U.S. patent application number 12/309549 was filed with the patent office on 2009-12-24 for electrode assembly having tab-lead joint portion of minimized resistance difference between electrodes and electrochemical cell containing the same.
This patent application is currently assigned to LG Chem, Ltd.. Invention is credited to Jeong Hee Choi, Ji Heon Ryu, Youngjoon Shin, Kwangho Yoo.
Application Number | 20090317717 12/309549 |
Document ID | / |
Family ID | 38981667 |
Filed Date | 2009-12-24 |
United States Patent
Application |
20090317717 |
Kind Code |
A1 |
Ryu; Ji Heon ; et
al. |
December 24, 2009 |
Electrode Assembly Having Tab-Lead Joint Portion of Minimized
Resistance Difference Between Electrodes and Electrochemical Cell
Containing The Same
Abstract
Disclosed herein is a stacking or stacking/folding type
electrode assembly of a cathode/separator/anode structure, wherein
the electrode assembly is constructed in a structure in which tabs
(electrode tabs), having no active material applied thereto,
protrude from electrode plates constituting the electrode assembly,
the electrode tabs are electrically connected to an electrode lead,
and the pluralities of electrode tabs are joined to the top and the
bottom of the electrode lead at an electrode lead-electrode tabs
joint portion such that the resistance difference between
electrodes at the electrode lead-electrode tabs joint portion is
minimized. Also disclosed is an electrochemical cell including the
electrode assembly.
Inventors: |
Ryu; Ji Heon; (Seoul,
KR) ; Choi; Jeong Hee; (Busan, KR) ; Yoo;
Kwangho; (Daejeon, KR) ; Shin; Youngjoon;
(Daejeon, KR) |
Correspondence
Address: |
LERNER, DAVID, LITTENBERG,;KRUMHOLZ & MENTLIK
600 SOUTH AVENUE WEST
WESTFIELD
NJ
07090
US
|
Assignee: |
LG Chem, Ltd.
Seoul
KR
|
Family ID: |
38981667 |
Appl. No.: |
12/309549 |
Filed: |
July 21, 2007 |
PCT Filed: |
July 21, 2007 |
PCT NO: |
PCT/KR2007/003530 |
371 Date: |
June 24, 2009 |
Current U.S.
Class: |
429/211 |
Current CPC
Class: |
H01G 11/06 20130101;
H01G 11/26 20130101; H01M 50/54 20210101; H01M 10/04 20130101; H01M
50/531 20210101; Y02E 60/10 20130101; H01M 2220/30 20130101 |
Class at
Publication: |
429/211 |
International
Class: |
H01M 4/02 20060101
H01M004/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 24, 2006 |
KR |
10-2006-0068825 |
Claims
1. A stacking or stacking/folding type electrode assembly of a
cathode/separator/anode structure, wherein the electrode assembly
is constructed in a structure in which tabs (electrode tabs),
having no active material applied thereto, protrude from electrode
plates constituting the electrode assembly, the electrode tabs are
electrically connected to an electrode lead, and the pluralities of
electrode tabs are joined to the top and the bottom of the
electrode lead at an electrode lead-electrode tabs joint portion
such that the resistance difference between electrodes at the
electrode lead-electrode tabs joint portion is minimized.
2. The electrode assembly according to claim 1, wherein the number
of the electrode tabs joined to the top of the electrode lead is
approximately equal to that of the electrode tabs joined to the
bottom of the electrode lead.
3. The electrode assembly according to claim 1, wherein the
electrode lead is made of a metal plate.
4. The electrode assembly according to claim 3, wherein the metal
plate is selected from a group consisting of an aluminum plate, a
copper plate, a nickel plate, a copper plate coated with nickel,
and a SUS plate.
5. The electrode assembly according to claim 1, wherein the
electrode lead is formed in the shape of a straight line in
vertical section, and the electrode lead is joined to the electrode
tabs by welding.
6. An electrochemical cell including an electrode assembly
according to claim 1.
7. The electrochemical cell according to claim 6, wherein the
electrochemical cell is a secondary battery or a capacitor.
8. The electrochemical cell according to claim 7, wherein the
secondary battery is constructed in a structure in which an
electrode assembly is mounted in a battery case made of a laminate
sheet including a metal layer and a resin layer in a sealed
state.
9. The electrochemical cell according to claim 8, wherein the
secondary battery is a unit cell for high-output, large-capacity
battery packs.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an electrode assembly
having a tab-lead joint portion of minimized resistance difference
between electrodes, and, more particularly, to a stacking or
stacking/folding type electrode assembly of a
cathode/separator/anode structure, wherein the electrode assembly
is constructed in a structure in which tabs (electrode tabs),
having no active material applied thereto, protrude from electrode
plates constituting the electrode assembly, the electrode tabs are
electrically connected to an electrode lead, and the pluralities of
electrode tabs are joined to the top and the bottom of the
electrode lead at an electrode lead-electrode tabs joint portion
such that the resistance difference between electrodes at the
electrode lead-electrode tabs joint portion is minimized.
BACKGROUND OF THE INVENTION
[0002] As mobile devices have been increasingly developed, and the
demand for such mobile devices has increased, the demand for
batteries has also sharply increased as an energy source for the
mobile devices. Also, much research on batteries satisfying various
needs has been carried out.
[0003] In terms of the shape of batteries, the demand for prismatic
secondary batteries or pouch-shaped secondary batteries, which are
thin enough to be applied to products, such as mobile phones, is
very high. In terms of the material for batteries, on the other
hand, the demand for lithium secondary batteries, such as lithium
ion batteries and lithium ion polymer batteries, having high energy
density, high discharge voltage, and high output stability, is very
high.
[0004] Furthermore, secondary batteries may be classified based on
the construction of an electrode assembly having a
cathode/separator/anode structure. For example, the electrode
assembly may be constructed in a jelly-roll (winding) type
structure in which long-sheet type cathodes and long-sheet type
anodes are wound while separators are disposed respectively between
the cathodes and the anodes, a stacking type structure in which
pluralities of cathodes and anodes having a predetermined size are
successively stacked while separators are disposed respectively
between the cathodes and the anodes, or a stacking/folding type
structure in which pluralities of cathodes and anodes having a
predetermined size are successively stacked while separators are
disposed respectively between the cathodes and the anodes to
constitute a bi-cell or a full-cell, and then the bi-cell or the
field-cell is wound.
[0005] FIG. 1 is a side view typically illustrating the general
structure of a conventional representative stacking type electrode
assembly.
[0006] Referring to FIG. 1, the stacking type electrode assembly 10
is constructed in a structure in which cathodes 20, each of which
has a cathode active material 22 applied to the opposite major
surfaces of a cathode current collector 21, and anodes 30, each of
which has an anode active material 32 applied to the opposite major
surfaces of an anode current collector 31, are sequentially stacked
while separators 70 are disposed respectively between the cathodes
20 and the anodes 30.
[0007] From one-side ends of the cathode current collectors 21 and
the anode current collectors 31 protrude pluralities of cathode
tabs 41 and anode tabs 51, to which an active material is not
applied, such that the cathode tabs 41 and the anode tabs 51 are
electrically connected to a cathode lead 60 and an anode lead (not
shown) constituting electrode terminals of a battery. The cathode
tabs 41 and the anode tabs 51 are joined in a concentrated state,
and are then connected to the cathode lead 60 and the anode lead,
respectively. This structure is more clearly illustrated in FIGS. 2
and 3, which are partially enlarged views typically illustrating
the joint portion between the cathode tabs and the cathode lead.
FIGS. 2 and 3 illustrate only the joint portion between the cathode
tabs and the cathode lead for convenience of description, although
this structure is also applied to the joint portion between the
anode tabs and the anode lead.
[0008] Referring to these drawings, the cathode tabs 40 are brought
into tight contact with each other in the direction indicated by an
arrow, and are connected to the cathode lead 60. The cathode lead
60 is normally joined to the cathode tabs by welding. The cathode
lead 60 may be joined to the cathode tabs while the cathode lead 60
is located at the top of the uppermost cathode tab 41, as shown in
FIG. 2. Alternatively, the cathode lead 60 may be joined to the
cathode tabs while the cathode lead 60 is located at the bottom of
the lowermost cathode tab 42, as shown in FIG. 3.
[0009] Due to this joint structure, however, the resistance
difference between the electrodes with respect to each electrode
lead may occur in the electrode assembly. Specifically, the
electrode resistance of the electrode tab at the shortest distance
from the electrode lead is different from that of the electrode tab
at the longest distance from the electrode lead. In a middle- or
large-sized battery pack including the electrode assembly with the
above-stated construction, large-capacity electricity is charged
and discharged. Consequently, the electrodes may be nonuniformly
operated or deteriorated, due to the resistance difference between
the electrodes, which may reduce the life span of the battery.
[0010] Also, when the electrode tabs are joined to the electrode
lead in the above-described structure, a welding process for the
joining the electrode tabs and the electrode lead is performed only
in one direction, with the result that the joint force between the
electrode tabs and the electrode lead may be lowered.
[0011] Consequently, there is a high necessity for an electrode
assembly having an improved structure in which the joint force
between the electrode tabs and the electrode lead is increased
while the resistance difference between the electrodes is
minimized.
SUMMARY OF THE INVENTION
[0012] Therefore, the present invention has been made to solve the
above problems, and other technical problems that have yet to be
resolved.
[0013] Specifically, it is an object of the present invention to
provide an electrode assembly having a structure in which the
resistance difference between electrodes is minimized.
[0014] It is another object of the present invention to provide an
electrode assembly having a structure in which the joint force
between electrode tabs and each electrode lead is increased,
whereby high reliability is secured.
[0015] It is a further object of the present invention to provide
an electrochemical cell including the electrode assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The above and other objects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0017] FIG. 1 is a typical view illustrating the general structure
of a conventional stacking type electrode assembly;
[0018] FIGS. 2 and 3 are partially enlarged views illustrating the
connection between cathode tabs, joined to each other in a
concentrated state, and a cathode lead of the electrode assembly
shown in FIG. 1; and
[0019] FIG. 4 is a partially enlarged view illustrating the
connection between cathode tabs, joined to each other in a
concentrated state, and a cathode lead of an electrode assembly
according to a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0020] In accordance with one aspect of the present invention, the
above and other objects can be accomplished by the provision of a
stacking or stacking/folding type electrode assembly of a
cathode/separator/anode structure, wherein the electrode assembly
is constructed in a structure in which tabs (electrode tabs),
having no active material applied thereto, protrude from electrode
plates constituting the electrode assembly, the electrode tabs are
electrically connected to an electrode lead, and pluralities of
electrode tabs are joined to the top and the bottom of the
electrode lead at an electrode lead-electrode tabs joint portion
such that the resistance difference between electrodes at the
electrode lead-electrode tabs joint portion is minimized.
[0021] In a preferred embodiment, the number of the electrode tabs
joined to the top of the electrode lead is approximately equal to
that of the electrode tabs joined to the bottom of the electrode
lead such that the electrode tabs are joined to the electrode lead
approximately in a symmetrical fashion. Specifically, when a total
of A electrode tabs are joined to the top of the electrode lead,
the same number of electrode tabs, i.e., a total of A electrode
tabs, or the similar number of electrode tabs, i.e., a total of A'
electrode tabs, may be joined to the bottom of the electrode
lead.
[0022] This structure will be described in more detail with
reference to FIG. 4. Referring to FIG. 4, electrode tabs 200 are
joined to the electrode lead 100 while three electrode tabs 210 are
located at the top 110 of the electrode lead 100, and three
electrode tabs 220 are located at the bottom 120 of the electrode
lead 100. Consequently, the electrode tabs 200 are disposed at the
electrode lead 100, at a joint region A, in a symmetrical structure
in which the electrode tabs 200 are disposed symmetrically at the
top 110 and the bottom 120 of the electrode lead 100.
[0023] The electrode tabs 200 are brought into tight contact with
each other in the direction indicated by an arrow, while the
electrode lead 100 is disposed between the electrode tabs 200, and
then the electrode lead 100 is joined to the electrode tabs 200 by
welding. According to circumstances, the electrode lead 100 may be
inserted between the electrode tabs 200, while the electrode tabs
are in tight contact with each other, and then the electrode lead
100 may be joined to the electrode tabs 200 by welding.
[0024] According to the present invention, the electrode lead is
not particularly restricted so long as the electrode lead is made
of a material that can be electrically connected to the electrode
tabs. Preferably, the electrode lead is made of a metal plate. The
metal plate may be selected from a group consisting of an aluminum
plate, a copper plate, a nickel plate, a copper plate coated with
nickel, and a SUS plate.
[0025] Also, the electrode lead is not particularly restricted so
long as the electrode lead is constructed in a structure in which
the electrode lead is easily connected to the electrode tabs. For
example, the electrode lead may be formed in the shape of a
straight line in vertical section. The electrode lead may be
connected to the electrode tabs in various manners. Preferably, the
electrode lead is more stably connected to the electrode tabs by
welding. The welding may include ultrasonic welding, laser welding,
and resistance welding.
[0026] In accordance with another aspect of the present invention,
there is provided an electrochemical cell including the electrode
assembly with the above-stated construction.
[0027] The electrochemical cell is one that provides electricity
through an electrochemical reaction. For example, the
electrochemical cell may be an electrochemical secondary battery or
an electrochemical capacitor. Especially, the electrochemical cell
is preferably applied to a lithium secondary battery.
[0028] The secondary battery includes an electrode assembly that
can be charged and discharged. Preferably, the secondary battery is
constructed in a structure in which an electrode assembly is
mounted in a battery case made of a laminate sheet including a
metal layer and a resin layer in a sealed state. The secondary
battery with the above-described structure may be referred to as a
pouch-shaped secondary battery.
[0029] Also, the secondary battery is preferably used as a unit
cell for high-output, large-capacity battery packs.
[0030] Hereinafter, examples of the present invention will be
described in more detail. It should be noted, however, that the
scope of the present invention is not limited by the illustrated
examples.
EXAMPLE 1
[0031] A cathode active material containing lithium and an anode
active material containing graphite were applied to opposite major
surfaces of an aluminum foil and a copper foil, respectively, and
then the aluminum foil and the copper foil were cut to manufacture
cathode plates and anode plates, having electrode tabs to which the
active materials were not applied. Subsequently, the cathode plates
and the anode plates were sequentially stacked while separators
were disposed respectively between the cathode plates and the anode
plates. After that, a cathode lead was welded to the cathode tabs,
while the cathode lead was disposed between the cathode tabs, and
an anode lead was welded to the anode tabs, while the anode lead
was disposed between the anode tabs, as shown in FIG. 4, to
manufacture an electrode assembly.
COMPARATIVE EXAMPLE 1
[0032] An electrode assembly was manufactured in the same method as
Example 1 except that the cathode lead was welded to the cathode
tabs, while the cathode lead was located at the bottom of the
lowermost cathode tab, and the anode lead was welded to the anode
tabs, while the anode lead was located at the bottom of the
lowermost anode tab, as shown in FIG. 3.
EXPERIMENTAL EXAMPLE 1
[0033] Resistance measurement experiments were carried out on 20
electrode assemblies manufactured respectively according to Example
1 and Comparative example 1. The experiment results are indicated
in Table 1 below. The experiments were repeatedly carried out on
the respective 20 electrode assemblies. The resistance at the joint
portion between the cathode tabs and the cathode lead was measured
using an Agilent milli-ohmmeter. The measured experiment values are
indicated in Table 1 below as an average resistance value.
[0034] Group A of Table 1 below indicates the cathode tabs located
at the upper part of the electrode assembly. For Example 1, Group A
indicates the cathode tabs located at the top of the cathode lead.
For Comparative example 1, Group A indicates the cathode tabs at
long distances from the cathode lead. Group B of Table 1 below
indicates the cathode tabs located at the lower part of the
electrode assembly. For Example 1, Group B indicates the cathode
tabs located at the bottom of the cathode lead. For Comparative
example 1, Group B indicates the cathode tabs at short distances
from the cathode lead.
TABLE-US-00001 TABLE 1 Average Average Average resistance of A-
resistance of B- resistance group cathode group cathode difference
between tabs (m.OMEGA.) tabs (m.OMEGA.) electrodes Example 1 5.32
5.31 0.01 Comparative 5.37 5.32 0.05 example 1
[0035] As can be seen from Table 1 above, the resistance of the
cathode tabs located at the top of the cathode lead was
approximately equal to that of the cathode tabs located at the
bottom of the cathode lead in the electrode assembly manufactured
according to Example 1. Specifically, the resistance difference did
not occur at all the cathodes. In the electrode assembly
manufactured according to Comparative example 1, on the other hand,
the resistance difference occurred between the cathode tabs at
short distances from the cathode lead and the cathode tabs at long
distances from the cathode lead. Even though the resistance
difference is slight, the resistance difference causes the
operational nonuniformity between the electrodes during the
repetitive charge and discharge of the electrode assembly or in a
high-output, large-capacity battery pack having a large amount of
electric current. Especially, the resistance difference causes
rapid deterioration of specific electrodes, during the long-term
use of the electrode assembly, with the result that the life span
of a battery is reduced.
INDUSTRIAL APPLICABILITY
[0036] As apparent from the above description, the electrode
assembly according to the present invention has the following
effects. The electrode assembly is constructed in a structure in
which the resistance difference between electrodes is minimized.
Furthermore, the electrode assembly is constructed in a structure
in which the joint force between electrode tabs and each electrode
lead is increased, whereby high reliability is secured.
[0037] Although the preferred embodiment of the present invention
has been disclosed for illustrative purposes, 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.
* * * * *