KR20040073076A - Cathode active material for lithium secondary battery, producing method thereof and lithium secondary battery using the same - Google Patents

Abstract

PURPOSE: Provided is a cathode active material for a lithium secondary battery, which is excellent in a thermal stability when over-charging. The lithium secondary battery produced by using the cathode active material, which is excellent in safety and reliability, is also provided. CONSTITUTION: The cathode active material contains a lithium compound and a surface coating layer containing at least one additive selected from LiI and Li2S and the cathode active material is produced by a process comprising the steps of: dissolving the additive containing LiI, Li2S, or a mixture thereof in a solvent; adding the lithium compound and stirring at an ordinary temperature; drying; heat-treating; cooling to an ordinary temperature. And the lithium secondary battery contains: a cathode containing the cathode active material; an anode containing an anode active material capable of detaching/inserting lithium ions; a non-water solution electrolyte impregnating the cathode, the anode, and a separator.

Description

A cathode active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery manufactured using the same TECHNICAL FIELD

(Industrial use)

The present invention relates to a positive electrode active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery produced using the same. More particularly, the present invention relates to a positive electrode active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery manufactured using the same, having excellent thermal stability during overcharging to ensure battery safety.

(Prior Art)

Lithium secondary batteries are prepared by reversibly inserting and desorbing lithium ions as positive and negative electrodes, and filling organic electrolyte or polymer electrolyte between the positive and negative electrodes, and lithium ions are inserted and removed from the positive and negative electrodes. When produced, electrical energy is generated by oxidation and reduction reactions.

Lithium secondary batteries, which are commercially available and in use, have an average discharge potential of 3.7V, or 4V, which correspond to the heart of the digital era, which is rapidly being applied to cellular phones, notebook computers, and camcorders, which are called 3C. to be.

The positive electrode active material for a lithium secondary battery is called a lithium intercalation compound. This means that the structural stability, capacity, etc. of the active material are determined by the desorption reaction of Li. Therefore, as the charging potential increases, the capacity of the active material increases, but there is a problem in that the thermal stability drops sharply due to the instability of the structure. That is, when the temperature of the active material continues to increase in the charged state, the oxygen is rapidly generated when the binding force between the metal ions and the oxygen in the structure drops rapidly above a certain temperature. This generation of oxygen eventually causes thermal runaway in the cell. When this happens, the battery's surface temperature is usually above 400 ° C, leading to explosions with flames. In particular, this phenomenon is mainly caused by the internal short circuit of the battery at 12 V during overcharging and must be overcome to ensure the safety of the battery.

In order to prevent such an explosion phenomenon that occurs during the overcharging of the lithium secondary battery, the conventional attempts have been made by stabilizing the additives (flame retardants) in the electrolyte which is highly reactive with the positive electrode active material. (reference: 1) K. Xu, MS Ding, S. Zhang, JL Allen, and TR Jow, J. Electrochem. Soc . 149 , A622 (2002). 2) SC Narang, SC Ventura, BJ Dougherty, M. Zhao, S. Smedley, and G. Koolpe, US Pat. 5830600 (1998). 3) M. Adachi, K. Tanaka, and K. Sekai, J. Electrochem. Soc. 4 , 1256 (1999). 4) X. Wang, E. Yasukawa, and S. Kasuya, J. Electrochem. Soc. 148 , A1058 (2001).) However, when these additives are added to the electrolyte, the reactivity with the electrolyte may be reduced to some extent, which may constitute a thermally safe cell even when overcharged, but in a more fundamental manner, a trigger when overcharged. It is necessary to improve the positive electrode active material.

In order to solve the above problems, an object of the present invention is to provide a positive electrode active material for lithium secondary batteries excellent in thermal stability during overcharging.

Another object of the present invention is to provide a method for producing a cathode active material for a lithium secondary battery excellent in thermal stability during overcharging.

Another object of the present invention is to provide a lithium secondary battery excellent in the safety and reliability of the battery.

1 is a graph showing the results of a 12 V overcharge test of a battery including a cathode active material prepared according to Example 1 of the present invention.

Figure 2 is a graph showing the results of the 12 V overcharge test of a battery comprising a positive electrode active material prepared according to Example 2 of the present invention.

3 is a graph showing the results of a 12 V overcharge test of a battery including a cathode cathode active material prepared according to Comparative Example 1. FIG.

The above purpose To achieve, The present invention Lithium compounds; And LiI and Li₂A surface coating layer comprising at least one additive selected from the group consisting of S; It provides a lithium secondary battery positive electrode active material comprising a.

The present invention also comprises: (a) a dissolving step of dissolving an additive comprising LiI, Li ₂ S or a mixture thereof in a solvent; (b) agitation step of adding a lithium compound and stirring at room temperature; (c) a drying step of drying the stirred compound; (d) a heat treatment step of heat treating the dried compound; And (e) quenching step of quenching the heat-treated compound to room temperature; It provides a method for producing a cathode active material for a lithium secondary battery comprising a.

The invention also relates to lithium compounds; And at least one additive selected from the group consisting of LiI and Li ₂ S; A positive electrode comprising a positive active material for a lithium secondary battery comprising a; A negative electrode including a negative electrode active material capable of deintercalation of lithium ions; And a nonaqueous electrolyte impregnated in the positive electrode, the negative electrode, and the separator. It provides a lithium secondary battery comprising a.

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

The present inventors studied the positive electrode active material for a lithium secondary battery excellent in thermal stability even when overcharged, and as a result of coating an additive including LiI, Li ₂ S or a mixture thereof on the positive electrode active material, the reaction between the positive electrode active material and the electrolyte solution It was confirmed that the positive electrode active material for a lithium secondary battery having excellent thermal stability by minimizing, and completed the present invention based on this.

In the cathode active material for a lithium secondary battery of the present invention, an additive containing LiI, Li ₂ S, or a mixture thereof in a lithium compound is coated on a surface thereof.

During charging of the lithium secondary battery, the positive electrode active material reacts violently with the electrolyte as Li ⁺ continuously escapes toward the negative electrode and changes to Co ₃ O ₄ , which is an oxidant, causing an exothermic reaction accompanied with generation of oxygen. This exothermic reaction leads to an explosion accompanied by a flame.

Since the positive electrode active material according to the present invention is coated with an additive including LiI, Li ₂ S or a mixture thereof on the surface thereof, the additive is decomposed at 2 V or less and remains as a coating layer on the surface of the positive electrode active material. By minimizing the reaction with the electrolyte solution has excellent thermal stability and battery stability to prevent thermal runaway (overall runaway) phenomenon completely overcharge.

As the lithium compound, at least one compound selected from the group consisting of the following Chemical Formulas 1 to 11 may be preferably used. Among these compounds, lithium-cobalt chalcogenide, lithium-manganese chalcogenide, lithium-nickel chalcogenide or lithium-nickel-manganese chalcogenide compound may be more preferably used in the present invention.

[Formula 1]

Li _x Mn _1-y M " _y A ₂

[Formula 2]

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

[Formula 3]

Li _x Mn ₂ O _4-z A _z

[Formula 4]

Li _x Mn _2-y M " _y A ₄

[Formula 5]

Li _x Co _1-y M " _y A ₂

[Formula 6]

Li _x Ni _1-y M " _y A ₂

[Formula 7]

Li _x CoO _2-z A _z

[Formula 8]

Li _x NiO _2-z A _z

[Formula 9]

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

[Formula 10]

Li _x Ni _1-yz Co _y M " _z A _α

[Formula 11]

Li _x Ni _1-yz Mn _y M " _z A _α

Wherein 0.95 ≦ x ≦ 1.1, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.5, 0 <α ≦ 2, and M ″ is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ac, Th, Pa, U, Np, Pu, Am, Cm, At least one element selected from the group consisting of Bk, Cf, Es, Fm, Md, No and Lr, and A is an element selected from the group consisting of O, F, S and P.)

The thickness of the surface coating layer formed on the surface of the lithium compound is preferably 1 to 1000 nm, more preferably 1 to 200 nm to obtain excellent thermal stability and electrochemical properties of the positive electrode active material. When the thickness of the surface coating layer is less than 1nm, the effect of coating with an additive for minimizing the reaction between the lithium compound and the electrolyte solution is insignificant. If the thickness exceeds 1000 nm, the thickness of the coating layer is too thick so that Li of the lithium compound It is not preferable because ionization becomes difficult.

The additive preferably further comprises at least one glass former selected from the group consisting of GeS _2, B ₂ O _3, SiO ₂ and P ₂ O ₅ .

The manufacturing method of the cathode active material for a lithium secondary battery of the present invention will be described in detail as follows.

First, an additive including LiI, Li ₂ S or a mixture thereof is dissolved in a solvent. (Step (a)) As the solvent, an alcohol such as methanol, ethanol or isopropanol may be preferably used.

Li in the dissolution step₂S content is 0.2 to 5 with respect to the positive electrode active material It is preferably in weight%. Li₂If the content of S is less than 0.2% by weight, Li to minimize the reaction of the lithium compound with the electrolyte₂The effect of coating the lithium compound with S is insignificant, and if the content exceeds 5% by weight, Li₂It is not preferable because the content of S is high.

LiI content of the dissolution step is 0.5 to 5 with respect to the positive electrode active material It is preferably in weight%. When the content of LiI is less than 0.5% by weight, the effect of coating the lithium compound with LiI to minimize the reaction between the lithium compound and the electrolyte is insignificant. When the content exceeds 5% by weight, the content of LiI is high. Not.

The additive preferably further comprises at least one vitrification agent selected from the group consisting of GeS _2, B ₂ O _3, SiO ₂ and P ₂ O ₅ . The content of the vitrification agent in the surface coating layer is preferably 2.0 to 2.5% by weight based on the positive electrode active material.

Second, add a lithium compound and stir at room temperature (step (b)).

Herein, the lithium compound is preferably at least one compound selected from the group consisting of Chemical Formulas 1 to 11.

Third, the stirred compound is dried. ((C) step) The drying process is preferably carried out at 50 ~ 200 ℃. When the drying process is carried out at a temperature lower than room temperature, the drying time is too long, which is not preferable.

Fourth, the dried compound is heat-treated. (D) Step) The heat treatment process is preferably performed at 600 ~ 800 ℃. During the heat treatment process, an additive including Li ₂ S, LiI, or a mixture thereof is melted to obtain a positive electrode active material uniformly coated on the lithium compound. In order to obtain a uniformly coated positive electrode active material, the heat treatment process is preferably performed under conditions of blowing dry air or oxygen. At this time, when the heat treatment process is carried out at a temperature lower than 600 ℃ is not preferable because the additive containing Li ₂ S, LiI or a mixture thereof is not dissolved, Li ₂ S, LiI, etc. are volatile when it exceeds 800 ℃ This is not desirable because the desired material is not obtained.

Fifth, the heat-treated material is then quenched to room temperature (step (e)). That is, a step of rapidly removing the heat-treated material into the air is performed. The cooling process is usually carried out in a furnace. According to this quenching process, an additive including Li ₂ S, LiI or a mixture thereof is present in an amorphous form on the surface of the lithium compound. Since the additive in the amorphous form is decomposed at 2V or less and remains on the surface, the reaction between the electrolyte and the electrolyte during the overcharging is minimized, thereby minimizing the reaction between the cathode active material and the electrolyte during the overcharging, thereby minimizing the exothermic reaction, thereby causing a thermal runaway phenomenon. Can be completely prevented. Therefore, the positive electrode active material for a lithium secondary battery according to the present invention shows thermal stability and battery safety.

Synthesis method of the lithium compound of Formula 1 to 11 is as follows.

First, 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, lithium hydroxide, and the like. Manganese salt, cobalt salt, nickel salt or manganese salt may be used as the metal salt. As the manganese salt, manganese acetate, manganese dioxide, or the like may be used. The cobalt salt may be cobalt oxide, cobalt nitrate or cobalt carbonate, and the like, and the nickel salt may be nickel hydroxide, nickel nitrate, or nickel. Acetates and the like 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, lithium fluoride, and the like may be used as the fluorine salt, and manganese sulfide, lithium sulfide, and the like 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.

As a mixing method, for example, mortar grinder mixing may be used, in order to promote the reaction of lithium salts and metal salts.

It is desirable to add appropriate solvents such as ethanol, methanol, water, acetone and mix the mortar grinder until the solvent is almost free.

The obtained mixture is heat-treated at a temperature of about 400 to 600 ° C. to produce lithium compound precursor powder 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 heat treatment or after the heat treatment process, the lithium salt may be uniformly distributed by remixing the precursor powder at room temperature while blowing dry air.

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 ℃ there is a problem that the crystalline material is difficult to form. The heat treatment process is carried out by increasing 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 prepared lithium compound at room temperature to distribute the lithium salt more uniformly.

The lithium secondary battery of the present invention is a lithium compound; And at least one additive selected from the group consisting of LiI and Li ₂ S; A positive electrode comprising a positive active material for a lithium secondary battery comprising a; A negative electrode including a negative electrode active material capable of deintercalation of lithium ions; And a nonaqueous electrolyte impregnated in the positive electrode, the negative electrode, and the separator. It includes.

Herein, the lithium compound is preferably at least one compound selected from the group consisting of Chemical Formulas 1 to 11.

The additive preferably further comprises at least one vitrification agent selected from the group consisting of GeS _2, B ₂ O _3, SiO ₂ and P ₂ O ₅ .

Using the positive electrode active material of the present invention, a positive electrode is prepared as follows.

A solvent such as a conductive material, a binder, and a binder is mixed with the cathode active material prepared by the above-described method to prepare a cathode active material composition, for example, a composition in the form of a slurry. The positive electrode active material composition is tape cast on a current collector such as Al foil to prepare a positive electrode. A lithium secondary battery is manufactured by a conventional method using the manufactured positive electrode.

As the electrolyte used in the lithium secondary battery of the present invention, a liquid electrolyte including a lithium salt and an organic solvent generally used in a lithium secondary battery may be used, or may be used in the form of a solid electrolyte separator. When used as a liquid electrolyte, a physical separator having a function of physically separating an electrode further includes a separator made of porous glass, plastic, ceramic, or polymer in the liquid electrolyte.

The electrolyte separator has a function of physically separating the electrode and a transfer medium for moving metal ions, and both an electrochemically stable electric and ion conductive material may be used. As such an electrically and ion conductive material, a glass electrolyte, a polymer electrolyte, or a ceramic electrolyte may be used. As the electrolyte separator, which is a particularly preferred solid electrolyte, an appropriate supporting electrolyte salt is mixed with a polymer electrolyte such as polyether, polyimine, polythioether, or the like. The solid electrolyte separator may include a non-aqueous organic solvent, and in this case, may further include a suitable gelling agent in order to reduce the fluidity of the organic solvent.

As the organic solvent, a generally known non-aqueous organic electrolyte such as ethylene carbonate, propylene carbonate, dioxorene, sulfolane, xylene, diglyme, tetrahydrofuran, tetraglyme, and the like may be widely used.

Lithium trifluoromethanesulfon imide (lithium trifluoromethanesulfon imide), lithium triflate, lithium perchlorate, LiPF ₆ or LiBF ₄ may be used as the lithium salt as the supporting electrolyte. .

As the negative electrode used in the lithium secondary battery of the present invention, one made of a crystalline or amorphous carbon-based negative electrode active material generally used in a lithium secondary battery can be used.

The lithium secondary battery of the present invention has excellent safety and reliability characteristics of the battery.

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.

(Example 1)

Mix Li ₂ S, LiI, GeS ₂ slowly while putting 0.1 g, 0.3 g, and 2 g into 50 g of ethanol, respectively. After mixing, 50 g of LiCoO ₂ powder was added as a lithium compound, stirred for 10 minutes using a magnetic bar, and then slowly dried at 100 ° C. The dried powder is heat-treated under conditions of blowing oxygen at 700 ° C. for 5 hours and then quenched. At this time, Li ₂ S + LiI + GeS ₂ phase is present in the amorphous form on the surface of the positive electrode active material. Using a quenched powder, a pouch-type cell of cell size 5.5 x 48 x 30 mm ³ (thickness x length x width) was prepared. The negative electrode was made of artificial graphite, and the electrolyte solution of ethylene carbonate (EC), diethylene carbonate (DEC), and ethyl-methyl carbonate (EMC) in which 1.03 M LiPF ₆ was dissolved. Mixed solution (3/3/4 volume ratio) was used.

(Example 2)

Li ₂ S: LiI: GeS ₂ was carried out in the same manner as in Example 1 except that 0.15 g: 0.6 g: 1.7 g was used, respectively.

(Example 3)

Li ₂ S: LiI: B ₂ O ₃ was carried out in the same manner as in Example 1, except that 0.1 g: 0.3 g: 2 g was used, respectively.

(Example 4)

Mix Li ₂ S, LiI, B ₂ O ₃ while slowly putting 0.1 g, 0.3 g, and 2 g into 50 g of ethanol, respectively. After mixing, 50 g of LiNi _0.75 Mn _0.25 O ₂ powder was added as a lithium compound, stirred for 10 minutes using a magnetic bar, and then slowly dried at 100 ° C. The dried powder is heat-treated under conditions of blowing oxygen at 700 ° C. for 5 hours and then quenched. At this time, Li ₂ S + LiI + GeS ₂ phase is present in the amorphous form on the surface of the positive electrode active material. Using a quenched powder, a pouch-type cell of cell size 5.5 x 48 x 30 mm ³ (thickness x length x width) was prepared. The negative electrode was made of artificial graphite, and the electrolyte solution of ethylene carbonate (EC), diethylene carbonate (DEC), and ethyl-methyl carbonate (EMC) in which 1.03 M LiPF ₆ was dissolved. Mixed solution (3/3/4 volume ratio) was used.

(Example 5)

It carried out similarly to Example 4 except having used LiNi _0.8 Co _0.2 O ₂ as a lithium compound.

(Example 6)

Li ₂ S: LiI: P ₂ O ₅ was carried out in the same manner as in Example 1, except that 0.1 g: 0.3 g: 2 g was used, respectively.

(Comparative Example 1)

A pouch-type cell having a thickness of 5.5 × 48 × 30 mm ³ (thickness × length × width) was manufactured using LiCoO ₂ positive electrode active material powder not coated with any material on its surface. The negative electrode was made of artificial graphite, and the electrolyte solution of ethylene carbonate (EC), diethylene carbonate (DEC), and ethyl-methyl carbonate (EMC) in which 1.03 M LiPF ₆ was dissolved. Mixed solution (3/3/4 volume ratio) was used.

Hereinafter, the following experiment was performed to find the thermal stability of the cathode active material of the present invention. A 12V overcharge experiment was performed with a battery including the cathode active material prepared according to Example 1, Example 2, and Comparative Example 1. First, after the battery was manufactured, the battery went through a formation process. That is, charging and discharging was performed once between 2.75 V and 4.2 V at 0.2 C rate. The open cell voltage after the battery was 0.2 V.

In order to confirm the thermal stability of the battery prepared according to Example 1 during overcharging, a 12 V overcharging experiment was performed and the results are shown in FIG. 1. As can be seen in FIG. 1, when the current flows through the battery at a 2 C rate (= 1.64 mA) up to 12 V, an internal short circuit occurs when the voltage suddenly drops to 0 V even when 12 V is reached. Did not do it. It can also be seen that the surface temperature of the battery is also 90 ° C. or less. That is, it can be seen that the heat generation phenomenon is minimized.

In order to confirm the thermal stability of the battery prepared according to Example 2 during overcharging, a 12 V overcharging experiment was performed and the results are shown in FIG. 2. As can be seen in FIG. 2, even when 12 V is overcharged, the short circuit of the battery in which the voltage drops to 0 V does not appear as in Example 1, and the heat generation is also minimized to minimize the surface temperature of the battery. It can be seen that 70 degrees or less.

In addition, 12 V overcharge experiments were carried out to confirm thermal stability of the battery prepared according to Comparative Example 1, and the results are shown in FIG. 3. As can be seen in FIG. 3, the battery exploded due to an internal short-circuit phenomenon in which the voltage of the battery dropped to 0 V after reaching 12 V, and the surface temperature of the battery was also raised to 400 ° C.

That is, the lithium secondary battery prepared according to Example 1 Example 2 of the present invention, compared to the battery prepared according to Comparative Example 1, did not generate a short circuit of the battery during 12 V overcharge, compared with the surface temperature of the battery It was confirmed that the exothermic phenomenon is less than 100 ℃ compared to 400 ℃ of Example 1.

This result is thought to be because the positive electrode active material according to the present invention minimizes the reaction with the electrolyte during filling because the amorphous additive on the surface decomposes at 2 V or less and remains as a coating layer on the surface. That is, when charging the lithium secondary battery, the positive electrode active material reacts violently with the electrolyte while changing Li in the form of oxidant (Co ₃ O ₄ ) because Li continues to escape to the negative electrode surface. It is believed that the additive comprising LiI, Li ₂ S or mixtures thereof coated on minimizes.

As described above, the positive electrode active material for a lithium secondary battery of the present invention is excellent in thermal stability because the surface is coated with an amorphous additive, thereby minimizing the reaction with the electrolyte during charging, thereby preventing the thermal runaway phenomenon even during overcharging. Do. Therefore, when the positive electrode active material of the present invention is applied to a lithium secondary battery, safety and reliability of the battery can be obtained.

Claims (16)

Lithium compounds; And A surface coating layer comprising at least one additive selected from the group consisting of LiI and Li ₂ S; A cathode active material for a lithium secondary battery comprising a. The method of claim 1, wherein the lithium compound, A cathode active material for a lithium secondary battery, which is at least one lithium compound selected from the group consisting of Chemical Formulas 1 to 11. [Formula 1] Li _x Mn _1-y M " _y A ₂ [Formula 2] Li _x Mn _1-y M " _y O _2-z A _z [Formula 3] Li _x Mn ₂ O _4-z A _z [Formula 4] Li _x Mn _2-y M " _y A ₄ [Formula 5] Li _x Co _1-y M " _y A ₂ [Formula 6] Li _x Ni _1-y M " _y A ₂ [Formula 7] Li _x CoO _2-z A _z [Formula 8] Li _x NiO _2-z A _z [Formula 9] Li _x Ni _1-y Co _y O _2-z A _z [Formula 10] Li _x Ni _1-yz Co _y M " _z A _α [Formula 11] Li _x Ni _1-yz Mn _y M " _z A _α Wherein 0.95 ≦ x ≦ 1.1, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.5, 0 <α ≦ 2, and M ″ is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ac, Th, Pa, U, Np, Pu, Am, Cm, At least one element selected from the group consisting of Bk, Cf, Es, Fm, Md, No and Lr, and A is an element selected from the group consisting of O, F, S and P.) The cathode active material of claim 1, wherein the surface coating layer has a thickness of 1 nm to 1000 nm. The cathode active material of claim 3, wherein the surface coating layer has a thickness of 1 to 200 nm. The method of claim 1, wherein the additive, A cathode active material for a lithium secondary battery, further comprising at least one vitrification agent selected from the group consisting of GeS _2, B ₂ O _3, SiO _2, and P ₂ O ₅ . (a) a dissolution step of dissolving an additive comprising LiI, Li ₂ S or a mixture thereof in a solvent; (b) agitation step of adding a lithium compound and stirring at room temperature; (c) a drying step of drying the stirred compound; (d) a heat treatment step of heat treating the dried compound; And (e) a quenching step of rapidly cooling the heat-treated compound to room temperature; Method for producing a positive electrode active material for a lithium secondary battery comprising a. The method of claim 6, wherein the lithium compound is at least one compound selected from the group consisting of Chemical Formulas 1 to 11 below. [Formula 1] Li _x Mn _1-y M " _y A ₂ [Formula 2] Li _x Mn _1-y M " _y O _2-z A _z [Formula 3] Li _x Mn ₂ O _4-z A _z [Formula 4] Li _x Mn _2-y M " _y A ₄ [Formula 5] Li _x Co _1-y M " _y A ₂ [Formula 6] Li _x Ni _1-y M " _y A ₂ [Formula 7] Li _x CoO _2-z A _z [Formula 8] Li _x NiO _2-z A _z [Formula 9] Li _x Ni _1-y Co _y O _2-z A _z [Formula 10] Li _x Ni _1-yz Co _y M " _z A _α [Formula 11] Li _x Ni _1-yz Mn _y M " _z A _α Wherein 0.95 ≦ x ≦ 1.1, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.5, 0 <α ≦ 2, and M ″ is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ac, Th, Pa, U, Np, Pu, Am, Cm, At least one element selected from the group consisting of Bk, Cf, Es, Fm, Md, No and Lr, and A is an element selected from the group consisting of O, F, S and P.) The method of claim 6, wherein the drying step, A method for producing a positive electrode active material for a lithium secondary battery, which is carried out at 50 to 200 ° C. The method of claim 6, wherein the heat treatment step, Process for producing a positive electrode active material for lithium secondary batteries, characterized in that carried out at 600 ~ 200 ℃. In claim 6, the content of Li ₂ S of the dissolution step, Method for producing a cathode active material for a lithium secondary battery, characterized in that 0.2 to 5% by weight based on the positive electrode active material. In claim 6, the content of LiI of the dissolution step, Method for producing a cathode active material for a lithium secondary battery, characterized in that 0.5 to 5% by weight based on the positive electrode active material. In claim 6, wherein the additive of the dissolution step, Method for producing a positive electrode active material for a lithium secondary battery, characterized in that it further comprises at least one vitrification agent selected from the group consisting of GeS _2, B ₂ O _3, SiO ₂ and P ₂ O ₅ . The method of claim 12, wherein the content of the vitrification agent, Method for producing a cathode active material for a lithium secondary battery, characterized in that 2.0 to 2.5% by weight relative to the positive electrode active material. Lithium compounds; And at least one additive selected from the group consisting of LiI and Li ₂ S; A positive electrode comprising a positive active material for a lithium secondary battery comprising a; A negative electrode including a negative electrode active material capable of deintercalation of lithium ions; And A non-aqueous electrolyte impregnated in the positive electrode, the negative electrode, and the separator; Lithium secondary battery comprising a. The method of claim 14, wherein the lithium compound, Lithium secondary battery which is at least one lithium compound selected from the group consisting of Formulas 1 to 11. [Formula 1] Li _x Mn _1-y M " _y A ₂ [Formula 2] Li _x Mn _1-y M " _y O _2-z A _z [Formula 3] Li _x Mn ₂ O _4-z A _z [Formula 4] Li _x Mn _2-y M " _y A ₄ [Formula 5] Li _x Co _1-y M " _y A ₂ [Formula 6] Li _x Ni _1-y M " _y A ₂ [Formula 7] Li _x CoO _2-z A _z [Formula 8] Li _x NiO _2-z A _z [Formula 9] Li _x Ni _1-y Co _y O _2-z A _z [Formula 10] Li _x Ni _1-yz Co _y M " _z A _α [Formula 11] Li _x Ni _1-yz Mn _y M " _z A _α Wherein 0.95 ≦ x ≦ 1.1, 0 ≦ y ≦ 0.5, 0 ≦ z ≦ 0.5, 0 <α ≦ 2, and M ″ is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Ac, Th, Pa, U, Np, Pu, Am, Cm, At least one element selected from the group consisting of Bk, Cf, Es, Fm, Md, No and Lr, and A is an element selected from the group consisting of O, F, S and P.) The method of claim 14, wherein the additive, A lithium secondary battery further comprising at least one vitrification agent selected from the group consisting of GeS _2, B ₂ O _3, SiO ₂ and P ₂ O ₅ .