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 (τ 0 = 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.

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Self-supporting highly conductive polymers are strongly demanded for high-rate flexible supercapacitors. In this work, we demonstrate that solution-processed poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires with tens of micrometers in length can facilely assemble into highly flexible PEDOT films for high-rate supercapacitors. Our results show that the conductivity of the films (50.8−100 S cm −1 ) relies on the polymerization time of the nanowires and longer time favors doping of dodecyl sulfate anions but results in a decrease of carrier mobility from 16.08 to 6.05 cm 2 V −1 s −1 . A specific capacitance of 137 F g −1 along with 98% capacitance retention after 10 000 cycles has been achieved in 1 M H 2 SO 4 . Moreover, due to the favorable ion and electron pathways and rapid pseudocapacitive redox reactions, these PEDOT films exhibit nearly thickness-independent capacitive performance even as the film thickness increases up to 100 μm. A solid-state capacitor built with a PEDOT film delivers an energy density of 1.38 mWh cm −3 at 27.9 mW cm −3 . Meanwhile, it also exhibits superior long-term electrochemical stability without obvious capacitance decay and excellent structural integrity under various deformation tests. These outstanding properties demonstrate that the PEDOT nanowires could become one of the promising building blocks for developing flexible electrodes with an interconnected network for future high-rate energy storage devices.

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The Ti3C2Tx film with metallic conductivity and high pseudo‐capacitance holds profound promise in flexible high‐rate supercapacitors. However, the restacking of Ti3C2Tx sheets hinders ion access to thick film electrodes. Herein, a mild yet green route has been developed to partially oxidize Ti3C2Tx to TiO2/Ti3C2Tx by introducing O2 molecules during refluxing the Ti3C2Tx suspension. The subsequent etching away of these TiO2 nanoparticles by HF leaves behind numerous in‐plane nanopores on the Ti3C2Tx sheets. Electrochemical impedance spectroscopy shows that longer oxidation time of 40 min yields holey Ti3C2Tx (H‐Ti3C2Tx) with a much shorter relax time constant of 0.85 s at electrode thickness of 25 µm, which is 89 times smaller than that of the pristineTi3C2Tx film (75.58 s). Meanwhile, H‐Ti3C2Tx film with 25 min oxidation exhibits less‐dependent capacitive performance in film thickness range of 10–84 µm (1.63–6.41 mg cm−2) and maintains around 60% capacitance as the current density increases from 1 to 50 A g−1. The findings clearly demonstrate that in‐plane nanopores not only provide more electrochemically active sites, but also offer numerous pathways for rapid ion impregnation across the thick Ti3C2Tx film. The method reported herein would pave way for fabricating porous MXene materials toward high‐rate flexible supercapacitor applications.