Annealing temperature-dependent phase structure and electrochemical hydrogen storage properties of AB4-type La1.5Y1.5Ni12-XMnX (X 1/4 0, 1.0) superlattice alloys

摘要

AB4-type La1.5Y1.5Ni12-xMnx (x = 0, 1.0) alloys with the rhombohedral structure were pre-pared by optimizing the annealing temperature. As the annealing temperature rises, the hexagonal Pr5Co19-type phase transforms into the rhombohedral AB4-type phase, and the 3R-AB4-type single-phase La1.5Y1.5Ni12 and La1.5Y1.5Ni11Mn1.0 alloys could be obtained at 1120 degrees C and 1088 degrees C, respectively. The partial Mn substitution for Ni increases the subunit volume but reduces the subunit volume mismatch of the AB4-type superlattice structure, thus lowering the hydrogen absorption/desorption plateau pressure and improving the electrochemical properties. Compared with annealed multi-phase alloys or single-phase A5B19-type alloy, the AB4-type single-phase alloy exhibits better overall electrochemical performance with a maximum discharge capacity of 345.6 mAh/g, a rate performance HRD600 of 84.03%, and a capacity retention S200 of 70.12%. The La1.5Y1.5Ni11Mn1.0 alloy with the rhombohedral structure demonstrates potential as a new anode for nickel-metal hy-dride batteries.

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