Fuel cell flexible graphite bipolar plate gas side seal structure and fuel cell stack

Abstract

The present application belongs to the technical field of proton exchange membrane fuel cell preparation, and particularly relates to a fuel cell flexible graphite polar plate gas side sealing structure and a fuel cell stack. The present application is provided with a concave line groove coated with epoxy glue in the sealing groove, and the elastic sealing rubber ring is tightly bonded with the flexible graphite polar plate through the transition glue layer as an intermediate material, so that the problem of low adhesion between the flexible graphite polar plate and the sealing rubber line is solved. In the process of stack integration, the stacked polar plates will produce a certain stacking error, thereby producing a lateral shear force at the top position of the sealing rubber line. The use of this structure can reduce the risk of the sealing line peeling off from the surface of the flexible polar plate under the action of lateral force.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membrane fuel cell manufacturing technology, specifically relating to a flexible graphite electrode gas-side sealing structure for fuel cells and a fuel cell stack. Background Technology

[0002] The gas field sealing design of bipolar plates in proton exchange membrane fuel cells (PEMFCs) is a core technology of the fuel cell stack, affecting safety, performance, lifespan, and industrialization. It is crucial to the feasibility and reliability of mass production of the plates. Under current processes, fuel cell stacks consist of multiple bipolar plates and membrane electrode assemblies (MEAs) stacked in series. The sealing performance between the plates directly determines the stack's performance level and safety reliability, making it a core factor influencing the overall performance of the stack. The quality of the sealing has a decisive impact on the stack's overall efficiency and operational safety. During assembly, the lateral shear force between the adhesive lines caused by plate misalignment, coupled with low adhesion, can easily lead to the separation of the sealing adhesive lines from the flexible graphite plates.

[0003] In existing technologies, the gas field sealing of bipolar plates is often achieved by dispensing liquid silicone into the sealing groove of the bipolar plate using a dispensing machine, then heating and curing it into a sealing line. The sealing effect is achieved by compressing the gas field sealing line. However, due to the inherent characteristics of flexible graphite materials, the adhesion between the flexible graphite bipolar plate and the cured silicone rubber sealing strip is relatively low. Moreover, due to stacking errors of each piece during assembly, the gas field sealing strip of the anode and cathode plates is prone to peeling off from the flexible plate under lateral forces due to its low adhesion.

[0004] To address the above issues, existing technologies have explored various improvement solutions: Patent application CN114784314A, for example, recognized the difficulty in bonding graphite bipolar plates and proposed applying a primer (liquid epoxy resin, polyisocyanate resin) to the bottom of the sealing groove to form a coating, thereby improving the adhesion between the plates and the sealant. However, this approach only forms a thin surface coating (10-30 μm) and lacks a structural design to resist lateral shear forces. Furthermore, the primer resin used has a high viscosity (300-5000 cps), limiting its penetration into the pores of the graphite surface, and the coating requires heating (90-130℃) for curing, thus limiting production efficiency. This technology also fails to consider the impact of lateral shear forces generated by plate misalignment during fuel cell assembly on the peeling of the sealant strip.

[0005] For example, the utility model with publication number CN214477569U adopts a structure combining a sealing ring and an elastic adhesive layer, with the elastic adhesive layer covering the surfaces of the sealing ring and the bipolar plate to fill assembly gaps. However, this technology mainly addresses the interface sealing between the membrane electrode and the bipolar plate, rather than the adhesion between the sealing strip body and the electrode plate; its elastic adhesive layer is a surface covering structure (only 1-10 μm thick), which cannot effectively anchor the sealing strip against lateral peeling; furthermore, this technology also does not address the technical challenge of the sealing strip peeling off the flexible graphite electrode plate under lateral shear force.

[0006] Patent application CN115548376A proposes a two-layer bonding method using "instant adhesive + primer." First, a low-viscosity instant adhesive (cyanoacrylate) is applied to penetrate the pores of the graphite surface. After curing, a primer is applied, and finally, a sealant is applied. Compared to the aforementioned methods, this technology significantly improves vertical tensile peel strength (0.03N → 0.36N), but it still has significant shortcomings: First, this technology addresses the problem of insufficient static adhesion, failing to recognize or solve the problem of lateral shear force peeling caused by electrode stacking errors during fuel cell assembly; second, the cured instant adhesive is a hard and brittle material, prone to brittle fracture under lateral shear force, potentially becoming a weak point; third, the two-layer coating and two-stage curing process is complex, resulting in low production efficiency; finally, this technology does not incorporate any physical anchoring structure in the sealing groove to resist lateral shear force, leaving the sealant strip's resistance to lateral peeling insufficient.

[0007] In summary, existing technologies all focus on improving the static bonding strength between the sealant and the graphite electrode plate through chemical bonding enhancement methods. However, none of them have addressed the core engineering problem of sealant strip peeling caused by lateral shear forces resulting from electrode plate stacking errors during fuel cell assembly. How to enhance interfacial adhesion through structural design while simultaneously endowing the sealing structure with the ability to resist assembly lateral shear forces has become a pressing technical challenge in this field. Therefore, developing a method to solve the low adhesion strength between flexible graphite electrode plates and gas-side sealant strips in fuel cells is of great significance. Summary of the Invention

[0008] To address the aforementioned technical problems in the prior art, this invention provides a sealing structure to solve the problem of low adhesion of the sealing strip on flexible graphite electrode plates.

[0009] To achieve the above objectives, the present invention provides a gas-side sealing structure for a flexible graphite electrode plate in a fuel cell, comprising a membrane electrode frame and two graphite bipolar plates that clamp the membrane electrode frame. A sealing groove is formed on the graphite bipolar plates, and a transition adhesive layer is provided on the bottom surface of the sealing groove. A sealing ring is then provided on the transition adhesive layer.

[0010] Furthermore, at least a portion of the bottom surface of the sealing groove is provided with a transition adhesive layer; the area covered by the sealing ring at least partially overlaps with the transition adhesive layer.

[0011] The sealing ring is fixed in the sealing groove by bonding, dispensing, or injection molding.

[0012] Furthermore, the transition adhesive layer is laid flat on the bottom surface of the sealing groove; Alternatively, the bottom surface of the sealing groove is provided with a concave groove, and the transition adhesive layer is located in the concave groove; Alternatively, the bottom surface of the sealing groove is provided with a concave groove, the bottom of the transition adhesive layer is filled with the concave groove, and the top surface protrudes and lies flat on the bottom surface of the sealing groove.

[0013] Preferably, the thickness of the transition adhesive layer laid flat on the bottom surface of the sealing groove is ≤0.05mm.

[0014] Preferably, the depth of the concave groove is 0.05~0.1mm and the width is 0.2~0.5mm. The main function of the concave groove is to store the applied epoxy sealant.

[0015] Preferably, the number of the concave grooves is 1 to 4 along the width direction of the sealing groove; each concave groove is continuously or intermittently distributed along the length direction of the sealing groove.

[0016] Preferably, the side of the sealing ring facing the membrane electrode frame is curved, or the cross-section of the sealing ring is rectangular.

[0017] Furthermore, the transition adhesive layer uses epoxy sealant.

[0018] The present invention also provides a fuel cell stack using the gas-side sealing structure of the flexible graphite electrode plate of the fuel cell.

[0019] Compared with existing technologies, the fuel cell sealing structure of this invention has the following advantages: A concave groove for applying epoxy adhesive is provided in the sealing groove, and a transition adhesive layer serves as an intermediate material, enabling the elastic sealing ring to bond tightly to the flexible graphite electrode plate, thus solving the problem of low adhesion between the flexible graphite electrode plate and the sealing adhesive line. During the stack integration process, the stacked electrode plates will produce certain stacking errors, resulting in lateral shear force at the top of the sealing ring. This structure reduces the risk of the sealing ring peeling off from the surface of the flexible electrode plate under lateral force. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of Embodiment 1 of the fuel cell sealing structure of the present invention; Figure 2This is a schematic diagram of Embodiment 2 of the fuel cell sealing structure of the present invention; Figure 3 This is a schematic diagram of Embodiment 3 of the fuel cell sealing structure of the present invention; Figure 4 This is a schematic diagram of Embodiment 4 of the fuel cell sealing structure of the present invention; Figure 5 This is a comparative example 1 schematic diagram of the fuel cell sealing structure of the present invention; The diagram is labeled as follows: 1. Membrane electrode frame; 2. First graphite bipolar plate; 3. Second graphite bipolar plate; 4. First sealing ring; 5. Second sealing ring; 6. Sealing groove; 7. Transition adhesive layer. Detailed Implementation

[0021] Example 1 A preferred embodiment of the fuel cell sealing structure of the present invention is that the fuel cell stack is composed of multiple sets of single cells stacked together, such as... Figure 1 As shown, the fuel cell sealing structure package is illustrated using a set of structures as an example.

[0022] The sealing structure is as follows Figure 1 As shown, the invention includes a membrane electrode frame (1) and at least two sets of graphite bipolar plates with sealing grooves and concave grooves, namely a first graphite bipolar plate (2) and a second graphite bipolar plate (3). The membrane electrode frame (1) is sandwiched between the first graphite bipolar plate (2) and the second graphite bipolar plate (3), specifically, it is arranged between the first sealing ring (4) and the second sealing ring (5) (the first graphite bipolar plate and the second graphite bipolar plate should be clamped and fitted together; this schematic diagram is used here for better illustration of the structure).

[0023] The bottom surface of the sealing groove (6) of the first graphite bipolar plate (2) and the second graphite bipolar plate (3) is provided with a concave groove. The sealing groove is 3mm wide and 0.3mm deep. The concave groove is 0.05mm deep and 0.5mm wide. In this embodiment, three concave grooves are intermittently distributed in the sealing groove of each graphite bipolar plate along the width direction of the sealing groove. The concave groove is provided with a transition adhesive layer (7). The transition adhesive layer is epoxy sealant.

[0024] As shown in the figure, the first sealing ring is applied to the sealing groove (6) of the first graphite bipolar plate (2), and the second sealing ring (3) is applied to the sealing groove (6) of the second graphite bipolar plate (3). The side of the first sealing ring facing the membrane electrode frame (1) is curved, and the side of the second sealing ring facing the membrane electrode frame (1) is also curved. Both the width of the first sealing ring and the height of the second sealing ring are 2 mm and 0.65 mm respectively.

[0025] In addition, the transition adhesive layer (7) is completely filled with the concave groove on the bottom surface of the sealing groove (6), and the surface of the groove is also coated with a flat epoxy adhesive layer of 0.05mm.

[0026] Example 2 A preferred embodiment of the fuel cell sealing structure of the present invention is that the fuel cell stack is composed of multiple sets of single cells stacked together, such as... Figure 2 As shown, the fuel cell sealing structure package is illustrated using a set of structures as an example.

[0027] The sealing structure is as follows Figure 2 As shown, the invention includes a membrane electrode frame (1) and at least two sets of graphite bipolar plates with sealing grooves and concave grooves, namely a first graphite bipolar plate (2) and a second graphite bipolar plate (3). The membrane electrode frame (1) is sandwiched between the first graphite bipolar plate (2) and the second graphite bipolar plate (3), specifically, it is arranged between the first sealing ring (4) and the second sealing ring (5) (the first graphite bipolar plate and the second graphite bipolar plate should be clamped and fitted together; this schematic diagram is used here for better illustration of the structure).

[0028] The bottom surface of the sealing groove (6) of the first graphite bipolar plate (2) and the second graphite bipolar plate (3) is provided with a concave groove. The sealing groove is 3mm wide and 0.3mm deep. The concave groove is 0.05mm deep and 0.5mm wide. In this embodiment, three concave grooves are intermittently distributed in the sealing groove of each graphite bipolar plate along the width direction of the sealing groove. The concave groove is provided with a transition adhesive layer (7). The transition adhesive layer is epoxy sealant.

[0029] As shown in the figure, the first sealing ring is applied to the sealing groove (6) of the first graphite bipolar plate (2), and the second sealing ring (3) is applied to the sealing groove (6) of the second graphite bipolar plate (3). The side of the first sealing ring facing the membrane electrode frame (1) is curved, and the width of the first sealing ring is 2 mm and the height is 0.65 mm. The cross-section of the second sealing ring is rectangular, with a width of 2.5 mm and a height of 0.6 mm.

[0030] In addition, the transition adhesive layer (7) is completely filled with the concave groove on the bottom surface of the sealing groove (6), and the surface of the groove is also coated with a flat epoxy adhesive layer of 0.05mm.

[0031] Example 3 A preferred embodiment of the fuel cell sealing structure of the present invention is that the fuel cell stack is composed of multiple sets of single cells stacked together, such as... Figure 3 As shown, the fuel cell sealing structure package is illustrated using a set of structures as an example.

[0032] The sealing structure is as follows Figure 3As shown, the invention includes a membrane electrode frame (1) and at least two sets of graphite bipolar plates with sealing grooves and concave grooves, namely a first graphite bipolar plate (2) and a second graphite bipolar plate (3). The membrane electrode frame (1) is sandwiched between the first graphite bipolar plate (2) and the second graphite bipolar plate (3), specifically, it is arranged between the first sealing ring (4) and the second sealing ring (5) (the first graphite bipolar plate and the second graphite bipolar plate should be clamped and fitted together; this schematic diagram is used here for better illustration of the structure).

[0033] The bottom surface of the sealing groove (6) of the first graphite bipolar plate (2) and the second graphite bipolar plate (3) is provided with a concave groove. The sealing groove is 3mm wide and 0.3mm deep. The concave groove is 0.05mm deep and 0.5mm wide. In this embodiment, three concave grooves are intermittently distributed in the sealing groove of each graphite bipolar plate along the width direction of the sealing groove. The concave groove is provided with a transition adhesive layer (7). The transition adhesive layer is epoxy sealant.

[0034] As shown in the figure, the first sealing ring is applied to the sealing groove (6) of the first graphite bipolar plate (2), and the second sealing ring (3) is applied to the sealing groove (6) of the second graphite bipolar plate (3). The side of the first sealing ring facing the membrane electrode frame (1) is curved, and the side of the second sealing ring facing the membrane electrode frame (1) is also curved. Both the width of the first sealing ring and the height of the second sealing ring are 2 mm and 0.65 mm respectively.

[0035] Example 4 A preferred embodiment of the fuel cell sealing structure of the present invention is that the fuel cell stack is composed of multiple sets of single cells stacked together, such as... Figure 4 As shown, the fuel cell sealing structure package is illustrated using a set of structures as an example.

[0036] The sealing structure is as follows Figure 4 As shown, the invention includes a membrane electrode frame (1) and at least two sets of graphite bipolar plates with sealing grooves and concave grooves, namely a first graphite bipolar plate (2) and a second graphite bipolar plate (3). The membrane electrode frame (1) is sandwiched between the first graphite bipolar plate (2) and the second graphite bipolar plate (3), specifically, it is arranged between the first sealing ring (4) and the second sealing ring (5) (the first graphite bipolar plate and the second graphite bipolar plate should be clamped and fitted together; this schematic diagram is used here for better illustration of the structure).

[0037] The first bipolar plate and the second bipolar plate sealing groove have concave grooves. The sealing grooves are 3mm wide and 0.3mm deep. The concave grooves are 0.05mm deep and 0.5mm wide.

[0038] The sealing groove (6) of the first graphite bipolar plate (2) and the second graphite bipolar plate (3) has a width of 3 mm and a depth of 0.3 mm. A transition adhesive layer (7) is provided on the bottom surface of the sealing groove (6), and a sealing ring is provided on the transition adhesive layer (7). The transition adhesive layer (7) is made of epoxy sealant and is laid flat on the bottom surface of the sealing groove (6) with a thickness of 0.05 mm.

[0039] Comparative Example 1 The proportion, such as Figure 5 As shown, we will use a set of structures as an example for illustration.

[0040] The sealing structure mentioned above is as follows: Figure 5 As shown, the invention includes a membrane electrode frame (1) and at least two sets of graphite bipolar plates with sealing grooves and concave grooves, namely a first graphite bipolar plate (2) and a second graphite bipolar plate (3). The membrane electrode frame (1) is sandwiched between the first graphite bipolar plate (2) and the second graphite bipolar plate (3), specifically, it is arranged between the first sealing ring (4) and the second sealing ring (5) (the first graphite bipolar plate and the second graphite bipolar plate should be clamped and fitted together; this schematic diagram is used here for better illustration of the structure).

[0041] As shown in the figure, the first sealing ring is applied to the sealing groove (6) of the first graphite bipolar plate (2), and the second sealing ring (3) is applied to the sealing groove (6) of the second graphite bipolar plate (3). The side of the first sealing ring facing the membrane electrode frame (1) is curved, and the side of the second sealing ring facing the membrane electrode frame (1) is also curved. Both the width of the first sealing ring and the height of the second sealing ring are 2 mm and 0.65 mm respectively.

[0042] Test Example 1 The adhesion force between the sealing ring and the flexible electrode sealing groove of the above five sealing structures was tested using a tensile testing machine. The testing equipment was from Shenzhen Kexing Instrument Co., Ltd., and the upward speed used during the test was 10 mm / min. The test values ​​are shown in Table 1 below.

[0043] Table 1 Comparing Examples 1, 2, 3, and 4 with Comparative Example 1, it can be seen that in Comparative Example 1, there is no epoxy adhesive layer between the sealing ring and the flexible electrode plate. In Examples 1, 2, 3, and 4, the use of epoxy adhesive as an intermediate material can effectively increase the adhesion between the sealing ring and the flexible electrode plate.

[0044] A comparison of Examples 1, 2 and 4 shows that adding a concave groove structure to the sealing groove of the flexible electrode plate can also improve the adhesion between the sealing ring and the flexible electrode plate.

[0045] In summary, this sealing structure can increase the adhesion between the flexible electrode plate and the sealing ring.

Claims

1. A gas-side sealing structure for a flexible graphite electrode plate in a fuel cell, comprising a membrane electrode frame and two graphite bipolar plates clamping the membrane electrode frame, wherein sealing grooves are formed on the graphite bipolar plates, characterized in that, The bottom surface of the sealing groove is provided with a transition adhesive layer, and a sealing ring is then provided on the transition adhesive layer.

2. The gas-side sealing structure of the flexible graphite electrode plate for fuel cells according to claim 1, characterized in that, The bottom surface of the sealing groove is provided with a transition adhesive layer in at least a portion of the area; the area covered by the sealing ring overlaps at least partially with the transition adhesive layer.

3. The gas-side sealing structure of the flexible graphite electrode plate for fuel cells according to claim 1, characterized in that, The transition adhesive layer is laid flat on the bottom surface of the sealing groove; Alternatively, the bottom surface of the sealing groove is provided with a concave groove, and the transition adhesive layer is located in the concave groove; Alternatively, the bottom surface of the sealing groove is provided with a concave groove, the bottom of the transition adhesive layer is filled with the concave groove, and the top surface protrudes and lies flat on the bottom surface of the sealing groove.

4. The gas-side sealing structure of the flexible graphite electrode plate for fuel cells according to claim 3, characterized in that, The thickness of the transition adhesive layer, which is laid flat on the bottom surface of the sealing groove, is ≤0.05mm.

5. The gas-side sealing structure of the flexible graphite electrode plate for fuel cells according to claim 3, characterized in that, The depth of the concave groove is 0.05~0.1mm and the width is 0.2~0.5mm.

6. The gas-side sealing structure of the flexible graphite electrode plate for fuel cells according to claim 3, characterized in that, The number of the concave grooves is 1 to 4, which are arranged along the width direction of the sealing groove; each concave groove is continuously or intermittently distributed along the length direction of the sealing groove.

7. The gas-side sealing structure of the flexible graphite electrode plate for fuel cells according to claim 1, characterized in that, The sealing ring has an arc surface on the side facing the membrane electrode frame, or the sealing ring has a rectangular cross-section.

8. The gas-side sealing structure of the flexible graphite electrode plate for fuel cells according to claim 1, characterized in that, The transition adhesive layer uses epoxy sealant.

9. A fuel cell stack, characterized in that, Use the gas-side sealing structure of the flexible graphite electrode plate for fuel cells according to any one of claims 1 to 8.

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