Electrolyte matrix structures for molten carbonate fuel cells which: have a fine, uniform, and controlled porosity; are stable under operating conditions; and readily meet acceptable performance levels. These structures or matrices are easily manufactured by a simple and scalable technique from a slip containing particulate LiAlO.sub.2 dispersed in an organic vehicle and an acrylic-based binder. The solvent is evaporated, leaving a flat, flexible, green structure. The green-structure is heated in a non-oxidizing atmosphere to thermally decompose and thereby remove the binder. This leaves a porous structure which is impregnated with molten carbonate by capillary action.