Enhanced supercapacitor performance by incorporating nickel in manganese oxide

Nickel manganese mixed oxides (NiyMn1-yOx; 0 <= y <= 0.4) have been synthesized by in situ inclusion of nickel during the growth of manganese oxide (MnOx). The effect of nickel concentration in MnOx is investigated by cyclic voltammetry, current-voltage characteristics, scanning electron microscopy and N-2 adsorption-desorption analysis. Variations in electronic conductivity and specific capacitance suggest that nickel concentration in the MnOx matrix significantly affects the supercapacitor electrode performance. At Ni/Mn similar to 0.25, i.e. Ni0.2Mn0.8Ox, the material crystallizes into spinel NiMn2O4 as a prominent phase and exhibits a specific surface area (118 m(2) g(-1)) with a granular morphology. Furthermore Ni0.2Mn0.8Ox exhibited low resistivity (2.07 x 10(4) Ohm cm) and consequently high specific capacitance similar to 380 F g(-1), endowing additional merits. The fabricated supercapacitor device (Ni0.2Mn0.8Ox//Ni0.2Mn0.8Ox) delivers 35 W h kg(-1) energy density and 3.74 kW kg(-1) power density with remarkably high capacitive retention similar to 92% after 3000 galvanostatic charge-discharge cycles. These encouraging results show great potential in developing energy storage devices from manganese oxide based electrodes incorporating nickel in the lattice.