Lithium insertion into purified and etched multi-walled carbon nanotubes synthesized on supported catalysts by thermal CVD

The effects of chemical processing on Li insertion into multi-walled carbon nanotubes (MWNTs) are reported. MWNTs were synthesized on the supported catalysts by the thermal CVD method, purified and chemically etched. And then the purified MWNTs and the etched MWNTs were electrochemically inserted with Li. The reversible capacity increased with increase in the etching time from 351 mAh/g (Li_0.9C₆) for the purified MWNTs to 681 mAh/g (Li_1.8C₆) for the etched MWNTs. The irreversible capacity also increased with increase in the etching time from 1012 mAh/g (Li _2.7C₆)) for the purified MWNTs to 1229 mAh/g (Li _3.3C₆) for the etched MWNTs. The structural and chemical modifications in the etched MWNTs facilitated an insertion of Li ions into the etched MWNTs and enhanced the reversible capacity, but the large surface area of the etched MWNTs induced the large irreversible capacity. The extraction of Li ions from the purified MWNTs and the etched MWNTs had a great hindrance.