Facile synthesis of hierarchical core-shell heterostructured NiCo2O4@MnMoO4 nanosheet hybrid arrays on nickel foam for high-performance asymmetric supercapacitors

Hierarchical core-shell heterostructured NiCo 2 O 4 @MnMoO 4 nanosheet hybrid arrays were successfully synthesized on nickel foam via a facile two-step hydrothermal reaction followed by a calcination process. The highly porous hierarchical core-shell heterostructure was fabricated by preforming a NiCo 2 O 4 nanosheet “core” as a substrate and then guiding the ultrathin MnMoO 4 nanosheet “shell” onto its surface. The growth thickness of ultrathin MnMoO 4 nanosheets was controlled by adjusting the hydrothermal reaction time. The optimized core-shell heterostructured NiCo 2 O 4 @MnMoO 4 electrode exhibited a specific capacity of 1205.75 C g −1 at a current density of 1 mA cm −2 in 2 M KOH solution and displayed outstanding cycling stability with a capacity retention rate of 100.49% after 5000 charge-discharge cycles at a current density of 30 mA cm −2 . An asymmetric supercapacitor (ASC) device was assembled using the optimal NiCo 2 O 4 @MnMoO 4 nanosheet hybrid arrays as the positive electrode and activated carbon (AC) as the negative electrode which achieved a maximum energy density of 39.04 W h kg −1 at a power density of 156.86 W kg −1 and retained 34.12 W h kg −1 even at the high power density of 1568.74 W kg −1 . In addition, the ASC device presented an excellent cycling performance, maintaining 95.00% retention of its initial specific capacitance after 10,000 cycles at a current density of 20 mA cm −2 , demonstrating its promising potential in energy storage.