Incremental improvements continue to be made year by year in the consumer carbon-zinc and alkaline zinc-manganese dioxide cells. In addition, primary and secondary zinc-air cells many with substantial amounts of manganese dioxide in the cathode are becoming more common in consumer use. The gain in the past fifteen years in the carbon zinc cells approaches fifteen percent and that in alkaline cells-twenty percent. None the less the progress in zinc-air cells is most impressive as more and more commercial, compact designs appear for special purposes. These cells can produce more service than lithium cells of the same size. Finally the commercial presence of small secondary alkaline zinc-manganese dioxide cells continues. These cells are able to compete on a primary basis on heavy loads and much more obviously as rechargeable cells.
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