Stabilizing 4.6 V LiCoO<sub>2</sub> via Surface‐to‐Bulk Titanium Modification
Liu Gao, Fujie Li, Guangfeng Zeng, Xin Jin, Zhenyou Li, Chao Wang
Abstract
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.