Stabilizing Surface Lattice O<i>ⁿ</i>⁻ (0 &lt; <i>n</i> &lt; 2) for Long‐Term Durability of LiCoO₂

Abstract

AbstractThe instability of surface lattice On− (0 &lt; n &lt; 2) in charged LiCoO₂ (LCO) limits its long‐term cycling stability beyond 4.55 V versus Li/Li⁺. Herein, the spinel and rock‐salt (RS) phases are constructed on LCO surface to stabilize lattice On−, namely S‐LCO and R‐LCO, respectively. Upon long‐term cycling at 4.6 V, the loss of lattice On− leads to a progressive deterioration of surface spinel phase, which ultimately transforms into a strong Li+‐blocking phase. In contrast, for R‐LCO, the surface lattice On− in the RS phase remains stable in long‐term cycles. Theoretical calculations reveal that the migration barriers of lattice On− are significantly higher in the RS phase than in the spinel phase. Due to the stabilized surface lattice On−, the R‐LCO||Li cell shows an impressive capacity retention of 78.6% after 1000 cycles at 4.6 V (at 1C rate) and superior floating charge durability at 45 °C. This study highlights the importance of surface structure tailoring in developing advanced LCO cathodes.