Environmental-Friendly and Facile Synthesis of CoO Nanowires and Their Promising Application with Graphene in Lithium-Ion Batteries.

In this work, we developed an eco-friendly strategy for preparing CoO nanowires. The process consisted of two steps: controllable synthesis of metal cobalt nanowires followed by a facile air-oxidization step. The 1D nanowire structure with a high aspect ratio was easily achieved via a magnetic-field-assisted self-assembly of cobalt ion complexes during reduction. After air-calcinations, the CoO nanowires were prepared in large scale and ready to be used as the anode material for lithium-ion batteries. The CoO nanowires, which possessed a length ranging from 3 to 8 μm with the aspect ratio more than 15, exhibited a reversible lithium storage capacity up to ~ 790 mAh/g when using a small amount of defect-free graphene flakes as conductive additives. The superior electrochemical performances were ascribable to the synergistic "flat-on" effect between the 1D nanowires and the 2D graphene. Therefore, the CoO nanowire/graphene composite holds promising application for lithium-ion batteries.