Polar plate, bipolar plate and fuel cell

Abstract

The utility model relates to a polar plate, a bipolar plate and a fuel cell. The polar plate comprises: a flow field region, the flow field region is provided with a flow channel, and the flow channel comprises a ridge and a groove; a first coating and a second coating are arranged on the flow channel surface of the flow field area; the first coating is a hydrophilic coating, and the hydrophilic coating covers the surfaces of the ridges and the grooves; the second coating is a porous coating which at least partially covers the surface of the groove and is located above the hydrophilic coating. Therefore, on the basis of the hydrophilic coating, the porous coating is additionally arranged at the position of the groove of the polar plate, the hydrophilicity in the groove is further improved, liquid can be more effectively evacuated, and the liquid is prevented from being gathered into water drops to block a flow channel, so that the polar plate has higher drainage capacity and gas conveying capacity, and is not easy to corrode due to water logging; the stability is improved; and the service life is prolonged.

Description

Technical Field

[0001] The present application relates to the technical field of fuel cells, and in particular to a polar plate, a bipolar plate and a fuel cell. Background Art

[0002] As the demand for environmental protection increases, fuel cells, as a new type of environmentally friendly energy means, are becoming more and more popular. Fuel cells can convert chemical energy into electrical energy, and have the advantages of high fuel energy conversion rate, low noise and zero emissions. They are widely used in transportation vehicles such as cars, airplanes, trains, and fixed power stations. Among them, the basic unit of the proton exchange membrane fuel cell (PEMFC) is composed of a membrane electrode sandwiched in the middle and polar plates on both sides. The polar plate is the core component of the PEMFC and can be used as a monopolar plate or connected into a bipolar plate (BPP). It mainly has the following key functions: discharge reaction products and heat, and play a transport role after the oxidant and fuel enter the battery to ensure that they can smoothly enter the electrode. Among them, the reaction product mainly refers to the water generated by the reaction of hydrogen and oxygen. If the water generated by the reaction cannot be well discharged from the outside of the battery, it will cause flooding problems, block the flow channel of the polar plate, affect gas transportation, and then affect the reaction; in addition, the polar plate is also used to conduct current between each battery cell, support the entire battery assembly, and work for a long time under acidic conditions and protect other components. Therefore, the electrode plate also needs to adapt to acidic, high temperature and other environments to protect the safety of components inside the battery and maintain normal operation of the battery. Utility Model Content

[0003] The present application provides a polar plate, a bipolar plate and a fuel cell to solve the problem in the prior art that water droplets in the polar plate flow channels of the fuel cell block the flow channels, affect the raw material gas delivery and corrode the polar plates.

[0004] A polar plate provided in the present application includes:

[0005] A flow field area, wherein the flow field area is provided with a flow channel, and the flow channel includes ridges and grooves;

[0006] The flow channel surface of the flow field area is provided with a first coating and a second coating; the first coating is a hydrophilic coating, which covers the surface of the ridges and grooves; the second coating is a porous coating, which at least partially covers the surface of the grooves and is located on the hydrophilic coating.

[0007] In some embodiments, the porous coating completely covers the surface of the groove, or the porous coating only covers the surface on one side of the groove facing downward along the gravity direction.

[0008] In some embodiments, the porous coating has a pore size of 8-20 nm and a pore volume of 1-4 cm 3 / g, specific surface area is 65-295m 2 / g.

[0009] In some embodiments, the porous coating is made of titanium dioxide.

[0010] In some embodiments, the porous coating has a thickness of 10-25 nm.

[0011] In some embodiments, the flow channel in the flow field area is a variable diameter flow channel, in which the width of the groove tends to decrease along the gas conveying direction of the flow field area.

[0012] In some embodiments, the hydrophilic coating is a multi-layer structure, including a passivation layer at the bottom layer and a conductive hydrophilic layer at the top layer.

[0013] In some embodiments, the thickness of the passivation layer is 2-5 nm, and the thickness of the conductive hydrophilic layer is 8-15 nm.

[0014] In some embodiments, the passivation layer is a dense titanium dioxide layer; and the conductive hydrophilic layer is a gold coating or a carbon coating.

[0015] According to another aspect of the present application, a bipolar plate is provided, which includes an anode plate and a cathode plate connected together, and the anode plate and / or the cathode plate is the above-mentioned polar plate.

[0016] According to another aspect of the present application, a fuel cell is provided, which includes the above electrode plate.

[0017] The electrode plate of the present application includes: a flow field area, the flow field area is provided with a flow channel, the flow channel includes ridges and grooves; the flow channel surface of the flow field area is provided with a first coating and a second coating; the first coating is a hydrophilic coating, the hydrophilic coating covers the surface of the ridges and grooves; the second coating is a porous coating, the porous coating at least partially covers the surface of the groove and is located on the hydrophilic coating. Therefore, on the basis of the hydrophilic coating, the present application adds a porous coating at the position of the groove of the electrode plate, further increases the hydrophilicity in the groove, can more effectively evacuate the liquid, and avoid the liquid from gathering into water droplets to block the flow channel, so it has a higher drainage capacity and gas transport capacity, and is not prone to flooding and corrosion, and the stability and service life are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0020] Figure 1 A schematic diagram of a flow channel cross section in a plate flow field region of an embodiment of the present application is shown;

[0021] Figure 2 A schematic diagram of a flow channel cross section in a flow field region of a second electrode plate according to an embodiment of the present application is shown;

[0022] Figure 3 The enlarged structural schematic diagram of the second electrode plate in the embodiment of the present application in the use state is shown;

[0023] The above drawings include the following reference numerals:

[0024] 1. Plate; 10. Flow field area; 11. Ridge; 12. Groove; 13. Hydrophilic coating; 14. Porous coating; 20. Manifold port area; 2. Membrane electrode. DETAILED DESCRIPTION

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0026] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0027] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" may include both "above" and "below". The device may also be positioned in other different ways, rotated 90 degrees or in other orientations, and the spatially relative descriptions used herein are interpreted accordingly.

[0028] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0029] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0030] The electrode plate 1 is an important structure in the fuel cell, which is installed on both sides of the membrane electrode 2 and forms a single cell structure with the membrane electrode 2. The electrode plates 1 on both sides of the membrane electrode 2 serve as positive and negative plates respectively, and transport hydrogen and air on both sides of the membrane electrode 2 through the flow channels on the electrode plates, so that hydrogen and air react through the membrane electrode 2 to generate current. Since the reaction process will generate product water, and the water will gather together to form water droplets, it will block the flow channel and affect the gas transportation on the electrode plate, so it is necessary to treat the surface of the electrode plate 1 to avoid blockage of the flow channel.

[0031] This application proposes a plate that is not easy to form clogging water droplets and has a stronger gas transmission capacity. Figure 1 A schematic diagram of a flow channel cross section in a plate flow field region of an embodiment of the present application is shown; Figure 2 A schematic diagram of a flow channel cross section in a flow field region of a second electrode plate according to an embodiment of the present application is shown; Figure 3 The enlarged structural schematic diagram of the second electrode plate in the embodiment of the present application in use state is shown.

[0032] like Figures 1 to 3 As shown, the present application discloses a plate 1, which includes: a flow field area 10, the flow field area 10 is provided with a flow channel, and the flow channel includes a ridge 11 and a groove 12. A first coating and a second coating are provided on the surface of the flow channel of the flow field area 10. The first coating is a hydrophilic coating 13, and the hydrophilic coating 13 covers the surface of the ridge 11 and the groove 12. The second coating is a porous coating 14, and the porous coating 14 at least partially covers the surface of the groove 12 and is located on the hydrophilic coating 13.

[0033] Among them, Figure 1 and Figure 2 As shown, it is known to those skilled in the art that the flow field area 10 of the electrode plate 1 is arranged corresponding to the active area of ​​the membrane electrode 2. The surface of the hydrophilic coating 13 is relatively smooth, and its contact angle with water is small, so it can quickly guide water. The position of the ridge 11 is covered with the hydrophilic coating 13, which can increase the contact area between the electrode plate 1 and the membrane electrode 2, and quickly guide the product water to the surface of the electrode plate 1 for discharge; at the same time, the contact area between the hydrophilic coating 13 and the membrane electrode 2 is large and tight, and has a low contact resistance, so it also has the effect of reducing the impedance of the battery stack during operation. In this embodiment, the position of the groove 12 of the electrode plate 1 is also covered with the hydrophilic coating 13, and the hydrophilicity of the hydrophilic coating 13 can be used to promote the extension of water droplets, so that the water collected in the groove 12 forms a water film covering the flow channel, rather than forming water droplets to block the flow channel. In addition, the embodiment of the present application also covers the position of the groove 12 of the electrode plate 1 with a layer of porous coating 14. The porous coating 14 utilizes a porous adsorptive structure to further improve the hydrophilicity of the surface of the electrode plate 1, and prevents the moisture from gathering into water droplets to block the flow channel by absorbing and retaining moisture. The moisture retained in the porous coating 14 can be discharged from the battery stack along with the airflow, thereby improving the drainage capacity of the electrode plate 1.

[0034] Therefore, through the combined design of the above-mentioned hydrophilic coating 13 and the porous coating 14, the embodiment of the present application adds a porous coating 14 at the position of the groove 12 of the electrode plate 1 on the basis of the hydrophilic coating 13, further increasing the hydrophilicity in the groove 12, which can more effectively disperse the liquid and prevent the liquid from gathering into water droplets to block the flow channel. Therefore, it has higher drainage capacity and gas transport capacity, is not easy to be flooded and corroded, and the stability and service life are improved.

[0035] In some embodiments of the present application, the porous coating 14 completely covers the surface of the groove 12. Figure 1 As shown, in order to achieve comprehensive absorption and storage of moisture, and ensure smooth flow channels to transport raw gas.

[0036] Or, in some other embodiments of the present application, such as Figure 2 and Figure 3 As shown, the porous coating 14 only covers the surface of one side of the groove 12 facing downward along the gravity direction, which can save material costs and reduce the weight of the fuel cell to a certain extent. Moreover, the larger the volume of the fuel cell and the more the number of plates 1, the more obvious the lightweight effect. Figure 3 As shown, in the flow field area 10 of the electrode plate 1, the surface of the lower side of the groove 12 in the flow channel is covered with a porous coating 14, thereby overcoming the gathering effect of gravity on moisture, absorbing the contained moisture, dispersing the moisture without forming water droplets to block the flow channel, and ensuring that the flow channel is unobstructed to transport the raw gas.

[0037] In the examples of this application, refer to Figure 3 As shown, the electrode plate 1 includes a flow field area 10 located in the middle and a manifold port area 20 located on the left and right sides. The manifold port area 20 is also called a common pipeline area, which is used to form supply pipelines for hydrogen, air, coolant, etc. The flow field area 10 can be further divided into a distribution area and a reaction area: the reaction area is located in the middle of the flow field area 10, corresponding to the active area of ​​the membrane electrode 2, and is the main area for gas reaction; the distribution area is located between the reaction area and the manifold port area 20, and is the transition area for gas to enter the reaction area from the manifold port area 20. Based on functional requirements, the distribution area and the reaction area are provided with flow channels for transporting gas, that is, the above-mentioned ridges 11 and grooves 12 are distributed. The coating improvement on the surface of the flow channel in the embodiment of the present application is at least located in the reaction zone to ensure that the gas is fully contacted and reacted by avoiding blockage of the flow channel, thereby ensuring the efficiency of battery power generation.

[0038] In some embodiments of the present application, the pore size of the porous coating 14 is 8-20 nm, and the pore volume is 1-4 cm 3 / g, specific surface area is 65-295m 2 / g. Through the above parameter design, the porosity of the porous coating 14 achieves better drainage performance, and can use the raw material gas flow such as hydrogen or air to quickly discharge the adsorbed product water therein, thereby avoiding the blockage and corrosion of the flow channel caused by the accumulation of water droplets, and improving the power generation efficiency and service life of the fuel cell.

[0039] In some embodiments of the present application, the material used for the porous coating 14 is titanium, titanium dioxide, tin or graphite. Titanium, titanium dioxide, tin or graphite have the advantages of stable properties and corrosion resistance. Among them, in a more preferred embodiment of the present application, the material used for the porous coating 14 is titanium dioxide. Titanium dioxide porous material has excellent stability and high surface quality, while titanium and titanium alloys have low density, high specific strength, a wide operating temperature range and good corrosion resistance, stable properties and structure, and a long service life. As known to those skilled in the art, these materials can be coated into a porous structure by existing commonly used physical or chemical coating methods to form a porous coating 14 of the present application embodiment.

[0040] In some embodiments of the present application, the thickness of the porous coating 14 is 10-25 nm, which is thick enough to absorb the retained water, but does not occupy too much cross-sectional area of ​​the flow channel, thereby taking into account both the drainage capacity and gas transmission capacity of the flow channel. When the porous coating 14 is made of different materials, due to differences in process and material properties, the optimal layer thickness may be different, which is specifically determined according to the actual structure of the electrode 1.

[0041] In some embodiments of the present application, the flow channel of the flow field area 10 of the electrode plate 1 is a variable diameter flow channel in conjunction with the hydrophilic coating 13 and the porous coating 14 of the electrode plate 1. In the variable diameter flow channel, the width of the groove 12 tends to decrease along the gas delivery direction of the flow field area 10, so that the cross-sectional area of ​​the flow channel can be gradually reduced, and the speed of the gas flow can be increased to take away the moisture on the coating more quickly.

[0042] In some embodiments of the present application, the electrode plates 1 located on both sides of the membrane electrode 2 serve as positive electrode plates and negative electrode plates respectively, and the gas transport directions on their surfaces are different, so the narrowing directions of their variable diameter flow channels are also different. It is specifically determined according to the shape and direction of the flow channel on the electrode plate 1, as long as the overall flow channel presents a trend of gradually narrowing to increase the airflow velocity.

[0043] In some embodiments of the present application, in order to further overcome the corrosion of the electrode plate 1 by the accumulation of the product liquid and extend the life of the electrode plate 1, the hydrophilic coating 13 is configured as a multi-layer structure, including a passivation layer at the bottom and a conductive hydrophilic layer at the top. The passivation layer at the bottom is close to the surface of the electrode plate 1 to block the influence of corrosion, and the surface of the passivation layer is covered with a conductive hydrophilic layer to achieve electrical connection and guide moisture.

[0044] In some embodiments of the present application, the thickness of the passivation layer is 2-5 nm, and the thickness of the conductive hydrophilic layer is 8-15 nm. The passivation layer is made of corrosion-resistant and high-temperature-resistant materials, and has stable properties to protect the electrode 1. The conductive hydrophilic layer is made of a material with a lower resistivity and has a greater thickness to overcome wear and reduce impedance.

[0045] In some embodiments of the present application, the passivation layer is a dense titanium dioxide layer. Since titanium and titanium alloys have low density, high specific strength, a wide operating temperature range and good corrosion resistance, their application on the surface of the plate 1 can achieve a lightweight and stable protective structure to prevent the plate 1 from being damaged by corrosion. In some embodiments of the present application, the plate 1 is a metal plate 1, which is formed by stamping, coating and other processes.

[0046] In some embodiments of the present application, the conductive hydrophilic layer is a gold coating or a carbon coating, and the gold coating or the carbon coating has the advantages of low resistivity and easy processing.

[0047] The present application also discloses a bipolar plate, which includes an anode plate and a cathode plate connected together, wherein the anode plate and / or the cathode plate adopts the polar plates of the above embodiments. In some embodiments of the present application, the anode plate and the cathode plate are connected together by welding or bonding. Both sides of the bipolar plate face a membrane electrode 2, which is used to provide a flow field area 10 to transport the raw material gas flow for reaction and power generation. The interior of the bipolar plate (i.e., between the anode plate and the cathode plate) can be used to circulate coolant to achieve rapid cooling of the fuel cell, take away the reaction heat, and inhibit the thermal decay of the fuel cell.

[0048] The present application also discloses a fuel cell, which includes the electrode plate 1 of each of the above embodiments. The electrode plate 1 and the membrane electrode 2 of the above embodiments form a single cell group, and multiple groups are connected in series to form a fuel cell, which can improve the drainage capacity and gas transmission capacity of the fuel cell, ensure that the fuel cell is not easily blocked by water and affects the reaction, so that the power generation efficiency of the fuel cell is stable and reliable, and it has the advantages of low attenuation rate, stable performance and long life.

[0049] In summary, the electrode plate of the embodiment of the present application includes: a flow field area, the flow field area is provided with a flow channel, and the flow channel includes ridges and grooves; the flow channel surface of the flow field area is provided with a first coating and a second coating; the first coating is a hydrophilic coating, and the hydrophilic coating covers the surface of the ridges and grooves; the second coating is a porous coating, and the porous coating at least partially covers the surface of the groove and is located on the hydrophilic coating. Therefore, on the basis of the hydrophilic coating, the present application adds a porous coating at the position of the groove of the electrode plate, further increases the hydrophilicity in the groove, can more effectively evacuate the liquid, and avoid the liquid from gathering into water droplets to block the flow channel, so it has a higher drainage capacity and gas transport capacity, and is not prone to flooding and corrosion, and the stability and service life are improved.

[0050] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A plate, characterized in that: include: A flow field area (10), wherein the flow field area (10) is provided with a flow channel, wherein the flow channel comprises a ridge (11) and a groove (12); The surface of the flow channel of the flow field area (10) is provided with a first coating and a second coating; the first coating is a hydrophilic coating (13), and the hydrophilic coating (13) covers the surface of the ridge (11) and the groove (12); the second coating is a porous coating (14), and the porous coating (14) at least partially covers the surface of the groove (12) and is located on the hydrophilic coating (13).

2. The electrode plate according to claim 1, characterized in that: The porous coating (14) completely covers the surface of the groove (12), or the porous coating (14) only covers the surface on one side of the groove (12) facing downward along the gravity direction.

3. The electrode plate according to claim 1, characterized in that: The porous coating (14) has a pore diameter of 8-20 nm and a pore volume of 1-4 cm 3 / g, specific surface area is 65-295m 2 / g.

4. The electrode plate according to claim 3, characterized in that: The porous coating (14) is made of titanium dioxide.

5. The electrode plate according to claim 1, characterized in that: The thickness of the porous coating (14) is 10-25 nm.

6. The electrode plate according to claim 1, characterized in that: The flow channel of the flow field area (10) is a variable diameter flow channel, and in the variable diameter flow channel, the width of the groove (12) tends to decrease along the gas conveying direction of the flow field area (10).

7. The electrode plate according to claim 1, characterized in that: The hydrophilic coating (13) is a multi-layer structure, comprising a passivation layer located at the bottom layer and a conductive hydrophilic layer located at the top layer.

8. The electrode plate according to claim 7, characterized in that: The passivation layer is a dense titanium dioxide layer; the conductive hydrophilic layer is a gold coating or a carbon coating.

9. A bipolar plate, characterized in that: The bipolar plate comprises an anode plate and a cathode plate connected together, and the anode plate and / or the cathode plate is the bipolar plate according to any one of claims 1 to 8.

10. A fuel cell, characterized in that: The fuel cell comprises the electrode plate according to any one of claims 1 to 8.

Images