JP2010097757A - Fuel cell, and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell and a fuel cell system capable of achieving excellent collection efficiency. <P>SOLUTION: The fuel cell (10) is provided with a membrane-electrode assembly (20), collectors (30, 40) arranged along an electrode face of the membrane-electrode assembly or at least with a part embedded inside the electrode, having conductivity and gas permeability, and with terminals (31, 32, 41, 42) for taking out generation current in the membrane-electrode assembly fitted at least at a part of an outer periphery part, and gas flow channel members (50, 60) fitted to the collectors at a side opposite to the membrane-electrode assembly and equipped with gas flow channels for supplying reaction gas to the membrane-electrode assembly. The terminals are arranged further toward an inlet side than outlets of the gas flow channels in a gas flow direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell and a fuel cell system.

  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 has, for example, a membrane-electrode assembly including an electrolyte membrane having proton conductivity. In such a fuel cell, a cathode gas containing oxygen is supplied to the cathode side electrode, and an anode gas containing hydrogen is supplied to the anode side electrode. Thereby, power generation is performed. Cathode gas and anode gas may be collectively referred to as reaction gas.

  Patent Document 1 discloses a fuel cell that includes a membrane-electrode assembly in which a current collector is embedded in an electrode, and that can extract electric power from the end in the surface direction of the current collector.

JP-A-2005-174872

  In the fuel cell of Patent Document 1, the output current amount of the membrane-electrode assembly may be distributed in the plane. In this case, current collection loss may occur depending on the position of the terminal provided on the outer peripheral portion of the current collector.

  An object of this invention is to provide the fuel cell and fuel cell system which can implement | achieve favorable current collection efficiency.

  The fuel cell according to the present invention has a membrane-electrode assembly and an electrode surface of the membrane-electrode assembly, or at least a part of the membrane-electrode assembly is embedded in the electrode, and has conductivity and gas permeability. A current collector provided with a terminal for taking out a generated current in the membrane-electrode assembly at least at a part of the outer peripheral portion; and a membrane-electrode assembly provided on a side of the current collector opposite to the membrane-electrode assembly And a gas flow path member in which a gas flow path for supplying a reaction gas is formed, and the terminal is disposed closer to the inlet side than the outlet of the gas flow path in the gas flow path direction. It is what.

  According to the fuel cell of the present invention, the terminal can be arranged on the side of the membrane-electrode assembly where the amount of output current is large. Thereby, current collection loss is reduced. As a result, good current collection efficiency can be realized.

  In the above configuration, the reaction gas may be a cathode gas. In this case, when air is used as the cathode gas, the terminal is disposed on the side of the membrane-electrode assembly where the amount of output current is large. In the above configuration, the gas flow path member may be a separator provided along the current collector, and the gas flow path may be a groove provided on a surface of the separator on the current collector side.

  In the above configuration, the gas channel is provided with an outer peripheral channel formed along the outer peripheral part of at least a part of the current collector from the inlet, and the terminal is arranged to extend along the outer peripheral channel. May be. In this case, the current collection efficiency from a region where the amount of output current is relatively large is improved.

  In the above configuration, the cross-sectional area of the current collector may be gradually or stepwise reduced from the inlet side to the outlet side of the gas channel in the gas channel direction. According to this configuration, the cross-sectional area of the current collector can be reduced in a region where the output current amount of the membrane-electrode assembly is small. As a result, the fuel cell can be reduced in weight while ensuring a predetermined current collection efficiency.

  A fuel cell system according to the present invention includes a membrane-electrode assembly, and a membrane having conductivity and gas permeability that is disposed along or at least partially embedded in the electrode along the electrode surface of the membrane-electrode assembly. A fuel cell comprising: a current collector provided with a terminal for taking out a generated current in the electrode assembly at least at a part of the outer periphery; and an output current in the membrane-electrode assembly gradually or gradually toward the terminal Distribution means for distributing the output current so as to increase stepwise.

  According to the fuel cell system of the present invention, the amount of output current on the side close to the terminal of the membrane-electrode assembly is increased by the distribution means. Thereby, good current collection efficiency can be realized.

  In the above configuration, the distribution means is a gas flow path member provided on the opposite side of the current collector to the membrane-electrode assembly in the fuel cell and having a gas flow path for supplying a reaction gas to the membrane-electrode assembly And a supply means for supplying the reaction gas to the gas flow path, and the supply means adjusts the supply amount of the reaction gas larger or the back pressure is higher on the side closer to the terminal of the gas flow path than the side far from the terminal. May be. According to this configuration, the distribution means can increase the amount of output current on the side close to the terminal of the membrane-electrode assembly.

  In the above configuration, the supply unit may adjust the supply amount of the reaction gas by adjusting the flow rate or concentration of the reaction gas. In the above configuration, the reaction gas may be a cathode gas. In the above configuration, the gas flow path member may be a separator provided along the current collector, and the gas flow path may be a groove provided on the current collector side of the separator.

  In the above configuration, the cross-sectional area of the current collector may be gradually or stepwise reduced from the inlet side to the outlet side of the gas channel in the gas channel direction. According to this configuration, the cross-sectional area of the current collector can be reduced in a region where the output current amount of the membrane-electrode assembly is small. Thereby, weight reduction of a fuel cell can be achieved.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell and fuel cell system which can implement | achieve favorable current collection efficiency can be provided.

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

  A fuel cell system 200 according to Embodiment 1 of the present invention will be described. FIG. 1A is a perspective view of the fuel cell system 200. FIG. 1B is a plan view of a cathode current collector 30 to be described later. FIG. 2 is a side view of the fuel cell 10 to be described later. FIG. 3 is a perspective view of a cathode separator 50 described later. A fuel cell system 200 will be described with reference to FIGS. 1 (a), 1 (b), 2 and 3. FIG. First, referring to FIG. 1A, a fuel cell system 200 includes a fuel cell 10, a cathode gas supply means 100 for supplying a cathode gas containing oxygen to the fuel cell 10, and an anode gas containing hydrogen for the fuel cell 10. Anode gas supply means 110 for supplying to

  Referring to FIGS. 1A, 1B, and 2, a fuel cell 10 includes a membrane-electrode assembly 20, a current collector (a cathode current collector 30 and an anode current collector 40), Separators (cathode separator 50 and anode separator 60). The membrane-electrode assembly 20 includes an electrolyte membrane 21 and a catalyst layer (a cathode catalyst layer 22 and an anode catalyst layer 23). As the electrolyte membrane 21, for example, a solid polymer electrolyte having proton conductivity can be used.

  The cathode catalyst layer 22 and the anode catalyst layer 23 are disposed so as to sandwich the electrolyte membrane 21. The cathode catalyst layer 22 and the anode catalyst layer 23 are made of a conductive material containing a catalyst. The catalyst of the cathode catalyst layer 22 promotes the reaction between protons and oxygen. The catalyst of the anode catalyst layer 23 promotes protonation of hydrogen. For example, the cathode catalyst layer 22 and the anode catalyst layer 23 contain platinum-supported carbon or the like.

  The cathode current collector 30 is disposed along the surface of the cathode catalyst layer 22 opposite to the electrolyte membrane 21. The anode current collector 40 is disposed along the surface of the anode catalyst layer 23 opposite to the electrolyte membrane 21. The cathode current collector 30 and the anode current collector 40 have conductivity and reaction gas permeability. As the cathode current collector 30 and the anode current collector 40, for example, a metal mesh, an expanded metal, a metal foam sintered body, a carbon fiber, or the like can be used.

  Further, a terminal 31 and a terminal 32 for taking out the generated current in the membrane-electrode assembly 20 are provided on at least a part of the outer peripheral portion of the cathode current collector 30. As shown in detail in FIG. 1B, in this embodiment, the term “terminal” refers to an outer peripheral portion where the membrane-electrode assembly 20 is not disposed in the current collector. Therefore, in the present embodiment, the terminal 31 is one of the regions on the outer peripheral side of the portion of the cathode current collector 30 that is in contact with the membrane-electrode assembly 20. The terminal 32 is a region on the opposite side to the terminal 31 in a portion on the outer peripheral side of a portion in contact with the membrane-electrode assembly 20 of the cathode current collector 30. Note that these terminals are arranged so as to extend along the cathode-side outer peripheral channel 71 described later.

  A terminal 41 and a terminal 42 for taking out the generated current in the membrane-electrode assembly 20 are provided on at least a part of the outer periphery of the anode current collector 40. In this embodiment, the shape of the anode current collector 40 is the same as that shown in FIG.

  The terminals 31 and 32 of the cathode current collector 30 and the terminals 41 and 42 of the anode current collector 40 are electrically connected to a load (not shown) such as an auxiliary machine. The cathode current collector 30, the anode current collector 40, and the load constitute an electric circuit.

  2 and 3, the cathode separator 50 is disposed on the opposite side of the cathode current collector 30 from the cathode catalyst layer 22. The anode separator 60 is disposed on the opposite side of the anode current collector 40 from the anode catalyst layer 23. On the surface of the cathode separator 50 on the cathode current collector 30 side, a cathode gas flow path for flowing the cathode gas is formed by a groove. On the surface of the anode separator 60 on the anode current collector 40 side, an anode gas flow path for flowing the anode gas is formed by a groove. That is, in this embodiment, the cathode separator 50 and the anode separator 60 have a function as a gas flow path member.

  The cathode gas channel has an outer peripheral channel 71 formed along the outer periphery of the cathode separator 50 and an inner peripheral channel 72 formed on the inner peripheral side of the outer peripheral channel 71. . One end of the outer peripheral channel 71 has a cathode gas inlet 73, and the other end is folded and connected to the inner peripheral channel 72. One end of the inner peripheral flow path 72 is connected to the outer peripheral flow path 71, and the other end has a cathode gas outlet 74. The cathode gas flows in from the cathode gas inlet 73, flows through the outer peripheral channel 71 and the inner peripheral channel 72, and is discharged from the cathode gas outlet 74.

  Similar to the cathode gas channel, the anode gas channel also has an outer peripheral channel and an inner peripheral channel. The anode gas flows in from the anode gas inlet 83, flows through the outer peripheral channel and the inner peripheral channel, and is discharged from the anode gas outlet 84.

  In addition, since the output current of the membrane-electrode assembly 20 can be taken out through the current collector, the cathode separator 50 and the anode separator 60 do not need to have conductivity. Therefore, restrictions on the materials of the cathode separator 50 and the anode separator 60 are suppressed. In the present embodiment, the material of the cathode separator 50 and the anode separator 60 is not particularly limited, and for example, resin, metal or the like is used. Resin is preferable in that the fuel cell 10 can be reduced in weight and cost compared to metal.

  The fuel cell 10 operates as follows. Referring to FIG. 1A, the anode gas supply means 110 supplies anode gas to the anode gas inlet 83. Referring to FIG. 2, the supplied anode gas passes through the anode current collector 40 while flowing through the anode gas flow path. The anode gas that has passed through the anode current collector 40 reaches the anode catalyst layer 23. In the anode catalyst layer 23, hydrogen in the anode gas is separated into protons and electrons. Protons are conducted through the electrolyte membrane 21 and reach the cathode catalyst layer 22. The electrons are collected by the terminal 41 and the terminal 42 of the anode current collector 40 and taken out to the outside, and then reach the cathode current collector 30.

  Referring to FIG. 1A, the cathode gas supply means 100 supplies the cathode gas to the cathode gas inlet 73. 2 and 3, the supplied cathode gas passes through the cathode current collector 30 while flowing in the cathode gas flow path. The cathode gas that has passed through the cathode current collector 30 reaches the cathode catalyst layer 22. In the cathode catalyst layer 22, water is generated from oxygen in the cathode gas, protons conducted through the electrolyte membrane 21, and electrons from the terminals 31 and 32. The anode gas and cathode gas after the reaction are discharged from the anode gas outlet 84 and the cathode gas outlet 74, respectively. As described above, the fuel cell 10 operates.

  Here, a distribution may occur in the amount of output current in the plane of the membrane-electrode assembly 20. For example, the oxygen partial pressure of the cathode gas decreases as oxygen is consumed by a chemical reaction during power generation. As a result, the output current amount is reduced on the downstream side of the upstream side of the cathode gas. Note that the same phenomenon as the cathode gas may occur in the anode gas. In this embodiment, it is assumed that air is used as the cathode gas and pure hydrogen is used as the anode gas. In this case, the output current distribution in the membrane-electrode assembly 20 depends on the oxygen partial pressure in the cathode gas. Therefore, the output current amount of the membrane-electrode assembly 20 increases on the upstream side of the cathode gas and decreases on the downstream side of the cathode gas.

  In the fuel cell system 200 according to the present embodiment, each terminal of each current collector is disposed closer to the inlet side than the outlet of the gas channel in the cathode gas channel direction. In this case, current collection loss due to the electrical resistance of the current collector is small. Therefore, current collection efficiency can be improved. Further, since each terminal is formed so as to extend along each outer peripheral flow path with a large amount of output current, it is possible to realize better current collection efficiency.

  In the present embodiment, the cathode current collector 30 and the anode current collector 40 are disposed along the electrode surface of the membrane-electrode assembly 20, but are not limited thereto. At least a part of the cathode current collector 30 and the anode current collector 40 may be embedded in the electrode of the membrane-electrode assembly 20.

(Modification 1)
In the first embodiment, the cathode separator 50 has a function as a gas flow path member for cathode gas, but is not limited thereto. The fuel cell 10 may have a gas flow path member for cathode gas separately from the cathode separator 50. FIG. 4 is a perspective view of the cathode separator 50a and the cathode gas flow path member 90 according to the first modification of the first embodiment. As shown in FIG. 4, a cathode gas flow path member 90 may be disposed on the surface of the plate-like cathode separator 50a on the membrane-electrode assembly 20 side. The anode-side separator may also have the same configuration as that shown in FIG.

(Modification 2)
The cross-sectional area of the cathode current collector 30 may be different depending on the distribution of the amount of generated current of the membrane-electrode assembly 20. FIG. 5 is a plan view of a cathode current collector 30b according to this modification. First, the cathode current collector 30b is classified into a plurality of regions along the flow direction of the cathode gas. In this embodiment, it is classified into four areas. The four regions are referred to as a region 300, a region 310, a region 320, and a region 330 in order from the terminal 31 side to the terminal 32, respectively. Next, the cross-sectional area of each of these regions was set so as to correspond to the distribution of the output current amount of the membrane-electrode assembly 20. Table 1 shows an example of a cross-sectional area of the cathode current collector 30b. Each value in Table 1 is a relative ratio.

  Since the oxygen partial pressure of the cathode gas decreases from the upstream side to the downstream side, the output current amount of the membrane-electrode assembly 20 also decreases from the upstream side to the downstream side. For example, it is assumed that the amount of output current flowing through the region 300 to the region 330 is 20, 5, 5, 20 in relative ratio. Accordingly, the cross-sectional areas of the regions 300 to 330 are set to 20, 5, 5, and 20 in relative ratios, respectively. That is, the cross-sectional area of the cathode current collector 30 according to this modification is reduced stepwise from the cathode gas inlet side to the outlet side. In this case, the weights of the region 300 to the region 330 are 20, 5, 5, and 20 in relative ratio, respectively. As a result, the total weight of the cathode current collector 30 is 50.

  In comparison with this, if all the cross-sectional areas of the region 300 to the region 330 are 20 corresponding to the current 20 of the region 300 or the region 330 that realizes the maximum value of the output current amount of the membrane-electrode assembly 20, the cathode collector The total weight of the electric body is 80. Therefore, the weight reduction of the fuel cell 10 can be realized by using the cathode current collector 30 according to this modification. Even if the cross-sectional area of the current collector in the region where the amount of output current is small is reduced, the reduction in current collection efficiency is suppressed.

  The anode current collector 40 may also have a large cross-sectional area in a region where the amount of output current is large, and may have a small cross-sectional area in a region where the amount of output current is small. In the present embodiment, the cross-sectional area of the anode current collector 40 may be reduced stepwise from the cathode gas inlet side to the cathode gas outlet side. Even in this case, the anode current collector 40 can be reduced in weight while ensuring a predetermined current collection efficiency.

  When the current collector is a metal mesh or expanded metal, the cross-sectional area of the current collector can be changed, for example, by adjusting the wire diameter of the metal wire. When the current collector is a metal foam, the cross-sectional area of the current collector can be changed, for example, by adjusting the porosity. When the current collector is a carbon cloth, the cross-sectional area of the current collector can be changed by adjusting the diameter of the carbon wire, for example.

  As described above, according to the fuel cell 10 according to this modification, it is possible to reduce the weight of the current collector while ensuring a predetermined current collection efficiency of the current collector. Thereby, the weight reduction of the fuel cell 10 is realizable.

  Next, a fuel cell system 200c according to Example 2 of the present invention will be described. FIG. 6 is a perspective view of the fuel cell system 200c. The fuel cell system 200c is different from the fuel cell system 200 in that a fuel cell 10c is provided instead of the fuel cell 10 and a cathode gas supply unit 100c is provided instead of the cathode gas supply unit 100.

  The fuel cell 10c is different from the fuel cell 10 in that a cathode separator 50c and an anode separator 60c are provided instead of the cathode separator 50 and the anode separator 60. The cathode separator 50c and the anode separator 60c are different from the cathode separator 50 and the anode separator 60 in the structure of the cathode gas channel and the anode gas channel, respectively.

  FIG. 7 is a perspective view of the cathode separator 50c. The cathode gas channel of the cathode separator 50c differs from the cathode gas channel of the cathode separator 50 in that the outer peripheral channel 71 and the inner peripheral channel 72 are not connected in the plane of the cathode separator 50c. In the cathode gas channel of the cathode separator 50c, a cathode gas inlet 73 is formed at one end of each of the outer peripheral channel 71 and the inner peripheral channel 72, and a cathode gas outlet 74 is formed at the other end. Yes. The anode gas flow path of the anode separator 60c has the same configuration as that shown in FIG.

  The cathode gas supply means 100 c supplies a cathode gas having a higher oxygen concentration to the outer peripheral channel 71 than the inner peripheral channel 72. In this case, the oxygen partial pressure on the side close to the terminal of the cathode gas channel is higher than the oxygen partial pressure on the side far from the terminal. That is, the supply amount of oxygen is increased on the side closer to the terminal of the gas flow path than on the side far from the terminal. Therefore, in the plane of the membrane-electrode assembly 20, the output current increases stepwise toward the terminal.

  According to the fuel cell system 200c according to the present embodiment, the amount of output current on the side closer to the terminal is increased, so that good current collection efficiency can be realized.

(Modification 1)
The cathode gas supply unit 100 c may increase the cathode gas flow rate supplied to the outer peripheral channel 71 compared to the inner peripheral channel 72. Even in this case, since the amount of output current on the side close to the terminal of the membrane-electrode assembly 20 increases, good current collection efficiency can be realized.

  The cathode gas supply unit 100 c may increase the back pressure of the cathode gas supplied to the outer peripheral channel 71 compared to the inner peripheral channel 72. Even in this case, the amount of output current on the side close to the terminal of the membrane-electrode assembly 20 increases.

  Note that the output current may increase toward the terminal in the membrane-electrode assembly 20 by adjusting the supply amount of the anode gas or the back pressure.

FIG. 1A is a perspective view of a fuel cell system 200 according to the first embodiment. FIG. 1B is a plan view of the cathode current collector 30 according to the first embodiment. FIG. 2 is a side view of the fuel cell 10 according to the first embodiment. FIG. 3 is a perspective view of the cathode separator 50 according to the first embodiment. FIG. 4 is a perspective view of the cathode separator 50a and the cathode gas flow path member 90 according to the first modification of the first embodiment. FIG. 5 is a plan view of the cathode current collector 30b according to the second modification of the first embodiment. FIG. 6 is a perspective view of the fuel cell system 200c according to the second embodiment. FIG. 7 is a perspective view of the cathode separator 50c according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell 20 Membrane-electrode assembly 21 Electrolyte membrane 22 Cathode catalyst layer 23 Anode catalyst layer 30 Cathode current collector 31 and 32 Terminal 40 Anode current collector 41 and 42 Terminal 50 Cathode separator 60 Anode separator 71 Outer peripheral flow path 72 Inner peripheral channel 73 Cathode gas inlet 74 Cathode gas outlet 83 Anode gas inlet 84 Anode gas outlet 90 Cathode gas channel member 100 Cathode gas supply means 110 Anode gas supply means 200 Fuel cell system

Claims (11)

A membrane-electrode assembly;
Along the electrode surface of the membrane-electrode assembly, or at least a part of the membrane-electrode assembly is embedded in the electrode, has conductivity and gas permeability, and takes out the generated current in the membrane-electrode assembly. A current collector provided with a terminal on at least a part of the outer periphery;
A gas flow path member provided on the opposite side of the current collector from the membrane-electrode assembly and having a gas flow path for supplying a reaction gas to the membrane-electrode assembly,
The fuel cell according to claim 1, wherein the terminal is disposed closer to an inlet side than an outlet of the gas channel in the gas channel direction.   The fuel cell according to claim 1, wherein the reaction gas is a cathode gas. The gas flow path member is a separator provided along the current collector;
The fuel cell according to claim 1, wherein the gas flow path is a groove provided on a surface of the separator on the side of the current collector. The gas channel is provided with an outer peripheral channel formed along the outer peripheral part of at least a part of the current collector from the inlet,
The fuel cell according to claim 1, wherein the terminal is disposed so as to extend along the outer peripheral flow path.   The cross-sectional area of the current collector decreases gradually or stepwise from the inlet side to the outlet side of the gas flow channel in the gas flow channel direction. Fuel cell. Membrane-electrode assembly and power generation in the membrane-electrode assembly having conductivity and gas permeability arranged along or at least partially embedded in the electrode along the electrode surface of the membrane-electrode assembly A current collector provided with a terminal for taking out an electric current at least at a part of the outer periphery; and a fuel cell,
A fuel cell system comprising: distribution means for distributing the output current so that the output current increases gradually or stepwise toward the terminal in the membrane-electrode assembly. In the fuel cell, the distribution means is provided on the opposite side of the current collector from the membrane-electrode assembly, and a gas flow channel is formed in which a gas flow channel for supplying a reaction gas to the membrane-electrode assembly is formed. A member and supply means for supplying the reaction gas to the gas flow path,
The fuel cell system according to claim 6, wherein the supply unit adjusts the supply amount of the reaction gas to be larger or the back pressure to be higher on a side closer to the terminal of the gas flow path than a side far from the terminal. .   8. The fuel cell system according to claim 7, wherein the supply means adjusts the supply amount of the reaction gas by adjusting a flow rate or concentration of the reaction gas.   9. The fuel cell system according to claim 7, wherein the reaction gas is a cathode gas. The gas flow path member is a separator provided along the current collector;
The fuel cell system according to any one of claims 7 to 9, wherein the gas flow path is a groove provided on the current collector side of the separator.   The cross-sectional area of the current collector decreases gradually or stepwise from the inlet side to the outlet side of the gas flow channel in the gas flow channel direction. Fuel cell system.

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