复合储氢合金Mg1.8Zr0.2Ni- (1.2-x)Ni -xMgTi3结构和电化学性能研究

Research on the Structure and Electrochemical Properties of the Composite Hydrogen Storage Alloys Mg1.8Zr0.2Ni- (1.2-x) -xMgTi3

摘要:

为改善Mg₂Ni储氢合金电化学性能,采用机械合金化法(Mechanical Alloying,MA),分别制备出改性合金Mg_1.8 Zr Ni以及MgTi₃,按一定比例和Ni混合球磨,制备出纳米晶或非晶化的Mg_1.8Zr_0.2Ni- (1.2-x)Ni -xMgTi₃复合储氢合金。研究结果表明,经部分取代改性和包覆修饰后的复合储氢合金,其表面和内部形成较多的纳米级褶皱、空隙层状和多相结构缺陷。随着MgTi₃含量增加,Mg_1.8Zr_0.2Ni- (1.2-x)Ni -xMgTi₃复合储氢合金初始放电比容量也逐渐增加,当MgTi₃含量为x=0.5时,合金初始放电比容量为973.3 mAh.g_-1。但MgTi3含量超过x=0.5时,其初始放电比容量又有所下降,研究表明添加MgTi₃却不利于复合储氢合金的循环稳定性和高倍率放电性能。通过对Mg_1.8Zr_0.2Ni- (1.0-x)Ni -xMgTi₃复合储氢合金进行线性极化、阳极极化和交流阻抗测试,进一步研究了系列合金电极的表面电化学反应、电荷转移过程、氢在合金中的扩散情况以及它们的电化学性能。

Abstract:

In order to improve the electrochemical properties of hydrogen storage alloys Mg2Ni, the modified alloy Mg_1.8 Zr_0.2Ni and MgTi₃ was prepared respectively by mechanical alloying (Mechanical Alloying, MA). Then the amorphous modified alloy Mg1.8Zr0.2Ni- (1.2-x) Ni -xMgTi₃ was prepared by ball milling a certain percentage Mg_1.8 Zr_0.2Ni, MgTi₃ and Ni. The results show that the composite hydrogen storage alloys after partially replace modified and coating modified have a large number of nanoscale folds, layered voids and multiphase structural defects in their the surface and the interior. With the increase of MgTi₃ content, the initial discharge specific capacity of Mg_1.8Zr_0.2Ni- (1.2-x) Ni -xMgTi₃ is also gradually increased. When the content of MgTi₃ was x=0.5, the initial discharge specific capacity was 973.3 mAh.g_-1. But when the content of MgTi₃ was more than x=0.5, the initial discharge specific capacity decreased rapidly. The study shows that the addition of MgTi₃ is not beneficial to the cycle stability and high rate discharge performance of the composite hydrogen storage alloys. By tested to the linear polarization,anodic polarization and exchange impedance of Mg_1.8Zr_0.2Ni- (1.2-x) Ni -xMgTi₃, the electrochemical reaction of surface, charge transfer process, the hydrogen diffusion in the alloy and the performance of their electrochemical kinetics of modified alloys were further researched.