Page 281 - Lindens Handbook of Batteries

CHAPTER 12

MERCURIC OXIDE BATTERIES

Nathan D. (Ned) Isaacs

12.1 GENERAL CHARACTERISTICS

The alkaline zinc/mercuric oxide battery is noted for its high capacity per unit volume, constant
voltage output, and good storage characteristics. The system has been known for over a century, but
it was not until World War II that a practical battery was developed by Samuel Ruben in response to
a requirement for a battery with a high capacity-to-volume ratio that would withstand storage under
tropical conditions. 1,2
Since that time, the zinc/mercuric oxide battery has been used in many applications where stable
voltage, long storage life, or high energy-to-volume ratios were required. The characteristics of
this battery system were particularly advantageous in applications such as hearing aids, watches,
cameras, some early pacemakers, and small electronic equipment, where it was widely used. The
battery has also been used as a voltage reference source and in electrical instruments and electronic
equipment, such as sonobuoys, emergency beacons, rescue transceivers, radio and surveillance sets,
small scatterable mines, and early satellites. These applications, however, did not become wide-
spread, except for military and special uses, because of the relatively higher cost of the mercuric
oxide system.
The use of cadmium in place of zinc results in a very stable battery with excellent storage and
performance at extreme temperatures due to the low solubility of cadmium in caustic alkali over a
wide range of temperatures. However, the cost of the material is high and the cell voltage is low,
less than 1.0 V. Hence, the cadmium/mercuric batteries were used, but to a lesser degree, in special
applications requiring the particular performance capabilities of the system. These include gas and
oil well logging, telemetry from engines and other heat sources, alarm systems, and for operation
of remote equipment, such as data-monitoring, surveillance buoys, weather stations, and emergency
equipment. 3
The market for mercuric oxide batteries has evaporated due to environmental problems associated
with mercury and cadmium. The 1996 Mercury-Containing and Rechargeable Battery Management
Act (P.L. 104-142) prohibits the sale of mercuric oxide batteries in the United States unless manu-
facturers provide for recycling and disposal. Furthermore, these batteries have been removed from
the International Electrotechnical Commission (IEC) and the American National Standards Institute
(ANSI) standards. In applications, they have been replaced by alkaline-manganese dioxide, zinc/air,
zinc/silver oxide, and lithium batteries.
The major characteristics of these two battery systems are summarized in Table 12.1.

12.1