Ammonia-alkali mixed precipitant route for preparation of Ni(OH)₂/reduced graphene oxide composites and electrochemical performance

Nickel hydroxide/reduced graphene oxide (Ni(OH)₂/RGO) composites were synthesized by simple and practicable chemical precipitation-reflux method. The influence of different ammonia-alkali mixed precipitant on electrochemical performance of composite materials was researched. The microstructure and morphology of the Ni(OH)₂/RGO composites were characterized by XRD, Raman spectra and SEM. The synthesized Ni(OH)₂/RGO composite shows that β-Ni(OH)₂ nano sheets are homogeneously dispersed and inserted into RGO sheets, thus mutually inserted structure is formed using ammonium hydroxide-sodium hydroxide as precipitant. The electrochemical characteristics of composite electrode materials were tested by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results show that the prepared Ni(OH)₂/RGO composite exhibits a high discharge specific capacity of 344.8 mAh/g at 0.2 C rate, and is 29% higher than the specific capacity of β-Ni(OH)₂. The discharge specific capacity of the β-Ni(OH)₂/RGO composite is 274.5 mAh/g at 5 C rate. Moreover, 98.8% of the initial specific capacity of the composite is maintained after 50 cycle test. Ni(OH)₂/RGO composite displays a better rate capability and cycle performance as electrode material.