Fluorophenyl‐Engineered Gel Electrolytes Enabling 4.8 V Lithium Batteries with Durable Electrolyte‐Electrode Interfaces

ABSTRACT Solid‐state lithium batteries (SSLBs) with lithium‐rich manganese‐based (LRM) cathodes and gel electrolyte offer a promising route toward high‐energy‐density electrochemical devices. However, high‐voltage operation causes cathode interface degradation via oxygen release and transition metal dissolution, while lithium metal anodes suffer from interfacial side reactions and uneven deposition. Herein, we propose a multifunctional additive based on a fluorophenyl scaffold, 3‐cyano‐5‐fluorophenylboronic acid (CFPBA), where tailored substituents synergistically stabilize both cathodic and anodic interfaces. The meta‐substituted boron electron‐deficient center mitigates oxygen release by trapping reactive oxygen species, while the cyano group suppresses transition metal dissolution via complexation, thereby cooperatively stabilizing the lattice oxygen and transition metal cations. Moreover, the introduction of the fluorine group promotes the generation of a LiF‐enriched SEI, enhancing lithium‐ion transport kinetics and suppressing lithium dendrite growth. Remarkably, the modified gel‐state SSLBs exhibit excellent cycling performance with 81.2% capacity retention over 400 cycles at 1C. Under high load cathode conditions, the 4.8 V LRM | Li pouch cell with a capacity of 2.5 Ah (∼467 Wh kg ⁻¹ based on the total mass of the cell) retains 91.7% capacity after 50 cycles. This work establishes a versatile additive‐engineering framework for high‐voltage SSLBs with prominent interfacial stability and prolonged cycling life.