PNNL

Abstract

Lithium sulfur (Li-S) batteries are promising alternatives to conventional Li-ion batteries in terms of specific capacity and energy. However, the technical challenges raised from the soluble polysulfide (PS) in organic electrolyte deter their implementation in practical applications. Nanoengineered structure and chemical adsorptive materials hold great promise in mitigating the PS migration problem. Here, we develop a tubular titanium oxide (TiO2)/reduced graphene oxide (rGO) composite structure (TG) as a sulfur hosting material for constructing better performed Li-S batteries. The TG/sulfur cathode (TG/S) is able to deliver ~1200 mAh g-1 specific capacity with stable operation for over 550 cycles. Moreover, the TG/S composite cathode shows stable Coulombic efficiencies of over ~95% at various C rates, which are ~10% higher than those of the rGO/sulfur (G/S) counterparts. The superior electrochemical performances of TG/S could be ascribed to the synergistic effects between the conductive rGO support and the physically/chemically absorptive TiO2, that is, the spatial tubular structure of TiO2 provides intimate contact and physical confinement for sulfur, while the polar TiO2 in TG/S shows strong chemical interaction towards the sulfur species.