CN106887633B - High-temperature fuel cell stack - Google Patents

Abstract

A high-temperature fuel cell stack, comprising two end plates and a single cell placed between the two end plates, the single cell comprising a bipolar plate and a membrane electrode, and the end plate is close to the inner side of the single cell The surface and/or both sides of the bipolar plate are coated with a molecular sieve coating. According to the design of the present invention, the problem that the performance of the high temperature proton exchange membrane fuel cell is degraded due to the inability to discharge water in time during the start and stop of the high temperature proton exchange membrane fuel cell can be effectively solved. Improve the stability of the battery during operation, so that the battery life can be improved. The water flooding phenomenon caused by the fact that the generated water cannot be removed in time during the operation of the battery is solved, the corrosion of the catalyst carrier, the noble metal catalyst, the diffusion layer and other materials in the membrane electrode is reduced, and the stability of the membrane electrode is improved. The water removal method of the invention has a simple structure and can effectively remove water without adding external facilities.

Description

A high temperature fuel cell stack

technical field

The invention relates to the technical field of fuel cells, in particular to a high temperature fuel cell stack.

Background technique

A fuel cell is a device that directly converts chemical energy stored in compound fuels into electrical energy through chemical reactions. A proton exchange membrane fuel cell usually consists of an anode, a cathode and a proton exchange membrane. During the operation of the battery, the fuel undergoes oxidation reaction on the surface of the anode catalyst to generate protons and electrons, the protons reach the cathode through the proton exchange membrane, oxygen undergoes a reduction reaction with protons on the surface of the cathode catalyst to generate water, and the electrons work through the external circuit to reach the cathode.

A large amount of water is generated during the discharge process of the PEM fuel cell. Due to the high operating temperature of the high temperature PEM fuel cell, the water is discharged into the atmosphere in a gaseous form along with the cathode exhaust gas, but the temperature is low during the start and stop process of the cell, and the liquid water is insufficient. Due to vaporization, the water produced by the battery cannot be discharged in time, resulting in a decrease in battery performance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an effective water removal method in order to solve the problem that the water generated during the startup and shutdown of the high temperature proton exchange membrane fuel cell system is difficult to discharge and causes flooding.

The present invention adopts the following concrete ways to realize:

A high-temperature fuel cell stack, comprising two end plates and a single cell placed between the two end plates, the single cell comprising a bipolar plate and a membrane electrode, and the end plate is close to the inner side of the single cell The surface and/or both sides of the bipolar plate are coated with a molecular sieve coating.

A molecular sieve coating is coated on the inner surface of the stack cathode outlet pipeline.

Molecular sieve coating is applied on the surface of the inner flow channel of the end plate close to the single cell and/or the surface of the flow channel on both sides of the bipolar plate.

The molecular sieve is a low-temperature water-absorbing and high-temperature dehydrating material.

The molecular sieve is one or a mixture of two or more of 3A, 4A, 5A, 10X, and 13X.

The molecular sieve coating is a molecular sieve membrane.

The thickness of the molecular sieve coating is 0.001-10 mm.

According to the design of the present invention, the problem that the performance of the high temperature proton exchange membrane fuel cell is degraded due to the inability to discharge water in time during the start and stop of the high temperature proton exchange membrane fuel cell can be effectively solved. Improve the stability of the battery during operation, so that the battery life can be improved. The water flooding phenomenon caused by the fact that the generated water cannot be removed in time during the operation of the battery is solved, the corrosion of the catalyst carrier, the noble metal catalyst, the diffusion layer and other materials in the membrane electrode is reduced, and the stability of the membrane electrode is improved. The water removal method of the invention has a simple structure and can effectively remove water without adding external facilities.

Description of drawings

Fig. 1 is bipolar plate flow channel distribution and molecular sieve coating distribution diagram;

1. End plate; 2. Molecular sieve coating; 3. Anode catalytic layer; 4. Proton exchange membrane; 5. Cathode catalytic layer; 6. Bipolar plate

Figure 2 is an assembly diagram of a high temperature fuel cell stack;

Figure 3 is a diagram of the membrane electrode assembly MEA.

Detailed ways

Specific embodiments of the present invention will be described below with reference to the accompanying drawings and the like.

Specific implementations include:

End plate 1, used for fluid distribution and current collection; Molecular sieve coating 2, water removal during battery start-up and shutdown; Anode catalytic layer 3, catalyzed fuel oxidation reaction; Proton exchange membrane 4, Proton transmission, isolation of cathode and anode reactants ; Cathode catalytic layer 5, catalyzes the reduction reaction of oxygen; Bipolar plate 6, fluid distribution of cathode and anode reactants. working principle:

The molecular sieve coating 2 is coated on the flow channel of the end plate 1 and the bipolar plate 6. The anode catalytic layer 3, the proton exchange membrane 4 and the cathode catalytic layer 5 together form the membrane electrode assembly MEA, which is assembled with the end plate and the bipolar plate and between the bipolar plates.

The high temperature proton exchange membrane fuel cell uses a PBI membrane, and its proton transport does not rely on the action of water, so it can be used in the case of low relative humidity. Molecular sieve coating is carried out in the channel and at the tail discharge port of the battery to achieve the purpose of removing water during the start-stop process. The molecular sieve must have the following functions: when the temperature is low (below 120°C), it can adsorb water, and when the temperature is high (higher than 150°C), it can desorb the water adsorbed at low temperature.

During the start-stop process of the high-temperature fuel cell stack, due to the low temperature, the water generated by the discharge of the battery cannot be discharged in a gaseous form in time and stays inside the battery, resulting in flooding of the high-temperature fuel cell stack and causing the high-temperature fuel cell stack to flood. performance degradation. If a molecular sieve coating with water-absorbing properties is coated on the flow channel, the water generated during the discharge process is adsorbed inside the molecular sieve by the water-absorbing molecular sieve coated on the flow channel, which can effectively avoid the occurrence of flooding. When the high temperature fuel cell stack operates to the normal operating temperature, the water generated at this time is discharged together with the exhaust gas in the form of gas. Due to the high normal operating temperature of the high-temperature fuel cell stack, the molecular sieve can desorb the water adsorbed at low temperature, and turn it into gaseous water and discharge it together with the exhaust gas.

Embodiment 1: In this embodiment, 20 single cells are placed between two end plates to form a high-temperature fuel cell stack. layer, the thickness of the molecular sieve membrane is 0.005mm.

The high temperature fuel cell stack assembled in this way did not find obvious decrease in cell performance after 100 times of continuous start and stop, but the high temperature fuel cell stack coated with the molecular sieve membrane was under the same conditions as the above high temperature fuel cell stack. After starting and stopping 73 times, the battery performance decreased obviously due to flooding. Through the comparison of the two methods, it is found that the above method can effectively improve the flooding phenomenon caused by the high temperature fuel cell stack during the start-stop process.

Embodiment 2: In this embodiment, 20 single cells are placed between two end plates to form a high-temperature fuel cell stack. layer, the thickness of the molecular sieve membrane is 0.01mm.

The high temperature fuel cell stack assembled in this way did not find obvious decrease in cell performance after 100 times of continuous start and stop, but the high temperature fuel cell stack coated with the molecular sieve membrane was under the same conditions as the above high temperature fuel cell stack. After starting and stopping 73 times, the battery performance decreased obviously due to flooding. Through the comparison of the two methods, it is found that the above method can effectively improve the flooding phenomenon caused by the high temperature fuel cell stack during the start-stop process.

The fuel cell dehumidification system described in this embodiment can effectively adsorb the water generated in the cell during the start and stop phases of the high temperature fuel cell stack, thereby avoiding the occurrence of flooding. When the temperature of the high-temperature fuel cell stack is high, the water adsorbed in the molecular sieve can be desorbed, thereby ensuring the recycling of the molecular sieve and realizing the method of coating the molecular sieve in the flow channel. The system is also coated with the molecular sieve at the tail discharge port of the battery, the main function of which is to ensure the drying of the battery in the non-operating state. Since the air in different places has different humidity in different seasons, the tail exhaust port of the high-temperature fuel cell stack is always in communication with the atmosphere when it is not in operation, which also means that the water in the air can enter the interior of the battery with the air. Causes corrosion of some devices inside the battery. The purpose of placing the water-absorbing molecular sieve at the tail discharge port is to absorb the water contained in the air and prevent the water in the air from entering the battery and corroding the battery.

Claims (4)

1. A high temperature proton exchange membrane fuel cell stack, comprising two end plates and a single cell placed between the two end plates, the single cell comprising more than 2 membrane electrode MEAs separated by bipolar plates, It is characterized in that: the surface of the inner flow channel of the end plate close to the single cell, the surface of the flow channel on both sides of the bipolar plate and the inner surface of the stack cathode outlet pipeline are coated with molecular sieve coating; The molecular sieve is a material that absorbs water at a low temperature lower than 120°C and dehydrates at a high temperature higher than 150°C. 2 . The high temperature proton exchange membrane fuel cell stack of claim 1 , wherein the molecular sieve is one or a mixture of two or more of 3A, 4A, 5A, 10X, and 13X. 3 . 3 . The high temperature proton exchange membrane fuel cell stack of claim 1 , wherein the molecular sieve coating is a molecular sieve membrane. 4 . 4 . The high temperature proton exchange membrane fuel cell stack of claim 1 , wherein the molecular sieve coating has a thickness of 0.001-10 mm. 5 .

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