Gas diffusion layer, membrane electrode structure and air-cooled fuel cell

Abstract

The utility model provides a gas diffusion layer suitable for a cathode gas diffusion layer, and the gas diffusion layer is a multi-layer foam metal gas diffusion layer. The porosity of the multiple foam metal gas diffusion layers ranges from 50% to 90%. The multi-layer foam metal gas diffusion layer at least comprises a first diffusion layer and a second diffusion layer which are arranged in an overlapped mode, and the first diffusion layer is arranged close to the CCM unit. The utility model further discloses a membrane electrode structure and an air-cooled fuel cell. The gas diffusion layer provided by the utility model has more excellent thermal conductivity, is more beneficial to transfer heat generated by chemical reaction to the cathode flow channel so as to take away the heat, and is beneficial to discharge of water generated by the reaction. The air-cooled fuel cell provided by the utility model has relatively good moisture retention capability, and can effectively avoid the phenomena that the performance of the cell is reduced and the service life of the cell is quickly attenuated due to insufficient infiltration of the membrane electrode which is too dry.

Description

Technical Field

[0001] The utility model relates to the technical field of fuel cells, in particular to a gas diffusion layer, a membrane electrode structure and an air-cooled fuel cell. Background Art

[0002] Hydrogen fuel cells have the advantages of being clean, environmentally friendly and having a simple structure. With the continuous in-depth research on hydrogen fuel cells, fuel cells have been integrated into our daily lives, such as various vehicle systems (hydrogen fuel cell buses, logistics vehicles, heavy trucks, sanitation vehicles, etc.), backup power supplies and household energy storage devices. A single fuel cell is usually composed of a plate electrode and a membrane electrode. Multiple single cells are connected in series to form a fuel cell, which can achieve high-voltage output and output the required voltage and power. This is the fuel cell stack.

[0003] Fuel cells are usually divided into liquid-cooled fuel cells and air-cooled fuel cells. Air-cooled fuel cells have more applications in low-power application scenarios such as small two-wheelers, three-wheelers, drones and emergency power supplies due to their advantages of fewer auxiliary devices, simple structure and simple control. However, since the cathode of the air-cooled fuel cell adopts a fully open flow channel, it is difficult to couple temperature and humidity. When the fan speed is fast, although the temperature of the fuel cell stack can be reduced, the membrane electrode is dried out. When the fan speed is slow, although the humidity of the membrane electrode can be maintained, it is difficult to keep the temperature of the fuel cell stack within the ideal range. Therefore, the air-cooled fuel cell has problems such as uneven heat dissipation and difficulty in temperature and humidity coupling. Summary of the Utility Model

[0004] Based on this, the embodiments of the present utility model provide a gas diffusion layer, 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 existing in the existing air-cooled fuel cells.

[0005] To achieve the above object, on the one hand, the embodiments of the present utility model provide a gas diffusion layer, which is applicable to the cathode gas diffusion layer. The gas diffusion layer is a multi-layered foam metal gas diffusion layer; the porosity of the multi-layered foam metal gas diffusion layer is 50% - 90%;

[0006] The multi-layered foam metal gas diffusion layer at least includes a first diffusion layer and a second diffusion layer which are stacked. The first diffusion layer is arranged close to the CCM unit.

[0007] As a preferred embodiment, the porosity of the first diffusion layer is 40% - 65%.

[0008] As a preferred embodiment, the porosity of the second diffusion layer is 60% - 95%.

[0009] As a preferred embodiment, the first diffusion layer is a titanium foam powder diffusion layer; the second diffusion layer is a copper foam powder diffusion layer or an aluminum foam powder diffusion layer.

[0010] As a preferred embodiment, the multi-layered metal foam gas diffusion layer is prepared by the following method: laminating the first diffusion layer and the second diffusion layer and then drying to obtain a formed plate; placing the formed plate in an environment of 800°C to 1200°C for heat preservation for 20 min to 30 min, and then cooling to obtain the multi-layered metal foam gas diffusion layer.

[0011] As a preferred embodiment,

[0012] The drying temperature is 40°C to 80°C.

[0013] The heat preservation is carried out in a non-oxidizing environment. The first spherical foaming agent and the second spherical foaming agent generate heat decomposition and release gas during heating to form spherical cell-like pores of different sizes.

[0014] As a preferred embodiment, the first diffusion layer is prepared by the following method: mixing first metal powder and a first spherical foaming agent in a mass ratio of 70:30 to 90:10 evenly to obtain a first mixture; hot-pressing the first mixture into shape to obtain the first diffusion layer; the temperature of the hot-pressing is 150°C to 350°C, the time is 30 s to 3 min, and the pressure is 0.2 MPa to 1 MPa.

[0015] As a preferred embodiment,

[0016] The first metal powder is dehydrogenated titanium powder.

[0017] The porosity of the first diffusion layer is 40% to 65%.

[0018] The first spherical foaming agent is NaCl or K2CO3.

[0019] The mixing is achieved by a planetary ball mill or a double-roll mixer.

[0020] The hot-pressing is achieved by a press.

[0021] As a preferred embodiment, the second diffusion layer is prepared by the following method: mixing second metal powder and a second spherical foaming agent in a mass ratio of 60:40 to 80:20 evenly to obtain a second mixture; hot-pressing the second mixture into shape to obtain a pre-pressed second diffusion layer; 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 s to 5 min to obtain the second diffusion layer.

[0022] As a preferred embodiment,

[0023] The second metal powder is copper powder or aluminum powder.

[0024] The porosity of the second diffusion layer is 60% to 95%.

[0025] The second spherical foaming agent is polystyrene (EPS).

[0026] The mixing is achieved by a planetary ball mill or a twin-roll internal mixer.

[0027] The hot pressing forming is achieved by a press machine.

[0028] In the embodiment of the present application, the cathode gas diffusion layer is prepared by using a multilayer foam metal material. Compared with the carbon-based gas diffusion layer, the cathode gas diffusion layer of the present application has better thermal conductivity, which is more conducive to transferring the heat generated by the chemical reaction to the cathode flow channel to take away the heat. Moreover, the foam metal gas diffusion layer has sufficient porosity, which is conducive to the discharge of the water generated by the reaction. In particular, it can be made into a composite gas diffusion layer with different porosities according to the requirements of drainage and moisture retention.

[0029] On the other hand, an embodiment of the present application further provides a membrane electrode structure, comprising a cathode gas diffusion layer, a CCM unit and an anode gas diffusion layer, wherein the CCM unit is disposed between the cathode gas diffusion layer and the anode gas diffusion layer, the cathode gas diffusion layer is disposed close to the cathode side of the CCM unit, and the anode gas diffusion layer is disposed close to the anode side of the CCM unit;

[0030] The cathode gas diffusion layer is the gas diffusion layer.

[0031] On the other hand, an embodiment of the present application provides an air-cooled fuel cell, which is prepared by the membrane electrode structure.

[0032] As a preferred embodiment, the air-cooled fuel cell includes a plate body and a membrane electrode structure; one side of the plate body is set as a cathode side, and the other side is set as an anode side; the membrane electrode structure is set between the cathode side and the anode side, the cathode gas diffusion layer of the membrane electrode structure is set close to the cathode side, and the anode gas diffusion layer of the membrane electrode structure is set close to the anode side.

[0033] As a preferred embodiment, a cathode flow channel is provided on the cathode surface, and the inlet of the cathode flow channel is provided at a C-shaped angle. In this way, the inlet side of the cathode flow channel is a semi-open flow field structure, which facilitates the entry of external cold air into the cathode flow channel, takes away the heat generated by the reaction, and also takes away the water generated by the cathode membrane electrode reaction, effectively avoiding flooding on the cathode side. Moreover, the anode of the present application is a closed structure, and the cathode is an open structure, which can reduce the system BOP accessories and requirements.

[0034] Compared with the prior art, the technical effects of the solution of the present application are as follows:

[0035] (1) The present application uses a multi-layer foam metal-like material to prepare the cathode gas diffusion layer of the membrane electrode structure. Compared with the carbon-based gas diffusion layer, the cathode gas diffusion layer of the present application has better thermal conductivity, which is more conducive to transferring the heat generated by the chemical reaction to the cathode flow channel to take away the heat. Moreover, the foam metal gas diffusion layer has a sufficient composite porosity, which is conducive to the discharge of the water generated by the reaction. The foam metal gas diffusion layer with different porosities can be made according to the requirements of drainage, moisture retention, different power levels or the environment (for example, the porosity and gas diffusion layer resistivity that meet the moisture retention requirements can be adjusted by adjusting the composition formula).

[0036] (2) The cathode of the air-cooled fuel cell of the present application adopts a semi-open flow field, which has good moisture retention ability and can effectively avoid the phenomenon of battery performance decline and rapid life attenuation caused by insufficient wetting due to over-drying of the membrane electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0038] Figure 1 It is a partial cross-sectional structure schematic diagram of the gas diffusion layer of an embodiment of the present invention;

[0039] Figure 2 It is a partial cross-sectional structure schematic diagram of the membrane electrode of an embodiment of the present invention;

[0040] Figure 3 It is an overall structure schematic diagram of the air-cooled fuel cell of another embodiment of the present application;

[0041] Figure 4 For Figure 3 The cross-sectional structure schematic diagram;

[0042] Figure 5 It is a schematic diagram of air entering the cathode flow channel;

[0043] Figure 6 For Figure 3 The detection result diagram of the surface humidity of the air-cooled fuel cell;

[0044] The realization of the object, functional characteristics and advantages of the present invention will be further described in conjunction with the embodiments and with reference to the drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] The following will clearly and completely describe the technical solutions in the embodiments of the present utility model in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without making creative efforts belong to the scope of protection of the present utility model.

[0046] It should be noted that if there are directional indications (such as up, down, left, right, front, back, top, bottom...) involved in the embodiments of the present utility model, then the directional indications are only used to explain the relative positional relationship and movement conditions between components in a certain specific posture (as shown in the accompanying drawings). If this specific posture changes, the directional indications will also change accordingly.

[0047] In the present utility model, unless otherwise clearly specified and defined, terms such as "installation", "connection", "connection", "fixation" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. It can be the communication inside two components or the interaction relationship between two components, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0048] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time.

[0049] In addition, if there are descriptions such as "first", "second", etc. involved in the embodiments of the present utility model, then the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" can explicitly or implicitly include at least one of such features. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0050] Currently, the prior art has the following disadvantages:

[0051] 1) Most of the existing air-cooled fuel cell plates are of an open cathode structure, and there are problems with the difficult coupling of moisture retention and heat dissipation.

[0052] 2) The existing membrane electrode generally uses thick carbon paper or carbon cloth as the gas diffusion layer. Protons pass through the fluorosulfonic acid proton exchange membrane to generate water, and the liquid water mostly forms in the porous layer or the flow field channel.

[0053] 3) Due to the fibrous structure of the existing gas diffusion layers (such as carbon cloth and carbon paper), their water retention capacity is limited. When a large flow of air passes through the open cathode flow field, it is very easy to cause the carbon paper (carbon cloth) on the cathode side of the membrane electrode to be too dry and unable to wet and humidify the polymer electrolyte.

[0054] Based on this, the embodiments of the present application provide a gas diffusion layer, a membrane electrode structure and an air-cooled fuel cell to solve the above technical problems.

[0055] Specifically, on the one hand, as Figure 1 shown, the embodiments of the present invention provide a gas diffusion layer 10, which is applicable to the cathode gas diffusion layer. The gas diffusion layer is a multi-layer foam metal gas diffusion layer; the porosity of the multi-layer foam metal gas diffusion layer is 50% - 90%.

[0056] The multi-layer foam metal gas diffusion layer at least includes a first diffusion layer 11 and a second diffusion layer 12 that are stacked. The first diffusion layer 11 is arranged close to the CCM unit.

[0057] As a preferred embodiment, the porosity of the first diffusion layer 11 is 40% - 65%.

[0058] As a preferred embodiment, the porosity of the second diffusion layer 12 is 60% - 95%.

[0059] As a preferred embodiment, the first diffusion layer 11 is a foam titanium powder diffusion layer; the second diffusion layer 12 is a foam copper powder diffusion layer or a foam aluminum powder diffusion layer.

[0060] In the embodiments of the present application, by setting the first diffusion layer 11 and the second diffusion layer 12 and controlling their porosities, and making the porosity of the first diffusion layer less than that of the second diffusion layer, it can be ensured that the prepared gas diffusion layer has better thermal conductivity, which is more conducive to transferring the heat generated by the chemical reaction to the cathode flow channel for heat dissipation; at the same time, it can also make the prepared gas diffusion layer have sufficient porosity, which is conducive to the discharge of the generated water while meeting the needs of wetting and moisturizing the membrane electrode.

[0061] As a preferred embodiment, the multi-layered foamed metal gas diffusion layer is prepared by the following method: laminating the first diffusion layer and the second diffusion layer and then drying to obtain a formed plate; placing the formed plate in an environment with a temperature of 800°C to 1200°C (which can be 800°C, or 900°C, or 1000°C, or 1200°C, etc. according to actual usage requirements) and keeping it warm for 20 min to 30 min (which can be 20 min, or 23 min, or 26 min, or 30 min, etc. according to actual usage requirements), and then cooling to obtain the multi-layered foamed metal gas diffusion layer.

[0062] As a preferred embodiment,

[0063] The drying temperature is 40°C to 80°C (which can be 40°C, or 50°C, or 65°C, or 80°C, etc. according to actual usage requirements).

[0064] The heat preservation is carried out in a non-oxidizing environment. In this way, it can be ensured that the first spherical foaming agent and the second spherical foaming agent in the gas diffusion layer generate heat decomposition and release gas during the heating process to form spherical cell-like pores of different sizes.

[0065] As a preferred embodiment, the first diffusion layer is prepared by the following method: mixing first metal powder and a first spherical foaming agent in a mass ratio of 70:30 to 90:10 to obtain a first mixture; hot-pressing the first mixture into shape to obtain the first diffusion layer; the temperature of the hot-pressing is 150°C to 350°C (which can be 150°C, or 200°C, or 280°C, or 350°C, etc. according to actual usage requirements), the time is 30 s to 3 min (which can be 30 s, or 1 min, or 2 min, or 3 min, etc. according to actual usage requirements), and the pressure is 0.2 MPa to 1 MPa (which can be 0.2 MPa, or 0.5 MPa, or 0.7 MPa, or 1 MPa, etc. according to actual usage requirements).

[0066] As a preferred embodiment,

[0067] The first metal powder is dehydrogenated titanium powder.

[0068] The porosity of the first diffusion layer is 40% to 65%; it can be 40%, or 50%, or 55%, or 65%, etc. according to actual usage requirements.

[0069] The first spherical foaming agent is NaCl or K2CO3.

[0070] The mixing is achieved by planetary ball milling or a double-roll mixer.

[0071] The hot pressing is realized by a press.

[0072] In this application, by controlling the mass ratio of the first metal powder and the first spherical foaming agent to be 70:30 - 90:10 (which can be 70:30, or 80:20, or 85:15, or 90:10, etc. according to actual needs), and combining with controlling the conditions of hot pressing, it can be ensured that the porosity of the prepared first diffusion layer can meet the needs of this application.

[0073] As a preferred embodiment, the second diffusion layer is prepared by the following method: mixing the second metal powder and the second spherical foaming agent evenly according to a mass ratio of 60:40 - 80:20 to obtain a second mixture; performing hot pressing on the second mixture to obtain a pre-pressed second diffusion layer; then sintering the pre-pressed second diffusion layer at 250°C - 500°C (which can be 250°C, or 300°C, or 350°C, or 500°C, etc. according to actual usage needs), under a pressure of 0.2 MPa - 1 MPa (which can be 0.2 MPa, or 0.5 MPa, or 0.7 MPa, or 1 MPa, etc. according to actual usage needs) for 30 s - 5 min (which can be 30 s, or 1 min, or 3 min, or 5 min, etc. according to actual usage needs) to obtain the second diffusion layer.

[0074] As a preferred embodiment,

[0075] The second metal powder is copper powder or aluminum powder, and copper powder or aluminum powder can be selected according to actual needs.

[0076] The porosity of the second diffusion layer is 60% - 95%; it can be 60%, or 70%, or 85%, or 95%, etc. according to actual usage needs.

[0077] The second spherical foaming agent is polystyrene (EPS).

[0078] The mixing is realized by a planetary ball mill or a double-roll mixer.

[0079] The hot pressing is realized by a press.

[0080] 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 can be ensured 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 flow channel for heat dissipation; at the same time, it can also make the prepared cathode gas diffusion layer have sufficient porosity, which is conducive to the discharge of generated water and meets the needs of membrane electrode wetting and moisturizing.

[0081] On the other hand, as Figure 2 shown, an embodiment of the present utility model further provides a membrane electrode structure, which includes 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 close to the cathode side of the CCM unit 20, and the anode gas diffusion layer 30 is disposed close to the anode side of the CCM unit 20;

[0082] The cathode gas diffusion layer 10 is the gas diffusion layer.

[0083] In this application, according to the requirements of drainage, moisture retention, different power levels, or the environment, the porosity and gas diffusion layer resistivity that meet the moisture retention requirements can be adjusted by adjusting the component formula of the multi-layered foam metal gas diffusion layer to fabricate multi-layered foam metal gas diffusion layers with different porosities. The porosity of the multi-layered foam metal gas diffusion layer is controlled to be 50% - 90%, for example, it can be 50%, or 60%, or 75%, or 90%, etc. If the porosity of the multi-layered foam metal gas diffusion layer is lower than 50%, it is not conducive to transferring the heat generated by the chemical reaction to the cathode flow channel to remove the heat, affecting the heat dissipation effect, and it is also not conducive to the discharge of the water generated by the reaction, resulting in water retention. If the porosity of the multi-layered foam metal gas diffusion layer is higher than 90%, it is likely to cause the membrane electrode to be too dry and insufficiently wetted, thereby leading to a decline in battery performance and rapid attenuation of the lifespan.

[0084] On yet another hand, as Figures 3 to 5 shown, an embodiment of this application provides an air-cooled fuel cell, which is prepared from the membrane electrode structure.

[0085] As a preferred implementation manner, the air-cooled fuel cell includes a plate body 100 and the membrane electrode structure 200; one side surface of the plate body 100 is set as a cathode surface 101, and the other side surface is set as an anode surface 102; the membrane electrode structure 200 is disposed between the cathode surface 101 and the anode surface 102. The cathode gas diffusion layer of the membrane electrode structure 200 is disposed close to the cathode surface 101, and the anode gas diffusion layer of the membrane electrode structure 200 is disposed close to the anode surface 102.

[0086] As a preferred implementation manner, as Figure 5As shown, a cathode flow channel 1011 is provided on the cathode surface 101, and the inlet of the cathode flow channel 1011 is provided at a C-shaped angle. In this way, the inlet side of the cathode flow channel is a semi-open flow field structure, which facilitates the entry of external cold air into the cathode flow channel, takes away the heat generated by the reaction, and also takes away the water generated by the cathode membrane electrode reaction, effectively avoiding flooding on the cathode side. Moreover, the anode of the present application is a closed structure, and the cathode is an open structure, which can reduce the system BOP accessories and requirements.

[0087] The present application uses a multilayer metal foam material to prepare the cathode gas diffusion layer of the membrane electrode structure. Compared with the carbon-based gas diffusion layer, the cathode gas diffusion layer of the present application has better thermal conductivity, which is more conducive to transferring the heat generated by the chemical reaction to the cathode flow channel to take away the heat. Moreover, the metal foam gas diffusion layer has sufficient composite porosity, which is conducive to the discharge of water generated by the reaction. Metal foam gas diffusion layers with different porosities can be made according to the requirements of drainage, moisturizing, different power sizes or environments (for example, the porosity and gas diffusion layer resistivity required for moisturizing can be met by adjusting the ingredient formula).

[0088] like Figure 6 As shown, the cathode of the air-cooled fuel cell of the present application adopts a semi-open flow field, which has good moisture retention ability and can effectively avoid the phenomenon of battery performance degradation and rapid life decay caused by insufficient infiltration of the membrane electrode due to excessive drying.

[0089] The above description is only a preferred embodiment of the utility model, and does not limit the patent scope of the utility model. All equivalent structural changes made by using the contents of the utility model specification and drawings under the utility model concept, or directly / indirectly used in other related technical fields are included in the patent protection scope of the utility model.

Claims

1. A gas diffusion layer, characterized in that, Suitable for a cathode gas diffusion layer, the gas diffusion layer being a multi-layered foam metal gas diffusion layer; the porosity of the multi-layered foam metal gas diffusion layer is 50% to 90%; The multi-layered foam metal gas diffusion layer at least includes a first diffusion layer and a second diffusion layer arranged in an overlapping manner, and the first diffusion layer is arranged close to the CCM unit.

2. The gas diffusion layer according to claim 1, wherein The porosity of the first diffusion layer is 40% to 65%.

3. The gas diffusion layer according to claim 1, wherein The porosity of the second diffusion layer is 60% to 95%.

4. The gas diffusion layer according to claim 1, wherein The first diffusion layer is a foam titanium powder diffusion layer; the second diffusion layer is a foam copper powder diffusion layer or a foam aluminum powder diffusion layer.

5. A membrane electrode structure, characterized in that, Comprising 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 the gas diffusion layer according to any one of claims 1 to 4.

6. An air-cooled fuel cell, characterized in that, The air-cooled fuel cell is prepared from the membrane electrode structure according to claim 5.

7. The air-cooled fuel cell according to claim 6, wherein The air-cooled fuel cell includes a plate body and the membrane electrode structure; one side surface of the plate body is set as the cathode surface, and the other side surface is set as the anode surface; the membrane electrode structure is arranged between the cathode surface and the anode surface, the cathode gas diffusion layer of the membrane electrode structure is arranged close to the cathode surface, and the anode gas diffusion layer of the membrane electrode structure is arranged close to the anode surface.

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