Silicon doped carbon nanotubes as high energy anode for lithium-ion batteries

Silicon-doped carbon nanotubes (Si-CNT) have been produced and modified n situ through substitutional silicon doping in the carbon network in one step by a modified chemical vapor deposition (M-CVD) process. Toluene, ferrocene, and triphenylsilane were used as carbon sources, the metal catalyst for the nanotubes' growth, and Si doping agent, respectively. The doping effect of Si-CNT and its application as an anode material for lithium-ion batteries was investigated using scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. Silicon content in Si-CNT was estimated between 0.29 and 0.76 at% by X-ray photoelectron spectroscopy. The electrochemical evaluation revealed that the Si-CNT electrode achieved an initial high discharge capacity of 1060 mAh g−1 and a reversible capacity of 400 mAh g−1 at 186 mA g−1, maintaining good cyclic stability over 120 cycles. The increase of capacity is the result of doping silicon, whose significant localized but distributed volume change induced defects in CNT structure resulting in enhanced Li-ion intercalation kinetics further accommodated by the flexible and mechanically robust carbon nanotubes. Therefore, Si doped-CNT could be considered as potential anode material for rechargeable lithium-ion batteries (LIB) with high capacity.