ECOCAPS

Hybrid supercapacitors employ a positive battery electrode and a negative electric double-layer (EDL) charging electrode in a single cell. In order to provide maximum charge storage, nanoporous carbons with high specific surface area of up to 2000 m²/g are used as electrode materials. The ECOCAPS project deals with the development of hybrid supercapacitors in aqueous iodide-based electrolytes and their long term testing. The iodide salt is the main component of the aqueous electrolyte, which results in reversible iodine electrodeposition in the pores of the positive carbon electrode causing a battery-like charging behaviour. The use of an aqueous electrolyte makes these energy storage devices environmentally friendly and safe to fabricate and operate. In addition, all the components including current collectors, separator, binder and electrodes are prepared from low cost materials. Assembling of a hybrid supercapacitor with an aqueous iodide electrolyte is far less tedious compared to organic electrolyte based supercapacitors. Thanks to the hybridization of battery and EDL electrodes, the device displays high energy and power densities and long cycle stability similar to organic electrolyte based supercapacitors. ECOCAPS proposes to use inexpensive water-in-salt electrolytes and aluminium current collectors to enhance the energy and power density as well as the cyclability and to reduce self-discharge. The envisioned eco-friendly supercapacitor prototype will lead to a design of energy storage devices at affordable cost that opens the door for commercial development. ECOCAPS is carried out in collaboration with the Surface Science Group at Karl-Franzens-University Graz and HRTec GmbH.

Funding by the Austrian Research Promotion Agency (FFG) in the 7^th Call Energieforschung of the Klima- und Energiefonds is acknowledged.