Silver-oxide battery

A silver-oxide battery uses silver(I) 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 half-cell reaction at the negative plate:

${\displaystyle {\ce {Ag2O + 2H+ + 2e- -> 2Ag (v) + H2O}}}$, ${\displaystyle (E^{\circ }=+1.17{\text{ V}})}$

The reaction in the electrolyte:

${\displaystyle {\ce {2H2O -> 2H+ + 2OH-}}}$, ${\displaystyle (E^{\circ }=-0.83{\text{ V}})}$

The half-cell reaction at the positive plate:

${\displaystyle {\ce {{Zn}+2OH^{-}->{\overset {Zinc~hydroxide}{Zn(OH)2}}+2e-}}}$ , ${\displaystyle (E^{\circ }=+1.22{\text{ V}})}$

Overall reaction:

${\displaystyle {\ce {Zn + H2O + Ag2O -> Zn(OH)2 + 2Ag(v)}}}$, ${\displaystyle (E^{\circ }=+1.56{\text{ V}})}$

Overall reaction (anhydrous form):

${\displaystyle {\ce {Zn + Ag2O ->[{\ce {KOH/NaOH}}] ZnO + 2Ag (v)}}}$

Silver-oxide batteries have a nominal voltage of 1.55V. Compared to other batteries they have a higher open-circuit voltage than a mercury battery, and a flatter discharge curve than a standard alkaline battery.

Several sizes of button and coin cells, some of which are silver-oxide

Silver-oxide batteries become hazardous on the onset of leakage; this generally takes 5 years from the time they are put into use (which coincides with their normal shelf life). Until recently, all silver-oxide batteries contained up to 0.2% mercury. The mercury was incorporated into the zinc anode to inhibit corrosion in the alkaline environment. Sony started producing the first silver-oxide batteries without added mercury in 2004.[3]

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• Comparison of battery types
• Battery nomenclature