U.S. patent application number 10/966927 was filed with the patent office on 2005-04-21 for positive active material for rechargeable lithium battery and method of preparing same.
Invention is credited to Kim, Geun-Bae, Kweon, Ho-Jin, Noh, Hyung-Gon, Park, Dong-Gon.
Application Number | 20050084757 10/966927 |
Document ID | / |
Family ID | 19575741 |
Filed Date | 2005-04-21 |
United States Patent
Application |
20050084757 |
Kind Code |
A1 |
Kweon, Ho-Jin ; et
al. |
April 21, 2005 |
Positive active material for rechargeable lithium battery and
method of preparing same
Abstract
A positive active material for rechargeable lithium batteries
includes an active material component processed from a
manganese-based compound. The transition metal compound is selected
from Li.sub.xMnO.sub.2, Li.sub.xMnF.sub.2, Li.sub.xMnS.sub.2,
Li.sub.xMnO.sub.2-zF.sub.z, Li.sub.xMnO.sub.2-zS.sub.z,
Li.sub.xMn.sub.1-yM.sub.yO.sub.2, Li.sub.xMn.sub.1-yM.sub.yF.sub.2,
Li.sub.xMn.sub.1-yM.sub.yS.sub.2,
Li.sub.xMn.sub.1-yM.sub.yO.sub.2-zF.sub.z,
Li.sub.xMn.sub.1-yO.sub.2-zS.s- ub.z, Li.sub.xMn.sub.2O.sub.4,
Li.sub.xMn.sub.2F.sub.4, Li.sub.xMn.sub.2S.sub.4,
Li.sub.xMn.sub.2O.sub.4-zF.sub.z, Li.sub.xMn.sub.2O.sub.4-zS.sub.z,
Li.sub.xMn.sub.2-yM.sub.yO.sub.4, Li.sub.xMn.sub.2-yM.sub.yF.sub.4,
Li.sub.xMn.sub.2-yM.sub.yS.sub.4,
Li.sub.xMn.sub.2-yM.sub.yO.sub.4-zF.sub.z, or
Li.sub.xMn.sub.2-yM.sub.yO.- sub.4-zS.sub.z where
0<x.ltoreq.1.5, 0.05.ltoreq.y.ltoreq.0.3, z.ltoreq.1.0 and M is
selected from Al, Co, Cr, Mg, Fe or La. A metallic oxide is coated
on the active material component.
Inventors: |
Kweon, Ho-Jin; (Cheonan-si,
KR) ; Kim, Geun-Bae; (Cheonan-si, KR) ; Park,
Dong-Gon; (Seoul, KR) ; Noh, Hyung-Gon;
(Cheonan-si, KR) |
Correspondence
Address: |
BLAKELY SOKOLOFF TAYLOR & ZAFMAN
12400 WILSHIRE BOULEVARD
SEVENTH FLOOR
LOS ANGELES
CA
90025-1030
US
|
Family ID: |
19575741 |
Appl. No.: |
10/966927 |
Filed: |
October 14, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10966927 |
Oct 14, 2004 |
|
|
|
09429262 |
Oct 29, 1999 |
|
|
|
Current U.S.
Class: |
429/231.1 ;
429/224; 429/232 |
Current CPC
Class: |
Y02E 60/10 20130101;
Y10T 29/49115 20150115; H01M 4/581 20130101; H01M 4/131 20130101;
H01M 10/0525 20130101; H01M 4/505 20130101; Y10T 29/49108 20150115;
H01M 4/1315 20130101 |
Class at
Publication: |
429/231.1 ;
429/224; 429/232 |
International
Class: |
H01M 004/50; H01M
004/58; H01M 004/62 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 1999 |
KR |
99-7430 |
Claims
What is claimed is:
1. A positive active material for rechargeable lithium batteries,
the positive active material comprising: an active material
component processed from a manganese-based compound, the
manganese-based compound being selected from the group consisting
of Li.sub.xMn.sub.1-yM.sub.yO.su- b.2,
Li.sub.xMn.sub.1-yM.sub.yO.sub.2-zF.sub.z,
Li.sub.xMn.sub.1-yM.sub.yO- .sub.2-zS.sub.z,
Li.sub.xMn.sub.2-yM.sub.yO.sub.4-zF.sub.z, and
Li.sub.xMn.sub.2-yM.sub.yO.sub.4-zS.sub.z, where 0<x<1.5,
0.05.ltoreq.y.ltoreq.0.3, 7.ltoreq.1.0 and M is selected from the
group consisting of Al, Co, Cr, Mg, Fe and La; and a metallic oxide
coated on the active material component, the metallic oxide
comprising a metal selected from the group consisting of Mg Al
wherein the positive active material is formed of metallic oxide
coated active material moieties.
2. The positive active material of claim 1 wherein the oxide has a
thickness range of 1-1000 nm.
3. The positive active material of claim 1 wherein the quantity of
metal content is a range of 1 to 10 weight percent of the
oxide.
4. A positive electrode for rechargeable lithium batteries, the
positive electrode comprising: a plurality of active material
particles processed from a manganese-based compound, the
manganese-based compound being selected from the group consisting
of Li.sub.xMnO.sub.2, Li.sub.xMn.sub.1-yM.sub.yO.sub.2,
Li.sub.xMn.sub.1-yM.sub.yO.sub.2-zF.sub- .z,
Li.sub.xMn.sub.1-yM.sub.yO.sub.2-zS.sub.z, Li.sub.xMn.sub.2O.sub.4,
Li.sub.xMn.sub.2-yM.sub.yO.sub.4,
Li.sub.xMn.sub.2-yM.sub.yO.sub.4-zF.sub- .z, and
Li.sub.xMn.sub.2-yM.sub.yO.sub.4-zS.sub.z, where 0<x<1.5,
0.05.ltoreq.y.ltoreq.0.3, z.ltoreq.1.0 and M is selected from the
group consisting of Al, Co, Cr, Mg, Fe and La, and a metallic oxide
coated on each of the active material particles, the metallic oxide
comprising a metal selected from the group consisting of Mg and Al;
wherein the positive electrode comprises the active material
particles coated with the metallic oxide, and wherein the positive
electrode is formed after the active material particles are coated
with the metallic oxide.
5. The positive electrode of claim 4, wherein the oxide has a
thickness range of 1 to 1000 nanometers.
6. The positive electrode of claim 4, wherein the quantity of metal
content is in a range of 1 to 10 weight percent of the oxide.
Description
BACKGROUND OF THE INVENTION
[0001] (a) Field of the Invention
[0002] The present invention relates to a positive active material
for rechargeable lithium batteries and a method of preparing the
same and, more particularly, to a manganese-based positive active
material for rechargeable lithium batteries which has a good cycle
life characteristic.
[0003] (b) Description of the Related Art
[0004] Generally, manganese-based compounds such as
LiMn.sub.2O.sub.4 and LiMnO.sub.2 are the positive active material
of choice for rechargeable lithium batteries because of their low
cost, abundance and environmentally friendly characteristics. Among
such manganese-based compounds, LiMn.sub.2O.sub.4 is particularly
stable for the battery use and thus attractive for the electric
vehicle application.
[0005] However, as compared to other lithiated transition metal
oxides such as LiCoO.sub.2 and LiNiO.sub.2, LiMn.sub.2O.sub.4 has a
relatively low discharge capacity. Furthermore, when high rate of
charge and discharge operations are cycled, the discharge capacity
is excessively reduced. In particular, when the charge and
discharge operations are continuously performed at high
temperatures, manganese distributed in the surface of
LiMn.sub.2O.sub.4 readily elutes to the electrolyte, causing a
disproportionation reaction. This reaction seriously deteriorates
the cycle life characteristic of the battery.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to provide a
manganese-based positive active material for rechargeable lithium
batteries which exhibits a good cycle life characteristic at high
temperatures.
[0007] This and other objects may be achieved by a positive active
material for rechargeable lithium batteries including an active
material component processed from a manganese-based compound. The
manganese-based compound is selected from Li.sub.xMnO.sub.2,
Li.sub.xMnF.sub.2, Li.sub.xMnS.sub.2, Li.sub.xMnO.sub.2-zF.sub.z,
Li.sub.xMnO.sub.2-zS.sub.z- , Li.sub.xMn.sub.1-yM.sub.yO.sub.2,
Li.sub.xMn.sub.1-yM.sub.yF.sub.2, Li.sub.xMn.sub.1-yM.sub.yS.sub.2,
Li.sub.xMn.sub.1-yM.sub.yO.sub.2-zF.sub- .z,
Li.sub.xMn.sub.1-yM.sub.yO.sub.2-zS.sub.z, Li.sub.xMn.sub.2O.sub.4,
Li.sub.xMn.sub.2F.sub.4, Li.sub.xMn.sub.2S.sub.4,
Li.sub.xMn.sub.2O.sub.4- -zF.sub.z,
Li.sub.xMn.sub.2O.sub.4-zS.sub.z, Li.sub.xMn.sub.2-yM.sub.yO.su-
b.4, Li.sub.xMn.sub.2-yM.sub.yF.sub.4,
Li.sub.xMn.sub.2-yM.sub.yS.sub.4,
Li.sub.xMn.sub.2-yM.sub.yO.sub.4-zF.sub.z, or
Li.sub.xMn.sub.2-yM.sub.yO.- sub.4-zS.sub.z where
0<x.ltoreq.1.5, 0.05.ltoreq.y.ltoreq.0.3, z.ltoreq.1.0 and M is
selected from Al, Co, Cr, Mg, Fe or La. A metallic oxide is coated
on the active material component.
[0008] A method of preparing the positive active material is
performed by obtaining a powder from a source material. The source
material is selected from Li.sub.xMnO.sub.2, Li.sub.xMnF.sub.2,
Li.sub.xMnS.sub.2, Li.sub.xMnO.sub.2-zF.sub.z,
Li.sub.xMnO.sub.2-zS.sub.z, Li.sub.xMn.sub.1-yM.sub.yO.sub.2,
Li.sub.xMn.sub.1-yM.sub.yF.sub.2, Li.sub.xMn.sub.1-yM.sub.yS.sub.2,
Li.sub.xMn.sub.1-yM.sub.yO.sub.2-zF.sub- .z,
Li.sub.xMn.sub.1-yM.sub.yO.sub.2-zS.sub.z, Li.sub.xMn.sub.2O.sub.4,
Li.sub.xMn.sub.2F.sub.4, Li.sub.xMn.sub.2S.sub.4,
Li.sub.xMn.sub.2O.sub.4- -zF.sub.z,
Li.sub.xMn.sub.2O.sub.4-zS.sub.z, Li.sub.xMn.sub.2-yM.sub.yO.su-
b.4, Li.sub.xMn.sub.2-yM.sub.yF.sub.4,
Li.sub.xMn.sub.2-yM.sub.yS.sub.4,
Li.sub.xMn.sub.2-yM.sub.yO.sub.4-zF.sub.z, or
Li.sub.xMn.sub.2-yM.sub.yO.- sub.4-zS.sub.z, where
0<x.ltoreq.1.5, 0.05.ltoreq.y.ltoreq.0.3, z.ltoreq.1.0 and M is
selected from Al, Co, Cr, Mg, Fe or La. The powder is then coated
with a metallic alkoxide solution to make an alkoxide-coated
powder. Thereafter, the metallic alkoxide-coated powder is
heat-treated such that it is changed into a metallic oxide-coated
powder.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] A more complete appreciation of the invention, and many of
the attendant advantages thereof, will be readily apparent as the
same becomes better understood by reference to the following
detailed description when considered in conjunction with the
accompanying drawings, wherein:
[0010] FIG. 1 is a graph illustrating high-temperature charge and
discharge characteristics of rechargeable lithium cells according
to an example of the present invention and a comparative
example;
[0011] FIG. 2 is a graph illustrating high-temperature cycle life
characteristics of the rechargeable lithium cells of FIG. 1;
and
[0012] FIG. 3 is a graph illustrating SIMS analysis results with
respect to a rechargeable lithium cell according to another example
of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0013] In a method of preparing a positive active material for
rechargeable lithium batteries, a powder, being an active material
precursor, is first processed from a manganese-based compound. The
manganese-based compound is selected from Li.sub.xMnO.sub.2,
Li.sub.xMnF.sub.2, Li.sub.xMnS.sub.2, Li.sub.xMnO.sub.2-zF.sub.z,
Li.sub.xMnO.sub.2-zS.sub.z, Li.sub.xMn.sub.1-yM.sub.yO.sub.2,
Li.sub.xMn.sub.1-yM.sub.yF.sub.2, Li.sub.xMn.sub.1-yM.sub.yS.sub.2,
Li.sub.xMn.sub.1-yM.sub.yO.sub.2-zF.sub.z,
Li.sub.xMn.sub.1-yM.sub.yO.sub- .2-zS.sub.z,
Li.sub.xMn.sub.2O.sub.4, Li.sub.xMn.sub.2F.sub.4,
Li.sub.xMn.sub.2S.sub.4, Li.sub.xMn.sub.2O.sub.4-zF.sub.z,
Li.sub.xMn.sub.2O.sub.4-zS.sub.z, Li.sub.xMn.sub.2-yM.sub.yO.sub.4,
Li.sub.xMn.sub.2-yM.sub.yF.sub.4, Li.sub.xMn.sub.2-yM.sub.yS.sub.4,
Li.sub.xMn.sub.2-yM.sub.yO.sub.4-zF.sub.z, or
Li.sub.xMn.sub.2-yM.sub.yO.- sub.4-zS.sub.z, where
0<x.ltoreq.1.5, 0.05.ltoreq.y.ltoreq.0.3, z.ltoreq.1.0 and M is
selected from Al, Co, Cr, Mg, Fe or La. The powder processing step
can be performed with a technique known in the related art.
[0014] Thereafter, the powder is coated with a metallic alkoxide
solution. The metallic alkoxide solution is formed by the reaction
of an alcohol with an alkali metal being 1 to 50 weight percent of
the alcohol. The alkali metal may be preferably selected from Mg,
Al, Co, K, Na, Ca, Si, Ti or Sr. More preferably, the alkali metal
is selected from Si, Mg, Ti or Al. The alcohol is preferably
selected from methanol or ethanol. When the alkali metal is less
than 1 weight percent of the alcohol, the coating effect of the
metallic alkoxide solution onto the powder is not induced. In
contrast, when the alkali metal is more than 50 weight percent of
the alcohol, the coating layer of the metallic alkoxide solution
becomes undesirably thick. A sputtering technique, a chemical vapor
deposition (CVD) technique, a dip coating technique and other
general-purpose coating techniques may be employed for the coating
use. Among the techniques, the dip coating technique may be
preferably used for coating the metallic alkoxide solution onto the
powder.
[0015] The alkoxide-coated powder is then dried at 120.degree. C.
for about 5 hours in an oven. The drying step is to uniformly
distribute lithium salts in the powder. Thereafter, the dried
powder is heat-treated at temperatures ranged from 200 to
1000.degree. C. for 1 to 20 hours under an oxidation atmosphere
where dry air or oxygen is blowing. When the heat-treating
temperature is lower than 200.degree. C., the metallic alkoxide
solution coated on the powder is not crystallized so that it
prohibits free movement of lithium ions in the active material. It
is preferable that the heat-treating step is performed at
temperatures ranged from 300 to 900.degree. C. for 1 to 10 hours.
This heat-treating operation makes the metallic alkoxide to be
changed into a metallic oxide. In this way, a metallic oxide-coated
active material is prepared.
[0016] The metallic oxide formed on the surface of the power may be
derived from the single metallic alkoxide source or the composite
sources of manganese of lithiated transition metal compound and
metallic alkoxide. The thickness of the metallic oxide layer
reaches up to 1 to 100 nm and the quantity of metal content is
ranged from 0.1 to 10 weight percent of the metallic oxide.
[0017] The following examples further illustrate the present
invention.
EXAMPLE 1
[0018] An aluminum isopropoxide solution having a 5 weight-percent
concentration was prepared by refluxing an aluminum isopropoxide
powder in ethanol at about 100.degree. C. for about half an hour.
The aluminum isopropoxide solution was then mixed with a powder of
Li.sub.xMn.sub.2-yAl.sub.yO.sub.4-zF.sub.z where 0<x.ltoreq.1.5,
0.05.ltoreq.y.ltoreq.0.3 and z.ltoreq.1.0 at an identical volume
ratio in a moisture free dry room such that an overall surface of
the power became wet sufficiently by the solution, and dried in the
same room. Thereafter, the mixture was heat-treated at about
300.degree. C. for about 10 hours under a dry air atmosphere to
thereby prepare a metallic oxide-coated active material. Then, the
active material was mixed with Super P carbon for a conductive
agent, KF-1300 polyvinylidene fluoride for a binder and
N-methylpyrrolidone for a solvent to prepare an active material
slurry. The slurry is cast into a tape shape to act as a positive
electrode. The positive electrode is then assembled with a lithium
metal foil for an opposite pole by using a lithium salt solution
for an electrolyte to thereby fabricate a coin cell-type half cell.
The lithium salt solution contained 1:1 volume ratio of ethylene
carbonate and dimethyl carbonate for a solvent and LiPF.sub.6 for a
solute.
EXAMPLE 2
[0019] The positive electrode preparing procedure was performed in
the same way as in Example 1 with the exception that the
heat-treating temperature was heightened up to 900.degree. C. A
coin-type half cell was fabricated with the resulting positive
electrode in combination with other components as described in
Example 1.
EXAMPLE 3
[0020] An aluminum isopropoxide solution having a 5 weight-percent
concentration was prepared by refluxing an aluminum isopropoxide
powder in ethanol at about 100.degree. C. for about half an hour.
The aluminum isopropoxide solution was then mixed with a powder of
Li.sub.xMn.sub.2O.sub.4 where 0<x.ltoreq.1.5 at an identical
volume ratio in a moisture free dry room such that an overall
surface of the power became wet sufficiently by the solution, and
dried in the same room. Thereafter, the mixture was heat-treated at
about 300.degree. C. for about 10 hours under a dry air atmosphere
to thereby prepare a metallic oxide-coated active material. The
subsequent positive electrode processing steps were performed in
the same way as in Example 1. A coin-type half cell was fabricated
with the resulting positive electrode in combination with other
components as described in Example 1.
COMPARATIVE EXAMPLE 1
[0021] The positive electrode preparing procedure was performed in
the same way as in Example 1 with the exception that
Li.sub.xMn.sub.2-yAl.sub- .yO.sub.4-zF.sub.z was directly used for
the active material without the metallic-alkoxide coating
operation. A coin-type half cell was fabricated with the resulting
positive electrode in combination with other components as
described in Example 1.
[0022] The coin type cells fabricated according to Example 1 and
Comparative Example 1 were charged and discharged at 50.degree. C.
from 0.1 C to 1 C rate over the voltage window between 4.3V and
3.0V. The charge and discharge characteristics of the cells in the
early cycles were illustrated in FIG. 1. Further, the cycle life
characteristics of the cells were illustrated in FIG. 2. In each of
the figures, the charge and discharge characteristic of the cell
according to Example 1 is indicated by a parenthesized alphabetic
symbol "(a)" and that of the cell according to Comparative Example
1 is indicated by another symbol "(b)". As shown in FIGS. 1 and 2,
the cell according to Example 1 exhibited a slightly lower specific
capacity but a better cycle life characteristic at high
temperatures than the cell according it Comparative Example 1. It
is presumed that the good cycle life characteristic of the cell is
resulted because the metallic oxide layer coated on the surface of
the manganese-based active material component prevents elution of
manganese to the electrolyte. The cells fabricated according to
Examples 2 and 3 also exhibited the desired performance
characteristic similar to that of Example 1.
[0023] Meanwhile, a secondary ion mass spectrometry (SIMS) analysis
was performed with respect to the positive active material prepared
according to Example 3 to measure the component distribution ratio.
The result was illustrated in FIG. 3. In the figure, the relative
intensity of the aluminum component is indicated by a parenthesized
alphabetic symbol "(a)" and that of the manganese component is
indicated by another symbol "(b)". As shown in FIG. 3, it could be
known that the aluminum component existed more in the surface
portion of the active material and the manganese component existed
more in the center portion of the active material. This proved that
the overall surface of Li.sub.xMn.sub.2O.sub.4 was completely
coated with aluminum oxide.
[0024] As described above, the positive active material for
rechargeable lithium batteries has a good high-temperature cycle
life characteristic.
[0025] While the present invention has been described in detail
with reference is to the preferred embodiments, those skilled in
the art will appreciate that various modifications and
substitutions can be made thereto without departing from the spirit
and scope of the present invention as set forth in the appended
claims.
* * * * *