REACTOR FOR PREPARWG PRECURSOR OF LITHIUM COMPOSITE
TRANSITION METAL OXIDE AND MJZTHOD FOR PREPARING
PRECURSOR
The present invention relates to a reactor for preparing a precursor of lithium
composite transition metal oxide and a method for preparing the precursor.
Technological development and increased demand for mobile equipment have
10 led to a rapid increase in the demand for secondaly batteries as energy sources.
Among these secondaty batteries, lithium secondaly batteries having high energy
density and voltage, long lifespan and low self-discharge are commercially available
and widely used.
Among components of lithium secondaty batteries, a cathode active material
15 has an important role in detennining capacity and performance of batteries.
Lithiutn cobalt oxide &iCoOz) having superior physical properties such as
superior cycle characteristics is generally used as a cathode active material. However,
-1-
cobalt used for LiCoO2 is a metal, so-called "rare metal", which is low in deposits and
are produced in limited areas, thns having an unstable supply. Also, LiCoO2 is
disadvantageously expensive due to unstable supply of cobalt and increased demand of
lithiinn secondary batteries.
Under these circumstances, research associated with cathode active materials
that are capable of replacing LiCoO2 has been contin~~ouslmya de. Representative
substitutes include lithium colnposite transition metal oxides containing hvo or more
transition metals of nickel (Ni), manganese (Mn) and cobalt (Co).
The lithium co~npositetr ansition metal oxide exhibits superior electrochemical
10 properties tluough combination of high capacity of lithium nickel oxide (LiNi02),
thermal stability and low price of manganese in layered-structure lithium manganese
oxide (LiMnO2), and stable electroche~nical properties of LiCoO2, but is not easy to
synthesize through a siinplc solid reaction.
Accordingly, the lithiutn composite transition tnetal oxide is prepared by
15 separately preparing a co~nposite transition metal precursor containing two or more
transition metals of nickel (Ni), manganese (Mn), and cobalt (Co) using a sol-gel
method, a hydrothermal method, spray pyrolysis, coprecipitation or the like, mixing
the composite transition metal with a lithium precursor, followed by mixing and baking
at a high temperature.
In terms of cost and production efficiency, a composite transition metal
precursor is generally prepared by coprecipitation.
In conventional methods, colnposite transition metal precursors were prepared
by coprecipitation, based on research that fociises 011 fortnation of spherical particles,
5 such as optimization of particle size, in order to prepare lithium composite transition
metal oxide that exhibits superior discharge capacity, lifespan, and rate characteristics
when used as a cathode active material. Structure properties of'composite transition
metal precursors as well as fortnation of spherical particles thereof are considerably
important.
However, a conventional coprecipitation reactor, for example, a continuous
stirred tank reactor (CSTR) has a problem of low retention time taken for controlling
the structure of composite transition metal precursors.
Also, .due to long retention time, precursor particles prepared using a
conventional coprecipitation reactor have a wide particle size distribution and a non-
15 uniform particle shape and contain a great amount of impurities.
Also, in a case in which precursor particles are prepared using a conventional
coprecipitation reactor, it is disadvantageously difficult to adjust the mean particle size
of the precursor particles to a level smaller than 6 p.
Therefore, the present invention has been made to solve the above problems
and other technical proble~nsth at have yet to be resolved.
As a result of a variety of extensive and intensive studies and experiments, the
inventors of the present invention have discovered that, when ring-shaped vortex pairs
that rotate in opposite directions are prepared in reaction areas that are opti~nized at
preparation of a precursor of lithium cornposite transition metal oxide for lithium
secondaly batteries, a retention time can be considerably reduced and uniform precursor
10 particles having a narrow particle size distribution and a small mean particle size can be
prepared. Based on this discovery, the present invention has been completed.
In accordance with one aspect of the present invention, provided is a reactor for
preparing a precursor of lithium cornposite transition metal oxide for lithium seconda~y
15 batteries, the reactor having a closed structure including: a stationa~yh ollow cylinder; a
rotary cylinder having the same axis as the stationary hollow cylinder and an outer
diameter stnaller than an inner diameter of the stationa~yh ollow cylinder; an electric
motor to generate power, enabling rotation of the rotary cylinder; a rotation reaction
area disposed behveen the stationary hollow cylinder and the rotary cylinder, wherein
ring-shaped vortex pairs that are uniformly arranged in a rotation axis direction and
rotate in opposite directions are formed in the rotation reaction area; and an inlet
through which a reactant fluid is fed into the rotation reaction area and an outlet through
5 which the reactant fluid is discharged from the rotation reaction area, wherein a ratio of
a distance between the stationary hollow cylinder and the rotaly cylinder to the outer
diameter of the rotaly cylinder is higher than 0.05 and lower than 0.4.
When a composite transition metal hydroxide is prepared using a conventional
coprecipitation reactor, for example, CSTR, a long retention time of about 6 hours or
10 more is required.
Meanwhile, when composite transition metal hydroxide is prepared using the
reactor of the present invention, a retention time of about 6 hours in maximum is
required and exhibits an about 1.5- to 10-fold increase in production amount per unit
volume of reactor, as compared to CSTR.
The effect can be obtained when the ratio of the distance behveen the
stationary hollow cylinder and the rotaly cylinder to the outer diameter of the rotary
cylinder is higher than 0.05. Specifically, when the ratio of the distance between the
stationaly hollo~vc ylinder and the rotary cylinder to the outer diameter of the rotary
cylinder is 0.05 or less, the distance behveen the stationa~y hollow cylinder and the
rota~y cylinder is excessively fine, making production impossible. Also, although
production is possible, disadvantageously, an active volume of rotation reaction area of
the vortex pairs produced is decreased and a retention time is thus greatly decreased.
Meanwhile, one vortex pair substantially serves as one fine CSTR, and vortex
5 pairs uniformly arranged along the rotational axis thus play the same role as connected
fine CSTRs. As the number of vortex pairs increases, flowability is enhanced.
However, since the size of one vortex pair is st~bstantially similar to the
distance between the stationary l~ollowc ylinder and the rotary cylinder, as the ratio of
the distance between the stationary hollow cylinder and the rotary cylinder to the outer
10 diameter of the rotary cylinder increases, or the distance between the stationary hollow
cylinder and the rotary cylinder increases, the number of the vortex pairs in the reactor
("number of CSTRs") gradually decreases.
Accordingly, when the ratio of the .distance between the stationa~y hollow
cylinder and the rotmy cylinder to the outer diameter of the rotary cylinder is 0.4 or
15 higher, formation of uniform precursor particles having a narrow particle size
distribution and a small mean particle size due to low flowability of the vortex pairs is
more difficult than when the ratio of the distance between the stationary hollow cylinder
and the rotary cylinder to the outer diameter of the rotaiy cylinder is higher than 0.05
and lower than 0.4.
Also, when the ratio of the distance between the stationary hollow cylinder and
the rotary cylinder to the outer diameter of the rota~yc ylinder is 0.4 or more, continuous
vortex properties of ring-shaped vortex pairs (vortex of "laminar flow"), wave voltexes,
. modulated wave vortexes and turbulent flow vortexes, which are uniformly arranged
5 along the rotation axis direction and rotate in opposite directions is not observed and
transition from the voltex region of the laminar flow to the vortex region of the
turbulent flow immediately occurs due to an increase in rotation speed of the rotary
cylinder. For this reason, flowability of the vortex pairs is deteriorated and production
of uniform precursor particles having a narrow particle size distribution and a small
10 mean particle size is thus difficult.
That is, composite transition metal hydroxide prepared using the reactor of the
present invention is prepared as uniform precursor particles having a s~nalpl article size
distribution and a small mean particle size, as compared to co~npositetr ansition metal
hydroxide prepared using CSTR, but this control of particle size distribution and mean
15 particle size can be obtained when the ratio of the distance between the stationary
hollow cylinder and the rota~yc ylinder to the outer diameter of the rotary cyli~ideri s
lower than 0.4.
The reactor is optimally designed for preparation of a precursor of lithium
co~npositetr ansition metal oxide, i.e., transition metal hydroxide, for lithium secondary
20 batteries. In this case, a kinematic viscosity of reactant fluid is 0.4 to 400 cP, and
-7-
power consumed per unit weight is 0.05 to 100 Wlkg. The power consumed per unit
weight is defined as a stirring speed of the rotaly cylinder.
A critical Reynolds number at which the vortex pairs are generated is about
300. The vortex pairs are formed over the entire surface of the rotation reaction area,
5 since fluids that flow between the stationaly hollow cylinder and the rotary cylinder that
have the same axis tend to travel in the stationary hollow cyliuder direction due to
centrifugal force and thus become unstable when the Reynolds number is 300 or more.
The reactor of the present invention enables production of i~nifonn precursor
particles having a smaller particle size, as compared to a case of the CSTR reactor,
10 using ring-shaped voltex pairs.
Specifically, the composite tra~lsition metal hydroxide prepared using CSTR
has a maximum mean particle size of 6 pm to 10 v, but the reactor of the present
invention enables preparation of precursor particles having a mean particle size smaller
than 6 pm. It is natural that composite transition metal hydroxide having a mean
15 particle size of 6 pm or more can be prepared using the reactor of the present inventio~~.
Also, composite transition metal hydroxide prepared using the reactor of the
present invention has a smaller particle size distribution than composite transition metal
hydroxide prepared using CSTR. A coefficient of variation conve~?ed from this
particle size distribution is within a range of 0.2 to 0.7. A coefficient of variation is a
value obtained by dividing a standard deviation by a mean particle diameter (D50).
In a specific embodiment of the present invention, composite trat~sition metal
hydroxide has a mean particle size of 1 pm to 8 pm, more specifically, 1 to 5 v. In
5 this case, the coefficient ofvariation may be within a range of 0.2 to 0.7.
Meanwhile, the inlet and/or outlet includes a stn~cturei t~cladingt wo or more
inlets and/or outlets, and more specifically, includes a structure it1 which two or more
inlets andlor outlets are spaced from one another on the statiot~aly cylinder by a
predetermined distatlce.
10' In a specific embodiment of the present invention, the reactor may include one
inlet and one outlet, and in some cases, include two or more inlets arrayed by a
predetermined distance in the outlet direction.
As such, in a case in which the two or more inlets are arrayed inthe outlet
directiot~b y a predetermined distance, raw materials may be injected into one inlet and
15 coating materials may be injected into the other inlet.
Also, the rotary cylinder has an outer surface provided with protrusions to
facilitate mixing of reactants.
The present invention also provides a method for preparing composite
transition metal hydroxide particles using the reactor.
The preparation method according to the present invention is characterized in
that composite transition metal hydroxide particles are produced by injecting raw
5 materials comprising an aqueous so111tion of two or more transition metal salts and an
aqueous solution of a complex-for~nit~agd ditive, and a basic aqueous solution for
maintailling pH of an aqueous solution of the raw materials within a range of 10 to 12,
into the rotation reaction area of the reactor through the inlet, and performing
coprecipitation reaction under a non-nitrogen atmosphere for 1 to 6 hours. The
10 composite trausition metal l~ydroxidep at-ticles can be obtained through the outlet.
Preferably, the transition metal salt has anions which are readily degraded and
volatile during baking, and may be sulfate or nitrate. Examples of the transition metal
sails include, but are not limited to, one or bvo or tnore selected from the group
consisting of nickel sulfate, cobalt sulfate, manganese sulfate, nickel nitrate, cobalt
15 nitrate and manganese nitrate.
Also, examples of the basic aqueous solution include all aqueous sodiutn
hydroxide solution, a11 aqueous potassium hydroxide solution, an aqueous lithium
hydroxide solution and the like. Preferably, the basic aqueous solution may be an
aqueous sodiutn hydroxide solutio~b~u, t is not limited thereto.
In a preferred embodiment, the aqueous solution of raw materials may further
comprise an additive andlor alkali carbonate that can form a complex with a transition
metal. The additive may be for example an ammonium ion donor, at1 ethylene dialnine
cotnpol~nd, a citric acid compound or the like. Examples of the arnmonium ion donor
5 include aqueous amtnonia, an ammoniucn sulfate aqueous solution, an ammo~~iu~n
nitrate aqueous solution and the like. The alkali carbonate may be selected from the
group consisting of ammonium carbonate , sodium carbonate, potassium carbonate and
carbonate lithium. In some cases, a combination of two or more of these alkali
carbonates may be also used.
10 The amounts of the added additive and alkali carbonate may be suitably
selected, taking into consideration amount of transition metal-containing salts, pH and
the like.
The inve~~toorfs t he present application identified that the anlount of complexforming
additive, for example, aqueous ammonia solutiot~, can be reduced, when
15 composite transition metal hydroxide is prepared in accordance with the preparation
method of the present invention.
In a specific embodiment of the present invention, the aqueous ammonia
solution is added in an amount of 5 to 90 mol%, based on the total amo11nt of two or
more transition metal salts.
As compared to a case in which composite transition metal hydroxide is
prepared using CSTR, a case it1 which composite transition metal hydroxide is prepared
only using about 60% of an additive, according to the preparation method of the present
invention, can provide lithium composite transition metal oxide at a relatively low cost.
The composite transition metal hydroxide may be a compound represented by
Formula 1 below:
wherein M comprises two or more selected from the group consisting of Ni,
Co, Mn, Al, Cu, Fe, Mg, B, Cr and transition metals of the second period; and 0Sx50.8.
In Fortnula 1, M cotnprises two or more selected from the elements defined
above. In a preferred embodiment, M comprises one or more transition metals
selected from the group consisting of Ni, Co and Mn, and is composed so that lithium
composite transition metal oxide can exhibit at least one physical property of the
transition metals. Patticularly preferably, M cotnprises two transition metals selected
15 from the group consisting of Ni, Co and Mn, or all of them.
As a preferred embodiment of a compound in which M comprises Ni, Co, Mn
or the like, a compound represented by Formula 2 below may be used.
wherein 0.35 b5 0.9, 0.15 c5 0.6, 05 d5 0.1, b+c+d5 1, 05 x5 0.8 and M"
is one, or two or more selected from the group consisting of AI, Mg, Cr, Ti and Si.
That is, the cotnpound of Formula 1 may be a compound of Formula 2 that comprises
Ni, Co and Mn and is partially substituted by one, or two .or more selected from the
5 group consisting of Al, Mg, Cr, Ti and Si.
The compound of For~nula2 contains a high Ni content and is thus particularly
preferably used in the preparation of a high-capacity cathode active material for lithium
secondary batteries.
The composite transition metal hydroxide has superior crystallinity as
10 compared to composite transition metal hydroxide using CSTR. Specifically, the
crystallinity may be evaluated, based on the content of impurities derived from
transition metal salts for preparing transition metal hydroxide.
The inventors of the present application demonstrated that the composite
transition metal hydroxide contains 0.4% by weight or less of impurities derived from
15 transition metal salts for preparing transition metal hydroxide, based on the total weight
of the co~npositetr ansition metal hydroxide particles.
The impurity may be a salt ion containing a sulfate ion (SO?.). The tsansition
metal salt derived from the sulfate ion containin^ in^ salt ion may be sulfate and
examples of sulfate include nickel sulfate, cobalt sulfate, manganese sulfate and the
like. The sulfate may be used alone or in combhiation of two or more thereof.
In some cases, the sulfate ion (~04~-)-contaitiisnal~t ion may further contain a
nitrate ion (NO<) and the nitrate ion may be derived from transition metal salts
5 including nickel nitrate, cobalt nitrate and manganese nitrate.
More preferably, the content of the sulfate ion co containin^ in^ salt ion is 0.3
to 0.4% by weight, based on the total weight of the co~nposite transition metal
hydroxide particles.
Methods for measuring the content present in the precursor inay be varied and,
10 preferably, detection using ion chromatography defined below may be used.
The present invention also provides lithium composite transition metal oxide
prepared by baking the precursor particles together with a lithium precursor.
The reaction conditio~is of the transition metal precursor and the lithiumcontaining
inaterial for preparation of lithium co~npositetr ansition metal oxide are well-
15 known in the art and a detailed description thereof is omitted herein.
The lithitun precursor may be used without particular limitation and examples
thereof include lithiotil hydroxide, lithium carbonate, lithium oxide and the like.
Preferably, the lithium precursor is lithium carbonate (Li2CO3) and/or lithium hydroxide
(LiOH).
Meanwhile, manganese (Mn) is readily oxidized and becomes MII~'. For
exatnple, MII" makes formatiot~o f homogeneous composite oxide with ~ i 2 'd ifficult.
5 For this reason, conventional coprecipitatiot~ methods include further introduction of
additives to prevent formation of Mn oxide. Since the preparation method according
to the present invention is performed in a sealed reactor, a risk of formation of Mn oxide
caused by incorporation of exterior air in the reaction solution can be eliminated.
Accordingly, advantageously, the preparation method according to the present
10 invention is performed under a non-nitrogen atmosphere witl~oout adding a reducing
agent, for exatnple, nitrogen, thus advantageously reducing nitrogen addition costs and
improving process efficiency.
As apparent from the afore-going, the reactor of the present invention is
15 effective in reducing retention titne and providing uniform precursor particles having a
small size.
Also, the preparation method according to the present invention provides
precursor particles having a low impurity content and high crystallinity.
As a result, the precursor particles prepared by the preparation method
according to the present invention is effective in improving reactivity with lithium
precursors, reducing baking tetnperature of lithium composite transition metal oxide,
and improving electroche~~~icparol perties such as rate characteristics and low- .
5 temperahre characteristics.
Also, the preparation method according to the present invention reduces
cons~im~tioonf energy per unit volume and provides a lithium composite transition
tnetal oxide at a low cost due to use of relatively small amounts of complex-formiag
additives.
FIG. 1 is a schematic side view illustrating a reactor according to one
embodiment of tlie present invention;
FIG. 2 is a schematic view illustrating flow behaviors of ring-shaped Gortex
pairs and reactant fluids generated in rotati011 reaction area of the reactor of FIG. 1;
15 FIG. 3 is a schematic side view illustrating a reactor according to another
etnbodiment of the present invention;
FIG. 4 is a graph showing comparison in power consumed per ut~it weight
between a CSTR and a reactor according to the present invention;
-16-
FIG. 5 is a graph showing a particle size distribution of precursor particles
(mean particle dianleter (D50) : 4.07 pm) of Exatnple 1;
FIGS. 6A and 6B are SEM images of Example 1 and Comparative Example 1,
as specific exarnples of the present invention; and
5 FIG. 7 is a graph showing electrochemical properties of lithium secondaly
batteries prepared in accordance with the method according to one embodiment of the
present invention.
Now, the present invention will be described in more detail with reference to
10 the following examples. These examples are provided only to illustrate the present
invention and should not be construed as limiting the scope and spirit of the present
invention.
FIG. 1 is a schematic side view illustrating a reactor according to one
e~nboditnent of the present invention, FIG. 2 is a schematic view illustrating fIow
15 behaviors of ring-shaped vortex pairs and reactant fluids generated in rotation reaction
area of the reactor of FIG. 1, and FIG. 3 is a schematic side view illustrating a reactor
according to another embodiment of the present invention.
Referring to FIG. 1, a reactor 100 for preparing a precursor of lithium
composite transition metal oxide for lithium secondary batteries according to the present
invention include a rotaly cylinder 120 mounted in the stationa~yh ollow cylinder 110,
wherein the rota~yc ylinder 120 has the same rotation axis as the stationaly hollow
5 cylinder 110 and has an outer diameter (2xr2) smaller than an inner diameter (2x11) of
the stationary hollow cylinder, rotation reaction area is formed between the stationary
hollow cylinder 110 and the rotary cylinder 120, a plurality of inlets 140, 141 and 142,
through which reactant fluids are injected into the rotation reaction area, and an outlet
150, through which reactant fluids are discharged from the rotation reaction area, are
10 formed on the stationa~y hollow cylinder 110, and an electric motor 130 to generate
power, enabling rotation of the rotary cylinder 120, is provided at a side of the
stationary hollow cylinder 110.
A ratio (dlr2) of the distance (d) between the stationary hollow cylinder 110
and the rotary cylinder 120 to the outer diameter (r2) of the rotaty cylinder 120
15 determines an effective volntne of the rotation reaction area,
Referring to FIGS. 1 and 2, when the rotary cylinder 120 is rotated by the
power generated fiom the electric motor 130 and an Reynolds number reaches a critical
level, reactant fluids such as aqueous solution of composite transition metal hydroxide,
aqueous atntnonia solution and an aqueous sodium hydroxide solution injected into the
20 rotation reaction area through the inlets 140, 141 and 142 receive centrifugal force in
-18-
the direction of the stationaly hollow cylinder 110 from the rotary cylinder 120 and thus
become unstable. As a result, ring-shaped vortex pairs 160 rotating in opposite
directions along the rotation axis direction are uniformly arrayed.
The length of the ring-shaped vortex pairs 160 in a direction of gravity is
5 substantially equivalent to the distance (d) between the stationary hollow cylinder 110
and the rotary cylinder 120.
In order to prevent permeation of air into the gap between a rotation axis and a
bear ring doring rotation of the rotary cylinder 120, the rotation axis may be sealed
using a sealing material such as O-ring.
10 Referring to FIGS. 1 and 3, reactant materials such as aqueous transition metal
salt solution, aqueous ammonia solution and aqueous sodium hydroxide solution may
be injected through the inlet 140 into the rotation reaction area and different kinds of
materials such as coating materials lnay be injected through the inlet 141 or the inlet
142 into the rotation reaction area.
As shown in FIG. 3, a reactor according to another embodiment of the present
invention includes storage tanks 180 and 181 to store reactant fluids such as at1 aqueous
transition metal salt solution, a11 aqueous ammonia soliitio~a~nd an aqueous sodium
hydroxide solution, and a metering pump 170 to control an amount of reactant fluids
injected into the rotation reaction area.
The aqueous transition metal salt solution may be injected into rotation
reaction area using the metering pump 170, while taking into consideration retention
time, the aqueous sodium hydroxide solution may be variably injected into the rotation
reaction area using the metering pump 170 such that pH is maintained at a
5 predetermined level, and the aqueous ammonia solution may be continnously supplied
through the metering putnp 170.
After co~npletion of reaction, the composite transition metal hydroxide is
obtained through the outlet 150.
The reactor 100 may further include a heat exchanger mounted on the
10 stationary hollow cylinder 110, to control a reaction temperature in the process of
mixing reactant fluids using vortex pairs 160 in the rotation reaction area between the
stationary hollow cylinder I10 and the rotary cylinder 120, and the heat exchanger may
be selected fiom heat exchangers weii-known in the art to which the present invention
pertains.
FIG. 4 is a graph showing comparison in power consumed per unit weight
between a CSTR and a reactor according to the present invention. A 4L CSTR
consumes a rotation power of 1,200 to 1,500 rptn to obtain a desired particle size in
precursor synthesis. This power is about 13 to 27 Wkg, when converted into a
rotation power per unit weight (region A). Meanwhile, the 0.5 L reactor according to
the present invention enables synthesis of precursors having a desired particle size in a
rotation power range of 600 to 1,400 rpm. This power is about 1 to 8 Wlkg, when
converted into a rotation power per unit weight (region B).
That is, the reactor of the present invention enables synthesis of precursors
5 having desired particle size using at a lower stirring power per unit weight, as compared
to CSTR. This mans that the reactor of the present invention has superior stirring
efticiet~cya s compared to CSTR.
Nickel sulfate, cobalt sulfate and manganese sulfate were mixed at a ratio
10 (molar ratio) of 0.50 : 0.20 : 0.30, a 1.5M aqueous transition metal solution was
prepared and a 3M aqueous sodiu~nh ydroxide solutio~w~a s then prepared. As the
ammonia solution, an aqueous solution in which amtnonium ions are dissolved at
25wt% was prepared.
The prepared aqueous transition metal solutio~w~a s injected into the reactor
15 using the metering pump for a retention titne of one hour. The aqueous sodium
hydroxide solutio~w~a s variably injected using a metering pump such that pH is
maintained at 11.0. The aqueous ammonia solution was continuously supplied at a
concentration of 30 mol%, based on the aqueous transition metal solution.
The mean retention time was one hour, the reaction was continued for 20 hours
after reached in a normal state, aud the resolting nickel-cobalt-manganese composite
transition metal precursor was washed with distilled water several times, and dried in a
120°C constant-temperature drier for 24 hours, to prepare a nickel-cobalt-manganese
5 composite transition metal precursor.
A nickel-cobalt-manganese composite transition metal precursor was prepared
in the same manner as in Example 1, except that supply amounts were changed so as to
adjust the retention time to 2 hours.
A nickel-cobalt-manganese composite transition metal precursor was prepared
in the same manner as in Example 1, except that supply amounts were changed so as to
adjust the retention time to. 3 hours.
A nickel-cobalt-manganese co~npositetr ansition tnetal precursor was prepared
in the same manner as in Example 1, except that supply amounts were changed so as to
adjust the retention time to G hours.

A nickel-cobalt-manganese composite transition metal precursor was prepared
in the same manner as in Example 4, except that a continuous stirred tank reactor
(CSTR) was used and an aqueous ammonia solution was added at a concentration 50
mol% of the aqueous transition metal solution.
- Comparison in production amount per reactor
volume according to retention time
Production amounts according to volumes of the reactors used in Examples 1
to 4 and Comparative Example 1 were compared and the results thus obtained are
shown in Table 1 below.
TABLE 1
- Analysis of impurity colltent
0.01 g of the prepared transition tnetal precursor was accurately metered and
Production amount per reactor volume
(g/L-hr)
5 . 4
27.7
18.5
9.2
6.1
Ex. 1
Ex. 2
Ex. 3
Ex4
Cotnp. Ex. 1
added to a 50 tnL coming tube, and a small amount of acid was added dropwise thereto,
-23-
Retention time
1 hour
2 hours
3 hours
6 hours
6 hours
followed by mixing while shaking. When the mixed sample was co~npletelyd issolved
and was transparent in color, a concentration of SO4 in the sample was measured using
an Ion Chromatograph (DX500, model produced by Dionex Corp.). The results thus
obtained are shown in Table 2 below.
TABLE 2
Retention t h e SO4 concentration (wt%)
I I .
I I
Ex. 1 0.40
I I
1 hour
Ex. 2 0.38
I I
- Particle size distribt~tiong raph
2 hours
Ex. 3 0.34
I I
FIG. 5 is a graph showing a particle size distribution of precursor particles
(mean particle diameter (D50): 4.07 pm) of Example 1, and FIGS. 6A and 6B are SEM
3 hours
Ex. 4 0.30
images of Example 1 and Co~nparativeE xalnple 1, as specific examples of the present
6 hours
Comp. Ex. 1 0.45
10 invention.
6 l~oours
The following Table 3 shows mean pa~ticle sizes (D50) and coefficient of
variation of precursor particles of Exalnple 1 and Comparative Example 1. It can be
seen from Table 3 that the precursor particles of Exalnple 1 had a mean particle
diameter of 5 pm or less, and coefficient of variation thereof had a single distribution of
0.375. On the other hand, the precursor particles of Comparative Example 1 had a
mean particle diameter larger than 8 pm, and coefficient of variation thereof was 0.706.
The precursor particles of Comparative Example 1 exhibited bad single distribution, as
5 compared to precursor particles of Example 1.
TABLE 3
- Production of coin cells and evaluation of
electrochemical properties
The prepared transition metal precursors and Li2C03 were mixed at a ratio
10 (weight ratio) of 1 : 1, heated at an elevation speed of S0C/tnin and baked at 920°C for
C.V.
0.375
0.706
Ex. 1
Comp. Ex. 1
10 hours to prepare a lithium composite transition metal oxide powder (catliode active
material). The cathode active material powder thus prepared was mixed with Denka as
a conductive agent and KF 1100 as a binder at a weight ratio of 95 : 2.5 : 2.5 to prepare
a slurry, and the slurry was uniformly coated on an A1 foil with a thickness of 20 pm.
15 The coated material was dried at 130°C to produce a cathode for lithium secondary
batteries.
Mean particle size (D50)
4.07 pil
9.46 pnl
2032 coin cells were produced using the cathode for lithiitm secondary
batteries thus produced, a lithium rnetal foil as a counter electrode (anode), a
polyethylene membrane (Celgard, thickness: 20 pm) as a separation membrane, and a
.liquid electrolyte in which 1M LiPF6 was dissolved in a mixed solvent containing
5 ethylene carbollate, dimethylene carbonate and diethyl carbonate at a ratio of 1 : 2 : 1.
For the coin cells, electric properties of cathode active material were evaluated
using an electrochemical analyzer (Toyo System, Toscat 3100U) at 3.0 to 4.25V. The
results thus obtained are shown in Table 4.
TABLE 4
disclosed for illustrative purposes, those skilled in the art will appreciate that various
2ClO. 1 C
("/.I
88.5
87.9
87.8
87.0
85.2
Althongll the preferred embodiments of the present invention have been
Initial efficiency
("/.I
89.8
89.1
89.4
89.6
87.6
Ex. 1
Ex. 2
Ex. 3
Ex. 4
Comp. Ex. 1
Initial discharge
capacity
(mAldgI
168.3
167.3
166.9
166.8
165.2
modifications, additions and substitutions are possible, without departing from the
scope and spirit of the invention as disclosed in the accompanying claims.
[Claim 1) A reactor for preparing a precursor of lithium composite transition
tnetal oxide for lithium secondary batteries, the reactor having a closed structure
comprising:
a stationary hollow cylinder;
a rotaiy cylinder having the same axis as the stationary hollow cylinder and an
outer diameter smaller than an inner diameter of the stationaly hollow cylinder;
an electric motor to generate power, enabling rotation of the rotary cylinder;
a rotation reaction area disposed behveen the stationa~yh ollow cylinder and
10 the rotary cylinder, wherein ring-shaped voltex pairs that are uniformly arranged in a
rotation axis direction and rotate in opposite directions are formed in the rotation
reaction area; and
an inlet though which a reactant fluid is fed into the rotation reaction area and
an outlet through which the reactant fluid is discharged froin the rotation reaction area,
wherein a ratio of a distance behveen the stationary hollow cylinder
and the rotary cylinder to the outer diameter of the rotary cylinder is higher than 0.05
and lower than 0.4.
[Claim 2) The reactor according to claim 1, wherein a kinematic viscosity of
reactant flnid is 0.4 to 400 cP and power consumed per unit weight thereof is 0.05 to
100 Wlkg.
[Claim 3) The reactor according to claim 1, wherein a critical Reynolds number
5 of the vortex pairs is 300 or more.
[Claim 4) The reactor according to claim 1, wherein the inlet comprises two or
more inlets.
[Claim 5) The reactor according to claim 4, wherein the two or more inlets are
arrayed in a line by a predetermined distance in a direction of the ot~tlet.
10 [Claim 6) A method for preparing transition metal composite hydroxide particles
using the reactor according to any one of claims 1 to 5, the method comprising:
injecting raw materials comprising an aqueous solution of two or more
transition metal salt's and an aqueous solution of a complex-fonning additive, and a
basic aqueous solt~tion for maintaining pH of an aqueous solution of the raw materials
15 within a range of 10 to 12, into the rotation reaction area of the reactor through the inlet;
and
performing coprecipitation reaction under a aon-nitrogen atmosphere for I to 6
hours.
[Claim 7) The method according to claim 6, wherein the aqueous solution of a
complex-forming additive is present in an amount of 0.01 to 10% by weight, based on
the total amount of the two or more transition metal salts.
[Claim 8) The method according to claim 7, wherein the aqueous solution of a
5 complex-forming additive is an aqueous ammonia solution.
[Claitn 9) The method according to claim 6, wherein the transition metal salt is
sulfate and/or nitrate.
[Claim 10) The method according to claim 9, wherein the sulfate comprises one
or two or more selected fiotn the group consisting of nickel sulfate, cobalt sulfate and
10 manganese sulfate, and the nitrate comprises one or two or more selected from the
group consisting of nickel nitrate, cobalt nitrate and manganese nitrate.
[Claim 11) The tnethod according to claim 6, wherein the transition metal
composite hydroxide is a compound represented by orm mu la' 1 below:
15 wherein M comprises two or more selected from the group consisting of Ni,
Co, Mn, Al, Cu, Fe, Mg, B, Cr and transition metals of the second period; and
05 ~50.8.
(Claicn 12) The method according to claim 11, wherein M co~ilprisestw o kinds of
transition metals or all selected from the group consisting of Ni, Co and Mn.