Effect of heat-treatment process on FeF3 nanocomposite electrodes for rechargeable Li batteries

An FeF3 nanocomposite with carbon materials is prepared by a ball milling process. The effect of the strain induced by ball milling on the electrochemical performance is examined using a combination of synchrotron X-ray diffraction (SXRD) and X-ray absorption spectroscopy (XAS). The strain of the FeF3 particles in the nanocomposite is analyzed by applying the Williamson-Hall method to the SXRD patterns. Heat-treatmenting the FeF3 nanocomposite drastically relieves the strain induced by the ball milling. The electrochemical performance of the FeF3 nanocomposite is also significantly improved by the heat-treatment process at 350 degrees C. The FeF3 nanocomposite heat-treated at 350 degrees C delivers 200 mA h g(-1) of reversible capacity with good capacity retention in a voltage range of 2.0-4.5 V. The heat-treatment process suppresses the increase in the poralization during the continuous cycling test. The power density of the heat-treated sample is superior to that of the ball milled sample without the heat treatment.