Flexible zinc-ion supercapacitor with 3D layered N-graphene/MXene heterostructure for wearable long-duration electronics

With the rapid development of wearable electronics, the key challenge of existing flexible energy storage devices is their low energy density, limited cycling ability, and safety concerns associated with carbon cathode materials and conventional electrolyte systems. In this paper, we present a strategy in which the MXene nanosheets and nitrogen-doped graphene (N-RGO/MXene) heterostructure are employed to assemble a flexible zinc-ion asymmetric supercapacitor (FZASC) using Zn(CF 3 SO 3 ) 2 /PVA as gel electrolyte. The MXene/N-RGO heterostructure composite forms a three-dimensional (3D) conductive network that facilitates the rapid deposition and transport of Zn 2+ . The quasi-solid-state FZASC with N-RGO/MXene heterostructure anode exhibits the highest capacitance of 133.53 F g −1 at 0.2 A g −1 , average energy density of 36.35 Wh kg −1 , and a power density of 140 W kg −1 , respectively. Notably, the prepared flexible FZASC exhibits a capacity retention of 84.67% after 10000 cycles at 6 A g −1 , with a coulombic efficiency approaching 100% and excellent mechanical flexibility under different bending angles and bending cycles. Moreover, the quasi-solid-state FZASC can keep an LED light illuminated for several minutes. The design strategy and performance metrics provide guidance for next-generation, flexible, and safe quasi-solid-state FASCs with high performance and long-duration stability, exhibiting great potential in energy-storage applications.