PURPOSE: To maintain the same performance as a matrix and give the function of a spacer by increasing density of the periphery of a matrix holding electrolyte than that of the matrix and containing electrolyte in this periphery.

CONSTITUTION: Slurry is prepared by adding 60∼80wt% of phosphoric acid to zirconium oxide. The slurry is spreaded in the periphery of a porous electrode substrate 4 in a width of 10∼25mm and a thickness of 0.3∼1.0mm, and heated at 50∼250°C for 10∼90min to form a solid spacer 7 of zirconium oxide. A mixture 5A of matrix material and phosphoric acid electrolyte is filled inside the dense periphery, then electrodes 3 and 4 are combined, and they are placed between separators 1 and 2 to form a unit cell.