Rational Design of Sandwiched Ni-Co Layered Double Hydroxides Hollow Nanocages/Graphene Derived from Metal-Organic Framework for Sustainable Energy Storage

In situ growth of Ni-Co layered double hydroxides on graphene nanosheets by virtue of metal-organic framework as a sacrifice template is reported, which yields hollow nanocages uniformly deposited on graphene nanosheets. The strong impact of graphene amount on the electrochemical performance of Ni-Co layered double hydroxides is illustrated. Controlling the mass of graphene (15 mg) leads to a maximum specific capacitance of 1265 F g(-1) high rate capability (50% capacitance retention after increasing current density ten times), and good cycling life (92.9% capacitance retention after 2000 circles). The combination of battery-type Ni-Co LDH hollow nanocages/graphene composite and active carbon allows for the excellent electrochemical performance measured in an asymmetric device. In detail, the assembled asymmetric supercapacitor is able to deliver maximum specific capacitance 170.9 F g(-1) in a potential window of 0-1.7 V, high energy density (68.0 Wh kg(-1)), as well as excellent power output (4759 W kg(-1)). These electrochemical performances, in combination with its facile fabrication, render hollow Ni-Co LDH/graphene composite as a promising electrode material in a sustainable energy storage device.