Non-Entangled Chains Enable Rapid Na+ Transport Through Ion-Traps in Gel Polymer Electrolytes at Low Temperatures.

Polymer electrolytes are promising for all-climate rechargeable batteries due to their safety and compatibility with high-energy-density battery systems. However, topological traps induced by chain entanglement become a major transport bottleneck limiting continuous ion motion and interfacial charge transfer as temperature and liquid-phase content decrease. Here, we unveil that temperature-dependent ion-traps in the entangled gel polymer are a key factor for slow Na+ transport at low temperatures. Specifically, we propose a low-temperature-tolerant gel polymer electrolyte, denoted as non-entangled poly(1,3-dioxolane) (NPDOL), which promotes sodium bis(trifluoromethylsulfonyl)imide (NaTFSI) dissociation and provides homogeneous coordination sites for continuous Na+ transport. Meanwhile, the non-entangled, high-entropy polymer framework decreases chain relaxation time and expands free volume, thereby reducing the density of ion-traps and enhancing Na+ diffusion kinetics. Furthermore, reduced ion-trap density improves the Na+ transference number (tNa+ = 0.85), resulting in a thin and uniform solid electrolyte interphase (SEI) with improved interfacial Na+ charge-transfer. The NPDOL electrolyte exhibits high ionic conductivity (σ) of 0.25 mS cm-1 at -50°C, enabling Na//NPDOL//Na3V2(PO4)3 full cells to deliver nearly 100% capacity retention at -40°C. This strategy of reducing chain entanglement to suppress Na+ traps widens the low-temperature operational window of batteries, paving the way for high-performance energy storage systems.