KR101075409B1 - Method for preparing positive active material for lithium secondary battery, positive active material prepared using same, and lithium secondary battery including same - Google Patents

Abstract

The present invention relates to a method for preparing a cathode active material for a lithium secondary battery, a cathode active material prepared therefrom, and a lithium secondary battery including the same. The method for preparing a mixed solution by dissolving a lithium salt, a cobalt salt, and an amine compound in a solvent. Manufacturing; And hydrothermally reacting the mixed solution at 150 ° C. to 200 ° C. to obtain a lithium cobalt composite metal oxide.

The positive electrode active material prepared by the manufacturing method according to the present invention is excellent in high rate characteristics, it can improve the discharge capacity and cycle life characteristics of the battery when applied to a lithium secondary battery.

Lithium secondary battery, positive electrode active material, hydrothermal reaction, lifetime characteristics, discharge capacity

Description

A method of manufacturing a cathode active material for a lithium secondary battery, a cathode active material manufactured therefrom, and a lithium secondary battery including the same.

The present invention relates to a method of manufacturing a cathode active material for a lithium secondary battery, a cathode active material prepared therefrom, and a lithium secondary battery including the same, and more particularly to a cathode active material of a lithium cobalt composite metal oxide having excellent high rate characteristics. The present invention relates to a method for preparing a positive electrode active material for a lithium secondary battery, a positive electrode active material prepared therefrom, and a lithium secondary battery including the same.

As portable electronic devices become smaller and lighter in recent years, the need for high performance and high capacity of batteries used as power sources for these devices is increasing.

A battery generates power by using a material capable of electrochemical reactions between a positive electrode and a negative electrode. A typical example of such a battery is a lithium secondary battery that generates electrical energy by a change in chemical potential when lithium ions are intercalated / deintercalated at a positive electrode and a negative electrode. The lithium secondary battery is prepared by using a material capable of reversible intercalation / deintercalation of lithium ions as an active material of a positive electrode and a negative electrode, and filling an organic electrolyte or a polymer electrolyte between the positive electrode and the negative electrode. It is the active material that has a decisive influence on the electrochemical performance of such a lithium secondary battery. As the negative electrode active material, crystalline carbon such as natural graphite, graphite and artificial graphite, and amorphous carbon such as soft carbon and hard carbon are used. In addition, a lithium composite metal compound is used as a cathode active material of a lithium secondary battery, and representative examples thereof include LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _1-x Co _x O ₂ (0 <x <1), LiMnO _2, and the like. Composite metal oxides thereof.

Recently, in order to improve the electrochemical properties of the positive electrode active material for lithium secondary batteries, various researches on active material composition change, particle size control, or surface treatment have been conducted. Accordingly, various active material manufacturing methods have been reported.

In the case of LiCoO ₂ , a production method such as a solid phase method, a sol-gel method, a hydrothermal synthesis method and an ion exchange method is known. In the solid phase method, a lithium salt of Li ₂ CO ₃ and cobalt oxide (Co ₃ O ₄ or CoCO ₃ ) are mixed according to a chemical equivalent and then calcined for at least 48 hours in an oxygen atmosphere of 800 ° C. to 1200 ° C. LiCoO ₂ is difficult to obtain precisely matched chemical equivalents due to lithium evaporating in the middle, but has the advantage of being able to be manufactured in a large amount. In the sol-gel method, a precursor solution prepared by controlling the molar number of lithium salt and cobalt salt is stabilized at a temperature of about 80 ° C. to form a sol, and then a precipitate is obtained by gelling the gel at a temperature of 400 ° C. or higher. In addition, this is a synthetic method for producing LiCoO ₂ by heating it to a high temperature of 800 ° C. or higher again, and the number of steps is large and complicated. In addition, the hydrothermal synthesis method is a synthesis method using an aqueous solution made of lithium hydroxide (LiOH) and cobalt hydroxide (Co (OH) ₂ ), it is synthesized at 100 to 200 ℃ lower temperature than the solid state method or sol-gel method Although this is done, there is a problem that the synthesis reaction requires a temperature above the boiling point of water and therefore must be synthesized under constant pressure in the autoclave. The ion exchange synthesis method has the same reaction mechanism as the hydrothermal synthesis method, but there is a difference in that a small amount of water is added. Specifically, the cobalt hydroxide is made of cobalt oxyhydroxide (CoOOH), and lithium hydroxide and a small amount of water (~ ml) are added to form a slurry, and then a pellet is applied by applying a high pressure (> 5000psi). It is a method of synthesizing LiCoO ₂ by maintaining a long time (about 5 days or more) at a temperature of 100 ° C. or more and allowing the hydrogen ions and the lithium ions of CoOOH to be exchanged with each other.

However, LiCoO ₂ prepared by the synthesis method as described above has a problem that the high rate characteristic is weak due to a particle diameter of 5 μm or more.

The present invention is to provide a method for producing a positive electrode active material for a lithium secondary battery having an optimum particle size and structure excellent in high rate characteristics, a positive electrode active material prepared therefrom and a lithium secondary battery comprising the same.

The present invention also provides an improved lithium secondary battery having improved lifetime characteristics and discharge capacity, including a positive electrode including the positive electrode active material.

In order to achieve the above object, according to an embodiment of the present invention, dissolving a lithium salt, cobalt salt and an amine compound in a solvent to prepare a mixed solution; And it provides a method for producing a positive electrode active material for a lithium secondary battery comprising the step of heating the mixed solution to 150 ℃ to 200 ℃ hydrothermal reaction to obtain a lithium cobalt composite metal oxide.

The present invention also provides a cathode active material for a lithium secondary battery comprising a lithium cobalt composite metal oxide prepared by the above production method.

The present invention also provides a lithium secondary battery comprising the positive electrode active material.

The positive electrode active material prepared by the manufacturing method according to the present invention is excellent in high rate characteristics, it can improve the discharge capacity and cycle life characteristics of the battery when applied to a lithium secondary battery.

Hereinafter, the present invention will be described in more detail.

Method for producing a cathode active material for a lithium secondary battery according to an embodiment of the present invention, dissolving a lithium salt, cobalt salt and an amine compound in a solvent to prepare a mixed solution; And hydrothermally reacting the mixed solution at 150 ° C. to 200 ° C. to obtain a lithium cobalt composite metal oxide.

Each step will be described in more detail below.

First, a lithium salt, a cobalt salt, and an amine compound are dissolved in a solvent to prepare a mixed solution.

In this case, the lithium salt may be selected from the group consisting of lithium-containing hydroxide, oxy hydroxide, nitrate, halide, carbonate, acetate, oxalate, citrate, and mixtures thereof, specifically lithium Hydroxides, lithium nitrate or lithium acetate and the like can be used.

The cobalt salt may be selected from the group consisting of cobalt-containing hydroxide, oxyhydroxide, nitrate, halide, carbonate, acetate, oxalate, citrate, and mixtures thereof, and specifically, cobalt nitrate , Cobalt hydroxide, cobalt carbonate, cobalt acetate, and mixtures thereof can be used.

The lithium salt and cobalt salt may be used in an appropriate chemical equivalent ratio in consideration of the lithium and cobalt content in the lithium cobalt complex rapid oxide to be prepared, preferably used in a molar ratio of 3: 1 to 6: 1. .

The amine compound serves as a surfactant for stabilizing the nanoparticles of the lithium cobalt composite metal oxide to be produced, and helps to produce uniform particles. As such an amine compound, a compound represented by the following Chemical Formula 1 may be used:

[Formula 1]

C _n NH ₂

Wherein C _n is a hydrocarbon group, where 3 ≦ _n ≦ 30, preferably 7 ≦ _n ≦ 30.

Specifically, it is selected from the group consisting of propylamine, butylamine, octylamine, decylamine, dodecylamine, oleylamine, laurylamine, trioctylamine, dioctylamine, hexadecylamine, and mixtures thereof. Can be used.

The amine compound is preferably used in an amount of 3 to 30 parts by weight based on 100 parts by weight of cobalt salt. When used in the above content range, it is preferable to form particles of the composite metal oxide having a uniform particle size more easily.

The solvent may be used without particular limitation as long as it can dissolve the lithium salt, cobalt salt and amine compound, and specifically, aromatic hydrocarbons such as toluene and benzene; Saturated hydrocarbons such as pentane and hexane; Halogenated saturated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride and methylene chloride; Aldehydes such as dimethyl formaldehyde; Alcohols such as methanol; Ethers such as diethyl ether, dioxane and tetrahydrofuran; Esters such as ethyl acetate and butyl acetate; Ketones such as acetone and 1-hexanone; Or nitriles such as acetonitrile.

In this case, in order to increase the solubility and dissolution rate of the lithium salt, cobalt salt and the amine compound in the solvent, a stirring treatment may be performed together with the preparation of the mixed solution, and the stirring treatment is performed using a conventional stirring apparatus. can do.

Next, the prepared mixed solution is heated and hydrothermally reacted to obtain a lithium cobalt composite metal oxide.

At this time, the mixed solution is preferably heated at a temperature of 150 ℃ to 200 ℃, more preferably from 170 ℃ to 200 ℃. If the heating temperature is lower than 150 ° C., sufficient hydrothermal reaction hardly occurs, and thus lithium cobalt composite metal oxide is not sufficiently formed. If the temperature exceeds 200 ° C., the lithium cobalt composite metal oxide having the desired characteristics is not easy to manufacture. not. Therefore, in order to obtain a lithium cobalt composite metal oxide having the desired properties, it is preferable to heat-treat it in the above temperature range.

In addition, the heating process is preferably carried out for 24 to 72 hours, more preferably for 50 to 72 hours. When carried out within the above time range it can be produced a lithium cobalt composite metal oxide having the desired characteristics.

At this time, the hydrothermal reaction may be carried out in a conventional reactor, for example, an autoclave.

Subsequently, the lithium cobalt composite metal oxide precipitated as a result of the prepared hydrothermal reaction is separated. In this case, in order to assist the precipitation of the lithium cobalt composite metal oxide, a cooling process may be further performed. The precipitated lithium cobalt composite metal oxide may be separated according to a method known in the art. The prepared solution may be cooled and then separated using a centrifuge.

In addition, the separated lithium cobalt composite metal oxide may be subjected to a drying step for removing the solvent used in the washing step.

At this time, the drying process is preferably carried out in a vacuum, the drying temperature range may be carried out under a temperature range that can remove the solvent used during the washing in the washing step using centrifugation. Specifically, the temperature is preferably 100 ° C to 200 ° C, preferably 120 ° C to 200 ° C, for smooth removal of the solvent used during centrifugation.

Subsequently, a heat treatment process may be selectively performed on the manufactured lithium cobalt composite metal oxide.

The heat treatment step may be carried out in an atmosphere.

The heat treatment step is preferably carried out at 400 ℃ to 700 ℃, more preferably at 500 ℃ to 700 ℃. It is preferable to carry out in the above temperature range because particles of a desired size can be obtained.

In addition, the heat treatment process is preferably performed for 3 to 5 hours, more preferably for 4 to 5 hours. When carried out within the above time range it can be produced a lithium cobalt composite metal oxide having the desired characteristics.

In this case, the prepared cathode active material may further include a Co ₃ O ₄ impurity due to phase decomposition of LiCoO ₂ during the heat treatment process, specifically, 3 wt% or less with respect to the total weight of the active material at a level that does not impair the characteristics of the active material. It may include a Co ₃ O ₄ .

By the manufacturing method as described above, a cathode active material including a lithium cobalt composite metal oxide having a predetermined level of lithium ion conductivity may be manufactured. In particular, the manufacturing method according to the present invention, by first synthesizing the lithium cobalt composite metal oxide of the nanoparticles and then performing a heat treatment at a high temperature, the prepared lithium cobalt composite metal oxide with a layered structure of several tens to hundreds of nanoscales It has a variety of particle sizes. Specifically, the prepared lithium cobalt composite metal oxide has a particle diameter of 50 to 300 nm, preferably 100 to 300 nm, more preferably 200 to 300 nm. Accordingly, the specific surface area is large, and lithium may react in more areas during charging and discharging of the lithium secondary battery. As a result, the discharge capacity and lifespan characteristics of the battery may be improved along with excellent high rate characteristics.

Accordingly, the present invention provides a lithium secondary battery having a positive electrode including the positive electrode active material.

The lithium secondary battery includes a positive electrode including the positive electrode active material, a negative electrode including a negative electrode active material, and an electrolyte impregnated with the positive electrode and the negative electrode.

The positive electrode is prepared by mixing the positive electrode active material, a conductive agent, a binder, and a solvent to prepare a slurry for forming a positive electrode, and then applying it directly onto a current collector and drying it, or a separate support for the positive electrode forming slurry. After casting on, the film obtained by peeling from this support can be manufactured by laminating on a collector.

The conductive agent is used to impart conductivity to the electrode and may be used as long as it is an electronic conductive material without causing chemical change. Specifically, carbon black, graphite, metal powder or the like can be used.

The binder acts as a paste for the active material, mutual adhesion between the active materials, adhesion between the active material and the current collector, and a buffering effect on the expansion and contraction of the active material, and specifically, vinylidene fluoride / hexafluoropropylene copolymer. (copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP)), polyvinylidene fluoride (polyvinyledene fluoride), polyacrylonitrile, polymethylmethacrylate, polytetrafluoroethylene And at least one selected from the group consisting of a mixture thereof.

N-methylpyrrolidone, acetone, acetone, tetrahydrofuran, decane and the like may be used as the solvent. In this case, the amount of the positive electrode active material, the conductive agent, the binder, and the solvent may be used at a level commonly used in a lithium secondary battery.

The current collector serves to collect electrons generated by the electrochemical reaction of the active material or to supply electrons required for the electrochemical reaction. Specifically, in addition to stainless steel, aluminum, nickel, copper, titanium, carbon, and conductive resin Carbon, nickel, or titanium treated on the surface of copper or stainless steel may be used.

Like the positive electrode, the negative electrode is mixed with a negative electrode active material, a binder, and a solvent to prepare a slurry for forming a negative electrode, which is then directly applied to a current collector or cast on a separate support, and the negative electrode active material film peeled from the support is copper It can be produced by laminating on the current collector. At this time, if necessary for the negative electrode active material composition, it may further contain a conductive agent.

The negative electrode active material includes lithium metal, a metal material alloyable with lithium, a transition metal oxide, a material capable of doping and undoping lithium, a material capable of forming a compound by reversibly reacting with lithium, or a lithium ion reversibly Intercalation / deintercalation materials and the like can be used. For example, lithium metal, a lithium alloy, coke, artificial graphite, natural graphite, an organic high molecular compound combustor, carbon fiber, etc. can be used. In addition, the conductive agent, the binder, the solvent, and the current collector may be the same as those described for the positive electrode.

As the electrolyte to be charged in the lithium secondary battery, a non-aqueous electrolyte or a known solid electrolyte may be used, and preferably, a lithium salt is dissolved.

Although the solvent of the said non-aqueous electrolyte is not specifically limited, Cyclic carbonate, such as ethylene carbonate, a propylene carbonate, butylene carbonate, vinylene carbonate; Chain carbonates such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate; Esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and γ-butyrolactone; Ethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane and 2-methyltetrahydrofuran; Nitriles such as acetonitrile; Amides, such as dimethylformamide, etc. can be used. These can be used 1 type or in combination of 2 or more types, and it is preferable to use the mixed solvent of a cyclic carbonate and a linear carbonate.

As the electrolyte, a gel polymer electrolyte in which an electrolyte solution is impregnated with a polymer electrolyte such as polyethylene oxide or polyacrylonitrile, or an inorganic solid electrolyte such as LiI or Li ₃ N may be used.

The lithium salt may be LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ One selected from the group consisting of, LiCl, and LiI can be used.

The lithium secondary battery having the above configuration may further include a separator capable of blocking electron conduction between the negative electrode and the positive electrode and conducting lithium ions.

The separator may be used without particular limitation as long as it is commonly used in lithium secondary batteries. For example, polyethylene, polypropylene, polyvinylidene fluoride or two or more multilayer films thereof may be used, and polyethylene / polypropylene 2 may be used. Mixed multilayer membranes such as layer separators, polyethylene / polypropylene / polyethylene three-layer separators, polypropylene / polyethylene / polypropylene three-layer separators, and the like can be used.

The shape of the lithium secondary battery according to the present invention having such a component may be any shape such as coin type, button type, sheet type, stacked type, cylindrical type, flat type, rectangular type, and those skilled in the art by those skilled in the art. Design and apply accordingly.

The lithium secondary battery of the present invention can be widely used in portable information terminals, portable electronic devices, small household power storage devices, motorcycles, electric vehicles, hybrid electric vehicles, and the like.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.

(Example 1)

7.23 g of Co (NO ₃ ) ₂ .H ₂ O was dissolved in 100 ml of 1-hexanol, and then 3.59 g of LiOH and 16 ml of oleylamine were added and dissolved with vigorous stirring to prepare a mixed solution. This mixed solution was transferred to an autoclave and reacted at 200 ° C. for 72 hours. After cooling to room temperature, unreacted LiOH was removed using a centrifuge, washed three times with distilled water and twice with ethanol to remove solvents and other salts. The washed product was dried under vacuum at 200 ° C. for 24 hours to obtain nanoparticles of lithium cobalt composite metal oxide (LiCoO ₂ ).

 (Example 2)

The LiCoO ₂ powder obtained in Example 1 was further heat treated at 500 ° C. for 5 hours to obtain nanoparticles of LiCoO ₂ .

(Example 3)

The LiCoO ₂ powder obtained in Example 1 was further heat treated at 700 ° C. for 5 hours to obtain nanoparticles of LiCoO ₂ .

(Comparative Example 1)

7.23 g of Co (NO ₃ ) ₂ .6H ₂ O was dissolved in 100 ml of distilled water, and then dissolved in 3.59 g of LiOH to prepare a mixed solution. This mixed solution was transferred to an autoclave and reacted at 200 ° C. for 72 hours. After cooling to room temperature, unreacted LiOH was removed using a centrifuge, followed by washing three times with distilled water and two times with ethanol to remove solvents and other salts. The washed product was dried under vacuum at 200 ° C. for 24 hours to obtain nanoparticles of lithium cobalt composite metal oxide (LiCoO ₂ ).

Experimental Example 1: XRD Analysis

X-ray diffraction (XRD) was performed on the cathode active materials prepared in Examples 1 to 3 and Comparative Example 1. The result is shown in FIG.

1 is a graph showing the results of XRD analysis for the positive electrode active material prepared according to Examples 1 to 3, and Comparative Example 1. At this time, the light source for XRD analysis was CuKα-ray, and experimented at a scan rate of 1 ° / min.

As shown in FIG. 1, the cathode active materials prepared according to Examples 1 to 3 and Comparative Example 1 had a c / a value of> 4.99. From this, it can be seen that the cathode active material prepared according to Examples 1 to 3 and Comparative Example 1 has a well-developed layered structure.

In addition, Example 1 and Comparative Example 1 except for the active material of the, in the embodiment 2 and the active material 3 is Co ₃ O ₄ of impurities due to the decomposition of LiCoO ₂ in the heat treatment were found, Co ₃ through further analysis It was found that the amount of O ₄ was 3% by weight or less.

Experimental Example 2: Raman Analysis

Raman spectrum analysis was performed on the cathode active materials prepared in Examples 1 to 3 and Comparative Example 1. The results are shown in Fig.

FIG. 2 is a graph showing Raman spectroscopic observation results of the cathode active materials prepared according to Examples 1 to 3 and Comparative Example 1. FIG.

As shown in FIG. 2, the positive electrode active materials prepared according to Examples 1 to 3 and Comparative Example 1 are all produced from the A _1g mode representing Co-O stretching and the E _g mode representing bending of O-Co-O. Approximately 590 cm ⁻¹ and 480 cm ⁻¹ two strong Raman bands were shown. From these results, it was confirmed that the cathode active materials prepared according to Examples 1 to 3 and Comparative Example 1 all had typical layered structures.

Experimental Example 3: Structure Analysis

The cathode active materials prepared in Examples 1 to 3 and Comparative Example 1 were observed using a scanning electron microscope (SEM). The results are shown in Fig.

3 (a) to (d) are photographs showing scanning electron microscope observation results of the cathode active materials prepared in Examples 1, 2 and 3 and Comparative Example 1, respectively.

As shown in (a) to (d) of Figure 3, the positive electrode active material according to Example 1 has a particle size of about 50nm, the positive electrode active material according to Example 2 has a particle size of about 100nm, according to Example 3 The cathode active material showed a particle size of about 300 nm, while the cathode active material according to Comparative Example 1 showed a particle size of about 1 μm. From these results, it can be seen that the cathode active material prepared according to the present invention has a significantly smaller particle size than the cathode active material of Comparative Example 1 prepared by a conventional method. In addition, it can be seen that the heat treatment is performed compared with the heat treatment from the particle sizes of the active materials of Examples 1 to 3, and the particle size of the positive electrode active material increases as the heat treatment temperature is increased.

In addition, it can be seen from FIG. 3C that the cathode active material according to Example 3 has a hexagonal form.

Experimental Example 4: Charge and Discharge Characteristics

The charge and discharge characteristics of the battery including the cathode active material prepared in Examples 1 to 3 and Comparative Example 1 were evaluated.

Specifically, the positive electrode active material prepared in Examples 1 to 3, and Comparative Example 1, polyvinylidene fluoride (PVDF: polyvinylidene fluoride, KF1100, Japan Kureha Chemical) binder, and Super P (Super P carbon black) A slurry for anode formation was prepared by mixing in an N-methylpyrrolidone (NMP) solution at a weight ratio of 8: 1: 1. The prepared anode forming slurry was coated on an aluminum foil (Al foil) with a thickness of about 30 μm, dried at 130 ° C. for 20 minutes, and then rolled at a pressure of 1 ton to prepare a positive electrode plate. The prepared positive electrode plate and lithium metal as counter electrodes were used to fabricate a coin cell type half cell of 2016-type. In this case, a mixed solution (1: 1 volume ratio) of ethylene carbonate (EC) and dimethyl carbonate (DMC) in which 1M LiPF ₆ was dissolved was used.

For the coin-type half cells each containing the positive electrode active material of Examples 1 to 3 and Comparative Example 1 prepared above, charged at 0.1 C, 1 C, 2 C, 4 C, and 7 C in a voltage range of 4.5 V to 3 V at room temperature. After discharge, the discharge capacity according to C-rate was measured. The results are shown in Figs. 4A to 4D.

4A to 4D show the first cycles of 0.1C, 1C, 2C, 4C, and 7C for each battery containing the positive electrode active material prepared according to Examples 1 to 3 and Comparative Example 1, respectively.

As shown in FIGS. 4A to 4D, the batteries including the cathode active materials according to Examples 1 to 3 and Comparative Example 1 showed little difference in charge capacity, but the discharge capacities were 103 mAh / g and 122 mAh /, respectively. g, 175 mAh / g, and 182 mAh / g. In particular, the battery including the positive electrode active material prepared according to Example 1 exhibited the largest irreversible capacity of 47% among the batteries containing the positive electrode active materials of Examples 2, 3 and Comparative Example 1 with a discharge capacity of 103 mAh / g. . In contrast, the positive electrode active material of Comparative Example 1 prepared according to the conventional active material manufacturing method had a specific surface area of 3 m ² / g and showed a significantly higher discharge capacity of 182 mAh / g compared to Examples 1 to 3.

In addition, it can be seen from the experimental results in the battery including the positive electrode active materials of Examples 1 to 3 that the heat treatment step in the positive electrode active material manufacturing process, the discharge capacity of the battery increases as the heat treatment temperature is higher. This tendency is due to the decrease in the surface area of the positive electrode active material (surface areas of the positive electrode active materials of Examples 1, 2, and 3: 14 m ² / g, 9 m ² / g, 5 m ² / g). It is believed that the occurrence of side reactions is reduced, and as a result, the formation of a thick solid electrolyte interface (SEI) can be prevented to reduce the resistance at the anode.

Experimental Example 5: Characteristics by Rate

Rate characteristics of the batteries including the cathode active materials prepared in Examples 1 to 3 and Comparative Example 1 were evaluated. The result is shown in FIG.

5 (a), (b), (c) and (d) are graphs showing the rate-specific characteristics of the battery including the positive electrode active material prepared according to Examples 1 to 3, and Comparative Example 1, respectively.

As shown in (a), (b), (c) and (d) of FIG. 5, a battery including the cathode active materials according to Examples 1 to 3 and Comparative Example 1 has a first discharge capacity at 2C-rate. These were 53 mAh / g, 79 mAh / g, 144 mAh / g, and 167 mAh / g, respectively, but after 50 cycles, they were 42 mAh / g, 60 mAh / g, 134 mAh / g, and 106 mAh / g, respectively. The capacity retention ratios of the batteries including the cathode active materials according to Examples 1 to 3 and Comparative Example 1 calculated from such a result are 79%, 76%, 93%, and 63%, respectively. The battery containing the positive electrode active material of the present invention exhibited better battery characteristics than the battery containing the positive electrode active material manufactured by the conventional positive electrode active material manufacturing method.

In addition, when the C-rate was increased to 4C and 7C, the battery containing the positive electrode active material according to Example 3 showed the highest discharge capacity of 87 mAh / g, the best capacity retention even in cycling at 7C. However, after the cycling up to 7C, the discharge capacity of the battery containing the positive electrode active materials according to Examples 1 to 3 and Comparative Example 1 recovered their initial capacity. This indicates that the higher the C-rate, the SEI layer as a "resistance" that interferes with lithium ions and electrical conductivity was formed during the first cycle.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

1 is a graph showing the results of XRD analysis for the positive electrode active material prepared according to Examples 1 to 3, and Comparative Example 1.

2 is a graph showing the results of Raman spectroscopy spectra for the cathode active material prepared according to Examples 1 to 3, and Comparative Example 1.

(A) to (d) of Figure 3 is a photograph showing the scanning electron microscope observation results for the positive electrode active material prepared according to Examples 1 to 3, and Comparative Example 1.

4A to 4D are graphs of charge and discharge curves of a battery including the cathode active materials prepared according to Examples 1 to 3 and Comparative Example 1. FIG.

5 is a graph showing the rate-specific characteristics of a battery including the cathode active material prepared according to Examples 1 to 3, and Comparative Example 1.

Claims (14)

Preparing a mixed solution by dissolving a lithium salt, cobalt salt, and an amine compound in a solvent; And Heating the mixed solution at 150 ° C. to 200 ° C. to obtain a lithium cobalt composite metal oxide by hydrothermal reaction; Including, The amine compound is a compound represented by the following formula (1), propylamine, butylamine, octylamine, decylamine, dodecylamine, oleylamine, laurylamine, trioctylamine, dioctylamine, hexadecylamine, and Method for producing a positive electrode active material for a lithium secondary battery that is selected from the group consisting of: [Formula 1] C _n NH ₂ (Wherein C _n : hydrocarbon, 3 ≦ _n ≦ 30). The method of claim 1, The lithium salt is a method of producing a positive electrode active material for a lithium secondary battery that is selected from the group consisting of lithium, hydroxide, oxy hydroxide, nitrate, halide, carbonate, acetate, oxalate, citrate, and mixtures thereof. The method of claim 1, The cobalt salt is a method of producing a positive electrode active material for a lithium secondary battery selected from the group consisting of hydroxide, oxyhydroxide, nitrate, halide, carbonate, acetate, oxalate, citrate, and mixtures thereof containing cobalt. The method of claim 1, The lithium salt and cobalt salt is a method of producing a positive electrode active material for a lithium secondary battery is used in a molar ratio of 3: 1 to 6: 1. delete delete The method of claim 1, The amine compound is a method for producing a positive electrode active material for a lithium secondary battery that is added in an amount of 3 to 30 hollow parts with respect to 100 parts by weight of cobalt salt. The method of claim 1, The solvent is an aromatic hydrocarbon, saturated hydrocarbons, halogenated saturated hydrocarbons, aldehydes, alcohols, ethers, esters, ketones, nitriles and the preparation of a positive electrode active material for lithium secondary batteries selected from the group consisting of Way. The method of claim 1, After the hydrothermal reaction process further comprises a heat treatment process at 400 ℃ to 700 ℃ manufacturing method of a positive electrode active material for a lithium secondary battery. A cathode active material for a lithium secondary battery manufactured by the method according to any one of claims 1 to 4 and 7 to 9. 11. The method of claim 10, The active material is a cathode active material for a lithium secondary battery having a layered structure. 11. The method of claim 10, The active material is a cathode active material for a lithium secondary battery having an average particle diameter of 50 to 300nm. 11. The method of claim 10, The active material is a lithium secondary battery positive electrode active material comprising less than 3% by weight of Co ₃ O _{4 based} on the total weight of the active material. A lithium secondary battery comprising a positive electrode active material prepared by the manufacturing method according to any one of claims 1 to 4.

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