A zinc-air battery is a type of metal-air electrical storage and discharge device that works through the oxidization of zinc. Cheap to produce and possessing a relatively large capacity, they are used in applications ranging from in-ear hearing aids to electric fences. For the most part, zinc-oxide batteries are non-rechargeable. New advances, however, have made rechargeable fuel-cell type designs possible in the 21st century.
The electrical properties of zinc were hit upon in the early 20th century by scientists building on 19th century techniques of producing a reaction by exposing various elements to oxygen. As with any battery, there are two ends. The positive end is known as the cathode, and the negative is called the anode. In the case of a zinc-air battery, the cathode is atmospheric oxygen and the negative is the supply of zinc. Rechargeable designs often simply work by having a zinc anode cartridge that can be switched out and replaced with a fresh one.
Like all metal-air designs, a zinc-air battery begins to work as soon as the cathode is introduced to the anode. In many cases, such as with hearing aid batteries, the zinc is sealed by means of a pull-tab. Before initial use, this tab is pulled and within five seconds the battery is fully energized.
One of the main benefits of zinc-air batteries is its longevity while sealed. A zinc-air battery with a pull-tab can sit for upwards of three years and still retain nearly 100% of its overall capacity. Larger models with more effective seals may last indefinitely. After they are first exposed to oxygen, zinc-air batteries discharge relatively quickly and should be used immediately.
A zinc-air battery can have as much as three times the capacity of a similarly sized alkaline one, and this high capacity has made them ideal for use in remote areas. They were first adapted to power items such as ocean buoys and railroad signals. Subsequently they were applied to smaller applications like watch batteries, which have similar long-term, low-current power demands.
The major downside to zinc-air batteries is related to their naturally high internal resistance. This means that while there is a high relative capacity for size, ability to generate high current is diminished. A zinc-air battery providing a high current would need to be much larger than a similar alkaline battery, so they are unsuitable for items such as consumer electronics. Zinc-air batteries are also more susceptible to moisture damage than other types of batteries and must be kept in sealed compartments for optimum performance.
In most cases, a small to medium-size zinc-air battery can be disposed of normally with other trash. Larger ones or rechargeable models may constitute a hazardous substance in some jurisdictions. As a result, they should be taken to a recycling or designated disposal facility.