U.S. patent application number 16/957027 was filed with the patent office on 2021-12-02 for positive pole active material for lithium secondary battery and manufacturing method thereof, lithium secondary battery.
This patent application is currently assigned to POSCO. The applicant listed for this patent is POSCO, POSCO Chemical Co., Ltd., Research Institute of Industrial Science & Technology. Invention is credited to Jeong Han Kim, Sung Hwan Min, Jung Hoon Song.
Application Number | 20210376317 16/957027 |
Document ID | / |
Family ID | 1000005824161 |
Filed Date | 2021-12-02 |
United States Patent
Application |
20210376317 |
Kind Code |
A1 |
Min; Sung Hwan ; et
al. |
December 2, 2021 |
POSITIVE POLE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY AND
MANUFACTURING METHOD THEREOF, LITHIUM SECONDARY BATTERY
Abstract
The present disclosure relates to a positive active material for
a lithium rechargeable battery and a lithium rechargeable battery
including the same, which include a first compound represented by
Chemical Formula 1 and a second compound represented by Chemical
Formula 2, and a content of the first compound is 65 wt % or more
based of the positive active material of 100 wt %.
Li.sub.a1Ni.sub.b1Co.sub.c1Mn.sub.d1M1.sub.e1M2.sub.f1O.sub.2-f1
[Chemical Formula 1]
Li.sub.a2Ni.sub.b2Co.sub.c2Mn.sub.d2M3.sub.e2M4.sub.f2O.sub.2-f2
[Chemical Formula 2] Chemical Composition 1 and 2 of each
composition and molar ratio is as defined in the specification.
Each composition and molar ratio of Chemical Formula 1 and 2 is as
defined in the specification.
Inventors: |
Min; Sung Hwan; (Gumi-si,
Gyeongsangbuk-do, KR) ; Kim; Jeong Han; (Gumi-si,
Gyeongsangbuk-do, KR) ; Song; Jung Hoon; (Seoul,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
POSCO
Research Institute of Industrial Science & Technology
POSCO Chemical Co., Ltd. |
Pohang-si, Gyeongsangbuk-do
Pohang-si, Gyeongsangbuk-do
Pohang-si, Gyeongsangbuk-do |
|
KR
KR
KR |
|
|
Assignee: |
POSCO
Pohang-si, Gyeongsangbuk-do
KR
POSCO Chemical Co., Ltd.
Pohang-si, Gyeongsangbuk-do
KR
Research Institute of Industrial Science & Techology
Pohang-si, Gyeongsangbuk-do
KR
POSCO Chemical Co., Ltd.
Pohang-si, Gyeongsangbuk-do
KR
|
Family ID: |
1000005824161 |
Appl. No.: |
16/957027 |
Filed: |
December 18, 2018 |
PCT Filed: |
December 18, 2018 |
PCT NO: |
PCT/KR2018/016148 |
371 Date: |
June 22, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 4/525 20130101;
H01M 2004/028 20130101; H01M 4/505 20130101; H01M 10/0525
20130101 |
International
Class: |
H01M 4/505 20060101
H01M004/505; H01M 4/525 20060101 H01M004/525; H01M 10/0525 20060101
H01M010/0525 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2017 |
KR |
10-2017-0178837 |
Claims
1. A positive active material for a lithium rechargeable battery,
comprising: a nickel-based lithium metal oxide particle doped with
Zr and Al; and a coating layer disposed on the surface of the
nickel-based lithium metal oxide particle, wherein the nickel-based
lithium metal oxide particle includes a core portion, and a shell
portion surrounding the core portion and forming a concentration
gradient in which a concentration of nickel gradually decreases
from an interface with the core portion toward an outer direction,
and the coating layer includes an oxyhydroxide of a rare earth
element.
2. The positive active material for the lithium rechargeable
battery of claim 1, wherein the rare earth element is at least one
among cerium (Ce), cobalt (Co), tungsten (W), lanthanum (La),
hafnium (Hf), and selenium (Se).
3. The positive active material for the lithium rechargeable
battery of claim 1, wherein a primary particle of the nickel-based
lithium metal oxide particle has a rod shape with an aspect ratio
of 1 or more.
4. The positive active material for the lithium rechargeable
battery of claim 1, wherein the nickel-based metal oxide particle
including the core portion and the shell portion has an average
composition represented by Chemical Formula 4 below:
Li.sub.m4[Ni.sub.1-w4-x4-y4-z4Co.sub.w4M1.sub.x4M2.sub.y4M3.sub.z4].sub.n-
4O.sub.2-p4X.sub.p4 [Chemical Formula 4] (in Chemical Formula 4, M1
is one element selected from a group including Mn, Mg, Sn, Ca, Ge,
and Ga, M2is Zr, M3 is Al, X is one element selected from a group
including F, N, and P, w4, x4, y4, z4, and p4 are respectively
0<w4.ltoreq.0.2, 0<x4.ltoreq.0.2, 0<y4.ltoreq.0.006,
0<z4.ltoreq.0.006, 0<w4+x4+y4+z4.ltoreq.0.4 and
0.ltoreq.p4.ltoreq.0.1, 0.95.ltoreq.m4.ltoreq.1.1, and
0.95.ltoreq.n4.ltoreq.1.1).
5. The positive active material for the lithium rechargeable
battery of claim 1, wherein a doping amount of Zr in the
nickel-based lithium metal oxide particle is 2000 ppm to 5000
ppm.
6. The positive active material for the lithium rechargeable
battery of claim 1, wherein a doping amount of A in the
nickel-based lithium metal oxide particle is 100 ppm to 1500
ppm.
7. The positive active material for the lithium rechargeable
battery of claim 1, wherein a molar ratio of Zr:Al in the
nickel-based lithium metal oxide particles is 15:1 to 0.4:1.
8. The positive active material for the lithium rechargeable
battery of claim 1, wherein the composition of the core portion of
the nickel-based lithium metal oxide particle is represented by
Chemical Formula 5 in the entire region:
Li.sub.m5[Ni.sub.1-w5-x5-y5-z5Co.sub.w5M1.sub.x5M2.sub.y5M3.sub.z5].sub.n-
5O.sub.2-p5X.sub.p5 [Chemical Formula 5] (in Chemical Formula 5, M1
is one element selected from a group including Mn, Mg, Sn, Ca, Ge,
and Ga, M2 is Zr, M3 is Al, X is one element selected from a group
including F, N, and P, w5, x5, y5, z5, and p5 are respectively
0.ltoreq.w5.ltoreq.0.1, 0.ltoreq.x5.ltoreq.0.1,
0<y5.ltoreq.0.005, 0<z5.ltoreq.0.006,
0.ltoreq.w5+x5+y5+z5.ltoreq.0.2, and 0.ltoreq.p5.ltoreq.0.1,
0.95.ltoreq.m5.ltoreq.1.1, and 0.95.ltoreq.n5.ltoreq.1.1).
9. The positive active material for the lithium rechargeable
battery of claim 8, wherein the composition of the shell portion of
the nickel-based lithium metal oxide particle is represented by
Chemical Formula 5 in the interface with the core portion, is
represented by Chemical Formula 6 at the outermost part of the
shell portion, and each molar content of the nickel (Ni), M1, M2,
and M3 is gradually changed from the interface to the outermost
part:
Li.sub.m6[Ni.sub.1-w6-x6-y6-z6Co.sub.w6M1.sub.x6M2.sub.y6M3.sub.z6].sub.n-
6O.sub.2-p6X.sub.p6 [Chemical Formula 6] (in Chemical Formula 6, M1
is one element selected from a group including Mn, Mg, Sn, Ca, Ge,
and Ga, M2 is Zr, M3 is Al, X is one element selected from a group
including F, N, and P, w6, x6, y6, z6, and p6 are respectively
0<w6.ltoreq.0.3, 0<x6.ltoreq.0.3, 0<y6.ltoreq.0.007,
0<z6.ltoreq.0.006, 0<w6+x6+y6+z6.ltoreq.0.5, and
0.ltoreq.p6.ltoreq.0.1, 0.95.ltoreq.m6.ltoreq.1.1, and
0.95.ltoreq.n6.ltoreq.1.1).
10. The positive active material for the lithium rechargeable
battery of claim 1, wherein the nickel-based lithium metal oxide
particle includes a first compound having an average particle
diameter of 10 .mu.m to 30 .mu.m, and a second compound having an
average particle diameter of 1 .mu.m to 6 .mu.m.
11. The positive active material for the lithium rechargeable
battery of claim 10, wherein the mixture weight ratio of the first
compound and second compound is 60:40 to 90:10.
12. The positive active material for the lithium rechargeable
battery of claim 1, wherein the nickel-based lithium metal oxide
particle has 50% or more of a value of Equation 3 below:
R2/(R2+D2)*100% [Equation 3] in Equation 3, R2 is a radius of the
core portion in the nickel-based metal oxide particle, and D2 is a
thickness of the shell portion in the nickel-based metal oxide
particle.
13. The positive active material for the lithium rechargeable
battery of claim 12, wherein the nickel-based lithium metal oxide
particle has 75% or more of a value of Equation 3 above.
14. A lithium rechargeable battery comprising: a negative
electrode; a positive electrode including the positive active
material for the lithium rechargeable battery of claim 1; and an
electrolyte.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to and the benefit of
Korean Patent Application No. 10-2017-0168545 filed in the Korean
Intellectual Property Office on Dec. 8, 2017, the entire contents
of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
(a) Field of the Invention
[0002] An exemplary embodiment of the present invention relates to
a positive active material for a lithium rechargeable battery,
which has an excellent output characteristic, cycle-life
characteristic, and resistance characteristic at a high
temperature, and a lithium rechargeable battery including the
same.
(b) Description of the Related Art
[0003] A positive active material, which is one of constituent
elements of a lithium rechargeable battery, not only directly
contributes to performance of battery energy, but also serves as a
factor in determining a cycle-life characteristic. In this regard,
studies on nickel-based lithium metal oxides having a layered
structure such as so-called NCM have been actively performed, and
an increase in a content of nickel (Ni) may lead to higher
capacity. However, the nickel-based lithium metal oxide becomes
structurally unstable as a content of nickel (Ni) increases, and
there is a problem in that resistance increases significantly when
a charge and discharge cycle is performed in a high temperature
environment. Therefore, it is urgent to develop a positive active
material having an excellent resistance characteristic in a high
temperature environment and excellent structural stability while
having a high nickel content.
SUMMARY OF THE INVENTION
[0004] Exemplary embodiments are to provide a positive active
material for a lithium rechargeable battery and a lithium
rechargeable battery including the same, which is capable of
simultaneously realizing high capacity and structure stabilization
while having excellent resistance characteristics even in a high
temperature environment.
[0005] A positive active material for a lithium rechargeable
battery according to an exemplary embodiment includes: a
nickel-based lithium metal oxide particle doped with Zr and Al; and
a coating layer disposed on the surface of the nickel-based lithium
metal oxide particle, wherein the nickel-based lithium metal oxide
particle includes a core portion, and a shell portion surrounding
the core portion and forming a concentration gradient in which a
concentration of nickel gradually decreases from an interface with
the core portion toward an outer direction, and the coating layer
includes an oxyhydroxide of a rare earth element.
[0006] The rare earth element may be at least one of cerium (Ce),
cobalt (Co), tungsten (W), lanthanum (La), hafnium (Hf), and
selenium (Se).
[0007] A primary particle of the nickel-based lithium metal oxide
particle may have a rod shape with an aspect ratio of 1 or
more.
[0008] The nickel-based metal oxide particle including the core
portion and the shell portion may have an average composition
represented by Chemical Formula 4 below.
Li.sub.m4[Ni.sub.1-w4-x4-y4-z4Co.sub.w4M1.sub.x4M2.sub.y4M3.sub.z4].sub.-
n4O.sub.2-p4X.sub.p4 [Chemical Formula 4]
[0009] In Chemical Formula 4, M1 is one element selected from a
group including Mn, Mg, Sn, Ca, Ge, and Ga, M2 is Zr, M3 is Al, X
is one element selected from a group including F, N, and P, w4, x4,
y4, z4, and p4 are respectively 0<w4.ltoreq.0.2,
0<x4.ltoreq.0.2, 0<y4.ltoreq.0.006, 0<z4.ltoreq.0.006,
0<w4+x4+y4+z4.ltoreq.0.4, and 0.ltoreq.p4.ltoreq.0.1,
0.95.ltoreq.m4.ltoreq.1.1, and 0.95.ltoreq.n4.ltoreq.1.1.
[0010] A doping amount of Zr in the nickel-based lithium metal
oxide particle may be 2000 ppm to 5000 ppm.
[0011] A doping amount of A in the nickel-based lithium metal oxide
particle may be 100 ppm to 1500 ppm.
[0012] A molar ratio of Zr:Al in the nickel-based lithium metal
oxide particles may be 15:1 to 0.4:1.
[0013] The composition of the core portion of the nickel-based
lithium metal oxide particle may be represented by Chemical Formula
5 in the entire region.
Li.sub.m5[Ni.sub.1-w5-x5-y5-z5Co.sub.w5M1.sub.x5M2.sub.y5M3.sub.z5].sub.-
n5O.sub.2-p5X.sub.p5 [Chemical Formula 5]
[0014] In Chemical Formula 5 above, M1 is one element selected from
a group including Mn, Mg, Sn, Ca, Ge, and Ga, M2 is Zr, M3 is Al, X
is one element selected from a group including F, N, and P, w5, x5,
y5, z5, and p5 are respectively 0.ltoreq.w5.ltoreq.0.1,
0.ltoreq.x5.ltoreq.0.1, 0<y5.ltoreq.0.005, 0<z5.ltoreq.0.006,
0.ltoreq.w5+x5+y5+z5.ltoreq.0.2, and 0.ltoreq.p5.ltoreq.0.1,
0.95.ltoreq.m5.ltoreq.1.1, and 0.95.ltoreq.n5.ltoreq.1.1.
[0015] The composition of the shell portion of the nickel-based
lithium metal oxide particle may be represented by Chemical Formula
5 in the interface with the core portion, may be represented by
Chemical Formula 6 at the outermost part of the shell portion, and
each molar content of the nickel (Ni), M1, M2, and M3 may be
gradually changed from the interface to the outermost part.
Li.sub.m6[Ni.sub.1-w6-x6-y6-z6Co.sub.w6M1.sub.x6M2.sub.y6M3.sub.z6].sub.-
n6O.sub.2-p6X.sub.p6 [Chemical Formula 6]
[0016] In Chemical Formula 6, M1 is one element selected from a
group including Mn, Mg, Sn, Ca, Ge, and Ga, M2 is Zr, M3 is Al, X
is one element selected from a group including F, N, and P, w6, x6,
y6, z6, and p6 are respectively 0<w6.ltoreq.0.3,
0<x6.ltoreq.0.3, 0<y6.ltoreq.0.007, 0<z6.ltoreq.0.006,
0<w6+x6+y6+z6.ltoreq.0.5, and 0.ltoreq.p6.ltoreq.0.1,
0.95.ltoreq.m6.ltoreq.1.1, and 0.95.ltoreq.n6.ltoreq.1.1.
[0017] The nickel-based lithium metal oxide particle may include a
first compound having an average particle diameter of 10 .mu.m to
30 .mu.m, and a second compound having an average particle diameter
of 1 .mu.m to 6 .mu.m.
[0018] The mixture weight ratio of the first compound and second
compound may be 60:40 to 90:10.
[0019] The nickel-based lithium metal oxide particle may have 50%
or more of a value of Equation 3 below.
R2/(R2+D2)*100% [Equation 3]
[0020] In Equation 3, R2 is a radius of the core portion in the
nickel-based metal oxide particle, and D2 is a thickness of the
shell portion in the nickel-based metal oxide particle.
[0021] The nickel-based lithium metal oxide particle may have 75%
or more of a value of Equation 3 above.
[0022] A lithium rechargeable battery according to an exemplary
embodiment may include a negative electrode; a positive electrode
including the positive active material for the lithium rechargeable
battery according to an exemplary embodiment of the present
disclosure; and an electrolyte.
[0023] The positive active material for the lithium rechargeable
battery according to exemplary embodiments may have an excellent
resistance characteristic in a high temperature environment, and
may minimize a resistance increasing rate after performing a charge
and discharge cycle.
[0024] In addition, the positive active material according to
exemplary embodiments may simultaneously realize high capacity and
structural stability by appropriately controlling the concentration
gradient in the shell portion of the nickel-based lithium metal
oxide particles.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0025] The present invention will be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplary embodiments of the invention are shown. As those skilled
in the art would realize, the described embodiments may be modified
in various different ways, all without departing from the spirit or
scope of the present invention.
[0026] In addition, unless explicitly described to the contrary,
the word "comprise" and variations such as "comprises" or
"comprising" will be understood to imply the inclusion of stated
elements but not the exclusion of any other elements.
[0027] In an exemplary embodiment of the present invention, a
positive active material for a lithium rechargeable battery
including a nickel-based lithium metal oxide particle including a
core portion and a shell portion, and a coating layer disposed on a
surface of the nickel-based lithium metal oxide particle, is
provided, wherein the coating layer includes an oxyhydroxide of a
rare earth element.
[0028] Specifically, the nickel-based lithium metal oxide particle
includes the core portion and the shell surrounding the core
portion and forming a concentration gradient in which the
concentration of nickel gradually decreases toward an outer
direction from the interface with the core portion.
[0029] Also, the coating layer surrounding the outer surface of the
shell portion is disposed on the surface of the nickel-based
lithium metal oxide particle, and the coating layer may include an
oxyhydroxide of the rare earth element.
[0030] In detail, the rare earth element, for example, may be at
least one among cerium (Ce), cobalt (Co), tungsten (W), lanthanum
(La), hafnium (Hf), and selenium (Se).
[0031] As above-described, by the oxyhydroxide of the rare earth
element included in the coating layer, a decomposition reaction due
to an electrolyte solution in a positive electrode interface may be
suppressed. In detail, it is possible to suppress a side reaction
between a Lewis acid present in the electrolyte solution and
elements disposed at the interface of the positive electrode.
Accordingly, even in a high temperature environment, the positive
active material with the significantly improved resistance
characteristic may be realized.
[0032] On the other hand, as described above, the nickel-based
metal oxide has a drawback that it becomes structurally unstable
while allowing high-capacity as the nickel content increases.
[0033] However, the positive active material provided in an
exemplary embodiment of the present invention includes a core-shell
concentration gradient (hereinafter referred to as "CSG").
[0034] The CSG means that the average concentration of nickel is
maintained with a high concentration of a predetermined level or
more in the core portion and the concentration of nickel drops
sharply at the interface between the core portion and the shell
portion, and then the concentration of nickel decreases gradually
toward the outermost direction of the shell portion from the
interface.
[0035] That is, since the positive active material contains a
nickel-based lithium metal oxide particle composed of the CSG, it
has excellent structural stability despite a high nickel
content.
[0036] Therefore, while making high-capacity by maintaining the
high molar content of nickel in the core portion, the structure of
the positive active material may be stabilized by increasing the
molar content of dissimilar metals (e.g., Mn, Co, Al, etc.) while
reducing the molar content of nickel in the shell portion.
[0037] Furthermore, in the nickel-based lithium metal oxide
particle having the CSG, as the metal concentration is changed in
the shell portion, a primary particle thereof may have a rod shape
in which an aspect ratio (a ratio of a short axis to a long axis)
is larger than 1.
[0038] In the case of having such a primary particle form, there is
an advantage that an a-plane of the crystal structure is directed
to the surface portion, and the lithium (Li) ion moves easily
between the electrolyte and the positive active material
[0039] Also, since ion conductivity and electrical conductivity are
high, in the case of applying the positive active material in the
present exemplary embodiment, there is a merit that it is
advantageous for improving initial efficiency and cycle-life
characteristics of the battery.
[0040] On the other hand, the nickel-based lithium metal oxide has
a problem that the crystalline size changes according to the
temperature at which the precursor is sintered, thereby the primary
particle characteristics (shape, size, etc.) may be changed
[0041] However, the positive active material provided in one
embodiment of the present invention includes the nickel-based
lithium metal oxide particles having the CSG and simultaneously
doped with Zr and Al, and then the crystalline size and the primary
particle characteristics can be controlled appropriately. As a
result, it is possible to realize the improvement of the output
characteristics and lifetime characteristics of the battery to
which the positive active material of the present exemplary
embodiment is applied, and the minimization of the increase rate of
a DCR resistance during a high-temperature charge/discharge
cycle.
[0042] Specifically, the molar ratio of Zr: Al in the nickel-based
lithium metal oxide particle may be 15:1 to 0.4:1, for example,
10:1 to 2:1. As the doping amount of Al doped with Zr in the above
range is increased, particles having a reduced crystalline size are
obtained at the same sintering temperature, whereby the primary
particle size of the active material is decreased and its shape is
more clearly controlled.
[0043] More specifically, the doping amount of Zr in the
nickel-based lithium metal oxide particle may be 2000 to 5000 ppm,
and may be 2000 to 4000 ppm, specifically, 2200 to 3800 ppm. When
the doping amount of Zr in the nickel-based lithium metal oxide
particles is less than 2000 ppm, the cycle performance is
deteriorated, and when it exceeds 5000 ppm, the discharge capacity
is deteriorated. Therefore, when the doping amount of Zr satisfies
the range, when applying the positive active material according to
the present exemplary embodiment, the rechargeable battery of which
the discharge capacity is not deteriorated and the cycle
performance is excellent may be realized.
[0044] In addition, the doping amount of Al doped therewith may be
100 to 1500 ppm, 100 to 500 ppm, and specifically 120 to 320 ppm.
When the doping amount of Al in the nickel-based lithium metal
oxide particles is less than 100 ppm, the cycle performance is
deteriorated, and when it exceeds 1500 ppm, the discharge capacity
is deteriorated. Therefore, there is a phenomenon when the doping
amount of Al satisfies the range, but when satisfying the range,
the rechargeable battery of which the discharge capacity is not
deteriorated and the cycle performance is excellent may be realized
when applying the positive active material according to the present
exemplary embodiment.
[0045] In addition, the nickel-based lithium metal oxide particles
may have a uniform internal composition (i.e., CSG and doping
amount) by particle size. That is, it is advantageous to mix the
two kinds of nickel-based lithium metal oxide particles having
different particle sizes at a certain ratio to increase the energy
density of the positive electrode.
[0046] This is because, by a so-called bi-modal technique, the gap
between large-sized particles (hereinafter referred to as
"large-particles") is filled by small-sized particles (hereinafter
referred to as "small-particles"), so that a large amount of
positive active material can be accumulated within a unit
volume.
[0047] That is, according to the present exemplary embodiment,
there may be multiple nickel-based lithium metal oxide particles
and they may be a mixture of two types of the nickel-based lithium
metal oxide particles having different particle diameters.
[0048] This is a mixture of the nickel-based lithium metal oxide
particles having the same CSG form and doping characteristics but
having different particle diameters. Therefore, as the pores
between the large-diameter particles may be filled with the
small-particle size particles, a large amount of the positive
active material can be accumulated within the unit volume.
Therefore, it is advantageous to increase the energy density of the
positive electrode.
[0049] Specifically, the mixture may include a first compound and a
second compound having different average particle diameters (D50
particle diameters).
[0050] For example, the first compound may be the large-particle
diameter nickel-based lithium metal oxide particle of which an
average particle diameter (the D50 particle diameter) is 10 .mu.m
to 30 .mu.m, in detail, 12 .mu.m to 20 .mu.m. When the average
particle diameter of the large-particle diameter nickel-based
lithium metal oxide particle satisfies the range, when
manufacturing the positive active material in a bi-modal form by
mixing it with the small particles, since a pellet density
increases, when applying the positive active material according to
the present exemplary embodiment, the capacity of the rechargeable
battery may be improved.
[0051] Also, for example, the second compound may be the
small-particle diameter nickel-based lithium metal oxide particles
of which the average particle diameter (the D50 particle diameter)
is 1 .mu.m to 6 .mu.m, in detail, 4 .mu.m to 6 .mu.m.
[0052] When the average particle diameter of the small-particle
diameter nickel-based lithium metal oxide particle satisfies the
range, when manufacturing the positive active material in a
bi-modal form by mixing it with the large particles, since a pellet
density increases, when applying the positive active material
according to the present exemplary embodiment, the capacity of the
rechargeable battery may be improved.
[0053] In the present specification, the D50 particle diameter
means the particle size when the particles are accumulated up to a
50% by volume ratio of the active material particles of the various
particle sizes distributed.
[0054] In this case, the mixture weight ratio of the large-particle
diameter nickel-based lithium metal oxide particles and the
small-particle diameter nickel-based lithium metal oxide particles
may be 60: 40 to 90:10.
[0055] In addition, as described above, in the nickel-based lithium
metal oxide particles according to the present exemplary
embodiment, the primary particle form may be a rod form.
[0056] Therefore, the first compound may have an a-axis crystal
constant (a lattice parameter) of 2.85 .ANG. to 2.88 .ANG., more
specifically, 2.86 .ANG. to 2.88 .ANG.. In addition, a c-axis
crystal constant (a lattice parameter) may be 14.13 .ANG. to 14.37
.ANG., more specifically, 14.17 .ANG. to 14.34 .ANG.. In addition,
the crystalline size may be 60 nm to 200 nm, more specifically, 80
nm to 120 nm.
[0057] However, even when Zr is doped alone on the large-particle
diameter nickel-based lithium metal oxide particle, it may have the
a-axis and c-axis crystal constants (the lattice parameters) of the
above-described ranges. That is, for the large-particle diameter
nickel-based lithium metal oxide particle, when simultaneously
doping Zr and Al, compared with the case of doping Zr alone, there
is no significant change in the a-axis and c-axis crystal constants
(the lattice parameters).
[0058] However, when simultaneously doping Zr and Al in the
large-particle diameter nickel-based lithium metal oxide particle,
compared with the case of doping Zr alone, there is a big change in
the crystalline size. Specifically, the crystalline size when Zr
and Al are simultaneously doped on the large-particle diameter
nickel-based lithium metal oxide particle may be 60 nm to 200 nm,
specifically 80 nm to 120 nm, or 80 nm to 100 nm. In addition, the
crystalline size when doped with Zr alone may exceed 100 nm.
[0059] Meanwhile, the nickel-based lithium metal oxide particles
may have the uniform internal composition (i.e., the CSG and the
doping amount) for each particle size. Accordingly, it is
advantageous to implement the bi-modal active material described
above.
[0060] The nickel-based lithium metal oxide particles may have a
value of Equation 3 below of 50% or more and 90% or less,
specifically 75% or more and 85% or less, by the particle size.
When the nickel-based lithium metal oxide particle satisfies 50% or
more of Equation 3 below, it is possible to improve the
electrochemical characteristic and thermal safety of the
rechargeable battery to which the positive active material
according to the present exemplary embodiment is applied.
R2/(R2+D2)*100% [Equation 3]
[0061] In Equation 3, R2 is the radius of the core portion in the
nickel-based metal oxide particle, and D2 is the thickness of the
shell portion in the nickel-based metal oxide particle.
[0062] The average composition of the nickel-based lithium metal
oxide particle, that is, the average composition of the
nickel-based lithium metal oxide including the first compound and
the second compound, may be represented by Formula 4.
Li.sub.m4[Ni.sub.1-w4-x4-y4-z4Co.sub.w4M1.sub.x4M2.sub.y4M3.sub.z4].sub.-
n4O.sub.2-p4X.sub.p4 [Chemical Formula 4]
[0063] In Formula 4 above, M1 is one element selected from a group
including Mn, Mg, Sn, Ca, Ge, and Ga, M2 is Zr, M3 is Al, X is one
element selected from a group including F, N, and P, w4, x4, y4,
z4, and p4 are respectively 0<w4.ltoreq.0.2, 0<x4.ltoreq.0.2,
0<y4.ltoreq.0.006, 0<z4.ltoreq.0.006,
0<w4+x4+y4+z4.ltoreq.0.4, and 0.ltoreq.p4.ltoreq.0.1,
0.95.ltoreq..ltoreq.m4.ltoreq.1.1, and
0.95.ltoreq.n4.ltoreq.1.1.
[0064] In detail, it may be that 0.002<y4.ltoreq..ltoreq.0.005,
0.0004.ltoreq.z4.ltoreq.0.0015, and p4 0.
[0065] Also, the composition of the core portion of the
nickel-based lithium metal oxide particle, that is, the composition
of the core portion in the nickel-based lithium metal oxide
including the first compound and the second compound, may be
represented by Formula 5 below.
Li.sub.m5[Ni.sub.1-w5-x5-y5-z5Co.sub.w5M1.sub.x5M2.sub.y5M3.sub.z5].sub.-
n5O.sub.2-p5X.sub.p5 [Chemical Formula 5]
[0066] In Formula 5 above, M1 is one element selected from a group
including Mn, Mg, Sn, Ca, Ge, and Ga, M2 is Zr, M3 is Al, X is one
element selected from a group including F, N, and P, w5, x5, y5,
z5, and p5 are respectively 0.ltoreq.w5.ltoreq.0.1,
0.ltoreq.x5.ltoreq.0.1, 0<y5.ltoreq.0.006, 0<z5.ltoreq.0.006,
0.ltoreq.w5+x5+y5+z5.ltoreq.0.2, and 0.ltoreq.p5.ltoreq.0.1,
0.95.ltoreq.m5.ltoreq.1.1, and 0.95.ltoreq.n5.ltoreq.1.1.
[0067] In detail, it may be that 0.002<y5.ltoreq.0.004,
0<z5.ltoreq.0.0015, and p5 0.
[0068] The composition of the shell portion of the nickel-based
lithium metal oxide particle, that is, the composition of the shell
portion in the nickel-based lithium metal oxide including the first
compound and the second compound, is represented by Formula 5 above
on the interface, is represented by Formula 6 below on the
outermost part, and each molar content of nickel (Ni), M1, M2, and
M3 from the interface to the outermost of the shell portion may
gradually change.
Li.sub.m6[Ni.sub.1-w6-x6-y6-z6Co.sub.w6M1.sub.x6M2.sub.y6M3.sub.z6].sub.-
n6O.sub.2-p6X.sub.p6 [Chemical Formula 6]
[0069] In Formula 6 above, M1 is one element selected from a group
including Mn, Mg, Sn, Ca, Ge, and Ga, M2 is Zr, M3 is Al, X is one
element selected from a group including F, N, and P, w6, x6, y6,
z6, and p6 are respectively 0<w6.ltoreq.0.3, 0<x6.ltoreq.0.3,
0<y6.ltoreq.0.007, 0<z6.ltoreq.0.006,
0<w6+x6+y6+z6.ltoreq.0.5, and 0.ltoreq.p6.ltoreq.0.1,
0.95.ltoreq.m6.ltoreq.1.1, and0.95.ltoreq.n6.ltoreq.1.1.
[0070] In detail, it may be that 0.002<y6.ltoreq.0.0065,
0<z6.ltoreq.0.002, and p6 0.
[0071] Therefore, the nickel-based lithium metal oxide particles
according to the present exemplary embodiment may have the stable
structure according to the composition of the shell portion of
Formula 6 while exerting the high-capacity according to the entire
composition of Formula 4 above and the composition of the core
portion of Formula 5 above.
[0072] The positive active material described above may be usefully
used for the positive electrode of the lithium rechargeable
battery. That is, the lithium rechargeable battery according to an
exemplary embodiment includes the positive electrode including the
positive active material described above and the electrolyte with a
negative electrode.
[0073] The lithium rechargeable battery according to an exemplary
embodiment may include an electrode assembly including the positive
electrode, the negative electrode, and a separator disposed between
the positive electrode and the negative electrode. The electrode
assembly is wound or folded by being accommodated in the case,
thereby configuring the lithium rechargeable battery.
[0074] At this time, the case may have a shape such as cylindrical,
prismatic, or a thin membrane type, and may be appropriately
modified according to a type of a device to be applied.
[0075] The negative electrode may be produced by mixing a negative
active material, a binder, and optionally a conductive agent to
prepare a composition for forming a negative electrode active
material layer, and then coating it to a negative current collector
such as copper.
[0076] As the negative active material, a material capable of
intercalating/deintercalating lithium is used, for example, a
lithium metal or a lithium alloy, coke, artificial graphite,
natural graphite, an organic polymer compound combust, a carbon
fiber, or the like are used.
[0077] The binder may use polyvinyl alcohol, carboxymethyl
cellulose/styrene-butadiene rubber, hydroxypropyl cellulose,
diacetylene cellulose, polyvinylchloride, polyvinylpyrrolidone,
polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or
polypropylene, but is not limited thereto. The binder may be
included in an amount of 1 wt % to 30 wt % based on a total amount
of the composition for forming the negative active material
layer.
[0078] The conductive agent is not particularly limited as long as
it does not cause a chemical change of a battery and has
conductivity, and may be, for example, a graphite such as natural
graphite or artificial graphite; a carbon-based material such as
carbon black, acetylene black, ketjen black, channel black, furnace
black, lamp black, summer black, and the like; a conductive fiber
such as a carbon fiber or a metal fiber, and the like; carbon
fluoride; a metal powder such as an aluminum or nickel powder; zinc
oxide, a conductive whisker such as potassium titanate, and the
like; a conductive metal oxide such as a titanium oxide; a
conductive material such as a polyphenylene derivative; and the
like. The conductive agent may be included in an amount of 0.1 wt %
to 30 wt % based on a total amount of the composition for forming
the negative active material layer.
[0079] The positive electrode may include the positive active
material according to an exemplary embodiment.
[0080] That is, it may be produced by mixing the above-described
positive active material, the binder, and optionally the conductive
agent to prepare the composition for forming the positive active
material layer and coating it to a positive electrode current
collector such as aluminum. In addition, the conductive agent, the
binder, and a solvent are used in the same manner as in the case of
the positive electrode described above.
[0081] As the electrolyte filled in the lithium rechargeable
battery, a non-aqueous electrolyte or a disclosed solid electrolyte
may be used, and a dissolved lithium salt may be used.
[0082] The lithium salt, for example, may be one kind or more
selected from a group consisting of LiPF.sub.6, LiBF.sub.4,
LiSbF.sub.6, LiAsF.sub.6, LiClO.sub.4, LiCF.sub.3SO.sub.3, Li
(CF.sub.3SO.sub.2).sub.2N, LiC.sub.4F.sub.9SO.sub.3, LiSbF.sub.6,
LiAlO.sub.4, LiAlCl.sub.4, LiCl, and LiI.
[0083] The solvent of the non-aqueous electrolyte, for example, may
be a cyclic carbonate such as ethylene carbonate, propylene
carbonate, butylene carbonate, and vinylene carbonate; a linear
carbonate such as dimethyl carbonate, methylethyl carbonate, and
diethyl carbonate; esters such as methyl acetate, ethyl acetate,
propyl acetate, methyl propionate, ethyl propionate, and
.gamma.-butyrolactone; ethers such as 1,2-dimethoxyethane,
1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane, and
2-methyltetrahydrofuran; nitriles such as acetonitrile; and amides
such as dimethylformamide, but is not limited thereto. These may be
used alone or in combination of two or more. Particularly, a mixed
solvent of a cyclic carbonate and a linear carbonate may be
preferably used.
[0084] In addition, as the electrolyte, a gel-phase polymer
electrolyte in which an electrolyte solution is impregnated in a
polymer electrolyte such as polyethylene oxide or
polyacrylonitrile, or an inorganic solid electrolyte such as LiI or
Li.sub.3N, is possible.
[0085] As the separator, an olefin-based polymer such as
polypropylene having chemical resistance and hydrophobicity; or
sheets made of glass fiber, polyethylene, or a non-woven fabric may
be used. When the solid electrolyte solution such as a polymer is
used as the electrolyte solution, the solid electrolyte solution
may also serve as the separator.
[0086] Hereinafter, the present invention is described in more
detail through experimental examples. The experimental examples are
only for illustrating the present invention, and the present
invention is not limited thereto.
PREPARATION EXAMPLE 1
A Large-Particle Diameter Positive Active Material Precursor
[0087] 1) Preparation of Metal Salt Solution
[0088] First, two metal aqueous solutions having different Ni, Co,
and Mn concentrations were prepared by using NiSO.sub.4.6H.sub.2O
as a raw material of nickel, CoSO.sub.4.7H.sub.2O as a raw material
of cobalt, and MnSO.sub.4.H.sub.2O as a raw material of
manganese.
[0089] The first metal salt aqueous solution for forming the core
portion is prepared by mixing the respective raw materials so as to
satisfy the stoichiometric molar ratio of
(Ni.sub.0.98Co.sub.0.01Mn.sub.0.01)(OH).sub.2 in distilled water,
wherein the molar concentration of the whole metal salt is 2.5
M.
[0090] Independently, the second metal salt aqueous solution for
forming the shell portion is prepared by mixing the respective raw
materials so as to satisfy the stoichiometric molar ratio of
(Ni.sub.0.64Co.sub.0.23Mn.sub.0.13)(OH).sub.2 in distilled water,
wherein the molar concentration of the whole metal salt is 2.5
M.
[0091] 2) Co-Precipitation Process
[0092] A co-precipitation reactor in which two metal salt aqueous
solution supply tanks are connected in series is prepared, and the
first metal salt aqueous solution and the second metal salt aqueous
solution are charged into respective metal salt aqueous solution
supply tanks.
[0093] 3 L of distilled water was placed in the co-precipitation
reactor (capacity 20 L, output of the rotary motor 200 W), nitrogen
gas was supplied at a rate of 2 L/min to remove dissolved oxygen,
and the reactor was stirred at 140 rpm while maintaining the
temperature at 50.degree. C.
[0094] In addition, NH.sub.4(OH) at a concentration of 14 M was fed
at 0.06 L/h as a chelating agent, and an 8 M NaOH solution as a pH
regulator was continuously fed into the reactor at a rate of 0.1
L/h. At this time, the amount thereof was appropriately controlled
so as to be maintained at pH 12.
[0095] In the reactor in which the pH was kept constant and the
chelating agent was supplied, the charging time and the amount of
each metal salt solution were controlled from the two metal salt
aqueous solution supply tanks connected in series.
[0096] Specifically, the impregnation rate of the reactor was
adjusted to 140 rpm while introducing the first metal salt aqueous
solution at 0.4 L/h, and the co-precipitation reaction was
performed until the diameter of the precipitate became about 11.1
.mu.m. In this case, an average residence time of the solution in
the reactor was adjusted to about 10 hours by adjusting a flow
rate, and a co-precipitation compound having a slightly higher
density was obtained by giving a steady state duration to the
reactant after the reaction reached the steady state.
[0097] Subsequently, the total feed solution was fed at 0.4 L/h
while changing the mixing ratio of the first metal salt aqueous
solution and the second metal salt aqueous solution, the feed rate
of the first metal salt aqueous solution was gradually decreased to
0.05 L/h, and the feed rate of the second metal salt aqueous
solution was gradually increased to 0.35 L/h. At this time, the
average residence time of the solution in the reactor was adjusted
to 20 h or less by controlling the flow rate, and finally the
co-precipitation reaction was performed until the diameter of the
precipitate became 14.8 .mu.m.
[0098] 3) Post-Treatment Process
[0099] The precipitate obtained by the series of co-precipitation
steps was filtered, washed with water, and then dried in an oven at
100.degree. C. for 24 h to obtain a plurality of large-particle
diameter particles of which a composition in the whole particles
was (Ni.sub.0.88Co.sub.0.095Mn.sub.0.025)(OH).sub.2 and the average
particle diameter was 15 .mu.m as an active material precursor of
Preparation Example 1.
PREPARATION EXAMPLE 2
A Small-Particle Diameter Positive Active Material Precursor
[0100] 1) Preparation of Metal Salt Solution
[0101] A first aqueous metal salt solution and a second aqueous
metal salt solution as in Preparation Example 1 were prepared.
[0102] 2) Co-Precipitation Process
[0103] Using the same reactor as in Preparation Example 1, the
other conditions were the same and the charging time and charging
amount of each metal salt solution were varied.
[0104] Specifically, the impregnation rate of the reactor was
adjusted to 140 rpm while introducing the first metal salt aqueous
solution at a rate of 0.4 L/h, and a co-precipitation reaction was
performed until the diameter of the precipitate became
approximately 3.8 to 4.5 .mu.m. At this time, the flow rate was
adjusted so that the average residence time of the solution in the
reactor was about 10 hours. After the reaction reached a steady
state, the steady state duration was given to the reactant to
obtain a denser co-precipitated compound.
[0105] Subsequently, the total feed solution was fed at 0.4 L/h
while changing the mixing ratio of the first metal salt aqueous
solution and the second metal salt aqueous solution, the feed rate
of the first metal salt aqueous solution was gradually decreased to
0.05 L/h, and the feed rate of the second metal salt aqueous
solution was gradually increased to 0.35 L/h. At this time, the
average residence time of the solution in the reactor was
controlled to be within 15 h by adjusting the flow rate, and the
co-precipitation reaction was performed until the diameter of the
precipitate finally reached 5.3 .mu.m.
[0106] 3) Post-Treatment Process
[0107] The precipitate obtained according to the series of
co-precipitation steps was filtered, washed with water, and then
dried in an oven at 100.degree. C. for 24 h to obtain a plurality
of small-particle diameter particles of which a composition in the
whole particles is (Ni.sub.0.88Co.sub.0.095Mn.sub.0.025)(OH).sub.2
and an average particle diameter is 5 .mu.m was obtained as an
active material precursor of Production Example 2.
EXAMPLE 1
A Bi-Modal Positive Active Material in which a CeO.sub.xOH.sub.y
Coating Layer is Formed, Simultaneously Doping of Zr: 0.0037 mol
and Al: 0.0005 mol
Preparation of a Positive Active Material
[0108] 1) Sintering Process
[0109] (1) Lithium salts LiOH.H.sub.2O (Samjun Chem, battery
grade), doping raw materials ZrO.sub.2 (Aldrich, 4N) and
Al(OH).sub.3 (Aldrich, 4N) were homogeneously mixed with the
positive active material precursor prepared in Preparation Example
1.
[0110] During the mixing, the molar ratio of the precursor to the
lithium salt was 1:1.05, and the content of Zr in the total amount
was 0.0037 mol while the content of Al was 0.0005 mol.
[0111] The mixture was charged into a tube furnace (inner diameter:
50 mm, length: 1000 mm) and heated while introducing oxygen at 200
mL/min.
[0112] The sintering temperature was maintained at 480.degree. C.
for 5 h and then maintained at 700 to 750.degree. C. for 16 h, and
the heating rate was 5.degree. C./min. Accordingly, a
large-particle diameter sintered body powder of which a composition
in the whole particles is
Li.sub.1.05(N.sub.0.88Co.sub.0.095Mn.sub.0.025)(.sub.0.9958)Zr.sub.0.0037-
Al.sub.0.0005O.sub.2 was independently obtained.
[0113] (2) A small-particle diameter sintered body powder of which
a composition in the whole particles is
Li.sub.1.05(Ni.sub.0.88Co.sub.0.095Mn.sub.0.025)(.sub.0.9958)Zr.sub.0.003-
7Al.sub.0.0005O.sub.2 was obtained by the same method as (1),
except for using the small-particle diameter positive active
material precursor obtained in Preparation Example 2 instead of the
large-particle diameter positive active material precursor.
[0114] 2) Mixing and Sintering Process
[0115] The large-particle diameter sintered body and the
small-particle diameter sintered body manufactured in (1) were
mixed, and a weight ratio of the large-particle diameter sintered
body to the small-particle diameter sintered body was 8:2.
[0116] After the sintering of the mixture, the surface residual
lithium was removed by washing with water.
[0117] 3) Coating Process
[0118] The material subjected to the mixing and sintering processes
was dry-mixed with Ce(OH).sub.4 (Aldrich) and then heat-treated to
uniformly coat CeO.sub.xH.sub.y (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1, x+y=1) on the surface, thereby preparing the
positive active material coated with the coating layer.
Preparation of Coin Cell
[0119] For the positive active material prepared as described
above, the weight ratio of PVDF (polyvinylidene fluoride, KF1100)
as a binder and Denka Black (commercial name: Super P) as a
conductive agent was 92.5:3.5:4 (the active material to the binder
to the conductive agent) was mixed and NMP (N-methyl-2-pyrrolidone)
was added to adjust the viscosity of the slurry.
[0120] The slurry was coated on an Al foil (thickness: 15 .mu.m) by
using a doctor blade, and dried and rolled to manufacture the
positive electrode. A loading amount of the positive electrode was
14.6 mg/cm.sup.2.
[0121] As the electrolytic solution, 1.5 vol % of VC was added to 1
M LiPF.sub.6 at EC:DMC:EMC=3:4:3 (vol %). A 2032 half-cell was
fabricated using the positive electrode, the electrolyte solution,
a PP separator, and a lithium negative electrode (200 .mu.m, Honzo
Metal) according to a conventional manufacturing method.
EXAMPLE 2
A CeO.sub.xH.sub.y Coating Layer is Simultaneously Doped with a
Bi-Modal Positive Active Material, Zr: 0.0037 mol and Al: 0.001
mol
Preparation of a Positive Active Material
[0122] 1) Sintering Process
[0123] (1) For the large-particle diameter positive active material
precursor obtained from Preparation Example 1, LiOH.H.sub.2O
(Samjeon Chemical, battery grade) as a lithium salt, ZrO.sub.2
(Aldrich, 4N) as a doping raw material, and Al(OH).sub.3 (Aldrich,
4N) were uniformly mixed.
[0124] During the mixing, the molar ratio of the precursor to the
lithium salt was 1:1.05, and the amount of Zr was 0.0037 mol while
the amount of Al was 0.001 mol among the total amount.
[0125] The mixture was charged into a tube furnace (inner diameter:
50 mm, length: 1000 mm) and heated while introducing oxygen at 200
mL/min.
[0126] The sintering temperature was maintained at 480.degree. C.
for 5 h, then maintained at 700 to 750.degree. C. for 16 h, and the
heating rate was 5.degree. C./min. Accordingly, a large-particle
diameter sintered body powder having a composition of
Li.sub.1.05(Ni.sub.0.88Co.sub.0.095Mn.sub.0.025).sub.0.09953Zr.sub.0.0037-
Al.sub.0.0001O.sub.2 in the whole particles was independently
obtained.
[0127] (2) A small-particle diameter sintered body powder of which
a composition of the whole particles is
Li.sub.1.05(Ni.sub.0.88Co.sub.0.095Mn.sub.0.025).sub.0.09953Zr.sub.0.0037-
Al.sub.0.001O.sub.2 was obtained by the same method as (1), except
for using the small-particle diameter positive active material
precursor obtained in Preparation Example 2 instead of the
large-particle diameter positive active material precursor.
[0128] 2) Mixing and Sintering Process
[0129] The large-particle diameter sintered body and the
small-particle diameter sintered body manufactured in (1) were
mixed, and a weight ratio of the large-particle diameter sintered
body to the small-particle diameter sintered body was 8:2.
[0130] After the sintering of the mixture, the surface residual
lithium was removed by washing with water.
[0131] 3) Coating Process
[0132] The material subjected to the mixing and sintering processes
was dry-mixed with Ce(OH).sub.4 (Aldrich) and then heat-treated to
uniformly coat CeO.sub.xH.sub.y(0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1, x+y=1) on the surface, thereby preparing the
positive active material formed with the coating layer.
Preparation of Coin Cell
[0133] The coin cell was prepared in the same method as in Example
1.
COMPARATIVE EXAMPLE 1
A Bi-Modal Positive Active Material in a Case without Forming a
Coating Layer
Preparation of a Positive Active Material
[0134] Except for the process of forming the coating layer in 3) in
Example 1, the positive active material was prepared without
forming the coating layer by the same method as described in 1) and
2).
Preparation of Coin Cell
[0135] The coin cell was prepared in the same manner as in Example
1.
COMPARATIVE EXAMPLE 2
A Case of Coating Boron
Preparation of a Positive Active Material
[0136] For the material subjected to the mixing and sintering
process after passing through 1) the sintering process and 2) the
mixing and sintering processes by the same method as Example 1, the
surface residual lithium was removed by a washing with water. The
material was dry-mixed with H.sub.3BO.sub.3 powder and then
heat-treated to uniformly coat B on the surface of each sintered
body particle.
[0137] Finally, with reference to the entire coating layer, the
positive active material on which B was coated at 800 ppm was
obtained.
Preparation of Coin Cell
[0138] A coin cell was manufactured by the same method as Example
1.
COMPARATIVE EXAMPLE 3
Bi-Modal Positive Active Material, Zr Doping Alone, Ce Coating
Preparation of a Positive Active Material
[0139] 1) Sintering Process
[0140] (1) For a large-particle diameter positive active material
precursor obtained from Preparation Example 1, LiOH.H.sub.2O
(Samjeon Chemical, battery grade) as a lithium salt and ZrO.sub.2
(Aldrich, 4N) as a doping raw material were uniformly mixed.
[0141] During the mixing, the molar ratio of the precursor to the
lithium salt was 1:1.05, and the amount of Zr was 0.0037 mol among
the total amount.
[0142] The mixture was charged into a tube furnace (inner diameter:
50 mm, length: 1000 mm) and heated while introducing oxygen at 200
mL/min.
[0143] The sintering temperature was maintained at 480.degree. C.
for 5 h, then maintained at 700 to 750.degree. C. for 16 h, and the
heating rate was 5.degree. C./min. Accordingly, the large-particle
diameter sintered body powder particle having the composition of
Li.sub.1.05(Ni.sub.0.88Co.sub.0.095Mn.sub.0.025).sub.0.9963Zr.sub.0.0037O-
.sub.2 in the whole particles was independently obtained.
[0144] (2) A small-particle diameter sintered body powder of which
a composition was
Li.sub.1.05(Ni.sub.0.88Co.sub.0.095Mn.sub.0.025).sub.0.9963Zr.sub.0.0037O-
.sub.2 was obtained by the same method as (1) except for using the
small-particle diameter positive active material precursor obtained
in Preparation Example 2 instead of the large-particle diameter
positive active material precursor.
[0145] 2) Mixing and Sintering Process
[0146] The large-particle diameter sintered body and the
small-particle diameter sintered body manufactured in (1) were
mixed, and a weight ratio of the large-particle diameter sintered
body to the small-particle diameter sintered body was 8:2.
[0147] After the sintering of the mixture, the surface residual
lithium was removed by washing with water.
[0148] 3) Coating Process
[0149] The material subjected to the mixing and sintering processes
was dry-mixed with Ce(OH).sub.4 (Aldrich) and then heat-treated to
uniformly coat CeO.sub.xH.sub.y (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1, x+y=1) on the surface, thereby preparing the
positive active material coated with the coating layer.
Preparation of Coin Cell
[0150] The coin cell was prepared in the same method as in Example
1.
COMPARATIVE EXAMPLE 4
A Bi-Modal Positive Active Material, Al Alone Doping, Ce
Coating
Preparation of a Positive Active Material
[0151] 1) Sintering Process
[0152] (1) For the large-particle diameter positive active material
precursor obtained from Preparation Example 1, LiOH.H.sub.2O
(Samjeon Chemical, battery grade) as a lithium salt, ZrO.sub.2
(Aldrich, 4N) as a doping raw material, and Al(OH).sub.3 (Aldrich,
4N) were uniformly mixed.
[0153] During the mixing, the molar ratio of the precursor to the
lithium salt was 1:1.05, and the amount of Al was 0.0005 mol among
the total amount.
[0154] The mixture was charged into a tube furnace (inner diameter:
50 mm, length: 1000 mm) and heated while introducing oxygen at 200
mL/min.
[0155] The sintering temperature was maintained at 480.degree. C.
for 5 h, and then maintained at 700 to 750.degree. C. for 16 h,
while the heating rate was 5.degree. C./min. Accordingly, the
large-particle diameter sintered body powder particle having the
composition of
Li.sub.1.05(Ni.sub.0.88Co.sub.0.095Mn.sub.0.025).sub.0.9995Al.sub.0.0005O-
.sub.2 in the whole particles was independently obtained.
[0156] (2) A small-particle diameter sintered body powder of which
a composition of the whole particles was
Li.sub.1.05(Ni.sub.0.88Co.sub.0.095Mn.sub.0.025).sub.0.9995Al.sub.0.0005O-
.sub.2 was obtained by the same method as (1), except for using the
small-particle diameter positive active material precursor obtained
in Preparation Example 2 instead of the large-particle diameter
positive active material precursor.
[0157] 2) Mixing and Sintering Process
[0158] The large-particle diameter sintered body and the
small-particle diameter sintered body manufactured in (1) were
mixed, and a weight ratio of the large-particle diameter sintered
body to the small-particle diameter sintered body was 8:2.
[0159] After the sintering of the mixture, the surface residual
lithium was removed by washing with water.
[0160] 3) Coating Process
[0161] The material subjected to the mixing and sintering processes
was dry-mixed with Ce(OH).sub.4 (Aldrich) and then heat-treated to
uniformly coat CeO.sub.xH.sub.y (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1, x+y=1) on the surface, thereby preparing the
positive active material formed with the coating layer.
Preparation of Coin Cell
[0162] The coin cell was prepared in the same method as in Example
1.
COMPARATIVE EXAMPLE 5
A Positive Active Material Formed with CeO.sub.2 Coating Layer
Preparation of a Positive Active Material
[0163] A material in which a residual lithium on the surface was
enhanced was obtained by the same method as described in 1) and 2)
in Example 1, and the material subjected to the mixing and
sintering processes was dry-mixed with CeO.sub.2 and then
heat-treated to uniformly coat CeO.sub.2 on the surface, thereby
manufacturing the positive active material formed with the coating
layer.
Preparation of Coin Cell
[0164] The coin cell was prepared in the same method as in Example
1.
REFERENCE EXAMPLE 1
Large-Particle Diameter Positive Active Material Precursor, Al and
Zr Doping, Ce Coating
[0165] For a large-particle diameter positive active material
precursor obtained in Preparation Example 1, LiOH.H.sub.2O (Samjeon
Chemical, battery grade) as a lithium salt, ZrO.sub.2 (Aldrich, 4N)
as a doping raw material, and Al(OH).sub.3 (Aldrich, 4N) were
uniformly mixed.
[0166] During the mixing, the molar ratio of the precursor to the
lithium salt was 1:1.05, and the amount of Zr was 0.0037 mol among
the total amount.
[0167] The mixture was charged into a tube furnace (inner diameter:
50 mm, length: 1000 mm) and heated while introducing oxygen at 200
mL/min.
[0168] The sintering temperature was maintained at 480.degree. C.
for 5 h, and then maintained at 700 to 750.degree. C. for 16 h,
while the heating rate was 5.degree. C./min. Accordingly, the
large-particle diameter sintered body powder having the composition
of
Li.sub.1.05(Ni.sub.0.88Co.sub.0.095Mn.sub.0.025)Zr.sub.0.0037Al.sub.0.000-
5O.sub.2 and the average particle diameter of 15 .mu.m in the whole
particles was obtained.
[0169] The large-particle diameter sintered body in which the
residual lithium of the surface was removed through the washing
after the sintering was thereby manufactured.
[0170] The material on which the surface residual lithium was
removed was dry-mixed with Ce(OH).sub.4 (Aldrich) and heat-treated
to uniformly coat CeO.sub.xH.sub.y (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1, x+y=1) on the surface, thereby preparing the
positive active material formed with the coating layer.
REFERENCE EXAMPLE 2
The Small-Particle Diameter Positive Active Material Precursor, Al
and Zr Doping, Ce Coating
[0171] Except for using the small-particle diameter positive active
material precursor obtained from Preparation Example 2, the
small-particle diameter sintered body powder having the composition
of
Li.sub.1.05(N.sub.0.88Co.sub.0.095Mn.sub.0.025)Zr.sub.0.0037AI.sub.0.0005-
O.sub.2 in the whole particles and the average particle diameter of
the 5 .mu.m was obtained by the same method as Reference Example
1.
[0172] The small-particle diameter sintered body in which the
residual lithium of the surface was removed through the washing
after the sintering was thereby manufactured.
[0173] The material from which the surface residual lithium was
removed was dry-mixed with Ce(OH).sub.4 (Aldrich) and heat-treated
to uniformly coat CeO.sub.xH.sub.y (0.ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1, x+y=1) on the surface, thereby preparing the
positive active material formed with the coating layer.
EXPERIMENTAL EXAMPLE 1
Evaluation of Charge and Discharge Characteristics
[0174] Lithium rechargeable batteries manufactured according to
Examples 1 and 2, Comparative Examples 1 and 2, and Reference
Example 1 were evaluated.
[0175] A charge capacity and a discharge capacity were measured by
being discharged with a constant current-constant voltage at 0.2C,
4.25 V, and 0.005C cut-off conditions and with a charge and
constant current of 0.2C and 2.5 V cut-off conditions.
[0176] Results are represented in Table 1 below.
TABLE-US-00001 TABLE 1 Charge Discharge Coulomb capacity capacity
efficiency Items [mAh/g] [mAh/g] [%] Example 1 234.2 213.8 91.3
Example 2 233.4 212.6 91.1 Comparative Example 1 232.2 209.1 90.1
Comparative Example 2 237.5 215.2 90.6 Reference Example 1 232.2
207.3 89.3
[0177] Referring to Table 1, in the case of the lithium
rechargeable battery manufactured according to Examples 1 and 2,
compared with the lithium rechargeable battery manufactured
according to Comparative Examples 1 and 2 and Reference Example 1,
it may be confirmed that the charge and discharge capacity is
excellent, and accordingly, Coulomb efficiency is also
excellent.
[0178] Therefore, it may be confirmed that the charge and discharge
characteristics may be improved when the positive active material
according to the present exemplary embodiment is applied to the
lithium rechargeable battery.
EXPERIMENTAL EXAMPLE 2
DC Internal Resistance (Direct Current, Internal Resistance:
DC-IR)
[0179] For the lithium rechargeable battery prepared according to
Examples 1 and 2, Comparative Examples 1 to 5, and Reference
Example 2, the charge and discharge was performed with the same
conditions as Experimental Example 2, and DC internal resistance
(DC-IR) was measured based on a voltage change during an initial
discharge of 60 s in each cycle.
[0180] The DC-IR value at the 1.sup.st cycle and the DC-IR value at
the 30.sup.th cycle are represented, and an increase amount was
calculated and is shown in Table 2 below.
TABLE-US-00002 TABLE 2 1.sup.st DC-IR 30.sup.th DC-IR Increase
amount Item [.OMEGA.] [.OMEGA.] [.OMEGA.] Example 1 11.8 25.3 13.5
Example 2 11.3 25.1 13.8 Comparative Example 1 12.5 35.0 22.5
Comparative Example 2 19.7 39.1 19.4 Comparative Example 3 11.8
29.1 17.3 Comparative Example 4 11.6 29.3 17.7 Comparative Example
5 11.5 28.3 16.8 Reference Example 2 10.0 45.0 35.0
[0181] Referring to Table 2, in the case of the lithium
rechargeable battery prepared according to Examples 1 and 2, it may
be confirmed that a resistance increase amount was not large even
after performing the charge and discharge30 times.
[0182] On the other hand, in the case of the lithium rechargeable
batteries manufactured according to Comparative Examples 1 to 5 and
Reference Example 2, the resistance increase amount was
significantly increased after 30 cycles.
[0183] Therefore, when applying the positive active material
according to the present exemplary embodiment, it can be confirmed
that the lithium rechargeable battery having the excellent
resistance characteristic may be implemented.
[0184] The exemplary embodiments and modified examples of the
present invention have been described and shown with reference to
the accompanying drawings, but the present invention is not limited
to the exemplary embodiments and may be manufactured in various
forms. As described above, it will be appreciated by those skilled
in the art that changes may be made in these embodiments without
departing from the principles and spirit of the general inventive
concept, the scope of which is defined in the appended claims, and
their equivalents. Therefore, it should be understood that the
exemplary embodiments described above are not limitative but are
exemplary in all the aspects.
* * * * *