液相阴离子对合成Al代α-Ni(OH)_2结构和电化学性能的影响

Effects of Liquid Anions on the Structure and Electrochemical Properties of Synthesized Al-Substituted α-Ni(OH)_2

采用尿素分解法制备了Al代α-Ni(OH)2粉体材料,主要考察了合成过程中液相阴离子(SO42-和NO3-)对Al代α-Ni(OH)2微观结构和电化学性能的影响。XRD分析表明液相中的NO3-有利于提高Al代α-Ni(OH)2的结晶度,并且合成的Al代α-Ni(OH)2具有较大的层间距。FT-IR和TGA测试表明液相阴离子在合成过程中会嵌入Al代α-Ni(OH)2的层间,进而影响其晶体结构、含水量和热稳定性。SEM图像表明尿素分解法制备的Al代α-Ni(OH)2是具有明显次级结构的球形颗粒,并且颗粒的次级结构形状与液相阴离子密切相关。采用CV、EIS和充放电测试表征了合成样品的电化学性能,发现液相含有NO3-条件下合成的Al代α-Ni(OH)2具有相对较好的电化学反应可逆性和高的放电比容量。

Al-substituted a-Ni（OH）2 powders were prepared by a homogeneous precipitation method with urea. The effects of anions （SO4^-2 and NO3^- ） in the reaction solution on the microstructure and electrochemical performance of Al-substituted a-Ni（OH）2 powders were studied. XRD results reveal that the presence of NO3^- in reaction solution facilitates the crystallization of Al-substituted a-Ni（OH）2 and induces a relatively larger interlayer space. FT-IR and TGA results indicate that these anions can embed in the interlayer of Al-substituted a-Ni（OH）2, which consequently affects its crystal structure, water content and thermal stability. SEM images show that the Al-substituted a-Ni（OH）2 synthesized by the homogeneous precipitation method has a hierarchical spherical structure which is closely related to these anions. The electrochemical performance of the Al-substituted a-Ni（OH）2 powders were characterized by cyclic voltammetry（CV）, electrochemical impedance spectroscopy（EIS）, and charge/discharge tests. The results demonstrate that the Al-substituted a-Ni（OH）2 prepared with the presence of NO3^- shows better reaction reversibility and larger specific discharge capacity.