Design, Synthesis, and Characterization of Carbon‐Supported β‐Ni(OH)2 Nanosheets for Miniaturized Nickel–Metal Hydride Batteries

Abstract

Carbon‐supported β‐Ni(OH)2 nanosheets are prepared for miniaturized nickel–metal hydride batteries. The nanomaterial consists of thin and unfolded nanosheets, which possess a hexagonal crystallographic structure. Its unique structure gives rise to a remarkable specific capability, with 81.5% of the nanomaterial being used in electrical energy storage. Repetitive charge–discharge cycling between charge and discharge cut‐off potentials (Ecut‐off,ch = 1.50 or 1.65 V and Ecut‐off,dis = 1.20 V) in aqueous NaOH solution is performed to examine the nanomaterial's specific charge and stability. The results show that the specific capacity gradually decreases upon repetitive charge–discharge cycling but still maintains a significant percentage of its initial value, 54% for Ecut‐off,ch = 1.50 V and 43% for Ecut‐off,ch = 1.65 V. A transmission electron microscopy analysis of the nanomaterial after the charge–discharge cycling demonstrates that the β‐Ni(OH)2 nanosheets are less‐organized and distorted. The structural and morphological changes give rise to new features in cyclic voltammetry profiles and charge–discharge curves, and a decrease in the specific capacity of the nanomaterial. The degradation of the specific capacity is attributed to a loss of the initial structure, a reduction of the number of anchoring sites, and weakening of the bond between the β‐Ni(OH)2 nanosheets and the carbon support.