Effects of chromium/fluorine co-doping on the electrochemical performance of Li1.2Ni0.13Co0.13Mn0.54O2 cathode material for lithium-ion batteries

Abstract

Li-rich layered oxides are identified as the most promising cathode material for lithium ion batteries due to their high specific capacity and energy density. However, capacity fading, voltage decay and inferior rate capability have restricted its development in industry. Herein, we developed a novel cation/anion (chromium/fluorine) co-doping methods to enhance the electrochemical performance of Li1.2Ni0.13Co0.13Mn0.54O2. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy images reveal the perfect crystal structure. The Cr and F co-doped Li1.2Ni0.13Co0.13Mn0.54O2 shows the best discharge specific capacity, the highest rate performance and the lowest voltage decay. The initial discharge capacity is improved from 264.4 to 273.7 mAhg−1. The capacity retention ratio is enhanced from 78.84% to 94.46% after 50 cycles. The Rct (charge transfer resistance) is decreased from 556.1Ω to 199.5Ω. The lower Rct and higher DLi+ of the Cr and F co-doped Li1.2Ni0.13Co0.13Mn0.54O2 contribute to the excellent rate capability. More importantly, the co-doped material exhibits elevated discharge voltage and shows lower discharge mean voltage decay (0.2945 V) than that of the pristine material (0.4396 V). These results fully suggest that cation and anion doping could effectively improve the electrochemical performances of Li1.2Ni0.13Co0.13Mn0.54O2.