Enhanced cycling stability and rate capability of Bi2O3-coated Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials for lithium-ion batteries

Li-rich layered oxide of Bi2O3-coated Li1.2Mn0.54Ni0.13Co0.13O2 was fabricated via a combined method of sol–gel and wet chemical coating processes. The crystal structure of Li1.2Mn0.54Ni0.13Co0.13O2 has no obvious change after the coating of 2 wt% Bi2O3. Bi2O3 is homogenously coated on the surface of Li1.2Mn0.54Ni0.13Co0.13O2 particles. The Bi2O3-coated Li1.2Mn0.54Ni0.13Co0.13O2 electrode presents an enhanced cycling stability, better rate performance and lower charge transfer resistance. After the coating of 2 wt% Bi2O3, the initial coulombic efficiency of the material has been improved to 76.9% compared to 72.6% for the bare Li1.2Mn0.54Ni0.13Co0.13O2. After 100 cycles at 0.1C, the Bi2O3-coated Li1.2Mn0.54Ni0.13Co0.13O2 electrode retains a discharge capacity of 182.9 mA h g−1 with capacity retention of 73.5%, which are much higher than those of Li1.2Mn0.54Ni0.13Co0.13O2 (146.9 mA h g−1 and 58.8%). In addition, the Bi2O3-coated Li1.2Mn0.54Ni0.13Co0.13O2 electrode exhibits better rate capability with discharge capacities of 155.8, 124.8 and 89.2 mA h g−1 at 1, 2 and 5C, respectively, superior to that of Li1.2Mn0.54Ni0.13Co0.13O2. The enhanced cycling stability and rate capability should be ascribed to the existence of Bi2O3 on the surface of the active material, which can efficiently restrain the side reactions between the electrode and electrolyte, stabilize the structure of Li1.2Mn0.54Ni0.13Co0.13O2 and improve the lithium ion diffusion.