Ester-ether synergistic interactions regulating the solvation structure of gel polymer electrolytes enable stable sodium metal batteries

Gel polymer electrolytes encounter challenges such as sodium dendrite formation and poor cycling stability caused by interfacial instability in practical sodium metal battery applications. Herein, a synergistic strategy focusing on ion transport behavior regulated by polymer chain design and solvation modulation is proposed. Using vinyl ethylene carbonate (VEC) as a polymerizable monomer, we establish a 3D crosslinked network via ETPTA with short-chain PVEC segments as the structural framework. Concurrently, by strategically leveraging the low polymerization degree of VEC, its residual monomers competitively modulate solvation structures with the G3 co-solvent, thereby optimizing ion conduction mechanisms and interfacial stability. Furthermore, a dual-salt strategy (NaTFSI/NaDFOB) is employed to broaden the electrochemical window and improve ionic conductivity. The optimized TBGV electrolyte achieves a high ionic conductivity of 1.8 mS/cm and exceptional cycling performance. The assembled Na||Na symmetric cell demonstrates stable cycling for 9000 h at 0.1 mA/cm², and the NVP||Na full cell exhibits excellent cycling stability and rate capability, which maintains 111.8 mAh/g discharge capacity at 1 C with 90.2 % capacity retention after 1000 cycles.