Microstructures and electrochemical characteristics of La0.7Ce0.3Ni4.2Mn0.9−xCu0.37(V0.81Fe0.19)x hydrogen storage alloys

Highlights: ► Commercial V0.81Fe0.19 is cheaper than pure V, and has lower melt point than pure V. ► Alloys containing V0.81Fe0.19 consist of LaNi5 matrix phase and V–Mn–Ni secondary phase. ► Activation property is improved by increasing V0.81Fe0.19 content. ► Maximum discharge capacity changes a little with increasing x value. ► The alloy with x = 0.10 exhibits the best HRD. - Abstract: Microstructures and electrochemical characteristics of La0.7Ce0.3Ni4.2Mn0.9−xCu0.37(V0.81Fe0.19)x hydrogen storage alloys were investigated. X-ray diffraction and scanning electron microscope results indicate that La0.7Ce0.3Ni4.2Mn0.9Cu0.37 alloy is single LaNi5 phase, and the alloys containing V0.81Fe0.19 consist of LaNi5 matrix phase and V–Mn–Ni secondary phase, and the abundance of secondary phase increases with increasing x value. The activation property of the alloy electrodes is improved by increasing V0.81Fe0.19 content. Maximum discharge capacity of the alloy electrodes changes a little with increasing x value. HRD1200 first increases from 60.4% (x = 0) to 70.8% (x = 0.10), and then decreases to 56.6% (x = 0.20). Cycling stability decreases with increasing x from 0 to 0.20. The adequate substitution of Mn by V0.81Fe0.19 can improve overall electrochemical performances of Co-free high-Mn AB5 alloy