Fuel cell single cell and fuel cell stack

Abstract

The application provides a fuel cell single cell, and belongs to the technical field of fuel cells, and solves the problem of low active area utilization rate of a fuel cell membrane electrode in the prior art. The fuel cell is characterized in that the distance L1 between the edge of the active area of the cathode catalyst layer and the edge of the outermost flow channel of the cathode bipolar plate, and the distance L2 between the edge of the active area of the anode catalyst layer and the edge of the outermost flow channel of the anode bipolar plate satisfy the following formula to reduce the gas flow resistance: L1=(P 11 -P 12 ) / [k1(Q 11 -Q 12 )], and L2=(P 21 -P 22 ) / [k2(Q 21 -Q 22 )]. P 11 is the gas pressure in the cathode flow channel, P 12 is the gas pressure at the edge of the active area of the cathode catalyst layer, Q 11 is the gas flow rate of a single cathode flow channel, Q 12 is the minimum tolerable gas flow rate of the membrane electrode in a single cathode flow channel, P 21 is the gas pressure in the anode flow channel, P 22 is the gas pressure at the edge of the active area of the anode catalyst layer, Q 21 is the gas flow rate of a single anode flow channel, Q 22 is the minimum tolerable gas flow rate of the membrane electrode in a single anode flow channel, and k is a coupling influence factor.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a fuel cell single cell and a fuel cell stack. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are devices that generate electricity through the reaction of hydrogen and oxygen, characterized by high efficiency, high environmental adaptability, and clean, pollution-free operation. With the continuous development of fuel cell-powered heavy-duty trucks, higher power and efficiency requirements are being placed on onboard fuel cells within limited space.

[0003] Membrane electrode assembly (MEA), as the core of a fuel cell, provides the site for electrochemical reactions. Hydrogen undergoes oxidation at the anode, and the resulting protons travel through the solid electrolyte in the MEA to the cathode, where they react with oxygen to produce clean water. This series of reactions occurs in the active region of the MEA. However, currently, the active region of the MEA accounts for less than 50% of the total area of ​​the fuel cell, resulting in significant loss of active area. This leads to reduced output power and efficiency of the fuel cell within a limited size, making it difficult to meet market demands.

[0004] The proportion of the active region in a membrane electrode is determined by the current design of the electrode plates. Membrane electrodes and bipolar plates are used in combination. The area of ​​a membrane electrode mainly consists of the sealing area, gas distribution area, insulation area, and active region area. The current main issue is that the proportion of the active region is insufficient. Summary of the Invention

[0005] Based on the above analysis, the embodiments of the present invention aim to provide a fuel cell single cell and a fuel cell stack to solve the problem of low utilization rate of active area of ​​membrane electrode assembly in existing fuel cells.

[0006] On one hand, embodiments of the present invention provide a single fuel cell, including a proton exchange membrane, a cathode catalyst layer, a cathode gas diffusion layer, and a cathode bipolar plate sequentially stacked on one side of the proton exchange membrane, and an anode catalyst layer, an anode gas diffusion layer, and an anode bipolar plate sequentially stacked on the other side of the proton exchange membrane. The distance L1 between the edge of the active region of the cathode catalyst layer and the edge of the outermost flow channel of the cathode bipolar plate, and the distance L2 between the edge of the active region of the anode catalyst layer and the edge of the outermost flow channel of the anode bipolar plate satisfy the relationship in the following formula to reduce gas flow resistance:

[0007] L1=(P 11 -P 12 ) / [k1(Q 11 -Q 12 )],

[0008] L2=(P 21 -P 22) / [k2(Q 21 -Q 22 )],

[0009] In the formula, P 11 P is the gas pressure in the cathode channel. 12 Q is the gas pressure at the edge of the active region of the cathode catalyst layer. 11 Q represents the gas flow rate of a single cathode channel. 12 P represents the minimum tolerable gas flow rate for a membrane electrode in a single cathode channel. 21 P is the gas pressure in the anode channel. 22 Q represents the gas pressure at the edge of the active region of the anode catalyst layer. 21 Q represents the gas flow rate of a single anode channel. 22 K is the minimum tolerable gas flow rate of the membrane electrode in a single anode channel, k1 is the cathode coupling influence factor, and k2 is the anode coupling influence factor.

[0010] The beneficial effects of the above technical solution are as follows: A design scheme that optimizes the utilization rate of the active area of ​​the fuel cell membrane electrode assembly (MEA) is designed. By limiting the distance between the edge of the active region and the edge of the outermost flow channel, the active area of ​​the MEA can be increased without reliability issues such as insufficient gas supply, thus achieving the goal of increasing the proportion of the active region area. The output power of the fuel cell is improved while maintaining the efficiency and volume unchanged.

[0011] Based on further improvements to the above device, the cathode coupling influence factor k1 and the anode coupling influence factor k2 satisfy the following relationship:

[0012] k1 = f(a1, b1, c1),

[0013] R1 = k1l1,

[0014] k2 = f(a2, b2, c2),

[0015] R2 = k2l2,

[0016] In the formula, R1 is the set cathode gas flow resistance, R2 is the set anode gas flow resistance, l1 is the distance from the edge of the inner cathode frame of the membrane electrode to the edge of the outermost flow channel of the cathode bipolar plate, l2 is the distance from the edge of the inner anode frame of the membrane electrode to the edge of the outermost flow channel of the anode bipolar plate, a1 is the porosity of the cathode bipolar plate, a2 is the porosity of the anode bipolar plate, b1 is the pore size of the cathode bipolar plate, b2 is the pore size of the anode bipolar plate, c1 is the pore size distribution coefficient of the cathode bipolar plate, c2 is the pore size coefficient of the anode bipolar plate, and f() is the fitting function.

[0017] Furthermore, the fuel cell employs a symmetrical structural design, with the cathode catalyst layer aligned with the outer edge of the flow channel on the cathode bipolar plate, and the anode catalyst layer aligned with the outer edge of the flow channel on the anode bipolar plate, to allow for the introduction of sufficient reactant gas; and satisfies the following relationship:

[0018] L1 = L2,

[0019] a1 = a2,

[0020] b1 = b2,

[0021] c1 = c2.

[0022] Furthermore, the cathode bipolar plate and the anode bipolar plate are respectively provided with a gas inlet and a gas outlet, and the gas inlet and gas outlet are connected by a flow channel; and...

[0023] On the surfaces of both the cathode and anode bipolar plates facing the proton exchange membrane, several longitudinally extending and equidistantly distributed plate ridges are formed. Plate grooves are formed between two adjacent plate ridges to increase the contact area between the reactant gas and the membrane electrode while reducing the flow resistance.

[0024] Furthermore, in the cathode bipolar plate and the anode bipolar plate, the height of the active region flow channel is greater than the height of the overlapping region flow channel, and also greater than the height of the inactive region flow channel.

[0025] Furthermore, the flow channels of both the cathode bipolar plate and the anode bipolar plate are either direct-flow or serpentine flow channels; and,

[0026] Within the active region, all electrode ridges have the same dimensions, and all electrode grooves have the same dimensions.

[0027] Furthermore, the set gas flow resistance R is less than or equal to 29 kPa.

[0028] Furthermore, the opening width of each electrode groove gradually decreases along the concave direction, and the width of each electrode ridge gradually decreases along the convex direction; and,

[0029] The bottom surface of each electrode slot and the top surface of each electrode ridge are horizontal planes.

[0030] Furthermore, each electrode groove and each electrode ridge is symmetrical about left and right with respect to its respective centerline.

[0031] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0032] 1. The membrane electrode frame was designed so that the cathode catalyst layer is aligned with the outer edge of the flow channel on the cathode bipolar plate, and the anode catalyst layer is aligned with the outer edge of the flow channel on the anode bipolar plate, so as to allow sufficient reaction gas to be introduced.

[0033] 2. By designing the porosity (a), pore size (b), and pore size distribution coefficient (c) of the bipolar plate, the gas flow resistance can be kept as low as possible.

[0034] On the other hand, embodiments of the present invention provide a fuel cell stack, comprising a plurality of the above-mentioned fuel cell individual cells, all of which are stacked sequentially to form a fuel cell stack.

[0035] The summary section is provided to present the chosen concepts in a simplified form, which will be further described in the detailed description below. The summary section is not intended to identify essential or essential features of the invention, nor is it intended to limit the scope of the invention. Attached Figure Description

[0036] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same parts.

[0037] Figure 1 A schematic diagram of the single cell composition of the fuel cell in Example 1 or 2 is shown;

[0038] Figure 2 A schematic diagram of parameter settings for Embodiment 1 or 2 is shown;

[0039] Figure 3 A schematic diagram of cathode air propagation is shown in Example 1 or 2.

[0040] Figure Labels

[0041] 1-Proton exchange membrane; 2-Cathode catalyst layer; 3-Cathode gas diffusion layer; 4-Cathode bipolar plate; 5-Plate ridge; 6-Plate groove; 7-Anode catalyst layer; 8-Anode gas diffusion layer; 9-Anode bipolar plate; P 11 -Gas pressure in the cathode channel; P 12 -Gas pressure at the edge of the active region of the cathode catalyst layer; Q 11 - Gas flow rate of a single cathode channel; P 21 -Gas pressure in the anode channel; P 22 -Gas pressure at the edge of the active region of the anode catalyst layer;

[0042] Q 21 - Gas flow rate of a single anode channel. Detailed Implementation

[0043] Embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0044] The term "comprising" and its variations as used herein signify open inclusion, i.e., "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "at least partially based on". The terms "one example embodiment" and "one embodiment" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". The terms "first", "second", etc., may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0045] Example 1

[0046] One embodiment of the present invention discloses a fuel cell single cell, comprising a proton exchange membrane, a cathode catalyst layer, a cathode gas diffusion layer (cathode GDL), and a cathode bipolar plate sequentially stacked on one side of the proton exchange membrane, and an anode catalyst layer, an anode gas diffusion layer (anode GDL), and an anode bipolar plate sequentially stacked on the other side of the proton exchange membrane. Figure 1 As shown, but not limited to Figure 1 The structure is understandable to those skilled in the art.

[0047] The distance L1 from the edge of the active region of the cathode catalyst layer to the edge of the outermost flow channel of the cathode bipolar plate, and the distance L2 from the edge of the active region of the anode catalyst layer to the edge of the outermost flow channel of the anode bipolar plate, satisfy the relationship in the following formula to reduce gas flow resistance:

[0048] L1=(P 11 -P 12 ) / [k1(Q 11 -Q 12 )],

[0049] L2=(P 21 -P 22 ) / [k2(Q 21 -Q 22 (1)

[0050] In the formula, P 11 P is the gas pressure in the cathode channel. 12 Q is the gas pressure at the edge of the active region of the cathode catalyst layer. 11 Q represents the gas flow rate of a single cathode channel. 12P represents the minimum tolerable gas flow rate for a membrane electrode in a single cathode channel. 21 P is the gas pressure in the anode channel. 22 Q represents the gas pressure at the edge of the active region of the anode catalyst layer. 21 Q represents the gas flow rate of a single anode channel. 22 K1 represents the minimum tolerable gas flow rate of the membrane electrode in a single anode channel, K2 represents the cathode coupling influence factor, and K3 represents the anode coupling influence factor. Figure 2 As shown.

[0051] The above-mentioned k1 and k2 can be obtained through experimental calibration or through the method described in Example 2.

[0052] The derivation process is as follows: Figure 3 As shown, gas enters the gas diffusion layer (GDL) from the flow channel of the bipolar plate. Mass transfer occurs within the GDL plane, and the gas diffuses into the non-flow channel region of the bipolar plate. The catalyst layer in contact with this region can still absorb the gas and react. In this process, the gas flow rate and pressure difference are related:

[0053] Q = P / R (2)

[0054] In the formula, Q is the gas flow rate difference between the edge of the active zone and the flow channel; P is the gas pressure difference between the edge of the active zone and the flow channel; and R is the gas flow resistance.

[0055] The ability of gas to diffuse within the GDL surface is related to the GDL's inherent properties, with directly related parameters including porosity, pore size, and pore size distribution. These parameters are interdependent and affect the mass transfer of the membrane electrode in the form of gas flow resistance R. According to experimental results, the gas flow resistance R is related to the distance of the measurement point from the edge of the outermost channel. That is:

[0056] R = kL (3)

[0057] In the formula, L is the distance from the measurement point to the outermost edge of the flow channel of the cathode bipolar plate or anode bipolar plate; k is the influence factor coupled with the physical properties of GDL materials such as porosity, pore size, and pore size distribution.

[0058] During the design process, the metering ratio range that the membrane electrode can adapt to must be considered. If the gas flow rate of a single channel calculated based on the design metering ratio is Q1, the minimum tolerable gas flow rate of the membrane electrode in a single channel can be calculated in the same way as Q2.

[0059] Since pressure is one of the main causes of gas diffusion, this design scheme also needs to consider the pressure difference between the edge of the active region and the outermost root channel. In general membrane electrode frame designs, there is no gas flow at the edge of the active region, so P2 is often 0 kPa. From the above analysis, the distance L from the edge of the active region to the edge of the outermost channel can be obtained, see the above formula (1).

[0060] In implementation, taking Company A's electrode plate and matching membrane electrode as an example, the original design had an active area of ​​315 cm². 2 The active area accounts for 49.2% of the total area, and the resulting fuel cell stack has a power output of 78.1 kW at 630 A. After adopting the above design scheme, the active area is increased to 326 cm². 2 The active area accounts for 51.2% of the total area, and the resulting fuel cell stack has a power output of 80.7 kW at 630 A. This demonstrates that the overall output power of the fuel cell stack is increased by 3.5% without affecting efficiency or size.

[0061] Compared with existing technologies, this embodiment provides a design scheme that optimizes the utilization rate of the active area of ​​the fuel cell membrane electrode assembly (MEA). By limiting the distance between the edge of the active region and the edge of the outermost flow channel, the active area of ​​the MEA can be increased without reliability issues such as insufficient gas supply, thus achieving the goal of increasing the proportion of the active region area. This improves the output power of the fuel cell while maintaining efficiency and volume.

[0062] Example 2

[0063] Based on Example 1, improvements are made, and the cathode coupling influence factor k1 and the anode coupling influence factor k2 satisfy the following formula relationship:

[0064] k1 = f(a1, b1, c1)

[0065] R1=k1l1

[0066] k2 = f(a2, b2, c2)

[0067] R2=k2l2 (4)

[0068] In the formula, R1 is the set cathode gas flow resistance, R2 is the set anode gas flow resistance, l1 is the distance from the cathode measurement point (the edge of the inner cathode frame of the membrane electrode) to the outermost flow channel edge of the cathode bipolar plate, l2 is the distance from the anode measurement point (the edge of the inner anode frame of the membrane electrode) to the outermost flow channel edge of the anode bipolar plate, a1 is the porosity of the cathode bipolar plate, a2 is the porosity of the anode bipolar plate, b1 is the pore size of the cathode bipolar plate, b2 is the pore size of the anode bipolar plate, c1 is the pore size distribution coefficient of the cathode bipolar plate, c2 is the pore size coefficient of the anode bipolar plate, and f() is the fitting function, obtained through calibration.

[0069] Preferably, the fuel cell employs a symmetrical structural design, with the cathode catalyst layer aligned with the outer edge of the flow channel on the cathode bipolar plate, and the anode catalyst layer aligned with the outer edge of the flow channel on the anode bipolar plate, to allow for the introduction of sufficient reactant gas. Furthermore, it satisfies...

[0070] L1 = L2,

[0071] a1 = a2,

[0072] b1 = b2,

[0073] c1 = c2 (5)

[0074] Preferably, the cathode bipolar plate and the anode bipolar plate are respectively provided with a gas inlet and a gas outlet, and the gas inlet and gas outlet are connected by a flow channel. Furthermore, as... Figures 2-3 As shown, several longitudinally extending and equidistantly distributed electrode ridges are formed on the surfaces of the cathode bipolar plate and the anode bipolar plate facing the proton exchange membrane. An electrode groove is formed between two adjacent electrode ridges to increase the contact area between the reactant gas and the membrane electrode while reducing the flow resistance.

[0075] Preferably, in the cathode bipolar plate and the anode bipolar plate, the height of the active region flow channel is 0.02–0.9 mm greater than the height of the overlapping region flow channel, and the height of the active region flow channel is 0.02–0.9 mm greater than the height of the inactive region flow channel. This dimensional design ensures that the heights of all regions (active region, overlapping region, and inactive region) of the bipolar plate are consistent during encapsulation.

[0076] Preferably, the flow channels of both the cathode bipolar plate and the anode bipolar plate are either direct-flow or serpentine flow channels. Furthermore, within the active region, the dimensions of all plate ridges and all plate grooves are identical, which helps to save on processing costs.

[0077] Preferably, based on the design requirements of the membrane electrode assembly (MEA), the gas flow resistance R should be less than or equal to 29 kPa. Specifically, for the anode, since it uses hydrogen and water, the anode flow resistance can be designed to be R2 < 19 kPa. For the cathode, since it uses air, the cathode flow resistance can be designed to be R1 < 29 kPa, thereby indirectly improving the utilization rate of the active area of ​​the fuel cell MEA.

[0078] Preferably, the opening width of each electrode groove gradually decreases along the concave direction, and the width of each electrode ridge gradually decreases along the convex direction. Furthermore, the bottom surface of each electrode groove and the top surface of each electrode ridge are both horizontal planes.

[0079] Preferably, each electrode groove and each electrode ridge are symmetrical about their respective centerlines.

[0080] Compared with the prior art, the fuel cell single cell provided in this embodiment has the following beneficial effects:

[0081] 1. The membrane electrode frame was designed so that the cathode catalyst layer is aligned with the outer edge of the flow channel on the cathode bipolar plate, and the anode catalyst layer is aligned with the outer edge of the flow channel on the anode bipolar plate, so as to allow sufficient reaction gas to be introduced.

[0082] 2. By designing the porosity (a), pore size (b), and pore size distribution coefficient (c) of the bipolar plate, the gas flow resistance can be kept as low as possible.

[0083] Example 3

[0084] The present invention also discloses a fuel cell stack, comprising several fuel cell single cells as described in Embodiment 1 or 2, wherein all fuel cell single cells are stacked sequentially to form a fuel cell stack.

[0085] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical applications, or improvements to the prior art of the embodiments, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A single fuel cell, comprising a proton exchange membrane, a cathode catalyst layer, a cathode gas diffusion layer, and a cathode bipolar plate sequentially stacked on one side of the proton exchange membrane, and an anode catalyst layer, an anode gas diffusion layer, and an anode bipolar plate sequentially stacked on the other side of the proton exchange membrane, characterized in that, The distance L1 from the edge of the active region of the cathode catalyst layer to the edge of the outermost flow channel of the cathode bipolar plate, and the distance L2 from the edge of the active region of the anode catalyst layer to the edge of the outermost flow channel of the anode bipolar plate, satisfy the relationship in the following formula to reduce gas flow resistance: L1=(P 11 -P 12 ) / [k1(Q 11 -Q 12 )], L2=(P 21 -P 22 ) / [k2(Q 21 -Q 22 )], In the formula, P 11 P is the gas pressure in the cathode channel. 12 Q is the gas pressure at the edge of the active region of the cathode catalyst layer. 11 Q represents the gas flow rate of a single cathode channel. 12 P represents the minimum tolerable gas flow rate for a membrane electrode in a single cathode channel. 21 P is the gas pressure in the anode channel. 22 Q represents the gas pressure at the edge of the active region of the anode catalyst layer. 21 Q represents the gas flow rate of a single anode channel. 22 K is the minimum tolerable gas flow rate of the membrane electrode in a single anode channel, k1 is the cathode coupling influence factor, and k2 is the anode coupling influence factor. The cathode coupling influence factor k1 and the anode coupling influence factor k2 satisfy the following formula: k1=f(a1,b1,c1), R1=k1 L1, k2=f(a2,b2,c2), R2=k2 L2, In the formula, R1 is the set cathode gas flow resistance, R2 is the set anode gas flow resistance, L1 is the distance from the edge of the active region of the cathode catalyst layer to the edge of the outermost flow channel of the cathode bipolar plate, L2 is the distance from the edge of the active region of the anode catalyst layer to the edge of the outermost flow channel of the anode bipolar plate, a1 is the porosity of the cathode bipolar plate, a2 is the porosity of the anode bipolar plate, b1 is the pore size of the cathode bipolar plate, b2 is the pore size of the anode bipolar plate, c1 is the pore size distribution coefficient of the cathode bipolar plate, c2 is the pore size coefficient of the anode bipolar plate, and f() is the fitting function.

2. The fuel cell single cell according to claim 1, characterized in that, The fuel cell employs a symmetrical structural design, with the cathode catalyst layer aligned with the outer edge of the flow channel on the cathode bipolar plate, and the anode catalyst layer aligned with the outer edge of the flow channel on the anode bipolar plate, to allow for the introduction of sufficient reactant gas; and satisfies the following relationship: L1=L2, a1=a2, b1=b2, c1=c2.

3. The fuel cell single cell according to claim 2, characterized in that, The cathode bipolar plate and the anode bipolar plate are respectively provided with a gas inlet and a gas outlet, which are connected by a flow channel; and... On the surfaces of both the cathode and anode bipolar plates facing the proton exchange membrane, several longitudinally extending and equidistantly distributed plate ridges are formed. Plate grooves are formed between two adjacent plate ridges to increase the contact area between the reactant gas and the membrane electrode while reducing the flow resistance.

4. The fuel cell single cell according to claim 3, characterized in that, In both the cathode and anode bipolar plates, the height of the flow channel in the active region is greater than the height of the flow channel in the overlapping region, and also greater than the height of the flow channel in the inactive region.

5. The fuel cell single cell according to claim 4, characterized in that, Both the cathode and anode bipolar plates have direct-flow or serpentine flow channels; and, Within the active region, all electrode ridges have the same dimensions, and all electrode grooves have the same dimensions.

6. The fuel cell single cell according to claim 5, characterized in that, The set gas flow resistance R is less than or equal to 29 kPa.

7. The fuel cell single cell according to any one of claims 3-6, characterized in that, The opening width of each electrode groove gradually decreases along the concave direction, and the width of each electrode ridge gradually decreases along the convex direction; and... The bottom surface of each electrode slot and the top surface of each electrode ridge are horizontal planes.

8. The fuel cell single cell according to claim 7, characterized in that, Each electrode slot and each electrode ridge is symmetrical about its own centerline.

9. A fuel cell stack, characterized in that, It includes several fuel cell units as described in any one of claims 1-8, and all fuel cell units are stacked sequentially to form a fuel cell stack.

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