Composite cathode active material, cathode including the same, and lithium battery and method for manufacturing the same

Abstract

Provided are a composite cathode active material, a cathode including the composite cathode active material, a lithium battery, and a method of manufacturing the composite cathode active material, wherein the composite cathode active material includes: a core including a lithium transition metal oxide; and a shell disposed on a surface of the core and conforming to the surface of the core, wherein the shell includes at least one first metal oxide, a carbonaceous material, and a doped fluorine (F) element, the first metal oxide is represented by the formula M a O b represents (0

Description

[0001] This application is based on and claims priority to Korean Patent Application No. 10-2021-0042810, filed on April 1, 2021, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0002] A composite positive electrode active material, a positive electrode and a lithium battery using the composite positive electrode active material are provided, as well as a method for preparing the composite positive electrode active material. Background Technology

[0003] As devices become increasingly miniaturized and perform better, it is becoming increasingly important for lithium batteries to have higher energy density in addition to miniaturization and weight reduction. In other words, high-capacity lithium batteries are becoming increasingly important.

[0004] To achieve lithium batteries suitable for the above purposes, high-capacity positive electrode active materials are being researched.

[0005] Due to side reactions, conventional nickel-based cathode active materials exhibit reduced lifetime characteristics and unsatisfactory thermal stability.

[0006] Therefore, a method is needed to prevent the degradation of battery performance while incorporating nickel-based cathode active materials. Summary of the Invention

[0007] One aspect provides a novel composite positive electrode active material that suppresses side reactions of composite positive electrode active materials and improves the reversibility of electrode reactions, thereby preventing the degradation of lithium battery performance.

[0008] On the other hand, a positive electrode comprising the aforementioned composite positive electrode active material is provided.

[0009] On the other hand, a lithium battery employing the aforementioned positive electrode is provided.

[0010] On the other hand, a method for preparing the composite positive electrode active material is provided.

[0011] Additional aspects will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practicing the disclosed embodiments.

[0012] According to one aspect, a composite positive electrode active material is provided, the composite positive electrode active material comprising: a core comprising a lithium transition metal oxide; and a shell disposed on and conformally shaped to the surface of the core, wherein the shell comprises at least one first metal oxide, a carbonaceous material, and doped fluorine (F), the first metal oxide being composed of M... a O bIt is represented that (0 < a ≤ 3 and 0 < b < 4, and if a is 1, 2, or 3, then b is not an integer), and the first metal oxide is disposed in a carbonaceous material matrix, and M is at least one metal selected from Groups 2 to 13, 15, and 16 of the Periodic Table of the Elements.

[0013] According to another aspect, a positive electrode including a composite positive electrode active material is provided. According to another aspect, a lithium battery including a positive electrode, a negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode is provided.

[0014] According to another aspect, a method for preparing a composite positive electrode active material is provided, the method including the steps of: providing a lithium transition metal oxide; providing a composite; and mechanically grinding the lithium transition metal oxide and the composite, wherein the composite includes at least one first metal oxide, a carbonaceous material, and a doped fluorine (F) element, and the first metal oxide is represented by the formula M a O b It is represented that (0 < a ≤ 3 and 0 < b < 4, and if a is 1, 2, or 3, then b is not an integer), wherein the first metal oxide is disposed within a carbonaceous material matrix, and M is at least one metal selected from Groups 2 to 13, 15, and 16 of the Periodic Table of the Elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other aspects, features, and advantages of some embodiments disclosed will become clearer through the following description in conjunction with the accompanying drawings, in which:

[0016] Figure 1 XPS spectra of the undoped composite prepared in Reference Preparation Example 1 and the fluorine (F)-doped composite prepared in Preparation Example 1 are shown.

[0017] Figure 2 is a schematic diagram of a lithium battery according to an example.

[0018] <Description of Reference Numerals in the Drawings>

[0019] 1: Lithium battery 2: Negative electrode

[0020] 3: Positive electrode 4: Separator

[0021] 5: Battery case 6: Cover assembly DETAILED DESCRIPTION

[0022] Reference will now be made in detail to embodiments, examples of which are shown in the accompanying drawings, wherein the same reference numerals always denote the same elements. In this regard, the presented embodiments may have different forms and should not be construed as limited to the description set forth herein. Therefore, the embodiments are described below only by reference to the accompanying drawings to explain aspects of this specification. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of…” modify the entire list of elements (elements) when following a list of elements (elements), without modifying the individual elements (elements) in the list.

[0023] The inventive concept described below can have various modifications and embodiments, and will be described in more detail with reference to the specific embodiments shown in the accompanying drawings. However, the inventive concept should not be construed as limited to the exemplary embodiments set forth herein, but should be understood to cover all modifications, equivalents, or substitutions falling within the scope of the inventive concept.

[0024] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the inventive concept. As used herein, the singular is intended to include the plural form as well, unless the context clearly indicates otherwise. It will also be understood that, when used in this specification, the terms “comprising” and / or “including” and variations thereof specify the presence of stated features, regions, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, regions, integrals, steps, operations, elements, components, and / or groups thereof. Depending on the context, “ / ” as used herein may be interpreted as “and” or “or”.

[0025] In the accompanying drawings, thicknesses may be enlarged or exaggerated to clearly show the various layers and regions. Throughout the drawings and the description below, the same reference numerals may refer to the same elements. It will be understood that when an element, layer, film, portion, sheet, etc., is referred to as being "on" or "above" another element, it may be directly on said other element, or there may be an intermediate element (intermediate element) between them. Although the terms "first," "second," etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another.

[0026] In the following sections, composite positive electrode active materials, positive electrodes including composite positive electrode active materials, lithium batteries, and methods for preparing composite positive electrode active materials will be described in more detail, with reference to exemplary examples.

[0027] The composite positive electrode active material includes: a core including a lithium transition metal oxide; and a shell disposed on the surface of the core and conforming to the surface of the core, wherein the shell includes at least one first metal oxide, a carbonaceous material, and a doped fluorine (F) element, and the first metal oxide is represented by the formula M a O b (where 0 < a ≤ 3 and 0 < b < 4, and if a is 1, 2, or 3, then b is not an integer), and the first metal oxide is disposed in a carbonaceous material matrix, and M is at least one metal selected from Groups 2 to 13, 15, and 16 of the periodic table of elements.

[0028] Hereinafter, the theoretical basis for the composite positive electrode active material according to the examples to provide excellent effects will be described, but this is only for helping to understand the inventive concept and should not be construed as limiting the inventive concept.

[0029] A shell including a first metal oxide, a carbonaceous material, and a fluorine (F) element is disposed on the core of the composite positive electrode active material. The fluorine (F) element included in the shell may be the fluorine (F) element doped in the shell. The fluorine (F) element doped in the shell may form a chemical bond with the first metal oxide and / or the carbonaceous material included in the shell. The fluorine (F) element doped in the shell may be distinguished from the fluorine (F) element physically disposed around the composite positive electrode active material. For example, the fluorine (F) element doped in the shell may be distinguished from the fluorine (F) element disposed around the composite positive electrode active material by mixing the composite positive electrode active material with a fluorine (F)-containing compound or by mixing the composite positive electrode active material with a composition containing a fluorine (F)-containing compound (e.g., a binder, a conductive agent, a liquid electrolyte, etc.). A fluorine (F) atom has a lower electronegativity than a carbon (C) atom, and thus increases the electrochemistry reactivity and conductivity. As a result, in the shell mainly composed of a carbonaceous material, a C-F bond between a fluorine atom and the carbonaceous material promotes, for example, the conduction of electrons and ions. Therefore, the electrochemical absorption and the release of high-density energy of the composite positive electrode active material can be promoted. For example, since the fluorine (F) element is included in the shell, the electrons of the fluorine (F) element are added to, for example, the π electron system of the carbonaceous material, and as a result, the density of charge carriers can be increased. Therefore, since the shell includes a doped fluorine (F) element, the reversibility of the electrode reaction on the surface of the composite positive electrode active material can be increased, and the conductivity of the electrode can be increased. As a result, the cycle characteristics and the charge-discharge capacity of a battery including such a composite positive electrode active material can be improved.

[0030] Conventional carbonaceous materials tend to aggregate, making it difficult to uniformly coat the core. However, composite positive electrode active materials using a carbonaceous material matrix utilize a complex comprising multiple first metal oxides disposed therein, thus preventing the aggregation of carbonaceous materials while uniformly depositing a shell on the core. Therefore, because the contact between the core and the electrolyte solution is effectively blocked, side reactions caused by this contact can be prevented. Furthermore, the formation of a resistive layer can be suppressed because the mixing of cations in the electrolyte solution is inhibited. Additionally, the dissolution of transition metal ions can be suppressed. The carbonaceous material can be, for example, a crystalline carbonaceous material. The carbonaceous material can be, for example, a carbonaceous nanostructure. The carbonaceous material can be, for example, a carbonaceous two-dimensional nanostructure. An example of a carbonaceous material can be graphene. In this case, because the shell comprising graphene and / or a graphene matrix is ​​flexible, it can easily adapt to the volume changes of the composite positive electrode active material during charging and discharging, thereby suppressing the formation of cracks within the composite positive electrode active material. Because graphene has high electron conductivity, it can reduce the interfacial resistance between the composite positive electrode active material and the electrolyte solution. Therefore, even if a graphene-containing shell is introduced into a lithium battery, the internal resistance of the lithium battery can remain unchanged or be reduced.

[0031] The carbonaceous material included in the shell of the composite positive electrode active material is derived from a graphene matrix, and therefore exhibits a relatively low density and higher porosity compared to conventional carbonaceous materials derived from graphite-based materials. The d002 interplanar spacing of the carbonaceous material included in the shell of the composite positive electrode active material can be, for example... or larger or larger or larger or larger or larger or larger or Or larger. The d002 interplanar spacing of the carbonaceous material included in the shell of the composite positive electrode active material can be, for example, approximately to approximately about to approximately about to approximately about to approximately or about to approximately Meanwhile, the d002 interplanar spacing of conventional carbonaceous materials derived from graphite-based materials can be, for example... or smaller or approximately to approximately

[0032] The first metal oxide has a withstand-voltage property, and therefore can prevent the lithium transition metal oxide included in the core from deteriorating during charging and discharging at high voltages. The shell may include, for example, a single type of first metal oxide or two or more different types of first metal oxides.

[0033] Therefore, lithium batteries including the above-mentioned composite positive electrode active materials can have improved high-rate performance (or "rate characteristics") and improved high-temperature and high-voltage cycling characteristics.

[0034] In the composite positive electrode active material, for example, the amount of the shell relative to the total weight of the composite positive electrode active material can be from about 0.5 wt% to about 3 wt%, from about 0.5 wt% to about 2.5 wt%, from about 0.5 wt% to about 2 wt%, or from about 0.5 wt% to about 1.5 wt%. Furthermore, relative to the total weight of the composite positive electrode active material, the amount of the first metal oxide can be, for example, from about 0.3 wt% to about 1.8 wt%, from about 0.3 wt% to about 1.5 wt%, from about 0.3 wt% to about 1.2 wt%, or from about 0.3 wt% to about 0.9 wt%. Because the composite positive electrode active material includes the shell and the first metal oxide in amounts within the above ranges, the lithium battery can have further improved cycle characteristics. The amount of fluorine (F) doped in the shell, relative to the total number of atoms in the shell, can be, for example, from about 1 at% (atomic %) to about 10 at%, from about 1 at% to about 9 at%, from about 2 at% to about 9 at%, from about 2 at% to about 8 at%, from about 3 at% to about 8 at%, from about 3 at% to about 7 at%, from about 4 at% to about 7 at%, or from about 4 at% to about 6 at%. Because the shell is doped with fluorine (F) in amounts within the aforementioned range, lithium-ion batteries incorporating composite cathode active materials can exhibit further improved cycle characteristics. The amount of fluorine (F) doped in the shell can be obtained, for example, from the peaks displayed on the XPS spectrum measured on the surface of the composite cathode active material.

[0035] The amount of metal included in the first metal oxide within the shell, relative to the total number of atoms in the shell, can be, for example, about 1 at% to about 10 at%, about 1 at% to about 9 at%, about 2 at% to about 9 at%, about 2 at% to about 8 at%, about 3 at% to about 8 at%, about 3 at% to about 7 at%, about 4 at% to about 7 at%, or about 4 at% to about 6 at%. Because the shell includes the amount of metal in the first metal oxide within the above range, lithium batteries including composite positive electrode active materials can have further improved cycle characteristics. The amount of metal included in the first metal oxide within the shell can be obtained, for example, from the peaks displayed on the XPS spectrum measured on the surface of the composite positive electrode active material.

[0036] The amount of oxygen (O) included in the shell, relative to the total number of atoms in the shell, can be, for example, about 1 at% to 20 at%, about 1 at% to about 18 at%, about 3 at% to about 18 at%, about 3 at% to about 16 at%, about 5 at% to about 16 at%, about 5 at% to about 14 at%, about 7 at% to about 14 at%, or about 7 at% to about 12 at%. Because the shell includes oxygen in amounts within the above ranges, lithium batteries including composite positive electrode active materials can have further improved cycle characteristics. The amount of oxygen (O) included in the shell can be obtained, for example, from the peaks displayed on the XPS spectrum of the surface of the composite positive electrode active material.

[0037] The shell may additionally include elements other than fluorine (F), the first metal, and oxygen. Other elements additionally included in the shell may be, for example, nitrogen (N), boron (B), etc. During the preparation process of the composite positive electrode active material, these additional elements may be included in the precursor containing fluorine (F).

[0038] The amount of nitrogen (N) included in the shell, relative to the total number of atoms in the shell, can be, for example, about 1 at% to 12 at%, about 2 at% to about 12 at%, about 2 at% to about 11 at%, about 3 at% to about 10 at%, about 4 at% to about 10 at%, about 4 at% to about 9 at%, about 5 at% to about 9 at%, about 5 at% to about 8 at%, or about 5 at% to about 7 at%. Because the shell includes nitrogen in amounts within the above ranges, lithium batteries including composite positive electrode active materials can have further improved cycle characteristics. The amount of nitrogen (N) included in the shell can be obtained, for example, from the peaks displayed on the XPS spectrum measured on the surface of the composite positive electrode active material.

[0039] The amount of boron (B) included in the shell, relative to the total number of atoms in the shell, can be, for example, greater than 0 at% to about 5 at%, about 0.01 at% to about 4 at%, about 0.1 at% to about 3 at%, about 0.1 at% to about 2 at%, about 0.1 at% to about 1.5 at%, or about 0.3 at% to about 1 at%. Because the shell includes boron (B) in amounts within the above ranges, lithium batteries including composite positive electrode active materials can have further improved cycle characteristics. The amount of boron (B) included in the shell can be obtained, for example, from the peaks displayed on the XPS spectrum measured on the surface of the composite positive electrode active material.

[0040] The amount of carbon included in the shell, relative to the total number of atoms in the shell, can be, for example, about 65 at% to about 99 at%, about 70 at% to about 99 at%, about 75 at% to about 99 at%, about 80 at% to about 99 at%, about 80 at% to about 95 at%, about 80 at% to about 93 at%, about 80 at% to about 91 at%, or about 83 at% to about 90 at%. Because the shell includes an amount of carbon within the above range, a lithium battery including the composite cathode active material can have further improved cycle characteristics. The amount of carbon included in the shell can be obtained, for example, from the peaks shown on the XPS spectrum of the surface of the composite cathode active material.

[0041] The metal included in the first metal oxide can be at least one metal selected from, for example, Al, Nb, Mg, Sc, Ti, Zr, V, W, Mn, Fe, Co, Pd, Cu, Ag, Zn, Sb, and Se. The first metal oxide 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 SeO y (0 < y < 2) among others. Because the first metal oxide is disposed within the matrix of the carbonaceous material, the uniformity of the shell disposed on the core can be improved, and the voltage resistance property of the composite cathode active material can be further improved. For example, the shell can include Al2O z (0 < z < 3) as the first metal oxide.

[0042] The shell can further include one or more second metal oxides, and the second metal oxide is represented by the formula M a O cIndicates (0 < a ≤ 3 and 0 < c ≤ 4, and if a is 1, 2, or 3, then c is an integer). M can be at least one metal selected from Groups 2 to 13, 15, and 16 of the periodic table of elements. For example, the second metal oxide can include the same metal as the first metal oxide, and the ratio of c to a (c / a) in the second metal oxide can have a value greater than the ratio of b to a (b / a) in the first metal oxide. For example, c / a > b / a. The second metal oxide can be, for example, selected from Al2O3, NbO, NbO2, Nb2O5, MgO, Sc2O3, TiO2, ZrO2, V2O3, WO2, MnO2, Fe2O3, Co3O4, PdO, CuO, AgO, ZnO, Sb2O3, and SeO2. The first metal oxide is the reduction product of the second metal oxide. When the second metal oxide is partially or completely reduced, the first metal oxide is obtained. Therefore, the first metal oxide has an oxygen content lower than that of the second metal oxide and has a low metal oxidation number (or oxidation value). For example, the shell can include Al2O as the first metal oxide z (0 < z < 3) and Al2O3 as the second metal oxide.

[0043] In the composite positive electrode active material, for example, the transition metal of the carbonaceous material included in the shell and the lithium transition metal oxide included in the core can be chemically bonded via a chemical bond. The carbon atom (C) of the carbonaceous material included in the shell and the transition metal (Me) of the lithium transition metal oxide can be chemically bonded, for example, through a C-O-Me bond (e.g., a C-O-Ni bond or a C-O-Co bond) via an oxygen atom. When the carbonaceous material included in the shell and the lithium transition metal oxide included in the core are chemically bonded via a chemical bond, the core and the shell are complexed. Therefore, the resulting complex can be distinguished from a simple physical mixture of the carbonaceous material and the lithium transition metal oxide.

[0044] In addition, the carbonaceous material included in the shell and the first metal oxide can be chemically bonded via a chemical bond. Here, the chemical bond can be, for example, a covalent bond or an ionic bond. The covalent bond can be a bond including at least one of, for example, an ester group, an ether group, a carbonyl group, an amide group, a carbonate group, and an acid anhydride group. The ionic bond can be a bond including, for example, a carboxylate ion, an ammonium ion, an acyl cation group, etc.

[0045] The thickness of the shell can be, for example, about 1 nm to about 5 μm, about 1 nm to about 1 μm, about 1 nm to about 500 nm, about 1 nm to about 200 nm, about 1 nm to about 100 nm, about 1 nm to about 90 nm, about 1 nm to about 80 nm, about 1 nm to about 70 nm, about 1 nm to about 60 nm, about 1 nm to about 50 nm, about 1 nm to about 40 nm, about 1 nm to about 30 nm, or about 1 nm to about 20 nm. Because the shell has a thickness within the above range, the electrode including the composite positive electrode active material has improved electrode conductivity.

[0046] The composite positive electrode active material may further include, for example, a third metal doped in the core or a third metal oxide coated on the core. Furthermore, a shell may be disposed on the doped third metal or the coated third metal oxide. For example, after doping a third metal on the surface of a lithium transition metal oxide included in the core or coating a third metal oxide on the surface of a lithium transition metal oxide, a shell 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 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, etc.

[0047] The shell included in the composite positive electrode active material may include, for example, at least one selected from the composite and a milling product thereof, the composite comprising a first metal oxide, a carbonaceous material (e.g., graphene), and doped fluorine (F), wherein the first metal oxide is disposed within a graphene-based material matrix (e.g., a graphene matrix). The shell may be made, for example, from a composite comprising a first metal oxide, a carbonaceous material (e.g., graphene), and doped fluorine (F). In addition to the first metal oxide, the composite may also include a second metal oxide. The composite may include, for example, two or more first metal oxides. The composite may include, for example, two or more first metal oxides and two or more second metal oxides.

[0048] Relative to the total weight of the composite positive electrode active material, the amount of at least one of the composite and its polished articles included in the composite positive electrode active material can be 3 wt% or less, 2 wt% or less, 1 wt% or less, 0.5 wt% or less, or 0.2 wt% or less. Relative to the total weight of the composite positive electrode active material, the amount of at least one of the composite and its polished articles can be about 0.01 wt% to about 3 wt%, about 0.01 wt% to about 1 wt%, about 0.01 wt% to about 0.7 wt%, about 0.01 wt% to about 0.5 wt%, about 0.01 wt% to about 0.2 wt%, about 0.01 wt% to about 0.1 wt%, or about 0.03 wt% to about 0.07 wt%. Because the composite positive electrode active material includes at least one of the composite and its polished articles in the amounts within the above ranges, the lithium battery including the composite positive electrode active material can have further improved cycle characteristics.

[0049] The amount of fluorine (F) doped in the composite, relative to the total number of atoms, can be, for example, about 1 at% to about 10 at%, about 1 at% to about 9 at%, about 2 at% to about 9 at%, about 2 at% to about 8 at%, about 3 at% to about 8 at%, about 3 at% to about 7 at%, about 4 at% to about 7 at%, or about 4 at% to about 6 at%. Because the composite is doped with amounts of fluorine (F) within the aforementioned range, lithium-ion batteries employing composite positive electrode active materials having a shell comprising the composite and / or its milled articles can have further improved cycle characteristics. The amount of fluorine (F) doped in the composite can be obtained, for example, from peaks displayed on an XPS spectrum measured on the surface of the composite or the surface of the composite positive electrode active material coating the composite.

[0050] At least one selected from the first and second metal oxides included in the composite can have an average particle size of about 1 nm to about 1 μm, about 1 nm to about 500 nm, about 1 nm to about 200 nm, about 1 nm to about 100 nm, about 1 nm to about 70 nm, about 1 nm to about 50 nm, about 1 nm to about 30 nm, about 3 nm to about 30 nm, about 3 nm to about 25 nm, about 5 nm to about 25 nm, about 5 nm to about 20 nm, about 7 nm to about 20 nm, or about 7 nm to about 15 nm. The first and / or second metal oxides have particle sizes in the nanoscale range, resulting in a more uniform distribution within the carbonaceous matrix of the composite. Therefore, the composite can uniformly coat the core without agglomeration, thereby forming a shell. Furthermore, the first and / or second metal oxides have particle sizes within the aforementioned ranges, resulting in a more uniform distribution on the core. Therefore, because the first and / or second metal oxides are uniformly disposed on the core, voltage withstand properties can be achieved more effectively.

[0051] The average particle size of the first and second metal oxides can be measured, for example, by using a measuring device that utilizes laser diffraction or dynamic light scattering. The average particle size is the value of the median particle size (D50) accumulated from the minimum particle size count within the volume distribution measured using a laser scattering particle size distribution system (e.g., LA-920 from HORIBA Inc.).

[0052] The uniformity deviation selected from at least one of the first metal oxide and the second metal oxide included in the composite can be 3% or less, 2% or less, or 1% or less. For example, uniformity can be obtained by XPS. Therefore, in the composite, at least one selected from the first metal oxide and the second metal oxide can be uniformly distributed with a deviation of 3% or less, 2% or less, or 1% or less.

[0053] The carbonaceous material included in the composite may have, for example, a branched structure, and at least one metal oxide selected from a first metal oxide and a second metal oxide may be distributed within the branched structure of the carbonaceous material. The branched structure of the carbonaceous material may include, for example, multiple carbonaceous material particles in contact with each other. Because the carbonaceous material has this branched structure, it can provide various conductive paths (or "conduction pathways").

[0054] The carbonaceous material included in the composite can be, for example, graphene. Graphene can have, for example, a branched structure, and at least one metal oxide selected from a first metal oxide and a second metal oxide can be distributed within the branched structure of the graphene. The branched structure of the graphene can include, for example, multiple graphene particles in contact with each other. Because graphene has this branched structure, it can provide various conductive pathways.

[0055] The carbonaceous material included in the composite can have, for example, a spherical structure, and at least one metal oxide selected from a first metal oxide and a second metal oxide can be distributed within the spherical structure. The spherical structure of the carbonaceous material can have a size of about 50 nm to about 300 nm. Multiple carbonaceous materials with spherical structures can be provided. Because the carbonaceous material has a spherical structure, the composite can have a stable structure.

[0056] The carbonaceous material included in the composite can be, for example, graphene. Graphene can have, for example, a spherical structure, and at least one metal oxide selected from a first metal oxide and a second metal oxide can be distributed within the spherical structure. The spherical structure of graphene can have a size of about 50 nm to about 300 nm. Multiple graphene particles with spherical structures can be provided. Because graphene has a spherical structure, the composite can have a stable structure.

[0057] The carbonaceous material included in the composite can have, for example, a spiral structure in which multiple spherical structures are connected, and at least one metal oxide selected from a first metal oxide and a second metal oxide can be distributed within the spherical structures of the spiral structure. The spiral structure of the carbonaceous material can have a size of about 500 nm to about 100 μm. Because the carbonaceous material has a spiral structure, the composite can have a stable structure.

[0058] The carbonaceous material included in the composite can be, for example, graphene. The graphene included in the composite can have, for example, a helical structure in which multiple spherical structures are connected, and at least one metal oxide selected from a first metal oxide and a second metal oxide can be distributed within the spherical structures of the helical structure. The helical structure of graphene can have a size of about 500 nm to about 100 μm. Because graphene has a helical structure, the composite can have a stable structure.

[0059] The carbonaceous material included in the composite can have a cluster structure, for example, in which multiple spherical clusters are arranged, and at least one metal oxide selected from a first metal oxide and a second metal oxide can be distributed within the spherical structures of the cluster structure. The cluster structure of the carbonaceous material can have a size of about 0.5 mm to about 10 cm. Because the carbonaceous material has a cluster structure, the composite can have a stable structure.

[0060] The carbonaceous material included in the composite can be, for example, graphene. The graphene included in the composite can have a cluster structure, for example, in which multiple spherical clusters are arranged, and at least one metal oxide selected from a first metal oxide and a second metal oxide can be distributed within the spherical structures of the cluster structure. The cluster structure of graphene can have a size of about 0.5 mm to about 10 mm. Because graphene has a cluster structure, the composite can have a stable structure.

[0061] The composite may have, for example, a faceted-ball structure, and at least one selected from a first metal oxide and a second metal oxide may be distributed within or on the surface of the structure. Because the composite is such a faceted-ball structure, it can be readily coated onto the irregular surface bumps of the core.

[0062] The composite may have, for example, a planar structure, and at least one selected from a first metal oxide and a second metal oxide may be distributed within or on the surface of the structure. Because the composite is such a two-dimensional planar structure, it can be easily coated onto the irregular surface bumps of the core.

[0063] The carbonaceous material included in the composite can extend from the first metal oxide by a distance of 10 nm or less, and can include at least one to 20 layers of carbonaceous material. For example, when multiple layers of carbonaceous material are deposited, carbonaceous material with a total thickness of 12 nm or less can be disposed on the first metal oxide. For example, the total thickness of the carbonaceous material can be from about 0.6 nm to about 12 nm.

[0064] The carbonaceous material included in the composite can be, for example, graphene. The graphene included in the composite can extend from the first metal oxide by a distance of 10 nm or less, and can comprise at least one to 20 layers of carbonaceous material. For example, when multiple graphene layers are deposited, graphene with a total thickness of 12 nm or less can be disposed on the first metal oxide. For example, the total thickness of the graphene can be from about 0.6 nm to about 12 nm.

[0065] The core included in the composite positive electrode active material may include, for example, a lithium transition metal oxide represented by Formula 1 below.

[0066] <Formula 1>

[0067] Li a Ni x Co y M z O 2-b A b

[0068] In Formula 1, 0.9 ≤ a ≤ 1.2 (for example, 1.0 ≤ a ≤ 1.2), 0 ≤ b ≤ 0.2, 0.8 ≤ x < 1 (for example, 0.8 ≤ x ≤ 0.95), 0 ≤ y ≤ 0.3 (for example, 0 ≤ y ≤ 0.2), 0 < z ≤ 0.3 (for example, 0 < z ≤ 0.2), 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), or a combination thereof, and A is F, S, Cl, Br, or a combination thereof.

[0069] The core included in the composite positive electrode active material may include, for example, lithium transition metal oxides represented by the following Formulas 2 to 4.

[0070] <Formula 2>

[0071] LiNi x Co y Mn z O2

[0072] <Formula 3>

[0073] LiNi x Co y Al z O2

[0074] In Formulas 2 to 3, 0.8 ≤ x ≤ 0.95, 0 < y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1.

[0075] <Formula 4>

[0076] LiNi x Co y Mn v Al w O2

[0077] In Formula 4, 0.8 ≤ x ≤ 0.95, 0 < y ≤ 0.2, 0 < v ≤ 0.2, 0 < w ≤ 0.2, and x + y + v + w = 1.

[0078] Relative to the total mole number of the transition metals, the lithium transition metal oxides of Formulas 1 to 4 have a high nickel content of 80 mol% or more, 85 mol% or more, or 90 mol% or more, and can also provide excellent initial capacity, room temperature life characteristics, and high temperature life characteristics. For example, relative to the total mole number of the transition metals, the nickel content in the lithium transition metal oxides of Formulas 1 to 4 may be from about 80 mol% to about 95 mol%, from about 85 mol% to about 95 mol%, or from about 90 mol% to about 95 mol%.

[0079] The core included in the composite positive electrode active material may include, for example, lithium transition metal oxides represented by Formulas 5 to 6 below.

[0080] <Formula 5>

[0081] Li a Co x M y O 2-b A b

[0082] In Equation 5, 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) or a combination thereof, and A is F, S, Cl, Br or a combination thereof.

[0083] <Formula 6>

[0084] LiCoO2

[0085] According to another example, the positive electrode includes the aforementioned composite positive electrode active material. The inclusion of the aforementioned composite positive electrode active material in the positive electrode results in improved cycle characteristics and increased conductivity.

[0086] The positive electrode can be prepared by the exemplary method described below, but the method is not limited thereto and can be adjusted according to the desired conditions.

[0087] First, the aforementioned composite positive electrode active material, conductive agent, binder, and solvent can be mixed to prepare a positive electrode active material composition. The prepared positive electrode active material composition can be directly coated onto an aluminum current collector and dried to form a positive electrode plate with a positive electrode active material layer formed thereon. Alternatively, the positive electrode active material composition can be cast onto a separate carrier, and a film layer peeled from the carrier can be stacked onto the aluminum current collector to form a positive electrode plate with a positive electrode active material layer formed thereon.

[0088] Examples of conductive materials (or conductive agents) may include: carbon black, graphite powder, natural graphite, artificial graphite, acetylene black, Ketjen black, and carbon fiber; carbon nanotubes; metal powders, metal fibers, or metal tubes such as copper, nickel, aluminum, silver, etc.; and conductive polymers such as polyphenylene derivatives, but are not limited to the foregoing components, and may be any material used as a conductive material in the relevant technical field.

[0089] Examples of adhesives may include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), mixtures of the aforementioned polymers, styrene-butadiene rubber polymers, and solvents such as N-methylpyrrolidone (NMP), acetone, water, etc., but are not limited thereto, and may be any solvent used in the relevant technical field.

[0090] Pores can also be created inside the electrode plate by further adding plasticizers and pore forming agents to the positive electrode active material composition.

[0091] The amounts of positive electrode active material, conductive agent, binder, and solvent used in the positive electrode are at levels commonly used in lithium batteries. Depending on the intended use and composition of the lithium battery, one or more of the conductive agent, binder, and solvent may be omitted.

[0092] The amount of binder included in the positive electrode may be from about 0.1 wt% to about 10 wt% or from about 0.1 wt% to about 5 wt% relative to the total weight of the positive electrode active material layer. The amount of composite positive electrode active material included in the positive electrode may be from about 90 wt% to about 99 wt% or from about 95 wt% to about 99 wt% relative to the total weight of the positive electrode active material layer.

[0093] In addition to the aforementioned composite positive electrode active materials, the positive electrode may additionally include other common positive electrode active materials.

[0094] Such common positive electrode active materials can be, but are not limited to, any lithium-containing metal oxide commonly used in the relevant technical field. Examples of such common positive electrode active materials include one or more composite oxides selected from lithium and metals selected from cobalt, manganese, nickel, and combinations thereof, and as specific examples include compounds represented by any of the following formulas: Li a A 1-b B b D2 (in this formula, 0.90≤a≤1 and 0≤b≤0.5); Li a E 1-b B b O 2-c D c (In this formula, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05); LiE 2-b B b O 4-c D c (In this formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B c Dα (In this formula, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li a Ni 1-b- c Co b B c O 2-α F α (In this formula, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b-c Co b B c O 2-α F2 (in this formula, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b-c Mn b B c D α (In this formula, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li a Ni 1-b-c Mn b B c O 2-α F α (In this formula, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b-c Mn b B c O 2-α F2 (in this formula, 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni b E c G d O2 (in this formula, 0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1); Li a Ni b Co c Mn d GeO2 (in this formula, 0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1); Li a NiG b O2 (in this formula, 0.90≤a≤1, 0.001≤b≤0.1); Li a CoG b O2 (in this formula, 0.90≤a≤1, 0.001≤b≤0.1); Lia MnG b O2 (in this formula, 0.90≤a≤1, 0.001≤b≤0.1); Li a Mn2G b O4 (in this formula, 0.90≤a≤1, 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.

[0095] In the formulas representing the above compounds, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0096] Compounds having a coating added to the surface of the above-described compounds can also be used, and mixtures of the above-described compounds and compounds having a coating added thereon can also be used. The coating added to the surface of the above-described compounds can include, for example, compounds of coating elements, such as oxides and hydroxides of coating elements, hydroxyoxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. The compounds forming the above-described coatings can be amorphous or crystalline. The coating elements included in the coating can be Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The method of forming the coating is selected from methods that do not adversely affect the physical properties of the positive electrode active material. The coating method can be, for example, spraying, dipping, etc. This particular coating method is known to those skilled in the art and will therefore not be described in further detail.

[0097] According to another example, the lithium battery uses a positive electrode that includes the aforementioned composite positive electrode active material.

[0098] Because lithium batteries use a cathode that includes the aforementioned composite cathode active material, they can provide improved cycle characteristics and thermal stability.

[0099] Lithium batteries can be prepared by the exemplary methods described below, but the methods are not limited thereto and can be adjusted according to desired conditions.

[0100] First, prepare the positive electrode according to the method for positive electrode preparation described above.

[0101] Next, prepare the negative electrode by the method described below. Except for using, for example, a negative electrode active material to replace the composite positive electrode active material, the negative electrode is prepared by substantially the same method as the positive electrode. In addition, substantially the same conductive agent, binder, and solvent as those used for the positive electrode can be used in the negative electrode active material composition.

[0102] For example, prepare a negative electrode active material composition by mixing a negative electrode active material, a conductive agent, a binder, and a solvent, and directly coat it on a copper current collector to form a negative electrode plate. Alternatively, the prepared negative electrode active material composition can be cast on a separate carrier, and the negative electrode active material film peeled off from the carrier can be laminated on the copper current collector to form a negative electrode plate.

[0103] The negative electrode active material can be any material used as a negative electrode active material for a lithium battery in the related art field. For example, the negative electrode active material includes one or more selected from the group consisting of lithium metal, metals that can be alloyed with lithium, transition metal oxides, non-transition metal oxides, and carbonaceous materials.

[0104] Examples of metals that can be alloyed with lithium include Si, Sn, Al, Ge, Pb, Bi, Sb, Si-Y alloy (here, Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, or a combination of the foregoing elements, but not Si), Sn-Y alloy (here, Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, or a combination of the foregoing elements, but not Sn), etc. The element Y can be, for example, 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, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof.

[0105] The transition metal oxide can be, for example, lithium titanium oxide, vanadium oxide, lithium vanadium oxide, etc.

[0106] The non-transition metal oxide can be, for example, SnO2, SiO x (0 < x < 2), etc.

[0107] Carbonaceous materials can be, for example, crystalline carbon, amorphous carbon, or mixtures thereof. Examples of crystalline carbon can include graphite, including amorphous, tabular, flake, spherical, or fibrous artificial or natural graphite. Examples of amorphous carbon can include soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbides, calcined coke, etc.

[0108] The amounts of negative electrode active material, conductive agent, binder, and solvent are at levels commonly used in lithium batteries. Depending on the intended use and composition of the lithium battery, one or more of the conductive agent, binder, and solvent may be omitted.

[0109] The amount of binder included in the negative electrode, relative to the total weight of the negative electrode active material layer, can be, for example, from about 0.1 wt% to about 10 wt% or from about 0.1 wt% to about 5 wt%. The amount of conductive agent included in the negative electrode, relative to the total weight of the negative electrode active material layer, can be, for example, from about 0.1 wt% to about 10 wt% or from about 0.1 wt% to about 5 wt%. The amount of negative electrode active material included in the negative electrode, relative to the total weight of the negative electrode active material layer, can be, for example, from about 90 wt% to about 99 wt% or from about 95 wt% to about 99 wt%. In the case where the negative electrode active material is lithium metal, the negative electrode may not include binder and conductive agent.

[0110] Next, a separator will be prepared to be placed between the positive and negative electrodes.

[0111] The separator can be any separator commonly used in lithium batteries. For example, it can be a separator that has low resistance to the movement of ions in the electrolyte and is capable of holding a large amount of electrolyte solution. The separator can be, for example, selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or combinations thereof, and can be in the form of non-woven or woven fabric. In lithium-ion batteries, wound separators (such as polyethylene, polypropylene, etc.) can be used, and in lithium-ion polymer batteries, separators capable of holding a large amount of organic electrolyte solution can be used.

[0112] The diaphragm can be prepared by the exemplary method described below, but the method is not limited thereto and can be adjusted according to the desired conditions.

[0113] First, a membrane composition can be prepared by mixing a polymer resin, filler, and solvent. The membrane composition can be directly coated onto an electrode and dried to form a membrane. Alternatively, the membrane composition can be cast onto a carrier and dried, and a membrane peeled from the carrier can be laminated onto the electrode to form a membrane.

[0114] There are no particular restrictions on the polymers used in the preparation of the diaphragm, and any polymer that can be used in the adhesive material for the electrode plates can be used. For example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or mixtures thereof can be used.

[0115] Next, electrolytes can be prepared.

[0116] Electrolytes can be, for example, organic electrolyte solutions. Organic electrolyte solutions can be prepared by dissolving lithium salts in organic solvents.

[0117] Organic solvents can be any material used as organic solvents in the relevant technical field. Examples of organic solvents may include propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butyl carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzyl nitrile, 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, or mixtures thereof.

[0118] Lithium salts can be any material used as lithium salts in the relevant technical field. Examples of lithium salts may include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, and LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2 (where x and y are natural numbers from 1 to 20), LiCl, LiI, or mixtures thereof.

[0119] Optionally, the electrolyte can be a solid electrolyte. Examples of solid electrolytes may include, but are not limited to, boron oxide, lithium oxynitride, etc., and can be any material used as a solid electrolyte in the relevant technical field. For example, a solid electrolyte can be formed on the negative electrode by methods such as sputtering, or individual solid electrolyte sheets can be stacked on the negative electrode.

[0120] Solid electrolytes can be, for example, oxide-based solid electrolytes or sulfide-based solid electrolytes.

[0121] For example, the solid electrolyte can be an oxide-based solid electrolyte. Oxide-based solid electrolytes can be selected from Li... 1+x+y Al x Ti 2-xSi y P 3-y O 12 (0 < x < 2, 0 ≤ y < 3), BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3 (PLZT) (0 ≤ x < 1, 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, 0 < y < 3), Li x Al y Ti z (PO4)3 (0 < x < 2, 0 < y < 3, 0 < z < 3), Li 1+x+y (Al, Ga) x (Ti, Ge) 2-x Si y P 3-y O 12 (0 ≤ x ≤ 1, 0 ≤ y ≤ 1), Li x La y TiO3 (0 < x < 2, 0 < y < 3), Li2O, LiOH, Li2CO3, LiAlO2, Li2O - Al2O3 - SiO2 - P2O5 - TiO2 - GeO2 and Li 3+x La3M2O 12 (M = Te, Nb or Zr, x is an integer from 1 to 10) or more than one of them. The solid electrolyte can be prepared by a sintering method or the like. For example, the oxide - based solid electrolyte can be a garnet - type solid electrolyte selected from Li7La3Zr2O 12 (LLZO) and Li 3+ x La3Zr 2-a M a O 12 (M - doped LLZO, M = Ga, W, Nb, Ta or Al, and x is an integer from 1 to 10).

[0122] Sulfide-based solid electrolytes can include, for example, 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. The sulfide-based solid electrolyte particles can be Li2S or P2S5. Sulfide-based solid electrolyte particles are known to have higher lithium ion conductivity than other inorganic compounds. For example, the sulfide-based solid electrolyte can include Li2S and P2S5. In the case where the sulfide solid electrolyte material in which the sulfide-based solid electrolyte is formed includes Li2S-P2S5, the mixing molar ratio of Li2S to P2S5 can be, for example, in the range of about 50:50 to about 90:10. In addition, by adding 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, 0 < y < 3), Li 3.25 Ge 0.25 P 0.75 S4 (“thio-LISICON”), Li2O-Al2O3-TiO2-P2O5 (“LATP”) to inorganic solid electrolytes such as Li2S-P2S5, SiS2, GeS2, B2S3, or combinations thereof, the prepared inorganic solid electrolyte can be used as a sulfide solid electrolyte. Non-limiting examples of sulfide 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, a sulfide-based solid electrolyte material can be prepared by treating starting materials (e.g., Li2S, P2S5, etc.) of the sulfide-based solid electrolyte material through processes such as the melt quenching method, mechanical grinding method, etc. In addition, a calcination process can be carried out after the above treatment. The sulfide-based solid electrolyte can be amorphous, crystalline, or in a mixed state thereof.

[0123] As Figure 2 shown, the exemplary lithium battery 1 includes a positive electrode 3, a negative electrode 2, and a separator 4. The wound or folded positive electrode 3, negative electrode 2, and separator 4 are accommodated in a battery case 5. An organic electrolyte solution can be injected into the battery case 5 and sealed with a lid assembly 6 to form the lithium battery 1. The battery case 5 has a cylindrical shape, but is not limited thereto and can have a polygonal shape, a thin film shape, etc.

[0124] A pouch-type lithium battery can include one or more battery structures. A separator is disposed between the positive electrode and the negative electrode to form a battery structure. The battery structures are stacked into a dual-battery structure and immersed in an organic electrolyte solution, and are accommodated and sealed in a pouch to form a pouch-type lithium battery.

[0125] Multiple lithium batteries are stacked to form a battery module and / or a battery pack, and such a battery module and / or battery pack can be used in all types of devices that require high capacity and high output. For example, such a battery module and / or battery pack can be used in laptop computers, smart phones, electric vehicles, etc.

[0126] A lithium battery using a solid electrolyte can be a solid battery or an all-solid-state battery. A lithium battery using a solid electrolyte can also include a solid electrolyte in the positive electrode or the negative electrode or both. For example, in a lithium battery in which an electrolyte layer including a sulfide-based solid electrolyte is disposed between the positive electrode and the negative electrode, the positive electrode or the negative electrode or both can include a sulfide-based solid electrolyte.

[0127] Lithium batteries have excellent life characteristics and high rate performance, and thus can be used in electric vehicles (EVs), energy storage systems (ESSs), etc. 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 field that requires a large amount of energy storage. For example, lithium batteries can be used in electric bicycles, power tools, etc.

[0128] A method for preparing a composite cathode active material according to another example includes the following steps: providing a lithium transition metal oxide; providing a composite; and mechanically grinding the lithium transition metal oxide and the composite, wherein the composite includes: at least one first metal oxide represented by the formula M a O b (where 0 < a ≤ 3 and 0 < b < 4, and if a is 1, 2, or 3, then b is not an integer); a carbonaceous material; and a doped fluorine (F) element, wherein the first metal oxide is disposed within the carbonaceous material matrix, and M is at least one metal selected from Groups 2 to 13, 15, and 16 of the periodic table. The grinding method used in the mechanical grinding is not particularly limited and is a method of bringing the lithium transition metal oxide and the composite into contact by using a machine, and can be any such method available in the relevant technical field.

[0129] Provide a lithium transition metal oxide. The lithium transition metal oxide can be, for example, a compound represented by Formulas 1 to 6 above.

[0130] The step of providing the composite can, for example, include: providing an undoped composite by supplying a reaction gas composed of a carbon source gas to a structure including a metal oxide; and preparing the composite by mixing the undoped composite with a fluorine (F)-containing compound.

[0131] The step of providing the composite can, for example, include: providing an undoped composite by supplying a reaction gas composed of a carbon source gas to at least one second metal oxide represented by M a O c (where 0 < a ≤ 3 and 0 < c ≤ 4, and if a is 1, 2, or 3, then c is an integer) and performing a heat treatment, wherein M is at least one metal selected from Groups 2 to 13, 15, and 16 of the periodic table.

[0132] The carbon source gas can be a compound represented by Formula 7 below, or a mixed gas of one or more selected from the group consisting of a compound represented by Formula 7 below, a compound represented by Formula 8 below, and an oxygen-containing gas represented by Formula 9 below.

[0133] <Formula 7>

[0134] C n H (2n+2-a) [OH] a

[0135] In Formula 7, n is from 1 to 20, and a is 0 or 1;

[0136] <Formula 8>

[0137] C n H2n

[0138] In Formula 8, n is from 2 to 6;

[0139] <Formula 9>

[0140] C x H y O z

[0141] In Formula 9, x is an integer of 0 or from 1 to 20, y is an integer of 0 or from 1 to 20, and z is 1 or 2.

[0142] The compound represented by Formula 7 and the compound represented by Formula 8 are at least one selected from the group consisting of methane, ethylene, propylene, methanol, ethanol, and propanol. The oxygen-containing gas represented by Formula 9 includes, for example, carbon dioxide (CO2) and carbon monoxide (CO), steam (H2O), or a mixture thereof.

[0143] In a process of supplying a reaction gas composed of a carbon source gas to a second metal oxide represented by M a O c (where 0 < a ≤ 3 and 0 < c ≤ 4, and if a is 1, 2, or 3, then c is an integer) and performing a heat treatment, a cooling process using one or more inert gases selected from the group consisting of nitrogen, helium, and argon can be further performed. The cooling process refers to a process of adjusting to room temperature (20 - 25 °C). The carbon source gas may include one or more inert gases selected from the group consisting of nitrogen, helium, and argon.

[0144] In the method for preparing a composite, according to the gas-phase reaction, a process for the growth of a carbonaceous material (such as graphene) can be carried out under various conditions.

[0145] According to the first condition, for example, methanol can be first supplied to a reactor containing a second metal oxide represented by M a O c (where 0 < a ≤ 3 and 0 < c ≤ 4, and if a is 1, 2, or 3, then c is an integer), and the temperature can be raised to the heat treatment temperature (T). The time for raising the temperature to the heat treatment temperature (T) can be 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 a reaction time. The reaction time can be, for example, about 4 hours to about 8 hours. The obtained product after the heat treatment can be cooled to room temperature to form an undoped composite. 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.

[0146] According to the second condition, for example, hydrogen can be first supplied to a reactor containing a second metal oxide represented by Ma O c In a reactor of a second metal oxide represented by (0 < a ≤ 3 and 0 < c ≤ 4, and if a is 1, 2, or 3, then c is an integer), the temperature can be raised to a heat treatment temperature (T). The temperature raising time to the heat treatment temperature (T) can be 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 performing the heat treatment at the heat treatment temperature (T) for a predetermined reaction time, methane gas can be supplied, and the heat treatment can be performed during the remaining reaction time. The reaction time can be, for example, about 4 hours to about 8 hours. The heat-treated product can be cooled to room temperature to form an undoped composite. Nitrogen 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.

[0147] According to the third condition, for example, hydrogen can be first supplied to a reactor containing a second metal oxide represented by M a O c In a reactor of a second metal oxide represented by (0 < a ≤ 3 and 0 < c ≤ 4, and if a is 1, 2, or 3, then c is an integer), the temperature can be raised to a heat treatment temperature (T). The temperature raising time to the heat treatment temperature (T) can be 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 performing the heat treatment at the heat treatment temperature (T) for a predetermined reaction time, a mixed gas of methane and hydrogen can be supplied, and the heat treatment can be performed during the remaining reaction time. The reaction time can be, for example, about 4 hours to about 8 hours. The heat-treated product can be cooled to room temperature to form an undoped composite. Nitrogen 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.

[0148] In the process of forming the composite, if the carbon source gas includes steam, a composite with excellent conductivity can be obtained. The amount of steam in the gas mixture is not limited, and relative to 100 volume% of the total carbon source gas, the amount of steam in the gas mixture can be, for example, about 0.01 volume% to about 10 volume%. The carbon source gas can be, for example, methane, a mixed gas containing methane and an inert gas, or a mixed gas containing methane and an oxygen-containing gas.

[0149] The carbon source gas can be, for example: methane; a mixed gas of methane and carbon dioxide; or a mixed gas of methane, carbon dioxide and steam. The molar ratio of methane to carbon dioxide in the mixed gas of methane and carbon dioxide can be about 1:0.20 to about 1:0.50, about 1:0.25 to about 1:0.45 or about 1:0.30 to about 1:0.40. The molar ratio of methane, carbon dioxide and steam in the mixed gas of methane, carbon dioxide and steam can be, for example, about 1: about 0.20 to 0.50: about 0.01 to 1.45, about 1: about 0.25 to 0.45: about 0.10 to 1.35 or about 1: about 0.30 to 0.40: about 0.50 to 1.0.

[0150] The carbon source gas can be, for example, carbon monoxide 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: about 0.20 to 1:0.50, about 1: about 0.25 to 1: about 0.45 or about 1: about 0.30 to 1: about 0.40. The carbon source gas may not include inert gases such as nitrogen.

[0151] The heat treatment pressure can be selected considering the heat treatment temperature, the composition of the gas mixture, the amount of the required carbon coating, etc. The heat treatment pressure can be controlled by adjusting the amount of the introduced gas mixture and the amount of the discharged gas mixture. The heat treatment pressure can be, for example, 0.5 atm or higher, 1 atm or higher, 2 atm or higher, 3 atm or higher, 4 atm or higher or 5 atm or higher.

[0152] The heat treatment time is not particularly limited and can be appropriately adjusted according to the heat treatment temperature, the pressure for heat treatment, the composition of the gas mixture and the amount of the required carbon coating. For example, the reaction 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 (for example, the amount of graphene (carbon)) increases, and as a result, the electrical properties of the composite can be improved. However, this trend may not necessarily be proportional to the time. For example, after a certain time, carbon deposition (for example, graphene deposition) may no longer occur, or the deposition rate may decrease.

[0153] Through the gas-phase reaction of the above carbon source gas, even at a relatively low temperature, it can be carried out by selecting from M a O c represented by (0 < a ≤ 3 and 0 < c ≤ 4, and if a is 1, 2 or 3, then c is an integer) and the second metal oxide which is the reduction product of the second metal oxide by M a O bA uniform coating (e.g., graphene coating) of a carbonaceous material is provided on at least one of the first metal oxides represented by (0 < a ≤ 3 and 0 < b < 4, and if a is 1, 2, or 3, then b is not an integer) to obtain an undoped composite.

[0154] The carbonaceous material may include a matrix of the carbonaceous material (e.g., graphene matrix), and the matrix of the carbonaceous material has at least one structure selected from a spherical structure, a spiral structure in which a plurality of spherical structures are connected, a cluster structure in which a plurality of spherical structures are clustered, and a sponge structure, and is selected from M a O b At least one of the first metal oxides represented by (0 < a ≤ 3, 0 < b < 4, and if a is 1, 2, or 3, then b is not an integer) and M a O c At least one of the second metal oxides represented by (0 < a ≤ 3 and 0 < c ≤ 4, and if a is 1, 2, or 3, then c is an integer) is distributed within the matrix of the carbonaceous material.

[0155] Next, a fluorine (F)-doped composite can be prepared by contacting the undoped composite with a fluorine (F)-containing compound.

[0156] For example, the undoped composite and the F-containing compound can be mixed in a solvent to prepare a solution, and after allowing the solution to stand for a predetermined time, the solvent can be removed, and washing and drying can be performed to prepare the F-doped composite. Through a chemical reaction in the solution containing the undoped composite and the F-containing compound, the fluorine (F) element included in the F-containing compound can be doped into the composite.

[0157] The solvent is not particularly limited and can be any solvent capable of dissolving the F-containing compound and dispersing the undoped composite. The solvent can be, for example, an organic solvent. The solvent can be, for example, an aprotic solvent. The solvent can be, for example, acetonitrile. The time for allowing the solution to stand is not particularly limited as long as the time is sufficient for the undoped composite and the F-containing compound to react and for fluorine (F) to be doped into the composite. The standing time can be, for example, about 1 day to about 10 weeks, about 1 week to about 5 weeks, about 2 weeks to about 5 weeks, or about 3 weeks to about 5 weeks. The temperature for allowing the solution to stand is not particularly limited as long as the temperature allows the undoped composite and the F-containing compound to react and for fluorine (F) to be doped into the composite. The temperature for allowing the solution to stand can be, for example, about 10°C to 50°C or about 20°C to about 30°C.

[0158] Optionally, a fluorine (F)-doped composite can be prepared by contacting the undoped composite with a gaseous fluorine (F)-containing compound.

[0159] There are no particular restrictions on compounds containing fluorine (F), as long as they contain a fluorine (F) atom, and they can be either organic or inorganic compounds containing fluorine. Examples of compounds containing fluorine (F) include fluorination agents.

[0160] F-containing compounds can be, for example, chemical substances in liquid, gaseous, or plasma states containing F.

[0161] Fluorine (F) compounds may be selected, for example, from hydrogen fluoride (HF), [NO2]BF4 (nitronium tetrafluoroborate), [Et2NSF2]BF4 ((diethylamino)difluorosulfonium tetrafluoroborate), HPF6, XeF2, F2 gas, F2 / Ar plasma, CF4 plasma, SF6 plasma, or combinations thereof.

[0162] Next, the lithium transition metal oxide and the complex can be mechanically milled. A NOBILTA mixer or similar device can be used during milling. The rotational speed of the mixer during milling can be, for example, from about 1000 rpm to about 2500 rpm. If the milling speed is less than 1000 rpm, the shear force applied to the complex and the lithium transition metal oxide is weak, resulting in difficulty for the lithium transition metal oxide and the complex to form chemical bonds. If the milling speed is too high, complexation will occur in too short a time, resulting in difficulty for the complex to uniformly coat the lithium transition metal oxide to form a uniform and continuous shell. The milling time can be, for example, from about 5 minutes to about 100 minutes, from about 5 minutes to about 60 minutes, or from about 5 minutes to about 30 minutes. If the milling time is too short, it will be difficult for the complex to uniformly coat the lithium transition metal oxide to form a uniform and continuous shell. If the milling time is too long, it may reduce production efficiency. The amount of the complex relative to the total weight of the complex and the lithium transition metal oxide can be 3 wt% or less, 2 wt% or less, or 1 wt% or less. The amount of the composite relative to the total weight of the composite and the lithium transition metal oxide can be, for example, from about 0.01 wt% to about 3 wt%, from about 0.1 wt% to about 2 wt%, or from about 0.1 wt% to about 1 wt%. For example, relative to 100 parts by weight of the mixture of lithium transition metal oxide and the composite, the amount of the composite can be from about 0.01 parts by weight to about 3 parts by weight, from about 0.1 parts by weight to about 3 parts by weight, from about 0.1 parts by weight to about 2 parts by weight, or from about 0.1 parts by weight to about 1 part by weight.

[0163] The average particle size (D50) of the lithium transition metal oxide used in the mechanical grinding of the composite and the lithium transition metal oxide can be, for example, about 1 μm to about 20 μm, about 3 μm to about 15 μm, or about 5 μm to about 10 μm. The average particle size (D50) of the composite used in the mechanical grinding of the composite and the lithium transition metal oxide can be, for example, about 50 nm to about 20 μm, about 50 nm to about 10 μm, about 50 nm to about 5 μm, about 50 nm to about 1 μm, about 50 nm to about 500 nm, about 50 nm to about 300 nm, or about 50 nm to about 250 nm.

[0164] Hereinafter, the exemplary embodiments will be described in more detail by the following examples and comparative examples. However, the following examples are for illustrative purposes only and should not be construed as limiting the scope of the inventive concept.

[0165] (Preparation of Composite)

[0166] Reference Preparation Example 1: Undoped Al2O3@Gr Composite

[0167] Al2O3 particles (average particle size: about 20 nm) were placed in a reactor, and while supplying CH4 at about 300 sccm and 1 atm for about 30 minutes, the temperature in the reactor was raised to 1000 °C.

[0168] Subsequently, heat treatment was performed while maintaining at the above temperature for 7 hours. Subsequently, the temperature in the reactor was adjusted to room temperature (20 °C - 25 °C) to obtain an undoped composite in which Al2O3 particles and their reduced product Al2O z (0 < z < 3) particles were embedded.

[0169] The amount of alumina included in the undoped composite was 60 wt%.

[0170] Preparation Example 1: Fluorine (F)-doped Al2O3@Gr Composite

[0171] 2.8 g of NO2BF4 (nitronium tetrafluoroborate) was dissolved in 100 mL of acetonitrile, and 0.13 g of the composite obtained in Reference Preparation Example 1 was dispersed therein to prepare a liquid dispersion. The prepared liquid dispersion was allowed to stand at room temperature for 4 weeks, and the composite was separated, washed with acetonitrile, then filtered and dried. The fluorine (F) element was doped into the composite by the reaction between NO2BF4 and the composite.

[0172] (Preparation of Composite Cathode Active Material)

[0173] Example 1: 0.4 wt% of fluorine (F)-doped Al2O3@Gr composite (0.24 wt% alumina) coated NCA91

[0174] LiNi was ground using a Nobilta mixer (Hosokawa, Japan) at approximately 1000 to 2000 rpm. 0.91 Co 0.05 Al 0.04 O2 (hereinafter referred to as NCA91) and the composite prepared in Preparation Example 1 were used to prepare a composite positive electrode active material for about 5 to 30 minutes.

[0175] The weight ratio of NCA91 to the complex obtained according to Preparation Example 1 was 99.6:0.4.

[0176] Example 2: 0.25 wt% fluorine (F)-doped Al2O3@Gr composite coating NCA91

[0177] Except for changing the mixing weight ratio of NCA91 to the composite obtained according to Preparation Example 1 to 99.75:0.25, the composite positive electrode active material was prepared using the same process as in Example 1.

[0178] Example 3: 0.1 wt% fluorine (F)-doped Al2O3@Gr composite coating NCA91

[0179] Except for changing the mixing weight ratio of NCA91 to the composite obtained according to Preparation Example 1 to 99.9:0.1, the composite positive electrode active material was prepared using the same process as in Example 1.

[0180] Example 4: 1.0 wt% fluorine (F)-doped Al2O3@Gr composite coating NCA91

[0181] Except for changing the mixing weight ratio of NCA91 to the composite obtained according to Preparation Example 1 to 99.0:1.0, the composite positive electrode active material was prepared using the same process as in Example 1.

[0182] Comparison Example 1: Bare NCA91

[0183] Bare NCA91 was used as the positive electrode active material.

[0184] Reference Example 1: 0.4 wt% undoped Al2O3@Gr composite coating NCA91

[0185] The composite positive electrode active material was prepared using the same process as in Example 1, except that the undoped Al2O3@Gr composite prepared in Reference Preparation Example 1 was used instead of the F-doped Al2O3@Gr composite prepared in Preparation Example 1.

[0186] (Preparation of lithium-ion batteries (half-cells))

[0187] Example 5

[0188] (Preparation of the positive electrode)

[0189] A slurry was prepared by mixing the composite positive electrode active material prepared in Example 1, the carbon conductive agent (superconducting acetylene black (DenkaBlack)), and polyvinylidene fluoride (PVdF) in a weight ratio of 96:2:2 with N-methylpyrrolidone (NMP) in an agate mortar.

[0190] The slurry rod was coated onto an aluminum current collector with a thickness of 15 μm and dried at room temperature, and then dried again under vacuum and 120°C. The plate was then rolled and stamped to prepare a positive electrode plate with a thickness of 55 μm.

[0191] The electrode loading level was 10.5 mg / cm². 2 The mixing density of the electrodes is 3.6 g / cc.

[0192] (Preparation of coin-type batteries)

[0193] A coin cell was prepared using the positive electrode plate prepared above and lithium metal as the counter electrode, and a PTFE membrane and a solution in which 1.15 M LiPF6 and 1.5 wt% vinylene carbonate (VC) were dissolved in EC (ethylene carbonate) + EMC (ethyl methyl carbonate) + DMC (dimethyl carbonate) (volume ratio 2:4:4) as the electrolyte.

[0194] Examples 6 to 8

[0195] Except that the composite positive electrode active material prepared in Examples 2 to 4 is used to replace the composite positive electrode active material prepared in Example 1, the coin cell is prepared using the same process as described in Example 5.

[0196] Comparison Example 2

[0197] Except for using the positive electrode active material prepared in Comparative Example 1 to replace the composite positive electrode active material prepared in Example 1, the coin cell was prepared using the same process as described in Example 5.

[0198] See Example 2

[0199] Except for using the composite positive electrode active material prepared in Reference Example 1 to replace the composite positive electrode active material prepared in Example 1, the coin cell is prepared using the same process as described in Example 5.

[0200] Evaluation Example 1: XPS Spectroscopic Evaluation

[0201] During the preparation of the undoped composite prepared in Reference Preparation Example 1, XPS spectra were measured over time using a Qunatum 2000 (Physical Electronics). XPS spectra of the C1s and Al 2p orbitals of the sample were measured before heating, at 1 minute, 5 minutes, 30 minutes, 1 hour, and 4 hours after heating. At the beginning of temperature rise, only the Al 2p orbital peak appeared, while the C1s orbital peak was absent. After 30 minutes, the C1s orbital peak became clearly visible, while the Al 2p orbital peak decreased significantly in size.

[0202] Thirty minutes later, the peaks of the C1s orbitals caused by C=C bonds and CC bonds due to graphene growth were clearly visible around 284.5 eV.

[0203] As the reaction time progresses, the peak position of the Al 2p orbital shifts to a lower binding energy (eV) due to the decrease in the oxidation number of aluminum.

[0204] Therefore, it can be confirmed that as the reaction proceeds, graphene grows on Al2O3 particles and forms Al2O3 as a reduction product of Al2O3. z (0 <z<3)。

[0205] The average content of carbon and aluminum was measured using XPS analysis of 10 regions of the composite sample prepared in Reference Preparation Example 1. The deviation of the aluminum content at each region was calculated based on the measurement results. The deviation of the aluminum content was expressed as a percentage relative to the average and was considered as uniformity. The percentage of the deviation of the aluminum content relative to the average (i.e., the uniformity of the aluminum content) was 1%. Therefore, it can be confirmed that alumina is uniformly distributed in the composite prepared in Reference Preparation Example 1.

[0206] Evaluation Example 2: XPS Spectroscopic Evaluation

[0207] exist Figure 1 The XPS spectra of the undoped composite prepared in Preparation Example 1 and the doped composite prepared in Preparation Example 1 are shown in the figure.

[0208] like Figure 1 As shown, the doped composite prepared in Preparation Example 1 additionally displays peaks for fluorine (F), nitrogen (N), and boron (B).

[0209] Therefore, it can be confirmed that the doped composite prepared in Preparation Example 1 is doped with fluorine (F).

[0210] Meanwhile, the undoped composite prepared in Preparation Example 1 did not show peaks of fluorine (F), nitrogen (N), and boron (B) elements.

[0211] The elemental contents obtained from the XPS spectra of the undoped composite prepared in Reference Preparation Example 1 and the doped composite prepared in Preparation Example 1 are shown in Table 1.

[0212]

Table 1

[0213]

[0214]

[0215] As can be shown in Table 1, the undoped composite prepared in Reference Preparation Example 1 does not contain fluorine (F), nitrogen (N), and boron (B) elements.

[0216] Meanwhile, the fluorine (F) element content of the F-doped composite prepared in Preparation Example 1 is 4.2 at%.

[0217] Evaluation Example 3: SEM, HR-TEM, and SEM-EDAX Analyses

[0218] Scanning electron microscopy, high-resolution transmission electron microscopy, and EDAX analysis were performed on the undoped composite prepared in Reference Preparation Example 1, the F-doped composite prepared in Preparation Example 1, the composite positive electrode active material prepared in Example 1, and the bare NCA of Comparative Example 1.

[0219] For SEM-EDAX analysis, FEI Titan 80-300 from Phillips Inc. was used.

[0220] It was found that the undoped composite prepared in Reference Preparation Example 1 has a structure in which Al2O3 particles and their reduced product Al2O z (0 < z < 3) particles are embedded in graphene. It was confirmed that the graphene layer is provided on the outside of one or more particles selected from Al2O z (0 < z < 3) and Al2O3 particles. One or more particles selected from Al2O z (0 < z < 3) and Al2O3 particles are uniformly dispersed in the graphene matrix. The particle size of one or more of the particles selected from Al2O z (0 < z < 3) and Al2O3 particles is about 20 nm. The particle size of the undoped composite prepared in Reference Preparation Example 1 is about 100 nm to 200 nm. The F-doped composite prepared in Preparation Example 1 shows a structure and particle size similar to those of the composite prepared in Reference Preparation Example 1.

[0221] It was confirmed that in the composite positive electrode active material prepared in Example 1, the shell formed by a composite including fluorine (F)-doped graphene was disposed on the NCA core.

[0222] SEM-EDAX analysis was performed on the bare NCA of Comparative Example 1 and the composite positive electrode active material prepared in Preparation Example 1.

[0223] It was confirmed that the aluminum (Al) concentration on the surface of the composite positive electrode active material of Example 1 had increased compared to the aluminum (Al) concentration on the surface of the bare NCA positive electrode active material of Comparative Example 1.

[0224] As a result, it was confirmed that the F-doped composite prepared in Example 1 uniformly coated the NCA core of the composite positive electrode active material of Example 1, thereby forming a shell.

[0225] Evaluation Example 4: Evaluation of Charge-Discharge Characteristics at Room Temperature (25℃)

[0226] The lithium batteries prepared in Examples 5 to 8, Comparative Example 2, and Reference Example 2 were charged at 25°C at a constant current rate of 0.1C until a voltage of 4.4V (relative to Li) was reached. Then, the voltage was maintained at 4.4V in constant voltage mode while being cut off at a current rate of 0.05C. Subsequently, the lithium batteries were discharged at a constant current rate of 0.1C until a voltage of 2.8V (relative to Li) was reached during discharge (formation cycling).

[0227] The lithium-ion battery, which had already undergone formation cycling, was charged at 25°C with a constant current rate of 0.2C until it reached a voltage of 4.4V (relative to Li). Then, it was kept at 4.4V in constant voltage mode while being cut off with a current rate of 0.05C. Subsequently, the lithium-ion battery was discharged at a constant current rate of 0.2C until it reached a voltage of 2.8V (relative to Li) during discharge (cycle 1). The above cycle was repeated under the same conditions (50 times) until cycle 50.

[0228] In all charge-discharge cycles, a 10-minute rest period was provided after each charge / discharge cycle. A portion of the room temperature charge-discharge test results are shown in Table 2 below. Initial efficiency is defined by Equation 1 below, and capacity retention is defined by Equation 2 below.

[0229] Equation 1

[0230] Initial efficiency [%] = [Discharge capacity during formation cycle / Charge capacity during formation cycle] × 100

[0231] Equation 2

[0232] Capacity retention rate [%] = [Discharge capacity in cycle 50 / Discharge capacity in cycle 1] × 100

[0233] Table 2

[0234]

[0235] As shown in Table 2, the lithium battery of Example 5 has improved initial efficiency compared to the lithium battery of Comparative Example 2.

[0236] Compared to the lithium battery in Comparative Example 2, the lithium batteries in Examples 5 to 8 have improved room temperature life characteristics.

[0237] Evaluation Example 5: Evaluation of High-Rate Performance at Room Temperature

[0238] The lithium batteries prepared in Examples 5 to 8, Comparative Example 2, and Reference Example 2 were charged at 25°C at a constant current rate of 0.1C until a voltage of 4.4V (relative to Li) was reached. Then, the voltage was maintained at 4.4V in constant voltage mode while being cut off at a current rate of 0.05C. Subsequently, the lithium batteries were discharged at a constant current rate of 0.1C until a voltage of 2.8V (relative to Li) was reached during discharge (formation cycling).

[0239] The lithium-ion battery, which had already undergone formation cycling, was charged at 25°C with a constant current rate of 0.2C until it reached a voltage of 4.4V (relative to Li). Then, it was kept at 4.4V in constant voltage mode while being cut off with a current rate of 0.05C. Subsequently, the lithium-ion battery was discharged at a constant current rate of 0.2C until it reached a voltage of 2.8V (relative to Li) during the discharge (Cycle 1).

[0240] The lithium-ion battery that had already undergone the first cycle was charged at 25°C with a constant current rate of 0.2C until it reached a voltage of 4.4V (relative to Li), and then cut off at a current rate of 0.05C while maintaining the voltage at 4.4V in constant voltage mode. Subsequently, the lithium-ion battery was discharged at a constant current rate of 0.5C until it reached a voltage of 2.8V (relative to Li) during the discharge (second cycle).

[0241] The lithium-ion battery that had already undergone the second cycle was charged at 25°C at a constant current rate of 0.2C until it reached a voltage of 4.4V (relative to Li), and then cut off at a current rate of 0.05C while maintaining the voltage at 4.4V in constant voltage mode. Subsequently, the lithium-ion battery was discharged at a constant current rate of 1.0C until it reached a voltage of 2.8V (relative to Li) during the discharge (the third cycle).

[0242] The lithium-ion battery that had already undergone the third cycle was charged at 25°C at a constant current rate of 0.2C until it reached a voltage of 4.4V (relative to Li), and then cut off at a current rate of 0.05C while maintaining the voltage at 4.4V in constant voltage mode. Subsequently, the lithium-ion battery was discharged at a constant current rate of 2.0C until it reached a voltage of 2.8V (relative to Li) during the discharge (fourth cycle).

[0243] The lithium-ion battery, which had already undergone its fourth cycle, was charged at 25°C with a constant current rate of 0.2C until it reached a voltage of 4.4V (relative to Li). Then, it was switched off at a constant voltage rate of 0.05C while maintaining the voltage at 4.4V. Subsequently, the lithium-ion battery was discharged at a constant current rate of 4.0C until it reached a voltage of 2.8V (relative to Li) during the discharge (fifth cycle).

[0244] A 10-minute rest period was provided after each charge / discharge cycle in all charge-discharge cycles. A portion of the room temperature charge-discharge test results are shown in Table 3 below. High-rate performance is defined by Equation 3 below.

[0245] Equation 3

[0246] High-rate performance [%] = [4.0C rate discharge capacity (5th cycle discharge capacity) / 0.2C rate discharge capacity (1st cycle discharge capacity)] × 100

[0247] Table 3

[0248]

[0249] As shown in Table 3, the lithium battery of Example 5 has improved high-rate performance compared to the lithium battery of Comparative Example 2.

[0250] Evaluation Example 6: Evaluation of High-Temperature (45℃) Charge-Discharge Characteristics

[0251] The lithium batteries prepared in Examples 5 to 8, Comparative Example 2, and Reference Example 2 were charged at 25°C at a constant current rate of 0.2C until a voltage of 4.4V (relative to Li) was reached. Then, the voltage was maintained at 4.4V in constant voltage mode while being cut off at a current rate of 0.05C. Subsequently, the lithium batteries were discharged at a constant current rate of 0.2C until a voltage of 2.8V (relative to Li) was reached during discharge (formation cycling).

[0252] The lithium-ion battery, which had already undergone formation cycling, was charged at 45°C with a constant current rate of 0.2C until it reached a voltage of 4.4V (relative to Li). Then, it was kept at 4.4V in constant voltage mode while being cut off with a current rate of 0.05C. Subsequently, the lithium-ion battery was discharged at a constant current rate of 0.2C until it reached a voltage of 2.8V (relative to Li) during discharge (cycle 1). The above cycle was repeated under the same conditions (100 times) until cycle 100.

[0253] In all charge-discharge cycles, a 10-minute rest period is provided after each charge / discharge cycle. A portion of the high-temperature charge-discharge test results are shown in Table 4 below. Initial efficiency is defined by Equation 4 below, and capacity retention is defined by Equation 5 below.

[0254] Equation 4

[0255] Initial efficiency [%] = [Discharge capacity during formation cycle / Charge capacity during formation cycle] × 100

[0256] Equation 5

[0257] Capacity retention rate [%] = [Discharge capacity in cycle 100 / Discharge capacity in cycle 1] × 100

[0258] Table 4

[0259]

[0260] As shown in Table 4, the lithium batteries of Examples 5 to 8 have improved initial efficiency compared to the lithium battery of Comparative Example 2.

[0261] Compared with the lithium battery in Comparative Example 2, the lithium batteries in Examples 5 to 8 have significantly improved high-temperature life characteristics.

[0262] Evaluation Example 7: Evaluation of Electrode Conductivity

[0263] The conductivity of the positive electrodes prepared in Example 5, Comparative Example 2 and Reference Example 2 was measured.

[0264] The conductivity of the positive electrode was measured using the HIOKI Inc. XF057 PROBE UNIT. Samples were prepared by stamping a circle with a diameter of Φ36 (36 mm) onto the positive electrodes prepared in Example 5, Comparative Example 2, and Reference Example 2, and the thickness of the electrode active material layer was calculated by measuring the thickness of the electrode plate. A probe was placed on the electrode active material layer to measure the resistance of the positive electrode, and the conductivity of the positive electrode was calculated from this.

[0265] The measurement results are shown in Table 5 below.

[0266] Table 5

[0267]

[0268]

[0269] As can be seen from Table 5, compared with the lithium battery of Comparative Example 2 without a casing, the lithium battery of Reference Example 2 exhibits reduced electrode conductivity due to having a casing introduced therein.

[0270] Meanwhile, compared with the lithium battery of Comparative Example 2, the lithium battery of Example 5 has significantly improved electrode conductivity by doping fluorine in the casing.

[0271] According to one aspect, since the composite positive electrode active material includes a shell containing doped fluorine (F) elements, carbonaceous materials and a first metal oxide, it can improve the high-temperature life characteristics and high-rate performance of lithium batteries.

[0272] It should be understood that the embodiments described herein are to be considered in a descriptive sense only and not for limiting purposes. The description of features or aspects within each embodiment should generally be considered applicable to other similar features or aspects in other embodiments. Although one or more embodiments have been described with reference to the accompanying drawings, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosure as defined by the claims.

Claims

1. A composite positive electrode active material, said composite positive electrode active material comprising: The core, including lithium transition metal oxides; as well as A shell is disposed on the surface of the core and conforms to the surface of the core. Among them, the shell includes at least one first metal oxide, a carbonaceous material, and doped fluorine element. The first metal oxide is selected from at least one of the following substances: Al2O z , where 0 < z < 3; NbO x , where 0 < x < 2.5; MgO x , where 0 < x < 1; Sc2O z , where 0 < z < 3; TiO y , where 0 < y < 2; ZrO y , where 0 < y < 2; V2O z , where 0 < z < 3; WO y , where 0 < y < 2; Fe2O z , where 0 < z < 3; Co3O w , where 0 < w < 4; PdO x , where 0 < x < 1; CuO x , where 0 < x < 1; AgO x , where 0 < x < 1; ZnO x , where 0 < x < 1; Sb2O z , where 0 < z < 3; and SeO y , where 0 < y < 2, and Wherein, the first metal oxide is disposed in a carbonaceous material matrix, and The carbonaceous material is a two-dimensional carbonaceous nanostructure.

2. The composite positive electrode active material according to claim 1, wherein, The amount of doped fluorine in the shell is from 1 at% to 10 at% relative to the total number of atoms in the shell.

3. The composite positive electrode active material according to claim 1, wherein, The amount of metal included in the first metal oxide in the shell is 1 at% to 10 at% relative to the total number of atoms in the shell; the amount of oxygen included in the shell is 1 at% to 20 at% relative to the total number of atoms in the shell; the amount of nitrogen included in the shell is 1 at% to 12 at% relative to the total number of atoms in the shell; and the amount of boron included in the shell is greater than 0 at% and less than or equal to 5 at% relative to the total number of atoms in the shell.

4. The composite positive electrode active material according to claim 1, wherein, The amount of carbon included in the shell is between 65 at% and 99 at%, relative to the total number of atoms in the shell.

5. The composite positive electrode active material according to claim 1, wherein, The shell has a thickness of 1 nm to 5 μm.

6. The composite positive electrode active material according to claim 1, wherein, The carbonaceous material is graphene.

7. The composite positive electrode active material according to claim 1, wherein, The shell comprises at least one selected from the composite and the polished article of the composite, wherein the composite comprises the first metal oxide, the carbonaceous material and the doped fluorine element, and the amount of at least one selected from the composite and the polished article of the composite is 3 wt% or less relative to the total weight of the composite positive electrode active material.

8. The composite positive electrode active material according to claim 7, wherein, The carbonaceous material has a branched structure, the first metal oxide is distributed within the branched structure, and the branched structure includes a plurality of carbonaceous material particles in contact with each other.

9. The composite positive electrode active material according to claim 7, wherein, The carbonaceous material has at least one structure selected from spherical structures, helical structures, and cluster structures, wherein the spherical structures are interconnected in the helical structure, and the spherical structures are aggregated in the cluster structure. The first metal oxide is distributed within the spherical structure, the spherical structure having a size of 50 nm to 300 nm; the helical structure having a size of 500 nm to 100 μm; the cluster structure having a size of 0.5 mm to 10 mm; the composite having a wrinkled polyhedral spherical structure or a planar structure; at least one selected from the first metal oxide and the second metal oxide is distributed within the wrinkled polyhedral spherical structure or the planar structure, or on the surface of the wrinkled polyhedral spherical structure or the planar structure; the carbonaceous material extends from the first metal oxide by a distance of 10 nm or less and comprises 1 to 20 layers of carbonaceous material, and the total thickness of the carbonaceous material is 0.6 nm to 12 nm. Among them, the second metal oxide is represented by M a O c where 0 < a ≤ 3 and 0 < c ≤ 4. If a is 1, 2 or 3, then c is an integer, and M is at least one metal selected from Groups 2 to 6, 8 to 13, 15 and 16 of the periodic table of elements, and The first metal oxide is a reduction product of the second metal oxide.

10. The composite positive electrode active material according to claim 1, wherein, The lithium transition metal oxide is represented by formula 1 or formula 5: <Formula 1> Li a Ni x Co y M z O 2-b A b In Formula 1, 0.9 ≤ 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 Mn, Nb, V, Mg, Ga, Si, W, Mo, Fe, Cr, Cu, Zn, Ti, Al, or a combination thereof, and A is F, S, Cl, Br, or a combination thereof. <Formula 5> Li a Co x M y O 2-b A b In Formula 5, 1.0 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.2, 0.9 ≤ x ≤ 1, 0 ≤ y ≤ 0.1, and x + y = 1, M is Mn, Nb, V, Mg, Ga, Si, W, Mo, Fe, Cr, Cu, Zn, Ti, Al, or a combination thereof, and A is F, S, Cl, Br, or a combination thereof.

11. The composite positive electrode active material according to claim 1, wherein, The lithium transition metal oxide is represented by at least one of Formulas 2 to 4: <Formula 2> LiNi x Co y Mr z O2 <Formula 3> LiNi x Co y Al z O2 In Formulas 2 to 3, 0.8 ≤ x ≤ 0.95, 0 < y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1. <Formula 4> LiNi x Co y Mr v Al w O2 In Formula 4, 0.8 ≤ x ≤ 0.95, 0 < y ≤ 0.2, 0 < v ≤ 0.2, 0 < w ≤ 0.2, and x + y + v + w = 1.

12. A positive electrode, which includes the composite positive electrode active material according to any one of claims 1 to 11.

13. A lithium battery, which includes the positive electrode according to claim 12, a negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode.

14. A method for preparing a composite positive electrode active material, the method including the following steps: Providing a lithium transition metal oxide; Providing a composite; And Mechanically grinding the lithium transition metal oxide and the composite, Among them, the composite includes at least one first metal oxide, a carbonaceous material, and doped fluorine element, and the first metal oxide is selected from at least one of the following substances: Al2O z , where 0 < z < 3; NbO x , where 0 < x < 2.5; MgO x , where 0 < x < 1; Sc2O z , where 0 < z < 3; TiO y , where 0 < y < 2; ZrO y , where 0 < y < 2; V2O z , where 0 < z < 3; WO y , where 0 < y < 2; Fe2O z , where 0 < z < 3; Co3O w , where 0 < w < 4; PdO x , where 0 < x < 1; CuO x , where 0 < x < 1; AgO x , where 0 < x < 1; ZnO x , where 0 < x < 1; Sb2O z , where 0 < z < 3; and SeO y , where 0 < y < 2, wherein the first metal oxide is disposed within a carbonaceous material matrix, and wherein the carbonaceous material is a carbonaceous two-dimensional nanostructure.

15. The method according to claim 14, wherein, The step of providing the composite includes: providing an undoped composite by supplying a reaction gas composed of a carbon source gas to at least one second metal oxide and performing a heat treatment to reduce the second metal oxide to the first metal oxide, the second metal oxide being represented by M a O c where 0 < a ≤ 3 and 0 < c ≤ 4, and if a is 1, 2, or 3, then c is an integer; and The composite is prepared by contacting the undoped composite with a fluorine-containing compound, wherein M is at least one metal selected from Groups 2 to 6, 8 to 13, 15, and 16 of the periodic table.

16. The method according to claim 15, wherein, The fluorine-containing compound is at least one selected from hydrogen fluoride, [NO2]BF4, [Et2NSF2]BF4, HPF6, XeF2, F2 gas, F2 / Ar plasma, CF4 plasma, and SF6 plasma.

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