Active Functional Interface Engineering Boosts Structural Stability for Single‐Crystalline Ni‐Rich Cathodes

Single‐crystalline LiNi 0.9 Co 0.05 Mn 0.05 O 2 (SCNCM90) cathodes can provide high specific capacities exceeding 200 mAh g −1 due to the additional contribution of oxygen redox. However, at deep oxidation stage, the formation of O (2‐n)− (0 < n < 2) and oxygen leads to structural transformation, electrolyte decomposition, and poor thermal stability, hindering their practical applications. Herein, a dual modification strategy of sulfur‐oxygen anion doping and FeS 2 &Fe 3 S 4 coating is proposed. Thereinto, the FeS 2 &Fe 3 S 4 interfacial protective layer can capture active oxygen to react to generate Fe 2 O 3 and Li 2 SO 4 , forming a nano‐hybrid heterostructure on SCNCM90, further inhibiting the outward migration of bulk oxygen anions. In addition, sulfur anions are incorporated into oxygen sites in the lattice structure and form polyanions on the surface, further participating reversibly in the redox process and improving overall coordination and anion redox stability by alleviating undesirable oxygen redox. The optimized SCNCM90‐2FS cathode materials showed superior cycling stability with a capacity retention of 97.5% after 200 cycles, alongside 87.3% capacity retention after 1000 cycles in the pouch‐type full cell with a graphite anode. This work highlights that the active functional interface modification in preventing lattice oxygen and structural deterioration provides an interesting insight for the design of single‐crystalline Ni‐rich cathodes.