Connecting PEDOT Nanotube Arrays by Polyaniline Coating toward a Flexible and High-Rate Supercapacitor

Abstract

As a conductive polymer with great potential, poly(3,4-ethylenedioxythiophene) (PEDOT) has been developed as a high-rate supercapacitor electrode but stores less energy due to its limited theoretical capacity. In this work, the growth of PEDOT nanotube arrays on flexible Ti foil (Ti@PEDOT) is reported with significantly enhanced performance by incorporating highly pseudocapacitive polyaniline (PANi). The as-prepared Ti@PEDOT nanotube arrays offer a three-dimensionally conductive network. Such arrays have been successfully connected with each other through the uniform coating of PANi onto the surface, thus contributing a substantial pseudocapacitance. By constructing the above novel structure, the Ti@PEDOT-PANi hybrid electrode delivers a nearly 10 times enhancement of areal capacitance (2876 mF cm–2 at 5 mA cm–2) together with a remarkable rate performance (85% capacitance retention at 100 mA cm–2). Moreover, a flexible supercapacitor assembled with the Ti@PEDOT-PANi electrode also exhibits a high-rate property with a relaxation time constant as small as 0.83 s (τ0 = 0.83 s) and a volumetric energy density of 15.9 mW h cm–3 under the power density of 178.9 mW cm–3. The cycling stability of such a device is also remarkable, indicating the great advantages of the Ti@PEDOT-PANi electrode. More gratifying, such device can endure continuous bending at a maximum angle of 145° for 200 cycles. The present work can provide theoretical and technical support for the design and development of polymer-based flexible electrodes which possess both large areal capacitance and fast charging–discharging rates.