Bipolar plate-gas diffusion layer structural body and fuel cell

Abstract

The invention relates to the field of fuel cells, in particular to a bipolar plate-gas diffusion layer structural body and a fuel cell. The structural body comprises a bipolar plate and a gas diffusion layer; the bipolar plate is composed of a first polar plate, a third polar plate and a second polar plate which are stacked in sequence, the first polar plate is a flat plate, the second polar plate is a flat plate with a lug boss, and the third polar plate is a polar plate with a runner; the first polar plate is connected with the anode gas diffusion layer; the second polar plate is connected with the cathode gas diffusion layer; grooves are formed in one side, close to the first polar plate, of the anode gas diffusion layer and one side, close to the second polar plate, of the cathode gas diffusion layer; the convex part of the second polar plate is embedded into the groove of the cathode gas diffusion layer; and a cavity formed by the second polar plate and the cathode gas diffusion layer is an air flow channel. The oxygen content under the ridge of the fuel cell can be improved, the drainage capacity under the ridge is enhanced, the power density of the fuel cell is improved, and the specific power of a fuel cell stack can be greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of fuel cells, and in particular to a bipolar plate-gas diffusion layer structure and a fuel cell. Background Art

[0002] Hydrogen energy is considered to be the link between the scale-up of renewable energy and the low-carbonization of terminal energy consumption, and has now become a technological highland that countries are vying for. In hydrogen energy technology, proton exchange membrane fuel cells play a vital role. They are devices that realize the direct and efficient conversion of hydrogen energy into electrical energy. At the same time, proton exchange membrane fuel cells have the characteristics of high energy density and rapid energy replenishment, showing great application prospects in the process of low-carbonization in the transportation field. At present, proton exchange membrane fuel cells are in the early stages of commercialization, and their overall technical level still needs to be further improved to meet the requirements of large-scale promotion, especially the need to improve the specific power of the stack. Traditional fuel cells are stacked by membrane electrode (CCM), gas diffusion layer (GDL) and bipolar plate (BP). The anode and cathode gas flow channels are usually obtained by stamping / molding unipolar plates, and the cooling flow channels are formed by combining the anode and cathode unipolar plates. Limited by the above-mentioned fuel cell structure, it is difficult to achieve a breakthrough in the specific power of fuel cells at present. There are two main reasons: First, the ridge under the contact between the electrode plate and the gas diffusion layer cannot directly contact the gas flow channel, so the reaction gas cannot be quickly transferred here, and the water generated here is difficult to discharge, which can easily cause local flooding and insufficient gas supply, seriously affecting the overall performance of the battery; second, the traditional bipolar plate structure needs to consider the anode and cathode gas flow channels and water flow channels at the same time, so the thickness of the bipolar plate is usually around 1 mm, which is difficult to further reduce, resulting in difficulty in reducing the volume of the fuel cell stack. Summary of the invention

[0003] The purpose of the present invention is to provide a bipolar plate-gas diffusion layer structure and a fuel cell to make up for the deficiencies of the prior art and further improve the specific power of the fuel cell.

[0004] In order to achieve the above object, the technical solution of the present invention is as follows: In one aspect, the present invention provides a bipolar plate-gas diffusion layer structure, comprising a bipolar plate and a gas diffusion layer; The gas diffusion layer comprises an anode gas diffusion layer and a cathode gas diffusion layer; The bipolar plate is composed of a first plate, a third plate and a second plate stacked in sequence, wherein the first plate is a flat plate, the second plate is a flat plate with raised portions, the raised portions are spaced apart along the air flow direction, and the vertical height of the raised portions gradually increases along the air flow direction, and the third plate is a plate with a flow channel; The first electrode plate is connected to the anode gas diffusion layer; The second electrode plate is connected to the cathode gas diffusion layer; The side of the anode gas diffusion layer close to the first electrode plate and the side of the cathode gas diffusion layer close to the second electrode plate are both provided with grooves; The protrusion of the second electrode plate is embedded in the groove of the cathode gas diffusion layer, and the cavity formed by the second electrode plate and the cathode gas diffusion layer is an air flow channel; The cavity formed by the first electrode plate, the second electrode plate and the third electrode plate is a cooling medium flow channel; the cavity formed between the first electrode plate and the anode gas diffusion layer is a hydrogen flow channel.

[0005] Preferably, the bipolar plate substrate is graphite, stainless steel or titanium.

[0006] Preferably, the maximum vertical height of the protrusion is a, the minimum vertical height of the protrusion is c, the depth of the groove on the cathode gas diffusion layer is b, 0≤c <a≤b。

[0007] Preferably, in adjacent air flow channels, the protrusions are distributed adjacent to each other or staggered.

[0008] Preferably, the first electrode plate, the second electrode plate and the third electrode plate are fixedly connected by welding or bonding.

[0009] Preferably, the groove shape includes any one of parallel grooves, serpentine grooves, wavy grooves and mesh grooves.

[0010] Preferably, the gas diffusion layer has a thickness of 0.3-0.6 mm, a groove depth of 0.2-0.4 mm, a groove width of 0.4-2 mm, and a ridge width between grooves of 0.4-2 mm.

[0011] Preferably, the opening width of the third electrode plate flow channel, the groove width of the cathode gas diffusion layer and the groove width of the anode gas diffusion layer are consistent; the ridge upper surface width of the third electrode plate flow channel, the ridge width of the cathode gas diffusion layer and the ridge width of the anode gas diffusion layer are consistent.

[0012] Preferably, the cathode gas diffusion layer grooves are aligned with the anode gas diffusion layer ridges.

[0013] Another aspect of the present invention provides a fuel cell, which is composed of a stack of single cells, each of which is composed of a membrane electrode and the above-mentioned bipolar plate-polar gas diffusion layer structure.

[0014] Preferably, the membrane electrode comprises an anode catalyst layer, a membrane and a cathode catalyst layer stacked in sequence, the anode catalyst layer is connected to the anode gas diffusion layer, and the cathode catalyst layer is connected to the cathode gas diffusion layer.

[0015] The beneficial effects of the present invention are: (1) The present invention integrates the gas flow channel into the gas diffusion layer and provides spaced and height-varying protrusions on the cathode side electrode plate. On the one hand, the ridge of the cathode flow field is transformed into a porous structure, so that the air in the flow channel has a velocity component perpendicular to the gas diffusion layer and the ridge, thereby strengthening the convective mass transfer from the flow channel to the gas diffusion layer and under the ridge, increasing the oxygen concentration in the catalyst layer, and overcoming the water accumulation under the ridge, which can significantly improve the performance of the fuel cell. On the other hand, the present invention uses three plates to form a bipolar plate. The cavity formed by the three plates is a cooling medium flow channel. The cooling medium flow channel has a large area. The grooves on the back of the protrusions also help to enhance the turbulence of the cooling medium flowing in the cooling cavity, thereby obtaining a larger heat exchange area and a better heat dissipation effect.

[0016] (2) In the bipolar plate-gas diffusion layer structure of the present invention, the hydrogen and air flow fields are not directly integrated on the bipolar plate through the design of the grooves on the gas diffusion layer. The bipolar plate only needs to consider the cooling medium flow channel. Compared with the prior art, the thickness of the bipolar plate is significantly reduced, which can reduce the volume of the fuel cell stack and improve the specific power of the fuel cell stack.

[0017] (3) The present invention utilizes the grooves of the gas diffusion layer and an integrated structure formed by the combination of three plates. The two side plates and the gas diffusion layer form air and hydrogen flow channels. The cavity formed by the three plates is a cooling medium flow channel. The contact resistance can be further reduced and the stack power can be improved through structural optimization, such as the staggered distribution of the grooves of the cathode gas diffusion layer and the anode gas diffusion layer.

[0018] (4) The bipolar plate-gas diffusion layer structure is simple in structure, which can simplify processing difficulty and reduce manufacturing costs compared with the existing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the overall structure of the bipolar plate-gas diffusion layer structure of Example 1; Figure 2 Schematic diagram of the cross-sectional structure of the bipolar plate-gas diffusion layer structure of Example 1; Figure 3 Schematic diagram of the overall structure of the bipolar plate-gas diffusion layer structure of Example 2; Figure 4 is a schematic diagram of the structure of a fuel cell in Example 1; Figure 5 is a schematic diagram of the cross-sectional structure of a fuel cell in Example 1; Figure 6 is a schematic diagram of the fuel cell structure of Example 2; Figure 7 Schematic diagrams of the structures of grooves of different shapes, (a) is a parallel groove, (b) is a serpentine groove, (c) is a wavy groove, and (d) is a mesh groove; Figure 8Schematic diagrams of structures of protrusions of different shapes, (a) shows that the vertical height of the protrusion increases linearly along the air flow direction, (b) shows that the vertical height of the protrusion increases in a convex function-like manner along the air flow direction, and (c) shows that the vertical height of the protrusion increases in a concave function-like manner along the air flow direction; Fig. 9 This is a performance comparison diagram of the fuel cell assembled in Example 1 and the comparative example; In the figure, 1, cathode gas diffusion layer, 2, protrusion, 3, second electrode plate, 4, third electrode plate, 5, first electrode plate, 6, anode gas diffusion layer, 7, air flow channel, 8, hydrogen flow channel, 9, cooling medium flow channel, 10, anode catalyst layer, 11, membrane, 12, cathode catalyst layer. DETAILED DESCRIPTION

[0020] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments only represent implementation examples of the present invention, rather than all implementation methods.

[0021] The present invention provides a bipolar plate-gas diffusion layer structure, comprising a bipolar plate and a gas diffusion layer; the bipolar plate is composed of a first polar plate 5, a third polar plate 4 and a second polar plate 3 stacked in sequence, the first polar plate 5 is a flat plate, the second polar plate 3 is a flat plate with a protrusion 2, the protrusions 2 of the second polar plate 3 are spaced apart along the air flow direction, and the vertical height of the protrusions 2 gradually increases along the air flow direction, and the third polar plate 4 is a polar plate with a flow channel; the gas diffusion layer comprises an anode gas diffusion layer 6 and a cathode gas diffusion layer 1; the first polar plate 5 and the anode are connected to each other by a plurality of channels; the gas diffusion layer comprises an anode gas diffusion layer 6 and a cathode gas diffusion layer 1; the first polar plate 5 and the anode are connected ... The first electrode plate 5, the second electrode plate 3 and the third electrode plate 4 are connected to the gas diffusion layer 6; the second electrode plate 3 is connected to the cathode gas diffusion layer 1; the side of the anode gas diffusion layer 6 close to the first electrode plate 5 and the side of the cathode gas diffusion layer 1 close to the second electrode plate 3 are both provided with grooves; the protrusion 2 of the second electrode plate 3 is embedded in the groove of the cathode gas diffusion layer 1, the cavity formed by the second electrode plate 3 and the cathode gas diffusion layer 1 is an air flow channel 7, the cavity formed by the first electrode plate 5, the second electrode plate 3 and the third electrode plate 4 is a cooling medium flow channel 9, and the cavity formed between the first electrode plate 5 and the anode gas diffusion layer 6 is a hydrogen flow channel 8.

[0022] As a preferred embodiment, the bipolar plate substrate is graphite, stainless steel or titanium.

[0023] As a preferred embodiment, the maximum vertical height of the protrusion 2 is a, the minimum vertical height of the protrusion 2 is c, the depth of the groove on the cathode gas diffusion layer 1 is b, 0≤c <a≤b。

[0024] As a preferred embodiment, in adjacent air flow channels 7, the protrusions 2 are distributed adjacent to each other or staggered.

[0025] As a preferred implementation, the first electrode plate 5, the second electrode plate 3, and the third electrode plate 4 are fixedly connected by welding or bonding.

[0026] As a preferred embodiment, the groove shape includes any one of parallel grooves, serpentine grooves, wavy grooves, and mesh grooves.

[0027] As a preferred embodiment, the opening width of the flow channel of the third electrode plate 4, the groove width of the cathode gas diffusion layer 1 and the groove width of the anode gas diffusion layer 6 are consistent; the ridge upper surface width of the flow channel of the third electrode plate 4, the ridge width of the cathode gas diffusion layer 1 and the ridge width of the anode gas diffusion layer 6 are consistent.

[0028] As a preferred embodiment, the grooves of the cathode gas diffusion layer 1 are aligned with the ridges of the anode gas diffusion layer 6 .

[0029] On the other hand, the present invention provides a fuel cell, comprising a first component, a membrane electrode and a second component stacked in sequence, wherein the first component and the second component are both the above-mentioned bipolar plate-gas diffusion layer structure; the membrane electrode comprises an anode catalyst layer 10, a membrane 11 and a cathode catalyst layer 12 stacked in sequence, the anode catalyst layer 10 is connected to the anode gas diffusion layer 6, and the cathode catalyst layer 12 is connected to the cathode gas diffusion layer 1.

[0030] Example 1 like Figure 1 and 2As shown, this embodiment provides a bipolar plate-gas diffusion layer structure, including a bipolar plate and a gas diffusion layer; the bipolar plate is composed of a first electrode plate 5, a third electrode plate 4 and a second electrode plate 3 stacked in sequence, the first electrode plate 5 is a flat plate, the second electrode plate 3 is a flat plate with a protrusion 2, and the third electrode plate 4 is a plate with a flow channel; the first electrode plate 5 is connected to the anode gas diffusion layer 6; the second electrode plate 3 is connected to the cathode gas diffusion layer 1; the thickness of the gas diffusion layer is 0.55 mm; the side of the anode gas diffusion layer 6 close to the first electrode plate 5 and the side of the cathode gas diffusion layer 1 close to the second electrode plate 3 are both provided with grooves, the groove depth is 0.3 mm, the groove width is 1.4 mm, and the ridge width between the grooves is 1 mm, the groove shape is parallel grooves; the groove of the cathode gas diffusion layer 1 is aligned with the ridge of the anode gas diffusion layer 6; the protrusion 2 of the second electrode plate 3 is embedded in the groove of the cathode gas diffusion layer 1, and the cavity formed between the second electrode plate 3 and the cathode gas diffusion layer 1 is the air flow channel 7; the vertical height of the protrusion 2 of the second electrode plate 3 increases linearly along the air flow direction, the minimum vertical height of the protrusion 2 of the second electrode plate 3 is 0, the maximum vertical height is 0.2 mm, and the depth of the groove on the cathode gas diffusion layer 1 is 0.3 mm raised portion 2; the raised portions 2 of the second electrode plate 3 are spaced apart along the air flow direction, and the raised portions 2 are adjacently distributed in adjacent air flow channels 7; the opening width of the flow channel of the third electrode plate 4, the groove width of the cathode gas diffusion layer 1 and the groove width of the anode gas diffusion layer 6 are consistent, and the ridge upper surface width of the flow channel of the third electrode plate 4, the ridge width of the cathode gas diffusion layer 1 and the ridge width of the anode gas diffusion layer 6 are consistent; the bipolar plate substrate is stainless steel, the first electrode plate 5, the second electrode plate 3, and the third electrode plate 4 are fixedly connected by welding, and the cavity formed by the first electrode plate 5, the second electrode plate 3, and the third electrode plate 4 is a cooling medium flow channel 9; the cavity formed between the first electrode plate 5 and the anode gas diffusion layer 6 is a hydrogen flow channel 8.

[0031] like Figure 4 and 5 As shown, the fuel cell is composed of a stack of single cells, each of which is composed of a membrane electrode and the above-mentioned bipolar plate-polar gas diffusion layer structure; the membrane electrode includes an anode catalyst layer 10, a membrane 11 and a cathode catalyst layer 12 stacked in sequence, the anode catalyst layer 10 is connected to the anode gas diffusion layer 6, and the cathode catalyst layer 12 is connected to the cathode gas diffusion layer 1.

[0032] In the embodiment, a commercially available membrane electrode (anode catalyst layer 10 with a platinum loading of 0.2 mg / cm 2 The platinum loading of the cathode catalyst layer 12 is 0.4 mg / cm 2 , proton exchange membrane is Gore12 μm proton exchange membrane), gas diffusion layer (carbon fiber felt with a thickness of 0.55 mm, 5% hydrophobic treatment).

[0033] Example 2 The implementation of this embodiment is similar to that of embodiment 1, except that the protrusions 2 of the second electrode plate 3 are staggered in adjacent air flow channels 7. The structure of the bipolar plate-gas diffusion layer structure is as follows: Figure 3 The structure of the fuel cell is shown in Figure 6 shown.

[0034] Comparative Example 1 In order to more intuitively reflect the advantages of the present invention over the prior art, a conventional structure fuel cell is assembled using the same membrane electrode and gas diffusion layer as in Example 1. Its structure is formed by a bipolar plate, a gas diffusion layer, and a membrane electrode stack. The anode and cathode gas flow channels are integrated on the bipolar plate. The bipolar plate is formed by stamping and welding two stainless steel plates. The flow field structure is a parallel flow field, and the flow channel depth is 0.35 mm.

[0035] Test Example 1 The performance of the fuel cells assembled in Example 1 and Comparative Example 1 was evaluated.

[0036] The test conditions were: battery temperature of 80 °C, anode hydrogen stoichiometric ratio of 1.3, 30% humidification, cathode air stoichiometric ratio of 2.0, 30% humidification.

[0037] Test results such as Fig. 9 As shown, from Fig. 9 It can be seen that the fuel cell structure proposed in the present invention has higher battery performance, indicating that the bipolar plate-gas diffusion layer structure and fuel cell proposed in the present invention have the effect of significantly improving the performance of the fuel cell.

[0038] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the implementation methods. The protection scope of the present invention shall be subject to the scope defined in the claims. Other different forms of changes or modifications may be made based on the above description. Obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A bipolar plate-gas diffusion layer structure, characterized in that: including bipolar plates and gas diffusion layers; The gas diffusion layer comprises an anode gas diffusion layer and a cathode gas diffusion layer; The bipolar plate is composed of a first plate, a third plate and a second plate stacked in sequence, wherein the first plate is a flat plate, the second plate is a flat plate with raised portions, the raised portions are spaced apart along the air flow direction, and the vertical height of the raised portions gradually increases along the air flow direction, and the third plate is a plate with a flow channel; The first electrode plate is connected to the anode gas diffusion layer; The second electrode plate is connected to the cathode gas diffusion layer; The side of the anode gas diffusion layer close to the first electrode plate and the side of the cathode gas diffusion layer close to the second electrode plate are both provided with grooves; The protrusion of the second electrode plate is embedded in the groove of the cathode gas diffusion layer, and the cavity formed by the second electrode plate and the cathode gas diffusion layer is an air flow channel; The cavity formed by the first electrode plate, the second electrode plate and the third electrode plate is a cooling medium flow channel; the cavity formed between the first electrode plate and the anode gas diffusion layer is a hydrogen flow channel.

2. The bipolar plate-gas diffusion layer structure according to claim 1, characterized in that: The maximum vertical height of the protrusion is a, the minimum vertical height of the protrusion is c, the depth of the groove on the cathode gas diffusion layer is b, 0≤c <a≤b。 3. The bipolar plate-gas diffusion layer structure according to claim 1, characterized in that: In adjacent air flow channels, the protrusions are distributed adjacently or staggered.

4. The bipolar plate-gas diffusion layer structure according to claim 1, characterized in that: The first electrode plate, the second electrode plate and the third electrode plate are fixedly connected by welding or bonding.

5. The bipolar plate-gas diffusion layer structure according to claim 1, characterized in that: The opening width of the third electrode channel is consistent with the groove width of the cathode gas diffusion layer and the groove width of the anode gas diffusion layer; the ridge upper surface width of the third electrode channel is consistent with the ridge width of the cathode gas diffusion layer and the ridge width of the anode gas diffusion layer.

6. The bipolar plate-gas diffusion layer structure according to claim 1, characterized in that: The groove shape includes any one of parallel grooves, serpentine grooves, wavy grooves, and mesh grooves.

7. The bipolar plate-gas diffusion layer structure according to claim 1, characterized in that: The grooves of the cathode gas diffusion layer are aligned with the ridges of the anode gas diffusion layer.

8. A fuel cell, characterized in that: The fuel cell is composed of a stack of single cells, each of which is composed of a membrane electrode and a bipolar plate-gas diffusion layer structure according to any one of claims 1 to 7.

9. The fuel cell according to claim 8, characterized in that The membrane electrode comprises an anode catalyst layer, a membrane and a cathode catalyst layer which are stacked in sequence. The anode catalyst layer is connected to the anode gas diffusion layer, and the cathode catalyst layer is connected to the cathode gas diffusion layer.

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