Zinc–air batteries (non-rechargeable), and zinc–air fuel cells, (mechanically-rechargeable) are electro-chemical 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.
In operation, a mass of zinc particles forms a porous anode, which is saturated with an electrolyte. Oxygen from the air reacts at the cathode and forms hydroxyl 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 have some properties of fuel cells as well as batteries: the zinc is the fuel, the reaction rate can be controlled by varying the air flow, and oxidized zinc/electrolyte paste can be replaced with fresh paste.
Zinc-air batteries can be used to replace the discontinued 1.35V mercury batteries (although with a significantly shorter operating life), which in the 1970s through 1980s were commonly used in photo cameras.
Possible future applications of this battery include its deployment as an electric vehicle battery and as a utility-scale energy storage system.
Read more about Zinc–air Battery: History, Reaction Formulas, Capacity-to-volume Ratio, Primary (unrechargeable) Cells, Secondary (rechargeable) Cells, Vehicle Propulsion, Alternative Configurations, Safety and Environment
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... Formerly, discarded zinc–air primary batteries were dropped into the water around buoys, which allowed mercury in the cells to escape to the environment ...