Intercalated carbon nanotube fibers with high specific electrical conductivity

Translating the conductivity of individual carbon nanotubes into practical, macroscopic conductors remains a challenge. We report highly aligned fibers of double-walled carbon nanotubes intercalated with chains of tetrachloroaluminate anions (AlCl₄^-) in the intertube channels. The AlCl₄^- intercalant acts as a noncovalent dopant, accepting 0.65 electrons per anion, mostly from the outer nanotube layer. Combined with a 17% intercalant volume fraction, it produces an increase in room-temperature conductivity to values as high as 24.5 mega-Siemens per meter, which is 41% of that of copper. Specific conductivity values reach 17,345 Siemens-meter squared per kilogram, which is superior to that of metals. These fibers are five times stronger and half the weight of conventional overhead cables while remaining stable in dry conditions and retaining 80% of their conductivity protected from moisture by a cable polymer sheath.