Manganese-doped nickel molybdate nanostructures for high-performance asymmetric supercapacitors

Abstract The inferior rate capability and unstable redox reactions of nickel molybdate (NiMoO 4 ) hinder its potential application for high-performance supercapacitors despite its stable crystal structure, high electrical conductivity, and high specific capacitance. The strategy of manganese doping of NiMoO 4 is proposed to address the above issues. The obtained hydrothermally grown Mn-doped NiMoO 4 (MNMO) nanostructures change from nanowires to nanorods as the doping concentration increases. At the optimal molar ratio of Mn to Ni, the electrode MNMO-0.2:1 manifest the highest specific surface area and the largest specific capacitance of 1262.6 F g −1 at 1 A g −1 , and favorable cycling stability (retain 74.4% of the initial specific capacitance after 14,000 cycles) among the MNMO electrodes. The device with MNMO as the positive electrode and activated carbon on carbon cloth/CNTs as the negative electrode perform a specific capacitance of 161.84 F g −1 , a high energy density of 64.95 Wh kg −1 at the power density of 864.5 W kg −1 , as well as considerable cycling stability (77% of the initial capacity after 5000 cycles at 20 A g −1 ). This improved performance can be ascribed to the stable reactions from synergistic effects of the nickel and manganese elements, and fast charge transport from hierarchical nanostructures. These results also suggest that manganese-doped nickel molybdate nanostructures can be a promising candidate for energy storage devices.