Ring Strain Engineering of Cyclic Ethers for High-Performance Sodium Metal Batteries

1,3-dioxolane is a promising solvent for low-temperature batteries owing to its low freezing point and low viscosity. However, its tendency toward ring-opening polymerization leads to reduced ionic conductivity and deteriorated electrochemical stability. Here, we establish an electronic-geometric coupling design principle to regulate solvent stability in weak-weak electrolyte systems for sodium metal batteries. A dual-descriptor framework combining ring strain energy (RSE) and a sterically corrected electrostatic descriptor, defined by the lowest negative electrostatic potential normalized by molecular volume (ESP_min/Volume), is introduced to guide cyclic ether solvent design. Following this principle, 2,4-dimethyl-1,3-dioxolane is identified with reduced RSE and moderate ESP_min/Volume, enabling enhanced resistance to polymerization and improved Na-compatibility/ion transport. Molecular dynamics simulations and density functional theory calculations reveal that, the electrolyte forms an aggregate-dominated solvation structure with a high lowest unoccupied molecular orbital level, promoting the formation of a thin, uniform, and inorganic-rich solid electrolyte interphase. Consequently, the electrolyte delivers accelerated interfacial kinetics and stable operation across a wide temperature range. Na||Na symmetric cells cycle stably for 1800 h at room temperature, while Na||Na₃V₂(PO₄)₃ full cells with high cathode loading (20 mg cm^-2) operate for over 200 cycles at 25 °C and more than 900 cycles at -40° C.