Asilver zinc battery is asecondary cell that utilizessilver(I,III) oxide andzinc.
Silver zinc cells share most of the characteristics of thesilver-oxide battery, and in addition, is able to deliver one of the highestspecific energies of all presently known electrochemical power sources. Long used in specialized applications, it is now being developed for more mainstream markets, for example, batteries inlaptops and hearing aids.[1][2]
Silver–zinc batteries, in particular, are being developed to powerflexible electronic applications, where the reactants are integrated directly into flexible substrates, such as polymers or paper, using printing[3] or chemical deposition methods.[4]
Experimental new silver–zinc technology (different to silver-oxide) may provide up to 40% more run time thanlithium-ion batteries and also features a water-based chemistry that is free from thethermal runaway and flammability problems that have plagued the lithium-ion alternatives.[1]
Thesilver–zinc battery is manufactured in a fully discharged condition and has the opposite electrode composition, thecathode being of metallic silver, while theanode is a mixture ofzinc oxide and purezinc powders. The electrolyte used is apotassium hydroxide solution in water.
During the charging process, silver is first oxidized tosilver(I) oxide
and then tosilver(II) oxide
while the zinc oxide is reduced to metallic zinc
The process is continued until the cell potential reaches a level where the decomposition of the electrolyte is possible at about 1.55 volts. This is taken as the end of a charge, as no further charge is stored, and anyoxygen that might be generated poses a mechanical and fire hazard to the cell.
This technology had the highestenergy density prior to lithium technologies. Primarily developed for aircraft, they have long been used in space launchers and crewed spacecraft, where their short cycle life is not a drawback. Non-rechargeable silver–zinc batteries powered the first SovietSputnik satellites, as well as USSaturn launch vehicles, theApollo Lunar Module,lunar rover andlife-support backpack.
The primary power sources for the Apollocommand module (CM) were the hydrogen/oxygenfuel cells in the service module (SM). They provided greater energy densities than any conventional battery, but peak-power limitations required supplementation by silver–zinc batteries in the CM that also became its sole power supply during re-entry after separation of the service module. Only these batteries were recharged in flight.
After theApollo 13 near-disaster, an auxiliary silver–zinc battery was added to the service module as a backup to the fuel cells. The Apollo service modules used as crew ferries to theSkylab space station were powered by three silver–zinc batteries between undocking and service module jettison, as the hydrogen and oxygen tanks could not store fuel-cell reactants through the long stays at the station.
These cells are found in applications for the military, for example inMark 37 torpedoes and onAlfa-class submarines.
in the 1960sGeneral Motors developed an electric car calledElectrovair, which was powered by a zinc-silver battery produced byEagle-Picher.[5] However, the battery was expensive and lasted only a hundred charge-discharge cycles.[6]
