Silver zinc battery
| Specific energy | 130 Wh/kg |
|---|---|
| Energy density | 500 Wh/L |
| Specific power | High |
| Charge/discharge efficiency | N/A |
| Energy/consumer-price | Low |
| Time durability | High |
| Cycle durability | N/A |
A silver-oxide battery (IEC code: S) is a primary cell with a very high energy to weight ratio. Available either in small sizes as button cells (where the amount of silver used is minimal and not a significant contributor to the product cost), or in large custom designed batteries where the superior performance of the silver-oxide chemistry outweighs cost considerations. These larger cells are mostly found in applications for the military, for example in Mark 37 torpedoes or on Alfa-class submarines. In recent years they have become important as reserve batteries for manned and unmanned spacecraft. Spent batteries can be processed to recover their silver content.
Silver-oxide primary batteries account for over 20% of all primary battery sales in Japan (67,000 out of 232,000 in September 2012).
A related rechargeable secondary battery usually called a silver–zinc battery uses a variation of silver–oxide chemistry. It shares most of the characteristics of the silver-oxide battery, and in addition, is able to deliver one of the highest specific energies of all presently known electrochemical power sources. Long used in specialized applications by both the military and NASA, rechargeable silver-zinc battery technology is now being developed as a microbattery for more mainstream markets such as hearing aids, where safety, combined with a high energy density to size ratio, is required.
A silver-oxide battery uses silver oxide as the positive electrode (cathode), zinc as the negative electrode (anode) plus an alkaline electrolyte, usually sodium hydroxide (NaOH) or potassium hydroxide (KOH). The silver is reduced at the cathode from Ag(I) to Ag and the zinc is oxidized from Zn to Zn(II). The chemical reaction that takes place inside the battery is the following:
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