Low rate performance and poor cyclic performance are vital factors undermining the practical application of Li-rich layered oxides as the cathode material for advanced Li-ion batteries. Herein, we demonstrate a significant enhancement in rate capability and cyclic performance of Li1.2Mn0.54Ni0.13Co0.13O2 via an L-ascorbic acid-based treatment. The discharge capacity ratio at different current rates (0.5C/0.05C) increases from 70.4% to 79.9% after L-ascorbic acid-based modification. Furthermore, the remaning energy for the modified sample after the 100th cycle is 628.6 Wh Kg(-1), which is 35.6% higher than the energy density of pristine sample (463.5 Wh Kg(-1)). The enhancement in electrochemical performance of the L-ascorbic acid treated Li1.2Mn0.54Ni0.13Co0.13O2 is attributed to the co-contribution of chemical activation of Li2MnO3 phase, exposure of high proportion of Li-conducting-favorable faces at the particle surface, increase in specific surface area and in-situ formation of minor spinel phase under the surface. (C) 2018 The Electrochemical Society.