Configuration‐Entropy‐Driven Electrolyte with Anion‐Enhanced Solvation Structures for Fast‐Charging Sodium Metal Batteries

Abstract Traditional strong‐solvating electrolytes exhibit high ionic conductivity but are limited by solvent‐dominated solvation structures. The unstable solvent‐derived electrode‐electrolyte interfaces (EEIs) are detrimental to the fast‐charging performance of sodium metal batteries (SMBs). Herein, a configuration‐entropy‐driven electrolyte with diverse solvation structures induced by a strongly solvating anion and cosolvent is proposed to realize a trade‐off between high ionic conductivity and anion‐enhanced solvation structures. The electrolyte possesses 75 types of Na + solvation structure, contributing to its higher solvation configurational entropy (Δ S conf , 33.09 J mol −1 K −1 ) compared to the conventional strong‐solvating ester electrolyte (24.28 J mol −1 K −1 ). The high Δ S conf facilitates ion transport and endows the electrolyte with diverse anion‐coordination solvation structures, which promote the formation of inorganic‐rich and stable EEIs. Therefore, the configuration‐entropy‐driven electrolyte with anion‐enhanced solvation structures can reinforce the stability of Na metal anode and enable superior rate performances and cycling stability of Na||Na 3 V 2 (PO 4 ) 3 (NVP) cells. The modified Na||NVP cells deliver a high capacity retention of 98.2% at an ultrahigh rate of 60 C after 10 000 cycles. Even paired with high‐loading NVP (≈12 mg cm −2 ), the Na||NVP cells steadily operate for over 600 cycles. This work provides a unique insight into electrolyte design from the perspective of solvation configurational entropy.