Zinc-mercury oxide batteries (Zn/HgO)
Electric batteries - Zinc batteries

Batteries with zinc anode, mercury oxide cathode and alkaline electrolyte (also known as mercury batteries) were developed because of the high volumetric capacities achievable with the mercury oxide cathode. The voltage stability and very low self-discharge of this system led to its development by Samuel Ruben [8] , during the Second World War; it is a high-capacity battery that can be stored under tropical conditions. Although cylindrical formats of the R20 type were produced for military applications, this pair has since been used almost exclusively for button cells.

These and other zinc-anode batteries have been around for over a hundred years. They are no longer sold, as mercury...