Fuel cell

Details Fuel cell Fuel cell

1999-07-08

2002-02-19

Huff, Mark F. (Department: 1756)

Chemistry: electrical current producing apparatus, product, and

With pressure equalizing means for liquid immersion operation

C429S006000, C429S006000, C429S006000

Reexamination Certificate

active

06348280

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel cell that generates electricity by using an electrochemical reaction which is used for, for example, an electric vehicle.
2. Description of the Related Art
A fuel cell is, as well known, a device in which a pair of electrodes are made to be brought into contact with each other through an electrolyte, a fuel is supplied to one of the electrodes, an oxidant is supplied to the other electrode, and oxidation of the fuel is made to take place electrochemically in the cell, so that chemical energy is directly converted into electrical energy.
Fuel cells have several types according to the electrolyte. In recent years, as a fuel cell capable of obtaining high output, attention has been paid to a solid polymer type fuel cell which uses a solid polymer electrolyte film as an electrolyte. For example, when a hydrogen gas as a fuel is supplied to an anode, an air as an oxidant is supplied to a cathode, and an electric current is extracted from an external circuit, reactions as indicated by the following chemical equations take place.
 Anode reaction: H
2
→2H
+
+2e
−
  (1)
Cathode reaction: 2H
+
+2e
−
+½O
2
→H
2
O  (2)
At this time, hydrogen is transformed into a proton at the anode, moves, together with water, to the cathode through the electrolyte, and reacts with oxygen on the cathode to produce water. Thus, for the operation of the foregoing fuel cell, it becomes necessary to supply and exhaust a reaction gas such as a hydrogen gas and air, and to extract an electric current.
A separator plate for extracting an electric current from a fuel cell and for enabling the reaction gas and water to effectively flow is disclosed in, for example, Japanese Patent Application Laid-open No. Hei 3-206763 (U.S. Pat. No. 5,108,849).
FIG. 10
is a sectional view for explaining a conceptual structure of a single cell in a fuel cell disclosed in Japanese Patent Application Laid-open No. Hei 3-206763 (U.S. Pat. No. 5,108,849). In the drawing, reference numerals
1
and
2
denote conductive separator plates,
3
denotes a cathode,
4
denotes an anode, and
5
denotes an electrolyte body using, for example, a proton conductive solid polymer. The electrolyte body
5
, the cathode
3
, and the anode
4
constitute a single cell. Reference numeral
10
denotes a plurality of oxidant flow channels which are formed on one surface of the separator plate
1
, like bellows grooves in parallel with each other, and are for supplying, for example, an air as an oxidant to the cathode
3
, and
11
denotes a plurality of fuel flow channels which are formed on the separator plate
2
, like bellows grooves, and are for supplying, for example, a hydrogen gas as a fuel to the anode
4
.
FIG. 11
is an explanatory view showing the upper surface of the separator plate
1
in the conventional fuel cell shown in FIG.
10
. Hereinafter, the explanation will be made using
FIG. 10
together with FIG.
11
.
Reference numeral
20
denotes a major surface of the separator plate
1
,
21
denotes an electrode support portion for supporting the electrode
3
at the separator plate
1
,
22
denotes an oxidant supply opening which is formed in the separator plate
1
and is for supplying air as the oxidant,
23
denotes an oxidant exhaust opening for exhausting air,
24
denotes a fuel supply opening for supplying the fuel, and
25
denotes a fuel exhaust opening for exhausting the fuel.
In the separator plates
1
and
2
, the oxidant flow channels
10
and the fuel flow channels
11
are made of spaces each surrounded with a groove which is formed by cutting the major surface, and the electrode
3
or
4
.
The operation of the fuel cell will be hereinafter described with reference to
FIGS. 10 and 11
.
The air supplied from the air supply opening
22
of the separator plate
1
is supplied to the cathode
3
while flowing through the plurality of parallel oxidant flow channels
10
. On the other hand, similarly to the oxidant, the hydrogen gas is supplied to the anode
4
through the fuel flow channels
11
. At this time, since the cathode
3
and the anode
4
are electrically connected to the outside, the reaction of the chemical equation (2) takes place at the side of the cathode
3
, and unreacted air, nitrogen gas and water are exhausted through the oxidant flow channels
10
to the oxidant exhaust opening
23
.
At this time, the reaction of the chemical equation (1) takes place at the side of the anode
4
, and unreacted hydrogen gas is similarly exhausted through the fuel flow channels
11
to the fuel exhaust opening
25
. Electrons obtained by the reaction flow from the electrodes
3
and
4
via the electrode support portion
21
and through the separator plates
1
and
2
.
In the conventional separator plates, it is designed such that a gas flow speed is made fast so that the produced water can be exhausted. However, if one of the plurality of flow channels is blocked, it becomes impossible to generate electricity at the electrode surface for which the one of the flow channels has responsibility, so that there has been such a case that a reaction area is substantially reduced and the characteristics are lowered.
In a laminate in which a plurality of cells are stacked on each other, there has been a problem that in the case where a deficiency of fuel occurs in even one cell of the laminate, corrosion occurs in carbon as a structural member of the electrode, separator plate, or the like as shown in the following chemical equation (3), so that fatal damage is produced and efficiency of electric power generation is extremely lowered.
C+2H
2
O→CO
2
+4H
+
+4e
−
  (3)
Besides, for the purpose of unifying a reaction distribution on a cell surface, and in order to disperse a load applied to the cell surface, such a contrivance has been made that a plurality of through holes are provided in an electrode effective surface and fastening is made as disclosed in U.S. Pat. No. 5,484,666. However, since the plurality of holes are provided in the electrode, there has been such problems that a gas flow channel becomes complicated, and a surplus area loss is increased by a gas seal or the like.
SUMMARY OF THE INVENTION
The present invention has been made to solve such problems, and an object of the invention is to provide a fuel cell which has stable characteristics and produces high voltage/high output.
According to a first aspect of the present invention, a fuel cell is comprised of a laminate in which single cells each including an anode, a cathode, and an electrolyte film sandwiched therebetween, are sequentially stacked on each other through a separator plate provided with fuel flow channels for supplying a fuel fluid to the anode and oxidant flow channels for supplying an oxidant fluid to the cathode, wherein a midway portion of the flow channels of the separator plate is provided with a communicating hole communicating with the flow channels of another separator plate for the same kind of fluid, so that on the way of reactions of the fuel and the oxidant, the same kind of fluids flow into each other through the communicating hole.
According to a second aspect of the present invention, in the fuel cell of the first aspect, a cross sectional area of the flow channel at a downstream side with respect to the communicating hole in the separator plate is smaller than a cross sectional area of the flow channel at an upstream side.
According to a third aspect of the present invention, in the fuel cell of the first or the second aspect of the present invention, an area of the anode supplied with the fuel flowing through the fuel flow channels at a downstream side with respect to the communicating hole in the separator plate is smaller than an area of the anode supplied with the fuel flowing through the fuel flow channels at an upstream side.
According to a fourth aspect of the present invention, in the fuel cell of any one of th

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