WO2013042986A2

WO2013042986A2 - Apparatus using couette-taylor vortex reaction equipment for preparing precursor of cathode active material for lithium secondary battery

Info

Publication number: WO2013042986A2
Application number: PCT/KR2012/007594
Authority: WO
Inventors: Hyung Mo Kim; Byoung Soo Kim; Young-Ho RHO
Original assignee: Skc Co., Ltd.
Priority date: 2011-09-21
Filing date: 2012-09-21
Publication date: 2013-03-28
Also published as: KR101275845B1; WO2013042986A9; WO2013042986A3; KR20130031588A

Abstract

There is provided an apparatus for preparing a cathode active material precursor for a lithium secondary battery, comprising: a Couette-Taylor reactor where a reaction mixture comprising a solution of mixed metal salts and an alkali solution is admixed to be coprecipitated to form a slurry including the cathode active material precursor; a particle separation unit comprising a separation tank connected to the Couette-Taylor reactor through a slurry supply line and a pulverizer for pulverizing the slurry including the cathode active material precursor, wherein the cathode active material precursor is separated and recovered; and a precipitation unit connected to the Couette-Taylor reactor through a waste solution discharge line, wherein a waste solution discharged from the Couette-Taylor reactor is cooled such that an alkali salt is precipitated and removed.

Description

DESCRIPTION

APPARATUS USING COUETTE-TAYLOR VORTEX REACTION EQUIPMENT FOR PREPARING PRECURSOR OF CATHODE ACTIVE MATERIAL FOR LITinUM SECONDARY BATTERY

FIELD OF THE INVENTION

The present invention relates to an apparatus for preparing a cathode active material precursor for a lithium secondary battery, and, more particularly, to an apparatus for preparing a cathode active material precursor for a lithium secondary battery using Couette-Taylor vortexes.

BACKGROUD OF THE INVENTION

As technologies for mobile appliances become more advanced and the demand for mobile appliances increases, there has been a rapid rise in the demand for secondary batteries as an energy source. Among such secondary batteries, lithium secondary batteries are commonly and widely used because they have high energy density, a high operating voltage, a long lifecycle and a low self-discharge rate.

Litlii n-containing cobalt oxide (LiCoO₂) is generally used as a cathode active material of a lithium secondary battery. Additionally, the use of Uthium-containing manganese oxide such as LiMnO₂ having a layered ciystal structure, LiMn₂O having a spinel crystal structure or the like, Uthium-containing nickel oxide (LiNiO₂) or lithium- containing three-component oxide (LiNi_xMn_yCO₍i_-x-y)0₂) as the cathode active material is also being considered. Generally, a cathode active material of a lithium secondary battery is prepared by a solid-state reaction at a high temperature of 700 ^°C or more. However, the method of preparing a cathode active material using a solid-state reaction is problematic in that, since raw materials are physically mixed and pulverized, the obtained mixture is nonuniform, so that the mixture must be further mixed and pulverized several times, with the result that the time required to prepare the cathode active material increases, thereby increasing the manufacturing cost thereof.

For this reason, a wet method represented by a sol-gel process including hydrolysis and condensation and a co-precipitation process was developed.

Here, the co-precipitation process is a process of preparing oxide powder by precipitating chloride, nitride or sulfide into hydroxide using a co-precipitation solution and then calcining the hydroxide precipitate. In order to prepare a cathode active material using the co-precipitation process, the pH, temperature and stirring condition of the co-precipitation solution must be controlled.

Conventionally, the preparation of a cathode active material using a co- precipitation process has been carried out using a continuous stirred tank reactor (CSTR). However, the preparation of a cathode active material using the CSTR was problematic in that it is not easy to scale up the reaction, the force causing eddies is changed depending on the distance from the turbine in the reactor, there is an increase in equipment cost and energy dissipation, and it is difficult to apply the CSTR to a continuous process.

In order to solve the above problem with the CSTR, a reactor using Couette- Taylor vortex was considered (Korean Unexamined Patent Application PubUcation No. 2010-0112843). However, this reactor has been used to conduct general mixing, extraction and chemical reaction, but has not been used to prepare a cathode active material. SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a novel apparatus for preparing a cathode active material which can solve the above problems.

It is another object of the present invention to provide a method of preparing a cathode active material precursor by using the apparatus according to the present invention.

In order to accomplish the above object, an aspect of the present invention provides an apparatus for preparing a cathode active material precursor for a lithium secondary battery, comprising:

a Couette-Taylor reactor where a reaction mixture comprising a solution of mixed metal salts and an alkali solution is admixed to be coprecipitated to form a slurry including the cathode active material precursor;

a particle separation unit comprising a separation tank connected to the Couette-Taylor reactor through a slurry supply line and a pulverizer for pulverizing the slurry including the cathode active material precursor, wherein the cathode active material precursor is separated and recovered; and

a precipitation unit connected to the Couette-Taylor reactor through a waste solution discharge line, wherein a waste solution discharged from the Couette-Taylor reactor is cooled such that an alkali salt is precipitated and removed.

According to the method of preparing a cathode active material precursor for a lithium secondary battery of the present invention, since the cathode active material precursor is prepared using a Couette-Taylor reactor, the cathode active material can be prepared in a short period of time to increase productivity, the particle size distribution of the prepared cathode active material can be improved, and the size of the reactor can be reduced so that the space for providing equipment is used more efficiently. Further, the apparatus and method for manufacturing a cathode active material precursor for a lithium secondary battery according to the present invention have many advantages, such as the reduction of waste water containing the alkali salts (side products) occurring during co-precipitation, the reduction of waste water over the entire process, the reduction of impurities in products, the improvement of production yield, and the like.

BRIEF DESCRIPTION OF DRAWINGS The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view showing an apparatus for preparing a cathode active material precursor for a lithium secondary battery according to the present invention;

FIG. 2 is a schematic view showing the Couette-Taylor reactor used in the apparatus for preparing a cathode active material precursor for a lithium secondary battery according to the present invention;

FIG. 3 is scanning electron microscope (SEM) photographs of the cathode active material precursors according to the present invention;

FIG. 4 is a graph of the results of X-ray diffraction analysis of the cathode active material precursors according to the present invention;

FIG. 5 is a graph of the charge-discharge capacity of the hthium secondary battery which was prepared by using the cathode active material precursors according to Example 1;

FIG. 6 is a graph of the charge-discharge capacity of the lithium secondary battery which was prepared by using the cathode active material precursors according to Example 2;

FIG. 7 is a graph of the charge-discharge capacity of the lithium secondary battery which was prepared by using the cathode active material precursors according to Example 3;

FIG. 8 is a graph of the charge-discharge capacity of the lithium secondary battery which was prepared by using the cathode active material precursors according to Example 4;

FIG. 9 is a graph of the charge-discharge capacity of the lithium secondary battery which was prepared by using the cathode active material precursors according to Example 5;

FIG. 10 is a graph of the charge-discharge capacity of the lithium secondary battery which was prepared by using the cathode active material precursors according to Comparative Example 1.

[Reference Numerals]

100: Couette-Taylor reactor 110: outer cylinder

111: first outlet 112: second outlet

120: rotary cylinder 121: closing wall

130: drive motor 131: motor shaft

140: inlet 150: bearing

160: outer cover 170: reaction mixture supply line

113: waste solution discharge line

200: particle separation unit

210: separation tank 211: ultrasonic generator

212: driving unit 220: slurry discharge line (or slurry supply line)

230: fine particle circulation line

240: storage tank 300: precipitation unit

310: first heat exchanger.

320: precipitation tank

321: waste water discharge line

330: chiller 340: second heat exchang

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be described in detail.

An apparatus for preparing a cathode active material precursor for a lithium secondary battery of the present invention, comprising:

The cathode active material precursor may be nickel-cobalt-manganese hydroxide represented by Formula 1 below: [Formula 1]

Ni_xCo_yMr^.^OH^

wherein 0.33 < x < 0.80, 0 < y < 0.33, 0 The cathode active material precursor may be prepared by precipitating the nickel-cobalt-manganese hydroxide precursor particles.

The mixed metal salt solution may be a mixture of nickel sulfate, cobalt sulfate and manganese sulfate.

The concentration of the mixed metal salt solution may be 1.0 ~ 4.0 M, preferably, 1.5 ~ 3.0 M. When the concentration thereof is less than 1.0 M, the yield of precursor particles is reduced.

The prepared cathode active material precursor is mixed with a suitable amount of a lithium raw material, and then the mixture is calcined at 800 ~ 1300°C for 15 - 24 hours to prepare a cathode active material including lithium-transition metal composite oxide. When the calcination process is conducted, the cathode active material particles are stably grown, and the adhesivity between crystals is improved, thus obtaining cathode active material particles having uniform particle size.

Meanwhile, the lithium-transition metal composite oxide prepared using the precursor containing Ni, Co and Mn exhibits excellent lifecycle characteristics when it is charged in a voltage of 4.3 V. However, when it is charged and discharged in a high voltage range of 4.5 V or more, its lifecycle characteristics remarkably deteriorate.

In order to solve the above problem, the Uthium-transition metal composite oxide is doped with a metal selected from the group consisting of Fe, Ga, Ge, Al, Ti, V, Cu, Zn, Si, P, Nb, Ta, Zr, Zn, Sn, Sb, Pt, hi, Ag, Au, Bi, Pd, W and Nb, thus remarkably improving the lifecycle characteristics thereof in a high voltage range. The doping of the lithium-transition metal composite oxide using the metal may be performed by additionally introducing a metal salt solution including the metal selected from the group consisting of Fe, Ga, Ge, Al, Ti, V, Cu, Zn, Si, P, Nb, Ta, Zr, Zn, Sn, Sb, Pt, In, Ag, Au, Bi, Pd, W and Nb in the step of introducing the mixed metal salt solution into a reactor.

The alkali solution may be a sodium hydroxide solution or an aqueous ammonia solution, or may include both a sodium hydroxide solution and an aqueous ammonia solution.

The sodium hydroxide solution or the aqueous ammonia solution can be used as a coprecipitating agent, and serves to appropriately control the pH of the metal salt solution introduced into the reactor.

The pH of the metal salt solution introduced into the reactor may be 10 ~ 13, preferably, 11 ~ 12. When the pH of the metal salt solution is less than 10, a part of the precursor particle precipitate is redissolved, and thus the desired composition ratio of the prepared precursor particles cannot be obtained. Further, when the pH thereof is more than 13, spherical precursor particles cannot be obtained, thus deteriorating the uniformity of the precursor particles.

The reaction mixture comprising the mixed metal salt solution and the alkali solution is introduced, stirred and coprecipitated to obtain a reaction product (a slurry) including precursor particles.

The stirring speed of the Couette-Taylor reactor may be 500 ~ 1000 rpm.

When the stirring speed thereof is less than 500 rpm, particles do not sufficiently collide with each other, and thus the agglomeration efficiency of particles becomes low. Further, when the stirring speed thereof is more than 1000 rpm, the collision frequency and collision strength of particles excessively increase to inhibit particles from agglomerating, thereby making it difficult to prepare precursor particles having the desired size. The method of preparing a cathode active material precursor for a lithium secondary battery according to the present invention comprises the steps of:

admixing a reaction mixture comprising a solution of mixed metal salts and an alkali solution in a Couette-Taylor reactor, wherein the reaction mixture is coprecipitated to form a slurry including the cathode active material precursor;

pulverizing the slurry including the cathode active material precursor in a particle separation unit comprising a separation tank connected to the Couette-Taylor reactor through a slurry supply line and a pulverizer, wherein the cathode active material precursor is separated and recovered; and

cooling a waste solution discharged from the Couette-Taylor reactor through a waste solution discharge line in a precipitation unit, wherein an alkali salt is precipitated and removed.

Hereinafter, an apparatus for preparing a cathode active material precursor for a lithium secondary battery according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic view showing an apparatus for preparing a cathode active material precursor for a lithium secondary battery according to an embodiment of the present invention.

Referring to FIG. 1, the apparatus for preparing a cathode active material precursor for a lithium secondary battery according to the present invention comprises: a Couette-Taylor reactor 100 where a reaction mixture comprising a solution of mixed metal salts and an alkali solution is admixed to be coprecipitated to form a slurry including the cathode active material precursor; a particle separation unit 200 for pulverizing agglomerated particles in the slurry obtained from the Couette-Taylor reactor 100 to separate the desired cathode active material precursor; and a precipitation unit 300 for continuously removing an alkali salt, which is a byproduct obtained during a coprecipitation reaction, to miriimize the generation of alkali salt-containing waste water.

Since the apparatus for preparing a cathode active material precursor for a hthium secondary battery according to the present invention further comprises the particle separation unit 200 for continuously and efficiently separating precursor particles and the precipitation unit 300 for removing an alkali salt, which is a byproduct, in addition to the Couette-Taylor reactor 100, uniform precursor particles can be produced with high yield and the occurrence of waste water can be minimized.

FIG. 2 is a schematic view showing the Couette-Taylor reactor 100 used in the apparatus for preparing a cathode active material precursor for a lithium secondary battery according to the present invention.

Referring to FIG. 2, the Couette-Taylor reactor 100 includes: an outer cylinder 110 which is provided at one end thereof with a first outlet 111 and a second outlet 112; and a rotary cylinder 120 which is provided in the outer cylinder 110 with a predetermined interval therebetween and is rotated by a drive motor 130, one end of which is located at the first inlet 111 and second inlet 112 of the outer cylinder 110 and is blocked by a closing wall 112, and the other end of which defines a passage between the outer cylinder 110 and the rotary cylinder 120.

The one end of the rotary cylinder 120 is provided with an inlet 140 that passes the outer cylinder 110 and is located near the closing wall 121 of the outer cylinder 110.

The outer cylinder 110 is provided with auxiliary inlets 141 through which reactants are additionally supplied. Both ends of the outer cylinder 110 are provided with pH sensors 180 such that the pH in the Couette-Taylor reactor 100 is measured and controlled. The outer cylinder 110 is provided with an outer cover 160, and a coolant flows between the outer cylinder 110 and the outer cover 160. The coolant is introduced through a coolant inlet 190, and serves to maintain the temperature of the outer cylinder 110. The introduced coolant is discharged through a coolant outlet 191, and is circulated by a coolant pump (not shown).

The space between a shaft 131 of the drive motor 130 and the outer cylinder 110 may be sealed such that reactants do not leak from the reactor, and may be provided with a bearing 150 such that the shaft 131 of the drive motor 130 easily rotates.

It is preferred that the reactants introduced through the inlet 140 flow between the outer cylinder 110 and the rotary cylinder 120 along the longest distance in an axial direction.

In the above-configured Couette-Taylor reactor 100 included in the apparatus for preparing a cathode active material for a lithium secondary battery according to the present invention, when a mixed metal salt solution and an alkali solution, which are a reaction mixture, are introduced into the reactor 100, the reaction mixture flows between the outer cylinder 110 and the rotary cylinder 120, and, when the rotary cylinder 120 is rotated by the operation of the drive motor 130, eddy flux, that is, Taylor vortexes are formed between the outer cylinder 110 and the rotary cylinder 120, and move along in the axial direction. Subsequently, the reaction mixture flows between the outer cylinder 110 and the rotary cylinder 120, and moves along an axial direction while forming Taylor vortexes. The reaction product is discharged through the first outlet 111 of the external cylinder 110.

As such, when the Couette-Taylor reactor 100 is used, since Couette-Taylor vortexes are formed between the outer cylinder 110 and the rotary cylinder 120, the introduced reaction mixture is efficiently reacted, so that a cathode active material precursor can be prepared in a short reaction time to increase the productivity thereof, and the particle size distribution of the prepared cathode active material precursor can become unifonn, and the space in the reactor 100 can be efficiently used.

Referring to FIG. 1 again, a reaction mixture supply line 170 for introducing a reaction mixture of a mixed metal salt solution and an alkali solution, a fine particle circulation line 230 connected to the particle separation unit 200, a slurry discharge line 220 connected to the particle separation unit 200, and a waste solution discharge line 113 connected to the precipitation unit 300 are respectively connected to the Couette- Taylor reactor 100.

The reaction mixture of a mixed metal salt solution and an alkali solution is continuously introduced into the Couette-Taylor reactor 100, and then stirred and coprecipitated to obtain a reaction product. The reaction product, the amount of which is equivalent to that of the introduced reaction mixture, is discharged to the particle separation unit 200 in the form of a slurry through the slurry discharge line 220 connected to the first outlet 111 of the Couette-Taylor reactor 100.

The particle separation unit 200 includes: a separation tank 210 for receiving the slurry-type reaction product from the Couette-Taylor reactor 100 and then loosening and dispersing the agglomerated particles in the slurry to separate the cathode active material precursor particles therefrom using gravity; a slurry supply line 220 which is connected between the Couette-Taylor reactor 100 and the slurry inlet of the separation tank 210 and through which the slurry-type reaction product is supplied from the Couette-Taylor reactor 100; a pulverizer for pulverizing the slurry-type reaction product transferred into the separation tank 210; and a fine particle circulation line 230 which is connected between the Couette-Taylor reactor 100 and the upper end of the separation tank 210 to recycle the solution including remaining fine particles separated from the precursor particles in the separation tank 210 into the Couette-Taylor reactor 100.

In the separation unit 200, the agglomerated particles in the slurry supplied from the Couette-Taylor reactor 100 are loosened and dispersed by the pulverizer, and then relatively heavy particles and relatively light particles become separated by gravity. That is, precursor particles which are relatively heavy move to the bottom of the separation tank 210, and are then stored in a storage tank 240 through a passage connected to the bottom of the separation tank 210. Further, the solution including relatively light fine particles separated from the precursor particles is recycled to the Couette-Taylor reactor 100 through a fine particle circulation line 230 connected to the top of the separation tank 210.

As the pulverizer for loosening and dispersing the agglomerated particles in the slurry, an ultrasonic disperser or a centrifugal disperser may be used. According to an embodiment of the present invention, the ultrasonic disperser may include: an ultrasonic generator 211 which is provided in the separation tank 210 and which is provided with an ultrasonic vibrator to transfer ultrasonic vibrations into the separation tank 210 to disperse the agglomerated particles in the slurry; and a driving unit 212 for driving the ultrasonic vibrator.

Further, the second outlet 112 of the Couette-Taylor reactor 100 is connected to a waste solution discharge line 113 such that the waste solution produced by a coprecipitation reaction is discharged. Meanwhile, the Couette-Taylor reactor 100 may be configured such that the waste solution is discharged together with the slurry solution through the first outlet U 1.

The waste solution produced by a coprecipitation reaction in the Couette- Taylor reactor 100 is discharged to the precipitation unit 300 through the waste solution discharge line 113. Here, the precipitation unit 300 serves to precipitate and remove an alkali salt from the waste solution, and includes: a cooling means; and a precipitation tank 320 in which an alkali salt is precipitated from the cooled waste solution.

The precipitated alkali salt may be an alkali metal salt which is generated in the Couette-Taylor reactor, but not coprecipitated. Exemplary alkali salts include metal hydroxides such as nickel hydroxide, cobalt hydroxide, manganese hydroxide and a mixture thereof.

The cooling means is configured such that the waste solution discharged from the Couette-Taylor reactor 100 through the waste solution discharge line 113 passes through the cooling means and such that a coolant also passes through the cooling means. The cooling means includes: a first heat exchanger 310 for cooling the waste solution using heat exchange between the waste solution and the coolant and then discharging the cooled waste solution to the precipitation tank 320 through the waste solution discharge line 113; and a chiller 330 for supplying the coolant to the first heat exchanger 320.

Therefore, the waste solution discharged from the Couette-Taylor reactor 100 to the precipitation tank 320 through the waste solution discharge line 113 passes through the first heat exchanger 310 to be cooled, and thus the alkali salt is precipitated on the bottom of the precipitation tank 320 to be removed from the waste solution.

Finally, waste water obtained by removing the alkali salt from the waste solution in the precipitation tank 320 is discharged through a waste water discharge line 321.

According to an embodiment of the present invention, the waste water from which the alkali salt is removed passes through an additionally-provided second exchanger 340 to be reheated, and then the reheated waste water is recycled to the Couette-Taylor reactor 100.

As described above, according to the apparatus of the present invention, a series of processes for preparing a cathode active material precursor for a lithium secondary battery are continuously and efficiently conducted so that the desired cathode active material precursor can be continuously obtained. Hereinafter, the present invention will be described in more detail with reference to the following Examples. However, these Examples are set forth to illustrate the present invention, and the scope of the present invention is not limited thereto.

Example 1

NiSO₄-6H₂O, CoSO₄-7H₂O and MnSO₄ H₂O were dissolved in distilled water at a molar ratio of 1 : 1 : 1 to prepare a 2 M metal salt solution. The prepared metal salt solution was introduced into a Couette-Taylor reactor at a flow rate of 120 mL/hr through a metal salt solution supply line. Further, a 6M NI^OH solution was prepared using a 25% N¾, and then the prepared 6M N¾OH solution was introduced into the Couette-Taylor reactor at a flow rate of 10 mL/hr through an aqueous ammonia solution supply line. Further, a 4M NaOH solution was automatically introduced into the Couette-Taylor reactor while maintaining the 4M NaOH solution at a pH of 11 using a pH meter and a controller. The temperature of the Couette-Taylor reactor was set at 40 ^°C, and the mixed solution was stirred at a rotation speed of 700 rpm to prepare a cathode active material precursor. Example 2

A cathode active material precursor was prepared in the same manner as in Example 1, except that NiSO₄-6H₂O, CoSO₄-7H₂O and MnSO₄-H₂O were mixed at a molar ratio of 5:2:3.

Example 3

A cathode active material precursor was prepared in the same manner as in Exainple 1, except that the prepared metal salt solution was introduced at a flow rate of 192 mL/hr, the N¾OH solution was introduced at a flow rate of 16 mL hr, and the mixed solution was stirred at a rotation speed of 900 rpm. Example 4

A cathode active material precursor was prepared in the same manner as in Example 1, except that the prepared metal salt solution was introduced at a flow rate of 80 mL/hr, the Ν¾ΟΗ solution was introduced at a flow rate of 6.67 mL/hr, and the mixed solution was stirred at a rotation speed of 600 rpm.

Example 5

A cathode active material precursor was prepared in the same manner as in Example 1, except that NiSO₄-6H₂O, CoSO₄-7H₂O and MnSO₄-H₂O were mixed at a molar ratio of 6:2:2, and the mixed solution was stirred at a rotation speed of 600 rpm.

Comparative Example 1

NiSO₄-6H₂O, CoSO₄-7H₂O and MnSO₄ H₂O were dissolved in distilled water at a molar ratio of 1 : 1 : 1 to prepare a 2 M metal salt solution. The prepared metal salt solution was introduced into a Couette-Taylor reactor at a flow rate of 152 mL/hr. Further, a 6M N¾OH solution was prepared using a 25% NH₃, and then the prepared 6M N]¾OH solution was introduced into the Couette-Taylor reactor at a flow rate of 30 mL/hr through an aqueous ammonia solution supply line. Further, a 4M NaOH solution was automatically introduced into the Couette-Taylor reactor while mamtaining the 4M NaOH solution at a pH of 11 using a pH meter and a controller. The temperature of the Couette-Taylor reactor was set at 40 ^°C, and the mixed solution was stirred at a rotation speed of 800 rpm for 12 firs to prepare a cathode active material precursor.

The reaction time, the time it takes to allow the average particle size (D50) of the prepared cathode active material precursor to reach 10 m, the sphericity and the tap density in the preparation of the cathode active materials of Examples 1 to 5 and Comparative Example 1 are given in Table 1 below.

[Table 1]

From Table 1 above, it can be ascertained that the time taken to allow the average particle size (D50) of each of the cathode active material precursors prepared in the present invention to reach 10 //m is short, the density of particles of each of the cathode active material precursors prepared in the present invention is uniform, and the tap density thereof is high, compared to the cathode active material precursor of Comparative Example 1. The reason for this is predicted that the reaction of the reactants is efficiently performed by Couette-Taylor vortexes.

SEM analysis

FIG. 3 shows the scanning electron microscope (SEM) photographs of the cathode active material precursors of Examples 1 to 5 and Comparative Example 1. Referring to FIG. 3, it can be ascertained that the particle size distribution of each of the cathode active material precursors of Examples 1 to 5 is uniform, and that the particle size distribution of the cathode active material precursor of Comparative Example 1 is nonuniform. XRD analysis

As the results of X-ray diffraction analysis of the cathode active material precursors of Examples 1 to 5 and Comparative Example 1, as shown in FIG. 4, it can be ascertained that typical metal hydroxide was obtained from the peak diffraction pattern of the cathode active material precursor of Example 1.

Preparation Example 1 : Preparation of cathode active material

Each of the cathode active material precursors of Examples 1 to 5 and Comparative Example 1 was mixed with Li₂CO₃ at a stoichiometric ratio (Li: M = 1.10:1), and then the mixture was sintered in the air at a temperature range of 700 ~ 1100 ^°C for 10 ~ 20 hours to prepare a cathode active material.

Preparation Example 2: Manufacture of secondary battery

The cathode active material prepared in Preparation Example 1 , a conducting material and a binder were mixed at a mixing ratio of 95: 3: 2 to obtain a slurry, and the slurry was applied onto aluminum (AT) foil using a doctor blade method to obtain an electrode. Lithium metal was used as an anode, and an electrolyte in which 1M LiPF₆ is included in a mixture of EC and EMC (1:2) was used as an electrolyte, and a separation membrane was disposed between the anode and the cathode to manufacture a coin half cell.

Experimental Example 1 : Evaluation of charge-discharge capacity 1C capacity was measured based on 140 mAh/g, and charge and discharge cut-off voltages were respectively set to 4.3 V and 3.0 V. Rated current was applied until 4.3 V, and then the voltage was maintained until a current of C/10 or less flows. The manufactured coin half cell was charged at 0.1 C and discharged at 0.1 C during the first cycle, and then charged at 0.2C and discharged at 0.2C, 0.5C, 1C and 2.0C, respectively, from the second cycle to measure the charge-discharge capacity of the cathode active material. The results thereof are shown in FIGS. 5 to 10.

Experimental Example 2: Evaluation of high-rate discharge characteristics The discharge capacity of the coin half cell manufactured in Preparation

Example 2 was measured by discharging a current of 0.1 C and 2 C until the discharge voltage thereof reached 3.0 V.

The results thereof are given in Table 2 below.

[Table 2]

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.

Claims

WHAT IS CLAIMED IS:

1. An apparatus for preparing a cathode active material precursor for a lithium secondary battery, comprising:

2. The apparatus for preparing a cathode active material precursor for a lithium secondary battery of claim 1, wherein the cathode active material precursor is nickel- cobalt-manganese hydroxide precursor represented by Formula 1 :

[Formula 1]

Ni_xCo_yMn_(1-x-y)(OH)₂

wherein 0.33 < x < 0.80, 0 < y < 0.33, 0 < x+y < 1.

3. The apparatus for preparing a cathode active material precursor for a lithium secondary battery of claim 1, wherein the solution of mixed metal salts is a solution of nickel sulfate, cobalt sulfate and manganese sulfate.

4. The apparatus for preparing a cathode active material precursor for a lithium secondary battery of claim 1 , wherein the alkali solution is a sodium hydroxide solution.

5. The apparatus for preparing a cathode active material precursor for a lithium secondary battery of claim 1, wherein the reaction mixture further comprises ammonia.

6. A method for preparing a cathode active material precursor for a lithium secondary battery, comprising the steps of: