Electrolytic copper foil

Abstract

Provided is an electrolytic copper foil having a surface roughness Rz of 2.0 μm or less, wherein a foil thickness difference in the width direction is 1.5% or less. Also provided is the electrolytic copper foil, wherein the foil thickness difference in the width direction is 1.3% or less. Further provided is the electrolytic copper foil, wherein a variation in the roughness in the width direction (Rzmax−Rzmin) / Rzavg is 15% or less. An object of the present invention is to provide an electrolytic copper foil having low surface roughness, wherein the formation of an “elongation wrinkle” and a discolored streak along the length direction is suppressed by allowing the thickness to be uniform in the width and length directions.

Description

TECHNICAL FIELD[0001]The present invention relates to an electrolytic copper foil, in particular relates to an electrolytic copper foil having a low roughness.BACKGROUND[0002]In general, a device for manufacturing an electrolytic copper foil comprises a metal cathode drum and an insoluble metal anode (anode), the metal cathode drum being rotatable and having a mirror polished surface, the insoluble metal anode being arranged at approximately lower half of the metal cathode drum and surrounding the metal cathode drum. A copper foil is continuously manufactured with the device by flowing a copper electrolytic solution between the cathode drum and the anode, applying an electrical potential between these to allow copper to be electrodeposited on the cathode drum, and detaching an electrodeposited copper from the cathode drum when a predetermined thickness is obtained.[0003]A copper foil obtained as described above, which is generally called a raw foil, is used for a copper foil for a n...

AI Technical Summary

Benefits of technology

The present invention provides a copper foil that does not have any wrinkle or discolored streaks when rolled up. This foil is effective for use in lithium batteries, especially for the negative electrode material, as it has low surface roughness and a small variation in foil thickness. The foil also has a high tensile strength and elongation.

Problems solved by technology

However, in recent years, an “elongation wrinkle” in a copper foil is becoming a problem because a foil becomes thinner and the roughness becomes lower.

This appears to cause the problem.

In the process of manufacturing an electrolytic copper foil as described above, the plate thickness is very difficult to be precisely controlled, and in particular, a more uniform plate thickness is not easily obtained in the case of a thin foil.

In a case where a small gap between a cathode drum and an anode is maintained while an electrolytic solution flows into the gap to allow electrodeposition, even a device designed for achieving uniformity may often cause a certain variation in a film thickness due to the issues specific to a manufacturing device and operating conditions.

However, in a case where split anodes are provided at a portion of the anode in the copper foil rolling-up side, and an amount of electric power supplied to these split anodes is individually controlled as in the above mentioned patent literatures in order to achieve a thin plate thickness and a lower surface roughness as well as a uniform thickness in the width and length directions, a problem of an observed discolored streak along the length direction is not solved.

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