FeS/C 3D nanostructures constructed by carbothermal reduction of lignin to restrain polysulfides shuttle effect towards high-performance sodium-ion batteries

Transition metal sulfides (TMSs) serve as promising anode materials for sodium-ion batteries (SIBs) because they offer high theoretical capacity, suitable intercalation voltage and abundant resources. However, the large sodium ion radius induces significant volume expansion and pulverization, resulting in slow kinetics and short cycle life. Additionally, polysulfides formed during cycling trigger “under-voltage failure” and capacity degradation, limiting their practical application. To overcome these challenges, we employ the complexation of Fe 2+ ions with hydroxyl groups in ammoniated lignin to generate amorphous spherical intermediates. Then, we synthesize FeS/C anode materials through pyrolysis-induced carbothermal reduction, where lignin-derived carbon acts as a reducing agent to convert Fe 2 O 3 (formed from FeSO 4 pyrolysis) into FeS. The FeS/C nanospheres are encapsulated by carbon shells and integrated into a 3D macroporous carbon matrix, effectively mitigating FeS volume expansion and polysulfide shuttling. The optimized FeS/C-31 anode demonstrates excellent performance, delivering a high specific capacity of 562.6 mAh g −1 at 0.1 A g −1 and maintaining 382.2 mAh g −1 at 20 A g −1 . It also exhibits outstanding cycling stability, with a capacity retention of 92.3 % after 1000 cycles at 10 A g −1 .This study presents a sustainable and scalable method for producing FeS/C anodes from industrial lignin waste, offering a practical solution for next-generation SIBs.