Interface and Oxygen‐Vacancy Dual‐Engineering of 2D NiFe ₂ O ₄ /N‐Doped Graphene Sheet Heterostructure Securing Superior Performance in Lithium‐Oxygen Batteries

Lithium‐oxygen batteries (LOBs) are regarded as highly promising energy storage systems due to their ultrahigh theoretical energy density (~3500 Wh kg −1 ), yet their practical application is severely hindered by sluggish oxygen reduction/evolution reaction (ORR/OER) kinetics. Herein, an efficient bifunctional oxygen catalyst is rationally designed by anchoring enriched‐oxygen‐vacancy NiFe 2 O 4 nanoparticles onto 2D nitrogen‐doped graphene nanosheets (NGS/Ov‐NiFe 2 O 4 ). The abundant oxygen vacancies from the acid etching and the generated heterostructures efficiently modulate the electronic structure, leading to optimized adsorption energies of oxygen intermediates to improve the intrinsic activity for OER/ORR. Besides, the highly conductive NGS prevents aggregation of NiFe 2 O 4 nanoparticles, thereby exposing plentiful active sites, but also ensures rapid charge transfer to accelerate the OER/ORR kinetics. The NGS/Ov‐NiFe 2 O 4 heterostructure facilitates the highly reversible deposition and decomposition of thin‐film‐like Li 2 O 2 , thus guaranteeing an exceptionally prolonged cycle life for LOBs. Consequently, the NGS/Ov‐NiFe 2 O 4 cathode delivers an ultrahigh full discharge capacity (>12,000 mAh g −1 ), a significantly reduced initial overpotential of 1.12 V, and exceptional long‐term cycling stabilities (198 cycles at a curtailed capacity of 1000 mAh g −1 and 60 cycles under a deep discharge of 4000 mAh g −1 ). This work provides a novel interfacial and oxygen‐vacancy dual‐engineering strategy for developing high‐performance cathode catalysts for LOBs.