Elaboration and electrochemical characterization of LaZr2Cr4Ni5-based metal hydride alloys

The elaboration of LaZr₂Cr₄Ni₅-based intermetallic compound was performed by mechanical alloying from LaNi₅ and ZrCr₂ precursors and characterized as active materials of negative electrodes in nickel-metal hydride (Ni-MH) batteries. The effect of the milling duration on the phase composition was investigated. The structural properties of the formed phases were determined by X-ray diffraction and quantified from the Rietveld refinement data. The increase of the milling time up to 40 h leads to the highest abundance of the LaZr₂Cr₄Ni₅ phase, estimated at a weight content of 60.6 %, and a complete elimination of the LaNi₅ intermetallic precursor. The chronopotentiometry, cyclic voltammetry, and chronoamperometry techniques were applied to characterize the electrochemical behavior of prepared LaZr₂Cr₄Ni₅-based compounds. The maximum discharge capacity was 152 mAh g⁻¹, and a high electrochemical stability was obtained in the alkaline solution. The value of the hydrogen diffusion coefficient is equal to 2.1 × 10⁻⁸ cm² s⁻¹, reflecting an appropriate electrochemical hydrogenation kinetic in the LaZr₂Cr₄Ni₅-based compounds.