Additive for high-tensile electrolytic copper foil and preparation method of electrolytic copper foil

The invention provides an additive for a high-tensile electrolytic copper foil and a preparation method of the electrolytic copper foil, and belongs to the technical field of electrolytic copper foils. The additive for the high-tensile electrolytic copper foil comprises two components, namely a composite grain refiner and hydroxyethyl cellulose, wherein the mass concentration of the composite grain refiner is 15-25 mg/L, and the mass concentration of the hydroxyethyl cellulose is 6-10 mg/L. The preparation method of the high-tensile electrolytic copper foil comprises the following steps: preparing sulfuric acid, copper and high-purity water into electrolyte in an electrolytic bath; adding the additive for the high-tensile electrolytic copper foil into an electrolyte; a core is formed and grown on a rotating cathode roller to manufacture an electrolytic copper foil by energizing an anode plate and the rotating cathode roller which are spaced apart from each other in an electrolyte solution in an electrolytic c