Open-ended N-doped carbon nanotubes array for Li-ion battery anode

Carbon nanotubes have been considered as promising candidate for anode materials of lithium ion batteries. Despite of superior electrical conductivity, the lithium ion capacity of CNTs is limited due to the closed tubular structure, restricting the use of inner surface and space as well as intercalation of lithium ion between CNT walls. Here, we present open-ended NCNT arrays maximizing the lithium ion capacity of CNT based materials. Reactive ion etching can selectively etch out the closed-tip of typical CNT arrays and enables to utilize the hidden inner surface and space for lithium ion storage. The resultant opened tubular structure shows improved the lithium ion capacity as much as 1.7 times, compared to closed-tubular structure.