Effect of FePO 4 coating on electrochemical and safety performance of LiCoO 2 as cathode material for Li-ion batteries

Abstract

LiCoO 2 was surface modified by a coprecipitation method followed by a high-temperature treatment in air. FePO 4-coated LiCoO 2 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.% FePO 4-coated LiCoO 2 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 LiCoO 2 is greatly enhanced. These improvements are attributed to the FePO 4 coating layer that hinders interaction between LiCoO 2 and electrolyte and stabilizes the structure of LiCoO 2. The FePO 4-coated LiCoO 2 could be a high performance cathode material for lithium-ion battery.