Electron-Withdrawing Chemistry Drives Ultrafast-Charging Interphases for Sodium-ion Batteries

Abstract

Fast charging and long-term cyclability in sodium-ion batteries are fundamentally limited by unstable, ion-transport-limited solid electrolyte interphases (SEI) arising from solvent-dominated Na⁺ solvation structures in conventional carbonate electrolytes. These intrinsic limitations have long confined practical fast-charging sodium-ion batteries (SIBs) to a ceiling of ~3C. Herein, we break through this bottleneck by designing a molecular strategy based on solvent electron-withdrawing chemistry: through stepwise fluorination of carbonate solvents, enabling ampere-hour-level full sodium-ion batteries based on hard carbon anodes to achieve ultrafast charging within 7 minutes with 1,800-cycle stability. This approach promotes preferential reduction of FSI⁻ anions and low desolvation energy, which is correlated with the formation of a thin, dense, and highly conductive NaF-rich inorganic SEI on hard carbon anodes. The resulting electrolyte delivers exceptional interfacial kinetics and stability, breaks the long-standing incompatibility between high ionic conductivity and low solvation energy in sodium-ion electrolytes. Notably, this performance is demonstrated for the first time in a 52 Ah prismatic full cell under industrially relevant conditions. This work provides a generalizable chemical framework for designing robust, fast-charging batteries, bridging molecular-level innovation with practical energy storage applications.