A bipolar plate flow field structure and fuel cell thereof

Abstract

The present invention relates to the field of fuel cell technology, and specifically discloses a bipolar plate flow field structure and a fuel cell thereof, comprising a substrate, wherein the substrate is provided with a fluid inlet, a flow field area and a fluid outlet which are connected in sequence, wherein the flow field area is provided on a side of the substrate for being bonded to a membrane electrode assembly; wherein the flow field area is filled with a porous medium, wherein the porous medium itself is provided with pores, wherein the pores are used for allowing a working fluid to pass through the flow field area from the fluid inlet to the fluid outlet; wherein a groove is provided on the porous medium, wherein the groove intersects with the connection direction between the fluid inlet and the fluid outlet, and wherein the groove is used for guiding the working fluid to each area of ​​the flow field area. The net output power of the fuel cell is improved by the present invention.

Description

Technical Field

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

[0002] In recent years, as the new energy vehicle industry has become increasingly mature, proton exchange membrane fuel cell technology, as one of the ways to achieve it, has been increasingly valued and hailed as the most promising power generation technology. Proton exchange membrane fuel cells are a power generation device that directly converts chemical energy in fuel into electrical energy. They have the advantages of high power density, high energy conversion efficiency, low operating temperature, fast start-up and zero greenhouse gas emissions. Their application in the automotive field will significantly promote the achievement of carbon peak and carbon neutrality in the medium and long term.

[0003] Among them, the bipolar plate is one of the core components of the proton exchange membrane fuel cell. It plays an important role in providing gas flow channels, drainage, preventing the penetration of reactants between the two poles, collecting current, transferring heat, mechanical support and reinforcing batteries. Its mass accounts for about 40-80% of the fuel cell stack, and its cost accounts for about 30-37% of the total cost of the battery stack. The bipolar plate flow field structure plays a vital role in the mass transfer of reactants and products. Its structure largely determines the uniformity of the reactant gas distribution and whether the product water can be discharged in time. In order to improve the performance and stability of fuel cells, the research and development of the bipolar plate flow field structure has always been the focus of fuel cell technology research and development.

[0004] The commonly used bipolar plate flow field structure at present is to use carving, stamping and other methods to process and manufacture the grooves for gas flow on the graphite, graphite composite or metal plate. This kind of groove flow field structure has the problems of high processing cost and heavy weight. In recent years, porous medium flow field structure has received more and more attention. The porous medium flow field structure is a structure that directly uses porous medium materials as flow fields to distribute gas reactants and remove product water, such as foam metal, graphene foam, etc. Compared with the groove flow field structure, the porous medium flow field structure has the advantages of light weight, easy processing and low cost. However, the proton exchange membrane fuel cell using the porous medium flow field structure still has the problem of low net output power of the fuel cell. Summary of the invention

[0005] The main purpose of the present invention is to provide a bipolar plate flow field structure and a fuel cell thereof, aiming to improve the net output power of the fuel cell.

[0006] To achieve the above-mentioned purpose, the present invention proposes a bipolar plate flow field structure, including a substrate, on which a fluid inlet, a flow field area and a fluid outlet that are connected in sequence are provided, and the flow field area is arranged on a side of the substrate for bonding with a membrane electrode assembly; the flow field area is filled with a porous medium, and the porous medium itself has pores inside, and the pores are used for allowing a working fluid to pass through from the fluid inlet through the flow field area to the fluid outlet; a groove is provided on the porous medium, and the groove intersects with the connection direction between the fluid inlet and the fluid outlet, and the groove is used to guide the working fluid to various areas of the flow field area.

[0007] Optionally, the flow field area is a square structure, and the fluid inlet and the fluid outlet are respectively located at two diagonal ends of the flow field area.

[0008] Optionally, a first channel and a second channel are further provided on the substrate, and two ends of the first channel are respectively connected to the fluid inlet and a first corner position of the flow field area, and two ends of the second channel are respectively connected to the fluid outlet and a second corner position of the flow field area, and the first corner position and the second corner position are respectively located at diagonal ends of the flow field area.

[0009] Optionally, a plurality of the grooves are included, the plurality of the grooves are arranged parallel to each other, and the length direction of the groove is perpendicular to the direction of the line between the fluid inlet and the fluid outlet.

[0010] Optionally, the distance between any two adjacent grooves gradually increases from the fluid inlet to the fluid outlet.

[0011] Optionally, both ends of the channel in the length direction are connected to the inner side wall of the flow field area.

[0012] Optionally, one of the channels is located on a diagonal line of the flow field area.

[0013] Optionally, the width of the groove is 1-2 mm.

[0014] Optionally, the porosity of the porous medium is 60% to 90%.

[0015] To achieve the above object, the present invention provides a fuel cell, comprising the above bipolar plate flow field structure.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] With regard to the problem of low net output power of fuel cells mentioned in the background technology, the inventors of the present application have discovered through research that this is mainly due to the uneven distribution of the working fluid (such as hydrogen or oxygen, etc.) in the flow area filled with porous media. In some areas of the flow field area, only a small amount of working fluid flows through, or even no working fluid flows through. This results in a low membrane utilization rate of the membrane electrode assembly that is in contact with the flow field area, that is, the active area of ​​the membrane electrode assembly cannot fully contact the working fluid to produce an electrochemical reaction, thereby resulting in a decrease in the amount of electricity generated and a decrease in the net output power of the fuel cell.

[0018] Based on the above research findings, the present invention provides channels in the flow field area filled with porous media, and guides the working fluid flowing from the fluid inlet through the flow field area to the fluid outlet to various areas of the flow field area through the channels, thereby improving the uniformity of fluid distribution on the flow field area, thereby increasing the membrane utilization of the membrane electrode assembly, making the electrochemical reaction more efficient, and improving the net output power of the fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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 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.

[0020] Figure 1 This is a structural schematic diagram of an embodiment of a bipolar plate flow field structure of the present invention;

[0021] Figure 2 This is the second structural schematic diagram of an embodiment of the bipolar plate flow field structure of the present invention.

[0022] The names of the components marked in the figure are as follows:

[0023] Label name Label name 1 substrate 101 First Channel 102 Second channel 2 Fluid inlet 3 Flow field area 4 Fluid outlet 5 Porous media 6 Groove DETAILED DESCRIPTION

[0024] The following will be combined with the accompanying drawings in the present invention to clearly and completely describe the technical solution in the present invention. Obviously, what is described is only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] With regard to the problem of low net output power of fuel cells mentioned in the background technology, the inventors of the present application have discovered through research that this is mainly due to the uneven distribution of the working fluid (such as hydrogen or oxygen, etc.) in the flow area filled with porous media. In some areas of the flow field area, only a small amount of working fluid flows through, or even no working fluid flows through. This results in a low membrane utilization rate of the membrane electrode assembly that is in contact with the flow field area, that is, the active area of ​​the membrane electrode assembly cannot fully contact the working fluid to produce an electrochemical reaction, thereby resulting in a decrease in the amount of electricity generated and a decrease in the net output power of the fuel cell.

[0026] Based on the above research findings, this embodiment discloses a bipolar plate flow field structure. Figure 1-2 , comprising a substrate 1, on which are provided a fluid inlet 2, a flow field area 3 and a fluid outlet 4 which are connected in sequence, the flow field area 3 being arranged on a side of the substrate 1 for being fitted with a membrane electrode assembly (not shown in the drawings); the flow field area 3 is filled with a porous medium 5, the porous medium 5 itself is provided with pores (not shown in the drawings), the pores being used for allowing a working fluid which flows from the fluid inlet 2 through the flow field area 3 to the fluid outlet 4 to pass through; a groove 6 is arranged on the porous medium 5, the groove 6 intersects with the connecting direction between the fluid inlet 2 and the fluid outlet 4, and the groove 6 is used for guiding the working fluid to various areas of the flow field area 3.

[0027] In this embodiment, a groove 6 is arranged in the flow field area 3 filled with the porous medium 5, and the working fluid flowing from the fluid inlet 2 through the flow field area 3 to the fluid outlet 4 is guided to various regions of the flow field area 3 through the groove 6, thereby improving the uniformity of the fluid distribution on the flow field area 3, thereby increasing the utilization rate of the membrane electrode assembly on the membrane, making the electrochemical reaction more efficient, and improving the net output power of the fuel cell. At the same time, the groove 6 is mutually connected with the connection direction between the fluid inlet 2 and the fluid outlet 4, so that the working fluid will inevitably pass through the groove 6 in the process of flowing from the fluid inlet 2 to the fluid outlet 4, thereby ensuring that the groove 6 can indeed guide and divert the working fluid to various regions of the flow field area 3.

[0028] It should be noted that the thinking process of the above research findings is the crystallization of the inventor's wisdom and is also one of the inventive points of the present invention. In the process of evaluating creativity, the thinking process of the above research findings should also be included in the evaluation scope.

[0029] Among them, regarding the processing method of the groove 6, a metal rod (not shown in the drawings) can be placed on the surface of the porous medium 5, and then pressure is applied to the metal rod in the direction of the porous medium 5. Since the hardness of the porous medium 5 is relatively soft, the metal rod will be partially or completely pressed into the porous medium 5. Finally, the metal rod is taken out, and the groove left by the metal rod on the porous medium 5 is the groove 6 in this application. Its processing method is simple, fast and practical. It should be noted that the above-mentioned processing technology is only one of many processing technologies, and this application does not make specific restrictions on its processing technology. After understanding the technical solution of this application, those skilled in the art can think of other processing technologies for the groove 6 without creative labor, which should also belong to the protection scope of this application.

[0030] The porosity of the porous medium 5 is 60% to 90%. By setting the porosity of the porous medium 5, that is, the percentage of the pore volume in the porous medium 5 to the total volume of the porous medium 5 in the natural state, it is ensured that the working fluid will not cause blockage when flowing inside the porous medium 5.

[0031] The porous medium 5 is any one of graphene foam, nickel foam, copper foam, stainless steel foam or titanium foam.

[0032] As a preferred solution of the above embodiment, the flow field area 3 is a square structure, and the fluid inlet 2 and the fluid outlet 4 are respectively located at the two diagonal ends of the flow field area 3. In this way, the flow field area 3 is set as a square structure, which is convenient for molding the flow field area 3 on the substrate 1 on the one hand, and for filling the porous medium 5 into the flow field area 3 on the other hand. The fluid inlet 2 and the fluid outlet 4 are respectively set at the two diagonal ends of the flow field area 3 of the square structure, based on the principle that the diagonal line is the longest in the square structure, so that the working fluid has enough flow time and a long enough flow path in the flow field area 3, so as to ensure that the working fluid can be distributed in various areas of the flow field area 3.

[0033] Furthermore, the substrate 1 is provided with a first channel 101 and a second channel 102, the two ends of the first channel 101 are respectively connected to the fluid inlet 2 and the first corner of the flow field area 3, the two ends of the second channel 102 are respectively connected to the fluid outlet 4 and the second corner of the flow field area 3, and the first corner and the second corner are respectively located at the diagonal ends of the flow field area 3. In this arrangement, by providing the first channel 101 between the fluid inlet 2 and the flow field area 3, and providing the second channel 102 between the fluid outlet 4 and the flow field area 3, the first channel 101 and the second channel 102 are used as the guide area of ​​the working fluid, so that the working fluid can flow to the flow field area 3 / fluid outlet 4 under the guidance of the first channel 101 / the second channel 102.

[0034] As a preferred solution of the above embodiment, a plurality of grooves 6 are provided, which are arranged in parallel with each other, and the length direction of the grooves 6 is perpendicular to the direction of the line between the fluid inlet 2 and the fluid outlet 4. In this way, the guiding efficiency of guiding the working fluid to flow to various areas of the flow field area 3 is improved by providing a plurality of grooves 6. Among them, the plurality of grooves 6 are arranged in parallel with each other, and are perpendicular to the direction of the line between the fluid inlet 2 and the fluid outlet 4, so that the working fluid flows evenly to both sides of the grooves 6, ensuring that the fluid distribution on the left and right sides of the flow field area 3 is uniform.

[0035] Furthermore, the spacing between any two adjacent grooves 6 gradually increases from the fluid inlet 2 to the fluid outlet 4. In this arrangement, considering that product water will be produced during the electrochemical reaction between the working fluid and the membrane electrode assembly, the accumulation of product water in the flow field area 3 will hinder the flow of the working fluid and needs to be discharged in time. Therefore, more parallel grooves 6 are distributed on the side close to the fluid inlet 2, on the one hand, the working fluid can flow quickly to various areas of the flow field area 3 under the guidance of the grooves 6 after entering the flow field area 3; on the other hand, relative to the porous medium 5, the forward resistance of the groove 6 area to the working fluid is relatively small, which can reduce the total pressure drop of the working fluid during the forward process, thereby reducing the auxiliary consumption of the fuel cell system (here mainly refers to the driving system of the working fluid), and further improving the net output power; fewer grooves are distributed in the area close to the fluid outlet, so that the working fluid can still maintain a sufficient pressure drop in the fluid outlet area, so that the working fluid has enough forward driving force to push the product water to flow in the direction of the fluid outlet 4, and accelerate the discharge of the product water. In addition, when a metal rod is used to press to form the groove 6, the porous medium 5 at the bottom of the groove 6 is compressed so that its porosity is relatively reduced and the pore size becomes smaller. Due to the action of capillaries, liquid water tends to flow into the porous medium at the bottom of the groove 6, and then flows toward the fluid outlet 4 driven by the working fluid. This also makes it difficult for product water to accumulate in the groove 6, reducing the obstruction of accumulated water to the transmission of the working fluid to the catalyst layer.

[0036] Furthermore, both ends of the length direction of the groove 6 are connected to the inner side wall of the flow field area 3. In this arrangement, considering that the edge area of ​​the square structure flow field area 3 is an area with weak working fluid transmission capacity, the two ends of the length direction of the groove 6 are connected to the inner side wall of the flow field area 3 to ensure that the working fluid can be transmitted to the edge position of the flow field area 3 along the groove 6, further improving the distribution uniformity of the working fluid.

[0037] Furthermore, one of the grooves 6 is located on the diagonal of the flow field area 3. In this arrangement, considering that the corner area of ​​the diagonal in the flow field area 3 of the square structure is the area with the weakest working fluid transmission capacity, one of the grooves 6 is set on the diagonal of the flow field area 3 (perpendicular to the diagonal where the connection direction between the fluid inlet 2 and the fluid outlet 4 is located) to ensure that the working fluid can be transmitted to the corner area of ​​the flow field area 3 along the groove 6, further improving the distribution uniformity of the working fluid. At the same time, based on the principle that the diagonal is the longest in the square structure, the working fluid has enough flow time and a long enough flow path in the flow field area 3 to ensure that the working fluid can be distributed in each area of ​​the flow field area 3.

[0038] Furthermore, the width of the groove 6 is 1-2 mm. In this way, by specifying the specific width of the groove 6 , it is ensured that the working fluid can be guided and transmitted along the groove 6 .

[0039] This embodiment also discloses a fuel cell, including the bipolar plate flow field structure of the above embodiment. In this way, by applying the bipolar plate flow field structure of the above embodiment to the fuel cell, the bipolar plate flow field structure is used to set a channel 6 in the flow field area 3 filled with a porous medium 5, and the working fluid flowing from the fluid inlet 2 through the flow field area 3 to the fluid outlet 4 is guided to each area of ​​the flow field area 3 through the channel 6, thereby improving the uniformity of the fluid distribution on the flow field area 3, thereby increasing the utilization rate of the membrane electrode assembly on the membrane, making the electrochemical reaction more efficient, and improving the net output power of the fuel cell.

[0040] It should be noted that the bipolar plate flow field structure and other contents of the fuel cell disclosed in the present invention are prior art and will not be described in detail here.

[0041] In addition, it should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0042] In addition, it should be noted that the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0043] The above are only optional embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any direct / indirect application of the present invention in other related technical fields is included in the patent protection scope of the present invention.

Claims

1. A bipolar plate flow field structure, characterized in that: The invention comprises a substrate, wherein the substrate is provided with a fluid inlet, a flow field area and a fluid outlet which are connected in sequence, wherein the flow field area is provided on a side of the substrate for being attached to a membrane electrode assembly; the flow field area is filled with a porous medium, wherein the porous medium itself is provided with pores, wherein the pores are used for allowing a working fluid which flows from the fluid inlet through the flow field area to the fluid outlet to pass through; a groove is provided on the porous medium, wherein the groove intersects with a connecting line direction between the fluid inlet and the fluid outlet, and wherein the groove is used for guiding the working fluid to each area of ​​the flow field area; Wherein, the bipolar plate flow field structure includes a plurality of grooves, the plurality of grooves are arranged parallel to each other, and the length direction of the grooves is perpendicular to the direction of the connection line between the fluid inlet and the fluid outlet; the spacing between any two adjacent grooves gradually increases from the fluid inlet to the fluid outlet; wherein the porosity of the porous medium at the bottom of the groove is relatively reduced and the pore size becomes smaller.

2. The bipolar plate flow field structure according to claim 1, characterized in that: The flow field area is a square structure, and the fluid inlet and the fluid outlet are respectively located at two diagonal ends of the flow field area.

3. The bipolar plate flow field structure according to claim 2, characterized in that: The substrate is also provided with a first channel and a second channel, wherein two ends of the first channel are respectively connected to the fluid inlet and a first corner position of the flow field area, and two ends of the second channel are respectively connected to the fluid outlet and a second corner position of the flow field area, and the first corner position and the second corner position are respectively located at diagonal ends of the flow field area.

4. The bipolar plate flow field structure according to claim 1, characterized in that: Both ends of the channel in the length direction are connected to the inner side wall of the flow field area.

5. The bipolar plate flow field structure according to claim 4, characterized in that: One of the channels is located on a diagonal line of the flow field region.

6. The bipolar plate flow field structure according to claim 1, characterized in that: The width of the groove is 1-2 mm.

7. The bipolar plate flow field structure according to claim 1, characterized in that: The porosity of the porous medium is 60% to 90%.

8. A fuel cell, characterized in that: It comprises a bipolar plate flow field structure as described in any one of claims 1 to 7.

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