Passive fuel cell cathode plate

Abstract

The utility model relates to the technical field of passive fuel cells, in particular to a passive fuel cell cathode plate. Comprising a pole plate main body, and a plurality of uniformly distributed through holes are formed in the middle of the pole plate main body; the polar plate main body is provided with a front surface and a rear surface, a flow field rib part on the front surface of the cathode polar plate is provided with a rhombic hydrophilic pattern, the center of the rhombic hydrophilic pattern is provided with a drain hole, and the surface, except the rhombic hydrophilic pattern, of the front surface of the cathode polar plate is provided with a hydrophobic part, so that the hydrophobic part and the rhombic hydrophilic pattern are alternately arranged on the front surface of the cathode polar plate. Therefore, a hydrophilic-hydrophobic coupling surface is formed. When a large amount of liquid water is accumulated on one side, facing a flow field, of the cathode gas diffusion layer of the fuel cell, the liquid water is captured by the rhombic hydrophilic pattern due to the coupling effect of the hydrophilic and hydrophobic parts, and then the liquid water is promoted to be discharged, the mass transfer efficiency is enhanced and the water logging is relieved under the effect of Laplace pressure difference existing in the rhombic hydrophilic pattern; and the performance of the passive fuel cell is further improved.

Description

Technical Field

[0001] The utility model relates to the technical field of passive fuel cells, in particular to a cathode plate of a passive fuel cell. Background Art

[0002] A fuel cell is an energy conversion machine that converts chemical energy stored in fuel and oxidant into electrical energy. When the battery is running, a chemical reaction occurs inside the battery, electrons travel along an external circuit to generate current, and the reaction products are discharged from the battery.

[0003] The flow field structure directly affects whether the battery can obtain sufficient fuel and whether the reaction products can be discharged smoothly from the battery. At present, liquid water and oxygen exist simultaneously in the cathode flow field of passive fuel cells. If the liquid water is not discharged in time, "flooding" will occur. Therefore, a stable water environment needs to be maintained inside the battery, which is related to the operating efficiency of the fuel cell. The cathode plate has been improved to address the water management problem of fuel cells.

[0004] Chinese patent CN115395040A discloses a passive fuel cell anode current collector, including a plate body, on which a plurality of through holes are formed, and the plurality of through holes are evenly arranged in the middle of the plate body; the plate body has a front side and a back side, the front side faces the anode diffusion layer of the battery after being assembled into a battery, and the back side faces the fuel storage tank of the battery after being assembled into a battery, the front side is formed with a plurality of protrusions, and the plurality of protrusions are evenly arranged between the through holes, the back side is formed with a hydrophobic portion, and the hydrophobic portion is composed of a plurality of guide grooves, and the guide grooves are connected to each through hole, and the surface of the front side except the protrusions is made into a hydrophilic surface.

[0005] Chinese patent CN115395040A improves the anode current collecting plate, which has different functions from the cathode current collecting plate in the battery. This application solves the problem of flooding of the cathode plate. Utility Model Content

[0006] In order to improve the problem of battery cathode water management, the utility model provides a passive fuel cell cathode plate, which is used to improve the internal mass transfer capacity of the battery, accelerate the discharge of liquid water, and improve the battery performance.

[0007] The technical solution to solve the problem of the utility model is:

[0008] The utility model provides a passive fuel cell cathode plate, including a plate body, wherein a plurality of evenly distributed through holes are manufactured in the middle of the plate body; the plate body has a cathode plate front surface and a cathode plate rear surface, wherein the cathode plate front surface is the surface of the cathode plate facing the battery cathode gas diffusion layer, and the cathode plate rear surface is the surface of the cathode plate facing the outside air. The flow field ribs on the cathode plate front surface are manufactured with a diamond-shaped hydrophilic pattern, and a drainage hole is manufactured in the center of the diamond-shaped hydrophilic pattern. The surface of the cathode plate front surface other than the diamond-shaped hydrophilic pattern is manufactured with a hydrophobic portion, thereby forming an alternating arrangement of the hydrophobic portion and the diamond-shaped hydrophilic pattern on the cathode plate front surface, so as to form a hydrophilic-hydrophobic coupling surface.

[0009] Furthermore, the solid-liquid contact angle of the surface of the diamond-shaped hydrophilic pattern is 0° to 60°; and the solid-liquid contact angle of the hydrophobic portion is 90° to 160°.

[0010] Furthermore, the solid-liquid contact angle of the surface of the diamond-shaped hydrophilic pattern is 0° to 10°; and the solid-liquid contact angle of the hydrophobic portion is 150° to 160°.

[0011] Furthermore, the longest diagonal length of the diamond-shaped hydrophilic pattern is 1 mm to 16 mm, and the smallest internal angle is 1° to 9°.

[0012] Furthermore, the through hole is circular, and the opening rate of the cathode plate is 45% to 55%.

[0013] Furthermore, the diameter of the drainage hole is 0.4 mm to 0.8 mm.

[0014] Furthermore, bolt holes are formed on the cathode plate.

[0015] The beneficial effects of the utility model are:

[0016] 1. The front surface of the cathode plate of the utility model is provided with a hydrophilic-hydrophobic coupling structure, so that the liquid water accumulated in the cathode gas diffusion layer can be captured and fixed on the diamond-shaped hydrophilic pattern in the first time, and the liquid water is further spontaneously and directionally discharged through the surface of the diamond-shaped hydrophilic pattern, thereby reducing the transmission resistance of the reaction gas, enhancing the mass transfer efficiency, alleviating water flooding, and thus improving the performance of the passive fuel cell.

[0017] 2. The utility model performs surface modification on the front surface of the cathode plate to separate the gas and liquid and conduct directional flow of the reaction products. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the structure of a fuel cell according to an embodiment of the utility model;

[0019] Figure 2 It is a schematic diagram of the three-dimensional structure of the front surface of the cathode plate;

[0020] Figure 3 It is a schematic diagram of the three-dimensional structure of the rear surface of the cathode plate;

[0021] Figure 4 It is a schematic diagram of the front surface of the cathode plate;

[0022] Figure 5 This is the schematic diagram of the discharge of cathode product liquid water;

[0023] Figure 6 These are the test diagrams of the cathode plate contact angle; (a) the solid-liquid contact angle of the hydrophobic part; (b) the solid-liquid contact angle of the hydrophilic diamond pattern surface.

[0024] 1. Fuel storage tank; 2. Anode plate; 3. Anode gas diffusion layer; 4. Membrane electrode; 5. Cathode gas diffusion layer; 6. Cathode plate; 7. Cathode plate front surface; 8. Cathode plate rear surface; 9. Bolt hole; 10. Through hole; 11. Diamond hydrophilic pattern; 12. Hydrophobic part; 13. Drain hole; 14. Flow field rib. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with specific embodiments and drawings. All technical and academic terms used in the following embodiments, unless otherwise specified, have the same conventional meanings as those in the technical field to which the present invention belongs.

[0026] This embodiment discloses a passive fuel cell cathode plate. The fuel is liquid methanol or the like.

[0027] Combination Figure 1 The battery disclosed in this embodiment includes a fuel storage tank 1, an anode plate 2, an anode gas diffusion layer 3, a membrane electrode 4, a cathode gas diffusion layer 5, and a cathode plate 6.

[0028] Combination Figure 2-Figure 4 The cathode plate 6 involved in the utility model is a 316L stainless steel plate with a size of 16mm×16mm and a thickness of 0.5mm, and includes: a plate body, a plurality of evenly distributed through holes 10 are manufactured in the middle of the plate body; the plate body has a cathode plate front surface 7 and a cathode plate rear surface 8, the cathode plate front surface 7 is the surface of the cathode plate 6 facing the battery cathode gas diffusion layer 5, and the cathode plate rear surface 8 is the surface of the cathode plate 6 facing the outside air. The flow field rib 14 of the cathode plate front surface 7 is made with a diamond-shaped hydrophilic pattern 11, and a drainage hole 13 is made in the center of the diamond-shaped hydrophilic pattern 11. The surface of the cathode plate front surface 7 except the diamond-shaped hydrophilic pattern 11 is made into a hydrophobic portion 12, so that the hydrophobic portion 12 and the diamond-shaped hydrophilic pattern 11 are alternately arranged on the cathode plate front surface 7, so as to form a hydrophilic-hydrophobic coupling surface.

[0029] The cathode plate 6 is also provided with bolt holes 9 for fixing.

[0030] The array of through holes 10 and drainage holes 13 formed on the cathode plate 6 are manufactured by the "double-sided photolithography-double-sided etching" processing technology. Circular holes are photoetched on the front surface 7 and the rear surface 8 of the cathode plate respectively. Then, stainless steel etching is used to etch both sides of the plate simultaneously until they are penetrated, and finally the photoresist is removed.

[0031] In this embodiment, the type of flow field is a point flow field; the through hole 10 is preferably circular with a diameter of 3 mm, and the opening rate of the cathode plate 6 is 45% to 55%; the width of the flow field rib 14 is 1 mm and the length is 16 mm; the longest diagonal length of the diamond-shaped hydrophilic pattern 11 is 1 mm to 16 mm, the smallest inner angle is 1° to 9°, preferably 9°, and the diameter of the drainage hole 13 is 0.4 mm to 0.8 mm, preferably 0.5 mm.

[0032] Hydrophobicity means that the contact angle of the liquid drop is greater than 90° and less than 180°; hydrophilicity means that the contact angle of the liquid drop is greater than or equal to 0° and less than 60°. In this embodiment, the solid-liquid contact angle of the surface of the diamond-shaped hydrophilic pattern 11 is 0° to 60°, preferably 0° to 10°; the solid-liquid contact angle of the hydrophobic portion 12 is 90° to 160°, preferably 150° to 160°.

[0033] The preparation process of surface modification of the cathode plate 6 in this embodiment is as follows: first, select an area on the front surface 7 of the cathode plate, use a nanosecond laser device to perform laser etching, and construct a micro-nanoscale concave-convex structure, then immerse the front surface 7 of the cathode plate in a low surface energy modification solution, take it out after a suitable time, let it air dry naturally, and then place it in a vacuum drying oven and heat it at 150°C, thereby preparing a super-hydrophobic cathode plate front surface 7. At this time, the front surface 7 of the cathode plate exhibits low-adhesion super-hydrophobicity. Furthermore, the flow field ribs 14 of the front surface 7 of the cathode plate are partially laser etched again to etch away the low surface energy film in the rhombus area, so that the etched rhombus area becomes hydrophilic, thereby forming a rhombus hydrophilic pattern 11, such as Figure 4 shown.

[0034] When the battery is working, Figure 1 As shown, the reaction gas oxygen enters the cathode gas diffusion layer 5 from the array of through holes 10, reacts at the membrane electrode 4, and then the reaction product liquid water enters the cathode gas diffusion layer 5, reaches the surface of the cathode gas diffusion layer 5 facing the flow field, and accumulates in the cathode flow field.

[0035] In this embodiment, the cathode product liquid water will be captured by the diamond hydrophilic pattern 11 at the first time; further, when the water production of the fuel cell is too large, the Laplace pressure of the wedge-shaped tip of the diamond hydrophilic pattern 11 is greater than the Laplace pressure of the wedge-shaped wide end at the center of the diamond hydrophilic pattern 11, thereby generating an unbalanced Laplace pressure gradient; under the action of the Laplace pressure gradient, the cathode product liquid water will spontaneously move from the wedge-shaped tip of the diamond hydrophilic pattern 11 to the drainage hole 13 at the center of the diamond hydrophilic pattern 11, so that the excess cathode product liquid water is discharged from the flow field in a directional manner. This greatly alleviates the problem of cathode flooding in the fuel cell, reduces the transmission resistance of the reaction gas, enhances the mass transfer efficiency, alleviates flooding, and thus improves the performance of the passive fuel cell.

[0036] The principle of discharge of cathode product liquid water is as follows:

[0037] The diamond-shaped hydrophilic pattern 11 is composed of two symmetrical wedge-shaped structures. The wedge-shaped structure has a geometric shape gradient. Looking at the left half of the diamond-shaped hydrophilic pattern 11 alone, the difference in hydrophilic and hydrophobic surface energy on both sides of the wedge-shaped structure causes the droplets to be confined within the wedge-shaped structure area, and then the droplets are squeezed within the wedge angle, resulting in a curved interface, thereby generating a Laplace pressure difference.

[0038] The Laplace pressure difference on the droplet on one side of the wedge tip is: The Laplace pressure difference on the droplet at the wide end of the wedge is: From geometric relationships and trigonometric functions, we get , is the surface tension, is the droplet curvature radius, is the wedge angle, is the trajectory length of the droplet on one side of the wedge tip, is the length of the droplet’s trajectory on the wide end of the wedge, is the trajectory length of the droplet on the wedge surface, is the contact angle of the droplet on the wedge surface, is the radius of curvature of the droplet cross section on the wedge surface, is the radius of curvature of the droplet cross section on the wedge tip side, is the radius of curvature of the droplet cross section on the wide end of the wedge, is the contact line width between the droplet and the wedge surface, is the contact line width between the droplet and the wedge surface on the wedge tip side, is the contact line width between the droplet and the wedge surface at the wide end of the wedge. Along The positive direction of the axis gradually increases, making , Thus, it is concluded Therefore, under the driving effect of the Laplace pressure difference, the droplet will spontaneously move from the tip of the wedge to the wide end of the wedge, and finally move to the drainage hole 13, and discharge the flow field through the drainage hole 13. See the schematic diagram Figure 5 .

[0039] The diamond hydrophilic pattern 11 is composed of two left-right symmetrical wedge-shaped structures, and the drainage holes 13 are located at the wide ends of the two wedge-shaped structures, so the droplets will move from the wedge-shaped tips of the diamond hydrophilic pattern 11 to the drainage holes 13 at the center of the diamond hydrophilic pattern 11, so that excess cathode product liquid water is discharged from the flow field in a direction.

[0040] Cathode plate contact angle test diagram Figure 6 , Figure 6 The solid-liquid contact angle of the hydrophobic portion 12 in (a) was tested to be 158°. Figure 6 The solid-liquid contact angle of the surface of the diamond-shaped hydrophilic pattern 11 in (b) is 0°.

[0041] The basic principle and beneficial effects of the technical solution of the utility model are described above.

[0042] The above embodiments of the utility model are only to help understand the utility model, and are not intended to limit the utility model. For those skilled in the art, various modifications are possible without departing from the scope of the utility model and the appended claims. The utility model is not limited to the contents provided by the above embodiments. All improvements and equivalent substitutions made within the spirit and scope of the utility model are included in the protection scope of the claims of the utility model.

Claims

1. A passive fuel cell cathode plate, comprising a plate body, wherein a plurality of evenly distributed through holes (10) are formed in the middle of the plate body; the plate body comprises a cathode plate front surface (7) and a cathode plate rear surface (8), wherein the cathode plate front surface (7) is a surface of the cathode plate (6) facing the battery cathode gas diffusion layer (5), and the cathode plate rear surface (8) is a surface of the cathode plate (6) facing the outside air, wherein: The flow field rib (14) of the cathode plate front surface (7) is provided with a diamond-shaped hydrophilic pattern (11), a drainage hole (13) is provided in the center of the diamond-shaped hydrophilic pattern (11), and the surface of the cathode plate front surface (7) other than the diamond-shaped hydrophilic pattern (11) is provided with a hydrophobic portion (12), so that the hydrophobic portion (12) and the diamond-shaped hydrophilic pattern (11) are alternately arranged on the cathode plate front surface (7), thereby forming a hydrophilic-hydrophobic coupling surface.

2. The passive fuel cell cathode plate according to claim 1, characterized in that: The solid-liquid contact angle of the surface of the diamond-shaped hydrophilic pattern (11) is 0° to 60°; and the solid-liquid contact angle of the hydrophobic portion (12) is 90° to 160°.

3. The passive fuel cell cathode plate according to claim 2, characterized in that: The solid-liquid contact angle of the surface of the diamond-shaped hydrophilic pattern (11) is 0° to 10°; and the solid-liquid contact angle of the hydrophobic portion (12) is 150° to 160°.

4. The passive fuel cell cathode plate according to claim 1, characterized in that: The longest diagonal length of the diamond-shaped hydrophilic pattern (11) is 1 mm to 16 mm, and the smallest internal angle is 1° to 9°.

5. The passive fuel cell cathode plate according to claim 1, characterized in that: The through hole (10) is circular, and the opening rate of the cathode plate (6) is 45% to 55%.

6. The passive fuel cell cathode plate according to claim 1, characterized in that: The diameter of the drainage hole (13) is 0.4 mm to 0.8 mm.

7. The passive fuel cell cathode plate according to claim 1, characterized in that: The cathode plate (6) is also provided with a bolt hole (9).

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