For the first time, a LiFePO4/C core–shell nanocomposite has been synthesized using a nano-FePO4/polythiophene (PTh) as an iron source. With this method, the PTh is in situ polymerized to restrain the growth of FePO4 particles, and the typical size of FePO4/PTh particles is in the range of 20–50nm. The optimized LiFePO4/C nanocomposite is synthesized at 750°C using 40% citric acid. The prepared LiFePO4 particles show a typical size of 50–100nm and they are fully coated by carbon of 2–4nm thickness. The LiFePO4/C core–shell nanocomposite gives an improved high electronic conductivity and a good electrochemical behavior at high rates. Thus, this novel method is an effective and facile strategy to improve the rate performance of the LiFePO4 cathode.