NOVELTY - An electrolytic copper foil consists of copper or copper alloy. The copper foil has a maximum value of change rate of 30% or less. The diffraction intensity ratio of the copper foil is the ratio of diffraction intensity of plane (200) with respect to plane (111) in X-ray diffraction using copper K-( alpha ) ray of copper or copper alloy as ray source, before and after heating for 1 hour at a temperature of 120 degrees C, 130 degrees C, 150 degrees C, or 200 degrees C.    USE - Electrolytic copper foil is used for electrical power collector used for secondary battery (all claimed) e.g. lithium ion secondary battery. Uses include but are not limited to mobile telephone, notebook computer, electric vehicle and hybrid vehicle.    ADVANTAGE - The electrolytic copper foil provides the secondary batteries with excellent charging or discharging cyclic characteristics.    DETAILED DESCRIPTION - An electrolytic copper foil consists of copper or copper alloy. The copper foil has a maximum value of change rate of 30% or less. The maximum value of change rate is determined using a formula: ((maximum value of diffraction intensity ratio after heating)-(maximum value of diffraction intensity ratio before heating))/(diffraction intensity ratio before heating)x 100 (I). The diffraction intensity ratio of the copper foil is the ratio of diffraction intensity of plane (200) with respect to plane (111) in X-ray diffraction using copper K-( alpha ) ray of copper or copper alloy as ray source, before and after heating for 1 hour at a temperature of 120 degrees C, 130 degrees C, 150 degrees C, or 200 degrees C. INDEPENDENT CLAIMS are included for the following:    (1) manufacture of electrolytic copper foil;    (2) secondary battery electrical power collector, which consists of the electrolytic copper foil; and    (3) secondary battery, which consists of the electrical power collector.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of the structure of secondary battery.    Sealing board (1)    Insulation gasket (2)    Positive electrode lead (3)    Top insulation board (4)    Separator (7)