Si-C composite with hollow spherical structure was synthesized using ultrasonic treatment of organosilica powder formed by hydrolysis of phenyltrimethoxysilane. The prepared powder was pyrolyzed at various temperatures ranging from 900 to 1300 ˚C under nitrogen atmosphere to obtain optimum conditions for Li-ion battery anode materials with high capacity and cyclability. The XRD and elemental analysis results show that the pyrolyzed Si/C composite at 1100 ˚C has low oxygen and nitrogen levels, which is desirable for increasing the electrochemical capacity and reducing the irreversible capacity of the first discharge. The solid Si-C composite electrode shows a first charge capacity of ~500 mAhg-1 and a capacity fade within 30 cycles of 0.93% per cycle. On the other hand, the electrochemical performance of the hollow Si-C composite electrode exhibits a reversible charge capacity of ~540 mAhg-1 with an excellent capacity retention of capacity loss 0.43% per cycle up to 30 cycles. The improved electrochemical properties are attributed to facile diffusion of Li ions into the hollow shell with nanoscale thickness. In addition, the empty core space provides a buffer zone to relieve the mechanical stresses incurred during Li insertion.

The microstructure and electrical conductivity of CNTs dispersed nanocomposites depending on the powder processing and CNTs content were demonstrated. The composite powders with homogeneous dispersion of CNTs could be synthesized by a catalytic route for direct formation of CNTs on nano-sized Fe dispersed powders. The sintered nanocomposite using the composite powder with directly synthesized CNTs showed homogeneous microstructure and enhanced elelctrical conductivity. The influence of powder processing on the properties of sintered nanocomposites was discussed by the observed microstructural features.