Enhanced Stability of Sodium‐Ion Batteries by Controlling the Synthesis Process of Binary Metal Sulfides

Abstract Binary metal sulfides hold significant promise as anode materials for advanced sodium‐ion batteries (SIBs), but their application is often limited by rapid capacity degradation and slow reaction kinetics. While carbon composites are frequently used to address these issues, the influence of the sequence of carbonization and sulfidation on anode performance has been largely overlooked. To bridge this gap, Co‐Sn sulfides are synthesized through various processes to examine the impact of synthesis methods on material properties. Among these, the one‐step synthesized CSS‐C1 exhibits enhanced sodium‐ion kinetics and excellent stability. It delivers a capacity of 220.4 mAh g −1 at an ultra‐high current density of 20 A g −1 and maintained 389 mAh g −1 over 2300 cycles at 10 A g −1 . When assembled into full‐cell devices (CSS‐C1||Na 3 V 2 (PO 4 ) 3 ), it demonstrates stable capacity retention for over 900 cycles, establishing it as a highly stable and efficient anode material for SIBs.