Effect of Milling Time on Microstructures and Electrochemical Properties of AB<sub>3.5</sub>-Type La-Mg-Ni-Co-Al Hydrogen Storage Alloys

La0.70Mg0.30Ni2.45Co0.75Al0.30 alloys were synthesized by milling and blending of the La0.70Ni2.45Co0.75Al0.30 pre-alloy prepared by melting and elemental Mg, followed by annealing. The effects of milling time on the microstructures and electrochemical properties of the La0.70Mg0.30Ni2.45Co0.75Al0.30 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)2Ni7 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 La0.70Mg0.30Ni2.45Co0.75Al0.30 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 La0.70Ni2.45Co0.75Al0.30 alloy is better than that of the milled La0.70Mg0.30Ni2.45Co0.75Al0.30 alloy.