KR100399634B1 - Positive active material for lithium secondary battery and method of preparing same - Google Patents

Abstract

The present invention relates to a cathode active material for a lithium secondary battery and a method of manufacturing the cathode active material, the core including a lithium compound selected from compounds of Formulas 1 to 14 and an amorphous or crystalline metal hydroxide layer formed on the core (wherein The metal has a physical property of being dissolved in an alcohol or an aqueous solution).

[Formula 1]

Li _x MnA ₂

[Formula 2]

Li _x MnO _2-z A _z

[Formula 3]

Li _x Mn _1-y M ' _y A ₂

[Formula 4]

Li _x Mn _1-y M ' _y O _2-z A _z

[Formula 5]

Li _x Mn ₂ O ₄

[Formula 6]

Li _x Mn ₂ O _4-z A _z

[Formula 7]

Li _x Mn _2-y M ' _y A ₄

[Formula 8]

Li _x BA ₂

[Formula 9]

Li _x BO _2-z A _z

[Formula 10]

Li _x B _1-y M " _y A ₂

[Formula 11]

Li _x Ni _1-y Co _y A ₂

[Formula 12]

Li _x Ni _1-y Co _y O _2-z A _z

[Formula 13]

Li _x Ni _1-yz Co _y M " _z A ₂

[Formula 14]

Li _{x '} Ni _1-y' Mn _{y '} M _z' A _α

Wherein 0.95 ≦ x ≦ 1.1, 0.01 ≦ y ≦ 0.1, 0.01 ≦ z ≦ 0.5, 0.95 ≦ x '≦ 1, 0.01 ≦ y ′ ≦ 0.5, 0 ≦ z' ≦ 0.1, 0.01 ≦ α ≦ 0.5, M 'is at least one of transition metals or lanthanide metals selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr and V, and M "is Al, Cr, Co, Mg, La At least one of transition metals or lanthanide metals selected from the group consisting of Ce, Sr and V, A is selected from the group consisting of O, F, S and P, and B is Ni or Co.)

Description

A cathode active material for a lithium secondary battery and a manufacturing method thereof {POSITIVE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY AND METHOD OF PREPARING SAME}

[Industrial use]

The present invention relates to a positive electrode active material for a lithium secondary battery and a method for manufacturing the same, and more particularly, to a positive electrode active material for a lithium secondary battery with improved lifespan, discharge potential and power amount characteristics and a method for manufacturing the same.

[Prior art]

Lithium secondary batteries, which are currently commercialized and used, correspond to the heart of the digital era, which is rapidly being applied to portable phones, notebook computers, camcorders, and the like, which have an average discharge potential of 3.7V, that is, 4C. The cathode material of the lithium secondary battery uses more than 95% of the high-priced LiCoO ₂ of the battery in circulation around the world, and efforts to replace the LiCoO ₂ have been in progress. Lithium secondary battery using LiCoO ₂ powder as a positive electrode material has a relatively long lifespan and excellent discharge flatness, but there is a demand for continuous performance improvement, such as life expectancy through continuous performance improvement and demand for improvement of power characteristics. Many studies are in progress.

One of the improvements of LiCoO ₂ , a cathode material, has been conducted to replace a part of Co with a metal oxide, and Sony has doped Al ₂ O ₃ by about 1 to 5% by weight to replace a part of Co with Al. LiCo _1-x Al _x O ₂ powder has been developed and applied to mass production, and ATB has been in progress or completed a study of doping SnO ₂ to replace a part of Co with Sn. The present applicant has also applied for a patent on the development of high-performance LiCoO ₂ powder whose surface structure and properties are modified by coating the surface of LiCoO ₂ with a metal-alkoxide solution and then heat-treating (Domestic Patent Application No. 98-3755) ). However, research is still underway to develop a positive electrode active material having excellent electrochemical characteristics such as lifetime and discharge potential.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a cathode active material for a lithium secondary battery having excellent life, discharge potential, and power amount characteristics.

Another object of the present invention is to provide a method for producing the positive electrode active material for a lithium secondary battery.

1 is a schematic diagram schematically showing a device used in a coating process of the positive electrode active material for a lithium secondary battery of the present invention.

2 is a process diagram briefly illustrating a process of producing a final positive electrode active material according to the manufacturing method of the present invention using LiCoO ₂ .

3 is a process diagram briefly showing a process of producing a final positive electrode active material obtained after a heat treatment process according to a conventional method using LiCoO ₂ .

4 is a process chart showing a process using a batch processing method and a conventional manufacturing process of the positive electrode active material for a lithium secondary battery of the present invention.

Figure 5a is a SEM photograph showing the surface of the positive electrode active material for a lithium secondary battery prepared according to an embodiment of the present invention.

Figure 5b is a SEM photograph showing the surface of the positive electrode active material for a lithium secondary battery prepared according to another embodiment of the present invention.

Figure 5c is a SEM photograph showing the surface of the positive electrode active material for lithium secondary batteries prepared by a conventional method.

5D is a SEM photograph showing the surface of pure LiCoO ₂ .

Figure 6 is a graph showing the discharge characteristics obtained by charging and discharging the positive electrode active material prepared by the method of the Example and Comparative Example of the present invention at 0.1C.

Figure 7 is a graph showing the discharge characteristics obtained by charging and discharging the positive electrode active material prepared by the method of the embodiment of the present invention and the comparative example at 0.5C.

Figure 8 is a graph showing the discharge characteristics obtained by charging and discharging the positive electrode active material prepared by the method of the Examples and Comparative Examples of the present invention at 1C.

9 is a graph showing XRD patterns of Al (OH) ₃ and Al ₂ O ₃ .

FIG. 10 is a JCPDS card describing reference data of Al (OH) ₃ and Al ₂ O ₃ ; FIG.

In order to achieve the above object, the present invention is a core containing a lithium compound selected from compounds of Formula 1 to 14; And an amorphous or crystalline metal hydroxide layer formed on the core, wherein the metal has physical properties dissolved in an alcohol or an aqueous solution.

[Formula 1]

Li _x MnA ₂

[Formula 2]

Li _x MnO _2-z A _z

[Formula 3]

Li _x Mn _1-y M ' _y A ₂

[Formula 4]

Li _x Mn _1-y M ' _y O _2-z A _z

[Formula 5]

Li _x Mn ₂ O ₄

[Formula 6]

Li _x Mn ₂ O _4-z A _z

[Formula 7]

Li _x Mn _2-y M ' _y A ₄

[Formula 8]

Li _x BA ₂

[Formula 9]

Li _x BO _2-z A _z

[Formula 10]

Li _x B _1-y M " _y A ₂

[Formula 11]

Li _x Ni _1-y Co _y A ₂

[Formula 12]

Li _x Ni _1-y Co _y O _2-z A _z

[Formula 13]

Li _x Ni _1-yz Co _y M " _z A ₂

[Formula 14]

Li _{x '} Ni _1-y' Mn _{y '} M _z' A _α

Wherein 0.95 ≦ x ≦ 1.1, 0.01 ≦ y ≦ 0.1, 0.01 ≦ z ≦ 0.5, 0.95 ≦ x '≦ 1, 0.01 ≦ y ′ ≦ 0.5, 0 ≦ z' ≦ 0.1, 0.01 ≦ α ≦ 0.5, M 'is at least one of transition metals or lanthanide metals selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr and V, and M "is Al, Cr, Co, Mg, La At least one of transition metals or lanthanide metals selected from the group consisting of Ce, Sr and V, A is selected from the group consisting of O, F, S and P, and B is Ni or Co.)

The present invention is also coated with a metal alkoxide solution or a metal aqueous solution of a lithium compound selected from the compounds of Formula 1 to 14; It provides a method for producing a cathode active material for a lithium secondary battery comprising the step of drying the compound coated with the metal alkoxide solution or the metal aqueous solution.

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

The present invention is modified by the metal alkoxide solution coating method filed by the present applicant, the conventional method is a metal oxide powder (LiCoO ₂ , LiNi _1-xy M _x used as a cathode material for a metal alkoxide solution and a lithium secondary battery) N _y O _2, etc.) are mixed with each other to prepare a slurry, and then dried and heat-treated between about 300 to 800 ° C. to form a new metal oxide layer or a metal oxide layer and a used metal on the surface of LiCoO ₂ . Metal oxides derived from alkoxide solutions were used to produce new forms of powders with altered surface structures and surface properties. On the contrary, in the present invention, the heat treatment process of the existing method is removed, and only the drying process is performed to form a new lithium secondary battery positive electrode material having a metal hydroxide instead of a metal oxide layer on the surface.

The cathode active material for a lithium secondary battery of the present invention includes a core including a lithium compound selected from Chemical Formulas 1 to 14 and a metal hydroxide layer formed on the core and surrounding the core.

In the metal hydroxide layer, any metal may be used as long as it can be dissolved in alcohol or aqueous solution, and representative examples thereof include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Ge, Ga, or B. Can be.

The positive electrode active material for a lithium secondary battery of the present invention having the above structure has improved cycle life, discharge potential, and power amount compared to LiCoO ₂ and LiNi _1-xy M _x N _y O ₂ powders that are currently commercially available. power) characteristic.

In order to manufacture the cathode active material for a lithium secondary battery of the present invention, first, a compound selected from Chemical Formulas 1 to 14 is encapsulated with a metal alkoxide solution or a metal aqueous solution.

As the coating method, a general coating method such as a sputtering method, a chemical vapor deposition (CVD) method, or a dip coating method may be used. Among these coating methods, the simplest method is a dip coating method that simply dips the powder into a coating solution to make a slurry and then removes the solution.

In addition to the above-described method, the coating method may be performed in a slurry state, and then may be subjected to a one-shot process in which a step of removing a solution and a subsequent drying step may be simultaneously performed. It is advantageous because the process is simple and economically advantageous, and the metal hydroxide layer may be more uniformly formed on the surface. In more detail about the unification process, the compound (lithium metal oxide) and the metal alkoxide solution or the metal aqueous solution selected from the formulas (1) to (14) are added to the mixer and stirred while increasing the temperature of the mixer, nitrogen gas or argon Inert gas such as gas is injected. At this time, the metal alkoxide solution or the metal aqueous solution is coated on the surface of the lithium metal oxide, the excess metal alkoxide solution or the metal aqueous solution is evaporated and removed by increasing the external temperature and stirring. Therefore, the slurry production process, the solution removal process, and the drying process can be performed in one mixer in a one-shot process. For uniform mixing, the lithium metal oxide and the metal alkoxide solution or the metal aqueous solution may be added to the mixer, followed by premixing for about 10 to 30 minutes.

The temperature increase of the mixer is carried out by circulating the hot water at a temperature at which the solvent alcohol or water can be evaporated, suitably 50 to 100 ° C., outside the mixer, and the hot water cooled through the mixer is generally a heat exchanger. The temperature is circulated again by increasing the temperature.

The mixer can be a good mixture of lithium metal oxide and metal alkoxide solution or aqueous metal solution, inert gas can be injected and the temperature can be increased, there is no particular limitation. As a representative example, a planetary mixer may be used. 1 shows a planetary mixer equipped with a heat exchanger. As shown in FIG. 1, nitrogen gas serving as an inert gas is introduced into the oil-based mixer, and hot water is circulated through the heat exchanger.

The metal alkoxide solution used in the coating process is prepared by mixing alcohol and metal in an amount corresponding to 0.1 to 10% by weight based on the alcohol, and then refluxing it. Alternatively, the metal alkoxide may be dissolved in alcohol to prepare a metal alkoxide solution at a concentration of 0.1 to 10% by weight. The aqueous metal solution is prepared by mixing water with a metal or metal oxide in an amount corresponding to 0.1 to 10% by weight, and refluxing it.

As the metal, any dissolved in alcohol or aqueous solution may be used, and representative examples thereof may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Ge, Ga, or B. As a solution containing Si, tetraorthosilicate commercially available from Aldrich can be used. As the metal alkoxide, metal methoxide, metal ethoxide or metal propoxide may be used, and the alcohol may be methanol, ethanol or isopropanol. As the metal aqueous solution, vanadium oxide (V ₂ O ₅ ) aqueous solution may be used.

When the concentration of the metal is lower than 0.1% by weight, there is no effect of coating a compound selected from the group consisting of the compounds of Formulas 1 to 14 with a metal alkoxide solution or an aqueous metal solution, and the concentration of the metal exceeds 10% by weight. If the coating layer is too thick, it is not preferable.

When the general purpose coating process is carried out, the metal alkoxide solution or the powder coated with the metal aqueous solution is dried at room temperature to 200 ° C. for 1 to 24 hours.

When the unitary coating process is performed, as described above, the drying process is performed simultaneously with the coating, and thus it is not necessary to perform the drying process separately.

According to this drying process, the metal alkoxide or aqueous metal layer formed on the surface reacts with moisture in the air to be primarily converted into metal-oxy hydroxide, and the changed material is converted into metal hydroxide as it is further dried. A new amorphous or crystalline metal hydroxide layer is formed. This mechanism is shown in FIG. The metal hydroxide layer formed on the surface can reduce the internal resistance, thereby reducing the drop in the discharge potential, thereby maintaining a high discharge potential characteristic according to the change of the charge-discharge rate (C-rate). When the positive electrode active material is applied to a battery, it is expected to exhibit better life characteristics and lowering discharge potential, thereby exhibiting power improvement characteristics.

As described above, the positive electrode active material for a lithium secondary battery of the present invention performs only a drying step without performing a heat treatment step after performing a coating step. In the conventional method, a coating step is performed, followed by a drying step and a heat treatment step to prepare a cathode active material having a metal oxide layer formed on a surface thereof (FIG. 3). In this case, the metal oxide layer formed on the surface was relatively low in ionic conductivity, so that the internal resistance was increased, thereby lowering the discharge potential and power amount characteristics. However, in the present invention, the positive electrode active material having the metal hydroxide layer formed on the surface was not manufactured by performing the heat treatment process, and the positive electrode active material was found to exhibit remarkable charge and discharge characteristics compared to the positive electrode active material having the metal oxide layer formed thereon. .

In the present invention, in order to facilitate the comparison between the case of using a unified process and the conventional manufacturing method, each process is shown in FIG. As shown in Fig. 4, in the conventional coating process, a slurry is prepared by mixing a metal alkoxide solution or a metal aqueous solution with lithium metal oxide (slurry manufacturing step), removing the solution from the slurry (solution removal step), and then After drying at 80 to 100 ° C. to produce a fine powder (drying step), a method of performing heat treatment was used.

On the other hand, the manufacturing method of the present invention described in FIG. 4 is simple and economical as the slurry production process, the solution removal drying process, and the drying process are carried out in a one-shot process in one container. The cathode active material for a lithium secondary battery can be prepared, and the lithium metal oxide can be more uniformly coated with a metal alkoxide solution or a metal aqueous solution than the conventional method. In addition, the metal hydroxide layer may be formed on the surface instead of the metal oxide layer by not performing the heat treatment process.

As the compound of Chemical Formulas 1 to 14 used in the present invention, a commercially available lithium compound of Chemical Formulas 1 to 14 may be used, or a lithium compound prepared by the following method may be used.

In order to synthesize the compounds of Formulas 1 to 14, lithium salts and metal salts are mixed at a desired equivalent ratio. As the lithium salt, any one generally used to prepare a cathode active material for a manganese-based lithium secondary battery may be used, and representative examples thereof may include lithium nitrate, lithium acetate, or lithium hydroxide. Manganese salt, cobalt salt, nickel salt or nickel manganese salt may be used as the metal salt. The manganese salt may be used, such as manganese acetate or manganese dioxide, the cobalt salt may be used cobalt oxide, cobalt nitrate or cobalt carbonate, nickel salt, nickel hydroxide, nickel nitrate or nickel acetate Can be used. The nickel manganese salt may be prepared by precipitating nickel salt and manganese salt by coprecipitation method. The metal salt may be precipitated together with manganese salt, cobalt salt, nickel salt, or nickel manganese salt with fluorine salt, sulfur salt or phosphorus salt. Manganese fluoride or lithium fluoride may be used as the fluorine salt, manganese sulfide or lithium sulfide may be used as the sulfur salt, and H ₃ PO ₄ may be used as the phosphate salt. The manganese salt, cobalt salt, nickel salt, nickel manganese salt, fluorine salt, sulfur salt and phosphorus salt are not limited to the compound.

The mixing method may use, for example, mortar grinder mixing, in which an appropriate solvent such as ethanol, methanol, water, acetone is added and there is little solvent in order to promote the reaction of lithium salt and metal salt. It is desirable to carry out mortar grinder mixing until solvent-free.

The obtained mixture is heat-treated at a temperature of about 400 to 600 ° C. to prepare compound precursor powders of formulas 1 to 14 in a semi-crystalline state. If the heat treatment temperature is lower than 400 ℃ there is a problem that the reaction between the lithium salt and the metal salt is not sufficient. In addition, after drying the precursor powder prepared by the heat treatment, or after the heat treatment process (blowing) dry air may be uniformly distributed by remixing the precursor powder at room temperature (remixing).

The semi-crystalline precursor powder obtained is subjected to secondary heat treatment at a temperature of 700 to 900 ° C. for about 10 to 15 hours. If the secondary heat treatment temperature is lower than 700 ° C, there is a problem that the crystalline material is difficult to form. The heat treatment process is carried out by raising the temperature at a rate of 1 to 5 ℃ / min under the conditions of blowing (dry) air or oxygen, and consists of natural cooling after maintaining for a predetermined time at each heat treatment temperature.

Subsequently, it is preferable to remix the powder of the compound selected from the group consisting of the compounds of Formulas 1 to 14 at room temperature to distribute the lithium salt more uniformly.

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

(Comparative Example 1)

Using a LiCoO ₂ (Nippon Chem, trade name: C-10) powder as the cathode active material, a cathode active material slurry was prepared at a ratio of 94/3/3 to an active material / conductive material / binder ratio. In this case, super P was used as the conductive material, and polyvinylidene fluoride was used as the binder. The positive electrode active material slurry was cast on Al-foil to a thickness of about 100 μm to prepare a positive electrode plate for a coin battery. The prepared positive electrode plate was punched to a diameter of 1.6 cm, and a coin battery was prepared in a glove box using a mixed solvent of ethylene carbonate and dimethyl carbonate in which 1 M LiPF ₆ was dissolved as an electrolyte.

(Comparative Example 2)

Except that UMEX LiCoO ₂ powder was used as the positive electrode active material was carried out in the same manner as in Comparative Example 1.

(Comparative Example 3)

A lithium active material was used in the same manner as in Comparative Example 1 except that LiNi _0.9 Sr _0.002 Co _0.1 O ₂ powder, manufactured by Honjo, was used.

(Comparative Example 4)

5% by weight of Al-isopropoxide was dissolved in 95% by weight of ethanol to prepare an Al-isopropoxide ethanol solution. LiCoO ₂ (Nippon Chem, trade name: C-10) powder was immersed in this ethanol solution and stirred to allow the Al-isopropoxide ethanol solution to sufficiently react on the surface of the LiCoO ₂ powder. It dried about time. The dried powder was heat-treated while blowing dry air at 500 ° C. for 10 hours to prepare a cathode active material having an Al ₂ O ₃ layer formed on its surface.

A positive electrode active material slurry composition was prepared at a ratio of the prepared positive active material, super P as the conductive material, polyvinylidene fluoride as the binder, and the ratio of the active material / conductive material / binder to 94/3/3. The prepared positive electrode active material slurry composition was cast on an Al-foil with a thickness of about 100 μm to prepare a positive electrode plate for a coin battery. The prepared positive electrode plate was punched to a diameter of 1.6 cm, and a coin battery was prepared in a glove box using a mixed solvent of ethylene carbonate and dimethyl carbonate in which 1M LiPF ₆ was dissolved as an electrolyte.

(Comparative Example 5)

An Al-isopropoxide ethanol solution at a concentration of 1% was used, and the same procedure as in Comparative Example 4 was carried out except that the heat treatment temperature was changed to 600 ° C.

(Comparative Example 6)

The same procedure as in Comparative Example 4 was carried out except that LiNi _0.9 Sr _0.002 Co _0.1 O ₂ powder commercially available from Honjo was used.

(Comparative Example 7)

Except that the Al-isopropoxide ethanol solution of 1% concentration was used in the same manner as in Comparative Example 6.

(Example 1)

1% Al-isopropoxide was dissolved in 99% ethanol to prepare an Al-isopropoxide ethanol solution at 1% concentration.

The Al-isopropoxide ethanol solution and LiCoO ₂ (Nippon Chem, trade name: C-10) were put in a planetary mixer, which is a device shown in FIG. 1, and mixed for about 10 minutes. After fixing the temperature of the thermostat at 60 ° C., the water was circulated, and at the same time, while purging nitrogen gas, the mixture was stirred for about 1 hour to form a LiCoO ₂ cathode active material having an Al (OH) ₃ layer formed on the surface thereof. Powder was prepared.

Using the positive electrode active material powder, a positive electrode active material slurry was prepared at a ratio of an active material / conductive material / binder at a ratio of 94/3/3. In this case, super P was used as the conductive material, and polyvinylidene fluoride was used as the binder. The positive electrode active material slurry was cast on Al-foil to a thickness of about 100 μm to prepare a positive electrode plate for a coin battery. This electrode plate was punched to a diameter of 1.6 cm, and a coin cell was prepared in a glove box using a mixed solvent of ethylene carbonate and dimethyl carbonate in which 1M LiPF ₆ was dissolved as an electrolyte.

(Example 2)

After drying, the same process as in Comparative Example 4 was carried out except that heat treatment was not performed.

(Example 3)

After drying, the same process as in Comparative Example 5 was carried out except that heat treatment was not performed.

(Example 4)

After drying, the same process as in Comparative Example 6 was conducted except that heat treatment was not performed.

(Example 5)

The same procedure as in Example 2 was conducted except that LiNi _0.9 Sr _0.002 Co _0.1 O ₂ powder from Honjo Co. was used.

(Example 7)

Except that 5% Al-isopropoxide ethanol solution was used in the same manner as in Example 6.

SEM pictures of the cathode active material for a lithium secondary battery prepared by the method of Examples 2 and 3 and Comparative Example 4 are shown in FIGS. 5A, 5B and 5C, respectively. For reference, SEM images of pure LiCoO ₂ (Nippon Chem, trade name: C-10) are shown in FIG. 5D. As shown in Figs. 5A-D, the surfaces of the positive electrode active materials of Examples 2 and 3 (Figs. 5A and 5B) subjected to only a drying process without heat treatment are smoothly similar to pure LiCoO ₂ powder surfaces (Fig. 5D). It can be seen that the positive electrode active material (FIG. 5C) of Comparative Example 4 subjected to the heat treatment has an uneven surface due to the metal oxide mass formed on the surface.

After charging and discharging the positive electrode active material for lithium secondary batteries of Examples 2 and 3 and Comparative Example 1 and pure LiCoO ₂ (Nippon Chem, trade name: C-10) at 0.1C, 0.5C, and 1C charge and discharge rates, respectively, And discharge characteristics are shown in FIGS. 6 to 8, respectively. 6 to 8, the discharge characteristics of the positive electrode active materials of Examples 2 and 3 did not show a large difference from Comparative Example 1 at low rates (FIGS. 6 and 0.1C), but gradually increased to higher rates (FIGS. 7 and 0.5C). 8, 1C) it can be seen that it shows a superior property than Comparative Example 1.

These results indicate that the positive electrode active material of Comparative Example 1 had a relatively poor ion conductivity formed on the surface layer, so that the discharge potential and power characteristics were decreased as the internal resistance was increased, whereas the metal hydroxide was formed on the surface. In the case of 3, it is considered that the internal resistance is relatively small, the drop of the discharge potential is reduced, and the high discharge potential characteristic is maintained in accordance with the charge / discharge rate change. Therefore, when the positive electrode active materials of Examples 2 and 3 are applied to a battery, it is expected to exhibit more excellent lifespan characteristics and discharge potential lowering characteristics, thereby exhibiting power improvement characteristics.

In addition, in order to determine the difference between amorphous Al (OH) ₃ and Al ₂ O ₃ , an experiment was performed to measure the XRD patterns of the two materials. After amorphous Al (OH) ₃ and Al ₂ O ₃ were mixed with 5 g of Al-isopropoxide solution and 95 g of ethanol solution, the mixture was stirred for about 3 hours to prepare a clear Al-isopropoxide ethanol solution. After dividing each solution into three beakers, No. 1 beaker is dried at room temperature for 1 day, 2 Beakers were dried in an oven at 130 ° C. for 1 day, and no. Three beakers were put into a 600 degreeC heat treatment furnace, and heat-treated for 1 day, respectively. XRD patterns of amorphous Al (OH) ₃ and Al ₂ O ₃ are shown in FIG. 9. As shown in FIG. 9, it can be seen that the XRD patterns of amorphous Al (OH) ₃ and amorphous Al ₂ O ₃ are clearly distinguished.

In addition, as shown in the results shown in FIG. 9, both powders (drying at 130 ° C. and heat treatment at 600 ° C. for 10 hours) showed an amorphous form. Because of its amorphous form, the exact structure was unknown, but as a result of comparison with the reference data shown on the JCPDS card shown in FIG. 10, JCPDS No. It is considered to be an amorphous form of Al (OH) ₃ shown in 83-2256, and when heat-treated at 600 ° C, JCPDS No. It is assumed to be an amorphous form of Al ₂ O ₃ shown in 02-1373. According to these results, it can be expected that the surfaces of the active materials prepared by the methods of Examples and Comparative Examples all have an amorphous coating layer.

As described above, the positive electrode active material for a lithium secondary battery of the present invention is formed with a metal hydroxide having excellent ion conductivity on the surface thereof, so that the internal resistance can be reduced, so that the discharge potential is decreased, and thus the discharge potential characteristics according to the charge / discharge rate change are high. It can represent the property to maintain. When the positive electrode active material is applied to a battery, it is expected to exhibit better life and discharge potential lowering characteristics, thereby improving power.

Claims (4)

(delete) (Correction) A core comprising a lithium compound selected from compounds of Formulas 1 to 14; And Amorphous or crystalline metal hydroxide layer formed on the core, wherein the metal has physical properties that are dissolved in alcohol or aqueous solution A cathode active material for a lithium secondary battery comprising a. [Formula 1] Li _x MnA ₂ [Formula 2] Li _x MnO _2-z A _z [Formula 3] Li _x Mn _1-y M ' _y A ₂ [Formula 4] Li _x Mn _1-y M ' _y O _2-z A _z [Formula 5] Li _x Mn ₂ O ₄ [Formula 6] Li _x Mn ₂ O _4-z A _z [Formula 7] Li _x Mn _2-y M ' _y A ₄ [Formula 8] Li _x BA ₂ [Formula 9] Li _x BO _2-z A _z [Formula 10] Li _x B _1-y M " _y A ₂ [Formula 11] Li _x Ni _1-y Co _y A ₂ [Formula 12] Li _x Ni _1-y Co _y O _2-z A _z [Formula 13] Li _x Ni _1-yz Co _y M " _z A ₂ [Formula 14] Li _{x '} Ni _1-y' Mn _{y '} M _z' A _α Wherein 0.95 ≦ x ≦ 1.1, 0.01 ≦ y ≦ 0.1, 0.01 ≦ z ≦ 0.5, 0.95 ≦ x '≦ 1, 0.01 ≦ y ′ ≦ 0.5, 0 ≦ z' ≦ 0.1, 0.01 ≦ α ≦ 0.5, M 'is at least one of transition metals or lanthanide metals selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr and V, and M "is Al, Cr, Co, Mg, La At least one of transition metals or lanthanide metals selected from the group consisting of Ce, Sr and V, A is selected from the group consisting of O, F, S and P, and B is Ni or Co.) Coating a lithium compound selected from compounds of Formulas 1 to 14 with a metal alkoxide solution or a metal aqueous solution; A method of manufacturing a cathode active material for a lithium secondary battery, comprising the step of drying the metal alkoxide solution or the compound coated with the metal aqueous solution. [Formula 1] Li _x MnA ₂ [Formula 2] Li _x MnO _2-z A _z [Formula 3] Li _x Mn _1-y M ' _y A ₂ [Formula 4] Li _x Mn _1-y M ' _y O _2-z A _z [Formula 5] Li _x Mn ₂ O ₄ [Formula 6] Li _x Mn ₂ O _4-z A _z [Formula 7] Li _x Mn _2-y M ' _y A ₄ [Formula 8] Li _x BA ₂ [Formula 9] Li _x BO _2-z A _z [Formula 10] Li _x B _1-y M " _y A ₂ [Formula 11] Li _x Ni _1-y Co _y A ₂ [Formula 12] Li _x Ni _1-y Co _y O _2-z A _z [Formula 13] Li _x Ni _1-yz Co _y M " _z A ₂ [Formula 14] Li _{x '} Ni _1-y' Mn _{y '} M _z' A _α Wherein 0.95 ≦ x ≦ 1.1, 0.01 ≦ y ≦ 0.1, 0.01 ≦ z ≦ 0.5, 0.95 ≦ x '≦ 1, 0.01 ≦ y ′ ≦ 0.5, 0 ≦ z' ≦ 0.1, 0.01 ≦ α ≦ 0.5, M 'is at least one of transition metals or lanthanide metals selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr and V, and M "is Al, Cr, Co, Mg, La At least one of transition metals or lanthanide metals selected from the group consisting of Ce, Sr and V, A is selected from the group consisting of O, F, S and P, and B is Ni or Co.) The method of claim 3, wherein the coating process is performed by adding the lithium compound and the metal alkoxide solution or the metal aqueous solution to the mixer, and then increasing the temperature while injecting an inert gas.