The Effect Of Surface Modification On The Electrochemical Characteristics Of R-Mg-Ni-Based Storage Hydrogen Alloy

In this paper, the effect of modification of the additives on electrochemical properties of R–Mg–Ni-based hydrogen storage alloys was studied. The electrochemical properties of the La_0.88Mg_0.12(Ni–Mn–Co–Al)_3.74 alloy were improved greatly after the additives of metal oxides were added to the electrode and the additives of the metal powders and rare earth oxide were added to the electrolyte, respectively. The discharge capacity at low temperature was improved by using the ZnO additive in the electrolyte, the discharge capacity at 233 K was increased from 108 mAh/g to 175 mAh/g, increased by 62.0%. The S100 was increased by 2.6% and 2.0% after the additives of ZnO and Y2O3 were added to the electrolyte, respectively. The high rate discharge capacity was improved greatly after the additives of metal Ni powder and Rare earth oxide La2O3 were added to the electrode, at the current density of 1200 mA/g, the high rate discharge capacity was increased by 4.2% and 17.6% respectively. The S100 was increased by 7.7% and 3.8% after the additives of Ti and La2O3 were added to the electrode, respectively.In addition, the La_0.88Mg_0.12(Ni–Mn–Co–Al)_3.74 AB3-type alloy powders were modified with surface displacement copper plating in this paper. The technology conditions of surface displacement copper plating were studied by using orthogonal design experiment. The optimum technology conditions were concluded. The results showed that the temperature was 298 K, the pH value of plating solution was 2, the concentration of CuSO4 was 0.001 g/L and the coating time was 2 min. The coated Cu layer has the good luster, homogeneous powders and the better plating quality, Therefore the Cu coatings alloy powders have the better properties of anti-oxidation, anti-pulverization and anti-corrosion in optimum technology conditions. The effect of surface displacement copper plating on surface appearance and electrochemical properties of the alloys wasstudied. The XRD showed that the phase structure of AB3 alloy wasn't changed after the modification. The SEM showed that the surface of the alloys appeared a lots defect and crack after the modification, as a result, the specific area of the alloys are expanded and the discharge capacity are improved. It has been found that not only the initial activation behavior and high rate discharge capacity of the alloy electrodes were improved by surface modification of surface displacement copper plating, but also the discharge capacity was increased from 75 mAh/g to 148 mAh/g at 233 K, increased by 97.3%. The maximum discharge capacity were increased from 378 mAh/g to 400 mAh/g, increased by 6.4%, the S100 was increased by 2.6%-4.6%, respectively.