Hierarchical Self-Supported Carbon Nanostructure Enables Superior Stability of Highly Nitrogen-Doped anodes

As the primary anode for both lithium- and sodium-ion batteries, carbonaceous anodes store more energy and own a higher rate capacity through nitrogen doping. Nevertheless, achieving a high nitrogen content in a carbonaceous anode is challenging because it tends to result in anode instability, owing to high-level structural defects. Here, by doping biotic ispaghula with nitrogen from melamine through hydrothermal and carbonization treatments, we design and prepare a nitrogen-enriched carbonaceous anode with a record-high 30 % nitrogen content primarily in pyridinic and pyrrolic forms. The anode owns a self-supported architecture that contains a highly-defected (I_D : I_G=1.34) nanosheet structure sandwiched and supported with carbon nanospheres. Through surface defects, Li and Na ions are stored and transported efficiently in both highly doped graphitic carbon and amorphous carbon. In situ Raman spectroscopy reveals that amorphous carbon can be crystallized in the Li storage process to contribute reversible capacity. The highly doped anode delivers capacities of 551 mAh g⁻¹ for 500 cycles for lithium storage and 278 mAh g⁻¹ for 2000 cycles of sodium storage at a current density of 1 A g⁻¹, surpassing those of the-state-of-the-art at an identical current density and with the same cycle number.