Fluorinated Functional Units for Li+ Flux Homogenization in Silica Framework‐Based Zwitterionic Single Ion Conductors for Stable Lithium Metal Batteries

We engineered a novel SF-ZSIC electrolyte by co-grafting fluorinated anionic and zwitterionic monomers onto a robust silica framework. This design forms powerful solvation channels that drive ultra-stable, excellent-performance lithium metal batteries (LMBs). With over 4000 h of cycle stability, high capacity, and outstanding performance, SF-ZSIC set the stage for safer, long-lasting LMBs and a new generation of energy storage innovation.

Abstract

Progress in commercializing solid polymer electrolytes (SPEs) for lithium metal batteries (LMBs) has been impeded by challenges, like concentration polarization, non-uniform Li⁺ flux, and an unstable solid electrolyte interface (SEI), which contribute to dendrite formation. To address these issues, silica framework (SF)-based single-ion conductors are proposed, featuring a unique solvation channel composed of a fluorinated segment, a high-dipole zwitterion, and a rotation-motion-driven ion-hopping medium. This design promotes low resistance at the cathode/electrode interface, suppresses dendrite growth at the anode/electrolyte interface, and maintains a uniform Li⁺ flux. This results show that continuous ion channels within a robust framework enhance Li-ion dissociation and transport, achieving high ionic conductivity (σ _DC =  8.8  × 10⁻⁴ S cm⁻¹), a modulus of 0.9 GPa, a high lithium transference number (≈0.83), and an extended electrochemical stability window (up to 5.2 V) at 25 °C. This design fosters the formation of a hybrid organic/inorganic SEI layer composed of Li₂CO₃, LiF, and Li₂O, enabling ultra-stable Li plating/stripping for over 4000 h at 0.1 mA cm⁻². Furthermore, the full cells demonstrate excellent rate performance and long-term cycling stability and capacity retention (81% for Li||LFP and 86% for Li||NCM811 after 400 cycles at 1 C) and high coulombic efficiency, offering a promising strategy to stable LMBs.