Özet:

La-Ni based alloys are being used in the commercial secondary nickel metal hydride batteries. Economical synthesis of these alloys may cause large scale utilization of them especially in the electrical vehicles. The electro-deoxidation, which is accepted as the revolutionary technique in the extractive metallurgy, is very promising in the metal hydride alloy synthesis since it provides direct synthesis of the alloys from their oxide raw materials. In this study La(Ni0.8Co0.2)5 (AB5 type) and La2(Ni0.8Co0.2)7 (A2B7 type) alloys were synthesized in the molten CaCl2 electrolyte at 850C and the charge/discharge characteristics of the synthesized alloys were observed. Sintering caused the hygroscopic La2O3 to disappear and the non-hygroscopic LaNiO3 to form. LaOCl was observed to form chemically upon contact of the sintered pellet with the melt. The X-ray diffraction peaks indicated that the sinter products reduced to LaNi5 and La2Ni7 phases within 2 h and 6 h electro-deoxidation process, respectively. The sluggish reduction kinetics of LaOCl phase was observed to retard the appearance of La2Ni7 phase. The discharge capacities of La(Ni0.8Co0.2)5 and La2(Ni0.8Co0.2)7 alloys were determined as 325 mA h g-1 and 332 mA h g-1, respectively. The results obtained in this study showed that the electro-deoxidation technique is very promising in the synthesizing of the high performance hydrogen storage alloys.

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