Synthesis of core-shell carbon sphere@nickel oxide composites and their application for supercapacitors

Herein, core-shell carbon sphere@nickel oxide (Cs@NiO) composites were fabricated by a facile hydrothermal method followed by calcination. The resultant Cs@NiO composites are composed of randomly distributed NiO nanoneedles coated on carbon sphere surfaces, which exhibit the rambutan-like structure. As electrode materials for supercapacitor, the core-shell Cs@NiO delivers a high specific capacitance of 555 F/g at the current density of 1 A/g, and an outstanding rate capability of about 85.6% capacity retention from 1 to 10 A/g. Meanwhile, the capacitance degradation is only 5% after 1000 continuous charge-discharge cycles with a current density of 10 A/g. These excellent electrochemical performances can be attributed to the enhanced electronic conductivity, the improved surface activity and the facilitated charge transportation during charging and discharging process, which are caused by the introduction of carbon sphere and the appropriate structure, respectively.