Construction of porous and free-standing film electrodes composed of MXene, carbon nanocoils and PEDOT:PSS for high-performance flexible supercapacitors

The development of high-performance and flexible supercapacitors is of urgent demand but still challenging. MXene, a novel two-dimensional material, has metallic conductivity, good hydrophilicity, and high redox activity. Significantly, its good electrochemical and mechanical properties suggest its great potential in flexible supercapacitors. However, the poor interlayer conductivity and self-stacking of MXene flakes hinder the charge transfer and ion transport. Herein, a three-dimensional porous structure composed of MXene, carbon nanocoils (CNCs) and Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) (denoted as MXene/CNC/PP) has been successfully prepared by a facile drop-coating method for flexible film electrode. The CNCs, having unique 3D helical structures and excellent dispersity, insert into the MXene flakes to prevent their over stack and provide spaces and channels for electrolyte storage and ion transport inside the composite structure. Meanwhile, the CNCs also act as highly conductive bridges to connect the MXene flakes, enhancing the charge transfer. To increase the stability of the composite structure, the conducting polymer PEDOT:PSS was selected as an conductive binder to prepare self-supported MXene/CNC/PP film electrodes without additional additives. The MXene/CNC/PP electrode exhibits an areal capacitance of 232 mF cm−2 at 10 mV s−1 with superior rate capability, excellent cycling stability and flexibility. This paper provides a new strategy for construction of wearable high-performance flexible electrodes and supercapacitors.