Causes of failure in sealed nickel-cadmium batteries : S. Gross, The Boeing Company, Seattle, Washington. Energy Conversion11, 39–45 (1971)

Abstract

Nickel-cadmium cells consist of alternately interleaved positive and negative plates kept apart by a porous separator, and wetted by an ionically conductive electrolyte. Plates are most commonly made by impregnating nickel and cadmium chemical compounds in highly porous thin nickel skeletons called plaques. The assembly is sealed in a metal or plastic case penetrated by insulated terminals. Much has been learned about the chemistry of the nickel-cadmium battery since its invention 50 yr ago, but it remains a complex chemical-physical system with considerable fundamental study remaining to be done. A complete understanding, particularly of the many internal interactions, would be invaluable in designing better, longer life batteries. Even with a complete understanding attainment of long life will be handicapped by design compromises, manufacturing limitations and manner of use. Battery design is a compromise of many requirements, including charge and discharge rate capability, overcharge capability, high and low temperature performance, charge and discharge voltage limits, storage capability, energy density, cost, safety and cycle life. The relative emphasis that manufacturers give to each of these factors will have an important impact on life. Battery life is intimately related to the manufacturing processes. Regardless of new knowledge on factors affecting battery life, most manufacturers are economically restrained from major modifications to their present processes. Unless sound electrochemical principles and process control are used during manufacture, reliable long cell-life cannot be achieved. The: way a battery is used will have important influences on lifetime. Life is known to be shortened by rapid charge and discharge, by deep depths of discharge, by high temperatures and by excessive overcharge. Use of an optimum charge control system can extend battery life significantly. The :failure of a cell or battery may be defined as current, voltage or power out of tolerance specified by the user, and can occur during charge, discharge or open circuit. Failure definition depends on the application, and can range from a slight degradation to a near-total loss. The causes of failure are those defects or imperfections in cells that ultimately give rise to failure. The failure ]process itself is often a complex sequence of chemi-