Synthesis and Electrochemical Properties of LiFePO<SUB>4</SUB>/Carbon Nanocomposites in Polyol Medium

Abstract

LiFePO4/Carbon nanocomposites with varying amounts of carbon were synthesized using polyol process without any further heating as a post step. The X-ray diffraction patterns of all samples were indexed on the basis of orthorhombic olivine-type structure. The field emission-TEM images of composites with the amount of 3 approximately 15 wt% carbon showed the average sizes of 45 approximately 80 nm with nanorod shape surrounded by carbon. The initial discharge curves of LiFePO4/Carbon show 166, 157, 142, and 119 mAh/g capacities at a current density of 0.1 mA/cm2 in the voltage range of 2.5-4.2 V, respectively, without capacity fading and excellent cycle retentions during the 20 cycles. Especially, the sample of amount of 3 wt% carbon shows the excellent high rate performances at 15 and 30 C rates with high capacity retention compared with previously reported results of high temperature processed results, due to the existence of conductive agents such as carbon which suppresses particle growth and exhibits improved electronic conductivity and lithium ion diffusivity, simultaneously.