Positive electrode active material, manufacturing method therefor, and positive electrode and lithium secondary battery including same

Abstract

A positive electrode active material of the present invention includes: lithium nickel-based oxide particles in which the molar ratio of nickel among total transition metals is 50 mol% to 70 mol%; and a coating layer formed on the surface of the lithium nickel-based oxide particles and including cobalt. The lithium nickel-based oxide particle is in the form of a single particle consisting of one single nodule or a quasi-single particle that is a composite of 30 or less nodules, and a full width at half maximum (FWHM) of a (104) peak of the positive electrode active material is 0.078 to 0.082 as measured by X-ray diffraction analysis (XRD).

Description

Anode active material, method for manufacturing the same, anode including the same, and lithium secondary battery

[0001] Cross-citation with related applications

[0002] The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0194811 filed on December 23, 2024 and Korean Patent Application No. 10-2025-0198149 filed on December 12, 2025, and all contents disclosed in said Korean patent application documents are incorporated herein as part of the specification.

[0003] Technology field

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

[0005]

[0006] Lithium-ion batteries are used in a wide range of fields, including small products such as digital cameras, Power-Digital Video Displays (P-DVDs), MP3 Players (MP3Ps), mobile phones, Personal Digital Assistants (PDAs), portable game devices, power tools, and E-bikes, as well as large products requiring high output such as electric vehicles and hybrid vehicles, and power storage devices and backup power storage devices that store surplus power or renewable energy.

[0007] Such lithium secondary batteries are generally manufactured by injecting or impregnating a non-aqueous electrolyte into an electrode assembly consisting of a positive electrode, a negative electrode, and a separator, and said positive and negative electrodes include an active material capable of lithium ion intercalation and deintercalation.

[0008] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMnO4, etc.), and lithium iron phosphate compound (LiFePO4) have been used as positive electrode active materials for lithium secondary batteries. In order to overcome the problems of lithium transition metal oxides containing Ni, Co, or Mn alone, lithium composite transition metal oxides containing two or more transition metals have been developed, and among these, lithium nickel cobalt manganese oxide containing Ni, Co, and Mn is widely used in the field of electric vehicle batteries.

[0009] Conventional lithium nickel-cobalt-manganese oxide was generally in the form of spherical secondary particles formed by the aggregation of tens to hundreds of primary particles. However, when lithium nickel-cobalt-manganese oxide in the form of secondary particles with many primary particles aggregated in this way is applied to the cathode, there are problems such as particle breakage where primary particles detach during the rolling process in cathode manufacturing and cracks occurring inside the particles during the charging and discharging process. If particle breakage or cracking occurs in the cathode active material, the contact area with the electrolyte increases, leading to increased gas generation and active material degradation due to side reactions with the electrolyte, which in turn reduces lifespan characteristics.

[0010] To solve the above problems, a technology has been proposed to manufacture a single-particle type cathode active material instead of a secondary particle type by increasing the calcination temperature during the production of lithium nickel-cobalt-manganese oxide. In the case of the single-particle type cathode active material, the contact area with the electrolyte is smaller compared to conventional secondary particle type cathode active materials, so there are fewer side reactions with the electrolyte, and the particle strength is excellent, resulting in less particle breakage during electrode manufacturing. Therefore, when applying the single-particle type cathode active material, there is an advantage of excellent gas generation and lifespan characteristics.

[0011] However, conventional single-particle cathode active materials are effective in enhancing high-temperature durability and reducing gas by improving reactivity with the electrolyte through reducing the surface area (reaction area) compared to secondary particles, but there is a problem in that the output performance is reduced due to an increase in lithium migration distance.

[0012] In addition, the above-mentioned anodes can be classified into high-capacity high-nickel anodes, mid-nickel anodes, etc., depending on the nickel content. Among these, mid-nickel anodes with a nickel content of 40% to 70% have a problem of high resistance due to the high manganese content and the size of the active material particles compared to high-nickel anodes. In particular, mid-nickel anodes tend to have reduced resistance performance in low-temperature environments.

[0013] Therefore, there is a need for technology capable of improving the electrochemical performance of anodes containing single-particle mid-nickel active materials.

[0014]

[0015] The present invention aims to solve the above-mentioned problems by providing a positive electrode active material and a method for manufacturing the same, which can improve the low-temperature resistance characteristics and electrochemical performance of the positive electrode despite the high manganese content.

[0016] In addition, the present invention provides a positive electrode and a lithium secondary battery comprising the aforementioned positive electrode active material.

[0017]

[0018] [1] The present invention relates to a positive electrode active material comprising: lithium nickel-based oxide particles having a molar ratio of nickel of 50 mol% to 70 mol% among the total transition metals; and a coating layer formed on the surface of the lithium nickel-based oxide particles and containing cobalt. The lithium nickel-based oxide particles are in the form of a single particle consisting of one single nodule or a pseudo-single particle consisting of 30 or fewer nodules, and the positive electrode active material satisfies Formula 1 below.

[0019] [Equation 1]

[0020] 0.078 ≤ F ≤ 0.082

[0021] In the above Equation 1,

[0022] F is the Full Width at Half Maximum (FWHM) of the (104) peak measured by X-ray diffraction analysis (XRD) of the above positive active material.

[0023] [2] The present invention can provide a positive electrode active material in which the molar ratio of nickel in the lithium nickel-based oxide particles is 60 mol% to 70 mol% based on the total transition metal in [1].

[0024] [3] The present invention may provide a positive electrode active material in which, in [1] and / or [2], the lithium nickel-based oxide particles are represented by the following chemical formula 1:

[0025] [Chemical Formula 1]

[0026] Li a Ni b Co c Mn d M 1 e O2

[0027] In the above chemical formula 1,

[0028] M 1 is one or more selected from the group consisting of Al, Ba, Zr, Ti, Ta, Nb, Y, W, Sr, B, Mg, Mo, Ce, F, and P, and

[0029] 0.9≤a≤1.1, 0.5≤b≤0.7, 0 <c≤0.5, 0<d≤0.4, 0≤e≤0.2이다.

[0030] [4] The present invention can provide a positive electrode active material in which, in at least one of [1] to [3], the cobalt content in the coating layer is 1 mol% to 5 mol% with respect to 100 mol of the lithium nickel-based oxide.

[0031] [5] The present invention provides a method for manufacturing a positive electrode active material comprising: a step of manufacturing a lithium nickel-based oxide by mixing a transition metal precursor including nickel, cobalt and manganese with a first lithium raw material and then calcining the mixture; and a step of manufacturing a positive electrode active material by mixing the manufactured lithium nickel-based oxide with a cobalt raw material and a second lithium raw material and heat treating the mixture to form a coating layer on the surface of the lithium nickel-based oxide, wherein the lithium nickel-based oxide is a single particle consisting of one single nodule or a composite of 30 or fewer nodules.

[0032] [6] The present invention can provide a method for manufacturing an anode active material in which, in [5] the second lithium raw material is mixed in an amount of 0.2 to 0.8 parts by weight relative to 100 parts by weight of the manufactured lithium nickel-based oxide.

[0033] [7] The present invention may provide a method for manufacturing a positive active material, wherein, in [5] or [6], the positive active material satisfies the following Equation 1 when X-ray diffraction analysis (XRD):

[0034] [Equation 1]

[0035] 0.078 ≤ F ≤ 0.082

[0036] In the above Equation 1,

[0037] F is the Full Width at Half Maximum (FWHM) of the (104) peak measured by X-ray diffraction analysis (XRD) of the above positive active material.

[0038] [8] The present invention can provide a method for manufacturing an anode active material in which, in at least one of [5] to [7], the coating layer heat treatment is performed at 735°C to 790°C.

[0039] [9] The present invention may provide an anode comprising an anode active material according to at least one of [1] to [4].

[0040]

[0010] The present invention may provide a lithium secondary battery comprising: an anode according to at least one of [1] to [4]; a cathode opposite to the anode; a separator interposed between the anode and the cathode; and an electrolyte.

[0041]

[0042] The positive electrode active material according to the present invention comprises lithium nickel-based oxide particles in which the molar ratio of nickel among the total transition metals is 50 mol% to 70 mol% and a cobalt coating layer formed on the surface of the lithium nickel-based oxide particles, and the full width at half maximum of the (104) peak measured by X-ray diffraction analysis (XRD) of the positive electrode active material is 0.078 to 0.082.

[0043] The lithium nickel-based oxide particles of the cathode active material according to the present invention are single-particle type particles that exhibit minimal adverse reactions with the electrolyte and possess excellent particle strength, thereby reducing particle breakage and improving energy density. The present invention allows for the reduction of the rock salt phase on the surface of the cathode active material by mixing a cobalt source material and a lithium source material together with the lithium nickel-based oxide particles and controlling the temperature to a specific temperature range, thereby causing the cobalt source material and lithium to react to form a coating layer having an LCO-like phase on the surface of the cathode active material. Consequently, the surface stability of the cathode active material is enhanced, which can improve resistance characteristics at low temperatures.

[0044] In addition, the cathode and lithium secondary battery containing the above-mentioned cathode active material can have excellent energy density, resistance characteristics, and electrochemical performance, while reducing gas generation, thereby providing excellent safety and lifespan characteristics.

[0045]

[0046] The following drawings attached to this specification illustrate embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0047] FIG. 1 is a flowchart illustrating a method for manufacturing a positive electrode active material according to one embodiment of the present invention.

[0048] Figure 2 is a graph showing the structure of an anode according to one embodiment of the present invention.

[0049] Figure 3 is a graph showing the structure of a lithium secondary battery according to one embodiment of the present invention.

[0050] FIG. 4 is an XRD graph of the positive active material prepared according to Examples 1 to 3 and Comparative Examples 1 to 5 of the present invention.

[0051] Figure 5 is a graph showing the (104) peak in Figure 4 enlarged.

[0052] FIG. 6 is a DSC graph measured using Example 1, Comparative Example 1, and Comparative Example 5 of the present invention.

[0053] In parts of the attached drawings, corresponding components are given the same reference numerals. Those skilled in the art understand that the drawings are intended to illustrate elements simply and clearly and are not necessarily drawn to scale. For example, to aid in understanding various embodiments, the dimensions of some elements depicted in the drawings may be exaggerated compared to others. Additionally, elements of known technology that are useful or essential in commercially viable embodiments may often be omitted so as not to hinder the spirit of the various embodiments of the present invention.

[0054]

[0055] 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 invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0056] 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.

[0057] In this specification, each of the phrases such as “A or B”, “at least one of A and B”, “at least one of A or B”, “A, B or C”, “at least one of A, B and C”, and “at least one of A, B, or C” may include any one of the items listed together in the corresponding phrase, or all possible combinations thereof.

[0058] In this specification, "single particle type" refers to a particle composed of 30 or fewer nodules, and is a concept that includes a single particle composed of one nodule and a pseudo-single particle which is a complex of 2 to 30 nodules.

[0059] The above “nodule” is a sub-grain unit constituting a single particle and a pseudo-single particle, and may be a single crystal that does not have crystalline grain boundaries, or a polycrystalline one in which no grain boundaries appear to exist when observed at a field of view of 5,000 to 20,000 times using a scanning electron microscope.

[0060] In this specification, "secondary particle" refers to a particle formed by the aggregation of a plurality of primary particles, for example, tens to hundreds of primary particles. For example, a secondary particle may be an aggregate of 5,031 or more primary particles.

[0061] In this specification, “particle” is a concept including any one or all of a single particle, a pseudo-single particle, a primary particle, a nodule, and a secondary particle.

[0062] In the present invention, the average particle size (D) of the nodule or primary particle mean ) refers to the arithmetic mean value calculated after measuring the particle size of nodules or primary particles observed in scanning electron microscope or backscatter electron diffraction (EBSD) images. For example, the particle size of the nodules or primary particles can be measured by manufacturing an electrode using the positive electrode active material powder to be measured, cutting the electrode before rolling with ion milling (e.g., HITACHI’s IM-500, acceleration voltage 6 kV) to obtain a cross-section, and then measuring the number of primary particles on a scale of approximately 400 ± 10 using a field emission scanning electron microscope (FE-SEM) (e.g., JEOL’s JSM7900F) under conditions of acceleration voltage 15 kV and WD 15 mm.

[0063]

[0064] The present invention will be described in more detail below.

[0065] The positive electrode active material according to the present invention, the method for manufacturing the same, the positive electrode including the same, and the lithium secondary battery comprise at least one of the configurations disclosed below, and may comprise any combination of technically feasible configurations among the configurations below.

[0066]

[0067] positive electrode active material

[0068] First, the positive active material according to the present invention will be described.

[0069] The positive electrode active material according to the present invention comprises: lithium nickel-based oxide particles in which the molar ratio of nickel among the total transition metals is 50 mol% to 70 mol%; and a coating layer formed on the surface of the lithium nickel-based oxide particles and containing cobalt.

[0070] High-nickel active materials, conventionally used as cathode active materials in lithium-ion batteries, have a molar ratio of nickel of 80 mol% or more among the total transition metals and offer the advantage of achieving excellent capacity and energy density. However, due to the relatively high nickel content, thermal stability is low, and the highly reactive Ni 4+ There is a problem with structural stability being compromised due to the increase in nickel content, so attention is being focused on mid-nickel active materials with a nickel content of 40% to 70%. However, when the nickel content is lowered and the manganese content is relatively higher, a problem of increased resistance occurs, and for example, a problem of rapidly decreasing resistance characteristics at low temperatures is caused.

[0071] The positive electrode active material of the present invention applies a cobalt coating to the surface of a single-particle lithium nickel-based oxide particle, and optimizes the degree of the cobalt coating by controlling the temperature during the cobalt coating process, thereby improving the resistance characteristics of the lithium secondary battery at low temperatures when applied to a lithium secondary battery. In addition, by utilizing the fact that the Full Width at Half Maximum (FWHM) value of the (104) peak measured by X-ray Diffraction (XRD) varies depending on the degree of the cobalt coating, the Full Width at Half Maximum (FWHM) of the (104) peak of the positive electrode active material with optimized cobalt coating is limited to a specific value range. Accordingly, the present invention provides a positive electrode active material satisfying the following Equation 1, comprising a lithium nickel-based oxide particle having a molar ratio of nickel among the total transition metals of 50 mol% to 70 mol% and a coating layer located on the surface of the lithium nickel-based oxide particle. This allows for the improvement of the increase in resistance caused by the relatively high manganese content in the lithium nickel-based oxide.

[0072] The coating layer according to the present invention comprises cobalt, and a heat treatment process is performed within a specific temperature range described above when forming the coating layer on the surface of the lithium nickel-based oxide particles. The coating layer comprising cobalt can improve surface stability by reconstructing the rock salt phase of the lithium nickel-based oxide into a layered structure through surface modification of the lithium nickel-based oxide particles. As a result, the coating layer can improve resistance to low-temperature environments.

[0073] The above lithium nickel-based oxide particles are single-particle type particles, having a single particle consisting of one nodule or a pseudo-single particle form consisting of a single particle or a composite of 30 or fewer nodules. Since the particle strength is higher compared to conventional secondary-particle lithium manganese-based oxides, there is less particle breakage during rolling. Furthermore, because the number of sub-particle units constituting the particles is small, there is less change due to volume expansion and contraction of the sub-particle units during charging and discharging, and thus the occurrence of internal cracks is significantly reduced. As particle breakage and internal cracking are reduced, the contact area between the lithium nickel-based oxide and the electrolyte is reduced. Consequently, the leaching of manganese or nickel due to reaction with the electrolyte at high temperatures can be suppressed, thereby improving storage and lifespan characteristics and reducing gas generation caused by side reactions in the electrolyte.

[0074] The positive active material according to the present invention satisfies the following Formula 1:

[0075] [Equation 1]

[0076] 0.078 ≤ F ≤ 0.082

[0077] In the above Equation 1,

[0078] F is the Full Width at Half Maximum (FWHM) of the (104) peak measured by X-ray diffraction analysis (XRD) of the above positive active material.

[0079] According to one embodiment, the measurement conditions were based on Cu-Kα radiation, and an X-ray diffraction analysis pattern was obtained by measuring the 2θ range of 43.0° to 45.5° at 40 kV. For example, the full width at half maximum (FWHM) refers to the full width at half maximum of the (104) peak observed at 44.5 ± 1.0° (2θ). During XRD analysis, a Cu Ka a1 radiation source was used as the x-ray source, and measurements were taken at 0.02° step intervals in the 10-120° (2θ) range using the θ-2θ scan (Bragg-Brentano parafocusing geometry) method. The full width at half maximum (FWHM) of the (104) peak was calculated by fitting the Lorentz function, and the fitting of the Lorentz function for the full width at half maximum (FWHM) measurement can be performed using various open / commercial software known to those skilled in the art.

[0080] In Equation 1 above, the (104) peak represents the peak intensity of the (104) plane in the X-ray diffraction graph of the positive electrode active material, and the full width at half maximum represents the peak width at a position that is half the height of the (104) peak. F represents the structural characteristics of the positive electrode active material with the coating layer formed thereon, and if F satisfies the above range, it means that an optimized coating layer has been formed on the surface of the lithium nickel-based oxide particles. The (104) plane peak represents the repetitive layered arrangement characteristic in the C-axis direction in the crystal structure of the positive electrode active material, which may mean that the degree of reconstruction of the surface of the lithium nickel-based oxide particles from a rock salt phase to a layered structure is optimized due to the cobalt coating. For example, the cobalt coating reconstructs the surface of the lithium nickel-based oxide particles from a rock salt phase to a layered structure, and the degree of reconstruction may vary depending on the cobalt raw material, lithium content, temperature, etc. For example, when cobalt coating, if there is a shortage of lithium when the cobalt raw material, such as Co3O4, reacts with lithium, the Co3O4 remains, reducing the reconfiguration effect. Consequently, a layered structure may not be sufficiently formed, which can lower the stability of the surface.

[0081] The molar ratio of nickel in the lithium nickel-based oxide particles according to the present invention may be 50 mol% to 70 mol%, for example, 60 mol% to 70 mol%, based on the total transition metal. When the nickel content satisfies the above range, it is possible to prevent or suppress the degradation of capacity characteristics while minimizing the degradation of lifespan characteristics during high-voltage operation. Specifically, when the nickel content exceeds 70 mol%, highly reactive Ni 4+There is a problem that the structural stability of the cathode active material decreases as the amount increases, and if the Ni content is too low, the capacity characteristics may deteriorate. Accordingly, preferably, the nickel content may be 50 mol% or more, 55 mol% or more, or 60 mol% or more, and the nickel content may be 70 mol% or less, or 65 mol% or less.

[0082] The lithium nickel-based oxide particles according to the present invention may be a positive electrode active material represented by the following chemical formula 1:

[0083] [Chemical Formula 1]

[0084] Li a Ni b Co c Mn d M 1 e O2

[0085] In the above chemical formula 1, M 1 may be one or more selected from the group consisting of Al, Ba, Zr, Ti, Ta, Nb, Y, W, Sr, B, Mg, Mo, Ce, F, and P, and M 1 When the element is included, the structural stability of the lithium nickel-based oxide particles is improved, enabling superior lifespan characteristics during high-voltage operation. According to one embodiment, the M 1 The elements may include one or more selected from the group consisting of Ti, Mg, Al, Zr, W, and Y, or two or more selected from the group consisting of Ti, Mg, Al, Zr, W, and Y.

[0086] In the above chemical formula 1, "a" represents the molar ratio of lithium in the lithium nickel-based oxide, and may be 0.9≤a≤1.1, 0.95≤a≤1.1, or 1.0≤a≤1.08. When the value of "a" satisfies the above range, a stable layered crystal structure can be formed.

[0087] The above "b" represents the molar ratio of nickel among the total metals excluding lithium in the lithium nickel-based oxide, and may be 0.5≤b≤0.7, 0.55≤b≤0.7, or 0.6≤b≤0.7. When the value of "b" satisfies the above range, high temperature and / or high voltage stability is excellent.

[0088] The above "c" represents the molar ratio of cobalt among the total metals excluding lithium in the lithium nickel-based oxide, 0 <c<0.5, 0.05≤c≤0.4 또는 0.1≤c≤0.4일 수 있다.

[0089] The above "d" represents the molar ratio of manganese among the total metals excluding lithium in the lithium nickel-based oxide, 0 <d<0.5, 0.05≤d≤0.4 또는 0.1≤d≤0.4일 수 있다.

[0090] The above "e" refers to M among the total metals excluding lithium in the lithium nickel-based oxide. 1 It represents the molar ratio of elements, 0≤e≤0.2, 0≤e≤0.1, or 0 <e≤0.1일 수 있다. 상기 M 1 When the molar ratio of the elements satisfies the above range, both the structural stability and capacity of the positive active material can be excellent.

[0091] In the present invention, the cobalt content included in the coating layer may be 1 mol% to 5 mol% with respect to 100 mol of the lithium nickel-based oxide, for example, 1 mol% to 4 mol%, or 2 mol% to 4 mol%. When the cobalt content in the coating layer satisfies the above range, the resistance of the lithium secondary battery at low temperatures may be reduced due to an increase in the content of the cobalt coating.

[0092]

[0093] Method for manufacturing positive electrode active material

[0094] Next, a method for manufacturing a positive electrode active material according to the present invention will be described.

[0095] When manufacturing a single-particle type cathode active material in which the molar ratio of Ni among the total transition metals is 50% to 70%, resistance may increase due to an increase in lithium paths, and when particles are manufactured to reduce the increase in resistance, problems such as increased gas generation occur, making it difficult to exhibit the advantages of single particles. Therefore, the method for manufacturing a cathode active material according to the present invention improves structural stability by forming a coating layer on the surface of a lithium nickel-based oxide, and through the optimization of coating conditions, it is possible to improve resistance characteristics while exhibiting the advantages of single particles, such as preventing particle breakage and improving lifespan characteristics.

[0096] FIG. 1 is a flowchart illustrating a method for manufacturing a positive electrode active material according to one embodiment of the present invention.

[0097] Referring to FIG. 1, a method for manufacturing a positive electrode active material according to the present invention comprises the step (S10) of mixing a transition metal precursor containing nickel, cobalt, and manganese with a first lithium raw material and then calcining to produce a lithium nickel-based oxide; and the step (S20) of mixing the prepared lithium nickel-based oxide with a cobalt raw material and a second lithium raw material and heat-treating to produce a positive electrode active material having a coating layer on the surface of the lithium nickel-based oxide. At this time, the method for manufacturing the positive electrode active material can realize an optimized coating layer by adding the second lithium raw material when forming the coating layer and controlling the coating temperature to a specific range. The method for manufacturing a positive electrode active material according to the present invention further comprises the step (S30) of checking whether the Full Width at Half Maximum (FWHM) value of the (104) peak measured by X-ray diffraction analysis (XRD) of the positive electrode active material having the coating layer falls within a specific range.

[0098] If the full half-width value measured in step (S30) does not fall within the range according to one embodiment, for example, between 0.078 and 0.082, the process can be returned to step S (20) to adjust the conditions for manufacturing the coating layer, for example, the heat treatment conditions. Meanwhile, the conditions for manufacturing the coating layer may include not only controlling the heat treatment temperature but also other conditions, for example, controlling the amount of cobalt raw material and controlling the amount of lithium raw material added during the manufacturing of the coating layer.

[0099] The above lithium nickel-based oxide is in the form of a single particle consisting of one single nodule or a pseudo-single particle being a complex of 30 or fewer nodules, and the above positive active material satisfies the following Formula 1:

[0100] [Equation 1]

[0101] 0.078 ≤ F ≤ 0.082

[0102] In the above Equation 1,

[0103] F is the Full Width at Half Maximum (FWHM) of the (104) peak measured by X-ray diffraction analysis (XRD) of the above-mentioned positive active material. Since this applies in the same way as described above, redundant explanations are omitted.

[0104]

[0105] Each step is explained in more detail below.

[0106] The step (S10) of manufacturing the above lithium nickel-based oxide can be performed by mixing a transition metal precursor containing nickel, cobalt, and manganese with a first lithium raw material and calcining it.

[0107] At this time, the transition metal precursor may be a commercially available precursor such as a nickel-cobalt-manganese hydroxide, or may be manufactured according to a precursor manufacturing method known in the relevant technical field, such as the co-precipitation method.

[0108] For example, a transition metal precursor can be prepared by first preparing a transition metal-containing solution containing nickel (Ni) and cobalt (Co) cations, and then adding an ammonium cation-containing complex-forming agent and a basic aqueous solution to the transition metal-containing solution to carry out a co-precipitation reaction.

[0109] The first lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it is soluble in water. For example, the lithium raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, or Li3C6H5O7, and any one or more of these may be used.

[0110] The above transition metal precursor and lithium raw material may be mixed in a molar ratio of, for example, about 1:1, about 1:1.05, about 1:1.10, about 1:1.15, or about 1:1.20, but are not limited thereto.

[0111] Subsequently, the step of manufacturing the positive electrode active material is a step (S20) of forming a coating layer on the manufactured lithium nickel-based oxide, wherein the manufactured lithium nickel-based oxide is mixed with a cobalt raw material and a second lithium raw material and heat-treated to form a coating layer on the surface of the lithium nickel-based oxide. By mixing the second lithium raw material during the heat treatment step to compensate for lithium, the low-temperature output characteristics and resistance characteristics of the lithium secondary battery can be improved.

[0112] According to one embodiment, the heat treatment may be performed at 735°C to 790°C, for example, 40°C to 785°C, or 745°C to 785°C. When the heat treatment temperature satisfies the above range, an anode with excellent low-temperature resistance and lifespan performance can be realized by implementing an optimized coating layer. An optimized coating layer means forming a coating layer formed by sufficient reaction between lithium and cobalt. Accordingly, the temperature at which the heat treatment is performed according to one embodiment may be 735°C or higher, 740°C or higher, 745°C or higher, 755°C or higher, 760°C or higher, or 765°C or higher, and the temperature at which the heat treatment is performed may be 790°C or lower, 780°C or lower, 775°C or lower, or 770°C or lower. According to one embodiment, in addition to performing the heat treatment conditions of the coating layer within the above range, the coating layer may be manufactured by adjusting other conditions, for example, the amount of the cobalt raw material and / or the second lithium raw material.

[0113] At this time, the type of the second lithium raw material may be the same as the first lithium raw material or may be different. For example, the second lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and is not particularly limited as long as it can be dissolved in water. For example, the lithium raw material may be Li2CO3, LiNO3, LiNO2, LiOH, LiOH·H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, or Li3C6H5O7, and any one or more of these may be used.

[0114] According to one embodiment, the second lithium raw material may be included in an amount of 0.2 to 0.8 parts by weight, for example, 0.2 to 0.6 parts by weight, relative to 100 parts by weight of the prepared lithium nickel-based oxide. When the content of the second lithium raw material satisfies the above range, an LCO liked phase is appropriately formed on the surface of the lithium nickel-based oxide particles, and the resistance of the lithium secondary battery can be lowered at about -10°C. Accordingly, the content of the second lithium raw material may be 0.2 parts by weight or more, or 0.3 parts by weight or more, and the content of the second lithium raw material may be 0.8 parts by weight or less, or 0.7 parts by weight or less.

[0115] The above cobalt raw material may be a cobalt-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, or oxyhydroxide, etc., and may be, for example, Co(OH)2, CoOOH, Co(OCOCH3)2ㆍ4H2O, Co(NO3)2ㆍ6H2O, CoSO4, Co(SO4)2ㆍ7H2O or a combination thereof, but is not limited thereto.

[0116] The method of mixing the above-mentioned cobalt raw material, the second lithium raw material, and the lithium nickel-based oxide is not particularly limited and can be performed by dry mixing or wet mixing. For example, the solid-phase coating raw material and the solid-phase lithium nickel-based oxide can be mixed dry by adding a mixer or the like and stirring, or the coating raw material and the lithium nickel-based oxide can be mixed wet by adding them to a solvent such as water or ethanol and stirring.

[0117]

[0118] anode

[0119] Figure 2 is a graph showing the structure of an anode according to one embodiment of the present invention.

[0120] Referring to FIG. 2, the anode (10) according to the present invention comprises the anode active material described above. The anode comprises an anode current collector (12) and an anode composite layer (14) located on the anode current collector, and the anode composite layer (14) may include an anode active material, a binder, and a conductive material. At this time, since the anode active material is the same as the anode active material according to the present invention described above, further explanation is omitted, and the remaining components excluding the anode active material will be described below.

[0121] The above positive current collector (12) is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used.

[0122] The above binder is a component that assists in the bonding of the positive active material and the conductive material, and in the bonding to the current collector. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers.

[0123] According to one embodiment, the binder may be included in an amount of 1% to 20% by weight, for example, 1% to 15% by weight, or 1% to 10% by weight, based on the total weight of the anode composite layer (14).

[0124] The above conductive material is a component for further improving the conductivity of the positive electrode active material, and is not particularly limited as long as it is conductive without causing chemical changes in the battery. For example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; conductive powder such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0125] According to one embodiment, the conductive material may be included in an amount of 1% to 20% by weight, for example, 1% to 15% by weight, or 1% to 10% by weight, based on the total weight of the anode composite layer.

[0126] The anode composite layer (14) may be manufactured by applying and drying an anode slurry composition prepared by dissolving or dispersing an anode active material, and optionally a binder and a conductive material, in an anode slurry solvent on an anode current collector (12), or by casting the anode slurry composition onto a separate support and then laminating the film obtained by peeling off from the support onto an anode current collector.

[0127] The anode slurry solvent may include organic solvents such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), and acetone, and may be used in an amount that results in an appropriate viscosity when including the anode active material, anode binder, and anode conductive material. According to one embodiment, the anode slurry solvent may be included such that the concentration of the solid component, which includes the anode active material and optionally the anode binder and anode conductive material, is about 50% to 95% by weight, or 0% to 95% by weight, or 70% to 90% by weight.

[0128]

[0129] lithium secondary battery

[0130] Figure 3 is a graph showing the structure of a lithium secondary battery according to one embodiment of the present invention.

[0131] Referring to FIG. 3, a lithium secondary battery (100) according to one embodiment of the present invention comprises an electrode assembly consisting of a positive electrode (10) described above, a negative electrode (20) facing the positive electrode (10), and a separator (30) interposed between the positive electrode (10) and the negative electrode (20), a non-aqueous electrolyte (40), and a battery case (50) that accommodates the electrode assembly and the non-aqueous electrolyte (40). Since the positive electrode (10) is identical to the positive electrode according to the present invention described above, further explanation is omitted, and the remaining components excluding the positive electrode (10) will be described below.

[0132] The above lithium secondary battery (100) can be manufactured by housing the electrode assembly in a battery case (50) and then injecting the aforementioned non-aqueous electrolyte (40).

[0133] A lithium secondary battery (100) according to one embodiment of the present invention may be manufactured in a prismatic type, pouch type, coin type, and cylindrical type, depending on the form in which it is manufactured.

[0134] (1) Cathode

[0135] In a lithium secondary battery (100) according to the present invention, the negative electrode (20) comprises a negative electrode current collector and a negative electrode composite layer located on the negative electrode current collector, and the negative electrode composite layer may include a negative electrode active material, a binder, and a conductive material.

[0136] 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, heat-treated carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used.

[0137] The above-mentioned negative current collector can typically have a thickness of 3 μm to 500 μm, and for example, can have a thickness of 300 μm or less, 200 μm or less, 100 μm or less, or 80 μm or less. Fine irregularities may be formed on the surface of the current collector to strengthen the bonding force with the negative active material. For example, it can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0138] The above-mentioned negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium, and may include at least one selected from the group consisting of carbon-based active materials and silicon-based active materials. For example, the carbon-based active material may include one or more selected from the group consisting of artificial graphite, natural graphite, softened carbon, and hardened carbon. Additionally, the silicon-based active material may include silicon (Si) and silicon oxide (SiO₂). x , 0 <x<2) 및 실리콘-탄소 복합체(Si / C composite)로 이루어진 군에서 선택된 적어도 1종을 포함할 수 있으며, 보다 적절하게는 실리콘-탄소 복합체를 포함할 수 있다.

[0139] The above-mentioned cathode active material may be included in an amount of 60% to 99% by weight based on the total weight of the cathode composite layer, for example, 70% or more, 80% or more, 85% or more, 90% or more by weight, and also 98% or less, 97% or less by weight, 95% or less by weight.

[0140] The above binder is a component that assists in the bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1% to 10% by weight based on the total weight of the cathode composite layer, and can be included in an amount of 0.2% or more, 0.3% or more, or 0.5% or more by weight, and can also be included in an amount of 8.0% or less, or 5.0% or less by weight. Examples of such binders may include one or more selected from the group consisting of styrene-butadiene copolymer, acrylate styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylenediene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, and polyvinyl alcohol. Among these, it may include one or more selected from the group consisting of styrene-butadiene copolymer, acrylate styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, carboxymethyl cellulose, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylfluran, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, and cyanoethyl sucrose. According to one embodiment, carboxymethyl cellulose, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, or a mixture thereof may be applied as a binder.

[0141] The above conductive material is a component for further improving the conductivity of the cathode active material, and may be added in an amount of 10% by weight or less, for example, 5% by weight or less, 3% by weight or less, 2% by weight or less, or 1% by weight or less based on the total weight of the cathode composite layer, and may also be included in an amount of 0.01% by weight or more, 0.05% by weight or more, 0.08% by weight or more, 0.1% by weight or more, or 0.3% by weight or more.

[0142] Such conductive materials are not particularly limited as long as they possess conductivity without causing chemical changes in the battery, and for example, graphite such as natural graphite or synthetic graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powders 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.

[0143] The above cathode composite layer may be manufactured by applying a cathode slurry composition, prepared by dissolving or dispersing a cathode active material and optionally a binder and a conductive material in a cathode slurry solvent, onto a cathode current collector and drying it, or by casting the cathode slurry composition onto a separate support and then laminating the film obtained by peeling it off from the support onto a cathode current collector.

[0144] The above cathode slurry solvent may include at least one selected from the group consisting of distilled water, NMP (N-methyl-2-pyrrolidone), ethanol, methanol, and isopropyl alcohol, for example, distilled water, in order to facilitate the dispersion of the cathode active material, binder, and / or conductive material. The solid content of the above cathode slurry composition may be 30% to 80% by weight, for example, 40% to 70% by weight.

[0145]

[0146] (2) Separator

[0147] The separator according to the present invention 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 commonly used as a separator in a lithium secondary battery. Specifically, the separator may be a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof. In addition, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength.

[0148]

[0149] (3) Electrolyte

[0150] The electrolyte (40) used in the present invention may include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc., which can be used when manufacturing a lithium secondary battery (100), but is not limited to these.

[0151] According to one embodiment, the electrolyte (40) may include an organic solvent and a lithium salt. The organic solvent may be used without special limitations as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. For example, the organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene or fluorobenzene; Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl 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. According to one embodiment, a carbonate-based solvent may be used, 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.) may be used.

[0152] The above lithium salt can be used without special restrictions as long as it is a compound capable of providing lithium ions used in lithium secondary batteries. For example, the anions of the lithium salt may be one or more selected from the group consisting of 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-, and the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, etc., may be used. The concentration of the lithium salt may be used within the range of 0.1M to 4.0M, for example, 0.5M to 3.0M, or 1.0M to 2.0M. 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.

[0153] 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 like 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 10.0% by weight based on the total weight of the electrolyte.

[0154]

[0155] In addition, since the lithium secondary battery (100) according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, and in electric vehicle fields such as hybrid electric vehicles (HEV).

[0156] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same may be provided.

[0157] 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 (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0158] The present invention will be explained in more detail below through examples. However, the present invention may be implemented in various different forms and is not limited to the examples described herein.

[0159]

[0160] Example 1

[0161] (Manufacturing of positive electrode active material)

[0162] A transition metal precursor with a molar ratio of Ni:Co:Mn of 63:7:30 and a first lithium raw material (Li2CO3) were mixed such that the molar ratio of transition metal (Ni+Co+Mn) : Li was 1:1.06, and then calcined at 920°C for 12 hours to produce a lithium nickel-based oxide.

[0163] Subsequently, a cobalt raw material (CoOOH, 3 mol%) and a second lithium raw material (Li2CO3, 0.6 wt%) were added to the above lithium nickel-based oxide, and heat-treated at 765°C for 10 hours to produce a single-particle cathode active material with a cobalt coating layer formed.

[0164]

[0165] Example 2

[0166] A positive electrode active material was prepared in the same manner as in Example 1, except that the heat treatment of the cobalt coating layer for preparing the positive electrode active material was performed at 745°C.

[0167]

[0168] Example 3

[0169] A positive electrode active material was prepared in the same manner as in Example 1, except that the heat treatment of the cobalt coating layer for preparing the positive electrode active material was performed at 785°C.

[0170]

[0171] Comparative Example 1

[0172] A positive electrode active material was prepared in the same manner as in Example 1, except that the second lithium raw material was not added.

[0173]

[0174] Comparative Example 2

[0175] A positive electrode active material was prepared in the same manner as in Example 1, except that the heat treatment of the cobalt coating layer for preparing the positive electrode active material was performed at 685°C.

[0176]

[0177] Comparative Example 3

[0178] A positive electrode active material was prepared in the same manner as in Example 1, except that the heat treatment of the cobalt coating layer for preparing the positive electrode active material was performed at 705°C.

[0179]

[0180] Comparative Example 4

[0181] A positive electrode active material was prepared in the same manner as in Example 1, except that the heat treatment of the cobalt coating layer for preparing the positive electrode active material was performed at 805°C.

[0182]

[0183] Comparative Example 5

[0184] A positive electrode active material was prepared in the same manner as in Example 1, except that a lithium nickel-based oxide was prepared using a transition metal precursor with a molar ratio of Ni:Co:Mn of 86:7:7.

[0185]

[0186] Experimental Example 1: XRD Analysis of Anode Active Material

[0187] In order to compare and analyze the coating layer contained in the positive electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 to 5, XRD analysis was performed on each positive electrode active material using a Bruker D8 Endeavor.

[0188] For example, based on (Cu-Kα1) radiation, an X-ray diffraction analysis graph was obtained by measuring the 2θ range from 35° to 50° at 40kV and is shown in Fig. 4, and the full width at half maximum (FWHM) of the (104) peak measured at 2θ from 43.0° to 45.5° was calculated.

[0189] The above full width at half maximum refers to the full width at half maximum of the (104) peak observed at 44.5±1.0° (2θ). For XRD analysis, a Cu Ka a1 radiation source was used as the x-ray source, and measurements were taken at 0.02° step intervals in the range of 10°–120° (2θ) using the θ–2θ scan (Bragg-Brentano parafocusing geometry) method. The full width at half maximum (FWHM) of the (104) peak was measured using the fitting of the Lorentz function, and the results are shown in Fig. 5 and Table 1 below.

[0190] Half-width Example 10.07845 Example 20.078 Example 30.07928 Comparative Example 10.07493 Comparative Example 20.0776 Comparative Example 30.07759 Comparative Example 40.08349 Comparative Example 50.07042

[0191] As described above, the half-width values ​​of Examples 1-3, in which the coating layer was heat-treated between 735℃ and 790℃, were 0.07845, 0.078, and 0.07928, respectively, showing values ​​between 0.078 and 0.082.

[0192]

[0193] Experimental Example 2: Measurement of Low-Temperature Performance of Lithium Secondary Battery

[0194] The low-temperature performance of a lithium secondary battery prepared as follows using the positive active materials of Examples 1 to 3 and Comparative Examples 1 to 4 above was evaluated.

[0195] Manufacture of Lithium Secondary Batteries

[0196] A positive electrode slurry was prepared by mixing the positive electrode active material, conductive material (carbon black), and PVDF binder prepared in Examples 1 to 3 and Comparative Examples 1 to 4, respectively, in N-methylpyrrolidone in a weight ratio of 95:2:3. The positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to produce a positive electrode.

[0197] Subsequently, an electrode assembly was manufactured by interposing a separator between the anode and the lithium metal electrode, and then the assembly was placed inside a battery case. An electrolyte was then injected into the case to manufacture a lithium secondary battery in the form of a coin half cell. The electrolyte was prepared by dissolving LiPF6 at a concentration of 0.6 M in a mixed organic solvent mixed in a volume ratio of ethylene carbonate (EC):dimethyl carbonate (DMC):ethylmethyl carbonate (EMC) = 1:2:1.

[0198] (1) Capacity measurement

[0199] A lithium secondary battery prepared using the positive active materials of Examples 1 to 3 and Comparative Examples 1 to 4 was charged to 4.4V at 25°C using an electrochemical charge / discharger under CC / CV and 0.1C conditions, discharged to 2.5V under CC and 0.1C conditions, and the capacity was measured and is shown in Table 2 below.

[0200] (2) Low temperature resistance measurement

[0201] A lithium secondary battery prepared using the positive active materials of Examples 1 to 3 and Comparative Examples 1 to 4 was charged at 25°C with a constant current of 0.1C until it reached 4.4V, and discharged with a constant current of 0.1C until it reached 2.5V, with 2 cycles of charging and discharging being performed.

[0202] Next, the voltage change (△V) was measured by charging to 20% SOC at a rate of 0.1C at 25℃ and then discharging at a rate of 2C for 18 seconds under conditions of -10℃. The resistance (R=△V / I) was calculated by dividing the measured voltage change by the current (I), and the results are shown in Table 2 below.

[0203] Capacity (mAh / g) Resistance (Ω) Example 1 197.498 Example 2 197.3104.3 Example 3 197104.7 Comparative Example 1 196.2144.5 Comparative Example 2 196113.1 Comparative Example 3 196.2109.6 Comparative Example 4 196.7119.4

[0204] Referring to Table 2 above, it can be seen that the lithium secondary batteries of Examples 1 to 3, in which the value of F is 0.078 to 0.082, have superior capacity and resistance compared to Comparative Example 1, in which the value of F does not satisfy the above range without adding the second lithium raw material, and for example, the resistance is significantly improved.

[0205] In addition, it can be confirmed that the lithium secondary batteries of Examples 1 to 3, which use the positive active material of the present invention in which the coating layer heat treatment is performed between 735℃ and 790℃, have improved capacity and resistance compared to the lithium secondary batteries of Comparative Examples 2 to 4, which use the positive active material in which the coating layer heat treatment is performed at a temperature outside the above temperature range. This is believed to be because the cobalt coating layer of the lithium secondary batteries of Examples 1 to 3 is formed in a more optimized form than the cobalt coating layer of Comparative Examples 2 to 4.

[0206]

[0207] Experimental Example 3: High-temperature stability evaluation

[0208] The heat flow according to temperature of the lithium secondary batteries prepared in Example 1, Comparative Example 1, and Comparative Example 5 was measured using a differential scanning calorimeter (METTLER TOLEDO, model name: DSC3). At this time, the lithium secondary battery using the cathode of Comparative Example 5 was prepared using the same method as described in Experimental Example 2.

[0209] For example, the lithium secondary batteries prepared in Example 1, Comparative Example 1, and Comparative Example 5 were each charged at 25°C with a constant current of 0.1C until they reached 4.4V, and then the lithium secondary batteries were disassembled to separate the positive electrodes. The separated positive electrodes were washed with dimethyl acetate, immersed in 20 μL of electrolyte (1M LiPF6, EC:DMC:EMC = 3:4:3 volume ratio), and DSC analysis was performed on the positive electrode active material. The temperature range for DSC analysis was set to 100°C to 400°C, and the heating rate was set to 10°C / min. DSC measurements were performed at least three times for each positive electrode, and the average value was calculated. The measurement results are shown in Table 3 and Figure 6 below.

[0210] DSC Exothermic Main Peak Temperature (°C) Example 1 276.0 Comparative Example 1 264.4 Comparative Example 5 221.0

[0211] Referring to Table 3 above, it can be seen that the temperature of the main peak of the positive electrode active material of Example 1 is higher than that of the positive electrode active material of Comparative Example 1, which was prepared without adding the second lithium raw material, and the positive electrode active material of Comparative Example 5, which has a high nickel content. Through this, it can be seen that the positive electrode active material of Example 1, prepared using the method for preparing the positive electrode active material of the present invention, has superior thermal stability compared to the positive electrode active materials of Comparative Example 1 and Comparative Example 5, which were prepared without using the method for preparing the positive electrode active material of the present invention.

[0212] Although the foregoing has been described with reference to the embodiments of the present disclosure, a person skilled in the art or having ordinary knowledge in the art will understand that various modifications and changes can be made to the various embodiments of the present disclosure without departing from the technical scope of the various embodiments of the present disclosure as set forth in the claims below. Accordingly, the technical scope of the various embodiments of the present disclosure should not be limited to the contents described in the detailed description of the specification, but should be determined by the claims.

Claims

1. A positive electrode active material comprising: lithium nickel-based oxide particles having a molar ratio of nickel among the total transition metals of 50 mol% to 70 mol%; and a coating layer formed on the surface of the lithium nickel-based oxide particles and containing cobalt; and The above lithium nickel-based oxide particles are in the form of a single particle consisting of one single nodule or a pseudo-single particle consisting of a complex of 30 or fewer nodules, and The above positive active material is a positive active material satisfying the following Formula 1: [Equation 1] 0.078 ≤ F ≤ 0.082 In the above Equation 1, F is the Full Width at Half Maximum (FWHM) of the (104) peak measured by X-ray diffraction analysis (XRD) of the above positive active material.

2. In Claim 1, A positive electrode active material in which the molar ratio of nickel in the lithium nickel-based oxide particles is 60 mol% to 70 mol% based on the total transition metal.

3. In Claim 1, A positive active material wherein the above lithium nickel-based oxide particles are represented by the following chemical formula 1: [Chemical Formula 1] Li a Ni b Co c Mr d M 1 e O2 In the above chemical formula 1, M 1 is one or more selected from the group consisting of Al, Ba, Zr, Ti, Ta, Nb, Y, W, Sr, B, Mg, Mo, Ce, F, and P, and 0.9≤a≤1.1, 0.5≤b≤0.7, 0 <c≤0.5, 0<d≤0.4, 0≤e≤0.2이다.

4. In Claim 1, A positive electrode active material having a cobalt content of 1 mol% to 5 mol% relative to 100 mol of the lithium nickel-based oxide in the coating layer.

5. A step of preparing a lithium nickel-based oxide by mixing a transition metal precursor including nickel, cobalt, and manganese with a first lithium raw material and then calcining the mixture; and The method comprises the step of mixing the above-manufactured lithium nickel-based oxide with a cobalt raw material and a second lithium raw material and heat-treating it to produce an anode active material having a coating layer on the surface of the lithium nickel-based oxide; A method for manufacturing a positive electrode active material in which the above lithium nickel-based oxide is in the form of a single particle consisting of one single nodule or a pseudo-single particle consisting of a complex of 30 or fewer nodules.

6. In Claim 5, A method for manufacturing a positive electrode active material in which the second lithium raw material is mixed in an amount of 0.2 to 0.8 parts by weight relative to 100 parts by weight of the manufactured lithium nickel-based oxide.

7. In Claim 5, A method for manufacturing a positive electrode active material in which the above positive electrode active material satisfies the following formula 1: [Equation 1] 0.078 ≤ F ≤ 0.082 In the above Equation 1, F is the Full Width at Half Maximum (FWHM) of the (104) peak measured by X-ray diffraction analysis (XRD) of the above positive active material.

8. In Claim 5, A method for manufacturing an anode active material in which the above heat treatment is performed at 735℃ to 790℃.

9. An anode comprising an anode active material according to any one of claims 1 to 4.

10. Anode according to claim 9; A cathode opposite to the anode above; A separator interposed between the anode and the cathode; and A lithium secondary battery containing an electrolyte.

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