Moderately cross-linked sulfonate ester functionalized poly(1,3-dioxolane) electrolyte toward stable long-cycling wide-temperature sodium-ion batteries

Sodium-ion batteries are promising candidates for large-scale energy storage applications. Nevertheless, conventional linear poly(1,3-dioxolane) (PDOL)-based electrolytes suffer from severe chain degradation, poor low-temperature ion conduction and unstable electrode interfacial properties, which severely limit their practical commercialization. Herein, ethylene sulfate and pentaerythritol bis(cyclic sulfate) are employed as functional modifiers to construct a three-dimensional cross-linked A2-DTD-TDT polymer electrolyte. The sulfonate ester groups work synergistically with Al³⁺ to regulate ring-opening polymerization, forming stable network architecture that effectively restrains structural deterioration and recrystallization at low temperature. The optimized electrolyte achieves a high ionic conductivity of 0.76 mS cm⁻¹ and a high Na⁺ transference number of 0.89 at -20 °C, with an expanded electrochemical stability window up to 4.79 V, and enables stable Na⁺ transport and electrode-electrolyte interfaces across a wide temperature range of -40 to 55 °C. Benefiting from optimized solvation configuration and robust inorganic-rich SEI film, the assembled Na||Na symmetric cells achieve stable cycling for >6000 h at -40 °C. This work proposes a reliable modification strategy for developing wide-temperature and high-performance PDOL-based polymer electrolytes, and provides new insights into the structure-performance relationship of advanced sodium-ion battery electrolytes.