Composite positive electrode active material, positive electrode and lithium battery employing same, and preparation method of composite positive electrode active material

Abstract

Provided are a composite positive electrode active material, a positive electrode and a lithium battery including the composite positive electrode active material, and a method of preparing the composite positive electrode active material, the composite positive electrode active material including: a first core including a first lithium transition metal oxide; a second core including a second lithium transition metal oxide; and a shell disposed along a surface of one or more of the first core and the second core. The shell includes: at least one first metal oxide; a first carbon-based material; and a second carbon-based material, a first metal oxide disposed in a matrix of the first carbon-based material, and a second metal oxide of the chemical formula MaOb (0lt; a < = 3, 0lt; blt; and b is not an integer if a is 1, 2 or 3), M is one or more metals selected from Group 2 to Group 13, Group 15 and Group 16 of the periodic table of the elements, and the second carbon-based material includes a fibrous carbon-based material having an aspect ratio of 10 or more. The first lithium transition metal oxide and the second lithium transition metal oxide have different particle sizes from each other, the first lithium transition metal oxide includes primary particles having a particle size of 3 [mu] m or more, and the second lithium transition metal oxide includes primary particles having a particle size of 1 [mu] m or more.

Description

Technical Field

[0001] One or more aspects of embodiments of the present disclosure relate to a composite positive electrode active material, a positive electrode and a lithium battery using the composite positive electrode active material, and a method for preparing the composite positive electrode active material. Background Art

[0002] With the miniaturization and high performance of one or more suitable devices (e.g., electronic devices), it has become important or desirable for lithium batteries to have a higher energy density and to be miniaturized (e.g., reduced in size) and lighter in weight. For example, lithium batteries with a relatively high capacity have become increasingly important or desirable.

[0003] To achieve a suitable lithium battery with desired characteristics, positive electrode active materials with a high capacity are being studied.

[0004] Positive electrode active materials of the prior art may have relatively poor life characteristics and poor thermal stability due to undesirable (e.g., side) reactions.

[0005] Therefore, a method capable of preventing or reducing the deterioration of the performance of a battery including a positive electrode active material is desired.

[0006] Disclosure

[0007] Technical Problem

[0008] One or more aspects of embodiments of the present disclosure relate to a novel composite positive electrode active material that can prevent or reduce the deterioration of the performance of a lithium battery by suppressing or reducing side reactions of the composite positive electrode active material and improving the reversibility of the electrode reaction.

[0009] One or more aspects of embodiments of the present disclosure relate to a positive electrode including the composite positive electrode active material.

[0010] One or more aspects of embodiments of the present disclosure relate to a lithium battery using (e.g., employing) the positive electrode.

[0011] One or more aspects of embodiments of the present disclosure relate to a method for preparing a composite positive electrode active material.

[0012] Technical Solution

[0013] According to one or more embodiments, the composite positive electrode active material includes:

[0014] A first core including a first lithium transition metal oxide;

[0015] A second core including a second lithium transition metal oxide; and

[0016] a shell, along the surface of at least one of the first core and the second core,

[0017] wherein the shell includes a first metal oxide (e.g., one or more first metal oxides or at least one first metal oxide), a first carbonaceous material, and a second carbonaceous material,

[0018] the first metal oxide is disposed within a matrix of the first carbonaceous material,

[0019] the first metal oxide is represented by M a O b (0 < a ≤ 3 and 0 < b < 4, where if (e.g., when) a is 1, 2, or 3, then b is not an integer), M is at least one metal selected from Groups 2 to 13, 15, and 16 of the periodic table,

[0020] the second carbonaceous material includes a fibrous carbonaceous material having an aspect ratio of 10 or greater,

[0021] the first lithium transition metal oxide and the second lithium transition metal oxide have different particle sizes from each other,

[0022] the first lithium transition metal oxide includes primary particles having a particle size of 3 μm or greater, and

[0023] the second lithium transition metal oxide includes primary particles having a particle size of 1 μm or greater.

[0024] According to one or more embodiments, the composite positive electrode active material includes:

[0025] a first core, including a first lithium transition metal oxide;

[0026] a second core, including a second lithium transition metal oxide; and

[0027] a shell, along the surface of at least one of the first core and the second core,

[0028] wherein the shell may include a first metal oxide, a first carbonaceous material, and a second carbonaceous material,

[0029] the first metal oxide may be disposed within a matrix of the first carbonaceous material,

[0030] the first metal oxide may be represented by M a O b (where 0 < a ≤ 3 and 0 < b < 4, and if (e.g., when) a is 1, 2, or 3, then b is not an integer),

[0031] M may be at least one metal selected from Groups 2 to 13, 15, and 16 of the periodic table,

[0032] The second carbon-based material may include a fibrous carbon-based material having an aspect ratio of 10 or greater,

[0033] The first lithium transition metal oxide and the second lithium transition metal oxide may have different particle sizes from each other,

[0034] The first lithium transition metal oxide may include primary particles having a particle size of 3 μm or greater, and

[0035] The second lithium transition metal oxide may include primary particles having a particle size of 1 μm or greater.

[0036] According to one or more embodiments, the second lithium transition metal oxide may be secondary particles, which are aggregates of a plurality of primary particles having a particle size of 1 μm or less.

[0037] According to one or more embodiments, the positive electrode may include:

[0038] The composite positive electrode active material.

[0039] According to one or more embodiments,

[0040] The lithium battery may include the positive electrode.

[0041] According to one or more embodiments, a method for preparing a composite positive electrode active material includes the following steps: preparing a first core / shell structure by mechanically grinding a first lithium transition metal oxide, a composite, and a second carbon-based material;

[0042] preparing a second core / shell structure by mechanically grinding the second lithium transition metal oxide, the composite, and the second carbon-based material; and

[0043] preparing a composite positive electrode active material by mixing the first core / shell structure and the second core / shell structure,

[0044] wherein the composite includes a first metal oxide represented by M a O b (0 < a ≤ 3 and 0 < b < 4, where, if (for example, when) a is 1, 2, or 3, then b is not an integer) and a first carbon-based material,

[0045] The first metal oxide is disposed in a matrix of the first carbon-based material, and M is at least one metal selected from Groups 2 to 13, 15, and 16 of the periodic table,

[0046] The second carbon-based material includes a fibrous carbon-based material having an aspect ratio of 10 or greater,

[0047] The first lithium transition metal oxide and the second lithium transition metal oxide have different particle sizes from each other,

[0048] The first lithium transition metal oxide includes primary particles having a particle size of 3 μm or more, and

[0049] the second lithium transition metal oxide includes primary particles having a particle size of 1 μm or more.

[0050] Advantageous Effects

[0051] According to one or more embodiments, since the composite positive electrode active material includes a shell containing a first metal oxide, a first carbonaceous material, and a second carbonaceous material, and the shell is disposed on a large-diameter lithium transition metal oxide core and a small-diameter lithium transition metal oxide core, and the large-diameter lithium transition metal oxide and the small-diameter lithium transition metal oxide have an integral particle form, the lithium battery including the composite positive electrode active material can have improved high-temperature cycle performance, suppressed or reduced increase in internal resistance, and improved high-rate performance. Description of the Drawings

[0052] Figure 1 is a schematic cross-sectional view of a core / shell structure according to an embodiment;

[0053] Figure 2 is a scanning electron microscope image of the surface of the particles of the first core / shell structure used in Example 1;

[0054] Figure 3 is a graph showing the results of a high-temperature cycle test of the lithium batteries prepared in Example 5 and Comparative Examples 7 to 10;

[0055] Figure 4 is a schematic diagram of a lithium battery according to an embodiment;

[0056] Figure 5 is a schematic diagram of a lithium battery according to an embodiment; and

[0057] Figure 6 is a schematic diagram of a lithium battery according to an embodiment.

[0058] <Description of the Reference Numerals Representing the Main Elements of the Drawings>

[0059] 1: Lithium battery 2: Negative electrode

[0060] 3: Positive electrode 4: Separator

[0061] 5: Battery case 6: Cover assembly

[0062] 7: Battery structure 8: Electrode tab

[0063] 10: Core 20: Shell

[0064] 21: First metal oxide 22: First carbonaceous material

[0065] 23: Second carbonaceous material 100: Core / shell structure Detailed implementation manners

[0066] Various embodiments are shown in the drawings. However, the present disclosure may be implemented in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. On the contrary, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art. In the drawings, the same reference numerals always refer to the same elements, and repeated descriptions thereof may not be provided.

[0067] It will also be understood that if (e.g., when) an element is referred to as being “on” or “above” another element, it can be directly on the other element (e.g., with no intervening element therebetween), or there may also be intervening elements. On the contrary, if (e.g., when) an element is referred to as being “directly on” or “directly above” another element, then there are no intervening elements.

[0068] It will be understood that although the terms “first,” “second,” “third,” etc. may be used herein to describe one or more suitable elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, and / or portion from another element, component, region, layer, and / or portion. For example, without departing from the teachings of the disclosure, a first element, first component, first region, first layer, and / or first portion may be referred to as a second element, second component, second region, second layer, and / or second portion.

[0069] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are also intended to include the plural forms, including “at least one.” The term “at least one” should not be construed as limited to the singular form. It will also be understood that if (e.g., when) the terms “comprises” and / or its variants, or “includes” and / or its variants are used in this specification, it is specified that there are the stated features, regions, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof.

[0070] In addition, spatial relative terms such as "lower", "bottom", or "beneath" and "upper", "top", or "above" may be used herein to facilitate description of the relationship of one element or feature 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 figures. For example, if (e.g., when) the device in one of the figures is turned over, an element described as "beneath" or "under" another element will then be oriented "above" or "on top of" the other element. Thus, the example term "lower" may (e.g., simultaneously) encompass both an orientation of "lower" and "upper". The device may be otherwise oriented (rotated 90 degrees or in different directions), and the spatial relative terms used herein may be interpreted accordingly.

[0071] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will also be understood that terms, such as those defined in a commonly used dictionary, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and the relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0072] Embodiments are described herein with reference to cross-sectional views that are schematic illustrations of idealized embodiments. As such, variations in the shapes of the illustrated regions are to be expected due to, for example, manufacturing techniques and / or tolerances. Thus, the embodiments described herein are not to be construed as limited to the particular shapes of the regions shown herein but will include, for example, shape variations resulting from manufacturing. For example, a region shown or described as flat may have rough and / or non-linear features. Additionally, angles that are sharply shown may be rounded. Thus, the regions shown in the figures are schematic in nature and their shapes are not intended to show the exact shape of a region and are not intended to limit the scope of the claims presented.

[0073] "Group" refers to a group in the Periodic Table of the Elements according to the 1-18 group numbering system of the International Union of Pure and Applied Chemistry ("IUPAC").

[0074] If (e.g., when) the particles are spherical, the term "particle size" as used herein refers to the average particle size, and if (e.g., when) the particles are non-spherical, the term "particle size" as used herein refers to the average major axis length. The particle size can be measured using suitable techniques (e.g., particle size analyzer (PSA), transmission electron micrographs, and / or scanning electron micrographs). Another method can be by using a measuring device with dynamic light scattering, analyzing the data to count the number of particles relative to each particle size, and then calculating to obtain the average particle size. The term "particle size" refers to, for example, the average particle size. The term "average particle size" refers to, for example, the median particle size (D50).

[0075] D50 can refer to the particle size corresponding to 50% cumulative volume calculated from the side of the particle with the smallest particle size in a particle size distribution measured, for example, by laser diffraction method.

[0076] D90 can refer to the particle size corresponding to 90% cumulative volume calculated from the side of the particle with the smallest particle size in a particle size distribution measured, for example, by laser diffraction method.

[0077] D10 can refer to the particle size corresponding to 10% cumulative volume calculated from the side of the particle with the smallest particle size in a particle size distribution measured, for example, by laser diffraction method.

[0078] In addition, in the present disclosure, if the cross-section of a structure, rod, tube, fiber, etc. is spherical or circular, "diameter" indicates the particle diameter or circular diameter or average particle diameter or average circular diameter, and if the cross-section of a structure, rod, tube, fiber, etc. is non-spherical or non-circular, "diameter" indicates the major axis length or average major axis length.

[0079] As used herein, the term "metal" refers to (e.g., simultaneously) metals and metalloids (such as silicon and / or germanium) in elemental or ionic state.

[0080] As used herein, the term "alloy" refers to a mixture of two or more metals.

[0081] The term "electrode active material" as used herein refers to a suitable electrode material capable of undergoing lithiation and delithiation.

[0082] As used herein, the term "positive electrode active material" refers to a suitable positive electrode material capable of undergoing lithiation and delithiation.

[0083] As used herein, the term "negative electrode active material" refers to a suitable negative electrode material capable of undergoing lithiation and delithiation.

[0084] As used herein, the term "lithiation" and its variants refer to the process of adding (e.g., diffusing) lithium ions into the electrode active material.

[0085] As used herein, the term "delithiation" and variations thereof refer to the process of removing lithium ions from an electrode active material.

[0086] As used herein, the term "charging" and variations thereof refer to the process of providing electrochemical energy to a battery.

[0087] As used herein, the term "discharging" and variations thereof refer to the process of removing electrochemical energy from a battery.

[0088] As used herein, the term "positive electrode" and variations thereof refer to an electrode at which electrochemical reduction and lithiation occur during discharge.

[0089] As used herein, the term "negative electrode" and variations thereof refer to an electrode at which electrochemical oxidation and delithiation occur during discharge.

[0090] Hereinafter, a composite positive electrode active material, a positive electrode including the same, a lithium battery, and a method for preparing the composite positive electrode active material according to one or more embodiments will be described in more detail.

[0091] The composite positive electrode active material may include: a first core including a first lithium transition metal oxide; a second core including a second lithium transition metal oxide; and a shell conformal with the surface of at least one of the first core and the second core, wherein the shell may include a first metal oxide (e.g., one or more first metal oxides or at least one first metal oxide), a first carbonaceous material, and a second carbonaceous material, the first metal oxide may be disposed within a matrix of the first carbonaceous material, and the first metal oxide may be represented by M a O b (0 < a ≤ 3 and 0 < b < 4, where, if (e.g., when) a is 1, 2, or 3, then b is not an integer), M may be at least one metal selected from Groups 2 to 13, 15, and 16 of the periodic table, the second carbonaceous material may include a fibrous carbonaceous material having an aspect ratio of 10 or greater, the first lithium transition metal oxide and the second lithium transition metal oxide have different particle sizes from each other, the first lithium transition metal oxide may include primary particles having a particle size of 3 μm or greater, and the second lithium transition metal oxide may include primary particles having a particle size of 1 μm or greater.

[0092] Hereinafter, the following description is provided for the purpose of providing a theoretical basis to support the excellent or suitable effects of the composite positive electrode active material according to the presented embodiments; however, it should be understood that the description is provided to further understand the present disclosure and should not be construed as limiting the present disclosure in any way.

[0093] The composite positive electrode active material may include: a first core / shell structure including a shell disposed on a first core; and a second core / shell structure including a shell disposed on a second core. The first core may include a first lithium transition metal oxide, and the second core may include a second lithium transition metal oxide. Since the first lithium transition metal oxide and the second lithium transition metal oxide have different particle sizes from each other, the first core / shell structure and the second core / shell structure may have, for example, different particle sizes from each other. The first core / shell structure and the second core / shell structure may both have, for example Figure 1 the structure shown in

[0094] Referring to Figure 1 , the core / shell structure 100 may include a core 10 and a shell 20 disposed substantially continuously or substantially discontinuously along the surface of the core 10. The shell 20 may completely or partially cover the core 10. The shell 20 may include a first metal oxide 21, a first carbonaceous material 22, and a second carbonaceous material 23. The second carbonaceous material 23 may include fibrous carbon having an aspect ratio of 10 or greater. If (e.g., when) the core / shell structure 100 is prepared, the shell 20 may be disposed on the lithium transition metal oxide core 10 by using a composite including a plurality of first metal oxides 21 disposed in a matrix of the first carbonaceous material 22. Accordingly, the shell 20 may be disposed substantially uniformly on the core 10 while preventing or reducing the aggregation of the first carbonaceous material 22. The shell 20 disposed on the core 10 may effectively or suitably prevent or reduce the contact between the core 10 and the electrolyte. At least in part due to effectively or suitably preventing or reducing the contact between the core 10 and the electrolyte, the shell 20 may prevent or reduce an undesired or side reaction that may occur if the core 10 and the electrolyte come into contact with each other. In addition, by disposing the shell 20 on the core 10, cation mixing that may occur during the contact between the core 10 and the electrolyte may be suppressed or reduced. The suppression or reduction of cation mixing due to the contact between the core 10 and the electrolyte may suppress or reduce the formation of a resistance layer inside and / or on the surface of the composite positive electrode active material. In addition, disposing the shell 20 on the core 10 may also suppress or reduce the elution (e.g., loss) of transition metal ions from the lithium transition metal oxide core 10.

[0095] The first carbonaceous material 22 may be, for example, a crystalline carbonaceous material. The first carbonaceous material 22 may be, for example, a carbonaceous nanostructure. The first carbonaceous material 22 may be, for example, a two-dimensional carbonaceous nanostructure. For example, the first carbonaceous material 22 may be graphene. In this case, since the shell 20 including graphene and / or its matrix has appropriate flexibility, it can easily or suitably adapt to the volume change of the core 10 during the cycling of the battery, and the crack formation inside the core 10 can be suppressed or reduced. Due to the high electronic conductivity of graphene, the interfacial resistance between the core 10 and the electrolyte can be reduced. Therefore, with the introduction of the shell 20 including graphene, the internal resistance of the resulting lithium battery including the composite positive electrode active material can be maintained or reduced. On the contrary, the carbonaceous nanostructure materials of the prior art may easily aggregate, so it may be difficult to form a substantially uniform coating on the lithium transition metal oxide core.

[0096] The second carbonaceous material 23 may be fibrous carbon with an aspect ratio of 10 or more. Since the shell 20 includes the second carbonaceous material, the conduction path in the core / shell structure 100 and the composite positive electrode active material including it can be further extended. The second carbonaceous material 23 can reduce the internal resistance of the positive electrode including the composite positive electrode active material by forming a three-dimensional conductive network between multiple particles of the core / shell structure 100. Since the fibrous carbon is fixed on the core / shell structure 100, a substantially uniform and stable three-dimensional conductive network can be formed between multiple particles of the core / shell structure 100. Therefore, since the core / shell structure 100 includes the second carbonaceous material 23, a lithium battery provided with (e.g., including) the composite positive electrode active material can have improved high-rate performance. As a comparable example, a simple mixture of a lithium transition metal oxide core and fibrous carbon (e.g., as the second carbonaceous material 23) may not be able to form a substantially uniform three-dimensional conductive network between multiple lithium transition metal oxide core particles due to the aggregation of fibrous carbon and the like.

[0097] Refer to Figure 2, the second carbonaceous material 23 may have an aspect ratio of 10 or greater, or 20 or greater. For example, the second carbonaceous material 23 may have an aspect ratio of from about 10 to about 100,000, from about 10 to about 80,000, from about 10 to about 50,000, from about 10 to about 10,000, from about 10 to about 5,000, from about 10 to about 1,000, from about 10 to about 500, from about 10 to about 100, or from about 10 to about 50. The aspect ratio of the second carbonaceous material 23 is, for example, the ratio of the length of the major axis passing through the center of the second carbonaceous material 23 to the length of the minor axis intersecting (e.g., substantially perpendicular to) the major axis, where the major axis passes through the center of the second carbonaceous material 23 and the second carbonaceous material 23 in its length (e.g., elongated) direction, and the minor axis intersects (e.g., substantially perpendicular to) the major axis and may be the diameter of the second carbonaceous material 23. For example, the second carbonaceous material 23 may have a diameter of 50 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less. For example, the second carbonaceous material 23 may have a diameter of from about 1 nm to about 50 nm, from about 1 nm to about 30 nm, or from about 1 nm to about 10 nm. If (e.g., when) the diameter of the second carbonaceous material 23 is too large (e.g., outside the recited range), the absolute number of filaments per unit volume (or the absolute number of strands per unit volume) decreases, and thus the effect of reducing the internal resistance may become insignificant or may be inappropriately reduced. If (e.g., when) the diameter of the second carbonaceous material 23 is too small (e.g., outside the recited range), it may be difficult to obtain a substantially uniform dispersion. For example, the second carbonaceous material 23 may have a length of 1,000 μm or less, 100 μm or less, 50 μm or less, 10 μm or less, 5 μm or less, 2 μm or less, 1 μm or less, 500 nm or less, or 300 nm or less. For example, the second carbonaceous material 23 may have a length of from about 100 nm to about 1,000 μm, from about 100 nm to about 500 μm, from about 100 nm to about 100 μm, from about 100 nm to about 50 μm, from about 100 nm to about 10 μm, from about 100 nm to about 5 μm, from about 100 nm to about 2 μm, from about 100 nm to about 1 μm, from about 100 nm to about 500 nm, or from about 100 nm to about 300 nm. For example, the second carbonaceous material 23 may have a length of from about 500 nm to about 1,000 μm, from about 500 nm to about 500 μm, from about 500 nm to about 100 μm, from about 500 nm to about 50 μm, from about 500 nm to about 10 μm, from about 500 nm to about 5 μm, or from about 500 nm to about 2 μm. As the length of the second carbonaceous material 23 increases, the internal resistance of the electrode can decrease. If (e.g., when) the length of the second carbonaceous material 23 is too small (e.g., outside the recited range), it may be difficult to provide an effective or suitable conduction path.

[0098] Refer toFigure 2 The first lithium transition metal oxide may include primary particles having a particle size of 3 μm or more. The primary particles having a particle size of 3 μm or more may have an integral particle form. Since the first lithium transition metal oxide is an integral particle having a particle size of 3 μm or more, the side reactions with the electrolyte during charging and discharging can be reduced due to the reduced specific surface area and the reduced crack formation during the charging and discharging process. The cycle performance of a lithium battery using a composite positive electrode active material including the first lithium transition metal oxide can be further improved. However, if the first lithium transition metal oxide is an aggregate of a plurality of primary particles having a particle size of 3 μm or less, for example, a secondary particle, the specific surface area of the aggregate increases, and thus the side reactions with the electrolyte during the charging and discharging process may increase. The primary particles having a particle size of 3 μm or more included in the first lithium transition metal oxide may be, for example, single crystal particles.

[0099] In some embodiments, the second lithium transition metal oxide may include primary particles having a particle size of 1 μm or more. The primary particles having a particle size of 1 μm or more may have an integral particle form. Since the second lithium transition metal oxide is an integral particle having a particle size of 1 μm or more, the side reactions with the electrolyte during charging and discharging can be reduced due to the reduced specific surface area and the reduced crack formation during the charging and discharging process. The cycle performance of a lithium battery using a composite positive electrode active material including the second lithium transition metal oxide can be further improved. However, if the second lithium transition metal oxide is an aggregate of a plurality of primary particles having a particle size of 1 μm or less (e.g., a secondary particle), the specific surface area of the aggregate increases, and thus the crack formation during charging and discharging and the side reactions with the electrolyte during the charging and discharging process may increase, which is likely to cause deterioration. The primary particles having a particle size of 1 μm or more included in the second lithium transition metal oxide may be, for example, single crystal particles.

[0100] The composite positive electrode active material may include a first core / shell structure including a first lithium transition metal oxide and a second core / shell structure including a second lithium transition metal oxide. Since the first core / shell structure and the second core / shell structure have different particle sizes from each other, the second core / shell structure may be disposed in the voids between the first core / shell structures, or the first core / shell structure may be disposed in the voids between the second core / shell structures. In the presented embodiments, additionally disposing another type or kind of core / shell structure particles having a size different from the size of the one type or kind of core / shell structure particles in the voids between the one type or kind of core / shell structure particles may shorten the ion movement path in the positive electrode and thus improve the ionic conductivity of the positive electrode including the composite positive electrode active material. Further, since the shell disposed on the core includes a carbonaceous material, additionally disposing another type or kind of core / shell structure particles having a different size in the voids between the one type or kind of core / shell structure particles may shorten the electron movement path in the positive electrode and improve the electronic conductivity of the positive electrode including the composite positive electrode active material. Accordingly, a lithium battery including the composite positive electrode active material may have improved high-temperature cycle performance while suppressing or reducing an increase in the internal resistance of the lithium battery. Further, additionally disposing another type or kind of core / shell structure particles having a different size in the voids between the one type or kind of core / shell structure particles increases the mixture density of the positive electrode, and as a result, the energy density of the lithium battery including the composite positive electrode active material may be further improved. For example, in a positive electrode including a positive electrode active material, providing a carbonaceous conductive material in the voids between the positive electrode active material particles (e.g., in the voids between the positive electrode active material particles) may improve the electronic conductivity of the positive electrode; however, due to the lack of ionic conductivity in the carbonaceous conductive material, the positive electrode may exhibit a reduced ionic conductivity. Further, as the total thickness of the positive electrode active material layer increases, the positive electrode including the positive electrode active material layer may exhibit a significant reduction in ionic conductivity. Accordingly, a lithium battery employing such a positive electrode may exhibit a significant reduction in performance.

[0101] In the composite positive electrode active material according to the presented embodiments, the first lithium transition metal oxide may be a large-diameter lithium transition metal oxide having a particle diameter larger than that of the second lithium transition metal oxide. The second lithium transition metal oxide may be a small-diameter lithium transition metal oxide having a particle diameter smaller than that of the first lithium transition metal oxide. For example, the first core may be a large-diameter lithium transition metal oxide, and the second core may be a small-diameter lithium transition metal oxide. For example, a second core / shell structure having an average particle diameter smaller than the average particle diameter of the first core / shell structure may be disposed in the void between the first core / shell structures. Since the small-diameter particles of the second core / shell structure are disposed in the void between the large-diameter particles of the first core / shell structure, the ionic conductivity and / or the electronic conductivity of the positive electrode including the composite positive electrode active material can be improved. In addition, the energy density of the positive electrode including the composite positive electrode active material can be improved. As a result, the energy density and the cycle performance of the lithium battery including the composite positive electrode active material can be improved.

[0102] The first lithium transition metal oxide and the second lithium transition metal oxide may have, for example, a bimodal particle size distribution in the particle size distribution graph. For example, in the particle size distribution graph obtained using a particle size analyzer (PSA) or the like, the composite positive electrode active material may exhibit a bimodal particle size distribution having two peaks. The bimodal particle size distribution may have a first peak corresponding to the first lithium transition metal oxide and a second peak corresponding to the second lithium transition metal oxide.

[0103] The first lithium transition metal oxide and the second lithium transition metal oxide may have a particle diameter ratio of, for example, about 2:1 to about 10:1, about 3:1 to about 10:1, about 3:1 to about 8:1, 3:1 to about 6:1, or about 3:1 to about 5:1. Since the first lithium transition metal oxide and the second lithium transition metal oxide have a particle diameter ratio within any of the above ranges, the energy density and / or the cycle characteristics of the lithium battery including the composite positive electrode active material can be further improved.

[0104] The first lithium transition metal oxide may have a particle size of, for example, about 3 μm to about 10 μm, about 3 μm to about 8 μm, or about 4 μm to about 7 μm. The particle size of the first lithium transition metal oxide may be, for example, the median particle size (D50). The second lithium transition metal oxide may have a particle size of, for example, about 1 μm to less than 5 μm, or about 1 μm to about 4 μm. The particle size of the second lithium transition metal oxide may be, for example, the median particle size (D50). Since the first lithium transition metal oxide and the second lithium transition metal oxide respectively have an average particle size within any of the above ranges, the energy density and / or cycle characteristics of the lithium battery including the composite positive electrode active material can be further improved. The particle sizes of the first lithium transition metal oxide and the second lithium transition metal oxide can be measured, for example, by using a measuring device of laser diffraction and / or dynamic light scattering. The particle size can be measured by, for example, a laser scattering particle size distribution analyzer (e.g., LA-920 manufactured by HORIBA), and may be the volume-based median particle size (D50) with a cumulative percentage of 50% by volume starting from the smallest particle size. In some embodiments, the particle sizes of the first lithium transition metal oxide and / or the second lithium transition metal oxide can be measured using scanning electron microscope (SEM) images and / or optical microscope images.

[0105] The weight ratio of the first lithium transition metal oxide to the second lithium transition metal oxide may be, for example, about 90:10 to about 60:40, about 85:15 to about 65:35, about 80:20 to about 65:35, or about 75:25 to about 65:35. Since the first lithium transition metal oxide and the second lithium transition metal oxide have a weight ratio within any of the above ranges, the energy density and / or cycle characteristics of the lithium battery including the composite positive electrode active material can be further improved.

[0106] The composite positive electrode active material may have, for example, a specific surface area of 0.8 m 2 / g or less, 0.5 m 2 / g or less, or 0.3 m 2 / g or less. The composite positive electrode active material may have, for example, about 0.1 m 2 / g to about 0.8 m 2 / g, about 0.1 m 2 / g to about 0.5 m 2 / g, or about 0.1 m 2 / g to about 0.3 m 2The specific surface area per g. Since the composite positive electrode active material has a relatively small specific surface area within any of the above ranges, side reactions with the electrolyte can be suppressed or reduced. As a result, the cycle performance of a lithium battery including the composite positive electrode active material with a reduced specific surface area can be further improved. For example, the specific surface area of a comparable composite positive electrode active material including secondary particles formed from a plurality of primary particles can be, for example, 1 m 2 / g or greater. Since the composite positive electrode active material including secondary particles has an increased specific surface area, side reactions with the electrolyte may increase. As a result, the cycle performance of a lithium battery including the composite positive electrode active material with an increased specific surface area may deteriorate.

[0107] The second carbonaceous material 23 may include, for example, carbon nanofibers, carbon nanotubes, or a combination thereof.

[0108] For example, the carbon nanotubes may include a primary carbon nanotube structure, a secondary carbon nanotube structure formed by aggregation of a plurality of primary carbon nanotube structures, or a combination thereof.

[0109] The primary carbon nanotube structure may be a single carbon nanotube unit. The carbon nanotube unit may be in the form of a cylinder having a nanosized diameter and having a sp 2 bond structure of graphene sheets. Depending on the bending angle and structure of the graphene sheets, the carbon nanotube unit may exhibit the characteristics of a conductor or a semiconductor. Depending on the number of bonds constituting the wall, the carbon nanotube unit can be classified as a single-walled carbon nanotube (SWCNT), a double-walled carbon nanotube (DWCNT), a multi-walled carbon nanotube (MWCNT), etc. The smaller the wall thickness of the carbon nanotube unit, the lower its resistance.

[0110] The primary carbon nanotube structure can include, for example, SWCNT, DWCNT, MWCNT, or a combination thereof. For example, the primary carbon nanotube structure can have a diameter of 1 nm or greater, or 2 nm or greater. For example, the primary carbon nanotube structure can have a diameter of 20 nm or less, or 10 nm or less. For example, the primary carbon nanotube structure can have a diameter of about 1 nm to about 20 nm, about 1 nm to about 15 nm, or about 1 nm to about 10 nm. For example, the primary carbon nanotube structure can have a length of 100 nm or greater, or 200 nm or greater. For example, the primary carbon nanotube structure can have a length of 2 μm or less, 1 μm or less, 500 nm or less, or 300 nm or less. For example, the primary carbon nanotube structure can have a length of about 100 nm to about 2 μm, about 100 nm to about 1 μm, about 100 nm to about 500 nm, about 100 nm to about 400 nm, about 100 nm to about 300 nm, or about 200 nm to about 300 nm. The diameter and length of the primary carbon nanotube structure can be measured from a scanning electron microscope (SEM) image and / or a transmission electron microscope (TEM) image. In one or more embodiments, the diameter and / or length of the primary carbon nanotube structure can be measured by a laser diffraction method.

[0111] The secondary carbon nanotube structure can be a structure formed by assembling the primary carbon nanotube structures to form a bundle type (or class) or a rope type (or class) wholly or partially. The secondary carbon nanotube structure can include, for example, bundle type (or class) carbon nanotubes, rope type (or class) carbon nanotubes, or a combination thereof. For example, the secondary carbon nanotube structure can have a diameter of 2 nm or greater, or 3 nm or greater. For example, the secondary carbon nanotube structure can have a diameter of 50 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less. For example, the secondary carbon nanotube structure can have a diameter of about 2 nm to about 50 nm, about 2 nm to about 30 nm, or about 2 nm to about 20 nm. For example, the secondary carbon nanotube structure can have a length of 500 nm or greater, 700 nm or greater, 1 μm or greater, or 10 μm or greater. For example, the secondary carbon nanotube structure can have a length of 1,000 μm or less, 500 μm or less, or 100 μm or less. For example, the secondary carbon nanotube structure can have a length of about 500 nm to about 1,000 μm, about 500 nm to about 500 μm, about 500 nm to about 200 μm, about 500 nm to about 100 μm, or about 500 nm to about 50 μm. The diameter and length of the secondary carbon nanotube structure can be measured from an SEM image and / or an optical microscope image. In some embodiments, the diameter and / or length of the secondary carbon nanotube structure can be measured by a laser diffraction method.

[0112] The secondary carbon nanotube structure can be used in the preparation of a composite positive electrode active material, for example, by being dispersed in a solvent or the like and converted into a primary carbon nanotube structure.

[0113] With respect to the total weight of the first carbonaceous material 22 and the second carbonaceous material 23, the content (e.g., amount) of the second carbonaceous material 23 can be, for example, about 5 wt% to about 95 wt%, about 10 wt% to about 90 wt%, about 20 wt% to about 80 wt%, about 30 wt% to about 70 wt%, or about 40 wt% to about 60 wt%. The first carbonaceous material 22 and the second carbonaceous material 23 included within any of the above ranges in the composite positive electrode active material can more effectively or appropriately ensure the conduction path in the composite positive electrode active material, and thus the internal resistance of the composite positive electrode active material can be further reduced. As a result, the cycle performance of the lithium battery including the composite positive electrode active material can be further improved. With respect to the total weight of the composite positive electrode active material, the content (e.g., amount) of the second carbonaceous material 23 can be, for example, about 0.01 wt% to about 1 wt%, about 0.01 wt% to about 0.8 wt%, about 0.01 wt% to about 0.5 wt%, 0.01 wt% to about 0.3 wt%, or about 0.01 wt% to about 0.1 wt%. The second carbonaceous material 23 included within any of the above ranges in the composite positive electrode active material can ensure the conduction path in the composite positive electrode active material, and thus the internal resistance of the composite positive electrode active material can be further reduced. As a result, the cycle performance of the lithium battery including the composite negative electrode active material can be further improved.

[0114] The second carbonaceous material 23 can be disposed on the surface of the composite positive electrode active material. Referring to Figure 2 the SEM image of Figure 1As shown, the second carbonaceous material 23 may protrude from the surface of the core / shell structure 100. Thus, the second carbonaceous material 23 can effectively or suitably provide an electrical conduction network between multiple core / shell structures 100. Since the second carbonaceous material 23 is disposed in the matrix of the first carbonaceous material 22, the second carbonaceous material 23 can be easily or suitably coated on the core 10. The matrix of the first carbonaceous material 22 can act as a binder that bonds the core and the second carbonaceous material 23 together. Thus, in the absence of the matrix of the first carbonaceous material 22, it may be difficult to coat the second carbonaceous material 23 on the core 10, or during the process of preparing the positive electrode paste, the second carbonaceous material 23 may relatively easily detach from the core 10. Different from the first carbonaceous material 22 including the presented embodiments, if (e.g., when) a binder is added to bond the lithium transition metal oxide core 10 and the second carbonaceous material 23, since the core 10 is covered with, for example, an insulating binder, the internal resistance of the composite positive electrode active material may increase. If (e.g., when) the core covered with the binder and the second carbonaceous material 23 are subjected to high-temperature heat treatment to carbonize the carbonized binder, the core 10 and the second carbonaceous material 23 may deteriorate during the heat treatment.

[0115] The shell 20 may further include a first metal oxide 21 and a first carbonaceous material 22. Since the first carbonaceous material 22 is derived from, for example, a graphene matrix, the first carbonaceous material 22 has a lower density and a higher porosity relative to the carbonaceous material derived from a graphite material. The crystal plane spacing d002 of the first carbonaceous material 22 may be, for example or greater, or greater, or greater, or greater, or greater, or greater, or or greater. The crystal plane spacing d002 of the first carbonaceous material 22 included in the shell 20 may be, for example, about to about about to about about to about about to about or about to about In some embodiments, the crystal plane spacing d002 of the carbonaceous material derived from a graphite material may be, for example or smaller, or about to about The first metal oxide 21 can prevent or reduce the deterioration of the lithium transition metal oxide included in the core 10 during charging / discharging at high voltage due to its withstand voltage property. For example, the shell 20 can include a single type or kind of the first metal oxide 21, or two or more different types (kinds) of the first metal oxide 21. Therefore, the high-temperature cycle performance of the lithium battery including the composite positive electrode active material can be improved. For example, with respect to the total weight of the composite positive electrode active material, the content (e.g., amount) of the shell 20 can be about 0.1 wt% to about 5 wt%, about 0.1 wt% to about 4 wt%, about 0.1 wt% to about 3 wt%, about 0.1 wt% to about 2.5 wt%, about 0.1 wt% to about 2 wt%, or about 0.1 wt% to about 1.5 wt%. With respect to the total weight of the composite positive electrode active material, the content (e.g., amount) of the first metal oxide 21 can be, for example, about 0.06 wt% to about 3 wt%, about 0.06 wt% to about 2.4 wt%, about 0.06 wt% to about 1.8 wt%, about 0.06 wt% to about 1.5 wt%, about 0.06 wt% to about 1.2 wt%, or about 0.06 wt% to about 0.9 wt%. Since the composite positive electrode active material includes the shell 20 and the first metal oxide 21 in amounts within any of the above ranges, the lithium battery can have further improved cycle performance.

[0116] The first metal oxide 21 can include a first metal, and the first metal can be at least one selected from Al, Nb, Mg, Sc, Ti, Zr, V, W, Mn, Fe, Co, Pd, Cu, Ag, Zn, Sb, and Se. The first metal oxide 21 can be, for example, selected from Al2O z (0 < z < 3), NbO x (0 < x < 2.5), MgO x (0 < x < 1), Sc2O z (0 < z < 3), TiO y (0 < y < 2), ZrO y (0 < y < 2), V2O z (0 < z < 3), WO y (0 < y < 2), MnO y (0 < y < 2), Fe2O z (0 < z < 3), Co3O w (0 < w < 4), PdO x (0 < x < 1), CuO x (0 < x < 1), AgO x (0 < x < 1), ZnO x (0 < x < 1), Sb2O z (0 < z < 3), and SeOy (At least one of) within (0 < y < 2). Since the first metal oxide 21 is disposed inside the matrix of the first carbonaceous material 22, the uniformity (or substantially uniformity) of the shell 20 disposed on the core 10 can be improved, and the voltage resistance property of the composite positive electrode active material can be further improved. For example, the shell 20 may include Al2O x (0 < x < 3) as the first metal oxide 21.

[0117] The shell 20 may further include one or more types (species) of second metal oxides represented by M a O c (0 < a ≤ 3 and 0 < c ≤ 4, where, if (for example, when) a is 1, 2, or 3, then c is an integer). M may be at least one metal among Groups 2 to 13, 15, and 16 of the periodic table. For example, the second metal oxide may include the same metal as the metal in the first metal oxide 21, and the ratio c / a of a and c in the second metal oxide may have a value greater than the ratio b / a of a and b in the first metal oxide 21. For example, c / a > b / a can be satisfied. The second metal oxide may be selected from, for example, Al2O3, NbO, NbO2, Nb2O5, MgO, Sc2O3, TiO2, ZrO2, V2O3, WO2, MnO2, Fe2O3, Co3O4, PdO, CuO, AgO, ZnO, Sb2O3, and SeO2. The first metal oxide 21 may be, for example, a reduction product of the second metal oxide. The first metal oxide 21 may be obtained by partial reduction or complete reduction of the second metal oxide. Therefore, the first metal oxide 21 may have a lower oxygen content (for example, amount) and a lower metal oxidation number relative to the second metal oxide. For example, the shell 20 may include Al2O x (0 < x < 3) as the first metal oxide 21 and Al2O3 as the second metal oxide.

[0118] For example, the shell 20 may include a first carbonaceous material 22, and for example, the core 10 may include a lithium transition metal oxide. Further, the transition metal of the first carbonaceous material 22 and the lithium transition metal oxide may be chemically bonded, for example, by a chemical bond. The carbon atoms (C) of the first carbonaceous material 22 and the transition metal (Me) of the lithium transition metal oxide may be chemically bonded by, for example, a C-Me bond (e.g., a C-Co bond). The carbon atoms (C) of the first carbonaceous material 22 and the transition metal (Me) of the lithium transition metal oxide may be chemically bonded via an oxygen atom by, for example, a C-O-Me bond (e.g., a C-O-Co bond). The chemical bonding by a chemical bond between the first carbonaceous material 22 provided in the shell 20 and the lithium transition metal oxide provided in the core 10 may result in the complexation of the core 10 and the shell 20. Thus, the resulting composite positive electrode active material may be distinguishable from a simple physical mixture of the first carbonaceous material 22 and the lithium transition metal oxide. Further, the first metal oxide 21 and the first carbonaceous material 22 may be chemically bonded by a chemical bond. Here, the chemical bond may be, for example, a covalent bond or an ionic bond.

[0119] The shell 20 may include at least one selected from among the first metal oxide 21 and the second metal oxide, and at least one selected from among the first metal oxide 21 and the second metal oxide may have a particle diameter of, for example, about 0.1 nm to about 100 nm, about 1 nm to about 50 nm, about 1 nm to about 30 nm, about 5 nm to about 30 nm, or about 10 nm to about 30 nm. Since the first metal oxide 21 and / or the second metal oxide has a particle diameter within the above nano-size range, the first metal oxide 21 and / or the second metal oxide may be more uniformly (e.g., more substantially uniformly) distributed within the matrix of the first carbonaceous material 22. If the particle diameter of one or more of the first metal oxide 21 and the second metal oxide is excessively increased (e.g., outside the recited range), the internal resistance of the composite positive electrode active material may increase due to an increase in the thickness of the shell 20. If the particle diameter of one or more of the first metal oxide 21 and the second metal oxide is excessively decreased (e.g., outside the recited range), it may be difficult to disperse substantially uniformly.

[0120] The shell 20 may include a first metal oxide 21 and / or a second metal oxide, and may include a first carbonaceous material 22. The first carbonaceous material 22 may be disposed in a direction protruding from the surface of the first metal oxide 21 and / or the second metal oxide. The first carbonaceous material 22 may be disposed in a direction protruding from the surface of the first metal oxide 21 and / or the second metal oxide by directly growing from the surface of the first metal oxide 21 and / or the second metal oxide. The first carbonaceous material 22 disposed in a direction protruding from the surface of the first metal oxide 21 and / or the second metal oxide may be, for example, a two-dimensional carbonaceous nanostructure, a carbonaceous flake, and / or graphene.

[0121] For example, the composite positive electrode active material may further include a third metal doped on the core 10 and / or a third metal oxide coated on the core 10. The core 10 is at least one of a first core and a second core. In addition, the shell 20 may be disposed on the third metal doped on the core 10 and / or the third metal oxide coated on the core 10. For example, after doping a third metal on the surface of the lithium transition metal oxide core 10 or coating a third metal oxide on the surface of the lithium transition metal oxide core, the shell 20 may be disposed on the third metal and / or the third metal oxide. For example, the composite positive electrode active material may include: a core; an intermediate layer disposed on the core; and a shell disposed on the intermediate layer, wherein the intermediate layer may include a third metal and / or a third metal oxide. The third metal may be at least one metal selected from Al, Zr, W, and Co, and the third metal oxide may be Al2O3, Li2O-ZrO2, WO2, CoO, Co2O3, Co3O4, or a combination thereof.

[0122] For example, the shell may have a thickness of about 0.1 nm to about 1 μm, about 0.5 nm to about 500 nm, about 1 nm to about 100 nm, about 1 nm to about 50 nm, or about 1 nm to about 20 nm. For example, the shell may have a thickness of about 0.1 nm to about 1 μm, about 1 nm to about 500 nm, about 1 nm to about 300 nm, about 10 nm to about 200 nm, or about 10 nm to about 100 nm. Since the shell has a thickness within any of the above ranges, the electronic conductivity of the positive electrode including the composite positive electrode active material can be further improved.

[0123] The shell can have, for example, a single-layer structure or a multi-layer structure. For example, the multi-layer structure can have a structure with two to five layers. For example, the single-layer structure can be a single-layer structure including a first metal oxide or can be a single-layer structure including a first metal oxide and a second metal oxide. For example, the multi-layer structure can have a structure including the following: a first layer including a first metal oxide; and a second layer including a second metal oxide. For example, the multi-layer structure can have a structure including the following: a first layer including a third metal oxide; and a second layer including a first metal oxide. For example, the multi-layer structure can have a structure including the following: a first layer including a third metal oxide; and a second layer including a first metal oxide and a second metal oxide. For example, the multi-layer structure can have a structure including the following: a first layer including a first metal oxide; and a second layer including a third metal oxide. For example, the multi-layer structure can have a structure including the following: a first layer including a first metal oxide and a second metal oxide; and a second layer including a third metal oxide.

[0124] The shell can be a dry coating prepared by a dry method. For example, the dry method can be mechanical grinding, but is not limited thereto and can be any suitable method used as a dry method in the art.

[0125] For example, relative to the total weight of the composite positive electrode active material, the content (e.g., amount) of the shell can be 5 wt% or less, 4 wt% or less, 3 wt% or less, 2 wt% or less, 1.5 wt% or less, or 1 wt% or less. For example, relative to the total weight of the composite positive electrode active material, the content (e.g., amount) of the shell can be from about 0.01 wt% to about 5 wt%, from about 0.03 wt% to about 3 wt%, from about 0.03 wt% to about 2 wt%, from about 0.03 wt% to about 1 wt%, from about 0.03 wt% to about 0.5 wt%, or from about 0.03 wt% to about 0.1 wt%. Relative to the total weight of the composite positive electrode active material, the content (e.g., amount) of the first metal oxide can be, for example, from about 0.006 wt% to about 3 wt%, from about 0.018 wt% to about 1.8 wt%, from about 0.018 wt% to about 1.2 wt%, from about 0.018 wt% to about 0.6 wt%, from about 0.018 wt% to about 0.3 wt%, or from about 0.018 wt% to about 0.06 wt%. Since the composite positive electrode active material includes the shell and the first metal oxide in amounts within any of the above ranges respectively, the cycle performance of the lithium battery can be further improved.

[0126] A shell that is conformal (or substantially conformal) with the surface of the core can be formed, for example, by coating the core with a composite including a first metal oxide and a first carbonaceous material (e.g., graphene), by grinding, etc. Thus, the shell disposed on the surface of the core, continuously or discontinuously, can include at least one selected from the group consisting of a composite including a first metal oxide and a first carbonaceous material (e.g., graphene) and a ground product of the composite. The first metal oxide can be disposed in a matrix of the carbonaceous material (e.g., a graphene matrix). For example, the shell can be prepared from a composite including a first metal oxide and a first carbonaceous material such as graphene. In addition to the first metal oxide, the composite can further include a second metal oxide. For example, the composite can include two or more types (species) of the first metal oxide. For example, the composite can include two or more types (species) of the first metal oxide and two or more types (species) of the second metal oxide.

[0127] The content (e.g., amount) of at least one of the composite and its ground product can be, for example, 5 wt% or less, 3 wt% or less, 2 wt% or less, 2.5 wt% or less, or 1.5 wt% or less, relative to the total weight of the composite positive electrode active material. For example, the content (e.g., amount) of at least one of the composite and its ground product can be from about 0.01 wt% to about 5 wt%, from about 0.03 wt% to about 3 wt%, from about 0.03 wt% to about 2 wt%, from about 0.03 wt% to about 1 wt%, from about 0.03 wt% to about 0.5 wt%, or from about 0.03 wt% to about 0.1 wt%, relative to the total weight of the composite positive electrode active material. Since the composite positive electrode active material includes at least one of the composite and its ground product in an amount within any of the above ranges, the cycle performance of the lithium battery including the composite positive electrode active material can be further improved.

[0128] The composite may further include at least one selected from a first metal oxide and a second metal oxide. At least one selected from the first metal oxide and the second metal oxide may have a particle size of about 1 nm to about 100 nm, about 1 nm to about 50 nm, about 1 nm to about 30 nm, about 5 nm to about 30 nm, or about 10 nm to about 30 nm. Since the first metal oxide and / or the second metal oxide has a particle size within the above nanometer size range, the first metal oxide and / or the second metal oxide can be more uniformly (e.g., substantially uniformly) distributed in the matrix of the first carbonaceous material of the composite. Thus, the composite can be uniformly (e.g., substantially uniformly) coated on the core without (or substantially without) aggregation and form a shell. In some embodiments, since the first metal oxide and / or the second metal oxide has a particle size within the above range, the first metal oxide and / or the second metal oxide can be more uniformly (e.g., substantially uniformly) disposed on the core. Thus, since the first metal oxide and / or the second metal oxide is uniformly (e.g., substantially uniformly) disposed on the core, the withstand voltage property can be achieved more effectively or suitably. The particle size of the first metal oxide and / or the second metal oxide can be measured, for example, by using a measuring device utilizing laser diffraction technology and / or dynamic light scattering technology. The particle size can be measured, for example, by a laser scattering particle size distribution analyzer (e.g., LA-920 manufactured by HORIBA), and is the volume-based median particle size (D50) at which the cumulative percentage from the smallest particle size is 50% by volume. The uniformity of at least one selected from the first metal oxide and the second metal oxide may have a deviation of 3% or less, 2% or less, or 1% or less. The uniformity can be measured by XPS, for example. Thus, at least one selected from the first metal oxide and the second metal oxide can be uniformly (e.g., substantially uniformly) distributed in the composite with a deviation of 3% or less, 2% or less, or 1% or less. In some embodiments, the particle size of the first metal oxide and / or the second metal oxide can be measured using a scanning electron microscope (SEM) image and / or an optical microscope image.

[0129] The composite may include a first carbonaceous material. For example, the first carbonaceous material may have a branched structure, and at least one metal oxide selected from the first metal oxide and the second metal oxide may be distributed in the branched structure of the first carbonaceous material. The branched structure of the first carbonaceous material may include, for example, a plurality of first carbonaceous material particles in contact with each other. Due to such a branched structure of the first carbonaceous material, one or more suitable conductive paths can be provided. For example, the first carbonaceous material may be graphene. For example, graphene may have a branched structure, and at least one metal oxide selected from the first metal oxide and the second metal oxide may be distributed within the branched structure of graphene. The branched structure of graphene may include, for example, a plurality of graphene particles in contact with each other. Due to such a branched structure of graphene, one or more suitable conductive paths can be provided.

[0130] The first carbonaceous material may have, for example, a spherical structure, and at least one metal oxide selected from the first metal oxide and the second metal oxide may be distributed in the spherical structure. The spherical structure of the first carbonaceous material may have a size of about 50 nm to about 300 nm. A plurality of first carbonaceous materials having a spherical structure can be provided. Due to the spherical structure of the first carbonaceous material, the composite may have a suitably firm structure. For example, the first carbonaceous material may be graphene. For example, graphene may have a spherical structure, and at least one metal oxide selected from the first metal oxide and the second metal oxide may be distributed within the spherical structure of graphene. The spherical structure of graphene may have a size of about 50 nm to about 300 nm. A plurality of graphene having an overall spherical structure (e.g., a plurality of graphene structures or particles) can be provided. Due to the spherical structure of graphene, the composite may have a suitably firm structure.

[0131] The first carbonaceous material may have, for example, a helical structure in which a plurality of spherical structures are connected, and at least one metal oxide selected from the first metal oxide and the second metal oxide may be distributed in the spherical structures of the helical structure. The helical structure of the first carbonaceous material may have a size of about 500 nm to about 100 μm. Due to the helical structure of the first carbonaceous material, the composite may have a suitably firm structure. For example, the first carbonaceous material may be graphene. Graphene may have, for example, a helical structure in which a plurality of spherical structures are connected, and at least one metal oxide selected from the first metal oxide and the second metal oxide may be distributed in the spherical structures of the helical structure. The helical structure of graphene may have a size of about 500 nm to about 100 μm. Due to the helical structure of graphene, the composite may have a suitably firm structure.

[0132] The first carbonaceous material may have, for example, a cluster structure in which a plurality of spherical structures are aggregated, and at least one metal oxide selected from among the first metal oxide and the second metal oxide may be distributed within the spherical structures of the cluster structure. The cluster structure of the first carbonaceous material may have a size of about 0.5 mm to about 10 cm. Since the first carbonaceous material has a cluster structure, the composite may have a suitably firm structure. For example, the first carbonaceous material may be graphene. Graphene may have, for example, a cluster structure in which a plurality of spherical structures are aggregated, and at least one metal oxide selected from among the first metal oxide and the second metal oxide may be distributed within the spherical structures of the cluster structure. The cluster structure of graphene may have a size of about 0.5 mm to about 10 cm. Since graphene has a cluster structure, the composite may have a firm structure.

[0133] The composite may have, for example, a wrinkled polyhedral sphere structure, and at least one selected from among the first metal oxide and the second metal oxide may be distributed inside or on the surface of the structure. Since the composite has such a polyhedral sphere structure, the composite can be easily or suitably coated on the irregularities of the irregular surface of the core.

[0134] The composite may be or have a planar structure, and at least one selected from among the first metal oxide and the second metal oxide may be distributed inside or on the surface of the structure. Since the composite has a two-dimensional planar structure, the composite can be easily or suitably coated on the irregularities of the irregular surface of the core.

[0135] The first carbonaceous material may extend a distance of 10 nm or less from the first metal oxide and may include at least 1 to 20 layers of the first carbonaceous material. For example, when a plurality of layers of the first carbonaceous material are stacked, the first carbonaceous material having a total thickness of 12 nm or less may be provided on the first metal oxide. For example, the total thickness of the first carbonaceous material may be about 0.6 nm to about 12 nm. For example, the first carbonaceous material may be graphene. Graphene may extend a distance of 10 nm or less from the first metal oxide and may include at least 1 to 20 layers of graphene. For example, when a plurality of layers of graphene are stacked, the graphene having a total thickness of 12 nm or less may be provided on the first metal oxide. For example, the total thickness of graphene may be about 0.6 nm to about 12 nm.

[0136] The composite positive electrode active material may include, for example, a first core and a second core, wherein the first core and the second core may each independently include, for example, a lithium transition metal oxide represented by at least one (e.g., any one) selected from Formula 1 to Formula 8.

[0137] Formula 1

[0138] Li a Cox M y O 2-b A b

[0139] In Formula 1,

[0140] 1.0 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0.9 ≤ x ≤ 1, 0 ≤ y ≤ 0.1, and x + y = 1,

[0141] M can be manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof, and

[0142] A can be F, S, Cl, Br, or a combination thereof.

[0143] Formula 2

[0144] Li a Ni x Co y M z O 2-b A b

[0145] In Formula 2,

[0146] 1.0 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0.8 ≤ x < 1, 0 ≤ y ≤ 0.3, 0 < z ≤ 0.3, and x + y + z = 1,

[0147] M can be manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof, and

[0148] A can be F, S, Cl, Br, or a combination thereof.

[0149] Formula 3

[0150] LiNi x Co y Mn z O2

[0151] Formula 4

[0152] LiNi x Co y Al z O2

[0153] In Formulas 3 and 4, 0.8 ≤ x ≤ 0.95, 0 ≤ y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1.

[0154] Formula 5

[0155] LiNi x Co y Mn z Al w O2

[0156] In Formula 5, 0.8 ≤ x ≤ 0.95, 0 ≤ y ≤ 0.2, 0 < z ≤ 0.2, 0 < w ≤ 0.2, and x + y + z + w = 1.

[0157] Formula 6

[0158] Li a Ni x Mn y M’ z O 2-b A b

[0159] In Formula 6,

[0160] 1.0 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0 < x ≤ 0.3, 0.5 ≤ y < 1, 0 < z ≤ 0.3, and x + y + z = 1,

[0161] M’ can be cobalt (Co), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof, and

[0162] A can be F, S, Cl, Br, or a combination thereof.

[0163] Formula 7

[0164] Li a M1 x M2 y PO 4-b X b

[0165] In Formula 7, 0.90 ≤ a ≤ 1.1, 0 ≤ x ≤ 0.9, 0 ≤ y ≤ 0.5, 0.9 < x + y < 1.1, and 0 ≤ b ≤ 2,

[0166] M1 can be chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof,

[0167] M2 can be magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y) or a combination thereof, and X can be O, F, S, P or a combination thereof.

[0168] Formula 8

[0169] Li a M3 z PO4

[0170] In Formula 8, 0.90 ≤ a ≤ 1.1, and 0.9 ≤ z ≤ 1.1, and

[0171] M3 can be chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof.

[0172] The positive electrode according to one or more embodiments may include a composite positive electrode active material. By including the composite positive electrode active material, the positive electrode can provide improved energy density, improved cycle performance, and / or increased conductivity.

[0173] Since the composite positive electrode active material includes a second lithium transition metal oxide as primary particles having a particle diameter of 1 μm or more, the second lithium transition metal oxide can be protected from rapid deterioration caused by side reactions during charging and discharging. Accordingly, the life characteristics of the lithium secondary battery can be improved. In addition, since the shell of the composite positive electrode active material includes a second carbonaceous material, the composite positive electrode active material can also be used as a conductive material. Accordingly, the amount of the conductive material used in the positive electrode can be reduced. Although the conductive material may be necessary or desirable for improving the conductivity of the battery, if (e.g., when) the amount of the conductive material increases, the mixture density of the positive electrode decreases, and as a result, the energy density of the lithium battery may decrease. In some embodiments, by using the above composite positive electrode active material, the positive electrode of the present disclosure can reduce the amount of the conductive material without increasing the internal resistance. Accordingly, as the mixture density of the positive electrode increases, the energy density of the lithium battery can thus increase. Specifically, in a high-capacity lithium battery, increasing the amount of the composite positive electrode active material while decreasing the amount of the conductive material can result in a significant or desirable increase in the energy density of the lithium battery.

[0174] The positive electrode can be prepared, for example, by a wet method. Here, the positive electrode can be prepared by the method described as an example below; however, the method of preparing the positive electrode is not necessarily limited to this method and can be adjusted according to the required or desired conditions.

[0175] First, a positive electrode active material composition can be prepared by combining the above positive electrode active material, conductive material, binder, and solvent. The prepared positive electrode active material composition can be directly coated on an aluminum current collector and dried to prepare a positive electrode plate provided with a positive electrode active material layer. In some embodiments, a film obtained by casting the positive electrode active material composition on a separate support and then separating the composition from the support can be laminated on the aluminum current collector to form a positive electrode plate having a positive electrode active material layer.

[0176] As the conductive material, carbon black, fine graphite particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fiber; carbon nanotubes; metal powders, metal fibers or metal tubes (such as copper, nickel, aluminum, and / or silver); and / or conductive polymers (such as polyphenylene derivatives) can be used, but the present disclosure is not limited thereto. Any suitable conductive material available in the art can be used. In some embodiments, for example, the positive electrode may not contain any conductive material.

[0177] As the binder, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), mixtures of the above polymers, and / or styrene-butadiene rubber polymers can be used, but the present disclosure is not limited thereto. Any suitable binder in the art can be used. As the solvent, N-methylpyrrolidone (NMP), acetone, and / or water can be used, but the present disclosure is not limited thereto. Any suitable solvent can be used.

[0178] It is also possible to form pores in the electrode plate by further adding a plasticizer and / or a pore former to the positive electrode active material composition.

[0179] The amount of each of the positive electrode active material, conductive material, binder, and solvent used in the positive electrode can be at a suitable level for use in a lithium battery. Depending on the intended or desired use purpose and configuration of the lithium battery, one or more of the conductive material, binder, and solvent may not be provided.

[0180] The amount of the binder used in the positive electrode can be about 0.1 wt% to about 10 wt%, or about 0.1 wt% to about 5 wt% relative to the total weight of the positive electrode active material layer. The amount of the composite positive electrode active material used in the positive electrode can be about 80 wt% to about 99 wt%, about 90 wt% to about 99 wt%, or about 95 wt% to about 99 wt% relative to the total weight of the positive electrode active material layer. The amount of the conductive material used in the positive electrode can be about 0.01 wt% to about 10 wt%, about 0.01 wt% to about 5 wt%, about 0.01 wt% to about 3 wt%, about 0.01 wt% to about 1 wt%, about 0.01 wt% to about 0.5 wt%, or about 0.01 wt% to about 0.1 wt% relative to the total weight of the positive electrode active material layer. In some embodiments, the conductive material may not be provided.

[0181] In addition to the above composite positive electrode active material, the positive electrode may further include a conventional positive electrode active material.

[0182] As the conventional positive electrode active material, any suitable lithium-containing metal oxide in the art can be used without limitation. For example, at least one of composite oxides of lithium and metals selected from cobalt, manganese, nickel, and combinations thereof can be used as the lithium-containing metal oxide. For example, the lithium-containing metal oxide can be represented by any of the following formulas: Li a A 1-b B b D2 (in the formula, 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B b O 2-c D c (in the formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.05); LiE 2-b B b O 4-c D c (in the formula, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B c D α (in the formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 < α ≤ 2); Li a Ni 1-b-c Co b B c O 2-α F α (in the formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 < α < 2); Li a Ni1-b-c Co b B c O 2-α F2 (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 < α < 2); Li a Ni 1-b-c Mn b B c D α (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 < α ≤ 2); Li a Ni 1-b-c Mn b B c O 2-α F α (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 < α < 2); Li a Ni 1-b-c Mn b B c O 2-α F2 (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, and 0 < α < 2); Li a Ni b E c G d O2 (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, and 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2 (where 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, and 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (where 0.90 ≤ a ≤ 1, and 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (where 0.90 ≤ a ≤ 1, and 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (where 0.90 ≤ a ≤ 1, and 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (where 0.90 ≤ a ≤ 1, and 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f)J2(PO4)3(0 ≤ f ≤ 2); Li (3-f) Fe2(PO4)3(0 ≤ f ≤ 2); and LiFePO4.

[0183] In the formula representing the above compounds, A may be nickel (Ni), cobalt (Co), manganese (Mn), or a combination thereof; B may be aluminum (Al), Ni, Co, Mn, chromium (Cr), iron (Fe), magnesium (Mg), strontium (Sr), vanadium (V), rare earth elements, or a combination thereof; D may be oxygen (O), fluorine (F), sulfur (S), phosphorus (P), or a combination thereof; E may be Co, Mn, or a combination thereof; F may be F, S, P, or a combination thereof; G may be Al, Cr, Mn, Fe, Mg, lanthanum (La), cerium (Ce), Sr, V, or a combination thereof; Q may be titanium (Ti), molybdenum (Mo), Mn, or a combination thereof; I may be Cr, V, Fe, Sc, yttrium (Y), or a combination thereof; and J may be V, Cr, Mn, Co, Ni, copper (Cu), or a combination thereof. A coating may be provided on the surface of the above compounds, and the resulting compounds with such a coating may be used, or a mixture of the above compounds and the compounds with a coating may be used. The coating provided on the surface of the above compounds may include coating element compounds, such as oxides of coating elements, hydroxides of coating elements, hydroxyoxides of coating elements, carbonate oxy-salts of coating elements, and / or hydroxycarbonates of coating elements. The compounds constituting the coating may be amorphous and / or crystalline. The coating elements included in the coating may be magnesium (Mg), aluminum (Al), cobalt (Co), potassium (K), sodium (Na), calcium (Ca), silicon (Si), titanium (Ti), vanadium (V), tin (Sn), germanium (Ge), gallium (Ga), boron (B), arsenic (As), zirconium (Zr), or a mixture thereof. The method of forming the coating may be selected within a range that does not adversely affect (or substantially does not affect) the physical properties of the positive electrode active material. The coating method may be, for example, spraying, dipping method, etc. A detailed description of the coating method will not be provided as it can be well understood by those skilled in the art.

[0184] The positive electrode current collector may be in the form of, for example, a plate and / or foil formed of indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof. The positive electrode current collector may have a thickness of, for example, about 1 μm to about 100 μm, about 1 μm to about 50 μm, about 5 μm to about 25 μm, or about 10 μm to about 20 μm.

[0185] The positive electrode current collector may include, for example, a substrate film and a metal layer provided on one or both sides (e.g., opposite sides) of the substrate film. The substrate film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may be, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or any combination thereof. The polymer may be an insulator. Since the substrate film includes an insulating thermoplastic polymer, in the event of a short circuit, the substrate film is softened and / or liquefied to block or reduce the operation of the battery, thereby suppressing or reducing a rapid increase in current. The metal layer may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or any alloy thereof. The metal layer acts as an electrochemical fuse and is cut off due to overcurrent, thereby preventing or reducing a short circuit. By controlling the thickness of the metal layer, the limiting current and the maximum current can be adjusted. The metal layer may be plated or deposited on the substrate film. As the thickness of the metal layer decreases, the limiting current and / or the maximum current of the positive electrode current collector decreases, such that the stability of the lithium battery in the event of a short circuit can be improved. A lead tab may be added to the metal layer for connection to the outside. The lead tab may be welded to the metal layer or the metal layer / substrate film stacked structure by ultrasonic welding, laser welding, spot welding, etc. Since the substrate film and / or the metal layer melts during welding, the metal layer can be electrically connected to the lead tab. To make the welding between the metal layer and the lead tab stronger, a metal sheet may also be added between the metal layer and the lead tab. The metal sheet may be a sheet of the same material as the metal of the metal layer. The metal sheet may be, for example, a metal foil and / or a metal mesh. The metal sheet may be, for example, an aluminum foil, a copper foil, and / or a stainless steel (SUS) foil. By performing welding after placing the metal sheet on the metal layer, the lead tab can be welded to the metal sheet / metal layer stacked structure or the metal sheet / metal layer / substrate film stacked structure. Since the substrate film, the metal layer, and / or the metal sheet melts during welding, the metal layer or the metal layer / metal sheet stacked structure can be electrically connected to the lead tab. A metal sheet and / or a lead tab may be further added to the metal layer. The substrate film may have a thickness of, for example, about 1 μm to about 50 μm, about 1.5 μm to about 50 μm, about 1.5 μm to about 40 μm, or about 1 μm to about 30 μm. In the case where the thickness of the substrate film is within any of the above ranges, the weight of the electrode assembly can be more effectively or appropriately reduced. The melting point of the substrate film may be, for example, about 100 °C to about 300 °C, about 100 °C to about 250 °C, or about 100 °C to about 200 °C. Since the substrate film has a melting point within any of the above ranges, the substrate film melts during the process of welding the lead tab and is easily or appropriately bonded to the lead tab.To improve the adhesion between the substrate film and the metal layer, the substrate film can be surface-treated, such as by corona treatment. The thickness of the metal layer can be, for example, about 0.01 μm to about 3 μm, about 0.1 μm to about 3 μm, about 0.1 μm to about 2 μm, or about 0.1 μm to about 1 μm. When the thickness of the metal layer is within any of the above ranges, appropriate stability of the electrode assembly can be obtained while maintaining the conductivity of the electrode assembly. The thickness of the metal sheet can be, for example, about 2 μm to about 10 μm, about 2 μm to about 7 μm, or about 4 μm to about 6 μm. When the thickness of the metal sheet is within any of the above ranges, the metal layer can be more easily or appropriately connected to the lead tab. Since the positive electrode current collector has the above structure, the weight of the positive electrode can be reduced, and the energy density of the positive electrode and the lithium battery can be increased.

[0186] A lithium battery according to one or more embodiments can employ a positive electrode including the above composite positive electrode active material.

[0187] By employing a positive electrode including a composite positive electrode active material, the lithium battery can provide improved energy density, cycle characteristics, and thermal stability.

[0188] Here, the lithium battery can be prepared by the method described as an example below; however, the method of preparing the lithium battery is not necessarily limited to this method and can be adjusted according to requirements or desired conditions.

[0189] First, the positive electrode can be prepared by the above positive electrode preparation method.

[0190] Next, the negative electrode can be prepared as follows. Except that, for example, a negative electrode active material can be used instead of the composite positive electrode active material, the negative electrode can be prepared by substantially the same method as the positive electrode. In some embodiments, in the negative electrode active material composition, substantially the same conductive material, binder, and solvent as those used for the positive electrode can be used.

[0191] For example, the negative electrode active material composition can be prepared by mixing a negative electrode active material, a conductive material, a binder, and a solvent, and the prepared negative electrode active material composition can be directly coated on a copper current collector to prepare a negative electrode plate. In some embodiments, the prepared negative electrode active material composition can be cast on a separate support, and the negative electrode active material film peeled from the support can be laminated on a copper current collector to prepare a negative electrode plate.

[0192] The negative electrode active material can be any suitable material used as the negative electrode active material in a lithium battery. For example, the negative electrode active material can include at least one selected from lithium metal, metals alloyable with lithium, transition metal oxides, non-transition metal oxides, and carbonaceous materials. Examples of metals alloyable with lithium can include Si, Sn, Al, Ge, Pb, Bi, Sb, Si-Y alloys (where Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth metal, or a combination thereof, but not Si), Sn-Y alloys (where Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth metal, or a combination thereof, but not Sn), etc. For example, Y can be Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof. Examples of transition metal oxides can include lithium titanate oxide, vanadium oxide, lithium vanadium oxide, etc. Non-transition metal oxides can be, for example, SnO2, SiO x (0 < x < 2), etc. Examples of carbonaceous materials can include crystalline carbon, amorphous carbon, or a mixture thereof. Examples of crystalline carbon can include graphite, such as artificial graphite and / or natural graphite in a shapeless, plate form, flake form, spherical form, and / or fibrous form. Examples of amorphous carbon can include soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbide, calcined coke, etc.

[0193] The amount of each of the negative electrode active material, conductive material, binder, and solvent can be at a suitable level for use in a lithium battery. Depending on the intended or desired use purpose and configuration of the lithium battery, one or more of the conductive material, binder, and solvent may not be provided.

[0194] Relative to the total weight of the negative electrode active material layer, the amount of the binder used in the negative electrode can be, for example, about 0.1 wt% to about 10 wt%, or about 0.1 wt% to about 5 wt%. Relative to the total weight of the negative electrode active material layer, the amount of the conductive material used in the negative electrode can be, for example, about 0.1 wt% to about 10 wt%, or about 0.1 wt% to about 5 wt%. Relative to the total weight of the negative electrode active material layer, the amount of the negative electrode active material used in the negative electrode can be, for example, about 80 wt% to about 99 wt%, about 90 wt% to about 99 wt%, or about 95 wt% to about 99 wt%. If (for example, when) the negative electrode active material is lithium metal, the negative electrode may not include (for example, any) binder and / or conductive material.

[0195] The negative electrode current collector can be formed of, for example, a material that does not react with lithium (e.g., a material that does not form an alloy and / or compound with lithium). The material constituting the negative electrode current collector can be, for example, copper (Cu), stainless steel (SUS), titanium (Ti), iron (Fe), cobalt (Co), and / or nickel (Ni), but is not limited thereto, and any suitable material can also be used as the electrode current collector. The negative electrode current collector can be formed of a single metal selected from the above materials, or can be formed of an alloy and / or coated material of two or more metals. The negative electrode current collector can be in the form of, for example, a plate and / or a foil.

[0196] The negative electrode current collector can include, for example, a base film and a metal layer provided on one side or (e.g., simultaneously) both sides of the base film. The base film can include, for example, a polymer. The polymer can be, for example, a thermoplastic polymer. The polymer can be, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or any combination thereof. The polymer can be an insulating polymer. Since the base film includes an insulating thermoplastic polymer, in the case of a short circuit, the base film is softened and / or liquefied to block or reduce the operation of the battery, so that a rapid increase in current can be suppressed or reduced. The metal layer can include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), or an alloy thereof. The negative electrode current collector can also include a metal sheet and / or a lead tab. For a more detailed description of the base film, metal layer, metal sheet, and lead tab of the negative electrode current collector, refer to the positive electrode current collector. Since the negative electrode current collector has the above structure, the weight of the negative electrode can be reduced, and thus, the energy density of the negative electrode and the lithium battery can be increased.

[0197] Next, a separator located between the positive electrode and the negative electrode can be prepared.

[0198] The separator can be any suitable separator to be used in a lithium battery. For the separator, for example, any suitable separator that can retain a large amount of electrolyte while exhibiting low resistance to ion migration in the electrolyte can be used. For example, the separator can be formed of a material selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof in the form of a non-woven fabric and / or a woven fabric. A lithium-ion battery can use, for example, a rollable separator formed of polyethylene, polypropylene, etc. A lithium-ion polymer battery can use, for example, a separator that can retain a large amount of organic electrolyte.

[0199] Here, the separator can be prepared by the method described as an example below; however, the method of preparing the separator is not necessarily limited to this method and can be adjusted according to the required or desired conditions.

[0200] First, a separator composition can be prepared by mixing a polymer resin, a filler, and a solvent. The separator composition can be directly coated on top of the electrode and dried to form a separator. In some embodiments, the separator can be formed by casting the separator composition on a support and drying, and then laminating the separator layer peeled from the support on top of the electrode.

[0201] The polymer used in the preparation of the separator is not particularly limited, and any suitable polymer can be used as the binder of the electrode plate. For example, the polymer can be a vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or a mixture thereof.

[0202] Next, an electrolyte can be prepared.

[0203] The electrolyte can be, for example, an organic electrolyte solution. The organic electrolyte solution can be prepared by dissolving a lithium salt in an organic solvent.

[0204] For the organic solvent, any suitable organic solvent can be used. Examples of the organic solvent can include propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, and mixtures thereof.

[0205] For the lithium salt, any suitable lithium salt can be used. For example, the lithium salt can be LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+ 1SO2) (wherein x and y are both natural numbers from 1 to 20), LiCl, LiI, or mixtures thereof.

[0206] In some embodiments, the electrolyte can be a solid electrolyte. The solid electrolyte can be, for example, boron oxide, lithium oxynitride, etc., but is not limited thereto, and can be any suitable solid electrolyte. For example, the solid electrolyte can be formed on the negative electrode by one or more suitable methods such as sputtering, or a separate solid electrolyte sheet can be placed on the negative electrode.

[0207] The solid electrolyte can be, for example, an oxide-based solid electrolyte and / or a sulfide-based solid electrolyte.

[0208] The solid electrolyte can be, for example, an oxide-based solid electrolyte. The oxide-based solid electrolyte can be selected from Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 (0 < x < 2, and 0 ≤ y < 3), BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3 (PLZT) (0 ≤ x < 1, and 0 ≤ y < 1), Pb(Mg3Nb 2 / 3 )O3 - PbTiO3 (PMN - PT), HfO2, SrTiO3, SnO2, CeO2, Na2O, MgO, NiO, CaO, BaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiO2, Li3PO4, Li x Ti y (PO4)3 (0 < x < 2, and 0 < y < 3), Li x Al y Ti z (PO4)3 (0 < x < 2, 0 < y < 1, and 0 < z < 3), Li 1+x+y (Al,Ga) x (Ti,Ge) 2-x Si y P 3-y O 12 (0 ≤ x ≤ 1, and 0 ≤ y ≤ 1), Li x La y TiO3 (0 < x < 2, and 0 < y < 3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O - Al2O3 - SiO2 - P2O5 - TiO2 - GeO2, and Li 3+x La3M2O 12 (M = Te, Nb or Zr, and x is a positive integer from 1 to 10) among at least one. The solid electrolyte can be prepared by a sintering method or the like. For example, the oxide-based solid electrolyte can be selected from Li7La3Zr2O 12 (LLZO) and Li 3+x La3Zr 2-a M a O 12A garnet-type (or similar) solid electrolyte among (M-doped LLZO, where M = Ga, W, Nb, Ta, or Al, and x is an integer from 1 to 10).

[0209] Examples of sulfide-based solid electrolytes can include lithium sulfide, silicon sulfide, phosphorus sulfide, boron sulfide, or combinations thereof. Sulfide-based solid electrolyte particles can include Li2S, P2S5, SiS2, GeS2, B2S3, or combinations thereof. Sulfide-based solid electrolyte particles can be Li2S and / or P2S5. Sulfide-based solid electrolyte particles are suitable for having a lithium ion conductivity higher than that of other inorganic compounds. For example, sulfide-based solid electrolytes can include Li2S and / or P2S5. If (e.g., when) the sulfide-based solid electrolyte material constituting the sulfide-based solid electrolyte includes Li2S-P2S5, the mixed molar ratio of Li2S to P2S5 can be, for example, in the range of about 50:50 to about 90:10. In some embodiments, materials such as Li3PO4, halogens, halogen compounds, Li 2+2x Zn 1-x GeO4 (“LISICON”, 0 ≤ x < 1), Li 3+y PO 4-x N x (“LIPON”, 0 < x < 4 and 0 < y < 3), Li 3.25 Ge 0.25 P 0.75 S4 (“thio-LISICON”) and / or Li2O-Al2O3-TiO2-P2O5 (“LATP”) can be added to inorganic solid electrolytes such as Li2S-P2S5, SiS2, GeS2, B2S3, or combinations thereof to prepare inorganic solid electrolytes, and the inorganic solid electrolytes can be used as sulfide-based solid electrolytes. Non-limiting examples of sulfide-based solid electrolyte materials can include Li2S-P2S5, Li2S-P2S5-LiX (X = halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (0 < m < 10, 0 < n < 10, Z = Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-Li p MO q(0 < p < 10, 0 < q < 10, M = P, Si, Ge, B, Al, Ga or In). In this regard, the sulfide-based solid electrolyte material can be prepared by treating starting materials of the sulfide-based solid electrolyte material (e.g., Li2S, P2S5, etc.) through processes such as the melt quenching method, mechanical grinding method, etc. In some embodiments, a calcination process can be carried out after the above treatment. The sulfide-based solid electrolyte can be amorphous, crystalline, or can be in their mixed state.

[0210] Referring to Figures 4 to 6 , the lithium battery 1 according to the embodiment can include a positive electrode 3, a negative electrode 2, and a separator 4. The positive electrode 3, the negative electrode 2, and the separator 4 can be wound or folded to form a battery structure 7. The formed battery structure 7 can be accommodated in a battery case 5. The battery case 5 can be injected with an organic electrolyte and sealed with a lid assembly 6, thereby completing the preparation of the lithium battery 1. The battery case 5 can have a cylindrical shape, but is not limited thereto, and can have a polygonal shape, a thin film shape, etc.

[0211] Referring to Figure 5 , the lithium battery 1 according to the embodiment can include a positive electrode 3, a negative electrode 2, and a separator 4. The separator 4 can be disposed between the positive electrode 3 and the negative electrode 2, and the positive electrode 3, the negative electrode 2, and the separator 4 can be wound or folded to form a battery structure 7. The battery structure 7 can be accommodated in a battery case 5. An electrode tab 8 can be included that serves as a circuit path for guiding the current generated in the battery structure 7 to the outside. The battery case 5 can be injected with an organic electrolyte and sealed, thereby completing the preparation of the lithium battery 1. The battery case 5 can have a polygonal shape, but is not limited thereto, and can also have, for example, a cylindrical shape, a thin film shape, etc.

[0212] Referring to Figure 6 , the lithium battery 1 according to the embodiment can include a positive electrode 3, a negative electrode 2, and a separator 4. The separator 4 can be disposed between the positive electrode 3 and the negative electrode 2 to form a battery structure 7. The battery structure 7 can be stacked in a dual-cell structure and then accommodated in a battery case 5. An electrode tab 8 can be included that serves as a circuit path for guiding the current generated in the battery structure 7 to the outside. The battery case 5 can be injected with an organic electrolyte and sealed, thereby completing the preparation of the lithium battery 1. The battery case 5 can have a polygonal shape, but is not limited thereto, and can also have, for example, a cylindrical shape, a thin film shape, etc.

[0213] Pouch-type (or similar) lithium batteries and Figures 4 to 6It corresponds to a lithium battery using a bag as a battery case as shown. The pouch-type (or pouch-like) lithium battery may include one or more battery structures. The battery structure may be formed by disposing a separator between a positive electrode and a negative electrode. The battery structures may be stacked in a dual-cell structure, immersed in an organic electrolyte, and then accommodated and sealed in a bag, thereby completing the preparation of the pouch-type (or pouch-like) lithium battery. For example, in some embodiments, the above positive electrode, negative electrode, and separator may simply be stacked in the form of an electrode assembly and then accommodated in a bag, or may be wound or folded into a jelly-roll-type (or jelly-roll-like) electrode assembly and then accommodated in a bag. Subsequently, the bag may be injected with an organic electrolyte and then sealed, thereby completing the preparation of the lithium battery.

[0214] Due to having excellent or suitable life characteristics and / or high rate performance, lithium batteries can be used in, for example, electric vehicles (EVs). For example, lithium batteries can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs), etc. In addition, lithium batteries can be used in any suitable field that requires or desires a large amount of energy storage. For example, lithium batteries can be used in electric bicycles, power tools, etc.

[0215] Multiple cells of a lithium battery can be stacked together to form a battery module, and multiple battery modules can form a battery pack. Such a battery pack can be used in all types (or kinds) of devices that require or desire high capacity and high output. For example, the battery pack can be used in laptop computers, smart phones, electric vehicles, etc. The battery module may include, for example, multiple batteries and a frame for holding the batteries. The battery pack may include, for example, multiple battery modules and a bus bar connecting these battery modules. The battery module and / or the battery pack may also include a cooling device. Multiple battery packs may be controlled or selected by a battery management system. The battery management system may include a battery pack and a battery control device connected to the battery pack.

[0216] A method for preparing a composite positive electrode active material according to one or more embodiments may include: preparing a first core / shell structure obtained by mechanically grinding a first lithium transition metal oxide, a composite, and a second carbonaceous material; preparing a second core / shell structure obtained by mechanically grinding a second lithium transition metal oxide, a composite, and a second carbonaceous material; preparing a composite positive electrode active material by mixing the first core / shell structure and the second core / shell structure, wherein the composite may include M a O b(0 < a ≤ 3 and 0 < b < 4, where if (e.g., when) a is 1, 2, or 3, then b is not an integer) represents a first metal oxide (e.g., at least one first metal oxide) and a first carbonaceous material. The first metal oxide can be disposed in the matrix of the first carbonaceous material. M can be at least one metal selected from Groups 2 to 13, 15, and 16 of the periodic table. The second carbonaceous material can include a fibrous carbonaceous material having an aspect ratio of 10 or greater. The first lithium transition metal oxide and the second lithium transition metal oxide can have different particle sizes from each other. The first lithium transition metal oxide can include primary particles having a particle size of 3 μm or greater, and the second lithium transition metal oxide can include primary particles having a particle size of 1 μm or greater.

[0217] A first lithium transition metal oxide can be provided. For example, the first lithium transition metal oxide can be a compound represented by at least one selected from the above Formulas 1 to 8. A second lithium transition metal oxide can be provided. For example, the second lithium transition metal oxide can be a compound represented by at least one selected from the above Formulas 1 to 8. The first lithium transition metal oxide and the second lithium transition metal oxide have different particle sizes from each other. For example, the first lithium transition metal oxide can have a larger particle size than the second lithium transition metal oxide. The second lithium transition metal oxide can be an integral particle, for example, can be primary particles having a particle size of 1 μm or greater.

[0218] A composite can be provided. Providing the composite can include, for example, supplying a reaction gas including a carbon source gas (e.g., consisting of a carbon source gas) to a structure including a metal oxide and performing a heat treatment to provide the composite. Providing the composite can include, for example, supplying a reaction gas including a carbon source gas (e.g., consisting of a carbon source gas) to at least one second metal oxide represented by M a O c (0 < a ≤ 3 and 0 < c ≤ 4, where if (e.g., when) a is 1, 2, or 3, b is an integer) and performing a heat treatment to prepare the composite, where M can be at least one metal selected from the elements of Groups 2 to 13, 15, and 16 of the periodic table.

[0219] The carbon source gas can be a gas including a compound represented by Formula 9 (e.g., consisting of a compound represented by Formula 9), or can be a mixed gas including at least one selected from the compound represented by Formula 9, the compound represented by Formula 10, and the oxygen-containing gas represented by Formula 11:

[0220] Formula 9

[0221] C n H (2n+2-a) [OH] a

[0222] In Formula 9, n can be an integer from 1 to 20, and a can be 0 or 1;

[0223] Formula 10

[0224] C n H 2n

[0225] In Formula 10, n can be an integer from 2 to 6; and

[0226] Formula 11

[0227] C x H y O z

[0228] In Formula 11, x can be 0 or an integer from 1 to 20, y can be 0 or an integer from 1 to 20, and z can be 1 or 2.

[0229] The compound represented by Formula 9 and the compound represented by Formula 10 can be one or more selected from methane, ethylene, propylene, methanol, ethanol, and propanol. The oxygen-containing gas represented by Formula 11 can include, for example, carbon dioxide (CO2), carbon monoxide (CO), water vapor (H2O), or a mixture thereof.

[0230] In supplying a reaction gas including a carbon source gas (for example, consisting of a carbon source gas) to a second metal oxide represented by M a O c (0 < a ≤ 3 and 0 < c ≤ 4, where, if (for example, when) a is 1, 2, or 3, then c is an integer) and performing heat treatment, a cooling process using at least one inert gas selected from nitrogen, helium, and argon can be performed further. The cooling process can refer to a process of adjusting the temperature to room temperature (20 °C to 25 °C). The carbon source gas can include at least one inert gas selected from nitrogen, helium, and argon.

[0231] In the method for preparing a composite, the process of growing a carbon-based material (for example, graphene) can be carried out under one or more suitable conditions according to a gas-phase reaction.

[0232] According to the first condition, for example, before raising the temperature to the heat treatment temperature (T), methane can be first supplied to a reactor loaded with M a O cA reactor for a second metal oxide represented by (0 < a ≤ 3 and 0 < c ≤ 4, where c is an integer if (for example, when) a is 1, 2, or 3). The heat treatment temperature (T) can be reached over a duration of about 10 minutes to about 4 hours, and the heat treatment temperature (T) can be in the range of about 700 °C to about 1100 °C. At the heat treatment temperature (T), the heat treatment can be carried out for the duration of the reaction time. The reaction time can be, for example, about 4 hours to about 8 hours. The heat treatment product can be cooled to room temperature to produce a composite. The process of cooling from the heat treatment temperature (T) to room temperature can take, for example, about 1 hour to about 5 hours.

[0233] According to the second condition, for example, before raising the temperature to the heat treatment temperature (T), hydrogen gas can first be supplied to the reactor loaded with the second metal oxide represented by M a O c A reactor for a second metal oxide represented by (0 < a ≤ 3 and 0 < c ≤ 4, where c is an integer if (for example, when) a is 1, 2, or 3). The heat treatment temperature (T) can be reached over a duration of about 10 minutes to about 4 hours, and the heat treatment temperature (T) can be in the range of about 700 °C to about 1100 °C. After carrying out the heat treatment at the heat treatment temperature (T) for a certain reaction time duration, methane gas can be supplied and the heat treatment can be carried out for the remaining reaction time. The reaction time can be, for example, about 4 hours to about 8 hours. The heat treatment product can be cooled to room temperature to produce a composite. Nitrogen gas can be supplied during the cooling process. The time taken for the process of cooling from the heat treatment temperature (T) to room temperature can be, for example, about 1 hour to about 5 hours.

[0234] According to the third condition, for example, before raising the temperature to the heat treatment temperature (T), hydrogen gas can first be supplied to the reactor loaded with the second metal oxide represented by M a O c A reactor for a second metal oxide represented by (0 < a ≤ 3 and 0 < c ≤ 4, where c is an integer if a is 1, 2, or 3). The heat treatment temperature (T) can be reached over a duration of about 10 minutes to about 4 hours, and the heat treatment temperature (T) can be in the range of about 700 °C to about 1100 °C. After carrying out the heat treatment at the heat treatment temperature (T) for a certain reaction time duration, a mixed gas of methane and hydrogen can be supplied, and the heat treatment can be carried out for the remaining reaction time. The reaction time can be, for example, about 4 hours to about 8 hours. The heat treatment product can be cooled to room temperature to produce a composite. Nitrogen gas can be supplied during the cooling process. The time taken for the process of cooling from the heat treatment temperature (T) to room temperature can be, for example, about 1 hour to about 5 hours.

[0235] If (e.g., when) the carbon source gas includes water vapor during the preparation of the composite, a composite with excellent or suitable conductivity can be obtained. The content (e.g., amount) of water vapor in the gas mixture is not limited and can be, for example, about 0.01 vol% to about 10 vol% relative to the total volume of the carbon source gas of 100 vol%. For example, the carbon source gas can be: methane; a mixed gas containing methane and an inert gas; or a mixed gas containing methane and an oxygen-containing gas.

[0236] For example, the carbon source gas can be: (1) methane; (2) a mixed gas of methane and carbon dioxide; or (3) a mixed gas of methane, carbon dioxide, and water vapor. In the (2) mixed gas of methane and carbon dioxide, the molar ratio of methane to carbon dioxide can be about 1:0.2 to about 1:0.5, about 1:0.25 to about 1:0.45, or about 1:0.3 to about 1:0.4. In the (3) mixed gas of methane, carbon dioxide, and water vapor, the molar ratio of methane, carbon dioxide, and water vapor can be about 1 (methane):0.2 to 0.5 (carbon dioxide):0.01 to 1.45 (water vapor), can be about 1:0.25 to 0.45:0.1 to 1.35, or can be about 1:0.3 to 0.4:0.5 to 1.

[0237] The carbon source gas can be, for example, carbon monoxide and / or carbon dioxide. The carbon source gas can be, for example, a mixed gas of methane and nitrogen. In the mixed gas of methane and nitrogen, the molar ratio of methane to nitrogen can be about 1:0.2 to 1:0.5, about 1:0.25 to 1:0.45, or about 1:0.3 to 1:0.4. The carbon source gas can exclude (e.g., can be free of) inert gases such as nitrogen.

[0238] The heat treatment pressure can be selected considering factors such as the heat treatment temperature, the composition of the gas mixture, and the desired or suitable amount of the carbon coating. The heat treatment pressure can be controlled or selected by adjusting the inlet amount and the outlet amount of the gas mixture. The heat treatment pressure can be, for example, 0.5 atm or greater, 1 atm or greater, 2 atm or greater, 3 atm or greater, 4 atm or greater, or 5 atm or greater. The heat treatment pressure can be, for example, about 0.5 atm to about 10 atm, about 1 atm to about 10 atm, about 2 atm to about 10 atm, about 3 atm to about 10 atm, about 4 atm to about 10 atm, or about 5 atm to about 10 atm.

[0239] The heat treatment time is not particularly limited and can be appropriately adjusted according to the heat treatment temperature, heat treatment pressure, composition of the gas mixture, and the amount of the desired or suitable carbon coating. For example, the heat treatment time at the heat treatment temperature can be, for example, about 10 minutes to about 100 hours, about 30 minutes to about 90 hours, or about 50 minutes to about 40 hours. For example, as the heat treatment time increases, the amount of deposited carbon (e.g., graphene (carbon)) increases, and thus, the electrical properties of the composite can be improved. It should be noted that this trend may not necessarily be proportional to the time. For example, after a certain period of time, carbon deposition (e.g., graphene deposition) may no longer occur, or the deposition rate may decrease.

[0240] Through the gas-phase reaction of the above carbon source gas, even at a relatively low temperature, a composite can be obtained by providing a substantially uniform coating (e.g., graphene coating) of a carbonaceous material to at least one selected from the following: by M a O c (0 < a ≤ 3 and 0 < c ≤ 4, where, if (e.g., when) a is 1, 2, or 3, then c is an integer) representing the second metal oxide and its reduction product (by M a O b (0 < a ≤ 3 and 0 < b < 4, where, if (e.g., when) a is 1, 2, or 3, then b is not an integer) representing the first metal oxide).

[0241] For example, the composite can include: a matrix of a carbonaceous material (e.g., a graphene matrix) having at least one structure selected from a spherical structure, a helical structure having a plurality of spherical structures connected to each other, a cluster structure having a plurality of aggregated spherical structures, and a sponge structure; and at least one selected from the first metal oxide represented by M a O b (0 < a ≤ 3 and 0 < b < 4, where, if (e.g., when) a is 1, 2, or 3, then b is not an integer) and the second metal oxide represented by M a O c (0 < a ≤ 3 and 0 < c ≤ 4, where, if (e.g., when) a is 1, 2, or 3, then c is an integer), disposed within the graphene matrix.

[0242] Next, the first core / shell structure can be prepared by mechanically grinding the first lithium transition metal oxide and the composite. For the grinding, a Nobilta mixer (Hosokawa Micron BV) or the like can be used. The rotation rate of the mixer during grinding can be, for example, 1,000 rpm to 5,000 rpm. The grinding time can be, for example, about 5 minutes to about 100 minutes. The average particle size (D50) of the composite used for mechanically grinding the first lithium transition metal oxide and the composite can be, for example, about 50 nm to about 200 nm, about 100 nm to about 300 nm, or about 200 nm to about 500 nm. The grinding method used during the mechanical grinding process is not particularly limited, and can be any suitable method that can bring the lithium transition metal oxide and the composite into contact with each other by mechanical means or components.

[0243] In addition, the second core / shell structure can be prepared by mechanically grinding the second lithium transition metal oxide and the composite. The second core / shell structure can be prepared using the same process as in the preparation method of the first core / shell structure, except that the second lithium transition metal oxide is used instead of the first lithium transition metal oxide.

[0244] Next, the composite positive electrode active material can be prepared by mixing the first core / shell structure and the second core / shell structure. The mixing of the first core / shell structure and the second core / shell structure can be carried out at a weight ratio of, for example, about 90:10 to about 60:40, about 85:15 to about 65:35, or about 80:20 to about 70:30. Since the first core / shell structure and the second core / shell structure have a weight ratio within any of the above ranges, the energy density and / or cycle characteristics of the lithium battery including the composite positive electrode active material can be further improved.

[0245] The present disclosure will be described in more detail by way of examples and comparative examples. However, it will be understood that the following examples are provided only for illustrative purposes and should not be construed as limiting the scope of the present disclosure.

[0246] Preparation of the composite

[0247] Preparation Example 1: Al2O3@Gr composite

[0248] Load Al2O3 particles (average particle size: about 20 nm) into a reactor, and supply CH4 to the reactor at 300 sccm and 1 atm for about 30 minutes, and raise the temperature inside the reactor to 1,000 °C.

[0249] Subsequently, heat treatment is carried out while maintaining the above temperature for 7 hours. Then, adjust the temperature inside the reactor to room temperature (20 °C to 25 °C) to obtain Al2O3 particles and their reduction product Al2O zA composite in which (0 < z < 3) particles are embedded in graphene.

[0250] The content (e.g., amount) of alumina included in the composite is 60 wt%.

[0251] Comparative Preparation Example 1: SiO2@Gr composite

[0252] Load SiO2 particles (average particle diameter: about 15 nm) into a reactor, and supply CH4 to the reactor at 300 sccm and 1 atm for about 30 minutes, and raise the temperature inside the reactor to 1,000 °C.

[0253] Subsequently, perform heat treatment while maintaining the above temperature for 7 hours. Then, adjust the temperature inside the reactor to room temperature (20 °C to 25 °C) to produce a composite in which SiO2 particles and their reduction product SiO y A composite in which (0 < y < 2) particles are embedded in graphene.

[0254] Preparation of composite positive electrode active material

[0255] Example 1: 0.025 wt% of Al2O3@Gr composite and 0.025 wt% of CNT-coated large-diameter integrated particles LCO, and 0.025 wt% of Al2O3@Gr composite and 0.025 wt% of CNT-coated small-diameter integrated particles LCO

[0256] Use a Nobilta mixer (Hosokawa Micron BV) to grind large-diameter LiCoO2 with an average particle diameter of 6 μm (hereinafter referred to as large-diameter LCO), the composite prepared in Preparation Example 1, and carbon nanotubes (hereinafter referred to as CNT) together at a rotation rate of about 1,000 rpm to about 2,000 rpm for about 5 minutes to 30 minutes to obtain a first core / shell structure. The mixing weight ratio of large-diameter LCO, the composite obtained in Preparation Example 1, and CNT is 99.95:0.025:0.025. The large-diameter LCO has an integrated particle shape and is a particle with a single crystal structure.

[0257] Use a Nobilta mixer (Hosokawa Micron BV) to grind small-diameter LiCoO2 with an average particle diameter of 2 μm (hereinafter referred to as small-diameter LCO), the composite prepared in Preparation Example 1, and CNT together at a rotation rate of about 1,000 rpm to about 2,000 rpm for about 5 minutes to 30 minutes to obtain a second core / shell structure. The mixing weight ratio of small-diameter LCO, the composite obtained in Preparation Example 1, and CNT is 99.95:0.025:0.025. The small-diameter LCO has an integrated particle shape and is a particle with a single crystal structure.

[0258] The composite positive electrode active material is prepared by mixing the first core / shell structure and the second core / shell structure in a weight ratio of 7:3.

[0259] By measuring the particle size distribution with a particle size analyzer (PSA), it is confirmed that the composite positive electrode active material has a bimodal particle size distribution.

[0260] As Figure 2 shown, it can be found that carbon nanotubes are provided on the surface of the large-diameter LCO integrated particles of the first core / shell structure. The carbon nanotubes include a primary carbon nanotube structure and a secondary carbon nanotube structure formed by the aggregation of a plurality of carbon nanotube units. The primary carbon nanotube structure may include one carbon nanotube unit (for example, composed of one carbon nanotube unit). The length of the carbon nanotube unit is 200 nm to 300 nm, and the diameter of the carbon nanotube is about 10 nm. The secondary carbon nanotube structure is formed by the aggregation of a plurality of carbon nanotube units. The length of the secondary carbon nanotube structure is 500 nm or more, and the diameter is about 40 nm.

[0261] It can also be found that carbon nanotubes are provided on the surface of the small-diameter LCO integrated particles of the second core / shell structure. The carbon nanotubes include a primary carbon nanotube structure.

[0262] Example 2: 0.02 wt% of Al2O3@Gr composite and 0.03 wt% of CNT-coated large-diameter integrated particle LCO, and 0.02 wt% of Al2O3@Gr composite and 0.03 wt% of CNT-coated small-diameter integrated particle LCO

[0263] The composite positive electrode active material is prepared according to a process that is substantially the same as the process in Example 1, except that the mixing ratio of the composite and CNT is changed from 0.025:0.025 to 0.02:0.03.

[0264] Example 3: 0.04 wt% of Al2O3@Gr composite and 0.01 wt% of CNT-coated large-diameter integrated particle LCO, and 0.04 wt% of Al2O3@Gr composite and 0.01 wt% of CNT-coated small-diameter integrated particle LCO

[0265] The composite positive electrode active material is prepared according to a process that is substantially the same as the process in Example 1, except that the mixing ratio of the composite and CNT is changed from 0.025:0.025 to 0.04:0.01.

[0266] Example 4: 0.01 wt% of Al2O3@Gr composite and 0.04 wt% of CNT-coated large-diameter monolithic LCO particles, and 0.01 wt% of Al2O3@Gr composite and 0.04 wt% of CNT-coated small-diameter monolithic LCO particles

[0267] A composite positive electrode active material was prepared according to a process substantially the same as the process in Example 1, except that the mixing ratio of the composite and CNT was changed from 0.025:0.025 to 0.01:0.04.

[0268] Comparative Example 1: Bare large-diameter monolithic LCO particles and bare small-diameter monolithic LCO particles

[0269] A composite positive electrode active material was prepared according to a process substantially the same as the process in Example 1, except that large-diameter LCO (e.g., NCA91) was used as it is instead of the first core / shell structure and small-diameter LCO was used as it is instead of the second core / shell structure.

[0270] Comparative Example 2: Large-diameter monolithic LCO particles individually coated with 0.025 wt% of Al2O3@Gr composite, and small-diameter monolithic LCO particles individually coated with 0.025 wt% of Al2O3@Gr composite

[0271] A composite positive electrode active material was prepared according to a process substantially the same as the process in Example 1, except that the mixing ratio of the composite and CNT was changed from 0.025:0.025 to 0.025:0.

[0272] Comparative Example 3: Large-diameter monolithic LCO particles individually coated with 0.05 wt% of Al2O3@Gr composite, and small-diameter monolithic LCO particles individually coated with 0.05 wt% of Al2O3@Gr composite

[0273] A composite positive electrode active material was prepared according to a process substantially the same as the process in Example 1, except that the mixing ratio of the composite and CNT was changed from 0.025:0.025 to 0.05:0.

[0274] Comparative Example 4: Large-diameter monolithic LCO particles individually coated with 0.1 wt% of Al2O3@Gr composite, and small-diameter monolithic LCO particles individually coated with 0.1 wt% of Al2O3@Gr composite

[0275] A composite positive electrode active material was prepared according to a process substantially the same as the process in Example 1, except that the mixing ratio of the composite and CNT was changed from 0.025:0.025 to 0.1:0.

[0276] Reference Example 1: 0.025 wt% of Al2O3@Gr composite and 0.025 wt% of CNT-coated large-diameter monolithic particle LCO, and 0.025 wt% of Al2O3@Gr composite and 0.025 wt% of CNT-coated small-diameter secondary particle LCO

[0277] A composite positive electrode active material was prepared according to a process substantially the same as the process in Example 1, except that small-diameter LCO as secondary particles formed by aggregation of a plurality of primary particles was used instead of small-diameter LCO as monolithic particles.

[0278] Comparative Example 5: 0.025 wt% of SiO2@Gr composite and 0.025 wt% of CNT-coated large-diameter monolithic particle LCO, and 0.025 wt% of SiO2@Gr composite and 0.025 wt% of CNT-coated small-diameter monolithic particle LCO

[0279] A composite positive electrode active material was prepared according to a process substantially the same as the process in Example 1, except that the SiO2@Gr composite prepared in Comparative Preparation Example 1 was used instead of the Al2O3@Gr composite prepared in Preparation Example 1.

[0280] Preparation of lithium battery half cell

[0281] Example 5

[0282] Preparation of positive electrode

[0283] The composite positive electrode active material prepared in Example 1, a carbon conductive material, and polyvinylidene fluoride (PVdF) were mixed at a weight ratio of 99:0.5:0.5, and the resulting mixture was mixed with N-methylpyrrolidone (NMP) using an agate mortar and pestle to prepare a slurry.

[0284] The carbon conductive material used was a mixture of carbon nanotubes (CNT) and Ketjen black (ECP) at a weight ratio of 7:3.

[0285] The slurry was bar-coated on a 15-μm-thick aluminum current collector and dried at room temperature, and then dried under vacuum at 120 °C again, and then roll-pressed and punched to prepare a 70-μm-thick positive electrode.

[0286] Preparation of coin cell

[0287] Using the positive electrode prepared above, and using lithium metal as the counter electrode, a PTFE separator, and a solution containing 1.5 M of LiPF6 dissolved in ethylene carbonate (EC) + ethyl methyl carbonate (EMC) + dimethyl carbonate (DMC) (in a volume ratio of 2:2:6) as the electrolyte, a coin cell was prepared.

[0288] Examples 6 to 8

[0289] A coin-type battery was prepared in substantially the same process as in Example 5, except that the composite positive electrode active materials prepared in Examples 2 to 4 were used respectively in place of the composite positive electrode active material prepared in Example 1.

[0290] Comparative Examples 6 to 10, Reference Example 2

[0291] A coin-type battery was prepared in substantially the same process as in Example 5, except that the composite positive electrode active materials prepared in Comparative Examples 1 to 5 and Reference Example 1 were used respectively in place of the composite positive electrode active material prepared in Example 1.

[0292] Evaluation Example 1: Evaluation of XPS spectrum

[0293] During the preparation process of the composite prepared in Preparation Example 1, the XPS spectrum was measured over time using Quantum 2000 (Physical Electronics). The XPS spectra of the C1s orbit and Al2p orbit of each sample were obtained before heating, 1 minute after heating, 5 minutes after heating, 30 minutes after heating, 1 hour after heating, and 4 hours after heating. At the start of temperature increase, the XPS spectrum showed only the Al2p peak and not the C1s peak. After 30 minutes, the C1s peak clearly appeared and the size of the Al2p peak decreased significantly.

[0294] After 30 minutes, the C1s peak attributed to C-C bonds and C═C bonds due to graphene growth clearly appeared near 284.5 eV.

[0295] Since the oxidation number of aluminum decreased with increasing reaction time, the peak position of the Al2p orbit shifted towards lower binding energy (eV).

[0296] From this, it was found, without being bound by any specific theory, that as the reaction proceeded, graphene grew on the Al2O3 particles and Al2O x (0 < x < 3) was produced as a reduction product of Al2O3.

[0297] The average contents of carbon and aluminum were measured from the XPS analysis results of 10 regions of the composite sample prepared in Preparation Example 1. Regarding the measurement results, the deviation of the aluminum content (e.g., amount) in each region was calculated. The deviation of the aluminum content (e.g., amount) was expressed as a percentage of the average value, and this percentage was called the uniformity. The percentage of the average value of the deviation of the aluminum content (e.g., amount) (i.e., the uniformity of the aluminum content (e.g., amount)) was 1%. Therefore, it was found that alumina was distributed uniformly (e.g., substantially uniformly) in the composite prepared in Preparation Example 1.

[0298] Evaluation Example 2: SEM, HR-TEM, and SEM-EDS Analyses

[0299] The composite prepared in Preparation Example 1, the first core / shell structure prepared in Example 1, and the bare large-diameter monolithic LCO particles prepared in Comparative Example 1 were subjected to scanning electron microscopy (SEM) analysis, high-resolution transmission electron microscopy (HR-TEM) analysis, and energy-dispersive X-ray spectroscopy (EDS) analysis.

[0300] For the SEM-EDS analysis, FEI Titan 80-300 (Philips) was used.

[0301] The composite prepared in Preparation Example 1 showed a structure in which Al2O3 particles and Al2O z (0 < z < 3) particles were embedded in graphene. Without being bound by any specific theory, it was found that a graphene layer was provided on the outer side of at least one of the Al2O3 particles and Al2O z (0 < z < 3) particles. At least one of the Al2O3 particles and Al2O z (0 < z < 3) particles was uniformly (e.g., substantially uniformly) distributed within the graphene matrix. It was found that at least one of the Al2O3 particles and Al2O z (0 < z < 3) particles had a particle size of about 20 nm. The particle size of the composite prepared in Preparation Example 1 was about 50 nm to 200 nm.

[0302] It was found that in the first core / shell structure prepared in Example 1, graphene and the composite prepared in Preparation Example 1 were coated on the large-diameter LCO core to have a core / shell structure.

[0303] SEM-EDS mapping analysis of the bare large-diameter LCO of Comparative Example 1 and the first core / shell structure prepared in Example 1 showed that the concentration of aluminum (Al) distributed on the surface of the first core / shell structure of Example 1 was higher than the concentration of aluminum (Al) on the surface of the bare large-diameter LCO of Comparative Example 1. It was found that in the first core / shell structure of Example 1, the composite prepared in Preparation Example 1 was coated on the large-diameter LCO core to form a core / shell structure.

[0304] Evaluation Example 3: Evaluation of XPS Spectrum (Graphene-LCO Chemical Bond)

[0305] Using Quantum 2000 (Physical Electronics), the XPS spectrum of the C1s orbital of the first core / shell structure prepared in Example 1 was measured.

[0306] Peaks due to the C-Co bonds in the composite positive electrode active material of Example 1 were observed. These peaks were identified as peaks attributable to the bonds between the carbon in graphene and the Co present on the surface of LCO. Thus, it was confirmed that graphene included in the shell formed on the core can form covalent bonds with the transition metal Co included in the core.

[0307] Evaluation Example 4: Evaluation of High Temperature (45 °C) Cycling Characteristics

[0308] The lithium batteries prepared in Examples 5 to 8, Comparative Examples 6 to 10, and Reference Example 2 were all charged at a constant current of 0.1 C rate at 25 °C until the battery voltage reached 4.3 V (vs. Li), and then charged was cut off at a current of 0.05 C rate while maintaining 4.3 V in the constant voltage mode. Then, during discharge, each battery was discharged at a constant current of 0.1 C rate until the battery voltage reached 2.8 V (vs. Li) (formation cycle).

[0309] The lithium batteries after the formation cycle were all charged at a constant current of 0.1 C rate at 45 °C until the voltage reached 4.58 V (vs. Li), and then charged was cut off at a current of 0.025 C rate while maintaining 4.58 V in the constant voltage mode. Then, during discharge, each battery was discharged at a constant current of 1.0 C rate until the battery voltage reached 3.0 V (vs. Li) (the 1st cycle). The above cycle was repeated under the same conditions until the 50th cycle.

[0310] During the entire above charge-discharge cycle, a rest period of 10 minutes was provided after each charge / discharge cycle. A part of the high temperature cycle test results is shown in Table 1 and Figure 3 in. The capacity retention rate is defined by Equation 1.

[0311] Equation 1

[0312] Capacity retention rate [%] = [Discharge capacity of the 50th cycle / Discharge capacity of the 1st cycle] × 100

[0313] Table 1

[0314]

[0315]

[0316] As shown in Table 1 and Figure 3 in, compared with the high temperature life characteristics of the lithium batteries of Comparative Examples 6 to 9, the lithium batteries of Examples 5 to 8 showed improved high temperature life characteristics.

[0317] In addition, compared with the high-temperature life characteristics of the lithium battery of Example 5, the lithium battery of Reference Example 2 shows poor high-temperature life characteristics.

[0318] This result is at least partly attributed to the fact that in the lithium battery of Reference Example 2, since secondary particles are used as small-diameter LCO particles, the increase in the surface resistance of the particles during cycling causes rapid deterioration of the small-diameter LCO particles.

[0319] Although not shown in Table 1, compared with the high-temperature life characteristics of the lithium battery of Comparative Example 6, the lithium battery of Reference Example 2 shows enhanced high-temperature life characteristics.

[0320] Although not shown in Table 1, compared with the high-temperature life characteristics of the lithium battery of Example 5, the lithium battery of Comparative Example 10 shows poor high-temperature life characteristics.

[0321] This result is at least partly attributed to the poor high-voltage stability of the SiO2@Gr composite provided on the LCO core in the lithium battery of Comparative Example 10.

[0322] Evaluation Example 5: Evaluation of DC-IR (Direct Current-Internal Resistance)

[0323] After the high-temperature cycle evaluation, the direct current internal resistance (DC-IR) of the lithium batteries prepared in Examples 5 to 8, Comparative Examples 6 to 10, and Reference Example 2 was measured as follows.

[0324] In the first cycle, each battery was charged to the voltage at 20% state of charge (SOC) at a current of 0.2C, then discharged at a constant current of 3.0C for 10 seconds, discharged at a constant current of 0.2C for 10 seconds, and finally, discharged at a constant current of 3.0C for 10 seconds.

[0325] The direct current internal resistance (DC-IR, R = ΔV / ΔI) was calculated based on the ratio of the average voltage change (ΔV) to the average current change (ΔI) during the constant current discharge at each C rate, and the average value thereof was used as the measured value.

[0326] Part of the results of the DC-IR measurement after the high-temperature cycle evaluation is shown in Table 2.

[0327] Table 2

[0328]

[0329] As shown in Table 2, compared with the DC-IR of the lithium batteries of Comparative Examples 6 to 9, the lithium batteries of Examples 5 to 8 show a reduced DC-IR.

[0330] Therefore, compared with the high-temperature stability of the lithium batteries of Comparative Examples 6 to 9, the lithium batteries of Examples 5 to 8 exhibit improved high-temperature stability.

[0331] Evaluation Example 6: Evaluation of High-Rate Performance at Room Temperature

[0332] The lithium batteries prepared in Examples 5 to 8, Comparative Examples 6 to 10, and Reference Example 2 were each charged at a constant current of 0.1C rate at 25 °C until the battery voltage reached 4.3 V (Vs.Li), and then charged was cut off at a current of 0.05C rate while maintaining 4.3 V in the constant voltage mode. Subsequently, during discharge, the battery was discharged at a constant current of 0.1C rate until the battery voltage reached 2.8 V (Vs.Li) (formation cycle).

[0333] After the formation cycle, the lithium batteries were each charged at a constant current of 0.2C rate at 25 °C until the battery voltage reached 4.3 V (Vs.Li), and then charged was cut off at a current of 0.05C rate while maintaining 4.3 V in the constant voltage mode. Subsequently, during discharge, the battery was discharged at a constant current of 0.2C rate until the battery voltage reached 2.8 V (the 1st cycle).

[0334] After the first cycle, the lithium batteries were each charged at a constant current of 0.2C rate at 25 °C until the battery voltage reached 4.3 V (Vs.Li), and then charged was cut off at a current of 0.05C rate while maintaining 4.3 V in the constant voltage mode. Subsequently, during discharge, the battery was discharged at a constant current of 0.5C rate until the battery voltage reached 2.8 V (Vs.Li) (the 2nd cycle).

[0335] After the second cycle, the lithium batteries were each charged at a constant current of 0.2C rate at 25 °C until the battery voltage reached 4.3 V (Vs.Li), and then charged was cut off at a current of 0.05C rate while maintaining 4.3 V in the constant voltage mode. Subsequently, during discharge, the lithium batteries were each discharged at a constant current of 2.0C rate until the battery voltage reached 2.8 V (Vs.Li) (the 3rd cycle).

[0336] During the entire above charge-discharge cycle, a rest period of 10 minutes was provided after each charge / discharge cycle. A part of the high-rate performance test results is shown in Table 3. The high-rate performance is defined by Equation 3.

[0337] Equation 3

[0338] High-rate performance [%] = [(Discharge capacity at 2.0C rate (discharge capacity of the 3rd cycle)) / (Discharge capacity at 0.2C rate (discharge capacity of the 1st cycle))] × 100

[0339] Part of the results of the room-temperature high-rate performance evaluation is shown in Table 3.

[0340] Table 3

[0341]

[0342]

[0343] As shown in Table 3, compared with the high-rate performance of the lithium batteries of Comparative Examples 6 to 9, the lithium batteries of Examples 5 to 8 show improved high-rate performance.

[0344] Industrial Applicability

[0345] According to one or more embodiments, since the composite positive electrode active material includes a shell containing a first metal oxide, a first carbonaceous material, and a second carbonaceous material, and the shell is disposed on a large-diameter lithium transition metal oxide core and a small-diameter lithium transition metal oxide core, and the large-diameter lithium transition metal oxide and the small-diameter lithium transition metal oxide have an integral particle form, the lithium battery including the composite positive electrode active material can have improved high-temperature cycle performance, suppressed or reduced increase in internal resistance, and improved high-rate performance.

Claims

1. A composite positive electrode active material, the composite positive electrode active material comprising: A first core, comprising a first lithium transition metal oxide; A second core, comprising a second lithium transition metal oxide; And A shell, conformal with the surface of at least one of the first core and the second core, Wherein, the shell comprises: a first metal oxide; a first carbonaceous material; and a second carbonaceous material, Wherein, the first metal oxide is within the matrix of the first carbonaceous material, The first metal oxide is represented by M a O b where 0 < a ≤ 3 and 0 < b < 4, and where, if a is 1, 2 or 3, b is not an integer M is at least one metal selected from Group 2 to Group 13, Group 15 and Group 16 of the periodic table, The second carbonaceous material comprises a fibrous carbonaceous material with an aspect ratio of 10 or greater, The first lithium transition metal oxide and the second lithium transition metal oxide have different particle sizes from each other, The first lithium transition metal oxide comprises primary particles with a particle size of 3 μm or greater, and The second lithium transition metal oxide comprises primary particles with a particle size of 1 μm or greater.

2. The composite positive electrode active material according to claim 1, Among them, The first lithium transition metal oxide is an integral primary particle, and the second lithium transition metal oxide is an integral primary particle.

3. The composite positive electrode active material according to claim 1, Among them, The first lithium transition metal oxide is a large-diameter lithium transition metal oxide having a particle size larger than that of the second lithium transition metal oxide, and The second lithium transition metal oxide is a small-diameter lithium transition metal oxide having a particle size smaller than that of the first lithium transition metal oxide.

4. The composite positive electrode active material according to claim 1, Among them, The first lithium transition metal oxide and the second lithium transition metal oxide show a bimodal particle size distribution in the particle size distribution diagram, and The ratio of the particle size of the first lithium transition metal oxide to the particle size of the second lithium transition metal oxide is 2:1 to 10:

1.

5. The composite positive electrode active material according to claim 1, Among them, The first lithium transition metal oxide has a particle size of 3 μm to 10 μm, and the second lithium transition metal oxide has a particle size of 1 μm to less than 5 μm.

6. The composite positive electrode active material according to claim 1, Among them, The weight ratio of the first lithium transition metal oxide to the second lithium transition metal oxide is 90:10 to 60:40, and The composite positive electrode active material has a specific surface area of 0.8 m 2 / g or less.

7. The composite positive electrode active material according to claim 1, Among them, The second carbonaceous material comprises carbon nanofibers, carbon nanotubes or a combination thereof, The carbon nanotubes comprise a primary carbon nanotube structure, a secondary carbon nanotube structure comprising an aggregate of a plurality of primary carbon nanotube structures, or a combination thereof, and The primary carbon nanotube structure is one carbon nanotube unit.

8. The composite positive electrode active material according to claim 7, Among them, The second carbonaceous material comprises the carbon nanotubes, and The carbon nanotubes comprise the primary carbon nanotube structure, and Wherein, the primary carbon nanotube structure comprises single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes or a combination thereof, and The primary carbon nanotube structure has a diameter of 1 nm to 20 nm and a length of 100 nm to 2 μm.

9. The composite positive electrode active material according to claim 7, Among them, The second carbonaceous material includes the carbon nanotubes, and The carbon nanotubes include the secondary carbon nanotube structure, wherein the secondary carbon nanotube structure includes bundled carbon nanotubes, rope-shaped carbon nanotubes, or a combination thereof, and The secondary carbon nanotube structure has a diameter of 2 nm to 50 nm and a length of 500 nm to 1,000 μm.

10. The composite positive electrode active material according to claim 1, Among them, With respect to the total weight of the first carbonaceous material and the second carbonaceous material, the content of the second carbonaceous material is 5 wt% to 95 wt%, With respect to the total weight of the composite positive electrode active material, the content of the second carbonaceous material is 0.01 wt% to 1 wt%, and The second carbonaceous material is on the surface of the composite positive electrode active material.

11. The composite positive electrode active material according to claim 1, Among them, The first metal included in the first metal oxide is at least one metal selected from Al, Nb, Mg, Sc, Ti, Zr, V, W, Mn, Fe, Co, Pd, Cu, Ag, Zn, Sb, and Se, and The first metal oxide is at least one selected from the following: Al2O z , 0 < z < 3; NbO x , 0 < x < 2.5; MgO x , 0 < x < 1; Sc2O z , 0 < z < 3; TiO y , 0 < y < 2; ZrO y , 0 < y < 2; V2O z , 0 < z < 3; WO y , 0 < y < 2; MnO y , 0 < y < 2; Fe2O z , 0 < z < 3; Co3O w , 0 < w < 4; PdO x , 0 < x < 1; CuO x , 0 < x < 1; AgO x , 0 < x < 1; ZnO x , 0 < x < 1; Sb2O z , 0 < z < 3; and SeO y , 0 < y < 2.

12. The composite positive electrode active material according to claim 1, Among them, The shell further includes a second metal oxide, wherein, the second metal oxide is represented by M a O c where 0 < a ≤ 3 and 0 < c ≤ 4, and wherein if a is 1, 2, or 3, then c is an integer The second metal oxide includes the same metal as the first metal oxide, The ratio c / a of c to a in the second metal oxide is greater than the ratio b / a of b to a in the first metal oxide, and The second metal oxide is in the matrix of the first carbonaceous material.

13. The composite positive electrode active material according to claim 12, Among them, The second metal oxide is selected from Al2O3, NbO, NbO2, Nb2O5, MgO, Sc2O3, TiO2, ZrO2, V2O3, WO2, MnO2, Fe2O3, Co3O4, PdO, CuO, AgO, ZnO, Sb2O3, and SeO2, and The first metal oxide is a reduction product of the second metal oxide.

14. The composite positive electrode active material according to claim 1, Among them, The first carbonaceous material included in the shell is chemically bonded to the transition metal of the lithium transition metal oxide included in the core through a chemical bond, The carbon (C) atoms of the first carbonaceous material included in the shell and the transition metal (Me) of the lithium transition metal oxide are chemically bonded through a C-Me bond, or The first metal oxide is chemically bonded to the first carbonaceous material through a chemical bond.

15. The composite positive electrode active material according to claim 1, The composite positive electrode active material further includes a third metal doped on the core or a third metal oxide coated on the core, Among them, The shell is on the third metal oxide, and The third metal oxide is an oxide of at least one third metal selected from Al, Zr, W, and Co.

16. The composite positive electrode active material according to claim 1, Among them, wherein the shell has a thickness of 0.1 nm to 1 μm, the shell is a single-layer structure or a multi-layer structure, the shell is a dry coating, and the content of the shell is 5 wt% or less relative to the total weight of the composite positive electrode active material.

17. The composite positive electrode active material according to claim 1, Among them, wherein the lithium transition metal oxide is represented by any one of Formula 1 to Formula 8: Formula 1 Li a Co x M y O 2-b A b , wherein, in Formula 1, 1.0 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0.9 ≤ x ≤ 1, 0 ≤ y ≤ 0.1, and x + y = 1, M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof, and A is F, S, Cl, Br, or a combination thereof, Formula 2 Li a Ni x Co y M z O 2-b A b , wherein, in Formula 2, 1.0 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0.8 ≤ x < 1, 0 ≤ y ≤ 0.3, 0 < z ≤ 0.3, and x + y + z = 1, M is manganese (Mn), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof, and A is F, S, Cl, Br, or a combination thereof, Formula 3 LiNi x Co y Mn z O2, and Formula 4 LiNi x Co y Al z O2, wherein, in Formulas 3 and 4, 0.8 ≤ x ≤ 0.95, 0 ≤ y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1, Formula 5 LiNi x Co y Mn z Al w O2, wherein, in Formula 5, 0.8 ≤ x ≤ 0.95, 0 ≤ y ≤ 0.2, 0 < z ≤ 0.2, 0 < w ≤ 0.2, and x + y + z + w = 1, Formula 6 Li a Ni x Mn y M’ z O 2-b A b , wherein, in Formula 6, 1.0 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0 < x ≤ 0.3, 0.5 ≤ y < 1, 0 < z ≤ 0.3, and x + y + z = 1, M' is cobalt (Co), niobium (Nb), vanadium (V), magnesium (Mg), gallium (Ga), silicon (Si), tungsten (W), molybdenum (Mo), iron (Fe), chromium (Cr), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), boron (B), or a combination thereof, A is F, S, Cl, Br, or a combination thereof, Formula 7 Li a M1 x M2 y PO 4-b X b , wherein, in Formula 7, 0.90 ≤ a ≤ 1.1, 0 ≤ x ≤ 0.9, 0 ≤ y ≤ 0.5, 0.9 < x + y < 1.1, and 0 ≤ b ≤ 2, M1 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr), or a combination thereof, M2 is magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), zinc (Zn), boron (B), niobium (Nb), gallium (Ga), indium (In), molybdenum (Mo), tungsten (W), aluminum (Al), silicon (Si), chromium (Cr), vanadium (V), scandium (Sc), yttrium (Y) or a combination thereof, and X is O, F, S, P or a combination thereof, Formula 8 Li a M3 z PO4, and wherein, in Formula 8, 0.90 ≤ a ≤ 1.1, and 0.9 ≤ z ≤ 1.1, and M3 is chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zirconium (Zr) or a combination thereof.

18. A positive electrode, the positive electrode comprising the composite positive electrode active material according to any one of claims 1 to 17.

19. A lithium battery, the lithium battery comprising: The positive electrode according to claim 18; A negative electrode; And An electrolyte, between the positive electrode and the negative electrode.

20. The lithium battery according to claim 19, Among them, The positive electrode comprises a positive electrode current collector, and the negative electrode comprises a negative electrode current collector, wherein at least one of the positive electrode current collector and the negative electrode current collector comprises a substrate film and a metal layer on one or both sides of the substrate film, wherein the substrate film comprises a polymer, the polymer comprises polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI) or a combination thereof, and The metal layer comprises indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li) or an alloy thereof.

21. A method for preparing a composite positive electrode active material, the method comprising the following steps: Preparing a first core / shell structure by mechanically grinding a first lithium transition metal oxide, a composite and a second carbonaceous material; Preparing a second core / shell structure by mechanically grinding a second lithium transition metal oxide, a composite and a second carbonaceous material; And Preparing a composite positive electrode active material by mixing the first core / shell structure and the second core / shell structure, Wherein, the composite includes a first metal oxide represented by M a O b and a first carbonaceous material, where 0 < a ≤ 3 and 0 < b < 4, and where, if a is 1, 2, or 3, then b is not an integer wherein the first metal oxide is in the matrix of the first carbonaceous material, M is at least one metal selected from Groups 2 to 13, 15 and 16 of the periodic table, The second carbonaceous material comprises a fibrous carbonaceous material with an aspect ratio of 10 or more, The first lithium transition metal oxide and the second lithium transition metal oxide have different particle sizes from each other, The first lithium transition metal oxide comprises primary particles with a particle size of 3 μm or more, and The second lithium transition metal oxide comprises primary particles with a particle size of 1 μm or more.

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