KR102078314B1 - Method for preparing positive electrode active material of secondary battery and positive electrode active material of secondary battery prepared by using the same - Google Patents

Abstract

In the present invention, the step of preparing a composition for forming a coating layer by dissolving selenium oxide in an alcohol solvent, and after mixing the composition for forming a coating layer with the core particles containing a lithium composite metal oxide, 1 at 180 ℃ to 250 ℃ Secondary heat treatment, and a method of manufacturing a positive electrode active material for a secondary battery comprising the step of secondary heat treatment at a temperature higher than the temperature of the first heat treatment within the temperature range of 250 ℃ to 350 ℃, and thus prepared to interface with the electrolyte Provided is a cathode active material for a secondary battery capable of suppressing a reaction and exhibiting excellent life and output characteristics by improving stability of a surface structure.

Description

Method of manufacturing positive electrode active material for secondary battery and positive electrode active material for secondary battery manufactured according to the present invention TECHNICAL FIELD

The present invention relates to a method for producing a cathode active material for a secondary battery that can suppress the interfacial reaction with the electrolyte and improve the stability of the surface structure and exhibit excellent life and output characteristics, and a cathode active material for a secondary battery manufactured accordingly.

Recently, market demand for IT electronic devices such as smartphones, tablet PCs, and high-performance notebook PCs is increasing. In addition, as a measure for global warming and resource depletion, the demand for large-capacity power storage devices such as electric vehicles and smart grids is greatly increased, and the demand for secondary batteries is rapidly increasing.

Among these, the lithium secondary battery is the most attracting secondary battery due to its excellent cycle life characteristics and high energy density. However, as the demand for high output, high capacity, and high stability increases, there is an urgent need for improvement measures for a lithium secondary battery that satisfies this.

Among the methods for implementing a high capacity and high output lithium secondary battery, increasing the operating voltage of the lithium secondary battery is the most efficient and easy method. However, there is a problem that the increase of the operating voltage causes the thermal stability of the battery and degradation of life characteristics. This problem is due to the interfacial reaction between the electrolyte and the positive electrode, and this phenomenon is more serious in a high capacity battery. Therefore, in order to develop high capacity and high output lithium secondary batteries, it is essential to develop individual materials such as a cathode, an anode, a separator, and an electrolyte, and to secure an interfacial reaction control and stabilization technology between the electrolyte and the electrode.

The technology related to the surface modification of the anode has been mainly focused on the research on the modification of the cathode active material by inorganic oxide.

As a related technology, a method for introducing a nanoparticle such as SiO ₂ , Al ₂ O ₃ , ZrO ₂ , or AlPO ₄ into the surface of the cathode active material to control the surface reaction with the electrolyte and to improve performance under high voltage conditions is proposed. It became. However, since the surface modification of the positive electrode active material using the inorganic oxide coating layer has a form in which the coating layer is finely dispersed in the form of nano-sized particles rather than covering the entire surface of the positive electrode active material, the positive electrode active material surface modification effect by the inorganic oxide coating Was bound to be limited. In addition, in terms of battery performance, the inorganic oxide coating layer is a kind of ion insulating layer which is difficult to move lithium ions, which may cause a decrease in ionic conductivity, and in the manufacturing process such as surface reaction at a high temperature of several hundred degrees or more. There is also a difficulty.

As a technique for solving the problem of the inorganic oxide coating, by introducing a polymer electrolyte such as imide or acrylate to the surface of the positive electrode active material to control the surface reaction with the electrolyte, as a result of improved battery performance under high voltage conditions One technique has been proposed. As described above, the cathode active material surface coating technology using only the chemically crosslinked polymer electrolyte can overcome the disadvantages of the inorganic oxide coating and form a continuous coating layer, and is easy to move ions due to the characteristics of the polymer electrolyte. However, since the chemically crosslinked polymer electrolyte layer is an inactive layer in electron transfer, it is not easy to use electrons, and as a result, there is a limit of reduction of reversible capacity and high output performance.

As a technique for compensating for the disadvantages of the coating using only the chemical crosslinked polymer, a cathode active material surface coating technique using polyimide / carbon black has been proposed. The method improves electron transfer by introducing carbon black in the coating layer, but there is a problem in that the electron conductivity of the polyimide layer is low due to non-uniform dispersion of carbon black in the polyimide layer.

Korea Patent Registration No. 277796 (Registration Date: 2000.10.13) Korean Patent Registration No. 560534 (Registration Date: 2006.03.07)

The first technical problem to be solved by the present invention is a method of manufacturing a cathode active material for a secondary battery that can suppress the interfacial reaction with the electrolyte solution and improve the stability of the surface structure and exhibit excellent life characteristics and output characteristics, and the secondary battery manufactured accordingly It is to provide a cathode active material for batteries.

The second technical problem to be solved of the present invention is to provide a lithium secondary battery, a battery module and a battery pack that can implement the characteristics of high life and high output, including the positive electrode active material.

In order to solve the above problems, according to an embodiment of the present invention, the step of preparing a composition for forming a coating layer by dissolving selenium oxide in an alcohol solvent, and the core particle comprising the lithium composite metal oxide composition for forming the coating layer After mixing with, the first heat treatment at 180 ℃ to 250 ℃, the second heat treatment to a temperature higher than the temperature of the first heat treatment within the temperature range of 250 ℃ to 350 ℃, the positive electrode active material for secondary batteries It provides a method of manufacturing.

In addition, according to another embodiment of the present invention, it comprises a core particle comprising a lithium composite metal oxide, and a coating layer located on the surface of the core particle, the coating layer comprises 400 ppm to 1,000 ppm of selenium It provides a cathode active material for phosphorus secondary batteries.

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

Furthermore, according to another embodiment of the present invention, a lithium secondary battery, a battery module, and a battery pack including the positive electrode are provided.

The positive electrode active material prepared by the manufacturing method according to the present invention controls the interfacial reaction with the electrolyte solution on the surface of the core particles containing lithium composite metal oxide capable of doping and undoping lithium, and improves the structural stability of the surface of the core particles. By including a coating layer that can be improved, it is possible to greatly improve the life characteristics and output characteristics during battery application.

In addition, the manufacturing method according to the present invention, by performing a wet coating method and two-step heat treatment during selenium coating to suppress the selenium from falling off during the coating layer formation process to increase the selenium content in the coating layer.

1 is a result of an electron probe micro analyzer (EPMA) analysis of a cathode active material precursor prepared in Example 1-1 of the present invention.
2 is a graph showing capacity retention rates according to cycles of the lithium secondary battery prepared in Example 2-1 and Comparative Example 2-1 of the present invention.
Figure 3 is a graph showing the resistance increase rate according to the cycle of the lithium secondary battery prepared in Example 2-1 and Comparative Example 2-1 of the present invention.

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

The terms or words used in this specification and claims are not to be construed as being limited to the common or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best describe their invention. It should be interpreted as meanings and concepts corresponding to the technical idea of the present invention based on the principle that the present invention.

In general, the positive electrode active material has a problem in that degeneration due to gas generation and instability of the surface structure occurs through reaction with the electrolyte as charging and discharging are repeated. In order to reduce the degradation rate of the positive electrode active material, a method of coating the surface of the positive electrode active material is mainly used. Among them, the formation of the coating layer using the boron-based compound is the most representative. In addition, among the boronic compounds, boronic acid has a low melting point and is frequently used because it is possible to form a uniform coating layer on the surface of an active material even by heat treatment at a relatively low temperature of about 300 ° C.

In the present invention, a coating layer was formed on the surface of the lithium composite metal oxide using selenium oxide, which has a low melting point, such as boronic acid, which enables uniform coating on the surface, but also exhibits superior output and life characteristics.

On the other hand, when the selenium coating layer was formed by using a dry coating method, the amount of selenium remaining in the coating layer was much lower than that of the input selenium due to the high loss of selenium during the process, and the amount of selenium remaining in the coating layer could be predicted. none. In addition, when using a dry process, there was a problem that the coating layer is not uniformly formed due to the loss of selenium.

Accordingly, in the present invention, the selenium coating layer may be formed on the surface of the lithium composite metal oxide with little loss of selenium using a wet process. In addition, by controlling the manufacturing conditions during the formation of the coating layer, a coating layer was formed to suppress the interfacial reaction with the electrolyte and to further improve the structural stability of the surface of the active material. As a result, the positive electrode active material produced by the manufacturing method of the present invention can greatly improve the life characteristics and output characteristics when the battery is applied.

Specifically, the manufacturing method of the positive electrode active material for a secondary battery according to an embodiment of the present invention,

Preparing a composition for forming a coating layer by dissolving selenium oxide in an alcohol solvent (step 1), and

After mixing the composition for forming the coating layer with the core particles containing a lithium composite metal oxide, the first heat treatment at 180 ℃ to 250 ℃, the temperature higher than the temperature at the first heat treatment within the temperature range of 250 ℃ to 350 ℃ Secondary heat treatment to temperature (step 2).

Hereinafter, each step will be described in detail.

Step 1 in the method of preparing the positive electrode active material is a step of preparing a composition for forming a coating layer by dissolving selenium oxide in an alcohol solvent.

In the preparation of the coating layer-forming composition, usable selenium oxides are specifically selenium dioxide (Selenium dioxide, SeO ₂ ) selenium trioxide (SeO ₃ ) and diselenium pentoxide (Se ₂ O ₅ ) At least one selected from the group consisting of may be used.

In addition, as the alcohol solvent, any one or a mixture of two or more alcohol compounds having 1 to 4 carbon atoms may be used, and preferably, acetone, methanol, ethanol, isopropyl alcohol, butyl alcohol, octyl alcohol, and allyl alcohol. At least one selected from the group consisting of. More preferably, the alcohol solvent may be ethanol in consideration of fairness in the active material manufacturing process and coating layer formation in the final active material.

In addition, the concentration of selenium oxide in the composition for forming a coating layer may be appropriately determined in consideration of processability and coating uniformity and core uniformity of the core particles during the active material manufacturing process.

In addition, step 2 in the method for producing a cathode active material is a step of forming a coating layer using the coating layer forming composition prepared in step 1.

Specifically, Step 2, after mixing the core particles containing the lithium composite metal oxide and the composition for forming the coating layer, the first heat treatment at 180 ℃ to 250 ℃, preferably 200 ℃ to 250 ℃, the first It may be carried out by secondary heat treatment at a temperature higher than the heat treatment temperature, preferably in the range of 250 ° C to 350 ° C, more preferably in the range of 300 ° C to 350 ° C.

The core particle includes a lithium composite metal oxide capable of reversible intercalation and deintercalation of lithium.

The lithium composite metal oxide may include nickel, cobalt, and metal elements M together with lithium, wherein M is at least one selected from the group consisting of Mn and Al.

In the lithium composite metal oxide, at least one of the metal elements except lithium is W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga And may be doped by at least one or more elements selected from the group consisting of Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. As described above, when the lithium composite metal oxide is further doped by the metal element, the structural stability of the cathode active material may be improved, and as a result, the output characteristics of the battery may be improved. In this case, the content of the doping element included in the lithium composite metal oxide may be appropriately adjusted within a range that does not lower the characteristics of the positive electrode active material, specifically, may be 0.02 atomic% or less.

In addition, when doped as described above, the lithium composite metal oxide doped with the doping element may be uniformly distributed in the core particles, or may have a concentration gradient that increases or decreases in content distribution from the center to the surface of the core particles. It may be present or may exist only on the surface side of the core particle. Among these, when the doping element is distributed in high concentration on the surface side of the core particles, and includes a concentration gradient in which the concentration decreases toward the particle center, it is possible to prevent a decrease in capacity while showing thermal stability.

In the present invention, the concentration gradient structure and concentration of the doping element in the core particles are determined by an electron beam microanalyzer (Electron Probe Micro Analyzer, EPMA), Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES). ) Or time-of-flight secondary ion mass spectrometry (ToF-SIMS), and specifically, X-ray photoelectron spectroscopy (XPS) for core particles. This can be performed by etching with argon gas for 0 to 1000 seconds and analyzing the element detection amount according to the etching time.

In addition, in the present invention, the 'surface side' of the lithium composite metal oxide particles means a region close to the surface excluding the center of the particles, specifically, the distance from the surface of the lithium composite metal oxide particles to the center, that is, the lithium composite An area corresponding to a distance of 0% or more and less than 100% from the particle surface, more specifically 0% to 50%, and more specifically 0% to 30% from the particle surface, with respect to the semi-diameter of the metal oxide. it means.

More specifically, the core particle may include a lithium composite metal oxide of Formula 1 below:

[Formula 1]

Li _α Ni _x Co _y M _z M ' _w O ₂

In Chemical Formula 1

M is at least one selected from the group consisting of Mn and Al,

M 'is W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B And at least one doping element selected from the group consisting of Mo,

α, x, y, z and w are the atomic fractions of the independent elements, respectively, 0.95 ≦ α ≦ 1.05, 0 <x <1, 0 <y <1, 0 <z <1, x + y + z = 1 , 0≤w≤0.02, more specifically 0.95≤α≤1.05, 0.6≤x <1, 0 <y≤0.4, 0 <z≤0.4, x + y + z = 1, 0≤w≤ 0.02. In this case, α is a value when uncharged, and the composition of Formula 1 is an average value.

More specifically, the core particles are LiNi _{0 . 6} Co _{0 . 2} Mn _{0 . 2} O ₂ , LiNi _{0 . 8} Mn _{0 . 1} Co _{0 . 1} O ₂ , LiNi _0.6 Co _0.2 Mn _0.2 W _0.02 O ₂ or LiNi _{0 . 85} Co _{0 . 09} Mn _{0 . 045} Al ₀ may be a lithium composite metal oxide and containing an amount of nickel, such as _0.015, there is at least one or more of these may be used.

In addition, at least one metal element of nickel, cobalt, and M included in the core particles may have a concentration gradient that gradually changes in the entire core particle.

In this way, by having a concentration gradient in which the concentration of the metal element gradually changes according to the position in the core particle, there is no abrupt phase boundary region from the center to the surface, so that the crystal structure is stabilized and the thermal stability is increased. In addition, by varying the concentration of each metal in the core particles through the concentration gradient, it is possible to easily utilize the characteristics of the metal to further improve the battery performance improvement effect of the positive electrode active material. In this case, the concentration gradient of the metal element may have a single gradient value in which the change in the concentration gradient is constant, or may have two or more gradient values due to changes in the concentration profile such as an inflection point and a slope change.

In the present invention, a metal "shows a gradually changing concentration gradient" means that the concentration of the metal is present in a concentration distribution that continuously changes in stages in the entire particle or in a specific region. Specifically, the concentration distribution is 0.1 atomic% to 30 atomic%, more specifically 0.1, based on the total atomic weight of the metal included in the active material particles in the change in the metal concentration per 1 μm toward the surface in the particles Atomic% to 20 atomic%, even more specifically may be a difference of 1 atomic% to 10 atomic%.

In addition, in the present invention, the concentration gradient or concentration profile of the metal element in the core particles can be measured by the same method as in the case of measuring the concentration gradient of the doping element.

More specifically, the concentration of nickel contained in the core particles may be gradually decreased while having a concentration gradient from the center of the core particles toward the surface of the particles. In this case, the gradient of the concentration gradient of nickel may be constant from the center of the core particle to the surface. As such, when the concentration of nickel maintains a high concentration at the particle center in the core particle and includes a concentration gradient that decreases toward the particle surface side, it may exhibit improved thermal stability while maintaining excellent capacity characteristics of the positive electrode active material.

In addition, the concentration of cobalt contained in the core particles may increase with a gradual concentration gradient from the center of the core particles toward the surface of the particles. At this time, the concentration gradient slope of the cobalt may be constant from the center of the core particles to the surface. As such, when the concentration of cobalt is kept low at the center of the particles in the core particles and has a concentration gradient that increases toward the surface side, the capacity characteristics of the cathode active material can be improved while reducing the amount of cobalt used.

In addition, the concentration of the metal element M contained in the core particles may increase while having a gradual concentration gradient from the center of the core particles toward the surface of the particles. At this time, the concentration gradient slope of M may be constant from the center of the core particles to the surface. As such, when the concentration of the metal element M, especially manganese, in the core of the particles is low at the center of the particle, and includes a concentration gradient that increases in concentration toward the particle surface side, thermal stability can be improved without decreasing the capacity of the positive electrode active material. have. More specifically, M may be Mn.

In addition, the region corresponding to 1% to 70% by volume of the total particle volume from the center of the particle is the first region; When the region corresponding to the outer surface of the first region is called the second region, the amount of nickel included in the first region may be greater than the amount of nickel included in the second region, and specifically, the first region. Silver contains nickel in a content of 60 mol% or more and less than 100 mol% based on the total moles of metal elements (excluding lithium) included in the first region, and the second region includes metal elements (excluding lithium) in the second region. Nickel may be included in an amount of 30 mol% or more and less than 60 mol% based on the total moles.

In addition, the content of manganese included in the first region may be less than the content of manganese included in the second region. In addition, in the cathode active material according to an embodiment of the present invention, the content of cobalt included in the first region may be less than the content of cobalt included in the second region.

More specifically, the nickel, cobalt, and metal elements M included in the core particles each independently represent a gradually changing concentration gradient throughout the core particles, and the concentration of nickel is gradually changed from the center of the core particles toward the surface. It decreases with a concentration gradient, and the concentrations of cobalt and M can each independently increase with a gradual concentration gradient from the center of the core particles towards the surface.

As such, the concentration of nickel decreases toward the surface side of the cathode active material particles throughout the core particles, and the cobalt and M concentrations include a combined concentration gradient, thereby maintaining excellent thermal stability while maintaining capacity characteristics. .

The core particle including the lithium composite metal oxide having the composition as described above may have an average particle diameter (D ₅₀ ) of 1 to 50 μm, more specifically, an average particle diameter (D ₅₀ ) of 5 to 30 μm. It may be.

In the present invention, the average particle diameter (D ₅₀ ) of the core particles may be defined as the particle size at 50% of the particle size distribution. The average particle diameter (D ₅₀ ) of the core particles may be measured using, for example, a laser diffraction method. More specifically, after dispersing the core particles in a dispersion medium, commercially available laser diffraction particle size measurement may be performed. Ultrasonic waves of about 28 kHz can be irradiated with an output of 60 W by introducing into an apparatus (for example, Microtrac MT 3000), and the average particle diameter (D ₅₀ ) based on 50% of the particle size distribution in the measuring apparatus can be calculated. .

On the other hand, in the method for producing a positive electrode active material according to an embodiment of the present invention, the mixing step of the composition for forming the coating layer and the core particles may be carried out according to a conventional mixing method, wherein the coating layer is formed on the surface of the core particles In consideration of efficiency, a mixing process using a stirring device such as a jet mill may be performed.

In addition, the composition of the coating layer forming composition and the core particles may be mixed in an amount such that the selenium content in the positive electrode active material to be finally prepared is 400 ppm to 1,000 ppm.

In addition, after mixing the core particles in the composition for forming the coating layer, a process for removing the solvent contained in the coating layer formed on the surface of the core particles used in the preparation of the coating layer forming composition may be optionally performed.

The solvent removal process may be performed by a conventional drying method such as natural drying, hot air drying or heat drying, or may be performed using a drying apparatus such as a rotary evaporator.

Subsequently, a heat treatment process is performed on the core particles having the coating layer formed on the surface by mixing with the composition for forming the coating layer.

In the method for producing a positive electrode active material according to an embodiment of the present invention, the heat treatment is a first heat treatment at 180 ℃ to 250 ℃, and a temperature higher than the temperature at the first heat treatment, preferably 250 ℃ to 350 ℃ It can be carried out in multiple stages including a secondary heat treatment within the temperature range.

Specifically, the primary heat treatment increases the adhesion to the core particles of the coating film for forming the coating layer formed on the surface of the core particles, and removes the alcohol-based solvent remaining in the coating film, and selenium oxide and lithium in a subsequent secondary heat treatment process. As a pretreatment step for promoting the reaction of the by-products, the above effects can be sufficiently obtained when performed in the above temperature range. For example, when the primary heat treatment is performed at a temperature of less than 180 ℃, it is not easy to remove the solvent remaining in the coating film, there is a fear that the selenium compound is not evenly distributed on the surface of the cathode material, the primary If the heat treatment is performed at a temperature exceeding 250 ° C., selenium oxide is vaporized, causing loss of Se, and thus there is a fear that less than the amount injected is coated. More specifically, the first heat treatment may be performed for 1 hour to 5 hours, more specifically for 3 hours to 5 hours at a temperature of 220 ℃ to 250 ℃.

In addition, the secondary heat treatment is performed to more effectively form the surface coating layer, and is performed to improve the reaction between the surface of the cathode material and the selenium compound and the reactivity of the residual lithium compound and the selenium compound. The temperature is higher than the temperature at the time of the first heat treatment, preferably in the temperature range of 250 ℃ to 350 ℃. When the secondary heat treatment temperature is carried out below 250 ℃, the surface of the positive electrode material and the reactivity with the residual lithium compound is lowered to exist in the form of selenium compound, there is a concern that it is dissolved in the electrolyte when the battery performance evaluation to degrade the battery performance In addition, when the secondary heat treatment temperature exceeds 350 ° C., since the boiling point of selenium oxide is 350 ° C., sublimation of the selenium oxide may occur. More specifically, the secondary heat treatment may be performed at a temperature of 300 ° C. to 350 ° C. for 5 hours to 20 hours, more specifically for 7 hours to 15 hours.

In addition, during the secondary heat treatment, a reaction between selenium oxide and lithium by-products such as LiOH and Li ₂ CO ₃ , which are inevitably left during the preparation of the core particles, may occur. When the lithium byproduct reacts with selenium oxide, lithium selenite may be formed. The lithium selenate increases the resistance in the coating layer when present in excess, but may improve the properties of the active material when present in the level of lithium by-products. For example, the content of the lithium selenate may be controlled by promoting or inhibiting the reaction of the lithium by-product and selenium oxide through controlling the content of the lithium by-product present on the surface of the core particle or controlling the processing conditions during the second heat treatment. .

In addition, the first and second heat treatment may be performed in an oxygen atmosphere, more specifically, may be performed in a condition that the oxygen content of the total heat treatment atmosphere is 20% by volume or more.

By the manufacturing method as described above, a cathode active material for a secondary battery in which a coating layer containing selenium is formed on a surface of core particles of a lithium composite metal oxide is manufactured. The positive electrode active material may further improve the structural stability of the surface of the active material at the same time by suppressing the interfacial reaction with the electrolyte due to the coating layer formed on the surface, as a result it can significantly improve the life characteristics and output characteristics when applying the battery.

In addition, the positive electrode active material prepared by the manufacturing method as described above suppresses selenium from falling off during the coating layer formation process, so that the amount of selenium added during the formation of the coating layer and the content of selenium contained in the final manufactured coating layer may be insignificant. have.

Accordingly, according to another embodiment of the present invention, a cathode active material for a secondary battery manufactured by the manufacturing method is provided.

Specifically, the positive electrode active material may include a core particle including a lithium composite metal oxide, and a coating layer located on the surface of the core particle, and the coating layer may include 400 ppm to 1,000 ppm of selenium. In this case, the core particles are the same as described above.

The coating layer may be formed in a continuous thin film form surrounding the entire core particle due to the characteristics of the selenium oxide forming the coating layer.

The cathode active material according to the embodiment of the present invention having the structure as described above may specifically have a BET specific surface area of 0.1 to 10 m ² / g and a tap density of 0.1 to 2 g / cm ³ . When satisfying the BET specific surface area and tap density in the above range at the same time, it shows an excellent charge density can further improve the capacity characteristics of the battery.

In the present invention, the specific surface area of the cathode active material is measured by Brunauer-Emmett-Teller (BET) method, specifically, nitrogen gas adsorption under liquid nitrogen temperature (77K) using Tristar II manufactured by Micrometritics. It can calculate from quantity.

In the present invention, the tap density of the positive electrode active material can be measured using a conventional tap density measuring device, and specifically, can be measured using a tap density tester.

Accordingly, according to another embodiment of the present invention provides a cathode and a lithium secondary battery including the cathode active material.

Specifically, the positive electrode is formed on the positive electrode current collector and the positive electrode current collector, and comprises a positive electrode active material layer containing the positive electrode active material.

The positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery. For example, carbon, nickel, titanium on the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface treated with silver, silver or the like can be used. In addition, the positive electrode current collector may have a thickness of typically 3 μm to 500 μm, and may form fine irregularities on the surface of the current collector to increase adhesion of the positive electrode active material. For example, it can be used in various forms, such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven body.

In addition, at least one surface of the current collector includes a positive electrode active material, and optionally a positive electrode active material layer further includes at least one of a conductive material and a binder.

At this time, the positive electrode active material may be included in an amount of 80 to 99% by weight, more specifically 85 to 98% by weight based on the total weight of the positive electrode active material layer. When included in the above content range may exhibit excellent capacity characteristics.

In addition, the conductive material is used to impart conductivity to the electrode. In the battery constituted, the conductive material can be used without particular limitation as long as it has electronic conductivity without causing chemical change. Specific examples thereof include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black and carbon fiber; Metal powder or metal fibers such as copper, nickel, aluminum, and silver; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Or conductive polymers such as polyphenylene derivatives, and the like, or a mixture of two or more kinds thereof may be used. The conductive material may be included in an amount of 1 wt% to 30 wt% with respect to the total weight of the cathode active material layer.

In addition, the binder serves to improve adhesion between the cathode active material particles and adhesion between the cathode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, and carboxymethyl cellulose (CMC). ), Starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubbers, or various copolymers thereof, and the like, and one or more of these may be used. The binder may be included in an amount of 1 wt% to 30 wt% with respect to the total weight of the positive electrode active material layer.

The positive electrode may be manufactured according to a conventional positive electrode manufacturing method except using the positive electrode active material described above. Specifically, the positive electrode active material and optionally, a composition for forming a positive electrode active material layer prepared by dissolving or dispersing at least one of a binder and a conductive material in a solvent is applied to at least one surface of the positive electrode current collector, and then dried and rolled. It can be prepared by. In this case, the type and content of the cathode active material, the binder, and the conductive material are as described above.

The solvent may be a solvent generally used in the art, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone or acetone. Single or a mixture of two or more selected from the group consisting of water may be used. The amount of the solvent is sufficient to dissolve or disperse the positive electrode active material, the conductive material and the binder in consideration of the coating thickness of the slurry, the production yield, and to have a viscosity that can exhibit excellent thickness uniformity during the application for the production of the positive electrode. Do.

Alternatively, the positive electrode may be prepared by casting the composition for forming the positive electrode active material layer on a separate support, and then laminating the film obtained by peeling from the support onto a positive electrode current collector.

According to another embodiment of the present invention, an electrochemical device including the anode is provided. The electrochemical device may be specifically a battery or a capacitor, and more specifically, a lithium secondary battery.

The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned to face the positive electrode, a separator and an electrolyte interposed between the positive electrode and the negative electrode, and the positive electrode is as described above. The lithium secondary battery may further include a battery container for accommodating the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member for sealing the battery container.

In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on at least one surface of the negative electrode current collector.

The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, the negative electrode current collector may be formed on the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or stainless steel. Surface-treated with carbon, nickel, titanium, silver, and the like, aluminum-cadmium alloy and the like can be used. In addition, the negative electrode current collector may have a thickness of 3 μm to 500 μm, and similarly to the positive electrode current collector, fine concavities and convexities may be formed on the surface of the current collector to enhance the bonding force of the negative electrode active material. For example, it can be used in various forms, such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven body.

The negative electrode active material layer includes a negative electrode active material, and optionally further includes at least one of a binder and a conductive material.

For example, the negative electrode active material layer is coated with a negative electrode active material, and optionally a composition for forming a negative electrode including a binder and a conductive material on a negative electrode current collector and dried, or casting the negative electrode forming composition on a separate support It can also be produced by laminating a film obtained by peeling from this support onto a negative electrode current collector.

As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; Metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys or Al alloys; Metal oxides capable of doping and undoping lithium such as SiO _v (0 <v <2), SnO ₂ , vanadium oxide, lithium vanadium oxide; Or a composite including the metallic compound and the carbonaceous material, such as a Si-C composite or a Sn-C composite, and any one or a mixture of two or more thereof may be used. In addition, a metal lithium thin film may be used as the anode active material. As the carbon material, both low crystalline carbon and high crystalline carbon can be used. Soft crystalline carbon and hard carbon are typical low crystalline carbon, and high crystalline carbon is amorphous, plate, scaly, spherical or fibrous natural graphite or artificial graphite, Kish graphite (Kish) graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch High-temperature calcined carbon such as derived cokes is typical.

In addition, the binder and the conductive material may be the same as described above in the positive electrode.

On the other hand, in the lithium secondary battery, the separator is to separate the negative electrode and the positive electrode and to provide a passage for the movement of lithium ions, if it is usually used as a separator in a lithium secondary battery can be used without particular limitation, in particular for ion transfer of the electrolyte It is desirable to have a low resistance against the electrolyte solution and excellent in electrolytic solution moisture content. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer and ethylene / methacrylate copolymer or the like Laminate structures of two or more layers may be used. In addition, a conventional porous nonwoven fabric, for example, a non-woven fabric made of high melting glass fibers, polyethylene terephthalate fibers, or the like may be used. In addition, a coated separator including a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may be optionally used as a single layer or a multilayer structure.

In addition, examples of the electrolyte used in the present invention include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, and the like, which can be used in manufacturing a lithium secondary battery. It doesn't happen.

Specifically, the electrolyte may include an organic solvent and a lithium salt.

The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may be an ester solvent such as methyl acetate, ethyl acetate, γ-butyrolactone or ε-caprolactone; Ether solvents such as dibutyl ether or tetrahydrofuran; Ketone solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate, Carbonate solvents such as PC); Alcohol solvents such as ethyl alcohol and isopropyl alcohol; Nitriles, such as Ra-CN (Ra is a C2-C20 linear, branched or ring-shaped hydrocarbon group, and may include a double bond aromatic ring or an ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Or sulfolanes may be used. Among these, a carbonate solvent is preferable, and a cyclic carbonate (for example, ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant which can improve the charge / discharge performance of a battery, and a low viscosity linear carbonate compound ( For example, a mixture of ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate and the like is more preferable. In this case, when the cyclic carbonate and the chain carbonate are mixed and used in a volume ratio of about 1: 1 to 1: 9, the performance of the electrolyte may be excellent.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (C ₂ F ₅ SO ₃ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ . LiCl, LiI, or LiB (C ₂ O ₄ ) ₂ and the like can be used. The concentration of the lithium salt is preferably used within the range of 0.1M to 2.0M. When the concentration of the lithium salt is included in the above range, since the electrolyte has an appropriate conductivity and viscosity, it can exhibit excellent electrolyte performance, and lithium ions can move effectively.

The electrolyte includes, in addition to the electrolyte components, haloalkylene carbonate-based compounds such as difluoroethylene carbonate and the like for the purpose of improving battery life characteristics, reducing battery capacity, and improving battery discharge capacity; Or pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N, N One or more additives such as -substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol or aluminum trichloride may be included. In this case, the additive may be included in an amount of 0.1% by weight to 5% by weight based on the total weight of the electrolyte.

As described above, since the lithium secondary battery including the cathode active material according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, portable devices such as mobile phones, laptop computers, digital cameras, and hybrid electric vehicles ( It is useful for electric vehicle fields such as hybrid electric vehicle (HEV).

Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

The battery module or the battery pack is a power tool (Power Tool); Electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); Or it can be used as a power source for any one or more of the system for power storage.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

[ Production Example  One]

In a batch 20 L reactor set at 60 ° C., nickel sulfate, cobalt sulfate and manganese sulfate were mixed in water in an amount such that the molar ratio of nickel: cobalt: manganese was 90: 5: 5 in water at a 2 M concentration. 5 L of the first metal-containing solution was prepared, and nickel sulfate, cobalt sulfate, and manganese sulfate were mixed in water in an amount such that the molar ratio of nickel: cobalt: manganese was 60:20:20, and the second solution at a concentration of 2M 20 L of a metal containing solution was prepared. The vessel containing the first metal containing solution was connected to enter the reactor, and the vessel containing the second metal containing solution was connected to enter the first metal containing solution container. In addition, 4M NaOH solution and 15% NH ₄ OH aqueous solution were prepared and connected to the reactor, respectively.

4 liters of deionized water was added to the coprecipitation reactor (capacity 20L), and nitrogen gas was purged at 4 L / min in the reactor to remove dissolved oxygen in water and to form a non-oxidizing atmosphere in the reactor. Thereafter, 10 mL of 4M NaOH and 200 mL of NH ₄ OH were added thereto, followed by stirring at a stirring speed of 500 rpm at 60 ° C. to maintain a pH of 12.0.

Thereafter, the first metal-containing solution was introduced into the reactor while maintaining the input amount at 5 mL / min. At the same time, the second metal-containing solution was added to the first metal-containing solution container at 5 mL / min and mixed uniformly and continuously. Over time, the first metal containing solution was introduced into the reactor, diluted by the second metal solution. At this time, the volume of the first metal solution was kept constant. Subsequently, while adding NH ₄ OH aqueous solution to the reactor at a rate of 1 mL / min, the initial pH of the reactor was changed as the reaction proceeds at 11.7, and the final pH was changed to 11.2, while the nickel cobalt manganese-based composite metal Induction of the growth of the hydroxide particles and at the same time induced a concentration gradient inside the particles. Since the reaction was maintained for 24 hours to grow nickel manganese cobalt-based composite metal hydroxide. The resulting nickel manganese cobalt-based composite metal-containing hydroxide particles were separated and washed with water and dried in an oven at 120 ℃ to prepare a precursor.

The precursor prepared above was dry mixed with lithium hydroxide (1.01 mol of lithium hydroxide per 1 mol of precursor) as a lithium raw material, and then heat-treated at 800 ° C. for 15 hours in an oxygen atmosphere to reduce the concentration gradient of the metal element in the active material particles. Particles of a lithium composite metal oxide were prepared.

[ Example  1-1: Of positive electrode active material  Produce]

7.1 mL of a 1 M solution prepared by dissolving selenium dioxide in ethanol and 1,000 g of the lithium composite metal oxide particles prepared in Preparation Example 1 were mixed. Then ethanol was slowly removed using a rotary evaporator. As a result, the lithium composite metal oxide particles having a coating layer formed on the surface of the particles were placed in a crucible, and gradually heated up at a rate of 2 ° C./min at room temperature (23 ± 5 ° C.), followed by primary heat treatment at 250 ° C. for 5 hours, followed by 350 ° C. The cathode active material was prepared by secondary heat treatment for 10 hours at.

[ Comparative example  1-1: Of positive electrode active material  Produce]

1,000 g of the lithium composite metal oxide particles prepared in Preparation Example 1 were mixed with 49.52 mL of a 1 M solution prepared by dissolving boronic acid in ethanol. Then ethanol was slowly removed using a Roatry evaporator. As a result, the lithium composite metal oxide particles having a coating layer formed on the surface of the particles were placed in a crucible, and gradually heated up at a rate of 2 ° C./min at room temperature, and heat-treated at 300 ° C. for 5 hours to prepare a cathode active material.

[ Comparative example  1-2: Of positive electrode active material  Produce]

A positive electrode active material was prepared by the same method as in Example 1-1, except that the heat treatment of the lithium composite metal oxide particles having the coating layer formed in Example 1-1 was performed once at 15 ° C. for 15 hours. It was.

[ Comparative example  1-3: Of positive electrode active material  Produce]

A positive electrode active material was carried out in the same manner as in Example 1-1 except that the second heat treatment was performed for 10 hours at 400 ° C. during the heat treatment of the lithium composite metal oxide particles having the coating layer formed in Example 1-1. Was prepared.

[ Comparative example  1-4: Of positive electrode active material  Produce]

For 100 parts by weight of the lithium composite metal oxide prepared in Preparation Example 1, 700 ppm of selenium dioxide was dry mixed and then heat-treated at 400 ° C. to prepare a cathode active material having a Se coating layer formed on the surface of the lithium composite metal oxide. .

[ Example  2-1: Fabrication of Lithium Secondary Battery]

The positive electrode active materials prepared in Example 1-1 were used, respectively, denca black as the conductive material, polyvinylidene fluoride (PVdF) as the binder was mixed at a weight ratio of 95: 2.5: 2.5, and N-methylpyrrolidone A composition for forming an anode was prepared using a (NMP) solvent. The prepared positive electrode forming composition was applied to an aluminum foil, roll-pressed and dried at 120 ° C. for 12 hours to prepare a positive electrode.

Also, natural graphite as a negative electrode active material, carbon black as a conductive material, and styrene-butadiene rubber (SBR) as a binder were mixed in a weight ratio of 96: 2: 2 to prepare a composition for forming a negative electrode. The prepared negative electrode composition was applied to a copper foil, and vacuum dried at 110 ° C. for 2 hours to prepare a negative electrode.

After interposing a polyethylene separator (Donensa, F20BHE, thickness = 20 μm) between the positive electrode and the negative electrode prepared above, an electrolyte (1M hexafluorophosphate (LiPF ₆ ), ethylene carbonate / dimethyl carbonate = 1: 1 part ratio) P) was injected to prepare a cell in the form of a coin cell.

[ Comparative example  2-1 to 2-4: Fabrication of Lithium Secondary Battery]

A lithium secondary battery was manufactured by the same method as in Example 2-1, except for using the cathode active materials prepared in Comparative Examples 1-1 to 1-4, respectively.

[ Experimental Example  One: Cathode active material  of mine Concentration gradient  analysis]

In order to confirm the structure of the positive electrode active material particles prepared in Example 1-1, the internal composition of the positive electrode active material particles was confirmed while moving in units of 0.5 μm using an electron probe micro analyzer (EPMA). Is shown in FIG.

As shown in FIG. 1, it was confirmed that the positive electrode active material particles prepared in Example 1 exhibited concentration gradients of nickel, cobalt, and manganese present in the particles from the center to the surface of the active material particles as the particles grew.

[ Experimental Example  2: Se content analysis in coating layer]

In order to determine the content of Se included in the coating layer of the positive electrode active material prepared in Example 1-1, Comparative Examples 1-2 to 1-4 using a high frequency inductively coupled plasma (ICP) method Analyzed. Specifically, 1 mL of hydrochloric acid is added to 0.1 g of the positive electrode active materials prepared in Examples 1-1 and Comparative Examples 1-2 to 1-4, respectively, and heated to 100 ° C. to dissolve, and when the sample is completely decomposed. Ultrapure water was added and diluted to 10 mL. The diluted solution was analyzed by ICP and the results are shown in Table 1 below.

Infused Se content (ppm) Se content in the coating layer (ppm) Example 1-1 500 489 Comparative Example 1-2 500 358 Comparative Example 1-3 500 315 Comparative Example 1-4 500 284

As shown in Table 1, the positive electrode active material prepared in Example 1-1 had a content of 489 ppm of element Se included in the coating layer. On the other hand, the content of the element Se contained in the coating layer of the positive electrode active material prepared in Comparative Example 1-2 and Comparative Example 1-3 is 358 ppm and 315 ppm, respectively, the content of Se remaining in the coating layer compared to Example 1-1 This deterioration was confirmed. In particular, the content of the element Se contained in the coating layer of the positive electrode active material prepared in Comparative Example 1-4 was 284 ppm. When the coating layer was formed on the surface of the positive electrode active material by using a dry process as described above, the loss of Se during the process was high, and the amount of Se remaining in the coating layer was about half of the amount of Se injected. Could not be formed.

[ Experimental Example  3: Battery Characteristic Evaluation of Lithium Secondary Battery]

Battery characteristics of the lithium secondary batteries prepared in Example 2-1 and Comparative Example 2-1 were evaluated in the following manner.

Specifically, the battery was charged at 45 ° C. with a constant current of 1C until 4.25V, and then charged at a constant voltage of 4.25V, and the charging was terminated when the charging current became 8mA. Thereafter, it was left for 20 minutes, and then discharged until reaching 2.5V at 1C constant current. With the charge and discharge behavior as one cycle, the cycle capacity retention and the resistance increase rate, which are the ratio of the discharge capacity at the 400th cycle to the initial capacity after the 400 cycles, were measured, respectively, and the following Tables 2 and 2, 3 is shown.

Example 2-1 Comparative Example 2-1 Capacity retention rate (%) 94.00 90.76 % Increase in resistance 20.11 31.42

In the lithium secondary battery prepared in Example 2-1, the resistance increase rate was significantly decreased at high temperature and exhibited excellent life characteristics compared to the lithium secondary battery including the cathode active material having the boron-containing coating layer prepared in Comparative Example 2-1. .

[ Experimental Example  4: Evaluation of Output Characteristics of Lithium Secondary Battery]

The output characteristics of the lithium secondary battery prepared in Example 2-1 and Comparative Example 2-1 were evaluated at SOC 50%.

Specifically, the battery charged and discharged at room temperature (25 ℃) was measured by applying a pulse for 10 seconds at a current of 150 mAh based on SOC 50%, the results are shown in Table 3 below. The 0 to 0.1 second section represents the resistance on the surface of the lithium secondary battery, and the 0.1 to 10 second section represents the internal resistance of the lithium secondary battery.

Output at SOC 50% at room temperature (25 ℃) 0 to 0.1 s (V) 0.1 ~ 10s (V) 0 ~ 10s (V) Voltage drop rate (%) Example 2-1 0.147 0.086 0.233 100 Comparative Example 2-1 0.159 0.087 0.246 105.6

As shown in Table 3, it was confirmed that the lithium secondary battery prepared in Example 2-1 shows a reduced voltage drop rate compared to the lithium secondary battery prepared in Comparative Example 2-1.

Claims (12)

Dissolving selenium oxide in an alcohol solvent to prepare a composition for forming a coating layer; And
After mixing the composition for forming the coating layer with the core particles containing the lithium composite metal oxide, the first heat treatment at 180 ℃ to 250 ℃, the temperature of the first heat treatment within the temperature range of 250 ℃ to 350 ℃ A second heat treatment at a high temperature,
Mixing of the coating layer-forming composition and the core particles is a method for producing a cathode active material for a secondary battery is mixed in an amount such that the content of selenium in the final active material is 400 ppm to 1,000 ppm.
The method of claim 1,
The alcohol solvent is a method for producing a cathode active material for a secondary battery containing at least one alcohol compound having 1 to 4 carbon atoms.
The method of claim 1,
The lithium composite metal oxide, together with lithium, includes nickel, cobalt and metal elements M (wherein M is at least one selected from the group consisting of Mn and Al),
At least one element of the nickel, cobalt, and metal element M is present in a concentration gradient that gradually changes from the center of the core particle to the surface.
The method of claim 3,
The nickel decreases with a concentration gradient from the center of the core particles to the surface direction,
The cobalt and the metal element M are each independently increased while having a concentration gradient from the center of the core particles to the surface direction of the secondary battery positive electrode active material manufacturing method.
The method of claim 1,
The lithium composite metal oxide is a method of producing a cathode active material for a secondary battery that is a compound represented by the following formula (1):
[Formula 1]
Li _α Ni _x Co _y M _z M ' _w O ₂
In Chemical Formula 1
M is at least one selected from the group consisting of Mn and Al,
M 'is W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B And at least one doping element selected from the group consisting of Mo,
α, x, y, z and w are 0.95 ≦ α ≦ 1.05, 0.6 ≦ x <1, 0 <y ≦ 0.4, 0 <z ≦ 0.4, x + y + z = 1 and 0 ≦ w ≦ 0.02.
delete The method of claim 1,
The method of manufacturing a cathode active material for a secondary battery further comprising the step of removing the alcohol-based solvent in the coating layer-forming composition after mixing the coating layer-forming composition and the core particles.
A core particle including a lithium composite metal oxide, and a coating layer on the surface of the core particle,
The coating layer is a positive electrode active material for secondary batteries containing selenium 400 ppm to 1,000 ppm.
The method of claim 8,
The lithium composite metal oxide, together with lithium, includes nickel, cobalt and metal elements M (wherein M is at least one selected from the group consisting of Mn and Al),
At least one element of the nickel, cobalt and metal element M is present in a concentration gradient that gradually changes from the center of the core particles to the surface of the positive electrode active material for a secondary battery.
The method of claim 8,
Wherein the lithium composite metal oxide is a compound represented by the formula (1), the positive electrode active material for secondary batteries.
[Formula 1]
Li _α Ni _x Co _y M _z M ' _w O ₂
In Chemical Formula 1
M is at least one selected from the group consisting of Mn and Al,
M 'is W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B And at least one doping element selected from the group consisting of Mo,
α, x, y, z and w are 0.95 ≦ α ≦ 1.05, 0.6 ≦ x <1, 0 <y ≦ 0.4, 0 <z ≦ 0.4, x + y + z = 1 and 0 ≦ w ≦ 0.02.
A positive electrode comprising the positive electrode active material according to any one of claims 8 to 10.
A lithium secondary battery comprising the positive electrode according to claim 11.

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