This invention provides an electrolytic additive composition and its application method. The electrolytic additive composition comprises the following components: a dithiopropanesulfonate accelerator; a
polyethylene glycol inhibitor; a
sodium saccharin derivative; a
hydroxamic acid complexation
regulator; and quaternized polyethyleneimine. The method for preparing high-strength electrolytic
copper foil using the electrolytic additive composition is characterized by the following steps: adding the electrolytic additive composition to a
copper sulfate-based
electrolyte and mixing it evenly to obtain an electrolytic working solution; using the electrolytic working solution, performing electrolytic deposition on a
cathode roller to obtain a deposited
copper layer; and sequentially cleaning,
drying, and tension conditioning the deposited copper layer to obtain a high-strength electrolytic
copper foil product that, while maintaining high tensile strength, achieves uniform
grain structure, optimized
residual stress distribution, and inhibits
abnormal grain growth, significantly improving the elongation performance and rolling stability of the
copper foil and reducing the risk of strip breakage.