High-Performance Flexible Supercapacitor Device Composed of a Hierarchical 2-D MXene-Ni(OH)₂ Nanocomposite and Biomass-Derived Porous Carbon Electrodes

Abstract

The periodic layered structure due to the well-arranged sheets and the presence of surface terminations (-OH, -O, and -F) on those sheets makes MXene an attractive aspirant for supercapacitor devices. Though MXene exhibits interesting redox behavior, the collapse of its layered structure and irreversible stacking of sheets retard its redox reaction and restrict the ion transport process. To enhance its electrochemical performance, we have developed a nanocomposite where the α-Ni(OH)2 petals are slid within the MXene structure as well as anchored on its surface. The multivalent character of Ni in Ni(OH)2 enhances the redox performance of the nanocomposite. Fabrication of a high-performance flexible all-solid-state asymmetric supercapacitor (ASC) device has been carried out using this 50MXene-50Ni(OH)2 nanocomposite as the cathode and the biomass-derived porous carbon as the anode. This ASC device manifested a high energy density of 29.3 W h kg–1 at a power density of 800 W kg–1 and 90% retention of specific capacitance (CS) even after ∼5000 GCD cycles. This supercapacitor device also demonstrated its mechanically flexible feature by showing its consistent electrochemical performance in diverse physical deformations. This flexible device illustrated its competence in real-world applications by illuminating an assembly of LED lights.