Improving the phase stability and cycling performance of Ce2Ni7-type RE-Mg-Ni alloy electrodes by high electronegativity element substitution.

In the present work, a high electronegativity element substitution strategy was employed to obtain a better corrosion resistance and cycling performance of Ce2Ni7-type La0.83-xYxMg0.17Ni3.1Co0.3Al0.1 (x = 0.0-0.6) alloys. The abundance of the Ce2Ni7-type phase increased as x increased from 0 to 0.2 but it decreased with a further increase in x up to 0.6. The alloy with x = 0.2 further showed a superior discharge capacity (400.6 mA h g-1) and high cycling stability (S320 = 75%). We found that the Y (electronegativity value χY = 1.22 > χLa = 1.10) element could play an essential role in enhancing the anti-corrosion of alloys based on a theoretical framework of the electronegativity of rare earth elements, thus leading to an excellent cycle lifetime of the alloys. The new alloying designs are expected to provide viable La-Mg-Ni-based intermetallic compounds as anode materials for commercial Ni-MH batteries.