Covalent Boron–Oxygen Bond Stabilizes Anion Redox for Lithium-Rich Manganese-Based Layered Oxide Cathodes

Lithium-rich manganese-based layered oxides (LRMs) have emerged as attractive cathode candidates for next-generation lithium-ion batteries with high energy density. Their exceptional capacity originates from the synergistic contribution of cationic redox and oxygen anionic redox (OAR). However, the utilization of OAR reactions at high voltages (>4.45 V) inevitably triggers irreversible oxygen release, leading to surface phase transitions and bulk structural degradation, consequent rapid capacity fading, and voltage decay. Therefore, simultaneously stabilizing the bulk lattice and the interface is critical to achieving durable OAR reversibility and long-term stability. Herein, we propose a one-step H₃BO₃ treatment strategy to construct boron-modified Li_1.098Ni_0.138Co_0.138Mn_0.552B_δO₂ (B-LRM) with borate species (BO₃/BO₄) doping and an amorphous lithium borate surface layer. The incorporation of boron introduces strong B-O bonding, which modulates Mn-O covalency, enhances OAR reversibility, and mitigates lattice distortion, while the amorphous surface layer effectively stabilizes the cathode-electrolyte interface. Consequently, the B-LRM cathode exhibits a high specific capacity of 306 mAh g^-1 at 0.1 C. Moreover, it demonstrates remarkable long-term durability, maintaining 86.3% of its initial capacity after 400 cycles at 1 C, accompanied by a minimal voltage decay of only 0.9 mV per cycle. This work provides a facile and scalable approach for achieving LRM cathodes with high energy density and long cycle life.