JP4176673B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell, and more particularly to a structure of a fuel cell.

  A fuel cell is based on an electrochemical reaction in a membrane electrode assembly (hereinafter referred to as “MEA (Membrane Electrode Assembly)”) including an electrolyte and electrodes (cathode and anode) disposed on both sides of the electrolyte. The generated electric energy is taken out through separators disposed on both sides of the MEA. Among fuel cells, polymer electrolyte fuel cells (hereinafter referred to as “PEFC (Polymer Electrolyte Fuel Cell)”) used in household cogeneration systems and automobiles are composed of MEAs, separators, etc. The theoretical voltage of the single cell is 1.23V. For this reason, a PEFC is generally used that can extract the target electromotive force by stacking a plurality of single cells to form a stack. In such a fuel cell, current collecting plates are arranged at both ends of a single cell laminate, and an insulating plate having electrical insulation is arranged outside thereof. And it uses in the state pressurized from the both sides of the insulating plate arrange | positioned at both ends.

  As described above, since the stack-like fuel cell is composed of multiple members, a contact resistance is generated between the separators or between the separator and the current collector plate, and this contact resistance reduces the output of the fuel cell stack. Invite. Therefore, it is possible to increase the output of the fuel cell by reducing the contact resistance in the fuel cell.

  Technological development aimed at reducing contact resistance has been studied so far. For example, in order to reduce contact resistance on a conductor contact surface, a technique of performing metal plating on the contact surface is actually used. Yes. Although this technique can be said to be an effective means for a member that can surface-treat the conductor contact surface, it has been regarded as a problem that it is difficult to reduce the contact resistance of a member that is difficult to surface-treat. Further, in the above technique, when the flatness and surface roughness of the contact surface in the workpiece are not sufficiently secured, even if the metal contact processing is performed on the conductor contact surface, the plating processing area is reduced. In other words, the contact resistance increases.

On the other hand, in Patent Document 1, contact resistance is obtained by interposing an unevenness between the separator and the current collector plate by interposing a flexible or fluid conductive material between the separator and the current collector plate. A technique for reducing the above is disclosed. In Patent Document 2, a composite material in which NiO and an interconnector material are mixed is interposed between the current collector and the interconnector, and a slurry made of the interconnector material is interposed on both sides of the composite material. Thus, a technique for reducing contact resistance is disclosed.
Japanese Patent Laid-Open No. 7-263013 JP-A-8-130022

However, if a fluid conductor is interposed between separators as in the technique of Patent Document 1, it is necessary to firmly seal the periphery of the conductor, and the conductor leaks from the sealed region. When it is put out, there is a problem that the conductivity is lowered and it is difficult to take out the electromotive force of the fuel cell.
Further, even with the technique of Patent Document 2, there is a problem that it is difficult to sufficiently reduce the contact resistance.

  Therefore, an object of the present invention is to provide a fuel cell that can extract more electromotive force than before by reducing the contact resistance in the fuel cell.

In order to solve the above problems, the present invention takes the following means. That is,
The invention according to claim 1 is a fuel cell comprising an electrolyte, a cathode and an anode disposed on both sides of the electrolyte, and a separator disposed outside the cathode and the anode, and further higher than the separator It has a spreadable material layer having a spreadability and conductivity, and the spreadable material layer has a metal layer that is liquid at the operating temperature of the fuel cell on both sides, and is disposed in contact with the separator. This is a fuel cell.
A second aspect of the present invention is the fuel cell according to the first aspect, wherein the extensible material layer contains a metal.
The invention described in claim 3 is the fuel cell according to claim 1 or 2, wherein the fuel cell is a solid polymer fuel cell, and the metal layer is made of an alloy containing indium and / or gallium. It is characterized by being configured.

  According to the first aspect of the present invention, for example, when a spreadable material layer and a metal layer are provided between the separators, fine irregularities on the separator surface can be filled with the metal layer, and comparison between the separators can be performed. The rough rough surface can be filled with a spreadable material layer provided on the metal layer. Therefore, since the space between the separators can be effectively filled with the spreadable material layer and the metal layer, the contact resistance between the separators can be reduced. Further, since the metal layer is sandwiched between the separator and the spreadable material layer, it is not necessary to tightly seal the metal layer. Even if the metal layer leaks from between the separator and the spreadable material layer, the conductivity of the fuel cell can be ensured because the spreadable material layer is disposed between the separators. . That is, according to the first aspect of the present invention, it is possible to provide a fuel cell that can extract more electromotive force than before by reducing the internal contact resistance.

  According to the second aspect of the present invention, it is possible to further reduce the contact resistance in the fuel cell by containing the metal having good conductivity in the spreadable material layer.

  According to the third aspect of the present invention, it is possible to provide a polymer electrolyte fuel cell that can extract more electromotive force than before by reducing the internal contact resistance.

FIG. 1 schematically shows an embodiment of the fuel cell of the present invention.
In the polymer electrolyte fuel cell 100 of the present invention, the first cell 10 is disposed so as to face the electrolyte membrane 11, the MEA 15 having the cathode 12 and the anode 13 disposed on both sides thereof, and the cathode 12 and the anode 13. The separator 17 and the separator 18 are provided. The second cell 20 having the same form as the first cell 10 is configured to face the electrolyte membrane 21, the MEA 25 having the cathode 22 and the anode 23 disposed on both sides thereof, and the cathode 22 and the anode 23. The separator 27 and the separator 28 which are arrange | positioned are provided. In the fuel cell 100 according to the present embodiment, the spreadable material layer 50 and the metal layers 70 and 70 are provided between the separator 17 of the first cell 10 and the separator 28 of the second cell 20. The separators 17, 18, 27, and 28 according to this embodiment are made of carbon.

  In the fuel cell 100 of the present invention, the contact resistance in the fuel cell 100 is reduced by providing the extensible material layer 50 and the metal layers 70 and 70 between the separator 17 and the separator 28. In the fuel cell 100 of the present invention, when the spreadable material layer 50 is sandwiched between at least the portions where the separators should come into contact with each other, when the pressure is applied from both sides of the fuel cell stack, the material layer comes before the separators 17 and 28. 50 is appropriately deformed, and the gap between the separators can be filled. In addition, even when the material layer 50 is sandwiched between the parts, the contact surface of the separator is rough, and there is a gap between the separators so that a sufficient contact area cannot be secured. Since the gap can be effectively filled, it is possible to eliminate the contact failure between the separators.

  Further, in the fuel cell 100 of the present invention, the metal layers 70 are provided between the spreadable material layer 50 and the separator 17 and the separator 28, so that it is difficult to completely fill the material layer 50 with the metal layer 70. Even if there is a gap between them, the gap can be effectively filled. In addition, by providing the metal layers 70, 70, the contact surfaces of the separator can be easily brought into contact with each other. Therefore, by providing the metal layers 70 and 70 on the surfaces of the separators 17 and 28 in the fuel cell 100 of the present invention, the contact resistance can be reduced as compared with the conventional case.

In the fuel cell 100 shown in FIG. 1, the contact resistance in the fuel cell 100 can be reduced to about 1/5 of the conventional one by sandwiching the spreadable metal layer 50 between the carbon material separators 17 and 28. Become. Furthermore, by using the spreadable metal layer 50 and the metal layers 70 and 70 together in the above-described form, it becomes possible to reduce the contact resistance to about 1/50 of the conventional one. Therefore, according to the present invention, it is possible to provide a fuel cell in which the internal resistance (contact resistance) of the stack type fuel cell is reduced.
The internal resistance that can be reduced by the present invention depends on the internal structure of the fuel cell. On the other hand, it is generally said that the ratio of contact resistance between separators to the total internal resistance is 20%. Therefore, according to the present invention, the contact resistance between the separators is reduced to about 1/50 of the conventional value, so that the power loss of the fuel cell due to the resistance is also improved by about 20%. It becomes possible to provide a fuel cell that can extract electric power.

  The spreadable material layer 50 used in the fuel cell 100 of the present invention is not particularly limited as long as it has a spreadability higher than that of the separator, but effectively fills the gap between the members and reduces the contact resistance of the fuel cell. From the viewpoint of reducing, it is preferable to include a metal having excellent conductivity. In the present invention, the metal contained in the material layer 50 can be indium. For example, when the material layer 50 is plate-like indium (indium plate), the material layer 50 can be easily formed, and the material layer 50 can be easily disposed between the separators.

  In the fuel cell 100 provided with a carbon separator, unevenness of about 50 μm exists between the separator 17 and the separator 28. Therefore, for example, by disposing an indium plate having a thickness of about 0.5 mm between the separators, the gap between the separators can be effectively filled. In addition, it is preferable to change suitably the thickness of the indium plate arrange | positioned between separators according to the pressure applied from the both ends of a fuel cell stack. The spreadable material layer 50 may be provided over the entire contact surface of the separators 17 and 28, or may be provided only on a part of the contact surface.

  The metal layer 70 used in the fuel cell 100 of the present invention is a metal that is liquid at a temperature during operation of the fuel cell 100 (in the present embodiment in which the fuel cell 100 is PEFC, about room temperature to 90 ° C.). It can be used suitably, and it does not ask | require whether the said metal is a liquid at room temperature. Examples of the metal in a liquid state at the above temperature include a metal containing indium and / or gallium. If the metal layer 70 is composed of such a metal, the metal can enter the gaps on the surface of the carbon separator due to the action of surface tension or the like. Therefore, the metal layer 70 can be uniformly applied to the separator surface.

  The laminated form of the separators 17 and 28, the metal layers 70 and 70, and the spreadable material layer 50 in the fuel cell 100 is preferably formed in the following order. That is, in this order, the metal layers 70 and 70 are provided on the surfaces of the separators 17 and 28, respectively, and then a spreadable material layer is provided between the metal layers 70 and 70. By providing in this order, the metal constituting the metal layers 70 and 70 can enter the gaps between the surfaces of the separators 17 and 28, so the contact area between the separators 17 and 28 and the stretchable material layer 50 is increased. It becomes possible to make it. As a result, the contact resistance in the fuel cell can be effectively reduced.

  The metal constituting the metal layer 70 may be composed of a metal containing only one of indium or gallium, but from the viewpoint of making it a metal that is liquid and harmless at room temperature and has excellent conductivity, indium and A metal containing both gallium is preferable. When a metal containing both of these is used, the metal layer 70 that can effectively reduce the contact resistance in the fuel cell 100 is obtained by setting the mixing ratio to indium: gallium = 24.5: 75.5. It becomes possible.

  In the fuel cell 100 of the present invention, by using the above-described spreadable material layer 50 and the metal layer 70, the internal contact resistance is reduced more easily and at a lower cost than when the separator surface is subjected to metal plating. A fuel cell can be provided.

  In the above description, the example in which the extensible material layer and the metal layer are provided between the separators is shown, but the place where the extensible material layer and the metal layer are provided is not limited to the separator, Any location where contact resistance occurs in the battery can be suitably provided. Examples of the portion other than between the separators include a portion between the separator and the current collector plate. In the above description, an example in which a carbon separator is provided is shown, but the separator that can be used in the fuel cell of the present invention is not limited to carbon. In addition, in the above description, an example in which the present invention is applied to a solid polymer fuel cell has been described. However, a fuel cell to which the present invention can be applied is not limited to a solid polymer fuel cell.

It is sectional drawing which shows the fuel cell of this invention roughly.

Explanation of symbols

11, 21 Electrolyte 12, 22 Cathode 13, 23 Anode 17, 18, 27, 28 Separator 50 Extensive material layer 70 Metal layer 100 Fuel cell

Claims (3)

A fuel cell comprising an electrolyte, a cathode and an anode disposed on both sides of the electrolyte, and a separator disposed outside the cathode and the anode,
Furthermore, it has a spreadability material layer having higher spreadability and conductivity than the separator,
The spreadable material layer is provided with a metal layer that is liquid at the operating temperature of the fuel cell on both sides, and is disposed in contact with the separator. The fuel cell according to claim 1, wherein the spreadable material layer contains a metal. The fuel cell is a polymer electrolyte fuel cell;
The fuel cell according to claim 1 or 2, wherein the metal layer is made of an alloy containing indium and / or gallium.

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