1,3,2-Dioxathiolane 2,2-dioxide additive in carbonate-based gel polymer electrolyte enables dual-Interface...

Sodium metal batteries (SMBs) are promising next-generation energy storage systems due to their exceptional theoretical capacity (1165 mAh g^-1) and the widespread availability of sodium. However, heterogeneous sodium deposition triggers irregular solid electrolyte interphase (SEI) formation, intensifies parasitic interfacial reactions, and accelerates persistent SEI deterioration. This study introduces a molecular engineering approach for constructing a novel carbonate-derived gel polymer electrolyte (GPE) system, denoted as THEP (composed of trimethylolpropane trimethacrylate (TMPTMA), 1,6-hexanediol diacrylate (HDDA), ethyl methyl carbonate (EMC), and propylene carbonate (PC)), via in-situ thermal polymerization. By incorporating the functional additive 1,3,2-Dioxathiolane 2,2-dioxide (DTD), we achieve simultaneous optimization of the solvation structure and enhancement of interfacial stability. Experimental characterizations indicate that DTD weakens the coordination between bis (trifluoromethyl sulfonyl) imide (TFSI^-) and Na⁺ and preferentially participates in SEI formation. The optimized electrolyte system containing 5 wt% DTD (THEP-D5) demonstrates significantly enhanced ionic transport properties, with a remarkable ionic conductivity of 4.26× 10^-3 S cm^-1. Na|THEP-D5|Na symmetric cells display ultralong cycling performance, operating stably for 1500 h at 0.1 mA cm^-2. Meanwhile, Na₃V₂(PO₄)₃ (NVP)|THEP-D5|Na cells preserve 82 % capacity after 2000 cycles at 1C (25 °C) and show 83 % capacity retention even at 5C. This work establishes a rational design principle for regulating solvation chemistry and interfacial dynamics, delivering fundamental insights for advancing safe and durable sodium metal batteries.