Positive electrode, method for manufacturing the same, and lithium secondary battery

Abstract

The present invention relates to a positive electrode comprising a positive electrode active material layer containing a first positive electrode active material and a second positive electrode active material having different average particle sizes, wherein the average particle size of the first positive electrode active material (D 50 ) is the average particle size (D) of the second positive electrode active material. 50 The present invention relates to a positive electrode in which the first positive electrode active material and the second positive electrode active material are larger than ), the first positive electrode active material and the second positive electrode active material contain single-particle type particles, the interface resistance of the positive electrode with a SOC of 50% measured in a coin half cell manufactured using the positive electrode is 6.5Ω to 8.5Ω, and the interface resistance of the positive electrode with a SOC of 10% measured in a coin half cell manufactured using the positive electrode is 15Ω to 19Ω.

Description

[Technical Field] 【0001】 This application claims priority rights based on Korean Patent Application No. 10-2023-0188990 filed on 21 December 2023 and Korean Patent Application No. 10-2024-0151560 filed on 30 October 2024, and all content disclosed in the documents of the said Korean patent applications is incorporated herein by reference. 【0002】 The present invention relates to a positive electrode, a method for manufacturing the same, and a lithium secondary battery, and more particularly to a positive electrode, a method for manufacturing the same, and a lithium secondary battery with improved capacity, resistance characteristics, and high-temperature life characteristics. [Background technology] 【0003】 In recent years, with the rapid proliferation of electronic devices using batteries, such as mobile phones, laptop computers, and electric vehicles, the demand for small, lightweight, and relatively high-capacity rechargeable batteries has been rapidly increasing. In particular, lithium-ion batteries are attracting attention as a power source for portable devices due to their light weight and high energy density. Therefore, research and development and efforts to improve the performance of lithium-ion batteries are being actively pursued. [Overview of the project] [Problems that the invention aims to solve] 【0004】 The present invention aims to provide a cathode with excellent resistance characteristics, high-temperature life characteristics, and capacity characteristics, a method for manufacturing the same, and a lithium secondary battery, by introducing a low-efficiency cathode material that can compensate for the problems caused by anode materials with high irreversible capacity loss during initial charging and discharging. [Means for solving the problem] 【0005】 [1] The present invention relates to a positive electrode comprising a positive electrode active material layer containing a first positive electrode active material and a second positive electrode active material having different average particle sizes, wherein the average particle size of the first positive electrode active material (D 50 ) is the average particle size (D) of the second positive electrode active material.50 ), and the first and second positive electrode active materials include single-particle shaped particles, and the interface resistance of the positive electrode at SOC 50% measured in a coin half-cell manufactured using the positive electrode is 6.5 Ω to 8.5 Ω, and the interface resistance of the positive electrode at SOC 10% measured in a coin half-cell manufactured using the positive electrode is 15 Ω to 19 Ω. A positive electrode is provided. 【0006】 [2] The present invention provides the positive electrode according to [1], wherein the first positive electrode active material includes a first lithium transition metal oxide represented by the following Chemical Formula 1. 【0007】 [Chemical Formula 1] Li 1+a1 Ni x1 Co y1 Mn z1 Al w1 M 1 v1 O2 【0008】 In Chemical Formula 1, 0 ≦ a1 ≦ 0.3, 0.82 ≦ x1 < 1.0, 0 < y1 ≦ 0.2, 0 < z1 ≦ 0.2, 0 < w1 ≦ 0.2, 0 ≦ v1 ≦ 0.1, and M 1 is one or more doping elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. 【0009】 [3] The present invention provides the positive electrode according to [1] or [2], wherein the second positive electrode active material includes a second lithium transition metal oxide represented by the following Chemical Formula 2. 【0010】 [Chemical Formula 2] Li 1+a2 Ni x2 Co y2 Mn z2 Al w2 M 2 v2 O2 【0011】 In the above chemical formula 2, 0 ≤ a² ≤ 0.3, 0.82 ≤ x² < 1.0, 0 <y2≦0.2、0<z2≦0.2、0<w2≦0.2、0≦v2≦0.1であり、M 2 This is one or more doped elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. 【0012】 [4] The present invention relates to the average particle size (D) of the first positive electrode active material. 50 The present invention provides a positive electrode according to any one of the above [1] to [3], wherein the diameter is 6 μm to 12 μm. 【0013】 [5] The present invention relates to the average particle size (D) of the second positive electrode active material. 50 The present invention provides a positive electrode according to any one of the above [1] to [4], wherein the diameter is 1.5 μm to 5 μm. 【0014】 [6] The present invention provides a positive electrode according to any one of [1] to [5] above, wherein the first positive electrode active material comprises a first lithium transition metal oxide and a first coating layer located on the surface of the first lithium transition metal oxide particles and containing 1.5 mol% to 5 mol% cobalt (Co). 【0015】 [7] The present invention provides a positive electrode according to any one of [1] to [6] above, wherein the second positive electrode active material comprises a second lithium transition metal oxide and a second coating layer located on the surface of the second lithium transition metal oxide particles and containing cobalt (Co) in an amount of 0.2 mol% to 2.5 mol%. 【0016】 [8] The present invention provides a positive electrode according to any one of [1] to [7] above, wherein the first positive electrode active material and the second positive electrode active material are contained in a weight ratio of 80:20 to 40:60. 【0017】 [9] The present invention relates to a positive electrode comprising a positive electrode active material layer containing a first positive electrode active material and a second positive electrode active material having different average particle sizes, wherein the average particle size of the first positive electrode active material (D 50) is the average particle size (D) of the second positive electrode active material. 50 The present invention provides a positive electrode in which the first positive electrode active material and the second positive electrode active material are larger than ), the first positive electrode active material and the second positive electrode active material contain single-particle particles, and the IRR value defined by the following formula 1 is 96 to 166. 【0018】 [Formula 1] IRR=R CT50 ×R CT10 【0019】 In formula 1, the R CT50 This is the dimensionless number of the interfacial resistance (unit: Ω) of the positive electrode with SOC 50% measured in a coin half cell manufactured using the aforementioned positive electrode, and R CT10 This is the dimensionless number of the interfacial resistance (unit: Ω) of the positive electrode with a SOC of 10%, measured in a coin half-cell manufactured using the aforementioned positive electrode. 【0020】

[10] The present invention provides a lithium secondary battery comprising an electrode assembly including a positive electrode and a negative electrode as described in any one of [1] to [9] above, an electrolyte, and a battery case in which the electrode assembly and the electrolyte are housed, wherein the negative electrode comprises a silicon-based negative electrode active material. 【0021】

[11] The present invention provides a lithium secondary battery according to

[10] , wherein the negative electrode comprises a carbon-based negative electrode active material, and the silicon-based negative electrode active material and the carbon-based negative electrode active material are present in a weight ratio of 1:99 to 30:70. 【0022】

[12] The present invention comprises the steps of: mixing a first positive electrode active material in distilled water and performing a first wash and drying (S1); mixing a second positive electrode active material in distilled water and performing a second wash and drying (S2); and forming a positive electrode active material layer containing the first positive electrode active material and the second positive electrode active material (S3), wherein the first wash is performed at a higher temperature than the second wash, and the average particle size (D 50 ) is the average particle size (D) of the second positive electrode active material. 50The invention provides a method for manufacturing a positive electrode, wherein the first positive electrode active material and the second positive electrode active material are larger than the given material, the first positive electrode active material and the second positive electrode active material contain single-particle particles, the interface resistance of a positive electrode with a SOC of 50% measured in a coin half cell manufactured using the positive electrode is 6.5Ω to 8.5Ω, and the interface resistance of a positive electrode with a SOC of 10% measured in a coin half cell manufactured using the positive electrode is 15Ω to 19Ω. 【0023】

[13] The present invention provides a method for manufacturing a positive electrode as described in

[12] , wherein the first washing is performed at 20°C to 40°C. 【0024】

[14] The present invention provides a method for manufacturing a positive electrode according to

[12] or

[13] , wherein the second washing is performed at 3°C ​​to 18°C. 【0025】

[15] The present invention provides a method for manufacturing a positive electrode according to any one of

[12] to

[14] , wherein the first washing is carried out by mixing the first positive electrode active material with distilled water in an amount of 50% to 70% by weight based on the total weight of the water. 【0026】

[16] The present invention provides a method for producing a positive electrode according to any one of

[12] to

[15] , wherein the second washing is carried out by mixing the second positive electrode active material with the total weight of distilled water in an amount of 65% to 85% by weight. 【0027】

[17] The present invention provides a method for manufacturing a positive electrode according to any one of

[12] to

[16] above, wherein the first positive electrode active material comprises a first lithium transition metal oxide represented by the following chemical formula 1. 【0028】 [Chemical formula 1] Li 1+a1 Ni x1 Co y1 Mn z1 Al w1 M 1 v1 O2 【0029】 In the above chemical formula 1, 0 ≤ a1 ≤ 0.3, 0.82 ≤ x1 < 1.0, 0 <y1≦0.2、0<z1≦0.2、0<w1≦0.2、0≦v1≦0.1であり、M 1 This is one or more doped elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. 【0030】

[18] The present invention provides a method for manufacturing a positive electrode according to any one of

[12] to

[17] above, wherein the second positive electrode active material comprises a second lithium transition metal oxide represented by the following chemical formula 2. 【0031】 [Chemical formula 2] Li 1+a2 Ni x2 Co y2 Mn z2 Al w2 M 2 v2 O2 【0032】 In the above chemical formula 2, 0 ≤ a² ≤ 0.3, 0.82 ≤ x² < 1.0, 0 <y2≦0.2、0<z2≦0.2、0<w2≦0.2、0≦v2≦0.1であり、M 2 This is one or more doped elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. 【0033】

[19] The present invention provides a method for manufacturing a positive electrode according to any one of

[12] to

[16] above, wherein the first positive electrode active material comprises a first lithium transition metal oxide and includes a first coating layer containing cobalt (Co) on the surface of the first lithium transition metal oxide particles, and the second positive electrode active material comprises a second lithium transition metal oxide and includes a second coating layer containing cobalt (Co) on the surface of the second lithium transition metal oxide particles, wherein the amount of cobalt (Co) contained in the first coating layer is greater than the amount of cobalt (Co) contained in the second coating layer. 【0034】

[20] The present invention provides a method for manufacturing a positive electrode as described in

[19] above, wherein the amount of cobalt (Co) in the first coating layer is 1.5 mol% to 5 mol%, and the amount of cobalt (Co) in the second coating layer is 0.2 mol% to 2.5 mol%. [Effects of the Invention] 【0035】 According to the present invention, by including a bimodal positive electrode active material and ensuring that the interfacial resistance of the positive electrode satisfies a specific range, the problem of irreversible capacity loss of the negative electrode can be compensated for without another sacrificial positive electrode material, resulting in excellent capacity characteristics, lifetime characteristics, and improved resistance characteristics. Furthermore, the positive electrode according to the present invention can reduce gas generation due to the generation of lithium byproducts during high-temperature storage, and lithium secondary batteries containing the positive electrode according to the present invention can exhibit excellent high-temperature lifetime characteristics. The following drawings attached to this specification are for illustrating preferred embodiments of the present invention and, together with the above-described content of the invention, serve to further illustrate the technical concept of the present invention; therefore, the present invention shall not be construed as being limited solely to the matters described in these drawings. [Brief explanation of the drawing] 【0036】 [Figure 1] This is a flowchart illustrating a method for manufacturing a lithium secondary battery according to one embodiment of the present invention. [Modes for carrying out the invention] 【0037】 The present invention will be described in more detail below. 【0038】 The terms and words used herein and in the claims shall not be interpreted in a manner limited to their ordinary or dictionary meanings, but in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention, and shall be interpreted in a manner consistent with the technical idea of ​​the present invention. 【0039】 The terms used herein are for illustrative purposes only and are not intended to limit the invention. Unless the context clearly indicates otherwise, singular expressions include plural expressions. 【0040】 In this specification, terms such as “includes,” “equip,” or “have” are intended to specify the presence of implemented features, figures, steps, components, or combinations thereof, and should be understood not to preemptively exclude the presence or possibility of adding one or more other features, figures, steps, components, or combinations thereof. 【0041】 In this invention, "single-particle type particle" refers to a particle formed by the aggregation of 30 or fewer sub-particles. The sub-particle unit that constitutes a single-particle type particle is called a nodule. Single-particle type particles include single particles consisting of one nodule, and pseudo-single particles which are composites of 2 to 30 nodules. 【0042】 The aforementioned "nodule" is a lower particle unit that constitutes a single particle or a pseudo-single particle, and may be a single crystal without crystalline grain boundaries, or a polycrystal in which grain boundaries appear to be absent when observed with a scanning electron microscope at a field of view of 5,000 to 20,000 times. 【0043】 In this invention, "secondary particle" refers to a particle formed by the aggregation of more than 30 sub-particles. To distinguish it from the sub-particles that constitute single-particle-type particles, the sub-particles that constitute secondary particles are called "primary particles." 【0044】 In the present invention, "particle" is a concept that includes any one or all of the following: a single particle, a pseudo-single particle, a primary particle, a nodule, and a secondary particle. 【0045】 In this invention, "average particle size D50 This refers to the particle size at the 50% reference point of the volume-cumulative particle size distribution of the positive electrode active material powder, and can be measured by the laser diffraction method. For example, after dispersing the positive electrode active material powder in a dispersion medium, it can be measured by introducing it into a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT 3000), irradiating it with ultrasound at approximately 28 kHz with an output of 60 W, obtaining a volume-cumulative particle size distribution graph, and determining the particle size corresponding to 50% of the volume-cumulative amount. 【0046】 In the present invention, "interface resistance of a positive electrode with SOC 50% or SOC 10%" means the resistance measured at the interface between the positive electrode current collector and the positive electrode active material layer in a positive electrode with SOC 50% or SOC 10%. Specifically, in the present invention, the "interfacial resistance of the positive electrode with SOC 50% or SOC 10%" can be measured by first manufacturing a coin half-cell by interposing a separator between the positive electrode and the lithium metal counter electrode according to the present invention and injecting an electrolyte. Then, the coin half-cell manufactured above is charged at 25°C under the conditions of CC (constant current) / CV (constant voltage), 0.1C, 4.2V, and 0.05C cut, and discharged to CC, 0.1C, 3.0V, which constitutes one cycle. After two cycles, the coin half-cell is charged to SOC (state of charge) 50% and SOC 10% at 0.1C, and then measured for each coin half-cell charged to SOC 50% or SOC 10% using a Biologic VMP3 device (100kHz~10mHz range, 25°C conditions). 【0047】 While carbon-based materials such as graphite are primarily used as negative electrode materials for lithium-ion batteries, they have the disadvantage of low capacity per unit mass, making it difficult to increase the capacity of lithium-ion batteries. Therefore, non-carbon negative electrode materials that exhibit higher capacity compared to carbon-based materials, such as silicon, tin, and their oxides, which form intermetallic compounds with lithium, have been developed and are in use. However, these negative electrode materials have the problem of significant irreversible capacity loss during initial charging and discharging. 【0048】 To address this, research and proposals have been conducted to overcome the irreversible capacity loss of the negative electrode by using a material that provides a lithium ion supply or storage as the positive electrode material and exhibits electrochemical activity after the first cycle without degrading the performance of the battery itself. Specifically, one method involves using a lithium nickel oxide such as Li2NiO2 as the positive electrode material or over-discharge inhibitor. 【0049】 However, most of the aforementioned lithium nickel oxides are expensive and have the problem of generating a large amount of lithium byproducts, resulting in high gas emissions. Therefore, alternative methods are needed. 【0050】 In order to address these issues, the present invention provides, in one embodiment, a positive electrode with excellent resistance characteristics and high-temperature life characteristics, as well as improved capacitance characteristics, a method for manufacturing the same, and a lithium secondary battery, by introducing a low-efficiency positive electrode material. 【0051】 To develop high-capacity cells, it is essential to use silicon-based negative electrode active materials with high capacity. However, silicon-based negative electrode active materials have the disadvantages of low charge-discharge efficiency and a high lithium-ion loss rate due to irreversible reactions. Therefore, the more charge-discharge cycles are repeated, the greater the loss of lithium in the positive electrode active material, which can cause a rapid decrease in battery capacity during charging and discharging, and potentially lead to the collapse of the positive electrode active material structure. 【0052】 To solve the above problem, when using a single-particle positive electrode active material, it is possible to realize a low-efficiency positive electrode active material that can supply lithium to the silicon-based negative electrode active material during initial charging and discharging. Even if irreversible occurs where lithium ions detached from the positive electrode active material are inserted into the negative electrode active material and then not detached, it is possible to suppress or prevent a decrease in the battery's lifespan characteristics. 【0053】 However, when using a cathode active material that is a single-particle form, the lithium diffusion path becomes longer compared to when using a lithium nickel-based oxide in a secondary particle form, and the mobility of lithium ions decreases, resulting in a problem of reduced resistance and capacitance characteristics. 【0054】 Therefore, the present inventors provide a positive electrode with excellent lifespan characteristics, prevents or suppresses a decrease in the battery's resistance characteristics, and has high energy density by preventing or suppressing the loss of lithium ions due to irreversible reactions of silicon-based negative electrode active materials. Specifically, the present invention uses a single-particle positive electrode active material having a bimodal particle size distribution, and a positive electrode in which the interfacial resistance of the positive electrode is adjusted to a specific range. This provides a positive electrode, a lithium secondary battery, and a method for manufacturing a positive electrode that have excellent lifespan characteristics, can improve the battery's resistance characteristics, and do not contain other lithium-rich substances such as conventional sacrificial positive electrode materials, thus minimizing gas generation due to the generation of lithium byproducts during storage at high temperatures, resulting in excellent high-temperature lifespan characteristics, high energy density, and excellent capacity characteristics. 【0055】 The present invention will be described in detail below. 【0056】 The positive electrode, method for manufacturing the same, and lithium secondary battery according to the present invention include at least one of the configurations disclosed below, and may include any combination of technically possible configurations from the following configurations. 【0057】 positive electrode The positive electrode according to the present invention is a positive electrode comprising a positive electrode active material layer containing a first positive electrode active material and a second positive electrode active material having different average particle sizes, wherein the average particle size of the first positive electrode active material (D 50 ) is the average particle size (D) of the second positive electrode active material. 50 The first and second positive electrode active materials are larger than the above, and the interfacial resistance of the positive electrode with a SOC of 50% measured in a coin half cell manufactured using the positive electrode is 6.5Ω to 8.5Ω, and the interfacial resistance of the positive electrode with a SOC of 10% measured in a coin half cell manufactured using the positive electrode is 15Ω to 19Ω. 【0058】 The positive electrode includes a positive electrode active material layer. Specifically, the positive electrode may include a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector. 【0059】 Various positive electrode current collectors used in the art can be used as the positive electrode current collector. For example, the positive electrode current collector may be stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. The positive electrode current collector may usually have a thickness of 3 to 500 μm, and the adhesion strength of the positive electrode active material may be increased by forming fine irregularities on the surface of the positive electrode current collector. The positive electrode current collector can be used in various forms such as film, sheet, foil, mesh, porous material, foam, nonwoven fabric, etc. 【0060】 The positive electrode active material layer is located on the positive electrode current collector, specifically on one or both sides of the positive electrode current collector. The positive electrode active material layer may be a single layer or a multilayer structure of two or more layers. 【0061】 The positive electrode active material layer includes a first positive electrode active material and a second positive electrode active material. 【0062】 The first positive electrode active material and the second positive electrode active material have an average particle size (D 50 ) differs, specifically the average particle size (D) of the first positive electrode active material. 50 ) is the average particle size (D) of the second positive electrode active material. 50 This is larger than ). As a result, when the electrode is rolled, the small-grained second positive electrode active material fills the voids in the large-grained first positive electrode active material, increasing the electrode density and enabling high energy density, thus allowing for high capacity characteristics. 【0063】 The first positive electrode active material includes single-particle particles. When the first positive electrode active material includes single-particle particles, the large size of the single-particle particles results in a longer lithium diffusion distance and increased diffusion resistance, leading to low efficiency of the positive electrode. However, when a silicon-based negative electrode active material is applied, the efficiency of the positive electrode is balanced with that of the negative electrode. This solves the problem of lithium ion loss due to irreversible capacity when using conventional silicon-based negative electrode active materials, prevents lithium deposition on the surface of the negative electrode, and improves the lifespan characteristics of a lithium secondary battery using the positive electrode according to the present invention. Furthermore, when using a first positive electrode active material that is single-particle particles, unlike when a sacrificial positive electrode material is used as in the past, the generation of lithium byproducts by the sacrificial positive electrode material during charging and discharging can be prevented or suppressed, resulting in superior high-temperature storage characteristics and high-temperature lifespan characteristics compared to when a sacrificial positive electrode material is used as in the past. 【0064】 The first positive electrode active material may include a first lithium transition metal oxide containing nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al). Unlike ternary lithium transition metal oxides containing nickel, cobalt, and manganese, the first positive electrode active material according to the present invention is structurally stable by further containing aluminum, which has a strong bonding force with oxygen atoms. This suppresses cation mixing during charging and discharging, and is electrochemically stable at high potential, thus further improving thermal stability and capacitance characteristics. 【0065】 Furthermore, the first positive electrode active material may contain a first lithium transition metal oxide containing 82 mol% or more nickel among all metals excluding lithium. In this case, high capacity characteristics of the lithium secondary battery can be achieved. 【0066】 Specifically, the first positive electrode active material may contain a first lithium transition metal oxide represented by the following chemical formula 1. 【0067】 [Chemical formula 1] Li 1+a1 Ni x1 Coy1 Mn z1 Al w1 M 1 v1 O2 【0068】 In Chemical Formula 1 above, the M 1 may be one or more doping elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and preferably may be one or more doping elements selected from the group consisting of W, Y, Ba, Ca, Ti, Mg, Ta, and Nb. 【0069】 The 1 + a1 represents the molar ratio of lithium (Li) in the first lithium transition metal oxide, and may be 0 ≦ a1 ≦ 0.3, 0 ≦ a1 ≦ 0.2, 0 ≦ a1 ≦ 0.15, or 0 ≦ a1 ≦ 0.1. When the above range is satisfied, it is possible to achieve a remarkable capacity characteristic improvement effect of the first positive electrode active material by controlling the content of Li, and a balance between the sinterability during the production of the first positive electrode active material. 【0070】 The x1 represents the molar ratio of nickel among all the metals excluding lithium in the first lithium transition metal oxide, and may be 0.82 ≦ x1 < 1, 0.85 ≦ x1 < 1, 0.90 ≦ x1 < 1, or 0.92 ≦ x1 < 1. When the above range is satisfied, a nickel content sufficient to contribute sufficiently to charge and discharge in the lithium transition metal oxide is ensured, and high capacity can be achieved. 【0071】 The y1 represents the molar ratio of cobalt among all the metals excluding lithium in the first lithium transition metal oxide, and may be 0 < y1 ≦ 0.2, 0 < y1 ≦ 0.18, 0.01 ≦ y1 ≦ 0.15, 0.03 ≦ y1 ≦ 0.12, or 0.05 ≦ y1 ≦ 0.10. When the above range is satisfied, by including a small content of cobalt, it is possible to achieve good resistance characteristics and output characteristics while having a cost advantage. 【0072】 In the first lithium transition metal oxide, z1 represents the molar ratio of manganese among all metals excluding lithium, and may be 0 < z1 ≦ 0.2, 0 < z1 ≦ 0.18, 0.01 ≦ z1 ≦ 0.15, or 0.03 ≦ z1 ≦ 0.10. When the above range is satisfied, the structural stability of the lithium transition metal oxide can be improved. 【0073】 In the first lithium transition metal oxide, w1 represents the molar ratio of aluminum among all metals excluding lithium, and may be 0 < w1 ≦ 0.2, 0 < w1 ≦ 0.18, 0.01 ≦ w1 ≦ 0.15, or 0.03 ≦ w1 ≦ 0.10. When the above range is satisfied, the thermal stability of the lithium transition metal oxide can be improved due to the high binding force with oxygen. 【0074】 In the first lithium transition metal oxide, v1 represents the molar ratio of M 1 among all metals excluding lithium, and may be 0 ≦ v1 ≦ 0.1, 0 ≦ v1 ≦ 0.08, or 0 ≦ v1 ≦ 0.05. 【0075】 The first positive electrode active material may include a first lithium transition metal oxide and a first coating layer located on the surface of the first lithium transition metal oxide particles, and the first coating layer may include cobalt (Co). The first coating layer can block the contact between the lithium transition metal oxide and the electrolyte, suppress the occurrence of electrolyte side reactions, and thereby suppress the deterioration of the surface structure of the lithium transition metal oxide that may occur during the charge and discharge process. As a result, the high-temperature life can be improved and the increase in resistance can be suppressed. 【0076】 The first coating layer may contain cobalt (Co) in amounts of 1.5 mol% to 5 mol%, 2 mol% to 4.5 mol%, 2.3 mol% to 4 mol%, 2.5 mol% to 3.5 mol%, or 2.7 mol% to 3.3 mol%. When the first coating layer contains cobalt within the above ranges, it contains a larger amount of cobalt than the second coating layer contained in the second positive electrode active material described later. This makes it possible to lower the resistance of the positive electrode interface when the SOC of the coin half cell containing the positive electrode according to the present invention is 50%, and prevents the problem of increased initial resistance during charging and discharging due to decreased ion mobility when using a positive electrode active material that is a single-particle particle. As a result, the battery's lifespan and high-temperature lifespan characteristics can be improved. 【0077】 The first coating layer may be formed on the entire surface of the first lithium transition metal oxide particles or on a portion of it. Specifically, when the first coating layer is partially formed on the surface of the first lithium transition metal oxide particles, it may be formed on an area of ​​5% or more but less than 100%, preferably 20% or more but less than 100%, of the total surface area of ​​the surface of the first lithium transition metal oxide. 【0078】 The average particle size (D) of the first positive electrode active material. 50The diameter may be between 6 μm and 12 μm. Specifically, the average particle size of the first positive electrode active material may be 6 μm or more, 6.2 μm or more, 6.4 μm or more, 6.6 μm or more, 6.8 μm or more, 7 μm or more, 7.2 μm or more, 7.4 μm or more, 7.6 μm or more, 7.8 μm or more, 8 μm or more, 8.2 μm or more, or 8.4 μm or more, and may be 12 μm or less, 11.8 μm or less, 11.6 μm or less, 11.4 μm or less, 11.2 μm or less, 11 μm or less, 10.8 μm or less, 10.6 μm or less, 10.4 μm or less, 10.2 μm or less, 10 μm or less, 9.8 μm or less, 9.6 μm or less, 9.4 μm or less, 9.2 μm or less, 9 μm or less, 8.8 μm or less, or 8.6 μm or less. For example, the average particle size of the first positive electrode active material may be 6 μm to 12 μm, 7.4 μm to 11 μm, 8 μm to 9.6 μm, or 8.2 μm to 9 μm. If the above range is met, the rolling density of the positive electrode material can be increased, thereby improving the electrode density during electrode manufacturing and achieving excellent energy density. 【0079】 The first positive electrode active material may be present in an amount of 20% to 80% by weight, preferably 30% to 70% by weight, and more preferably 40% to 60% by weight, based on the total weight of the positive electrode active material layer. When the above range is met, the rolling density can be improved and a high energy density can be achieved. 【0080】 On the other hand, the second positive electrode active material contains single-particle particles. When the second positive electrode active material contains single-particle particles, the large size of the single-particle particles results in a longer lithium diffusion distance and increased diffusion resistance, leading to low efficiency of the positive electrode. This balances the efficiency with that of the negative electrode when a silicon-based negative electrode active material is applied. This solves the problem of lithium ion loss due to irreversible capacity when using conventional silicon-based negative electrode active materials, prevents or suppresses lithium deposition on the surface of the negative electrode, and improves the life characteristics of a lithium secondary battery using the positive electrode according to the present invention. Furthermore, when a second positive electrode active material consisting of single-particle particles is applied, unlike when a sacrificial positive electrode material is used as in the past, the generation of lithium byproducts from the sacrificial positive electrode material during charging and discharging can be prevented, resulting in superior high-temperature storage characteristics and high-temperature life characteristics compared to when a sacrificial positive electrode material is used as in the past. 【0081】 The second positive electrode active material may contain a second lithium transition metal oxide comprising nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al). Unlike ternary lithium transition metal oxides containing nickel, cobalt, and manganese, the second positive electrode active material according to the present invention is structurally stable by further containing aluminum, which has a strong bonding force with oxygen atoms. This suppresses cation mixing during charging and discharging, and is electrochemically stable at high potentials, thereby further improving thermal stability and capacitance characteristics. 【0082】 Furthermore, the second positive electrode active material may contain a lithium transition metal oxide containing 82 mol% or more nickel among all metals excluding lithium. In this case, high capacity characteristics of the lithium secondary battery can be achieved. 【0083】 Specifically, the second positive electrode active material may contain a second lithium transition metal oxide represented by the following chemical formula 2. 【0084】 [Chemical formula 2] Li 1+a2 Ni x2 Coy2 Mn z2 Al w2 M 2 v2 O2 【0085】 In Chemical Formula 2, the M 2 may be one or more dopant elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, or may be one or more dopant elements selected from the group consisting of W, Y, Ba, Ca, Ti, Mg, Ta, and Nb. 【0086】 The 1 + a2 represents the molar ratio of lithium (Li) in the second lithium transition metal oxide, and may be 0 ≦ a2 ≦ 0.3, 0 ≦ a2 ≦ 0.2, 0 ≦ a2 ≦ 0.15, or 0 ≦ a2 ≦ 0.1. When the above range is satisfied, it is possible to achieve a remarkable capacity characteristic improvement effect of the second positive electrode active material by controlling the content of Li and a balance between the sinterability during the production of the second positive electrode active material. 【0087】 The x2 represents the molar ratio of nickel among all the metals excluding lithium in the second lithium transition metal oxide, and may be 0.82 ≦ x2 < 1, 0.85 ≦ x2 < 1, 0.90 ≦ x2 < 1, or 0.92 ≦ x2 < 1. When the above range is satisfied, a nickel content sufficient to contribute sufficiently to charge and discharge in the lithium transition metal oxide is ensured, and high capacity can be achieved. 【0088】 The y2 represents the molar ratio of cobalt among all the metals excluding lithium in the second lithium transition metal oxide, and may be 0 < y2 ≦ 0.2, 0 < y2 ≦ 0.18, 0.01 ≦ y2 ≦ 0.15, 0.03 ≦ y2 ≦ 0.12, or 0.05 ≦ y2 ≦ 0.10. When the above range is satisfied, by including a small content of cobalt, it is possible to achieve good resistance characteristics and output characteristics while having a cost advantage. 【0089】 In the second lithium transition metal oxide, z2 represents the molar ratio of manganese among all the metals excluding lithium, and may be 0 < z2 ≤ 0.2, 0 < z2 ≤ 0.18, 0.01 ≤ z2 ≤ 0.15, or 0.03 ≤ z2 ≤ 0.10. When the above range is satisfied, the structural stability of the lithium transition metal oxide can be improved. 【0090】 In the second lithium transition metal oxide, w2 represents the molar ratio of aluminum among all the metals excluding lithium, and may be 0 < w2 ≤ 0.2, 0 < w2 ≤ 0.18, 0.01 ≤ w2 ≤ 0.15, or 0.03 ≤ w2 ≤ 0.10. When the above range is satisfied, due to the high binding force with oxygen, the thermal stability of the lithium transition metal oxide can be ensured. 【0091】 In the second lithium transition metal oxide, v2 represents the molar ratio of M 2 among all the metals excluding lithium, and may be 0 ≤ v2 ≤ 0.1, 0 ≤ v2 ≤ 0.08, or 0 ≤ v2 ≤ 0.05. 【0092】 The second positive electrode active material may include a second lithium transition metal oxide and a second coating layer located on the surface of the second lithium transition metal oxide particles, and the second coating layer may include cobalt (Co). The second coating layer can block the contact between the lithium transition metal oxide and the electrolyte, suppress the occurrence of electrolyte side reactions, thereby suppressing the deterioration of the surface structure of the lithium transition metal oxide that may occur during the charge and discharge process, and thereby suppressing the increase in resistance and improving the high-temperature life characteristics. 【0093】 The amount of cobalt (Co) contained in the first coating layer can be greater than the amount of cobalt (Co) contained in the second coating layer. In this case, the resistance of the positive electrode interface when the SOC of the coin half cell containing the positive electrode according to the present invention is 50% can be lowered, and the problem of increased initial resistance during charging and discharging due to a decrease in ion mobility when a positive electrode active material in the form of single particles can be prevented or suppressed, thereby improving the battery's lifespan and high-temperature lifespan characteristics, and improving energy density. 【0094】 The second coating layer may contain cobalt (Co) in amounts of 0.2 mol% to 2.5 mol%, 0.3 mol% to 2 mol%, 0.5 mol% to 1.5 mol%, or 0.7 mol% to 1.3 mol%. When the second coating layer contains cobalt within the above ranges, by containing less cobalt than the first coating layer contained in the first positive electrode active material described above, the resistance of the positive electrode interface when the SOC of the coin half cell containing the positive electrode according to the present invention is 50% can be lowered. This prevents or suppresses the problem of increased initial resistance during charging and discharging due to decreased ion mobility when using a positive electrode active material that is a single-particle particle, thereby improving the battery's lifespan and high-temperature lifespan, and improving energy density. 【0095】 The second coating layer may be formed on the entire surface of the second lithium transition metal oxide particles or on a partial surface. Specifically, when the second coating layer is partially formed on the surface of the second lithium transition metal oxide particles, it may be formed on an area of ​​5% or more but less than 100%, or 20% or more but less than 100%, of the total surface area of ​​the second lithium transition metal oxide surface. 【0096】 The average particle size (D) of the second positive electrode active material 50The particle size of the second positive electrode active material may be 1.5 μm to 5 μm. Specifically, the average particle size of the second positive electrode active material may be 1.5 μm or more, 1.7 μm or more, 1.9 μm or more, 2 μm or more, 2.2 μm or more, 2.4 μm or more, 2.6 μm or more, 2.8 μm or more, 3 μm or more, and 5 μm or less, 4.8 μm or less, 4.6 μm or less, 4.4 μm or less, 4.2 μm or less, 4 μm or less, 3.8 μm or less, 3.6 μm or less, 3.4 μm or less, or 3.2 μm or less. For example, the average particle size of the second positive electrode active material may be 1.5 μm to 5 μm, 2 μm to 4.5 μm, 2.6 μm to 4.2 μm, 3 μm to 4 μm, or 3 μm to 3.4 μm. If the above range is met, the rolling density of the positive electrode material can be increased, which improves the electrode density during electrode manufacturing and enables the achievement of superior energy density. 【0097】 The second positive electrode active material may be included in an amount of 20% to 80% by weight, 30% to 70% by weight, or 40% to 60% by weight, based on the total weight of the positive electrode active material layer. When the above ranges are met, the rolling density can be improved and a high energy density can be achieved. 【0098】 The first positive electrode active material and the second positive electrode active material may be present in weight ratios of 80:20 to 40:60, 75:25 to 45:55, 70:30 to 50:50, or 65:45 to 55:45. When these weight ratios are met, the energy density can be improved, and the effect of improving high-temperature lifetime characteristics and resistance characteristics can be maximized. 【0099】 On the other hand, when a silicon-based active material is included as the negative electrode active material, the silicon-based active material acts in the discharge terminal voltage region. In this case, if the discharge terminal resistance of the positive electrode is low, a problem arises in which lithium is deposited on the surface of the negative electrode due to the resistance difference between the positive and negative electrodes. Therefore, in order to reduce the resistance difference between the discharge terminals of the positive and negative electrodes, it is necessary to increase the discharge terminal resistance of the positive electrode. However, if the interfacial resistance of the positive electrode increases across the entire region, it results in an increase in cell resistance. 【0100】 Therefore, the positive electrode according to the present invention solves the above-mentioned problems by maintaining the interfacial resistance of a positive electrode with an SOC of 50% in a coin half cell manufactured using the positive electrode, and increasing the interfacial resistance of a positive electrode with an SOC of 10% as measured in a coin half cell manufactured using the positive electrode. 【0101】 In a coin half-cell manufactured using the aforementioned positive electrode, the interface resistance of the positive electrode at SOC 50% is 6.5Ω to 8.5Ω. Specifically, the positive electrode in a coin half-cell may have an interface resistance of 6.5Ω or more, 6.7Ω or more, 6.9Ω or more, 7.0Ω or more, or 7.2Ω or more at SOC 50%, and may be 8.5Ω or less, 8.3Ω or less, 8.1Ω or less, 8.0Ω or less, 7.8Ω or less, 7.6Ω or less, or 7.4Ω or less. For example, the positive electrode in a coin half-cell may have an interface resistance of 6.5Ω to 8.5Ω, 6.7Ω to 8.0Ω, or 6.9Ω to 7.4Ω at SOC 50%. By keeping the interface resistance of the positive electrode at SOC 50% within the above range, the overall resistance of the battery does not increase, thus preventing the problem of increased initial resistance during charging and discharging, and thereby improving the battery's lifespan characteristics. 【0102】 Furthermore, the interface resistance of the positive electrode at SOC 10% measured in a coin half cell manufactured using the positive electrode is 15Ω to 19Ω. Specifically, the positive electrode may have an interface resistance of 15Ω or more, 15.2Ω or more, 15.4Ω or more, 15.6Ω or more, 15.8Ω or more, 16Ω or more, 16.2Ω or more, 16.4Ω or more, 16.6Ω or more, 16.8Ω or more, 17Ω or more, 17.2Ω or more, or 17.4Ω or more in a coin half cell, and may be 19Ω or less, 18.8Ω or less, 18.6Ω or less, 18.4Ω or less, 18.2Ω or less, 18Ω or less, 17.8Ω or less, or 17.6Ω or less. For example, the positive electrode may have an interfacial resistance of 15Ω to 19Ω, 15.2Ω to 18Ω, 16Ω to 17.8Ω, or 17Ω to 17.6Ω at 10% SOC in a coin half-cell. When the above range is met, the resistance difference between the positive and negative electrodes at the discharge end can be reduced, and the phenomenon of lithium ions being deposited on the surface of the negative electrode can be suppressed, thereby suppressing the degradation of the negative electrode. This solves the problem of reduced battery cycle characteristics and prevents the problem of increased initial resistance during charging and discharging, thereby improving the battery's lifespan characteristics. 【0103】 In this case, the interfacial resistance of the positive electrode with a SOC of 50% or 10% in the coin half cell can be adjusted by the composition of the first positive electrode active material and the second positive electrode active material, the cobalt content of the first coating layer contained in the first positive electrode active material and the second coating layer contained in the second positive electrode active material, and the water washing conditions during the manufacturing of the first positive electrode active material and the second positive electrode active material. 【0104】 The positive electrode according to the present invention has an IRR value of 96 to 166 as defined by the following formula 1. Specifically, the IRR value defined by the following formula 1 may be 96 or more, 98 or more, 100 or more, 102 or more, 104 or more, 106 or more, 108 or more, 110 or more, 112 or more, 116 or more, 118 or more, 120 or more, 122 or more, 124 or more, 126 or more, 166 or less, 164 or less, 162 or less, 160 or less, 158 or less, 156 or less, 154 or less, 152 or less, 150 or less, 148 or less, 146 or less, 144 or less, 142 or less, 140 or less, 138 or less, 136 or less, 134 or less, 132 or less, 130 or less, or 128 or less. For example, the IRR value defined by the following formula 1 may be 96-166, 100-140, 104-130, 120-130, or 124-128. When the IRR value is within the range described above, the interfacial resistance of the positive electrode is adjusted to a range that reduces the resistance difference between the discharge ends of the positive and negative electrodes and prevents the resistance of the positive electrode from increasing across the entire range, thereby enabling the lithium secondary battery to exhibit excellent high-temperature life characteristics. 【0105】 [Formula 1] IRR=R CT50 ×R CT10 【0106】 In formula 1, the R CT50 This is the dimensionless number of the interface resistance (unit: Ω) of the positive electrode with SOC 50% measured in a coin half cell manufactured using the aforementioned positive electrode, and R CT10 This is the dimensionless number of the interfacial resistance (unit: Ω) of the positive electrode with a SOC of 10%, measured in a coin half-cell manufactured using the aforementioned positive electrode. 【0107】 The aforementioned R CT50 In this case, the interfacial resistance of the positive electrode with a SOC of 50%, measured in a coin half-cell manufactured using the aforementioned positive electrode, is as described above. 【0108】 The aforementioned R CT10 In this case, the interfacial resistance of the positive electrode with a SOC of 10% measured in a coin half cell manufactured using the aforementioned positive electrode is as described above. 【0109】 On the other hand, the positive electrode active material layer may selectively further include at least one of a positive electrode conductive material and a positive electrode binder. 【0110】 The positive electrode conductive material is used to impart conductivity to the electrode and can be used in the battery without particular limitations, as long as it does not cause chemical changes and has electronic conductivity. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these can be used alone, or a mixture of two or more. The positive electrode conductive material may typically be included in an amount of 1 to 30% by weight, 1 to 20% by weight, or 1 to 10% by weight relative to the total weight of the positive electrode active material layer. 【0111】 The positive electrode binder plays a role in improving the adhesion between positive electrode material particles and the adhesion between the positive electrode material and the positive electrode current collector. Specific examples include fluororesin binders containing polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber binders containing styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; cellulose binders containing carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyalcohol binders containing polyvinyl alcohol; polyolefin binders containing polyethylene and polypropylene; polyimide binders; polyester binders; and silane binders. One of these can be used alone, or a mixture of two or more. The positive electrode binder may be present in an amount of 1 to 30% by weight, 1 to 20% by weight, or 1 to 10% by weight relative to the total weight of the positive electrode active material layer. 【0112】 The positive electrode can be manufactured by applying a positive electrode slurry to one or both sides of a long, sheet-like positive electrode current collector, removing the solvent from the slurry through a drying process, and then rolling it. Alternatively, a positive electrode including a plain area can be manufactured by not applying the positive electrode slurry to a part of the positive electrode current collector, for example, one end of the positive electrode current collector. 【0113】 Furthermore, the positive electrode slurry can be produced by dispersing the first positive electrode active material and the second positive electrode active material according to the present invention in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water. 【0114】 Lithium-ion rechargeable battery Next, the lithium secondary battery according to the present invention will be described. 【0115】 The lithium secondary battery according to the present invention includes an electrode assembly containing the aforementioned positive electrode and negative electrode, an electrolyte, and a battery case in which the electrode assembly and the electrolyte are housed, wherein the negative electrode contains a silicon-based negative electrode active material. 【0116】 The following describes in more detail each component of the lithium secondary battery according to the present invention. 【0117】 (1) Electrode assembly The electrode assembly according to the present invention includes a positive electrode and a negative electrode, and more specifically, the electrode assembly may include a positive electrode, a negative electrode, and a separator. 【0118】 Specifically, the electrode assembly can be formed by stacking a positive electrode, a separator, and a negative electrode in that order, and the positive electrode and the negative electrode can be insulated from each other by the separator. 【0119】 Examples of electrode assemblies include stack type, jelly roll type, and stack-and-fold type, but are not limited to these. 【0120】 The following describes in detail each component of the electrode assembly according to the present invention. 【0121】 1) Positive electrode As the positive electrode is as described above, a detailed explanation will be omitted. 【0122】 2) Negative electrode The negative electrode includes a silicon-based negative electrode active material. Specifically, the negative electrode may include a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer may include a silicon-based negative electrode active material. 【0123】 The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. The negative electrode current collector may also typically have a thickness of 3 to 500 μm. 【0124】 Furthermore, similar to the positive electrode current collector, the negative electrode current collector may have fine irregularities formed on its surface to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric. 【0125】 The negative electrode active material layer is located on the negative electrode current collector, specifically on one or both sides of the negative electrode current collector. The negative electrode active material layer may be a single layer or a multilayer structure of two or more layers. 【0126】 The silicon-based negative electrode active material may be particles containing silicon (Si). 【0127】 The silicon-based negative electrode active material is SiO x (0≦x≦2), Si / C composite, or a combination thereof. The SiO x (0≦x≦2) may be a form containing Si and SiO2. That is, x is the SiO x This corresponds to the ratio of the number of O atoms to Si contained in (0≦x≦2). The silicon-based negative electrode active material is SiO x (0 ≤ x ≤ 2), most preferably SiO. 【0128】 When a silicon-based negative electrode active material is included in the negative electrode, it has the advantage of having a much higher charge / discharge capacity compared to conventional carbon-based negative electrode active materials. However, the silicon-based negative electrode active material has a large irreversible capacity, which leads to a problem of reduced battery life characteristics. As mentioned above, the lithium secondary battery according to the present invention solves this problem by including a positive electrode active material in the positive electrode form, which is a single-particle type, and by adjusting the interfacial resistance of the positive electrode to a specific range. 【0129】 The silicon-based anode active material may be included in the anode active material layer in amounts of 1% to 30% by weight, 1% to 25% by weight, or 2% to 20% by weight. When these ranges are met, sufficient capacitance characteristics can be achieved. 【0130】 On the other hand, the negative electrode active material layer may further contain a carbon-based negative electrode active material as the negative electrode active material. 【0131】 The carbon-based anode active material may be one or more selected from the group consisting of graphite such as natural graphite or artificial graphite, and carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes. When the carbon-based anode active material is included, the deterioration of the lifetime characteristics due to volume changes of the silicon-based anode active material during charging and discharging can be suppressed. 【0132】 If a carbon-based anode active material is further included, the silicon-based anode active material and the carbon-based anode active material may be included in a weight ratio of 1:99 to 30:70, 1.5:98.5 to 20:80, 2:98 to 15:85, or 2.5:97.5 to 10:90. When the above ranges are met, excellent capacity characteristics and excellent life characteristics can be achieved. 【0133】 The carbon-based anode active material may be included in the anode active material layer in amounts of 70% to 99% by weight, 75% to 99% by weight, or 80% to 98% by weight. When these ranges are met, sufficient capacity characteristics can be achieved and the battery life characteristics can be improved. 【0134】 On the other hand, the negative electrode active material layer may selectively further contain a negative electrode conductive material and a negative electrode binder in addition to the negative electrode active material. 【0135】 The negative electrode conductive material is used to impart conductivity to the electrode and can be used in the battery without particular limitations as long as it does not cause chemical changes and has electronic conductivity. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these can be used alone, or a mixture of two or more. The negative electrode conductive material may typically be included in an amount of 1 to 30% by weight, 1 to 20% by weight, or 1 to 10% by weight relative to the total weight of the negative electrode active material layer. 【0136】 The negative electrode binder plays a role in improving the adhesion between negative electrode active material particles and the adhesion between the negative electrode active material and the negative electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, of which one or more can be used individually or in mixtures of two or more. The negative electrode binder may be present in an amount of 1 to 30% by weight, 1 to 20% by weight, or 1 to 10% by weight relative to the total weight of the negative electrode active material layer. 【0137】 3) Separator Next, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move, and can be used without particular limitations as long as it is a separator that is commonly used in lithium secondary batteries. In this case, the separator can be interposed between the positive electrode and the negative electrode. 【0138】 Specifically, the separator can be a porous polymer film, for example, a porous polymer film made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof. Alternatively, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, a coated separator containing ceramic components or polymeric substances may be used to ensure heat resistance or mechanical strength. 【0139】 (2) Electrolyte The electrolyte according to the present invention comprises a lithium salt and an organic solvent. 【0140】 The lithium salt can be any compound capable of providing lithium ions for use in lithium secondary batteries, and is not particularly limited. Specifically, the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably within the range of 0.1 to 5.0 M or 0.1 to 3.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, exhibiting excellent electrolyte performance and allowing lithium ions to move effectively. 【0141】 The organic solvent may include at least one of the following: a cyclic carbonate organic solvent, a linear carbonate organic solvent, a linear ester organic solvent, and a cyclic ester organic solvent. 【0142】 The cyclic carbonate-based organic solvent is a highly viscous organic solvent and may typically include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate. 【0143】 Furthermore, the linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and as a typical example, at least one organic solvent selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate, and ethyl propyl carbonate may be used, and specifically, it may include ethyl methyl carbonate (EMC). 【0144】 Specific examples of the linear ester-based organic solvent include at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate. 【0145】 The cyclic ester organic solvents include at least one organic solvent selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone. 【0146】 Preferably, the electrolyte according to the present invention may contain ethylene carbonate and dimethyl carbonate as organic solvents. 【0147】 On the other hand, the electrolyte may also contain other additives in addition to the components of the electrolyte, for purposes such as improving the battery's lifespan, suppressing the decrease in battery capacity, and improving the battery's discharge capacity. 【0148】 Such other additives may include, as representative examples, at least one other additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds different from the lithium salt contained in the electrolyte. 【0149】 Specifically, the aforementioned other additives include vinylene carbonate (VC), vinylethylene carbonate, fluoroethylene carbonate (FEC), 1,3-propanesultone (PS), 1,4-butanesultone, ethensultone, 1,3-propensultone (PRS), 1,4-butensultone, 1-methyl-1,3-propensultone, ethylene sulfate (Esa), trimethylene sulfate (TMS), and methyl trimethylene sulfate. Examples include one or more compounds selected from the group consisting of sulfate (MTMS), tetraphenyl borate, lithium oxalyl difluoroborate, succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonile, cyclohexanecarbonile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, 4-fluorophenylacetonitrile, fluorobenzenetriethanolamine, ethylenediamine, tetravinylsilane, LiN(SO2F)2 (Lithium bis(fluorosulfonyl)imide, LIFSI), LiN(SO2CF3)2 (lithium bis(trifluoromethane sulfonyl)imide, LiTFSI), LiPO2F2, LiODFB, LiBOB (lithium bisoxalate borate (LiB(C2O4)2)), and LiBF4. 【0150】 The aforementioned other additives may be included in an amount of 0.01 to 20% by weight, or 0.05 to 5.0% by weight, based on the total weight of the electrolyte. When these ranges are met, high-temperature lifetime characteristics and low-temperature power characteristics can be improved, and side reactions in the electrolyte can be prevented. 【0151】 (3) Battery case The battery case is for housing the electrode assembly and electrolyte, and various battery cases known in the art, such as cylindrical battery cases, rectangular battery cases, pouch-type battery cases, etc., may be used. 【0152】 The lithium secondary battery according to the present invention can be usefully used in portable devices such as mobile phones, notebook computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs). 【0153】 Furthermore, a battery module or battery pack containing the lithium secondary battery as a unit cell can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); and power storage systems. 【0154】 The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for small devices, but also suitably as a unit battery in medium- and large-sized battery modules containing a large number of battery cells. 【0155】 Examples of the aforementioned medium- and large-sized devices include, but are not limited to, electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems. 【0156】 Method for manufacturing a positive electrode Next, a method for manufacturing a positive electrode according to the present invention will be described with reference to Figure 1. 【0157】 The method for manufacturing a positive electrode according to the present invention includes the steps of: mixing a first positive electrode active material in distilled water, performing a first water wash, and drying (S1); mixing a second positive electrode active material in distilled water, performing a second water wash, and drying (S2); and forming a positive electrode active material layer containing the first positive electrode active material and the second positive electrode active material (S3), wherein the first water wash is performed at a higher temperature than the second water wash, and the average particle size (D) of the first positive electrode active material is reduced. 50 ) is the average particle size (D) of the second positive electrode active material. 50 The first and second positive electrode active materials are larger than the above, and the interfacial resistance of the positive electrode with a SOC of 50% measured in a coin half cell manufactured using the positive electrode is 6.5Ω to 8.5Ω, and the interfacial resistance of the positive electrode with a SOC of 10% measured in a coin half cell manufactured using the positive electrode is 15Ω to 19Ω. 【0158】 The steps for manufacturing a positive electrode according to the present invention will be described in detail below with reference to Figure 1. 【0159】 (1) S1 step: First positive electrode active material washing step First, the first positive electrode active material is mixed with distilled water, washed once, and dried (step S1). 【0160】 The first positive electrode active material contains single-particle particles. 【0161】 Since the first positive electrode active material is as described above, a detailed explanation will be omitted. 【0162】 The S1 step adjusts the interfacial resistance of the positive electrode to a specific range by performing a water washing intensity of the first positive electrode active material higher than the water washing intensity of the second positive electrode active material in the S2 step described later. 【0163】 Specifically, the first rinse is performed at a higher temperature than the second rinse. 【0164】 The first rinse is performed at 20°C to 40°C, 25°C to 35°C, or 27°C to 38°C. When the first rinse is performed at these temperatures, the interfacial resistance of the positive electrode can be adjusted to the desired range. 【0165】 Furthermore, the first washing may be carried out by mixing the first positive electrode active material with distilled water in an amount of 50% to 70% by weight, 55% to 65% by weight, or 57% to 63% by weight based on the total weight of the distilled water. In this case, the amount of residual lithium on the surface of the positive electrode active material can be reduced, and deterioration of high-temperature durability can be prevented. 【0166】 The drying may be carried out at 60°C to 200°C, 70°C to 180°C, or 80°C to 160°C. 【0167】 (2) S2 step: Second positive electrode active material washing step Next, the second positive electrode active material is mixed with distilled water for a second wash and then dried (step S2). 【0168】 The second positive electrode active material includes single-particle particles. When the second positive electrode active material is single-particle particles, the large size of the single-particle particles results in a longer lithium diffusion distance and increased diffusion resistance, leading to low efficiency of the positive electrode. However, when a silicon-based negative electrode active material is applied, the efficiency of the positive electrode is balanced with that of the negative electrode. This solves the problem of lithium ion loss due to irreversible capacity when using conventional silicon-based negative electrode active materials, prevents or suppresses lithium deposition on the surface of the negative electrode, and improves the lifespan characteristics of lithium secondary batteries using the positive electrode according to the present invention. Furthermore, when a second positive electrode active material consisting of single-particle particles is applied, unlike when a sacrificial positive electrode material is used as in the past, the generation of lithium byproducts from the sacrificial positive electrode material during charging and discharging can be prevented or suppressed, resulting in excellent high-temperature storage characteristics and high-temperature lifespan characteristics. 【0169】 The average particle size (D) of the first positive electrode active material. 50 ) is the average particle size (D) of the second positive electrode active material. 50 It is larger than ). 【0170】 Since the second positive electrode active material is as described above, a detailed explanation will be omitted. 【0171】 The S2 step prevents deterioration of the high-temperature durability of the second positive electrode active material and adjusts the interfacial resistance of the positive electrode to a specific range by applying a lower water washing intensity to the second positive electrode active material, which has a smaller particle size and a larger specific surface area than the first positive electrode active material, than to the first positive electrode active material. 【0172】 The second washing may be performed on the second positive electrode active material at a temperature of 3°C to 18°C, 5°C to 15°C, or 7°C to 13°C. When the second washing is performed within these ranges, the interfacial resistance of the positive electrode can be adjusted to the desired range, and deterioration of high-temperature durability can be prevented. 【0173】 Furthermore, the second washing may be carried out by mixing the second positive electrode active material with distilled water in an amount of 65% to 85% by weight, 70% to 80% by weight, or 72% to 78% by weight, based on the total weight of the distilled water. In this case, the residual lithium on the surface of the positive electrode active material can be reduced, and deterioration of high-temperature durability can be prevented. 【0174】 The drying may be carried out at 60°C to 200°C, 70°C to 180°C, or 80°C to 160°C. 【0175】 (3) Step S3: Step to form positive electrode active material layer Next, a step (S3 step) is performed to form a positive electrode active material layer containing the first positive electrode active material and the second positive electrode active material. 【0176】 First, the first positive electrode active material, the second positive electrode active material, and the solvent can be mixed to produce a positive electrode slurry. 【0177】 In this case, since the first positive electrode active material and the second positive electrode active material are as described above, a detailed explanation will be omitted. 【0178】 The positive electrode slurry may further selectively contain a positive electrode binder and / or a positive electrode conductive material. 【0179】 Since the positive electrode binder and positive electrode conductive material are as described above, a detailed explanation will be omitted. 【0180】 On the other hand, the solvent used in the positive electrode slurry may be an aqueous solvent, an organic solvent, or a combination thereof. 【0181】 The aqueous solvent may, for example, include water, and the organic solvent may contain one or more selected from the group consisting of N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dihydrolevoglucosenone (Cyrene), γ-valerolactone, dimethyl isosorbide (DMI), and methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate, and preferably contains N-methylpyrrolidone. 【0182】 Next, the positive electrode slurry can be applied to the positive electrode current collector and dried to form a positive electrode active material layer. Specifically, the positive electrode can be manufactured by applying the positive electrode slurry to one or both sides of the positive electrode current collector, then drying and rolling it to form a positive electrode active material layer. 【0183】 As the positive electrode current collector is as described above, a detailed explanation will be omitted. 【0184】 On the other hand, the coating may be carried out continuously or discontinuously using various coating methods known in the art, such as slot die coating, slide coating, curtain coating, etc. 【0185】 The drying may be carried out at 40°C to 180°C, 60°C to 160°C, or 70°C to 150°C. 【0186】 The rolling may be carried out by a roll press method in which the thickness of the positive electrode is adjusted by adjusting the upper / lower distance of the rolls, but is not limited to this method. 【0187】 On the other hand, in a coin half cell manufactured using the above positive electrode, the interface resistance of the positive electrode at SOC 50% is 6.5Ω to 8.5Ω. Specifically, the positive electrode in a coin half cell may have an interface resistance of 6.5Ω or more, 6.7Ω or more, 6.9Ω or more, 7.0Ω or more, or 7.2Ω or more at SOC 50%, and may be 8.5Ω or less, 8.3Ω or less, 8.1Ω or less, 8.0Ω or less, 7.8Ω or less, 7.6Ω or less, or 7.4Ω or less. For example, the positive electrode in a coin half cell may have an interface resistance of 6.5Ω to 8.5Ω, 6.7Ω to 8.0Ω, or 6.9Ω to 7.4Ω at SOC 50%. By keeping the interface resistance of the positive electrode at SOC 50% within the above range, the overall resistance of the battery does not increase, thus preventing the problem of increased initial resistance during charging and discharging, and thereby improving the battery's lifespan characteristics. 【0188】 Furthermore, the interface resistance of the positive electrode at SOC 10% measured in a coin half cell manufactured using the positive electrode is 15Ω to 19Ω. Specifically, the positive electrode may have an interface resistance of 15Ω or more, 15.2Ω or more, 15.4Ω or more, 15.6Ω or more, 15.8Ω or more, 16Ω or more, 16.2Ω or more, 16.4Ω or more, 16.6Ω or more, 16.8Ω or more, 17Ω or more, 17.2Ω or more, or 17.4Ω or more in a coin half cell, and may be 19Ω or less, 18.8Ω or less, 18.6Ω or less, 18.4Ω or less, 18.2Ω or less, 18Ω or less, 17.8Ω or less, or 17.6Ω or less. For example, the positive electrode may have an interfacial resistance of 15Ω to 19Ω, 15.2Ω to 18Ω, 16Ω to 17.8Ω, or 17Ω to 17.6Ω at 10% SOC in a coin half-cell. When the above range is met, the resistance difference between the positive and negative electrodes at the discharge end can be reduced, and the phenomenon of lithium ions being deposited on the surface of the negative electrode can be suppressed, thereby suppressing the degradation of the negative electrode. This solves the problem of reduced battery cycle characteristics and prevents the problem of increased initial resistance during charging and discharging, thereby improving the battery's lifespan characteristics. 【0189】 As the manufactured positive electrode is as described above, a detailed explanation will be omitted. 【0190】 Hereinafter, embodiments of the present invention will be described in detail so that those with ordinary skill in the art to which the present invention pertains can easily implement it. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein. 【0191】 Example 1 <Manufacturing of the first positive electrode active material> Transition metal aqueous solutions were prepared by mixing NiSO4, CoSO4, and MnSO4 in distilled water in amounts such that the molar ratio of nickel, cobalt, and manganese was 83:7:10. 【0192】 Next, after adding deionized water to the reactor, nitrogen gas is purged into the reactor to remove dissolved oxygen from the water, creating a non-oxidizing atmosphere inside the reactor. Then, the coprecipitation reaction proceeds while adding NaOH, and the average particle size (D50 ) is 8.6 μm, and Ni 0.83 Co 0.07 Mn 0.1 A precursor represented by (OH)2 was produced. 【0193】 The precursor and LiOH were mixed at a ratio of 1:1.05, Al was mixed as a doping element, and by firing at 910 °C for 16 hours, Li[Ni 0.81 Co 0.07 Mn 0.10 Al 0.02 O2 was produced as the first lithium transition metal oxide. 【0194】 Thereafter, the first lithium transition metal oxide was mixed in distilled water at 30 °C so that the solid content was 60% by weight, washed with water, dried, and then Co(OH)2 was mixed. Thereafter, heat treatment was performed at 750 °C for 5 hours to produce a first positive electrode active material coated with Co. The first positive electrode active material contains 3 mol% of Co, and the average particle diameter (D 50 ) was 8.6 μm, and it was confirmed that it was single-particle-shaped particles. 【0195】 <Production of the second positive electrode active material> NiSO4, CoSO4, and MnSO4 were mixed in distilled water in amounts such that the molar ratio of nickel, cobalt, and manganese was 83:7:10 to prepare an aqueous transition metal solution. 【0196】 Next, after putting deionized water into the reactor, nitrogen gas was purged into the reactor to remove dissolved oxygen in the water, and after making the inside of the reactor a non-oxidizing atmosphere, NaOH was added while proceeding with the coprecipitation reaction, and the average particle diameter (D 50 ) was 3.1 μm, and Ni 0.83 Co 0.07 Mn​​​​​​​​​​​Al 0.02 A lithium-2 transition metal oxide represented by ]O2 was produced. 【0198】 Subsequently, the second lithium transition metal oxide was mixed in distilled water at 10°C to a solid content of 75% by weight, washed with water, dried, and then mixed with Co(OH)2. Afterward, it was heat-treated at 750°C for 5 hours to produce a second positive electrode active material coated with Co. The second positive electrode active material contained 1 mol% Co and had an average particle size (D 50 The particle size was 3.1 μm, confirming that it was a single-particle type particle. 【0199】 <Manufacturing of positive electrodes> A positive electrode material was manufactured by mixing the first positive electrode active material and the second positive electrode active material produced above in a weight ratio of 60:40. A positive electrode slurry was manufactured by mixing the positive electrode material, carbon black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone solvent in a weight ratio of 96:2:2. The positive electrode slurry was applied to one surface of an aluminum current collector with a thickness of 20 μm, dried at 130°C, and then rolled to manufacture a positive electrode with a thickness of 70 μm. 【0200】 Example 2 <Manufacturing of the first positive electrode active material> Transition metal aqueous solutions were prepared by mixing NiSO4, CoSO4, and MnSO4 in distilled water in amounts such that the molar ratio of nickel, cobalt, and manganese was 83:7:10. 【0201】 Next, after adding deionized water to the reactor, nitrogen gas is purged into the reactor to remove dissolved oxygen from the water, creating a non-oxidizing atmosphere inside the reactor. Then, the coprecipitation reaction proceeds while adding NaOH, and the average particle size (D 50 ) is 8.4 μm, Ni 0.83 Co 0.07 Mn 0.1 A precursor represented by (OH)2 was prepared. 【0202】 The aforementioned precursor and LiOH are mixed in a ratio of 1:1.05, Al is added as a doping element, and the mixture is calcined at 910°C for 16 hours to obtain Li[Ni 0.81 Co 0.07 Mn 0.10 Al 0.02 We produced a lithium first transition metal oxide represented by ]O2. 【0203】 Subsequently, the first lithium transition metal oxide was mixed in distilled water at 25°C to a solid content of 60% by weight, washed with water, dried, and then mixed with Co(OH)2. Afterward, it was heat-treated at 750°C for 5 hours to produce a first positive electrode active material coated with Co. The first positive electrode active material contained 3 mol% Co and had an average particle size (D 50 The particle size was 8.4 μm, confirming that it was a single-particle type particle. 【0204】 <Manufacturing of the second positive electrode active material> Transition metal aqueous solutions were prepared by mixing NiSO4, CoSO4, and MnSO4 in distilled water in amounts such that the molar ratio of nickel, cobalt, and manganese was 83:7:10. 【0205】 Next, after adding deionized water to the reactor, nitrogen gas is purged into the reactor to remove dissolved oxygen from the water, creating a non-oxidizing atmosphere inside the reactor. Then, the coprecipitation reaction proceeds while adding NaOH, and the average particle size (D 50 ) is 3.3 μm, Ni 0.83 Co 0.07 Mn 0.1 A precursor represented by (OH)2 was prepared. 【0206】 The aforementioned precursor and LiOH are mixed in a ratio of 1:1.05, Al is added as a doping element, and the mixture is calcined at 910°C for 16 hours to obtain Li[Ni 0.81 Co 0.07 Mn 0.10 Al 0.02 A lithium-2 transition metal oxide represented by ]O2 was produced. 【0207】 Subsequently, the second lithium transition metal oxide was mixed in distilled water at 15°C to a solid content of 75% by weight, washed with water, dried, and then mixed with Co(OH)2. Afterward, it was heat-treated at 750°C for 5 hours to produce a second positive electrode active material coated with Co. The second positive electrode active material contained 1 mol% Co and had an average particle size (D 50 The particle size was 3.3 μm, confirming that it was a single-particle type particle. 【0208】 <Manufacturing of positive electrodes> The positive electrode was manufactured in the same manner as in Example 1, except that the first positive electrode active material and the second positive electrode active material manufactured as described above were used. 【0209】 Example 3 <Manufacturing of the first positive electrode active material> Transition metal aqueous solutions were prepared by mixing NiSO4, CoSO4, and MnSO4 in distilled water in amounts such that the molar ratio of nickel, cobalt, and manganese was 83:7:10. 【0210】 Next, after adding deionized water to the reactor, nitrogen gas is purged into the reactor to remove dissolved oxygen from the water, creating a non-oxidizing atmosphere inside the reactor. Then, the coprecipitation reaction proceeds while adding NaOH, and the average particle size (D 50 ) is 8.1 μm, Ni 0.83 Co 0.07 Mn 0.1 A precursor represented by (OH)2 was prepared. 【0211】 The aforementioned precursor and LiOH are mixed in a ratio of 1:1.05, Al is added as a doping element, and the mixture is calcined at 910°C for 16 hours to obtain Li[Ni 0.81 Co 0.07 Mn 0.10 Al 0.02 We produced a lithium first transition metal oxide represented by ]O2. 【0212】 Subsequently, the first lithium transition metal oxide was mixed in distilled water at 30°C to a solid content of 60% by weight, washed with water, dried, and then mixed with Co(OH)2. Afterward, it was heat-treated at 750°C for 5 hours to produce a first positive electrode active material coated with Co. The first positive electrode active material contained 2.5 mol% Co and had an average particle size (D 50 The particle size was 8.1 μm, confirming that it was a single-particle type particle. 【0213】 <Manufacturing of the second positive electrode active material> Transition metal aqueous solutions were prepared by mixing NiSO4, CoSO4, and MnSO4 in distilled water in amounts such that the molar ratio of nickel, cobalt, and manganese was 83:7:10. 【0214】 Next, after adding deionized water to the reactor, nitrogen gas is purged into the reactor to remove dissolved oxygen from the water, creating a non-oxidizing atmosphere inside the reactor. Then, the coprecipitation reaction proceeds while adding NaOH, and the average particle size (D 50 ) is 3.5 μm, Ni 0.83 Co 0.07 Mn 0.1 A precursor represented by (OH)2 was prepared. 【0215】 The aforementioned precursor and LiOH are mixed in a ratio of 1:1.05, Al is added as a doping element, and the mixture is calcined at 910°C for 16 hours to obtain Li[Ni 0.81 Co 0.07 Mn 0.10 Al 0.02 A lithium-2 transition metal oxide represented by ]O2 was produced. 【0216】 Subsequently, the second lithium transition metal oxide was mixed in distilled water at 10°C to a solid content of 75% by weight, washed with water, dried, and then mixed with Co(OH)2. Afterward, it was heat-treated at 750°C for 5 hours to produce a second positive electrode active material coated with Co. The second positive electrode active material contained 1.5 mol% Co and had an average particle size (D 50 The particle size was 3.5 μm, confirming that it was a single-particle type particle. 【0217】 <Manufacture of the positive electrode> A positive electrode was manufactured in the same manner as in Example 1, except that the first positive electrode active material and the second positive electrode active material manufactured above were used. 【0218】 Comparative Example 1 <Manufacture of the first positive electrode active material> NiSO4, CoSO4, and MnSO4 were mixed in distilled water in amounts such that the molar ratio of nickel, cobalt, and manganese was 83:7:10 to prepare an aqueous transition metal solution. 【0219】 Next, after deionized water was put into the reactor, nitrogen gas was purged into the reactor to remove dissolved oxygen in the water, and the inside of the reactor was made into a non-oxidizing atmosphere. Then, while adding NaOH, a coprecipitation reaction was allowed to proceed, and the average particle size (D 50 ) was 7.2 μm, and Ni 0.83 Co 0.07 Mn 0.1 A precursor represented by (OH)2 was manufactured. 【0220】 [[ID=2 June 26]]The precursor and LiOH were mixed at a ratio of 1:1.05, Al was mixed as a doping element, and by firing at 910 °C for 16 hours, Li[Ni 0.81 Co 0.07 Mn 0.10 Al 0.02 O2, a first lithium transition metal oxide was manufactured. 【0221】 Thereafter, the first lithium transition metal oxide was mixed in distilled water at 10 °C so that the solid content was 75% by weight, washed with water, dried, and then Co(OH)2 was mixed. Thereafter, heat treatment was performed at 750 °C for 5 hours to manufacture a first positive electrode active material coated with Co. The first positive electrode active material contains 3 mol% of Co, and the average particle size (D 50 ) was 7.2 μm, and it was confirmed that it was single-particle-shaped particles. 【0222】 <Manufacture of the second positive electrode active material> Transition metal aqueous solutions were prepared by mixing NiSO4, CoSO4, and MnSO4 in distilled water in amounts such that the molar ratio of nickel, cobalt, and manganese was 83:7:10. 【0223】 Next, after adding deionized water to the reactor, nitrogen gas is purged into the reactor to remove dissolved oxygen from the water, creating a non-oxidizing atmosphere inside the reactor. Then, the coprecipitation reaction proceeds while adding NaOH, and the average particle size (D 50 ) is 2.5 μm, Ni 0.83 Co 0.07 Mn 0.1 A precursor represented by (OH)2 was prepared. 【0224】 The aforementioned precursor and LiOH are mixed in a ratio of 1:1.05, Al is added as a doping element, and the mixture is calcined at 910°C for 16 hours to obtain Li[Ni 0.81 Co 0.07 Mn 0.10 Al 0.02 A lithium-2 transition metal oxide represented by ]O2 was produced. 【0225】 Subsequently, the second lithium transition metal oxide was mixed in distilled water at 10°C to a solid content of 75% by weight, washed with water, dried, and then mixed with Co(OH)2. Afterward, it was heat-treated at 750°C for 5 hours to produce a second positive electrode active material coated with Co. The second positive electrode active material contained 1 mol% Co and had an average particle size (D 50 The particle size was 2.5 μm, confirming that it was a single-particle type particle. 【0226】 <Manufacturing of positive electrodes> The positive electrode was manufactured in the same manner as in Example 1, except that the first positive electrode active material and the second positive electrode active material manufactured as described above were used. 【0227】 Comparative Example 2 <Manufacturing of the first positive electrode active material> Transition metal aqueous solutions were prepared by mixing NiSO4, CoSO4, and MnSO4 in distilled water in amounts such that the molar ratio of nickel, cobalt, and manganese was 83:7:10. 【0228】 Next, after adding deionized water to the reactor, nitrogen gas is purged into the reactor to remove dissolved oxygen from the water, creating a non-oxidizing atmosphere inside the reactor. Then, the coprecipitation reaction proceeds while adding NaOH, and the average particle size (D 50 ) is 7.7 μm, Ni 0.83 Co 0.07 Mn 0.1 A precursor represented by (OH)2 was prepared. 【0229】 The aforementioned precursor and LiOH are mixed in a ratio of 1:1.05, Al is added as a doping element, and the mixture is calcined at 910°C for 16 hours to obtain Li[Ni 0.81 Co 0.07 Mn 0.10 Al 0.02 We produced a lithium first transition metal oxide represented by ]O2. 【0230】 Subsequently, the first lithium transition metal oxide was mixed in distilled water at 30°C to a solid content of 60% by weight, washed with water, dried, and then mixed with Co(OH)2. Afterward, it was heat-treated at 750°C for 5 hours to produce a first positive electrode active material coated with Co. The first positive electrode active material contained 1 mol% Co and had an average particle size (D 50 The particle size was 7.7 μm, confirming that it was a single-particle type particle. 【0231】 <Manufacturing of the second positive electrode active material> Transition metal aqueous solutions were prepared by mixing NiSO4, CoSO4, and MnSO4 in distilled water in amounts such that the molar ratio of nickel, cobalt, and manganese was 83:7:10. 【0232】 Next, after adding deionized water to the reactor, nitrogen gas is purged into the reactor to remove dissolved oxygen from the water, creating a non-oxidizing atmosphere inside the reactor. Then, the coprecipitation reaction proceeds while adding NaOH, and the average particle size (D 50 ) is 2.9 μm, Ni 0.83 Co 0.07 Mn 0.1 A precursor represented by (OH)2 was prepared. 【0233】 The precursor and LiOH are mixed at a ratio of 1:1.05, Al is mixed as a doping element, and they are calcined at 910 °C for 16 hours to obtain Li[Ni 0.81 Co 0.07 Mn 0.10 Al 0.02 O2, a second lithium transition metal oxide. 【0234】 Thereafter, the second lithium transition metal oxide is mixed in distilled water at 10 °C so that the solid content is 70% by weight, washed with water, dried, and then Co(OH)2 is mixed. Thereafter, it is heat-treated at 750 °C for 5 hours to produce a second positive electrode active material coated with Co. The second positive electrode active material contains 1 mol% of Co, and the average particle size (D 50 ) is 2.9 μm, and it was confirmed that it is single-particle-shaped particles. 【0235】 <Manufacture of positive electrode> A positive electrode was manufactured in the same manner as in Example 1, except that the first positive electrode active material and the second positive electrode active material manufactured above were used. 【0236】 Comparative Example 3 <Manufacture of first positive electrode active material> NiSO4, CoSO4, and MnSO4 are mixed in distilled water in amounts such that the molar ratio of nickel, cobalt, and manganese is 83:7:10 to prepare an aqueous transition metal solution. 【0237】 Next, after putting deionized water into the reactor, nitrogen gas is purged into the reactor to remove dissolved oxygen in the water, and after making the inside of the reactor a non-oxidizing atmosphere, NaOH is added while proceeding with the coprecipitation reaction, and the average particle size (D 50 ) is 8.5 μm, and a precursor represented by Ni 0.83 Co 0.07 Mn 0.1 (OH)2 was manufactured. 【0238】 The precursor and LiOH are mixed at a ratio of 1:1.05, Al is mixed as a doping element, and they are calcined at 910 °C for 16 hours to obtain Li[Ni 0.81 Co0.07 Mn 0.10 Al 0.02 We produced a lithium first transition metal oxide represented by ]O2. 【0239】 Subsequently, the first lithium transition metal oxide was mixed in distilled water at 10°C to a solid content of 75% by weight, washed with water, dried, and then mixed with Co(OH)2. Afterward, it was heat-treated at 750°C for 5 hours to produce a first positive electrode active material coated with Co. The first positive electrode active material contained 3 mol% Co and had an average particle size (D 50 The particle size was 8.5 μm, confirming that it was a single-particle type particle. 【0240】 <Manufacturing of the second positive electrode active material> Transition metal aqueous solutions were prepared by mixing NiSO4, CoSO4, and MnSO4 in distilled water in amounts such that the molar ratio of nickel, cobalt, and manganese was 83:7:10. 【0241】 Next, after adding deionized water to the reactor, nitrogen gas is purged into the reactor to remove dissolved oxygen from the water, creating a non-oxidizing atmosphere inside the reactor. Then, the coprecipitation reaction proceeds while adding NaOH, and the average particle size (D 50 ) is 3.0 μm, Ni 0.83 Co 0.07 Mn 0.1 A precursor represented by (OH)2 was prepared. 【0242】 The aforementioned precursor and LiOH are mixed in a ratio of 1:1.05, Al is added as a doping element, and the mixture is calcined at 910°C for 16 hours to obtain Li[Ni 0.81 Co 0.07 Mn 0.10 Al 0.02 A lithium-2 transition metal oxide represented by ]O2 was produced. 【0243】 Subsequently, the second lithium transition metal oxide was mixed in distilled water at 10°C to a solid content of 70% by weight, washed with water, dried, and then mixed with Co(OH)2. Afterward, it was heat-treated at 750°C for 5 hours to produce a second positive electrode active material coated with Co. The second positive electrode active material contained 1 mol% Co and had an average particle size (D 50 The particle size was 3.0 μm, confirming that it was a single-particle type particle. 【0244】 <Manufacturing of positive electrodes> The positive electrode was manufactured in the same manner as in Example 1, except that the first positive electrode active material and the second positive electrode active material manufactured as described above were used. 【0245】 Experimental Example 1 - Measurement of positive electrode interface resistance and evaluation of IRR value In each of the above-mentioned Examples 1-3 and Comparative Examples 1-3, a porous polyethylene separator was interposed between the positive electrode and the lithium metal negative electrode to produce an electrode assembly. This assembly was then placed inside a battery case, and an electrolyte was injected into the case to produce a coin half cell. In this case, the electrolyte used was a mixed organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7, to which 1.0 M LiPF6 was dissolved. 【0246】 Next, each coin half-cell manufactured as described above was charged at 25°C under the conditions of CC / CV, 0.1C, 4.2V, and 0.05C cutoff, and discharged to CC, 0.1C, 3.0V. This constituted one cycle, and two cycles were performed. After that, the cells were charged to 0.1C to 50% and 10% SOC, and then the positive electrode interface resistance of each coin half-cell at 50% and 10% SOC was measured using a Biologic VMP3 device (100kHz~10mHz range, 25°C conditions). The measurement results are shown in Table 1 below. 【0247】 Furthermore, the IRR values ​​defined by the following formula 1 were calculated using the positive electrode interface resistances at SOC 50% and SOC 10% of coin half-cells manufactured using the positive electrodes of Examples 1-3 and Comparative Examples 1-3 as measured above. The calculated IRR values ​​are shown in Table 1 below. 【0248】 [Formula 1] IRR=R CT50 ×R CT10 【0249】 In formula 1, the R CT50 This is the dimensionless number of the interfacial resistance (unit: Ω) of the positive electrode with SOC 50% measured in a coin half cell manufactured using the aforementioned positive electrode, and R CT10 This is the dimensionless number of the interfacial resistance (unit: Ω) of the positive electrode with a SOC of 10%, measured in a coin half-cell manufactured using the aforementioned positive electrode. 【0250】 [Table 1] 【0251】 Referring to Table 1 above, it can be seen that, as in Examples 1, 2, and 3, the interface resistance of a positive electrode with a 50% SOC measured in a coin half cell manufactured using the positive electrode of the present invention is 6.5Ω to 8.5Ω, and the interface resistance of a positive electrode with a 10% SOC measured in a coin half cell manufactured using the positive electrode is 15Ω to 19Ω. Furthermore, it can be seen that the IRR value is in the range of 96 or higher and 166 or lower. 【0252】 Experimental Example 2 - Evaluation of Initial Resistance A negative electrode slurry was prepared by mixing SiO and artificial graphite in a weight ratio of 5:95 as the negative electrode active material, carbon black as the conductive material, SBR as the binder, and CMC as the thickener in a weight ratio of 95.6:1.0:2.3:1.1 in distilled water. The negative electrode slurry was applied to one surface of a 12 μm thick copper current collector, dried at 130°C, and then rolled to produce a negative electrode (solid content of slurry: 50% by weight based on the total weight of the negative electrode slurry). 【0253】 In Examples 1-3 and Comparative Example 2, electrode assemblies were manufactured by interposing porous polyethylene separators between the positive and negative electrodes of each assembly. These assemblies were then placed inside a battery case, and an electrolyte was injected to produce a lithium secondary battery. The electrolyte used was an organic solvent mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7, to which 1.0 M LiPF6 was dissolved. 【0254】 Each lithium secondary battery manufactured as described above was charged at 25°C in CC / CV mode to 4.2V at 0.1C, and the discharge resistance (HPPC) was measured at 50% SOC and 10% SOC while discharging with a constant current of 0.1C. The results are shown in Table 2. 【0255】 [Table 2] 【0256】 Referring to Table 2 above, it can be confirmed that the lithium secondary batteries manufactured using the positive electrodes produced in Examples 1 to 3 have lower discharge resistance at SOC 50% and SOC 10% compared to the lithium secondary batteries manufactured using the positive electrode produced in Comparative Example 2. 【0257】 Experimental Example 3 - Evaluation of High-Temperature Lifetime Characteristics Lithium secondary batteries containing the positive electrodes of Examples 1-3 and Comparative Examples 1-3, manufactured in Experimental Example 2, were charged to 4.2V at 45°C under CC / CV, 0.5C conditions with a 0.05C cutoff condition, and then discharged to 3.0V under CC, 1.0C conditions. One cycle of this process was defined as 100 charge-discharge cycles. 【0258】 (1) Capacity maintenance rate The capacity retention rate was calculated using the following formula, and the results are shown in Table 3 below. 【0259】 Capacity retention rate (%) = {(Discharge capacity after 100 cycles / Discharge capacity after 1 cycle)} × 100 【0260】 (2) Resistance increase rate After one charge-discharge cycle, the discharge capacity after one cycle was measured using an electrochemical charger. After adjusting the SOC to 50%, a 2.5C pulse was applied for 10 seconds, and the initial resistance was calculated from the difference between the voltage before and after pulse application. 【0261】 After 100 charge-discharge cycles, the resistance after 100 cycles was calculated using the same method as described above, and the resistance increase rate was calculated using the following formula. The results are shown in Table 3 below. 【0262】 Resistance increase rate (%) = (Resistance after 100 cycles - Initial resistance) / Initial resistance × 100 【0263】 [Table 3] 【0264】 Referring to Table 3 above, it can be confirmed that the lithium secondary batteries manufactured using the positive electrodes produced in Examples 1 to 3 have a higher capacity retention rate and a lower resistance increase rate at 45°C compared to the lithium secondary batteries manufactured using the positive electrodes produced in Comparative Examples 1 to 3. From this, it can be seen that the lithium secondary batteries manufactured using the positive electrodes produced in Examples 1 to 3 have excellent high-temperature life characteristics. 【0265】 Although preferred embodiments of the present invention have been described above with reference to the present invention, it will be understood that those skilled in the art, or those with ordinary knowledge in the art, can modify and change the present invention in various ways without departing from the spirit and technical scope of the invention as set forth in the appended claims. Therefore, the technical scope of the present invention is not limited to what is described in the detailed description of the specification, but is determined solely by the claims.

Claims

[Claim 1] A positive electrode comprising a positive electrode active material layer containing a first positive electrode active material and a second positive electrode active material having different average particle sizes, The average particle size (D) of the first positive electrode active material ５０ ) is the average particle size (D) of the second positive electrode active material. ５０ Larger than ) The first positive electrode active material and the second positive electrode active material contain single-particle particles. A positive electrode having an interface resistance of 6.5Ω to 8.5Ω for a positive electrode with 50% SOC measured in a coin half cell manufactured using the aforementioned positive electrode, and an interface resistance of 15Ω to 19Ω for a positive electrode with 10% SOC measured in a coin half cell manufactured using the aforementioned positive electrode. [Claim 2] The first positive electrode active material includes a first lithium transition metal oxide represented by the following chemical formula 1, [Chemical formula 1] Li １＋ａ１ Ni ｘ１ Co ｙ１ Mn ｚ１ Al ｗ１ M １ ｖ１ O ２ In the aforementioned chemical formula 1, 0 ≤ a1 ≤ 0.3, 0.82 ≤ x1 < 1.0, 0 < y1 ≤ 0.2, 0 < z1 ≤ 0.2, 0 < w1 ≤ 0.2, 0 ≤ v1 ≤ 0.1, M １ The positive electrode according to claim 1, wherein is one or more doping elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. [Claim 3] The second positive electrode active material comprises a second lithium transition metal oxide represented by the following chemical formula 2, [Chemical formula 2] Li １＋ａ２ Ni ｘ２ Co ｙ２ Mn ｚ２ Al ｗ２ M ２ ｖ２ O ２ In the aforementioned chemical formula 2, 0 ≤ a² ≤ 0.3, 0.82 ≤ x² < 1.0, 0 < y² ≤ 0.2, 0 < z² ≤ 0.2, 0 < w² ≤ 0.2, 0 ≤ v² ≤ 0.1, M ２ The positive electrode according to claim 1, wherein is one or more doping elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, In, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. [Claim 4] The average particle size (D) of the first positive electrode active material ５０ The positive electrode according to claim 1, wherein the thickness is 6 μm to 12 μm. [Claim 5] The average particle size (D) of the second positive electrode active material ５０ The positive electrode according to claim 1, wherein the diameter is 1.5 μm to 5 μm. [Claim 6] The positive electrode according to claim 1, wherein the first positive electrode active material comprises a first lithium transition metal oxide and a first coating layer located on the surface of the particles of the first lithium transition metal oxide and containing 1.5 mol% to 5 mol% cobalt (Co). [Claim 7] The positive electrode according to claim 1, wherein the second positive electrode active material comprises a second lithium transition metal oxide and a second coating layer located on the surface of the particles of the second lithium transition metal oxide and containing 0.2 mol% to 2.5 mol% cobalt (Co). [Claim 8] The positive electrode according to claim 1, wherein the first positive electrode active material and the second positive electrode active material are contained in a weight ratio of 80:20 to 40:

60. [Claim 9] A positive electrode comprising a positive electrode active material layer containing a first positive electrode active material and a second positive electrode active material having different average particle sizes, The average particle size (D) of the first positive electrode active material ５０ ) is the average particle size (D) of the second positive electrode active material. ５０ Larger than ) The first positive electrode active material and the second positive electrode active material contain single-particle form particles. The IRR value defined by the following formula 1 is between 96 and 166. [Formula 1] IRR=R ＣＴ５０ ×R ＣＴ１０ In the above formula 1, The aforementioned R ＣＴ５０ This is the dimensionless number of the interfacial resistance (unit: Ω) of the positive electrode with SOC 50% measured in a coin half cell manufactured using the aforementioned positive electrode. The aforementioned R ＣＴ１０ This is the dimensionless number of the interfacial resistance (unit: Ω) of a positive electrode with a SOC of 10%, measured in a coin half-cell manufactured using the aforementioned positive electrode. [Claim 10] An electrode assembly including a positive electrode and a negative electrode as described in any one of claims 1 to 9, an electrolyte, and a battery case in which the electrode assembly and the electrolyte are housed, The aforementioned negative electrode is a lithium secondary battery containing a silicon-based negative electrode active material. [Claim 11] The aforementioned negative electrode contains a carbon-based negative electrode active material. The lithium secondary battery according to claim 10, wherein the silicon-based anode active material and the carbon-based anode active material are contained in a weight ratio of 1:99 to 30:

70. [Claim 12] Step (S1) involves mixing the first positive electrode active material in distilled water, performing a first wash, and drying it. Step (S2) involves mixing the second positive electrode active material in distilled water, performing a second water wash, and drying it. A method for manufacturing a positive electrode, comprising the step (S3) of forming a positive electrode active material layer containing the first positive electrode active material and the second positive electrode active material, The first rinse is performed at a higher temperature than the second rinse. The average particle size (D) of the first positive electrode active material ５０ ) is the average particle size (D) of the second positive electrode active material. ５０ Larger than ) The first positive electrode active material and the second positive electrode active material contain single-particle form particles. A method for manufacturing a positive electrode, wherein the interface resistance of a positive electrode with 50% SOC measured using the positive electrode is 6.5Ω to 8.5Ω, and the interface resistance of a positive electrode with 10% SOC measured using the positive electrode is 15Ω to 19Ω. [Claim 13] The method for manufacturing a positive electrode according to claim 12, wherein the first washing is performed at 20°C to 40°C. [Claim 14] The method for manufacturing a positive electrode according to claim 12, wherein the second washing is performed at 3°C ​​to 18°C. [Claim 15] The method for producing a positive electrode according to claim 12, wherein the first washing is carried out by mixing the first positive electrode active material with distilled water in an amount of 50% to 70% by weight based on the total weight of the water. [Claim 16] The method for producing a positive electrode according to claim 12, wherein the second washing is carried out by mixing the second positive electrode active material with the total weight of distilled water in an amount of 65% to 85% by weight. [Claim 17] The first positive electrode active material includes a first lithium transition metal oxide represented by the following chemical formula 1, [Chemical formula 1] Li １＋ａ１ Ni ｘ１ Co ｙ１ Mn ｚ１ Al ｗ１ M １ ｖ１ O ２ In the aforementioned chemical formula 1, 0 ≤ a1 ≤ 0.3, 0.82 ≤ x1 < 1.0, 0 < y1 < 0.18, 0 < z1 < 0.18, 0 < w1 < 0.2, 0 ≤ v1 ≤ 0.1, M １ The method for producing a positive electrode according to claim 12, wherein is one or more doping elements selected from the group consisting of W, Mo, Cr, Zr, Ti, Mg, Ta, and Nb. [Claim 18] The second positive electrode active material comprises a second lithium transition metal oxide represented by the following chemical formula 2, [Chemical formula 2] Li １＋ａ２ Ni ｘ２ Co ｙ２ Mn ｚ２ Al ｗ２ M ２ ｖ２ O ２ In the aforementioned chemical formula 2, 0 ≤ a² ≤ 0.3, 0.82 ≤ x² < 1.0, 0 < y² < 0.18, 0 < z² < 0.18, 0 < w² < 0.2, 0 ≤ v² ≤ 0.1, M ２ The method for producing a positive electrode according to claim 12, wherein is one or more doping elements selected from the group consisting of W, Mo, Cr, Zr, Ti, Mg, Ta, and Nb. [Claim 19] The first positive electrode active material comprises a first lithium transition metal oxide and includes a first coating layer containing cobalt (Co) on the surface of the particles of the first lithium transition metal oxide. The second positive electrode active material comprises a second lithium transition metal oxide and includes a second coating layer containing cobalt (Co) on the surface of the particles of the second lithium transition metal oxide. The method for manufacturing a positive electrode according to claim 12, wherein the amount of cobalt (Co) contained in the first coating layer is greater than the amount of cobalt (Co) contained in the second coating layer. [Claim 20] A method for producing a positive electrode according to claim 19, wherein the amount of cobalt (Co) in the first coating layer is 1.5 mol% to 5 mol%, and the amount of cobalt (Co) in the second coating layer is 0.2 mol% to 2.5 mol%.

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