Defect engineering of porous carbon with high N/S doping for potassium ion storage

The primary research challenge concerning K-ion batteries revolves around ensuring their optimal cycle stability and specific capacity, particularly the inherent sluggish kinetics induced by the relatively large radius of K⁺. In this study, we report a pore-size controllable synthetic approach employing salt-template precursors. Herein, nitrogen and sulfur co-doped porous carbon materials with rich carbon defect engineering was synthesized through the salt template method, where the doped heteroatoms can both offer a lot of carbon defect content and redox active sites that are helpful for enhancing potassium ion storage kinetics. As a result, the electrode with abundant doping atom content realizes a good capacity and long cycle lifespan (274.8 mA h g⁻¹ after 200 cycles at 0.05 A/g). Inspiringly, PIHCs assembled by N/S co-doped carbon anode exhibit excellent cycling stability (93.4 % capacity retention for 1000 cycles) and a high energy density of 141.2 Wh kg⁻¹ and a power density of 1.6 kW kg⁻¹. Importantly, the density functional theory calculation combining electrochemical kinetic analysis further demonstrates that role of N and S doping plays dominant roles in total storage mechanism. This work gives a deep insight about the roles of external defects in doping carbon materials for potassium storage.