| In order to further improve the self-discharge property of the R–Mg–Ni- based (R = RE, Ca, Y) AB3-type hydrogen storage alloys, as well as to investigate effect of constituent elements on self-discharge, Nd0.88Mg0.12Ni3.1+x- Al0.20 (x = 0.00, 0.10, 0.20, 0.30) and (LaxNdy)0.9Mg0.10Ni3.09Mn0.12Co0.60Al0.13 (x/y = 5, 4, 3, 2, 1) alloys were prepared by inductive melting. The change of structure and surface morphologies on alloy electrodes were characterized by XRD and FESEM-EDS. P–C–T and Tafel polarization methods were used to test thermodynamic stability of metal hydrides and corrosion of hydrogen storage alloys. The mechanism for self-discharge of metal hydride electrodes was discussed.XRD analyses showed that Nd0.88Mg0.12Ni3.1+xAl0.20 (x = 0.00, 0.10, 0.20, 0.30) consisted of NdNi5 phase, Nd2Ni7 phase and some minor NdNi2 phase. Charge retention rate (CRT) of alloy electrodes first increased from 22.5% (x = 0.00) to 82.1% (x = 0.20), and then decreased to 33.2% (x = 0.30) with the increase in Ni content. P–C–T measurements indicated that the stability of the hydride first increased and then decreased, resulting in difference in reversible capacity loss. XRD and FESEM-EDS showed that Mg(OH)2 and Nd(OH)3 were formed on surface of the alloy particles after storage under an open circuit condition for 28 d. The corrosion rate was characterized by Icorr first decreased from 564.9 mA/g(x = 0.00) to 368.1 mA/g(x = 0.20), and then increased to 503.5 mA/g (x = 0.30), the alloy electrodes have a better anti-corrosion ability in the alkaline electrolyte when x was 0.20.LaxNdy)0.9Mg0.10Ni3.09Mn0.12Co0.60Al0.13 (x/y = 5, 4, 3, 2, 1) hydrogen storage alloys consisted of La2Ni7 phase, LaNi5 phase and LaNi3 phase. The stability of metal hydride first increased and then decreased, the charge retention rate of alloy electrodes first increased from78.0% (x/y = 5) to 80.8% (x/y = 4), and then decreased to 71.1% (x/y = 1) with the increase in Nd content.
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