Highly Glossy Copper Foil Electrodeposition Used As a Negative Electrode of Lithium Batteries

Abstract

Lithium batteries have been an attractive power source for electronic product applications nowadays. The negative electrode material in the lithium battery dominates its discharge-recharge cycles and affects battery performance. Electrodeposited (ED) copper foils with excellent electrical characteristics and a low cost would be a promising candidate to replace rolled copper foils. However, ED copper foils decrease retention rate of capacity when they were used as the negative electrode material of a lithium battery. Therefore, an ED copper foil with a smooth surface on both sides has been developed for the lithium battery fabrication. In this work, 8μm thick ED copper foils were fabricated in a jet flow plating bath at a high temperature and a high current density (i.e., above 30 ASD). The surface roughness (Rz) of both mat and shiny sides is less than 2 μm. To smoothen the shiny side of the ED copper foil, a novel surface modification treatment of cathode were developed. With the pretreatment of the cathodic surface, the shiny side of the ED copper foil exhibited a smooth surface with gloss higher than 350 and a low roughness (i.e., Rz < 2 μm). For the mat side of copper foil, its gloss was higher than 500 and the roughness (Rz) was lower than 1 μm. The copper plating bath contained chloride ions, an accelerator, a suppressor and a leveler. ED copper foils were successfully fabricated with smooth surfaces on mat and shiny sides. As a consequence, large scale ED copper foils (>100 cm2) with very low roughness were fabricated, the ED nucleation was studied and the surface morphologies, roughness and structure orientation of these ED copper foils were characterized by SEM, AFM and XRD, respectively.