Positive electrode active material and method for preparing same

Abstract

The present invention relates to a positive electrode active material, a method for preparing same, and a positive electrode and lithium secondary battery comprising same. The positive electrode active material has a coating layer containing boron-containing compounds, the amount of the compounds satisfying a specific range, and thus can improve the capacity and resistance performance of a lithium secondary battery comprising the positive electrode active material.

Description

Cathode active material and method for manufacturing the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0177276 filed on December 3, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of this specification.

[0003] Technology field

[0004] The present invention relates to a positive electrode active material, a method for manufacturing the same, a positive electrode including the same, and a lithium secondary battery.

[0005]

[0006] Lithium secondary batteries consist of four major components: a positive electrode, a negative electrode, a separator, and an electrolyte. Among these, the positive electrode active material included in the positive electrode plays a significant role in determining the battery's capacity, output, and lifespan. Improving the performance of the positive electrode active material is essential for lithium secondary batteries to achieve high energy density, output, and lifespan; consequently, much research has recently been conducted to develop high-performance positive electrode active materials.

[0007] Since the co-precipitation method is used to manufacture the cathode active material used in lithium secondary batteries, the manufactured cathode active material takes the form of secondary particles formed by the aggregation of primary particles. A washing process is essential to remove lithium byproducts present on the surface of the cathode active material in the form of secondary particles. However, because the washing process creates defects on the surface of the cathode active material, additional coating and heat treatment processes must be performed; consequently, coating and heat treatment processes using boron have generally been applied. However, during long-term charging and discharging, microcracks in the active material with secondary particle forms continuously enlarge, causing inter-particle cracking, which leads to structural degradation, gas release, and battery instability.

[0008] Recently, single-particle cathode active materials have been developed to address the problems associated with such secondary particle-type cathode active materials. However, while single-particle cathode active materials do not require a washing process, their specific surface area is smaller compared to secondary particles, which limits their reversible capacity. Therefore, there is a need to develop technology to improve the capacity of single-particle cathode active materials.

[0009]

[0010] The problem to be solved by the present invention is to improve the capacity characteristics of a battery containing the same by controlling the content ratio of specific boron-containing compounds included in the coating layer of the positive electrode active material.

[0011] In addition, the present invention aims to provide a method for manufacturing the above-mentioned positive active material.

[0012] In addition, the present invention aims to provide a positive electrode and a lithium secondary battery comprising the above-mentioned positive electrode active material.

[0013]

[0014] (1) The present invention comprises a lithium composite transition metal oxide in the form of a single particle; and a coating layer formed on the lithium composite transition metal oxide, wherein the lithium composite transition metal oxide comprises nickel and one or more selected from the group consisting of cobalt, manganese, and aluminum, and the coating layer comprises a boron-containing compound, and as a result of ToF-SIMS analysis, (LiBO3) - (LiB2O3) for peak intensity (a) - A positive electrode active material is provided in which the ratio (b / a) of the peak intensity (b) is less than 0.5.

[0015] (2) The present invention provides a positive electrode active material in the above (1), wherein the single particle form is a single particle form consisting of one primary particle or a form in which two or more and ten or fewer primary particles are aggregated.

[0016] (3) The present invention, in accordance with (1) or (2) above, has an average particle size (D) of the positive active material. 50 ) provides a positive electrode active material having a size of 5 μm or more and 10 μm or less.

[0017] (4) The present invention provides a positive electrode active material in any one of (1) to (3) above, wherein the lithium composite transition metal oxide contains 60 mol% or more of nickel with respect to the molar amount of metal excluding lithium.

[0018] (5) The present invention, in any one of (1) to (4) above, the (LiBO3) - (LiB2O3) for peak intensity (a) - A positive electrode active material is provided having a ratio (b / a) of peak intensity (b) of 0.1 or more and less than 0.5.

[0019] (6) In any one of (1) to (5) above, the present invention, as a result of ToF-SIMS analysis, (LiBO3) - Peak, (LiB2O3) - Peak, (LiB2O4) - Peak, (B3O5) - Peak and (Li2B3O6) - (LiBO3) for the total sum of peak intensities (c) - A positive electrode active material is provided, wherein the percentage ((a / c) × 100) of the peak intensity (a) is 10.0% or more and 16.0% or less.

[0020] (7) In any one of (1) to (6) above, the present invention, as a result of ToF-SIMS analysis, among the boron-containing compounds (LiBO3) - Peak, (LiB2O3) - Peak, (LiB2O4) - Peak, (B3O5) - Peak and (Li2B3O6) - (LiB2O3) for the total sum of peak intensities (c) -A positive electrode active material is provided in which the percentage ((b / c) × 100) of the peak intensity (b) is 1.0% or more and 7.0% or less.

[0021] (8) The present invention provides a positive electrode active material in any one of (1) to (7) above, wherein the lithium composite transition metal oxide has a composition represented by the following chemical formula 1.

[0022] [Chemical Formula 1]

[0023] Li x Ni a Co b M 1 c M 2 d O2

[0024] In the above chemical formula 1,

[0025] M 1 is Mn, Al, or a combination thereof, and

[0026] M 2 is one or more selected from the group consisting of W, B, Zr, Y, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, Cr, V, Cu, Sr, Ti, Mg, Mo, Sn, Fe, Zn, and Si, and

[0027] 0.9≤x≤1.1, 0.6≤a<1, 0 <b<0.4, 0<c<0.4, 0≤d≤0.2이다.

[0028] (9) The present invention comprises the step of preparing a lithium composite transition metal oxide by mixing a composite transition metal hydroxide and a lithium-containing raw material and then calcining (S0); and the step of forming a coating layer on the lithium composite transition metal oxide by mixing the lithium composite transition metal oxide and a boron-containing raw material and then heat treating (S1).

[0029] The present invention provides a method for manufacturing an anode active material comprising: a first heat treatment step (S1-1) in which the heat treatment of the above S1 step is performed by increasing the temperature from room temperature to a temperature of 340°C or higher and 380°C or lower at a rate of 1°C / min or higher and 10°C / min or lower, and maintaining the increased temperature while performing heat treatment; and a second heat treatment step (S1-2) in which the heat treatment is performed by decreasing the temperature from the first heat treatment temperature of the above S1-1 step to a temperature of 100°C or higher and 150°C or lower at a rate of 0.1°C / min or higher and 1.0°C / min or lower, and maintaining the decreased temperature while performing heat treatment.

[0030] (10) The present invention provides a method for manufacturing a positive electrode active material according to (9) above, wherein in step S1, the boron-containing raw material is mixed such that the boron content is 0.2 parts by weight or more and 1.0 parts by weight or less per 100 parts by weight of the lithium composite transition metal oxide.

[0031] (11) The present invention provides a method for manufacturing an anode active material, wherein the first heat treatment of the S1-1 step is performed for 1 hour or more and 10 hours or less in accordance with (9) or (10) above.

[0032] (12) The present invention provides a method for manufacturing an anode active material in which, in any one of (9) to (11) above, the secondary heat treatment of step S1-2 is performed for 1 hour or more and 10 hours or less.

[0033] (13) The present invention provides a method for manufacturing an anode active material, wherein in any one of (9) to (12) above, the S0 step of the sintering is performed by first sintering at a temperature of 700°C or higher and 1000°C or lower, and then second sintering at a temperature of 700°C or higher and 1100°C or lower.

[0034] (14) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (8) above.

[0035] (15) The present invention provides a lithium secondary battery comprising a positive electrode according to (14) above.

[0036]

[0037] The positive electrode active material of the present invention comprises a coating layer containing a boron-containing compound formed on a lithium complex transition metal oxide, and as a result of ToF-SIMS analysis, (LiBO3) - (LiB2O3) for peak intensity (a) - The ratio (b / a) of the peak intensity (b) satisfies a specific range, thereby improving the capacity characteristics and resistance performance of the lithium secondary battery containing it.

[0038] The method for manufacturing a positive electrode active material of the present invention divides the heat treatment during boron coating into two stages and performs the heat treatment by setting the second heat treatment temperature lower than the first heat treatment temperature, thereby controlling the content of boron-containing compounds present in the coating layer, and thus can improve the capacity characteristics and resistance performance of a lithium secondary battery containing a positive electrode active material manufactured by the above method.

[0039]

[0040] The present invention will be described in more detail below to aid in understanding. In this regard, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0041] The terms used in this specification are used merely to describe exemplary embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0042] In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0043] In this specification, 'primary particle' refers to a minimum particle unit that is distinguished as a single mass when the cross-section of the positive active material is observed through a scanning electron microscope (SEM), and may consist of one crystal grain or multiple crystal grains.

[0044] In this specification, 'secondary particle' refers to a secondary structure formed by the aggregation of a plurality of primary particles. The average particle size of the secondary particle can be measured using a particle size analyzer.

[0045] In this specification, the term 'single particle form' refers to a form composed of 50 or fewer primary particles, as opposed to a spherical secondary particle form formed by the aggregation of tens to hundreds of primary particles manufactured by conventional methods. Specifically, in the present invention, the single particle form may be a single particle composed of one primary particle, or it may be a form in which 2 or more, 3 or more, 4 or more, 5 or more, and 10 or fewer, 20 or fewer, 30 or fewer, 40 or fewer, or 50 or fewer primary particles are aggregated.

[0046] In this specification, 'D n ' represents the particle size at the n% point of the cumulative volume distribution according to particle size. That is, D 50 is the particle size at the 50% point of the cumulative volume distribution according to particle size, and D 90 is the particle size at the 90% point of the cumulative volume distribution according to particle size, and D 10 is the particle size at the 10% point of the cumulative volume distribution according to particle size. The above D nIt can be measured using the laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Malvern Panalytic, Mastersizer 3000) to calculate the particle size distribution by measuring the difference in diffraction patterns according to particle size as the particles pass through the laser beam. By calculating the particle diameters at the points corresponding to 10%, 50%, and 90% of the cumulative volume distribution according to particle size in the measuring device, D 10 , D 50 and D 90 It can measure.

[0047]

[0048] positive electrode active material

[0049] The present invention comprises a lithium composite transition metal oxide in the form of a single particle; and a coating layer formed on the lithium composite transition metal oxide, wherein the lithium composite transition metal oxide comprises nickel and one or more selected from the group consisting of cobalt, manganese, and aluminum, and the coating layer comprises a boron-containing compound, and according to ToF-SIMS analysis results, (LiBO3) - (LiB2O3) for peak intensity (a) - A positive electrode active material is provided in which the ratio (b / a) of the peak intensity (b) is less than 0.5.

[0050] The inventors of the present invention have a positive electrode active material comprising a coating layer containing a boron-containing compound formed on the lithium complex transition metal oxide, and when the positive electrode active material is analyzed by ToF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry), (LiBO3) - (LiB2O3) for peak intensity (a) -The present invention was completed by discovering that when the ratio (b / a) of the peak intensity (b) is less than 0.5, the charge and discharge capacity of the lithium secondary battery containing the positive electrode active material can be improved and the resistance characteristics can also be improved.

[0051] ToF-SIMS is a method that injects a high-energy ion beam into a sample to cause collisions on the surface of the sample and analyzes the ions emitted due to the collisions. By using this, the components of the coating layer of the cathode active material of the present invention and the content of each component can be analyzed.

[0052] The above (LiBO3) obtained from the ToF-SIMS analysis results - (LiB2O3) for peak intensity (a) - Specifically, the ratio (b / a) of the peak intensity (b) may be less than 0.5, 0.49 or less, 0.47 or less, 0.45 or less, 0.43 or less, 0.41 or less, 0.39 or less, 0.37 or less, 0.35 or less, and may also be 0.3 or more, 0.25 or more, 0.2 or more, 0.15 or more, 0.1 or more. When the ratio (b / a) satisfies the above range, the charge / discharge capacity and resistance characteristics of the lithium secondary battery containing the positive electrode active material can be improved. If the ratio (b / a) is greater than the above range, the charge / discharge capacity and resistance characteristics may be degraded. If the ratio (b / a) is smaller than the above range, the thickness of the coating layer becomes thinner, and the LiB2O3 layer fails to protect the surface layer of the positive electrode active material, which may result in a decrease in lifespan characteristics.

[0053] The above single particle form may be a single particle form consisting of one primary particle or a form in which two or more and ten or fewer primary particles are aggregated.

[0054]

[0055] According to the present invention, the average particle size (D) of the positive electrode active material 50The average particle size may be 5 μm or more and 10 μm or less. Specifically, the average particle size may be 5 μm or more, 5.1 μm or more, 5.2 μm or more, 5.3 μm or more, 5.4 μm or more, or 5.5 μm or more, and may be 10 μm or less, 9 μm or less, 8 μm or less, or 7 μm or less. When the average particle size satisfies the above range, the cathode active material has a specific surface area within an appropriate range, so not only the capacity characteristics but also the lifespan characteristics can be improved.

[0056]

[0057] According to the present invention, as a result of ToF-SIMS analysis of the anode active material, (LiBO3) - Peak, (LiB2O3) - Peak, (LiB2O4) - Peak, (B3O5) - Peak and (Li2B3O6) - (LiBO3) for the total sum of peak intensities (c) - The percentage ((a / c) × 100) of the peak intensity (a) may be 10.0% or more and 16.0% or less. More specifically, the percentage ((a / c) × 100) may be 10.0% or more, 10.5% or more, 11.0% or more, 11.5% or more, 12.0% or more, 12.5% ​​or more, and 15.5% or less, 15.7% or less, 15.9% or less, and 16.0% or less. When the percentage ((a / c) × 100) satisfies the above range, a LiBO3 layer of the most appropriate thickness is formed, and thereby, charge / discharge capacity and efficiency characteristics can be improved.

[0058] According to the present invention, as a result of ToF-SIMS analysis of the anode active material, among the boron-containing compounds (LiBO3) - Peak, (LiB2O3) - Peak, (LiB2O4) - Peak, (B3O5) - Peak and (Li2B3O6) - (LiB2O3) for the total sum of peak intensities (c) -The percentage ((b / c) × 100) of the peak intensity (b) may be 1.0% or more and 7.0% or less. More specifically, the percentage ((b / c) × 100) may be 1.0% or more, 1.5% or more, 2.0% or more, 2.5% or more, 3.0% or more, 3.5% or more, 4.0% or more, and 7.0% or less, 6.5% or less, 6.0% or less, 5.5% or less. When the percentage ((b / c) × 100) satisfies the above range, the resistance characteristics may be improved.

[0059]

[0060] According to the present invention, the lithium composite transition metal oxide may contain 60 mol% or more of nickel with respect to the molar amount of metal excluding lithium. Specifically, it may contain 60 mol% or more, 70 mol% or more, 80 mol% or more, or 90 mol% or more of nickel. That is, the lithium composite transition metal oxide may be a high-nickel (High Ni) lithium composite transition metal oxide. In this case, the energy density of a lithium secondary battery containing the positive electrode active material can be further improved.

[0061] The above lithium complex transition metal oxide may have a composition represented by the following chemical formula 1.

[0062] [Chemical Formula 1]

[0063] Li x Ni a Co b M 1 c M 2 d O2

[0064] In the above chemical formula 1,

[0065] M 1 is Mn, Al, or a combination thereof, and

[0066] M 2is one or more selected from the group consisting of W, B, Zr, Y, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, Cr, V, Cu, Sr, Ti, Mg, Mo, Sn, Fe, Zn, and Si, and

[0067] 0.9≤x≤1.1, 0.6≤a<1, 0 <b<0.4, 0<c<0.4, 0≤d≤0.2이다.

[0068] The above a represents the atomic fraction of nickel among the metal elements in the lithium composite transition metal oxide, and may be 0.6≤a<1, 0.8≤a≤0.98, or 0.85≤a≤0.98.

[0069] The above b refers to the atomic fraction of cobalt among the metal elements in the lithium complex transition metal oxide, where 0 <b<0.4, 0.01≤b≤0.15 또는 0.01≤b≤0.1일 수 있다.

[0070] The above c refers to the atomic fraction of manganese, aluminum, or a combination thereof among the metal elements in the lithium composite transition metal oxide, where 0 <c<0.4, 0.01≤c≤0.15 또는 0.01≤c≤0.1일 수 있다.

[0071] The above d is M among the metal elements in the lithium complex transition metal oxide. 2 It refers to the atomic fraction of, which can be 0≤d≤0.2, 0≤d≤0.05, or 0.005≤d≤0.05.

[0072]

[0073] Method for manufacturing positive electrode active material

[0074] The present invention provides a method for manufacturing an anode active material comprising: a step (S0) of mixing a composite transition metal hydroxide and a lithium-containing raw material and then calcining to produce a lithium composite transition metal oxide; and a step (S1) of mixing the lithium composite transition metal oxide and a boron-containing raw material and then heat treating to form a coating layer on the lithium composite transition metal oxide, wherein the heat treatment in step S1 comprises a first heat treatment step (S1-1) of increasing the temperature from room temperature to a temperature of 340°C or higher and 380°C or lower at a rate of 1°C / min or higher and 10°C / min or lower, and performing heat treatment while maintaining the increased temperature; and a second heat treatment step (S1-2) of decreasing the temperature from the first heat treatment temperature of step S1-1 to a temperature of 100°C or higher and 150°C or lower at a rate of 0.1°C / min or higher and 1.0°C / min or lower, and performing heat treatment while maintaining the decreased temperature.

[0075] The aforementioned positive electrode active material can be manufactured using the above manufacturing method.

[0076]

[0077] Hereinafter, the method for manufacturing the above-mentioned positive active material is described in more detail.

[0078]

[0079] S0 level

[0080] Step S0 is a step of manufacturing a lithium complex transition metal oxide by mixing a complex transition metal hydroxide and a lithium-containing raw material and then calcining it.

[0081] According to the present invention, when mixing the composite transition metal hydroxide and the lithium-containing raw material in step S0, a raw material containing a doping element may be further mixed. That is, the raw material containing the doping element may be optionally added.

[0082]

[0083] The above-mentioned complex transition metal hydroxide may be produced by purchasing and using a precursor such as a commercially available nickel-cobalt-manganese-based hydroxide, or by manufacturing it according to a precursor manufacturing method known in the relevant technical field.

[0084] The above composite transition metal hydroxide may include nickel and one or more selected from the group consisting of cobalt, manganese, and aluminum.

[0085]

[0086] The above lithium-containing raw material may be, for example, a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and more specific examples may be Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, Li3C6H5O7, or a mixture thereof.

[0087] The raw material containing the doping element may be a carbonate, sulfate, nitrate, hydroxide, or oxide of the doping element. The doping element may be one or more selected from the group consisting of W, Co, B, Zr, Y, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, Cr, V, Cu, Sr, Ti, Mg, Mo, Sn, Fe, Zn, and Si.

[0088]

[0089] The above firing may be performed by first firing at a temperature of 700°C or higher and 1000°C or lower, and then second firing at a temperature of 700°C or higher and 1100°C or lower.

[0090] Specifically, the first firing temperature may be 700°C or higher, 720°C or higher, 740°C or higher, 760°C or higher, 780°C or higher, 800°C or higher, or 820°C or higher, and may be 900°C or lower, 920°C or lower, 940°C or lower, 960°C or lower, 980°C or lower, or 1000°C or lower.

[0091] In addition, the above first firing time may be 5 hours or more and 20 hours or less, specifically 5 hours or more, 7 hours or more, 9 hours or more, and 11 hours or more, and also 13 hours or less, 15 hours or less, 17 hours or less, 19 hours or less, and 20 hours or less.

[0092] In addition, the above-mentioned first firing may be performed in an atmospheric or oxygen atmosphere, and preferably in an oxygen atmosphere. In the present invention, an oxygen atmosphere refers to an atmosphere containing a sufficient amount of oxygen for firing, including an atmospheric atmosphere. In particular, it refers to an atmosphere in which the partial pressure of oxygen is higher than that of an atmospheric atmosphere.

[0093] During the first calcination, the lithium-containing raw material can be mixed such that the molar ratio of lithium to the total molar amount of transition metal included in the composite transition metal hydroxide is 0.9 or more and 1.3 or less, preferably 0.93 or more and 1.05 or less, and more preferably 0.95 or more and 1.03 or less. When the molar ratio of the lithium-containing raw material mixed during the first calcination satisfies the above range, the layered structure of the lithium transition metal oxide can be properly formed to improve electrochemical properties, and lithium by-products remaining on the surface can be minimized to reduce resistance or adverse reactions with the electrolyte.

[0094] Specifically, the above secondary firing temperature may be 700°C or higher, 720°C or higher, 740°C or higher, 760°C or higher, and 850°C or lower, 900°C or lower, 950°C or lower, 1000°C or lower, 1050°C or lower, 1100°C or lower.

[0095] In addition, the above secondary firing time may be 5 hours or more and 20 hours or less, specifically 5 hours or more, 7 hours or more, 9 hours or more, and 11 hours or more, and also 13 hours or less, 15 hours or less, 17 hours or less, 19 hours or less, and 20 hours or less.

[0096] In addition, the above secondary firing may be performed in an atmospheric or oxygen atmosphere, and preferably in an oxygen atmosphere. In the present invention, an oxygen atmosphere refers to an atmosphere containing a sufficient amount of oxygen for firing, including an atmospheric atmosphere. In particular, it refers to an atmosphere in which the partial pressure of oxygen is higher than that of an atmospheric atmosphere.

[0097] The above first firing and second firing may be performed continuously, or a grinding step may be further included between the first firing and the second firing.

[0098] During the second calcination described above, the pulverized product after the first calcination may be mixed with a lithium-containing raw material or a doping element-containing raw material, and then calcined. At this time, the types of the lithium-containing raw material and the doping element-containing raw material may be within the aforementioned range. In this case, the lithium-containing raw material may be mixed such that the molar ratio of lithium to the total molar amount of transition metal included in the pulverized product after the first calcination is 0.01 or more and 0.1 or less, preferably 0.01 or more and 0.09 or less, and more preferably 0.01 or more and 0.07 or less. If the molar ratio of the lithium-containing raw material mixed during the second calcination satisfies the above range, lithium does not remain on the surface but penetrates evenly into the structure, contributing to structural stabilization and improving electrochemical properties.

[0099] The above grinding step is intended to break down aggregated cathode active materials and appropriately control the particle size and shape of particles within the cathode material, and can be performed using a grinding device well known in the art, such as a jet-mill grinder or a ball-mill grinder.

[0100] In the grinding step above, the particle size distribution and primary particle shape of the lithium transition metal oxide particles can be controlled by appropriately adjusting grinding conditions such as grinding pressure and input speed. For example, the grinding may be performed by adjusting the grinding conditions so that the average particle size of the cathode active material after grinding is approximately 2.0 to 10.0 μm, 3.0 to 8.0 μm, 4.0 to 7.0 μm, or 5.0 to 6.0 μm.

[0101]

[0102] S1 stage

[0103] Step S1 is a step of mixing the lithium composite transition metal oxide and the boron-containing raw material and then heat-treating to form a coating layer on the lithium composite transition metal oxide.

[0104] The above heat treatment specifically includes a first heat treatment step (S1-1) and a second heat treatment step (S1-2).

[0105] The above first heat treatment step involves increasing the temperature from room temperature to a temperature of 340°C or higher and 380°C or lower at a rate of 1°C / min or higher and 10°C / min or lower, and performing heat treatment while maintaining the increased temperature, and the above second heat treatment step involves decreasing the temperature from the first heat treatment temperature to a temperature of 100°C or higher and 150°C or lower at a rate of 0.1°C / min or higher and 1.0°C / min or lower, and performing heat treatment while maintaining the decreased temperature.

[0106] If a first heat treatment is performed under the conditions described above, residual lithium compounds remaining in the lithium composite transition metal oxide can react with boron compounds to form lithium-boron compounds, thereby reducing residual lithium. Additionally, if a second heat treatment is performed under the conditions described above, the lithium-boron compounds formed during the first heat treatment can bond with the surface of the lithium composite transition metal oxide to form a uniform coating layer. On the other hand, if the heat treatment is performed at a single temperature rather than divided into first and second stages, the coating layer may not be formed as a uniform layer. The content ratio of boron-containing compounds included in the coating layer of the manufactured cathode active material may vary depending on whether the heat treatment is performed in stages during coating, and if so, how the heat treatment temperature and the heating and cooling rates are controlled at each stage.

[0107]

[0108] According to the present invention, in step S1, the boron-containing raw material may be mixed such that the boron content is 0.2 parts by weight or more and 1.0 parts by weight or less with respect to 100 parts by weight of the lithium composite transition metal oxide. Specifically, it may be mixed such that the boron content is 0.2 parts by weight or more, 0.3 parts by weight or more, 0.4 parts by weight or more, 0.5 parts by weight or more, and 0.6 parts by weight or more, and may also be mixed such that the boron content is 0.8 parts by weight or less, 0.9 parts by weight or less, and 1.0 parts by weight or less. In this case, optimal capacitance characteristics and resistance characteristics can be achieved.

[0109]

[0110] Specifically, the heat treatment temperature of the above S1-1 step may be 340°C or higher, 345°C or higher, or 350°C or higher. Specifically, the heating rate may be 1°C / min or higher, 2°C / min or higher, 3°C / min or higher, or 4°C / min or higher, and may be 6°C / min or lower, 7°C / min or lower, 8°C / min or lower, 9°C / min or lower, or 10°C / min or lower.

[0111] Specifically, the heat treatment temperature of the above S1-2 step may be 100°C or higher, 110°C or higher, 120°C or higher, and 140°C or lower, 150°C or lower. Specifically, the cooling rate may be 0.1°C / min or higher, 0.2°C / min or higher, 0.3°C / min or higher, 0.4°C / min or higher, and 0.6°C / min or lower, 0.7°C / min or lower, 0.8°C / min or lower, 0.9°C / min or lower, 1.0°C / min or lower.

[0112]

[0113] In addition, the heat treatment of the above S1-1 step may be performed for 1 hour or more and 10 hours or less. Specifically, it may be performed for 1 hour or more, 2 hours or more, 3 hours or more, or 4 hours or more, and may be performed for 6 hours or less, 7 hours or less, 8 hours or less, 9 hours or less, or 10 hours or less.

[0114] In addition, the heat treatment of the above S1-2 step may be performed for 1 hour or more and 10 hours or less. Specifically, it may be performed for 1 hour or more, 2 hours or more, 3 hours or more, 4 hours or more, 5 hours or more, or 6 hours or more, and may be performed for 8 hours or less, 9 hours or less, or 10 hours or less.

[0115]

[0116] anode

[0117] The present invention provides a positive electrode comprising the above positive electrode active material.

[0118] The above positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer may include the positive electrode active material.

[0119] The above positive current collector may include a highly conductive metal, and is not particularly limited as long as it facilitates the adhesion of the positive active material layer and is non-reactive within the voltage range of the battery. The above positive current collector may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. Additionally, the above positive current collector may typically have a thickness of 3 μm to 500 μm, and may form fine irregularities on the surface of the current collector to increase the adhesion of the positive active material. It may be used in various forms, such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

[0120] The positive active material layer may include, together with the positive active material, a conductive material and a binder as needed. In this case, the positive active material may be included in an amount of 80% to 99% by weight, more specifically 85% to 98.5% by weight, based on the total weight of the positive active material layer, and may exhibit excellent capacity characteristics within this range.

[0121] The above conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powder or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above conductive material may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive electrode active material layer.

[0122] The above binder serves to improve the adhesion between positive active material particles and the adhesion between the positive active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which hydrogens thereof are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included in an amount of 0.1% to 15% by weight relative to the total weight of the positive active material layer.

[0123] The above-described anode may be manufactured according to a conventional anode manufacturing method, except for using the above-described anode active material. Specifically, the above-described anode may be manufactured by applying a composition for forming an anode active material layer (anode slurry), prepared by dissolving or dispersing the above-described anode active material and, optionally, a binder, a conductive material, and a dispersant in a solvent, onto an anode current collector, followed by drying and rolling, or by casting the composition for forming an anode active material layer onto a separate support and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0124] The above solvent may be a solvent generally used in the relevant technical field, and may include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of the above solvent used is sufficient if it is sufficient to dissolve or disperse the anode active material, conductive material, binder, and dispersant, taking into account the coating thickness of the slurry and the manufacturing yield, and to have a viscosity that can exhibit excellent thickness uniformity when coated for anode manufacturing thereafter.

[0125]

[0126] lithium secondary battery

[0127] The present invention provides a lithium secondary battery comprising the above positive electrode.

[0128] The above lithium secondary battery may comprise the positive electrode; the negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte. Additionally, the lithium secondary battery may optionally further comprise a battery container housing an electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member sealing the battery container.

[0129] The above cathode may include a cathode current collector and a cathode active material layer located on the cathode current collector.

[0130] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative current collector may typically have a thickness of 3 μm to 500 μm, and, similar to the positive current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0131] The above-mentioned cathode active material layer may optionally include a binder and a conductive material together with the cathode active material.

[0132] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂ βExamples include metal oxides capable of doping and dedoping lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Furthermore, the carbon material may include low-crystallinity carbon and high-crystallinity carbon. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes. The above-mentioned cathode active material may be included in an amount of 80% to 99% by weight based on the total weight of the cathode active material layer.

[0133] The binder of the above-mentioned negative electrode active material layer is a component that assists in the bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0134] The conductive material of the above-mentioned negative electrode active material layer is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, preferably 5% by weight or less, based on the total weight of the negative electrode active material layer. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives may be used.

[0135] The above cathode may be manufactured by applying a composition for forming a cathode active material layer (cathode slurry), prepared by dissolving or dispersing a cathode active material and optionally a binder and a conductive material in a solvent, onto a cathode current collector and drying it, or by casting the composition for forming a cathode active material layer onto a separate support and then laminating the film obtained by peeling off from the support onto a cathode current collector.

[0136] The above separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. It can be used without special limitations as long as it is typically used as a separator in a lithium secondary battery, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and it may optionally be used in a single-layer or multi-layer structure.

[0137] Examples of the above electrolytes include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which can be used in the manufacture of lithium secondary batteries, but are not limited to these. As a specific example, the above electrolyte may include an organic solvent and a lithium salt.

[0138] The above organic solvent may be used without special restrictions as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery, and a low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.

[0139] The above lithium salt may be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. Specifically, the anion of the above lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - The lithium salt may be at least one selected from the group consisting of LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc. It is preferable to use the lithium salt within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0140] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1% to 5% by weight based on the total weight of the electrolyte.

[0141]

[0142] Since the lithium secondary battery containing the positive electrode active material according to the present invention exhibits high capacity and improved resistance characteristics, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the field of electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0143] The external shape of the lithium secondary battery of the present invention is not particularly limited, but can be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

[0144] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also preferably be used as a unit cell in a medium-to-large battery module comprising a plurality of battery cells.

[0145] Accordingly, a battery module including the above-mentioned lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0146] The above battery module or battery pack can be used as a power source for one or more medium-to-large devices, including a power tool; an electric vehicle, including an electric vehicle, a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0147]

[0148] Examples

[0149] The present invention will be explained in more detail below through examples. However, the following examples are intended to illustrate the present invention and do not limit the scope of the present invention.

[0150]

[0151] Example 1

[0152] Cathode active material precursor [Composition: Ni 0.96 Co 0.03 Mn 0.01 [OH]2 and LiOH as a lithium raw material were mixed in a molar ratio of Me(Ni+Co+Mn):Li=1:0.98, placed in an alumina crucible, and subjected to primary calcination at 830°C for 12 hours under an oxygen atmosphere to produce a primary calcined product. The primary calcined product was finely ground using an air jet mill so that the average particle size of the cathode active material was 5.0~6.0㎛.

[0153] The pulverized primary calcined product and the lithium raw material were additionally mixed with LiOH at a molar ratio of Me(Ni+Co+Mn):Li=1:0.05, and subjected to secondary calcination at 770°C for 12 hours under an oxygen atmosphere to obtain a monoparticle form of lithium complex transition metal oxide (Composition: [Li 1.03 Ni 0.96 Co 0.03 Mn 0.01 O2], average particle size (D 50 ): 5.9㎛) was manufactured.

[0154] H3BO3 was mixed with the above lithium composite transition metal oxide such that B was 0.6 parts by weight relative to the total weight of the lithium composite transition metal oxide, and then the temperature was raised from room temperature to 350°C at a rate of 5°C / min, and then a first heat treatment was performed for 5 hours while maintaining the temperature. After that, the temperature was lowered from the temperature of the first heat treatment to 130°C at a rate of 0.5°C / min, and then a second heat treatment was performed for 7 hours while maintaining the temperature to produce an anode active material having a coating layer containing a boron-containing compound formed on the above lithium composite transition metal oxide.

[0155]

[0156] Example 2

[0157] Cathode active material precursor [Composition: Ni 0.86 Co 0.06 Mn 0.08 [OH]2 and LiOH as a lithium raw material were mixed in a molar ratio of Me(Ni+Co+Mn):Li=1:1, placed in an alumina crucible, and subjected to primary calcination at 880°C for 12 hours under an oxygen atmosphere to produce a primary calcined product. The primary calcined product was finely ground using an air jet mill so that the average particle size of the cathode active material was 5.0~6.0㎛.

[0158] The pulverized primary calcined product and the lithium raw material were additionally mixed with LiOH at a molar ratio of Me(Ni+Co+Mn):Li=1:0.05, and subjected to secondary calcination at 810°C for 12 hours under an oxygen atmosphere to obtain a monoparticle form of lithium complex transition metal oxide (Composition: [Li 1.03 Ni 0.86 Co 0.06 Mn 0.08 O2], average particle size (D 50 ): 6.5㎛) was manufactured.

[0159] H3BO3 was mixed with the above lithium composite transition metal oxide such that B was 0.8 parts by weight relative to the total weight of the lithium composite transition metal oxide, and then the temperature was raised from room temperature to 380°C at a rate of 5°C / min, and then a first heat treatment was performed for 5 hours while maintaining the temperature. After that, the temperature was lowered from the temperature of the first heat treatment to 130°C at a rate of 0.5°C / min, and then a second heat treatment was performed for 7 hours while maintaining the temperature to produce an anode active material having a coating layer containing a boron-containing compound formed on the above lithium composite transition metal oxide.

[0160]

[0161] Comparative Example 1

[0162] Cathode active material precursor [Composition: Ni 0.96 Co 0.03 Mn 0.01 [OH]2 and LiOH as a lithium raw material were mixed in a molar ratio of Me(Ni+Co+Mn):Li=1:0.98, placed in an alumina crucible, and subjected to primary calcination at 830°C for 12 hours under an oxygen atmosphere to produce a primary calcined product. The primary calcined product was finely ground using an air jet mill so that the average particle size of the cathode active material was 5.0~6.0㎛.

[0163] The pulverized primary calcined product and the lithium raw material were additionally mixed with LiOH at a molar ratio of Me(Ni+Co+Mn):Li=1:0.05, and subjected to secondary calcination at 770°C for 12 hours under an oxygen atmosphere to obtain a monoparticle form of lithium complex transition metal oxide (Composition: [Li 1.03 Ni 0.96 Co 0.03 Mn 0.01 O2], average particle size (D 50 ): 5.9㎛) was manufactured.

[0164] H3BO3 was mixed with the above lithium composite transition metal oxide such that B was 0.6 parts by weight relative to the total weight of the lithium composite transition metal oxide, and then the temperature was raised from room temperature to 270°C at a rate of 5°C / min, and then a first heat treatment was performed for 5 hours while maintaining the temperature. After that, the temperature was lowered from the temperature of the first heat treatment to 130°C at a rate of 0.5°C / min, and then a second heat treatment was performed for 7 hours while maintaining the temperature to produce an anode active material having a coating layer containing a boron-containing compound formed on the above lithium composite transition metal oxide.

[0165]

[0166] Comparative Example 2

[0167] Cathode active material precursor [Composition: Ni 0.96 Co 0.03 Mn 0.01 [OH]2 and LiOH as a lithium raw material were mixed in a molar ratio of Me(Ni+Co+Mn):Li=1:0.98, placed in an alumina crucible, and subjected to primary calcination at 830°C for 12 hours under an oxygen atmosphere to produce a primary calcined product. The primary calcined product was finely ground using an air jet mill so that the average particle size of the cathode active material was 5.0~6.0㎛.

[0168] The pulverized primary calcined product and the lithium raw material were additionally mixed with LiOH at a molar ratio of Me(Ni+Co+Mn):Li=1:0.05, and subjected to secondary calcination at 770°C for 12 hours under an oxygen atmosphere to obtain a monoparticle form of lithium complex transition metal oxide (Composition: [Li 1.03 Ni 0.96 Co 0.03 Mn 0.01 O2], average particle size (D 50 ): 5.9㎛) was manufactured.

[0169] H3BO3 was mixed with the above lithium composite transition metal oxide such that B was 0.6 parts by weight relative to the total weight of the lithium composite transition metal oxide, and then the temperature was raised from room temperature to 350°C at a rate of 5°C / min, and then a first heat treatment was performed for 5 hours while maintaining the temperature. After that, the temperature was rapidly lowered from the temperature of the first heat treatment to 130°C at a rate of 5°C / min to produce an anode active material having a coating layer containing a boron-containing compound formed on the lithium composite transition metal oxide.

[0170]

[0171] Comparative Example 3

[0172] Cathode active material precursor [Composition: Ni 0.86 Co 0.06 Mn 0.08 [OH]2 and LiOH as a lithium raw material were mixed in a molar ratio of Me(Ni+Co+Mn):Li=1:1, placed in an alumina crucible, and subjected to primary calcination at 880°C for 12 hours under an oxygen atmosphere to produce a primary calcined product. The primary calcined product was finely ground using an air jet mill so that the average particle size of the cathode active material was 5.0~6.0㎛.

[0173] The pulverized primary calcined product and the lithium raw material were additionally mixed with LiOH at a molar ratio of Me(Ni+Co+Mn):Li=1:0.05, and subjected to secondary calcination at 810°C for 12 hours under an oxygen atmosphere to obtain a monoparticle form of lithium complex transition metal oxide (Composition: [Li 1.03 Ni 0.86 Co 0.06 Mn 0.08 O2], average particle size (D 50 ): 6.5㎛) was manufactured.

[0174] H3BO3 was mixed with the above lithium composite transition metal oxide such that B was 0.8 parts by weight relative to the total weight of the lithium composite transition metal oxide, and then the temperature was raised from room temperature to 310°C at a rate of 5°C / min, and then a first heat treatment was performed for 5 hours while maintaining the temperature. After that, the temperature was lowered from the temperature of the first heat treatment to 130°C at a rate of 0.5°C / min, and then a second heat treatment was performed for 7 hours while maintaining the temperature to produce an anode active material having a coating layer containing a boron-containing compound formed on the above lithium composite transition metal oxide.

[0175]

[0176] Comparative Example 4

[0177] Cathode active material precursor [Composition: Ni 0.86 Co 0.06 Mn 0.08 [OH]2 and LiOH as a lithium raw material were mixed in a molar ratio of Me(Ni+Co+Mn):Li=1:1, placed in an alumina crucible, and subjected to primary calcination at 880°C for 12 hours under an oxygen atmosphere to produce a primary calcined product. The primary calcined product was finely ground using an air jet mill so that the average particle size of the cathode active material was 5.0~6.0㎛.

[0178] The pulverized primary calcined product and the lithium raw material were additionally mixed with LiOH at a molar ratio of Me(Ni+Co+Mn):Li=1:0.05, and subjected to secondary calcination at 810°C for 12 hours under an oxygen atmosphere to obtain a monoparticle form of lithium complex transition metal oxide (Composition: [Li 1.03 Ni 0.86 Co 0.06 Mn 0.08 O2], average particle size (D 50 ): 6.5㎛) was manufactured.

[0179] H3BO3 was mixed with the above lithium composite transition metal oxide such that B was 0.8 parts by weight relative to the total weight of the lithium composite transition metal oxide, then the temperature was raised from room temperature to 290°C at a rate of 5°C / min, then heat-treated for 5 hours while maintaining the temperature, and then lowered to room temperature by air cooling without an additional heat treatment step, thereby producing an anode active material having a coating layer containing a boron-containing compound formed on the lithium composite transition metal oxide.

[0180]

[0181] Experimental Example

[0182] Experimental Example 1: Confirmation of Type and Content of Boron-Containing Compounds

[0183] Surface analysis was performed on each cathode active material prepared in the examples and comparative examples to identify the types of boron-containing compounds included in the coating layer and the peak intensities, which are shown in Table 1 below. Table 1 below shows the peak intensity of each compound as a percentage (%) relative to the total sum of the peak intensities of the boron-containing compounds. Specifically, the surface analysis of the cathode active materials was conducted using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The TOF-SIMS 5-100 model from Ion-TOF (Germany) was used, and the analysis was performed under the following conditions.

[0184] 1) Spectra acquisition conditions

[0185] - Analysis mode: spectrometry mode

[0186] - Primary ion: Bi3+

[0187] - Polarity: negative & positive

[0188] - Flood gun: On

[0189] - Cycle time: 100㎲ (mass range 1~907 u)

[0190] - Analysis area (pixel): 500㎛ x 500㎛ (128x128)

[0191]

[0192] 2) 2D ion mapping (imaging) condition

[0193] -Analysis mode: delayed extraction mode

[0194] - Primary ion: Bi3+

[0195] - Polarity: negative & positive

[0196] - Flood gun: Off, Air flooding

[0197] - Cycle time: 50㎲ (mass range 1~214 u)

[0198] - Analysis area (pixel): 250㎛ x 250㎛ (1024x1024)

[0199]

[0200] Boron-containing compound peak intensity (%)(LiBO3) - (LiB2O3) for peak intensity (a) - Ratio of peak intensities (b) (b / a) type (LiBO3) - (LiB2O3) - (LiB2O4) - (B3O5) - (Li2B3O6) - mass667793113143 Example 1 15.15.16 6.96.76.30.34 Example 2 13.54.5 74.04.43.30.33 Comparative Example 19.37.75 9.5 12.8 10.70.83 Comparative Example 2 14.7 13.5 35.021.6 15.30.92 Comparative Example 3 16.1 13.92 9.321.8 18.90.86 Comparative Example 49.019.318.5 32.72 0.52.15

[0201]

[0202] Experimental Example 2: Battery Performance Evaluation

[0203] For Examples 1 and 2 and Comparative Examples 1 to 4, a positive electrode slurry was prepared by mixing carbon black as the positive electrode active material, carbon black as the conductive material, and polyvinylidene fluoride (PVDF) as the binder in a weight ratio of 95:2:3 in an N-methylpyrrolidone (NMP) solvent. The positive electrode slurry was applied to one surface of an Al current collector, dried, and then rolled to produce a positive electrode.

[0204] An electrode assembly was manufactured by using a lithium metal electrode as the negative electrode and interposing a porous polyethylene separator between the positive and negative electrodes. This was placed inside a battery case, and a coin-type half-cell was manufactured by injecting an electrolyte solution in which 1.0 M LiPF6 was dissolved in an organic solvent mixed with ethylene carbonate (EC):ethyl methyl carbonate (EMC):diethyl carbonate (DEC) in a volume ratio of 3:4:3.

[0205] Using the coin-type half-cell manufactured as described above, the formation process was performed by charging at 0.1C in CC-CV mode at 25°C until the voltage reached 4.25V, and discharging at a constant current of 0.1C until the voltage reached 2.5V. The charging capacity and discharging capacity at this time are shown in Table 2 below, and the percentage of the discharging capacity relative to the charging capacity at this time is used as the efficiency of the formation process and is shown in Table 2 below. Additionally, the DC internal resistance (DCIR) was calculated and is shown in Table 2 below. For reference, the DCIR value is calculated by dividing the difference between the initial voltage and the voltage at 60 seconds while discharging at a constant current of 0.1C by the applied current.

[0206]

[0207] Charge Capacity (mAh / g) Discharge Capacity (mAh / g) Efficiency (%) DCIR (Ω) Example 1 246.7 212.9 86.3 30.8 Example 2 233.8 209.4 89.6 20.9 Comparative Example 1 240.5 206.9 86.0 33.3 Comparative Example 2 245.0 211.5 86.3 34.8 Comparative Example 3 230.5 206.4 89.6 23.1 Comparative Example 4 226.8 205.6 90.6 29.1

[0208]

[0209] Referring to Tables 1 and 2 above, the ToF-SIMS analysis results for the cathode active material show that among the boron-containing compounds included in the coating layer, (LiBO3) - and (LiB2O3) - It can be confirmed that a battery containing the positive active material of Example 1, in which the ratio of strength (b / a) is less than 0.5, has an equivalent superior level of charge / discharge capacity and efficiency compared to Comparative Examples 1 and 2, which have the same positive active material composition as Example 1 and have a ratio of 0.5 or higher, and has significantly lower DC internal resistance.

[0210] In addition, it can be confirmed that a battery containing the positive active material of Example 2, in which the ratio (b / a) is less than 0.5, has an efficiency equivalent to that of Comparative Examples 3 and 4, in which the ratio is 0.5 or higher, while having the same positive active material composition as Example 2, has a higher charge / discharge capacity and lower DC internal resistance.

Claims

1. A lithium composite transition metal oxide in the form of a single particle; and a coating layer formed on the lithium composite transition metal oxide, comprising The above lithium composite transition metal oxide comprises nickel and one or more selected from the group consisting of cobalt, manganese, and aluminum. The above coating layer comprises a boron-containing compound, and ToF-SIMS analysis results, (LiBO3) - (LiB2O3) for peak intensity (a) - A positive active material having a ratio (b / a) of peak intensity (b) of less than 0.

5.

2. In Claim 1, The above single particle form is a positive active material in the form of a single particle consisting of one primary particle or in the form of two or more and ten or fewer primary particles aggregated.

3. In Claim 1, Average particle size (D) of the above positive active material 50 ) is a positive electrode active material having a size of 5 μm or more and 10 μm or less.

4. In Claim 1, The above lithium composite transition metal oxide is a positive electrode active material containing 60 mol% or more of nickel relative to the molar amount of metals excluding lithium.

5. In Claim 1, The above (LiBO3) - (LiB2O3) for peak intensity (a) - A positive active material having a ratio (b / a) of peak intensity (b) of 0.1 or more and less than 0.

5.

6. In Claim 1, ToF-SIMS analysis results, (LiBO3) - Peak, (LiB2O3) - Peak, (LiB2O4) - Peak, (B3O5) - Peak and (Li2B3O6) - (LiBO3) for the total sum of peak intensities (c) - A positive active material having a peak intensity (a) percentage ((a / c) × 100) of 10.0% or more and 16.0% or less.

7. In Claim 1, As a result of ToF-SIMS analysis, among the boron-containing compounds above, (LiBO3) - Peak, (LiB2O3) - Peak, (LiB2O4) - Peak, (B3O5) - Peak and (Li2B3O6) - (LiB2O3) for the total sum of peak intensities (c) - A positive active material having a peak intensity (b) percentage ((b / c) × 100) of 1.0% or more and 7.0% or less.

8. In Claim 1, The above lithium complex transition metal oxide is a positive electrode active material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li x Ni a Co b M 1 c M 2 d O2 In the above chemical formula 1, M 1 is Mn, Al, or a combination thereof, and M 2 is one or more selected from the group consisting of W, B, Zr, Y, Ce, Hf, La, Ba, F, P, S, Nb, Ta, Sc, Cr, V, Cu, Sr, Ti, Mg, Mo, Sn, Fe, Zn, and Si, and 0.9≤x≤1.1, 0.6≤a<1, 0 <b<0.4, 0<c<0.4, 0≤d≤0.2이다.

9. A step of preparing a lithium composite transition metal oxide by mixing a composite transition metal hydroxide and a lithium-containing raw material and then calcining (S0); and The method includes the step (S1) of mixing the lithium composite transition metal oxide and the boron-containing raw material and then heat-treating to form a coating layer on the lithium composite transition metal oxide. The heat treatment of the above S1 step is a first heat treatment step (S1-1) in which the temperature is increased from room temperature to a temperature of 340℃ or higher and 380℃ or lower at a rate of 1℃ / min or higher and 10℃ / min or lower, and the heat treatment is performed while maintaining the increased temperature; and A method for manufacturing an anode active material comprising a second heat treatment step (S1-2) of lowering the temperature from the first heat treatment temperature of the above S1-1 step to a temperature of 100℃ or higher and 150℃ or lower at a rate of 0.1℃ / min or higher and 1.0℃ / min or lower, and performing heat treatment while maintaining the lowered temperature.

10. In Claim 9, A method for manufacturing a positive electrode active material, wherein in step S1 above, the boron-containing raw material is mixed such that the boron content is 0.2 parts by weight or more and 1.0 parts by weight or less per 100 parts by weight of the lithium composite transition metal oxide.

11. In Claim 9, A method for manufacturing a positive electrode active material, wherein the first heat treatment of the above S1-1 step is performed for 1 hour or more and 10 hours or less.

12. In Claim 9, A method for manufacturing a positive electrode active material, wherein the secondary heat treatment of the above S1-2 step is performed for 1 hour or more and 10 hours or less.

13. In Claim 9, A method for manufacturing an anode active material, wherein the calcination of the above S0 step is performed by first calcining at a temperature of 700°C or higher and 1000°C or lower, and then second calcining at a temperature of 700°C or higher and 1100°C or lower.

14. A positive electrode comprising a positive electrode active material according to any one of claims 1 to 8.

15. A lithium secondary battery comprising a positive electrode according to claim 14.