Microstructure and electrochemical properties of LaMMMgNiCoAl ( x = 0, 0.1, 0.2, 0.3) alloys.

The present study aims to improve electrochemical properties of the La-Mg-Ni-based hydrogen storage alloys through partial substitution for La by mischmetal (MM). The LaMMMgNiCoAl ( x = 0, 0.1, 0.2, 0.3) alloys were prepared by inductive melting, and their phase structures and electrochemical properties were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectrometry (EDX) and electrochemical tests. Results show that the alloys mainly consist of LaNi-type phase, LaNi-type phase, LaNi-type phase and LaNi-type phase. The addition of MM does not change the phase compositions, while it leads to more uniform phase distribution and obviously promotes the formation of LaNi-type phase which possesses favorable electrochemical properties. Electrochemical studies indicate that the substitution for La by MM could effectively improve the high rate dischargeability (HRD) of the alloy electrode, and the optimal value of HRD (HRD at 1500 mA·g) increases from 40.63 % ( x = 0) to 60.55 % ( x = 0.3). Although the activation properties of the alloy electrodes keep almost unchanged, both the maximum discharge capacity ( C ) and the cycling stability are significantly improved by MM addition. [ABSTRACT FROM AUTHOR]