Selenized Binary Transition Metals-MXene Composite for High-Performance Asymmetric Hybrid Capacitors

The exploration of innovative and high-efficiency energy storage materials is crucial for advancing high-performance supercapacitors. In this study, a novel composite material is synthesized, comprising multilayered MXene (Ti₃C₂T_x) nanoparticles integrated with porous NiCo₂Se₄ nanosheets. The accordion-like nanostructure of MXene and its strong interfacial interactions enhance the surface area and cycling stability of the nanocomposite. Additionally, substituting selenium (Se) for Ni-Co-based hydroxides modulates orbital hybridization with the corresponding metal cations, significantly improving electrochemical activity and reducing the adsorption/desorption energy barrier for electrolyte ions. The synergistic interaction between these two materials enabled the composite electrode to achieve a high specific capacity of 796.25 C g^-1 at 1 A g^-1 while maintaining over 90% of its initial capacity after 8000 cycles. Furthermore, the as-fabricated asymmetric hybrid capacitor, employing activated carbon as the negative electrode, delivered an energy density of 64.36 Wh kg^-1 at a power density of 0.8 kW kg^-1, surpassing the performance of most previously reported hybrid capacitors. The developed composite structure holds significant potential for integration into various electrochemical devices, such as batteries, sensors, and electrolyzers.