Microstructure and Electrochemical Hydrogen Storage Properties of Ball-milled Mg_xNi_(100-x)+5wtTiF_3 (x=50, 60, 70) Composite

摘要

The nanocrystalline and amorphous Mg_xNi_(100-x)+5wt.%TiF_3 (x=50, 60, 70) hydrogen storage alloys were synthesized by mechanical ball milling method. Microstructure and electrochemical performances of ball-milled alloys were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), electrochemical discharge capacity and cycling stability. The results show that the ball-milled hydrogen storage alloys hold a multiphase structure consisted of two main phases Mg_2Ni and Ni as well as a small amount of third phase MgNi_2 and TiNi. The ball milling Mg_(50)Ni_(50)+5wt.%TiF_3 composite possesses optimal electrochemical discharge capacity, which is relevant to amorphous/nanocrystalline structure and hydride Mg_2NiH_4 phase after absorbing hydrogen. X-ray diffraction analysis indicates that ball-milled Mg_(50)Ni_(50)+5wt.%TiF_3 composite exhibits the best electrochemical discharge properties.