Enhanced high-voltage performance of LiCoO2 cathode by directly coating of the electrode with Li2CO3 via a wet chemical method

Surface modification is an effective method for improving the high-voltage cycling stability of LiCoO2. In this work, lithium carbonate (Li2CO3), the main component of solid electrolyte interphase (SEI) films, is selected as the coating material to modify LiCoO2 composite electrodes by a wet chemical method, and the effect of the Li2CO3 coating time on the electrochemical performance of the LiCoO2 electrode is investigated. Results show that the Li2CO3 coating significantly improves the cycling performances and initial coulombic efficiencies of the LiCoO2 electrodes in the potential range of 3.0–4.5 V. The electrode with a coating time of 2 min exhibits the best electrochemical performance, in which the capacity retention rate is 90.9% after 100 cycles at 0.2C while the initial coulombic efficiency is 90.04%, whereas the capacity retention rate and initial coulombic efficiency of the uncoated electrode are only 73.11% and 74.66%, respectively. The capacity of the electrode with the 2-min coating reaches 134.3 mA h g−1 after 500 cycles, while that of the uncoated electrode is only 37.7 mA h g−1 under the same conditions. The results of cyclic voltammetry, electrochemical impedance spectroscopy, X-ray diffraction, and scanning electron microscopy show that the Li2CO3 coating stabilizes the electrode surface and structure to effectively inhibit the increase in electrode polarization.