U.S. patent application number 16/508595 was filed with the patent office on 2019-11-07 for negative electrode for rechargeable lithium battery and rechargeable lithium battery including the same.
The applicant listed for this patent is SAMSUNG SDI CO., LTD.. Invention is credited to Yeon-Joo Choi, Eon-Mi Lee, Jung-Hyun Nam, Jong-Hwan Park, Hoon Seok.
Application Number | 20190341656 16/508595 |
Document ID | / |
Family ID | 50389362 |
Filed Date | 2019-11-07 |
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United States Patent
Application |
20190341656 |
Kind Code |
A1 |
Nam; Jung-Hyun ; et
al. |
November 7, 2019 |
NEGATIVE ELECTRODE FOR RECHARGEABLE LITHIUM BATTERY AND
RECHARGEABLE LITHIUM BATTERY INCLUDING THE SAME
Abstract
A negative electrode for a rechargeable lithium battery, the
negative electrode including: a current collector; a negative
active material layer on the current collector; and a coating layer
directly contacting the negative active material layer, the coating
layer including an organic material and an inorganic material, is
disclosed. A rechargeable lithium battery including the same is
also disclosed.
Inventors: |
Nam; Jung-Hyun; (Yongin-si,
KR) ; Park; Jong-Hwan; (Yongin-si, KR) ; Choi;
Yeon-Joo; (Yongin-si, KR) ; Lee; Eon-Mi;
(Yongin-si, KR) ; Seok; Hoon; (Yongin-si,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAMSUNG SDI CO., LTD. |
Yongin-si |
|
KR |
|
|
Family ID: |
50389362 |
Appl. No.: |
16/508595 |
Filed: |
July 11, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14228118 |
Mar 27, 2014 |
10381690 |
|
|
16508595 |
|
|
|
|
61865985 |
Aug 14, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 2004/021 20130101;
H01M 4/366 20130101; H01M 4/628 20130101; H01M 10/4235 20130101;
H01M 10/0525 20130101 |
International
Class: |
H01M 10/42 20060101
H01M010/42; H01M 10/0525 20060101 H01M010/0525; H01M 4/36 20060101
H01M004/36; H01M 4/62 20060101 H01M004/62 |
Claims
1. A negative electrode for a rechargeable lithium battery, the
negative electrode comprising: a current collector; a negative
active material layer on the current collector; and a coating layer
directly contacting the negative active material layer, the coating
layer comprising an organic material and an inorganic material,
wherein the coating layer is a composite layer comprising the
organic material and the inorganic material in a single layer.
2. The negative electrode of claim 1, wherein the organic material
comprises a polymer particle comprising a polyolefin, a polyolefin
derivative, a polyolefin wax, an acryl-based compound, or a
combination thereof.
3. The negative electrode of claim 1, wherein the organic material
comprises a polymer particle having a melting point in a range from
85 to 130.degree. C.
4. The negative electrode of claim 1, wherein the organic material
comprises a polymer particle having a particle size in a range from
0.1 to 5 .mu.m.
5. The negative electrode of claim 1, wherein the organic material
is included in the negative electrode in an amount in a range from
0.5 to 10 wt % based on the total amount of the negative active
material layer and the coating layer.
6. The negative electrode of claim 1, wherein the inorganic
material comprises an inorganic particle having a particle size in
a range from 0.1 to 5 .mu.m.
7. The negative electrode of claim 1, wherein the inorganic
material is included in the negative electrode in an amount in a
range from 1 to 20 wt % based on the total amount of the negative
active material layer and the coating layer.
8. A rechargeable lithium battery, the rechargeable lithium battery
comprising: a negative electrode comprising: a current collector, a
negative active material layer on the current collector, and a
coating layer comprising an inorganic layer directly contacting the
negative active material layer and including an inorganic material
and an organic layer directly contacting the inorganic layer,
wherein the organic layer does not include any inorganic material;
a positive electrode facing the negative electrode; an electrolyte
solution impregnating the negative electrode and the positive
electrode; and a separator between the negative electrode and the
positive electrode.
9. A rechargeable lithium battery, the rechargeable lithium battery
comprising: a negative electrode comprising: a current collector, a
negative active material layer on the current collector, and a
coating layer comprising an inorganic material and an organic
material, wherein the coating layer is a composite layer comprising
the organic material and the inorganic material in a single layer;
a positive electrode facing the negative electrode; an electrolyte
solution impregnating the negative electrode and the positive
electrode; and a separator between the negative electrode and the
positive electrode.
10. The rechargeable lithium battery of claim 9, wherein the
separator comprises an organic material and wherein the melting
point of the organic material of the separator is higher than a
melting point of the organic material of the coating layer.
11. The negative electrode of claim 9, wherein the organic material
comprises a polymer particle having a melting point in a range from
85 to 130.degree. C.
12. The negative electrode of claim 9, wherein the organic material
comprises a polymer particle having a particle size in a range from
0.1 to 5 .mu.m.
13. The negative electrode of claim 9, wherein the organic material
is included in the negative electrode in an amount in a range from
0.5 to 10 wt % based on the total amount of the negative active
material layer and the coating layer.
14. The negative electrode of claim 9, wherein the inorganic
material comprises an inorganic particle having a particle size in
a range from 0.1 to 5 .mu.m.
15. A negative electrode for a rechargeable lithium battery, the
negative electrode comprising: a current collector; a negative
active material layer on the current collector; and a coating layer
directly contacting the negative active material layer, the coating
layer comprising an organic material and an inorganic material,
wherein the coating layer comprises an organic layer comprising the
organic material, and an inorganic layer comprising the inorganic
material, wherein the organic layer does not include the inorganic
material, wherein the organic layer directly contacts the negative
active material layer and the inorganic layer directly contacts the
organic layer, and wherein the organic material comprises a
combination of an acryl-based rubber and a polymer particle
comprising at least one selected from the group consisting of a
polyolefin, a polyolefin derivative, a polyolefin wax, or a
combination thereof.
16. The negative electrode of claim 15, wherein the polymer
particle comprises a polyolefin, a polyolefin derivative, a
polyolefin wax, an acryl-based compound, or a combination
thereof.
17. The negative electrode of claim 15, wherein the polymer
particle has a melting point in a range from 85 to 130.degree.
C.
18. The negative electrode of claim 15, wherein the polymer
particle has a particle size in a range from 0.1 to 5 .mu.m.
19. The negative electrode of claim 15, wherein the organic
material is included in the negative electrode in an amount in a
range from 0.5 to 10 wt % based on the total amount of the negative
active material layer and the coating layer.
20. The negative electrode of claim 15, wherein the inorganic
material comprises an inorganic particle having a particle size in
a range from 0.1 to 5 .mu.m.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. patent application
Ser. No. 14/228,118, filed on Mar. 27, 2014, which claims priority
to and the benefit of U.S. Provisional Application No. 61/865,985,
filed on Aug. 14, 2013 in the U.S. Patent and Trademark Office, the
entire content of each of which is incorporated herein by
reference.
BACKGROUND
1. Field
[0002] A negative electrode for a rechargeable lithium battery and
a rechargeable lithium battery including the same are
disclosed.
2. Description of the Related Art
[0003] Recently, due to reductions in size and weight of portable
electronic equipment, there has been a need to develop rechargeable
lithium batteries for portable electronic equipment that have both
high performance and large capacity.
[0004] Oxides that include lithium and transition elements and are
capable of intercalating and deintercalating lithium ions, for
example, LiCoO.sub.2, LiMn.sub.2O.sub.4,
LiNi.sub.1-xCo.sub.xO.sub.2 (0<x<1) and the like, have been
used as positive active materials for rechargeable lithium
batteries. As for negative active materials for a rechargeable
lithium battery, various carbon-based materials such as artificial
graphite, natural graphite, and hard carbon, which intercalate and
deintercalate lithium ions, have been used.
[0005] A rechargeable lithium battery including the above-described
positive and negative active materials has stability and safety
problems, because the positive and negative electrodes become
thermally unstable, depending on the charge state of the battery,
at a temperature of greater than or equal to 25.degree. C., and
thus, the positive and negative active materials, electrolyte salt,
and an organic solvent of the battery are decomposed.
[0006] In addition, due to an increasing demand for higher capacity
batteries, it has become more difficult to provide higher battery
stability and safety.
SUMMARY
[0007] An aspect of one embodiment of the present disclosure is
directed toward a negative electrode for a rechargeable lithium
battery having excellent safety, thermal stability, and cycle-life
characteristics by initially suppressing (or reducing)
exothermicity of the battery and preventing (or reducing the
likelihood of) a short-circuit between a positive electrode and the
negative electrode.
[0008] Another aspect of an embodiment of the present disclosure is
directed toward a rechargeable lithium battery including the
negative electrode.
[0009] According to one embodiment of the present disclosure a
negative electrode for a rechargeable lithium battery includes: a
current collector; a negative active material layer on the current
collector; and a coating layer directly contacting the negative
active material layer, the coating layer including an organic
material and an inorganic material. In some embodiments, the
coating layer is a single layer or has a multi-layered
structure.
[0010] In some embodiments, the coating layer partially penetrates
a surface of the negative active material layer.
[0011] The coating layer may be a composite layer including the
organic material and the inorganic material in a single layer.
[0012] The coating layer may include an inorganic layer including
the inorganic material; and an organic layer including the organic
material.
[0013] In an embodiment of the negative electrode, the inorganic
layer may directly contact the negative active material layer, and
the organic layer may directly contact the inorganic layer; or the
organic layer may directly contact the negative active material
layer, and the inorganic layer may directly contact the organic
layer.
[0014] The organic material may comprise a polymer particle
including a polyolefin, a polyolefin derivative, a polyolefin wax,
an acryl-based compound, or a combination thereof.
[0015] The organic material may include a polymer particle having a
melting point in a range from 85 to 130.degree. C. The polymer
particle may include a polyolefin, a polyolefin derivative, a
polyolefin wax, an acryl-based compound, or a combination thereof.
The organic material may have a weight average molecular weight in
a range from 300 to 10,000 g/mol. A particle size of the polymer
particle may be in a range from 0.1 to 5 m.
[0016] The organic material may be included in the negative
electrode in an amount in a range from 0.5 to 10 wt % based on the
total amount of the negative active material layer and the coating
layer.
[0017] The inorganic material may include SiO.sub.2,
Al.sub.2O.sub.3, Al(OH).sub.3, AlO(OH), TiO.sub.2, BaTiO.sub.2,
ZnO.sub.2, Mg(OH).sub.2, MgO, Ti(OH).sub.4, aluminum nitride,
silicon carbide, boron nitride, or a combination thereof.
[0018] The inorganic material may have a particle size of 0.1 to 5
.mu.m.
[0019] The inorganic material may be included in the negative
electrode in an amount in a range from 1 to 20 wt % based on the
total amount of the negative active material layer and the coating
layer.
[0020] A thickness of the composite layer may be in a range from 1
to 20 .mu.m.
[0021] A thickness of the inorganic layer may be in a range from 1
to 10 m, and a thickness of the organic layer may be in a range
from 1 to 10 .mu.m.
[0022] The coating layer may further include a binder different
from the organic material, and the binder may include a
styrene-butadiene rubber (SBR), a carboxylmethyl cellulose (CMC), a
polyvinylidene fluoride (PVdF), a polyvinylidene
fluoride-hexafluoropropylene (PVdF-HFP) copolymer, an
ethylenevinylacetate (EVA), a hydroxyethyl cellulose (HEC), a
polyvinyl alcohol (PVA), a polyvinylbutyral (PVB), an
ethylene-acrylic acid copolymer, an acrylonitrile, a vinyl acetate
derivative, a polyethylene glycol, an acryl-based rubber, or a
combination thereof.
[0023] According another embodiment of the present disclosure, a
rechargeable lithium battery includes the negative electrode; a
positive electrode facing the negative electrode; an electrolyte
solution impregnating the negative electrode and the positive
electrode; and a separator between the negative electrode and the
positive electrode.
[0024] The separator may include an organic material, and a melting
point of the organic material of the separator may be higher than a
melting point of the organic material of the coating layer.
[0025] Additional embodiments of the present disclosure are
included in the following detailed description.
[0026] According to aspects of the present disclosure, a
rechargeable lithium battery having excellent safety, thermal
stability, and cycle-life characteristics may be realized by
initially suppressing (or reducing) exothermicity and preventing
(or reducing the likelihood of) a short-circuit between the
positive electrode and the negative electrode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The accompanying drawings, together with the specification,
illustrate embodiments of the present invention, and, together with
the description, serve to explain the principles of the present
invention.
[0028] FIG. 1 is a schematic view showing a rechargeable lithium
battery according to one embodiment in an unassembled state.
[0029] FIG. 2 is a cross-sectional view of a negative electrode for
a rechargeable lithium battery according to one embodiment.
[0030] FIG. 3 is a cross-sectional view of a negative electrode for
a rechargeable lithium battery according to another embodiment.
[0031] FIG. 4 is a cross-sectional view of a negative electrode for
a rechargeable lithium battery according to yet another
embodiment.
[0032] FIG. 5 is a graph of a temperature and resistance of the
negative electrodes for a rechargeable lithium battery according to
Examples 1 and 2 and Comparative Examples 1 and 2.
DETAILED DESCRIPTION
[0033] Hereinafter, only certain embodiments of the present
invention are shown and described, by way of illustration. However,
these embodiments are exemplary, and this disclosure is not limited
thereto. As those skilled in the art would recognize, the invention
may be embodied in many different forms and should not be construed
as being limited to the embodiments set forth herein. Also, in the
context of the present application, when a first element is
referred to as being "on" a second element, it can be directly on
the second element or be indirectly on the second element with one
or more intervening elements interposed therebetween. Like
reference numerals designate like elements throughout the
specification.
[0034] A rechargeable lithium battery according to one embodiment
will now be described with reference to FIG. 1.
[0035] FIG. 1 is a schematic view of a rechargeable lithium battery
according to one embodiment.
[0036] Referring to FIG. 1, a rechargeable lithium battery 100
according to one embodiment includes an electrode assembly 110, a
battery case 120 housing the electrode assembly 110, and an
electrode tab 130 that provides an electrical channel for
transmitting a current formed in the electrode assembly 110 out of
the rechargeable lithium battery. The battery case 120 may include
two sides that are overlapped with one another and sealed. In
addition, an electrolyte solution is injected into the battery case
120 housing the electrode assembly 110.
[0037] The electrode assembly 110 includes a positive electrode, a
negative electrode facing the positive electrode, and a separator
between the positive electrode and the negative electrode.
[0038] The negative electrode according to one embodiment includes
a current collector, a negative active material layer on the
current collector, and a coating layer on (e.g., directly
contacting) the negative active material layer. The coating layer
may be a single layer or may have a multi-layered structure and may
include an organic material and an inorganic material. In some
embodiments, the coating layer partially penetrates a surface of
the negative active material layer. For example, the coating layer
may be directly coated on the negative active material layer to
partially penetrate the negative active material layer.
[0039] In some embodiments, the organic material is coated on the
negative active material layer. For example, the organic material
may be directly coated on the negative active material to directly
contact the negative active material layer. The organic material
may prevent (or reduce) movement of lithium ions at a temperature
of 85 to 130.degree. C. due to a shut-down function of the organic
material, thereby increasing internal resistance of the battery and
deteriorating electrical/chemical reactivity of the battery at the
temperature.
[0040] For example, when the organic material of the coating layer
has a shut-down function, the organic material may melt at
temperatures of 85 to 130.degree. C., thereby blocking or occluding
pores of the separator and/or pores of the coating layer to prevent
(or reduce) the movement of lithium ions between the negative
electrode and the positive electrode. Accordingly, when an organic
material capable of shutting down (e.g., an organic material having
a shut-down function) is coated on an electrode, for example, on
the surface of the negative electrode, exothermicity of a battery
including the electrode may be initially suppressed (or reduced).
For example, the coating layer described herein may prevent (or
reduce the likelihood) of thermal runaway of the battery and
improve the safety of the battery by blocking (or reducing)
movement of lithium ions between the positive electrode and the
negative electrode at temperatures of 85 to 130.degree. C., or
higher.
[0041] In addition, the inorganic material may be coated (e.g.,
directly coated) on the negative active material layer and may form
an electrically insulating layer on an electrode, for example, on
the surface of a negative electrode and thus, the inorganic
material may prevent (or reduce the likelihood of) a short-circuit
between the positive electrode and the negative electrode.
[0042] Accordingly, when the organic material and the inorganic
material are coated on the surface of a negative electrode,
exothermicity of a battery of including the negative electrode may
be initially suppressed (or reduced), and a short-circuit between
the positive electrode and the negative electrode may be prevented
(or the likelihood of such a short circuit may be reduced), thereby
improving safety, thermal stability, and cycle-life characteristics
of the rechargeable lithium battery.
[0043] On the other hand, when the organic material and the
inorganic material are coated on a surface of a separator
substrate, the separator may be broken due to a physical impact,
thereby nullifying the effects of the organic material. According
to one embodiment of the present disclosure, the organic material
and/or the inorganic material are directly coated on a surface of
an electrode, which provides strong support for the organic
material and the inorganic material, and thus, results in a more
stable rechargeable lithium battery having improved safety, as
compared to a rechargeable lithium battery prepared by coating the
organic material and the inorganic material on a surface of a
separator substrate. In addition, the organic material and the
inorganic material may protect the electrode, prevent (or reduce)
detachment of an electrode active material of the electrode and
decrease surface roughness of the electrode, thereby preventing (or
reducing the likelihood of) the occurrence of a defect due to
electrode friction during assembly of the battery.
[0044] The structures of embodiments of the negative electrode are
illustrated in FIGS. 2 to 4. FIGS. 2 to 4 provide illustrations of
embodiments of the negative electrode, but the negative electrode
is not limited thereto.
[0045] FIG. 2 is a cross-sectional view showing a structure of one
embodiment of a negative electrode for a rechargeable lithium
battery.
[0046] Referring to FIG. 2, one embodiment of a negative electrode
10 for a rechargeable lithium battery includes a current collector
11, a negative active material layer 12 on the current collector
11, and a coating layer on the negative active material layer 12.
In the embodiment shown in FIG. 2, the coating layer has a single
layer structure. For example, the coating layer may be a composite
layer 13 in which an organic material 14 and an inorganic material
15 form a single layer.
[0047] When an organic material and an inorganic material are
coated on an electrode, for example, on a surface of a negative
electrode as a single layer, the organic material may shut down a
battery including the layer when the battery reaches high
temperatures and, thus, initially suppress (or reduce)
exothermicity of the battery. The inorganic material has an
electrical insulation property and, thus, may prevent (or reduce
the likelihood of) a short-circuit between a positive electrode and
the negative electrode. Accordingly, safety, thermal stability, and
cycle-life characteristics of the rechargeable lithium battery may
be improved by including the organic material and the inorganic
material in a coating layer of the rechargeable lithium
battery.
[0048] FIG. 3 is a cross-sectional view showing a structure of
another embodiment of a negative electrode for a rechargeable
lithium battery.
[0049] Referring to FIG. 3, one embodiment of a negative electrode
20 for a rechargeable lithium battery includes a current collector
21, a negative active material layer 22 on the current collector
21, and a coating layer on (e.g., directly contacting) the negative
active material layer 22. In FIG. 3, the coating layer has a
multi-layered structure and, includes an inorganic layer 23
including an inorganic material 25 and an organic layer 24
including an organic material 26. Herein, in this embodiment, the
inorganic layer 23 may be coated on (e.g., directly coated on) the
negative active material layer 22, and the organic layer 24 may be
coated on (e.g., directly coated on) the inorganic layer 23.
[0050] When an organic material and an inorganic material are
coated on an electrode, for example, on a surface of a negative
electrode (e.g., the inorganic material is coated, or directly
coated, on the surface of the negative electrode, and the organic
material is coated, or directly coated, as a separate layer
thereon), the organic material may initially suppress (or reduce)
exothermicity of a battery including the organic material and the
inorganic material due to a shut-down function of the organic
material. The inorganic material may prevent (or reduce the
likelihood of) a short-circuit between a positive electrode and the
negative electrode due to an electrical insulation property of the
inorganic material. Accordingly, safety, thermal stability, and
cycle-life characteristics of the rechargeable lithium battery may
be improved.
[0051] FIG. 4 is a cross-sectional view showing a structure of yet
another embodiment of a negative electrode for a rechargeable
lithium battery.
[0052] Referring to FIG. 4, one embodiment of a negative electrode
30 for a rechargeable lithium battery includes a current collector
31, a negative active material layer 32 on the current collector
31, and a coating layer on the negative active material layer 32.
In FIG. 4, the coating layer has a multi-layered structure. For
example, the coating layer may include an organic layer 33
including an organic material 35 and an inorganic layer 34
including an inorganic material 36. Herein, in this embodiment, the
organic layer 33 may be coated on (e.g., directly coated on) the
negative active material layer 32, and the inorganic layer 34 may
be coated on (e.g., directly coated on) the organic layer 33.
[0053] When an organic material and an inorganic material are
coated on an electrode, for example on a surface of a negative
electrode (e.g., the organic material is coated, or directly
coated, on the surface of the negative electrode, and an inorganic
material is coated, or directly coated, thereon as a separate
layer), the organic material may initially suppress (or reduce)
exothermicity of a battery including the organic material and the
inorganic material due to a shut-down function of the organic
material. The inorganic material may prevent (or reduce the
likelihood of) a short-circuit between a positive electrode and the
negative electrode due to an electrical insulation property of the
inorganic material. Accordingly, safety, thermal stability, and
cycle-life characteristics of the rechargeable lithium battery may
be improved.
[0054] The organic material included in the composite layer and the
organic layer in FIGS. 2 to 4 may include a polymer particle having
a melting point in a range from 85 to 130.degree. C. When the
organic material has a melting point within the foregoing range,
exothermicity of a battery including the organic material may be
initially suppressed (or reduced) due to a shut-down function of
the organic material.
[0055] According to an embodiment, the separator includes an
organic material such as a polyolefin based polymer, and the
melting point of the organic material of the separator is higher
than the melting point of the organic material of the coating
layer.
[0056] The organic material of the separator may have a melting
point of 130.degree. C. or more, and thus, the separator may carry
out a shut-down function at a temperature of 130.degree. C. or
more. However, in the case of a battery having a high energy
density for high capacity or in the case of using an active
material having decreased structural or chemical stability, initial
exothermicity of the battery rapidly increases when the battery has
abnormal exothermicity, and thus, it is difficult to control the
stability of the battery with only the shut-down function of the
separator. Accordingly, in one embodiment, an organic material
having a lower melting point than that of the organic material of
the separator is coated on the negative active material layer, and
the organic material coated on the negative active material layer
may be first melted and shut-down at a temperature lower than
130.degree. C. Thus, electrical/chemical reactivity may be
suppressed at a lower temperature and exothermicity of the battery
may be initially suppressed. In other words, the reactivity of a
battery may be primarily suppressed by a shut-down of an organic
material coated on the negative active material layer, and then
shut-down of the organic material of the separator may be
secondarily generated. Accordingly, the stability of a battery may
be effectively obtained or improved.
[0057] For example, the polymer particle may include a polyolefin,
a polyolefin derivative, a polyolefin wax, an acryl-based compound,
or a combination thereof. The polyolefin may be, for example,
polyethylene, polypropylene, or a combination thereof.
[0058] In some embodiments of the negative electrode, the polymer
particle of the organic material includes polyethylene.
[0059] A weight average molecular weight of the organic material
may be in a range from 300 to 10,000 g/mol, for example, 2,000 to
6,000 g/mol. An average particle size of the polymer particle may
be in a range from 0.1 to 5 .mu.m, for example, 0.2 to 3 .mu.m.
[0060] When the polymer particle has a weight average molecular
weight and an average particle size within one of the foregoing
ranges, the polymer may minimize (or reduce) resistance to the
movement of lithium ions, secure good performance of a battery
including the organic material, reinforce a shut-down function of
the organic material, and thus, initially suppress (or reduce)
exothermicity of the battery.
[0061] The organic material may be included in the negative
electrode in an amount in a range from 0.5 to 10 wt %, for example,
3 to 7 wt %, based on the total amount of the negative active
material layer and the coating layer. When the organic material is
included within either of the foregoing ranges, its shut-down
function is further reinforced, and exothermicity of a battery
including the organic material may be initially suppressed (or
reduced).
[0062] The inorganic material included in the composite layer and
the inorganic layer in FIGS. 2 to 4 may include SiO.sub.2,
Al.sub.2O.sub.3, Al(OH).sub.3, AlO(OH), TiO.sub.2, BaTiO.sub.2,
ZnO.sub.2, Mg(OH).sub.2, MgO, Ti(OH).sub.4, aluminum nitride,
silicon carbide, boron nitride, or a combination thereof.
[0063] An average particle size of the inorganic material may be in
a range from 0.1 to 5 .mu.m, for example, 0.3 to 1 .mu.m. When the
inorganic material particle has an average particle size within
either of the foregoing ranges, the inorganic material may be
uniformly coated on the negative active material layer and thus,
prevent (or prevent the likelihood of) a short-circuit between a
positive electrode and the negative electrode due to an excellent
electrical insulation property of the inorganic material. In
addition, the inorganic material layer may minimize (or reduce)
resistance to the movement of lithium ions and secure good battery
performance.
[0064] The inorganic material may be included in an amount in a
range from 1 to 20 wt %, for example, 5 to 12 wt % based on the
total amount of the negative active material layer and the coating
layer. When the inorganic material is included within either of the
above ranges, the inorganic material has an excellent electrical
insulation property and may prevent (or reduce the likelihood of) a
short-circuit between a positive electrode and the negative
electrode.
[0065] In FIG. 2, a thickness of the composite layer including the
organic material and the inorganic material may be in a range from
1 to 20 .mu.m, for example, 2 to 10 .mu.m. When the composite layer
has a thickness within either of the foregoing ranges, the
composite layer has an excellent shut-down function and electrical
insulation property and, thus, may initially suppress (or reduce)
exothermicity of a battery and prevent (or reduce the likelihood
of) a short-circuit between a positive electrode and the negative
electrode. In addition, the composite layer may minimize (or
reduce) resistance to the movement of lithium ions and minimize (or
reduce) the thickness of the coating layer and, thus, secure good
battery performance.
[0066] In FIGS. 3 and 4, a thickness of the inorganic layer may be
in a range from 1 to 10 .mu.m, for example, 2 to 7 .mu.m, and a
thickness of the organic layer may be in a range from 1 to 10
.mu.m, for example, 3 to 7 .mu.m. When the inorganic and organic
layers each have a thickness within one of their respective ranges,
a short-circuit between the positive electrode and the negative
electrode may be prevented (or the likelihood of such a
short-circuit may be reduced) due to an excellent electrical
insulation property, and exothermicity of a battery may be
initially suppressed (or reduced) due to a reinforced shut-down
function. In addition, the inorganic and organic layers may
minimize (or reduce) resistance to movement of lithium ions and may
minimize (or reduce) the thickness of a coating layer and, thus,
secure good battery performance.
[0067] The coating layer, for example, the composite layer of FIG.
2, may further include a binder as well as the organic material and
the inorganic material. In FIGS. 3 and 4, the organic layer may
further include a binder as well as the organic material, and the
inorganic layer may further include a binder as well as the
inorganic material.
[0068] The binder may be a material that is different from the
organic material. Examples of the binder may include a
styrene-butadiene rubber (SBR), a carboxylmethyl cellulose (CMC), a
polyvinylidene fluoride (PVdF), a polyvinylidene
fluoride-hexafluoropropylene (PVdF-HFP) copolymer, an ethylenevinyl
acetate (EVA), hydroxyethyl cellulose (HEC), a polyvinyl alcohol
(PVA), a polyvinylbutyral (PVB), an ethylene-acrylic acid
copolymer, an acrylonitrile, a vinyl acetate derivative, a
polyethylene glycol, an acryl-based rubber, and a combination
thereof. In some embodiments of the negative electrode, the
styrene-butadiene rubber (SBR), a mixture of the styrene-butadiene
rubber (SBR) and the carboxylmethyl cellulose (CMC), the
ethylenevinylacetate (EVA), the polyvinyl alcohol (PVA), the
ethylene-acrylic acid copolymer, and/or the acryl-based rubber may
be used as the binder.
[0069] When the binder is included in the coating layer, adherence
to the surface of the negative electrode is improved, and adherence
between organic material particles, between inorganic material
particles, and/or between the organic material particles and the
inorganic material particles may be improved.
[0070] The current collector of the negative electrode may be a
copper foil.
[0071] The negative active material layer includes a negative
active material, a binder, and, optionally, a conductive
material.
[0072] The negative active material may include a material that
reversibly intercalates/deintercalates lithium ions, a lithium
metal, a lithium metal alloy, a material capable of doping and
dedoping lithium, or a transition metal oxide.
[0073] The material that reversibly intercalates/deintercalates
lithium ions is a carbon material, and may be any suitable
carbon-based negative active material generally used in
rechargeable lithium batteries. Examples of the carbon-based
negative active material may include crystalline carbon, amorphous
carbon or a mixture thereof. The crystalline carbon may be
non-shaped, or sheet, flake, spherical, or fiber shaped natural
graphite or artificial graphite, and the amorphous carbon may be a
soft carbon (e.g., carbon sintered at a low temperature), a hard
carbon, mesophase pitch carbonized products, fired coke, and the
like.
[0074] The lithium metal alloy may be an alloy of lithium and a
metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb,
In, Zn, Ba, Ra, Ge, Al, and Sn.
[0075] The material capable of doping and dedoping lithium may be
Si, SiO.sub.x (0<x<2), a Si--C composite, a Si-Q alloy
(wherein Q is an alkali metal, an alkaline-earth metal, Group 13 to
16 elements, transition metal, a rare earth element, or a
combination thereof, and is not Si), Sn, SnO.sub.2, a Sn--C
composite, Sn--R (wherein R is an alkali metal, an alkaline-earth
metal, Group 13 to 16 elements, transition metal, a rare earth
element, or a combination thereof, and not Sn), and the like, and
at least one of these materials may be mixed with SiO.sub.2.
Examples of the Q and R may include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti,
Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru,
Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti,
Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof.
[0076] The transition metal oxide may be vanadium oxide, lithium
vanadium oxide, and the like.
[0077] The binder of the negative active material layer improves
binding properties of the negative active material particles with
one another and with a current collector. Examples of the binder of
the negative active material layer may include a polyvinyl alcohol,
a carboxylmethyl cellulose, a hydroxypropyl cellulose, a
polyvinylchloride, a carboxylated polyvinylchloride, a
polyvinylfluoride, an ethylene oxide-containing polymer, a
polyvinylpyrrolidone, a polyurethane, a polytetrafluoroethylene, a
polyvinylidene fluoride, a polyethylene, a polypropylene, a
styrene-butadiene rubber, an acrylated styrene-butadiene rubber, an
epoxy resin, nylon, and the like, but the binder is not limited
thereto.
[0078] The conductive material improves conductivity of an
electrode. Any suitable, electrically conductive material may be
used as the conductive material, unless it causes a chemical change
in the battery. Examples of the conductive material may include a
carbon-based material such as natural graphite, artificial
graphite, carbon black, acetylene black, ketjen black, carbon fiber
and the like; a metal-based material such as a metal powder or a
metal fiber and the like of copper, nickel, aluminum, silver, and
the like; a conductive polymer such as a polyphenylene derivative
and the like; or a mixture thereof.
[0079] The negative electrode may be manufactured by a method
including mixing the negative active material, the binder and the
conductive material in a solvent to prepare a negative active
material composition, and coating the negative active material
composition on a negative current collector. Examples of the
solvent include N-methylpyrrolidone and the like, but the solvent
is not limited thereto.
[0080] The positive electrode may include a current collector and a
positive active material layer on the current collector.
[0081] An example of the current collector may include aluminum,
but the current collector is not limited thereto.
[0082] The positive active material layer includes a positive
active material.
[0083] The positive active material may be a compound (e.g., a
lithiated intercalation compound) capable of intercalating and
deintercalating lithium, for example, a lithium metal oxide.
[0084] The lithium metal oxide may be, for example, an oxide
including lithium and at least one metal selected from cobalt,
manganese, nickel, and aluminum. For example, compounds represented
by the following chemical formulae may be used.
[0085] Li.sub.aA.sub.1-bX.sub.bD.sub.2 (0.90.ltoreq.a.ltoreq.1.8,
0.ltoreq.b.ltoreq.0.5); Li.sub.aA.sub.1-bX.sub.bO.sub.2-cD.sub.c
(0.90.ltoreq.a.ltoreq.1.8, 0.ltoreq.b.ltoreq.0.5,
0.ltoreq.c.ltoreq.0.05); Li.sub.aE.sub.1-bX.sub.bO.sub.2-cD.sub.c
(0.90.ltoreq.a.ltoreq.1.8, 0.ltoreq.b.ltoreq.0.5,
0.ltoreq.c.ltoreq.0.05); Li.sub.aE.sub.2-bX.sub.bO.sub.4-cD.sub.c
(0.90.ltoreq.a.ltoreq.1.8, 0.ltoreq.b.ltoreq.0.5,
0.ltoreq.c.ltoreq.0.05);
Li.sub.aNi.sub.1-b-cCo.sub.bX.sub.cD.sub..alpha.
(0.90.ltoreq.a.ltoreq.1.8, 0.ltoreq.b.ltoreq.0.5,
0.ltoreq.c.ltoreq.0.05, 0<.alpha.<2);
Li.sub.aNi.sub.1-b-cCo.sub.bX.sub.cO.sub.2-.alpha.T.sub..alpha.
(0.90.ltoreq.a.ltoreq.1.8, 0.ltoreq.b.ltoreq.0.5,
0.ltoreq.c.ltoreq.0.05, 0<.alpha..ltoreq.2);
Li.sub.aNi.sub.1-b-cCo.sub.bX.sub.cO.sub.2-.alpha.T.sub.2
(0.90.ltoreq.a.ltoreq.1.8, 0.ltoreq.b.ltoreq.0.5,
0.ltoreq.c.ltoreq.0.05, 0<.alpha.<2);
Li.sub.aNi.sub.1-b-cMn.sub.bX.sub.cD.sub..alpha.
(0.90.ltoreq.a.ltoreq.1.8, 0.ltoreq.b.ltoreq.0.5,
0.ltoreq.c.ltoreq.0.05, 0<.alpha..ltoreq.2);
Li.sub.aNi.sub.1-b-cMn.sub.bX.sub.cO.sub.2-.alpha.T.sub..alpha.
(0.90.ltoreq.a.ltoreq.1.8, 0.ltoreq.b.ltoreq.0.5,
0.ltoreq.c.ltoreq.0.05, 0<.alpha.<2);
Li.sub.aNi.sub.1-b-cMn.sub.bX.sub.cO.sub.2-.alpha.T.sub.2
(0.90.ltoreq.a.ltoreq.1.8, 0.ltoreq.b.ltoreq.0.5,
0.ltoreq.c.ltoreq.0.05, 0<.alpha..ltoreq.2);
Li.sub.aNi.sub.bE.sub.cG.sub.dO.sub.2 (0.90.ltoreq.a.ltoreq.1.8,
0.ltoreq.b.ltoreq.0.9, 0.ltoreq.c.ltoreq.0.5,
0.001.ltoreq.d.ltoreq.0.1);
Li.sub.aNi.sub.bCo.sub.cMn.sub.dGeO.sub.2
(0.90.ltoreq.a.ltoreq.1.8, 0.ltoreq.b.ltoreq.0.9,
0.ltoreq.c.ltoreq.0.5, 0.ltoreq.d.ltoreq.0.5,
0.001.ltoreq.e.ltoreq.0.1); Li.sub.aNiG.sub.bO.sub.2
(0.90.ltoreq.a.ltoreq.1.8, 0.001.ltoreq.b.ltoreq.0.1);
Li.sub.aCoG.sub.bO.sub.2 (0.90.ltoreq.a.ltoreq.1.8,
0.001.ltoreq.b.ltoreq.0.1); Li.sub.aMn.sub.1-bG.sub.bO.sub.2
(0.90.ltoreq.a.ltoreq.1.8, 0.001.ltoreq.b.ltoreq.0.1);
Li.sub.aMn.sub.2G.sub.bO.sub.4 (0.90.ltoreq.a.ltoreq.1.8,
0.001.ltoreq.b.ltoreq.0.1); Li.sub.aMn.sub.1-gG.sub.gPO.sub.4
(0.90.ltoreq.a.ltoreq.1.8, 0.ltoreq.g.ltoreq.0.5); QO.sub.2;
QS.sub.2; LiQS.sub.2; V.sub.2O.sub.5; LiV.sub.2O.sub.5; LiZO.sub.2;
LiNiVO.sub.4; Li.sub.(3-f)J.sub.2(PO.sub.4).sub.3
(0.ltoreq.f.ltoreq.2);
Li.sub.(3-f)Fe.sub.2(PO.sub.4).sub.3(0.ltoreq.f.ltoreq.2);
LiFePO.sub.4.
[0086] In the above chemical formulae, A is selected from Ni, Co,
Mn, and a combination thereof; X is selected from Al, Ni, Co, Mn,
Cr, Fe, Mg, Sr, V, a rare earth element, and a combination thereof;
D is selected from O, F, S, P, and a combination thereof; E is
selected from Co, Mn, and a combination thereof; T is selected from
F, S, P, and a combination thereof; G is selected from Al, Cr, Mn,
Fe, Mg, La, Ce, Sr, V, and a combination thereof; Q is selected
from Ti, Mo, Mn, and a combination thereof; Z is selected from Cr,
V, Fe, Sc, Y, and a combination thereof; and J is selected from V,
Cr, Mn, Co, Ni, Cu, and a combination thereof.
[0087] The lithium metal oxide may be, for example, lithium nickel
cobalt manganese oxide, lithium nickel cobalt aluminum oxide, or a
combination thereof. In some embodiments of the negative electrode,
a mixture of lithium nickel cobalt manganese oxide and lithium
nickel cobalt aluminum oxide may be used as the lithium metal
oxide.
[0088] The positive active material layer may further include a
binder and a conductive material as well as the above-described
positive active material.
[0089] The binder of the positive active material layer improves
binding properties between the electrode active material particles
and also attaches the electrode active material to the positive
current collector. Examples of the positive active material layer
may include a polyvinyl alcohol, a carboxylmethyl cellulose, a
hydroxypropyl cellulose, a diacetyl cellulose, a polyvinylchloride,
a carboxylated polyvinylchloride, a polyvinylfluoride, an ethylene
oxide-containing polymer, a polyvinylpyrrolidone, a polyurethane, a
polytetrafluoroethylene, a polyvinylidene fluoride, a polyethylene,
a polypropylene, a styrene-butadiene rubber, an acrylated
styrene-butadiene rubber, an epoxy resin, nylon, and the like, but
the binder of the positive active material layer is not limited
thereto.
[0090] The conductive material of the positive active material
layer improves conductivity of the positive electrode. Any
suitable, electrically conductive material may be used as the
conductive material, unless it causes a chemical change in the
battery. Examples of the conductive material may include a
carbon-based material such as natural graphite, artificial
graphite, carbon black, acetylene black, ketjen black, a carbon
fiber, or the like; a metal-based material such as a metal powder
or a metal fiber or the like of copper, nickel, aluminum, silver,
or the like; a conductive polymer such as a polyphenylene
derivative or the like; or a mixture thereof.
[0091] The electrolyte solution may include a non-aqueous organic
solvent and a lithium salt.
[0092] The non-aqueous organic solvent serves as a medium for
transmitting ions taking part in the electrochemical reaction of
the battery. The non-aqueous organic solvent may be selected from a
carbonate-based solvent, an ester-based solvent, an ether-based
solvent, a ketone-based solvent, an alcohol-based solvent, and an
aprotic solvent.
[0093] The carbonate-based solvent may include, for example,
dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl
carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl
carbonate (EPC), methylethyl carbonate (MEC), ethylmethyl carbonate
(EMC), ethylene carbonate (EC), propylene carbonate (PC), butylene
carbonate (BC), and/or the like.
[0094] The carbonate-based solvent may include linear carbonate
compounds and/or cyclic carbonate compounds. When the linear
carbonate compounds and cyclic carbonate compounds are mixed, an
organic solvent having high dielectric constant and low viscosity
can be provided. The cyclic carbonate and the linear carbonate are
mixed together in a volume ratio in a range from about 1:1 to about
1:9.
[0095] The ester-based solvent may include, for example,
n-methylacetate, n-ethylacetate, n-propylacetate, dimethylacetate,
methylpropionate, ethylpropionate, .gamma.-butyrolactone,
decanolide, valerolactone, mevalonolactone, caprolactone, and/or
the like. The ether solvent may include, for example, dibutylether,
tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran,
tetrahydrofuran, and/or the like, and the ketone-based solvent may
include cyclohexanone, and/or the like. The alcohol-based solvent
may include, for example, ethyl alcohol, isopropyl alcohol, and/or
the like.
[0096] The non-aqueous organic solvent may be used singularly or in
a mixture. When the organic solvent is used in a mixture, the
mixing ratio of the mixture may be controlled in accordance with a
desirable battery performance.
[0097] The non-aqueous electrolyte solution may further include an
overcharge inhibitor additive such as ethylenecarbonate,
pyrocarbonate, and/or the like.
[0098] The lithium salt is dissolved in an organic solvent,
supplies lithium ions in a battery, enables operation of the
rechargeable lithium battery, and improves lithium ion
transportation between positive and negative electrodes
therein.
[0099] The lithium salt may include LiPF.sub.6, LiBF.sub.4,
LiSbF.sub.6, LiAsF.sub.6, LiN(SO.sub.3C.sub.2F.sub.5).sub.2,
LiC.sub.4F.sub.9SO.sub.3, LiCIO.sub.4, LiAIO.sub.2, LiAlCl.sub.4,
LiN(C.sub.xF.sub.2x+1SO.sub.2)(C.sub.yF.sub.2y+1SO.sub.2) (where x
and y are natural numbers), LiCl, LiI, LiB(C.sub.2O.sub.4).sub.2
(lithium bis(oxalato) borate, LiBOB), or a combination thereof, as
a supporting electrolytic salt.
[0100] The lithium salt may be used in a concentration in a range
from about 0.1 M to about 2.0 M. When the lithium salt is included
within the above concentration range, the electrolyte may have
improved performance and lithium ion mobility due to good
electrolyte conductivity and viscosity.
[0101] The separator may include any materials commonly used in
lithium batteries as long as the separator is capable of separating
a negative electrode from a positive electrode and providing a
transporting passage for lithium ions. For example, the separator
may be made of a material having a low resistance to ion
transportation and an improved ability for impregnation of an
electrolyte. For example, the material of the separator may be
selected from glass fiber, polyester, TEFLON.RTM.
(tetrafluoroethylene; TEFLON is a registered trademark of E. I. Du
Pont de Nemours and Company, Wilmington, Del.), polyethylene,
polypropylene, polytetrafluoroethylene (PTFE), and a combination
thereof. It may have a form of a non-woven fabric or a woven
fabric. For example, a polyolefin-based polymer separator such as
polyethylene, polypropylene or the like is mainly used for a
lithium ion battery. In order to ensure good heat resistance and/or
mechanical strength, a coated separator including a ceramic
component and/or a polymer material may be used. For example, the
separator may have a mono-layered or multi-layered structure.
[0102] Hereinafter, embodiments of the present disclosure are
described in more detail with reference to examples by way of
illustration. However, the present disclosure is not limited to the
examples disclosed herein.
[0103] Furthermore, what is not described in this disclosure may be
sufficiently understood by those who have knowledge in the field
relevant to this disclosure and will not be illustrated or
described here.
Example 1
(Manufacture of Negative Electrode)
[0104] An organic layer composition was prepared by mixing 98 wt %
of polyethylene particles (Mitsui Chemicals, Inc, Chemipearl W401)
having a melting point of 110.degree. C., an average particle size
of 1 .mu.m, and a weight average molecular weight of 5,000 g/mol;
and 2 wt % of an acryl-based rubber (ZEON Corporation, BM-900B) in
water.
[0105] An inorganic layer composition was prepared by mixing 95 wt
% of Al.sub.2O.sub.3 (Sumitomo Chemical Co., AES-12) having a
particle size of 0.45 m, and 5 wt % of an acryl-based rubber (ZEON
Corporation, BM-520B) in an N-methylpyrrolidone solvent.
[0106] A slurry was prepared by adding 97.5 wt % of graphite, 1.5
wt % of a styrene-butadiene rubber (SBR), and 1 wt % of
carboxylmethyl cellulose (CMC) to water as a solvent.
[0107] The slurry was coated on a copper foil and dried, and then
pressed with a roll presser to form a negative active material
layer. Subsequently, the inorganic layer composition was coated on
the negative active material layer to form an inorganic layer, and
the organic layer composition was coated on the inorganic layer to
form an organic layer, thereby manufacturing a negative electrode.
In this example, the inorganic layer was 6 .mu.m thick, and the
organic layer was 2 .mu.m thick. Herein, the polyethylene particle
and the Al.sub.2O.sub.3 were included in amounts of 1.6 wt % and
9.8 wt %, respectively, based on the total weight of the negative
active material layer and a coating layer including the inorganic
layer and the organic layer.
(Manufacture of Positive Electrode)
[0108] A slurry was prepared by combining 94 wt % of a mixture
including 90 wt % of LiNi.sub.0.33Co.sub.0.33Mn.sub.0.33O.sub.2 and
10 wt % of LiNi.sub.0.8Co.sub.0.15Al.sub.0.05O.sub.2, 3 wt % of
carbon black, and 3 wt % of polyvinylidene fluoride in an
N-methylpyrrolidone (NMP) solvent. The slurry was coated on an
aluminum (Al) thin film and dried, and then pressed with a roll
presser, thereby manufacturing a positive electrode.
(Preparation of Electrolyte Solution)
[0109] An electrolyte solution was prepared by mixing ethylene
carbonate, ethylmethyl carbonate, and dimethyl carbonate in a
volume ratio of 2:4:4 and adding 1.15 M LiPF.sub.6 to the mixed
solvent.
(Manufacture of Rechargeable Lithium Battery Cell)
[0110] A rechargeable lithium battery cell was manufactured using
the positive electrode, the negative electrode, and the electrolyte
solution described above, and a polyethylene separator.
Example 2
[0111] A rechargeable lithium battery cell was manufactured as in
Example 1 except that the organic layer was formed to be 4 .mu.m
thick.
Example 3
[0112] A rechargeable lithium battery cell was manufactured as in
Example 1 except that the negative electrode was manufactured as
follows.
[0113] The organic layer composition was coated on the negative
active material layer to form an organic layer, and the inorganic
layer composition was coated on the organic layer to form an
inorganic layer, thereby manufacturing a negative electrode. In
this example, the organic layer was 4 .mu.m thick, and the
inorganic layer was 6 m thick.
Example 4
[0114] The rechargeable lithium battery cell was manufactured as in
Example 1 except that the negative electrode was manufactured as
follows.
[0115] A composite layer composition was prepared by mixing 47.5 wt
% of polyethylene particle (Mitsui Chemicals, Inc, Chemipearl W401,
which were vacuum-dried after being dispersed in water) having a
melting point of 110.degree. C., an average particle size of 1
.mu.m, and a weight average molecular weight of 5,000 g/mol; 47.5
wt % of Al.sub.2O.sub.3(Sumitomo Chemical Co., Ltd., AES-12) having
a particle size of 0.45 m; and 5 wt % of an acryl-based rubber
(ZEON Corporation, BM-520B) in an N-methylpyrrolidone solvent. The
composite layer composition was coated on the negative active
material layer to form a composite layer, thereby manufacturing a
negative electrode. In this example, the composite layer was 8 m
thick. Herein, the polyethylene particle and the Al.sub.2O.sub.3
were included in amounts of 4.9 wt % and 4.9 wt %, respectively,
based on the total weight of the negative active material layer and
a coating layer including the inorganic layer and the organic
layer.
Comparative Example 1
[0116] A rechargeable lithium battery was manufactured as in
Example 1 except that the slurry was coated on a copper foil,
dried, and then pressed with a roll presser to manufacture the
negative electrode.
Comparative Example 2
[0117] A rechargeable lithium battery cell was manufactured as in
Example 1 except that the negative electrode was manufactured as
follows.
[0118] The inorganic layer composition was coated on the negative
active material layer to form an inorganic layer, thereby
manufacturing a negative electrode. In this comparative example,
the inorganic layer was 6 .mu.m thick.
Evaluation 1: Thermal Resistance Evaluation of Rechargeable Lithium
Battery Cell
[0119] Resistance changes depending on a temperature of the
rechargeable lithium battery cells according to Examples 1 to 4 and
Comparative Examples 1 and 2 were evaluated, and the results are
shown in FIG. 5.
[0120] FIG. 5 is a graph showing a relationship between temperature
and resistance of the rechargeable lithium battery cells according
to Examples 1 to 4 and Comparative Examples 1 and 2.
[0121] Referring to FIG. 5, the rechargeable lithium battery cells
using a negative electrode having a coating layer including an
organic material and an inorganic material on a negative active
material layer according to Examples 1 to 4 showed a lower
temperature at which resistance starts to increase compared with
the rechargeable lithium battery cell using a negative electrode
having no coating layer according to Comparative Example 1 and the
rechargeable lithium battery cell using a negative electrode coated
by only an inorganic material according to Comparative Example 2.
Accordingly, the organic material of Examples 1 to 4 suppressed (or
reduced) exothermicity of the battery due to a shut-down function
of the organic material.
Evaluation 2: Penetration Safety of Rechargeable Lithium Battery
Cell
[0122] Penetration safety of the rechargeable lithium battery cells
according to Examples 1 to 4 and Comparative Examples 1 and 2 were
evaluated, and the results are shown in the following Table 1.
[0123] The rechargeable lithium battery cells were charged at a
charge current of 0.5 C up to 4.20V and cut off at 0.05 C and
penetration evaluation was performed by using a penetration pin
having a diameter of 2.5 mm at a speed of 80 mm/sec.
TABLE-US-00001 TABLE 1 Comparative Examples Examples 1 2 3 4 1 2
Evaluation Non-ignition Non-ignition Non-ignition Non-ignition
Explosion Ignition result of (maximum (maximum (maximum (maximum
penetration temperature temperature temperature temperature safety
125.degree. C.) 79.degree. C.) 81.degree. C.) 78.degree. C.)
[0124] Referring to Table 1, the rechargeable lithium battery cells
using a negative electrode having a coating layer including an
organic material and an inorganic material on a negative active
material layer according to Examples 1 to 4 showed excellent
penetration safety compared with the rechargeable lithium battery
cell using a negative electrode having no coating layer according
to Comparative Example 1 and the rechargeable lithium battery cell
using a negative electrode coated by only an inorganic material
according to Comparative Example 2. In addition, the rechargeable
lithium battery cell using a negative electrode including the
organic material of Examples 1 and 2, for example, a thicker
organic layer according to Example 2 showed better penetration
safety. Accordingly, the negative electrode coated with an organic
material and an inorganic material on the surface showed excellent
penetration safety due to a shut-down function of the organic
material.
[0125] While the present invention has been described in connection
with certain embodiments, it is to be understood that the invention
is not limited to the disclosed embodiments, but, on the contrary,
is intended to cover various modifications and equivalent
arrangements included within the spirit and scope of the appended
claims, and equivalents thereof. While this disclosure has been
described in connection with what are presently considered to be
practical exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed embodiments, but, on the
contrary, is intended to cover various modifications and equivalent
arrangements included within the spirit and scope of the appended
claims, and equivalents thereof.
DESCRIPTION OF SYMBOLS
[0126] 10, 20, 30: negative electrode [0127] 11, 21, 31: current
collector [0128] 12, 22, 32: negative active material layer [0129]
13: composite layer [0130] 14, 26, 35: organic material [0131] 15,
25, 36: inorganic material [0132] 23, 34: inorganic layer [0133]
24, 33: organic layer [0134] 100: rechargeable lithium battery
[0135] 110: electrode assembly [0136] 120: battery case [0137] 130:
electrode tab
* * * * *