U.S. patent application number 11/050973 was filed with the patent office on 2005-09-22 for electrode additives coated with electro conductive material and lithium secondary comprising the same.
Invention is credited to Chun, Kyungmin, Jang, Jae-Up, Kim, Kwang Hoon, Kim, Sun kyu, Kwon, Yong Hoon, Park, Hong-Kyu, Yoo, Seung Il.
Application Number | 20050208380 11/050973 |
Document ID | / |
Family ID | 36968329 |
Filed Date | 2005-09-22 |
United States Patent
Application |
20050208380 |
Kind Code |
A1 |
Park, Hong-Kyu ; et
al. |
September 22, 2005 |
Electrode additives coated with electro conductive material and
lithium secondary comprising the same
Abstract
Provided are an electrode additive coated with a coating
material made of electrically conductive materials such as metal
hydroxides, metal oxides or metal carbonates, and an electrode and
a lithium secondary battery comprising the same. The electrode
additive in accordance with the present invention can improve high
temperature storage characteristics of the battery, without
deterioration of performance thereof.
Inventors: |
Park, Hong-Kyu; (Yuseong-gu,
KR) ; Kim, Kwang Hoon; (Seoul, KR) ; Kim, Sun
kyu; (Seongnam-si, KR) ; Yoo, Seung Il;
(Gumi-si, KR) ; Jang, Jae-Up; (Yuseong-gu, KR)
; Kwon, Yong Hoon; (Seongnam-si, KR) ; Chun,
Kyungmin; (Yuseong-gu, KR) |
Correspondence
Address: |
CANTOR COLBURN, LLP
55 GRIFFIN ROAD SOUTH
BLOOMFIELD
CT
06002
|
Family ID: |
36968329 |
Appl. No.: |
11/050973 |
Filed: |
February 4, 2005 |
Current U.S.
Class: |
429/232 ;
252/182.1; 429/212 |
Current CPC
Class: |
H01M 4/13 20130101; H01M
4/626 20130101; Y02E 60/10 20130101; H01M 4/62 20130101; H01M
10/0525 20130101; H01M 4/624 20130101 |
Class at
Publication: |
429/232 ;
252/182.1; 429/212 |
International
Class: |
H01M 004/62 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 7, 2004 |
KR |
10-2004-0008135 |
Claims
1. An electrode additive for a secondary battery electrode in which
electro-conductive material ("coating material") is coated on the
surface of material ("core particle") that is added to electrode
material so as to improve battery characteristics.
2. The electrode additive according to claim 1, wherein the core
particle is a material of Formula 1 that is added to battery
electrodes for improving high temperature storage characteristics:
M.sub.xA.sub.y (1) wherein, M is a metal, A is selected from the
group consisting of OH, O and CO.sub.3, and x represents the
valence of M and y represents the oxidation number of A.
3. The electrode additive according to claim 1, wherein the coating
material is composed of one or more materials selected from the
group consisting of carbon, an electro-conductive metal, an
electro-conductive inorganic material and an electro-conductive
polymer.
4. The electrode additive according to claim 3, wherein the carbon
is selected from the group consisting of carbon black, acetylene
black and Super-P, the electro-conductive metal is selected from
the group consisting of Cu, Ag, Pt and Ni, the electro-conductive
inorganic material is selected from the group consisting of indium
tin oxide (In.sub.2O.sub.3SnO.sub.2), tin oxide (SnO.sub.2), zinc
oxide (ZnO), ruthenium oxide (RuO.sub.2) and TiB.sub.2, and the
electro-conductive polymer is selected from the group consisting of
polypyrrole and polyaniline.
5. The electrode additive according to claim 1, wherein the coating
material has an electrical conductivity of more than
2.0.times.10.sup.2/cm.OMEGA..
6. The electrode additive according to claim 1, wherein the coating
material has a particle size of 10 nm to 1000 nm.
7. The electrode additive according to claim 2, wherein M in
Formula 1 is one or more elements selected from the group
consisting of Al, B, Mg, K, Be, Ca, Sr, Ba, Na, Cr, Sn, Ga, Bi, Ni,
Co, Fe, Cr, Y and Zr.
8. The electrode additive according to claim 1, wherein the amount
of the coating material is within the range of 0.01 to 20% by
weight, relative to the core particle.
9. An electrode fabricated by preparing an electrode slurry using
electrode material containing the electrode additive according to
claims 1 and electrode active material and applying the
thus-prepared electrode slurry to a current collector.
10. The electrode according to claim 9, wherein the electrode
additive is included in the range of 0.05 to 10% by weight,
relative to the electrode active material.
11. A lithium secondary battery comprising the electrode of claim
9.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an electrode additive that
is capable of improving battery performance and high temperature
storage characteristics when it is added to an electrode of a
lithium secondary battery, and an electrode and lithium secondary
battery comprising the same.
BACKGROUND OF THE INVENTION
[0002] In order to keep pace with the continuing trend towards
portabilization, miniaturization, and higher functionalization of a
variety of electronic devices and instruments with development of
the Information-Electronic Industry, higher capacity, smaller and
lighter lithium secondary batteries are increasingly in demand.
Recently, with diversification of functions of the electronic
devices and instruments, there is also a strong need for
realization of higher capacity, functionality, and performance of
lithium secondary batteries, as a main power source. In addition,
as the temperature range of lithium secondary batteries in use is
also further extended, environmental conditions to which batteries
are applied become more severe such that maintenance of initial
performance without degradation in battery performance even when
being maintained at higher temperatures of more than 80.degree. C.
for a prolonged period of time is required.
[0003] However, when material such as LiCoO.sub.2,
LiMn.sub.2O.sub.4 or the like is used as a cathode active material
for the lithium secondary battery, reaction between electrolyte and
electrode surface leads to poor high-temperature characteristics,
such as swelling and bulking in storage at a higher temperature of
more than 80.degree. C. Additionally, when charge/discharge cycles
are repeatedly performed at the higher temperature, the
electrochemical reaction continuously occurring at a cathode or
anode surface contributes to production of decomposed by-products
of the electrolyte and gas in the battery, thereby severely
swelling the battery.
[0004] A variety of study and research has been made to solve those
problems. Korean Patent Laid-open Publication No. 2003-0057321
discloses a technique of forming a protective coating film using
electrolyte additives such as vinylene carbonate, alkenylethylene
carbonate and the like, wherein the electrolyte additives are used
to inhibit electrolyte decomposition reaction of the cathode at
higher temperatures, such that these additives are first decomposed
at cathode potential, thereby forming the protective film. However,
although such additives may effectively inhibit battery swelling at
higher temperatures, the additives may result in reduction of
battery capacity or deterioration of battery life characteristics.
For these reasons, various kinds of additives should be utilized to
improve one functionality of the battery, when such electrolyte
additives are used.
[0005] In addition, Korean Patent Laid-open Publication No.
2001-35700 and Japanese Patent Laid-Open Publication No.
1998-255389 disclose techniques of improving battery life
characteristics and high temperature storage characteristics by
addition of metal oxides or metal hydroxides to an electrode
(cathode). However, metal oxides or metal hydroxides are
electrically non-conductive and thus, when they are used as
additives, interfere with electrical flow in the electrodes,
thereby resulting in decreased high rate discharge characteristics
of the battery, as well as increased resistance thereof leading to
lowering of battery life characteristics.
[0006] Japanese Patent Laid-Open Publication Nos. 2003-86174 and
1997-22733 disclose a method of coating the cathode active material
with an electro-conductive material such as conductive material
using a mechanofusion apparatus and a binder. However, due to
integration between the cathode active material and the conductive
material in this method, it may be possible to improve battery
capacity or diminish electrical resistance, thereby improving high
rate discharge characteristics, but the conductive material coated
on the surface of the cathode active material rather hampers
migration of lithium ions, resulting in deterioration of battery
performance.
[0007] Therefore, there is a strong need for an electrode additive
that facilitates excellent high temperature storage performance of
the lithium secondary battery and simultaneously does not inhibit
high rate discharge and other battery performance
characteristics.
SUMMARY OF THE INVENTION
[0008] Therefore, the present invention has been made to solve the
above problems, and other technical problems that have yet to be
resolved.
[0009] The present inventors have surprisingly found that battery
performance and high temperature storage characteristics can be
improved by preparing an electrode additive having core particles
such as metal hydroxides, metal oxides or metal carbonates coated
with electro-conductive material and adding the electrode additive
to a cathode and/or anode of a lithium secondary battery.
[0010] On the basis of this finding, it is an object of the present
invention to provide an electrode additive that is capable of
improving battery performance and high temperature storage
characteristics, and an electrode for a lithium secondary battery
and lithium secondary battery comprising the same.
[0011] In accordance with an aspect of the present invention, the
above and other objects can be accomplished by the provision of an
electrode additive for a secondary battery electrode in which
electro-conductive material is coated on the surface of a material
that is added to the electrode material so as to improve battery
characteristics.
[0012] As used herein, the term "electrode additive" refers to
materials that are added to electrodes for various purposes such as
improving high temperature characteristics and charge/discharge
cycle characteristics of the battery. Since, among those materials,
there are various kinds of low conductivity materials, as described
above, such materials generally interfere with electron migration
due to their high resistivity, when added to electrodes, and
thereby lower battery performance. In accordance with the present
invention, there is provided an electrode additive that can exert
original effects without causing deterioration of battery
performance, by coating the surface of the electrode additive with
electro-conductive materials.
[0013] In accordance with the present invention, additive material
(hereinafter, referred to as "core particle"), which is coated with
electro-conductive materials, is added to electrodes for
improvement of high temperature storage characteristics, and is
exemplified as compounds represented by Formula 1 below:
M.sub.xA.sub.y Formula 1
[0014] wherein, M is a metal, A is selected from the group
consisting of OH, O and CO.sub.3, and x represents the valence of M
and y represents the oxidation number of A.
[0015] Metal hydroxides, metal oxides, and metal carbonates of
Formula 1 may be used alone or in any combination thereof.
[0016] Electro-conductive materials (hereinafter, referred to as
"coating materials"), which are coated on core particles, are not
particularly limited, so long as they exhibit excellent
conductivity without causing chemical changes in the battery of
interest. For example, there may be preferably used at least one
selected from the group consisting of carbon that has been used as
conductive material for a conventional lithium secondary battery,
electro-conductive materials, electro-conductive metals,
electro-conductive inorganic materials and electro-conductive
polymers.
[0017] In accordance with another aspect of the present invention,
there are provided an electrode fabricated by preparing an
electrode slurry using electrode material containing the electrode
additive and electrode active material and then applying the
thus-prepared electrode slurry to a current collector, and a
lithium secondary battery comprising the same.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] 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:
[0019] FIG. 1 schematically shows a cross-sectional view of an
electrode additive in accordance with the present invention;
[0020] FIG. 2 is a micrograph showing carbon-coated Mg(OH).sub.2
particles in accordance with the present invention;
[0021] FIG. 3 graphically shows battery life characteristics, i.e.
changes in cell capacity with respect to charge/discharge cycles,
for bicells in which the electrode additive of the present
invention is added to cathodes thereof (Examples) and bicells in
which the electrode additive of the present invention is not added
to cathodes thereof (Comparative Examples); and
[0022] FIG. 4 graphically shows battery life characteristics, i.e.
changes in cell capacity with respect to charge/discharge cycles,
for bicells in which the electrode additive of the present
invention is added to anodes thereof (Examples) and bicells in
which the electrode additive of the present invention is not added
to anodes thereof (Comparative Examples).
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0023] Now, the present invention will be described in more
detail.
[0024] In accordance with the present invention, by addition of an
electrode additive to a cathode and/or anode of a battery, it is
possible to inhibit battery swelling due to formation of
decomposition by-products or gas production even when the battery
is stored at high temperatures for a prolonged period of time, and
also to improve battery performance such as life characteristics
and charge/discharge rate at room temperature.
[0025] Conventionally, materials such as metal hydroxides, metal
oxides and metal carbonate were used per se as cathode additives,
but these materials are coated on the surface of the cathode active
material and then impede migration of cathode active material and
electrons, thereby deteriorating high rate discharge
characteristics of the battery. In the present invention, via use
of core particles, such as metal hydroxides, metal oxides or metal
carbonates, coated with the coating material, it was possible to
solve the problem associated with lowering of high rate discharge
characteristics.
[0026] In accordance with the present invention, the coating
material preferably has high electronic conductivity and small
particle size to the maximum extent possible. Where electronic
conductivity is lower, this may disadvantageously result in
increase of electrode resistance thereby degrading battery
performance. In addition, where the particle size of the coating
material is too large, it may be difficult to coat the surface of
core particles. On the other hand, the smaller the particle size of
the coating material the denser and more uniform the coating on the
core particles.
[0027] In the present invention, electrical conductivity of the
coating material is preferably more than
2.0.times.10.sup.2/cm.OMEGA. and the particle size thereof is
preferably within the range of 10 to 1000 nm.
[0028] There is no particular limit to kinds of carbon,
electro-conductive metals, electro-conductive inorganic materials
and electro-conductive polymers, as described above as being
preferred examples of the coat materials. Preferably, for example,
carbon may be selected from the group consisting of carbon black,
acetylene black and Super-P. Electro-conductive metals may be
selected from the group consisting of Cu, Ag, Pt and Ni.
Electro-conductive inorganic materials may be selected from the
group consisting of indium tin oxide (In.sub.2O.sub.3SnO.sub.2),
tin oxide (SnO.sub.2), zinc oxide (ZnO), ruthenium oxide
(RuO.sub.2) and TiB.sub.2. Electro-conductive polymers may be
selected from the group consisting of polypyrrole and polyaniline.
Among the above-mentioned coating materials, acetylene black
preferably has a particle size of 100 nm and electrical
conductivity of more than 6.1.times.10.sup.2/cm.OMEGA.. Ni
preferably has a particle size of 1000 nm and electrical
conductivity of more than 9.17.times.10.sup.4/cm.OMEGA..
Polypyrrole preferably has a particle size of 200 nm and electrical
conductivity of more than 2.0.times.10.sup.2/cm.OMEGA..
[0029] There is no particular limit to kinds of metal elements (M),
which are contained in metal hydroxides, metal oxides or metal
carbonates, those being described as preferred examples of the core
particles. For example, metals may be preferably selected from the
group consisting of Al, B, Mg, K, Be, Ca, Sr, Ba, Na, Cr, Sn, Ga,
Bi, Ni, Co, Fe, Cr, Y and Zr. More preferably, metals may be
selected from the group consisting of Al, B, Mg, Ba, Y and Zr.
[0030] A process for preparing an electrode additive in accordance
with the present invention will be exemplified as follows.
[0031] Core particles to be coated are mixed with the coating
material to prepare a mixture. In preparing the mixture, the amount
of the coating material is preferably within the range of 0.01 to
20% by weight, relative to that of the core particles. Where the
amount of the coating material exceeds the above-mentioned range,
the resulting coating layer is too thick. On the other hand, where
the amount of the coating material is less than the above range,
core particles may be incompletely and partially coated.
[0032] Next, the mixture thus obtained was fused using a
mechanofusion apparatus, for example, so as to coat core particles
with the coating material. During such a fusion process, rotation
speed and treatment time of the mechanofusion apparatus can be
controlled as desired. Preferably, the rotation speed of the
mechanofusion apparatus is between 1500 and 3000 rpm, and treatment
time is in the range of 0.1 to 10 hours.
[0033] The extent that core particles are coated by the coating
material may vary depending on the amount of the coating material
added. Core particles need not necessarily be completely coated by
the coating material to effect desired effects of the present
invention. FIG. 1 schematically shows a coating material-coated
core particle. FIG. 2 is a micrograph showing carbon-coated
Mg(OH).sub.2 particles. As can be seen from FIG. 2, carbon, which
is coating material, uniformly surrounded core particles.
[0034] In accordance with the present invention, there is provided
an electrode fabricated by adding the thus-prepared electrode
additive of the present invention to an electrode material
including electrode active material so as to prepare an electrode
slurry and coating a current collector with the thus-prepared
electrode slurry. There is no limit to a method for fabricating an
electrode, and well-known conventional methods in the art may be
employed.
[0035] Preferably, the electrode additive may be included in the
range of 0.05 to 10% by weight in the electrode, relative to the
electrode active material.
[0036] Further, in accordance with the present invention, there is
provided a lithium secondary battery comprising the above-prepared
electrode. The lithium secondary battery of the present invention
may be prepared by conventional methods known in the art, for
example disposing a porous separator between the cathode and anode,
followed by introduction of a non-aqueous electrolyte.
[0037] There is no limit to shapes of the lithium secondary battery
in accordance with the present invention, and for example, mention
may be made of can-shaped cylinders, squares or pouches.
[0038] As cathode active materials that can be used in fabricating
the electrode of the present invention, lithium-containing
transition metal oxides may be preferably used. For example, the
cathode active material may be at least one selected from the group
consisting of LiCoO.sub.2, LiNiO.sub.2, LiMnO.sub.2,
LiMn.sub.2O.sub.4, Li(Ni.sub.aCo.sub.bMn.sub.c)- O.sub.2
(0<a<1, 0<b<1, 0<c<1, a+b+c=1),
LiNi.sub.1-YCo.sub.YO.sub.2, LiCo.sub.1-YMn.sub.YO.sub.2,
LiNi.sub.1-YMn.sub.YO.sub.2 (0.ltoreq.Y<1),
Li(Ni.sub.aCo.sub.bMn.sub.- c)O.sub.4 (0<a<2, 0<b<2,
0<c<2, a+b+c=2, LiMn.sub.2-zNi.sub.zO.sub.4,
LiMn.sub.2-zCo.sub.zO.sub.4 (0<Z<2), LiCoPO.sub.4 and
LiFePO.sub.4. Among those materials, more preferred is
LiCoO.sub.2.
[0039] As anode active materials that can be used in fabricating
the electrode of the present invention, mention may be made of
graphite, carbon, lithium metals, alloys and complexes thereof,
which are capable of occluding and releasing lithium ions.
[0040] In addition, in preparing the battery in accordance with the
present invention, the porous separator may be preferably used as
the separator. For example, the separator may include, but is not
limited to, polypropylene-based, polyethylene-based, and other
polyolefin-based porous separators.
[0041] The non-aqueous electrolyte of the lithium secondary battery
that can be utilized in the present invention may contain cyclic
carbonates and linear carbonates. The cyclic carbonates include,
for example ethylene carbonate (EC), propylene carbonate (PC) and
gamma-butyro lactone (GBL). The linear carbonate may be at least
one selected from the group consisting of diethylcarbonate (DEC),
dimethylcarbonate (DMC), ethylmethylcarbonate (EMC) and
methylpropylcarbonate (MPC). Further, the non-aqueous electrolyte
of the lithium secondary battery in accordance with the present
invention may contain lithium salts, in addition to carbonate
compounds. As specific examples, preferably, lithium salts may be
selected from the group consisting of LiClO.sub.4,
LiCF.sub.3SO.sub.3, LiPF.sub.6, LiBF.sub.4, LiAsF.sub.6 and
LiN(CF.sub.3SO.sub.2).sub.2.
EXAMPLES
[0042] Now, the present invention will be described in more detail
with reference to the following Examples and Comparative Examples.
These examples are provided only for illustrating the present
invention and should not be construed as limiting the scope and
spirit of the present invention.
Example
[0043] 1.1. Preparation of Electrode Additive
[0044] Acetylene black, which is a carbon material, as a coating
material and Mg(OH).sub.2, which is a metal hydroxide, as a core
particle, were used to prepare an electrode additive. The content
of acetylene black was 5% by weight, relative to that of the core
particle, Mg(OH).sub.2. A mixture of acetylene black and
Mg(OH).sub.2 was loaded on a mechanofusion apparatus, and subjected
to low speed rotation at 250 rpm for 3 min and subsequently to high
speed rotation at 1400 rpm for 20 min so as to coat carbon on the
surface of the metal hydroxide, thereby preparing the electrode
additive (C.sub.0.05Mg(OH).sub.2).
[0045] 1.2. Preparation of Cathode
[0046] LiCoO.sub.2 was used as a cathode active material, and 0.5%
by weight of the above-prepared electrode additive
(C.sub.0.05Mg(OH).sub.2) was added thereto, relative to the cathode
active material. Then, together with 2.5% Super-P(conductive
material) and 2.5% polyvinylidene difluoride (PVdF) as a binding
agent, a cathode active material powder (LiCoO.sub.2) and the
electrode additive were dispersed in an n-methylpyrolidone (NMP)
solvent to obtain a slurry. The slurry thus obtained was coated on
aluminum foil and heated to evaporate the NMP solvent to dryness,
followed by compression at a pressure of about 500 kg/cm.sup.2 to
prepare a cathode.
[0047] 1.3. Preparation of Anode
[0048] Artificial graphite was used as an anode active material,
and was dispersed, together with 0.8% acetylene black (conductive
material), 3.9% PVdF as a binding agent and 0.2% oxalic acid,
relative to the anode active material, in an NMP solvent to obtain
slurry. The slurry thus obtained was coated on copper foil and
heated to evaporate the NMP solvent to dryness, followed by
compression at a pressure of about 500 kg/cm.sup.2 to prepare an
anode.
[0049] 1.4. Battery Preparation and Evaluation
[0050] A conventional pouch-type bicell was prepared using the
above-prepared cathode and anode, and as an electrolyte, a solution
in which 1M LiPF.sub.6 was dissolved in a 1:2 (v/v) mixed solvent
of ethylene carbonate (EC) and ethyl methyl carbonate (EMC).
[0051] For the above-prepared battery, voltage of charge and
discharge was established in the range of 3.0 to 4.2 V. Evaluation
of battery life characteristics was made by 1 C/1 C
charge/discharge. Evaluation of high rate discharge characteristics
was carried out by charging the battery to 0.5 C, followed by
measurement of capacity of 0.2 C, 0.5 C, 1 C, 1.5 C and 2 C and
calculation of percentage of respective capacity thus measured,
relative to capacity of 0.2 C. In addition, in order to evaluate
high temperature storage characteristics, the battery was
charged/discharged to 0.5 C/0.5 C two times and then charged to 0.2
C. This was followed by placement of the battery in an oven at
80.degree. C. and determination of thickness changes with respect
to the passage of time.
Example 2
[0052] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that 10% by weight of
acetylene black as a coating material was added, relative to core
particles, when preparing an electrode additive.
Example 3
[0053] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that, relative to an
anode active material, there was added 1.0% by weight of an
electrode additive, which was prepared in a manner that an
electrode additive was not added to a cathode and 10% by weight of
acetylene black as a coating material was added to an anode,
relative to core particles (Mg(OH).sub.2).
Example 4
[0054] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that 10% by weight of
acetylene black as a coating material was added, relative to core
particles and LiMn.sub.2O.sub.4 powder was used as a cathode active
material, when preparing an electrode additive.
Example 5
[0055] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that 10% by weight of
acetylene black as a coating material was added, relative to core
particles and LiNi.sub.1/3Mn.sub.1/3Co.sub.1/3O.sub.2 powder was
used as a cathode active material, when preparing an electrode
additive.
Example 6
[0056] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that 10% by weight of
acetylene black as a coating material was added, relative to core
particles and BaCO.sub.3 was used as core particles, when preparing
an electrode additive.
Example 7
[0057] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that 10% by weight of
acetylene black as a coating material was added, relative to core
particles and MgO was used as core particles, when preparing an
electrode additive.
Example 8
[0058] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that 10% by weight of
acetylene black as a coating material was added, relative to core
particles and Al.sub.2O.sub.3 was used as core particles, when
preparing an electrode additive.
Example 9
[0059] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that 10% by weight of
acetylene black as a coating material was added, relative to core
particles and Y(OH).sub.3 was used as core particles, when
preparing an electrode additive.
Example 10
[0060] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that 10% by weight of
acetylene black as a coating material was added, relative to core
particles and Al(OH).sub.3 was used as core particles, when
preparing an electrode additive.
Example 11
[0061] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that Ag metal powder was
used as a coating material and 10% by weight of the coating
material was added, relative to core particles, when preparing an
electrode additive.
Example 12
[0062] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that Al metal powder was
used as a coating material and the coating material was added in an
amount of 10% by weight, relative to core particles, when preparing
an electrode additive.
Example 13
[0063] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that TiB.sub.2 powder
was used as a coating material and the coating material was added
in an amount of 10% by weight, relative to core particles, when
preparing an electrode additive.
Example 14
[0064] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that a conductive
polymer, polypyrrole powder was used as a coating material and the
coating material was added in an amount of 10% by weight, relative
to core particles, when preparing an electrode additive.
Example 15
[0065] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that a coating material
was added in an amount of 10% by weight, relative to core
particles, when preparing an electrode additive, and an electrode
additive was added in an amount of 10% by weight, relative to a
cathode active material, when preparing an electrode.
Example 16
[0066] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that a coating material
was added in an amount of 10% by weight, relative to core
particles, and an electrode additive was added to a cathode and
anode, in amounts of 1% by weight and 2% by weight, respectively,
relative to a cathode active material and an anode active material,
when preparing an electrode additive.
Example 17
[0067] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 3, except that metal Si was used
as an anode active material.
Example 18
[0068] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 3, except that Al metal powder was
used as a coating material, the coating material was added in an
amount of 10% by weight, relative to core particles and metal Si
was used as an anode active material, when preparing an electrode
additive.
Comparative Example 1
[0069] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that an electrode
additive was not used
Comparative Example 2
[0070] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 1, except that pure Mg(OH).sub.2
was added as a cathode additive.
Comparative Example 3
[0071] An electrode and a battery were prepared and evaluated using
the same procedure as in Example 3, except that pure Mg(OH).sub.2
was added as an anode additive.
[0072] Evaluation results of batteries prepared in Examples 1
through 18 and Comparative Examples 1 through 3 are shown in FIGS.
3 and 4, and Tables 1 through 3.
1TABLE 1 Changes in thickness of bicell, with or without addition
of electrode additive to cathode, and with time Comp. Comp. Ex. 1
Ex. 2 Ex. 1 Ex. 2 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 1 day 3.08 3.09
3.10 3.08 3.09 3.08 3.10 3.09 3.08 3 days 3.20 3.24 3.11 3.08 3.10
3.11 3.13 3.12 3.09 5 days 3.42 3.42 3.15 3.15 3.16 3.17 3.19 3.18
3.11 7 days 3.91 3.62 3.31 3.31 3.37 3.35 3.33 3.37 3.35 9 days
4.43 3.97 3.48 3.44 3.43 3.46 3.49 3.48 3.45 11 days 4.87 4.31 3.57
3.52 3.61 3.57 3.58 3.60 3.56 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex.
14 Ex. 15 Ex. 16 1 day 3.09 3.10 3.10 3.09 3.09 3.09 3.10 3.10 3
days 3.11 3.10 3.12 3.11 3.12 3.13 3.13 3.14 5 days 3.15 3.17 3.30
3.31 3.18 3.20 3.17 3.19 7 days 3.32 3.35 3.39 3.38 3.39 3.38 3.32
3.37 9 days 3.44 3.49 3.49 3.48 3.51 3.52 3.50 3.42 11 days 3.59
3.55 3.54 3.59 3.58 3.59 3.59 3.64
[0073] As can be seen from Table 1, batteries prepared in Examples
1, 2 and 4 through 16 exhibited less changes in thickness under
high temperature storage, compared to batteries prepared in
Comparative Examples 1 and 2.
2TABLE 2 Changes in thickness of bicell, with or without addition
of electrode additive to anode, and with time Comp. Comp. Ex. 1 Ex.
3 Ex. 3 Ex. 16 Ex. 17 Ex. 18 1 day 3.08 3.09 3.10 3.10 3.11 3.10 3
days 3.20 3.26 3.12 3.14 3.19 3.18 5 days 3.42 3.41 3.16 3.19 3.21
3.32 7 days 3.91 3.87 3.38 3.37 3.45 3.50 9 days 4.43 4.11 3.42
3.42 3.55 3.56 11 days 4.87 4.22 3.57 3.64 3.66 3.2
[0074] As can be seen from Table 2, batteries prepared in Examples
3, 16, 17 and 18 exhibited less changes in thickness under high
temperature storage, compared to batteries prepared in Comparative
Examples 1 and 3.
3TABLE 3 Changes in battery capacity with respect to discharge rate
Discharge Comp. Comp. Comp. rate (C) Ex. 1 Ex. 2 Ex. 3 Ex. 1 Ex. 2
Ex. 3 Ex. 4 0.2 100 100 100 100 100 100 100 0.5 99.61 99.61 99.45
99.64 99.51 99.88 99.78 1 99.36 99.38 99.29 99.52 99.40 99.62 99.63
1.5 99.86 99.85 99.75 99.89 94.92 99.61 99.67 2 99.56 99.78 99.58
99.87 99.06 99.41 99.78 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11
0.2 100 100 100 100 100 100 100 0.5 99.51 99.71 99.44 99.58 99.51
99.47 99.46 1 99.42 99.48 99.35 99.32 99.34 99.35 99.31 1.5 99.66
99.55 99.54 99.77 99.76 99.71 99.75 2 99.56 99.48 99.52 99.59 99.54
99.50 99.56 Ex. 12 Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18 0.2
100 100 100 100 100 100 100 0.5 99.54 99.53 99.88 99.81 99.53 99.71
99.49 1 99.50 99.47 99.65 99.73 99.52 99.58 99.32 1.5 99.81 94.82
99.71 99.70 99.65 99.65 99.69 2 99.86 99.36 99.49 99.78 99.66 99.58
99.48
[0075] As can be seen from Table 3, batteries prepared in Examples
1 through 18, to which the electrode additive in accordance with
the present invention was added, exhibited relatively little drop
in high rate discharge, compared to batteries of Comparative
Examples 1 through 3.
[0076] Further, as shown in FIGS. 3 and 4, batteries prepared in
Examples 1 through 18 exhibited relatively less changes in battery
capacity with respect to charge/discharge cycles, compared to
batteries prepared in Comparative Examples 1 through 3.
INDUSTRIAL APPLICABILITY
[0077] As described above, the electrode additive in accordance
with the present invention, when introduced to a cathode and/or
anode of a lithium secondary battery, can exert characteristics
intrinsic to the additive such as improvement of high temperature
storage characteristics, without deteriorating battery
performance.
[0078] Although the preferred embodiments of the present invention
have 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.
* * * * *