Phase Structure and Electrochemical Characteristics of MI(Ni_(3.35)Co_(0.75)Mn_(0.40)Al_(0.30)_(5x)(x=0.88,0.92,0.96,1.00)Hydrogen Storage Alloys

摘要

The phase structure and electrochemical characteristics of Ml(Ni_(3.55)Co_(0.75)Mn_(0.40)AL_(0.30))_(5x) (x =0.88, 0.92, 0.96, 1 .00) hydrogen storage alloys were studied. The effect of the stoichiometric ratio on the phase structure and electrochemical characteristics was analyzed. The results of XRD reveal that all the alloys consist mainly of LaNi_5 phase with the hexagonal CaCus structure. But a few of the diffraction peaks of La_2Ni+7 phase on XRD pattern are observed when x < = 0.92, and with decreasing x , the intensity of La_2Ni_7 diffraction peaks increases and the values of lattice parameters a and cell volume increase, c and cla of LaNi_5 phase decrease gradually. When x > =0.96, La_2Ni_7 phase disappears and the alloys become single CaCu_5-type. The electrochemical tests show that the maximum discharge capacity, high rate discharge-ability and low temperature dischargeability are improved to different degrees by adjusting the stoichiometric ratio.