Co替代Ni对A_2B_7型贮氢电极合金相结构及电化学性能的影响  

Effects of Substitution of Co for Ni on the Structure and Electrochemical Properties of La-Mg-Ni System A_2B_7-type Hydrogen Storage Alloys

作　　者：许剑轶[1,2] 阎汝煦[2] 罗永春[2] 张胤[1] 陈江平[2,3] 

机构地区：[1]内蒙古科技大学稀土学院,内蒙古包头014010 [2]兰州理工大学甘肃省有色金属新材料省部共建国家重点实验室,甘肃兰州730050 [3]惠州超霸电池有限公司,广东惠州516023

出　　处：《稀土》2011年第5期72-77,共6页Chinese Rare Earths

摘　　要：采用感应熔炼方法制备了La0.75Mg0.25Ni3.5-xCox(x=00,.250,.751,)四元贮氢合金,系统地研究了合金B侧Co对Ni部分替代对合金相结构及电化学性能的影响。X衍射(XRD)分析表明,La0.75Mg0.25Ni3.5-xCox由(La,Mg)2Ni7相(包括Gd2Co7型高温相和Ce2Ni7型低温相)组成。此外,随着Co元素的加入,该类合金中出现CaCu5型LaNi5相。电化学测试表明,随Co含量的增加,合金电极活化次数增大,合金电极的最大放电容量增大,合金的最大放电容量由x=0.25时的376.53 mAh/g增加到x=1时的401.62mAh/g,氢扩散系数增大,循环稳定性变差,合金的高倍率放电性能降低,Co含量对合金电极高倍率放电性能HRD值的影响与对合金电极交换电流密度的影响趋势一致,这表明电极合金表面的电化学反应对合金的动力学性能影响更大。The phase structure and electrochemical properties of La0.75Mg0.25Ni3.5-xCox（x=0,0.25,0.75,1）quaternary alloys were investigated.XRD analysis shows that the La0.75Mg0.25Ni3.5-xCox consists of（La,Mg）2Ni7 phase and LaNi5 phase,and CaCu5 type phase appears with addition of Co.The electrochemical analysis shows that the substitutions lead to some increase in the maximum discharge capacity and the hydrogen diffusion coefficient and a little effect on the activation property.The cyclic stability of alloy electrodes decreases with increasing Co content in alloys.S100 for La0.75Mg0.25Ni3.5-xCox are 73.77%,73.66%,72.37% and 70.00% respectively.For the discharge current density of 900 mA/g,the high rate discharge ability（HRD） of the alloy electrodes decreases from 83.66%（x=0） to 73.97%（x=1）.The exchange current densities of the alloy electrodes are consistent with the variation of the high rate discharge ability,which implies that the electrochemical reaction on the surface of alloy electrodes has a great influence on the kinetic property.

关 键 词：A2B7型贮氢合金 Co替代 晶体结构 电化学性能 

分 类 号：TG146.4[一般工业技术—材料科学与工程]