(1) Field of the Invention
The present invention relates to a fuel cell comprising at least one cell structure that includes a cell having an anode and a cathode with an electrolyte being interposed therebetween.
(2) Description of the Related Art
A fuel cell is an energy-conversion device that directly converts an energy of a supplied gas into an electric energy, and researchers have been actively studying a phosphoric acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), a solid oxide fuel cell (SOFC), and a polymer electrolyte fuel cell (PEFC) to utilize the fuel cell's potential high energy-generation efficiency. The base unit of the fuel cell is a cell having a cathode on one surface, and an anode on the other surface, of an electrolyte membrane.
Since an output voltage (V) and a current density (mA/cm.sup.2) of a single cell is limited, a stack is formed by accumulating a plurality of the cells with separators being interposed therebetween to connect the same in series, thereby yielding an output voltage and a current density as desired for individual applications.
For example, given that one cell outputs about 0.6 V, two hundred cells are accumulated to yield about 120 V. However, the resulting stack will be about 2 m high including the thickness of the separators, whereas a space where the fuel cell is installed limits the height of the stack. In addition, manifolds must be attached to all the side surfaces of the stack along the direction in which the cells are accumulated to supply a reactant gas, making the resulting fuel cell considerably large and heavy.
A method to eliminate such a problem is disclosed in Japanese Laid-open Patent Application No. 62-200666. In this method, the cells are inserted in a plurality of through holes formed on an insulating base, and the cells are connected either in series or parallel. Because one base contains a plurality of the cells, a compact, high-voltage generating fuel cell can be assembled. However, although materials forming the cell, such as an electrolyte plate, must be placed accurately in the through hole when assembled, it is by no means easy to do so. Particularly, in case of the PEFC, the electrolyte membrane serving as the electrolyte plate is so soft that considerable skill is required to place the same in the through hole. Also, an anode and a cathode gas pressure cause the electrolyte membrane to sag or the gases to leak during operation.
Moreover, the arrangement of the cells, or the matrix, can not be changed easily because it is inevitably determined by the arrangement of the through holes. Thus, the number and arrangement of the cells can be changed only by replacing the base with a new one having the through holes in a different arrangement.