Deep Surface Engineering Toward Stable Cycling of Single‐Crystal Li‐rich Mn‐Based Cathode

Single‐crystal Li‐rich Mn‐based cathode materials (SLRMs) are promising for high‐energy lithium‐ion batteries due to their structural robustness. However, interfacial instability under high voltage triggers structural collapse and rapid capacity fading, hindering practical applications. Herein, an innovative strategy is proposed to deeply enhance the surface stability of SLRMs by constructing an Al3+‐reinforced spinel shallow surface structure and an Al3+ gradient‐doped layered subsurface structure in single‐crystal Li1.2Mn0.54Ni0.13Co0.13O2. This composite structure effectively protects reactive oxygen species from electrolyte attack, mitigating capacity fading caused by interfacial side reactions. Theoretical calculations reveal that the oxygen vacancy formation energy of the Al3+‐reinforced spinel shallow surface structure increases from 4.21 to 5.40 eV, while that of the Al3+‐doped layered subsurface structure rises from 3.88 to 4.05 eV. Such enhancedoxygen vacancy formation energy effectively suppressed irreversible oxygen release and phase transitions, thereby strengthening the interfacial stability of SLRMs. The modified SLRMs deliver a discharge capacity of 232 mAh g−1 at 1 C, with only 5% capacity loss after 200 cycles. This study resolves interfacial degradation in SLRMs via atomic‐level tailored deep surface engineering, establishing a blueprint for designing cathode materials with structural robustness.