Original Article

Citation: NPG Asia Materials (2015) 7, e183; doi:10.1038/am.2015.42
Published online 5 June 2015

Ultra-small, size-controlled Ni(OH)2 nanoparticles: elucidating the relationship between particle size and electrochemical performance for advanced energy storage devices
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Rutao Wang1, Junwei Lang1, Yonghuan Liu1, Zongyuan Lin1 and Xingbin Yan1

1Laboratory of Clean Energy Chemistry and Materials, State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, China

Correspondence: Professor X Yan, Laboratory of Clean Energy Chemistry and Materials, State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Tianshui road 18, Lanzhou, Gansu 730000, China. E-mail: xbyan@licp.cas.cn

Received 24 November 2014; Revised 9 March 2015; Accepted 30 March 2015

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Abstract

Nanosizing is the fashionable method to obtain a desirable electrode material for energy storage applications, and thus, a question arises: do smaller electrode materials exhibit better electrochemical performance? In this context, theoretical analyses on the particle size, band gap and conductivity of nano-electrode materials were performed; it was determined that a critical size exist between particle size and electrochemical performance. To verify this determination, for the first time, a scalable formation and disassociation of nickel-citrate complex approach was performed to synthesize ultra-small Ni(OH)2 nanoparticles with different average sizes (3.3, 3.7, 4.4, 6.0, 6.3, 7.9, 9.4, 10.0 and 12.2nm). The best electrochemical performance was observed with a specific capacity of 406Cg−1, an excellent rate capability was achieved at a critical size of 7.9nm and a rapid decrease in the specific capacity was observed when the particle size was <7.9nm. This result is because of the quantum confinement effect, which decreased the electrical conductivity and the sluggish charge and proton transfer. The results presented here provide a new insight into the nanosize effect on the electrochemical performance to help design advanced energy storage devices.

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