Elaboration and electrochemical characterization of two hydrogen storage alloy types: LaNi3-x Mn x Cr2 (x=0, 0.1, and 0.3) and La2Ni7

The LaNi3 - x Mn (x) Cr-2 (x = 0.0, x = 0.1, and x = 0.3) intermetallic compounds were prepared by a high-energy ball milling process. XRD studies and Rietveld refinement indicated that the as-prepared alloys showed multi-phase structures: the main phases were LaNi2Cr2, LaNi2.9Cr2Mn0.1, and LaNi2.7Cr2Mn0.3; and the two secondary phases: La2Ni3 and residual Cr. The increase in the amount of Mn substituting Ni improves the reversibility and the kinetic absorption-desorption of the electrode's electrochemical reaction and inhibits the cycling capacity degradation. The La2Ni7-type intermetallic compound is elaborated by mechanical alloying and investigated as a negative electrode material for nickel-metal hydride (Ni-MH) batteries. This study aims to optimize the milling time. The structural properties of the La2Ni7 phases were determined by X-ray diffraction and quantified from the Rietveld refinement data. The hydrogen absorption/desorption properties are determined by electrochemical measurements using galvanostatic cycling process. Discharge capacities of La2Ni7 alloys reached 438.58 mAh/g.