Ultrasonically carbon coated Si nanoparticles for lithium ion batteries

A new and simple method for making nano-sized silicon/carbon composite materials was developed. The composite powders were prepared by dispersing HF-etched SiNPs in CHCl3, followed by bath sonication. Transmission Electron Microscopy (TEM) was used to identify the carbon layer outside the silicon particle. Impedance spectroscopy and cyclic voltammetry confirmed the improved electrode conductivity due to the carbon layer and the subsequent increased involvement of the silicon in the lithiation/delithiation process. The optimal composition of the composite, 20 wt.% SiNP/C, and 20 wt.% graphite, exhibited excellent cyclability after ten cycles with a reversible discharging capacity near 465 mAhg(-1) which is 1.5 times larger than that of the graphite and SiNPs electrode without ultrasonic process.