The Reasons of Thermal Runaway in Nickel-Cadmium Batteries

Background: A thermal runaway phenomenon occurs in batteries of all the electrochemical systems. In the case of the thermal runaway occurrence, a battery heats up sharply and afterwards a battery body inflammation is possible followed by an explosion. In this case inevitably, a system contained the battery goes unserviceable. Objective: The goal of this work is to review the most important results received on thermal runaway by the present moment. Results: It has been established experimentally that a probability of a thermal runaway in the nickel-cadmium accumulators KSX-25 grows with an increase of a constant-voltage charge as well as of an environmental temperature and an accumulator time in service. It was shown on the basis of charge cur-rent, terminal voltage, and change in battery temperature that during thermal runaway, the observed changes cannot be explained by the self-acceleration of known reactions (due to overheating), battery charging and electrolyte decomposition. The observed changes can only be explained if we assume, that the thermal runaway is associated with a powerful electrochemical reaction going within the battery with a terminal voltage approximately 0.55 V. It is shown that the recombination reaction of atomic hydrogen accumulated in the electrodes is exothermic thermal runaway reaction in alkaline batteries. Conclusion: New mechanism of thermal runaway in Ni-Cd batteries, which explains all the experimental data known currently is proposed. Based on the proposed mechanism received patents for a method of diagnosing a predisposition of batteries to thermal runaway.