Bipolar plate-cathode gas diffusion layer assembly and fuel cell

Abstract

The invention discloses a bipolar plate-cathode gas diffusion layer assembly and a fuel cell, and belongs to the technical field of fuel cells. The assembly comprises a cathode gas diffusion layer, a cathode side monopolar plate and an anode side monopolar plate which are stacked in sequence, the cathode side monopolar plate is a flat plate, and the anode side monopolar plate is a polar plate with a runner; a groove is formed in the side, close to the cathode side monopole plate, of the cathode gas diffusion layer, a cavity formed by the cathode side monopole plate and the groove of the cathode gas diffusion layer is an air flow channel, and a cavity formed between the cathode side monopole plate and the anode side monopole plate is a cooling medium flow channel. Compared with the prior art, the cathode flow field has strong under-ridge drainage capacity and no under-ridge water logging problem, the performance and the service life of the fuel cell are improved, meanwhile, the thickness of the bipolar plate and the volume of the electric pile can be obviously reduced, and the volume power density of the electric pile of the fuel cell is improved.

Description

Technical Field

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

[0002] Building a new energy system with renewable energy as the main body and multiple energy forms complementing each other is an effective way to solve environmental problems and energy crises. In the new energy system, hydrogen energy plays a vital role. It provides a feasible technical route for the large-scale utilization of renewable energy and the low-carbonization of terminal energy use. Fuel cells, as a key technology of hydrogen energy, can achieve efficient conversion of hydrogen and electricity. At the same time, fuel cells are recognized as efficient, clean and green energy devices, and are ideal substitutes for internal combustion engines. It is precisely because of these outstanding advantages that fuel cell technology, especially proton exchange membrane fuel cell (PEMFC) technology, has attracted more and more attention and interest from the international community. It can be applied to transportation vehicles such as automobiles, airplanes, trains, and fixed power stations.

[0003] Traditional fuel cells are formed by stacking bipolar plates and membrane electrode assemblies. The bipolar plates are usually made of monopolar plates with flow channels bonded or welded together. The reaction gas flow field and coolant flow field are integrated on the bipolar plates. The part where the plates contact the membrane electrode assembly is called the ridge. Since the reaction gas flow field of the fuel cell is usually in a laminar state, the gas velocity under the ridge (in the gas diffusion layer and the catalyst layer) is very low. Therefore, the water produced by the electrochemical reaction on the cathode side is easy to accumulate here and cannot be discharged, causing local flooding. This is a key factor that limits the performance improvement of fuel cells and threatens the battery life. In addition, since the flow field is integrated on the bipolar plate, the thickness of the bipolar plate of a traditional fuel cell is usually around 1 mm, which is difficult to further reduce, so the volume of the stack is difficult to further reduce. This is also a key factor that limits the volume power density of the traditional fuel cell stack. Summary of the invention

[0004] The purpose of the present invention is to provide a bipolar plate-cathode gas diffusion layer assembly and a fuel cell to make up for the deficiencies of the prior art, further improve the drainage capacity under the ridge of the fuel cell and reduce the thickness of the bipolar plate.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows: On the one hand, the present invention provides a bipolar plate-cathode gas diffusion layer assembly, which includes a cathode gas diffusion layer, a cathode side monopolar plate and an anode side monopolar plate stacked in sequence; the cathode side monopolar plate is a flat plate, and the anode side monopolar plate is a plate with a flow channel; the cathode gas diffusion layer has a groove on one side close to the cathode side monopolar plate, and the cavity formed by the grooves of the cathode side monopolar plate and the cathode gas diffusion layer is an air flow channel, and the cavity formed between the cathode side monopolar plate and the anode side monopolar plate is a cooling medium flow channel.

[0006] Preferably, the cathode side monopolar plate substrate and the anode side monopolar plate substrate are both graphite, stainless steel or titanium.

[0007] Preferably, the cathode side monopolar plate and the anode side monopolar plate are fixedly connected by bonding or welding.

[0008] Preferably, the groove shape includes any one of parallel grooves, serpentine grooves, wavy grooves and mesh grooves.

[0009] Preferably, the cathode gas diffusion layer has a thickness of 0.3-0.6 mm, a groove depth of 0.2-0.5 mm, a groove width of 0.4-2 mm, and a ridge width between grooves of 0.4-2 mm.

[0010] Preferably, the cross-section of the flow channel of the anode-side monopolar plate is a trapezoid, a square, or a parallelogram.

[0011] Preferably, the grooves of the cathode gas diffusion layer are aligned with the cooling medium flow channels.

[0012] Preferably, the opening width of the anode side unipolar plate flow channel is consistent with the groove width of the cathode gas diffusion layer; the ridge upper surface width of the anode side unipolar plate flow channel is consistent with the ridge width of the cathode gas diffusion layer.

[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 an anode gas diffusion layer, a membrane electrode and the above-mentioned bipolar plate-cathode gas diffusion layer assembly.

[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 bipolar plate-cathode gas diffusion layer assembly of the present invention is an integrated design of the cathode side gas flow channel and the cathode side gas diffusion layer, so that the ridge of the cathode flow field becomes a porous structure, which is conducive to the gas entering under the ridge and the drainage under the ridge, avoiding the problem of water accumulation under the ridge of the fuel cell, and is conducive to improving the performance and life of the fuel cell.

[0016] (2) In the bipolar plate-cathode gas diffusion layer assembly of the present invention, the cathode side monopolar plate is a flat plate, and the anode side monopolar plate is a conventional plate with a flow channel. The cathode gas diffusion layer groove structure and the flat plate are used to form an air flow channel, which can effectively reduce the thickness of the bipolar plate, reduce the volume of the battery stack, and improve the volume power density of the battery stack.

[0017] (3) The present invention utilizes an integrated structure formed by the combination of the grooves, the flat plate and the flow channel plate of the gas diffusion layer. The flat plate and the gas diffusion layer form an air flow channel, the flat plate and the flow channel plate form a cooling medium flow channel, and the flow channel plate can form a hydrogen flow channel with the anode diffusion layer. Through structural optimization, the flow field effect can be achieved and the contact resistance can be further reduced.

[0018] (4) The bipolar plate-cathode gas diffusion layer assembly of the present invention has a simple structure, which can simplify the difficulty of plate processing and reduce the cost of plate manufacturing compared with the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the overall structure of the bipolar plate-cathode gas diffusion layer of Example 1; Figure 2 Schematic diagram of the overall cross-sectional structure of the bipolar plate-cathode gas diffusion layer of Example 1; Figure 3 Schematic diagrams of groove structures of different shapes, including (a) parallel grooves, (b) serpentine grooves, (c) wavy grooves, and (d) mesh grooves; Figure 4 is a schematic diagram of the overall structure of the fuel cell of Example 1; Figure 5 is a schematic diagram of the cross-sectional structure of a fuel cell in Example 1; Figure 6 This is a comparison chart of the fuel cell performance of Example 1 and Comparative Example 1; Figure 7 Schematic diagram of a square cross section of the flow channel of the anode side monopolar plate; Figure 8 Schematic diagram of a flow channel cross section of the anode side monopolar plate being a parallelogram; In the figure: 1, cathode gas diffusion layer, 2, cathode side monopolar plate, 3, anode side monopolar plate, 4, hydrogen flow channel, 5, air flow channel, 6, cooling medium flow channel, 7, anode gas diffusion layer, 8 is anode catalyst layer, 9, membrane, 10, cathode catalyst layer. DETAILED DESCRIPTION

[0020] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0021] The present invention provides a bipolar plate-cathode gas diffusion layer assembly, comprising a cathode gas diffusion layer 1, a cathode side monopolar plate 2 and an anode side monopolar plate 3 stacked in sequence; the cathode side monopolar plate 2 is a flat plate, and the anode side monopolar plate 3 is a plate with a flow channel; the cathode gas diffusion layer 1 has a groove on one side close to the cathode side monopolar plate 2, the cavity formed by the grooves of the cathode side monopolar plate 2 and the cathode gas diffusion layer 1 is an air flow channel 5, and the cavity formed between the cathode side monopolar plate 2 and the anode side monopolar plate 3 is a cooling medium flow channel 6.

[0022] As a preferred embodiment, the substrates of the cathode side monopolar plate 2 and the anode side monopolar plate 3 are both graphite, stainless steel or titanium, wherein the stainless steel or titanium is subjected to conductive corrosion resistance treatment on its surface.

[0023] As a preferred embodiment, the cathode side monopolar plate 2 and the anode side monopolar plate 3 are fixedly connected by bonding or welding.

[0024] As a preferred embodiment, the grooves on the cathode gas diffusion layer 1 are any one of parallel grooves, serpentine grooves, wavy grooves and mesh grooves.

[0025] As a preferred embodiment, the flow channel cross section of the anode-side monopolar plate 3 is a trapezoid, a square, or a parallelogram.

[0026] As a preferred embodiment, the thickness of the cathode gas diffusion layer 1 is 0.3-0.6 mm, the depth of the groove is 0.2-0.5 mm, the width of the groove is 0.4-2 mm, and the ridge width between the grooves is 0.4-2 mm.

[0027] As a preferred embodiment, the grooves of the cathode gas diffusion layer 1 are aligned with the cooling medium flow channels.

[0028] As a preferred embodiment, the opening width of the flow channel of the anode side monopolar plate 3 is consistent with the groove width of the cathode gas diffusion layer 1; the ridge upper surface width of the flow channel of the anode side monopolar plate 3 is consistent with the ridge width of the cathode gas diffusion layer 1.

[0029] On the other hand, the present invention provides a fuel cell, which is composed of a single cell stack, wherein the single cell is composed of an anode gas diffusion layer 7, a membrane electrode and the above-mentioned bipolar plate-cathode gas diffusion layer assembly; the membrane electrode includes an anode catalyst layer 8, a membrane 9 and a cathode catalyst layer 10 stacked in sequence, the anode catalyst layer 8 is connected to the anode gas diffusion layer 7, and the cathode catalyst layer 10 is connected to the cathode gas diffusion layer 1.

[0030] Example 1 like Figure 1 and 2As shown, the present embodiment provides a bipolar plate-cathode gas diffusion layer assembly, comprising a cathode gas diffusion layer 1, a cathode side monopolar plate 2, and an anode side monopolar plate 3 stacked in sequence; the cathode side monopolar plate 2 is a flat plate, and the anode side monopolar plate 3 is a plate with flow channels on both sides; the cathode side monopolar plate 2 and the anode side monopolar plate 3 are both stainless steel plates, the anode side monopolar plate 3 is formed by a stamping process, and the cathode side monopolar plate 2 and the anode side monopolar plate 3 are connected by welding; the cathode gas diffusion layer 1 adopts commercially available carbon fiber felt with a thickness of 0.55 mm, the cathode gas diffusion layer 1 has grooves on one side close to the cathode side monopolar plate 2, the grooves are parallel grooves, the groove depth is 0.3 mm, the groove width is 1.4 mm, and the interval between adjacent grooves is 1 mm, the cross section of the flow channel of the anode side monopolar plate 3 is trapezoidal, the opening width of the flow channel of the anode side monopolar plate 3 is consistent with the groove width of the cathode gas diffusion layer 1, and the ridge upper surface width of the flow channel of the anode side monopolar plate 3 is consistent with the ridge width of the cathode gas diffusion layer 1.

[0031] like Figure 4 and 5 As shown, the above-mentioned bipolar plate-cathode gas diffusion layer assembly is assembled into a fuel cell, and the fuel cell consists of a single cell stack, and the single cell consists of an anode gas diffusion layer 7, a membrane electrode and the above-mentioned bipolar plate-cathode gas diffusion layer assembly; the membrane electrode includes an anode catalyst layer 8, a membrane 9 and a cathode catalyst layer 10 stacked in sequence, the anode catalyst layer 8 is connected to the anode gas diffusion layer 7, and the cathode catalyst layer 10 is connected to the cathode gas diffusion layer 1.

[0032] The cavity formed by the grooves of the cathode side monopolar plate 2 and the cathode gas diffusion layer 1 is an air flow channel 5, the cavity formed between the anode side monopolar plate 3 and the anode gas diffusion layer 7 is a hydrogen flow channel 4, and the cavity formed between the cathode side monopolar plate 2 and the anode side monopolar plate 3 is a cooling medium flow channel 6, and the grooves of the cathode gas diffusion layer are aligned with the cooling medium flow channel 6.

[0033] In the embodiment, a commercially available membrane electrode (anode catalyst layer 8 with a platinum loading of 0.2 mg / cm 2 , the cathode platinum loading is 0.4 mg / cm 2 , the proton exchange membrane is Gore 12 μm proton exchange membrane), the anode gas diffusion layer 7 in this embodiment is commercially available carbon fiber felt with a thickness of 0.55 mm and 5% hydrophobic treatment.

[0034] Example 2 The implementation of this embodiment is similar to that of Embodiment 1, except that both the cathode side monopolar plate 2 and the anode side monopolar plate 3 are titanium plates, and the anode side monopolar plate 3 is formed by an etching process.

[0035] Example 3 The implementation of this embodiment is similar to that of Embodiment 1, except that the cathode side monopolar plate 2 and the anode side monopolar plate 3 are both graphite plates, and the anode side monopolar plate 3 is formed by compression molding.

[0036] Comparative Example 1 In order to more intuitively demonstrate the advantages of the present invention over the prior art, a conventional structure fuel cell is assembled using the same membrane electrode and carbon fiber felt 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.

[0037] Test Example 1 The performance of the fuel cells assembled in Example 1 and Comparative Example 1 was evaluated.

[0038] 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.

[0039] The test results of Example 1 and Comparative Example 1 are as follows Figure 6 As shown, from Figure 6 It can be seen that the bipolar plate-cathode gas diffusion layer assembly and the fuel cell proposed in the present invention have higher performance at high current density, indicating that the fuel cell structure proposed in the present invention has excellent drainage capacity.

[0040] 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-cathode gas diffusion layer assembly, characterized in that: The component includes a cathode gas diffusion layer, a cathode side monopolar plate and an anode side monopolar plate stacked in sequence; the cathode side monopolar plate is a flat plate, and the anode side monopolar plate is a plate with a flow channel; the cathode gas diffusion layer has a groove on one side close to the cathode side monopolar plate, the cavity formed by the grooves of the cathode side monopolar plate and the cathode gas diffusion layer is an air flow channel, and the cavity formed between the cathode side monopolar plate and the anode side monopolar plate is a cooling medium flow channel.

2. The bipolar plate-cathode gas diffusion layer assembly according to claim 1, characterized in that: The cathode side monopolar plate substrate and the anode side monopolar plate substrate are both graphite, stainless steel or titanium.

3. The bipolar plate-cathode gas diffusion layer assembly according to claim 1, characterized in that: The cathode side monopolar plate and the anode side monopolar plate are fixedly connected by bonding or welding.

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

5. The bipolar plate-cathode gas diffusion layer assembly according to claim 1, characterized in that: The cross section of the flow channel of the anode side monopolar plate is a trapezoid, a square or a parallelogram.

6. The bipolar plate-cathode gas diffusion layer assembly according to claim 1, characterized in that: The thickness of the cathode gas diffusion layer is 0.3-0.6 mm, the depth of the groove is 0.2-0.5 mm, the width of the groove is 0.4-2 mm, and the ridge width between the grooves is 0.4-2 mm.

7. The bipolar plate-cathode gas diffusion layer assembly according to claim 1, characterized in that: The grooves of the cathode gas diffusion layer are aligned with the cooling medium flow channels.

8. The bipolar plate-cathode gas diffusion layer assembly according to claim 1, characterized in that: The opening width of the anode side monopolar plate flow channel is consistent with the groove width of the cathode gas diffusion layer; the ridge upper surface width of the anode side monopolar plate flow channel is consistent with the ridge width of the cathode gas diffusion layer.

9. A fuel cell, characterized in that: The fuel cell is composed of a stack of single cells, each of which is composed of an anode gas diffusion layer, a membrane electrode, and a bipolar plate-cathode gas diffusion layer assembly as claimed in any one of claims 1 to 8.

10. The fuel cell according to claim 9, 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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