Page 295 - Lindens Handbook of Batteries

CHAPTER 13

Button Cell Batteries:
silver oxide–ZinC and

ZinC-air systems

Joseph Passaniti, denis Carpenter, and rodney mcKenzie

SECTion A

silver oxide−ZinC Batteries

13.1 GENERAL CHARACTERISTICS OF THE SILVER
OXIDE-ZINC BATTERY

The zinc/silver oxide system (zinc/alkaline electrolyte/silver oxide) offers several advantages for an
aqueous battery system: high capacity, a steady discharge voltage, and good storage capacity retention.
The theoretical capacity of monovalent silver oxide (Ag O) is 231 mAh per gram. The zinc/silver oxide
2
battery will discharge at a flat, constant voltage typically between 1.5 and 1.6 V at both high and low
discharge rates. The battery has long storage life, retaining more than 95% of its initial capacity after
1 year of room-temperature storage. It also has good low-temperature discharge capabilities, delivering
about 70% of its nominal capacity at 0°C and 35% at -20°C. These features have enabled the zinc/
silver oxide battery to be an important micropower source for electronic devices and equipment, such
as watches, calculators, electronic thermometers, glucometers, cameras, and other applications that
require small, thin, high-capacity, long-service-life batteries that discharge at a constant voltage. The
commercial primary zinc/silver oxide batteries are manufactured mainly in the button cell configura-
tion, with the sizes ranging from 5 to 250 mAh. There are a few applications for this battery system in
larger sizes, such as for the military, but its use is limited by the high cost of silver (see Chap. 34).
Of the three oxidation states of silver as an oxide, the monovalent state or silver (I) oxide (Ag O)
2
is most commonly used for commercial button cells. The divalent silver oxide or silver (II) oxide
(AgO) has a higher theoretical capacity (432 mAh per gram) but also has the disadvantages of a dual
voltage discharge and greater instability in alkaline solutions. The divalent silver oxide button cell
was sold commercially as “Ditronic” or “Plumbate” batteries. These formulations were discontinued
approximately two decades ago; the availability of divalent silver oxide button cells is limited. The
trivalent silver oxide or silver (III) oxide (Ag O ) is very unstable and is not used in batteries.
3
2
The major advantages and disadvantages of the zinc/monovalent silver oxide battery are sum-
marized in Table 13.1.
13.1