Batteries made from paper

A dip in nanotube ink turns ordinary office paper into a high-energy electrode. Ordinary paper can be turned into a battery electrode simply by dipping it into carbon-nanotube inks. The resulting electrodes, which are strong, flexible, and highly conductive, might be used to make cheap energy storage devices to power portable electronics. It is now possible to print lightweight circuits and screens for electronics like e-readers, but conventional batteries still weigh these devices down. Carbon nanotubes are a promising material for printing batteries because, in addition to their strength, light weight, and conductivity, they can store a large amount of energy--a quality that helps portable electronics run longer between charges. Now a group of Stanford University researchers have demonstrated that ordinary office paper soaks up carbon nanotubes like a sponge and can be turned into electrodes for batteries and supercapacitors. The advantage of paper is that it is cheap and interacts strongly with nanotubes without the need for putting additives in the ink. The advantage of the porous structure of paper is taken here. Carbon nanotubes absorb into the paper and stick on really tightly. After paper is dipped in the nanotube ink and air-dried, it becomes highly conductive. The Stanford group tested the thin films as electrodes in supercapacitors and found that they could store more total energy, and operate at higher currents, than previous printed nanotube devices. The paper supercapacitors store a surprisingly high amount of charge. The Stanford group also tested the paper electrodes as current collectors in lithium-ion batteries. Their performance matched that of the metal current collectors used in these batteries, even though the metal collectors are much heavier.