MUCH attention has been given recently to developing a high energy density secondary battery based on the zinc/air electrochemical system. These batteries consist of several divided cells comprising a zinc anode, air cathode, and an electrolyte of aqueous potassium hydroxide of strength ranging from 2 to 9 M. During discharge the overall chemical reaction occurring in the battery may be regarded simply as the formation of zinc oxide from its elements. During the charging cycle the zinc is recovered according to the following reactions © 1969 Nature Publishing Group.