Fabrication of Ni-Mn LDH/Co3O4 on carbon paper for the application in supercapacitors

In this work, the hydrothermal method is adopted to synthesize needle-like Co3O4 on the carbon fiber paper (CP) followed by the growth of nickel-manganese layered double hydroxide (Ni-Mn LDH) using the water bath method. Accordingly, the Ni-Mn LDH could be deposited onto the needle-like Co3O4 to form Ni-Mn LDH/Co3O4/CP composite electrode with a hierarchical structure. The electrochemical performance and the material properties are measured, and the influences of different concentrations of Ni(NO3)(2)center dot 6H(2)O, Mn(NO3)(2)center dot 4H(2)O on the performances of Ni-Mn LDH/Co3O4/CP are investigated. Based upon the results, it is concluded that although Co3O4 contributes some of the specific capacitance, Ni-Mn LDH and its uniform deposition on the Co3O4 surface play a key factor to enhance the specific capacitance. At a current density of 1 A/g, a specific capacitance of 219 F/g of the Co3O4/CP electrode is obtained, while an extremely high specific capacitance of 1327 F/g of the Ni-Mn LDH/Co3O4/CP electrode can be attained. In addition, the asymmetric supercapacitor which is built using the NiMn LDH/Co3O4/CP electrode as the positive electrode and active carbon on CP electrode as the negative electrode, shown an energy density of 35.87 Wh/kg with a power density of 449.99 W/kg as well as a power density of up to 9000 W/kg and an energy density of 18.20 Wh/kg. By connecting two asymmetric supercapacitors in series, charging the supercapacitors for three seconds can light a 1.8 V red LED shine for 1320 s, indicating that the as-synthesized composite electrode possessing outstanding potential can be used in supercapacitors.