The Li₃Ru_yNb_1–yO₄ (0 ≤ y ≤ 1) System: Structural Diversity and Li Insertion and Extraction Capabilities

Searching for novel high-capacity electrode materials combining cationic and anionic redox processes is an ever-growing activity within the field of Li-ion batteries. In this respect, we report on the exploration of the Li₃Ru_yNb_1–yO₄ (0 ≤ y ≤ 1) system with an O/M ratio of 4 to maximize the number of oxygen lone pairs, responsible for the anionic redox. We show that this system presents a very rich crystal chemistry with the existence of four structural types, which derive from the rocksalt structure but differ in their cationic arrangement, creating either zigzag, helical, jagged chains or clusters. From an electrochemical standpoint, these compounds are active on reduction via a classical cationic insertion process. The oxidation process is more complex, because of the instability of the delithiated phase. Our results promote the use of the rich Li₃MO₄ family as a viable platform for a better understanding of the relationships between structure and anionic redox activity.