Surfactant-free scalable synthesis of hierarchically spherical Co_3O_4 superstructures and their enhanced lithium-ion storage performances

摘要

Unique hierarchically porous spherical Co_3O_4 superstructures were synthesized via a surfactant-free hydrothermal process followed by a calcination treatment, in which the concentration of reactant cobalt (II) nitrate hexahydrate is a key factor affecting the morphology of products. X-ray powder diffraction, electron microscopies (TEM and SEM), and thermogravimetric analysis were employed to investigate the formation of Co_3O_4 spherical superstructures. Our results suggest that they formed from numerous cubic Co_3O_4 nanocrystals via an oriented attachment mechanism. These superstructures exhibit a high specific capacity of 1750mAhg~(-1) after the first chargedischarge cycle, and the capacity retention remains at a constant of 1600 mA h g~(-1) at 0.2C after 50 cycles. The facile, scalable, energy-efficient and environmentally friendly nature of the presented approach renders it particularly attractive from a technological standpoint. In addition, this scalable and facile synthesis method could be extended to the preparation of other transition metal oxides with specific morphologies and surface textures.