Abstract:Carbon nanotubes (CNTs) and acetylene black (AB) were dispersed synchronously or separately between LiFePO₄ (LFP) particles as conducting agents during the course of manufacture of LiFePO₄ cathodes. The morphology and electrochemical performances of as-prepared LiFePO₄ were evaluated by means of transmission electron microscopy (TEM), charge-discharge test, electrochemical impedance spectroscope (EIS) and cyclic voltammetry (CV). CNTs contribute to the interconnection of the isolated LiFePO₄ or carbon particles. For the CNTs-modified LiFePO₄, it exhibits excellent performance in terms of both specific capacity and cycle life. The initial discharge capacity is 147.9 mA∙h/g at 0.2C rate and 134.2 mA∙h/g at 1C rate, keeping a capacity retention ratio of 97% after 50 cycles. The results from EIS indicate that the impedance value of the solid electrolyte interface decreases. The cyclic voltammetric peak profiles is more symmetric and spiculate and there are fewer peaks. CNTs are promising conductive additives candidate for high-power Li-ion batteries.

Key words: LiFePO₄; carbon nanotubes; cyclic voltammetry (CV); electrochemical impedance spectroscopy (EIS); Li-ion batteries