Augmenting the electrochemical performance of NiMn2O4 by doping of transition metal ions and compositing with rGO

Doped NiMn 2 O 4 /rGO nanocomposite shows very high specific capacitance of 710 F/g at 1 A/g. Fabricated aqueous symmetric supercapacitor exhibits excellent energy density and power density of 43 Wh/kg and 10 kW/kg, respectively with 90% of capacitance retention over 10,000 cycles. • Specific capacitance of NiMn 2 O 4 increased from 254 to 710 F/g by doping. • High energy (43 Wh/kg) and power density (10 kW/kg) was achieved for NCZMOR-II. • High capacitanceretention of 90% over 10,000 cycles attained for NCZMOR-II. The transition metal ions (TMIs) such as Co 2+ and Zn 2+ doped NiMn 2 O 4 (NMO)/rGO nanocomposite synthesized by facile sol-gel method was used for the fabrication of supercapacitor. The presence of metal ions in the nanocomposite was confirmed by X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscope (HR-TEM) mapping techniques. The fabricated electrode showed high specific capacitance of 710 F/g which was 3-fold higher than NMO (254 F/g). The addition of RGO in the nanocomposite increased the cycle stability of TMIs doped NMO significantly from 51 to 91%. In addition, the symmetric supercapacitor (SSC) fabricated using TMIs doped NMO/rGO nanocomposite with 3.5 M KOH as an electrolyte delivered a maximum energy density of 43 Wh/kg and power density of 10 kW/kg. Furthermore, the SSC device retained 90% of capacitance retention over 10,000 cycles with coulombic efficiency of 99% at 5 A/g. These result suggested that the TMIs doped NMO/rGO nanocomposite electrode is a promising material for high-energy supercapacitors.