Template-assisted synthesis of NiCoO₂ nanocages/reduced graphene oxide composites as high-performance electrodes for supercapacitors

Here we reported a coordinating etching and precipitating method to synthesize a complex binary metal oxides hollow cubic structure. A novel NiCoO₂/rGO composite with a structure of NiCoO₂ nanocages anchored on layers of reduced graphene oxide (rGO) were synthesized via a simple template-assisted method and the electrochemical performance was investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy tests as a faradaic electrode for supercapacitors at a graphene weight ratio of 1 wt% (1%). When used as electrode materials for electrochemical capacitors, the NiCoO₂/rGO composites achieved a specific capacity of 1375 F g^-1 at the current density of 1 A g^-1 and maintained 742 F g^-1 at 10 A g^-1. After 3000 cycles, the supercapacitor based on these nanocage structures shows long-term cycling performance with a high capacity of 778 F g^-1 at a current density of 1 A g^-1. These outstanding electrochemical performances are primarily attributed to the special morphological structure and the combination of mixed transition metal oxides and rGO, which not only maintains a high electrical conductivity for the overall electrode but also prevents the aggregation and volume expansion of electrochemical materials during the cycling processes.