Porous gas diffusion layer-flow field integrated structural body and fuel cell

Abstract

The invention relates to the field of fuel cells, in particular to a porous gas diffusion layer-flow field integrated structural body and a fuel cell. The porous gas diffusion layer-flow field integrated structural body provided by the invention is prepared from a porous gas diffusion layer subjected to hydrophobic treatment by a fluorine-containing high polymer material through laser etching, and a groove is formed in one side of the porous gas diffusion layer subjected to hydrophobic treatment by the fluorine-containing high polymer material; and the ridges on the two sides of the groove form gradient hydrophilicity and hydrophobicity through laser etching. The invention also provides a fuel cell. The porous gas diffusion layer-flow field integrated structure provided by the invention can effectively enhance the drainage and gas mass transfer capabilities under the ridge of the flow field, reduce the contact resistance, simplify the polar plate structure and greatly improve the specific power of the fuel cell.

Description

A porous gas diffusion layer-flow field integrated structure and fuel cell Technical Field

[0001] This invention relates to the field of fuel cells, and more particularly to a porous gas diffusion layer-flow field integrated structure and a fuel cell. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) directly convert the chemical energy stored in hydrogen into electrical energy based on electrochemical principles. The conversion process is highly energy efficient and pollution-free. In addition, it can start up quickly at room temperature, adapt well to low temperatures, and recharge quickly, and is expected to replace traditional internal combustion engines to promote the low-carbon transformation of the transportation sector.

[0003] When a fuel cell operates, it requires a continuous supply of oxygen and hydrogen to the catalyst layer. Simultaneously, water generated inside the catalyst layer due to electrochemical reactions needs to be promptly removed from the cell. This is especially important when the fuel cell operates at high current densities (>2 A / cm³). 2 When operating under these conditions, oxygen within the catalyst layer is rapidly consumed, while a large amount of liquid water is generated. The slow diffusion of oxygen and the accumulation of liquid water lead to severe mass transfer polarization in the fuel cell, thereby reducing the cell's output voltage. This is one of the main reasons currently limiting the improvement of fuel cell performance. Therefore, improving the oxygen mass transfer and drainage capacity within the fuel cell is an effective way to improve its performance. However, in traditional fuel cells, the ridges under the plates that contact the porous gas diffusion layer are not directly exposed to the surrounding gas flow channels. The reactant gas cannot be quickly transferred to this area, and the water generated under the ridges is difficult to drain, easily causing local flooding and insufficient gas supply, which seriously affects the overall performance of the cell. In addition, traditional fuel cells integrate the gas flow field onto the bipolar plates, and the cooling channel is a space formed by welding two monopolar plates. This structure causes the anode and cathode flow fields and the water flow field to interfere with each other, resulting in a complex bipolar plate structure and increased processing costs. Summary of the Invention

[0004] To address the aforementioned technical problems and further enhance the drainage and gas mass transfer capabilities under the flow field ridges, thereby increasing the specific power of fuel cells, this invention provides a porous gas diffusion layer-flow field integrated structure and a fuel cell. The porous gas diffusion layer-flow field integrated structure and fuel cell provided by this invention can effectively enhance the drainage and gas mass transfer capabilities under the flow field ridges, reduce contact resistance, simplify the electrode structure, and significantly improve the specific power of fuel cells.

[0005] In a first aspect, the porous gas diffusion layer-flow field integrated structure provided by the present invention is prepared by laser etching of a porous gas diffusion layer treated with hydrophobic fluorinated polymer material. A groove is provided on one side of the porous gas diffusion layer treated with hydrophobic fluorinated polymer material, and the ridges on both sides of the groove are formed by laser etching to form a gradient hydrophilicity and hydrophobicity. In this invention, porous materials (such as carbon paper support layers) are hydrophobically treated with fluorinated polymers (such as PTFE), resulting in a uniform distribution of the fluorinated polymers within the material. The high-energy nature of the laser allows for rapid carbonization. Furthermore, during laser etching, the laser energy is strongest at the focal point and gradually decreases away from the focal point. Utilizing this principle, by adjusting the laser focus to the surface of the ridges on both sides of the trench in the porous gas diffusion layer, the surface area receives the highest energy when the laser irradiates it, leading to rapid carbonization of the fluorinated polymers. Simultaneously, because the porous gas diffusion layer is porous with high porosity, its energy decreases as the laser penetrates through the holes, gradually reducing the carbonization rate of the fluorinated polymers. This decrease in energy further decreases with increasing laser penetration depth. Therefore, during laser etching, the fluorinated polymers near the surface exhibit the highest degree of carbonization, while the porous gas diffusion layer itself shows the weakest carbonization. This results in a gradient of hydrophilicity and hydrophobicity between the ridges on both sides of the trench in the gas diffusion layer and the surface.

[0006] Preferably, the porous gas diffusion layer is carbon paper, carbon cloth, carbon felt, or porous metal foam; and / or, the fluorinated polymer material is PTFE.

[0007] In a further preferred embodiment, the fluorinated polymer material accounts for 1% to 30% of the mass of the hydrophobic porous gas diffusion layer.

[0008] Preferably, the thickness of the porous gas diffusion layer is 100~600 μm; more preferably, the thickness of the porous gas diffusion layer is 200~500 μm.

[0009] Preferably, the groove includes a parallel groove, a serpentine groove, or a spiral groove; preferably, the groove has a depth of 100~400 μm, a width of 0.5~2 mm, and a spacing of 0.3~1.5 mm between adjacent grooves.

[0010] Preferably, the hydrophilicity of the ridge gradually increases from the ridge body to the surface.

[0011] Further preferably, the body contact angle of the ridge is ≥120°.

[0012] Preferably, the laser used for laser etching is an ultraviolet laser, a fiber laser, or a semiconductor laser.

[0013] Further preferably, during the laser etching, the focal length is adjusted to the upper surface of the porous gas diffusion layer.

[0014] In a second aspect, the present invention provides a fuel cell comprising a fuel cell stack composed of stacked single cells; wherein, the single cell is assembled from a porous gas diffusion layer-flow field integrated structure, a membrane electrode and a conductive plate; one side of the porous gas diffusion layer-flow field integrated structure with grooves is in contact with the conductive plate, and the other side is in contact with the membrane electrode.

[0015] The beneficial effects of the present invention are at least as follows: 1) The porous gas diffusion layer-flow field integrated structure provided by the present invention integrates the gas flow channel in the porous gas diffusion layer by setting the gas diffusion layer groove, so that the ridge becomes a porous structure and a gradient hydrophilicity and hydrophobicity are formed on the ridge, which is conducive to the gas entering the electrode and enhancing the gas mass transfer. At the same time, due to the porous structure ridge and the gradient hydrophilicity and hydrophobicity characteristics, the liquid water under the ridge can be easily discharged from the electrode, which is conducive to reducing the mass transfer polarization of the fuel cell and improving the performance of the fuel cell.

[0016] 2) This invention employs laser etching to etch the ridges on a porous gas diffusion layer. Due to the high-energy nature of lasers, the hydrophobic agent (PTFE) within a certain depth of the etched area can be carbonized. Since the porous gas diffusion layer matrix typically has a high porosity (approximately 0.7), the laser can penetrate to a certain depth during the etching process. Simultaneously, because the laser energy is highest at the focal point and decreases downwards away from the focal point, different degrees of carbonization occur in the PTFE at different depths, with the highest degree of carbonization at the focal point on the upper surface, gradually decreasing downwards. Based on this principle, a gradient of hydrophilicity and hydrophobicity can be formed from the surface of the porous gas diffusion layer to a certain depth, i.e., hydrophilicity gradually increases from the ridge body to the surface. Driven by this hydrophilicity-hydrophobicity gradient, liquid water under the ridges undergoes capillary flow, spontaneously moving from the body to the surface, thereby alleviating the problem of water accumulation under the ridges and improving the performance of the fuel cell at high current densities.

[0017] 3) The present invention uses laser etching to carbonize the ridge surface with PTFE, thereby reducing the contact resistance when the ridge contacts the conductive plate and improving the performance of the fuel cell.

[0018] 4) When the present invention adopts the integrated structure of porous gas diffusion layer-flow field, there is no need to design gas flow channels on the electrode plate, only heat dissipation water flow channels. Therefore, the electrode plate structure is simple. Compared with the prior art, it can simplify the electrode plate processing difficulty and reduce the electrode plate manufacturing cost. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 is a schematic diagram of the integrated porous gas diffusion layer-flow field structure provided in an embodiment of the present invention.

[0021] Figure 2 is a schematic diagram of the fuel cell structure provided in an embodiment of the present invention.

[0022] In the figure, 11-porous gas diffusion layer body, 12-groove, 13-ridge, 21-porous gas diffusion layer-flow field integrated structure, 22-fuel cell membrane electrode, 23-conductive plate. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0024] Unless otherwise specified in the embodiments of this invention, the techniques or conditions described in the literature in this field, or the product instructions, shall apply. All devices, instruments, reagents, etc., used are conventional products that can be purchased from legitimate channels, and all experimental reagents and raw materials involved are commercially available.

[0025] In the description of the embodiments of the present invention, it should be noted that the terms "top," "bottom," "inner," "outer," "upper," and "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0027] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0028] The porous gas diffusion layer-flow field integrated structure provided in some embodiments of the present invention is prepared by laser etching of a porous gas diffusion layer treated with hydrophobic fluorinated polymer material. A groove is provided on one side of the porous gas diffusion layer treated with hydrophobic fluorinated polymer material, and the ridges on both sides of the groove are formed by laser etching to form a gradient hydrophilicity and hydrophobicity. In this invention, porous materials (such as carbon paper support layers) are hydrophobically treated with fluorinated polymers (such as PTFE), resulting in a uniform distribution of the fluorinated polymers within the material. The high-energy nature of the laser allows for rapid carbonization. Furthermore, during laser etching, the laser energy is strongest at the focal point and gradually decreases away from the focal point. Utilizing this principle, by adjusting the laser focus to the surface of the ridges on both sides of the porous gas diffusion layer trenches, the surface area receives the highest energy when the laser irradiates it, leading to rapid carbonization of the fluorinated polymers. Simultaneously, because the porous gas diffusion layer trenches are porous with high porosity, the laser energy decreases as it penetrates the porous gas diffusion layer, gradually reducing the carbonization rate of the fluorinated polymers. This decrease in energy further decreases with increasing laser penetration depth. Therefore, during laser etching, the degree of carbonization of the fluorinated polymers near the ridge surface is the highest, while the degree of carbonization is lowest towards the interior of the gas diffusion layer, creating a gradient of hydrophilicity and hydrophobicity from the surface to the bulk.

[0029] In a preferred embodiment, the porous gas diffusion layer is carbon paper, carbon cloth, carbon felt, or porous metal foam; and / or, the fluorinated polymer material is PTFE.

[0030] In a further preferred embodiment, the fluorinated polymer material accounts for 1% to 30% of the mass of the hydrophobic porous gas diffusion layer. For example, 1%, 5%, 10%, 15%, 20%, 25%, 30%, etc.

[0031] In a preferred embodiment, the thickness of the porous gas diffusion layer is 100~600 μm; more preferably, the thickness of the porous gas diffusion layer is 200~500 μm. For example, 250 μm, 300 μm, 350 μm, 450 μm, 500 μm, etc. If the thickness is too large, the internal resistance of the battery will be too high; if the thickness is too small, trenches cannot be formed.

[0032] In a preferred embodiment, the groove includes a parallel groove, a serpentine groove, or a spiral groove, and other shapes of grooves may be used; preferably, the depth of the groove is 100~400 μm, the width is 0.5~2 mm, and the spacing between adjacent grooves is 0.3~1.5 mm.

[0033] In a further preferred embodiment, the depth of the trench is 150~350 μm, for example 150 μm, 200 μm, 250 μm, 265 μm, 280 μm, 300 μm, 325 μm, 350 μm, etc.; the width is 0.8~2 mm, for example 0.8 mm, 0.9 mm, 1.0 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, 2 mm, etc.; the spacing between adjacent trenches is 0.8~1.8 mm, for example 0.8 mm, 0.9 mm, 1.0 mm, 1.2 mm, 1.4 mm, 1.6 mm, 1.8 mm, etc.

[0034] As a preferred embodiment, the grooves on the porous gas diffusion layer can be obtained using conventional methods in the art, and in this invention, they are preferably obtained by machining.

[0035] In a preferred embodiment, the hydrophilicity of the ridge gradually increases from the ridge body to the surface.

[0036] In a further preferred embodiment, the body contact angle of the ridge is ≥120°, such as 120°, 125°, 130°, 140°, 150°, etc.

[0037] In a preferred embodiment, the laser used for laser etching is an ultraviolet laser, a fiber laser, or a semiconductor laser.

[0038] In a further preferred embodiment, during laser etching, the focal length is adjusted to the upper surface of the porous gas diffusion layer.

[0039] Some embodiments of the present invention also provide a fuel cell, which includes a fuel cell stack composed of single cells; wherein, the single cell is assembled from the porous gas diffusion layer-flow field integrated structure, the membrane electrode and the conductive plate; one side of the porous gas diffusion layer-flow field integrated structure with grooves is in contact with the conductive plate and the other side is in contact with the membrane electrode.

[0040] Example 1 As shown in Figure 1, this embodiment of the invention provides a porous gas diffusion layer-flow field integrated structure, including a porous gas diffusion layer body 11 with a carbon paper support layer, grooves 12 on the carbon paper support layer, and ridges 13 on both sides of the grooves of the carbon paper support layer.

[0041] In a preferred embodiment, the porous gas diffusion layer has a thickness of 380 μm and a PTFE content of 5%. If the thickness of the porous gas diffusion layer is too small, the depth of the grooves on it will be limited, which will result in a large pressure loss when used in a fuel cell. If the thickness is too large, it will generate a large ohmic resistance. Therefore, the preferred thickness range of the porous gas diffusion layer in this invention is 300~500 μm.

[0042] In a preferred embodiment, the grooves on the porous gas diffusion layer are obtained by milling with a depth of 200 μm, a width of 1 mm, and a spacing of 1 mm between adjacent grooves. Furthermore, the shape of the grooves can be designed and modified using design software, resulting in various structures such as parallel grooves, serpentine grooves, spiral grooves, and dotted grooves. This embodiment uses parallel grooves.

[0043] In a preferred embodiment, the ridges of the porous gas diffusion layer trenches possess gradient hydrophilicity and hydrophobicity. This gradient is achieved by preparing the porous gas diffusion layer through a laser etching process after hydrophobic treatment. The carbon paper support layer undergoes a 5% PTFE hydrophobic treatment, resulting in a uniform PTFE distribution within it. The laser, being high-energy, can rapidly carbonize the PTFE. Furthermore, during laser etching, the laser energy is strongest at the focal point and gradually decreases away from the focal point. Utilizing this principle, by adjusting the laser focus to the surface of the porous gas diffusion layer trenches, when the laser... When the laser reaches the surface of the porous gas diffusion layer trench, the surface region has the highest energy, and PTFE is rapidly carbonized. Simultaneously, because the porous gas diffusion layer trench is a porous material with high porosity, its energy decreases as the laser penetrates through the holes into the interior of the trench, gradually reducing the PTFE carbonization rate. Furthermore, the energy decreases with increasing laser penetration depth. Therefore, during laser etching, the degree of PTFE carbonization is greatest near the ridge surface, while the carbonization of the porous gas diffusion layer trench body is weakest, creating a gradient of hydrophilicity and hydrophobicity from the surface to the body of the ridge. Preferably, the hydrophilicity gradually increases from the body of the ridge to the surface, with a body contact angle ≥120°.

[0044] As shown in Figure 2, this embodiment of the invention also provides a fuel cell, which is formed by stacking the aforementioned porous gas diffusion layer-flow field integrated structure 21, a fuel cell membrane electrode 22, and a conductive plate 23. Specifically, the grooved side of the aforementioned porous gas diffusion layer-flow field integrated structure is in contact with the conductive plate, and the other side is in contact with the membrane electrode.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A porous gas diffusion layer-flow field integrated structure, characterized in that, The porous gas diffusion layer, which has been hydrophobically treated with fluorinated polymer material, is prepared by laser etching. A groove is provided on one side of the porous gas diffusion layer, and the ridges on both sides of the groove are formed by laser etching to create a gradient of hydrophilicity and hydrophobicity.

2. The porous gas diffusion layer-flow field integrated structure according to claim 1, characterized in that, The porous gas diffusion layer is carbon paper, carbon cloth, carbon felt, or porous metal foam; and / or, the fluorinated polymer material is PTFE.

3. The porous gas diffusion layer-flow field integrated structure according to claim 2, characterized in that, In the hydrophobic porous gas diffusion layer, the mass percentage of the fluorinated polymer material is 1% to 30%.

4. The porous gas diffusion layer-flow field integrated structure according to any one of claims 1-3, characterized in that, The thickness of the porous gas diffusion layer is 100~600 μm; preferably, the thickness of the porous gas diffusion layer is 200~500 μm.

5. The porous gas diffusion layer-flow field integrated structure according to any one of claims 1-4, characterized in that, The grooves include parallel grooves, serpentine grooves, or spiral grooves; preferably, the depth of the grooves is 100~400 μm, the width is 0.5~2 mm, and the spacing between adjacent grooves is 0.3~1.5 mm.

6. The porous gas diffusion layer-flow field integrated structure according to any one of claims 1-5, characterized in that, The hydrophilicity of the ridge gradually increases from the ridge body to the surface.

7. The porous gas diffusion layer-flow field integrated structure according to claim 6, characterized in that, The body contact angle of the ridge is ≥120°.

8. The porous gas diffusion layer-flow field integrated structure according to any one of claims 1-7, characterized in that, The laser used for laser etching is an ultraviolet laser, a fiber laser, or a semiconductor laser.

9. The porous gas diffusion layer-flow field integrated structure according to claim 8, characterized in that, During laser etching, the focal length is adjusted to the upper surface of the porous gas diffusion layer.

10. A fuel cell, characterized in that, The invention includes a fuel cell stack consisting of stacked single cells; wherein each single cell is assembled from a porous gas diffusion layer-flow field integrated structure as described in any one of claims 1-9, a membrane electrode, and a conductive plate; one side of the porous gas diffusion layer-flow field integrated structure with grooves is in contact with the conductive plate, and the other side is in contact with the membrane electrode.

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