The influence of crystal growth mechanism based on various sulfur sources on the morphology, component and electrochemical performance of cobalt sulfide as anode material for sodium-ion batteries

Abstract

Cobalt sulfides (CoS x ) have been paid lots of attention as promising anode candidates for sodium-ion batteries owing to their merits of high theoretical capacity, good electrochemical reversibility and superior thermal stability. However, the preparation of cobalt sulfide with the excellent rate capability and long-term cyclic stability is still a great challenge. Herein, we have prepared cobalt sulfides by one-step solvothermal method using four sulfur sources including sodium thiosulfate, thioacetamide, thiourea and L -Cysteine, respectively. And the mechanism of the bond energies and groups of sulfur source molecules influence the crystal growth process are studied. Moreover, the four cobalt sulfides with different components, morphologies and structures are tested and analyzed as the anode materials for sodium-ion batteries (SIBs). The CoS x using sodium thiosulfate as the sulfur source achieves an excellent cycling performance, which still has a capacity of 690.0 mAh g −1 after 1000 cycles at 2 A g −1 with the retention of 98.1% and an outstanding rate capability of 626.6 mAh g −1 at 5 A g −1 . This superiority may be attributed to its pure component cobalt disulfide (CoS 2 ) with abundant active sites and the unique morphology leading to the high material utilization. Our studies give a clear evidence that sulfur sources play an important role in the crystal growth and constructing high-performance sulfide-based anode materials. • Cobalt sulfides were prepared by solvothermal method with different sulfur sources. • The bond energies and amino group of sulfur sources play an important role in the cobalt sulfide crystal growth mechanism. • The phase components and micromorphologies of cobalt sulfides are influenced by the species of sulfur source. • A high-performance cobalt sulfide is obtained with 626.6 mAh g −1 at 5 A g −1 and 690.0 mAh g −1 after 1000 cycles at 2 A g −1 .