Solid electrolyte fuel cell

Details Solid electrolyte fuel cell Solid electrolyte fuel cell

1999-05-21

2001-04-17

Huff, Mark F. (Department: 1756)

Chemistry: electrical current producing apparatus, product, and

With pressure equalizing means for liquid immersion operation

C252S062200, C204S421000, C204S429000

Reexamination Certificate

active

06218036

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a solid electrolyte fuel cell.
2. Description of the Related Art
A solid electrolyte fuel cell directly converts chemical potential energy contained in fuel into electric energy by an electrochemical reaction.
FIG. 1
shows a minimum unit of the solid electrolyte fuel cell for generation of electric power. As shown in
FIG. 1
, the cell
1
comprises a generation section
2
, charge collectors
3
and
4
between which the generation section
2
is inserted, and separators
5
and
6
between which the generation section
2
and charge collectors
3
and
4
are inserted. The generation section
2
is a three-layer film and comprises an air electrode
7
, a solid electrolyte film
8
and a fuel electrode
9
.
Lanthanum manganite (LaMnO
3
) has been used for the material of the air electrode
7
, and yttria-stabilized zirconia (referred to as YSZ hereinafter) has been used for the material of the solid electrolyte film
8
. A cermet prepared by mixing, for example, Ni with YSZ has been used for the material of the fuel electrode
9
.
Lanthanum manganite (LaMnO
3
) has also been used for the charge collectors
3
at the air electrode side and Ni has been used for the charge collectors
4
at the fuel electrode side. Lanthanum chromite (LaCrO
3
) has been used for the material of the separators
5
and
6
.
The conventional solid electrolyte film
8
of the solid electrolyte fuel cell
1
having the cell construction described above has a sufficient thickness so that the cell can endure the stress generated during operation or when the temperature is increased or decreased. This causes a problem in that the cell suffers a large potential drop during power generation, thereby resulting in a low generation performance.
In order to solve this problem, it has been proposed that the solid electrolyte film be reinforced by adding alumina (Al
2
O
3
) into the solid electrolyte film while reducing its thickness. It is true that alumina enhances the mechanical strength of the solid electrolyte film, but alumina also increases the potential drop. As a result, the solid electrolyte film has a good mechanical strength but also has a large potential drop, or the solid electrolyte film has a lower potential drop, but also has less mechanical strength.
SUMMARY OF THE INVENTION
The present invention can solve the aforementioned problems associated with the conventional solid-electrolyte fuel cell and provides a solid-electrolyte fuel cell having a sufficient mechanical strength, lower thickness and lower potential drop.
The solid electrolyte fuel cell comprises an air electrode, a fuel electrode and a solid electrolyte film disposed between the air electrode and the fuel electrode. The solid electrolyte film is formed of yttria-stabilized zirconia in which alumina is added, the concentration of the supplemented alumina at the surface layer section of the solid electrolyte film being larger than that at the center layer section of the solid electrolyte film.
According to the present invention, the internal resistance can be reduced by reducing the thickness of the solid electrolyte film without lowering the fracture stress of the solid electrolyte film in the solid electrolyte fuel cell. Accordingly, the generation section is not fractured during operation or during temperature increase and decrease, enabling one to reduce the potential drop in the generation section. The construction allows electric power generation characteristics of the solid-electrolyte fuel cell to be improved besides stabilizing power generation performance with a prolonged life span.
For the purpose of illustrating the invention, there is shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.


REFERENCES:
patent: 4347114 (1982-08-01), Kimura et al.
patent: 5130210 (1992-07-01), Iwasaki et al.
patent: 5547556 (1996-08-01), Kobayashi et al.
patent: 1471770 (1970-08-01), None
patent: 034718 (1966-06-01), None
patent: 1048839 (1966-11-01), None

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