Insights into Synergistic Effect of g-C3N4/Graphite Heterostructures for Boosting Sodium Ion Storage with Long Cycle Stability

Sodium-ion batteries (SIBs) have attracted significant attention as promising next-generation energy storage devices. However, the research and development of SIBs are still in their infancy due to the lack of suitable high-performance anode materials. As a commercial anode material for lithium-ion batteries (LIBs), graphite often shows a low sodium storage capacity. Herein, a graphite heterojunction material was prepared through a facile ball-milling method. During the ball-milling process, a defect-enriched g-C3N4/graphite heterojunction was formed and the nitrogen-containing functional groups were regulated, which promoted the sodium storage capacity. The resulting g-C3N4/graphite electrode can exhibit excellent long cycle stability and rate performance, delivering a high reversible capacity of 202 mAh g–1 at 1.0 A g–1 after 6000 cycles and 90.06 mAh g–1 at 5.0 A g–1 after 10000 cycles. Moreover, an ultrahigh rate capability can also be obtained at 1.0 A g–1 with a capacity of 111 mAh g–1. The superiority of heterostructures for sodium storage and diffusion was proved via DFT calculations, which verified the synergistic effect between graphite and g-C3N4. This study provides a simple and efficient method for preparing g-C3N4/graphite heterostructures as well as a deep insight into the sodium storage mechanism of a heterostructure anode.