Lithium iron phosphate (LiFePO₄) is a very hopeful positive electrode material of lithium-ion power battery, because of its abundance of raw materials, low cost, stable structure, excellent cycling performance and high theoretical capacity. However, pristine LiFePO₄ has two main disadvantages of slow lithium-ion diffusion and low electronic conductivity, which lead to poor rate capability and limit its wide applications. To overcome these disadvantages, in this work, we synthesized the composites of LiFePO₄ and nanocarbon (carbon nanotube, nitrogen-doped carbon nanotube, etc.), and investigated the effects of the various additives on their morphology, microstructure and electrochemical performance. The structure and morphology of the composites were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM, typical images as shown in Fig.1a and b). The electrochemical performance of the composites was evaluated by charge-discharge test, cyclic voltammetry and impedance spectroscopy. The LiFePO₄ and nitrogen doped carbon nanotube composite materials presented more uniform dispersion, stronger interaction, greatly improved lithium storage capacity, rate capability and cycling stability, which are promising for high performance lithium-ion power battery applications.

Fig.1 SEM images of LiFePO₄-CNT (a) and LiFePO₄-NCNT (b). Acknowledgements: This work was supported by the National Natural Science Foundation of China (No. 51372178) and the Natural Science Foundation for Distinguished Young Scholars of Hubei Province of China (No. 2013CFA021).