Long-term cycle stability at a high current for nanocrystalline LiFePO4 coated with a conductive polymer

Hung-Cuong Dinh, Hanjo Lim, Ki Dong Park, In-Hyeong Yeo, Yongku Kang and Sun-il Mho

Abstract

Highly uniform hierarchical-microstructured LiFePO₄ particles with dumbbell- and donut-shape and individual LiFePO₄ nanocrystals were prepared by a hydrothermal method utilizing citric acid or a triblock copolymer (Pluronic P123) as a surfactant. The cathode composed of the individual nanocrystalline LiFePO₄ particles exhibited higher specific capacity than the cathodes composed of the hierarchically assembled microparticles. Coating a conductive polymer, poly-3,4-ethylenedioxythiophene (PEDOT), on the surface of LiFePO₄ particles improved the battery performances such as large specific capacities, high rate capability and an improved cycle stability. The nanocrystalline LiFePO₄particles coated with PEDOT (20 wt%) exhibited the highest discharge capacities of 175 and 136 mAh g⁻¹ for the first battery cycle and 163 and 128 mAh g⁻¹ after 500 battery cycles, with a degradation rate of 6–7%, at the rates of 1 and 10 C, respectively