Positive electrode active material and preparation method therefor

Abstract

The present invention relates to a positive electrode active material capable of improving the performance and stability of a lithium-rich oxide and consequently improving the performance of a battery including same, and to a positive electrode active material, a preparation method therefor, and a positive electrode and a lithium secondary battery including same, the positive electrode active material comprising: a lithium-rich transition metal oxide having a layered structure simultaneously containing a Li2MnO3 phase and a LiMO2 phase, wherein M is an element including at least one selected from Ni, Co, and Mn; and a coating layer including boron and carbon formed on the lithium-rich transition metal oxide, wherein the positive electrode active material satisfies at least one of the following conditions (1) to (3): -Condition (1): the atomic ratio (B / Mn) of boron (B) and manganese (Mn) present on the surface analyzed by XPS is 1 to 5; -Condition (2): the intensity ratio (ICarbonate,1:IC-C) of a peak (ICarbonate,1) at 287.5-288.5 eV and a peak (IC-C) at 284-285 eV in the XPS spectrum of the surface is 0.05 to 0.15: 1; and -Condition (3): the intensity ratio (ICarbonate,2:IC-C) of the peak (ICarbonate,2) at 288.6-290.5 eV and the peak (IC-C) at 284-285 eV in the XPS spectrum of the surface is 0.05-0.15:1.

Description

Positive electrode active material and method for producing the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0087326, filed July 5, 2023, and Korean Patent Application No. 10-2023-0086034, filed July 3, 2023, the entire contents of which are incorporated herein by reference.

[0003] Technology field

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

[0005]

[0006] Lithium secondary batteries are composed of four major components: a cathode, an anode, a separator, and an electrolyte. Among these, the cathode active material contained in the cathode plays a significant role in determining the battery's capacity, output, and lifespan. For lithium secondary batteries to achieve high energy density, output, and lifespan, improving the performance of the cathode active material is essential. Consequently, extensive research has been conducted recently to develop high-performance cathode active materials.

[0007] Li-rich layered oxide, a type of cathode active material, is a mixed phase of Li2MnO3 phase and LiMO2 (M=Ni, Mn, Co) phase and has a high operating voltage (>3.5 V vs. Li / Li). + ) has the characteristic of providing a very large capacity of 250 mAh / g. Therefore, the lithium excess oxide is attracting attention as a low-cost, high-capacity cathode active material.

[0008] However, the lithium-excess oxide has problems that arise due to its structural characteristic of being a mixture of two phases. Specifically, when a battery containing the lithium-excess oxide is operated under high voltage, there is a problem that irreversible capacity loss occurs in the first formation process, resulting in reduced efficiency, and during charge / discharge cycles, voltage fading occurs as the layered structure changes to a spinel structure and then to a rock salt structure, resulting in problems such as the generation of O2 gas.

[0009] Therefore, it is necessary to secure a technology to improve the performance and stability of the lithium-excess oxide.

[0010]

[0011] The problem to be solved in the present invention is to improve the performance and stability of lithium-excess oxide, thereby improving the performance of a battery containing the same.

[0012] In addition, the present invention aims to provide a method for manufacturing the positive electrode active material.

[0013] In addition, the present invention aims to provide a positive electrode and a lithium secondary battery including the positive electrode active material.

[0014]

[0015] To solve the above problem, the present invention provides a cathode active material, a method for producing the cathode active material, a cathode, and a lithium secondary battery.

[0016] (1) The present invention provides a positive electrode active material comprising a lithium-rich transition metal oxide having a layered structure simultaneously including a Li2MnO3 phase and a LiMO2 (wherein M is an element including at least one selected from Ni, Co, and Mn) phase; and a coating layer including boron and carbon formed on the lithium-rich transition metal oxide; and satisfying at least one of the following conditions (1) to (3).

[0017] - Condition (1): The atomic ratio (B / Mn) of boron (B) and manganese (Mn) present on the surface analyzed by XPS is 0.3 to 5.

[0018] - Condition (2): Peak at 287.5~288.5 eV in the XPS spectrum of the surface (I Carbonate,1 ) and peak at 284–285 eV (I C-C ) intensity ratio (I Carbonate,1 :I C-C ) is 0.05~0.15:1

[0019] - Condition (3): Peak at 288.6~290.5 eV in the XPS spectrum of the surface (I Carbonate,2 ) and peak at 284–285 eV (I C-C ) intensity ratio (I Carbonate,2 :I C-C ) is 0.05~0.15:1

[0020] (2) The present invention provides a positive electrode active material in the above (1), wherein the lithium-excess transition metal oxide is in the form of a single particle.

[0021] (3) In the present invention, in the above (1), the lithium-excess transition metal oxide has an average particle diameter (D 50 ) provides a positive electrode active material having a diameter of 0.75㎛ to 10㎛.

[0022] (4) The present invention provides a positive electrode active material in any one of the above (1) to (3), wherein the lithium-excess transition metal oxide has a Mn content of 50 mol% or more among all metals excluding lithium.

[0023] (5) The present invention provides a positive electrode active material in any one of the above (1) to (4), wherein the lithium-excess transition metal oxide has a composition represented by the following chemical formula 1.

[0024] [Chemical Formula 1]

[0025] Li(Li a Ni b Co c Mn d Me e )O2

[0026] In the above chemical formula 1,

[0027] Me is one or more selected from W, Mo, Zn, Mg, Nb, and Al,

[0028] 0.01≤a≤0.20, 0≤b≤0.50, 0≤c≤0.10, 0.50≤d≤1.0, 0≤e≤0.10, a+b+c+d+e=1.

[0029] (6) The present invention provides a positive electrode active material in any one of the above (1) to (5), wherein the lithium-excess transition metal oxide is doped with W, Mo or a combination thereof.

[0030] (7) The present invention provides a positive electrode active material in any one of the above (1) to (6), wherein the coating layer includes a compound in which lithium, boron, and oxygen are chemically bonded to each other and a compound including carbon.

[0031] (8) The present invention provides a positive electrode active material according to any one of (1) to (7), wherein the coating layer has a thickness of 1 nm to 80 nm.

[0032] (9) The present invention provides a method for producing a positive electrode active material according to any one of (1) to (8), including the steps of (A) dry mixing a lithium-containing raw material and a transition metal-containing raw material, and then calcining to produce a lithium-rich transition metal oxide; and (B) dry mixing the lithium-rich transition metal oxide and the boron-containing raw material, and then heat-treating to form a coating layer on the lithium-rich transition metal oxide.

[0033] (10) The present invention provides a method for producing a positive electrode active material, wherein, in the above (9), the calcination is performed at a temperature of 850°C to 1,050°C.

[0034] (11) The present invention provides a method for producing a positive electrode active material, wherein, in (9) or (10), the boron-containing raw material is mixed in an amount such that boron (B) is 300 ppm to 1,500 ppm relative to the total weight of the lithium-excess transition metal oxide.

[0035] (12) The present invention provides a method for producing a positive electrode active material, wherein the heat treatment is performed at a temperature of 300°C to 450°C in any one of the above (9) to (11).

[0036] (13) The present invention provides a method for producing a positive electrode active material, wherein, when dry mixing the lithium-containing raw material and the transition metal-containing raw material in any one of the above (9) to (12), a doping element-containing raw material is further mixed.

[0037] (14) The present invention provides a positive electrode comprising a positive electrode active material according to any one of (1) to (8).

[0038] (15) The present invention provides a lithium secondary battery including a positive electrode according to (14) above.

[0039]

[0040] The cathode active material of the present invention includes a coating layer including boron and carbon formed on a lithium-excess transition metal oxide, and satisfies at least one of conditions (1) to (3) described herein with respect to XPS data, thereby improving the performance of a lithium secondary battery including the cathode active material, for example, efficiency during an activation process, 0.33C discharge capacity, and resistance performance.

[0041]

[0042] Figure 1 is EELS data of the positive electrode active material of Example 1 of the present invention.

[0043] Figure 2 is an XRD spectrum of the positive electrode active materials of Examples 1 to 4 of the present invention.

[0044] Figure 3 is an XPS spectrum of Examples 1 to 3 and Comparative Example 1 of the present invention.

[0045]

[0046] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0047] The terms or words used in the description and claims of the present invention should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0048] In this specification, the term "single particle form" refers to a form composed of 10 or fewer primary particles, as opposed to a secondary particle form formed by the agglomeration of tens to hundreds of primary particles. Specifically, the "single particle form" may be a single particle form composed of one primary particle, or a secondary particle form composed of agglomerations of several primary particles.

[0049] In this specification, 'primary particle' means the smallest particle unit recognized when observing a positive electrode active material using a scanning electron microscope (SEM), and 'secondary particle' means a secondary structure formed by the aggregation of multiple primary particles.

[0050] In this specification, the term 'average particle diameter (D 50 )' means the particle size at the 50% point of the volume cumulative distribution according to particle size. The above average particle size is calculated by dispersing the powder to be measured in a dispersion medium, introducing it into a commercially available laser diffraction particle size measuring device (e.g., Bluewave of Microtrac), and measuring the difference in diffraction pattern according to particle size when the particles pass through the laser beam to calculate the particle size distribution, and calculating the particle diameter at the point where it becomes 50% of the volume cumulative distribution according to particle size in the measuring device, thereby obtaining D 50 can be measured.

[0051]

[0052] positive electrode active material

[0053] The present invention relates to a Li2MnO3 phase and LiMO2 (wherein M is an element including at least one selected from Ni, Co and Mn, and specifically, M=Ni x Co y Mn z , 0≤x≤0.9, 0≤y≤0.1, 0.1≤z≤1.0, x+y+z=1) and a coating layer including boron and carbon formed on the lithium-rich transition metal oxide; and a cathode active material is provided, which satisfies at least one of the following conditions (1) to (3).

[0054] - Condition (1): The atomic ratio (B / Mn) of boron (B) and manganese (Mn) present on the surface analyzed by XPS is 0.3 to 5.

[0055] - Condition (2): Peak at 287.5~288.5 eV in the XPS spectrum of the surface (ICarbonate,1 ) and peak at 284–285 eV (I C-C ) intensity ratio (I Carbonate,1 :I C-C ) is 0.05~0.15:1

[0056] - Condition (3): Peak at 288.6~290.5 eV in the XPS spectrum of the surface (I Carbonate,2 ) and peak at 284–285 eV (I C-C ) intensity ratio (I Carbonate,2 :I C-C ) is 0.05~0.15:1

[0057]

[0058] The inventors of the present invention have found that when a positive electrode active material includes a coating layer including boron and carbon formed on the lithium-excess transition metal oxide, and when the surface of the positive electrode active material is analyzed by XPS and satisfies at least one of the conditions (1) to (3), the discharge capacity and efficiency in the first formation process of a battery including the positive electrode active material can be improved, the 0.33C discharge capacity can be improved, and the resistance characteristics can also be improved, and thus the present invention has been completed.

[0059] XPS is a device that analyzes the components or chemical bonding state from the surface to a depth of 10 nm. In this specification, the surface analyzed by XPS may be a region from the outermost surface of the positive electrode active material to a depth of 10 nm.

[0060] Meanwhile, when the positive electrode active material does not include the coating layer, there are problems arising due to the structural characteristic of two phases being mixed, so that the initial activation efficiency and 0.33C discharge capacity of the battery including the same are reduced, and when the coating layer does not include carbon, there is a problem that the conductivity of the coating layer is low and the resistance of the positive electrode active material is high. In addition, the positive electrode active material is a Mn-rich positive electrode active material, and when the surface of the positive electrode active material is analyzed by XPS, the content of manganese present on the surface is high compared to the NCM-based positive electrode active material, so that the atomic ratio (B / Mn) of boron (B) and manganese (Mn) present on the surface is relatively small. Specifically, the atomic ratio (B / Mn) of boron (B) and manganese (Mn) present on the surface may be 0.30 or more, 0.40 or more, 4.50 or less, or 5.00 or less.

[0061] According to the present invention, the positive electrode active material may have a lower resistance than the lithium-excess transition metal oxide. That is, the coating layer included in the positive electrode active material may include a material having a low resistance, thereby improving the electronic conductivity and ionic conductivity of the positive electrode active material.

[0062] According to the present invention, the positive electrode active material has a peak (I) at 287.5 to 288.5 eV in the XPS spectrum of the surface. Carbonate,1 ) and peak at 284–285 eV (I C-C ) intensity ratio (I Carbonate,1 :I C-C ) may be 0.05 to 0.15:1. In addition, the positive electrode active material has a peak (I) at 288.6 to 290.5 eV in the XPS spectrum of the surface. Carbonate,2 ) and peak at 284–285 eV (I C-C ) intensity ratio (I Carbonate,2 :I C-C) may be 0.05 to 0.15:1. This is because, in the case of the positive electrode active material according to the present invention, as a coating layer is formed on the lithium-excess transition metal oxide, the content of Li2CO3 among the by-products (residual lithium) present in the lithium-excess transition metal oxide is significantly reduced, and the content of carbonate present on the surface of the positive electrode active material is significantly reduced. Meanwhile, in the XPS spectrum of the surface of the positive electrode active material, I Carbonate,1 :I C-C and / or I Carbonate,2 :I C-C When the above-described range is satisfied, the battery including the positive electrode active material according to the present invention can further improve the charge / discharge efficiency, 0.33C discharge capacity, and resistance characteristics.

[0063] The peak at 287.5–288.5 eV (I Carbonate,1 ) and peak at 284–285 eV (I C-C ) intensity ratio (I Carbonate,1 :I C-C ) can be specifically 0.05~0.15:1, 0.06~0.15:1, 0.07~0.14:1, 0.08~0.13:1, or 0.09~0.12:1. And, the peak (I at 288.6~290.5 eV Carbonate,2 ) and peak at 284–285 eV (I C-C ) intensity ratio (I Carbonate,2 :I C-C ) can be specifically 0.05~0.15:1, 0.06~0.14:1, 0.07~0.13:1, or 0.08~0.12:1.

[0064]

[0065] According to the present invention, the lithium-rich transition metal oxide may be in the form of single particles in terms of improving the energy density of a lithium secondary battery and reducing gas generation.

[0066]

[0067] According to the present invention, the lithium-rich transition metal oxide has an average particle diameter (D 50) may be 0.75㎛ to 10㎛, specifically 0.9㎛ to 10㎛ or less. In this case, electrode defects due to particle agglomeration during electrode manufacturing can be prevented.

[0068] Meanwhile, when the lithium-rich transition metal oxide is in the form of a single particle, the average particle diameter (D) of the lithium-rich transition metal oxide 50 ) can be 0.75㎛ to 2㎛.

[0069] And, when the lithium-rich transition metal oxide is in the form of secondary particles formed by agglomeration of tens to hundreds of primary particles, the average particle diameter (D) of the lithium-rich transition metal oxide 50 ) can be 3㎛ to 10㎛.

[0070]

[0071] According to the present invention, the lithium-rich transition metal oxide may have a manganese content of 50 mol% or more, specifically 60 mol% or more, and more specifically 65 mol% or more, of the total metal content excluding lithium. In this case, high capacity can be exhibited even when charged at high voltage.

[0072]

[0073] According to the present invention, the lithium-excess transition metal oxide may have a composition represented by the following chemical formula 1. In this case, the charge / discharge efficiency in the first activation (first formation) process of a battery including the positive electrode active material according to the present invention and the discharge capacity (particularly, the discharge capacity at 0.33 C) after the activation process can be improved.

[0074] [Chemical Formula 1]

[0075] Li(Li a Ni b Co c Mn d Me e )O2

[0076] In the above chemical formula 1,

[0077] Me is one or more selected from W, Mo, Zn, Mg, Nb, and Al,

[0078] 0.01≤a≤0.20, 0≤b≤0.50, 0≤c≤0.10, 0.50≤d≤1.0, 0≤e≤0.10, a+b+c+d+e=1.

[0079] The above lithium-rich transition metal oxide may not contain expensive cobalt, and may improve the performance of a lithium secondary battery without containing cobalt.

[0080]

[0081] According to the present invention, the lithium-rich transition metal oxide may be doped with W, Mo, or a combination thereof. When the lithium-rich transition metal oxide is doped with tungsten (W), the performance of the battery may be improved, and when the lithium-rich transition metal oxide is doped with molybdenum (Mo), not only the particle size of the positive electrode active material may be increased, but also the particle shape may be improved. Meanwhile, tungsten (W) may be doped in an amount of 14,700 ppm or less with respect to the lithium-rich transition metal oxide, and molybdenum (Mo) may also be doped in an amount of 5,500 ppm or less with respect to the lithium-rich transition metal oxide.

[0082] The content of the tungsten (W) may be 6,300 ppm or more, 7,500 ppm or more, 8,500 ppm or more, or 9,000 ppm or more, and 10,500 ppm or less, 12,000 ppm or less, 13,000 ppm or less, 14,000 ppm or less, or 14,700 ppm or less, based on the total content of the lithium-rich transition metal oxide. When the content of the tungsten (W) is within the above range, structural stability may be improved since W ions form WO bonds. Specifically, during the first charge, when all lithium in the transition metal layer on Li2MnO3 is desorbed, oxygen is released to adjust the chemical equivalence, and at this time, the amount of oxygen released from the surface is reduced due to the WO bond. In addition, since the cation mixing phenomenon is suppressed during the charge / discharge process due to the WO bond, deformation of the layered structure is prevented, thereby improving the capacity characteristics and resistance characteristics of a secondary battery including the positive electrode active material.

[0083] The content of the above molybdenum (Mo) may be 1,100 ppm or more, 1,500 ppm or more, or 2,000 ppm or more, or 2,500 ppm or more, and may be 3,300 ppm or less, 3,500 ppm or less, 4,000 ppm or less, 4,500 ppm or less, or 5,500 ppm or less, based on the total content of the lithium-rich transition metal oxide. When the content of the above molybdenum (Mo) is within the above range, since the Mo ion has a relatively large cation radius, the particle size of the positive electrode active material can be increased and the particle shape can be improved, thereby improving the life characteristics of a secondary battery including the positive electrode active material.

[0084]

[0085] According to the present invention, the coating layer may include a compound in which lithium, boron, and oxygen are chemically bonded to each other and a compound containing carbon. That is, an amorphous compound containing lithium, boron, and oxygen and a carbon-based compound may coexist.

[0086]

[0087] According to the present invention, the coating layer may have a thickness of 1 nm to 80 nm, specifically 1 nm to 50 nm, and more specifically 2 nm to 20 nm. In this case, the coating layer may contribute to improving electrical properties, particularly reducing resistance.

[0088]

[0089] Method for manufacturing positive electrode active material

[0090] The present invention provides a method for producing a positive electrode active material according to the present invention, comprising the steps of: (A) dry mixing a lithium-containing raw material and a transition metal-containing raw material, and then calcining to produce a lithium-rich transition metal oxide; and (B) dry mixing the lithium-rich transition metal oxide and the boron-containing raw material, and then heat-treating to form a coating layer on the lithium-rich transition metal oxide.

[0091]

[0092] (A) Step

[0093] (A) Step is to dry mix lithium-containing raw materials and transition metal-containing raw materials, then calcinate them to form Li2MnO3 phase and LiMO2(M=Ni x Co y Mn z , 0≤x≤0.9, 0≤y≤0.1, 0.1≤z≤1.0, x+y+z=1) is a step for manufacturing a lithium-rich transition metal oxide having a layered structure that simultaneously includes phases.

[0094]

[0095] According to the present invention, when dry mixing the lithium-containing raw material and the transition metal-containing raw material in step (A), a doping element-containing raw material may be further mixed. That is, the doping element-containing raw material may be selectively added.

[0096]

[0097] The above lithium-containing raw material may be a lithium-containing raw material that can be used in manufacturing a positive electrode active material, for example, lithium hydroxide, lithium carbonate, lithium oxide, etc.

[0098] The above transition metal-containing raw material may include a nickel compound, a cobalt compound, a manganese compound, etc.

[0099] The above nickel compound is a nickel raw material that can be used in the manufacture of a positive electrode active material, and may be, for example, nickel carbonate, sulfate, nitrate, hydroxide, and oxide.

[0100] The above cobalt compound is a cobalt raw material that can be used in the manufacture of a positive electrode active material, and may be, for example, a carbonate, sulfate, nitrate, hydroxide, or oxide of cobalt.

[0101] The above manganese compound is a manganese raw material that can be used in the manufacture of a positive electrode active material, and may be, for example, manganese carbonate, sulfate, nitrate, oxide, etc.

[0102]

[0103] The above doping element-containing raw material includes at least one selected from W and Mo, and may be tungsten oxide, molybdenum oxide, ammonium molybdate, lithium molybdate, etc.

[0104] For example, tungsten (W) containing raw materials include WO3, WC, WS2, and C8H 16At least one selected from the group consisting of O8W may be used, and a mixture of one or more of these may be used. Specifically, WO3 may be used considering economic feasibility, the amount of gas generated during heat treatment, and the heat treatment temperature.

[0105] And, molybdenum (Mo) containing raw materials are Li2MoO4, MoO3, and (NH4)6Mo7O 24 It may be at least one selected from the group consisting of, and a mixture of one or more of these may be used. Specifically, Li2MoO4 may be used considering the raw material used in mixing, the content of Mo, and the heat treatment temperature.

[0106]

[0107] The above lithium-containing raw material, transition metal-containing raw material, and doping element-containing raw material can be introduced in an amount such that the resulting lithium-rich transition metal oxide has a composition represented by the above chemical formula 1.

[0108]

[0109] According to the present invention, the sintering in step (A) can be performed at a temperature of 850°C to 1,050°C. In this case, the crystallinity of the positive electrode active material can be increased.

[0110] The above firing can be performed for 1 to 15 hours.

[0111]

[0112] Specifically, the step (A) may be a process for producing a first fired product by dry mixing a lithium-containing raw material and a transition metal-containing raw material, then performing a first firing (corresponding to the above firing), pulverizing the first fired product for the first time, then performing a second firing to remove fine particles generated by the pulverization to produce a second fired product, and then pulverizing the second fired product for the second time to produce a lithium-rich transition metal oxide. At this time, the second firing does not affect the phase of the lithium-rich transition metal oxide, and is a heat treatment process for causing fine particles with very small particle sizes to receive heat energy and become lumps, and may be performed at a temperature (700 to 800°C) lower than the first firing temperature.

[0113] The above primary crushing is performed to reduce the size distribution among the multi-particles, which are randomly aggregated multiple particles (several to several dozen) in the above primary sintered product. The above primary crushing is a process of crushing particles with weak force, and has aspects similar to the disintegration process.

[0114] The above secondary crushing is a process of crushing the particles with a strong force so that the multi-particles included in the secondary sintered product can exist in the form of single particles by dropping them one by one. After the secondary crushing is completed, the particles have the form of single particles, and the average particle diameter of the lithium-rich transition metal oxide in the present specification may be the average particle diameter of the lithium-rich transition metal oxide in the form of single particles after the secondary crushing.

[0115]

[0116] (B) Step

[0117] Step (B) is a step of dry mixing the lithium-rich transition metal oxide and the boron-containing raw material, and then heat-treating the mixture to form a coating layer on the lithium-rich transition metal oxide.

[0118] On the surface of the lithium-rich transition metal oxide manufactured in the above step (A), by-products such as residual lithium exist. In the case of the present invention, even though a step of washing the residual lithium is not included, the amount of residual lithium decreases through the above step (B), and in particular, the Li2CO3 content is significantly reduced, so that the performance of the positive electrode active material manufactured as a result can be excellent.

[0119] Specifically, when the lithium-excessive transition metal oxide boron-containing raw material is dry-mixed and then heat-treated, the boron-containing raw material melts, and Li2CO3 among the by-products (residual lithium) present in the lithium-excessive transition metal oxide also participates in the reaction, thereby forming a coating layer including boron and carbon. That is, the boron present in the coating layer may be derived from the boron-containing raw material, and the carbon may be derived from Li2CO3 among the by-products (residual lithium) present in the lithium-excessive transition metal oxide. Accordingly, the positive electrode active material according to the present invention may have a significantly low carbonate content present on the surface. In addition to boron and carbon, the coating layer may further include lithium and oxygen, and the coating layer may include a compound in which lithium, boron, and oxygen are chemically bonded to each other, and a compound including carbon.

[0120]

[0121] According to the present invention, in the step (B), the boron-containing raw material may be mixed in an amount such that boron (B) is 300 ppm to 1,500 ppm relative to the total weight of the lithium-rich transition metal oxide. Specifically, the boron-containing raw material may be mixed in an amount such that the boron (B) content is 300 ppm or more, 500 ppm or more, 1,000 ppm or more, or 1,500 ppm or less relative to the total weight of the lithium-rich transition metal oxide. In this case, a coating layer containing boron and carbon of an appropriate thickness is formed, so that the electrical characteristics of the manufactured positive electrode active material can be improved.

[0122]

[0123] According to the present invention, the heat treatment in step (B) can be performed at a temperature of 300°C to 450°C. Specifically, the heat treatment temperature can be 300°C or higher, 310°C or higher, 320°C or higher, 330°C or higher, 340°C or higher, 360°C or lower, 380°C or lower, 400°C or lower, or 450°C or lower. In this case, a coating layer having high electrical conductivity and improving battery performance can be formed.

[0124] The above heat treatment can be performed for 3 to 7 hours, specifically 3 to 5 hours.

[0125]

[0126] anode

[0127] The present invention provides a positive electrode comprising the positive electrode active material.

[0128] The 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.

[0129] The positive electrode current collector may include a highly conductive metal, and is not particularly limited as long as it is easily adhered to by the positive electrode active material layer and does not react within the voltage range of the battery. The positive electrode current collector may be made of, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. In addition, the positive electrode current collector may typically have a thickness of 3 ㎛ to 500 ㎛, and fine unevenness may be formed on the surface of the current collector to increase the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0130] The above-mentioned positive electrode active material layer may optionally include a conductive material and a binder, together with the positive electrode active material, as needed. In this case, the positive electrode active material may be included in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics may be exhibited within this range.

[0131] The conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any special restrictions. 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 fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The conductive material may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0132] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and polymers in which hydrogens of these are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above binder may be included in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0133] The positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used. Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, which is manufactured by dissolving or dispersing the positive electrode active material and optionally a binder, a conductive agent, and a dispersant in a solvent as needed, onto a positive electrode current collector, followed by drying and rolling, or by casting the composition for forming a positive electrode active material layer onto a separate support, peeling the film from the support, and laminating the resulting film onto a positive electrode current collector.

[0134] The solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water. One of these may be used alone or a mixture of two or more thereof may be used. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant in consideration of the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0135]

[0136] lithium secondary battery

[0137] The present invention provides a lithium secondary battery including the positive electrode.

[0138]

[0139] The lithium secondary battery may include the positive electrode; the negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte. In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0140] The above negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0141] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0142] The above negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material.

[0143] As the 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 alloy, Sn alloy, or Al alloy; SiO β(0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical or fibrous shapes, 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 negative electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0144] The binder of the above-described negative electrode active material layer is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0145] The conductive material of the above-described 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 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and 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; and conductive materials such as polyphenylene derivatives.

[0146] The above negative electrode can be manufactured by applying and drying a composition for forming a negative electrode active material layer prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0147] The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as 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, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0148] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

[0149] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylenecarbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, 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 linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

[0150] The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in a lithium secondary battery. 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 - At least one selected from the group consisting of may be used, and the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the concentration of the lithium salt within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0151] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

[0152]

[0153] A lithium secondary battery including a cathode active material according to the present invention stably exhibits excellent capacity characteristics, output characteristics, and life characteristics, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0154] There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0155] 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 be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0156] Accordingly, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0157] The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as 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]

[0159] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0160]

[0161] Example

[0162] Example 1

[0163] Li2CO3, NiCO3 and MnCO3 were dry mixed so that the molar ratio of lithium:nickel:manganese was 1.143:0.287:0.57, and then fired at 1,000℃ for 12 hours in an air atmosphere to manufacture a fired product. The fired product was pulverized with a UCM equipment (Retsch, ZM 200, 18,000 rpm), fired at 750℃ for 5 hours in an air atmosphere to remove fine particles, and pulverized with a jet-mill equipment (Isac E&C, Micron-master air jetmill, 3.5 bar) to obtain lithium-rich transition metal oxides in the form of single particles (composition: Li 1.143 Ni 0.287 Mn 0.57 O2, average particle size (D50): 1.05㎛) was manufactured.

[0164] After mixing H3BO3 with the lithium-excess transition metal oxide so that boron (B) is 1,200 ppm based on the total weight of the lithium-excess transition metal oxide, heat treatment was performed at 350°C for 5 hours to form a coating layer (thickness: 2 to 10 nm) containing lithium, boron, carbon, and oxygen on the lithium-excess transition metal oxide, thereby manufacturing a cathode active material.

[0165]

[0166] Example 2

[0167] A mixture was prepared by dry mixing Li2CO3, NiCO3, and MnCO3 so that the molar ratio of lithium:nickel:manganese was 1.143:0.287:0.57. WO3 was additionally mixed into the mixture so that tungsten (W) was 10,500 ppm based on the total weight of the lithium-rich transition metal oxides to be finally produced, and then fired at 1,050°C for 12 hours to produce a fired product. The fired product was pulverized with a UCM device (Retsch, ZM 200, 18,000 rpm), fired at 750°C for 5 hours in an air atmosphere to remove fine particles, and then pulverized with a jet-mill device (Isac E&C, Micron-master air jetmill, 3.5 bar) to produce a lithium-rich transition metal oxide in the form of single particles (composition: Li 1.143 Ni 0.287 Mn 0.565 W 0.005 O2, average particle size (D 50 ): 0.93㎛) was manufactured.

[0168] After mixing H3BO3 with the lithium-excess transition metal oxide so that boron (B) is 1,200 ppm based on the total weight of the lithium-excess transition metal oxide, heat treatment was performed at 350°C for 5 hours to form a coating layer (thickness: 2 to 10 nm) containing lithium, boron, carbon, and oxygen on the lithium-excess transition metal oxide, thereby manufacturing a cathode active material.

[0169]

[0170] Example 3

[0171] A mixture was prepared by dry mixing Li2CO3, NiCO3, and MnCO3 so that the molar ratio of lithium:nickel:manganese was 1.143:0.287:0.57. WO3 and Li2MoO4 were additionally mixed into the mixture so that tungsten (W) and molybdenum (Mo) were 10,500 ppm and 3,300 ppm, respectively, based on the total weight of the lithium-rich transition metal oxide to be produced, and then fired at 1,050°C for 12 hours to produce a fired product. The fired product was pulverized with a UCM device (Retsch, ZM 200, 18,000 rpm), fired at 750°C for 5 hours in an air atmosphere to remove fine particles, and then pulverized with a jet-mill device (Isac E&C, Micron-master air jetmill, 3.5 bar) to produce a lithium-rich transition metal oxide (composition: Li) in the form of single particles. 1.143 Ni 0.287 Mn 0.562 W 0.005 Mo 0.003 O2, average particle size (D 50 ): 1.05㎛) was manufactured.

[0172] After mixing H3BO3 with the lithium-excess transition metal oxide so that boron (B) is 1,450 ppm based on the total weight of the lithium-excess transition metal oxide, heat treatment was performed at 350°C for 5 hours to form a coating layer (thickness: 2 to 10 nm) containing lithium, boron, carbon, and oxygen on the lithium-excess transition metal oxide, thereby manufacturing a cathode active material.

[0173]

[0174] Example 4

[0175] Li2CO3, NiCO3 and MnCO3 were added to pure water in an amount such that the molar ratio of lithium:nickel:manganese was 1.145:0.282:0.572 (solid content: 20 wt%), and wet mixing was performed in a ball mill using zirconia balls for 1 hour. Afterwards, the zirconia balls were removed, and the solids were pulverized using wet grinding equipment (NETZCH, MiniCer) to obtain the average particle size (D) of the solids. 50 ) was prepared as a slurry having a particle size of 0.2 μm. Afterwards, the slurry was spray-dried using a spray drying device (Buchi, B-290) at an inlet hot air temperature of 200°C and an exhaust hot air temperature of 90°C or higher to obtain a dried product. The dried product was fired at 975°C for 12 hours in an air atmosphere to produce a fired product. The fired product was pulverized using a jet-mill device (Isac E&C, Micron-master air jetmill, 1.7 bar) to obtain a lithium-rich transition metal oxide (composition: Li) in the form of single particles. 1.145 Ni 0.282 Mn 0.572 O2, average particle size (D 50 ): 1.01㎛) was manufactured.

[0176] After mixing H3BO3 with the lithium-excess transition metal oxide so that boron (B) is 300 ppm relative to the lithium-excess transition metal oxide, heat treatment was performed at 350°C for 5 hours to form a coating layer (thickness: 1 to 10 nm) containing lithium, boron, carbon, and oxygen on the lithium-excess transition metal oxide, thereby manufacturing a cathode active material.

[0177]

[0178] Comparative Example 1

[0179] The lithium-rich transition metal oxide manufactured in Example 1 was used as the positive electrode active material of Comparative Example 1.

[0180]

[0181] Comparative Example 2

[0182] The lithium-rich transition metal oxide manufactured in Example 2 was used as the positive electrode active material in Comparative Example 2.

[0183]

[0184] Comparative Example 3

[0185] The lithium-rich transition metal oxide manufactured in Example 3 was used as the positive electrode active material in Comparative Example 3.

[0186]

[0187] Comparative Example 4

[0188] In the form of secondary particles, LiNi 0.88 Co 0.05 Mn 0.07 High-Ni lithium transition metal oxides with a layered structure having a composition represented by O2 (average particle diameter (D 50 ): 10㎛) was prepared.

[0189] After mixing H3BO3 with the lithium transition metal oxide so that boron (B) is 1000 ppm relative to the lithium transition metal oxide, heat treatment is performed at 350°C for 5 hours to form a coating layer (thickness: 2 to 10 nm) containing lithium, boron, carbon, and oxygen on the lithium-excess transition metal oxide, thereby manufacturing a cathode active material.

[0190]

[0191] Comparative Example 5

[0192] The lithium-rich transition metal oxide manufactured in Example 4 was used as the positive electrode active material in Comparative Example 5.

[0193]

[0194] Comparative Example 6

[0195] In Example 4, H3BO3 was mixed into the lithium-excess transition metal oxide so that boron (B) was 150 ppm relative to the lithium-excess transition metal oxide, and then heat-treated at 350°C for 5 hours to form a coating layer (thickness: 1 to 10 nm) containing lithium, boron, carbon, and oxygen on the lithium-excess transition metal oxide, thereby manufacturing a cathode active material.

[0196]

[0197] Experimental example

[0198] Experimental Example 1: EELS Analysis

[0199] After performing EELS analysis on the electrodes containing the positive electrode active materials manufactured in Examples 1 to 4, the EELS data for Example 1 are shown in Fig. 1.

[0200] Specifically, samples for cross-sectional images for STEM-EELS analysis were prepared using a TFS Helios 5 UX (acceleration voltages of 30, 5, and 2 kW, Pt coating), and HAADF images and EELS images were obtained at an acceleration voltage of 200 kV using a TFS Spectra 300 STEM. The obtained images were line-scanned to confirm the thickness of the coating layer and the presence of constituent elements.

[0201] Referring to Figure 1, it can be confirmed that the thickness of the coating layer in the analyzed portion is approximately 2 nm, and that boron and carbon are present in the coating layer.

[0202]

[0203] Experimental Example 2: XRD Analysis

[0204] After performing XRD analysis on the positive electrode active materials manufactured in Examples 1 to 4, the XRD spectrum is shown in Fig. 2.

[0205] Specifically, XRD analysis was performed using Bruker's D8 endeavor under the conditions of 40 kV, 40 mA, 2 theta: 15~80 degree at λ = 1.5418 Å (Cu target).

[0206] Referring to FIG. 2, it can be confirmed that all of the positive electrode active materials manufactured in Examples 1 to 4 have peaks corresponding to the A, B, and C regions shaded in FIG. 2, thereby simultaneously including the Li2MnO3 phase and the LiMO2 phase, and that a layered lithium-excess oxide is formed.

[0207]

[0208] Experimental Example 3: XPS Analysis

[0209] - Analysis of element content on the surface of positive electrode active material

[0210] After XPS analysis was performed on the positive electrode active materials manufactured in Examples 1 to 4 and Comparative Examples 4 and 6, the contents of O, C, Li, Mn, Ni, and B among the elements present on the surface were analyzed and shown in Table 1 below. In addition, the atomic ratio (B / Mn) of boron (B) and manganese (Mn) was calculated and shown in Table 1 below.

[0211] Specifically, Nexsa from Thermo Fisher Scientific Inc. was used, monochromatic Al Ka ​​(1486.6 eV) as the X-ray source, CAE (Constant Analyzer Energy) mode as the operation mode, and Avantage software (version 5.9925) was used. The sample was filled into the powder holder, fixed on a Cu foil with carbon tape, and loaded into the equipment. After loading the sample, when the vacuum of the load lock was sufficiently low, the experiment was conducted according to the K-Alpha standard operating method (SOP-0524-0k). After a survey scan on each sample surface (as-received state), a qualitative analysis was performed, and based on the qualitative analysis results, a narrow scan (snap) for each element was obtained at three points per sample, and quantitative analysis was performed.

[0212] Classification O(atomic%) C(atomic%) Li(atomic%) Mn(atomic%) Ni(atomic%) B(atomic%) B / Mn Example 145.612.119.95.84.810.71.84 Example 246.611.619.55.65.49.51.70 Example 347.310.118.73.43.2154.41 Example 449.4010.6120.587.019.532.870.41 Comparative Example 446.817.220.30.26.28.944.50 Comparative Example 648.3211.8721.587.009.471.750.25

[0213] Referring to Table 1, it can be confirmed that the positive electrode active materials of Examples 1 to 4 have a large amount of manganese on the surface compared to the NCM-based positive electrode active material of Comparative Example 4, and thus the B / Mn value is relatively much lower. In addition, it can be confirmed that the positive electrode active materials of Examples 1 to 4 have a B / Mn value of 0.3 to 5, while the positive electrode active material of Comparative Example 6 has a B / Mn value of less than 0.3.

[0214]

[0215] - Analysis of carbonate content on the surface of positive electrode active material

[0216] For the positive electrode active materials manufactured in Examples 1 to 3 and Comparative Example 1, XPS analysis was performed in the same manner as in the analysis of the element content on the surface of the positive electrode active material, and the XPS spectrum obtained is shown in Fig. 3. In addition, the peak (I) at 287.5 to 288.5 eV in the XPS spectrum of the surface Carbonate,1 ) and peak at 284–285 eV (I C-C ) intensity ratio (I Carbonate,1 :I C-C ) and peaks at 288.6–290.5 eV (I Carbonate,2 ) and peak at 284–285 eV (I C-C ) intensity ratio (I Carbonate,2 :I C-C ) was calculated and shown in Table 2 below.

[0217] Category I Carbonate,1 :IC-C I Carbonate,2 :I C-C Example 10.1180.115 Example 20.0990.091 Example 30.1060.089 Comparative Example 10.1770.205

[0218] Referring to FIG. 3 and Table 2, it can be seen that the carbonate content of the positive electrode active materials of Examples 1 to 3 was significantly reduced compared to the positive electrode active material of Comparative Example 1, as the intensity of the carbonate peak was significantly lower.

[0219]

[0220] Experimental Example 4: Analysis of Residual Lithium Content

[0221] The residual lithium content of the positive electrode active materials manufactured in Examples 1 to 4 and Comparative Examples 1 to 6 was analyzed using the following method, and the results are shown in Table 3 below. In addition, the residual lithium content was analyzed using the lithium transition metal oxide of Comparative Example 4 as the positive electrode active material using the same method as in Experimental Example 4, and is shown as Reference Example 1 in Table 3 below.

[0222] Specifically, when analyzing the residual lithium content, Metrohm's 888 Titrandeo, 814 USM Sample Processor, and tiamo 2.5 software were used. 2.5 g of the cathode active material was added to 100 ml of ultrapure water and stirred at 300 rpm for 5 minutes. After stirring, the solution was filtered under reduced pressure using a PES04547A filter, and the filtered liquid was analyzed for residual lithium content using 0.1 N HCl.

[0223] Classification Residual Lithium (wt%) Li2CO3LiOHTotal Example 10.1410.3050.446 Example 20.1780.3020.480 Example 30.1280.1410.268 Example 40.1480.0980.246 Comparative Example 10.3790.1150.494 Comparative Example 20.3810.1100.491 Comparative Example 30.2430.1270.370 Comparative Example 40.1450.2770.422 Reference Example 10.1650.1630.328 Comparative Example 50.2260.0510.276 Comparative Example 60.1740.0830.257

[0224] Referring to Table 3 above, it can be confirmed that the total amount of residual lithium decreased in the case of the positive electrode active material of Example 1 compared to the positive electrode active material of Comparative Example 1, in the case of the positive electrode active material of Example 2 compared to the positive electrode active material of Comparative Example 2, in the case of the positive electrode active material of Example 3 compared to the positive electrode active material of Comparative Example 3, and in the case of the positive electrode active material of Example 4 compared to the positive electrode active materials of Comparative Examples 5 and 6, and in particular, it can be confirmed that the content of Li2CO3 among the residual lithium decreased significantly. In addition, it can be confirmed that the rate of decrease in the content of Li2CO3 was significantly higher in the case of the positive electrode active materials of Examples 1 to 4 compared to the NCM-based positive electrode active material including a coating layer including boron.

[0225]

[0226] Experimental Example 5: Battery Characteristics Evaluation

[0227] A positive electrode slurry was prepared by mixing 92.5 wt% of the positive electrode active materials manufactured in Examples 1 to 4 and Comparative Examples 1 to 6, 3 wt% of Super P as a conductive agent, and 4.5 wt% of polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone (NMP) solvent. The prepared positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to prepare a positive electrode.

[0228] An electrode assembly was manufactured using a lithium metal electrode as the negative electrode and a porous polyethylene separator interposed between the positive and negative electrodes. This was placed inside a battery case and an electrolyte solution (additives: LiBF 42%, FEC 5%) containing 1 M LiPF6 dissolved in an organic solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7 was injected to manufacture a coin-type half-cell.

[0229]

[0230] Using the coin-type half-cells including the positive electrode active materials of Examples 1 to 4 and Comparative Examples 1 to 3, 5 and 6 manufactured above, the cells were charged to 4.65 V at a constant current of 0.1 C at 45°C, and then discharged to 2.0 V at a constant current of 0.1 C to perform an activation process (formation). The charge and discharge capacities at this time are shown in Table 4 below, and the percentage of the discharge capacity to the charge capacity at this time is shown in Table 4 below as the efficiency of the activation process.

[0231]

[0232] The battery that went through the activation process was charged to 4.4 V at a constant current of 0.1 C at 25°C, and then discharged to 2.5 V at a constant current of 0.1 C to check the initial charge-discharge performance. Then, the charge-discharge process was performed by changing this process from 0.1 C to 0.33 C, and this cycle was considered 1 cycle. The discharge capacity was measured while repeating the charge and discharge for a total of 30 cycles. The discharge capacity at 1 cycle is shown in Table 4 below, and the percentage of the discharge capacity at 30 cycles to the discharge capacity at 1 cycle is shown in Table 4 below as the capacity retention rate.

[0233]

[0234] The battery that went through the activation process was charged to 4.4 V at 0.1 C constant current at 25°C, discharged to 2.5 V at 0.1 C constant current, and the initial voltage and the voltage after 60 seconds were measured, and the direct current internal resistance (DCIR) was calculated, which is shown in Table 4 below. For reference, the DCIR value is a value calculated by dividing the difference between the voltage after 60 seconds and the initial voltage while discharging at 0.1 C constant current by the applied current.

[0235]

[0236] Meanwhile, for the coin-type half-cells containing the positive electrode active material of Comparative Example 4 manufactured above, the battery evaluation conditions were carried out differently because the type of positive electrode material was different. Specifically, the battery that did not undergo the activation process was charged to 4.25 V at a constant current of 0.1 C at 25°C, and discharged to 2.5 V at a constant current of 0.1 C, while measuring the initial voltage and the voltage at 60 seconds, and calculating the direct current internal resistance (DCIR), which is shown in Table 4 below.

[0237] For reference, a battery was manufactured using the lithium transition metal oxide of Comparative Example 4 as a positive electrode active material using the same method as in Experimental Example 5, and the DCIR value obtained using the same method as the battery evaluation method of Comparative Example 4 was 18.6Ω.

[0238] Discharge capacity (mAh / g) Capacity retention rate (%) in the 1st cycle of the activation process DCIR (Ω) Charge capacity (mAh / g) Discharge capacity (mAh / g) Efficiency (%) Example 1 309.20 266.03 86.04 180.49 7.73 28.6 Example 2 299.42 70.09 0.19 187.196.122 3.8 Example 3 305.9 265.28 6.70 176.2-30.3 Example 4 316.128 5.49 0.30 197.30-30.77 Comparative example 1317.41 267.39 84.24 179.197.15 43.7 Comparative example 2301.4268.389.01183.196.3029.5Comparative Example 3304.8262.486.09175.397.3832.2Comparative Example 4-----27.01Comparative Example 5315.9284.390.0196.03-37.82Comparative Example 6314.8283.690.1194.24-31.84

[0239] Referring to Table 4 above, it can be confirmed that the battery including the positive electrode active material of Example 1 has superior efficiency during the activation process, superior discharge capacity (0.33C discharge capacity) in 1 cycle, and significantly lower DC internal resistance compared to the battery including the positive electrode active material of Comparative Example 1. In addition, it can be confirmed that the battery including the positive electrode active material of Example 2 has superior efficiency during the activation process, superior discharge capacity (0.33C discharge capacity) in 1 cycle, and significantly lower DC internal resistance compared to the battery including the positive electrode active material of Comparative Example 2. In addition, it can be confirmed that the battery including the positive electrode active material of Example 3 has superior efficiency during the activation process, superior discharge capacity (0.33C discharge capacity) in 1 cycle, and significantly lower DC internal resistance compared to the battery including the positive electrode active material of Comparative Example 3. In addition, it can be confirmed that the battery including the positive electrode active material of Example 4 has superior efficiency during the activation process, superior discharge capacity (0.33C discharge capacity) in 1 cycle, and significantly lower DC internal resistance compared to the battery including the positive electrode active material of Comparative Example 5.

[0240] From this, it can be confirmed that the positive electrode active material according to the present invention has lower resistance than lithium-rich transition metal oxides without a coating layer. In addition, it can be confirmed that when the atomic ratio (B / Mn) of boron (B) and manganese (Mn) present on the surface analyzed by XPS satisfies 0.3 to 5, the overall performance of the battery is improved.

[0241]

[0242] Meanwhile, in the case of a battery including the cathode active material of Comparative Example 4 including a coating layer formed on a high-Ni lithium transition metal oxide, it can be confirmed that the DC internal resistance is higher compared to a battery including a high-Ni lithium transition metal oxide.

[0243] This appears to be because the coating layer included in the positive electrode active material of the present invention includes a material with low resistance, whereas the coating layer included in the positive electrode active material of Comparative Example 4 includes a material with high resistance.

[0244]

[0245] As a result, it can be seen that the cathode active material of the present invention includes a coating layer including boron and carbon formed on a lithium-rich transition metal oxide having a layered structure including both a Li2MnO3 phase and a LiMO2 phase, and satisfies at least one of the following conditions (1) to (3), thereby improving the performance of a lithium secondary battery including the same.

[0246] - Condition (1): The atomic ratio (B / Mn) of boron (B) and manganese (Mn) present on the surface analyzed by XPS is 0.3 to 5.

[0247] - Condition (2): Peak at 287.5~288.5 eV in the XPS spectrum of the surface (I Carbonate,1 ) and peak at 284–285 eV (I C-C ) intensity ratio (I Carbonate,1 :I C-C ) is 0.05~0.15:1

[0248] - Condition (3): Peak at 288.6~290.5 eV in the XPS spectrum of the surface (I Carbonate,2 ) and peak at 284–285 eV (I C-C ) intensity ratio (I Carbonate,2 :I C-C ) is 0.05~0.15:1

Claims

1. A lithium-rich transition metal oxide having a layered structure that simultaneously includes a Li2MnO3 phase and a LiMO2 (wherein M is an element including at least one selected from Ni, Co, and Mn) phase; and A coating layer including boron and carbon formed on the lithium-excess transition metal oxide; A positive electrode active material satisfying at least one of the following conditions (1) to (3): - Condition (1): The atomic ratio (B / Mn) of boron (B) and manganese (Mn) present on the surface analyzed by XPS is 0.3 to 5. - Condition (2): Peak at 287.5~288.5 eV in the XPS spectrum of the surface (I Carbonate,1 ) and peak at 284–285 eV (I C-C ) intensity ratio (I Carbonate,1 :I C-C ) is 0.05~0.15:1 - Condition (3): Peak at 288.6~290.5 eV in the XPS spectrum of the surface (I Carbonate,2 ) and peak at 284–285 eV (I C-C ) intensity ratio (I Carbonate,2 :I C-C ) is 0.05~0.15:

1.

2. In claim 1, The above lithium-rich transition metal oxide is a cathode active material in the form of single particles.

3. In claim 1, The above lithium-rich transition metal oxide has an average particle diameter (D 50 ) A positive electrode active material having a diameter of 0.75㎛ to 10㎛.

4. In claim 1, The above lithium-rich transition metal oxide is a cathode active material having a Mn content of 50 mol% or more among all metals excluding lithium.

5. In claim 1, The above lithium-excess transition metal oxide is a positive electrode active material having a composition represented by the following chemical formula 1: [Chemical Formula 1] Li (Li a Ni b Co c Mr d Along with e )O2 In the above chemical formula 1, Me is one or more selected from W, Mo, Zn, Mg, Nb, and Al, 0.01≤a≤0.20, 0≤b≤0.50, 0≤c≤0.10, 0.50≤d≤1.0, 0≤e≤0.10, a+b+c+d+e=1.

6. In claim 1, The above lithium-rich transition metal oxide is a cathode active material doped with W, Mo or a combination thereof.

7. In claim 1, The above coating layer is a positive electrode active material comprising a compound in which lithium, boron, and oxygen are chemically bonded to each other and a compound containing carbon.

8. In claim 1, A positive electrode active material having a coating layer having a thickness of 1 nm to 80 nm. 9.(A) A step of dry mixing a lithium-containing raw material and a transition metal-containing raw material, and then calcining to produce a lithium-excess transition metal oxide; and (B) A method for producing a positive electrode active material according to claim 1, comprising the step of dry mixing the lithium-rich transition metal oxide and the boron-containing raw material, and then heat-treating the dry mixing to form a coating layer on the lithium-rich transition metal oxide.

10. In claim 9, A method for producing a positive electrode active material, wherein the above-mentioned calcination is performed at a temperature of 850°C to 1,050°C.

11. In claim 9, A method for producing a positive electrode active material, wherein the boron-containing raw material is mixed in an amount such that boron (B) contained in the boron-containing raw material is 300 ppm to 1,500 ppm relative to the total weight of the lithium-excess transition metal oxide.

12. In claim 9, A method for producing a positive electrode active material, wherein the above heat treatment is performed at a temperature of 300°C to 450°C.

13. In claim 9, A method for producing a cathode active material, wherein when dry mixing the above lithium-containing raw material and the transition metal-containing raw material, a doping element-containing raw material is further mixed.

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.

Images