Low‐Temperature Carbonization Synthesis of Sulfonic Group Dominated N/S Co‐Doped Carbon for High‐Performance Potassium‐Ion Batteries

The nitrogen/sulfur (N/S) co-doping strategy has gained significant attention in the development of carbon-based anodes for potassium-ion batteries (PIBs) due to its capapcity to enhance specific capacity and accelerate reaction kinetics. Yet, the C─S bond-driven conversion reaction would inevitably induce critical challenges, including poor stability and high charging voltage, thereby severely impeding the commercialization of N/S co-doped carbon anodes. Herein, a novel sulfonic group dominated N/S co-doped carbon (NSAC-600) is synthesized via a facile low-temperature carbonization strategy with coal tar pitch as a precursor. The sulfonic groups in NSAC-600 have strong sulfur-locking ability, that can suppress the formation of potassium polysulfides during K storage. Moreover, the N and sulfonic groups synergistically create abundant active sites for K⁺ adsorption, expand the carbon interlayer spacing, and help to create rapid charge diffusion pathways. Thereby, the NSAC-600 can deliver high-rate performance (217.0 mAh g^-1 at 5 A g^-1), good cycling stability (without any capacity decay after 1400 cycles at 2 A g^-1 and stable operation for 5600 cycles at a high current density of 5 A g^-1) and low depotassium voltage. An "adsorption/intercalation/limited-conversion" mechanism is proposed to elucidate the potassium storage behavior in this novel carbon material. This work may provide a new horizon for advanced N/S co-doped carbon anodes.