Ultra-high conductivity and metallic conduction mechanism of scale-up continuous carbon nanotube sheets by mechanical stretching and stable chemical doping

Abstract

Carbon nanotube (CNT) electrically conductive cables, fibers, or tapes are undergoing extensive research. However, the research conducted on these materials with high conductivity has been primarily limited to small samples, such as fibers around 5–10 μm in diameter or sheets less than 1 μm thick. The need for scaling up these samples to manufacture CNT lightweight conducting materials is urgent, yet challenging. This paper reports on our study to produce large-scale continuous CNT sheets with ultra-high electrical conductivity. After mechanical stretching to achieve a high degree of CNT alignment, iodine doping and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) capping was performed, resulting in high electrical conductivity in the range of 10,000 S/cm (the highest value achieved as ∼13,000 S/cm). High CNT alignment and carrier concentration after iodine doping significantly improved the overall conductivity. The superior open air stability of samples, benefiting from the capping layer of PEDOT:PSS, was demonstrated by the very small changes of the conductivity during test period. Additionally, this doping process is scalable for producing continuous highly conductive and lightweight CNT sheets. Metallic conduction behaviors of the aligned and doped large size CNT sheets could provide lightweight conductor applications of CNT materials.