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 at 100 mA g, ultra-long cycle life (840 cycles with a capacity of 244 mAh g at 200 mA g), and excellent rate performance (undergo six consecutive currents changing from 100 to 500 mA g, high capacity 185 mAh g at 500 mA g), 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.