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

摘要

To supply an electrolytic copper foil for lithium-ion secondary battery negative electrodes with which it is possible to produce a long-life lithium-ion secondary battery in which there is no decline in the capacity retention ratio even when the charge/discharge cycle is repeated, and no deformation of a negative electrode current collector: the electrolytic copper foil for configuring the negative electrode current collector of a lithium-ion secondary battery has, after heat treatment at 200-400°C, a 0.2% yield strength of 250N/mm2 or more, and elongation of 2.5% or more; and the surface on which the active material layer of the electrolytic copper foil is provided has been rust-proofed, or roughened and rust-proofed. Analysis of the depth profile (depth direction) obtained by performing secondary ion mass spectrometry (SIMS) in the thickness direction of the copper foil results in the following: chlorine (Cl), carbon (C), and oxygen (O) are each contained in a concentration of 1017-5x1020 atoms/cm3, and sulfur (S) and nitrogen (N) are each contained in a concentration of 1015-1019 atoms/cm3.