Abstract
Mg, the A-site atom in C14 (MgZn2), C15 (MgCu2), and C36 (MgNi2) Laves phase alloys, was added to the Zr-based AB2 metal hydride (MH) alloy during induction melting. Due to the high melting temperature of the host alloy (>1500 °C) and high volatility of Mg in the melt, the Mg content of the final ingot is limited to 0.8 at%. A new Mg-rich cubic phase was found in the Mg-containing alloys with a small phase abundance, which contributes to a significant increase in hydrogen storage capacities, the degree of disorder (DOD) in the hydride, the high-rate dischargeability (HRD), and the charge-transfer resistances at both room temperature (RT) and −40 °C. This phase also facilitates the activation process in measurement of electrochemical discharge capacity. Moreover, through a correlation study, the Ni content was found to be detrimental to the storage capacities, while Ti content was found to be more influential in HRD and charge-transfer resistance in this group of AB2 metal hydride (MH) alloys.
Highlights
Laves phase-based AB2 metal hydride (MH) alloy is one of the high-capacity negative electrode materials used in nickel/metal hydride (Ni/MH) batteries
AB2 MH alloys suffered from a harder activation and a shorter cycle life when compared to AB5 MH alloys [5,6,7,8]
We summarize our findings regarding the use of one of the alkaline earth elements, Mg, as an additive in AB2 MH alloys
Summary
Laves phase-based AB2 metal hydride (MH) alloy is one of the high-capacity negative electrode materials used in nickel/metal hydride (Ni/MH) batteries. 25% higher than the conventional AB5 MH alloys based on rare earth metals (330 mAhg ́1 ) [3,4]. In their development, AB2 MH alloys suffered from a harder activation and a shorter cycle life when compared to AB5 MH alloys [5,6,7,8]. The high-rate dischargeability (HRD) of the AB2 MH alloys, especially at low temperature, is still significantly inferior to the AB5 MH alloys because of the relatively low nickel content in the AB2 alloy [10]. We summarize our findings regarding the use of one of the alkaline earth elements, Mg, as an additive in AB2 MH alloys
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