Microstructures and electrochemical characteristics of the La0.75Mg0.25Ni2.5Mx (M=Ni, Co; x=0–1.0) hydrogen storage alloys
Microstructures and electrochemical characteristics of the La0.75Mg0.25Ni2.5Mx (M=Ni, Co; x=0–1.0) hydrogen storage alloys
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DOI：
10.1016/j.ijhydene.2008.01.016
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发表时间：
2008-04
影响因子：
7.2
通讯作者：
Yang-huan Zhang;Dong-liang Zhao;Bao-wei Li;Xiao-long Zhao;Zhong-wang Wu;Xin-lin Wang
中科院分区：
文献类型：
--
作者：
Yang-huan Zhang;Dong-liang Zhao;Bao-wei Li;Xiao-long Zhao;Zhong-wang Wu;Xin-lin Wang
为了研究B/A （A：总A位元素，B：总B位元素）的化学计量比和Co取代Ni对ab2.5 - 3.5型电极合金结构和电化学性能的影响，在氦气氛中通过感应熔融法制备了La-Mg-Ni-Co体系La0.75Mg0.25Ni2.5Mx（M=Ni, Co; x= 0,0.2, 0.4, 0.6, 0.8, 1.0）合金。系统地测量了合金的结构和电化学性能。结果表明，合金的结构和电化学性能与M含量密切相关。所有合金均表现为LaNi2、（La,Mg）Ni3和lani5相的多相结构，随着M含量的变化，合金的主要相由LaNi2变为（La,Mg）Ni3+ lani5。随着M含量的增加，合金的放电容量、高倍率放电（HRD）能力、活化能力和放电电位特性等电化学性能均有显著提高。当M含量x从0增加到1.0时，合金（M=Ni）的放电容量从177.7 mAh/g增加到343.62 mAh/g，合金（M=Co）的放电容量从177.7 mAh/g增加到388.7mAh/g。随着M含量的增加，合金的循环稳定性先上升后下降。钴取代镍显著改善了电化学性能。当M含量固定（x=1.0）时，Co取代Ni使电池的放电容量从343.62 mah /g提高到388.7mAh/g， 100次充放电循环后的容量保持率（S100）从51.45%提高到61.1%。
In order to investigate the influences of the stoichiometric ratios of B/A (A: gross A-site elements, B: gross B-site elements) and the substitution of Co for Ni on the structure and the electrochemical performances of the AB2.5–3.5-type electrode alloys, the La–Mg–Ni–Co system La0.75Mg0.25Ni2.5Mx(M=Ni, Co; x=0, 0.2, 0.4, 0.6, 0.8, 1.0) alloys were prepared by induction melting in a helium atmosphere. The structures and electrochemical performances of the alloys were systemically measured. The obtained results show that the structures and electrochemical performances of the alloys are closely relevant to the M content. All the alloys exhibit a multiphase structure, including LaNi2, (La,Mg)Ni3and LaNi5phases, and the major phase in the alloys changes from LaNi2to (La,Mg)Ni3+LaNi5with the variety of M content. The electrochemical performances of the alloys, involving the discharge capacity, the high rate discharge (HRD) ability, the activation capability and the discharge potential characteristics, significantly improve with increasing M content. When M content x increases from 0 to 1.0, the discharge capacity rises from 177.7 to 343.62 mAh/g for the alloy (M=Ni), and from 177.7 to 388.7mAh/g for the alloy (M=Co). The cycle stability of the alloy first mounts up then declines with growing M content. The substitution of Co for Ni significantly ameliorates the electrochemical performances. For a fixed M content (x=1.0), the substitution of Co for Ni enhances the discharge capacity from 343.62 to 388.7mAh/g, and the capacity retention ratio (S100) after 100 charging–discharging cycles from 51.45% to 61.1%.