JP2005310586A - Fuel battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To discharge liquid and water efficiently from a catalyst layer and a gas diffusion layer. <P>SOLUTION: A fuel battery cell comprises catalyst layers 11a, 11c and gas diffusion layers 12a, 12c on both sides of a solid polyelectrolyte membrane 10, and further, comprises separators 13a, 13c so as to sandwich these. A hole 19 is formed at the cathode gas diffusion layer 12c, and though penetrating this hole 19, a rib 15 of the cathode separator 13c and the solid polyelectrolyte membrane 10 or the cathode catalyst layer 11c are connected, and a connecting member 17 having a capillary phenomenon is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell using a solid polymer electrolyte.

  A polymer electrolyte fuel cell is configured as a fuel cell stack by sandwiching unit fuel cells (cells) each composed of a proton-conductive solid polymer membrane and an anode and a cathode respectively disposed on both sides thereof with a separator. Yes.

  In this type of fuel cell, a fuel gas, for example, hydrogen gas, supplied to the anode is hydrogen ionized on the catalyst electrode and moves to the cathode side through a polymer film that is appropriately humidified. At that time, the generated electrons are taken out to an external circuit and used as direct current electric energy. Since an oxidant gas, for example, oxygen gas or air is supplied to the cathode, water is generated by reaction of hydrogen ions (protons), electrons, and oxygen at the cathode.

  The proton conductive solid polymer membrane needs to be sufficiently humidified in order to maintain proton conductivity. For this reason, in general, by using a gas humidifier provided outside the fuel cell, the oxidant gas and the fuel gas are humidified, and the humidified reaction gas is supplied to the fuel cell. The molecular film is configured to be humidified.

  Since the polymer electrolyte fuel cell has a relatively low operating temperature (for example, 80 to 100 [° C.]), the moisture that has not been absorbed by the polymer membrane among the moisture supplied for humidification, and the reaction The water produced by may be present in a liquid (water) state. This water clogs the gas passage of the gas diffusion layer, and the diffusibility to the electrode catalyst layer of the fuel gas and the oxidant gas as the reaction gas is lowered, and the cell performance is markedly deteriorated. Yes.

  For example, when the gas flow path in the gas diffusion layer is blocked by water existing as a liquid (flooding), deterioration such as corrosion of carbon in the catalyst layer proceeds. Therefore, in the polymer electrolyte fuel cell, a technique for increasing the liquid water discharge capability is required.

For this reason, a fuel cell is disclosed in which a drainage groove that is continuous from the inlet side to the outlet side is provided on the wall surface of the gas flow path (Patent Document 1).
JP 2000-123848 A (page 3, FIG. 2)

  However, in the above-described conventional fuel cell, the drainage grooves provided on the wall surface of the gas flow path are independent and continuous from the inlet to the outlet, so that the water generated by the reaction is efficiently transferred to the drainage grooves. There was a problem that it could not be imported.

  In addition, the taken-in water is transported to the outlet by capillary action in a narrow drainage groove, but even if there are multiple narrow grooves near the gas diffusion surface, especially in the vicinity of the gas outlet, due to water vapor condensation in the gas and power generation The capillarity may not function due to the generated water, which is insufficient in terms of the certainty of drainage.

  In order to solve the above problems, the present invention provides a fuel cell in which a catalyst layer and a gas diffusion layer are disposed on both sides of a solid polymer electrolyte membrane, and a separator is disposed so as to sandwich the catalyst layer and the gas diffusion layer. The gist is that a connecting member having a capillary action is provided while connecting the gas diffusion layer side rib portion of the separator and the solid electrolyte membrane or the catalyst layer through the hole.

  According to the present invention, water existing as a liquid in the catalyst layer and the gas diffusion layer has an effect of being smoothly drained to the gas flow path side of the separator by the capillary action of the connecting member. Therefore, the gas passage can be prevented from being blocked by liquid water, and the power generation state of the fuel cell can be stably maintained.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic vertical sectional view of a fuel cell unit unit (fuel cell) constituting a fuel cell according to the present invention. In FIG. 1, in the fuel cell unit, the anode catalyst layer 11a and the cathode catalyst layer 11c are formed on both surfaces of the solid polymer membrane 10, and the anode gas diffusion layer 12a and the cathode gas diffusion layer 12c are arranged on the outer sides, respectively. The membrane electrode assembly and the anode separator 13a and the cathode separator 13c are arranged so as to sandwich the membrane electrode assembly.

  Although not particularly limited, in this embodiment, the fuel cell uses hydrogen as the fuel gas and air as the oxidant gas. Therefore, in the following description, the fuel gas channel is called a hydrogen channel, and the oxidant gas channel is called an air channel.

  On the surface of the anode separator 13a on the anode gas diffusion layer side, rib portions 20 and hydrogen flow paths 21 through which hydrogen gas flows are alternately formed. A cooling medium flow path 22 is formed on the opposite surface of the anode separator 13a to the anode gas diffusion layer side.

  On the other hand, on the cathode gas diffusion layer side surface of the cathode separator 13c, rib portions 14 or 15 and air flow paths 16 through which air as an oxidant gas flows are alternately formed. A connecting member 17 having a capillary action is disposed on the rib portion 15. There may be one connecting member 17 having a capillary action or a plurality of connecting members 17 independent of each other. Further, a drainage groove 18 is formed in the air flow path 16.

  The seal members 23, 24, and 25 are used when the fuel cell stack is formed by stacking the membrane electrode assembly (10, 11, 12), the anode separator 13 a, and the cathode separator 13 c, and the reaction gas and the cooling medium. The seal is performed.

  The cathode gas diffusion layer 12 c is provided with a hole 19 at a position corresponding to the connection member 17. The connecting member 17 passes through the hole 19 of the cathode gas diffusion layer 12c and connects the cathode separator 13c and the cathode catalyst layer 11c or the solid polymer membrane 10. The connecting member 17 is composed of a member having a capillary action, such as a porous member, a fiber assembly member in which fibers are bundled. As the porous member, porous carbon, porous ceramic, or the like can be used. As the fiber assembly member in which the fibers are bundled, chemical fibers such as acrylic, rayon, and nylon, and those in which carbon fibers are bundled can be used.

  Since the connecting member 17 has a capillary action, excess water present in the cathode catalyst layer 11c or the solid polymer membrane 10 can be sucked out by the capillary action and discharged to the air flow path 16 of the cathode separator 13c. .

  FIG. 2 is an enlarged cross-sectional view of a main part showing the first embodiment of the fuel cell according to the present invention, and is an enlarged view around the cathode separator 13c in FIG.

  In FIG. 2, a connecting member 17 in which fibers are bundled in a columnar shape is installed at the tip of the rib portion 15 of the cathode separator 13c, penetrates the cathode gas diffusion layer 12c, and is formed on the surface of the solid polymer membrane 10. The layer 11c is reached. Water generated by the reaction of hydrogen ions, electrons, and oxygen in the cathode catalyst layer 11c moves from the cathode catalyst layer 11c side to the cathode separator 13c side and is discharged by the capillary action of the connecting member 17. The drainage by the connecting member 17 having the capillary action can prevent the catalyst layer and the gas diffusion layer from being blocked by the liquid water. Therefore, the reaction gas is smoothly supplied through the gas diffusion layer, and the power generation state of the fuel cell is stably maintained. There is an effect that can be maintained.

  FIG. 3 is a schematic cross-sectional view of a fuel cell for explaining Example 2 of the fuel cell according to the present invention, and is a horizontal cross-sectional view of the fuel cell shown in FIG.

  In FIG. 3, a plurality of connecting members 17 having a capillary action are discretely installed on the rib portion 15 of the cathode separator 13c. The shape of the portion where the connecting member 17 penetrates the cathode gas diffusion layer 12c is, for example, a cone, a cylinder, a pyramid, a prism, etc. The water discharge capacity can be increased.

  FIG. 4 is an enlarged cross-sectional view of a main part showing a third embodiment of the fuel cell according to the present invention, and is an enlarged view around the cathode gas diffusion layer 12c in FIG.

  The connection member 17 formed by bundling the fibers penetrates the cathode gas diffusion layer 12, and its tip end branches radially in the cathode catalyst layer 11c, and each branch branches into the cathode catalyst layer 11c. By extending, the liquid water dischargeable region of the cathode catalyst layer 11c can be expanded.

  In the present embodiment, an example is shown in which the tip of the connecting member 17 branches radially in the cathode catalyst layer 11c. However, the present invention is not limited to this, and the tip of the connecting member 17 branches radially at the portion in contact with the solid polymer film 10. However, the same effect can be expected.

  FIG. 5 is a separator plan view showing Example 4 of the fuel cell according to the present invention, and shows an example of the cathode separator shown in FIG.

  The gas flow path formed in the separator of the fuel cell is a parallel groove type in which the gas flow paths shown in FIG. 5 (a) are parallel, and a meandering groove type in which the gas flow paths shown in FIGS. 5 (b) and 5 (c) meander. Are known. 5 (c) is a type in which a plurality of gas flow paths parallel to each other meander.

  In this embodiment, as shown in FIGS. 5A, 5B, and 5C, a plurality of connecting members 17 are discretely arranged on the rib portions 15 separating the air flow paths 16 of the cathode separator. In this case, the arrangement density of the connection members 17 is increased on the downstream side near the gas outlet 32 from the upstream side near the gas inlet 31.

  According to this embodiment, since the arrangement density of the connecting members having a capillary action on the outlet side of the reaction gas in the cell is increased, the drainage property on the outlet side of the reaction gas in the cell where flooding is likely to be a problem can be improved. The relative humidity of the reaction gas increases with the flow direction, and the moisture present in the catalyst layer and the gas diffusion layer increases on the reaction gas outlet side. Therefore, there is an effect that flooding can be effectively suppressed by increasing the arrangement density of the connecting members having a capillary action provided in the separator rib portion on the reaction gas outlet side.

  As described above, according to the present invention, the drainage from the catalyst layer and the gas diffusion layer can be enhanced, and the drained liquid water can be smoothly removed through the drainage groove. As a result, flooding can be prevented, and an unstable operation of the fuel cell due to flooding can be prevented, and deterioration of the fuel cell can be suppressed.

It is a vertical direction schematic sectional drawing of the fuel cell unit unit (fuel cell) which comprises the fuel cell which concerns on this invention. It is a principal part expanded sectional view which shows Example 1 of the fuel cell which concerns on this invention. It is a fuel cell schematic sectional drawing explaining Example 2 of the fuel cell which concerns on this invention. Example 3 It is a separator top view which shows Example 4 of this invention in (a) parallel groove type separator, (b) meandering groove type separator, and (c) meandering groove type separator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Solid polymer membrane 11a ... Anode catalyst layer 11c ... Cathode catalyst layer 12a ... Anode gas diffusion layer 12c ... Cathode gas diffusion layer 13a ... Anode separator 13c ... Cathode separator 14, 15 ... Rib part 16 ... Air flow path 17 ... Connection Member 18 ... Drainage groove 19 ... Hole 20 ... Rib portion 21 ... Hydrogen flow path 22 ... Cooling medium flow path 23, 24, 25 ... Sealing member

Claims (5)

In a fuel cell in which a catalyst layer and a gas diffusion layer are disposed on both sides of a solid polymer electrolyte membrane, and a separator is disposed so as to sandwich them,
Providing a hole in the gas diffusion layer;
A fuel cell comprising a connecting member penetrating the hole to connect the gas diffusion layer side rib portion of the separator and the solid electrolyte membrane or the catalyst layer and having a capillary action.   2. The fuel cell according to claim 1, wherein the connecting member is provided discretely in a length direction of a rib portion of the separator and does not hinder gas movement in a plane direction inside the gas diffusion layer.   3. The fuel cell according to claim 1, wherein the catalyst layer side end portion of the connecting member branches radially when contacting the surface of the solid polymer electrolyte membrane or the catalyst layer. 4.   The fuel cell according to any one of claims 1 to 3, wherein the separator-side end portion of the connection member reaches a drainage groove formed in a gas flow path of the separator.   5. The fuel cell according to claim 1, wherein an arrangement density of the connection members is increased on a reaction gas outlet side in a separator surface.

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