N, S Co-Doped Carbon Derived From Lignosulfonate Sodium Synergized With Bismuth for Enhanced Sodium-Ion Storage

Developing high-performance anode materials is crucial for advanced sodium-ion batteries. Bismuth (Bi)-based anodes offer high capacity but suffer from significant volume expansion. To address this, we synthesized Bi particles embedded within an N, S co-doped porous carbon matrix (Bi@NSC-x) using biomass-derived sodium lignosulfonate. The optimal Bi@NSC-600 electrode demonstrates exceptional performance with a high reversible capacity of 324.3 mAh g^-1 at 0.1 A g^-1, outstanding rate capability (313.1 mAh g^-1 at 20 A g^-1, 268.8 mAh g^-1 at 50 A g^-1), and remarkable long-term stability (retaining 300.3 mAh g^-1 after 4800 cycles at 1 A g^-1 and 296.9 mAh g^-1 after 5600 cycles at 5 A g^-1). Moreover, a full cell with a Na₃V₂(PO₄)₃ cathode delivers 107.9 mAh g^-1 at 0.5 C and maintains 84.4 mAh g^-1 after 2300 cycles at 10 C. The superior performance stems from the synergistic effect in which the heteroatom-doped carbon framework enhances conductivity and Na⁺ adsorption, while its porous structure confines Bi particles, buffering volume changes and facilitating efficient ion/electron transport.