Si film electrodes with surface-modified Cu current collectors for micro Li batteries

Abstract

Si film electrodes were fabricated on surface-modified Cu current collectors using an oxidation-reduction process. Flower-like nanostructures (FLNSs) with diameters of 2–3μm and plate-like nanostructures (PLNSs) with lengths of 1μm were formed on the Cu foil oxidized at 423K for 0.5h, but only the PLNSs remained after sonication. Reduction of the preoxidized Cu foil at 673K resulted in the formation of plate-like and coral-like nanostructures on the Cu foils reduced for 1 and 3h and a smooth surface without specific structures on the Cu foil reduced for 6h. The best electrochemical properties in terms of the first columbic efficiency (85.4%) and the cycle performance (67.3% at 50 cycles) were obtained from the Si film electrode fabricated on the Cu foil that had been reduced for 3h because the coral-like nanostructures on the Cu foil enhanced the adhesion of the Si film and improved the structural stability of the Si film electrode during the electrochemical reactions.