Coordination engineering of metal single atom on carbon for enhanced and robust potassium storage

Carbonaceous materials are promising anodes for potassium-ion batteries (PIBs) due to their abundant resources, stable structure, and low cost. However, the limited K+ storage and sluggish kinetics are still major challenges. Herein, on hollow carbon spheres, a Zn single atom (∼12 wt%) was introduced and its chemical coordination was tuned by a facile template method, greatly improving their potassium storage performance. The PIBs with S and N bicoordinated Zn anodes exhibited a high specific capacity, excellent rate capability, and long-term cycling stability, suitable for commercial applications. It was revealed that the Zn single atom can store and release extra charge and improve the reactivity of the attached anions in potassiation and depotassiation. The addition of S modifies the charge density of Zn-N4-S moieties and promotes the K+ adsorption. The single-atom engineering strategy developed by this work opens an avenue for rational design of high-performance carbon materials for PIBs.