Chelation-frustrated molecular design enables diverse solvation structures for wide-temperature sodium metal batteries

The practical application of sodium metal batteries (SMBs) in grid-scale energy storage requires electrolytes that remain stable over a wide temperature range. Although high-entropy electrolytes (HEEs) can improve temperature adaptability by enriching Na⁺ solvation environments through multiple salts and solvents, their complex formulations and high cost hinder practical application. Herein, we report a compositionally simple single-salt and single-solvent electrolyte, 1 M NaPF₆ in 2-(ethoxymethyl) tetrahydrofuran (EMTHF), that achieves diverse solvation structures through chelation-frustrated molecular design. The spatially separated ring and chain ether oxygen sites in EMTHF enable three concurrent Na⁺ coordination modes, namely κ¹-O_ring-coordinated, κ¹-O_chain-coordinated, and κ²-O_ring, O_chain-chelated Na⁺–EMTHF configurations. This diverse yet weakly solvating environment facilitates Na⁺ desolvation and promotes the formation of anion-derived interphases, thereby stabilizing Na anodes. Consequently, Na–Cu cells sustain stable cycling for more than 1000 cycles at 5 mA·cm⁻² and 5 mAh·cm⁻². Na–Na₃V₂(PO₄)₃ (NVP) cells exhibit excellent temperature adaptability, retaining 86.5% of their capacity after 3000 cycles at −20 °C and 72.9% after 300 cycles at 80 °C. Moreover, a Na–NVP full cell assembled with a 70 μm Na anode and an NVP cathode loading of 10 mg·cm⁻² delivered highly stable long-term cycling, with a capacity retention of 97.0% after 1000 cycles. These findings demonstrate that diverse solvation structures can be achieved through rational solvent molecular design, offering a simple route toward wide-temperature SMBs.