Cation-doped V2O5 microsphere as a bidirectional catalyst to activate sulfur redox reactions for lithium-sulfur batteries

Abstract

An ideal electrocatalyst for sulfur redox reactions (SRRs) should afford an exception catalysis upon the conversion between different sulfur compounds during both discharge and charge processes. Herein, we report transition-metal (M = Fe, Co, Ni) doped V2O5 yolk-shell microspheres (M-V2O5-YS) as a bidirectional catalytic host of sulfur. After doping, the M-V2O5-YS samples show abundant lattice defects and improved conductivity. Moreover, the doped metal ions enrich the active sites for the adsorption-catalysis of sulfur species. Kinetics tests results demonstrate the role of bidirectional catalyst for M-V2O5-YS hosts in speeding up the kinetics of the reduction of LiPSs, as well as the re-oxidation of the deposited Li2S. In particular, the S/Co-V2O5-YS composite shows an outstanding initial discharge capacity up to 1168.1 mAh/g at 0.3 C, rate capability (693.7 mAh/g at 5 C) and cycle stability. Even at low E/S ratio (6 μL mg−1) and high sulfur loading (4.9 mg cm−2), S/Co-V2O5-YS composite still harvest excellent capacity and satisfactory cycle stability. Therefore, this study displays an effective and feasible method to explore bidirectional catalytic materials to activate SRRs for high performance Li-S batteries.