METALS AND METAL MATRIX COMPOSITES |
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Effects of Phase Composition on Electrochemical Properties of La0.75Mg0.25Ni3.5 Hydrogen Storage Alloy |
JIAO Qitong, PAN Wei, ZHU Shuai, CHEN Xiangyu, YANG Ning, CHEN Jian, GU Chenyu, QIU Tian, LIU Jingjing
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School of Mechanical Engineering, Yangzhou University, Yangzhou 225127, China |
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Abstract Compared with traditional AB5-type alloys, La-Mg-Ni-based superlattice hydrogen storage alloys have superior electrochemical capacity, which has attracted extensive attention in recent years. In this work, an A2B7-type La0.75Mg0.25Ni3.5 alloy containing only (La,Mg)2Ni7 and (La,Mg)5Ni19 superlattice structure was prepared by annealing the as-cast alloy at 1 203 K for 40 h, and the effects of phase transformation on the electrochemical properties of the alloy has been studied. The results showed that the as-cast alloy contained (La,Mg)Ni3, (La,Mg)2Ni7 and (La,Mg)5Ni9 superlattice phases and LaNi5 phase. During annealing process, LaNi5 and (La,Mg)Ni3 phases at the relative edge of the phase diagram disappeared, resulting in the alloy containing only (La,Mg)2Ni7 and (La,Mg)5Ni9 superlattice phases. The increase of the superlattice phase amount was accompanied by the homogenization of the element composition and the reduction of stress, which not only effectively improved the hydrogen storage capacity of the alloy, but also reduced the pulverization and oxidation during charge/discharge cycling, thus significantly improving the cycling stability of the alloy electrode. The maximum discharge capacity of the alloy electrode increased from 355 mAh·g-1 of the as-cast alloy to 367 mAh·g-1 of the annealed alloy, and the cyclic stability significantly increased from 57.97% to 81.47%. However, because of the reduction of the defects and grain boundaries in the alloy, the high-rate discharge capacity of the alloy was slightly reduced.
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Published: 23 March 2021
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Fund:National Natural Science Foundation Youth Fund of China (51801176), Natural Science Foundation Youth Fund of Jiangsu Province (BK20170502), Undergraduate Practice Innovation Training Program for College Students of Jiangsu Province (20191111707Y) and Undergraduate Innovation and Entrepreneurship Training Program/Academic Science and Technology Innovation Fund Program of Yangzhou University (X20190335). |
About author:: Qitong Jiao, studying in the Material Forming and Control Engineering Department of the School of Mechanical Engineering, Yangzhou University, is a member of the “New Energy Materials” research team. He has been studying the negative materials of Ni/MH batteries for more than two years, and is proficient in alloy preparation and crystal structure analysis. Wei Pan, studying in the Material Forming and Control Engineering Department of the School of Mechanical Engineering, Yangzhou University, joined the research team of “New Energy Materials” from Jun. 2017. He has been devoted to improving the electrochemical performance of power batteries, mainly Ni/MH batteries, and is proficient in battery assembly, electrochemical performance testing and analysis. Jingjing Liu received her Ph.D. degree in chemical engineering from Yanshan University in 2016. She is currently an associate professor in School of Mechanical Engineering, Yangzhou University. Her research inte-rests are advanced hydrogen storage alloys, power batte-ries and metallic functional materials. |
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