Improvement of structural and electrochemical properties of commercial LiCoO2 by coating with LaF3

Commercial LiCoO2 has been modified with LaF3 as a new coating material. The surface modified materials were characterized by X-ray diffraction (XRD), transmission electronic microscopy (TEM), field emission scanning electron microscopy (FE-SEM), auger electron spectroscopy (AES) and galvanostatic charge–discharge cycling. The LaF3-coated LiCoO2 had an initial discharge specific capacity of 177.4 mAh g−1 within the potential ranges 2.75–4.5 V (vs. Li/Li+), and showed a good capacity retention of 90.9% after 50 cycles. It was found that the overcharge tolerance of the coated cathode was significantly better than that of the pristine LiCoO2 under the same conditions – the capacity retention of the pristine LiCoO2 was 62.3% after 50 cycles. The improvement could be attributed to the LaF3 coating layer that hinders interaction between LiCoO2 and electrolyte and stabilizes the structure of LiCoO2. Moreover, DSC showed that the coated LiCoO2 had a higher thermal stability than the pristine LiCoO2.

► LaF3 has been introduced as a new coating material for the LiCoO2 cathode.
► The LaF3-coated LiCoO2 showed an excellent overcharge tolerance and structure stability.
► The thermal stability of the LaF3-coated cathode is significantly enhanced. Therefore, LaF3 is a probably potential coating material.