Investigation on the enhanced electrochemical performances of Li1.2Ni0.13Co0.13Mn0.54O2 by surface modification with ZnO

Li-rich Li1.2Ni0.13Co0.13Mn0.54O2 cathode material is synthesized via a sol-gel method and subsequently surface-modified with ZnO layer by a wet chemical process. The effect of ZnO-coating on the electrochemical performances of Li1.2Ni0.13Co0.13Mn0.54O2@ZnO cells is investigated systematically by the charge/discharge testing, cyclic voltammograms and AC impedance spectroscopy, respectively. In comparison with the bare Li1.2Ni0.13Co0.13Mn0.54O2, Li1.2Ni0.13Co0.13Mn0.54O2@ZnO demonstrates higher rate capability and better cyclability. Analysis from the electrochemical measurements reveals that the remarkably improved performances of the surface-modified composites is mainly ascribed to the smaller charge-transfer resistances, higher lithium diffusion rate and the stable electrolyte/ electrode interfacial structure due to the suppression of the electrolyte decomposition. Furthermore, it is interesting that the electrochemical performances of Li1.2Ni0.13Co0.13Mn0.54O2@ZnO might be related with the conductivity and oxygen vacancies of ZnO, which could be modulated via changing defects in ZnO by thermal annealing. (C) 2015 Elsevier Ltd. All rights reserved.