Preparation of N/S co-doped graphene/polypyrrole composites for binder-free flexible supercapacitors

Abstract

Flexible electrodes have been extensively studied and developed, but how to maintain flexibility and increase capacitance at the same time is still challenging. In this work, nitrogen/sulfur co-doped reduced graphene oxide (RGO) and a series of polypyrrole (PPy) composite (RGP-i, i = 1, 2, 3, 4, 5, 6) aerogel materials are prepared by adjusting the mass ratio of graphene oxide (GO) and PPy and using thiourea (CS(NH2)2) as a reducing agent. Binder-free flexible electrodes are assembled by using carbon cloth (CC) as substrates. Among these samples, RGP-5 prepared with the ratio of m(GO):m(PPy) = 1:1 exhibits excellent comprehensive electrochemical performance, with high specific capacitance (394 F g−1 at 1 A g−1) and high capacitance retention (55.4% from 1 to 20 A g−1) simultaneously. The assembled RGP-5//RGP-5 flexible quasi-solid symmetric supercapacitor shows an energy density of 6.25 Wh kg−1 at a power density of 500 W kg−1, and a power density of 2501 W kg−1 at an energy density of 4.37 Wh kg−1. After 1000 cycles of charging and discharging, its capacitance can maintain 80%. The specific capacitance of RGP-5//RGP-5 under different bending angles is almost unchanged, indicating that it shows good flexibility.