Biodegradable batteries represent the holy grail of our current technological obstacles to achieving the transition to an electric economy. New research published in Advanced Materials reports a development in this pursuit, describing a supercapacitor made exclusively from 3D-printed organic ingredients (alas, not yet snackable though). The capacitor, developed at the Empa lab, is capable of storing electricity for hours, and get this: it’s compostable.
The battery is composed of a 3D-printed flexible substrate, a conductive layer, the electrode and the electrolyte, all made from a mixture of cellulose nanofibers and cellulose nanocrystallites, carbon black, graphite and activated carbon. The materials are converted into liquid form (i.e. ink) with glycerin, water, two different types of alcohol and a dash of salt for flavor (i.e. ionic conductivity).
"It sounds quite simple, but it wasn't at all," says Xavier Aeby of Empa's Cellulose & Wood Materials lab. "As researchers, we don't want to just fiddle about, we also want to understand what's happening inside our materials," which required a long series of experiments.
The capacitor has the potential to greatly reduce e-waste and Nyström and Aeby comment that, "In the future, such capacitors could be briefly charged using an electromagnetic field, for example, then they could provide power for a sensor or a microtransmitter for hours." The possible applications for such a technology are endless, from environmental and agricultural monitoring to the shipping industry to near-patient laboratory diagnostic medical devices such as blood sugar monitors. "A disposable cellulose capacitor could also be well suited for these applications," says Gustav Nyström, who supervised the project.
Among its hailed renewable and biodegradable properties, the capacitor boasts other important characteristics, such as resistance to pressure and shock. It has also been demonstrated to be able to withstand thousands of charge and discharge cycles and can be stored for years even in freezing temperatures. Best of all says the team, it only takes about two months to degrade, disappearing into just a few wisps of carbon.