Positive electrode active material, method for preparing same, positive electrode, and lithium secondary battery comprising same

Abstract

The present invention relates to a positive electrode active material capable of improving the performance of a lithium secondary battery, the positive electrode active material comprising a lithium-rich manganese-based oxide simultaneously comprising a Li2MnO3 phase and a LiMO2 (wherein M is an element comprising Ni, Mn or a combination thereof) phase, the lithium-rich manganese-based oxide having a composition represented by Formula 1 disclosed in the specification; the invention also relates to a method for preparing the positive electrode active material, and a positive electrode and a lithium secondary battery comprising the positive electrode active material.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2023-0109714, filed on August 22, 2023, with the Korean Intellectual Property Office, the contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to positive electrode active materials, methods for preparing the same, and positive electrodes and lithium secondary batteries containing the same. Background Technology

[0004] Lithium-ion batteries consist of four main components: the positive electrode, the negative electrode, the separator, and the electrolyte. Among these, the positive electrode active material plays a major role in determining the battery's capacity, output, and lifespan. To achieve high energy density, output, and lifespan in lithium-ion batteries, improving the performance of the positive electrode active material is essential. Therefore, much research has recently been conducted to develop high-performance positive electrode active materials.

[0005] As a type of positive electrode active material, lithium-rich oxide (Li-rich layered oxide) is a mixed phase of Li₂MnO₃ and LiMO₂ (where M is an element containing Ni, Mn, Co, or a combination thereof) phases, exhibiting high operating voltage (>3.5 V vs. Li / Li). + It offers a very large capacity of 250 mAh / g. Therefore, lithium-rich oxides have attracted much attention as high-capacity cathode active materials.

[0006] However, lithium-rich oxides have problems due to their two-phase mixed structure. Specifically, if a battery containing lithium-rich oxides operates at high voltage, the following problems exist: irreversible capacity loss occurs during the first activation (first formation), leading to reduced efficiency, and voltage decay occurs during charge-discharge cycles as the layered structure transforms into a spinel structure and then into a rock salt structure, leading to problems such as the generation of O2 gas.

[0007] Furthermore, the rising price of cobalt raw materials, which are found in lithium-rich oxides, is also a significant issue. The price of cobalt raw materials is expected to continue rising, necessitating the development of cathode active materials with reduced cobalt content.

[0008] Therefore, technologies are needed to ensure the stability, performance, and economy of lithium-rich oxides.

[0009] [Existing technical documents]

[0010] [Patent Literature]

[0011] (Patent Document 1) Korean Patent Application Publication No. 10-2014-0025102 Summary of the Invention

[0012] Technical Problem

[0013] The present invention aims to solve the above problems and provides a positive electrode active material and a method for preparing the same, which can improve the capacity characteristics, efficiency characteristics and output characteristics of a battery and reduce costs.

[0014] In addition, the present invention aims to provide an economical positive electrode and a secondary battery, which have excellent capacity characteristics, efficiency characteristics and output characteristics by including the positive electrode active material.

[0015] Technical Solution

[0016] (1) The present invention provides a positive electrode active material comprising a lithium-rich manganese-based oxide, the lithium-rich manganese-based oxide comprising a Li2MnO3 phase and a LiMO2 phase (where M is an element comprising Ni, Mn or a combination thereof), and the lithium-rich manganese-based oxide having a composition represented by the following Formula 1.

[0017] [Formula 1]

[0018] Li 1+x Ni a Mn b W c M 1 d O2

[0019] In Formula 1, M 1 is one or more selected from Al, P, V, Y, Ti and Nb, 0.10 ≤ x ≤ 0.20, 0 < a < 0.5, 0.5 ≤ b < 1.0, 0 < c < 0.008, and 0 ≤ d < 0.005.

[0020] (2) The present invention provides the positive electrode active material according to (1), wherein a is 0.30 to 0.35.

[0021] (3) The present invention provides the positive electrode active material according to (1) or (2), wherein b is 0.55 to 0.60.

[0022] (4) The present invention provides the positive electrode active material according to any one of (1) to (3), wherein c is 0.0005 to 0.007.

[0023] (5) The present invention provides the positive electrode active material according to any one of (1) to (4), wherein, based on the total weight of the lithium-rich manganese-based oxide, the content of W is 800 ppm to 15000 ppm.

[0024] (6) The present invention provides a positive electrode active material according to any one of (1) to (5), wherein the tap density of the lithium-rich manganese-based oxide is 1.5 g / cm³. 3 Up to 2.5 g / cm 3 .

[0025] (7) The present invention provides a positive electrode active material according to any one of (1) to (6), wherein the average particle size (D) of the lithium-rich manganese-based oxide is [missing information]. 50 The size ranges from 2μm to 12μm.

[0026] (8) The present invention provides a method for preparing a positive electrode active material according to any one of (1) to (7), the method comprising: (A) mixing a composite transition metal hydroxide, a lithium (Li) raw material and a tungsten (W) raw material to prepare a mixture; and (B) heat-treating the mixture to prepare a lithium-rich manganese-based oxide, wherein the heat treatment is performed at a temperature of 600°C to 1000°C.

[0027] (9) The present invention provides a method for preparing the positive electrode active material described in (8), wherein the tungsten (W) raw material is mixed in an amount of 1,000 ppm to 17,000 ppm based on the total weight of the composite transition metal hydroxide.

[0028] (10) The present invention provides a method for preparing the positive electrode active material as described in (8) or (9), wherein the heat treatment in step (B) is carried out in an air atmosphere.

[0029] (11) The present invention provides a positive electrode comprising any one of (1) to (7) positive electrode active materials.

[0030] (12) The present invention provides a lithium secondary battery comprising the positive electrode described in (11).

[0031] Beneficial effects

[0032] The positive electrode active material of the present invention comprises a lithium-rich manganese-based oxide containing both Li2MnO3 phase and LiMO2 (where M is an element containing Ni, Mn or a combination thereof) phase, and contains tungsten (W), which can improve the performance of lithium secondary batteries, such as capacity characteristics, efficiency characteristics and output characteristics, and has the effect of saving costs.

[0033] Furthermore, the above-mentioned positive electrode active material can be effectively prepared using the method for preparing the positive electrode active material according to the present invention. Attached Figure Description

[0034] Figure 1 The XRD data represent the positive electrode active materials prepared in Examples 1 to 5.

[0035] Figure 2 XRD data of each positive electrode active material prepared in Comparative Examples 1 to 4 are shown.

[0036] Figure 3 SEM data of the positive electrode active material prepared in Example 1 are shown. Detailed Implementation

[0037] The invention will be explained in more detail below to aid in understanding it.

[0038] The words or terms used in this specification and claims should not be construed as having the meanings defined in common dictionaries. Based on the principle that the inventors may appropriately define the meanings of words or terms to best interpret the invention, the words or terms should be interpreted as having meanings consistent with the technical concept of the invention.

[0039] In this specification, the terms “comprising,” “provided with,” or “having” should be understood to specify the presence of the implemented feature, quantity, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, components, or combinations thereof.

[0040] In this specification, the tap density can be measured by filling approximately 20 cm³ of 10 g of powder using a common tap density meter (e.g., Micromeritics Co.'s GEOPYC-1360). 3 In a container, a pressure of 108 N is applied, the density of the particles is measured twice, and then the average value of the measurements is calculated.

[0041] In this specification, the average particle size (D) 50 The average particle size can be defined as the particle size of each particle corresponding to 50% of the cumulative volume on the particle size distribution curve (particle size distribution graph). The average particle size can be determined by dispersing the target powder in a dispersion medium, introducing it into a commercially available laser diffraction particle size analyzer (e.g., Microtrac Co.'s S3500), measuring the difference in the diffraction pattern corresponding to the particle size as it passes through the laser beam, calculating the particle size distribution, and then calculating the particle size at the point where the cumulative volume distribution corresponding to the particle size is 50% in the analyzer. 50 This allows for the determination of the average particle size.

[0042] In this specification, primary particles refer to the smallest particle unit identified when observing positive electrode active materials using a scanning electron microscope (SEM), while secondary particles refer to secondary structures formed by the aggregation of multiple primary particles.

[0043] Positive electrode active material

[0044] The positive electrode active material of the present invention will be described below.

[0045] The positive electrode active material of the present invention comprises a lithium-rich manganese-based oxide containing both a Li2MnO3 phase and a LiMO2 phase (where M is an element containing Ni, Mn or a combination thereof), and the lithium-rich manganese-based oxide has a composition represented by the following formula 1.

[0046] [Formula 1]

[0047] Li 1+x Ni a Mn b W c M 1 d O2

[0048] In formula 1, M 1 is one or more selected from Al, P, V, Y, Ti and Nb, 0.10 ≤ x ≤ 0.20, 0 < a < 0.5, 0.5 ≤ b < 1.0, 0 < c < 0.008 and 0 ≤ d < 0.005.

[0049] As a kind of positive electrode active material, the lithium-rich oxide (lithium-rich layered oxide) is a mixed phase of a Li2MnO3 phase and a LiMO2 phase (where M is an element containing Ni, Mn, Co or a combination thereof). If Co is contained, Co acts as an impurity, which reduces the capacity characteristics of the secondary battery containing the lithium-rich oxide, and has the problem of high manufacturing cost. [[ID=3憨逗1]]

[0050] The inventors of the present invention repeatedly conducted research to solve this problem, and as a result, it was found that by doping a certain amount of W without containing Co in the lithium-rich oxide, the phenomenon of capacity reduction can be suppressed, and the activation of Mn can be improved, thereby improving the capacity characteristics, efficiency characteristics, output characteristics and economic feasibility of the common lithium-rich manganese-based oxide, and thus the present invention was completed.

[0051] M 1 is a doping element. Specifically, M 1 can be at least one or more selected from Al, P, V, Y, Ti and Nb. M 1 does not necessarily contain, but if contained in an appropriate amount, it can improve the particle shape of the positive electrode active material and can improve the stability of the crystal structure.

[0052] x can be 0.10 or more, 0.11 or more, 0.12 or more, 0.14 or more, 0.145 or more or 0.150 or more, and can be 0. less than 155, 0.16 or less, 0.18 or less or 0.20 or less. If x satisfies the above range, a high energy density per unit g can be exhibited, thereby achieving high capacity characteristics.

[0053] 'a' can be greater than 0, greater than 0.2, greater than 0.3, greater than 0.305, greater than 0.306, greater than 0.307, or greater than 0.310, and can be less than 0.313, less than 0.32, less than 0.35, less than 0.4, less than 0.45, or less than 0.5. If 'a' meets the above ranges, high energy density can be exhibited, thus achieving high capacity characteristics. In particular, if 'a' is between 0.30 and 0.35, stability and economic feasibility can be improved.

[0054] b can be greater than 0.50, greater than 0.52, greater than 0.54, or greater than 0.55, and can be less than 0.57, less than 0.60, less than 0.65, less than 0.7, less than 0.8, less than 0.9, or less than 1. If b meets the above ranges, high energy density can be exhibited, thus achieving high capacity characteristics. In particular, if b is between 0.55 and 0.60, stability and economic feasibility can be improved.

[0055] c can be greater than 0, greater than 0.0005, greater than 0.0009, greater than 0.001, greater than 0.002, or greater than 0.004, and can be less than 0.006, less than 0.007, or less than 0.008. If c meets the above ranges, the capacity characteristics, efficiency characteristics, and output characteristics can be improved. In particular, if c is between 0.0005 and 0.007, the activation degree of Mn can be effectively increased to improve the capacity characteristics. On the other hand, if the lithium-rich oxide does not contain W, there is a problem that the capacity characteristics, efficiency characteristics, and output characteristics of the lithium secondary battery containing the lithium-rich oxide are degraded due to the structural instability of the lithium-rich oxide. If c is greater than 0.008, there is a problem that the capacity characteristics, efficiency characteristics, and output characteristics of the lithium secondary battery containing the lithium-rich oxide are degraded due to the excess of tungsten (W) as an impurity.

[0056] d can be greater than 0, greater than 0.001, greater than 0.003, or greater than 0.002, or less than 0.004 or less than 0.005. If d meets the above range, the particle shape of the positive electrode active material can be improved, and the stability of the crystal structure can be enhanced.

[0057] Lithium-rich manganese-based oxides can be oxides that do not contain cobalt (Co). In this case, there is a cost-saving effect, and the performance of lithium secondary batteries can be improved even without cobalt.

[0058] In Equation 1 above, x, a, b, c, and d can satisfy x + a + b + c + d ≥ 1.

[0059] Lithium-rich manganese-based oxides can have a composition represented by the following formula 2.

[0060] [Equation 2]

[0061] αLi2Mn y1 W z1 O3·(1-α)Li(Ni x2 Mn y2 W z2 O2

[0062] In Equation 2, 0.2≤α≤0.4, y1+z1≤1, 0.4≤x2≤0.6, 0.4≤y2≤0.6, 0.0007≤z1+z2<0.011, and x2+y2+z2≤1.

[0063] α refers to the molar ratio of the Li₂MnO₃ phase in lithium-rich manganese-based oxides, which can be greater than or equal to 0.2, 0.25, or 0.27, or less than or equal to 0.33, 0.35, or 0.4. If α meets the above range, a high energy density per unit g can be exhibited, thereby achieving high capacity characteristics. Furthermore, the charge / discharge capacity, initial charge / discharge efficiency, and rate performance of batteries containing positive electrode active materials can be further improved.

[0064] y1 and z1 satisfy y1+z1≤1. If y1 and z1 satisfy the above range, they can exhibit high energy density and achieve high capacity characteristics.

[0065] x2 can be greater than or equal to 0.4, 0.44, or 0.48, and can be less than or equal to 0.52, 0.56, or 0.6. If x2 meets the above ranges, it can exhibit high energy density and achieve high capacity characteristics.

[0066] y2 can be above 0.4, above 0.44, or above 0.48, and can be below 0.52, below 0.56, or below 0.6. If y2 meets the above ranges, it can exhibit high energy density and achieve high capacity characteristics.

[0067] z1+z2 can be greater than 0.0007, greater than 0.003, or greater than 0.005, and can be less than 0.006, less than 0.008, or less than 0.011. If z1+z2 meets the above ranges, the capacity characteristics, efficiency characteristics, and output characteristics can be improved.

[0068] x2, y2, and z2 satisfy x2 + y2 + z2 ≤ 1. If x2, y2, and z2 satisfy the above range, the capacity characteristics, efficiency characteristics, and output characteristics can be improved.

[0069] According to one aspect of the present invention, the content of W relative to the total weight of lithium-rich manganese-based oxide can be 800 ppm or more, 1000 ppm or more, 2000 ppm or more, 4000 ppm or more, 6000 ppm or more, or 8700 ppm or more, and can be 12000 ppm or less, 13500 ppm or less, or 15000 ppm or less. If the content of W is within the above range, the capacity characteristics, efficiency characteristics, and output characteristics of the positive electrode active material can be improved.

[0070] According to one embodiment of the present invention, the tap density of lithium-rich manganese-based oxide can be 1.5 g / cm³. 3 Above, 1.7 g / cm 3 Above, 1.9 g / cm 3 Above, 2.1 g / cm 3 Above or 2.2 g / cm 3 The above, and the tap density can be 2.3 g / cm³. 3 Below, 2.4 g / cm 3 Below or 2.5 g / cm 3 Below. If the tap density is within the above range, the electrode packing density increases, thereby achieving high capacity characteristics and improving economic feasibility.

[0071] According to one aspect of the present invention, the average particle size (D) of lithium-rich manganese-based oxides 50 The particle size can be greater than 2μm, greater than 2.5μm, or greater than 3μm, or less than 9μm, less than 10μm, less than 11μm, or less than 12μm. If the average particle size (D...) 50 Within the above range, electrode rolling can be performed without damaging the particles of the positive electrode active material, thereby improving capacity characteristics.

[0072] Preparation method of positive electrode active material

[0073] Next, the preparation method of the positive electrode active material of the present invention will be described. The preparation method of the positive electrode active material of the present invention is the preparation method of the positive electrode active material of the present invention.

[0074] The method for preparing the positive electrode active material of the present invention includes: (A) a step of mixing a composite transition metal hydroxide, a lithium (Li)-containing raw material and a tungsten (W)-containing raw material to prepare a mixture; and (B) a step of heat-treating the mixture to prepare a lithium-rich manganese-based oxide, wherein the heat treatment is carried out at a temperature of 600°C to 1000°C.

[0075] According to the present invention described above, in order to prepare the product, the type of raw materials, the mixing ratio of the raw materials, the heat treatment temperature, the heat treatment time, etc., can be appropriately adjusted.

[0076] The following is a detailed description of each step of the present invention.

[0077] Step (A)

[0078] It may also include the step (A) of preparing a mixture by mixing a composite transition metal hydroxide, a lithium (Li)-containing raw material and a tungsten (W)-containing raw material.

[0079] Mixing can be performed by dry mixing or wet mixing. If the components are mixed by dry mixing, the sintering process can be carried out without a separate drying process. If the components are mixed by wet mixing, the mixture can be prepared by adding the components to a solvent, specifically water or a mixture of water and an organic solvent (specifically alcohols, etc.) that is homogeneous with water, or by preparing and mixing a solution containing the raw materials, specifically an aqueous solution, followed by spray drying and then sintering. The raw materials and composite transition metal hydroxides can be used in appropriate amounts, taking into account the content of each metal element in the final manufactured lithium composite transition metal oxide.

[0080] Complex transition metal hydroxides can be prepared by co-precipitation reaction of introducing an aqueous solution of a complex transition metal, an ammonium cation complexing agent, and a basic compound into a reactor.

[0081] Aqueous solutions of complex transition metals can be prepared by dissolving transition metal-containing raw materials in a solvent such as water. For example, nickel-containing (Ni) and manganese-containing (Mn) raw materials can be dissolved in water. Furthermore, depending on the requirements, the aqueous solution of transition metals may further contain metal-containing raw materials.

[0082] The nickel-containing raw material can be at least one selected from NiO, Ni(OH)2, NiO·OH, NiCO3·2Ni(OH)2·4H2O, NiC2O4·2H2O, Ni(NO3)2·6H2O, NiSO4·6H2O, nickel fatty acids, and nickel halides, and any one or a mixture of two or more of them can be used. Specifically, considering economic efficiency and ease of manufacturing process, NiSO4·6H2O can be used as the nickel-containing raw material.

[0083] The manganese (Mn)-containing raw material can be at least one selected from MnCO3, Mn2O3, MnO2, Mn3O4, Mn(NO3)2, MnSO4·H2O, manganese acetate, manganese dicarboxylate, manganese citrate, manganese salts of fatty acid manganese, hydroxy oxides, and halides of manganese chloride, and any one or a mixture of two or more of them can be used. Specifically, MnSO4·H2O can be used as the manganese-containing raw material if economic efficiency and ease of manufacturing are taken into consideration.

[0084] Nickel-containing (Ni) and manganese-containing (Mn) raw materials can be used in appropriate amounts, taking into account the content of each metal element in the composite transition metal hydroxide to be manufactured.

[0085] Meanwhile, the ammonium cation complex forming agent may include at least one compound selected from the group consisting of NH4OH, (NH4)2SO4, NH4NO3, NH4Cl, CH3COONH4, and NH4CO3, and may be introduced into the reactor in the form of a solution in which the compound is dissolved in a solvent. In this case, water or a mixture of water and an organic solvent (specifically, an alcohol, etc.) that is homogeneous with water may be used as the solvent.

[0086] The basic compound can be at least one compound selected from the group consisting of NaOH, KOH, and Ca(OH)2, and can be introduced into the reactor in the form of a solution dissolved in a solvent. In this case, water or a mixture of water and an organic solvent (specifically, an alcohol, etc.) that is homogeneous with water can be used as the solvent.

[0087] As described above, if a complex transition metal aqueous solution, an ammonium cation complex forming agent, and an alkaline compound are introduced into the reactor, precursor particles in the form of complex transition metal hydroxides are generated due to the co-precipitation reaction between the transition metal ions in the complex transition metal aqueous solution and the hydroxide ions in the alkaline compound.

[0088] The coprecipitation reaction can proceed for 24 to 80 hours. If the coprecipitation reaction is carried out within this range, the crystallinity of the precursor particles can be controlled to a sufficient degree.

[0089] In this case, the amount of alkaline compound added can bring the pH of the reaction solution into the desired range.

[0090] If precursor particles are formed in the manner described above, the particles are separated from the reaction solution to obtain the composite transition metal. Specifically, the reaction solution is filtered, the particles are separated from the reaction solution, and then the separated particles are washed and dried to obtain the composite transition metal. In this case, further processing such as pulverization and / or classification can be performed as needed.

[0091] Complex transition metal hydroxides can have the properties of Ni p Mn q M 2 r (OH)2 represents the composition (where M) 2 The material is selected from at least one of Al, P, V, Y, Ti, and Nb, and p, q, and r satisfy 0 < p < 0.5, 0.5 ≤ q < 1.0, and 0 ≤ r < 0.005.

[0092] Furthermore, the composite transition metal hydroxide can be cobalt-free (Co). In this case, it has the effect of saving costs and can improve the performance of lithium secondary batteries without containing cobalt in the composite transition metal hydroxide.

[0093] The lithium (Li) raw material can be at least one selected from LiOH, Li₂CO₃, LiNO₃, LiNO₂, LiOH·H₂O, LiH, LiF, LiCl, LiBr, LiII, CH₃COOLi, Li₂O, Li acetate, Li dicarboxylic acid, Li citric acid, fatty acid Li, alkyl lithium, and lithium halides, and any one or a mixture of two or more of them can be used. Specifically, LiOH can be used in particular, taking into account high-temperature sintering.

[0094] Tungsten (W)-containing raw materials can be selected from WO3, WC, WS2, and C8H. 16 At least one of the following groups, O8W, may be used, or any one or a mixture of two or more of them may be used. Specifically, considering economic feasibility, gas production during heat treatment, and heat treatment temperature, WO3 may be used.

[0095] According to embodiments of the present invention, based on the total weight of the composite transition metal hydroxide, the tungsten (W)-containing raw material can be mixed in amounts of 1000 ppm or more, 1500 ppm or more, 5000 ppm or more, or 10000 ppm or more, and amounts of 15000 ppm or less, 16000 ppm or less, or 17000 ppm or less. If the mixing amount of the tungsten (W)-containing raw material is within the above range, the capacity characteristics, efficiency characteristics, and output characteristics of the positive electrode active material can be improved.

[0096] According to the present invention, in step (A), a composite transition metal hydroxide containing nickel and manganese but not cobalt, a lithium (Li)-containing raw material and a tungsten (W)-containing raw material may be mixed in amounts having the composition represented by Formula 1 or Formula 2 above.

[0097] Step (B)

[0098] Then, step (B) of producing the lithium-rich manganese-based oxide of the present invention may be included by heat treating the mixture.

[0099] If the above mixture is heat-treated, the composite transition metal hydroxide, lithium (Li)-containing raw material, and tungsten (W)-containing raw material react to prepare the lithium-rich manganese-based oxide of the present invention. Specifically, a lithium-rich manganese-based oxide comprising a Li2MnO3 phase and a LiMO2 phase (where M is an element containing Ni, Mn, or a combination thereof) and having a composition represented by Formula 1 is produced.

[0100] [Formula 1]

[0101] Li 1+x Ni a Mn b W c M 1 d O2

[0102] In Formula 1, M 1 is one or more selected from Al, P, V, Y, Ti, and Nb, 0.10 ≤ x ≤ 0.20, 0 < a < 0.5, 0.5 ≤ b < 1.0, 0 < c < 0.008, and 0 ≤ d < 0.005.

[0103] The heat treatment can be carried out at a temperature above 600 °C, above 700 °C, above 750 °C, or above 800 °C, and below 900 °C, below 950 °C, below 975 °C, or below 1000 °C. If the heat treatment temperature is within the above range, sufficient thermal energy required for doping can be provided. If the heat treatment is carried out at a temperature below 600 °C, sufficient thermal energy required for doping may not be provided, and if it is carried out at a temperature above 1000 °C, there is a problem that the crystal size becomes large due to excessive sintering, resulting in a reduction in the capacity characteristics of the lithium-rich manganese-based oxide.

[0104] According to an embodiment of the present invention, the heat treatment can be carried out in an air atmosphere. In this case, the sintering atmosphere can be easily maintained, and it is advantageous in terms of economy. The heat treatment can be maintained at a constant temperature for 6 to 15 hours. In this case, sufficient thermal energy required for doping can be provided to prepare a cathode active material without impurities and with high crystallinity.

[0105] Cathode

[0106] Next, the cathode of the present invention will be described.

[0107] The cathode of the present invention has a cathode active material layer containing the cathode active material of the present invention. Specifically, the cathode includes a cathode current collector and a cathode active material layer formed on the cathode current collector and including the cathode active material. Since the cathode active material has been described above, its detailed description is omitted, and only the remaining components will be described in detail below.

[0108] As a positive electrode current collector, there are no particular limitations as long as it is conductive and does not cause chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel with surface treatments of carbon, nickel, titanium, silver, etc., can be used. Furthermore, the positive electrode current collector can typically have a thickness from 3μm to 500μm, and fine non-uniformities can be formed on its surface to improve the adhesion strength with the positive electrode active material. For example, the positive electrode current collector can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics.

[0109] The positive electrode active material layer may contain conductive materials and binders together with the positive electrode active material. In this case, based on the total weight of the positive electrode active material layer, the content of the positive electrode active material can be from 80% to 99% by weight, and more specifically, from 85% to 98.5% by weight. Within this range, excellent capacity characteristics can be exhibited.

[0110] Conductive materials are used to provide conductivity to the electrodes. Their use is not particularly restricted as long as they do not cause chemical changes in the formed battery and possess electronic conductivity. Specific examples include: graphite such as natural 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 powders or 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 one or more of these can be used alone or in mixtures thereof. Based on the total weight of the positive electrode active material layer, the conductive material can be included in 0.1% to 15% by weight.

[0111] Adhesives are used to improve the adhesion between positive electrode active material particles and between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), PVDF-co-HFP copolymer, polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and may be used alone or in mixtures of two or more thereof. Based on the total weight of the positive electrode active material layer, the adhesive may be included in amounts from 0.1% to 15% by weight.

[0112] Besides using the aforementioned positive electrode active material, the positive electrode can be manufactured according to common methods for manufacturing positive electrodes. Specifically, the positive electrode can be manufactured by coating a composition for forming a positive electrode active material layer, prepared by dissolving or dispersing the positive electrode active material and optionally a binder and conductive material in a solvent, onto a positive electrode current collector, followed by drying and rolling. In this case, the types and amounts of the positive electrode active material, binder, and conductive material are the same as described above. Alternatively, as another method, the positive electrode can be manufactured by casting a composition for forming a positive electrode active material layer onto a separate support, and then laminating the film layer obtained by peeling it off from the support onto the positive electrode current collector.

[0113] The solvent can be one commonly used in the relevant field and may include dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone, or water. One or more of these solvents may be used alone. Considering the coating thickness and preparation yield of the slurry, the amount of solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, and binder, and has a viscosity that will exhibit excellent thickness uniformity if subsequently coated to manufacture the positive electrode.

[0114] Lithium secondary batteries

[0115] Next, the lithium secondary battery of the present invention will be described.

[0116] This invention can manufacture an electrochemical device including the aforementioned positive electrode. Specifically, the electrochemical device can be a battery, a capacitor, etc., and more specifically, a lithium secondary battery.

[0117] A lithium-ion secondary battery specifically includes a positive electrode, a negative electrode located on the opposite side of the positive electrode, and a separator and electrolyte between the positive and negative electrodes. The positive electrode is the same as described above, so detailed description is omitted. The following only describes the remaining components in detail.

[0118] In addition, the lithium secondary battery may optionally further include a battery container and a sealing component that houses an electrode assembly of a positive electrode, a negative electrode and a separator, the sealing component sealing the battery container.

[0119] In a lithium secondary battery, the negative electrode includes a negative electrode current collector and a layer of negative electrode active material located on the negative electrode current collector.

[0120] There are no particular restrictions on the type of negative electrode current collector, as long as it does not cause a chemical change in the battery and possesses high conductivity. For example, it can be made of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, or copper or stainless steel, or aluminum-cadmium alloys, with surface treatments using carbon, nickel, titanium, silver, etc. Furthermore, negative electrode current collectors typically have a thickness ranging from 3 μm to 500 μm, and like positive electrode current collectors, fine non-uniformities can be formed on the surface of the current collector to enhance the bonding strength with the negative electrode active material. For example, negative electrode current collectors can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, and non-woven fabrics.

[0121] Optionally, the negative electrode active material layer includes a binder and a conductive material together with the negative electrode active material.

[0122] As anode active materials, compounds capable of reversibly inserting and deintercalating lithium can be used. Specific examples include: carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; metal compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, and Al alloys; and metal oxides capable of doping and dedoping lithium, such as SiO₂. β (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composite materials containing metal compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more thereof. Additionally, lithium metal films can also be used as negative electrode active materials. Furthermore, low-crystallinity carbon and high-crystallinity carbon can be used as carbon materials. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, sheet-like, spherical, fibrous natural or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microspheres, mesophase pitch, and high-temperature calcined carbon such as coke from petroleum or coal tar pitch.

[0123] The content of the negative electrode active material can be 80% to 99% by weight relative to the total weight of the negative electrode active material layer.

[0124] Adhesives are components that facilitate bonding between conductive materials, active materials, and current collectors, and are typically added in amounts ranging from 0.1% to 10% by weight of the total weight of the negative electrode active material layer. Examples of such adhesives include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile rubber, fluororubber, and various copolymers thereof.

[0125] Conductive materials are components used to further improve the conductivity of the negative electrode active material. They can be added in amounts of 10% by weight or less, particularly 5% by weight or less, relative to the total weight of the negative electrode active material layer. There are no particular limitations on conductive materials as long as they are conductive without causing a chemical change in the battery. Examples include natural graphite, artificial graphite, etc.; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fiber; metal powders such as fluorinated carbon, aluminum, and nickel; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can also be used.

[0126] The negative electrode active material layer can be manufactured as follows: a negative electrode active material layer forming composition is coated onto a negative electrode current collector; the negative electrode active material and optionally a binder and conductive material prepared by dissolving or dispersing in a solvent are dried; or the negative electrode active material layer forming composition is cast onto a separate support, and then the film layer obtained by peeling off from the support is stacked on the negative electrode current collector.

[0127] Meanwhile, in lithium-ion secondary batteries, the separator separates the negative and positive electrodes and provides a channel for lithium-ion movement. Any separator used in ordinary lithium-ion secondary batteries can be used without specific limitations; however, separators with low resistance to electrolyte ion movement and excellent electrolyte impregnation capabilities are particularly preferred. Specifically, porous polymer membranes can be used, such as porous polymer membranes composed of polyolefin polymers like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminates of two or more of these. Alternatively, conventional porous nonwoven fabrics can be used, such as nonwoven fabrics composed of high-melting-point glass fibers or polyethylene terephthalate fibers. Furthermore, coated separators containing ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength, and single-layer or multi-layer structures can be optionally used.

[0128] Furthermore, the electrolytes used in this invention may include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used to manufacture lithium secondary batteries.

[0129] In particular, electrolytes may include organic solvents and lithium salts.

[0130] As organic solvents, any solvent that can serve as a medium through which ions involved in the electrochemical reactions of the battery can move can be used, without particular limitation. Specifically, organic solvents may include: ester solvents, such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethanol and isopropanol; nitriles such as R-CN (where R represents a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and may include double-bonded aromatic rings or ether bonds); amides such as dimethylformamide; dioxolane such as 1,3-dioxolane; and sulfolane. Preferably, the solvent is a carbonate, and more preferably a mixture of cyclic carbonates (e.g., ethylene carbonate, propylene carbonate, etc.) with high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery, and chain carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, etc.) with low viscosity. In this case, if the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the electrolyte can exhibit excellent performance.

[0131] As a lithium salt, any compound capable of providing lithium ions for use in lithium-ion secondary batteries is acceptable, without particular limitations. Specifically, lithium salts that can be used include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, and LiB(C2O4)2. The concentration of the lithium salt used can range from 0.1 M to 5.0 M, particularly from 0.1 M to 3.0 M. If the concentration of the lithium salt is within this range, the electrolyte can have suitable conductivity and viscosity, exhibiting excellent electrolyte performance, and lithium ions can move efficiently.

[0132] To improve battery life characteristics, suppress battery capacity reduction, and increase battery discharge capacity, the electrolyte may contain one or more additives in addition to the aforementioned electrolyte components. These additives may include ethylene difluorocarbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, N-glycol dimethyl ether, triammonium hexaphosphate, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolides, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, and other halogenated alkyl carbonate compounds. In this case, based on the total weight of the electrolyte, the additive content may be from 0.1% to 10% by weight, particularly from 0.1% to 5% by weight.

[0133] Lithium secondary batteries incorporating the positive electrode active material of the present invention exhibit excellent lifespan and capacity characteristics, and therefore can be used in portable devices such as mobile phones, laptops, and digital cameras, as well as electric vehicles such as hybrid electric vehicles (HEVs).

[0134] Therefore, according to another embodiment of the present invention, a battery module including a lithium secondary battery as a unit battery and a battery pack including the battery module are provided.

[0135] The battery module or battery pack can be used as a power source for one or more medium or large-sized devices, including: power tools; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0136] The shape of the lithium secondary battery of the present invention is not particularly limited, and it can be cylindrical, prismatic, bag-shaped, or coin-shaped like a can.

[0137] The lithium secondary battery of the present invention can be used not only as a battery cell for powering small devices, but also preferably as a unit cell in medium or large battery modules containing multiple battery cells.

[0138] The embodiments described below will be explained in detail to particularly illustrate the invention. However, the embodiments of the invention can be modified in various other ways, and the scope of the invention should not be construed as limited to the following embodiments.

[0139] Invention Embodiments

[0140] Examples and Comparative Examples

[0141] Example 1

[0142] Using Li:(Ni+Mn):W with a molar ratio of 1.30:1:0.001, LiOH and Ni 0.35 Mn 0.65(OH)2 (Product name: Nickel manganese hydroxide, Manufacturer: Huayou, D) 50 A mixture of Ni (10 μm) and WO3 was used to prepare the positive electrode active material (lithium-rich manganese-based oxide) by heating at 800°C to 1000°C for 10 hours in air atmosphere. In this case, WO3 was used relative to Ni... 0.35 Mn 0.65 The total weight of (OH)2 is 1300 ppm.

[0143] Example 2

[0144] Besides using LiOH and Ni 0.35 Mn 0.65 (OH)2 (Product name: Nickel manganese hydroxide, Manufacturer: Huayou, D) 50 A mixture of Li:(Ni+Mn):W (10 μm) and WO3 was used to prepare a positive electrode active material (lithium-rich manganese-based oxide) by the same method as in Example 1 above, except that the molar ratio of Li:(Ni+Mn):W was 1.30:1:0.003. In this case, WO3 was used relative to Ni... 0.35 Mn 0.65 The total weight of (OH)2 was 5200 ppm.

[0145] Example 3

[0146] Besides using LiOH and Ni 0.35 Mn 0.65 (OH)2 (Product name: Nickel manganese hydroxide, Manufacturer: Huayou, D) 50 A mixture of Li:(Ni+Mn):W (10 μm) and WO3 was prepared using the same method as in Example 1 above, except that the molar ratio of Li:(Ni+Mn):W was 1.30:1:0.005. In this case, WO3 was used in a ratio relative to Ni... 0.35 Mn 0.65 The total weight of (OH)2 was 10400 ppm.

[0147] Example 4

[0148] Besides using LiOH and Ni 0.35 Mn 0.65 (OH)2 (Product name: Nickel manganese hydroxide, Manufacturer: Huayou, D) 50 A mixture of Li:(Ni+Mn):W (10 μm) and WO3 was prepared using the same method as in Example 1 above, except that the molar ratio of Li:(Ni+Mn):W was 1.30:1:0.008. In this case, WO3 was used in a ratio relative to Ni... 0.35 Mn 0.65The total weight of (OH)2 was 15,600 ppm.

[0149] Example 5

[0150] Besides using LiOH and Ni 0.35 Mn 0.65 (OH)2 (Product name: Nickel manganese hydroxide, Manufacturer: Huayou, D) 50 A positive electrode active material (lithium-rich manganese-based oxide) was prepared by the same method as in Example 1 above, except that the molar ratio of Li:(Ni+Mn):W was 1.30:1:0.005. In this case, WO3 was used in a ratio relative to Ni... 0.35 Mn 0.65 The total weight of (OH)2 was 10400 ppm.

[0151] Comparative Example 1

[0152] Besides using LiOH and Ni 0.35 Mn 0.65 (OH)2 (Product name: Nickel manganese hydroxide, Manufacturer: Huayou, D) 50 Apart from the mixture of 10 μm and 10 μm, the positive electrode active material (lithium-rich manganese-based oxide) was prepared by the same method as in Example 1 above, such that the molar ratio of Li:(Ni+Mn) was 1.30:1.

[0153] Comparative Example 2

[0154] Besides using LiOH and Ni 0.35 Mn 0.65 (OH)2 (Product name: Nickel manganese hydroxide, Manufacturer: Huayou, D) 50 A positive electrode active material (lithium-rich manganese-based oxide) was prepared by the same method as in Example 1 above, except that the molar ratio of Li:(Ni+Mn):W was 1.30:1:0.009. In this case, WO3 was used in a ratio of 10 μm to Ni. 0.35 Mn 0.65 The total weight of (OH)2 was 18200 ppm.

[0155] Comparative Example 3

[0156] Besides using LiOH and Ni 0.35 Mn 0.65 (OH)2 (Product name: Nickel manganese hydroxide, Manufacturer: Huayou, D) 50A positive electrode active material (lithium-rich manganese-based oxide) was prepared by the same method as in Example 1 above, except that the molar ratio of Li:(Ni+Mn):Co:W was 1.30:1:0.05:0.005. In this case, WO3 was prepared relative to Ni. 0.35 Mn 0.65 The total weight of (OH)2 was 10400 ppm.

[0157] Comparative Example 4

[0158] Besides using LiOH and Ni 0.35 Mn 0.65 (OH)2 (Product name: Nickel manganese hydroxide, Manufacturer: Huayou, D) 50 A positive electrode active material (lithium-rich manganese-based oxide) was prepared by the same method as in Example 1 above, except that the molar ratio of Li:(Ni+Mn):Co:W was 1.30:1:0.05:0.009. In this case, WO3 was used relative to Ni... 0.35 Mn 0.65 The total weight of (OH)2 was 18200 ppm.

[0159] Experimental Example

[0160] Experimental Example 1: XRD Analysis

[0161] For each positive electrode active material prepared in Examples 1 to 5 above, the XRD data are shown after XRD measurement. Figure 1 In addition, for each positive electrode active material prepared in Comparative Examples 1 to 4 above, the XRD data are shown below after XRD measurement. Figure 2 .

[0162] In this case, 2g to 3g of positive electrode active material particles were collected from each positive electrode active material powder and X-ray diffraction analysis was performed using Cu-Kα rays (wavelength 1.54Å) at an accelerating voltage of 40kV / 40mA, a scanning speed of 0.2° / second, and within a 2θ range of 15° to 80°.

[0163] pass Figure 1 It was confirmed that the positive electrode active materials prepared in Examples 1 to 5 simultaneously contain two phases. Specifically, it was confirmed that they contain a Li2MnO3 phase as a small peak present at 20° to 25°, and a LiMO2 phase (where M is an element containing Ni, Mn, or a combination thereof) as a large peak present at 18°.

[0164] pass Figure 2In the case of the positive electrode active material prepared in Comparative Example 1 without W doping, it was confirmed that it had the same peaks at 20° to 25° and 18° as the example, thus simultaneously containing the Li2MnO3 phase and the LiMO2 phase (where M is an element containing Ni, Mn, or a combination thereof). On the other hand, in the case of the positive electrode active material prepared in Comparative Example 2 with excessive W doping, additional peaks expected to be impurities were confirmed at 20° to 40°, confirming that the peak pattern was different from that of the example. In the case of the positive electrode active material prepared in Comparative Example 3 with additional Co doping, different peaks were confirmed near 23°, 38°, 45°, and 58° compared to the example and Comparative Example 1, confirming that the overall peak pattern was different. In the case of Comparative Example 4 with additional Co doping and excessive W doping, the peak pattern at 20° to 35° was the same as that of Comparative Example 3, and the peak pattern at 35° to 60° was the same as that of Comparative Example 2.

[0165] In summary, it was confirmed that the positive electrode active material of the present invention simultaneously contains the Li2MnO3 phase and the LiMO2 phase (where M is an element containing Ni, Mn or a combination thereof). If excessive W is doped (Comparative Example 2) or additional Co is doped (Comparative Examples 3 and 4), it was confirmed that the positive electrode active material exhibits a different crystal structure from that of the present invention due to the excessive W and / or Co.

[0166] Experimental Example 2: ICP Analysis

[0167] Take 0.1 g of each of the positive electrode active material prepared in Examples 1 to 5 and Comparative Examples 1 to 4, add 1 ml of hydrochloric acid, and heat to dissolve the positive electrode active material. Then, add a small amount of hydrogen peroxide to promote the reaction and completely dissolve the positive electrode active material to prepare a solution. Then, dilute the solution with deionized water to a total volume of 10 mL to prepare an analytical sample. The weight ratio of the constituent elements present in the analytical sample was determined using an ICP apparatus (Perkin Elmer Co., OPTIMA 7300DV). The composition of the positive electrode active material, the content of W (ppm), and the content of Co (ppm) relative to the total weight of lithium-rich manganese-based oxide are shown in Table 1 below.

[0168] [Table 1]

[0169]

[0170] As confirmed by Table 1, the W content in the positive electrode active materials prepared in Examples 1 to 5 was 1101 ppm to 13010 ppm relative to the total weight of lithium-rich manganese-based oxides.

[0171] Experimental Example 3: Measurement of Tap Density and Average Particle Size

[0172] Using a tap density meter (e.g., Micromeritics GEOPYC-1360), 10g of each of the positive electrode active materials prepared in Examples 1 to 5 above were packed into a container of approximately 20cm². 3 The container was pressurized to 108 N, and the particle density was measured twice. The average value of the measured values ​​was then calculated, and the tap density was measured. The results are shown in Table 2 below.

[0173] To determine the average particle size of each positive electrode active material prepared in Examples 1 to 5 above, the particle size of the positive electrode active material was measured using a PSA (Microtrac Co., S3500), and the results are shown in Table 2 below.

[0174] [Table 2]

[0175]

[0176] Table 2 confirms that the tap density of the positive electrode active materials prepared in Examples 1 to 5 is 2.17 g / cm³. 3 Up to 2.20 g / cm 3 Average particle size (D) 50 The micrometer diameter ranges from 3.82 μm to 9.59 μm.

[0177] Experiment Example 4: Morphological Analysis

[0178] For the positive electrode active material prepared in Example 1, SEM images were obtained using scanning electron microscopy (SEM), and the images are shown below. Figure 3 middle.

[0179] pass Figure 3 This confirmed that the positive electrode active material prepared in Example 1 was composed of secondary particles formed by the aggregation of multiple primary particles.

[0180] Experiment Example 5: Battery Characteristic Evaluation

[0181] Manufacturing of coin-type half-cells

[0182] In an N-methylpyrrolidone (NMP) solvent, 92.5% by weight of each of the positive electrode active materials prepared in Examples 1 to 5 and Comparative Examples 1 to 4, 3.0% by weight of Super P as a conductive material, and 4.5% by weight of polyvinylidene fluoride (PVDF) as a binder were mixed to prepare a positive electrode slurry. The prepared positive electrode slurry was coated onto one side of an aluminum current collector, dried at 130°C, and then rolled to form a positive electrode.

[0183] An electrode assembly is manufactured by using a lithium metal electrode as the negative electrode and inserting a porous polyethylene separator between the positive and negative electrodes. This assembly is then placed inside a battery casing, and an electrolyte solution containing 1M LiPF6 dissolved in an organic solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a 3:7 volume ratio is injected to manufacture a coin-shaped half-cell.

[0184] Battery capacity characteristics evaluation

[0185] Coin-shaped half-cells containing the positive electrode active materials prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were charged to 4.65V at 45°C using a CC-CV method (0.1C), then discharged to 2.0V using a CC method (0.1C) for activation treatment (formation), and the charge-discharge capacity was measured. The measured charge-discharge capacity and the percentage of discharge capacity to charge capacity (efficiency (%)) are shown in Table 3 below.

[0186] Then, the capacitor was charged (0.1C) to 4.4V at 25°C using a CC-CV method, and then discharged (0.1C) to 2.5V using a CC method for the initial charge-discharge process. The charge-discharge capacity was then measured. The measured charge-discharge capacity and the percentage of discharge capacity to charge capacity (efficiency (%)) are shown in Table 3 below.

[0187] After charging to 4.4V using CC-CV method at 25°C (0.33C), an initial charge-discharge process was performed by discharging to 2.5V using CC method (0.33C), and the charge-discharge capacity was measured. The measured charge-discharge capacity and the percentage of discharge capacity to charge capacity (efficiency (%)) are shown in Table 3 below.

[0188] [Table 3]

[0189]

[0190] As confirmed by Table 3, compared with the battery containing the undoped W-containing positive electrode active material prepared in Comparative Example 1, the battery containing the positive electrode active material prepared in the examples maintained similar levels in activation process, charge and discharge capacity at 0.1 C and 0.33 C, and showed improved efficiency and rate characteristics. Compared with the battery containing the overdoped W-containing positive electrode active material prepared in Comparative Example 2, the battery containing the positive electrode active material prepared in the examples exhibited excellent activation process, charge and discharge capacity at 0.1 C and 0.33 C, and excellent efficiency and rate characteristics. Compared with the batteries containing the additionally doped Co-containing positive electrode active materials prepared in Comparative Examples 3 and 4, the battery containing the positive electrode active material prepared in the examples exhibited excellent activation process, charge and discharge capacity at 0.1 C and 0.33 C, and activation process efficiency, as well as improved efficiency and rate characteristics at 0.1 C and 0.33 C.

[0191] In summary, it can be found that the positive electrode active material according to the present invention effectively improves the activation degree of Mn, resulting in small irreversible capacity loss during activation and stability with almost no structural changes during charge-discharge cycles.

Claims

1. A positive electrode active material comprising a lithium-rich manganese-based oxide, the lithium-rich manganese-based oxide comprising a Li2MnO3 phase and a LiMO2 phase, where M is an element comprising Ni, Mn, or a combination thereof, in, The lithium-rich manganese-based oxide has a composition represented by Formula 1: [Formula 1] Li 1+x Ni a Mr b W c M 1 d O2 In Formula 1, M 1 It is selected from one or more of Al, P, V, Y, Ti, and Nb. 0.10 ≤ x ≤ 0.20, 0 < a < 0.5, 0.5 ≤ b < 1.0, 0 < c < 0.008, and 0 ≤ d < 0.

005.

2. The positive electrode active material according to claim 1, wherein, a is from 0.30 to 0.

35.

3. The positive electrode active material according to claim 1, wherein, b is from 0.55 to 0.

60.

4. The positive electrode active material according to claim 1, wherein, c is from 0.0005 to 0.

007.

5. The positive electrode active material according to claim 1, wherein, Based on the total weight of the lithium-rich manganese-based oxide, the content of W is from 800 ppm to 15000 ppm.

6. The positive electrode active material according to claim 1, wherein, The tap density of the lithium-rich manganese-based oxide is 1.5 g / cm³. 3 Up to 2.5 g / cm 3 .

7. The positive electrode active material according to claim 1, wherein, The average particle size (D) of the lithium-rich manganese-based oxide 50 The thickness ranges from 2 μm to 12 μm.

8. A method for preparing the positive electrode active material according to claim 1, the method comprising: (A) A step of mixing a composite transition metal hydroxide, a lithium (Li)-containing raw material, and a tungsten (W)-containing raw material to prepare a mixture; and (B) A step of heat-treating the mixture to prepare a lithium-rich manganese-based oxide, where the heat treatment is carried out at a temperature of 600°C to 1000°C.

9. The method according to claim 8, wherein, Based on the total weight of the composite transition metal hydroxide, the tungsten (W)-containing raw material is mixed in an amount of 1000 ppm to 17000 ppm.

10. The method according to claim 8, wherein, The heat treatment in step (B) is carried out in an air atmosphere.

11. A positive electrode comprising the positive electrode active material according to any one of claims 1 to 7.

12. A lithium secondary battery comprising the positive electrode according to claim 11.

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