Hydrogenation of the rare earth alloys for production negative electrodes of nickel-metal hydride batteries

In this work were studied of La0.7-xMgx Pr0.3Al0.3Mn0.4Co0.5Ni3.8 (X = 0 and 0.7) alloys for negative electrodes of the nickel-metal hydride batteries. The hydrogenation of the alloys was performed varying pressing of H2 (2 and 10 bar) and temperature (room and 500 ℃). The discharge capacity of the nic kel-metal hydride batteries were analyzed in ARBIN BT- 4 electrical test equipment. The as-cast alloys were analyzed by scanning electron microscopy (SEM), energy disperse spectroscopy (EDX) and X-Ray diffraction. The increasing Mg addition in the alloy increases maximum discharge capacity but decrease cycle life of the batteries. The maximum discharge capacity was obtained with the Mg0.7Pr0.3Al0.3Mn0.4Co0.5Ni3.8 alloy (60 mAh) and the battery which presented the best performance was La0.4Mg0.3Pr0.3Al0.3Mn0.4Co0.5Ni3.8 alloy (53 mAh and 150 cycles). The H2 capability of absorption was diminished for increased Mg addition and no such effect occurs for Mg0.7Pr0.3Al0.3Mn0.4Co0.5Ni3.8 alloy. (author)