Tailoring biphasic high-halogen SEI via organochlorine isomeric effect for stable lithium metal anodes

Abstract

The fragile nature of the solid electrolyte interphase (SEI) formed on lithium metal anodes, particularly due to irregular lithium deposition and sluggish ion transport, presents a major challenge to the wider deployment of lithium-sulfur (Li-S) batteries. In this study, a high halogen-containing SEI of the lithium anode was prepared and finely tuned using the variance in chlorine substitution sites as a regulatory mechanism with the positional isomerism of dichloropyridines (DCPs). Remarkably, a highly halogenated inorganic layer was composed predominantly of LiF and LiCl, reaching up to 62 % coverage, which not only mitigated lithium dendrite proliferation and accommodated volume changes during cycling but also facilitated efficient Li+ ion conduction. Under demanding conditions with a high sulfur loading of 3.0 mg cm−2 and a lean electrolyte ratio (electrolyte to sulfur ratio = 13.3 μL mg−1), the cells retained a capacity of 520.65 mA h g−1 after 300 cycles at 0.5 C.