Sandwich-structured integrated gas diffusion layer and application thereof

Abstract

The invention relates to the technical field of energy and cleaning, in particular to an integrated gas diffusion layer of a sandwich structure and application of the integrated gas diffusion layer. The gas diffusion layer sequentially comprises a microporous layer, a porous substrate layer and a conductive filler layer; one surface of the porous substrate layer, which is in contact with the conductive filler layer, is provided with spaced grooves, and the conductive filler layer is positioned on the surface of a spaced region between the adjacent grooves. According to the integrated gas diffusion layer with the sandwich structure prepared by the invention, the conductive filler layer is arranged on the substrate layer and is combined with the processing groove, and a flat and compact surface is provided by filling the pores in the surface of the unprocessed area of the substrate layer, so that the effective contact area between the substrate layer and a polar plate is increased, and the contact resistance is reduced; the effects of greatly shortening the mass transfer path and greatly improving the mass transfer efficiency are achieved, and the effects of overcoming the problems of gas permeability reduction, mass transfer efficiency reduction, cell performance reduction and the like caused by preparation of a compact conductive filler layer on the surface of a traditional gas diffusion layer are achieved.

Description

Technical Field

[0001] This invention relates to the fields of energy and clean technology, and specifically to an integrated gas diffusion layer with a sandwich structure and its application. Background Technology

[0002] Hydrogen energy, as a zero-carbon emission energy source and an excellent energy carrier, plays a significant role in the clean transition of energy systems. Proton exchange membrane fuel cells (PEMFCs), as hydrogen energy conversion devices, have attracted considerable attention due to their high energy conversion efficiency, fast dynamic response, and clean, pollution-free operation. However, the performance degradation caused by the limited water vapor transport capacity of PEMFCs at high current densities has also limited their large-scale application.

[0003] The gas diffusion layer is responsible for transporting the reactant gases in the flow channel to the catalyst layer and promptly removing water generated in the catalyst layer, thus being considered one of the key components of a PEMFC. However, when the traditional gas diffusion layer is combined with the flow field plates, water accumulation under the ridges occurs, leading to reduced uniformity of water vapor distribution within the catalyst layer and a decline in battery performance. Therefore, redesigning the structure of the gas diffusion layer to solve the water vapor transport problem is extremely important.

[0004] To address the aforementioned issues, some technologies have disclosed methods for processing flow channels on carbon paper. For example, patent CN118610665A discloses a gas diffusion layer, its preparation method, and a fuel cell. This involves etching multiple grooves on the surface of a fiber layer and coating the other side with a microporous slurry to obtain the gas diffusion layer. However, the relatively rough and porous surface of this gas diffusion layer increases the contact resistance at the interface with the flat electrode plate, limiting the battery's performance output. Patent CN116826073A discloses an integrated gas diffusion layer for a fuel cell, its preparation method, and its application. This method obtains the gas diffusion layer by etching flow channels on the surface of carbon fiber paper, improving water vapor transport performance and battery power. However, this gas diffusion layer has not yet overcome the problem of increased contact resistance at the interface between its relatively rough and porous surface and the flat electrode plate. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an integrated gas diffusion layer with a sandwich structure, aiming to solve the problem of high contact resistance at the interface between the integrated gas diffusion layer and the flat plate electrode in existing technologies.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: The present invention provides an integrated gas diffusion layer with a sandwich structure, wherein the gas diffusion layer comprises a microporous layer, a porous substrate layer and a conductive filler layer in sequence; the side of the porous substrate layer in contact with the conductive filler layer is provided with spaced grooves, and the conductive filler layer is located on the surface of the spaced area between adjacent grooves to fill the pores of the surface.

[0007] Preferably, the conductive filler layer is composed of conductive carbon material and binder, wherein the conductive carbon material is at least one of XC-72, acetylene black, conductive carbon black Super P, carbon nanofibers, carbon nanotubes, and high specific surface area graphite. The adhesive includes at least one of polyaniline (PANI) based adhesive, polypyrrole (PPy) based adhesive, polythiophene (PT) based adhesive, polytetrafluoroethylene (PTFE) based adhesive, and polyvinylidene fluoride (PVDF) based adhesive; The mass ratio of the conductive carbon material to the binder is (9.0~9.9):(1.0~0.1).

[0008] Preferably, the thickness of the conductive filler layer is 2~20μm.

[0009] Preferably, the porous substrate layer includes at least one of carbon paper, carbon felt, carbon cloth, and titanium felt.

[0010] Preferably, the porous substrate layer has a thickness of 0.1~0.6 mm, a porosity of 60%~85%, an average pore size of 1~50 μm, and a hydrophobic angle of 120~155°.

[0011] Preferably, the thickness of the microporous layer is 5~20μm, the porosity is 65%~85%, the average pore diameter is 0.05~5μm, and the hydrophobic angle is 130~160°.

[0012] Preferably, the depth of the groove is 0.1~0.5mm.

[0013] Preferably, the groove is formed by one or more of the following processes: mechanical milling, laser etching, ion beam etching, chemical etching, and mold pressing; the shape of the groove and the space between adjacent grooves is not limited and can be a regular polygon or an irregular curve.

[0014] Another aspect of the present invention provides an application of the aforementioned sandwich structure of an integrated gas diffusion layer, wherein the integrated gas diffusion layer is applied to a fuel cell or water electrolysis.

[0015] The beneficial effects of this invention are as follows: 1. The integrated gas diffusion layer with a sandwich structure provided by the present invention has a sandwich structure composed of a microporous layer, a porous substrate layer and a conductive filler layer. The porous substrate layer has spaced grooves on the side in contact with the conductive filler layer. The conductive filler layer is located in the spaced area between adjacent grooves and fills the pores on the surface, providing a flat and dense surface. This increases the contact area between the spaced area in the porous substrate layer and the electrode plate, significantly reduces the contact resistance between the integrated gas diffusion layer and the electrode plate, reduces battery performance loss, and thus improves battery efficiency.

[0016] 2. The porous substrate layer of the present invention is provided with grooves, which serve as the main transmission channels and the interval between adjacent grooves serve as secondary transmission channels. This realizes the integration of the three transmission channels of microporous layer, substrate layer and flow channel, which greatly shortens the mass transfer path, improves mass transfer efficiency, simplifies battery and volume, thereby significantly enhancing battery performance, battery volumetric power density and reducing battery cost.

[0017] 3. The integrated gas diffusion layer with a sandwich structure of the present invention utilizes a conductive filler layer on a porous substrate combined with a processing groove. By filling the pores on the surface of the unprocessed area of ​​the porous substrate, a flat and dense surface is provided. This increases the effective contact area between the substrate and the electrode, reduces contact resistance, and significantly shortens the mass transfer path, thereby greatly improving mass transfer efficiency. This overcomes the problems of decreased gas permeability, reduced mass transfer efficiency, and decreased battery performance caused by the preparation of a dense conductive filler layer on the surface of the traditional gas diffusion layer.

[0018] 4. The integrated gas diffusion layer with a sandwich structure provided by the present invention, by forming spaced grooves on the base layer, changes the way gas is transported to the catalyst layer from diffusion to convection, thereby changing the way and path of water vapor transport in the battery; the conductive filler layer is located in the space between adjacent grooves as a ridge. Since the ridge is a porous structure, it also solves the problem of water accumulation under the ridge of the flow channel in traditional batteries, thereby improving the oxygen concentration and uniformity in the catalyst layer, enhancing battery water management, and greatly improving battery performance. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the integrated gas diffusion layer with a sandwich structure in Example 1; Figure 2 This is a schematic diagram of the integrated gas diffusion layer in Comparative Example 1; Figure 3 This is a schematic diagram of the porous substrate layer in Example 1; Figure 4 This is a schematic diagram of the mask used to prepare the conductive filler layer in Example 1; Figure 5This is a comparison graph of the polarization curves of the battery assembled in Example 1 and the battery assembled in Comparative Example 2. Figure 6 This is a comparison graph of the power density curves of the battery assembled in Example 1 and the battery assembled in Comparative Example 2. In the figure: 1. Microporous layer, 2. Porous substrate layer, 3. Electrode plate, 4. Conductive filler layer. Detailed Implementation

[0020] The following embodiments are further illustrations of the present invention, which also protects obvious variations and equivalent alternatives.

[0021] The present invention provides an integrated gas diffusion layer with a sandwich structure, comprising a microporous layer 1, a porous substrate layer 2, and a conductive filler layer 4 in sequence; the porous substrate layer 2 and the conductive filler layer 4 are provided with spaced grooves on the side in contact with each other, and the conductive filler layer 4 is located on the surface of the spaced area between adjacent grooves.

[0022] In a preferred embodiment, the conductive filler layer 4 is composed of conductive carbon material and binder, wherein the conductive carbon material is at least one of XC-72, acetylene black, conductive carbon black Super P, carbon nanofibers, carbon nanotubes, and high specific surface area graphite. In a preferred embodiment, the adhesive includes at least one of polyaniline-based adhesive, polypyrrole-based adhesive, polythiophene-based adhesive, polytetrafluoroethylene adhesive, and polyvinylidene fluoride adhesive.

[0023] In a preferred embodiment, the mass ratio of conductive carbon material to binder is (9.0~9.9):(1.0~0.1).

[0024] In a preferred embodiment, the thickness of the conductive filler layer 4 is 2~20μm.

[0025] In a preferred embodiment, the porous substrate layer 2 includes at least one of carbon paper, carbon felt, carbon cloth, and titanium felt.

[0026] In a preferred embodiment, the porous substrate 2 has a thickness of 0.1~0.6 mm, a porosity of 60%~85%, an average pore size of 1~50 μm, and a hydrophobic angle of 120~155°.

[0027] In a preferred embodiment, the microporous layer 1 has a thickness of 5~20μm, a porosity of 65%~85%, an average pore diameter of 0.05~5μm, and a hydrophobic angle of 130~160°.

[0028] In a preferred embodiment, the depth of the groove is 0.1~0.5mm.

[0029] As a preferred embodiment, the groove is formed by one or more of the following processes: mechanical milling, laser etching, ion beam etching, chemical etching, and die pressing.

[0030] Example 1 Toray TGP-H-120 carbon paper (22.5 mm long, 22.5 mm wide, and 370 μm thick) was used as a porous transport layer. Grooves with a depth of 0.2 mm, a width of 1 mm, a length of 22.5 mm, and a spacing of 1 mm were machined by mechanical milling as the main mass transfer channels, and the spaced parts were secondary mass transfer channels. The machined carbon paper was cleaned with deionized water and treated with PTFE hydrophobicity. The PTFE loading was 5 wt%, and the hydrophobicity angle of the treated carbon paper was 150°. To prepare the microporous layer slurry, 3 g of XC-72 carbon powder was added to 100 ml of ethanol and ultrasonically dispersed evenly. Then, 10 g of 5 wt% PTFE emulsion was added and stirred evenly to obtain the microporous layer slurry. The microporous layer slurry was sprayed onto the side of the unprocessed groove of the hydrophobic carbon paper using an ultrasonic spraying process and dried at 80℃ for 2 hours to obtain the microporous layer. The thickness of the microporous layer was 7 μm, the porosity was 71%, the average pore diameter was 0.06 μm, and the hydrophobic angle was 140°. To prepare the conductive filler layer slurry, add 3 g of XC-72 carbon powder to 100 ml of ethanol, ultrasonically disperse it evenly, then add 3.16 g of 5 wt% PTFE emulsion, stir evenly to obtain the slurry. The mass ratio of conductive material to binder in the slurry is 9.5:0.5. Place a mask on the grooved side of the carbon paper, such as... Figure 4 As shown, the location and size of the blank area of ​​the mask correspond to Figure 3 The location and size of the spacer region between adjacent grooves in the porous substrate layer are shown. The conductive filler slurry is sprayed onto the mask using an ultrasonic spraying process, so that the surface of the spacer region below the blank area of ​​the mask is loaded with conductive filler. The sample is dried at 80°C for 2 hours, and the thickness of the conductive filler layer is measured to be 4 μm. After drying, the sample is placed in a nitrogen-filled oven and sintered at 350°C for 1 hour to obtain an integrated gas diffusion layer with a sandwich structure.

[0031] Example 2 The difference between this embodiment and Embodiment 1 is that the conductive material in the conductive filler layer slurry is different; the conductive material is acetylene black.

[0032] Example 3 The difference between this embodiment and Embodiment 1 is that the thickness of the conductive filler layer is 10 μm.

[0033] Example 4 The difference between this embodiment and Embodiment 1 is that the mass ratio of conductive material to binder in the conductive filler layer slurry is 9.0:1.0.

[0034] Comparative Example 1 The difference between this comparative example and Example 1 is that the integrated gas diffusion layer has no conductive filler layer, and its structural diagram is shown below. Figure 2 As shown.

[0035] Comparative Example 2 The difference between this comparative example and Example 1 is that the porous substrate layer does not have grooves, and the conductive filler layer completely covers the surface of the porous substrate layer and fills the pores on the surface of the substrate layer.

[0036] Test results: A 1mm thick stainless steel plate was brought into contact with the surface near the groove, and the contact resistance between the stainless steel plate and Examples 1, 2, 3, 4, Comparative Example 1, and Comparative Example 2 was tested using a universal testing machine. Since the integrated gas diffusion layer of the sandwich structure was prepared using the controlled variable method, the measured resistance change can be considered as being caused by the presence of the conductive filler layer and parameter changes.

[0037] Table 1. Comparison of contact resistance between gas diffusion layer and electrode in Examples 1-4 and Comparative Examples 1-2

[0038] As can be seen from the comparison of contact resistance values ​​between Example 1 and Comparative Example 1 in Table 1, preparing a conductive filler layer on the integrated gas diffusion layer can significantly reduce the contact resistance between the gas diffusion layer and the electrode, confirming the role of the conductive filler layer. In Example 2, replacing the conductive material with acetylene black, which has better conductivity, further reduced the contact resistance. Further analysis of the resistance values ​​in Examples 3 and 4 reveals that increasing the thickness of the conductive filler layer has little effect on the contact resistance, while increasing the content of non-conductive binder in the conductive filler layer leads to a significant increase in the contact resistance value. Therefore, while ensuring the adhesion of carbon particles, the amount of binder used should be minimized. Comparing the contact resistance values ​​between Example 1 and Comparative Example 2 shows that processing grooves on the carbon paper reduces the effective contact area between the gas diffusion layer and the electrode, leading to increased contact resistance. This further confirms the necessity of preparing a conductive filler layer on the integrated gas diffusion layer.

[0039] The sandwich-structured integrated gas diffusion layer prepared in Example 1 was combined with a commercially available CCM (anode catalyst layer with a platinum loading of 0.2 mg / cm²). 2 The platinum loading of the cathode catalyst layer is 0.4 mg / cm³. 2A fuel cell membrane electrode assembly (MEA) was formed by assembling a Gore 8 μm proton exchange membrane (PEM). This MEA was then assembled with a graphite bipolar plate (with grooves 0.2 mm deep to accommodate a porous transport layer) to form an integrated fuel cell. Electrochemical performance was evaluated using a single-cell evaluation device. In Comparative Example 2, a gas diffusion layer was assembled with a CCM to form a fuel cell MEA. The MEA was then used in conjunction with a conventional graphite parallel flow field for MEA fabrication, cell assembly, and performance evaluation.

[0040] The test conditions were: battery temperature 80℃, anode hydrogen flow rate 0.3L / min. -1 53% humidification, cathode air flow rate of 1.2 L / min -1 53% humidification.

[0041] like Figure 5 As shown, thanks to the grooved flow channels fabricated on the sandwich-structured gas diffusion layer, the microporous layer, substrate layer, and flow channels are integrated into a single transport system, significantly shortening the mass transfer path and greatly improving mass transfer efficiency. This results in a substantial enhancement of battery performance, with a current density of 3300 mA cm⁻¹ at 0.6V. -2 The current density at 0.4V is 5700 mA cm⁻¹. -2 The highest power density is 2.34 W / cm². -2 However, the lack of grooved channels in the sandwich-structured gas diffuser layer affects the efficiency of reactant gas transport from the channels through the gas diffuser layer to the catalyst layer. Because the conductive filler layer is denser than the microporous layer, the resistance to reactant gas passing through the filler layer increases, reducing the amount of reactant gas reaching the catalyst surface through the substrate and microporous layers. This leads to a sharp drop in oxygen concentration at the catalyst surface, resulting in severe mass transfer polarization during battery testing and a drastic performance degradation; the current density at 0.6V is only 1600 mA cm⁻¹. -2 The current density at 0.4V is only 2600 mA cm⁻¹ -2 The highest power density is only 1.10 W / cm². -2 .

[0042] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. An integrated gas diffusion layer with a sandwich structure, characterized in that, The gas diffusion layer comprises a microporous layer, a porous substrate layer, and a conductive filler layer in sequence; the porous substrate layer has spaced grooves on the side in contact with the conductive filler layer, and the conductive filler layer is located on the surface of the spaced area between adjacent grooves.

2. The integrated gas diffusion layer with a sandwich structure according to claim 1, characterized in that, The conductive filler layer is composed of conductive carbon material and binder, wherein the conductive carbon material is at least one of XC-72, acetylene black, conductive carbon black Super P, carbon nanofibers, carbon nanotubes, and high specific surface area graphite. The adhesive includes at least one of polyaniline-based adhesive, polypyrrole-based adhesive, polythiophene-based adhesive, polytetrafluoroethylene-based adhesive, and polyvinylidene fluoride-based adhesive; The mass ratio of the conductive carbon material to the binder is (9.0~9.9):(1.0~0.1).

3. The integrated gas diffusion layer with a sandwich structure according to claim 1, characterized in that, The thickness of the conductive filler layer is 2~20μm.

4. The integrated gas diffusion layer with a sandwich structure according to claim 1, characterized in that, The porous substrate layer includes at least one of carbon paper, carbon felt, carbon cloth, and titanium felt.

5. The integrated gas diffusion layer with a sandwich structure according to claim 1, characterized in that, The porous substrate has a thickness of 0.1~0.6 mm, a porosity of 60%~85%, an average pore size of 1~50 μm, and a hydrophobic angle of 120~155°.

6. The integrated gas diffusion layer with a sandwich structure according to claim 1, characterized in that, The microporous layer has a thickness of 5~20μm, a porosity of 65%~85%, an average pore size of 0.05~5μm, and a hydrophobic angle of 130~160°.

7. The integrated gas diffusion layer with a sandwich structure according to claim 1, characterized in that, The depth of the groove is 0.1~0.5mm.

8. The integrated gas diffusion layer of the sandwich structure according to claim 1, characterized in that the groove is formed by one or more of the following processes: mechanical milling, laser etching, ion beam etching, chemical etching, and die pressing.

9. An application of an integrated gas diffusion layer with a sandwich structure as described in any one of claims 1-8, characterized in that, The integrated gas diffusion layer is used in fuel cells or water electrolysis.

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