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.