Formation of Rocksalt Domains by Dual Substitution to Boost Electrochemical Capability of Co-Free Li-Rich Layered Cathodes

Li-rich layered cathode materials possess a high capacity by activating both cation and anion oxygen redox, while structural instability and irreversible transition metal migration during cycling lead to severe capacity decay and voltage drop. Structural design and modification are essential to obtain high-capacity and long-cycling Li-rich cathode materials. Herein the present work, the cation-disordered rocksalt domains form and interweave in layered Li-rich cathode materials by partially replacing Li and Ni with Na and Mg. The presence of the rocksalt phase in the layered Li-rich cathode promotes the formation of stronger and more distortable metal–oxygen bonds and thus displays superior capacity by leveraging more oxygen activities and oxygen redox and suppressing the irreversible oxygen loss. More importantly, the rocksalt phase with a minimal isotopic structural change can stabilize the bulk layered structure and afford rapid Li-ion diffusing ability at long-term cycling and high-rate Li⁺ insertion and extraction, thus resulting in outstanding cycling and rate capability.