Thin-film zinc/manganese dioxide electrodes

Thin-film electrodes allow the manufacturing of flat batteries of variable design. Their electric performance is better than that of customary cells b ecause of a larger contact area between anode and cathode and better utiliz ation of the electrochemically active materials. Bipolar thin-film electrod es for the rechargeable alkaline zinc/manganese dioxide system were assembl ed using graphite-filled plastics thigh-density polyethylene and polyisobut ylene). In a different approach. extremely thin electrodes were obtained us ing 25 mum thick foils made of non-conductive microporous polypropylene. Th e electroactive materials were electrolytically deposited into the pores of the previously metallized foil, providing the required conductive connecti on through the plastic matrix by themselves. Cycle behavior, cumulated capa cities, and energies of batteries with up to two bipolar units were measure d. At this early stage of development, batteries based on graphite-filled p olymer foils showed better results with regard to storage capacity per unit area and to cycle life. Prototypes based on micro-porous polypropylene suf fered from the relatively small fraction of pore volume available for the d eposition of active material (about 38%) and from current collector corrosi on.