Electrostatic Interactions versus Second Order Jahn–Teller Distortion as the Source of Structural Diversity in Li3MO4 Compounds (M = Ru, Nb, Sb and Ta)

With the advent of layered rocksalt oxides showing anionic redox activity toward Li, there has been an increased focus on designing new rocksalt structures and, more particularly, compounds pertaining to the Li3MO4 family. The structural richness of this family is nested in its ability to host many different cations, leading to the formation of superstructure patterns whose predictability is still limited. Thus, there is a need to understand the formation of such superstructures, as cationic arrangements have a crucial effect on their physical properties. Herein we propose a combined experimental and theoretical approach to understand the interactions governing cation ordering in binary systems of general composition given by Li3MyM′1–yO4 (M and M′ being Ru, Nb, Sb, and Ta). Through complementary X-ray diffraction and X-ray absorption spectroscopy techniques, we reveal a solid-solution behavior for the Li3RuySb1–yO4 system, as opposed to Li3SbyNb1–yO4 that enlists four rocksalt structures with different c...