The Applications Of CNTs As Anode And Conductive Agent In Lithium Ion Batteries

The electrochemical properties of CNTs are closely related to their structure and morphology, when used as anode of lithium ion battery?LIB?. In this paper, we introduce two kinds of CNT films having different structure and morphology, and measure their electrochemical properties. The defective carbon nanotube film has bigger specific surface?163.6 cm²? and higher rate capacity of 134 mAh g^-1 at current density of 3000 mA g^-1?over 500 cycles?, comparing to well-crystalined CNT^-1 film(specific surface 122.7 cm² g^-1, 90 mAhg^-1). The defective structure of CNT-2 is favorable to transportation of lituium ions?Li+? and CNT-2 film is a promising material for high power LIB. We also introduce TiO₂ to improve the electrochemical properties of CNTs. The CNTs/TiO₂ composite film was prepared by adding tetrabutyl titanate in the precursor solution of CNT. The 19.0 wt.%-CNTs/TiO₂, prepared by 19 wt.% tetrabutyl titanate, delivers improved electrochemical properties compared with CNTs. In 19.0 wt.%-CNTs/TiO₂ film, the TiO₂ is mainly rutile with a content of 17.6 wt.%. Coulombic efficiency, rate capacity and cycle performance of CNTs was improved by decoration of TiO₂ nanoparticles. The capacity and coulombic efficiency(at 30 mA g^-1) of 19.0 wt.%-CNTs/TiO₂ are 500 mAh g^-1 and 60.3%, respectively, larger than that of CNTs(30.3%, 350 mAh g^-1). 19.0 wt.%-CNTs/TiO₂ shows stable cycle performance over 500 cycles with reversible capacity of 134 mAhg^-1(under 3000 mA g^-1), compared to CNTs(90 mAh g^-1). It is an effective way to modify CNTs by TiO₂.We also prepared LiFePO₄/CNTs composites by in-situ CVD method. Acetylene is carbon source and nickel acetate is catalyst which is mixed with the precursor of LiFePO₄. CNTs was synthized at 700°C. When the flow acetylene is 12 ml/min and the content of nickel acetate is 4 wt.%, the as-synthesized LiFePO₄/CNTs showed an improved charge-discharge efficiency compared to LiFePO₄.