Uniform Electron Clouds in Solvation Structures Enable High‐Performance Sodium‐Ion Batteries

Abstract Electrolytes are critical components of sodium‐ion batteries (SIBs), requiring high ionic conductivity, a wide operating temperature range, high voltage capability, and the ability to form an effective interphase. In this study, an ultra‐stable solvation structure is developed, where two triethylene glycol dimethyl ether (G3) molecules are arranged perpendicularly and tightly wrapped around Na⁺. This configuration ensures an even distribution of electron clouds, resulting in high binding energy and small electrostatic potential (ESP) difference, which significantly enhances oxidative and reductive stability. Consequently, the developed electrolyte demonstrates high‐voltage stability exceeding 5 V versus Na + /Na, and the solid electrolyte interphase (SEI) layer is predominantly derived from anion and additive. As a result, electrodes such as hard carbon (HC), Na 3 V 2 (PO 4 ) 3 (NVP), Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 (NFPP) and high‐voltage cathode Na 3 V 2 (PO 4 ) 2 F 3 (NVPF) can cycle stably for over 500 and 1500 cycles with negligible capacity decay at room temperature, and over 500 cycles with 99.2% capacity retention even at −20 °C. Furthermore, they also show a surprising rate performance. Additionally, NVP||HC and commercial NFPP||HC pouch full cell can exhibit a high Coulombic Efficiency (CE) exceeding 99.9% with 89.2% capacity retention after 500 cycles. This work provides an innovative pathway for the development of high‐performance SIBs and other cation‐based batteries.