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

摘要

PROBLEM TO BE SOLVED: To provide electrolytic copper foil for a negative electrode for a lithium ion secondary battery capable of constituting a lithium ion secondary battery prevented from decreasing in capacity maintenance factor over repeated cycles of charge and discharge to achieve a long life, and preventing deformation of a negative electrode collector.

SOLUTION: The electrolytic copper foil constitutes a negative electrode collector of a lithium ion secondary battery, the electrolytic copper foil has a 0.2% proof stress of 250 N/mm2or greater and an extension of 2.5% or greater after a heat treatment at 200 to 400°C, and the surface of the electrolytic copper foil to be provided with an active material layer is provided with rust-proofing, or provided with roughening and then rust-proofing. An electrode for a lithium ion secondary battery comprises the electrolytic copper foil as a collector, and a lithium ion secondary battery comprises the electrode as a negative electrode.

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