Co-electro-deposition of the MnO2–PEDOT:PSS nanostructured composite for high areal mass, flexible asymmetric supercapacitor devices

To meet the rapidly growing demand, it is necessary to develop novel flexible energy storage devices with a high energy density in a limited area, a fast charging ability, a low cost for mass production and a miniaturized device size. To address the above issues, here we introduce the co-electro-deposition strategy, which is able to prepare an electrode material with a high areal capacitance (1670 mF cm−2 at 0.5 mA cm−2), a high areal mass (8.5 mg cm−2), an excellent mechanical robustness, a high through-put and great convenience even on a piece of a ubiquitous stainless steel mesh current collector. Based on this advancement, we are able to obtain an ultrathin (less than 200 μm) aqueous asymmetric supercapacitor device with a high energy density (1.8 × 10−3 W h cm−3), a high power density (0.38 W cm−3 at 3.62 × 10−4 W h cm−3) and an excellent rate capability. This energy storage device is integrated into a prototype smart card to drive a light emitting diode (LED) indicator, which is charged for 5 seconds and can light up the indicator for more than 2 hours, demonstrating great promise in miniaturized novel flexible energy storage devices.