• By adding a novel doping agent through intercalation in carbon nanotubes (CNTs), researchers produced a significant increase in electrical conductivity over existing CNT fibres.
• The results confirm the current industrial applicability of CNT fibres, marking a key transition from laboratory-scale performance to use as real-world conductive materials.

Spanish researchers have demonstrated a scalable manufacturing process for carbon nanotube (CNT) fibres with electrical conductivity comparable to that of copper and aluminium.

The result, published in Science, is a breakthrough for the future of electrification in aerospace, electric vehicles (EVs), drones and related applications, which require lightweight and high-strength electrical wiring.

CNTs have long been considered as ideal building blocks for electrical conductors, owing to their unique combination of low density and electrical, thermal and mechanical properties.

Until now, however, they have not offered the electrical conductivity required to present a realistic alternative at an industrial scale to traditional materials, in particular copper. 

“This is the first time that researchers have produced results with CNT fibres demonstrating sufficient performance in this regard to offer a realistic industrial alternative to traditional conductive materials,” said IMDEA Materials Principal Investigator, Dr. Juan José Vilatela, one of the authors behind the recent publication.

Specifically, researchers were able to produce gas-phase intercalated CNT fibres with room-temperature conductivity as high as 24.5 MS/m (MegaSiemens per meter), nearly half that of copper, but six times lighter.

Given this substantial weight advantage, these results demonstrate electrical conductors that combine not only a significantly improved weight-to-performance ratio, but also absolute conductivity levels that meet industrial requirements.

One of the key elements of the research, carried out by IMDEA Materials Institute in collaboration with the Technical University of Madrid (UPM) and researchers from the University of Zaragoza at the INMA (CSIC-Unizar), was the introduction of tetrachloroaluminate(AlCl₄) to intercalate into the CNT fibres.

AlCl₄ acts as a dopant that can be introduced into the CNT fibre array without disrupting it. By retaining the original structure of the CNT bundles, the doping process increases conductivity while preserving their exceptional mechanical properties.

“In addition, AlCl₄⁻  provides a large doping effect without increasing weight excessively, compared to other dopants we have studied,” explained lead author and fellow IMDEA Materials researcher, Ana Inés de Isidro Gómez.

Specifically, researchers demonstrated that, by doping the highly aligned CNT fibres with AlCl₄, they were able to achieve a more than 17-fold increase in electrical conductivity of the bulk fibres.

This resulted in a mean specific conductivity in excess of that of copper, with a highest measured value above that of aluminium.

“This is particularly significant for the electrification of transport, be it EVs, drones or aircraft, which require large numbers of conductors at the lowest possible weight,” said Dr. Vilatela. “It also holds promise for overhead power cables, which are often limited by their own weight”.

According to the authors behind the study, the doped CNT fibres would be five times stronger than conventional overhead cables, while half the weight.

The research was carried out by IMDEA Materials’ doctoral researcher Isidro Gómez, Dr. Vilatela, Dr. Anastasiia Mikhalchan and Prof. Javier LLorca, IMDEA Materials Scientific Director and UPM professor, in conjunction with former IMDEA Materials researcher Dr. Valentín Vassilev Galindo.

The paper is the result of a collaboration with the Nanoscopy on Low Dimensional Materials (NLDM) group at the Institute of Nanoscience and Materials of Aragon (INMA), a joint centre of the Spanish National Research Council (CSIC) and the University of Zaragoza (UNIZAR), led by Dr. Raúl Arenal (ARAID researcher).

This work, carried out by Dr. Mario Peláez Fernández and Dr. Arenal, was conducted at the Advanced Microscopy Laboratory (LMA), one of the nodes of the ELECMI Singular Scientific and Technical Infrastructure (ICTS ELECMI).

“We have effectively demonstrated that gas-phase intercalation can increase the conductivity of commercial CNT fibres substantially above their previous ceiling, offering both record-high electrical conductivity, and the prospect of further increases,” concluded de Isidro Gómez.