Fabrication of Porous Carbon with Controllable Nitrogen Doping as Anode for High‐Performance Potassium‐Ion Batteries

Abstract Potassium‐ion batteries (PIBs) are a potential alternative for lithium‐ion batteries (LIBs) due to the abundant reserves of potassium and the low redox potential of K + /K. Nonetheless, the practical application of PIBs is hampered by the fact that K + has a large ion radium and cannot smoothly and reversibly insert/extract into the existing electrode materials. Herein, a series of nitrogen‐doped porous carbon materials with varied N content are synthesized and the effect of nitrogen content on the performance of PIBs is investigated. It is demonstrated that the N content is not in direct proportion to the K‐storage capacity of porous carbon considering the irregular change of specific surface area. Porous carbon with 12.44 at% N content (NPC‐2) exhibits the best performance among the synthesized samples on account of its large specific surface area associated with the superior porous structure as well as abundant defects. It delivers a high reversible capacity of 385 mAh g −1 at 0.05 A g −1 , remarkable rate performance of 218 mAh g −1 at 2 A g −1 , and long‐term cycling stability maintaining 242 mAh g −1 after 800 cycles at 0.5 A g −1 . The quantitative kinetics analysis verify that the K‐storage mechanism is mainly dominated by surface‐driven capacitive controlled process, which explains the superior rate capability. The theoretical simulation of different types of nitrogen adsorption and density of states (DOS) prove that pyridinic‐N and pyrrolic‐N exhibit higher affinity to K atoms and thus N‐doping is beneficial to the adsorption of K + on the surface of electrode. This work provides a basic reference for the subsequent development of carbon anode materials for potassium‐ion batteries.