Zhiqiang Lan

Study on electrochemical property of La0.75Mg0.25Ni2.85Co0.45-x(AlSn)x (x=0.0, 0.1, 0.2, 0.3) alloys

Abstract La0.75Mg0.25Ni2.85Co0.45-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 mAh/g, respectively, then for the alloy electrode with x=0.2, even though the Cmax was only 309.0 mAh/g less than 348.9 mAh/g, the C150 of 231 mAh/g was much higher than 185 mAh/g. And the values of the limit current density, anodic peak current density and hydrogen diffusion coefficient of the La0.75Mg0.25Ni2.85Co0.35(AlSn)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 La0.75Mg0.25Ni2.85Co0.45-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.

Influence of magnesium on electrochemical properties of RE3–xMgx(Ni0.7Co0.2Mn0.1)9 (x=0.5–1.25) alloy electrodes

Abstract RE 3– x Mg x (Ni 0.7 Co 0.2 Mn 0.1 ) 9 ( x =0.5–1.25) alloys were prepared by induction melting and the influence of the partial substitution of RE (where RE stands for La-rich mischmetal) by Mg on the hydrogen storage and electrochemical properties of the alloys were investigated systematically. These alloys mainly consisted of three phases, La(Ni,Mn,Co) 5 phase, La 2 Ni 7 phase and Mg 2 Ni phase. The P-C-T isotherms showed that with Mg content increasing in the alloys, the hydrogen storage capacity first increased and reached the maximum capacity of 1.36 wt.% when x =1.0, and then decreased with x increasing further. Electrochemical studies revealed that the discharge capacity reached the maximum value of 380 mAh/g and the alloy electrode presented better cyclic stability when RE/Mg=2. The high rate discharge ability of the alloy electrodes was also improved by the substitution of Mg for RE. The RE 2 Mg(Ni 0.7 Co 0.2 Mn 0.1 ) 9 alloy exhibited better hydrogen absorption kinetics ( x =1.0).