CURRENT COLLECTOR COPPER FOIL OF NEGATIVE ELECTRODE FOR LITHIUM ION SECONDARY BATTERY, METHOD OF MANUFACTURING THE CURRENT COLLECTOR COPPER FOIL OF NEGATIVE ELECTRODE FOR LITHIUM ION SECONDARY BATTERY, NEGATIVE ELECTRODE FOR LITHIUM ION SECONDARY BATTERY, METHOD OF MANUFACTURING THE NEGATIVE ELECTRODE FOR LITHIUM ION SECONDARY BATTERY, AND LITHIUM ION SECONDARY BATTERY

摘要

PROBLEM TO BE SOLVED: To maintain sufficient mechanical strength even after experienced heat treatment in a manufacturing process of a negative electrode for a lithium ion secondary battery.SOLUTION: A current collector copper foil 10 of a negative electrode for a lithium ion secondary battery contains 0.15-0.40 wt.% of Cr, with the balance comprising Cu, wherein a Cr solid solution index Z in the following formula (1) is 0.05Z0.3. (1) Z=(R-R)/(R-R), wherein Ris an actual measured value (%IACS) of conductivity R of the current collector copper foil of a negative electrode, Ris a calculated value (%IACS) of conductivity R of the current collector copper foil 10 of a negative electrode when the entire Cr is solid-soluted, and Ris a calculated value (%IACS) of conductivity R of the current collector copper foil 10 of a negative electrode when the entire Cr is precipitated.