Bifunctional effects of carbon coating on high-capacity Li1.2Ni0.13Co0.13Mn0.54O2 cathode for lithium-ion batteries

Coating the Li-rich layered oxide cathode Li1.2Ni0.13Co0.13Mn0.54O2 with small amount of conductive carbon is realized by low-temperature sucrose carbonization in air. Carbon coating gives rise to a small amount of Mn3+ on the surface of the Li1.2Ni0.13Co0.13Mn0.54O2. The 1.2 wt% carbon-coated Li1.2Ni0.13Co0.13Mn0.54O2 shows obviously enhanced electrochemical performances, especially in improving rate capability and suppressing the voltage fading during long-term and high-rate cycling. According to the analysis from cyclic voltammetry (CV) and electrochemical impedance spectra (EIS), the improvements on the electrochemical performances are mainly because the coated carbon layer can function by not only increasing the electronic conductivity at the interface with electrolyte but also improving bulk electronic and ionic conductivity by small amounts of Mn3+. Therefore, carbon coating is a promising approach to improve the cyclic stability of the Li-rich layered oxides.