Ultrathin carbon nanosheets with carbon composite structure of amorphous carbon and pseudo-graphite domains for high-capacity, stable and fast potassium storage

Although great progress has been made in carbon anodes for potassium-ion batteries, the development of advanced carbon anodes with fast reaction kinetics and high cycle stability is still a great challenge due to the large radius of K+ (0.138 nm). In this work, novel ultrathin carbon nanosheets (UCNs) fabricated by vaporinduced bubbling strategy are reported to address current challenge. The results show that the UCNs are composed of 3D interconnected 30 nm-thick sheet units with well-developed hierarchical micro-/meso-/macropores, which can not only increase the contact area between electrode/electrolyte, but also effectively buffer the volume expansion caused by the (de)potassiation. In addition, UCNs have a carbon composite structure of intertwined pseudo-graphite domains and amorphous carbon domains, providing abundant storage active sites and fast transport channels for K+. Specifically, the UCN-1300 delivers a K+ storage capacity of approximate to 350 mAh g-1 at a current density of 0.05 A g-1. Moreover, it presents excellent cycle stability, maintaining a capacity of 120 mAh g-1 after 5000 cycles at a current density of 5 A g-1, with a capacity retention rate of more than 99%. In prior reports, carbon anodes demonstrating such a high K + storage capacity and outstanding cycle stability are rarely obtained.