Lithium-ion secondary battery, electrode for the secondary battery, and electrolytic copper foil for electrode for the secondary battery

Abstract

To provide an electrolytic copper foil for a negative electrode for a lithium-ion secondary battery 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 cycling is repeated, that has long life, and no deformation of a negative electrode current collector occurs. The electrolytic copper foil constituting the negative electrode current collector for the lithium-ion secondary battery has, after heat treatment at from 200 to 400° C., a 0.2% proof stress of 250 N/mmor more, and elongation of 2.5% or more; and the surface on which an active material layer of the electrolytic copper foil is provided has been rust-proofed, or roughened and rust-proofed. As a result of analysis of the depth profile (depth direction) obtained by performing secondary ion mass spectrometry (SIMS) in the thickness direction of the copper foil, the copper foil including: chlorine (Cl), carbon (C), and oxygen (O) each in a concentration of 10to 5×10atoms/cm, and sulfur (S) and nitrogen (N) each in a concentration of 10to 10atoms/cm.