Fuel cell and process for producing the same

Details Fuel cell and process for producing the same Fuel cell and process for producing the same

2001-08-16

2004-02-24

Bell, Bruce F. (Department: 1746)

Chemistry: electrical current producing apparatus, product, and

With pressure equalizing means for liquid immersion operation

C429S006000, C429S006000

Reexamination Certificate

active

06696191

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a fuel cell and a process for producing the same. More particularly, the invention relates to a fuel cell which has a simple structure and can realize improved yield and reduced production cost, and a process for producing a fuel cell which can simplify a production process and can realize improved yield and reduced production cost.
2. Prior Art
In recent years, fuel cells using a solid electrolyte (for example, a solid polymeric film) as an electrolyte have drawn attention, for example, by virtue of no fear of liquid leakage unlike liquid electrolytes and, in addition, low mobility and easy uneven distribution of charges and polarization.
As shown in
FIG. 1
, this type of conventional fuel cells basically comprise a fuel battery cell
70
comprising a solid electrolyte film (for example, a solid polymeric film)
73
sandwiched between a pair of electrodes (a negative electrode
71
and a positive electrode
72
) and, in its turn, between catalysts
71
b
,
72
b
(a waterproof layer
72
c
).
Further, as shown in
FIG. 2
, fuel gas (hydrogen gas and oxygen gas) supply pipings
76
,
77
and a drainage pipe
78
are provided in the fuel battery cell
70
so that fuel gases are supplied through these pipings
76
,
77
and the produced water is discharged through the pipe
78
.
The power generation mechanism will be explained in conjunction with FIG.
1
.
In the negative electrode
71
, externally supplied hydrogen gas is passed through the negative electrode
71
and reaches near a reaction zone. Hydrogen molecules are divided into protons and electrons through the action of the catalyst
71
b
. Only the protons are passed through the solid electrolyte
73
, while the electrons move to the negative electrode
71
.
H
2
→2H
+
+2
e
−
On the other hand, in the positive electrode
72
, as represented by the following formula, two electrons are received from the positive electrode
72
in the presence of the catalyst
72
b
, and externally supplied oxygen molecules are reacted with water from the solid electrolyte
73
to produce hydroxyl ions.
1/2O
2
+H
2
O+2
e
−
→2OH
−
The protons, which have been passed through the solid electrolyte
73
, are reacted with the hydroxyl ions to produce water. Thus, the whole circuit is formed. Therefore, the reaction of the whole fuel cell is represented by the following formula, and hydrogen and oxygen in the fuel gas are reacted with each other to produce water.
H
2
+1/2O
2
→H
2
O
Further, as shown in
FIG. 3
, the above fuel battery cell
70
generally has a construction comprising: a portion comprising a catalyst
71
b
and a waterproof layer
71
c
provided respectively on both sides of the negative electrode
71
formed of an electrode sheet
71
a
; a portion comprising a catalyst
72
b
and a waterproof layer
72
c
provided respectively on both sides of the positive electrode
72
formed of an electrode sheet
72
a
; and the electrolyte
73
sandwiched between these two portions. Further, fuel gas passages (a hydrogen gas passage
74
and an oxygen gas passage
75
) are provided respectively on both external sides of the above construction.
Further, in order to increase the capacity (voltage/current), a plurality of battery cells are stacked on top of each other or one another, and separation for insulation between electrodes is made, for example, through a separator.
Regarding this type of conventional fuel cells, for example, Japanese Patent Laid-Open No. 233128/1999 discloses a fuel cell having a construction such that a fuel gas passage is also provided in a separator and a circumferential groove is provided so as to surround an electrode. The claimed advantage of the fuel cell disclosed in this publication is that the adoption of the above construction can eliminate gas leakage and the like.
Japanese Patent Laid-Open No. 334928/1998 discloses a phosphoric acid fuel cell comprising: an electrolyte reservoir provided with a fuel gas supply groove; a gas-impermeable separator; a plurality of battery cells stacked on top of each other or one another to constitute a battery stack; and a cooling plate which has been inserted for each several cells in the battery stack. The claimed advantage of the fuel cell disclosed in this publication is that the adoption of the above construction can realize prolonged service life of the battery.
In the fuel cell disclosed in Japanese Patent Laid-Open No. 233128/1999, however, since the fuel gas passage is also provided in the separator, for each electrode in each battery cell, a circumferential groove surrounding the electrode should be provided from the viewpoint of preventing gas leakage. This renders the structure of the fuel cell complicate and thus inevitably leads to high production cost.
In the case of the phosphoric acid fuel cell disclosed in Japanese Patent Laid-Open No. 334928/1998 as well, a cooling plate should be inserted for each several cells in the battery stack. Therefore, here again this renders the structure of the fuel cell complicate and thus inevitably leads to high production cost.
SUMMARY OF THE INVENTION
In view of the above problems of the prior art, the invention has been made, and it is an object of the invention to provide a fuel cell which has a simple structure and can realize improved yield and reduced production cost, and a process for producing a fuel cell which can simplify the production process and can realize improved yield and reduced production cost.
The above object can be attained by the following features of the invention.
[1] A fuel cell comprising a fuel battery cell, said fuel battery cell comprising: an internal electrode and an external electrode respectively with predetermined lengths which are coaxially disposed while leaving a predetermined space between the internal electrode and the external electrode; and a composite layer with a predetermined length, comprising an electrolyte layer and internal and external catalyst layers provided respectively on both sides of the electrolyte layer,
said composite layer being disposed in the predetermined space between the internal electrode and the external electrode while providing a gas passage between the composite layer and the internal electrode and providing a gas passage between the composite layer and the external electrode.
[2] The fuel cell according to the above item [1], wherein
the internal electrode is a hollow or solid internal continuous member having a plurality of grooves on its external surface,
the external electrode is a hollow external continuous member having a plurality of grooves on its internal surface, and
the gas passages are defined by the plurality of grooves in the internal continuous member and the plurality of grooves in the external continuous member.
[3] The fuel cell according to the above item [1], wherein the internal and external catalyst layers are provided respectively in face contact with both sides of the electrolyte layer.
[4] The fuel cell according to the above item [2], wherein the internal and external catalyst layers are provided respectively in face contact with a plurality of grooves in the internal and external continuous members.
[5] The fuel cell according to the above item [1], wherein at least one of the internal and external catalyst layers in the composite layer is covered with a waterproof layer.
[6] The fuel cell according to the above item [1], wherein the fuel battery cell is one of a plurality of fuel battery cells connected to each other or one another either in series or in parallel.
[7] A process for producing a fuel cell, comprising the steps of:
providing an internal electrode with a predetermined length;
providing a composite layer with a predetermined length, comprising an electrolyte layer and internal and external catalyst layers provided respectively on both sides of the electrolyte layer;

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