WO2019066275A2 - Positive electrode active material for lithium secondary battery, and method for producing positive electrode active material - Google Patents

Abstract

Provided is positive electrode active material for a lithium secondary battery, the positive electrode active material comprising vanadium oxide doped with zirconium (Zr) ions.The vanadium oxide is doped with 0.1-10 mol% zirconium ions with respect to the former. By applying the positive electrode active material for a lithium secondary battery to same, elution of vanadium from the positive electrode is controlled, and consequently, the lifespan of the battery is extended.

Description

Cathode active material for lithium secondary battery and manufacturing method thereof

This application claims the benefit of priority based on Korean Patent Application No. 10-2017-0124807, filed on September 27, 2017, which is incorporated herein by reference in its entirety.

The present invention relates to a cathode active material for a lithium secondary battery and a method of manufacturing the same. More specifically, the present invention relates to a cathode active material for a lithium secondary battery including a zirconium (Zr) ion-doped vanadium oxide and a method for manufacturing the same.

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

Lithium secondary battery technology has been applied to various fields at present through remarkable development. However, in view of capacity, safety, output, enlargement and miniaturization of batteries, various batteries capable of overcoming the limitations of current lithium secondary batteries have been studied . Metal-air batteries, which have a theoretical capacity in terms of capacity in comparison with current lithium secondary batteries, all solid batteries that do not have explosion risk in terms of safety, lithium secondary batteries in terms of output, (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 cathode active material and a carbon material as a negative electrode active material, and a polyolefin-based porous separator is sandwiched between a cathode and an anode, and a non-aqueous electrolytic solution having a lithium salt such as LiPF ₆ Impregnated. However, LiCoO _{2, which} is used as a cathode active material in most commercial lithium secondary batteries, has a high operating voltage and a large capacity. However, due to the limit of the amount of resources, LiCoO ₂ is relatively expensive and has a charge / discharge current of about 150 mAh / g And the crystal structure is unstable at a voltage of 4.3 V or more, causing a reaction with the electrolytic solution, and there is a risk of ignition. Moreover, LiCoO ₂ has a disadvantage in that it exhibits a very large change in physical properties even when some parameters are changed on the manufacturing process.

One of the alternatives to this 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 have excellent crystallinity. Therefore, in order to crystallize the two materials, it is necessary to carry out the heat treatment process during the manufacture of the thin film or the post-process. Therefore, the fabrication of a battery using these two materials on a polymer (e.g., plastic) material for medical or special purposes is impossible up to now because the polymer material can not withstand the heat treatment temperature.

In order to solve the disadvantages of the two materials, vanadium oxide is 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. The amorphous vanadium oxide synthesized at room temperature is superior to the crystalline vanadium oxide in its performance (for example, life or efficiency). 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. 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 has a problem that the charge / discharge capacity (C-rate capability), output characteristics, and water surface performance of the battery are insufficient by the lithium ion de-intercalation process. Thus, there is a need in the art for improved vanadium oxide as a cathode active material.

[Prior Art Literature]

[Patent Literature]

(Patent Document 1) Korean Patent Application No. 2011-0066585

In order to solve the problems of the conventional cathode active material containing vanadium oxide, the present invention relates to a lithium secondary battery which can improve the life characteristics of a battery by suppressing elution of vanadium by doping zirconium ions into vanadium oxide, which is a component of the cathode active material, A cathode active material for a secondary battery, and a method of manufacturing the same.

According to a first aspect of the present invention,

The present invention provides a cathode active material for a lithium secondary battery including a zirconium ion-doped vanadium oxide.

In one embodiment of the present invention, the vanadium oxide is 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.

In one embodiment of the present invention, the zirconium ion is doped with 0.1 mol% or more and less than 10 mol% based on the vanadium oxide.

According to a second aspect of the present invention,

The present invention relates to a process for preparing a mixture comprising dissolving an organic acid, a vanadium oxide precursor and a zirconium ion precursor in a solvent and then mixing to produce a mixture; Drying the resulting mixture; And heat treating the dried mixture. The present invention also provides a method for producing the above-described cathode active material for a lithium secondary battery.

According to a third aspect of the present invention,

The present invention relates to a positive electrode active material layer comprising the above-mentioned positive electrode active material, a conductive material and a binder; And a positive electrode collector, wherein the positive electrode active material layer provides a positive electrode for a lithium secondary battery formed on a positive electrode collector.

According to a fourth aspect of the present invention,

The present invention provides a lithium secondary battery comprising the above-described positive electrode.

The use of vanadium oxide doped with zirconium ions according to the present invention as a positive electrode active material of a lithium secondary battery suppresses the elution of vanadium that may occur during charging and discharging of the lithium secondary battery and consequently improves the life characteristics of the lithium secondary battery can do.

1 is a graph showing a specific capacity of a lithium secondary battery manufactured according to Examples 1 and 2 and Comparative Example 1 according to a cycle.

FIG. 2 is a graph showing the results of XRD analysis of the cathode active material prepared according to Examples 1 and 2 and Comparative Example 1. FIG.

FIG. 3 is a graph showing the elution amount of vanadium relative to initial vanadium after the charge and discharge cycles of the lithium secondary battery produced in Example 1 and Comparative Example 1 were carried out 50 times.

The embodiments provided in accordance with the present invention can be all achieved by the following description. It is to be understood that the following description is of a preferred embodiment of the present invention and that the present invention is not necessarily limited thereto.

In the following description, for the numerical range, the expressions " to " are used to mean both of the upper and lower limits of the range. When the upper and lower limits are not included, Quot; over, " " below, " or " abnormal "

Cathode active material and manufacturing method thereof

The present invention provides a cathode active material for a lithium secondary battery including a zirconium (Zr) ion-doped vanadium oxide.

As described above, since vanadium oxide (Vanadium Oxide) can have a high specific capacity in theory, it can be suitable as a material for a cathode active material in a lithium secondary battery. However, when the vanadium oxide is used as a cathode active material of a lithium secondary battery, the electric conductivity and the ion diffusion coefficient are substantially low, vanadium is eluted into the electrolyte, and the electrode structure may collapse . In order to solve such a problem, in the present invention, zirconium ions are doped into vanadium oxide which is a cathode active material.

The vanadium oxide according to the present invention is 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.

The degree of oxidation of vanadium varies depending on the values of a and b in the above formula (1). In fact, when the vanadium oxide has an oxidation number of 2, 3, 4 and 5, and when the oxidation number of vanadium is 2 and 3, the vanadium oxide has a basicity. When the oxidation number of vanadium is 4 and 5, It has both sexes. Among them, VO ₂ having an oxidation number of 4 of vanadium and V ₂ O ₅ having an oxidation number of vanadium of ₅ are stable. According to one embodiment of the present invention, the vanadium oxide may be VO ₂ , V ₂ O ₃ , V ₂ O _5, or a combination thereof, and preferably vanadium pentoxide (V ₂ O ₅ ). The vanadium pentoxide (V ₂ O ₅ ) has good ion exchange ability with respect to lithium ions and has a high potential of about 4 V with respect to lithium metal, and is utilized as a cathode material of a lithium secondary battery. In addition, it is used as an electrode material suitable for a solid electrolyte and a polymer electrolyte lithium secondary battery. In particular, V ₂ O ₅ of the mesoporous structure has a high surface area due to porosity, thereby improving the diffusion speed of lithium ions, the electric storage capacity, and the electric conductivity.

In the present invention, in order to improve the problem of the cathode active material containing vanadium oxide, zirconium ions are doped into vanadium oxide, but the structure formed by vanadium oxide in the cathode active material is not modified by doping with zirconium ions. Zirconium ions are present in the structure to impart stability to the structure, thereby inhibiting the elution of vanadium. According to one embodiment of the present invention, the zirconium ion is doped in an amount of 0.1 mol% to less than 10 mol%, preferably 3 mol% to 7 mol%, based on the vanadium oxide. When the zirconium ion is doped to less than 0.1 mol%, the stability of the structure due to the zirconium ion is improved and the vanadium dissolution inhibiting effect is insignificant. When the zirconium ion is doped to 10 mol% or more, zirconium ions and vanadium oxide are combined to form ZrV ₂ O ₇ can be formed, and the capacity of the lithium secondary battery can be reduced by this crystal.

The cathode active material may be prepared by dissolving an organic acid, a vanadium oxide precursor, and a zirconium ion precursor in a solvent and then mixing to produce a mixture; Drying the resulting mixture; And heat-treating the dried mixture. The positive electrode active material for a lithium secondary battery according to claim 1,

The organic acid as a constituent of the mixture helps the vanadium oxide precursor form a vanadium oxide structure with a suitable oxidation number and suitably doping zirconium ions from the zirconium ion precursor within the structure. The organic acid may be selected from the group consisting of citric acid, oxalic acid, tannic acid, or a combination thereof, and is preferably selected from the group consisting of May be citric acid.

The vanadium oxide precursor as a constituent of the mixture is a substance before the conversion to vanadium oxide by reaction with an organic acid. The vanadium oxide precursor has a ratio of vanadium to oxygen in the vanadium oxide and a ratio of vanadium oxide to vanadium oxide in the cathode active material. . ≪ / RTI > The vanadium oxide precursor may be vanadium oxide, ammonium vanadium or a combination thereof. Preferably, the vanadium oxide precursor is at least one selected from the group consisting of NH ₄ VO ₃ .

The zirconium ion precursor as a constituent of the mixture is a substance which provides a zirconium ion in the vanadium oxide structure, and the kind of the zirconium ion precursor may affect the doping of the zirconium ion in the vanadium oxide structure. Although the zirconium ion precursor is not particularly limited as long as it is a material generally used in the related art, according to one embodiment of the present invention, the zirconium ion precursor is a zirconium salt hydrate, and preferably ZrOCl ₂ .8H ₂ O have.

The mixing ratio of the organic acid, the vanadium oxide precursor and the zirconium ion precursor in the mixture may be adjusted within a range in which the prepared cathode active material satisfies the above-described doping amount of the zirconium ion. According to one embodiment of the present invention, the mixture comprises 40 to 70 parts by weight, preferably 50 to 60 parts by weight of an organic acid, 30 to 60 parts by weight, preferably 10 to 60 parts by weight, based on 100 parts by weight of the total of the organic acid, vanadium oxide precursor and zirconium ion precursor, Preferably 40 to 50 parts by weight of a vanadium oxide precursor, and 1 to 5 parts by weight, preferably 2 to 4 parts by weight of a zirconium ion precursor.

The solvent during the preparation of the mixture is not particularly limited as long as it is a commonly used solvent in the related art, but a solvent that does not remain in the cathode active material that remains after drying and heat treatment may be preferable. According to one embodiment of the present invention, the solvent may be water. The resulting mixture is dried to remove all or part of the solvent. The drying method is not particularly limited, and a method generally used in the related art is used.

The dried mixture is heat treated to remove additional residual solvent and form a suitable vanadium oxide structure. In order to achieve the above object, the heat treatment is carried out at 350 to 650 ° C, preferably 450 to 550 ° C, for 1 to 10 hours, preferably 4 to 8 hours, under an air atmosphere.

Anode and manufacturing method thereof

The present invention provides a positive electrode for a lithium secondary battery comprising the positive electrode active material according to the above-mentioned contents. Specifically, the cathode for a lithium secondary battery includes a cathode active material layer and a cathode current collector, and the cathode active material layer is formed on the cathode current collector and includes a cathode active material, a conductive material, and a binder.

The binder contained in the positive electrode active material layer is a component that assists in bonding between the positive electrode active material and the conductive material and bonding to the current collector. Examples of the binder include polyvinylidene fluoride (PVdF), polyvinylidene fluoride-polyhexafluoro Propylene copolymer (PVdF / HFP), polyvinyl acetate, polyvinyl alcohol, polyvinyl ether, polyethylene, polyethylene oxide, alkylated polyethylene oxide, polypropylene, polymethyl (meth) acrylate, polyethyl Butadiene rubber, ethylene-propylene-diene monomer (EPDM) rubber, polyvinyl pyrrolidone, polyvinyl pyrrolidone, styrene-butadiene rubber, acrylonitrile- Sulfonated EPDM rubber, styrene-butylene rubber, fluororubber, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose At least one selected from the group consisting of celluloses, regenerated celluloses, and mixtures thereof, but is not limited thereto.

The binder is added in an amount of 1 to 30 parts by weight, preferably 5 to 20 parts by weight based on 100 parts by weight of the positive electrode active material layer. If the content of the binder is less than 1 part by weight, the adhesive force between the cathode active material and the current collector may be insufficient. If the amount of the binder is more than 30 parts by weight, the adhesive strength may be improved, but the content of the cathode active material may be decreased.

The conductive material contained in the positive electrode active material layer is not particularly limited as long as it does not cause side reactions in the internal environment of the lithium secondary battery and does not cause chemical changes in the battery but has excellent electrical conductivity. Typically, the conductive material includes graphite or conductive carbon For example, graphite such as natural graphite and artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, black black, thermal black, channel black, furnace black, lamp black, and summer black; A carbon-based material whose crystal structure is graphene or graphite; Conductive fibers such as carbon fiber and metal fiber; Carbon fluoride; Metal powders such as aluminum and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive oxides such as titanium oxide; And polyphenylene derivatives may be used singly or in combination of two or more, but the present invention is not limited thereto.

The conductive material is added in an amount of 1 to 30 parts by weight, preferably 5 to 20 parts by weight based on 100 parts by weight of the positive electrode active material layer. If the content of the conductive material is less than 1 part by weight, the effect of improving electrical conductivity may not be expected or the electrochemical characteristics of the battery may deteriorate. If the content of the conductive material exceeds 30 parts by weight, the amount of the cathode active material And the capacity and the energy density may be lowered.

The method of incorporating the conductive material into the cathode active material layer is not particularly limited, and conventional methods known in the art such as coating on the cathode active material can be used. In some cases, since the conductive second coating layer is added to the positive electrode active material, the addition of the conductive material as described above may be substituted.

In the positive electrode active material layer constituting the positive electrode of the present invention, a filler may be optionally added as a component for suppressing the expansion of the positive electrode. Such a filler is not particularly limited as long as it can inhibit the expansion of the electrode without causing chemical change in the battery, and examples thereof include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers; Etc. may be used.

The positive electrode active material layer including the positive electrode active material, the binder and the conductive material is prepared by dispersing and mixing the above materials in a dispersion medium (solvent) to prepare a slurry, applying it on the positive electrode current collector, drying and rolling, .

N-methyl-2-pyrrolidone (DMF), dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), ethanol, isopropanol, water and mixtures thereof may be used as the dispersion medium.

The positive electrode current collector may be formed of a metal such as platinum (Pt), gold (Au), palladium (Pd), iridium (Ir), silver (Ag), ruthenium (Ru), nickel (Ni), stainless steel (STS) ), Molybdenum (Mo), chromium (Cr), carbon (C), titanium (Ti), tungsten (W), ITO (In doped SnO ₂ ), FTO (F doped SnO ₂ ) , A surface of aluminum (Al) or a stainless steel surface treated with carbon (C), nickel (Ni), titanium (Ti) or silver (Ag) may be used. The shape of the anode current collector may be in the form of a foil, a film, a sheet, a punched, a porous body, a foam or the like.

The positive electrode for a lithium secondary battery includes the above-described positive electrode active material layer and a positive electrode collector.

Lithium secondary battery

The present invention provides a lithium secondary battery comprising a positive electrode according to the above-described contents.

Generally, a lithium secondary battery comprises a positive electrode composed of a positive electrode active material layer and a positive electrode collector, a negative electrode composed of a negative electrode active material layer and a negative electrode collector, and a separator intercepting electrical contact between the positive electrode and the negative electrode, And an electrolytic solution impregnated with them to conduct lithium ions.

The negative electrode may be manufactured according to a conventional method known in the art. For example, a negative electrode may be prepared by dispersing and mixing a negative electrode active material, a conductive material, a binder, and a filler as necessary in a dispersion medium (solvent) to prepare a slurry, coating the dispersion on an anode current collector, followed by drying and rolling .

As the negative electrode active material, lithium metal or a lithium alloy (for example, an alloy of lithium and a metal such as aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium or indium) may be used.

The negative electrode collector may be formed of at least one selected from the group consisting of Pt, Au, Pd, Ir, Ag, Ru, Ni, STS, ), Molybdenum (Mo), chromium (Cr), carbon (C), titanium (Ti), tungsten (W), ITO (In doped SnO ₂ ), FTO (F doped SnO ₂ ) (C), nickel (Ni), titanium (Ti), or silver (Ag) on the surface of copper, copper or stainless steel may be used. The anode current collector may be in the form of a foil, a film, a sheet, a punched, a porous body, a foam or the like.

The separation membrane is interposed between the positive electrode and the negative electrode to prevent a short circuit therebetween and to provide a movement path of lithium ions.

As the separation membrane, an olefin-based polymer such as polyethylene or polypropylene, glass fiber or the like may be used in the form of a sheet, a multilayer, a microporous film, a woven fabric and a nonwoven fabric, but is not limited thereto. On the other hand, when a solid electrolyte such as a polymer (for example, an organic solid electrolyte, an inorganic solid electrolyte or the like) is used as the electrolyte, the solid electrolyte may also serve as a separation membrane. Specifically, an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally from 0.01 to 10 mu m, and the thickness generally ranges from 5 to 300 mu m.

As the electrolyte solution, carbonate, ester, ether, or ketone may be used alone or as a mixture of two or more of them as a non-aqueous liquid electrolyte (non-aqueous organic solvent), but the present invention is not limited thereto.

Examples of the solvent include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, Ethyl acetate, n-propyl acetate, phosphoric acid triester, dibutyl ether, dimethyl ether, N-methyl-2-pyrrolidinone, 1,2-dimethoxyethane, tetrahydroxyfurfurane (Franc) Tetrahydrofuran derivatives such as tetrahydrofuran and tetrahydrofuran, dimethyl sulfoxide, formamide, dimethylformamide, dioxolane and derivatives thereof, acetonitrile, nitromethane, methyl formate, methyl acetate, trimethoxymethane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, methyl propionate, ethyl propionate and the like can be used. This is not limited.

(Lithium salt-containing non-aqueous electrolyte solution), and the lithium salt may be a known one which is soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO _{4 , LiBF 4, LiB 10 Cl 10} , LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiPF 3 (CF 2 CF 3) 3, LiAlCl 4, CH 3 SO 3 Li, CF 3 SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, LiFSI, chloroborane lithium, lower aliphatic carboxylate lithium, lithium tetraphenylborate, imide, and the like.

The above (non-aqueous) electrolytic solution may contain, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, Amide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxyethanol, . In some cases, a halogen-containing solvent such as carbon tetrachloride, ethylene trifluoride or the like may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve high-temperature storage characteristics.

The lithium secondary battery of the present invention can be produced by a conventional method in the art. For example, a porous separator may be placed between the anode and the cathode, and a non-aqueous electrolyte may be added.

The lithium secondary battery according to the present invention not only exhibits improved capacity characteristics (rapid capacity decrease prevention) under high-speed charge / discharge cycle conditions, but also excellent cycle characteristics, rate characteristics and life characteristics, The present invention can be suitably used as a unit cell of a battery module which is a power source of a medium and large-sized device.

In this respect, the present invention also provides a battery module in which two or more lithium secondary batteries are electrically connected (in series or in parallel). It is needless to say that the number of lithium secondary batteries included in the battery module may be variously controlled in consideration of the use and capacity of the battery module.

Further, the present invention provides a battery pack in which the battery module is electrically connected according to a conventional technique.

The battery module and the battery pack may include a power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV); Electric truck; Electric commercial vehicle; Or a power storage system, but is not limited thereto.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the present invention is not limited thereto.

Example

Example  One

1. Preparation of cathode active material

Citric acid (Sigma Aldrich Co.), vanadium oxide precursor (NH ₄ VO _3, vena hwageum Co., Ltd.) and zirconium ion precursor to prepare a mixture by mixing and then dissolving (ZrOCl ₂ · 8H ₂ O, Sigma-Aldrich Co.) in distilled water Respectively. The mixture was dried and then heat-treated at 500 ° C for 6 hours in an air atmosphere to prepare a cathode active material. Here, the mixing weight ratio of the citric acid: vanadium oxide precursor: zirconium ion precursor was 54: 43: 3 (cathode active material containing 5 mol% of Zr ion relative to vanadium oxide).

2. Preparation of anode for lithium secondary battery

The cathode active material prepared by the above method was mixed with a conductive material and a binder and dispersed in N-methyl pyrrolidone (NMP) to prepare a slurry. The slurry was applied to an aluminum current collector and dried to prepare a positive electrode. Here, Super-C was used as the conductive material, and polyvinylidene fluoride (PVDF) was used as the binder. The mixing ratio by weight of the cathode active material: conductive material: binder was 8: 1: 1.

3. Preparation of lithium secondary battery

After the prepared positive electrode was positioned to face the negative electrode, a separator was interposed between the positive electrode and the negative electrode. Thereafter, an electrolytic solution was injected into the case to prepare a coin cell. Here, lithium metal was used as the negative electrode, a polyethylene separator was used as the separator, and an electrolytic solution in which LiFSI of 4M concentration was dissolved in an organic solvent of dimethyl ether (DME) was used.

Example  2

A lithium secondary battery was finally prepared in the same manner as in Example 1 except that the mixing weight ratio of citric acid: vanadium oxide precursor: zirconium ion precursor in the production step of the cathode active material was 53: 43: 4 (10 mol % ≪ / RTI > Zr ion).

Comparative Example  One

A lithium secondary battery was finally prepared in the same manner as in Example 1, except that zirconium ion precursor and citric acid and vanadium oxide precursor were mixed in a weight ratio of 56:44 in the production step of the cathode active material.

Experimental Example  1: Analysis of battery life characteristics

In order to analyze the lifespan characteristics of the battery, the coin cell (4.0 to 2.1 V) manufactured in Examples 1 and 2 and Comparative Example 1 was repeatedly charged / discharged under the conditions of 0.2 C / discharge 0.5 C, Specific Capacity was measured. The results are shown in Fig. 1, it can be seen that the coin cells of Examples 1 and 2 are significantly reduced in the amount of non-capacity reduction in the course of the cycle as compared with the coin cell of Comparative Example 1. [

Experimental Example  2: XRD  analysis

The cathode active materials prepared in Examples 1 and 2 and Comparative Example 1 were subjected to XRD analysis, and the results are shown in FIG. 2, it can be confirmed that a ZrV ₂ O ₇ crystal peak appears in the graph of Example 2. Since the ZrV ₂ O ₇ crystal can reduce the capacity of the electrode, the initial specific capacity value of the coin cell of Example 2 was low as shown in Fig.

Experimental Example  3: Analysis of vanadium leaching

After 50 cycles, the elution amount of vanadium in the coin cells of Example 1 and Comparative Example 1 was measured and shown in Fig. The elution amount was measured by dissolving the cell after 50 cycles of charging and discharging, measuring the remaining amount of vanadium by ICP analysis of the separator and the lithium anode, and calculating the amount of remaining vanadium in the separator and the lithium cathode compared to the cathode active material. 3, when the vanadium oxide was doped with zirconium ions as in Example 1, it was confirmed that the amount of vanadium elution was reduced to a significant level.

It is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims (14)

1. A cathode active material for a lithium secondary battery comprising a vanadium oxide doped with zirconium (Zr) ions.
2. The method according to claim 1,

   Wherein the vanadium oxide is 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.
3. The method of claim 2,

   Wherein the vanadium oxide is vanadium pentoxide (V ₂ O ₅ ).
4. The method according to claim 1,

   Wherein the zirconium ion is doped in an amount of 0.1 mol% or more and less than 10 mol% based on the vanadium oxide.
5. The method of claim 4,

   Wherein the zirconium ion is doped in an amount of 3 mol% to 7 mol% based on the vanadium oxide.
6. A method for producing a positive electrode active material for a lithium secondary battery according to claim 1,

   In the above manufacturing method,

   (1) dissolving an organic acid, a vanadium oxide precursor and a zirconium ion precursor in a solvent, and then mixing to produce a mixture;

   (2) drying the resulting mixture; And

   (3) heat-treating the dried mixture.
7. The method of claim 6,

   Wherein the organic acid in step (1) is citric acid, oxalic acid, tannic acid, or a combination thereof.
8. The method of claim 6,

   Wherein the vanadium oxide precursor in step (1) is vanadium oxide, ammonium vanadium, or a combination thereof.
9. The method of claim 6,

   Wherein the zirconium ion precursor is a zirconium salt hydrate in the step (1).
10. The method of claim 6,

    The mixture in the step (1)

    Based on 100 parts by weight of the organic acid, the vanadium oxide precursor and the zirconium ion precursor in total,

    40 to 70 parts by weight of an organic acid;

    30 to 60 parts by weight of a vanadium oxide precursor; And

    And 1 to 5 parts by weight of a precursor of zirconium ion.
11. The method of claim 6,

    Wherein the step (3) comprises heat-treating the dried mixture at 350 to 650 ° C for 1 to 10 hours in an air atmosphere.
12. A cathode active material layer comprising a cathode active material, a conductive material and a binder according to claim 1; And a positive electrode collector,

    Wherein the positive electrode active material layer is formed on the positive electrode collector.
13. The method of claim 12,

    The positive electrode active material layer

    Based on the total 100 parts by weight of the positive electrode active material layer,

    50 to 90 parts by weight of a cathode active material;

    1 to 30 parts by weight of a conductive material; And

    1. A positive electrode for a lithium secondary battery, comprising: 1 to 30 parts by weight of a binder.
14. A lithium secondary battery comprising a positive electrode according to claim 12.

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