The synthesis of hierarchical ZnCo2O4@MnO2 core–shell nanosheet arrays on Ni foam for high-performance all-solid-state asymmetric supercapacitors

Abstract

Hierarchical ZnCo₂O₄@MnO₂ core–shell nanosheet arrays were successfully synthesized on Ni foam via a facile hydrothermal method followed by a calcination process. The fabricated ZnCo₂O₄@MnO₂ electrode exhibited a specific capacitance as high as 2170.00 F g⁻¹ (2.60 F cm⁻²) at a current density of 3 mA cm⁻² in a 1 M KOH solution. Furthermore, an all-solid-state asymmetric supercapacitor (ASC) device fabricated with the as-prepared ZnCo₂O₄@MnO₂ as the positive electrode and activated carbon (AC) as the negative electrode in the PVA/KOH gel electrolyte achieved a high energy density of 29.41 W h kg⁻¹ at a power density of 628.42 W kg⁻¹ and retained 95.3% of its initial capacitance after 3000 cycles at a high current density of 10 mA cm⁻². With the smart design and remarkable electrochemical properties, the hierarchical ZnCo₂O₄@MnO₂ core–shell nanosheet arrays on Ni foam demonstrated great potential for further applications in the energy storage field.