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

Abstract

In the present work, a high electronegativity element substitution strategy was employed to obtain a better corrosion resistance and cycling performance of Ce₂Ni₇-type La_0.83−xY_xMg_0.17Ni_3.1Co_0.3Al_0.1 (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 χ_Y = 1.22 > χ_La = 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.