Page 270 - Battery Reference Book

22/4 Carbon-zinc and carbon-zinc chloride batteries

22.2 Carbon-zinc chloride primary current densities are minimized by the more uniform
batteries and higher diffusion rates that exist in an electrolyte
containing only zinc chloride. Because of their abil-
The zinc chloride LeclanchC cell is a special modifi- ity to operate at high electrode efficiencies, the use-
cation of the carbon-zinc cell. They differ principally ful current output of zinc chloride cells is usually
higher than that of carbon-zinc, and zinc chloride
in the electrolyte systems used. The electrolyte in a cells will operate at high current drains for a consid-
zinc chloride cell contains only zinc chloride, while erably longer time than carbon-zinc cells of the same
in a carbon-zinc cell the electrolyte contains a satu- size. In addition, the voltage level under load holds up
rated solution of ammonium chloride in addition to longer.
zinc chloride. The omission of ammonium chloiide Because of the electrochemical reactions that occur
improves the electrochemistry of the cells but places in the zinc chloride cell during use, water in the cell is
greater demands on the cell seal. Zinc chloride cells consumed (by a reaction product which is an oxide
therefore have either a new type of seal not previ- compound) along with the electrochemically active
ously used in carbon-zinc cells or an improved con- materials, so that the cell is almost dry at the end of
ventional seal so that their shelf life is equivalent its useful life.
to that of carbon-zinc cells. Electrode blocking by A cross-section view of a D-size zinc chloride cell
reaction products and electrode polarization at high is shown in Figure 22.3.