Preparation And Electrochemical Performance Of Nickel Hydroxide For Ni/MH Battery

The preparation, struction and properties of nickel hydroxide as anode material for the foam and fibrous Ni/MH batteries were systematically studied .The paper investigated the relations between the preparation technology conditions, physical and electroclemical properties of nickel hydroxide.Spherical Ni(OH)2 was prepared with the two ammonia feeding modes of complexation precipitation method respectively. The effects of main preparation technology conditions such as reation pH value, NH3.H2O, time, temperature were studied in detail. With the two feeding modes, spherical Ni(OH)2 with high tapping density (≥2.0g/cm3), high electrochemical activity (≥220mAh/g) were prepared . Then it got the scopes of optimum technical conditions with different feeding modes. In the merging mode, the reation pH was 11.0; the ratio of NH3 and Ni2+ was 7.3:1; the reation temperation was 40-70℃; the reation time was 12 hours. In the mixing mode, the reation pH was 11.5; the volume ratio of NH3 and OH- was 0.3; the reation temperation was 65 ℃; the reation time was 12 hours.In the thesis, the effects of F-, Cl-, Br-, CO32-, SO42-, PO43- and NO3-, which worked as the electrolyte additives, on the electrochemical properties of the nickel hydroxide electrode were studied by using constant current and cyclic voltammetry technique .Some negative ions, Cl-, Br-, SO42-, PO43-, could improve the reduction potential so great that the reversibility and discharge time of nickel electrode were increased. SO42- and NO3- could improve the reduction current greatly.The metal additives such as Al, Ce, Co, Mg, Mn, Zn, Ba and Ca were put into the foam nickel electrode. The effect of additives on the capacity was studied. At the same time electrochemical machamism was dicussed. The cyclic voltammetry on the nickel hydroxide maked it clear that the nickel hydroxide electrode was controlled by solid-phase proton diffiusion. Additives, Al, Co, Mg, Mn, Zn and Cd, could improve reduction potential. Ce, Co, Zn, Ba, Ca,Cr, Cu, Pb, Sn and Ti could imprve reduction current, during the cathodic reduction , that additives, Ce, Co, Ba, Ca, Sn and Zn, could improve coefficient of solid-phase proton diffiusion.At last, the additives, Co, Zn, Ce, Ba, Ca, Sn, were better.