Direct synthesis of La-Mg-Ni-Co type hydrogen storage alloys from oxide mixtures

(La1-xMgx)2(Ni0.8Co0.2)7（x = 0.125, 0.25, 0.5） alloys were synthesized from the sintered mixture of La2O3+ Ni O + Co O + Mg O in the molten CaCl2 electrolyte at 750 °C and the electrochemical hydrogen storage capacities of the synthesized alloys were measured. Non-hygroscopic LaNiO3 phase formed during sintering（at 1200 °C for 2 h） as a result of the reaction of hygroscopic La2O3 with NiO. Another sinter product was Mg0.4Ni0.6O phase. Both mixed oxide sinter products facilitated the La-Ni and Mg-Ni phase formations. X-ray diffraction peaks indicated that the first stable phase appeared in the alloy structure was LaNi5 which formed upon reduction of La2NiO4 phase. Increase in Mg content caused formation of La1.5Mg0.5Ni7 phase in the alloy structure and the presence of this phase improved the hydrogen storage performance of the electrodes. It was observed that(La1-xMgx)2(Ni0.8Co0.2)7（x = 0.125, 0.25, 0.5） alloys have promising discharge capacities change between 319 m Ah/g and 379 m Ah/g depending on the alloy Mg content.