A Near-Surface Structure Reconfiguration Strategy to Regulate Mn³⁺/Mn⁴⁺ and O^2-/(O₂)^n- Redox for Stabilizing Lithium-Rich Oxide Cathode

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-/(O-2)(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 3D 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 modified LROs disclose higher initial Coulombic efficiency and discharge-specific capacity and improve cyclability compared with pristine LROs. Further, it is revealed that the F- impact becomes easier for the O sites at the lattice interface of C2/m and R3 over bar $\bar{3}$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 over bar $\bar{3}$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.