High energy density supercapacitors using macroporous kitchen sponges

Macroporous, low-cost and recyclable kitchen sponges are explored as effective electrode platforms for supercapacitor devices. A simple and scalable process has been developed to fabricate MnO2-carbon nanotube (CNT)-sponge supercapacitor electrodes using ordinary kitchen sponges. Two organic electrolytes (1 M of tetraethylammonium tetrafluoroborate (Et4NBF4) in propylene carbonate (PC), 1 M of LiClO4 in PC) are utilized with the sponge-based electrodes to improve the energy density of the symmetrical supercapacitors. Compared to aqueous electrolyte (1 M of Na2SO4 in H2O), the energy density of supercapacitors tripled in Et4NBF4 electrolyte, and further increased by six times in LiClO4 electrolyte. The long-term cycling performance in different electrolytes was examined and the morphology changes of the electrode materials were also studied. The good electrochemical performance in both aqueous and organic electrolytes indicates that the MnO2-CNT-sponge is a promising low-cost electrode for energy storage systems.