镁掺杂氢氧化镍的结构和电化学性能

Structure and electrochemical performance of Mg-doping nickel hydroxide

采用化学共沉淀法制备出不同含量Mg掺杂的氢氧化镍样品。应用X-射线衍射(XRD),傅里叶变换红外光谱(FTIR)和热重分析(TG)手段对样品的结构进行了表征,并用循环伏安法研究了样品的电化学性能。结果表明:与Mn、Al等元素掺杂到一定含量后使Ni(OH)2晶型由!型转化为"型不同,即使Mg掺杂含量达到30%,样品仍为#型。但样品晶格产生畸变,晶粒尺寸随Mg含量的增加先变小后增大,电化学性能随Mg含量的增加先变好后变坏。Mg最佳含量为5%左右,此时OH-数量增多,产生了大量的晶格畸变,c轴拉长,有利于质子扩散系数的变大,增强了反应的可逆性,提高了电极充电效率和活性物质的利用率,从而改善了电极的电化学性能。

The different amount of Mg-doping Ni （OH）2 samples were prepared by a coprecipitation method. The crystal structures were characterized by XRD, FTIR and TG methods. The electrochemical performances were also investigated by cyclic voltammetry method. The results show that even the Mg-doping content reaches 30%, the sample still is/3-phase, which is different from Mn-doping or AI-doping samples in which the samples are changed to e-phase from/3--phase when the doping amount reaches some levels. The distortion of crystal lattices are hap- pened. The size of crystalline grains diminishes and then increases, and the electrochemical performances also are better and then worse when the Mg-doping amounts increases. The suitable Mg-doping amount is about 5%. In this case, the number of OH- increases, the crystal lattice distortion is engendered, and the interlayer distance c is stretched, which are favorable to enhancement of the proton transfer between electrode materials. Therefore, the re- versibility of electrode reaction is improved, the charge efficiency is increased and the utilization of active materials is promoted, which results in improvement of electrochemical performance.