MnO(2)/ZnCo(2)O(4) with binder-free arrays on nickel foam loaded with graphene as a high performance electrode for advanced asymmetric supercapacitors

ZnCo(2)O(4) nanosheets were successfully arrayed on a Ni foam surface with graphene using a hydrothermal method followed by annealing treatment; then MnO(2) nanoparticles were electrodeposited on the ZnCo(2)O(4) nanosheets to obtain a synthesized composite binder-free electrode named MnO(2)/ZnCo(2)O(4)/graphene/Ni foam (denoted as MnO(2)/ZnCo(2)O(4)/G/NF). After testing the binder-free composite electrode of MnO(2)/ZnCo(2)O(4)/G/NF via cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy testing, we found that it exhibited ultrahigh electrochemical properties, with a high specific areal capacitance of 3405.21 F g(−1) under a current density of 2 A g(−1), and wonderful cycling stability, with 91.2% retention after 5000 cycles. Moreover, an asymmetric supercapacitor (ASC) based on MnO(2)/ZnCo(2)O(4)/G/NF//G/NF was successfully designed. When tested, the as-designed ASC can achieve a maximum energy density of 46.85 W h kg(−1) at a power density of 166.67 W kg(−1). Finally, the ASC we assembled can power a commercial red LED lamp successfully for more than 5 min, which proves its practicability. All these impressive performances indicate that the MnO(2)/ZnCo(2)O(4)/graphene composite material is an outstanding electrode material for electrochemical capacitors.