Ultra-Fast, High-Energy Supercapacitor for Wireless Electronics

Micro-supercapacitors are poised to work as energy conversion and storage unit for on-chip electronics. However, their practical application was limited by the low areal power and energy densities and high leakage current due to the self-discharge process. Here, layer-by-layer electro-deposition of an open-shell conjugated polymer and reduced graphene oxide was developed to fabricate hierarchical composite electrode materials with high areal capacitance up to 145 mF cm^-2 (460.3 F cm^-3) and 3 V potential window. The extended delocalization within the conjugated polymer facilitates the wide potential window and high areal capacitance. The hierarchical electrode promotes ultrafast kinetics during the charging/discharging process. Thus, the fabricated device reached 12.7 mF cm^-2 areal capacitance at the fast scan rate of 10 V s^-1, and enable a record energy density of 21.9 μWh cm^-2 at power density of 227 mW cm^-2. Meanwhile, a novel separator that contained sulfonate ion-exchange resin was employed to trap impurities in electrolyte and thereby suppress the self-discharge in supercapacitors. Compared to devices using commercially available separators, the device here exhibited a lower leakage current and higher charging efficiency. These attributes allow the fabricated device to work with radio frequency energy-harvesting circuits and serve as high-endurance energy storage for wireless electronics