Structural and electrochemical properties of high-capacity Ml-Mg-Ni-based hydrogen storage alloys

Abstract

The Ml-Mg-Ni-based (Ml= La-rich mixed lanthanide) hydrogen storage alloy Ml_0.88Mg_0.12Ni_3.0Mn_0.10Co_0.55Al_0.10 was prepared by inductive melting. The micro-structure was analyzed by XRD and SEM. The alloy consists mainly of CaCu₅-type phase, Ce₂Ni₇-type phase and Pr₅Co₁₉-type phase. The electrochemical measurements show that the maximum discharge capacity is 386 mAh/g, 16.3% higher than that of the commercial AB₅-type alloy (332 mAh/g). At discharge current density of 1 100 mA/g, high rate dischargeability is 62%, while that of the AB₅-type alloy is only 45%. The discharge capacity decreases to 315 mAh/g after 300 charge/ discharge cycles, 81.5% of the maximum discharge capacity.

Keywords

Ni/MH batteries / hydrogen storage alloys / Ml-Mg-Ni-based alloys / electrochemical properties

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