Effect of Y substitution on the high rate dischargeability of AB4.6 alloys as an electrode material for nickel metal hydride batteries

Abstract

AB4.6 alloys exhibit excellent high rate dischargeability (HRD) performance but the quick capacity degradation and low discharge capacity restrict application of nickel metal hydride batteries. This study investigated the effect of substituting La with Y on the multiphase structures and overall electrochemical characteristics of the La0.90-xCe0.08YxZr0.02Ni3.91Co0.14Mn0.25Al0.30 (x = 0, 0.3, 0.5, and 0.7) alloys. The results showed that Y tended to form stable [A2B4] subunit rather than [AB5] subunit, thus the Ce2Ni7-type phase abundance increased from 16.00 wt% to 26.30 wt%, and improved the maximum discharge capacity and hydrogen diffusion. The decrease of icorr and particle size demonstrated that the addition of Y enhanced anti-corrosion capability but degraded anti-pulverization capability, where small particles obtained via pulverization were very sensitive to corrosion, thus leading to degradation in discharge capacity. The La0.6Ce0.08Y0.3Zr0.02Ni3.91Co0.14Mn0.25Al0.30 alloy exhibited excellent electrochemical properties, with maximum discharge capacity of 350.4 mAh g−1, cycle stability of 80.15% after 100 cycles and HRD of 73.56% (3000 mA g−1).