ELECTROLYTIC COPPER FOIL, NEGATIVE ELECTRODE FOR LITHIUM ION SECONDARY BATTERY, AND LITHIUM ION SECONDARY BATTERY

摘要

Provided are an electrolytic copper foil, a negative electrode that is for a lithium ion secondary battery, and a lithium ion secondary battery into which the electrode is incorporated. The electrolytic copper foil exhibits good conductivity and superior tensile strength, with no significant decline in tensile strength exhibited even after one hour of heating at 300°C. The negative electrode has heightened cycle properties due to the use of the electrolytic copper foil as a current collector. Using x-ray diffraction, in the electrolytic copper foil, in normal conditions, the diffraction intensity (I)<220> in the <220> orientation, the diffraction intensity (I)<200> in the <200> orientation, and the diffraction intensity (I)<111> in the <111> orientation, satisfy the following formula (1): I<220>/{I<220>+I<200>+I<111>}>0.13 ... (1). The lithium ion secondary battery has the negative electrode using the electrolytic copper foil as a current collector incorporated therein.