Sulfur-modified needle coke-based carbon anode synthesized by molten salts medium for high-capacity sodium ion batteries

Needle coke-based carbon is a promising anode candidate for sodium ion batteries, but its application is restricted by limited capacity and cycling performance. To address these problems, a sulfur-containing carbon composite (SCS-P) derived from needle coke is fabricated using molten salts as a medium, which generates closed pores to confine sulfur, thereby enhancing the electrochemical properties. Meanwhile, to prevent corrosion of the Cu current collector due to side reactions with sulfur, a carbon-coated Cu foil is used as the current collector to construct SCS-P/C. Consequently, SCS-P delivers a high reversible capacity of 505.4 mAh g⁻¹ and an ICE of 74.98%. Even though the carbon-coated Cu foil is employed to effectively suppress Cu corrosion, the resulting SCS-P/C electrode maintains a similarly high capacity and ICE to SCS-P. Moreover, the full-cell NVP||SCS-P/C retains 58.1 mAh g⁻¹ at 1 A g⁻¹ after 300 cycles. This work demonstrates that the introduction of heteroatoms through molten salts, combined with an optimal current collector, is an effective design for achieving a high-capacity and durable sodium-ion battery anode.