different porosities. The porosity of the multilayer foamed metal gas diffusion layer is controlled between 50% and 90%, for example, it can be 50%, 60%, 75%, or 90%, etc. If the porosity of the multilayer foamed metal gas diffusion layer is less than 50%, it is not conducive to transferring the heat generated by the chemical reaction to the cathode channel to remove heat, affecting the heat dissipation effect, and it is also not conducive to the drainage of water generated by the reaction, leading to water retention. If the porosity of the multilayer foamed metal gas diffusion layer is greater than 90%, it is easy to cause the membrane electrode to become too dry and insufficiently wetted, which in turn leads to a decrease in battery performance and a rapid decline in battery life.

[0054] In a preferred embodiment, the multilayer foamed metal gas diffusion layer includes at least a first diffusion layer 11 and a second diffusion layer 12 stacked together, with the first diffusion layer 11 disposed close to the CCM unit 20.

[0055] In a preferred embodiment, the multilayer foamed metal gas diffusion layer is prepared by the following method: the first diffusion layer and the second diffusion layer are stacked and dried to obtain a shaped plate; the shaped plate is placed at 800℃~1200℃ (depending on the actual use, it can be 800℃, 900℃, 1000℃, or 1200℃, etc.) for 20min~30min (depending on the actual use, it can be 20min, 23min, 26min, or 30min, etc.) and cooled to obtain the multilayer foamed metal gas diffusion layer.

[0056] As a preferred embodiment.

[0057] The drying temperature is 40℃~80℃ (depending on the actual needs, it can be 40℃, 50℃, 65℃, 80℃, etc.).

[0058] The insulation is carried out in a non-oxidizing environment. This ensures that the first and second spherical foaming agents in the gas diffusion layer decompose and release gas during heating, forming spherical cellular pores of different sizes.

[0059] In a preferred embodiment, the first diffusion layer is prepared by the following method: mixing a first metal powder and a first spherical foaming agent at a mass ratio of 70:30 to 90:10 to obtain a first mixture; hot-pressing the first mixture to obtain the first diffusion layer; the hot-pressing temperature is 150℃ to 350℃ (which can be 150℃, 200℃, 280℃, 350℃, etc., depending on the actual use requirements), the time is 30s to 3min (which can be 30s, 1min, 2min, 3min, etc., depending on the actual use requirements), and the pressure is 0.2MPa to 1MPa (which can be 0.2MPa, 0.5MPa, 0.7MPa, 1MPa, etc., depending on the actual use requirements).

[0060] As a preferred embodiment.

[0061] The first metal powder is dehydrogenated titanium powder.

[0062] The porosity of the first diffusion layer is 40% to 65%; depending on the actual needs of use, it can be 40%, 50%, 55%, 65%, etc.

[0063] The first spherical foaming agent is NaCl or K2CO3.

[0064] The mixing is achieved by a planetary ball mill or a two-roll internal mixer.

[0065] The hot pressing is achieved using a press.

[0066] In this application, by controlling the mass ratio of the first metal powder and the first spherical foaming agent to 70:30 to 90:10 (which can be 70:30, 80:20, 85:15, or 90:10, etc., depending on actual needs), and by controlling the hot pressing conditions, it can be ensured that the porosity of the first diffusion layer can meet the requirements of this application.

[0067] In a preferred embodiment, the second diffusion layer is prepared by the following method: a second metal powder and a second spherical foaming agent are mixed uniformly at a mass ratio of 60:40 to 80:20 to obtain a second mixture; the second mixture is hot-pressed to obtain a pre-pressed second diffusion layer; then, the pre-pressed second diffusion layer is sintered at 250°C to 500°C (which can be 250°C, 300°C, 350°C, or 500°C, etc., depending on the actual use requirements) and at a pressure of 0.2MPa to 1MPa (which can be 0.2MPa, 0.5MPa, 0.7MPa, or 1MPa, etc., depending on the actual use requirements) for 30s to 5min (which can be 30s, 1min, 3min, or 5min, etc., depending on the actual use requirements) to obtain the second diffusion layer.

[0068] As a preferred embodiment.

[0069] The second metal powder is either copper powder or aluminum powder, and copper powder or aluminum powder can be selected according to actual needs.

[0070] The porosity of the second diffusion layer is 60% to 95%; depending on the actual needs of use, it can be 60%, 70%, 85%, 95%, etc.

[0071] The second spherical foaming agent is polystyrene (EPS).

[0072] The mixing is achieved by a planetary ball mill or a two-roll internal mixer.

[0073] The hot pressing is achieved using a press.

[0074] In the embodiments of this application, by controlling the preparation conditions of the first diffusion layer and the second diffusion layer, and making the porosity of the first diffusion layer less than that of the second diffusion layer, it is possible to ensure that the prepared cathode gas diffusion layer has better thermal conductivity, which is more conducive to transferring the heat generated by the chemical reaction to the cathode channel for heat dissipation; at the same time, it is also possible to make the prepared cathode gas diffusion layer have sufficient porosity, which is conducive to the discharge of generated water while meeting the needs of membrane electrode wetting and moisturizing.

[0075] On the other hand, such as Figures 3 to 5 As shown in the figure, this application provides an air-cooled fuel cell, which is fabricated from the membrane electrode structure.

[0076] In a preferred embodiment, the air-cooled fuel cell includes an electrode body 100 and a membrane electrode structure 200; one side of the electrode body 100 is configured as a cathode surface 101, and the other side is configured as an anode surface 102; the membrane electrode structure 200 is disposed between the cathode surface 101 and the anode surface 102, with the cathode gas diffusion layer of the membrane electrode structure 200 disposed close to the cathode surface 101, and the anode gas diffusion layer of the membrane electrode structure 200 disposed close to the anode surface 102.

[0077] As a preferred embodiment, such as Figure 5 As shown, a cathode flow channel 1011 is provided on the cathode surface 101, and the inlet of the cathode flow channel 1011 is arranged in a C-shape. This creates a semi-open flow field structure on the inlet side of the cathode flow channel, facilitating the entry of external cold air into the cathode flow channel to remove the heat generated by the reaction and the water generated by the cathode membrane electrode reaction, effectively preventing flooding on the cathode side. Furthermore, the anode of this application has a closed structure, while the cathode has an open structure, which reduces the number of system BOP accessories and requirements.

[0078] This application employs a multilayer foamed metal material to fabricate the cathode gas diffusion layer of a membrane electrode structure. Compared to carbon-based gas diffusion layers, the cathode gas diffusion layer of this application exhibits superior thermal conductivity, which is more conducive to transferring the heat generated by the chemical reaction to the cathode channel for heat removal. Furthermore, the foamed metal gas diffusion layer has sufficient composite porosity, facilitating the drainage of water generated during the reaction. Foamed metal gas diffusion layers with different porosities can be fabricated according to requirements for drainage, moisture retention, different power levels, or environmental conditions (for example, the porosity and resistivity of the gas diffusion layer can be adjusted to meet moisture retention requirements through component formulation).

[0079] like Figure 6 As shown, the cathode of the air-cooled fuel cell of this application adopts a semi-open flow field, which has good moisturizing ability and can effectively avoid the phenomenon of battery performance degradation and rapid life decay caused by insufficient wetting of membrane electrode due to excessive dryness.

[0080] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A membrane electrode structure, characterized in that, It includes a cathode gas diffusion layer, a CCM unit, and an anode gas diffusion layer. The CCM unit is disposed between the cathode gas diffusion layer and the anode gas diffusion layer. The cathode gas diffusion layer is disposed near the cathode side of the CCM unit, and the anode gas diffusion layer is disposed near the anode side of the CCM unit. The cathode gas diffusion layer is a multilayer foamed metal gas diffusion layer; the porosity of the multilayer foamed metal gas diffusion layer is 50%–90%. The multilayer foamed metal gas diffusion layer includes at least a first diffusion layer and a second diffusion layer stacked together, with the first diffusion layer disposed close to the CCM unit; The multilayer foamed metal gas diffusion layer is prepared by the following method: the first diffusion layer and the second diffusion layer are stacked and dried to obtain a shaped plate; the shaped plate is placed at 800℃~1200℃ for 20min~30min and cooled to obtain the multilayer foamed metal gas diffusion layer. The drying temperature is 40℃~80℃; the heat preservation is carried out in a non-oxidizing environment; The first diffusion layer is prepared by the following method: mixing the first metal powder and the first spherical foaming agent at a mass ratio of 70:30 to 90:10 to obtain a first mixture; hot-pressing the first mixture to obtain the first diffusion layer; the hot-pressing temperature is 150℃ to 350℃, the time is 30s to 3min, and the pressure is 0.2MPa to 1MPa. The porosity of the first diffusion layer is 40%–65%; The second diffusion layer is prepared by the following method: a second metal powder and a second spherical foaming agent are mixed evenly at a mass ratio of 60:40 to 80:20 to obtain a second mixture; the second mixture is hot-pressed to obtain a pre-pressed second diffusion layer; then the pre-pressed second diffusion layer is sintered at 250°C to 500°C and a pressure of 0.2 MPa to 1 MPa for 30 seconds to 5 minutes to obtain the second diffusion layer. The porosity of the second diffusion layer is 60% to 95%.

2. The membrane electrode structure according to claim 1, characterized in that, The first metal powder is dehydrogenated titanium powder; The first spherical foaming agent is K2CO3; The mixing is achieved by a planetary ball mill or a two-roll internal mixer; The hot pressing is achieved using a press.

3. The membrane electrode structure according to claim 1, characterized in that, The second metal powder is copper powder or aluminum powder; The second spherical foaming agent is polystyrene; The mixing is achieved by a planetary ball mill or a two-roll internal mixer; The hot pressing is achieved using a press.

4. An air-cooled fuel cell, characterized in that, The air-cooled fuel cell is prepared using the membrane electrode structure described in any one of claims 1 to 3.

5. The air-cooled fuel cell according to claim 4, characterized in that, The air-cooled fuel cell includes an electrode body and a membrane electrode structure; one side of the electrode body is configured as a cathode surface and the other side as an anode surface; the membrane electrode structure is disposed between the cathode surface and the anode surface, the cathode gas diffusion layer of the membrane electrode structure is disposed close to the cathode surface, and the anode gas diffusion layer of the membrane electrode structure is disposed close to the anode surface.

6. The air-cooled fuel cell according to claim 5, characterized in that, A cathode flow channel is provided on the cathode surface, and the inlet of the cathode flow channel is arranged in a C-shape.

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