Building the Robust Fluorinated Electrode–Electrolyte Interface in Rechargeable Batteries: From Fundamentals to Applications

Endowed by high energy density and high conversion efficiency between chemical and electric energy, rechargeable batteries are indispensable in a variety of different energy-level applications, ranging from portable devices (W-level) to electric vehicles (kW-level) and large-scale energy storage systems (MW-level). However, many lingering scientific and technical challenges still inhibit their wide applications, including low Coulombic efficiency, inferior cycle/rate performance, and safety hazards. After decades of extensive research, it is widely accepted that these challenges are largely influenced by the interfacial chemistry occurring at the electrode–electrolyte interface (EEI). EEI includes both the solid electrolyte interphase on the anode and the cathode electrolyte interphase on the cathode, and the great protective capability of the fluorinated interface is gradually unveiled. Although intensive research efforts have been devoted to fabricating various ex situ artificial and in situ interfacial fluorinated layers, the fundamental approaches to the fluorinated interface are still inferior and not systematically categorized and analyzed. In this contribution, we have confined and proposed five principles regarding obtaining fluorinated interfaces from pretreatment, solvent-separated ion pairs, contact ion pairs, aggregates, and feasible decomposition from numerous reports and built up a systematic design framework to guide the construction of the protective fluorinated interfaces for rechargeable batteries, offering target-oriented guidelines to tackle interface issues in secondary batteries.