Effect of hydrogen decrepitation pressure on the particle size of rare earth based alloys for Ni-MH battery production

Abstract

This paper presents the results obtained from the hydrogenation and decrepitation of three LaNi-based alloys, La0.7Mg0.3Al0.3Mn0.4Co0.5Ni3.8, La0.7Mg0.3Al0.3Mn0.4Cu0.5Ni3.8 and La0.7Mg0.3Al0.3Mn0.4Sn0.5Ni3.8, in the as-cast condition. The procedure for decrepitating the alloys to be used in the negative electrode of the batteries was carried out using a combination of various hydrogen pressures (2-9 bar) at room temperature. At 2 bar of H2 it was revealed that Co, Cu and Sn have influence on the microstructures of the hydrogenated alloys and on the efficiency of hydrogen decrepitation. None of these alloys required thermal heating to activate and start the hydrogen absorption process. The decrepitated materials were characterized by scanning electron microscopy (SEM). The electrochemical measurements were performed using the tested negative electrode between two Ni(OH)2 electrodes as a battery cell.