U.S. patent application number 11/474877 was filed with the patent office on 2006-12-21 for method for treating electrode tabs of crude cell for lithium secondary battery, and crude cell and lithium secondary battery according to the method.
This patent application is currently assigned to Kokam Co., Ltd.. Invention is credited to Ji-Jun Hong.
Application Number | 20060286454 11/474877 |
Document ID | / |
Family ID | 29728630 |
Filed Date | 2006-12-21 |
United States Patent
Application |
20060286454 |
Kind Code |
A1 |
Hong; Ji-Jun |
December 21, 2006 |
Method for treating electrode tabs of crude cell for lithium
secondary battery, and crude cell and lithium secondary battery
according to the method
Abstract
A method for treating electrode tabs of a crude cell for a
lithium secondary battery, a crude cell for a lithium secondary
battery manufactured according to the method, and a lithium
secondary battery employing the crude cell are disclosed. The
method for treating electrode tabs of a crude cell provided with a
plurality of anode plates having respective anode grids, a
plurality of anode plates having respective anode grids includes
the steps of: (a) gathering the anode grids and the cathode grids
cutting the end portions to have the shortest length required for
being welded to respective tab members; (b) welding anode and
cathode tab members to respective end portions of the anode and
cathode grids; (c) attaching insulating tape to wrap the welded
portions; (d) bending the anode and cathode grids; and (e) bending
the respective tab members.
Inventors: |
Hong; Ji-Jun;
(Chungcheongnam-do, KR) |
Correspondence
Address: |
BAKER & DANIELS LLP
205 W. JEFFERSON BOULEVARD
SUITE 250
SOUTH BEND
IN
46601
US
|
Assignee: |
Kokam Co., Ltd.
Kyounggi-DO
KR
|
Family ID: |
29728630 |
Appl. No.: |
11/474877 |
Filed: |
June 26, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10446272 |
May 23, 2003 |
7067218 |
|
|
11474877 |
Jun 26, 2006 |
|
|
|
Current U.S.
Class: |
429/211 ;
228/176; 429/129 |
Current CPC
Class: |
H01M 50/531 20210101;
H01M 10/052 20130101; H01M 10/0583 20130101; H01M 10/0525 20130101;
Y10T 29/49108 20150115; H01M 50/463 20210101; H01M 10/0431
20130101; H01M 50/411 20210101; H01M 50/54 20210101; Y10T 29/49114
20150115; Y02E 60/10 20130101 |
Class at
Publication: |
429/211 ;
429/129; 228/176 |
International
Class: |
H01M 2/26 20060101
H01M002/26; H01M 2/14 20060101 H01M002/14; F01N 7/18 20060101
F01N007/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 12, 2002 |
KR |
10-2002-0032762 |
Claims
1. A method of treating electrode tabs of a crude cell for a
lithium secondary battery including the steps of: (a) welding a tab
member to an end of a grid of said crude cell to create a welded
portion; (b) attaching an insulating tape to the circumference of
an electrode tab so that said insulating tape can wrap around said
electrode tab which is formed by said welded portion.
2. A method of treating electrode tabs of a crude cell for a
lithium secondary battery including the steps of: (a) gathering a
plurality of anode grids and a plurality of cathode grids of said
crude cell provided with a plurality of anode plates having
respective said anode grids, a plurality of cathode plates having
respective said cathode grids, and a separator strip interposed
between said anode plates and said cathode plates which are
disposed alternately; (b) welding an anode tab member and a cathode
tab to respective end portions of said anode grids and said cathode
grids to form an anode side welded portion and a cathode side
welded portion; and (c) attaching an insulating tape to said anode
side welded portion and said cathode side welded portion with an
adhesive so that said insulating tape wraps around said welded
portions.
3. A crude cell for a lithium secondary battery including: (a) a
plurality of anode plates having respective grids; (a) a plurality
of cathode plates having respective grids; (b) a separator; (c) an
anode tab member and a cathode tab member; and (d) an insulating
tape; wherein said anode tab member and said cathode tab member are
welded to said anode grids and said cathode grids, respectively,
and the welded portions are wrapped with said insulating tape.
4. The crude cell as claimed in claim 3, wherein at least two bend
portions are formed at a grid portion and a tab member portion.
5. A crude cell as claimed in claim 3, wherein said crude cell is
utilized in a lithium secondary battery including: (a) a package
member for receiving the crude cell; and (e) an electrolyte filled
in the package member.
Description
[0001] This divisional application claims the benefit of Korean
Patent Application Number 10-2002-0032762 filed Jun. 12, 2002, and
U.S. patent application Ser. No. 10/446,272, filed May 23, 2003,
the complete disclosures of which are hereby expressly incorporated
by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a lithium secondary
battery, and more particularly, to a method for treating electrode
tabs of a crude cell for a lithium secondary battery, in which the
capacity of the battery can be increased by increasing the length
of electrode members without changing the predetermined
specification of a battery package member, and stability of
portions of electrode tabs where the tabs are welded to grids,
respectively, can be enhanced by using insulation tap, and a crude
cell for a lithium secondary battery manufactured according to the
method and a lithium secondary battery employing the crude
cell.
[0004] 2. Description of the Related Art
[0005] In general, since portable electronic appliances such as a
video camera, a portable phone, and a portable PC become lighter in
weight and are designed to do various functions, various research
and development concerning a battery used as an electric source of
such electronic appliances have been performed. Such a battery is
usually made to be rechargeable and can be used continuously.
[0006] Usually, among batteries, a nickel cadmium battery, nickel
hydrogen battery, nickel zinc battery, lithium secondary battery,
or the like is used as an electric power source of electronic
appliances, and the lithium secondary battery of those batteries is
generally used in consideration of its life time and capacity.
[0007] According to the type of electrolyte, the lithium secondary
battery can be classified into a lithium metal battery and a
lithium ion battery, which employ a liquid electrolyte, and a
lithium polymer battery, which employs a polymer solid electrolyte.
According to the type of polymer solid electrolyte, the lithium
polymer battery can be classified into a full-solid type lithium
polymer battery, which does not contain an organic electrolyte, and
a lithium ion polymer battery, which employs a gel type electrolyte
containing organic electrolyte liquid.
[0008] FIG. 1 is a perspective view schematically illustrating a
structure of a conventional lithium secondary battery.
[0009] Referring to FIG. 1, the lithium secondary battery 10
comprises a crude cell 20 and a package member 40 for receiving the
crude cell 20.
[0010] The crude cell 20 has a structure stacked with a plurality
of unit cells 28 or bi-cells 27 according to a capacity of a
battery. Here, as shown in FIG. 2A, each unit cell 28 is composed
of an anode plate 22, a separator 24, and a cathode plate 26 in
sequence, and as shown in FIG. 2B, each bi-cell 27 is composed of
an anode plate 21, a separator 23, a cathode plate 25, a separator
23, and a cathode plate 25 in sequence.
[0011] As shown in FIG. 1, the crude cell 20 includes an anode tab
12 and a cathode tab 14. The anode tab 12 is formed by gathering
anode grids 16 provided at respective anode plates and joining the
anode grids 16 to an anode tab member 11 by welding. The cathode
tab 14 is formed by gathering cathode grids 18 provided at
respective cathode plates and joining the cathode grids 18 to a
cathode tab member 13 by welding. The tab members 11 and 13 are
provided with resin members 17 adhered to non-resin members 15 made
of aluminum or nickel, respectively.
[0012] As shown in FIGS. 1 and 3, the package member 40 is provided
with a receiving portion 32 into which the crude cell 20 is
received and a sealing portion 34 which is hermetically sealed
after the receiving portion 32 is filled with an electrolyte. The
receiving portion 32 is composed of a first receiving portion 36
into which the anode and cathode plates are substantially received,
and a second receiving portion 38 into which anode and cathode tabs
16 and 18 are received. The resin members 17 are interposed between
the sealing portions 34, prevent the electrolyte (not shown) from
leaking out, and prevent possible short circuit in the region of
the tab members 11 and 13.
[0013] As shown in FIG. 3, in the structure of the conventional
lithium secondary battery 10, when the width of the battery, and
the thickness of the battery, i.e., the number of electrode plates
are assumed to be the same as those of the other one, the capacity
of the battery depends on the length of the battery, in particular,
the length of electrode plates which contains an electrode
material. Therefore, in order to increase the capacity of the
battery, there is a method of increasing the length d3 of the first
receiving portion 36 by decreasing the length d1 or length d2 of
the whole length d of the battery, i.e., the length d1 of the
second receiving portion 38 which is occupied by the anode/cathode
tabs 12 and 14, or the length d2 of the sealing portion 34. That is
to say, the length d3 of the first receiving portion 36 can be
relatively increased as much as the decreased length of the length
d1 of the second receiving portion 38 or the length d2 of the
sealing portion 34. However, in the crude cell 20 of the
conventional lithium secondary battery 10, since the minimum length
of anode/cathode grids 16 and 18 and the minimum length of a weld
portion 19 must be secured in the anode/cathode tabs 12 and 14,
there is a limitation in which the second receiving portion 38 is
to be considered as a dead space in the manufacturing process of
the lithium secondary battery until now.
[0014] As shown in FIG. 3, there is a strong possibility that the
package member 40 is damaged by the welded portion 19 to which the
grids 16 and 18 and the tab members 11 and 13 are welded, or rough
and sharp portions existing in the anode/cathode tabs 12 and 14.
Therefore, in the conventional lithium secondary battery 10, there
is a problem in which the package member 40 can be damaged by such
a welded portion 19, or portions of the electrode tabs 12 and 14,
this causes short-circuit to occur, and, therefore, the battery may
malfunction.
SUMMARY OF THE INVENTION
[0015] To solve the above-described problems, it is an objective of
the present invention to provide a method for treating electrode
tabs of a crude cell for a lithium secondary battery which has an
improved structure capable of preventing short-circuit occurring
when a package member is torn by electrode tabs, in particular, a
sharp portion of a welded portion to which grids and tab members
are welded, or the like, and capable of increasing the capacity of
the battery by increasing the length of electrode plates as much as
a decreased portion of the length of a dead space of an electrode
tab portion, and a crude cell and a lithium secondary battery
according to the method.
[0016] Accordingly, to achieve the above object, there is provided
a method of treating electrode tabs of a crude cell for a lithium
secondary battery including the steps of: (a) welding a tab member
to one ends of grids of the crude cell; and (b) attaching
insulating tape to the circumference of an electrode tab so that
the insulating tape can wrap around the electrode tab which is
formed by a welded portion of the grids and the tab member.
[0017] To achieve the above object, there is provided a method of
treating electrode tabs of a crude cell for a lithium secondary
battery including the steps of: (a) respectively, gathering anode
grids and cathode grids of the crude cell provided with a plurality
of anode plates having respective anode grids, a plurality of
cathode plates having respective cathode grids, and a separator
strip interposed between the anode plates and the cathode plates
which are disposed alternately; (b) welding an anode tab member and
a cathode tab to respective end portions of the anode grids and the
cathode grids to form an anode side welded portion and a cathode
side welded portion; and (c) attaching insulating tape to the anode
side welded portion and the cathode side welded portion with an
adhesive so that the insulating tape wraps around the welded
portions.
[0018] To achieve the above object, there is provided a method of
treating electrode tabs of a crude cell provided with a plurality
of anode plates having respective anode grids, a plurality of
cathode plates having respective cathode grids, and a separator
strip interposed, in a fold to fold manner, between the anode
plates and the cathode plates which are disposed alternately
including the steps of: (a. gathering the anode grids and the
cathode grids, respectively, so that the grids can be close to a
first surface and be substantially parallel to the first surface,
and cutting the end portions of the anode grids and the cathode
grids so that the anode grids and the cathode grids can have the
shortest length required for being welded to respective tab
members; (b) welding an anode tab member and a cathode tab member
to respective end portions of the anode grids and the cathode grids
to form an anode side welded portion and a cathode side welded
portion having lengths as short as possible; (c) attaching
insulating tape to the anode side welded portion and the cathode
side welded portion so that the insulating tape can wrap the welded
portions; (d) bending the anode grids and the cathode grids at
respective first bend portions so that the grids can be close to a
second surface which is opposite to the first surface, and be
substantially perpendicular to the second surface; and (e) bending
the respective tab members at respective second bend portions so
that the tab members can be close to the respective first bend
portion, and be substantially parallel to the first surface.
[0019] It is preferable that in the insulating tape attaching step,
the insulating tape is made of polyimide or polypropylene film
having characteristics of heat-resistance and chemical inertness,
and the insulating tape is attached with an acrylate-based adhesive
or silicone-based adhesive.
[0020] It is preferable that the first bend portions are formed at
respective positions within respective areas where the insulating
tape is attached to the anode grids and the cathode grids except
the areas of the welded portions.
[0021] It is preferable that each of the second bend portions are
formed at a position which is at least farther than the welded
portion from the first bend portion, and is positioned within the
portion of the tab member to which the insulating tape is
attached.
[0022] It is preferable that in the first bend portion and the
second bend portion may be formed at positions which are
substantially close to both sides of the insulating tape.
[0023] It is preferable that (a) the separator is provided with a
single-layered or multi-layered porous polymer film made of
polyethylene or polypropylene, has the form of a single strip, and
is multiply folded in a fold to fold fashion so that the anode
plates and the cathode plates can be stacked alternately; (b) the
anode plates having the same predetermined size are equidistantly
attached to one surface of the separator with an ion conductive
polymer adhesive; and (c) the cathode plates having the same
predetermined size are attached to the other surface of the
separator at positions corresponding to the anode plates with an
ion conductive polymer adhesive.
[0024] It is preferable that the circumferential surface of the
crude cell formed in a fold to fold configuration is wrapped with
wrapping tape.
[0025] It is preferable that in the welding step, welding is not
performed at the same time at the cathode side and the anode side,
and any one of two tab members is welded to corresponding grids
first and the other tab member is welded to the other grids.
[0026] To achieve the above object, there is provided a lithium
secondary battery including a crude cell made according to any one
of the above-mentioned methods; and a package member which receives
the crude cell so that any substantial dead space may not be formed
at an electrode tab portion of the crude cell, and can be
hermetically sealed after an electrolyte is filled into the package
member.
[0027] To achieve the above object, there is provided a crude cell
for a lithium secondary battery including: a plurality of anode
plates having respective grids; a plurality of cathode plates
having respective grids; a separator; an anode tab member and a
cathode tab member; and insulating tape; wherein the anode tab
member and the cathode tab member are welded to the anode grids and
the cathode grids, respectively, and the welded portions are
wrapped with the insulating tape.
[0028] It is preferable that at least two bend portions are formed
at a grid portion and a tab member portion.
[0029] To achieve the above object, there is provided a lithium
secondary battery including: a crude cell of claim; a package
member for receiving the crude cell; and an electrolyte filled in
the package member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] The above objective and advantages of the present invention
will become more apparent by describing in detail preferred
embodiments thereof with reference to the attached drawings in
which:
[0031] FIG. 1 is a perspective view schematically illustrating a
conventional lithium secondary battery;
[0032] FIG. 2A is a diagram schematically illustrating a structure
of a unit cell of a conventional lithium secondary battery;
[0033] FIG. 2B is a diagram schematically illustrating a structure
of a bi-cell of a conventional lithium secondary battery;
[0034] FIG. 3 is a section view schematically illustrating a
structure of a conventional lithium secondary battery;
[0035] FIG. 4 is an exploded perspective view schematically
illustrating a lithium secondary battery according to a preferred
embodiment of the present invention;
[0036] FIG. 5 is a section view of the battery of FIG. 4 in the
assembled state;
[0037] FIG. 6 is a section view schematically illustrating a
structure of the package member shown in FIGS. 4 and 5;
[0038] FIGS. 7A through 7H are process diagrams conceptually
illustrating a method of treating electrode tabs according to a
preferred embodiment of the present invention;
[0039] FIG. 8 is a flowchart illustrating the steps of the method
of treating electrode tabs of a crude cell for a lithium secondary
battery according to a preferred embodiment of the present
invention;
[0040] FIG. 9 is a process diagram illustrating a process of
gathering grids of a crude cell toward a position, in the step of
gathering and cutting grids in FIG. 8;
[0041] FIG. 10 is a perspective view illustrating the step of
attaching insulating tape to a welded portion with an adhesive;
[0042] FIG. 11 is a perspective view illustrating the step of
forming a first bend portion in FIG. 8;
[0043] FIG. 12 is a perspective view illustrating the step of
forming a second bend portion in FIG. 8;
[0044] FIGS. 13 through 15 are process diagrams schematically
illustrating the steps of a method of treating electrode tabs of a
crude cell for a lithium secondary battery according to another
embodiment of the present invention;
[0045] FIG. 16 is a schematic section view of a lithium secondary
battery employing the crude cell shown in FIG. 15; and
[0046] FIG. 17 is a schematic section view illustrating a structure
of a lithium secondary battery employing a crude cell according to
still another embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0047] Now, a method of treating electrode tabs of a crude cell for
a lithium secondary battery according to a preferred embodiment of
the present invention, and a crude and a lithium secondary battery
according to the method will be described in detail with reference
to the attached drawings.
[0048] FIG. 4 is an exploded perspective view schematically
illustrating a lithium secondary battery according to a preferred
embodiment of the present invention, and FIG. 5 is a section view
of the battery of FIG. 4 in the assembled state.
[0049] Referring to FIGS. 4 and 5, a lithium secondary battery
according to a preferred embodiment of the present invention is
comprised of a crude cell 110 having a structure of an anode
plate/a separator/a cathode plate, and a package member 120 capable
of receiving the crude cell 110 and being sealed.
[0050] Theoretically, crude cell 110 may be a lithium secondary ion
battery or a lithium secondary polymer battery. In addition, the
crude cell 110 may be a unit cell or bi-cell, or a cell formed by
stacking the unit cells or the bi-cells. Further, each electrode
plate (the anode plate or the cathode plate) is comprised of a main
body of an electrode plate, and a grid extending from the electrode
plate.
[0051] The grids are classified into anode grids and cathode grids,
and the anode grids and the cathode grids may be disposed at
opposite side positions with respect to the lengthwise direction of
the crude cell 110. However, in this embodiment, it is assumed that
the anode grids and the cathode grids are disposed at the same side
position with respect to the lengthwise direction of the crude cell
110.
[0052] In general, the crude cell 110 is distinguished from a
battery 100, in itself, in which the crude cell 110 is received in
the package member 120, an electrolyte is filled in the package
member 120, and the package member 120 is hermetically sealed. In
addition, although the term `crude cell` is used together with the
term `battery assembly (electrode assembly)`, the term `crude cell`
is used in this embodiment unless specifically stated
otherwise.
[0053] Although the crude cell may have any of various structures
described above, it is preferable that the crude cell 110 is
manufactured by the apparatus as disclosed in Korean Patent
Application No. 10-2001-28493 (Automated system for manufacturing
lithium secondary battery), Korean Patent Application No.
10-2001-28494 (Lamination Apparatus for automated system for
manufacturing lithium secondary battery), and Korean Patent
Application No. 10-2001-28495 (Packing apparatus for automated
system for manufacturing lithium secondary battery), which were
filed on May 23, 2001 by the applicant of the present
invention.
[0054] A schematic structure of the crude cell 110 is a laminated
structure having 3 layers of an anode plate/a separator/a cathode
plate, and will be described as follows.
[0055] In the crude cell 110, the anode plate 111 is made by
coating a positive active material on one or both surfaces of a
metal foil collector such as an aluminium foil collector, and
drying the positive active material, and an anode grid is formed to
be extended from a portion of the collector where the positive
active material is not coated. The cathode plate 113 is made by
coating a negative active material on one or both surfaces of a
metal foil collector such as a copper foil collector, and drying
the negative active material, and a cathode grid is formed to be
extended from a portion of the collector where the negative active
material is not coated. The separator 115 includes at least one
porous polymer membrane of polyethylene (PE) or polypropylene (PP),
and has a single-layered or multi-layered structure. The separator
115 further includes adhesive portions to which the anode plate 111
and the cathode plate 113 are attached, an insulating portion for
insulating the anode plate and the cathode plate from each other,
and a winding portion for winding the surface of a laminate when
the laminate is finally formed with the anode/cathode plates. Here,
the adhesive portion and the insulating portion are formed in
sequence, and the length of the insulating portion is set to be
slightly longer than that of the adhesive length. The reason is
that although the adhesive portion has the same width as the width
of the anode plate or the cathode plate, the insulating portion
must have an additional length as much as the thickness of the
anode plate or the cathode plate since the insulating portion must
be folded about a side of the anode plate or the cathode plate. In
addition, it is preferable that the winding portion has a
sufficient length enough to wind the electrode laminate. It is
preferable that an ion-conductive polymer adhesive (not shown)
which is applied to the surface of the separator 115 is selected
among solvent type adhesives utilizing ion-conductive polymers, for
example, an styrene-butadiene rubber (SBR) latex-based adhesive, an
acrylic solvent adhesive, an adhesive utilizing polyacrylonitrile
(PAN), an adhesive using a blend of PAN and polyvinylidene fluoride
(PVDF), an polymer adhesive using polymethyl methacrylate (PMMA),
or their like. After the separator 115 is folded in a zigzag
manner, more accurately in a fold to fold manner so that the anode
plates and the cathode plates may alternate with each other, the
folded separator 115 is taped with a given length of tape 117 for
convenience of subsequent processes.
[0056] As shown in FIGS. 4 and 5, the package member 120 comprises
a first receiving portion 121 for receiving a main body of the
crude cell 110, a sealing portion 123 provided around the first
receiving portion 121, and a second receiving portion 131 for
receiving an electrode tab 130 portion. As shown in FIG. 6, the
package member 120 is made of a thin aluminium plate having a
thickness of about 20.about.50 .mu.m, and a polypropylene film 129
having a thickness of about 30 .mu.m is attached with an adhesive
127 to the inner surfaces of the aluminum member 125, i.e., the
surfaces for receiving the crude cell 110, and a nylon film 122 is
attached with an adhesive 127 to the outer surfaces of the aluminum
member 125.
[0057] As shown in FIGS. 4 and 5, when the crude cell 110 is
received in the first receiving portion 121 of the package member
120, the length of the electrode plates can be lengthened while the
space of the electrode tab portion is reduced on the premise that
the width of the battery and the number of the electrode plates
(the anode plates and the cathode plates) are the same as a
conventional battery.
[0058] Referring to FIGS. 4 and 5, in the lithium secondary battery
100 according to a preferred embodiment of the present invention,
since the length D1 of the second receiving portion 131 occupied by
the electrode tab 130 portion is reduced less than the length d1 of
that of a conventional battery, the length D3 of the first
receiving portion 121 can be longer than the length d3 of that of
the conventional battery. Consequently, the unnecessary dead space
can be reduced and the capacity of the battery can be increased. As
a matter of course, the thickness T of the battery, i.e., the
number of the electrode plates, and the width W of the battery have
constant values since the specification of a battery is
predetermined by requirements of electronic appliances which use
the battery.
[0059] Now, separate processes of a method of treating electrode
tabs of a crude cell for a lithium secondary battery will be
described as follows.
[0060] FIGS. 7A through 7H are process diagrams conceptually
illustrating a method of treating electrode tabs according to a
preferred embodiment of the present invention, and FIG. 8 is a
flowchart illustrating the steps of the method.
[0061] In the following descriptions of the steps of this
embodiment, the members related to anode and cathode plates such as
grids, tabs, or the like are generally described without specifying
their polarity. Therefore, such members whose polarity is not
specified denote both anode members and cathode members unless
specifically stated otherwise. As a matter of course, in a specific
process, it should be understood that members having any one
polarity may be processed first, and then members having the other
polarity may be processed.
[0062] Referring to FIGS. 7A through 7H and FIG. 8, a method of
treating electrode tabs according to a preferred embodiment of the
present invention includes the steps of gathering and cutting grids
141 of a crude cell 110 (S10), welding the grids 141 to a tab
member 143 (S20), attaching an insulating tape 147 to a welded
portion 145 (S30), bending the grids 141 to form a first bend
portion (S40), and bending the tab member 143 to form a second bend
portion (S50).
[0063] First, in the step S10, the grids 141 are gathered so that
the end portions of the grids 141 may be close to a first surface
116 of the crude cell 110, and be substantially parallel to the
first surface 116. Then, the end portions of the grids 141 are
cut.
[0064] As shown in FIG. 7A, generally, the grids 141 of the crude
cell 110 are disposed to be substantially parallel to the direction
of electrode plates (anode plates or cathode plates), or are
randomly scattered. Therefore, in order to weld such grids 141 to
the tab member 143 at one position, it is necessary to gather and
arrange the grids 143. In addition, in order to minimize the dead
space, it is necessary that the grids 141 are cut to have a minimum
length.
[0065] In the step S10, as shown in FIG. 9, when a slope 151 is
moved to contact the grids 141 while the crude cell 110 shown in
FIG. 7A is fixed by a jig 150, the grids 141 are pushed to the
direction of the first surface 116 of the crude cell 110, and are
gathered to be substantially parallel to the first surface 116, as
shown in FIG. 7B. Subsequently, as shown in FIG. 7C, when a cutter
160 having a predetermined shape is raised while the crude cell is
fixed, unnecessary portions of the end portions of the grids 141
are cut away, and the end portions of the grids 141 are gathered
more compactly, as shown in FIG. 7D.
[0066] Thereafter, in the step S20, the tab member 143 comprising a
resin portion 142 and a non-resin portion 144 is welded to the
grids 141 of the crude cell 110 shown in FIG. 7D, and laser
welding, ultrasonic welding, spot welding or the like is mainly
used in this embodiment. Usually, the width of the tab member 143
is wider than that of the grids 141. Therefore, although welding
may be performed with the tab member 143 disposed under the grids
141, it is preferable that welding is performed with the tab member
143 disposed on the grids 141. The length of a welded portion 145
formed by welding the grids 141 to the end portion of the non-resin
portion 144 of the tab member 143 is in a range of about 1.0
through 2.5 mm. As a matter of course, although welding can be
performed so that the length of the welded portion 145 may be
shorter than a minimum length of the range, the possibility of
welding defects increases. To the contrary, when the length of the
welded portion 145 is longer than a maximum length of the range, it
is undesirable that the unnecessary dead space and material cost
increase.
[0067] Thereafter, in the step S30, as shown in FIG. 7F and FIG.
10, the welded portion is wrapped with tape so that metal
(aluminum) portions 127 (FIG. 6) of the package member 120 can be
prevented from being damaged by the grids 141 or the tab member
143, and therefore the battery 100 can be prevented from being
short-circuited. Insulating tape 147 is attached with an adhesive
(not shown) to the upper and lower surfaces of the welded portion
145. Here, it is preferable that the insulating tape 147 is made of
polyimide or polypropylene film having characteristics of
heat-resistance and chemical inertness. In addition, it is
preferable that an acrylate-based adhesive or a silicone-based
adhesive is used as an adhesive for attaching the insulating tape
147 to the welded portion 145. It is preferable that dimensions of
the insulating tape 147 attached to the upper and lower surfaces of
the welded portion 145 are sufficiently extended in the lengthwise
direction of the grids 141 and the tab member 143 and in the
widthwise direction of the grids 141 with reference to the center
of the welded portion 145.
[0068] Subsequently, in the step S40, as shown in FIGS. 7G and FIG.
11, the grids 141 are bent at a first bend portion 171 in the
direction of arrow A in FIG. 11 so that the grids 141 may be close
to a second surface 118 which is opposite to the first surface 116
of the crude cell 110, and may be perpendicular to the second
surface 118. Here, it is not preferable that the first bend portion
171 is formed at the welded portion 145. In addition, although the
first bend portion 171 may be formed at a portion of the grids 141
to which the insulating tape is not attached, it is preferable that
the first bend portion 171 is formed at the portion of the grids
141 to which the insulating tape 147 is attached. This is intended
to maintain the first bend portion 171 in the bent shape by using
the dimensionally stable insulating tape 147 since the grids 141
may have a property of restoration to its original shape, and may
exhibit a tendency to be straightened. In addition, when the grids
141 are bent together with the insulating tape 147, the strength of
the grids 141 can be maintained at the bent portion. For example,
in a battery employing mesh type grids, although the grids suffer
damage at the first bend portion 171, there is an advantage in
which the insulating tape 147 can protect the grids 141 from
damage.
[0069] Subsequently, in step S50, as shown in FIGS. 7H and FIG. 12,
the tab member 143 is bent at the second bend portion 173 in the
direction of arrow B so that the tab member 143 may be close to the
first bend portion 171 and may be substantially parallel to the
first surface 116. It is not preferable that the second bend
portion 173 is formed at the welded portion 145, and it is
preferable that the second bend portion 173 is formed at a position
which is at least farther than the welded portion 145 from the
first bend portion 171, and is positioned within the portion of the
tab member 143 to which the insulating tape 147 is attached. The
reason is that, as described above, the bent portions can be
maintained in a stable state, the strength of the tab member 143
and the welded portion 145 can not be degraded, and the bend
portions 171 and 173 and the welded portion 145 can be protected
from damage. In addition, it is preferable that the distance
between the first bend portion 171 and the second bend portions 173
is adjusted to be appropriate for the number of stacked electrode
plates of the crude cell 110 (the thickness of the crude cell 110).
That is, it is preferable that when the number of stacked electrode
plates is relatively large, the distance is set to be
correspondingly long, and when the number of stacked electrode
plates is relatively small, the distance is set to be
correspondingly short.
[0070] On the contrary, the first bend portion 171 and the second
bend portion 173 may be formed at positions which are substantially
close to both sides of the insulating tape 147. That is, the first
bend portion 171 may be formed at a position within the portion
composed of the grids 141 only, and the second bend portion 173 may
be formed at a position within the portion composed of the tab
member 143 only so that the insulating tape 147 may not be
bent.
[0071] Referring to FIGS. 4 and 5 again, since the lithium
secondary battery 100 of the preferred embodiment of the present
invention is. manufactured by the above-described method of
treating electrode tabs of a crude cell, the welded portion of the
tab member 143 to the grids 141 can be protected by the insulating
tape 147, and since the first bend portion 171 and the second bend
portion 173 are formed at portions to which the insulating tape 147
are attached, the bent configuration of the bent portions can be
more stably fixed, and the grids 141 and the tab member 143 can be
protected from damage.
[0072] FIGS. 13 through 15 are process diagrams schematically
illustrating the steps of a method of treating electrode tabs of a
crude cell for a lithium secondary battery according to another
embodiment of the present invention, and FIG. 16 is a schematic
section view of a lithium secondary battery employing the crude
cell shown in FIG. 15.
[0073] A method of treating electrode tabs of a crude cell 210 for
a lithium secondary battery according to this embodiment further
includes the step of forming a third bend portion 250 in addition
to a first bend portion 220 and a second bend portion 240.
[0074] Although such a third bend portion 250 are necessary for
various reasons, the third bend portion 250 is mainly intended to
flexibly meet different processing conditions due to variations in
the length of a welded portion 245, for example, a longer length of
the welded portion 245, and variations in the thickness of a
battery determined by the number of stacked electrode plates (anode
plates and cathode plates). As a matter of course, in this
embodiment, the number of processing steps increases
correspondingly. As shown in FIGS. 13 and 14, it is preferable that
a non-resin portion 242 of a tab member 243 is set to be relatively
longer, and, as shown in FIG. 16, the tab member 243 is bent
together with insulating tape 247 at the third bend portion 250. To
this end, the insulating tape 247 having a length longer than that
of the insulating tape 147 of the previous embodiment is used.
[0075] FIG. 17 is a schematic section view illustrating a structure
of a lithium secondary battery employing a crude cell according to
still another embodiment of the present invention.
[0076] Referring to FIG. 17, a crude cell 310 according to this
embodiment has a structure in which after grids 311 are gathered
and are welded to a tab member 313 to form a welded portion 315,
insulating tape 317 is attached to the circumference of the welded
portion 315 without forming any bent portion. When such a crude
cell 310 is received in a receiving portion 322 of a package member
320, a liquid electrolyte (not shown) is filled into the receiving
portion 322, and then the package member 320 is hermetically
sealed, the manufacture of a lithium secondary battery is
completed.
[0077] Here, since the welding step and the insulating tape
attaching step have been described above, detailed descriptions
concerning those steps are omitted. In addition, the crude cell 310
may be a unit cell or bi-cell, or a cell formed by stacking the
unit cells or the bi-cells. The lithium secondary battery 300
according to this embodiment is not related to a decrease of the
dead space, and is intended to prevent a short circuit from being
formed.
[0078] As described above, the method of treating electrode tabs of
a crude cell for a lithium secondary battery according to the
present invention, and the crude cell and the battery according to
the method have the following effects.
[0079] First, since the circumferences of welded portions formed by
welding tab members to grids of the lithium secondary battery are
insulated by attaching insulating tape and, accordingly, the
battery is prevented from forming a short circuit due to a sharp
portion around welded portions or a foreign material from a welding
defect or the like, safety and reliability of the battery can be
enhanced.
[0080] Second, since the electrode tabs including the welded
portions formed by welding the tab members to the grids of the
lithium secondary battery are bent and disposed to be nearly
parallel to a section of the battery, the dead space can be reduced
to be smaller than that of a conventional battery, and since the
length of the electrode plates can be lengthened as much as the
reduced dead space, there is an effect that the capacity of the
battery can be increased when the battery is compared to a
conventional battery having the same dimensional
specifications.
[0081] Third, since the grids or the tab members are bent together
with the dimensionally stable insulating tape in the steps of
bending the electrode tabs, the strength of the bent portions can
be enhanced, and there is an effect in which the bent portions are
prevented from being damaged when the portions are being bent.
[0082] While this invention has been particularly shown and
described with reference to preferred embodiments thereof, it will
be understood by those skilled in the art that various changes in
form and details may be made therein without departing from the
spirit and scope of the invention as defined by the appended
claims.
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