In situ Raman spectra of the discharge products of calcium and lithium-anoded thionyl chloride cells — sulphur dioxide generation in oxyhalide systems

A cell has been constructed that allows a calcium or lithium-anoded oxyhalide cell of conventional composition to be analysed for catholyte-soluble discharge products using laser Raman spectroscopy. Both cells showed the presence of sulphur dioxide solvated by thionyl chloride. Species of the type M(SOCl2)(SO2)n+(AlCl4)n− could only be detected in cells having calcium or lithium anodes with LiAlCl4 as the supporting electrolyte in thionyl chloride. Vapour pressure measurements of discharging cells confirmed that Ca(AlCl4)2 was less likely to form a complex with sulphur dioxide than the analogous lithium salt.