镁含量对稀土-镁-镍系A_2B_7型储氢合金电极自放电性能的影响  

Influence of Magnesium Content on Self-Discharge Property of A_2B_7-Type RE-Mg-Ni Hydrogen Storage Alloys

作　　者：张书成[1] 罗永春[1,2] 曾书平[2] 王可[2] 康龙[1] 

机构地区：[1]兰州理工大学材料科学与工程学院,甘肃兰州730050 [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

出　　处：《稀有金属》2013年第4期511-520,共10页Chinese Journal of Rare Metals

基　　金：国家科技部高技术研究发展计划(863计划)(2011AA03A408)资助项目

摘　　要：系统研究了Mg元素对退火态A2B7型储氢合金La0.7-xY0.1Gd0.2MgxNi3.35Al0.15(x=0～0.4)电极自放电性能的影响。结果表明,退火态合金主要由Ce2Ni7(或Gd2Co7)型、Pr5Co19型、CaCu5型和PuNi3型相组成,Mg含量对合金组成和相结构有重要的影响,低镁含量有利于提高合金组织中Ce2Ni7型相的丰度,高镁含量易出现大量的CaCu5型和PuNi3型相。电化学测试表明,循环稳定性及电化学放电容量随Mg含量的增加而呈现先降低后升高的趋势,x=0.15,0.17合金电极具有最高的循环稳定性(S100=90%)和最大的电化学放电容量(368mAh.g-1)。Mg含量对合金电极的荷电保持率和开路电位影响显著,搁置7 d后的电极荷电保持率从7.9%(x=0)增加到59.7%(x=0.17),然后又降低到1.8%(x=0.4),表明适量的Mg含量可以改善合金的自放电性能,其中合金电极自放电时的可逆容量损失占97.5%以上,不可逆损失仅占0.4%～2.5%。合金电极的荷电保持率随合金PCT曲线放氢平台压力的升高而减小,其中氢致非晶态(x=0)和具有较高放氢平台压力的多相组织合金电极(x=0.4)的自放电率较大,荷电保持率最小。合金的腐蚀电流Icorr与电极的不可逆容量损失存在一定对应关系,当x=0.15～0.17时,合金的耐腐电流较小,其自放电时的不可逆容量损失最低,循环寿命也较佳。Effect of Mg element on the microstructure and self-discharge property of annealed Lao. 7 _xY0.1G d0.2 Mgx Ni3.35 A10. x5 （x = 0 - 0.4） hydrogen storage alloy electrodes was studied systematically. The results showed that the annealed alloys mainly o0nsisted of Ce2 NiT （or C,d2 Co7 ）-type, Pr5 Co19-type, CaCu5 -type and PuNi3 -type phase. The influence of Mg content on the alloy coml：position and phase structure was great. Lower Mg content was beneficial to increase the phase abundance of Ce2 Ni7-type. In addition, more CaCu5- type and PuNi3-type phase would appear at higher Mg content. Electrochemical measurements showed that as the Mg content increased, the discharge capacity and cyclic stability of alloy electrodes both first increased and then decreased. The alloy electrodes with x = O. 15, 0.17 had a good cycling stability（ Sloo = 90% ） and the maximum discharge capacity of 368 mAh＇g-1. Moreover, the influence of Mg content in alloys on the charge retention ratio and OCP was obvious. The charge retention ratio of the alloys after 7 d increased from 7.9% （x =0） to 59.7% （x =0.17）, and then reduced to 1.8% （x =0.4）, which showed that the appropriate content of Mg could improve the self-discharge property of the alloy electrodes. In the process, the reversible capacity loss of Lao.7_~ Y0.1Gd0.2 MgxNi3.35 A10.15 alloy accounted for over 97.5%, and the irreversible capacity loss was only 0.4% - 2.5%. The charge retention ratio of the elec- trodes decreased with the increase of dehydroing pressure platform of PCT curves, in which both the hydrogen-induced amorphous alloy （x =0） and the polyphase structure alloy（x =0.4） with high pressure platform had higher self-discharge ratio. The corrosion current Iorr of the alloys had a corresponding relationship with the irreversible capacity loss of the electrodes, when x = 0.15 -0.17, the Ioo, was smaller, the irreversible capacity loss was the minimum with a better circle life.

关 键 词：La-Mg-Ni系储氢合金 微观组织 电化学和自放电性能 P—C—T曲线 腐蚀曲线 

分 类 号：TG139.7[一般工业技术—材料科学与工程]