Hydrothermal Synthesis of Hierarchical Cage-like Co9S8 Microspheres Composed of Nanosheets as High-Capacity Anode Materials

Co9S8 is considered to be one of the most promising anode materials because of its high theoretical capacity. In this work, hierarchical cage-like Co9S8 microspheres composed of well-crystallized nanosheets are successfully synthesized at 180 °C by a hydrothermal method using KOH and disodium ethylenediamine tetraacetate (Na2EDTA) 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 Co9S8, avoiding the formation of impurities, while Na2EDTA 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 Co9S8 nanosheets in the cage-like microspheres can offer much more active sites for Li+ accommodation, and thus the hierarchical cage-like Co9S8 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.