Improved electrochemical performance of interface modified MoS2/CNT nano-hybrid and understanding of its lithiation/delithiation mechanism

Efficient interfacial interaction between MoS2 nanosheets and functionalized carbon nanotube (CNT) has been achieved via adopting an engineered, but facile hydrothermal process using ammonium hepta molybdate and thiourea as precursors. The importance of the route lies in enabling strong and easy coupling between Mo7O246- anion and functionalized CNT at low pH, since the zeta potential of CNT has been found to be positive at low pH. The strong interfacial interaction between MoS2 and CNT enhances the overall electronic conductivity and structural stability which leads to better electrochemical performance. The as-developed composite, with just similar to 8% carbon, possesses high Li-storage capacity, excellent rate capability and good cycle-life. Impedance spectra indicate least charge transfer resistance in the case of CNT-containing composites, with post-cycling Scanning Electron Microscopic (SEM) images confirms maintenance of integrity after repeated cycling. The cyclic voltammograms, along with x-ray diffraction and Extended X-ray Absorption Fine Structure (EXAFS), confirm that during lithiation step, MoS2 gets converted to Li2S and Mo via formation of LixMoS(2) (0 < x <= 1). The detection of formation of lithiation MoS2 (LixMoS(2)) is very important as the reaction processes through this intermediate. The asformed Mo does not transform back completely to MoS2 during delithiation step, with only Li2S gets delithiated to form elemental sulfur. In subsequent cycles, it is elemental sulfur which primarily gets lithiated and delithiated. (c) 2020 Elsevier B.V. All rights reserved.