Smart textiles will require electronic yarns and fibres that are strong, flexible and light. Such fibres, which will play the part of electrodes in these textiles, will also need to store energy efficiently if they are to act as integrated capacitors and batteries. Although researchers have made much progress in this field by developing yarns from carbon nanotubes and graphene, most of these fibres are still far from ideal. In particular, the best capacitance values reported to date (of 265 F/g) still fall far short of the theoretical value of 550 F/g for graphene-based structures.

Now, Gordon Wallace of the University of Wollongong in Australia and colleagues have made yarns and fibres from graphene oxide and reduced graphene oxide that are not only highly flexible and lightweight but that have an unrivalled electrochemical capacitance of as high as 410 F/g. “Our structure is a first for graphene oxide,” team member Seyed Hamed Aboutalebi told, “because, until now, 3D architectures of graphene-based capacitors were mainly limited to graphene ‘papers’ and micro-supercapacitors, which although interesting in their own right, are not really practical for when it comes to making intelligent fabric.”

The researchers used a novel wet-spinning technique to produce unlimited lengths of highly porous yet dense, mechanically robust and flexible graphene yarns from liquid crystals of very large graphene oxide sheets. The yarns, which could be directly used as the building blocks for supercapacitors in fully functioning smart textiles, are very strong, with a Young’s modulus that is greater than 29 GPa. They also have a high electrical conductivity of around 2500 S/m and a very large surface area – about 2600 m2/g for graphene oxide and 2210 m2/g for the reduced material. The high capacitance of 410 F/g per graphene oxide electrode (in a practical two-electrode configuration set up) comes thanks to the fact that ions can travel fairly fast and without resistance in the fibres, says Aboutalebi.

“The yarns might be ideal in powerful next-generation multifunctional renewable wearable energy storage systems,” he adds. “Our method to make these yarns is simple and can be scaled up to produce mass quantities of the structures.”

The team, which includes researchers from Dublin City University and the University of Sydney, says that it is now busy working on making easily processed self-assembled, self-oriented and molecularly ordered graphene-based hybrids for use in intelligent fabrics.

The current work is detailed in ACS Nano DOI: 10.1021/nn406026z.

Further reading

Carbon nanotubes spin a yarn (Jan 2011)
Laser-etched CNT array delivers uniform yarn (Feb 2010)
'Buckypaper' stretches in a strange way (Apr 2008)