A Bifunctional Fluoroborate‐Based Additive Capable of Regulating Electrode‐Electrolyte Interphases for Highly Stable Lithium Metal Batteries

ABSTRACT The practical deployment of lithium metal anodes is severely constrained by interfacial instability and poor compatibility with high‐energy cathodes, with the electrolyte serving as the critical mediator of these interactions. Herein, we propose potassium 3‐(trifluoroborate)propionate ethyl ester (KTFBP) as a novel bifunctional electrolyte additive that simultaneously stabilizes both anode and cathode interfaces. The trifluoroborate moiety of KTFBP reconstructs the Li + solvation sheath through fluorine‐dominated primary coordination, thereby enhancing Li + transport and preferentially promoting the formation of compact, robust, fluorine‐rich solid‐electrolyte interphase (SEI) and cathode‐electrolyte interphase (CEI) layers. Meanwhile, the dissociated K + ions provide localized electrostatic shielding, homogenizing the Li + flux and suppressing non‐uniform Li deposition. This synergistic solvation‐interphase regulation effectively stabilizes the Li metal anode while preserving the structural integrity of ultrahigh‐nickel cathodes. Remarkably, the incorporation of only 0.5 wt.% KTFBP into a commercial carbonate‐based electrolyte significantly enhances the cycling stability and high‐voltage durability of Li metal batteries, enabling long‐life full‐cell operation with LiNi 0.9 Co 0.05 Mn 0.05 O 2 cathodes. This work demonstrates a powerful electrolyte‐additive design strategy that amplifies intrinsic interphase fluorination to simultaneously regulate both electrodes, offering a viable pathway toward practical high‐energy‐density Li metal batteries.