ZnNi₂O₄/WS₂ Nanoflake-Based Electrodes for Quasi-Solid-State Asymmetric Supercapacitors

The spinel compounds are a class of intriguing electrode materials for redox-based supercapacitors owing to their high specific capacity and variable redox sites, but they are constrained by cyclic instability and an inadequate rate capability. The integration of suitable two-dimensional (2D) electrode nanomaterials with spinel compounds not only facilitates an effective charge transfer but also introduces more redox active sites, presenting significant electrochemical performance. Herein, a 0D/2D ZnNi 2 O 4 /WS 2 (WZNO) hybrid nanostructure has been developed where WS 2 nanoflakes (WNFS) act as a supportive matrix, allowing effective dispersion of ZnNi 2 O 4 nanoparticles (ZNO) over its surface and thereby exposing numerous electrochemically active sites. The developed flexible electrode shows remarkable faradaic redox phenomena, exhibiting significant specific capacitance (184.8 F/g), impressive cyclic stability (38.5 ± 0.03%), and coulombic efficiency (94.7 ± 0.004%) up to 10,000 cycles. The ab initio calculations have demonstrated synergistic coupling between the constituents of the metallic ZnNi 2 O 4 /WS 2 hybrid nanostructure, via interfacial charge transport, elucidating its significant electrochemical properties. The asymmetric supercapacitor exhibits superior specific capacitance (171.3 F/g), showcasing remarkable energy (61.6 W h/kg) and power density (1236.5 W/kg). Conversely, the quasi-solid-state supercapacitor demonstrates significant power (20.4 W h/kg) and energy density (921.2 W/kg) with impressive capacitance retention (97.2 ± 0.03%). The fabricated devices can illuminate different-colored LEDs, along with a fully operational clock and calculator, highlighting their significant potential as electrode materials in storage applications.