Enhanced electrochemical performance of LiFePO4/C cathode material modified with highly conductive TiN

Highly conductive titanium nitride (TiN) modified LiFePO4/C powders have been prepared via a suspension mixing process followed by heat treatment at 60 degrees C. The structures and compositions of LiFePO4 samples modified with TiN are characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is found that nano-sized TiN particles together with the amorphous carbon layer form an integrated network on the surface of LiFePO4. Galvanostatic charge/discharge test indicates that TiN modification is effective to improve the discharge capacity and cycle performance, especially at high rates. Electrochemical impedance spectroscopy (EIS) and potential step chronoamperometry (PSCA) measurements prove that the co-coating layer of C and TiN dramatically alleviates the charge transfer impedance and enhances the Li-ion diffusion coefficient, respectively. The sample with 5 wt.% TiN exhibits the best electrochemical performance among several samples investigated in this work. (C) 2013 Elsevier B.V. All rights reserved.