Hydrogen storage and electrochemical properties of 3R- and 2H-A5B19 structures in La-Y-Ni-based alloys

Abstract

The A5B19 phase of La-Y-Ni-based alloys presents two isomers of 2H and 3R phase due to the different A2B4 subunits. In this work, the hydrogen storage, and electrochemical properties of A5B19-type LaY2Ni10.6Mn0.5Al0.3 alloys with different 2H and 3R content is investigated. The results show that 2H- and 3R-A5B19 phases have comparable hydrogen storage and electrochemical properties but different structural stability during cycling, which is caused by the volume difference (∆V) between A2B4 and AB5 subunits during hydrogen absorption process. Compared with 3R-A5B19 phase, the smaller volume expansion of A2B4 subunits of 2H-A5B19 phase after cycling leads to a smaller ∆V, and therefore, better structural/cycling stability. Furthermore, the alloys composed by the two phases present a high-rate discharge ability (HRD) of ca. 76 % as well as a discharge capacity of 265 mAh/g at a discharge current density of 1500 mA/g, demonstrating the potential applications of La-Y-Ni alloy in high-power nickel-metal hydride battery.