Nickel-coated copper foil and method for manufacturing the same
A nickel-coated copper foil suitable for mass production, to which YAG laser welding can be applied while reducing the electrical resistivity by forming a nickel plating layer with a thickness of 0.5 μm or less on a surface of a copper foil by Ni plating, is provided. The nickel-coated copper foil has an overall thickness of 200 μm or less, and includes a copper layer made of Cu or a Cu alloy, and a nickel plating layer made of Ni or a Ni alloy, covering a surface of the copper foil, having a thickness of 0.01 μm or more and 0.5 μm or less, and including a surface having an a* value of 0 or more and 10 or less and a b* value of 0 or more and 14 or less in an L*a*b* color system obtained by an SCI measurement method in accordance with JIS Z 8722.
1. A nickel-coated copper foil comprising:
a copper layer made of Cu or a Cu alloy; and
an upper exposed nickel plating layer made of Ni or a Ni alloy, the upper exposed nickel plating layer covering an upper surface of the copper layer and exposing a surface opposite to a surface in contact with the copper layer in order to be welded to a portion of an other material used in batteries by YAG laser,
a bottom exposed nickel plating layer made of Ni or a Ni alloy, the bottom exposed nickel plating layer covering a bottom surface of the copper layer and exposing a surface opposite to a surface in contact with the copper layer in order to be welded to a portion of an other material used in batteries by YAG laser,
the upper exposed nickel plating layer and the bottom exposed nickel plating layer having a thickness of 0.01 μm or more and less than 0.1 μm,
surfaces of the upper exposed nickel plating layer and the bottom exposed nickel plating layer have an L* value of 70 or more and 78 or less, an a* value of 0 or more and 4 or less and a b* value of 0 or more and 14 or less in an L*a*b* color system obtained by an SCI measurement method in accordance with JIS Z 8722,
at least one of the surfaces of the upper exposed nickel plating layer and the bottom exposed nickel plating layer are welded to a portion of an other material used in batteries by YAG laser,
and wherein the nickel-coated copper foil has an overall thickness of 100 μm or more and 200 μm or less.
2. The nickel-coated copper foil according to claim 1 , wherein the upper exposed nickel plating layer and the bottom exposed nickel plating layer have the thickness of 0.03 μm or more and less than 0.1 μm.
3. The nickel-coated copper foil according to claim 2 , having a volume resistivity of 2 μΩ-cm or less, the volume resistivity being obtained in a room temperature environment by a 4-terminal method in accordance with JIS C 2525.
4. The nickel-coated copper foil according to claim 1 , having a volume resistivity of 2 μΩ-cm or less, the volume resistivity being obtained in a room temperature environment by a 4-terminal method in accordance with JIS C 2525.
5. A method for manufacturing the nickel-coated copper foil according to claim 1 , the method comprising:
forming a nickel plating layer made of Ni or a Ni alloy on a surface of the copper foil made of Cu or the Cu alloy by a plating process; wherein
the plating process is performed such that the nickel plating layer has a thickness of 0.01 μm or more and less than 0.1 μm and includes a surface having an a* value of 0 or more and 4 or less and a b* value of 0 or more and 14 or less in an L*a*b* color system obtained by an SCI measurement method in accordance with JIS Z 8722.
6. The method for manufacturing a nickel-coated copper foil according to claim 5 , wherein after the plating process, a heat treatment is performed such that the nickel plating layer includes the surface having the a* value of 0 or more and 4 or less and the b* value of 0 or more and 14 or less in the L*a*b* color system obtained by the SCI measurement method in accordance with JIS Z 8722.
7. A battery containing the nickel-coated copper foil according to claim 1 .
8. A lithium-ion secondary battery containing the nickel-coated copper foil according to claim 1 .