Lithium-Rich Antifluorite Li₅Fe_xAl_1-xO₄: Phase-Controllable Syntheses, Local Structural Evolution, and...

Lithium-rich antifluorite oxides formed by metal ion substitution in Li₂O are highly promising cathode prelithiation materials. Understanding the connection between their structure and performance is crucial for this type of material. In this paper, by forming solid solutions of α/β-Li₅AlO₄ and Li₅FeO₄, a group of continuous solid solutions, α-Li₅Fe_xAl_1-xO₄, and another group of phase transition solid solutions, β-Li₅Fe_xAl_1-xO₄, which underwent a phase transition at x = 0.5 were obtained, respectively. Changes in the local and electronic structures of the FeO₄ polyhedra were observed in the α-phase solid solution, and the decrease in electrochemical activity led to a linear attenuation of battery capacity. The structural changes after the phase transition of the β-phase solid solution led to the enhancement of the Li-Fe interaction, resulting in the disappearance of the delithiation performance within the working voltage. This study established a direct connection among local coordination structure, electronic structure, and electrochemical activity in lithium-rich antifluorite with abundant lithium content, providing a key theoretical basis for the rational design of high-performance prelithiation agents.