A significant limiting factor in pushing new technologies forward is often the size of the batteries needed to keep them electrified. Mobile phones have been around since the mid-1980s -- but they swept across the globe and became one of the most transformative technologies ever in part because their batteries became small and powerful instead of chunky, clunky and weak. So this development is interesting: Researchers at Rensselaer Polytechnic University in Troy, New York have found a way to create small, thin, incredibly flexible batteries by impregnating cellulose (i.e., wood pulp, the same stuff paper's made from) with carbon nano-tubes, which act as the battery's electrodes:
It sounds simple, but proved tricky to do; cellulose is insoluble in almost all solvents, making it difficult to embed the nanotubes. But Ajayan used a kind of solvent known as an ionic liquid to dissolve the woody stuff, so that it could be impregnated with multiwalled carbon nanotubes.
After the cellulose/nanotube paper is made in this way, the ionic liquid can be completely removed, leaving a sheet of paper that can be cut to size, bent, rolled up or twisted, and which springs back into shape with ease. When the paper is layered with a thin layer of lithium metal, a battery is created.
As a bonus, if some of the ionic liquid is left behind it acts as a built-in electrolyte, turning a stack of such paper into a supercapacitor.
Supercapacitors can't store energy the way batteries can, but they can charge and discharge more quickly. The paper battery may be a way to get the best of both, says researcher Pulickel Ajayan: "a device capable of storing useful quantities of electricity which can be discharged very quickly." He thinks there could be commercial applications for the paper batteries in a few years.
I'm very much looking forward to developments like these. Soon enough, we'll make composite structures that are also batteries!