Breaking Diffusion Limit in Ester-Flame-Proof Na-Ion Electrolytes Through Solvent Coordination Chemistry.

Traditional electrolyte systems are struggle to meet practical needs for high performance of sodium-ion batteries (SIBs) due to their limited functionality. The design of electrolytes today relies largely on expensive trial-and-error methodologies and intricate solvent-structure engineering, in which various additives and solvents are arbitrarily used without any reasonable selection rules. Motivated by this, we herein establish a descriptor-guided framework centered on solvent oxidative stability and Na+-solvent coordination chemistry to identify intrinsically flame-proof, ester-based electrolytes that overcome conventional diffusion limits. By screening a number of fluorinated phosphate and cyclic carbonate candidates, the electrolytes with the comprehensive properties, including the electrolyte desolvation processes, oxidation resistance, and flame retardancy, were successfully designed and synthesized, thereby realizing intrinsic flameproofing with fast-charging capability. Impressively, our optimized electrolytes sustain over 98% capacity retention for 350 cycles at 1.0 C with a Coulombic efficiency of nearly 100% when deployed in Na3V2(PO4)3 (NVP) cells, whereas benchmark carbonate systems fail within a few tens of cycles. By linking the explicit performance descriptors of solvent electronic structure and ion-solvent coordination, this work delivers a rational pathway to flame-proof and high-rate SIB electrolytes, breaking the long-standing diffusion limit and brute-force screening.