Study on Mechanical Properties and Microstructural Evolution of Composite Copper Foils Following Long-Term Storage

Composite copper foil, a novel negative electrode current collector developed in recent years, can significantly enhance battery safety and energy density while also conserving metallic resources. It is found that after 9 months of long-term storage, the tensile strength of the composite copper foil decreases by 9.76%, and the elongation rate drops by 26.32%. The internal texture of the composite copper foil shifts from a highly oriented (111) plane to a more random crystal plane orientation and the bonding strength is significantly improved. The study reveals that the residual stress within the copper layer provides the driving force for the changes in the microstructure; the intermediate PET layer plays a buffering and absorbing role in the stress-release process. It regulates the redistribution of stress, promoting the alteration of the copper layer’s texture and the refinement of grains.