Low-Co La_(1.8)Ti_(0.2)MgNi_(8.9)Co_(0.1) alloys were prepared by magnetic levitation melting followed by annealing treatment. The effect of annealing on the hydrogen storage properties of the alloys was investigated systematically by X-ray diffraction(XRD), pressure-composition isotherm(PCI), and electrochemical measurements. The results show that all samples contain LaNi_5 and LaMg_2Ni_9 phases. LaCo_5 phase appears at 1,000 ℃. The enthalpy change of all hydrides is close to -30.6kJ·mol^(-1)H_2 of LaNi_5 compound. Annealing not only increases hydrogen capacity and improves cycling stability but also decreases plateau pressure at 800 and 900 ℃. After annealing, the contraction of cell volume and the increase of hydride stability cause the high rate dischargeability to reduce slightly. The optimum alloy is found to be one annealed at 900 ℃, with its hydrogen capacity reaching up to 1.53 wt%, and discharge capacity remaining 225.1mAh·g^(-1) after 140 charge–discharge cycles.
La_(0.75)Mg_(0.25)Ni_(2.85)Co_(0.45–x)(AlSn)_x(AlSn)_x(x=0.0,0.1,0.2,0.3) alloys were prepared by magnetic induction melting method, and the phase composition and electrochemical properties were investigated systematically. The alloys were mainly composed of LaNi5, La2Ni7 and LaNi3 phase, and the cell volume of LaNi5 increased with the Al and Sn contents. For the alloy corresponding to x=0.0, the Cmax and C150 were 348.9 and 185 mA h/g, respectively, then for the alloy electrode with x=0.2, even though the Cmax was only 309.0 mA h/g less than 348.9 mA h/g, the C150 of 231 mA h/g was much higher than 185 mA h/g. And the values of the limit current density, anodic peak current density and hydrogen diffusion coefficient of the La0.75Mg0.25Ni2.85Co0.35(AlS n)0.1(x=0.1) alloy were 1079.5, 1023.8 mA /g and 5.71×10–10 cm2/s, respectively. Which were the highest than that of any other electrodes. These results suggested that the kinetic property of the La_(0.75)Mg_(0.25)Ni_(2.85)Co_(0.45–x)(AlSn)_x(AlSn)_x(x=0.0, 0.1, 0.2, 0.3) electrodes could be improved effectively by adding moderate contents of Al and Sn.
