Zr-Cr-Ni BASED MULTICOMPONENT METAL HYDRIDE ELECTRODES

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The electrochemical discharge capacity, cyclic stability, self discharge properties of Zr Cr Ni based multicomponent hydride electrodes were investigated. Research result for electrodes of Zr(Cr x Ni 1- x ) 2 Laves phase alloys with Cr content in the range of 0.30≤ x ≤0.50 was introdused. Substitution effect of Cr or Ni by V or Mn in the form of Zr(Cr x M y Ni 2- x-y ) (M=V or Mn, x+y =0.7～1.2) on the electrochemical discharge capacity were also studied. The alloys with x+y =0.7～1.0/ AB 2 formula has larger hydrogen storage and electrochemical discharge capacities. When Ti is used to substitute Zr partly in Ti y Zr 1- y M 2( y =0.0～0.3) alloys, the plateau pressure of the hydride tends to increase with increasing y , however its electrochemical capacity decreases as well due to lower reversible hydrogen storage density. The electrochemical cycling deterioration increases with increasing Ti content. Electrodes with no Ti or very low Ti content preserve 86% of their discharge capacities after 820 cycles under 65% depth of discharge, exhibit excellent electrochemical stability. It was found that the activation of Zr 0.9 La 0.1 Cr 0.36 Mn 0.36 V 0.18 Ni 1.4 electrode is improved with LaNi 5 synthesized by arc melting, but its cyclic stability is deteriorated severely. The charge retention of hydride electrodes is related to the hydrogen pressure plateau, therefore more Mn substituted for Cr, Ti for Zr and higher superstoichiometric degree and storing temperature will decline its self discharge property.