Abstract
Sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) are potential cost-effective electrochemical energy storage devices for future grid-scale energy storage. However, the limited capacities of carbonaceous anodes hamper their commercial development. Edge-nitrogen doping has been demonstrated as an effective strategy to enhance the reversible capacities of carbonaceous anodes. In this work, we demonstrate a general strategy to synthesize three-dimensional high edge-nitrogen doped turbostratic carbons (3D-ENTC) through catalytic pyrolysis of graphitic carbon nitride, which is enabled by metal cyanamides. The 3D-ENTC exhibits a three-dimensional carbon nanosheet framework with a high edge-nitrogen doping level of 18.9 at% and a total nitrogen doping level of 21.2 at%. Further, 3D-ENTC displays high capacities of 420 and 403 mA h g−1 at a current density of 50 mA g−1, high rate capabilities, and superior cycling stability when used as the anodes of PIBs and SIBs, respectively. The different charge storage mechanisms of 3D-ENTC anodes in PIBs and SIBs are elucidated by in situ electrochemical impedance spectroscopy. We find that 3D-ENTC stores Na+ ions mainly by adsorption, while 3D-ENTC stores K+ ions by adsorption and intercalation. This work opens a new avenue for designing high edge-nitrogen doped carbon anodes for SIBs and PIBs.
Catalytic pyrolysis enables high edge-nitrogen doped carbon by annealing g-C3N4 and ZnO. The carbonization mechanism of g-C3N4 was uncovered using multiple techniques. The highly edge-nitrogen doped 3D-ENTC electrode shows remarkable performance towards Na and K ion storage. This work uncovers the different storage behavior of mobile K and Na in amorphous carbon anodes. This work presents a general synthesis strategy for high-edge nitrogen-doped carbon anodes for Na and K ion storage. [Display omitted]
•Catalytic pyrolysis is developed for the synthesis of high edge-nitrogen doped carbon anodes.•Zinc cyanamide acts as the catalyst for retarding the complete decomposition of C3N4.•The obtained carbon anode shows a high edge-nitrogen doping level of 18.9 at%.•The obtained carbon anode shows high performance for Na and K storage.•The different behaviors of Na and K storage are elucidated.