The Silver-Zinc Cell: A Button Battery

The cell diagram of a silver-zinc cell is:Zn(s), ZnO(s)|KOH(satd)|Ag2O(s), Ag(s)

The half reactions on discharging are:Reduction: Ag2O(s) + H2O(l) + 2e- 2 Ag(s) +

2OH-(aq)Oxidation: Zn(s) + 2OH-(aq) ZnO(s) +

H2O(l) + 2e-

Overall: Zn(s) + Ag2O(s)ZnO(s) + 2 Ag(s)

Characteristics:0Because no solution species is involved in the cell

reaction, the quantity of electrolyte is very small and electrode can be maintained very close together.

0Cell voltage is 1.8 V0Storage capacity is six times greater than that of a

lead-acid battery of the same sizeUses:0These characteristics make batteries such as silver

zinc cell useful in button batteries. These miniature batteries are used in watches, hearing aids and cameras.

0Silver-zinc batteries fulfill the requirements of spacecraft, satellites, missiles, rockets, space launch vehicles, torpedoes, underwater vehicles and life support systems

0On the Mars Pathfinder mission, the rover and the cruise system were powered by solar cells. The energy storage requirements of the lander were met by modified silver-zinc batteries with about three times the storage capacity of the standard nickel-cadmium rechargeable battery