Enhanced electrochemical performance of Li1.2Mn0.54Ni0.13Co0.13O2 by surface modification with graphene-like lithium-active MoS2

In order to improve the high-rate capacity and cycleability, the graphene-like structured MoS2 is successfully coated on Li1.2Mn0.54Ni0.13Co0.13O2 via wet chemical method followed by a solid state reaction. Transmission electron microscopy and energy dispersive X-ray spectrometry indicate that the surface of cathode particles is uniformly covered with a crystalline MoS2 layer (similar to 5 nm thick) after 3 wt% MoS2 surface coating. Compared with the bare sample, MoS2-coated electrode exhibits the improved Coulombic efficiency, cycleability and rate capability in the voltage range of 2.0-4.8 V, even at elevated temperature. Based on the analysis from cyclic voltammetry and electrochemical impedance spectra, the remarkably improved electrochemical performances of the surface-modified electrode are ascribed to the presence of lithium-active MoS2 coating with the layered structure, which could not only suppress the undesirable side reaction and increasing impedance, and enhance the structural stability of host material, but also provide the additional sites for insertion of extracted lithium to compensate the lost Li sites during the activation of Li[Li0.2Mn0.54Ni0.13Co0.13]O-2 to effectively increase the initial Coulombic efficiency. (C) 2015 Elsevier Ltd. All rights reserved.