Synthesis and electrochemical characterization of LiFePO4/C-polypyrrole composite prepared by a simple chemical vapor deposition method

A LiFePO4/C-polypyrrole (LiFePO4/C-PPy) composite as a high-performance cathode material is successfully prepared through a simple chemical vapor deposition (CVD) method. According to the transmission electron microscope (TEM) analysis, the surface of the LiFePO4/C is surrounded with PPy in the LiFePO4/C-PPy composite. The as-prepared LiFePO4/C-PPy material shows outstanding rate capability at 20A degrees C and good cycle performance at 55A degrees C in comparison with those of the bare LiFePO4/C material against Li anode. After 700 cycles, the discharge capacity of LiFePO4/C-PPy could still remain 110 mA h g(-1) with the retention of 82% at 5 C rate at 55A degrees C. This could be ascribed to the fact that PPy coating on LiFePO4/C could significantly improve the ionic conductivity of the LiFePO4/C-PPy composite and could greatly reduce the electrode resistance. Furthermore, the PPy coating on LiFePO4/C could effectively decrease the dissolution of Fe in the LiPF6 electrolyte and subsequently suppress the reduction of Fe ions on anode.