Synergistic Long‐ and Short‐Range Sodium‐Ion Transport Pathways for Enhanced Low‐Temperature Performance in Ceramic‐DEE‐Polymer Electrolytes

Abstract The sluggish movement of polymer chains at low temperatures limits the performance of polymer‐based solid‐state batteries, especially for transporting large sodium ions. This study introduces a synergistic ion transport strategy integrating short‐ and long‐range pathways for enhanced sodium‐ion mobility. Electrospun ceramic nanofibers, modified with acylamino groups, form interfacial transport channels, while deep eutectic electrolytes (DEE) confined within these channels enable temperature‐independent, long‐range ion transport. Surrounding polymer electrolytes facilitate short‐range ion migration between the polymer and DEE. This composite electrolyte achieves high ionic conductivity (0.088 mS cm⁻¹ at −50 °C) and exceptional rate performance up to 20 C. The structure confines the DEE to ceramic fiber interfaces, preventing the formation of a gel‐like state due to DEE‐polymer mixing, and maintaining robust mechanical properties. The DEE interacts with polar groups on both the ceramic fibers and polymer matrix, reducing side reactions with the metal anode and improving cycle stability. The electrolyte retains 92.2% capacity retention at −30 °C after 100 cycles and 97.7% after 1000 cycles at 26 °C, with stable performance over 10 000 cycles at 5 C. This design offers an efficient and stable ion transport pathway for solid‐state sodium‐ion batteries, enabling superior performance even at ultra‐low temperatures.