Surface BO₃ Configuration in Li-Rich Cathode Materials Enabling Highly-Stable Anionic Redox Reactions

Li-rich Mn-based layered oxides (LRMOs) are considered promising cathode candidates for next-generation high-energy-density lithium batteries, owing to their high capacity and low cost. However, they are plagued by lattice-oxygen release and surface-driven structural degradation, which lead to low initial coulombic efficiency and poor cycling stability. Here, a B-heterogeneous coordination structure is incorporated into the Li-rich materials, forming a ≈4 nm surface layer enriched in BO₃ units while retaining BO₄ units within the bulk. Both of tetrahedral BO₄ and trigonal BO₃ display stronger bonding interaction than those of transition metal (TM)─O bonds (i.e., Mn─O, Ni─O, and Co─O), while surface BO₃ further strengthens the B─O bonds compared with bulk BO₄, thus robustly anchoring lattice oxygen to suppress irreversible oxygen loss. Benefiting from this synergistic heterogeneous coordination, the modified LRMOs deliver a high reversible capacity of ∼300 mAh g^-1 at 0.1C, an enhanced initial Coulombic efficiency of 93.5% and excellent capacity retention of 85.8% after 300 cycles at 1C. This work demonstrates the surface BO₃ structure as an effective paradigm to reconcile oxygen-redox activity with long-term stability in high-energy-density lithium batteries.