Electrochemical studies of LaNi4.3Co0.4Al0.3 hydrogen storage alloy

Abstract

The performance of a nickel–metal hydride (Ni–MH) battery depends on the characteristics of the negative electrode. The electrochemical characteristics of the LaNi4.3Co0.4Al0.3 alloy, including the discharge capacity, the exchange current density and the hydrogen diffusion coefficient were studied as functions of the number of cycles. The electrochemical measurements show that the LaNi4.3Co0.4Al0.3 alloy electrode had a maximum capacity of 310 mA h g−1 at a discharge current density of 100 mA g−1. The exchange current density increases with the increasing number of charge/discharge cycles and then remains almost constant after activation. The multi-potential steps technique was used to estimate the hydrogen diffusion coefficient through the LaNi4.3Co0.4Al0.3 alloy electrode. It is seen that the diffusion coefficient is almost independent of cycling with an average value of 8·10−11 cm2 s−1. The high rate dischargeability (HRD) of LaNi4.3Co0.4Al0.3 strongly decreases for the alloy when the discharge current density increases over 400 mA g−1.