Reduction of iodine complexed with sulfoxides and organophosphorus esters near 4.0 V vs. Li/Li+

It is accepted that the reduction of iodine species in non-aqueous solvents occurs through one-electron or two-electron processes below roughly 3.5 V vs. Li/Li+. In some iodine solutions, the molecular complexation of iodine with the organic solvent proceeded via a charge–transfer interaction. Reduction of iodine in non-aqueous solvents having SO or PO groups, as well as interactions of iodine molecules with these solvents, were studied. Iodine molecules associated with dimethyl sulfoxide (DMSO), tetramethylene sulfoxide (TMSO), and trimethyl phosphate (TMP) showed anomalous reduction above+1.0 V vs. NHE. We demonstrated the operation of lithium–iodine batteries using DMSO, TMSO and TMP near 4.0 V vs. Li/Li+.

► We detected reduction of iodine in organic solvents over +1.0 V vs. NHE.
► The organic solvents were sulfoxides and trimethyl phosphate.
► Li–iodine batteries using those iodine solutions drive voltages near +4.0 V.