Bipolar plate structure based on snowflake bionic composite flow field

Abstract

The invention provides a bipolar plate structure based on a snowflake bionic composite flow field, and relates to the technical field of proton exchange membrane batteries, the bipolar plate structure comprises a polar plate body, the interior of the polar plate body is hollow, a flow field is limited, the polar plate body is at least provided with two opposite corners, and the two corners are respectively provided with an air inlet and an air outlet which are communicated with the flow field; the multiple check blocks are arranged in the flow field, and the multiple check blocks define a main flow channel and an auxiliary flow channel in the flow field. A bionic composite flow field is designed on the basis of the shape of snowflakes, main flow channels and auxiliary flow channels located between the main flow channels are included in the flow field, and compared with a traditional flow field structure, the flow field provides multiple paths for gas transmission, effective convection of gas to a membrane electrode is promoted, the gas transmission efficiency is improved, and the gas transmission efficiency is improved. The performance of the battery is improved by 35.5% compared with that of a traditional flow field structure, the material distribution uniformity of the cathode side is remarkably improved, and the working efficiency and the stability of the battery are improved.

Description

Technical Field

[0001] The invention relates to the technical field of proton exchange membrane batteries, and in particular to a bipolar plate structure based on a snowflake bionic composite flow field. Background Art

[0002] Proton exchange membrane fuel cell (PEMFC) is a device that converts hydrogen and oxygen (usually oxygen in the air) into electrical energy through electrochemical reactions. It has many advantages such as high efficiency, fast start-up, low temperature operation, zero emissions and quietness, and is widely used in transportation, portable electronic devices, and residential and commercial power systems.

[0003] The main components of PEMFC include bipolar plates, gas diffusion layers, catalyst layers and proton exchange membranes. Among them, bipolar plates play a key role in material transfer and stack performance. The shape and size of the bipolar plate flow field structure determine the distribution of the flow field, which in turn affects performance such as gas transfer efficiency. Therefore, optimizing the flow field structure of the bipolar plate is an effective way to improve battery performance.

[0004] In recent years, many new flow channels have been derived based on traditional flow field structures, including bionic flow channels and 3D complex flow channels. Traditional flow channel structures include parallel straight flow channels, single serpentine flow channels, multi-serpentine flow channels, forked flow channels, spiral flow channels and grid flow channels; bionic flow channels include leaf vein type and lung type bionic flow channels; and 3D complex flow channels include representative structures such as microchannels, which are currently used in Toyota Mirai cars. In the above structures, traditional flow channels usually have problems such as poor drainage performance, large pressure drop, low gas utilization rate, and easy clogging; and although the 3D complex flow channel has improved performance, its structure is complex, the assembly of the bipolar plate is difficult, and the processing cost is high; the bionic flow channel can improve the uniformity of gas distribution and heat dissipation effect to a certain extent, but the improvement is very limited, and the gas transmission efficiency is generally low.

[0005] In view of this, how to provide a bipolar plate flow field structure with a simple structure that can effectively improve gas distribution uniformity and heat dissipation effect and improve gas transmission efficiency is a problem that technical personnel in this field urgently need to solve. Summary of the invention

[0006] The purpose of the present invention is to provide a bipolar plate structure based on a snowflake bionic composite flow field to solve the problems existing in the prior art.

[0007] To achieve the above object, the present invention provides the following solution: The present invention provides a bipolar plate structure based on a snowflake bionic composite flow field, comprising:

[0008] The plate body is hollow inside and defines a flow field, the plate body having at least two oppositely disposed corners, the two corners being respectively provided with an air inlet and an air outlet connected to the flow field;

[0009] A block, wherein the block is in plurality and arranged in the flow field, and the plurality of blocks define a main flow channel and a secondary flow channel in the flow field.

[0010] Furthermore, there is a flow channel center between the air inlet and the air outlet, the straight line where the main flow channel is located passes through the flow channel center, there are multiple main flow channels and are arranged circumferentially with the flow channel center as the center of the circle; there is an installation area between adjacent main flow channels, and multiple blocks are arranged in the installation area, and secondary flow channels are formed between multiple blocks in the same installation area.

[0011] Furthermore, there are three main channels in total, and six installation areas are formed between adjacent main channels; a plurality of the blocks are evenly spaced and arranged in the installation areas, with their transverse arrangement direction being parallel to an adjacent main channel, and their longitudinal arrangement direction being parallel to another adjacent main channel, and the secondary channel is arranged in parallel with the main channel.

[0012] Furthermore, the width of the main flow channel is 1.5 mm, and the width of the secondary flow channel is 1 mm.

[0013] Furthermore, the flow field is arranged obliquely, and the height ratio of the air inlet to the air outlet is 0.7.

[0014] Furthermore, the plate body is a cathode plate and an anode plate of the same structure, the cathode plate and the anode plate are staggered to form the plate body, and the plate body is assembled into a proton exchange membrane fuel cell by a press machine.

[0015] The present invention discloses the following technical effects:

[0016] 1. The present invention takes "snowflake" as the morphological basis and designs a bionic composite flow field, which includes a main flow channel and a secondary flow channel located between the main flow channels. Compared with the traditional flow field structure, the flow field in the present application provides multiple paths for gas transmission, promotes the effective convection of gas to the membrane electrode and improves the gas transmission efficiency. It not only improves the battery performance by 35.5% compared with the traditional flow field structure, but also significantly improves the uniformity of material distribution on the cathode side, which helps to improve the working efficiency and stability of the battery.

[0017] 2. The present invention adopts a flow field with a slope structure, and the height of the air outlet is slightly higher than the height of the air inlet, which can further optimize the uniformity of gas distribution and the heat dissipation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 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 will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 Schematic diagram of the flow field in the plate body;

[0020] Figure 2 It is the side view of the plate;

[0021] Figure 3 It is a schematic diagram of the assembly of the plate body;

[0022] Figure 4 It is a schematic diagram for comparing the performance of this embodiment and multiple traditional flow fields;

[0023] Figure 5 A schematic diagram comparing oxygen distribution in this embodiment and multiple conventional flow fields;

[0024] Among them, 1. Plate body; 2. Air inlet; 3. Air outlet; 4. Main flow channel; 5. Secondary flow channel; 6. Block. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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. 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.

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] An embodiment of the present invention provides a bipolar plate structure based on a snowflake bionic composite flow field, including: a plate body 1, the plate body 1 is a cathode plate and an anode plate with the same structure. Taking the cathode plate as an example, its interior is hollow and defines a flow field. The plate body 1 is generally square, and an air inlet 2 and an air outlet 3 connected to the flow field are respectively provided on two corners corresponding to the two ends of the diagonal; the block 6 is generally diamond-shaped, and there are multiple blocks 6 and they are arranged in the flow field. The multiple blocks 6 define a main flow channel 4 and a secondary flow channel 5 in the flow field.

[0028] like Figure 1 As shown, there is a flow channel center between the air inlet 2 and the air outlet 3 (the flow channel center is not a specific structure but a symbol. Figure 1The main flow channel 4 is roughly located in the center of the structure), the straight line where the main flow channel 4 is located passes through the center of the flow channel, there are multiple main flow channels 4 and they are arranged circumferentially with the center of the flow channel as the center of the circle; between adjacent main flow channels 4 is an installation area, multiple blocks 6 are arranged in the installation area, and secondary flow channels 5 are formed between multiple blocks 6 in the same installation area.

[0029] In this embodiment, there are three main channels 4, and six installation areas are formed between adjacent main channels 4. The arrangement of the main channels 4 is similar to the skeleton structure of a snowflake, which is a regular hexagon; a plurality of blocks 6 are evenly spaced in the installation area, and their lateral arrangement direction is parallel to an adjacent main channel 4, and their longitudinal arrangement direction is parallel to another adjacent main channel 4. The secondary channel 5 is arranged parallel to the main channel 4, and the arrangement of the secondary channel 5 is similar to the petal structure of a snowflake. Therefore, as a whole, this embodiment discloses a flow field structure imitating a snowflake shape, and each area is connected and material is transferred through the main channel 4.

[0030] The flow field is arranged obliquely, and the height ratio of the air inlet 2 to the air outlet 3 is 0.7. In this embodiment, the height of the air inlet 2 is d=0.7 mm, and the height of the air outlet 3 is D=1 mm. The gas enters the flow field from the air inlet 2 in a diagonal direction, and is discharged from the air outlet 3 after passing through the main flow channel 4 and the secondary flow channel 5. The height difference between the air inlet 2 and the air outlet 3 can promote the lateral transmission of the gas and the convection to the cathode catalyst layer.

[0031] A too wide main flow channel 4 will cause the gas to flow out of the system too quickly, which is not conducive to the uniform diffusion of the gas on the entire bipolar plate, while a too narrow secondary flow channel 5 will hinder the gas from flowing in, affecting the uniform distribution of the reactants in the system. Therefore, in this embodiment, the width of the main flow channel 4 is limited to 1.5 mm, and the width of the secondary flow channel 5 is limited to 1 mm.

[0032] In this embodiment, the cathode plate and the anode plate are arranged in a staggered manner, and the inclination directions of the flow fields of the two are opposite. The air inlet 2 of the cathode plate and the air outlet 3 of the anode plate are located on the same side, and the air outlet 3 of the cathode plate and the air inlet 2 of the anode plate are located on the same side. The two cooperate with each other to form the plate body 1. The plate body 1 can be made of materials such as graphite, metal, and composite materials. Taking graphite as an example, the internal structure of the plate body 1 is formed by carving, and it is assembled into the proton exchange membrane fuel cell by a press machine, for example, with the gas diffusion layer, the catalyst layer and the proton exchange membrane. Considering the material properties of graphite, the pressure applied during assembly should not be too large. During the assembly process of the battery stack, the multilayer battery is fixedly connected to the current collecting plate, the insulating plate and the end plate by bolts and nuts, and the end plate only needs to be processed with corresponding holes. In this embodiment, the size of the bipolar plate is 67.17mm×35.75mm, and the size of the end plate is set to 80mm×50mm.

[0033] During actual operation, the gas enters the flow field from the air inlet 2. Since the outer edge of the flow field is rectangular, there is a gap between the main channel 4 and the secondary channel 5 and the outer edge of the flow field, and there is no block 6 in the main channel 4. The gas will first enter the main channel 4, and then gradually move and transfer to each secondary channel 5, and finally discharge from the flow field from the air outlet 3.

[0034] like Figure 4 As shown, the performance of this embodiment and multiple traditional flow fields are compared. The traditional flow fields used for comparison include traditional parallel flow fields, serpentine flow fields and honeycomb bionic flow fields with the same activation area.

[0035] The results show that when the voltage is 0.6 V, the current density of the honeycomb bionic flow field is the lowest, followed by the parallel flow field and the serpentine flow field, while the current density of the bionic composite flow field in this embodiment is the highest, reaching 1.164 A cm -2 . In addition, it can be seen from the power density curve that the power density of the four flow fields increases with the increase of current density and begins to decline after reaching the peak value. The power density trend between the structural flow fields is consistent with the polarization curve. Compared with the honeycomb bionic flow field, the ultimate power density of other flow fields is increased by 21.0%, 17.5% and 35.5%, respectively.

[0036] like Figure 5 As shown, the oxygen distribution of this embodiment and multiple traditional flow fields are compared.

[0037] The results show that there is an obvious uneven distribution of oxygen in the parallel flow field, especially in the area near the air inlet 2, where a low oxygen zone appears. In contrast, the uniformity of oxygen distribution in the serpentine flow field and the honeycomb bionic flow field has improved, but the cloud map shows that the oxygen content in the non-flow channel area is still low. Relatively speaking, the bionic composite flow field has the highest oxygen content and is relatively evenly distributed, providing good conditions for the reaction in the catalytic layer. In summary, the bionic composite flow field structure in this embodiment performs well in gas distribution, significantly improves battery performance, and is superior to parallel flow fields, serpentine flow fields, and honeycomb bionic flow fields of the same size.

[0038] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0039] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A bipolar plate structure based on a snowflake bionic composite flow field, characterized in that: include: A plate body (1) having a hollow interior and defining a flow field, the plate body (1) having at least two oppositely disposed corners, the two corners being respectively provided with an air inlet (2) and an air outlet (3) connected to the flow field; A block (6), wherein a plurality of the blocks (6) are arranged in the flow field, and the plurality of the blocks (6) define a main flow channel (4) and a secondary flow channel (5) in the flow field.

2. The bipolar plate structure based on the snowflake bionic composite flow field according to claim 1, characterized in that: There is a flow channel center between the air inlet (2) and the air outlet (3), and the straight line where the main flow channel (4) is located passes through the flow channel center. There are multiple main flow channels (4) and they are arranged circumferentially with the flow channel center as the center of the circle; between adjacent main flow channels (4) is an installation area, and multiple blocks (6) are arranged in the installation area, and a secondary flow channel (5) is formed between multiple blocks (6) in the same installation area.

3. The bipolar plate structure based on the snowflake bionic composite flow field according to claim 2, characterized in that: There are three main flow channels (4) in total, and six installation areas are formed between adjacent main flow channels (4); a plurality of the block blocks (6) are evenly spaced and arranged in the installation areas, with their transverse arrangement direction being parallel to an adjacent main flow channel (4) and their longitudinal arrangement direction being parallel to another adjacent main flow channel (4); and the secondary flow channel (5) is arranged in parallel with the main flow channel (4).

4. The bipolar plate structure based on the snowflake bionic composite flow field according to claim 3 is characterized in that: The width of the main flow channel (4) is 1.5 mm, and the width of the secondary flow channel (5) is 1 mm.

5. The bipolar plate structure based on the snowflake bionic composite flow field according to claim 3 is characterized in that: The flow field is arranged obliquely, and the height ratio between the air inlet (2) and the air outlet (3) is 0.

7.

6. The bipolar plate structure based on the snowflake bionic composite flow field according to claim 5, characterized in that: The plate body (1) comprises a cathode plate and an anode plate of the same structure, the cathode plate and the anode plate are staggered to form the plate body (1), and the plate body (1) is assembled into a proton exchange membrane fuel cell by a press machine.

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