Improvement of electrochemical performance for AlF-coated LiMnNiCoO cathode materials for Li-ion batteries.

Li-rich layered-layered-Spinel structure spherical LiMnNiCoO particles was successfully prepared and coated with a uniform layer by a two-step co-precipitation method and evaluated in lithium cells. The structures and electrochemical properties of pristine LiMnNiCoO and AlF-coated LiMnNiCoO were characterized. When the coating amount was 2 wt%, the cathode showed the best cycling performance and rate capability compared to others. The AlF-coated LiMnNiCoO Li-ion cell cathode had a capacity retention of 90.07 % after 50 cycles at 0.5 C over 2.0-4.8 V, while the pristine LiMnNiCoO exhibited capacity retention of only 80.73 %. Moreover, the rate capability and cyclic performance also improved. Electrochemical impedance spectroscopy testing revealed that the improved electrochemical performance might attribute to the AlF coating layer which can suppress the increase of impedance during the charging and discharging process by preventing direct contact between the highly delithiated active material and electrolyte. [ABSTRACT FROM AUTHOR]