IMPROVED LOW-TEMPERATURE DISCHARGEABILITY OF C-14-TYPE ZR-CR-NI LAVES PHASE ALLOY

The low-temperature discharge characteristics of C14-type Zr-Cr-Ni Laves phase alloys were investigated. ZrCr1.1Ni alloy shows very good discharge capacity (320 mAh g(-1)) and cyclic stability (19% of capacity decay after 1000 cycles), but its discharge capacity decreases drastically as the temperature decreases. Considerable improvement in the low-temperature dischargeability was obtained by substituting Mn and V for Cr. This improvement is attributed to the porous Ni-enriched surface and the increased pulverization rate. The low-temperature dischargeability of 1000 cycled ZrCr1.1Ni alloy is much better than that of Zr(Cr,Mn,V)(1.1)Ni alloy. From surface analysis of the cycled Zr-Cr-Ni alloys it is found that the surface is covered with an Ni-enriched layer formed by the dissolution of Zr and Cr into the KOH electrolyte. The low-temperature dischargeability of the Zr-Cr-Ni alloy can be improved considerably by the Ni-enriched surface layer.