Simultaneous defect-engineered and thiol modified of MoO2 for improved catalytic activity in lithium-sulfur batteries:A study of synergistic polysulfide adsorption-conversion function

Abstract Rational design of nanostructure and proper interfacial engineering is of significant in pursuing high performance Li-S batteries. Here we report a strategy to fabricate reduced graphene oxide coated MoO2 with defect engineered and thiol modified nanotubes (H-S@MoO2/rGO) as highly stable host material for cathode in Li-S batteries. Thiourea was used as sulfur source and etching agent to construct the hollow architecture and realize thiol modification of MoO2 with the aid of ethanol. The modifying H-S@MoO2/rGO nanotubes offer improved affinity with LiPSs and accelerating the conversion kinetics from LiPSs to final Li2S. Oxygen vacancy remarkably reduce energy barrier and facilitating charge transfer, improving catalytic activity, regulating the deposition of Li2S on electrode surface. Furthermore, H-S@MoO2/rGO nanotubes offer enough interior capacity for high sulfur loading of 84 wt% (donate as S-S@MoO2/rGO), effectively confine sulfur through confinement effect. The simultaneous defect-engineered and thiol modified of MoO2 effectively cooperate the adsorption, diffusion and conversion of LiPSs in sulfur redox process, synergistically enable host material effective adsorption-conversion function for polysulfide. The developed S-S@MoO2/rGO cathodes exhibit excellent rate performance and superior reliability with a high specific capacity of 927 mAh g-1 and small capacity fading rate of 0.042% per cycle over 500 cycles at 0.1 Ag-1. This work shows a feasible and effective method to analyze the systematic kinetic and in-depth mechanism explanation of functional groups modifying metal oxide to guide the design of effective catalysts for practical application in lithium-sulfur batteries.