Structure and electrochemical performance of Cu singly doped and Cu/Al co-doped nano-nickel hydroxide

Nanometer Cu singly doped and Cu/Al co-doped nickel hydroxides were synthesized by ultrasonic-assisted precipitation method. Their crystal structure, particle size, morphology, tap density and electrochemical performance were investigated. The results show that the samples have α-phase structure with narrow particle size distribution. Cu singly doped nano-Ni(OH)2 contains irregular particles, while Cu/Al co-doped nano-Ni(OH)2 displays a quasi-spherical shape and has a relatively higher tap density. Composite electrodes were prepared by mixing 8% (mass fraction) nanometer samples with commercial micro-size spherical nickel. The charge/discharge test and cyclic voltammetry results indicate that the electrochemical performance of Cu/Al co-doped nano-Ni(OH)2 is better than that of Cu singly doped nano-Ni(OH)2, the former's discharge capacity reaches 330 mA·h/g at 0.2C, 12 mA·h/g and 91 mA·h/g larger than that of Cu singly doped sample and pure spherical nickel electrode, respectively. Moreover, the proton diffusion coefficient of Cu/Al co-doped sample is 52.3% larger than that of Cu singly doped sample.