A Large Scalable and Low-Cost Sulfur/Nitrogen Dual-Doped Hard Carbon as the Negative Electrode Material for High-Performance Potassium-Ion Batteries

Among the negative electrode materials for potassium ion batteries, carbon is very promising because of its low cost and environmental benignity. However, the relatively low storage capacity and sluggish kinetics still hinder its practical application. Herein, a large scalable sulfur/nitrogen dual-doped hard carbon is prepared via a facile pyrolysis process with low-cost sulfur and polyacrylonitrile as precursors. The dual-doped hard carbon exhibits hierarchical structure, abundant defects, and functional groups. The material delivers a high reversible potassium storage capacity and excellent rate performance. In particular, a high reversible capacity of 213.7 and 144.9 mA h g⁻¹ can be retained over 500 cycles at 0.1 A g⁻¹ and 1200 cycles at 3 A g⁻¹, respectively, demonstrating remarkable cycle stability at both low and high rates, superior to the other carbon materials reported for potassium storage, to the best of the authors' knowledge. Structure and kinetics studies suggest that the dual-doping enhances the potassium diffusion and storage, profiting from the formation of a hierarchical structure, introduction of defects, and generation of increased graphitic and pyridinic N sites. This study demonstrates that a facile and scalable pyrolysis strategy is effective to realize hierarchical structure design and heteroatom doping of carbon, to achieve excellent potassium storage performance.