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 positive plate:

${\displaystyle {\ce {Ag2O + H2O + 2e- -> 2Ag (v) + 2OH-}}}$, ${\displaystyle (E^{\circ }=+0.34{\text{ V}})}$

The half-cell reaction at the negative 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):

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

Until 2004, all silver oxide batteries contained up to 0.2% mercury, incorporated into the zinc anode to inhibit corrosion from the alkaline environment.[7] This corrosion would occur regardless of whether or not the battery was providing power, making shelf life an important consideration with silver oxide batteries. Sony started producing the first mercury-free silver oxide batteries in 2004.

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• List of battery types

• SR (Silver Oxide Battery) from Maxell