High-Energy-Density Asymmetric Supercapacitor Based on a Durable and Stable Manganese Molybdate Nanostructure Electrode for Energy Storage Systems

3D interconnected MnMoO4 nanosheet arrays with abundant open spaces and ordered arrangements deposited on nickel foam (NF@MnMoO4) are fabricated by a mild one-step hydrothermal method. As an integrated binder-free electrode for supercapacitors, the optimized NF@MnMoO4 electrode exhibits a super-high specific capacitance of 4609 F g–1 (640 mAh g–1) at a current density of 1 A g–1, remarkable rate capability (2800 F g–1 (388.89 mAh g–1) even at a current density as high as 20 A g–1), and outstanding cycling stability (92.4% of the initial specific capacitance after 20,000 cycles). The fabricated NF@MnMoO4//AC asymmetric supercapacitors (ASCs) with excellent cycling performance and high Coulombic efficiency achieve an ultrahigh energy density of 107.38 Wh kg–1 at a power density of 801.34 W kg–1 (72.18 Wh kg–1 at a power density of 3987.85 W kg–1). As the practical application, the self-charging power packs of commercial solar cells and NF@MnMoO4//AC ASCs are demonstrated to power an LED without extra recharging by other devices, indicating their promising applications in self-power energy-harvesting storage systems.