U.S. patent application number 15/773046 was filed with the patent office on 2018-11-08 for electrolytic copper foil, electrode comprising the same, secondary battery comprising the same, and method for manufacturing the same.
The applicant listed for this patent is KCF Technologies Co., Ltd.. Invention is credited to Seung Min KIM.
Application Number | 20180323438 15/773046 |
Document ID | / |
Family ID | 58695702 |
Filed Date | 2018-11-08 |
United States Patent
Application |
20180323438 |
Kind Code |
A1 |
KIM; Seung Min |
November 8, 2018 |
ELECTROLYTIC COPPER FOIL, ELECTRODE COMPRISING THE SAME, SECONDARY
BATTERY COMPRISING THE SAME, AND METHOD FOR MANUFACTURING THE
SAME
Abstract
Disclosed are an electrolytic copper foil the fold and/or
wrinkle of which can be avoided or minimized during a roll-to-roll
process, a method for manufacturing the same, and an electrode and
a secondary battery which are produced with such electrolytic
copper foil so that high productivity can be guaranteed. An
electrolytic copper foil of the invention has a longitudinal rising
of 30 mm or less and a transverse rising of 25 mm or less, and the
transverse rising is 8.5 times the longitudinal rising or less.
Inventors: |
KIM; Seung Min; (Osan-si
Gyeonggi-do, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KCF Technologies Co., Ltd. |
Anyang-si, Gyeonggi-do |
|
KR |
|
|
Family ID: |
58695702 |
Appl. No.: |
15/773046 |
Filed: |
October 13, 2016 |
PCT Filed: |
October 13, 2016 |
PCT NO: |
PCT/KR2016/011494 |
371 Date: |
May 2, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/667 20130101;
H01M 2004/027 20130101; H01M 4/661 20130101; H01M 4/13 20130101;
C25D 1/04 20130101; H01M 10/0525 20130101; C25D 7/06 20130101; Y02E
60/10 20130101; H01M 4/66 20130101 |
International
Class: |
H01M 4/66 20060101
H01M004/66; C25D 1/04 20060101 C25D001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 9, 2015 |
KR |
10-2015-0156349 |
Claims
1. An electrolytic copper foil having a first surface and a second
surface opposite to the first surface, the electrolytic copper foil
comprising: a first protective layer at the first surface; a second
protective layer at the second surface; and a copper film between
the first and second protective layers, wherein the electrolytic
copper foil has a longitudinal rising of 30 mm or less and a
transverse rising of 25 mm or less, the transverse rising is 8.5
times the longitudinal rising or less, and the longitudinal rising
and transverse rising are, when a center portion of the
electrolytic copper foil is cut along a X-shaped cutting line of 5
cm.times.5 cm in a first direction which makes an angle of
35.degree. to 55.degree. with a longitudinal direction parallel
with a transferring mark formed on the electrolytic copper foil and
in a second direction perpendicular to the first direction so that
a pair of first segments arranged side by side along the
longitudinal direction and a pair of second segments arranged side
by side along a transverse direction perpendicular to the
longitudinal direction are formed, the greater of risings of the
first segments in a direction the first or second surface is facing
and the greater of risings of the second segments in a direction
the first or second surface is facing, respectively.
2. The electrolytic copper foil according to claim 1, wherein the
first and second protective layers are respectively formed by
depositing an anticorrosion material on the copper film, and a
difference between deposition amount of the anticorrosion material
of the first and second protective layers is 2.5 ppm/m2 or
less.
3. The electrolytic copper foil according to claim 2, wherein the
anticorrosion material comprises at least one of chromate,
benzotriazole, chromic oxide, and a silane compound.
4. The electrolytic copper foil according to claim 1, wherein the
electrolytic copper foil has a thickness of 4 to 35 .mu.m.
5. The electrolytic copper foil according to claim 1, wherein the
first and second surfaces have a ten-point mean roughness RzJIS of
3.5 .mu.m or less, and a ten-point mean roughness deviation of the
first and second surfaces, which is calculated according to
following formula, is 70% or less: formula:
RD=[|R1-R2|/(R1,R2)max].times.100 wherein R1 is the ten-point mean
roughness of the first surface, R2 is the ten-point mean roughness
of the second surface, RD is the ten-point mean roughness deviation
of the first and second surfaces, |R1-R2| is a difference between
the ten-point mean roughness of the first and second surfaces, and
(R1, R2) max is the greater of the ten-point mean roughness of the
first and second surfaces.
6. An electrode for a secondary battery, the electrode comprising:
the electrolytic copper foil according to claim 1; and an active
material layer on the electrolytic copper foil, wherein the active
material layer comprises at least one active material selected from
the group consisting of: carbon; a metal of Si, Ge, Sn, Li, Zn, Mg,
Cd, Ce, Ni or Fe; an alloy including the metal; an oxide of the
metal; and a complex of the metal and carbon.
7. A secondary battery comprising: a cathode; an anode; an
electrolyte for providing an environment enabling lithium ions to
move between the cathode and the anode; and a separator for
electrically insulating the cathode from the anode, wherein the
anode comprises: the electrolytic copper foil according to claim 1;
and an active material layer on the electrolytic copper foil,
wherein the active material layer comprises at least one active
material selected from the group consisting of: carbon; a metal of
Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; an alloy including the
metal; an oxide of the metal; and a complex of the metal and
carbon.
8. A method for manufacturing an electrolytic copper foil, the
method comprising: allowing a current to flow between an anode
plate and a rotational cathode drum to form a copper film on the
rotational cathode drum, the anode plate and rotational cathode
drum spaced apart from each other in an electrolytic solution
contained in an electrolytic bath; and dipping the copper foil in
an anticorrosion solution, wherein the anode plate comprises first
and second anode plates electrically insulated from each other, the
forming the copper film comprises forming a seed layer by allowing
a current to flow between the first anode plate and the rotational
cathode drum, and then growing the seed layer by allowing a current
to flow between the second anode plate and the rotational cathode
drum, and a current density provided by the first anode plate is
1.5 times or more higher than a current density provided by the
second anode plate.
9. The method according to claim 8, wherein the anode plate further
comprises a third anode plate between the first and second anode
plates, and a current density provided by the third anode plate is
lower than the current density provided by the first anode plate
and higher than the current density provided by the second anode
plate.
10. The method according to claim 8, wherein the current density
provided by the anode plate is 40 to 70 A/dm2.
11. The method according to claim 8, further comprising taking the
copper film out of the anticorrosion solution, wherein the copper
film is guided by a guide roll disposed in the anticorrosion
solution when the copper film is dipped in and taken out of the
anticorrosion solution.
12. The method according to claim 11, further comprising, after
taking the copper film out of the anticorrosion solution, spraying
an anticorrosion solution onto a surface of the copper film which
was in contact with the guide roll during the dipping process.
13. The method according to claim 8, wherein the electrolytic
solution comprises 50 to 100 g/L of a copper ion, 50 to 150 g/L of
sulfuric acid, 50 ppm or less of a chlorine ion and an organic
additive.
14. The method according to claim 13, wherein the organic additive
is gelatin, hydroxyethyl cellulose (HEC), organic sulfide, organic
nitride, a thiourea compound, or a mixture of two or more
thereof.
15. The method according to claim 8, wherein the electrolytic
solution is supplied into the electrolytic bath at a flow rate of
40 to 46 m3/hour when the copper film is formed.
Description
TECHNICAL FIELD
[0001] The present invention relates to an electrolytic copper
foil, an electrode including the same, a secondary battery
including the same, and a method for manufacturing the same.
BACKGROUND ART
[0002] An electrolytic copper foil is used to produce a variety of
products such as anode current collectors for secondary batteries
and flexible printed circuit boards (FPCBs).
[0003] In general, an electrolytic copper foil is produced through
a roll-to-roll (RTR) process and is used to produce anode current
collectors for secondary batteries, flexible printed circuit boards
(FPCBs) and the like, through a roll-to-roll (RTR) process.
[0004] A roll-to-roll (RTR) process is known to be suitable for
mass-production because it enables continuous production. However,
in practice, because of fold and/or wrinkle of an electrolytic
copper foil which often occurs during a roll-to-roll (RTR) process,
it is necessary to stop a roll-to-roll (RTR) process equipment,
solve the problems, and then re-operate the equipment. Repetition
of stop and reoperation of the process equipment causes a serious
problem of low productivity.
[0005] In other words, the fold and/or wrinkle of an electrolytic
copper foil which occurs during a roll-to-roll (RTR) process
prevent continuous production of products, thus making it
impossible to enjoy the advantages unique to the roll-to-roll (RTR)
process and resulting in poor productivity.
DETAILED DESCRIPTION OF INVENTION
Technical Problem
[0006] Therefore, the present invention is directed to an
electrolytic copper foil, an electrode including the same, a
secondary battery including the same and a method for manufacturing
the same capable of preventing these limitations and drawbacks of
the related art.
[0007] An aspect of the present invention is to provide an
electrolytic copper foil the fold and/or wrinkle of which can be
avoided or minimized during a roll-to-roll (RTR) process.
[0008] Another aspect of the present invention is to provide an
electrode which is produced with an electrolytic copper foil
through a roll-to-roll (RTR) process without fold and/or wrinkle of
the electrolytic copper foil during the process, thereby
guaranteeing high productivity.
[0009] Further another aspect of the present invention is to
provide a secondary battery which is produced with an electrolytic
copper foil through a roll-to-roll (RTR) process without fold
and/or wrinkle of the electrolytic copper foil during the process,
thereby guaranteeing high productivity.
[0010] Yet another aspect of the present invention is to provide a
method of manufacturing an electrolytic copper foil the fold and/or
wrinkle of which can be avoided or minimized during a roll-to-roll
(RTR) process.
[0011] Additional aspects and features of the present invention
will be set forth in part in the description which follows and in
part will become apparent to those having ordinary skill in the art
upon examination of the following or may be learned from practice
of the invention. The objectives and other advantages of the
invention may be realized and attained by the structure
particularly pointed out in the written description and claims.
Technical Solution
[0012] In accordance with the one aspect of the present invention,
there is provided an electrolytic copper foil having a first
surface and a second surface opposite to the first surface, the
electrolytic copper foil comprising: a first protective layer at
the first surface; a second protective layer at the second surface;
and a copper film between the first and second protective layers,
wherein the electrolytic copper foil has a longitudinal rising of
30 mm or less and a transverse rising of 25 mm or less, and the
transverse rising is 8.5 times the longitudinal rising or less.
[0013] When a center portion of the electrolytic copper foil is cut
along a X-shaped cutting line of 5 cm.times.5 cm in a first
direction which makes an angle of 35.degree. to 55.degree. with a
longitudinal direction parallel with a transferring mark formed on
the electrolytic copper foil and in a second direction
perpendicular to the first direction so that a pair of first
segments arranged side by side along the longitudinal direction and
a pair of second segments arranged side by side along a transverse
direction perpendicular to the longitudinal direction are formed,
the longitudinal rising and transverse rising are the greater of
risings of the first segments in a direction the first or second
surface is facing and the greater of risings of the second segments
in a direction the first or second surface is facing,
respectively.
[0014] In accordance with another aspect of the present invention,
there is provided an electrode for a secondary battery, the
electrode comprising: the electrolytic copper foil; and an active
material layer on the electrolytic copper foil, wherein the active
material layer comprises at least one active material selected from
the group consisting of: carbon; a metal of Si, Ge, Sn, Li, Zn, Mg,
Cd, Ce, Ni or Fe; an alloy including the metal; an oxide of the
metal; and a complex of the metal and carbon.
[0015] In accordance with further another aspect of the present
invention, there is provided a secondary battery comprising: a
cathode; an anode; an electrolyte for providing an environment
enabling lithium ions to move between the cathode and the anode;
and a separator for electrically insulating the cathode from the
anode, wherein the anode comprises: the electrolytic copper foil;
and an active material layer on the electrolytic copper foil,
wherein the active material layer comprises at least one active
material selected from the group consisting of: carbon; a metal of
Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe; an alloy including the
metal; an oxide of the metal; and a complex of the metal and
carbon.
[0016] In accordance with yet another aspect of the present
invention, there is provided a method for manufacturing an
electrolytic copper foil, the method comprising: allowing a current
to flow between an anode plate and a rotational cathode drum to
form a copper film on the rotational cathode drum, the anode plate
and rotational cathode drum spaced apart from each other in an
electrolytic solution contained in an electrolytic bath; and
dipping the copper foil in an anticorrosion solution, wherein the
anode plate comprises first and second anode plates electrically
insulated from each other, the forming the copper film comprises
forming a seed layer by allowing a current to flow between the
first anode plate and the rotational cathode drum, and then growing
the seed layer by allowing a current to flow between the second
anode plate and the rotational cathode drum, and a current density
provided by the first anode plate is 1.5 times or more higher than
a current density provided by the second anode plate.
[0017] General description related to the present invention given
above serves to illustrate or disclose the present invention and
should not be construed as limiting the scope of the present
invention.
Advantageous Effects
[0018] According to the present invention, a electrolytic copper
foil the fold and/or wrinkle of which can be avoided or minimized
during a roll-to-roll (RTR) process is used to produce a
subassembly and a final product, such as a flexible printed circuit
board, a secondary battery, and the like, so that the productivity
of the final product as well as the subassembly can be
increased.
BRIEF DESCRIPTION OF DRAWINGS
[0019] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this application, illustrate embodiments of
the invention and together with the description serve to explain
the principle of the invention. In the drawings:
[0020] FIG. 1 is a sectional view of an electrolytic copper foil
according to an embodiment of the present invention;
[0021] FIG. 2 shows how the longitudinal direction and transverse
direction of the electrolytic copper foil is defined in the present
invention;
[0022] FIG. 3 shows a method for measuring the longitudinal rising
and transverse rising of the electrolytic copper foil;
[0023] FIG. 4 is a sectional view of an electrode for secondary
battery according to an embodiment of the present invention;
and
[0024] FIG. 2 illustrates an apparatus for manufacturing an
electrolytic copper foil according to an embodiment of the present
invention.
MODE FOR INVENTION
[0025] Hereinafter, embodiments according to the present invention
will be described in detail with reference to the annexed
drawings.
[0026] Those skilled in the art will appreciate that various
modifications, additions and substitutions are possible, without
departing from the scope and spirit of the invention as disclosed
in the accompanying claims. Accordingly, the present invention
includes modifications and alterations which fall within the scope
of inventions as claimed and equivalents thereto.
[0027] FIG. 1 is a sectional view of an electrolytic copper foil
110 according to an embodiment of the present invention.
[0028] As illustrated in FIG. 1, an electrolytic copper foil 110 of
the present invention has a first surface 110a and a second surface
110b opposite to the first surface 110a and comprises a first
protective layer 112 at the first surface 110a, a second protective
layer 113 at the second surface 110b, and a copper film 111 between
the first and second protective layers 112 and 113.
[0029] An electrolytic copper foil 110 according to one embodiment
of the present invention has a thickness of 4 to 35 .mu.m. An
electrolytic copper foil 110 having a thickness less than 4 .mu.m
causes a deterioration of the workability when it is manufactured.
On the other hand, when a secondary battery is produced with an
electrolytic copper foil 110 having a thickness more than 35 .mu.m,
it is difficult to make a secondary battery of high capacity due to
the thick copper foil 110.
[0030] The copper film 111 may be formed on a rotational cathode
drum through an electroplating process and has a shiny surface 111a
which was in contact with the rotational cathode drum and a matte
surface 111b opposite thereto.
[0031] An anticorrosion material is deposited on the copper film
111 to form the first and second protective layers 112 and 113
respectively. The anticorrosion material may comprise at least one
of chromate, benzotriazole (BTA), chromic oxide, and a silane
compound. The first and second protective layers 112 and 113
inhibit oxidation and corrosion of the copper film 111 and improve
the heat resistance thereof so that the lifespan of the product
including the electrolytic copper foil 110 can be increased.
[0032] To inhibit a fold and/or curl of the electrolytic copper
foil 110, it is preferred that the portions of the electrolytic
copper foil 110, which are disposed adjacent to the first and
second surfaces 110a and 110b respectively, have identical or very
similar properties. Thus, according to one embodiment of the
present invention, the copper film 111 has the shiny and matte
surfaces 111a and 111b having identical or very similar roughness.
The term "roughness" as used herein means a ten-point mean
roughness (R.sub.zJIS). Further, the difference between the
deposition amount of the anticorrosion material of the first and
second protective layers 112 and 113 which are formed by depositing
the anticorrosion material on the copper film 111 is preferably 2.5
ppm/m.sup.2 or less.
[0033] For example, the deposition amount of the first protective
layer 112 is 0.6 to 4.1 ppm/m.sup.2 and the deposition amount of
the second protective layer 113 is 0.6 to 4.1 ppm/m.sup.2. If the
difference between the deposition amount of the anticorrosion
material of the first and second protective layers 112 and 113 is
more than 2.5 ppm/m.sup.2, the fold and/or curl of the electrolytic
copper foil 110 would occur during a roll-to-roll process, which
would inevitably lead to the stop of the processing equipments.
[0034] The electrolytic copper foil 110 of the present invention
has a longitudinal rising LR of 30 mm or less and a transverse
rising TR of 25 mm or less, and the transverse rising TR is 8.5
times the longitudinal rising LR or less.
[0035] If the longitudinal rising LR is more than 30 mm, a fold of
the electrolytic copper foil 110 would be caused between the two
rolls adjacent to each other during the roll-to-roll process. If
the transverse rising TR is more than 25 mm, the wrinkles would be
caused at the right and left end portions of the electrolytic
copper foil 110 during the roll-to-roll process.
[0036] Further, if the transverse rising TR is more than 8.5 times
the longitudinal rising LR while the longitudinal rising LR and
transverse rising TR of the electrolytic copper foil 110 satisfy
the aforementioned ranges respectively, the force is applied to the
electrolytic copper foil 110 in the transverse direction during the
roll-to-roll process, thereby causing the wrinkles at the right and
left end portions of the electrolytic copper foil 110.
[0037] Hereinafter, referring to FIG. 2 and FIG. 3, a method for
measuring the longitudinal rising LR and transverse rising TR will
be explained in detail.
[0038] First, the center portion of the electrolytic copper foil
110 is cut along a X-shaped cutting line of 5 cm.times.5 cm in the
first direction D1 which makes an angle of 35.degree. to 55.degree.
with a longitudinal direction LD parallel with the transferring
mark formed on the electrolytic copper foil 110 and in the second
direction D2 perpendicular to the first direction D1 so that a pair
of the first segments A and A' arranged side by side along the
longitudinal direction LD and a pair of second segments B and B'
arranged side by side along a transverse direction HD perpendicular
to the longitudinal direction LD are formed. The transferring mark
is the mark formed on the shiny surface 111a of the copper film 111
by the rotational cathode drum and can be identified by observing
the first surface 110a adjacent to the shiny surface 111a with a
microscope.
[0039] Then, the risings of the first segments A and A' in the
direction the first or second surface 110a or 110b is facing are
measured respectively, and the greater of the measured values is
regarded as the longitudinal rising LR of the electrolytic copper
foil 110. Likewise, the risings of the second segments B and B' in
the direction the first or second surface 110a or 110b is facing
are measured respectively, and the greater of the measured values
is regarded as the transverse rising TR of the electrolytic copper
foil 110.
[0040] As mentioned above, according to the present invention, the
portions of the electrolytic copper foil 110, which are disposed
adjacent to the first and second surfaces 110a and 110b
respectively, have identical or very similar properties.
[0041] Therefore, according to one embodiment of the present
invention, each of the first and second surfaces 110a and 110b has
a ten-point mean roughness R.sub.zJIS of 3.5 .mu.m or less, and the
ten-point mean roughness deviation of the first and second surfaces
110a and 110b, which is calculated according to following formula,
is 70% or less:
formula:
R.sub.D=[|R.sub.1-R.sub.2|/(R.sub.1,R.sub.2).sub.max].times.100
[0042] wherein R.sub.1 is the ten-point mean roughness of the first
surface 110a, R.sub.2 is the ten-point mean roughness of the second
surface 110b, R.sub.D is the ten-point mean roughness deviation of
the first and second surfaces 110a and 110b, |R.sub.1-R.sub.2| is
the difference between the ten-point mean roughness of the first
and second surfaces 110a and 110b, and (R.sub.1, R.sub.2).sub.max
is the greater of the ten-point mean roughness of the first and
second surfaces 110a and 110b.
[0043] If the ten-point mean roughness R.sub.zJIS of the first and
second surfaces 110a and 110b of the electrolytic copper foil 110
is more than 3.5 .mu.m, the adhesive strength between the
electrolytic copper foil 110 and the anode active material which is
coated on both surfaces of the electrolytic copper foil 110 to
produce a secondary batter would be insufficient.
[0044] Hereinafter, only for the sake of explanation, the present
invention will be described based on an embodiment in which the
electrolytic copper foil 110 of the present invention is used to
produce a secondary battery. However, as mentioned above, the
electrolytic copper foil 110 of the present invention can be
similarly used to produce a variety of other products which can be
manufactured through a roll-to-roll process, e.g., a flexible
printed circuit board (FPCB).
[0045] A lithium ion secondary battery includes a cathode, an
anode, an electrolyte for providing an environment enabling the
lithium ions to move between the cathode and the anode, and a
separator for electrically insulating the cathode from the anode to
prevent the electrons generated by one electrode from moving toward
the other electrode through the inside part of the secondary
battery and being worthless consumed.
[0046] FIG. 4 is a sectional view of an electrode for secondary
batteries according to an embodiment of the present invention.
[0047] As illustrated in FIG. 4, the electrode 100 for a secondary
battery according to an embodiment of the present invention
comprises an electrolytic copper foil 110 of one of the embodiments
of the present invention and an active material layer 120.
[0048] FIG. 4 illustrates the active material layer 120 which is
formed on both of the first and second surfaces 110a and 110b of
the electrolytic copper foil 110, but the present invention is not
limited thereto and the active material layer 120 may be formed on
only one surface of the electrolytic copper foil 110.
[0049] In general, in a lithium secondary battery, an aluminum foil
is used as a cathode current collector coupled to a cathode active
material and an electrolytic copper foil 110 is used as an anode
current collector coupled to an anode active material.
[0050] According to one embodiment of the present invention, the
electrode 100 for a secondary battery is an anode, the electrolytic
copper foil 110 is used as an anode current collector, and the
active material layer 120 includes an anode active material.
[0051] The active material layer 120 comprises, as the anode active
material, at least one active material selected from the group
consisting of: carbon; a metal of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce,
Ni or Fe; an alloy including the metal; an oxide of the metal; and
a complex of the metal and carbon.
[0052] In order to increase the charge/discharge capacity of the
secondary battery, the active material layer 120 may be formed
using a mixture of the anode active materials containing a
predetermined amount of Si.
[0053] As the charge and discharge of the secondary battery is
repeated, the active material layer 120 contracts and expands
alternately and repeatedly, which induces separation of the active
material layer 120 from the electrolytic copper foil 110, causing
deterioration in charge/discharge efficiency of the secondary
battery. Accordingly, in order for the secondary electrodes to
secure predetermined levels of capacity maintenance and lifespan
(i.e., in order to prevent deterioration in charge/discharge
efficiency of the secondary battery), the electrolytic copper foil
110 should have excellent coatability with respect to the active
material so that adhesion strength between the electrolytic copper
foil 110 and the active material layer 120 can be increased.
[0054] In a broad sense, the lower the ten-point mean roughness
R.sub.zJIS of the first and second surfaces 110a and 110b of the
electrolytic copper foil 110 is, the less the charge/discharge
efficiency of the secondary battery deteriorates.
[0055] Accordingly, each of the first and second surfaces 110a and
110b of the electrolytic copper foil 110 according to one
embodiment of the present invention has a ten-point mean roughness
R.sub.zJIS of 3.5 .mu.m or less. If the first or second surface
110a or 110b has a ten-point mean roughness R.sub.zJIS exceeding
3.5 .mu.m, the contact uniformity between the electrolytic copper
foil 110 and the active material layer 120 would not reach a
desired level and the secondary battery thus cannot satisfy the
capacity maintenance of 90% or higher, which is required in the
art.
[0056] Hereinafter, referring to FIG. 5, a method manufacturing an
electrolytic copper foil 110 according to an embodiment of the
present invention will be described in detail.
[0057] The method of the present invention comprises allowing a
current to flow between an anode plate 30 and a rotational cathode
drum 40 to form a copper film 111 on the rotational cathode drum
40, the anode plate 30 and rotational cathode drum 40 spaced apart
from each other in an electrolytic solution 20 contained in an
electrolytic bath 10, and dipping the copper foil 111 in an
anticorrosion solution 60.
[0058] As illustrated in FIG. 5, the anode plate 30 comprises the
first anode plate 31 and the second anode plate 32 electrically
insulated from each other.
[0059] The process for forming the copper film 111 comprises
forming a seed layer by allowing a current to flow between the
first anode plate 31 and the rotational cathode drum 40, and then
growing the seed layer by allowing a current to flow between the
second anode plate 32 and the rotational cathode drum 40.
[0060] The current density provided by the first and second anode
plates 31 and 32 may be 40 to 70 A/dm.sup.2.
[0061] According to the present invention, the current density
provided by the first anode plate 31 is 1.5 times or more higher
than the current density provided by the second anode plate 32. In
other words, relatively high current density is applied when the
seed layer is formed so that the grain size of the seed layer can
be decreased and, as a result, the shiny surface 111a and matte
surface 111b of the copper film 111 can have identical or similar
grain size.
[0062] Since the shiny surface 111a and matte surface 111b of the
copper film 111 have identical or similar grain size, the
electrolytic copper film 110 of the present invention can have the
longitudinal rising LR of 30 mm or less and the transverse rising
TR of 25 mm or less, and the transverse rising TR can be 8.5 times
the longitudinal rising LR or less.
[0063] According to another embodiment of the present invention,
the anode plate 30 may further comprise the third anode plate
between the first and second anode plates 31 and 32. In this
instance, the current density provided by the third anode plate is
lower than the current density provided by the first anode plate 31
and higher than the current density provided by the second anode
plate 32.
[0064] According to one embodiment of the present invention, the
electrolytic solution 20 may comprise 50 to 100 g/L of a copper
ion, 50 to 150 g/L of sulfuric acid, 50 ppm or less of a chlorine
ion, and an organic additive. The organic additive may be gelatin,
hydroxyethyl cellulose (HEC), organic sulfide, organic nitride, a
thiourea compound, or a mixture of two or more thereof. When the
copper film 111 is formed, the electrolytic solution 20 may be
maintained at 50 to 60.degree. C. and the electrolytic solution 20
may be supplied into the electrolytic bath 10 at the flow rate of
40 to 46 m.sup.3/hour. If the flow rate of the electrolytic
solution 20 is less than 40 m.sup.3/hour, the copper ion could not
be effectively supplied to the surface of the rotational cathode
drum 40 and a non-uniform film would be plated. On the other hand,
if the flow rate of the electrolytic solution 20 is more than 46
m.sup.3/hour, such a high flow velocity of the electrolytic
solution 20 would cause the rapid drop of the lifespan of the
filter.
[0065] The surface of the rotational cathode drum 40 affects the
ten-point mean roughness R.sub.zJIS of the shiny surface 111a of
the copper film 111. According to one embodiment of the present
invention, the surface of the rotational cathode drum 40 may be
polished with a polishing brush of #800 to #1500 grit.
[0066] As described above, the anticorrosion solution 60 comprises
at least one of chrome-containing compound, benzotriazole, and
silane compound. For example, the copper film 111 may be dipped in
a solution containing 0.2 to 2.5 g/L of chromate for 0.2 to 20
seconds.
[0067] The method of the present invention may further comprise
taking the copper film 111 out of the anticorrosion solution 60. As
illustrated in FIG. 5, the copper film 111 is guided by a guide
roll 70 disposed in the anticorrosion solution 60 when the copper
film 111 is dipped in and taken out of the anticorrosion solution
60.
[0068] When the dipping process is performed, the amount of the
anticorrosion solution 60 coated on the surface of the copper film
111 which is in contact with the guide roll 70 (e.g., the shiny
surface 111a) is necessarily smaller than the amount of
anticorrosion solution 60 coated on the other surface of the copper
film 111 exposed to the anticorrosion solution 60 (e.g., the matte
surface 111b). Consequently, when the first and second protective
layers 112 and 113 are formed on the shiny and matte surfaces 111a
and 111b respectively, a serious difference in the deposition
amount of the anticorrosion material occurs, which may induce the
fold and/or curl (wrinkle) of the electrolytic copper foil 110.
[0069] Therefore, the method of the present invention may further
comprise, after taking the copper film 111 out of the anticorrosion
solution 60, spraying an anticorrosion solution 90 by means of a
nozzle 80 onto the surface of the copper film 111 which was in
contact with the guide roll 70 during the dipping process. Spraying
the anticorrosion solution 90 can avoid or minimize the difference
in the deposition amount of the anticorrosion material, which
otherwise would be caused when the first and second protective
layers 112 and 113 are formed respectively.
[0070] At least one active material selected from the group
consisting of a carbon, a metal of Si, Ge, Sn, Li, Zn, Mg, Cd, Ce,
Ni or Fe, an alloy including the metal, an oxide of the metal, and
a complex of the metal and carbon is coated on the first surface
110a and/or the second surface 110b of the electrolytic copper foil
110 of the present invention manufactured through the method as
described above to produce an electrode (i.e., anode) of the
present invention for a secondary battery.
[0071] For example, 100 parts by weight of carbon as an anode
active material, 1 to 3 parts by weight of styrene butadiene rubber
(SBR) and 1 to 3 parts by weight of carboxymethyl cellulose (CMC)
are mixed and produced into a slurry using a distilled water as a
solvent. Subsequently, the slurry is coated on the electrolytic
copper foil 110 using a doctor blade to a thickness of 20 to 60
.mu.m and pressed at 110 to 130.degree. C. and at a pressure of 0.5
to 1.5 ton/cm.sup.2.
[0072] A lithium secondary battery can be manufactured using the
electrode (anode) of the present invention for a secondary battery
produced through the method as described above, in combination with
the conventional cathode, electrolyte and separator.
[0073] Hereinafter, the present invention will be described in more
detail with reference to the following examples and comparative
examples. The following examples are only given for better
understanding of the present invention and should not be construed
as limiting the scope of the present invention.
Example 1
[0074] By allowing a current to flow between an anode plate and a
rotational cathode drum, which are spaced apart from each other in
an electrolytic solution contained in an electrolytic bath, a
copper film was formed on the rotational cathode drum. The
electrolytic solution included 85 g/L of copper ions, 75 g/L of
sulfuric acid, 20 ppm of chlorine ions, and organic additives.
Gelatin, hydroxyethyl cellulose (HEC), organic sulfide, and organic
nitride were used as the organic additives. While the copper film
was formed, the electrolytic solution was maintained at about
55.degree. C. and was supplied into the electrolytic bath at the
flow rate of 40 m.sup.3/hour.
[0075] The anode plate included the first and second anode plates
electrically insulated from each other. The current density
provided by the first anode plate was 60 A/dm.sup.2 and the current
density provided by the second anode plate was 40 A/dm.sup.2.
[0076] The copper film was dipped in the 2 g/L chromate solution
for 10 seconds, and then the 2 g/L chromate solution was sprayed
onto the surface which was in contact with the guide roll during
the dipping process. Subsequently, the chromate solution was dried
to form the protective layers on both surfaces of the copper film.
As a result, an electrolytic copper foil having thickness of 4
.mu.m was obtained.
Example 2
[0077] An electrolytic copper foil was produced in the same manner
as that of the Example 1 except that the current density provided
by the first anode plate was 70 A/dm.sup.2.
Example 3
[0078] An electrolytic copper foil was produced in the same manner
as that of the Example 1 except that there was further provided the
third anode plate between the first and second anode plate and the
current density provided by the third anode plate was 55
A/dm.sup.2.
Comparative Example 1
[0079] An electrolytic copper foil was produced in the same manner
as that of the Example 1 except that the same current density of 50
A/dm.sup.2 was provided by each of the first and second anode
plates.
Comparative Example 2
[0080] An electrolytic copper foil was produced in the same manner
as that of the Example 1 except that the same current density of 50
A/dm.sup.2 was provided by each of the first and second anode
plates and the process of spraying the chromate solution was
omitted.
Comparative Example 3
[0081] An electrolytic copper foil was produced in the same manner
as that of the Example 1 except that the process of spraying the
chromate solution was omitted.
[0082] The longitudinal rising, transverse rising, ratio of
transverse rising to longitudinal rising, deposition amount of the
anticorrosion material (chrome), ten-point mean roughness
(R.sub.zJIS), and ten-point mean roughness deviation of the
electrolytic copper foils of the Examples and Comparative Examples
were measured respectively according to the following methods, and
the results of the measurements are shown in the following Table
1.
[0083] Longitudinal Rising (LR), Transverse Rising (TR), and Ratio
of Transverse Rising to Longitudinal Rising (TR/LR)
[0084] The center portion of the electrolytic copper foil was cut
along a X-shaped cutting line of 5 cm.times.5 cm in the first
direction which makes an angle of 35.degree. to 55.degree. with a
longitudinal direction parallel with the transferring mark formed
on the electrolytic copper foil and in the second direction
perpendicular to the first direction so that a pair of the first
segments arranged side by side along the longitudinal direction and
a pair of second segments arranged side by side along a transverse
direction perpendicular to the longitudinal direction LD were
formed. The transferring mark, a mark formed on the shiny surface
of the copper film by the rotational cathode drum, was identified
by observing the first surface adjacent to the shiny surface with a
microscope.
[0085] Then, the risings of the first and second segments in the
direction the first surface (a surface adjacent to the shiny
surface of the copper film) or the second surface opposite to the
first surface was facing were measured respectively by means of a
ruler. The greater of the measured risings of the first segments
and the greater of the measured risings of the second segments were
regarded as the longitudinal rising (LR) and the transverse rising
(TR) of the electrolytic copper foil, respectively. Then, the ratio
of the transverse rising to the longitudinal rising (TR/LR) was
obtained by dividing the transverse rising (TR) by the longitudinal
rising (LR).
[0086] Deposition Amount of the Anticorrosion Material (Chrome)
[0087] The amount of the chrome deposited on each of the first
surface (a surface adjacent to the shiny surface of the copper
film) and the second surface opposite to the first surface of the
electrolytic copper foil was measured by means of Atomic Absorption
Spectrometry (AAS).
[0088] Ten-Point Mean Roughness (R.sub.zJIS) and Ten-Point Mean
Roughness Deviation
[0089] The ten-point mean roughness (R.sub.zJIS) of the first
surface (a surface adjacent to the shiny surface of the copper
film) and second surface opposite thereto of the electrolytic
copper foil were measured respectively by the method regulated by
JIS B 0601-1994, using a contact type surface roughness measuring
instrument.
[0090] Then, the ten-point mean roughness deviation (%) of the
electrolytic copper foil was calculated in accordance with the
following formula.
Formula:
R.sub.D=[|R.sub.1-R.sub.2|/(R.sub.1,R.sub.2).sub.max].times.100
[0091] wherein R.sub.1 is the ten-point mean roughness of the first
surface, R.sub.2 is the ten-point mean roughness of the second
surface, R.sub.D is the ten-point mean roughness deviation of the
first and second surfaces, |R.sub.1-R.sub.2| is the difference
between the ten-point mean roughness of the first and second
surfaces, and (R.sub.1, R.sub.2).sub.max is the greater of the
ten-point mean roughness of the first and second surfaces.
TABLE-US-00001 TABLE 1 Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 1
Ex. 2 Ex. 3 Current 1.sup.st anode plate 60 70 60 50 50 60 density
2.sup.nd anode plate 40 40 40 50 50 40 (A/dm.sup.2) 3.sup.rd anode
plate -- -- 55 -- -- -- Whether chromate solution .smallcircle.
.smallcircle. .smallcircle. .smallcircle. x x was sprayed or not LR
(mm) 3.5 28.9* 2.9 31.5* 3.5 1.3 TR (mm) 2.5 3.1 24.3* 2.5 25.5*
11.4 TR/LR 0.7 0.1 8.4 0.1 7.3 8.8 Deposition 1.sup.st surface 1.5
2.1 4.1 1.0 4.8 1.2 amount of 2.sup.nd surface 2.2 3.9 1.7 4.6 1.1
4.3 anticorrosion material (ppm/m.sup.2) Difference in deposition
0.7 1.8 2.4 2.8 3.7 3.2 amount of anticorrosion material
(ppm/m.sup.2) R.sub.zJIS (.mu.m) 1.sup.st surface 1.6 1.1 0.6 0.5
2.1 2.7 2.sup.nd surface 1.3 1.2 1.9 1.9 0.5 0.6 R.sub.zJIS
deviation (%) 19 8 68 74 76 78 Whether fold occurs or not No No No
Yes No No Whether wrinkle occurs or not No No No No Yes Yes Note:
The longitudinal rising (LR) and transverse rising (TR) with the
mark * are rising in the direction the first surface (a surface
adjacent to the shiny surface of the copper film) of the
electrolytic copper foil is facing, and the ones without the mark *
are rising in the direction the second surface of the electrolytic
copper foil is facing.
[0092] The Table 1 above shows that the fold of the electrolytic
copper foil occurs between the rolls adjacent to each other during
a roll-to-roll process if the longitudinal rising (LR) of the
electrolytic copper foil is more than 30 mm (Comp. Ex. 1) and the
wrinkles of the electrolytic copper foil are caused at the right
and left end portions of the electrolytic copper foil during a
roll-to-roll process if the transverse rising (TR) of the
electrolytic copper foil is more than 25 mm (Comp. Ex. 2).
[0093] Additionally, it has been found that, as in the case of the
Comparative Example 3, if the transverse rising (TR) is more than
8.5 times the longitudinal rising (LR), even the electrolytic
copper foil having the longitudinal rising (LR) of 30 mm or less
and transverse rising (TR) of 25 mm or less wrinkles at the right
and left end portions thereof during a roll-to-roll process.
* * * * *