Unravelling Charge Carrier Mobility in d₀ ‐Metal‐based Spinels

Enabling high Mg ion mobility, spinel-type materials are promising candidates for cathode or solid electrolyte applications. To elucidate the factors governing the observed high mobility of multivalent ions, periodic DFT calculations of various charge carriers (A=Li, Na, K, Mg, Ca, Zn and Al) in the ASc₂S₄ and ASc₂Se₄ spinel compounds were performed, resulting in the identification of a Brønsted-Evans-Polanyi-type scaling relation for the migration barriers of the various charge carriers. Combining this scaling relation with the derivation of a descriptor, solely based on easily accessible observables, constitutes a conceptual framework to investigate ion mobility in d₀-metal-based spinel chalcogenides with significantly reduced computational effort. This approach was exemplarily verified for various d₀-metal-based spinel chalcogenide compounds AB₂X₄ (B=Sc, Y, Ga, In, Er and Tm; X=O, S and Se) and led to the identification of d₀-metal-based CaB₂O₄ spinels as promising compounds possibly enabling high Ca ion mobility.