Dependence of microstructure and mechanical properties of electrodeposited copper foils on electrochemical behavior of sodium saccharin

Electrodeposited copper foils with engineered properties are in high demand as critical components in lithium-ion batteries (LIBs) and printed circuit boards (PCBs). In this study, the effects of sodium saccharin (SAC) on the 9 μm-thick electrodeposited copper foils were systematically investigated. SAC is found to markedly reduce the surface roughness of the copper foils, attaining a minimum Rz value of 0.91 μm. As the SAC concentration increases, the grain size of the copper foils decreases markedly, accompanied by an enhancement in dislocation density. Moreover, the (220) crystallographic texture becomes increasingly pronounced. These microstructural changes induced by SAC collectively contribute to a significant improvement in mechanical performance, with the tensile strength reaching up to 617 MPa. To elucidate the working mechanism of the electrodeposition additive, a series of electrochemical analyses were conducted, revealing that SAC forms complexes with cupric ions, thereby altering the electrochemical reduction kinetics and elevating the electrodeposition overpotential. Furthermore, SAC exhibits a potential-dependent behavior that stems from the imbalance between the consumption and transport rates of cupric ions during the electrodeposition process. These findings shed light on the role that complexing agents play in electrodeposited copper foil production, providing both mechanistic insight and a practical basis for engineering high-performance electrodeposited copper foils.