A storage battery is provided comprising appositive electrode of lead, a negative electrode of mercury, and an electrolyte consisting of an aqueous solution of a salt of an alkali metal. Upon charging the battery, lead is converted to lead dioxide and the alkali metal forms the amalgam with the mercury. During discharge, the lead dioxide is reduced to the plumbous state and the alkali metal is oxidized to the positive ion and goes into solution. The mercury is immobilized in one of several alternative ways.