Flexible carbonized cellulose/single-walled carbon nanotube films with high conductivity

A carbonized cellulose/single-walled carbon nanotube composite film (cell/SWCNT_carbon) was prepared with well-dispersed cellulose/SWCNT doped in N-methylmorpholine N-oxide (NMMO) monohydrate. After carbonization at 400 °C, the SWCNT content at electrical threshold of the cell/SWCNT_carbon nanocomposite decreased from 2 wt% to 1 wt%, and the electrical conductivity of the cell/SWCNT(1 wt%)_carbon nanocomposite (0.6 S cm^-1) increased by more than 6 orders of magnitude compared to that of pure carbonized cellulose (1.1 × 10^-7 S cm^-1). Further, it continuously increased as the carbonization temperature increased and reached 100 S cm^-1 when the cell/SWCNT(1 wt%) nanocomposite was carbonized at 1400 °C. This drastic increase in the electrical conductivity at low carbonization temperatures (e.g. 400 °C) was due to the percolation of small carbon clusters with conducting SWCNTs. The incorporated SWCNTs improved flexibility and mechanical stability during carbonization so that the cell/SWCNT(1 wt%)_carbon nanocomposite could be bent even after carbonization at 1400 °C; however, the carbonized cellulose prepared using the same method was too brittle. This cell/SWCNT_carbon nanocomposite may render the eco-friendly production of flexible electrodes for various applications, including heat sink parts, electromagnetic interference shielding materials, and electronic devices, feasible.