An investigation into LiFePO4/C electrode by medium scan rate cyclic voltammetry

A LiFePO4/C sample was prepared via solid state reaction and characterized with X-ray powder diffraction, scanning electron microscopy and charge-discharge test. Conductive carbon and highly crystallized LiFePO4 were embedded in each other to form the as-prepared LiFePO4/C, which exhibited an excellent rate capability and capacity retention. The LiFePO4/C electrode reaction was investigated by the method of medium scan rate cyclic voltammetry (CV) under temperature variation. The limit values for the CV redox peak potentials of the LiFePO4/C electrode scanned at different rates were obtained by curve fitting. The reversibility of the LiFePO4/C electrode was studied and found to be both scan rate and temperature dependent. A higher temperature led to a higher critical CV scan rate for a reversible LiFePO4/C electrode. In the electrode process, a higher temperature resulted in a smoother Fe3+/Fe2+ redox reaction, better reversibility, lower R (cv), smaller charge transfer resistance and higher Li+ ion diffusion coefficient at the cathode of the LiFePO4/C.