General Polyethyleneimine-Mediated Synthesis of Ultrathin Hexagonal Co3O4 Nanosheets with Reactive Facets for Lithium-Ion Batteries

Ultrathin hexagonal Co3O4 nanosheets with exposed reactive facets and porous architectures are synthesized by using a polyethyleneimine (PEI)-mediated hydrothermal strategy. Characterization of the material indicates typical Co3O4 nanosheets of hexagonal shape that are approximately 100 nm in side length and 15 nm thick. PEI plays crucial roles in the synthesis of hexagonal Co3O4. The effects of the reaction conditions on the precursor morphologies and dimensions are investigated to understand the various roles of PEI. Electrochemical tests reveal the superior performance of ultrathin hexagonal Co3O4 nanosheets, including a remarkable specific capacity (e.g. 1007 mAhg(-1) at 100 mAg(-1) and 858 mAhg(-1) at 500 mAg(-1)), excellent cyclability (e.g. capacity retention: 96-99%), and a high rate capability. The improved performance is attributed to the combined effects from the high percentage reactive facets as well as the ultrathin and porous structures. This synthesis strategy can be extended to fabricate other anode materials for lithium-ion batteries.