Preparation of single-walled carbon nanotube/silicon composites and their lithium storage properties.

Single-walled carbon nanotube (SWCNT)/silicon composites were produced from the purified SWCNTs and Si powder by high-energy ball-milling and then electrochemically inserted with Li using Li/(SWCNT/Si) cells. The highest reversible capacity and lowest irreversible capacity of the SWCNT/Si composites were measured to be 1845 and 474 mAh g(-1) after ball-milling for 60 min, respectively. During the charge/discharge process, most of the Li ions were inserted into the SWCNT/Si composites by alloying with Si particles below 0.2 V and extracted from the SWCNT/Si composites by dealloying with Si particles around 0.5 V. The enhanced capacity and cycle performance of the SWCNT/Si composites produced by high-energy ball-milling were due primarily to the fact that SWCNTs provided a flexible conductive matrix, which compensated for the dimensional changes of Si particles during Li insertion and avoided loosening of the interparticle contacts during the crumbling of Si particles. The ball-milling contributed to a decrease in the particle size of SWCNTs and Si particles and to an increase in the electrical contact between SWCNTs and Si particles in the SWCNT/Si composites.