Microstructure and electrochemical characteristics of LaPrMgALMnCoNi hydrogen storage alloys for nickel-metal hydride batteries

Abstract

The effect of the substitution of La with Pr on the microstructure and some electrochemical properties of La0.7-xPrxMg0.3Al0.3Mn0.4Co0.5Ni3.8 (x=0.0, 0.1, 0.3, 0.5, and 0.7) ingot alloys as powder electrode was studied in this paper. XDR and SEM (+EDX) analyses revealed that the as-cast alloys consist mainly of similar LaNi5 and (La,Pr)Mg2Ni9 phases. With the increase in Pr content, both the relative abundance of the phases and microstructure changed. The electrochemical studies showed that the maximum discharge capacity decreased with the increase in Pr content. For the alloy without Pr, the self-discharge studies revealed a major stability of the hydride until the first 984 hours (41 days) of the charge/discharge cycles. The high-rate dischargeability of this alloy electrode showed the best result HRD=88% at a discharge current density of Id=250 mA/g.