China Nonferrous Metallurgy

Copper foil is a key material for the negative current collector of lithium-ion batteries. During the electrochemical cycling process, it is subjected to alternating stress, so its tensile strength and elongation have a significant impact on the safety performance and lifespan of lithium-ion batteries. Lithium ion copper foil with both high tensile strength and high elongation has not yet appeared on the market, The 8μm high elongation lithium copper foil with E% ≥14% has a tensile strength below 350MPa at room temperature. This study prepared 8μm thick double-sided lithium battery copper foil with high tensile strength and elongation by introducing two new types of additives, namely thiourea derivative SP and nitrogen-containing organic compound HF, and the process parameters were optimized, the copper foil performance was tested. The main conclusions are as follows. SP-500 has an inhibitory effect on copper ion electrodeposition process, while HF-1000 has a promoting effect on copper ion electrodeposition. Under the conditions of copper ion concentration of 100-120g/L, sulfuric acid concentration of 80-100g/L, electrolyte temperature of 40±5℃, and electrolyte flow rate of 50±5m³/h in the electrolysis process, the dosage ratio of HEC 80mL/min, gelatin 30mL/min, SP-500 20mL/min, and HF-1000 40mL/min can achieve the elongation (E%) of copper foil to 13.95% at high temperature of 190℃/1h, and the tensile strength (T/S) at room temperature to 450.25MPa, with a surface gloss of ≥40. The optimal aging treatment conditions are 70℃/16h, which can minimize the attenuation of the tensile strength at room temperature and elongation at high temperature of copper foil within 60 days, maintaining above 434.21MPa and 13.91%, respectively. This study provides new ideas for the development of high tensile strength and high elongation copper foils, which can further improve the stability of lithium batteries to a certain extent.