Hierarchically Structured Nitrogen-Doped Carbon Microspheres for Advanced Potassium Ion Batteries

Because of their unique properties, microstructured carbons have received widespread attention in various fields, such as energy storage, medicine, and biosensors. In this study, hierarchically structured nitrogen-doped carbon microspheres (CMSs) are synthesized for use as electrodes in a potassium ion battery (PIBs). Compared to traditional carbon nanomaterials, the CMSs possess rich internal structure, which not only provide additional active sites and better electron transport but also mitigate the volume expansion related challenges caused by potassium ion intercalation. As the anode material for PIBs, the CMSs could deliver high reversible discharge capacities of 328 and 125 mAh g^–1 at 100 and 3000 mA g^–1, respectively. Moreover, the CMSs anodes also exhibit durable cycling performance with a remaining capacity of 136 mAh g^–1 even after 10000 cycles at a high current density of 2000 mA g^–1. Notably, a full cell assembled with the CMSs anode and an organic cathode exhibits excellent electrochemical characteristics with 78% capacity retention after 1900 cycles at 500 mA g^–1, and high energy and power densities of 141Wh kg^–1 and 4382 W kg^–1, respectively. Considering the rich microstructure of CMSs and their facile synthesis method, this study delineates the merits of employing CMSs in battery applications over other electrode materials.