Novel helical carbon nanotubes-embedded reduced graphene oxide in three-dimensional architecture for high-performance flexible supercapacitors

Abstract

The rapid development of flexible and portable electronics has brought great opportunities to develop flexible and lightweight energy-storage systems. Herein, a free-standing, mechanically flexible and binder-free three-dimensional (3D) sandwich-type network film electrode with reduced graphene oxide (RGO)-wrapped helical carbon nanotubes (HCNT) is designed and synthesized by a synergistic and applicable self-assembly strategy. HCNT in the composites serve as the inner skeleton, impede the stacking of RGO and enlarge the space between RGO effectively, which facilitate the creation of conductive 3D architectures and reinforce the structural stability. Moreover, the RGO coating and the voids are beneficial in improving electrochemical conductivity. As a result, the as-prepared RGO/HCNT electrodes show excellent electrochemical characteristics, yielding the specific capacitances of 336 F g−1 at a current density of 0.25 A g−1, and it offers the energy density of 7.5 Wh kg−1 with the corresponding power density of 100 W kg−1 as well as excellent cycling stability at approximately 89.5% capacitance retention exceeding 3000 cycles. The bending tests indicate that the flexible supercapacitors (SCs) can operate under different static bending angles, and the capacitance is hardly affected. The HCNT and corresponding flexible SCs are novel materials with potential applications in the next generation of wearable energy devices.