Carbon Nitride Transforms into a High Lithium Storage Capacity Nitrogen-Rich Carbon

We describe here the metal-templated transformation of carbon nitride (C₃N₄) into nitrogen-containing carbons as anodes for Li-ion batteries (LIBs). Changing the template from the carbon- and nitrogen-immiscible Cu powder to the carbon- and nitrogen-miscible Fe powder yields different carbons; while Fe templating produces graphitized carbons of low (<10%) nitrogen content and moderate pore volume, Cu templating yields high defect-density carbons of high (32-24%) nitrogen content and larger pore volume. The Li⁺ storage capacity of the high nitrogen content and larger pore volume Cu-templated carbons exceeds that of the more graphitic Fe-templated carbons due to added contribution from Li⁺ insertion/extraction from pores and defects and to reversible faradaic Li⁺ reaction with nitrogen atoms. The Cu-templated carbon annealed at 750 °C delivers the highest specific capacity of 900 mAh g^-1 at 0.1 A g^-1 and 275 mAh g^-1 at 20 A g^-1, while also achieving a 96% capacity retention after 2000 cycles at 2 A g^-1. The fabrication of higher mass loading electrodes (4.5 mg cm^-2) provided a maximum areal capacity of 2.6 mAh cm^-2 at 0.45 mA cm^-2 (0.1 A g^-1), comparable to the capacities of commercial LIB cells and favorable compared to other reported carbon materials.