PNNL

Abstract

Mg batteries utilizing oxide cathodes can theoretically surpass the energy density of current Li-ion technologies. The absence of functional devices so far has been ascribed to poor Mg2+ mobility within oxides, which severely handicaps intercalation reactions at the cathode. Furthermore, existing knowledge of divalent cation mobility in solid frameworks is acutely deficient. Here we present a combined structural, ion dynamics, and theoretical study of Mg mobility within three spinel oxides. The results provide insight into features influencing the mobility of Mg2+ cations in these compounds. The experimental activation energies for a Mg2+ hop to an adjacent vacant Mg site, as low as ~600 meV, are reported for the first time. The values support the possibility of functional electrodes based on the intercalation of Mg2+. Our findings enhance the understanding of cation transport in solid structures and renew the prospects of finding novel materials capable of high energy density.