Hydrothermal synthesis of silicon nanosphere embedded on carbon nanotubes for high-performance lithium-ion batteries

In the present work, we report a versatile and facile method to develop a Si-based negative material for Li-ion batteries. Silicon nanoparticles have been synthesised from the cost-effective silica and magnesium powder using the hydrothermal method. The X-ray diffraction profile confirms the presence of Si nano-crystals. FE-SEM micrographs show the uniform decoration of silicon nanoparticles on CNT in the actual negative electrode. This unique structure of Si/CNT nano-networks enhances the electronic conductivity and accommodate the large volume change during Li-ion insertion/extraction. Si/CNT networks based negative electrode delivers significantly high discharge and charge capacity of 1000 mAh g−1 and 950 mAh g−1 respectively at 0.96 A g−1 in the initial cycle. The high reversible capacity of 850 mAh g−1 shows enhanced sites for Li diffusion along with the improved conductivity of Si/CNT nanocomposite material. The electrochemical interactions at the negative electrode-electrolyte interface have been further studied by electrochemical impedance spectroscopy. These results show that the CNT incorporation in Si enhances the kinetics at the interface and accommodate volume expansion during the charge-discharge process.