Hollow mesoporous carbon spheres enwrapped by small-sized and ultrathin nickel hydroxide nanosheets for high-performance hybrid supercapacitors

Ni(OH)₂-based composites are promising electrode materials for high-performance hybrid supercapacitors due to their high theoretical specific capacity and unique nanostructures. Unfortunately, most regular Ni(OH)₂-based electrodes can deliver much lower specific capacity in comparison with the theoretical value and exhibit poor rate capability and cycling stability due to the low electrical conductivity and large volume variation. Herein, we present a facile chemical precipitation method to fabricate a hierarchical core-shell nanocomposite of hollow mesoporous carbon spheres enwrapped Ni(OH)₂ nanosheets. The Ni(OH)₂ nanosheets possess unique small-sized and ultrathin morphology, which endues the resulting nanocomposite with a large specific surface area (481.64 m² g⁻¹) and good conductivity, thus giving a high specific capacity of 844 C g⁻¹ at a current density of 1 A g⁻¹ with excellent cycling stability and superior rate capability. Furthermore, a hybrid supercapacitor is constructed which presents a high energy density of 45.84 Wh kg⁻¹ at a power density of 799 W kg⁻¹ and delivers an excellent cycling stability of capacitance retention rate of 91.4% after 10,000 cycles at 10 A g⁻¹, demonstrating potential application for high-performance hybrid supercapacitor.