Effect of Mn content in the Ti/Zr-based AB₂ Laves type alloys on their electrochemical performance

In this work, we studied the impact of Manganese content on the structural and electrochemical properties of the AB₂ Laves phase alloys. These multicomponent alloys were composed of 7 individual constituents with a composition Ti_0.15Zr_0.85La_0.03V_0.12Mn_0.7+xFe_0.12Ni_1.2 and a variable Manganese content, x = 0.021, 0.035, 0.070. The alloys were prepared using arc melting and rapid solidification techniques. These alloys were characterized by X-ray diffraction and Scanning Electron Microscopy with X-ray Energy Dispersive Spectroscopy allowing to probe the phase-structural composition of the alloys, their microstructures, and elemental distribution among the phase constituents. The rapidly solidified alloys exhibited refined microstructures with a more uniform elemental distribution compared to their as-cast counterparts, the latter containing larger grain sizes and clustered La-rich phases. C15 and C14 Laves type structures contributed to the phase-structural composition of the alloys, with their proportions influenced by the Manganese content and the chosen preparation method. The study revealed a multi-feature relationship between the Manganese content, the phase abundances, and the electrochemical performances, with notable disparities between as-cast and rapidly solidified alloys. The alloy containing 3 wt% Manganese demonstrated the highest discharge capacity and superior activation performance for both preparation methods, suggesting the best choice when optimizing the composition of the anodes for achieving the best battery performance. The highest hydrogen diffusion rate was observed for the alloy containing 10 wt% Manganese which can be related to the catalytic role of Manganese in the processes of hydrogen exchange when present in these alloys.