Structural investigation and hydrogen storage properties of Ca3-xLaxMg2Ni13 alloys

The phase structures and hydrogen storage properties of the Ca3-xLaxMg2Ni13 alloys were investigated. It was found that the La substitution is unfavorable for the formation of the Ca3Mg2Ni13-type phase. The La-substituted alloys consist of multiple phases. Increasing La content to x = 2.25 leads to a disappearance of Ca3Mg2Ni13-type phase. Among these alloys, the Ca1.5La1.5Mg2Ni13 alloy has highest equilibrium pressures of hydrogen absorption–desorption and a highest hydrogen desorption capacity of 1.34 wt.% at 318 K. The discharge capacity decreases for La-substituted alloys. However, the cycling capacity retention rate (S30) increases from 13.7 to 67.6% when x increases from 0 to 3.