Anode-limited cell reversal in lithium-sulfur oxyhalide cells

In situ infrared spectroscopy and mass spectrometry were used to investigate the gas and liquid phases in lithium-sulfur oxyhalide cells driven into anode-limited reversal at 1-5 mA/sq cm. In the lithium-thionyl chloride system the species HCl, CS2, SO2, S2O, SCl2, and SO2Cl2 were identified in the gas phase and HCl, AlCl3OH(-), SO2, SO2Cl2, and SOCl(+) AlCl4(-) in the liquid phase. A species giving rise to three absorption bands at 1337, 1070, and 665/cm was observed in the liquid phase of that system during anode-limited reversal only, and in the lithium sulfuryl chloride system during normal discharge and during reversal; this compound was tentatively identified as Li(SO2, SO2Cl2(+)AlCl4(-) and is analogous to the well-known complexes involving LiAlCl4, SO2, and SOCl2. The lithium-sulfuryl chloride cell behaved similarly to the thionyl chloride cell, specifically with respect to formation of SO2(-) and SOCl(+)-like species - the latter tentatively identified as SO2CL(+). Indirect evidence suggests that chlorine may accumulate in both systems at -20 C, but at 25 C its accumulation in the cells is prevented by its reaction with SO2 to form SO2Cl2.