Engineering one-dimensional and two-dimensional birnessite manganese dioxides on nickel foam-supported cobalt-aluminum layered double hydroxides for advanced binder-free supercapacitors

We report a facile decoration of the hierarchical nickel foam-supported CoAl layered double hydroxides (CoAl LDHs) with MnO2 nanowires and nanosheets by a chemical bath method and a hydrothermal approach for high-performance supercapacitors. We demonstrate that owing to the sophisticated configuration of binder-free LDH@MnO2 on the conductive Ni foam (NF), the designed NF/LDH@MnO2 nanowire composites exhibit a highly boosted specific capacitance of 1837.8 F g(-1) at a current density of 1 A g(-1), a good rate capability, and an excellent cycling stability (91.8% retention after 5000 cycles). By applying the hierarchical NF/LDH@MnO2 nanowires as the positive electrode and activated microwave exfoliated graphite oxide activated graphene as the negative electrode, the fabricated asymmetric supercapacitor produces an energy density of 34.2 Wh kg(-1) with a maximum power density of 9 kW kg(-1). Such strategies with controllable assembly capability could open up a new and facile avenue in fabricating advanced binder-free energy storage electrodes.