Unlocking highly stable and reversible in-situ integration of defect-rich 2D vanadium sulfide with Ti₃C₂T_x MXene heterostructures: Boosting asymmetric supercapacitor performance

To broaden the functionalities of transition metal dichalcogenides and two-dimensional transition metal carbides such as MXenes (Ti₃C₂T_x-MX), it is necessary to appropriately integrate them with each other to form heterostructures. The integrated heterostructures should maintain functionality through strong covalent interaction and offer excellent electrochemical properties. The requirement for developing appropriately integrated heterostructures is the control of nucleation and growth by governing the reaction kinetics. However, developing heterostructures over MXenes on a large scale is extremely challenging. Herein, we propose an investigation to elucidate the formation of defect-rich conductive heterostructures by in-situ integration of vanadium sulfide (VS₂) on the surface of Ti₃C₂T_x-MX (VS₂–Ti₃C₂T_x-MX) via controlled nucleation and growth in a facile hydrothermal process. The scrutinized binder-free flexible fabric-based VS₂–Ti₃C₂T_x-MX_0.25 electrode exhibits an excellent specific capacitance of 750 F g⁻¹ and long-term stability (∼93 % retention after 10000 cycles). Moreover, these defect-rich and interlayer-expanded integrated heterostructures showed exceptional cycling stability and an impressive energy density of 52.08 Wh kg⁻¹ at a power density of 750 W kg⁻¹ when employed as fabric-based asymmetric supercapacitor (ASC) devices with VS₂–Ti₃C₂T_x-MX_0.25//Ti₃C₂T_x-MX configuration. We anticipate that the approach presented in this work will promote the development of various MXene-based heterostructures for manipulating the versatile properties of MXenes and VS₂ in energy storage applications.