Characteristics Before and After Heat Treatment of Co-Free AB3-Type Fe Substituted Hydrogen Storage Alloys Used for Ni-MH Batteries
In this paper, a series of hydrogen storage Co-free AB3-type alloys were directly synthesized with vacuum mid-frequency melting method, and melted alloys were treated by low temperature-short time heat annealing. XRD results indicate that the main phase of melted La0.7Mg0.3Ni3-xFex (x=0.0~0.4) alloys are LaMg2Ni9 and LaNi5 phase. After heat treatment, some LaMg2Ni9 phase transferred into LaNi3 phase because of the loss of Mg during the heat proceeding. The content of Fe element affects phase structure of alloys and led to different electrochemical properties. Heat treatment has positive effects on cycle stability of La0.7Mg0.3Ni3-xFex (x=0.0~0.4) alloys but could cause little reduction of discharge capacity of Fe substituted alloy. However, the discharge capacity of La0.7Mg0.3Ni2.8Fe0.2 alloy increased after heat treatment. The EIS results show that heat treatment has positive effect on H transfer within alloy, and Fe content is related to the diffusion coefficient of H atoms within alloys.
Xie Yi and Li Mi
F. Wu et al., "Characteristics Before and After Heat Treatment of Co-Free AB3-Type Fe Substituted Hydrogen Storage Alloys Used for Ni-MH Batteries", Advanced Materials Research, Vols. 129-131, pp. 1049-1054, 2010