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

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 (LiClO4) 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 PF6 - rather than solvent molecules within the IHP owing to its considerable B-F affinity with PF6 -, thereby reducing solvent participation at the interface and enhancing the oxidative stability of the electrolyte. Meanwhile, LiClO4 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.