Ultrathin-ZrO 2 -coated LiNi 0.4 Co 0.2 Mn 0.4 O 2 cathode material for Li-ion batteries: Synthesis and electrochemical performance

The ZrO 2 -coated LiNi 0.4 Co 0.2 Mn 0.4 O 2 with significantly improved electrochemical performance was successfully synthesized by molten salt method. The ZrO 2 -coated cathode material exhibited a significantly improved cycle performance and the rate performance. The 0.5 wt% ZrO 2 coating material showed an excellently electrochemical cycleability and a high rate capability in the voltage range of 2.5–4.6 V. The capacity retention of 0.5 wt% ZrO 2 coating material was 89.86% after 100 cycles at 0.5 C rate, which was much higher than that of raw material (82.02%). The discharge specific capacity was 106.13 mAh·g −1 after once activation at 0.1 C and 10 charge–discharge cycles at 5 C, which was much higher than that of raw material (81.71 mAh·g −1 ). The charge transfer impedance of coated material at high cut off voltage (4.6 V), as indicated by EIS results, was effectively suppressed, which precisely explained the distinct improvement of electrochemical performances. Graphical abstract