Designing Al2O3 shell promotes high voltage LiCoO2 cathode for high stable lithium-ion batteries

High voltage LiCoO₂ (LCO) evokes much interest of researchers because of the high volumetric energy density and its potential application in consumer electronics market. However, the practical application was impeded by the instable structure and interface side reaction under high voltage. Herein, core-shell structured LCO with Al₂O₃ shell and homogenous Al doping was prepared and its high voltage performance was systematically evaluated. Benefiting to the core-shell structured design, the LCO sample delivered much improved electrochemical performance whatever room temperature or high temperature over 4.6 V high voltage. Especially, the specific capacity of LCO-2 reached 174.0 mAh g⁻¹ after 40 cycles even at 4.65 V, delivering a retention of 85.5 %. Besides that, the retention ratio of LCO-2 still maintained at 88.2 % at 45 °C after 50 cycles. As a comparison, the value of LCO-0 was only 71.4 %. When assembled into full cells, the value reached 608 cycles which is nearly 1.65 times higher than the homogenous one under the cut capacity of 80 %, showing a well potential application in commercial high voltage products.