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

Li 3 PO 4 coated Li 1.18 Co 0.15 Ni 0.15 Mn 0.52 O 2 cathode materials were prepared by the precipitation method. The Li 3 PO 4 coating process cleans the Li 2 CO 3 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 Li 3 PO 4 coating improves the activation of Mn 4+ ions, prohibits the growth of solid electrolyte interface film and facilitates the charge transfer reactions at the electrode/electrolyte interface. As a result, the Li 3 PO 4 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 °C to 289.7 °C after Li 3 PO 4 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 Li 3 PO 4 coated material. [ABSTRACT FROM AUTHOR]