Trace Anion‐Receptor Chemistry for Stable Carbonate Electrolytes Toward Long‐Life Sodium Metal Batteries

Abstract

Sodium metal batteries (SMBs) offer a promising route toward cost‐effective energy storage, but their operation in carbonate electrolytes is limited by coupled NaPF6 degradation and interfacial instability. Trace moisture triggers salt hydrolysis and HF formation, continuously disrupting SEI/CEI chemistry and aggravating nonuniform Na deposition. Here, lithium 4,5‐dicyano‐2‐(trifluoromethyl)imidazol‐1‐ide (LiTDI) is introduced as a trace anion‐receptor additive to stabilize NaPF6‐based carbonate electrolytes. Spectroscopic analyses and theoretical calculations reveal that LiTDI preferentially scavenges H2O/HF to suppress hydrolysis, while its electron‐rich N sites coordinate with PF6− to weaken Na+‐anion coupling and reconstruct the solvation sheath, reducing aggregated ion pairs from 18.3% to 7.2%. Meanwhile, LiTDI‐derived interfacial reactions promote the formation of a NaF/Na3N‐rich SEI on Na metal and a compact F/N‐enriched CEI on cathodes, enabling homogeneous Na deposition and reduced interfacial polarization. As a result, Na||Na symmetric cells with 0.1% LiTDI achieve stable cycling for 400 h at 1 mA cm−2, while the Na+ transference number increases from 0.417 to 0.603. Na||Na3V2(PO4)3 full cells achieve exceptional durability with 80.36% capacity retention after 2000 cycles at 1 C, with a stabilized Coulombic efficiency of 99.87%. This work establishes a multifunctional anion‐receptor strategy for stabilizing NaPF6‐based carbonate electrolytes and provides a practical avenue toward high‐durability SMBs.