A structure for improving the weak plate of the end plate of a fuel cell stack

Abstract

The present invention relates to a structure for improving the weak piece of the end plate of a fuel cell stack, comprising a power generation cell, a pseudo cell, an end plate, an insulating plate and a current collecting plate, wherein the width of the plate flow channel of the power generation cell is L1, the depth is H1, and the width of the flow channel ridge is R1, and the width of the plate flow channel of the pseudo cell is L2, the depth is H2, and the width of the flow channel ridge is R2, wherein L2=1.1-1.3L1, H2=1.1-1.3H1, and R2=0.7-0.9R1. Compared with the prior art, the present invention provides pseudo cells without power generation function at both ends of the fuel cell stack as transmission channels for reaction gas and cooling water, which is conducive to discharging excess liquid water generated during the operation of the stack, and at the same time improves the phenomenon of low voltage of single cells at both ends of the end plate of the stack, thereby improving the output performance, cold start performance and durability of the stack.

Description

Technical Field

[0001] The invention relates to a fuel cell, and in particular to a structure for improving a weak piece of an end plate of a fuel cell stack. Background Art

[0002] A fuel cell is a device that can directly convert the chemical energy of a fuel into electrical energy through an electrochemical reaction. Its energy conversion efficiency is not limited by the theoretical efficiency of the Carnot heat engine cycle, and the conversion efficiency is relatively high (45-60%). At the same time, the only product is water, which does not pollute the environment. Therefore, it has broad development prospects in many fields. Among them, proton exchange membrane fuel cells have the characteristics of high power density, fast startup, and fast response to load changes, and have become an important development direction in the field of transportation energy. However, in actual use, fuel cells still face many problems, and the end plate effect is one of them. The so-called end plate effect means that when the fuel cell works at room temperature or low temperature, the output voltage of the single cell near the end plate is lower than that of the middle cell. The end plate effect is affected by many factors. For example, the single cell inside the fuel cell stack mainly dissipates heat through the coolant, while the single cells on both sides of the fuel cell end plate. In addition to dissipating heat through the coolant, it also radiates heat to the external air, resulting in a low temperature and a lower output voltage than the internal single cell, that is, the end plate effect.

[0003] The end plate effect not only affects the output performance of the fuel cell stack, but also affects the cold start performance and life of the stack. When the stack is cold started, the single cells at both ends of the end plate dissipate heat to the environment quickly, and the end plate effect is more serious. It is a key factor in determining whether the stack can be started successfully. During use, the performance degradation of the single cells on both sides of the end plate of the fuel cell stack is also much higher than that of the internal single cells, which greatly reduces the service life of the stack. Therefore, it is necessary to study appropriate solutions to solve the end plate effect of the fuel cell stack and improve the service life and cold start performance of the fuel cell stack.

[0004] Patent CN201911065235.8 sets a pseudo-battery at the end, and adds a flexible resistor plate between the electrode plate and the current collecting plate. When the current passes through the flexible resistor plate, heat can be generated to heat the electrode plate to ensure that the temperature of the electrode plate is the same as the temperature of the single cell inside the stack, or slightly exceeds the temperature of the internal single cell, thereby extending the life of the stack. This patent adjusts the temperature difference between the two during cold start by adjusting the ratio of the gas diffusion layer porosity of the pseudo-battery and the gas diffusion layer porosity of the power generation cell, but its drainage effect is poor. Patent CN201480053101.3 sets a pseudo-battery at the end plate of the fuel cell stack, which is conducive to removing excess liquid water in the stack and can improve the phenomenon of low voltage at both ends of the end plate of the stack to a certain extent. Patent CN201911065235.8 sets a pseudo-battery at the end plate, and inserts a heater between the pseudo-battery and the end plate. During cold start, the temperature difference between the end plate and the middle part of the stack can be reduced to improve the cold start performance of the stack.

[0005] However, the above technology has the following disadvantages:

[0006] 1. Only dummy batteries are set on the end plates, which can discharge the excess liquid water in the battery stack to a certain extent, but the improvement on the end plate effect is not obvious.

[0007] 2. Compared with ordinary power generation batteries, the flow field structure of pseudo batteries has not changed much, and the drainage effect is average.

[0008] 3. It is necessary to add other structures between the pseudo-battery and the end plate to improve the end plate effect, which increases the complexity of the battery stack structure. Summary of the invention

[0009] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a structure for improving the weak plate of the end plate of the fuel cell stack, which is beneficial to discharge the excess liquid water generated during the operation of the stack, and at the same time improve the phenomenon of low voltage of single cells at both ends of the stack end plate, thereby improving the output performance, cold start performance and durability of the stack.

[0010] The object of the present invention can be achieved through the following technical scheme: a structure of improving the weak plate of the end plate of a fuel cell stack, comprising a power generation cell, a pseudo cell, an end plate, an insulating plate and a collecting plate, characterized in that the plate flow channel width of the power generation cell is L1, the depth is H1, and the width of the flow channel ridge is R1, and the plate flow channel width of the pseudo cell is L2, the depth is H2, and the width of the flow channel ridge is R2, wherein L2=1.1~1.3L1, H2=1.1~1.3H1, and R2=0.7~0.9R1.

[0011] The pseudo battery comprises a cathode plate a, an anode plate a and a graphite plate, wherein the graphite plate is arranged between the cathode plate a and the anode plate a.

[0012] The cathode plate a and the anode plate a are provided with flow channels for the cathode and cathode reaction gases on one side facing the graphite plate, and with flow channels for the cooling liquid on the other side.

[0013] The electrical conductivity of the graphite plate is 6.5S / m, and the thermal conductivity is 32.4W / (m*K).

[0014] A heater is arranged inside the graphite plate.

[0015] The heater is a heating plate arranged in a graphite plate. The graphite plate is composed of two plates bonded together by an adhesive. A groove is arranged in each plate for placing the heating plate.

[0016] The width and length of the graphite plate are the same as those of the cathode plate a, and the thickness is 3 mm.

[0017] The graphite plate, the cathode plate a and the anode plate a are sealed with sealant.

[0018] The power generation cell comprises a cathode plate b and an anode plate b, and a membrane electrode sandwiched between the cathode plate b and the anode plate b.

[0019] The pseudo-battery is arranged at both ends of the power generation battery, and a current collecting plate, an insulating plate and an end plate are arranged in sequence on the outer side of the pseudo-battery.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. At the normal operating temperature of the fuel cell (60-80°C), the heater in the graphite plate 302 does not work. Since the width and depth of the flow channel in the pseudo-battery are greater than that of the normal power generation cell, the flow resistance is small, and the excess liquid water in the stack can easily flow through the pseudo-battery, thereby reducing the amount of liquid water entering the power generation cell, improving the phenomenon of flooding in the fuel cell stack during long-term operation, and improving the output performance of the fuel cell stack. At the same time, the pseudo-battery also has a certain heat insulation effect, which can reduce the heat dissipation of the power generation cell at the end plate of the stack to the air, increase the output voltage of the power generation cell at the end plate of the stack, improve the end plate effect of the fuel cell stack, and increase the life of the fuel cell stack.

[0022] 2. When the fuel cell stack is started at low temperature (temperature below 0℃), the temperature sensor in the system detects that the temperature is below 0℃. When the stack is started, the two ends of the stack are heated by the heater. Due to the action of the heater, the temperature difference between the end plate of the stack and the temperature in the middle of the stack is reduced, the output voltage of the single cell at the end plate is increased, and the end plate effect is significantly improved. At the same time, the pseudo-battery can also discharge excess liquid water in the stack to prevent water from freezing in the power generation cell and improve the cold start performance of the stack. When the temperature of the stack is higher than 0℃, the heater plate stops heating.

[0023] 3. The present invention sets pseudo-batteries without power generation function at both ends of the fuel cell stack as transmission channels for reaction gas and cooling water, which is beneficial to discharge excess liquid water generated during the operation of the stack, while improving the phenomenon of low voltage of single cells at both ends of the stack end plate, thereby improving the output performance, cold start performance and durability of the stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic structural diagram of a fuel cell stack of the present invention;

[0025] Figure 2 This is a schematic diagram of the structure of a single cell of a power generation battery of the present invention;

[0026] Figure 3 This is a schematic diagram of the pseudo battery structure of the present invention;

[0027] Figure 4 It is a schematic diagram of the structure of the heating plate in the graphite plate;

[0028] Figure 5 This is the single chip voltage diagram of the battery stack without pseudo batteries when starting at -20℃ low temperature;

[0029] Figure 6 When starting at -20℃ low temperature, a single-chip voltage diagram of a pseudo battery stack is provided at the end plate; DETAILED DESCRIPTION

[0030] The following is a detailed description of an embodiment of the present invention. This embodiment is carried out based on the technical solution of the present invention. A detailed implementation method and specific operation process are now given, but the protection scope of the present invention is not limited to the following embodiments.

[0031] Example 1

[0032] A structure for improving the weak plate of the end plate of a fuel cell stack includes a power generation cell, a pseudo cell, an end plate, an insulating plate and a current collecting plate. The specific structure is as follows Figure 1 As shown, both ends of the power generation cell 105 are provided with a pseudo battery 104 and a pseudo battery 106 without power generation function, the outer side of the pseudo battery 104 is provided with a current collecting plate 103, an insulating plate 102 and an end plate 101 in sequence, and the outer side of the pseudo battery 106 is provided with a current collecting plate 107, an insulating plate 108 and an end plate 109 in sequence, assembled into a fuel cell stack, and the fuel cell stack is provided with three inlets and three outlets: an air inlet 110, an air outlet 115, a hydrogen inlet 113, a hydrogen outlet 112, a coolant inlet 111, and a coolant outlet 114.

[0033] like Figure 2 As shown, the power generation cell includes a cathode plate b201 and an anode plate b203, and a membrane electrode 202 sandwiched between the cathode plate b201 and the anode plate b203.

[0034] like Figure 3 As shown, the pseudo-battery includes a cathode plate a301, an anode plate a303 and a graphite plate 302, wherein the graphite plate 302 is arranged between the cathode plate a301 and the anode plate a303. The cathode plate a301 and the anode plate a303 are provided with flow channels for the cathode and cathode reaction gases on one side facing the graphite plate 302, and are provided with flow channels for the coolant on the other side. The electrical conductivity of the graphite plate 302 is 6.5S / m, and the thermal conductivity is 32.4W / (m*K). A heater is provided in the graphite plate 302. The graphite plate is composed of two plates bonded together with an adhesive, and each plate is provided with a groove for placing a heating plate, such as Figure 4 As shown, the heating plate 401, the heating plate 402, and the heating plate 403 are all embedded in the grooves of the graphite plate. The width and length of the graphite plate 302 are the same as those of the cathode plate a301, and the thickness is 3 mm. The graphite plate 302 is sealed with the cathode plate a301 and the anode plate a303 by a sealant.

[0035] The cathode plate b201 of the power generation cell is provided with an oxidant flow channel, the anode plate b203 is provided with a hydrogen flow channel, and a cooling fluid flow channel is provided between the cathode plate b201 and the anode plate b203, wherein the width of the cooling fluid flow channel is L1, the depth is H1, and the width of the flow channel ridge is R1. The width of the cooling fluid flow channel on the cathode plate a301 and the anode plate a303 of the pseudo-battery is L2, the depth is H2, and the width of the flow channel ridge is R2, wherein L2=1.2L1, H2=1.2H1, and R2=0.8R1.

[0036] At the normal operating temperature of the fuel cell (60-80°C), the heater in the graphite plate 302 does not work. Since the width and depth of the cooling fluid flow channel in the pseudo-battery are greater than those of the normal power generation cell, the flow resistance is small, and the excess liquid water in the stack can easily flow through the pseudo-battery, thereby reducing the amount of liquid water entering the power generation cell, improving the phenomenon of flooding in the fuel cell stack during long-term operation, and improving the output performance of the fuel cell stack. At the same time, the pseudo-battery also has a certain heat insulation effect, which can reduce the heat dissipation of the power generation cell at the end plate of the stack to the air, increase the output voltage of the power generation cell at the end plate of the stack, improve the end plate effect of the fuel cell stack, and increase the life of the fuel cell stack.

[0037] When the fuel cell stack is started at low temperature (temperature below 0℃), the temperature sensor in the system detects that the temperature is below 0℃. When the stack is started, the two ends of the stack are heated by the heater. Due to the action of the heater, the temperature difference between the end plate of the stack and the temperature in the middle of the stack is reduced, the output voltage of the single cell at the end plate is increased, and the end plate effect is significantly improved. At the same time, the pseudo-battery can also discharge excess liquid water in the stack to prevent water from freezing in the power generation cell and improve the cold start performance of the stack. When the temperature of the stack is higher than 0℃, the heater plate stops heating.

[0038] Example 2

[0039] The width of the cooling fluid flow channel of the power generation cell is L1, the depth is H1, and the width of the flow channel ridge is R1. The width of the cooling fluid flow channel on the cathode plate a301 and the anode plate a303 of the pseudo battery is L2, the depth is H2, and the width of the flow channel ridge is R2, where L2=1.1L1, H2=1.1H1, and R2=0.7R1.

[0040] Example 3

[0041] The width of the cooling fluid flow channel of the power generation cell is L1, the depth is H1, and the width of the flow channel ridge is R1. The width of the cooling fluid flow channel on the cathode plate a301 and the anode plate a303 of the pseudo battery is L2, the depth is H2, and the width of the flow channel ridge is R2, where L2=1.3L1, H2=1.3H1, and R2=0.9R1.

[0042] Figure 5 When starting at -20℃ low temperature, there is no single-chip voltage of the pseudo battery stack. Figure 6 When starting at -20℃, the single-chip voltage of the pseudo battery stack is set at the end plate. Figure 5 and Figure 6 It can be seen that the voltage of the single cell of the end plate with the pseudo battery stack arranged at the end plate is significantly higher than the voltage of the single cell of the end plate without the pseudo battery stack.

[0043] Table 1 shows the performance degradation of the battery stack without dummy batteries and the battery stack with dummy batteries installed at the end plates after 2000 hours of operation. The performance degradation of the battery stack with dummy batteries installed at the end plates is also much lower than that of the battery stack without dummy batteries.

[0044] Table 1

[0045]

Claims

1. A structure for improving the weak piece of the end plate of a fuel cell stack, comprising a power generation cell, a pseudo cell, an end plate, an insulating plate and a current collecting plate, characterized in that: The plate flow channel width of the power generation cell is L1, the depth is H1, and the width of the flow channel ridge is R1. The plate flow channel width of the pseudo battery is L2, the depth is H2, and the width of the flow channel ridge is R2, wherein L2=1.1~1.3L1, H2=1.1~1.3H1, and R2=0.7~0.9R1; The pseudo battery comprises a cathode plate a (301), an anode plate a (303) and a graphite plate (302), wherein the graphite plate (302) is arranged between the cathode plate a (301) and the anode plate a (303); The pseudo-battery is arranged at both ends of the power generation battery, and a current collecting plate, an insulating plate and an end plate are arranged in sequence on the outside of the pseudo-battery; a heater is arranged inside the graphite plate (302).

2. The structure for improving the weak piece of the end plate of a fuel cell stack according to claim 1, characterized in that: The cathode plate a (301) and the anode plate a (303) are provided with flow channels for cathode and cathode reaction gases on one side facing the graphite plate (302), and with flow channels for cooling liquid on the other side.

3. The structure for improving the weak piece of the end plate of a fuel cell stack according to claim 1, characterized in that: The electrical conductivity of the graphite plate (302) is 6.5S / m, and the thermal conductivity is 32.4W / (m*K).

4. The structure for improving the weak piece of the end plate of a fuel cell stack according to claim 1, characterized in that: The heater is a heating plate arranged in a graphite plate. The graphite plate is composed of two plates bonded together by an adhesive. A groove is arranged in each plate for placing the heating plate.

5. The structure for improving the weak piece of the end plate of a fuel cell stack according to claim 1, characterized in that: The width and length of the graphite plate (302) are the same as those of the cathode plate a (301), and the thickness is 3 mm.

6. The structure for improving the weak piece of the end plate of a fuel cell stack according to claim 1, characterized in that: The graphite plate (302) is sealed with a sealant between the cathode plate a (301) and the anode plate a (303).

7. The structure for improving the weak piece of the end plate of a fuel cell stack according to claim 1, characterized in that: The power generation cell comprises a cathode plate b (201) and an anode plate b (203), and a membrane electrode (202) sandwiched between the cathode plate b (201) and the anode plate b (203).

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