Effects of pretreatments on the electrochemical properties of MlNi4.0Co0.6Al0.4 alloy electrode and the performance of a Ni/metal hydride battery

MlNi(4.0)Co(0.6)Al(0.4) hydrogen storage alloy used as negative electrode material was pretreated in 6 M KOH or 6 M KOH + 0.02 M KBH4 solution It was found that the pretreatment improved greatly the electrochemical properties of the metal hydride (MH) electrode. The cycle life at 1C of the Ni/MH battery after employing the treated alloy as negative electrode material increased from 40 cycles to above 300 cycles. The results of the electron probe microanalysis and inductively coupled plasma spectrometry analysis showed that a Ni-rich surface layer with high electrocatalytic activity was produced by the preferential dissolution of aluminium and the oxides on the alloy surface. It believed to be the main cause of the improved properties of the MI-I electrode and longer cycle life of the Ni/MH battery. (C) 1999 Published by Elsevier Science S.A. All rights reserved.