The faradaic efficiency of the lithium-thionyl chloride battery

Abstract

In lithium / thionyl chloride (LflC) cells, a lithium limited design was thought to be safer than a cathode limited design because the amount of lithium left in discharged cells would be minimal. However, lithium corrosion reduces the capacity faster than does cathode degradation during storage. The optimization of the ratio of lithium to c h o n was studied, considering storage time and temperature. The efficiency of converting chemical energy into electrical energy has been studied for the case of D cells with surface area from 45 to 345 cm2, under constant and various pulsed loads. Microcalorimetric monitoring of the heat output during discharge allowed the direct measurement of the faradaic efficiency, and showed that self-discharge is far more pervasive than previously acknowledged.' Typical faradaic efficiencies for constant load varied from 30% at low current density to 90% at moderate and 75% at high current density. Pulsed current further depresses these efficiencies, except at very low average current density.