A core–shell heterostructured nickel manganese layered double hydroxide@ZnCo2O4 nanocomposite electrode for enhanced asymmetric supercapacitor applications

Abstract

Designing hierarchically core–shell heterostructured nanocomposite electrode materials with more active sites and delivering enhanced electrochemical performances for supercapacitors is pursued with great interest. With this motivation, herein, we report a facile two-step reflux condensation method for developing heterostructured core–shell nickel manganese layered double hydroxide nanosheets@ZnCo₂O₄ on a flexible stainless steel mesh substrate (NM-LDH@ZCO/SSM) as a nanocomposite electrode. The ZnCo₂O₄ nanorods/SSM core structure (ZCO/SSM) facilitates the deposition of the NiMn-LDH shell structure (NM-LDH), forming a core–shell NM-LDH@ZCO/SSM nanocomposite electrode. The structural and morphological characterization studies were done using XRD, FT-IR, FE-SEM, EDAX, XPS, and TEM to confirm the synthesis of the nanocomposite electrode. The NM-LDH@ZCO/SSM nanocomposite demonstrated an ultrahigh specific capacitance of 3169.14 F g⁻¹ at 10 mA cm⁻² with a capacitance retention (CR) of 89.3% after 3000 galvanometric charging–discharging (GCD) cycles at a higher current density (CD) of 55 mA cm⁻². An asymmetric supercapacitor device fabricated by using the NM-LDH@ZCO/SSM nanocomposite as the cathode and activated carbon (AC/SSM) as the anode exhibited an energy density of 58.7 Wh kg⁻¹ at 2492 W kg⁻¹, and 91% CR after 5000 GCD cycles at 25 mA cm⁻². The results reveal that the NM-LDH@ZCO/SSM nanocomposite is one of the potential candidates for high-performance supercapacitors and is expected to pave the way for its future exploration in energy storage devices.