Reconfiguring Polymer Chain for Regulating Na+ Solvation Structure in a Gel Polymer Electrolyte toward Sodium Metal Batteries

Abstract

Gel polymer electrolytes (GPEs) instead of liquid electrolytes can greatly improve the lifespan and safety of sodium metal batteries (SMBs). However, inferior interface stability against Na metal and sluggish reaction kinetics restrict their practical use. Herein, a cross-linked GPE (c-GPE) is proposed by in situ copolymerization of ethoxylated trimethylolpropane triacrylate (ETT) and trifluoroethyl methacrylate (TM) in a liquid electrolyte. The uniquely fabricated c-GPE exhibits impressive ionic conductivity, a wide electrochemical window, low flammability, and favorable Na metal compatibility. Particularly, the functional copolymer chain regulates the Na⁺ solvation structure with lower desolvation energy by a strong cation-dipole (in polymer) interaction. Consequently, full cells based on the Na₃V₂(PO₄)₃ (NVP) cathode (NVP|c-GPE|Na) display an ultralong cycle life (>3000 cycles), remarkable rate capability (up to 15C), and wide temperature adaptability. The work offers new insight into constructing a Na⁺ coordination environment, achieving more facile desolvation by the polymer chain design of the GPE used for developing advanced SMBs.