One‐Step Sintering Synthesis Achieving Multiple Structure Modulations for High‐Voltage LiCoO₂

Abstract The structure instability issues of the highly delithiated LiCoO₂ have significantly hindered its high‐voltage applications (≥4.55 V vs Li/Li⁺). Herein, for the first time, multiple modifications of Li_0.9Mg_0.05CoO₂ (L_0.9M_0.05CO) via a simple one‐step sintering synthesis are reported. A combination of the bulk Li/Co antisites, a Mg‐pillar enriched surface, and a thin MgO coating layer is achieved to maintain both the bulk and surface structural stability of L_0.9M_0.05CO upon cycling at an upper cut‐off voltage of 4.6 V. The bulk Li/Co antisites are discovered to enhance the H1‐3 phase evolution reversibility, the Mg pillars that substitute the Li sites effectively reinforces the surface structure, and the thin MgO coating layer can effectively prevent the cathode from severe side reactions. Benefiting from the reduced but reversible H1‐3 phase transition and the reinforced surface structure, L_0.9M_0.05CO shows an excellent cycle stability. This work provides a new structure modulation route for developing high‐voltage LiCoO₂ cathodes.