Mesoporous cobalt oxide film prepared by electrodeposition as anode material for Li ion batteries

A mesoporous cobalt oxide (CoO) film has been successfully prepared by electrodeposition using surfactant Brij 56 as the structure-directing agent. The scanning electron microscopy and transmission electron microscopy results indicate that the as-prepared CoO film has a highly porous structure constructed by many interconnected nanoflakes with a thickness of about 20 nm. The CoO flakes with continuous mesopores ranging from 5 to 10 nm arrange vertically to the substrate, forming a net-like structure and leaving pores of 30–250 nm. As anodes for Li ion batteries, the porous CoO film exhibits higher coulombic efficiency, weaker polarization and better cycling performance, compared to dense CoO film. The specific capacity after 50 cycles for the porous CoO film electrode is 509 mAh g⁻¹ at 1C rate, much higher than that of dense film (283 mAh g⁻¹). The better electrochemical performances of the porous film are attributed to its highly porous morphology, which shortens the Li ion diffusion paths within the bulk of CoO and relaxes the volume change caused by the reaction between CoO and Li ion.