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

Abstract

Provided are a cathode active material and a method for producing the same, which improve capacity and lifespan while minimizing structural damage and degradation due to washing. 【Solution means】The cathode active material includes core particles containing a lithium nickel-based composite oxide represented by the following formula, and a coating layer containing one or more elements of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr on the surface of the particles. Li a11 Ni x11 M 11 y11 M 12 z11 O 2-b11 X b11 (0.9 ≦ a11 ≦ 1.2, 0.3 ≦ x11 < 1, 0 < y11 ≦ 0.7, 0 ≦ z11 ≦ 0.7, 0.9 ≦ x11 + y11 + z11 ≦ 1.1, and 0 ≦ b11 ≦ 0.1, M 11 and M 12 are independently one or more elements of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements of F, P, and S)

Description

[Technical Field]

[0001] This invention relates to a positive electrode active material for lithium secondary batteries and a method for manufacturing the same. [Background technology]

[0002] Lithium-ion batteries offer high energy density while being easily portable, and are widely used as power sources for mobile information terminals such as smartphones and laptops. Recently, there has been active research into lithium-ion batteries that ensure high capacity, long lifespan, and high output for use as power sources for hybrid and electric vehicles, or as power storage devices.

[0003] Lithium nickel-based composite oxides, which offer high energy density and high capacity, are attracting attention as positive electrode active materials for lithium secondary batteries. However, in the case of such lithium nickel-based composite oxides, residual lithium such as LiOH and Li2CO3 is formed on the surface during manufacturing. Lithium secondary batteries manufactured from positive electrode active materials containing this residual lithium have the problem that carbon dioxide is generated during long-term charging and discharging, reducing the stability of the lithium secondary battery cells.

[0004] Consequently, conventionally, in order to reduce the residual lithium, the surface of the positive electrode active material is additionally washed with washing water after the positive electrode active material is manufactured.

[0005] However, such cleaning can cause structural damage to the positive electrode active material, leading to structural degradation.

[0006] This necessitates a method for manufacturing positive electrode active materials that can improve battery capacity and lifespan while minimizing structural damage and degradation caused by cleaning. [Overview of the project] [Problems that the invention aims to solve]

[0007] One embodiment provides a cathode active material capable of improving the capacity and lifespan of a battery while minimizing structural damage and degradation caused by washing, and a method for manufacturing the same. **Means for Solving the Problem**

[0008] One embodiment provides a cathode active material including core particles containing a lithium nickel-based composite oxide represented by Chemical Formula 11 below, and a coating layer located on the surface of the core particles and containing one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr or a combination thereof, wherein the cathode active material has a value defined by the following Mathematical Formula 1 of 5 or more. [Chemical Formula 11] Li

[0009] , , , Ni x11 M 11 y11 M 12 z11 O 2-b11 X b11 In Chemical Formula 11 above, 0.9 ≤ a11 ≤ 1.2, 0.3 ≤ x11 < 1, 0 < y11 ≤ 0.7, 0 ≤ z11 ≤ 0.7, 0.9 ≤ x11 + y11 + z11 ≤ 1.1, and 0 ≤ b11 ≤ 0.1, and M 11 and M 12 are each independently one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S. [Mathematical Formula 1] Σ[Mx(EP-EDS) / Mx(ICP)] In Mathematical Formula 1, Mx means the metal component contained in the coating layer, Mx(EP-EDS) is the mol% of metal Mx with respect to the content of all elements present on the surface of the cathode active material excluding lithium, and Mx(ICP) is the mol% of metal Mx with respect to the content of all elements present in the entire (surface and core) cathode active material excluding lithium.

[0009] Another embodiment is a method for producing a positive electrode active material for a lithium secondary battery, comprising the steps of: mixing a nickel-based composite hydroxide and a first lithium compound to produce a first mixture; subjecting the first mixture to primary heat treatment to obtain a first lithium nickel-based composite oxide; washing the first lithium nickel-based composite oxide with an aqueous solvent; mixing the washed first lithium nickel-based composite oxide and a second lithium compound to produce a second mixture; and subjecting the second mixture to secondary heat treatment to obtain a positive electrode active material; The first lithium nickel-based composite oxide after the aforementioned cleaning has a BET specific surface area of ​​0.3 m². 2 / g~2.0m 2 The value is / g, and the porosity is 0.01 cm 3 / g~0.15cm 3 This invention provides a method for producing a positive electrode active material for lithium secondary batteries that is [value missing] / g.

[0010] Another embodiment provides a positive electrode comprising a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material manufactured by the method for manufacturing the positive electrode active material described above.

[0011] Another embodiment provides a lithium secondary battery comprising the positive electrode, negative electrode, and electrolyte described above. [Effects of the Invention]

[0012] One embodiment of the positive electrode active material and its manufacturing method can improve the capacity and lifespan of a battery while minimizing structural damage and deterioration caused by cleaning. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram showing a lithium secondary battery according to one embodiment. [Figure 2] This is a schematic diagram showing a lithium secondary battery according to one embodiment. [Figure 3] This is a schematic diagram showing a lithium secondary battery according to one embodiment. [Figure 4]This is a schematic diagram showing a lithium secondary battery according to one embodiment. [Modes for carrying out the invention]

[0014] The following describes specific embodiments in detail so that they can be easily implemented by those with ordinary skill in the art. However, the present invention can be realized in various different forms and is not limited to the embodiments described herein.

[0015] The terms used herein are for illustrative purposes only and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0016] Here, "these combinations" refers to mixtures of components, laminates, composites, copolymers, alloys, blends, reaction products, etc.

[0017] Here, terms such as “include,” “equip,” or “possess” are intended to specify the existence of the implemented features, figures, stages, components, or combinations thereof, and should be understood not to preemptively exclude the existence or possibility of adding one or more other features, figures, stages, components, or combinations thereof.

[0018] To clearly represent various layers and regions in the drawings, thicknesses are shown enlarged, and similar parts are given the same drawing reference numerals throughout the specification. When a layer, film, region, plate, or other part is said to be "on top of" or "on" another part, this includes not only when it is "directly on top of" another part, but also when there is another part in between. Conversely, when a part is said to be "directly on top of" another part, it means that there is no other part in between.

[0019] Furthermore, the term "layer" here includes not only the shapes formed on the entire surface when observed in a plan view, but also the shapes formed on a portion of the surface.

[0020] The average particle size can be measured by methods widely known to those skilled in the art, for example, by a particle size analyzer, or by transmission electron microscope images or scanning electron microscope images. Alternatively, it can be measured using dynamic light scattering, and after performing data analysis to count the number of particles for each particle size range, the average particle size value can be calculated from this. Unless otherwise defined, the average particle size (D 50 ) can mean the diameter of the particle whose cumulative volume in the particle size distribution is 50% by volume. Also, unless otherwise defined, the average particle size is obtained by measuring the size (diameter or length of the major axis) of more than 20 random particles in a scanning electron microscope image to obtain the particle size distribution, and the diameter of the particle whose cumulative volume in the said particle size distribution is 50% by volume is defined as the average particle size (D 50 It could be taken as such.

[0021] Here, "or" is not interpreted as having an exclusive meaning; for example, "A or B" is interpreted as including A, B, A+B, etc.

[0022] The term "metal" is interpreted as encompassing general metals, transition metals, and metalloids.

[0023] Method for manufacturing positive electrode active material for lithium secondary batteries In one embodiment, a method for producing a positive electrode active material for a lithium secondary battery is provided, comprising the steps of: mixing a nickel-based composite hydroxide and a first lithium compound to produce a first mixture; subjecting the first mixture to primary heat treatment to obtain a first lithium nickel-based composite oxide; washing the first lithium nickel-based composite oxide with an aqueous solvent; mixing the washed first lithium nickel-based composite oxide and a second lithium compound to produce a second mixture; and subjecting the second mixture to secondary heat treatment to obtain a positive electrode active material, wherein the washed first lithium nickel-based composite oxide has a BET specific surface area of ​​0.3 m². 2 / g~2.0m 2 The value is / g, and the porosity is 0.01 cm 3 / g~0.15cm 3 This invention provides a method for producing a positive electrode active material for lithium secondary batteries that is [value missing] / g.

[0024] Conventionally, in the case of lithium nickel-based composite oxides, residual lithium is formed on the surface during the manufacturing of the positive electrode active material. Lithium secondary batteries containing this material generate carbon dioxide during long-term charging and discharging, leading to a decrease in cell stability. To improve this, cleaning was performed after the manufacturing of the positive electrode active material. While this had the advantage of removing residual lithium, it also had the problem of causing structural damage and degradation. Ideally, cleaning should remove only lithium compounds such as Li2CO3 and LiOH present on the surface of the positive electrode active material particles. However, there is a problem in that active lithium inside the positive electrode active material is also removed, which not only reduces the reversible capacity but can also cause changes in crystal structure and phase transitions, leading to a decrease in performance. For example, when lithium dissolves, the form of lithium-nickel-oxide changes to a form such as nickel-oxide, forming NiO, for example. This causes a kind of reduction reaction in which the oxidation state of Ni decreases from 3+ to 2+. Compounds such as NiO are not converted back into lithium-containing compounds, which not only reduces the reversible capacity but can also promote side reactions between the surface of the positive electrode active material particles and the electrolyte, leading to a decrease in overall performance.

[0025] One embodiment of the method for producing a positive electrode active material can improve the cell capacity and lifespan of a lithium secondary battery compared to conventional methods for producing positive electrode active materials by adjusting the cleaning conditions to minimize structural damage and deterioration, and by adjusting the content of the lithium compound added to the lithium nickel-based composite oxide after cleaning to restore structural damage caused by cleaning.

[0026] The aforementioned nickel-based composite hydroxide can be represented by the following chemical formula 1. [Chemical formula 1] Ni x1 M 1 y1 M 2 z1 (OH)2

[0027] In the above chemical formula 1, 0.3 ≤ x1 < 1, 0 <y1≦0.7、0≦z1≦0.7、および0.9≦x1+y1+z1≦1.1であり、M 1 and M 2 Each of these elements is independently Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zr, Zn, or a combination thereof.

[0028] In the aforementioned chemical formula 1, 0.3 ≤ x1 ≤ 0.99, 0.01 ≤ y1 ≤ 0.7, and 0 ≤ z1 ≤ 0.69; 0.6 ≤ x1 < 1, 0 <y1≦0.4、および0≦z1≦0.4;0.7≦x1<1、0<y1≦0.3、および0≦z1≦0.3;0.8≦x1<1、0<y1≦0.2、および0≦z1≦0.2;または0.9≦x1<1、0<y1≦0.1、および0≦z1≦0.1であってもよい。

[0029] The aforementioned nickel-based composite hydroxide can be specifically represented by the following chemical formula 2 or 3.

[0030] [Chemical formula 2] Ni x2 Co y2 M 3 z2 (OH)2 In the above chemical formula 2, 0.3 ≤ x² < 1, 0 <y2≦0.7、0≦z2≦0.7、および0.9≦x2+y2+z2≦1.1であり、M 3 These are Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zr, Zn, or combinations thereof.

[0031] In the aforementioned chemical formula 2, 0.3 ≤ x² ≤ 0.99, 0.01 ≤ y² ≤ 0.7, and 0 ≤ z² ≤ 0.69; 0.6 ≤ x² < 1, 0 <y2≦0.4、および0≦z2≦0.4;0.7≦x2<1、0<y2≦0.3、および0≦z2≦0.3;0.8≦x2<1、0<y2≦0.2、および0≦z2≦0.2;または0.9≦x2<1、0<y2≦0.1、および0≦z2≦0.1であってもよい。

[0032] [Chemical formula 3] Ni x3 Co y3 M 4 z3 M 5 w3 (OH)2 In the above chemical formula 3, 0.3 ≤ x³ ≤ 0.98, 0.01 ≤ y³ ≤ 0.69, 0.01 ≤ z³ ≤ 0.69, 0 ≤ w³ ≤ 0.68, and 0.9 ≤ x³ + y³ + z³ + w³ ≤ 1.1, M 4 is Al, Mn, or a combination thereof, M 5 These are B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zr, Zn, or combinations thereof.

[0033] In the aforementioned chemical formula 3, 0.6≦x3≦0.98, 0.01≦y3≦0.39, 0.01≦z3≦0.39, and 0≦w3≦0.38; 0.8≦x3≦0.98, 0.01≦y3≦0.18, 0.01≦z3≦0.18, and 0≦w3≦0.18; or 0.9≦x3≦0.98, 0.01≦y3≦0.08, 0.01≦z3≦0.08, and 0≦w3≦0.08.

[0034] The nickel-based composite hydroxide can contain nickel at a high concentration. For example, the nickel content of the nickel-based composite hydroxide may be 80 mol% or more relative to 100 mol% of the total metal, and other examples include 81 mol% or more, 82 mol% or more, 83 mol% or more, 84 mol% or more, 85 mol% or more, 89 mol% or more, 90 mol% or more, 91 mol% or more, or 92 mol% or more, and may be 100 mol% or less, 99 mol% or less, or 95 mol% or less.

[0035] The nickel-based composite hydroxide is in the form of secondary particles in which multiple primary particles are aggregated, and the average particle size (D 50 The particle size may be, for example, 1 μm to 25 μm, 2 μm to 20 μm, 5 μm to 18 μm, or 8 μm to 16 μm. Here, the average particle size (D 50) may be obtained by measuring the size of any 20 or more particles through scanning electron microscope (SEM) images to obtain a particle size distribution, and the size of the particle with a cumulative volume of 50% of the total volume may be taken as the average particle size.

[0036] The first lithium compound may be, for example, Li2CO3, LiOH, LiF, their hydrates, or a combination thereof.

[0037] The nickel-based composite hydroxide and the first lithium compound may be mixed such that the molar ratio of lithium in the first lithium compound to the total metal of the nickel-based composite hydroxide is 0.9 to 1.1, or 1 to 1.05. When the molar ratio of lithium in the first lithium compound to the total metal of the nickel-based composite hydroxide is adjusted to this range, a structurally stable first lithium nickel-based composite oxide with a high lithium content can be obtained.

[0038] The nickel-based composite hydroxide and the first lithium compound are mixed to produce a first mixture, and the first mixture is subjected to primary heat treatment to obtain a first lithium nickel-based composite oxide, during which a phase transition and grain growth occur.

[0039] The primary heat treatment can be carried out in an oxidizing gas atmosphere, and the temperature is not specifically limited, but may be, for example, 600°C to 1200°C, 600°C to 1100°C, 600°C to 1000°C, 600°C to 900°C, 600°C to 800°C, or 700°C to 800°C. The oxidizing gas atmosphere means an oxidizing gas such as oxygen or air, and for example, the oxidizing gas atmosphere consists of an oxygen atmosphere with 90% or more oxygen by volume.

[0040] The primary heat treatment time can be appropriately adjusted depending on the primary heat treatment temperature, for example, it can be 8 to 20 hours, 10 to 18 hours, or 12 to 16 hours.

[0041] The BET specific surface area of ​​the primary lithium nickel-based composite oxide before cleaning was 0.1 m². 2 / g~0.4m 2It may also be / g. For example, the BET specific surface area of ​​the first lithium nickel-based composite oxide before washing is 0.1m². 2 / g or more, 0.15m 2 / g or more, 0.2m 2 / g or more, 0.25m 2 / g or more, or 0.3m 2 It may be 0.4m or more. 2 / g or less, 0.39m 2 / g or less, 0.38m 2 / g or less, 0.37m 2 / g or less, 0.36m 2 / g or less, 0.35m 2 / g or less, 0.34m 2 / g or less, 0.33m 2 / g or less, 0.32m 2 / g or less, 0.31m 2 Less than / g, or 0.3m 2 The amount may be less than or equal to / g. For example, the BET specific surface area of ​​the first lithium nickel-based composite oxide before washing is 0.15 m². 2 / g~0.4m 2 / g, 0.2m 2 / g~0.4m 2 / g, or 0.25m 2 / g~0.35m 2 The BET specific surface area may also be measured by nitrogen gas adsorption using the HM model-1208 specific surface area measuring device manufactured by MOUNTECH.

[0042] The first lithium nickel-based composite oxide may also be in the form of secondary particles formed by the aggregation of multiple primary particles, and the average particle size (D) of the secondary particles is 50 The particle size may be, for example, 1 μm to 25 μm, 2 μm to 20 μm, 5 μm to 18 μm, or 8 μm to 16 μm. Here, the average particle size (D 50 ) may be obtained by measuring the size of any 20 or more particles through scanning electron microscope (SEM) images to obtain a particle size distribution, and the size of the particle with a cumulative volume of 50% of the total volume may be taken as the average particle size.

[0043] The manufacturing method further includes the step of washing the first lithium nickel-based composite oxide obtained by primary heat treatment with an aqueous solvent. The aqueous solvent may be water.

[0044] The cleaning process may include adding the first lithium nickel-based composite oxide to water, mixing it, and drying it. Residual lithium can be removed in this process. By appropriately adjusting the cleaning conditions in one embodiment, the method for producing a positive electrode active material can improve the battery capacity and lifespan by minimizing structural damage and degradation while removing residual lithium.

[0045] The aforementioned cleaning can be performed by appropriately adjusting the amount of water used during cleaning.

[0046] The amount of water used during the cleaning process may be less than 100 parts by weight per 100 parts by weight of the first lithium nickel composite oxide. For example, the amount of water used during the cleaning process may be 10 to 90 parts by weight, 20 to 80 parts by weight, 30 to 60 parts by weight, 40 to 60 parts by weight, or 50 parts by weight per 100 parts by weight of the first lithium nickel composite oxide. By satisfying the above range for the amount of water used during cleaning, structural damage and deterioration during cleaning can be minimized.

[0047] The cleaning can be performed for 1 to 30 minutes, 2 to 30 minutes, 3 to 30 minutes, 4 to 30 minutes, or 5 to 30 minutes, provided that the amount of water is sufficient. When the cleaning is performed for the aforementioned durations, provided that the amount of water is sufficient, structural damage and deterioration of the first lithium nickel composite oxide due to the cleaning can be minimized. The cleaning time may be calculated based on the time when the first lithium nickel composite oxide is added to the aqueous solvent.

[0048] The method for manufacturing a positive electrode active material according to an embodiment can remove residual lithium so that the first lithium nickel-based composite oxide after washing satisfies the range of the BET specific surface area and porosity described below, and structural damage and structural deterioration are minimized, by adjusting the amount of water during washing within the aforementioned range. A lithium secondary battery including a positive electrode active material manufactured using the first lithium nickel-based composite oxide that has undergone such a washing process can have further improved capacity and lifespan.

[0049] The BET specific surface area of the first lithium nickel-based composite oxide after the washing is 0.3 m 2 / g to 2 m 2 / g, for example, 0.4 m 2 / g to 2 m 2 / g, 0.5 m 2 / g to 2 m 2 / g, 0.6 m 2 to 2 m 2 / g, 0.7 m 2 / g to 2 m 2 / g, 0.8 m 2 / g to 2 m 2 / g, 0.9 m 2 / g to 2 m 2 / g, 1 m 2 / g to 2 m 2 / g, 1 m 2 / g to 1.8 m 2 / g, 1 m 2 / g to 1.6 m 2 / g, or 1.2 m 2 / g to 1.4 m 2 / g may be used. The BET specific surface area may be measured by a nitrogen gas adsorption method using an HM model-1208, a specific surface area measuring device manufactured by MOUNTECH. The BET specific surface area can be utilized as an index indicating the degree of structural damage of the active material generated during the washing process. Since pores are formed inside the structure of the first lithium nickel-based composite oxide during washing, and thereby the BET specific surface area increases, a larger value of the BET specific surface area may mean that the degree of structural damage has deteriorated.

[0050] The porosity of the first lithium nickel-based composite oxide after the washing is 0.01 cm3 / g to about 0.15 cm 3 / g, for example, 0.01 cm 3 / g to about 0.12 cm 3 / g, 0.01 cm 3 / g to about 0.1 cm 3 / g, 0.05 cm 3 / g to about 0.1 cm 3 / g, or 0.06 cm 3 / g to about 0.08 cm 3 / g may also be used. The porosity may be measured through BJH (Barrett-Joyner-Halenda) analysis. For example, the porosity can be measured by performing nitrogen adsorption measurement using BELSORP-max, a measuring device manufactured by Microtrac, interpreting the pore distribution in the range of pore diameters of 2 nm or more and 300 nm or less for the sample by the BJH method, and calculating the numerical value of the porosity. Similar to the aforementioned BET specific surface area, the porosity can be utilized as an index indicating the degree of structural damage of the active material generated during the cleaning process. A larger porosity may mean that the degree of structural damage of the first lithium nickel-based composite oxide due to cleaning has deteriorated.

[0051] After the cleaning, the cation mixing value of the first lithium nickel-based composite oxide may be 2% or less. For example, the cation mixing value of the first lithium nickel-based composite oxide after the cleaning may be 1% - 2%, 1% - 1.8%, 1% - 1.6%, 1% - 1.4%, or 1.2% - 1.4%. The cation mixing refers to the phenomenon in which Li + (0.76 Å) and Ni 2+ (0.69 Å) change their positions with each other to form a crystal. Specifically, since nickel tends to be biased towards a divalent valence rather than a trivalent valence, during high-temperature firing, due to the volatilization of the raw material lithium salt, lithium deficiency occurs in the lithium layer, and in the vacant space, nickel ions (Ni 2+ ) having a divalent valence similar to the ionic radius of lithium ions are mixed in, resulting in the problem of manufacturing a lithium nickel oxide with a non-stoichiometric composition. Also, Ni 2+This not only hinders the diffusion of lithium ions but also significantly increases the irreversibility of the ion oxidation-reduction reaction in the battery, leading to a problem of reduced capacity in lithium secondary batteries. The cation mixing value can be satisfied by appropriately adjusting the amount of water used when washing the first lithium nickel composite oxide. The cation mixing value (%) is determined by the amount of nickel (Ni) at the lithium site (Li site). 2+ This refers to the percentage (%) of ions present and can be measured and calculated using X-ray diffraction (XRD). For example, the cation mixing value may be calculated by performing X-ray diffraction (XRD) analysis using Cu-Kα on the first lithium nickel composite oxide after washing, and then calculating the profile through Rietveld refinement. By appropriately adjusting the amount of water used during washing, the first lithium nickel composite oxide after washing can satisfy the aforementioned cation mixing value.

[0052] The residual lithium content of the first lithium nickel composite oxide after cleaning may be 0.1% by weight or more, based on 100% by weight of the first lithium nickel composite oxide after cleaning. For example, the residual lithium content of the first lithium nickel composite oxide after cleaning may be 0.1% to 0.2% by weight, 0.1% to 0.15% by weight, 0.1% to 0.13% by weight, or 0.1% to 0.12% by weight, based on 100% by weight of the first lithium nickel composite oxide after cleaning. The residual lithium content of the first lithium nickel composite oxide after cleaning can be measured by acid-salt titration using diluted hydrochloric acid (HCl). By adjusting the residual lithium content of the first lithium nickel composite oxide after cleaning to fall within the aforementioned range, the capacity and lifespan of the battery can be improved. The residual lithium content of the first lithium nickel composite oxide after cleaning can be achieved within the aforementioned range by appropriately adjusting the amount of water used during cleaning.

[0053] The electrical conductivity of the first lithium nickel composite oxide after washing may be 0.22 S / cm or less, for example, 0.1 S / cm to 0.22 S / cm, 0.15 S / cm to 0.21 S / cm, or 0.18 S / cm to 0.21 S / cm. The electrical conductivity can be determined by measuring the resistivity of the powder of the first lithium nickel composite oxide after washing using a powder resistance measuring device, and converting the reciprocal value of the measured resistivity into an electrical conductivity value. For example, the electrical conductivity of the first lithium nickel composite oxide after washing may be determined by measuring the resistivity at the point where the powder density is 3.3 g / cc using a powder resistance measuring device, and calculating it inversely. By appropriately adjusting the amount of water during washing, structural changes to a rock salt structure can be suppressed, and the first lithium nickel composite oxide after washing can satisfy the aforementioned electrical conductivity.

[0054] The manufacturing method includes the steps of mixing the first lithium nickel-based composite oxide and the second lithium compound after cleaning to produce a second mixture, and subjecting the second mixture to secondary heat treatment to obtain a positive electrode active material. The method for producing a positive electrode active material according to one embodiment can restore structural damage and deterioration caused by cleaning by additionally adding the lithium compound after cleaning, thereby improving the capacity and lifespan of the battery.

[0055] The second lithium compound may be, for example, Li2CO3, LiOH, LiF, their hydrates, or a combination thereof. The second lithium compound may be the same as or different from the first lithium compound.

[0056] The second lithium compound may be mixed with the first lithium nickel composite oxide after cleaning so that the lithium content is 10 moles or less per 100 moles of the total metal excluding lithium. For example, the lithium in the second lithium compound may be mixed in amounts of 0.1 to 10 moles, 0.5 to 7 moles, 1 to 8 moles, or 1 to 5 moles per 100 moles of the total metal excluding lithium in the first lithium nickel composite oxide. By mixing the second lithium compound with the first lithium nickel composite oxide after cleaning within the above ranges, structural damage and deterioration caused by cleaning can be restored, thereby improving the capacity and lifespan of the battery. Increasing the content of the lithium compound can restore structural damage and deterioration caused by cleaning, but if it is excessively high, it may cause a decrease in electrical conductivity. Therefore, it is necessary to adjust the content of the second lithium compound so that it satisfies the above ranges. The amount of the second lithium compound added varies depending on whether or not coating materials are added during the secondary heat treatment described later. For example, the amount of the second lithium compound added may be greater when coating materials are added during the secondary heat treatment described later than when they are not.

[0057] The secondary heat treatment can be carried out in an oxidizing gas atmosphere, and the temperature is not specifically limited, but can be within the range of, for example, 600°C to 1200°C, 600°C to 1000°C, 600°C to 800°C, or 600°C to 700°C. The secondary heat treatment time can be appropriately adjusted depending on the secondary heat treatment temperature, for example, within 20 hours, 10 to 20 hours, 14 to 18 hours, or 16 hours.

[0058] During the process of manufacturing the second mixture, additional coating materials may be added.

[0059] That is, the step of producing the second mixture can be carried out by mixing the washed first lithium nickel-based composite oxide, the second lithium compound, and the coating raw material. When the coating material is further added to produce a second mixture and a subsequent secondary heat treatment is performed to obtain a positive electrode active material, the positive electrode active material may include core particles containing a lithium nickel-based composite oxide, and a coating layer located on the surface of the core particles and containing the coating elements of the coating material. When the positive electrode active material further includes a coating layer, the surface resistance characteristics are improved, the electrical conductivity is further improved, and the initial charge-discharge efficiency and life characteristics can be further improved.

[0060] The coating raw material is not particularly limited as long as it contains known coating elements. For example, the coating element may include one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr. For example, the coating element may include Co, Al, Zr, or a combination thereof. In this case, the cobalt raw material can be a Co-containing hydroxide, Co oxide, or Co-containing carbonate, the aluminum raw material can be an Al-containing hydroxide or Al-containing oxide, and the zirconium raw material can be a Zr-containing hydroxide, Zr-containing oxide, or Zr-containing chloride. For example, the cobalt raw material can be Co(OH)2, the aluminum raw material can be AlOOH, Al2O3, or Al(OH)3, and the zirconium raw material can be ZrO2, Zr(OH)4, or ZrOCl2. The specific examples of the coating raw materials described above were explained assuming that the coating elements are Co, Al, and Zr, but other known raw materials can also be freely used for coating elements other than those mentioned above.

[0061] The amount of the coating material added can be appropriately adjusted according to the purpose. For example, the coating material can be added in such a way that the coating element of the coating material is in an amount of 0.01 to 10 moles relative to 100 moles of the total metal excluding lithium in the first lithium nickel composite oxide after washing, but is not limited to this. The amount of the coating material added may be appropriately adjusted depending on the coating element.

[0062] For example, the cobalt raw material may be added in such a way that, relative to 100 moles of the total metal excluding lithium in the first lithium nickel composite oxide after washing, the cobalt in the cobalt raw material amounts to 0.1 to 5 moles, 0.1 to 3 moles, 0.5 to 3 moles, 1 to 3 moles, or 2 moles. Similarly, the aluminum raw material may be added in such a way that, relative to 100 moles of the total metal excluding lithium in the first lithium nickel composite oxide after washing, the aluminum in the aluminum raw material amounts to 0.01 to 3 moles, 0.01 to 1 mole, 0.05 to 1 mole, 0.1 to 1 mole, or 0.5 moles. Furthermore, the zirconium may be added in amounts of 0.01 to 1 mole, 0.01 mole, 0.8 mole, 0.01 to 0.5 mole, 0.01 to 0.3 mole, 0.05 to 0.3 mole, 0.1 to 0.2 mole, or 0.15 mole.

[0063] The positive electrode active material produced by the above manufacturing method can be subjected to all the same conditions as the positive electrode active material described below. positive electrode active material A positive electrode active material according to one embodiment comprises core particles containing a lithium nickel-based composite oxide represented by the following chemical formula 11, and a coating layer located on the surface of the core particles containing one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, wherein the positive electrode active material satisfies the value defined by the following formula 1 to be 5 or greater. [Chemical formula 11] Li a11 Nix11 M 11 y11 M 12 z11 O 2-b11 X b11 In the above chemical formula 11, 0.9 ≤ a11 ≤ 1.2, 0.3 ≤ x11 < 1, 0 <y11≦0.7、0≦z11≦0.7、0.9≦x11+y11+z11≦1.1、および0≦b11≦0.1であり、M 11 and M 12 Each of the elements is independently selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S. [Formula 1] Σ[Mx(EP-EDS) / Mx(ICP)] In the above formula 1, Mx represents the metallic component contained in the coating layer, Mx(EP-EDS) is the mole percentage of metal Mx relative to the total elemental content present on the surface of the positive electrode active material excluding lithium, and Mx(ICP) is the mole percentage of metal Mx relative to the total elemental content present in the entire positive electrode active material (surface and core) excluding lithium.

[0064] By including the above-described configuration, the positive electrode active material according to one embodiment may have further improved electrical conductivity, and thus improved initial charge / discharge capacity and life characteristics. The positive electrode active material may be manufactured by the method for manufacturing the positive electrode active material according to the above-described embodiment, and may be the same as the positive electrode active material obtained after adding a coating material and performing a secondary heat treatment when manufacturing the second mixture in the method for manufacturing the positive electrode active material.

[0065] In the aforementioned chemical formula 11, 0.3≦x11≦0.99, 0.01≦y11≦0.7, and 0≦z11≦0.69; 0.6≦x11<1, 0 <y11≦0.4、および0≦z11≦0.4;0.7≦x11<1、0<y11≦0.3、および0≦z11≦0.3;または0.9≦x11<1、0<y11≦0.1、0≦z11≦0.1であってもよい。

[0066] The term defined in Formula 1 above is an index indicating the relative distribution of metallic components coated on the surface of the core particles of the positive electrode active material. In Formula 1, Mx can be similarly applied to known coating components other than the aforementioned Co, Al, Zr, or combinations thereof. EP-EDS is a surface analysis technique that can determine how much metal is present in the coating layer, and ICP represents the average value relative to the overall composition of the positive electrode active material. The ratio of the two values ​​indicates the degree to which the metallic components are concentrated on the surface of the coating layer. The EP-EDS and ICP measurement methods for the positive electrode active material can be similarly applied to the methods described in the evaluation examples below. If the value of Σ[Mx(EP-EDS) / Mx(ICP)] defined in Formula 1 is 5 or greater, it indicates that there is an even greater amount of metallic components contained in the coating layer on the surface of the particles, and that the coating layer has been effectively formed. The values ​​defined by the above formula 1 can satisfy 5-10, 6-9, 7-9, 7-8.5, or 7-8.

[0067] The aforementioned lithium nickel-based composite oxide can be specifically represented by the following chemical formula 12 or 13. [Chemical formula 12] Li a12 Ni x12 Co y12 M 13 z12 O 2-b12 X b12 In the above chemical formula 12, 0.3 ≤ x 12 < 1, 0 <y12≦0.7、0≦z12≦0.7、0.9≦x12+y12+z12≦1.1、および0≦b12≦0.1であり、M 13 X is Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zr, Zn, or a combination thereof, and X is one or more elements selected from F, P, and S.

[0068] In the above chemical formula 12, 0.3 ≤ x 12 ≤ 0.99, 0.01 ≤ y 12 ≤ 0.7, and 0 ≤ z 12 ≤ 0.69; 0.6 ≤ x 12 < 1, 0 <y12≦0.4、および0≦z12≦0.4;0.7≦x12<1、0<y12≦0.3、および0≦z12≦0.3;0.8≦x12<1、0<y12≦0.2、および0≦z12≦0.2;または0.9≦x12<1、0<y12≦0.1、および0≦z12≦0.1であってもよい。

[0069] [Chemical formula 13] Li a13 Ni x13 Co y13 M 14 z13 M 15 w13 O 2-b13 X b13 In the above chemical formula 13, 0.3≦x13≦0.98, 0.01≦y13≦0.69, 0.01≦z13≦0.69, 0≦w13≦0.68, 0.9≦x3+y3+z3+w3≦1.1, and 0≦b13≦0.1, M 14 is Al, Mn, or a combination thereof, M 15 X is one or more elements selected from F, P, and S, and X is B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zr, Zn, or a combination thereof.

[0070] In the above chemical formula 13, 0.6≦x13≦0.98, 0.01≦y13≦0.39, 0.01≦z13≦0.39, and 0≦w13≦0.38; 0.8≦x13≦0.98, 0.01≦y13≦0.18, 0.01≦z13≦0.18, and 0≦w13≦0.18; or 0.9≦x13≦0.98, 0.01≦y13≦0.08, 0.01≦z13≦0.08, and 0≦w13≦0.08.

[0071] The core particles of the positive electrode active material may be in the form of secondary particles formed by the aggregation of multiple primary particles, and the average particle size (D) of the secondary particles. 50The particle size may be, for example, 1 μm to 25 μm, 2 μm to 20 μm, 5 μm to 18 μm, or 8 μm to 16 μm. Here, the average particle size (D 50 This may be obtained by measuring the size of any 20 or more particles through scanning electron microscope (SEM) images to obtain a particle size distribution, where the size of the particle with a cumulative volume of 50% is taken as the average particle size.

[0072] The core particles of the positive electrode active material may be identical to the positive electrode active material obtained by secondary heat treatment of a second mixture, which is a mixture of the first lithium nickel-based composite oxide and the second lithium compound after cleaning, without adding any additional coating material when producing the second mixture in the method for producing the positive electrode active material described above. The positive electrode active material does not include a coating layer located on the surface of the core particles, and even when the positive electrode active material produced by the method for producing the positive electrode active material described above, i.e., when it consists only of core particles, it is possible to improve the capacity and lifespan of the battery while minimizing structural damage and deterioration due to cleaning. Hereinafter, the physical properties of the positive electrode active material include all positive electrode active materials consisting only of core particles without a coating layer, and positive electrode active materials including a coating layer located on the surface of the core particles.

[0073] The BET specific surface area of ​​the positive electrode active material is 0.4 m². 2 It is less than or equal to / g, for example, 0.15m 2 / g~0.4m 2 / g, 0.2m 2 / g~0.4m 2 / g, 0.25m 2 / g~0.4m 2 / g, 0.3m 2 / g~0.4m 2 / g, or 0.3m 2 / g~0.38m 2 The BET specific surface area may be measured by nitrogen gas adsorption using the HM model-1208 specific surface area measuring device manufactured by MOUNTECH.

[0074] The porosity of the positive electrode active material is 0.01 cm². 3It is less than or equal to / g, for example, 0.001cm 3 / g~0.01cm 3 / g, 0.002cm 3 / g~0.01cm 3 / g, 0.003cm 3 / g~0.01cm 3 / g, 0.004cm 3 / g~0.01cm 3 / g, 0.005cm 3 / g~0.01cm 3 / g, 0.005cm 3 / g~0.009cm 3 / g, 0.005cm 3 / g~0.008cm 3 / g, or 0.005cm 3 / g~0.007cm 3 The porosity may be expressed as / g. The porosity may also be measured by BJH (Barrett-Joyner-Halenda) analysis. For example, the porosity can be measured by performing nitrogen adsorption measurement using a BELSORP-max measuring device manufactured by Microtrac, interpreting the void distribution in the range of void diameters from 2 nm to 300 nm using the BJH method, and calculating the porosity value.

[0075] The electrical conductivity of the positive electrode active material is 0.05 S / cm to 0.15 S / cm, and may be, for example, 0.05 S / cm to 0.13 S / cm, or 0.07 S / cm to 0.12 S / cm. The electrical conductivity can be determined by measuring the resistivity of the powder of the positive electrode active material using a powder resistance measuring device, and converting the reciprocal value of the measured resistivity into an electrical conductivity value. For example, the electrical conductivity of the positive electrode active material may be determined by measuring the resistivity at the point where the powder density is 3.3 g / cc using a powder resistance measuring device, and then calculating it inversely.

[0076] positive electrode A positive electrode for a lithium secondary battery may include a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector. The positive electrode active material layer comprises the positive electrode active material and may further optionally include a binder, a conductive material, or a combination thereof.

[0077] The positive electrode active material may be the positive electrode active material described above, or it may be manufactured by the method for manufacturing the positive electrode active material described above. Specific details regarding the positive electrode active material and the method for manufacturing the positive electrode active material have been described above and will be omitted below.

[0078] The binder plays a role in ensuring that the positive electrode active material particles adhere well to each other and that the positive electrode active material adheres well to the current collector. Typical examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0079] In the positive electrode active material layer, the binder content may be approximately 1% to 5% by weight relative to 100% by weight of the positive electrode active material layer.

[0080] The conductive material is used to impart conductivity to the electrodes, and any electronically conductive material that does not cause chemical changes can be used in the battery that is constructed. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0081] In the positive electrode active material layer, the content of the conductive material may be 1% to 5% by weight relative to 100% by weight of the positive electrode active material layer.

[0082] Aluminum foil can be used as the positive electrode current collector, but is not limited to this.

[0083] Lithium-ion rechargeable battery Another embodiment provides a lithium secondary battery comprising a positive electrode, a negative electrode, and an electrolyte.

[0084] The lithium secondary battery can have excellent capacity and lifespan by including a positive electrode and a negative electrode containing the positive electrode active material described above, or a positive electrode active material manufactured by the method for manufacturing the positive electrode active material described above.

[0085] The lithium secondary battery may, for example, be a lithium secondary battery comprising a positive electrode, a negative electrode, a separator located between the positive and negative electrodes, and an electrolyte, in which case the electrolyte may be a liquid or in the form of a gel polymer. As another example, the lithium secondary battery may be an all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte, or a semi-solid-state battery comprising a positive electrode, a negative electrode, and a semi-solid electrolyte. The semi-solid can mean a state that contains all solid and liquid components, or a state that is mostly solid but contains some liquid components. The all-solid-state battery and semi-solid-state battery do not need to include a separator. The positive electrode active material according to one embodiment can achieve high capacity, very high charge / discharge efficiency and high-temperature life while achieving high capacity depending on its shape, making it suitable for application to the above-mentioned types of batteries and capable of showing excellent performance in each battery.

[0086] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch-type, coin-type, and other types depending on their form. Figures 1 to 4 are schematic diagrams showing a lithium secondary battery according to one embodiment, with Figure 1 being cylindrical, Figure 2 being prismatic, and Figures 3 and 4 being pouch-type batteries. Referring to Figures 1 to 4, the lithium secondary battery 100 may include an electrode assembly 40 with a separator 30 interposed between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is housed. The positive electrode 10, negative electrode 20, and separator 30 may be immersed in an electrolyte (not shown). The lithium secondary battery 100 may include a sealing member 60 that seals the case 50, as shown in Figure 1. Also, in Figure 2, the lithium secondary battery 100 may include a positive electrode lead tab 11 and a positive electrode terminal 12, a negative electrode lead tab 21 and a negative electrode terminal 22. As shown in Figures 3 and 4, the lithium secondary battery 100 may include electrode tabs 70, namely a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical pathways for guiding the current formed in the electrode assembly 40 to the outside.

[0087] negative electrode A negative electrode for a lithium secondary battery includes a current collector and a negative electrode active material layer located on the current collector. The negative electrode active material layer comprises a negative electrode active material and may further optionally include a binder, a conductive material, or a combination thereof.

[0088] The negative electrode active material includes a substance capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a substance that can be doped and dedoped with lithium, or a transition metal oxide.

[0089] A carbon-based negative electrode active material is an example of a material that can reversibly intercalate / deintercalate the aforementioned lithium ions.

[0090] The carbon-based anode active material may include crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, while examples of amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, and calcined coke. Soft carbon refers to a carbon material that can be graphitized, and is easily graphitized by heat treatment at high temperatures, for example, about 2800°C. Hard carbon is a carbon material that cannot be graphitized or is finely graphitized by heat treatment.

[0091] The anode active material layer may further contain other types of anode active materials in addition to carbon-based anode active materials, such as lithium metal, lithium metal alloys, and lithium-doped and dedoped materials.

[0092] As the lithium metal alloy, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn can be used.

[0093] As the material that can be doped and dedoped with lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used, and as the Si-based negative electrode active material, silicon, silicon-carbon composite, SiO x(0 < x ≤ 2), Si-Q alloy (where Q is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and combinations thereof, and is not Si), examples of the Sn-based negative electrode active material include Sn, SnO2, Sn-R alloy (where R is an element selected from the group consisting of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and combinations thereof, and is not Sn), etc., and at least one of these can be mixed with SiO2 and used. As the elements Q and R, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof can be used.

[0094] As an example, the negative electrode active material can include silicon-carbon composite particles. The average particle size (D 50 ) of the silicon-carbon composite particles may be, for example, 0.5 μm to 20 μm. The average particle size (D 50 ) is measured by a particle size analyzer and means the diameter of the particle with a cumulative volume of 50% by volume in the particle size distribution. With respect to 100% by weight of the silicon-carbon composite particles, silicon may be contained at 10% to 60% by weight, and carbon may be contained at 40% to 90% by weight. The silicon-carbon composite particles can include, for example, a core containing silicon particles and a carbon coating layer located on the surface of the core. In the core, the average particle size (D 50 ) of the silicon particles may be 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles can exist alone as silicon, or in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon can be represented by SiOx (0 < x ≤ 2). Also, the thickness of the carbon coating layer may be about 5 nm to 100 nm.

[0095] As an example, the silicon-carbon composite particles may include a core containing silicon particles and crystalline carbon, and a carbon coating layer located on the surface of the core and containing amorphous carbon. As an example, in the silicon-carbon composite particles, amorphous carbon may not be present in the core but only in the carbon coating layer. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof, and the amorphous carbon may be formed from coal-based pitch, mesophase pitch, petroleum-based pitch, coal-based oil, petroleum-based heavy oil, or polymer resin (phenol resin, furan resin, polyimide resin, etc.). In this case, the content of crystalline carbon may be 10% to 70% by weight per 100% by weight of the silicon-carbon composite particles, and the content of amorphous carbon may be 20% to 40% by weight.

[0096] In the silicon-carbon composite particles, the core may contain a void in the center. The radius of the void may be 30% to 50% of the radius of the silicon-carbon composite particle.

[0097] The aforementioned silicon-carbon composite particles effectively suppress problems such as volume expansion, structural collapse, or particle fragmentation due to charging and discharging, preventing the disruption of conductive pathways, enabling high capacity and high efficiency, and are advantageous for use under high voltage and fast charging conditions.

[0098] The Si-based or Sn-based anode active material can be used in mixture with a carbon-based anode active material. When using a mixture of the Si-based or Sn-based anode active material and a carbon-based anode active material, the mixing ratio may be 1:99 to 90:10 by weight.

[0099] In the aforementioned negative electrode active material layer, the content of the negative electrode active material may be 95% to 99% by weight relative to 100% by weight of the negative electrode active material layer.

[0100] The negative electrode active material layer may further selectively include a binder, a conductive material, or a combination thereof, along with the negative electrode active material.

[0101] The binder plays a role in ensuring that the negative electrode active material particles adhere well to each other and that the negative electrode active material adheres well to the current collector. The binder can be a non-water-soluble binder, a water-soluble binder, or a combination thereof.

[0102] Examples of the water-insoluble binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, ethylene propylene copolymer, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0103] Examples of the water-soluble binder include rubber-based binders and polymer resin binders. The rubber-based binder may be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and combinations thereof. The polymer resin binder may be selected from polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0104] When a water-soluble binder is used as the negative electrode binder, a cellulosic compound may be further included as a thickening agent that can impart viscosity. One or more of these cellulosic compounds can be used, such as carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, or alkali metal salts thereof. Na, K, or Li can be used as the alkali metal. The amount of such thickening agent used may be 0.1 to 3 parts by weight per 100 parts by weight of the negative electrode active material.

[0105] The conductive material is used to impart conductivity to the electrodes, and any electronically conductive material that does not cause chemical changes can be used in the battery that is constructed. Examples of such materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, and carbon nanotubes; metallic materials in the form of metal powders or metal fibers, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or conductive materials containing mixtures thereof.

[0106] In the negative electrode active material layer, the binder content may be 1% to 5% by weight relative to the total weight of the negative electrode active material layer. Furthermore, if a conductive material is further included, the negative electrode active material layer may contain 90% to 98% by weight of the negative electrode active material, 1% to 5% by weight of the binder, and 1% to 5% by weight of the conductive material.

[0107] As the negative electrode current collector, one can be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0108] electrolyte Lithium-ion batteries can also contain electrolytes.

[0109] The electrolyte for lithium secondary batteries may be, for example, an electrolyte solution, which contains a non-aqueous organic solvent and a lithium salt.

[0110] The aforementioned non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0111] The non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0112] Examples of carbonate-based solvents that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0113] Suitable ester solvents include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone.

[0114] As ether-based solvents, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran can be used. As ketone-based solvents, cyclohexanone can be used. As alcohol-based solvents, ethyl alcohol and isopropyl alcohol can be used, and as aprotic solvents, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group with 2 to 20 carbon atoms, and can include double bonds, aromatic rings, or ether groups); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes can be used.

[0115] The aforementioned non-aqueous organic solvents can be used alone or in combination of two or more.

[0116] Furthermore, when using carbonate-based solvents, cyclic carbonates and linear carbonates can be mixed, and the cyclic carbonates and linear carbonates can be mixed in a volume ratio of 1:1 to 1:9.

[0117] The aforementioned lithium salts dissolve in organic solvents and act as a source of lithium ions within the battery, enabling the operation of basic lithium secondary batteries and promoting the movement of lithium ions between the positive and negative electrodes. Typical examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N(lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1SO2) (where x and y are integers from 1 to 20) may contain one or more selected from lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB), and lithium bis(oxalato)borate (LiBOB).

[0118] Separator Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators can be made of polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers of these materials. Mixed multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, and polypropylene / polyethylene / polypropylene three-layer separators can also be used.

[0119] The separator may include a porous substrate and a coating layer comprising organic, inorganic, or a combination thereof located on one or both sides of the porous substrate.

[0120] The porous substrate may be a polymer film formed from one polymer selected from polyethylene, polyolefins such as polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., TEFLON®), or from a copolymer or mixture of two or more of these polymers.

[0121] The aforementioned organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0122] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0123] The organic and inorganic materials may exist mixed in a single coating layer, or they may exist in a form in which a coating layer containing organic materials and a coating layer containing inorganic materials are laminated together.

[0124] Example 1 (1) Manufacturing of positive electrode active material Step to obtain the first lithium nickel-based composite oxide. Nickel-based composite hydroxide (Ni 0.93 Co 0.04 Mn 0.03 A first mixture was prepared by mixing (OH2) with LiOH as the first lithium compound. During the preparation of the first mixture, the nickel-based composite hydroxide was mixed so that the lithium of the first lithium compound was in a molar ratio of 1.05 to the total metal. The first mixture was subjected to primary heat treatment at 750°C for 16 hours in an oxygen atmosphere to obtain a first lithium nickel-based composite oxide (LiNi 0.93 Co 0.04 Mn 0.03 O2) was obtained. At this time, the first lithium nickel-based composite oxide is in the form of secondary particles in which multiple primary particles are aggregated, and the average particle size of the secondary particles (D 50 The diameter was 13.5 μm.

[0125] Step 1: Washing lithium nickel-based composite oxide with an aqueous solvent. After crushing and filtering the above-mentioned first lithium nickel composite oxide, it was washed by adding it to distilled water as an aqueous solvent (50 parts by weight per 100 parts by weight of the first lithium nickel composite oxide). This washing was carried out for 5 minutes from the time the first lithium nickel composite oxide was added to the aqueous solvent to remove residual lithium from the surface of the first lithium nickel composite oxide. After drying at 190°C for 12 hours, the washed first lithium nickel composite oxide (LiNi 0.93 Co 0.04 Mn 0.03 O2) was obtained. At this time, the first lithium nickel-based composite oxide after washing maintained the form of secondary particles in which multiple primary particles were aggregated.

[0126] The stage in which the positive electrode active material is manufactured. A second mixture was prepared by mixing the first lithium nickel-based composite oxide, after cleaning, with LiOH as the second lithium compound. When preparing the second mixture, the lithium in the second lithium compound was mixed in such an amount of 1 mole for every 100 moles of the total metal (excluding lithium) from the first lithium nickel-based composite oxide after cleaning. Subsequently, the second mixture was subjected to a secondary heat treatment at 680°C for 16 hours in an oxygen atmosphere to obtain the final positive electrode active material. The composition of the final positive electrode active material was LiNi 0.93 Co 0.04 Mn 0.03 It is O2, and is a secondary particle form in which multiple primary particles are aggregated, and the average particle size of the above secondary particles (D 50 The diameter was 13.5 μm.

[0127] (2) Manufacturing of the positive electrode A composition for forming a positive electrode active material layer was prepared by mixing the above-mentioned positive electrode active material, polyvinylidene fluoride as a binder, and carbon nanotubes as a conductive material in a weight ratio of 98.5:1:0.5. This composition was then dispersed in an N-methylpyrrolidone solvent to produce a positive electrode slurry. The above positive electrode slurry was applied to an aluminum foil current collector, dried, and rolled to produce a positive electrode.

[0128] (3) Manufacturing of lithium secondary batteries A coin half-cell was manufactured using the manufactured positive electrode and lithium metal counter electrode, with a multilayer polyethylene and polypropylene separator interposed between them. The electrolyte solution consisted of ethylene carbonate and diethyl carbonate mixed in a 50:50 volume ratio, to which 1.0 M LiPF6 lithium salt was added, and this solution was injected.

[0129] Example 2 In Example 1, in the "Step of obtaining the positive electrode active material" of "(1) Production of positive electrode active material," the positive electrode active material, positive electrode, and lithium secondary battery were produced in substantially the same manner as in Example 1, except that when producing the second mixture, the lithium of the second lithium compound was mixed in such a way that it was 2 moles for every 100 moles of the total metal excluding lithium in the first lithium nickel composite oxide after washing.

[0130] Example 3 Except for the step in "(1) Production of positive electrode active material" of Example 1, "washing the first lithium nickel-based composite oxide with an aqueous solvent," the first lithium nickel-based composite oxide was added to distilled water and then stirred for 30 minutes to wash it, the positive electrode active material, positive electrode, and lithium secondary battery were produced in substantially the same manner as in Example 1.

[0131] Example 4 In the "Step for manufacturing the positive electrode active material" of "(1) Manufacturing the positive electrode active material" in Example 1, when manufacturing the second mixture, the lithium of the second lithium compound was mixed in such a way that 5 moles of lithium were added to 100 moles of the total metal excluding lithium in the first lithium nickel composite oxide after washing, and Co(OH)2 as a cobalt raw material, AlOOH as an aluminum raw material, and ZrO2 as a zirconium raw material were further added and mixed. Except for these differences, the positive electrode active material, positive electrode, and lithium secondary battery were manufactured in substantially the same manner as in Example 1. At this time, the cobalt of the cobalt raw material was added in such a way that 2 moles of cobalt, 0.5 moles of aluminum, and 0.15 moles of zirconium were added to 100 moles of the total metal excluding lithium in the first lithium nickel composite oxide after washing.

[0132] The positive electrode active material produced by the above method has a composition of LiNi 0.93 Co 0.04 Mn 0.03 It is O2, and is in the form of secondary particles formed by the aggregation of multiple primary particles, and the average particle size of the above secondary particles (D 50 Core particles with a diameter of 13.5 μm, and a coating layer containing Co, Al, and Zr is formed on the surface of the core particles.

[0133] Comparative Example 1 Except for the step in "(1) Production of positive electrode active material" of Example 1, "washing the first lithium nickel-based composite oxide with an aqueous solvent," in which 100 parts by weight of the first lithium nickel-based composite oxide was washed by adding it to 100 parts by weight of distilled water, the positive electrode active material, positive electrode, and lithium secondary battery were produced in substantially the same manner as in Example 1.

[0134] Comparative Example 2 In Example 1, the positive electrode active material, positive electrode, and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that in the step of "(1) Manufacturing of positive electrode active material" "Washing the first lithium nickel-based composite oxide with an aqueous solvent," 100 parts by weight of the first lithium nickel-based composite oxide was added to 100 parts by weight of distilled water, and the mixture was stirred for 30 minutes after adding it.

[0135] Comparative Example 3 In Example 1, the positive electrode active material, positive electrode, and lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that, in the "Step for manufacturing the positive electrode active material" of "(1) Manufacturing the positive electrode active material," the first lithium nickel-based composite oxide and the second lithium compound after washing were not mixed to produce a mixture, and the first lithium nickel-based composite oxide after washing was subjected to secondary heat treatment.

[0136] Comparative Example 4 In Example 1, in (i) "(1) Production of positive electrode active material," specifically in the step of "washing the first lithium nickel-based composite oxide with an aqueous solvent," 100 parts by weight of the first lithium nickel-based composite oxide was added to 100 parts by weight of distilled water, and the mixture was stirred and washed for 30 minutes after adding the oxide. In (ii) "Step of producing positive electrode active material," when producing the second mixture, the lithium of the second lithium compound was mixed so that it was 5 moles for every 100 moles of the total metal of the first lithium nickel-based composite oxide after washing, and Co(OH)2 as a cobalt raw material, AlOOH as an aluminum raw material, and ZrO2 as a zirconium raw material were further added and mixed. Except for these differences, the positive electrode active material, positive electrode, and lithium secondary battery were produced in substantially the same manner as in Example 1.

[0137] The positive electrode active material produced by the above method has a composition of LiNi 0.93 Co 0.04 Mn 0.03 It is O2, and is a secondary particle form in which multiple primary particles are aggregated, and the average particle size of the above secondary particles (D 50Core particles with a diameter of 13.5 μm, and a coating layer containing Co, Al, and Zr is formed on the surface of the core particles.

[0138] Evaluation Example 1: Evaluation of BET specific surface area The BET specific surface area was measured for each of the following: the first lithium nickel-based composite oxide obtained in the "Step of obtaining the first lithium nickel-based composite oxide" of "(1) Production of positive electrode active material" in Examples 1 to 4 and Comparative Examples 1 to 4 (i.e., the first lithium nickel-based composite oxide before washing), the first lithium nickel-based composite oxide after washing obtained in the "Step of washing the first lithium nickel-based composite oxide with an aqueous solvent", and the positive electrode active material obtained in the "Step of obtaining the positive electrode active material" of "(1) Production of positive electrode active material". The results are shown in Tables 1 and 2 below.

[0139] At this time, the BET specific surface area was measured using a nitrogen gas adsorption method with a MOUNTECH HM model-1208 specific surface area measuring device. Specifically, 0.3 g each of the first lithium nickel composite oxide before washing, the first lithium nickel composite oxide after washing, and the positive electrode active material from Examples 1-3 and Comparative Examples 1-4 were heated in a pretreatment chamber at 300°C in a nitrogen atmosphere for 1 hour. Then, an additional 15 minutes of pretreatment was performed at 300°C using the specific surface area measuring device, and the material was cooled to the temperature of liquid nitrogen and saturated with a gas of 30% nitrogen and 70% helium. After that, the material was heated to room temperature and the amount of desorbed gas was measured, and the specific surface area was calculated from the obtained results using the normal BET method.

[0140] Evaluation Example 2: Voiding Measurement The porosity of the washed lithium nickel-based composite oxide obtained in the "(1) Production of positive electrode active material" step of Examples 1 to 4 and Comparative Examples 1 to 4, and the porosity of the positive electrode active material obtained in the "(1) Production of positive electrode active material" step of Examples 1 to 4 and Comparative Examples 1 to 4, was calculated by BJH (Barrett-Joyner-Halenda) analysis, and the results are shown in Tables 1 and 2 below.

[0141] Specifically, nitrogen adsorption measurements were performed using the BELSORP-max measuring instrument manufactured by Microtrac. The void distribution in the void diameter range of 2 nm to 300 nm was interpreted using the BJH method, and the void fraction value was calculated.

[0142] Evaluation Example 3: Numerical Analysis of Cation Mixing Table 1 below shows the cation mixing values ​​calculated by Rietveld refinement of the profiles obtained by performing X-ray diffraction (XRD) analysis using Cu-Kα on the washed first lithium nickel-based composite oxide obtained in the "(1) Production of positive electrode active material" step of Examples 1 to 4 and Comparative Examples 1 to 4, and then performing Rietveld refinement on the profiles obtained.

[0143] Evaluation Example 4: Measurement of Residual Lithium Content The residual lithium content on the surface of the first lithium nickel-based composite oxide obtained after washing in the "(1) Production of positive electrode active material" step of Examples 1-4 and Comparative Examples 1-4 with an aqueous solvent was measured by acid-salt titration using hydrochloric acid (HCl) diluted at room temperature (25°C), and the results are shown in Table 1 below. At this time, the residual lithium content refers to the content based on 100% by weight of the first lithium nickel-based composite oxide after washing.

[0144] Evaluation Example 5: Electrical Conductivity Measurement The electrical conductivity of the washed lithium nickel-based composite oxide obtained in the "(1) Production of positive electrode active material" step of Examples 1-4 and Comparative Examples 1-4, and the positive electrode active material obtained in the "(1) Production of positive electrode active material" step of Comparative Examples 1-4, was measured. Specifically, the resistivity was measured at the point where the powder density of the washed lithium nickel-based composite oxide and the positive electrode active material was 3.3 g / cc, using Loresta-GXII, a powder resistance measuring device manufactured by Nittoseiko Analytech. The electrical conductivity values ​​were calculated by working backward from these values ​​and are shown in Tables 1 and 2 below.

[0145] Evaluation Example 6: Initial Charge / Discharge Capacity and Efficiency Lithium secondary batteries (half-cells) produced in Examples 1-4 and Comparative Examples 1-4 were manufactured, and these were charged at 25°C with a constant current of 0.2 C-rate up to an upper voltage limit of 4.3V, then with a constant voltage down to 0.05 C-rate, and finally discharged at 0.2 C-rate down to a cutoff voltage of 3.0V to perform initial charge and discharge. The initial charge capacity, initial discharge capacity, and the ratio of the latter to the former were calculated using efficiency and are shown in Table 2 below.

[0146] Evaluation Example 7: High-Temperature Life Evaluation The lithium secondary batteries (half-cells) manufactured in Examples 1-4 and Comparative Examples 1-4 underwent initial charging and discharging according to Evaluation Example 6. Subsequently, the charging and discharging cycles were repeated 50 or more times at 45°C in a voltage range of 3.0V to 4.3V at a rate of 1.0C-rate. The ratio of the discharge capacity after 50 cycles to the initial discharge capacity was calculated and is shown in Tables 1 and 2 below.

[0147] Evaluation Example 8: ICP and EP-EDS evaluation of the final cathode active material To confirm the overall composition of the positive electrode active material and the composition of the surface portion of the positive electrode active material, inductively coupled plasma (ICP) analysis and electron probe-energy dispersive X-ray spectroscopy (EP-EDS) analysis were performed on the positive electrode active materials produced in Example 4 and Comparative Example 4, respectively.

[0148] Specifically, 0.2 g of the cathode active material samples prepared in Example 4 and Comparative Example 4 were dispersed on carbon tape, and the types and content of elements in the entire cathode active material were analyzed using an Agilent 5800 inductively coupled plasma spectrometer manufactured by Agilent.

[0149] Furthermore, 0.2 g of the positive electrode active material samples prepared in Example 4 and Comparative Example 4 were dispersed on carbon tape. The samples were then irradiated with a scanning electron microscope (Helios G4 HX) manufactured by Thermo Fisher at an accelerating voltage of 15 keV, and the emitted X-rays were detected to analyze the types and content of elements on the surface of the positive electrode active material.

[0150] The results of ICP and EP-EDS analyses of the positive electrode active materials produced in Example 4 and Comparative Example 4 are shown in Table 1 below. The content of each element is expressed as the mole percentage of the metal relative to 100 mole percent of the total metal content excluding thium in the positive electrode active material. The EP-EDS / ICP values ​​for each metal component are shown in Table 1 below using the analytical values, and the values ​​in Equation 1 are also shown using these values.

[0151] [Table 1]

[0152] Referring to Table 1, it can be confirmed that the BET specific surface area of ​​the first lithium nickel composite oxide after cleaning is greater than the BET specific surface area of ​​the first lithium nickel composite oxide before cleaning. The BET specific surface area can be used as an indicator of the degree of structural damage to the active material that occurs during the cleaning process. Pores are formed inside the structure of the first lithium nickel composite oxide by the cleaning process, and in all of the examples and comparative examples, the BET specific surface area of ​​the first lithium nickel composite oxide increased after cleaning. On the other hand, it can be confirmed that the first lithium nickel composite oxide after cleaning of Comparative Examples 1, 2, and 5, which were cleaned by adding 100 moles of distilled water per 100 moles of first lithium nickel composite oxide, and the first lithium nickel composite oxide after cleaning of Examples 1-4 and Comparative Examples 3 and 4, which were cleaned by adding 50 moles of distilled water per 100 moles of first lithium nickel composite oxide, have higher BET specific surface area, porosity, cation mixing, and electrical conductivity values, and lower residual lithium compared to the first lithium nickel composite oxide after cleaning of Examples 1-4 and Comparative Examples 3 and 4.

[0153] [Table 2]

[0154] Table 2 allows us to confirm the physical properties and evaluation results of the final positive electrode active material after secondary heat treatment. In Examples 1 to 3, where distilled water is added at a rate of 50 parts by weight per 100 parts by weight of the first lithium nickel composite oxide during cleaning, and the lithium of the lithium hydroxide added during secondary heat treatment is in the range of 0.5 to 10 moles per 100 moles of the total metal excluding lithium in the first lithium nickel composite oxide after cleaning, it can be confirmed that high initial charge-discharge efficiency and life retention rate are achieved.

[0155] In Comparative Example 3, where distilled water was added at a rate of 50 parts by weight per 100 parts by weight of the first lithium nickel composite oxide during cleaning, the degree of damage to the lithium nickel composite oxide due to cleaning was less than in Comparative Examples 1 and 2, where distilled water was added at a rate of 100 parts by weight per 100 parts by weight of the first lithium nickel composite oxide during cleaning. This resulted in relatively higher initial charge-discharge efficiency and life retention rates. However, in Comparative Example 3, where lithium hydroxide was not added during the secondary heat treatment, the initial charge-discharge efficiency and life retention rates were lower than in Examples 1-3, where lithium hydroxide was added at an appropriate concentration during the secondary heat treatment.

[0156] On the other hand, in Example 4, which was prepared under the same conditions as Examples 1 and 2, by adding lithium hydroxide in a quantity of 5 moles during the secondary heat treatment to the first lithium nickel composite oxide after cleaning, and simultaneously adding the coating material to form a coating layer, it was confirmed that the electrical conductivity did not deteriorate despite the larger amount of lithium hydroxide added compared to Examples 1-3, and that the initial charge-discharge efficiency and high-temperature life characteristics were further improved compared to Examples 1-4. Furthermore, in Comparative Example 4, which was prepared under the same conditions as Comparative Example 2, by adding lithium hydroxide in the same content as in Example 4 during the secondary heat treatment to the first lithium nickel composite oxide after cleaning, and simultaneously adding the coating material, it was confirmed that structural damage occurred due to cleaning, with a BET specific surface area and porosity in a range similar to Comparative Example 2, due to the excessive addition of 100 parts by weight of distilled water during cleaning. However, it was confirmed that the electrical conductivity and battery performance were improved compared to Comparative Example 2 and the other comparative examples due to the formation of the coating layer. However, it was confirmed that Comparative Example 4 had inferior electrical conductivity and battery performance compared to Example 4, which formed the coating layer with the same coating material and coating content.

[0157] [Table 3]

[0158] Referring to Table 3 above, it can be seen that although Example 4 and Comparative Example 4 differed only in their cleaning conditions and the amount of coating material added was controlled to be the same, the coating material was formed more effectively on the surface of the particles in the positive electrode active material of Example 4 than in the positive electrode active material of Comparative Example 4. In Example 4, 50 parts by weight of distilled water were added based on 100 parts by weight of the first lithium nickel-based composite oxide, and the cleaning time was adjusted to 5 minutes. In contrast, in Comparative Example 5, 100 parts by weight of distilled water were added based on 100 parts by weight of the first lithium nickel-based composite oxide, and the cleaning time was adjusted to 30 minutes. In Example 4, the content of distilled water and the cleaning time were appropriately adjusted during cleaning, whereas in Comparative Example 4, the cleaning time was longer than in Example 4 with an excessive amount of distilled water. As a result, in Comparative Example 4, structural damage to the first lithium nickel-based composite oxide after cleaning occurred more than in Example 1, and it was found that the coating material was not formed as effectively on the surface of the particles despite being coated under the same coating conditions.

[0159] While desirable embodiments have been described above, the scope of the present invention is not limited thereto. Various modifications and improvements made by those skilled in the art, utilizing the basic concepts defined in the claims, also fall within the scope of the present invention. [Explanation of symbols]

[0160] 100: Lithium-ion rechargeable battery 10: Positive electrode 11: Positive lead tab 12: Positive terminal 20: Negative electrode 21: Negative lead tab 22: Negative terminal 30: Separator 40: Electrode assembly 50: Case 60: Sealing member 70: Electrode Tab 71: Positive Tab 72: Negative electrode tab

Claims

1. It is a positive electrode active material, Core particles containing a lithium nickel-based composite oxide represented by the following chemical formula 11, A coating layer located on the surface of the core particles, comprising one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, Includes, The value defined by formula 1 below is 5 or greater. Positive electrode active material for lithium secondary batteries. [Chemical formula 11] Li a11 Ni x11 M 11 y11 M 12 z11 O 2-b11 X b11 (In the above chemical formula 11, 0.9 ≦ a11 ≦ 1.2, 0.3 ≦ x11 < 1, 0 < y11 ≦ 0.7, 0 ≦ z11 ≦ 0.7, 0.9 ≦ x11 + y11 + z11 ≦ 1.1, and 0 ≦ b11 ≦ 0.1, and M 11 and M 12 are each independently one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more elements selected from F, P, and S.) [Formula 1] Σ[Mx(EP-EDS) / Mx(ICP)] (In the above formula 1, Mx represents the metal component contained in the coating layer, Mx(EP-EDS) is the mole percentage of metal Mx relative to the total elemental content present on the surface of the positive electrode active material excluding lithium, and Mx(ICP) is the mole percentage of metal Mx relative to the total elemental content present in the entire positive electrode active material (surface and core) excluding lithium.)

2. The BET specific surface area of ​​the positive electrode active material is 0.4 m². 2 The positive electrode active material for a lithium secondary battery according to claim 1, wherein the amount is less than or equal to / g.

3. The porosity of the positive electrode active material is 0.01 cm². 3 The positive electrode active material for a lithium secondary battery according to claim 1, wherein the amount is less than or equal to / g.

4. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the electrical conductivity of the positive electrode active material is 0.05 S / cm to 0.15 S / cm.

5. A method for producing a positive electrode active material for lithium secondary batteries, A step of preparing a first mixture by mixing a nickel-based composite hydroxide and a first lithium compound; A step of obtaining a first lithium nickel-based composite oxide by subjecting the first mixture to primary heat treatment; The first step involves washing the lithium nickel-based composite oxide with an aqueous solvent; A step of mixing the washed first lithium nickel-based composite oxide and the second lithium compound to produce a second mixture; and A step of obtaining a positive electrode active material by performing a secondary heat treatment on the second mixture; Includes, The first lithium nickel-based composite oxide after the aforementioned cleaning has a BET specific surface area of ​​0.3 m². 2 / g~2m 2 The porosity is 0.01 cm / g. 3 / g ~ 0.15cm 3 / g is A method for producing positive electrode active material for lithium secondary batteries.

6. The method for producing a positive electrode active material for a lithium secondary battery according to claim 5, wherein the nickel-based composite hydroxide is represented by the following chemical formula 1. [Chemical formula 1] Ni x1 M 1 y1 M 2 z1 (OH) 2 (In the above chemical formula 1, 0.3 ≤ x1 < 1, 0 < y1 ≤ 0.7, 0 ≤ z1 ≤ 0.7, and 0.9 ≤ x1 + y1 + z1 ≤ 1.1, M 1 and M 2 Each of these elements is independently selected from one or more elements: Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zr, and Zn.

7. In the step of preparing the first mixture by mixing a nickel-based composite hydroxide and a first lithium compound, The method for producing a positive electrode active material for a lithium secondary battery according to claim 5, wherein the nickel-based composite hydroxide and the first lithium compound are mixed such that the molar ratio of lithium in the first lithium compound to the total metal of the nickel-based composite hydroxide is 0.9 to 1.

1.

8. The BET specific surface area of ​​the primary lithium nickel-based composite oxide before cleaning was 0.1 m². 2 / g to 0.4m 2 A method for producing a positive electrode active material for a lithium secondary battery according to claim 5, wherein the amount is / g.

9. The aqueous solvent is water. The method for producing a positive electrode active material for a lithium secondary battery according to claim 5, wherein the amount of water used for washing is 10 to 90 parts by weight per 100 parts by weight of the first lithium nickel-based composite oxide.

10. The method for producing a positive electrode active material for a lithium secondary battery according to claim 5, wherein the cation mixing value of the first lithium nickel-based composite oxide after washing, as measured by X-ray diffraction analysis, is 1% to 2%.

11. The method for producing a positive electrode active material for a lithium secondary battery according to claim 5, wherein the residual lithium content of the first lithium nickel-based composite oxide after cleaning is 0.1% to 0.2% by weight, based on 100% by weight of the first lithium nickel-based composite oxide after cleaning.

12. The method for producing a positive electrode active material for a lithium secondary battery according to claim 5, wherein the electrical conductivity of the first lithium nickel-based composite oxide after cleaning is 0.1 S / cm to 0.22 S / cm.

13. The method for producing a positive electrode active material for a lithium secondary battery according to claim 5, wherein the second lithium compound is mixed so that the lithium content is 0.5 to 10 moles per 100 moles of the total metal of the first lithium nickel composite oxide after washing, excluding the lithium.

14. The method for producing a positive electrode active material for a lithium secondary battery according to claim 5, wherein the secondary heat treatment is performed in an oxidizing gas atmosphere at a temperature in the range of 600°C to 1200°C for 20 hours or less.

15. A positive electrode comprising a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector, The positive electrode active material layer comprises a positive electrode containing a positive electrode active material described in any one of claims 1 to 4, or a positive electrode active material manufactured by a manufacturing method described in any one of claims 5 to 14, The negative electrode and, Electrolytes, Lithium-ion batteries, including lithium-ion batteries.

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