Simultaneously Constructing a TiO2–LiF Composite Coating Enhancing the Cycling Stability of LiCoO2 at 4.6 V High Voltage

The surface and interface stability of the electrode is an important factor affecting the electrochemical performance of the battery, and surface modification is an effective means to stabilize the electrode surface interface. In this paper, a TiO2–LiF composite coating layer with very stable chemical properties on the LiCoO2 (LCO) surface is prepared in one step. At the same time, surface doping is realized, which provided a stable surface structure for LCO and stabilized the interface between the electrode and electrolyte. Electrochemical test results show that in the range of 3–4.5 V, the capacity retention rate of the sample with a coating amount of 1% is 97.4% after 110 cycles at 0.2 C and a discharge capacity of 151.5 mAh g–1 at 5 C, while the bare electrode is only 67% (110th cycle) and 50.7 mAh g–1 under the same conditions. Even at 0.5 C within 3–4.6 V, the capacity retention rate of the coated sample is still as high as 88.6% after 100 cycles, showing excellent high-voltage cycle stability. Studies such as cyclic voltammetry and electrochemical impedance spectroscopy show that the improvement in electrochemical performance is due to the coating layer effectively stabilizing the LCO surface composition and structure, alleviating the structural degradation of LCO, and optimizing the lithium-ion transport channel.