The paper battery can furthermore be recharged much faster than a lithium battery. The cellulose that Stromme and her colleagues use comes from a type of polluting algae found in seas and lakes. Although the algae’s cell walls contain cellulose, it has a very different nanostructure, which gives it 100 times the surface area. The researchers coat the paper made from this cellulose with a conducting polymer and then sandwich a salt-solution-soaked filter paper between the paper electrodes.
Chlorine ions flow from the positive electrode to the negative one, while electrons travel through the external circuit, providing current. The paper electrode stores charge while recharging in tens of seconds because ions flow through the thin electrode quickly. In contrast, lithium batteries take 20 minutes to recharge. “The combination of large capacity and small charging time is very unique,” Stromme says.
Bradford says that the new paper battery is at a relatively early research stage compared to other thin-film technologies. “For a battery to succeed, you need to have a good cost and manufacturing process in place, but performance is the key aspect,” she says. “If it’s not a several-degrees improvement on existing technology, it’s very hard to make the battery profitable.”
Stromme, meanwhile, is confident that the environmentally friendly design will find niche applications. She says that it could be produced commercially within three years.