Abstract
In order to find out the effect of lattice configuration on the structural stability of Rare earth magnesium nickel compounds, two La0.65Nd0.15Mg0.20Ni3.50 isomerides with single Ce2Ni7-type (2H) and single Gd2Co7-type (3R) structure, respectively, have been prepared for the first time. It is found that, after hydrogenation/dehydrogenization cycles, the volume of [A2B4] subunit in 3R-type structure shrinks while that of [A2B4] in 2H-type structure gets expanded. Meanwhile, the [AB5] subunits in both structures expand, which have smaller initial volumes than [A2B4] subunits. The standard deviation of subunit volumes σ(V[A2B4], V[AB5]) in 3R-type structure is always smaller than that of 2H-type structure, and the σ(V[A2B4], V[AB5]) in 3R-type structure is only 0.45 Å3, far less than that of 2H-type compound (2.11 Å3) after 50 cycles. The lattice microstrain in 3R-type structure is quite lower than that in 2H-type structure and the 3R-type structure possesses a superior structural stability and higher anti-pulverization ability. After 50 cycles, the capacity retention of 3R-type compounds is 100% while that of 2H-type compounds is only 87.44%. Transmission electron microscope and X-ray diffraction analyses show that the crystal structure of 3R-type compound is almost unchanged after 50 cycles, while, severe lattice deformation is observed in 2H-type structure.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call