N/S Co-Doped Graphene Aerogels as Superior Anode Materials for High-Rate Lithium-Ion Batteries

Abstract

The nitrogen and sulfur co-doped graphene aerogel (SNGA) was synthesized by a one-pot hydrothermal route using graphene oxide as the starting material and thiourea as the S and N source. The obtained SNGA with a three-dimensionally hierarchical structure, providing more available pathways for the transport of lithium ions. The existing form of S and N was regulated by changing the calcination temperature and thiourea doping amount. The results revealed that high temperature could decompose −SO_X− functional groups and promote the transformation of C−S−C to C−S, ensuring the cyclic stability of electrode materials, and increasing the thiourea dosage amount introduced more pyridine nitrogen, improving the multiplicative performance of electrode materials. Benefiting from the synergistic effect of sulfur and nitrogen atoms, the prepared SNGA showed superior rate capability (107.8 mAh g⁻¹ at 5 A g⁻¹), twice more than that of GA (52.8 mAh g⁻¹), and excellent stability (232.1 mAh g⁻¹ at 1 A g⁻¹ after 300 cycles), 1.85 times more than that of GA (125.6 mAh g⁻¹). The present study provides a detailed report on thiourea as a dopant to provide a sufficient basis for SNGA and a theoretical guide for further modifying.