A Methyl Propionate-Based Electrolyte for Wide-Temperature Sodium-Ion Batteries

High-concentration electrolytes (HCE) with unique anion-rich solvation chemistry have attracted extensive attention for sodium-ion full batteries. Unfortunately, they suffer from unsatisfactory physicochemical properties, which inevitably hinder their practical application. Herein, a trade-off between the physicochemical properties and anion-rich solvation chemistry in HCE is achieved by employing methyl propionate (MP) with moderate coordination ability and low viscosity as the sole solvent. The enhanced ionic conductivity and low viscosity of the MP-based HCE significantly enhance ion transport efficiency and electrode wettability, whereas the anion-rich solvation chemistry promotes the formation of robust electrode–electrolyte interphase, which effectively suppresses transition metal dissolution and continuous electrolyte decomposition as well as accelerates the interfacial ion transport kinetics. As a result, the Prussian blue||hard carbon (PB||HC) full cell shows an enhanced rate performance and cycling stability at a wide temperature range of −20–100 °C. This work highlights the importance of solvent coordination ability in electrolyte design for sodium-ion batteries.