Improved Electrochemical Performance and Thermal Stability of Li-excess Li1.18Co0.15Ni0.15Mn0.52O2 Cathode Material by Li3PO4 Surface Coating

Li3PO4 coated Li1.18Co0.15Ni0.15Mn0.52O2 cathode materials were prepared by the precipitation method. The Li3PO4 coating process cleans the Li2CO3 impurity on the surface of the material. In addition, a continuous stacking faults region forms in the near-surface region of the material. Electrochemical studies show that Li3PO4 coating improves the activation of Mn4+ ions, prohibits the growth of solid electrolyte interface film and facilitates the charge transfer reactions at the electrode/electrolyte interface. As a result, the Li3PO4 coated materials show larger discharge capacities, longer cycle life and better rate capability than the un-coated one. With the coating content as small as 1.0 wt%, the material shows a high discharge capacity of 272.5 mAh g(-1) at the 0.4C rate and 121.1 mAh g(-1) at the 10C rate. The capacity fading rate at 0.4C is only 0.08 % per cycle. Differential scanning calorimetry shows that the exothermic temperature of the fully charged electrode increases from 203.0 degrees C to 289.7 degrees C after Li3PO4 coating. And the thermal release reduces from 832.4 J g(-1) to 305.5 J g(-1) highlighting the improved thermal stability of the Li3PO4 coated material. (C) 2015 Elsevier Ltd. All rights reserved.