Tailoring Carbonate Electrolytes toward Fast-Charging and Wide-Temperature Sodium-Ion Full Batteries

Abstract The large-scale multiscenario application of sodium-ion batteries (SIBs) remains constrained by critical challenges, such as suboptimal fast-charging performance and poor temperature adaptability. The ideal electrolyte must simultaneously possess intrinsic nonflammability, rapid charge-transfer kinetics, and robust interphases, yet balancing these key parameters poses significant challenges. Herein, a multifunctional cosolvent (ethoxy(pentafluoro) cyclotriphosphazene, PFPN), featuring weak coordination capability, F/N/P-rich, and nonflammable characteristics, is employed to revolutionize the carbonate electrolyte. The weak coordination ability of PFPN creates an anion-reinforced solvation chemistry, greatly enhancing the charge-transfer kinetics. Meanwhile, the F/N/P-rich characteristic of PFPN and the unique anion-reinforced solvation chemistry facilitate the construction of robust, inorganic-rich electrode/electrolyte interfaces, effectively preventing continuous electrolyte decomposition and the dissolution of transition metals. Furthermore, PFPN endows the electrolyte with a wide electrochemical window and inherent nonflammable properties. As a result, the Prussian blue∥hard carbon (PB∥HC) full cell demonstrates favorable fast-charging performance (with a capacity retention of up to 72.5% after 600 cycles at 3.0 C) and temperature adaptability (–20 to 80 °C). Furthermore, 18650-type cylindrical cells and Ah-level PB∥HC pouch cells deliver reliable electrochemical performance, indicating the practical viability of the designed electrolyte for SIBs across diverse operating scenarios.