Highly conductive paper was fabricated through polypyrrole (PPy) coating on common printing paper by a simple and low-cost “soak and polymerization” method. The as-fabricated porous, flexible and conductive paper shows a high electrical conductivity of 15 S cm−1 and a low sheet resistance of 4.5 Ω sq−1. Flexible solid-state supercapacitors assembled with PPy/paper composite electrodes had an average weight of 55 mg and an areal capacitance of 0.42 F cm−2, indicating a high energy density of 1 mW h cm−3 at a power density of 0.27 W cm−3 normalized to the volume of the whole cell (electrode, electrolyte, and separator). Furthermore, this method could be easily scaled up to large-scale fabrication of conductive paper and opened up new opportunities for flexible energy storage.
