Ultrafast Potassium Storage in F-Induced Ultra-High Edge-Defective Carbon Nanosheets.

Carbonaceous materials have been considered as promising anodes for potassium-ion batteries (PIBs) because of their high electronic conductivity, eco-friendliness, and structural stability. However, the small interlayer spacing and serious volume expansion caused by the repeated insertion/extraction of large K-ions restrict their potassium-ion storage performance. Herein, F and N codoped carbon nanosheets (FNCS) with rich-edge defects are designed to resolve these problems. The F doping is in favor of the formation of more edge defects in the carbon layer, offering strong K+ adsorption capability and promoting the K+ storage. The ultrathin carbon nanosheets can provide a large contact area for the electrochemical reactions and shorten the transportation pathways for both K-ions and electrons. Consequently, the FNCS anode shows a high reversible capacity (610 mAh g-1 at 0.1 A g-1) and ultrastable cyclability over 4000 cycles at 5 A g-1. Moreover, K-ion full cells (FNCS|K2FeFe(CN)6) display excellent cycling stability (128 mAh g-1 at 1 A g-1 after 500 cycles) and rate capability (93 mAh g-1 at 20 A g-1). This design strategy can be extended to design other electrode materials for high-performance energy storage, such as magnesium-ion batteries, supercapacitors, and electrocatalysis.