Y. Zhang, S.H. Zheng, C.X. Meng, H.Q. Liu, C. Dong, X.Y. Shi, P. Das, R. Huang, Y. Yu*, Z.-S. Wu*

Advanced Functional Materials, 2023, 33.

DOI: 10.1002/adfm.202300987 [PDF]

Lithium-rich layered oxides (LROs) are one class of the most competitive high-capacity cathode materials due to their anion/cation synergistic redox activity. However, excessive oxidation of the oxygen sublattices can induce serious oxygen loss and structural imbalance. Hence, a near-surface reconfiguration strategy by fluorinating graphene is proposed to precisely regulate Mn3+/Mn4+ and O2-/(O2)n- redox couples for remarkably stabilizing high-capacity LROs and realizing the simultaneous reduction of the lattice stress, regulation of the Mn metal at a lower charge state, and construction of three-dimensional Li+ diffusion channels. Combining with a highly conductive graphene-coating layer, the surface oxygen loss, transition metal dissolution and electrolyte catalytic decomposition are suppressed. Benefiting from this synergy, the LROs disclose higher initial Coulombic efficiency and discharge-specific capacity, and improved cyclability compared with pristine LROs and recently reported anion-doped LROs. Further, it is revealed that the F- impact becomes easier for the O sites at the lattice interface of C2/m and R3 ̅m to sufficiently buffer lattice stress. Moreover, lithium ions coupled to the doped F atoms at the lattice interface migrate to the Ni-rich R3 ̅m lattice sites with lower migration energies. This consolidated understanding will open new avenues to regulate reversible oxygen redox of LROs for high-energy-density lithium-ion batteries.