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

• Li1.2Ni0.13Co0.13Mn0.54O2@ZnO exhibits better electrochemical performances in terms of cyclability and rate capability.
• The enhanced performances with ZnO-coating result from improved conductivity, lower charge-transfer resistances and higher Li+ diffusion rate.
• The electrochemical performances of Li1.2Ni0.13Co0.13Mn0.54O2@ZnO are found to be related with the conductivity and defects of 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.