Monday, July 29, 2013

What is a Zinc–air battery?

Zinc–air batteries (non-rechargeable), and zinc–air fuel cells (mechanically-rechargeable) are metal-air batteries powered by oxidizing zinc with oxygen from the air. These batteries have high energy densities and are relatively inexpensive to produce. Sizes range from very small button cells for hearing aids, larger batteries used in film cameras that previously used mercury batteries, to very large batteries used for electric vehicle propulsion.
During discharge, a mass of zinc particles forms a porous anode, which is saturated with an electrolyte. Oxygen from the air reacts at the cathode and formshydroxyl ions which migrate into the zinc paste and form zincate (Zn(OH)2−
4
), releasing electrons to travel to the cathode. The zincate decays into zinc oxide and water returns to the electrolyte. The water and hydroxyls from the anode are recycled at the cathode, so the water is not consumed. The reactions produce a theoretical 1.65 volts, but this is reduced to 1.35–1.4 V in available cells.
Zinc-air batteries can be used to replace now discontinued 1.35 V mercury batteries(although with a significantly shorter operating life), which in the 1970s through 1980s were commonly used in photo cameras.
Source Wikapedia