Noncovalent Interaction-Regulated Polymerizable Deep Eutectic Solvent Electrolyte for Sodium Metal Batteries

Abstract

Sodium metal batteries (SMBs) face significant challenges, including interfacial instability, parasitic reactions, and thermomechanical stresses. To address these issues, we report a polymerizable deep eutectic solvent electrolyte comprising sodium perchlorate (NaClO4), N-isopropylacrylamide (NIPAM), and succinonitrile (SN) that synergistically leverages the plasticity of SN, while NIPAM monomer serves a dual function, facilitating salt dissociation through Na+-carbonyl coordination and establishing a robust polymer matrix via in-situ thermal polymerization. The optimized PDES–1 electrolyte shows a high ionic conductivity of 1.39 mS cm–1 at 30 °C, Na+ transference number of 0.58, and an electrochemical stability window of 5.0 V. These properties enable sodium symmetric cells to achieve stable plating/stripping for over 1000 hours. Furthermore, Na3V2(PO4)3 based cells exhibit rate capability (90 mAh g–1 at 5C) and long-term cycling stability with 90.4% capacity retention (1000 cycles, 2C). A pouch cell powers an LED even in folded and cut states, demonstrating flexibility and safety. Spectroscopic analysis and molecular dynamics simulations reveal that NIPAM-driven noncovalent interactions reorganize the Na+ solvation shell, weakening contact ion pairs and enhancing ion dissociation. This PDES electrolyte offers a practical pathway toward safe, high-performance solid-state SMBs.