Safety Improvement of Military Lithium Thionyl Chloride Battery via Internal Pressure Reduction

This study investigates the frequent rupture and leakage of military Li/thionyl chloride (Li/SOCl<sub>2</sub>) batteries, a failure mode attributed to elevated internal pressure resulting from a 2004 design modification that incorporates excessive active material. To enhance operational safety, a redesigned cell was developed in which Li and separator contents were each reduced by more than 10%, and the conventional aluminum additive was replaced with gallium. The substitution of gallium mitigated “cathode freeze-over,” thereby improving discharge efficiency without compromising performance. The modified design achieved a 28.6% reduction in internal pressure and extended discharge duration by more than 3 h. Field trials confirmed high user satisfaction with respect to both safety and performance, indicating strong potential for integration into a broad range of weapon systems.