Polyrotaxane‐Based Polymer Electrolytes With Selective Na ⁺ Channels for Stable, Long‐Cycling Sodium Metal Batteries

ABSTRACT Sodium metal batteries (SMBs) with polymer electrolytes are promising for high‐energy‐density storage due to high theoretical capacity and low production cost. However, conventional polymer electrolytes suffer from low ionic conductivity, anion‐induced interfacial instability, and uncontrollable dendrite growth. In this study, a crosslinked polyrotaxane based network with selective sodium‐ion transport pathways and physically confined anion domains is designed. The electrolyte features such pathways from PEG and α‐CDs that facilitate directional Na ⁺ migration, while steric and size‐sieving effects can restrict the mobility of counterion, yielding a high ionic conductivity of 2.1 mS cm ⁻¹ at room temperature and an exceptional Na ⁺ transference number of 0.88. Furthermore, molecular dynamics simulations confirm the enhanced Na ⁺ transport kinetics, which stabilize Na plating/stripping and inhibit dendrite formation. Notably, the assembled Na ₃ V ₂ (PO ₄ ) ₃ (NVP) full cells exhibit excellent rate capability and stable cycling performance over 2500 cycles with a high capacity retention of 95.9% at 2.0 C.