Practical and Versatile Sodium‐Ion Batteries Realized With Nitrile‐Based Electrolytes

An optimized acetonitrile-based electrolyte, characterized by high-voltage tolerance, high ionic conductivity, and anion-enriched solvation structure, fosters the formation of a highly stable solid-electrolyte interphase on hard carbon. This advanced nitrile-based electrolyte enables practical sodium-ion batteries to operate at 4.15 V, support fast charging at 5 C, and perform reliably across a wide temperature range of −60 to 50 °C.

Abstract

Sodium-ion batteries (SIBs) hold tremendous potential in next-generation energy storage. However, no SIB has yet achieved simultaneous support for high voltage, rapid charging, and all-climate adaptability due to electrolyte limitations. This study successfully constructs versatile SIBs using an optimized acetonitrile (AN)-based electrolyte, which offers excellent high-voltage tolerance, high ionic conductivity, anion-enriched solvation structure, and a wide liquidus temperature range. The engineered solid electrolyte interphase (SEI) exhibits low resistance and exceptional stability, effectively supporting fast charging, temperature-adaptive operation, and long-term cycling stability. Consequently, this tailored electrolyte, combined with a robust SEI, enables hard carbon (HC) anodes to achieve a high reversible capacity of 223 mAh g⁻¹ at a fast rate of 5 C. When paired with a high-voltage NaNi_1/3Fe_1/3Mn_1/3O₂ (NFM) cathode, the HC||NFM full cells operate stably at a high cut-off voltage of 4.15 V, sustaining over 1400 cycles at 5 C. Furthermore, a practical 3 Ah pouch cell demonstrates excellent stability, retaining 90.7% of its capacity after 1000 cycles, and shows all-climate adaptability, maintaining 56.4% of its room-temperature capacity at −60 °C and 97.3% retention after 350 cycles at 50 °C. This work provides valuable insights for developing advanced electrolytes for versatile and practical SIBs.