New strategy to the controllable synthesis of CuInS2 hollow nanospheres and their applications in lithium ion batteries

A new strategy has been presented to the controllable synthesis of CuInS2 hollow nanospheres based on the Cu2O solid nanospheres as the precursor in the absence of any surfactant. Specifically, the CuInS2 hollow nanospheres result from hydrothermal transformation of the intermediate Cu7S4 hollow nanospheres derived from Cu2O solid nanosphere precursor by the Kirkendall effect in the conversion process. The CuInS2 hollow nanospheres with diameters of about 250 nm are assembly of nanoparticles with an average size of 20–30 nm. The composition, structure, and morphology of the Cu2O precursor, the Cu7S4 intermediate, and final CuInS2 product have been, respectively, characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) with selected area electron diffraction (SAED). Different from investigation of photovoltaic properties, in this work, the as-prepared CuInS2 hollow nanospheres have been explored as anode materials for rechargeable lithium ion batteries. They deliver a large initial discharge capacity of 1144 mAh g−1 and exhibit good cycle performance with a discharge capacity of 265 mAh g−1 after 20 cycles, which are superior to those of CuInS2 nanoparticles. The suitable surface area and relatively stable structure of the CuInS2 hollow nanospheres play an important role in their enhanced electrochemical performance as anode materials.