Fuel cell device

A fuel cell device individually has an electrolyte layer which is connected, in an ion conductive manner, to the electrolyte layer of a fuel cell and a half cell formed by a single electrode and a gas chamber. An electrochemical circuit for the purpose of transferring electrolyte is provided by using the single electrode of the half cell, the electrolyte layer of the corresponding fuel cell and the half cell, and either of an oxidant gas side electrode or a fuel gas side electrode. With this circuit, quick and quantitative replenishing electrolyte can be performed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a fuel cell device, and more particularly to a 
fuel cell device having an electrolyte replenishing function capable of 
realizing an easy and effective replenishment of electrolyte. 
2. Related Art Statement 
FIG. 1 is a perspective view, a part of which is omitted, illustrating an 
example of the general structure of a molten carbonate type of fuel cell 
device. A fuel cell device of the type described above comprises a fuel 
cell stacked body that is structured in such a manner that single fuel 
cells 4 (to be called "cells" hereinafter) are stacked with separator 
members interposed therebetween. The cell 4 comprises an oxidant gas side 
electrode 1, a fuel gas side electrode 2, and an electrolyte layer 3 which 
is interposed therebetween. A positive side terminal member 6a and a 
negative side terminal member 6b are mounted on the corresponding positive 
side end and negative side end portions. The above-described positive side 
terminal and the negative side terminal members 6a and 6b and the 
separator member 7 each has a gas impermeability, and form reaction gas 
flow lines 81a and 81b for supplying an oxidant gas and a fuel gas to the 
oxidant gas side electrode 1 and the fuel gas side electrode 2, 
respectively. These members 6a, 6b and the separator member 7 each has an 
electron conductivity so that they act to electrically connect the cells 4 
in a series. The side surfaces of the stacked body 5 are provided with gas 
manifolds 8a and 8b for distributing and supplying (or discharging) that 
oxidant gas and the fuel gas to the corresponding reaction gas flow lines 
81a and 81b. A gasket 9 is interposed between the stacked body 5 and the 
gas manifolds 8a and 8b to be abutted against each other. An arrow A in 
the figure designates the oxidant gas flow, while an arrow B designates 
the fuel gas flow. 
FIG. 2 shows a separator member 7a for replenishing electrolyte to which a 
replenishing pipe 10 is connected, this replenishing pipe 10 replenishing 
electrolyte from outside of the fuel cell device into the electrolyte 
layer 3 which is disclosed, for example, in Japanese Patent Laid-Open No. 
61-24159. A fuel cell device in which electrolyte can be replenished from 
outside thereof can be obtained by using the separator member 7a for 
replenishing electrolyte as the separator member 7. 
An operation of the fuel cell device will now be described. 
The electrolyte layer 3 in a molten carbonate type of fuel cell is 
constituted in such a manner that a substance (such as LiKCO.sub.3) which 
acts as the electrolyte is retained in a porous structure made of a 
material (such as LiAlO.sub.2) which is chemically stable and which has 
electrical insulation. It therefore acts as the electrolyte layer of a 
fuel cell and also acts as a gas separator layer for preventing mixing of 
the fuel gas to be supplied to the fuel gas side electrode and the oxidant 
gas to be supplied to the oxidant gas side electrode. If the quantity of 
the electrolyte contained in the electrolyte layer 3 becomes lacking for 
some reason, the internal resistance of the cell increases, causing for 
the cell characteristics to be deteriorated. If it becomes depleted 
excessively, the gas separating function becomes insufficient, causing the 
operation of the fuel cell to become difficult because of the resulting 
partial mixing of the fuel gas and the oxidant gas. 
In an actual molten carbonate type of fuel cell since the electrolyte 
diminishes from the electrolyte layer as the cell works, the insufficient 
quantity of the electrolyte causes the life of the fuel cell to be 
restricted because of the above-described reason. For example, the life 
test to which a cell is subjected resulted substantially in 10,000 hours, 
and the same to a stacked battery resulted in substantially 5,000 hours. 
Therefore, it is critical for lengthening the life of the fuel cell and 
improving the characteristics of the same to prevent depletion of the 
electrolyte in the electrolyte layer by some measures. 
The effect obtained by replenishing the electrolyte performed in the life 
test for the cell was, as shown in FIG. 3, confirmed by a group including 
an inventor of the present invention. That is, in this test, it was 
confirmed that replenishment of electrolyte was effective since the 
internal resistance was successively reduced and the electrical 
characteristics were improved. In this test, a first replenishment of the 
electrolyte was, as designated by a symbol A in FIG. 3, performed 3,200 
hours after the start of operation and the second replenishment was, as 
designated by a symbol B in FIG. 3, performed 5,500 hours after the same. 
However, in a conventional device which is, as shown in FIG. 2, constructed 
in such a manner that the electrolyte is directly replenished from outside 
to the electrolyte layer 3 of each cell 4 by means of a replenishing pipe 
10 which is provided for each separator member 7a, although an excellent 
replenishment of the electrolyte can be effected similarly to the test 
result shown in FIG. 3, the structure of the stacked layer becomes 
excessively complicated. 
Since the conventional fuel cell device is structured as described above, 
problems arise in that the structure of the stacked body is too 
complicated, causing the whole stacked body to be made thin, and cost to 
become great. Furthermore, since electrolyte needs in be replenished to 
each of the cells, the replenishing work becomes complex. 
FIG. 4 is a cross-sectional view illustrating an example of a fuel cell 
device comprising the conventional cells of a type disclosed in Japanese 
Patent Laid-Open No. 62-98568. 
Referring to this figure, a cell 4 comprises, similar to the device shown 
in FIG. 1, an oxidant gas side electrode 1, fuel gas side electrode 2, and 
electrolyte layer 3. The cell 4 is sandwiched by cell frames 11, and 
collector plates 12 are each disposed between the cell frame 11 and the 
electrode 1 or 2. A surface where the electrolyte layer 3 and the cell 
frame 11 are positioned in contact with each other is provided with a wet 
seal 13. An electrolyte retaining member 14 for retaining excessive 
electrolyte is accommodated in an electrolyte stoking space 15 disposed in 
the edge portion 11a of the cell frame 11. 
FIG. 5 is a cross-sectional view illustrating another example of a fuel 
cell device which is similar to that shown in FIG. 4 and which comprises 
the conventional cells of a type disclosed in Japanese Patent Laid-Open 
No. 62-98568. An electrolyte replenishing pipe 10 for replenishing, via 
the wet seal portion 13, electrolyte from outside to the electrolyte layer 
3 is provided. The remainder structure is constructed similarly to the 
conventional device shown in FIG. 4. 
As described above, replenishment of electrolyte has received growing 
interest as means for preventing depletion of electrolyte, and a variety 
of methods of replenishing the electrolyte and the replenishing structures 
have been examined. 
Referring to FIG. 4, the electrolyte retaining member 14 is a member 
constituted in such a manner that a surplus electrolyte is retained in a 
porous body such as zirconia felt. When the electrolyte retained in the 
electrolyte layer 3 becomes depleted, the surplus electrolyte contained in 
the electrolyte retaining member 14 is first moved to the electrolyte 
layer of the wet seal 13, next it is distributed over the entire surface 
of the electrolyte layer 3 due to the capillary phenomenon so that 
electrolyte replenishment is performed. 
At this time, the force to cause the electrolyte to be moved is the 
difference in the electrolyte retaining force between the electrolyte 
layer 3 and the electrolyte retaining member 14, and the electrolyte 
retaining force between the portion of the electrolyte layer 3 lacking in 
the electrolyte and the portion of the same which sufficiently retains the 
electrolyte. The difference in the electrolyte retaining force can be 
obtained by an arrangement conducted in such a manner that the diameter of 
the small apertures in the electrolyte layer 3 is made smaller than that 
of the electrolyte retaining member 14. 
In FIG. 5, the electrolyte which has been replenished, through the 
electrolyte replenishing pipe 10, to the electrolyte layer adjacent the 
wet seal portion 13 is distributed to the portion lacking electrolyte in 
the electrolyte layer 3 due to the capillary phenomenon so that 
electrolyte replenishment is performed. 
The above described methods of replenishing electrolyte is based on the 
following two phenomena: 
(1) The distribution of the electrolyte in a plurality of porous bodies in 
an equilibrium state is defined by the electrolyte retaining force of each 
porous body. 
(2) The movement of the electrolyte is a capillary phenomenon based on the 
electrolyte retaining force. 
The conventional electrolyte replenishing means that is based on the 
above-described phenomena can be effected in small cells having the 
effective electrode area of, for example, 300 cm.sup.2. However, the 
following problems arise when a large and long life fuel cell is intended. 
(1) The electrolyte retaining force which defines the distribution of the 
electrolyte can be generally obtained by arranging the small apertures 
distribution in the porous body which retains the electrolyte. However, 
since aperture distribution arrangement is difficult and this distribution 
is changed due to sintering and conversion of the crystal structure, it is 
difficult for the electrolyte retaining force to be stably controlled for 
a long time. 
(2) Since the movement of the electrolyte is due to the capillary 
phenomenon, the moving speed is insufficient. The moving speed of the 
electrolyte greatly depends upon the composition of the electrolyte, the 
diameter of the small apertures in the electrolyte layer, and the 
temperature. For example, it takes substantially 1000 hours for the 
electrolyte to be moved through an electrolyte layer of 30 cm. Since the 
time required for an electrolyte to be moved through a predetermined 
length is proportional to the square of the distance of movement, this 
raises a problem when a large size fuel cell is intended. 
(3) For the above-described two reasons, it is difficult for the effective 
degree of replenishment of the electrolyte which has been replenished from 
outside to be quantitatively assayed. 
Since the fuel cell device having the conventional electrolyte replenishing 
function is constructed as described above, it is difficult to quickly, 
uniformly and effectively replenish the electrolyte and a stable and 
constant electrolyte replenishment cannot be conducted over a long time 
when the battery has a large size and long life. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a fuel cell 
device capable of overcoming the above described problems. The device has 
an electrolyte replenishment function which realizes quick, uniform 
effective replenishment of electrolyte and in which electrolyte can be 
stably replenished over a long time period with the quantity of 
electrolyte replenishment acknowledged, even if in a large size fuel cell. 
The device according to the present invention comprises: a fuel cell 
including an oxidant gas side electrode and a fuel gas side electrode 
which are disposed away from each other, and an electrolyte layer 
sandwiched therebetween; a half cell including an electrolyte layer, a 
single electrode and a gas chamber; a connecting electrolyte layer for 
connecting, in an ion conductive manner, the electrolyte layer of the fuel 
cell and the electrolyte layer of the half cell; and a electrochemical 
circuit which is formed by a single electrode of the half cell and either 
of the electrodes of the fuel cell, and which electrochemically transfers 
the electrolyte between the fuel cell and the half cell, whereby the 
quantity or the composition of the electrolyte contained in the fuel cell 
is maintained by the transference of the electrolyte. 
Another fuel cell device according to the present invention comprising: a 
fuel cell stacked body formed by stacking single cells with separator 
members sandwiched therebetween, each of the single cells having an 
electrolyte layer, an oxidant gas side electrode disposed on one side of 
the electrolyte layer and a fuel gas side electrode disposed on the other 
side of the electrolyte layer; a positive terminal member and a negative 
terminal member which are disposed on the corresponding positive terminal 
and negative terminal which terminals are disposed along the direction of 
stacking the stacked body; means for supplying an oxidant gas via a gas 
manifold to each single cell of the fuel cell; electrolyte replenishing 
means for replenishing electrolyte to the single cell which is located at 
the most positive end portion of the stacked body; and a connecting bridge 
for connecting neighboring electrolyte layers of the single cell in an ion 
conductive manner, the connecting bridge having ion conductivity capable 
of transferring the electrolyte which has been replenished by the 
electrolyte replenishing means to the negative terminal portion.

DESCRIPTION OF PREFERRED EMBODIMENTS 
An embodiment of the present invention will now be described with reference 
to the accompanying drawings. FIG. 6 is a schematic structural view of a 
fuel cell device according to an embodiment of the present invention, in 
which electrolyte is replenished from a half cell to a single cell is 
described. 
This fuel cell device provides a single cell as a fuel cell 4, this fuel 
cell 4 comprising an oxidant gas side electrode 1, a fuel gas side 
electrode 2 and an electrolyte layer 3 interposed therebetween. 
Surrounding this fuel cell 4 is provided a cell frame 11, and a wet seal 
13 is provided between the cell frame 11 and the electrolyte layer 3. 
Current collecting plates 12 are disposed adjacent to the corresponding 
outer surfaces of the electrodes 1 and 2 in a contacting manner and in the 
cell frame 11. 
A half cell 16 is disposed in an extension direction of the electrolyte 
layer 3 in the fuel cell 4, this half cell 16 comprises an electrolyte 
layer 3a which is ion-conductively connected, with a connecting 
electrolyte layer 17, to the electrolyte layer 3 in the fuel cell 4 and a 
single electrode 18 disposed adjacent to this electrolyte layer 3a. A 
current collecting plate 12 is disposed adjacent to the single electrode 
18, and a cell frame 11b is disposed in such a manner that it surrounds 
this current collecting plate 12. A gas chamber 19 is formed between the 
cell frame 11b and the current collecting plate 12. The cell frame 11b is 
provided with an electrolyte replenishing pipe 20 for replenishing 
electrolyte. An electrochemical circuit 21 for transferring electrolyte is 
provided between the cell frame 11 and the cell frame 11b. This circuit 21 
comprises a circuit-driving power source 22 and an ammeter 23. The fuel 
cell 4 is provided with a loading circuit 24 so that a direct output can 
be obtained from the fuel cell 4 by actuating this circuit 24. 
An operation of this embodiment will now be described. 
In FIG. 6, the half cell 16 and the electrochemical circuit 21 are provided 
in addition to the fuel cell 4 and the loading circuit 24 which form a 
usual fuel cell device. 
The electrolyte layer 3a forming the half cell 16 is, for example, the same 
as the electrolyte layer 3 in the fuel cell 4. The single electrode 18 is 
a porous or non-porous electrode which is composed by in the main NiO, Cu 
and Au. 
When the electrochemical circuit 21 is operated, the following reactions 
occur on the whole in the oxidant gas side electrode 1 and the single 
electrode 18: 
in the oxidant gas side electrode 1; 
EQU 1/2O.sub.2 +CO.sub.2 +2e.sup.- .fwdarw.CO.sub.3.sup.2- (1) 
in the single electrode 18; 
EQU CO.sub.3.sup.2 -.fwdarw.1/2O.sub.2 +CO.sub.2 +2e.sup.- (2) 
With the progress of the reactions, positive ions such as K.sup.+ and 
Li.sup.+ which can be moved easier than the carbonic acid ion are moved 
in the main from the half cell 16 to the fuel cell 4 for the purpose of 
retaining the electrical neutrality of the electrolyte retained in the 
fuel cell 4 and that retained in the half cell 16, respectively. At this 
time, the connecting electrolyte layer 17 serves as a passage through 
which the ions pass. 
As a whole, in this embodiment, the electrolyte is electrochemically 
transferred from the half cell 16 to the fuel cell 4 as a result of the 
operation of the electrochemical circuit 21. Therefore, the electrolyte to 
be replenished to the fuel cell 4 is first stored in the half cell 16, and 
it may be replenished to the fuel cell 4 as needed by operating the 
electrochemical circuit 21. In this embodiment, the electrolyte 
replenishing pipe 20 is provided for the purpose of replenishing the 
electrolyte to the half cell 16. 
Since the moving speed of the electrolyte is proportional to the quantity 
of the electric current passing through the electrochemical circuit 21, 
the ammeter 23 is provided for the purpose of monitoring the moving speed 
of the electrolyte, that is, the quantity of the electric current. 
Furthermore, in this embodiment, the circuit driving power source 22 in 
the above circuit 21 is made to serve as a variable voltage type of direct 
current power source in order to control the quantity of electric current 
as needed. 
According to this embodiment, carbonic acid ion is electrochemically 
generated on the entire surface of the oxidant gas side electrode 1, and 
the moving speed of the positive ions is more efficient with respect to 
the capillary phenomenon which performs the basic roll in the conventional 
replenishment of electrolyte. Therefore, relatively quick and uniform 
replenishment of electrolyte with respect to the convention device can be 
performed. Furthermore, the amount of movement of the electrolyte and the 
moving speed of the same can be controlled by measuring and controlling 
the electric current passing through the electrochemical circuit 21. The 
following methods are conventionally well known as means for detecting the 
quantity and the composition of the electrolyte contained in the fuel cell 
4: a method of measuring the internal resistance of the fuel cell; a 
method of evaluating the rate of gas flow which penetrates the electrolyte 
layer 3; and a method of examining the operating condition dependency of 
the overvoltage of the reactions of the electrodes in the fuel cell. By 
using the above-described type of means with the present invention, a more 
effective control of the electrolyte can be conducted. 
In the electrochemical circuit 21 shown in FIG. 6, electrolyte is 
replenished to the fuel cell 4 by providing the single electrode 18 with a 
more noble potential than that of the oxidant gas side electrode 1. On the 
other hand, in a case where electrolyte is intended to be partially 
removed from the fuel cell 4, it can be removed from the fuel cell 4 by 
connecting the polarity of the circuit driving power source 22 in the 
electrochemical circuit in a reversed manner to that conducted in the 
device shown in FIG. 6. 
FIG. 7 is a schematic structural view of a fuel cell device according to 
another embodiment of the present invention illustrating a case where 
electrolyte is transferred from the fuel cell to the half cell. 
In FIG. 7, the electromotive force of a cell is used as the circuit driving 
power source of the electrochemical circuit which transfers the 
electrolyte, this cell being formed in the electrochemical circuit and 
formed by the electrolyte layer and the single electrode of the half cell, 
the electrolyte layer and the electrode on the one side of the fuel cell. 
In FIG. 7, such cell is formed in the electrochemical circuit 21 in 
addition to the fuel cell 4, this cell being formed by the fuel gas side 
electrode 2, single electrode 18 of the half cell 16, the electrolyte 
layer 3a of the half cell 16, the electrolyte layer 3 of the fuel cell 4, 
and the connecting electrolyte layer 17. The cell formed in this circuit 
21 acts as the driving power source thereof. 
Referring to FIG. 7, when a porous electrode which is in the main composed 
by NiO is used and a gas mixture composed in the main by oxygen and carbon 
dioxide is supplied to the gas chamber 19, the following reactions occur 
in the corresponding electrodes 2 and 18 so that electrolyte is 
transferred from the fuel cell 4 to the half cell 16: 
in the fuel gas side electrode 2; 
EQU H.sub.2 +CO.sub.3.sup.2- .fwdarw.H.sub.2 O+CO.sub.2 +2e.sup.-(3) 
in the single electrode 18; 
EQU 1/2O.sub.2 +CO.sub.2 +2e.sup.- .fwdarw.CO.sub.3.sup.2- (4) 
The speed at which the electrolyte is transferred is in proportional to the 
electric current passing through the electrochemical circuit 21. This 
speed can be easily adjusted by changing the composition of the gas to be 
supplied to the gas chamber 19, causing the electromotive force of the 
battery which acts as the driving power source of the circuit 21 to be 
changed or by adjusting a variable resistor 25 in the circuit 21 as shown 
in FIG. 7. 
An electrolyte storage space 26 and an electrolyte retaining member 27 act 
as an electrolyte reservoir for stocking the surplus electrolyte which has 
been transferred or to be transferred. 
In the present invention, it is a critical factor for electrochemically 
transferring the electrolyte to assure that the predetermined reactions 
progress as shown in equations (1), (2), (3), and (4) in the electrode 
portions in the electrochemical circuit 21. 
If the operating conditions for the electrochemical circuit 21 are not 
suitable, undesirable subreactions such as solution of the components in 
the electrolyte can occur, and furthermore, pollution of the electrolyte 
and corrosion of the members can occur. Referring to FIG. 8, an example 
(Advances in Molten Salt Chemistry Vol. 4, (1981) Plenum Press, New York) 
of the oxidation-reduction potentials of a variety of substances with 
respect to an (O.sub.2, CO.sub.2 /CO.sub.3.sup.2-) electrode are cited. 
According to this figure, if the operating voltage for the circuit driving 
power source 22 shown in FIG. 6 exceeds, for example, 1 to 2 V, solution 
of Fe and Cr can occur. Therefore, it is preferable for the circuit 
driving power source 22 to be driven with a voltage below the 
above-described level. 
In the above-described embodiment, although a case is described in which, 
in a single fuel cell, an electrochemical circuit which has a function of 
transferring electrolyte and which accompanies the fuel cell is employed, 
an electrochemical circuit may be provided in a fuel cell device in which 
plurality of single cells are stacked, this electrochemical circuit having 
a function of transferring electrolyte by way of respectively accompanying 
single or a plurality of the cells. It is a known fact that, in a fuel 
cell device in which a plurality of single cells are electrically 
connected to each other in a series, the single cell having the most 
positive potential becomes excessively lacking in the electrolyte with 
time, while the fuel cell which has the most negative potential increases 
electrolyte with time. Therefore, it is very effective for the fuel cell 
which is has the most positive or the most negative potential to be 
subjected to this embodiment. 
In a case where two or more types of electrolyte are mixed with each other 
to be used as the electrolyte in the fuel cell, a specific electrolyte 
component sometimes diminishes excessively. In this case, the specific 
electrolyte component which has diminished needs to be in the main 
replenished in the fuel cell. Specifically, the specific electrolyte 
component which is intended to be transferred to the half cell is arranged 
to be in a greatest quantity. 
Then, the other embodiment of the present invention will be described with 
reference to the drawings. 
In FIG. 9, on each side surface of the stacked body 5 is provided a 
connecting bridge 28 for electrically connecting, in an ion conductive 
manner, the neighboring electrolyte layers 3 of a plurality of stacked 
cells 4. In this embodiment, a gasket 9 serves as the connecting bridge 
28. The connecting bridge 28 may be individually provided from the gasket 
9. Reference numeral 29 represents electrolyte replenishing means for 
replenishing electrolyte to the cell 4a located in the most positive 
potential. The gasket 9 is constructed, for example, in such a manner that 
electrolyte contains zirconia dust, and it serves as the connecting bridge 
15 having the ion conductivity. The electrolyte replenishing pipe 10 is 
provided for the positive side terminal member 6a disposed adjacent to the 
cell 4a which is located in the most positive potential (in the uppermost 
position in the figure). Electrolyte can be supplying to the electrolyte 
layer 3 via the oxidant gas side electrode 1 by supplied the electrolyte 
to this pipe 10 so that means 29 for replenishing electrolyte can be 
formed. The positive side terminal member 6a having the characteristic 
electrolyte replenishing function of the present invention is shown in 
FIG. 10. The electrolyte replenishing pipe 10 is connected to a 
replenishing hole 30 provided in the terminal member 6a so that 
electrolyte can be replenished from the oxidant gas flow line to the 
electrolyte layer 3 via the oxidant gas side electrode 1. Since the 
electrolyte (for example, LiKCO.sub.3) is usually a solid body at low 
temperatures (for example at or near room temperature), the electrolyte 
replenishment can be further readily performed by the following methods: 
the electrolyte is powdered or granulated before it is supplied to the 
electrolyte replenishing pipe 10, and the electrolyte replenishing pipe 10 
is vibrated; the electrolyte is liquefied by heating the electrolyte 
replenishing pipe 10 above the fusing point of the electrolyte; or the 
electrolyte replenishing pipe 10 and the replenishing hole 30 are inclined 
in order to make the liquefied electrolyte easily flow downwards. 
With the electrolyte replenishing means 29 in this embodiment, the 
electrolyte supplied to the cell which has the most positive potential in 
the cell stacked body can effectively prevent the cell having the most 
positive potential from lacking in electrolyte, this cell having the most 
positive potential being the cell in which a lack of electrolyte most 
easily occurs. Therefore, propagation of the lacking in the electrolyte to 
the neighboring cell in the direction of the negative potential sequence 
can be prevented. Furthermore, since the thus-replenished electrolyte can 
be successively propagated in part to the other cells via the connecting 
bridge 28, the same effect as that obtained by replenishing the 
electrolyte to each cell can be obtained in the long term. As described 
above, the present invention provides a fuel cell device in which easy 
replenishment of electrolyte can be performed with only a simple 
structure, and which can operate with stable and excellent characteristics 
for long periods. 
The following four factors can be exemplified which cause diminishment of 
the electrolyte from the electrolyte layer 3: 
(1) vaporization of the electrolyte; 
(2) consumption due to the corrosive reaction with the components of the 
fuel cell; 
(3) oozing of the electrolyte into gaps; and 
(4) electrochemical movement of the electrolyte due to generation of local 
single cell. 
The inventors of the present invention measured the distribution of the 
content of the electrolyte in the fuel cell which has been subjected to a 
life test for the purpose of examining the relationship between the 
electrolyte consumption and each diminishing factor and the structure of 
each factor, resulting as follows: 
(1) The major reason for the diminishment of the electrolyte observed in 
the single cell test lies in that the electrolyte is transferred due to 
local generation of a short circuit cell (for example, 50 to 60% of the 
overall amount of diminished electrolyte is due to the diminishment caused 
by electrochemical transference of the electrolyte). 
(2) The electrolyte diminishing speed of the electrolyte in the cell 
stacked body is higher than that experienced with the single cell. The 
reason for this lies in that, since the gasket of the manifold provides 
the ion conductivity, the same effect as that obtained by connecting, with 
a bridge, the electrolyte layers of a plurality of cells can be obtained. 
Therefore, relatively many single cells having a short circuit therein are 
formed with respect to the single cell, causing the electrolyte to be 
transferred through the gasket of the manifold. 
As a result of this, the diminished electrolyte and the deterioration of 
the characteristics in the fuel cell are first observed in the cell having 
the most positive polarity of a plurality of single cells which forms the 
stacked body of the fuel cell. Then, this phenomenon propagates to the 
adjacent single cell. 
According to the present invention, lacking for electrolyte in the positive 
end cell and the propagation of the electrolyte to the neighboring cells 
in the negative potential direction due to the transference of the 
electrolyte can be effectively prevented. 
In the above-described embodiment, the described as what is electrolyte 
replenishing means 29 is a passage through which the electrolyte is 
replenished and which is formed by using the electrolyte replenishing pipe 
10 and the replenishing hole 30 for the purpose of replenishing the 
electrolyte from outside. This invention is not, of course, limited to 
this description. For example, a structure may be employed in which an 
electrolyte reservoir is used for excessively storing the electrolyte in 
the stacked body of the fuel cell for the purpose of supplying the 
electrolyte as needed to the single cell 4a. FIG. 11 shows an example of a 
case where an electrolyte reservoir is disposed in the positive terminal 
member 6a. Referring to this figure, the electrolyte which is first 
retained in a electrolyte retaining member 32 having a porous structure is 
moved to the electrolyte layer 3 when the electrolyte in the electrolyte 
layer 3 becomes lacking. Such movement of the electrolyte from an 
electrolyte reservoir 31 corresponding to the lack of the electrolyte in 
the electrolyte layer 3 can, as known, be realized by providing the 
diameter of the distributed small apertures in the electrolyte retaining 
member 32 to be greater than that of the distributed small apertures in 
the electrolyte layer 3 for the purpose of utilizing the capillary force. 
In this embodiment, the electrolyte replenishing means 29 is constructed 
from the electrolyte reservoir 31 and the electrolyte retaining member 32. 
In the above-described embodiment, all of the descriptions made are for the 
case in which the gasket 9 serves as the connecting bridge 28 for the 
electrolyte in the outer manifold type of fuel cell device in which the 
gas manifold 8a is secured to the side surface of the fuel cell stacked 
body 5. However, the present invention can be applied to an internal 
manifold type of fuel cell device (omitted from illustration) which does 
not need any gasket by individually providing an electrolyte connecting 
bridge. 
The electrolyte supplied having the cell 4a in the most positive potential 
is finally transferred to the most negative potential cell as a result of 
the action of the connecting bridge, as a result of which, the cell in the 
most negative cell exceeds in the electrolyte content over a long term. 
Therefore, it is preferable when the present invention is performed to 
simultaneously employ a structure in which the electrolyte which becomes 
excessive in a cell in the most negative potential can be absorbed. 
Specifically, this can be easily achieved by, in the cell having the most 
negative potential, providing an electrolyte reservoir for absorbing and 
retaining the electrolyte for either of the fuel gas side electrode or the 
oxidant gas side electrode, or by providing the above-described type of 
electrolyte reservoir for the negative terminal member.