Electrochemical Properties of LaNi_5-xGa_x Alloys Used as the Negative Electrodes of Ni-MH Batteries

Abstract

The effects of the substitution of nickel by gallium on the structures and the electrochemical properties of LaNi_5-xGa_x (x = 0.1−0.5) alloys were studied systematically. The structure of the alloy was tested by X-ray diffraction (XRD) measurements. Electrochemical properties and battery parameters were measured by bipotentiostat and battery tester equipment. The results showed that when gallium is doped into alloys, the lattice of the LaNi_5-xGa_x is slightly increased but retains the CaCu₅ structure. Gallium has a low melting temperature. When gallium replaces nickel in the LaNi₅ alloy, it covers material particles and reduces oxidation process, which leads to a longer lifetime and makes charge/discharge process more stable. The shapes of electrochemical impedance spectroscopy measurements of all the LaNi_5-xGa_x samples were similar, and the value increases as the substitution of Ni by Ga increases. The cyclic voltammograms of all the LaNi_5-xGa_x samples were similar to the one of pure LaNi₅. For the same Ga-doped concentration and experimental conditions, the current density J_max and charge quantity Q of the samples were increased cycle by cycle of charge/discharge.

Keywords:

• Cyclic voltammetry
• Electrochemical impedance spectroscopy
• Electrochemical properties
• LaNi₅
• Ni-MH batteries