Preparation Of Low-profile Electrolytic Copper Foil For Li-ion Battery And Surface Treatment Process Research

Fabrication of low profile ultra-thin electrolytic copper foil for Li-ion batteries had been studied in this thesis. The effects of gelatin(G), thiourea(TU), polyacrylamide(PAM), hydroxyethyl cellulose(HEC), and other additives addition, added individually and compound on properties of copper foil were systematically analyzed. The plating of passivation layer of Zn-Ni in Cr-Zn-Ni-H system was optimized by means of experiments. Effects of annealing within the range of 160-240℃ and natural aging on mechanical properties of copper foil were studied. The chemical polishing and electrochemical polishing process of copper foil were also explored.The experimental results showed that organic additives could suppress the electro-crystallization process and contribute to obtaining dense and smooth surface. Among those additives, G had the best effect. Under the condition of compound addition of G, TU and HEC, the 9um thick copper foils with optimum properties was produced. The tensile strength of 371 MPa, elongation ratio of 3.5%, and the matte surface roughness Rz of about 2.0 um were obtained.After being plated the Zn-Ni layer in the solution containing Zn2+ 25 g/L, Ni2+ 4 g/L under a current density of 200 A/m2 for 5-10 s, the copper foil with thickness of 9 um could obtain good corrosion resistance and high temperature mechanical property. The optimum parameters for obtaining best electrochemical passivation in Cr-Zn-Ni-H system were: Cr+6 1 g/L, Zn2+ 1 g/L, Ni2+ 6 g/L, current density of 200 A/m2. The copper foil could remain non-discoloration at 200℃ for 15 min after being plated.Annealing could remarkably reduce the tensile strength of copper foil. And the tensile strength decreased obviously with the increasing holding time. However, annealing could improve the elongation of copper foil. The natural aging could also reduce the tensile strength but had little effect on the elongation of copper foil.When using the H2SO4-H2O2-acetic acid system for chemical polishing of copper foil, the best content of H2SO4, H2O2, and acetic acid contents were 80,300,100 ml / L, respectively. The copper foil could obtain the optimum polishing quality by adding BTA, SDS and EDTA ? 2Na simultaneously. The shiny and smooth surface with the matte side roughness of about Rz 1.8-2.0 was obtained. The roughness difference between the matte side and shiny side was reduced significantly. When using the phosphoric acid- ethanol system for electrochemical polishing, the polishing effect of copper foil was obtained in the solution containing 80% phosphoric acid. The bright and smooth surface with the matte side surface roughness of about Rz1.7 was obtained, when the contents of BTA, SDS, EDTA ? 2Na, G were 1.5, 0.6, 1, 0.2- 0.8 g/L, respectively.