Zinc-air battery

Overview
Zinc-air batteries and zinc-air fuel cells are electro-chemical cells that product power through the oxidation between zinc and ambient oxygen in the air. Due to the last of an integrated anode (produced by oxygen in the air), these batteries have high energy density and are inexpensive to produce. The come in a large variety of shapes an sizes, from small hearing-air batteries, to large batteries to power electric vehicles.

Zinc-air batteries are non-rechargeable due to the gradual evaporation of the included electrolyte and problems with crystallization, however, future developments may develop a way to circumvent this problem. In contrast, zinc-air fuel cells are mechanically rechargeable though refurbishing the anode and replacing the electrolyte.

Zinc-air batteries generate a general voltage os 1.65V. However, cells are typically developed to operate the the more standard 1.35-1.4V range. Due to the evaporating electrolyte, zinc-air cells tend to have a rather limited shelf life once used. Before use, they contain an air-tight seal that is typically good for several years. Removal of the seal begins a limited life-span. Likewise, since the cathode state does not change (oxygen), the cells product a fairly stable voltage throughout their lifespan.

Technical Details
Zinc-air cells operate through the following reaction:

Anode: Zn + 4OH– → Zn(OH)42– + 2e– (E0 = 1.25 V)

Fluid: Zn(OH)42– → ZnO + H2O + 2OH–

Cathode: O2 + 2H2O + 4e– → 4OH– (E0 = 0.4 V)

Overall: 2Zn + O2 → 2ZnO (E0 = 1.65 V)

While this generates a theoretical 1.65V, commercial cells are commonly developed to operate within a 1.35-1.4V range.