A Novel Sultone‐Based Electrolyte Additive for Ultra‐Long Cycle Life Sodium‐Ion Batteries

ABSTRACT For sodium‐ion batteries, addressing the issue of limited cycle life is crucial for their widespread industrial application, and the electrolyte plays a pivotal role in this context. In this study, a practically viable electrolyte with industrial potential is proposed, introducing sulfone and borate as cooperative electrolyte additives to improve cycling stability. The optimized electrolyte formulation is composed of NaPF ₆ (sodium hexafluorophosphate) dissolved in a mixed solvent of PC (propylene carbonate)/EMC (ethyl methyl carbonate), supplemented with PES (prop‐1‐ene‐1,3‐sultone) and NaODFB (sodium difluoro(oxalato)borate). In this system, the decomposition of PES generates S‐O _x species, which modify the interfacial chemical environment and promote a more complete decomposition of ODFB ⁻ . As a result, B‐ and S‐containing organic intermediates are further transformed into oxygen‐coordinated inorganic species (e.g., B‐O _x and S‐O _x ), which subsequently reconstruct into a crosslinked inorganic interphase. This cooperative interfacial evolution leads to the formation of more uniform, compact, and chemically stable CEI/SEI layers, thereby enabling superior cycling stability. As a demonstration, the Na||NVP (sodium vanadium phosphate) half‐cell retains a specific capacity of 109.8 mAh·g ⁻¹ after 5000 cycles, corresponding to a capacity retention of 96.7%. This work offers valuable insights and experimental support for the large‐scale industrialization of long‐life sodium‐ion battery electrolytes.