KR20190041669A - Positive electrode active material for lithium secondary battery including vanadium oxide coated with carbon and method for preparing the same - Google Patents

Abstract

A positive electrode active material for a lithium secondary battery comprising vanadium oxide subjected to carbon surface treatment, in which vanadium oxide used as a positive electrode active material for a lithium secondary battery is coated with carbon, and a method for manufacturing the same are disclosed. The positive electrode active material for a lithium secondary battery comprising a vanadium oxide subjected to carbon surface treatment comprises: vanadium oxide; and a carbon layer formed on a surface of the vanadium oxide and formed of a carbon source including citric acid and glucose. Vanadium is not eluted into an electrolyte by the carbon layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode active material for a lithium secondary battery including a carbon surface-treated vanadium oxide and a method for preparing the same.

The present invention relates to a cathode material for a lithium secondary battery, and more particularly, to a cathode active material for a lithium secondary battery comprising a carbon surface-treated vanadium oxide and a vanadium oxide used as a cathode active material for a lithium secondary battery, ≪ / RTI >

With the development of technology and demand for mobile devices, the demand for secondary batteries as energy sources is also rapidly increasing. Recently, the use of a secondary battery as a power source has been realized in an electric vehicle (EV) and a hybrid electric vehicle (HEV). As a result, much research has been conducted on secondary batteries capable of meeting various demands, and in particular, there is a high demand for lithium secondary batteries having high energy density, high discharge voltage and output stability, .

Lithium secondary battery technology has recently been applied in various fields through remarkable development, but it has been studied to overcome limitations such as capacity, safety, output, enlargement and miniaturization of batteries. Typical examples are metal-air batteries with a theoretical capacity in terms of capacity compared to current lithium secondary batteries, all solid batteries with no risk of explosion in terms of safety, lithium rechargeable batteries (Na-S) or redox flow battery (RFB) in the aspect of enlargement, and a thin film battery in the aspect of miniaturization. Continuous research is underway in academia and industry.

Generally, a lithium secondary battery uses a metal oxide such as LiCoO ₂ as a positive electrode active material and a carbon material as a negative electrode active material, and a polyolefin-based porous separator is sandwiched between the negative electrode and the positive electrode, and a nonaqueous electrolyte solution containing a lithium salt such as LiPF ₆ is impregnated . However, LiCoO ₂ has a high operating voltage and a large capacity, but is relatively expensive due to the limitation of the amount of resources, the charge / discharge current is as low as about 150 mAh / g, and the crystal structure is unstable at a voltage higher than 4.3 V , There is a danger of ignition due to the reaction with the electrolytic solution. Moreover, LiCoO ₂ has a disadvantage in that it exhibits a very large property change only by a change of some parameters in the manufacturing process.

One of the alternatives to such LiCoO ₂ is LiMn ₂ O ₄ . LiMn ₂ O ₄ has a lower capacity than LiCoO ₂ but has a low cost and no pollution factor. Looking at the typical examples of the structure of LiCoO ₂ and LiMn ₂ O ₄ of the positive electrode active material, LiCoO ₂ has a layered structure (Layered structure), LiMn ₂ O ₄ has a spinel if (Spinel) structure. These two materials commonly have excellent performance as a battery when they are excellent in crystallinity. Therefore, in particular, in order to crystallize the two materials when fabricating a thin film battery, a heat treatment step must be accompanied with the manufacturing process of the thin film or the subsequent process. Therefore, it is difficult to implement a battery using these two materials on a polymer material such as a plastic material for medical or special purposes, because the polymer material can not withstand the heat treatment temperature.

To solve these drawbacks, vanadium oxide has been proposed. The vanadium oxide has an advantage that it has very good electrode characteristics even in the amorphous state although the capacity is low. In the case of vanadium oxide, the synthesis of the vanadium oxide is relatively easy and the synthesis is possible at room temperature. In the case of amorphous vanadium oxide synthesized at room temperature, its performance (lifetime or efficiency) is superior to that of crystalline vanadium oxide. Therefore, if vanadium oxide is used as a cathode active material, a room temperature process becomes possible, and it becomes possible to manufacture a secondary battery on a polymer material such as a plastic. In addition, the vanadium oxide has a high-capacity layered structure containing no lithium, has a high energy density, and exhibits a theoretical capacity of 290 mAh / g on two electron reactions.

For this reason, vanadium oxides by various chemical methods and vacuum thin film synthesis methods are expected to be highly applicable to cathode active materials of secondary batteries in the future. However, the vanadium oxide exhibits a low lithium ion diffusion coefficient, and there is a problem that vanadium is eluted into the electrolytic solution and the life of the battery is reduced. Accordingly, in the related art, research and development of improved vanadium oxide as a cathode active material have been made.

Korean Patent Registration No. 10-1617836

Accordingly, an object of the present invention is to provide a positive electrode active material for a lithium secondary battery comprising a carbon surface-treated vanadium oxide, which can improve elongation of a battery by suppressing elution of vanadium and improving a conductive structure, .

Another object of the present invention is to provide a method for producing a cathode active material for a lithium secondary battery comprising a carbon surface-treated vanadium oxide in which a carbon layer coated on the surface of vanadium oxide is not removed even when a heat treatment process is performed.

In order to achieve the above object, And a carbon layer formed on the surface of the vanadium oxide and formed of a carbon source including citric acid and glucose, wherein the carbon layer does not allow vanadium to elute into the electrolyte solution. to provide.

The present invention also relates to a method for producing a vanadium oxide catalyst, comprising the steps of: a) dissolving and mixing a vanadium oxide raw material containing a carbon source including citric acid and glucose and ammonium metavanadate in a solvent; b) drying the prepared mixture, followed by heat treatment in a gas atmosphere; And c) subjecting the heat-treated mixture to further heat treatment in an air atmosphere to produce a vanadium oxide having a carbon layer on its surface. The present invention also provides a method for producing a cathode active material for a lithium secondary battery.

According to the cathode active material for a lithium secondary battery including the carbon surface-treated vanadium oxide according to the present invention and the method for producing the same, by treating the vanadium oxide with a carbon coating, the elution of vanadium is suppressed and the conductive structure is improved, The carbon layer coated on the surface of the vanadium oxide is not removed even if the heat treatment process is performed.

1 is a graph showing a thermogravimetric analysis of a cathode active material according to one embodiment of the present invention and a comparative example.
FIG. 2 is a graph showing Raman spectroscopy of a carbon layer coated with vanadium oxide in a cathode active material according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

The cathode active material for a lithium secondary battery comprising a carbon surface-treated vanadium oxide according to the present invention comprises vanadium oxide and a carbon layer formed on a surface of the vanadium oxide and formed by a carbon source including citric acid and glucose, And the vanadium is not eluted into the electrolytic solution by the layer.

The cathode active material (cathode material) including vanadium oxide (Vanadium Oxide) is suitable as an electrode material because vanadium oxide (especially V ₂ O ₅ ) has theoretically high capacity and energy density. However, there is a problem that the ion diffusion coefficient is low, and vanadium is eluted into the electrolytic solution and the electrode structure can be collapsed.

The present invention solves the above problems by forming a carbon layer on the surface of the vanadium oxide, thereby preventing the elution of vanadium and thus improving the conductive structure.

Since vanadium, which is a transition metal, can have various oxidation numbers, there exist vanadium oxides having various ratios of vanadium and oxygen, and thus the kind thereof is not limited. However, considering the stability of the structure, the vanadium oxide used in the present invention may be a compound represented by the following formula (1).

[Chemical Formula 1]

V _a O _b

In the above formula (1), 1? A? 6 and 2? B? 13.

Of these, the vanadium oxide is preferably a compound having an oxidation number of 2 to 5, and VO ₂ , V ₂ O ₃ , V ₂ O _5, or a combination thereof can be exemplified. At this time, when the oxidation number is 2 or 3, it is basic, while when the oxidation number is 4 or 5, it is amphoteric. In particular, vanadium pentoxide (V ₂ O ₅ ) is most stable when the oxidation number is 5, Use is most preferred.

The vanadium pentoxide (V ₂ O ₅ ) is a metal oxide having a yellow or yellowish red color and is also referred to as vanadium acid anhydride. It has a melting point of about 690 ° C and a specific gravity of about 3.375 (18 ° C). It dissolves in alkaline and becomes vanadate although it is not soluble in water. In addition, vanadium pentoxide has excellent intercalation power to lithium ions and has a high potential of about 4 V with respect to lithium metal, thereby being utilized as a cathode material for lithium secondary batteries. In addition, vanadium pentoxide is used as an electrode material for solid electrolytes and polymer electrolyte lithium secondary batteries. Particularly, the vanadium pentoxide in the mesoporous structure has a high surface area due to the porosity, and the diffusion rate of the lithium ion, the electric storage capacity and the electric conductivity are improved. On the other hand, the particle size of the vanadium oxide does not significantly affect the present invention, and particles of any size may be used.

The carbon layer coated or laminated on the surface of the vanadium oxide may be coated on at least a part of the surface of the vanadium oxide (here, 'part' means not 100% of the total vanadium oxide surface area), vanadium It is preferable that the coating is applied over a wide area as much as possible in order to minimize the elution of the vanadium oxide.

The carbon layer includes a carbon compound containing 3 to 20 carbon atoms, preferably 5 to 10 carbon atoms, and hydrogen atoms and oxygen atoms present in the carbon source (precursor) are removed as a gas during the formation of the carbon layer , Or may be contained in a trace amount in the carbon layer (or carbon compound). The content of the carbon layer may vary depending on the surface area of the vanadium oxide coated with the carbon layer. When the carbon layer (carbon compound) is coated on the entire surface of the vanadium oxide, the content of the carbon layer is preferably 0.1 To 10 parts by weight, preferably from 0.1 to 5 parts by weight, more preferably from 1 to 3 parts by weight. If the content of the carbon layer is less than 0.1 parts by weight based on 100 parts by weight of the vanadium oxide, the coating area is not sufficient and the effect of inhibiting vanadium dissolution may be deteriorated. If the content of the carbon layer exceeds 10 parts by weight, The active material ratio is decreased and the thickness to be coated is excessively increased, which may interfere with the reaction of the battery, thereby reducing the overall efficiency.

As described above, when the carbon layer is coated or laminated (formed) on the surface of the vanadium oxide, direct contact between the vanadium oxide and the electrolytic solution can be avoided, and the diffusion coefficient of lithium ion is lowered, and the problem that vanadium is eluted into the electrolytic solution And ultimately, the lifetime of the lithium secondary battery can be improved. On the other hand, a conventional coating layer can act as a resistance, but the carbon coating layer used in the present invention solves this resistance problem.

The above-described carbon surface-treated vanadium oxide can be used in combination with a binder and a conductive material to produce a positive electrode. Explanation of a conventional positive electrode material such as a binder and a conductive material, .

Next, a method for producing a cathode active material for a lithium secondary battery comprising a carbon surface-treated vanadium oxide according to the present invention will be described. A method for producing a cathode active material for a lithium secondary battery comprising the carbon surface-treated vanadium oxide includes the steps of: a) dissolving a vanadium oxide raw material containing a carbon source including citric acid and glucose and ammonium metavanadate in a solvent and mixing b) drying the prepared mixture, followed by heat treatment in a gaseous atmosphere, and c) further heat treating the heat-treated mixture in an air atmosphere to produce vanadium oxide having a carbon layer on its surface Through this, it is possible to prevent the vanadium carbide oxidation layer from being changed in the inert atmosphere or the reducing atmosphere, or to remove the carbon layer coated on the surface of the vanadium oxide even if the heat treatment process is performed.

The citric acid serves to dissolve carbon forming and ammonium metavanadate in water, and its content is 40 to 80% by weight based on the total weight of the vanadium oxide raw material including the carbon source and ammonium metavanadate, and the citric acid When the content exceeds 80% by weight, the proportion of the active material may decrease. When the content is less than 40% by weight, the solubility of ammonium metavanadate may decrease or the formation of a carbon layer may be difficult.

The content of the glucose is 10 to 40% by weight based on the total weight of the vanadium oxide raw material. When the content of the glucose exceeds 40% by weight, ammonium metabisulfite And the proportion of the active material may decrease. When the amount of the active material is less than 10% by weight, the formation of the carbon layer may be difficult.

Also, the ammonium metavanadate is used to form vanadium oxide, and its content is at least 5% by weight based on the total weight of the vanadium oxide raw material. Since the solubility is determined according to the concentration of the citric acid, It is not easy to further refine the content of ammonium. In addition, it is preferable that such citric acid, glucose and ammonium metavanadate are supplied (used) at a weight ratio of 6: 7: 2 to 3: 1.

The solvent may be an organic solvent such as acetone or alcohol, water such as distilled water or purified water, and the citric acid, glucose and ammonium metavanadate are dispersed. In the step b), a carbon source is carbonized to form a carbon layer on the surface of the vanadium oxide. In the step b), the heat treatment is performed using argon, helium, nitrogen, In an inert gas (or inert gas) atmosphere at a temperature of 400 to 700 占 폚, preferably 450 to 600 占 폚 for 4 to 6 hours. In the step c), a desired vanadium oxide such as V ₂ O ₅ is formed and the thickness of the carbon layer is controlled. In the step c), the heat treatment is performed at a temperature of 150 to 300 ° C, Preferably 150 to 250 < 0 > C for 1 to 3 hours. On the other hand, the heat treatment process in an inert gas atmosphere may be performed one or more times after the heat treatment process in an air atmosphere.

When the above processes a) to c) are performed, a vanadium oxide composite (or a cathode active material for a lithium secondary battery including a vanadium oxide) having a carbon compound coated on at least a part of the surface of the vanadium oxide is produced.

Manufacture of anode

Meanwhile, a slurry prepared by preparing a cathode composition further comprising a conductive material and a binder in a cathode active material according to the present invention is diluted in a predetermined solvent (dispersion medium), and is directly coated on a cathode current collector and dried. . Alternatively, the slurry may be cast on a separate support, and then the film may be peeled off from the support to laminate the cathode current collector on the anode current collector to produce a cathode layer. In addition, the anode can be manufactured in a variety of ways using methods well known to those skilled in the art.

The conductive material serves as a path through which electrons move from the positive electrode current collector to the positive electrode active material and not only provides electron conductivity but also electrically connects the electrolyte and the positive electrode active material to form a lithium ion Li + ) Moves to this sulfur to react. Therefore, if the amount of the conductive material is insufficient or fails to perform its role properly, the portion of the sulfur in the electrode that does not react increases and eventually causes a reduction in capacity. In addition, since high-rate discharge characteristics and charge-discharge cycle life are adversely affected, it is necessary to add an appropriate conductive material. The conductive material is preferably added in an amount of 0.01 to 30% by weight based on the total weight of the cathode composition.

The conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples thereof include graphite; Carbon black such as denka black, acetylene black, ketjen black, channel black, furnace black, lamp black and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used. Concrete examples of commercially available conductive materials include acetylene black series such as Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, Ketjenblack, Armak Company products, Vulcan XC-72 Cabot Company products and Super-P (Timcal) products can be used.

The binder is used to adhere the positive electrode active material well to the current collector. The binder should be well dissolved in a solvent, and it should not only constitute a conductive network between the positive electrode active material and the conductive material, but also have adequate electrolyte impregnation properties. The binder applicable to the present invention may be any binder known in the art and specifically includes a fluororesin binder containing polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE) ; Rubber-based binders including styrene-butadiene rubber, acrylonitrile-butadiene rubber, and styrene-isoprene rubber; Cellulosic binders including carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, and regenerated cellulose; Polyalcohol-based binders; A polyolefin-based binder including polyethylene and polypropylene; But are not limited to, polyimide-based binders, polyester-based binders, and silane-based binders.

The content of the binder may be 0.5 to 30% by weight based on the total weight of the cathode composition, but is not limited thereto. If the content of the binder resin is less than 0.5% by weight, the physical properties of the positive electrode may deteriorate and the positive electrode active material and the conductive material may fall off. When the amount of the binder resin is more than 30% by weight, the ratio of the active material and the conductive material is relatively decreased The battery capacity may be reduced, and the efficiency may be lowered by acting as a resistance element.

The cathode composition comprising the cathode active material, the conductive material and the binder may be diluted with a predetermined solvent and coated on the anode current collector by a conventional method known in the art. First, a positive electrode current collector is prepared. The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, and examples thereof include stainless steel, aluminum, nickel, titanium, sintered carbon, The surface of the steel may be surface treated with carbon, nickel, titanium, silver, or the like. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible.

Next, a slurry obtained by diluting a positive electrode composition containing a positive electrode active material, a conductive material and a binder in a solvent is applied on the positive electrode current collector. The cathode composition including the above-mentioned cathode active material, conductive material and binder may be mixed with a predetermined solvent to prepare a slurry. At this time, the solvent should be easy to dry, and it is most preferable that the binder can be dissolved well, but the cathode active material and the conductive material can be maintained in a dispersed state without dissolving. When the solvent dissolves the cathode active material, the specific gravity (D = 2.07) of the sulfur in the slurry is high, so that the sulfur is submerged in the slurry, which causes sulfur in the current collector to cause problems in the conductive network, . The solvent (dispersion medium) may be water or an organic solvent, and the organic solvent may be at least one selected from the group consisting of dimethylformamide, isopropyl alcohol, acetonitrile, methanol, ethanol, and tetrahydrofuran.

Subsequently, there is no particular limitation on the method of applying the cathode composition in the slurry state. For example, a doctor blade coating, a dip coating, a gravure coating, a slit die coating coating, coating, spin coating, comma coating, bar coating, reverse roll coating, screen coating, and cap coating. . After the coating process, the cathode composition is evaporated through evaporation of the solvent (dispersion medium), denseness of the coating film and adhesion between the coating film and the current collector through the drying process. At this time, the drying is carried out according to a conventional method, and the drying is not particularly limited.

Manufacture of lithium secondary battery

Finally, the secondary battery including the cathode active material according to the present invention, preferably a lithium secondary battery, has a structure in which a lithium salt-containing non-aqueous electrolyte is impregnated in an electrode assembly having a separator interposed between an anode and a cathode . The separation membrane is not particularly limited in its material and can be used without any particular limitation as long as it separates the anode and the cathode physically and has an electrolyte and an ion permeability and is usually used as a separator in an electrochemical device. It is preferable that the material is a conductive or insulating material, particularly a material having low resistance against ion movement of the electrolytic solution and excellent ability to impregnate the electrolytic solution. For example, a polyolefin-based porous film or a nonwoven fabric may be used, but the present invention is not limited thereto.

The thickness of the separation membrane is not particularly limited, but is preferably 1 to 100 占 퐉, more preferably 5 to 50 占 퐉. If the thickness of the separator is less than 1 탆, the mechanical properties can not be maintained. If the thickness exceeds 100 탆, the separator will act as a resistive layer and the performance of the battery will be deteriorated. The pore size and porosity of the separation membrane are not particularly limited, but preferably the pore size is 0.1 to 50 μm and the porosity is 10 to 95%. If the pore size of the separator is less than 0.1 μm or the porosity is less than 10%, the separator will act as a resistive layer. If the pore size exceeds 50 μm or the porosity exceeds 95%, mechanical properties can not be maintained .

The electrolyte applicable to the present invention is a nonaqueous electrolyte or a solid electrolyte which does not react with lithium metal, but is preferably a nonaqueous electrolyte, and includes an electrolyte salt and an organic solvent. The electrolyte salt contained in the non-aqueous electrolyte is a lithium salt, and the lithium salt may be used without limitation as those conventionally used in an electrolyte for a lithium secondary battery. For example is the above lithium salt anion ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF _{^{4 -, (CF 3) 3}} PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 - _{, (CF 3 SO 2) 2} N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, ( CF ₃ SO _{2) 3} C ^- from the group consisting of ^{_{-, CF 3 (CF 2)}} 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN - , and _{(CF 3 CF 2 SO 2)} 2 N Any one selected, or two or more of them.

The organic solvent contained in the nonaqueous electrolyte solution may be any of those conventionally used in an electrolyte for a lithium secondary battery. Examples of the organic solvent include ether, ester, amide, linear carbonate, cyclic carbonate, etc., Can be mixed and used. Among them, a carbonate compound which is typically a cyclic carbonate, a linear carbonate or a mixture thereof may be included. The injection of the nonaqueous electrolyte solution can be performed at an appropriate stage of the manufacturing process of the electrochemical device according to the manufacturing process and required properties of the final product. That is, it can be applied before assembling the electrochemical device or in the final stage of assembling the electrochemical device.

The lithium secondary battery including the cathode active material according to the present invention can be laminated, stacked, and folded in addition to a general process such as winding. The battery case may have a cylindrical shape, a square shape, a pouch shape, a coin shape, or the like. As described above, the lithium secondary battery including the cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention ratio, and therefore can be applied to portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles electric vehicle (HEV), and the like.

According to another aspect of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell and a battery pack including the same. The battery module or the battery pack may include a power tool; Electric vehicles including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); Or a power storage system, as shown in FIG.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as set forth in the appended claims. Such changes and modifications are intended to be within the scope of the appended claims.

[Example 1] Production of cathode active material

Citric acid, glucose and ammonium metavanadate (NH ₄ VO ₃ ) were added to distilled water at a weight ratio of 64: 26: 10, dissolved and mixed. Subsequently, the mixture was dried and heat-treated at 600 ° C for 5 hours in an argon gas atmosphere using a tube furnace (Koryu Denki, Korea). Subsequently, the resultant was heat-treated at 200 ° C for 2 hours in an air atmosphere, and then heat-treated at 450 ° C for 5 hours in an argon gas atmosphere to prepare a cathode active material coated with a carbon layer on vanadium pentoxide (V ₂ O ₅ ) .

[Comparative Example 1] Production of cathode active material

A cathode active material coated with a carbon layer on vanadium pentoxide (V ₂ O ₅ ) was prepared in the same manner as in Example 1, except that citric acid was changed to oxalic acid.

[Experimental Example 1] Evaluation of phase of vanadium oxide in the cathode active material

The phase change of the vanadium oxide in the cathode active material prepared in Example 1 and Comparative Example 1 was evaluated by thermogravimetric analysis (TGA). FIG. 1 is a graph showing a thermogravimetric analysis of a cathode active material according to one embodiment of the present invention and Comparative Example. As shown in FIG. 1, the vanadium oxide of Example 1 is composed of vanadium pentoxide (V ₂ O ₅ ), While the vanadium oxide of Comparative Example 1 was reduced to be changed to vanadium oxide (V ₂ O).

[Experimental Example 2] Evaluation of carbon coating layer on the surface of vanadium oxide in the cathode active material

Raman spectroscopy was used to evaluate whether or not a carbon coating layer was normally formed on the surface of the vanadium oxide in the cathode active material prepared in Example 1. FIG. 2 is a graph showing Raman spectroscopic measurement of a carbon layer coated with vanadium oxide in a cathode active material according to an embodiment of the present invention. FIG. 2 is a graph showing the Raman spectrum of the vanadium oxide It was confirmed that the carbon layer was normally coated on the surface without loss.

Claims (10)

Vanadium oxide; And
And a carbon layer formed on the surface of the vanadium oxide and formed of a carbon source including citric acid and glucose,
Wherein the carbon layer does not allow vanadium to elute into the electrolyte solution. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the vanadium oxide is represented by the following formula (1).
[Chemical Formula 1]
V _a O _b
In the above formula (1), 1? A? 6 and 2? B? 13. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the vanadium oxide is vanadium pentoxide (V ₂ O ₅ ). The positive electrode active material for a lithium secondary battery according to claim 1, wherein the carbon layer comprises a carbon compound containing 3 to 20 carbon atoms. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the content of the carbon layer is 0.1 to 10 parts by weight based on 100 parts by weight of the vanadium oxide. a) mixing and mixing a vanadium oxide raw material containing a carbon source including citric acid and glucose and ammonium metavanadate in a solvent;
b) drying the prepared mixture, followed by heat treatment in a gas atmosphere; And
c) subjecting the heat-treated mixture to further heat treatment in an air atmosphere to produce a vanadium oxide having a carbon layer on the surface thereof. [7] The method of claim 6, wherein the citric acid, glucose and ammonium metavanadate are supplied at a weight ratio of 6: 7: 2 to 3: 1. 7. The method of claim 6, wherein the solvent is an organic solvent or water. 7. The method of claim 6, wherein the heat treatment in step b) is performed at a temperature of 400 to 700 占 폚 in an inert gas atmosphere selected from the group consisting of argon (Ar), helium (He), nitrogen (N) To about 6 hours. ≪ RTI ID = 0.0 > 8. < / RTI > [7] The method of claim 6, wherein the heat treatment in step c) is performed at a temperature of 150 to 300 [deg.] C for 1 to 3 hours under an air atmosphere.

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