Investigation on the structure and electrochemical properties of the laser sintered La0.7Mg0.3Ni3.5 hydrogen storage alloys

The structure and electrochemical properties of the _{La0.7Mg0.3Ni3.5}${\mathrm{La}}_{0.7}{\mathrm{Mg}}_{0.3}{\mathrm{Ni}}_{3.5}$ alloys laser sintered at different powers were investigated. It is found that all alloys contain three phases _La3MgNi14${\mathrm{La}}_3{\mathrm{MgNi}}_{14}$ with the _Ce2Ni7${\mathrm{Ce}}_2{\mathrm{Ni}}_7$ structure, _LaNi5${\mathrm{LaNi}}_5$ and _LaMgNi4${\mathrm{LaMgNi}}_4$. The abundance of the main phase _La3MgNi14${\mathrm{La}}_3{\mathrm{MgNi}}_{14}$ is 43, 68 and 63 wt%, respectively, when sintering power varies from 1000 to 1200 and 1400 W. The laser sintered _{La0.7Mg0.3Ni3.5}${\mathrm{La}}_{0.7}{\mathrm{Mg}}_{0.3}{\mathrm{Ni}}_{3.5}$ alloys can be activated to their maximum discharge capacity within three cycles. The discharge capacities of those alloys prepared by laser sintering at 1000, 1200 and 1400 W are 324.6, 352.8 and 340.5 mAh/g, respectively. The _{La0.7Mg0.3Ni3.5}${\mathrm{La}}_{0.7}{\mathrm{Mg}}_{0.3}{\mathrm{Ni}}_{3.5}$ alloy laser sintered at 1200 W has a best cyclic stability (_S100=58.4%)$(S_{100}=58.4\%)$ and high-rate dischargeability (_HRD800=79.4%)$({\mathrm{HRD}}_{800}=79.4\%)$ due to the high amount of the main phase _La3MgNi14${\mathrm{La}}_3{\mathrm{MgNi}}_{14}$.