Scientists store energy in paper

Stanford scientists are using nanotechnology to quickly produce lightweight and bendable charge-storage devices in the form of everyday paper.

Simply coating a sheet of paper with ink made of single-walled carbon nanotube (CNT) and silver nanowire films makes a highly conductive storage device, said Yi Cui, assistant professor of materials science and engineering at Stanford University.

The paper storage-device can last through 40,000 charge-discharge cycles – at least an order of magnitude more than lithium batteries.

The commercially available paper can be made highly conductive with a sheet resistance as low as one ohm per square (Ω/sq), and when only the mass of the CNTs are considered, a specific capacitance of 200F/g, a specific energy of 30-47Wh/kg, and a specific power of 200,000W/kg can be achieved.

Cui had previously created nanomaterial energy-storage devices using plastics. His new research shows that a paper storage-device is more durable because the ink adheres more strongly to paper.

A paper storage-device may be especially useful for applications such as electric or hybrid cars, which depend on the quick transfer of electricity.

‘This technology has the potential to be commercialised within a short time,’ said Peidong Yang, professor of chemistry at the University of California-Berkeley.

‘I don’t think it will be limited to just energy storage devices.

‘This is potentially a very nice, low-cost flexible electrode for any electrical device.’

Post doctoral students in the lab of Prof Yi Cui, materials science and engineering, light up a diode from a storage device made from treated paper. The paper devices are treated with a nanotube ink, baked and folded into electrical-generating sources such as the one wrapped in foil seen here.

Cui’s work was reported this week in the paper ‘Highly Conductive Paper for Energy Storage Devices,’ published online in the Proceedings of the National Academy of Sciences.