Unlocking Fast-Charging Capability in Graphite Anodes via Sulfite-Based Electrolytes with Optimized Solvation Structure and Interfacial Kinetics

Abstract

Sluggish Li+ transport kinetics during fast-charging operations frequently precipitates deleterious lithium plating on graphite anodes, leading to rapid capacity decay and catastrophic short circuits. Herein, we report a sulfite-based electrolyte (SSF) constructed via moderate solvation structure engineering, which is formulated from ethylene sulfite (ES), diethyl sulfite (DES), and highly dissociable lithium bis(fluorosulfonyl)imide (LiFSI) with a small amount of fluoroethylene carbonate (FEC). This SSF electrolyte promotes the formation of abundant, loosely coordinated contact ion pairs (CIPs) and aggregates (AGGs), which simultaneously expedite bulk Li+ transport and lower the interfacial desolvation energy barrier. Furthermore, the high reducibility of sulfite solvents enables synergistic decomposition with FSI– anions (coordinated within CIPs/AGGs) and FEC, constructing a hierarchical bilayer solid electrolyte interphase (SEI), which comprises an organic-rich outer layer for Li+ desolvation and an inorganic-rich (Li2SO3, Li2S, Li2Sx, and LiF) inner layer for rapid Li+ migration. Consequently, the SSF electrolyte delivers superior high-rate capability, yielding reversible capacities of 291 and 182 mAh g–1 at 5C and 10C, respectively, significantly outperforming carbonate-based counterparts (198/87 mAh g–1) and commercial benchmarks (53/22 mAh g–1 for 1 M LiPF6 in EC:DEC:EMC). Moreover, Li||graphite cells exhibit exceptional durability, retaining 92.6% capacity after 400 cycles at 4C. This work demonstrates that sulfite-based electrolytes effectively bolster Li+ transport kinetics at graphite anodes, representing a promising solvent paradigm for next-generation fast-charging batteries.