Effect and mechanism of Mg on crystal structures and electrochemical cyclic stability of Ce2Ni7-type La-Mg-Ni-based hydrogen storage alloys
Effect and mechanism of Mg on crystal structures and electrochemical cyclic stability of Ce2Ni7-type La-Mg-Ni-based hydrogen storage alloys
复制标题
Mg对Ce2Ni7型La-Mg-Ni基储氢合金晶体结构和电化学循环稳定性的影响及机制
DOI：
10.1016/j.ijhydene.2018.07.152
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发表时间：
2018
影响因子：
7.2
通讯作者：
Li Yuan
中科院分区：
文献类型：
--
作者：
Cao Juan;Zhao Yumeng;Zhang Lu;Jia Zeru;Wang Wenfeng;Dong Zhentao;Han Shumin;Li Yuan
制备了单相ce2ni7型储氢合金lani3.50和la0.80 mg0.20 ni3.50。发现含镁合金的[A2B4]亚基体积膨胀大于无镁合金，而两种合金的[AB5]亚基体积膨胀几乎相同，因此含镁合金的[A2B4]和[AB5]亚基体积和超堆积结构应变值的偏差值明显高于无镁合金，且含镁合金在充放电循环过程中更容易被粉碎。相同循环次数下，含镁合金表面裂纹明显增多，说明含镁合金抗粉化性能较差。此外，正六边形氢氧化物的存在使含镁合金的表面变得松散，在充放电循环后容易被氧化。含镁合金的腐蚀电流密度比无镁合金大，所以含镁合金更容易被氧化。因此，降低超层结构[A2B4]和[AB5]亚基的偏差值以及合金元素Mg的腐蚀是提高激光单键dmg -单键ni合金电化学循环稳定性的基本解决方案。
LaNi3.50and La0.80Mg0.20Ni3.50hydrogen storage alloys with single-phase Ce2Ni7-type structure are prepared, respectively. It is found that the expansion of [A2B4] subunits volumes of Mg-containing alloy is bigger than that of Mg-free alloy, while the expansion of [AB5] 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 Mg-containing alloy are obviously higher than those of Mg-free alloy, and Mg-containing alloy is easier to be pulverized during charge/discharge cycles. Mg-containing alloy has more apparent cracks on the surface of alloy at the same cycle numbers, which demonstrate that Mg-containing alloy has poorer anti-pulverization. Besides, the presence of Mg hydroxides with a regular hexagon shape makes the surface of Mg-containing alloy become loose enough to be easily oxidized after charge/discharge cycles. The corrosion current density of Mg-containing alloy is larger than that of Mg-free alloy, so Mg-containing alloy is easier to be oxidized. Therefore, reducing the deviation value of [A2B4] and [AB5] subunits of super stacking structure and the corrosion of alloying element Mg is the basic solution to enhance the electrochemical cycling stability of Lasingle bondMgsingle bondNi alloy.