High performance symmetric solid state supercapacitor based on electrode of RuxNi1-xCo2O4 grown on nickel foam

Symmetric solid state supercapacitors attract increasing attention. We report one kind of high performance symmetric solid state supercapacitor composed with RuxNi1-xCo2O4 electrode. Ruthenium (Ru) element is doped into nickel cobaltite (NiCo2O4), and the material is grown on conductive nickel foam directly to act as electrode. The synthesis involves two procedure: one hydrothermal procedure to fabricate metal oxide precursor, and another annealing procedure to transform precursor into RuxNi1-xCo2O4. Chemical composition, crystal structure, morphology and specific superficial area are characterized through various techniques. Doping of ruthenium improve the electrochemical performance of electrode in a large extent. RuxNi1-xCo2O4(x = 0.1) electrodes deliver lower electric resistance than NiCo2O4, superior specific capacitance (1526.8 F g-1 at current density of 1 A g−1 in 2.0 M KOH) to NiCo2O4 (831.3 F g-1 at 1 A g−1), and better stability (94.3% retention after 3000 cycles at 10A g−1) than NiCo2O4 (91.9% retention). We assemble symmetric solid state supercapacitors, which deliver an outstanding energy density (48.5 Wh kg−1 at a power density of 2000 W kg−1 and 8.44 Wh kg−1 at 15000 W kg−1). These superior merits suggest their wide potential application in industrial area.