Gas diffusion layer for fuel cell, preparation method and fuel cell

Abstract

The invention provides a gas diffusion layer for a fuel cell, a preparation method of the gas diffusion layer and the fuel cell, and belongs to the field of fuel cells. Comprising a substrate layer; the water repellent contents of a plurality of substrate grade intervals of the substrate layer are gradually reduced from the substrate starting interval; and a microporous layer; the microporous layer is arranged on the outer side surface of the substrate layer; and the water repellent content of a plurality of pore layer grade intervals of the microporous layer is gradually increased from the pore layer starting interval. The gradient gas diffusion layer microporous layer is designed, high-hydrophobicity arrangement is adopted at the position, close to a flow channel, of a gas inlet, it is guaranteed that water brought by gas can be well discharged, low-hydrophobicity arrangement is adopted at the position close to a catalyst layer, and the situation that produced water is led in and is too dry is avoided; the low-hydrophobic arrangement is adopted at the air outlet close to the flow channel, and the high-hydrophobic arrangement is adopted at the air outlet close to the catalyst layer, so that the uniformity of overall water-air distribution is ensured while water is discharged, and the uniformity of mass transfer of the membrane electrode is ensured. Therefore, the drainage and mass transfer capabilities of the microporous layer of the gas diffusion layer of the fuel cell are improved.

Description

Technical Field

[0001] The present application relates to the field of fuel cell technology, and in particular to a gas diffusion layer for a fuel cell and a preparation method thereof. Background Art

[0002] Proton exchange membrane fuel cells are mainly composed of membrane electrodes (including gas diffusion layer, catalyst layer and proton exchange membrane), bipolar plates and sealing materials. The gas diffusion layer mainly plays an important role in supporting the catalyst layer, collecting current, conducting gas and discharging water. The reaction gas needs to pass through the gas diffusion layer to reach the three-phase junction for reaction. Therefore, the quality of the gas diffusion layer will directly affect the gas permeability, etc., thereby affecting the performance of the fuel cell.

[0003] The gas diffusion layer (GDL) is mainly composed of carbon paper and a microporous layer. As a base layer, carbon paper provides strength support and basic skeleton. The microporous layer is brushed on the carbon paper to provide the battery with more stable and reliable gas and water channels. Under normal circumstances, the microporous layer of the gas diffusion layer mainly plays a role in ensuring the water-gas balance of the fuel cell. However, in the actual operation of the stack, due to the reaction of the membrane electrode itself to generate a large amount of water, coupled with the humidification of the gas supplied from the outside of the stack, water flooding will occur under long-term operation. The occurrence of this situation will lead to insufficient gas supply and mass transfer problems. In severe cases, local reverse polarity will occur, which will seriously affect the performance of the battery. At the same time, due to the accumulation of some internally generated water at the gas outlet, the humidification of the outlet and the inlet is different, the outlet is flooded, and the overall mass transfer of the membrane electrode is uneven. How to improve the drainage capacity of the microporous layer of the gas diffusion layer of the fuel cell to avoid problems such as partial flooding is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides a gas diffusion layer for a fuel cell, a preparation method thereof, and a fuel cell to solve the following technical problem: how to improve the drainage and mass transfer capabilities of a microporous layer of a gas diffusion layer of a fuel cell.

[0005] In a first aspect, the present application provides a gas diffusion layer for a fuel cell, the gas diffusion layer comprising:

[0006] A substrate layer; the substrate layer comprises a plurality of substrate level intervals, with the substrate level interval close to the air inlet of the high-temperature fuel cell being the substrate starting interval, and the water repellent content of the plurality of substrate level intervals decreasing step by step from the substrate starting interval; and

[0007] A microporous layer; the microporous layer is arranged on the outer surface of the substrate layer; the microporous layer includes a plurality of pore layer grade intervals matching the substrate grade interval, with the pore layer grade interval close to the air inlet of the high-temperature fuel cell as the pore layer starting interval, and the water repellent content of the plurality of pore layer grade intervals increases step by step from the pore layer starting interval;

[0008] Wherein, the hole layer starting interval is arranged outside the substrate starting interval.

[0009] Optionally, the number of level intervals is 3 to 7.

[0010] Optionally, the base level intervals are set to base A 1 Area, base B 1 Area and base C 1 district;

[0011] The substrate A 1 The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 25wt% to 35wt%;

[0012] The substrate B 1 The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 20wt% to 25wt%;

[0013] The substrate C 1 The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 10wt% to 20wt%;

[0014] The pore layer level intervals are set as pore layer A 2 Area, hole layer B 2 Area and hole layer C 2 district;

[0015] The hole layer A 2 The content of the water repellent in the slurry of the zone is 5wt% to 15wt%;

[0016] The hole layer B 2 The content of the water repellent in the slurry of the zone is 15wt% to 20wt%;

[0017] The hole layer C 2 The content of the water repellent in the slurry of the zone is 20wt% to 40wt%.

[0018] Optionally, the base level intervals are set to base A 1 Area, base B 1 Area, base C 1 Area, base D 1 Area and base E 1 district;

[0019] The substrate A 1The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 30wt% to 35wt%;

[0020] The substrate B 1 The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 25wt% to 30wt%;

[0021] The substrate C 1 The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 20wt% to 25wt%;

[0022] The substrate D 1 The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 15wt% to 20wt%;

[0023] The substrate E 1 The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 10wt% to 15wt%;

[0024] The pore layer level intervals are set as pore layer A 2 Area, hole layer B 2 Area, hole layer C 2 Area, hole layer D 2 Area and hole layer E 2 district;

[0025] The hole layer A 2 The content of the water repellent in the slurry of the zone is 5wt% to 10wt%;

[0026] The hole layer B 2 The content of the water repellent in the slurry of the zone is 10wt% to 15wt%;

[0027] The hole layer C 2 The content of the water repellent in the slurry of the zone is 15wt% to 20wt%;

[0028] The hole layer D 2 The content of the water repellent in the slurry of the zone is 20wt% to 30wt%;

[0029] The hole layer E 2 The content of the water repellent in the slurry of the zone is 30wt% to 40wt%.

[0030] Optionally, the slurry also includes: conductive carbon black and dispersion liquid.

[0031] Optionally, the water repellent includes one or more of polytetrafluoroethylene, polyvinylidene fluoride and a copolymer of tetrafluoroethylene and ethylene.

[0032] In a second aspect, the present application provides a method for preparing a gas diffusion layer according to any one embodiment of the first aspect, the method comprising:

[0033] According to the number of base grade intervals of the base layer, a corresponding number of hydrophobic treatment liquids are selected, and the corresponding base grade intervals are subjected to hydrophobic treatment using the hydrophobic treatment liquids respectively;

[0034] According to the number of base grade intervals of the base layer, a corresponding number of slurries are selected, and the slurries are respectively coated on the outer surfaces of the corresponding base grade intervals, and then dried and calcined to obtain a gas diffusion layer with multiple pore layer grade intervals matching the base grade intervals.

[0035] Optionally, the coating is sprayed, the spraying temperature is 70°C to 90°C, and the spraying flow rate is 5mL / min to 20mL / min; wherein,

[0036] Base A 1 Area and base B 1 The flow rate in the zone is 5mL / min to 10mL / min;

[0037] Base C 1 Area and base D 1 The flow rate in the zone is 10mL / min to 15mL / min;

[0038] Base E 1 The flow rate in the zone is 15mL / min~20mL / min.

[0039] Optionally, the using the hydrophobic treatment liquid to perform hydrophobic treatment on corresponding base grade intervals respectively includes:

[0040] The hydrophobic treatment liquid is used to immerse the corresponding base grade intervals, and then dried and calcined; the calcination temperature is 300°C to 400°C.

[0041] In a third aspect, the present application provides a fuel cell, comprising the gas diffusion layer described in any one of the embodiments in the first aspect.

[0042] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0043] The present application provides a gas diffusion layer for a fuel cell, comprising: a substrate layer; the substrate layer comprises a plurality of substrate grade intervals, with the substrate grade interval close to the air inlet of the high-temperature fuel cell being the substrate starting interval, and the hydrophobic agent content of the plurality of substrate grade intervals decreasing step by step from the substrate starting interval; and a microporous layer; the microporous layer is arranged on the outer surface of the substrate layer; the microporous layer comprises a plurality of pore layer grade intervals matching the substrate grade interval, with the pore layer grade interval close to the air inlet of the high-temperature fuel cell being the pore layer starting interval, and the hydrophobic agent content of the plurality of pore layer grade intervals increasing step by step from the pore layer starting interval; wherein the pore layer starting interval is arranged on the outer side of the substrate starting interval. The present application designs a gradient gas diffusion layer microporous layer, which adopts a high hydrophobic setting near the flow channel at the air inlet to ensure that the water brought in by the gas can be well discharged, and a low hydrophobic setting is adopted near the catalyst layer to introduce the produced water to prevent over-drying; a low hydrophobic setting is adopted near the flow channel at the air outlet, and a high hydrophobic setting is adopted near the catalyst layer, which is conducive to discharging water while ensuring the uniformity of the overall water vapor distribution and the uniformity of the membrane electrode mass transfer. In this way, the longitudinal and transverse gradient settings can well ensure the uniformity of the water vapor distribution inside the flow channel and the membrane electrode. The high hydrophobic setting at the position prone to flooding makes it easy to discharge water without causing a dry situation. On the contrary, the low hydrophobic setting at the water-deficient position makes it easier for the membrane electrode to achieve a better hydration state without flooding. At the same time, the overall moisture uniformity will make the gas transmission smoother, providing the overall performance and reliability of the membrane electrode. Thereby improving the drainage and mass transfer capacity of the microporous layer of the gas diffusion layer of the fuel cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0045] In order to more clearly illustrate the embodiments of the present application 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, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0046] Figure 1 A schematic plan view of a gas diffusion layer provided in an embodiment of the present application;

[0047] Figure 2 A schematic longitudinal cross-sectional view of a gas diffusion layer provided in an embodiment of the present application;

[0048] Figure 3 A flow chart of a method for preparing a gas diffusion layer provided in an embodiment of the present application;

[0049] Figure 4 This is a comparison diagram of polarization curves of the gas diffusion layer provided in the embodiments and comparative examples of the present application. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0051] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0052] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc or abc, where a, b, c can be single or plural, respectively.

[0053] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0054] The creative ideas of this application are:

[0055] In the actual operation of the fuel cell, flooding mostly occurs at the battery outlet, and there is an uneven distribution of water vapor between the air inlet and the air outlet. To address this problem, the present application has designed a gradient gas diffusion layer microporous layer, which uses a high hydrophobic setting near the flow channel at the air inlet to ensure that the water brought in by the gas can be discharged well, and a low hydrophobic setting is used near the catalyst layer to introduce the produced water to prevent over-drying; a low hydrophobic setting is used near the flow channel at the air outlet, and a high hydrophobic setting is used near the catalyst layer, which is conducive to discharging water while ensuring the uniformity of the overall water vapor distribution and the uniformity of the membrane electrode mass transfer. In this way, the longitudinal and transverse gradient settings can well ensure the uniformity of the water vapor distribution inside the flow channel and the membrane electrode. The high hydrophobic setting at the position prone to flooding makes it easy to discharge water and will not cause a dry situation. On the contrary, the low hydrophobic setting at the water-deficient position makes it easier for the membrane electrode to achieve a better hydration state without flooding. At the same time, the overall moisture uniformity will make the gas transmission smoother, providing the overall performance and reliability of the membrane electrode.

[0056] Figure 1 A schematic plan view of a gas diffusion layer provided in an embodiment of the present application; Figure 2 A schematic longitudinal cross-sectional view of a gas diffusion layer provided in an embodiment of the present application.

[0057] See also Figure 1 and Figure 2 The present application provides a gas diffusion layer for a fuel cell, the gas diffusion layer comprising:

[0058] A substrate layer; the substrate layer comprises a plurality of substrate level intervals, with the substrate level interval close to the air inlet of the high-temperature fuel cell being the substrate starting interval, and the water repellent content of the plurality of substrate level intervals decreasing step by step from the substrate starting interval; and

[0059] A microporous layer; the microporous layer is arranged on the outer surface of the substrate layer; the microporous layer includes a plurality of pore layer grade intervals matching the substrate grade interval, with the pore layer grade interval close to the air inlet of the high-temperature fuel cell as the pore layer starting interval, and the water repellent content of the plurality of pore layer grade intervals increases step by step from the pore layer starting interval;

[0060] Wherein, the hole layer starting interval is arranged outside the substrate starting interval.

[0061] In some implementations, the number of level intervals is 3 to 7.

[0062] In some embodiments, the base level intervals are set to base A 1 Area, base B 1 Area and base C 1 Area; said substrate A 1 The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 25wt% to 35wt%; the substrate B 1 The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 20wt% to 25wt%; the substrate C 1 The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 10wt% to 20wt%; the pore layer grade intervals are successively set as pore layer A 2 Area, hole layer B 2 Area and hole layer C 2 Area; the hole layer A 2 The content of the water repellent in the slurry of the zone is 5wt% to 15wt%; the porous layer B 2 The content of the water repellent in the slurry of the zone is 15wt% to 20wt%; the porous layer C 2 The content of the water repellent in the slurry of the zone is 20wt% to 40wt%.

[0063] In some embodiments, the base level intervals are set to base A 1 Area, base B 1 Area, base C 1 Area, base D 1 Area and base E 1 Area; said substrate A 1 The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 30wt% to 35wt%; the substrate B 1 The content of the hydrophobic agent in the hydrophobic treatment liquid in the zone is 25wt% to 30wt%; the substrate C 1 The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 20wt% to 25wt%; the substrate D 1 The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 15wt% to 20wt%; the substrate E 1 The content of the hydrophobic agent in the hydrophobic treatment liquid of the zone is 10wt% to 15wt%; the pore layer grade intervals are successively set as pore layer A 2 Area, hole layer B 2 Area, hole layer C 2 Area, hole layer D 2 Area and hole layer E 2 Area; the hole layer A 2 The content of the water repellent in the slurry of the zone is 5wt% to 10wt%; the porous layer B 2 The content of the water repellent in the slurry of the zone is 10wt% to 15wt%; the porous layer C 2The content of the water repellent in the slurry of the zone is 15wt% to 20wt%; the porous layer D 2 The content of the water repellent in the slurry of the zone is 20wt% to 30wt%; the porous layer E 2 The content of the water repellent in the slurry of the zone is 30wt% to 40wt%.

[0064] It should be noted that the present application has a lateral gradient design of the hydrophobicity of the substrate layer from high to low, and a lateral gradient design of the hydrophobicity of the microporous layer from low to high; at the same time, there is a longitudinal gradient design of the hydrophobicity from the substrate layer to the microporous layer from high to low. The longitudinal and lateral gradient settings can well ensure the uniformity of the water vapor distribution inside the flow channel and the membrane electrode. The high hydrophobic setting of the position prone to flooding makes it easy to drain the water without causing a dry situation. On the contrary, the low hydrophobic setting of the water-deficient position makes it easier for the membrane electrode to achieve a better hydration state without flooding. At the same time, the overall moisture uniformity will make the gas transmission smoother, providing the overall performance and reliability of the membrane electrode.

[0065] In some embodiments, the slurry further includes: conductive carbon black and a dispersion liquid.

[0066] In some embodiments, the conductive carbon black includes one or more of acetylene black, Vulcan XC-72, Black pearls, carbon nanotubes and graphene powder.

[0067] In some embodiments, the dispersion includes: one or more of ethanol, isopropanol, and ethylene glycol.

[0068] In some embodiments, the base layer includes carbon paper and carbon cloth.

[0069] In some embodiments, the water repellent comprises one or more of polytetrafluoroethylene, polyvinylidene fluoride, and a copolymer of tetrafluoroethylene and ethylene.

[0070] Figure 3 A flow chart of a method for preparing a gas diffusion layer provided in an embodiment of the present application.

[0071] See also Figure 3 Based on a general inventive concept, the present application provides a method for preparing a gas diffusion layer as described in any one of the above embodiments, the method comprising:

[0072] S1. Selecting a corresponding number of hydrophobic treatment liquids according to the number of base grade intervals of the base layer, and using the hydrophobic treatment liquids to perform hydrophobic treatment on the corresponding base grade intervals respectively;

[0073] S2. According to the number of base grade intervals of the base layer, a corresponding number of slurries are selected, and the slurries are respectively coated on the outer surfaces of the corresponding base grade intervals, followed by drying and calcining to obtain a gas diffusion layer having multiple pore layer grade intervals matching the base grade intervals.

[0074] In some embodiments, the coating is performed by spraying, the spraying temperature is 70°C to 90°C, and the spraying flow rate is 5mL / min to 20mL / min; wherein,

[0075] Base A 1 Area and base B 1 The flow rate in the zone is 5mL / min to 10mL / min;

[0076] Base C 1 Area and base D 1 The flow rate in the zone is 10mL / min to 15mL / min;

[0077] Base E 1 The flow rate in the zone is 15mL / min~20mL / min.

[0078] In some embodiments, the step of using the hydrophobic treatment liquid to perform hydrophobic treatment on corresponding substrate level intervals comprises:

[0079] The hydrophobic treatment liquid is used to immerse the corresponding base grade intervals, and then dried and calcined; the calcination temperature is 300°C to 400°C.

[0080] The product prepared by the method for preparing the gas diffusion layer is the above-mentioned gas diffusion layer. The structure of the gas diffusion layer prepared by the method for preparing the gas diffusion layer can refer to the above-mentioned embodiment. Since the method for preparing the gas diffusion layer adopts part or all of the technical solutions of the gas diffusion layer embodiment, it at least has all the beneficial effects brought by the technical solutions of the gas diffusion layer embodiment, which will not be described one by one here.

[0081] Based on a general inventive concept, the present application provides a fuel cell, which includes the gas diffusion layer described in any one of the above embodiments.

[0082] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0083] Example 1

[0084] This embodiment provides a method for preparing a gas diffusion layer, comprising the following steps:

[0085] S11, obtain polytetrafluoroethylene emulsions with polytetrafluoroethylene contents of 35wt%, 30wt%, 25wt%, 20wt% and 15wt%, respectively, and divide the commercial carbon paper into substrate A uniformly along the long side direction. 1 Area, base B 1 Area, base C 1 Area, base D 1 Area and base E 1 In the five areas of the area, the base A is covered with a local film. 1 The substrate B was immersed in a 35wt% polytetrafluoroethylene emulsion for 30 min. 1 The substrate C 1 The substrate D 1 The substrate E was immersed in a 20wt% polytetrafluoroethylene emulsion for 30 min. 1 The area is immersed in a 15wt% polytetrafluoroethylene emulsion for 30min, then dried at 60°C, and then calcined at 300°C to obtain a base layer with 5 base grade intervals;

[0086] S12, isopropanol and water were mixed, and then Vulcan XC-72 carbon powder and polytetrafluoroethylene emulsions of different masses were added, and magnetic stirring and ultrasonic dispersion were performed to obtain a uniform microporous layer slurry, wherein the polytetrafluoroethylene content in the microporous layer slurry was 10wt%, 15wt%, 20wt%, 30wt%, and 40wt%, respectively, and the microporous layer slurry with a polytetrafluoroethylene content of 10wt% was sprayed onto the substrate A at a flow rate of 5mL / min by using a local coating shielding method. 1 On the outer side of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 15 wt% was sprayed onto the substrate B at a flow rate of 5 mL / min. 1 On the outer surface of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 20 wt% was sprayed onto the substrate C at a flow rate of 10 mL / min. 1 On the outer side of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 30 wt% was sprayed onto the substrate D at a flow rate of 10 mL / min. 1 On the outer side of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 40 wt% was sprayed onto the substrate E at a flow rate of 15 mL / min. 1 The outer surface of the region was dried and calcined for 4 hours to obtain the porous layer A 2 Area, hole layer B 2 Area, hole layer C 2 Area, hole layer D 2Area and hole layer E 2 The gas diffusion layer in the region. Figure 1 and Figure 2 shown.

[0087] Example 2

[0088] This embodiment provides a method for preparing a gas diffusion layer, comprising the following steps:

[0089] S11, obtain polytetrafluoroethylene emulsions with polytetrafluoroethylene contents of 30wt%, 25wt%, 20wt%, 15wt% and 10wt%, respectively, and divide the commercial carbon paper into substrate A uniformly along the long side direction. 1 Area, base B 1 Area, base C 1 Area, base D 1 Area and base E 1 In the five areas of the area, the base A is covered with a local film. 1 The substrate B was immersed in a 30wt% polytetrafluoroethylene emulsion for 30 min. 1 The substrate C 1 The substrate D 1 The substrate E was immersed in a 15wt% polytetrafluoroethylene emulsion for 30 min. 1 The area is immersed in a 10wt% polytetrafluoroethylene emulsion for 30min, then dried at 60°C, and then calcined at 300°C to obtain a base layer with 5 base grade intervals;

[0090] S12, isopropanol and water are mixed, and then Vulcan XC-72 carbon powder and polytetrafluoroethylene emulsions of different masses are added, and the mixture is subjected to magnetic stirring and ultrasonic dispersion to obtain a uniform microporous layer slurry, wherein the polytetrafluoroethylene content in the microporous layer slurry is 5wt%, 10wt%, 15wt%, 20wt%, and 30wt%, respectively. The microporous layer slurry with a polytetrafluoroethylene content of 5wt% is sprayed onto the substrate A at a flow rate of 10mL / min by using a local coating shielding method. 1 On the outer side of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 10 wt% was sprayed onto the substrate B at a flow rate of 10 mL / min. 1 On the outer side of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 15 wt% was sprayed onto the substrate C at a flow rate of 15 mL / min. 1 On the outer side of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 20 wt% was sprayed onto the substrate D at a flow rate of 15 mL / min. 1On the outer surface of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 30 wt% was sprayed onto the substrate E at a flow rate of 20 mL / min. 1 The outer surface of the region was dried and calcined for 4 hours to obtain the porous layer A 2 Area, hole layer B 2 Area, hole layer C 2 Area, hole layer D 2 Area and hole layer E 2 The gas diffusion layer in the region. Figure 1 and Figure 2 shown.

[0091] Example 3

[0092] This embodiment provides a method for preparing a gas diffusion layer, comprising the following steps:

[0093] S11, obtain polytetrafluoroethylene emulsions with polytetrafluoroethylene contents of 32wt%, 27wt%, 22wt%, 17wt% and 12wt%, respectively, and divide the commercial carbon paper into substrate A uniformly along the long side direction. 1 Area, base B 1 Area, base C 1 Area, base D 1 Area and base E 1 In the five areas of the area, the base A is covered with a local film. 1 The substrate B was immersed in a 32wt% polytetrafluoroethylene emulsion for 30 min. 1 The substrate C was immersed in a 27wt% polytetrafluoroethylene emulsion for 30 min. 1 The substrate D 1 The substrate E was immersed in a 17 wt% polytetrafluoroethylene emulsion for 30 min. 1 The area is immersed in a 12wt% polytetrafluoroethylene emulsion for 30min, then dried at 60°C, and then calcined at 300°C to obtain a base layer with 5 base grade intervals;

[0094] S12, isopropanol and water were mixed, and then Vulcan XC-72 carbon powder and polytetrafluoroethylene emulsions of different masses were added, and magnetic stirring and ultrasonic dispersion were performed to obtain a uniform microporous layer slurry, wherein the polytetrafluoroethylene content in the microporous layer slurry was 7wt%, 12wt%, 17wt%, 22wt%, and 32wt%, respectively, and the microporous layer slurry with a polytetrafluoroethylene content of 7wt% was sprayed onto the substrate A at a flow rate of 7mL / min by using a local coating shielding method. 1 On the outer side of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 12 wt% was sprayed onto the substrate B at a flow rate of 7 mL / min.1 On the outer surface of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 17 wt% was sprayed onto the substrate C at a flow rate of 12 mL / min. 1 On the outer side of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 22 wt% was sprayed onto the substrate D at a flow rate of 12 mL / min. 1 On the outer side of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 32 wt% was sprayed onto the substrate E at a flow rate of 17 mL / min. 1 The outer surface of the region was dried and calcined for 4 hours to obtain the porous layer A 2 Area, hole layer B 2 Area, hole layer C 2 Area, hole layer D 2 Area and hole layer E 2 The gas diffusion layer in the region. Figure 1 and Figure 2 shown.

[0095] Comparative Example 1

[0096] This comparative example provides a method for preparing a gas diffusion layer, comprising the following steps:

[0097] S11, immersing the commercial carbon paper in a polytetrafluoroethylene emulsion with a polytetrafluoroethylene content of 25 wt% for 30 minutes, drying at 60° C., and then calcining at 300° C. to obtain a base layer;

[0098] S12, isopropanol and water are mixed, and then Vulcan XC-72 carbon powder and polytetrafluoroethylene emulsion are added, and magnetic stirring and ultrasonic dispersion are performed to obtain a uniform microporous layer slurry with a polytetrafluoroethylene content of 15wt%. The obtained microporous layer slurry is sprayed on the outer surface of the base layer, and dried and calcined for 4h to obtain a gas diffusion layer.

[0099] Comparative Example 2

[0100] This comparative example provides a method for preparing a gas diffusion layer, comprising the following steps:

[0101] S11, obtain polytetrafluoroethylene emulsions with polytetrafluoroethylene contents of 35wt%, 30wt%, 25wt%, 20wt% and 15wt%, respectively, and divide the commercial carbon paper into substrate A uniformly along the long side direction. 1 Area, base B 1 Area, base C 1 Area, base D 1 Area and base E 1 In the five areas of the area, the base A is covered with a local film. 1 The substrate B was immersed in a 35wt% polytetrafluoroethylene emulsion for 30 min.1 The substrate C 1 The substrate D 1 The substrate E was immersed in a 20wt% polytetrafluoroethylene emulsion for 30 min. 1 The area is immersed in a 15wt% polytetrafluoroethylene emulsion for 30min, then dried at 60°C, and then calcined at 300°C to obtain a base layer with 5 base grade intervals;

[0102] Isopropyl alcohol was mixed with water, and then Vulcan XC-72 carbon powder and polytetrafluoroethylene emulsion were added, and magnetic stirring and ultrasonic dispersion were performed to obtain a uniform microporous layer slurry with a polytetrafluoroethylene content of 15 wt%. The obtained microporous layer slurry was sprayed on the outer surface of the substrate layer, and dried and calcined for 4 hours to obtain a gas diffusion layer.

[0103] Comparative Example 3

[0104] S11, immersing the commercial carbon paper in a polytetrafluoroethylene emulsion with a polytetrafluoroethylene content of 25 wt% for 30 minutes, drying at 60° C., and then calcining at 300° C. to obtain a base layer;

[0105] S11, divide the base layer evenly into base A along the long side direction 1 Area, base B 1 Area, base C 1 Area, base D 1 Area and base E 1 In five areas of the zone, isopropanol and water are mixed, and then Vulcan XC-72 carbon powder and polytetrafluoroethylene emulsions of different masses are added, and magnetic stirring and ultrasonic dispersion are performed to obtain a uniform microporous layer slurry, wherein the polytetrafluoroethylene content in the microporous layer slurry is 10wt%, 15wt%, 20wt%, 30wt%, and 40wt%, respectively. The microporous layer slurry with a polytetrafluoroethylene content of 10wt% is sprayed onto the substrate A at a flow rate of 5mL / min by using a local coating shielding method. 1 On the outer side of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 15 wt% was sprayed onto the substrate B at a flow rate of 5 mL / min. 1 On the outer surface of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 20 wt% was sprayed onto the substrate C at a flow rate of 10 mL / min. 1 On the outer side of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 30 wt% was sprayed onto the substrate D at a flow rate of 10 mL / min. 1 On the outer side of the zone, a microporous layer slurry with a polytetrafluoroethylene content of 40 wt% was sprayed onto the substrate E at a flow rate of 15 mL / min.1 The outer surface of the region was dried and calcined for 4 hours to obtain the porous layer A 2 Area, hole layer B 2 Area, hole layer C 2 Area, hole layer D 2 Area and hole layer E 2 gas diffusion layer in the region.

[0106] The gas diffusion layers obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were assembled into a single cell and the performance test was performed. The results are as follows: Figure 4 shown.

[0107] Figure 4 This is a comparison chart of the polarization curves of the gas diffusion layer provided by the embodiments of the present application and the comparative examples. Figure 4 It can be seen that under high current density conditions, the embodiment has higher performance and smaller mass transfer loss than the comparative example, which proves that the embodiment has better water vapor transmission capacity, and therefore the embodiment is superior.

[0108] In addition, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0109] (1) In the embodiments of the present invention, the gas diffusion layer with a microporous layer having a gradient structure design has better hydrophobicity and a certain self-draining ability compared with commercial gas diffusion layers due to the gradient water vapor transmission channel design.

[0110] (2) In the embodiment of the present invention, the uniformity of membrane electrode mass transfer is ensured through the lateral and longitudinal gradient design, the membrane electrode mass transfer performance is improved, the local flooding problem caused by long-term high current operation is reduced, the smooth flow of gas and liquid dual channels is ensured, and the performance and life of the battery are improved.

[0111] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A gas diffusion layer for a fuel cell, characterized in that: The gas diffusion layer comprises: A substrate layer; the substrate layer comprises a plurality of substrate level intervals, with the substrate level interval close to the air inlet of the high-temperature fuel cell being the substrate starting interval, and the water repellent content of the plurality of substrate level intervals decreasing step by step from the substrate starting interval; and A microporous layer; the microporous layer is arranged on the outer surface of the substrate layer; the microporous layer includes a plurality of pore layer grade intervals matching the substrate grade interval, with the pore layer grade interval close to the air inlet of the high-temperature fuel cell as the pore layer starting interval, and the water repellent content of the plurality of pore layer grade intervals increases step by step from the pore layer starting interval; Wherein, the hole layer starting interval is arranged outside the substrate starting interval.

2. The gas diffusion layer according to claim 1, characterized in that The level intervals are set to 3 to 7.

3. The gas diffusion layer according to claim 1, characterized in that: The base level intervals are set as base A1 area, base B1 area and base C1 area in sequence; The content of the hydrophobic agent in the hydrophobic treatment liquid in the substrate A1 area is 25wt% to 35wt%; The content of the hydrophobic agent in the hydrophobic treatment liquid in the substrate B1 region is 20wt% to 25wt%; The content of the hydrophobic agent in the hydrophobic treatment liquid in the substrate C1 region is 10wt% to 20wt%; The pore layer grade intervals are set to pore layer A2 area, pore layer B2 area and pore layer C2 area in sequence; The content of the water repellent in the slurry of the porous layer A2 region is 5wt% to 15wt%; The content of the water repellent in the slurry of the porous layer B2 region is 15wt% to 20wt%; The content of the water repellent in the slurry of the porous layer C2 region is 20wt% to 40wt%.

4. The gas diffusion layer according to claim 1, characterized in that: The base level intervals are set to base A1 area, base B1 area, base C1 area, base D1 area and base E1 area in sequence; The content of the hydrophobic agent in the hydrophobic treatment liquid in the substrate A1 area is 30wt% to 35wt%; The content of the hydrophobic agent in the hydrophobic treatment liquid in the substrate B1 region is 25wt% to 30wt%; The content of the hydrophobic agent in the hydrophobic treatment liquid in the substrate C1 region is 20wt% to 25wt%; The content of the hydrophobic agent in the hydrophobic treatment liquid in the substrate D1 region is 15wt% to 20wt%; The content of the hydrophobic agent in the hydrophobic treatment liquid in the substrate E1 region is 10wt% to 15wt%; The pore layer grade intervals are set to pore layer A2 area, pore layer B2 area, pore layer C2 area, pore layer D2 area and pore layer E2 area in sequence; The content of the water repellent in the slurry of the porous layer A2 region is 5wt% to 10wt%; The content of the water repellent in the slurry of the porous layer B2 region is 10wt% to 15wt%; The content of the water repellent in the slurry of the porous layer C2 region is 15wt% to 20wt%; The content of the water repellent in the slurry of the porous layer D2 region is 20wt% to 30wt%; The content of the water repellent in the slurry of the porous layer E2 region is 30wt% to 40wt%.

5. The gas diffusion layer according to claim 3 or 4, characterized in that: The slurry also includes: conductive carbon black and dispersion liquid.

6. The gas diffusion layer according to claim 3 or 4, characterized in that: The water repellent includes one or more of polytetrafluoroethylene, polyvinylidene fluoride and a copolymer of tetrafluoroethylene and ethylene.

7. A method for preparing a gas diffusion layer according to any one of claims 1 to 6, characterized in that: The method comprises: According to the number of base grade intervals of the base layer, a corresponding number of hydrophobic treatment liquids are selected, and the corresponding base grade intervals are subjected to hydrophobic treatment using the hydrophobic treatment liquids respectively; According to the number of base grade intervals of the base layer, a corresponding number of slurries are selected, and the slurries are respectively coated on the outer surfaces of the corresponding base grade intervals, and then dried and calcined to obtain a gas diffusion layer with multiple pore layer grade intervals matching the base grade intervals.

8. The method according to claim 7, characterized in that The coating is sprayed, the spraying temperature is 70°C to 90°C, and the spraying flow rate is 5mL / min to 20mL / min; wherein, The flow rate of the substrate A1 area and the substrate B1 area is 5 mL / min to 10 mL / min; The flow rate of the substrate C1 area and the substrate D1 area is 10mL / min to 15mL / min; The flow rate in the substrate E1 zone is 15 mL / min to 20 mL / min.

9. The method according to claim 7, characterized in that: The step of using the hydrophobic treatment liquid to perform hydrophobic treatment on corresponding base grade intervals respectively comprises: The hydrophobic treatment liquid is used to immerse the corresponding base grade intervals, and then dried and calcined; the calcination temperature is 300°C to 400°C.

10. A fuel cell, characterized in that: The fuel cell comprises the gas diffusion layer according to any one of claims 1 to 6.

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