The Biodegradable Battery

The fabrication device for the battery revolution looks quite unconspicuous: it is a modified, commercially available 3D printer, located in a room in the Empa laboratory building. But the real innovation lies within the recipe for the gelatinous inks this printer can dispense onto a surface. The mixture in question consists of cellulose nanofibers and cellulose nanocrystallites, plus carbon in the form of carbon black, graphite and activated carbon. To liquefy all this, the researchers use glycerin, water and two different types of alcohol. Plus a pinch of table salt for ionic conductivity. A sandwich of four layers To build a functioning supercapacitor from these ingredients, four layers are needed, all flowing out of the 3D printer one after the other: a flexible substrate, a conductive layer, the electrode and finally the electrolyte. The whole thing is then folded up like a sandwich, with the electrolyte in the center.