Binderless Cobalt Oxide Nanoparticle Films Through Electrophoretic Deposition, for Li-Ion Batteries

            Nanoscale materials for Li-ion battery electrodes have received great attention due to their high surface-to-volume ratio and reduced Li-ion diffusion length which results in faster charge/discharge. Nanomaterials also show the ability to accommodate strain through volume expansion without pulverization or capacity fading. In this work we have developed a hollow cobalt oxide NP film for Li-ion battery electrodes that require no additional support materials such as carbon black or polymers to establish good electrical pathways. The colloidal cobalt NPs are prepared by decomposition of organometallic precursors in non-aqueous conditions. The NP film is formed by using electrophoretic deposition (EPD). During EPD, a film is formed on both the cathode and anode but the film on the anode is slightly thicker than that of the cathode, which indicates that more particles are negatively charged. The EPD deposited films are calcined to form hollow cobalt oxide (Co₃O₄) NPs that act as the battery anode. Battery cycling of these anodes show low degradation and are near the theoretical capacity limits for this material. These results are surprising since control experiments made from dropcast films form poor battery contacts under the same calcination and battery-test conditions.