COPPER FOIL HAVING EXCELLENT HEAT RESISTANCE PROPERTY

Electrodeposited copper foils are described having improved thermal properties. The copper foils include a drum side and deposited side where both sides have a roughness Rz lower than 2 μm and wherein, when the electrodeposited copper foil is subjected to a thermal gravimetric analysis (TGA), the electrodeposited copper foil exhibits a primary weight increase of 105 wt. % when a primary temperature (T) is reached during the TGA, wherein the Tis in a range of 350° C. to 501° C. The TGA characterization comprises heating at a rate of 5° C./min and an air flow at a rate of 95 mL/min. Ultrasonic welding of the copper foils to nickel foils provides an excellent weld with low detachment providing a good mechanical and electrical contact for applications such as in lithium-ion secondary batteries.