Binder-Free Core–Shell Zinc Cobalt Layered Double Hydroxide@NiCo2O4Flexible Composite Electrodes for High-Performance Supercapacitors

Synthesis of composite electrode materials intended for high-performance supercapacitor (SC) applications has attracted the attention of researchers due to their highly porous nature, enhanced electrochemical performance, and longer cycle life than their respective pristine components. With this motivation, in this study, a binder-free core–shell zinc cobalt layered double hydroxide@NiCo2O4thin film composite electrode on a flexible stainless steel mesh (ZnCo-LDH@NiCo2O4/FSSM) was synthesized by a two-step facile and simple reflux-condensation-mediated method for SC application. The ZnCo-LDH@NiCo2O4composite electrode with a NiCo2O4nanosheet core structure and a ZnCo-LDH nanoflake as a shell layer exhibited a higher specific surface area (122.04 m2g–1) with enhanced porous nature than the pristine ZnCo-LDH (67.4 m2g–1) and NiCo2O4(50.76 m2g–1) components. The ZnCo-LDH@NiCo2O4/FSSM delivered a specific capacitance (Csp) of 2378.0 F g–1at a current density (CD) of 6 mA cm–2and maintained Cspretention of 99% after 2000 cycles at a high CD of 40 mA cm–2. Moreover, the device (ZnCo-LDH@NiCo2O4/FSSM//AC/FSSM) assembled by using ZnCo-LDH@NiCo2O4/FSSM (+ve electrode) and activated carbon (AC/FSSM, −ve electrode) exhibited an energy density of 33.3 Wh kg–1at a power density of 1109.5 W kg–1and maintained an appreciable Cspretention of 91.7% after 4000 cycles at a higher CD (25 mA cm–2). These findings signify that the ZnCo-LDH@NiCo2O4/FSSM composite electrode is a promising electrode material and will help open avenues for in further exploration of electrode material synthesis for SC applications.