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

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 Li0.9Mg0.05CoO2 (L0.9M0.05CO) 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 L0.9M0.05CO 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, L0.9M0.05CO shows an excellent cycle stability. This work provides a new structure modulation route for developing high-voltage LiCoO2 cathodes.