Gas-expansion strategy for synchronizing high-rate and ultra-stable sodium storage of Fe7S8@NSC anode

Due to its high reversible capacity, Fe 7 S 8 has emerged as a promising anode material for sodium-ion batteries (SIBs). However, its application is limited by slow reaction kinetics and significant volume expansion during the charging and discharging process, resulting in poor rate capacity and reduced cycling stability. To address these issues, a novel high-temperature gas-expansion method is proposed to uniformly incorporate Fe 7 S 8 nanoparticles into N and S co-doped porous carbon (Fe 7 S 8 @NSC). It effectively reduces the volume expansion of Fe 7 S 8 and improves its electron/ion conductivity. As a result, when used as an anode material in SIBs, Fe 7 S 8 @NSC demonstrates excellent rate performance, delivering a capacity of 500.0 mAh/g at a current density of 5 A/g. Additionally, it exhibits remarkable stability, maintaining 99.83 % of its capacity after 600 cycles at the same high current density.