Layered NiCo2O4/reduced graphene oxide composite as an advanced electrode for supercapacitor

Abstract

To solve the poor intrinsic conductivity and inevitable agglomeration of NiCo2O4 electrode materials available, herein a well-controlled layered NiCo2O4/RGO nanocomposite has been successfully prepared by a layer-by-layer assembly of exfoliated Co-Ni LDH and GO nanosheets with opposite charges, followed by freeze-drying and annealing treatment. The obtained NiCo2O4/RGO nanocomposite with loose layered structure exhibits a large surface area, increased electronic conductivity and more electroactive sites. The unique architecture not only effectively prevents the restacking of RGO and aggregation of NiCo2O4 nanosheets, but also improves the electrochemical activity toward the fast reversible redox reactions with long-term stability for supercapacitors. These excellent structural characteristics boost the capacitive performances of the NiCo2O4/RGO nanocomposite with an ultrahigh specific capacity of 1388Fg−1 at 0.5Ag−1, remarkable rate performance of 840Fg−1 even at 30Ag−1, and ultra-long cycle life with 90.2% retention after 20,000 cycles at 5Ag−1. An asymmetric supercapacitor was further assembled using the NiCo2O4/RGO composite and activated carbon as positive electrode and negative electrode, respectively, which achieves a high energy density of 57Whkg−1 at a power density of 375Wkg−1 in a working potential of 0–1.5V. Moreover, two NiCo2O4/RGO//AC devices connected inseries can light a LED, implying the potential applications in energy storage.