Preparation and Characterization of Porous Carbon Nanotubes for High Rate Capability Li-S Batteries

Abstract

Porous carbon nanotubes were prepared by KOH activation and investigated for the application of high performance lithium sulfur batteries. The enhanced specific surface area, increased pore volume and functionalization for the interaction with polysulfide and lithium sulfide were realized on the carbon matrix. The morphological and chemical changes of porous carbon nanotubes were examined with the electrochemical performances. The effects of the uniformity of sulfur loaded on carbon nanotubes were also investigated in the viewpoint of electrochemistry. Three methods of preparing CNT/sulfur composites were studied. For the result, the uniform distribution of sulfur on the carbon matrix and the best electrochemical performance were obtained with the solution based sulfur precipitation method followed by thermal treatment. Porous CNT/sulfur composite which was activated for 2 hours delivered the highest performance of 688 mAh/g at 5 C and retained 672 mAh/g even after 50 cycles. This outstanding performance was proven to be originated from the shorten electron penetration depth and guaranteed lithium ion diffusion pathway in the composite.