Bipolar plate and preparation method thereof

Abstract

The bipolar plate comprises a base plate, a flow field area is arranged on the base plate, flow channel ridges are arranged in the flow field area, and a flow channel groove is formed between every two adjacent flow channel ridges; linear flow channel ridges are arranged on the outermost side of the flow field area, linear flow channel ridges and snakelike flow channel ridges are arranged in the middle of the flow field area in a staggered mode, the linear flow channel ridges are provided with air storage channels, air inlet holes are formed in top inlets of the air storage channels, and air outlet holes are formed in bottom inlets and outlets of the air storage channels. The air inlet hole and the air outlet hole of the first air storage channel on the outermost side of the flow field area face the nearest snake-shaped flow channel ridge; the linear flow channel ridges not located on the outermost side of the flow field area are each provided with two second air storage channels, and air inlet holes and air outlet holes of the second air storage channels directly face the S-shaped flow channel ridges on the two sides of the second air storage channels correspondingly. The invention can balance the flowing durability of the reaction gas, make up the insufficient consumption of the second half section, improve the energy conversion efficiency of the cell, reduce the concentration polarization risk, is suitable for various fuel cells, and can improve the power output and reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of bipolar plates, and in particular to a bipolar plate and a method for preparing the same. Background Art

[0002] Fuel cells are mainly composed of proton exchange membranes, catalyst layers, air diffusion layers and bipolar plates. As the core component of fuel cells, bipolar plates play many important roles in fuel cells, including supporting the membrane electrode structure, separating hydrogen and oxygen, collecting electrons, conducting heat, providing hydrogen and oxygen channels, discharging water generated by the reaction, and providing coolant channels. Their performance depends largely on the flow field structure.

[0003] The common bipolar plate flow field structure is mainly composed of the inlet and outlet area, transition area and reaction area. Whether the design of each area is reasonable directly affects the performance of the fuel cell. Since the emergence of fuel cell technology, people have conducted a lot of research on the flow field. At present, the conventional flow fields include direct current parallel flow channel, serpentine, spiral, grid, etc., among which direct current parallel flow channel and serpentine are the most widely used.

[0004] The direct-flow parallel flow channel has the advantage of a small pressure drop, but since the gas flow channel from the top to the bottom of the flow field is a straight through channel, the flow persistence of the reaction gas in the flow channel is poor; the serpentine flow channel ridge has multiple direction changes, so the reaction gas flows in a staggered manner in the flow field, which can improve the uniform distribution of the pressure load of the battery stack between each single cell and the distribution of the reaction gas on the electrode surface. However, the disadvantage of the serpentine flow channel ridge is that in addition to the greater pressure drop than the direct-flow parallel flow channel, the concentration of the reaction gas will be greatly reduced due to the excessive length of the flow channel and the gradual consumption of the gas along the flow direction. The reaction near the outlet end is incomplete due to the reduction in concentration, resulting in increased concentration polarization and the catalyst cannot be fully utilized. Summary of the invention

[0005] According to the above, a bipolar plate and a method for preparing the same are provided to effectively balance the durability of the reaction gas when it flows in the flow field, and to make up for the technical problem that the reaction gas is insufficient due to consumption in the second half of the flow field. The present invention forms a flow field structure by staggering serpentine flow channel ridges and linear flow channel ridges, and is provided with a gas storage channel, and an air inlet and an air outlet are provided on the gas storage channel, so that multiple gas replenishments can be achieved during the reaction process, avoiding the insufficient reaction gas due to consumption in the second half of the flow field.

[0006] The technical means adopted by the present invention are as follows:

[0007] A bipolar plate, comprising: a base plate, a flow field region is provided on the base plate, the flow field region is provided with flow channel ridges, and flow channel grooves are formed between adjacent flow channel ridges; the outermost side of the flow field region is a straight flow channel ridge, and the middle part is a straight flow channel ridge and a serpentine flow channel ridge interlaced with each other;

[0008] The linear flow channel ridges are all provided with air storage channels, the top entrance of the air storage channel is provided with an air inlet, and the bottom entrance and exit are provided with an air outlet.

[0009] The air inlet and the air outlet of the first air storage channel at the outermost side of the flow field area face the nearest serpentine flow channel ridge;

[0010] The straight-line flow channel ridges not located at the outermost position of the flow field area are all provided with two second air storage channels, and the air inlet and the air outlet of the second air storage channels are respectively opposite to the serpentine flow channel ridges on both sides thereof.

[0011] Furthermore, according to the direction of gas movement in the flow field, the first gas storage channel and the second gas storage channel array have a plurality of gas outlet holes facing the serpentine flow channel ridge, and the distance between every two gas outlet holes tends to gradually increase;

[0012] The diameter of the air inlet hole is 0.5mm-3mm, and the diameter of the air outlet hole is 0.5mm-3mm.

[0013] Furthermore, according to the direction of gas movement in the flow field, the diameter of the gas outlet hole tends to gradually increase, and the hole diameter is 1.05-1.25 times the diameter of the previous gas outlet hole.

[0014] Furthermore, the width of the straight flow channel ridge is 1.2-1.5 times the width of the serpentine flow channel ridge.

[0015] A method for preparing a bipolar plate comprises the following steps:

[0016] S1. Use metal plates and perform surface pretreatment on them, including grinding, removing the passivation layer, and coating the surface with an anti-corrosion protective layer;

[0017] S2. A flow field structure including a plurality of straight flow channel ridges and serpentine flow channel ridges with air storage channels is formed on the surface of the metal plate by using a rubber pad stamping process;

[0018] S3. Use laser engraving technology to form air inlet and air outlet holes on the side wall of the air storage channel.

[0019] Furthermore, in S1, 50-200 mesh sandpaper is used for grinding; the passivation layer is removed by soaking in a weak acid with a pH of 6.6-6.9 for 1-5 hours; and the surface is coated with an anti-corrosion protection layer by sputtering precious metals such as Pt and C using a PVD method.

[0020] Furthermore, the groove width between the parallel flow field and the serpentine flow channel ridge in S2 is 0.5-4 mm, and the groove depth is 0.2-2 mm.

[0021] Furthermore, the power of laser engraving in S3 is 5-100W, using pulse or continuous engraving.

[0022] Due to the adoption of the above technical solution, compared with the prior art, the present invention has the following advantages:

[0023] 1. A bipolar plate and a preparation method thereof provided by the present invention adopt a flow field structure formed by staggered serpentine flow channel ridges and straight flow channel ridges. Since the two forms of flow channel ridges are distributed in a uniform array and staggered design, the problem of poor flow persistence of the reaction gas in the straight flow channel ridges or large pressure drop in the serpentine flow channel ridges can be effectively balanced, and the flow is uniform, which effectively improves the flow persistence in the flow field, and at the same time does not cause the problem of long duration and increased reaction consumption; the energy conversion efficiency of the battery is improved, and the overall working performance of the system is improved.

[0024] 2. The present invention provides a bipolar plate and a preparation method thereof. After the reaction gas enters from the top of the bipolar plate flow field structure, a part of it is diverted from the top air inlet hole into the gas storage channel of the linear flow channel ridge. Since it is closed while flowing in the gas storage channel, it will not be consumed at this time. The other part of the reaction gas flows in the flow channel groove between the linear flow channel ridge and the serpentine flow channel ridge, and reacts with the gas diffusion layer and is gradually consumed. The reaction gas in the gas storage channel flows out from the air outlet to make up for the insufficient consumption of the reaction gas in the latter part of the flow field. The designed gas storage channel and its air outlet can realize multiple gas replenishment during the reaction process, ensuring sufficient supply of reaction gas in the entire flow field and balanced gas supply, effectively preventing insufficient catalysis caused by insufficient consumption of reaction gas in the latter part of the flow, and reducing the risk of concentration polarization.

[0025] 3. The present invention provides a bipolar plate and a preparation method thereof, wherein a plurality of gas outlet holes are provided in the gas storage channel, and the hole diameter and orientation are designed according to the flow process of the reaction gas in the flow field, so that the reaction gas in the gas storage channel can be automatically replenished to the flow field in batches multiple times, which can significantly improve the power output and reliability of the fuel cell.

[0026] 4. The bipolar plate and preparation method provided by the present invention are suitable for different types of fuel cells, so that they have a wider application potential and can meet the needs of various types of fuel cells in actual use; the flow channel design effectively reduces the accumulation of reaction exhaust gas in the flow field, reduces corrosion and wear of materials, thereby extending the service life of the bipolar plate; simplifies the manufacturing process, avoids multiple processing and high-energy-consuming processes in traditional technologies, and helps to reduce production costs and improve production efficiency.

[0027] Based on the above reasons, the present invention can be promoted in the field of bipolar plate technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention 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, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 It is a schematic diagram of the overall structure of a bipolar plate flow field according to the present invention;

[0030] Figure 2 It is a schematic diagram of the internal structure of a bipolar plate according to the present invention;

[0031] Figure 3 It is a flow chart of a method for preparing a bipolar plate according to the present invention.

[0032] In the figure: 1. Straight flow channel ridge; 2. Serpentine flow channel ridge; 3. Flow channel groove; 4. First air storage channel; 5. Second air storage channel; 6. Air inlet; 7. First air outlet; 8. Second air outlet; 9. nth air outlet. DETAILED DESCRIPTION

[0033] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. 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 "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0036] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0037] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0038] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here 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 their position devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0039] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0040] Example 1

[0041] like Figures 1 to 2 As shown, the present invention provides a bipolar plate, comprising: a base plate, a flow field area is provided on the base plate, the flow field area is provided with flow channel ridges, and flow channel grooves are formed between adjacent flow channel ridges; the outermost side of the flow field area is a straight flow channel ridge, and the middle is a straight flow channel ridge and a serpentine flow channel ridge interlaced with each other, the width of the straight flow channel ridge is 1.2 times the width of the serpentine flow channel ridge, the groove width between the parallel flow field and the serpentine flow channel ridge is 2mm, and the groove depth is 1mm. In the flow field structure of the bipolar plate, both sides of the bipolar plate are straight flow channel ridges, and the straight flow channel ridges are provided with air storage channels, and the top inlet of the air storage channel is provided with an air inlet 3, and the bottom inlet and outlet are provided with an air inlet 3 and an air outlet, and the air inlet 3 and the air outlet of the outermost first air storage channel 1 of the flow field area face the nearest serpentine flow channel ridge; the straight flow channel ridges not located at the outermost position of the flow field area are provided with two second air storage channels 2, and the air inlet 3 and the air outlet are respectively facing the serpentine flow channel ridges on both sides thereof.

[0042] Example 2

[0043] According to the direction of gas movement in the flow field, the first air storage channel 1 and the second air storage channel 2 array have multiple air outlet holes facing the serpentine flow channel ridge, and the distance between every two air outlet holes gradually increases at a rate of 1.2 times. The diameter of the air inlet hole 3 is 0.5-3mm, and the diameter of the air outlet hole is 0.5mm-3mm. Among them, the diameter of the air outlet hole gradually increases, and its aperture is 1.05-1.25 times the diameter of the previous air outlet hole. In the present embodiment, the diameter of the air inlet hole 3 is 0.5mm, the diameter of the first air outlet hole 4 is 0.5mm, and the aperture of the second air outlet hole 5 is 1.05 times the diameter of the first air outlet hole 4, until the nth air outlet hole 6.

[0044] Example 3

[0045] like Figure 3 As shown, the present invention also provides a method for preparing a bipolar plate, comprising the following steps:

[0046] S1. Two metal plates are used for surface pretreatment, wherein the pretreatment includes polishing with 50-200 mesh sandpaper, specifically 150 mesh sandpaper, soaking in weak acid with pH=6.6 for 3 hours to remove the passivation layer, and finally coating the surface with an anti-corrosion protective layer by sputtering Pt precious metal by PVD method;

[0047] S2. A flow field structure including a plurality of straight flow channel ridges and serpentine flow channel ridges with air storage channels is formed on the surface of the metal plate by using a rubber pad stamping process;

[0048] S3. Use laser engraving technology to form air inlet holes 3 and air outlet holes on the side wall of the air storage channel. The laser engraving power is 50W. Pulse or continuous welding is used to form anode plates and cathode plates with smooth structures.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bipolar plate, characterized in that: The invention comprises a base plate, a flow field area is arranged on the base plate, the flow field area comprises flow channel ridges, and flow channel grooves are formed between adjacent flow channel ridges; the outermost side of the flow field area is a straight flow channel ridge, and the middle part is a straight flow channel ridge and a serpentine flow channel ridge interlaced with each other; The linear flow channel ridges are all provided with air storage channels, the top entrances of the air storage channels are all provided with air inlet holes, and the bottom entrances and exits are all provided with air outlet holes; The air inlet and the air outlet of the first air storage channel at the outermost side of the flow field area face the nearest serpentine flow channel ridge; The straight-line flow channel ridges not located at the outermost position of the flow field area are all provided with two second air storage channels, and the air inlet and the air outlet of the second air storage channels are respectively opposite to the serpentine flow channel ridges on both sides thereof.

2. A bipolar plate according to claim 1, characterized in that: According to the flow direction of the reaction gas in the flow field area, the first gas storage channel and the second gas storage channel array have a plurality of gas outlet holes facing the serpentine flow channel ridge, and the distance between every two gas outlet holes tends to gradually increase; The diameter of the air inlet hole is 0.5mm-3mm, and the diameter of the air outlet hole is 0.5mm-3mm.

3. A bipolar plate according to claim 1, characterized in that: According to the direction of gas movement in the flow field, the diameter of the gas outlet hole tends to gradually increase, and the hole diameter is 1.05-1.25 times the diameter of the previous gas outlet hole.

4. A bipolar plate according to claim 1, characterized in that: The width of the straight flow channel ridge is 1.2-1.5 times the width of the serpentine flow channel ridge.

5. A method for preparing a bipolar plate, characterized in that: The following steps are involved: S1. Use metal plates and perform surface pretreatment on them, including grinding, removing the passivation layer, and coating the surface with an anti-corrosion protective layer; S2. A flow field structure including a plurality of straight flow channel ridges and serpentine flow channel ridges with air storage channels is formed on the surface of the metal plate by using a rubber pad stamping process; S3. Laser engraving technology is used to open air inlet and outlet holes connected to the air storage channel on the side wall of the linear flow channel ridge.

6. The method for preparing a bipolar plate according to claim 5, characterized in that: In S1, 50-200 mesh sandpaper is used for grinding; the passivation layer is removed by soaking in weak acid with a pH of 6.6-6.9 for 1-5 hours; the surface is coated with an anti-corrosion protective layer by sputtering precious metals such as Pt and C using the PVD method.

7. The method for preparing a bipolar plate according to claim 5, characterized in that: The groove width between the straight flow channel ridge and the serpentine flow channel ridge in S2 is 0.5-4mm, and the groove depth is 0.2-2mm.

8. The method for preparing a bipolar plate according to claim 5, characterized in that: The power of laser engraving in S3 is 5-100W, and it adopts pulse or continuous engraving form.

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