Effects of metal oxides addition on the electrochemical performance of M1Ni_3.5Co_0.6Mn_0.4Al_0.5 hydrogen storage alloy

The AB₅-type M1Ni_3.5Co_0.6Mn_0.4Al_0.5 alloy (where M1 denotes mixed lanthanide) was modified with different additives (ZnO and MnO₂), and the effects of metal oxides on the electrochemical properties of the M1Ni_3.5Co_0.6Mn_0.4Al_0.5 − x% M (x = 5, 10; M = ZnO, MnO₂) alloy were studied. The results showed that the addition of metal oxides had a positive effect on the activation property of the alloy electrode. With the addition of ZnO, the maximum discharge capacity of the alloy increased from 315 to 334 mAh/g (x = 5) and 341 mAh/g (x = 10) with good cycle capability (C₃₀/C_max) (87% for x = 5 and 85% for x = 10), while the maximum discharge capacity remained invariable and the cyclic stability was deteriorated by the addition of MnO₂. Linear polarization (LP), cycle voltammetry (CV), and electrochemical impedance spectroscopy (EIS) measurements were also performed to investigate the electrochemical kinetics of alloy electrodes.