Effects Of Additives On Electrocrystallization Process Of Cu And Cu-Zn Alloys And Preparation Of Porous Copper Foils

With the continuous development of new energy batteries,inductors,and other fields,the performance of electrolytic copper foil has put forward higher requirements.As one of the best candidates for cathode collectors for lithium-ion batteries,porous copper foil is widely favored due to its open porous structure,high specific surface area,excellent thermal conductivity,calenderability and low manufacturing cost.In this paper,strippable Cu-Zn alloy foils were prepared by electrodeposition in a cyanide-free complexation system using ultra-thin copper foil as a carrier,and the preparation of porous copper foil was realized by a two-step chemical dealloying method.This paper systematically studies the electrocrystallization process of copper and Cu-Zn alloys and analyzes the reaction mechanism and characteristics of porous copper foil in detail.The main contents of this paper are as follows:1.The effects of additives such as sodium polydithiopropane sulfonate（SPS）,Cl^-and collagen on the electrocrystallization process of copper ions were studied by electrochemical analysis.The electrocrystallisation of copper in acidic copper sulphate electrolytes is an irreversible reaction under diffusion control and follows instantaneous three-dimensional nucleation,and the additives added to the experiments do not alter this process.When sodium polydithiodipropane sulfonate（SPS）,Cl^-and collagen are added simultaneously to the electrolyte,the number density of copper electrocrystallisation nucleation increases significantly,resulting in incredibly fine grains.This is due to the synergistic effect of additives,which significantly increases the nucleation density of copper electro-crystallization,and realizes the bright surface and fine crystallization of electrolytic copper foil.2.The thesis studies the electrocrystallization mechanism of Cu-Zn alloy in the xylitol complex system,and prepares the Cu-Zn alloy foil with a dense and uniform structure.Xylitol is used as the main complexing agent in the Cu-Zn alloy plating solution.It is concluded that Cu-Zn alloy co-deposition is an irreversible reaction under diffusion control in this system.The initial stage of electrodeposition follows the Scharifker three-dimensional nucleation model and theoretically tends to the instantaneous nucleation mechanism.The reaction rate constants,diffusion coefficients,and nucleation number densities at various potentials of the system were calculated.Based on the xylitol system,the effect of additives on the co-deposition of Cu-Zn alloys was studied,and then crack-free Cu-Zn alloy foils were prepared.3.The Cu-Zn alloy foil is dealloyed by a two-step method,and a porous copper foil with a smooth and uniform surface,a complete,continuous and dense structure,and no cracks on the surface is obtained.The average thickness of the porous layer was tested to be approximately 4-5μm,the overall thickness of the porous copper foil was approximately 11-14μm,the specific surface area could reach 13.6026 m2·g^-1,the pore volume could reach0.02744 cm2·g^-1 and the average pore diameter was 7.4471 nm.