Positive electrode active material for lithium secondary battery and lithium secondary battery including positive electrode active material

Abstract

Disclosed are a positive electrode active material for a lithium secondary battery and a lithium secondary battery including the same. The positive electrode active material includes: i) first secondary particles having a size in a range of 13 [mu] m to 20 [mu] m and including an aggregate of primary particles having a size in a range of 1 [mu] m or less; ii) second secondary particles having a size in the range of 7 [mu] m to 13 [mu] m and comprising aggregates of primary particles having a size in the range of 1 [mu] m or less; and iii) unitary particles having a size in the range of 1 [mu] m to 7 [mu] m and comprising primary particles, in which the nickel content of each of the particles satisfies relational expression 1: the nickel content gt of the unitary particles in relational expression 1; the nickel content gt of the first secondary particles; the nickel content of the second secondary particles.

Description

[0001] Cross - reference to related applications

[0002] This application claims the priority and benefit of Korean Patent Application No. 10 - 2023 - 0172412, filed with the Korean Intellectual Property Office on December 1, 2023, the entire content of which is incorporated herein by reference. Technical field

[0003] One or more aspects of embodiments of the present disclosure relate to a positive electrode active material for a lithium secondary battery and a lithium secondary battery including the positive electrode active material. Background art

[0004] In recent years, in response to the rapid increase in the use of battery - powered electronic devices such as mobile phones, laptop computers, and / or electric vehicles, the demand for high - energy - density and high - capacity lithium secondary batteries has increased significantly. Therefore, research and development aimed at improving the performance of lithium secondary batteries have been steadily carried out.

[0005] A lithium secondary battery includes a positive electrode and a negative electrode, both the positive electrode and the negative electrode containing an active material that allows lithium ions to be intercalated and de - intercalated; and an electrolyte. The lithium battery generates electricity through oxidation and reduction reactions when lithium ions are intercalated / de - intercalated in the positive electrode and the negative electrode.

[0006] As the positive electrode active material, nickel - based active materials having a suitably high nickel content and good or appropriate capacity characteristics can be used. Summary of the invention

[0007] One or more aspects of embodiments of the present disclosure provide a positive electrode active material for a lithium secondary battery, which has good or appropriate characteristics in terms of capacity and lifespan at relatively high temperatures, reduces the resistance in an electrochemical reaction, allows a uniform (or substantially uniform) electrochemical reaction, and suppresses or reduces outgassing.

[0008] One or more aspects of embodiments of the present disclosure provide a lithium secondary battery including a positive electrode active material for a lithium secondary battery (hereinafter, may be simply referred to as "positive electrode active material").

[0009] According to one or more aspects of embodiments of the present disclosure,

[0010] The active material of the positive electrode (e.g., for a lithium secondary battery) includes: i) first secondary particles having a size in the range of 13 μm to 20 μm and including an aggregate of primary particles having a size in the range of 1 μm or less; ii) second secondary particles having a size in the range of 7 μm to 13 μm and including an aggregate of primary particles having a size in the range of 1 μm or less; and iii) integral particles having a size in the range of 1 μm to 7 μm and including primary particles, wherein the nickel content of each of the first secondary particles, the second secondary particles, and the integral particles satisfies Relationship 1:

[0011] Relationship 1

[0012] Nickel content of integral particles > Nickel content of first secondary particles > Nickel content of second secondary particles.

[0013] In some embodiments, the positive electrode active material may satisfy Relationship 2:

[0014] Relationship 2

[0015] Size of first secondary particles > Size of second secondary particles > Size of integral particles.

[0016] In some embodiments, based on the total content of 100 mol% of metals other than lithium in the positive electrode active material, the positive electrode active material may have a nickel content of 94 mol% or more.

[0017] In some embodiments, relative to 100 parts by weight of the first secondary particles, the integral particles may be present in an amount of 5 to 25 parts by weight.

[0018] In some embodiments, based on the total weight of 100 wt% of the positive electrode active material, the first secondary particles, the second secondary particles, and the integral particles may be present in a total amount of 95 wt% or more.

[0019] In some embodiments, based on the total content of 100 mol% of metals other than lithium in the first secondary particles, the first secondary particles may have a nickel content of 85 mol% to 97 mol%, based on the total content of 100 mol% of metals other than lithium in the second secondary particles, the second secondary particles may have a nickel content of 80 mol% to 90 mol%, and based on the total content of 100 mol% of metals other than lithium in the integral particles, the integral particles may have a nickel content of 90 mol% to 99 mol%.

[0020] In some embodiments, relative to 100 parts by weight of the positive electrode active material, the first secondary particles may be present in an amount of 60 to 80 parts by weight, the second secondary particles may be present in an amount of 5 to 35 parts by weight, and the integral particles may be present in an amount of 5 to 25 parts by weight.

[0021] In some embodiments, the molar ratio of the nickel content of the first secondary particles to the nickel content of the second secondary particles may be in the range of 1.01 to 1.06.

[0022] In some embodiments, the molar ratio of the nickel content of the first secondary particles to the nickel content of the integral particles may be in the range of 0.94 to 0.99.

[0023] In some embodiments, the positive electrode active material includes a compound represented by Formula 1 or a compound represented by Formula 2:

[0024] Formula 1

[0025] Li x Ni 1-y Co y O 2-z X z ,

[0026] wherein, in Formula 1, x, y, and z satisfy the relationship: 0.9 ≤ x ≤ 1.2, 0 < y ≤ 0.2, 0 ≤ z ≤ 0.5, and 0.8 ≤ 1 - y < 1, and X represents F, S, P, or a combination thereof.

[0027] Formula 2

[0028] Li x Ni 1-y-z Co y M z O 2-a X a , and

[0029] wherein, in Formula 2, x, y, z, and a satisfy the relationship: 0.9 ≤ x ≤ 1.2, 0 < y < 0.5, 0.8 ≤ 1 - y - z < 1, 0 ≤ z ≤ 0.5, 0 < y + z ≤ 0.2, and 0 ≤ a < 2;

[0030] M represents Mn, Mg, Ca, Sr, Ba, Ti, Zr, Nb, Mo, W, Zn, Al, Si, Cr, Fe, V, rare earth elements, or a combination thereof; and

[0031] X represents F, S, P, or a combination thereof.

[0032] In some embodiments, the positive electrode active material includes a compound represented by Formula 3 or a compound represented by Formula 4:

[0033] Formula 3

[0034] Li x Co a Ni b Mn c O 2 ,

[0035] Wherein, in Formula 3, x, a, b, and c satisfy the relational expressions: 0.9 < x ≤ 1.2, 0 < a < 0.5, 0.8 ≤ b < 1, 0 < c < 0.5, and a + b + c = 1,

[0036] Formula 4

[0037] Li x Co a Ni b Al c O 2 ,and

[0038] Wherein, in Formula 4, x, a, b, and c satisfy the relational expressions: 0.9 < x ≤ 1.2, 0 < a < 0.5, 0.8 ≤ b < 1, 0 < c < 0.5, and a + b + c = 1.

[0039] In some embodiments, at least one of the first secondary particles, the second secondary particles, and the integral particles may include a cobalt coating on its surface.

[0040] According to one or more embodiments of the present disclosure, a lithium secondary battery includes: a positive electrode including a positive electrode active material as described herein; a negative electrode; and an electrolyte.

[0041] Embodiments of the present disclosure provide a positive electrode active material for a lithium secondary battery, which has good or appropriate characteristics in terms of capacity and life at relatively high temperatures, reduces the resistance in an electrochemical reaction, allows a uniform (or substantially uniform) electrochemical reaction, and suppresses or reduces outgassing. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figures 1 to 4 Each is a schematic illustration of a lithium secondary battery according to one or more embodiments of the present disclosure.

[0043] Figure 5 Is a scanning electron micrograph (SEM) image of the positive electrode active material prepared in Example 1.

[0044] Figure 6 Is a graph depicting the high-temperature life characteristics of the lithium secondary batteries of the examples and comparative examples.

[0045] REFERENCE SIGNS

[0046] 100: Lithium secondary battery 10: Positive electrode

[0047] 11: Positive electrode lead terminal piece 12: Positive electrode terminal

[0048] 20: Negative electrode 21: Negative electrode lead terminal piece

[0049] 22: Negative electrode terminal 30: Diaphragm

[0050] 40: Electrode assembly 50: Housing

[0051] 60: Sealing member 70: Electrode terminal piece

[0052] 71: Positive electrode terminal piece 72: Negative electrode terminal piece Detailed implementation manners

[0053] Hereinafter, exemplary implementation manners of the present disclosure will be described in more detail with reference to the accompanying drawings. However, it should be understood that the following implementation manners are provided in an illustrative manner, and the present disclosure is not limited thereto and is only defined by the claims and their equivalents.

[0054] When an element is referred to as being “on” (or “under”) or “above” (or “below”) a component (i.e., the first component), it may refer to a case where the element is placed in contact with the upper (or lower) surface of the first component, and may also refer to a case where another (e.g., additional) component may be inserted between the first component and the element that is arranged (or located or placed) on (or below) the first component.

[0055] Throughout the specification, unless otherwise indicated, each element may be singular or plural. Additionally, the term “and / or” includes any and all combinations of one or more of the related listed items. For example, throughout the specification, unless otherwise indicated, if (e.g., when) it is stated “A and / or B”, it refers to “only A”, “only B”, or “A and B”.

[0056] As used herein, expressions such as “at least one of...”, “one of...”, and “selected from...”, when before / after a list of elements, modify the entire list of elements and not a single element of the list. For example, “at least one selected from a, b, and c” may indicate only a, only b, only c, both a and b (e.g., simultaneously), both a and c (e.g., simultaneously), both b and c (e.g., simultaneously), all of a, b, and c, or variants thereof. Further, when describing the implementation manners of the present disclosure, the use of “may” refers to “one or more implementation manners of the present disclosure”.

[0057] As used herein, “a combination thereof” may refer to a mixture, stack, composite, copolymer, alloy, blend, and / or reaction product of components.

[0058] Unless otherwise defined herein, "particle size" may refer to the average particle size. In one or more embodiments, the particle size refers to the average particle size (D 50 ), which refers to the particle size corresponding to 50 volume % of the cumulative volume in the corresponding particle size distribution. The average particle size can be measured by any suitable method, for example, by a particle size analyzer, by a transmission electron microscope (TEM) image (e.g., a photograph), and / or by a scanning electron microscope (SEM) image (e.g., a photograph). In one or more embodiments, the average particle size (D 50 ) can be measured by the following: counting the number of particles in each particle size range using an apparatus employing a dynamic light scattering method to analyze the data, and then calculating the average particle size (D 50 ) based on the analyzed data. In one or more embodiments, the average particle size (D 50 ) can be measured by laser diffraction. More specifically, in the measurement by laser diffraction, the target particles are dispersed in a dispersant, introduced into a commercially available laser diffraction particle analyzer (e.g., Micro-Trac MT 3000 TM ), and irradiated with ultrasonic waves of about 28 kHz at a power of 60 W, and then the average particle size (D 50 ) corresponding to 50 volume % of the cumulative volume in the particle size distribution in the measurement device is calculated. In this specification, when the particle is spherical, "diameter" indicates the particle size, and when the particle is non-spherical, "diameter" indicates the major axis length.

[0059] In this document, the "nickel content" of the positive electrode active material may refer to the molar ratio of the content (e.g., amount) of nickel to the total content (e.g., amount) of all metals other than lithium in the positive electrode active material.

[0060] As used herein to represent a specific numerical range, "X to Y" refers to a value greater than or equal to X and less than or equal to Y (X ≤ and ≤ Y).

[0061] It will be further understood that when used in this specification, the terms "includes", "including", "comprises", and / or "comprising" indicate the presence of the recited features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0062] As used herein, the terms "use", "using", and "used" may be regarded as synonymous with the terms "utilize", "utilizing", and "utilized", respectively.

[0063] For ease of description, spatial relative terms such as "below", "beneath", "under", "above", "on", "bottom", "top", etc. may be used herein to describe the relationship of one element or feature illustrated in the drawings to another element or feature. It will be understood that the spatial relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the drawings. For example, if the device in the drawings is flipped, an element described as "below" or "beneath" another element or feature will then be oriented "above" or "on" the other element or feature. Thus, the term "below" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations), and the spatial relative descriptors used herein should be interpreted accordingly.

[0064] As used herein, the terms "substantially", "about", and similar terms are used as approximate terms and not as terms of degree, and are intended to account for the inherent deviations of measured or calculated values that would be recognized by one of ordinary skill in the art. As used herein, "about" and "approximate" include the recited value and mean within an acceptable deviation range of the particular value as determined by one of ordinary skill in the art in view of the measurements discussed and the errors associated with the measurement of a particular quantity (e.g., the limitations of the measurement system). For example, "about" and "approximate" may refer to within one or more standard deviations, or within ±30%, ±20%, ±10%, or ±5% of the recited value.

[0065] Any numerical range recited herein is intended to include all sub-ranges of the same numerical precision subsumed within the recited range. For example, the range "1.0 to 10.0" is intended to include all sub-ranges between the recited minimum value of 1.0 and the recited maximum value of 10.0 (and including 1.0 and 10.0), that is, all sub-ranges having a minimum value equal to or greater than 1.0 and a maximum value equal to or less than 10.0 (such as, for example, 2.4 to 7.6). Any maximum numerical limit recited herein is intended to include all lower numerical limits falling therein, and any minimum numerical limit recited in this specification is intended to include all higher numerical limits falling therein. Accordingly, the applicant reserves the right to modify this specification (including the claims) to expressly recite any sub-ranges subsumed within the ranges expressly recited herein.

[0066] Positive electrode active material for a lithium secondary battery

[0067] The positive electrode active material for a lithium secondary battery according to one or more embodiments includes: i) a first secondary particle having a size in the range of 13 μm to 20 μm (e.g., an average particle diameter D 50 ) and including an aggregate of primary particles each having a size in the range of 1 μm or less (e.g., an average particle diameter D 50 ); ii) a second secondary particle having a size in the range of 7 μm to 13 μm (e.g., an average particle diameter D 50 ) and including an aggregate of primary particles each having a size in the range of 1 μm or less (e.g., an average particle diameter D 50 ); and iii) a single particle having a size in the range of 1 μm to 7 μm (e.g., an average particle diameter D 50 ) and including primary particles.

[0068] In this document, if (e.g., when) the positive electrode active material particles are spherical, the term "size" refers to the average diameter of the positive electrode active material particles for a lithium secondary battery. When the positive electrode active material particles are non-spherical, the term "size" refers to the average value of the major axis lengths obtained from the cross-sections of the particles.

[0069] The average particle diameter can be measured by, for example, a particle size distribution (PSD) instrument and / or by SEM. Unless otherwise defined, the average particle diameter (D 50 ) refers to the particle diameter corresponding to a cumulative volume of 50% by volume in the particle size distribution. The major axis length can be measured by, for example, SEM or the like.

[0070] In this document, a "single particle" refers to a structure in which the particles form a morphologically distinct phase without mutual aggregation. Compared with single particles, there is such a particle structure in which small particles (primary particles) physically aggregate and / or chemically aggregate to form relatively large particles (secondary particles). A "single particle" has a structure in which many crystalline particles are dispersed and / or separated from each other such that each crystalline particle forms an independent and / or distinct phase rather than an aggregated phase, and may also include a structure in which 10 or fewer particles are attached to each other (but not aggregated). For example, single particles may exist alone or as an aggregate of multiple single particles. For example, single particles may be an aggregate of 2 to 10 single particles in contact with each other (but not aggregated).

[0071] The positive electrode active material for a lithium secondary battery according to an embodiment may satisfy the relational expression between the nickel contents (e.g., amounts) of the first secondary particles, the second secondary particles, and the single particles, which is represented by Relational Expression 1.

[0072] Relational Expression 1

[0073] The nickel content of the integral particle > the nickel content of the first secondary particle > the nickel content of the second secondary particle

[0074] The first secondary particle may have a relatively fast lithium diffusion rate, but may also experience an undesirably fast degradation rate, thus causing an undesired reduction in the life of the lithium secondary battery. The second secondary particle according to the present embodiment can help alleviate the problems of the first secondary particle. The second secondary particle has a lower nickel content than the nickel content of the first secondary particle, and thus can solve or help alleviate the degradation problem. The integral particle has a higher nickel content than the nickel content of the first secondary particle and the nickel content of the second secondary particle. The integral particle can increase the lithium diffusion rate, which would otherwise be reduced due to the presence of the secondary particles.

[0075] According to one or more embodiments, based on the total content (e.g., amount) of metals other than lithium in 100 mol% of the positive electrode active material for a lithium secondary battery, the positive electrode active material for a lithium secondary battery has a nickel content of 94 mol% or more.

[0076] The positive electrode active material for a lithium secondary battery including the first secondary particle, the second secondary particle, and the integral particle can satisfy the nickel content relationship among the first secondary particle, the second secondary particle, and the integral particle represented by Equation 1, and based on the total content of metals other than lithium in 100 mol% of the positive electrode active material for a lithium secondary battery, can have a nickel content of 94 mol% or more, and thus can have a remarkable effect (e.g., desired result) of improving the capacity characteristics and the life at a relatively high temperature, while suppressing or reducing outgassing.

[0077] For example, based on the total content of metals other than lithium in 100 mol% of the positive electrode active material for a lithium secondary battery, the positive electrode active material for a lithium secondary battery can have a nickel content of 94 mol% - 99 mol%, 95 mol% - 98 mol%, or 95 mol% - 98 mol%.

[0078] According to one or more embodiments, in a positive electrode active material for a lithium secondary battery, if (e.g., when) the amount of integral particles is 5 parts by weight to 25 parts by weight relative to 100 parts by weight of primary secondary particles, the secondary secondary particles can significantly or suitably improve the capacity and life characteristics. For example, relative to 100 parts by weight of the primary secondary particles, the integral particles may be present in an amount of 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 10 parts by weight to 25 parts by weight, 10 parts by weight to 20 parts by weight, or 15 parts by weight to 20 parts by weight.

[0079] The primary secondary particles refer to secondary particles having a size of 13 μm to 20 μm and are formed by physical aggregation and / or chemical aggregation of primary particles having a size of 1 μm or less. If the size of the primary secondary particles is less than 13 μm, there may be a problem of deterioration of the energy density, and if the size of the primary secondary particles exceeds 20 μm, there may be a problem of deterioration of the battery life due to collision and / or breakage between the primary secondary particles during the electrode plate winding process. For example, the primary secondary particles may have a size of 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 14 μm to 20 μm, 15 μm to 20 μm, or 16 μm to 20 μm.

[0080] In the primary secondary particles, the primary particles may have an average particle diameter of 0.01 μm to 1 μm, 0.02 μm to 0.8 μm, 0.03 μm to 0.5 μm, 0.04 μm to 0.1 μm, or 0.05 μm to 0.07 μm (50 nm to 70 nm). According to one or more embodiments, the primary secondary particles may have a polycrystalline structure. As used herein, "polycrystalline" refers to an aggregated structure of multiple crystalline particles.

[0081] The integral particles may have a size of 1 μm to 7 μm (e.g., 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, or 7 μm) and may include primary particles. The primary particles may have an average particle diameter of 0.01 μm to 1 μm, 0.02 μm to 0.8 μm, 0.03 μm to 0.5 μm, 0.04 μm to 0.1 μm, or 0.05 μm to 0.07 μm (50 nm to 70 nm).

[0082] The second secondary particle refers to a secondary particle having a size of 7 μm to 13 μm and formed by physical aggregation and / or chemical aggregation of primary particles having a size of 1 μm or less. The second secondary particle has a smaller size than the first secondary particle. If the size of the second secondary particle is less than 7 μm, or if the size of the second secondary particle exceeds 13 μm, the positive electrode may have poor or inappropriate composite density. For example, the size of the second secondary particle may be 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, a size of 7 μm to 12 μm, or a size of 8 μm to 12 μm.

[0083] In the second secondary particle, the primary particle may have an average particle diameter of 0.01 μm to 1 μm, 0.02 μm to 0.8 μm, 0.03 μm to 0.5 μm, 0.04 μm to 0.1 μm, or 0.05 μm to 0.07 μm (50 nm to 70 nm). According to one or more embodiments, the second secondary particle may have a polycrystalline structure.

[0084] According to one or more embodiments, the positive electrode active material for a lithium secondary battery may satisfy relation 2.

[0085] Relation 2

[0086] Size of the first secondary particle > Size of the second secondary particle > Size of the integral particle

[0087] According to one or more embodiments, based on the total content of 100 mol% of metals other than lithium in the first secondary particle, the first secondary particle may have a nickel content (e.g., amount) of 85 mol% to 97 mol%. Within this range, the positive electrode active material may easily or appropriately satisfy relation 1. For example, based on the total content of 100 mol% of metals other than lithium in the first secondary particle, the first secondary particle may have a nickel content of 85 mol%, 86 mol%, 87 mol%, 88 mol%, 89 mol%, 90 mol%, 91 mol%, 92 mol%, 93 mol%, 94 mol%, 95 mol%, 96 mol%, 97 mol%, 90 mol% to 97 mol%, 94 mol% to 97 mol%, or 94 mol% to 97 mol%.

[0088] According to one or more embodiments, based on the total content of 100 mol% of metals other than lithium in the second secondary particles, the second secondary particles may have a nickel content of 80 mol% to 90 mol% (e.g., amount). Within this range, the positive electrode active material can easily or suitably satisfy Equation 1. For example, based on the total content of 100 mol% of metals other than lithium in the second secondary particles, the second secondary particles may have a nickel content of 80 mol%, 81 mol%, 82 mol%, 83 mol%, 84 mol%, 85 mol%, 86 mol%, 87 mol%, 88 mol%, 89 mol%, 90 mol%, 85 mol% to 90 mol%, 85 mol% to 89 mol% or 85 mol% to 89 mol%.

[0089] According to one or more embodiments, based on the total content of 100 mol% of metals other than lithium in the integral particles, the integral particles may have a nickel content of 90 mol% to 99 mol% (e.g., amount). Within this range, the positive electrode active material can easily or suitably satisfy Equation 1. For example, based on the total content of 100 mol% of metals other than lithium in the integral particles, the integral particles may have a nickel content of 90 mol%, 91 mol%, 92 mol%, 93 mol%, 94 mol%, 95 mol%, 96 mol%, 97 mol%, 98 mol%, 99 mol%, 95 mol% to 99 mol%, 95 mol% to 97 mol% or 95 mol% to 97 mol%.

[0090] According to one or more embodiments, the molar ratio of the nickel content of the first secondary particles to the nickel content of the second secondary particles may be in the range of 1.01 to 1.06, and may be, for example, 1.01, 1.02, 1.03, 1.04, 1.05 or 1.06. Within this range, the positive electrode active material can contribute to improving the capacity and lifespan of the battery.

[0091] According to one or more embodiments, the molar ratio of the nickel content of the first secondary particles to the nickel content of the integral particles may be in the range of 0.94 to 0.99, and may be, for example, 0.94, 0.95, 0.96, 0.97, 0.98 or 0.99. Within this range, the positive electrode active material can contribute to improving the capacity and lifespan of the battery.

[0092] The average particle size of the primary particles constituting each of the first secondary particles, the second secondary particles, and the integral particles can be determined by SEM. For example, the average particle size of the primary particles can be obtained by averaging the particle sizes of 10 to 30 primary particles.

[0093] The positive electrode including a positive electrode active material (including primary secondary particles, secondary secondary particles, and integral particles) for a lithium secondary battery can provide such a lithium secondary battery that stabilizes or improves the electro-chemical reactivity, reduces the outgassing at high voltages, and ensures improved reliability, safety, and appropriate high-power and long-life characteristics.

[0094] The positive electrode active material for a lithium secondary battery according to an embodiment may have an average particle diameter of, for example, 10 μm to 20 μm (for example, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, or 20 μm).

[0095] According to one or more embodiments, with respect to a total of 100 parts by weight of the positive electrode active material for a lithium secondary battery, the content (for example, amount) of the primary secondary particles may be higher than the content (for example, amount) of each of the secondary secondary particles and the integral particles. If (for example, when) the positive electrode active material for a lithium secondary battery includes primary secondary particles having a content (for example, amount) higher than the content (for example, amount) of each of the secondary secondary particles and the integral particles, the positive electrode active material for a lithium secondary battery can further improve the capacity.

[0096] According to one or more embodiments, with respect to 100 parts by weight of the positive electrode active material (for example, the total of 100 parts by weight of the primary secondary particles, secondary secondary particles, and integral particles), the positive electrode active material for a lithium secondary battery may include, for example, 60 parts by weight to 80 parts by weight of the primary secondary particles. Within this range, the positive electrode active material can achieve an improvement in capacity and life characteristics. For example, with respect to 100 parts by weight of the positive electrode active material (for example, the total of 100 parts by weight of the primary secondary particles, secondary secondary particles, and integral particles), the primary secondary particles may be present in an amount of 60 parts by weight, 61 parts by weight, 62 parts by weight, 63 parts by weight, 64 parts by weight, 65 parts by weight, 66 parts by weight, 67 parts by weight, 68 parts by weight, 69 parts by weight, 70 parts by weight, 71 parts by weight, 72 parts by weight, 73 parts by weight, 74 parts by weight, 75 parts by weight, 76 parts by weight, 77 parts by weight, 78 parts by weight, 79 parts by weight, 80 parts by weight, 70 parts by weight to 80 parts by weight, or 75 parts by weight to 80 parts by weight.

[0097] According to one or more embodiments, with respect to 100 parts by weight of the positive electrode active material (e.g., the total of the first secondary particles, the second secondary particles, and the integral particles is 100 parts by weight), the positive electrode active material for a lithium secondary battery may include, for example, 5 to 35 parts by weight of the second secondary particles. Within this range, the positive electrode active material can achieve improvements in capacity and life characteristics. For example, with respect to 100 parts by weight of the positive electrode active material (e.g., the total of the first secondary particles, the second secondary particles, and the integral particles is 100 parts by weight), the second secondary particles may be present in an amount of 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 26 parts by weight, 27 parts by weight, 28 parts by weight, 29 parts by weight, 30 parts by weight, 31 parts by weight, 32 parts by weight, 33 parts by weight, 34 parts by weight, 35 parts by weight, 5 to 30 parts by weight, 5 to 20 parts by weight, or 5 to 15 parts by weight.

[0098] According to one or more embodiments, with respect to 100 parts by weight of the positive electrode active material (e.g., the total of the first secondary particles, the second secondary particles, and the integral particles is 100 parts by weight), the positive electrode active material for a lithium secondary battery may include, for example, 5 to 25 parts by weight of the integral particles. Within this range, the positive electrode active material can achieve improvements in capacity and life characteristics. For example, with respect to 100 parts by weight of the positive electrode active material (e.g., the total of the first secondary particles, the second secondary particles, and the integral particles is 100 parts by weight), the integral particles may be present in an amount of 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, 20 parts by weight, 21 parts by weight, 22 parts by weight, 23 parts by weight, 24 parts by weight, 25 parts by weight, 10 to 25 parts by weight, or 10 to 20 parts by weight.

[0099] According to one or more embodiments, in the positive electrode active material for a lithium secondary battery, the first secondary particles, the second secondary particles, and the integral particles may be present in a total amount of 95 wt% or more (e.g., 98 wt% to 100 wt% or 100 wt%). Within this range, the positive electrode active material for a lithium secondary battery can easily or appropriately achieve the desired effects of these particles.

[0100] According to one or more embodiments, the positive electrode active material for a lithium secondary battery may have a plate-like structure (e.g., in the form of a plate), and the plate-like structure has one or more suitable detailed (set) shapes (e.g., spherical shape; ellipsoidal shape; polygonal nanoplate shape such as hexagonal nanoplate shape, etc.; nanodisk shape; parallelepiped shape; etc.). When the positive electrode active material for a lithium secondary battery is non-spherical, the size refers to the average value of the major axis length.

[0101] According to one or more embodiments, in the positive electrode active material for a lithium secondary battery, each of the first secondary particles, the second secondary particles, and the integral particles may be a lithium nickel-based composite oxide.

[0102] For example, the lithium nickel-based composite oxide may include a compound represented by Formula 1 or a compound represented by Formula 2.

[0103] Formula 1

[0104] Li x Ni 1-y Co y O 2-z X z ,

[0105] where x, y, and z satisfy the following relational expressions: 0.9 ≤ x ≤ 1.2, 0 < y ≤ 0.2, 0 ≤ z ≤ 0.5, and 0.8 ≤ 1 - y < 1; and X represents F, S, P, or a combination thereof.

[0106] Formula 2

[0107] Li x Ni 1-y-z Co y M z O 2-a X a ,

[0108] where x, y, z, and a satisfy the following relational expressions: 0.9 ≤ x ≤ 1.2, 0 < y < 0.5, 0.8 ≤ 1 - y - z < 1, 0 ≤ z ≤ 0.5, 0 < y + z ≤ 0.2, and 0 ≤ a < 2; M represents Mn, Mg, Ca, Sr, Ba, Ti, Zr, Nb, Mo, W, Zn, Al, Si, Cr, Fe, V, rare earth elements, or a combination thereof; and X represents F, S, P, or a combination thereof.

[0109] In Formula 1 and Formula 2, based on the total content of 100 mol% of metals other than lithium in the lithium nickel-based composite oxide, the lithium nickel-based composite oxide may have a nickel content (e.g., amount) of 80 mol% or more (e.g., 80 mol% to 95 mol% or 85 mol% to 92 mol%); x may be in the range of 1 to 1.05; and y may be in the range of, for example, 0.01 to 0.2. In Formula 2, M may represent Al, and z may be in the range of, for example, 0.01 to 0.05.

[0110] According to one or more embodiments, the lithium nickel-based composite oxide may be a compound represented by Formula 3 or a compound represented by Formula 4.

[0111] Formula 3

[0112] Li x Co a Ni b Mn c O 2 ,

[0113] wherein x, a, b, and c satisfy the following relational expressions: 0.9 < x ≤ 1.2, 0 < a < 0.5, 0.8 ≤ b < 1, 0 < c < 0.5, and a + b + c = 1.

[0114] Formula 4

[0115] Li x Co a Ni b Al c O 2 ,

[0116] wherein x, a, b, and c satisfy the following relational expressions: 0.9 < x ≤ 1.2, 0 < a < 0.5, 0.8 ≤ b < 1, 0 < c < 0.5, and a + b + c = 1.

[0117] In Formula 3 and Formula 4, x may be in the range of 1.0 to 1.2, 1.0 to 1.1, or 1.0 to 1.05; a may be in the range of, for example, 0.001 to 0.45, 0.01 to 0.4, 0.01 to 0.3, 0.01 to 0.2, 0.01 to 0.1, 0.02 to 0.08, or 0.04 to 0.09; and b may be in the range of, for example, 0.8 to 0.99, 0.8 to 0.98, or 0.85 to 0.95. For example, c may be in the range of 0.001 to 0.3, 0.001 to 0.2, 0.001 to 0.1, 0.005 to 0.02, or 0.005 to 0.01.

[0118] According to one or more embodiments, the size of the positive electrode active material for a lithium secondary battery can be adjusted to improve the high-temperature characteristics and rate performance and reduce outgassing at high voltages when implementing the lithium secondary battery using the positive electrode active material, while ensuring appropriate reliability and safety.

[0119] According to one or more embodiments, in the process of preparing the positive electrode active material for a lithium secondary battery, the molar ratio of lithium to metals other than lithium and the heat treatment conditions (heat treatment temperature, atmosphere, and time) can be adjusted to control (e.g., change) the size of the primary particles and the size of the secondary particles of the positive electrode active material, thereby reducing its specific surface area and removing residual lithium as much as possible to suppress or reduce the surface side reaction between the residual lithium and the electrolyte. In one or more embodiments, by controlling or performing the preparation process as described above, a positive electrode active material with improved crystallinity and stability at high voltages can be obtained.

[0120] According to one or more embodiments, the positive electrode active material for a lithium secondary battery may further include a cobalt coating. The cobalt coating can further improve the life characteristics of the lithium secondary battery while achieving a higher or improved capacity.

[0121] According to one or more embodiments, at least one of the first secondary particles, the second secondary particles, and the integral particles may include a cobalt coating on its surface.

[0122] For example, the first secondary particles may include a cobalt coating on the surface of the secondary particles. The first secondary particles may include a cobalt coating on the surface of the primary particles and / or the secondary particles.

[0123] For example, the second secondary particles may include a cobalt coating on the surface of the secondary particles. The second secondary particles may include a cobalt coating on the surface of the primary particles and / or the secondary particles.

[0124] For example, the integral particles may include: primary particles; and a cobalt coating on the surface of the primary particles.

[0125] Next, a method for preparing the positive electrode active material for a lithium secondary battery will be described.

[0126] According to one or more embodiments, the positive electrode active material for a lithium secondary battery can be prepared by: preparing the first secondary particles, the second secondary particles, and the integral particles, and then mixing these particles.

[0127] For example, each of the first secondary particles, the second secondary particles, and the integral particles can be prepared by: mixing a nickel-based active material precursor and a lithium precursor in a specific molar ratio to prepare a mixture, and performing a primary heat treatment on the mixture.

[0128] The nickel-based active material precursor includes nickel-based hydroxides, which can be prepared by co-precipitation of a nickel precursor and other transition metal precursors. For example, the nickel-based active material precursor can be a hydroxide or oxide including nickel, cobalt, and other metals.

[0129] According to one or more embodiments, the nickel-based active material precursor can be prepared by the following: mixing a nickel precursor, a cobalt precursor, and an aluminum precursor in a first solvent, followed by co-precipitation. The nickel precursor, cobalt precursor, and aluminum precursor can be any suitable substances available in the art. The content (e.g., amount) of each of the nickel precursor, cobalt precursor, and aluminum precursor can be stoichiometrically controlled or selected to obtain the compound of Formula 4.

[0130] The first solvent can be water, ethanol, propanol, butanol, etc. Relative to 100 parts by weight in total of the nickel precursor, cobalt precursor, and aluminum precursor, the first solvent can be present in an amount of 100 parts by weight to 2,000 parts by weight.

[0131] The nickel-based active material precursor can be represented, for example, by Formula 5:

[0132] Formula 5

[0133] Ni 1-y-z Co y M z (OH) 2 ,

[0134] where y and z satisfy the following relational expressions: 0 < y < 0.5, 0.8 ≤ 1 - y - z < 1, and 0 ≤ z < 0.5; and

[0135] M represents Mn, Mg, Ca, Sr, Ba, Ti, Zr, Nb, Mo, W, Zn, Al, Si, Cr, Fe, V, rare earth elements, or a combination thereof.

[0136] The lithium precursor can include, for example, lithium hydroxide, lithium fluoride, lithium carbonate, lithium sulfate, lithium nitrate, or a mixture thereof. The mixing ratio of the lithium precursor and the nickel-based active material precursor can be stoichiometrically adjusted to prepare, for example, the positive electrode active material for a lithium secondary battery represented by Formula 2.

[0137] According to one or more embodiments, the mixing of the lithium precursor and the nickel-based active material precursor can be carried out by dry mixing using a mixer or the like. The dry mixing can be carried out by grinding. Although the grinding conditions are not particularly limited, grinding can be carried out to allow little deformation (e.g., to reduce deformation) to allow refinement of the precursor such as the raw material used. The size of the lithium precursor to be mixed with the nickel-based active material precursor can be pre-controlled or selected. The lithium precursor can have a size (average particle diameter) of 5 μm to 15 μm (e.g., about 10 μm). A desired or required mixture can be obtained by grinding the lithium precursor having such a size and the nickel-based active material precursor at 300 rpm to 3,000 rpm. During the grinding process, when the internal temperature of the mixer rises above 30°C, a cooling process can be carried out to keep the inside of the mixer at room temperature (25°C).

[0138] According to some embodiments, if (e.g., when) the nickel-based active material precursor is mixed with the lithium precursor, a second solvent can be used. Similar to the above-mentioned first solvent, the second solvent can include water, ethanol, butanol, propanol, etc., and can be present in an amount of 100 parts by weight to 2,000 parts by weight relative to 100 parts by weight of the lithium precursor. A complexing agent and a pH regulator can be added to and mixed with the mixture including the nickel-based active material precursor and the lithium precursor.

[0139] The primary heat treatment can be carried out in air or in an oxygen atmosphere. The primary heat treatment can be carried out, for example, at 600°C to 900°C, e.g., at 650°C to 900°C.

[0140] The method for preparing the nickel-based active material (i.e., the positive electrode active material for a lithium secondary battery) can further include a secondary heat treatment carried out in air or in an oxygen atmosphere after the primary heat treatment. The secondary heat treatment can be carried out, for example, at 600°C to 900°C.

[0141] According to one or more embodiments, in the preparation of the first secondary particles, the primary heat treatment can be carried out in air or in an oxygen atmosphere. The primary heat treatment can be carried out, for example, at 600°C to 800°C, e.g., at 650°C to 800°C.

[0142] According to one or more embodiments, in the preparation of the second secondary particles, the primary heat treatment can be carried out in air or in an oxygen atmosphere. The primary heat treatment can be carried out, for example, at 600°C to 800°C, e.g., at 650°C to 800°C.

[0143] According to one or more embodiments, in the preparation of the integrated particles, the primary heat treatment can be carried out in air or in an oxygen atmosphere. The primary heat treatment can be carried out, for example, at 800°C to 900°C.

[0144] According to some embodiments, a positive electrode active material for a lithium secondary battery can be prepared by mixing a first secondary particle, a second secondary particle, and an integral particle to prepare a mixture, and performing cobalt coating on the mixture.

[0145] Since the mixing of the first secondary particle, the second secondary particle, and the integral particle can be performed by the above method, a detailed description thereof will not be provided. Hereinafter, only the cobalt coating process will be described.

[0146] The cobalt coating can be performed by dry coating and / or wet coating.

[0147] For example, dry coating of cobalt can be performed by introducing a cobalt source into a mixture of the first secondary particle, the second secondary particle, and the integral particle, and then performing a second heat treatment.

[0148] For example, wet coating of cobalt can be performed by introducing a solvent (such as distilled water) into a mixture of the first secondary particle, the second secondary particle, and the integral particle, washing the mixture while mixing, and adding a cobalt source to the mixture.

[0149] The cobalt source can include, for example, cobalt hydroxide, cobalt carbonate, cobalt sulfate, cobalt oxide, cobalt nitrate, etc.

[0150] The cobalt source can be added to the mixture such that, based on the total content of 100 mol% of the metals other than lithium in each of the first secondary particle, the second secondary particle, and the integral particle, the cobalt content (e.g., amount) in each of the first secondary particle, the second secondary particle, and the integral particle is 0.01 mol% to 5 mol% (e.g., 0.01 mol% to 3 mol% or 0.1 mol% to 2.5 mol%). As a result, a cobalt coating can be formed in a suitable or appropriate content (e.g., amount).

[0151] After adding the cobalt source, the cobalt coating process can further include filtering to remove the solvent and drying the cobalt coating. The drying can be performed, for example, at a temperature of 100 °C to 300 °C for 5 hours to 15 hours, for example, at 200 °C for 10 hours.

[0152] Then, the obtained product is mixed with a lithium source and fed into a furnace, and then sintered (i.e., third heat treatment) at 650 °C to 900 °C, 650 °C to 800 °C, or 650 °C to 800 °C in an oxygen atmosphere for 5 hours to 30 hours, or sintered for 10 hours to 24 hours.

[0153] Lithium secondary battery

[0154] According to one or more embodiments, a lithium secondary battery includes: a positive electrode including a positive electrode active material for a lithium secondary battery according to an embodiment of the present disclosure; a negative electrode; and an electrolyte.

[0155] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector. The positive electrode active material layer may include a positive electrode active material and may further include a binder and / or a conductive material.

[0156] In one or more embodiments, the positive electrode may further include a component capable of acting as a sacrificial positive electrode.

[0157] Based on 100 wt% of the positive electrode active material layer, the positive electrode active material may be present in an amount of 90 wt% to 99 wt%, and based on 100 wt% of the positive electrode active material layer, each of the binder and the conductive material may be present in an amount of 0.5 wt% to 5 wt%.

[0158] The positive electrode active material layer includes a positive electrode active material according to one or more embodiments of the present disclosure.

[0159] In addition to the positive electrode active material for a lithium secondary battery according to the present embodiment, the positive electrode active material layer may further include a different positive electrode active material.

[0160] The different positive electrode active materials according to one or more embodiments may include at least one composite oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof.

[0161] The composite oxide may be a lithium transition metal composite oxide. For example, the composite oxide may include lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate compound, cobalt-free lithium manganese oxide, or a combination thereof.

[0162] By way of example, the composite oxide may be a compound represented by any one of the following chemical formulas: Li a A 1- b X b O 2-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Mn 2-b X b O 4-c D c (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b X c O 2-α D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 < α < 2); Li a Ni 1-b-cMn b X c O 2-α D α (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.5, 0 < α < 2); Li a Ni b Co c L 1 d G e O 2 (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0 ≤ e ≤ 0.1); Li a NiG b O 2 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a CoG b O 2 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn 1-b G b O 2 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn 2 G b O 4 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn 1-g G g PO 4 (0.90 ≤ a ≤ 1.8, 0 ≤ g ≤ 0.5); Li (3-f) Fe 2 (PO 4 ) 3 (0 ≤ f ≤ 2); and Li a FePO 4 (0.90 ≤ a ≤ 1.8).

[0163] In the above formulas, A is Ni, Co, Mn, or a combination thereof; X represents Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; and L 1 is Mn, Al, or a combination thereof.

[0164] In one or more embodiments, the positive electrode active material may be a positive electrode active material with a high nickel content. Based on 100 mol% of the metals other than lithium in the lithium transition metal composite oxide (i.e., the positive electrode active material with a high nickel content), the positive electrode active material with a high nickel content includes 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% to 99 mol% of nickel. The positive electrode active material with a high nickel content can achieve an appropriate high capacity, and thus can be applied to high-capacity / high-density lithium secondary batteries.

[0165] The binder is used to attach the positive electrode active material particles to each other (or improve the attachment between the positive electrode active material particles), and is also used to attach (or bond) the positive electrode active material to the positive electrode current collector. The binder may include, for example, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylate esterified styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc., but is not limited thereto.

[0166] The conductive material is used to impart conductivity to the electrode and can be any suitable conductive material that does not cause an undesired chemical change in the constructed battery cell (e.g., in the battery cell being manufactured). The conductive material may include: for example, carbon materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.); metal-based materials in the form of metal powders and / or metal fibers containing copper, nickel, aluminum, silver, etc.; conductive polymers (such as polyphenylene derivatives, etc.); and mixtures thereof.

[0167] The positive electrode current collector may be Al foil, but is not limited thereto.

[0168] The negative electrode includes a negative electrode current collector and a negative electrode material layer disposed on the negative electrode current collector. The negative electrode material layer includes a negative electrode material (i.e., a negative electrode active material), and may further include a binder and / or a conductive material.

[0169] For example, based on 100 wt% of the negative electrode active material layer, the negative electrode material layer may include 90 wt% to 99 wt% of the negative electrode material, 0.5 wt% to 5 wt% of the binder, and 0 wt% to 5 wt% of the conductive material.

[0170] The negative electrode material includes: a material that allows reversible intercalation / deintercalation of lithium ions, lithium metal, a lithium metal alloy, a material into which lithium can be doped and from which it can be de-doped, and / or a transition metal oxide.

[0171] Materials that allow reversible insertion / extraction of lithium ions may include carbonaceous negative electrode materials, such as crystalline carbon, amorphous carbon, or a combination thereof. Crystalline carbon may include, for example, graphite in amorphous, plate-like, flake-like, spherical, and / or fibrous forms (such as natural graphite and / or artificial graphite), and amorphous carbon may include, for example, soft carbon, hard carbon, mesophase pitch carbide, calcined coke, etc.

[0172] As a lithium metal alloy, an alloy of lithium with a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn may be used.

[0173] Materials into which lithium can be doped and from which it can be de-doped may be Si-based negative electrode materials and / or Sn-based negative electrode materials. The Si-based negative electrode materials may be silicon, silicon-carbon composites, SiO x (0 < x ≤ 2), Si-Q alloys (where Q is selected from alkali metals, alkaline earth metals, Group XIII elements, Group XIV elements (except Si), Group XV elements, Group XVI elements, transition metals, rare earth elements, and combinations thereof), or combinations thereof. The Sn-based negative electrode materials may be Sn, SnO x (0 < x ≤ 2) (for example, SnO 2 ), Sn alloys, or combinations thereof.

[0174] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one or more embodiments, the silicon-carbon composite may be prepared in the form of silicon particles having an amorphous carbon coating formed on their surface. For example, the silicon-carbon composite may include secondary particles (cores) composed of primary silicon particles and an amorphous carbon coating (shells) formed on the surfaces of the secondary particles. Amorphous carbon may also be placed between the primary silicon particles such that, for example, the primary silicon particles are coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0175] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include: a core containing crystalline carbon and silicon particles and an amorphous carbon coating formed on the core.

[0176] The Si-based negative electrode materials and / or the Sn-based negative electrode materials may be used in combination with the carbonaceous negative electrode materials.

[0177] A binder is used to attach the negative electrode material particles to each other (or improve the attachment between the negative electrode material particles), while attaching (e.g., bonding) the negative electrode material to the negative electrode current collector. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0178] The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0179] The aqueous binder may be selected from the group consisting of: styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, epichlorohydrin rubber, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0180] When the aqueous binder is used as a binder in the negative electrode active material layer, a cellulose compound capable of imparting viscosity may be further included. The cellulose compound may be a mixture of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and / or an alkali metal salt thereof. The alkali metal may be Na, K, and / or Li.

[0181] The dry binder may be a polymeric material capable of fibrillation and may include, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0182] The conductive material is used to impart conductivity to the electrode and may be any suitable conductive material that does not cause an undesired chemical change in the constructed battery cell (e.g., in the battery cell being manufactured). For example, the conductive material may include: carbon materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube, etc.; metal-based materials in the form of metal powders and / or metal fibers containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives, etc.; or mixtures thereof.

[0183] The negative electrode current collector may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0184] The electrolyte for the lithium secondary battery includes a non-aqueous organic solvent and a lithium salt.

[0185] The non-aqueous organic solvent serves as a medium through which ions participating in the electrochemical reaction of the battery cell can move.

[0186] The non-aqueous organic solvent may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0187] The carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC) and / or butylene carbonate (BC).

[0188] The ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc.

[0189] The ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. In one or more embodiments, the ketone solvents may include cyclohexanone, etc. The alcohol solvents may include ethanol, isopropanol, etc., and the aprotic solvents may include nitriles such as R-CN (where R is a straight-chain, branched-chain or cycloalkyl group having 2 to 20 carbon atoms and may include double bonds, aromatic rings and / or ether bonds); amides (such as dimethylformamide); dioxolanes (such as 1,3-dioxolane, 1,4-dioxolane, etc.); sulfolane; and so on.

[0190] The non-aqueous organic solvents may be used alone or as a mixture of two or more.

[0191] As the carbonate solvents, a mixture of cyclic carbonates and chain (e.g., straight-chain) carbonates may be used, and the cyclic carbonate and the chain carbonate may be mixed at a volume ratio of 1:1 to 1:9.

[0192] The lithium salt is a substance that is soluble in non-aqueous organic solvents and used as a lithium ion source in the battery, ensuring or facilitating the basic operation of the lithium secondary battery while facilitating the transfer of lithium ions between the positive electrode and the negative electrode. Examples of the lithium salt may include those selected from LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiClO 4 , LiAlO 2 , LiAlCl 4 , LiPO 2 F 2 , LiCl, LiI, LiN(SO 3 C 2 F 5 ) 2 , Li(FSO 2 ) 2 N (lithium bis(fluorosulfonyl)imide (LiFSI)), LiC 4 F 9 SO3 , LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 )(wherein x and y are each an integer from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro bis(oxalate) phosphate (LiDFBOP), and lithium bis(oxalate) borate (LiBOB), or at least one of them

[0193] Depending on the type or kind of the lithium secondary battery, a separator may be inserted between the positive electrode and the negative electrode. For such a separator, a polyethylene separator, a polypropylene separator, a polyvinylidene fluoride separator, or at least two layers thereof (such as a polyethylene / polypropylene bilayer separator, a polyethylene / polypropylene / polyethylene trilayer separator, a polyethylene / polyethylene / polypropylene trilayer separator, etc.) may be used.

[0194] The separator may include a porous substrate and a coating on one or both (e.g., both simultaneously) surfaces (e.g., opposite surfaces) of the porous substrate, and the coating includes an organic material, an inorganic material, or a combination thereof.

[0195] The porous substrate may be a polymer layer formed of: polymers, copolymers, and / or mixtures thereof selected from polyolefins (such as polyethylene, polypropylene, etc.), polyesters (such as polyethylene terephthalate, polybutylene terephthalate, etc.), polyacetals, polyamides, polyimides, polycarbonates, polyether ketones, polyarylether ketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene ethers, cycloolefin copolymers, polyphenylene sulfides, polyethylene naphthalate, glass fibers, and polytetrafluoroethylene (Teflon TM ).

[0196] The organic material may include polyvinylidene fluoride polymers and / or (meth)acrylic polymers.

[0197] The inorganic material may include inorganic particles selected from Al 2 O 3 , SiO 2 , TiO 2 , SnO 2 , CeO 2 , MgO, NiO, CaO, GaO, ZnO, ZrO 2 , Y 2 O 3 , SrTiO 3 , BaTiO 3 , Mg(OH) 2 , boehmite, and combinations thereof, but not limited thereto.

[0198] Organic materials and inorganic materials can exist in a mixed state in a coating or can exist in the form of a stacked structure including a coating of organic materials and a coating of inorganic materials.

[0199] Based on their shape, lithium secondary batteries can be classified as cylindrical lithium secondary batteries, faceted (e.g., prismatic) lithium secondary batteries, pouch-type or quasi-pouch-type lithium secondary batteries, coin-type lithium secondary batteries, etc. Figures 1 to 4 FIG. is a schematic view of a lithium secondary battery according to one or more embodiments of the present disclosure, wherein Figure 1 a cylindrical lithium secondary battery is shown, Figure 2 a prismatic lithium secondary battery is shown, and Figure 3 and Figure 4 each shows a pouch-type or quasi-pouch-type lithium secondary battery. Referring to Figures 1 to 4 , the lithium secondary battery 100 may include: an electrode assembly 40 in which a separator 30 is inserted between a positive electrode 10 and a negative electrode 20; and a case 50 in which the electrode assembly 40 is accommodated. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte. As Figure 1 shown, the lithium secondary battery 100 may include a sealing member 60 that seals the case 50. In one or more embodiments, as Figure 2 shown, the rechargeable lithium battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. Referring to Figure 3 and Figure 4 , the lithium secondary battery 100 may include an electrode tab 70 including a positive electrode tab 71 and a negative electrode tab 72, which serves as a circuit path for leading the current formed in the electrode assembly 40 to the outside.

[0200] The lithium secondary battery according to one or more embodiments of the present disclosure can be applied to an automobile (e.g., as a driving power source for a hybrid vehicle or an electric vehicle), a mobile phone, and / or one or more other suitable electronic devices, but is not limited thereto.

[0201] Next, the present disclosure will be described in more detail with reference to examples. However, it should be understood that these examples are provided for illustration only and should not be construed as limiting the present disclosure in any way.

[0202] Preparation Example 1-1: Preparation of Primary Secondary Particles LiNi 0.94 Co 0.04 Al 0.02 O 2 with an average particle diameter of 18 μm

[0203] An aluminum precursor Al 2 (SO 4 ) 3 ·(H 2 O)18 Mix with NaOH, NH 4 OH and water to prepare an aqueous solution of an aluminum precursor.

[0204] In one or more embodiments, the nickel precursor NiSO 4 ·(H 2 O) 6 and the cobalt precursor CoSO 4 ·(H 2 O) 7 are each mixed with water to separately prepare an aqueous solution of the nickel precursor and an aqueous solution of the cobalt precursor.

[0205] Place the aqueous solution of the aluminum precursor in a reactor, and dropwise add the aqueous solution of the nickel precursor and the aqueous solution of the cobalt precursor to the reactor to obtain a reaction mixture, and then stir the reaction mixture for 10 to 20 hours. Chemometrically control or select the content (e.g., amount) of each of the nickel precursor, cobalt precursor, and aluminum precursor in the reaction mixture until the molar ratio of nickel, cobalt, and aluminum reaches 94:4:2.

[0206] Add an aqueous solution of sodium hydroxide to the reaction mixture to adjust the pH of the reaction mixture to 10 to 12. Dry the obtained product obtained by filtering and rinsing the resulting precipitate in vacuo at 100 °C, thereby preparing Ni 0.94 Co 0.04 Al 0.02 (OH) 2 (i.e., nickel cobalt aluminum hydroxide) powder.

[0207] After mixing the obtained nickel cobalt aluminum hydroxide with lithium hydroxide (LiOH) as a lithium precursor in a bowl, place the mixture in a furnace, and then, while supplying O 2 to the furnace, perform a primary heat treatment at 730 °C for 20 hours to prepare a nickel-based active material. Control or select the content (e.g., amount) of each of the nickel cobalt aluminum hydroxide and the lithium precursor such that the mixed molar ratio of the metals other than lithium to lithium reaches 1:1.03.

[0208] The prepared nickel-based active material is in the form of secondary particles (NCA, LiNi 0.94 Co 0.04 Al 0.02 O 2 )(i.e., the first secondary particles), the average particle size of the secondary particles is 18 μm, and one secondary particle is composed of two or more primary particles with an average particle size of 1 μm or less.

[0209] Preparation Example 1-2: Preparation of the First Secondary Particles

[0210] The first secondary particles were prepared in substantially the same manner as in Example 1, except that the content (e.g., amount) of each of the nickel precursor, cobalt precursor, and aluminum precursor, the primary heat treatment temperature, and the primary heat treatment time were changed to obtain the particles described in Table 1.

[0211] Preparation Examples 1-3: Preparation of First Secondary Particles

[0212] The first secondary particles were prepared in substantially the same manner as in Example 1, except that the content (e.g., amount) of each of the nickel precursor, cobalt precursor, and aluminum precursor, the primary heat treatment temperature, and the primary heat treatment time were changed to obtain the particles described in Table 1.

[0213] Preparation Example 2: Preparation of Second Secondary Particles LiNi 0.89 Co 0.09 Al 0.02 O 2 of

[0214] The aluminum precursor Al 2 (SO 4 ) 3 ·(H 2 O) 18 was mixed with NaOH, NH 4 OH, and water to prepare an aqueous solution of the aluminum precursor.

[0215] The nickel precursor NiSO 4 ·(H 2 O) 6 and the cobalt precursor CoSO 4 ·(H 2 O) 7 were each mixed with water to separately prepare an aqueous solution of the nickel precursor and an aqueous solution of the cobalt precursor.

[0216] The aqueous solution of the aluminum precursor was placed in a reactor, and the aqueous solutions of the nickel precursor and the cobalt precursor were added dropwise to the reactor to obtain a reaction mixture, which was then stirred for 10 to 20 hours. The content (e.g., amount) of each of the nickel precursor, cobalt precursor, and aluminum precursor in the reaction mixture was stoichiometrically controlled or selected until the molar ratio of nickel, cobalt, and aluminum reached 89:9:2.

[0217] An aqueous solution of sodium hydroxide was added to the reaction mixture to adjust the pH of the reaction mixture to 10 to 12. The resulting product obtained by filtering and rinsing the resulting precipitate was dried in vacuo at 100 °C to prepare Ni 0.89 Co 0.09 Al 0.02 (OH) 2 (i.e., nickel cobalt aluminum hydroxide) powder.

[0218] After mixing nickel cobalt aluminum hydroxide with lithium hydroxide (LiOH) as a lithium precursor, the mixture is placed in a furnace, and then while supplying O 2 to the furnace, primary heat treatment is carried out at 730 °C for 20 hours to prepare a nickel-based active material. The content (e.g., amount) of each of the nickel cobalt aluminum hydroxide and the lithium precursor is controlled or selected such that the mixing molar ratio of the metal other than lithium to lithium reaches 1:1.03.

[0219] The nickel-based active material prepared by the above method is in the form of secondary particles (NCA, LiNi 0.89 Co 0.09 Al 0.02 O 2 ), the average particle size of the secondary particles is 10.4 μm, and one secondary particle is composed of two or more primary particles with an average particle size of 1 μm or less.

[0220] Preparation Example 3-1: Preparation of monolithic particles LiNi with an average particle size of 4.1 μm 0.97 Co 0.02 Al 0.01 O 2 (NCA)

[0221] Mix aluminum precursor Al 2 (SO 4 ) 3 ·(H 2 O) 18 with NaOH, NH 4 OH and water to prepare an aqueous solution of the aluminum precursor.

[0222] Mix nickel precursor NiSO 4 ·(H 2 O) 6 and cobalt precursor CoSO 4 ·(H 2 O) 7 each with water to separately prepare an aqueous solution of the nickel precursor and an aqueous solution of the cobalt precursor.

[0223] Place the aqueous solution of the aluminum precursor in a reactor, and dropwise add the aqueous solution of the nickel precursor and the aqueous solution of the cobalt precursor to the reactor to obtain a reaction mixture, and then stir the reaction mixture for 10 hours to 20 hours. Chemometrically control or select the content (e.g., amount) of each of the nickel precursor, cobalt precursor, and aluminum precursor in the reaction mixture until the molar ratio of nickel, cobalt, and aluminum reaches 97:2:1.

[0224] An aqueous solution of sodium hydroxide is added to the reaction mixture to adjust the pH of the reaction mixture to 10 to 12. The resulting product obtained by filtering and rinsing the resulting precipitate is dried in vacuo at 100 °C to prepare Ni 0.97 Co 0.02 Al 0.01 (OH) 2 (i.e., nickel cobalt aluminum hydroxide) powder.

[0225] After mixing nickel cobalt aluminum hydroxide with lithium hydroxide (LiOH) as a lithium precursor, the mixture is placed in a furnace, and then, while supplying O 2 to the furnace, a primary heat treatment is carried out at 900 °C for 20 hours to prepare a nickel-based active material. The content (e.g., amount) of each of nickel cobalt aluminum hydroxide and the lithium precursor is controlled or selected such that the mixing molar ratio of metals other than lithium to lithium reaches 1:1.05.

[0226] The nickel-based active material prepared by the above method is in the form of integral particles (NCA, LiNi 0.97 Co 0.02 Al 0.01 O 2 ) having an average particle diameter of 4.1 μm.

[0227] Preparation Examples 3-2 to 3-4: Preparation of integral particles

[0228] Integral particles are prepared in substantially the same manner as in Example 3-1, except that the content (e.g., amount) of each of the nickel precursor, cobalt precursor, and aluminum precursor, the primary heat treatment temperature, and the primary heat treatment time are changed to obtain the particles described in Table 1.

[0229] Details of the particles obtained in the above preparation examples are as follows.

[0230] Table 1

[0231]

[0232] Preparation of a positive electrode active material for a lithium secondary battery and preparation of a lithium secondary battery including the positive electrode active material

[0233] Example 1

[0234] A lithium nickel-based composite oxide is prepared by mixing the first secondary particles prepared in Preparation Example 1-1, the second secondary particles prepared in Preparation Example 2, and the integral particles prepared in Preparation Example 3-1 in a mixer at the contents (e.g., amounts) listed in Table 2 (by weight).

[0235] Then, a first process is carried out by adding distilled water as a solvent and cobalt sulfate (as a cobalt source) to a mixer, adding the prepared lithium nickel-based composite oxide to the mixer, and then stirring. Cobalt sulfate is added to the mixer such that the cobalt content (e.g., amount) in the lithium nickel-based composite oxide is 2.5 mol% relative to the total content (e.g., amount) of all elements other than lithium and oxygen in 100 mol of the lithium nickel-based composite oxide (i.e., the total content of 100 mol of metals other than lithium in the lithium nickel-based composite oxide). In the first process, after adding the lithium nickel-based composite oxide, sodium hydroxide as a precipitant and a pH regulator are added together to wash the mixture for 70 minutes.

[0236] The obtained product is mixed with a lithium source and then placed in a sintering furnace, and a third heat treatment is carried out in an oxygen atmosphere at about 710 °C for 15 hours. The lithium source is added to the obtained product such that the lithium content (e.g., amount) in the obtained product is 5 mol% relative to the total content (e.g., amount) of all elements other than lithium and oxygen in 100 mol% of the obtained product (i.e., the total content of 100 mol of metals other than lithium in the obtained product). Then, the furnace is cooled to room temperature to obtain a final positive electrode active material having a cobalt coating formed on the surface of the lithium nickel-based composite oxide.

[0237] The prepared nickel-based active material is used as the positive electrode active material. In Table 2 below, "-" means that the corresponding component is absent.

[0238] A positive electrode active material slurry is prepared by mixing a positive electrode active material, a carbon conductor (Super P), and a polyvinylidene fluoride (PVDF) binder in a solution. In the positive electrode active material slurry, the weight ratio of the positive electrode active material, the carbon conductor, and the PVDF binder is 98:1:1. The prepared positive electrode active material slurry is coated on an aluminum current collector with a thickness of 12 μm at a loading level of 36 mg / cm 2 and then dried at 120 °C for 1 hour or longer and roll-pressed to prepare a positive electrode.

[0239] Graphite powder (Japan carbon) as a negative electrode material and a mixture of styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) with a weight ratio of 1:1 are mixed at a weight ratio of 98:2 (the weight ratio of the negative electrode material to SBR to CMC is 98:1:1) to prepare a negative electrode active material slurry.

[0240] The prepared negative electrode active material slurry is applied at a loading level of 19.5 mg / cm 2The load level is coated on a copper foil current collector with a thickness of 8 μm. The coated copper foil current collector is dried at 100 °C for 1 hour or longer, and then roll-pressed to prepare a negative electrode with a composite density of 1.66 g / cm 3 of the negative electrode.

[0241] A lithium secondary battery with a capacity of 2,000 mAh is prepared using a positive electrode, a negative electrode, a polyethylene separator (separator, STAR 20, Asahi), and an electrolyte (in which 1.15 M of LiPF 6 is dissolved in a mixed solvent of EC (ethylene carbonate), EMC (ethyl methyl carbonate), and DMC (dimethyl carbonate) (volume ratio of 3:3:4)).

[0242] Example 2

[0243] A lithium secondary battery is prepared in substantially the same manner as in Example 1, except that, as listed in Table 2, the type or kind and content (e.g., amount) of the particles in the nickel-based active material are changed.

[0244] Comparative Examples 1 to 4

[0245] A lithium secondary battery is prepared in substantially the same manner as in Example 1, except that, as listed in Table 2, the type or kind and content (e.g., amount) of the particles in the nickel-based active material are changed.

[0246] Table 2

[0247]

[0248] Evaluation Example 1: Size analysis of primary particles, secondary particles, and integral particles by scanning electron microscopy (SEM)

[0249] The SEM image of the positive electrode active material for the lithium secondary battery prepared in Example 1 is evaluated. SEM (Sirion, FEI, USA) is used as the measuring instrument.

[0250] The results of the SEM analysis are shown in Figure 5 .

[0251] Reference Figure 5 , it can be seen that the positive electrode active material for the lithium secondary battery prepared in Example 1 includes all of the first secondary particles A, the second secondary particles B, and the integral particles C.

[0252] Evaluation Example 2: Charge capacity, discharge capacity, and efficiency

[0253] For each of the lithium secondary batteries of the examples and comparative examples, the initial charge capacity and the initial discharge capacity were measured as follows: at 25 °C, the battery was charged from 2.8 V to the upper limit voltage of 4.3 V at a constant current of 0.2 C, and while maintaining 4.3 V, the battery was charged until the current dropped to the termination condition of 0.05 C, and then discharged at 0.2 C to the discharge termination voltage of 3.0 V.

[0254] The ratio of the initial discharge capacity (primary discharge capacity) to the initial charge capacity (primary charge capacity) was calculated as the efficiency.

[0255] Evaluation Example 3: High-temperature life characteristics

[0256] Formation stage: At 45 °C, each of the lithium secondary batteries prepared in the examples and comparative examples was charged at a constant current of 0.2 C until the voltage reached 4.3 V, and then charged at a constant voltage while maintaining 4.3 V until the current dropped to 0.05 C; then, the battery was discharged at a constant current of 0.2 C until the voltage reached 3.0 V.

[0257] Next, standard stage: The battery was charged at a constant current of 0.7 C until the voltage reached 4.35 V, and then charged at a constant voltage while maintaining 4.35 V until the current dropped to 0.05 C; then, the battery was discharged at a constant current of 0.5 C until the voltage reached 3.0 V.

[0258] At 25 °C and 45 °C, each of the lithium secondary batteries that had undergone the formation stage was charged at a constant current of 0.5 C until the voltage reached 4.35 V, and charged at a constant voltage while maintaining 4.35 V until the current dropped to 0.05 C; then, the battery was discharged at a constant current of 0.5 C until the voltage dropped to 3.0 V, and the cycle was repeated 50 times. The high-temperature life was evaluated by the discharge capacity retention rate, which was calculated as the ratio of (the discharge capacity of the 50th cycle) to (the discharge capacity of the 1st cycle). The high-temperature life characteristics obtained from the charge / discharge experimental results are shown in Figure 6 and Table 3.

[0259] Table 3

[0260]

[0261] In Table 3, *: The nickel content is based on the total content of metals other than lithium in 100 mol% of the nickel-based active material (e.g., amount).

[0262] As shown in Table 3, it can be seen that the lithium secondary batteries prepared in the examples not only have appropriate high efficiency, but also have improved high-temperature life characteristics. This result can also be seen from Figure 6 seen. Refer to Figure 6, It can be seen that at the 50th cycle, the lithium secondary battery prepared in the example has improved high-temperature life characteristics compared with the lithium secondary battery prepared in the comparative example.

[0263] Although the present disclosure has been described with reference to some embodiments and the accompanying drawings, it should be understood that the present disclosure is not limited thereto, and one or more appropriate modifications, changes, variations, and equivalent embodiments can be made by those skilled in the art without departing from the spirit and scope of the present disclosure as set forth in the claims and their equivalents.

[0264] In view of the overall content of the present disclosure, those of ordinary skill in the art will recognize that each appropriate feature of the various embodiments of the present disclosure can be combined in part or in whole or with each other, and can be technically interlocked and operated in various suitable ways. Unless otherwise stated or implied, the various embodiments can be implemented independently of each other or in any suitable combination with each other.

Claims

1. A positive electrode active material comprising: i) first secondary particles having a size in the range of 13 μm to 20 μm and including aggregates of primary particles having a size in the range of 1 μm or less; ii) second secondary particles having a size in the range of 7 μm to 13 μm and comprising aggregates of primary particles having a size in the range of 1 μm or less; and iii) integral particles having a size in the range of 1 μm to 7 μm and comprising primary particles, The nickel content of each of the first secondary particle, the second secondary particle and the integral particle satisfies Relationship 1: Relation 1 The nickel content of the integral particle>the nickel content of the first secondary particle>the nickel content of the second secondary particle.

2. The positive electrode active material according to claim 1, wherein the positive electrode active material satisfies Relational Formula 2: Relation 2 The size of the first secondary particle>the size of the second secondary particle>the size of the integral particle. 3 . The positive electrode active material according to claim 1 , wherein the positive electrode active material has a nickel content of 94 mol % or more based on 100 mol % of the total content of metals excluding lithium in the positive electrode active material. 4 . The positive electrode active material according to claim 1 , wherein the integrated particles are present in an amount of 5 to 25 parts by weight relative to 100 parts by weight of the first secondary particles. 5 . The positive electrode active material of claim 1 , wherein the first secondary particles, the second secondary particles, and the integrated particles are present in a total amount of 95 wt % or more based on 100 wt % of the total weight of the positive electrode active material.

6. A positive electrode active material as described in claim 1, wherein based on 100 mol% of the total content of metals other than lithium in the first secondary particles, the first secondary particles have a nickel content of 85 mol% to 97 mol%, based on 100 mol% of the total content of metals other than lithium in the second secondary particles, the second secondary particles have a nickel content of 80 mol% to 90 mol%, and based on 100 mol% of the total content of metals other than lithium in the integrated particles, the integrated particles have a nickel content of 90 mol% to 99 mol%.

7. The positive electrode active material of claim 1, wherein the first secondary particles are present in an amount of 60 to 80 parts by weight, the second secondary particles are present in an amount of 5 to 35 parts by weight, and the integral particles are present in an amount of 5 to 25 parts by weight, relative to 100 parts by weight of the positive electrode active material. 8 . The positive electrode active material of claim 1 , wherein a molar ratio of the nickel content of the first secondary particles to the nickel content of the second secondary particles ranges from 1.01 to 1.

06.

9. The positive electrode active material according to claim 1, wherein a molar ratio of the nickel content of the first secondary particle to the nickel content of the integral particle ranges from 0.94 to 0.

99.

10. The positive electrode active material according to claim 1, wherein the positive electrode active material comprises a compound represented by Formula 1 or a compound represented by Formula 2: Formula 1 Li x Ni 1-y Co y O 2-z X z , In Formula 1, 0.9 ≤ x ≤ 1.2, 0 < y ≤ 0.2, 0 ≤ z ≤ 0.5, and 0.8 ≤ 1 - y < 1, and X represents F, S, P, or a combination thereof, Formula 2 Li x Ni 1-y-z Co y M z O 2-a X a , In Formula 2, 0.9 ≤ x ≤ 1.2, 0 < y < 0.5, 0.8 ≤ 1 - y - z < 1, 0 ≤ z ≤ 0.5, 0 < y + z ≤ 0.2, and 0 ≤ a < 2; M represents Mn, Mg, Ca, Sr, Ba, Ti, Zr, Nb, Mo, W, Zn, Al, Si, Cr, Fe, V, a rare earth element, or a combination thereof; and X represents F, S, P, or a combination thereof.

11. The positive electrode active material according to claim 1, wherein the positive electrode active material comprises a compound represented by Formula 3 or a compound represented by Formula 4: Formula 3 Li x Co a Ni b Mr c O2, In Formula 3, 0.9 < x ≤ 1.2, 0 < a < 0.5, 0.8 ≤ b < 1, 0 < c < 0.5, and a + b + c = 1, Formula 4 Li x Co a Ni b Al c O2, and In Formula 4, 0.9 < x ≤ 1.2, 0 < a < 0.5, 0.8 ≤ b < 1, 0 < c < 0.5, and a + b + c = 1.

12. The positive electrode active material according to claim 1, wherein at least one of the first secondary particle, the second secondary particle, and the integral particle comprises a cobalt coating on its surface.

13. The positive electrode active material according to claim 1, wherein the positive electrode active material is used in a lithium secondary battery.

14. A lithium secondary battery, comprising: a positive electrode comprising the positive electrode active material according to any one of claims 1 to 13; a negative electrode; and an electrolyte.

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