Effects of Ce/Y on the cycle stability and anti-plateau splitting of La5-xCexNi4Co (x = 0.4, 0.5) and La5-yYyNi4Co (y = 0.1, 0.2) hydrogen storage alloys

Abstract Rare-earth based AB 5 -type alloys are one of the most popular and potential hydrogen storage materials. However, their overall hydrogen storage performance, especially hydrogen absorption/desorption durability needs to be further optimized. In this study, the microstructure and long-term hydrogen absorption/desorption properties of La 5- x Ce x Ni 4 Co ( x  = 0.4, 0.5) and La 5- y Y y Ni 4 Co ( y  = 0.1, 0.2) alloys are investigated. All the alloys are composed of CaCu 5 -type hexagonal single-phase structure. The addition of either Ce or Y increases the anisotropic c / a factor of cell lattices, thus enhancing the alloys' pulverization resistance and structural stability. Ce and Y elements also help to eliminate the second plateau in the alloys’ P–C-T curves and increase their application efficiency. In particular, La 4.5 Ce 0.5 Ni 4 Co alloy shows a single and long P–C-T plateau which reaches 95.5% of the full capacity compared with 67%–77% of the other three alloys. Furthermore, it experiences low microstrains and possesses high pulverization resistance during hydrogen absorption/desorption, exhibiting an excellent cycling retention of 96.0% after 1000 cycles. In addition, this alloy boosts the feeding hydrogen pressure from 1.5 MPa at room temperature to above 20 MPa at 175 °C with small hysteresis and flat and long plateau, showing a potential in the application of hydrogen compressor.