Study on charge storage mechanism in working electrodes fabricated by sol-gel derived spinel NiMn2O4 nanoparticles for supercapacitor application.

Graphical abstract Highlights • Sol-gel derived spinel NiMn 2 O 4 is synthesized in pure phase. • The structural analysis has been carried out using Rietveld refinement. • The dependence of EIS on potential is extensively demonstrated for first time. • NiMn 2 O 4 electrode exhibits maximum specific capacitance of 875 F g−1. • NiMn 2 O 4 electrode shows excellent ASC device performance. Abstract We report the synthesis of porous spinel-structured binary NiMn 2 O 4 metal oxide nanoparticles and their performance as electrode material for supercapacitors. Spherical NiMn 2 O 4 nanoparticles of ∼8 nm average diameter have been synthesized using inexpensive and simple sol-get method, and characterized by X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The electrodes made of this single phase spinel nanoparticles exhibit superior electrochemical performance with excellent rate capability, offering highest specific capacitance value of 875 F g−1 at 2.0 mV s−1 scan rate in 1 M Na 2 SO 4 electrolyte solution. Furthermore, an asymmetric supercapacitor is also assembled and possesses a wide operating voltage window of 1.8 V, exhibiting an energy density of 75.01 W h kg−1 at a power density of 2250.91 W kg−1. The results infer this highly porous binary metal oxide nanostructures are promising candidates for high performance energy storage applications. [ABSTRACT FROM AUTHOR]