Electrochemical Performance Studies on Nickel-cobalt Electroplated La-Mg-Ni-based Hydrogen Storage Alloys

Abstract

In order to improve cycling stability and overall electrochemical properties of La-Mg-Ni-based hydrogen storage alloys,an electroplating treatment was applied on La0.88Mg0.12Ni2.95Mn0.10Co0.55Al0.10 alloy powders.The effect of cobalt-nickel coating on the morphological and electrochemical properties was studied.FESEM results show that spherical nickel-cobalt alloy particles are deposited on the surface of the alloys.Electrochemical tests indicate that the maximum discharge capacity,the cycling stability and the high rate dischargeability(HRD) are remarkably improved.After 200 charge/discharge cycles,the capacity retention rate increases from 60%(uncoated) to 80%(nickel-cobalt coated).The HRD at 1080mA/g rises by 23% for the nickel-cobalt coated alloy electrodes.Linear polarization and Electrochemical Impedance Spectroscope(EIS) results reveal that the surface of alloy electrodes with cobalt-nickel coatings is more catalytic for the electrochemical charge transfer reactions.