Hydrogen sorption and corrosion properties of La₂Ni₉CoSn_0.2 alloy

The hydrogenation and corrosion behaviour of La₂Ni₉ . CoSn_0.2 alloy was analysed in respect of its use in Ni-MH batteries. It has been proved that the presence of tin in the alloy causes a decrease in hydrogen equilibrium pressure. In the electrochemical studies several techniques, such as chronopotentiometry, multi-potential steps, linear sweep voltammetry and the potentiokinetic polarization were applied to characterize the electrochemical properties of a La₂Ni₉CoSn_0.2 powder composite electrode. During long cycling, powder particles undergo micro-cracking or other forms of surface development causing a progressive increase in the exchange current density of the H₂O/H₂ system, but, on the other hand, this increase favours corrosion processes such as the electrode material's oxidation. This is also reflected in the capacity loss values.