Effect of Milling Time on Microstructures and Electrochemical Properties of AB_(3.5)-Type La-Mg-Ni-Co-Al Hydrogen Storage Alloys

摘要

La_(0.70)Mg_(0.30)Ni_(2.45)Co_(0.75)Al_(0.30) alloys were synthesized by milling and blending of the La_(0.70)Ni_(2.45)Co_(0.75)Al_(0.30) pre-alloy prepared by melting and elemental Mg, followed by annealing. The effects of milling time on the microstructures and electrochemical properties of the La_(0.70)Mg_(0.30)Ni_(2.45)Co_(0.75)Al_(0.30) hydrogen storage alloys were investigated. The structure, microstructure and electrochemical properties of the alloys were investigated by XRD, SEM and electrochemical measurements. The results showed that a noticeable (La,Mg)_2Ni_7 phase can be observed in the alloy milled for 2 h. Moreover, the distribution of the Mg element in the alloy milled for 15 h presents some aggregation phenomena. The La_(0.70)Mg_(0.30)Ni_(2.45)Co_(0.75)Al_(0.30) alloy milled for 2 h exhibits the best maximum discharge capacity (313.5 mAh/g) and discharge potential characteristic. The cyclic stability of the as-cast La_(0.70)Mg_(0.30)Ni_(2.45)Co_(0.75)Al_(0.30) alloy is better than that of the milled La_(0.70)Mg_(0.30)Ni_(2.45)Co_(0.75)Al_(0.30) alloy.