Carbon Dots@rGO Paper as Freestanding and Flexible Potassium‐Ion Batteries Anode

Carbonaceous materials, especially with graphite‐layers structure, as anode for potassium‐ion batteries (PIBs), are the footstone for industrialization of PIBs. However, carbonaceous materials with graphite‐layers structure usually suffer from poor cycle life and inferior stability, not to mention freestanding and flexible PIBs. Here, a freestanding and flexible 3D hybrid architecture by introducing carbon dots on the reduced graphene oxide surface (CDs@rGO) is synthesized as high performance PIBs anode. The CDs@rGO paper has efficient electron and ion transfer channels due to its unique structure, thus enhancing reaction kinetics. In addition, the CDs provide abundant defects and oxygen‐containing functional groups, which can improve the electrochemical performance. This freestanding and flexible anode exhibits the high capacity of 310 mAh g(−1) at 100 mA g(−1), ultra‐long cycle life (840 cycles with a capacity of 244 mAh g(−1) at 200 mA g(−1)), and excellent rate performance (undergo six consecutive currents changing from 100 to 500 mA g(−1), high capacity 185 mAh g(−1) at 500 mA g(−1)), outperforming many existing carbonaceous PIB anodes. The results may provide a starting point for high‐performance freestanding and flexible PIBs and promote the rapid development of next‐generation flexible batteries.