Effect of composition and particle morphology on the electrochemical properties of LaNi5-based alloy electrodes

Abstract

Al and Co substituted LaNi5-based intermetallic compounds were investigated as negative electrode materials in alkaline KOH-electrolyte. The structure, morphology and electrochemical properties of gas-atomised and cast LaNi4.5Al0.5 and LaNi2.5Co2.4Al0.1 alloys were investigated and the effect of the substitutions and the production method on the surface and bulk composition is compared to cast LaNi5 as a reference.While the rapid solidification of the gas-atomised alloys affects the site energy distribution for hydrogen on the interstitial sites, the activation and degradation mechanism of the electrodes cycle life is dominated by the elemental composition of the alloy and especially the surface. Therefore, the alloys with the larger Al content activate within a few cycles and also degrade faster as compared to the alloys with a high Co content. Furthermore, the dissolution of Al leads to a highly active surface with a lower reaction resistance, which leads to an order of magnitude increased high rate dischargeability.