NOVELTY - A rolled copper foil is copper alloy foil containing silver, chromium, iron, indium, nickel, phosphorus, silicon, tin, tellurium, titanium, zinc and/or zirconium (0.01-0.5 %mass) and remainder of copper and unavoidable impurities, and has electroconductivity of 80% IACS or more. The rolled copper foil has maximum Young's moduli and minimum Young's moduli of 1.3 or less, and tensile strength of 400 MPa or more after heating at 300 degrees C for 30 minutes.    USE - Rolled copper foil is used for negative electrode collector for negative electrode plate used for secondary battery (all claimed) for hybrid vehicle and electric vehicle.    ADVANTAGE - The rolled copper foil has excellent metal-plating property, tensile strength and heat resistance. The secondary battery comprising the rolled copper foil has excellent charging/discharging cycling characteristics.    DETAILED DESCRIPTION - A rolled copper foil is copper alloy foil containing silver, chromium, iron, indium, nickel, phosphorus, silicon, tin, tellurium, titanium, zinc and/or zirconium (0.01-0.5 %mass) and remainder of copper and unavoidable impurities, and has electroconductivity of 80% IACS or more. The rolled copper foil has maximum Young's moduli and minimum Young's moduli of 1.3 or less, and tensile strength of 400 MPa or more after heating at 300 degrees C for 30 minutes. The Young's modulus is measured along 5 directions at angles of 0 degrees , 22.5 degrees , 45 degrees , 67.5 degrees and 90 degrees with respect to rolling direction, and maximum value and minimum value of 5 Young's moduli are measured. INDEPENDENT CLAIMS are included for the following:    (1) negative electrode plate (6), which has negative electrode active material layer containing carbonaceous material or graphite material, or metallic lithium, tin metal, tin compound, silicon and/or silicon compound on negative electrode collector; and    (2) secondary battery.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of the secondary battery.    Sealing board (1)    Top insulation board (4)    Positive electrode plate (5)    Negative electrode plate (6)    Separator (7)