Regioisomeric Engineering of Pyridone Electrolyte Additives Enables Stably High‐Voltage LiCoO 2 Cathodes Lithium‐Ion Batteries

ABSTRACT Achieving high‐energy‐density lithium‐ion batteries (LIBs) requires deep delithiation of layered oxides, yet operating LiCoO 2 (LCO) above 4.55 V triggers Co‐O electronic instability and accelerates electrolyte degradation. Electrolyte additives can passivate this interface, yet which molecular features control surface coordination and interphase chemistry remains unclear. Here we show that the regioisomeric substitution pattern of pyridone additives couples surface coordination to protective interphase formation, producing distinct stabilization mechanisms. Among the isomers, the para‐isomer 5‐fluoro‐2‐hydroxy‐3‐nitropyridine (p‐HNFP) yields the most effective stabilization. Spectroscopic and computational analyses indicate that p‐HNFP adsorbs preferentially on the delithiated LCO surface through σ‐type lone‐pair donation from the pyridone carbonyl oxygen to electron‐deficient Co 4+ centers, lowering the O 2p band center and widening the Co 3d‐O 2p gap, consistent with a reduced thermodynamic driving force for lattice‐oxygen oxidation. This interaction operates in tandem with a compact, LiF‐ and nitrogen‐enriched cathode‐electrolyte interphase (CEI) formed by regioselective oxidative decomposition of p‐HNFP, suppressing dehydrogenation‐initiated carbonate decomposition and preserving LCO structural integrity. Consequently, 1 wt% p‐HNFP enables fast‐charging 2 Ah Gr||LCO pouch cells (2.46 mAh cm −2 ) to retain 92.4% capacity after 400 cycles at 4.6 V. These findings establish regioisomeric engineering as a molecular design strategy for stabilizing high‐voltage LiCoO 2 interphases in LIBs.