Positive electrode active material for lithium secondary batteries and method for manufacturing the same

Abstract

The positive electrode active material for a lithium secondary battery according to this embodiment includes a lithium manganese-rich type first positive electrode active material represented by the following chemical formula 1; and a high-nickel type single-particle second positive electrode active material represented by the following chemical formula 2; The average particle size (D50_1) of the lithium manganese-rich type first positive electrode active material can be larger than the average particle size (D50_2) of the high-nickel type single-particle second positive electrode active material. [Chemical formula 1] Li 1+x1 (Ni (1-a1-b1) Co a1 Mn b1 )O2 (where, -0.5 ≦ x1 ≦ 0.5, 0 ≦ a1 ≦ 0.5, 0.5 ≦ b1 ≦ 1.) [Chemical formula 2] Li 1+x2 (Ni (1-a2-b2-c2) Co a2 Mn b2 M c2 )O2 (where, -0.5 ≦ x2 ≦ 0.5, 0 ≦ a'2 ≦ 0.2, 0 ≦ b2 ≦ 0.1, 0 ≦ c2 ≦ 0.03, M is one or more elements selected from the group consisting of Fe, Cr, Ti, Zn, V, Al, Mg, and Zr.)

Description

[Technical Field]

[0001] This embodiment relates to a positive electrode active material for lithium secondary batteries and a method for producing the same, and more specifically, to a positive electrode active material for lithium secondary batteries including a manganese-rich positive electrode active material and a high-nickel positive electrode active material, and a method for producing the same. [Background technology]

[0002] NCM-based layered cathode active materials exhibit a characteristic where capacity increases linearly with increasing Ni content, and are known as suitable materials for increasing electric vehicle driving range by increasing energy density. However, a disadvantage is that the price of the cathode active material itself fluctuates greatly each year due to the instability of Ni supply and demand. On the other hand, Mn is relatively inexpensive, and when the manganese content is increased compared to nickel in layered cathode materials, a composite of Li2MnO3 and LiNi(Co,Mn,Al) is formed inside the cathode material particles. When charged at a high voltage of 4.5V or higher, not only cation redox in the LiNiO2 phase of LiNi(Co,Mn,Al) but also oxygen redox in the Li2MnO3 phase occurs simultaneously, enabling high capacity of 250mAh / g or more. However, despite numerous studies, such Mn-rich cathode active materials have not been commercialized because, as the charge and discharge cycles progress, voltage decay occurs due to structural instability, and oxygen generation continues due to persistent anion redox.

[0003] The present invention aims to solve these problems, and the core of the present invention is a bimodal configuration in which large particles of manganese-rich layered cathode active material and high-nickel NCM layered single-crystal cathode material are mixed in a fixed ratio. By using dual redox, which utilizes the advantages of manganese-rich cathode active material such as cation and anion redox, and by having the advantages of single particles such as reduced gas generation and improved lifetime characteristics, the performance can be improved compared to the conventional bimodal configuration in which large and small particles of manganese-rich cathode active material are mixed. [Overview of the project] [Problems that the invention aims to solve]

[0004] The present invention aims to provide a cathode active material with improved commercialization potential by significantly reducing gas generation and voltage decay due to sustained anion redox during the charge and discharge cycles of manganese-rich cathode active materials, which were the biggest obstacles to commercialization of existing materials.

[0005] Furthermore, the present invention aims to provide a novel concept of a positive electrode active material and a method for producing the same, which enhances safety compared to positive electrode materials composed of large and small particle sizes of high-nickel positive electrode active material, while reducing raw material costs by at least 10%. [Means for solving the problem]

[0006] An embodiment of the present invention provides a positive electrode active material for a lithium secondary battery that may include a lithium manganese-rich first positive electrode active material shown in the following chemical formula 1, and a high-nickel single-particle second positive electrode active material shown in the following chemical formula 2, wherein the average particle size (D50_1) of the lithium manganese-rich first positive electrode active material is greater than the average particle size (D50_2) of the high-nickel single-particle second positive electrode active material. [Chemical formula 1] Li 1+x1 (Ni (1-a1-b1) Co a1 Mn b1)O2 (Here, -0.5 ≤ x1 ≤ 0.5, 0 ≤ a1 ≤ 0.5, 0.5 ≤ b1 ≤ 1.) [Chemical formula 2] Li 1+x2 (Ni (1-a2-b2-c2) Co a2 Mn b2 M c2 )O2 (Here, -0.5 ≤ x2 ≤ 0.5, 0 ≤ a2 ≤ 0.2, 0 ≤ b2 ≤ 0.1, 0 ≤ c2 ≤ 0.03, and M is one or more elements selected from the group consisting of Fe, Cr, Ti, Zn, V, Al, Mg, and Zr.)

[0007] The value of the ratio D50_1 / D50_2 of the average particle size (D50_1) of the lithium manganese rich first positive electrode active material to the average particle size (D50_2) of the high nickel single particle second positive electrode active material can be 2.5 to 4.5.

[0008] The average particle size (D50_1) of the lithium manganese rich first positive electrode active material is 7 μm to 15 μm, and the average particle size (D50_2) of the high nickel single particle second positive electrode active material can be 3 μm to 6 μm.

[0009] The lithium manganese rich first positive electrode active material can be secondary particles composed of a plurality of primary particles.

[0010] The weight ratio w1 / w2 of the weight (w1) of the lithium manganese rich first positive electrode active material to the weight (w2) of the high nickel single particle second positive electrode active material can be 85:15 to 55:45.

[0011] In the high nickel single particle second positive electrode active material, the manganese molar content (C Mn2 ) based on the total metal amount excluding lithium, compared to the manganese molar content (C Mn1 ) in the lithium manganese rich first positive electrode active material based on the total metal amount excluding lithium, the ratio (C Mn1 / C Mn2) can be between 15.0 and 70.0.

[0012] In the first positive electrode active material, the manganese molar content (C) is based on the total amount of metals excluding lithium. Mn1 ) and the manganese molar content (C) in the second positive electrode active material based on the total amount of metals excluding lithium. Mn2 ) difference (C Mn1 -C Mn2 The concentration can be between 50 mol% and 70 mol%.

[0013] In the first positive electrode active material, the nickel molar content (C) is based on the total amount of metals excluding lithium. Ni1 ) in the second positive electrode active material, based on the total amount of metals excluding lithium (C Ni2 ) ratio (C Ni2 / C Ni1 ) can be between 2.0 and 3.0.

[0014] In the second positive electrode active material, the nickel molar content (C) is based on the total amount of metals excluding lithium. Ni2 ) and nickel molar content (C) based on the total amount of metals excluding lithium in the first positive electrode active material. Ni1 ) difference (C Ni2 -C Ni1 The concentration can be between 45 mol% and 65 mol%.

[0015] The lithium manganese-rich first positive electrode active material can be a material that has been subjected to a formation treatment at a voltage of 4.6V to 4.8V.

[0016] The tap density of the positive electrode active material for the lithium secondary battery is 1.90 g / cm³. 3 ~2.20g / cm 3 ) and the specific surface area is 2.0 cm². 2 / g~3.0cm 2 It can be / g

[0017] Furthermore, the positive electrode active material for the lithium secondary battery can satisfy the following relational equation 1.

[0018] [Relationship 1] 0.77 ≤ m / B*10^4 ≤ 0.95 (Here, m is the tap density (g / cm³) of the positive electrode active material for lithium secondary batteries.) 3 ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. 2 ( / g)

[0019] In the second positive electrode active material, the molar content of nickel based on the total amount of metals excluding lithium may be 80 mol% or more, and in the first positive electrode active material, the molar content of manganese based on the total amount of metals excluding lithium may be 50 mol% or more.

[0020] A method for producing a positive electrode active material for a lithium secondary battery according to another embodiment of the present invention may include the steps of: preparing a lithium manganese-rich first positive electrode active material shown in the following chemical formula 1; preparing a high-nickel single-particle second positive electrode active material shown in the following chemical formula 2; and mixing the first positive electrode active material and the second positive electrode active material to produce a positive electrode active material. [Chemical formula 1] Li 1+x1 (Ni (1-a1-b1) Co a1 Mn b1 )O2 (Here, -0.5 ≤ x1 ≤ 0.5, 0 ≤ a1 ≤ 0.5, and 0.5 ≤ b1 ≤ 1.) [Chemical formula 2] Li 1+x2 (Ni (1-a2-b2-c2) Co a2 Mn b2 M c2 )O2 (Here, -0.5≦x2≦0.5, 0≦a2<0.2, 0≦b2≦0.1, 0≦c2<0.03, M is one or more elements selected from the group consisting of Fe, Cr, Ti, Zn, V, Al, Mg, and Zr.

[0021] On the other hand, the average particle size (D50_1) of the lithium manganese-rich first cathode active material is larger than the average particle size (D50_2) of the high-nickel single-particle second cathode active material.

[0022] The step of preparing the lithium manganese-rich first positive electrode active material may include the step of forming the lithium manganese-rich first positive electrode active material at a voltage of 4.6V to 4.8V.

[0023] The step of forming the lithium manganese-rich first positive electrode active material at a voltage of 4.6V to 4.8V may include charging it from 4.6V to 4.8V at a temperature of 40°C to 50°C under a current condition of 0.1C, and then applying a constant voltage to maintain the charge until the current decreases to a condition of 1 / 20C.

[0024] Furthermore, the step of forming the lithium manganese-rich first positive electrode active material under voltage conditions of 4.6V to 4.8V may include the step of discharging it under current conditions of 0.1C.

[0025] The step of preparing the lithium manganese-rich first cathode active material involves preparing a lithium manganese-rich first cathode active material having an average particle size (D50_1) in the range of 7 μm to 15 μm, and the step of preparing the high-nickel single-particle second cathode active material involves preparing a high-nickel single-particle second cathode active material having an average particle size (D50_2) in the range of 3 μm to 6 μm.

[0026] The step of mixing the first positive electrode active material and the second positive electrode active material to produce a positive electrode active material allows for mixing at a ratio w1 / w2 of the weight (w1) of the lithium manganese-rich first positive electrode active material to the weight (w2) of the high-nickel single-particle second positive electrode active material, from 85:15 to 55:45.

[0027] The step of mixing the aforementioned first positive electrode active material and second positive electrode active material to produce a positive electrode active material can produce a positive electrode active material that satisfies the following relational expression 1. [Relationship 1] 0.77 ≤ m / B*10^4 ≤ 0.95 (Here, m is the tap density (g / cm³) of the positive electrode active material for lithium secondary batteries.) 3 ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. 2 ( / g)

[0028] A positive electrode for a lithium secondary battery according to another embodiment of the present invention may include a current collector; and a positive electrode active material layer located on at least one surface of the current collector and containing the positive electrode active material for a lithium secondary battery.

[0029] Another embodiment of the present invention provides a lithium secondary battery that includes the positive electrode for the lithium secondary battery.

[0030] Furthermore, the lithium secondary battery can have an average voltage drop (voltage decay) of 40mV to 65mV after 50 charge and discharge cycles.

[0031] The aforementioned lithium secondary battery satisfies the following relational equation 2. [Relationship 2] 50 ≤ △V / (m / B*10^4) ≤ 80 (Here, △V is the voltage decay after 50 charge and discharge cycles relative to the initial charge and discharge of the lithium secondary battery, and m is the tap density (g / cm³) of the positive electrode active material for the lithium secondary battery.) 3 ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. 2 ( / g)

[0032] The aforementioned lithium secondary battery satisfies the following relational equation 3. [Relationship 3] 3.0 ≤ G / (m / B*10^4) ≤ 5.0 (Here, G is the amount of gas generated in the lithium secondary battery, and m is the tap density (g / cm³) of the positive electrode active material for the lithium secondary battery.) 3 ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. 2 ( / g)

[0033] The aforementioned lithium secondary battery satisfies the following relational equation 4. [Relationship Equation 4] 250.0≦(G / Em) / (m / B*10^4)≦400.0 (Here, G is the gas generation amount of the lithium secondary battery, Em is the loading amount of positive electrode active material at the positive electrode of the lithium secondary battery, and m is the tap density (g / cm³) of the positive electrode active material for lithium secondary batteries.) 3 ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. 2 ( / g) [Effects of the Invention]

[0034] The positive electrode active material for lithium secondary batteries according to the present invention has the advantage of reducing gas generation and voltage drop.

[0035] Furthermore, the method for producing a positive electrode active material for lithium secondary batteries according to the present invention has the advantage of being able to produce a positive electrode active material for lithium secondary batteries with reduced gas generation and voltage drop. [Brief explanation of the drawing]

[0036] [Figure 1] This figure shows a cross-sectional SEM image of a positive electrode plate containing positive electrode active material for a lithium secondary battery according to one embodiment.

[0037] [Figure 2] This figure shows the results of EDS (Energy-dispersive X-ray spectroscopy) analysis of the positive electrode active material according to Example 1.

[0038] [Figure 3] This figure shows a cross-sectional SEM image of the positive electrode plate after 100 charging and discharging cycles of a coin cell to which the positive electrode active material according to Example 1 was applied.

[0039] [Figure 4] This figure shows a cross-sectional SEM image of the positive electrode plate after 100 charge and discharge cycles of a coin cell using the positive electrode active material according to Comparative Example 1. [Modes for carrying out the invention]

[0040] In describing the present invention, terms such as first, second, and third are used to describe various parts, components, regions, layers, and / or sections, but are not limited to these. These terms are used solely to distinguish one part, component, region, layer, or section from other parts, components, regions, layers, or sections. Accordingly, the first part, component, region, layer, or section described below may be referred to as the second part, component, region, layer, or section without departing from the scope of the present invention.

[0041] The technical terms used herein are for the sole purpose of referring to specific embodiments and are not intended to limit the invention. The singular form used herein also includes the plural form unless the context clearly indicates the opposite. The meaning of “includes” as used in this specification is to embody a particular characteristic, area, integer, step, operation, element, and / or component, and does not preclude the presence or addition of other characteristics, areas, integers, steps, operations, elements, and / or components.

[0042] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries are to be interpreted as having the meaning consistent with the relevant technical literature and the present disclosures, and are not to be interpreted as ideal or highly formal unless otherwise defined.

[0043] The following describes embodiments of the present invention in detail. However, these are presented as examples only and do not limit the present invention, which is defined solely by the claims described below.

[0044] <Active material for positive electrode in lithium secondary batteries> A positive electrode active material for a lithium secondary battery according to one embodiment of the present invention may include a lithium manganese-rich first positive electrode active material and a high-nickel single-particle second positive electrode active material.

[0045] The lithium manganese-rich first cathode active material can be a manganese-rich cathode active material, and the high-nickel single-particle second cathode active material can be a high-nickel cathode active material.

[0046] The ratio D50_1 / D50_2, which is the ratio of the average particle size (D50_1) of the lithium manganese-rich first positive electrode active material to the average particle size (D50_2) of the high-nickel single-particle second positive electrode active material, can be in the range of 1 to 10, more specifically in the range of 1.5 to 5.0, and more specifically in the range of 2 to 4.

[0047] On the other hand, the lithium manganese-rich first positive electrode active material can also be a secondary particle composed of multiple primary particles, and can be represented by the following chemical formula 1. [Chemical formula 1] Li 1+x1 (Ni (1-a1-b1) Co a1 Mn b1 )O2 Here, -0.5 ≤ x1 ≤ 0.5, 0 ≤ a1 ≤ 0.2, and 0.5 ≤ b1 < 1. The aforementioned high-nickel single-particle second positive electrode active material can be represented by the following chemical formula 2. [Chemical formula 2] Li 1+x2 (Ni (1-a2-b2-c2) Co a2 Mn b2 M c2 )O2 Here, -0.5 ≤ x² ≤ 0.5, 0 ≤ a² < 0.2, 0 ≤ b² ≤ 0.1, and 0 ≤ c² < 0.03. M is one or more elements selected from the group consisting of Fe, Cr, Ti, Zn, V, Al, Mg, and Zr.

[0048] The lithium-manganese-rich first cathode active material can also be a manganese-rich (Mn-rich) cathode active material, and the manganese molar content (CMn1) can be 55 mol% or more based on the total amount of metals excluding lithium. Furthermore, the average particle size (D50_1) of the secondary particles can be in the range of 7 μm to 15 μm, specifically in the range of 8 μm to 14 μm.

[0049] The aforementioned high-nickel single-particle second positive electrode active material may also be a high-nickel (high Ni) positive electrode active material, and the nickel molar content (C) is based on the total amount of metals excluding lithium. Ni1 The content can be 80 mol% or more, specifically 85 mol% or more. In addition, the average particle size (D50_2) of the high-nickel single-particle second positive electrode active material can be in the range of 3 μm to 6 μm, specifically 3 μm to 5 μm.

[0050] On the other hand, the ratio D50_1 / D50_2, which is the ratio of the average particle size (D50_1) of the lithium manganese-rich first positive electrode active material to the average particle size (D50_2) of the high-nickel single-particle second positive electrode active material, can be between 1.0 and 5.0, more specifically between 1.5 and 4.5, and more specifically between 2.5 and 4.5.

[0051] In this invention, the "average particle size (D50)" of the positive electrode active material can be measured by a general method using a particle size analyzer.

[0052] In this invention, the metal composition and content of the positive electrode active material can be analyzed using ICP-OES (OPTIMA8300, Perkin Elmer).

[0053] In the aforementioned high-nickel single-particle second positive electrode active material, the manganese molar content (C) is based on the total amount of metals excluding lithium. Mn2) In lithium manganese-rich first cathode active material, the manganese molar content (C) is based on the total amount of metals excluding lithium. Mn1 ) ratio (C Mn1 / C Mn2 ) can be between 15.0 and 70.0, more specifically between 19.0 and 66.0, and more specifically between 19.2 and 65.5.

[0054] In the first positive electrode active material, the manganese molar content (C) is based on the total amount of metals excluding lithium. Mn1 ) and the manganese molar content (C) in the second positive electrode active material based on the total amount of metals excluding lithium. Mn2 ) difference (C Mn1 -C Mn2 The concentration can be 50 mol% to 70 mol%, specifically 54 mol% to 65 mol%.

[0055] In the first positive electrode active material, the nickel molar content (C) is based on the total amount of metals excluding lithium. Ni1 ) in the second positive electrode active material, based on the total amount of metals excluding lithium (C Ni2 ) ratio (C Ni2 / C Ni1 ) can also be 2.0 to 3.0, specifically 2.4 to 2.8. In addition, the nickel molar content (C) based on the total amount of metals excluding lithium from the second positive electrode active material Ni2 ) and nickel molar content (C) based on the total amount of metals excluding lithium in the first positive electrode active material. Ni1 ) difference (C Ni2 -C Ni1 The concentration can be between 45 mol% and 65 mol%, specifically between 48 mol% and 60 mol%.

[0056] Furthermore, the ratio w1 / w2 of the weight of the lithium manganese-rich first cathode active material to the weight of the high-nickel single-particle second cathode active material (w2) can be in the range of 85:15 to 55:45, specifically 80:20 to 60:40.

[0057] When the lithium manganese-rich first cathode active material and the high-nickel single-particle second cathode active material satisfy the aforementioned size range and ratio, the aggregation density of the cathode active material for lithium secondary batteries within a unit volume is improved, and the energy density per unit volume can be increased.

[0058] The lithium manganese-rich first positive electrode active material according to the present invention may be formed by high voltage, specifically, the active material may be formed by a voltage of 4.6V to 4.8V. By forming the manganese-rich lithium manganese-rich first positive electrode active material in this manner at high voltage, it is possible to sufficiently release oxygen (O2), significantly reduce gas generation and voltage decay due to sustained negative ion redox during the charge and discharge cycle, and is advantageous for achieving high capacity.

[0059] The tap density of the positive electrode active material for the lithium secondary battery is 1.90 g / cm³. 3 ~2.20g / cm 3 Specifically, it is 1.91 g / cm³. 3 ~2.15 g / cm³ 3 It can be.

[0060] In the present invention, "tap density" may be measured by dividing the weight of the positive electrode active material by the volume of the graduated cylinder measured after placing a graduated cylinder containing the positive electrode active material into a tap density measuring instrument and tapping it periodically 3,000 times or more.

[0061] When the tap density of the positive electrode active material for the lithium secondary battery satisfies the aforementioned range, there is the advantage of being able to improve the excellent output characteristics and cycle life characteristics of the battery.

[0062] A positive electrode active material for a lithium secondary battery, comprising a lithium manganese-rich first positive electrode active material and a high-nickel single-particle second positive electrode active material according to one embodiment of the present invention, has a specific surface area of ​​2.0 cm².2 / g~3.0cm 2 It can also be expressed as / g, specifically 2.1cm 2 / g~2.6cm 2 It can be / g

[0063] In this invention, the "specific surface area" is measured using the Brunauer-Emmett-Teller Analysis method based on nitrogen adsorption. This method involves adsorbing and desorbing nitrogen gas onto the surface of a solid sample using the BET (Brunauer Emmett Teller) formula, and measuring the amount of adsorption at different pressures to determine the specific surface area of ​​the material.

[0064] When the specific surface area of ​​the positive electrode active material for the lithium secondary battery satisfies the aforementioned range, there is the advantage of being able to improve the excellent output characteristics and cycle life characteristics of the battery.

[0065] On the other hand, a positive electrode active material for a lithium secondary battery comprising a lithium manganese-rich first positive electrode active material and a high-nickel single-particle second positive electrode active material according to one embodiment of the present invention can satisfy the following relational expression 1. [Relationship 1] 0.77 ≤ m / B*10^4 ≤ 0.95 Here, m is the tap density (g / cm³) of the positive electrode active material for lithium secondary batteries. 3 ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. 2 It is / g).

[0066] The value of relational expression 1 for a lithium secondary battery positive electrode active material containing the lithium manganese-rich first positive electrode active material and the high-nickel single-particle second positive electrode active material can be 0.77 to 0.95, specifically 0.82 to 0.95. When the value of relational expression 1 satisfies the above range, there is an advantage in that the output characteristics and cycle life characteristics of the battery can be improved.

[0067] <Method for manufacturing positive electrode active material for lithium secondary batteries> Another embodiment of the present invention provides a method for manufacturing a positive electrode active material for a lithium secondary battery, including steps of preparing a lithium manganese-rich first positive electrode active material; preparing a high nickel single-particle second positive electrode active material; and mixing the first positive electrode active material and the second positive electrode active material to manufacture a positive electrode active material.

[0068] The lithium manganese-rich first positive electrode active material can be a manganese-rich positive electrode active material and can be represented by the following Chemical Formula 1. The high nickel single-particle second positive electrode active material can be a high nickel positive electrode active material and can be represented by the following Chemical Formula 2.

[0069] The ratio D50_1 / D50_2 of the average particle size (D50_1) of the lithium manganese-rich first positive electrode active material to the average particle size (D50_2) of the high nickel single-particle second positive electrode active material can be in the range of 1.5 to 5.0, and specifically can be in the range of 2.5 to 3.5.

[0070] On the other hand, the lithium manganese-rich first positive electrode active material can be secondary particles composed of a plurality of primary particles and can be represented by the following Chemical Formula 1. [Chemical Formula 1] Li 1+x1 (Ni (1-a1-b1) Co a1 Mn b1 )O2 Here, -0.5 ≤ x1 ≤ 0.5, 0 ≤ a1 ≤ 0.2, 0.5 ≤ b1 < 1.

[0071] The high nickel single-particle second positive electrode active material can be represented by the following Chemical Formula 2. [Chemical Formula 2] Li 1+x2 (Ni<00**********e Here, -0.5 ≤ x2 ≤ 0.5, 0 ≤ a2 < 0.2, 0 ≤ b2 ≤ 0.1, 0 ≤ c2 < 0.03,

[0072] ​​​​​​​​M is one or more elements selected from the group consisting of Fe, Cr, Ti, Zn, V, Al, Mg, and Zr.

[0073] The lithium-manganese-rich first cathode active material can also be a manganese-rich (Mnrich) cathode active material, and its manganese molar content (CMn1) based on the total amount of metals excluding lithium can be 55 mol% or more. Furthermore, the average particle size (D50_1) of the secondary particles can be in the range of 7 μm to 15 μm, specifically in the range of 8 μm to 14 μm.

[0074] The aforementioned high-nickel single-particle second positive electrode active material has a nickel molar content (C) based on the total amount of metals excluding lithium. Ni1 The content can be 80 mol% or more, specifically 85 mol% or more. In addition, the average particle size (D50_2) of the high-nickel single-particle second positive electrode active material can be in the range of 3 μm to 6 μm, specifically 3 μm to 5 μm.

[0075] The characteristics of the lithium manganese-rich first cathode active material and the high-nickel single-particle second cathode active material have been described above and will be omitted here.

[0076] Furthermore, the lithium manganese-rich first cathode active material and the high-nickel single-particle second cathode active material are manufactured using the first cathode active material precursor and the second cathode active material precursor as raw materials, respectively, and there are no particular limitations on the manufacturing method or raw material materials.

[0077] The lithium manganese-rich first positive electrode active material can be formed at a temperature of 40°C to 50°C and a voltage of 4.6V to 4.8V.

[0078] Specifically, a lithium-manganese-rich first cathode active material, which is a manganese-rich cathode active material, can be subjected to high-voltage formation treatment using the following method.

[0079] To perform the initial formation of the lithium manganese-rich first positive electrode active material, the initial charging and discharging processes can be carried out in a separate formation device. While the general method of manufacturing an electrode plate and then disassembling it to separate only the positive electrode active material is complex and time-consuming, a flow battery method can be adopted to quickly and easily perform the initial formation of the manganese-rich lithium manganese-rich first positive electrode active material. The flow battery method involves mixing the lithium manganese-rich first positive electrode active material powder, conductive material, and electrolyte to prepare a first positive electrode active material slurry with a certain viscosity. A cell containing a positive electrode, a negative electrode, and a separation membrane is then fabricated. Here, the negative electrode is a negative electrode plate with a thick graphite electrode coated on a Cu current collector, and the separation membrane is a polypropylene separation membrane. The positive electrode is equipped with an Al current collector and a first positive electrode active material slurry inlet and outlet on the Al current collector. High-voltage charging was performed by continuously circulating the positive electrode active material slurry to the negative electrode fluid (catholyte) section where the positive electrode Al current collector is located. After charging was complete, the direction of the applied current was changed and discharge was performed. In order to maximize the amount of oxygen generated initially, the formation was carried out at a temperature of 40°C to 50°C, and the charging voltage at this time was set to 4.6V to 4.8V, specifically to 4.65V, under a 0.1C current condition. After that, a constant voltage was applied and charging was carried out sufficiently until the current decreased to a 1 / 20C condition. Subsequently, the direction of the current was reversed and discharge was performed, maintaining the same temperature of 40°C to 50°C and 0.1C condition. The electrolyte used in the initial formation was a 1M LiPF6 lithium salt with EC:EMC = 3:7 (vol%) and 3 vol% FEC added. The conductive material was carbon black, and the 1C current reference was 200 mAh / g.

[0080] Performing the aforementioned formation within the aforementioned voltage range has the advantage of activating Li2MnO3, which is the internal composition of the positive electrode active material, allowing oxygen (negative ions) to participate sufficiently in the reaction. Furthermore, it has the advantage of being able to sufficiently remove the oxygen generated in the side reaction at a high temperature of 45°C in the initial stages, thereby reducing side reactions during the charging and discharging processes of the lithium secondary battery and improving battery performance.

[0081] After the formation is completed, the cathode active material slurry is recovered again, the electrolyte is separated, and the dried and formed lithium manganese-rich first cathode active material is mixed with high-nickel single-particle second cathode active material. To ensure uniform mixing of the lithium manganese-rich first cathode active material and the high-nickel single-particle second cathode active material, methods such as mechanical stirring or mixing using an inert gas can be used. In this invention, the method of mixing the lithium manganese-rich first cathode active material and the high-nickel single-particle second cathode active material is not particularly limited.

[0082] Thus, the manganese-rich (Mi-rich) lithium-manganese-rich first cathode active material is advantageous for achieving high capacity because, by forming a high voltage configuration, it can sufficiently release oxygen (O2), significantly reducing gas generation and voltage decay due to sustained anion redox during the charge and discharge cycles.

[0083] On the other hand, in the step of mixing the first positive electrode active material and the second positive electrode active material to produce a positive electrode active material, the produced positive electrode active material can satisfy the following relational expression 1. [Relationship 1] 0.77 ≤ m / B*10^4 ≤ 0.95 Here, m is the tap density (g / cm³) of the positive electrode active material for lithium secondary batteries. 3 ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. 2 It is / g).

[0084] The value of relational expression 1 can be between 0.77 and 0.95, specifically between 0.82 and 0.95. When the value of relational expression 1 satisfies the above range, there is an advantage in being able to manufacture a positive electrode active material that can improve the output characteristics and cycle life characteristics of a battery.

[0085] <Positive electrode for lithium secondary batteries and lithium secondary batteries> Another embodiment of the present invention relates to a positive electrode for a lithium secondary battery, comprising a current collector; and a positive electrode active material layer located on at least one surface of the current collector and containing the positive electrode active material for lithium secondary batteries described above.

[0086] The current collector can be selected from the group consisting of, for example, aluminum, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, aluminum foam, copper foam, polymer substrates coated with conductive metals, and combinations thereof.

[0087] The positive electrode active material layer may further include a binder and a conductive material.

[0088] The binder can serve to ensure that the positive electrode active material particles for the lithium secondary battery adhere well to each other, and that the positive electrode active material for the lithium secondary battery adheres well to the current collector.

[0089] The conductive material can be used in the battery in which it is constructed, as long as it does not cause a chemical change and is an electronically conductive material.

[0090] The lithium secondary battery may include a negative electrode and a non-aqueous electrolyte.

[0091] The negative electrode includes a current collector and a negative electrode active material layer formed on the current collector, and the negative electrode active material layer may contain a negative electrode active material.

[0092] The negative electrode active material can include a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, or a transition metal oxide.

[0093] As the material capable of reversibly intercalating / deintercalating lithium ions, for example, it can be a carbon material, and any carbon-based negative electrode active material generally used in the lithium secondary battery can be used. For example, crystalline carbon, amorphous carbon, or both of them can be used.

[0094] As the alloy of lithium metal, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0095] As the material capable of doping and undoping lithium, for example, Si, SiO x (0 < x < 2), Si - Y alloy (where Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and combinations thereof, and is not Si), Sn, SnO2, Sn - Y (where Y is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, and combinations thereof, and is not Sn), etc. can be mentioned.

[0096] As the transition metal oxide, for example, vanadium oxide, lithium vanadium oxide, etc. can be mentioned. The negative electrode active material layer contains a binder and can selectively further contain a conductive material.

[0097] The binder can play a role of well adhering the negative electrode active material particles to each other and well adhering the negative electrode active material to the current collector.

[0098] The conductive material is used to impart conductivity to the electrodes, and any electronically conductive material that does not cause chemical changes can be used in the battery that is constructed.

[0099] As the current collector, for example, one can be selected from the group consisting of aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam, aluminum foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0100] The negative electrode and positive electrode can be manufactured by mixing an active material, a conductive material, and a binder in a solvent to produce an active material composition, and then applying this composition to a current collector. The present invention does not limit the method of manufacturing the electrodes.

[0101] The aforementioned solvent may be N-methylpyrrolidone or the like, but is not limited to this.

[0102] The electrolyte can be a non-aqueous electrolyte or a solid electrolyte, and a solution of lithium salt is used.

[0103] The non-aqueous electrolyte may include an organic solvent, which can act as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0104] The organic solvent can be, for example, a cyclic carbonate such as ethylene carbonate, propylene carbonate, butylene carbonate, or vinylene carbonate; a linear carbonate such as dimethyl carbonate, methyl ethyl carbonate, or diethyl carbonate; an ester such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or γ-butyrolactone; an ether such as 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,2-dioxane, or 2-methyltetrahydrofuran; a nitrile such as acetonitrile; or an amide such as dimethylformamide. These can be used individually or in combination. In particular, a mixed solvent of a cyclic carbonate and a linear carbonate is preferably used.

[0105] Furthermore, as electrolytes, gel-like polymer electrolytes such as polyethylene oxide and polyacrylonitrile impregnated with an electrolyte solution, as well as inorganic solid electrolytes such as LiI and Li3N, are possible.

[0106] The aforementioned lithium salt dissolves in an organic solvent and acts as a source of lithium ions within the battery, enabling the operation of a basic lithium secondary battery and playing a role in promoting the movement of lithium ions between the positive and negative electrodes.

[0107] The lithium salt can be any commonly used in the industry, without limitation, as long as it does not hinder the objectives of the present invention. For example, the lithium salt can be one selected from the group consisting of LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiSbF6, LiAlO4, LiAlCl4, LiCl, and LiI.

[0108] Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators can be polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof. Needless to say, mixed multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, and polypropylene / polyethylene / polypropylene three-layer separators can also be used.

[0109] Lithium secondary batteries can be classified into lithium-ion batteries, lithium-ion polymer batteries, and lithium polymer batteries depending on the type of separator and electrolyte used. They can also be classified into cylindrical, prismatic, coin-type, pouch-type, etc., depending on their shape, and into bulk type and thin-film type depending on their size.

[0110] The present invention does not limit the structure and manufacturing method of the battery.

[0111] A lithium secondary battery according to one embodiment of the present invention may have an average voltage decay of 40mV to 65mV after 50 charge and discharge cycles relative to the initial charge and discharge, specifically 45mV to 65mV.

[0112] The aforementioned lithium secondary battery can satisfy the following relational equation 2. [Relationship 2] 50 ≤ △V / (m / B*10^4) ≤ 80 Here, △V is the voltage decay after 50 charge and discharge cycles relative to the initial charge and discharge of the lithium secondary battery, and m is the tap density (g / cm³) of the positive electrode active material for the lithium secondary battery. 3 ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. 2 It is / g).

[0113] On the other hand, the lithium secondary battery can satisfy the following relational equation 3. [Relationship 3] 3.0 ≤ G / (m / B*10^4) ≤ 5.0 Here, G is the gas generation rate of the lithium secondary battery, and m is the tap density (g / cm³) of the positive electrode active material for the lithium secondary battery. 3 ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. 2 It is / g).

[0114] In this invention, the amount of gas generated was measured by the following method. After initially charging a coin cell to which the positive electrode active material manufactured according to the above examples and comparative examples was applied, the coin cell was disassembled and only the electrodes were removed. The electrodes were placed in a pouch together with the electrolyte and sealed, and when stored at 60°C for 4 weeks, the pouch expanded due to gas generation. The expanded volume was measured using the Archimedes method.

[0115] Furthermore, the lithium secondary battery can satisfy the following relational equation 4. [Relationship Equation 4] 250.0≦(G / Em) / (m / B*10^4)≦400.0 Here, G is the gas generation rate of the lithium secondary battery, Em is the loading rate of the positive electrode active material at the positive electrode of the lithium secondary battery, and m is the tap density (g / cm³) of the positive electrode active material for the lithium secondary battery. 3 ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. 2 It is / g).

[0116] The aforementioned Em is calculated considering the positive electrode loading amount and the content of the positive electrode active material in the positive electrode. [Examples]

[0117] Embodiments of the present invention will be described in detail. However, these are presented as examples only and are not limited thereto, and the present invention is defined solely by the scope of the claims described below.

[0118] (Manufacturing Example 1: Manufacturing of lithium and manganese-rich first cathode active material) Nickel-cobalt-manganese coprecipitation hydroxide was produced using a 20L coprecipitation reactor.

[0119] For precursor production, a 2.5M metal salt aqueous solution was prepared by dissolving NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O in DI water. N2 was then purged to prevent oxidation of metal ions during the coprecipitation reaction, and the reactor temperature was maintained at 50°C. The metal salt aqueous solution and NH4(OH) were added to the coprecipitation reactor as a coprecipitation chelating agent, and NaOH was used to adjust the pH. The precursor was grown to an average particle size (D50) of 10 μm. After filtering, the prepared precursor was washed with DI water and then vacuum-dried in a 100°C oven for 24 hours.

[0120] The first cathode active material precursor produced above and the lithium raw material LiOH·H2O were weighed according to the design value of the first cathode active material and mixed using a mixer. The mixture was charged into a refractory material (Saggar) and then placed in a box furnace. The box furnace was heated to 850°C for 5 hours while injecting 180 LPH of air, maintained at 850°C for 10 hours, and then calcined using a temperature profile that allowed it to cool to room temperature over 5 hours. The material obtained from calcination was subjected to induced crushing and then classified using a 325 mesh to produce lithium and manganese-rich first cathode active material.

[0121] The composition and average particle size (D50) of the manufactured lithium and manganese-rich first cathode active material are shown in Table 1.

[0122] A slurry of the lithium and manganese-rich first positive electrode active material, a conductive material, and an electrolyte was prepared by mixing these to obtain a slurry of the first positive electrode active material having a certain viscosity. A cell was also fabricated having a positive electrode, a negative electrode, and a separation membrane to separate them. Here, the negative electrode was a negative electrode plate in which a graphite electrode was thickly coated on a lithium metal or Cu current collector, and a polypropylene separation membrane was used for the separation membrane. The positive electrode had an Al current collector and an inlet and outlet section for injecting the positive electrode active material slurry onto the Al current collector. High-voltage charging was performed by continuously circulating the first positive electrode active material slurry into the catholyte section where the positive electrode Al current collector was located using a motor. After charging was complete, the direction of the applied current was changed again and discharge was performed. To maximize oxygen generation in the initial stages, the formation process was carried out at a temperature of 45°C. At this time, the charging voltage was set to 4.65V under a 0.1C current condition. Subsequently, a constant voltage was applied to ensure sufficient charging until the current decreased to a 1 / 20C condition. After that, the current direction was reversed and discharge was performed, maintaining a temperature of 40°C to 50°C and a 0.1C condition. The electrolyte used for the initial formation was 1M LiPF6 lithium salt with EC:EMC = 3:7 (vol%) and 3% FEC added. The conductive material was carbon black, and the 1C current reference was 200mAh / g.

[0123] Table 1 below shows the initial formation discharge capacity and tap density for lithium and manganese-rich first cathode active materials by composition and size.

[0124] [Table 1]

[0125] Referring to Table 1 above, it can be seen that the initial discharge capacity is higher when Co is present, and that the discharge capacity decreases as the average particle size increases, but the tap density increases.

[0126] As described above, after performing the initial discharge, the first positive electrode active material slurry was recovered again, and the powder was dried with only the electrolyte separated to finally produce a large-particle first positive electrode active material.

[0127] (Manufacturing Example 2: Manufacturing of High Nickel Single Particle Second Cathode Active Material) A high-nickel single-particle second cathode active material precursor was produced using the same method as described above for producing a lithium and manganese-rich first cathode active material precursor.

[0128] The previously manufactured second cathode active material precursor, along with the lithium raw material LiOH·H2O and Al(OH)3 precursor, were weighed according to the design values ​​for the high-nickel single-particle second cathode active material and then mixed using a mixer to produce a mixture. The mixture was then placed in a refractory material (Saggar) and positioned in a box furnace. 200 LPH of oxygen (O2) was added to the box furnace, and the temperature was raised to 750°C to 850°C for 5 hours. This temperature was maintained for 10 hours, and then the mixture was calcined using a temperature profile that allowed for cooling to room temperature over 5 hours. The material was then heat-treated to 850°C for 5 hours and cooled for 5 hours to produce a small-particle high-nickel single-particle second cathode active material.

[0129] The composition and average particle size (D50) of the manufactured second positive electrode active material are shown in Table 2.

[0130] (Manufacturing of positive electrode active materials for lithium secondary batteries) A lithium secondary battery cathode active material was manufactured by uniformly mixing a small-particle high-nickel single-particle second cathode active material produced by manufacturing example 2 and a large-particle lithium and manganese-rich first cathode active material produced by manufacturing example 1, based on design values.

[0131] Table 2 below shows the composition and mixing ratio of the formed large-particle lithium and manganese-rich first cathode active material and the small-particle high-nickel single-particle second cathode active material contained in the lithium secondary battery cathode active materials manufactured according to the examples and comparative examples.

[0132] On the other hand, in Comparative Example 1, a small-particle lithium and manganese-rich cathode active material was used as the small-particle second cathode active material.

[0133] [Table 2]

[0134] (Characteristic analysis 1-SEM analysis) Figure 1 shows an analysis of the SEM image of the cross-section of an electrode manufactured using the positive electrode active material for lithium secondary batteries produced according to Example 1.

[0135] Referring to Figure 1, it can be confirmed that the large-particle first positive electrode active material and the small-particle second positive electrode active material are uniformly distributed. In this case, the large spherical particles have a lithium and manganese-rich composition, while the smaller particles randomly located around them are small-particle high-nickel single particles.

[0136] (Characteristic analysis 2-EDS analysis) Figure 2 shows the results of measuring the main composition of the positive electrode active material from Example 1 using an elemental mapping method with EDS (Energy-dispersive X-ray spectroscopy) over the rectangular region shown in Figure 1.

[0137] Referring to Figure 2, it was shown that Ni is more abundant in small particle sizes, while Mn is relatively more abundant in large particle sizes.

[0138] Table 3 below shows the tap density and BET analysis results for the positive electrode active materials produced by the examples and comparative examples, as well as the calculated correlation between tap density and BET.

[0139] [Table 3]

[0140] (Manufacturing of coin-shaped half-cells) After manufacturing a CR2032 coin cell using the positive electrode active material produced according to the above examples and comparative examples, electrochemical evaluation was performed.

[0141] The slurry for manufacturing the electrode plates was prepared by mixing the materials in a weight ratio (wt%) of positive electrode active material: conductive material (denka black): binder (PVDF, KF1100) = 92.5:3.5:4, and adjusting the slurry viscosity by adding NMP (N-Methyl-2-pyrrolidone) so that the solid content concentration was approximately 30 wt%. The manufactured slurry was coated onto 15 μm thick aluminum foil using a doctor blade, then dried and rolled. The electrode loading amount at this time was approximately 14 mg / cm². 2 The electrolyte used was 1M LiPF6in EC:EMC=3:7 (vol%) with 3% FEC added. After manufacturing coin cells using a PP separation membrane and a lithium anode (200um, Honzo metal), they were aged at room temperature for 10 hours, and then charged and discharged.

[0142] Charging and discharging tests were performed under 4.4V charging and 2.5V discharging conditions, and the electrochemical evaluation results are shown in Table 4 below.

[0143] In Table 4 below, the loading amount Em of the positive electrode active material is 14 mg / cm³. 2 Considering the mixing ratio of the positive electrode active material in the slurry for electrode manufacturing, the conductive material (denka black), and the binder (PVDF, KF1100) is 92.5 wt%, the concentration is 12.95 mg / cm³. 2 This was the calculation.

[0144] [Table 4]

[0145] Referring to Table 4 above, it can be confirmed that in the case of a battery to which the positive electrode active material manufactured according to Examples 1 to 9 of the present invention is applied, the capacity is 95% or more of that of one cycle after 50 cycles.

[0146] This measurement assessed the decrease in average voltage after cycle charging and discharging. The voltage drop after 50 charge and discharge cycles was converted numerically compared to the initial measurement result.

[0147] In this invention, the discharge curve of a coin half-cell undergoing one charge-discharge cycle in the 4.4V-2.5V range is integrated, and the voltage at the point where the energy reaches 50% is defined as the initial voltage. Charge and discharge are then performed 50 times in succession, and the discharge curve of the final 50th cycle is similarly integrated to measure the voltage at the point where the energy reaches 50%, which is defined as the final voltage. Furthermore, the voltage drop is defined from the measured values ​​of the final voltage and the initial voltage.

[0148] Referring to Table 4 above, in the case of coin cells using the positive electrode active material manufactured according to Examples 1 to 9 of the present invention, the voltage drop after 50 charge and discharge cycles is 70mV or less, specifically 40mV to 65mV, and more specifically 45mV to 65mV. However, in the case of coin cells using the positive electrode active material manufactured according to Comparative Examples 1 to 8 of the present invention, the voltage drop after 50 charge and discharge cycles is 70mV or more, indicating a relatively large voltage drop.

[0149] On the other hand, in the case of coin cells using the positive electrode active material manufactured according to Examples 1 to 9, the value of relation 2△V / (M / B*10^4) is 50 or greater and at the same time 80 or less, but in the case of Comparative Examples 1 to 8, it was confirmed that the value of relation 2 is greater than 80.

[0150] Furthermore, the amount of gas generated by batteries using the positive electrode active materials produced according to the above examples and comparative examples was measured and is shown in Table 4.

[0151] Referring to Table 4 above, when the positive electrode active materials manufactured according to Examples 1 to 9 are applied, the G / (M / B*10^4) value in relational equation 3 is 3.0 to 5.0, specifically 3.5 to 4.9. However, in the case of Comparative Examples 1 to 8, it was confirmed that the value of relational equation 3 is greater than 5.0.

[0152] Furthermore, the (G / Em) / (m / B*10^4) value of relational equation 4, which indicates the amount of gas generated according to the loading amount of the positive electrode active material produced in the examples and comparative examples, was shown to be in the range of 250.0 to 400.0, specifically 270.0 to 380, for Examples 1 to 9, and it was confirmed that the value of relational equation 4 was greater than 400 for Comparative Examples 1 to 8.

[0153] Figure 3 shows a cross-sectional SEM image of the positive electrode plate of a coin cell using the positive electrode active material according to Example 1 after 100 charge and discharge cycles, and Figure 4 shows a cross-sectional SEM image of the positive electrode plate of a coin cell using the positive electrode active material according to Comparative Example 1 after 100 charge and discharge cycles. When high-nickel single particles were applied to the small-particle second positive electrode active material of Example 1, it can be confirmed that the degree of crack occurrence in the large-particle first positive electrode active material was significantly reduced after 100 charge and discharge cycles, compared to when lithium and manganese-rich secondary particles were applied to the small-particle second positive electrode active material of Comparative Example 1.

[0154] On the other hand, referring to Figure 3, when high-nickel single particles were used as the small-particle second positive electrode active material in Example 1, it can be confirmed that there was almost no cracking of the positive electrode active material after 100 charge and discharge cycles.

[0155] On the other hand, referring to Figure 4, when lithium and manganese-rich secondary particles were used as the small-particle second positive electrode active material in Comparative Example 1, it can be confirmed that cracks occurred not only in the large-particle first positive electrode active material but also in the small-particle second positive electrode active material after 100 charge and discharge cycles. Such cracks cause problems that accelerate gas generation and life degradation by continuously increasing the specific surface area of ​​the positive electrode active material during the charge and discharge process and promoting the reaction with the electrolyte.

[0156] The present invention is not limited to the embodiments described above and can be manufactured in a variety of different forms. A person with ordinary skill in the art to which the present invention belongs will understand that it can be carried out in other specific forms without altering the technical idea or essential features of the present invention. Therefore, the embodiments described above should be understood in all respects as illustrative and not limiting.

Claims

1. Lithium manganese-rich first cathode active material represented by the following chemical formula 1; and The material contains a high-nickel single-particle second positive electrode active material represented by the following chemical formula 2; The average particle size (D50_1) of the lithium manganese-rich first positive electrode active material is larger than the average particle size (D50_2) of the high-nickel single-particle second positive electrode active material. Positive electrode active material for lithium secondary batteries. [Chemical formula 1] Li １＋ｘ１ (N （１－ａ１－ｂ１） Co ａ１ Mn ｂ１ )O ２ (Here, -0.5 ≤ x1 ≤ 0.5, 0 ≤ a1 ≤ 0.5, and 0.5 ≤ b1 ≤ 1.) [Chemical formula 2] Li １＋ｘ２ (N （１－ａ２－ｂ２－ｃ２） Co ａ２ Mn ｂ２ M ｃ２ )O ２ (Here, -0.5 ≤ x² ≤ 0.5, 0 ≤ a² ≤ 0.2, 0 ≤ b² ≤ 0.1, 0 ≤ c² ≤ 0.03, M is one or more elements selected from the group consisting of Fe, Cr, Ti, Zn, V, Al, Mg, and Zr.

2. The ratio D50_1 / D50_2 of the average particle size (D50_1) of the lithium manganese-rich first cathode active material to the average particle size (D50_2) of the high-nickel single-particle second cathode active material is 2.5 to 4.

5. The positive electrode active material for a lithium secondary battery according to claim 1.

3. The average particle size (D50_1) of the lithium manganese-rich first positive electrode active material is 7 μm to 15 μm. The positive electrode active material for a lithium secondary battery according to claim 1.

4. The average particle size (D50_2) of the aforementioned high-nickel single-particle second positive electrode active material is 3 μm to 6 μm. The positive electrode active material for a lithium secondary battery according to claim 1.

5. The lithium manganese-rich first positive electrode active material is a secondary particle composed of multiple primary particles. The positive electrode active material for a lithium secondary battery according to claim 1.

6. The weight (w) of the aforementioned high-nickel single-particle second positive electrode active material ２ The weight of the lithium manganese-rich first cathode active material relative to (w １ ) ratio w １ / w ２ It is from 85:15 to 55:

45. The positive electrode active material for a lithium secondary battery according to claim 1.

7. In the aforementioned high-nickel single-particle second positive electrode active material, the manganese molar content (C) is based on the total amount of metals excluding lithium. Ｍｎ２ ) In lithium manganese-rich first cathode active material, the manganese molar content (C) is based on the total amount of metals excluding lithium. Ｍｎ１ ) ratio (C Ｍｎ１ / C Ｍｎ２ ) is between 15.0 and 70.

0. The positive electrode active material for a lithium secondary battery according to claim 1.

8. In the first positive electrode active material, the manganese molar content (C) is based on the total amount of metals excluding lithium. Ｍｎ１ ) and the manganese molar content (C) in the second positive electrode active material based on the total amount of metals excluding lithium. Ｍｎ２ ) difference (C Ｍｎ１ -C Ｍｎ２ The concentration is 50 mol% to 70 mol%, The positive electrode active material for a lithium secondary battery according to claim 1.

9. ） In the first positive electrode active material, the nickel molar content (C) is based on the total amount of metals excluding lithium. Ｎｉ１ ) The nickel molar content (C) in the second positive electrode active material based on the total amount of metals excluding lithium Ｎｉ２ ) ratio (C Ｎｉ２ / C Ｎｉ１ ) is between 2.0 and 3.

0. The positive electrode active material for a lithium secondary battery according to claim 1.

10. In the second positive electrode active material, the nickel molar content (C) is based on the total amount of metals excluding lithium. Ｎｉ２ ) and the nickel molar content (C) of the first positive electrode active material based on the total amount of metals excluding lithium. Ｎｉ１ ) difference (C Ｎｉ２ -C Ｎｉ１ The concentration is between 45 mol% and 65 mol%. The positive electrode active material for a lithium secondary battery according to claim 1.

11. The lithium manganese-rich first positive electrode active material is subjected to a formation treatment at a voltage of 4.6V to 4.8V. The positive electrode active material for a lithium secondary battery according to claim 1.

12. The tap density of the positive electrode active material for the lithium secondary battery is 1.90 g / cm³. ３ ~2.20 g / cm ３ That is, The positive electrode active material for a lithium secondary battery according to claim 1.

13. The specific surface area of ​​the positive electrode active material for the lithium secondary battery is 2.0 cm². ２ / g to 3.0cm ２ / g is The positive electrode active material for a lithium secondary battery according to claim 1.

14. The positive electrode active material for the lithium secondary battery satisfies the following relational equation 1: The positive electrode active material for a lithium secondary battery according to claim 1. [Relationship 1] 0.77≦m / B*10^4≦0.95 (Here, m is the tap density (g / cm³) of the positive electrode active material for lithium secondary batteries.) ３ ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. ２ ( / g) is.

15. In the second positive electrode active material, the nickel molar content based on the total amount of metals excluding lithium is 80 mol% or more. The positive electrode active material for a lithium secondary battery according to claim 1.

16. In the first positive electrode active material, the manganese molar content based on the total amount of metals excluding lithium is 50 mol% or more. The positive electrode active material for a lithium secondary battery according to claim 1.

17. Steps to prepare the lithium manganese-rich first positive electrode active material represented by the following chemical formula 1: The steps include: preparing a high-nickel single-particle second cathode active material represented by the following chemical formula 2; and The process includes the step of mixing the first positive electrode active material and the second positive electrode active material to produce a positive electrode active material; The average particle size (D50_1) of the lithium manganese-rich first positive electrode active material is larger than the average particle size (D50_2) of the high-nickel single-particle second positive electrode active material. A method for producing positive electrode active material for lithium secondary batteries. [Chemical formula 1] Li １＋ｘ１ (N （１－ａ１－ｂ１） Co ａ１ Mn ｂ１ )O ２ (Here, -0.5 ≤ x1 ≤ 0.5, 0 ≤ a1 ≤ 0.2, and 0.5 ≤ b1 < 1.) [Chemical formula 2] Li １＋ｘ２ (N （１－ａ２－ｂ２－ｃ２） Co ａ２ Mn ｂ２ M ｃ２ )O ２ (Here, -0.5 ≤ x² ≤ 0.5, 0 ≤ a² < 0.2, 0 ≤ b² ≤ 0.1, 0 ≤ c² < 0.03, M is one or more elements selected from the group consisting of Fe, Cr, Ti, Zn, V, Al, Mg, and Zr.

18. The step of preparing the lithium manganese-rich first cathode active material is as follows: The method includes the step of forming the lithium manganese-rich first positive electrode active material at a voltage of 4.6V to 4.8V. A method for producing a positive electrode active material for a lithium secondary battery according to claim 17.

19. The step of forming the lithium manganese-rich first positive electrode active material with a voltage of 4.6V to 4.8V is as follows: This process is carried out at a temperature of 40°C to 50°C. A method for producing a positive electrode active material for a lithium secondary battery according to claim 17.

20. The step of forming the lithium manganese-rich first positive electrode active material under voltage conditions of 4.6V to 4.8V is as follows: After charging to 4.6V to 4.8V under a 0.1C current condition, The method includes the step of applying a constant voltage and maintaining the charge until the current drops to a level that meets the 1 / 20C condition. A method for producing a positive electrode active material for a lithium secondary battery according to claim 17.

21. The step of forming the lithium manganese-rich first positive electrode active material under voltage conditions of 4.6V to 4.8V is as follows: This includes a step of discharging under a current condition of 0.1C. A method for producing a positive electrode active material for a lithium secondary battery according to claim 17.

22. The step of preparing the lithium manganese-rich first cathode active material is as follows: A lithium manganese-rich first cathode active material is prepared, having an average particle size (D50_1) in the range of 7 μm to 15 μm. A method for producing a positive electrode active material for a lithium secondary battery according to claim 17.

23. The step of preparing the high-nickel single-particle second positive electrode active material is as follows: The objective is to prepare a high-nickel single-particle second cathode active material with an average particle size (D50_2) in the range of 3 μm to 6 μm. A method for producing a positive electrode active material for a lithium secondary battery according to claim 17.

24. The step of mixing the first positive electrode active material and the second positive electrode active material to produce a positive electrode active material is: The weight (w) of the aforementioned high-nickel single-particle second positive electrode active material ２ The weight of the lithium manganese-rich first cathode active material relative to (w １ ) ratio lol １ / w ２ The mixture is in a ratio of 85:15 to 55:

45. A method for producing a positive electrode active material for a lithium secondary battery according to claim 17.

25. The step of mixing the first positive electrode active material and the second positive electrode active material to produce a positive electrode active material is: This invention produces a positive electrode active material that satisfies the following relational equation 1. A method for producing a positive electrode active material for a lithium secondary battery according to claim 17. [Relationship 1] 0.77≦m / B*10^4≦0.95 (Here, m is the tap density (g / cm³) of the positive electrode active material for lithium secondary batteries.) ３ ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. ２ ( / g) is.

26. Current collector; and A positive electrode active material layer located on at least one surface of the current collector, comprising the positive electrode active material for a lithium secondary battery according to any one of claims 1 to 16; Positive electrode for lithium secondary batteries.

27. A positive electrode for a lithium secondary battery as described in claim 26, Lithium-ion rechargeable battery.

28. The average voltage decay after 50 charge and discharge cycles is 40mV to 65mV. The lithium secondary battery according to claim 27.

29. The following relational equation 2 is satisfied: The lithium secondary battery according to claim 27. [Relationship Equation 2] 50≦△V / (m / B*10^4)≦80 (Here, ΔV is the voltage decay after 50 charge and discharge cycles relative to the initial charge and discharge of the lithium secondary battery, and m is the tap density (g / cm³) of the positive electrode active material for the lithium secondary battery.) ３ ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. ２ ( / g) is.

30. The following relation 3 is satisfied: The lithium secondary battery according to claim 27. [Relationship Equation 3] 3.0≦G / (m / B*10^4)≦5.0 (Here, G is the gas generation rate of the lithium secondary battery, and m is the tap density (g / cm³) of the positive electrode active material for the lithium secondary battery.) ３ ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. ２ ( / g) is.

31. The following relational equation 4 is satisfied: The lithium secondary battery according to claim 27. [Relational Equation 4] 250.0≦(G / Em) / (m / B*10^4)≦400.0 (Here, G is the gas generation amount of the lithium secondary battery, Em is the loading amount of positive electrode active material at the positive electrode of the lithium secondary battery, and m is the tap density (g / cm³) of the positive electrode active material for lithium secondary batteries.) ３ ) and B is the specific surface area (m²) of the positive electrode active material for lithium secondary batteries. ２ ( / g) is.

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