Rationally regulating pore structures of porous carbon anodes by sulfur-doped carbon coating for high-rate sodium-ion storage

Abstract

Designing porous carbon anodes with high reversible capacity and rate capability is critical for sodium-ion storage. Herein, the pore structure of pitch-derived porous carbon is modified by the sulfur-doped carbon coating, as sodium-ion battery anodes. Firstly, the pitch-derived porous carbon (MP) with a large number of mesopores and macropores was obtained by regulation of the metal-assisted method. Then, these pore structures were designed and modified by filling with sulfur-doped carbon coating through the liquid phase coating method to obtain modified pitch-derived porous carbon (MPSC). The experimental results indicate that the carbon coating reduces specific surface area via a filling effect, enhancing reversible capacity. Meanwhile, 12.45 wt% sulfur doping widens interlayer spacing in both carbon coating and internal pitch matrix, promoting Na⁺ diffusion and creating reversible reaction sites that form a high potential plateau in charge/discharge curves. The MPSC anode exhibits excellent sodium-ion storage performance in a half-cell (293 mAh g⁻¹ at 1 A g⁻¹ after 2000 cycles) and outstanding high-rate performance (167 mAh g⁻¹ at 10 A g⁻¹ after 2000 cycles). This study provides a universal method for rationally modifying the porous carbon anodes to enhance sodium-ion storage performance.