Improving the electrochemical properties of high-energy cathode material LiNi0.5Co0.2Mn0.3O2 by Zr doping and sintering in oxygen

• Pure phase LiNi0.5Co0.2Mn0.3 −xZrxO2 powders are synthesized when x ≤ 0.02.
• Sintering in oxygen can decrease the degree of cationic mixing.
• Optimized LiNi0.5Co0.2Mn0.29Zr0.01O2 electrode exhibits high capacity retention and a high rate capability.

The powders of layered structured LiNi0.5Co0.2Mn0.3O2 cathode material are synthesized by a thermal polymerization method in the temperatures range from 750 °C to 950 °C in air and oxygen. It is found that the LiNi0.5Co0.2Mn0.3O2 powder sintered in oxygen has significantly decreased degree of cationic mixing. The discharge capacities of the samples sintered in oxygen are higher than those of the samples sintered in air. The sample sintered at 900 °C in oxygen has the highest ratio of I003/I104 and the highest initial discharge capacities of 200 mAh g− 1 at a rate of 0.1C in the voltage range of 2.8–4.5 V. In order to improve the cycling stability of the LiNi0.5Co0.2Mn0.3O2 electrode, a series of Zr-doped LiNi0.5Co0.2Mn0.3O2 electrodes (LiNi0.5Co0.2Mn0.3 −xZrxO2, x = 0.01, 0.02, 0.03, 0.04, 0.05) are also prepared. The LiNi0.5Co0.2Mn0.3 −xZrxO2 electrodes show much enhanced cycling performance compared to the un-doped LiNi0.5Co0.2Mn0.3O2 electrode. The LiNi0.5Co0.2Mn0.29Zr0.01O2 electrode exhibits the best electrochemical performance with the capacity retention of 93.92% after 100 cycles at 0.2C in the voltage range of 2.8–4.5 V, while the un-doped LiNi0.5Co0.2Mn0.3O2 electrode exhibits capacity retention of only 83.33% after 100 cycles. The LiNi0.5Co0.2Mn0.29Zr0.01O2 electrode also shows obvious improved rate capability relative to that of the un-doped electrode.