Electrochemical properties of La_1.5Mg_0.5Ni_7-xCu_x（x=0.1~1.2）hydrogen storage alloy

The structural and electrochemical properties of the La_1.5Mg_0.5Ni_7-xCu_x hydrogen storage alloy with x=0.1-1.2 were investigated. It is found that when x changes from 0.1 to 1.2, La₂Ni₇ type phase is formed with well-distributed structure but a small amount of unknown phase is found in the alloy with x≥0.9. The investigation on electrochemical properties of the MH alloy electrodes indicate that with increasing Cu content in the alloys the discharge capacities decrease from 380mAh/g to 340mAh/g. The cycle stability of the alloys with x from 0.3 to 0.9 is improved in comparison to x=0.1.The high rate discharge ability（HRD）, the exchange current density I₀,and the limiting current density I_L of the alloy electrodes decrease with increasing x from 0.1 to 0.6 and then increase with increasing x from 0.6 to 1.2. The electrochemical kinetic properties of the electrodes decrease in the following order:Cu0.1＞Cu0.3＞Cu1.2＞Cu0.9＞Cu0.6.