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

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 LiFePO4 particles 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.