The Study On Electrochemical Properties Of AB₃ Type Hydrogen Storage Alloy By The Coprecipitation-Reduction-Diffusion Method

In this paper, sorts of hydrogen storage alloys have been extensively reviewed and analyzed. On this basis, the La-Mg-Ni based of PuNi3-type hydrogen storage electrode alloys was selected as the subject of this study. This work aims to improve the cycling number discharge capacity and cycling stability of PuNi3-type hydrogen storage alloys .The Nickel of La-Mg-Ni and La0.4Ce0.1Nd0.2Pr0.3-Mg-Ni alloys were substituted by Coblat, Manganese and Copper. The LaMg2Ni9-xMx based alloys and La0.4Ce0.1Nd0.2Pr0.3Mg2Ni9-xMx(M=Copper. or Manganese or Copper)based alloys were prepared and the electrochemical properties of alloys analyzed. We draw optimum condition with Coprecipitation-Reduction-Diffusion method, and studied systematically by XRD, SEM and the electrochemical properties and different elemental substitution of PuNi3 -type alloys, and draw some useful conclusions.The hydrogen storage alloys were prepared in the condition as below: at the beginning of mixed nitrate liquor, the total of metallic ions concentration is 40g/L.Each of metallic ions is stoichiometrically added, and the number of rare earth is more 5% than that of normal. The precipitator is oxalic acid—ethanol liquor, then the precipitator is added into mixed nitrate liquor with dripping method, and the number of precipitator is more 50% than that of normal, and the reaction is undertaken at 60~70℃. The number of CaH2 is 1.5-2.0 times as the theoretical value, and the temperature is risen slowly to 950℃ and kept 4 hours in hydrogen atmosphere . Then the pure alloys are prepared. XRD and SEM analysis show that:the alloys are single-phase and the size of the particles of the alloys is distributed about 1μm.The LaMg2Ni9-xMx based alloys and La0.4Ce0.1Nd0.2Pr0.3Mg2Ni9-xMx (M=Copper or Manganese or Copper) based alloys were studied and tested. The result shows that:different elemental substitutions and different substituted amount greatly affect discharge capacity and rates of capacity decay of the alloys. The better comprehensive electrochemical properties of hydrogen storage alloys are LaMg2Ni6.oMn3.o alloy and Lao.4Ceo.iNdo.2Pro.3Mg2Ni5.7Mn3.3 by means of electrochemical measurements. The activated numbers of LaMg2Ni6.oMn3.o alloy is 12 and the maximum discharge capacity is 149.9mAh/g. The rates of capacity decay of the alloy is 14.27% after 100 cycles. The activated numbers of Lao.4Ceo.iNdo.2Pro.3Mg2Ni5.7Mn3.3 alloy is 14 and the maximum discharge capacity is 122.5mAh/g. The rates of capacity decay of the alloy is 7.36% after 100 cycles. The electrochemical properties of the two hydrogen storage alloys are obviously improved compared with the non-substituting alloys LaMg2Nig and Lao.4Ceo. i...