Effect of FePO4 coating on electrochemical and safety performance of LiCoO2 as cathode material for Li-ion batteries

LiCoO2 was surface modified by a coprecipitation method followed by a high-temperature treatment in air. FePO4-coated LiCoO2 was characterized with various techniques such as X-ray diffraction (XRD), auger electron spectroscopy (AES), field emission scanning electron microscope (FE-SEM), energy dispersive spectroscopy (EDS), transmission electron microscope (TEM), electrochemical impedance spectroscopy (EIS), 3 C overcharge and hot-box safety experiments. For the 14500R-type cell, under a high charge cutoff voltage of 4.3 and 4.4 V, 3 wt.% FePO4-coated LiCoO2 exhibits good electrochemical properties with initial discharge specific capacities of 146 and 155 mAh g−1 and capacity retention ratios of 88.7 and 82.5% after 400 cycles, respectively. Moreover, the anti-overcharge and thermal safety performance of LiCoO2 is greatly enhanced. These improvements are attributed to the FePO4 coating layer that hinders interaction between LiCoO2 and electrolyte and stabilizes the structure of LiCoO2. The FePO4-coated LiCoO2 could be a high performance cathode material for lithium-ion battery.