Mg-Pillared LiCoO : Towards Stable Cycling at 4.6 V.

LiCoO is used as a cathode material for lithium-ion batteries, however, cationic/anodic-redox-induced unstable phase transitions, oxygen escape, and side reactions with electrolytes always occur when charging LiCoO to voltages higher than 4.35 V, resulting in severe capacity fade. Reported here is Mg-pillared LiCoO . Dopant Mg ions, serving as pillars in the Li-slab of LiCoO , prevent slab sliding in a delithiated state, thereby suppressing unfavorable phase transitions. Moreover, the resulting Li-Mg mixing structure at the surface of Mg-pillared LiCoO is beneficial for eliminating the cathode-electrolyte interphase overgrowth and phase transformation in the close-to-surface region. Mg-pillared LiCoO exhibits a high capacity of 204 mAh g at 0.2 C and an enhanced capacity retention of 84 % at 1.0 C over 100 cycles within the voltage window of 3.0-4.6 V. In contrast, pristine LiCoO has a capacity retention of 14 % within the same voltage window.