2,4,6‐Tris(4‐Fluorophenyl)Boroxine‐Mediated Inner Helmholtz Plane Passivation Enables High‐Safety Lithium‐Metal Batteries

ABSTRACT Lithium metal batteries (LMBs) are regarded as promising next‐generation high‐energy‐storage systems. However, unstable cathode/electrolyte interphases (CEIs) and interfacial parasitic reactions under high‐voltage operation severely compromise their cycling stability and safety. Herein, 2, 4, 6‐tris(4‐fluorophenyl)boroxine (TFPB) and lithium perchlorate (LiClO 4 ) are proposed as mediators to regulate the inner Helmholtz plane (IHP) at the cathode interface for stabilizing high‐voltage LMBs. It is demonstrated that TFPB can positively regulate anion solvation behavior and preferentially interacts with PF 6 − rather than solvent molecules within the IHP owing to its considerable B‐F affinity with PF 6 − , thereby reducing solvent participation at the interface and enhancing the oxidative stability of the electrolyte. Meanwhile, LiClO 4 acts as an electric‐field‐responsive additive that preferentially accumulates at the cathode interface during charging, forming a Li + ‐enriched and thermodynamically favorable IHP with optimized solvent coordination structures. Benefiting from a rationally engineered IHP, the oxidative stability of the electrolyte is greatly extended from 4.1 to 5.9 V. The Li||NCM811 cells operated under harsh conditions (4.7 V and 60°C) achieve a high capacity retention of 90% after 120 cycles. Furthermore, 1.6 Ah graphite||NCM811 pouch cells with this electrolyte still show 66.2% capacity retention after 100 cycles at 4.7 V and 60°C.