Transparent Supercapacitor Display with Redox-Active Metallo-Supramolecular Polymer Films

Abstract

The use of metallo-supramolecular polymer (MSP) as a thin-film based redox supercapacitor electrode material is reported for the first time. Fe(II)- and Ru(II)-based MSPs (polyFe and polyRu, respectively) were synthesized by complexation of appropriate metal salts with 4',4''-(1,4-phenylene)bis-2,2':6',2''-terpyridine and thin films of these polymers were prepared by a spray coating onto an indium tin oxide (ITO) glass substrate. A study of the energy-storage performances of the polyFe and polyRu films in a nonaqueous electrolyte system revealed volumetric capacitances of ~62.6 ± 3 F/cm3 for polyFe and 98.5 ± 7 F/cm3 for polyRu at a current density of 2 A/cm3. To improve the energy-storage performance over a wider potential range, asymmetric supercapacitor (ASC) displays were fabricated with suitable combinations of the MSPs as cathodic materials and Prussian blue as the anodic counter material in a sandwich configuration with a transparent polymeric ion gel as the electrolyte. The fabricated ASCs showed a maximum volumetric energy density (~10-18 mWh/cm3) that was higher than that of lithium thin-film batteries and a power density (7 W/cm3) comparable to that of conventional electrolyte capacitors, with superb cyclic stability for 10 000 cycles. To demonstration the practical use of the MSP, the illumination of an LED bulb was powered by a laboratory-made device. This work should inspire the development of high-performance thin-film flexible supercapacitors based on MSPs as active cathodic materials.