Stabilizing 4.6 V LiCoO2 via Surface‐to‐Bulk Titanium Modification

Abstract Elevating the charging cut‐off voltage is an effective strategy to increase the energy density of LiCoO 2 . However, unstable interfacial structures and unfavorable phase transitions in bulk are inevitably triggered during deep de‐lithiation at high voltage. Herein, an integrated surface‐to‐bulk Ti‐modification strategy is applied to LiCoO 2 , enabling uniform Li 2 TiO 3 coating on the surface and gradient Ti‐doping toward the structural bulk. The resultant Ti‐modified LiCoO 2 (T‐LCO) electrode can be stably cycled up to 4.6 V, providing a high‐rate capability of 137 mAh g −1 at 5C and a long‐life stability with 80.5% capacity retention after 400 cycles at 1C, far outperforming the unmodified LiCoO 2 electrode with only 50.7% capacity retention. In situ X‐ray diffraction characterization and density functional theory calculation reveal that the synergistic modification of T‐LCO enhances Li + diffusion, facilitates the construction of high‐quality cathode/electrolyte interphase, reduces the phase transition from O3 to H1‐3 and Co3d/O2p band overlap, and restrains layer‐to‐spinel phase distortion, thus improving structural stability at 4.6 V. This work presents a “two birds one step” strategy to enhance the cycling stability and achievable capacity of high‐voltage LiCoO 2 for developing high energy density lithium‐ion batteries.