Mg-doped LiNi0.84Co0.11Mn0.05O2 cathode material is synthesized from introducing Mg by high temperature solid state method. X-ray diffraction analysis confirms the formation of ordered alpha-NaFeO2 rock-salt like structure with R-3m symmetry. Rietveld refinement results confirm the expansion in a and c lattice parameters as the amount of Mg increases. All the Mg-doped samples show significant improvement in structure stability and electrochemical properties, such as capacity retention and rate capability. The 1 wt% Mg-doped LiNi0.84Co0.11Mn0.05O2 delivers the high discharge capacity of 196.7 mAh g(-1) (0.1 C) and maintains the capacity retention of 85.95% after 80 cycles indicating outstanding cycling performance. Furthermore, at high cut-off voltage the Mg-doped samples exhibit superior electrochemical performance than the un-doped sample. Cyclic voltammetry results show that the addition of Mg has suppressed the phase transition between H2-H3. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.