Mg对Ce2Ni7型单相La-Sm-Ni系贮氢合金结构和电化学性能的影响  

The effect of Mg on the crystal structures and the electrochemical performances of Ce2Ni7-type single-phase La-Sm-Ni-based hydrogen storage alloys

作　　者：曹娟 Cao Juan(Beijing Beiye Functional Materials Corporation,Beijing 100192)

机构地区：[1]北京北冶功能材料有限公司理化研究室,北京100192

出　　处：《金属材料研究》2020年第3期33-43,共11页Research on Metallic Materials

摘　　要：本文通过粉末烧结的方法,分别制备了Ce2Ni7型单相La0.75Sm0.25Ni3.50和La0.55Sm0.25Mg0.20合金,对比研究了Mg对Ce2Ni7型单相La-Sm-Ni系贮氢合金结构和电化学性能的影响。结果表明,Ce2Ni7型单相La0.55Sm0.25Mg0.20Ni3.50合金的放电容量在第一周充/放电循环后就达到364 mAh g^-1,其活化性能和放电容量优于La0.75Sm0.25Ni3.50合金。但是,合金经过120周充/放电循环后其放电容量基本没有发生改变,表明其拥有优良的电化学循环稳定性。研究发现,相同充放电循环周数时.La0.55Sm0.25Mg0.20Ni3.50合金中[A2B4]亚单元体积的膨胀远远大于合金,且这两个合金中[ABS]亚单元体积的膨胀几乎差不多,所以La0.55Sm0.25Mg0.20Ni3.50合金的超堆垛结构的[A2B4]和[ABS]亚单元体积偏差及应力值均大于La^SmonNija合金,使该合金电极更容易粉化腐蚀。因此,Mg的加入虽然在某种程度上能够增加合金的放电容量,但是降低了合金的循环稳定性。另外,La0.75Sm0.25Ni3.50合金的高倍率放电性能优于La0.55Sm0.25Mg0.20Ni3.50合金,而荷电保持率却低于La0.55Sm0.20Ni3.50合金。To study the effect of Mg on the crystal structure and the electrochemical performances of La-Sm-Nibased alloy,La0.75SmO.25Ni3.5O and La0.55Sm0.25Mg0.20Ni3.50 alloys consisted of Ce2Ni7-type single-phase structure are prepared by powder sintering methods,respectively.The discharge capacity of La0.55Sm0.25Mg0.20Ni3.50 alloy is 364 mAh g^-1 at the first charge/discharge cycle,the activation property and discharge capacity of La0.55Sm0.25Mg0.20Ni3.50 is superior to La0.75Sm0.25Ni3.50 alloy.However,the discharge capacity of La0.75Sm0.25Ni3.50 alloy remains unchanged as the charge/discharge cycle numbers increase up to 120,which show better electrochemical cyclic stability.It is found that the expansion of[A2B4]subunits volumes of the Mg-containing alloy is bigger than that of the Mg-free alloy,while the expansion of[AB] subunits volumes of the two alloys are almost the same,hence the deviation value of[A2B4]and[AB5]subunits volumes and strain value of super stacking structure for the Mg-contai ing alloy is obviously higher than that of the Mg-free alloy,and Mg-containing alloy is easier to be pulverized during charge/discharge cycles.The addition of Mg to some extent increases the discharge capacity,but it de・creases the cycling stability because of pulverization and oxidization.Moreover,the high rate discharge ability of LaO.75SmO.25Ni3.50 alloy is superior to La0.55Sm0.25Mg0.2ONi3.50 alloy,while the charge retention property is lower to La0.55Sm0.25Mg0.20Ni3.50 alloy.

关 键 词：镰氢电池 RE-Mg-Ni合金 单相合金 超堆垛结构 电化学性能 

分 类 号：TG1[金属学及工艺—金属学]