Hydrothermal Synthesis of Hierarchical Cage-like Co 9 S 8 Microspheres Composed of Nanosheets as High-Capacity Anode Materials

Co 9 S 8 is considered to be one of the most promising anode materials because of its high theoretical capacity. In this work, hierarchical cage-like Co 9 S 8 microspheres composed of well-crystallized nanosheets are successfully synthesized at 180 °C by a hydrothermal method using KOH and disodium ethylenediamine tetraacetate (Na 2 EDTA) as a mineralizer and a complexing agent, respectively. X-ray diffraction and scanning electron microscopy measurements show that KOH is beneficial in promoting the crystallization and development of Co 9 S 8 , avoiding the formation of impurities, while Na 2 EDTA is conducive to the generation of cage-like microspheres with the micro/nano architecture and better crystallization. The unique hierarchical cage-like micro/nano architecture can effectively relieve the volume change in the cycling process, and the well-crystallized Co 9 S 8 nanosheets in the cage-like microspheres can offer much more active sites for Li + accommodation, and thus the hierarchical cage-like Co 9 S 8 microspheres composed of well-crystallized nanosheets show superior cycling stability and rate capability, e.g., a high capacity of 303.5 mAh g −1 after 1000 cycles at a high rate of 1.0 A g −1 . This work provides a new approach for improving the electrochemical performance of LIBs by constructing a hierarchical anode material.