JP2010250958A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell capable of ensuring electrical contact between a current collector and a membrane-electrode assembly.
A fuel cell (100) includes a membrane-electrode assembly (10) and a current collector (20, 21) disposed adjacent to the membrane-electrode assembly and having gas permeability. The electric body is characterized by having a lower rigidity than the membrane-electrode assembly. According to the fuel cell, even if a differential pressure is generated between the anode gas and the cathode gas, the current collector is deformed following the deformation of the membrane-electrode assembly. Thereby, electrical contact between the membrane-electrode assembly and the current collector can be ensured.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell.

  A fuel cell is a device that generally obtains electric energy using hydrogen and oxygen as fuel. Since this fuel cell is excellent in terms of the environment and can realize high energy efficiency, it has been widely developed as a future energy supply system.

  The fuel cell includes a membrane-electrode assembly having an electrolyte membrane and a catalyst layer. A cathode gas containing oxygen is supplied to the cathode side electrode of the membrane-electrode assembly, and an anode gas containing hydrogen is supplied to the anode side electrode. Thereby, power generation is performed in the membrane-electrode assembly.

  In recent years, fuel cells that further include a gas permeable current collector on both surfaces of the membrane-electrode assembly have been developed (see, for example, Patent Documents 1 to 3). In such a fuel cell, the electric power generated by the membrane-electrode assembly can be taken out by the current collector.

JP-A-5-315000 JP-A-8-111226 JP-A-8-162123

  However, sufficient electrical contact may not be obtained between the membrane-electrode assembly and the current collector due to the differential pressure between the anode gas and the cathode gas.

  An object of this invention is to provide the fuel cell which can ensure the electrical contact between a collector and a membrane-electrode assembly.

  A fuel cell according to the present invention includes a membrane-electrode assembly and a gas permeable current collector disposed adjacent to the membrane-electrode assembly, the current collector being compared with the membrane-electrode assembly. It has a low rigidity. According to the fuel cell of the present invention, even if a differential pressure is generated between the anode gas and the cathode gas, the current collector is deformed following the deformation of the membrane-electrode assembly. Thereby, electrical contact between the membrane-electrode assembly and the current collector can be ensured.

  In the above configuration, the membrane-electrode assembly and the current collector may be bonded. The fuel cell according to the above configuration may further include a separator that is provided on the opposite side of the current collector from the membrane-electrode assembly and divides a space for the reaction gas to flow between the current collector and the current collector.

  In the above configuration, the current collector may be a sheet-like conductive fiber, a metal foam sintered body, an expanded metal, or a metal mesh. According to this configuration, the current collector can have gas permeability.

  In the above configuration, the current collector may be a cathode-side current collector. According to this configuration, even when the pressure of the cathode gas is higher than that of the anode gas, electrical contact between the cathode-side current collector and the membrane-electrode assembly can be ensured. . In the above configuration, the current collector may be an anode-side current collector. According to this configuration, even when the pressure of the anode gas is higher than that of the cathode gas, electrical contact between the anode-side current collector and the membrane-electrode assembly can be ensured. .

  In the above configuration, the electrolyte membrane included in the membrane-electrode assembly may be a solid polymer electrolyte.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell which can ensure the electrical contact between a collector and a membrane-electrode assembly can be provided.

FIG. 1 is a schematic cross-sectional view of a fuel cell. FIG. 2A is a schematic cross-sectional view showing a state where the pressure of the cathode gas is higher than the pressure of the anode gas and electrical contact between the current collector and the membrane-electrode assembly cannot be secured sufficiently. . FIG. 2 (b) shows that when the anode current collector and the cathode current collector are deformed following the deformation of the membrane-electrode assembly, the membrane-electrode assembly, the anode current collector, and the cathode current collector are deformed. It is typical sectional drawing which shows the state by which the electrical contact between was ensured. FIG. 3A is a schematic cross-sectional view showing a state in which the pressure of the anode gas is higher than the pressure of the cathode gas, and sufficient electrical contact between the current collector and the membrane-electrode assembly cannot be secured. . FIG. 3B shows that the anode-cathode current collector and the cathode current collector follow the deformation of the membrane-electrode assembly, thereby deforming the membrane-electrode assembly, the anode current collector, and the cathode current collector. It is typical sectional drawing which shows the state by which the electrical contact between was ensured.

  Hereinafter, modes for carrying out the present invention will be described.

  A fuel cell 100 according to Embodiment 1 of the present invention will be described. FIG. 1 is a schematic cross-sectional view of the fuel cell 100. The fuel cell 100 includes a membrane-electrode assembly 10, a pair of current collectors (anode current collector 20 and cathode current collector 21), a pair of separators (anode separator 30 and cathode separator 31), and a seal member 40. And comprising. The membrane-electrode assembly 10 includes an electrolyte membrane 11, an anode catalyst layer 12, and a cathode catalyst layer 13. As the electrolyte membrane 11, for example, a solid polymer electrolyte having proton conductivity can be used. As a solid polymer electrolyte membrane having proton conductivity, for example, a perfluorosulfonic acid membrane can be used.

  The anode catalyst layer 12 and the cathode catalyst layer 13 are arranged so as to sandwich the electrolyte membrane 11. The catalyst of the anode catalyst layer 12 promotes protonation of hydrogen. The catalyst of the cathode catalyst layer 13 promotes the reaction between protons and oxygen. For example, the anode catalyst layer 12 and the cathode catalyst layer 13 contain platinum-supported carbon or the like.

  The anode current collector 20 and the cathode current collector 21 are disposed adjacent to the membrane-electrode assembly 10. Specifically, the anode current collector 20 is disposed along the surface of the anode catalyst layer 12 opposite to the electrolyte membrane 11 side. The cathode current collector 21 is disposed along the surface of the cathode catalyst layer 13 opposite to the electrolyte membrane 11 side. The anode current collector 20 and the cathode current collector 21 are adhesively bonded to the membrane-electrode assembly 10. The anode current collector 20 and the cathode current collector 21 are electrically connected to a load such as a motor or an auxiliary machine.

  The anode current collector 20 and the cathode current collector 21 have conductivity and reaction gas permeability. As the anode current collector 20 and the cathode current collector 21, for example, a sheet body in which conductive fibers such as carbon fibers are formed in a sheet shape such as cloth, felt, paper, or the like can be used. Further, as the anode current collector 20 and the cathode current collector 21, a metal foam sintered body, an expanded metal, a metal mesh, or the like can be used. For example, nickel (Ni), titanium (Ti), gold (Au), stainless steel (SUS), or the like can be used as a metal material such as a foamed sintered body, expanded metal, or metal mesh. A more detailed description of the anode current collector 20 and the cathode current collector 21 will be described later.

  The anode separator 30 and the cathode separator 31 have a contact portion that protrudes and contacts the membrane-electrode assembly 10 at the outer peripheral portion. As a result, an anode gas flow path 32 for flowing the anode gas is defined between the anode separator 30 and the membrane-electrode assembly 10. In addition, a cathode gas flow path 33 for flowing a cathode gas is defined between the cathode separator 31 and the membrane-electrode assembly 10.

  The anode separator 30 and the cathode separator 31 may have a contact portion that contacts the membrane-electrode assembly 10 in addition to the outer peripheral portion as long as the flow of the reaction gas is not hindered. However, in consideration of the diffusibility of the reaction gas into the membrane-electrode assembly 10, it is preferable that a reaction gas flow space is formed over the entire surface or almost the entire surface of the membrane-electrode assembly 10.

In the present embodiment, as an example, the anode gas is hydrogen (H ₂ ) and the cathode gas is air. The material of the anode separator 30 and the cathode separator 31 is not specifically limited, For example, resin, a metal, etc. are used.

  The seal member 40 covers the outer peripheral surfaces of the anode catalyst layer 12 and the cathode catalyst layer 13. The seal member 40 suppresses leakage of anode gas and cathode gas from the anode catalyst layer 12 and the cathode catalyst layer 13.

  The fuel cell 100 operates as follows. The anode gas flowing through the anode gas flow path 32 passes through the anode current collector 20 and reaches the anode catalyst layer 12. In the anode catalyst layer 12, hydrogen in the anode gas is separated into protons and electrons. Protons conduct through the electrolyte membrane 11 and reach the anode catalyst layer 12. The electrons are collected by the anode current collector 20 and taken out of the fuel cell 100. The electrons taken out of the fuel cell 100 reach the cathode current collector 21 after being used for load work.

  The cathode gas flowing through the cathode gas flow path 33 passes through the cathode current collector 21 and reaches the cathode catalyst layer 13. In the cathode catalyst layer 13, water is generated by oxygen in the cathode gas, protons conducted through the electrolyte membrane 11, and electrons conducted from the anode current collector 20. The generated water (generated water) mainly flows through the cathode gas flow path 33 and is discharged to the outside of the fuel cell 100. The anode gas and the cathode gas after the reaction flow through the anode gas channel 32 and the cathode gas channel 33, respectively, and are discharged to the outside of the fuel cell 100. As described above, the fuel cell 100 operates.

  Incidentally, in the fuel cell 100, when a differential pressure is generated between the anode gas and the cathode gas, a deformation pressure is applied to the membrane-electrode assembly 10. For example, as shown in FIG. 2A, when one reaction gas has a higher pressure than the other reaction gas, deformation pressure is applied from the high pressure side to the low pressure side in the membrane-electrode assembly 10. Since the anode current collector 20 and the cathode current collector 21 are gas permeable, deformation pressure is avoided. In this case, there is a possibility that sufficient electrical contact between the current collector and the membrane-electrode assembly 10 cannot be ensured.

  Therefore, in this embodiment, the anode current collector 20 and the cathode current collector 21 have lower rigidity than the membrane-electrode assembly 10. In this case, as shown in FIG. 2B, even when a differential pressure is generated between the anode gas and the cathode gas, the anode current collector 20 and the cathode current collector 21 are deformed by the deformation of the membrane-electrode assembly 10. Follow and deform. Thereby, electrical contact between the membrane-electrode assembly 10 and the anode current collector 20 and the cathode current collector 21 is ensured. In the present embodiment, the rigidity is a strain amount with respect to a load. Therefore, when the same load is applied, the strain amount is small when the rigidity is high, and the strain amount is large when the rigidity is low.

  In order to set the rigidity of the anode current collector 20 and the cathode current collector 21 to be smaller than the rigidity of the membrane-electrode assembly 10, the distortion of the anode current collector 20 and the cathode current collector 21 when the same load is applied. The anode current collector 20 and the cathode current collector 21 may be configured so that the amount is larger than the strain amount of the membrane-electrode assembly 10. For example, the Young's modulus of the anode current collector 20 and the cathode current collector 21 may be made smaller than the Young's modulus of the membrane-electrode assembly 10. When the Young's modulus of the membrane-electrode assembly 10 has a Young's modulus of about 2 GPa, a current collector having a Young's modulus smaller than 2 GPa may be used. Since the Young's modulus of sheet bodies such as carbon paper, carbon cloth, and carbon felt is about 40 MPa, these sheet bodies may be used as current collectors.

  Further, the structure of the current collector may be adjusted. For example, the current collector can be bent easily (for example, in a wave shape), the porosity of the current collector is increased, or when the current collector is an expanded metal or a metal mesh, the wire diameter is reduced. The rigidity of the electric body may be lower than the rigidity of the membrane-electrode assembly 10.

  In this embodiment, the rigidity of the anode current collector 20 and the cathode current collector 21 is smaller than the rigidity of the membrane-electrode assembly 10, but the present invention is not limited to this. It is sufficient that the rigidity of at least one of the anode current collector 20 and the cathode current collector 21 is smaller than the rigidity of the membrane-electrode assembly 10.

  In this case, it is preferable that the rigidity of the current collector on the side of the anode side and the cathode side where the reaction gas pressure is high is lower than the rigidity of the membrane-electrode assembly 10. For example, when pure hydrogen is used for the anode gas and air is used for the cathode gas, the pressure of the anode gas is about 1 to 700 kPa, the pressure of the cathode gas is about 100 to 701 kPa, and a differential pressure of about 60 kPa is generated. There is. Therefore, as shown in FIG. 2A, when the cathode gas pressure is higher than the anode gas pressure, the cathode current collector 21 is made less rigid than the membrane-electrode assembly 10, thereby making the cathode Electrical contact between the current collector 21 and the membrane-electrode assembly 10 can be ensured. On the other hand, when the pressure of the anode gas is higher than the pressure of the cathode gas as shown in FIG. 3A, the rigidity of the anode current collector 20 is made lower than the rigidity of the membrane-electrode assembly 10, thereby As shown in FIG. 3B, electrical contact between the anode current collector 20 and the membrane-electrode assembly 10 can be ensured.

  Regardless of the rigidity, it is conceivable to ensure electrical contact by increasing the adhesive force between the membrane-electrode assembly 10 and the current collector. However, when a differential pressure is generated that exceeds the adhesive strength of the adhesive, electrical contact between the membrane-electrode assembly 10 and the current collector cannot be obtained. Therefore, as in the present embodiment, by causing the current collector to follow the deformation of the membrane-electrode assembly 10, the membrane-electrode assembly 10 and the current collector are not affected by the magnitude of the differential pressure. Electrical contact can be ensured.

DESCRIPTION OF SYMBOLS 10 Membrane-electrode assembly 11 Electrolyte membrane 12 Anode catalyst layer 13 Cathode catalyst layer 20 Anode current collector 21 Cathode current collector 30 Anode separator 31 Cathode separator 32 Anode gas channel 33 Cathode gas channel 40 Seal member 100 Fuel cell

Claims (7)

A membrane-electrode assembly;
A current collector disposed adjacent to the membrane-electrode assembly and having gas permeability;
The fuel cell according to claim 1, wherein the current collector has a lower rigidity than the membrane-electrode assembly.   The fuel cell according to claim 1, wherein the membrane-electrode assembly and the current collector are bonded to each other.   The separator further comprising a separator provided on a side of the current collector opposite to the membrane-electrode assembly and defining a space for the reaction gas to flow between the current collector and the current collector. 2. The fuel cell according to 2.   4. The fuel cell according to claim 1, wherein the current collector is a sheet-like conductive fiber, a metal foam sintered body, an expanded metal, or a metal mesh. 5.   The fuel cell according to claim 1, wherein the current collector is a cathode-side current collector.   The fuel cell according to claim 1, wherein the current collector is an anode-side current collector.   The fuel cell according to claim 1, wherein the electrolyte membrane contained in the membrane-electrode assembly is a solid polymer electrolyte.

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