Effects of Ti substitution for Zr on the electrochemical characteristics and structure of AB2-type Laves-phase alloys as metal hydride anodes

The structural composition and electrochemical capacity of four AB2 Laves-type intermetallic alloys with various Ti/Zr ratios (TixZr1?xLa0.03Ni1.2Mn0.7V0.12Fe0.12, x = 0.12, 0.15, 0.18, 0.22) were investigated in this study. characterized by X-ray diffraction, scanning electron microscopy energy dispersive spectroscopy. These data revealed the coexistence main phase C15-type FCC compounds a secondary La–Ni that was present minor amounts. Increasing Ti substitution for Zr caused gradual shrinkage unit cells C15 phase. neutron powder diffraction studies demonstrated trihydride (Ti, Zr, V)(Ni, Mn, Fe, V)2D3.2, D atoms filled A2B2 tetrahedra, whereas V occupied not only conventional 16d sites but also partially replaced Zr/Ti at 8a sites. All studied showed similar activation behaviors, wherein cycles required to realize highest anodes. Ti12/Zr88 alloy excellent full discharge reached 466 mAh/g. Ti22/Zr78 electrode exhibited good cycling stability (retention rate ~71%) after 500 superior high-rate capability current density 400 mA/g. impedance spectroscopy (EIS) understand reasons deterioration capacity, which related pulverization increase irreversible capacity.