Effect of Carbon Coating on the Structure and Electrochemical Performance of LiFePO4 for Lithium- ion Batteries

Olivine-type lithium iron phosphate (LiFePO4) attracted much attention as a promising cathode material for lithium-ion batteries (LIBs). Various processes have been developed to synthesize LiFePO4 or LiFePO4/C (carbon coating on LiFePO4), and some of them are being used to mass produce LiFePO4/C at the commercial or pilot scale. The solid-state method has already been widely adopted by industry for mass production, and it will remain one of the most used processes for manufacturing LiFePO4/C due to process simplicity and low cost. LiFePO4 and LiFePO4/C are successfully prepared by a simple solid-state reaction. The structure of the LiFePO4 and LiFePO4/C is investigated by X- ray diffraction (XRD). The morphology, particle size and carbon coating layer of the samples are observed using scanning electron microscopy (SEM), Brunauer, Emmett, and Teller (BET) method and transmission electron microscopy (TEM). Furthermore, the electrochemical properties are evaluated by cyclic voltammograms (CVs), electrochemical impedance spectra (EIS) and constant current charge/discharge cycling tests. The results show that LiFePO4/C can deliver better battery performance than the bare LiFePO4. It delivers a discharge capacity of 168 (0.1C), 152 (0.2C), 138 (1C), 130 (2C) and 105 mAh g-1 (5C), respectively.