LONDON Scientists at the University of Stanford (Palo Alto, Calif.) have developed a method for turning paper into a lightweight bendable battery or supercapacitor. The research is expected to have impact in novel energy storage for electric vehicles and supply grid, and improving established systems, such as lithium-ion batteries.
The paper battery is simply made using normal paper coated with a carbon nanotube "ink" and silver nanowires. The arrangement can charge and discharge very quickly making it closer to a supercapacitor than a battery and can withstand 40,000 charge-discharge cycles, according to a Stanford University write up of the technology development.
The research team was led by Yi Cui, assistant professor of materials science and engineering, and their work reported in "Highly conductive paper for energy storage devices," published in the Proceedings of the National Academy of Sciences.
Professor Cui has been working on the use of silicon nanowires to improve the performance of lithium-ion batteries for some time. One of the main thrusts of the latest research is to demonstrate that paper is an inherently better substrate than plastics. "Paper substrates can dramatically improve film adhesion, greatly simplify the coating process, and significantly lower the cost. Supercapacitors based on CNT-conductive paper show excellent performance," the introduction to the paper says.
When only the weight of the carbon nanotubes is considered the set up achieves a specific energy of 30 to 40-watt-hours per kilogram and a specific power of 200,000 watts per kilogram. What's more the paper can be crumpled or folded without affecting performance. It can even be soaked in acidic or basic solutions without degrading performance, the report said.