Ab initio characterization of layered MoS2 as anode for sodium-ion batteries

Identifying suitable layered materials as electrodes with desirable electrochemical properties remains a key challenge for rechargeable Na-ion batteries (NIBs). Using first principles methods, here we examine the efficacy of layered molybdenum disulphide (MoS2) as a host electrode material for NIBs. We identify various low energy Na adsorption sites and evaluate the stability of the hexagonal and tetragonal polytypes of MoS2 upon Na intercalation. Our results illustrate a moderately strong binding between Na and MoS2 that is thermodynamically favorable against the cluster formation and phase separation of Na. We find that while Na intercalation in MoS2 results in a phase transformation from the hexagonal phase to the tetragonal phase, it gives rise to a maximum theoretical capacity of 146 mAh g(-1) and a low average electrode potential in the range of 0.75-1.25 V. Our calculations of Na diffusion kinetics indicates a moderately fast mobility of Na in the van der Waals interlayer spaces of MoS2. These results highlight the promise of MoS2 as an appealing negative electrode (anode) for rechargeable NIBs. (C) 2014 Elsevier B.V. All rights reserved.