A Flexible, Lightweight, and High-Performance Supercapacitor Made of Nanofibrous Polypyrrole Electrodes.

High-performance and lightweight supercapacitors are in high demand in personal electronics and electric vehicles. In this work, the pseudocapacitance of a metal-free symmetric supercapacitor made of polypyrrole (PPy) membrane electrodes and a gel electrolyte containing 3% poly-(vinyl alcohol) (PVA) dissolved in 1 M sulfuric acid (PVA-HSO) was investigated. It was observed that the soft PPy membrane synthesized through docusate sodium and methyl orange-assisted interfacial polymerization (PPy-AOT) had a unique nanofibrous structure throughout the thickness of 1 mm. The PPy-AOT/PVA-HSO electrode is flexible, lightweight, free-standing, and free of metal, showing a lower environmental impact with respect to that of the high-performance supercapacitors using metals. A hypothetic mechanism was proposed to explain how such a nanofibrous structure is formed. The weight-based performance of the device was compared with different categories of supercapacitors and batteries, with its advantages and disadvantages discussed. The supercapacitor and electrode material were analyzed with various analytical techniques. Without using metals and carbon materials, the polymeric supercapacitor recorded a high areal capacitance of 4817.9 mF/cm and gravimetric capacitance of 430.0 F/g, with energy densities of 0.4 mWh/cm and 14.6 Wh/kg and power densities of 0.6 mW/cm and 174.6 W/kg. Such polymeric supercapacitors may find applications in cost- and environmentally sensitive areas.