A Quasi‐Solid‐State Polyether Electrolyte for Low‐Temperature Sodium Metal Batteries

Abstract Taken the unlimited Na reservoir worldwide, battery technology based on Na‐ion chemistry poses as an ideal candidate for large‐scale energy storage systems. Especially, with metallic Na replacing traditional carbon anodes, it's able to maximize the energy density inexpensively. Nevertheless, sodium metal batteries (SMBs) face intrinsically poor stability due to their highly‐reactive nature, where low Coulombic efficiency and short lifetime are often witnessed. The situation can be further aggravated at low temperatures due to insurmountable kinetic barriers. Herein, a 1,3‐dioxolane‐based quasi‐solid‐state electrolyte (PDGE) is proposed with a high ionic conductivity of 3.68 mS cm⁻¹ even at −20 ^◦C for SMBs. Moreover, a weak solvation environment is tailored by PDGE, which possesses a high Na⁺ transference number of 0.7. Concurrently, the solid electrolyte interphase induced from PDGE presents inorganic Na₂O, NaF as the major components, which offers accelerated Na⁺ diffusion and superior stability upon long‐term cycling. With such a quasi‐solid‐state electrolyte, the Na/Na₃V₂(PO₄)₃ full cell exhibits great stability over 1000 cycles at −20 ^◦C. This study has significant implications to the development for SMBs under low‐temperature conditions.