KR101407606B1 - Method for preparing positive active material for rechargeable lithium battery, positive active material prepared using same, and rechargeable lithium battery including same - Google Patents

Abstract

Dissolving a lithium source and an oxidizing agent in a solvent to prepare a first mixed solution; Dissolving a manganese source in a solvent to prepare a second mixed solution; Mixing the first mixed solution and the second mixed solution and adding a solvent having a boiling point of 100 ° C or lower to prepare a mixed solution; And a step of subjecting the mixed solution to a hydrothermal reaction by heating at a temperature of about 60 ° C to about 200 ° C to obtain a lithium manganese composite metal oxide, a method for producing a lithium secondary battery for a lithium secondary battery, A lithium secondary battery comprising the positive electrode active material and the positive electrode active material for the lithium secondary battery.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode active material for a lithium secondary battery, a positive electrode active material prepared therefrom, and a lithium secondary battery comprising the same. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive active material,

The present invention relates to a method for producing a positive electrode active material for a lithium secondary battery, a positive electrode active material produced therefrom, and a lithium secondary battery comprising the same.

2. Description of the Related Art [0002] With the recent trend toward miniaturization and light weight of portable electronic devices, there is an increasing need for high performance and large capacity of batteries used as power sources for these devices.

The battery is a material that generates electricity by using a material capable of electrochemically reacting with the positive electrode and the negative electrode. A representative example of such a battery is a lithium secondary battery that generates electrical energy by a change in chemical potential when the lithium ions are intercalated / deintercalated in the positive electrode and the negative electrode. The lithium secondary battery is manufactured by using a material capable of reversible intercalation / deintercalation of lithium ions as an active material for the positive electrode and the negative electrode, and filling an organic electrolyte solution or a polymer electrolyte between the positive electrode and the negative electrode. The active material 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. Further, a lithium composite metal compound is used as a positive electrode active material of a lithium secondary battery.

Currently available lithium secondary batteries mainly use LiCoO ₂ as an anode and carbon as an anode. However, cobalt is required to develop alternative cathode materials because of its low storage capacity, high price, toxicity to human body and environmental pollution problem. For example, various metal oxides such as LiMn ₂ O ₄ , LiNiO ₂ , LiNi _{1 -xy} Co _x Mn _y O ₂ (0 <x <1, 0 <y <1) are used. 4V Spinel LiMn ₂ O ₄ , a cathode active material, is environmentally friendly, has a higher potential difference (4V) than lithium, has excellent thermal stability, is cheap, and has abundant reserves. Therefore, it is attracting attention as a cathode active material of a large-capacity battery such as an electric vehicle or an energy storage system. However, the rapid deterioration of capacity due to the elution of manganese ions during high temperature charge and discharge, and the rapid decrease in capacity during high charge / discharge cycles due to low electron conductivity and low ionic conductivity have been overcome.

In recent years, researches on active material composition change, particle size control, surface treatment, and the like have been variously carried out in order to improve the electrochemical characteristics of a cathode active material for a lithium secondary battery.
[Prior Art Literature]
(1) Direct Hydrothermal Synthesis of Ternary Li-Mn-O Oxide Ion-Sieves (Zhang et al. Interdisciplinary Transport Phenomena: Ann. NY Acad. Sci. 1161: 500-507 (2009))
(2) Synthesis of Spinel LiMn ₂ O ₄ by a Hydrothermal Process in Supercritical Water with Heat-Treatment (Kiyoshi Kanamura et al., Journal of The Electrochemical Society, 152 (2) A391-A395 (2005)
(3) Improvement of the high-rate discharge capability of phosphate-doped spinel LiMn ₂ O ₄ by a hydrothermal method (SH Ye et al., Electrochimica Acta 55 (2010) 2972-2977)
(4) Synthesis of spinel LiMn ₂ O ₄ nanoparticles through one-step hydrothermal reaction (CH Jiang et al., Journal of Power Sources 172 (2007) 410-415)
(5) A self-seeded, surfactant-directed hydrothermal growth of single crystalline lithium manganese oxide nanobelts from the commercial bulky particles (Lizhi Zhang, CHEM, COMMUN., 2003, 2910-2911)
(6) Enhancing the performances of Li-ion batteries by carbon-coating: present and future (Huiqiao Li and Haoshen Zhou, The Royal Society of Chemistry 2011)

One embodiment provides a method for producing a cathode active material for a lithium secondary battery having an optimal particle size and structure and excellent high-rate characteristics.

Another embodiment provides a cathode active material for a lithium secondary battery produced by the method for producing a cathode active material for a lithium secondary battery.

Another embodiment provides a lithium secondary battery including the positive electrode including the positive electrode active material for the lithium secondary battery and having improved lifetime characteristics and discharge capacity.

According to an embodiment, there is provided a method of preparing a cathode active material for a lithium secondary battery, comprising: preparing a first mixed solution by dissolving a lithium source and an oxidizing agent in a solvent; Dissolving a manganese source in a solvent to prepare a second mixed solution; Mixing the first mixed solution and the second mixed solution and adding a solvent having a boiling point of 100 ° C or lower to prepare a mixed solution; And heating the mixed solution to a temperature of about 60 캜 to about 200 캜 to hydrothermal reaction to obtain a lithium manganese composite metal oxide.

The lithium source may include one selected from the group consisting of hydroxides, oxides, nitrates, halides, carbonates, acetates, oxalates, citrates, and combinations thereof including lithium.

The oxidizing agent may include one selected from hydrogen peroxide, glycolic acid, citric acid, potassium permanganate, ammonium peroxodisulfate, nitric acid, chloric acid, chromic acid, manganese dioxide, and combinations thereof.

The manganese source may include one selected from hydroxides, oxyhydroxides, nitrates, halides, carbonates, acetates, oxalates, citrates, and combinations thereof including manganese.

The solvent may include one selected from water, aromatic hydrocarbons, saturated hydrocarbons, halogenated saturated hydrocarbons, aldehydes, alcohols, ethers, esters, ketones, nitriles and combinations thereof.

In the method for producing a cathode active material for a lithium secondary battery, the lithium source and the manganese source may be used in a molar ratio of about 1: 1 to about 5: 1.

The solvent having a boiling point of 100 ° C or less may include one selected from a polar solvent, a non-polar solvent, and a combination thereof.

Specifically, the solvent having a boiling point of 100 ° C or lower may be a C1 to C15 alkane, a C1 to C15 haloalkane, a C3 to C15 cycloalkane, a C6 to C20 areene, a C1 to C15 aliphatic ether, a C3 to C15 alicyclic ether, C15 acetate, C2 to C15 ketone, C1 to C15 amide, C1 to C15 nitrile, C1 to C15 sulfoxide, C1 to C15 aliphatic organic acids, C1 to C15 alcohols, and combinations thereof.

More specifically, the solvent having a boiling point of 100 ° C or lower may be selected from the group consisting of pentane, hexane, chloroform, dichloromethane, cyclopentane, cyclohexane, benzene, diethyl ether, tetrahydrofuran, ethyl acetate, acetone, acetonitrile, methanol, ethanol , n-propanol, isopropanol, and combinations thereof.

In the method for preparing a cathode active material for a lithium secondary battery, the solvent having a boiling point of 100 ° C or lower may be added in an amount of about 500 parts by weight to about 5000 parts by weight based on 100 parts by weight of the manganese source.

The hydrothermal reaction may be conducted for about 1 hour to about 24 hours.

The method for preparing a cathode active material for a lithium secondary battery may further include a step of performing heat treatment at a temperature of about 400 ° C. to about 700 ° C. after the hydrothermal reaction.

The method for preparing a cathode active material for a lithium secondary battery may further include adding a carbon source before the heat treatment step after the hydrothermal reaction.

The carbon source may be selected from the group consisting of sucrose, glucose, polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), colloidal carbon, citric acid, But not limited to, one selected from the group consisting of tartaric acid, glycolic acid, polyacrylic acid, adipic acid, glycine, aminobenzoic acid, and combinations thereof. .

In the method for producing a cathode active material for a lithium secondary battery, the carbon source may be added in an amount of about 5 parts by weight to about 50 parts by weight based on 100 parts by weight of the lithium manganese composite metal oxide.

Another embodiment provides a cathode active material for a lithium secondary battery produced by the method for producing a cathode active material for a lithium secondary battery.

The cathode active material for a lithium secondary battery may include a lithium manganese composite metal oxide represented by the following general formula (1).

[Chemical Formula 1]

Li _{1 + x} Mn _{2 - x} O ₄

In Formula 1,

x is 0? x? 0.3.

The cathode active material for lithium secondary batteries may have an average particle diameter of about 10 nm to about 100 nm.

The cathode active material for a lithium secondary battery may have a single crystal structure.

The cathode active material for the lithium secondary battery may further include a carbon coating layer positioned on the surface of the lithium manganese composite metal oxide.

The carbon contained in the carbon coating layer may be included in an amount of about 0.05 wt% to about 3 wt% based on the total amount of the cathode active material for a lithium secondary battery including the carbon coating layer.

Another embodiment includes a cathode comprising the cathode active material for the lithium secondary battery; A negative electrode comprising a negative electrode active material; And a lithium secondary battery comprising the electrolyte.

According to the method for producing a cathode active material for a lithium secondary battery, the cathode active material for a lithium secondary battery having excellent crystallinity and uniform particle size can be produced at a relatively low temperature in a short time. The cathode active material for a lithium secondary battery thus produced has excellent rate characteristics and can be rapidly charged and discharged, and can have excellent life characteristics and capacity characteristics.

1 is a schematic view illustrating a structure of a lithium secondary battery according to an embodiment.
Fig. 2 is a graph of X-ray diffraction patterns of Examples 1 to 4, Comparative Example 1 and Comparative Example 2. Fig.
3 is an X-ray diffraction pattern graph of the precipitate before heat treatment in Example 1. Fig.
FIG. 4A is a scanning electron microscope (SEM) photograph of the cathode active material for a lithium secondary battery manufactured in Example 1. FIG. FIG. 4B is an SEM photograph enlarged in FIG. 4A. FIG.
FIG. 5A is a scanning electron microscope (SEM) photograph of the cathode active material for a lithium secondary battery manufactured in Example 2. FIG. FIG. 5B is an SEM photograph enlarged in FIG. 5A. FIG.
FIG. 6A is a scanning electron microscope (SEM) photograph of the cathode active material for a lithium secondary battery manufactured in Example 3. FIG. FIG. 6B is an SEM photograph enlarged in FIG. 6A. FIG.
FIG. 7A is a scanning electron microscope (SEM) photograph of the cathode active material for a lithium secondary battery manufactured in Example 4. FIG. 7B is an SEM photograph enlarged in FIG. 7A.
FIG. 8A is a scanning electron microscope (SEM) photograph of the cathode active material for a lithium secondary battery manufactured in Comparative Example 1. FIG. 8B is an SEM photograph showing an enlarged view of FIG. 8A.
9A is a scanning electron microscope (SEM) photograph of a cathode active material for a lithium secondary battery manufactured in Comparative Example 2. Fig. FIG. 9B is an SEM photograph showing an enlarged view of FIG. 9A.
FIG. 10A is a transmission electron microscope (TEM) photograph of the cathode active material for a lithium secondary battery manufactured in Example 1. FIG. Fig. 10B is a graph obtained by fourier transforming Fig. 10A.
FIG. 11A is a transmission electron microscope (TEM) photograph of the cathode active material for a lithium secondary battery manufactured in Example 2. FIG. FIG. 11B is a graph obtained by Fourier transforming FIG. 11A.
FIGS. 12A and 12C are transmission electron microscope (TEM) photographs of the cathode active material for a lithium secondary battery manufactured in Example 2, showing a carbon coating layer. FIG. FIG. 12B is a graph obtained by Fourier transforming FIG. 12A. FIG.
13 is a graph showing a discharge rate characteristic of the lithium secondary battery manufactured in Example 5, Example 6, and Comparative Example 3. Fig.
FIG. 14 is a graph showing the charging rate characteristics of the lithium secondary batteries manufactured in Example 5, Example 6, and Comparative Example 3. FIG.
15 is a graph showing a high rate charge / discharge cycle of the lithium secondary battery manufactured in Example 6. Fig.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto, and the present invention is only defined by the scope of the following claims.

Unless otherwise specified herein, "aliphatic" means C1 to C30 alkyl, C2 to C30 alkenyl, C2 to C30 alkynyl, C1 to C30 alkylene, C2 to C30 alkenylene, or C2 to C30 alkynylene. C2 to C15 alkenyl, C2 to C15 alkynyl, C1 to C15 alkylene, C2 to C15 alkenylene, or C2 to C15 alkynylene, and "alicyclic" means C3 Means C3 to C30 cycloalkenyl, C3 to C30 cycloalkynyl, C3 to C30 cycloalkylene, C3 to C30 cycloalkenylene, or C3 to C30 cycloalkynylene, specifically C3 to C30 cycloalkynyl, Cycloalkyl, C3 to C15 cycloalkenyl, C3 to C15 cycloalkynyl, C3 to C15 cycloalkylene, C3 to C15 cycloalkenylene, or C3 to C15 cycloalkynylene, and "aromatic & It means a group C30 aryl group or a C6 to C30 arylene, and specifically, means a C6 to C16 aryl group or a C6 to C16 arylene.

As used herein, "combination" means mixture unless otherwise specified.

According to an embodiment, there is provided a method of preparing a cathode active material for a lithium secondary battery, comprising: preparing a first mixed solution by dissolving a lithium source and an oxidizing agent in a solvent; Dissolving a manganese source in a solvent to prepare a second mixed solution; Mixing the first mixed solution and the second mixed solution and adding a solvent having a boiling point of 100 ° C or lower to prepare a mixed solution; And heating the mixed solution to a temperature of about 60 캜 to about 200 캜 to hydrothermal reaction to obtain a lithium manganese composite metal oxide.

Each step will be described in more detail below.

First, a first mixed solution is prepared by dissolving a lithium source and an oxidizing agent in a solvent.

The lithium source is used as a lithium source of a lithium manganese composite metal oxide to be produced and is selected from a hydroxide containing lithium, an oxyhydroxide, a nitrate, a halide, a carbonate, an acetate, a oxalate, a citrate, But is not limited thereto. Specifically, the lithium source may include, but is not limited to, lithium hydroxide, lithium nitrate, lithium acetate, and combinations thereof.

The oxidizing agent serves to oxidize manganese or promote oxidation of manganese.

The oxidizing agent may include, but is not limited to, one selected from hydrogen peroxide, glycolic acid, citric acid, potassium permanganate, ammonium peroxodisulfate, nitric acid, chloric acid, chromic acid, manganese dioxide and combinations thereof.

The oxidizing agent may be used in an amount of about 100 parts by weight to about 300 parts by weight based on 100 parts by weight of the lithium source. When the amount of the oxidizing agent is within the above range, the production time of the cathode active material for a lithium secondary battery can be shortened, and the composition of the formed cathode active material for a lithium secondary battery can be appropriately controlled. Specifically, the oxidizing agent may be used in an amount of about 110 parts by weight to about 150 parts by weight based on 100 parts by weight of the lithium source.

The manganese source is then dissolved in a solvent to prepare a second mixed solution.

The manganese source is used as a manganese source of the lithium manganese composite metal oxide to be produced and is selected from the group consisting of manganese-containing hydroxides, oxyhydroxides, nitrates, halides, carbonates, acetic acid salts, oxalic acid salts, citric acid salts and combinations thereof But is not limited thereto. Specifically, the manganese source may include one selected from the group consisting of manganese hydroxide, manganese nitrate, manganese carbonate, manganese acetate, and combinations thereof , But is not limited thereto.

The solvent is not particularly limited as long as it can dissolve the lithium source and the manganese source. Specific examples thereof include water; 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 dimethylformaldehyde; Alcohols such as methanol, ethanol and propanol; Ethers such as diethyl ether, dioxane, and tetrahydrofuran; Esters such as methyl acetate, ethyl acetate, butyl acetate and the like; Ketones such as acetone and 1-hexanone; Nitriles such as acetonitrile; And a combination thereof.

The lithium source and the manganese source can be used in a suitable chemical equivalent ratio taking into consideration the content of lithium and manganese in the lithium manganese composite metal oxide to be produced. Specifically, they can be used in a molar ratio of about 1: 1 to about 5: 1 have.

Then, the first mixed solution and the second mixed solution are mixed, and a solvent having a boiling point of 100 ° C or lower is added thereto to prepare a mixed solution. When the first mixed solution and the second mixed solution are separately prepared and mixed, the concentrations of the lithium source and the manganese source can be easily controlled. However, the present invention is not limited thereto, and a mixed solution may be prepared by dissolving a lithium source, a manganese source and an oxidizing agent in a solvent, and adding a solvent having a boiling point of 100 DEG C or less thereto.

The solvent having a boiling point of 100 DEG C or lower may be a solvent having a saturated vapor pressure higher than that of water at the same temperature. The solvent having a boiling point of 100 ° C or lower is boiled at a temperature lower than that of a solvent in which the lithium source and the manganese source are dissolved, for example, water, so that the hydrothermal reaction proceeds at a lower temperature than in the conventional hydrothermal synthesis method It is possible to shorten the hydrothermal reaction time and improve the crystallinity of the cathode active material for the lithium secondary battery to be produced, to obtain particles of uniform size and to control the shape of the particles to be formed.

The solvent having a boiling point of 100 ° C or lower may include one selected from a polar solvent, a non-polar solvent, and combinations thereof. Specifically, the polar solvent may be polar protic ) Solvent, a polar aprotic solvent, and combinations thereof. &Lt; RTI ID = 0.0 &gt; Preferably, the solvent having a boiling point of 100 DEG C or lower may be used for polarity everyday.

Specifically, the solvent having a boiling point of 100 ° C or lower may be a C1 to C15 alkane, a C1 to C15 haloalkane, a C3 to C15 cycloalkane, a C6 to C20 areene, a C1 to C15 aliphatic ether, a C3 to C15 alicyclic ether, And may include one selected from the group consisting of C 1 -C 15 acetate, C 2 to C 15 ketone, C 1 to C 15 amide, C 1 to C 15 nitrile, C 1 to C 15 sulfoxide, C 1 to C 15 aliphatic organic acids, C 1 to C 15 alcohols and combinations thereof. It is not.

More specifically, the solvent having a boiling point of 100 ° C or lower may be selected from the group consisting of pentane, hexane, chloroform, dichloromethane, cyclopentane, cyclohexane, benzene, diethyl ether, tetrahydrofuran, ethyl acetate, acetone, acetonitrile, , n-propanol, isopropanol, and combinations thereof, but is not limited thereto.

The solvent having a boiling point of 100 ° C or lower may be contained in the reaction vessel in an amount that can produce a saturated vapor pressure within a temperature range of about 60 ° C to about 200 ° C. For example, about 100 parts by weight of the manganese source 500 parts by weight to about 5000 parts by weight. When the amount of the solvent having a boiling point of 100 ° C or lower is within the above range, the hydrothermal reaction time can be effectively shortened, the crystallinity of the produced cathode active material for lithium secondary batteries can be effectively improved, It is possible to effectively control the particle shape to be obtained and formed. Specifically, the solvent having a boiling point of 100 ° C or lower may be added in an amount of about 1000 parts by weight to about 5000 parts by weight based on 100 parts by weight of the manganese source.

In the production of the first mixed solution, the first mixed solution and the mixed solution, an agitation treatment may be carried out together to increase the solubility and the dissolution rate of each substance in the solvent. And the like.

Subsequently, the prepared mixed solution is heated to a temperature of about 60 캜 to about 200 캜 for hydrothermal reaction to obtain a lithium manganese composite metal oxide. When the hydrothermal reaction is carried out within the above-mentioned temperature range, the hydrothermal reaction is sufficiently carried out to sufficiently form a lithium manganese composite metal oxide, and a lithium manganese composite metal oxide having a desired particle diameter and structure can be formed. The crystallinity of the cathode active material for the secondary battery can be effectively improved and the reaction time can be effectively shortened. Specifically, the hydrothermal reaction may be carried out at a temperature of about 100 ° C to about 150 ° C, more specifically, at a temperature of about 110 ° C to about 120 ° C.

The hydrothermal reaction may be carried out for about 1 hour to about 24 hours. When the hydrothermal reaction is performed within the time range described above, a lithium manganese composite metal oxide can be sufficiently formed, a lithium manganese composite metal oxide having a desired particle diameter and structure can be formed, and a crystal of a cathode active material for a lithium secondary battery to be produced It is possible to effectively improve the property. Specifically, the hydrothermal reaction may be carried out for about 1 hour to about 15 hours.

The hydrothermal reaction may be carried out in a conventional reactor, for example, an autoclave.

Then, the precipitated lithium manganese composite metal oxide is separated as a result of the hydrothermal reaction. At this time, a further cooling step may be further performed to assist precipitation of the lithium manganese composite metal oxide. The lithium manganese complex metal oxide precipitated may be separated according to a method known in the art. For example, The solution can be cooled and then separated using a centrifuge.

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

In this case, the drying process is preferably performed under vacuum, and the drying temperature range may be a temperature range in which the solvent used in the washing in the washing step using centrifugation can be removed. Specifically, drying at a temperature of about 100 ° C to about 200 ° C, preferably about 120 ° C to about 200 ° C is preferable for smooth removal of the solvent used in centrifugation.

The lithium manganese composite metal oxide thus prepared may be further subjected to a heat treatment process.

The heat treatment step can be performed in an atmospheric environment.

The heat treatment process may be performed at a temperature of about 400 ° C to about 700 ° C. When the heat treatment is performed in the temperature range, the water molecules on the surface of the lithium manganese composite metal oxide and the water molecules penetrated into the lattice of the lithium manganese composite metal oxide can be effectively removed. The particle growth of the lithium manganese composite metal oxide does not occur during the heat treatment in the above temperature range. Specifically, the heat treatment may be performed at a temperature of about 500 ° C to about 700 ° C.

The heat treatment may be performed for about 1 minute to about 2 hours. When the heat treatment process is performed within the time range, a lithium manganese composite metal oxide having desired characteristics can be effectively produced. Specifically, the heat treatment may be performed for about 5 minutes to about 1 hour.

Meanwhile, a carbon source may be added to the surface of the lithium manganese composite metal oxide after the hydrothermal reaction process, but the present invention is not limited thereto, and addition of the carbon source may be omitted. The carbon coating layer may be formed on all or a part of the surface of the lithium manganese composite metal oxide.

When the carbon coating layer is formed on the surface of the lithium manganese composite metal oxide by the addition of the carbon source, the aggregation between the cathode active materials for the lithium secondary battery can be suppressed, the polarization phenomenon can be suppressed, The cycle life characteristics can be improved. Further, by improving the conductivity of the positive electrode active material for a lithium secondary battery so as to lower the resistance, rapid charging / discharging can be performed more effectively. In particular, it achieves high electrode plate density while maintaining excellent charge / discharge characteristics at a high rate.

The carbon source may be selected from the group consisting of sucrose, glucose, polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), colloidal carbon, citric acid, But not limited to, one selected from the group consisting of tartaric acid, glycolic acid, polyacrylic acid, adipic acid, glycine, aminobenzoic acid, and combinations thereof. But is not limited thereto.

The carbon source may be added in an amount of about 5 parts by weight to about 50 parts by weight based on 100 parts by weight of the lithium manganese composite metal oxide. When the amount of the carbon source used is within the above range, residual carbon remains in the heat treatment in the atmosphere to effectively form the carbon coating layer. Specifically, the carbon source may be added in an amount of about 10 parts by weight to about 20 parts by weight based on 100 parts by weight of the lithium manganese complex metal oxide.

The cathode active material for a lithium secondary battery including the lithium manganese composite metal oxide may be prepared according to the method for producing the cathode active material for a lithium secondary battery.

For example, in the method for producing a cathode active material for a lithium secondary battery, LiOH.H ₂ O is used as a lithium source, Mn (CH ₃ COO) ₂ .4H ₂ O is used as a manganese source, and a boiling point of 100 ° C. or lower When methanol is used as a solvent, the reaction proceeds as shown in Reaction Scheme 1 below to form LiMn ₂ O ₄ on spinel, which is a lithium manganese composite metal oxide.

[Reaction Scheme 1]

^{4Mn 2 + + 16OH - + 2Li} + + 2H 2 O 2 → 2LiMn 2 O 4 + 10H 2 O + O 2 ↑ ( overall reaction)

Mn ^{2 +} + 3OH ^- + 2H ₂ O ₂ → Mn (III / IV) OOH + 3H ₂ O + O ₂ ↑ (redox and precipitation)

2Mn (III / IV) OOH + 2OH ^- + Li ^{+ -} LiMn ₂ O ₄ + 2H ₂ O (ion exchange and intercalation)

In the above Reaction Scheme 1,

Mn (III / IV) OOH has a birnessite-like structure.

Another embodiment provides a cathode active material for a lithium secondary battery produced by the method for producing a cathode active material for a lithium secondary battery.

The cathode active material for a lithium secondary battery may include a lithium manganese composite metal oxide represented by the following general formula (1).

[Chemical Formula 1]

Li _{1 + x} Mn _{2 - x} O ₄

In Formula 1,

x is 0? x? 0.3, specifically 0? x? 0.2, and more specifically 0.005 < x <

The cathode active material for lithium secondary batteries may have an average particle diameter of about 10 nm to about 100 nm. When the average particle diameter of the cathode active material for the lithium secondary battery is within the above range, the specific surface area is large and the area of reacting with the electrolyte is large, and the moving distance of the lithium ion in the cathode active material for the lithium secondary battery is short, And the charge transfer rate between the positive electrode active material for a lithium secondary battery and the electrolyte can be effectively increased. Specifically, the cathode active material for a lithium secondary battery may have an average particle diameter of about 10 nm to about 50 nm, more specifically about 20 nm to about 30 nm.

The cathode active material for a lithium secondary battery may form secondary particles having a particle size of 1 to 20 탆, specifically 1 to 10 탆.

The cathode active material for a lithium secondary battery may have a single crystal structure. In this case, a high energy density and a high power density can be obtained, and a high density electrode plate can be easily manufactured.

The cathode active material for a lithium secondary battery may have a specific surface area of about 10 m ² / g to about 100 m ² / g. When the specific surface area of the cathode active material for the lithium secondary battery is within the above range, rapid charge and discharge can be effectively performed. Specifically, the cathode active material for a lithium secondary battery may have a specific surface area of about 60 m ² / g to about 70 m ² / g.

The cathode active material for the lithium secondary battery may further include a carbon coating layer positioned on the surface of the lithium manganese composite metal oxide. In this case, the secondary particles composed of the cathode active material for the lithium secondary battery may form a conductive network therein. As a result, the aggregation of the cathode active materials for the lithium secondary battery can be suppressed and the polarization phenomenon can be suppressed to improve the capacity characteristics and the cycle life characteristics. Further, by improving the conductivity of the positive electrode active material for a lithium secondary battery so as to lower the resistance, rapid charging / discharging can be performed more effectively. In particular, it achieves high electrode plate density while maintaining excellent charge / discharge characteristics at a high rate.

The carbon coating layer may have a thickness of from about 0.1 nm to about 3 nm, and more specifically from about 0.5 nm to about 2 nm, and more specifically from about 1 nm to about 2 nm, It is not.

The carbon contained in the carbon coating layer may be included in an amount of about 0.05 wt% to about 3 wt% based on the total amount of the cathode active material for a lithium secondary battery including the carbon coating layer. When the amount of carbon contained in the carbon coating layer is within the above range, aggregation of the cathode active materials for lithium secondary batteries can be effectively suppressed, polarization effect can be suppressed, and capacity characteristics and cycle life characteristics can be effectively improved can do. Further, by improving the conductivity of the positive electrode active material for a lithium secondary battery so as to lower the resistance, rapid charging / discharging can be performed more effectively.

The positive electrode active material for a lithium secondary battery may be usefully used as a positive electrode of an electrochemical cell such as a lithium secondary battery.

The lithium secondary battery according to another embodiment includes a cathode including the cathode active material for the lithium secondary battery, a cathode including the anode active material, and an electrolyte.

The positive electrode includes a positive electrode collector and a positive electrode active material layer formed on the positive electrode collector.

The cathode active material layer also includes a binder and a conductive material.

The binder serves to adhere the positive electrode active material particles to each other well and adhere the positive electrode active material to the positive electrode collector well. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl Polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-acrylonitrile, styrene-butadiene rubber, Butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any conductive material can be used without causing any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, Metal powders such as black, carbon fiber, copper, nickel, aluminum, and silver, metal fibers, and the like, and conductive materials such as polyphenylene derivatives may be used alone or in combination.

Al may be used as the positive electrode collector, but the present invention is not limited thereto.

The negative electrode includes a negative electrode collector and a negative electrode active material layer formed on the negative electrode collector, and the negative electrode active material layer includes a negative electrode active material.

Examples of the negative electrode active material include a material capable of reversibly intercalating and deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

As the material capable of reversibly intercalating and deintercalating lithium ions, any carbonaceous anode active material commonly used in lithium ion secondary batteries can be used as the carbonaceous material, and typical examples thereof include crystalline carbon, amorphous carbon, Can be used. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in the form of amorphous, plate-like, flake, spherical or fibrous type. Examples of the amorphous carbon include soft carbon (soft carbon) Or hard carbon, mesophase pitch carbide, fired coke, and the like.

Examples of the lithium metal alloy include lithium and a metal such as Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Alloys may be used.

As the material capable of doping and dedoping lithium, Si, SiO _x (0 <x <2), Si-C composite, Si-M alloy (M is an alkali metal, an alkaline earth metal, , transition metal, rare earth element or a combination of these, Si is not), Sn, SnO _2, Sn-C composite, Sn-M (wherein M is an alkali metal, alkaline earth metal, a Group 13 to 16 element, a transition metal, A rare earth element or a combination thereof, but not Sn). As the element M, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, , Se, Te, Po, or a combination thereof.

Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like.

The negative electrode active material layer also includes a binder, and may optionally further include a conductive material.

The binder serves to adhere the negative electrode active material particles to each other and adhere the negative electrode active material to the negative electrode current collector. Typical examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, Such as polyvinyl chloride, polyvinyl fluoride, polymers comprising ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, Styrene-butadiene rubber, epoxy resin, nylon, and the like may be used, but the present invention is not limited thereto.

The conductive material is used for imparting conductivity to the electrode. Any material can be used as long as it does not cause any chemical change in the battery. Examples of the conductive material include natural graphite, artificial graphite, carbon black, acetylene black, , Carbon-based materials such as carbon fibers; Metal powders such as copper, nickel, aluminum, and silver, or metal-based materials such as metal fibers; Conductive polymers such as polyphenylene derivatives; Or a mixture thereof may be used.

The anode current collector may be a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foil, a copper foil, a polymer substrate coated with a conductive metal, or a combination thereof.

The positive electrode and the negative electrode are prepared by mixing an active material, a conductive material and a binder in a solvent to prepare an active material layer composition, and applying the composition to a current collector. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein. As the solvent, N-methylpyrrolidone or the like can be used, but it is not limited thereto.

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

Examples of the solvent for the non-aqueous electrolyte include cyclic carbonates such as ethylene carbonate, diethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; Chain carbonates such as dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate; Esters such as methyl acetate, ethyl acetate, propyl acetate, 1,1-dimethyl ethyl acetate, methyl propionate, ethyl propionate and? -Butyrolactone; Ethers such as tetrahydrofuran, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane and 2-methyltetrahydrofuran, nitriles such as acetonitrile, Amides, and the like can be used, but the present invention is not limited thereto. These can be used singly or in combination. In particular, a mixed solvent of cyclic carbonate and chain carbonate can be used.

As the electrolyte, a gelated 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 can be used, but is not limited thereto.

As the lithium salt, 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 , LiAlO ₂ , LiAlCl ₄ , LiCl, and LiI may be used, but the present invention is not limited thereto.

Depending on the type of the lithium secondary battery, a separator may exist between the positive electrode and the negative electrode. The separator may be polyethylene, polypropylene, polyvinylidene fluoride or a multilayer film of two or more thereof. The separator may be a polyethylene / polypropylene double layer separator, a polyethylene / polypropylene / polyethylene triple layer separator, a polypropylene / It is needless to say that a mixed multilayer film such as a propylene three-layer separator and the like can be used.

The lithium secondary battery can be classified into a lithium ion battery, a lithium ion polymer battery, and a lithium polymer battery depending on the type of the separator and electrolyte used. The lithium secondary battery can be classified into a cylindrical shape, a square shape, a coin shape, Depending on the size, it can be divided into bulk type and thin type. The structure and the manufacturing method of these cells are well known in the art, and detailed description thereof will be omitted.

1 schematically shows a structure of a lithium secondary battery according to an embodiment. 1, the lithium secondary battery 100 includes a cathode 112; An anode 114 facing the cathode 112; A separator (113) disposed between the cathode (112) and the anode (114); A battery container 120 including an electrolyte (not shown) for impregnating the cathode 112, the anode 114, and the separator 113; And a sealing member 140 for sealing the battery container 120. The shape of the lithium secondary battery according to one embodiment is not particularly limited, and any shape such as a cylindrical shape, a coin shape, and a pouch shape can be used as long as it can operate as a battery.

The lithium secondary battery according to one embodiment of the present invention can be widely used in a portable information terminal, a portable electronic device, a small-sized power storage device for a home, a motorcycle, an electric vehicle, a hybrid electric vehicle and the like.

Example

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the following examples and comparative examples are for illustrative purposes only and are not intended to limit the present invention.

Example  1: Preparation of cathode active material for lithium secondary battery

30 ml of pure water, 1.2 g of LiOH.H ₂ O and 1.5 mg of H ₂ O ₂ were added to one container and stirred to prepare a first mixed solution.

30 ml of pure water and 2.5 g of Mn (CH ₃ COO) ₂ .4H ₂ O were added to another container and stirred to prepare a second mixed solution.

The first mixed solution and the second mixed solution were sequentially put in a Teflon container and stirred, and then 100 ml of methanol was added.

The Teflon container was placed in an autoclave and heat-treated at 110 ° C for 12 hours, followed by natural cooling for 2 hours.

The resulting solid was washed several times with water and ethanol, and then dried in a vacuum oven at 150 캜 for 24 hours. Then, it was placed in a furnace preheated to 600 DEG C, held for 20 minutes, and then cooled at a rate of 30 DEG C / minute.

Thus, a positive electrode active material LiMn ₂ O ₄ for a lithium secondary battery was prepared.

Example  2: Preparation of cathode active material for lithium secondary battery

30 ml of pure water, 1.2 g of LiOH.H ₂ O and 1.5 mg of H ₂ O ₂ were added to one container and stirred to prepare a first mixed solution.

30 ml of pure water and 2.5 g of Mn (CH ₃ COO) ₂ .4H ₂ O were added to another container and stirred to prepare a second mixed solution.

The first mixed solution and the second mixed solution were sequentially put in a Teflon container and stirred, and then 100 ml of methanol was added.

The Teflon container was placed in an autoclave and heat-treated at 110 ° C for 12 hours, followed by natural cooling for 2 hours.

The resulting solid was washed several times with water and ethanol, and then dried in a vacuum oven at 150 캜 for 24 hours.

In another container, 0.2 g of sucrose was dissolved in 10 ml of pure water to prepare a solution containing a carbon source.

30 ml of ethanol and 1 g of the washed and dried solid were added to the solution containing the carbon source, ultrasonicated and dispersed, and then dried in a vacuum oven at 150 캜. Then, it was placed in a furnace preheated to 600 DEG C, held for 20 minutes, and then cooled at a rate of 30 DEG C / minute.

Thus, a positive electrode active material LiMn ₂ O ₄ for a lithium secondary battery was prepared.

Example  3: Preparation of cathode active material for lithium secondary battery

Except that 100 ml of tetrahydrofuran (THF) was used in place of 100 ml of methanol, to prepare a cathode active material LiMn ₂ O ₄ for a lithium secondary battery.

Example  4: Preparation of cathode active material for lithium secondary battery

A positive electrode active material LiMn ₂ O ₄ for a lithium secondary battery was prepared in the same manner as in Example 1 except that 100 ml of ethanol was used instead of 100 ml of methanol.

Comparative Example  1: Preparation of cathode active material for lithium secondary battery

Lithium carbonate (Li ₂ CO ₃ ) and manganese dioxide (MnO ₂ , particle diameter 30 μm) were mixed so that the atomic ratio of Li and Mn was 1: 2. Subsequently, heat treatment was performed at 780 캜 for 18 hours to prepare stoichiometric LiMn ₂ O ₄ having a size of 30 탆.

Comparative Example  2: Preparation of cathode active material for lithium secondary battery

A positive electrode active material LiMn ₂ O ₄ for lithium secondary batteries was prepared in the same manner as in Example 1, except that 100 ml of water was used in place of 100 ml of methanol.

Example  5: Preparation of lithium secondary battery

A positive electrode active material for a lithium secondary battery, a polyvinylidene fluoride (PVdF) binder, and super P carbon black prepared in Example 1 were dispersed in a weight ratio of 65:10:25 to N-methylpyrrolidone (N-methylpyrrolidone, NMP) and mixed to prepare a slurry. Subsequently, the slurry was uniformly applied on an aluminum foil to a uniform thickness using a doctor blade coater, vacuum-dried at 130 DEG C for 20 minutes, and used as an anode.

The prepared anode and lithium foil were used as a counter electrode, and a porous polyethylene membrane (Celgard 2300, thickness: 25 탆, manufactured by Cellard EL) was used as a separator. Ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 3: 7 A pouch type coin half cell was prepared according to a conventional manufacturing process using a liquid electrolyte in which LiPF ₆ was dissolved in a solvent at a concentration of 1.15M.

Example  6: Manufacture of lithium secondary battery

A pouch-type coin half cell was fabricated in the same manner as in Example 5, except that the cathode active material for a lithium secondary battery prepared in Example 2 was used in place of the cathode active material for a lithium secondary battery prepared in Example 1.

Comparative Example  3 and 4: Preparation of lithium secondary battery

A pouch-type coin half cell was prepared in the same manner as in Example 5, except that the cathode active materials for lithium secondary batteries of Comparative Examples 1 and 2 were used instead of the cathode active material for lithium secondary battery prepared in Example 1, respectively.

Test Example  1: X-ray diffraction (X- ray diffraction , XRD ) analysis

X-ray diffraction analysis of the cathode active materials for lithium secondary batteries of Examples 1 to 4, Comparative Examples 1 and 2 was carried out. In the X-ray diffraction analysis, a Cu-K ray was used as a light source. The results are shown in Fig.

2, it can be confirmed that the cathode active material for lithium secondary batteries prepared in Examples 1 to 4, Comparative Examples 1 and 2 is LiMn ₂ O ₄ .

At this time, the positive electrode active material for a lithium secondary battery produced in Comparative Example 2 had an impurity peak at about 30 degrees and 65 degrees, and it was found that the positive active material for lithium secondary batteries had a larger half-width than the positive active material for lithium secondary batteries prepared in Examples 1 to 4. This indicates that the cathode active material for lithium secondary battery produced in Comparative Example 2 had poor crystallinity.

On the other hand, in Example 1, the first mixed solution and the second mixed solution were sequentially put into a Teflon vessel and stirred, and the obtained precipitate was subjected to X-ray diffraction analysis. In the X-ray diffraction analysis, a Cu-K ray was used as a light source. The results are shown in Fig.

In FIG. 3, K _x MnO ₂ having a Bernese-like structure as a reference is shown in a black graph, and the precipitate is shown in a blue graph. The final cathode active material for a lithium secondary battery manufactured in Example 1 is shown in a red graph.

As shown in FIG. 3, the blue graph shows a pattern similar to that of the black graph, so that it can be confirmed that the precipitates have a layered type birnessite-like structure. The red graph shows the pattern of the spinel structure. It can be seen that the cathode active material for the lithium secondary battery forms a spinel structure in the hydrothermal process.

Test Example  2: Scanning electron microscope ( scanning electron microscope , SEM Photographic and Transmission Electron Microscope transmission electron microscope , TEM ) Picture

The cathode active materials for lithium secondary batteries prepared in Examples 1 to 4, Comparative Examples 1 and 2 were each sampled on a carbon tape, and platinum (Pt) plasma coating was used to take an SEM photograph. In addition, a solution in which a sample is dispersed on a carbon-coated copper grid was sampled, the solution was dried, and a TEM photograph was taken. (FE-SEM) NanoSem 230 (manufactured by FEI) and a high resolution transmission electron microscope (HR-TEM) JEM-2100F (manufactured by JEOL Co., Ltd.) operating at 200 kV. ) Was used.

Scanning electron micrographs of the cathode active material for a lithium secondary battery manufactured in Example 1 are shown in Figs. 4A and 4B, and a transmission electron microscope photograph is shown in Fig. 10A. A graph obtained by Fourier transforming Fig. 10A is shown in Fig. 10B.

As shown in FIGS. 4A, 4B, 10A, and 10B, the cathode active material for lithium secondary battery manufactured in Example 1 is formed into uniform particles having an average particle diameter of about 20 nm, and it can be confirmed that it is a single crystal spinel structure.

Scanning electron micrographs of the cathode active material for a lithium secondary battery prepared in Example 2 are shown in Figs. 5A and 5B, and a transmission electron microscope photograph is shown in Fig. 11A. Fig. 11B shows a graph obtained by Fourier transforming Fig. 11A. 12A and 12C show transmission electron microscope photographs showing the carbon coating layer, and FIG. 12B shows a graph obtained by Fourier transforming FIG. 12A.

As shown in Figs. 5A, 5B, 11A, 11B, 12A, 12B and 12C, the cathode active material for lithium secondary battery manufactured in Example 2 is formed into uniform particles having an average particle diameter of about 20 nm , It can be confirmed that it is a single crystal spinel structure. Even if the cathode active material is carbon-coated, it can be confirmed that there is no structural change of the cathode active material itself for the lithium secondary battery.

Scanning electron micrographs of the cathode active material for a lithium secondary battery manufactured in Example 3 are shown in Figs. 6A and 6B.

6A and 6B, it can be confirmed that the cathode active material for lithium secondary battery manufactured in Example 3 has a single crystal spinel structure.

Scanning electron micrographs of the cathode active material for a lithium secondary battery manufactured in Example 4 are shown in FIGS. 7A and 7B.

As shown in FIGS. 7A and 7B, it can be confirmed that the cathode active material for a lithium secondary battery manufactured in Example 4 has both a particle shape and a wire shape.

Scanning electron micrographs of the positive electrode active material for a lithium secondary battery manufactured in Comparative Example 1 are shown in Figs. 8A and 8B.

As shown in FIGS. 8A and 8B, it can be seen that the cathode active material for lithium secondary battery manufactured in Comparative Example 1 is secondary particles of about 30 um consisting of several hundreds of nano-sized primary particles.

Scanning electron micrographs of the cathode active material for a lithium secondary battery manufactured in Comparative Example 2 are shown in Figs. 9A and 9B.

As shown in FIGS. 9A and 9B, the cathode active material for lithium secondary battery manufactured in Comparative Example 2 can be confirmed that the shape and size of the particles are irregular.

Test Example  3: Evaluation of high rate discharge characteristics

The pouch half cells prepared in Example 5, Example 6 and Comparative Example 3 were filled at 0.5 C-rate, and the cells were subjected to 1 C-rate (120 mA / g), 3 C-rate, 10 C- rate, 100 C-rate, 200 C-rate, and 300 C-rate. The results are shown in FIG. Only the pure discharge characteristics of the active material were evaluated by fixing the charge at 0.5C-rate. 1 C is 120 mAh / g, the loading level is 2 to 3 mg / cm ² , and the electrode density is 2.3 g / cc.

High-rate discharge characteristics are an essential requirement for high-power applications. 1 C means the current value that can be generated for 1 hour. As the C-rate increases, the current value also increases proportionally. At this time, the current polarization increases and the capacitance decreases.

As shown in FIG. 13, Comparative Example 3 shows a rapid capacity decrease phenomenon at a high rate discharge of 10 C-rate or more, but Example 5 shows a high rate discharge characteristic even at a 10 C-rate. In Example 6, 88.6% at 50 C-rate versus 1 C-rate discharge capacity, 83.7% at 100 C-rate, 69.7% at 200 C-rate, and an initial capacity of 40% It can be confirmed that the high-rate discharge characteristics are excellent.

In Fig. 13, the 1C recovery portion shows the capacity recovered when the discharge is performed at a low rate of 1 C-rate after the high rate discharge. It can be seen that both of Example 5 and Example 6 maintained the capacity well without deterioration even during high rate discharge.

Test Example  4: Evaluation of high rate charging characteristics

The pouch half cells prepared in Example 5, Example 6 and Comparative Example 3 were discharged at 1 C-rate, and 0.5 C-rate, 1 C-rate, 5 C-rate, 10 C- , 30 C-rate, 50 C-rate, and 100 C-rate. The results are shown in FIG. Only the pure charging characteristics of the active material were evaluated by fixing the discharge at 1 C-rate. In FIG. 14, the vertical axis indicates the discharge capacity. Since the discharge capacity is higher than the charged capacity at a high rate, the discharge capacity at each C-rate can be measured to confirm the charge capacity.

In Comparative Example 1, the capacity was reduced at a high rate of 30 C-rate or more, but Example 5 showed a high rate of charging at 10 C-rate. The initial capacity of Example 6 was 95.3% (at 6 C minutes), 90 C at 90 C, and 83 C (59 seconds) at 50 C-rate at 10 C-rate versus 0.5 C- It can be confirmed that the high-rate charging property is excellent.

In Fig. 14, the 1C recovery portion shows the capacity recovered when charging at a low rate of 0.5 C-rate after high-rate charging. It can be seen that both of Example 5 and Example 6 maintained the capacity well without deterioration even during high-rate charging.

Test Example  5: high rate Charging and discharging  Capacity retention rate evaluation

The pouch half cells prepared in Example 6 were charged and discharged at the same C-rate, and the capacity retention rate was repeatedly shown in FIG. 15 at 20 cycles per C-rate.

In Example 6, the capacity of 94.6% was maintained at 10 C, and the capacity of 91.8% at 20 C, 89.2% at 30 C, 86.6% at 40 C, 88.5% at 50 C and 64% at 100 C And it can be seen that the high rate charge / discharge capacity retention ratio is excellent.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

100: lithium secondary battery, 112: negative electrode,
114: positive electrode, 113: separator,
120: battery container, 140: sealing member

Claims (22)

Dissolving a lithium source and an oxidizing agent in a solvent to prepare a first mixed solution;
Dissolving a manganese source in a solvent to prepare a second mixed solution;
Mixing the first mixed solution and the second mixed solution and adding a solvent having a boiling point of 100 ° C or lower to prepare a mixed solution; And
Heating the mixed solution to a temperature of 60 ° C to 200 ° C to hydrothermal reaction to obtain a lithium manganese composite metal oxide;
Wherein the positive electrode active material is a positive electrode active material.
The method according to claim 1,
Wherein the lithium source comprises one selected from the group consisting of lithium hydroxide, oxyhydroxide, nitrate, halide, carbonate, acetate, oxalate, citrate, and combinations thereof.
The method according to claim 1,
Wherein the oxidizing agent comprises one selected from the group consisting of hydrogen peroxide, glycolic acid, citric acid, potassium permanganate, ammonium peroxodisulfate, nitric acid, chloric acid, chromic acid, manganese dioxide, and combinations thereof.
The method according to claim 1,
Wherein the manganese source comprises one selected from the group consisting of hydroxides, oxyhydroxides, nitrates, halides, carbonates, acetates, oxalates, citrates and combinations thereof including manganese.
The method according to claim 1,
The solvent in the step of preparing the first mixed solution by dissolving the lithium source and the oxidizing agent in a solvent, and
The solvent in the step of dissolving the manganese source in the solvent to prepare the second mixed solution is at least one selected from the group consisting of water, aromatic hydrocarbons, saturated hydrocarbons, halogenated saturated hydrocarbons, aldehydes, alcohols, ethers, esters, ketones , Nitriles, and combinations thereof. &Lt; / RTI &gt;
The method according to claim 1,
Wherein the lithium source and the manganese source are used in a molar ratio of 1: 1 to 5: 1.
The method according to claim 1,
Wherein the solvent having a boiling point of 100 DEG C or lower includes one selected from a polar solvent, a non-polar solvent, and a combination thereof.
The method according to claim 1,
The solvent having a boiling point of 100 DEG C or lower is selected from the group consisting of C1 to C15 alkanes, C1 to C15 haloalkanes, C3 to C15 cycloalkanes, C6 to C20 arenes, C1 to C15 aliphatic ethers, C3 to C15 alicyclic ethers, C1 to C15 acetates, Wherein the positive electrode active material comprises one selected from the group consisting of a C2 to C15 ketone, a C1 to C15 amide, a C1 to C15 nitrile, a C1 to C15 sulfoxide, a C1 to C15 aliphatic organic acid, a C1 to C15 alcohol, Gt;
The method according to claim 1,
The solvent having a boiling point of 100 DEG C or lower may be selected from the group consisting of pentane, hexane, chloroform, dichloromethane, cyclopentane, cyclohexane, benzene, diethyl ether, tetrahydrofuran, ethyl acetate, acetone, acetonitrile, methanol, , Isopropanol, and combinations thereof. &Lt; / RTI &gt;
The method according to claim 1,
Wherein the solvent having a boiling point of 100 占 폚 or less is added in an amount of 500 to 5000 parts by weight based on 100 parts by weight of the manganese source.
The method according to claim 1,
Wherein the hydrothermal reaction is performed for 1 hour to 24 hours.
The method according to claim 1,
Wherein the heat treatment is performed at a temperature of 400 ° C to 700 ° C after the hydrothermal reaction.
13. The method of claim 12,
Further comprising the step of adding a carbon source before the heat treatment step after the hydrothermal reaction step.
14. The method of claim 13,
The carbon source may be selected from the group consisting of sucrose, glucose, polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), colloidal carbon, citric acid, But not limited to, one selected from the group consisting of tartaric acid, glycolic acid, polyacrylic acid, adipic acid, glycine, aminobenzoic acid, and combinations thereof. Wherein the positive electrode active material is a negative electrode active material.
14. The method of claim 13,
Wherein the carbon source is added in an amount of 5 to 50 parts by weight based on 100 parts by weight of the lithium manganese composite metal oxide.
16. A cathode active material for a lithium secondary battery produced by the method according to any one of claims 1 to 15.
17. The method of claim 16,
Wherein the positive electrode active material for a lithium secondary battery comprises a lithium manganese composite metal oxide represented by the following Formula 1:
[Chemical Formula 1]
Li _{1 + x} Mn _{2 - x} O ₄
In Formula 1,
x is 0? x? 0.3.
17. The method of claim 16,
Wherein the cathode active material for a lithium secondary battery has an average particle diameter of 10 nm to 100 nm.
17. The method of claim 16,
Wherein the positive electrode active material for a lithium secondary battery has a single crystal structure.
18. The method of claim 17,
Wherein the cathode active material for a lithium secondary battery further comprises a carbon coating layer positioned on the surface of the lithium manganese composite metal oxide.
21. The method of claim 20,
Wherein the carbon contained in the carbon coating layer is included in an amount of 0.05 wt% to 3 wt% with respect to the total amount of the cathode active material for a lithium secondary battery including the carbon coating layer.
A cathode comprising a cathode active material;
A negative electrode comprising a negative electrode active material; And
Comprising an electrolyte,
The lithium secondary battery according to claim 16, wherein the cathode active material is a cathode active material for a lithium secondary battery according to claim 16.

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