In a new paper published in the current edition of the Proceedings of the National Academy of Sciences, a Stanford University research team reports on startlingly easy and inexpensive way to make a supercapacitor: Just brush an ink made of single wall carbon nanotubes and silver nanowires onto ordinary paper.
The team, led by Yi Cui, says they have been able to make sheet paper coated with the special ink highly conductive (resistance of about one ohm). The paper remains flexible and can be rolled up, folded, layered or configured in nearly any way someone can imagine.
The group had previously test the concept by applying the ink to plastics, but had a eureka! moment when they realized that the porosity and composition of regular paper would actually let the ink adhere better, is a cheaper feedstock for commercial production and can be scaled to any size use.
The paper-ink combination produces superior performance. The team writes:
When only CNT mass is considered, a specific capacitance of 200 F/g, a specific energy of 30–47 Watt-hour/kilogram (Wh/kg), a specific power of 200,000 W/kg, and a stable cycling life over 40,000 cycles are achieved. These values are much better than those of devices on other flat substrates, such as plastics. Even in a case in which the weight of all of the dead components is considered, a specific energy of 7.5 Wh/kg is achieved.
Cui and the others suggest that the paper would be an excellent lightweight substitute for the metallic current collectors used in lithium-ion batteries and in grid-scale energy storage applications
In a story published yesterday on the Standford University website, Peidong Yang, a professor of chemistry at the University of California Berkeley, said the group’s work may have a big payoff. “This technology has potential to be commercialized within a short time,. I don’t think it will be limited to just energy storage devices,” Yang said. “This is potentially a very nice, low-cost, flexible electrode for any electrical device. The most important part of this paper is how a simple thing in daily life – paper – can be used as a substrate to make functional conductive electrodes by a simple process. It’s nanotechnology related to daily life, essentially.”
Check out how easy they make it look: