KR101013938B1 - Positive active material for rechargeable lithium battery, method for preparing same, and rechargeable lithium battery using same - Google Patents

Abstract

The present invention relates to a positive electrode active material for a lithium secondary battery, a manufacturing method thereof, and a lithium secondary battery including the same, wherein the positive electrode active material includes a lithium-containing compound; And a coating layer comprising a metal oxide or metal hydroxide surrounding the lithium containing compound, wherein the standard deviation of the thickness of the coating layer is from 2 nm to 300 nm.

The positive electrode active material for lithium secondary batteries of the present invention can improve the charge and discharge characteristics, life characteristics, high rate characteristics, and thermal stability of lithium secondary batteries.

Cathode active material, coating, metal oxide, metal hydroxide, chelating agent, high rate, life

Description

A positive electrode active material for a lithium secondary battery, a method of manufacturing the same, and a lithium secondary battery including the same TECHNICAL FIELD

The present invention relates to a positive electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same, and more particularly, for a lithium secondary battery having excellent charge and discharge characteristics, life characteristics, high voltage and high rate characteristics, and excellent thermal stability. The present invention relates to a positive electrode active material, a method of manufacturing the same, and a lithium secondary battery including the same.

Secondary batteries are used as power sources for portable electronic devices, electric bicycles, and electric vehicles for information and communication such as PDAs, mobile phones, and notebook computers, and the demand for them is rapidly increasing. In particular, the performance of these products is highly dependent on the secondary battery, so the demand for a high performance battery is very large. The characteristics required for the secondary battery include charge and discharge characteristics, life characteristics, high rate characteristics, high temperature stability, and the like.

In the case of a lithium secondary battery, there is an advantage of having a high voltage and an energy density. The lithium secondary battery may be classified into a lithium battery using lithium metal as a negative electrode active material, and a lithium ion battery using an interlayer compound such as carbon into which lithium ions may be inserted or desorbed. Moreover, depending on the electrolyte used, it may be divided into a liquid battery using a liquid, a gel polymer battery using a mixture of a liquid and a polymer, and a solid polymer battery using purely a polymer.

Commercially available small lithium ion batteries use LiCoO ₂ as the positive electrode active material and carbon as the negative electrode active material. In addition, Moly Energy Japan uses LiMn ₂ O ₄ as the positive electrode active material, but the amount thereof is negligible compared to LiCoO ₂ . In addition, positive electrode active materials currently being actively researched and developed include LiNiO ₂ , LiCo _x Ni _{1 - x} O ₂ and LiMn ₂ O ₄ . LiCoO ₂ has the advantages of stable charging and discharging characteristics, excellent electronic conductivity, high thermal stability, and flat discharge voltage characteristics, but Co is required to be developed for other cathode active materials because of its low reserves, high cost, and toxicity to human body. have. In addition, LiNiO ₂ is difficult to synthesize, there is also a problem in thermal stability is not commercialized, LiMn ₂ O ₄ is part of the low-priced products are commercialized. However, LiMn ₂ O _{4, which} has a spinel structure, has a theoretical capacity of 148 mAh / g, which is smaller than other materials, and has a three-dimensional tunnel structure. _It is lower than ₂ and LiNiO ₂ and has poor cycle characteristics due to the Jahn-Teller effect. In particular, the high temperature property at 55 ° C or higher is inferior to LiCoO ₂ and is not widely used in actual batteries.

Therefore, many studies have been conducted on a method of improving the electrochemical properties by coating the surface of the cathode active material as a material that can overcome the above problems. Samsung SDI Korea Co., Ltd. has researched this coating method and submitted a patent.

As an example, Korean Patent Publication No. 2003-0032363 discloses an organic suspension containing a coating element or a coating element-containing compound in an organic solvent to prepare a coating element-containing organic suspension, and then adding water to the organic suspension to prepare a coating liquid. A method of coating on the surface of an active material is described. Specifically, hydroxides, oxyhydroxides, and oxycarbonates containing Mg, Al, Co, K, Na, Ca, Si, Ti, Sn, V, Ge, Ga, B, As, or Zr on the surface of the positive electrode active material. A technique for coating hydroxycarbonate salts has been proposed.

In addition, Korean Patent Publication No. 2003-0033912 discloses a cathode active material in which a coating layer is formed of a coating element-containing oxide on a lithium-containing compound, but until now, a cathode active material having a desired performance has not been developed.

The present invention provides a cathode active material for a lithium secondary battery that is excellent in charge and discharge characteristics, lifespan characteristics, high voltage, and high rate characteristics, and has excellent thermal stability.

This invention also provides the manufacturing method of the said positive electrode active material for lithium secondary batteries.

This invention also provides the lithium secondary battery containing the said positive electrode active material for lithium secondary batteries.

In order to achieve the above object, according to an embodiment of the present invention includes a coating layer containing a metal oxide or metal hydroxide, surrounding the lithium-containing compound and the lithium-containing compound, the thickness standard deviation of the coating layer is 2nm to 300nm It provides a positive electrode active material for a lithium secondary battery.

According to another embodiment of the present invention, by mixing a lithium-containing compound, a carboxyl group-containing amino acid chelating agent, and a solvent, to prepare an aqueous solution containing a lithium-containing compound having a hydroxyl group on the surface; And adding a precursor and a basic solution of a metal oxide or a metal hydroxide to the aqueous solution and drying the same to prepare a cathode active material.

According to another embodiment of the present invention, a lithium secondary battery including the cathode active material is provided.

Other details of the embodiments of the present invention are included in the following detailed description.

In the cathode active material according to the present invention, a coating layer containing a metal oxide or a metal hydroxide is formed on a surface of a lithium-containing compound, thereby suppressing a reaction between an electrolyte solution and a lithium-containing compound. Therefore, it is possible to improve the phenomenon that the capacity of the battery is sharply reduced, excellent in charge and discharge characteristics, life characteristics, high voltage and high rate characteristics, and excellent thermal stability. Therefore, the battery performance can be improved when applied to a lithium secondary battery.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, whereby the present invention is not limited and the present invention is defined only by the scope of the claims to be described later.

Hereinafter, the "standard deviation of the thickness of the coating layer" referred to in the present invention means the standard deviation of the thickness of the coating layer, and the standard deviation is well known to those skilled in the art, and thus detailed description thereof will be omitted.

The positive electrode active material according to the embodiment of the present invention includes a coating layer including a metal oxide or a metal hydroxide, surrounding the lithium-containing compound and the lithium-containing compound, wherein the coating layer has a thickness standard deviation of 2 nm to 300 nm.

The coating layer is formed by uniformly surrounding the entire surface of the lithium-containing compound. Such a coating layer can suppress side reactions between an electrolyte solution and a lithium-containing compound as compared to a lithium-containing compound or a lithium-containing compound that is not coated and surrounding a portion of the lithium-containing compound.

The metal oxide or metal hydroxide forming the coating layer is MOx and M (OH) _x (wherein M is at least one element selected from Al, Mg, Ni, Co, Cr, Mo, and W, 1 ≦ x ≦ 4) one or more selected from the group consisting of.

The coating layer preferably has a thickness standard deviation of 2 nm to 300 nm, more preferably 2 nm to 100 nm, still more preferably 10 nm to 100 nm, and most preferably 20 nm to 50 nm. When the thickness standard deviation of the coating layer is in the above range, there is an advantage that the metal oxide or metal hydroxide particles can be uniformly coated on the surface of the lithium-containing compound, but if outside the above range, the coating is made locally, the uncoated portion There is a problem of reacting with the electrolyte, and the excessively coated portion is not preferable because there is a problem acting as a resistor.

The metal oxide or metal hydroxide of the coating layer may be contained in an amount of 0.1 to 10% by weight based on the total amount of the positive electrode active material. If the content is less than 0.1% by weight, the coating effect is insignificant, and if it exceeds 10% by weight, there is a problem that the capacity or energy density decreases due to its own weight, which is not preferable.

In addition, when the coating layer includes a metal hydroxide, it may further include a carboxyl group-containing amino acid chelating agent in addition to the metal hydroxide. At this time, the carboxyl group (COOH) includes a hydroxyl group (OH).

The carboxyl group-containing amino acid chelating agent is capable of chelating a metal hydroxide and a lithium-containing compound, and examples thereof include aspartic acid, glutamic acid, phenylalanine, glycine, histidine (histidine), isoleucine (isoleucine), lysine, leucine, methionine, asparagine, proline, glutamine, arginine, threonine, threonine, Selenocysteine, valine, tryptophan, tyrosine, and the like.

The amino group of the carboxyl group-containing amino acid chelating agent serves to bind the positive electrode active material, and the carboxyl group of the carboxyl group-containing amino acid chelating agent serves to connect the positive electrode active material combined with the chelating agent and the coating material. In particular, the hydroxy group included in the carboxyl group-containing amino acid chelating agent introduces a hydroxy group on the surface of the lithium-containing compound to increase the affinity with the metal element of the metal hydroxide to induce a stable bond, thereby forming a uniform coating layer. That is, by the carboxyl group-containing amino acid chelating agent, the coating layer can be uniformly formed on the surface of the lithium-containing compound, so that the standard deviation of the thickness of the coating layer can be significantly reduced.

The carboxyl group-containing amino acid chelating agent may be contained in an amount of 0.01 to 1 mol, and preferably 0.05 to 0.2 mol, based on 1 mol of the metal hydroxide. When the content of the carboxyl group-containing amino acid chelating agent is less than 0.01 mole, there is almost no effect of addition, and when it exceeds 1 mole, the thickness becomes too thick and may cause a problem of acting as resistance, which is not preferable.

The coating layer may be amorphous, crystalline, or a mixture of crystalline and amorphous.

In addition, the lithium-containing compound, a compound having a hexagonal layered rock salt structure represented by the following formulas 1 to 16, a compound having an olivine structure represented by the following formula 17, having a cubic structure represented by the following formulas 18 to 21 It is preferred that it is a spinel compound.

[Formula 1]

Li _{1 + a} [Co _{1 - x} M _x ] O _{2- b} F _b

[Formula 2]

Li _{1 + a} [Co _{1 - x} M _x ] O _{2- b} S _b

(In Formulas 1 and 2, 0≤a≤0.2, 0≤b≤0.2, 0.01≤x≤0.1, M is Mg, Al, Ni, Mn, Zn, Fe, Cr, Ga, Mo, and W At least one element selected from the group consisting of: preferably 0.01 ≦ a ≦ 0.2 and 0.01 ≦ b ≦ 0.2)

(3)

Li _{1 + a} [Ni _{1 - x} M _x ] O _{2- b} F _b

[Formula 4]

Li _{1 + a} [Ni _{1 - x} M _x ] O _{2- b} S _b

(In Formulas 3 and 4, 0≤a≤0.2, 0≤b≤0.2, 0.01≤x≤0.5, M is Mg, Al, Co, Mn, Zn, Fe, Cr, Ga, Mo, and W At least one element selected from the group consisting of: preferably 0.01 ≦ a ≦ 0.2 and 0.01 ≦ b ≦ 0.2)

[Chemical Formula 5]

Li _{1 + a} [Ni _{1 -x- y} Co _x Mn _y ] O _{2- b} F _b

[Formula 6]

Li _{1 + a} [Ni _{1 -x- y} Co _x Mn _y ] O _{2- b} S _b

(In the formulas 5 and 6, 0≤a≤0.2, 0≤b≤0.1, 0.05≤x≤0.3, 0.1≤y≤0.35, 0.15≤x + y≤0.6, preferably 0.01≤a≤0.2 And 0.01≤b≤0.1)

[Formula 7]

Li [Li _a (Ni _x Co _{1 -2 x} Mn _x ) _1-a ] O _{2- b} F _b

[Formula 8]

Li [Li _a (Ni _x Co _{1 -2 x} Mn _x ) _1-a ] O ₂ S _b

(In the formulas 7 and 8, 0≤a≤0.2, 0.01≤x≤0.5, 0≤b≤0.1, preferably 0.01≤a≤0.2 and 0.01≤b≤0.1)

[Formula 9]

Li [Li _a (Ni _x Co _{1 -2 x} Mn _{x -y / 2} M _y ) _1-a ] O _{2- b} F _b

[Formula 10]

Li [Li _a (Ni _x Co _{1 -2 x} Mn _{x -y / 2} M _y ) _1-a ] O _{2- b} S _b

(In the formulas 9 and 10, 0≤a≤0.2, 0.01≤x≤0.5, 0.01≤y≤0.1, 0≤b≤0.1, M is selected from the group consisting of Mg, Ca, Cu, and Zn At least one element, preferably 0.01 ≦ a ≦ 0.2 and 0.01 ≦ b ≦ 0.1)

[Formula 11]

_{Li [Li a (Ni 1/} 3 Co (1 / 3-2x) Mn (1/3 + x) M x) 1-a] O 2 - b F b

[Chemical Formula 12]

_{Li [Li a (Ni 1/} 3 Co (1 / 3-2x) Mn (1/3 + x) M x) 1-a] O 2 - b S b

(In the formulas 11 and 12, 0≤a≤0.2, 0.01≤x≤0.5, 0.01≤y≤0.1, 0≤b≤0.1, M is selected from the group consisting of Mg, Ca, Cu, and Zn At least one element, preferably 0.01 ≦ a ≦ 0.2 and 0.01 ≦ b ≦ 0.1)

[Formula 13]

Li [Li _a (Ni _x Co _{1 -2x- y} Mn _x M _y ) _1-a ] O _{2- b} F _b

[Formula 14]

Li [Li _a (Ni _x Co _{1 -2x- y} Mn _x M _y ) _1-a ] O _{2- b} S _b

(In the formulas 13 and 14, 0≤a≤0.2, 0.01≤x≤0.5, 0.01≤y≤0.1, 0≤b≤0.1, M is selected from the group consisting of B, Al, Fe, and Cr At least one element, preferably 0.01 ≦ a ≦ 0.2 and 0.01 ≦ b ≦ 0.1)

[Formula 15]

Li [Li _a (Ni _x Co _{1 -2x- y} Mn _{x -z / 2} M _y N _z ) _1-a ] O _{2- b} F _b

[Formula 16]

Li [Li _a (Ni _x Co _{1 -2x- y} Mn _{x -z / 2} M _y N _z ) _1-a ] O _{2- b} S _b

(In Formulas 15 and 16, 0≤a≤0.2, 0.01≤x≤0.5, 0.01≤y≤0.1, 0≤b≤0.1, M is selected from the group consisting of B, Al, Fe, and Cr At least one element, N is Mg or Ca, preferably 0.01 ≦ a ≦ 0.2 and 0.01 ≦ b ≦ 0.1)

[Formula 17]

LiM _x Fe _{1 - x} PO ₄

(In Formula 17, 0≤x≤1, M is at least one element selected from the group consisting of Co, Ni, Mn)

[Formula 18]

Li _{1 + a} [Mn _{2 - x} M _x ] O _{4- b} F _b

[Formula 19]

Li _{1 + a} [Mn _{2 - x} M _x ] O _{4- b} S _b

(In Formula 18 or 19, 0≤a≤0.15, 0≤b≤0.2, 0.01≤x≤0.1, M is selected from the group consisting of Co, Ni, Cr, Mg, Al, Zn, Mo, W At least one element, preferably 0.01 ≦ a ≦ 0.15 and 0.01 ≦ b ≦ 0.2)

[Formula 20]

_{Li 1 + a [Ni 0 .5} Mn 1 .5- x M x] O 4- b F b

[Formula 21]

_{Li 1 + a [Ni 0 .5} Mn 1 .5- x M x] O 4- b S b

(In Formula 20 or 21, 0≤a≤0.15, 0≤b≤0.2, 0.01≤x≤0.1, M is selected from the group consisting of Co, Ni, Cr, Mg, Al, Zn, Mo, W At least one element, preferably 0.01 ≦ a ≦ 0.15 and 0.01 ≦ b ≦ 0.2)

At this time, the lithium-containing compound preferably has an average particle size of 1㎛ 50㎛, more preferably have an average particle size of 5㎛ 20㎛, but is not limited thereto. When the average particle size of the lithium-containing compound is in the above range, the coating layer may be evenly coated on the surface, which is preferable.

Method for producing a positive electrode active material according to another embodiment of the present invention, by mixing a lithium-containing compound, a carboxyl group-containing amino acid chelating agent, and a solvent to prepare an aqueous solution containing a lithium-containing compound having a hydroxyl group on the surface (S1) ; And adding a precursor and a basic solution of a metal oxide or a metal hydroxide to the aqueous solution and drying the same to prepare a cathode active material (S2).

1 is a flow chart showing a manufacturing method according to an embodiment of the present invention, with reference to Figure 1 will be described for the manufacturing method of the positive electrode active material.

First, an aqueous solution containing a lithium-containing compound, a carboxyl group-containing amino acid chelating agent, and a solvent is mixed to prepare a lithium-containing compound having a hydroxy group on its surface (S1).

The lithium-containing compound and the carboxyl group-containing amino acid chelating agent are the same as described above.

In addition, a water-soluble solvent may be used as the solvent, and representative examples thereof include water, ethanol, methanol, and the like. It is not limited to this.

Through the above process, the lithium-containing compound having a plurality of hydroxy groups on the surface thereof is prepared by combining the surface of the lithium-containing compound with the carboxyl group-containing amino acid chelating agent. have.

Subsequently, a precursor and a basic solution of a metal oxide or a metal hydroxide are added to the previously prepared aqueous solution and dried to prepare a cathode active material (S2).

The precursor of the metal oxide or the metal hydroxide is preferably a metal salt containing at least one element selected from the group consisting of Al, Mg, Ni, Co, Cr, Mo, and W. Representative examples include alkoxide salts, sulfates, nitrates, acetates, chlorides, phosphates, or combinations thereof comprising at least one of the above elements.

The metal oxide or the metal hydroxide precursor may be added in a salt state or dissolved in a solvent.

As a solvent used for dissolving the metal oxide or metal hydroxide precursor, a water-soluble solvent may be used, and representative examples thereof include water, ethanol and methanol, but are not limited thereto.

The basic solution may be an aqueous ammonia solution, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, or the like, but is not limited thereto.

In addition, the concentration of the basic solution is preferably about 0.5 to 5M, but is not limited thereto.

In addition, the basic solution is preferably added until the pH of the mixture containing the aqueous solution and the metal oxide or metal hydroxide and the basic solution prepared above is 7 to 10. When the pH is in the above range is preferable because the material to be coated is formed. In addition, the reaction temperature is preferably 50 to 100 ° C, and the reaction time is preferably 5 to 24 hours, but is not necessarily limited thereto.

It is preferable that the said drying temperature is 80-130 degreeC. When drying at the temperature it is preferable to remove the moisture that can remain in the positive electrode active material after the coating reaction proceeds. In addition, the drying time is preferably 6 to 24 hours, but is not limited thereto.

The dried positive electrode active material includes a lithium-containing compound, a metal hydroxide uniformly coated on the surface of the lithium-containing compound, and an amino acid chelating agent, and in particular, the metal hydroxide is coated on the lithium-containing compound by an amino acid chelating agent. It may be in the form.

In addition, the dried and prepared positive electrode active material may be further heat treated. It is preferable to perform heat processing at 200-700 degreeC, and it is more preferable to carry out in oxidative, reducing, or vacuum state. If the heat treatment process is further performed, impurities that could not be removed can be removed, thereby obtaining a positive electrode active material having a desired metal oxide coating layer, and further improving the bonding strength between the metal oxide and the lithium-containing compound. .

In addition, the heat treatment time is preferably 1 to 10 hours, but is not limited thereto.

Since the surface of the cathode active material of the present invention is coated with a metal oxide or metal hydroxide, there is little influence on the acid generated near the cathode active material, the reaction between the cathode active material and the electrolyte can be suppressed. Therefore, it is possible to improve the phenomenon in which the battery capacity is drastically reduced, and is excellent in charge and discharge characteristics, life characteristics, high voltage and high rate characteristics, and excellent in thermal stability.

Hereinafter, the present invention will be described in more detail with reference to examples, but these examples are for illustrative purposes only and should not be construed as limiting the present invention.

< Example  1>

By glutamic acid Co ₃ O ₄ Coated Spinel type  Preparation of Cathode Active Material

1200 ml of distilled water, spinel-type lithium-containing compound LiAl _{0 .05} Mn _{1 .95} O _{4 in} 2L reactor 100 g and 0.06 mol of glutamic acid were added thereto, followed by stirring for 4 hours. At this time, the temperature of the reactor was maintained at about 40 ℃. Thereafter, Co (NO ₃ ) ₂ 6H ₂ O was dissolved in 100 ml of distilled water at 5% by weight relative to the positive electrode active material, and then put in a reactor and stirred for 1 hour. At this time, a pH meter was installed inside the reactor, and ammonia solution of 2M concentration was added until the pH was 7. The prepared cobalt hydroxide coated spinel positive electrode active material was washed with distilled water and filtered. Then, after drying for 12 hours in a 110 ℃ hot air thermostat, a spinel type positive electrode active material coated with Co ₃ O ₄ by heat treatment at 500 ℃ in an oxidizing atmosphere. At this time, Co ₃ O ₄ contained in the coating layer of the positive electrode active material was 1% by weight based on 100% by weight of the positive electrode active material, the standard deviation of the thickness of the coating layer was 10nm to 30nm, the average thickness of the coating layer was 20nm to 50nm.

< Comparative example  1>

A positive electrode active material was prepared in the same manner as in Example 1 except that glutamic acid was changed to citric acid. At this time, the thickness standard deviation of the coating layer of the positive electrode active material was 500 nm.

< Comparative example  2>

A positive electrode active material was prepared in the same manner as in Example 1 except that glutamic acid was changed to ammonium citrate. At this time, the thickness standard deviation of the coating layer of the positive electrode active material was 500 nm.

< Comparative example  3>

A non-conducting coating LiAl _{0 .05} Mn _{1 .95} O ₄ was used as a positive electrode active material.

Characterization of Cathode Active Material

(i) XRD evaluation

The X-ray diffraction pattern of the cathode active material prepared in Example 1 was measured using an X-ray diffraction analyzer (trade name: Rint-2000, company name: Rigaku, Japan), and the result is illustrated in FIG. 2. From the peaks shown in FIG. 2, it was confirmed that the spinel-type cathode active material had a cubic-structured FD3m space group.

(ii) FE- SEM (field emission scanning electron microscopy)

The positive electrode active materials prepared in Examples 1 and Comparative Examples 1 and 2 and the positive electrode active materials of Comparative Example 3 were photographed by FE-SEM with a field emission scanning electron microscope (trade name: JS 6400, company name: JEOL, Japan). 3 to 6 are shown.

Referring to Figure 3, it can be seen that the positive electrode active material prepared according to Example 1 has a uniform coating layer formed as a whole. However, referring to FIGS. 4 and 5, the cathode active materials according to Comparative Examples 1 and 2 were formed by agglomeration of coating materials, and only the coating materials were locally applied.

In addition, referring to FIG. 6, the shape of the cathode active material in which the coating layer according to Comparative Example 3 was not formed could be confirmed.

(Ⅲ) Transmission electron microscope (TEM)

The positive electrode active material prepared in Example 1 was TEM photographed with a transmission electron microscope (trade name: JSM 2010, company name: JEOL, Japan), and is shown in FIG. 7. Referring to Figure 7, it can be seen that the thickness of the coating layer formed on the surface is uniform.

Manufacture of anode

The slurry was prepared by mixing the positive electrode active materials prepared in Example 1 and Comparative Examples 1 to 3, acetylene black conductive agent, and polyvinylidene fluoride binder in a weight ratio of 85: 7.5: 7.5, respectively, in NMP solvent. This slurry was uniformly applied to an aluminum foil having a thickness of 20 μm, and vacuum dried at 120 ° C. to prepare respective positive electrodes.

Manufacture of coin battery

Each of the positive electrode and the lithium foil prepared as a counter electrode, a porous polyethylene membrane (Celgard ELC, Celgard 2300, thickness: 25㎛) as a separator, the electrolyte of 1M LiPF ₆ (ethylene carbonate: dimethyl carbonate = 1: 1, volume ratio) to prepare a coin cell (coin cell) of the 2032 standard by a conventional method, respectively.

In order to evaluate the characteristics of the battery, the electrochemical analyzer (Toscat3000U, Japan, manufactured by Toyo) was charged and charged at 55 ° C, a potential region of 3.0 to 4.3V, and a current density of 0.8 mA / cm ² . Discharge experiments were made.

After the experiment, the capacity according to the cycle of the battery prepared using the positive electrode active material of Example 1, Comparative Examples 2 to 3 is shown in FIG. Referring to FIG. 8, in the case of a battery using a spinel positive electrode active material coated with Co ₃ O ₄ using glutamic acid of Example 1, the capacity of 98.9% at 55 ° C. and a current density of 0.8 mA / cm ² until the 100th cycle was used. Although there was almost no capacity decrease according to the number of cycles due to the retention rate, the battery life using the positive electrode active materials of Comparative Examples 2 and 3 was significantly lower.

In addition, in order to evaluate the rate characteristics of the manufactured battery, a potential region of 3.0 to 4.3 V, and various current density conditions at 30 ° C and 55 ° C using an electrochemical analyzer (Toscat3000U, Japan, manufactured by Toyo) Charge and discharge experiments were conducted at.

After the experiment, the standard capacity according to the cycle of the battery prepared using the positive electrode active material of Example 1 and Comparative Example 3 is shown in FIG. Referring to FIG. 9, in the case of a battery using a spinel positive electrode active material coated with Co ₃ O ₄ using glutamic acid of Example 1, compared to Comparative Example 3, excellent rate characteristics were obtained at various current density conditions at 55 ° C. high temperature. Indicated.

The present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention. It is possible.

1 is a flowchart illustrating a method of manufacturing a cathode active material according to an embodiment of the present invention.

2 is an X-ray diffraction analysis photograph of the positive electrode active material prepared in Example 1 of the present invention.

3 is an FE-SEM photograph of the positive electrode active material prepared in Example 1 of the present invention.

Figure 4 is a FE-SEM picture of the positive electrode active material prepared in Comparative Example 1 of the present invention.

5 is an FE-SEM photograph of the cathode active material prepared in Comparative Example 2 of the present invention.

6 is an FE-SEM photograph of the cathode active material prepared in Comparative Example 3 of the present invention.

7 is a TEM photograph of the positive electrode active material prepared in Example 1 of the present invention.

8 is a cycle characteristic graph of a half cell using the positive electrode active material prepared in Example 1 and Comparative Examples 2 and 3 of the present invention.

9 is a graph showing the rate characteristic of the half-cell using the positive electrode active material prepared in Example 1 and Comparative Example 3.

Claims (10)

Lithium-containing compounds; And A coating layer comprising a metal oxide or a metal hydroxide and a carboxyl group-containing amino acid chelating agent surrounding the lithium-containing compound, The coating layer has a thickness standard deviation of 2nm to 300nm positive electrode active material for a lithium secondary battery. delete The method of claim 1, The lithium-containing compound is a compound having a hexagonal layered rock salt structure selected from the group consisting of Formulas 1 to 16, a compound having an olivine structure represented by the formula (17), having a cubic structure represented by the formulas 18 to 21 A spinel compound, and a positive electrode active material for a lithium secondary battery selected from the group consisting of a combination thereof. [Formula 1] Li _{1 + a} [Co _{1 - x} M _x ] O _{2- b} F _b [Formula 2] Li _{1 + a} [Co _{1 - x} M _x ] O _{2- b} S _b (In Formulas 1 and 2, 0≤a≤0.2, 0≤b≤0.2, 0.01≤x≤0.1, M is Mg, Al, Ni, Mn, Zn, Fe, Cr, Ga, Mo, and W At least one element selected from the group consisting of: (3) Li _{1 + a} [Ni _{1 - x} M _x ] O _{2- b} F _b [Formula 4] Li _{1 + a} [Ni _{1 - x} M _x ] O _{2- b} S _b (In Formulas 3 and 4, 0≤a≤0.2, 0≤b≤0.2, 0.01≤x≤0.5, M is Mg, Al, Co, Mn, Zn, Fe, Cr, Ga, Mo, and W At least one element selected from the group consisting of: [Chemical Formula 5] Li _{1 + a} [Ni _{1 -x- y} Co _x Mn _y ] O _{2- b} F _b [Formula 6] Li _{1 + a} [Ni _{1 -x- y} Co _x Mn _y ] O _{2- b} S _b (In the formulas 5 and 6, 0≤a≤0.2, 0≤b≤0.1, 0.05≤x≤0.3, 0.1≤y≤0.35, 0.15≤x + y≤0.6) [Formula 7] Li [Li _a (Ni _x Co _{1 -2 x} Mn _x ) _1-a ] O _{2- b} F _b [Formula 8] Li [Li _a (Ni _x Co _{1 -2 x} Mn _x ) _1-a ] O ₂ S _b (In the formulas 7 and 8, 0≤a≤0.2, 0.01≤x≤0.5, 0≤b≤0.1) [Formula 9] Li [Li _a (Ni _x Co _{1 -2 x} Mn _{x -y / 2} M _y ) _1-a ] O _{2- b} F _b [Formula 10] Li [Li _a (Ni _x Co _{1 -2 x} Mn _{x -y / 2} M _y ) _1-a ] O _{2- b} S _b (In the formulas 9 and 10, 0≤a≤0.2, 0.01≤x≤0.5, 0.01≤y≤0.1, 0≤b≤0.1, M is selected from the group consisting of Mg, Ca, Cu, and Zn 1 or more elements) [Formula 11] _{Li [Li a (Ni 1/} 3 Co (1 / 3-2x) Mn (1/3 + x) M x) 1-a] O 2 - b F b [Chemical Formula 12] _{Li [Li a (Ni 1/} 3 Co (1 / 3-2x) Mn (1/3 + x) M x) 1-a] O 2 - b S b (In the formulas 11 and 12, 0≤a≤0.2, 0.01≤x≤0.5, 0.01≤y≤0.1, 0≤b≤0.1, M is selected from the group consisting of Mg, Ca, Cu, and Zn 1 or more elements) [Formula 13] Li [Li _a (Ni _x Co _{1 -2x- y} Mn _x M _y ) _1-a ] O _{2- b} F _b [Formula 14] Li [Li _a (Ni _x Co _{1 -2x- y} Mn _x M _y ) _1-a ] O _{2- b} S _b (In the formulas 13 and 14, 0≤a≤0.2, 0.01≤x≤0.5, 0.01≤y≤0.1, 0≤b≤0.1, M is selected from the group consisting of B, Al, Fe, and Cr 1 or more elements) [Formula 15] Li [Li _a (Ni _x Co _{1 -2x- y} Mn _{x -z / 2} M _y N _z ) _1-a ] O _{2- b} F _b [Formula 16] Li [Li _a (Ni _x Co _{1 -2x- y} Mn _{x -z / 2} M _y N _z ) _1-a ] O _{2- b} S _b (In Formulas 15 and 16, 0≤a≤0.2, 0.01≤x≤0.5, 0.01≤y≤0.1, 0≤b≤0.1, M is selected from the group consisting of B, Al, Fe, and Cr One or more elements, N being Mg or Ca) [Formula 17] LiM _x Fe _{1 - x} PO ₄ (In Formula 17, 0≤x≤1, M is at least one element selected from the group consisting of Co, Ni, and Mn) [Formula 18] Li _{1 + a} [Mn _{2 - x} M _x ] O _{4- b} F _b [Formula 19] Li _{1 + a} [Mn _{2 - x} M _x ] O _{4- b} S _b (In Formulas 18 and 19, 0≤a≤0.15, 0≤b≤0.2, 0.01≤x≤0.1, M is in the group consisting of Co, Ni, Cr, Mg, Al, Zn, Mo, and W At least one element selected) [Formula 20] _{Li 1 + a [Ni 0 .5} Mn 1 .5- x M x] O 4- b F b [Formula 21] _{Li 1 + a [Ni 0 .5} Mn 1 .5- x M x] O 4- b S b (In the formulas 20 and 21, 0≤a≤0.15, 0≤b≤0.2, 0.01≤x≤0.1, M is in the group consisting of Co, Ni, Cr, Mg, Al, Zn, Mo, and W At least one element selected) The method of claim 1, The metal oxide or metal hydroxide, MO _x and M (OH) _x (wherein M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Cr, Mo, and W, 1≤x≤4) A positive electrode active material for lithium secondary batteries that is at least one species. The method of claim 1, The metal oxide or the metal hydroxide is contained in 0.1 to 10% by weight based on the total amount of the positive electrode active material positive electrode active material for lithium secondary batteries. The method of claim 1, The said carboxyl group-containing amino acid chelating agent is contained in 0.01-1 mol with respect to 1 mol of metal hydroxides. The method of claim 1, The coating layer has a thickness standard deviation of 2nm to 100nm positive electrode active material for a lithium secondary battery.  Mixing a lithium-containing compound, a carboxyl group-containing amino acid chelating agent, and a solvent to prepare an aqueous solution containing a lithium-containing compound having a hydroxy group on its surface; And Preparing a cathode active material by adding and drying a metal oxide or metal hydroxide precursor and a basic solution to the aqueous solution A method for producing a cathode active material for a lithium secondary battery according to any one of claims 1 and 3 to 7. The method of claim 8, A method of manufacturing a cathode active material for a lithium secondary battery, which further performs a heat treatment step after the drying step. A lithium secondary battery comprising a positive electrode comprising the positive electrode active material according to any one of claims 1 and 3.

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