Crystalline molybdenum carbide−amorphous molybdenum oxide heterostructures: In situ surface reconfiguration and electronic states modulation for Li−S batteries

Designing heterostructure electrocatalysts synergizing highly polar component and conductive matrix hold great promise to regulate lithium polysulfides (LiPSs) toward high−performance Li−S batteries based on anchoring−diffusion−conversion mechanism. Nevertheless, performance ceiling exists, restrict severely by the significant LiPSs diffusion barrier, which inevitably decrease the conversion efficiency of LiPSs. Amorphization can not only promote the diffusion of LiPSs on catalyst surface but also induce the modulation of surface electronic states and strengthen the adsorption toward LiPSs, in comparison with crystalline counterpart. Herein, crystalline Mo2C−amorphous MoO3 heterostructure grown on nitrogen doped carbon nanosheets is meticulously designed as an efficient sulfur immobilizer and promoter through a facile oxygen plasma treatment strategy. With the integrated advantage of improved adsorption and facilitated diffusion of LiPSs by amorphous MoO3, superior LiPSs redox kinetics by the catalytic effect of conductive Mo2C, and long-range electron transfer network arising from nitrogen doped carbon nanosheets, the assembled battery based on the as-developed modified separator endows excellent electrochemical performance and satisfactory cycling stability. This work provides an easy route to synergistic regulate crystallinity and heterogeneous interfaces of multifunctional catalysts for high energy density Li−S batteries.