Zwitterionic Polymer Electrolytes With Dipole‐Rotation‐Assisted Ion Conduction for Solid Lithium Metal Batteries

Abstract

ABSTRACT Solid polymer electrolytes are promising for lithium metal batteries, yet achieving both high ionic conductivity and interfacial stability remains a major challenge. Here, we report a molecular rotor strategy that addresses this trade‐off by incorporating 3‐(1‐Pyridinio)‐1‐propanesulfonate zwitterions (PP‐Z) into a polyvinylidene difluoride electrolyte. This design establishes a dipole‐rotation‐assisted ion transport mechanism distinct from conventional polymer relaxation‐dependent conduction. Molecular dynamics simulations and experiments reveal that the anchored cationic group of PP‐Z serves as a pivot, while the mobile anionic end creates a dynamic coulombic field. This configuration facilitates rapid Li + migration through coordinated intrachain transport and interchain hopping, significantly enhancing ionic conductivity (5.1 × 10 −4 S cm −1 at 25°C and 1.5 × 10 −4 S cm −1 at 0°C) and the Li + transference number (0.52). The anionic terminals further participate in Li + solvation and promote formation of a LiF‐rich solid electrolyte interphase, enabling stable cycling for 1200 h in Li||Li cells at 0.3 mA cm −2 and >  500 cycles in Li||LiFePO 4 cells at 1C (25°C). Even at 0°C, the Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 (1.8 mAh cm −2 ) pouch cell retains 85.1% capacity over 50 cycles while delivering 78.3% of its room‐temperature capacity initially.