Effect of fluorination on the lanthanum-doped AB2-type metal hydride electrodes

The effect of fluorination on the surface of an AB2-type hydrogen-storage alloy with the composition Zr0.7Ti0.3V0.4Mn0.4Ni1.2 is investigated. Electron probe microanalysis (EPMA), scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and X-ray diffraction (XRD) techniques show that the fluorinated AB2-type alloys have a unique surface morphology and high reactivity with a protective film. The treatment is found to be effective when lanthanum is incorporated in the alloy. The cycle-life of the metal hydride (MH) electrode increases significantly as a result of a decrease in the overpotential by electrode polarization. The degradation rate of the MH electrode is less than 3% after 100 cycles when lanthanum is added at 1–3 wt.%.