Fabrication and electrochemical performance of 3D hierarchical β-Ni(OH)2 hollow microspheres wrapped in reduced graphene oxide

Abstract

A novel structured reduced graphene oxide/Ni(OH)₂ (rGO/Ni(OH)₂) hybrid composite with enhanced electrochemical performance was prepared by wrapping β-Ni(OH)₂ hollow microspheres in rGO sheets via a facile solvothermal route, using poly(L-lysine) (PLL) as reductant and ethylene glycol (EG) as coupling agent. The structural, morphological and electrochemical properties of the composite were well examined. The results show that single-crystalline β-Ni(OH)₂ hollow microspheres are enveloped in rGO sheets after thermal treatment in the hybrid composite, which exhibits a high specific capacitance of 1551.8 F g⁻¹ at a current density of 2.67 A g⁻¹ and a capacity retention of 102% after 2000 cycles. Notably, in comparison with pure β-Ni(OH)₂ hollow microspheres and the simple mixture (mixture of rGO and Ni(OH)₂ spheres), the rGO/β-Ni(OH)₂ composite exhibited superior electrochemical properties, which may be due to the wrapped electrically conducting graphene sheets and the unique three-dimensional (3D) structure of the composite. The rational design, interesting structure and the ideal electrochemical performance of this graphene-based composite suggest its potential applications in high energy storage systems.