U.S. patent application number 17/578881 was filed with the patent office on 2022-05-05 for transition metal precursor having low tap density and lithium transition metal oxide having high particle strength.
This patent application is currently assigned to LG Chem, Ltd.. The applicant listed for this patent is LG Chem, Ltd.. Invention is credited to Sung-Kyun Chang, Won Seok Chang, Jung Min Han, Wang Mo Jung, Dong Hun Lee, Jinhyung Lim, Hyun Jin Oh, Sin Young Park, Ho Suk Shin, In Sung Uhm.
Application Number | 20220135428 17/578881 |
Document ID | / |
Family ID | |
Filed Date | 2022-05-05 |
United States Patent
Application |
20220135428 |
Kind Code |
A1 |
Lim; Jinhyung ; et
al. |
May 5, 2022 |
Transition Metal Precursor Having Low Tap Density And Lithium
Transition Metal Oxide Having High Particle Strength
Abstract
Disclosed are a lithium transition metal oxide and a lithium
secondary battery, in which a ratio of average particle diameter
D50 of the lithium transition metal oxide to average particle
diameter D50 of a transition metal precursor for preparation of the
lithium transition metal oxide satisfies the condition represented
by Equation 3 below: 0 < Average .times. .times. particle
.times. .times. diameter .times. .times. D .times. .times. 50
.times. .times. of .times. .times. lithium .times. .times.
transition .times. metal .times. .times. oxide Average .times.
.times. particle .times. .times. diameter .times. .times. D .times.
.times. 50 .times. .times. of .times. .times. transition .times.
.times. metal .times. precursor < 1.2 . ( 3 ) ##EQU00001##
Inventors: |
Lim; Jinhyung; (Daejeon,
KR) ; Chang; Sung-Kyun; (Daejeon, KR) ; Chang;
Won Seok; (Daejeon, KR) ; Park; Sin Young;
(Daejeon, KR) ; Shin; Ho Suk; (Daejeon, KR)
; Oh; Hyun Jin; (Daejeon, KR) ; Han; Jung Min;
(Daejeon, KR) ; Uhm; In Sung; (Daejeon, KR)
; Jung; Wang Mo; (Daejeon, KR) ; Lee; Dong
Hun; (Daejeon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG Chem, Ltd. |
Seoul |
|
KR |
|
|
Assignee: |
LG Chem, Ltd.
Seoul
KR
|
Appl. No.: |
17/578881 |
Filed: |
January 19, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14441580 |
May 8, 2015 |
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PCT/KR2014/001107 |
Feb 11, 2014 |
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17578881 |
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International
Class: |
C01G 53/04 20060101
C01G053/04; C01G 53/00 20060101 C01G053/00; H01M 10/0525 20060101
H01M010/0525; H01M 10/052 20060101 H01M010/052; H01M 4/505 20060101
H01M004/505; H01M 4/525 20060101 H01M004/525 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 13, 2013 |
KR |
10-2013-0015206 |
Claims
1. A lithium transition metal oxide in which a ratio of average
particle diameter D50 of the lithium transition metal oxide to
average particle diameter D50 of a transition metal precursor for
preparation of the lithium transition metal oxide satisfies the
condition represented by Equation 3 below: 0 < Average .times.
.times. particle .times. .times. diameter .times. .times. D50
.times. of .times. .times. lithium .times. .times. transition
.times. .times. metal .times. .times. oxide Aaverage .times.
.times. particle .times. .times. diameter .times. .times. D50 of
.times. .times. transition .times. .times. metal .times. .times.
precursor < 1.2 . ( 3 ) ##EQU00004##
2. The lithium transition metal oxide according to claim 1, wherein
the lithium transition metal oxide comprises Ni, Mn and Co.
3. The lithium transition metal oxide according to claim 2, wherein
the lithium transition metal oxide is a compound represented by
Formula 4 below:
Li.sub.aNi.sub.xMn.sub.yCo.sub.zM.sub.wO.sub.2-tA.sub.t (4) wherein
0<a.ltoreq.1.2, 0<x.ltoreq.0.9, 0<y.ltoreq.0.9,
0<z.ltoreq.0.9, 0.ltoreq.w.ltoreq.0.3,
2.ltoreq.a+x+y+z+w.ltoreq.2.3, and 0.ltoreq.t<0.2; M is at least
one metal cation selected from Al, Cu, Fe, Mg, B, Cr, or transition
metals of 2 period in the Periodic Table of the Elements; and A is
at least one monovalent or divalent anion.
4. The lithium transition metal oxide according to claim 3,
wherein, in Formula 4, x>y and x>z.
5. The lithium transition metal oxide according to claim 1, wherein
the transition metal precursor consists of transition metal
hydroxide particles represented by Formula 2 below:
NiCoMn(OH.sub.1-x).sub.2 (2) wherein 0.ltoreq.x.ltoreq.0.5; and
wherein a tap density of the transition metal precursor is from 1.3
g/cc to 1.6 g/cc, and a ratio of tap density to average particle
diameter D50 of the precursor satisfies a condition represented by
Equation 1 below: 2000 < Tap .times. .times. density Average
.times. .times. particle .times. .times. diameter .times. .times.
D50 of .times. .times. transition .times. .times. metal .times.
.times. precursor .times. .times. < 3500 .times. ( g / cc cm ) .
( 1 ) ##EQU00005##
6. The lithium transition metal oxide according to claim 5, wherein
the transition metal precursor has an average particle diameter D50
of 1 to 30 .mu.m.
7. A lithium secondary battery in which a unit cell comprising a
positive electrode comprising the lithium transition metal oxide
according to claim 1, a negative electrode, and a polymer membrane
disposed between the positive electrode and the negative electrode
is accommodated in a battery case.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a divisional of U.S. application
Ser. No. 14/441,580, filed May 8, 2015, which is a national phase
entry under 35 U.S.C. .sctn. of International Application No.
PCT/KR2014/001107, filed Feb. 11, 2014, which claims priority to
Korean Patent Application No. 10-2013-0015206, filed Feb. 13, 2013,
the disclosures of which are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a repeatedly chargeable and
dischargeable lithium secondary battery. More particularly, the
present invention relates to a lithium transition metal oxide used
as a positive electrode active material of lithium secondary
batteries and a transition metal precursor for preparation of a
lithium transition metal oxide.
BACKGROUND ART
[0003] In line with development of information technology (IT),
various portable information and communication devices have entered
widespread use and thus the 21.sup.st century is developing into a
"ubiquitous society" where high quality information services are
available regardless of time and place.
[0004] Lithium secondary batteries play a key role in such
development towards the ubiquitous society.
[0005] Lithium secondary batteries have higher operating voltage
and energy density, are used for a longer period of time than other
secondary batteries and, thus, can satisfy sophisticated
requirements according to diversification and increasing complexity
of devices.
[0006] Recently, much effort globally has been put into expanding
applications to eco-friendly transportation systems such as
electric vehicles and the like, power storage, and the like through
further advancement of conventional lithium secondary
batteries.
[0007] As use of lithium secondary batteries is expanding to middle
and large-scale devices, demand for lithium secondary batteries
having larger capacity, higher output and higher safety
characteristics than conventional lithium secondary batteries is
increasing.
[0008] First, to obtain larger capacity, capacity per unit weight
or unit volume of an active material must be high.
[0009] Secondly, tap density of an active material must be high.
Packing density of an electrode may increase with increasing tap
density. In particular, to manufacture an electrode, an active
material is mixed with a binder or a conductive material and then
coated on a current collector to form a thin film, and the
electrode is hardened by applying pressure thereto. In this regard,
when the active material is not satisfactorily filled, the
electrode cannot be thinly manufactured and the volume thereof is
large and, thus, larger capacity cannot be realized under given
volume conditions of batteries.
[0010] Thirdly, a specific surface area of an active material must
be small. When the specific surface area of the active material is
large, a liquid phase is present on a surface of the active
material. Accordingly, when the active material is coated on a
current collector, a ratio of the liquid phase to the active
material is high and, even after manufacturing an electrode, many
surfaces exist between particles. Accordingly, electric flow is
hindered and a large amount of binder for adhesion is required.
Therefore, to reduce resistance of an electrode and enhance
adhesion, a larger amount of a conductive material and a binder
must be added and, as such, the amount of an active material
decreases. Accordingly, larger capacity may not be obtained under
limited volume conditions.
[0011] There is a tendency that the tap density of an active
material increases with increasing precursor tap density.
Therefore, technologies of the art are generally developed towards
increase in tap density of the precursor. Tap density of a
precursor is proportional to an average particle diameter of
particles constituting the precursor.
DISCLOSURE
Technical Problem
[0012] However, apart from technologies for increasing tap density
of an active material, particles constituting an active material
are broken or crushed in a slurry preparation process and a rolling
process when manufacturing an electrode.
[0013] Surfaces, which are not stabilized through heat treatment,
of the broken or crushed particles side react with an electrolyte
and, as such, forms films having high resistance. In addition,
by-products formed by continuous reaction with the electrolyte are
deposited at a negative electrode and, as such, performance of the
negative electrode is deteriorated. In addition, the electrolyte is
continuously consumed and, thus, swelling occurs due to generation
of gases.
Technical Solution
[0014] The inventors of the present invention aim to address the
aforementioned problems of the related art by using a transition
metal precursor in which a ratio of tap density to average particle
diameter D50 of the precursor satisfies the condition represented
by Equation 1 below.
[0015] In accordance with one aspect of the present invention,
provided is a transition metal precursor for preparation of a
lithium transition metal oxide, in which the ratio of tap density
to average particle diameter D50 of the precursor satisfies the
condition represented by Equation 1 below:
0 < Tap .times. .times. density Average .times. .times. particle
.times. .times. diameter .times. .times. D50 of .times. .times.
transition .times. .times. metal .times. .times. precursor .times.
.times. < 3500 .times. ( g / cc cm ) . ( 1 ) ##EQU00002##
[0016] In Equation 1 above, the tap density indicates a bulk
density of a powder obtained by vibrating a container under a
constant conditions when filled with the powder, and the average
particle diameter D50 of the transition metal precursor indicates a
particle diameter corresponding to 50% of passed mass percentage in
a grain size accumulation curve.
[0017] The ratio of tap density to average particle diameter D50 of
the transition metal precursor may be 500:1 to 3500:1, 1000:1 to
3500:1, 1500:1 to 3500:1, or 2000:1 to 3500:1.
[0018] The transition metal precursor is a powder of an aggregate
of particles (hereinafter, referred to as precursor particles)
constituting the transition metal precursor. Similarly, a lithium
composite transition metal oxide described below is a powder of an
aggregate of particles (hereinafter, referred to as oxide
particles) constituting the lithium composition transition metal
oxide.
[0019] The transition metal precursor may be composed of one kind
of transition metal or include two or more kinds of transition
metals. The two or more kinds of transition metals may be at least
two selected from the group consisting of nickel (Ni), cobalt (Co),
manganese (Mn), aluminum (Al), copper (Cu), iron (Fe), magnesium
(Mg), boron (B), chromium (Cr), and period 2 transition metals.
[0020] The transition metal precursor particles may be transition
metal oxide particles, transition metal sulfide particles,
transition metal nitride particles, transition metal phosphide
particles, transition metal hydroxide particles, or the like.
[0021] In particular, the transition metal precursor particles may
be transition metal hydroxide particles, more particularly a
compound represented by Formula 2 below:
M(OH.sub.1-x).sub.2 (2)
[0022] wherein M represents at least two selected from the group
consisting of Ni, Co, Mn, Al, Cu, Fe, Mg, B, Cr, and period 2
transition metals; and 0.ltoreq.x.ltoreq.0.5. In this regard, M may
include two transition metals selected from the group consisting of
Ni, Co, and Mn or all thereof.
[0023] The average particle diameter D50 of the transition metal
precursor may be 1 .mu.m to 30 .mu.m.
[0024] The present invention provides a lithium transition metal
oxide prepared by mixing the transition metal precursor and a
lithium precursor and sintering the mixture. A lithium transition
metal oxide including at least two kinds of transition metals may
be defined as a lithium composite transition metal oxide.
[0025] In this regard, a ratio of an average particle diameter D50
of lithium transition metal oxide to an average particle diameter
D50 of transition metal precursor for preparation of the lithium
transition metal oxide may satisfy the condition represented by
Equation 3 below:
0 < Average .times. .times. particle .times. .times. diameter
.times. .times. D50 .times. of .times. .times. lithium .times.
.times. transition .times. .times. metal .times. .times. oxide
Aaverage .times. .times. particle .times. .times. diameter .times.
.times. D50 of .times. .times. transition .times. .times. metal
.times. .times. precursor < 1.2 . ( 3 ) ##EQU00003##
[0026] The oxide particles constituting the lithium composite
transition metal oxide may be a compound represented by Formula 4
below:
Li.sub.aNi.sub.xMn.sub.yCo.sub.zM.sub.wO.sub.2-tA.sub.t (4)
[0027] wherein 0<a.ltoreq.1.2, 0.ltoreq.x.ltoreq.0.9,
0.ltoreq.y.ltoreq.0.9, 0.ltoreq.z.ltoreq.0.9,
0.ltoreq.w.ltoreq.0.3, 2.ltoreq.a+x+y+z+w.ltoreq.2.3, and
0.ltoreq.t<0.2;
[0028] M is at least one metal cation selected from the group
consisting of Al, Cu, Fe, Mg, B, Cr, and period 2 transition
metals; and
[0029] A is at least one monovalent or divalent anion.
[0030] In addition, the lithium composite transition metal oxide
particles may be the compound of Formula 4 where x>y and
x>z.
[0031] The lithium transition metal oxide may be composed of one
kind of transition metal or include two or more kinds of transition
metals. The two or more kinds of transition metals may be at least
two selected from the group consisting of Ni, Co, Mn, Al, Cu, Fe,
Mg, B, Cr, and period 2 transition metals.
[0032] The present invention also provides a lithium secondary
battery in which a unit cell including a positive electrode
including the lithium transition metal oxide described above, a
negative electrode, and a polymer membrane disposed between the
positive electrode and the negative electrode is accommodated in a
battery case.
[0033] The lithium secondary battery may be a lithium ion battery,
a lithium ion polymer battery, or a lithium polymer battery.
[0034] A positive electrode active material according to the
present invention may further include other lithium-containing
transition metal oxides in addition to the lithium transition metal
oxide described above.
[0035] Examples of other lithium-containing transition metal oxides
include, but are not limited to, layered compounds such as lithium
cobalt oxide (LiCoO.sub.2) and lithium nickel oxide (LiNiO.sub.2),
or compounds substituted with one or more transition metals;
lithium manganese oxides such as compounds of Formula
Li.sub.1+yMn.sub.2-yO.sub.4 where 0.ltoreq.y.ltoreq.0.33,
LiMnO.sub.3, LiMn.sub.2O.sub.3, and LiMnO.sub.2; lithium copper
oxide (Li.sub.2CuO.sub.2); vanadium oxides such as
LiV.sub.3O.sub.8, LiV.sub.3O.sub.4, V.sub.2O.sub.5, and
Cu.sub.2V.sub.2O.sub.7; Ni-site type lithium nickel oxides having
the formula LiNi.sub.1-yM.sub.yO.sub.2 where M=Co, Mn, Al, Cu, Fe,
Mg, B, or Ga, and 0.01.ltoreq.y.ltoreq.0.3; lithium manganese
composite oxides having the formula LiMn.sub.2-yM.sub.yO.sub.2
where M=Co, Ni, Fe, Cr, Zn, or Ta, and 0.01.ltoreq.y.ltoreq.0.1 or
the formula Li.sub.2Mn.sub.3MO.sub.8 where M=Fe, Co, Ni, Cu, or Zn;
LiMn.sub.2O.sub.4 where some of the Li atoms are substituted with
alkaline earth metal ions; disulfide compounds; and
Fe.sub.2(MoO.sub.4).sub.3.
[0036] The positive electrode may be available from coating, on a
positive electrode current collector, a slurry prepared by mixing a
positive electrode mixture including the positive electrode active
material and a solvent such as NMP or the like and drying and
rolling the coated positive electrode current collector.
[0037] The positive electrode mixture may selectively include a
conductive material, a binder, a filler, and the like, in addition
to the positive electrode active material.
[0038] The positive electrode current collector is generally
manufactured to a thickness of 3 to 500 .mu.m. The positive
electrode current collector is not particularly limited so long as
it does not cause chemical changes in the manufactured battery and
has high conductivity. For example, the positive electrode current
collector may be made of copper, stainless steel, aluminum, nickel,
titanium, sintered carbon, copper, or stainless steel
surface-treated with carbon, nickel, titanium, silver, or the like,
aluminum-cadmium alloys, or the like. The positive electrode
current collector may have fine irregularities at a surface thereof
to increase adhesion between the positive electrode active material
and the positive electrode current collector. In addition, the
positive electrode current collector may be used in any of various
forms including films, sheets, foils, nets, porous structures,
foams, and non-woven fabrics.
[0039] The conductive material is typically added in an amount of 1
to 30 wt % based on the total weight of a mixture including a
positive electrode active material. There is no particular limit as
to the conductive material, so long as it does not cause chemical
changes in the manufactured battery and has conductivity. Examples
of conductive materials include graphite such as natural or
artificial graphite; carbon black such as carbon black, acetylene
black, Ketjen black, channel black, furnace black, lamp black, and
thermal black; conductive fibers such as carbon fibers and metallic
fibers; metallic powders such as carbon fluoride powder, aluminum
powder, and nickel powder; conductive whiskers such as zinc oxide
and potassium titanate; conductive metal oxides such as titanium
oxide; and polyphenylene derivatives.
[0040] The binder is a component assisting in binding between an
active material and a conductive material and in binding of the
active material to a current collector. The binder may be added in
an amount of 1 wt % to 30 wt % based on the total weight of a
mixture including a positive electrode active material.
Non-limiting examples of the binder include polyvinylidene
fluoride, polyvinyl alcohols, carboxymethylcellulose (CMC), starch,
hydroxypropylcellulose, regenerated cellulose, polyvinyl
pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene,
ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM,
styrene butadiene rubber, fluorine rubber, and various
copolymers.
[0041] The filler is used as a component to inhibit positive
electrode expansion. The filler is not particularly limited so long
as it is a fibrous material that does not cause chemical changes in
the manufactured battery. Examples of the filler include
olefin-based polymers such as polyethylene and polypropylene; and
fibrous materials such as glass fiber and carbon fiber.
[0042] As a dispersion solution, isopropyl alcohol,
N-methylpyrrolidone (NMP), acetone, or the like may be used.
[0043] A method of uniformly coating a metal material with a paste
of an electrode material may be selected from among known methods
or an appropriate new method in consideration of properties and the
like of materials. For example, a paste may be applied to a current
collector and then uniformly dispersed thereon using a doctor blade
or the like. In some cases, the application and dispersing
processes may be simultaneously performed as a single process. In
addition, die casting, comma coating, screen-printing, or the like
may be used. In another embodiment, a paste of an electrode
material may be molded on a separate substrate and the adhered to a
current collector by pressing or lamination.
[0044] The paste coated on the metal plate is preferably dried in a
vacuum oven at 50.degree. C. to 200.degree. C. for one day.
[0045] The negative electrode may be available from, for example,
coating a negative electrode active material on a negative
electrode current collector and drying the coated negative
electrode current collector. As desired, as described above,
components such as a conductive material, a binder, a filler, and
the like may be selectively further added to the negative electrode
active material.
[0046] The negative electrode current collector is typically
manufactured to a thickness of 3 to 500 .mu.m. The negative
electrode current collector is not particularly limited so long as
it does not cause chemical changes in the manufactured battery and
has conductivity. For example, the negative electrode current
collector may be made of copper, stainless steel, aluminum, nickel,
titanium, sintered carbon, copper, or stainless steel
surface-treated with carbon, nickel, titanium, silver, or the like,
aluminum-cadmium alloys, or the like. As in the positive electrode
current collector, the negative electrode current collector may
have fine irregularities at a surface thereof to enhance adhesion
between the negative electrode current collector and the negative
electrode active material. In addition, the negative electrode
current collector may be used in various forms including films,
sheets, foils, nets, porous structures, foams, and non-woven
fabrics.
[0047] Examples of the negative electrode active material include,
but are not limited to, carbon such as hard carbon and
graphite-based carbon; metal composite oxides such as
Li.sub.xFe.sub.2O.sub.3 where 0.ltoreq.x.ltoreq.1, Li.sub.xWO.sub.2
where 0.ltoreq.x.ltoreq.1, Sn.sub.xMe.sub.1-xMe'.sub.yO.sub.z where
Me:Mn, Fe, Pb, or Ge; Me':Al, B, P, Si, Group I, Group II and Group
III elements, or halogens; 0.ltoreq.x.ltoreq.1;
1.ltoreq.y.ltoreq.3; and 1.ltoreq.z.ltoreq.8; lithium metal;
lithium alloys; Si-based alloys; tin-based alloys; metal oxides
such as SnO, SnO.sub.2, PbO, PbO.sub.2, Pb.sub.2O.sub.3,
Pb.sub.3O.sub.4, Sb.sub.2O.sub.3, Sb.sub.2O.sub.4, Sb.sub.2O.sub.5,
GeO, GeO.sub.2, Bi.sub.2O.sub.3, Bi.sub.2O.sub.4, and
Bi.sub.2O.sub.5; conductive polymers such as polyacetylene; and
Li--Co--Ni-based materials.
[0048] A separator is disposed between the positive electrode and
the negative electrode and, as the separator, an insulating thin
film having high ion permeability and mechanical strength is used.
The separator typically has a pore diameter of 0.01 to 10 .mu.m and
a thickness of 5 to 300 .mu.m. As the separator, sheets or
non-woven fabrics, made of an olefin polymer such as polypropylene,
glass fibers or polyethylene, which have chemical resistance and
hydrophobicity, or Kraft papers are used. Examples of commercially
available separators include, but are not limited to, Celgard.RTM.
series such as Celgard.RTM. 2400 and 2300 (available from Hoechest
Celanese Corp.), polypropylene separators (available from Ube
Industries Ltd., or Pall RAI Co.), and polyethylene series
(available from Tonen or Entek).
[0049] In some cases, to enhance battery stability, a gel polymer
electrolyte may be coated on the separator. Examples of such gel
polymers include, but are not limited to, polyethylene oxide,
polyvinylidenefluoride, and polyacrylonitrile.
[0050] When a solid electrolyte such as a polymer or the like is
used as an electrolyte, the solid electrolyte may also serve as
both the separator and electrolyte.
[0051] A lithium salt-containing non-aqueous electrolyte is
composed of a non-aqueous electrolyte and a lithium salt. As the
non-aqueous electrolyte, a non-aqueous electrolytic solution, an
organic solid electrolyte, or an inorganic solid electrolyte may be
used.
[0052] For example, the non-aqueous electrolytic solution may be an
aprotic organic solvent such as N-methyl-2-pyrrolidone, propylene
carbonate, ethylene carbonate, butylene carbonate, dimethyl
carbonate, diethyl carbonate, ethylmethyl carbonate,
gamma-butyrolactone, 1,2-dimethoxy ethane, 1,2-diethoxy ethane,
tetrahydrofuran, 2-methyl tetrahydrofuran, dimethylsulfoxide,
1,3-dioxolane, 4-methyl-1,3-dioxene, diethylether, formamide,
dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl
formate, methyl acetate, phosphoric acid triester, trimethoxy
methane, dioxolane derivatives, sulfolane, methyl sulfolane,
1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives,
tetrahydrofuran derivatives, ether, methyl propionate, ethyl
propionate, or the like.
[0053] Examples of the organic solid electrolyte include
polyethylene derivatives, polyethylene oxide derivatives,
polypropylene oxide derivatives, phosphoric acid ester polymers,
poly agitation lysine, polyester sulfide, polyvinyl alcohols,
polyvinylidene fluoride, and polymers containing ionic dissociation
groups.
[0054] Examples of the inorganic solid electrolyte include
nitrides, halides and sulfates of lithium (Li) such as Li.sub.3N,
LiI, LisNI.sub.2, Li.sub.3N--LiI--LiOH, LiSiO.sub.4,
LiSiO.sub.4--LiI--LiOH, Li.sub.2SiS.sub.3, Li.sub.4SiO.sub.4,
Li.sub.4SiO.sub.4--LiI--LiOH, and
Li.sub.3PO.sub.4--Li.sub.2S--SiS.sub.2.
[0055] The lithium salt is a material that is readily soluble in
the non-aqueous electrolyte. Examples thereof include LiCl, LiBr,
LiI, LiClO.sub.4, LiBF.sub.4, LiB.sub.10Cl.sub.10, LiPF.sub.6,
LiCF.sub.3SO.sub.3, LiCF.sub.3CO.sub.2, LiAsF.sub.6, LiSbF.sub.6,
LiAlCl.sub.4, CH.sub.3SO.sub.3Li, CF.sub.3SO.sub.3Li, LiSCN,
LiC(CF.sub.3SO.sub.2).sub.3, (CF.sub.3SO.sub.2).sub.2NLi,
chloroborane lithium, lower aliphatic carboxylic acid lithium,
lithium tetraphenyl borate, and imides.
[0056] In addition, in order to improve charge/discharge
characteristics and flame retardancy, for example, pyridine,
triethylphosphite, triethanolamine, cyclic ether, ethylenediamine,
n-glyme, hexaphosphoric triamide, nitrobenzene derivatives, sulfur,
quinone imine dyes, N-substituted oxazolidinone, N,N-substituted
imidazolidine, ethylene glycol dialkyl ether, ammonium salts,
pyrrole, 2-methoxy ethanol, aluminum trichloride, or the like may
be added to the non-aqueous electrolyte. In some cases, in order to
impart incombustibility, the electrolyte may further include a
halogen-containing solvent such as carbon tetrachloride and
ethylene trifluoride. In addition, in order to improve
high-temperature storage characteristics, the electrolyte may
further include carbon dioxide gas, fluoro-ethylene carbonate
(FEC), propene sultone (PRS), fluoro-propylene carbonate (FPC), or
the like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0057] 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 drawing, in which:
[0058] FIG. 1 is a graph illustrating a relationship between tap
density and average particle diameter D50 of each of transition
metal precursors according to examples and comparative examples of
the present invention;
[0059] FIG. 2 is a graph illustrating a relationship between
changes in particle sizes before and after forming into powder of
each of lithium transition metal oxides according to examples and
comparative examples of the present invention and a degree of
particle growth after calcination of the lithium transition metal
oxides; and
[0060] FIG. 3 is a graph illustrating lifespan characteristics of
lithium secondary batteries manufactured using the lithium
transition metal oxides of examples and comparative examples of the
present invention.
BEST MODE
[0061] Now, the present invention will be described in more detail
with reference to the following examples. These examples are
provided for illustrative purposes only, should not be construed as
limiting the scope and spirit of the present invention and are
obvious to those of ordinary skill in the art to which the present
invention pertains. In addition, those of ordinary skill in the art
may carry out a variety of applications and modifications based on
the foregoing teachings within the scope of the present invention,
and these modified embodiments may also be within the scope of the
present invention.
Example 1
[0062] Nickel sulfate, cobalt sulfate, and manganese sulfate were
mixed in a molar ratio of 0.45:0.15:0.40 to prepare a 1.5 M aqueous
transition metal solution, and a 3 M aqueous sodium hydroxide
solution was prepared.
[0063] The aqueous transition metal solution was added to a wet
reactor maintained at 45.degree. C. to 50.degree. C. and containing
distilled water, the aqueous sodium hydroxide solution was added
thereto so that pH of the distilled water inside the wet reactor
was maintained at 10.5 to 11.5, and a 30% ammonia solution as an
additive was continuously supplied to the wet reactor at a flow
rate of 1/20 to 1/10 that of the aqueous transition metal
solution.
[0064] The flow rates of the aqueous transition metal solution, the
aqueous sodium hydroxide solution, and the ammonia solution were
adjusted so that average residence time thereof in the wet reactor
was approximately 6 hours.
[0065] The number of revolutions per minute of a stirrer during
reaction was maintained at 800 to 1000 rpm.
[0066] After reaching a normal state, a nickel-cobalt-manganese
composite transition metal precursor prepared through continuous
reaction for 20 hours was washed several times with distilled water
and dried in a constant temperature dryer at 120.degree. C. for 24
hours, resulting in obtainment of a nickel-cobalt-manganese
composite transition metal precursor.
Example 2
[0067] A transition metal precursor was prepared in the same manner
as in Example 1, except that, during reaction, the 30% ammonia
solution as an additive was continuously supplied to the wet
reactor at a flow rate of 1/10 to 1/5 that of the aqueous
transition metal solution.
Example 3
[0068] A transition metal precursor was prepared in the same manner
as in Example 1, except that the number of revolutions per minute
of the stirrer during reaction was maintained at 600 rpm to 800
rpm.
Comparative Example 1
[0069] Nickel sulfate, cobalt sulfate, and manganese sulfate were
mixed in a molar ratio of 0.45:0.15:0.40 to prepare a 1.5 M aqueous
transition metal solution, and a 3 M aqueous sodium hydroxide
solution was prepared.
[0070] The aqueous transition metal solution was added to a wet
reactor maintained at 45.degree. C. to 50.degree. C. and containing
distilled water, the aqueous sodium hydroxide solution was added
thereto so that pH of the distilled water inside the wet reactor
was maintained at 9.5 to 10.5, and a 30% ammonia solution as an
additive was continuously supplied to the wet reactor at a flow
rate of 1/20 to 1/10 that of the aqueous transition metal solution.
The flow rates of the aqueous transition metal solution, the
aqueous sodium hydroxide solution, and the ammonia solution were
adjusted so that average residence time thereof in the wet reactor
was approximately 6 hours.
[0071] The number of revolutions per minute of a stirrer during
reaction was maintained at 1200 to 1400 rpm.
[0072] After reaching a normal state, a nickel-cobalt-manganese
composite transition metal precursor prepared through continuous
reaction for 20 hours was washed several times with distilled water
and dried in a constant temperature dryer at 120.degree. C. for 24
hours, resulting in obtainment of a nickel-cobalt-manganese
composite transition metal precursor.
Comparative Example 2
[0073] A transition metal precursor was prepared in the same manner
as in Comparative Example 1, except that, during reaction, the
ammonia solution as an additive was not continuously supplied.
Experimental Example 1
[0074] 50 g of each of the transition metal precursor prepared
according to each of Examples 1 to 3 and Comparative Examples 1 and
2 was added to a 100 cc cylinder for tapping using a KYT-4000
measuring device (available from SEISHIN) and then was tapped 3000
times. In addition, powder distribution based on volume was
obtained using S-3500 (available from Microtrac), D50 values were
measured, and tap density with respect to D50 was calculated.
Results are shown in Table 1 below.
TABLE-US-00001 TABLE 1 Tap density D50 Tap density/D50 (g/cc)
(.mu.m) (g/cc cm) Example 1 1.42 5.62 2527 Example 2 1.52 5.66 2686
Example 3 1.60 5.70 2807 Comparative 1.99 5.48 3631 Example 1
Comparative 1.81 5.13 3528 Example 2
[0075] As shown in Table 1 above, it can be confirmed that the
transition metal precursors according to the present invention
(Examples 1 to 3) have a low ratio of tap density to D50, namely,
3500 or less, while the transition metal precursors of Comparative
Examples 1 and 2 have a high ratio of tap density to D50, namely,
3500 or more.
Experimental Example 2
[0076] Each of the transition metal precursors of Examples 1 to 3
and Comparative Examples 1 and 2 was mixed with Li.sub.2CO.sub.3 so
that a molar ratio of Li to Ni+Co+Mn was 1.10 and the mixture was
heated at a heating rate of 5.degree. C./min and calcined at
950.degree. C. for 10 hours, to prepare a lithium transition metal
oxide powder as a positive electrode active material.
[0077] D50 corresponding to powder distribution based on volume of
each of the prepared positive electrode active material powders was
measured using S-3500 (available from Microtrac) and each positive
electrode active material powder was subjected to ultrasonic
dispersion for 60 seconds. Subsequently, D50 corresponding to
powder distribution based on volume thereof was measured again.
Subsequently, changes in particle sizes before and after
pulverization following the two processes were calculated, and
results are summarized in Table 2 below.
TABLE-US-00002 TABLE 2 D50 of active material/D50 of D50 precursor
D50 (.mu.m) (changes in (.mu.m) of particle sizes of active before
and precursor material after calcination Example 1 5.62 5.65 1.005
Example 2 5.66 5.64 0.996 Example 3 5.70 5.68 0.996 Comparative
5.48 6.60 1.204 Example 1 Comparative 5.13 6.31 1.230 Example 2
[0078] As shown in Table 2 above, it can be confirmed that, in the
same transition metal composition, the lithium transition metal
oxides prepared from the transition metal precursors according to
the present invention (Examples 1 to 3) have small changes in
particle sizes before and after calcination, namely, 1.2 or less,
while the lithium transition metal oxides prepared from the
transition metal precursors of Comparative Examples 1 and 2 have
large changes in particle sizes before and after calcination,
namely, 1.2 or more.
Experimental Example 3
[0079] 10 g of the positive electrode active material powder using
each of the transition metal precursors of Examples 1 to 3 and
Comparative Examples 1 and 2 was added to a PDM-300 paste mixer,
alumina beads with a diameter of 5 mm were added thereto, and each
positive electrode active material powder was pulverized using a
ball mill under a condition of 600.times.600 based on revolutions
(rpm) per minute (rpm).times.revolutions per minute (rpm). The
pulverized active material powder was subjected to ultrasonic
dispersion for 60 seconds using S-3500 available from Microtrac and
then D50 corresponding to powder distribution based on volume
thereof was measured again.
[0080] Subsequently, changes in particle sizes before and after
pulverization following the two processes were calculated, and
results are summarized in Table 3 below.
TABLE-US-00003 TABLE 3 D50 D50 D50 after (.mu.m) (.mu.m)
pulverization/ before after D50 before pulverization pulverization
pulverization Example 1 5.65 5.05 0.894 Example 2 5.64 5.00 0.887
Example 3 5.68 4.98 0.847 Comparative 6.60 4.04 0.612 Example 1
Comparative 6.31 4.20 0.666 Example 2
[0081] As shown in Table 3 above, it can be confirmed that, in the
same transition metal composition, the lithium transition metal
oxides prepared from the transition metal precursors according to
the present invention (Examples 1 to 3) exhibit small changes in
particle sizes during pulverization and, thus, the positive
electrode active materials exhibit high strength. On the contrary,
the lithium transition metal oxides prepared from the transition
metal precursors of Comparative Examples 1 and 2 exhibit low
strength.
[0082] 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.
INDUSTRIAL APPLICABILITY
[0083] A transition metal precursor according to the present
invention has a lower tap density than conventional transition
metal precursors consisting of conventional transition metal
precursor particles, when average particle diameter D50 of the
transition metal precursor of the present invention is
substantially the same as those of conventional transition metal
precursors.
[0084] In this regard, the expression "substantially the same as"
means average particle diameter D50 within a measurement error
range of 0.2 .mu.m or less.
[0085] As a result, a lithium transition metal oxide prepared using
the transition metal precursor according to the present invention
exhibits a smaller change in average particle diameter D50 during
sintering, when compared with conventional lithium transition metal
oxides, and has a higher strength, when compared with lithium
transition metal oxides prepared using conventional transition
metal precursors.
[0086] Therefore, by using a lithium secondary battery using the
lithium transition metal oxide as a positive electrode active
material, breaking or crushing of lithium transition metal oxide
particles during rolling may be minimized and, as such, the lithium
secondary battery exhibits improved high temperature
characteristics, lifespan characteristics, and safety.
[0087] In addition, reduction in capacity may be minimized and
output characteristics may be improved.
* * * * *