Flexible Energy Storage Device Based on Poly(<i>N</i>-phenylglycine), an Incentive-Energy Pseudocapacitive Conducting Polymer, and Electrochemically Exfoliated Graphite Sheets
Vedi Kuyil Azhagan Muniraj, Rabah Boukherroub, Manjusha V. Shelke
Abstract
Poly(N-phenylglycine) (PNPG), an original pseudocapacitive conjugative conducting polymer (CP), was synthesized by the electro-oxidative polymerization method. The synthesis process involves in situ polymerization and electrodeposition of N-phenylglycine onto the surface of highly conductive, few-layered, exfoliated flexible graphite sheets (E-FGSs). At first, the promising features of the conjugative structure of the as-prepared protonated PNPG were thoroughly investigated by UV–vis absorption spectrophotometry, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy analysis. The protonated nitrogen groups facilitate the rapid accessibility of counter ions from the electrolyte. Electrochemical studies revealed that the PNPG/E-FGS electrode exhibits an extraordinary areal specific capacitance of 367 mF cm–2 at 10 mV s–1. A flexible solid-state symmetrical supercapacitor was further fabricated using PNPG/E-FGS electrodes, exhibiting a specific capacitance as high as 199 mF cm–2 at 1 mA cm–2 with an operating voltage of 1.1 V. Furthermore, the device delivered an excellent specific energy of 8.36 μW h cm–2 at a power density of 1.65 mW cm–2 in a working potential window of 1.1 V. More significantly, the energy density was nearly doubled to 16.1 μW h cm–2 upon extending the potential window from 1.1 to 1.5 V. The extremely redox-active CP electrode is highly suitable for applications in high-energy electrochemical capacitors with wide operating potential window.