Abstract:The mechanical property of electrolytic copper foil used in lithium battery will change rapidly after the formation of copper foil until it becomes stable. The aging process in room temperature showed that：the tensile strength of copper foil attenuation of 42%, and the elongation increased about 1.2-1.4 times, but the changes take place within 36 hours before aging. This may have occurred because the organic additive that participated in the process of electro-deposition is decomposed on the process of aging, the size of grain get bigger, and the grains recrystallized. After the aging treatment, the mechanical property of copper foil is stable, when the customers design the lithium battery and use the copper foil, they can precisely forecast the tensile strength and the elongation of the copper foil which is used inside the lithium battery, to avoid various safety issues that are happened by the changes of the performance of the copper foil.