High-Level Pyridinic-N-Doped Carbon Nanosheets with Promising Performances Severed as Li-Ion Battery Anodes

Defects engineering is recognized as one promising strategy to enhance the electrochemical performance of carbon materials applied in energy storage field. Different from the commonly used methods, high-level N-doped carbon nanosheets are synthesized in this work via controllable removal of nitrogen atoms from nitrogen-rich graphite carbon nitride (g-C₃N₄). The nitrogen doping levels and the relative amount of variable nitrogen types, including pyridinic-, pyrrolic-, and graphitic-N, are easily engineered for the obtained carbon nanosheets. Ultrahigh pyridinic-N content as high as 19.1 at% is achieved, closing to the highest values among the reported nitrogen-doped carbon materials. Extraordinary initial discharging capacity of 5190 mAh g⁻¹ at a current density of 50 mA g⁻¹ and excellent cycling stability (1639 mAh g⁻¹ after 200 cycles) as well as promising rate performance (517 mAh g⁻¹ at 2 A g⁻¹) are demonstrated when serving as Li-ion battery anodes. The high nitrogen doping level, especially for the high pyridinic-N doping content in materials, is responsible for these outstanding electrochemical Li-ion storage performances. This work opens a new gateway to develop promising nitrogen-doped carbon materials for the practical application in energy storage devices.