Si film electrodes containing surface-modified Cu current collectors prepared by a low temperature oxidation-reduction process

A low-temperature oxidation-reduction process was used to modify the surface of a Cu current collector (foil) for a Si film electrode. The surfaces of the modified Cu foils were investigated under various oxidation-reduction conditions, and the electrochemical properties of Si film electrodes containing the surface modified foils were evaluated. Various nanostructures were found to have formed on the surface; for example, Cu(OH)2 needles, CuO flowers, and CuO plates formed on Cu-foil surfaces oxidized at 313 K for 1, 10, and 30 min, respectively. Furthermore, these nanostructures were transformed to coral-like Cu2O structures after reduction at 673 K. The amount of Cu2O and the surface roughness decreased on increasing reduction time. The Si film electrode containing a Cu foil reduced for 6 h showed the best electrochemical performance (83.5% of the initial efficiency and 74.8% of capacity retention) due to the small amount of Cu2O and the formation of coral-like structures.