In-Situ Fabrication of MOF-Derived Co-Co Layered Double Hydroxide Hollow Nanocages/Graphene Composite: A Novel Electrode Material with Superior Electrochemical Performance.

Rational design of a transition metal layered double hydroxide (LDH) and graphene composite is vitally important for designing high-performance supercapacitor electrodes. Although various methods are performed, the realization of high-performance is still impeded by the agglomeration of graphene and layered double hydroxide. Here, metal-organic framework derived cobalt-cobalt layered double hydroxide (Co-Co LDH) hollow nanocages, uniformly deposited on graphene nanosheets, are fabricated through facile in situ co-deposition and thermal ion-exchange reaction. Electrochemical investigation reveals that Co-Co LDH/15 mg graphene is rather outstanding, which delivers high specific capacitance of 1205 F g-1 , excellent rate capability (60.3 % capacitance retention is obtained after the current density increased 6.67 times), and cycling stability. The excellent performance of electrode is also confirmed by assembling an asymmetric supercapacitor, which delivers high energy density of 49.5 Wh kg-1 as well as the maximum power density of 7000 W kg-1 . The Co-Co LDH/graphene composite proves a promising concept for constructing hierarchical structure materials in the future.