Mg‐Pillared LiCoO₂: Towards Stable Cycling at 4.6 V

LiCoO₂ 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 LiCoO₂ to voltages higher than 4.35 V, resulting in severe capacity fade. Reported here is Mg-pillared LiCoO₂ . Dopant Mg ions, serving as pillars in the Li-slab of LiCoO₂ , 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 LiCoO₂ is beneficial for eliminating the cathode-electrolyte interphase overgrowth and phase transformation in the close-to-surface region. Mg-pillared LiCoO₂ exhibits a high capacity of 204 mAh g⁻¹ 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 LiCoO₂ has a capacity retention of 14 % within the same voltage window.