Tailoring the Thermodynamics and Kinetics of Mg–Li Alloy for a MgH2‐Based Anode for Lithium‐Ion Batteries

Abstract

AbstractUnderstanding the lithiation–delithiation of the Mg–Li alloy during the absorption–desorption of hydrogen is essential for the development of Li‐ion batteries with MgH2 as a negative electrode. Tuning the hydrogenation–dehydrogenation kinetics and thermodynamics of the Mg–Li alloy could also be helpful to develop a lightweight material for on‐board hydrogen‐storage applications. Single‐phase Li3Mg7 (the highest % of lithium compound) was prepared by ball milling of LiH and MgH2 as precursors of Li and Mg followed by dehydrogenation at 400 °C under dynamic vacuum conditions. The cyclic hydrogenation–dehydrogenation behavior of the intermetallic was studied in detail. During hydrogenation, Li3Mg7 was delithiated to LiH and MgH2, whereas during dehydrogenation, LiH and MgH2 were lithiated to form the Li3Mg7 phase along with a Mg–Li solid solution. The hydrogenation–dehydrogenation kinetics of pristine Li3Mg7 were found to be slow. The hydrogenation–dehydrogenation kinetics were remarkably improved by doping with ZrCl4 as a catalyst. The activation energy and the thermodynamic parameters of the uncatalyzed and catalyzed alloy were evaluated, and the results were compared.