Superior high-rate cycling performance of LiFePO 4/C-PPy composite at 55 °C

Abstract

A facile chemical polymerization method was applied to prepare LiFePO 4/C-PPy composite using Fe(III)tosylate as oxidant. The as-prepared LiFePO 4/C-PPy sample with PPy content of approximately 4 wt% showed great rate capability with a discharge capacity of 115 mAh/g at 20C. High temperate cycling performance of the LiFePO 4/C-PPy sample was compared with bare LiFePO 4/C at 5C charge–discharge rate at 55 °C. The LiFePO 4/C-PPy cathode showed superior cycling stability with an initial capacity of 155 mAh/g. Ninety percentage of this initial capacity was retained after 300 cycles, compared to 40% of that of bare LiFePO 4/C. The LiFePO 4/C-PPy electrode showed stable discharge plateau voltage of 3.35–3.25 V vs. Li +/Li during long term cycling. The superior performance of the LiFePO 4/C-PPy electrode was due to the enhanced electrical conductivity, negligible iron dissolution and alleviated electrode cracking contributed by PPy coating.