High temperature lithium-sulphur cells

The high-rate capability of the cells is favoured by the high conductivity of the electrolyte and the small effect of temperature on the conductivity. Heat dissipation structures are recommended for lithium-sulphur dioxide cells and batteries that operate at high power levels. Lithium-sulphur dioxide cells can operate at 460W/kg while delivering lOOW/kg in suitable high-rate configurations. 

Honeywell have described their work on the development of an alternative electrolyte for a multi-cell lithium-sulphur dioxide resen e battery. In developing a multi-cell lithium reserve battery, the lithium bromide-sulphur dioxide acetonitrile electrolyte system used in their primary batteries was found to be unstable when stored by itself at high temperature - a functional capability required for all resen e applications. In addition to consumption of the oxidant sulphur dioxide in reactions causing instability, some of the products of electrolyte degradation arc solid, which would cause nrajor problems in activation. Primary active cells after storage do not undergo such degradation reactions. 

The capacity or service life of a lithium-sulphur dioxide cell at various discharge rates and temperatures is shown in Figure 30.55. The data are normalized for one cell and presented in terms of hours of service at various discharge rates. The linear shape of these curs es, except for the fall-off at high current levels and low temperatures, is again indicative of the capability of the lithium-sulphur dioxide battery to be efficiently discharged at these extreme conditions. These data are applicable to the standard cells and can be used in several ways to calculate the performance of a given cell or to select a cell of a suitable size for a particular application. 

Applications for lithium-thionyl chloride cells and active batteries include all those for which active lithium-sulphur dioxide cells and batteries are recotmnended, and also high-temperature applications. 

Hazardous incidents have been experienced with some lithium systems, particularly those using sulphur dioxide and thionyl chloride cathodes. These incidents generally occur at later stages in battery life under reverse current conditions, during voltage reversal and while operating at high temperatures. Safety incidents have not been experienced with lithium-iodine cells, which is why they power 90% of the cardiac pacemakers presently in use. 

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