Engineering of Co9S8–CoS nanoparticles encapsulated into N-doped graphitic carbon tubes for high-performance lithium storage

Abstract

Sulfide/carbon composites are promising anode candidates for lithium-ion batteries owing to the synergy of the two components. Their electrochemical performances are highly dependent on their structures. Herein, Co9S8–CoS nanoparticles encapsulated into N-doped graphitic carbon tubes (Co9S8–CoS/NGCT) are synthesized by a controllable in-situ self-assembly method assisted by a freeze-drying process. The hollow carbon tubes with a thin wall have an enough interior void space, which can effectively accommodate the volume expansion and prevent the aggregation of Co9S8–CoS nanoparticles during cycling. Moreover, benefiting from high specific surface area and efficient electron transport pathways, pseudocapacitive-controlled process accounts for a large proportion in the electrochemical lithium storage of Co9S8–CoS/NGCT. As a result, the Co9S8–CoS/NGCT shows a high specific capacity (1004 mAh g−1 at 0.1 A g−1 after 150 cycles), good cycling stability (517 mAh g−1 at 1 A g−1 after 1000 cycles) and excellent rate capability (410 mAh·g−1 at 5 A g−1).