Effect of the discharge rate on the electrochemical properties of LaY2Ni9 hydrogen storage alloy. Journal of Alloys and Compounds, Elsevier, 2015, 631, pp.
AbstractThe use of new hydrogen absorbing alloys as negative electrodes in rechargeable batteries has allowed the consideration of nickel-metal hydride batteries to replace the conventional nickelcadmium alkaline or lead acid batteries. In this study the LaY 2 Ni 9 hydrogen storage alloys was prepared and the effect of the discharge rate on the electrochemical properties of the active material was investigated. For this case, several electrochemical methods such as the galvanostatic charging and discharging, the constant potential discharge, and the potentiodynamic polarization are used to better understand the effect of the discharge rate on the behavior of the LaY 2 Ni 9 electrode.The decrease of the discharge rate, firstly, facilitates the activation of the alloy and other hand, causes the decrease of the drop potential that can be correlated with both the maximum discharge capacity and the cycle number of activation. After activation the electrochemical discharge capacity undergoes a rapid decay before slowing during a long cycling. A good stability and cycling lifetime are observed for C/10 rate. This degradation is mainly due to the corrosion of the electrode surface overlooked to the aggressive electrolyte (1M).The corrosion current density at the first activation cycle increases as a function of the electrochemical cycling. This growth becomes faster when the discharge rate becomes smaller.The corrosion potential during the first activation cycles, and for all rates, undergoes an increase to the direction of the positive potential. For a long cycling and except of the C/20 rate, an oscillating stabilization of both the corrosion current density and potential are observed and is better for the C/10 rate which is in good agreement with the good holding to cycling for this medium rate.